E-Posters

Arthroplasty-Cervical

77

P001: Anterior cervical hybrid constructs reduce upper adjacent segment hypermobility compared to anterior cervical discectomy and fusion

Fenil Bhatt ¹ , Lindsay Orosz ² , Tarek Yamout ¹ , Christopher Good ¹ , Anthony Bucci ² , Brandon Allen ² , Thomas Schuler ¹ , Ehsan Jazini ¹ , and Colin Haines ¹

¹ The Virginia Spine Institute, Reston, United States

² National Spine Health Foundation, Reston, United States

Introduction: The traditional surgical treatment for symptomatic cervical degenerative disc disease is anterior cervical discectomy and fusion (ACDF). Despite its effectiveness, one long-term consequence of fusion may be an increased risk of adjacent segment degeneration resulting in the need for additional surgery. Cervical disc arthroplasty has been shown to preserve physiologic range of motion (ROM) and decrease the need for adjacent segment surgery. For patients with multilevel pathology requiring at least one level of fusion, there is growing interest in combining anterior cervical fusion with arthroplasty to maintain as much motion as possible with a partial motion-preserving procedure. This study primarily aims to compare postoperative adjacent segment motion between anterior cervical hybrid surgery (ACH) and ACDF. Secondarily, total global (C2-7) motion, construct motion, and alignment parameters will be compared between groups. Material and Methods: In this retrospective cohort study at a multi-surgeon spine practice, 2- and 3-level ACH and ACDF cases were identified between 2013 and 2021. Patients with incomplete records, imaging, or less than 6 months of follow-up were excluded. Demographic and radiographic data were obtained from medical and imaging records. Motion detection in degrees was analyzed on flexion/extension views using Cobb angles to measure lordosis at C2-C7 (global), the construct, and upper and lower adjacent segments. Pre- and post-operative neutral lateral x-rays were analyzed for alignment parameters: C2-C7 global lordosis, cervical sagittal vertical axis (cSVA), and T1 slope (T1S). Differences between ACH and ACDF cohorts were determined using independent t-tests for continuous variables and Fisher’s exact test for categorical variables. Results: There were 50 patients in each cohort (2-level cases: 18 ACH, 20 ACDF) (3-level cases: 32 ACH, 30 ACDF). Hybrid patients were overall younger in age, (51 ACH, 59 ACDF, p < 0.001) with lower CCI scores (0.8 ACH, 1.7 ACDF, p < 0.001). Postoperatively, total ROM across the construct was significantly greater in the ACH cohort (16.3° ACH, 4.7° ACDF, p < 0.001) as was total global ROM (38.0° ACH, 28.0°, p < 0.001). The degrees of motion that decreased at the level of the construct (postoperative minus preoperative construct motion) were significantly less in the ACH cohort (-10.0° ACH, -18.1° ACDF, p < 0.001). Postoperatively, the degrees of motion at the upper adjacent segment were significantly increased compared to preoperatively in the ACDF cohort (-1.3° ACH, 1.6° ACDF, p < 0.005). Conclusion: In this study, 2- and 3-level ACH constructs partially preserved motion across the operative levels compared to ACDF constructs. As a result, postoperative total global ROM was better in the ACH cohort and postoperative upper adjacent segment hypermobility was seen only in the ACDF cohort. This supports the consideration of combining fusion with arthroplasty in patients with multilevel cervical pathology that require at least 1 level of fusion.

423

P002: To accomplish laminoplasty cross tightening and C3 laminectomy for laminoplasty

Takahiro Iizuka ¹ , Tokuji Kashiro ¹ , Tetsuro Takai ¹ , and Hiroshige Debata ¹

¹ Kouseikai Takai Hospital, Orthopaedic Spine Surgery, Nara, Japan

Introduction: Neck pain following cervical laminoplasty and loss of kinematic ROM are still the major concerns as well as neurological recovery. We reported Cross Tightening for laminoplasty at Global Spine Congress 2023 in Las Vegas. This procedure dramatically reduces postoperative neck pain. Considering ROM of cervical motion, kinematic ROM is limited by laminoplasty because enlarged lamina may interrupt the cervical extension. From a kinematic point of view, the upper cervical spine C0-1-2 is more flexible in extension and flexion of the cervical spine. We arranged the procedure for the next step to make it a cutting-edge method for cervical laminoplasty. We combined Cross Tightening and C3 laminectomy for postoperative axial neck pain and also postoperative neck motion preservation. We report the preliminary results of cervical laminoplasty with Cross Tightening and C3 laminectomy regarding axial pain and kinematical ROM after surgery. Aim: We aimed to report the results of Cross Tightening and C3 laminectomy (combined laminoplasty) regarding postoperative neck pain (axial pain) and kinematic ROM of the cervical spine. Materials and Methods: We introduce the preliminary results of 5 patients who had Cross Tightening and C3 laminectomy compared with 21 patients who had C3-7 laminoplasty with Cross Tightening. Techniques of Cross Tightening Muscle and C3 laminectomy. 1. Patients positioned in the prone position with Mayfield. 2. Skin incision was made in the midline over C2-Th1. 3. Multifidus Muscles attached to C2 were ligated with 5 Ethbond before detaching. 4. Multifidus Muscles attached to C7 were also ligated with 5 Ethbond before detaching. 5. Laminoplasty C4-7 and C3 laminectomy was performed with the left side open using spacers Camber from NuVasive. 6. Muscles were reconstructed in anatomical direction tightening to the opposite fascia. We evaluated the cervical vertebral alignment (C1-Th1) for each patient and neck pain (VAS) and ROM on lateral X-rays at 12 weeks after surgery. Results: Laminoplasty with C3 laminectomy improved ROM of the cervical spine compared with C3-7 laminoplasty. Neck Pain was also significantly reduced at 12 weeks after surgery in all of them. Conclusion: CSM often requires C3 to C7 laminoplasty, but post-operative neck pain is the major concern though many reports suggest us the preservation of C7 muscle structures. In preparing laminoplasty we require the removal of muscle attachment from the laminae. We often observe Multifidus Muscles attached to spinous processes are shortened as if they were gum bands. Besides C2 and C7 have a larger spinous process which seems to have a major role in cervical motion. Enlargement of the laminae would interrupt the extension motion. We focused on muscle function restoration to reduce postoperative neck pain and ROM. We report the preliminary restoration methods for cervical motor function with Cross Tightening Multifidus Muscles. This procedure which is combined with Cross Tightening and C3 laminectomy may restore the muscular function in cervical motion in the normal anatomical direction and may be superior to the conventional procedure in terms of postoperative neck pain and ROM.

566

P003: Comparison of relative value units per operative time between anterior cervical discectomy and fusion (ACDF) vs cervical disc replacement (CDR)

Amanda Faust ¹ , Don Moore ¹ , and Mathew Resnick ¹

¹ Missouri Orthopedic Institute, Orthopedic Surgery, Columbia, United States

Introduction: Anterior cervical discectomy and fusion (ACDF) has been the gold standard for surgical treatment of cervical radiculopathy for many years. Recently however, cervical disc replacement (CDR) has become an alternative to treat cervical radiculopathy and myelopathy. Data supports favorable outcomes for both myelopathy and non-myelopathy use of disc arthroplasty (Samuel). It is important to assess and contrast all aspects of the two procedures to compare their strengths and weaknesses and assist surgeons in procedure selection. Material and Methods: Retrospective study including patients treated at the University of Missouri Hospital and the Missouri Orthopaedic Institute from 2019-2022. Patients will be identified via CPT codes used for 1-level ACDF and CDR and data will be extracted via chart review. Results: The total patient cohort consisted of 361 patients. 124 patients met inclusion criteria, but of these patients only 33 underwent a CDR. Due to the relatively smaller CDR patient population, data analysis was collected on the most recent 33 ACDF operations to keep the two groups of comparable size. The mean RVU per hour for ACDF was 24.21 (p < 0.001) while the mean RVU per hour for CDR was 14.83 (p < 0.001). Patients who had a pre-op diagnosis of myelopathy and/or stenosis were more likely to receive an ACDF than a CDR. Older age, hypertension, and an ASA score of greater than 3 were more common in the ACDF group. Pre-operatively ACDF patients had higher PROMIS Pain Intensity scores (67.59 vs. 62.55 p < 0.03) as well as higher Neck Disability Index (NDI) scores (47.43 for ACDF vs. 34.33 for CDR p < 0.01). Post-op length of stay was significantly longer for patients who underwent an ACDF than those in the CDR group (0.89 vs. 0.49 days p < 0.05). Post-operatively ACDF patients had higher NDI scores within the 6-12 week follow up window than patients who underwent CDR (27.75 vs 16.15 p < 0.03). There were not significant differences in NDI scores between the two groups within the 6-12 month follow up period. Conclusion: ACDF was associated with significantly higher RVUs per minute compared to CDR. The difference in pre-operative pain and disability scores shows that patients with more severe symptoms are more likely to undergo an ACDF than a CDR. Despite the difference in patient population, patients in both groups had similar 6-12-month NDI and PROMIS scores post-operatively. These findings highlight the importance of considering physician reimbursement and patient reported outcomes in selecting surgical treatment options for patients with cervical spinal problems.

1101

P004: Wear-related osteolysis after implantation of the M6-C artificial cervical disc: first longterm follow-up results

Sonja Häckel ^1,2,3 , Jessica Gaff ² , Andrew Miles ^2,4 , Paul Taylor ^2,4 , Michael Kern ^2,4 , and Gregory Cunningham ^1,2,4

¹ Department of Orthopaedic Surgery, Fiona Stanley Hospital, Murdoch, Australia

² NeuroSpine Institute, Murdoch, Australia

³ Department of Orthopaedic Surgery and Traumatology, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland

⁴ Department of Orthopaedic Surgery, St John of God Hospital, Murdoch, Australia

Introduction: The M6-C™ artificial cervical disc (Orthofix, Lewisville, Texas) is a routinely used cervical total disc replacement (CTDR) implant. In June 2020 Australian Therapeutic and Goods Administration published an implant hazard report because the Instructions for Use contained insufficient information regarding the potential consequences of peri-prosthetic osteolysis associated with the use of the M6-CTM. In a recent study, it was reported that after mid-term follow-up, 34% of patients implanted with the M6-C™ required revision surgery for wear-related osteolysis with an average of 5.5 years postop. However, their study did not report on the incidence and grade of osteolysis, as well as indication for revision surgery. Methods: We retrospectively analysed the radiographic and clinical outcomes (EuroQuol-5D, Neck Disability Index, Visual analogue scale for neck and arm pain) of data collected during long-term follow-up of patients who underwent CTDR with the M6-C^TM implant at a multi-centre between 2011 and 2015. All patients were followed up with radiographic imaging (conventional X-ray, CT scan) of the cervical spine to detect osteolysis. Clinical outcome was determined by collecting patient-related questionnaires (EuroQuol-5D, Neck Disability Index, Visual analogue scale for neck and arm pain). Ethical approval was obtained from the local Institutional Review Board. Results: A total of 86 patients underwent CTDR with the M6-C™. Follow-up was completed in 40 patients with a mean age of 44 years (53% women). The mean follow-up time was 8.6 years (7.5-11 years). Prior to our follow-up, only 4 patients (10 %) had revision surgery, but not due to osteolysis. Radiographs showed abnormal findings in 33/40 patients (83 %): 17/40 patients (40 %) had osteolysis. Three patients had mild, 8 patients had moderate, and 5 patients had severe osteolysis. In addition, 16/40 patients (40 %) had various degrees of heterotopic ossification which led to a fused and immobile disc in 13 of these patients. There was no significant correlation between osteolysis and clinical outcome. Conclusion: In our cohort, we see a lower reoperation rate of the M6-C™ implant compared to the literature. However, osteolysis can be asymptomatic. Additional revision surgeries might have to be done after imaging and clinical follow-up will be completed. Our study has some limitations. The study design is retrospective, and we do not have a control group. Furthermore, 20% of patients refused to follow up which is a potential bias. The long-term radiographic follow-up results of the M6-C™ in this cohort are not favourable. Patients with this implant should undergo interval monitoring for major osteolysis or implant failure.

1257

P005: The position of the cervical prosthesis in hybrid surgery for two-level cervical degenerative disc disease and its effect on cervical range of motion

Matjaz Vorsic ¹ , Rok Koncnik ¹ , and Valentin Rokavec ¹

¹ Neurosurgery, University Hospital Maribor, Maribor, Slovenia

Background: There are no clear indications at which level the cervical disc arthroplasty (CDA) should be performed in the Hybrid surgery (HS), involving the combination of ACDF and CDA. Retrospective analysis comparing the clinical and radiographic results in the treatment of two-level cervical degenerative disease was performed comparing the patients who underwent the HS and had the artificial disc implanted at different levels. Materials and Methods: After applying the inclusion criteria, 34 patients with two-level cervical degenerative disc disease where conservative treatment failed were included in the study. All the patients had been operated with the hybrid procedure. The CDAs in 18 patients were implanted above and in 16 patients bellow the ACDF level. Clinical outcomes were assessed before and at regular intervals until one year after the procedure using neurological examination, the Neck Disability Index (NDI) and Visual Analogue Scale (VAS) for neck and arm pain, with 15% improvement in NDI and 20% in VAS defined as a clinically significant. The cervical range of motion was evaluated using flexion-extension parameters. Results: The groups were similar at baseline both clinically and statistically. Both groups had a statistically significant improvement in NDI and VAS for neck and arm pain (p > .05) and there was no statistically significant difference between groups at any point of investigation. There was no statistically significant difference in the C2-C7 ROM between the two groups at 12 and 24 months postoperatively (p > .05). The location of the arthroplasty at the level C5/6 or C4/5 provided better ROM compared to the level C6/7. Conclusions: Both groups resulted in significant pain reduction and functional outcome for the patients in short and long term period. The combination of fusion and arthroplasty can be adjusted to each level allowing segmental motion preservation at the affected levels and minimizing hypermobility at adjacent levels. The ROM was more affected by the level of the artificial disc implantation than relationship of the CDA towards ACDF.

1288

P006: Static finite element method analysis of 3D printed compressible non-articulating cervical disc prosthesis

Samuel Brehm ¹ , Miguel Ruiz Cardozo ¹ , Hau-Ju Ting ² , Aspen Chadderdon ² , Aneesh Syal, ² , Gabriel Trevino Verastegui ¹ , Abby Carey-Ewend ¹ , Matthew De la Paz ¹ , Ahmed Hanafy ¹ , Julio Jauregui ³ , Magalie Cadieux ¹ , and Camilo Molina ¹

¹ Neurosurgery

² Biomedical Engineering

³ Orthopaedic Surgery, Washington University in St. Louis, St. Louis, United States

Introduction: Non-articulating disc prothesis were created to mimic the compressive and flexural stiffness of natural discs. These discs are designed with two metallic endplates with a homogeneous elastic core or a mobile central core with peripheral fibers. However, these non-articulating discs have a variety of issues including an unstable center of rotation, friction of fibers on endplates, endplate to elastomeric core binding failure, and anteroposterior shift of one endplate relative to the other. In order to solve some of these problems, we designed a unibody, all metal, compressible, non-articulating cervical disc arthroplasty (CDA). We quantified the theoretical elastic stiffness of the design in compression, flexion-extension bending, lateral bending, and axial rotation and compared the numbers to that of natural cervical discs. A prototype was also produced to check manufacturability. Material and Methods: We ran finite element analysis (FEA) using Fusion 360 for the novel disc prosthesis in compression, lateral bending, and axial rotation. In all simulations the material choice was Ti-6Al-4V the inferior endplate was rigidly fixed, and the superior endplate had the external force/moment distributed evenly over its superior surface. For compression, lateral bending, and axial rotation the applied force/moment was 1 N, 1 Nm, and 1 Nm respectively. Stiffness was calculated by dividing the resultant displacements by the applied force/moment. The prototype of the novel disc prothesis was 3D printed out of Ti-6Al-4V alloy by a direct metal laser sintering service. Manufacturability was assessed by gross examination of the geometry of the delivered prototype. Results: The artificial disc and natural cervical discs have a compressive stiffness of 513 N/mm and 492 N/mm respectively (4.4% error). Due to symmetry, the artificial disc had equal flexion-extension and lateral bending stiffnesses. The artificial disc and natural cervical discs have a lateral bending stiffness of 0.12 Nm/deg and 0.9 Nm/deg respectively (87% error). The artificial disc and natural cervical discs have a axial rotation stiffness of 5 Nm/deg and 0.8 Nm/deg respectively (525% error). The gross examination of the printed prototype revealed correct geometrical features with no missing or additional features. Additionally, the prototype length, width, and height were all within 0.5 mm error. Conclusion: The novel device produced overall similar mechanics to natural discs in terms of elastic stiffness. The disc was the worst at matching axial stiffness rotation, which would mean loss of axial rotation range of motion when implanted. The gross examination of the prototype showed that the device was manufacturable and had no feature size errors or overhang errors common to 3D prints. The 3D printable nature of the device means it has the potential to be easily individualized to each patient. This is good because optimizing disc height would minimize over or under distraction and optimizing endplate convexity and size would minimize bone preparation and lower heterotopic ossification. The next steps would be static and dynamic mechanical testing of the prototype as a further proof of concept.

2020

P007: How does the type of multilevel anterior cervical constructs influence cervical sagittal parameters and adjacent disk measurements? A retrospective analysis

Diogo Morgado ¹ , João Paulo Andrade ¹ , and Mário Vale Campos ¹

¹ Neurosurgery, Centro Hospitalar Lisboa Ocidental, Lisbon, Portugal

Introduction: Cervical sagittal parameters are related with clinical outcomes after multilevel anterior cervical discectomy and fusion. However, there is no comparison of these parameters after fusion (cage or cage plus plate), total disc replacement (TDR) or hybrid constructs. The aim of this work was to assess the impact of the type of multilevel anterior cervical constructs in the cervical sagittal parameters and adjacent levels. Material and Methods: The authors performed a retrospective analysis of all the multilevel (more than one) anterior cervical spine surgeries performed between 2015 and 2021 due to degenerative disease. Cervical sagittal parameters included: superior and inferior level disk height and angle, cervical lordosis using the Jackson physiological stress line method, C2-C7 Sagittal Vertical Axis (SVA), Thoracic Inlet Angle (TIA), neck tilt, T1 Slope and cervical tilt. Then a delta of the pre- and postoperative of the superior and inferior disk height and angle, and cervical lordosis was performed. Clinical data was evaluated by IBM^® SPSS Statistics (version 27.0). Quantitative data was first tested for its normality and homogeneity of variance and according to different situations, they were tested by Student’s t test or Mann–Whitney U test. Qualitative data was tested by Chi-square test. p value < 0.05 was considered statistically significant. Results: There were 140 patients analysed with a mean age of 57.7 (± 11.6). From these 54.3% were female and 36.5% were smokers. Myelopathy was present in 52.7% and radiculopathy in 63%. Longer constructs were associated with myelopathy (p < 0.05). In 83.6% a 2-level construct was performed, in 15.7% a 3-level and in 0.7% a 4-level. In 81.4% fusion was performed, in 5.7% a TDR and in 12.9% a hybrid construct. Operative complications were described in three cases (all fusion) and four patients underwent second surgery (three after fusion procedures and one after TDR). The following values are organized respectively according to the sequence - cage, cage plus plate, TDR and hybrid construct. The mean superior level disc height delta was 0.64, 0.18, 0.74, and 0.08, the mean superior level disc angle was 0.34°, 1.00°, -1.90° and -1.13°. The mean preoperative cervical lordosis was 9.52°, 13.48°, 7.42° and 7.74°. The mean cervical lordosis delta was 4.84°, 4.06°, 7.02° and 6.98°. The mean TIA was 79.21°, 81.98°, 81.68° and 73.86°. The correlation between the mean preoperative cervical lordosis and the mean TIA was statistically significant (p < 0.01). Conclusion: There was no significant difference in the type of construct and the rate of reoperation or complications, rendering them all equally safe. There was a significant association between the TIA and pre-operative cervical lordosis, providing support that there’s a compensating increase in cervical lordosis with higher TIA. While the TIA was lower in hybrid constructs, both these and TDR were associated with a greater increase in cervical lordosis. Further studies, namely prospective randomized studies are needed to evaluate the impact of TDR and hybrid constructs in cervical sagittal parameters and adjacent segment disease.

Arthroplasty-Lumbar

485

P008: Efficacy and safety of the ultrasound bone scalpel in lumbar laminectomies

Anthony Steinle ¹ , Jeffrey Chen ¹ , Alexander O'Brien ¹ , Wilson Vaughan ¹ , Andrew Croft ¹ , William Waddell ¹ , Justin Vickery ¹ , Robert Elrod ¹ , Hani Chanbour ² , Julian Lugo-Pico ¹ , Scott Lawrence Zuckerman ^1,2 , Amir Abtahi ^1,2,3 , and Byron Stephens ^1,2,3

¹ Department of Orthopaedic Surgery

² Department of Neurological Surgery

³ Center for Musculoskeletal Research, Vanderbilt University Medical Center, Nashville, TN, United States

Introduction: Lumbar laminectomy is commonly performed to address complaints of neurogenic claudication or radicular leg pain. Despite recent advances in applied instruments and surgical techniques, the incidence of inadvertent dural injuries caused by traditional laminectomy techniques is still considerable. The ultrasonic bone scalpel (UBS) uses high-frequency oscillation to create localized tissue disruption and preferentially cut through hard surfaces such as bone. It has been shown to improve speed and reduce intraoperative complications in laminectomies for cervical and thoracic spondylotic myelopathy when compared to traditional methods using a high-speed burr, punch forceps, rongeurs, etc. We sought to evaluate whether the use of the UBS in lumbar laminectomies would result in equivalent safety, efficacy, and PROs compared to traditional methods. We hypothesize that using the UBS will demonstrate equivalent safety, efficacy and PROs while decreasing rates of durotomies compared to traditional methods. Material and Methods: Data from a prospectively collected, single-institution registry was queried between 01/01/2019 - 09/01/2021 for patients with a primary diagnosis of lumbar stenosis who underwent an isolated laminectomy, laminectomy and fusion, or laminectomy and fusion with an interbody. Two patient groups included: laminectomies using traditional methods vs UBS method. Outcomes included 3-month values for all PROMIS subdomains, NRS pain scores, ODI percentage, and PHQ-9 scores, as well as complications, reoperations, or readmissions within 3 months. Patients who received a lumbar laminectomy by traditional methods were propensity matched against patients who received a lumbar laminectomy by the UBS in 2:1 fashion. Covariates selected for matching included age, operation type, and number of levels. A variety of statistical tests were used to compare groups. Results: 231 patients who received a laminectomy with traditional methods were propensity matched against 32 patients treated with the ultrasound bone scalpel, resulting in 64 “traditional group” patients and 32 “UBS group” patients. Analysis found no differences between groups for demographic and baseline measures except for race and ethnicity. There were no differences between groups at 3 months for all PROMIS subdomain scores, NRS back/leg pain scores, %ODI or PHQ-9. Additionally, there were no significant differences for any PROs at 12 months. There was a significant difference in rates of durotomies between the traditional and UBS groups (12.5% vs 0.0%, p = 0.049). Among those experiencing intraoperative durotomy, 16.67% required re-operation. There were no significant differences between groups in any other complication rate as well as reoperation and readmission rates. Conclusion: Laminectomies are commonly performed on the lumbar spine to remedy a variety of spine pathologies, with the most common complication being an iatrogenic durotomy. We sought to compare outcomes between patients who received a lumbar laminectomy through traditional methods versus the UBS. Our results suggest the UBS helps decrease the rate of injury to the dura, thus reducing the incidence of durotomies. We believe this data provides valuable information to surgeons and patients about the safety and efficacy of the UBS in lumbar laminectomies. Further studies should investigate if the UBS decreases operative time for lumbar laminectomies compared to traditional methods.

656

P009: Patterns of opioid use prior to single-level lumbar fusion are associated with postoperative opioid use and adverse events

Jayme Koltsov ¹ , Tanmaya Sambare ² , John Kleimeyer ¹ , Eugene Carragee ¹ , Kirkham Wood ¹ , Todd Alamin ¹ , and Serena Hu ¹

¹ Orthopaedic Surgery, Stanford University School of Medicine, Palo Alto, United States

² Orthopaedic Surgery, Harbor-UCLA Medical Center, West Carson, United States

Introduction: Opioid pain medication use is common among lumbar spine surgery patients and has been related to increased rates of chronic dependence, poorer surgical outcomes, and increased surgical costs. We hypothesize that it is possible to identify phenotypes of patients based on their patterns of pain medication use preoperatively, and that these phenotypes will relate to postoperative opioid use, complications, discharge disposition, length of stay, costs and healthcare resource utilization. Materials and Methods: Adult patients undergoing primary single level lumbar fusion with a diagnosis of stenosis were identified from the IBM^® Marketscan^® databases (2007-2015). Patients were required to have at least 1 year of continuous health plan enrollment pre and postoperatively in a plan providing outpatient pharmacy data. Group based trajectory modeling was used to identify distinct patient phenotypes based on their preoperative patterns of opioid usage. Multivariable logistic regression was used to assess relationships between these phenotypes and postoperative outcomes after adjusting for patient and surgical factors. Results: The final analysis comprised 9,464 patients (age 58 ± 12 years, 58.6% female). 60% of patients used opioids within the 3 months preceding their fusion procedure. 5 distinct phenotypes of preoperative opioid use were identified: A high dose phenotype (17.1% of patients), using on average 60 morphine milligram equivalents (MME) per day 1 year prior to surgery and increasing linearly to > 80 MME per day preoperatively; a medium dose phenotype (16.4%), using 10 MME per day 1 year prior to surgery and increasing linearly to 25 MME per day preoperatively, a phenotype with no use 1 year prior to surgery who began using increasing amounts of opioids ∼6 months preoperatively, increasing to > 30 MME per day ( steep 6m rise phenotype, 11.6%); a phenotype with very low opioid use 1 year preoperatively (likely those taking intermittently only as needed) who began increasing 3 months prior to surgery, reaching 15 MME per day ( intermittent to 3m phenotype, 19.8%); and a group using no opioids until 3 months prior to surgery, who began increasing 3 months prior to surgery, reaching 15 MME per day ( naïve to 3m phenotype, 35.0%). These phenotypes were related in a dose-response manner (based on duration and maximum preoperative dosage) to postoperative opioid use at 3m, 6m, 1yr, and 2 years, and complications and all-cause readmissions within 90-days (p < 0.001 for all). For example, patients in the intermittent to 3m phenotype had 8.3 (4.7, 14.6) times the odds for opioid use 3m postoperatively, those in the medium phenotype had 16.7 (7.4, 38.1) times the odds for use 3m postoperatively, and those in the high phenotype had 90.7 (12.6, 653.1) times the odds for opioid use 3 months postoperatively relative to patients not taking opioids prior to surgery (p < 0.001 for each). Interestingly, patients in the naïve to 3m phenotype did not have increased odds for opioid use at 3m postoperatively relative to those who did not use opioids preoperatively. Conclusion: Distinct phenotypes of preoperative opioid use can be identified and are associated with postoperative opioid use, complications, and readmissions. Analysis of LOS, discharge disposition, costs and HCRU are ongoing.

1379

P010: Spondylolysis with vertebral listhesis: choice of the surgical technique according to the injury degree

Carlos Mariano Nirino ¹

¹ Orthopedics and Traumatology, Hospital Santamarina, Monte Grande, Argentina

Introduction: The aim of this paper is to describe the correct choice of the surgical technique depending on the injury degree in diagnosis of spondylolysis with listhesis grade 1, 2 and 3 according to Meyerding classification and the results obtained. 31 patients were evaluated between 2010 and 2021; all operated by the Orthopedics and Traumatology department of the Santamarina Hospital of Monte Grande in Buenos Aires, Argentina. As service criteria for listhesis grade 1 and 2 we use the “smile” technique due to the great postoperative reduction achieved; this consists of fixing the lysis with total or partial reduction of the listhesis with transpedicular screws and a subspinous bar. For grade 3, we performed a two level arthrodesis with screws and bars because of the great risk of injury with a great reduction and the complexity of the previous technique in this grade. Surgical treatment was indicated in all cases for low back and/or sciatic pain. Postoperative follow-up is 10 months to 3 years. Materials and methods: 31 patients were evaluated. 18 men and 13 women. All studied by Rx and CT and treated by the same surgeon. All lysis and listhesis were at L4-L5 (11 cases) and L5-S1 (20 cases) level, only patients with grades 1, 2 and 3 were included. Higher grades and patients older than 45 years old were excluded from this study. Surgical technique: Smile technique (grade 1-2): Remove the periostium of the lamina; locate of the lysis, clean it until leaving two facing bone surfaces. Placement of two transpedicular screws in the lytic vertebra and a “U” bar under its spinous process. Reduction of the listhesis using an approximator which grasps the bar under the spinous and above the tulip transpedicular screw, upon placing in the lysis a bone graft taken from the spiny overlying vertebra. Arthrodesis (grade 3): Posterior fixation of two levels with 4 screws and 2 bars. Arthrodesis was made by performing a decortication of the lamina, imbrication of the spinous and using blood from the posterior superior iliac crest pulled out through an abbocath and chipped local bone. Results: The results were uniformly good with total or partial remission of the symptoms, consolidation of the lysis and total or partial reduction of listhesis in grades 1 and 2 with recovery of the ability of flexion extension of the lumbar spine in all grades. Only in one case we had a postoperative complication with the smile technique (listhesis grade 2) with partial deficit of the peroneal muscles which was fully recovered after 3 months; we attribute this to a root compression during the reduction of the listhesis with this technique. The rest of the patients did not present postoperative complications. Conclusions: We consider that the correct choice of surgical technique is imperative to obtain good results and to avoid possible injuries and secuelas. We have used this selection of surgical techniques for years with great results; the patients do not present postoperative complications with a good remission of their symptoms.

Basic Science

90

P011: Pin fracture in magnetically controlled growing rods: influence of the year of manufacture

Martina Tognini ¹ , Harry Hothi ¹ , Elisabetta Dal Gal ¹ , Johann Henckel ¹ , Masood Shafafy ² , Stewart Tucker ³ , Edel Broomfield ³ , John Skinner ¹ , and Alister Hart ¹

¹ University College London, The Royal National Orthopaedic Hospital and Institute of Orthopaedics and Musculoskeletal Science, Stanmore, United Kingdom

² Department of Trauma and Orthopaedics, Nottingham University Hospitals NHS Trust, Nottingham, United Kingdom

³ Great Ormond Street Hospital for Children NHS Foundation Trust, London, United Kingdom

Introduction: In 2019 the manufacturer released a field safety notice, indicating that rods manufactured prior to 26^th March 2015 had a 5% risk of post-implantation pin fracture occurring. Rods made after this date have locking pins that are thicker in diameter and of a tougher stainless-steel alloy; the FSN indicated that these rods did not exhibit the same fracture issue based on post-market surveillance data available at the time. A previous retrieval study reported evidence of locking pin fractures in 62 out of 105 (59%) and 6 out of 29 (21%) of rods collected at their centre that had been manufactured before and after this date, respectively. The aim of this retrieval study was to better understand the impact of the design changes on the performance of MCGRs collected at our retrieval centre. To achieve this, we compared the prevalence of locking pin fractures between MAGEC rods manufactured before and after 26^th March of 2015. Material and Methods: This was a retrieval study investigating 86 MCGRs that were consecutively received at our centre after having been removed from fifty-two patients. The implants were explanted by 11 different surgeons across 8 different hospitals. The implants were divided into two groups: those manufactured before 26^th March 2015 (n = 54) and those that were manufactured on or after this date (n = 32). Clinical and implant data was collected for all MCGRs. Retrieval analysis comprised plain radiographs evaluations, force and elongation testing, disassembly and scanning electron microscopy (SEM) of 5 pin surfaces. Results: The two patient groups were statistically comparable. We found that 15 out of 31 patients belonging implanted with rods manufactured before 26^th March 2015 had a fracture of their locking pins. 3 of the 18 (7%) patients with rods manufactured after this date were also found to have a fractured pin. Rods with a pin fracture had been implanted for a significantly longer period of time than those with an intact pin (39 months versus 30.5 months). Analysis of the fracture sites of the pins showed that all examined had failed due to brittle fractures. Conclusion: We found that 21 out of 54 retrieved rods at our centre that had been manufactured before 26^th March 2015 had a fracture of their locking pins. 3 of the 32 rods manufactured after this date were also found to have a fractured pin. Rods with a fractured pin had been implanted for significantly more time than those with an intact pin (median 39 versus 32 months). Whilst the mechanisms and risk factors for failure are multifactorial, our retrieval evidence and clinical experience to date suggests that the use of thicker, tougher locking pins in newer designs have had a beneficial impact on their performance.

107

P012: Blood titanium levels in patients with large and sliding titanium implants

Martina Tognini ¹ , Harry Hithi ¹ , Stewart Tucker ² , Edel Broomfield ² , Masood Shafafy ³ , Panos Gikas ¹ , Anna Di Laura ¹ , Johann Henckel ¹ , and Alister Hart ¹

¹ University College London, The Royal National Orthopaedic Hospital and Institute of Orthopaedics and Musculoskeletal Science, Stanmore, United Kingdom

² Great Ormond Street Hospital for Children NHS Foundation Trust, London, United Kingdom

³ Department of Trauma and Orthopaedics, Nottingham University Hospitals NHS Trust, Nottingham, United Kingdom

Introduction: Titanium, which is known to be a highly biologically inert, is one of the most commonly used metals in orthopaedic implants. While cobalt and chromium blood metal ion testing is routinely used in the clinical monitoring of patients with metal-on-metal hip implants, much less is known about the levels of titanium in patients with other implant types. A better understanding is required about the levels of titanium in these patients, and the potential for using blood titanium tests as a biomarker for function, in particular those that are susceptible to generating greater titanium particles or ions. In the current study, we investigated these levels in three such titanium-based implant groups: (1) MCGRs, (2) massive acetabular implants, and (3) long bone tumour implants. The aim of this study was to better understand the normal ranges of blood titanium levels in patients implanted with large and sliding titanium constructs by comparison with reference levels from conventional titanium hips. Material and Methods: This study examined data collected from 136 patients. Over a period of 24 months, whole blood samples were collected from 41 patients implanted with large titanium implants: Magnetically Controlled Growing Rods (MCGRs, n = 18), long bone tumour implants (n=13) and 3D-printed customised massive acetabular defect implants (n = 10). Blood samples were collected during routine outpatient visit (tumour and massive acetabular implants) or before surgery (MCGRs). Whole blood samples were quantified for titanium content on an Element 2 high resolution ICP-MS instrument. This data was compared with previously established reference levels in well-functioning, conventional titanium hip implants (n=95). Clinical, imaging and blood titanium levels data were collected for all patients and compared statistically between the different groups. Results: The median (range) follow-up time of the standard hips, MCGRs, tumour implants and massive acetabular implants were 102 months (64-143), 30 months (12-57), 60 months (28-221) and 36.5 (14-200) respectively. The median (range) of blood titanium levels of the standard hip, MCGRs, tumour implants and massive acetabular implants were 1.2 ppb (0.6-4.9), 9.7 ppb (4.0-25.4), 2.6 ppb (0.4-104.4) and 5.7 ppb (1.6-31.5) respectively. Age at first implantation was significantly different between each of the large/sliding implants groups and the titanium hips reference group. Follow-up time differed significantly between the MCGRs vs. both the standard hips and the long bone tumour implants, also between the massive acetabular implants vs. the standard hips group. Both MCGRs and the massive acetabular implants groups blood titanium levels were significantly higher than the standard hip implants group (p < 0.001). No correlation between follow-up time and blood titanium levels was found. Conclusion: This study showed that larger constructs and/or the presence of sliding mechanisms leads to increased blood titanium levels, compared to well-functioning standard titanium unilateral hip constructs. Reassuringly, these increased levels did not appear to induce adverse metal reactions. The relationship between implant failure and titanium release remains unclear and threshold levels for the different construct types should be determined, in order to understand the role of blood titanium testing as a biomarker for function.

108

P013: Rod fracture in magnetically controlled growing rods

Martina Tognini ¹ , Harry Hithi ¹ , Sean Bergiers ¹ , Johann Henckel ¹ , Edel Broomfield ² , Stewart Tucker ² , and Alister Hart ¹

¹ University College London, The Royal National Orthopaedic Hospital and Institute of Orthopaedics and Musculoskeletal Science, Stanmore, United Kingdom

² Great Ormond Street Hospital for Children NHS Foundation Trust, London, United Kingdom

Introduction: Magnetically Controlled Growing Rods (MCGRs) have been shown to experience implant failure in several ways, including an inability to distract due to corrosion or internal pin fracture issues. A fracture of the MCGR itself is estimated occur in 10.6% of the total number of complications however the risk factors for this are poorly understood. The mechanisms of fracture in Magnetically Controlled Growing Rods (MCGRs) and the risk factors associated with this are poorly understood. The aim of this study was to identify the mechanisms of fracture of explanted fracture MCGRs and assess the risk factors for this by 1) assessing the implant’s state at retrieval (by means of retrieval analysis) 2) analysing the fracture surface (fractographic analysis) and 3) using imaging analysis to evaluate eventual patient or surgical risk factors for rod fracture, through comparison with a control group of intact rods. Material and Methods: From our cohort of over 120 retrieved MCGRs, we identified seven rods that had fractured; all were single rod constructs, retrieved from six patients. These were examined and compared with fifteen intact single rod constructs. Clinical data (age at implantation surgery, gender, time to removal, aetiology, and eventual prior surgeries) and implant data (rod configuration, rod size, rod generation) were recorded for all implants. Retrieval and fractographic analysis were used to determine the failure mode at the fracture site and the implants functionality. Cobb angle, degree of rod contouring and the distance between anchoring points were computed on antero- posterior (AP) and lateral radiographs. Results: Age at insertion surgery was higher in the fractured rod group (5 vs 9 years old in the control and fractured groups, respectively) without reaching statistical significance (p = 0.0954). Time to removal was significantly lower in the fractured rods group (p = 0.0143). Five of the fractured rods had been inserted following removal of a previously inserted rod (Figure 4), while in the control group 3 constructs were revisions. 5/7 vs 3/15 rods had been inserted following removal of a previously inserted rod, in the fractured vs control groups. All fractured rods failed due to bending fatigue. Fractured rods had greater rod contouring angles in the frontal plane (p = 0.0407) and lateral plane (p = 0.0306), and greater distances between anchoring points in both AP and lateral planes (p = 0.0061 and p = 0.0074 respectively). Conclusion: This is the first study to investigate the mechanisms of failure of explanted, fractured MCGRs and to assess eventual risk factors. We found fatigue failure as the failure mode for all fractured implants, with the crack initiation point in correspondence with mechanical indentation marks on the rod, probably induced during implantation surgery. We also found that fractured constructs, usually revisions of previous implants, had a significantly greater distance between anchoring points and more pronounced contouring compared to the control group. These results suggest the use of double rod constructs when proceeding with rod exchange if the patient’s characteristics allow it.

110

P014: The performance of the latest generation of magnetically controlled growing spine rods: a comparative retrieval study

Martina Tognini ¹ , Harry Hothi ¹ , Sean Bergiers ¹ , Masood Shafafy ² , Edel Broomfield ³ , Stewart Tucker ³ , Johann Henckel ¹ , and Alister Hart ¹

¹ University College London, The Royal National Orthopaedic Hospital and Institute of Orthopaedics and Musculoskeletal Science, Stanmore, United Kingdom

² Department of Trauma and Orthopaedics, Nottingham University Hospitals NHS Trust, Nottingham, United Kingdom

³ Great Ormond Street Hospital for Children NHS Foundation Trust, London, United Kingdom

Introduction: Magnetically Controlled Growing Rods (MCGRs) are distraction-based systems that use an external magnetic distraction system aimed at avoiding repeated surgery for rod lengthening used for the treatment of severe early-onset scoliosis. Recently, concerns regarding the risks associated with the use of MCGRs have been raised. The latest design iteration (MAGEC X) was recalled in 2020 following an Urgent Field Safety Notice (FSN) describing a .5% probability of post-implantation separation of an actuator end cap component. On 1st April 2020, a second FSN was issued by the manufacturer, voluntarily suspending the supply of all MAGEC rods to the UK. The Medicines & Healthcare products Regulatory Agency (MHRA, UK) on the same day released an Medical Device Alert (MDA) advising surgeons not to implant MAGEC rods until further notice in the UK and Republic of Ireland. Currently, the supply of all MCGRs was temporarily suspended in the UK. Objective of this study is to compare the performance of MAGEC X to the earlier design iteration MAGEC 1.3, by means of retrieval analysis. Material and Methods: Fifteen of both latest and earlier rods were consecutively collected from five different hospitals following removal surgery and matched by time to removal. Clinical data (age at implantation surgery, gender, time to removal, reason for revision) and implant data (rod generation, length size, diameter size, configuration) were recorded for all MCGRs. Analysis comprised visual assessments of external damage, plain radiograph evaluations, force and elongation testing, MAGEC X end-cap torque testing and disassembly. Mann-Whitney U tests were used to statistically compare groups. Results: Rod distraction reached in vivo was significantly higher in the MAGEC 1.3 group (p = 0.002). There was no statistically significant difference in the total external damage score (p = 0.870), maximum force produced (p = 0.695) or distraction reached during force test (p = 0.880). No pin fracture was detected. Elongation of stroke was mildly higher (p = 0.051) for the MAGEC X group. One MAGEC X implant had evident end cap component loosening, yet it did not show any evident sign of internal wear or corrosion. Internal damage scores were mildly lower in the MAGEC X group. Conclusion: This is one of the first studies to present comparative retrieval findings of the latest generation of MCGRs (MAGEC X). We found no evidence of pin fracture in MAGEC X rods nor in the control group, MAGEC 1.3. There was comparatively less evidence of internal damage in the MAGEC X designs, de- spite a variability in the measured loosening torque of the end- cap component. One MAGEC X was revised due to evident end-cap component loosening, however the implant was found to be functional at mechanical testing and there was no greater sign of internal damage at disassembly.

309

P015: A novel "Yadav-Kunal" reflex for UMN lesion spasticity

Sandeep Yadav ¹ and Kishor Kunal ¹

¹ Orthopaedics, AIIMS, Jodhpur, India

Introduction: Various reflexes have been described as modification to Babinski sign in UMN lesion, though rarely has been a reflex described other than these, which is independent to extensor plantar response in some sort. Mostly these reflexes form a polysynaptic arc with a nociceptive stimulus as afferent. Here we present a novel reflex which is different from above in many ways- it’s response in independent of extensor plantar response and thus cannot be classified as a modification of Babinski’s sign and its afferent is forced motor afferent in a spastic muscle. Material and Methods: The reflex was demonstrated incidentally in patients suffering from UMN lesion spasticity and followed up until loss of spasticity after surgery and was validated in patients admitted in the centre with spastic and flaccid paraplegia. Results: It was found that this reflex was present in patients having spastic paraparesis and resolved once spasticity resolved. Also, it was absent in patients suffering from flaccid paraplegia Yadav-Kunal reflex. The reflex can be stated as, “a forced plantarflexion of toes in spastic parparesis shall lead to sudden jerky knee flexion in the same limb”. Conclusion: Spasticity is a stretch reflex disorder, manifested clinically as an increase in muscle tone that becomes more apparent with more rapid stretching movement, commonly caused by upper motor neuron lesion. The muscle spindle of toe dorsiflexors (predominantly by L5) gets activated when they are forcefully stretched. In this case, due to UMN lesion above L5, these inhibitions have been dropped off and the response is flexion of knee joint due to action of hamstrings (supplied by L5-S2 predominantly).

402

P016: Characteristics of baseline frequency data in spinal RCTs do not suggest widespread fraud

Manon Levayer ¹ , Gem Chew ² , Kyle Sheldrick ² , and Ashish Diwan ^3,4

¹ School of Biomedical Engineering, The University of Sydney, Darlington, Australia

² Faculty of Medicine

³ Spine Labs, University of New South Wales, Kensington, Australia

⁴ Spine Service, St George Private Hospital, Koagarah, Australia

Introduction: Fraud in clinical research is a reality. A recent scandal identified apparent non-genuine data in a set of randomised clinical trials investigating cognitive therapy in back pain. This has highlighted the risk of fraud impacting the assessment of treatment effects. In this case, fraudulent data appears to have exaggerated treatment efficacy in recent meta-analyses. Clinical treatment of spinal conditions is guided by such influential RCT evidence, so it is urgent to understand whether the conclusions of other RCTs published in spine journals are genuine or infected with fraud. We sought to investigate whether evidence of non-random baseline data in purportedly randomized studies in spine was a widespread problem or if the previously identified case was an anomaly. Material and Methods: We performed a PubMed search to identify all papers published in 4 major spine journals (Spine, The Spine Journal, the Journal of Neurosurgery Spine, and the European Spine Journal) classified by the journal as RCTs between 2016 and 2020. We extracted all baseline covariates which were reported as frequencies and calculated p values using a Pearson Chi Square test of independence. Individual variable p-values were combined into a study wise p-value using the Stouffer method. We calculated the proportion of studies with a study wise p-value of < 0.01, < 0.05, > 0.95 and > 0.99. All studies with p values > 0.99 or < 0.01 were examined for possible explanations. Results: Our literature search returned 228 studies, of which 169 were included. In total, we extracted 938 variables. After calculating all study wise p-values and calculating the proportions that presented a study wise p-value of < 0.01, < 0.05, > 0.95 or > 0.99. The distribution of variable wise p-values follows the expected distribution for genuine trial data without any signs of fraud. We observed the expected number of trials with p-values < 0.01, < 0.05 and > 0.95. There were three more trials with a p-value of > 0.99 than expected, however, these had either obvious innocent explanations or had already been identified as fraudulent. Conclusion: We conclude that the overall distribution of frequency baseline similarities between study arms in RCTs published in major spine journals is not suspicious. No evidence of systemic presentation of false data was found. While research fraud is a threat requiring vigilance, we did not find any evidence that it is common in spinal RCTs. However, these results were derived from major spine journals and may not be applicable to research published in non-spine journals or predatory journals. We will examine continuous variables in future work.

414

P017: Functional recovery in relation to the posttraumatic restitution of the blood-spinal-cord-barrier after experimental spinal cord injury in the mouse

Lea Meyer ¹ , Lilly Waldmann ¹ , Laurens Roolfs ¹ , Nima Taheri ¹ , Katharina Kersting ¹ , Melina Nieminen-Kelhä ¹ , Irina Kremenetskaia ¹ , Adnan Ghori ¹ , Andre Rex ² , Michael Fehlings ³ , Peter Vajkoczy ¹ , and Vanessa Hubertus ¹

¹ Neurosurgery

² Experimental Neurology, Charité Universitätsmedizin Berlin and Berlin Institute of Health, Berlin, Germany

³ Division of Spine Surgery, Toronto Western Hospital, University Health Network, Toronto, Canada

Introduction: Spinal Cord Injury (SCI) is a devastating condition that presents a major socioeconomic burden for healthcare systems. The posttraumatic disruption of the Blood-Spinal-Cord-Barrier (BSCB) is a leading pathophysiology in SCI and its restitution plays a crucial role in structural spinal cord regeneration. A deeper understanding of the pathophysiology and its timeframe will enhance the search for restorative therapies facilitating functional regeneration. With this study we characterize the posttraumatic BSCB disruption and restitution in relation to functional recovery in a mouse model up to 28 days post SCI. Material and Methods: Adult C57BL/6J mice (m/f, n = 55) underwent mid-thoracic (Th6/7) clip-compression SCI using a modified aneurysm clip (5g, 60s) or sham injury (two-level-laminectomy). Perioperative antibiotic therapy with amoxicillin and postoperative pain medication with buprenorphine was applied. Longitudinal neurobehavioral analysis was performed (n = 23) using Catwalk® automated gait analysis and Basso Mouse Scale with Tally sub-score at days 1, 3, 7, 14 and 28 post SCI. Additionally, in vivo imaging with 7T MRI was performed for tissue morphology analysis. Individual specimens were sacrificed at each time point for qualitative histological analysis (Luxol-Fast-Blue + H&E, CD31+Evans-Blue, n = 5). BSCB disruption was quantified by measuring Evans-Blue (EVB)–extravasation via fluorescence microplate reader (Tecan, n = 50). Results: As the posttraumatic disruption of the BSCB is most severe up to day 7 post SCI, histological analysis up to this point showed vast structural damage and edema to the spinal cord with considerable EVB-leakage, supported by MRI findings, with an increasing restitution in the chronic phase (14d, 28d). Quantitative assessment of EVB-extravasation displayed a significant disruption of the BSCB up to 14 days post SCI (14d: p = 0.001), with restitution after 28 days (p = 0.096). Neurological recovery started between days 7 and 14 post SCI, with most specimens having regained hindlimb function by day 28 (p = 0.552). Conclusion: Functional recovery following SCI is associated with the restitution of the BSCB, which remains significantly disrupted up to 14d post SCI, revealing a potential time frame for therapy application. Further detailed examinations of the regenerative capacities and the molecular players involved in BSCB regeneration are necessary for the development of restorative therapies targeting the neurovascular unit.

417

P018: Posttraumatic disruption of the blood-spinal-cord-barrier is aggravated in the acute and subacute phase by the endothelial cell-specific knock-out of Ephrin-B2 signaling after experimental spinal cord injury

Katharina Kersting ¹ , Laurens Roolfs ¹ , Lilly Waldmann ¹ , Lea Meyer ¹ , Melina Nieminen-Kelhä ¹ , Irina Kremenetskaia ¹ , Adnan Ghori ¹ , Andre Rex ¹ , Frank Heppner ² , Michael Fehlings ³ , Peter Vajkoczy ¹ , and Vanessa Hubertus ¹

¹ Neurosurgery

² Neuropathology, Charité Universitätsmedizin Berlin and Berlin Institute of Health, Berlin, Germany

³ Division of Spine Surgery, Toronto Western Hospital, University Health Network, Toronto, Canada

Introduction: The disruption of the Blood-Spinal-Cord-Barrier (BSCB) is a leading pathophysiology in traumatic Spinal Cord Injury (SCI), and its restitution plays a crucial role in spinal cord regeneration. The guidance molecule Ephrin-B2 promotes cell-cell-contacts in the neurovascular unit. However, its specific role in endothelial cells following SCI is unknown. With this study, we characterize the posttraumatic BSCB disruption and restitution dependent on the endothelial cell-specific knock-out (KO) of Ephrin-B2 in a mouse model up to 7d post SCI. Material and Methods: Adult CDH5-CreERT2-Efnb2^lox/lox (KO) and littermate wildtype (WT) mice (m/f, n = 66) underwent mid-thoracic (Th6/7) clip-compression SCI via modified aneurysm clip (5g, 60s) or sham-injury (two-level laminectomy). Endothelial cell-specific Ephrin-B2 KO was induced via the promotor CDH5 in a cre-lox-system with consecutive injections of tamoxifen (5d period). Neurobehavioral analysis was performed (n = 16) using Catwalk^® gait analysis and Basso Mouse Scale at 1, 3, and 7d post SCI. Additionally, in vivo 7Tesla-MRI was performed, and individual specimens were sacrificed for qualitative histological analysis at each time point (LFB+H&E; CD31+Evans-Blue, n = 31). BSCB disruption was quantified using Evans-Blue fluorescence assay (Tecan, n = 35). Results: Quantitative assessment of EVB-extravasation displayed a significant BSCB disruption in KO SCI animals compared to WT SCI animals at 1d and 3d but not at 7d post SCI (1d:p = 0.0107, 3d:p = 0.0002, 7d:p = 0.1785). Neurobehavioral analyses showed no differences between KO SCI and WT SCI animals, with no significant regaining of hindlimb function in the course up to 7d post SCI in both groups (1-7d:p > 0.05). Conclusion: Ephrin-B2 signaling plays a significant role in BSCB maintenance and repair, as the posttraumatic BSCB disruption is aggravated by the endothelial cell-specific KO of Ephrin-B2, leading to aggravated secondary injury. Whilst no significant recovery of hindlimb function is achieved post SCI up to 7d, analyses of longer recovery periods are necessary to evaluate the impact on functional recovery.

418

P019: An implanted spinal window chamber allows for chronic longitudinal in vivo microscopy following experimental spinal cord injury in the mouse

Laurens Roolfs ¹ , Katharina Kersting ¹ , Lilly Waldmann ¹ , Lea Meyer ¹ , Nima Taheri ¹ , Melina Nieminen-Kelhä ¹ , Irina Kremenetskaia ¹ , Jan-Erik Ode ² , Andre Rex ³ , Christian Uhl ¹ , Asylkhan Rakhymzan ⁴ , Anja Hauser ⁴ , Raluca Niesner ⁴ , Michael Fehlings ⁵ , Peter Vajkoczy ¹ , and Vanessa Hubertus ¹

¹ Neurosurgery

² Scientific Workshops

³ Experimental Neurology, Charité Universitätsmedizin Berlin and Berlin Institute of Health, Berlin, Germany

⁴ DRFZ (German Rheumatism Research Center), Berlin, Germany

⁵ Division of Spine Surgery, Toronto Western Hospital, University Health Network, Toronto, Canada

Introduction: Longitudinal in vivo microscopy allows for a direct real-time insight into pathophysiological processes in the living organism. After experimental Spinal Cord Injury (SCI) it can contribute to a deeper understanding of pathophysiological processes and potential therapeutic approaches. The implantation of a spinal window chamber enables longitudinal in vivo imaging of the spinal cord without the necessity for repeated surgery. With this study, we show the modification of an established spinal window chamber for chronic longitudinal in vivo imaging after experimental SCI in the mouse. Material and Methods: Adult C57BL/6J mice (m/f, n=8) underwent low-thoracic (Th11/12) clip-compression SCI using a modified aneurysm clip (5g, 60s) or sham-injury (two-level-laminectomy), followed by the implantation of a spinal window chamber for later in vivo microscopy. Perioperative antibiotic therapy with amoxicillin and postoperative pain medication with buprenorphine was applied. In vivo white light and fluorescence microscopy to image blood flow (FITC) and inflammation (Rhodamine-dextran) was performed at postoperative days 1, 3, 7, 14 and 28. Additionally, neurobehavioral assessment (Catwalk^® automated gait analysis and Basso Mouse Scale) was performed at the given time points. Neurobehavioral analysis was compared to specimens (C57BL/6J mice, m/f, n = 12) with SCI or sham-injury without spinal window chamber implantation. Histological analysis for tissue integrity assessment (Luxol-Fast-Blue + H&E) was performed after 7 and 28 days follow-up. Results: Chronic longitudinal in vivo white light and fluorescence microscopy was possible up to 28 days postoperatively after both SCI and sham injury. Only mild inflammation was observed in individual specimens at early timepoints (up to 7d). Specimens with an implanted spinal window chamber did not show any differences in automated gait analysis (Catwalk^®), Basso Mouse Scale, postoperative body weight development or histologically assessed spinal cord integrity compared with specimens which received the same surgery without spinal window chamber implantation. Conclusion: The implantation of a spinal window chamber after clip compression SCI in the mouse is feasible and allows for longitudinal in vivo imaging up to the chronic injury phase without modifying neurological function or spinal cord integrity compared to specimens without chamber implantation. To achieve more detailed in vivo imaging at a greater depth, longitudinal two-photon microscopy can be integrated in the setup.

655

P020: Nanomechanical properties of native human ligamentum flavum

Jakub Jezek ¹ , Jiri Skala-Rosenbaum ¹ , Josef Sepitka ² , and Vaclav Tolar ¹

¹ Department of Orthopedics and Traumatology, Third Medical Faculty of Charles University and University Hospital Kralovske Vinohrady, Prague, Czech Republic

² Division of Biomechanics, Faculty of Mechanical Engineering, Czech Technical University in Prague, Czech Republic

Introduction: Degenerative changes of ligamentum flavum (LF) significantly contribute to the development of lumbar spinal stenosis (LSS), which is a serious and relatively common disease in the aging population. LSS often leads to disability. There is no prophylaxis of this disease in current knowledge yet. Although it is natural to consider that the mechanical properties of ligamentum flavum can be altered due to ligamentous hypertrophy, only few studies have mentioned on this point. Only one study shows significantly inferior stiffness of LF in cases with LSS. However, to date, there are no reports describing local nanomechanical properties of ligamentum flavum depending on anatomical localization. The aim of this study was (1) to quantify and compare nanomechanical properties of the insertion part with central part of LF and (2) to compare nanomechanical properties of each ligamentum flavum regardless of spinal segment levels (L3-4, L4-5 and L5-S1). Design of study: measurement of micromechanical properties of degenerated and healthy human ligamentum flavum. Materials and Methods: The study involved patients who underwent surgery for lumbar spinal stenosis. The tissues used for analysis of nanomechanical properties from 12 patients were sectioned into 1-2 mm thick sections using microtome blade and glued using Epiglu on the Petri dishes. All testing was performed submerged in 1x Phosphate buffered saline (PBS) containing 1% (v/v) Protease Inhibitors. Quasistatic nanoindentation of samples was performed to obtain loading curves from the cuts on the cranial, medial, and caudal part of each ligamentum flavum. Results: Average elastic moduli were in the range from 3 kPa up to 178 kPa. We described the local nanomechanical properties of ligamentum flavum depending on anatomical localization. We found the gradients of the mechanical properties across the cranial, medial, and caudal cuts of native ligamentum flavum. Conclusion: This study showed that: (1) medial part of ligamentum is significantly stiffer than cranial and caudal, (2) central region of cranial, medial, and caudal cut is significantly stiffer than outer region.

Acknowledgment: This work has been supported by the Czech Health Research Council [Project number NU21-06-00356].

686

P021: Comparison of bone density between traditional pedicle screw, cortical bone screw and modified cortical bone screw tract of lumbar spine

Dipak Shrestha ¹ , Bikash Parajuli ¹ , Sabik Kayastha ¹ , and Suman Lamichhane ¹

¹ Orthopedics, Dhulikhel Hospital, Kathmandu University Hospital, KUSMS, Dhulikhel, Nepal

Introduction: Cortical bone trajectory (CBT) has better pullout strength, insertional torque, and toggle test performance. However, divergent oblique caudo-cranial trajectory and shorter screws are limiting factors. The Dhulikhel Hospital modification in CBT (CBT-DH) has been proposed with straight caudo-cranial trajectory without divergence which allows longer screw placement with technical ease. The aim of this study is to compare bone density of CBT, CBT-DH, and traditional pedicle screw (TPS) tract of lumbar vertebrae by using CT Hounsfield Unit (HU) as surrogate marker of bone density. Material and Methods: Abdomen CT scan with non-spinal pathologies of 200 patients (1000 lumbar vertebrae) were selected (Male :112 and Female: 88). Axial slices of each lumbar vertebra (L1 to L5) were cut into three planes representing TPS (parallel to the pedicle in sagittal section), CBT (caudo-cranial plane parallel to inferior pedicle boarder targeting midpoint of superior endplate) and CBT-DH (caudo-cranial plane along the inferior pedicle boarder targeting anterio-superior margin of vertebral body) representing tract for the pedicle screw in each technique. For each trajectory, CT HU at four points, namely near cortex, mid pedicle, mid-body, and far cortex was measured. Inter and Intra observer variation was analyzed in 40 vertebrae separately. Results: The mean age of the patients was 40.4 ± 13 years. The difference of mean value of CT HU of TPT, CBT-DH and CBT were 354.2 ± 70, 457.3 ± 90, and 529.9 ± 75 respectively were statistically significant (p < 0.05). The difference was highly significant for near cortex. The CT HU value of the near cortex in CBT-DH was 65.6% higher compared to TPS but 14.9% lesser compared to CBT. The difference in density between CBT-DH (305 HU) and CBT (302 HU) in mid pedicle was not significantly different. The average specific value SV1 (mean value CT HU of CBT-DH/ mean CT HU of TPS) and SV2 (mean value CT HU of CBT/ mean CT HU of TPS) was 1.31 ± 0.25 and 1.53 ± 0.29 respectively with significant positive correlation with age (Pearson coefficient: 0.2, p < 0.01 for SV1 and age, Pearson coefficient: 0.3, p < 0.01 for SV2 and age). Conclusion: CBT-DH has significantly higher bone density compared to traditional pedicle screw (TPS) tract but lesser than CBT for lumbar vertebrae.

863

P022: Is facet tropism associated with recurrent herniated disc after full-endoscopic discectomy? A nested case control study

Kanthika Wasinpongwanich ^1,2 , Verapan Kuansongtham ¹ , Khin Myat Myat Lwin ¹ , and Krit Pongpirul ³

¹ Spine, Spine, Bangkok, Thailand

² Spine, Orthopedics, Nakhon Ratchasima, Thailand

³ Research, Bangkok, Thailand

Background: Lumbar herniated disc recurrence is not uncommon and might be related to the facet tropism. This study aims to explore if recurrent herniated disc patients have different facet angle or tropism. Methods: This case-control study was nested in the Bumrungrad Spine Cohort containing data of 545 patients underwent full endoscopic discectomy during 2011-2015. A patient was considered a case if he/she experience a recurrent herniated disc. An age and gender matched controls were randomly selected from the non-case group. Facet angle were measured on both group. Facet tropism is indicated by difference of facet angles more than 10 degree. Results: Of 545, 60 cases with recurrent herniated disc and another 60 age-and-gender matched controls were reviewed. The overall mean age of the patients was 47.38 years and 30.83% were female. Mean facet angle was 14.59 with no significant difference between case and control (14.93 vs 14.25 mm; p = 0.5021). Both group had similar facet tropism (p = 0.543). Conclusion: Facet angle and facet tropism were not associated with the herniated disc recurrence in patient who underwent full-endoscopic discectomy.

920

P023: A large animal in vitro model to study nerve ingrowth in the intervertebral disc

Junxuan Ma ¹ , Janick Eglauf ^1,2 , Riccardo Tognato ¹ , Sibylle Grad ^1,2 , Mauro Alini ¹ , and Tiziano Serra ¹

¹ AO Research Institute Davos, Davos, Switzerland

² ETH Zürich, Zürich, Switzerland

Introduction: Low back pain (LBP) is one leading cause of disability worldwide. In many cases LBP is discogenic in origin. The painful intervertebral disc (IVD) is associated with a deep ingrowth of axons, or nerve fibers, which express neuropeptides such as substance P and calcitonin gene-related peptide (CGRP). For basic investigation of this pathology, clinically relevant models are needed. Commonly used LBP models are based on rodents which cannot always predict human condition. In addition, the experimental manipulation and optical observation in vivo are challenging. Animal models investigating pain conditions also raise ethical concerns. To address these problems, an in vitro IVD-nerve co-culture model was created using large animal tissues. We furthermore hypothesized that IVD inflammation would trigger axon growth. Material and Methods: Bovine dorsal root ganglion (DRG) and caudal IVD tissues were obtained from a local abattoir. Explants of the outer annulus fibrosus (AF) (1.5x1.5x1.5 mm³) were treated with IL-1β and TNF-α (each 10 ng/mL) for 24h to induce an inflammatory condition. AF explants without cytokine treatment served as control. After a wash-out, each AF tissue was placed in the center of a tissue culture frame. DRG were enzymatically disintegrated into micro-tissue units and then re-assembled at predetermined distances to the AF explant using "Sound Induced Morphogenesis" (SIM). SIM also formed a dense cell-packing multicellular system to recapitulate the native DRG tissue architecture. The viability and the morphology of the multicellular system were evaluated by live-dead staining and immunofluorescence, respectively. The multicellular system was functionally evaluated using calcium imaging (Fluo4). In the AF-DRG co-culture system, axons were labelled by CGRP and neurofilament immunofluorescence. The axons in the immunofluorescent images were segmented and statistically evaluated. Results: The SIM assembling did not influence DRG cell viability (92.8%). Neurons in the DRG multicellular system could be potassium depolarized, confirming their functionality. The multicellular system supported spontaneous calcium signal transmitting from one cell to its close counterparts at day 4. Satellite cells self-organized to an oriented structure at day 8. The cytokine-treated AF tissue increased the axon length of CGRP(+) neurons by 52% compared to non-cytokine control at day 2. The axons had a turning angle pointing towards AF in 86.7% and 50.0% of CGRP(+) neurons in cytokine-treated AF and non-cytokine control, respectively. There was no obvious turning angle for non-cytokine control (-0.4°), while the turning angle was averaged to be 4.3° towards the cytokine-treated AF. These axons were influenced only when neurons were positioned within 1.3 mm from AF explants (n = 27 neurons and 355 axons). Conclusion: Large animal AF and DRG can be cultured in a physiologically relevant multicellular system recapitulating native tissue architecture and supporting tissue-level functions. The AF-DRG communication depends on their distance which can be controlled by SIM. The axon of CGRP(+) neurons is elongated and attracted by the cytokine-treated AF tissue. This pioneering study demonstrates the AF's influence on guided axon sprouting can be reproduced in vitro. This model will be instrumental to test new treatments targeting nerve ingrowth mechanisms, replacing animal models in line with 3Rs principles.

927

P024: Prevalence of low back pain in nurses at Santa Marcelina Hospital

Luiz Claudio Rodrigues ¹ , Fernanda Andrea Navarro ² , Rodrigo Nakao ¹ , and Nathalia Adelina Pereira ¹

¹ Spine Surgery, Santa Marcelina College of Medicine, São Paulo, Brazil ²Spine Surgery, Hospital Santa Marcelina, São Paulo, Brazil

The present work is a study on the prevalence of low back pain in nurses at Santa Marcelina Hospital. The survey was applied in the form of a questionnaire containing social issues such as weight, age, height, work sector, workload, physical activity, presence and frequency of low back pain, in addition to the Oswestry questionnaire, which is a tool used to quantify the degree of disability of low back pain in daily activities. This research has the general objective of determining the prevalence of low back pain in nurses at Santa Marcelina Hospital and establishing a relationship with social aspects. According to the bibliographic study developed, it is possible to show the high prevalence of low back pain in nurses and how much work is affected due to the high rate of disability in activities caused by low back pain. The method used in the research was an epidemiological cross-sectional cohort. From the results of this work, it is concluded that there is a high prevalence of low back pain in nurses at Santa Marcelina Hospital. It was not possible to determine a direct risk factor for low back pain. Therefore, it is assumed that several factors such as sex, age, BMI, sedentary lifestyle, working time, work sector, posture and work activities addressed in the research such as psychological factors, musculoskeletal changes and socioeconomic conditions not addressed in the research can be in set predisposing to low back pain.

1108

P025: Matching sub-groups of neck pain patients and best fit specific functional PROMs

Julia Szita ¹ , Istvan Klemencsics ¹ , Balazs Szollosi ¹ , Zoltan Hoffer ¹ , and Aron Lazary ^1,2

¹ National Center for Spinal Disorders, Hungary

² Department of Spine Surgery, Semmelweis University, Hungary

Neck pain is one of the leading causes of days lived with disability by generating an immense burden of an individual’s quality of life. To objectively measure the impact of musculoskeletal diseases patient reported outcome measures (PROMs) have been developed which now are considered as gold standard tools in research and everyday practice in spinal care.

The primary aim of our study was the cross-cultural language adaptation into Hungarian language and the evaluation of the psychometric properties for the NDI, NPAD and COMI-neck. Secondly, we focused on forming a recommendation of appliance by investigating how well the PROMs perform in specific subgroups of neck pain related symptoms.

At the outpatient clinic of the National Center for Spinal Disorders, 110 neck pain (with or without irradiating pain to the upper extremity) patients were prospectively recruited. Internal consistency, construct validity, reliability and responsiveness were explored for each questionnaire. Subgroups were generated based on pain localization, radicular pain, type of therapy and neurological deficit.

The COMI- neck, NDI and NPAD showed excellent reliability (ICC > 0.7), construct validity and adequate responsiveness (AUC > 0.7) in relation of global treatment outcome at 6 months follow up. All investigated PROMs had a comparable factor structure as the original version and Cronbach α proved to be < 0.70 thus adequate internal consistency was found. Based on our results, the COMI neck proved to be superior compared to the NDI and NPAD in most of the subgroups. Considering the available evidence which shows that musculoskeletal neck pain should be considered as a multifactorial disease where several non-biomedical factors play an immense role thus in our opinion the multidimensional COMI-neck should be advocated in clinical research as it is a short questionnaire and covers a wide aspect of the disease.

1151

P026: Multimodal evaluation of physiological ovine cervical intervertebral disc from a tissue-engineering perspective

Nikolaos Gkantsinikoudis ^1,2 , Savvas Koltsakidis ³ , Panagiotis Prodromou ^1,2 , Eleni Aggelidou ^1,2 , Stylianos Kapetanakis ^1,2 , Eleftherios Tsiridis ⁴ , Ioannis Magras ⁵ , Dimitra Psalla ⁶ , Georgios Kazakos ⁷ , Dimitrios Tzetzis ³ , and Aristeidis Kritis ^1,2

¹ Department of Physiology and Pharmacology

² cGMP Regenerative Medicine Facility, Department of Physiology and Pharmacology

³ School of Science and Technology, International Hellenic University, Digital Manufacturing and Materials Characterization Laboratory, Thessaloniki, Greece

⁴ Papageorgiou General Hospital, Aristotle University Medical School, Nea Efkarpia, Academic Orthopaedic Department, Thessaloniki, Greece

⁵ Department of Neurosurgery, Hippokration General Hospital, School of Medicine

⁶ Laboratory of Pathology

⁷ Companion Animal Clinic, School of Veterinary Medicine, Faculty of Health Sciences, Aristotle University of Thessaloniki (A.U.Th.), Thessaloniki, Greece

Introduction: Degenerative Disc Disease (DDD) constitutes the major etiology of low back pain in current years, being unfavorably associated with disability and morbidity. Despite the ever-growing incidence of DDD, existent therapeutic selections exhibit remarkably limited efficacy, being practically not capable of reversing natural course of underlying disease. In this framework, Tissue-Engineering (TE), a novel and multidisciplinary field of Regenerative Medicine, has been demonstrated to render the de novo development of a Tissue-Engineered Intervertebral Disc (TE-IVD) construct feasible in recent years. Considering the relative adequacy of literature data regarding in vitro evaluation of TE-IVD constructs, the respective necessity for in vivo assessment in large homolog animal models remains imperative. Hence, we hereby present our results from multifaceted assessment of physiological ovine cervical intervertebral discs, an animal model that is increasingly utilized in cervical spine TE applications, from a TE perspective. Material and Methods: Ovine cervical intervertebral discs (n = 9) were dissected from fresh-frozen specimens of 5-months aged sheep of Greek origin (“Chiotikon” species). Harvested specimens were subjected to morphometric, mechanical and microscopic evaluation according to a standard protocol. Morphometric evaluation was conducted with dimensions measurement with digital caliber, whereas mechanical assessment via compressive and tensile testing in conjunction with investigation of critical failure point in controlled laboratory conditions. Microscopic evaluation was conducted with hematoxylin-eosin, Alcian Blue and Masson’s trichrome staining under optical microscope. Results: Maximal dimensions of harvested discs in antero-posterior and transverse diameter as well as mean of measured thickness were analytically recorded. Furthermore, results of mechanical evaluation regarding compressibility, tensility and failure point of specimens were evaluated to be in concordance with current literature. Microscopic assessment demonstrated anticipated spatial arrangement of proteoglycans, collagen and cellular population inside intervertebral disc physiological architecture. Conclusion: Morphological data of ovine cervical intervertebral disc are rendered for the first time in current literature analytically available. Furthermore, results of biomechanical behavior and microscopic architecture of cervical intervertebral disc of the predominant Greek ovine species provide valuable information for construction of TE-IVD constructs for in vivo application in future relative studies.

1514

P027: Comparison of two methods between saline injection model and external fixator model in rat tail disc degeneration

Jae-Hoon Kim ¹ , Jong-Beom Park ² , Abdul Khaleque ¹ , and Young-Yul Kim ¹

¹ Orthopedics, Daejeon St. Mary's Hospital, Deajeon, South Korea

² Orthopedics, Eijeonbu St. Mary's Hospital, South Korea

Purpose: The degeneration of the intervertebral disc of the spine causes many diseases. Apoptosis has been raised as the cause of this, and many animal models have been developed and used. However, comparisons of animal models associated with autophagy have become necessary. The purpose of this study is to find out which animal models are suitable for this study in the mechanical model and the structural model. Methods: Sixteen 9-week-old male Sprague–Dawley rat tails were treated with 0.9% saline and external fixator (two-cross Kirschner wires) for 6 weeks and 12 weeks as well. Treated discs were dissected for checking out the mechanical force can induce the involvement of autophagy and apoptosis mediated intervertebral disc degradation where we performed H&E staining, Masson’s trichrome staining, IHC staining for LC3, Beclin-1and P62 as well as for MMP-2, MMP-3 and TIMP-1, besides, we performed qPCR for beclin-1, LC3 and P62 and for MMP-2, MMP-3 and TIMP-1 respectively. Results: More insidious nucleus pulposus cell degeneration was observed in external fixator group than control group as well as injection saline group. The rate of degradation was inclined with inclining the duration of compression whereas injection groups cannot distinguish the margin between annulus fibrosus and central nucleus pulposus. Immuno positive cells for LC3, Beclin-1, P62 as well as MMP-2, MMP-3 and TIMP-1 was advanced and expressed sideways for both group than control. But external fixator group showed more laterally than saline injection group while saline injection group cannot distinguish the margin between nucleus pulposus and annulus. Highest autophagy related gene expression was observed in external fixator group than saline injection group even if the autophagy beginning gene expression was elevated in both external fixator group and saline injection group but it condensed after 12 weeks. In addition to, utmost autophagy accumulating materials was found in external fixator group than saline injection group and it was amplified along with increasing the duration of compression and maximum amount of apoptotic related gene expressed in saline injection group whereas external fixator group showed lowest expression. Conclusion: Intervertebral disc degradation after mounting the mechanical force which is actively associated with autophagy and apoptosis but there may not have autophagy and apoptosis mediated central nucleus pulposus cell degradation. However, further extensive investigation is to be needed for more clarification.

Keywords: Intervertebral disc degeneration; nucleus pulposus; autophagy; apoptosis; external fixator; saline injection.

1913

P028: The effect of mini-open thoracotomy on pulmonary function in Lenke type 1 adolescent idiopathic scoliosis patients treated with nonfusion anterior scoliosis correction (NFASC): is it detrimental

Umesh P. Kanade ¹ , Sharan Achar T ¹ , keyur Akbari ¹ , Vignesh Badikillaya ¹ , and DR Sajan Hegde ¹

¹ Orthopaedics, Apollo Hospitals, Chennai, India

Introduction: Existing literature is teeming with studies that have evaluated pulmonary function test (PF) after spinal fusion and have shown conflicting results. There is paucity of literature on the effect of non fusion anterior scoliosis correction (NFASC) surgery over PF in Lenke 1 Adolescent Idiopathic Scoliosis (AIS) patients. The current study aims to find the effect of mini-open thoracotomy approach for NFASC on PF in AIS patients. Material and Methods: 16 Lenke type 1 AIS patient with a minimum follow up of 2 years were evaluated. Absolute and percent-predicted values of forced expiratory volume in 1 second (FEV1), forced vital capacity (FVC), and total lung capacity (TLC) were evaluated preoperatively and at follow ups at 6 months, 1 year and 2 years. An improvement or detriment of more than 10% was considered significant. Paired t test was used for statistical analysis. Results: The cohort included 15 female and 1 male with a mean age of 13.5 at the time of surgery. Mean Sanders score was 7.1 ± 0.6 and mean Risser score was 4.2 ± 0.5. Mean pre op main thoracic (MT) cobbs was 52.1° ± 6.7° Baseline. Conclusion: Our study showed improving trend in PF up to 1 year post-surgery and thereafter PF remained stable at 2 years post-surgery. NFASC via mini-open thoracotomy does not have detrimental effect on PF in AIS patients at 2 years follow up.

287

P028.1: Epigenetic and genetic factors related to curve progression in adolescent idiopathic scoliosis: a systematic scoping review of the current literature

Marco Manzetti ¹ , Francesca Barile ¹ , Giovanni Viroli ¹ , matteo traversari ¹ , Marco Ialuna ¹ , fabio vita ¹ , azzurra paolucci ¹ , Simona Neri ² , Francesco Ursini ² , Alberto Ruffilli ¹ , and Cesare Faldini ¹

¹ Clinica Ortopedica e TraumatologicaI

² Medicine and Rheumatology Unit, IRCCS - Istituto Ortopedico Rizzoli, Bologna, Italy

Introduction: Adolescent idiopathic scoliosis (AIS) is a progressive three-dimensional deformity of the spine, with different grade of involvement of the frontal, sagittal and axial planes. Scoliotic curves progress until skeletal maturity, causing important aesthetic problems, such as humps, with psychological issues and loss of self-esteem, coronal and\or sagittal imbalance and muscle fatigue. In rare cases, the curve may progress to develop a severe deformity. While the Cobb angle is a straightforward tool in initial curve magnitude measurement, assessing the risk of curve progression at the time of diagnosis may be more challenging. Epidemiological and genetic studies indicated AIS as a polygenic disease and several studies investigated genetic and epigenetic factors associated with an increased risk of onset of the scoliotic curve. Less information is available regarding candidate genetic and epigenetic factors related to scoliotic curve progression and its prediction. Thus, epigenetic and genetic markers could represent potential prognostic tools to predict curve progression. The aim of this study is to review the available literature regarding the epigenetic and genetic factors associated with the risk of AIS curve progression. Material and Methods: Pubmed-MEDLINE, The Cochrane Central Registry of Controlled Trials, Google Scholar and Embase Biomedical Database were searched over the years 1990-2022 to identify eligible studies in the English literature describing the epigenetic and genetic factors associated to AIS curve progression. Inclusion criteria considered papers describing genetic and epigenetic factors associated with AIS curve progression published in English peer-reviewed journals. Isolated case reports\series with less than 5 patients, literature reviews and meta-analyses were excluded. The study selection was carried out in accordance with Preferential Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines and has been accepted for registration in PROSPERO database for systematic reviews. The search was carried out in January 2022. Results: Forty studies were included; 15 genes were reported as having SNPs with significant association with progressive AIS, but none showed sufficient power to sustain clinical application. Therefore, available data on genetic factors correlated to AIS evolution did not allow the prediction of disease progression only based on genetic information. In contrast, 9 studies reporting epigenetic modifications showed promising results in terms of reliable markers. Epigenetic marks principally included DNA methylation, histone post-translational modifications and regulation by non-coding RNAs, such as microRNA. Conclusion: In conclusion, prognostic testing for AIS has the potential to significantly modify disease management. This will be achieved only after the identification of reliable markers and an understanding of the underlying biologic pathways. Genetic studies identified a series of loci associated with disease progression, whose power appears, however, insufficient to guide clinical choices. More recent evidence suggests epigenetics as a more promising field for the identification of factors associated with AIS progression, offering a rationale for further investigation in this field. More data are needed, and studies on tissues involved in the pathology, rather than peripheral blood, are necessary.

Biomechanics

134

P029: Are augmented lumbar soft tissue properties indicative of physiological stress shielding as a potential biomarker for female low back pain patients? An in vivo study

Emily Newell ¹ , Jean Ouellet ² , and Mark Driscoll ¹

¹ Department of Mechanical Engineering

² Department of Paediatic Surgery & Surgery, McGill University Health Centre, Montreal, Canada

Introduction: Despite 85% of low back pain (LBP) cases being considered idiopathic, few biomarkers are available to diagnose LBP. Previous clinical studies have correlated LBP with changes to spine-stabilizing lumbar soft tissues, including atrophy in the multifidus (MF) and erector spinae (ES), and increased thoracolumbar fascia (TLF) thickness. Tissue morphology augmentation of the quadratus lumborum (QL) and psoas major (PM) within LBP patients has been inconsistent. Collectively, these tissue property modifications suggest a load allocation bias within the lumbar soft tissues with the potential for physiological stress shielding. Thus, this study seeks to analyze changes within tissue properties of LBP and healthy subjects to investigate the potential for physiological stress shielding as a contributor to LBP. Materials and Methods: MRI data of 100 female subjects was obtained from the Mayo Clinic following ethical approval. Exclusion criteria included subjects with spinal pathology, prior musculoskeletal surgical intervention, and pregnancy. Healthy control subjects had no known LBP at the time of the MRI scan. A total of 36 subjects (16 control, 20 LBP) were included in this study. Using T2-weighted axial images the total and functional cross-sectional areas (tCSA, fCSA) and fatty infiltration of the MF, ES, QL, and PM were measured from the midline of the L1/L2 to L5/S1 intervertebral discs (IVDs). The TLF tCSA was measured at the L3/L4 and L4/L5 IVD levels. ANCOVA was conducted to compare the tCSA, fCSA, and fatty infiltration of the soft tissues at each IVD level between control and LBP subjects. Results obtained were adjusted for age and BMI during statistical analysis. P-values < 0.05 were deemed statistically significant. Results: The tCSA and fCSA demonstrated no significant differences between control and LBP subjects regardless of IVD level. However, LBP subjects demonstrated significantly larger average fatty infiltration within the L1/L2 MF (p = 0.034), L2/L3 MF (p = 0.040) and ES (p = 0.016), and L4/L5 QL (p = 0.013). Increased fatty infiltration within the L3/L4 PM of LBP subjects approached significance (p = 0.080). Conclusion: Results suggest degenerative tissue property modification of the LBP MF, ES, and PM at the L3/L4 IVD level due to increased fatty infiltration coupled with minimal change in the tissues’ tCSA and fCSA. Additionally, the LBP TLF tCSA at L3/L4 increased by 7.86% (p = 0.183) and may be clinically significant. This increase in TLF tCSA may suggest tissue hypertrophy consequential of elevated loading, while increased muscle fatty infiltration may suggest muscle disuse. As such, LBP may result in physiological stress shielding wherein the TLF withstands the majority of stress due to physiological motion, preventing the ES, MF, and PM from receiving regular loading. In turn, the muscles may undergo elevated fatty infiltration and eventual muscle atrophy. These muscles may become unable to withstand normal stress, resulting in LBP subjects subconsciously recruiting other muscles to accommodate the desired motion, further distorting stress distributions and leading to degenerative stress shielding. Therefore, this study suggests that the progression of LBP may be due to stress shielding caused by mechanical property changes to the lumbar soft tissues.

299

P030: A biomechanical analysis of sex-specific differences between load distribution and intersegmental motion in the thoracolumbar spine: a finite element study

Brittany Stott ^1,2 and Mark Driscoll ^1,2

¹ McGill University, Montreal, Canada

² Montreal General Hospital, Montreal, Canada

Introduction: Musculoskeletal disorders and low back pain (LBP) are a leading cause of global disability, but despite this, many LBP cases are idiopathic. Further, female patients tend to experience a higher occurrence of LBP and musculoskeletal disorders compared to males. Finite element models (FEM) provide a means to objectively study the biomechanics of the spine. While there is a growing interest in the influence of biological sex on pain, current biomechanical modelling approaches seldom consider the differences between male and female spines. Hence, utilizing FEM to study important differences between biological sexes with respect to physiological motion and load distribution may better guide targeted treatments in clinical settings. Thus, this study aimed to compare the load distribution between male and female spines through FEM. Material and Methods: A male thoracolumbar spine model was developed, consisting of the vertebrae and adjacent intervertebral discs (IVDs) (T1-S1), tendons, thoracolumbar fascia, and surrounding muscles. From this model, the cross-sectional area of the geometry and the material properties of the tendons and IVDs were adapted to represent female anatomy, resulting in two FEMs (one male and one female). The lumbar portion of the models (L1-S1) were subjected to a 1175N follower load with 7.5Nm moment, as well as pure moments from -10 to 10Nm applied at L1. The full thoracolumbar spine models were subjected to pure moments from -7.5 to 7.5Nm applied at T1. The models underwent extensive validation against in silico, ex vivo, and in vivo comparators from previously published literature. Following validation, intersegmental rotation, IVD stress, and vertebral body stress were assessed. Results: Model validation was successfully completed through comparison of published literature for IVD stress and intersegmental rotation. Under the follower load scenario, the lumbar FEMs demonstrated negligible change in intersegmental rotation, however, the female model was subjected to a 23% increase in IVD stress. When subjected to pure moments inducing flexion and extension, the female lumbar and thoracolumbar spine models exhibited a larger range of motion relative to the male model. Under pure moments inducing flexion, the female lumbar model demonstrated an 18% and 51% increase IVD stress and vertebral body stress, respectively, meanwhile the female thoracolumbar spine model experienced a 36% and 55% increase in IVD and vertebral body stress, respectively, when compared to the male model. Conclusion: Sex-specific lumbar and thoracolumbar spine FEMs were successfully developed and validated, demonstrating substantial differences in load sharing and stress distribution between biological sexes. The female model was subjected to augmented stresses; these differences maybe be attributed to the reduced bone volume and cross-sectional area in females, as well as the changes in tissue material properties. The observed higher stresses may contribute to the greater occurrences of LBP and musculoskeletal disorders observed in female patients as the female body may be subjected to augmented loading on a daily basis. This study highlights the importance of utilizing biologically accurate models for each sex, as the resultant stress distribution, and consequently the patient outcomes and suggested treatment approaches, may differ significantly.

312

P031: Comparison of dynamic spinal cord stress for single and multi-level anterior cervical discectomy and fusion using a 3D patient-specific finite element spinal cord model

Aditya Vedantam ¹ , Yuvaraj Purushothaman ¹ , Balaji Harinathan ¹ , Matthew Budde ¹ , and Narayan Yoganandan ¹

¹ Medical College of Wisconsin, Milwaukee, United States

Introduction: Dynamic spinal cord stress is a known contributor to the pathophysiology of degenerative cervical myelopathy (DCM). Although the goal of surgery is to eliminate static spinal cord compression in DCM, its impact on dynamic spinal cord stress is unclear. The effect of surgery on dynamic spinal cord stress is expected to change with the number of surgical levels as well as patient-specific anatomy. The aim of this study was to use patient-specific 3D finite element model (FEM) of the cervical spinal cord to model single- and multi-level anterior cervical diskectomy and fusion (ACDF) to determine differences in post-surgical spinal cord stress patterns. Material and Methods: A 3D patient-specific FEM of the cervical spine and spinal cord was created using MRI-derived geometries from a single patient with mild DCM (modified Japanese Orthopedics score = 16). Using a MRI-derived patient-specific finite element model, we simulated one-, two- and three-level anterior cervical diskectomy and fusion surgery for DCM. The model uses material properties from human spinal cord tissue that have been reported previously. The single-level ACDF procedure was simulated by inserting a bone graft centrally at C5-C6 and a titanium plate with variable angle screws. A similar procedure was performed for 2-level ACDF at C5-C6 and C6-C7, and 3-level ACDF at C4-C5, C5-C6 and C6-C7. The model was constrained at the inferior surface of the T1 vertebra in all degrees-of-freedom, and the sagittal moment loads were applied at the superior vertebra. The pure moment load level was 2 Nm each in flexion and extension modes. An additional follower force of 75N to simulate the head mass and muscle force was applied. Von Mises stress of the spinal cord was calculated at each segment during flexion and extension, and compared to segmental range of motion and intradiscal pressures. Results: Decrease in spinal cord stress at the level of surgical decompression was equivalent in all simulations (-62% [1-level] vs 61.5% [2-level] vs 59% [3-level]). There was an increase in spinal cord stress rostral to the surgical level, and the change in spinal cord stress at the superior adjacent segment during neck flexion was greater in multi-level surgery compared to single-level surgery (160% [3-level] vs 56% [2-level] vs 20% [1-level]). Increased segmental spinal cord stress after surgery correlated with a corresponding increase in segmental range of motion (r = 0.69, p = 0.002) and disk pressure (r = 0.57, p = 0.05). Conclusion: This is the first study to use a patient-specific cervical spinal cord model to simulate surgical intervention and measure post-surgical spinal cord stress specific to the patient. Our results indicate that ACDF for DCM does not completely eliminate dynamic spinal cord stress, and adverse stress patterns are seen adjacent to the fusion construct. Further research is needed to determine if the altered spinal cord stress is associated with the pathogenesis of clinical adjacent segment disease in DCM.

366

P032: Rotational stiffness in a fully 3D printed biomechanical analogue of the lumbar spine

Siril Teja Dukkipati ^1,2 and Mark Driscoll ^1,2

¹ Musculoskeletal Biomechanics Research Lab, Department of Mechanical Engineering, McGill University, Montréal, Canada

² Orthopaedic Research Laboratory, Research Institute MUHC, Montreal General Hospital, Montréal, Canada

Introduction: Conventional spine biomechanical studies deal with cadavers and finite element models, both of which have their respective limitation in cost and time. Cadaveric studies introduce high variability in measurements across patients due to their dependency in patient medical history. Finite element models are constrained by the quality of patient data available and are computationally demanding. Validated analogue spine models can aid and compliment these conventional methods with low cost and increased fidelity. Materials and Methods: A 3D printed L1-S1 analogue model of the spine was developed which consisted of vertebral bodies, intervertebral discs along with intertransverse, interspinous ligaments. Stereolithography 3D printing was used to manufacture these models and assembled post printing. The soft tissues and the vertebrae were 3D printed using Flexible 80A and Durable resins on Form 3L printer (Formlabs, MA, USA). The model was then subjected to load-controlled pure bending loading up to a cyclic amplitude of 7.5Nm at 1/60Hz in flexion-extension, lateral bending, and axial rotation along with a custom bending jig (Instron Electroplus E10000, MA, USA). The resulting rotation of motion (ROM) was recorded and plotted against applied load to calculate model rotational stiffness. The performance of the model was compared to that of existing in vitro and in silico models in literature. Results: Due to the viscoelastic nature of the materials used in the model, a hysteretic response was exhibited while loading and unloading much like the human lumbar spine. At +7.5Nm flexion, the model ROM was 12.92 ± 0.11° (in vitro: 16.58°[1] and in silico: 14.92°[1]; 12.96°[2]). In lateral bending and axial rotation, the model exhibited left-right symmetry owing to its superior manufacturing process. The model ROM in lateral bending was found to be 13.55 ± 0.11° at +7.5Nm (in vitro: 13.32°[1] and in silico: 16.1°[1]; 15.26°[2]) and -13.79 ± 0.19° at -7.5Nm (in vitro: -17.1°[1] and in silico: -16.45°[1]; -15.73°[2]). In axial rotation, the model ROM was recorded as 19.82 ± 0.19° at +7.5Nm (in vitro: 14.44°[1] and in silico: 16.21°[1]; 15.63°[2]) and -15.57 ± 0.12° at -7.5Nm (in vitro: -13.81°[1] and in silico: -16°[1]; -16.2°[2]). In extension, the model exhibited approximately twice the stiffness compared to its human counterpart. But in all the other five bending modes, the model stiffness response is strongly comparable to that of in vitro and in silico literature. Conclusion: This custom 3D printed analogue model of the lumbar spine has rotational stiffness comparable to existing cadaveric, finite element models in flexion, lateral bending, and axial rotation motions and offers high degree of reproducibility. More material choices and testing is needed to statistically quantify the model. Within the context of use, such analogue experimental models can be effective tools in upcoming spinal biomechanics research.

References

1. Rao M. Explicit Finite Element Modeling of the Human Lumbar Spine. University of Denver, Denver, CO, 2012.

2. Campbell JQ, Coombs DJ, Rao M, Rullkoetter P J, Petrella AJ. Automated finite element meshing of the lumbar spine: Verification and validation with 18 specimen-specific models. J Biomech 2016; 49: 2669-76, doi: 10.1016/J.JBIOMECH.2016.05.025.

526

P033: Changes of the biomechanical environment during intervertebral fusion process after anterior cervical discectomy and fusion: a finite element study

Yi-Wei Shen ¹ , Yi Yang ¹ , and Hao Liu ¹

¹ Department of Orthopedics, Orthopedic Research Institute, West China Hospital, Sichuan University, Department of Orthopedics, Chengdu, China

Introduction: Anterior cervical discectomy and fusion (ACDF) is a widely-accepted surgical procedure in the treatment of cervical radiculopathy and myelopathy. A solid interbody fusion is of critical significance in achieving satisfactory outcomes after ACDF. However, the current radiographic techniques to determine the degree of fusion are inaccurate and radiative. Several animal experiments suggested that the mechanical load on the spinal instrumentation could reflect the fusion process and evaluate the stability of the implant. This study aims to investigate the changes in the biomechanical environment during the fusion process and explore the feasibility of reflecting the fusion status after ACDF through the load changes borne by the interbody fusion cage. Material and Methods: The computed tomography (CT) scans preoperatively, immediately after surgery, at 3 months, and 6 months follow-up of a patient who underwent ACDF at C5/6 were used to construct the C2-C7 finite element (FE) models representing the different course of fusion stages. A 75-N follower load with 1.0 N·m moments was applied to the top of the C2 vertebra in the models to simulate flexion, extension, lateral bending, and axial rotation with the C7 vertebra fixed. The Von Mises stress at the surfaces of instrumentation and the adjacent intervertebral disc and force at the facet joints were analyzed. Results: The facet contact force at C5/6 suggested a significantly stepwise reduction as the fusion proceeded while the intradiscal pressure and facet contact force of adjacent levels changed slightly. The stress on the surfaces of the titanium plate and screws significantly decreased at 3 months and 6 months follow-up. A markedly changed stress distribution in extension among the three models was noted in different fusion stages. After solid fusion is achieved, the stress was more uniformly distributed interbody fusion in all loading conditions. Conclusion: Through a follow-up study of 6 months, the stress on the surfaces of cervical instrumentation remarkably decreased in all loading conditions. After solid intervertebral fusion formed, the stress distributions on the surfaces of the interbody cage and screws were more uniform. The stress distribution in extension altered significantly in different fusion statuses. Future studies are needed to develop the interbody fusion device with wireless sensors to achieve longitudinal real-time monitoring of the stress distribution during the course of fusion.

598

P034: Titanium mesh cage placement after corpectomy. Does the anatomical location have an effect on stability? A biomechanical comparison of three different cage localizations. A finite element analysis

Tuna Pehlivanoglu ¹ , Bahadir Gokcen ² , Tugrul Ergun ³ , O. Nuri Eroglu ¹ , Ufuk Aydinli ² , and Cagatay Ozturk ¹

¹ Dept. of Orthopaedic Surgery and Traumatology, Liv Hospital Ulus, Liv Spine Center certified by AOSpine, Istanbul, Turkey

² Dept. of Orthopaedic Surgery and Traumatology, Liv Hospital Vadi, Liv Spine Center certified by AOSpine, Istanbul, Turkey

³ Dept. of Orthopaedic Surgery and Traumatology, Istinye University Liv Hospital, Liv Spine Center certified by AOSpine, Istanbul, Turkey

Introduction: Anterior column restoration following corpectomy is paramount to restore the vertebral body height and to reconstruct the corpectomy defect, in order to have a stable spinal segment yielding a balanced spine in coronal and sagittal planes. The aim of this study based on a finite element analysis was to compare the biomechanical properties of three different titanium mesh cage localizations (anterior/middle/posterior) in the vertebral body simulated to reconstruct the corpectomy defect to question the ideal localization providing the highest stability. Materials and Methods: A three-dimensional, non-linear finite element model (FEM) of L4-L6 segment combined with corpectomy at the level of L5 was constructed. It was modified to test the titanium mesh cage (1 cm in diameter) placed on L6’s vertebral body’s upper endplate centrally to reconstruct the L5-corpectomy defect under three conditions: (Group 1) the cage is placed centrally on anterior 1/3^rd of vertebral body, (Group 2) the cage is placed centrally in the middle of the vertebral body, (Group 3) the cage is placed centrally on posterior 1/3^rd of vertebral body. Finite element analyses were performed to investigate the effect of axial compressive loadings, while average tensions recorded from the surface of cages were recorded and assessed for distal force transmission and segmental stability. Results: Average surface tension (AST) in Group 1 was 320 MPa. AST in Group 2 was 124 MPa. AST in Group 3 was 45 MPa. Intergroup comparison yielded the superiority of cages in Group 3 (p < 0.001 for all), indicating the lowest axial compressive load transmission to cages placed centrally on posterior 1/3^rd of the vertebral body providing least amount of force transmission to distal segments accompanied with highest segmental stability. Conclusion: The present study based on finite element analysis concluded, that following corpectomy, titanium mesh cages placed centrally on the posterior 1/3^rd of the lower vertebral endplate to reconstruct the corpectomy defect in order to restore the vertebral height and restore the spinal balance together with spinal stability, was subjected to least axial compressive loading resulting in the least amount of force transmitted to distal segments and was therefore detected to yield highest stability against axial loading.

761

P035: Influence of the iliolumbar ligament on the lumbar segmental range of motion in the sagittal plane: a finite element approach

Adi Mithani ¹ , Ahmed Aoude ² , and Mark Driscoll ³

¹ Biological and Biomedical Engineering

² Department of Surgery, McGill University Health Centre, Canada

³ Mechanical Engineering, McGill University, Canada

Introduction: The iliolumbar ligament (ILL) is a major lumbopelvic ligament that has been implicated in the stability of the sacroiliac and lumbosacral joints, particularly in cases with increasing disc degeneration or L5 spondylolysis. While the ILL plays a role in lower lumbar dysfunction, no biomechanical modelling has been conducted to evaluate the relationship between changes in the material properties of the ILL and the lumbar range of motion (ROM). The primary objective of this research was to develop a validated and representative finite element (FE) spine model to evaluate the influence of the ILL on the lumbar segmental ROM in the sagittal plane under flexion-extension conditions. Material and Methods: In this study, a FE spine model was developed and validated against in-vivo published findings of intervertebral rotations (IVR) at lumbar spine levels L2-S1. The model included the thoracolumbar vertebrae, rib cage, intervertebral disc, facet cartilage, joint capsule, pelvis, and spinal ligaments (ILL, supraspinous, intertransverse, and interspinous ligaments). The ILL was modelled as a tension-only spring element, originating at the transverse process of the 5th vertebra and inserted onto the ilia of the pelvis, anteriorly and posteriorly. A follower load of 1000N was applied perpendicularly to the surface of the T1 vertebra’s superior endplate to S1 using pre-loaded springs, increasing by 2.4% at each vertebral level. The perpendicular orientation of loading ensured the resultant forces remained tangential to the spinal profile. A 60˚ and -55˚ remote rotation was applied to the body of the T1 vertebra to simulate forward flexion and maximum extension, respectively, with the pelvis as the fixed support. Case scenarios were executed and IVRs were calculated based on the intersection between lines running parallel to the superior and inferior endplate at an intervertebral level. Results: The application of flexion and extension generated IVRs that fell within a 20% margin of the mean values acquired from in-vivo studies by Breen et al. (2021) and Lin et al. (1994), respectively, remaining within the standard deviation associated with each intervertebral segment. Flexion-extension rotation following bilateral ILL removal increased IVR at L5-S1 and decreased it at L4-L5, by 23.37% and 12.33%, respectively. Sensitivity analysis relating ILL stiffness to lumbar segmental IVRs in the sagittal plane found that as stiffness increased from 50 N/mm to 3000 N/mm, IVR decreased at L5-S1 and increased at L4-L5 by 21.94% and 15.53%, respectively. Lumbar ROM varied by a maximum of 2.5% across all stiffness values tested. Conclusion: Removal of the ILL or changes to its material properties alters the IVRs at L5-S1, producing a compensatory rotation at L4-L5 in the sagittal plane. Decreasing the magnitude of support at L5-S1 increases the amount of flexion-extension rotation imparted at this level, which reduces rotation at adjacent levels until the maximum allowable rotation is achieved. This permits the lumbar spine to retain its normal ROM. Clinically, in patients with iliolumbar syndrome, the inflammation of the ILL may not directly contribute to lumbar dysfunction as adjacent vertebral levels could alter their segmental rotation to preserve some degree of lumbar ROM.

853

P036: There is significant variability in segmental lumbar motion

Emily Mills ¹ , Jennifer Wang ¹ , Brian Chung ¹ , Lucas Mayer ¹ , Mary Richardson ¹ , Andy Ton ¹ , Raymond Hah ¹ , and Nathanael Heckmann ¹

¹ Orthopaedic Surgery, Keck School of Medicine of USC, Los Angeles, United States

Introduction: The variability in change of lordosis throughout common positions has not been well-studied. Additionally, the relationship between lumbar and hip motion has not been established. Here, we sought to establish 1) normative values for lumbar segmental motion and 2) the relationship between hip and lumbar flexion. Material and Methods: Fifty subjects, 25 male and 25 female, without prior hip or spine disease were prospectively recruited to participate in this study. Three lateral radiographs were obtained: standing, relaxed seated, and flexed-forward seated. Radiographic variables measured included lumbar lordosis (LL), motion at each lumbar level (L1-L2, L2-L3, L3-L4, L4-L5, L5-S1), and pelvic-femoral angle (PFA), an established measure of hip motion used in the arthroplasty literature. The motion through each lumbar segment was calculated as the change in angle between a standing position and the target motion (i.e. seated or flexed-forward seated). Each segment’s contribution to overall lumbar motion was calculated as the ratio of the individual segment to the overall lumbar lordosis. The correlation between hip flexion and lumbar flexion between the standing and seated positions was evaluated. Results: Subjects had an average age of 25.70 ± 2.34 years and body mass index (BMI) of 24.10 ± 3.02 kg/m². From standing to relaxed seated, the most mobile segment was L4-L5 (10.92 ± 3.95°) and from standing to a seated flexed-forward position was L4-L5 (16.42 ± 4.22°). The largest percentage contribution to lordosis was L4-L5 while standing (26.81 ± 5.78%) and was L1-L2 while seated (28.12 ± 25.42%). During the standing to relaxed seated position, maximal motion occurred at L4-L5 (25/50, 50.0%) followed by L5-S1 (13/50, 26.0%), L3-L4 (10/50, 20.0%), and L2-L3 (2/50, 4.0%). During the standing to flexed-forward seated position, maximal motion occurred at L4-L5 in 26/50, (52.0%), L3-L4 in 11/50 (22.0%), L5-S1 in 10/50 (20.0%), and L2-L3 in 3/50 (6.0%). Hip flexion (ΔPFA) was strongly negatively correlated with lumbar flexion (ΔLL). For every degree increase of hip flexion, the lumbar flexion decreased 0.86° (R = -0.75, p < 0.001). Conclusion: The greatest contribution to segmental motion and lumbar lordosis was L4-L5; however, there was significant variability, with some subjects having the greatest contribution from upper lumbar segments. Additionally, hip flexion was found to be strongly negatively correlated with lumbar flexion.

867

P037: Biomechanical evaluation of different fixation strategies for S1 pedicle subtraction osteotomy (PSO); A finite element analysis

Niloufar Shekouhi ¹ , Sudharshan Tripathi ¹ , Vijay Goel ¹ , and Alekos Theologis ²

¹ Departments of Bioengineering, Engineering Center for Orthopaedic Research Excellence (E-CORE), University of Toledo, Toledo, United States

² Orthopaedic Surgery, UCSF, San Francisco, United States

Introduction: While pedicle subtraction osteotomies (PSO) are most commonly performed in the middle/low lumbar spine, sacral PSOs are ideal for correcting sacral deformities. As sacral PSOs raise unique challenges for stabilization given relatively limited fixation caudal to the PSO, this study’s purpose is to compare biomechanics of different instrumentation configurations used to stabilize a S1-PSO. Material and Methods: A validated spinopelvic finite element model was used to create a 300 PSO in S1. Fixation cranial to the PSO was T11-L5 pedicle screws and distal to the PSO was dual iliac screws. The PSO was stabilized with a combination of the following rods to create different multi-rod (4-,5-,6-) constructs: (1) main midline rods (10R) engaging the T11-L5 pedicle screws; (2) a horizontal rod (HR) connecting the two distal iliac screws; (3) lateral accessory rods (LR) connected to the cranial iliac screws and 10R proximally; (4) medial accessory rods (MR) connected to the HR and 10R proximally. Five different instrumentation strategies were evaluated: (A) 4-Rod(LR): 10R + bilateral LR; (B) 4-Rod(MR+HR): 10R combined with a MR connected to a HR; (C) 4-Rod(LR+HR): 10R connected to a HR combined with bilateral LR; (D) 5-Rod(LR+HR+1MR): 10R connected to a HR combined with bilateral LR and one MR; 6-Rod(LR+HR+2MR): 10R connected to a HR combined with bilateral LR and two MR. After loadings of 300N, 400N, and 400N were applied to the thoracic, lumbar, and sacrum, respectively, pure moments (7.5Nm) were applied to the top endplate (T10) in all anatomic directions. The L5-S1 ranges of motion (PSO-ROM) were recorded. PSO-force and maximum von Mises stresses on 10R, LR, and HR were recorded. Results: Maximum PSO-ROM was noted for 4-Rod(MR+HR) in flexion, extension, and lateral-bendin. Compared to 4-Rod(MR+HR), 4-Rod(LR), 4-Rod(LR+HR), 5-Rod, and 6-Rod showed up to 49%, 41%, 35%, and 36% lower PSO-ROMs, respectively. Von Mises stresses were lowest on 10Rs in 5- and 6-Rod constructs. Of the 4-Rod techniques, 4-Rod(LR+HR) had the lowest von Mises stresses. 4-Rod(MR+HR) showed lowest von Mises stresses on accessory rods and horizontal rods in all directions. 5-Rod and 6-Rod configurations demonstrated greatest von Mises stresses on HR. Maximum PSO-force was observed in 4-Rod(MR+HR) in all motions except extension. Conclusion: In this finite element analysis of various multi-rod (4-,5-,6-) constructs stabilizing a S1 PSO, the construct consisting of primary midline rods connected to cranial iliac bolts supplemented with medial accessory rods connected vertically to a horizontal rod connecting distal iliac screws [4-Rod(MR+HR)] demonstrated highest PSO-ROMs and greatest PSO forces.

Acknowledgement: Work supported by NSF Industry/University Cooperative Research Center, UCSF, UT, and Ohio State University.

940

P038: Influence of the rib cage on the lumbar segmental range of motion in the sagittal plane: a finite element approach

Adi Mithani ¹ , Ahmed Aoude ² , and Mark Driscoll ³

¹ Biological and Biomedical Engineering

² Department of Surgery

³ Mechanical Engineering, McGill University, Montreal, Canada

Introduction: Local and distant tissues influence the degree of lumbar range of motion (ROM), eluding to multiple causes of spinal dysfunction. A recent systematic review further supports that rib cage removal leads to reduced thoracic stiffness and increased ROM at the thoracic spine level. However, no biomechanical studies have evaluated the impact of the rib cage on the lumbar ROM. The primary objective of this research was to develop a validated and representative finite element (FE) spine model to evaluate the contribution of the rib cage to the lumbar segmental ROM in the sagittal plane under flexion-extension conditions. Material and Methods: In this study, a FE spine model was developed and validated against in-vivo published findings of intervertebral rotations (IVR) at the lumbar spine levels L2-S1. The model included the thoracolumbar vertebrae, rib cage, intervertebral disc, facet cartilage, joint capsule, pelvis, and spinal ligaments (iliolumbar, supraspinous, intertransverse, and interspinous ligaments). Rib-vertebrae contact was modelled as a fixed joint with zero degrees of freedom. A follower load of 1000N was applied perpendicularly to the surface of the T1 vertebra’s superior endplate to S1 using pre-loaded springs, increasing by 2.4% at each vertebral level. The perpendicular orientation of loading ensured the resultant forces remained tangential to the spinal profile. A 60˚ and -55˚ remote rotation was applied to the body of the T1 vertebra to simulate forward flexion and maximum extension, respectively, with the pelvis as the fixed support. Different components of the rib cage were removed and IVRs were calculated based on the intersection between lines running parallel to the superior and inferior endplate at a given intervertebral level. Results: The application of flexion and extension generated IVRs that fell within a 20% margin of the mean values acquired from in-vivo studies by Breen et al. (2021) and Lin et al. (1994), respectively, remaining within the standard deviation associated with each intervertebral segment. Flexion-extension rotation during removal of the rib cage decreased IVR at L4-L5 and L5-S1 by -20.81% and -15.48%, respectively, with lumbar ROM dropping by 10.12% compared to the validated model. Removal of the true ribs bilaterally decreased IVR at L4-L5 and L5-S1 by -18.29% and -19.26%, respectively. However, no significant change in ROM was observed after the removal of the sternum and the false and floating ribs. Flexion-extension rotation following the sternal release with non-in-tact ribs reduced IVR at L4-L5 and L5-S1 by 14.63% and 15.48%, respectively, and was associated with a 7.46% reduction in lumbar ROM. Conclusion: The findings reveal the importance of the rib cage, specifically the true ribs, in contributing to the lumbar ROM in the sagittal plane during flexion-extension conditions. The sternal release, a potential treatment for spinal sagittal plane deformity, increased segmental ROM in the lower lumbar levels but only in the case when the ribs were removed. Therefore, unless another method is implemented to account for the rib cage’s stiffness contribution, the inclusion of ribs may be necessary to produce a representative FE spinal model that reflects the lumbar spine’s ROM.

984

P039: Effect of ligaments on spinal stiffness by systematic construction of an L1-S1 analogue spine model

Siril Teja Dukkipati ^1,2 and Mark Driscoll ^1,2

¹ Department of Mechanical Engineering, Musculoskeletal Biomechanics Research Lab, McGill University, Montréal, Canada

² Orthopaedic Research Laboratory, Research Institute MUHC, Montreal General Hospital, Montréal, Canada

Introduction: Conventional spine biomechanical studies deal with cadavers and finite element models, both of which have their respective limitation in cost and time. These can be overcome by incorporating validated analogue models of the spine for biomechanical testing. To develop such models, it is important to quantify the effects of all the underlying soft tissues on the model biomechanical response. This study considered the effect of intertransverse and interspinous ligaments on the overall rotational stiffness of the lumbar spine by sequential construction of an analogue lumbar spine. Materials and Methods: A 3D printed L1-S1 analogue model of the spine was developed which consisted of vertebral bodies, intervertebral discs (IVDs) along with intertransverse, interspinous ligaments. Stereolithography 3D printing was used to manufacture the individual tissues. The soft tissues and the vertebrae were 3D printed using Flexible 80A and Durable resins on Form 3L printer (Formlabs, MA, USA). The model construction had three phases (P1, P2, P3) and after each phase, the corresponding model rotational stiffness was estimated by subjecting it to load-controlled pure bending load up to a cyclic amplitude of 5Nm at 1/60Hz in flexion-extension, lateral bending, and axial rotation along with a custom bending jig (Instron Electroplus E10000, MA, USA). Five cycles of loading is applied and the resulting rotation of motion (ROM) was recorded and plotted against applied load to calculate rotational stiffness. P1 consisted of the assembly of vertebral bodies and the corresponding IVDs. P2 consisted of adding the interspinous ligament to the P1 model. P3 completed the model construction by adding the intertransverse ligaments on both sides of the P2 model. Results: The analogue spine model exhibited hysteretic behavior during load-unload cycles very much like the human spine due to the viscoelastic elastomers used in its construction. In flexion-extension motion, addition of ligaments considerably increased model rotational stiffness (flexion – P1 = 9.87 ± 0.05°; P2 = 9.41 ± 0.1°; P3 = 8.33 ± 0.11° and extension – P1 = 8.99 ± 0.09°; P2 = 6.7 ± 0.05°; P3 = 7.12 ± 0.04°). In lateral bending motion, there was no noticeable change in rotational stiffness from P1 to P2 but an increase from P2 to P3 on both directions (left – P1 = 9.01 ± 0.07°; P2 = 8.93 ± 0.1°; P3 = 8.66 ± 0.09° and right – P1 = 9.11 ± 0.09°; P2 = 9.18 ± 0.06°; P3 = 8.5 6± 0.05°). In axial rotation, there was no noticeable trends in the stiffness as construction progressed on either direction (left – P1 = 12.8 ± 0.11°; P2 = 14.3 ± 0.2°; P3 = 12.56 ± 0.14° and right - P1 = 12.08 ± 0.24°; P2 = 10.75 ± 0.04°; P3 = 11.41 ± 0.15°). The model exhibited noticeable left-right symmetry in lateral bending and axial rotation motions. Conclusion: The presence of interspinous and intertransverse ligaments increases the flexion and lateral bending stiffnesses respectively in the model. This observation agrees with the consensus of the current understanding of lumbar spine biomechanics. In extension and axial rotation motions, the model stiffness does not follow any trends with the addition of ligaments. Further testing with more material choices is needed to statistically quantify the results. The developed L1-S1 analogue spine model can be an effective research and educational tool in studying dependency of ligaments and any of their damage modes on the lumbar spine structure.

986

P040: On the effect of thoracolumbar fascia on lumbar spine stiffness under loading in an analogue spine setup

Siril Teja Dukkipati ^1,2 and Mark Driscoll ^1,2

¹ Department of Mechanical Engineering, Musculoskeletal Biomechanics Research Lab, McGill University, Montréal, Canada

² Orthopaedic Research Laboratory, Research Institute MUHC, Montreal General Hospital, Montréal, Canada

Introduction: Analogue biomechanical models serve as fast and reliable alternatives to conventional spine biomechanical studies which involve cadaveric and finite element studies. Both these methods have their respective limitations in cost and time as opposed to analogue models. To develop and validate such models, it is important to characterize the dependency of all the underlying soft tissues on model performance. An analogue model of the thoracolumbar fascia (TLF) was developed and integrated with a previously validated L1-S1 analogue lumbar spine model and its effect on spinal stiffness was characterized. Materials and Methods: A 3D model of the TLF based on patient MRI data was constructed from L1 to S1 level. Stereolithography 3D printing was used to manufacture the model with Flexible 80A resin and printed on Form 3L (Formlabs, MA, USA). A custom jig was developed to anchor the model along the iliac arch. Prior to integrating with the analogue lumbar spine, the TLF model was tested in tension and its mechanical hysteresis and stress relaxation were determined. Then the model was attached to the analogue lumbar spine and the combined model was subjected to pure bending loading in all three axes (Instron Electroplus E10000, MA, USA). Five cycles of load-controlled moments up to 7.5Nm at 1/60Hz were applied in flexion-extension, lateral bending, and axial rotation. The rotational stiffness of the TLF integrated analogue lumbar spine was determined by plotting the resultant rotation of motion against applied moment. Results: The analogue TLF model exhibited viscoelastic properties much like its human counterpart. The TLF model hysteresis was estimated to be 34.3 ± 0.68% as compared to 28.3 ± 7.4% in a porcine TLF model (Nelson-Wong et al., 2018). Force-time curve at a constant deformation of 10mm revealed that there was a 40.1 ± 3.0% drop in resisting force after 500 sec. This is comparable to 42.3% drop in human TLF samples according to (Yahia et al., 1993). When the TLF model was attached to the L1-S1 analogue lumbar spine, its rotational stiffness significantly increased in flexion-extension and axial rotation motions under pure bending loading. The combined model recorded 9.95 ± 0.05° and 7.1 ± 0.08° in flexion and extension as opposed to 12.92 ± 0.11° and 10.15 ± 0.1° respectively in the original L1-S1 analogue spine model. Similarly in axial rotation, the combined model recorded 16.3 ± 0.18° and 12.25 ± 0.12° in left and right directions as opposed to 19.82 ± 0.19° and 15.5 ± 0.12° respectively in the original model. In lateral bending, no significant impact of TLF on spinal stiffness was noticed. The combined model recorded 12.6 ± 0.1° and 13.37 ± 0.17° in left and right as compared to 13.55 ± 0.11° and 13.79 ± 0.19° respectively in the original model. Conclusion: The developed TLF model mechanical response is comparable to that of the human tissue. The combined model stiffness response suggests that the presence of TLF aids in restricting the lumbar spine in flexion-extension and axial rotation motions. Further testing with more material choices is warranted to increase model accuracy. The developed TLF model along with the L1-S1 analogue spine model can act as cost effective spinal biomechanics educational and research tools in future research.

1293

P041: Biomechanics of the spine while wearing different types of orthopedic braces

Justyna Fercho ¹ , Michal Krakowiak ¹ , Rami Yuser ¹ , Tomasz Szmuda ¹ , Grzegorz Mi´kisiak ² , and Piotr Zieliński ¹

¹ Neurosurgery Department, Medical University of Gdansk, Gdańsk, Poland

² Department of Neurosurgery, Institute of Medicine, Opole, Poland

Aim: Despite the frequent use of orthopedic braces or spine stabilizers in diseases such as kyphosis, lordosis, and scoliosis, as well as in the case of injuries and rehabilitation and after surgeries, there is no clear evidence of their proper stabilization of the spine while performing day-to-day activities. This study sought to assess the spine's mobility while wearing three different types of orthopedic braces while performing certain basic activities. Methods: Ten healthy subjects were enrolled. Three inertial measuring units were attached superficially along the spine at the T2, T12, and sacrum. The angle between sensors was monitored to provide data on the sagittal profile. In addition, the displacement along the longitudinal axis of the spine was measured (rotation). Three types of orthopedic braces: the semi-rigid LSO orthosis, Jewett brace, and TLSO orthosis. Three tasks were monitored: when standing, sitting, walking, and picking up an item from the floor with one hand. Results: When performing a dynamic task of lifting an item all braces provide a similar level of stability in both the sagittal plane and rotational axis. On the other hand during walking and sitting the TLSO was the only orthosis providing a statistically significant rigidity in the sagittal plane. The findings from this study currently provide the most precise understanding of the biomechanics behind the spine parameters while wearing orthopedic braces. Conclusion: Despite various levels of perceived rigidity the three orthoses performed similarly during deliberate dynamic testing (pick up an item). This is likely caused by the increased kinesthetic effect of all devices. On the other hand, when performing rather involuntary postures when walking and standing the superiority of the most rigid TLSO brace was apparent.

Keywords: spine, motion analysis, wearable sensors, biomechanics, braces

1539

P042: Differences across various ideal lumbar lordosis measurement formulas for patient-specific sagittal alignment goals

David Polly ¹ , Paul Soriano ¹ , Jason Haselhuhn ¹ , Gurmit Singh ¹ , Kenneth Holton ¹ , Kristen Jones ¹ , and Jonathan N. Sembrano ¹

¹ University of Minnesota, Minneapolis, United States

Introduction: Multiple studies in the past have developed differing equations to determine the ideal lumbar lordosis (ILL) in the sagittal plane. These equations differ slightly, but all look to accomplish the same goal of providing the surgeon with specific alignment targets during surgery. However, to the authors’ knowledge, no study has compared the different equations of ILL against each other. This study aims to compare five different target alignment formulas in high, normal, and low pelvic incidence (PI) patients. Methods: We conducted a retrospective chart review from January 2015 through April 2022 and reviewed available full-standing spine radiographs. We classified patients by PI: high (65-95°), normal (50-60°), and low (30-45°), and included five patients for each classification. A single faculty member performed all PI measurements. We calculated ILL based on the measured PI using five different formulas: Hamamatsu University (2016), ESSG-GAP score (2017), Abelin-Genevois et al. (2018), Hyun et al. (2019), and Dial et al. (2022). We employed Tukey’s HSD post hoc pair-wise comparison of homogenous groups of means (α=0.05) to determine if there were significant differences. We considered any measurement ±3° as equivalent to account for measurement variability. Results: Fifteen patients were included in the data analysis, five in each PI cohort. The GAP score, Hyun, and Dial equations differ statistically from Hamamatsu University and Abelin-Genevois (p<0.001). At high and normal PI classification, GAP score, Hyun, and Dial significantly differ from Hamamatsu University and Abelin-Genevois (p<0.05). At low PI classification, only the GAP score and Dial significantly differ from Hamamatsu University and Abelin-Genevois (p<0.05); Hyun does not differ significantly from all the other formulas. Conclusion: Variation exists among the five different ILL equations, with three formulas being statistically different from the other two. The equations for high and low PI patients predict differing ideal lumbar lordosis. One must take note of these differences when considering patient-specific sagittal alignment goals. Further study is needed to refine the understanding of ideal lumbar alignment.

1749

P043: Biomechanical analysis of cortical bone trajectory screwcombined with pedicle screw fixation in lumbar spine: in-vitro experiments and finite element validation

Zihao Ding ¹ , Hongtao Ding ¹ , Yuzeng Liu ¹ , and Yong Hai ¹

¹ Spine Surgery, Beijing Chaoyang Hospital, Capital Medical University, Beijing, China

Introduction: To compare the mechanical characteristics of pedicle screw fixation (PS), cortical bone trajectory screw (CBTS) fixation and the combination use of PS and CBTS (PS-CBTS) in L4/5 fixation. Material and Methods: A three-dimensional finite element (FE) analysis model (T12-Sacral) based on a patient with osteoporosis was developed to analyze the range of motion (RoM) and internal fixation stress of three different groups, which were PS fixation (group A), CBTS fixation (group B), and hybrid fixation (L4-CBTS and L5-PS) (group C). And six human cadaveric lumbar spine specimens (L1-Sacral) were used for the biomechanical experiment to further compare the different fixations’ strengths and weaknesses. Results: In the cadaveric specimen study, group C had the highest stiffness, followed by groups B and A. The range of motion (RoM) of the cranial adjacent segment was significantly higher in group C than in groups A and B. In the FE model, group C had the highest screws and connecting rod fixation stress in the six-dimensional motion of the lumbar spine, followed by Groups B and A. The stresses of interbody cage in the three groups were 318.8 Mpa (group A), 319.6 Mpa (group B), and 311.4 Mpa (group C), respectively. Group B had the smallest RoM in flexion and extension, and the largest RoM in lateral flexion and rotation. Conclusion: The combined application of CBTS and PS can increase the stress of internal fixation, improve lumbar stiffness, and decrease stress on the interbody cage. However, the impact on the adjacent segments requires further research.

1817

P044: Elasticity change of the paravertebral fascia and muscle in adolescent idiopathic scoliosis after posterior selective fusion surgery

Aixing Pan ¹ and Yong Hai ¹

¹ Orthopedic, Beijing Chaoyang Hospital, Capital Medical University, Beijing, China

Introduction: We sought to assess the elasticity change of the paravertebral fascia and muscle in adolescent idiopathic scoliosis patients with Lenke Type 1, 2, or 3 curves after posterior selective fusion surgery. Material and Methods: The shear wave elasticity imaging system was used to assess the elasticity of the thoracic paravertebral muscles and fascia both on the concave and convex sides. Three regions of interest, including the apex, upper end, and lower end of the main curve, were tested. Results: Ten female patients, with an average age of 16.6 ± 2.7 years old, were included. The average post-operation follow-up period was 9.0 ± 2.4 months. The Cobb angle was significantly corrected from 63.6 ± 12.0° to 10.7 ± 5.4° (p < 0.05). The length of the trunk increased from 40.4 ± 2.5 cm to 46.0 ± 2.8 cm (p < 0.05). The elasticity of deep fascia didn't show a significant change post-operation (p > 0.05). The elasticity of the paravertebral muscle on the concave side had a significant increase at the final follow-up (p < 0.05). The elasticity of the paravertebral muscle on the convex side also increased at the upper end (p < 0.05). The elasticity asymmetry of the deep fascia decreased, but the elasticity asymmetry of the paravertebral muscle increased at the upper end of the curve (p < 0.05). Conclusion: The paravertebral muscle on the concave side is stiffer after surgery. Elastic asymmetry of paravertebral muscle increased and elastic asymmetry of the deep fascia decreased at the upper end of the curvature. Further study is needed to elucidate the mechanism by which the paravertebral soft tissue responds after surgery.

Deformity-Cervical

208

P045: Extracranial dural venous sinus: a rare vascular anomaly in a a case of atlantoaxial instability

Umang Sheth ¹ , Tushar Rathod ² , and Punith K ³

¹ Orthopaedics, Dr. R.N. Cooper Municipal Hospital, Mumbai, India

² Orthopaedics, Seth G.S. Medical College and K.E.M. Hospital, Mumbai, India

³ Orthopaedics, Grant Government Medical College, Mumbai, India

Background: Cases of atlatonaxial instability usually are accompanied with bonyt and vascular abberations which make the management of these cases challenging. Case Description: We report a rare and challenging case of an 8 year old boy with atlantoaxial instability presenting with features of cervical myelopathy and CT angiograpm revealing an extracranial course of the dural venous sinus which is a first of it’s kind to be present in cases of atlantoaxial instability along with an aberrant vertebral artery course in the V3 segment, occipitalisation of atlas and facet malalignment. The patient was managed with intraoperative reduction by traction and posterior occipitocervical fusion. Conclusion: It is of utmost importance to actively look for venous and arterial anomalies while planning surgery on the supraaxial cervical spine as damage to these structures can have catastrophic consequences.

213

P046: Ideal surgical strategy for dropped head syndrome (DHS)

Takahiro Iizuka ¹ , Tetsuro Takai ¹ , Tokuji Kashiro ¹ , and Hiroshige Debata ¹

¹ Orthopedic Surgery, Takai Hospital, Nara, Japan

Background of Data: Dropped Head Syndrome (DHS) is little known in Spine Community. Patients complain of difficulties in forwarding gaze. Some reports on these clinical symptoms are reported in the literatures as a case report. Most DHS surgeries report posterior cervical reconstruction with posterior cervical long fusions. We report four patients with DHS who underwent anterior segmental correction of cervical vertebrae as possible as short. And the patients are enabled to gaze forward after surgery. Patients and Methods: Four patients are enrolled in this report (Average age: 74.5, female 3, male1). They complained of difficulties in forwarding gaze and posterior neck stiffness preoperatively. All patients had no other pathologies ie Parkinson’s syndrome. They were evaluated by MRI, myelography, and CT myelography for making surgical strategies. Cervical alignment (C3-C7 cervical kyphosis angle) and Cervico-Thoracic Inlet Angle (between C2-Th1 line and clavicle line) were recorded by lateral X-ray at upright position preoperatively and postoperatively. Clinical complaints were also documented on gazing forward and neck pain/stiffness. All patients performed anterior segmental reconstruction for correction of cervical kyphosis. Results: All patients are enabled to gaze forward. No apparent neurological deficit and complications associated with surgery were not reported in those patients. Cervical kyphosis C3-7 angle was improved. Conclusion: Dropped Head Syndrome is little-known pathology in the Spine community. In this report, patients complained of difficulties in forwarding gaze and swallowing foods and neck stiffness preoperatively. Anterior segmental reconstruction spinal fusion (ASR-SF) is less invasive than posterior cervical correction with instruments because of less damage to PVM, mechanical reduction with instruments, and possible short segmental fusions. We conclude that ASR-SF is the most suitable surgical strategy for DHS as less invasive surgery.

302

P047: Endoscopic endonasal odontoidectomy: a long-term follow-up for a cohort of 21 patients

Federica Penner ¹ , Raffaele De Marco ¹ , giuseppe di perna ¹ , irene portonero ¹ , Diego Garbossa ¹ , Bianca Baldassarre ¹ , and francesco zenga ¹

¹ Neuroscience, University of Turin, Turin, Italy

Introduction: Endoscopic endonasal odontoidectomy (EEO) has been described as a potential approach for craniovertebral junction (CVJ) diseases that could cause anterior bulbomedullary compression and encroaching. Due to the atlantoaxial junction’s uniqueness and complex biomechanics, treating CVJ pathologies uncovers the challenge of preventing C1–C2 instability. A large series of patients treated with endonasal odontoidectomy is reported, analyzing the feasibility and necessity of whether or not to perform a posterior stabilization. Furthermore, the focus is on the long-term follow-up of both posteriorly fixed patients, especially those who only underwent partial C1 arch preservation without posterior fixation. Material and Methods: This study is a retrospective analysis of patients with ventral spinal cord compression for non-reducible CVJ malformation, consecutively treated with EEO from July 2011 to March 2019. Postoperative dynamic X-ray and CT scans were obtained in each case in order to document CVJ decompression and to exclude instability. The anterior atlas‐dens interval, posterior atlas‐dens interval and C1-C2 total lateral overhang were measured as morphological criteria to determine the upper cervical spine stability. Results: Twenty-one patients (11:10 F:M) with a mean age at surgery of 60.6 years (range 34 - 84 years), encountered the inclusion criteria. For all 21 patients a successful decompression was achieved at the first surgery. In 11 patients the partial C1 arch integrity did not require a posterior cervical instrumentation on the bases of post-operative and constant follow up radiological examination. In 13 cases, an improvement of motor function was recorded at discharge. Only one patient had further motor function improvement at follow-up. Among the patients that did not show any significant motor change at discharge, 4 patients showed an improvement at the last follow-up. Conclusion: The outcomes, even in C1 arch preservation without posterior fixation, are promising and it could be said that the endonasal route potentially represents a valid option to treat lesions above the nasopalatine line.

479

P048: Concomitant atlantoaxial and atlanto-occipital rotatory dislocation in children: radiological features, diagnostic pitfalls, and long-term outcome

Paul Koljonen ¹ and Kenneth Man Chee Cheung ¹

¹ Department of Orthopaedics and Traumatology, The University of Hong Kong, Hong Kong

Introduction: While the pathological manifestation of atlantoaxial rotatory dislocation has been well described in the medical literature, the combined dislocation of the atlantoaxial and atlanto-occipital joints, or OAARD - short for occipital-atlantoaxial rotatory dislocation - is a condition which has been poorly elucidated and probably underdiagnosed. We believe that the pathogenesis of combined atlantoaxial and atlanto-occipital dislocation is most likely a result of untreated atlantoaxial rotatory dislocation leading to chronic secondary compensation measures occurring at the occiput-C1 joints. Unique clinical and radiological features lead to difficulty in diagnosis, and conventional treatment algorithms may not apply. This paper describes a combination of clinical and radiological features which can help clinicians correctly diagnose and treat OAARD. Material and Methods: A case series of paediatric occipital atlantoaxial rotatory dislocation is presented in this abstract. 3D-reconstructed computer tomography images and 3D printed models of the cervical spine are used to illustrate the deformity as well as dysplastic changes occurring in the dislocated occipital condyles, C1 and C2 facet surfaces. Xray and Dynamic CT scans for rotational deformity are discussed in detail, including the introduction of 2 novel radiological signs termed the “trapezoidal anterior C1 shadow” and “isolated C1 spin-out” sign, which are pathognomonic of dislocation of the C1 ring. Diagnostic pitfalls, surgical technique, and long-term outcome are presented. Conclusion: Concomitant occiput-atlantoaxial dislocation is a unique condition that is probably underdiagnosed in common daily practice. We emphasize the need for clinicians to exercise a high index of suspicion in children presenting with neck pain and torticollis. Early diagnosis and aggressive treatment of isolated atlantoaxial dislocation may help prevent chronic secondary dislocation at the occiput-C1 level. This paper describes a combination of clinical and radiological features which can help clinicians correctly diagnose and treat OAARD. More research is required on the long-term outcome following upper cervical spinal fusion in children.

690

P049: Diffuse idopathic skeletal hyperostosis with dysphagia: surgical treatment

Adnene Benammou ¹ , Sofiene Kallel ² , Cherif Kamoun ¹ , Balti Walid ¹ and Mohamed Ben Salah ¹

¹ Charles Nicolle Hospital, Orthopedic Surgery Department, Tunis, Tunisia

² Maghreb Medical, Tunis, Tunisia

Introduction: Diffuse Idiopathic Skeletal Hyperostosis (DISH) is an ossification of spinal entheses and tendons. Its cervical location can lead to dysphagia. We report a case report of a patient treated for dysphagia caused by cervical DISH. Material and Methods: A 65-year-old male was addressed for cervical DISH. Symptoms were dysphagia with neck pain and limitation of spinal mobility. Esophago-gastro-duodenal transit showed brutal stop of contrast agent at the level of C4. Surgery was decided mainly on dysphagia not on pain. Computed Tomography (CT) scan showed anterior osteophytes and reduction of the diameter of the trachea. Osteophytes were removed from an anterior cervical approach. Results: At day one postoperative, swallowing was significantly improved with reduction of local pain. At 6 months postoperative, the patient reported a significant improvement in swallowing, breathing and range of motion. Conclusion: Although rare, dysphagia in DISH patient is a rising problem. Surgical treatment with removal of osteophytes is effective for treating it. Surgery can be decided mainly on dysphagia with no other signs.

733

P050: A case report: C1-C2 rotatory dislocation with C1 arch defect managed with modified Harms-Goel technique

Ziad Mohamed ¹ and Antony Michael ¹

¹ Neuro Spinal Hospital, Dubai, United Arab Emirates

Atlantoaxial rotatory dislocation represents a rare presentation, although more common in paediatric patients. The management of this condition is not well defined in the current literature due to the limited number of cases described in the literature. Here, we describe a case of C1-2 rotatory dislocation in a female adolescent patient following acute onset of neck pain that was corrected with C1-C2 fusion using the modified Harms-Goel technique after skull traction and closed reduction failed to offer long-term management.

879

P051: Comparison of the efficacy of anterior combined with posterior approach and posterior-only approach in the treatment of basilar invagination with irreducible atlantoaxial dislocation: minimum 5-year follow-up outcomes

Xiaoyu Cai ¹ and Tao Xu ¹

¹ Department of Spine Surgery, First Affiliated Hospital of Xinjiang Medical University, Urumqi, China

Introduction: To compare the clinical efficacy of anterior combined with posterior (A-P) approach and posterior-only (P-O) approach release, reduction, and internal fixation in the treatment of BI with irreducible AAD. Material and Methods: The clinical records of 49 patients diagnosed with BI with irreducible AAD from July 2000 to June 2017 were analyzed retrospectively. The patients were divided into the A-P group (n = 24) and P-O group (n = 25) according to the operation modes. The primary outcome measures included Chamberlain line (CL), Wackenheim line (WL), McRae line (ML), atlanto-dens interval (ADI), cervicomedullary angle (CMA), clivus-canal angle (CCA), Japanese Orthopaedic Association (JOA) score, and Ranawat grade. Results: The follow-up periods were 68.7 ± 11.2 months in the A-P group and 64.4 ± 13.2 months in the P-O group. The JOA score of the A-P group was 8.25 ± 2.74 before operation and 14.96 ± 1.09 at the last follow-up. The improvement rate was 77.32 ± 11.31%. The JOA score of the P-O group was 8.10 ± 2.48 before operation and 14.69 ± 0.60 at the last follow-up. The improvement rate was 74.32 ± 10.42%. The preoperative CL, WL, ML, ADI, CMA, and CCA of the A-P group were 13.14 ± 5.72 mm, 6.91 ± 3.52 mm, 7.12 ± 4.51 mm, 9.78 ± 2.10 mm, 110.79°± 13.2°, 95.28° ± 18.1°. At the last follow-up, the CL, WL, ML, ADI, CMA, and CCA were 1.69 ± 2.51 mm, -2.71 ± 2.19 mm, -1.50 ± 2.41 mm, 1.13 ± 1.52 mm, 149.16° ± 12.5°, 141.38° ± 13.6° with significant difference compared with the preoperative results. The preoperative CL, WL, ML, ADI, CMA, and CCA of the P-O group were 12.50 ± 5.09 mm, 6.54 ± 3.12 mm, 6.88 ± 4.28 mm, 9.81 ± 1.89 mm, 115.29° ± 12.3°, 97.21° ± 16.6°. At the last follow-up, the CL, WL, ML, ADI, CMA, and CCA were 2.04 ± 3.61 mm, -3.12 ±1.81 mm, -1.72 ± 2.79 mm, 1.15 ± 1.20 mm, 146.69 °± 11.2 °, 137.49° ± 10.3°, which were statistically significant compared with the preoperative results. The bone graft fusion time was 9.1 ± 5.0 months in the A-P group and 9.4 ± 4.8 months in the P-O group. A total of 8 patients presented postoperative complications, including 6 patients in the A-P group (25.0%) and 2 patients in the P-O group (8.0%). The incidence of postoperative complications in the P-O was significantly lower than that in the A-P group. Conclusion: The clinical efficacy of the P-O approach release, reduction, and internal fixation in the treatment of BI with irreducible AAD is basically the same as that of the A-P approach. However, the incidence of complications of the P-O approach is significantly lower than that of the A-P approach.

1093

P052: Hybrid surgery for the treatment of cervical myelopathy and adjacent level radiculopathy

David Felzensztein ¹ , Eilat Sapirstein ¹ , and Eyal Itshayek ¹

¹ Neurosurgery, Rabin Medical Center, Holon, Israel

Introduction: Patients with multilevel degenerative disc disease suffering from cervical myelopathy and adjacent foraminal stenosis, tend to be managed with multilevel anterior cervical discectomy and fusion (ACDF) or cervical laminectomy and fusion. Fusion sparing techniques have been used in an attempt to decrease the number of fused levels. The combination of ACDF and Transvertebral Foraminotomy could reduce the need for adjacent segment fusion, reduce costs and decrease the number of fused levels in such cases. We present our experience and preliminary results with patients undergoing ACDF and skip level transvertebral foraminotomy. Material and Methods: We retrospectively evaluated prospectively collected clinical and radiological data from January 2017. Currently a total of 15 patients have been assessed. All procedures included single level ACDF and unilateral transvertebral foraminotomy at an adjacent disc space. The Modified Japanese Orthopedic Association (mJOA) score and Odom’s criteria were analyzed. Radiological assessment included the C2-7 Cobb angle and disc height of segments adjacent to the ACDF. Adjacent segment degeneration, which includes disc degeneration, was evaluated. All surgeries were performed at two adjacent segments. Results: The JOA scores significantly improved. There were no significant differences in the C2-7 Cobb angle and DH of the adjacent segment to ACDF. Conclusion: Combination of ACDF and transvertebral foraminotomy provides a safe and effective method in reducing the number of levels fused with good clinical outcome.

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P053: Unilateral spacer distraction (USD) of the subaxial cervical facet joint for the treatment of fixed coronal malalignment of the craniovertebral junction

Juan P. Cabrera ¹ , Igor Ebert Cechin ² , Alderico Girão Campos de Barros ² , and Luis Eduardo Carelli Texeira da Silva ²

¹ University of Concepción, Concepcion, Chile

² Instituto Nacional de Traumatologia e Ortopedia Jammil Haddad (INTO), ARCOL, Rio de Janeiro, Brazil

Introduction: The standard treatment for a fixed coronal malalignment of the craniovertebral junction is an anterior and/or posterior column osteotomy plus instrumentation. However, the procedure is very challenging, carrying an inherently high risk of complications even in experienced hands. This study aims to demonstrate the usefulness of a novel alternative treatment by adding a unilateral spacer distraction (USD) to the subaxial cervical facet joint to promote coronal realignment and fusion. This technique allows the achievement of coronal correction performing the surgery in the subaxial cervical spine, which can decrease the associated morbidity of an osteotomy at the craniovertebral junction, a challenging location. Material and Methods: Single-center retrospective study of the patients with fixed coronal malalignment of the craniovertebral junction caused by different etiologies treated with USD in the concavity side with posterior column osteotomy (PCO) in the convexity side of the subaxial cervical spine. Demographic and radiological characteristics were collected with special emphasis on clinical and radiological measurements of coronal alignment of the cervical spine. Results: During 2012-2019 four patients were treated with USD of the subaxial cervical spine complementing an asymmetrical PCO at the same level. The causes of coronal imbalance were congenital, tuberculosis, post-traumatic, and ankylosing spondylitis. The level of USD was C2-3 in three patients and C3–4 in one patient. A substantial coronal realignment was achieved in all four. All the patients haves at least two years of follow-up. One had an iatrogenic vertebral artery injury during the dissection and facet distraction, with partial recovery on follow-up. Conclusion: USD of the concave side with unilateral PCO of the convexity side in the subaxial cervical spine is an alternative treatment for fixed coronal malalignment of the craniovertebral junction from different causes.

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P054: Cross-sectional area of the longus colli and cervical degenerative spondylolisthesis: a retrospective review evaluating this anatomic consideration

Aditya Mazmudar ¹ , Khoa Tran ¹ , Taylor Paziuk ¹ , Mark Lambrechts ¹ , Eric Tecce ¹ , Olivia Blaber ¹ , Daniel Habbal ¹ , Kamil Okroj ¹ , Brian Karamian ¹ , Jose Canseco ¹ , Jeffrey Rihn ¹ , Alan Hilibrand ¹ , Christopher Kepler ¹ , Alexander Vaccaro ¹ , and Gregory Schroeder ¹

¹ Rothman Orthopedic Institute at Thomas Jefferson University, Philadelphia, United States

Introduction: Limited literature is available to define the impact of the longus colli muscle, a deep flexor of the spine, on cervical spine stability despite its close proximity to the vertebrae. No studies have investigated longus colli cross-sectional area (CSA) in patients with cervical spondylolisthesis. The purpose of this study was to determine if longus colli CSA is associated with the severity preoperative cervical degenerative spondylolisthesis. Material and Methods: A retrospective cohort study was conducted on patients who underwent one- to five-level ACDF between 2010 and 2021 at a single, academic center for clinical symptoms of radiculopathy, myelopathy, or mixed radiculomyelopathy in the setting of cervical spondylolisthesis. Patient data was obtained using a Structured Query Language search and manual chart review. Patients who lacked a preoperative cervical spine MRI or radiograph or had surgical intervention to address infection, trauma, tumor, or revision of a prior instrumented cervical fusion surgery were excluded from analysis. Longus colli cross-sectional areas (CSA) were measured from preoperative MRI images at the C5 level. Preoperative spondylolisthesis measurements were recorded with cervical radiographs. For each patient, the highest degree of spondylolisthesis measured among levels fused was determined as the “maximum spondylolisthesis measured.” Patients were grouped by quartiles respectively according to longus colli CSAs. Statistical tests compared patient demographics, surgical characteristics, and surgical outcomes between groups. Multiple linear regression analysis was utilized to assess if longus colli CSA predicted cervical spondylolisthesis. Results: A total of 157 patients met inclusion criteria. Group 1 (first quartile) was the oldest (60.4 ± 12.0 years, p = 0.024) and was predominantly female (59.0%, p = 0.001). Group 1 also had the highest maximum spondylolisthesis (0.19 mm, p = 0.031) and highest proportion of grade 2 spondylolisthesis (23.1%, p = 0.003). On regression analysis, lowest quartile of longus colli CSA was an independent predictor of larger measured maximum spondylolisthesis (β: 0.04, p = 0.012). There were no differences for levels fused, revisions, readmissions, or surgical complications between groups (p > 0.05). Conclusion: Smaller longus colli CSA is independently associated with a higher grade and degree of preoperative cervical spondylolisthesis, but this finding does not result in adverse postsurgical outcomes. Further research targeted at improving our understanding of how longus colli strengthening affects cervical spondylolisthesis is indicated given our findings.

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P055: Lower hounsfield units at the planned lowest instrumented vertebra is an independent risk factor for distal junctional kyphosis following adult cervical deformity surgery

Peter Passias ¹ , Tyler Williamson ¹ , Rachel Joujon-Roche ¹ , Peter Tretiakov ¹ , Bailey Imbo ¹ , Pooja Dave ¹ , Kimberly McFarland ¹ , Jamshaid Mir ¹ , Stephane owusu-saprong ¹ , Jordan Lebovic ¹ , Bassel Diebo ² , Shaleen Vira ³ , Andrew Schoenfeld ⁴ , Heiko Koller ⁵ , Renaud Lafage ⁶ , Virginie Lafage ⁶ , and Themistocles Protopsaltis ¹

¹ NYU Langone Medical Center, New York, United States

² SUNY Downstate Medical Center, New York, United States

³ UT Southwestern Medical Center, Dallas, United States

⁴ Brigham and Women’s Hospital/Harvard Medical Center, Boston, United States

⁵ University of Munchen, Germany

⁶ Lenox Hill Hospital, New York, United States

Introduction: The association of Hounsfield units (HU) and junctional pathologies has emerged as a topic of interest in thoracolumbar surgery. The relationships between HUs and complications like distal junctional kyphosis (DJK) in cervical deformity (CD) surgery have not been elucidated. The objective of this study is to assess whether bone mineral density of the LIV, as assessed by HUs, is prognostic for the risk of DJK after CD surgery. Methods: CD patients with 2-year (2Y) data included. HUs were measured at the LIV, LIV+1, C3 and C7 on all preoperative CT scans, averaging the widest region of interest (ROI) ellipse within sub-cortical bone across three axial slices for each vertebra. The primary outcome measure was complications, including DJK, defined radiographically as ≥10° change between the end plates of a vertebra and vertebra+2. Means comparison test assessed differences in HUs based on occurrence of complications, linear regression assessed correlation of HUs with risk factors, and multivariable logistic regression followed by conditional inference tree (CIT) run machine learning derived HU thresholds based on developing complications. Results: Included: 107 CD patients. HU means- LIV: 272 ± 79, LIV+1: 252 ± 71, C3: 338 ± 109, C7: 294 ± 97. By two years, 20.6% developed DJK and 6.3% developed DJF. There was a significant correlation between more distal LIVs and lower HUs (r = .351, p = .01), as well as age and HUs at the LIV (r = .364, p <. 001). Both age and HUs did not correlate with change in the DJK angle (both p > .1). HUs were lower at the LIV for patients who developed DJK (219 vs 286, p = .018). Upon CIT analysis, an LIV threshold of 245 HUs was predictive of DJK (OR: 5.0, [1.2-17.7]; p = .023). Conclusion: Low bone mineral density at the lowest instrumented vertebra, as assessed by a threshold lower than 245 Hounsfield units, may be a crucial risk factor for the development of distal junctional kyphosis after cervical deformity surgery. Preoperative CT scans should routinely be performed in at-risk patients to mitigate this modifiable risk factor.

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P056: Are we getting better at optimizing surgery for high risk adult cervical deformity patients over time? A retrospective multicenter analysis

Peter Passias ¹ , Peter Tretiakov ¹ , Justin Smith ² , Breton Line ³ , Bassel Diebo ⁴ , Alan Daniels ⁴ , Jeffrey Gum ⁵ , Themistocles Protopsaltis ¹ , D. Kojo Hamilton ⁶ , Alex Soroceanu ⁷ , Justin Scheer ⁸ , Robert Eastlack ⁹ , Gregory Mundis ⁹ , Michael Kelly ¹⁰ , Nitin Agarwal ¹¹ , Pierce Nunley ¹² , Khoi Than ¹³ , Richard Fessler ¹⁴ , Robert Hart ¹⁵ , Douglas Burton ¹⁶ , Christopher Shaffrey ¹³ , Frank Schwab ¹⁷ , Shay Bess ³ , Virginie Lafage ¹⁷ , and Christopher Ames ⁸

¹ Neurological and Orthopaedic Surgery, NYU Langone Health, New York City, United States

² Department of Neurosurgery, University of Virginia Medical Center, Charlottesville, United States

³ Department of Spine Surgery, Denver International Spine Center, Presbyterian St. Luke's/Rocky Mountain Hospital for Children, Denver, United States

⁴ Department of Orthopaedic Surgery, Warren Alpert School of Medicine, Providence, United States

⁵ Norton Leatherman Spine Center, Louisville, United States

⁶ Department of Neurological Surgery, University of Pittsburgh School of Medicine, Pittsburgh, United States

⁷ Department of Orthopaedic Surgery, University of Calgary, Calgary, Canada

⁸ Department of Neurological Surgery, University of California, San Francisco, United States

⁹ Division of Orthopaedic Surgery, Scripps Clinic, La Jolla, United States

¹⁰ Department of Orthopaedic Surgery, Rady Children's Hospital, San Diego, United States

¹¹ Department of Orthopaedic Surgery, Washington University, St. Louis, United States

¹² Spine Institute of Louisiana, Shreveport, United States

¹³ Department of Neurosurgery, Duke University Medical Center, Durham, United States

¹⁴ Rush University Medical Center, Chicago, United States

¹⁵ Department of Orthopaedic Surgery, Swedish Neuroscience Institute, Seattle, United States

¹⁶ Department of Orthopaedic Surgery, University of Kansas Medical Center, Kansas City, United States

¹⁷ Department of Orthopaedics, Lenox Hill Hospital, Northwell Health, New York City, United States

Introduction: Surgical correction of adult cervical deformity (CD) has high rates of complication. However, patients often derive significant benefits in functional status and quality of life from surgical intervention despite being deemed at high risk of complication. It has yet to be investigated whether spine surgeons are improving surgery for high risk patients and minimizing poor outcomes. Material and Methods: Operative CD patients ≥ 18yrs with complete pre-(BL) and 2-year(2Y) multi-center data were stratified by year of surgery from 2013 to 2018. Patients were categorized as 2013 to 2014[Early] or 2015 to 2018[Recent]. High risk [HR] patients were defined as meeting ≥ 2 of the following criteria: 1) Baseline C2-C7 Cobb > 15° or T1S-CL ≥ 35° or C2-C7 cSVA > 4 cm or CBVA > 25° 2) being elderly [≥ 70 years], 3) severe BL frailty [Miller frailty index], 4) CCI ≥ 1 SD above the cohort mean, 5) undergoing 3-column osteotomy (3CO), and 6) fusion of > 10 levels, or > 7 levels for elderly patient. Means comparison analysis assessed differences in demographics, HRQLs, radiographic alignment, and complications between groups. Stepwise multivariable linear regression described associations between increasing year of surgery and complication rates. Results: 82 CD pts met high-risk inclusion criteria (62.11 ± 10.87 yrs, 63.7%F, BMI:29.70 ± 8.16 kg/m², CCI: 1.07 ± 1.45), and underwent surgery (levels fused 9.4 ± 3.9, EBL: 866.51 mL). 39.0% of HR patients underwent 3CO. The proportion of HR patients increased with time, with 41.8% of Early patients classified as HR compared to 47.6% of Recent patients. Recent HR patients were more likely to be female (p = .008) and have a lower BMI (p = .038), but also presented with higher baseline CCI (p = .024). Surgically, Recent HR patients were more likely to undergo a partial facet joint osteotomy (p = .042), though less likely to undergo a PSO (p = .003). In terms of HRQLs, at 1Y Recent HR patients were more likely to improve in SWAL-QOL – Communication (p = .035) and 2Y Eating Duration domains (p = .038). By post-op complications, Recent HR patients were significantly less likely to experience bladder incontinence at 1Y (p = .024). Furthermore, Recent HR patients were significantly less likely to experience any post-operative adverse events overall (p = .020), or complications such as dysphagia (p = .045). Regression revealed increasing year of surgery to be correlated with decreasing minor complication rates (β = -0.166, p = .030), as well as lowered rates of DJK by 2Y (β = -0.152, p = .048). Kaplan-Meier 2Y survival analysis revealed that of 9 Early (15.25%) and 1 Recent (4.35%) HR patients had expired, with mean survival time was 71.56 weeks for Early HR patients, and 70.00 weeks for Recent HR patients (p = .636). Conclusion: Over time, high-risk cervical deformity patients have increased in frequency and comorbidity rates, yet have demonstrated improved clinical, radiographic, and post-operative outcomes. These findings suggest that spine surgeons have improved over time in optimizing outcomes and patient selection, and reducing potential adverse events associated for high-risk patients.

1613

P057: Redefining cervical spinal deformity - When are sagittal plan realignment procedures necessary?

Venu Nemani ¹ , Philip Louie ¹ , Caroline Drolet ¹ , and John Rhee ²

¹ Neurosurgery, Virginia Mason Franciscan Health, Seattle, United States

² Orthopaedic Surgery and Neurosurgery, Emory University, Atlanta, United States

Introduction: Cervical sagittal deformity (CSD) is an extremely disabling condition and can be associated with concomitant myelopathy, radiculopathy, or both. While there are radiographic parameters that define the presence of CSD, the question remains as to whether these criteria are sufficient to warrant a diagnosis of CSD. Further, it is unclear when a CSD realignment procedure is warranted versus a less invasive procedure only to address cervical myelopathy or radiculopathy, given the increased complexity and risk of CSD realignment surgery. Material and Methods: With these questions in mind, we conducted a REDCap survey of cervical spine surgeons to determine if there is a consensus as to 1) the definition of a cervical sagittal plane deformity, and 2) when a cervical sagittal plane deformity merits a sagittal realignment procedure with its associated risks. The survey was distributed to 82 surgeons with differing experience, training background (neurosurgery vs orthopaedic surgery), and practice environment (University setting vs private or hospital employed). The questions were designed to determine whether the current published radiographic criteria were sufficient alone to establish a diagnosis of CSD or whether other clinical and physical exam factors were also thought to be necessary in the diagnosis of CSD. We presented clinical vignettes to determine which radiographic parameters would require correction in the setting of clinical signs and symptoms such as radiculopathy, myelopathy, axial neck pain, and difficulty holding head upright, and when a more extensive “deformity” procedure was warranted. Results: We received responses from 41 surgeons (33 orthopaedic surgeons, 8 neurosurgeons) with 93% working in an academic environment. 41% of surgeons had 6-15 years of experience and 59% had 16+ years of experience. 80% of the surgeons devote greater than 50% of their surgical practice to treating patients with cervical spine disorders. 93% of the surgeons perform a realignment procedure for CSD at least once every three months. There was no consensus on whether isolated radiographic abnormalities previously defined as associated with the need for cervical deformity surgery or a history of difficulty holding one’s head upright was sufficient to establish a diagnosis of CSD. However, when one or more of these radiographic criteria were also associated with a clinical history of difficulty holding one’s head upright, 29% of surgeons felt this was sufficient establish a diagnosis of CSD. Surgeons generally felt that a CSD realignment procedure was more necessary in patients presenting with cervical myelopathy compared to cervical radiculopathy. While there was no clear consensus on what radiographic criteria needed CSD correction in patients with myelopathy, the most common parameters deemed important were C2-C7 SVA and C2-C7 kyphosis. Conclusion: Despite numerous published studies, there is no consensus amongst a diverse group of cervical spine surgeons as to what radiographic and/or clinical criteria are necessary to define the presence of CSD. Surgeons are more apt to perform CSD realignment procedures in patients with myelopathy versus those with radiculopathy alone. More work is necessary to refine the definition of CSD and what patients will benefit from a sagittal plane realignment procedure.

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P058: Are two surgeries necessary for correction of one deformity - Cervical kyphosis in neurofibromatosis? A rare case report

Jayprakash Modi ^1,2 and Pratikkumar Prajapati ²

¹ Orthopaedic, Nutan Medical College, Mehsansa, India

² Orthopaedic, B J Medical College, Ahmedabad, India

Introduction: Dystrophic neurofibromatosis type I, involving upper cervical spines, is rare, which can cause serious complications. Myelopathy develops due to compression of the cord posteriorly. Surgical correction has its inherent risks and difficulties because of poor bone quality, difficult anterior approach because of bizarre deformities, and the necessary manipulation, which might cause more cord damage and ischemia. Anterior decompression with alignment correction was an early popular choice. But without posterior shortening, the technique proved unsatisfactory in restoring normal alignment. It tended to expose the graft bone at increased risk of insufficient union or extruding. So a combination of anterior decompression and posterior correction was generally recommended. Materials and Methods: This is a rare case study of a patient operated at tertiary care centre having non-traumatic involvement of spinal cord affecting neurology with history, clinical and radiological features suggesting Cervical Nuerofibromatosis as the cause of compression. This report describes surgical technique applicable to cases of severe cervical kyphosis using only anterior approach. Result: A 13-year-old boy, a case of neurofibromatosis type 1 presented with neck pain, and bilateral upper limb radiculopathy for 2 months with affected daily living, with intact neurology. Imaging demonstrated 46° kyphosis (C3-C5),marked dystrophic changes of the C4 and C5, extreme dorsal angulation indenting the cord. Anterior surgery was planned for the patient with neuro-monitoring. Through left anterior approach, total C3, C4 and C5 corpectomy was accomplished, keeping the PLL intact. The defect was filled with a fibular cortical graft which was stabilized with 48 mm cervical screw plate, showing full correction of kyphosis postoperatively. At the follow-up 6 months postoperatively, lateral plain radiograph showed stability of the cervical spine fusion without correction loss. The patient had full relief from tingling and numbness with no neurological deficit and could resume his daily duties. Patient is asymptomatic at 2 years follow up. Conclusion: Only anterior decompression and fusion are effective in satisfactorily correcting cervical kyphosis in cases of neurofibromatosis without neurologic compromise and avoids the risk of damage to vital neurovascular structures because of pedicle or lateral mass screw fixation.

1918

P059: Cervical medullary compression due to a retro- odontoid pseudotumor in 65 year-old patient with Forrestier's disease: a case report and literature review

Zohra Souei ¹ , Maher Hadhri ¹ , Mohamed Boukhit ¹ , Asma Elmir ¹ , Kais Maamri ¹ , Atef Ben Nsir ¹ , and Mehdi Darmoul ¹

¹ Neurosurgery, Fattouma Bourguiba University Hospital, Monastir, Tunisia

Introduction: The retro-odontoid pseudotumor or pannus is often associated with inflammatory diseases. It is typically located between the dens and the anterior arch of the atlas. It can also be due to noninflammatory causes such as chronic atlantoaxial instability. Only a few cases have reported an association between retro-odontoid pannus, craniocervical chronic instability, and Forestier’s disease. Material and Methods: We report the case of a 65-year-old male who presented with impaired ambulation and neck pain following minor trauma. Detailed neurologic exam showed weakness in all four limbs, with hypoglossal nerve palsy, dysphagia, and bladder dysfunction. The CT and MR studies showed cervical ankylosis with a retro-odontoid pannus and craniocervical stenosis with myelopathy associated with diffuse idiopathic skeletal hyperostosis. Results: The patient underwent an urgent occipitocervical fixation with occipital craniotomy and C1 laminectomy. The postoperative course was uneventful and the neurological symptoms improved rapidly with the normalization of strength in four limbs. Within 2 weeks, he was able to walk independently. Postoperative imaging showed excellent craniocervical decompression with pannus regression and adequate fusion. Conclusion: Retro-odontoid pseudotumor not associated with an inflammatory disease is a rare condition and may lead to cervicomedullary compression or myelopathy. To date, transoral spinal cord decompression followed by posterior stabilization has been a widely accepted treatment. In the past years, however, several authors have reported a pannus reduction and even regression after a posterior atlantoaxial stabilization only.

Deformity-Thoracolumbar (Adolescent)

137

P060: Comparison of adolescent idiopathic scoliosis (AIS) correction-open vs. minimally invasive cohorts: a 2 years radiographic and surgical outcome study

Matthew Geck ¹ , Devender Singh ¹ , Ashley Duncan ¹ , John Stokes ¹ , and Eeric Truumees ¹

¹ Spine, Ascension Texas Spine and Scoliosis, Austin, United States

Introduction: Both open and minimally invasive surgery (MIS) techniques are used to surgically address AIS. MIS techniques are purported to preserve the midline spinal musculature and to decrease estimated blood loss (EBL) and hospital length of stay (LOS). Aim: We report the surgical and deformity corrections outcomes in matched cohorts of Adolescent Idiopathic Scoliosis (AIS) patients with similar Lenke types that had undergone either open or MIS at 2 years follow-up at one institution. Materials and Methods: From a single surgeon’s practice, 21 patients who underwent MIS correction were case matched with 19 patients that had open surgical correction. All were idiopathic Lenke 1A and 5C types. Age, surgery duration, estimated blood loss (EBL), length of hospital stays (LOS), preoperative (pre-op) and postoperative (post-op) Cobb angles, Oswestry Disability Index (ODI), Visual Analogue Scale (VAS) and Scoliosis Research Society-22r (SRS-22r) were evaluated. MIS technique was uniform in all patients using two or three para-midline incisions. Results: Mean patient age was 16.5 years (11-47 years) in MIS group and 18 years (12-39 years) in open group. Mean pre-op Cobb angles for MIS and open were 53.7° (±3.1°) and 51.7° (±3.6°), respectively. The main curve’s mean flexibility index was 55.4% and 56.1% for MIS and open group, respectively. Mean surgical time for MIS and open group were 343 and 393 minutes, respectively (p < 0.05). Mean EBL were 156 mls (±89.4 mls) and 275 mls (±75.2 mls) for MIS and open group, respectively (p < 0.05). Mean LOS for MIS was 3.0 days (±1.2 days) and 5.1 (±1.8 days) for open group (p < 0.05). Mean corrections for MIS at post-op 1 and 2 years were 75.6% (±8.2%) and 77.4 % (±6.8%) respectively. For open group, these corrections were 76.4% (±8.1%) and 76.8% (±7.4%) respectively. The differences in correction did not reach statistical significance. Mean 1- and 2-years post-op VAS scores for MIS and open groups were 3.3 and 3.6, and 3.3 and 3.8, respectively (p > 0.05). For MIS and open group, mean 1- and 2-years post-op ODI scores were 6.4 and 10, and 4 and 8, respectively (p > 0.05). Mean 1- and 2-years post-op SRS scores for MIS and open groups were 4.3 and 4.1, and 4.6 and 4.2, respectively (p > 0.05). Conclusions: In these specific curve types, our cohort data indicates that MIS technique for scoliosis correction is a viable option and can attain corrections equivalent to open surgery with lower EBL and shorter LOS. Additionally, patient reported outcomes over 2 years follow up, as indicated by VAS, ODI and SRS were comparatively better in the MIS over the open group.

139

P061: Does a minimally invasive surgical technique affect intraoperative and post-operative blood glucose levels in adolescent idiopathic scoliosis correction?

Matthew Geck ¹ , Devender Singh ¹ , Ashley Duncan ¹ , John Stokes ¹ , and Eeric Truumees ¹

¹ Spine, Ascension Texas Spine and Scoliosis, Austin, United States

Introduction: Surgical intervention induces trauma and stimulates the neuroendocrine stress response, releasing a cascade of hormones ultimately resulting in hyperglycemia. Uncontrolled hyperglycemia has long been associated with increased risk of surgical site infections and complications with wound healing. Aim: To examine if a minimally invasive surgical (MIS) technique influences perioperative blood glucose levels of patients undergoing surgical correction for Adolescent Idiopathic Scoliosis (AIS). Materials and Methods: The charts of 35 patients undergoing surgical correction for AIS were reviewed. Patients were divided into two cohorts based on surgical approach, open or MIS. Variables including blood glucose levels at preoperative, intraoperative, and post-operative day three were collected. Average Intraoperative Blood Glucose was the mean of three blood glucose levels taken from intraoperative blood gases. The presence of endocrine pathology was defined broadly but included diabetes as well as abnormal vitamin D levels (< 30 nmol/L). Results: The open cohort was comprised of 18 patients, and the MIS included 17. 24% of the open were male, in comparison to 6% of the MIS. Mean age and Body Mass Index were similar in both groups. Overall presence of an endocrine issue was 60%. Of these, 95% were abnormal vitamin D levels (8 deficiency, 12 insufficiency) and one patient had a diagnosis of hypothyroidism. The incidence of endocrine issues varied significantly in the open (n = 14) versus the MIS (n = 7). Mean preoperative glucose was 89.3 ± 13.1 mg/dL, with no significant difference between MIS and Open. Three blood glucose levels were averaged from blood gases samples taken intraoperatively, with a mean of 90.7 ± 7.9 mg/dL. There was no significant difference in mean intraoperative blood glucose levels between MIS (89.7 ± 8 mg/dL) and Open (90.4 ± 11.8 mg/dL). Blood glucose levels were highest on postoperative day 1 (POD1), mean 117.1 ± 12.5 mg/dL, and consistently decreased over postoperative days 2 and 3, 106.6 ± 16.3 mg/dL and 99.3 ± 8.4 mg/dL respectively. There was no significant difference in postoperative blood glucose levels between the two groups. Conclusion: Though there was a significantly higher incidence of endocrine issues in the open, there was no statistical difference in blood glucose levels at any of the defined intervals between the two groups. Blood glucose was the highest on POD1 in both groups and tapered down each subsequent postoperative day in alignment with literature. Though this sample population did not demonstrate significant differences between groups, a larger prospective study to better understand the role of endocrine issues and glucose levels on the risks and outcomes of AIS correction is still warranted.

140

P062: Pre-operative fibrinogen testing is not associated with total blood loss in mini open correction and fusion for adolescent idiopathic scoliosis (AIS) correction: a single center analysis

Matthew Geck ¹ , Devender Singh ¹ , Ashley Duncan ¹ , John Stokes ¹ , and Eeric Truumees ¹

¹ Spine, Ascension Texas Spine and Scoliosis, Austin, United States

Introduction: Intra- and post-operative bleeding is associated with higher operative morbidity and greater costs of care. Aim: This study sought to investigate the potential association between fibrinogen, bleeding and transfusion requirements in patients undergoing adolescent idiopathic scoliosis (AIS) reconstruction using minimally invasive surgical (MIS) technique. Materials and Methods: 64 consecutive AIS patients over 2 years undergoing scoliosis corrections were reviewed. Age, gender, operative time (OR), pre-operative (pre-op) hemoglobin (Hb), platelet count, prothrombin time [PT], activated partial thromboplastin time [aPTT], Prothrombin time (INR), pre-op fibrinogen, thromboelastography (TEG: G, K, angle), total bleeding volume and transfusions were collected. Pearson’s test was used to investigate the correlation between bleeding and clinical variables with level of significance set at α = 0.05. Results: In this cohort, mean patient age was 17 years (11-48 years) with 94% of female patients. Mean BMI was found to be 19.8 (±3.2). Curves were classified as: 42 Lenke 1A, 13 Lenke 1B, 4 Lenke 1C; 8 Lenke 5C. Mean TEG values were within normal range in both males and females. Mean Hb, platelet count and fibrinogen concentration were 11.12 (±1.3) g/L, 238.24 (±72.18) (x10⁹/L) and 216.4 (±33.6) g/dL, respectively. Mean total bleeding was 152 ± 75 ml. Pre-op fibrinogen did not correlate significantly with the total bleeding (r = 0.34, p > 0.05). Other variables such as OR, PT, aPTT, INR, TEG and platelet count did not correlate significantly with fibrinogen (p > 0.05). Total bleeding volume correlated significantly with cell saver (r = 0.687, p < 0.05). None of the other variables correlated significantly with total bleeding volume (p > 0.05). Conclusions: Our cohort analysis indicates that pre-op fibrinogen concentration does not correlate significantly with the total bleeding volume in patients undergoing AIS reconstruction using MIS technique. However, there was a strong positive relationship between the total bleeding volume and transfusion requirements.

142

P063: Does Cobb angle correlate with self-reported outcomes of patients undergoing adolescent idiopathic scoliosis (AIS) reconstruction?

Matthew Geck ¹ , Devender Singh ¹ , Ashley Duncan ¹ , John Stokes ¹ , and Eeric Truumees ¹

¹ Spine, Ascension Texas Spine and Scoliosis, Austin, United States

Introduction: Cobb Angle is widely used to quantify the magnitude of spinal deformity. Clinicians use this tool to track the degree of scoliosis correction following surgical interventions. Aim: This study investigates the correlation between Cobb angles and self-reported outcomes of patients undergoing minimally invasive surgical (MIS) stabilization of adolescent idiopathic scoliosis (AIS). Materials/Methods: 67 consecutive patients undergoing MIS correction of AIS were prospectively studied. Age, Body mass index (BMI), Lenke curve, preoperative (pre-op) and postoperative (post-op) Cobb angles, Scoliosis Research Society-22r (SRS-22r), Oswestry Disability Index (ODI) and Visual Analogue Scale (VAS) were evaluated. Mean (standard deviations) were calculated. Surgical technique was uniform in all patients using two or three para-midline incisions. At different pre-op and post-op time periods, linear regressions were conducted in which the Cobb angle was the independent variable and outcome scores were the dependent variables. Results: Mean patient age was 16.5 years (11 - 47 years). Mean BMI was found to be 21.5 (±1.9) Curves were classified as: 42 Lenke 1A, 13 Lenke 1B, 4 Lenke 1C; 8 Lenke 5C. Mean flexibility index of main curve was 54.46% (±10.43%). Pre-op VAS and ODI were weakly correlated with pre-op Cobb Angles with r² = 0.05 and 0.110, respectively. At 2 weeks, 6 months, 1 year and 2 years post-op, the correlation between post-op Cobb angles and VAS gradually improved from weak to moderate with r² = 0.0027, 0.0067, 0.085 and 0.404, respectively. Similarly, post-op Cobb angles and ODI at 2 weeks, 6 months, 1 year and 2 years follow-ups were consistently correlated weakly with r² = 0.118, 0.112, 0.091 and 0.118, respectively. SRS-22r and post-op Cobb angles at 1- and 2-years follow-ups were weakly correlated with r² = 0.028 and 0.035, respectively. Conclusions: Our cohort’s data indicate that Cobb angle and self-reported patient outcomes are weakly correlated. There is no gold standard to measure the surgical outcomes in MIS; rather clinicians should rely on combination of tools varying from radiographic evaluations, patient reported outcome measures to their own clinical judgments.

145

P064: Posterior vertebral tethering as an outpatient surgical option for select cases of pediatric scoliosis: a case series

Kira Furie ¹ , Hao-Hua Wu ² , and Mohammad Diab ³

¹ School of Medicine

² Orthopaedic Spine Surgery, Harvard Medical School/ Massachusetts General Hospital & Brigham and Women's Hospital, Boston, United States

³ Orthopaedic Surgery, University of California, San Francisco, United States

Introduction: Surgical treatment for scoliosis is typically an inpatient procedure. Posterior vertebral tethering (PVT) is a novel fusionless surgery that can be performed as an outpatient procedure in select patients. The purpose of this case series is to describe outpatient PVT and to report on minimum 12-month follow-up. Material and Methods: In this retrospective case series, skeletally immature patients diagnosed with idiopathic scoliosis who underwent outpatient PVT performed by a single surgeon at an academic medical center from 2018-2022 were included. The primary outcome was no significant progression of Cobb angle ± 5° for measurement error. Cobb angles were measured and recorded for the most recent preoperative visit and all postoperative visits. Surveys were administered via phone to assess for pain, satisfaction, and return to activities. Pain ratings were given on a visual analogue scale (VAAS) from 0-10. Results: Four patients (mean age 12 ± 1.2 years) were enrolled with mean 24.3 ± 10.2 months follow-up. Patients had a 17.8 ± 5.4° reduction in Cobb angle that was significant at most recent postoperative visit (p = 0.03). Patients reported lower current pain compared to preoperative pain (1.5 ± 1.91 vs. 6.0 ± 0.82, p = 0.005). There were no complications, revisions, or readmissions. All four patients discharged on the same day of index operation. Additionally, all patients (100%) reported their back feeling normal during both daily life and sports. Patients took on average 2.8 ± 1.0 weeks to return to school and 14.0 ± 6.9 weeks to fully return to sports. All patients (100%) reported having no stiffness, instability, or decreased range of motion. All four patients (100%) reported they were satisfied with the operative treatment and would elect to have the procedure again. Conclusion: This is the first paper to describe outpatient PVT. At minimum 12 months postoperatively, PVT patients had significantly reduced Cobb angles, no complications, no revisions, and reported being able to return to both daily life and sport. This may be a less morbid surgical approach to pediatric scoliosis.

165

P065: Posterior scoliosis surgery method that preserves motion by curve correction and fusion within the major curve(s) and by posterior vertebral tethering

Saechin Kim ¹

¹ Orthopedic Surgery, Harvard Medical School - Massachusetts General Hospital, Boston, United States

Introduction: The surgical goals for pediatric scoliosis are to arrest curve progression, create a balanced/stable spine, and preserve spinal motion by fusing fewer levels, especially in the lumbar spine. In standard posterior surgery, spinal fixation is applied above, within, and below the curve and after corrective maneuvers, the levels are fused. In doing so, levels where the disc angle fully corrects or reverses on side bending are also fused. We describe a posterior scoliosis surgical method that can change the disc angle at each individual level and allow the surgeon to either capture the change with rod for fusion or with polyester fiber for non-fusion or tethering. Our hypothesis is that this method is safe and effective and can preserve motion. Material and Methods: The novel technique is based on the observation that manipulation of rods placed intravertebral interpedicle (IVIP) in two adjacent vertebrae can directly change the disc angle between the vertebrae. In this IVIP method, IVIP constructs with open lateral offset connectors correct the deformity at the apex of the major curve(s) and the correction is captured by placing rods into the open tulips of the constructs. IVIP constructs with closed lateral offset connectors correct the deformity along the convexity of the major curve(s) above or below the apical fusion or of the minor compensatory curve and the correction is captured by polyester fiber bands for IVIP tethering. This prospective study presents the first ten consecutive cases by a single surgeon using this IVIP method (min 1 yr f/u). The number of levels fused is compared to matched standard posterior surgery controls. Radiographic measurements from xrays at first and final f/u assess for adding on phenomenon (AO) and from side bending xrays at preop and 1 year f/u determine lateral range of motion (ROM) at the tethered lumbar levels. Results: The IVIP group included 8 patients with adolescent idiopathic scoliosis (Lenke classification: 1 1A, 1 1B, 2 1C, 2 3C, 1 4C, and 1 5C), 1 with tethered cord syndrome and 1 with tuberous sclerosis (female:male 9:1, avg age = 16 yrs, range 13-19). 4 to 10 fewer levels were fused in the IVIP cases compared to the control cases (p =< 0.0001). There was no adding on phenomenon and no reoperation. 4 patients had at least 2 lumbar levels with IVIP tethering that would have been fused in standard posterior surgery and side bending xrays showed increase in the lateral lumbar ROM post op compared to preop by 18%, 22%, 43%, and 50%; in standard posterior surgery, these lumbar levels would have been fused resulting in significantly decreased lumbar lateral ROM. Conclusion: IVIP method is safe and effective and can preserve motion by fusing fewer levels at 1 year f/u. A concern with fusing fewer levels is the risk for spinal decompensation (SD) such as AO that may lead to worse outcome. IVIP tethering may prevent SD while preserving motion even in skeletally mature adolescents. Further studies are needed to show the long-term effectiveness of this IVIP method.

265

P066: Changes in curve between 40 degrees and 50 degrees in adolescent idiopathic scoliosis after skeletal maturity: over 5-year follow-up

Yunjin Nam ¹ , Young Bin Lee ¹ , Young Ha Kim ¹ , Jungwook Lim ¹ , Seong Chul Park ² , Hong Jin Kim ³ , Dong-Gune Chang ³ , Jae Hyuk Yang ² , and Seung Woo Suh ¹

¹ Department of Orthopaedics, Korea University Guro Hospital, Seoul, South Korea

² Department of Orthopaedics, Korea University Anam Hospital, Seoul, South Korea

³ Department of Orthopaedics, Inje University Sanggye Paik Hospital, Seoul

Introduction: Although adolescent idiopathic scoliosis rarely causes clinical symptoms, it causes cosmetic and emotional effects and can cause pulmonary complication with severe deformity. Female, large magnitude of curvature, and skeletal immaturity are known to be the risk factors for progression of curve. Surgical treatment is recommended if curvature is larger than 50 degrees even after skeletal maturity or if curvature is larger than 40 degrees with remaining growth potential. However, few articles have reported on progression of curve between 40 and 50 degrees after skeletal maturation. Material and Methods: This study is a single center, retrospective study using medical record. From 1999 to 2016, 87 patients were included. The inclusion criteria were as follows: (i) skeletally matured patients who diagnosed with adolescent idiopathic scoliosis, (ii) who have curve between 40 and 50 degrees, and (iii) who followed up more than 5 years after initial period without surgical treatment. Skeletal maturation was defined as Risser stages 4 and 5. The initial period was defined as the first time point that satisfies both (i) and (ii). The sex, age, magnitude of curve, location of apex, Risser stage, height and weight were measured at initial period. The age, magnitude of curve, height and weight were also measured at end of follow-up. A change in the magnitude of curve, magnitude of curve per a year, height and weight were measured. More than 5 degrees of progression in curve was defined as significant curve progression. Results: A total of 97 curves were observed in 87 patients (19 male, 69 female). Mean follow-up period was 97 months. The mean age was 14.6 years at initial period and 22.6 years at the end of follow-up. Initially, 65 patients had Risser stage 4 and 32 patients had Risser stage 5. The mean magnitude of curve was 42.6 degrees at initial period and 45.1 degrees at the final follow-up. The mean change in curve was 2.7 degree and the annual change was 0.35 degrees. Progression in curve more than 5 degrees were observed in 38 cases (39.2%). In 24 cases (24.7%), the magnitude of curve reached 50 degrees at the end of follow-up. There was a difference only in the age (13.9 vs. 15.0 years, p = 0.004) and Risser stage (stage 4: 47.7% vs. stage 5: 5.21%, p = 0.014) between the group with a significant curve progression or not. Risser stage (p = 0.05) and magnitude of curve at initial period (p = 0.045) showed significant difference between the group of curve size reached 50 degrees or not. Conclusion: In patients with AIS, significant curve progression was observed at 39.2% even after skeletal maturation. Younger age and Risser stage 4 were risk factors of curve progression. Larger initial curve and Risser stage 4 were risk factors of curve progression over 50 degrees.

267

P067: The accuracy and safety of a pedicle screw using the freehand technique in minimally invasive scoliosis surgery

Yunjin Nam ¹ , Dong-Gune Chang ² , Sangmin Lee ¹ , Young Ha Kim ¹ , Jungwook Lim ¹ , Seong Chul Park ³ , Hong Jin Kim ² , Jae Hyuk Yang ³ , and Seung Woo Suh ¹

¹ Department of Orthopaedics, Korea University Guro Hospital, Seoul, South Korea

² Department of Orthopaedics, Inje University Sanggye Paik Hospital, Seoul, South Korea

³ Department of Orthopaedics, Korea University Anam Hospital, Seoul, South Korea

Introduction: The safety and clinical usefulness of minimally invasive scoliosis surgery (MISS) has been reported in various studies. However, freehand pedicle screwing in MISS remains technically challenging. The purpose of this study is to evaluate the accuracy and safety of pedicle screw placement using the freehand technique in adolescent idiopathic scoliosis (AIS) patients treated with MISS compared to conventional open scoliosis surgery (COSS). Material and Methods: We included 76 patients who underwent deformity correction for AIS. CT scans were used to assess screw violations divided into two groups according to the surgical technique: MISS or COSS. Anterior violations were classified into Grade 0, 1 (no contact with internal organs), and 2 (contact with internal organs). Medial and lateral violations were classified into Grade 0, 1 (< 2 mm), and 3 (≥ 2 mm). Grade 2 were considered critical violations. Results: A total of 630 and 634 pedicle screws were inserted in the MISS and COSS groups, respectively. The overall critical violation rates of the MISS and COSS groups were 16.8% (106 screws) and 14.0% (165 screws) (p = 0.116). Medial critical violations on the left side in the middle thoracic region frequently occurred in the MISS group compared to the COSS group (p = 0.003). There were no statistical differences in the complications. Conclusion: Pedicle screw placement using the freehand technique in MISS for AIS patients provided similar accuracy and safety compared to COSS. Pedicle screws inserted on the left side of the middle thoracic region, exhibited more medial critical violations in the MISS group.

401

P068: Substantial mismatch of skeletal maturity assessment between Risser sign and Simplified Skeletal Maturity Scale (SSMS) / Thumb Ossification Composite Index (TOCI) in patients with adolescent idiopathic scoliosis

Masaaki Chazono ¹ , Takashi Inoue ² , and Shintaro Obata ²

¹ Orthopaedic Surgery, Utsunoimya National Hospital, Utsunomiya, Tochigi, Japan

² Orthopaedic Surgery, Jikei University School of Medicine, Minato-ku, Tokyo, Japan

Introduction: The Risser sign (RS) has been used as a primary skeletal maturity marker in patients with adolescent idiopathic scoliosis (AIS) for more than half a century. However, there is considerable argument about the ambiguous visibility of iliac apophyseal ossification, decreased intra- and inter-rater reliability, and the insensitivity of the Risser sign in predicting the timing of peak height velocity (PHV) and estimating the remaining growth potential. Additionally, PHV and two-thirds of pubertal growth typically have passed before the first stage of RS. Nevertheless, it is still commonly used to manage the evaluation of skeletal maturity of AIS patients in clinical practice. Currently, there are several radiograph-based skeletal maturity scoring systems used to gauge the amount of childhood growth and determine the timing of PHV. In particular, hand skeletal maturity systems such as the Simplified Skeletal Maturity Scale (SSMS) or the Thumb Ossification Composite Index (TOCI) are popular in the attempt to predict the occurrence of PHV in adolescents. This study aims to compare the frequency of the mismatch in estimation of HV between Risser sign (RS) and SSMS/TOCI stages in adolescent idiopathic scoliosis (AIS) patients. Material and Methods: One hundred twenty-six female patients with AIS were included. The mean age of the patients was 12.9 years. A whole spine and hand X-rays were obtained to establish skeletal maturity stage according to RS, SSMS, and TOCI systems. A mismatch resulting in overestimation (MOE) with RS compared to SSMS/TOCI was defined as the combination of RS 2-4/SSMS 3-5 or RS 2-4/TOCI 4-6, whereas a mismatch resulting in underestimation (MUE) with RS and SSMS/TOCI was defined as RS 0-1/SSMS 6-7 or RS 0-1/TOCI 7-8. Height velocity (HV) was compared between MOE/non-MOE and MUE/non-MUE groups. Results: Between RS and SSMS, the rates of the MOE and MUE groups were 9.3% and 1.6%, respectively. Between RS and TOCI, rates were 7.1% and 1.6%, respectively. With the combination of RS and SSMS stages, an estimate of HV of 5.6 cm/year in the MOE group was significantly larger than that of 2.9 cm/year in the non-MOE group, and 3.7 cm/year in the MUE group was significantly smaller than 6.7 cm/year in the non-MUE group. Likewise, with the combination of RS and TOCI stages, an estimate of HV of 5.6 cm/year in the MOE group was significantly greater that of 2.8 cm/year in the non-MOE group, and 3.7 cm/year in the MUE group was significantly smaller than 6.7 cm/year in the non-MUE group. Conclusion: The present study showed that approximately 10% of mismatch of those skeletal maturity assessments in RS/SSMS and RS/TOCI groups occurred. Given those results, the authors advocate that either SSMS or TOCI classification rather than RS should be used for managing patients with AIS.

465

P069: Quality of life and satisfaction in patients with adolescent idiopatic scoliosis surgically managed in a third-level hospital in Mexico

Cristian Yiovanny Pinzón Largo ¹ , and Hugo Vilchis Samano ¹

¹ Hospital de Traumatologia y Ortopedia Lomas Verdes, Estado de Mexico, Naucalpan de Juarez, Mexico

Introduction: Deciding on the management of adolescent idiopathic scoliosis is not always easy, it requires a joint decision between the medical team, family members and the patient. Patient-reported outcome measures have gained interest in recent years to assess treatment outcomes, and could help us have tools to decide the best option for each patient. Objective: Evaluate the quality of life and satisfaction with the spinal fusion arthrodesis treatment by filling out a questionnaire of results filled out by the patient (SRS-22). Material and Methods: Cross-sectional, descriptive, retrospective design, patients diagnosed with adolescent idiopathic scoliosis surgically managed between 2016 and 2021 at Lomas Verdes Hospital in Naucalpan, Mexico were included. The patient filled out the SRS-22 questionnaire before the surgical procedure and at least 12 months later. Results: Data were obtained from 54 patients, 44 (74%) women and 10 (18%) men, with an age range at the time of surgery between 10 and 17 years (mean 14.5 years), Cobb angles between 45 and 94 degrees in its main curvature (average 63.2 degrees). Time elapsed between the procedure and the completion of the questionnaire 1-5 years (average 2.5 years). Scores were obtained before the procedure (total score 3.6 function 4.1, pain 3.7, body image 2.3, mental health 3.8), after the surgical procedure total score 4.4, function 4.4, pain 4.5, body image 4.2, mental health 4.3, Significance was obtained statistics both in total score and in each of the individual topics of the questionnaire in the following order: body image (1.1E-27), total score (9.0668E-17), pain (2.8E-09) mental health (1.2E-05), function (8.3 E-4). With a satisfaction with the surgical treatment of 4.8. Conclusions: Patients diagnosed with adolescent idiopathic scoliosis managed with posterior instrumented arthrodesis show improvement in both the total score and the individual items of the SRS-22 questionnaire after the surgical procedure, all with statistical significance, with more strength in the imaging component. body and pain, in addition to a high degree of satisfaction reported by patients.

487

P070: Hybrid posterior instrumentation and mini-open anterior release for treatment of adolescent idiopathic scoliosis: a retrospective analysis

Vijay Kumar Loya ¹ and Charanjit Singh Dhillon ²

¹ MRMCW, Orthopaedics & Spine, Hyderabad, India

² MIOT International, Spine, Chennai, India

Objective: A retrospective analysis of the role of hybrid instrumentation, mini-open anterior release in the treatment of adolescent idiopathic scoliosis. Methods: Medical records and imaging of 43 patients operated between January 2008 to June 2014 were retrospectively analyzed. Subgroup analysis was done for patients managed with mini-open anterior release+ posterior instrumentation [APSF](13 patients) vs. all posterior approach [PSF] (30 patients). Hybrid instrumentation was used involving the use of hooks and sublaminar wires in conjunction with pedicle screws. A mini open thoracotomy (< 10 cm incision) was used for anterior release. The free-hand technique was used to insert all the pedicle screws. Stagnara wake up test was used after correction maneuvers. Appearance scores were collected before and after the surgery. Results: The mean age of operated cases was 15.2 (range 10-28) years, and majority cases were females (86.05%). The average follow-up time was 46.86 months. Lenke 1 was the most common curve pattern [74.42%]. Significant correction was achieved and maintained at the end of the follow-up period for all the curve patterns [PT 66.67%, MT 75.20%, DL/L – 70.83%]. The sagittal plane alignment was maintained in all but one patient. Mean [81.25° vs. 49.16°] and bending [66.89° vs. 32°] Cobb angles were significantly higher in the APSF group. Improvement in the appearance scores was significant for both the groups [APSF - 25 vs. 10.78, PSF - 18.9 vs. 9.03]. Two of the APSF patients had prolonged ICU stay. Two patients required secondary suturing for wound dehiscence. One case had chylothorax, which was medically managed. One patient required revision surgery for hook pull-out after 34 months of index surgery. There were no neurological deficits, vascular or visceral injuries. Conclusion: Adolescent idiopathic scoliosis represents a different set of challenges in developing nations with limited re- sources. Hybrid instrumentation with the use of sublaminar wires is still an effective and valid strategy to reduce the cost of spinal deformity surgeries. A mini-open anterior release, along with the use of posterior hybrid instrumentation, helps achieve optimal coronal and sagittal correction, especially in bigger and stiffer curves, compared to all posterior hybrid constructs. A decision tree is provided to guide the treatment selection for the adolescent idiopathic scoliosis cases.

504

P071: Medium term outcomes in early onset scoliosis patients who have graduated from magnetically controlled growing rods to final fusion

Henry Turner ¹ , Robin McManus ¹ , Flavia Alberghina ¹ , Jim Kennedy ¹ , Jacques Noel ¹ , and Patrick Kiely ¹

¹ Trauma and Orthopaedic Surgery, Children's Health Ireland (CHI) at Crumlin, Dublin, Ireland

Introduction: There is paucity in the literature regarding outcomes in patients with early onset scoliosis (EOS) who have graduated from magnetically controlled growing rods (MCGR) to final fusion (FF). We present our findings analyzing EOS patients who graduated to FF from MCGR. Material and Methods: All EOS patients who had FF after MCGR treatment and had a minimum follow-up time of 1 year were included. The outcomes included additional unplanned surgeries (AUS), pre-and post-operative Scoliosis Major Cobb (MCA) and Major Kyphosis (MKA) angles, space available for lung ratios (SALR), T1- T12 and T1-S1 heights. Results are presented as means with standard deviation (SD) and 95% Confidence interval (CI). Results: 16 patients (9 Females and 7 Males) were included. C-EOS classification breakdown was as follows: 1 Congenital, 6 Idiopathic, 4 Syndromic and 5 Neuromuscular patients. 14 patients were excluded due to insufficient follow-up time. The mean age at index MCGR surgery was 9.8 years (SD ±2.2, CI 8.6 - 10.9) and the mean implant time of MCGR instrumentation was 38 months (SD ± 15, CI 30 - 46). The mean follow-up after FF was 27 months (SD ±15, CI 20 - 37). Two (12.5%) patients needed unplanned additional surgery after FF complications. All complications were related to wound breakdown and infection. The preoperative and latest MCAs post MCGR insertion were 73° (SD ±13, CI 66-80) and 51° (SD ±14, CI 44 - 59), respectively. The final MCA after FF was 30° (SD ±12, CI 25 - 38). The preoperative and latest MKAs post MCGR insertion were 37° (SD ±25, CI 24 - 50) and 33° (SD ±25, CI 24 - 42) respectively. The final MKA after FF was 38° (SD ±19, CI 29 - 50). This is a significant final decrease of 59% (p < 0.001) in the MCA but not in the MKA (p = 0.54). The preoperative and latest SALRs post MCGR insertion were 90% (SD ± 113, CI 83-96) and 98% (SD ±5, CI 96-101), respectively. The final SALR after FF was 99% (SD ±7, CI 94-103): a final significant increase of 9% (p < 0.001). The preoperative and latest T1- T12 heights post MCGR insertion were 184mm (SD ±22, CI 169 - 199) and 224 mm (SD ±35, CI 205-243) respectively. The final T1- T12 height is 245 mm (SD ±33, CI 224-264), indicating a final increase of 33% (p < 0.001). The preoperative and latest T1-S1 heights post MCGR insertion were 291 mm (SD ±54, CI 262-320) and 354 mm (SD ±62, CI 321 - 387), respectively. The final T1- S1 height after FF is 378mm (SD ±60, CI 343 - 413), showing a total increase of 30 % (p < 0.001). Conclusion: Our findings show that EOS patients who have graduated to final definitive fusion (FF) from magnetically controlled growing rods (MCGR) can achieve satisfactory outcomes over the short to medium term. Our study also shows that there is potential for further deformity correction when progressing to FF from MCGR. It must be noted that additional surgery may be required after FF in some cases.

593

P072: Nonunion and implant failure following kyphectomy for severe khyphosis secondary to myelodysplasia - A case report

Rohan Parihar ¹ , Samir Dalvie ¹ , Kshitij Chaudhary ¹ , and Pramod NK ¹

¹ Spine, P.D. Hinduja Hospital, Mumbai, India

Introduction: 15% of patients with open neural tube defects develop severe kyphosis requiring kyphectomy, a high-risk surgery .50% cases develop non-union and implant failure. We presented an unreported cause of non-union at the rudimentary L5-S1 disc following a kyphectomy. Also, we describe preoperative planning using 3D printed spine model of patient. Materials and Methods: 10-year-old girl, previously operated for meningomyelocele closure at age 6 months, presented with a non healing ulcer that the apex of lumbar kyphosis. She has no neurological function below T9 since birth. She underwent a cordectomy at T9 level, and one month later she underwent a kyphectomy from L1-L4, with docking of T12 over L5 with posterior fusion from T7 to pelvis. The surgery planned on her real-size 3D printed model. Results: At 3 months, postoperative CT scan showed union at the kyphectomy site. At 6 months after surgery, she had kyphosis recurrence and failure of bilateral iliac screws. Progressive widening of the rudimentary L5-S1 disc was identified as the cause of the failure. The pseudarthrosis was repaired and revised iliac screws were augmented with modified Dunn-McCarthy rods. The rods for this fixation were precontoured on the 3D printed model and autoclaved preoperatively for use during the surgery. 2-year follow up CT scan shows complete fusion at the nonunion site without any wound problems. Conclusion: Nonunion at adjacent disc levels is known following kyphectomy, we present an unusual cause of nonunion at the rudimentary L5-S1 disc (S1 sacralized). During surgery, special attention should be given to fusion of all disc levels, including rudimentary disc that lie within the fixation levels. 3D printed model are of enormous help in planning this complex surgery.

616

P073: Interobserver findings in the validation process of an smartphone application as a tool for screening patients with scoliosis

Andre Castilho ¹ , Pedro Torres ¹ , Asdrubal Falavigna ² , Henrique Darmstadter ¹ , Orlando Righesso ² , and Kamila Rayane Campos Lopes ¹

¹ Spine Surgery, Hospital Unimed, Belo Horizonte, Brazil

² Health Science Postgraduate Program, Universidade de Caxias do Sul (UCS), Caxias do Sul, Brazil

Introduction: Scoliosis is a spinal condition that is common among children, adolescents, and young adults, affecting approximately 1%-4% of children and adolescents worldwide. Most patients with scoliosis have a mild abnormal curvature of the spine and the curvature does not progress in adulthood. However, a more pronounced curvature and a late diagnosis can lead to reduced quality of life of patients. Early diagnosis of scoliosis allows treatment in its initial stages and avoids surgical treatment and deformity progression. The present study aims to analyze the best correlated clinical parameters among examiners using an application for smartphone developed for screening of idiopathic scoliosis and to evaluate the friendly use of this application. Material and Methods: This study assesses a smartphone mobile application that analyzes several clinical parameters related to the changes observed in scoliosis. Comparative analyses between medical and non-medical examiners were performed to define parameters with the greatest inter- observer correlation. Results: 89 participants. None of the parameters between ExL and Ex1 achieved almost perfect concordance. Substantial concordance was noted in reduced lordosis and mid-thoracic scoliometer. Fair agreement was achieved in increased kyphosis, presence of a hump and waist asymmetry. All the other parameters had slight or poor agreement. The presence of a hump, scapular asymmetry, and waist asymmetry were statistically significant changes found between examiners. In subjects diagnosed with shoulder asymmetry, scapular, waist and pelvic, ribcage asymmetry was found between ExL and Ex1 with statistical difference. None of the parameters between Ex1 and Ex2 achieved almost perfect and substantial concordance. Moderate concordance was noted in pelvic asymmetry. Ribcage asymmetry and pelvic asymmetry had fair concordance. In subjects diagnosed with shoulder asymmetry, scapular, waist and pelvic, ribcage asymmetry had statistically significant concordance between them. The results of the app friendly use evaluation showed complete satisfaction of users in effectiveness, easiness to learn, productive possibility and system interface satisfaction. The worst results in the evaluation were easiness to use and capacity of solving problems by the system and the user. Conclusion: This study is the first to evaluate almost all the parameters in the physical examination between medical and nonmedical examiners to improve the screening of adolescent idiopathic scoliosis. Our findings showed that reduced lordosis, mid thoracic scoliometer, presence of hump, waist asymmetry, increased kyphosis, ribcage asymmetry and pelvic asymmetry had substantial to fair concordance. Shoulder asymmetry, one the parameters used as an alert in the app showed a poor interobserver correlation. The inclusion of several physical examination parameters of a patient with scoliosis will allow an evaluation of which parameters present the greatest agreement, while outpatient assessment by a spine specialist will permit the validation of the application as a screening tool. In our initial results reduced lordosis, mid-thoracic scoliometer and pelvic asymmetry had better agreement between examiners. These parameters needed to be checked in outpatient assessment to be validated. The main objective of the study is to create a simple and effective tool for the screening of adolescent idiopathic scoliosis by non-medical professionals, especially in the school environment.

621

P074: Is shoulder imbalance a useful parameter in the screening of idiopathic scoliosis? A preliminary study

Pedro Torres ¹ , Andre Castilho ¹ , Asdrubal Falavigna ² , Orlando Righesso ² , David Israel ¹ , and Kamila Rayane Campos Lopes ¹

¹ Spine Surgery, Hospital Unimed, Belo Horizonte, Brazil

² Health Science Postgraduate Program, Universidade de Caxias do Sul (UCS), Caxias do Sul, Brazil

Introduction: Adolescent idiopathic scoliosis is a structural, lateral, rotated curvature of the spine that arises in otherwise healthy children at or around puberty. It is the most common spinal disorder in adolescents, with a prevalence of 1-4%. Early diagnosis of scoliosis allows timely treatment of the condition in its initial stages, further avoiding surgical treatment and deformity progression. Consequently, scoliosis screening has been advocated for early detection of reversible spinal curves before their progression. Screening of idiopathic scoliosis is widely discussed in medical literature. It involves different types of assessment methods, including appearance inspection, forward bending tests, scoliometer measurements, and individual Moiré topography, which are direct and easily accessible. Main findings of scoliosis on physical examination are asymmetry of the shoulders, scapulae, pelvis, trunk, and ribcage. Adam's forward bend test is used to assess the presence of a hump and quantify the lateral curvature; it is considered essential for the screening of scoliosis in schools. In The Netherlands and Singapore, countries with strong scoliosis screening program, the most frequent parameter are the Adam’s forward bending test and the measuring of trunk rotation using a scoliometer. Between all parameters on physical examination, shoulder imbalance has received a great deal of attention among spine surgeons and researchers. The normal healthy population is considered to have level shoulders. In any measured biological parameter, it is of prime importance that the variability of what is classified as ‘normal’ is known, especially if surgery is planned to correct that parameter from what is judged as ‘abnormal’ back to being ‘normal’. To define what is normal, Kuklo et al. proposed shoulder balance as a less than 1 cm side-to-side difference between the shoulders on clinical examination in adolescent idiopathic scoliosis patients. The deficiencies of traditional assessment methods in screening scoliosis remain unresolved. Regardless, a most effective method is still crucial for reducing morbidities associated with scoliosis. The present study aims to analyze the use of shoulder imbalance as a parameter for scoliosis screening and its relationship with other parameters of physical examination. Material and Methods: This study assesses a smartphone application that analyzes several parameters of the physical examination in adolescent idiopathic scoliosis. Medical and non-medical examiners applied the screening tool in students in a public school and in a sports club. After data collection, interobserver correlation was done to verify shoulder imbalance and to compare shoulder imbalance with Adam’s bending test and with trunk rotation. Results: 89 participants were examined, 18 women and 71 men. The mean age of subjects from the public school was 11.30 years and from the sports club was 11.92 years. The examiners had poor to slight interobserver concordance on shoulder asymmetry in the anterior and posterior view. No significant statistical correlation was found between shoulder asymmetry and positive Adam’s forward bending test. Conclusion: Our preliminary study shows that the shoulder asymmetry has a poor correlation with Adam’s forward bending test and measuring trunk rotation using a scoliometer. Therefore, the use of shoulder imbalance might not be useful for idiopathic scoliosis screening.

628

P075: Surgical treatment of severe adolescent idiopathic scoliosis through one-stage posterior-only approach: systematic review and meta-analysis

Giovanni Viroli ¹ , Matteo Traversari ¹ , Marco Manzetti ¹ , Francesca Barile ¹ , Fabio Vita ¹ , Tosca Cerasoli ¹ , Azzurra Paolucci ¹ , Alberto Ruffilli ¹ , and Cesare Faldini ¹

¹ 1 ^st Orthopaedic and Traumatologic Clinic, IRCCS Istituto Ortopedico Rizzoli, Bologna, Italy

Introduction: Severe adolescent idiopathic scoliosis (AIS) is a complex, stiff, three-dimensional spinal deformity whose treatment remains controversial. Historically, severe AIS has often been treated with combined anterior release, followed by posterior correction and instrumentation, resulting in good three-dimensional curve correction, but with high risk of pulmonary complications. Some authors have also used preoperative traction or internal distraction as a part of a staged correction, in order to achieve better correction and shorter fusion. However, pre-operative traction implies an increased risk of perioperative complications such as pin loosening, pin tract infection and cranial nerve palsies. Combined anterior and posterior or all-posterior vertebral column resection has also been used to treat severe and rigid scoliosis, but this demanding procedure is affected by a considerably high rate of perioperative complications. Then, the introduction of all pedicle screws constructs allowed the all-posterior procedures to gradually gain popularity due to the high reliability of three-columnar fixation systems. In fact, powerful corrective forces were exerted and spine mobilization through anterior release was not necessarily needed. Aim of this metanalysis is to systematically review the literature and analyse the results of one-stage all posterior fusion for severe adolescent idiopathic scoliosis. Material and Methods: A systematic search of articles about one stage posterior spinal fusion for severe adolescent idiopathic scoliosis was conducted according to the PRISMA guidelines. Studies were included if they involved patients affected by severe adolescent idiopathic scoliosis who underwent surgical correction through one stage posterior-only approach [variably combined with posterior column osteotomies (PCOs), maximum grade 2 S] and if they described perioperative outcomes including correction rate and complications. Only articles in English who met the PICO (Population, Intervention, Comparison and Outcomes) criteria on systematic reviews were included. Randomized controlled trials (RCTs), prospective and retrospective cohort studies (PCS and RCS) and case series (CS) were considered for inclusion. Data about population, pre and postoperative radiographical data, surgical procedure details and complications were extracted. Metanalyses were performed with the application of a random effect model. Results: Thirteen studies (613 patients) were included. The mean Cobb angle of the major curve varied from 80.0° ± 7.3 to 110.8° ± 12.1. Meta-analysis showed a comprehensive coronal correction rate of the major curve of 58.6%, a comprehensive operative time of 252.1 min and a comprehensive EBL of 866.5 mL (95% CI 659.3 - 1073.6, I²≈0%). A total of 47 complications (5.4%) were reported. Overall metanalysis showed a major complication rate of 4%. In 6 cases revision surgery was needed. Conclusion: Our results suggest that posterior-only approach (eventually combined with PCOs) offers enough corrective power to effectively treat severe scoliosis curves, with acceptable blood loss and complications rate. Further, it allows to avoid possible adverse events and pulmonary function impairment related to anterior approaches. Moreover, it is not burdened by the high complications rate of VCR.

671

P076: Correlation between single pulse and pulse train stimulation during neuromonitoring of thoracic pedicle screws in scoliosis surgery

Luiz Eduardo Almeida ¹ and Luis Eduardo Carelli Texeira da Silva ²

¹ Spine Surgery, Children’s State Hospital, Rio de Janeiro, Brazil

² Spine Surgery, National Institute of Traumatology and Orthopedics, Rio de Janeiro, Brazil

Introduction: The use of thoracic pedicle screws (TPSs) during scoliosis surgery entails an inherent risk of neurological deficit. Triggered electromyography (t-EMG) is an accurate neuromonitoring test for detection of malpositioned TPSs. However, single-pulse (SP) t-EMG stimulation has shown variable capability for detecting medial pediclebreaches, while pulse-train (PT) t-EMG could be more accurate. The aim of this study was to analyze the correlation between SP t-EMG and PT t-EMG. Material and Methods: This retrospective study included 20 patients who underwent scoliosis correction with 294 TPSs placed. A total of 588 tests with both SP t-EMG and PT t-EMG were performed, analyzed, and compared. The results of both t-EMG techniques were stratified into 3 different groups according to threshold obtained: group 1 (≤ 6 mA), group 2 (6.1–11.9 mA), and group 3 (12 mA). A generalized linear modelwas used to analyze the correlation between the methods. Results: SP t-EMG elicited response in 5 screws (1.7%) at ≤ 6 mA, 28 screws (9.5%) at 6.1-11.9 mA, and 261 screws (88.8%) at 12 mA. PT t-EMG elicited response in 16 screws (5.4%) at ≤ 6 mA, 30 screws (10.2%) at 6.1-11.9 mA, and 248 screws (84.4%) at 12 mA. There is a strong positive and significant association between SP t-EMG and PT t-EMG with a decrease ratio of 2% (95% confidence interval 1% to 3%). Conclusion: SP t-EMG and PT t-EMG stimulation techniques had similar results when the stimuli were applied to TPSs, but PT t-EMG may have better efficacy in low-threshold group.

706

P077: Minimally invasive surgery vs standard posterior approach in the treatment of adolescent idiopathic scoliosis: a two years follow up retrospective study

Giovanni Ciani ¹ , Francesco Vommaro ¹ , Chiara Cini ¹ , Bruna Maccaferri ¹ , Luca Boriani ¹ , Elisa Carretta ² , and Alessandro Gasbarrini ¹

¹ Spine Surgery

² Medical Statistics, Istituto Ortopedico Rizzoli, Bologna, Italy

Study Design: Monocenter retrospective control study. Purpose: To compare the safety and efficacy of posterior minimally invasive surgery (MIS) to standard posterior spinal fusion (PSF) surgery in adolescent idiopathic scoliosis (AIS). Methods: We retrospective collected 111 patients with Lenke type 1-6 AIS with Cobb angle curve ≤ 70° who treated with MIS (n = 47) or PSF (n = 64) between February 2018 and February 2020. All of them attempted an outpatient follow-up consisting of clinical and radiological evaluation for at least two years from surgery. We collected values of Cobb angles degrees to study the correction rate of the structural major curve. MIS technique was applied via 2 midline noncontiguous skin incisions. Smaller incisions and muscle-spearing approach could reduce the blood loss significantly. We obtained an RD maneuver that takes advantages of the flexibility resulting from the rising of the level arm and the consequent force exerted at the caudocranial edges using MIS. Level of apical and distal fusion, operative time, preoperative hemoglobin and second postoperative day hemoglobin, full length of hospitalization and time to accomplish verticalization were recorded. NRS medium score was assessed immediately after surgery and during the whole physiotherapeutic treatment. Complications recorded included: temporary or permanent nerve lesions, intraoperative or postoperative nerve lesions, fever, surgical wound dehiscence and infection, mechanical complication and postoperative pain assessment. Results: There was no significant difference between the 2 groups in terms of radiographic and clinical features. The correction rates of the structural curve were not observed to be significantly different between group 1 (MIS) and 2 (PSF) (64.6% ± 11.7 vs 60.9% ± 13.2) as for the correction rate of secondary curve (59.1 ± 13.2 vs 59.2 ± 12.4). The two groups had non significantly longer operative time (209.9 ± 34.8 min vs 215.2 ± 45.2). The MIS group had a significantly lower decrease of postoperative hemoglobin in comparison to PSF group (2.8 ± 1.3 vs 4.3 ± 1.5) (p < 0.001). The evaluation of pain using NRS score showed a lower score in MIS group (1.8 ± 0.8 vs 2.8 ± 0.9). PSF group was observed to have significantly lengthier time of hospitalization (5.2 ± 1.4 vs 6.3 ± 2.9) (p = 0.02) than MFS group. Complications were more frequent in PSF group rather than in MFS group (11 vs 3), with no infectious complication in MIS group and 6 events of post operatory infections in PSF group. Only one mechanical complication (breakage of rod) was observed in MSF group. The mechanical complication recorded was successfully treated with a surgical approach. Conclusion: Posterior MIS is a safe and capable alternative to standard open approach for Lenke Type 1-6 AIS patients with curves < 70°, with analogue capacity of scoliosis correction. The average number of fusion segments in MIS group was lower than in PSF group (9.1 vs 10.2). For these reasons MIS technique could reduce the risk of post-operative adding-on and permits to spare motion segments. Even though there were no difference in term of operative time between MIS and PSF, our results showed that MIS had the advantages of less blood loss, length of stay and pain.

786

P078: Experience using internal distraction systems for scoliosis correction between surgical stages

Andres Reinoso ¹ , Fernando Alvarado Gómez ¹ , Nahala Aborashed-Amador ¹ , Martha Cecilia Santos-Barros ¹ , Maria Garcia-Rueda ¹ , Maria Camila Giraldo Bernal ¹ , Mario Herrera Méndez ¹ , and Carlos Montero-Silva ¹

¹ Instituto Roosevelt, Bogota, Colombia

Introduction: In the surgical treatment of severe scoliosis, the risk of neurological injury increases when definitive correction is attempted in a single stage. For this reason, devices like the gravitational traction halo have been widely used over the years to partially and progressively correct the deformity between surgical stages in an attempt at improving lung capacity and reducing the risk of spinal cord ischemia. However, this treatment is not risk-free. Complications have been described, including transient nystagmus, osteitis, upper limb paresthesia and myelopathy progression in up to 27% of cases. In 2006, Buchowski et al. described the use of internal distraction as a method for temporary correction in order to reduce deformities on the coronal and sagittal planes before definitive fusion. Material and Methods: Retrospective case series including 9 patients in total, with 7 patients requiring a two-stage procedure and 2 requiring three stages. Patients considered for more than one surgical stage in whom the internal distraction system was used between surgeries were included. Demographic, clinical, radiological, and surgical variables, as well as associated complications, were assessed. Results: Average blood loss at the time of definitive fusion was 911 ml, approximately. The mean number of osteotomies was 4.1, the most frequently used being Ponte osteotomy. Additional techniques included oblique osteotomy and corpectomy. The distraction system was used during a mean of 11,11 days. Pre-operatively, average Cobb angle was 88°; with the distraction system, the size of the curvature diminished by 30.6% in average, with a residual deformity of 32° (36.4% of the initial curve). Complications included one catheter-associated bacteremia, one urinary tract infection, two cases of durotomy, and one case of phlebitis. No surgical site infection complications occurred and there was no loss of somatosensory evoked potentials. Conclusion: The use of internal distraction systems in the intervening time between surgical procedures for the correction of severe scoliosis has been shown to diminish the complexity and number of osteotomies required to restore coronal balance. This technique is associated with lower bleeding rates and a lower risk of nerve damage.

833

P079: Tranexamic acid reduces preoperative blood loss in pediatric spinal deformity surgery - a retrospective analysis in non-idiopathic scoliosis patients

Anna Bichmann ¹ , Ali Güven ² , Edda Klotz ¹ , Thomas Ocker ¹ , Pumberger Matthias ² , and Friederike Schömig ²

¹ Department of Anesthesiology and Intensive Care Medicine

² Center for Musculoskeletal Surgery, Charité - Universitätsmedizin Berlin, Berlin, Germany

Introduction: Posterior spinal fusion in scoliosis patients is associated with high volumes of perioperative blood loss and transfusion requirements. Even though it has previously been shown that patients with non-idiopathic scoliosis tend to lose higher blood volumes and more often require allogenic blood transfusions perioperatively compared with idiopathic scoliosis patients, there is a lack of studies investigating the effect of tranexamic acid (TXA) in this patient group. We therefore analyzed the efficacy of TXA in reducing perioperative blood loss and blood transfusion requirements in non-idiopathic scoliosis patients undergoing primary posterior spinal fusion. Material and Methods: We retrospectively included patients who underwent primary posterior fusion for non-idiopathic scoliosis between November 2014 and December 2020. Patients were assigned to the TXA- or No-TXA-group depending on intraoperative administration of TXA. Perioperative data including demographic and laboratory data, spinal levels operated on, surgical duration, hemodynamic parameters, administration of blood products, crystalloid fluids, and catecholamines as well as radiographs were reviewed. Descriptive summaries for the TXA- and No-TXA-groups were analyzed using Pearson Chi-squared test, Student t-test, or Mann-Whitney-U-test. Changes in laboratory data were compared using the two-way repeated-measures analysis of variance (ANOVA). The influence of different variables on the estimated blood loss was calculated by multiple linear regression. The association of various parameters with surgery duration was analyzed by calculating Spearman’s rank correlation. Results: Sixty-six patients were included, 35 of which received intravenous TXA intraoperatively. Demographic and preoperative laboratory data did not show significant differences between the two groups. Surgical duration (p = 0.009) and number of levels fused (p = 0.004) were significantly higher in the TXA-group. Estimated blood loss (p = 0.531) and administration of allogenic packed erythrocytes (p = 0.508) did not differ significantly. TXA administration had a significant negative effect on estimated blood loss (B = -510.98, p = 0.020). Postoperative Hb-levels were significantly higher in the TXA-group (9.13 ± 1.27 g/dL) compared with the No-TXA-group (8.41 ± 1.47 g/dL) on the first postoperative day (p = 0.038). There were no postoperative thromboembolic events prior to patient discharge in either group. Other postoperative complications including systemic inflammatory response syndrome (p = 0.818), hypovolemia (p = 0.177), pneumonia (p = 0.628), pleural effusion (p = 0.177), urinary tract infection (p = 0.628), and gastrointestinal complications (p = 0.209) did not differ significantly between the two groups. Conclusion: Despite longer surgical durations and more spinal levels fused, patients receiving TXA when undergoing primary posterior spinal fusion for non-idiopathic scoliosis had similar estimated perioperative blood loss and allogenic transfusion rates as patients who did not receive TXA. We show that TXA has a significant negative effect on estimated blood loss in non-idiopathic scoliosis patients. Thus, as already practiced in idiopathic scoliosis surgery, TXA should be considered to be part of blood management strategies in non-idiopathic scoliosis surgery as well.

852

P080: The etiological understanding of spine deformities in patients with neuromuscular disorders

Egor Filatov ¹ , Olga Sergeenko ¹ , and Polina Ochirova ¹

¹ Iizarov Centre, Kurgan, Russian Federation

Introduction: The etiology understanding is the corner stone for proper management of the spine deformities in patients with neuromuscular disorders. Material and Methods: Progressive spine deformities have been encountered in 71 patients. All showed different forms of neuromuscular disorders. We proceeded with applying prompt evaluation criteria which was mainly based on the etiological diagnosis of each type of NMS (clinical phenotype and genotype). Assessing the Functional Independence Measure (FIM), we observed deterioration in some aspects. The Cobb’s angle was assessed in two occasion’s i.e prior to corrective surgeries plus the post-surgery results. Followed by one year postoperative re-assessment. Surgical corrections have been performed via posterior pedicle screw fixation. Results: Surgical correction to re-align the C-shaped thoracolumbar scoliosis. Lumbar hyper lordosis were common in cerebral palsy patients, though decreased thoracic kyphosis or even thoracic lordosis occurs more frequently in Duchenne Muscular atrophy patients. There was noticeable improvement in functional status according to Functional Independence Measure (FIM). Conclusion: Etiology understanding is the paramount element in re-aligning corrective surgeries of the spine in patients with progressive spine deformities. We concluded that rigid hyper lordosis has been and still the key problem encountered in patients with neuromuscular disorders.

858

P081: Congenital lordosis: a systematic review

Egor Filatov ¹ , Alex Evsukov ¹ , Dmitriy Savin ¹ , and Dmitry Klyuchnikov ¹

¹ Iizarov Centre, Kurgan, Russian Federation

Introduction: Study Design - Systematic review. The paper provides a systematic review of literature data on treatment of congenital thoracic lordosis. Material and Methods: The literature data on the subject were collected in the PubMed, GoogleScholar and eLibrary databases using the following keywords: congenital lordosis and congenital lordoscoliosis. The search depth was maximized to comprise 100 years (1916-2020). The inclusion criteria were as follows:

• Patients with congenital thoracic lordosis or lorsoscoliosis;

• Surgical correction of the deformity;

• Catamnesis with a follow-up period of at least 12 months.

The exclusion criteria were as follows:

• Verified acquired etiology of the primary disease.

The review methodology followed the PRISMA guidelines.

Results: In total, information on 18 patients was obtained, their age varying from 3 to 16 years, (mean 9.3 yrs). The level of sclerotic deformation before correction varied from 16 to 105 degrees (mean 51.2) at the thoracic level, and their thoracic kyphosis – from -94 to -10 degrees (mean -31.4). In the postoperative period, the sclerosis degree changed from 0 to 60 degrees (mean 25.5), and thoracic kyphosis – from -42 to 30 degrees (mean 6.4). The correction degree comprised from 60 to -9 degrees, and from 97 to 4 – for the thoracic kyphosis. The follow-up duration varied from 1 to 11.3 years (mean 5.4 yrs). Conclusion: Congenital thoracic lordosis is a rare pathology, which explains its insufficient state of knowledge. The treatment mainly aims to eliminate hypoventilation by restoration of a proper thoracic kyphosis through increasing the retrosternal distance, reduction of airway compression, improving pulmonary artery perfusion and extending the thoracic spine.

881

P082: Factors associated with incorrect placement of pedicle screw in adolescent idiophatic scoliosis instrumentation surgery with free-hands technique

Kaori Guadalupe Honda Partida ¹ , Hugo Vilchis Samano ¹ , and José Alfonso Corona De la Torre ¹

¹ Spine Surgery Department, UMAE Hospital de Traumatología y Ortopedia Lomas VerdesMexico City, Mexico

Objective: To analyze the factors associated with incorrect placement of pedicle screw in adolescent idiopatic scoliosis instrumentation surgery with the hands-free technique. Material and Methods: Descriptive, retrospective study was carried out by reviewing the postoperative tomographic control of patients with idiopathic scoliosis less than 80 degrees who underwent scoliosis corrective surgery with the hands-free technique, in a period of four years. Patient data was collected through clinical records, pre-surgical and post-surgical tomography. It was assessed Cobb coronal angle, Lenke type curvature, pedicle dysplasia (Watannabe classification), screw placement by Gertzbein classification and Heary classification. Results: A total of 172 patients was obtained. As a result, 43 idiopathic scoliosis in total, of which 28 of them, had a Cobb angle less than 80 degrees. 100% of the patients were female with an average age of 15 years old. 666 pedicles was assessed, of which the majority was classified as Watanabe B (41.74% n=), Watanabe A (33.33% n=), Watanabe C (21.32% n=) and Watanabe D (3.60% n=). Accuracy of pedicle screw was defined as Grade 0 and 1 in Gertzbein classification, in our study resulted a 91.9% of “perfect trajectory” (n = 467 screws). Incorrect pedicle trajectory was defined as grade 3 in the Gertzbein classification, according to the magnitude of pedicle violation, associated with a higher incidence of neurological deficit. A total of 3 screws were found in grade 3, which represents 0.59% of incorrect trajectory placement screw. These screws were located according to Heary classification with grade 3 (lateral localization). According to Heary classification grade 4 locate medial placement of the screw, in which our cases were obtained 63.8% (n = 30) grade 1 of Gertzbein classification and 36.1% (n = 17) grade 2 of Gertzbein classification. There was not a pedicle violation higher than 4 mm. Conclusions: The freehand technique is a safe and effective method of instrumentation of pedicle screws for the correction of AIS, having a high rate of precision in screw placement, however the factors that modify the success results such as the Cobb angle, pedicle dysplasia must be taken into consideration for the success of surgery.

894

P083: Outcome of surgical treatment of scoliosis with navigation and neuromonitoring description of surgical technique

Ziad Mohamed ¹ , Mohamed Zayan ¹ , Loay Abukwedar ¹ , and Antony Michael ¹

¹ Neuro Spinal Hospital, Dubai, United Arab Emirates

Introduction: Scoliosis is a spinal deformity that comprises a lateral curvature and rotation of the patient’s vertebrae .The most prevalently employed method of scoliosis correction surgery is posterior fusion with instrumentation, representing the current gold standard approach. Novel adaptations to this method have been made in recent years resulted in enhanced correction and a reduced number of complications. Improved intraoperative navigation permits a higher surgical accuracy during spinal surgery and addresses limitations. Navigation and intraoperative neuromonitoring represent novel technologies that can be employed in scoliosis correction surgeries to optimize surgical outcomes due to enhanced patient safety and improved surgical accuracy. In this study we evaluated the clinical and radiologic outcome of using navigation and intraoperative neuro-monitoring in scoliosis correction surgeries. Methods: In this retrospective study, 24 patients with scoliosis who underwent scoliosis correction surgery under navigation and intraoperative neuromonitoring. The procedure in these patients was after positioning the patient in prone, pressure areas padded, warming and calf pumps applied, a baseline spinal multimodal monitoring recorded. Followed by Level check with x-ray to identify the upper instrumented vertebrae(UIV) and lower instrumented vertebrae (LIV). Posterior midline incision, bilateral sub-periosteal dissection from transverse process. Furthermore, X-ray to confirm levels of UIV and LIV. Followed by O-arm run in 2 stages for navigation installing, pedicle screws inserted under navigation guidance. Screws stimulation are carried out at this stage to check the screws insertion at 15mA and Checking the insertion by X-ray. Then spinal releases done by inferior facetectomy and superficial flavectomy, spinous processes and transverse processes harvested for bone graft. In the correction stage rods inserted after cutting and contouring via dual rod reduction technique. Checking the correction achieved by final x-ray and final spinal multimodal monitoring recorded. Results: In all 24 patients, the mean age was 16 (range,10-35). The mean preoperative Cobb angle of major curve in coronal plane was 61.4° (range, 50°-92°) changed post operatively to 17.2° (range, 5°-50°) with mean correction rate of 72.5% (range, 45.6% – 90.9%). The total number of screws inserted was 413 screws with mean of 17.2 (range, 10-21) and the total number of instrumented segments was 283 segments with mean of 11.7 (range, 5-15). The mean operation time was 336 minutes (range, 240 m - 453 m), while the mean hospital stay was 9 days, (range, 4 d-32 d). In the all patients there was no intraoperative complications inform of alerts in INM, Dural tear and bleeding. There were no perioperative neurologic deficits or mal-positioned screws requiring reoperation. The percentage of other post-operative complications was 8.33% (2 patients). Conclusion: Combinations using of navigation and intraoperative neuromonitoring can provide better safety for the patients, however, long-term data are needed.

947

P084: Selective anterior scoliosis fusion is comparable to vertebral body tethering

Edward King ¹ , Priyanshu Saha ¹ , Zion Hwang ¹ , Emily Tsang ¹ , Bisola Ajayi ¹ , Darren Lui ¹ , Jason Bernard ¹ , and Timothy Bishop ¹

¹ St George's, University of London, United Kingdom

Introduction: Selective Anterior Thoracic Fusion (SATF) or Selective Lumbar Anterior Fusion (SLAF) have been proven to reduce fusion levels compared to posterior surgery for similar curve types in the past. Vertebral body tethering (VBT) is a novel type of spinal surgery which can preserve range of spinal motion compared to fusion. VBT can be used in similar anatomic fashion in the thoracic or thoracolumbar regions similar to SATF or SLAF. The aim of this study is to observe how VBT compares to anterior fusion and identify any differences between them. Methods: Retrospective review of Operation data was obtained for 82 patients who have had scoliosis surgery between 2014 - 2021. We analysed the British Spinal Registry, digital clinical notes and radiology. Anterior fusion data was then compared with VBT. Results: 52 patients had Adolescent Idiopathic Scoliosis (AIS). There were 56 Anterior Fusions SATF (70% n = 40) SLAF 15% n = 8 Two Stage SLAF + PSF 15% n = 8. 26 VBT cases. 14 Lumbar and 12 Thoracic VBT surgeries. 6 cases of Double VBT. Anterior Fusion vs VBT operation length (334.5 vs 368.5 minutes). Pre-operative Cobb angle STAF was 53⁰ and SLAF mean 52⁰, VBT 46⁰. Preoperative fulcrum Cobb angle major Anterior vs VBT (26.5⁰ vs 25.7⁰), pre-operative SRS22 scores (3.4 vs 2.8). Mean levels instrumented: SATF (7.6), SLAF (3.8), VBT Thoracic (8.2) and VBT Lumbar (5.5) blood loss (413.6 ml vs 192.4 ml). Postoperative Cobb angles were (10.8⁰ Fusion vs 21⁰ VBT). 3% of VBT patients (n = 1) went on to have a fusion. There were 4 over corrections and 2 releases. 1 patient in the Anterior group required return to theatre for chest drain re-insertion. Conclusions: Selective anterior fusion and VBT of both thoracic and lumbar spine have satisfactory outcome and are safe procedures. VBT closely matches anterior fusion for screw density and fusion levels, average length of operation. VBT has lower blood loss than anterior and has higher screw use and levels instrumented in the lumbar spine. Anterior Fusion Surgeries as expected since there are no endplate to endplate discectomies. Fusion surgery had less unplanned return to surgeries than VBT. Further evaluation of patient outcomes and comparison of range of movement are required. Anterior Fusion surgery can be considered in cases where the patient may not be eligible for VBT.

957

P085: A comparative study of anterior thoracic and anterior thoraco columbar surgeries

Edward King ¹ , Priyanshu Saha ¹ , Zion Hwang ¹ , Bisola Ajayi ¹ , Emily Tsang ¹ , Darren Lui ¹ , Jason Bernard ¹ , and Timothy Bishop ¹

¹ St George's, University of London, United Kingdom

Introduction: Five decades ago Anterior Scoliosis Surgery was the favoured approach compared to posterior. Limitations in instrumentation for posterior surgery meant that limited derotation control was possible. Harrington Rod surgery utilised level selection based on vertebra in the midline with parallel discs to the floor. Anterior instrumentation allowed shorter fusions and improved derotation and correction of kyphosis. They also had their limitations with hardware failure and large incisional approaches. With the advent of pedicle screw technology both monoblock and then polyaxial, control of scoliosis improved and posterior surgery became the modern gold standard. Vertebral body tethering (VBT) has ushered in a return to the era of Anterior Screw placement and VBT has limited scope in limited patient groups. Further improved hardware such as staples and HA coated screws straight inner shanks and techniques have improved the failure rates. We examined our group of Selective Anterior Thoracic Fusion (SATF) and Selective lumbar-thoracic Anterior Fusion (SLAF). Methods: Retrospective review of Anterior scoliosis fusion cases between 2017 and 2020. Analysis of radiographs and electronic patient records were conducted as well as British spinal registry. Results: There were 56 anterior fusions. 71.4% were SATF and 28.6% were SLAF. The mean levels for SATF were 7.6 and 3.8 for SLAF. Screw density was segmental in each group. The average blood loss was 400ml per case. The Hospital length of stay was 5.8 days for SATF vs 6.1 days for SLAF, the mean stay in PICU was 1.4 days for SATF vs 1.5 days for SLAF. Conclusion: SATF and SLAF in our instituion are in vogue again. In patients that are not suitable for VBT an anterior fusion may have advantages for cosmesis and smaller fusion levels compared to posterior surgery. There is a mean blood loss of 400mls. Fusion levels are low compared to posterior surgery in the literature but similar to VBT. HLOS is 5.8 days for SATF and 6.1 for SLAF and is comparable to our previously reported posterior cases. There were no unplanned return to theatre incidents. We conclude that anterior fusions can play a safe role again in the correction of scoliosis with advantages over other techniques particularly in lower fusion levels preserving more mobile segments.

959

P086: The rate of major complications after Lenke 5 and 6 adolescent idiopathic scoliosis deformity correction is low, but back pain is common

Josephine Coury ¹ , Zeeshan Sardar ¹ , Yong Shen ¹ , Mark Ren ¹ , Michael Vitale ¹ , and Lawrence Lenke ¹

¹ Och Spine Hospital, Columbia University Medical Center, New York, United States

Introduction: Lenke Type 5 and 6 adolescent idiopathic scoliosis (AIS) curves are less common than the main thoracic curve subtypes. Few studies have outlined the long-term outcomes and complications after surgical correction of major thoracolumbar curves. In this study, we investigated the incidence and type of complications associated with all posterior deformity correction for Lenke type 5 and 6 curves. Material and Methods: A retrospective review of prospectively collected multicenter data was performed. 193 patients were identified, 191 with 2-year and 93 with 5-year follow up were included in the final analysis. All radiographic and clinical complications were recorded at 1, 2, and 5 years postoperatively. All analyses were performed with SAS and alpha was set at p < 0.05 to declare significance. Results: Lenke type 5CN (n = 147) was the most common curve type. T10 to L4 were the most frequently fused levels (n = 54) followed by T11 to L3 (n = 38) and T9 to L3 (n = 34). Patients underwent an average 5-level fusion (range 3-9). 4 patients developed symptomatic proximal junctional kyphosis (PJK) of which 1 underwent revisions surgery. 7 patients (3.6%) had revision surgery: 4 for pseudarthrosis, 1 hardware prominence, 1 for distal adding on, and 1 for PJK. 18 patients (9.4%) had persistent low back pain that was managed nonoperatively. Other complications included surgical site infection (n = 2), thigh numbness which resolved (n = 7), hardware prominence (n = 4), and other neurologic complaints (n = 6). Conclusion: The rate of revision surgery was low at 3.6% after posterior based surgery for Lenke type 5 and 6 curves. Persistent low back pain after surgery was the most common complication at 9.4%. The rate of symptomatic PJK within 2 years was only 2.1%.

961

P087: Upper instrumented vertebra within 3 levels of the thoracic apex is the most significant risk factor for proximal junctional kyphosis in Lenke type 5 and 6 adolescent idiopathic scoliosis patients

Josephine Coury ¹ , Zeeshan Sardar ¹ , Yong Shen ¹ , Mark Ren ¹ , Michael Vitale ¹ , and Lawrence Lenke ¹

¹ Och Spine Hospital, Columbia University Medical Center, New York, United States

Introduction: Proximal junctional kyphosis (PJK) is a known complication of adolescent idiopathic scoliosis (AIS) deformity correction surgery. In specifically Lenke type 5 and 6 curves, the rates of PJK are reported as high as 18 to 50%. Previous smaller studies have identified high pelvic incidence, elevated preoperative proximal junctional angle (PJA), and increased thoracic kyphosis (TK) as possible risk factors for developing PJK in Lenke type 5 and 6 curves. In this study, we investigated multiple factors for PJK in a multicenter cohort of patients following surgical correction for Lenke type 5 and 6 AIS patients. Material and Methods: A retrospective review of prospectively collected multicenter data was performed. 193 patients were identified, 191 with 2-year and 93 with 5-year follow up were included in the final analysis. Radiographic clinical parameters were measured preoperatively and at postoperative year 1, 2, and 5. Radiographic measurements were performed and confirmed by three authors. PJK was defined as the proximal junctional angle from the UIV and 2 levels cephalad to the UIV of at least 10° and 10° greater than preoperative measurement. All analyses were performed with SAS and alpha was set at P < 0.05 to declare significance. Results: Lenke type 5CN (n = 147) was the most common curve type. T10 to L4 were the most frequently fused levels (n = 54) followed by T11 to L3 (n = 38) and T9 to L3 (n = 34). 17 patients (8.9%) developed radiographic PJK; 1 at 1 year, 7 at 2 years, and another 9 at 5 years. All 17 patients had an upper instrumented vertebra (UIV) within 3 levels or less caudal of the thoracic kyphosis apex (the most horizontal vertebra on the sagittal); no patient with a UIV 4 or more levels from the thoracic apex (n = 96) developed PJK (X2 = 13.03, p < 0.001). Higher preoperative PJA, pelvic incidence, thoracic kyphosis, hooks, BMI, and the Roussouly classification were all not found to be significant predictors of PJK. Total SRS-22 scores were significantly worse at postoperative years 2 and 5 in patients who developed PJK (2 years: PJK 4.16 ± 0.58 vs. 4.45 ± 0.43, p = 0.018; 5 years: 3.96 ± 0.42 vs. 4.37 ± 0.48, p = 0.021). At 2 years, SRS-22 pain and general function categories were significantly lower in PJK patients. At 5 years, SRS-22 pain, self-image, and general function categories were significantly lower in PJK patients. Between postoperative years 2 and 5, the PJK patients overall had lower scores, in particular self-image significantly lowered (p = 0.0499). Conclusion: In Lenke 5/6 Curve Types, UIV selection 4 or more levels caudal to the apex of the thoracic kyphosis resulted in no PJK up to 5 years postop. UIV within 3 or more levels caudal to the thoracic apex was the most significant factor leading to development of radiographic PJK. This is the first study to demonstrate significantly worse SRS-22 scores in AIS patients with radiographic PJK.

966

P088: The spinal appearance quetionnare is a valid instrument for the evaluation of congenital scoliosis patients over 10 yeras old

Mohammad Fanid ¹ , Dilek YAPAR ² , Aliekber Yapar ³ , İsmail Daldal ⁴ , Mehmet Cetinkaya ⁵ , Alim Can Baymurat ¹ , and Alpaslan Senkoylu ¹

¹ Department of Orthopedics and Traumatology, Gazi University Faculty of Medicine, Ankara, Turkey

² Gazi University Faculty of Medicine, Ankara, Turkey

³ Department of Orthopedics and Traumatology, Health Sciences University, Antalya Education and Research Hospital, Antalya, Turkey

⁴ Department of Orthopedics and Traumatology, Ankara Lokman Hekim Akay Hospital, Ankara, Turkey

⁵ Department of Orthopedics and Traumatology, Istanbul Basaksehir Pine and Sakura City Training and Research Hospital, Istanbul, Turkey

Introduction: The spinal appearance questionnaire (SAQ) was developed by Sanders in 2007 out of the Walter Reed Visual Assessment Scale, a visual test consisting of seven questions on spinal deformity, and its validity and reliability were tested. When the overall literature was reviewed, no disease-specific scale/questionnaire was developed to evaluate body perception and the expectations of congenital scoliosis patients. We aimed to evaluate the validity and the reliability of the Turkish version of the SAQ questionnaire in Turkish patients over 10 years of age with congenital scoliosis by assessing construct and convergent validity, analyzing internal consistency, and test-retest validity. Hypothesis: Evaluating the validity and reliability of the spinal appearance questionnaire (SAQ) for congenital scoliosis patients. Study Design: Prospective questionnaire validation study. Material and Methods: Applied to 52 patients with congenital scoliosis, the SAQ was applied to the same patients for the second time with an average interval of 14.9 ± 0.9 days. Construct validity was evaluated using factor analysis. SRS-22 was used to test the convergent validity of SAQ. Internal consistency analysis and test-retest reliability was evaluated to show the reliability of SAQ. Results: A two-factor structure with eigenvalues greater than one, namely “6.1” and “2.6” belonging to the SAQ, was obtained. The total variance of the factors is 62.1%. The factor load of each item in the first-factor ‘Appearance’ domain varies between 0.7 and 0.8. The second-factor ‘Expectations’ consists of four items. The factor load of each item varies between 0.7 and 0.8. A significant negative correlation was found between the SAQ appearance score and the self-image/appearance score of SRS-22 (r = -0.5; p < 0.001). Cronbach alpha for SAQ was found to be 0.9. The intraclass correlation coefficient (ICC) calculated for test-retest reliability was 0.991. Conclusion: Previous validity and reliability studies of SAQ have been performed in idiopathic scoliosis patients. This is the first study containing patients diagnosed with congenital scoliosis. In this piece of work, the 2-factor structure of the SAQ consisting of 14 items was found to be valid and reliable in patients over 10 years of age with a diagnosis of congenital scoliosis.

970

P089: Decreasing the rate of unnecessary pediatric deformity surgery allogenic blood transfusions

Josephine Coury ¹ , Taylor Paskey ¹ , Lawrence Lenke ¹ , and Michael Vitale ¹

¹ Columbia University Medical Center, Morgan Stanley Children's Hospital, New York

Introduction: Spinal deformity surgery is associated with a high perioperative blood loss and risk for allogenic blood transfusion (ABT). Previous studies have shown ABT has an increased risk of surgical site infection, acute hemolytic reaction, and transfusion-related lung injury. During our yearly review, our institution was noted to have a high rate of ABT compared to others in the United States. In this study, we examined the strategies taken to decrease our transfusion rate. Material and Methods: Patients included had a diagnosis of AIS, underwent posterior instrumentation and fusion (PSIF), were between ages 10-18, and had a major cobb angle between 45 to 70 degrees. Interventions to reduce ABT included a meeting with the postoperative care units where scoliosis patients recovered, a change in our protocol template stating “notify spine surgery team if transfusion is considered”, and a review of transfusions that occurred. Results: A total of 197 patients met criteria over 3 years. The rate of ABT from January 2019 to 2020 was 19.5% (15/77) and from January 2020 to 2021 13.3% (8/60). The interventions to reduce ABT rates were implemented between November 2020 to January 2021. From January 2021 to November 2021 only 5% (3/60) of patients received an ABT, representing a significant decrease from 2020 to 2021 (p < 0.01). No significant difference in demographics between groups existed including gender or age. Conclusion: The rate of ABT at our institution was significantly lowered from 13.1% to 5% by increasing scrutiny prior to transfusion, including meeting with the postoperative care units and change in our protocol template, and after transfusion, including a review of transfusions that occurred.

1026

P090: Risk factors associated with intraoperative blood transfusion in adolescent idiopathic scoliosis

Robert Koucheki ^1,2 , Andrew Howard ^3,4 , Mark McVey ⁵ , David Levin ⁵ , Conor McDonnell ⁵ , and David Lebel ^3,4

¹ Temerty Faculty of Medicine - University of Toronto, Toronto, Canada

² Biomedical Engineering, University of Toronto, Toronto, Canada

³ Division of Orthopaedic Surgery, The Hospital for Sick Children, Toronto, Canada

⁴ Division of Orthopaedic Surgery, University of Toronto, Toronto, Canada

⁵ Department of Anesthesia and Pain Medicine, The Hospital for Sick Children, Toronto, Canada

Introduction: Adolescents Idiopathic Scoliosis (AIS) surgeries are associated with significant blood loss requiring high rates of blood transfusion. This study aimed to identify factors associated with increased allogenic blood transfusion (ABT) rates in patients with adolescent idiopathic scoliosis (AIS) treated with posterior spinal fusion. We hypothesized that in addition to patient and scoliosis characteristics, non-patient factors, including peri-operative practices, influence transfusion rates in AIS surgery. Material and Methods: A retrospective case-control study was performed for AIS patients treated at a large children’s hospital between August 2018 and December 2020. All patients who underwent surgical repair for AIS were evaluated. Data on patient demographics, AIS, and transfusion parameters were collected. We conducted multivariate logistic modelling and calculated odds ratio (OR) and confidence intervals (CI) to identify risk factors associated with requiring transfusion. Results: A total of 157 AIS patients were included, of whom 56 (35.7%) were transfused RBC units (cases), and 101 (64.3%) did not receive any RBC transfusion (controls). Intraoperative care was provided by three surgeons and thirty anesthesiologists. Multivariate logistic regression demonstrated pre-operative hemoglobin of 130-139 g/L (OR 0.18), pre-operative hemoglobin of > 140g/L (OR 0.04), number of scoliosis cases done by the attending anesthesiologist (OR 9.1), and influence from individual surgeons (OR 3.8) as significant contributors to ABT (p < 0.0001). Conclusion: In this cohort, we demonstrated that higher pre-operative hemoglobin was protective against ABT. Patients with hemoglobin of more than 140, had a lower odds of receiving ABT (approximately 95% less likely). In addition, we identified contributions from individual provider practice preferences. Although further studies are required to better understand non-patient factors contributing to transfusion in AIS patients, we suggest standardized, peri-operative evidence-based strategies to potentially help reduce variations due to individual provider preferences.

1079

P091: Congenital failure of formation of the anterior column: is a VCR always needed?

Alfredo Guiroy ¹ , and Jahangir Asghar ¹

¹ Spine Surgery, Elite Spine Health and Wellness Center, Fort Lauderdale, United States

Introduction: Congenital failure of formation of the anterior column of the spine is uncommon pathology but often leads to focal deformity of the vertebrae and severe neurological deficits. The objective of this study is to describe and analyze the author’s experience treating this infrequent pathology and to evaluate if a Vertebral Column Resection (VCR) is always needed for the treatment. Material and Methods: We reviewed the charts and imaging of patients treated for the deformity from 2010 to 2020. Demographic data, neurological status, type of deformity (sagittal, coronal or both), kyphosis angle, scoliosis angle, defect location operative treatment performed and complications were recorded. A descriptive statistical analysis of the variables was done and the results were expressed as mean and percentages. Results: We analyzed 13 patients who were operated on for congenital failures of the anterior spine (8 male, 5 female). Mean age of diagnosis was 19 months. Three were thoracic (from T1-T10), 6 were thoracolumbar (from T10-L2) and 4 were lumbar dislocations. Ten had some neurological impairment pre-operatively and 5 of those had shown progression of their impairment. Seven patients had evidence of low lying conus and 4 underwent detethering prior to surgical intervention. The mean age at surgery was 6 years (range: 24 months to 12 years). All the patients were treated posterior only with decompression, deformity correction and instrumented fusion. Five had vertebral column resection for kyphosis and the remaining 8 had posterior column osteotomies (PCO) only. The percent correction of kyphosis for VCR patients was 42% and for PCO it was only 44%. In 2 cases there was acute worsening of neurological status in the immediate postoperative setting with 1 returning to baseline and the other showing continued improvement greater than baseline; 10 patients showed significant improvement postoperatively. Complications involved 3 incidental durotomies and 3 cases returned to OR in a 90-day time period: 1 for hardware revision, 1 for progression of neurology and 1 for Irrigations and debridement. Mean follow up was 38 months (range: 11-72 months). Conclusion: Congenital failure of formations of the anterior spine has a high rate of intraspinal pathology, neurological deficit, and deformity progression. In certain cases decompression and posterior only fusion may be sufficient for a good neurological outcome.

1083

P092: Evaluation of complications related to prolonged use of halo-gravitational traction in spinal deformity surgeries

Igor Ebert Cechin ¹ , Gabriel Alves ¹ , Luis Eduardo Carelli Texeira da Silva ¹ , and Alderico Girão Campos de Barros ¹

¹ Instituto Nacional de Traumatologia e Ortopedia Jammil Haddad (INTO), Coluna, Rio de Janeiro, Brazil

Introduction: To evaluate the complications related to the prolonged pre and interoperative use of halo-gravitational traction (HGT) as an adjuvant method in the treatment of severe spinal deformities. Material and Methods: We evaluated 27 patients who underwent surgical treatment using pre- or interoperative HGT, between May 2014 and August 2020, through a database consultation. Inclusion criteria were the presence of severe deformity (>100 degrees) in the coronal and/or sagittal plane and permanence with HGT for a minimum period of 7 days. A division into 2 subgroups was performed: patients with severe deformity in the sagittal plane accompanied by coronal deformity (11); patients with severe deformity only in the coronal plane (16). Clinical data were analyzed retrospectively by consulting medical records, incorporating the variables: age, sex, diagnosis, traction time and Cobb angle. The radiographic evaluation was retrospective by visualization in a specific program. Results: Among the 27 patients, 13 (48%) were male and 14 (52%) were female. The age at the time of surgery ranged from 6-47 years, with a mean of 19.6 years. The initial diagnosis was idiopathic scoliosis in 14 patients, syndromic scoliosis in 5, neuromuscular scoliosis in 3, congenital scoliosis in 3 and 2 cases of neurofibromatosis. In the subgroup of patients with severe deformity only in the coronal plane, the mean Cobb angle was 123.4 degrees (100-153). The subgroup of patients with combined deformity had a mean value of the Cobb angle for the coronal deformity of 123.6 degrees (71-159), and in the sagittal plane a mean value of 125.3 degrees (100-178). In 26 cases, 4 pins were used for cranial fixation, and in only 1 case, 6 pins. Patients remained under traction for an average of 27 days (7-108). The mean percent correction was 17.8% in the coronal plane and 18.4% in the sagittal plane in the subgroup with deformity in both planes, and 23.6% in the subgroup with coronal deformity. The overall complication rate was 37%. The incidence of complications in the subgroup with severe sagittal deformity was 54.5%, while in the subgroup with severe coronal deformity it was 12.5%. There were 5 complications related to the pins, with 4 loosening treated with retightening, and 1 case of local infection. Three patients developed less severe neurological conditions attributed to the use of traction – two cases of diffuse paresthesia in the limbs and one patient with blurred vision, which resolved after decreasing the load. Two patients complained of neck pain in which traction had to be provisionally discontinued, with complete improvement. No serious complications related to pins and traction were identified. Conclusion: Halo-gravitational traction has been shown to be an important adjunctive method in the treatment of severe spinal deformities. Despite having a considerable complication rate, there were no serious events.

1087

P093: Neural arch posterior vertebral column resection (NA-PVCR): a new technique for angular kyphotic deformity treatment

Francisco Del Pont ¹ , Igor Ebert Cechin ² , Alderico Girão Campos de Barros ² , and Luis Eduardo Carelli Texeira da Silva ²

¹ Department of Neurosurgery, Fleni, Buenos Aires, Argentina

² Instituto Nacional de Traumatologia e Ortopedia Jammil Haddad (INTO), ARCOL, Rio de Janeiro, Brazil

Introduction: Posterior Vertebrectomy is a highly complex and helpful tool used in the treatment of severe and rigid spine deformities, but neurological complications are not infrequent. Changes in the position of the spinal cord during bone resection, throughout correction maneuvers and even after correction can generate neurological deficits. Meningovertebral ligaments (MVL) and its biomechanical properties has been increasingly studied in the last years, being tensioned in kypshosis and keeping the attachment of the dural sac to the posterior arch. We believe that the partial preservation of the neural arch (supra and interspinous ligaments, ligamentum flavum, laminae, spinal process and part of facet joints) in the Neural Arch Posterior Vertebrectomy (NA-PVCR) technique maintains the MVL functions preventing spinal cord shift, with other theoretical advantages: mechanical protection of the posterior aspect of the spinal cord, additional surface for bone fusion and less bleeding from the epidural space. The objective of this paper is to describe the NA-PVCR technique and analyze the results of a initial cohort of kyphotic patients. Material and Methods: Neural Arch Posterior Vertebrectomy technique description. Retrospective analysis and presentation of 10 patients with acute sagittal spine deformity treated with this technique. Results: Between February 2020 - July 2022, 10 patients underwent correction of acute sagittal spine deformity with the use of NA-PVCR technique. Seven patients were adults and the other three ranged from 11 to 16 years old. The diagnosis was active infection in three patients, sequelae tuberculosis in two patients and congenital kyphosis in the other five. Two patients were submitted to removal of one vertebral segment, and one had an asymmetrical resection of one segment. In five patients two vertebral segments were removed, in one three segments and another case five segments were removed. There were no postoperative new neurological alterations and two patients with preoperative neurological deficits partially recovered during follow-up assessments. Pseudoarthrosis, loss of correction, titanium mesh cage collapses, dural tear or implant failures were not detected. Conclusion: NA-PVCR showed to be an effective and safe technique for the treatment of angular kyphotic deformities. Even though there was no circumferential decompression of the spinal cord, there was no limitation to the correction or neurological damage. This is a description of an initial cohort of kyphotic patients, therefore, future studies will be necessary for a better evaluation.

1197

P094: Effect of non-fusion anterior scoliosis correction (NFASC) on thoracic and lumbar sagittal parameters in adolescent idiopathic scoliosis (AIS): is it detrimental?

Umesh P. Kanade ¹ , keyur Akbari ¹ , Vignesh Badikillaya ¹ , and Sajan Hegde ¹

¹ Orthopaedics, Apollo Hospitals, Chennai, India

Introduction: The gold standard for surgical management Adolescent idiopathic scoliosis patients remains spinal fusion. Surgical treatment of Adolescent idiopathic scoliosis (AIS) has experienced some innovations in recent years particularly with regard to treatment of growing spine. Non-fusion anterior scoliosis correction (NFASC) is a new, fusionless revolutionary motion preserving treatment method for surgical management of Adolescent idiopathic scoliosis. Non-fusion anterior scoliosis correction (NFASC) has been successful in correcting coronal deformity in patients with Adolescent idiopathic scoliosis, there is paucity of literature on its effect on sagittal parameters. We present our series of 40 patients with a minimum follow up of 2 years. 72.5% of patients had a physiological sagittal profile after NFASC, while 27.5% had physiological profile before NFASC. Age and curve magnitude did not influence postoperative thoracic kyphosis (TK) and lumbar lordosis (LL). This study evaluates the effects of non-fusion anterior scoliosis correction on sagittal parameters of spine. Material and Methods: It is a retrospective cohort study. Data of 40 Adolescent idiopathic scoliosis patients treated with NFASC at a single Centre with a minimum of 2 years of follow up were analysed. Coronal cobbs’ angle, Thoracic kyphosis (TK), Lumbar Lordosis (LL), Pelvic Tilt (PT) and Pelvic Incidence (PI) preoperatively, immediate post op and at final follow up were measured. A Post hoc analysis following repeated measures ANOVA test was used to examine statistically significant trends. Results: 40 AIS patients (39 female,1 male). The mean age was 14.57 ± 1.98 years (Range 13-18 years). The mean Risser score and Sanders’s score was noted to be 4.22 ± 0.6 and 7.15 ± 0.59 respectively. The cohort included 14 Lenke type 1, 3 type 3, 18 type 5, and 5 type 6. On average 7.3 vertebrae were instrumented. Mean pre operative (pre-op) thoracic and thoracolumbar/lumbar cobbs were 51.05 ± 7.1 °and 50.96 ± 12.07° respectively. Mean pre-op, immediate post-operative(post-op), and at 2 years Thoracic kyphosis were 27.20 ± 8.20, 30.83 ± 5.85 and 31.09 ± 6.06 respectively. Mean pre-op, immediate post-op, and at 2 years lumbar lordosis were 48.92 ± 8.41, 47.23 ± 7.58 and 48.32 ± 6.06 (p > 0.05) respectively. There was no significant change in Pelvic incidence and Pelvic tilt preoperatively and at 2 years follow up. (p > 0.05). Conclusion: Non-fusion anterior scoliosis correction surgery offers fusionless correction with a positive influence on thoracic kyphosis without having any detrimental effect on lumbar lordosis. As a result, most of the patients achieved normal physiologic kyphosis, where as some maintained their pre-operative alignment. There was no kyphotic effect on lumbar spine. Non-fusion anterior scoliosis correction surgery offers fusionless correction of deformity with positive effect on sagittal parameters.

1400

P095: Deformity correction of congenital thoracolumbar kyphoscoliosis presenting with neurological deficit

Kang Kai Lim ¹

¹ Orthopaedic Spine Unit, Hospital Kuala Lumpur, Kuala Lumpur, Malaysia

A 10-year old male presented to our outpatient clinic with spine deformity which was first detected when he was 8-year old. The thoracolumbar deformity gradually worsened as he grew, and he subsequently developed bilateral lower limb neurological deficit during his clinic surveillance visit at age 14-year old. Radiographic examination showed T12 hemivertebra with conus medullaris effacement. An urgent T6 to L3 Posterior Spinal Instrumented Fusion with 4-rod technique, T11 to L1 decompressive laminectomy, and T12 hemivertebrectomy and Harm’s cage insertion was performed. Post-operatively his neurological deficit gradually improved and at 5 year follow up he had good fusion mass and normal daily function with no neurological deficit.

1480

P096: Vertebral body tethering for immature adolescent idiopathic scoliosis: a retrospective review of 2 to 5 years postoperative follow-up

Meric Enercan ¹ , Hamisi Mraja ¹ , Celaleddin Bildik ¹ , Halil Gok ¹ , Ayhan Mutlu ¹ , Onur Levent Ulusoy ¹ , Tunay Sanli ¹ , Selhan Karadereler ¹ , and Azmi Hamzaoglu ¹

¹ Scoliosis-Spine Center Istanbul, Istanbul, Turkey

Introduction: Anterior vertebral body tethering (VBT) has become a popular growth modulation technique that allows spontaneous curve correction with spinal growth in skeletally immature AIS patients. Overcorrection and cord rupture have been reported as the most common mechanical complications in the previous series. The aim of this study was to evaluate the curve behaviors, mechanical complications and assess the efficacy of vertebral body tethering technique in patients who had more than 2 years f/up. Methods: Skeletally immature patients AIS patients with Sanders score < 4 who underwent VBT and had min. 2 years f/up were included. Preop, first erect and latest follow-up radiographs were reviewed and correction rates were noted. SRS-22r was used for clinical assessment. Results: 15 patients (14F, 1M) with mean age 12,1 (10-14) and f/up 37,2 (24-62) months. There were 10 patients with Sanders score 3 and 5 patients with Sanders score 2. A mean of 9,2 (6-13) level was tethered. 8 patients had undergone thoracic-VBT, 2 patients had undergone TL/L-VBT and 5 patients had undergone double VBT for both MT and TL/L curves. Mean MT curve 58° was corrected to 22° at first erect (64% correction rates) and 16° at latest f/up with 72% correction rates. Mean TL/L curve 61° was corrected to 20° at first erect (68% correction rates) and 12° at last f/up with 80% correction rates. Mechanical complications were observed in 3 (19%) patients (2 tether breakage with a single cord, 1 overcorrection). All 3 patients had > 75% correction rates at the first erect. None of the patients require revision surgery for tether breakage or overcorrection. On the latest f/up, 93% of the MT curves and all (100%) of the TL/L curves were below 30°. SRS-22r subtotal score increased from a mean of 3.8 to 4.39 with a mean satisfaction score of 4.75 over 5 at the latest f/up. Conclusion: Vertebral body tethering is an effective growth modulation technique that provided satisfactory clinical and radiological results at the end of a mean 3 years f/up. The success rate was 93% for MT and 100% for TL/L curves. Tether breakage (13%) and overcorrection (6%) rates were lower than the previous series. Estimation of the remaining growth is challenging, curve correction should not be more than 60-70% at the index surgery in immature AIS to avoid overcorrection. Double cord fixation can minimize tether breakage. Patient satisfaction (4.75/5) was high at the latest f/up.

1481

P097: Restoration of ideal sagittal alignment in AIS with thoracic hypokyphosis/lordosis with hybrid technique: combination of posterior thoracic fusion with non-fusion thoracolumbar/lumbar vertebral body tethering

Meric Enercan ¹ , Hamisi Mraja ¹ , Tunay Sanli ¹ , Onur Levent Ulusoy ¹ , Halil Gok ¹ , Celaleddin Bildik ¹ , Ayhan Mutlu ¹ , Selhan Karadereler ¹ , and Azmi Hamzaoglu ¹

¹ Scoliosis-Spine Center Istanbul, Istanbul, Turkey

Introduction: Restoration of the ideal sagittal alignment is essential in AIS deformity correction. We introduced Hybrid technique including posterior surgery with or without Ponte osteotomy in order to restore sagittal alignment better and thoracolumbar/lumbar (TL/L) vertebral body tethering (VBT) with Double Screw-Double Cord fixation in order to preserve lumbar flexibility and motion. The aim of this study to evaluate the efficacy of hybrid technique for the restoration ideal sagittal alignment in patients with double major curves with thoracic hypokyphosis/lordosis. Methods: 24 AIS patients who had double major curves with thoracic hypokyphosis/lordosis treated with hybrid technique were included. Coronal and sagittal parameters were measured on preop, first erect and f/up x-rays and lumbar ROM were compared. SRS-22r was used for clinical assessment. Results: Mean age 14 (11-18) years and f/up was 28(24-62) months. Mean MT 48° was corrected to 8° at f/up (84%). Mean TL/L of 52° was corrected to 8.5° at f/up (83.5%). 20 patients with thoracic hypokyphosis of 13° restored to 33°. 4 patients with thoracic lordosis of -7° restored to 25° thoracic kyphosis. Ponte osteotomy was performed in 11 (45%) patients (7 patients with thoracic hypokyphosis, 4 patients with thoracic lordosis). 17 (70%) patients with preop. cervical kyphosis had improved cervical alignment postoperatively (11 patients straight, 6 patients cervical lordosis). ROC analysis showed thoracic kyphosis restoration > 30° and T1 slope > 25° was correlated with improved cervical lordosis restoration (area = 0.77). According to TL/L sagittal alignment, ant or post cord was tightened first to restore TL/L alignment. 12 patients with thoracolumbar kyphosis of 16° were restored to 2.3°. There was no cord rupture. Preop lumbar ROM was preserved at f/up. Conclusion: Hybrid technique provided satisfactory corrections on both planes. Posterior surgery w/o Ponte osteotomy enables restoration of the thoracic kyphosis. Cervical alignment improved better when thoracic kyphosis was restored > 30° and T1 slope > 25°. TL/L vertebral body tethering with Double Screw-Double Cord fixation provided deformity correction, restored TL/L alignment, preserved flexibility and motion of lumbar spine without cord rupture.

1502

P098: Severe kyphoscoliosis in non-ambulatory patients with type II spinal muscular atrophy and concomitant serious respiratory restriction: a novel surgical strategy to correct spinal deformity and pelvic obliquity

Tianyuan Zhang ¹ , Wenyuan Sui ¹ , Jingfan Yang ¹ , Yaolong Deng ¹ and Junlin Yang ¹

¹ Spine Center, Xinhua Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China

Introduction: To propose a novel surgical strategy to correct severe kyphoscoliosis and pelvic obliquity in non-ambulatory patients with type II spinal muscular atrophy and concomitant serious respiratory restriction. Material and Methods: Type II SMA patients with severe kyphoscoliosis and concomitant serious respiratory restriction who underwent posterior spinal fusion in our center from January 2019 to December 2021 were retrospectively reviewed. A novel surgical strategy based on alternate distraction on the concave side between a Domino connector and distal screws was proposed to correct spinal deformity and pelvic obliquity. Patients’ demographics and clinical data were detailed, including anthropometric parameters, nutrition status, pulmonary function and surgical outcomes. The scoliosis curve, kyphosis curve and pelvic obliquity were measured before and after surgery. The ability of sitting balance was evaluated during follow-up. Complications were also recorded. Results: 20 patients (9 males and 11 females) with type II SMA were included in this study. The average age at surgery was 18.7 ± 6.1 years (range, 11-30 years). Average body mass index (BMI) was 18.47 ± 4.68 kg/m² and 60% (12/20) patients were with poor nutrition. The mean percentage forced vital capacity (FVC%) and forced expiratory volume in one second (FEV₁%) was 35.3% ± 12.8% and 37.3% ± 13.8%, respectively, indicating serious respiratory restriction. Severe kyphoscoliosis was developed for all patients with highly rotated vertebra, deformed chest wall and pelvic imbalance. No one was able to sit independently without hands supporting and six patients was bound to bed preoperatively. All patients underwent one-stage posterior spinal fusion, instrumented from the upper thoracic vertebra to the pelvis. Multiple rods construct with a Domino connector was installed on the concave side to alternately distract collapsed trunk and achieve pelvic balance. The main scoliotic curve, kyphotic curve and pelvic obliquity averaged 120.6° ± 17.0°, 116.8° ± 25.6° and 36.5° ± 13.6° respectively before surgery. After surgery, it decreased to 57.7° ± 19.5°, 47.0° ± 15.0° and 15.5° ± 7.3° respectively. The mean operation time was 351.3 ± 64.5 mins (range, 240 to 525 mins). The mean blood loss was 1377.5 ± 1107.9 ml (range, 300 to 4500 ml). 13 (65%) patients were extubated in the operating room postoperatively and the average extubation time was 6.75 ± 11.2 hours for all. After surgery, they stayed in ICU for mean 2.5 ± 1.6 days (range, 1 to 7 days). The mean duration of hospital stay was 22.3 ± 9.4 days. As for postoperative complications, only 3 patients happened pneumonia and no one needed re-intubation due to respiratory problems. The sitting ability was recovered with balanced pelvis and all patients could sit independently during follow-up. Conclusions: This article presented the characteristics of non-ambulatory type II SMA patients with severe kyphoscoliosis and seriously restricted pulmonary function. Our novel surgical strategy could provide substantial correction and recover patients’ sitting balance, while limited the risks of respiratory complications. Its safety and effectiveness needed to be evaluated for severe neuromuscular scoliosis in the future.

1591

P099: Scoliosis in cerebral palsy patients. Fusion to the fifth lumbar vertebra, the sacrum or the ilia?

Ib Green Petersen ¹ , Luigi Magnano ² , Anastasios Charalampidis ³ , and Paul Gerdhem ⁴

¹ Karolinska University Hospital, Dep of Surgery, Sweden

² Enna Hospital, Sicily, Italy, Department of Trauma and Orthopaedics, Italy

³ Karolinska University Hospital, Dep of Acute Surgery, Trauma and Orthopaedics, Sweden

⁴ Uppsala University, Dep of Surgical Sciences, Uppsala, Sweden

Introduction: There is no consensus on the lowest level of fusion in patients with cerebral palsy treated surgically for scoliosis, although some previous studies have suggested a better radiological outcome after fusion to the pelvis in individuals with various types of neuromuscular scoliosis. We compared complications, reoperations and radiological outcome in individuals with cerebral palsy fused to the fifth lumbar vertebra (L5), the sacrum, or the ilia. Material and Methods: 208 individuals with cerebral palsy undergoing surgery for scoliosis aged 10 through 25 years were identified in the national quality registry Swespine. Lowest level of fusion was L5 in 58, the sacrum in 92, and the ilia in 58 individuals. The Cobb method was used for curve size analysis and the Maloney method for pelvic obliquity analysis. Reoperations were collected from the registry. An analysis on 58 matched pairs operated to L5 or the pelvis (sacrum = 42, ilia = 16) with similar pelvic obliquity (± 5°) was also performed. Statistics was performed with the Mann-Whitney, Kruskal-Wallis, Chi-square or Fisher’s exact tests. Results: The median (interquartile range) follow-up for the last radiograph was 1.7 (1.7) years and for reoperations 6.0 (5.9) years. Preoperatively, the median Cobb angle of the major curve was 65° (23°) in the L5 group, 68° (28°) in the sacrum group, and 78° (25°) in the ilia group (p = 0.006). Preoperative median pelvic obliquity was 16° (19°), 21° (13°), and 27° (28°), respectively (p = 0.004). Immediate postoperative Cobb angles were 28° (18°), 28° (16°), and 32° (25°), respectively (p = 0.11). Immediate postoperative pelvic obliquity was 7° (10°), 7° (8°), and 8° (10°), respectively (p = 0.28). The median change in pelvic obliquity from the first to the last postoperative radiograph was -5° (7°), -3° (6°), -3° (6°), respectively (p = 0.55). 7 (12%), 11 (12%), and 7 (12%) patients required at least one reoperation (p = 1.0), respectively. In the matched analysis based on pelvic obliquity, no significant differences in the radiological outcomes were found (all p > 0.38). Conclusion: Both fusion to L5, the sacrum, and the ilia results in sustained curve and pelvic obliquity correction, with no significant difference in reoperation rates. This indicates that choice of distal fusion level can be individualized in individuals with cerebral palsy.

1616

P100: The intervention effect of serial growing rod procedure on shoulder balance in EOS patients and analysis of risk factors for final shoulder imbalance

Ziyang Liu ¹ and Yong Hai ¹

¹ Department of Orthopedic Surgery, Beijing Chaoyang Hospital, Capital Medical University, Beijing, China

Introduction: To analyze the risk factors for final shoulder imbalance, observe shoulder balance changes during growing rod (GR) treatments in early-onset scoliosis (EOS) patients, and evaluate the satisfaction of families of patients with shoulder balance after GR treatment. Material and Methods: 24 consecutive EOS patients treated with GR at our institution from March 2008 to August 2018 were studied. Demographic data, surgical-related factors, and radiographic parameters were analyzed to identify the risk factors for final shoulder imbalance in 'growing-rod graduates', and the shoulder balance changes from GR implantation to the last follow-up after fusion were analyzed. The radiographic shoulder balance parameters included the radiographic shoulder height (RSH), clavicle angle (CA), and T1 tilt angle (T1T). The satisfaction of EOS patients' parents was evaluated by an adapted questionnaire. Results: Early postoperative shoulder imbalance (p = 0.015; odds ratio (OR): 19.500; 95% confidence interval (CI) = 1.777-213.949) was an independent risk factor for shoulder imbalance at the last follow-up. Radiographic shoulder height (RSH) was significantly improved after GR implantation (p = 0.036), further improved during the post-fusion period (p = 0.021), and through the whole treatment period (p = 0.011). The changing trend of CA was similar. RSH of patients with prefusion shoulder imbalance was significantly improved after final fusion (p = 0.045), and there was no significant difference in the RSH value at the early after fusion and the last follow-up compared with that of the prefusion shoulder balance group. The parents (100%) were satisfied with the final shoulder condition and the entire serial GR treatment. Conclusion: Growing rod surgery improved shoulder balance. However, shoulder balance status after GR implantation did not determine the final status. Final fusion could further adjust the shoulder balance of patients with prefusion shoulder imbalance. For patients with early shoulder imbalance after final fusion, there was a high probability of shoulder imbalance at the final follow-up.

1633

P101: Hoursfield unit for assessing asymmetric loss of vertebral bone mineral density and its correlation with curve serverity in AIS

Yunzhong Cheng ¹ , Honghao Yang ¹ , and Yong Hai ¹

¹ Department of Orthopedic Surgery, Beijing Chaoyang Hospital, Capital Medical University, Beijing, China

Introduction: Low bone mass concomitantly occurs in patients with adolescent idiopathic scoliosis (AIS) and can persist until skeletal maturity. The purpose of this study was to assess the asymmetrical loss of vertebral bone mineral density (vBMD) and its correlation with curve severity in patients with AIS using Hounsfield unit (HU) values were measured from computed tomography scans. Methods: A total of 93 AIS patients were retrospectively recruited. The HU values of the vertebral body (VB-HU) and pedicle screw trajectory (PST-HU) were measured from four vertebrae above (Apex − 4) to four below (Apex + 4) the apical vertebra (Apex) of the major curve. The VB-HU and PST-HU at the upper-end vertebra, Apex, and lower-end vertebra within the concave and convex sides of the major and minor curves and stable vertebrae were obtained. Results: A significant correlation was found between the Cobb angle and VB-HU at the periapical levels of the major curve. VB-HU and PST-HU at periapical levels were significantly greater within the concavity than the convexity of both major and minor curves. The asymmetric ratios of VB-HU and PST-HU were significantly correlated with the major curve Cobb angle, peaked at the apex, and gradually diminished from the apex to the end vertebrae. The asymmetrical loss of vBMD aggravated with the progression of curve severity, presenting as VB-HU, significantly decreased within the convexity and insignificantly decreased within the concavity of the major curve. Conclusion: The asymmetrical loss of vBMD was associated with the progression of curve severity in AIS. For patients with severe AIS, the distraction of the pedicle screws at the concave side should be a priority in correcting the major curve, and supplemental anchors and larger-sized screws should be placed within the convex side around the apex of the major curve to reduce the risk of screw loosening after surgery.

1638

P102: Halo-pelvic traction combined with staged correction surgery for the treatment of extrem severe and rigid kyphoscoliosis

Lijin Zhou ¹ and Yong Hai ¹

¹ Department of Orthopedic Surgery, Beijing Chaoyang Hospital, Capital Medical University, Beijing, China

Introduction: Severe and rigid spinal deformities are real challenges for us with unfavorable correction and a high rate of complications. To evaluate the efficacy and safety of halo-pelvic traction (HPT) combined with staged corrective surgery in the treatment of extremely severe and rigid scoliosis (Cobb’s angle > 140°), a retrospective study was conducted. Materials and Methods: Twelve consecutive cases of extremely severe rigid kyphoscoliosis were treated with one-stage HPT traction and a staged posterior procedure was included in the study. There were five males and seven females with an average age of 24.3 years. All underwent staged correction surgery. The patient had a major coronal curve or kyphosis > 140° and flexibility < 30%. The patient’s height, main curve, the height difference between the two shoulders, the height difference between the two iliac, and C7PL-CSVL distance were evaluated before traction, after HPT, as well as after correction surgery. Results: All patients underwent HPT traction and posterior surgery safely. The average time for HPT traction was 13.2 weeks. None of the patients underwent high-grade osteotomy. The main curve or kyphosis was improved from (162.5 ± 17.3)° before the operation to (75.7 ± 14.3)° after HPT, and to (57.7 ± 16.1)° after correction surgery. The corrective rate was 64.5%. The height, shoulder height difference and C7PL-CSVL distance of patients after HPT and correction surgery were also significantly improved compared with those before traction. One patient developed C5 root palsy during traction, one patient developed skin ulceration infection, one patient developed cerebrospinal fluid leakage during correction surgery, and one patient developed transient lower extremity paralysis. Complications in all patients were relieved after treatment. Conclusions: The combination of HPT and correction surgery is a safe and effective method for the treatment of extremely severe rigid scoliosis with Cobb’s angle > 140°, with less severe complications, and can avoid high-grade osteotomy during the procedure.

Key words: Traction; Scoliosis; Orthopedic procedures

1641

P103: The efficacy of pre-operative halo-gravity traction for severe kyphoscoliosis surgery on radiographic outcme and pulmonry function

Jianqiang Wang ¹ , Yong Hai ¹ , and Lijin Zhou ¹

¹ Department of Orthopedic Surgery, Beijing Chaoyang Hospital, Capital Medical University, Beijing, China

Introduction: Halo-gravity traction (HGT) has been proven that can decrease the severity of the curve in the process of correction before surgery. Currently, few studies have evaluated the efficacy of HGT on the pulmonary function of the patient. Our study was to evaluate the efficacy of preoperative Halo-gravity traction in treating severe spinal deformity on both radiographic outcome and pulmonary function. Materials and Methods: This study retrospectively included 30 consecutive patients (male 8, female 22) with severe kyphoscoliosis who were admitted to our department from April 2018 to January 2022 and underwent HGT before the correction surgery. The average age of patients was 17.79 ± 7.96 years old and the average of the pre-operative main curve was 120.66 ± 3.89°. There were 17 patients with AIS, 11 with congenital and 2 with NF-I. The change of radiographic outcome of deformity and pulmonary function tests (PFTs) were analyzed before and after HGT. Results: After an average of 122 ± 58 days traction, with 44.2 ± 12.7% of body weight, the main curve was corrected from an average of 112.42 ± 34.53° to 87.15 ± 27.77° (22.5%, p < 0.05); PFTs also showed a significant increase in FVC%, FEV1%, and MEF% after traction [42.82 ± 15.03% VS. 45.75 ± 15.82%;40.71 ± 13.77% VS. 44.21 ± 15.20%; 40.78 ± 17.15% VS. 45.49 ± 19.14%, p < 0.05]. No significant difference was found in deformity correction and lung function improvement between patients with traction for more or less than three months (p > 0.05). Two patients developed brachial plexus palsy during traction and recovered after decreasing of the traction weight. No other complication occurred during the traction period. Conclusions: Halo gravity traction can partially correct spinal deformity and improve pulmonary function. It could be used as a preoperative adjuvant treatment for severe spinal deformity. But traction for more than three months might not be necessary, according to the present study.

1670

P104: Clincal application of individualized digital surgical planning and precised execution for severe complex spinal deformity correction

Hongtao Ding ¹ , Yong Hai ¹ , Chaofan Han ¹ , and Yangpu Zhang ¹

¹ Department of Orthopedic Surgery, Beijing Chaoyang Hospital, Capital Medical University, Beijing, China

Introduction: Severe rigid adult deformities are composed of the characteristics of the complexity of anatomy, rigidity, and severe kyphosis or scoliosis, with or without neurological dysfunction, which may lead to physical disability or even death. The treatment strategy for such severe deformities is comprehensive. Different levels of spinal osteotomy have been developed and applied rapidly with good correction outcomes. However, due to the complex anatomy of spine structure, the screw insertion, vertebrae osteotomy, correction, and decompression procedures increase the incidence of intra- or postoperative neurological complications significantly. This study is to report the preliminary outcomes utilizing of Individualized pre-operative digital planning and three-dimensional printing (3DP) guidance template in the treatment of severe and complex spinal deformity. Materials and Methods: After being approved by the Institutional Review Board of our hospital, 8 adult patients with severe rigid kyphoscoliosis were included. Based on the preoperative radiological data, the surgery planning was simulated by software, and screw insertion and osteotomy guidance templates were designed and manufactured utilizing 3D printing techniques. The designed osteotomy and correction surgeries were performed utilizing the guidance templates. The perioperative, and radiological parameters and complications were collected and analyzed, including surgery duration, estimated blood loss, pre-and post-operative cobb angle, trunk balance, the ratio of osteotomy simulation and execution, screw accuracy, etc. Results: Of the 8 patients, the primary pathology consisted of 2 adult idiopathic scoliosis (ADIS), 4 congenital scoliosis (CS), 1 ankylosing spondylitis (AS), and 1 kyphosis secondary to tuberculosis (TB). There are 5 kyphoscoliosis and 2 kyphosis regarding deformity characteristics. The pedicle subtraction osteotomy (PSO) in 3 patients and vertebral column resection (VCR) osteotomies in 5 patients were performed with the application of the guidance templates. The average surgical duration is 361.25 mins, average blood loss of 800 ml, and no surgery and instrument-related complications occurred. The main cobb angle was corrected from 99.33° to 34.17°, the kyphosis was corrected from 110.00° to 42.00°. The match ratio of osteotomy simulation and execution was 94.67%. The average screw accuracy rate was 93.04% in the cohort. Conclusions: The clinical application of individualized digital surgical planning and precise execution and 3D printing guidance templates in the treatment of severe adult rigid deformity is feasible, effective, and easy to promote. The preoperative osteotomy simulation is executed with high precision by utilizing the described guidance templates. It could be used to reduce the surgical risk and difficulty of screw placement and high-level osteotomy.

1698

P105: Operative considerations for surgical management of scoliosis in GGPS1, a rare muscular dystrophy: a rare disease operative case report

Matt Bellamy ¹ , Raveen Jayasuriya ¹ , Edward Bayley ¹ , Ian Scivill ² , and Robert John ³

¹ Paediatric Orthopaedics and Trauma

² Department of Neurophysiology

³ Department of Anaesthetics, Sheffield Children's Hospital, Sheffield, United Kingdom

Background: GGPS1 is a rare variant of the geranylgeranyl diphosphate synthase gene. GGPS1 causes a genetic muscular dystrophy which is associated with progressive scoliosis, osteoporosis, and hearing loss. This commonly results in early wheelchair dependence by the 2^nd decile of life. Of the 21 globally reported cases, 15 have undergone spinal fusion surgery at a mean age of 14 years. There is no published literature on spinal management or surgical considerations to guide preoperative planning. Methods: A rare disease case study of an 8-year-old girl with GGPS1 and rapidly progressing left thoracic scoliosis who failed full time rigid bracing, and subsequently underwent T2-L3 posterior spinal fusion. This report focuses on intra operative learning points to optimise surgical management and early post-operative results. Results: Preoperatively this patient mobilised independently, with no history of low energy mechanism fractures, and required nocturnal non-invasive ventilatory (NIV). Due to her early onset of rapid curve progression and curve size, early onset scoliosis deformity correction and fusion was considered with the aim to protect her ambulatory status and pulmonary function. Prior to surgery the patient had normal motor function, thus full sensory-motor neuromonitoring was expected prior to proceeding with surgery. Intraoperative monitoring was adjusted from 1mS (standard for adolescent idiopathic scoliosis) to 4mS interstimulus interval to achieve adequate, repeatable, morphology and amplitude of MEP waveforms. Sub cortical and cortical responses for SEPs were obtained. No indications of metabolic bone abnormalities had been identified prior to surgery. However very poor bone quality was clinically evident intraoperatively, prompting a change to a higher instrumentation density (1.5) construct that originally planned. Full correction was not attempted due to risk of screw displacement. This achieved acceptable coronal plane correction from 65 degrees to 29 degrees. Probing pedicle screw holes was highly haemorrhagic, resulting in estimated blood loss of 750 mls (80% of circulating volume), with 303ml returned by cell salvage and 166mls of donor blood. Surgical progress was paused whilst fluid resuscitation with blood products reinstated haemodynamic stability. Neurological function was normal postoperatively and no further blood products required. Length of stay was 13 days due to slow wean off daytime NIV on the critical care unit. Discussion: Learning points:1) Fusion surgery may be necessary at a younger age due to rapidly progressing scoliosis neuromuscular scoliosis. 2) Neuromonitoring needs adapting in view of GGPS1 neuromuscular pathology. 3) Consider DEXA scan and metabolic bone specialist involvement preoperatively 4) High implant density required, 5) Prepare for high volume blood loss with pause for resuscitation and cross-matched donor blood.

1771

P106: A single surgeon's experience of thoracoscopic VBT: 5 50 8 years follow-up results

Ahmet Alanay ¹ , Altug Yucekul ¹ , Kadir Abul ² , Ilkay Karaman ³ , Atahan Durbas ³ , Tais Zulemyan ⁴ , Gokhan Ergene ⁵ , Sahin Senay ⁶ , Sule Turgut Balci ⁷ , Yasemin Yavuz ⁸ , and Caglar Yilgor ¹

¹ Department of Orthopaedics and Traumatology

² Istanbul Basaksehir Pine and Sakura City Training and Research Hospital, Department of Orthopaedics and Traumatology, Istanbul, Turkey

³ Acibadem Mehmet Ali Aydinlar University School of Medicine, Istanbul, Turkey

⁴ Comprehensive Spine Center

⁵ Department of Operating Room Services, Acibadem Mehmet Ali Aydinlar University Vocational School of Health Sciences, Istanbul, Turkey

⁶ Department of Cardiovascular Surgery, Acibadem Mehmet Ali Aydinlar University School of Medicine, Istanbul, Turkey

⁷ Anesthesiology Service, Acibadem Mehmet Ali Aydinlar University Maslak Hospital, Istanbul, Turkey

⁸ Department of Biostatistics, Ankara University School of Medicine, Ankara, Turkey

Introduction: Previously described growth-sparing techniques typically have a definitive fusion planned at the end of growth. Vertebral body tethering has emerged as the first promising definitive non-fusion surgical technique that has the theoretical advantages of achieving curve stabilization, preservation of functional motion and continued spinal and chest cage growth. Although experimental and clinical evidence has been growing for the last two decades, there still is a paucity of information on mid to long term clinical and radiographical outcomes of VBT surgery. Aim was to report mid-term outcomes of thoracoscopic thoracic-only anterior VBT surgery. Materials and Methods: Data were collected preoperatively, at 6-weeks, 1-year, 2-years and ≥ 5-years follow-up. Demographic, perioperative, clinical, radiographic data and complications were analyzed. Curve sizes at each follow-up were compared using repeated measures ANOVA. Clinical outcome was assessed by using SRS-22. Results: 23 AIS patients (22F, 1M; 12.1 ± 1.5 years) with a mean follow-up of 63 (60-92) months were included. 96% were Lenke 1 (11A, 2Ar, 9B and 1C) and 4% were Lenke 2. Preoperatively, 14 (64%) patients were premenarchal (median Sanders: 3 (1-7), median Risser: 0 (0-5)). A median of 7 (7-9) levels were tethered. Mean surgical time was 245 ± 75 (123-360) minutes. Patients grew 7 cm on average; height measurements showing significant increase at each follow-up timepoint (p < 0.001). All patients reached skeletal maturity at final follow-up. Upper Thoracic (UT), Main Thoracic (MT) and Thoracolumbar/lumbar (TLL) curves showed significant decrease in each follow-up timepoint. No significant changes were noted in kyphosis and lordosis (p < 0.05). Pulmonary, mechanical and curve behavior complications rates were 13%, 22% and 35%, respectively. 2 (8.7%) patients were converted to fusion. At final follow-up, 91% patients had ≤ 3 0° residual curve. SRS-22 MH, SI and subtotal scores increased significantly. Conclusions: This study reports a single European center experience on 23 consecutive patients with ≥5-years follow-up who had undergone thoracic-only VBT surgery. Surgical correction was followed by growth-dependent correction attained during follow-up. Spontaneous correction in the non-operated upper thoracic and thoracolumbar levels were also noted. Thoracoscopic VBT surgery prevented fusion following ≥5-years after surgery in 91% of the patients. 90% of patients that are not converted to fusion had good radiographic and clinical outcomes at latest follow-up; however, it is not without complications. Some complications may be avoided with a better understanding of the growth modulation and advancement of technical skills and technology.

1773

P107: The effectiveness & safety of scoliosis surgery: experience of 161 cases in the tertiary level hospital

Shah Alam ¹ , Sarwar Jahan ² , Dr Sharif Ahmed Jonayed ² , and Abdullah Al Mamun ²

¹ Orthopedics & Spine Surgery, Bangladesh Spine & Orthopedic Hospital (BSOH), Dhaka, Bangladesh

² Orthopedics & Spine Surgery,National Institute of Traumatology & Orthopedic Rehabilitation (NITOR), Dhaka, Bangladesh

Introduction: A significant number of Scoliosis needs surgical intervention. Revolutionary design & capability of spinal instruments have drastically changed the principle of scoliosis correction. Material and Methods: From February 2009-July 2022, 161 cases underwent surgery. 93 were female and 68 were male and age ranged 14-38 years. The pedicle is a power nucleus of the vertebra and offers a secure grip of all 3 columns. Pedicle screw instrumentation ensures rigid fixation with improved 3D correction. Accurate placement of screws is important to reduce possible irreversible complication. All cases were corrected by transpedicular screws and rods and 1 case stabilized by sub laminar wring. 152 cases were managed by only posterior approach and 9 cases required both anterior releases, costoplasty, posterior stabilization as well. Fusion was done in selected segments. Total follow up time was about 10 years (6 months-7 yrs). All patients were assessed by deformity correction, cosmesis, and functional outcome. Use of Neuromonitor is an excellent & effective method for prevention of post operative neuro deficit. Results: 71 patients had average coronal plane cobb’s angle measuring about 70⁰ pre-operatively and 17.12⁰ immediate post-operative period. 8 patients (5%) developed neurodeficit. 3 regained completely but other regaining her neurological deficit very slowly. There were malposition of screws in 21 (13.04%), painful prominence of screws in 17 (10.56%), superficial infection in 7(4.35%). 80% patients improved cosmetically. Conclusion: Overall outcome in surgical treatment of Scoliosis by transpedicular screws and rods system was satisfactory.

1774

P108: Comparison of patient-reported outcomes after vertebral body tethering and posterior spinal fusion

Altug Yucekul ¹ , Gokhan Ergene ² , Sahin Senay ³ , Sule Turgut Balci ⁴ , Pinar Yalinay Dikmen ⁵ , Caglar Yilgor ¹ , and Ahmet Alanay ¹

¹ Department of Orthopaedics and Traumatology

² Acibadem Mehmet Ali Aydinlar University Vocational School of Health Sciences, Department of Operating Room Services, Istanbul, Turkey

³ Department of Cardiovascular Surgery

⁴ Anesthesiology Service, Acibadem Mehmet Ali Aydinlar University Maslak Hospital, Istanbul, Turkey

⁵ Department of Neurology, Acibadem Mehmet Ali Aydinlar University School of Medicine, Istanbul, Turkey

Introduction: Posterior spinal fusion (PSF) is the standard surgical approach in the treatment of adolescent idiopathic scoliosis. Vertebral body tethering (VBT) emerged as an alternative minimally invasive, non-fusion, growth modulating technique. The aim of this study was to compare the patient-reported outcomes of patients who had undergone PSF and VBT. Materials and Methods: Matched cohorts were created among patients having main thoracic curves ranged between 40⁰-70⁰ and having ≥ 2 years follow-up. Double-curve VBT and thoracolumbar PSF surgeries where lumbar curves were also instrumented were excluded. Demographic data, and preoperative radiographic measurements were compared to confirm matching. Early and latest follow-up radiographic measurements and SRS-22r scores were used as outcome measures. Results: 16 PSF and 18 VBT patients (30F, 4M) were included. The mean age and the follow-up were 13.4 (10-17) years and 25.7 (24-32) months. Preoperative proximal thoracic (28.6° vs 29.6°), main thoracic (MT) (56.8° vs 51°), and thoracolumbar (TL) curves (32.5° vs 37°) were similar among groups (p = 0.732, p = 0.126 and p = 0.088). The surgical correction percentage in the MT curve was greater in the PSF group (84% vs 53%, p < 0.001), while the overall correction percentages at 2-years were similar (80 vs 76%, p = 0.616). For both PSF and VBT groups, self-image and subtotal scores significantly increased at 2-years compared to preoperative values (p < 0.001, p = 0.037 and p < 0.001, p = 0.016), while pain, function and mental-health did not show significant pre-to-post changes (p > 0.05 for all comparisons). Self-image scores were improved at 6-months and were maintained in PSF group, while they incrementally increased in the VBT cohort. SRS function scores were higher in VBT group both at 6-months and 2-years (p = 0.027, p = 0.027) compared to PSF group. SRS pain and subtotal scores were found to be worse in PSF group at 2-years (p = 0.020, p = 0.036) in comparison to VBT group. Conclusions: PSF and VBT resulted in similar main thoracic and thoracolumbar curve correction rates 2-years after surgery. PSF resulted in earlier improvement in self-image scores while latest follow-up scores were similar. VBT resulted in better patient-reported function and pain scores. Further studies in larger patient cohorts with longer follow-up are warranted.

1783

P109: Overcoming the challenges in management of neglected and severe spine deformities: our case series and strategies

Harvinder Singh Chhabra ¹ , and Anuj Gupta ²

¹ Spine Service, Indian Spinal Injuries Centre, New Delhi, India

² Spine Service, Max Super Speciality Hospital, Noida, India

Introduction: Severe deformity of the spine is defined as Cobb angle more than 90 degrees. The term neglected spinal deformity has not formally defined but most surgeons consider it if age is more than 16 years and no treatment has been sought till then Patients with neglected severe scoliosis may have very low pulmonary reserve along with cosmetic deformity. Moreover, there can be neurological compromise due to compression on spinal cord. The challenges associated with the surgery in these patients are rigidity of the curve, poor pulmonary reserve and compromised spinal cord in patients with neurological deficit. The objective of our study was to assess the outcomes of correction of severe deformities in our series and to compile the strategies to overcome the challenges in management of neglected and severe spine deformities. Materials and Methods: This is a single centre retrospective study. Patients with Cobb angle > 90⁰, flexibility on bending radiographs < 30% and age > 16 years were included in the study. 14 patients were managed in single stage (vertebral column resection with posterior instrumentation and fusion) and 06 in two stages (Halo-pelvic distractor application and later posterior instrumentation and fusion). We collected data for all patients which include age, sex, type of surgery, pre and post-op Cobb angle, T1-T12, T1-S1 length, Sagittal & Coronal alignment, Apical vertebral translation and SRS-22 score. Results: Total of 20 patients were included in the study. The aetiology included Congenital (12), Neuromuscular (5), Idiopathic (2) and syndromic (1). The mean duration of follow-up was 38.6 months. The mean pre-op Cobb angle was 99.75 (50-180) in coronal plane and 60.8 (10-93) in sagittal plane. The mean post-op Cobb angle was 46.85 (22-66) in coronal plane and 35.9 (10-48) in sagittal plane (p < 0.005). The mean pre-op and post op coronal and sagittal alignment were +4.96 cms & +4.35 cms +2.52 cms and +2.06 cms respectively (p < 0.005). The mean pre- and post-op apical vertebrae translation was 7.38 cms and 3.33 cms respectively (p < 0.005). The mean pre- and post-op T1-T12 length was 15.8 cms and 21 cms respectively (p < 0.0001). Similarly, the mean pre- and post-op T1-S1 length was 31.1 cms and 37.7 cms respectively (p < 0.0001). In our patients, there was significant improvement in all aspects of functional scores with p value < 0.001. There were 6 patients with pulmonary compromise pre-op and after surgery there was significant improvement in both FVC and FEV1. We experienced no major complications like implant failure, infection or neurological deficit. 7 patients had incomplete neurological deficit pre-op which improved after surgery. We also have compiled 10 strategies which can be used for management of such deformities. Conclusion: The management of Neglected Severe Spinal deformities may be very challenging. However, the successful outcome after planned surgical treatment is a life changing event with improvement in thoracic height, pulmonary function, and a profound effect on cosmesis and self-image.

1895

P110: Structural scoliosis secondary to thoracic osteoid osteoma: a case report of delayed diagnosis

Nessrine Nessib ¹ , Mohamed Zairi ² , Eya Chahed ¹ , Sofiene Bouali ¹ , Ahmed Msakni ³ , Mohsni Ahmed Amine ² , Rim Boussetta ² , and Nessib Mohamed Nabil ²

¹ Neurosurgery, Mongi ben Hamida Institute of Neurology, Tunis, Tunisia

² Orthopedics

³ Neurosurgery, Bechir Hamza Children's Hospital, Tunis, Tunisia

Introduction: Osteoid osteoma (OO) is a small benign bone tumor that is primarily localized in long bone; lumbar osteoid osteoma combined with scoliosis has rarely been reported. The aim of this case report is to show that a late diagnosis of vertebral osteoid osteoma gives rise to structural scoliosis, which can require long-term management. Materials and Methods: We report a case of an osteoid osteoma in the thoracic spine associated with structural scoliosis. We describe a 14-year-old boy who complained chronic nightly left back pain and scoliosis. Spine’s X-ray reported thoraco-lumbar scoliosis without bone lesion. Results: MRI as well as technetium-99m total body bone scan and a computed tomography scan revealed a bony lesion in the left superior articular process of T11 vertebra consistent with the diagnosis of Osteoid Osteoma. Anatomopathological study of the resection piece confirmed the diagnosis. Surgical excision of the tumor resolved pains, but scoliosis needed a non-operative treatment for one year. Conclusion: Through this case, it has been demonstrated that late diagnosed vertebral Osteoid osteoma can be the cause of structural scoliosis. Clinical and radiological results indicate that OO resection is an effective and safe method of treatment.

1927

P111: Single centre experience of intraoperative neuromonitoring (IONM) in pediatric scoliosis deformity correction surgeries

Umesh P. Kanade ¹ , Sharan Achar T ¹ , Harith Reddy ¹ , Keyur Akbari ¹ , Vignesh Badikillaya ¹ , Appaji Krishnan ² , and Dr Sajan Hegde ¹

¹ Orthopaedics, Apollo Hospitals, Chennai, India

² Orthopaedics, SIMS Hospitals, Chennai, India

Introduction: Neurological deficit following surgical correction of spinal deformity is a major concern for any surgeon. Intraoperative neuromonitoring (IONM) in the form of Somatosensory evoked potential (SSEP) and Transcranial motor evoked potential (TcMEP) are real-time assessment tools to decrease the likelihood of iatrogenic neurological injuries. We aim to present our experience of multimodal IONM in pediatric scoliosis surgery. Methods: Prospective analysis of 121 consecutive scoliosis patients who underwent posterior scoliosis correction with IONM at our institute between January 2015 to July 2018. All surgeries were monitored by an experienced neuromonitoring specialist and were performed under total intravenous anesthesia. Alerts were described as a decrease in amplitude by 50% or greater in SSEP, TcMEP, or both. Results: There were 91 females and 30 males with a mean age of 15 years 5 months. 11 patients (9%) had positive neuro alerts of which 7 (63%) of alerts were due to intraoperative traction, 2 (18%) were due to mean arterial pressure, 1 was due to screw placement and 1 was due to correction of the curve. We observed 10 true positives, 1 false-positive, and 1 false-negative alert for TcMEPs with sensitivity of 90.9% and specificity of 99%. The sensitivity and specificity of SSEP was 18% and 100% respectively. 2 cases had postoperative neurological deficit which recovered over time. Conclusion: Our results support the use of IONM as a standard of care during pediatric deformity correction surgery. The combined use of TcMEP and SSEP is a valuable tool for improving intraoperative safety and postoperative outcomes.

2021

P112: Clinical impact of apical gliding screws in the management of early onset scoliosis

Saleh Alfaisali ¹ , and Abdullah Alshammari ¹ , Rodrigo Navarro- Ramirez ² , Neil Saran ¹ and Jean Ouellet ¹

¹ Orthopedic, Division of Orthopedic Surgery, McGill Scoliosis and Spine Centre, McGill University Health Centre, Montreal, Canada

² Department of Neurological Surgery, Weill Cornell Medicine - New York Presbyterian, New York, United States

Introduction: Management of early onset scoliosis (EOS) carries significant challenges. The key to successful management is the prevention of curve progression while maintaining spinal growth with the least number of complications. Few spinal implants have been designed to allow vertebral capture while still allowing vertebrae to glide along a rod or construct. Over the last 7 years, our centre has been involved in the assessment of a pedicle screw based gliding anchor that captures one or two rods with a PEEK cable tie lined with a polyethylene spacer allowing for maximal gliding properties. Method: We carried out a retrospective analysis of the first 36 patients with Early Onset scoliosis treated with at least one TGV in combination with a growing rod construct (Modern Luque Trolley Growing Rods (MLTGR); Traditional Growing Rods (TGR); Magnetically Controlled Growing Rods (MCGR); Shilla Growing Rods (SGR). Chart and imaging were reviewed at our institution between Dec. 2014 and Jan. 2020 for all patient that had a minimum of two year follow up. We recorded: age at initial surgery; diagnosis; spinal deformity parameters; surgical technique; complications as per implant, alignment, wound and medically related. Planned and unplanned surgeries (UPROR) were also tabulated. Results: A total of 228 gliding screws (average of 6 screws (1-10) per pts) were implanted at and around the apex in 36 pts who had growth sparing surgeries. Average age at implantation was 8.2 (4-11) yrs. Diagnoses were as follows: 17 pts. had neuromuscular EOS, 15 pts had a syndromic EOS, while only 4 pts had an idiopathic EOS. The mean follow up was 3.5 yr (2-7) yr. Surgical technique: 24 patients had MLTGR, 8 pts TGR, 3 MCGR, 1 SGR. Constructs spanned10 vertebrae (7-13). Average growth for self growing systems (MLTGR) was 0.6 mm/seg/yr while for active distraction (MCGR, TGR) was 0.8 mm/seg/yr. The number of UPROR in self growing constructs per patient per category prior to expected skeletal maturity a) wound: 1 pt; b) implant related: 3 pts (c) alignment issues: 4pts for a total of 32% (8 UPROR out of 25pt). Number complications requiring UPROR in active distraction construct per category a) wound: 1pt b) implant related 3pts c) alignment issues: 2 pts for a total of 55% (6 out of 11 pts). Number of planned returns to OR in self growing construct: 3 pts final fusion av age 13 yr. old. Number of planned return to surgery in active distraction construct: 32pts. Discussion / Conclusion: Drawing conclusions with the current data set is too early as the cohort is too small and lacks a control group. However, the following trends were found: Overall deformity correction and maintenance may be slightly better with the addition of apical gliding screws: our 60% vs 38% for TGR&MGR (SRS 2022 abstract 85) Average complication rate remains high in EOS with 40% of our patients having a major complication. Self-guided growth surgery appears to have less spinal growth but also less planned and unplanned surgery.

Deformity-Thoracolumbar (Adult)

116

P113: Type 3 bone-disc-bone osteotomy combined with pre-surgical halo-traction: a safe and effective solution to correct severe angular-like kyphoscoliosis

Tianyuan Zhang ¹ , Wenyuan Sui ¹ , Jingfan Yang ¹ , Yaolong Deng ¹ , and Junlin Yang ¹

¹ Spine Center, Xinhua Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China

Introduction: Treatment of severe angular-like kyphoscoliosis is a technically demanding surgical challenge and often requires high-risk vertebral column resection (VCR). Bone-disc-bone osteotomy (BDBO) refers to the resection of disc and adjacent vertebral endplates and has 3 different types according to different ranges of resection. The resection ranges of type 3 BDBO contains three parts: (i) partial vertebral body (includes pedicles); (ii) superior intervertebral disc; (iii) superior partial vertebral body (not includes pedicles). For the first time, this study proposes a novel method that combines type 3 BDBO with pre-surgical halo-pelvic traction (HPT) and evaluates its safety and effectiveness to correct severe angular-like kyphoscoliosis. Material and Methods: Patients with severe angular-like kyphoscoliosis who underwent pre-surgical HPT and type 3 BDBO from 2017 to 2019 were retrospectively reviewed. Patients’ demographics and clinical data were recorded. The coronal Cobb angle and sagittal Cobb angle were measured in the pre-operation, post-traction, post-operation, and final follow-up. Complications were also recorded. Patients’ health-related quality of life was compared by SRS-22 questionnaire. Results: Thirty patients (18 females and 12 males) were included with an average age of 20.2 years (range, 13–33 years). The mean preoperative coronal and sagittal Cobb angle was 123.1° ± 16.4° (range, 90°-155°) and 120.3° ± 19.9° (range, 90°-156°). After 2.9 ± 0.7 months of (range, 2-4 months) HPT, the coronal and sagittal Cobb angle decreased significantly to 81.9° ± 13.2° and 76.0° ± 12.6°. Postoperatively, the scoliotic and kyphotic angle further decreased to 42.4° ± 12.2° and 33.9° ± 8.8°. After mean follow-up of 2.93 ± 1.05 years, the correction rates maintained at 64.3% ± 10.6% and 70.5% ± 6.3%, respectively, without obvious correction loss. The mean operative time was 410.8 ± 126.2 minutes (range, 220-660 min), and average estimated blood loss was 1364.2 ± 619.8 mL (range, 600-3000 mL). There were nine patients encountering positive evoked potential events during surgery. After surgery, five patients demonstrated different degrees of transient neurological deficits, including two with lower limbs numbness and three with lower limbs weakness. All of them recovered within 1 to 6 months of rehabilitation. Respiratory complications, including 4 pneumonia and 6 pleural effusions, happened. One patient had surgical site infection postoperatively and we performed irrigation and debridement. One patient encountered leakage of cerebrospinal fluid and we performed dural repair. During follow-up, two patients had unilateral rod fracture but no obvious correction loss, so revision surgery was not performed. The SRS-22 scores were calculated and compared between pre-operation and last follow-up. The scores of self-images were significantly improved from 2.66 ± 0.27 to 3.36 ± 0.23 (p < 0.001). Other scores showed slightly improvement but with no statistical significance. Conclusion: This study proposed a novel strategy to correct severe angular-like spinal deformities. The combination of pre-surgical HPT and type 3 BDBO achieved substantial correction and satisfactory aesthetic outcomes. No permanent neurological deficits and serious complications happened postoperatively. Comparison of this technique with VCR was needed to further evaluate its efficiency in the future.

154

P114: Clinical and radiographic outcomes in the treatment of patients with Scheuermann kyphosis using posterior instrumented fusion

Matthew Geck ¹ , Devender Singh ¹ , John Stokes ¹ , Ashley Duncan ¹ , and Eeric Truumees ¹

¹ Spine, Ascension Texas Spine and Scoliosis, Austin, United States

Introduction: Scheuermann Kyphosis (SK) is one the leading causes of deformity and back pain in adolescents. Its prevalence is approximated to be between 0.4% -10%. Several factors may contribute to the etiology of this disease including genetics, mechanical and growth abnormalities, poor bone quality etc. Aim: This study reports the clinical and radiographic outcomes of patients with SK who underwent posterior instrumented fusion at a single institution. Materials and Methods: Medical records on 30 patients with SK were reviewed. Patients ≤ 30 years were included in the study. Age, sex, body mass index (BMI), operative time, estimated blood loss (EBL), length of hospital stays (LOS), levels treated, sanders score, preoperative (pre-op) and postoperative (post-op) thoracic kyphosis (TK) , cobb angle (in case of scoliosis correction), lumbar lordosis (LL), pelvic incidence (PI), pelvic tilt (PT), sacral slope (SS), tibial plateau angle (TPA), Scoliosis Research Society-22r (SRS-22r), Oswestry Disability Index (ODI), Visual Analogue Scale (VAS) and complications were evaluated. Matched pair t-tests were conducted for statistical significance (α = 0.05). Results: Mean patient age was 18.7 years (12-30 yrs.) with 58% being female. Mean BMI was 24.7 (± 5.3). Mean sanders score was 7.5 (± 1.0). Most treated spinal level was T3-L3. Post-op follow-up landmarks of our cohort were 21 patients with less than 2 years and 9 with 2-6 years follow ups. Mean operative time was 312 (± 35.5) minutes with mean EBL of 406 (± 216 mls). Mean LOS was 5.1 (± 1.4 days). Mean pre-op and the last post-op follow-up TK were 83.7° (± 8.2°), and 43.8 º (± 9.6°), respectively (p < 0.05). Mean correction at the last visit was 47.1% (± 13%). Similarly, LL were 69.3° (± 7.8°) and 50.2° (± 7.4°), respectively (p < 0.05) with mean correction of 26.9° (± 9.2°). Mean pre-op PI, PT and SS were 37.2° (± 12.6°), 8.6° (± 13.8°) and 27.3° (10.9°), respectively. Post-op last visit mean PI, PT and SS were 38.7° (± 8.4°), 9.7° (± 8.4°), respectively. Nine patients underwent additional scoliosis correction with mean pre-op and the last visit of 27.5° (± 10.1°) and 8.4° (± 4.5°), respectively. Mean TPA were 0.9° (± 8.3°) and 8.3° (± 4.2°), respectively. Pre-op mean VAS and ODI scores were 3.4 and 18.1 and 1.9 and 11.3 at the last visit post-op. The mean SRS-22r scores were 3.7 (± 0.47) and 4.3 (± 0.7), respectively. One patient developed acute hypercapnic respiratory failure post-op which was associated with anesthesia/narcotics. Two patients underwent revision: one due to distal segment breakdown and other developed proximal junction kyphosis/ligamentous injury. No other complications or revisions were observed in our cohort. Conclusions: Our cohort data showed that adequate correction with well-balanced spine can be achieved while preserving the motion segments and reducing the risk of junctional failure with posterior instrumented fusion. Patient reported outcomes improved over long run as indicated by VAS, ODI and SRS scores.

259

P115: Predictive models to assess risk of extended length of stay in adults with spinal deformity and lumbar degenerative pathology: development and internal validation

Ayush Arora ¹ , Joshua Demb ² , Daniel Cummins ¹ , and Alekos Theologis ¹

¹ Department of Orthopaedic Surgery, University of California, San Francisco, United States

² Department of Medicine, Division of Gastroenterology, University of California, San Diego, United States

Introduction: Post-operative recovery after adult spinal deformity (ASD) operations is arduous, frought with complications, and often requires extended hospital stays. A need exists for a method to rapidly predict patients at risk for extended length of stay (eLOS) in the preoperative setting. The purpose of this study is to develop a machine learning model to preoperatively estimate the likelihood of eLOS following elective multi-level lumbar/thoracolumbar spinal instrumented fusions (≥ 3 segments) for ASD. Material and Methods: Data were collected retrospectively from a state-level inpatient database hosted by the Healthcare cost and Utilization Project (HCUP). Included for analysis were patients of age ≥ 50 with ASD undergoing elective lumbar or thoracolumbar multi-level instrumented fusions. Predictive variables consisted of demographics, comorbidities, and operative information. The primary outcome was eLOS (> 7 days). Significant variables from univariate and multivariate analyses were used to develop a logistic regression-based predictive model that utilized six predictors. Model accuracy was assessed through area under the curve (AUC), sensitivity, and specificity. Results: 8,866 patients met inclusion criteria. A saturated logistic model with all significant variables from multivariate analysis was developed (AUC = 0.77), followed by generation of a simplified logistic model through stepwise logistic regression (AUC = 0.76). Peak AUC was reached with inclusion of six selected predictors (combined anterior and posterior approach, surgery to both lumbar and thoracic regions, ≥ 8 level fusion, malnutrition, congestive heart failure, and academic institution). A cutoff of 0.18 for eLOS yielded a sensitivity of 77% and specificity of 68%. Conclusion: This predictive model can facilitate identification of adults at risk for eLOS following elective multi-level lumbar/thoracolumbar spinal instrumented fusions for ASD. With a fair diagnostic accuracy, the predictive calculator will ideally enable clinicians to improve preoperative planning, guide patient expectations, enable optimization of modifiable risk factors, facilitate appropriate discharge planning, stratify financial risk, and accurately identify patients who may represent high-cost outliers.

263

P116: Risk factors for extended length of stay and non-home discharge in adults treated with multi-level fusion for lumbar degenerative pathology and deformity

Ayush Arora ¹ , Aboubacar Wague ¹ , Matt Callahan ¹ , Thomas Peterson ¹ , Alekos Theologis ¹ , and Sigurd Berven ¹

¹ Department of Orthopaedic Surgery, University of California, San Francisco, United States

Introduction: Surgical intervention for adult spinal deformity (ASD) patients often necessitates considerable time for recovery in the hospital and after discharge. Extended length of stay(eLOS) and discharge to a rehabilitation center following operations for multi-level instrumented spinal fusions are important outcomes that are significantly associated with complications and higher costs. There is thus a need to accurately identify granular risk factors pre-operatively associated with eLOS and non-home discharges for patients undergoing multi-level fusions for ASD and lumbar degenerative pathology. The purpose of this study is to identify independent risk factors, including the Risk Assessment and Prediction Tool (RAPT) score, associated with eLOS and non-home discharge following elective multi-level instrumented spine fusion operations for diagnosis of adult spinal deformity and lumbar degenerative pathology. Material and Methods: Adults who underwent multi-level (≥3 segments) instrumented spine fusions for ASD and lumbar degenerative pathology at a single institution (2016-2021) were reviewed. Presence of a pre-operative RAPT score was used as an inclusion criterion. Excluded were patients who underwent non-elective operations, revisions, operations for trauma, malignancy, and/or infections. Outcomes were eLOS (>7 days) and discharge location (home vs. non-home). Predictor variables included demographics, comorbidities, operative information, Surgical Invasiveness Index (SII), and RAPT score. Fisher’s exact test was used for univariate analysis, and significant variables were implemented in multivariate binary logistic regression, with generation of 95% percent confidence intervals (CI), odds ratios (OR), and p-values. Results: Included for analysis were 355 patients. Post-operatively, 36.6% (n = 130) had eLOS and 53.2% (n = 189) had a non-home discharge. Risk factors significant for a non-home discharge were older age (> 70 years), SII > 36, pre-op RAPT < 10, DMII, diagnosis of depression or anxiety, and eLOS. Risk factors significant for an eLOS were SII > 20, RAPT < 6, and an ASA score of 3. Conclusion: The RAPT score and SII were most important significant predictors of eLOS and non-home discharges following multi-level instrumented fusions for lumbar spinal pathology and deformity. Preoperative identification of patients with the significant risk factors identified in this study is important for financial risk minimization, patient informed choice, preemptive administration action, and better shared decision-making ability. Preoperative optimization of the RAPT’s individual components may provide a useful strategy for decreasing LOS and modifying discharge disposition.

466

P117: Prospective enrollment of primary vs. revision adult spinal deformity patients: are they different in their preoperative characteristics, intraoperative techniques utilized, and early postoperative complications?

Lawrence Lenke ¹ , Fthimnir Hassan ¹ , Douglas Burton ² , Alan Daniels ³ , Munish Gupta ⁴ , Richard Hostin ⁵ , Khaled Kebaish ⁶ , Michael Kelly ⁴ , Han Jo Kim ⁷ , Eric Klineberg ⁸ , Stephen Lewis ⁹ , Peter Passias ¹⁰ , Themistocles Protopsaltis ¹⁰ , Frank Schwab ¹¹ , Christopher Shaffrey ¹² , Justin Smith ¹² , Renaud Lafage ¹³ , Virginie Lafage ¹³ , Shay Bess ¹⁴ , and International Spine Study Group (ISSG) ¹⁵

¹ Department of Orthopaedic Surgery, Columbia University Medical Center, The Och Spine Hospital at New York-Presbyterian, New York, United States

² Department of Orthopaedic Surgery, University of Kansas Medical Center, Kansas City, United States

³ Department of Orthopaedic Surgery, University Orthopedics, Providence, United States

⁴ Department of Orthopaedic Surgery, Washington University, SOM St. Louis, United States

⁵ Department of Orthopaedic Surgery, Southwest Scoliosis Institute, Dallas, United States

⁶ Department of Orthopaedic Surgery, Johns Hopkins Medical Institute, Baltimora, United States

⁷ Department of Orthopaedic Surgery, Hospital for Special Surgery, New York, United States

⁸ Department of Orthopaedic Surgery, University of California, Davis, United States

⁹ Department of Surgery and Spine Program, University of Toronto, Canada

¹⁰ Department of Orthopaedic Surgery, NYU Hospital for Joint Diseases - Langone Medical Center, New York, United States

¹¹ Department of Orthopaedic Surgery, Lenox Hill Hospital, New York, United States

¹² Department of Neurosurgery, University of Virginia Medical Center, Charlottesville, United States

¹³ Department of Orthopaedic Surgery, Northwell Health

¹⁴ Department of Orthopaedic Surgery, Denver International Spine Center/Presbyterian St. Luke's Medical Center, Denver, United States

¹⁵ International Spine Study Group

Introduction: Adult spinal deformity (ASD) is highly heterogeneous especially in the setting of Primary (P) versus Revision (R) surgical patients, but a thorough preoperative, intraoperative and early postoperative comparison of both groups has not been performed. Methods: Complex surgical ASD patients were dichotomized as either P or R if they had a prior thoracolumbar/lumbar (TL/L) surgery. These outcome domains were evaluated at preop: demographics, radiographs and health-related quality of life (HRQoL); intraop: surgical techniques and periop complications; early postop (6 week) complications and interventions were compared using standard statistical tests. Results: Of the 301 patients enrolled, 164 (55%) were P and 137 (45%) were R. Preoperative demographics showed the 2 groups differed significantly in BMI (P:26.4 vs R:28.6; p = 0.006); preoperative morphine mg equivalent (P:15mg vs R:35 mg; p < 0.0001), and Edmonton Frailty Score (P:2 vs R:4; p < 0.0001). Radiographic parameters differed significantly in 11/15 (73%) measurements with P patients having larger coronal curves while R patients had worse sagittal parameters (eg PI-LL P:12 vs R:26; p < 0.0001). 13/16 (81%) HRQOL domains were statistically superior in P patients (eg ODI P:37 vs R:48; p < 0.0000). Intraoperatively, P and R patients all underwent posterior procedures covering the similar total levels (P:12.8 levels vs R:12.2 levels; p = 0.66. P patients had more interbody fusions (2.4 levels vs 1.8 levels; p < 0.001); more PCOs (5.7 vs 2.9, p < 0.0000), more levels decompressed levels (3.3 vs 2.6, p = 0.006). However, more PSOs were performed in R patients (p = 0.029). Intraoperative data showed similar OR times (P:431min vs R:427 min; p = 0.866), EBL (P:1472cc vs R:1623cc; p = 0.163), and PRBC units transfused (P:1.4 vs R:1.7; p = 0.461) between P vs R groups. 6 week postop complications were similar between both P and R for all medical and surgical complications except for a higher rate of implant-related issues in P patients (6/164 = 3.66% vs 0/137 = 0%; p = 0.0334). Conclusion: Preoperatively, Revision ASD patients are frailer, take more narcotics, have greater sagittal and sacropelvic radiographic malalignment, and have inferior HRQoL measures compared to Primary patients. However, perioperative morbidity and early postop complications are similar between these 2 groups. These findings suggest that primary and revision ASD patients may need to be investigated separately with respect to surgical outcome research.

553

P118: Effect of transverse process hook of UIV instruments on prevention of re-operation associated myelopathy following adult spinal deformity surgery

Sun Joon Yoo ¹ , Kyung-Hyun Kim ¹ , Jeong-Yoon Park ¹ , Dongkyu Chin ¹ , Keun-Su Kim ¹ , and Yong-Eun Cho ¹

¹ Department of Neurosurgery, Gangnam Severance Hospital, Yonsei University, Seoul, South Korea

Introduction: Proximal junctional kyphosis (PJK) is widely known as complication after adult spinal deformity (ASD) surgery, and myelopathy with PJK is the factor that causes re-operation. Less-rigid fixation using transverse process hooks in UIV is thought to best prevent myelopathy in ASD surgery. The aim of this study was to compare the incidence of reoperation associated myelopathy between pedicle screws (PS) and transverse process hooks (TPH) at uppermost instrumented vertebra (UIV) following ASD surgery. Material and Methods: We retrospectively reviewed radiographic and clinical data of 90 consecutive patients (mean age, 68.8 years; mean follow-up period, 24.5 months) who underwent instrumented fusion from sacrum to thoracic spine for the treatment of ASD with a minimum 24months follow-up. Radiologic outcomes including the incidence of PJK and clinical outcomes including the presence of postoperative myelopathy were compared between 33 patients with TPH group and 57 patients with PS group. Results: The myelopathy did not occur in the TPH group but occurred 38.6% in the PS group (p < 0.001). In the TPH group, UIV hook dislodgement in one patient, sacral fracture in one patient, and rod fracture in one patient. In the PS group, reoperation was performed in sixteen patients. The change in proximal junctional angle (PJA) pre- and post-operation were lower in the TPH group (0.2 ± 6.7) than in the PS group (6.6 ± 10.0, p = 0.002). The surgical outcome was almost same results at each groups, except back VAS and SRS-22 domains including pain and satisfaction. The post-operative VAS in the TPH and PS groups were 3.5 and 4.1, respectively (p = 0.010). The pain domain and the satisfaction domain in SRS-22 were significantly difference in the TPH and PS groups (3.3 vs. 2.9; p = 0.033, 3.7 vs. 3.3; p = 0.041). There was no intergroup difference in the SF-36. Conclusion: Our results show that using TPH as a UIV implant can prevent the progress of PJK, reduce the pain, and increase the patient satisfaction after surgery. The TPH of UIV level can prevent post-operative myelopathy and prevent the accompanying re-operation.

751

P119: Retrospective case series of expandable meshed bag for vertebral osteomyelitis interbody fusion and vertebral compression fractures

Zachary Crawford ¹ , Brian Johnson ¹ , Kellsa Mbah-Feng ¹ , Nihar Shah ¹ , and Anthony Guanciale ¹

¹ Orthopaedic Surgery, University of Cincinnati College of Medicine, Cincinnati, United States

Introduction: There are multiple techniques and approaches for insertion of interbody cages to promote fusion, restore alignment, and support posterior instrumentation. Patients with history of osteoporosis, end plate injury, or irregular end plates, all of which may limit implant contact area and stress, are at risk for subsidence and failure of fusion. OptiMesh deployable grafting system (Spineology Inc., Saint Paul, MN, USA) has been previously used for interbody fusion, traumatic injuries, and vertebral compression fracture without subsidence of graft. The objective of this retrospective case series is to evaluate the need for revision surgery and post-operative outcomes associated with use of the OptiMesh grafting system in the setting of vertebral osteomyelitis and traumatic vertebral compression fractures. Methods: Electronic health record was queried for patients with OptiMesh implant by orthopaedic spine surgeon. Patients were included if they underwent vertebroplasty or interbody fusion with OptiMesh at our institution by an orthopaedic spine surgeon. General demographic information including age, gender, medical comorbidities, smoking status, and infectious disease information were collected from retrospective chart review. The primary outcome was revision surgery. Secondary outcomes included post-operative infection, any return to the operating room, and any post-operative complications. Results: Twenty-five patients underwent vertebroplasty or interbody fusion with OptiMesh during the study period. The average age was 61.3 years (range 31.7-87.6 years) with 16 males (64%) and 9 females (36%). Nineteen patients were current or former smokers and 7 patients had diabetes with a hemoglobin A1c of 7.61% (range 5.7-13.2). The most common indication was infection (12 cases), followed by fracture (8 cases), proximal junctional kyphosis (4 cases), and thoracolumbar scoliosis (2 cases). There were no patients in our cohort that required a return to the operating room for graft failure or revision. There were 3 patients with complications of post operative surgical site infection requiring 4 operative irrigation and debridement. There were no additional complications. Conclusion: The use of OptiMesh has previously been studied for vertebral compression fractures and interbody fusion for degenerative spondylolisthesis. Our limited, case series retrospective review utilizing this product for vertebral compression fracture and interbody fusion in the setting of vertebral osteomyelitis has shown to be a valuable option with limited complications and no revision for graft subsidence.

774

P120: Is sexual dysfunction an issue after undergoing a C2-sacrum posterior spinal fusion?

Justin Mathew ¹ , Joseph Lombardi ¹ , Hannah Lin ¹ , Nathan Lee ¹ , Venkat Boddapati ¹ , Zeeshan Sardar ¹ , Lawrence Lenke ¹ , and Ronald A. Lehman ¹

¹ Columbia University, Irving Medical Center, New York, United States

Summary: Patients who have undergone C2-sacrum posterior spinal fusion (PSF) generally continue to be sexually active, though nearly all note some physical limitations during sexual activity. Hypothesis: Patients who have undergone C2-sacrum PSF experience postoperative sexual dysfunction. Study Design: Consecutive case series of open posterior spinal instrumented fusion from C2-sacrum. Introduction: Patient who have undergone C2-sacrum posterior spinal fusion (PSF) comprise a poorly studied population. Limitations in sexual function are unreported in the literature among those with any major spinal reconstruction. While many of these patients resume hobbies and activities, they will often query surgeons preoperatively about their postoperative sexual function. The ability to adequately counsel this patient population is hampered by the dearth of literature on this subject. Methods: 25 patients who had undergone C2-sacrum PSF at a single institution were contacted by email and telephone. A standardized, validated questionnaire (ASEX) was administered, as well as specific questions addressing arousal, physical limitations during sex, and sexual satisfaction. Responses were assigned numerical values and assessed using descriptive statistics and student’s t test. Sexual dysfunction was defined as an ASEX score > 19. Results: Of 25 patients who had undergone C2-sacrum PSF, 60% (15/25) responded. 48% (12/25) were able to complete to the questionnaire. 8% (2/25) had never had sex (before or after surgery) and were excluded. 4% (1/25) had an underlying medical condition and felt unable to answer the questionnaire. The average follow up time was 3.3 ± 1.2 years. Over 90% of respondents had more than two years follow up since their C2-sacrum PSF. Of those who responded, 33% (4/12) experience sexual dysfunction as defined by ASEX > 19. Though the ASEX questionnaire generally addresses arousal, the responses did not differ significantly from the responses to our tailored questions (p = 0.28). Of the patients who reported being in the upper quartile of difficulty with physical limitations (discomfort, muscle tightness, or motion restriction), only one had sexual dysfunction. 92% of the respondents report return to sexual activity following C2-sacrum PSF. Conclusion: This is the first study to evaluate sexual dysfunction after a C2-sacrum fusion. Interestingly, 92% of those who underwent C2-sacrum PSF report a return to sexual activity, with only 33% demonstrating sexual dysfunction.

Take Home Message: Nearly all patients who have undergone C2-sacrum PSF remain sexually active, though with limitations and changes in their sex lives.

816

P121: Skin adhesive tapes are an effective wound closure method for percutaneous vertebral body stenting: a retrospective cohort study

Cassie Yang ¹ , Theophilus Qiu ² , Reuben Soh ¹ , and Youheng Ou Yang ¹

¹ Department of Orthopaedic Surgery, Singapore General Hospital, Singapore, Singapore

² Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore

Introduction: Percutaneous Vertebral Body Stenting (VBS) is performed via a balloon-expandable metallic stent introduced through a stab incision. It aims to reduce and maintain the reduction of vertebral body fractures, as well as minimise bone cement extravasation. The delivery of the balloon and stent implant requires the insertion of a larger access kit as compared to traditional vertebroplasty (PVP) systems (4.7 vs 2.59mm diameter, 330% increase in surface area). The larger skin incision, soft tissue disruption and pedicle bore tract with exposed raw bone increases the risk of bleeding and wound complications. Skin Adhesive Tapes (SATs) are effective in treating small non-gaping wounds and have been used as a method of wound closure for PVP. This study aims to evaluate the use of SATs in closure of larger VBS wounds. Methods: A retrospective cohort of patients who underwent percutaneous VBS (DePuy Synthes, USA) was obtained from electronic medical records of patients treated at a tertiary hospital from May 2019 to March 2021. Data was collected for wound closure method (conventional non-absorbable suture closure, SAT closure), number of operative levels and postoperative skin-related wound complications, wound dehiscence, wound infection, postoperative bleeding, symptomatic haematomas and return to operating theatre. At clinic follow-up post-discharge, the wounds were also reviewed for complete healing and unsightly scarring requiring wound revision. SAT closure was performed by applying 3 strips of SATs to loosely oppose the wound edges. Results: 36 patients were identified with 45 levels of VBS performed. 3 (8.3%) patients received conventional suture closure, 33 (91.6%) received SAT closure. Conventional suture closure was performed in view of ongoing bleeding at the wound site for 2 patients who had coagulopathy. The remaining patient received a planned suture closure in view of surgical expediency as part of a staged procedure. 32 (97.0%) of SAT closures were uneventful. 1 (3.0%) patient developed blood soaked dressings that required early removal and reapplication of the SATs at the ward a day later with uneventful recovery thereafter. No patient with SAT closure developed any surgical site infection, wound dehiscence, symptomatic haematoma or required return to theatre. All SAT closure patients had complete wound healing at outpatient follow up with no wound revision for cosmesis. Conclusion: SATs are a simple, safe and effective means of wound closure for the majority of percutaneous VBS procedures. Patients who could not undergo SAT closure had pre-existing coagulopathy or had been planned for additional procedures.

874

P122: No significant radiological signs of adult spinal deformity progression after a mean of 11 years of follow-up following Harrington rod instrumentation removal: a single-institution case series

Peter Brumat ¹ , Janez Mohar ¹ , Dejan Čeleš ¹ , Nikša Hero ¹ , and Matevž Topolovec ¹

¹ Department of Spine Surgery, Valdoltra Orthopaedic Hospital, Ankaran, Slovenia

Introduction: Instrumentation with Harrington rod used to be the standard of care for scoliosis treatment in children. Such a method of spinal instrumentation is frequently associated with residual deformity and sagittal malalignment in adults. The adult spinal deformity can be managed with nonsurgical methods or surgical treatment. Surgical correction for Harrington rod instrumentation sequelae presents a challenge in adult spinal deformity surgery due to complex conditions involving residual structural alterations and technically demanding procedures frequently needing osteotomies, with the high surgical risk involved. Although surgical treatment may be better than nonsurgical methods for improving the function of patients with adult spinal deformity and achieving good pain improvement and deformity correction, the surgical treatment of adult spine deformity correlates with frequent complications, substantial financial burden, and resource utilization. Our study aimed to assess radiological outcomes in patients from our institution who were treated primarily for adolescent idiopathic scoliosis with surgical correction using Harrington rod instrumentation and secondarily with conservative management of residual spinal deformity after Harrington rod removal, whereby no patient consented to adult spinal deformity correction. Material and Methods: We evaluated single-institution case series of 12 adult patients after a mean of 11 years of follow-up following Harrington rod instrumentation removal, with a minimum 1 year of follow-up. Preoperative and most recent post-instrumentation removal radiographic measurements were obtained and compared, along with baseline demographics. Results: The average age of patients (all females) at the time of instrumentation removal was 38 ± 10 years, the average BMI was 25 ± 6, and the average ASA physical status score was 2 ± 1. The mean follow-up from the Harrington rod instrumentation implantation to the Harrington rod instrumentation removal was 21 ± 10 years, with a further mean of 11 ± 10 years following instrumentation removal. No significant change in radiological parameters was observed.: LL (p = 0.433), TK (p = 0.173), PT (p = 0.260), SS (p = 0.076), PI (p = 0.210), PI-LL mismatch (p = 0.504), SVA (p = 0.218), C7-CSVL (p = 0.370), SSA (p = 1.000), C7 ratio (p = 0.099), and coronal Cobb angle (proximal (p = 0.488), main thoracic (p = 0.130) and lumbar (p = 0.317)). Conclusion: This study suggests that adults with no significant change in coronal or sagittal parameters following Harrington rod instrumentation removal may be amenable to conservative management of residual spinal deformity if surgical correction of spinal deformity is not consented to.

946

P123: Using proximal hooks as a soft-landing strategy for prevention of proximal junctional kyphosis in the surgical treatment of Scheuermann's kyphosis

Alim Can Baymurat ¹ , Aliekber Yapar ² , Mehmet Tokgoz ¹ , İsmail Daldal ³ , Yagiz Akcan ¹ , and Alpaslan Senkoylu ¹

¹ Department of Orthopedics and Traumatology, Gazi University Faculty of Medicine, Ankara, Turkey

² Department of Orthopedics and Traumatology, Health Sciences University, Antalya Education and Research Hospital, x Antalya, Turkey

³ Department of Orthopedics and Traumatology, Ankara Lokman Hekim Akay Hospital, Ankara, Turkey

Introduction: PJK after surgical treatment of SK still remains a serious problem, although good results have been reported in the literature. For preventing the PJK in SK surgery, some spine surgeons use hook fixation in the upper end as a soft-landing strategy. The current study mainly focused on PJK development and aimed to compare the clinical and radiological outcomes of only pedicle screw constructs and hybrid constructs with hooks for the treatment of SK. Hypothesis: There is no difference in long-term results between only pedicle screw constructs, and hybrid fixation with hooks in terms of proximal junctional kyphosis (PJK) development after Scheuermann's kyphosis (SK) surgery. Study Design: A retrospective case series with a minimum of 2 years of follow-up. Material and Methods: The data of 22 only pedicle screws (14 men and 8 women; mean age: 26.58 ± 7.55 years) and 15 hybrid constructs with hooks and pedicle screws (8 men and 7 women; mean age: 25.46 ± 9.04 years) implanted patients who underwent corrective surgery for SK between January 2005 and December 2019 were reviewed. The preoperative, early postoperative, and minimum 24-month follow-up radiographs and the Scoliosis Research Society-22 (SRS-22) scores were evaluated. The C7 sagittal vertical axis (C7-SVA), T2-T12 kyphosis angle, proximal and distal junctional angles were measured. The radiological differences between preoperative, early postoperative, and last follow-up X-Ray evaluations were compared. Results: While the mean follow-up period of the pedicle screw group was 94.7 ± 53.1 months, it was 103 ± 64.4 months in the hybrid group. As a result of the analyzes performed, no statistically significant result was observed in the measurements made in the SRS-22 total score and subscores, preoperative, postoperative, and last follow-up radiographs (p>0.05). The change in proximal and distal junctional kyphosis angles (p: 0.045, p: 0.03, respectively) increased more than hybrid structures in patients who only used pedicle screws. Conclusion: Although there was no significant difference between the two groups, the PJK angle was found higher in patients with pedicle screw fixation. Therefore, PJK development should be carefully followed when pedicle screw fixation is used in the upper segment. Furthermore, using hooks at the upper end seems to prevent PJK.

962

P124: Effect of the brace on apical vertebra in adolescent idiopathic scoliosis

Alim Can Baymurat ¹ , Mehmet Tokgoz ¹ , İsmail Daldal ² , and Alpaslan Senkoylu ¹

¹ Department of Orthopedics and Traumatology, Gazi University Faculty of Medicine, Ankara, Turkey

² Department of Orthopedics and Traumatology, Ankara Lokman Hekim Akay Hospital, Ankara, Turkey

Introduction: Scoliosis is a three-dimensional spinal deformity. The brace application is widely used in the control of spinal curvatures in the coronal plane in suitable scoliosis patients. In the current study, it was aimed to evaluate the effect of corset (Boston type) use on the apical vertebra in patients treated conservatively for Adolescent Idiopathic Scoliosis (AIS) and to evaluate the effect of the Scoliosis Research Society's Health-Related Quality of Life-22 (SRS-22) questionnaire. Material and Methods: The current study was conducted in Gazi University Faculty of Medicine - Department of Orthopedics and Traumatology between 2010-2020 and conservatively treated patients with a Boston type brace for at least 2 years with the diagnosis of AIS were included in the study (Mean age: 12.2 ± 1.3, – 43 Female, 8 male). Before the brace, early in-brace, and at the last follow-up whole spinal radiographs of the patients were evaluated. Apical vertebral rotation (AVR) was evaluated according to the Nash Moe classification. Besides, the apical vertebral translation (AVT), which is the distance between the apical vertebra to the central sacral perpendicular line, was measured. The SRS-22 questionnaire was performed to evaluate the patients' quality of life and their perception of deformity. Results: The mean follow-up period was 32.4 ± 8.7 (24-52) months, the AVR before the brace was 2.1 ± 0.6, while it was 1.14 ± 0.5 in the brace. At the last control, AVR was measured as 1.3 ± 0.5 (p < 0.001). While the AVT before the brace was 36.4 ± 9.6, it was measured as 16.7 ± 7.3 with the brace (p < 0.001). At the last follow-up, the AVT was determined as 19.8 ± 8.1 (p < 0.001). A significant improvement was observed in cobb angles in thoracic, thoracolumbar, and lumbar curvatures compared to pre-corset period (p < 0.001). Pain, function, and satisfaction domains of the patients reached satisfying levels according to normative data of SRS-22. On the other hand, the means of mental health and self-image domains were fall short of the mark. Conclusion: In the study, it was observed that the use of a brace in the conservative treatment of AIS was effective in controlling the coronal curve of thoracic, thoracolumbar, and lumbar curves, as well as in correcting the rotation and translation of the apical vertebrae. There was no corrective effect on upper thoracic curvatures.

1029

P125: Comparison of posterior vs double appoach in the treatment of adult degenerative scoliosis

Clauio Mauricio Uribe Alpizar ¹ , Alejandro Reyes-Sánchez ¹ , and Carla Garcia Ramos ¹

¹ Orthopedic, National Institute of Rehabilitation, Mexico City, Mexico

Introduction: An increase in the adult population is currently occurring worldwide. World literature has identified that the prevalence of scoliosis increases with age and that curvatures may appear in a previously aligned spine, unlike idiopathic scoliosis in young people, it presents with pain and disability in adults. Currently, a prevalence in the population of 2 to 32% is reported in those over 50 years of age and up to 60% in those over 60 years of age. Given that its main symptom is pain, this condition has an impact on the quality of life of those who suffer it, limiting their personal and work activities, becoming disabling. It is most frequently observed in adult patients of productive age, progressing with disability. Previous studies have shown that scoliotic curvature correction is over 70% with a double approach vs. 44% with a posterior approach. Controversy exists regarding lordosis, complications, pseudoarthrosis and complication rate. This research proposes to carry out a comparative study between the clinical, radiological and functional results of two surgical techniques and their variants, as well as to establish if there is correspondence between the radiographic changes and the clinical situation of the patient. The number of studies comparing the posterior approach with a dual approach for management of adult degenerative scoliosis is minimal. When searching with the search terms: "surgery" + "degenerative scoliosis" + "double approach" search in PubMed, Google Scholar, Ovid, Cochrane we obtained a total of 11 references, however, when we searched the Mexican literature, we did not find any reference to the subject. Therefore, we conclude that there is no precedent where the results of double surgical treatment in patients with this disease are analyzed in our country. Material and Methods: Prospective, longitudinal, comparative controlled study with two-year follow-up, In adult degenerative scoliosis, divided into two groups Group I treated with posterior approach and Group 2 treated with double approach. 43 patients with an average age of 63.2 years, 30 women (69.76%), with curves with magnitude from 10 to 42°. 35 were subjected to a posterior approach, while 8 were treated with a double approach (ALPA + posterior). Results: The Roland-Morris scale in group 1 was 13.17 (0-22), and at 2 years 9.75 (0-22) for group 2 with a preoperative mean of 14.71 (8-20) and 7.28 (0-14) at 2 years. No statistical significance between groups (p = 0.356). The Oswestry in preoperative group 2 patients was 49.71 (26-74); 2 years in 21.85 (2-44). For group 1 in 54.27 (18-82), and 35.51 (2-82) in 2 years. Pelvic parameters have no difference and only correction of scoliosis and sagittal balance was better in the double-approach group. Conclusions: The ALPA + posterior approaches, compared to only the posterior approach, have an advantage in reducing the magnitude of scoliosis and restoring sagittal balance. In terms of quality of life and perception of pain, both approaches show to be equally effective.

1078

P126: Surgical treatment of ankylosing spondylitis complicated with thoracolumbar sagittal-coronal deformity

Tao Xu ¹ , Xiaoyu Cai ¹ , Jarkenay Abudulayi ² , and Weibin Sheng ¹

¹ Department of Spine Surgery, Urumqi, China

² Department of Breast Surgery, First Affiliated Hospital of Xinjiang Medical University, Urumqi, China

Introduction: To investigate the incidence and clinical characteristics of coronal imbalance in patients with ankylosing spondylitis (AS) complicated with thoracolumbar sagittal coronal deformity, and to explore the surgical methods and clinical efficacy in patients with AS complicated with thoracolumbar sagittal coronal deformity. Material and Methods: The case data of 22 patients (17 males and 5 females) with AS complicated with kyphosis from January 2010 to January 2021 were retrospectively analyzed. The average age was 40.3 ± 6.5 years (range, 27-61 years). All patients were measured coronal parameters: coronal balance distance (CBD); coronal imbalance angle (CIA) and sagittal parameters: C7-SVA, global kyphosis (GK), thoracolumbar kyphosis (TLK), thoracic kyphosis (TK), lumbar lordosis (LL), pelvic incidence (PI), pelvic inclination (PT), sacral inclination (SS). Paired t-test was used for statistical analysis. Results: Ten patients (45.5%) were type A and 12 patients (54.5%) were type B. All patients underwent PSO osteotomy to correct sagittal and coronal deformities. All 22 cases were successfully operated, including 19 cases of one-stage operation and 3 cases of staged operation. The operation time ranged from 185 to 405 minutes (mean 215 minutes). The intraoperative blood loss was 450-1200ml (mean 550 ml). There were 8-16 fixed fusion segments, with an average of 10.8 segments. The mean follow-up time was 39.0 ± 13.8 months (range: 12-131 months). CBD was corrected from 10.07 ± 6.68 cm to 3.21 ± 2.01 cm and 3.33 ± 2.0 cm. CIA improved from 18.16 ± 5.23° to 6.11 ± 3.78° and 5.99 ± 3.74°. C7-SVA was corrected from 24.38 ± 8.65 cm to 10.7 ± 5.15 cm. GK was corrected from 61.52 ± 15.38° to 24.66 ± 13.24°. TLK was corrected from 54.99 ± 11.73° to 19.68 ± 12.19°. TK was corrected from 56.64 ± 6.54° to 41.51 ± 9.9°. LL was corrected from 12.56 ± 8.57° to -32.64 ± 18.21°. PI was corrected from 44.64 ± 8.57° preoperatively to 45.56 ± 9.5°. PT was corrected from 35.39 ± 9.59° to 27.65 ± 6.98°. SS was corrected from 14.12 ± 8.63° to 17.97 ± 9.36°. Significant differences were observed between the postoperative and preoperative deformities except for PI and SS. At the last follow-up, the correction rates of CBD, CIA, C7-SVA and GK were 80.2%, 76.2%, 76.1% and 58.9%, respectively. The mean VAS score of 22 patients was (7.42 ± 1.37) preoperative and (4.22 ± 0.98) at the last follow-up with significant difference (t = 20.249, P = 0.000). The average ODI was 58.68% ± 7.45% preoperative and 26.52% ± 4.21% at the last follow-up significantly (t = 42.543, P = 0.000). The mean score of SRS⁃22 was 9.62 ± 3.06 preoperatively, which was improved to 22.84 ± 3.15 at the last follow-up significantly (t = 25.023, p = 0.000). Perioperative complications occurred in 7 patients (32%). Conclusion: A distance of more than 3cm between the C7 plumb line and the sacral midline was used as a diagnostic criterion for coronal disequilibrium. Asymmetrical PSO osteotomy was used to correct coronal imbalance at the apex of coronal imbalance, and CWO osteotomy was used to correct kyphosis at the apex of sagittal kyphosis. For type A patients with single-segment PSO osteotomy, asymmetrical COWO osteotomy was used to correct both sagittal and coronal imbalance at the apex of sagittal and coronal imbalance. The evaluation of intraoperative coronal balance by point-line method can effectively reduce the incidence of postoperative coronal imbalance in patients with AS complicated with sagittal and coronal imbalance.

1109

P127: Physiotherapy scoliosis specific exercise improves pelvic obliquity in adults with idiopathic scoliosis

Charles Impey ¹ , Georgina Frere ¹ , Erika Maude ¹ , Zion Hwang ¹ , Emily Tsang ¹ , Priyanshu Saha ¹ , Bisola Ajayi ¹ , Timothy Bishop ¹ , Jason Bernard ¹ , and Darren Lui ¹

¹ St George's University Hospital, London, United Kingdom

Introduction: Pelvic obliquity (PO) contributes to altered gait patterns, causing asymmetrical loading, increased muscular work, and prolonged activation of lumbar muscles. It can cause waistline asymmetry which is a well-documented complaint in scoliosis. This study aimed to determine the effects of an intensive course of Physiotherapy Scoliosis Specific Exercise (PSSE) on PO in patients with idiopathic scoliosis (IS). Method: Consecutive patients with IS with primary thoraco-lumbar or lumbar curvatures completing an intensive course of PSSE over a 4-week timeframe between April 2019 and December 2021 were recruited. Patients who had undergone bracing treatment or surgery for scoliosis were excluded. All patients were routinely scanned using a Formetric Scanner pre- and post-treatment. The PO, expressed in millimetres, was documented. Adults (>17 years old) (group 1) and children (group 2) were analysed separately. Results: In Group 1 (n = 19) the ages ranged from 18 to 73 with a median age of 25. 89.5% were female. The average Cobb angle was 36.3°. There was a 35% improvement in PO from 6.63mm (SD = 4.3) pre-treatment to 4.32mm (SD = 10.23) post-treatment (p < 0.05). In Group 2 (n = 31) the ages ranged from 8 to 16 with a median age of 14. 90% were female. The average Cobb angle was 31.3°. There was a 23% improvement in PO from 4.68mm (SD = 4.14) pre-treatment to 3.58mm (SD = 2.51) post-treatment (p = 0.09). Conclusion and Significance: An intensive course of PSSE has shown to improve PO in adult patients with IS. This can contribute to improving the patients’ biomechanics and self-image and therefore health-related quality of life.

1114

P128: Physiotherapy scoliosis specific exercise improves truncal shift in idiopathic scoliosis

Charles Impey ¹ , Georgina Frere ¹ , Erika Maude ¹ , Zion Hwang ¹ , Emily Tsang ¹ , Priyanshu Saha ¹ , Jason Bernard ¹ , Timothy Bishop ¹ , and Darren Lui ¹

¹ St George's University Hospital, London, United Kingdom

Introduction: Truncal shift caused by scoliosis can be measured with a Formetric Scanner using the Maximal Thoracic Apical Deviation (MTAD) measurement. It is an important measure in pre-operative assessment and post-operative outcomes. The aim of this retrospective cohort study was to determine the effectiveness of Physiotherapy Scoliosis Specific Exercise in improving MTAD in patients with idiopathic scoliosis (IS). Methods: Consecutive patients with IS with right-sided thoracic major curvatures, completing an intensive course of PSSE over a 4-week timeframe between April 2019 and December 2021 were recruited. Patients who had undergone bracing treatment or surgery for scoliosis were excluded. All patients were routinely scanned using a Formetric Scanner pre- and post-treatment. MTAD, measured in millimetres was documented. Adults (>17 years old) (group 1) and children (group 2) were analysed separately. Results: In Group 1 (n = 20) the ages ranged from 20 to 79 with a median age of 29.5. 84% were female. The average Cobb angle was 44.1°. There was a 19.1% improvement in MTAD from 40.05mm (SD = 17.67) pre-treatment to 32.42mm (SD = 13.46) post-treatment (p < 0.05). In Group 2 (n = 20) the ages ranged from 8 to 16 with a median age of 13. 95% were female. The average Cobb angle was 42.6°. There was an 18.2% improvement in MTAD from 35.65mm (SD = 10.10) pre-treatment to 29.15mm (SD = 12.87) post-treatment (p < 0.005). Significance and Conclusion: PSSE significantly improves MTAD in both adults and children with IS and therefore may aid in enhancing surgical outcomes.

1133

P129: Analysis of the difference in sitting ability based on fusion level in patients with adult spinal deformity corrective surgery

Jaeyoung So ¹ and Kyung-Hyun Kim ¹

¹ Department of Neurosurgery, Spine and Spinal Cord Institute, Gangnam Severance Hospital, Seoul, South Korea

Introduction: There is still debate how surgeons could decide treatment methods for adult spinal deformity, operatively or not. There was lack of information how long level fusion impacts daily activities, especially sitting ability. The primary goal of surgical arthrodesis is to eliminate the motion of spinal segments in an effort to alleviate pain, improve deformity, and reduce disability. However, decreased spinal mobility may impair performance of activities of daily living due to the resulting stiffness or the lack of mobility of the fused segment. We aimed to assess the sitting ability in patients undergoing adult spinal deformity corrective surgery, comparing L4-5 or L3-4-5 fusion, L4-5 or L4-5-S1 lumbar fusion surgeries through a patient-reported outcome questionnaire measuring the impact of lumbar stiffness. Materials and Methods: A total 113 patients, who underwent adult spinal deformity corrective surgery, 1 or 2 levels of fusion including L4 and L5 without sacropelvic fixation (L4-5 or L3-4-5 fusion), and 1 or 2 levels of fusion including L5 and S1 with sacropelvic fixation (L5-S1 or L4-5-S1 fusion) in our neurosurgery clinic. Data of the patients were obtained from electronic patients records and Sitting ability questionnaire. Patients were divided into three groups, each consisting of 47 patients, who underwent L4-5 fusion or L3-4-5 fusion (L4-5 Group), 33 patients who underwent L5-S1 fusion or L4-5-S1 fusion (L5-S1 Group) and, 33 patients who underwent adult spinal deformity corrective surgery (Deformity Group). We investigate the basic demographics (age, gender, follow duration, etc.), Sitting ability score and Lifestyle through Sitting ability questionnaire. The factors affecting sitting ability were also investigated. Results: The average sitting ability score was 80.67 ± 14.28 for L4-5 Group, 79.48 ± 16.25 for L5-S1 Group, 60.70 ± 19.75 for Deformity Group, respectively. There was no significant difference between L4-5 Group and L5-S1 Group (p = 0.753). There were significant differences between L4-5 Group and Deformity Group (p < 0.0001), between L5-S1 Group and Deformity Group (p < 0.0001). The mean follow-up duration was 70.25 ± 38.80 months for L4-5 Group, 75.27 ± 59.53 months for L5-S1 Group, 40.86 ± 20.80 months for Deformity Group, respectively and there was significant difference among these groups. (p < 0.0001). Conclusion: Multilevel lumbar fusion significantly limits the lumbar mobility and affects the ability to compensate postural changes. Reducing the fusion segments as much as possible is of particular value in preserving lumbar mobility and maintaining the compensatory mechanism of spinopelvis. Not only the fusion level, but also the sitting ability will be different with the difference of UIV and LIV level, so this should be considered during lumbar fusion surgery.

1196

P130: Unplanned reoperation and readmission following adult spinal deformity surgery: an analysis over 8,500 spinal deformity patients

Daniel Gallagher ¹ , William Huffman ² , Jacob Harris ² , Rex Marco ³ , Paul Holman ³ , and Comron Saifi ⁴

¹ Robert Wood Johnson Medical School, Rutgers University, New Brunswick, United States

² Perelman School of Medicine, University of Pennsylvania, Philadelphia, United States

³ Department of Orthopedics and Sports Medicine

⁴ Spine Surgery, Houston Methodist Hospital, Houston, United States

Introduction: It was estimated that 30-day readmissions across all specialties resulted in $41.3 billion in hospital costs in 2011. Unplanned reoperations require additional resources and add further financial strain on the healthcare system and patients. The utilization of Adult Spinal Deformity (ASD) surgery has been rapidly growing but, the complication rate remains high. Although prior research has identified factors associated with adverse outcomes of spinal deformity surgery, the few studies that have evaluated factors predictive of reoperation and readmission rates included fewer than 800 patients, limiting their statistical power to detect infrequent predictors. The purpose of this study is to use the American College of Surgeons National Surgical Quality Improvement Program (ACS NSQIP) to identify risk factors associated with unplanned reoperation and readmission within 30 days following surgical correction of ASD with ≥ 7 levels of correction. A reoperation rate of 5% and a readmission rate of 10% were hypothesized based on prior literature. Materials and Methods: A retrospective observational study was conducted using the ACS-NSQIP database for patients undergoing ASD surgery from 2010 to 2019. The NSQIP database collects more than 150 variables from over 600 participating hospitals in the United States. Each participating site has a trained and certified surgical clinical reviewer to extract preoperative to 30-day postoperative data for randomly assigned patients. The NSQIP has developed multiple processes to optimize accuracy and reliability of data collection, including an inter-rater reliability audit of selected sites. Using the ACS-NSQIP participant user file, patients from participating institutions, aged 18 years and older having surgical correction of ASD with ≥ 7 levels of correction, were identified using Current Procedural Terminology (CPT) codes 22843 and 22844. Methods were conducted in accordance with the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) guidelines. Results: 8,533 patients met the inclusion criteria, with a mean age of 62 years and a female predominance (55%). The 30-day unplanned reoperation and readmission rates were 7.55% and 9.72%, with 13.43% having either an unplanned reoperation or readmission. Independent predictors of both reoperation and readmission were African American race, bleeding disorders, and chronic steroid use. Independent predictors of unplanned reoperation alone included >10% loss of body weight in last 6 months and emergency cases. Independent predictors of readmission alone included disseminated cancer, partially dependent functional status, and totally dependent functional status. The most frequent reoperation was incision and drainage (8.07%). The most common causes of readmission were surgical site infection (SSI) (16.89%) and wound disruption (4.70%). Conclusion: Patients undergoing spine surgery for adult spinal deformity with >6 levels of instrumentation had an 8% and 10% rate of unplanned reoperation and readmission, respectively. There was a 13% rate of either unplanned reoperation or readmission. African American race, bleeding disorders, disseminated cancer, immunosuppressant use for a chronic condition, and lower functional status were the most significant predictors of 30-day unplanned reoperation or readmission. These individual factors were associated with increases in the rates of reoperation or readmission of 36-152%. SSI was the most common reason for both reoperation and readmission.

1263

P131: The summit versus the base: which aspect of the construct has more influence on the development of proximal junctional kyphosis following adult spinal deformity surgery?

Peter Passias ¹ , Tyler Williamson ¹ , Bailey Imbo ¹ , Pooja Dave ¹ , Peter Tretiakov ¹ , Kimberly McFarland ¹ , Jamshaid Mir ¹ , Andrew Schoenfeld ² , Stephane owusu-saprong ¹ , Jordan Lebovic ¹ , Shaleen Vira ³ , Bassel Diebo ⁴ , Justin Smith ⁵ , Virginie Lafage ⁶ , and Renaud Lafage ⁶

¹ NYU Langone Medical Center, New York, United States

² Brigham and Women’s Hospital/Harvard Medical Center, Boston, United States

³ UT Southwestern Medical Center, Dallas, United States

⁴ SUNY Downstate Medical Center, New York, United States

⁵ University of Virginia, Charlottesville, United States

⁶ Lenox Hill Hospital, New York, United States

Purpose: Evaluate the surgical technique that has greatest influence on the rate of junctional failure following ASD surgery. Introduction: Due to the severity and complexity of adult spinal deformity (ASD), differing presentations may influence the extent of surgical intervention and use of prophylaxis at the base or the summit of a fusion construct to influence junctional failure rates. It is unclear whether interventions at the base, summit or both are needed to effectively mitigate junctional failure. Methods: ASD patients with 2Y data and at least 5-level fusion to pelvis were included. Patients were divided based on UIV: [Longer Construct: T1-T4; Shorter Construct: T8-T12]. Parameters assessed included matching in age-adjusted PI-LL or PT, aligning in GAP-Relative Pelvic Version or Lordosis Distribution Index. Combination of realigning the two parameters with the greatest minimizing effect of PJF constituted a Good Base. Good Summit defined as having all 3: 1) prophylaxis at UIV (tethers, hooks, cement), 2) no lordotic change (under-contouring) greater than 10° of the UIV during surgery, 3) preoperative UIV inclination angle < 30°. Multivariable regression analysis assessed effects of junction characteristics and radiographic correction individually and collectively on development of PJK and PJF in differing construct lengths, adjusting for confounders. Results: 261 patients were included, with 38% developing PJK, 10% developing PJF. The cohort that had summit and base addressed had lower odds of PJK (OR: 0.5, [0.2-0.9]) and PJF was less likely (OR: 0.1, [0.0-0.7]; p = .014) in the presence of a Good Summit. Normalizing pelvic compensation had the greatest radiographic effect on preventing PJF overall (OR: 0.6, [0.3-1.0]; p = .044). Stratifying by UIV, 114 were Longer Constructs, 147 Shorter Constructs. In Shorter Constructs, realignment had greater effect on decreasing the odds of PJF (OR: 0.2, [0.02-0.9]; p = .036). With Longer Constructs, a Good Summit lowered likelihood of PJK (OR: 0.3, [0.1-0.9]; p = .027). Good Base had reducing effects on PJF (0% vs. 20%, p < .001). In patients with severe frailty/osteoporosis, a Good Summit lowered rates of PJK (20.0% vs. 39.3%, p = .017) and PJF (4.0% vs. 13.4%, p = .020). Conclusion: To mitigate junctional failure, our study demonstrated the utility of individualizing surgical approaches to emphasize an optimal basal construct. Achievement of tailored goals at the cranial end of the surgical construct may be equally important, especially for higher risk patients with longer fusions.

1316

P132: Maintenance of pelvic tilt normalization following adult spinal deformity corrective surgery: analysis of prevalence, timing, and predictors influencing occurrence

Peter Passias ¹ , Pooja Dave ¹ , Peter Tretiakov ¹ , Jamshaid Mir ¹ , Kimberly McFarland ¹ , Andrew Schoenfeld ² , Bassel Diebo ³ , Renaud Lafage ⁴ , Virginie Lafage ⁴ , and Shaleen Vira ⁵

¹ NYU Langone Medical Center, New York, United States

² Brigham and Women's Hospital, Boston, United States

³ Warren Alpert Medical School, Providence, United States

⁴ Lenox Hill Hospital, New York, United States

⁵ UT Southwestern, Dallas, TX, United States

Introduction: Increasing pelvic tilt (PT) is a primary compensatory mechanism in adult spinal deformity (ASD). Some ASD patients improve their PT following ASD correction, while others do not. The driving forces behind this lack of PT-response are not well defined.

Hypothesis: To determine the surgical and radiographic parameters associated with and predict maintaining PT normalization after ASD corrective surgery. Methods: ASD patients fused to S1/pelvis with full preoperative data as well as preoperative (BL), 6-week (6W), and 2-year (2Y) post-op PT measurements were included. Patients were stratified into four groups based on PT measurements at 6 week and 2 year follow-up: Early Normalization with PT < 20° by 6 weeks (PTNorm6w); Delayed Normalization with PT < 20° by 2 years (PTNorm2y); Non-normalized with PT >20° by 2 years (Non); Reversal Normalization with PT < 20° by 6 weeks and PT >20° by 2 years (RevNorm). Univariate analyses were used to compare normalized (PTNorm6w and PTNorm2Y) and non-normalized (Non and RevNorm) in terms of postoperative alignment (PI-LL, SVA, and GAP score) and clinical outcomes (complication rates, HRQL). Multivariable logistic regression were used to develop a model consisting of significant predictors for 6 week and 2 year normalization. Results: 253 ASD patients met inclusion criteria (64.6 ± 9.06 years, 79% female, BMI 27.9 ± 5.57 kg/m2, CCI: 1.9 ± 1.6, levels fused 11.8 ± 4.4, EBL: 1841.6 mL, op time: 449.6 min). Mean PT was as follows: BL: 30.5°, 6W: 22.5°, and 2Y: 25°. By SRS-Schwab criteria (Normal: PT < 20°; Moderate: PT 20-30°; Severe: PT > 30°), 56.5% (n = 143) had a moderate pelvic tilt at baseline and 43.5% (n = 110) had severe pelvic tilt at baseline. 37.9% (n = 96) were normalized at 6 weeks and 6.3% (n = 16) normalized between 6 weeks and 2 years, with a total of 43.1% (n = 109) normalized by 2 years. 33 (13%) had reversal of normalization at 2 years. PT6WNorm and PT2YNorm groups were more likely to be overcorrected in radiographic goals including PI-LL, SVA, and PT at 6 weeks (p < .05). GAP score at 6 weeks (.55 vs 1.34, p = 0.08) was greater for non-normalized patients. RevNorm patients had significantly lower PI (56.5 vs 61.6, p < .05) and GAP score (1 vs 1.5, p < .05) compared those achieving normalization at 2 years. Compared to non-normalized patients, those achieving normalization by 2 years had lower rates of implant failure (8.9% vs 19.5%, p < .05), rod breakage (1.3% vs 13.8%, p < .05) and pseudoarthrosis (0% vs 4.6%, p < .05). Total complication rate was significantly lower for those achieving normalization (56.7% vs 66.1%, p = .02). No significant difference in ODI, EQ5D, or SRS22 Pain scores. Multivariate regressions used to create a model for normalization showed 88% of patients achieved significantly greater normalization with lower baseline and 6 week PI-LL (OR .82 [.7 - .95], p < .05). Conclusion: PT normalization following ASD correction occurred in almost 40% of patients by 6 weeks and 43% by 2 years after surgery. Normalization was more likely to occur in patients where reconstruction addressed lumbopelvic mismatch and extended above the apex of the thoracic kyphosis. PT normalization and maintenance remains an important factor for improved post-surgical outcomes.

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P133: Incremental benefit of revision surgery after adult spinal deformity corrective surgery: at what point does the value of multiple revisions diminish in ASD corrective surgery and does it depend on etiology

Peter Passias ¹ , Pooja Dave ¹ , Peter Tretiakov ¹ , Kimberly McFarland ¹ , and Jamshaid Mir ¹

¹ NYU Langone Medical Center, New York, Unitede States

Introduction: Incidence of revision surgery after surgical correction of ASD remains high. However, the benefits of multiple revision surgery on patient outcomes are not well-defined. Hypothesis: To assess impact of revision surgery on surgical outcomes, alignment, and HRQLs. Methods: ASD patients with BL, 2Y data, and ≥ 1 revisions included. Patients were stratified by number of revisions (R1, R2, or R3 defined as > 2 revisions). Baseline demographic and surgical details were taken from visit prior to revision surgery. Differences between groups were assessed using ANOVA. Follow-up was based on timepoint 2Y after final revision. 3 revision groups were propensity score matched (PSM) using many-to-one matching, while adjusting for differences at baseline. Radiographic parameters SVA, PI-LL, and PT were used to assess alignment post-revision via ANOVA. MVA assessed differences in outcomes after final revision surgery while controlling for relevant covariates. Results: 252 patients included (R1: 108; R2: 108; R3: 36). Baseline demographic and surgical differences found no significant differences between cohorts. Revision baseline deformity (as defined by radiographic alignment measures SVA, PI-LL, PT) showed no significant differences between groups (all p>.05). 2 years after final revision surgery, ANOVA showed significant differences between R1 and R3, and R2 and R3, with those undergoing greatest number of revisions R3 demonstrating less improvement in deformity measures (all p < .001). Pre-revision ODI scores for each group showed a decline with increasing revision number. Of note, R1 and R2, as compared to R3, had greater difference between baseline and 2 year ODI scores, indicating a sustained benefit to revision surgery (-13.0 vs -13.9 vs -9.7). Percentage of those reaching SCB in ODI from pre-revision baseline to years were R1 71.3%, R2 60.2%, and R3 38.9%, with significant difference found between R1 and R3, and R2 and R3 (all p < .05). The percentage of patients reaching MCID in ODI for each cohort was 35.2% R1, 25.9% R2, and 13.9% R3. MVA demonstrated a significantly lower odds of reaching MCID in ODI for R2 and R3 compared to R1. Overall, patients undergoing multiple revision surgery were 25% less likely to reach MCID in ODI as compared to R1 group. Despite the inferior functional outcomes as measured by ODI scores, patient satisfaction measured by SRS scores were maintained from baseline to 2 years between revision groups. The rates of complications increased with revisions, with R3 having the greatest overall complication rate compared to R1 and R2. Overall, surgical indications for revisal increased with number of revisions: R3 had significantly greater percentage of surgical and mechanical complications leading to revision as compared to R2 and R1. Conclusion: This study attempted to quantify the impact of multiple revision surgeries by comparing patient alignment and outcomes after each revision. Patients requiring multiple revision surgeries had lower odds of reaching minimal clinically important difference in ODI scores as well as maintaining clinical benefit. Despite inferior functional outcomes, alignment improved, and patient satisfaction was maintained across revision groups. These results suggest that surgical correction may still maintain benefit with the appropriate indication.

1343

P134: Disparities in recovery and survival rates in cervical versus thoracolumbar spinal deformity patients are attributable to frailty status at presentation

Peter Passias ¹ , Peter Tretiakov ¹ , Jamshaid Mir ¹ , Bailey Imbo ¹ , Tyler Williamson ¹ , Zach Thomas ¹ , Pooja Dave ¹ , and Kimberly McFarland ¹ , Rachel Joujon-Roche ¹ , Shaleen Vira ² and Bassel Diebo ³

¹ Department of Orthopaedic Surgery, NYU Langone Orthopedic Hospital, New York, United States

² UT Southwestern, Dallas, United States

³ SUNY Downstate, New York, United States

Introduction: Previous studies have demonstrated relatively higher risk of death in CD surgeries, yet there remains a paucity of literature comparing and contrasting the comorbidities and predictive factors associated with death in ASD vs CD surgery. Methods: Operative CD patients ≥ 18yrs with pre-(BL) and up to two-year (2Y) data were included. Group differences were assessed via means comparison analysis. Backstep logistic regression identified mortality predictors. Kaplan-Meier analysis assessed survivorship of expired patients. Cox regression assessed survivability adjusting for BL frailty status. Log rank analysis determined differences in survival distribution groups. Results: 625 total patients were included (417 ASD, 208 CD). Within 5Y, 12 ASD patients (2.88% of ASD cohort) and 16 CD patients (7.69% of CD cohort) expired (p = 0.004). At baseline, ASD and CD patients differed significantly in BL Frailty score (0.29 vs 0.41, p < .001), though not in age, gender, nor BMI (all p > .05). The most common self-reported comorbidities in ASD patients were: arthritis (46%), hypertension (31%), and anemia (23%); in CD patients: osteoporosis (50%), previous myocardial infarction (17%), and any cancer (17%). No significant differences in major, minor, nor intraoperative complications between living or expired ASD or CD patients were observed (all p > .05). Accounting for age, BMI, and gender, regression revealed only frailty status remained a significant predictor of death overall (p = .047). Mean survival time for ASD was 84.11 weeks versus 65.17 in CD patients (χ2(1) = .748, p = .387). Conclusion: Total two-year all-cause mortality in adult spinal deformity and cervical deformity patients remains below 3% despite high rates of comorbidities, suggesting rigorous patient selection criteria plays an important role in maintaining patient safety. While cervical deformity patients demonstrate greater incidence of death post-operatively, increased baseline frailty status may be the principle cause of such results and should be considered when assessing surgical risks versus benefits.

1361

P135: Calibration of comprehensive predictive model for the development of proximal junctional failure in adult spinal deformity patients with consideration of contemporary goals and techniques

Peter Tretiakov ¹ , Kimberly McFarland ¹ , Renaud Lafage ² , Justin Smith ³ , Breton Line ¹ , Alan Daniels ⁴ , Jeffrey Gum ⁵ , Themistocles Protopsaltis ¹ , D. Kojo Hamilton ⁶ , Alex Soroceanu ¹ , Justin Scheer ⁷ , Robert Eastlack ⁸ , Gregory Mundis ⁸ , Pierce Nunley ⁹ , Eric Klineberg ⁷ , Richard Hostin ¹⁰ , Munish Gupta ¹¹ , Christopher Ames ¹² , Robert Hart ¹³ , Douglas Burton ¹⁴ , Christopher Shaffrey ¹⁵ , Frank Schwab ¹⁶ , Shay Bess ¹⁷ , Han Jo Kim ² , Virginie Lafage ¹⁶ , and Peter Passias ¹

¹ Orthopaedic and Neurological Surgery, NYU Langone Medical Center, New York, United States

² Department of Orthopedics, Hospital for Special Surgery, New York, United States

³ Department of Neurosurgery, University of Virginia, Charlottesville, United States

⁴ Department of Orthopaedic Surgery, Brown University, Providence, United States

⁵ Department of Orthopaedic Surgery, Norton Leatherman Spine Center, Louisville, United States

⁶ Department of Neurosurgery, University of Pittsburgh Medical Center, Pittsburgh, United States

⁷ University of California Davis, Department of Orthopedic Surgery, Sacramento, United States

⁸ Scripps Clinic, Division of Orthopaedic Surgery, La Jolla, United States

⁹ Louisiana, Spine Institute of Louisiana, United States

¹⁰ Department of Orthopaedic Surgery, Baylor Scoliosis Center, Dallas, United States

¹¹ Department of Orthopaedic Surgery, Washington University of St. Louis, St. Louis, United States

¹² Department of Neurosurgery, University of California, San Francisco, San Francisco, United States

¹³ Department of Orthopaedic Surgery, Swedish Neuroscience Institute, Seattle, United States

¹⁴ Department of Orthopedic Surgery, University of Kansas Medical Center, Kansas City, United States

¹⁵ Departments of Neurosurgery and Orthopaedic Surgery, Duke University School of Medicine, Durham, United States

¹⁶ Department of Orthopaedics, Lenox Hill Hospital, Northwell Health, New York, United States

¹⁷ Department of Spine Surgery, Denver International Spine Clinic, Presbyterian St. Luke's/Rocky Mountain Hospital for Children, Denver, United States

Introduction: Proximal junctional kyphosis (PJK) and failure (PJF) development remains a major concern after adult spinal deformity (ASD) corrective surgery. There remains a paucity of literature utilizing contemporary alignment metrics and novel prophylaxis measures to predict occurrence of PJK and PJF. Material and Methods: Operative ASD patients with complete baseline (BL) and 2-year (2Y) postoperative radiographic data were included. PJK was defined as ≥ 10° measure for the sagittal Cobb angle between the inferior endplate of the UIV and the superior endplate of the UIV+2. PJF was defined as meeting Lafage et al. PJF criteria by 2Y. Baseline demographic, clinical and surgical information were used to predict the occurrence of PJK and PJF using backstep binary logistic regression analysis. Internal cross validation of the model was performed. Receiver operating characteristic curve determined area-under-curve (AUC). Conditional inference tree (CIT) analysis determined thresholds at (α = .05). Odds ratio (OR) < 1.0 represents protection against PJK/PJF. Results: 779 ASD patients (59.87 ± 14.24 years, 78% female, 27.78 ± 6.02kg/m², mean CCI: 1.74 ± 1.71) were included. 60.5% of patients (n = 471) developed PJK, and 10.5% (n = 82) developed PJF by their last recorded visit. Significant predictors assessed at BL included: age, osteoporosis, arthritis, lower extremity paresthesia, Passias et al. frailty categorization, TS-CL, PI-LL, sagittal age-adjusted score (SAAS) modifiers, BL maximal kyphosis at thoracic apex (MaxTK), levels fused, upper instrumented vertebra (UIV), and PJK prophylaxis techniques: cement, hooks, percutaneous screw fixation, or hybrid measures (hybrid), rod diameter, and rod composition (all p < .05). The six most significant demographic, radiographic, surgical, and post-operative predictors of PJK/PJF were: BL age ≥ 74 (OR: 1.06 [1.014 – 1.107], p = .005), BL SAAS T1PA modifier >1 (OR: 0.352 [0.169 - 0.733], p = .004), BL SAAS PT modifier > 0 (OR: 0.547 [0.344 – 0.870], p = .008, levels fused > 16 (OR: 1.139 [1.022 – 1.269], p = .015), use of prophylactic hooks (OR: 0.122 [0.040 – 0.372], p < .001), and 6W SAAS PI-LL modifier > 1 (OR: 3.604 [1.840 – 7.061], p < .001). Overall, the predictive model was deemed significant (p < .001), and internally validated ROC analysis returned an AUC of .923, indicating robust model fit. Conclusion: Proximal junctional kyphosis and failure remain critical concerns in adult spinal deformity surgery, and efforts to reduce the occurrence of PJK and PJF have resulted in the development of novel prophylactic techniques and enhanced clinical and radiographic selection criteria. This study demonstrates a validated model incorporating such techniques that may allow for the prediction of clinically significant PJK and PJF, and thus assist in optimizing patient selection, enhance intraoperative decision making, and reduce post-operative complications in ASD surgery.

1404

P136: Effects of bone cement augmentation for uppermost instrumented vertebra on adjacent segment degeneration in lumbar fusions

Young-Hoon Kim ¹ , Sang-Il Kim ¹ , and Hyung Youl Park ²

¹ Orthopedic Surgery, Seoul St. Mary's Hospital, The Catholic University of Korea, Seoul, South Korea

² Orthopedic Surgery, Eunpyong St. Mary's Hospital, The Catholic University of Korea, Seoul, South Korea

Introduction: Bone cement-augmented screw is one of the techniques used to reduce early mechanical failure in multilevel lumbar fusions, especially in the elderly. However, there is little information regarding the long-term effects. This retrospective study is designed to investigate the effects of bone cemented augmentation on adjacent level degeneration. Material and Methods: Fifty one patients who underwent more than three levels of lumbar fusion were divided into two groups according to bone cement-augmented screw fixation involving the upper instrumented vertebra (UIV): 22 patients (cemented group, group I) and 29 patients (non-cemented group, group II). The analysis of radiographic adjacent segment degeneration (ASD) involved patients with lumbosacral fusion showing a similar degree of osteoporosis. Radiologic ASD was defined as more than two UCLA grades of progression at 2 years postoperatively. Other radiographic parameters including sagittal profiled and preoperative MR Pfirrmann grades for adjacent level were analyzed. Results: Even when no significant differences existed in preoperative demographic and radiographic parameters between the two groups, the postoperative kyphotic changes at 3 months were higher in the non-cemented group. In terms of long-term effects, radiologic ASD (20 patients (95.2%) in group I; 15 (53.6%) in group II) was significantly higher in the cemented group. Logistic regression analysis of radiologic ASD including other clinical and radiological parameters, postoperative PI-LL mismatch (OR 5.201, 95% CI 1.123-24.090, p = 0.035) and cement augmentation (OR 20.193, 95% CI 2.195-185.729, p = 0.008) showed a significant correlation with the development of radiologic ASD at postoperative 2 years. Conclusion: Although bone cement-augmented screw implantation can prevent kyphotic deformation at the proximal junction of UIV in early postoperative stages of multi-level lumbar fusion, a discreet selection of patients is required due to possible accelerated degeneration of adjacent segments.

Keywords: adjacent segment degeneration; bone cement augmentation; spinal fusion; sagittal alignment

1477

P137: Distal junctional failure after corrective surgery without pelvic fixation for thoracolumbar junctional kyphosis due to osteoporotic vertebral fracture

Yoshifumi Kudo ¹ , Ichiro Okano ¹ , Hiroshi Maruyama ¹ , Ryo Yamamura ¹ , Chikara Hayakawa ¹ , Yushi Hoshino ² , and koutaro tsuchiya ¹

¹ Orthopedic Surgery, Showa University, Shinagawa-ku, Tokyo, Japan

² Orthopedic Surgery, Asahi University Hospital, Japan

Objective: Thoracolumbar junctional kyphosis (TLJK) due to osteoporotic vertebral fracture (OVF) had a substantially negative impact on quality of life. The necessity of pelvic fixation in correction surgery for TLJK due to OVF remains controversial. The aims of this study are: 1) to evaluate the surgical outcomes of major corrective surgery for TLJK due to OVF, and 2) to identify the risk factors for distal junctional failure (DJF) to identify potential candidates for pelvic fixation. Methods: The records of patients with TLJK due to OVF who underwent surgical correction (fixed kyphotic deformity >40°, OVF located at T11–L2, the lowermost instrumented vertebra (LIV) at or above L5) were retrospectively reviewed. Spinopelvic parameters such as sagittal vertical axis (SVA), pelvic tilt (PT), pelvic incidence (PI), thoracic kyphosis (TK), lumbar lordosis (LL: L1-S1), local kyphosis (LK) and lower lumbar lordosis (LLL: L4-S1) were assessed. Proximal and distal junctional kyphosis (PJK/DJK), and proximal and distal junctional failure (P/DJF) were evaluated. Demographic data and pre/postoperative spinopelvic parameters were compared between DJF and non-DJF patients. Results: Thirty-one patients (the mean age 72.3 ± 7.9) were included in the final analysis. PJK was observed in five patients (16.1%), while DJK was observed in 11 (35.5%). The main cause (15/16 cases, 93.8%) of PJK/DJK was vertebral fracture. 12 cases (38.7%) were categorized as failure. Among the patients with PJK, there was only one patient (20%) categorized as PJF and required an additional surgery. Contrary, all of eleven patients (100%) with DJK were categorized as DJF, among whom six (54.5%) required additional surgery for pelvic fixation. In comparisons between DJF and non-DJF patients, there was no significant difference in pre/postoperative LK (pre/post, p = 0.725, p = 0.950). However, statistically significant differences were observed in the following preoperative alignment parameters: SVA (p = 0.014), LL (p = 0.001), LLL (p = 0.006), PT (p = 0.003), and PI-LL (p < 0.001). Conclusions: Spinopelvic parameters, which represent the compensatory function of lumbar hyperlordosis and pelvic retroversion, have notable impacts on surgical outcomes in correction surgery for TLJK due to OVF. To recognize the potential risks of DJF and revision surgery, surgeons should pay attention not only to the local angles but also to the whole spinopelvic alignment and consider each patient’s compensatory function when choosing a surgical approach.

1484

P138: Where is the point of inflection from thoracic kyphosis to lumbar lordosis in a multi-ethnic population of asymptomatic volunteers

Zeeshan Sardar ¹ , Matan Malka ² , Meghan Cerpa ² , Jean Charles Le Huec ³ , Stephane Bourret ³ , Kazuhiro Hasegawa ⁴ , Wong Hee Kit ⁵ , Gabriel Liu ⁵ , Denni Hey ⁵ , Hend Riahi ⁶ , Michael Kelly ⁷ , and Lawrence Lenke ¹

¹ Spine Unit, Och Spine Hospital at New York Presbyterian/Allen, New York, United States

² Orthopaedic Surgery, Columbia University Medical Center, New York, United States

³ CHU de Bordeaux, Bordeaux, France

⁴ Niigata Spine Surgery Center, Niigata, Japan

⁵ NUH University Spine Center, Singapore

⁶ Kassab Institute, Manouba, Tunisia

⁷ Washington University School of Medicine, Saint Louis, United States

Introduction: The point of inflection (POI) between the Thoracic Kyphosis (TK) and the Lumbar Lordosis (LL) is an important consideration for treatment of spinal deformity. Previous literature has shown that the classically accepted POI of L1 is not constant among the population. The purpose of this study is to show the population variance in POI and its role in defining the maximum TK and LL. Material and Methods: Asymptomatic adult volunteers between the ages of 18-80 years were enrolled prospectively across 5 different countries/centers (France, Japan, Singapore, Tunisia, and United States) forming the MEANS cohort. Volunteers included in the study reported no significant neck or back pain (Visual Analog Scale≤2), nor any known spinal disorder(s), and had no history of prior surgical or non-surgical treatment for a spine related disorder. All volunteers underwent a standing full body or full spine low dose stereoradiograph (EOS imaging, Paris, France) for enrollment in the study. Following exclusion, a total of 468 volunteers were included in MEANS. Basic demographic data included age, sex, body mass index (BMI), and ethnicity. One more patient was removed from the data analysis because the POI was missing. The data from the 467 patients was then evaluated. In order to find parameters that correlate with the location of the POI as well as a possible linear regression model predicting the POI, a new numbering system of the vertebrae and discs was created in the following manner: C7 was given the numerical value of 0, T1 was 1, with T1T2 being 1.5, etc. Results: The overall mean POI was found to be 12.44 approximately corresponding to T12L1 with the median being 12.50 (also T12L1). The patient population was then stratified by sex and ethnicity but no significant difference was found in POI between all the groups. Though the ranges of the POI are different among the population stratifications, the mean and median POI’s remain relatively around T12L1. The mode POI was L1. However, the POI varied from T8 to L4. No strong correlation was found between POI and age, LL, Sacral Slope, or PI. Conclusion: The most common POI was L1. However, POI ranged from T8 to L4 with the mean being around T12-L1. A strong correlation between POI and any of the demographic or radiographic parameters was not found. The variation in POI should be taken into account when planning a reconstructive surgery.

1511

P139: Diastematomyelia: a study of 15 cases

Sliti Firas ¹ , Khalil Ghedira ¹ , Abdelhafidh Slimane ¹ , Nessrine Nessib ¹ , Alaa Belhadj ¹ , Sofiene Bouali ¹ , and Jalel Kallel ¹

¹ Neurosurgery, National Institute of Neurology, Tunis, Tunisia

Introduction: Diastematomyelia is a rare congenital spinal malformation consisting of two spinal cords separated by a bony, cartilaginous or fibrous septum on one or more segments. It has a good prognosis when diagnosed and treated early. Material and Methods: We collected the cases of diastematomyelia operated between 2009 and 2019 at the neurosurgery departments of the National Institute of Neurology and the Center of Traumatology of Ben Arous Tunisia. Results: Our series consisted of 13 patients, including 9 children and 4 adults. The mean age in children was 6 years, and in adults 58 years. The sex ratio was 0.44. Clinical signs were represented by scoliosis (7 cases), motor deficit (7 cases), skin signs (6 cases) including hairy patch (hypertrichosis) (4 cases), urinary disorders (4 cases) and spinal and radicular pain (4 cases). All patients underwent a radiological study by spinal MRI and CT scan. We identified 10 cases of type I diastematomyelia and 3 cases of type II. Associated dysraphic disorders were present in 10 cases. There were 4 cases of postoperative complications: 1 case of anemia due to intraoperative hemorrhage, 1 case of CSF leakage, 1 case of wound infection and 1 case of transient motor deficit. Motor deficit and pain improved in all patients. Two patients recovered completely from their deficit. Sphincter disorders improved in only one case. Conclusion: Diastematomyelia, also known as a split cord malformation, is a rare occult spinal dysraphism, which is easy to diagnose given the frequent cutaneous signs and neuro-orthopaedic syndrome. Surgery is indicated to avoid irreversible neurological sequelae.

1567

P140: Melorheostosis of thoracic spine: a rare clinical entity managed surgically

Jayprakash Modi ^1,2 , and Pratikkumar Prajapati ¹

¹ Orthopaedic, B J Medical College, Ahmedabad, India

² Orthopaedic, Nutan Medical College, Mehsana, India

Introduction: Melorheostosis is a medical developmental disorder and mesenchymal dysplasia in which bone cortex widens and becomes hyperdense in a sclerotomal distribution. Most of the cases reported till now are confined to appendicular skeleton, rarely affecting spine. It is well known by its characteristic appearance of “melting wax flowing down a candle” on radiographs. Materials and Method: This is a rare case study of a patient operated at tertiary care centre having non-traumatic involvement of spinal cord affecting neurology with history, clinical and radiological features suggesting melorheostosis as the cause of compression. Result: Here we report a rare case of melorheostosis of thoracic spine in a middle‐aged male patient with features of myelopathy treated by early decompression surgery, leading to complete relief of symptoms postoperatively. Final follow‐up was of 2 years. It is a very rare, benign and disabling entity, and the diagnosis Is primarily a radiological one. Conclusion: Early diagnosis and decompression surgery leads to dramatic improvement in clinical outcome and prevents unwarranted biopsy.

Keywords: Laminectomy, melorheostosis, sclerotomal

1629

P141: Factors affecting opioid use of European adult spinal deformity patients: minimum 5 years follow-up study

Kadir Abul ¹ , Nezih Arin Alanay ² , Caglar Yilgor ³ , Altug Yucekul ³ , Yasemin Yavuz ⁴ , Louis Boissiere ⁵ , Anouar Bourghli ⁶ , Ibrahim Obeid ⁵ , Javier Pizones ⁷ , Frank Kleinstuck ⁸ , Francisco J. Sanchez Perez-Grueso ⁹ , Ferran Pellisé ¹⁰ , Ahmet Alanay ³ , and European Spine Study Group ESSG ¹¹

¹ Department of Orthopedics and Traumatology, Istanbul Basaksehir Pine and Sakura City Training and Research Hospital, Istanbul, Turkey

² Lycee Français Notre Dame de Sion, Istanbul, Turkey

³ Department of Orthopedics and Traumatology, Acibadem Mehmet Ali Aydinlar University School of Medicine, Istanbul, Turkey

⁴ Department of Biostatistics, Ankara University School of Medicine, Ankara, Turkey

⁵ Department of Spinal Surgery Unit 1, Bordeaux University Hospital, C.H.U Tripode Pellegrin, Bordeaux, France

⁶ Spine Surgery Department, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia

⁷ Spine Surgery Unit, La Paz University Hospital, Madrid, Spain

⁸ Spine Center, Schulthess Klinik, Zurich, Switzerland

⁹ Spine Surgery Unit, La Paz University Hospital, Madrid

¹⁰ Spine Surgery Unit, Hospital Vall d'Hebron, Barcelona, Spain

¹¹ Spine Research Unite, Vall d'Hebron Institute of Research, Barcelona, Spain

Introduction: Although appropriate pain control is a critical aspect of patient management, past few decades have been associated with major increases in opioid-related overdoses and addiction treatment. Current literature focuses on chronic back pain and degenerative conditions and information regarding long-term opioid use following adult spinal deformity surgery is limited. This study aims to analyze factors associated with minimum 5-year postoperative continued opioid use in patients who underwent surgical treatment for adult spinal deformity. Materials and Methods: This was a retrospective analysis of a prospectively collected data of patients undergoing elective spinal deformity surgery. Patients with ≥ 4-levels fusion and ≥ 5y follow-up were included. Analgesic use was divided into 4 groups: No Analgesics; Non-Opioid Analgesics; Weak Opioids and Strong Opioids. Clinically-relevant 6 scenarios were investigated: Pre-op use; 6 weeks use; Continued use at 6 months and beyond; Opioid cessation; Restart on opioids and Persistent use at 5 years and beyond. A total of 37 factors comprising patient characteristics, radiographic measurements, operative details, preoperative and early postoperative opioid use, and mechanical complications and revisions were analysed in a univariate-multivariate setup to determine risk factors for pre-op, 6-months and ≥ 5-years post-op usage. Results: 265 patients (215 F, 50 M) from five sites were included. The mean follow-up duration was 68.4 ± 11.7 (60-102) months. On average, 10.6 ± 3.5 levels were fused. Preoperatively, 64 (24.2%) patients were using opioids. The rate of opioid users increased to 33.6% at 6 weeks and decreased to 21.5% at 6 months. During follow-up, there were patients who discontinued opioids, while others have started and/or restarted using opioids. As a result, 59 (22.3%) patients were still on opioids at the latest follow-up. Multivariate analyses showed that factors independently affecting opioid use at an average of 68 months postoperatively, in order of significance, were opioid use at sixth weeks, preoperative opioid use and opioid use at sixth months with the odds ratios of 2.88, 2.51 and 2.38 respectively. At these time points, factors such as age, number of comorbidities, tobacco use, the time of the last prior spine surgery and postoperative sagittal plane alignment affected opioid usage rates. Conclusions: Approximately 15% of patients who received no preop opioids ended up receiving long-term (5+ years) postop opioids. Of the preop opioid users, only 56% could quit. Opioid usage at six weeks was found to be more predictive of long-term opioid use compared to preoperative use. Among identified risk factors, sagittal plane correction seems to be the only parameter that is directly at the surgeon’s discretion. Observed differences among sites can point towards a room for improvement. Identifying patients at higher risk for opioid use at different time points and discussing their long-term expectations may be beneficial in the shared decision-making process. Current global efforts on preventing chronic opioid use warrants further research to better understand the cascade of events in order to determine actionable items.

1636

P142: Loads at adjacent segment level before and after surgery: combined clinical and simulation study of 205 adult spinal deformity patients

Dominika Ignasiak ¹ , Pascal Behm ¹ , Mannion Anne ² , Frank Kleinstuck ³ , Tamas Fekete ⁴ , Daniel Haschtmann ⁵ , Dezsö Jeszenszky ³ , Laura Zimmermann ³ , Sarah Richner-Wunderlin ³ , Alba Vila-Casademunt ⁶ , Ferran Pellisé ⁶ , Ibrahim Obeid ⁷ , Francisco J. Sanchez Perez-Grueso ⁸ , Ahmet Alanay ⁹ , Caglar Yilgor ⁹ , Stephen Ferguson ¹ , and Markus Loibl ⁵

¹ Institute for Biomechanics, ETH Zurich, Zurich, Switzerland

² Department of Teaching, Research and Development

³ Spine Center

⁴ Department of Orthopedics and Neurosurgery

⁵ Department of Spine and Neurosurgery,Schulthess Clinic, Spine Center, Zurich, Switzerland

⁶ Spine Unit, Hospital Vall d'Hebron, Barcelona, Spain

⁷ Department of Spinal Surgery Unit 1, Bordeaux University Hospital, C.H.U Tripode Pellegrin, Bordeux, France

⁸ Spine Surgery Unit, La Paz University Hospital, Madrid, Spain

⁹ Department of Orthopaedics and Traumatology, Acibadem Mehmet Ali Aydinlar University School of Medicine, Istanbul, Turkey

Introduction: Sagittal malalignment is a risk factor for mechanical complications after surgery for adult spinal deformity (ASD). Mechanical complications – caused by continuous or repetitive mechanical stress – are estimated to affect 28-61% of ASD patients with longer fusion constructs. Spinal loads, modulated by sagittal alignment, may explain this relationship. The aims of this study were to investigate the relationships between: (1) postoperative changes in loads at the proximal segment and realignment, and (2) absolute postoperative loads and postoperative alignment measures. Materials and Methods: A previously validated musculoskeletal (AnyBody) model of the whole spine, including articulated thorax with ribcage, was applied to study a clinical sample of 205 ASD patients. The data were collected within a multicenter study group. The dataset included patient demographic parameters, surgical treatment details, prior fusion, occurrence and type of mechanical complications, as well as sagittal alignment measures obtained from preoperative and 6 weeks postoperative long lateral radiographs. Based on clinical and radiographic data, patient-specific sagittal spinopelvic alignment profiles were represented in the musculoskeletal spine model. Pre- and postoperative patient-specific alignments were simulated to predict loads at the proximal segment adjacent to the spinal fusion. To allow between-subjects comparability, the loads were normalized to individual body mass. Results: The mean age (and standard deviation) was 52.1 ± 19.2 years (range 18-84 years), mean BMI was 25.7 ± 5.1 kg/m² (range, 13.4-44.6 kg/m²). The sample included both primary (72%) and revision (28%) surgery cases, representing a variety of fusion lengths (median number of fused motion segments = 9, range 3-16), and upper (T2-L3) and lower (T12- pelvis) instrumented levels, with T10-pelvis fusion being the most common (13%). Weak-to-moderate associations were found between pre-to-postop changes in lumbar lordosis, LL (r = -0.23, r = -0.43; p < 0.001), global tilt, GT (r = 0.26, r = 0.38; p < 0.001) and the Global Alignment and Proportion score, GAP (r = 0.26, r = 0.37; p < 0.001), and changes in compressive and shear forces at the proximal segment. GAP score parameters, thoracic kyphosis measurements and the slope of upper instrumented vertebra were associated with changes in shear. In patients with T10-pelvis fusion, moderate-to-strong associations were found between several postoperative sagittal alignment measures and compressive and shear loads, with GT showing the strongest correlations (r = 0.75, r = 0.73, p < 0.001). Conclusions: Spinal loads were estimated for patient-specific full spinal alignment profiles in a large cohort of patients with ASD pre- and postoperatively. Loads on the proximal segments correlated with sagittal alignment measures. In a subset of T10-pelvis fusion cases, postoperative GT, UIV slope, GAP, and T10-L2 angles were associated with both postoperative compressive and shear loads. Broader analysis of larger clinical samples should be performed in the future to unravel whether or not (or to what degree) spinal loads provide a causal mechanism explaining the previously reported association between sagittal alignment and mechanical complications.

1644

P143: The reliability of computer-assisted 3D surgical simulation of posterior osteotomies in

Yiqi Zhang ¹ and Yong Hai ¹

¹ Department of Orthopedic Surgery, Beijing Chaoyang Hospital, Capital Medical University, Beijing, China

Background: Correction surgery for patients with thoracolumbar kyphosis secondary to ankylosing spondylitis (TLKAS) is desired with the aim to restore the normal sagittal balance and generally performed with posterior osteotomies including pedicle subtraction osteotomy, Smith-Petersen osteotomy (SPO), and Ponte osteotomy. A precise and flexible surgical planning is required for osteotomy strategy. The study was aimed at investigating the reliability of computer-assisted three-dimensional surgical simulation (CA3DSS) of posterior osteotomies in TLKAS patients. Methods: Eligible TLKAS patients who underwent posterior correction surgery with posterior osteotomies were consecutively included. Simulated posterior osteotomies were performed in Mimics and 3-Matic Medical software. Coronal and sagittal angle and alignment parameters were measured in preoperative full-length X-ray, preoperative original 3D spine (Pre-OS), simulated 3D spine (SS), and postoperative original 3D spine (Post-OS). Reliability was tested by both intraclass correlation coefficients (ICCs) and Bland-Altman analysis. Results: A total of 30 TLKAS patients were included. Excellent consistency of radiological parameters was shown between preoperative X-ray and Pre-OS model. In SS and Post-OS models, excellent reliabilities were shown in global kyphosis (ICC 0.832, 95% CI 0.677-0.916), thoracic kyphosis (ICC 0.773, 95% CI 0.577-0.885), and lumbar lordosis (ICC 0.896, 95% CI 0.794-0.949) and good reliabilities were exhibited in the main curve (ICC 0.680, 95% CI 0.428- 0.834) and sagittal vertical axis (ICC 0.619, 95% CI 0.338-0.798). ICCs of correction angle achieved by pedicle subtraction osteotomy (PSO) was 0.754 (95% CI 0.487-0.892), and that of posterior column osteotomies (PCO) was 0.703 (95% CI 0.511- 0.829). Bland-Altman analysis also showed good agreement for both Cobb angle and distance measurements in Pre-OS and SS models, and good reliabilities were shown in PCO and PSO in real spine and SS models. Conclusions: CA3DSS can provide an accurate measurement, and it is a reliable and effective method to conduct proper simulation for correction surgery with posterior osteotomies in TLKAS patients.

1654

P144: Human recombinant bone morphogenetic protein-2 (rhBMP-2) injection into the uppermost instrumented vertebra (UIV) reduced the acute bony failure type proximal junctional kyphosis (PJK) in adult spinal deformity (ASD) correction

Ho-Joong Kim ¹ , Ohsang Kwon ¹ , and Junyoung Choi ¹

¹ Orthopedic Surgery, Seoul National University Bundang Hospital, South Korea

Introduction: Numerous attempts on reducing the proximal junctional kyphosis (PJK) and thus proximal junctional failure (PJF) have resulted in substantial but yet not complete resolution of the troublesome complication. We attempted local transpedicular injection of human recombinant bone morphogenetic protein-2 (rhBMP-2) into the uppermost instrumented vertebra (UIV) for prevention of bony failure type PJK in adult spinal deformity (ASD) correction surgery. Material and Methods: A mixture of 1mg rhBMP-2 and 0.5g β-tricalcium phosphate were injected intraoperatively into the body of UIV through the predrilled transpedicular corridor in 25 consecutive patients from August 2021 to January 2022. Age and sex matched 25 patients who received ASD correction surgery just before the study period were set as control group. The primary outcome was the PJK and PJF incidence rates at 6 months after surgery. And the radiographic evidence of new bone formation at the UIV was also studied. Results: The baseline patient characteristics and patient reported outcome measurements (PROM) were similar between the two groups while the pelvic incidence – lumbar lordosis mismatch was greater in the study group. PJK occurred in 2 patients (8%) of the study group while it occurred in 7 patients (28%) in the control group (p-value = 0.138). PJF occurred in 1 patient (4%) of the study group while it occurred in 3 patients (12%) in the control group and all of them were bony failures. PROM at 6 months after surgery were significantly better in the study group. The Hounsfield unit of the UIV significantly increased at 6 months after surgery than the preoperative scan and the increment at the UIV was also significantly greater than that of the UIV-1. Conclusion: Intraoperative transpedicular injection of rhBMP-2 into the UIV reduces the PJK and PJF rate at 6 months after surgery, by diminishing the occurrence of bony failure. The Hounsfield unit at the UIV increased significantly which might be interpreted as a sign of new bone formation.

1725

P145: Intradiscal osteotomy (IDO): high resolution cadaveric technique guide and single institute experiences using expandable interbody devices in complex spinal pathology

Jerry Robinson ¹ , Abraham Schlauderaff ² , Yevgeniy Freyvert ³ , Jared Cooke ² , Amir Abdul-Jabbar ² , Jens Chapman ² , and Rod Oskouian ²

¹ Department of Orthopedics, Cedars Sinai Medical Center, United States

² Department of Spine Surgery, Swedish Neuroscience Institute, United States

³ Department of Neurosurgery, Houston Methodist, Houston, TX, United States

Introduction: As the number of spinal fusion procedures has risen over the past few decades there has also been a reported decrease in the utilization of three column osteotomies. Many surgeons are familiar with the traditional posterior spinal osteotomy classification; however, a lesser-known osteotomy, the bone-disc-bone osteotomy, exists outside of this classification. We present the “intradiscal osteotomy” (IDO) technique, a type of bone-disc-bone osteotomy that utilizes expandable interbody devices to achieve all-posterior correction of complex spinal pathology. Materials and Methods: A fresh-frozen cadaver was prepared for demonstration of the IDO technique in the mid-lumbar spine. The procedure was documented through serial, high-resolution photographs in stepwise progression. Standard fluoroscopy was used to document the procedure’s corrective ability. Additionally, a narrative case series was chosen from within a single institute to demonstrate the procedure’s utility and feasibility in a variety of complex spinal clinical scenarios. Results: Intradiscal osteotomy with the use of expandable interbody devices was successfully demonstrated on a cadaveric model. A high-resolution technique guide was produced through serial photographs. Our narrative case series demonstrates the IDO’s utility and feasibility in complex spinal pathology; specifically, correction of cervicothoracic and thoracolumbar adult spinal deformity (ASD), proximal junctional failure (PJF), distal junctional failure (DJF), isthmic spondylolisthesis, and pseudarthrosis. We additionally demonstrate its feasibility in iatrogenic flat-back syndrome through an all-posterior, attritional release of the anterior longitudinal ligament (ALL). Conclusions: The intradiscal osteotomy combined with expandable interbody devices can achieve powerful correction without the use of conventional three column osteotomies. Surgeons may find this technique desirable and rapidly adoptable due to its similarity to a traditional transforaminal interbody fusion. Our technique guide and narrative case series is meant to assist surgeons looking for alternatives to traditional three column osteotomies.

1803

P146: Postoperative complications of Schwab-Grade-I versus Schwab-Grade-II posterior column osteotomies (PCOs) in treating severe rigid kyphoscoliosis patients: a minimum 2-year follow-up comparative outcome

Nicholas Van Halm-Lutterodt ^1,2,3 , Aixin Pan ³ , Ziyang Ye ^2,4 , Yangpu Zhang ³ , Tie Liu ³ , Lijin Zhou ³ , Sunny Kim ² , Yuzeng Liu ³ , Jincai Yang ³ , and Yong Hai ³

¹ School of Professional Studies, Brown University, Providence, United States

² Department of Orthopedic and Neurosurgery, Inspired Spine Health, Burnsville, United States

³ Department of Orthopedics Surgery, Beijing Chaoyang Hospital Affiliated-Capital Medical University, Beijing, China

⁴ Department of Data Science and Analytics, University of Chicago, Chicago, United States

Background: Smith-Petersen osteotomy, [SPO], (Schwab-grade-I) and Ponte osteotomy, [PO], (Schwab-grade-II) are narrowly akin and collectively appreciated as posterior column shortening osteotomies (PCOs). The former is considered as a more gentler osteotomy grade than the latter. In the spine literature, little information is provided on their comparison regarding perioperative complications and major curve correction rates. A clinical study to evaluate the perioperative complication incidence and major curve corrective rates between these two osteotomy techniques would be pragmatic in highlighting their safety and efficacy outcomes and inform the spine practice of their value-based impacts in indicated deformity patients. Methods: Following approval by the institutional review board (IRB) of Beijing Chaoyang Hospital-Affiliated Capital Medical University in Beijing, a pool of 38 propensity-matched adult (≥ 18 years) severe rigid scoliosis or kyphoscoliosis patients (curved ≥ 80^o) who underwent spinal deformity primary corrective surgery were retrospectively evaluated. The patients were dichotomized into two (2) osteotomy technique groups: Smith-Petersen osteotomy (SPO-treated), (i.e., Schwab-grade-I PCO) and Ponte osteotomy, (PO-treated), (i.e., Schwab-grade-II PCO). The minimum follow-up period was 2 years. Primary outcomes included baseline and clinical features between the two osteotomy groups. Secondary outcomes included perioperative [intraoperative, immediate, and within 2-year postoperative] complication rates between the two types of osteotomies. Tertiary outcomes included preoperative and final follow-up ODI and SRS-22 scores. Statistical analyses were carried out by Student t-test and Pearson’s Chi-squared test (Fisher’s Exact Test), through Python statistical software package. Statistical significance was set at p < 0.05. Results: Of the 38 matched severe rigid scoliosis or kyphoscoliosis patients, 55.30% (n = 21) were SPO-treated and 44.70% (n = 17) were PO-treated patients, respectively. The overall average age of patients was 23.97 years, with a female incidence of 76.32%. Major curve correction rates were 49.19% and 57.40% in SPO-treated and PO-treated patients, respectively, (p > 0.05). Immediately following surgery, comparable overall complication rates of 28.57% (n = 6/21) vs 29.41% (n = 5/17) were observed in the SPO-treated and PO-treated patients, respectively, (p = 0.726). We observed 9.52%, (n = 2/21) vs 5.88%, (n = 1/17) incidence of surgical intensive care unit (SICU) admission and 4.76%, (n = 1/21) vs 5.88%, (n = 1/17) incidence of cardiopulmonary events in SPO-treated and PO-treated patients after surgery, respectively, (p = 0.679). Neurological deficits incidence in the SPO-treated and PO-treated patients were respectively, 14.29%, (n = 3/21) vs 17.65%, (n = 3/17) immediately following surgery, (p > 0.05) and 0.00%, (n = 0/21) vs 17.65%, (n = 3/17) at ≥ 2 years postoperative, (p < 0.05), but there was only 5.88% (n = 1/17) new incidence of neurological deficits in the PO-treated patients at ≥ 2 years postoperative, ( p > 0.05). The ODI score in the PO-treated group was significantly inferior at minimum 2-year follow-up, (p < 0.05), while preoperative and postoperative SRS-22 scores were comparable in both patient groups, (p > 0.05). Conclusion: In the current study, both SPO-treated and PO-treated patients demonstrated comparable surgical complication rates immediately following corrective surgery whereas PO-treated patients showed an increased tendency of accruing postoperative neurological sequela. To achieve value-based and effective outcomes in these severe rigid scoliosis or kyphoscoliosis patients, prudence in patient selection, enhanced patient management protocols and technical sophistication are profoundly critical to maximizing safety outcomes with Schwab-grade-I or -II PCO.

1821

P148: Questionnaires from AO spine members performing adult spinal deformity surgery on wound closure and antibiotic use by specialty and by developing and developed countries

Shin Oe ¹ , Yukihiro Matsuyama ¹ , Kenneth Man Chee Cheung ² , Kenny Yat Hong Kwan ² , So Kato ³ , Stephen Lewis ⁴ , Christopher Shaffrey ⁵ , Lawrence Lenke ⁶ , and AO Spine KF Deformity ⁷

¹ Orthopedic Surgery, Hamamatsu University School of Medicine, Hamamatsu, Japan

² Orthopaedics and Traumatology, The University of Hong Kong, China

³ Orthopaedic Surgery, The University of Tokyo, Tokyo, Japan

⁴ Surgery and Spine Program, University of Toronto, Canada

⁵ Orthopaedic Surgery, Duke University, United States

⁶ Orthopedic Surgery, The Spine Hospital, Columbia University Medical Center, United States,

⁷ AO spine KF deformity, Switzerland

Introduction: Wound closure and perioperative antibiotic use are practiced by all surgeons involved in surgery, but methods can vary widely depending on surgeon preference, country, and social context. The purpose of this study is to conduct a survey of AO spine members involved in Adult Spinal Deformity (ASD) surgery in two categories: 1. developing and developed countries, 2. orthopedic surgeons and neurosurgeons. Material and Methods: One hundred and sixty-four members from 49 countries were included. The evaluation items included method of skin closure, method of dressing, type of drain, type and duration of prophylactic antibiotics, and the presence or absence of intra-wound application of vancomycin powder. Results: 1. There were 133 doctors in the developed country group and 31 doctors in the developing country group. The most common responses for each endpoint were subcuticular absorbable suture for skin closure (38% vs. 35%), dry dressing for dressing (74% vs. 63%), Cephalosporins for antibiotics (91% vs. 100%), and 24 hours for the duration of postoperative antibiotics (40% vs. 42%), but there were no significant differences. The use of vancomycin powder was 68% in developed countries and 42% in developing countries, it was not significantly different but higher in developed countries (p = 0.077). Closed suction type was the most common type of drain (81% vs. 63%), but respondents in developing countries were more likely to report not using a drain (6% vs. 12%, p = 0.047). 2. There were 130 orthopedic surgeons and 34 neurosurgeons. The most common responses were skin closure with subcuticular absorbable suture (40% vs. 29%), dressing with dry dressing (52% vs. 47%), type of drain with closed suction type (86% vs. 90%), antibiotics with Cephalosporins (91% vs. 100%) and the duration of antibiotics with 24 hours (35% vs. 42%). However, 90% of neurosurgeons use vancomycin powder, whereas those of orthopedic surgeons were 67%. (p = 0.021). Conclusion: There was significant difference the way of setting the drain between developed and developing countries. But there was no difference in the method of wound closure or use of antibiotics. On the other hand, there was no significant difference between orthopedic surgeons and neurosurgeons, but the intraoperative use of vancomycin powder was significantly higher among neurosurgeons.

1977

P149: Treatment of a thoracic fracture-dislocation with a posterior only approach

Joana Tavares ¹ , Ana Luís ¹ , and Diogo Morgado ¹

¹ Neurosurgery, Centro Hospitalar Lisboa Ocidental, Lisboa, Portugal

Introduction: Fracture-dislocations of the thoracic and lumbar spine are highly unstable injuries, frequently resulting in neurologic injuries. The primary goals in its surgical treatment when there is complete spinal cord transection are the reduction of deformity and rigid spine stabilization with fusion. The current treatment of vertebral fracture-dislocation when there is partial or total telescoping of the involved vertebrae is combined anterior-posterior approach with corpectomy, anterior support implant and further posterior instrumentation. These procedures may require two surgical teams, longer operating times and greater risk of surgical complications related to the anterior approach, and commonly entail longer postoperative care before discharge. A viable alternative is opting for treatment from a posterior approach alone: with partial vertebrectomy shortening (resection of the upper part of the lower vertebra involved, the posterior arch and the disc), which results in apposition of two flat surfaces of healthy bone; reduction and fixation using long segment posterior transpedicular constructs. Material and Methods: The authors report a case of a low thoracic fracture-dislocation (T-11/T-12) treated with a partial vertebrectomy from a posterior approach. Results: A 26 year-old male presented to our emergency room after being evacuated from Cape Verde, with a complete thoracic spinal cord section as a result of a car accident 1 month earlier. Computed tomography scan revealed an AOSpine T11-T12: C (B3) with severe antero-posterior dislocation. Briefly: Through an open posterior approach pedicle screws were inserted, under fluoroscopic guidance, in T9-T10-T11-L1-L2-L3 bilaterally; posterior arches of T11 and T12 (including bilateral locked facets), were removed. Right laminectomy of T10, bilateral laminectomy of L1 and partial laminectomy of L2 were preformed The dura mater was surrounded by a dense fibrous tissue but no CSF leak was observed. Total discectomy of T11-T12 disc was done, as well as partial T12’s corpectomy (using an ultrasonic device), reducing to half the height of T12’s body. Titanium bars were place to allow compression and apposition of T11 with the rest of T12’s body. After this, the patient was repositioned to promote additional reduction (both on the sagittal and coronal axes), the rods were fixed and a cross-link was applied. Autologus bone was used for postero-lateral fusion. The immediate postoperative image showed adequate realignment of the thoracic spine. Conclusion: To date, there is no conclusive clinical studies available to help spine surgeons decide on the optimal surgical treatment of thoracic fracture-dislocations. Nonetheless, a posterior-only approach may be used safely and effectively minimizing the disadvantages associated with the anterior approach.

2022

P150: External validation of the global alignment and proportion (GAP) score as a prognostic tool for corrective surgery in adult spinal deformity: a systematic review and meta-analysis

Julian Gendreau ¹ , Nolan Brown ¹ , Andrew Nguyen ¹ , Neal Patel ¹ , Alexander Lopez ¹ , Chenyi Yang ¹ , Noah Pierzchajlo ¹ , Shane Shahrestani ¹ , Gaston Camino-Willhuber ¹ , Stephen Albano ¹ , Michael Oh ¹ , and Martin Pham ²

¹ Neurosurgery, UC Irvine, United States ² Neurosurgery, UC San Diego, United States

Introduction: The Global Alignment and Proportion (GAP) score has been previously touted as an improved method for predicting mechanical complications following adult spinal deformity (ASD) correction surgery when compared to pelvic incidence-lumbar lordosis (PI-LL) mismatch parameters. Since its proposal, the GAP score has been the topic of several external validation studies, which have yielded conflicting results. Given the lack of consensus regarding this prognostic tool, the authors aim to assess the accuracy of GAP scores in predicting mechanical complications following ASD correction surgery by reviewing all evidence in the published literature to date. Materials and Methods: A systematic search was performed using PubMed, Embase and Cochrane Library for the purpose of identifying all trials evaluating the GAP score as a predictive tool for mechanical complications. Study quality was assessed according to Newcastle-Ottawa criteria. GAP scores were pooled using a random-effects model to compare patients reporting mechanical complications after surgery versus those reporting no mechanical complications. Where receiver operator curves (ROC) were provided, the area under the curve (AUC) was pooled. All statistical analyses was performed using R software. Results: A total of 15 studies featuring 2,092 patients were selected for inclusion in the analysis. Qualitative analysis using Newcastle-Ottawa criteria revealed moderate quality among all included studies (5.99/9). With respect to sex, the cohort was predominantly female (82%). The pooled mean age among all patients in the cohort was 58.55 years, with a mean follow-up of 33.86 months after surgery. Upon pooled analysis, we found that mechanical complications were associated with higher mean GAP scores, albeit minimal (mean difference = 0.571 [ 95% CI: 0.163-0.979]; p = 0.006, n = 864). Additionally, age (p = 0.136, n = 202), levels of fusion (p = 0.207, n = 358) and body mass index (BMI) (p = 0.616, n = 350) were similar among all patients, irrespective of complication status. Pooled AUC revealed poor discrimination overall (AUC = 0.69; n = 1206). There was no indication of publication bias. Conclusion: GAP scores may have a minimal-to-moderate predictive capability for mechanical complications associated with ASD correction.

2037

P151: Whole-transcriptome sequencing identifies key differentially expressed circRNAs/IncRNAs/mRNAs and linked ceRNA networks in adult degenerative scoliosis

Xin Shi ^1,2 , Panpan Li ^1,2 , Xiang Wu ¹ , Zhihua Wang ¹ , Gang Zhao ¹ , Yinglan Wang ³ , and Jun Shu ¹

¹ The Second Affiliated Hospital of Kunming Medical University, Kunming, China

² Faculty of Medicine and University Hospital of Cologne, University of Cologne, Cologne, Germany

³ Shangqiu First People's Hospital, Shangqiu, China

Background: With an increasing elderly population, adult degenerative scoliosis (ADS), is forecast to be a prevalent disabling condition in an aging society. Universally, its pathogenesis is perceived as intervertebral disc degeneration (IDD), which does not differ from other degenerative spinal disorders. However, a thought-provoking issue is why precisely a subset of patients with disc degeneration develop ADS. Exploring the diversities between common disc degeneration and ADS would contribute to unraveling the etiological mechanisms of ADS. Although the function of ncRNAs in ADS has been proposed, crosstalk between the various transcripts has not been systematically investigated. Therefore, we aimed to integrate the circRNA, lncRNA, miRNA, and mRNA expression profiles from normal adults (Normal), patients with disc herniation (LDH), and ADS by whole transcriptome sequencing, which identifies key functional ncRNA and ceRNA networks. Methods: The fresh whole blood samples (n = 3/group) were collected from ADS patients (asymmetric disc degeneration, ADS group), LDH patients (symmetric disc degeneration, LDH group), and healthy volunteers (non-degenerative changes, Normal group), which were examined for mRNA, miRNA, lncRNA, and circRNA expression and screened for differentially expressed (DE) RNAs. Then, Gene Ontology (GO) and KEGG analyses were performed for gene annotation and enrichment pathways on the DE RNAs, which were constructed as a lncRNA-miRNA-mRNA network. Eventually, DE RNAs were validated by qRT-PCR targeting disc nucleus pulposus tissue in ADS and LDH group (n = 10 / group). Results: Compared to the LDH group, we identified 3322 DE mRNAs, 221 DE lncRNAs, 20 DE miRNAs, and 15 DE circRNAs in the ADS. In contrast to Normal, 21 miRNAs and 19 circRNAs were differentially expressed in the ADS. The expression of multiple differentially expressed ncRNAs was confirmed by qRT-PCR analysis to be consistent with the sequencing results. In addition, GO and KEGG analysis demonstrated that most DE mRNAs and ncRNAs target genes are involved in various biological processes, including Endocytosis, Apoptosis, Rap1 signaling pathway, Notch signaling pathway, and others. The constructed lncRNA-miRNA-mRNA co-expression network was primarily related to angiogenesis and regulation. Conclusion: By focusing on comparing asymmetric and symmetric disc degeneration, whole-transcriptome sequencing and bioinformatics analysis systematically screened for key ncRNAs in the development of ADS, which provided an abundance of valuable candidates for the elucidation of regulatory mechanisms. The DE ncRNAs and the lncRNA-miRNA-mRNA network are intrinsically involved in the regulation of mediator and angiogenesis, which may contribute to the insight into the pathogenesis of ADS.

916

P151.1: What is the value of measuring intraoperative coronal alignment for adult spinal deformity patients with coronal malalignment?

Nathan Lee ¹ , Michael Fields ¹ , Fthimnir Hassan ¹ , Christopher Mikhail ¹ , Stephen Stephan ¹ , Joshua Baksheshian ¹ , Andrew Platt ¹ , Joseph Lombardi ¹ , Zeeshan Sardar ¹ , Ronald A. Lehman ¹ , Lawrence Lenke ¹

¹ Orthopedic Surgery, Columbia University, Och Spine Hospital, New York, United States

Introduction: Optimizing coronal alignment is an important goal for adult spinal deformity (ASD) surgery. Recently, the horizontal distance from C7 to the Central Sacral Pelvic Line (CSPL = line bisecting the sacrum and perpendicular to the line touching the acetabular sourcils) measured on intraoperative prone radiographs was introduced as an accurate target for postoperative coronal alignment, particularly for patients without leg length discrepancy. However, the clinical utility of this intraoperative measure in predicting patient reported outcomes and postoperative lower extremity (LE) compensatory changes have not yet been described. Material and Methods: ASD patients with minimum 6 level fusion (including pelvic fixation), preoperative coronal malalignment (CVA≥3cm), no LLD (<1 cm), and minimum 2 year follow up were reviewed. Patient demographics, comorbidities, baseline PROs, surgical factors, and radiographic factors (both coronal and sagittal) were collected. The intraoperative distance (cm) from C7 to CSPL was measured for each patient. The outcome of interests included the minimum clinically important difference (MCID) for ODI/SRS and postoperative LE changes (pelvic obliquity>1deg, asymmetric knee bending, LE mechanical axis difference (LMAD)>2deg) at 2 years postop. Bivariate and multivariate logistic regression were performed to determine the independent factors for the outcomes of interest. Results: 76 patients (age 58.3 ± 13.7, female 77.6%, levels fused 14.1 ± 3.9) with preop/2yr CVA 5.0 ± 1.9/2.1 ± 1.8 cm and SVA 5.7 ± 6.0/3.0 ± 3.9 cm were reviewed. Preop/2yr ODI 39.3 ± 17.5/18 ± 17, SRS function 3.2 ± 0.9/3.8 ± 0.8, SRS pain 2.7 ± .9/3.8 ± 1.1, and SRS appearance 2.4 ± 0.8/4.0 ± 0.9. The rate of preop LE changes was 57.9% (pelvic obliquity PO = 2.4⁰, LMAD = 4.2⁰, and 27% had asymmetric knee bending). The rate of 2yr LE changes was 26.3% (pelvic obliquity PO = 2.0⁰, LMAD = 3.9⁰, and 42.9% had asymmetric knee bending). The mean error between intraop C7-iCSPL and 2yr CVA was 0.5 ± 1.3 cm. Worse C7-iCSPL was associated with higher risk for LE changes (2.9 vs. 1.9 cm, p = 0.04) and remained significant in the multivariate (OR 3.0, p < 0.01). Lower C7-iCSPL was associated with improved 2 year ODI MCID (1.8 vs. 3.2cm, p = 0.03), but did not remain significant in the multivariate. Instead, patients with LE changes was the strongest independent predictor for worse ODI MCID (OR 15.9, p < 0.01). Conclusion: For ASD patients with coronal malalignment, optimizing intraoperative coronal correction may reduce iatrogenic LE compensation, which was found to significantly contribute to worse patient reported outcomes at 2 years.

Degenerative Cervical

28

P152: Laminoplasty for the treatment of multi-level cervical radiculopathy; clinical outcome

Min-gu Jang ¹ and Woo-jin Shin ¹

¹ Orthopaedic Surgery, Konyang University Hospital, Seo-gu, Daejeon, South Korea

Introduction: To evaluate the improvement of surgical outcome of open-door laminoplasty for multilevel cervical radiculopathy. Material and Methods: This study was conducted on 36 patients who underwent laminoplasty surgery from January 2014 to December 2020. As inclusion criteria, only patients with multilevel cervical radiculopathy symptoms were included, patients with a modified JOA of 16 or higher and Nurick grade 1 or lower were included, and patients with multilevel spinal stenosis confirmed by MRI were included. All patients had mild to moderate central stenosis, with or without neural foraminal stenosis. Patients who also had myelopathy symptoms such as hand clumsiness, numbness, gait disturbance, dysdiadokinesia, imbalance, hyperreflexia, or positive Hoffman's reflex were excluded. To confirm the surgical outcome, the pain severity, patient satisfaction, neurologic outcome, functional status, and ADL, VAS and NDI were measured. As a surgical technique, a double-bent mini-plate fixation after open-door laminoplasty was used through a posterior approach. Results: The average age of the patients was 62 years old. There were 25 men and 11 women. The average follow-up period after surgery was 13 months. There were 13 cases with symptoms on the right side, 14 cases with symptoms on the left, and 9 cases on both sides. The level where the patient complained the most was C3456, and the level that showed the most spinal stenosis in MRI was C34567. Considering the patient's pain symptoms and MRI, the most frequently performed laminoplasty level was C3456. Additional surgeries were C2 domeplasty (6 cases), C6 domeplasty (1 case), C7 domeplasty (5 cases), and unilateral foraminotomy (4 cases). VAS, pain severity, satisfaction, neurologic outcomes, functional status, ADL, and NDI all showed statistically significant improvement immediately after laminoplasty surgery and final follow-up compared to before surgery. Conclusion: Open-door laminoplasty may be a useful treatment option for patients who have multilevel radiculopathy with mild to moderate spinal stenosis on MRI without myelopathy symptoms.

127

P153: Incidence and risk factors for dysphagia following anterior or posterior cervical spine surgery: a prospective study - interim analysis

Vache Hambardzumyan ¹ , Ryan Smith ¹ , Tyler Pease ¹ , Alexandra Thomson ¹ , Ivan Ye ¹ , Eugene Koh ¹ , Daniel Gelb ¹ , Steven Ludwig ¹ , and Daniel Cavanaugh ¹

¹ Orthopaedics, University of Maryland, Spine Division, Baltimore, United States

Introduction: Postoperative dysphagia is a well-known complication following anterior cervical spine surgery, which includes anterior cervical diskectomy and fusion (ACDF) and cervical disc replacement (CDR). The reported incidence varies widely from 4-71% with an estimated 12-14% of patients experiencing persistent dysphagia after 1 year. Dysphagia after posterior cervical decompression with or without fusions has been reported to range in incidence from 9-11%. This study compares the incidence of dysphagia following anterior and posterior cervical spine surgery. Materials and Methods: Consecutive adult patients undergoing primary, elective anterior or posterior cervical spine surgery were included in this prospective observational study. The incidence of dysphagia was determined by the Bazaz Dysphagia Scoring System and HSS Dysphagia and Dysphonia Inventory (HSS-DDI) preoperatively, and at 2 weeks, 6 weeks, and 12 weeks postoperatively. The incidence of new onset postoperative dysphagia was compared between the anterior and posterior cervical spine surgery cohorts. Results: Currently 54 patients have been enrolled in this study. A total of 46 patients underwent anterior cervical spine surgery and 8 underwent posterior cervical spine surgery. The mean age of all patients enrolled is 56.5 years old with 48.1% female. Using the Bazaz grading, at the two-week follow-up 14 patients (35.0%) of the anterior cohort and 1 patient (20.0%) in the posterior cohort experienced moderate dysphagia. At the six-week follow-up, 9 patients (25.7%) in the anterior cohort and 1 patient (14.3%) in the posterior cohort had moderate dysphagia. At the twelve-week follow-up, 4 patients (16.0%) in the anterior cohort and no patients in the posterior cohort reported moderate dysphagia. There was no significant difference between the two cohorts using the Bazaz grading. Using HSS-DDI, at the two-week follow-up, the anterior and posterior cohorts experienced equivalent declines in HSS-DDI scores (101.7 vs. 105.6, p = 0.600). At six-week follow-up, the anterior and posterior cohorts recovered to similar HSS-DDI scores (110.2 vs. 115.0, p = 0.825). At twelve-week follow-up, there was no difference in the average HSS-DDI score between the anterior and posterior cohorts (108.2 vs. 117.6, p = 0.351). Conclusions: The preliminary results of this study suggest there is no difference in the incidence of postoperative dysphagia between patients undergoing anterior and posterior cervical surgery.

143

P154: Using machine learning to identify patients likely to choose surgery for one level anterior cervical disc herniations

Eeric Truumees ¹ , Devender Singh ¹ , Jeremiah Alexander ² , Calvin Chandler ² , Ashley Duncan ¹ , Matthew Geck ² , and John Stokes ¹

¹ Spine, Ascension Texas Spine and Scoliosis, Austin, United States

² Orthopedics, The University of Texas at Austin, Austin, United States

Introduction: While machine learning has shown great value in medical diagnostics, its potential in assisting treatment decision making continues to be explored. Aim: This study aims to investigate if machine learning can identify factors associated with the likelihood of a patient will ultimately choose surgical intervention for one level cervical disc herniation? Materials/Methods: 130 retrospective chart reviews were conducted on patients who presented with cervical disc herniations causing radiculopathy to non-operative spine care providers at an interdisciplinary clinic between 2015-2021. A course of non-operative care was undertaken, however, if significant symptoms remains, surgical consultation was offered. 88 patients were ultimately included in the analysis, and 18 independent variables were collected across demographic, clinical and patient reported outcome domains. Values were encoded using one-hot encoding techniques, analyzed and subject to logistic regression using SKLean, StatsModel and Logit models, with a focus on the recall metric. By focusing on the recall metric, we aim to reduce the number of false positives, or Type II errors in the model. Models were further optimized by assessing multicollinearity of independent variables and employing Area Under the Curve/Receiver Operating Characteristic (AUC-ROC) and Precision-Recall threshold techniques. Results: Overall, 27.3% of the patients eventually choose surgical intervention with median time to surgery 17 weeks from intake appointment. Sex was the only demographic factor to have a significant impact on surgical intervention. While the ratio of male to female patients was almost equal, 51% to 49%, 38% of males underwent surgery compared to 16% of females. Body Mass Index (BMI), smoking status and comorbidities did not significantly influence the decision to have surgery, nor did any specific non-operative treatment modality (physical therapy, prescriptions, epidural steroid injections). The final optimized model yielded a test recall of 0.73. Three variables significantly impacted the odds of surgical intervention. Male sex increased the odds ratio of surgical intervention by 3.2 (p = 0.003); left symptom laterality increased the odds ratio of surgical intervention by 3.2 (p = 0.01); and, interestingly, an increase in baseline Oswestry Disability Index (ODI) score decreased the odds of surgical intervention marginally by 0.4 (p = 0.02), although mean ODI scores were slightly higher in surgical patients compared to non-operative patients(30 and 28, respectively). Conclusions: Male gender and left symptom laterality increased the odds of surgical intervention, while increase in baseline ODI decreased the odds of surgical intervention in this data set. This may be due in part to the use of ODI, which is typically used to determine disability for low back pain, instead of the Neck Disability Index, which is tailored to cervical spine symptoms. Sample size and variability between physicians’ treatment protocols for acute cervical radiculopathy are limitations of this study. A larger, prospective study would be the next step in utilizing machine learning to predict which patients are most likely to report satisfaction and a successful outcome.

345

P155: An evaluation of the effects of surgical approach for cervical degenerative disease on postoperative opioid use

Tariq Issa ¹ , Yunsoo Lee ¹ , Gregory Toci ¹ , Parker Brush ¹ , Yashas Reddy ¹ , Sebastian Fras ¹ , Skylar Nahi ¹ , Delano Trenchfield ¹ , Jeremy Heard ¹ , Jose Canseco ¹ , Alan Hilibrand ¹ , Alexander Vaccaro ¹ , Christopher Kepler ¹ , and Gregory Schroeder ¹

¹ Division of Spine Surgery, Rothman Orthopaedic Institute, Philadelphia, United States

Introduction: Posterior cervical fusion (PCF) and anterior cervical discectomy and fusion (ACDF) are two main surgical management options for the treatment of cervical spondylotic myelopathy. While ACDF is less invasive than PCF which should theoretically reduce post-operative pain, it is still unknown whether this leads to reduce opioid use in patients with similar construct lengths. Therefore, the primary objective of this study was to evaluate whether PCF increases post-operative opioid use compared to ACDF for patients undergoing 2-4-level fusion. Material and Methods: A retrospective review was conducted of all patients who underwent 2- to 4-level ACDF or PCF at an urban academic medical center and our affiliated sites from January 2017 to August 2021. Our state’s prescription drug monitoring program (PDMP) was queried for filled opioid prescriptions, using milligrams morphine equivalents (MME). Prescriptions filled up to two months prior to surgery were identified to determine the number of patients taking opioids pre-operatively. Post-operative opioid prescriptions were evaluated for 1-year post-operatively. Univariate analysis was utilized to compare PCF and ACDF cohorts. Multivariate linear regression was performed to assess independent predictors of short-term (0-30 days), subacute (30-90 days), and long-term (3-12 months) opioid prescription habits. Results: A total of 239 patients undergoing ACDF and 101 patients undergoing PCF who could be identified in the PDMP were included in this analysis. Patients undergoing PCF were older (61.5 vs. 57.8 years, p = 0.0049) and more likely to have more levels fused (3.08 vs. 2.45, p < 0.001). While a similar percent of patients were using opioids both 1-2 months and 0-30 days pre-operatively, patients undergoing PCF refilled greater MMEs during both time periods. Post-operatively, patients undergoing PCF refilled more MMEs in the first 30 days (127.4 vs 86.4, p = 0.0001) and refilled a non-significantly greater quantity from 30-90 days (39.3 vs 23.7, p = 0.086) and 3-12 months (105.3 vs 60.2, p = 0.059). A similar percent of patients in both groups had refilled at least one prescription after 90 days (42.6% vs 36.0%, p = 0.252). On multivariate linear regression, PCF (β = 33.9, p = 0.003), 30-day preoperative MMEs (β = 0.17, p = 0.029) and a history of depression (β = 39.4, p = 0.001) predicted increased 30-day post-operative MMEs. Only 30-day preoperative MMEs predicted opioid prescriptions filled from 30-90 days (β = 0.31, p < 0.001) and 3-12 months (β = 1.15, p < 0.001). Conclusion: Posterior cervical fusion independently predicted increased short-term opioid usage up to 30-days post-operatively irrespective of other patient risk factors, but these effects did not persist. However, short-term pre-operative opioid prescription MMEs were independently predictive of the quantity of opioids refilled and persistent long-term opioid use up to 1 year post-operatively. Providers should carefully consider prescribing opioids pre-operatively as it may impact long-term patient reliance on opioids for pain relief.

434

P156: Retro-odontoid pseudotumor in tourette Syndrome a case report

Felipe Mourao ¹ , Juan Aquino ¹ , and Felipe Sanchez Ribeiro ¹

¹ Neurosurgery, Nova Neuro, Nova Iguaçu, Brazil

Introduction: A retro-odontoid pseudotumour compressing the spinal cord and causing myelopathy is often associated with an inflammatory condition such as rheumatoid arthritis. A degenerative non-inflammatory retro-odontoid pseudotumour responsible for clinically relevant spinal cord compression is a rare condition described in small clinical series and is likely associated with craniovertebral junction hypermobility or instability – like conditions. Tourette syndrome is a disorder that involves repetitive movements or unwanted sounds (tics), including offensive words, that can be difficult to be controlled. Males are about four times more likely than females to develop this disorder. Tics are sudden, brief and intermittent movements and the hallmark sign of Tourette Syndrome. The head jerking is a common motor tic of patient that have the Tourette Syndrome. Patient that have repetitive movement of the head like in the Tourette Syndrome have a higher risk to develop chronic atlanto-axial instability and form retro odontoid non-neoplasic mass (pseudotumor) that can cause myelopathy. Material and Methods: A 63 year old male with more than 40 years of head jerking tics caused by Tourette Syndrome, began in 2019 feeling numbness in upper extremity and difficult to walk. Examination showed that he had marked spastic tetraparesis, with muscle power of at least Grade 4 in the right upper and lower extremities. Sensory disturbance in a distal (stocking-glove) distribution and bilateral clumsiness of the hands were observed. There was hyperreflexia throughout the upper and lower extremities. He did not show any evidences of rheumatoid arthritis that met the criteria of the American Rheumatism Association and bone scintigraphy study was negative for any malignancy disorder. Magnetic resonance imaging (MRI) showed a large and smooth mass behind the odontoid process compressing the spinal cord. The density of the mass was intermediate on T1-weighted images and low on T2-weighted images with a intramedullary T2 hyperintense signal in the same level. Results: A posterior surgical approach was used, the patient was undergone to a Goel and Harms technique of stabilizing C1C2 and the posterior arch of atlas was resected. In a segment MRI in five months after the surgery the retro odontoid mass have reduced and have no more compression of the spinal cord at that level. Conclusion: For several years, direct removal of the lesion through an anterior or lateral approach has been advocated as the best surgical option. However, in the last decade the posterior approach to the craniovertebral junction, to perform C1-C2 fixation and C1 laminectomy without removal of the retro-odontoid tissue, has demonstrated its efficacy in reducing retro-odontoid pannus as well as in obtaining improvement of myelopathy.

459

P157: Is there an association between rotator cuff tear and cervical spine pathology? A single-center retrospective study

Filipa Cordeiro ¹ , Sérgio Pita ² , Ana Ribau ¹ , Sara Diniz ¹ , and Pedro Neves ³

¹ Ortopedia, Centro Hospitalar Universitário do Porto, Porto, Portugal

² Ortopedia, Centro Hospitalar Baixo Vouga, Aveiro, Portugal

³ Hôpital Privé Arnault Tzanck Mougins-Sophia Antipolis, Mougins, France

Introduction: Patients with rotator cuff tendinopathy normally present shoulder pain and weakness. These symptoms are similar to those presented by some patients with cervical radiculopathy, making the differential diagnosis sometimes difficult. Since the innervation of shoulder girdle musculature is provided by cervical roots (C4, C5 and C6), the aim of this study was to investigate if there is a correlation between cervical neurological compression and rotator cuff degenerative pathology. Material and Methods: It was conducted a single center retrospective study through the analysis of all shoulder Magnetic Resonance Imaging (MRI) performed between 2017 and 2021, in a total of 1129 patients. Patients with non-degenerative rotator cuff pathology were excluded (285 patients). In 175 of the remaining 844 patients, a cervical MRI was performed in relation to cervical and/or radicular symptoms. Patients were grouped in 6 categories based on shoulder MRI findings: no injuries, calcifying tendinopathy, tendinosis, partial tear, complete tear and massive rotator cuff tear. With regards to cervical MRI, patients were grouped in seven categories: no degenerative changes, C3-C4 central compression, C4 foraminal compression, C4-C5 central compression, C5 foraminal compression, C5-C6 central compression and C6 foraminal compression. A statistical analysis was performed to study the correlation between rotator cuff pathology and cervical radiculopathy. Results: A total of 175 patients were included in this study, 121 females (69%) and 54 males (31%). The mean age was 56 years-old (SD 11.5). Sixty-six of these patients presented with tendinosis (38%), 49 with partial tear (28%), 32 with complete tear (18%), 9 with calcifying tendinopathy (5%) and 9 with massive tear (5%). The remaining patients had no rotator cuff lesions (6%). Concerning the cervical MRIs, 54 patients (31%) had no radicular or cord compression. The most affected levels were C5 and C6, with 14 patients with foraminal compression of C6 (8%), 11 with C5-C6 central compression (6%) and 9 with foraminal compression of C5 (5%). From the statistical analysis, it was found that men presented with a significant higher cervical pathology - 88,9% (p < 0.01). Advanced age was also associated with more cervical lesions – mean age with lesions was 58 years (SD 10.6) vs. mean age with no lesions was 49 years (SD 12), p < 0.01. There was no statistically significant correlation between degenerative findings in cervical MRI and shoulder MRI (p = 0.870), namely the association between C4, C5 and C6 and rotator cuff pathology. Conclusion: Despite the anatomical relationship between shoulder musculature and cervical roots, it was not possible to establish a correlation between rotator cuff injury patterns and cervical neurological compression.

Based on this study, we cannot affirm that central or foraminal compression predispose or potentiate rotator cuff tears.

489

P158: Myoarchitectonic spinolaminoplasty using hydroxyapatite spacer versus new titanium plate

Seishi Matsui ^1,2 and Naoki Shinohara ²

¹ Neurosurgery, Kajiura Hospital, Matsuyama City, Japan

² Neurosurgery, HITO Hospital, Shikokuchuo City, Japan

Introduction: Myoarchitectonic spinolaminoplasty (MSLP) is an effective spinous process-splitting double door laminoplasty for compressive cervical myelopathy. It preserves all musculoskeletal attachments of the posterior neck, so that it could prevent postoperative neck pain and loss of cervical lordosis. In the procedure of MSLP, an original hydroxyapatite (HA) spacer is usually utilized as a substitute for the spinous process, which is fixed to the laminar flaps and the spinous process flaps with surgical sutures. The authors, however, have used a newly designed titanium plate (Baslet2) instead of the original HA spacer since 2018. The Basket2 is fixed to the laminar flaps with titanium screws and to the spinous process flaps with surgical sutures. The fixation with the titanium screw must be more rigid and technically easier than the fixation with the surgical suture. This study aimed to compare the operative time, the clinical and radiological outcomes of MSLP using the HA spacer and the Basket2 in patients with compressive cervical myelopathy. Material and Methods: 52 patients with compressive cervical myelopathy who underwent MSLP in three or four laminae were enrolled. 28 patients (19 males and 9 females, a mean age of 65.8 years) with the use of the HA spacer were classified as HA group and 24 patients (12 males and 12 females, a mean age of 63.6 years) with the Basket2 were as B2 group. The operation time was assessed. Preoperative and two-year follow-up evaluations included the Neurosurgical Cervical Spine Scale (NCSS, full score 14 points) for neurological condition and radiological analysis including C2-C7 lordotic angle in neutral position (LA), flexion-extension range of motion for C2-C7 (ROM) and C2-C7 sagittal vertical axis (SVA). Results: The mean operative time was 150 minutes in HA group and 112 minutes in B2 group, while the mean number of treated laminae was 3.6 in both groups. Mean NCSS was improved from 8.5 to 12.5 in HA group and from 9.5 to 12.9 in B2 group. Mean LA increased from 4.8° to 8.2° in HA group and from 6.0° to 10.1° in B2 group. Mean ROM decreased from 31.5° to 20.5° in HA group and from 35.0° to 26.1° in B2 group. Mean SVA extended from 18.5 mm to 21.6 mm in HA group and from 23.4 mm to 24.7 mm in B2 group. As a result, significant differences between the two groups were observed in operative time and ROM at two-year follow-up. Conclusion: In MSLP, the Basket2 was more useful than the HA spacer in terms of shorter operative time and less postoperative ROM loss. It was speculated that the differences of material, profile, fixation method between these two spacers were involved in the results.

653

P159: Is plating necessary in two-level ACDF surgery? Prospective controlled study

Velmurugan Kandasamy ¹ and Sathish Muthu ²

¹ Department of Orthopaedics, Government Royapettah Hospital, Chennai, India

² Department of Orthopaedics, Government Medical College, Dindigul, India

Introduction: Anterior cervical decompression and fusion (ACDF) surgeries are one of the most commonly performed spinal procedures. Despite its frequent usage, there is no consensus among surgeons on the usage of implants to achieve fusion when performed at two levels. We aim to investigate the necessity of an additional anterior cervical plate over the cages used in two-level ACDF surgery concerning the clinical and radiological outcomes. Methods: We performed a prospective comparative controlled clinical trial among 48 patients who underwent two-level ACDF surgery for degenerative conditions of the spine with a minimum follow-up of 1 year. The patients received either standalone cages (SAC) or cage with plate (CP) constructs to achieve fusion at the two levels operated. Clinical outcomes such as neck disability index (NDI) and visual analog scale (VAS) score for pain were assessed at preoperative, 3,6, and 12 months post-operative period along with complications. During the above-mentioned visits, radiological parameters such as fusion status, subsidence, C2-C7 lordosis angle, fusion segment angle, and adjacent segment disc space narrowing were analyzed. Results: The mean age of the population included in the study was 49.4 ± 4.5 years with 14 females in each group. In comparison to the CP construct for two-level ACDF surgery, the SAC group demonstrated better NDI scores at 3, 6, and 12 months follow-up but the difference was not statistically significant (p = 0.070). We did not note any significant difference in the VAS scores between the two groups (p = 0.208). At 1 year follow-up, we noted significant cage subsidence in 33% of patients in the SAC group and while subsidence was noted only in 16.6% of patients in the CP group (p = 0.021). However, none of the patients with subsidence reported any symptoms that required revision surgery. We noted a significant increase in post-operative dysphagia in the CP group compared to the SAC group (p < 0.001). We also did not note any significant difference in the other radiological parameters such as C2-C7 lordosis or fusion segment angle or adjacent segment disc space narrowing. We did not note any significant difference in the fusion rate at one year for both SAC (91.6%) and CP (95.8%) constructs of two-level ACDF surgery (p = 0.32). Conclusion: The use of plating in two-level ACDF surgery significantly reduced the incidence of asymptomatic cage subsidence compared to the SAC group along with a significant increase in the incidence of postoperative dysphagia. We did not find any other additive advantage with the use of an anterior cervical plate over a cage construct in two-level ACDF surgeries to recommend its routine use.

721

P160: Laminectomy alone for cervical spondylotic myelopathy: a CSORN study

Mathieu Laflamme ¹ , Nicolas Dea ² , and Greg McIntosh ³

¹ Division of Neurosurgery, CHU de Québec - Université Laval, Québec City, Canada

² Neurosurgery, University of British Columbia, Vancouver, Canada

³ Canadian Spine Outcomes and Research Network, Markdale, Canada

Introduction: Most posterior cervical decompression is supplemented by instrumentation and fusion in North America. However, laminectomy alone remains a common procedure in certain parts of the world, including Europe. Results comparing these two interventions are contradictory in the literature. Our objectives were 1) to better defined the cervical myelopathy population who are treated with a decompression alone; 2) to assess the outcome of patient treated with a decompression alone and 3) to compare their outcomes to a cohort of posterior decompression and fusion patients. Methods: The Canadian Spine Outcomes and Research Network (CSORN) is a multicenter national prospective registry. Patients with CSM who underwent laminectomy without instrumentation as their index surgery were identified from this registry. Clinical, surgical and radiological data were extracted at baseline and post-operatively. A propensity match analyses was conducted with patients from the same registry who underwent decompression and instrumentation. Groups were matched according to age, mJOA, C2-7 Cobb angle and number of levels decompressed on 1:1 ratio. Primary outcome was the Neck Disability Index (NDI) at 1 year post-operatively. Secondary outcomes included reoperation, SF-36, post-operative cervical alignment, neck and arm pain and satisfaction at 1 year. Results: From the 274 patients enrolled in the registry, 34 met inclusion criteria. The mean age was 66.12 years and 28 (82.4%) were males. The mean mJOA at baseline was 13.15 and the mean Cobb angle (C2-7) was -7.70° (lordotic). These two baseline parameters were significantly different from the rest of the cohort (240 patients) who underwent posterior instrumentation with a mJOA of 11.82 and a Cobb angle of 2.57°. There was no significant difference at baseline between the cohorts for PROs (Neck pain, NDI, SF-36). The number of levels involved (3.77 vs 2.06), the operative time (174 vs 102 min) and the estimated blood loss (330 vs 184 ml) were significantly higher in the instrumented group, but length of stay (6.42 vs 4.67 days) was similar. At 12 months, there was no significant difference for NDI mean change between the laminectomy alone (-14.07) and the laminectomy with fusion (-11.90). There was also no difference at one year for mean change in mJOA and SF-36. Conclusions: In this population of Canadian patients who underwent posterior surgery for CSM, patients selected for a laminectomy alone had a better mJOA score and a more lordotic alignment at baseline. Laminectomy alone involved less decompressed levels, shorter operative time and decreased blood loss. The improvement in mJOA and PROs was not different at one year post-operatively between the laminectomy alone group and the laminectomy with fusion. In a carefully selected population, a simple decompression is a good treatment alternative.

727

P161: Application of posterior endoscopic cervical foraminotomy (PECF) for recurrent radiculopathy after anterior cervical discectomy and fusion (ACDF) surgery

Se-yi Chen ¹

¹ Neurosurgery, Chung Shan Medical University Hospital, Taiwan, Taichung, Taiwan

Introduction: Anterior cervical discectomy and fusion (ACDF) surgery is a standard treatment for cervical spondylosis myelopathy or radiculopathy disease. Though the outcome of ACDF is quite satisfactory, recurrent radiculopathy due to re-stenosis or adjacent degeneration are inevitable. We applied posterior endoscopic cervical foraminotomy (PECF) as salvage surgery after ACDF in 10 patients (14 levels). Material and Method: We performed PECF in 10 patients (14 levels) in the past 5 years for recurrent radiculopathy after ACDF. The time to developing recurrent radiculopathy ranges from 8 months to 3 years. Mostly were unilateral radiculopathy and single level. Before surgery intervention, all patients were treated with adequate medication and rehabilitation. Routine image study include bilateral oblique view X-ray, computed tomography (CT) and magnetic resonance image (MRI) of cervical spine. Result: Only one of the 10 patients didn’t response immediately but showed gradual subtle recovery after decompression surgery in the following 6 months. There’s another 1 patient showed good sensory function recovery, but transient motor palsy for 2 weeks. Otherwise, all the other patients showed motor or sensory function recovery, without symptom deterioration. None of these patients presented instability or mechanical pain after operation. None of these patient need repeat anterior surgery. Conclusion: PECF, a minimal invasive posterior cervical surgery, serves as an efficient and effective salvage surgery for re-stenosis after ACDF. This procedure prevents the patients and surgeons suffering from scarring trajectory and longer fusion levels.

891

P162: Forestier's disease presenting as dysphagia and Dysphonia - a rare case report

Dr Sajan Hegde ¹ , Sharan Achar T ¹ , Vigneshwara Badikkilaya ¹ , and Umesh Kanade P ¹

¹ Orthopaedics, Apollo Hospitals Chennai India, Chennai, India

Introduction: Diffuse idiopathic skeletal hyperostosis (DISH) or Forestier’s disease is a common, but under reported disease affecting the elderly population. It is characterized by the ossification of soft tissues, primarily of ligament, tendon, or joint capsule insertion, and can cause back pain and spinal stiffness. Exuberant osteophyte formation of the anterior longitudinal ligament of the cervical spine can cause dysphagia, most frequently and dysphonia very rarely. In this study we report one such rare case. Material and Method: A 77 years old male K/C/O DM, HTN, BPH, CAD, suffering from progressive dysphagia since 1 year and acute onset dysphonia since 10 days. Semi-solid as well as liquid diet caused aspiration necessitating ryle’s tube usage. After thorough evaluation by otolaryngologist, neurologist, Large anterior cervical osteophytic spur at C6 vertebrae level was detected on x-ray and computed tomography (CT) compressing oesophagus with impingement of right recurrent laryngeal nerve. Results: Patient was operated for DISH through anterior Smith Robinson’s approach and the C6-7 osteophyte complex was excised. The patient’s symptoms gradually improved and the same was confirmed by resolution of the protruding submucosal mass, edema and inflammation along the posterior pharyngeal wall by fiberscope examination. Conclusions: Forestier’s disease is currently a growing source of complications in elderly, mostly dysphagia and less commonly upper respiratory airway obstruction and dysphonia. Surgical intervention is a good way to relieve these symptoms. We rarely see the symptoms of dysphonia, and the management of this complication requires a multidisciplinary team and thorough approach, with spine surgeons, otolaryngologist and dieticians.

904

P163: Endoscopic transforaminal cervical foraminoplasty after anterior cervical arthrodesis: case report

Filipa Adan e Silva ¹ , Melanie Ribau da Costa ¹ , Pedro Neves ² , Arnaldo Sousa ¹ , and Paulo Costa ¹

¹ Centro Hospitalar Universitário do Porto, Porto, Portugal

² Hôpital Privé Arnault Tzanck, Mougins-Sophia Antipolis, France

Introduction: Percutaneous Endoscopic Spine Surgery is a minimally invasive surgical technique with good clinical results, and in the last decades it has been a widely used procedure and in constant development, mainly in its use at the lumbar spine level. In fact, its use to treat cases of degenerative cervical pathology refractory to conservative treatment has been increasing and following this paradigm in recent years. Material and Methods: Case report of a patient submitted to C6-C7 left Posterior Cervical Foraminoplasty via endoscopic transforaminal approach after C6-C7 Anterior Cervical Arthrodesis. Results: A 41-year-old patient referred because of neck pain with irradiation to the left upper limb with ipsilateral paresthesia, no other changes in the neurological examination. In the CT and MRI study, C6-C7 spondylodyscarthrosis with bilateral foraminal disc-osteophitary protrusions more pronounced on the left was observed, with radicular compromise. Thus, in January 2020, he underwent Discectomy and Anterior Cervical Arthrodesis C6-C7 without intercurrences, with improvement of the complaints in the postoperative period. However, after the fourth month of postoperative follow-up, there was a recurrence of complaints of left brachialgia, without paresthesias or other changes in the neurological examination. A new CT and MRI imaging study was performed, which revealed residual left foraminal stenosis at the same level. In November 2021, he underwent C6-C7 left Posterior Cervical Foraminoplasty via endoscopic transforaminal route under general anesthesia, with consequent verification of C7 root release, without any complication. In the postoperative period, the patient had a good clinical evolution, being asymptomatic at 6 months of postoperative follow-up. Conclusion: Percutaneous Endoscopic Spine Surgery has numerous advantages well reported in the literature, such as less damage to the surrounding tissues, less postoperative pain, shorter hospital stay and faster recovery, among others. Indeed, among the various indications for this technique, degenerative foraminal stenosis has been increasingly taken into account for the use of it, namely in the lumbar region, using endoscopic drill for foraminoplasty. However, the use of this technique for cervical pathology is still scarce and little reported in the literature, and the clinical advantages that can arise from its development are notorious. In fact, this technique has very gratifying clinical results that have encouraged investment and development, particularly in the cervical region, with promising prospects for the future.

907

P164: Predisposing factors for dysphagia after anterior cervical discectomy and fusion (ACDF): a retrospective review of 461 patients

Tuna Pehlivanoglu ¹ , Bahadir Gokcen ² , Kursat Kara ¹ , Tugay Yagci ¹ , O. Nuri Eroglu ¹ , and Cagatay Ozturk ¹

¹ Dept. of Orthopaedic Surgery, Liv Hospital Ulus, Liv Spine Center certified by AOSpine, Istanbul, Turkey

² Dept. of Orthopaedic Surgery, Liv Hospital Vadi, Liv Spine Center certified by AOSpine, Istanbul, Turkey

Introduction: Dsyphagia as a common problem following ACDF procedure, was reported to deteriorate patient’s quality of life with significance. However, no certain data exists regarding the prevalence and predisposing factors in terms of dysphagia. The aim of the present study was to assess the predisposing factors on the development of dysphagia after single to double level ACDF surgery on a large, homogenous group of patients, while reporting about the prevalence. Materials and Methods: 507 consecutive patients with cervical degenerative disc disease (DDD), who underwent 1 to 2 levels of ACDF between 2015-2020 in a single institution were analyzed. Patients with myelopathy (21), history of trauma (14), history of previous cervical spine surgery (11) were excluded. Remaining 461 patients (238F, 223M) with a mean age at surgery of 51.4 and mean follow-up duration of 68.4 months were included. Patients were evaluated with NDI scores, JOA scores, dysphagia handicap index DHI, and SF-36 scores. Subgroup analyses were conducted to assess the possible relation between high DHI scores and possible predisposing factors of dysphagia. Results: Patients had a mean duration of operation of 102.7mins. 18 patients were detected to have pre-operative dysphagia. Early post-operative transient dysphagia and persistent (> 6 months) dysphagia were detected in 146 (31.7%) - 52 patients (11.2%). All patients with persistent dysphagia were detected to have complete recovery at the latest follow-up. Mean NDI and JOA scores were detected to be improved from 35.4-11.1 to 10.6-16.2 (all Grade I) at the final follow-up (p < 0.001 for both). SF-36 PCS (from 44.1 to 52.8) and MCS scores (from 45.3 to 53 showed significant improvements at the last FU. Subgroup analysis yielded significantly higher DHI scores in: smokers, in patients with 2-level ACDF, in single level ACDF involving C2-3 and/or C3-4, longer duration of operations (> 90 mins), pre-op NDI-score > 36 and history of pre-operative dysphagia. Conclusion: The present study shed a light to the multivariate etiology of dysphagia following 1 to 2 level ACDF procedures. It was concluded, that being a smoker, having a pre-operative history of dysphagia, having a high pre-operative NDI-score, having 2 levels of fusion, having single level ACDF procedure comprising upper cervical levels (C2-3 or C3-4) were predisposing factors to dysphagia after ACDF. However, even persisting dysphagia was noted to be resolved at the last follow-up. It was also reported that, ACDF procedure was providing successful clinical and functional outcomes, together with significantly improved quality of life underlining its safety and efficacy in cervical DDD.

926

P165: Posterior cervical decompression and fusion - is there an advantage of going to C2? - a retrospective data base review

Anna Rienmueller ^1,2 , Thorsten Jentzsch ^2,3 , Jamie Wilson ^2,4 , Armaan Malhotra ² , and Eric Massicotte ²

¹ Orthopaedic Surgery, Medical University Vienna, Vienna, Austria

² Department of Neurosurgery, University of Toronto, Toronto, Canada

³ Department of Orthopedics, University Hospital Balgrist, Zurich, Switzerland

⁴ Department of Neurosurgery, University of Nebraska, Omaha, United States

Introduction: Posterior cervical decompression and fusion (PCDF) is a common procedure to treat patients with multilevel degenerative cervical myelopathy (CM). Standard of care includes decompression and fusion of spinal levels involved, which is most often C3-6. Adjacent segment deterioration at the upper instrumented vertebra (UIV) C3 due to construct failure and loss of deformity correction might lead to increased strain on the spinal cord and its clinical implications within follow-up time. We hypothesize that loss of deformity correction and revision surgery in patients undergoing PCDF can be avoided with inclusion of C2 in comparison to ending the fusion at C3. Methods: In a retrospective database review, we included all patients who underwent multilevel (minimum 3 level) primary PCDF for CM with an UIV of C3 or C2 between July 2005 and December 2018. Patients with incomplete clinical and radiological data as well as follow up < 1 year were excluded. Intraoperative parameters such as surgical time, blood loss and complications as well as follow up and revision surgeries were compared. C2-C7 lordosis, T1 slope, proximal and distal lordosis, as well as proximal and distal anterolisthesis were measured on pre-, post-op and follow-up radiographs and compared. To compare between groups the Wilcoxon rank sum and chi-square tests were used. A logistic regression model accounted for the a priori confounder age and the confounder levels fused. Results: A total of 91 patients were included, 33 with an UIV of C2 and 58 ending at C3. Although no difference in number of levels fused the surgical time (215 min versus 185 min, p = 0.017) and blood loss (650ml versus 500 ml, p = 0-042) was significantly higher in the UIV C2 group, no difference was found for complications. Clinical outcome represented by the neck disability index (NDI), number of revisions, and reason for revision showed no difference between the two groups. Post-op proximal lordosis was significantly greater in the UIV C2 group (p = 0.001), change of overall lordosis was significantly higher in the UIV C2 group (0.020). Discussion: We didn’t find a statistically significant difference in clinical outcome between PCDF UIV C2 and UIV C3. Surgical time and blood loos very significantly higher. Ending the fusion construct at C2 lead to higher proximal lordosis as well as significantly higher change in overall lordosis in the UIV C2 group. Further prospective studies including longer follow-ups will have to prove if better biomechanical alignment is necessary to avoid clinically relevant adjacent segment degeneration at C2/3.

950

P166: Anomalous vertebral artery course causing radiculopathy: a case report and review of relevant literature

Hussam Jabri ¹ , Kuo-Tai Chen ² , Sagar Sharma ³ , Yanting Liu ⁴ , and Jin-Sung Luke Kim ⁴

¹ Neurosurgery/Spine, Prince Sultan Military Medical City, Riyadh, Saudi Arabia

² Chang Gung Memorial Hospital, Chia-Yi, Taiwan

³ Smt. SCL General Hospital, Smt NHL Municipal Medical College, Ahmedabad, India

⁴ Seoul St. Mary Hospital, Seoul, South Korea

We present a case of cervical radiculopathy caused by an abnormal vertebral artery course. Ectatic vertebral artery course remains one of the rare causes of cervical radiculopathy. Therefore, overlooking this anomaly might lead to vertebral artery injury during cervical radiculopathy surgery. We include a review of all 18 surgically treated cases present in literature to date; and their relevant clinical course.

Discussion: Cervical radiculopathy is commonly caused by degenerative/discogenic herniated disc. However, other rare causes like ectatic vertebral artery course, congenital lesions, arteriovenous malformation, and tumors should be ruled out, especially when no disc herniation is identified on imaging. Most surgeons should continue to locate the vertebral artery and its course during the preoperative evaluation for anterior or posterior cervical spine surgery, as this is a crucial step to avoid iatrogenic injury to these vessels. As previously mentioned, the prevalence of vertebral artery loop formation (VALF) in a cadaveric study of 222 cervical spines was 2.7%.In another series of cervicobrachial pain without disc pathology, 13 out of 173 patients had VALF, suggesting that the incidence is around 7.51%.The etiology of this loop formation remains unknown but congenital abnormality, or as postulated degenerative theory, might be implicated. Oga et al., concluded after reviewing 22 cases that the extent of tortuosity is correlated with the severity of cervical spondylosis. This degenerative theory was also backed by Sakiadia et al., who postulated that the initial step in a process which is flowed by pulsatile pressure leads to migration and erosion of the adjacent structures. This theory might be supported by the higher occurrence of this pathology in older population. Clinical presentation of cases with VALF varies based on pain, radiculopathy, myelopathy or a combination of symptoms. Most patients may be asymptomatic and only diagnosed incidentally during imaging for trauma or other purposes. In neurologically symptomatic cases, X-ray demonstrates an enlargement of the foramen transversarium with an erosion of the adjacent bone and sclerotic margins related to pulsatile arterial pressure. These bony details are better appreciated in axial and reconstructed CT images. Contrasted CT and MRI show signal void in the foramen with nerve compression. Other radiologic examinations such as CT, MRI, and MRA might also be equally informative in demonstrating the course and exact location of tortuosity. Furthermore, Doppler ultrasonography can help intraoperatively in confirming the location of artery. Intraoperative indocyanine green video angiography could be utilized; however, interpretation of the signal intensity should be carefully monitored, which varies with bolus timing, artery distance from the periosteal sheath, and presence of robustious venous plexus. The ultimate surgical goal is freeing the compressed neural structure. Although, the anterior approach that exposes and frees the vertebral artery carries the risk of recurrent laryngeal nerve and carotid artery injuries. Exposure carried out using laterally passed longus colli to expose the transverse process might damage the sympathetic nerves and may lead to Horner’s syndrome. The vessel loop can also be relocated, but the anterior approach is not possible above C3 level.

974

P167: Anterior cervical surgery for non-contiguous, "skip-level" cervical degeneration: a PRISMA systematic review

Jerry Robinson ¹ , Kortnie Broschinsky ² , David Gendelberg ³ , Andrew Chung ⁴ , Jose Jimenez-Almonte ⁵ , Babak Khandehroo ¹ , Sheila Kahwaty ¹ , Neel Anand ¹ , Rod Oskouian ⁶ , and Jens Chapman ⁶

¹ Department of Orthopedics, Cedars Sinai Medical Center, Los Angeles, United States

² Department of Orthopedics, Summa Health System, Akron, United States

³ Department of Orthopedics, San Francisco Orthopedics Trauma Institute, University of California, San Francisco, United States

⁴ Banner Health, Department of Orthopedics, Pheonix, AZ, United States

⁵ Department of Orthopedics, Central Florida Bone & Joint Institute, Orange City, FL, United States

⁶ Department of Spine Surgery, Swedish Neuroscience Institute, Seattle, WA, United States

Introduction: Non-contiguous, “skip-level” cervical degeneration is a phenomenon where two degenerative cervical discs are separated by a normal, intermediate cervical disc. Skip-level degeneration presents an interesting challenge to the spine surgeon because there is not a clear consensus regarding optimal treatment. To date, no systematic review has assessed the literature for guidance on this condition. Materials and Methods: We conducted a search of the PubMed, Cochran, and OVID databases through February 2022 using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. We limited the search to include full-text, English language publications that had any reference to “non-contiguous” or “skip-level” cervical pathology to answer the following questions: (1) What is the incidence of non-contiguous, “skip-level” cervical degeneration? (2) What biomechanical data exists regarding anterior cervical ‘skip-level” constructs? (3) What does the clinical data suggest regarding outcomes for anterior cervical “skip-level” surgery? Results: Our initial PRISMA search yielded 861 publications, which resulted in 21 unique publications after application of inclusion/exclusion criteria. The first question resulted in one unique publication describing the incidence of non-contiguous, “skip level” cervical degeneration ranging from 1.6% to 22% depending on the number of cervical levels involved. For question two, the biomechanical data is conflicting. Cadaveric models may indicate that skip-level constructs result in an equal distribution of forces to the remaining cervical segments, while finite element analyses indicate that the distribution of forces may depend on the specific “skip-level” construct. For the last question, the clinical data suggests that any anterior surgical construct alters the normal biomechanics of the cervical spine and can lead to adjacent/intermediate degeneration; however, constructs including arthroplasty might alter the normal biomechanics to a lesser degree. Conclusions: There remains a significant deficit of quality publications regarding non-contiguous, “skip-level” cervical degeneration. Spine researchers may benefit from radiographic reports that specifically name and innumerate the incidence of non-contiguous, “skip-level” cervical degeneration. Due to discrepancy in biomechanical data, further publications regarding the biomechanics of skip-level anterior cervical constructs are necessary. The literature may benefit from non-contiguous anterior cervical clinical studies that differentiate post-operative intermediate disc degeneration rates from adjacent level degeneration rates.

1059

P168: Diagnosis of C4 radiculopathy

Yasuhisa Tanaka ¹

¹ Orthopaedics, Tohoku Central Hospital, Yamagata, Japan

Introduction: Cervical nerve root compression causes neck and scapular pain, and its location indicates the affected root. Furthermore, C5 to C8 radiculopathy is usually accompanied by specific neurologies. However, features of C4 radiculopathy are not well-known. Material and Methods: We retrospectively studied patients who underwent posterior foraminotomy of the unilateral C3-4 intervertebral level between 2012 and 2018 and showed improvements within 1 month after surgery. We collected data on symptom duration, site of neck pain, Spurling test, imaging findings, selective root block (SRB) effect, and surgical results using a cervical radiculopathy scoring system (normal = 20 points). Results: In total, eight patients were included, with mean age of 73 (range, 52-83) years, and mean follow-up of 2 years. Symptom durations were 3 months to 5 years and exceeded 1 year in five patients. All patients reported unilateral nape pain of the suboccipital and upper trapezius region. Spurling test elicited reproduction or increase of nape pain in every patient. Plain radiographs showed facet joint hypertrophy and foraminal stenosis at C3-4 level on the symptomatic side in every case. Those findings were also clear on magnetic resonance imaging and computed tomography scans. In five patients who underwent SRB, pain reproduction and its temporary relief were obtained. Cervical radiculopathy scores ranged from 9 to 15 points before surgery, and from 16 to 20 after surgery. Mean improvement rate was 90%. Conclusion: Elderly patients suffering for long time from unilateral nape pain with positive Spurling test may have C4 radiculopathy.

1060

P169: Translation and validation of a Hindi version of Japanese Orthopedic Association Score for cervical myelopathy and radiculopathy - Cross sectional Study

Varun Agarwal ¹

¹ Orthopedics, Rohilkhand Medical College and Hospital, Bareilly, India

Introduction: Objective is to evaluate the validity and cross-cultural adaptation of the translated Hindi version with Indian modification of the Japanese Orthopedic Association (In-mJOA-H score) for Cervical Myelopathy and compare Nurick scale with JOA scores. A translated Hindi version of the Indian modification of Japanese Orthopedic Association (In-mJOA-H) score has never been studied. This is one of the biggest limitations especially in Northern part of India where majority are Hindi speaking and surgeons have difficulty in assessing disease severity. Material and Methods: The study included a cross-sectional study of 193 patients, from November 2020 to May 2021 with cervical myelopathy or neck pain with radiculopathy. The acceptability, validity, responsiveness, reproducibility, and cross-cultural adaptation were evaluated for the Hindi version (In-mJOA-H). Results: The evaluation of In-mJOA-H score on one ninety-three patient exhibited strong correlation with modified Nurick scale with English version and its individual component of English version Indian modification of JOA scale (In-mJOA-E). Conclusion: Our study shows good correlation between Nurick scale, Hindi version (In-mJOA-H) and English version of JOA scores with Indian modification (In-mJOA-E). The acceptability, validity, responsiveness, and reproducibility were established for the Hindi version with Indian modification.

1106

P170: Predictors of patient satisfaction following laminoplasty and posterior cervical fusion for degenerative cervical myelopathy

Justin Vickery ¹ , Mitchell Bowers ¹ , Andrew Croft ¹ , Anthony Steinle ¹ , Wilson Vaughan ¹ , Jacquelyn Pennings ² , Claudia Davidson ² , Raymond Gardocki ¹ , Scott Lawrence Zuckerman ^1,3 , Amir Abtahi ^1,2,3 , and Byron Stephens ^1,2,3

¹ Department of Orthopaedic Surgery

² Center for Musculoskeletal Research

³ Department of Neurological Surgery, Vanderbilt University Medical Center, Nashville, TN, United States

Introduction: Degenerative cervical myelopathy (DCM) is the most common cause of spinal cord dysfunction. Symptom onset is usually insidious in nature and can vary widely in clinical severity. Surgical management options include decompression through either an anterior or posterior approach. The two most common posterior operations are laminectomy and fusion (LF) and laminoplasty (LP). While both LF and LP are appropriate treatments for DCM, there is a paucity of data to identify patient characteristics associated with patient satisfaction following these procedures. To improve this knowledge gap, we conducted a retrospective review of a large multi-center prospective spine outcomes registry investigating which patient characteristics accurately predict patient satisfaction following either LF or LP for DCM. Material and Methods: The Quality Outcomes Database, a national prospective spine surgery registry, was queried for patients who underwent LF or LP for DCM. Included were 88 LP and 976 LF patients who received surgery between 04/2013 and 07/2019. The primary outcome was the North American Spine Surgery patient satisfaction ordinal questionnaire, which is measured on a 4-point scale (1 = surgery met my expectations and 4 = I am the same or worse as compared to before surgery), but we converted it to a dichotomous outcome of being satisfied (1 or 2) or not (3 or 4). Pearson chi-square tests, unpaired t-test, and Mann Whitney U test were used to assess initial differences in demographics, clinical characteristics and satisfaction based on surgical technique. A multivariate logistic regression model was conducted to assess the association of surgical technique (LF vs LP) with patient satisfaction, controlling for baseline demographics and clinical characteristics. Results: No statistically significant differences in patient satisfaction were found between LF and LP (78.3% vs 76.1%, p = 0.642) at 12-month follow-up. LP patients had significantly higher proportions of advanced education, worse myelopathic symptoms, private insurance, absence of depression/anxiety, and absence of adjacent segment disease. Length of stay (LOS), neck disability index (NDI), and baseline arm/neck pain were significantly worse in LF patients. In the regression model, procedure type was not significantly associated with patient satisfaction when adjusting for demographic and clinical characteristics. Symptom duration > 3 months, increasing LOS, and race (non-white) were significant predictors of decreased patient satisfaction in both groups. Conclusion: Our present study found that patients achieve equal satisfaction following either procedure at 12-month follow-up. Symptom duration of less than 3 months, decreased length of hospital stay, and identifying as white race were all significant positive predictors of patient satisfaction. LP patients were better educated, less anxious/depressed, and were more commonly privately insured than LF patients, which highlights an important inequity in the socioeconomic access to LP. Additionally, further research investigating the satisfaction disparity between white and non-white patients is a critical area of future research. As with all elective spine surgeries, proper surgical indication and establishing post operative expectations is critical to successful outcomes. The data from our study will aid surgeons when counseling patients regarding satisfaction following LP and LF.

1155

P171: Comparative effectiveness of laminoplasty and laminectomy and fusion for the treatment of cervical myeloradiculopathy

Justin Vickery ¹ , Mitchell Bowers ¹ , Anthony Steinle ¹ , Wilson Vaughan ¹ , Andrew Croft ¹ , Jacquelyn Pennings ² , Claudia Davidson ² , Raymond Gardocki ¹ , Scott Lawrence Zuckerman ^1,3 , Amir Abtahi ^1,2,3 , and Byron Stephens ^1,2,3

¹ Department of Orthopaedic Surgery

² Center for Musculoskeletal Research

³ Department of Neurological Surgery, Vanderbilt University Medical Center, Nashville, TN, United States

Introduction: Cervical myeloradiculopathy is the clinical manifestation of degenerative cervical spine disease resulting in concomitant central and foraminal stenosis. Surgical treatment options include both anterior and posterior approaches. The most commonly utilized posterior surgical option is laminectomy and fusion (LF). While laminoplasty (LP) is commonly utilized to treat myelopathy alone, debate exists regarding the efficacy of LP with respect to adequate treatment of radicular complaints in patients with myeloradiculopathy. To improve this clinical knowledge gap, our study investigated the efficacy of LP in improving radicular symptoms and how that change compares to the improvement seen with posterior cervical fusion. Additionally, we investigated which patient and operative characteristics were associated with arm pain scores at 12 months. Material and Methods: The Quality Outcomes Database, a multi-center national prospective spine surgery registry, was retrospectively queried for patients with myeloradiculopathy who underwent LF or LP from 4/2013 and 07/2019. The primary outcome was Numeric Rating Scale (NRS) arm pain, which asks the patient to rate their arm pain on a scale of 0-10 in the past seven days. Patients who reported a preoperative NRS arm pain score of 0 (no pain) were excluded. Differences in patient demographics, clinical characteristics, and PROs were assessed between the LP and LF groups (chi square/parametric and nonparametric t-tests). Changes in NRS arm pain from preop to 12 months postop were assessed for both groups (nonparametric paired t-tests). Linear regression was used to model predictors of 12-month arm pain based on type of procedure (LP vs LF), controlling for baseline arm pain and other demographic and clinical variables. Results: There were no significant differences in arm pain scores at 12 months between LF and LP (2.9 vs 2.0, p = 0.100), and both demonstrated similar significant improvements in arm pain over that time period (p < 0.001). Patients undergoing LF had significantly higher levels of preoperative arm pain compared to LP (p = 0.003). Type of procedure (LP vs LF) was not a significant predictor of arm pain at 12 months when adjusting for preoperative arm pain. Higher preoperative arm pain, increased hospital length of stay, and increased neck disability index were all significant predictors of increased arm pain at 12 months, even when controlling for other factors. No factors were found to be significant in predicting the change in arm pain from baseline to 12 months in LP or LF patients. Conclusion: Laminoplasty has been questioned as an appropriate treatment for patients with myeloradiculopathy. While laminoplasty has been shown to adequately decompress the central canal in myelopathic patients, uncertainty exists regarding its ability to provide adequate decompression of the neural foramen and therefore relief of concomitant radicular pain. These data demonstrate that patients with myeloradiculopathy undergoing posterior cervical fusion or laminoplasty experienced similar levels of arm pain improvement. Additionally, the type of decompression performed was not a predictor of arm pain at 12 months. These findings demonstrate that in patients with myeloradiculopathy, laminoplasty is a viable treatment option for both the myelopathic and radicular complaints.

1161

P172: Comparison of cross-sectional area of lumbar and cervical muscle mass in degenerative cervical myelopathy

Hyunjun Jang ¹ , Kyung-Hyun Kim ¹ , Jeong-Yoon Park ¹ , Keun-Su Kim ¹ , Yong-Eun Cho ¹ , and Dongkyu Chin ¹

¹ Spine and Spinal Cord Institute, Gangnam Severance Hospital, Yonsei University College of Medicine, Department of Neurosurgery, Seoul, South Korea

Introduction: Degenerative cervical myelopathy (DCM) could causes muscle weakness due to damage to neurons below the injury site of spinal cord. The purpose of this study was to investigate the ratio of lumbar and cervical cross-sectional area (CSA) according to myelopathic symptoms. Material and Methods: We reviewed medical records of 90 patients retrospectively. The patients were divided in three groups; Group A, who had both cervical and lumbar MRIs for the purpose of health check-up, Group B with signal change in cord on MRI without symptoms (Asymptomatic DCM), and Group C, who underwent surgery for symptomatic cervical myelopathy. CSA of cervical extensor muscle and lumbar muscle (psoas, extensor muscles) of three groups were measured using Image J (Image J 1.53, NIH, USA) program. Results: Each group of 30 people was investigated. There were no significant differences in basic demographics between each group. The lumbar CSA to cervical CSA ratios of B and C showed significantly lower values than those of group A (p < 0.05). Conclusion: The lumbar CSA to cervical CSA ratios was lower in not only the patients of degenerative cervical myelopathy, but also in those with no symptoms who had cord signal change in MRI, than normal people. The ratio could be a helpful predictor of detecting degenerative cervical myelopathy.

1215

P173: Comparison of anterior and posterior approaches for cervical spondylotic myelopathy in terms of clinical and radiological outcome

Usama Muhammad ¹ , Ammar Dogar ¹ , Haseeb Hussain ¹ , and Ahsan Atta ¹

¹ Orthopedics, Ghurki Trust Teaching Hospital, Lahore, Pakistan

Background: With higher life expectancy because of better healthcare facilities around the globe, chronic diseases like cervical spondylotic myelopathy are at rise. In cases of severe myelopathy surgical intervention is the only management option. Since cervical spine is approachable from both anterior and posterior aspect, both approaches have been used previously with overlapping indication. Thus, here comparison between anterior and posterior approach in terms of outcome and complications is the objective. Methodology: A total of 53 patients that were treated with either approach at GTTH Lahore after June 2018 were retrospectively assessed, both radiologically and clinically. In this non-randomized comparative study, the patient that underwent anterior decompression, instrumentation and fusion constituted group A (n = 32) and those that were treated with posterior decompression and instrumentation were added in group B (n = 21). Japanese Orthopedic Association (JOA) score, Nurick grading and cervical alignment on follow-up was assessed to compare the outcome. Results: Mean age was 53.2 ± 8.1 & 54.9 ± 7.2 years, follow-up period was 17.2 ± 4.1 & 16.1 ± 7.2 months and segments operated upon were 2.1 ± 0.8 & 2.7 ± 0.7 in group A and B respectively: that were comparable. Preoperative JOA scores in both the study groups were significantly alike (group A = 8.91 ± 2.6 and group B = 8.79 ± 2.8, p > 0.05) but on last follow-up anterior approach showed better clinical results than the posterior approach (JOA score group A = 13.35 ± 2.3 and group B = 12.51 ± 2.1, p < 0.05). However, Nurick grading of both the categories showed no statistically significant difference in either preop or final follow-up grading (Preop group A = 3.01 ± 0.6, group B = 2.89 ± 0.8, p > 0.05: Postop group A = 2.06 ± 0.8, group B = 1.99 ± 0.7, p > 0,05). Cobbs angle in both the groups were alike preoperatively (group A = -1.2 ± 8.2, group B = -1.8 ± 9.6, p > 0.05), but better restoration on last follow up was evident on radiology for anterior approach in comparison (group A = 13.9-4.2, group B = 9.1-3.6, p < 0.05). Postoperatively, anterior approach was associated with temporary dysphonia and dysphagia in a few cases whereas posterior approach cases reported persistent axial symptoms. Conclusion: Both the approaches are effective in treatment of cervical myelopathy symptoms and are associated with good radiological outcome as well. Though, anterior approach was more effective as per JOA score improvement and restoration in Cobb’s angle.

Keywords: cervical spondylotic myelopathy, anterior approach, posterior approach.

1250

P174: Anterior cervical discectomy and fusions are associated with greater subsidence when compared to anterior cervical corpectomies for degenerative pathology

Spencer Raub ^1,2 , Caroline Drolet ¹ , Jesse Shen ^1,3 , Nicole Vivelo ¹ , Michelle Gilbert ¹ , Kellen Nold ¹ , Venu Nemani ¹ , Jean Christophe Leveque ¹ , and Philip Louie ¹

¹ Neurosurgery, Virginia Mason Franciscan Health, Seattle, United States

² School of Medicine, University of Washington, Seattle, USA

³ Université de Montréal, Canada

Introduction: Anterior cervical discectomy and fusion (ACDF) or anterior cervical corpectomy and fusion (ACCF) surgery has been demonstrated to be an effective surgical treatment for degenerative cervical conditions. ACCF, when directly compared to ACDF, has been described as the more invasive of the two procedures, but may be more effective to improve anterior-based stenosis that is present posterior to a vertebral body, rather than at the disc spaces themselves. Graft subsidence is a known complication of both procedures, but no study has compared the subsidence rates and risk factors between these two procedures performed for degenerative pathology utilizing the same surgical techniques. We sought to compare subsidence, based on interscrew distance and height between ACCF and ACDF, with a specific focus on the impact of screw-to-vertebral body ratio and change in angle of variable screws placed at the cephalad and caudal aspects of the construct. Material and Methods: A retrospective cohort analysis was performed on consecutive patients who underwent a 2-level ACDF (allograft) or 1-level ACCF (titanium expandable cage) for degenerative pathology between January 2017 and June 2021 with 6 months follow-up. Procedures were performed by 3 spine-fellowship trained surgeons who perform both procedures with the same surgical technique. Pre- and 6-month post-operative radiographic assessment included height (ant/mid/post), intervertebral screw distance, and screw-vertebral body ratio of the cephalad and caudal screws. Demographic information, operative times, complications, and re-operation data was obtained. All analyses predict subsidence change scores (ant/mid/post height, interscrew distance) from screw angle change (cephalad or caudal depending on top or bottom), postop screw angle, screw-to-vertebral body ratio, ACDF vs ACCF, postop subsidence measurement and demographic variables (age, sex, BMI, CCI). Screw angle change was included as an intermediate variable and was predicted by postop screw angle, screw to vertebral body ratio, and demographic variables. Results: In total, 65 ACDF patients and 13 ACCF patients fulfilled inclusion criteria. There were no significant differences between the demographics of both groups. Dysphagia requiring consultation were similar between both groups (15.4% ACDF, 17.6% ACCF; p > 0.05). Across all 4 measurements of subsidence, ACDF procedures resulted in greater subsidence than ACCF (p < 0.05). Additionally, greater screw-to-vertebral body ratio was associated with less subsidence (p < 0.05). Overall, no re-operations were performed for subsidence-related pathology. Three ACDF patients underwent re-operation for pseudarthrosis. One ACCF underwent re-operation for early-onset adjacent segment pathology. Conclusion: At a single center with similar surgical techniques, ACDF procedures were associated with greater subsidence when compared to ACCFs when performed for degenerative pathology. Greater screw-to-vertebral body ratio may be protective against radiographic subsidence. The clinical impact of these subsidence differences require further evaluation.

1317

P175: Dysphagia in the anterior approach in spinal surgery

Marcos Joaquin Robles Ortiz ¹

¹ Spine Surgery, Instituto Nacional de Rehabilitacion, Mexico City, Mexico

Dysphagia after the anterior cervical approach has been reported in up to 60% in the literature. These symptoms affect the well-being of patients during their postoperative period. The anterior cervical approach is used to treat multiple disorders including degenerative, traumatic, oncological, inflammatory, congenital, vascular, and infectious,with the goal of restoring nerve function, relieving pain, numbness, tingling, and weakness. Of the anterior approaches, the Smith-Robinson approach is the most commonly used for access to the cervical spine, as it allows the surgeon access to the discs, bony structures, and anterior lesions without directly affecting the spinal cord. Its use has increased , because anterior discectomies and fusions are performed more frequently. Surgery to the anterior cervical spine requires dissection in the vicinity of the laryngeal and pharyngeal muscles, as well as traction and manipulation of the esophagus, trachea, and pharynx. Subsequently, there is a risk of nerve disruption, tissue damage, hematoma formation, or edema, which can result in dysphonia and dysphagia, these being the most common complications of this procedure. Prospective analytical descriptive observational study to measure the immediate postoperative prevalence of dysphagia in patients with a diagnosis of narrow cervical canal undergoing an anterior cervical approach.

Inclusion criteria

Patients between 40 and 80 years old

Candidates for surgical management with anterior cervical approach.

They have signed informed consent.

Exclusion criteria

History of previous cervical surgery.

ASA III and IV.

BMI > 30.

Presence of dysphagia prior to surgery

History of diseases in the esophagus and/or laryn

Results: The values showed a normal distribution according to the Kolmogorov-Smirnov test. A sample of 52 patients who met the inclusion criteria was obtained, the average age was 63.17 ± 9.57 years old, 40.4% (21/52) of the sample were male and 59.6% (31/52) The sample had homogeneous anthropometric variables, with height 1.60 ± 0.085, weight 69.79 ± 10.62kg, BMI 27.31 ± 3.68 kg/m2. The patients presented a history of symptoms of 38.87 ± 41.62 months, the number of affected levels was 1.88 ± 0.74. Clinical Scales: The symptomatology evaluated in clinical scales was pain measured in VAS in the cervical region of 7.31 ± 1.59 points and in the extremities of 6.77 ± 2.02 points, disability according to the mJOA in 9.56 ± 3.22, IDC 54.73 ± 21.56%, quality of according to the SF-36 in the physical field of 26.87 ± 8.02, mental 38.54 ± 13.32, the average Nurick was 2.40 ± 1.63, regarding the evaluation of dysphagia according to the preoperative scales Bazaz 0, EAT-10 2.60 ± 4.55, HIV-10 3.77 ± 4.95, HIV-30 14.90 ± 21.05. Within the surgical variables we take into account the anesthetic time 192.48 ± 58.97min, intubation attempts with an average of 1.06 ± 0.32, number of probe 7.76 ± 0.43Fr, Aldrete classification 8.16 ± 2.15 points , surgical time 147.56 ± 56.11min, mean bleeding 107.21 ± 85.55cc, no complications were reported during surgery. The days of hospital were 5.87 ± 3.42 days. Conclusions: In patients undergoing spinal surgery using the anterior cervical approach, 55.7% immediate dysphagia was reported. Previous dysphagia patiens (30.8%), no changes were observed after surgical treatment.

Limitations Pandemic. Limited number of patients. Intubation variables were not taken into account.

1339

P176: Pack years of tobacco cigarette smoking as a predictor of bony fusion following anterior cervical discectomy and fusion surgery

Marissa Kruk ¹ , Mohamed Soliman ^1,2 , Alexander Aguirre ¹ , Cathleen Kuo ¹ , Nicco Ruggiero ¹ , Andrea Kassay ¹ , Asham Khan ¹ , Moleca Ghannam ¹ , David Smolar ¹ , John Pollina ¹ , and Jeffrey Mullin ¹

¹ Neurosurgery, University at Buffalo, Buffalo, United States

² Neurosurgery, Cairo University, Cairo, Egypt

Introduction: Smoking tobacco cigarettes negatively impacts the process of bone healing after spinal fusion surgery. Patient smoking history is often assessed based on current smoker, former smoker, and nonsmoker status. However, few studies quantify smoking history in terms of pack years to estimate lifetime exposure and assess its effects. This study aimed to investigate the influence that smoking history quantified in terms of pack years has on bony fusion following anterior cervical discectomy and fusion (ACDF) surgery. Material and Methods: A retrospective chart review was conducted to identify patients who had undergone prior ACDF surgery. Data collection for analysis included patient demographics, procedural variables, and postoperative outcomes. Multivariate linear regression analysis was performed to identify predictive factors of bony fusion and cage subsidence after ACDF surgery. Results: A total of 97 patients were identified with 162 levels fused. Of the 97 patients, 90 (92.7%) demonstrated bony fusion on postoperative imaging. The mean number of pack years for the fusion and non-fusion groups were 6.06 ± 12.66 and 16.14 ± 20.70 respectively. On multivariate linear regression analysis, a greater number of pack years of tobacco cigarette smoking was a significant predictor of non-fusion (b-coefficient, -0.00424; 95% Confidence Interval, [0.991,0.999], p < 0.05). Conclusion: A greater estimated lifetime exposure to tobacco smoking, quantified in terms of pack years, increases the risk of non-fusion following ACDF surgery.

1411

P177: A randomised controlled trial comparing the effectiveness of surgical and nonsurgical treatment for cervical radiculopathy

Mirad Taso ^1,2 , Håvard Sommernes ³ , Frode Kolstad ³ , Jarle Sundseth ³ , Siri Bjorland ¹ , Are Pripp ^2,4 , John Anker Zwart ^1,2 , and Jens Ivar Brox ^2,4

¹ Department of Physical Medicine and Rehabilitation

² Faculty of Medicine, University of Oslo, Oslo, Norway

³ Department of Neurosurgery

⁴ Oslo Centre of Biostatistics and Epidemiology, Oslo University Hospital, Oslo, Norway

Background: Cervical radiculopathy is usually caused by disc herniation or spondylosis. The prognosis is expected to be good in most patients, but there is limited scientific evidence on the indications for nonsurgical and surgical treatments. Research question: The aim of the present study is to evaluate and compare the effectiveness of surgical and nonsurgical treatment in two trials - including disc herniation and spondylosis, respectively, and to evaluate factors that contribute to better decision making. Design: RCT. Patients with disabling radicular arm pain and MRI proven cervical disc herniation or spondylosis will be randomised to receive nonsurgical or surgical treatment. Methods: The follow-up period is 1-year and the sample size is estimated to 50 for each arm in the two trials, giving a total of 200 patients. The primary outcomes are the Neck Disability Index and arm pain. Secondary outcomes include neck pain; EQ-5D and costs to evaluate cost-effectiveness; prognostic factors; CT and MRI to estimate intervertebral foraminal area and nerve root compression; and the expected minimal improvement for willingness to undergo treatment. Discussion: The outcomes of this study will contribute to better decision making in the treatment of cervical radiculopathy.

1463

P178: Anterior cervical discectomy and fusion with ventral plate: Influence of preoperative and postoperative sagittal balance on re-operation rate

Magnus Michaelis ^1,2 , Martin Erhard ¹ , Anna C. Rienmüller ³ , Bernhard Mayer ⁴ , and Yu-Mi Ryang ⁵

¹ Department for Neurosurgery, Klinikum rechts der Isar (TUM), Munich, Germany

² Department for Orthopedics, Sportsmedicine and Traumasurgery, München Klinik Bogenhausen, Munich, Germany

³ Department for Orthopedic Surgery and Trauma Surgery, Medical University Vienna, Vienna, Austria

⁴ Department for Neurosurgery, Klinikum Rechts der Isar der Technischen Universität München, Munich, Germany

⁵ Neurosurgery, Helios Klinikum Berlin Buch, Berlin, Germany

Introduction: Anterior cervical discectomy and fusion (ACDF) with ventral plate is a common way to treat several cervical degenerations. Adjacent segment disease (ASD) and instability are frequent postoperative complications, that lead to re-operation. We therefore investigated if parameters of the cervical sagittal balance correlate with the number of re-operations caused by ASD and instability. Material and Methods: All Patients who underwent ACDF with ventral plate between 2010-2016 at our institution were included and a retrospective analysis to evaluate reoperation-rate due to ASD and instability was performed. Cervical lordosis, k-line, segmental lordosis, T1-slope, C2 sagittal vertical axis (SVA), C7 SVA and Center of gravity (COG) SVA were measured on preoperative and postoperative x-ray images. A binary logistic regression analysis was performed to evaluate possible mechanical and osseus risk factors for re-operation. Results: 155 patients were included (86 men, 69 women; mean age: 68.8 ± 14.4). 25 out of 155 patients (16.1%) underwent re-operation. 17 (68%) due to ASD, 8 patients (32%) due to instability. On preoperative x-ray images correlation was found for T1-slope (OR = 0.920; p = 0.067). Re-operated patients had a smaller T1-slope preoperative. On postoperative x-ray images correlation was found for segmental lordosis (OR = 1.074; p = 0.063) and C2 SVA (OR = 1.169; p = 0.115). Re-operated patients had a larger segmental lordosis and a larger C2 SVA after the first surgery. Conclusion: A smaller T1-slope preoperative seems to increase the risk of re-operation caused by ASD and instability after ACDF with ventral plate. A larger segmental lordosis and a larger C2 SVA after first surgery seem to increase the risk of re-operation as well. Although none of these correlations was significant, the direction of our results matches with common literature. Further investigations are necessary in order to verify our results and to find out more about the influence of the sagittal balance on re-operation-rate.

1490

P179: Autologous clavicle graft for anterior cervical discectomy and fusion

Mandar Borde ¹ , K Venugopal Menon ¹ , Akash Mane ¹ , and Sangram Rajale ¹

¹ Spine Surgery, Bharati Vidyapeeth (deemed to be University) Medical College and Hospital, Pune, India

Introduction: Iliac crest has been the most common source of autologous bone grafting for anterior cervical discectomy and fusion (ACDF). Donor site complications like postoperative persistent pain and paraesthesia, hematoma, infection, lateral femoral cutaneous nerve injury, peritoneal perforations, iliac fractures and pelvic instability have been reported with an incidence of 10-39%. To avoid occurrence of such morbidities, alternative sources for autologous bone graft like sternum, patella, fibula and rib have been tried but haven’t become popular. We present a series of 25 cases with anterior cervical discectomy and fusion using autologous cancellous graft from medial end of the clavicle and polyetheretherketone (PEEK) cage. Material and Methods: Between January 2020 and January 2021, 25 patients and 33 levels (21 males and 4 females), ranging in age from 31 to 65 years underwent single-level (17 patients) or two-level (8 patients) anterior cervical discectomy and fusion using this technique. Nine patients presented with radiculopathy, 6 had myelopathy, 5 presented with myeloradiculopathy and 5 patients had traumatic disc herniations with varying degrees of neurological deficit (4 patients were ASIA A; 1 patient was ASIA B). Surgical decision was made after thorough assessment of the preoperative clinical and radiological examinations. The cervical discectomy was performed using the standard Smith- Robinson technique. The bone graft was obtained by doing a small corticotomy at the medial end of clavicle about 2.5 cm lateral to the sternoclavicular joint and scooping out the cancellous bone with a curette. A PEEK cage filled with the cancellous bone graft was fit in the discectomy defect. Results: Clinical and radiological evaluation of all the patients was done at 6 weeks, 3 months, 6 months, and 12 months after the surgery. All patients showed significant improvement in their clinical symptoms and showed radiographic evidence of solid bony fusion between 6-9 months. The mean Visual Analogue Score (VAS) at the end of 1-year was 0.2. Radiological assessment involved anteroposterior and lateral radiographs and lateral view radiographs in flexion and extension. Amongst the 5 patients with neurological deficit, at the end of 1 year, 4 patients improved from ASIA A to ASIA C while patient with ASIA B improved to ASIA D. Twenty-four patients were highly satisfied by the cosmetic appearance of the scar at 1- year follow up. One patient developed a keloid-like scar but was not concerned by the cosmetic appearance. Conclusion: Cancellous bone from the medial end clavicle is a safe, reliable, and technically easy source of autologous bone graft that yields optimal fusion rates and patient satisfaction with ACDF surgery. The advantages are easy access as the medial end of clavicle lies in close proximity to the surgical field and does not require any additional preparation or draping, no donor site pain and a cosmetic scar; its disadvantages being the less volume of available graft and a lack of structural support.

1574

P180: Degenerative cervical pathologies on magnetic resonance imaging: retrospective analysis of prevalence in a single centre

Arkaprabha Banerjee ¹ , Oliver Mowforth ² , Mark Kotter ² , Virginia Newcombe ³ , and Benjamin Davies ²

¹ School of Clinical Medicine

² Department of Clinical Neurosciences, University of Cambridge, United Kingdom

³ Addenbrooke's Hospital, Division of Anaesthesia, United Kingdom

Introduction: Degenerative cervical myelopathy (DCM) is a condition of symptomatic spinal cord compression secondary to various cervical spine degenerative pathologies. A diagnosis of DCM requires degenerative cervical pathology, cord compression and myelopathic symptoms. We studied the prevalence of degenerative pathologies in a cohort of 133 patients with asymptomatic cord compression. The objective was to compare this cohort to previously studied asymptomatic cord compression and DCM cohorts to identify if previously determined trends of DCM pathology applied to our cohort. Methods: Radiological reports of cervical MRI scans conducted at a tertiary neurosciences centre between January and December 2015 were screened for degenerative cervical spinal changes. Of the total 1123 cervical MRI scans screened, 133 met the inclusion criteria. Degenerative pathology was classified into key categories. Prevalence of each category and accompanying 95% confidence interval was calculated and compared to asymptomatic cord compression and DCM cohorts. Within the cohort, age and gender were used for subgroup analysis. Mean age (55.69 years) was used to dichotomise the cohort into two age-based subgroups; patients < 55 years old and patients > 56 years old to allow for effective comparison of relatively younger and relatively older patients. 95% Confidence Intervals were calculated and a Fisher’s Exact Test was carried out for sub-group analysis. Results: The most prevalent pathology was degenerative multilevel disc pathology (73.7%, 95% CI 66.2-81.2%), followed by degenerative single level disc pathology (23.3%, 95% CI 15.9-30.1%). Enlargement of ligamentum flavum (ELF) had a prevalence of 9.8% (95% CI 4.7-14.8%) and spondylolisthesis/subluxation had a prevalence of 9.8% as well (95% CI 4.7-14.8%). Congenital stenosis was the fifth most prevalent pathology (3.8%, 95% CI 0.5-7.0%). Cranio-cervical joint abnormalities and KFS both had prevalence values of 2.3% (95% CI 0.0-4.8%). OPLL had a prevalence of 0% (95% CI 0.0-2.7%). Non-lordotic cervical alignment in our cohort was found to have a prevalence of 30.1% (95% CI 22.3-37.9%). Comparison to the asymptomatic cohort revealed the local cohort to have greater prevalence of single-level disc pathology. Comparison to the symptomatic cohort revealed a significant increased prevalence in multilevel disc pathology, OPLL and ELF in symptomatic patients compared to our cohort, while our cohort at a greater prevalence of single-level disc pathology. Given the high baseline prevalence of multilevel disc pathology, however, this is most striking for OPLL and ELF. Conclusion: OPLL and ELF are rare in asymptomatic populations. Their further targeted investigation may have relevance to exploring the natural history of DCM, a global research priority.

1577

P181: Respiratory dysfunction in degenerative cervical myelopathy: a systematic review

Lorcan Elliott ¹ , Oliver Mowforth ¹ , Aref-Ali Gharooni ¹ , Mark Kotter ¹ , and Benjamin Davies ¹

¹ Neurosurgery, University of Cambridge, United Kingdom

Introduction: Degenerative cervical myelopathy is a condition of symptomatic cervical spinal cord compression secondary to a range of degenerative spinal pathology. Respiratory dysfunction has been described in several cohort studies and shortness of breath is not uncommonly reported by people with DCM. The objective of this systematic review was therefore to synthesise current evidence on the relationship between DCM and respiratory function. Material and Methods: The review was registered on PROSPERO and followed PRISMA guidelines. Ovid MEDLINE, and Embase were searched to 24^th September 2022. DCM studies reporting any respiratory measure, including spirometry and outcomes relating to respiratory disease were eligible. Reference lists were hand searched. Title and abstract and full text screening, risk of bias and GRADE assessments was completed in duplicate. A quantitative synthesis is presented. Results: A total of 517 studies identified by literature searching; 14 met inclusion criteria, including 3 cohort studies, 5 case control studies and 6 case studies. There was conflicting evidence across 2 cohort studies and 5 case/control studies as to whether surgical decompression for DCM was associated with improvements in spirometric measures such as FEV1 and FVC. Similarly, there was inconsistency in differences in FEV1 reported between DCM patients and controls. FVC, vital capacity and peak expiratory flow rate were consistently reported to be lower in patients than controls. Higher spinal compression was associated with more significant respiratory impairments than more caudal lesions. One cohort study reported a higher prevalence of cervical spondylosis in patients with obstructive sleep apnoea. All case reports described respiratory dysfunction in DCM patients, some of which showed improvements following management of ventilation or diaphragmatic function. Conclusion: DCM may be associated with respiratory dysfunction; however the current quality of evidence is poor. Further work should address aetiology, such as disruption to diaphragmatic innervation by cervical spine nerve roots or projections from brainstem respiratory centres.

1685

P182: How do patient comorbidities affect the choice of osteobiologics for anterior cervical discectomy and fusion?

Stipe Corluka ¹ , Michael Collins ² , Aidin Abedi ² , Timothy S. Yoon ³ , Meisel Hans-Jorg ⁴ , Jeffrey C. Wang ² , Zorica Buser ⁵ , and AO Spine Knowledge Forum Degenerative ⁶

¹ Spinal Surgery Division, Traumatology Department, University Hospital Centre Sestre Milosrdnice, Zagreb, Croatia

² Department of Orthopaedic Surgery, University of Southern California, Keck School of Medicine, United States

³ Department of Orthopaedics, Emory University, Atlanta, United States

⁴ Department of Neurosurgery, Bergmannstrost Hospital, Halle, Germany

⁵ Gerling Institute, New York, United States

⁶ AO Foundation, AO Spine, Davos, Switzerland

Introduction: Anterior cervical discectomy and fusion (ACDF) is a well-known, effective, and frequently performed surgical technique in the treatment of cervical spine degenerative conditions. Fusion can be promoted and achieved by several biomaterials with the autologous bone graft (ABG) still being the gold standard because of its osteogenic, osteoinductive and osteoconductive properties. The acute and chronic donor-site complications have been reported as a postoperative complication. Therefore, utilization of allogenic graft materials has gained interest. Although ACDF commonly necessitates short hospital admission and is well-tolerated by most patients, surgical delays, complications, and increased length of stay can be influenced by identifiable risk factors, but long-term impact on fusion rate is not observed. Pseudoarthrosis after ACDF surgery represents a challenging complication and the aim of the current study was to determine the impact of patient comorbidities on choice of osteobiologic use. Material and Methods: This systematic review was designed based on the PRISMA methodology by electronic literature searches on MeSH terms. The search phrases were formulated to capture the studies on ‘anterior cervical spine’ AND ‘decompression/fusion’. To be included in the final review, studies needed assess the factors affecting the choice of osteobiologics in adult patients undergoing a one- to four-level ACDF. Results: Search string resulted in 5012 records which were screened based on title/abstract sections. At the end 68 studies were included for full-text assessment and finally, 0 studies evaluated how patient comorbidities (osteoporosis, smoking, history of RA, history of steroid use, obesity, etc.) affected the choice of osteobiologics used in elective ACDF surgery. Conclusion: Lack of studies meeting the criteria of the review reflect the paucity of the literature on patient comorbidities. This is particularly critical given the increased choice of available osteobiologics and very limited evidence to support their extensive use.

1695

P183: Pretic-I was a safe and effective artificial cervical disc prothesis-a retrospective and comparative study with 5-year follow-up

Chengyi Huang ¹ and Hao Liu ¹

¹ Department of Orthopedics, West China Hospital, Sichuan University, Chengdu, China

Introduction: The newly designed cervical disc prosthesis, Pretic-I, had been finished its limited clinical use for over 5 years. At a short-term follow-up of 2 years, we obtained satisfactory clinical results. The long-term clinical efficacy and safety of Pretic-I will now be analyzed. Material and Methods: Peri-operative parameters included intra-operative blood loss, operation time, of-bed time. Clinical parameters included visual analogue scale (VAS) for arm and neck, neck disability index (NDI), and Japanese Orthopaedic Association (JOA) score. Radiological parameters included C2–7 Cobb angle, Shell angle, and the range of motion (ROM) of C2–7, functional segment unit (FSU), and adjacent FSU. The CDA-related complications included adjacent segment degeneration (ASDeg), adjacent segment disease (ASDis), heterotopic ossifcation (HO), prosthesis subsidence, prosthesis displacement, and dysphagia. Results: A total 64 patients from two independent centers received a single-level CDA with Discover (n = 32) and Pretic-I (n = 32), and all of patients finished a 5-year follow-up. There are no significant differences between two groups in peri-operative parameters. The clinical parameters improved greatly in Pretic-I group (p < 0.0001), and there’s no statistical difference from Discover group. Furthermore, Pretic-I could slightly improve the cervical curvature (15.08 ± 11.75 to 18.00 ± 10.61, p = 0.3079) and perfectly maintain the Shell angle (3.03 ± 3.68 to 2.23 ± 4.10, p = 0.1988), cervical ROM (52.48 ± 14.31 to 53.30 ± 11.71, p = 0.8062) and FSU ROM (12.20 ± 4.52 to 10.73 ± 4.45, p = 0.2002). The incidence of high-grade HO (Grade III-IV) at the fnal follow-up was significantly lower in Pretic-I group than in Discover group (12.50% vs. 34.38%, p = 0.0389, Statistical Power = 95.36%). The incidences of other CDArelated complications in Pretic-I group were also well-accepted, comparable to the Discover group, without significant differences. Conclusion: CDA with Pretic-I demonstrated a well-accepted and sustained clinical outcome, with a significantly lower incidence of high-grade HO. This newly designed prosthesis is expected to become an alternative choice for cervical disc prosthesis in the future.

Keywords: Cervical disc arthroplasty, Pretic-I, Discover, Adjacent segment disease, Heterotopic ossifcation

1721

P184: Acute quadriplegia and death following a routine MRI for undiagnosed degenerative cervical myelopathy

Cylene Yang ¹ , Oliver Mowforth ¹ , Benjamin Davies ¹ , and Rodney Laing ¹

¹ Neurosurgery, Addenbrookes, Cambridge, United Kingdom

Bilateral upper limb paraesthesia and pain are common symptoms of degenerative cervical myelopathy (DCM). Such symptoms instigate investigation by cervical spine magnetic resonance imaging (MRI). This was the case for patient AB, who was an otherwise fit male in his early seventies. During the scan AB unfortunately developed sudden onset quadriplegia secondary to an intervertebral disc prolapse. This necessitated intubation due to respiratory failure and urgent transfer to the neurosciences critical care unit at a tertiary neurosciences centre. Despite prompt surgical decompression, AB did not regain function. Extubation was unsuccessful on three occasions. Following discussion between AB and his family, ventilation was withdrawn, and AB died the following day. This case highlights the potentially devastating consequences of DCM and poses questions about the aetiology of DCM.

1726

P185: 23 hour stay anterior cervical discectomy and intervertebral fusion

Kathryn Kneale ¹ and Timothy Woodacre ¹

¹ Neurosurgery, University Hospitals Plymouth NHS Trust, Plymouth, United Kingdom

Introduction: Anterior cervical discectomy and interbody fusion (ACDF) is a commonly performed operation, with a mean length of stay of two days. There has been a drive to increase Day Case surgery within the NHS to increase efficiency, reduce costs and improve the patient experience. Our Trust introduced a new 23 hour stay pathway for suitable ACDF patients, to be discharged from the Day Case Unit by 9am (thus avoiding impacting the functioning of the Unit), following the successful implementation of a Day Case pathway for lumbar microdiscectomy patients. We modified practice by introducing specific patient selection criteria, educating patients preoperatively, changing operative scheduling and standardising the postoperative management including analgesia. We aimed to ascertain if this was a feasible pathway, if patients were satisfied with their experience and how we could improve it. We also wanted to see what is required to move to same day ACDF surgery. Material and Methods: All patients who had undergone ACDF on this pathway under a single surgeon cohort were identified and demographics and operation details recorded. They were contacted to complete a telephone survey about their experience, including the quality/quantity of information given pre and postoperatively, adequacy of analgesia on discharge, and their overall experience. Results were analysed. Results: A total of 17 patients underwent ACDF on this pathway between July 2021 to September 2022. Of these, 13 were contactable, and completed the survey. There were eight males and five females. The average age was 48 years (39-64 years). All patients rated it as a positive experience, with six (46%) rating it very good, and the remaining seven (54%) good. Three patients (25%) felt there was a lack of information on the postoperative course/poor communication postoperatively, and two patients (15%) reported inadequate analgesia. There were two complications with one patient requiring a washout at two weeks and another patient who represented with neck swelling which resolved spontaneously. Conclusion: Overall patients in this small cohort reported a positive experience. This suggests it is feasible to adopt this pathway for suitable patients, and we encourage other surgeons in the Trust to use it. Ways of improving it would be to do a more detailed patient information leaflet on the postoperative course, and an educational video for those who cannot read well. Limitations of this study are a small sample size and recall bias when answering questions. We plan to develop this to offer same day ACDF surgery to selected patients.

1847

P186: Cage subsidence prevalence between different cervical self-locking cages and it´s impact in cervical lordosis and clinical outcomes in a cohort of 111 patients after anterior cervical discectomy and fusion for cervical degenerative disease in two hospitals of mexico city: a multicenter comparative study

Anabel Euán Gutiérrez ¹ , Alejandro Reyes-Sánchez ¹ , Juan Nicasio Arriada Mendicoa ² , Serio Ramirez Aragon ² , Luis Miguel Rosales Olivarez ¹ , Armando Alpizar Aguirre ¹ , Baron Zarate Kalfopulos ¹ , and Carla García-Ramos ¹

¹ Spine Surgery, Instituto Nacional de Rehabilitacion, Spine Surgery, Mexico City, Mexico, Spine Surgery, Instituto Nacional de Neurologia Y Neurocirugia, Mexico City, Mexico

Introduction: To assess the rate of subsidence, it's relation with cervical lordosis and clinical outcomes, in postoperative patients who underwent multilevel anterior cervical decompression and fusion with the use of different types of self-locking cervical cages, minimum follow-up of 12 months. Material and Methods: Retrospective study. Patients with diagnosis of cervical spinal stenosis, who underwent multilevel anterior cervical discectomy and fusion at the National Institute of Rehabilitation “Luis Guillermo Ibarra Ibarra” and National Institute of Neurology and Neurosurgery “Manuel Velasco Suarez” in Mexico City. Clinical outcome was assessed using the Visual Analogue Scale (VAS), Neck Disability Index (NDI), modified Japanese Orthopaedic Association (JOAm), Nurick scale and SF-36 scale. The radiographic evaluation included cervical lordosis, disc height and self-locking cervical cage subsidence. Descriptive statistics were carried out for quantitative variables through measurements of central tendency and dispersion, the Cohen's kappa coefficient was used to measure the Interobserver variation of 0.84. Results: Records of 111 patients (70 females and 41 males), average age of 62 years old. A total of 239 intervened levels, the most frequent intervened level was C5 -C6. After 12 months of follow-up, the mean IDC, JOA, EVA, SF-36 (PCS, MCS) and Nurick improved (p = 0.000). The radiographic follow-up after12 months showed an improvement in cervical lordosis as well as in disc height (p = 0.000). A correlation of r = 0.169 (p = 0.076) was obtained between the number of intervened levels and subsidence at 12 months of follow-up, the height of the self-locking cervical cage was associated with subsidence with a value of r = 0.228 (p = 0.0001) and the subsidence was negatively associated with the number of screws per level r = -0.346 (p = 0.0001). Conclusion: An improvement was showed in clinical scales as well as an improvement in postoperative lordosis and disc height. The subsidence was associated with the self- locking cervical cage height and a poor relation with the subsidence and the type of self-locking cervical cage and intervened levels was found, therefore more research is needed in order to find the best characteristics for the ideal implant. Even though our patients presented postoperative subsidence, they showed significant decrease in pain and an improvement in the quality of life.

Degenerative Lumbar

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P187: Pelvic incidence-lumbar lordosis mismatch and early reoperation for adjacent segment disease after lumbar fusion

Manaf Younis ¹ , Ivan Ye ¹ , Alexandra Thomson ¹ , Aneesh Patankar ¹ , Ryan Smith ¹ , Tyler Pease ¹ , Brittany Oster ¹ , Daniel Cavanaugh ¹ , Eugene Koh ¹ , Daniel Gelb ¹ , Steven Ludwig ¹ , and Vache Hambardzumyan ¹

¹ Spine Surgery Division, Orthopaedics, University of Maryland School of Medicine, Baltimore, United States

Introduction: To compare the 2-year reoperation rates for adjacent segment disease between patients with PI-LL mismatch postoperatively to patients with normal PI-LL measurements. Materials and Methods: Patients undergoing elective 1-to-2 level lumbar fusion for degenerative conditions between 2016-2018 were retrospectively reviewed. Spinopelvic radiographs immediately post-operation were measured and PI-LL mismatch was determined using the age adjusted thresholds defined in Lafage et al. Following propensity score matching, early reoperation rates were compared between the PI-LL mismatch and normal PI-LL cohorts. Early reoperation was defined as symptomatic adjacent segment disease (ASD) requiring reoperation within 2 years of the index surgery. Results: A total of 219 patients were identified. The average age was 59 years old with 59.8% female. The PI-LL mismatch cohort (N = 148) were younger (57.5 vs. 63.5, p < 0.001) and had a higher proportion of black patients (31.8% vs. 11.3%, p = 0.001) compared to the normal PI-LL cohort. A total of 100 patients in the PI-LL mismatch cohort were propensity score matched to 66 patients in the normal PI-LL cohort, resulting in no difference in age (p = 0.177), sex (p = 0.302), race (p = 0.727), or BMI (p = 0.892). Using these matched cohorts, the rate of early reoperation for ASD was 8.0 % in the PI-LL mismatch cohort and 9.1% in the normal PI-LL cohort (p = 0.805) with a mean time to reoperation of 1.28 and 1.33 years, respectively. Conclusions: After propensity score matching, PI-LL mismatch was not associated with early reoperation for ASD in patients undergoing 1-to-2 level lumbar fusions for degenerative conditions.

152

P188: The role of machine learning in surgical decision making for lumbar disc herniation

Devender Singh ¹ , Eeric Truumees ¹ , Jeremiah Alexander ² , Calvin Chandler ² , Ashley Duncan ¹ , Matthew Geck ¹ , and John Stokes ¹

¹ Spine, Ascension Texas Spine and Scoliosis, Austin, United States

² Orthopedics, The University of Texas at Austin, Austin, United States

Introduction: Current care pathways recommend exhausting all non-operative measures for at least six weeks in patients presenting with uncomplicated lumbar disc herniation. Intent to treat analyses suggest that overtime, the advantages of surgical intervention decline relative to non-operative care, further complicating surgical decision making. Aim: Using machine learning identify factors associated with the likelihood of a patient will choose surgical intervention for lumbar disc herniation. Materials and Methods: 300 retrospective chart reviews were conducted on patients who presented from January 2019 to January 2021 with lumbar disc herniation. 27 independent variables were collected across various domains including demographic, medical history, clinical presentation, patient-reported outcomes, and encoded using one-hot encoding techniques. The encoded data was analyzed and subject to logistic regression using SKLean, StatsModel and Logit models, with a focus on the recall metric. By focusing on recall, we aim to reduce the number of false positives, or Type II errors in the model. Models were further optimized by assessing multicollinearity of independent variables and employing Area Under the Curve/Receiver Operating Characteristic (AUC-ROC) and Precision-Recall techniques. Results: Overall surgical rate was 25.3%, with median time to surgery eight weeks from intake appointment. Demographic factors did not have a statistical impact on surgical intervention, although men chose surgery at a higher rate than women (29% vs 21.2%) Comorbidities and clinical presentation were not found to have an effect on odds of surgical intervention. The median patient reported back/leg pain and disability scores were higher in patients that did have surgery (38 vs 34 and 7 vs 6, respectively), but this was not statistically significant. The final optimized model yielded a test recall of 0.4. In the end, only three variables were found to impact the odds of surgical intervention. Patients who received a prescription for non-narcotic medication and had at least one epidural injection, increased the odds of surgical intervention by 3.4 and 2.6, respectively. Prescribing opioids decreased odds of surgical intervention by 0.37. Conclusion: Non-narcotic medication and injections increased the odds of later surgical intervention. Given the current standard of care, this is not surprising as one should exhaust all non-operative measures before culminating in surgical intervention. Prescribing opioid medications during this minimal six-week time frame lowered the odds of surgical intervention. This could be due to the fact that opioids were prescribed to patients that had comorbidities or other factors that do not lend themselves to the preferred physical rehabilitation plan of care. These patients would already be unlikely surgical candidates due to increased risk associated with medical comorbidities. Limitations include variability between physicians’ practice and sample size. A larger, prospective study would be the next step in utilizing machine learning to predict which patients are most likely to report satisfaction and a successful outcome.

178

P189: Perioperative and radiographic outcomes between single position surgery (lateral decubitus) and dual position surgery for lateral lumbar interbody fusion and percutaneous pedicle screw fixation: meta-analysis

Gun Keorochana ¹ and Jatupon Kongtharvonskul ²

¹ Orthopedics Department

² Department of Clinical Epidemiology and Biostatistics, Faculty of Medicine Ramathibodi Hospital, Bangkok, Thailand

Introduction: Lateral Lumbar Interbody Fusion (LLIF) and percutaneous posterior screw fixation (PPSF) techniques is used to treat degenerative lumbar pathologies. Dual position (DP) lumbar surgery involves repositioning the patient from the supine or lateral decubitus position to prone for posterior fixation. Single-position (SP) lumbar surgery (LS) is commonly performed nowadays, minimally invasive alternative performed entirely from the lateral decubitus position. However, there is still controversial. This meta-analysis aimed to compare peri-operative outcomes between SPLS and DPLS for LLIF and PPSF. Material and Methods: We conducted this meta-analysis according to the PRISMA guidelines and searched Medline and Scopus from inception to November 11, 2021 for relevant studies. Results: Six studies were identified, which contained totals of 502 and 447 patients in the SP and DP groups, respectively. The unstandardized mean difference in operative time, length of hospital stay, intraoperative blood loss, radiation doses, lumbar lordosis, and PI-LL mismatch were -86.1 (95%CI: -149.2 to -23.1) minutes, -1.6 (95%CI: -2.4 to -0.9) days, -55.6 (95%CI: -127.5 to 16.2) ml, -30.3 (95%CI: -80.5 to 19.8) mGy, 1.34 (95%CI: -1.17 to 3.86) degree, and -4.06 (95%CI: -5.65 to -2.47) lower in SP when compared to DP. The chances of having complications and reoperations in SP were 0.75 (95%CI: 0.49 to 1.14) and 0.77 (95%CI: 0.44 to 1.36) times, respectively, compared to DP group. No significant differences were found for intraoperative blood loss, radiation dose, lumbar lordosis, complications and re-operations between two groups. Conclusions: This meta-analysis found that SP have lower operative time and length of hospital stay compared to DP LLIF and PPSF. However, no differences in intraoperative blood loss, radiation dose, radiographic change, complications, and re-operation rates were found.

184

P190: Intravenous corticosteroid therapy for acute lumbar radicular pain

Oded Hershkovich ¹ and Raphael Lotan ¹

¹ Edith Wolfson Medical Center, Holon, Israel

Introduction: The efficacy of pharmacological interventions for acute lumbar radicular pain (ALRP) is limited, and systemic steroid use remains controversial. We evaluated the effectiveness and tolerance of systemic steroid use in a cohort of patients with ALRP. Methods: A retrospective cohort of 56 patients (24 females) admitted with intractable ALRP resistance to conservative treatment of NSAIDs and opiates between the years 2016-2018. Medical records were studied for demographics, physical examination findings, Visual Analogue Score (VAS), IV steroids side effects, and recent imaging findings. All patients received a daily dose of IV 24 mg Dexamethasone until discharge, SNRB or Surgery. Results: The average IV Steroid treatment was 3.9 (± 2.8) days, with most patients showing significant pain relief to allow discharge (69.7%). SNRB was required in 19.6% and surgical intervention in 10.7% within the same admission. Multivariate analysis did not find any parameter to predict treatment failure (Age, gender, motor/sensory deficit, CT/MRI findings). The motor deficit, positive Straight leg raising (SLR) and dural sac compression on CT were higher in the intervention group but did not reach statistical significance. One patient required discontinuation of IV steroids due to elevated blood pressure. Conclusion: Despite the insufficient evidence in the literature, IV steroid treatment is still a viable option in ALRP treatment, with pain relief allowing discharge in 70% of patients and a low complication rate. Our study found daily 24mg IV dexamethasone for ALRP to be an effective treatment and helpful in most patients admitted. This study supports the common practice used by spine units.

Keywords: Sciatica; Radiculopathy; Herniated disc; Steroid treatment; Pharmacotherapy

Synonyms: ALRP = Acute lumbar radicular pain, SNRB = Selective nerve root block, SLR = Straight leg raising

194

P191: Is stabilisation of contralateral side necessary while using unilateral approach in lumbar fusion surgery at 2 adjacent levels?

Sathish Muthu ^1,2 and Girinivasan Chellamuthu ²

¹ Department of Orthopaedics, Government Medical College, Dindigul, India

² Department of Spine Surgery, Orthopaedic Research Group, Coimbatore, India

Introduction: Generally, fusion supplemented with bilateral pedicle screw fixation is the widely accepted method of stabilisation to create an ideal environment for fusion of the unstable and the degenerated disc area. Rigid internal fixation by bilateral pedicle screw fixation has its shortcomings in the form of adjacent lumbar segment degeneration and implant-related osteoporosis. Moreover, bilateral fixation was associated with longer surgical time, greater blood loss and involving greater costs. A relatively less rigid fixation in the form of unilateral pedicle screw fixation could reduce the stress shielding and adjacent intervertebral disc degeneration caused by bilateral pedicle screw fixation. Biomechanical studies supported his concept stating that unilateral pedicle screw fixation was sufficient to maintain the stability of the spine. We performed this meta-analysis to compare the safety of unilateral with bilateral instrumented fusion in two-level degenerative disorders of lumbar spine. Materials and Methods: We conducted independent and duplicate electronic database search including PubMed, Embase and Cochrane Library till January 2020 for Randomised Controlled Trials(RCTs) comparing unilateral pedicle screw fixation with bilateral pedicle screw fixation for multi-level lumbar degenerative disorders. Fusion and complication rates were the primary outcomes analysed. Analysis was performed in R platform using OpenMeta[Analyst] software. Results: 5 RCTs including 215 patients (Unilateral/Bilateral = 106/109) were included in meta-analysis. There was no significant difference between the two groups regarding fusion rate, complication rate, blood loss, duration of hospital stay, functional outcome scores like Visual Analog Scale (VAS), Oswestry Disability Index (ODI) and Short-Form health survey (SF-36) at final follow-up. Unilateral pedicle screw fixation was associated with a significant reduction in operation time (p < 0.001). Compared to open approach, minimally invasive approach showed significant difference in terms of factors like operative time, blood loss, hospital stay, VAS and ODI (p = 0.004). Conclusion: Our meta-analysis establishes the immediate safety and significant lesser operative period of unilateral pedicle screw fixation in lumbar fusion. However, due to lack of evidence on complications like cage subsidence and adjacent segment disease, unilateral pedicle screw fixation cannot be recommended as an alternative to bilateral pedicle screw fixation for two-level degenerative spinal disease. Our analysis established the lacunae in literature for high-quality evidence on the subject hence we recommend further large multicentre studies with longer follow-up to arrive at a conclusion.

246

P192: Management of discal cyst: case report and narrative review

Pedro Torres ¹ , Andre Castilho ¹ , Rodrigo Cruzeiro ¹ , and Henrique Darmstadter ¹

¹ Spine Surgery, Hospital Unimed, Brazil

Introduction: Lumbar discal cyst (LDC) is a rare clinical entity with unclear etiology. First described by Chiba et al. in 2001, is believed to be originated from the disc material and as a result of previous disc injury. LDC is defined as an intraspinal extradural cyst with distinct communication with the corresponding intervertebral disc. Clinical history is similar to patients with disc herniation, manifesting as a unilateral single nerve root lesion with neurologic deficits corresponding to the involved nerve root. Discal cyst is one of the different types of cysts that can exist extradurally in the lumbar spine, specifically in the spinal canal and neuroforamen. Imaging nuances such as the location of the cyst, bony changes on CT, contrast filling with discography or myelography, and MRI characteristics can be useful to differentiate between different types of cysts. LDC is almost always located behind the posterior vertebral body, which is also a typical location for herniated discs. On MRI, LDC appears as hypointense on T1-weighted image and hyperintense on T2-weighted image and enhances homogenously after gadolinium. There are no guidelines regarding the best treatment option for LDC. Therefore, we present a case of LDC who underwent surgical treatment and try to identify evidence-based treatment strategies for patients diagnosed with discal cyst. Material and Methods: We report a case of a 21-year-old man with radiculopathy of L5 root in the left side. The MRI showed a left-sided extradural cyst at the level of L4/5. The cyst was hypointense and hyperintense on T1- and T2-weighted images, respectively. After 4 weeks of conservative treatment without good outcomes, the patient underwent microscopic surgery. The literature listed in MEDLINE/PubMed was reviewed to identify related articles using the terms “Disc cyst AND treatment NOT disc herniation”. We also made a manual search, and 15 papers were included in this review. Results: At the first appointment the VAS was 9 and the L5 motor grade was 5. The patient was submitted initially to conservative treatment with physical therapy and analgesic drugs. After 04 weeks of treatment the pain increased (VAS 10), ODI was 40% and L5 motor grade was 3. During surgery, the cist capsule was at intimate contact with the L5 root and with a hemorrhagic content. After surgery, patient sciatica had a great reduction (VAS 3). After 6 months of surgery the ODI score was 0% and the motor grade of strength was 5. The histopathologic analysis described simple fibrous tissue corresponding to capsule. No atypia was found. Conclusion: Despite numerous reports, the explicit pathophysiology of intraspinal discal cysts remains obscure. MRI is both noninvasive and sensitive in diagnosing discal cysts and identifying surrounding structures. For patients with mild to moderate symptoms, conservative treatment can be successful, even inducing spontaneous regression. Low grade evidence suggest that surgical treatment is the best option for discal cysts. Excision of the cyst alone without excision of the corresponding intervertebral disc could be considered as an option for surgical treatment. Endoscopic surgery could also be a safe and promising treatment.

268

P193: Stand-alone lateral lumbar interbody fusion (LLIF) in patients with aborted second-stage procedures: a case series

Benjamin Catoe ^1,2 , David Barnes ³ , Cameron Kersey ² , Sohrab Vatsia ² , L. Erik Westerlund ² , and Douglas Pahl ²

¹ Orthopedic Surgery Residency Program, Jack Hughston Memorial Hospital Phenix City, AL, United States

² Hughston Clinic, Columbus, GA, United States ³ St. George Orthopedic Spine, St. George, UT, United States

Introduction: Lateral lumbar interbody fusion (LLIF), has gained significant popularity over the last decade. LLIF is typically supplemented with posterior or lateral fixation and decompression when necessary. We hereby report a case series of patients who underwent stand-alone LLIF as part of the first of a two-stage procedure whose second stage was subsequently aborted due to risks of anesthesia or patient preference. Material and Methods: Patients who had an aborted second stage with a resulting stand-alone LLIF between 2014-2020 at our institution were retrospectively identified. Chart and radiograph review were utilized to evaluate for evidence of fusion, implant migration, implant subsidence, minor and major complications, revisions, and symptom resolution. Oswestry Disability Index (ODI) and Visual Analog Score (VAS) were assessed at the initial and one-year interval follow-up visits postoperatively. Results: Seventeen cases, involving 31 levels, were identified with at least 12 months of follow up. At final follow up, 28 levels (90.3%) have shown radiographic evidence of fusion with evidence of cage migration in one case (3.2%). The average disc height increased by 25.6%. Twenty-four levels (77.4%) demonstrated Grade 0 (0-24%) subsidence and four levels (12.9%) had Grade I (25-49%) subsidence. There were no revisions, no major complications, and no additional procedures were recommended. Pre- and post-operative VAS and ODI were 6.4/3.5 (p < 0.0001) and 39.9/24.8 (p < 0.032). Conclusion: Stand-alone LLIF is a viable option in patients with refractory back and leg pain due to a lumbar spine condition and should be considered for patients with significant risk factors to decrease anesthetic time and perioperative complications.

315

P194: Analysis of risk factors for early adjacent segment disease who underwent revision surgery within 5 years after lumbar spinal fusion

Jaewan Soh ¹

¹ Orthopaedic Surgery, Sahmyook Seoul Medical Center, Seoul, South Korea

Introduction: There are many concerns about adjacent segment disease after lumbar spinal fusion. Of them, we analyze the risk factors about early adjacent segment disease (EASD) in patients who underwent revision surgery within 5 years from first operation. Material and Methods: 657 patients underwent lumbar spinal fusion of 3 and less segment to treat degenerative lumbar disease. Among them, 137 patients underwent revision surgery within 5 years due to adjacent segment disease or previously followed more than 5 years were included in this study. Gender, age, fusion method, preoperative diagnosis, number of fusion segments and radiological measurements were analyzed. In radiological measurement, pre-& post-operative lumbar lordotic angle (LLA), pre-& post-operative fusion segment lordotic angle (FSLA), pre-& post-operative FSLA per level, correction of LLA, correction of FSLA, and correction of FSLA per level were estimated. Statistical univariate analysis was performed with the Chi-square test and multivariate logistic regression analysis was done by using SPSS 14.0. Results: There were 13 patients with revision surgery due to EASD. In univatiate analysis, the frequency of EASD was significantly high in cases where PLIF was more than PLF (p = 0.023), correction of LLA was > 15° (p = 0.021) and correction of FSLA per level was > 5° (p = 0.049). In multivariate logistic regression analysis, the frequency of ESAD was significantly high in case where PLIF was more than PLF (odd ratio = 17.866) and correction of LLA was > 15° (odd ratio = 19.282). Conclusion: There was no statistical significance between EASD and all other factors except fusion method and correction of LLA. PLIF and correction of LLA more than 15 degree increased risk of EASD.

319

P195: The impact of coccgectomy in chronic coccygodynia cases on sexual and social function, in females

Albert Gellert ¹ , Leah Carreon ¹ , Mikkel Østerheden Andersen ¹ , and Ane Simony ¹

¹ Center for Spine Surgery & Research, Middelfart Hospital, Middelfart, Denmark

Objective: To investigate the effect of coccygectomy on sexual and social function in female patients with persistent coccydynia. Design: Retrospective longitudinal cohort study. Setting: Single-center secondary care in the region of southern Denmark. Participants: 91 female patients from the Dane Spine Database with persistent coccydynia who had coccygectomy between 2011 and 2022 and had pre-op, one- and two-year post-operative Oswestry Disability Index (ODI) available. A majority of patients presented with pain during coitus, which has not previously been examined. Main outcome measure: ODI item 8 (ODI8) regarding Sex Life, and item 9 (ODI9) regarding Social Function. Methods: A total of 91 patients were included in this study, all had coccygectomy performed by a single surgeon due to persistent pain, and had prior to surgery a history of 12 months conservative treatment including repeated steroid blocks. All patients had pre op and post op ODI available in the Danespine database. Results: All patients were female (91) with a mean age of 40.4 years. A significant improvement (< 0.001) in their ODI8 one-year after surgery was seen from pre-op of 2.01 ± 1.3 to 0.85 ± 1.3 after one year. The ODI9 score for social function also showed a significant improvement from 2.12 ± 1.0 preoperative to 0.99 ± 1.2 postoperative (< 0.001). No significant change in ODI8 or ODI9 was observed between one and two years after surgery. Conclusion: In female patients with persistent coccydynia and impaired sexual function, coccygectomy improves their sexual function. An improvement of social function is also observed.

426

P196: An analysis of out of hours referrals for cauda equina syndrome in Ireland: emergency physicians versus surgeons

Michael Kelly ¹ , Nic Christodoulou ¹ , Iain Feeley ² , and Marcus TImlin ¹

¹ National Spinal Injuries Unit, Mater Misericordiae University Hospital, Dublin, Ireland

² Trauma & Orthopaedic Surgery, Tullamore University Hospital, Tullamore, Ireland

Introduction: Cauda equina syndrome (CES) is an orthopaedic and neurosurgical emergency that warrants emergent evaluation and treatment. In Ireland out of hours MRI of the lumbosacral spine is performed in the national spine injuries unit in the Mater hospital, Dublin. This represents a significant clincal and logistical challenge. Patients from the institutions emergency department are referred directly for MRI by emergency physicians whilst external referrals are assessed by orthopaedic surgical teams and referred accordingly for radiogicical investigation for suspected CES. Methods: A prospective database was collated of all referrals to our radiology department for out of hours MRI over a period for January to July 2022. Out of hours was defined as all hours outside of 0900-1700 Monday to Friday. The clinical outcome – surgery or no surgery, was recorded as well as time of surgery. Results: 112 patients underwent out of hours MRI. 32% were external referrals. 14% of patients required surgical management for CES. Internal emergency department referrals were as likely to require surgical management as those assessed by surgical teams prior to MRI (external referrals). 44% of surgically managed patients underwent out of hours surgery. Conclusions: Out of hours MRI represents a significant challenge for resource management. 86% of patients undergoing emergent out of hours MRI did not require surgery. Specialist referrals can be avoided by direct referral from appropriately trained emergency physicians for MRI. This is particularly relevant for health care systems where inter hospital transfer is required for specialist assessment or for radiological investigation.

438

P197: Radiographic robustness of lumbar interbody fusion techniques

Alice Bouchard ¹ , Jeffrey Mun ¹ , Frank Vazquez ¹ , Alex Tang ² , Edward DelSole ³ , Russell Strom ⁴ , and Tan Chen ³

¹ Geisinger Commonwealth School of Medicine, Scranton, United States

² Orthopaedic Surgery, Geisinger, Northeast Residency, Wilkes-Barre, United States

³ Orthopaedic Surgery

⁴ Neurosurgery, Geisinger Medical Center, Danville, United States

Introduction: Lumbar interbody fusion (LIF) can be achieved with various techniques, each with its own advantages and disadvantages. Differences in long-term radiographic outcomes remain unclear. The purpose of this study was to (1) evaluate the changes in sagittal parameters in the preoperative, immediate post-operative, and latest follow-up phase, and (2) to evaluate the radiographic maintenance of these parameters over time. Material and Methods: Patients who had undergone single level anterior (ALIF), lateral (LLIF), posterior (PLIF), or transforaminal (TLIF) lumbar interbody fusion in an integrated health system from 2007 to 2022 were identified. Orthopaedic spine and neurosurgical patients were included. Exclusion criteria included a non-degenerative diagnosis, inadequate radiographs, multilevel and revision surgery, and postoperative follow-up less than one month. Retrospective chart review was conducted to collect patient demographics and diagnosis at time of surgery. Upright lumbar radiographs taken prior to surgery, at the time of surgery, and at most recent follow-up were analyzed. Each radiograph was measured for pelvic incidence (PI), lumbar lordosis (LL), segmental lordosis (SL), posterior disc height (PDH), and foraminal height (FH). Results: A total of 158 patients met inclusion criteria. There were 24 ALIFs (follow-up = 27.2 mon), 14 LLIFs (follow-up = 14.0 mon), 74 TLIFs (follow-up = 12.8 mon) and 46 PLIFs (follow-up = 26.4 mon). Differences were found in patient age, gender, and BMI between cohorts. PDH and FH spinal parameters increased immediately following ALIF (ΔPDH = +5.3 mm ΔFH = +3.7 mm p < 0.0001), LLIF (ΔPDH = +4.1 mm ΔFH = +4.2 mm p < 0.01), TLIF (ΔPDH = +3.5 mm ΔFH = +3.6 mm p < 0.001), and PLIF (ΔPDH = +4.7 mm ΔFH = +4.2 mm p < 0.0001). SL changed immediately only for ALIF (ΔSL = +5.7deg, p = 0.002) and LLIF (ΔSL = +4.4deg, p = 0.0002). Compared to the immediate post-operative phase, PDH and FH decreased at latest follow-up for ALIF (ΔPDH = -1.9 mm p = 0.005, ΔFH = -1.2 mm p = 0.16), LLIF (ΔPDH = -0.9 mm ΔFH = -1.9 mm p < 0.05), TLIF (ΔPDH = -1.1 mm ΔFH = -2.3 mm p < 0.001), and PLIF (ΔPDH = -1.0 mm ΔFH = -1.8 mm p < 0.01). SL decreased for ALIF (ΔSL = -5.4deg, p = 0.0005), LLIF (ΔSL = -0.8deg, p = 0.34), TLIF (ΔSL = -1.1deg, p = 0.04), and PLIF (ΔSL = -1.5deg, p = 0.07). LL did not change at any time point postoperatively across techniques. Accounting for interobserver reliability, no significant differences in the change in radiographic parameters was noted across all techniques at final follow up (p > 0.05). Conclusion: Lumbar interbody fusion, regardless of technique, was shown to provide significant radiographic changes in posterior disc height and foraminal height. Techniques utilizing larger intervertebral cage sizes (ALIF and LLIF) improved segmental lordosis. Single level LIF did not affect overall lumbar lordosis. Over time, all LIF techniques demonstrated a degree of loss of correction and radiographic settling. No LIF technique demonstrated superior radiographic robustness over time. A limitation of this study was that ALIF and LLIF were not subdivided into standalone LIF versus LIF supplemented with posterior instrumentation. Further studies are warranted to study the relationship of these parameters to the degree of indirect decompression, as well as its relationship to clinical outcomes.

513

P198: Preliminary results of our first 10 cases of ALIF in degenerative disc disease - A prospective unicenter study

Filipa Adan e Silva ¹ , Diogo Rocha Carvalho ¹ , João Francisco Lemos ¹ , Bianca Sousa Barros ¹ , Pedro Neves ² , Arnaldo Sousa ¹ , and Paulo Costa ¹

¹ Centro Hospitalar Universitário do Porto, Portugal

² Hôpital Privé Arnault Tzanck, Mougins-Sophia Antipolis, France

Introduction: Lumbar degenerative pathology is an increasing health problem with a widely prevalence among the elderly population. In many cases it fails to respond to conservative treatment, therefore surgical procedures must be taken in account. Anterior Lumbar Interbody Fusion (ALIF) is a well-established procedure to be considered for the lower lumbar levels. From a vast number of degenerative diseases that can be addressed by this surgical technique, this study focuses on single-level Degenerative Disc Disease (DDD) with lower back pain as the major indication. The aim is to assess the clinical and radiological efficacy of ALIF and its complications. Material and Methods: This is a prospective study involving the first 10 patients who underwent ALIF performed by the same surgeon in one institution, in a period from July 2019 and March 2022 for L5-S1 DDD. The minimum follow up time was 6 months. Time of symptoms’ duration before surgery, operative time, intraoperative blood loss, length of hospital stay and complications were determined. Clinical results were assessed by preoperative and postoperative (2 weeks, 3 months, 6 months and 1 year) Visual Analog Scale (VAS) leg and back pain and Oswestry Disability Index (ODI) of all the patients. Disc Height Index (DHI), Segmental Lordosis Angle (SLA) and Lumbar Lordosis Angle (LLA) were obtained on preoperative and postoperative (2 weeks, 3 months, 6 months and 1 year) plain radiographs. Results: A total of 10 patients (3 men and 7 women) were included in this study with a mean age of 48 years (BMI from 25 to 28 kg/m²). The duration of symptoms range from 1 to 10 years (mean 51 months). The mean operative time was 140 minutes (115-160 minutes), most cases with negligible intraoperative blood losses (maximum of 300mL). The average length of hospital stay was 3 days. No early or late complications were observed and there was no need of reintervention in any patient. There was a significative improvement (p < 0.01) in VAS leg and back pain (from a mean of 9 preoperative to a mean of 3 at 6 months postoperative) and ODI (from 31 to 7 in the same period). In terms of radiological measurements, it was observed an improvement in all the variables (DHI from 0,226 to 0,369; SLA from 19,6º to 25,5º; LLA from 53,5º to 61º). Maximum upgrading was registered in the first 2 weeks postoperative, maintaining this significant improvement 6 months after surgery. Conclusion: Regarding the results of this preliminary study, ALIF seems to be a surgical technique with excellent clinical and imaging results, in selected patients, with isolated DDD at the L5-S1 level and pain that is refractory to conservative treatment. It also seems to be a procedure associated with low risk (not only of iatrogenic injury but also of complications associated with the need for reintervention) mild postoperative pain, reduced hospital stay and rapid recovery.

543

P199: Decompression with fusion versus decompression alone in patients with degenerative spondylolisthesis. A systematic review and meta-analysis

Pravesh Gadjradj ¹ , Fabian Sommer ¹ , Jake Goldberg ¹ , and Roger Hartl ¹

¹ Neurological Surgery, Weill Cornell, New York, United States

Introduction: Surgical decompression is standard care in the treatment of degenerative spondylolisthesis in patients with symptomatic stenosis, but there remains controversy over the benefits of adding fusion. The persistent lack of consensus on this matter and the availability of new data warrants a contemporary systematic review and meta-analysis of the literature. Material and Methods: Multiple online databases were systematically searched up to August 2022 for randomized controlled trials (RCTs) and prospective studies comparing outcomes of decompression alone versus decompression with fusion for lumbar spinal stenosis in patients with degenerative spondylolisthesis. Primary outcome was the Oswestry Disability Index (ODI). Secondary outcomes included leg and back pain, surgical outcomes, and radiological outcomes. Pooled effect estimates were calculated and presented as standard mean differences (SMD) with their 95% confidence intervals (CI) at two-year follow-up. Results: Of the identified 2403 studies, eventually five RCTs and two prospective studies were included. Overall, most studies had a low or unclear risk of selection bias and most studies were focused on low grade degenerative spondylolisthesis. All patient-reported outcomes showed low statistical heterogeneity. Overall, there was high quality evidence suggesting no difference in functionality at two years of follow-up (SMD -0.02, 95% CI -0.22 to 0.18). Furthermore, there was high quality evidence of no difference in leg pain (SMD -0.11, 95% CI -0.30 to 0.07) or back pain (SMD -0.11, 95% CI -0.30 to 0.07) between patients undergoing decompression vs. decompression with fusion. Pooled surgical outcomes showed less blood loss after decompression only, and similar length of hospital stay and reoperations compared to decompression with fusion. Conclusion: Based on the current literature, there is high quality evidence of no difference in functionality after decompression alone compared to decompression with fusion in patients with degenerative lumbar spondylolisthesis at 2 years of follow-up. Further studies should focus on long-term comparative outcomes, health economic evaluations, and identifying those patients that may benefit more from decompression with fusion instead of decompression alone.

This review was registered at Prospero (CRD42021291603).

577

P200: Risk factors for ambulatory surgery conversion to extended stay among patients undergoing posterior lumbar decompression

Yusuke Dodo ^1,2 , Ichiro Okano ² , Neil Kelly ³ , Leonardo Sanchez ³ , Haffer Henryk ¹ , Maximilian Muellner ¹ , Erika Chiapparelli ¹ , Lisa Oezel ¹ , Jennifer Shue ¹ , Darren Lebl ¹ , Frank Cammisa ¹ , Federico Girardi ¹ , Alexander Hughes ¹ , Gbolabo Sokunbi ¹ , and Andrew Sama ¹

¹ Spine Care Institute, Hospital for Special Surgery, New York, United States

² Department of Orthopaedic Surgery, Showa University Hospital, Shinagawa, Japan

³ Weill Cornell Medicine, New York, United States

Introduction: Ambulatory surgery (AMS) is becoming increasingly common in the U.S. because it is associated with a similar or even higher quality of care compared to inpatient surgery, significant cost reduction, and patients’ desire to recuperate at home. However, there are instances when AMS patients may be subjected to extended hospital stays. Unanticipated extension of hospitalization stays can be a great burden not only to patients, but to medical providers and insurance companies alike. Our study aimed to investigate the factors associated with the conversion of patient status from AMS to observation service (OS) (fewer than 48 hours) or Inpatient (greater than 48 hours). Material and Methods: One thousand and ninety-six patients underwent one- or two-level lumbar decompression AMS at a single orthopedic specialized hospital between January 1, 2019 to March 16, 2020 were retrospectively reviewed. Patients were categorized in three groups based on length of stay: 1) AMS, 2) OS, or 3) Inpatient. Demographics, comorbidities, surgical information, and administrative information such as operation start time were collected. Simple and multivariable logistic regression analyses were conducted comparing AMS patients and OS/Inpatient as well as OS and Inpatients. Results: Of the 1,096 patients, 641 (58%) patients were converted to either OS (n = 486; 44%) or Inpatient (n = 155; 14%) status. The multivariable analysis demonstrated that age (> 80 years old), high ASA grade, history of sleep apnea, drain use, high estimated blood loss, long operation, a high pain score in the acute care unit, late operation start time, drain use, and laminectomy for spinal stenosis were considered independent risk factors for AMS conversion to OS/Inpatient status. The risk factors for OS conversion to Inpatient were an ASA Class 3 or higher, CAD, DM, hypothyroidism, steroid use, dural tear, drain use, and laminectomy for spinal stenosis. Conclusion: Several surgical factors along with patient specific factors were significantly associated with AMS conversion. Addressing modifiable surgical factors, such as blood loss, surgery duration time, post-operative pain management, operation start time, and drain use, might reduce the AMS conversion rate and be beneficial to patients and facilities.

581

P201: Management of osteoporotic vertebral fractures adjacent to degenerative lumbar canal stenosis

Ahmed Shawky Abdelgawaad ^1,2 , Hamdan Abdelrahman ^1,2 , Drazen Prsa ¹ , and Ali Ezzati ¹

¹ Spine Center, Helios Klinikum Erfurt, Erfurt, Germany

² Department of Orthopaedics and Trauma, Assiut University Hospitals, Assiut, Egypt

Introduction: Osteoporotic vertebral fractures adjacent or subjacent to degenerative lumbar spinal canal stenosis or spondylolisthesis represents a clinical challenge. Patients commonly present with combined symptoms of low back pain as well as radicular or claudication pain. The main options for treatment include conservative treatment, cement augmentation (kyphoplasty/vertebroplasty), or cement augmentation and decompression fusion surgery. Patients and Methods: Between January 2018 and December 2021, ten patients with acute or subacute osteoporotic vertebral fractures adjacent or subjacent to lumbar spinal canal stenosis or degenerative spondylolisthesis were operated upon in our center. Six patients were operated upon after failure of the conservative treatment: two patients with kyphoplasty and decompression, four patients with interbody fusion surgery and cement-augmentation of the screws. Results: Of total ten patient, 4 women and 2 men were operated upon. The mean age was 79.2 years. Two patients received Kyphoplasty with decompression (mean operative time 75 minutes, mean blood loss 100 ml). Four patients were operated upon with instrumented fusion using cemented screws and interbody cages (mean operative time 150 minutes, mean blood loss 450 ml). No intraoperative complications were detected. The mean VAS of back pain improved from 7.2 ± 2 preoperatively to 2 ± 1.8, VAS for leg pain from 7 ± 1 to 1 ± 1 at the last follow-up. The mean ODI preoperatively was 52.3 that improved to 10.4 postoperatively. Conclusion: Combined kyphoplasty with microsurgical decompression is a valid treatment option for acute or subacute osteoporotic vertebral fractures adjacent to lumbar spinal canal stenosis. In cases with spondylolisthesis, fusion surgery with cement augmentation of the screws is recommended. Both achieved good clinical and radiographic outcomes.

583

P202: Modified pedicle screw insertion technique at the lumbosacral junction

Hamdan Abdelrahman ¹ , Ali Ezzati ¹ , and Ahmed Shawky Abdelgawaad ^1,2

¹ Spine Center, Helios Klinikum Erfurt, Erfurt, Germany

² Orthopaedics and Trauma, Assiut University Hospitals, Egypt

Introduction: Instrumented fusion of or extended to the lumbosacral junction is a common surgical procedure indicated for different pathological conditions affecting the lumbar and lumbo-sacral junction. A high incidence of pseudoarthrosis and screw loosening is well described in this junctional zone. Given the specific anatomical and biomechanical characters of the L5 and S1 pedicles, optimal positioning of pedicle screws is sometimes challenging due to the wide interpedicular distance and the need to medialize the tip of the screw to get optimal projection of the S1 screw. We modified L5 and S1 screw insertion technique to get the optimal trajectory and length of the screw aiming to reduce the incidence of screw loosening. Materials and Methods: In patients indicated for instrumented fusion including L5 and S1, a modified technique was used. After standard posterior approach to the lumbosacral junction, the L5 or S1 entry points were identified. Excessive soft tissue dissection was avoided though doing an extra postero-lateral 1.5 cm skin incision. The site of the incision was usually about 5 cm from the midline and about 3 cm cranial to S1. The paravertebral muscles were bluntly separated to allow for the introduction of the awl and then the cannulated pedicle finder. The pedicle was prepared, then the trocar of the pedicle finder was removed, and a guide wire was inserted. 3D image intensifier scan was then conducted, and the position of the wires was controlled. Once the wires position is accepted, the screw was then inserted over the wire. Results: We operated 450 patients. In 350 cases instrumentation was extended to S1, most of the cases were operated due to degenerative spine diseases. In all cases, bi-cortical purchase was achieved. The mean screw diameter was 7 mm and the length varied between 50 to 60 mm. There were no re-operations due to screw malposition in these patients. Six Patients had wound healing problems; four needed wound revisions. Conclusion: The modified pedicle screw insertion through additional postero-latero-cranial skin incision achieved optimal screw trajectory and longer screws aiming to reduce screw loosening in area with high incidence of pseudoarthrosis. It avoids excessive soft tissue dissection especially in muscular and fatty patients.

626

P203: Randomized clinical trial evaluating 2 closure techniques in lumbar spine surgery (SCAR - Spinal Closure Aesthetic Reconstruction Trial) - Pilot study

Juan Del Castillo-Calcáneo ^1,2 , Ezequel Rodriguez-Talavera ¹ , and Guy Gilbert Broc - Haro ^1,2

¹ Neurosurgery, ISSSTE - Hospital Regional Adolfo Lopez Mateos, Mexico City, Mexico

² Neurosurgery, ABC Medical Center, Mexico City, Mexico

Introduction: Low back pain is the main cause of loss of years due to disability throughout the world. The global rate of lumbar spine surgery increased by 54% from 1999 to 2013, from 78 to 120 per 100,000 population. Various methods of closing surgical wounds in the lumbar spinal region have been used finding that there is no increased incidence of complications between them. Currently, there is no consensus on which method of skin closure is the most appropriate for patients undergoing lumbar spine surgery using the posterior approach. One of the main complaints of patients in the postoperative period is the notoriety of the scar caused by this type of surgery. In this study we made a comparison between two closure techniques, evaluating the aesthetic result and the rate of complications in each group. Material and Methods: In this pilot study, we evaluated the aesthetic result between two types of skin closure for posterior lumbar spine surgery (subcuticular suture (group 1) and simple running suture (group 2)), randomly assigned, using the Patient and Observer Scar Assessment Scale (POSAS) at 24 hours, 2 weeks, 1 month and 3 months. Likewise, the rate of complications in each group was determined as well as their general information. Results: A total of 10 patients undergoing lumbar spine surgery by posterior approach were randomized (5 men and 5 women), with an average age of 60.7 years (40-73 years). Of all the cases, only one had a complication by the presence of seroma but did not required additional intervention, this subject belonged to group 2. The result on the POSAS scale at 24 hours was 120 in group 1 and 241 in group 2. 2 weeks: group 1 of 107 and group 2 of 244. At one month: group 1 of 107 and group 2 of 188. At 3 months: group 1 of 90 and group 2 of 159. The average time for closure with subcuticular technique it was 10.4 minutes and 8.8 minutes for the simple running suture group. The average time for removal of the suture material was 10 seconds for group 1 and 72 seconds for group 2. No subjects with cerebrospinal fluid leak were identified. Conclusion: Our pilot study suggests that subcuticular closure in posterior lumbar surgery, in addition to being accompanied by a better aesthetic result, does not increase the rate of complications compared to the simple running suture technique. The time for removal of suture material is significantly shorter in the subcuticular closure group.

652

P204: A retrospective observational study to evaluate adjacent segmental degenerative change with the dynesys-transition-optima instrumentation system

Chiruei Li ¹ , Hsi-Kai Tsou ^2,3,4 , Shih-Hao Chen ⁵ , Chung-Yuh Tzeng ⁶ , and Wen-Hsien Chen ⁷

¹ Department of Neurosurgery, Neurological Institute

² Functional Neurosurgery Division, Neurological Institute

³ College of Medicine, National Chung Hsing University, Taichung City, Taiwan

⁴ Nursing and Management, Department of Rehabilitation, Jen-Teh Junior College of Medicine, Taiwan

⁵ Department of Orthopaedics, Tzu Chi General Hospital at Dalin and Tzu Chi University, Taiwan

⁶ Department of Orthopaedics

⁷ Department of Radiology, Taichung Veterans General Hospital, Taiwan

Introduction: In clinical scenarios, adjacent segmental disease (ASD) is problematic because further surgical management might be necessary and adverse effects on functional outcomes might be encountered in those patients who received lumbar spine operation. Hybrid dynamic stabilization technique with Dynesys-Transition-Optima (DTO) seems to be a practicable answer for ASD. The purpose of this retrospective observational study was to evaluate the adjacent segmental degenerative change with instrumentation method of DTO system. Material and Methods: One hundred and fourteen lumbar spinal stenosis patients complicated with spondylolisthesis that refractory to nonsurgical management were recruited. These patients received dynamic stabilization with DTO system in a single medical center by a single neurosurgeon between 2012 to 2020. Initially 33 patients were excluded that received more than 1 segment fusion or additional decompression at other segments. Among the remaining 81 cases, we analyzed patients that received rigid fixations applied at the L4-5 segment only with complete postoperative data. Finally, 32 patients were enrolled into our study. Follow-up visit was planned after 6, 12, and 24 months postoperatively. Radiologic assessment included disc height, listhesis distance and angular change while in motion. Implant failure and screw loosening sign were both documented. All radiologic assessments were applied at the L2-3, L3-4 and L5-S1 segments separately which reviewed by two neurosurgeons and one neuro-radiologist independently. Results: Our study showed that takes longer time interval to see a significant reduction in disc height at L3-4 segment than other. For the L3-4 segment, the significant disc height reduction appears a year after the operation, however, the alteration on other segments showed in merely half a year after the surgery. For the 2-year change in listhesis distance, the L3-4 segment showed significantly less increase comparing with the L2-3 and L5-S1 segments. In the assessment of motion angular change, only the L3-4 segment revealed significant decrease between the preoperative and 2-year postoperative data. Conclusion: Regarding our study, disc height decreased and listhesis distance revealed the minor trend and later ASD change in the index level compared to the L2-3 and L5-S1 levels. Less angular change occurred at the index level while in motion is also noted in our study. Although evidence in ASD prevention did not show significant differences compared with other clinical studies, the minor and delayed index level degeneration still showed optimistic results. As mentioned above, this dynamic stabilization technique could be a promising surgical strategy for delaying ASD.

Keywords: adjacent-segment disease, dynamic stabilization, dynesys-transition-optima, lumbar spinal fusion, motion preservation, degenerative disc disease, loading force sharing

694

P205: Clinical outcomes of lumbar interbody fusion combined with cortical bone trajectory screw fixation technique

Jong Tae Kim ¹

¹ Neurosurgery, The Catholic University of Korea, Incheon Saint Mary's Hospital, Incheon, South Korea

Introduction: Cortical bone trajectory (CBT) pedicle screw fixation is alternative new technique, and some biomechanical or anatomical studies, which demonstrate the priority of pullout strength of CBT screws comparing to the conventional pedicle screws, especially in osteoporotic patients have been reported. And also several clinical reports have been published recently in terms of the benefit as well as lessening of the complications of the CBT screw method. We report, the clinical and radiological results of the short level lumbar interbody fusion with CBT pedicle screw insertion. Material and Methods: 21 patients (8 males and 13 females) with at least 6months follow-up were enrolled, who were underwent single or two levels lumbar interbody fusion using PLIF or TLIF using CBT screw fixation method in single hospital, between October 2014 and August, 2015. All CBT screws were inserted by one surgeon under intraoperative C-arm fluoroscopic guidance. The medical records and pre- and postoperative imaging studies were reviewed retrospectively. Mean age of the patients was 63 (range: 49-81) and the mean follow-up period was 28.9 months (range 7-69 months). The 9 cases (42.9%) were revisional surgery. All patients was underwent interbody fusion, and the total number of interbody fusion level was 21 (12 single level, 9 two levels). Interbody fusion methods were PLIF, TLIF, or OLIF (16, 12 and 1, respectively). A total number of 104 CBT screws were analyzed radiologically. Results: Average T-score of BMD was -2.0 SD. Preoperatively mean VAS score was 7.5(SD ± 1.12), and postoperative mean VAS score was 2.8 (SD ± 0.93). Mean operation time for the single level fusion and two level fusion was 209 (SD ± 45.5) and 267 (SD ± 35) minutes respectively, and the estimated blood loss was 496ml (SD ± 150) and 722ml (SD ± 380). Postoperative CT was conducted immediately after surgery, except for two patients among the 21 patients. In the 96 screws analyzed, 14 screws (14.6%) were not inserted correctly, but there was no case of the violation or compromise of the neural foramen. In one patient, intraoperative dura injury was developed. Postoperative screw loosening or halo was detected in the 3 patients (6 screws). In the follow-up period, the posterior displacement of the interbody cage was detected just 4 weeks after surgery, in a case of severe osteoporosis patient (T-score -5.0). Nevertheless, in most of patients (17/21), favorable surgical results were achieved. Conclusion: The CBT screw fixation is a good alternative method, especially in the case of osteoporosis, and this technique has several advantages that minimize paraspinal muscle disruption and decrease operation time, as well as that allows to avoid exposure or injury of the adjacent facet joint. However, some limitations and possible disadvantages reside simultaneously. Comparative or controlled study and larger numbers of patients with longer durations of follow-up will be need for the universal use of the CBT screw method.

715

P206: Comparative evaluation of transforaminal lumbar endoscopic discectomy versus open microdiscectomy for lumbar disc herniation: a retrospective analysis of 885 cases

Nikolaos Gkantsinikoudis ¹ , Christos Siopis ¹ , and Stylianos Kapetanakis ^1,2

¹ Spine Department and Deformities, Interbalkan European Medical Center, Thessaloniki, Greece

² Department of Minimally Invasive and Endoscopic Spine Surgery, Athens Medical Center, Athens, Greece

Introduction: Lumbar Disc Herniation (LDH) represents a frequently encountered clinical entity and the leading etiology of low back pain in young and middle-aged individuals in recent years, being unfavorably associated with considerable morbidity and mortality. Open Microdiscectomy (MD) represents the current gold standard for surgical management of LDH. Transforaminal Lumbar Endoscopic Discectomy (TLED) constitutes a novel, full-endoscopic, minimally invasive technique that is increasingly recruited for surgical management of LDH in a worldwide basis in recent years. Published data regarding comparison of these two techniques remain limited in current literature. Hence, we hereby present our experience from conduction of TLED versus MD for surgical treatment of patients with LDH. Material and Methods: Eight-hundred and eighty-five (885) patients with symptomatic LDH according to clinical and radiologic criteria were retrospectively evaluated. All patients fulfilled established indications for surgical treatment. Enrolled individuals underwent surgical management either with TLED (TLED group) or with MD (MD group) from the same experienced spine surgeon in two distinct tertiary centers in the period 2013-2019. Medical archives were searched for predetermined demographical and clinical data as well as for assortment of values of standard primary and secondary outcome measures. Primary outcome measures were operation time, length of incision, timing of postoperative mobilization, hospitalization duration and specific patient-reported outcome measures as Visual Analogue Scale (VAS), Oswestry Disability Index (ODI) and Short-Form 36 (SF-36) Medical Health Survey Questionnaire. Secondary outcome measures were recorded complications and recurrence rates. Retrieved data were derived from conducted evaluation on an outpatient basis at specific intervals preoperatively and at 6 weeks, 3, 6, 12 months and at 2 and 5 years postoperatively. Results: All patients were subjected to uneventful TLED or MD, exhibiting no major perioperative complications. Demographical data were not significantly differentiated in the two groups. Primary outcome measures analysis demonstrated that operation time, length of incision as well as timing of postoperative mobilization and hospitalization duration were statistically significantly ameliorated in TLED group (p < 0.05). Furthermore, self-reported outcome measures (VAS, ODI, SF-36) featured a statistically significant amelioration at each follow-up intervals in comparison with preoperative values in both groups, demonstrating albeit no statistically significant differentiation between them at determined intervals. Moreover, incidence of recorded complications and recurrences was not found to be significantly differentiated between the two groups. Conclusion: In this retrospective analysis, TLED was demonstrated to be non-inferior in terms of clinical efficacy in comparison with conventional MD, alongside exhibiting relative superiority in terms of operation time, length of incision and postoperative mobilization-hospitalization time. Our results advocate that TLED should be considered as a beneficial alternative for surgical management of LDH, concerning, however, the relatively high and steep learning curve that may crucially compromise favorable clinical outcomes, especially for beginner spine surgeons.

729

P207: Correction of spinal sagittal alignment after posterior lumbar decompression: does severity of central canal stenosis matter?

Delano Trenchfield ¹ , Yunsoo Lee ¹ , Mark Lambrechts ¹ , Jeremy Heard ¹ , Nick D'Antonio ¹ , Sydney Somers ¹ , John Paulik ¹ , Parker Brush ¹ , Tariq Issa ¹ , Jose Canseco ¹ , Alan Hilibrand ¹ , Alexander Vaccaro ¹ , Chris Kepler ¹ , and Gregory Schroeder ¹

¹ Division of Spine Surgery, Rothman Orthopaedic Institute, Philadelphia, United States

Introduction: Maintaining a balanced posture is essential in patients with lumbar central canal stenosis and understanding sagittal spinopelvic alignment is necessary to achieve that. A previous study has shown that central canal stenosis severity is associated with greater preoperative sagittal misalignment. However, no study has evaluated postoperative differences. Our study aims to identify if there is a difference in the degree of correction of spinal sagittal alignment between severe and non-severe central canal stenosis. Materials and Methods: Patients undergoing < 4 level posterior lumbar decompression were retrospectively identified. Patients were excluded if they had no preoperative MRI or if there was inadequate visualization of the femoral head and lumbar spine on lateral x-ray. Patients were divided into two cohorts based on the Lee MRI grading system: Grade 3 (severe) central canal stenosis and Grades 0-2 (non-severe) central canal stenosis. Patient demographics, surgical characteristics, clinical outcomes, and sagittal measurements were collected and compared using independent t-tests, Mann-Whitney U tests, and Pearson’s chi-square tests. A multivariable logistic regression model accounting for age, sex, BMI, CCI, and preoperative MRI Grade 3 stenosis was performed to measure their effects on preoperative, postoperative, and delta pelvic tilt (PT), sacral slope (SS), lumbar lordosis (LL), and pelvic incidence minus lumbar lordosis (PI-LL). Statistical significance was set at P < 0.05. Results: Of 153 patients, 40 had severe stenosis, and 113 had non-severe stenosis. Patients with severe stenosis were older (67.0 ± 12.9 vs. 54.4 ± 13.7, p < 0.001) with higher CCIs (3.00 ± 1.50 vs. 1.42 ± 1.37, p < 0.001), operative times (123 ± 39.5 vs. 89.8 ± 32.2 minutes, p < 0.001), lengths of stay (1.68 ± 1.54 vs. 0.64 ± 0.94 days, p < 0.001), and levels decompressed (2.40 ± 1.10 vs. 1.42 ± 0.76, p < 0.001). There were no significant differences in 90-day readmission or revision rates. Patients with severe stenosis demonstrated lower preoperative SS and LL but higher PI-LL (p < 0.05). Postoperatively, SS and LL remained lower in patients with severe stenosis (P < 0.05). Postoperative PT and PI-LL trended towards being higher in severe stenosis but were not statistically significant (p = 0.051 and p = 0.058, respectively). Both groups showed improvement in sagittal balance postoperatively but there were no significant differences in delta LL (1.40 ^o ± 7.15 ^o vs 2.37 ^o ± 6.68 ^o, p = 0.44), SS (0.96 ^o ± 4.65 ^o vs 1.07 ^o ± 5.38 ^o, p = 0.91), PT (-0.18 ^o ± 5.84 ^o vs 0.55 ^o ± 7.60 ^o, p = 0.583), or PI-LL (-1.40 ^o ± 7.15 ^o vs -2.37 ^o ± 6.68 ^o, p = 0.440) between the groups. Multivariate logistic regression found no significant predictors of delta LL, SS, PT, or PI-LL. However, severe stenosis was predictive of a lower preoperative LL (estimate = -5.403, p = 0.031), and a higher preoperative PI-LL (estimate = 6.853, p = 0.12), postoperative PT (estimate = 3.751, p = 0.033), and postoperative PI-LL (estimate = 5.903, p = 0.033). Conclusions: Severe stenosis was associated with greater spinopelvic mismatch preoperatively. Sagittal balance improved in patients with severe and non-severe central canal stenosis after posterior lumbar decompression. However, the degree of correction is not statistically different, and differences in sagittal parameters remain postoperatively.

745

P208: Association between preoperative lumbar fat infiltration and clinical outcomes after posterolateral lumbar fusion: A retrospective study

Filipa Cordeiro ¹ , Tiago Barbosa ¹ , João Seixas ¹ , and Ricardo Rodrigues-Pinto ²

¹ Orthopaedics Department, Centro Hospitalar Universitário do Porto, Porto, Portugal

² Orthopaedics Department, Centro Hospitalar Universitário do Porto, Unidade Vertebro-Medular (UVM), Porto, Portugal

Introduction: The lumbar musculature is a fundamental stabilizer of the spine, and the relationship between chronic low back pain and paraspinal muscle atrophy has been well established. In several studies, fat infiltration has been associated with low back pain and lower limb pain. Thus, the preoperative condition of the lumbar musculature may interfere with the results of the surgical treatment. The aim of this study was to assess whether there is an association between preoperative fat infiltration and clinical outcomes after posterolateral lumbar fusion. Material and Methods: All patients who underwent elective posterolateral lumbar fusion between 2014 and 2019 were retrospectively evaluated. The classification of fat infiltration was performed through the analysis of preoperative Magnetic Resonance Imaging (MRI) and the correlation with the postoperative clinical results evaluated by Oswestry Disability Index (ODI), persistence of low back pain and/or lower limb pain and Visual Analogue Scale (VAS). Results: A total of 64 MRI were evaluated, most of which (89.1%) belonged to patients undergoing surgery for spondylolisthesis. Nine patients (14.1%) did not respond to the postoperative evaluation questionnaire. Forty-seven patients (73,4%) were women and mean age was 65,8 years old. Preoperative fat infiltration was higher in women than in men (p = 0.043). In addition, women had higher postoperative ODI scores, that is, worse clinical outcomes (p = 0.007). However, preoperative fat infiltration was not associated with ODI, VAS for low back pain/radicular pain or return to work. Conclusion: The results obtained show that women have higher levels of preoperative fat infiltration and worse ODI scores. However, it was not demonstrated an association between the degree of fat infiltration and clinical outcomes after posterolateral fusion. Further studies are needed to validate a possible correlation.

794

P209: Fatty infiltration of paraspinal muscle served as an independent risk factor in cage subsidence and nonunion amongst single level anterolateral approach lumbar interbody fusion

Kuan Kai Tung ¹ , Cheng-Sheng Liu ¹ , Kun-Hui Chen ^1,2,3,4 , Chien-Chou Pan ^1,5 , Cheng-Min Shih ¹ , Yun-Che Wu ¹ , and Cheng-Hung Lee ^1,6,7

¹ Taichung Veterans General Hospital, Taichung, Taiwan, Department of Orthopedics, Taichung, Taiwan

² Department of Biomedical Engineering

³ Providence University, Department of Computer Science and Information Engineering, Taichung, Taiwan

⁴ Department of Nursing

⁵ Department of Rehabilitation Science, Jenteh Junior College of Medicine, Taichung, Taiwan

⁶ Post Baccalaureate Medicine, School of Medicine, National Chung Hsing University, Taiwan

⁷ Department of Food Science and Technology,Hung Kuang University, Taichung, Taiwan

Introduction: Clinical outcomes amongst degenerative lumbar disease patients have shown satisfactory results being reported after minimal invasive lumbar interbody fusion surgery. Additionally, the importance of paraspinal muscle (PM) degeneration on clinical outcomes has been revealed. However, the risk factors in related to fatty infiltration (FI) of paraspinal musculature effect led to nonunion and cage subsidence in lumbar interbody fusion has been scarcely discussed. Material and Methods: This study aimed to discover how FI of paraspinal muscle affects bone fusion and cage subsidence after single level anterolateral lumbar interbody fusion surgery. After application of inclusion and exclusion criteria, 127 patients received anterior lumbar interbody fusion (ALIF) and oblique LIF (OLIF) were enrolled in current study. Adjusted total cross-sectional area of PM and FI proportion of supra-adjacent, superior, inferior and infra-adjacent level PM was assessed via pre-operative magnetic resonance imaging. Fusion status and cage subsidence outcome were evaluated at 2-years after surgery. Results: More than 70% of the study subjects were diagnosed spondylolisthesis. 55% if the operation level was at L4/5. FI of supra-adjacent, superior, inferior and infra-adjacent level was significantly higher in the nonunion group and cage subsidence group (p < 0.001 for all). Multivariate logistic regression revealed FI of supra-adjacent level PM served as an independent risk factor for nonunion and cage subsidence (p = 0.041, odds ratio [OR] = 1.15 and p = 0.036, odds ratio [OR] = 1.13). ROC curve analysis showed cut-off value of 40.4% and 35.8% in supra-adjacent FI of PM in predicting bone fusion and cage subsidence, respectively (sensitivity 71.4% and specificity 92.9%, area under curve = 0.869 and sensitivity 93.8% and specificity 60.6%, area under curve = 0.818). Conclusion: Higher fatty infiltration rate of supra-adjacent paraspinal muscle was strongly associated with bone nonunion and cage subsidence after single level anterolateral lumbar fusion surgery. Patients with more than 35-40% FI of supra-adjacent PM may result in nonunion and cage subsidence. Therefore, appropriate intraoperative endplate preparation and close following-up the fusion outcome after surgery are important.

839

P211: Transpsoas versus ante-psoas technique in lateral approaches: pros and cons

Alessandro Longo ¹ , Federica Penner ^1,2 , Mario Allevi ² , Armando Massara ² , and Alessandro Ducati ¹

¹ Spine Surgery Unit, Humanitas Cellini, Turin, Italy

² Department of Neurosciences “Rita Levi Montalcini”, Neurosurgery Unit, Neurosurgery, University of Turin, Turin, Italy

Introduction: The lateral transpsoas approach (LLIF) is the most commonly used among the minimally invasive technique for degenerative spine diseases and is supported by several recognized advantages over posterior interbody fusion, such as lower post-operative pain, greater disk removal, better footprint, good indirect foramen and central canal decompression and lower adjacent segment disease rates. The oblique lumbar interbody fusion (OLIF) technique is an ante-psoas approach which brings all the advantages of an anterior approach and other benefits when compared to the transpsoas technique, such as excellent visualisation of anterior longitudinal ligament, avoiding muscular trauma and lumbar plexus injury risk, cost reduction due to the possibility of not using a monitoring system for lumbar plexus, no need to use jack knife position. Furthermore using the orthogonal manoeuvre ante-psoas cage insertion can reach a favourable angle to correct coronal imbalance and scoliosis. The increased vascular injury risk is the main drawback of the OLIF technique. The aim of this study is to compare the LLIF and OLIF techniques focusing on intraoperative challenges and complications. Material and Methods: The authors performed a retrospective review on 199 consecutive patients treated over a 4-year period for lumbar degenerative disease and adult scoliosis. We implanted 59 cages through the OLIF approach. 38 patients underwent single level surgery, 14 patients underwent double level surgery and 7 patients also implanted other cages through mixed approaches (such as TLIF). We also implanted 198 cages through the LLIF approach. 62 patients underwent single level surgery, 62 patients underwent double level surgery and 7 patients also implanted other cages through mixed approaches. Results: Our experience showed 19 (9,6 %) intraoperative complications during cage implants in the LLIF group (such as subsidence, anterior longitudinal ligament rupturing and anterior cage migration), while only 3 (5,1 %) intraoperative complications during cage implants in the ante-posas group (one peritoneum rupturing, one cage rotation, one cage subsidence). Conclusion: The ante-psoas technique is a valuable alternative to the transpsoas approach. We identified several advantages and some cons of using the ante-psoas approach instead of the transpsoas technique, and different rates of intraoperative complications. In our experience we observed that the two techniques could be complementary and they should be performed according to the specific patient anatomy and clinical needs.

850

P212: The intersection of perioperative polypharmacy and surgical outcomes after lumbar spinal fusion: a retrospective cohort study

Cathleen Kuo ¹ , Mohamed Soliman ^1,2 , Alexander Aguirre ¹ , Marissa Kruk ¹ , Joseph Iskander ¹ , Hannon Levy ¹ , Asham Khan ¹ , Moleca Ghannam ¹ , Patrick Jowdy ¹ , John Pollina ¹ , and Jeffrey Mullin ¹

¹ Neurosurgery, University at Buffalo, Buffalo, United States

² Neurosurgery, Cairo University, Cairo, Egypt

Introduction: Spine fusions are one of the most common procedures in elderly patients. Among this group, these patients typically also balance a multitude of other medical conditions that can require a delicate management of medications. The objective of this study was to identify the impact of an increased number of medications, polypharmacy, and its impact to various postoperative outcomes. Material and Methods: A retrospective review of patient charts was completed. Data collection included the number of pharmaceutical drugs a patient was actively taken, as self-reported by the patients. Polypharmacy was defined according to previous literature as the patient taking five or more drugs at a single time. Other data collection included patient demographics, preoperative comorbidities, intraoperative outcomes, and postoperative outcomes. Uni-variate analysis was utilized to identify potential differences between groups. Results: A total of 713 patients were identified. Among these patients 539 (75.6%) of patients utilized five or more drugs at a single time. Preoperatively, the polypharmacy group had significantly higher history of illicit drug abuse (p = 0.003), increased American Association of Anesthesiologist (ASA) scores (p < 0.001), increased Charlson Comorbidity index scores (p < 0.001) and were significantly older (p = 0.01). In the operating room polypharmacy patients required a larger number of fusion levels (p = 0.01), had greater estimated blood loss (p < 0.001), and increased length of stay (p = 0.01). The polypharmacy group also had significantly greater estimated blood loss (p < 0.001) and longer hospital stay (p = 0.01). Conclusion: Polypharmacy is an extremely common before and after spine fusions, which leads to an increased rate of adverse perioperative outcomes.

857

P213: Preoperative degrees of fat infiltration, intervertebral disc degeneration and Modic changes do not influence the outcomes of lumbar fusion

Filipa Cordeiro ¹ , Tiago Barbosa ¹ , João Seixas ¹ , and Ricardo Rodrigues-Pinto ¹

¹ Orthopaedics Department, Spinal Unit, Centro Hospitalar Universitário do Porto, Portugal

Introduction: The lumbar musculature is a fundamental stabilizer of the spine. Several studies have associated fat infiltration, especially of the multifidus and erector spinae, to low back pain and radiculopathy. In addition, discogenic low back pain has been described as the most common cause of chronic low back pain. Thus, the preoperative condition of the lumbar spine may interfere with the results of its surgical treatment. The aim of this study assess the influence of the degrees of pre-operative fat infiltration, intervertebral disc degeneration and MODIC changes on the clinical status of patients submitted to lumbar fusion. Material and Methods: A retrospective study with patients submitted to lumbar fusion between 2014 and 2019 was performed. The preoperative degree of fat infiltration was measured and the degree of intervertebral disc degeneration was analyzed using the Pfirmann and Modic classifications, and then correlated with the postoperative clinical results, using the Oswestry Disability Index (ODI), Visual Analogue Scale (VAS) and subjective improvement of low back pain and radicular pain. Results: One hundred thirty-nine patients were included, of which 64 were submitted to posterolateral fusion (PLF) and 75 to interbody fusion (51 via transforaminal - TLIF - and 24 via posterior - PLIF). The most frequent surgical indication was spondylolisthesis (77%). Patients undergoing interbody fusion reported greater subjective improvement in low back pain and radicular pain when compared to patients undergoing PLF (p < 0.05), regardless of the degree of fat infiltration. No statistically significant association was found between the type of surgery (interbody fusion vs. PLF) with ODI (30.32 vs. 31.70), VAS for low back pain (5.4 vs. 4.2), for radicular pain (4.1 vs. 2.8), respectively. No relation was found between previous disc status with ODI, VAS low back pain/radicular pain or return to work. An association was found between patients with a greater degree of fat infiltration and greater persistence of postoperative radicular pain (p = 0.041). There was no association between the degree of fat infiltration and other postoperative clinical parameters, such as ODI, VAS low back pain/radicular pain or return to work. Conclusion: Results in this study failed to identify an association between the degree of intervertebral disc degeneration or fat infiltration and the postoperative clinical outcomes of lumbar fusion, regardless of the surgical technique utilized.

888

P214: Comparison of unilateral versus bilateral instrumentation in transforaminal lumbar interbody fusion for lumbar degenrerative disorders- an mid term analysis of 806 cases

Dr Sajan Hegde ¹ , Sharan Achar T ¹ , Vigneshwara Badikkilaya ¹ , and Umesh Kanade P ¹

¹ Orthopaedics, Apollo Hospitals Chennai India, Chennai, India

Introduction: Transforaminal lumbar interbody fusion (TLIF) has become gold standard technique for management degenerative lumbar disc disease, traditionally performed with bilateral pedicle screw fixation. Alternatively, Unilateral instrumented in TLIF has been reported to be effective. This study compares the clinical and radiological outcomes in a select series of patients treated with Unilateral versus Bilateral Pedicle Screw instrumented TLIF (UPSF vs BPSF TLIF). Materials: Single center, Single surgeon, retrospective study with minimum 2-year follow up. Retrospective cohort study including 806 patients with 396 patients operated with UPSF TLIF compared to 410 patients with BPSF TLIF with at least 2 years follow-up. Demographic data, operative time, blood loss, hospital stay, implant costs, complications were evaluated. Functional outcome assessed using Oswestry Disability Index (ODI), Short-Form health survey (SF-36) and visual analog score (VAS) preoperatively and 6 months, 1 year, and 2 years after surgery. Fusion rates assessed with Bridwell grading at 2 yrs follow up. Data analyzed using X² test, t test, and Fisher exact test. Results: The mean follow-up was 33 months (24-86 months). A significant improvement in VAS, SF-36 and ODI in both groups at 2 years follow-up was noted, and there was no significant difference between the groups. The complication rates between the groups were similar, except for radiological cage migration with bullet cage in UPSF group causing no symptoms (p > 0.05). The fusion rate in UPSF TLIF was 97.1% and 98.2% in BPSF TLIF; difference was not statistically significant. The UPSF group had a significantly shorter operative time, less blood loss, shorter hospital stay and reduced implant cost compared with BPSF group (p < 0.001). Conclusions: UPSF in TLIF is comparable with BSPF in terms of patient-reported clinical outcomes, fusion rates, and complication rates with the additional benefits of less operative time, less blood loss, shorter hospitalization, and less cost in selective cases.

1022

P215: Comparison of total health operational cost for 1-stage vs 2-stage anterior lumbar interbody fusion procedures

Miguel Ruiz Cardozo ¹ , Som Singh ¹ , Michael Olufawo ¹ , Samuel Brehm ¹ , Abby Carey-Ewend ¹ , Karma Barot ¹ , Ahmed Hanafy ¹ , Gabriel Trevino Verastegui ¹ , Matthew De la Paz ¹ , Raj Lavadi ¹ , Magalie Cadieux ¹ , Julio Jauregui ² , and Camilo Molina ^{1 2}

¹ Neurosurgery, Washington University, St. Louis, United States

² Orthopaedic Surgery, Washington University, St. Louis, United States

Introduction: Anterior lumbar interbody fusions (ALIF) are a common operative procedure for the management of degenerative lumbar spinal pathology. Anatomically, an ALIF techniques allows for midline workflow of disc space and endplate preparation which can maximize surface area during fusion-based restoration. Let alone, the widespread practice of ALIF has increased compared to its posterior, transforaminal, lateral, and oblique lumbar fusion cohorts. This has led to ALIF often being among the highest Medicare reimbursement expenditures over the past 2 decades. As healthcare utilization and expenditures continue to rise within spinal surgery, there becomes more of an imperative need to evaluate lumbar interbody fusion approaches for value-based care when determining approaches between levels. The aim of this study is to describes the costs of operations between 1-level and 2-level ALIF surgeries being performed as 1-stage vs 2-stage procedures. Material and Methods: This was a single institutional retrospective cohort study of 212 patients who underwent spinal fusion surgeries at Barnes Jewish Hospital in Saint Louis from January 2021 to January 2022. Among this cohort, patients who underwent 1-level or 2-level ALIF were evaluated for medical billing costs incurred during their individual operating room (OR) and hospital courses (HC). All Hospital Costs (HC) incurred for 18 functional areas were obtained from Hospital billing for each patient’s surgical admission. We performed comparisons of ancillary costs (AC) and operating costs (OC) across the 1-level or 2-level ALIF procedures. We used tableau desktop and R Studio for data visualization and statistical analyses. Cost distributions were compared using the non-paired samples Wilcoxon rank sum test. Descriptive statistical analysis was performed using tableau desktop and R studio for both cohorts. Additionally, the distribution of costs were compared using independent U tests. Statistical significance was established as p < 0.05. Results: A total of 16 1-level or 2-level ALIF surgeries were identified in the database. 7 cases were 1-Stage and 9 were 2-Stage surgeries. The mean OR time of 1-stage surgeries was 403 min (CI 365.59-440.69) and for 2-stage procedures was 530 min (CI 424.85-636.65). The mean LOS of 1-stage surgeries was 2.86 days (CI 1.61-4.1) and for 2-stage procedures was 4.13 days (CI 2.75-5.5). Neither group developed complications during the hospital course. In terms of total operational cost (including ancillary, hospital stay and operating room cost), the median cost was 50203.14 USD (SD 8012.21) for 1-stage surgeries and 60849.22 USD (SD 11744.04) for 2-stage procedures. The differences in OR time, LOS and total operational cost were not statistically significant. Conclusion: This study establishes economic profile of medical costs associated with 1-level and 2-level ALIF among patients with degenerative disease. Based on the data distributions of the total operational cost total, it seems 1-stage procedures are able to provide more efficiency in terms of resource utilization for equitable patient outcomes compared to 2-stage procedures. However, this study failed to showed a statistically significant difference. Validation with a larger cohort of patients will help to determine the most cost-effective ALIF approach.

1072

P216: Radiographic outcomes for bilateral versus unilateral cages in TLIFs

Jeremy Heard ¹ , Mark Lambrechts ¹ , Nicholas D'Antonio ¹ , Yunsoo Lee ¹ , John Bodnar ² , Gregory Schneider ² , Evan Bloom ² , Parker Brush ¹ , Jose Canseco ¹ , Tariq Issa ¹ , Christopher Kepler ¹ , Alan Hilibrand ¹ , Alexander Vaccaro ¹ , and Gregory Schroeder ¹

¹ Orthopedic Surgery, The Rothman Orthopedic Institute at Thomas Jefferson University Hospital, Philadelphia, United States

² Thomas Jefferson University, Philadelphia, United States

Introduction: While unilateral cage placement likely confers less surgical risk to the patient than bilateral cage placement, there is limited and conflicting literature regarding surgical outcomes when comparing bilateral and unilateral cages. There is little published literature comparing radiographic parameters following unilateral and bilateral cage placement, which may allow us to understand whether one technique is superior in its restoration of sagittal alignment, disc space distraction, or endplate obliquity. There is no clear evidence to dictate whether bilateral or unilateral cages promote superior radiographic or surgical outcomes in posterior-based spinal fusions. Our study aims to (1) compare radiographic outcomes between unilateral and bilateral cage placement in transforaminal lumbar interbody fusions (TLIF) and to (2) determine if the rate of fusion at the one-year postoperative point was different between patients who received bilateral versus unilateral cages. Methods: Patients > 18 years of age who underwent primary one- or two-level TLIFs at our institution were identified and propensity matched in a 3:1 fashion (unilateral compared to bilateral). Patient demographics, surgical characteristics, and radiographic outcomes including vertebral endplate obliquity, segmental lordosis, subsidence, and fusion status were compared between groups. Multivariable regression analysis was performed. Significance was set to p < 0.05. Results: Of 184 patients included, 46 received bilateral cages. Bilateral cage placement was associated with greater subsidence (1.06 ± 1.25 vs. 0.59 ± 1.16 mm, p = 0.028) and enhanced restoration of segmental lordosis (5.74^o ± 14.1^o vs. -1.57^o ± 10.9^o, p = 0.002) at the one-year postoperative point, while unilateral cage placement was associated with an increased correction of endplate obliquity (-2.02^o ± 4.42^o vs. 0.24^o ± 2.81^o, p < 0.001). Bilateral cage placement was significantly associated with radiographic fusion on bivariate analysis (89.1% vs. 70.3%, p = 0.018) and significantly predictive of radiographic fusion on multivariable regression (1.35 [1.51 - 12.05], p = 0.010) analysis. Conclusions: In comparing unilateral and bilateral TLIF procedures, TLIFs with bilateral cages resulted in greater improvements in segmental lordosis and bony arthrodesis. Unilateral cages were more likely to affect endplate obliquity. Given that this is one of the few studies comparing radiographic between unilateral and bilateral cages in patients undergoing TLIF procedures, additional high-quality prospective studies are needed to verify the results of the present study and add further context to whether the improvements in segmental lordosis and endplate obliquity result in greater long-term clinical outcomes.

1100

P217: Titanium coated PEEK interbody fusion device performance for treatment of degenerative spine conditions

Madilyn Riegel ¹ , Jillian Mohn ¹ , Matthew Gary ² , Joseph Lee ³ , Safdar Khan ⁴ , Elizabeth Yu ⁴ , Benjamin Chen ⁵ , and Hallie Murray ¹

¹ Tyber Medical, LLC, Clinical Affairs, Bethlehem, United States

² Neurosurgery, Emory Spine Center, Atlanta, United States

³ Orthopedic Spine Surgery, Rothman Orthopedics, Tarrytown, United States

⁴ Orthopedic Spine Surgery, The Ohio State University, Columbus, United States

⁵ Orthopedic Spine Surgery, MultiCare Institute of Research and Innovation, Puyallup, United States

Introduction: Interbody fusion devices designed using an integrated technology consisting of an organic thermoplastic polymer, polyetheretherketone (PEEK), and a porous titanium coating (ProTi) are FDA cleared and CE marked to treat patients with lumbar degenerative spine conditions. These degenerative spine conditions include, but are not limited to, degenerative disc disease, stenosis, and radiculopathy. The objective of this research is to examine the clinical outcomes and time to fusion for patients who have received the ProTi interbody fusion devices to evaluate the device’s performance in treating these degenerative spine conditions. Material and Methods: Approval from the Institutional Review Board was obtained to gather clinical and radiographic outcomes on patients treated retrospectively and prospectively for one-level lumbar fusion with a ProTi interbody fusion device to correct degenerative disc disease or other spinal deformities. The ProTi interbody fusion device is designed with pyramidal teeth to resist expulsion in all directions, tracks on the surface to lead and turn the spacer into position, and a self-distracting bullet-nose to allow easy insertion. The subjects in this study were evaluated by using patient reported outcome measurements including the Oswestry Disability Index (ODI) and the Visual Analog Scale (VAS), along with radiographic outcomes using x-rays and computed tomography (CT) scans. Results: The patients treated with the ProTi interbody fusion devices demonstrated solid bony fusion with CT scans displaying bone bridging across the interbody space with an average time to fusion of 10.93 months (range of 3 to 21 months). Patient reported outcome measurements had significant (p = 0.001) improvement in VAS back pain, significant (p = 0.007) improvement in VAS right leg pain, and significant (p < 0.05) improvement in VAS left leg pain at the 12-month follow-up when compared to pre-operative VAS pain scores. Patient ODI scores also demonstrated improvement from an average score of 42.46 pre-operatively to an average score of 24.23 at 12-month follow-up (p = 0.053). These results demonstrated the ability of ProTi devices to successfully alleviate pain caused by a degenerative spine condition managed through spine fusion. Conclusion: The preliminary analysis for this on-going study was the most recent to evaluate the clinical outcomes and time to fusion of one-level lumbar fusion using a ProTi interbody fusion device for the treatment of degenerative disc disease and other degenerative spine conditions. Study results demonstrated significant improvements in reported pain that resulted from the degenerative spinal deformities patients presented with prior to surgery and proved successful in obtaining solid bony fusion in one-level lumbar spine fusion procedures. Additional research will need to be done to fully evaluate the performance of ProTi interbody fusion devices.

1125

P218: Evaluating 5-years outcomes of interlaminar devices as an adjunct to decompression for symptomatic lumbar canal stenosis

Naresh Kumar ¹ , Andrew Thomas ¹ , Meetrra Seyher ¹ , Kasia Chua ¹ , Sean Lee ¹ , Liang Shen ² , and Laranya kumar ¹

¹ Orthopaedic Surgery

² Medical Statistics, National University of Singapore, Singapore, Singapore

Introduction: Lumbar spinal stenosis(LSS) is a common spine condition encountered in clinical practice, having an increasing prevalence especially with an ageing population. The SPORT trial established that surgical treatment of spinal stenosis yields greater improvement in pain and function. Currently, the gold standard of treatment of symptomatic LSS is open decompression and fusion, but it has several drawbacks such as increased soft tissue morbidity and adjacent segment degeneration. As such, the interlaminar device (ILD) has been proposed as an alternative solution that allows for a less invasive procedure with dynamic stabilisation, thus reducing surgical morbidity. Current literature on the effectiveness of ILD for patients with symptomatic LSS is limited to short term studies only. Our study is the first to assess and compare 5-year outcomes following non-instrumented spinal decompression with and without an ILD insertion to determine if there was a statistically significant improvement in clinical outcomes and radiological parameters. Materials and Methods: A retrospective review of prospectively collected data under a single surgeon cohort study, consisting of 116 patients who underwent spinal decompression with and without an ILD insertion between 2007 - 2015 was performed. Patients who met the study criteria were offered the choice of an ILD device insertion. Those who accepted an ILD insertion were placed in the D+ILD group (n = 61) and underwent an additional step involving the insertion of an ILD (Coflex or Stenofix) at the involved level through the same surgical incision; while those opting for decompression alone were placed in the DA group (n = 55). All patients in both groups received the same postoperative care. Clinical outcomes such as the Oswestry disability index, EuroQoL-5d (Eq5d), VAS-back pain & VAS-leg pain, and SF-36 scores were measured while radiological indices comprising of the anterior disc height, posterior disc height and foraminal height were assessed both preoperatively and up to 5-years postoperatively. Results: Both arms of our study showed statistically significant (p < 0.001) improvement in all clinical outcome indicators measured at all time points as compared to their preoperative state. However, the D+ILD group achieved and maintained significant radiological correction in posterior disc (p < 0.01) and foraminal height (p < 0.01) at all time points measured while the DA group did not attain this. This is in concordance with existing literature that supports the adjunct use of an ILD for its increased stability in extension and reduction in intradiscal pressure which translates into better clinical outcome scores for axial back pain and preservation of radiological parameters at varying time points. There were no major complications in both groups. Conclusion: The use of an ILD in conjunction with spinal decompression in patients with symptomatic LSS has been shown to offer positive clinical outcomes with reproducible correction in radiological parameters as compared to decompression alone.

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P219: Predict the culprit segment in percutaneous transforaminal endoscopic surgery (PTES) under local anesthesia for surgical treatment of lumbar degenerative disease: radiologic images or patient's symptoms?

YuTong Gu ¹

¹ Orthopedic Surgery, Zhongshan Hospital Fudan University, Shanghai, China

Objective: Percutaneous transforaminal endoscopic surgery (PTES) is a novel minimally invasive technique that has been used in the treatment of lumbar degenerative diseases (LDDs). It is very important to predict the culprit segment in surgical treatment of LDDs. Generally, we predict the culprit segment according to lumbar degenerations and neurologic compression on MRI and CT. Additionally different lumbar nerve root being compressed can lead to the pain in special place of buttock and leg, and the culprit segment can be predicted according to the position of leg pain. When radiologic images are not in accordance with neurologic symptoms, how to predict the culprit segment? PTES under local anesthesia was performed to treat the culprit segment of LDDs predicted by radiologic images or clinical symptoms, and the efficacy, security and feasibility were evaluated. Methods: 87 cases of LDDs with nerve root symptoms, which were not consistent with lumbar degenerative levels and degree on MRI and CT, were treated with PTES under local anesthesia in day surgery ward from Jan 2015 to Dec 2019. 42 patients, whose culprit segment was predicted by radiologic images are included in group A. The other 45 patients, whose culprit segment was predicted by clinical symptoms are included in group B. Leg pain VAS and ODI before and after surgery are recorded. The outcome is defined according to MacNab grade at 2-year follow-up. Postoperative complications are recorded. Results: In group A, 2 patients underwent PTES for 1 segment, 37 patients for 2 segments and 3 patients for 3 segments. One of 1-segment PTES had no relief of symptoms and underwent another PTES for other culprit segment 3 months after surgery. In group B 44 of 45 patients were treated using PTES for 1 segment and 1 patient for 2 segments. Group B showed significantly less operative duration, less blood loss and less fluoroscopy frequency than group A (p < 0.001). VAS score of leg pain and ODI significantly dropped after operation in both groups (p < 0.001). The leg pain VAS of group B was significantly lower than that of group A immediately, 1 week, 1 month, 2 months and 3 months after surgery (p < 0.001), but there was no statistical difference between two groups 6 months, 1 year, 2 years after surgery. Five patients (11.9%, 5/42) in group A and one patient (2.2%, 1/45) in group B had rebound effect of leg pain. VAS score of these patients rose 1 week after surgery and got relieved within 2 months. The excellent and good rate was 97.6% (41/42) in group A and 100% (45/45) in group B at 2-year follow-up. There was no statistical difference in ODI and the excellent and good rate between two groups. No complications such as wound infection, permanent nerve injury were observed. Conclusion: It is much more accurate to predict the culprit segment according to clinical symptoms than radiologic images in PTES under local anesthesia for surgical treatment of LDDs, which can decrease operative duration, blood loss, fluoroscopy frequency, and postoperative rebound effect of leg pain.

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P220: Evaluating 5-year outcomes of between the use of Coflex compared to Stenofix device as an adjunct to decompression for symptomatic lumbar canal stenosis

Naresh Kumar ¹ , Kasia Chua ¹ , Meetrra Seyher ¹ , Sean Lee ¹ , Laranya kumar ¹ , Liang Shen ² , and Andrew Thomas ¹

¹ Orthopaedic Surgery

² Medical Statistics, National University of Singapore, Singapore, Singapore

Objective: Literature on benefits of interlaminar devices (ILD) compared to decompression alone for symptomatic lumbar spinal stenosis (LSS) is limited past the 2-year timeframe. Additionally, no radiological parameters for quantifying patients with positive surgical outcomes have been correlated. First, to assess and compare 5-year outcomes following the use of the Coflex device compared to the Stenofix device as an adjunct to spinal decompression. Second, to determine whether improvement in radiological indices correlated with clinical outcomes. Methods: We conducted a prospective single surgeon cohort study of 116 patients who underwent spinal decompression with or without ILD insertion between 2007 - 2015. Patients with a single level symptomatic LSS were offered spinal decompression with either ILD insertion. An exclusion criteria of patients < 21 years-age, spondylolysis/listhesis grade 2 or higher, multiple level LSS, previous lumbar surgery and malignancy was applied to our study. Clinical outcomes were assessed preoperatively & up to 5-years postoperatively, using the Oswestry disability index, EuroQoL-5d (Eq5d), VAS score and SF-36. Radiological indices were assessed preoperatively and up to 5-years postoperatively. Results: We had a total number of 70 patients in our study, with 21 in the Stenofix group and 49 in the Coflex group. In term of anterior disc height, the Stenofix group had a significant reduction at 5 years from 12.5 to 11.2mm (p < 0.01) while the Coflex group had an unsustained improvement postoperatively that reverted back to preoperative height at 5 years (p = 0.34). The Stenofix group had an unsustained increase in posterior disc height and foraminal height postoperatively that reverted back to preoperative height at 5 years. The Coflex group had significant maintained improvement in posterior disc height from 6.9 to 7.9mm (p = 0.01) and foraminal height of 17 to 20.7mm (p = 0.03) at the 5 year mark. Comparing between the groups, there was significant improvement in posterior disc height favouring Coflex (p < 0.01). There was no significant difference in sagittal balance, overall lordosis and sagittal angle of the index level. Both groups had significant improvement post-operatively at all time points for all clinical outcomes. For the SF36-MCS score, Coflex had a greater improvement than Stenofix (p < 0.01) from 54.5 to 69.5 compared to 48.2 to 51.8 at 5 years postoperative respectively. For the VAS score, Coflex had a greater improvement than Stenofix (p = 0.03) from 6.0 to 1.0 compared to 6.2 to 2.3 at 5 years postoperative respectively. There was no significant difference in the remining clinical outcomes between the groups. Conclusions: Interlaminar device insertion with spinal decompression in symptomatic LSS with up to grade I spondylolisthesis offers good clinical outcomes as compared to decompression alone with sustained radiological correction. Our study highlights that in the treatment of symptomatic LSS (with up to grade I spondylolisthesis), the use of the Coflex device is superior to the Stenofix interlaminar device with greater improvement in posterior disc height and clinical outcomes such as SF-36 MCS and VAS overall.

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P221: Comparing TLIF vs PLF for patient reported outcomes, complications, readmissions, and revisions

Anthony Steinle ¹ , Wilson Vaughan ¹ , Andrew Croft ¹ , Alicia Hymel ¹ , Jacquelyn Pennings ^1,2 , Hani Chanbour ³ , Anthony Asher ^1,4 , Raymond Gardocki ¹ , Scott Lawrence Zuckerman ^1,3 , Amir Abtahi ^1,2,3 , and Byron Stephens ^1,2,3

¹ Department of Orthopaedic Surgery

² Center for Musculoskeletal Research

³ Department of Neurological Surgery, Vanderbilt University Medical Center, Nashville, TN, United States

⁴ Atrium Health Neurosciences Institute & Department of Neurosurgery, Carolinas Medical Center, Charlotte, NC, United States

Introduction: Elective lumbar fusion is commonly used to treat various lumbar pathologies when conservative therapy fails. Two common approaches for posterior lumbar fusions include transforaminal lumbar interbody fusion (TLIF) and posterolateral fusion (PLF) alone without an interbody. Whether TLIF or PLF leads to better patient-reported outcomes (PROs) and reduced complications remains an area of active research. The current study sought to compare TLIF vs PLF alone in regard to 1) patient reported outcomes (PROs), and 2) rates of complications, readmissions, and reoperations. Material and Methods: The Lumbar Module of the Quality Outcomes Database (QOD), a national multi center prospective spine registry, was queried between 04/2013-06/2019 for patients older than 18 years of age who underwent TLIF or PLF. Patients with previous lumbar surgery and all minimally invasive, multi-stage, and revision cases were excluded. Covariates included age, BMI, race, education, smoking status, comorbidities, primary spine diagnosis, number of levels fused, ASA grade, and baseline PROs. 12-month PROs included Oswestry Disability Index (ODI), North American Spine Society (NASS) patient satisfaction index, numeric rating scale (NRS) back and leg scores, and Euroqol 5-Dimension (EQ-5D). Other outcomes included 30-day complications, 30-day reoperations, 3-month readmissions, 12-month return to work (RTW), and 12-month return to activities. For most outcomes of interest, multivariate regression analysis was run controlling for covariates and the baseline measure of the outcome when applicable. Unadjusted univariate analysis was performed to evaluate 12-month RTW, 3-month readmission, and 30-day reoperation outcomes due to the low frequency of these outcomes in the PLF group. Results: 3,318 patients met inclusion criteria. 3,101 patients underwent TLIF while 217 patients underwent PLF. Patients with TLIF were more likely to have a single level fused vs multiple levels fused when compared to patients who underwent PLF (64.1% vs 51.2%, p = .001). No differences were found for the other baseline covariates or any demographic variable. Unadjusted univariate regression revealed no significant differences between the TLIF and PLF groups for the following outcomes: 12-month RTW (p = 0.2113), readmissions within 3 months (p = 0.4610), and reoperations within 30 days (0.8247). The adjusted multivariate analysis demonstrated no significant differences between TLIF and PLF groups for all 12-month outcomes including ODI, NRS back pain, NRS leg pain, EQ-5D and NASS patient satisfaction. Additionally, TLIF was not a significant predictor of 12-month return to activities (p = 0.0523) or 30-day complication rates (p = 0.8026). Conclusion: In summary, there were no discernible differences in 12-month PROs, 30-day complication or reoperation rates, or 3-month readmission rates in patients undergoing TLIF vs. PLF alone in elective lumbar fusion. Though long-term follow up is needed, these data add to the growing body of evidence that interbody fusion does not offer superior benefit with respect to outcomes following lumbar fusion for degenerative spine conditions. Given the additional concerns with increased time of procedure and potential complications raised by previous studies, surgeons should carefully select which patients would potentially benefit from transforaminal lumbar interbody fusion.

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P222: Observational prospective study of predictors of clinical and neurological recovery in operated degenerative lumbosacral spine disorders

Ankit Singh ¹ and Nishat Goda ²

¹ Orthopaedics, Max Smart Superspeciality Hospital, New Delhi, India

² Orthopaedics, Parakh Hospital, Mumbai, India

Introduction: Majority of the elderly population deal with nagging backache and claudication resulting in disability and poor quality of life. Surgical intervention employed in patients not amenable to conservative management not only decreases chronic pain but prevent dreaded complication of instability and neurodeficits. Assessing the clinical and neurological outcomes of operated patients enable us to dictate predictors thereby improving patient selection and thus the outcome. Material and Methods: Consecutive 30 patients with diagnosed degenerative lumbosacral spine diseases not showing improvement to conservative treatment for 6 weeks were subjected to surgical intervention. Clinical history, demographics and examination findings with relevant radiographic parameters were recorded. Clinical examination findings, VAS (Visual analogue scale) score, Roland Morris disability questionnaire (RMDQ), Oswestry disability index (ODI) and radiological findings were assessed at 3 months,6 months and 9 months’ follow up after surgery. Counselling regarding compliance was carried at each follow up and whenever deemed necessary. Patients were classified then into successful v/s unsuccessful based on pain scale, neurodeficit and duration to return to work. Results: Patients’ mean age was 51.17 ± 10.03 years with equal sex distribution.63% patients had single level involvement and 43 % were symptomatic for < 6 months. Majority (60%) were subjected to decompression alone. Back pain followed by deformity were chief complaints with VAS score and ODI score being 6.74 ± 0.55 and 42.40 ± 16.13 respectively. Nine months following treatment, noteworthy reduction in the VAS score (p < 0.05), ODI scores (p < 0.05) and RMDQ (p < 0.05) were found, with VAS score and ODI score improving by 45.1% and 47.70% respectively. 81% were classified as successful outcomes. Conclusion: With the increasing longevity of the population, the incidence of degenerative spine disease is increasing. Proper selection of patients subjected to surgery often show improvement maximally after 12 weeks post surgery. Age < 60 years, lower duration of symptoms less than 9 months and lower number of levels are positively correlated with better results.

Keywords: clinical, degenerative, lumbo-sacral spine, neurological recovery, predictors

1205

P223: Effect of timing of total joint replacement on elective lumbar surgery outcomes

Anthony Steinle ¹ , Alex Volkmar ¹ , Hani Chanbour ² , Eric Dilbone ¹ , William Waddell ¹ , Andrew Croft ¹ , Wilson Vaughan ¹ , Scott Lawrence Zuckerman ^1,2 , Byron Stephens ^1,2,3 , Ryan Martin ¹ , and Amir Abtahi ^1,2,3

¹ Department of Orthopaedic Surgery

² Department of Neurological Surgery

³ Center for Musculoskeletal Research, Vanderbilt University Medical Center,Nashville, TN, United States

Introduction: Concurrent hip/knee and spine pathology is common in the elderly population, and many patients require both total joint arthroplasty and lumbar spine surgery. It is unknown whether the timing of total joint arthroplasty in relation to lumbar surgery affects lumbar surgery outcomes. The aim of the current study was to determine whether lumbar surgery outcomes differed between patients who underwent THA/TKA before or after lumbar spine surgery. We hypothesized that patients who undergo THA/TKA before lumbar spine surgery will have better lumbar spine surgery outcomes due to improved hip/knee range of motion and reduced hip/knee pain at the time of lumbar surgery. Material and Methods: A retrospective cohort study was performed utilizing data from a prospectively collected registry. The registry was queried for patients who underwent THA/TKA and lumbar surgery within a 3-year timeframe. THA/TKA revisions, lumbar disc herniations, lumbar revisions, and lumbar deformity cases were excluded. Patients were dichotomized into: 1) THA/TKA before lumbar surgery and 2) THA/TKA after lumbar surgery. Covariates included age, gender, BMI, type of joint replacement (unilateral vs bilateral), spine pathology, spine approach, number of operated spine levels, length of hospital stay, and discharge disposition. Outcomes included 1) 3- and 12-month numeric rating scale (NRS) back pain, NRS leg pain, Oswestry Disability Index, Patient Health Questionnaire-9 (PHQ-9) scores and North American Spine Society patient satisfaction scores, 2) Length of hospital stay and discharge disposition, and 3) 3-month rate of complications, readmissions, and revisions. Three separate analyses were performed: THA/TKA grouped together, THA alone, and TKA alone. Results: Of 108 eligible patients, 52 underwent THA/TKA before lumbar surgery, while 56 underwent THA/TKA after lumbar surgery. There were no significant differences in any demographic or baseline variable. Bivariate analysis showed no differences in spine surgery outcomes between groups. Multivariate regression showed timing of THA/TKA in relation to lumbar surgery was not associated with a change in any 3- or 12-month PROs or complications. A sub-analysis consisting of only THA patients included 34 patients, of which 17 underwent THA before lumbar surgery and 17 underwent THA after lumbar surgery. Bivariate analysis showed no differences in any spine surgery outcome. Multivariate regression showed THA after spine surgery was associated with higher/worse 12-month PHQ-9 scores (p < 0.001). A sub-analysis consisting of only TKA patients included 74 patients, of which 35 underwent TKA before lumbar surgery and 39 underwent TKA after lumbar surgery. The group that underwent TKA after lumbar surgery had higher baseline NRS leg pain scores (p = 0.046). Bivariate analysis showed no differences in any spine surgery outcome. Multivariate regression showed TKA after lumbar surgery was associated with lower/better 12-month PHQ-9 scores (p = 0.043). Conclusion: These results suggest that timing of THA and TKA in relation to lumbar surgery was not associated with a change in clinical outcomes following lumbar surgery with the exception of PHQ-9 scores in the individual THA and TKA sub-analyses. Thus, we recommended that the severity of symptoms as well as patient preference dictate surgical order for patients with concomitant hip/knee pathology and degenerative lumbar spine disease.

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P224: Predictive factors for discharge disposition after surgery for degenerative lumbar spondylolisthesis

Anna Filley ¹ , Avionna Baldwin ¹ , Khuzaima Rangwalla ¹ , Faisal Bawahab ¹ , Ashraf El Naga ¹ , David Gendelberg ¹ , and Sigurd Berven ¹

¹ Orthopaedic Surgery, University of California, San Francisco, United States

Introduction: Early discharge planning is important for reducing length of hospital stay, minimizing unnecessary utilization of inpatient resources, and optimizing the cost-efficacy of surgical treatment. Particularly for orthopaedic surgical patients, a period of rehabilitation or additional assistance may be required in the immediate postoperative period, making an accurate assessment of each patient’s functional needs crucial for facilitating a safe, efficient discharge from the hospital. The purpose of this paper is to identify medical and socioeconomic factors that may impact discharge disposition. Material and Methods: Retrospective study of 184 consecutive patients who underwent elective surgical treatment of symptomatic degenerative spondylolisthesis at our institution between January 2016 and June 2020. The primary outcome was discharge disposition, either to home (with or without additional services) or to a non-home location (acute rehab or skilled nursing facility). Bivariate analysis was used to compare patient groups by preoperative demographics, medical comorbidities, and surgical characteristics in order to identify factors associated with discharge disposition. Results: Eighty-eight patients (47.6%) were discharged to home, 60 (32.4%) home with additional support services, 17 (9.2%) to acute rehab, and 19 (10.3%) to a skilled nursing facility (SNF). Among all patients, those who were not partnered (single, divorced, or widowed) had greater odds of a non-home discharge (OR: 3.57, p = 0.001) than those who were partnered (married or with significant other). Compared to patients discharged home, those discharged to acute rehab were also more likely to identify as black or multi-racial (OR: 4.88, p = 0.0049). Despite undergoing similar procedures (operation type, surgical invasiveness index, procedure duration, blood loss), patients with a non-home discharge had a significantly longer length of hospitalization than those discharged home (p < 0.0001). A non-home discharge was also associated with older patient age, lower baseline functional status, and a greater number and severity of comorbidities. Conclusion: Patient age, race, relationship status, baseline functional capacity, and comorbidities are predictive of discharge disposition following surgical treatment of degenerative lumbar spondylolisthesis. Attention to these factors may assist with early discharge planning and identification of patients who may need additional assistance postoperatively.

1254

P225: Adjacent segments disc disease to lumbar and lambosacral arthrodesis: clinical asepcts, risk factors and management

Safouen Ben Brahim ¹ , Mzid Ahmed ¹ , Benjeddou Wassim ¹ , Khalil Habboubi ¹ , Hassen Makhlouf ¹ , and Mondher Mestiri ¹

¹ Adult Orthopedic Departement Pr Mestiri, Mohamed Taib Kassab, Mannouba, Tunisia

Introduction: Lumbar fusion has shown to be an effective surgical management option when indicated, improving patient outcomes and functional status. However it produces abnormal mechanical conditions at mobile segments above or below the site of spinal disorders and is clinically referred to as adjacent segments disc disease (ASDD) or transition syndrome in the case of a previous surgical treatment. Methods and Designs: It’s a retrospective descriptive study of 32 patients who had undergone decompression and instrumented lumbar fusion of two or more vertebrae over 8 years. The parameters studied were - after an initial arthrodesis - clinical signs including pain, use of analgesics, neurogenic claudication and neurological deficit. It should be noted that radiological exploration by cross-sectional imaging was done in patients with severe symptomatology only. Results: 32 patients were contacted and completed the clinical form with a follow-up of 8 years. The average age was 58.6 years. The re-intervention rate was 7.8%. A neurological deficit was present in 11.3%. Radiological degeneration was present in 78.3%. The results of our study are consistent with those of the literature and are in favor of an acceleration of adjacent level degeneration and confirm a statistically significant relationship between age, weight, extent of arthrodesis and its level and surgical technique. Conclusion: Adjacent segment disease and degeneration remain a multifactorial problem with several techniques being developed recently to minimize them. However, there is no definitive data or knowledge about the incidence or risk factor to ASDD.

1290

P226: International validation of the SORG machine learning algorithm for predicting prolonged opioid prescriptions in opioid-naive lumbar spine surgery using 2,795 patients from Taiwan

Shin-Fu Chen ¹ , Chih-Chi Su ¹ , Chuan-Ching Huang ¹ , Paul Ogink ² , Yin-Tien Kao ¹ , Hung-Kuan Yen ¹ , Olivier Groot ² , Aditya Karhade ¹ , Yen-Po Lin ¹ , Chih-Wei Chen ¹ , Wei-Hsin Lin ¹ , Juin-Jen Yang ¹ , Mao-Hsu Yen ¹ , Jorrit-Jan Verlaan ² , Joseph Schwab ³ , Tze Hong Wong ¹ , Shu-Hua Yang ¹ , and Ming-Hsiao Hu ¹

¹ National Taiwan University Hospital, Taiwan

² University Medical Center Utrecht

³ Massachusetts General Hospital

Introduction: Identifying patients at risk of prolonged opioid use after surgery could lead to appropriate prescription and more personalized treatment plans. The Skeletal Oncology Research Group machine learning algorithm (SORG-MLA) had been developed to predict the risk of prolonged opioid use in opioid-naive patients after lumbar spine surgery. However, its utility in a geographically and medicolegally distinct country remains unknown. Therefore, we sought to externally validate the SORG-MLA in a Taiwanese patient cohort undergoing lumbar spine surgery. Material and Methods: This is a retrospective study at a large academic medical center in Taiwan. Overall, 2,795 patients were included who were 20 years or older undergoing a primary procedure for lumbar decompression surgery from 2010 to 2018. The outcome of interest was prolonged opioid prescription defined as sustained prescription opioid use exceeding 90 days after surgery Discrimination (area under received characteristic operating curve [AUROC] and area under precision-recall curve [AUPRC]), calibration, overall performance (Brier score), and decision curve analysis were used to assess the performance of SORG-MLA in the validation cohort. Results: Among 2,795 patients, the prolonged opioid prescription rate was 5.2%. The validation cohort differed with the developmental cohort on several variables, such as older age, more impatient disposition, and more common pharmaceutical history of NSAIDs. Despite the differences, the SORG-MLA provided a good discriminative ability (AUROC of 0.71 and AURPC of 0.36), a good overall performance (Brier score of 0.044 compared to that of 0.039 in the developmental cohort). However, the probability of prolonged opioid prescription tended to be overestimated (calibration intercept of -0.07 and calibration slope of 1.45. Decision curve analysis suggested greater clinical net benefit in a wide range of clinical scenarios. Conclusion: The SORG-MLA retains good discriminative abilities and good overall performances despite being applied in a medicolegally different region. It is validated for use in Taiwan to predict high-risk patients preoperatively. Future studies should test this model in real clinical practice by targeting high risk patients with instrumentations.

1334

P227: Management of massive lumbar intervertebral disc herniation in young adults: discectomy versus arthrodesis by posterior lumbar interbody fusion

Benjeddou Wassim ¹ , Khalil Habboubi ¹ , Ben Mohamed Oussema ¹ , Meddeb Mehdi ¹ , Hassen Makhlouf ¹ , and mondher mestiri ¹

¹ Adults Service, Institut Med Taieb Kassab, Mannouba, Tunisia

Background: Symptomatic massive lumbar intervertebral disc herniation (LDH) is not rare in young adults. To date, the treatments available for young adults LDH, and the effect of each treatment, have not been fully reviewed. In our serie, two surgical techniques were used: discectomy and arthrodesis by PLIF. Objective: The purpose of this retrospective study is to report the etiology, familial history, presenting symptoms, level of herniation, duration of symptoms, radiological findings, as well as treatment methods and outcome. Methods: We retrospectively reviewed medical records of all patients with inclusion criteria with ages ranging from 18 to 45 years and with massive disc herniation; we used magnetic resonance imaging (MRI) or saccoradiculography to confirm herniations between 2003 and 2018. All patients were followed up for a minimum of 4 years. 11 Our patients were treated conservatively, 37 were treated with surgical procedures, 23 patients with discectomy, 11 patients with arthrodesis by PLIF. The Visual Analogue Scale (VAS), as well as the Oswestry Disability Scale (ODS) was used to analyze physical examination findings both before and after treatment. To detect lumbar disc degeneration, we used the modified Pfirrmann grading system with MRI. All statistical analyses were performed with commercially available SPSS 20.0 software, while p ≤ 0.05 was considered statistically significant. Results: A total of 48 cases with lumbar disc herniation have been treated. The mean age was 35,02 years (range 18-45 years). The male to female ratio was 1.18. concerning the delay of consultation 50% consulted within the first 6 months, 18.8% between 7 months and one year, and 31.2% within more than one year. The most common level was L4-5 in 47,9 % patients and the second was L5-S1 in 27.1% patients. Subligamentous protruded discs were found in 55.8%, extruded in 43.9%, and disc bulge with intact annulus in 10.3% cases.. The ODS was indexed before and after treatment, a change from major disability to minimal or moderate disability was noted during the follow-up. VAS and the OSD were both significantly decreased after treatment (p < 0.05). Conclusions: Either conservative or surgical methods can be performed comfortably for young adult lumbar disc herniations. We proposed surgical treatment for patients with persistent disabling low back pain or radicular pain that lasted more than 6 weeks, in spite of a well conducted medical treatment. We also looked for recurrent pain that disrupted normal life activities, the appearance of neurological deficits and neurogenic claudication. All these parameters contributed to the therapeutic decision.

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P228: Surgical outcome following lumbar interbody fusion in a low income population: quality of life improvement

Houssem Eddine Chahed ¹ , Mohamed Amine Gharbi ¹ , Ahmed zendeoui ¹ , Moatassem Belleh Jlassi ¹ , and Mouadh Nefiss ¹

¹ Orthopedic and Trauma Surgery, Mongi Slim Marsa University Hospital Center, Tunis, Tunisia

Introduction: Health-related quality of life in patients who underwent Lumbar interbody fusion surgeries including transforaminal lumbar interbody fusion (TLIF), posterior lumbar interbody fusion (PLIF), oblique lumbar interbody fusion/anterior to psoas (OLIF/ATP), and anterior lumbar interbody fusion (ALIF), has been emphasized recently. Yet, there is no data on Lumbar interbody fusion outcomes from developing regions. Our aim of our study was to determine the changes in quality-of-life following Lumbar interbody fusion repair in a low-income population. Material and Methods: This is a retrospective case series. 128 patients subjected to lumbar interbody fusion surgeries with a minimum of 2 year’s follow-up were evaluated. Patients were asked about monthly family income and completed the visual analog scale (VAS) pain score, the Roland–Morris disability scale, and the World Health Organisation Quality-of-life Scale Abbreviated Version (WHOQOL-BREF) before surgery, and at 3, 6, and 12 months after surgery. Satisfaction was estimated by a yes or no question. Results: The mean age of patients was 58 years-old, there were 105 (82%) women and 23 (18%) men. Over 95% declared < 1000 US$ monthly family income. The mean duration of symptoms was 35 months (range, 4– 60 months). procedures were performed by different surgeons. Satisfied were 58% of patients, partially satisfied were 23% and dissatisfied were 19% of patientsThe mean WHOQOL-BREF score increased from 56.8 before surgery to 64.1 at 12 months after surgery. The mean VAS pain score decreased from 7.1 before surgery to 2.9 at 12 months after surgery. Conclusion: Surgical outcomes lumbar interbody fusion surgeries in a low-income population showed an improvement in health-related quality of life with decreasing pain and increasing functional ability from 3 months after surgery. Our findings suggest that successful Lumbar interbody fusion may improve quality of life.

1401

P229: The technique of unilateral biportal endoscopic (UBE) assisted fusion extension for symptomatic adjacent segmental disease : a case series and technical tips and advantages

Jisoo Ha ¹

¹ Neurosurgery, Yonsei Okay Hospital, Gyeonggi do, South Korea

Objective: Conventional fusion extension surgery has long been considered the treatment option for symptomatic adjacent segmental disease (ASD) after lumbar interbody fusion surgery. However, extensive muscle dissection and revision of previous operation scar were problems of fusion extension surgeries. If we used endoscopic assistant procedure of fusion extension, extensive muscle dissection and skin incision may be reduced and, it might be easier to achieve fusion extension which relieves the rigors of open surgery. The purpose of our study is to introduce our technique of endoscopic fusion extension surgery using biportal endoscopic systems with video clips. Material and Method: From December 2019 to June 2020, 8 patients underwent fusion extension surgery for symptomatic ASD using the new-designed biportal endoscopy assisted surgical technique. As with primary endoscopic fusion surgery, this technique allows for the entire operation, including the removal of old screws and rods, through small skin incisions for percutaneous screws insertion. Old screws and rods were able to be removed under endoscopic guidance through the small step wounds over the pedicles. Interbody fusion procedures of ASD level were achieved by usual biportal endoscopic fusion approach. Thus, there is no need to periosteal dissection on the previously operated area with encountering serious surgical adhesions. Postoperative Magnetic resonance imaging (MRI) were taken routinely to measure the area of muscle damaged. Functional outcomes were evaluated using Oswestry Disability Index score, and Visual Analogue Scale, respectively. Results: We successfully performed biportal endoscopy assistant fusion extension surgery in 8 patients. There were no complications related with surgery. VAS and ODI were significantly improved after surgeries (p < 0.05). The mean operation time and estimated blood loss per one level extension were 216.3mins (185-250) and 163.8 cc (150-200). Conclusion: This procedure may be a safe and efficacious treatment option for revisional lumbar fusion extension with less morbidity than open surgery. Thus, this new-designed endoscopic based technique could be a feasible alternative to conventional fusion extension surgery, although more cases and long-term follow up studies are needed to obtain accurate clinical results.

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P230: Predictive factors of lumbar pseudarthrosis following primary lumbar fusion

Hania Shahzad ¹ , Moizzah Ahmad ² , Nazihah Bhatti ¹ , Elizabeth Yu ¹ , Frank Phillips ³ , and Safdar Khan ¹

¹ Wexner Medical Center, The Ohio State University, Columbus, United States

² The Ohio State University, Columbus, United States

³ Rush University Medical Center, Chicago, United States

Introduction: A common iatrogenic complication of lumbar fusion is pseudarthrosis which commonly presents with worsening back pain necessitating surgical intervention. Results for such revision surgeries have been relatively poor historically. Identifying demographic comorbid characteristics that are predictive of developing pseudarthrosis can enable physicians to optimize care for potentially high-risk patients. The objective of this study is to identify predictors that may be associated with a higher risk of developing pseudarthrosis in patients that undergo lumbar fusion surgery for the management of degenerative spinal diseases. Material and Methods: The PearlDiver database over 92 million MEDICARE and MEDICAID patients was utilized to identify patients who underwent lumbar spinal fusion. Patients were further grouped into those that had a claim for pseudarthrosis and those who did not within the 10-year interval following the initial lumbar spinal fusion. The primary outcome was the odds of selected demographic/comorbid factors in patients who were grouped under the claim of pseudarthrosis within 10-years following lumbar spinal fusion. Univariable model results were reported as odds ratios (OR) and 95% confidence intervals (CI). All data were analyzed in aggregate form using R Statistical Software version 4.1.0 in the PearlDiver Software. Results: The results of the query revealed a total of 304,627 patients who had undergone spinal fusion in the period 2010 to 2021. Out of the total patients, 11,401 (3.74%) received the diagnosis of pseudarthrosis following their primary surgery while 293,226 (96.26%) had no associated claim of pseudarthrosis following 10 years of their primary lumbar fusion. The average time from the first procedure to the diagnosis of pseudarthrosis was 2.5 years (SD 2.36). Chi-square analysis and univariable regression modeling revealed the factors that were associated with patients who developed pseudarthrosis. A significantly lower proportion of patients who developed pseudarthrosis were 65 years or older (OR: 0.78 [0.75, 081], p-value < 0.001). For all comorbid conditions, a significantly higher proportion of patients who developed pseudarthrosis were male (OR:1.06 [1.02, 1.10], p-value < 0.001), had a CCI score of 2 or more (OR: 1.25 [1.20, 1.30], p-value < 0.001), a prior diagnosis of alcohol abuse (OR: 1.86 [1.72, 2.00], p-value < 0.001), tobacco use (OR: 1.85 [1.78, 1.93], (p-value < 0.001), a positive history of opioid use (OR: 3.18 [2.77, 3.66], p-value < 0.001) a positive history of cannabinoid use disorder (OR: 1.72 [1.46, 2.02], p-value < 0.001), a prior diagnostic claim of osteoarthritis (OR: 1.58 [1.52, 1.64], p-value < 0.001), diabetes (OR: 1.24 [1.19, 1.30], p-value < 0.001), vitamin D deficiency (OR: 1.50 [1.43, 1.56], p-value < 0.001), and claims of a wound infection within 30 days of the primary surgery (OR: 1.45 [1.35, 1.56], p-value < 0.001). These comorbidities were only included if their claims were made before the primary lumbar fusion surgery on the patient record. Conclusion: Pseudarthrosis is a common complication of lumbar spine surgery. Our analysis outlines potential demographic and co-morbid risk factors that are associated with the development of pseudarthrosis. In these patients, physicians should optimize the modifiable risk factors while counseling the patients for the potential development of pseudarthrosis, especially in patients at higher risk.

1494

P231: Surgeon preference regarding post-operative dressing management in lumbar fusion surgery: a global cross-sectional study

Luca Ambrosio ^1,2 , Gianluca Vadalà ^1,2 , Timothy S. Yoon ³ , Matthew Gary ^3,4 , Ho-Joong Kim ⁵ , Vincenzo Denaro ² , and AO Spine Knowledge Forum Degenerative ⁶

¹ Research Unit of Orthopaedic and Trauma Surgery, Department of Orthopaedic and Trauma Surgery, Università Campus Bio-Medico di Roma, Rome, Italy

² Operative Research Unit of Orthopaedic and Trauma Surgery, Fondazione Policlinico Universitario Campus Bio-Medico, Rome, Italy

³ Department of Orthopaedics

⁴ Department of Neurosurgery, Emory University, Atlanta, United States

⁵ Department of Orthopedic Surgery, Seoul National University Bundang Hospital, Seoul National University College of Medicine, Seoul, South Korea

⁶ AO FOundation, Davos, Switzerland

Introduction: Surgical site infection (SSI) is a major cause of morbidity following lumbar spine surgery, with increased risk of pseudoarthrosis, deformity, and even death. Wound care is essential to lower the rates of post-surgical SSI, although there is no high-level evidence regarding optimal management of postoperative dressings. Indeed, indications concerning dressing policy is fragmentary and often related to local protocols rather than international guidelines. The aim of this study is to evaluate the global practice pattern of dressing use after lumbar fusion surgery in terms of type of dressing and timing of dressing change. Material and Methods: A survey issued by AO Spine Knowledge Forums Deformity and Degenerative was sent out to AO Spine members across the world. Participants’ country of practice, gender, age, years of practice, specialty, practice setting and information about spine surgery fellowship were retrieved, as well as surgical case volume. Surgeons were also asked if performing long fusions (> 5 levels) including or excluding the pelvis for adult deformities, open 1-to-2 level fusions, minimally invasive 1-to-2 level fusions or open 3-to-5 level fusions for degenerative conditions. Participants were then asked about the type of post-operative dressing usually employed, timing of initial dressing removal and type of subsequent dressing applied. Chi-squared test was performed to evaluate statistical significance. Results: A total of 280 participants from North America (18.21%), Latin America (14.29%), Europe & Southern Africa (36.07%), Middle East & North Africa (8.21%), Asia Pacific (23.21%) completed the survey. Most surgeons were male (94.64%), aged between 35 and 44 (42.14%), and practicing for at least 5 years (84.29%). Most respondents were orthopaedic surgeons (75%), practiced in and academic hospital (46.43%), completed a spine surgery fellowship (64.29%) and operated between 50 and 150 cases per year (48.21%). Following lumbar spine surgery, 71.42% utilized a dry dressing, 24.60% a plastic occlusive dressing, 5.55% applied glue, 5.95% used the DERMABOND™ PRINEO™ Skin Closure System, 3.17% an incisional wound vacuum, and 4.19% other dressings. Initial dressing was removed either on postoperative day 1 (11.63%), 2 (39.22%), 3 (20.25%), 4 (1.72%), 5 (4.31%), 6 (0.43%), 7 or later (12.5%), or depending on drain removal (9.91%). Following initial dressing removal, 75.86% applied a dry dressing, 17.67% a plastic occlusive dressing, 1.29% glue, while 12.06% used no dressing. No statistically significant differences were found when comparing type of initial dressing, timing of dressing removal and type of subsequent dressing with the type of surgery performed (i.e., length of fusion, deformity vs. degenerative cases, open vs. minimally invasive). Conclusion: Most spine surgeons utilized a dry or a plastic occlusive dressing initially applied at the end of surgery. The first dressing tended to be changed during the first 3 post-operative days and replaced with the same type of dressing in the majority of cases. However, no significant differences regarding the type of dressing and timing of dressing change were reported taking into account the length of fusion or the use of either an open or minimally invasive approach.

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P232: Clinical outcomes of percutaneous endoscopic lumbar annuloplasty and nucleoplasty for discogenic low back pain: meta-analysis

Saran Pairuchvej ¹ and Jatupon Kongtharvonskul ²

¹ Orthopedics Department, Queen Savang Vadhana Memorial Hospital, Sriracha, Cholburi, Thailand

² Orthopedics Department, Faculty of Medicine Ramathibodi Hospital, Mahidol University, Bangkok, Thailand

Objective: Percutaneous endoscopic lumbar discectomy and annuloplasty (PELDA) and nucleoplasty (PELAN) is a minimally invasive spinal technique for relief back pain in lumbar disc herniation and chronic, non-radicular, and discogenic low back pain (DLBP). The aim of the present article is to present the outcomes of the systematic review and meta-analysis regarding the short-term outcomes of this surgical technique. Methods: We searched all prospective and retrospective studies that reported post-operative VAS ODI and modified Mcnab’s criteria, complications and reoperation of percutaneous endoscopic lumbar discectomy and annuloplasty and nucleoplasty for surgical treatment of lumbar disc herniation and chronic discogenic back pain from the PubMed and Scopus databases up to 01 September 2022. Data were independently extracted by two reviewers. A meta-analysis was applied to assess treatment outcomes. Results: 13 cohort studies (N = 708 patients) met inclusion criteria. Interventions were percutaneous endoscopic lumbar discectomy and annuloplasty and nucleoplasty (PELAN) in lumbar disc herniation (N = 155) and chronic discogenic back pain (N = 553). A meta-analysis showed that the UMD of back pain Visual Analog Score (VAS), leg pain VAS and Oswestry disability index after PELAN in lumbar disc herniation were significantly difference of -2.67 (95%CI: -5.24 to -0.10), -4.10 (95%CI: -7.64 to -0.56) and -34.71 (95%CI: -55.08 to -14.34) scores when compared to before surgery while the UMD of back pain Visual Analog Score (VAS) and Oswestry disability index after PELAN in chronic discogenic back pain were significantly difference of -4.64 (95%CI: -5.28 to -4.01), and -30.56 (95%CI: -38.66 to -22.47) scores when compared to before surgery. Results by the modified Macnab’s criteria showed an excellent and good outcome, with a success rate of 34%-90% in chronic discogenic back pain and 81%-99% in lumbar disc herniation. The prevalence of complication including dura tear and nerve root injury and reoperation of PELAN in Lumbar disc herniation were 0.116 (95%CI: 0.020 to 0.212) and 0 respectively while in chronic discogenic back pain were 0.064 (95%CI: 0.022 to 0.106) and 0.045 (95%CI: 0.017 0.106) respectively. Conclusions: Percutaneous endoscopic lumbar discectomy and annuloplasty and nucleoplasty provides favorable outcomes for carefully selected groups of patients with lumbar disc herniation and chronic discogenic back pain.

Keywords: annuloplasty, nucleoplasty, PELD, Percutaneous endoscopic lumbar discectomy, ODI, VAS

1694

P233: The impact of diabetes on lumbar spinal stenosis

Peter Udby ¹ , Søren Ohrt-Nissen ² , and Thomas Vestergaard ¹

¹ Spine Surgery and Research, Zealand University Hospital, Køge, Denmark

² Spine Unit, Rigshospitalet, København Ø, Denmark

Introduction: Lumbar spinal stenosis (LSS) is a condition with a severe impact on walking distance and exercise capacity. Reduced physical activity due to LSS can increase the risk of obesity and diabetes. Diabetes (DM), an autoimmune and lifestyle disease, has been associated with a less successful outcome and increased risk of complications after spine surgery. The question is what impact Diabetes has on spine degeneration and Patient Reported Outcomes (PROs) before and after surgery in LSS patients? Material and Methods: We performed a cohort study over a nine-year period (2010-19) on patients undergoing lumbar decompression surgery due to LSS. All patients were registered in the Danish National spine registry (DaneSpine). Prospective data were collected preoperatively and at two-year follow-up. Primary outcomes were the Oswestry Disability Index (ODI), back- and leg pain scores on the visual analog scale (VAS), and quality of life (QOL) measured by the European Quality of Life-5 Dimensions (EQ-5D) index score. Results: A total of 362 patients were included, 311 patients without Diabetes (-DM) and 51 with Diabetes (+DM). The DM+ group had significantly worse disability scores and reduced QOL compared to the -DM group preoperatively (p > 0.05). Both groups obtained significant improvement in all primary outcomes at two-year follow-up (p > 0.01). The improvement was similar for both groups (ΔODI and ΔEQ-5D, p < 0.05). At two-year follow-up, the +DM still had significantly worse ODI and EQ-5D-scores compared to the -DM group (p > 0.05). Pre- and postoperatively back and leg pain scores including Δ-values were similar for the two groups (p < 0.05). Conclusion: Patients suffering from LSS and DM have significantly worse QOL and disability both preoperatively and at two-year follow-up compared to patients without DM. Both groups of patients experience a significant improvement in disability, QOL, and pain scores at two-year follow-up. Physical exercise is important in the management of DM. Therefore, we advise that additional focus is directed at the identification and treatment of LSS patients with concomitant DM.

1759

P234: Surgeon preferences in peri-operative drain utilization in open 1- or 2- level fusion surgery for lumbar degenerative pathologies

Juan P. Cabrera ¹ , Timothy S. Yoon ² , Matthew Gary ³ , Ho-Joong Kim ⁴ , Jeffrey C. Wang ⁵ , Samuel Cho ⁶ , Zorica Buser ⁷ , Patrick Hsieh ⁸ , and AO Spine Knowledge Forum Degenerative ⁹

¹ Department of Neurosurgery, Hospital Clínico Regional de Concepción, Concepción, Chile

² Department of Orthopedics

³ Department of Neurosurgery, Emory University, Atlanta, United States

⁴ Spine Center and Department of Orthopedic Surgery, Seoul National University Bundang Hospital and Seoul National University College of Medicine, Seoul, South Korea

⁵ Department of Orthopedic Surgery, Keck School of Medicine, University of Southern California, Los Angeles, United States

⁶ Department of Orthopedic Surgery, Icahn School of Medicine at Mount Sinai, New York, United States

⁷ Department of Orthopedic Surgery, NYU Grossman School of Medicine, New York, United States

⁸ Department of Neurological Surgery, Keck School of Medicine, University of Southern California, Los Angeles, United States

⁹ Research Department, AO Spine International, Davos, Switzerland

Introduction: Avoiding wound-related complications in open fusion surgery for degenerative lumbar conditions is critical to patients and surgeons. The variation in peri-operative management can be associated with differences in the incidence of such complications, including post-operative drain use. Therefore, this study aims to analyze the surgeon preferences related to drain utilization and the factors influencing drain use and management. Material and Methods: A survey was distributed to AO Spine members worldwide to elucidate the variation in drain use and management around the globe. Surgeon demographics and factors related to peri-operative drain use in 1 or 2-level open fusion surgery for lumbar degenerative pathologies were collected. In addition, we conducted a comparative analysis between surgeons that use peri-operative drain (DG) and surgeons that do not use drains (ND) with univariate and multivariate analysis using binary logistic regression. Results: 231 surgeons responded to the survey, including 220 males (95.2%) and 11 females (4.8%) between the ages of 25 and 44. There were 100 responses (43.3%) from Europe, 83 from (35.9%) Southern Africa, and 50 responses (21.6%) from the Asia Pacific. Most surgeons are orthopedics (178, 77.1%), and almost half of the respondents are in academic/university-affiliated practices (114, 49.4%). The survey revealed that the overwhelming majority of surgeons worldwide utilize drains in their surgery for degenerative lumbar conditions (186, 80.5%). In comparison, less than 20% of surgeons do not use drains (45, 19.5%). In addition, almost all surgeons prefer to place subfascial drains (178, 77.1%). Drain duration after placement is variable, with drain removal on day 2 for 33.3% of surgeons, while 29.4% of surgeons based their decision on drain duration outputs. 15.6% of surgeons remove drains when output is < 50 mL per 24 hrs, while 10% remove drains when the output is between 50 to 100 mL in 24 hrs. On multivariable analysis, significant predictors of drain use were age 35 - 44 (OR = 11.9, 95% CI = 1.2-117.2, p = 0.034), age 45 – 54 (29.1, 3.1-269.6, p = 0.003), age 55 - 64 (8.9, 1.4-56.5, 0.019), and wound closure using Steri-Strips (6.0, 1.2-29.0, p = 0.025). Conclusion: The majority of spine surgeons worldwide prefer to place a post-operative drain for open lumbar fusion surgery. Subfascial drain placement is preferred by most, but drain duration after surgery varies widely based on surgeon preference. Finally, the choice for peri-operative drain placement is significantly associated with the surgeon's age and the use of Steri-strips for wound closure.

1824

P235: Cauda equina syndrome following decompression for spinal stenosis. A very rare yet fearsome complication in a very common spinal procedure

Mariano Vitelli ¹ , Giovanni Barbagli ¹ , Elisabetta Peppucci ¹ , Nicoletta Gargiuoli ¹ , Alexander Evins ² , Alessandro DiChirico ¹ , and Sandro Carletti ¹

¹ Neurosurgery, IFCA Firenze, Italy

² Weill Cornell Medical College, Neurosurgery, New York, United States

Introduction: Cauda equina syndrome (CES) is one of the fearest complication of lumbar disc herniation; however, a cauda equina syndrome (with or without motor symptoms) is a very rare complication following a spinal decompression procedure for spinal stenosis. When this complication occurs surgical exploration remains the prevailing type of management. In this study we describe a case of post-operative partial cauda equina syndrome, without motor dysfunction, following decompression for spinal stenosis. Material and Methods: We present a case of a 47 years old man admitted at our institution for a Adjacent Segment Disease (ASD) at L3-L4 following a L4-L5 posterior lumbar fixation (PLF) in another hospital. Physical Examination (PE) at admission showed back pain with bilateral radicular pain at lower legs. The patient underwent a L3-L4 decompression with posterior screw fixation in order to connect this segment to the one already fixed. The decompression was achieved under the guidance of the operative microscope. The procedure has been reported uneventful and blood loss was less than 100 mL. On the post-operative day 1 (POD) patient developed a pinpoint anesthesia in the perineal area (encompassing the entire scrotal area and the penile surface) without any sensitive or motor deficits at the lower limbs. Patient underwent imaging studies (CT scan and MRI) that showed no extrinsic compression or alteration to the neural structures. Patient underwent intermittent catheterization and start to recover spontaneously both the sensation and the urinary retention from the POD 5. Authors carried out a complete literature review examining the current data on PubMed and MEDLINE. Results: The literature about this tricky situation lacks of sources; however, a cauda equina syndrome following spinal decompression for spinal stenosis is somewhere reported. The literature shows that the incidence ranges from 0.08-2%, and the principal factors implicated are compressive lesions such as epidural hematomas, fat pad grafts or gel foam. In rare cases there is no evidence of extrinsic compression at imaging studies. In our belief, according with the Parke's neuro-ischemic theory, it might depend on scarce blood supply below the conus medullaris. Moreover, the chance to get a CES following a spinal decompression could be related to the severity of the stenosis and consequent edema at the decompression. We should also consider that, in our case, the stenosis was not related to arthrosis yet was due to a ASD which, as well known, is an even more stressful situation for the neural structures. Conclusion: Cauda equina syndrome (CES) following a spinal decompression for lumbar stenosis is a very rare yet frightful complication. The vast majority of cases solve spontaneously in weeks but not all patient completely recover from it. Further studies, as clinical series or meta-analysis of current literature are needed to provide more awareness of this serious complication.

1829

P236: Anterior lombar interbody fusion (ALIF) surgery - the first seven consecutive cases

Ricardo Sousa ¹ , Pedro Batista ¹ , Raquel Ricardo ¹ , Bárbara Costa ¹ , Filipe Castelo ¹ , and Alfredo Carvalho ¹

¹ Orthopaedics, Centro Hospitalar Universitário Cova da Beira, Covilhã, Portugal

Introduction: Anterior lumbar interbody fusion (ALIF) surgery, though introduced in the mid 20th century, has only been universally accepted in recent years. This approach allows direct access to the anterior spinal column through the abdomen, hence mitigating the potential for severe neurological lesions. Injury to the iliac vessels and hypogastric plexus are the primary concerns. The present study aims to describe the initial experience and outcomes with ALIF surgery in a district hospital. Material and Methods: By review of patients’ medical files, questionnaires and direct examination, we analysed seven individuals with a mean age of 50 years (range 42 to 63 years), 29% males and 71% females. All seven patients presented L5-S1 degenerative disc disease, four of which additionally suffered from instability. Therefore, all patients underwent ALIF surgery with further posterior percutaneous screw fixation in those cases of instability. All procedures were performed by the same surgical team with both the abdominal approach and lumbar exposure beeing carried out by general surgeons. The Oswestry Disability Index (ODI) and Numeric Pain Rating Scale (NPRS) for both lower back and radicular pain were applied. We also registered post-operative complications and established a timeline between the patients’ first symptoms, the surgery and the final interview. Additionally, patient’s satisfaction levels regarding the treatment were surveyed. Results: An overall positive response to the treatment was clear. Apart from mild constipation felt in some cases, major surgical complications were not reported and the postoperative period was uneventful. After a minimum follow-up of six months, all seven patients were experiencing either minimal or moderate disability (ODI) and only one had more than mild pain (NPRS). At the final interview, all patients showed elevated levels of satisfaction regarding the surgical outcome. Conclusion: We conclude that ALIF surgery can be a safe, well-tolerated, effective technique in carefully selected cases. Convincing results were obtained even in the early stages of the learning curve. Thus, it should be considered as a viable alternative to other conventional approaches in the treatment of L5-S1 degenerative disc disease, particularly if spondylolisthesis is present or previous posterior surgery was performed.

1857

P237: Degree of fat degeneration of preoperative paraespinal muscles as prognostic factors of clinical outcomes in post-operated patients with l4-l5 lumbar degenerative spondylolithesis

Saul Solorio Pineda ¹ , Alejandro Reyes-Sánchez ¹ , Luis Miguel Rosales Olivarez ¹ , Baron Zarate-Kalfopulos ¹ , Armando Alpizar Aguirre ¹ , and Carla García-Ramos ¹

¹ Spine Surgery Department, Instituto Nacional de Rehabilitacion, Mexico City, Mexico

Background: The multifidus muscle is the most important stabilizer of the lumbar spine, spanning the lumbosacral junction and having a prominent influence on sagittal alignment. Defects of the paraspinal muscles cause degeneration of the intervertebral disc. Its size is reduced in patients with chronic low back pain compared to healthy individuals. Objectives: To evaluate the influence of the degree of fatty degeneration of the preoperative paraspinal muscles on the clinical results of lumbar spine surgery. Material and Methods: A retrospective, observational and descriptive analysis of 53 patients aged 30 to 59 years with a diagnosis of lumbar degenerative spondylolisthesis, operated on fixation and posterior lumbar L4-L5 arthrodesis at the National Institute of Rehabilitation "LGII" in a period of 5 years was carried out. January 2015 to December 2020. An analysis of the epidemiological, clinical and post-surgical variables of interest was performed. Preoperative T2-weighted images (T2WI) axial fast spin-echo sequence spin-echo magnetic resonance imaging examinations of the lumbar spine were reviewed, evaluating the volume and degree of fatty degeneration of the paraspinal muscles at the L4-L5 level by 2 Independent observers, these results were correlated with the aforementioned variables as well as with the pre- and post-surgical functional scales (VAS, ODI, Roland-Morris and SF36 physical/mental). Results: 32.1% (17/53) belonged to male patients and 67.9% (36/53) belonged to female patients. The age at the time of surgery was 53.72 ± 4.7 years. The degree of degenerative spondylolisthesis was presented in 54.7% (29/53) grade 1 and 45.3% (24/53) grade 2. An evaluation of the 4 degrees of fatty degeneration was made, being grade 2 the most frequent in 37.7% (20/53). Surgical time in minutes 187.28 ± 81.62 (Minimum 80 – Maximum 480); Bleeding in milliliters 437.92 ± 322.18 (Minimum 100 – Maximum 1600). Correlations were made using the Pearson test, between the degree of clinical improvement using scales (VAS, Oswestry, Roland-Morris and SF36 physical/mental) and fatty degeneration. For this purpose, groups 1 and 2 were joined under the term "mild degeneration" and groups 3 and 4 under the term "severe degeneration". It was determined if the degree of fatty degeneration influenced bleeding, surgical time, presence of complications without finding any association between the variables. Just as the rest of the correlations and associations did not show differences between other factors, such as gender or the rest of the comorbidities, no factor was associated with complications. Conclusion: With the present study we determined that the fatty degeneration of the paraspinal muscles does not influence the clinical results at one year of follow-up in patients with degenerative spondylolisthesis L4-L5.

Keywords: Degenerative spondylolisthesis, fatty muscle degeneration, low back pain

1887

P238: Intradural lumb disc herniation

Eya Chahed ¹ , Sliti Firas ¹ , Nessrine Nessib ¹ , Khalil Ghedira ¹ , Abdelhafidh Slimane ¹ , and nadhir karmani ¹

¹ Neurosurgery, National Institute of Neurology, Tunisia

Although lumbar disc herniation is very common, intra dural lumbar discal hernia is one of its rare complications. Less than 100 cases have been documented to this day. The frequency of intra dural lumbar discal hernia is very low. The most common level is L4-L5. Research have proven that it is mainly seen in men. Age is approximatively around 40-60. Symptoms vary between acute cauda equine syndrome and simple radiculalgia. Sciatic pain evolving for many years before the diagnosis is very usual. In 26% of cases there is a spinal intervention during the weeks preceding the diagnosis. MRI is the modality of choice for the diagnosis. It shows the intra dural hernia and even some epidural bone fragments. Enhancement on Gadolinium injection in T1 weighted sequences can indicate an arachnoiditis. We present the description of two cases of two male patients who were operated at the National Institute of Neurology in Tunisia. The first one is 42 years old, who came for sciatica and urinary incontinence. The exam showed a neurological L5 deficit. Lumbar CT scan showed a rounded intra canal lesion in L5S1 suggesting a neuroma. MRI however proved that it was in fact an excluded hernia at the level of L5-S1. The patient had a laminectomy of L5 and S1 and we discovered disc material on the posterior surface of the dura mater. Post operatively, the patient recovered from his neurological deficit. The second patient is a 36 year old male who presented for lumbosciatalgia that has been evolving for 7 years and urinary impetuosity evolving for 3 months. The exam objectified a L5 band hypoesthesia. Lumbar MRI showed a mediane disc herniation in L3-L4 migrated upwards conflicting with the 2 L4 roots and the contents of the dural sheath. He also had a laminectomy of L3 and L4. During surgery, we discovered disc material on the anterior surface of the dura mater. Postoperative course was uneventful. In conclusion, intra dural lumb disc hernia is a rare pathology. In most cases, it translates as an acute cauda equine syndrome or a lumbar radicular syndrome. MRI is the modality of choice for the diagnosis. Prognosis in uncertain.

1892

P239: Prospective study of functional and radiological outcome of TLIF (Transforaminal Lumbar Interbody Fusion) in lumbar spine instability in adults

Yash Mehta ¹ , Sunny Shethna ¹ , and Vishal Mandlewala ¹

¹ Orthopedics, New Civil Hospital, Surat, India

Introduction: Prospective Study Of Functional And Radiological Outcome Of TLIF (Transforaminal Lumbar Interbody Fusion) In Lumbar Spine Instability. Instability mainly due to Spondylolisthesis, is anterior slippage of vertebra on to the one below. Lumbosacral junction is most commonly involved. Spinal fusion, indicated in patients with severe symptoms and radiographic evidence of increased instability, is performed by grafting intervertebral disc space, preventing its collapse after discectomy and maintaining height of neural foramen, keeping root free of bony compression. Methods and Materials: Study was carried out in New Civil Hospital, Surat from December 2019 to October 2021.The prospective study consisted of total 20 patients of Lumbar Instability who satisfied inclusion criteria. All cases were treated with TLIF surgery. TLIF is posterior interbody fusion through lateral unilateral approach to disc space through neural foramen by removing facet joint, allowing access to disc space through triangular “safe zone” between the exiting nerve root and lateral dural edge. All patients were followed up immediately, 3^rd month, 6^th month,1 year. In each follow up, X ray were taken to assess radiological outcome and ODI, VAS score for functional outcome. Results: 90% Patients showed radiological Fusion, 10% patients showing no fusion. Both ODI, VAS scores progressively decreased after surgery. Mean values of ODI of patients with fusion vs those without fusion, pre operatively were 53.2 vs 63.5. At immediate, 3 month, 6 month, 1 year postoperative period were 50.1 vs 59.5; 34.5 vs 42.5; 21.6 vs 26; 12.2 vs 19.5. Mean values of VAS scores of patients with fusion vs those without fusion, pre operatively were 8.9 vs 9.5. At immediate, 3 month, 6 month,1 year postoperatively were 5.2 vs 6; 2.8 vs 3.5; 1.5 and 1.5; 0.6 vs 1.Study showed 15% complication rate. Conclusion: Patients treated with TLIF using posterior pedicle screw instrumentation + anterior cage yields good functional, radiological outcome with high fusion rate and low complication rate.

Keywords: TLIF, Lumbar instability, VAS, ODI

1904

P240: Mini open SA-ALIF with hyperlordotic cages in surgical treatment of degenerative disc disease and cerrection of spinal sagittal misalignment

Dimitar Haritonov ¹

¹ Neurosurgery and Spinal Surgery, Heart and Brain Hospital, Pleven, Bulgaria

Introduction: Since the introduction of threaded devices in the mid-1990s, anterior lumbar interbody fusion (ALIF) has become a staple in the armamentarium of the spine surgeon. We aim at analysing the impact of stand alone anterior lumbar interbody fusion (SA-ALIF) in treatment of degenerative disc disease (DDD) and restoring the main spinopelvic parameters, along with its potentials and limitations in correcting sagittal imbalance of the approach and implanted hardware. Material and Methods: Total 72 patients with DDD and spinal misalignment were treated surgically and followed up in Department of Neurosurgery and Spinal Surgery – University Hospital Heart and Brain Pleven for period of 2 years. The following spinopelvic parameters were observed and corrected: pelvic tilt (PT), sacral slope (SS), lumbar lordosis (LL), segmental lumbar lordosis (LLseg) and sagittal vertical axis (SVA). Most of the patients (80 %) received hyperlordotic cages (HLC). The indirect decompression potential of ALIF was also assessed. The clinical outcome was obtained by collecting visual analogue scale (VAS) for back and leg pain and Oswestry Disability Index (ODI) scores. Global fusion rate and main complications were collected. Preoperative dynamic X-Ray, CT scan with venogram, bone density and MRI were performed. Postoperative CT scan on 3 and 6 month were done. Results: PT, SS, LL, LLseg and SVA spinopelvic parameters all improved postoperatively by - 4.3 ± 5.2°, 3.9 ± 4.5°, 10.6 ± 12.5°, 6.7 ± 3.5° and 51.1 ± 44.8 mm, respectively. HLC were statistically more effective in restoring LL and LLseg (p < 0.05). Postoperative disc height, anterior disc height, posterior disc height and foraminal height, respectively, increased by 58.5%, 87.2%, 80.9% and 18.1%. Postoperative improvements were observed in VAS back and leg and ODI scores (p < 0.05). The global fusion rate was 94.5 ± 5.5%; the overall complication rate was less than 5%. Conclusion: When managing degenerative disc disease and sagittal imbalance, SA-ALIF can be considered as a valid and reliable technique to achieve the correct spinopelvic parameters even in single level surgery based on preoperative planning. This technique permits to obtain an optimal LL distribution and a solid anterior column support, with lower complications and higher fusion rates when compared to posterior approaches. Using a hyperlordotic cages is a milestone for improving the postoperative results.

1961

P241: Association between preoperative paraspinal muscle mass and quality, and clinical outcomes after lumbar spinal fusion: an observational cohort study

Esther Janssen ^1,2 , Bart Bongers ³ and Paul Willems ¹

¹ Orthopaedics, Maastricht UMC+, Maastricht, The Netherlands

² VieCuri MC, Orthopaedics, Venlo, The Netherlands

³ School of Nutr and Transl Res in Metab, Maastricht University, Maastricht, The Netherlands

Introduction: Patients suffering from a spinal disorder may show a reduction of muscle mass (atrophy) and increased fat infiltration (myosteatosis) in the paraspinal muscles on MRI. Studies have identified that muscle atrophy and myosteatosis in the paraspinal muscles is predictive of morbidity and mortality after major abdominal surgery. As lumbar spinal fusion (LSF) is major surgery, atrophy and myosteatosis of the paraspinal muscles may also be predictive of outcomes after LSF. If so, preoperative MRI results can be used as a predictor to aid the surgeon in calculating a patient’s expected outcome and risk for complications after surgery. Therefore, the aim of this study was to investigate whether muscle atrophy and myosteatosis in paraspinal muscles, is associated with complications, length of stay (LoS), functional recovery, and one-year postoperative reduction in pain in patients undergoing elective LSF. Material and Methods: Patients undergoing elective 1-3 level LSF because of a degenerative disorder of the lumbar spine were included in this retrospective cohort. Patients filled out the visual analogue scale (VAS) for leg and back pain both pre- and postoperatively, and the difference between pre- and one-year postoperative VAS was used as a dependent variable. Functional recovery was measured using the modified Iowa level of assistance scale (mILAS). To measure muscle atrophy, the cross-sectional area (CSA) was calculated. To determine myosteatosis, the functional cross-sectional area (FCSA) was measured. The amount of fatty infiltration (lean muscle ratio) was measured by calculating a ratio of FCSA divided by CSA. Measurements were taken from the transversal coupes of L5 from the preoperative MRI scan. To determine the association between muscle atrophy, myosteatosis and lean muscle ratio, and surgical outcomes, a Pearson’s or Spearman’s correlation was calculated. Results: 130 patients were eligible, of which 12 were excluded as their MRI-scan showed scattering. Eighteen patients (15,2%) had a complication of which 11 were minor. Mean LoS was 7.02 days (SD ± 3.02) and the mean functional recovery time was 5.33 days (SD ± 2.70). Analysis of the complications, LoS and functional recovery time in relation to the CSA, FCSA, and lean muscle ratio of the paraspinal muscles showed no correlation (r: -0.417 to 0.124). The difference between one-year postoperative and baseline pain also showed there was no correlation between any of the dependent variables with the CSA, FCSA, or lean muscle ratio of the paraspinal muscles (r: -0.190 to 0.377). Conclusion: Muscle atrophy, myosteatosis, and lean muscle ratio of the paraspinal muscles on preoperative MRI showed no association with any of outcome after LSF. These parameters measured at a single time point may therefore not be predictive of clinical outcome after LSF. However, these parameters do not consider individual changes in muscle over time. Moreover, we did not explore the association with physical functioning. Therefore, a next step would be to study the relation between paraspinal muscle atrophy and fatty infiltration over time and functional outcomes after LSF.

1971

P242: Role of pedicle screw augmentation in decreasing the reparations rate following posterior lumbar inter body fusion

Pablo Mendivil ¹

¹ Neurocirugía, Unidad de Cirugía Espinal Compleja y Minimamente Invasiva - Neurocentro Salta - IMAC Instituto Medico de Alta Complejidad, Salta, Argentina

Objective & Background: Posterior spinal arthrodesis is the most commonly used spinal fusion procedure. The main middle and long-term causes of reoperation are adjacent segment disease and screw loosening. The objective of the present work is to determine the relevance of pedicle screw loosening in the reoperation rate after lumbar interbody fusion, identify risk factors and incidence, and assess the impact of pedicle screw augmentation. Methods: We analyse retrospectively the data of 318 patients, mean age 54 years (± 9.6, range 18 to 84) who underwent posterior lumbar interbody fusion (miss 163 - open 155) and 57 patients, 69 years mean age (± 8.1, range 53 to 82) who underwent posterior lumbar interbody fusion with pedicle screw augmentation between March 2015 and March 2022 looking for screw loosening, reoperation rate and other surgical complication. The mean of follow-up was 31.8 ± 8.2 months (range, 6 to 84 months). As part of the post-operative patient’s study protocol, 24 Hs. 6 months ± 12 months CT scan was performed. Results: 41 patients underwent a reoperation (10.9 %) at our spinal unit after lumbar interbody fusion. Revision because wound or deep infection was excluded. The main reoperation causes were ASD (13 patients /3.73%) and screw loosening (24 patients /6.4 %), other causes 3 patients (0.8 %). Although screw loosening was diagnosed in 27 patients (7.2%). Distribution according age groups was; under 40 years old 2 of 84 patients (2.3%) between 40 and 65 years 8 of 136 patients (5.8%) and in patients older than 65 years 13 of 98 patients (13.2%). Screw loosening in patients with augmented screws could be diagnosed in 1 of 57 patients (1.7%). Conclusion: Efforts toward prevention adverse occurrences are the next step for the quality improvement in spinal surgery. Knowledge of rates of PLIF complications are essential when indicating surgery and informing the patient of its risks. Screw loosening becomes the most important quantitative long term surgical complication, as lumbar interbody fusion is increasingly common in osteopenic or osteoporotic patients due to the aging of the population. Pedicle screw augmentation decreases significantly the screw loosening and the reoperation rate.

1978

P243: Utilizing viseon camera for minimally invasive lumbar decompression surgery in low and middle-income countries: a technique and feasibility study

Costansia Bureta ¹ , Francois Waterkeyn ² , Chibuikem Ikwuegbuenyi ² , Fabian Sommer ² , Hamisi Shabani ¹ , and Roger Härtl ²

¹ Neurosurgery, Muhimbili Orthopedic and Neurosurgery Institute, Bujumbura, Republic of Burundi

² Neurological Surgery, New York Presbyterian Hospital/Och Spine, Weill Cornell Medicine, New York United States

Introduction: Minimally invasive spinal surgery (MISS) offers better outcomes and quality of life than traditional methods. However, MISS is yet to be adopted in low-and middle-income countries (LMICs) owing to limited knowledge and resources, such as a lack of access to endoscopes or microscopes, which are cumbersome, expensive, and require specific maintenance. Objective: We aim to describe our initial experience utilizing the Viseon MaxView camera system for MISS at Muhimbili Orthopedic Institute, highlighting this system's safety, feasibility, and applicability. Methods: We report four cases of unilateral laminectomy for bilateral decompression (ULBD) using the Viseon Max camera system in a resource-constrained setting. The Viseon MaxView System is a novel visualization system that utilizes a miniature, single-use camera attached to a tubular retractor and projects 4K resolution images onto a head-up display. Data on the surgery duration, blood loss, perioperative complications, and technique mishaps were collected. Short-term clinical outcome was assessed using the visual analog scale (VAS) and the Oswestry disability index (ODI). Result: Four patients, two male, and two females, with a mean age of 62 years, had severe radicular pain that was worse on the left, and mild back pain. Additionally, two patients had severe claudication, and another had a motor deficit. The duration of symptoms of the patients was, on average, 49 months. Magnetic resonance imaging showed disc prolapse or canal stenosis in the lumbar spine (L4-S1). All patients were obese with BMI >30kg/m2. All patients underwent tubular MISS with the Viseon system, with a 60- or 70-mm tube size. The system setup was quick and easy and did not require any assistance from the company. The image quality was very sharp but could not offer 3D visualization. The average duration of surgery was 146 min, with an average blood loss of 63 mls. All patients were ambulant on the first-day post op with no post-op complications. The average time from admission to surgery was four days. Conclusion: Despite the lack of depth perception and a few episodes of frozen images while using monopolar, the Viseon MaxView camera system appears to be a feasible solution for MISS cases for patients in LMIC countries, and could be used an alternative to the surgical microscope.

1992

P244: Risk factors for additional lumbar fusion surgery at the index level after posterior decompression surgery for lumbar canal stenosis

Tetsuryu Mitsuyama ¹ and Kaiji Ota ²

¹ Neurosurgery

² Orthopedic Surgery, Shinagawa Shishoukai Hospital, Tokyo, Japan

Introduction: It has been reported that decompression plus fusion surgery does not result in better clinical outcomes than decompression surgery alone among patients with lumbar spinal stenosis. However, some patients require additional lumbar fusion surgery due to symptomatic foraminal stenosis after posterior decompression for lumbar canal stenosis. The aim of this study is to investigate predictable factors of additional fusion surgery after decompression surgery alone for lumbar canal stenosis. Methods: Fifty-four consecutive patients undergoing posterior central decompression for lumbar canal stenosis by a single surgeon from 2016 to 2019 were retrospectively analyzed. Age, sex, range of posterior decompression and preoperative radiological findings at the decompressed levels were compared between patients with and without additional lumbar fusion surgery at the index levels. Predictive risk factors of additional fusion surgery after central decompression for lumbar spinal stenosis were determined with multivariate logistic regression analyses and Mann-Whitney U tests. Results: Seven patients (13%) underwent additional lumbar interbody fusions for symptomatic foraminal stenosis at the decompressed levels. Five of them (9%) had additional fusion surgery within two years after initial decompression surgery. Significant risk factors for additional fusion surgery were intervertebral disc wedge angle over 5 degrees (OR = 9.11, 95% CI = 1.62-51.1, p < 0.012), posterior spondylolisthesis over 5 mm (OR = 6.3. 95% CI = 1.08-36.7, P = 0.041) and intradiscal vacuum phenomenon on X-ray (OR = 5.63 95% CI = 1.07-29.7, P = 0.042). Range of posterior decompression was significantly larger in patients with additional fusion surgery (mean 2.6 levels) than in patients without additional fusion surgery (mean 1.9 levels). On analyses of additional fusion surgery within two years, significant risk factors were also intradiscal vacuum on X-ray (OR = 17.8. 95% CI = 1.77-17.9, p = 0.015), posterior spondylolisthesis (OR = 13.2. 95% CI = 1.76-98.9, p = 0.012) and disc wedge (OR = 9.0. 95% CI = 1.27-63.9, p = 0.028). Discussion: This study demonstrated that 9% of patients with posterior decompression surgery alone for lumbar canal stenosis required additional lumbar fusion surgery for symptomatic foraminal stenosis at the index levels within two years. Intradiscal vacuum phenomenon on X-ray, posterior spondylolisthesis over 5 mm and intervertebral disc wedge angle over 5 degrees were predictive risk factors for such additional lumbar fusion surgery. Lumbar interbody fusion surgery may be indicated for patients with all of above radiological findings.

2035

P245: Effects of social determinants of health on preoperative presentation of patients who underwent operative management of degenerative spondylolisthesis

Avionna Baldwin ¹ , Anna Filley ¹ , Khuzaima Rangwalla ¹ , Ashraf El Naga ¹ , David Gendelberg ¹ , and Sigurd Berven ¹

¹ Orthopedic Surgery, University of California, San Francisco, United States

Introduction: Degenerative spondylolisthesis (DS), is one of the most common causes of back pain and disability worldwide. Recent data has supported the role of surgical intervention for improving outcomes in symptomatic DS. As we study DS treatment efficacy, it is important to look at populations’ access to surgical care. The purpose of this study was to investigate the relationship between social determinants of health (SDoH) and the clinical presentation of patients with operative DS in order to better understand factors influencing patient access to surgical care. Methods: Retrospective study of 184 consecutive patients who underwent surgical treatment of symptomatic DS at UCSF, January 2016 and June 2020. Primary outcomes were duration of baseline, worsening, and severity symptoms at first consultation, time from referral to surgical consultation and time from consultation to surgical procedure. Univariate analysis was used to assess the influence of SDoH on these outcomes. Results: Patients with estimated median income in the lowest two quartiles had a significantly longer duration of baseline (112.4 vs 54.5 months, p = 0.00139) and worsening symptoms (17.4 vs 9 months, p = 0.0262) and waited longer for surgical consultation after initial referral (52 v 35 days, p = 0.0143) than those in the top two quartiles. Patients living > 50 miles from UCSF had a significantly longer duration of baseline symptoms (104 vs 61 months p = 0.018) and waited longer for surgical consultation after initial referral (53 vs 34 days, p = 0.0086). Following surgical consultation, patients with public insurance waited longer for procedures than those with private insurance (440 vs 251 days; p = 0.046). Conclusion: Low income was a risk factor for worse preoperative presentation. In order to ensure equitable access to appropriate surgical care, SDoH must be considered as these are modifiable risk factors to improve patient outcomes. By understanding factors that may predispose patients to presenting in a worse clinical state prior to surgery, we can not only increase access, but also improve surgical outcomes.

Diagnostics

73

P246: The legal and socioeconomic considerations of spine telemedicine in Canada

Jessica Jung ¹ , Shawn Baldeo ² , Markian Pahuta ³ , Sunjay Sharma ⁴ , and Daipayan Guha ⁴

¹ Faculty of Health Sciences

² Department of Psychiatry, University of Toronto, Canada

³ Department of Orthopedic Surgery

⁴ Department of Neurosurgery, McMaster University, Hamilton, Canada

Introduction: While the COVID-19 crisis had accelerated the use of telemedicine in Canadian healthcare, there remains significant uncertainty as to its efficacy and future directions. There are inherent challenges to telemedicine, including questions of clinical reliability and privacy, balanced against the possibility of efficiency and increased access to specialists. Here, we review the current landscape of telemedicine in Canadian healthcare, with applications to spine surgery. Material and Methods: This narrative review provides an overview of both the pragmatic elements of conducting virtual assessments in spinal surgery, along with a synthesis of its legal implications. This review was supported by a search of the Lexis Advance Quicklaw database to evaluate the prevalence of medical negligence lawsuits in Canada. Results: The Canadian healthcare system poses significant challenges in the evaluation and systemic implementation of telemedicine, given the lack of a national legal framework and separate provincial or territorial regulation systems across the country. Telemedicine is of a particular interest to spinal surgeons, given the prevalence, morbidity, and economic costs associated with spinal pathologies. Despite perceptions of increase liability, to date, there have not been any malpractice suits specifically related to the use of virtual care or telemedicine. Conclusion: The role of telemedicine in Canada continues to evolve with the dynamic aftermath of the COVID-19 pandemic. Its ability to expedite access to medical care makes it a valuable resource, particularly given the health disparities across geographically isolated regions in Canada. However, there are significant challenges navigating the widespread upstart of telemedicine, given the lack of a national legal framework and the inherent difficulties of navigating individual provincial systems. Without a unifying policy, there is uncertainty regarding best practice policies, along with unclear legal implications of confidentiality and privacy, which may serve as a barrier for clinicians to integrate telehealth into their practice.

181

P247: Bone turnover markers in the preoperative assessment of bone quality - A prospective investigation of bone microstructure and advanced glycation endproducts in lumbar fusion patients

Henryk Haffer ^1,2 , Maximilian Muellner ¹ , Erika Chiapparelli ² , Yusuke Dodo ² , Jiaqi Zhu ² , Yi Xin Han ³ , Eve Donnelly ³ , Jennifer Shue ² , Andrew Sama ² , Frank Cammisa ² , Federico Girardi ² , and Alexander Hughes ²

¹ Center for Musculoskeletal Surgery, Charité - Universitätsmedizin Berlin, Germany

² Hospital for Special Surgery, Spine Care Institute

³ Department of Materials Science and Engineering, Cornell University, New York, United States

Introduction: Effective tools to evaluate bone quality preoperatively are scarce and the standard method to determine bone quality requires an invasive biopsy. Therefore, a non-invasive, and preoperatively available method for bone quality assessment would be of clinical value. We hypothesized that bone turnover marker are associated to volumetric bone mineral density (vBMD), posttranslational bone collagen modifications and the bone microstructure. Therefore the study aimed to investigate the associations of bone formation marker, serum bone alkaline phosphatase (BAP), and bone resorption marker, urine collagen cross-linked N-telopeptide (uNTX) to 1) vBMD, 2) fluorescent advanced glycation endproducts (fAGEs) and 3) bone microstructure. Material and Methods: A cross-secional analysis using prospective data of patients undergoing lumbar spinal fusion from from 2014 to 2021 was performed. The study was approved by the institutional review board and informed consent was obtained from all patients. BAP and uNTX were preoperatively collected. Quantitative computed tomography (QCT) was performed at the lumbar spine (vBMD ≤ 120 mg/cm³ osteopenic/osteoporotic). Bone biopsies from the posterior superior iliac spine were obtained and evaluated with multiphoton fluorescence microscopy for fAGE crosslink density and microcomputed tomography (μCT) for bone microarchitecture. Correlations between BAP/uNTX to 1) vBMD, 2) fAGEs and 3) μCT parameters were assessed with Spearman’s ρ. Receiver operating characteristic (ROC) analysis evaluated BAP and uNTX as predictors for osteopenia/osteoporosis. Multivariable linear regression models with adjustments for age, sex, BMI, race and diabetes mellitus determined associations between BAP/uNTX and fAGEs. Results: 127 prospectively enrolled patients (50.4% female, 62.5 years, BMI 28.7 kg/m2) were analyzed. uNTX (ρ = -0.331, p < 0.005) and BAP (ρ = -0.245, p < 0.025) decreased with cortical fAGEs, and uNTX (ρ = -0.380, p < 0.001) decreased with trabecular fAGEs. BAP and uNTX revealed no significant correlation with vBMD. ROC analysis for BAP and uNTX discriminated osteopenia/osteoporosis with an AUC of 0.477 and 0.561, respectively. In the multivariable analysis, uNTX decreased with increasing trabecular fAGEs after adjusting for covariates (β = 0.923; p = 0.031). Conclusion: This study demonstrated an inverse association of bone turnover markers and fAGEs. Both uNTX and BAP could not predict osteopenia/osteoporosis in the spine. uNTX reflects collagen characteristics and might have a complementary role to vBMD, as a non-invasive tool for bone quality assessment in spine surgery.

252

P248: The Hoffmann parallax: a prospective study to determine the benefit of Hoffmann's sign

Eric Gruenberger ¹ , Sohrab Vatsia ¹ , Rourke Stay ¹ , Cameron Kersey ¹ , Mudassar Khan ¹ , and Douglas Pahl ¹

¹ Hughston Clinic, Columbus, GA, United States

Introduction: Degenerative cervical myelopathy (DCM) is the most common cause of age-related spinal dysfunction worldwide. Despite the widespread use of provocative physical exam maneuvers in the workup of DCM, the clinical significance of Hoffmann’s sign is controversial and its diagnostic benefit in patients with cervical cord compression remains unclear. Therefore, the purpose of this study was to prospectively assess the diagnostic performance of Hoffmann’s sign in a cohort of patients treated by a single spine surgeon. Material and Methods: Patients were divided into two groups in keeping with the presence of a Hoffmann sign on physical examination. Advanced imaging studies were independently reviewed by four raters for confirmation of a diagnosis of cervical cord compression. Prevalence, sensitivity, specificity, likelihood, and relative risk ratios for the Hoffmann sign were calculated, with subsequent Chi-square and receiver operator characteristic (ROC) analysis to further characterize correlative findings. Results: Fifty-two patients were included in this study – of whom, thirty-four (58.6%) patients presented with a Hoffmann sign, and eleven (21.1%) patients demonstrated cord compression on imaging. The Hoffmann sign demonstrated a sensitivity of 20% and a specificity of 35.7% (LR = 0.32; 0.16-1.16). Chi-square analysis revealed that imaging findings positive for cord compression were proportionally greater for patients lacking a Hoffmann sign than those with a confirmed Hoffmann sign (p = 0.032) ROC analysis demonstrated that a negative Hoffmann sign performed moderately well in predicting cord compression (AUC.721; p = 0.031). Conclusion: The Hoffmann sign is an unreliable marker for cervical cord compression, and the lack of a Hoffmann sign may be more predictive of cervical cord compression.

338

P249: Reliability of manual intervetebral disc measurment

Philipp Schenk ¹ , Nadya Guellil ² , Ingmar Kaden ³ , Magnus Krieghoff ³ , Christian Hohaus ⁴ , and Hans-Jörg Meisel ⁵

¹ Department of Science and Research

² Department of Plastic and Hand Surgery, Burn Unit

³ Institute of Radiology and Neuroradiology

⁴ Department of Neurosurgery, Hospital Dessau, Dessau, Germany

⁵ Department of Neurosurgery, BG Klinikum Bergmannstrost, Halle (Saale), Germany

Introduction: Reliable methods to quantify disc degeneration are mandatory for treatment evaluation of degenerated discs. Since MRI have been used to diagnose vertebral diseases to objectify and quantify disc degeneration. The aim of this study was to investigate the inter- and intra-observer reliability (interRR, intraRR) of manual measures of disc height and volume in healthy and degenerated lumbar intervertebral discs (IVD) in MRI scans. In addition, the reliability of the Pfirrmann-classification was investigated. Material and Methods: T2w images of 60 Patients with mono-segmental lumbar disc herniation at L4/5 (N = 10) or L5/S1 (N = 50) and healthy, non-degenerated IVD at L3/4 were investigated in this study. IVD height were measured using three manual methods: H1: disc height in the center of the midsagittal layer. H2: mean of anterior and posterior disc height in midsagittal layer. H3: mean of nine defined locations, three in the midsagittal layer, three each in a defined left and a right layer, respectively. IVD volume was calculated by multiplying the slice thickness (4mm) with the sum of the measured disc areas in every sagittal layer. The Pfirrmann-classification was determined for the degenerated IVD. Two observers (observer1: surgeon, observer2: radiologist) carried out the measurements. To calculate intraRR, observer1 performed the measurements two times with an interval of 4 weeks. Intra -class-correlation coefficient (ICC(3, 1)) was used for intraRR and interRR. The reliability of the Pfirrmann classification was calculated using Kenadalls Tau. InterRR was calculated two times, comparing the results of both measures from observer1 (1a and 1b) with the results of observer 2. SPSS v28 was used for statistical analyses. Results: Data of 34 male and 26 female patients with an age of 36 ± 10 years were analyzed. The highest intraRR for IVD height measures was found for H3 with 0.822 for healthy and 0.910 for degenerated IVD (healthy IVD: H1 0.815, H2 0.677; degenerated IVD: H1 0.874, H2 0.842). For volume measures the intraRR was 0.887 and 0.913 for healthy and degenerated, respectively. The interRR showed for the healthy IVD for H3 with 0.634 the highest and for H2 with 0.396 the lowest reliability. For the degenerated IVD, again, H3 showed with 0.792 the highest and H2 with 0.630 the lowest interRR. The interRR of the volume measures of the healthy IVD was 0.701 for observer1a and observer 2 and 0.728 for observer1b and observer 2. For the degenerated IVD interRR was 0.860 and 0.791. Degenerated IVD showed Pfirrmann-classification of Grade II (N = 16), Grade III (N = 17), Grade IV (N = 20) and Grade V (N = 7). The intra-observer reliability (Kendalls Tau) was 0.628. The inter-observer reliability was 0.457 and 0.615. All reliability values showed a p < 0.01. Conclusion: Overall, reliability showed values from moderate up to very height. The H3 method (9-points) showed the best reliability for IVD height measures. Using 2 Points (H2) for height measures showed the lowest reliability. The reliability of the measures of healthy IVD was slightly lower, compared to degenerated IVD. Studies, which address IVD height and volume, should report the reliability of their measures.

436

P250: New bone formation in ossification of the posterior longitudinal ligament and its possible mechanisms: Inflammation or degeneration

Tran Canh Tung Nguyen ¹ , Zhongyuan He ² , Hiroto Makino ¹ , and Kawaguchi Yoshiharu ¹

¹ Department of Orthopaedic Surgery, University of Toyama, Toyama City, Japan

² Department of Orthopaedic Surgery, The Seventh Affiliated Hospital of Sun Yat-sen University, Shenzhen, China

Introduction: Ossification of the posterior longitudinal ligament (OPLL) is characterized by the ectopic bone formation that occurs in the PLL due to hyperostotic changes. The pathogenesis of OPLL is multifactorial and remained to be fully elucidated. Objectives of this study are to clarify whether and how spinal inflammation or degeneration is associated with the new bone formation in ossification of the posterior longitudinal ligament (OPLL). Material and Methods: The whole spinal computed tomography and serum high-sensitive C-reactive protein (hs-CRP) levels were obtained in 162 patients with cervical OPLL. Patients were divided into plateau-shaped (51 males and 33 females; mean age: 67.7 years) and hill-shaped groups (50 males and 28 females; mean age: 67.2 years). Sacroiliac (SI) joint changes were classified into four types and three subtypes, as previously described. Interactions among ossification shapes, hs-CRP levels, and morphological changes in the SI joint were investigated. Results: The maximum ossified lesion thickness of the Hill shape was larger and more common in the intervertebral regions (65.4%) compared to the plateau shape, which was predominant in the vertebral segments (59.5%). Serum hs-CRP levels in the plateau-shaped group (0.11 ± 0.10 mg/dL) were significantly higher than that in the hill-shaped group (0.07 ± 0.08 mg/dL). SI joint intra-articular fusion was the main finding in the plateau-shaped group and showed significantly higher hs-CRP levels compared to the anterior para-articular bridging, which more frequently occurred in the hill-shaped group. Conclusion: OPLL classification based on the two opposite morphological appearances may be beneficial for understanding its underlying mechanism. Our findings indicate that the plateau shape OPLL is similar to syndesmophyte in ankylosing spondylitis, probably due to inflammatory pathogenesis, whereas the hill-shaped ossification appears as a degenerative process.

784

P251: Gorham-Stout disease with abdominal chylous effusion and osteolytic lesions of the lumbar spine. Case report and review of the literature

Fernando Alvarado Gómez ¹ , Nahala Aborashed-Amador ¹ , Mario Herrera Méndez ¹ , Maria Garcia-Rueda ¹ , Carlos Montero-Silva ¹ , Sergio Alejandro Nossa ¹ , María Alejandra Asmar ¹ , Maria Camila Giraldo Bernal ¹ , Maria Bravo-Otero ¹ , Germán Mogollón ¹ , and Gilmar Hernández ¹

¹ Instituto Roosevelt, Bogota, Colombia

Introduction: The Gorham-Stout syndrome is a rare condition characterized by progressive osteolysis and bone destruction. Chylous effusion is present only in 17% of patients with this disease, and when it occurs, it is located in the thorax. Osteolytic lesions described in the spine are even more infrequent. Material and Methods: A 14-year male patient came for vomiting and abdominal pain for six months. The US and contrast-enhanced CT scan documented a multi-lobulated retroperitoneal cyst associated with multiple lytic lesions of the vertebral bodies and iliac bones. The cyst was sclerosed by interventional radiology. Symptoms reappeared five months later. Results: The persistence of the retroperitoneal cyst and multiple lytic lesions with cord involvement in all the spine segments led to the diagnosis of Gorham-Stout syndrome. The retroperitoneal cyst was sclerosed again, and the patient received adjuvant therapy with sirolimus. Spine lytic lesions were treated with a brace and bisphosphonates without recurrence. Conclusion: The Gorham-Stout disease is considered a benign condition that may resolve spontaneously in some situations. The manifestations are usually thoracic. However, it can debut with abdominal symptoms. In this scenario, the diagnosis can be focused thanks to the bone findings that characterize this pathology and the age of presentation.

914

P252: Prospective clinical study of the diagnostic accuracy of SPECTRAL-CT in the primary diagnosis of osteoporotic pelvic ring fractures

Bernhard Ullrich ¹ , Mark Unthan ² , Heinen Camilla ² , Felix Kohler ² , Philipp Schenk ³ , Tobias Franiel ⁴ , and Florian Buerckenmeyer ⁴

¹ Trauma and Reconstructive Surgery

² Hand-, Traum- and Reconstructive Surgery

³ Department of Science, Research and Education, BG Clinic Bergmannstrost Halle, Halle, Germany

⁴ Radiology, University Hospital, Friedrich Schiller University, Jena, Germany

Introduction: The WHO defines fragility or insufficiency fractures as injuries without adequate trauma due to reduced bone quality. Demographic changes have resulted in an increase in pelvic ring insufficiency fractures. These patients require special attention in clinical care and should be considered differently than bone healthy patients with pelvic ring fractures. When a pelvic ring insufficiency fracture is suspected, for diagnostic purposes a native CT is employed. However, the CT shows poorer sensitivity compared to MRI (CT: 77%, MRI: 96.3%) in the diagnosis of sacral fractures. SPECTRAL CT can visualize bone marrow edema using different absorption spectra, similar to MRI. The study aims to evaluate the diagnostic accuracy of SPECTRAL CT compared to MRI in the detection of fractures in the posterior pelvic ring. Material and Methods: The monocentric, prospective cohort study included patients presenting to the central emergency department with low back pain. Patients with adequate trauma and patients younger than 55 years were excluded. Each patient initially received a SPECTRAL CT (GE RevolutionCT, GSI, rapid kilovolt switching), and promptly underwent a basin MRI during the inpatient stay. The study was approved by the ethics committee of the medical faculty of the University of Jena (2021-2124MV). The evaluation was performed in a randomized blinded procedure by a diagnostician experienced in musculoskeletal radiology using a standardized reporting form. Diagnostic accuracy of SPECTRAL CT and native CT was calculated in comparison to MRI pelvis, which is the current gold standard. Results: To date, 34 patients (age: 78 ± 10 years, female n = 20, male n = 14) have been included in the currently ongoing study. Compared to MRI pelvis, SPECTRAL CT shows high sensitivity (96%) and specificity (75%) in detecting pathology in the posterior pelvic ring region. CT pelvis native shows significantly worse sensitivity in comparison (sensitivity 70%, specificity 75%). Conclusion: The data show a high diagnostic sensitivity of SPECTRAL CT compared to CT pelvis. In everyday clinical practice, this enables the correct diagnosis and classification already in primary diagnostics, for example according to the osteoporotic fractures (OF) pelvis or fragility fractures of the pelvis (FFP) classification. SPECTRAL CT could thus represent a time- and resource-saving alternative diagnostic method to the MRI.

934

P253: Fracture-like lesions could potentially be a red herring for the clinician. Langerhans cell histiocytosis initially misdiagnosed as a pancake fracture secondary to a neck injury. A case report

Grigorios Delaportas ¹ and Georgios Manolarakis ²

¹ University of Vermont Medical Center, South Burlington, United States

² Orthopaedic Sophisticated Surgical Techniques (MOSST), Heraklion, Greece

Introduction: Difficulties in the clinical diagnoses arise from cases in which medical history, physical examination, imaging, and lab tests are contradicting. Bone pain of traumatic etiology may sometimes aggravate and consequently reveal a preexisting painless bone pathology while painful, non-traumatic bone lesions may often present as fractures after radiographic evaluation. Material and Methods: We present the case of a 16-year old female who was referred to our spine clinic due to persisting and worsening neck pain that started about 6 months prior to her visit to us. Initially, the patient presented to the emergency department (ED) as a result of falling and landing on her head while bouncing on a trampoline. The patient was observed for a couple of hours and was later discharged. Since the patient had mild pain without neurological deficits, no radiographs were ordered by the ED physician. However, the pain gradually increased and, approximately two months after her initial injury, the patient presented to her primary doctor for further evaluation. The primary doctor ordered plain radiographs and referred the patient to our clinic with the diagnosis of a pancake fracture of the C6 vertebra. The radiographs were reviewed, but the appearance of the fracture in the context of the traumatic circumstances raised concerns challenging the initial diagnosis. Results: New radiographs were obtained and compared to the previous ones. The lesion appeared worse with conspicuous erosion of the C6 endplates and loss of the vertebral height. We proceeded in ordering an MRI. MRI revealed a lesion compatible with "Langerhans Cell Histiocytosis" and not with a pancake fracture. The patient was immediately referred to hematology/oncology which scheduled a bone biopsy. Bone biopsy confirmed the MRI results. Subsequently, the patient started the indicated treatment with excellent prognosis. Conclusion: Several times an accurate diagnosis may be sacrificed in the altar of the "apparent or obvious." However, a ruminative analysis of the medical history and how it relates to diagnostic tests may unravel a camouflaged contradiction. In our case, we speculated that a traumatic impact forceful enough to cause a pancake fracture at one's C6 vertebra would have most likely caused more intense pain as well as apparent neurological deficits thus prompting the ED physician to order at least plane radiographs. Our prudent approach led to an accurate and timely diagnosis of a sinister condition with excellent prognosis.

1066

P254: Clinically significant radiologic parameter of thoracic ossification of the ligamentum flavum on lateral view X-ray?

Hyunjun Jang ¹ , Kyung Hyun Kim ¹ , Jeong Yoon Park ¹ , Keun Su Kim ¹ , Yong-Eun Cho ¹ , and Dong Kyu Chin ¹

¹ Department of Neurosurgery, Spine and Spinal Cord Institute, Gangnam Severance Hospital, Yonsei University College of Medicine, Seoul, Korea, Rep. of South

Introduction: Thoracic ossification of the ligamentum flavum (OLF) is one of the major cause of motor and sensory deficit of lower extremity. Since it is hard to detect the disease unless taking MR images of thoracic spine, it often takes time to get the final diagnosis. The purpose of this study is to find the parameters that could be useful to screen thoracic OLF on pre-operative lateral view X-ray. Material and Methods: We investigated patients who underwent surgery for thoracic OLF (n = 114) and those who had thoracic OLF but did not undergo surgery (n = 114) from 2015-2021. Various parameters such as shape and thickness of OLF were measured on lateral X-ray. Thoracic disc herniation or ossification of the posterior longitudinal ligament was excluded. Thickness of OLF (TOLF), Foraminal antero-posterior diameter (FD) – TOLF, OLF free diameter, TOLF / FD were measured. Results: Beak-type was the most common OLF morphology type, and 88% of patients who underwent surgery had paralysis symptoms. TOLF / FD was found as the best radiologic parameter. The optimal cut-off point was 0.42, 82% Sensitivity, and 83% Specificity. Conclusion: A TOLF / FD of 42% or less is the best way to diagnose clinically significant thoracic OLF on lateral X-ray. In this case, the patient may have paralysis due to thoracic OLF, so further evaluation such as MRI or CT should be actively considered.

1077

P255: Emergency decompression for spontaneous spinal epidural hematoma in octogenarians: risk factors, clinical outcome and complications

Pavlina Lenga ¹ , Guelec Gelo ¹ , Karl L. Kiening ¹ , Andreas W. Unterberg ¹ , and Basem Ishak ¹

¹ Neurosurgery, Heidelberg University Hospital, Heidelberg, Germany

Introduction: Spontaneous spinal epidural hematoma (SSEH) is a rare but disabling disease with a high morbidity. Although several cases have been reported in the literature, the pathogenesis, diagnosis, and timing of treatment remain unclear, especially in patients with advanced age. Owing to the lack of clinical evidence on this topic, we aimed to describe the clinical outcomes of cervical SSEH in octogenarians with an acute onset of neurological illness undergoing laminectomy, assess morbidity and mortality rates, and determine potential risk factors for a non-ambulatory outcome. Material and Methods: Electronic medical records from a single institution between September 2005 and December 2020 were retrieved. Data on patient demographics, neurological conditions, functional status, degree of disability, surgical characteristics, complications, hospital course, and 90-day mortality were also collected. Results: Over a period of 15 years, 22 patients aged ≥ 80 years with SSEH undergoing surgical decompression via laminectomy were enrolled in this study. The mean age was 84.3 ± 3.1 years. The mean Charlson comorbidity index was 9.1 ± 2.0, indicating a poor baseline reserve. Cardiovascular diseases were the most prevalent comorbidity. Ten individuals (45.5%) were taking anticoagulant agents and had a pathologic partial thromboplastin time (PTT) of 46.5 ± 3.4 s. Progressive neurological decline, as defined by the motor score (MS) of the American Spinal Injury Association impairment grading system, was observed on admission with a mean score of 63.8 ± 14.0. The in-hospital and 90-day mortality were 4.5% and 9.1%, respectively. Notably, the MS (93.6 ± 8.3) improved significantly after surgery (p < 0.05). Revision surgery was necessary in 5 cases due to recurrent hematoma. Anticoagulant agents and pathological PTT are significant risk factors for its occurrence. Motor weakness and comorbidities were unique risk factors for loss of ambulation. Conclusion: Decompressive laminectomy and evacuation of the hematoma in octogenarians with progressive neurological decline showed beneficial effects on the functional outcomes at discharge. Emergent surgery seems to be the “state of the art” treatment for symptomatic SSEH even in such a frail cohort. However, potential complications associated with adverse prognostic factors, such as the use of anticoagulants, should be clearly discussed with the patient and their relatives.

1179

P256: The role of neurophysiological monitoring during patient positioning in cervical spine procedures

David Felzensztein ¹ , Eilat Sapirstein ¹ , and Eyal Itshayek ¹

¹ Neurosurgery, Rabin Medical Center, Holon, Israel

Introduction: IONM allows intraoperative assessment of spinal cord function through real time feedback from sensory tracts, motor tracts, and nerve roots. IONM assess the functional integrity of the spinal cord and nerve roots, allowing early detection and reversal of neurological deficits. The pattern of signal loss during monitoring is important - sudden signal loss is associated with severe and irreversible injury, and gradual degeneration is more likely to represent mild recoverable damage. Different evidence exists regarding the sensitivity and specificity regarding the detection of new neurological deficits and current studies show multimodal ION (SSEP, MEP, and EMG) to provide a more accurate interpretation of the information acquired. Positioning during cervical procedures is a potentially damaging manoeuvre that may require an adequate neurophysiological monitoring technique to prevent damage to the spinal cord. IONM can be useful in detecting positioning-related brachial plexopathy during cervical spine surgery and thus serves as a tool for predicting neurological outcomes. Despite advancements in understanding IONM and the popularity of this technique in modern spine surgery, controversies still exist regarding its effectiveness and the necessity for its use in routine spinal procedures. Material and Methods: We retrospectively reviewed prospectively collected data from 2017 and currently going. All patients who underwent cervical spine surgery with neuromonitoring at Rabin medical center Beilinson hospital from 2017 till current were included. Demographic data, medical history, findings at neurological examination and imaging, electrophysiological data recorded during surgery, and neurological outcomes were collected and analysed. Results: Five hundred and one patients met the inclusion criteria. Loss of potentials detected in twenty patients during patient positioning and repositioning was performed with the aim of restoring electrophysiological signals. In 15/20 patients, repositioning resulted in immediate restoration of the baseline potentials. In 5/20, repositioning did not immediately restore electrophysiological signals out of those 5, in ¼ potentials reappeared later during the decompression and in ¾ potentials had not recovered till the conclusion of surgery. Conclusion: According to the above data, we believe that multimodal IONM is a useful method to prevent spinal cord injury during neck positioning in cervical spine surgical procedures and can be used to reduce the risk of neurological damage caused during patient positioning.

1233

P257: Validity of sedimentation sign of nerve root in the diagnosis of lumbar canal stenosis

Zion Hwang ¹ , Jason Bernard ² , Timothy Bishop ² , Jan Herzog ² , Shahnawaz Haleem ² , Tesfaladet Kurban ² , Emily Tsang ¹ , Priyanshu Saha ¹ , Bisola Ajayi ² , Thamer Hamdan ² , and Darren Lui ²

¹ St. George's University of London, London, United Kingdom

² Trauma and Orthopaedics, St. George's University Hospital, London, United Kingdom

Introduction: Lumbar spine canal stenosis induces a series of clinical features due to reduction of the lumbar spinal canal capacity which leads to compression of the neural tissues. At present, the most promising imaging test for diagnosis of this condition is magnetic resonance imaging (MRI). These clinical features correlate poorly with the severity of stenosis and the cross-sectional area of the dural sac in MRI examination. Therefore, there is a real need to improve the ability to diagnose lumbar canal stenosis by a special imaging findings. The sedimentation sign is a new measurement tool that can enable physicians to objectively assess and quantify spinal stenosis. The sign is most often present in patients who have clinically significant lumbar stenosis and require surgery. This study aims to evaluate the validity of the nerve root sedimentation sign in diagnosing central lumbar canal spinal stenosis. Material and Methods: This cross-sectional analytic study assessed the MRI of 711 patients complaining of lower back pain with or without sciatica between 1^st of April 2019 and 1^st of December 2020. The patients were divided into three groups according to lumbosacral spine MRI findings: Group I individuals with normal MRI, Group II with lumbar disc prolapse and Group III with lumbar canal stenosis. We measured the spinal canal and dural sac diameter at each level from first lumbar (L1) to fifth lumbar (L5) vertebrae. We looked for the nerve root sedimentation sign above and below these levels. Results: Positive nerve root sedimentation sign was seen in 15.2% of normal MRI group, 50.42% of disc prolapse group and in 86.4% of lumbar canal stenosis group. The sensitivity and specificity of nerve root sedimentation sign for the diagnosis of lumbar canal stenosis were 86.4% and 84.74% respectively. Conclusion: The nerve root sedimentation sign is sensitive but not specific for diagnosis of lumbar canal stenosis. It is unable to differentiate between lumbar canal stenosis and other dural compressing diseases like intervertebral disc herniation. Therefore, the authors suggest that it can be used as an added tool to clinical examination for diagnosis of lumbar canal stenosis and its severity but may not add specific diagnostic information beyond the traditional clinical diagnostic standard.

1283

P258: Awareness of degenerative cervical myelopathy in the primary care setting in Portugal: results of a survey

Catarina Nogueira ¹ , Carolina Luísa Lemos ¹ , Oliver Mowforth ¹ , Benjamin Davies ¹ , and Ricardo Rodrigues-Pinto ¹

¹ Department of Orthopaedics, Centro Hospitalar Universitário do Porto, Spinal Unit (UVM), Porto, Portugal

Introduction: Degenerative cervical myelopathy (DCM) is the most common cause of spinal cord impairment. DCM is often misdiagnosed, and it is not as discussed as other less debilitating diseases. As DCM might significantly affect patients’ quality of life, there is an urgency to detect this condition at its earliest stages. As primary care physicians (PCPs) are often the first to assess these patients, it is imperative to ensure a strong knowledge base of DCM amongst primary care physicians. However, the existing literature suggests PCPs typically fail to diagnose DCM. This study aimed to assess DCM knowledge amongst family physicians in Portugal and to address potential factors perpetuating the present issues regarding DCM awareness. As a secondary aim, this study intended to provide information to family physicians that may aid them in diagnosing and managing patients with DCM. Material and Methods: We created an online questionnaire and shared it with registered general practitioners (GPs), GP trainees, and physicians without a speciality that practise family medicine. We advertised our survey via social media platforms and mailing lists with the help of several medical institutions. An informed consent explaining the study preceded the questionnaire. All responses were voluntary and well-informed. All PCPs working in Portugal were considered eligible for inclusion in this survey. At the end of the questionnaire, respondents could leave their email if they were interested in participating in a learning module regarding DCM. To objectively evaluate PCPs’ knowledge of DCM, we attributed a score to some of the questions inquired. We surveyed for almost three months. Statistical analysis of this study was conducted using SPSS software. Results: We collected a total of 341 responses. Most participants scored Low in questions regarding DCM presentation. The majority of PCPs disregarded lower-limb and autonomic symptoms as possible DMC manifestations. Most participants checked hyporeflexia as a typical sign of DCM; every other physical sign presented in our questionnaire was much less chosen, although typically related to DCM. PCPs recognise there is a lack of knowledge of DCM in primary care and reported that it was mainly due to insufficient practising in DCM assessment during speciality training. Having heard or had any teaching about DCM was associated with Averagescores in questions related to disease presentation. Regarding DCM management, conservative treatment was always the first choice for almost 28% of the population. The main reason for delaying the referral of a patient to specialist care is the long waiting time for a specialist consultation. Conclusion: There is a lack of awareness in primary care, and PCPs appear to mistake myelopathy for radiculopathy. Our study reinforced the need to develop diagnostic tools to facilitate DCM detection in primary care. PCPs demonstrated interest in learning more about this condition.

1335

P259: Gait characterization for patients with cervical myelopathy using three dimensional motion capture

Miguel Ruiz Cardozo ¹ , J.D. Peiffer ¹ , Jie Fei ² , Jennifer Lee ¹ , Michele Santacatterina ³ , Ismael Seanez ² , and Brenton Pennicooke ¹

¹ Neurosurgery

² McKelvey School of Engineering, Washington University in St. Louis, St. Louis, United States

³ Department of Population Health, New York University, New York, United States

Introduction: Cervical myelopathy (CM) symptoms include recognizable gait disturbances (with a wide, ataxic pattern) and balance issues. Our current methods to assess functional status before and after surgery rely on health-related quality of life metrics with poor sensitivity and modest reliability. Kinematic analysis is an emerging tool in the evaluation of movement dysfunction in neurologic populations. The purpose of this study was to develop a gait analysis algorithm capable of characterizing CM gait dysfunction compared to normal subjects using objective measurements of motor function using a motion capture system. Methods: A control subject without CM (male, height 1.75 m, weight 76 kg) and a subject with CM underwent kinematic recordings before, 6 weeks and 3 months following a C5-C6 anterior discectomy and fusion (ACDF) using a 10 camera motion capture system (Qualisys, Göteborg Sweden). Tasks consisted of an 8-meter walking test completed at casual and fast speeds and a tandem gait test. Each task was repeated three times. Kinematic metrics including step length, step width, step height, joint flexion angles, and normalized pelvic jerk were calculated from markerless pose estimation. Results: Before surgery, the subject with CM had significantly decreased step length (0.1 m/m) and increased step width (0.015 m/m) when compared to control. In addition, the subject with CM had increased normalized pelvic jerk while walking and during the tandem gait task. Finally, the subject with CM had decreased joint flexion angles (12° hip, 4° knee). The shorter and wider steps along with the decreased joint angles could be a compensatory mechanism for gait disturbances caused by CM. Further, the increased pelvic jerk indicates an unstable center of mass during walking and while performing the tandem gait task. Following ACDF, the subject’s pelvic jerk significantly decreased when compared to preoperative data during both the walking and tandem gait tasks. This indicates that their center of mass moved more smoothly over a step and which indicates the efficacy of the spinal surgery to return y have returned some balance. Step length and height increased as well, with the increase in step height occurring at the 3-month timepoint indicating greater confidence during walking. Conclusion: The subject with CM had significant differences in kinematic metrics with the control subject before surgery. Following surgery, these kinematic measures regressed towards the control subject’s baseline values. These results establish kinematic measures assessed via motion capture technology as a possible method to evaluate neurological recovery and predict outcomes following spinal procedures.

1603

P260: Spinal adhesive arachnoiditis: an underestimated entity

Jorge Morales- del Angel ¹ and Armando Díaz ¹

¹ Hospital Angeles Valle Oriente, Cien, San Pedro Garza García, Mexico

Introduction: The chronic adhesive spinal arachnoiditis is a complex entity, with multiple radiologic findings. It was first recognized in 1909 by Horsley. In the last 55 years around 1000 cases have been reported. This number is dramatically underrated because of the lack of recognition, or omission of the patient. It is of uttermost importance to recognize the spinal adhesive arachnoidtis as a complex entity with many and various symptoms that can cause severe neurological deficit. Material and Methods: We present the case of a 61 year old female patient with history of multiple falls treated with spinal injections and physiotherapy, who underwent a craniotomy and fenestration for a left temporal arachnoid cyst. She suffered from dorsalgia, cervicalgia, and chronic lumbalgia. The patient also experienced a shoulder arthroscopy for joint wear. Immediately after the procedure she complained of sudden left arm weakness and thermoalgesic stimuli alteration with C6 hypoesthesia. Because of these symptoms a cervical MRI was performed, showing cervicodorsal syringomyelia. The lumbar MRI exposed radiologic features compatible with spinal adhesive arachnoiditis, with an overt clumping and syryngomyelia caused by a spinal cord tethering phenomenon because of the multiple adhesions. Undergoing multiple spinal injections, as well as having brain surgery are well known risk factor for adhesive arachnoiditis, which may have caused subarachnoid hemorrhage at some level. Results: We performed a L4 laminoplasty and adhesiolysis. Histopathological analysis exposed a dense tissue associated with chronic and acute inflammation. The patient had a great recovery with MRI imaging showing a decrease in the syryngomielia. Conclusion: The spinal adhesive arachnoiditis is an under diagnosed entity that causes neurological deficit that can be as severe as cuadriparesis or tetraparesis. The importance of this case lies in the acknowledge of this disease and to remind all spine surgeons that it is of great importance to know how to recognize this entity.

1699

P261: An extremely rare case of vertebral artery dissection as the cause of ventral spine epidural hematoma

Joana Tavares ¹ , Tiago Lorga ² , Inês Freire ² , Cristina Branco ² and Ana Luís ¹

¹ Neurosurgery

² Neuroradiology, Centro Hospitalar Lisboa Ocidental, Lisboa, Portugal

Introduction: Acute spinal epidural hematoma occurring in the absence of any trauma or iatrogenic procedure is described as spontaneous spine epidural hematoma (SSEH) and has an incidence of 0.1/100,000 inhabitants/year. The anterior location (ventral) of the hematoma is very uncommon since the dural sac is firmly attached to the posterior longitudinal ligament. Vertebral artery dissection (VAD) as cause of SSEH is extremely rare with only two cases reported in the literature. Material and Methods: We report the case of a patient with a VAD complicated with SSEH. Results: A 31-year-old female presented at the emergency room (ER) with a 2h history of sudden onset cervicalgia while resting, initially radiating to her right arm but that very quickly progressed to bilateral cervicobraquialgia and tetraparesis. In her medical history stood out an apparently uneventful eutocic delivery with epidural anesthesia 4 months earlier and the diagnosis of SARS-CoV-2 infection at this ER admission. She denied any trauma, taking any medication (including anticoagulants and antiplatelets) or prior neck pain. On neurologic examination she presented neck stiffness, tetraparesis with paraplegia and upper limbs severe paresis (grade 2/5 bellow C6), sensitive level T2 e urinary retention. Neuro-axis CT showed a voluminous hyperdense collection compatible with a spinal ventral epidural hematoma extending from C2 to T10, with mass effect, especially between C5-T9. Angio-CT showed a possible right VAD without other vascular malformations. She was submitted to an emergent and uneventful C5-T9 laminectomy. Five days after the surgery the patient was submitted to a digital subtraction angiography which revealed a dissecting aneurysm of the right vertebral artery at V3 segment. Given the previous hemorrhage the patient was proposed for endovascular treatment with stents that took place one month after the event. The procedure went without complications and the patient was discharged one week later oriented to a rehabilitation center. At 3-month evaluation she presented normal light touch and proprioceptive sensation, hypoesthesia for thermic and pain sensation below T2, need for bladder emptying with clean intermittent catheterisation when unsuccessful voiding attempt and significantly improve in upper limbs muscle strength (4/5 at elbow extensors bilaterally, 3/5 at grip and at finger extensors on the left side and 2/5 on the right). In the lower limbs despite still not recovering useful strength, she recovered to a grade 2/5 strength. Conclusion: VAD with subsequent perivascular hemorrhage is one of the possible causes of SEEH, especially, when ventrally located in the cervical and/or high thoracic column. Hence the importance of a thorough investigation of the vertebral arteries.

1744

P262: Spinal intradural arachnoid cyst: a case report

Sliti Firas ¹ , Alaa Belhadj ¹ , Abdelhafidh Slimane ¹ , Nessrine Nessib ¹ , Khalil Ghedira ¹ , Eya Chahed ¹ , and Jalel Kallel ¹

¹ Neurosurgery, National Institute of Neurology, Tunis, Tunisia

Introduction: Spinal intradural arachnoid cyst is a benign condition of uncertain pathophysiology. It is most often asymptomatic but can cause serious neurological sequelae especially when treatment is not initiated in time. We report the case of a 47 years old male patient treated at the Neurosurgery Department of the National Institute of Neurology, Tunisia. Material and Methods: We report here the case of a 47 year old man with no notable pathological history, who consulted for continuous back pain with bilateral sciatica evolving for 3 months, the evolution of which was marked by the onset of intermittent medullary claudication severely reducing the walking range, as well as the onset of urinary disorders. On clinical examination, we find a patient suffering from pain, with a spastic paraparesis and a pyramidal syndrome, as well as a T12 sensory level. A spinal MRI revealed an elongated well-defined epidural lesion extending from T9 to T11 with a high T2 signal and a low T1 signal with no enhancement. The patient was operated on via posterior approach for cyst resection with simple postoperative course. Neurological symptoms gradually resolved. Results: Spinal intradural arachnoid cyst is a rare cause of spinal cord compression. It can be seen at any age; its pathogenesis is not clear and remains a subject of debate, it can be congenital or acquired. The clinical presentation is that of a slow spinal cord compression. Spinal MRI is therefore essential to confirm the diagnosis of spinal intradural arachnoid cysts and to eliminate other differential diagnoses. It is therefore the exam of choice to study the spinal content as a whole, to characterize the cystic nature of the lesion and to better assess the extent of the cystic and to better appreciate the spinal cord implications. Once the diagnosis is made, surgery is the best way to restore the normal flow of CSF by removing the compression exerted by the cyst on the spinal cord. The prognosis is generally good. Conclusion: Despite its high rarity, the spinal arachnoid cyst is one of the etiologies of spinal cord compression syndrome to think about because its diagnosis allows for a complete cure by radical surgical treatment.

1986

P263: Sarcoidosis inaugurated by vertebral lesion mimicking metastatic disease

Mouadh Nefiss ¹ , Mohamed yassine Belhedi ¹ , ben aissa ali ¹ , Mohamed Amine Gharbi ¹ , Hedi Ezzine ¹ , Ramzi Bouzidi ¹ , Ezzaouia Khelil ¹ , and Tborbi Anis ¹

¹ Orthopeadic and Traumatology, Mongi Slim Hospital, Marsa, Tunisia

Introduction: Sarcoidosis is a systemic granulomatous disease characterized by the formation of granulomas without necrosis in various organs, most frequently in the lungs and lymphatic system. Because of its complexity and heterogeneous multisystem involvement, it is usually a diagnosis of exclusion based on a range of evidence. Bone involvement is rare (1-13%), and vertebral involvement is even rarer. Most often, this bone lesion is either concomitant with pulmonary or lymphatic involvement or occurs in a known patient with the disease. To our knowledge, isolated vertebral involvement has not been described so far. We report the case of a young Tunisian woman presenting with back pain in connection with spinal lesions suggestive of metastatic disease. However, biopsies were consistent with sarcoidosis. Clinical Presentation: This is a 43-year-old Tunisian woman with no previous history of SARS-COV2 pneumonia who presented with bilateral, poorly systematized lumbosciatic pain without neurological signs. An MRI of the lumbar spine was requested and came back without abnormalities. Thus the symptomatology was linked to Covid-19 and the patient was put on symptomatic treatment. The evolution was marked by the improvement of the lumbosciatic pain and the appearance of back pain associated with mixed bilateral cervico-brachial neuralgia with poorly systematized tilt without neurological signs. Moreover, the patient reported asthenia and a weight loss of 10 kg in one year without night sweats, evolving in a context of apyrexia. A cerebral-medullary MRI was performed showing spinal cord replacement lesions with vertebral compression of D4 and epidural and foraminal extension D3-D4 and D4-D5 on the left side with compression of the spinal cord opposite D4 and spinal cord replacement lesions D1, D2 and D3. The metastatic origin was evoked in the first place, from which a CT scan was requested, but no other lesion was found. This was completed by a scannoguided biopsy of D4. Finally, the anatomopathological examination showed epithelioid granulomatous and gigantocellular inflammatory remodeling without caseous necrosis consistent with sarcoidosis. The patient then received a Neofrakt brace and was referred to internal medicine for specific medical treatment. Conclusion: Sarcoidosis is a complex multi-systemic disease. Spinal involvement is difficult to differentiate from metastatic lesions on MRI. Hence the interest of biopsy and anatomopathological examination at the slightest doubt.

Disc Degeneration

68

P264: Cervical intradural disc herniation: a systematic review

Qing Guan ¹

¹ Spine Surgery, The First People’s Hospital of Yibin, Yibin, China

Background: Cervical intradural disc herniation (CIDH) is rare, and diagnosis and treatment are challenging.We conducted a systematic review and meta-analysis of the literature on the diagnosis and treatment of CIDH. Method: The presentation, imaging manifestations, diagnosis, management, prognosis and possible pathogenesis were reviewed following Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. English-language studies and case reports published from inception to recent were retrieved. Data on presentation, imaging characteristics, diagnosis, management, outcomes and pathogenesis were extracted. Results: Twenty articles involving 23 patients were selected. The most common involved level was C5-6 (43.5%), followed by C6-7 (30.4%), C4-5 (13%), and C3-4 (13%). Spontaneous IDH occurred in 61% of the patients, and relevant cervical trauma was present in 39%. Brown–Sequard’s syndrome (56.5%), quadriparesis (34.8%), and radiculopathy (8.7%) were the main presentations. Magnetic resonance imaging (MRI) was the most commonly used diagnostic technique, and the ‘‘halo” and ‘‘Y-sign” were strong indicators of CIDH. Three (13%) patients were diagnosed as having CIDH preoperatively, and 87% were confirmed intraoperatively. All patients underwent surgical intervention primarily (73.9%) through an anterior approach. Neurological function improved postoperatively in all patients but one. Dural and arachnoid mater tears were managed by direct suture or covering with a substitute, and only one patient sustained cerebrospinal fluid (CSF) leakage after surgery. Conclusion: IDH mostly involves the lower cervical spine. More than half of the patients had spontaneous CIDH, and some had a relevant cervical trauma history. BSS was the main presentation. It is difficult to diagnose CIDH depending on clinical presentations and radiographic findings. Surgery is an effective treatment for CIDH and can provide a definitive diagnosis. With meticulous management of dural and arachnoid tears, the postoperative incidence of CSF leakage is found to be low.

533

P265: Lumbar disc herniations in females: comparative risk factors for pre-menopausal versus post-menopausal cohorts and emerging etiopathogenesis of disc disease in younger patients

Jake McDonnell ¹ , Kielan Wilson ² , Gráinne Cunniffe ² , Stacey Darwish ² , Conor Buckley ¹ , and Joseph Butler ²

¹ Biomedical Engineering, Trinity Biomedical Sciences Institute, Dublin, Ireland

² National Spinal Injuries Unit, Mater Misericordiae University Hospital, Dublin, Ireland

Introduction: Lumbar disc disease can prove a debilitating injury. Typically, it is believed to be a multifactorial process inclusive of aging, obesity and abnormal biomechanical loading patterns in the spine. Nevertheless, traditional theories of pathophysiology may not hold true for younger populations. That serves the premise for this study, to investigate comparative risk factors for lumbar disc herniation (LDH) in pre- and post-menopausal female cohorts. Materials and Methods: A retrospective review was conducted at our institution, a national tertiary referral centre, for female patients who underwent surgery for symptomatic lumbar disc herniation between June 2016 and May 2020. Patients were separated into two specific cohorts; (i) those aged < 45 years of age at the time of injury, termed the pre-menopausal cohort and (ii) those aged ≥ 45 years of age at the time of injury, termed the post-menopausal cohort. Demographic, clinical and radiological characteristics were collected and compared between groups. Results: 110 patients were identified (43 pre-menopausal, 67 post-menopausal). On univariate analysis, the pre-menopausal cohort had a significantly higher BMI (29.6 kg/m² vs 27.1 kg/m²; p = 0.02), history of LDH (p = 0.02) history of lumbar spine surgery (p = 0.02), greater degree of psoas fat infiltration (p < 0.001), lumbar lordosis (p < 0.01) and proportion of distal lumbar lordosis (p = 0.01). On multivariate analysis, only psoas fat infiltration retained its significance (OR: 1.78, 95% CI 1.22:2.97, p < 0.01). Conclusion: Our findings show that pre-menopausal patients who presented with LDH were at risk of LDH due to a significantly greater degree of psoas fat infiltration when compared to the post-menopausal group. This may be related to a possible relationship between oestrogen, adipokines and myokines. The authors encourage further robust studies in order to elucidate this potential relationship.

540

P266: Percutaneous laser disc decompression: a prospective study with clinical results and radiation exposure

Marc Prod'homme ¹ , Grasset Didier ¹ , and Duccio Boscherini ¹

¹ Neuro Orthopedic Center, Clinic La Source, Lausanne, Switzerland

Introduction: In case of a contained disc herniation (CDH), percutaneous laser disc decompression (PLDD) may be an alternative to microdiscectomy. Its percutaneous approach aims to decompress the bulging disc when not yet an authenticated fragment excluded from the disc. Computerized navigation with O-arm allows more accurate surgery with the advantage of providing no irradiation to the surgeon. The aim of the study is to assess O-arm PLDD in terms of clinical results and irradiation. Material and Methods: A prospective inclusion of all consecutive patients was performed when they presented with a lumbar CDH and related sciatica without any neurological deficit, confirmed by magnetic resonance imaging, showing a high intensity zone, and operated on by O-arm PLDD. Demographic data, clinical scores such as numerical rating scale of pain (NRS) and Oswestry Disability Index (ODI) were recorded. Disc level of the surgery, operative time and irradiation data were also collected. Radiation exposure and its absolute risk of radiation-induced cancer (AR, in%) were calculated using the dose length product (DLP) and the dose area product (DAP) coming from the dosimetric report of the O-arm, and the effective dose E was calculated according to the recommendations of the International Commission on Radiological Protection. Complications were collected. Results: 26 patients were included, with a follow-up between 1 and 24 months. Mean age was 47 years. L4/5 and L5/S1 were the most operated levels. Multi-level surgery was performed on 4 patients. Average operative time was 32 minutes. NRS decreased from 7 to 4/10, p = 0.04. ODI decreased from 51 to 20%, p < 0.01. Mean E was 4.03 mSv, with a related AR of 2.1x10^-4 %. No intraoperative complication occurred. One patient presented with a contralateral recurrence after 10 days and another with ipsilateral recurrence after 1 month and they were both scheduled for microdiscectomy with good evolution. Conclusion: Clinical results are encouraging. O arm PLDD was safe and effective and also minimally invasive with an acceptable level of irradiation. This technique plays a role in conditions where surgery is not mandatory and patients have significant pain.

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P267: Results in patients undergoing outpatient lumbar discectomy in a third level clinic in the city of Bogota

Mario Herrera Méndez ¹ , Madeline Bilbao ¹ , and Geraldine Alvarez ¹

¹ Spine Surgery, Clinica Universitaria Colombia, Bogota , Colombia

Introduction: Lumbar discectomies are the most common procedure in spinal surgery, for two decades it has been safely performed on an outpatient basis in the world, and it is important to report the results that have been obtained in Bogotá, Colombia in patients undergoing lumbar discectomy outpatient. Methodology: Descriptive observational study in patients who underwent laminectomy, foraminotomy and microdiscectomy between January 2014 and January 2021, evaluating pain, postoperative complications, and readmissions 30 days after surgery among patients with outpatient management in a high-level University Clinic complexity. Results: From January 2014 to December 2021, 101 lumbar discectomies were performed in patients with a mean age of 41.9 years (SD: 12.6). The median bleeding was 30 ml (IQR: 30), a median surgical time of 63 minutes (IQR: 16), and a postoperative visual analog pain scale of 1 (IQR: 1). An improvement percentage of 100% was obtained in 52 patients. Two patients were readmitted, one with deep vein thrombosis that required anticoagulation with adequate evolution and another patient with dyspnea in whom PTE was ruled out. There were no reinterventions or mortality at 30 postoperative days. Conclusion: The outpatient management of patients undergoing lumbar discectomies in a University Clinic in Bogotá, showed low rates of complications, few readmissions and no cases of reintervention and mortality during the study follow-up, considering that it is a safe procedure to perform on an outpatient basis. considering an adequate selection of patients.

Keywords (MeSH): Diseases of the spine, hernia, laminectomy, discectomies, ambulatory care

952

P268: Predictive factors for disc degeneration at the levels above and below instrumented posterior fusion in thoracolumbar junction fractures

Mouldi Lamouchi ¹ , Jlidi Mohamed ¹ , Mohamed Hedi Gharbi ¹ , Walid Bouaicha ¹ , Ayachi Montassar ¹ , and Selim Daas ¹

¹ Orthopedics and Traumatology Department, Hospital of Mohamed Taher Maamouri, Nabeul, Tunisia

Introduction: Disc degeneration is a physiological aging process. The disc above or below a spinal fixation appears to be exposed to accelerated degeneration. The objective of our work is to determine the predictive factors of adjacent segment degeneration after treatment of thoracolumbar jonction fractures. The objective of our work is to determine the predictive factors of adjacent segment disease (ASD) after treatment of thoracolumbar junction fractures with posterior arthrodesis. Material and Methods: We conducted a single-centre retrospective descriptive and analytical study over a period of 10 years. The fractures were classified according to the Magerl classification. The DSA was studied before surgery and at the last follow-up according to the UCLA classification. All fractures were operated on through a posterior approach. Our patients were divided according to the number fixed vertebrae: a long fixation (2 vertebrae above the fracture and 2 vertebrae below), a mixed fixation (2 vertebrae above the fracture and one vertebra below) and a short fixation (one vertebra above the fracture and one vertebra below). Results: Our series included 120 patients with a mean age of 48.39 years. The sex ratio was 1.6. The body mass index (BMI) was 28 kg/m² with extremes of 20.7 kg/m² and 38.21 kg/m². The initial radiological control shows an average of 20.51° for the vertebral kyphosis, an average of 18.03° for traumatic regional angulation of 18.03° and an average of 0.6 for the beck index. 57% of the patients were grade 1 according to the UCLA classification. Type A3 according to the Magerl classification was the most frequent 54.2% of the patients had a long fixation. 33 of our patients had a mixed fixation. The short fixation was used with 22 patients. The average follow-up was 57 months. X-rays at the last follow-up showed an average of 13.49° for the vertebral kyphosis, an average of 10.39° for the traumatic regional angulation and an average of 0.77 for the beck index. 27% of our patients were grade 3 or 4 according to the UCLA classification at the last follow-up. The segment above the fractured vertebra is the most affected. In a univariate study, the predictive factors for DSA were: BMI, age, female gender, short fixation and Magerl type A3. In a multivariate study, the only factor predicting osteoarthritic degeneration was age (p = 0.019). The radiological parameters before and after surgery were not predictive factors. Conclusion: ASD after treatment of thoracolumbar junction fractures is commonly accepted despite some clinical discordance. The frequency and main factors of ASD have been analyzed in various biomechanical and clinical studies. The multifactorial nature of disc degeneration is well established. The only predictive factor found in our series was gender. BMI, type of fixation and type of fracture should be taken into consideration in order to prevent adjacent segment disease during thoracolumbar junction fixation.

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P269: Analysis of umbilical cord stem cell-derived microparticles effects on disc cells: implications in intervertebral disc metabolism and regeneration

Julia Martins de Oliveira ¹ , Lucas Seabra Fernandes ¹ , Gustavo Ribeiro ¹ , Mario Lenza ¹ , Luciano Rodrigues ¹ , Andrea Aparecida de Aro ² , Rafael Maza Barbosa ² , Alexandre Leite Rodrigues de Oliveira ² , Eliane Antonioli ¹ , and Pedro Pohl ¹

¹ Projeto Locomotor, Hospital Israelita Albert Einstein, São Paulo, Brazil

² Universidade de Campinas, Campinas, Brazil

Introduction: Spinal diseases related to intervertebral disc degeneration (IDD) represent a public health problem due to physical and social limitation and economic losses. Researchers have demonstrated benefits of mesenchymal stem cells (MSCs) over intervertebral disc cells. Pathways of cell-cell communication were recently identified, including a new way of cellular communication mediated by microparticles (MPs) (microvesicles (MVs) or extracellular exosomes), that can be isolated from conditioned media of cellular cultures. There are different sources of MSCs and umbilical cord mesenchymal stem cells (UC-MSCs) has got attention as a potential cell source for regenerative medicine, as well as their MPs. Cell free therapy is a hot topic in treatment of diseases and correlating to this project can bring together the benefits that UC-MSCs products can provide through their cellular microparticles. Methodology: Umbilical cord samples will be collected for isolation of mesenchymal cells following the protocol described. Human intervertebral disc cells will be obtained from intervertebral disc waste material during elective spinal surgical procedures, with the annulus fibrosus and nucleus pulposus being anatomically separated, washed, fragmented and digested for 60 minutes at 37ºC in an enzyme solution with 0.2% pronase. The material will be subjected to further digestion and incubated at 37° C in a humidified atmosphere of 5% carbon dioxide and 20% oxygen and cultured in a monolayer until confluence of 70-80%. MPs from UC-MSCs will be isolated from the culture medium of UC-MSCs until the seventh passage. After 95% cell confluency, the cells will be washed and incubated for 48h in a new medium. Confirmation of the extraction of MPs from UC-MSCs will be done by direct electron microscopy image, the criteria for MPS approval will be obtaining MPs with 0.1 to 1 µm, validating the protocol, and reserved for use. The results will be evaluated using flow cytometry to confirm and quantify the internalization of MPs derived from UC-MSCs in intervertebral disc cells, AF and NP, using the described technique. Controls will be performed with the supernatant and culture medium without MPs. Gene expression analysis of key factors in the production and maintenance of the extracellular matrix of intervertebral disc cells exposed to UC-MSCs MPs will be performed in comparison to their soluble products present in the supernatant and untreated controls. The level of gene expression of extracellular matrix molecules by AF and NP cells will be analyzed after 72h of treatment: collagen types I and II, aggrecan and enzymes responsible for the degradation of the extracellular matrix. Results: This is an ongoing project supported by AO Spine Start-Up Grant. It is expected to present positive effects on IVD cells when exposed to UC- MSCs MPs. We are analyzing the results, but they are progressing well. We’ll have them by the Global Spine Congress. Conclusion: We expect to find that UC-MSCs MPs will be internalized by intervertebral disc cells, resulting in a change in their gene and protein expression, stimulating the expression of aggrecan and collagen and inhibiting the production of factors that favor the degradation of the extracellular matrix.

1402

P270: Biportal endoscopic trans-laminar approach for the lateral recess stenosis and scontra-lateral extraforaminal disc herniation: technical report

Jisoo Ha ¹ and Do Hyung Kim ¹

¹ Neurosurgery, Yonsei Okay Hospital, Gyeonggi do, South Korea

Objective: Biportal interlaminar approach for unilateral laminotomy and bilateral decompression (ULBD) has long been considered the first treatment option for symptomatic lumbar degenerative disease such as central canal stenosis or foraminal disc extrusions and stenosis. Interlaminar approaches. It is satisfactory for central canal stenosis. However, limited to the contra lateral side lesion with foraminal/extraforaminal stenosis or herniated disc. If we used ‘translaminar’ approaches. It is not difficult to perform full decompression from the central canal to the contralateral extra foraminal area. The purpose of our study is to introduce our technique of translaminar approach for the lesions with contra-lateral recess stenosis and extraforaminal stenosis at the same time. Techniques: The “trans-laminar” approach targets lamina more directly than the “inter-laminar” approach, which used generally in central canal decompression. It is the same principle as the full endoscopic PSLD's keyhole laminotomy for discectomy and the thoracic decompression technique by UBE. Since the translaminar approaches make the portal more proximally than interlaminar approaches, the initial point of the laminotomy would be more proximal than formar decompression. When approaching the epidural space after sufficient bone work, the working portal becomes parallel to the exiting root-disc level compared to the interlaminar approach. This allows access to bony spurs, hard disks, and even to the extraforaminal area around the exiting root. Thus, you can achieved the contra-lateral side foraminotomy more easily. Results: We successfully performed “translaminar approach” for the patient who got central stenosis, traversing root compression due to contra lateral recess stenosis and even extraforaminal stenosis. There were no complications related with surgery. VAS and ODI were significantly improved after surgeries. Conclusion: This procedure may be a safe and efficacious treatment option for contralateral lesions or multiple-sites stenosis. Thus, this new-designed endoscopic based technique could be a feasible alternative to staged decompression surgeries for multiple site stenosis. although more cases and long-term follow up studies are needed to obtain accurate clinical results.

1850

P271: Pronostic factors for cauda equina syndrome

Nessrine Nessib ¹ , Mahmoud Ben Messaoud ¹ , Abdelhafidh Slimane ¹ , Eya Chahed ¹ , Nadhir Karmani ¹ , Khalil Ghedira ¹ , and Jalel Kallel ¹

¹ Neurosurgery, Mongi ben Hamida Institute of Neurology, Tunis, Tunisia

Introduction: Cauda equina syndrome is a rare clinical entity which is secondary to the compression of the cauda equina roots. It is a diagnostic and therapeutic emergency, marked by motor, sensory and genitourinary sequelae that may be irreversible, with a significant impact on the patient's life and his social rehabilitation. We carried out this study to analyze the epidemiological, clinical, para-clinical and evolutionary characteristics and to study and identify the different prognostic factors.

Materials and Methods: We performed a retrospective study of 54 cases of Cauda equina syndrome operated in emergency at the neurosurgery department of the National Institute of Neurology of Tunis over a period of 10 years from 2010 to 2019. Results: The average age of our patients was 45 years. The most represented age group was between 40 and 49 years (42.6%). Our series included 41 men (76%) and 13 women (24%). The time course varied from one day to 6 months. Only 14.8% of the cases had a delay of less than 48 hours. The onset was progressive in 74% of cases. The functional signs were dominated by genital-sphincter disorders (100% of cases). The other signs were low back pain in 79% of cases, radiculalgia in 90.7% of cases, paresthesia in 51% of cases and motor disorders in 87.1% of cases. Perineal sensory disorders were observed in 37% of cases. Our series included an incomplete form of cauda equina syndrome in 63% of the patients and a complete form in 37% of the cases. Lumbar MRI, performed in all our patients, was the examination of choice and allowed to confirm the diagnosis and to orient the etiology. The etiological origin was dominated by lumbar disc herniations, which were found in 87% of cases, followed by tumor causes in 13% of cases. Urgent surgical decompression was performed in all patients. The long-term evolution (2 years of follow-up) was stationary in 37% of the cases, favorable in 61.1% of the cases of which 33.3% had a complete recovery, with only one case of aggravation (1.9%). Our analytical study showed significantly a favorable evolution in the age group below 45 years. The incomplete form was significantly associated with a favorable evolutionary prognosis. A duration of evolution lower than 48 hours is associated with better prognosis. The presence of anaesthesia in the saddle is a statistically significant factor of poor prognosis. Conclusion: Cauda equina syndrome is a neurosurgical emergency marked by severe motor and sphincter sequelae. Urgent surgical decompression within 48 hours of the onset of signs and the incomplete form are associated with a favorable evolution.

1914

P272: Mechanical characterization of flexible and reservable support materials for tissue engineered intervertebral discs

Pravesh Gadjradj ¹ , Branden Medary ¹ , Alikhan Fidai ² , Byumsu Kim ² , Ibrahim Hussain ¹ , Roger Härtl ³ , and Lawrence Bonassar ²

¹ Neurosurgery, Weill Cornell Medical College, New York, United States

² Biomedical Engineering, Cornell University, New York, United States

³ Department of Neurological Surgery, Weill Cornell Medicine and Och Spine, New York Presbyterian Hospital, New York, United States

Introduction: An enduring challenge in implementing a tissue engineered replacement for end stage intervertebral disc (IVD) degeneration is mechanically stabilizing the construct at early timepoints. Previously, polylactic acid (PLA) cages were used to provide mechanical reinforcement for tissue engineered intervertebral discs (TE-IVDs) in a pilot minipig study. While these materials have properties that should far exceed those needed to support loads in the spine, stress concentrations arising from vertebral anatomy led to failure of these implants in vivo. Identifying materials with sufficient flexibility is key to the successful implementation of a support cage for TE-IVDs. FlexiFil (FormFutura) is an elastomeric 3D printer filament that is amenable to the fabrication of support cages, but little is known on how the mechanical performance of FlexiFil printed cages compares to PLA. Therefore, the objective of this study was to compare the mechanical performance of printed PLA and FlexiFil cages and assess microscale damage as revealed by scanning electron microscopy (SEM). Methods: To assess how TE-IVD cage materials behave under loading, force-displacement testing was performed on PLA and FlexiFil cages. Specifically, 3 PLA and 3 FlexiFil cages with a height of 2.5 mm were printed using a Prusa i3 MK3S+. To simulate compressive forces arising from differences in vertebral anatomy, a flat ended indenter with a triangular cross-section was used to load samples through the mid-plane. Printed cages were mounted and subjected to 2 mm of indentation at a rate of 0.1 mm/s. After loading, samples were sputter coated with Au-PD and imaged using a Tescan Mira SEM. Results: Force-displacement testing revealed that at 2 mm of indentation, PLA cages were significantly stiffer than FlexiFil cages (p = 0.0007) with average loads of 79.6 ± 8.9 N and 30.4 ± 1.3 N, respectively. Notably, plastic deformation occurred at much lower displacements for PLA (0.98 mm) compared to FlexiFil (1.75 mm). Consistent with mechanical testing, SEM imaging of indented cages revealed that the PLA samples had a wide footprint of plastic deformation, extending > 2 mm from the indentation site. Plastic deformation of PLA samples led to delamination of printed layers and brittle failure of the material at the indentation site. In contrast, FlexiFil samples showed only a narrow band of plastic deformation ∼25 µm from the indentation site with no signs of delamination or brittle failure. Discussion: Force-displacement testing and SEM imaging reveal early yield and mechanical failure of PLA cages. In contrast, FlexiFil was able to withstand nearly twice the deformation without any detrimental changes in mechanical performance and minimal damage as seen in SEM. To fully recapitulate compressive forces seen in vivo, future work will load TE-IVD cages in a minipig spine ex vivo. Collectively, our studies suggest that FlexiFil is a promising material for fabricating a TE-IVD support structure. Significance: FlexiFil cages exhibited a wider range of elastic behavior than PLA cages, with less microscale damage. As such, FlexiFil is a promising candidate for fabrication of support structures for IVD tissue engineering.

2000

P273: Diagnosis and management of thoracolumbar spinal disorders presenting as cardiac, gastrointestinal, and other false pain syndromes

Nolan Brown ¹ , Angie Zhang ¹ , Andrew Chan ² , Shane Shahrestani ¹ , Alexander Himstead ¹ , Rohin Singh ¹ , Alvin Chan ¹ , Julian Gendreau ¹ , Martin Pham ³ , and Michael Oh ¹

¹ Neurosurgery, UC Irvine, United States

² Neurosurgery, Columbia University, United States

³ Neurosurgery, UC San Diego, Unite States

Introduction: Although pseudoangina is most commonly caused by cervical disc herniation, several cases have been described where thoracic herniation produced symptoms of pseudoangina. If thoracic herniation can produce angina-like pain, then it is important to consider whether pathology of the thoracolumbar spine in general can trigger false pain syndromes distinct from pseudoangina. Materials and Methods: We seek to provide the most comprehensive study regarding the diagnosis and treatment of spinal conditions causing false pain syndromes. In order to accomplish this objective, we queried the literature and systematically selected relevant studies according to PRISMA guidelines. Results: Across 22 selected studies, the sample size was 30 patients, and a total of 26 met criteria for statistical analysis. 7 (26.9%) of these patients presented with a chief complaint of pseudoangina resulting from thoracic disc herniation. 73.1% (19/26) of patients exhibited pain mimicking visceral origin. Overall, 13/19 (68.4%) patients exhibited thoracic spine disease only and 4/19 (21.1%) patients were affected at lumbar levels only, while 2 (10.5%) patients exhibited thoracolumbar herniation. Presentations included abdominal pain (11/19) mimicking appendicitis or pancreatitis, flank pain mimicking renal colic (8/19), and 2 cases of scrotal pain/orchalgia. Symptom durations ranged from acute (< 24 hours) to 7 years. Treatments were reported for 18/19 patients and all treated patients reported alleviated pain. 7/18 were managed conservatively while 11/18 were treated surgically. Misdiagnosis resulted in unnecessary surgery (pancreaticojejunostomy) or other invasive procedures. Conclusion: In spinal disorders manifesting with atypical pain syndromes, delay in proper diagnosis and unnecessary treatments can unfortunately cause prolonged patient suffering and increased cost of healthcare. As a result, some have proposed that spinal screening should be incorporated into clinical examinations involving false visceral pain syndromes.

Epidemiology

47

P274: Comparison of opioid use and prescribing patterns among orthopedic surgeons and other orthopedic subspecialties in the United States

Chadi Tannoury ¹ , Rahul Bhale ¹ , Justin Koh ¹ , Aziz Saade ¹ , Christopher Maatouk ¹ , and Tony Tannoury ¹

¹ Orthopaedic Surgery, Boston University, Boston, United States

Introduction: The US opioid epidemic has received particular attention with 33091 reported deaths from narcotic overdose in 2015. A recent survey comparing US and Japanese opioid prescribing patterns from the AOA-JOA traveling fellows included 76 US orthopedic surgeons representing 8 subspecialties. We used this data to compare opioid prescribing patterns among US spine surgeons to other orthopaedic subspecialties. Methods: The survey included data based on surgeon demographics (gender, age, years in practice), patient baseline opioid use(pre/post-operative opioid use, types of opioid agents, duration of opioid use), perioperative pain management (procedure/institution factors, multimodal analgesic therapy), and responses to questions regarding opioid use attitudes. Survey responses were recorded as either categorical or semi-continuous variables. Statistical analysis was performed using chi-squared analysis for categorical responses and Kolmogorov-Smirnov testing to a statistical significance level of p < 0.05. Parameters that trended toward significance to p < 0.10 were also recorded. Statistical analysis was performed using Stata statistical analysis software [StataCorp, College Station, Texas]. Results: Spine patients were more likely using opioid medications prior to evaluation by spine surgeons compared to non-spine patients (p = 0.029). Patients with spine pathologies treated non-operatively were also more likely to be prescribed opioids (p = 0.006). Post-operatively, spine patients were less likely to stop opioid prescriptions on the intended time (p = 0.046). Peri-operatively, spine patients were more likely to be given muscle relaxant medications, and less likely to receive local/regional anesthesia (p = 0.0025). Additionally, spine patients showed a trend toward association for requesting additional opioids beyond their initial prescription (p = 0.057). Spine surgeons showed a trend toward association for choice of opioid agent prescribed-spine patients were less likely to receive codeine/tramadol analogs (p = 0.062). When surveyed on opinions regarding opioid use, US spine surgeons did not show significantly different opinions regarding opioid use compared to surgeons in other subspecialties. Conclusion: Spine patients did demonstrate statistically significant patterns of opioid use, particularly regarding opioid use prior to evaluation by orthopedic surgeon and use of opioids for nonoperative pathologies. They were also less likely to stop opioid prescriptions on time. Surgeon prescription patterns and perceptions of opioid use were not significantly different for spine surgeons compared to other subspecialties.

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P275: Epidemiology of work related neck pain among spine surgeons

Sameh Abolfotouh ¹ , Omar Alnori ² , Theodore Choma ³ , Don Moore ³ , and Mostafa Abolfotouh ⁴

¹ Orthopedics Department, MEDCARE Hospital, Dubai, United Arab Emirates

² Orthopedics Departmen, Hamad Medical Corporation, Doha, Qatar

³ Spine Unit, Orthopedics Department, University of Missouri, Missouri, United States

⁴ King Abdulaziz Medical City (KAMC), National Guard Health Affairs, Riyadh, Saudi Arabia

Background: Spine surgeons are at risk of musculoskeletal pain and injuries possibly due to their work-related activities, posture and affected body mechanics. Aims: to investigate work-related neck pain among spine surgeons in different AO SPINE regions, by (1) estimation of the prevalence of work-related neck pain, and (2) determination of its predictors, its personal and occupational consequences, and the different management methods adopted for it. Methods: A cross-sectional survey of 411 spine surgeon members of AO spine was conducted during March–May 2021, using the Modified Nordic Questionnaire and the Neck Disability Index. Data on experience of neck pain during the last 12 months, and its consequences and risk factors were collected. Logistic regression analysis was done to identify significant predictors of neck pain. Statistical significance was considered at p < 0.05. Results: The majority of spine surgeons were married (360, 92.3 %), and their average age was 45.31 ± 7.86 years, and average BMI was 26.95 ± 4.07 kg/m². They experienced 66.7% 1-year neck pain prevalence. According to the Neck Disability Index, more than one-half (52.8%) of surgeons experienced disability due to neck pain of mild (45.5%), moderate (6.5%) and severe (0.8%) grades. Neck pain was responsible for stopping work in 17.5% of surgeons, with a median 3.5 (IQR, 2-7.8) days off work during the last year. One half of participants (56.3%) were treated by medical care, 31.5% by physiotherapy, and 16.5% requested rest days and/or sick leave. Physical stress (p < 0.001) and non-exercising (p = 0.04) were significant predictors of neck pain, while demographics, workload-related factors and the use of surgical magnification (Loupes and microscopes) were not significantly associated with neck pain prevalence (p > 0.05 each). Conclusion: The 12-month prevalence of neck pain was high among spine surgeons, with an impact on activities of daily living, mostly of mild degree, reported by one-half of surgeons. Physical stress was the only significant predictors while sports practice was ta protective factor of neck pain. Medication was the main management adopted. An increased focus on pain prevention through improved workplace ergonomics, and sports activity programs to reduce the risk of neck pain and arrange for proper rest periods is recommended.

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P276: Analysis of the implications of cervical spine alignment on lumbopelvic alignment

Taryn Ludwig ¹ , Sarup Sridharan ¹ , Ariana Frederick ¹ , Brent Edwards ² , Michael Asmussen ³ , and Fred Nicholls ¹

¹ Department of Surgery

² Faculty of Kinesiology, University of Calgary, Canada

³ Department of Biology, Mount Royal University, Calgary, Canada

Introduction: To date, normal patterns of alignment in the cervical spine have not been conclusively defined. Previous studies have attempted to correlate cervical spine alignment with the remainder of the spine and pelvis. Results however, were inconsistent and limited by small sample size. Knowledge of normal alignment is essential in evaluation and preoperative planning for deformity correction. This study aims to establish normative values and correlate these with established patterns of lumbopelvic alignment. We hypothesize alignment of the cervical spine can predict lumbopelvic morphotype. Material and Methods: Healthy volunteers (N = 497) between 20-40 years of age with no pre-existing spine pathology were recruited. Baseline demographics, Oswestry Disability Index, and Neck Disability Index were collected. Whole body 2D EOS imaging was obtained for all participants. Using a semi-automated image analysis software (KEOPS, by SMAIO), standard measures of alignment of the pelvis, lumbar, thoracic, and cervical spine were obtained. Roussouly morphotype (RM) was identified for each participant. Principal components (PC) of cervical vertebral body centroids were input into a support vector machine algorithm to predict RM. Results: Average age of participants was 28.4 ± 5.2 years. Fifty six percent of participants were female, average BMI was 24.9 ± 4.2. Number of participants of each RM were: Type 1 = 26, Type 2 = 126, Type 3 = 221, Type 4 = 124. When PC explaining 90% of variability were used, RM was appropriately predicted as follows: Between Type 1, 2, 3 and 4 = 50%, Type 2, 3, 4 = 53%, Type 2, 3 = 69%, Type 2, 4 = 47%, Type 3, 4 = 69%. Including nearly all PC (99.99% of the variance), classification rates improved: Between Type 1, 2, 3 and 4 = 68%, Type 2, 3, 4 = 88%, Type 2, 3 = 89%, Type 2, 4 = 99%, Type 3, 4 = 99%. Conclusion: This study demonstrates that a predictable relationship between cervical and lumbopelvic alignment exists; this relationship is sensitive to subtle features of cervical spine shape, captured by higher order PCs. It provides a robust normative database for cervical spine alignment and will provide insight into normal patterns of lumbopelvic compensation with “abnormal” cervical spine alignment. Future work will aim to classify patterns of cervical spine alignment, and identify features specifically captured by each principal component, particularly the higher components.

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P277: Level of spin in the abstracts of RCTs in spine surgery - an ORG-LOC tool based assessment

Sathish Muthu ^1,2 and Girinivasan Chellamuthu ²

¹ Department of Orthopaedics, Government Medical College, Dindigul, India

² Orthopaedic Research Group, Quality Appraisal Committee, Coimba

Introduction: There has been a massive surge in published spine literature in the last few years. Even in highly credible research models like Randomised Control Trials (RCTs), many pitfalls do exist that a reader must be aware of. One common but less explored pitfall is the spin. Particularly in the abstracts, it is a potential source of deception. Grading of RCTs based on spin will help readers to interpret their results better. Hence we aim to grade the RCTs of spine surgery based on spin in their abstracts, analyze its prevalence, and highlight on the usefulness of spin grading for any RCT. Materials and Methods: We selected 250 recent RCTs from top 5 spine journals. Baseline data were collected. CONSORT Adherence Score (CAS) based on the adherence of the abstracts of the RCTS to CONSORT checklist was calculated. The abstracts of the RCTs were graded using the Level Of Confidence (LOC) grading tool developed by the Orthopaedic Research Group. The association of spin grade with other characteristics of the articles were analyzed. Results: The median CAS was 11 (IQR 10-12). Only 47.6% (n = 119) articles had High LOC with no or one non-critical spin in abstract and 12.4% (n = 31) had Moderate LOC with more than one non-critical spin. 28% (n = 70) had at least one critical spin and 12% (n = 30) had more than one critical flaw making their results have Low and Critically Low LOC respectively. Of the ten variables analyzed in multivariate regression analysis, CAS was the only significant factor that determines the level of confidence in the abstract of RCTs. Conclusion: Spin based grading of RCTs is the need of the hour to aid readers to interpret the true essence of research papers. 40% of the RCTs in top spine journals had low to critically low LOC. Structuring of abstracts is the way forward to prevent spin.

209

P278: Does English speaking status affect post-acute care in thoracolumbar fusions? A retrospective study in a multiethnic population

Henry Hoang ¹ , Aaron Hui ¹ , Dan Berman ¹ , Ananth Eleswarapu ¹ , Jonathan Krystal ¹ , and Zach Sharfman ¹

¹ Orthopedics, Montefiore Medical Center, Bronx, United States

Introduction: English speaking status is an often-overlooked risk factor that influences the longitudinal progression of patient care. Obstacles such as the procurement of physician appointments, comprehension of treatment plans, misdiagnoses, and delayed treatment are all amplified in the setting of a language barrier. Thoracolumbar fusions are indicated for the management of degenerative disc disease, degenerative spondylolisthesis, spinal stenosis, tumors, and fractures with more than 300,000 performed annually. Post-operative clinical outcomes of non-English speaking patients who undergo thoracolumbar fusion have not been thoroughly studied. A comprehensive understanding of the post-operative sequelae of non- English speaking and minority patients is crucial for the development of interventions aimed at reducing complications and post-operative readmissions. The purpose of this study is to compare rates of readmission, complications, and treatment durations between English and non-English speaking patients undergoing thoracolumbar fusions. Material and Methods: A retrospective study of 301 patients who underwent a thoracolumbar fusion at a level 1 trauma center in the Bronx from 2016 was performed. Demographic, surgical, and post-operative measures were collected. The primary outcome were readmission to the emergency department (ED) within 30 days, 90 days and chief complaint. Our secondary outcome was length of stay defined as days patient spent in inpatient admission post-operatively. Odds ratio were calculated using SPSS to determine differential rates of re-presentation to the ED post-operatively. An independent-samples t-test was run to determine if there were differences in postoperative length of stay(days) between non-English speakers and English speakers. Results: All 301 patients who undergone thoracolumbar fusions in 2016 were analyzed in this study, consisting of 62 non-English speakers and 239 English speakers. There were 7 non-English patients that returned to ED within 30-days post-operation compared to 36 English speakers. The odds ratio of returning to the ED within 30-days post-operation in non-English speakers versus English speakers was 1.393 (95% CI, .588 to 3.302). There were 21 non-English speakers who returned to the ER compared to 63 English speakers. The odds ratio of returning to the ED within 90 days post-operation was .699 (95% CI, .384 to 1.273). There was no significant different in length of stay between non-English speakers (7.8 ± 6.4) and English speakers (8.5 ± 8.8) with a difference of 1.2 (95% -3.05 to 1.67), T (299) = -.579, p = .563. Conclusion: We have described that a large portion of patients undergoing thoracolumbar surgery in the Bronx present back to the ED within 30 and 90 days of operation. English speaking status was determined not to be associated with different rates of presentation to the emergency room within 30 and 90 days of thoracolumbar fusion, or different lengths of stay. Taken together, English-speaking status is not evidenced to be a risk factor that influenced post-operative readmission of patients undergoing thoracolumbar fusion.

336

P279: Epidemiological features of traumatic spinal cord injury in a tertiary hospital in Cagayan Valley: a 5-year cross-sectional study

Jake Albert Miguel ¹ and Niccolo Mamba ¹

¹ Orthopaedics, Cagayan Valley Medical Center, Tuguegarao, Philippines

Introduction: Globally, the recorded prevalence and incidence of people with Traumatic Spinal Cord Injury (TSCI) is maybe underreported due to the lack of a national registry system for spinal cord injuries particularly in developing countries, hindering injury prevention, health care, and other social planning. Numerous articles on TSCI epidemiology have been published in Europe, North America, and Australia because most Western nations have implemented TSCI registries or databases. In the Philippines, Cagayan Valley Medical Center (CVMC) is the largest medical facility and has the greatest number of admitted patients in the entire region. However, little is known and documented about the prevalence of TSCI at this time. The overall objective of this study is to describe the epidemiological and demographic characteristics of patients with TSCI admitted in CVMC as well as to determine its prevalence. Material and Methods: The researchers retrospectively reviewed the medical records of patients with traumatic spinal cord injuries admitted in Cagayan Valley Medical Center from 2016 to 2020. Variables included age, sex, civil status, occupation, and the clinical profile: mechanism of injury, spinal level of injury, American Spinal Injury Association Impairment (ASIA) Scale, imaging studies, treatment received (conservative or surgery), and condition upon discharge. Results: Between 2016 and 2020, a total of 145 patients had traumatic spinal cord injuries. The mean age of the patients was 42.13 years, and 93.10% were males with a male/female ratio of 13.5:1. The occupations with the highest risk were the unemployed (59.31%) with falls from a height (51.72%) were the leading cause of injuries. This was followed by motor vehicular collisions (43.45%). The most common level of spinal injury was the cervical region, accounting for 57.24%, with the majority of documented cases having an American Spinal Injury Association Impairment (ASIA) Scale of A. Nonoperative management was done in most of the cases (80%). For those operated cases, instrumented posterior decompression and spinal fusion were done (65.52%). Most of the patient’s conditions improved upon discharge (57.93%) Conclusion: The result of this study is comparable to other previous literature. The majority of the patients are typically males sustaining injuries in the cervical spine secondary from falls from a height in the workplace. The formulation of preventive strategies should focus on identified high-risk groups sustaining such injuries. In addition, to precisely document the epidemiological profile of patients with TSCI, a standardized spine trauma form should be created. Moreover, the establishment of a national registry system will accurately describe the incidence and prevalence of TSCI not only in CVMC but in the entire Philippines.

341

P280: Patient reported function outcomes versus objective fitness assessments: are patients telling the truth about their fitness level?

Fthimnir Hassan ¹ , Yen-Lou Lee ¹ , LaRae Klarenbeek-Mitchell ² , David Ruderman ² , Eric Schaum ² , and Lawrence Lenke ¹

¹ Department of Orthopaedics, Columbia University Medical Center, The Och Spine Hospital at New York-Presbyterian, New York, United States

² Department of Physical Therapy, The Och Spine Hospital at New York-Presbyterian, New York, United States

Introduction: Adult Spinal Deformity (ASD) patients provide subjective outcomes to assess overall fitness on various patient reported outcomes (PROs). However, these outcomes may be subject to response bias leading pts to answer survey questions untruthfully. This analysis aims to determine whether pt. reported fitness outcomes correlate with the results of objective fitness assessments. Methods: ASD patients ≥ 18 who underwent prehabilitation (prehab) fitness assessments prior to agreeing to surgery were evaluated from 2017-2020. Prehab included a variety of fitness tests such as 5x sit-to-stand test (5xSST), gait speed, Hand Grip Strength, and the 6 minute walk test (6MWT). Surgical factors included surgery type, total fusion levels (TFL), total instrumented vertebrae (TIV), and length of stay. PROs (SRS22r and ODI) were collected at preop. Prehab measures were analyzed alongside the SRS function domain to determine correlation using pearson/spearman correlation coefficients and multiple linear regression (MLR). Results: Of the 39 patients evaluated, mean age was 52 ± 11yrs, 34 (83%) were women, 25 (61%) were revision cases, and 34 (87%) were fused to the pelvis averaging 12 ± 5 TFL, 13 ± 4 TIV and a length of stay of 6.4 ± 2days. Preoperatively, Mean HR, SpO2, BP were 75 ± 14 bpm, 98 ± 2%, 127/80 ± 13/9 mmMg, respectively. Mean SRS22r and ODI were 65 ± 13 and 38 ± 19, respectively, with a mean SRS function domain of 3.2 ± 1. SRS function domain correlated with the following: age (r = -0.4; p = 0.0049), 5xSTT (r = -0.6; p = 0.0001), gait speed (r = 0.6; p < 0.001), and 6MWT (r = 0.6; p < 0.0001) demonstrating weak negative, moderately negative, moderately positive, and moderately positive correlations, respectively. The best fitted MLR model utilized the distance covered in the 6MWT, 5xSST, age, HR, SpO2, and lung capacity to predict the outcome of the SRS function domain leading to an Adj-R-squared = 0.5 suggesting a moderate effect size. Conclusion: ASD PRO’s provide a subjective value on their overall level of function that has moderate correlation to a variety of objective fitness tests utilized in this comparative study. Thus, it is safe to say that ASD patients are telling the truth when reporting functional status on the SRS outcomes instrument.

371

P281: Variations in treatment for vertebral compression fractures and impact on the incidence of subsequent hip fractures

Jennifer Bell ¹ , Thomas Alter ² , Mary Kate Erdman ^1,3 , Hyunwoo Kang ^1,4 , Emily Mills ¹ , Andy Ton ¹ , Jeffrey C. Wang ¹ , Ram Alluri ¹ , and Raymond Hah ¹

¹ Orthopaedic Surgery, Keck School of Medicine of USC, Los Angeles, United States

² Orthopaedic Surgery, Mayo Clinic, Rochester, United States

³ Orthopaedic Surgery, Harborview Medical Center, University of Washington School of Medicine, Seattle, United States

⁴ Orthopaedic Surgery, Massachusetts General Hospital, Harvard Medical School, Boston, United States

Introduction: The purpose of this study is to evaluate the incidence of hip fractures following a vertebral compression fracture (VCF) in patients treated with and without anti-osteoporotic medication and/or surgical intervention. Material and Methods: A deidentified patient database from a large, private insurer was utilized, identifying patients from January 2007 to December 2016. Exclusion criteria were patients less than 50 years of age and patients with less than one-year follow-up. Patients were grouped based on if they received anti-osteoporotic medication within one year prior to and following VCF, and whether or not treatment included surgical intervention (vertebroplasty or kyphoplasty). Results: Our query resulted in 73,907 patients with VCF, 66.8% of which were female. The most common age group was 70-74 (18.0%). A total of 9,077 (12.2%) patients received surgical treatment. At one-year and all-time follow up, 3.5% and 9.3% of patients sustained a hip fracture, respectively. Of the surgically treated, 4.6% and 12.7% of patients suffered a hip fracture at one-year and all-time follow up, respectively. Older, female patients with a higher Elixhauser Comorbidity Index (ECI) had higher hip fracture rates. A 1:3 match on age, gender, and ECI identified 648 patients initiated on new anti-osteoporotic medication following VCF and 1579 without anti-osteoporotic medication. Patients who were initiated on AOT had higher rates of subsequent hip fractures (11.6% vs 9.4% at all-time follow up). Conclusion: Our data displays higher rates of hip fractures in patients with surgically treated VCF and patients initiated on anti-osteoporotic medication following VCF. This may be due to the fact that patients with more severe osteoporosis are more likely to be surgically and medically treated. Further studies are necessary to identify if patients with surgically treated VCF and patients initiated on anti-osteoporotic medication following VCF have more severe osteoporosis at the time of index VCF.

390

P282: The relationship between handgrip strength and thoracolumbar vertebral compression fracture

Hirokazu Inoue ¹ , Yukinori Hayashi ² , Hideaki Sawamura ¹ , Atsushi Kimura ¹ , Masayuki Masubuchi ² , and Katsushi Takeshita ¹

¹ Department of Orthopaedics, Jichi Medical University, Shimotsuke, Japan

² Department of Orthopaedic Surgery, Shiobara Spring Hospital, Nasushiobara, Japan

Introduction: As the elderly population grows, the number of patients with osteoporosis is increasing, and the prevalence of thoracolumbar vertebral compression fractures (VCFs) and hip fractures due to falls is increasing. Loss of lower leg muscle mass and handgrip strength are also risk factors for the development of VCF, and may be closely related to the pathogenesis of sarcopenia. Handgrip strength (HGS) is easy to measure and useful, so it has been used to predict the patient’s condition in many studies. This study assesses the relationship between HGS and activities of daily living (ADL), walking speed, and calf circumference for VCF. Material and Methods: A cross-sectional study in a single hospital was performed, and elderly patients diagnosed with VCF were enrolled. After admission, we evaluated HGS, 10m-walk test (speed), Barthel Index, Berg Balance Score (BBS), numerical rating scale (NRS) of body pain, and calf circumference. We used low HGS (< 28 kg for male and < 18 kg for female) and walking speed < 1.0 m/s to define sarcopenia in this study, according to the 2019 Asian Working Group for Sarcopenia. A multi-frequency validated bioelectrical impedance analysis instrument, the Inbody S10 (Biospace, Seoul, Korea), was performed with the patient in the supine position. Skeletal muscle mass and fat mass were also measured. Skeletal muscle mass index (SMI) was the measured skeletal muscle mass divided by the square of the height in meters. Results: A total of 112 patients who admitted for VCF were included in this study (26 males, 86 females; mean age 83.3 years). The prevalence of sarcopenia according to 2019 Asian Working Group for Sarcopenia guideline was 61.6%. HGS was significantly correlated with walking speed (p < 0.001, r = 0.485), Barthel index (p < 0.001, r = 0.430), BBS (p < 0.001, r = 0.511), calf circumference (p < 0.001, r = 0.491), and SMI (p < 0.001, r = 0.629). Height, weight, age, and muscle mass were correlated with HGS, but body mass index and NRS were not correlated with HGS. Conclusion: Sarcopenia was 61.6% in the patients with VCF. HGS is associated with walking speed, muscle mass, ADL such as Barthel index and BBS in the patients with thoracolumbar VCF. HGS is suggested to be important as a parameter of ADL as well as whole-body muscle strength.

455

P283: Correlation between neurological compromise and projectile trajectory in vertebral gunshot injuries; a case series study

Juan Mandujano-Sanchez ¹ , Jose Maria Jimenez Avila ¹ , Fernando Carrillo ¹ , and Hao Hua Wu ²

¹ Clínica de Columna, Campus Guadalajara, Instituto Tecnológico y de Estudios Superiores de Monterrey, Zapopan, Mexico

² Orthopaedic Spine Service, Brigham and Women's Hospital, Boston, United States

Introduction: Gunshot wounds to the spine account for about 13 to 17% of spinal trauma today, being the third leading cause of spinal cord injury only behind car accidents and fall from heights. Trajectory of the projectile and its anatomical location infer the neurological status of the patient and its prognosis. Material and Methods: Retrospective, descriptive case series study which included 50 patients with spinal gunshot wounds diagnosed by simple CT scan who arrived at a first level trauma hospital from July 2019 to July 2021. Firearm projectile trajectory was assessed through the GATA SMI classification. Type I: anteroposterior, type II: Tangential to spinal canal (oblique trajectory) type III: Side-to-side trajectory (bullet passed through both facet joints and/or pedicles) and type IV: Tangential to vertebral column (oblique trajectory). Neurological compromise was assessed through ASIA International Standards for Neurological Classification of Spinal Cord Injury (ISNCSCI). Neurological and projectile trajectory correlation was described using correlation charts. Results: 50 patients were included. 82% were men and 18% women, the average age was 32.66 years. Thoracic spine injuries were the most prevalent with 46% of the total. 54% of patients had complete spinal cord injury (ASIA A). Type III trajectory had more patients with complete spinal cord injury with 57% of the total in ASIA A. The thoracic segment presented a higher prevalence of complete spinal cord injury with 67% of all patients in ASIA A. 14% presented a type I trajectory, 32% a type II trajectory, 42% type III and 12% type IV according to the GATA SMI classification. Conclusion: The neurological status of the patient who presents with a gunshot wound to the spine will depend on the trajectory of the projectile in relation to the spinal cord and the segment of the spine affected. The thoracic segment is the segment with the highest incidence of GS injuries and the one with the highest incidence of complete spinal cord injury (ASIA A). The type III trajectory according to the GATA SMI classification presented the highest incidence of patients with complete spinal cord injury. The type IV trajectory, being a tangential lesion that does not cross the spinal canal, presented the lowest number of patients with spinal cord injury. None of these patients presented complete spinal cord injury. Knowing the projectile trajectory and neurological status in spinal GS injuries can help ER and spine doctors to determine the prognosis and the use of future treatment algorithms for patient care.

457

P284: The incidence of vertebral compression fractures and spinal instability in newly diagnosed multiple myeloma patients

Hester Zijlstra ^1,2 , Nienke Wolterbeek ¹ , Noa Ponds ¹ , Harry Koene ³ , Wim Terpstra ⁴ , Diyar Delawi ¹ , and Diederik Kempen ²

¹ Department of Orthopedic Surgery, St. Antonius Hospital, Utrecht, The Netherlands

² Department of Orthopedic Surgery

³ Department of Hematology/Oncology, St. Antonius Hospital, Nieuwegein, The Netherlands

⁴ Department of Hematology/Oncology, OLVG Amsterdam, Amsterdam, The Netherlands

Introduction: Multiple myeloma (MM) is a malignant neoplastic plasma cell disorder that is characterized by clonal proliferation of malignant plasma cells in the bone marrow. These plasma cell proliferations often cause extensive skeletal destruction with scattered osteolytic bone lesions. Myeloma bone lesions are frequently located in de spine and are associated with severe and debilitating bone pain, pathologic fractures, and increased mortality. With this study, we aim to investigate the incidence of vertebral compression fractures (VCFs) and spinal instability in patients with multiple myeloma. Material and Methods: Newly diagnosed patients with MM with computed tomography (CT) scans of the spine within 3 months of diagnosis were identified through an electronic patient database. Relevant clinical baseline data were extracted from the patient charts. Affected levels were graded on a CT-scan following the Genant grading system and spinal instability was assessed through the Spinal Instability Neoplastic Score (SINS). Results: A total of 385 patients with 6,289 eligible vertebrae were included in the study. Mean age at diagnosis was 67 years and 60% were male. At least one VCF was present in 180 patients (46.8%). A quarter of fractures were classified as severe according to the Genant grading system. The incidence of fractures was found to increase with more advanced disease stage and men were more likely to have a fracture than women. Conclusion: Our data show that almost half of multiple myeloma patients present with one or more VCFs at the onset of their disease of which almost 20% was classified as instable, meaning a surgical consultation is recommended. While no association between VFCs at baseline and survival was found, the number of VFCs was associated with a more advanced disease stage.

467

P285: Independent prognostic factors associated with improved patient-reported outcomes in the Prospective Evaluation of Elderly Deformity Surgery (PEEDS) study: can we identify "the winners"?

Fthimnir Hassan ¹ , Sigurd Berven ² , Michael Kelly ³ , Justin Smith ⁴ , Christopher Shaffrey ⁵ , Benny Dahl ⁶ , Marinus De Kleuver ⁷ , Maarten Spruit ⁸ , Ferran Pellisé Urquiza ⁹ , Kenneth Man Chee Cheung ¹⁰ , Ahmet Alanay ¹¹ , David Polly ¹² , Jonathan N. Sembrano ¹² , Yukihiro Matsuyama ¹³ , Yong Qiu ¹⁴ , Stephen Lewis ¹⁵ , Lawrence Lenke ¹ , and AO Spine KF Deformity ¹⁶

¹ Department of Orthopaedic Surgery, Columbia University Medical Center, The Och Spine Hospital at New York-Presbyterian, New York, United States

² Department of Neurosurgery and Orthopaedic Surgery, University of California San Francisco Medical Center, United States

³ Department of Orthopaedic Surgery, Washington University - SOM St. Louis, United States

⁴ Department of Neurosurgery, University of Virginia Medical Center, Charlottesville, United States

⁵ Department of Orthopaedic Surgery, Duke University, Durham, United States,

⁶ Department of Orthopaedic Surgery, University of Copenhagen, Denmark, United States

⁷ Department of Orthopedics, Radboud University Medical Center, Nijmegen, The Netherlands

⁸ Sint Maartenskliniek, Nijmegen, The Netherlands

⁹ Hospital Universitari de la Vall d’Hebron, Barcelona, Spain

¹⁰ Department of Orthopaedics and Traumatology, The University of Hong Kong, Hong Kong

¹¹ Department of Orthopaedics and Traumatology, Acibadem Mehmet Ali Aydinlar University School of Medicine, Istanbul

¹² Department of Orthopaedic Surgery, University of Minnesota, Minneapolis, United States

¹³ Department of Orthopedic Surgery,Hamamatsu University School of Medicine, Hamamatsu, Japan

¹⁴ Spine Surgery, Drum Tower Hospital of Nanjing University Medical School, China

¹⁵ Department of Surgery and Spine Program, University of Toronto, Canada

¹⁶ AO Spine Knowledge Forum Deformity

Introduction: Surgery for spinal deformity in the elderly can be effective, but outcomes are difficult to predict resulting in a large variation in outcomes. To identify patients who will predictably benefit from surgery, this study aimed to identify independent prognostic factors that can be associated with improved PROs and achieving minimal clinically important difference(MCID) among ASD patients ≥ 60 years of age undergoing primary reconstructive surgery. Methods: A prospective, multicenter, multi-continental, observational longitudinal study was conducted of patients ≥ 60 years undergoing primary ASD surgery and having ≥ 5 levels fused. Three approaches were used to assess MCID:(1) absolute change – 0.5 point increase in the SRS-22r sub-total/0.18 point increase in the EQ-5D index;(2) relative change – 15% increase in the SRS-22r sub-total and in the EQ-5D index;(3) relative change with a cut-off in the outcome at baseline – 15% increase in the SRS-22r score and EQ-5D index with a baseline score ≤ 3.2 and ≤ 0.7, respectively. Results: 171 patients completed the SRS-22r and 170 patients completed the EQ-5D at baseline and 2 years postop. 74% and 75% of patients reached MCID in the SRS22r in both the absolute and relative approaches, respectively. Patients who reached MCID experienced more pain and worse health at baseline (absolute:EQ-5D:0.5 ± 0.2 vs 0.6 ± 0.2, p = 0.009; SRS-22r: 2.6 ± 0.6 vs 3.0 ± 0.6, p = 0.002; relative:EQ-5D: 0.5 ± 0.2 vs 0.6 ± 0.2, p = 0.001;SRS-22r:2.6 ± 0.6 vs 3.0 ± 0.6, p < 0.001). Baseline PRO scores and number of severe adverse events (AEs) were the only identified risk factors (absolute: no. of AEs:OR = 0.48 [0.28 – 0.82, p = 0.044]; EQ-5D:OR = 0.01 [0.00 – 0.12], p = 0.003; relative: no. of AEs:OR = 0.39 [0.23 – 0.69, p = 0.007]; EQ-5D:OR: 0.00 [0.00 – 0.07], p < 0.001). 51% and 62% of patients reached MCID in the EQ-5D using the aforementioned approaches, respectively, demonstrating similar characteristics regarding pain and health at baseline (absolute: ODI:48.6 ± 14.1 vs 42.1 ± 15.8, p = 0.017; relative: ODI:47.7 ± 15.4 vs 41.5 ± 14.3, p = 0.017). Baseline PROs and number of severe AEs were identified as risk factors (absolute: no. of AEs:OR = 0.58 [0.38 – 0.89], p = 0.024; ODI:OR = 1.05, [1.02 – 1.07], p < 0.001; relative: SRS22r:OR = 0.31 [0.16 – 0.57], p < 0.001). In the relative/cutoff approach, 81% reached MCID in the SRS22r. These patients experienced worse health at baseline (EQ-5D:0.5 ± 0.2 vs 0.6 ± 0.2, p = 0.040). The number of AEs and baseline PROs were the only identified risk factors (no. of AEs: OR = 0.44, [0.25 – 0.77], p = 0.007; EQ-5D:OR: 0.01 [0.00 – 0.22], p = 0.007). 83% of patients reached MCID with the EQ-5D index using the same approach. Patients experienced less AEs (1.3 ± 1.7 vs 3.1 ± 2.8, p = 0.001) and a lower number of actions taken due to the occurrence of AEs (1.0 ± 1.2 vs 2.9 ± 2.6, p < 0.001). The number of actions taken due to AEs (OR = 0.50 [0.35 – 0.73], p < 0.001) was found to be the only risk factor. No surgical, clinical, or radiographic variables were identified as risk factors using either of the aforementioned approaches. Conclusion: In this large multicenter prospective cohort of elderly patients undergoing primary reconstructive surgery for ASD, surprisingly no clinical, radiological, or surgical parameters were identified as factors that can be prognostic for reaching MCID. However, patients who experienced more pain at baseline were more likely to reach MCID. Conversely, patients who experienced severe AEs were less likely to reach MCID.

578

P286: The impact of the COVID-19 pandemic on ambulatory lumbar spine decompression surgery

Yusuke Dodo ^1,2 , Ichiro Okano ² , Neil Kelly ³ , Leonardo Sanchez ³ , Haffer Henryk ¹ , Maximilian Muellner ¹ , Erika Chiapparelli ¹ , Lisa Oezel ¹ , Jennifer Shue ¹ , Darren Lebl ¹ , Frank Cammisa ¹ , Federico Girardi ¹ , Alexander Hughes ¹ , Gbolabo Sokunbi ¹ , and Andrew Sama ¹

¹ Spine Care Institute, Hospital for Special Surgery, New York, United States

² Department of Orthopaedic Surgery, Showa University Hospital, Shinagawa, Japan

³ Weill Cornell Medicine, New York, United States

Introduction: The coronavirus disease 2019 (COVID-19) outbreak spread worldwide in a rapid and unpredicted scale in the beginning of 2020. During the height of the pandemic, the U.S. Centers for Medicare and Medicaid Services (CMS) announced that all elective surgery should be delayed to enhance the clinical response to COVID-19. This recommendation led to clinical and ethical challenges for spine surgeons in deciding practical management and triaging of patients. However, little is known on how the pandemic affected surgeons’ and patients’ attitudes towards ambulatory spinal surgery, including factors such as patient selection, and hospital length of stay (LOS). This study aim to investigate patient characteristics and hospital LOS trends during the pre-pandemic period and three pandemic stages in patients undergoing lumbar decompression procedures in the ambulatory surgery (AMS) setting. Material and Methods: A total of 2670 adult patients undergoing one- or two-level lumbar decompression surgery planned for AMS were retrospectively reviewed. Patients were categorized into four groups: 1: pre-pandemic (before the pandemic restriction from January 1, 2019 to March 16, 2020), 2: restricted period (when elective surgery was cancelled from March 17, 2020 to June 30, 2020), 3: post-restricted 2020 (July 1, 2020 to December 31, 2020 before vaccination) and 4: post-restricted 2021 (January 1, 2021 to December 31, 2021 after vaccination). Data on patient demographics, comorbidities, LOS, admission patient class, surgical information, and administrative information was collected. Simple and multivariable logistic regression analyses as well as retrospective interrupted time series (ITS) analysis were conducted comparing AMS patients in the four periods. Results: 1096 patients were classified as pre-pandemic, 128 patients as restricted, 481 patients as post-restricted 2020, and 965 patients as post-restricted 2021. The three pandemic periods had a lower admission rate (7.8% to 9.1%) compared to the pre-pandemic period (13.2%). The ITS analysis demonstrated a significant drop in mean LOS at the beginning of the restricted period. Hospital LOS gradually increased after the sudden drop and recovered to the pre-pandemic levels in one year’s time. Compared to the pre-pandemic period, the patients who underwent surgery during the restricted period were younger and had fewer comorbidities. After adjusting for these patient factors, post-restricted 2020 patients still showed significant association with decreased LOS. Multivariable logistic regression analyses indicated that the pandemic was an independent factor influencing the LOS in post-restricted phases. Conclusion: Our results suggest that spine surgery patients from the restricted period were younger and healthier, which led to a shorter LOS. Hospital LOS that significantly decreased in the beginning of the restricted period gradually increased and recovered to the pre-pandemic levels in one year’s time. Since the results might be independently influenced by the pandemic, these results should be taken into account when interpreting the LOS of the patients undergoing ambulatory lumbar spine surgery in post-restricted phases.

728

P287: Epidemiology of scoliosis in the United Arab Emirates (UAE) - single centre experience

Ziad Mohamed ¹ and Antony Michael ¹

¹ Neuro Spinal Hospital, Dubai, United Arab Emirates

Purpose: To explore the demographics and clinical presentation of patients with scoliosis in the United Arab Emirates. Methods: A questionnaire was filled from the medical records of the patients with scoliosis who had been seen in our hospital. The questionnaire was specifically devised for this study and included questions on patient demographics and clinical presentation. Responses were expressed as frequencies for qualitative analysis. Results: One hundred and forty-five patients were included in the study, of which 102 (71%) were female, and 50 (35%) were of the Emirati ethnicity. Ninety-six patients (67%) had a neuromuscular disease, and 88 patients (61%) primarily presented with back pain. The onset of scoliosis did not arise until after age 10 in 115 (80%) of patients, and the degree of spinal curvature was more than 25-degrees in 107 (74%) of patients. Conclusion: Scoliosis is more prevalent in females and those of Emirati origin in the UAE. Furthermore, patients with neuromuscular disease are at an increased risk of developing scoliosis, as corroborated by the current literature, with back pain as the primary presentation. No notable findings with regards to delayed developmental milestones or family history were observed. Future research should focus on quantitative outcomes and adopt a prospective or retrospective design to yield valid and reproducible evidence.

Keywords: Scoliosis, qualitative, idiopathic scoliosis, nonidiopathic scoliosis, UAE

738

P288: Metropolitan versus non-metropolitan location of patients' zip code before surgery and outcomes of lumbar spine fusion surgery: a retrospective cohort study analysis

Alexander Aguirre ¹ , Mohamed Soliman ^1,2 , Cathleen Kuo ¹ , Joseph Iskander ¹ , Justin Im ¹ , Hannon Levy ¹ , Asham Khan ¹ , Moleca Ghannam ¹ , Patrick Jowdy ¹ , John Pollina ¹ , and Jeffrey Mullin ¹

¹ Neurosurgery, University at Buffalo, Buffalo, United States

² Neurosurgery, Cairo University, Cairo, Egypt

Introduction: Tertiary medical centers are often located in the middle of large metropolitan areas. The distance or access to these institutions can be a hurdle for patients seeking surgical intervention for spine pathology. The objective of this study was to investigate and report the surgical outcomes of patients located in both metropolitan and non-metropolitan areas. The objective of this study was to investigate and report the surgical outcomes of patients located in both metropolitan and non-metropolitan areas. Material and Methods: A retrospective chart review was completed of 792 consecutive patients who underwent lumbar spine fusion. Once these patients were identified, an analysis of their zip code was completed using the most updated United States Department of Agriculture Rural-Urban Continuum Codes. Once this was established, a statistical analysis was completed to investigate potential differences in outcomes during and after spine fusion surgeries. Results: A total of 660 (83.3%) patients lived in a metropolitan area, with the remaining 132 (16.7%) patients living in a non-metropolitan area. The distribution of race (p < 0.001) and gender (p = 0.04) differed significantly between the two groups, as a larger proportion of African American/Black and a greater proportion of men lived in metropolitan areas. 15 (1.9%) patients required admittance to the intensive care unit (ICU), of which a significantly greater proportion of these patients came from a non-metropolitan area (5.3% vs. 1.2%, p = 0.005). No other intraoperative or postoperative outcomes differed significantly between groups. Conclusion: Accessibility to healthcare to tertiary hospitals that can complete complex surgical interventions is not equal in all parts of the country, which can significantly impact the outcomes of spine surgery.

840

P289: Median household income based in patients' zip code and perioperative surgical outcomes after lumbar spine fusions: a retrospective cohort analysis

Alexander Aguirre ¹ , Mohamed Soliman ^1,2 , Cathleen Kuo ¹ , Marissa Kruk ¹ , Joseph Iskander ¹ , Hannon Levy ¹ , Asham Khan ¹ , Moleca Ghannam ¹ , Patrick Jowdy ¹ , John Pollina ¹ , and Jeffrey Mullin ¹

¹ Neurosurgery, University at Buffalo, Buffalo, United States

² Neurosurgery, Cairo University, Cairo, Egypt

Introduction: The social determinants of health have long been investigated and a strong negative association between them and the outcomes after spinal fusions has proven significant. The impact of economic instability has been shown to correlate with increased rates of hospital readmission and increased length of stay (LOS). However, the current study reports the findings between the mean household income and intraoperative and postoperative outcomes. The current study aimed to report the findings between the mean household income and intraoperative and postoperative outcomes. Material and Methods: A total of 792 consecutive patients who underwent a spine fusion were identified and then data was collected, which included the patients’ zip code at the time of surgery and both intraoperative and postoperative outcomes. Using the 2020 United States Census report, the median household income for each zip code was identified. Within the sample, a quartile distribution was completed, and an analysis was completed between the median household income quartile and perioperative outcomes. Results: Of the 792 patients, 193 (24.4%) were in the lowest quartile, 124 (15.7%) in the second, 171 (21.6%) in the third, and 304 (38.4%) in the fourth quartile of median household income. Distribution of races (p < 0.001), gender (p = 0.005), and metropolitan vs. non-metropolitan location (p < 0.001) all differed significantly with increased rates of the African American/Black race, women, and metropolitan location in the lower quartiles. No rates of postoperative complications or perioperative surgical outcomes differed significantly between quartiles. Conclusion: While the median household income differs significantly among patients who undergo spine fusions, the surgical outcomes of patients are independent of the patients socioeconomic status.

931

P290: Prevalence of low back and assessment of risk factors for development of low back pain in patients care at a school hospital in the Eastern Area of São Paulo

Luiz Claudio Rodrigues ¹ , Fernanda Andrea Navarro ² , Rodrigo Nakao ² , and Nathalia Adelina Pereira ¹

¹ Spine Surgery, Santa Marcelina College of Medicine, São Paulo, Brazil

² Spine Surgery, Santa Marcelina Hospital, São Paulo, Brazil

Introduction: Low back pain is part of a range of musculoskeletal disorders (MSD), considered important health problems that can significantly affect people's quality of life. The diagnosis requires a careful anamnesis and a good physical examination. The risk factors involved are possibly linked to psychosocial, behavioral, and occupational aspects such as high task demand, dissatisfaction with the work environment, as well as lower socioeconomic status, obesity, smoking, sedentary lifestyle, and sleep quality.

Objective: To determine the prevalence of low back pain and establish a correlation with risk factors for the development of low back pain in a Teaching Hospital in the East Zone of São Paulo. Methodology: This is a cross-sectional observational analytical study, interviewing 90 patients from the wards of Hospital Escola using internationally validated instruments. They were asked about clinical/epidemiological and behavioral aspects. Results: The prevalence rate obtained was 57.73%, considered high compared to the rates of those surveyed carried out outside the hospital environment. 30.13% female predominance with a standard deviation of 5.32%. Sleep disorders seem to act as a risk factor, indirectly measured through hours of sleep and the mean pain score (p = 0.007). Pain assessment instruments seem to be more effective when used together, seen in the association between the Owestry questionnaire (ODI) and analogue pain scale (VAS) (p = 0.000). Conclusion: There is a higher prevalence rate of low back pain among institutionalized individuals, mainly hospitalized, compared to rates observed outside this context of hospitalization. Therefore, more research needs to be carried out in this area, since there are difficulties in finding systematic studies carried out in Brazil that discuss the prevalence rates of low back pain in the population and among its subgroups.

972

P291: Underweight as a risk factor for vertebral fracture: nationwide cohort study

Jiwon Park ¹ , Joonhyeok Boo ¹ , and Jae-Young Hong ¹

¹ Orthopaedic Surgery, Korea University Ansan Hospital, Ansan, South Korea

Introduction: Underweight, a known risk factor for osteoporosis and sarcopenia that is strongly associated with vertebral fractures, particularly in the elderly, can accelerate bone loss, contribute to impaired coordination, and increase the risk of falls in the elderly as well as the general population. The purpose of this study is to identify the degree of underweight as a risk factor for vertebral fractures in the South Korean population. Material and Methods: This study included data from nationwide regular health checkup in 2009 conducted by the Korean National Health Insurance Service. Participants were followed up from 2010 to2018 to find incidence of newly developed fractures. Based on their body mass index, the study population was categorized into normal (18.50-22.99 kg/m2), mild underweight (17.50-18.49kg/m²), moderate underweight (16.50-17.49 kg/m²), and severe underweight (< 16.50 kg/m²) groups. Cox proportional hazards analyses were performed to calculate the hazard ratios for vertebral fractures based on the degree of underweight with respect to normal weight to identify the associated risk. Results: This study evaluated 962,533 eligible participants, of whom 907,484 were classified as normal weight, 36,283 as mild underweight, 13,071 as moderate underweight, and 5,695 as severe underweight. The adjusted hazard ratio of vertebral fractures increased as the degree of under weight increased. Severe underweight was associated with a higher likelihood of occurrence of vertebral fractures. The adjusted hazard ratio was 1.11 (95% confidence interval,1.04-1.17) in the mild underweight group, 1.15 (1.06-1.25) in the moderate underweight group, and 1.26 (1.14-1.40) in the severe underweight group when compared with the normal weight group. Conclusion: Underweight is a risk factor for vertebral fractures in the general population. Furthermore, underweight of greater severity was associated with a higher risk of vertebral fractures, even after adjustment for other factors. Clinician can educate the patients to gain weight through adequate nutritional support and exercise in order to reduce the risk of the vertebral fractures in under weight patients.

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P292: Traumatic versus non traumatic spinal cord injury: epidemiological data from Bio Bio Province, Chile

Oscar González ^1,2 , Boris Fuentealba ² , and Cristian Flores Ferrada ²

¹ Neurology, Universidad Católica de la Santísima Concepción, Concepción, Chile

² Neurosurgery, Complejo Asistencial Víctor Ríos Ruíz, Los Ángeles, Chile

Introduction: Spinal cord injury (SCI) is a devastating condition that can lead to significant neurological impairment and reduced quality of life. Literature about SCI epidemiology in Chile is sparse. The aim of the study is to describe the characteristics of patients with SCI admitted to our Center and compare outcome for patients with traumatic (TSCI) and non-traumatic spinal cord injuries (NTSCI) after primary rehabilitation regarding neurological improvement, length of stay and complications. Material and Methods: We reviewed retrospectively 51 patients hospitalized in our center, admitted to the neurosurgery unit over the last decade. Data was collected from their initial admission and from follow-up and electronics records. Statistical analysis was performed using Microsoft Excel 2010 and STATA v12. Results: All 51 cases. Mean age was 44,2 (SD: 17 - 82) years. 86.2% were men (44/51), 62.7% TSCI and 37.3% NTSCI. In the TSCI group: mean age was 41.1 years, 87.5% (28/32) were men and 12.5% (4/32) were women. In the NTSCI group: mean age was 49 years, 84.2% (16/19) were men and 15.8% (3/19) were women. The leading causes of TSCI was Diving Injuries and Falls, follow by fire weapons injuries and traffic accidents. The main causes of NTSCI was Tumors, follow by degenerative and infectious conditions of the spine. Length of Hospital stays was longer in TSCI group 29.8 vs. 24 days. Urinary tract infections frequency were similar in both groups TSCI (21.9%) vs NTSCI (21%). Pressure ulcers were more frequent among TSCI (21.9%) vs NTSCI (5.3%). Pneumonia were more frequent in TSCI (31.3%) vs NTSCI (5.3%). Neurogenic bladder were more frequent in TSCI (75%) vs NTSCI (63.2%). At discharge, 56.3% in TSCI group were able to walk vs 42.1% in NTSCI group. The rate of surgery was similar in both group TSCI (65.6%) vs NTSCI (63.2%). 37.5% in TSCI group improve ASIA score vs 26.3% in NTSCI Group. Conclusion: For the first time, we are able to provide local epidemiological status on TSCI and NTSCI based on available data from hospital registry in Biobío Province, Chile. Further studies are required to improve the capture of TSCI and NTSCI for future studies. Patients with SCI have a rehabilitation potential regardless of etiology. Complications are frequent in both groups and often prolong hospitalization. Complication patterns differ between the two groups, and specific prevention and optimal treatment will shorten and optimize the length of primary rehabilitation.

1005

P293: Familial arachnoiditis with syringomyelia: analysis of a family of 15 affected individuals and a systematic review

Ali Moghaddamjou ¹ , Alex Bak ² , Francois Mathieu ¹ , Jerry Ku ¹ , and Michael Fehlings ¹

¹ Neurosurgery, University of Toronto, Canada

² University of Toronto, Canada

Introduction: We report a case of a 61-year-old male with non-communicating thoracic syringomyelia living in Canada of Japanese descent with 15 known family members with the same condition . Most cases of idiopathic syringomyelia are sporadic, with no family history of the disease. Familial syringomyelia is an extremely rare form of non-traumatic spinal cord injury and is defined by the presence of syringomyelic cavities in 2 or more patients within the same family. Our patient has been diagnosed in 2011 and after an initial progressive phase causing significant lower extremity spasticity, has remained clinically and radiologically stable. He has no history of trauma, Chiari malformation or associated scoliosis. He has been started on riluzole 50 mg b.i.d. as an off-label use since 2017. We aim to report on our case of familial arachnoiditis with syringomyelia and to conduct a systematic review of similar cases to provide a summary of our current understanding of this condition. Material and Methods: Ten keywords relating to familial trait and 23 keywords relating to syringomyelia were used as search terms on MEDLINE, EMBASE and Cochrane libraries. Abstracts were screened by two reviewers following the PRIMSA checklist. Papers reporting cases of familial syringomyelia in English were included for quantitative analysis. Results: The search revealed 476 results of which 25 were included in the quantitative analysis. Overall, there are 131 cases reported of which 16% had associated scoliosis and 65% associated Chiari Malformation. Most of the patients had surgery as a treatment (71.7%). Among reported outcomes, most patients showed improvement in their symptoms (n = 18). This was followed by patients that showed stable symptoms (n = 9) after treatment. Four patients showed progression of symptoms and one patient experienced peri-operative death after treatment for FS. Conclusion: After a systematic review of the current English literature, we can conclude that our case is one of the largest known family clusters of syringomyelia not associated with a Chiari Malformation in North America. Although it is difficult to demonstrate efficacy, we propose the off-label use of riluzole as a potential conservative therapy. Apart from these results, there is basic science support for the use riluzole for arachnoiditis-associated secondary injury. Given the autosomal dominant pattern in our case, whole exome sequencing would be an interesting avenue of investigation into the pathophysiology of this condition. Currently there are no known genetic causes.

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P294: The experience of junior spine surgeon in their first years after the AO Spine fellowship in Latin America

Jose Dangond ¹ , Alfredo Guiroy ² , Guisela Quinteros Rivas ³ , Pedro Couri ⁴ , omar marroquin ⁵ , Fernando Alvarado Gómez ⁶ , and Nelson Astur ⁴

¹ Fundación Clinica Campbell/ Centro Hospitalario Serena del Mar, Atlántico/Bolivar, Barranquilla, Brazil

² Hospital Español de Mendoza, Mendoza, Argentina,

³ Hospital Regional de Talca, Talca, Chile

⁴ Hospital Israelita Albert Einstein, Sao Paulo, Brazil

⁵ Centro Médico Esperanza, Puebla, Mexico

⁶ Fundacion Santa Fe de Bogota, Bogota, Colombia

Study Design: Descriptive study. Introduction: Currently there are no publications that show the reality faced by junior spine surgeons in Latin America in the first three years after completing the AO Spine fellowship; This descriptive study is a direct way to show the relevance and importance of the AO Spine fellowship program in Latin America and also opens the doors to new studies that will help improve the AO Spine fellowship program. Objective: Describe the reality and actuality of the fellows trained by AO Spine in Latin America and describe fears faced by a junior spine surgeon in his first three years as a surgeon. Material and Methods: We send to all AOSpine Associate Fellows of the last 5 years a questionnaire or survey with multiple answers about their professional activity in the first 3 years of practice after the fellow has finished their studies; The results will be analyzed comparatively country by country according to the activity carried out and the answers given by the surgeons and in this way we will be able to describe the local and regional results in Latin America. Results: Currently, the countries with the highest participation in the AO Spine fellowship program are Argentina (30.7%), Brazil and Colombia (28.21%), the age ranges with the highest participation in the AO Spine fellowship program are between 36-45 years (30.7%); 75% of program participants are orthopedists and among other significant data, 95% of respondents have greater experience and feel more confortable in degenerative spine pathology. Conclusion: At present, the junior fellowships of the AO Spine program report feeling comfortable with the program, however there is much data in our study that will help improve it, on the other hand it is clear that the greater affinity for the standard posterior approach is still evident, however every day junior surgeons show greater interest in endoscopic and minimally invasive techniques; this study is an open door with very important data for new studies and to help improve the fellowship education program in Latin America.

1219

P295: A single site review of COVID-19's impact on elective spine surgery: temporary decrease in volume, but business as usual?

Jon Raso ¹ , Pramod Kamalapathy ¹ , Lawal Labaran ¹ , Eric Solomon ² , Hamid Hassanzadeh ² , and Amit Jain ²

¹ Department of Orthopaedics, University of Virginia, Charlottesville, United States

² Department of Orthopaedics, Johns Hopkins Medicine, Bethesda, United States

Introduction: The COVID-19 pandemic has had large impacts on patient care across all fields, including orthopaedic spine surgery. At many institutions, elective procedures were cancelled or postponed for a time to mitigate the risks of COVID exposure. The effects of reduced case volume and changing practice parameters has been incompletely explored. Our goal was to evaluate the effect of the pandemic on pre-operative characteristics and surgical outcomes for patients undergoing elective spine surgery. We hypothesized that patients selected for elective surgery would overall be younger, have less comorbidity, and lower American Society of Anesthesiologists (ASA) scores as compared to pre-COVID. Similarly, we hypothesized that patient outcomes would not be significantly worse during the pandemic. Material and Methods: We identified all patients undergoing elective spine surgery at our single tertiary institution from January 1^st 2019, to December 31^st 2020. All surgeries were performed by five board certified orthopaedic spine surgeons. They were divided into two cohorts, those receiving surgery before and after March 15^th, 2020, which corresponds to the date the elective procedure deferment was implemented. Demographic and procedural information for each patient was collected, including age, comorbidities, ASA classification, and procedure type. Outcomes data up to 90 days was collected, including major and minor medical complications, reoperation and readmission rates, length of stay greater than 3 days, and discharge location. Results: 1545 elective spine surgeries were identified. Of those, 957 were before March 15^th, 2020 (Pre-COVID), and 588 occurred after. 266 patients underwent lumbar fusions, 149 underwent cervical fusions, and 319 underwent lumbar decompression pre-COVID, compared to 166, 112, and 111 in the COVID cohort. Surgical volume was lowest in March 2020, in which 34 elective cases were performed in total- average pre-COVID volume was 69.6 cases per month. Surgical volume returned to baseline within three months after elective surgery deferment began, faster than anticipated by the authors. There was a significant decrease in reoperation rates in the COVID cohort compared to pre-COVID (p = 0.006) for all procedures. When divided by procedure type, fusion patients experienced a significant decrease in reoperation rates (p < 0.001). Decompression patient outcomes were not statistically different across cohorts. Discharge location (long-term care facilities, home) did not change significantly across the study period. Rates of common post-operative outcomes were not statistically different for all procedure types both before and during the cutoff date. Conclusion: Our study suggests that, despite the COVID-19 pandemic, elective spine procedures did not carry significantly increased risk. Elective procedure volume returned to baseline within three months. Further research assessing multiple different surgical sites is necessary to corroborate these findings. These findings have a positive implication for future COVID variants or pandemics.

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P296: Demographics and economic trends in vertebral fracture surgeries throughout the United States

Khaled Taghlabi ¹ , Alexander Beschloss ² , Daniel Rodriguez ² , Nathan Lee ³ , Sachin Gupta ² , Kevin Bondar ⁴ , Joseph Lombardi ³ , Amir Faraji ¹ , and Comron Saifi ⁴

¹ Neurosurgery

² Orthopaedic Surgery, University of Pennsylvania, Philadelphia, United States

³ Orthopaedic Surgery, Columbia University Vagelos College of Physicians and Surgeons, New York, United States

⁴ Orthopaedic Surgery, Houston Methodist Hospital, Houston, United States

Introduction: Vertebral fractures represent a large public health concern given the diagnostic challenge and proclivity for re-fracture. In case of progressive neurological deficits, gross spinal instability, or intractable pain, surgical intervention is required. Prior studies have evaluated the costs associated with vertebral fractures; however, there is little information about the economic and demographic factors associated with vertebral fracture surgery. The purpose of this study was to investigate economic and demographic trends pertaining to the surgical treatment of vertebral fractures between 1993 and 2015 using data from the National Inpatient Sample (NIS) database. The present papers tests the hypothesis that the number of vertebral fracture surgeries and costs increased between 1997 and 2014 due to more common operative management for vertebral fractures. Materials and Methods: The National Inpatient Sample (NIS) was queried for patients who underwent surgical treatment of a vertebral fracture (ICD-9-CM-3.53) (excluding kyphoplasty and vertebroplasty) between 1993 and 2015. Demographic data included patient age, sex, income, insurance type, hospital size, and location. Economic data including aggregate charge, aggregate cost, hospital cost, and hospital charge were analyzed. Results: The number of vertebral fracture surgeries, excluding kyphoplasty and vertebroplasty, increased 461% from 3,331 in 1993 to 18,675 in 2014. Inpatient mortality increased from 1.9% to 2.5%. The mean age of patients undergoing vertebral fracture surgeries increased from 42 in 1993 to 53 in 2015. The aggregate cost of surgery increased from $189,164,625 in 2001 to $1,060,866,580 in 2014, a 461% increase. Conclusion: The increase in vertebral fracture surgeries between 1993 and 2014 may reflect an increased rate of fractures, an increased propensity for surgical management, or a multifactorial combination. The increasing rate of vertebral fracture surgery, coupled with increasing hospital costs and mortality, signifies that efficient and effective treatment of vertebral fractures is a challenge and that further research in epidemiology and management will be beneficial.

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P297: Time to fixation after traumatic spinal cord injury prolonged with certain race and insurance statuses

Jon Raso ¹ , Pramod Kamalapathy ¹ , Eric Solomon ² , Elizabeth Driskill ³ , Kristina Kurker ³ , Hamid Hassanzadeh ² , and Amit Jain ²

¹ Department of Orthopaedics

² Department of Orthopaedics, Johns Hopkins Medicine, Bethesda, United States

³ School of Medicine, University of Virginia, Charlottesville, United States

Introduction: Traumatic spinal cord injuries (TSCIs) are potentially catastrophic injuries to the spine with historically poor functional outcomes for patients. The management of TSCI requires prompt evaluation and may necessitate urgent intervention to preserve neurologic function, therefore time to fixation as a predictor of patient outcomes is of great interest. Although the optimal timing of surgical intervention for TSCI is somewhat controversial, early intervention has been recognized as being beneficial in several studies. The objective of this study was to evaluate the role of various socioeconomic factors on the time to surgical fixation in the management of TSCI. Our primary goal was to identify socioeconomic factors that may delay treatment. Material and Methods: The present study utilized the Trauma Quality Improvement Program (TQUIP) dataset to collect adult patient records from 2007-2016. Patients were divided into subgroups based on race. Patients were also categorized by insurance type into subgroups for additional analysis. Demographic information for each patient including patient age, gender, presence of comorbidities, injury location and procedure type were collected. Additional facility information was also included. Polytrauma patients were excluded from analysis. A univariate and multivariate linear regression analysis was used to compare time to procedure based on primary race, and payer type while adjusting for demographic, hospital, information, levels involved, region of the spine fixed, accident patterns, and emergency room disposition. Significance was set at p < 0.05. Results: 8,773 patients were included in the study. The largest group was White patients (n = 5902, 67.3%) followed by Black (n = 1217, 13.9%), Hispanic (n = 771, 8.8%), Other (n = 545, 6.2%), and Unknown (n = 338, 3.9%). Most patients were male (n = 6,499, 74%), and the average GCS score was 14.24 ± 2.26 for the overall group. Hispanic and Black race was associated with a significantly increased time to fixation of 12.1 hours (95% CI 5.5-18.7, p < 0.001), and 20.1 hours (95% CI 12.1-28.1, p < 0.001), respectively compared to white race. Both Other and Unknown cohorts were not associated with a statistically significant difference in time to fixation compared to white patients (p > 0.05). Univariate analysis showed that Medicare, Medicaid, government and military-based insurances, and self-pay were all associated with significant increases in time to fixation compared to private insurance (p < 0.05). However, with multivariate analysis, only Medicaid insurance was associated with a statistically significant increased time to fixation when compared with private insurance (11.6 hours, 95% CI 3.9-19.2, p = 0.003). Conclusion: Race and certain insurance statuses were associated with statistically significant increases in time to fixation following TSCI, potentially compromising quality of patient care and resulting in poorer outcomes. More research is needed to better understand these trends and ensure equitable care.

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P298: Prevalelence of global spinal malalignment in the sagittal plane - A cross sectional analysis of associations with LBP and HR-QOL in a general non-elderly population

Koichiro Okuyama ¹

¹ Department of Orthpaedic Surgery, Akita Rosai Hospital, Odate, Japan

Background Context: Understanding of normal parameters’ range in the sagittal alignment of the spine is very important to treat degenerative spinal disorders. For Mongoloid heritage, prevalence of global spine mal-alignment in the sagittal plane (GS mal-Algin) remains unknown in general non-elderly populations (18 < age < 65 years). Moreover the clinical significance and associations between GS mal-Algin and bone mineral density (BMD), skeletal muscle index (SMI), back muscle extensors strength (BMES), and HR-QOL has not been disclosed enough. Purpose: To investigate prevalence of GS mal-Algin, and the associations between BMD, SMI, BMES, low back pain (LBP), and HR-QOL in non-elderly populations in East Asia. Study Design: A monocentric, cross-sectional survey. Patients Samples: Two hundred and sixty-three non-elderly participants with Mongoloid heritage were consecutively enrolled. Outcome Measures: Sagittal parameters of the spine and the pelvis on whole spine radiograms, BMD and SMI using Dual Energy X-ray Absorptiometry, BMES calculated by a strain-gause dynamotor, and participants-self reported LBP, and score of Medical Outcome Study Short-Form36-Health Survey (SF-36). Methods: Two hundred sixty-three healthy non-elderly participants (84 females and 179 males) were studied. Participants’ LBP was checked through interview and physical examination. HR-QOL were ascertained by SF-36. Sagittal parameters of the spine and the pelvis, including pelvic incident (PI), mismatch between PI and LL (PI-LL), and pelvic tilt (PT) C7 sagittal vertical axis (SVA) were measured on whole spine radiograms. BMD and SMI were measured using Dual Energy X-ray Absorptiometry. BMES was defined as a maximum extension force at the T4 to T7 level in the supine position. Results: PI-LL ≧ 10°, PT ≧ 20°, and SVA ≧ 40 mm were found in 10.6% (28/263), 11.8% (31/263), and 6.1% (16/263) of the participants, and each mean value was 15.3 ± 5.9°, 25.1 ± 4.0°, and 52.7 ± 12.2 mm, respectively. Prevalence of LBP was significantly higher in the participants with PI-LL ≧ 10°: 42.8% (12/28) than those with PI-LL < 10°; 21.2% (50/235) (p < 0.05). PI-LL ≧ 10°only had a significant association with LBP (OR: 3.043, 95%CI 1.138-8.141, p < 0.05). In SF 36 scores, BMD, SMI, and BMES, no significant differences were found between the participants with PI-LL ≧ 10°and those with < 10°, PT ≧ 20° and < 20°, and SVA ≧ 40 mm and < 40mm. However, 1.5% (4/263) of the participants associated with all of PI-LL ≧ 10°, PT ≧ 20°, and SVA ≧ 40 mm had a significantly lower SF-36 mental component score than others (p < 0.05). Conclusions: In a general non-elderly population (18 < age < 65 years, Mongoloid heritage in East Asia, n = 263), PI-LL ≧ 10°, PT ≧ 20° , and SVA ≧ 40 mm was found in 10.6%, 11.8% , and 6.1%, and each mean value was 15.3 ± 5.9°, 25.1 ± 4.0°, and 52.7 ± 12.2 mm. PI-LL ≧ 10° only had an association with LBP, and it is also speculated that coexistence of PI-LL ≧ 10° plus PT ≧ 20° and SVA ≧ 40 mm leads to a poor mental HR-QOL.

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P299: Impact of the COVID-19 pandemic on the corrections of spinal deformities through the posterior approach in the Unified Health System in Brazil

Rodolfo Gomes Dias ¹ and Mohammad Zarrabian ²

¹ Orthopaedic and Traumatology Department, Santa Casa de Misericórdia de Araçatuba, Araçatuba, Brazil

² Department of Spine Surgery, Winnipeg Spine Centre, University of Manitoba, Winnipeg, Canada

Introduction: In regards on spine deformities, scoliosis consists of deformities that affect the spine and are characterized by involving the three reference planes: lateral deviation in the frontal plane, vertebral rotation in the axial plane and lordosis in the sagittal plane (1). Data from epidemiological studies point to a high prevalence of postural alterations in the spine of children and adolescents; presenting an overall prevalence between 1% and 2%, where idiopathic scoliosis is the most common subgroup (2). The pandemic caused by COVID-19 considerably affected elective surgeries in the country, but there are no studies that show its influence when performing corrections of spinal deformities with posterior approach (CSDP) in the Unified Health System (UHS). Material and Methods: This is an observational study using aggregate national data from the Hospitals Information System (SIH/SUS) and the Brazilian Institute of Geography and Statistics (IBGE). These databases capture all procedures performed in the public health care system which comprises 75% of the Brazilian health care system. There was no need for ethics committee approval due to the data being public. We analyzed the number of procedures, total and mean value in Brazilian reals(R$) of CSDP procedures in 1 to 12 or more levels in the five Brazilian. The results were organized in a spreadsheet and then descriptive statistics were used for comparison during the pre-and ongoing period of the pandemic, consisting of April 2018 to March 2020 (period 1) and April 2020 to March 2022 (period 2). For the statistical analysis, the Chi-Square test was used, considering p < 0.05 as significant. Results: In period 1, 1,379 CSDP were carried out by the UHS, 19, 161, 670, 488 and 41, in the North, Northeast, Southeast, South and Center-West regions respectively; at a total cost of R$ 14,715,548.44 and an average of R$ 10,671.17 per procedure and hospitalization. During period 2, 985 CSDP were carried out, at a cost of R$11,076,589.99 at an average value of R$11,245.27; being 11, 174, 513, 243, and 44 in the North, Northeast, Southeast, South and Center-West regions, respectively. A reduction of: 42.105%, 23.433%, 50.205%, in the North, Southeast and South regions respectively; and an increase of 8.075% and 7.317% in the Northeast and Midwest regions, respectively. With a cost reduction of 24.729%. Conclusion: There was an overall reduction of 28.571% of CSDP during the pandemic in Brazil, with the most affected region being the South region, with a reduction of 50.205% (p < 0.05). It is extremely important to analyze these data to identify the impact of the COVID-19 pandemic in relation to the performance of the studied procedure. This data from this study may assist the competent authorities in identifying and correcting discrepancies and reduction of the procedure studied caused by the COVID-19 pandemic in different Brazilian regions.

1516

P300: 2 years of COVID-19 pandemic: current overview of the posterior thoraco-lumbosacral fusion surgeries in the Unified Health System in Brazil

Rodolfo Gomes Dias ¹ and Mohammad Zarrabian ²

¹ Orthopaedic and Traumatology Department, Santa Casa de Misericórdia de Araçatuba, Araçatuba, Brazil

² Department of Orthopaedic Surgery, Spine Surgery Division, Winnipeg Spine Centre, University of Manitoba, Winnipeg, Canada

Introduction: Thoraco-lumbosacral spine fusion (TLSF) is a surgical technique widely used for the treatment of several pathologies of the spine, including degenerative diseases, trauma and deformities. The initial objective of this procedure is to obtain fusion between the vertebral segments to promote the restoration of stability and alignment lost due to pathologies that affect the spine. It is known that the pandemic significantly affected elective medium and high complexity surgeries in Brazil; however, there are no studies regarding its influence on the performance of TLSF surgeries in the Unified Health System (UHS) in Brazil. Material and Methods: This is an observational study using aggregate national data from the Hospitals Information System (SIH/SUS) and the Brazilian Institute of Geography and Statistics (IBGE). These databases capture all procedures performed in the public health care system which comprises 75% of the Brazilian health care system. There was no need for ethics committee approval due to the data being public. All one to seven level TLSF procedures performed in pediatric and adult populations between April 2018 and March 2020 (pre-pandemic) and April 2020 and March 2022 (post-pandemic), all five Brazilian regions were analyzed. TLSF procedures during the pre-pandemic period were compared to the post-pandemic period in terms of total procedures performed, as well as total and average cost in Brazilian Reals(R$), included all direct costs to the health system such as hospitalization and fees. For the statistical analysis, the Chi-Square test was used, considering p < 0.05 as significant. Results: In the pre-pandemic period, 12,645 TLSF surgeries were performed by the UHS. Regional analysis demonstrated 456, 1,447, 4,706, 4,814 and 1,222 procedures were performed in the Northern, Northeastern, Southeastern, Southern and Center-West regions respectively. The total cost was R$100,087,353.45 (Brazilian reais) with an average cost of R$7,915.17 per procedure. During the post-pandemic period 8,891 TLSF surgeries were performed with 318, 1,226, 3,546, 2,952, and 849 performed in the Northern, Northeastern, Southeastern, Southern and Center-West regions respectively. This represented a relative reduction of 30.3%, 15.3%, 24.7%, 38.7% and 30.5% in the Northern, Northeastern, Southeastern, Southern and Center-West regions respectively as compared to pre-pandemic levels. Total cost was R$71,330,939.05 with an average cost of R$8,022.83. Conclusion: There was an overall reduction of 29.7% in TLSF surgeries during the pandemic in Brazil, with the most affected region being the Southern region, with a reduction of 38.7% (p < 0.05). It is important to analyze this data to identify the impact of the COVID-19 pandemic in relation to the performance of posterior spinal surgeries and its implications on wait lists in the various health regions. Future projects would look for underlying causes for the decrease in surgeries and its regional variation.

1568

P301: Surgical management of compressive myelopathy due to spinal fluorosis

Jayprakash Modi ^1,2 and Pratikkumar Prajapati ²

¹ Orthopaedic, Nutan Medical College, Mehsansa, India

² Orthopaedic, B J Medical College, Ahmedabad, India

Introduction: Fluorosis is an endemic disease of India which causes compressive cervical and/or dorsal myelopathy. This study aims to evaluate the role of surgical management in the crippling fluorosis along with evaluation of radiological imaging as screening/diagnosing tool for the disease. Materials and Methods: This is a prospective cohort study of 33 patients operated at tertiary care center having non-traumatic involvement of spinal cord affecting neurology with history, clinical and radiological features (Ossified Posterior Longitudinal Ligament, Ossified Ligamentum flavum) suggesting fluorosis as the cause of compression. Outcomes were measured in terms of improvement in Nurick grading, Rankins scale, spasticity, Oswestry Disability Index, modified Japanese Orthopaedic Association scores. Results: Spinal fluorosis is a male predominant disease affecting the elderly after years of fluorine intake. Cervical and/or dorsal spine are predominantly involved at multiple levels (> = 2). Diagnosis of the disease poses difficulty due to lack of established laboratory parameters with high sensitivity, availability, and lack of awareness among surgeons. Skeletal survey alone has > 90% sensitivity for diagnosing the disease. Once evaluated properly, decompression at correctly identified levels invariably improves the spasticity and quality of life immediately post-surgery. At final follow-up, there was on average improvement of 2 scales in Nurick grade, Rankins scale and Ashworth grading whereas average improvement in ODI, mJOA and dorsal specific mJOA were 52%, 3.17 points and 2.7 points respectively. However, preoperative counselling for “apparent neurological deterioration” in immediate postoperative period is very important. Complications like infection and dural tear have to be prevented with special surgical tactics. Conclusion: Skeletal survey along with computed tomography and magnetic resonance imaging is cost-effective modality for the screening/diagnosis for fluorosis. Once developed, surgery, either curative or palliative, is the best treatment at crippling stage of the disease.

Keywords: Dorsal myelopathy, endemic, fluorosis, laminectomy, ossified ligamentum flavum, ossified posterior longitudinal ligament.

1605

P302: A multidisciplinary approach does not discriminate based on socioeconomic factors in patients presenting with an adult spinal deformity

Caroline Drolet ¹ , Jesse Shen ^1,2 , Michelle Gilbert ¹ , Kellen Nold ¹ , Venu Nemani ¹ , Jean Christophe Leveque ¹ , Rajiv Sethi ¹ , and Philip Louie ¹

¹ Neurosurgery, Virginia Mason Franciscan Health, Seattle, United States

² Université de Montréal, Canada

Introduction: Adult spinal deformity surgery (ASD) is partly a high-risk procedure due to the comorbid aging population it often affects. Multidisciplinary approaches were developed to improve outcomes and decrease complications and have shown their efficacy in optimizing and screening patients. However, socioeconomically disadvantaged populations are more burdened with comorbidities. Whether multidisciplinary teams are biased towards healthier and more socioeconomically advantaged patients warrants further investigation. We sought to assess whether patients received surgery following a multidisciplinary conference review will differ by socioeconomic status, as defined by the area deprivation index. Material and Methods: A single-center retrospective analysis of patients operated for ASD was performed. Patients presented at a multidisciplinary conference for surgical clearance between August 2015 and March 2021 were reviewed. Patients were categorized based on their operative status. Each patient’s residence was ranked using the Area Deprivation Index based on the Neighborhood Atlas. This index ranks every zip code based on deciles, with one being the least disadvantaged and ten being the most disadvantaged within a state. Using logistic regression, we examined whether demographic variables, ADI rank for Washington (median split into low/advantaged and high/disadvantaged), distance from the hospital, and the interactions predicted whether patients received surgery after the conference. Results: Our analysis identified 330 patients (209 female, 121 male; 19-86 years old, M = 64.6, SD = 12.1). Patients with a history of psychiatric disorders were less likely to receive surgery, p = .02. No other main effects approached significance. There was a significant interaction between ADI and distance, p = .04. More advantaged patients were less likely to receive surgery if they were closer than farther from the hospital, p = .03. Distance did not significantly affect whether more disadvantaged patients received surgery, p = .51. Conclusion: This analysis suggests that a multidisciplinary approach does not discriminate based on socioeconomic status. Further investigation is needed to understand the relationship between distance and ADI, and their interactive effect on surgery.

1607

P303: Disparities in access to timely spine surgeon evaluation for degenerative lumbar pathology

Karissa Yamaguchi ^1,2 , Caroline Drolet ¹ , Mary Kim ^1,2 , Thomas Hanks ^1,2 , Lisa Depledge ^1,2 , Rajiv Sethi ¹ , and Philip Louie ¹

¹ Neurosurgery, Virginia Mason Franciscan Health, Seattle, United States

² School of Medicine, University of Washington, United States

Introduction: Studies have demonstrated the association between race, socioeconomic status (SES),and insurance type and worse preoperative physical and mental health at presentation in patients indicated for spine surgery. Unfortunately, these factors negatively impact postoperative clinical outcomes as well. Little research characterizes how race, SES, and insurance type impact patients’ abilities to navigate the health system from the initial referral to consultation with a spine surgeon. This study aimed to evaluate the impact of race, SES (as measured by the Area Deprivation Index [ADI]), and insurance type on timeliness to a spine surgeon appointment after initial referral; specifically, evaluating patients presenting with symptoms of lumbar radiculopathy. We hypothesized that patients with Medicaid, living in areas of higher deprivation (thus, lower SES), and of non-white race experience longer wait times between the initial referral to a spine surgeon and their initial consultation presentation. Material and Methods: This retrospective observational study was approved by the institutional review board (IRB). New patients evaluated for lumbar radiculopathy between March 2021 to September 2021 by four fellowship-trained spine surgeons at a single-center outpatient clinic were included. Patients seen as a part of the Centerof Excellence program or for a second opinion were excluded. A review of the electronic medical record and patient-staff communication logs obtained the following variables: Initial referral date, initial spine surgeon visit date, type of visit (virtual vs. in-person), symptom duration at presentation, referring provider, referring institution (internal vs. external), and referral timing. Demographic data including race, insurance type, zip code of residence, and location of initial consultation were extracted last to avoid bias in the depth of chart review. Multivariable analyses were performed to determine if specific demographic characteristics are associated with prolonged wait times for neurosurgery consultation. Results: Of the 305 new patients seen for initial neurosurgery consultation, 245 met our criteria. In our study, patients with Medicaid experienced significantly longer wait times when compared with patients with Medicare and private insurance (p = 0.007). Asian patients experienced the longest mean wait time (mean = 59.1 days), followed by White patients (mean = 30.6), then Black patients (mean = 21.3), but this was not statistically significant (p = 0.08). Living in an area of high deprivation was also not associated with significantly prolonged wait times (R = 0.025, p = 0.696). Conclusion: This study highlighted structural disparities in access to timely neurosurgery evaluation. Our results indicate that a patient's insurance status prolongs wait times for consultation. Further qualitative research is needed to identify specific barriers contributing to delays in care and solutions.

1631

P304: Scoliosis among children in Qinghai-Tibetan Plateau of China: a cross -sectional epidemiological study

Lijin Zhou ¹ , Yong Hai ¹ , and Honghao Yang ¹

¹ Department of Orthopedic Surgery, Beijing Chaoyang Hospital, Capital Medical University, Beijing, China

Introduction: The average altitude of the Qinghai-Tibetan Plateau is 4,500 m and most of the residents are of Tibetan ethnicity. The purpose of this study was to investigate the prevalence of scoliosis and associated factors among children in this region through a scoliosis screening program. Methods: A cross-sectional study was performed between May 2020 and December 2020 in Qinghai-Tibetan Plateau. A total of 9,856 children aged 6-17 years from schools and nearby villages were screened using visual inspection, the Adams forward-bending test, the angle of trunk rotation, and radiography. A self-designed questionnaire was used to collect demographic data. The prevalence of scoliosis and associated factors were analyzed. Results: The overall prevalence of scoliosis among children in Qinghai-Tibetan Plateau was 3.69%, with 5.38% for females and 2.11% for males. The prevalence of scoliosis was 3.50% in children who resided below 4,500 m while 5.63% in those resided above 4,500 m (p = 0.001). The prevalence of congenital scoliosis (2.14 vs. 0.42%, p < 0.001) and neuromuscular scoliosis (0.34 vs. 0.07%, p = 0.041) were significantly higher in the altitude above 4,500 m. 50.00% of patients resided above 4,500m were recommended for surgery while 16.24% in those resided below 4,500 m (p < 0.001). Independent associated factors were detected as female (OR = 2.217, 95 CI% 1.746-2.814, p < 0.001), BMI < 18.5 (OR = 1.767, 95 CI% 1.441–2.430, P = 0.005), altitude of residence ≥ 4,500 m (OR = 1.808, 95 CI% 1.325-2.483, p = 0.002), and sleep time < 8 h (OR = 2.264, 95 CI% 1.723-2.846, p = 0.001). Conclusion: The prevalence of scoliosis among children in Qinghai-Tibetan Plateau was 3.69%. With increasing altitudes, the prevalence of scoliosis and its major type were different from that at lower altitudes. Female, BMI < 18.5, altitude of residence ≥ 4,500 m, and sleep time < 8 h were independently associated with the prevalence of this disease. Early screening should be carried out before the age of 7 years, especially in high-altitude, underdeveloped, and rural areas.

1745

P305: Differences in spinal cord astrocytoma treatment across urbanicity

David Sykes ¹ , Nancy Abu-Bonsrah ² , Jacob Sperber ¹ , Edwin Owolo ¹ , Romaric Waguia Kouam ¹ , Tara Dalton ¹ , Mackenzie Price ¹ , Quinn Ostrom ¹ , Harrison Hockenberry ¹ , Dana Rowe ¹ , Emily Luo ¹ , Corey Neff ¹ , Brandon Bishop ¹ , Antoinette Charles ¹ , Margaret Johnson ¹ , Melissa Erickson ¹ , and C. Rory Goodwin ¹

¹ Department of Neurosurgery, Duke University School of Medicine, Durham, United States

² Department of Neurosurgery, Johns Hopkins School of Medicine, Baltimora, United States

Background: Spinal cord astrocytomas (SCAs) are highly infiltrative gliomas of the spinal cord, representing the second most common intramedullary spinal cord tumor. The management of SCAs may include surgery, radiation therapy, and/or systemic therapy, with patient outcomes potentially affected by their location. However, the role urbanicity in SCA treatment remains unknown. The authors, therefore, set out to determine the association between urbanicity and SCA outcomes. Methods: The Central Brain Tumor Registry of the United States (CBTRUS) analytic dataset, a combination of the CDC’s National Program of Cancer Registries and NCI’s Surveillance, Epidemiology and End Results datasets, was used to identify individuals with histopathologically-confirmed SCAs between 2004 and 2019. US Department of Agriculture 2013 Rural Urban Continuum Code definitions were used to classify patients as metropolitan or non-metropolitan. Multivariable logistic regression models were used to evaluate associations between urbanicity and SCA treatments adjusted for age at diagnosis, sex, race and ethnicity. Treatment was defined as radiation, surgery (excisional biopsy), systemic and comprehensive (radiation, surgery and systemic). Cox proportional hazard models were constructed to understand the effect of treatment, urbanicity, and age at diagnosis on the survival time of patients. Results: 2021 patients were included in this analysis. Of these, 1744 patients lived in a metropolitan (metro) area and 277 in non-metropolitan (non-metro) area, with a median age at diagnosis of 30 years and 28 years, respectively. There was a higher proportion of White Non-Hispanic (NH) individuals in the non-metro group (86% vs 66%, p < 0.001), and a higher proportion of Black NH individuals in the metro group (14% vs 9.9%, p < 0.001). No statistically significant difference was found on survival between the two groups. Non-metro group had a higher incidence of Grade I and II astrocytoma than the metro group, (51% vs 44%, p < 0.001) and (30% vs 19%, p < 0.001) respectively. No statistically significant difference was found between metro and non-metro groups in regard to treatment options. However, Hispanic ethnicity was associated with increased odd of receiving radiation [1.5 CI (1.13; 1.99)], systemic therapy [1.45, CI (1.07; 1.97)] and comprehensive treatment [1.64; CI (1.08; 2.43); p = 0.018]. Conclusions: Although metropolitan patients present with severe SCA (higher grade SCA), living in a metro or non-metro county was not associated with decreased odds of receiving SCA treatment. Further work is necessary to understand the role of urbanicity in outcomes of patients with SCA.

1879

P306: Pull-up bar associated spine injury: an analysis of the 2012-2021 NEISS database

Angelo Changas ¹ , Sohrab Vatsia ² , Grant Reviere ³ , Gerald McGwin ⁴ , Brent Ponce ² , L. Erik Westerlund ² , Douglas Pahl ² , James McGrory ² , and David Gloystein ²

¹ Philadelphia College of Osteopathic Medicine, Suwanee Campus, Suwanee, GA, United States

² Hughston Clinic, Columbus, GA, United States

³ Edward Via College of Osteopathic Medicine, Auburn Campus, Auburn, AL, United States

⁴ Department of Epidemiology, University of Alabama at Birmingham, Birmingham, AL, United States

Introduction: Interest in the use of home exercise regimens in the United States has risen considerably in the past several years. The use of pull-up bars allows for ease of access to strength training exercise, yet faulty manufacturing or improper installation of such equipment has led to a multitude of serious injuries and even litigation. Therefore, the purpose of this study was to analyze the mechanism of spinal injuries associated with pull-up bar usage. Material and Methods: The National Electronic Injury Surveillance System (NEISS) database was queried to estimate the incidence of injuries related to pull-up bar consumer products from 2012-2021 in the United States. Resultant data was analyzed to describe trends in demographics, incidence, and injury patterns associated with pull-up bar usage. Results: A total of 1470 pull-up bar-related injury cases were identified from review of the NEISS database query resulting in a weighted estimate of 50,108 injuries from 2012-2021 in the United States. Demographically, pull-up bar-related injuries were more common in males (74.3%), and the highest incidence of cases was reported in the 19-44 years old age group (50.4%) followed by the less than 18 years old age group (36%). Additionally, injuries were 1.55 times more likely to occur in a “Home” setting versus “Places of Recreation”. The NEISS codes for “Neck”, “Upper Trunk”, and “Lower Trunk” were utilized to distinguish anatomic regions of the spinal column – with a majority of cases (54.5%) localized to the “Upper Trunk” zone. Mechanistically, “Sprain/Strain” accounted for 24.0% of all injury cases, followed by “Lacerations” (12.5%) and “Fractures” (10.8%). In total, there were 529 weighted cases of spinal fracture due to pull-up bar malfunction, of which, 63 estimated “Neck” spinal fractures all occurred secondary to pull-up bar malfunction. Conclusion: Pull-up bar-related injuries are largely attributed to the use of home exercise equipment. These injuries are likely preventable, as pull-up bar malfunction injuries were 11 times more likely to occur in the “Home” setting in comparison to all other recorded locales. Improved product design and education underlying best practices for the use of pull-up bars and home exercise equipment may prevent an increasingly prevalent and deleterious mechanism of spinal injury.

1906

P307: Differential interspinous process device adoption and utilization across the United States

Justin Chan ¹ , Nicholas Peterman ² , Sohaib Hashmi ¹ , Yu-po Lee ¹ , and Henry Hoang ³

¹ Orthopaedic Surgery, University of California, Irvine Medical Center, Orange, United States

² Carle Illinois College of Medicine, Medicine, Urbana, United States ³ Montefiore Medical Center, Bronx, USA

Introduction: Interlaminar/interspinous process stabilization/distraction devices (IPDs) are relatively new treatment options for spinal stenosis that have recently been given identifiable billing codes by Medicare in 2017. This project utilizes publicly available Medicare physician billing databases, among other population level databases, to track the practice patterns, utilization, and expansion of IPDs in the 4-year period of 2017 to 2020 and catalog potential geospatial disparities in IPD adoption and the sociodemographics of those most effected. Material and Methods: The yearly Medicare Physician & Other Practitioners dataset containing all codes billed to Medicare, the location of billing, and the quantity of reimbursement was utilized for 2017 to 2020. This dataset was filtered to contain only IPD codes 22867, 22868, 22869, and 22870 and combined with the year-matched Medicare Geographic Variation dataset which contained the sociodemographics of the Medicare population on a county-level. The total dataset was then merged with the American Community Survey dataset from the United States (US) Census Bureau to obtain county-level economic data. Moran’s I clustering analysis was then conducted using GeoDa, a geospatial analysis software, to identify significant, p < 0.05, hotspots and coldspots of IPD insertions per 10,000 Medicare patients. The resulting hotspot and coldspot county groupings were then compared for significant differences across all recorded variables with a Mann-Whitney U Test. Results: 30,889 IPD insertion procedures costing a total of $111,472,207 to Medicare were captured in this analysis. 12.5% of procedures had PID insertions at two levels. The number of IPD procedures increased by 95.5% per year while costs increased by 132.3% per year on average across the 4-year period. 2019 was an outlier year, with a 17.4% reduction in total procedures from 2018, likely due to the impact of COVID on elective procedures. Cost increase was primarily driven by increased utilization of ambulatory surgical centers (ASCs), which Medicare reimburses at a higher rate. IPD insertion in ASCs increased by 10.7% per year to 37.6% overall in 2020. Geospatial clustering analysis of IPD insertions per 10,000 Medicare patients revealed hotspot clusters of IPD adoption in Los Angeles CA, Denver CO, Las Vegas NV, Jacksonville FL, Lincoln NE, Wichita KS, and Savannah GA. Coldspot clusters were predominantly along the Eastern Coast and in the Midwest Region. Compared to hotspots, coldspots were significantly more rural, whiter, less educated, more impoverished, and with higher Medicare participation rates. Conclusion: IPD insertion procedures have grown rapidly in recent years as a valid treatment strategy, but this growth has not been equally distributed across the United States. Rural, predominantly white, areas in the Eastern Coast and Midwest have lagged behind nationally. COVID, ASC utilization, socioeconomics, and the practice patterns of the surgeons themselves may all play a part in the geographic disparities identified in this work.

1910

P308: Subsequent fusion following multilevel lumbar decompression surgery

Ryan Hoel ¹ , Melissa Albersheim ² , Sharon Yson ² , Jeffrey Luna ³ , Paul Soriano ² , Jason Haselhuhn ² , and Jonathan N. Sembrano ²

¹ Twin Cities Orthopedics, Edina, United States

² University of Minnesota, Minneapolis, United States

³ Minneapolis VA Health Care System, Minneapolis, United States

Introduction: In select patients with lumbar spinal stenosis, surgical decompression is efficacious in reducing pain and improving quality of life. However, there is a debate about the role of posterior decompression and the number of operative levels contributing to spinal stability and reoperation rate. In this study, we sought to investigate the incidence of reoperation of patients after multilevel adjacent lumbar decompression, with a particular interest in the rate of subsequent fusion at the previously decompressed levels. We hypothesize a moderate incidence of subsequent fusion surgery after multilevel decompression surgery. Materials and Methods: After IRB approval, we retrospectively reviewed the charts of all spine surgeries performed over 15 years at a single Veterans Affairs tertiary referral hospital. We identified patients who underwent three or more level of lumbar decompression without concomitant fusion and determined if surgeons performed any subsequent spinal operations. We excluded patients with less than a year follow-up period. We attempted to contact all patients by phone for a follow-up to inquire if they had received spine surgery outside our institution. We determined and calculated the reoperation type and rates for each case and the time it took before a reoperation occurred. Results: Forty-five patients (44M:1F) with a mean age of 68 met the inclusion criteria and were included in the final analysis. The median follow-up time was 27 months. Three (7%) underwent subsequent fusion surgery at a previously decompressed level at 14, 23, and 25 months. Another three (7%) patients underwent revision decompression at previously decompressed levels at 6, 24, and 130 months. Five (11%) other patients underwent reoperation in the first two months for wound complications related to infection or hematoma. One (2%) patient underwent debridement of an epidural abscess located three levels cranial to the most proximal decompression six years after his index surgery; the abscess was deemed unrelated to the prior decompression. Overall, 12 patients (27%) underwent reoperation during their follow-up period. Conclusion: Our results suggest that the need for subsequent arthrodesis in decompressions of three or more consecutive levels without concomitant fusion may be less than intuitively suspected and that concomitant fusion at the time of index surgery is not warranted. We recommend mid-term and long-term analysis of rates of subsequent fusion. This study lends information for preoperative discussion with patients considering the risks and benefits of decompression alone versus decompression with fusion for multilevel lumbar surgery.

1945

P309: Effects of COVID-19 pandemic on spinal deformity operations and discectomies in the Unified Health System in Brazil

Rodolfo Gomes Dias ¹ and Mohammad Zarrabian ²

¹ Orthopaedic and Traumatology Department, Santa Casa de Misericórdia de Araçatuba, Araçatuba, Brazil

² Spine Surgery Division, Department of Orthopaedic Surgery,Winnipeg Spine Centre, University of Manitoba, Winnipeg, Canada

Introduction: Although the COVID-19 pandemic affected elective surgeries in Brazil there is no data on its effect on spinal surgeries. To better understand this we analysed data on the number and costs of spinal deformity operations and discectomy operations done from April 2018 to March 2022. These two categories were chosen for analysis as spinal deformity operations and discectomies represent opposite ends of the spectrum in terms of surgical risks, resource utilisation, and costs. Material and Methods: National data from the Hospitals Information System (SIH/SUS) and the Brazilian Institute of Geography and Statistics (IBGE) collected. These databases capture all procedures performed in the public health care system which comprises 75% of the Brazilian health care market. There was no need for ethics committee approval due to the data being public. The number of posterior spinal deformity operations (PSDO) and cervical, lumbar or lumbo-sacral discectomies performed between April 2018 and March 2020 (period 1) were compared to the number performed between April 2020 and March 2022 (period 2) in the five Brazilian health regions. These procedures were analysed in terms of total procedures performed, as well as average cost using the chi-square test with p < 0.05 considered significant. Costs included all direct costs to the health system such as hospitalisation and fees. Results: In period 1 1,379 PSDOs were performed with 19, 161, 670, 488 and 41 performed in the Northern, Northeastern, Southeastern, Southern and Centre-West regions respectively. During period 2, 985 PSDOs were performed with 11, 174, 513, 243, and 44 performed in the Northern, Northeastern, Southeastern, Southern and Centre-West regions respectively. The average cost of a PSDO was R$10,671.17 in period 1 and R$11,245.27 in period 2. By comparison 8,130 discectomies were performed in period 1 with 367, 878, 4,402, 1,877 and 606 performed in the Northern, Northeastern, Southeastern, Southern and Center-West regions respectively. In period 2 5,696 discectomies were performed with 212, 597, 3,228, 1,150, and 515 performed in the Northern, Northeastern, Southeastern, Southern and Centre-West regions, respectively. The average cost of a discectomy increased from R$ 1,592.02 in period 1 to R$ 1,637.36 in period 2. Conclusion: There was a 28.6% decrease in the number of PSDOs (p < 0.05) performed in the Brazilian public health care system between period 1 and period 2 while the average cost per case rose. The Southern region was the most affected with a reduction of 50.205% (p < 0.05) but the number of PSDOs in the Northeastern and Midwestern regions paradoxically increased by 8.08% and 7.32% respectively. In comparison nationally there was a 29.9% decrease in the total number of discectomy operations during the same time period (p < 0.05) and costs increased. Decreases occurred in every health region although the most affected was the Northern region with a 42.2% decrease. Despite significant differences between the risks, resource utilisation and costs of a spinal deformity operations and discectomies both types of operations decreased by similar amounts relative to their pre-pandemic levels while their costs increased. The Northern region suffered the greatest relative reduction in spinal surgeries.

2005

P310: Portal utilization in surgical spine patients: sociodemographic factors and social determinants of health

Edwin Owolo ¹ , Zoey Petitt ¹ , Antoinette Charles ¹ , Cesar Baeta ¹ , Emily Poehlein ² , Cynthia Green ² , Chad Cook ² , Jacob Sperber ¹ , Melissa Erickson ³ , and C. Rory Goodwin ¹

¹ Department of Neurosurgery

² Department of Biostatistics and Bioinformatics

³ Department of Orthopedic Surgery, Duke University School of Medicine, Durham, United States

Summary of Background Data: Patient portals (PP) have been shown to improve outcomes and quality of care. Engaging them requires internet access, technological literacy, and dexterity, which may serve as access barriers. The aim of this study is to examine patient portal use among the surgical spine patient population across different sociodemographic groups and assess impact of patient portal use on clinical outcomes. Methods: After exclusion criteria were applied, the study included data for 9,211 encounters from 7,955 patients. PP utilization was defined as having activated and used the patient portal system, MyChart, at least once. Sociodemographic characteristics included urbanicity, age, race, ethnicity, language, employment, and primary insurer. Clinical outcomes included length of hospital stay during procedure, 30-day return to the emergency department, 30-day readmission and being discharged somewhere other than home. Results: Being older than 65, non-White, unemployed, non-English speaking, male, not-partnered, uninsured or publicly insured (Medicaid, Medicare and under 65 years of age, or other government insurance), and living in a rural environment were all risk factors for decreased PP utilization among surgical spine patients. A one-risk factor decrease in the number of social risk factors was associated with a 78% increase in the odds of PP utilization [odds ratio (OR): 1.78; 95% CI: 1.69-1.87; p < 0.001]. Patients not utilizing the portal at the time of their procedure had higher odds of 30-day readmission (OR: 1.59; 95% CI: 1.26-2.00), discharge somewhere other than home (OR: 2.41, 95% CI: 1.95-2.99), and increased length of hospital stay (geometric mean ratio: 1.21; 95% CI: 1.12-1.30) compared to those who utilized it. Conclusions: In patients undergoing spine procedures, PPs are not equally utilized amongst different sociodemographic groups. PP utilization is also associated with better outcomes. Interventions aimed at increasing PP uptake may improve care for certain patients.

2024

P311: Impact of measures to fight the COVID-19 pandemic on posterior discectomies in the Unified Health System in Brazil

Rodolfo Gomes Dias ¹ and Mohammad Zarrabian ²

¹ Orthopaedic and Traumatology Department, Santa Casa de Misericórdia de Araçatuba, Araçatuba, Brazil

² Spine Surgery Division, Department of Orthopaedic Surgery, Winnipeg Spine Centre, University of Manitoba, Winnipeg, Canada

Introduction: The first description of a disc herniation causing sciatica was made as early as 1934. Symptoms of radiculopathy associated with a herniated disc, mostly resolves nonoperatively; but some patients whose conservative management fails, surgical interventions can be considered. The pandemic caused by COVID-19 considerably affected elective surgeries in the country, but there are no studies that show its influence on the performance of posterior cervical, lumbar and lumbosacral Discectomies in the Unified Health System (UHS). Material and Methods: This is an observational study using aggregate national data from the Hospitals Information System (SIH/SUS) and the Brazilian Institute of Geography and Statistics (IBGE). These databases capture all procedures performed in the public health care system which comprises 75% of the Brazilian health care system. There was no need for ethics committee approval due to the data being public. We analyzed the number of procedures, total and mean value in Brazilian reals(R$) of posterior cervical, lumbar and lumbosacral discectomy procedures ranging 1, 2 or more levels with and without the use of a microscope (LSPD); from the five Brazilian regions were analyzed. The results were organized in a spreadsheet and then descriptive statistics were used for comparison during the pre-and ongoing period of the pandemic, consisting of April 2018 to March 2020 (period 1) and April 2020 to March 2022 (period 2). For the statistical analysis, the Chi-Square test was used, considering p < 0.05 as significant. Results: In period 1, 8,130 LSPD were performed by the UHS; being 367, 878, 4,402, 1,877 and 606, in the North, Northeast, Southeast, South and Center-West regions respectively; at a total cost of R$ 12,943,109.63 and an average of R$ 1,592.02 per procedure and hospitalization. During period 2, 5,696 LSPD were carried out, at a cost of R$9,336,243.76 at an average value of R$1,637.36; with 212, 597, 3,228, 1,150, and 515 in the North, Northeast, Southeast, South and Center-West regions, respectively. A reduction of: 42.234%, 32.005%, 26.670%, 38.732% and 15.017% in the North, Northeast, Southeast, South and Midwest respectively. With a cost reduction of 28,731%. Conclusion: There was an overall reduction of 29,688% of LSPD during the pandemic in Brazil, with the most affected region being the North region, with a reduction of 42,234% (p < 0.05). It is extremely important to analyze these data to identify the impact of the COVID-19 pandemic on the procedure studied. This data, may assist the competent authorities in identifying and correcting discrepancies and reduction of the procedure studied caused by the COVID-19 pandemic in different Brazilian regions.

Imaging

172

P312: Invertertebral vacuum phenonemon, prevalence and severity in patients older than 50 years

Gaston Camino-Willhuber ¹ , Santiago Vildoza ¹ , Ezequiel Martinez ¹ , Lucia Canestrari ² , Fernando Holc ¹ , Michael Oh ³ , Yu-po Lee ⁴ , Nitin Bhatia ⁴ , Homero Bianchi ² , and Mariana Bendersky ²

¹ Orthopaedic and Traumatology Department, Institute of Orthopedics “Carlos E. Ottolenghi”, Hospital Italiano de Buenos Aires, Buenos Aires, Argentina

² Department of Anatomy, Universidad de Buenos Aires, Ciudad Autonoma de Buenos Aires, Argentina

³ Department of Neurosurgery

⁴ Department of Orthopaedic Surgery, UCI Medical Center, Orange, United States

Introduction: Degenerative low back pain is a common cause of disability and disc degeneration is one of the most frequent imaging findings. Intervertebral vacuum phenomenon is usually observed in advanced degeneration. Recently, this phenomenon has gained interest due to a relatively new surgical technique called Percutaneous Discoplasty aimed to treat low back pain secondary to degenerative disc disease in elderly patients. The objective of this study is to analyze the prevalence and related factors of vacuum phenomenon in adult patients. Material and Methods: A retrospective cohort study of patients that underwent abdominal CT scan for non-spine related reasons was performed. Age, body mass index, smoking and CT-based characteristics as presence of intervertebral vacuum phenomenon, subchondral sclerosis and facet joint degeneration at the lumbar spine from L1 to Sacrum were included in order to determine the prevalence of vacuum phenomenon in this population and establish relationship between this condition and patients demographics and other signs of spine degeneration such as sclerosis and facet joint disease. Results: 238 patients were included in the study, (124 feminine/114 masculine), mean age of 75.6 ± 12.3. 91 patients had at least one level of intervertebral vacuum phenomenon (38%). 59 patients exhibited subchondral sclerosis (25%), and 235 facet joint degeneration (98%). Among risk factors, age, smoking and subchondral sclerosis were significantly associated with the presence of vacuum. Conclusion: Intervertebral vacuum phenomenon was present in 38% of the patients included. Risk factors associated with vacuum were age, smoking and subchondral sclerosis.

519

P313: Functional paraspinal muscle area at L3 in the diagnosis of sarcopenia: establishing normative data in the Asian population and proposing new surrogate measurements of muscle mass

Julia Ng ¹ and Jacob Oh ¹

¹ Orthopaedic Surgery, Tan Tock Seng Hospital, Singapore, Singapore

Introduction: Low back pain and sarcopenia are highly prevalent conditions in the elderly with significant correlations. A diagnosis of sarcopenia requires both structural and functional measurements. Our study sought to investigate two potential estimates of sarcopenia of paraspinal muscles from routine imaging and to establish normative data for these indices for the Asian population. Materials and Methods: 250 consecutive non-reformatted magnetic resonance imaging (MRI) lumbosacral spine studies of patients performed at our institution from 1 October 2018 to 31 December 2018 were reviewed in the unenhanced T2 sequence in the axial slice closest to the level of the lumbar three (L3) superior end plate. For each patient, bilateral multifidus and erector spinae muscles were measured using two measurements each: functional muscle area (muscle without intra-muscular fat) and total muscle area (muscle with its intramuscular fat) were objectively measured using Fiji, an open-source biological image analysis software⁸. Two ratios relevant to functional muscle area were obtained: functional-to-total muscle area (fCSA:tCSA), and intramuscular fat-to-functional muscle area (IFA:fCSA; i.e. Goutallier staging). Multiple regression analysis was done to analyse the correlation between symptoms of low back pain and the ratios of functional muscle area for each of the 4 muscle groups, adjusting for age and gender. Results: 166 patients were included in the study, with 63 aged ≥ 65 years old and 110 reporting symptoms of low back pain during the scan. Gender distribution was equal. After adjusting for age and gender, our study found no significant correlation between the presence of low back pain and neither the fCSA:tCSA ratio nor the Goutallier staging for all 4 paraspinal muscles studied (p values > 0.05 for all measurements). Both age and gender were significantly correlated to both ratios for all 4 paraspinal muscles (p < 0.05 for all ratios), except for the left ES Goutallier staging ratio, where the effect of gender was not significant (p = 0.295). Age- and gender-specific normative data for the two ratios were further obtained. Older females consistently had the lowest fCSA:tCSA and highest IFA:fCSA ratios across all 4 paraspinal muscles. Conclusion: Our study is the first to describe normative functional paraspinal muscle area data at the L3 level for the Asian population. We show that functional paraspinal muscle area is poorly correlated with the presence of low back pain, but is strongly related to both age and gender. We propose a new measurement incorporating the extent of myosteatosis, akin to the Goutallier staging of rotator cuff muscles, as surrogate for muscle area in the diagnosis of sarcopenia.

589

P314: Utility of seated lateral radiographs for the assessment of degenerative spondylolisthesis

Tariq Issa ¹ , Yunsoo Lee ¹ , Mark Lambrechts ¹ , Qudratallah Qadiri ¹ , Caroline Zaworski ¹ , Henley Spracklen ¹ , Parker Brush ¹ , Delano Trenchfield ¹ , Jeremy Heard ¹ , Jose Canseco ¹ , Alan Hilibrand ¹ , Alexander Vaccaro ¹ , Christopher Kepler ¹ , Gregory Schroeder ¹ , and Joseph Lee ¹

¹ Division of Spine Surgery, Rothman Orthopaedic Institute, Philadelphia, United States

Introduction: The clinical heterogeneity in degenerative spondylolisthesis (DS) requires multiple imaging view to assess for the degree of vertebral translation, loss of disc space, slip angle, and the presence of instability. Traditional dynamic flexion and extension radiographs have been demonstrated to have poor reliability for detection of instability, are often pain-limited, and are not possible in patients with limited mobility. While supine magnetic resonance imaging (MRI) is used for preoperative planning and traditional four view radiographs may offer information regarding DS, traditional protocols may expose patients to unnecessary radiation at repeated office visits. Therefore, the primary objective of this study was to evaluate which radiographic images and are most important for the detection of DS severity and instability. Material and Methods: A retrospective review was conducted of all patients who received a clinical diagnosis of DS by a single provider from January 2021 to May 2022. All patients receive baseline standing lateral upright, lateral flexion, and seated flexion radiographs during their office visits. Slip measurement parameters were collected from all radiographs and MRI, when available. Angular instability was defined as a change of at least 10 degrees, and translation instability was defined as a change in vertebral translation of at least 8%. DS was classified according to Meyerding and CARDS classifications. Univariate ANOVA was utilized to compare continuous imaging parameters between images, and paired chi-square tests were utilized to compare categorical variables. Results: A total of 136 patients were included in this review. Most spondylolisthesis occurred at L4-L5 (78.7%), followed by L5-S1 (11.8%), and L3-L4 (9.6%). Seated flexion (Si) and standing flexion (Flex) radiographs revealed the greatest degree of slip percentage (16.0% and 16.7%), while supine MRI revealed the lowest slip percentage (12.2%). Seated flexion and standing flexion radiographs produced more kyphosis (4.66 and 4.97 degrees, respectively) than standing upright and MRI (7.19 and 7.20, respectively) (p < 0.001). Seated flexion performed similarly to standing flexion in identifying slip percentage, slip angle, and detecting the presence of disc space collapse or kyphotic angulation (p > 0.05). Comparable numbers of patients were classified in each CARDS (CARDS A, 19.1%; vs 18.4% CARDS B, 21.3% vs 24.3%; CARDS C, 47.1% vs. 40.4%; CARDS D, 12.5% vs 16.9%, p = 0.602) or Meyerding subgroup. Combination of seated flexion or standing flexion with MRI performed better in detecting translational instability than when combined with lateral upright films (31.5% vs 20.2%, p = 0.041, and 28.1% vs 14.6%, p = 0.014, respectively). However, there was no difference between seated flexion or standing flexion in detecting translational or angular instability (all, p > 0.20). Conclusion: Standing upright films do not provide any additional information in the detection of DS and expose patients to unnecessary radiation. The detection of instability may be reserved for detection using MRI that will likely be indicated pre-operatively and may combined with a single seated flexion radiograph rather dynamic flexion/extension radiographs.

603

P315: Dynamic standing lateral X-rays used to detect instability in patients with lumbar spondylolisthesis: how accurate is the standard technique? A modification aimed to obtain more precise results

Tuna Pehlivanoglu ¹ , Bahadir Gokcen ² , Gorkem Muratoglu ³ , Tugay Yagci ¹ , O. Nuri Eroglu ¹ , and Cagatay Ozturk ¹

¹ Dept. of Orthopaedic Surgery, Liv Hospital Ulus, Liv Spine Center certified by AOSpine, Istanbul, Turkey

² Dept. of Orthopaedic Surgery, Liv Hospital Vadi, Liv Spine Center certified by AOSpine, Istanbul, Turkey

³ Dept. of Orthopaedic Surgery, Istinye Uni. Liv Hospital, Liv Spine Center certified by AOSpine, Istanbul, Turkey

Introduction: Surgical decision making based on the level of instability in patients with lumbar spondylolisthesis is of crucial importance. However, no consensus exists in terms of the ideal radiographic modality for the most accurate detection of instability, while standard standing lateral dynamic (flexion-extension) X-rays (SSLDXR), which are extremely subjective and totally dependend on patients’ physical and cognitive abilities, are the most frequently used method to evaluate lumbar instability. Hence, these functional X-rays might provide variable results. The aim of the present study was to assess, if a modified version of traditional dynamic X-rays might provide higher accuracy of instability detection, together with more precise measurement of parameters used to define instability (ST > 3 mm / > 8%, SA > 20°, PVO > 5°). Methods: 37 consecutive patients with an average age of 68.7, who had a diagnosis of lumbar spondylolisthesis at the level L3-L4 were enrolled. They underwent first SSLDXR, and then the same X-rays were taken as the patients in standing position leaned on a chair fixed to the ground while doing the flexion and extension movements (modified standing lateral dynamic X-Ray (mSLDXR)). Segmental angulation (SA), sagittal translation (ST), posterior vertebral opening (PVO), lumbar lordosis and rates of clinically detected instability were calculated and compared between SSLDXR and its modified version. Results: Mean SA of the SSLDXR and mSLDXR were 8.4°(3.8°-22.4°) and 14.9° (10.6°-31.2°) (p < 0.001). Mean ST of the SSLDXR and mSLDXR were 5.4% (4.3%-8.7%) and 10.2% (7.4%-14.1%) (p < 0.001). Mean PVO of the SSLDXR and mSLDXR were -2.7°(-6.1°-5.2°) and 5.2° (0.4°-6.8°) (p < 0.001). All parameters showed significant difference between the two modalities. Average instability detection rate of the SSLDXR and mSLDXR were 32.4% (12/37) and 78.3% (28/37) (p < 0.001) underlining the superiority of the modification. Mean LL in flexion of the SSLDXR and mSLDXR were 29.1° (15.2°-40.8°) and 18.4° (4.6°-32.4°) (p = 0.003), while no significant difference was detected in terms of LL in extension. As a result of the correlation analysis a significant negative correlation was detected between LL in flexion and differences of SA, ST and PVO, while no significant correlation was detected between LL in extension and any of the parameters of instability. Conclusion: Using the chair fixed to the ground a physical assistive device and as a hinge point for lumbar flexion, provided a forced lumbar movement, resulting in the provocation of the abnormal lumbar mobility caused by lumbar instability due to spondylolisthesis. Hence, radiographic parameters regarding the instability (SA, ST, PVO), which are hindered by utilizing standard technique, are more pronounced are less biased. This study concluded, that as compared to SSLDXR, by using the mSLDXR technique, more precise values regarding the lumbar instability could be obtained resulting in a superior rate of instability detection, preventing cases that could be missed as a result of patients’ physical or cognitive incapabilities leading to biased results if assessed for instability with SSLDXR.

640

P316: Relationship between lumbar disc herniation and sedimentation sign in upright magnetic resonance images

Kishan Patel ¹ , Seung Min Son ² , Qiwen Zhang ¹ , Jeffrey C. Wang ¹ , and Zorica Buser ³

¹ Orthopaedic Surgery, Keck School of Medicine, Los Angeles, United States

² Orthopaedic Surgery, Yangsan Hospital, Pusan National University, Busan, South Korea

³ Grossman School of Medicine, Orthopaedic Surgery, New York, United States

Introduction: The nerve root sedimentation sign is a radiological sign that can serve as a predictor of lumbar spinal stenosis (LSS) in symptomatic patients on supine and upright MRIs. Pathogenesis of a positive sedimentation sign is hypothesized to occur due to compression of the spinal canal. While the sedimentation sign has been seen in cases of non-specific lower back pain, there are few studies determining the presence of the sedimentation sign in other causes of spinal canal compression besides LSS. Lumbar disc herniation can cause compression of the spinal canal leading to radiculopathy. This study’s goal was to determine the relationship between lumbar disc herniation and a positive nerve root sedimentation sign on upright kinematic MRI patients. Material and Methods: T2-weighted axial upright kMRI images were obtained of 100 patients with the presence of disc herniation in at least one lumbar disc between L1/L2 and L4/L5. Sedimentation sign, spinal canal anterior-posterior (AP) diameter, and disc height were measured. Size of disc herniation, type of herniation, and zone of herniation were evaluated. A positive sedimentation sign was defined as having either the majority of nerve roots running ventrally or centrally in the canal or conglomeration of the nerve roots at the mid-disc level. Herniation types were defined as either no herniation, disc bulge, protrusion, extrusion, or sequestration. Zones of herniation were categorized as either central, lateral, or far lateral per MSU classification. T-test and Chi-Square test were performed to determine measurements’ significance. Cohen’s kappa values were calculated for intra-observer reliability. Results: The kappa value of intra-observer reliability was 0.915. The kappa value of disc levels with a negative sedimentation sign were seen more frequently (n = 326, 65.2%) than those with a positive sedimentation sign (n = 174, 34.8%). A positive sedimentation sign was seen most frequently at the L4/L5 (n = 50, 50%) disc level. The incidence of Grade IV and V Pfirrmann grades were higher in patients with a positive sedimentation sign at all disc levels. The spinal canal AP diameter was found to be significantly decreased at the L3/L4 and L4/L5 level in patients with a positive sedimentation sign. At all levels, discs with a negative sedimentation sign were more likely to have no herniation compared to those with a positive sign. Discs with a positive sedimentation sign were seen to have a larger average size of disc herniation compared to those with a negative sign at all levels. The Chi-square statistic was significant at the L2/L3, L3/L4, and L4/L5 disc levels for a relationship between positivity of the sedimentation sign and type of disc herniation. No relationship was seen between herniation zones and positivity of sedimentation sign. Conclusion: In the current study a relationship between disc herniation and a positive sedimentation sign in the lumbar spine was seen. Patients with a positive sedimentation sign were seen to have larger disc herniations and more severely degenerated discs. Further studies may elucidate if a positive sedimentation sign indicates improved post-operative outcomes in discectomy patients.

929

P318: MRI appropriateness in the evaluation of chronic neck pain: comparison of ordering practices and treatment outcomes for primary care physicians and specialists

Danny Lynch ¹ , Andrew Mr. ¹ , Evan Johnson ² , Xiang Zhu ³ , and John S. Kirkpatrick ⁴

¹ Orthopaedic Surgery, University of Central Florida/HCA Healthcare GME Consortium, Ocala, United States

² Orthopaedic Surgery, University of Tennessee - Campbell Clinic, Mephis, United States

³ Biostatistics, University of Central, Orlando, United States

⁴ Orthopaedic Surgery, 13800 Veterans Way, Orlando, United States

Introduction: Chronic neck pain is one of the most common reasons for doctor visits in the U.S. This presentation can be effectively evaluated through judicious use of patient history, physical and radiographs. However, magnetic resonance imaging (MRI) ordering frequently precedes complete patient evaluation, posing a financial and medical risk to patients. It was hypothesized that no difference in ordering practices, treatment outcomes or ordering appropriateness would be appreciated based upon ordering physician specialty. Material and Methods: Retrospective chart review of consecutive charts was performed for cervical spine MRIs at a VA medical center and its surrounding VA clinics between January 2014 and June 2018. An American College of Radiology (ACR) appropriateness score between 1 and 9 was determined for each MRI based on duration and location of pain, accompanying symptoms, red flags (e.g. incontinence, fever, chills, weight loss), and physical exam findings. Results: 332 cases from neurologists (n = 24), orthopaedic surgeons (n = 76), primary care physicians (n = 203), pain medicine physicians (n = 21) and physiatrists (n = 8) were reviewed. Orthopaedic surgeons ordered MRIs most appropriately with an average ACR appropriateness score of 8.4 (p < 0.05). Orthopaedic surgeons had more comprehensive physical exams, as they tested range of motion (p < 0.005) and sensory (p < 0.005), performed a graded motor exam (p < 0.005), and utilized provocative maneuvers such as Spurling’s test (p < 0.005) and differentiating maneuvers such as Tinel’s test (p < 0.005) more often than other specialties. Treatment outcomes did not vary by physician specialty or ACR appropriateness score, except for patients of pain medicine physicians who received interventional pain management more often (p = 0.000). Conclusion: Orthopaedic surgeons utilize MRI most appropriately and have more comprehensive physical exams. These findings suggest a need for increased physician education on what indicates an appropriate MRI in order to improve the use of resources and further protect patient risk-benefit profiles. Further research elucidating factors to minimize negative findings in “appropriate” MRIs is indicated.

1030

P319: Decay variance processing for multi-echo MRI in diagnosing intervertebral disc degeneration - First in human results

Kyle Sheldrick ¹ and Ashish Diwan ¹

¹ University of New South Wales, Kensington, Australia

Introduction: Intervertebral disc degeneration is a cause of back pain, however current diagnostic techniques in clinical practice perform poorly. The work of Corniola et al demonstrated that changes in Pfirrmann grade using T2 weighted MRI correlates poorly with patients’ self rated levels of pain and disability. Further it does not predict patient response to surgical intervention. We have previously described and published “Decay Variance”, a non-relaxometry post-processing technique for multi-echo T2 data, which correlated strongly with histological disc degeneration in rabbits. Here we describe the first pilot usage in humans. Material and Methods: We performed the Decay Variance scan in adults with back pain and healthy controls. All participants with back pain met inclusion criteria including: meeting the NIH definition of chronic low back pain; pain present on > 50% of days over preceding 6 months, other potential radiologically identified causes of back pain excluded on structural MRI performed in the previous 12 months; aged at least 18. Results: 15 participants were recruited, 12 with back pain and 3 without back pain, 1 to 1 age matching of controls was planned but abandoned due to the permanent closure of our MRI provider during the COVID-19 pandemic. Participants with higher self-rated back pain severity had worse Decay Variance scores. Participants with severe back pain (≥ 7/10) had worse Decay Variance scores than those without (≤ 6/10), 3.03 ± 0.58 vs 1.87 ± 0.47. Self-rated back pain also correlated moderately strongly with Decay Variance score using a Pearson correlation co-efficient (r^2 = 0.44, p = 0.007). Conclusion: The results of this first in human pilot study suggest that patients with more severe back pain have worse Decay Variance values in their intervertebral discs, however caution is needed in interpreting the results. The selection of participants, especially given the NIH definition of chronicity limits the generalizability of this finding, especially in regards to effect size and coefficient of correlation. Further a cross sectional design, especially one without patient matching such as ours, cannot address causality and is vulnerable to residual confounding. The small sample size makes the estimates of effect size imprecise. We have commenced a large longitudinal cohort study, funded by the Australian government, to overcome these limitations, expected to be complete 2024.

1429

P320: Signal intensity changes of the second sacrum on MRI targeting the lumbar spine indicate sacral insufficiency fracture

Kohei Ohta ¹ , Hiroki Ikuchi ² , Takayuki Ogawa ³ , and Akihiro Nagamachi ¹

¹ Orthopedic Surgery, Yoshinogawa Medical Center, Tokushima, Japan

² Orthopedic Surgery, Takamatsu Municipal Hospital, Kagawa, Japan

³ Orthopedic Surgery, Sakaide Kaisei Hospital, Kagawa, Japan

Introduction: The incidence of sacral insufficiency fracture (SIF) has been reported to be 1.0% to 1.8% in at-risk patient populations. Patients with SIF most commonly complain low back pain, buttock pain, hip pain or other symptoms similar to the lumbar spine diseases. Diagnosis of SIF often delayed because appropriate diagnostic imaging studies sometimes lack due to the characteristics of the symptoms. Tamaki reported signal changes in the second sacrum on sagittal view of MRI targeting the lumbar spine indicated SIF in 4 patients. This finding will help early diagnosis of SIF. The purpose of this study was to clarify the clinical features of SIF and verify the usefulness of the signal changes in the second sacrum on sagittal view of MRI targeting the lumbar spine in diagnosis of SIF. Material and Methods: Forty-two patient with SIF participated in this study. There were 6 male and 36 females and their mean age was 81 years. Mean bone mineral density was 0.681g/cm². Cause of injury and initial symptom extracted from the electric medical record. Twenty-nine of 42 patients underwent MRI targeting the lumbar spine at the first visit. We observed signal intensity changes of T1-weighted image, T2-weighted image and Short T1 Inversion Recovery (STIR) on MRI sagittal view. Results: The causes of injury were falling down in 28 cases (66.7%), falling in 4 cases (9.5%), farm work in 2 cases (4.8%), massage in 1 case (2.4%) and unknown in 7 cases (16.7%). The initial symptoms were low back pain in 27 cases (64.3%), buttock pain in 21 cases (50%), leg pain in 6 cases (14.3%), hip pain in 8 cases (19.0%) and sacral pain in 4 cases (9.5%). Signal intensity changes of the second sacrum on MRI sagittal view were observed in all 29 patients. Low signal intensity of T1-weighted image was observed in all patients. High signal intensity, low signal intensity and both high and low signal intensity on T2-weighted images were observed in 11 (37.9%), 14 (48.3%) and 4 patients (13.8%), respectively. High signal intensity changes on STIR image were observed in all 29 patients. Conclusion: Linstrom et al. reported an anatomical and biomechanical analysis showing that the horizontal component of the fracture seems to develop at a later stage after loss of support of the central sacrum from the laterally positioned vertical fracture in the sagittal plane. The loss of lateral sacral alar support causes the entire weight of the upper body to be longitudinally transferred down the central portion of the sacral bodies, which include the second sacrum. We consider that signal changes at the second sacrum on lumbar MRI indicate an insufficiency fracture or bone marrow lesion caused by this mechanism. The initial symptoms of SIF are similar to those of lumbar spine disease. Signal intensity changes on sagittal view of the second sacrum of MRI targeting the lumbar spine was a valuable finding in early diagnosis of SIF.

1537

P321: Discrepancies between radiologist and spine surgeon interpretations of cervical and lumbar stenosis

Graysen Petersen-Fitts ¹ , Edwin Chaharbakhshi ² , John France ² , Sanford Emery ² , Shari Cui ² , and Scott Daffner ²

¹ Bluegrass Orthopaedics, Lexington, United States

² Department of Orthopaedics, West Virginia University, Morgantown, United States

Introduction: Previous studies have demonstrated poor interrater reliability of imaging interpretation between surgeons of various specialties and radiologists for a variety of pathologic conditions. Discrepancies in radiologic interpretations can lead to diagnostic frustration and difficulty formulating treatment plans. Moreover, third-party payors often rely on documented radiology reports rather than surgeons’ independent interpretation of imaging studies (and never review the actual images), which can impact insurance authorization for surgery or reimbursement. Ultimately, conflicting radiologic interpretations may negatively impact patient care. The purpose of this study was to evaluate the rate of and degree to which radiologists and spine surgeons differ in interpreting magnetic resonance imaging (MRI) studies in the setting of cervical and lumbar spinal stenosis. Material and Methods: A retrospective review was performed at a single academic institution of 100 consecutive patients undergoing decompressive surgery of either cervical or lumbar spine in 2018. Patients’ documented preoperative MRI interpretation from both the radiologist and the orthopaedic spine surgeon were compared. Degree of pathology was classified as “mild,” “moderate,” or “severe.” Demographic data was also recorded. Outcomes included the frequency of discrepancies as well as the degree of discrepancy (ie “mild” vs “moderate”). Chi squared analysis was performed to evaluate for differences between observed and expected outcomes. Results: A total of 100 patients were included (49 males) including 44 cervical and 56 lumbar studies. Discrepancies were identified in 65 cases (65%). There was no statistically significant association between patient age, gender, or BMI and whether a discrepancy existed. There was a trend toward discrepancies being more common when interpreting cervical MRI than lumbar (p = 0.063). There were 14 instances (21.5%) of two-grade discrepancy where radiologists interpreted pathology as “mild” and the spine surgeon interpreted the same pathology as “severe.” Conclusion: Our data found that disagreements in MRI interpretation between orthopaedic spine surgeons and radiologists occur more often than not. Moreover, the discrepancies were often two-grades, with spine surgeons rating pathology as more severe. Although this study was not designed to elucidate the reasons behind discrepancies, we hypothesize that this is due to the spine surgeons also having information from the physical examination of the patient when interpreting imaging studies. Given the implications of these discrepancies including denial or delay of care by third-party payors, we propose that when such differences exist, payors should defer to the interpretation provided by the physician who has actually examined the patient.

1548

P322: Evaluating the safe zone for lumbar pedicle screws: a 3D image analysis using virtual screws

Tony Tannoury ¹ , Henry Hojoon Seo ¹ , Aziz Saade ¹ , Bachir Atallah ² , Mirna Chahine ² , and Chadi Tannoury ¹

¹ Orthopaedic Surgery, Boston University School of Medicine, Boston, United States

² Lebanese University, Beirut, Lebanon

Introduction: Pedicle screw breach (PSB) is not uncommon following lumbar instrumentation, and in some instances, it may lead to vascular and/or neurologic complications. Previous literature suggested that screws crossing the vertebral midline on an anterior-posterior (AP) radiograph (or midsagittal on CT) are concerning for medial pedicle breach.Our primary aim was to map out the safe zones (SZ) of bilateral pedicle instrumentation and their relationship at each lumbar vertebral level. Our secondary aim was to evaluate the presence of SZs’ intersection at each lumbar level, denoting safe midline pedicle screws crossing not otherwise associated with medial pedicle breach. Material and Methods: CT scans of 51 patients were randomly selected from “The Cancer Imaging Archive” (TCIA) online database for analysis. The Sectra 3D Spine software was used to create 3D renderings, place virtual screws, and make measurements. At each lumbar vertebra, the right and left pedicle corridors were mapped. At each pedicle, two screw positions were templated, the “medial limit screw” (MLS) and the “lateral limit screw” (LLS). Each limit screw was the most extreme position that the screw could exist in without causing a medial or lateral breach. The safe zone was defined as the zone between MLS and LLS. Measurements were taken for each level (between L1-L5) and side (Left, Right). Results: A total of 253 lumbar vertebrae from 51 patients (mean age 53.1, 56.9% male) were included. Two vertebrae from two patients were removed for poor image quality. Out of the 506 screw positions analyzed in our study, 97.4% had overlapping SZ and crossed the midplane without medial pedicle breach. The significant factors (p < 0.01) for safe midplane-crossing screws included: the screw length (L1-L5); laterality of the screw entry point (L1-L4); and pedicle diameter (L2 and L5). Conclusion: A midline crossing pedicle screw on a lumbar AP radiograph is not necessarily indicative of a medial pedicle screw breach. Anatomical (i.e. larger pedicles diameter) and technical (i.e. longer screws, and lateral entry points) factors allow for safety zone intersections and indicate safe midline crossing by pedicle screws.

1647

P323: Management protocol of patients with lumbar spinal stenosis, using the qualitative grading as a tool

Jayprakash Modi ^1,2 and Pratikkumar Prajapati ²

¹ Orthopaedic, Nutan Medical College, Mehsansa, India

² Orthopaedic, B J Medical College, Ahmedabad, India

Objectives: Several parameters exist for assessment of lumbar spinal stenosis (LSS) but these parameters lack clinical correlation. To formulate a protocol for management of these group of patients using the qualitative grading as a tool. Materials and methods: A prospective study was undertaken using the qualitative grading on magnetic resonance imaging (MRI) to assess the clinical outcome of LSS at a single level. Irrespective of the grade every patient underwent a minimum 3 months period of conservative management after which depending on the Oswestry disability index (ODI) and visual analogue scale (VAS) for pain he was grouped into success or failure and the failed patients were advised for decompression surgery at the involved level. These patients were then further assessed after a period of 3 months after surgery. A decrease in ODI by 10 points and a 20 points decrease in VAS was considered as a success. Results: Out of the 90 patients, there were 61 failures in conservative group, out of these 57 were operated of which only nine did not match the success criteria, while the other four either refused surgery or were lost to follow-up. In grades A1 to 3, only two patients failed conservative trial while from A4 to D, there was a gradual decline in success of conservative trial. Conclusion: Qualitative grading is a useful tool in LSS and correlates with the clinical outcome and to decision making of these patients.

1671

P324: Evaluation of axonal injury with filtered diffusion weighted magnetic resonance imaging in cervical spondylotic myelopathy

Saman Shabani ¹ , Shekar N. Kurpad ¹ , and Matthew Budde ¹

¹ Neurological Surgery, Medical College of Wisconsin, Wauwatosa, United States

Introduction: In cervical spondylotic myelopathy (CSM), axonal injury is believed to be the main correlate with functional outcome. Although diffusion tensor imaging (DTI) is sensitive to microscopic pathologies, its utility has been limited in CSM in setting of substantial edema or myelomalacia. The purpose of this study was to assess the spinal cord diffusion measures in patients with CSM using a new filtered diffusion weighted imaging (fDWI) technique that aims to reduce the confounding effects of edema and extracellular water on the measured diffusion values. Materials and Methods: Twenty-one patients with CSM underwent pre-surgical fDWI and DTI scans on 3T MRI system. DTI was obtained with 25 directions at a b-value of 800 s/mm². fDWI employed spinal cord-optimized diffusion weighting along 26 directions with a “filter” b-value of 2000 s/mm² and “probe” max b-value of 1000 s/mm². Parallel diffusivity metrics obtained from DTI and fDWI were compared to one another and with metrics derived from T₂-weighted MRI including relative signal changes and lesion size. Results: The parallel apparent diffusion coefficient (fADC_||) acquired from fDWI at the level of maximum compression (-15.16 ± 12.07%) decreased relative to most cranial slice and had a larger change than axial diffusivity (AD) acquired by DTI (-3.18 ± 14.41%). A linear regression identified a significant relationship between AD and T2 metrics (r² = 0.453, p = 0.05) whereas fADC_|| was not significantly related to T2 metrics (r² = 0.069, p = 0.70). AD was significantly increased at spinal cord slices with T2 intensities (t(81) = 1.65, p = 0.05) compared to slices without T2 abnormalities, whereas fADC_||was not significantly different between spinal cord slices with or without T2 abnormalities. Conclusions: The results demonstrate that filter diffusion encoding reduces the coupling between T2 spinal cord changes and diffusion measurements that are presumed to reflect extracellular water and can considerably affects DTI metrics. Future studies evaluating the relationships with functional status and outcomes in a larger cohort of CSM patients would be beneficial.

1953

P325: MRI-tractography as a method to predict neurological recovery in patients with cervical spinal cord injury

Oleksii Nekhlopochyn ¹ , Ievgenii Slynko ¹ , Vadim Verbov ² , and Yurii Derkach ¹

¹ Spinal Neurosurgery

² Restorative Neurosurgery Department, Romodanov Neurosurgery Institute, Kyiv, Ukraine

Introduction: The achievement of scientific and technical progress in recent decades, the introduction of computer and magnetic resonance imaging (MRI) into clinical practice made it possible to review both tactical approaches to the treatment of neurologically complicated cervical spine injuries, as well as the criteria for predicting the long-term results of therapy. Currently, MRI is the gold standard in the diagnosis of traumatic injuries of the spinal cord in patients with neurological deficits. This is due to the high informativeness of visualization of soft tissue structures, in particular the spinal cord, the possibility of detecting damage to the disc-ligamentous apparatus of the spinal column, and the absence of ionizing radiation. However, the data of the literature ambiguously interpret the correlation between MRI results and the degree of neurological disorders. The idea of our study is the primary assessment of the prognostic features of MRI tractography in patients with severe subaxial cervical spine and spinal cord injury. Material and Methods: The clinical group consisted of 5 patients hospitalized in the Department of Spine Surgery Romodanov Neurosurgery Institute during period from April to July 2019 with severe traumatic injury of the cervical spine and spinal cord. MRI was performed in the following modes: T1W, T2W, FLAIR, STIR, T2W FFE, CSF flow and DTI in 5-7 days after surgery. The dynamics of neurological disorders regression were evaluated according to the International Standards for Neurological Classification of Spinal Cord Injury. The level of spinal canal traumatic stenosis of the was determined by SCT both before and after surgical correction. Due to the small clinical group, statistical processing of the obtained digital indicators was not performed. The main task was to identify general patterns in order to determine the direction of further detailed studies. Results: Spinal cord edema at the damage level was observed in 100% of patients, that corresponded to the level of neurological disorders. The presence of hemorrhagic component was detected in 3 patients, while post-traumatic spinal stenosis was: more than 50% - 1 patient, up to 50% - 1 patient and less than 25% - 1 patient. Spinal cord parenchyma edema was accompanied by varying degrees of compression of the cerebrospinal spaces, from subtotal to total, with the presence or absence of a hemorrhagic component that did not affect the intensity of cerebrospinal fluid flow disorders. Evaluation of DTI results showed a moderate inverse relationship between fractional anisotropy (FA) and mean diffusivity (MD) indicators. In 2 patients, a regression of neurological disorders was registered. Restoration of sensory-motor functions did not correlate with the degree of compression of the spinal canal or the nature of changes in the parenchyma of the spinal cord, but was noted in patients with maximum FA values and low MD. Conclusion: Tractography is an informative predictor of the regression of neurological disorders in patients with severe spine and spinal cord injury. Further studies are needed to identify the optimal timing of its implementation and to establish diagnostically significant values of anisotropic diffusion indices.

Infections

69

P326: Incidence and predictors of postoperative wound infection in the MENA region: a multicenter retrospective cohort study

Sameh Abolfotouh ¹ , Mohamed Khattab ² , Atiq Uz Zaman ³ , Omar Alnori ⁴ , Alaa Zakout ⁴ , Faisal Konbaz ⁵ , Tarek ElHawala ⁶ , Ghazwan Hassan ⁷ , Sami Aleissa ⁵ , and Mostafa Abolfotouh ⁵

¹ Orthopedics Department, MEDCARE Hospital, Dubai, United Arab Emirates

² Orthopedics Department, Ain Shams University, Cairo, Egypt

³ Orthopedics and Spine Surgery Department, Lahore Medical and Dental College, Ghurki Trust Teaching Hospital, Lahore, Pakistan

⁴ Orthopedics and Spine Surgery Department, Hamad Medical Corporation, Doha, Qatar

⁵ Orthopedics Department, King Abdulaziz Medical City (KAMC), National Guard Health Affairs, Riyadh, Saudi Arabia

⁶ Orthopedics Department, Faculty of Medicine, Zagazig University, Spine Unit, Zagazig, Egypt

⁷ Orthopedics Department, Royal Private Hospital, Baghdad, Iraq

Study Design: Retrospective cohort study. Objectives: This study aimed to estimate the incidence of postoperative surgical site infection (SSI) following spine surgeries and its associated factors. Methods: This is a multicenter retrospective study of all patients ≥ 14 years of age, who had undergone spine surgeries between January 2014 to December 2019, at 6 tertiary referral centers in the MENA region (n = 5,872). Patients’ medical records were examined to collect data on: (1) Patient’s characteristics, (2) Disease characteristics, (3) Spine surgery approach, and (4) characteristics of Postoperative SSI. Logistic regression analysis was applied to identify the predictors of postoperative SSI. Significance was considered at p ≤ 0.05. Results: The overall incidence of SSI was 4.2 percent (95% CI: 3.72-4.77), in the form of deep (46.4%), superficial (43.1%), dehiscence (9.3%) and organ space (1.2%) infections. After adjusting for all possible confounders, significant predictors of postoperative SSI were; diabetes (OR=2.12, p < 0.001), smoking (OR = 1.66, p = 0.002), revision surgery (OR = 2.20, p < 0.001), open surgery (OR = 2.73, p < 0.001, perioperative blood transfusion (OR = 1.45, p = 0.033), ASA class III (OR = 2.08, p = 0.002), and ≥ 4 days length of stay “LOS” (OR, 1.71, p = 0.001). A cut-off 4 days was the optimum LOS at which the postoperative SSI is more likely to occur, with 0.70 sensitivity, 0.47 specificity, and 0.61 area under the curve. Conclusion: This is the first study that highlighted the incidence of postoperative SSI in spine surgery in the MENA region. Incidence figures are comparable to figures in different regions of the world. Identifying predictors of SSI might help high‐risk patients benefit from more intensive wound management.

81

P327: Intraoperative topical antibiotics administration in instrumented spine surgery as a efficient tool to reduce post-operative infections. A multicenter comparative analysis and literature review

Giovanni Barbagli ¹ , Elisabetta Peppucci ¹ , Mariano Vitelli ¹ , Nicoletta Gargiuoli ¹ , Giulio Wembagher ² , Matteo Capozza ³ , Giuseppe Cavallo ¹ , Alexander Evins ⁴ , Alessandro DiChirico ¹ , Stefano Romoli ² , and Sandro Carletti ¹

¹ Neurosurgery, IFCA, Firenze, Italy

² Spine Surgery Unit, Azienda Ospedaliero Universitaria Careggi, Firenze, Italy

³ Neurosurgery, Azienda USL Toscana Nord-ovest, Livorno, Italy

⁴ Neurosurgery, Weill Cornell Medical College, New York, United States

Introduction: The use of topical antibiotic (i.e. vancomycin) in addition to intravenous administration of antibiotics has been reported as an effective tool in reducing the rate of surgical site infections (SSI), which could be very serious complications, in particular in fusion spine surgery. However, it is not widely used yet. The recent trend in fusion surgical spine procedures carries along an increased rate of revision surgeries that are associated with more durotomies and prolonged surgical length. Both these factors are well-known predictors of SSI; other important point is an increasing incidence of well-known risk factors such as obesity, diabetes and smoking. Moreover, SSIs may require surgical debridement, which leads to higher postoperative morbidity and mortality. The aim of the study is to evaluate the rate of infections between different cohorts, treated in different high-volume centers in Italy and estimate the efficacy in reducing SSIs when a topical antibiotic is added to a routinary intravenous one. Material and Methods: Six hundred fifty-eight patients underwent elective lumbar and lumbosacral fusion procedures from 01/02/2021 to 28/2/2022 were evaluated. Descriptive and inferential statistics were performed using IBM^®SPSS^® Statistics v.27.0.1.0 analysis software. Descriptive analyses were performed using the frequency for the nominal variables and the means (± standard deviation) for the continuous variables. Statistical inference with continuous numerical variables stratified by groups (patients treated with vancomycin / patients not treated with vancomycin) was performed with the non-parametric Mann-Whitney U test with independent samples. The analysis to assess any difference in risk factors and complications of an infectious nature between the two groups (vancomycin / only iv antibiotic) was carried out using the Fisher's exact test. An error α = 0.05 was considered for statistical significance. Authors carried out a complete literature review and compared the results of the study with the current data on Pubmed and MEDLINE. Results: The gender distribution of our series was quite balanced, with 50.9% of patients being female and 49.1% male. The mean age of the patients was 58.4 (± 14.2) years, while the mean surgical time was 128.7 (± 68.7) minutes with a minimum of 15 and a maximum of 495 minutes. Surgical time was found to be higher in the group of treated with vancomycin than in the untreated one, with a statistically significant difference (p = 0.001), while there was no significance for the difference in age between the two groups (p = 0.09). 71.6% of patients received intraoperative vancomycin powder and, in this group, the infection rate was 1.5% while in the non-vancomycin group the rate of infection was 16%. The use of vancomycin was found to be associated with a lower occurrence of infectious post-operative complications, with a very high statistical significance (p = 0.001). Conclusion: The intrawound application of vancomycin powder in addition to intravenous administration of antibiotics may significantly reduce the risk of surgical site infections (SSIs) after spinal surgeries. Further studies with larger sample size and high quality are needed to provide more evidence.

135

P328: Epidemiological and clinical features of infections spondylodiscitis

Baghdedi Nahla ¹ , Imen Chaabeen ¹ , Jlidi Mohamed ² , Sabrine Bachrouch ¹ , Haifa Tounssi ¹ , Mohamed Hedi Gharbi ² , Mouldi Lamouchi ² , Walid Bouaicha ² , Zeineb Alaya ¹ , Selim Daas ² , and Raja Amri ¹

¹ Internal Medicine Department, Hospital of Mohamed Taher Maamouri, Nabeul, Tunisia

² Hospital of Mohamed Taher Maamouri, Orthopedics and Traumatology Departments, Nabeul, Tunisia

Introduction: Infectious spondylodiscitis (SPI) is a disease with increasing prevalence that can result in poor functional outcome and progressive spinal deformity. The objective of our study is to summarize the epidemiological characteristics, clinical features, diagnosis and the treatment of SPI. Material and Methods: We analyzed the medical records of cases of SPI hospitalized in internal medicine department of the HMTM hospital in Nabeul Tunisia during the period from January 2018 to December 2021. Results: Thirty-two patients were included (25 males and 7 females). The mean age was 59.5 years. A history of diabetes was found in 13 cases, recent surgery in 2 cases, immunosuppression in 1 case and end stage kidney failure in 13 cases (Hemodialysis patients). The most common symptom was back pain (96.8%) and fever (50%). Three patients presented neurological deficit. The average time to diagnosis was 2 months and 7 days [3days-6months]. Spinal MRI and CT, performed respectively in 90% and 59%. The lumbar level was the most common site of infection (71.9%). Twenty three patients had complicated abscess formation over the epidural space (71.9%), psoas muscle (11 cases), and paraspinal area (13 cases). Spinal cord compression was noted in 8 cases. Blood cultures were positive in 17 cases. 14 patients underwent a CT guided biopsy, and one patient underwent a surgical biopsy. SPI was pyogenic spondylodiscitis in 25 cases, tuberculous spondylodiscitis in 5 cases and 2brucella spondylitis. All patients received a specific antibiotic treatment, and the average treatment duration was 14 weeks. Two deaths were observed. Neurological sequelae were noted in 2 cases. Conclusion: SPI remain a difficult diagnosis. The clinico-radiological presentation as well as the treatment vary according to the germ in question. Tuberculosis spondylitis remain frequent in our country. A good etiological investigation is necessary to initiate adequate treatment.

136

P329: Clinical characteristics of 96 patients presenting with hematogenous spinal osteomyelitis - a retrospective study

Eeric Truumees ¹ , Devender Singh ¹ , Jeremiah Alexander ² , Calvin Chandler ³ , Ashley Duncan ¹ , Matthew Geck ¹ , and John Stokes ¹

¹ Spine, Ascension Texas Spine and Scoliosis, Austin, United States

² Orthopedics

³ Spine, The University of Texas at Austin, Austin, United States

Introduction: Most spinal infection in adults occurs in the wake of invasive procedures, wherein flora have been directly inoculated into the spine and its surrounding soft tissues. Hematogenous spinal osteomyelitis, on the other hand, results from bacterial spread from a distant site. Aim: This study aims to detail our series of patients with hematogenous spinal osteomyelitis. Materials and Methods: The medical records of patients presenting to two tertiary care centers with hematogenous spinal osteomyelitis were abstracted using ICD-10 codes M46.20 to M46.59. We collected age, sex, body mass index (BMI), comorbidities, affected spinal region, microbiological details, type and duration of pre and postop antibiotics, length of hospital stay (LOS), reoperation, and mortality. Long-term antibiotics were those in use > 6 months. Results: Ninety-six consecutive patients with hematogenous vertebral osteomyelitis were included. The median age was 59.5 years; 64% were male; median BMI was 27.7. Most infections occurred in the lumbar region (44.2%), followed by the thoracic spine (37.9%), more than two spinal regions (10%) and cervical spine (8.9%). Biopsy was performed in 94.1% of cases and returned positive cultures in 93.4%. Of the cultures taken, MRSA accounted for 9%; MSSA, 26%; Streptococcus species, 12%; other gram-positive bacteria, 23%; gram-negative, 17%; fungal, 2.6%; and 11.5% of cultures returned no growth. Sixty-one patients ultimately underwent surgery to treat their disease. Of the 61-undergoing surgery, 41% underwent secondary surgeries due to a heavy wound burden of necrotic tissue and pus, or the failure of multimodal care including antibiotics and debridement. Of these, 57% of the patients had undergone a trial of antibiotics preoperatively, with a mean course of 37.2 ± 25.7 days. Postoperative antibiotics were prescribed to all patients, with a mean length of 70.2 days. Mean LOS was 17.9 ± 15.3 days. Additionally, 51.6% of the patients were prescribed long-term antibiotic therapy. The overall mortality rate was 3.1%. All three patients underwent surgery. Demographic and clinical characteristics of the deceased patients include a mean age of 64 years, majority male (66.7%), who had major comorbidities such as diabetes, anemia, obstructive lung disease and hypertension. Major cause of death was septic shock. Major post-infection sequelae occurred in 24.5% of patients. Patients suffering sequelae had a mean age of 69.3 years, were mostly male (83%) and carried major comorbidities including diabetes, anemia, hypertension and renal disease. The most common sequelae were persistent infection, sepsis, and abscess. Conclusions: The presence of major comorbidities (diabetes, hypertension, and renal failure) appear to increase the risk of post-infection sequelae and death. Our population included patients hospitalized in a tertiary care center with spinal osteomyelitis. They were therefore more likely to carry concomitant diagnoses such as epidural abscess, resulting in a high rate of surgical intervention. A future study with a larger sample size utilizing logistic regression would be able to identify significant risk factors both for hematogenous infection itself, and for failure of non-operative and initial operative care. In the meanwhile, available data suggests that patients presenting with hematogenous osteomyelitis be followed closely as failure of non-operative management was high.

207

P330: Comparison of outcomes in thoracolumbar fusion wound closure done by spine surgeons versus plastic surgeons in varying levels of vertebral fusion

Jini Jeon ¹ , Aaron Hui ¹ , Henry Hoang ¹ , Dan Berman ¹ , Ananth Eleswarapu ¹ , and Jonathan Krystal ¹

¹ Orthopedics, Montefiore Medical Center, Bronx, United States

Introduction: Plastic surgeons are often involved in closure of complex thoracolumbar fusion surgeries performed by spine surgeons. Indications for plastic surgeon involvement is not standardized. A possible indication that may be used is the number of spinal levels fused. This study aims to further evaluate and compare outcomes for thoracolumbar fusion wound closures performed by spine surgeons versus those done by plastic surgeons across varying levels of total fused vertebrae. Material and Methods: A retrospective cohort analysis of 301 patients who underwent a thoracolumbar fusion at a single institution in the Bronx from 2016-2018 was performed. Demographic, surgical, and post-operative variables were collected. The patients were placed into two cohorts: wound closure done by a spine surgeon (S) and wound closure done by a plastic surgeon (P). Cases were also categorized based on number of vertebrae fused: 1-2 levels, 3-6 levels, and ≥ 7 levels. The primary outcomes were length (days) of postoperative hospital stay, and return to operating room for culture positive infection and debridement. Our secondary outcome outcomes were return to the emergency department (ED) within 90 days. An independent two sample t-test assuming unequal variances was conducted to compare the average length of postoperative hospital stay. A Fisher’s exact test of independence was done to determine if there was a difference in rates of returning to the operating room for culture positive infection and debridement, revision and emergency room within 90 days. Results: Three hundred and one patients were identified and categorized into spine surgeon closure (N = 272), and plastic surgeon closure (N = 29). In the S cohort: N= 186, 73, 13 were categorized into 1-2 levels, 3-6 levels, and ≥ 7 levels fused respectively. In the P cohort: N = 6, 13, and 10 cases were categorized into 1-2 levels, 3-6 levels, and ≥ 7 levels fused respectively. There was no statistically significant difference in mean days of postoperative hospital stay between the S and P cohorts across all levels of fusion. For return to OR for positive culture I&D, there was statistical significance for 1-2 levels and 3-6 levels of fusion. There was no significant statistical different between the two cohorts in return to ED within 90 days of operation for any spinal level fusions. Conclusion: Findings suggest that a plastic surgery wound closure in thoracolumbar fusion does not reduce length of postoperative hospital stay when compared to spine closure across all levels of vertebral fusion. Plastic surgery closure was found to be non-advantageous over spine surgeon closure with higher rates of return to OR due to infection in shorter levels of fusion, which may be explained by patient factors not explored in this study, such as age, BMI, smoking history, and degree of complex anatomy. There was no difference in rates of return to ED within 90 days post-op between the cohorts across all levels. Additional studies may be conducted to further evaluate different factors of complexity that indicate for plastic surgery wound closure versus spine surgeon wound closure, and patient outcomes.

237

P331: Removal of instrumentation is not required to successfully treat post-operative wound infections in most cases

Viral Patel ¹ , Benjamin Mueller ¹ , Amir Mehbod ¹ , Manuel Pinto ¹ , James Schwender ¹ , Timothy Garvey ¹ , John Dawson ¹ , and Joseph Perra ¹

¹ Twin Cities Spine Center, Minneapolis, United States

Introduction: Recommendations for treating surgical site infections (SSI) in instrumented spine cases include both removing the implants and retaining the implants. In either case, successful treatment means eradicating the infection and preventing its recurrence. Retaining the implants may be advantageous because they help maintain stability. We studied the persistence of SSI in relation to retaining or removing spinal implants. Material and Methods: Spine surgery patients who underwent irrigation and debridement (I&D) for a SSI were studied. Persistence (recurrence or non-recurrence) of infection in relation to implant status, fusion status, and patient reported outcomes were analyzed. Results: One hundred thirty five patients were studied. Implants were retained in 64% (87/135) of patients; 7% (6/87) had a persistent infection. Implants were removed in 36% (48/135) of patients; 6% (3/48) had a persistent infection. Thus, we detected no difference between persistence with implants present versus implants removed (p = 1.0). Fifty patients (37%) patients received irrigation and debridement (I&D) and primary wound closure and 85 patients (63%) received I&D and vacuum-assisted closure (VAC) treatment. There was no statistical difference in SSI persistence between primary wound closure and VAC treatment (p = 0.15). Fusion status and persistent infection were unrelated. At minimum one-year follow up, achieving a minimum clinically important difference (MCID) for functional outcome was independent of recurrence or non-recurrence of the infection. Conclusion: Persistent infection was unrelated to the retention or removal of implants. Those with a persistent infection were no more likely to exhibit pseudoarthrosis than those with no persistent infection. All our patients' self-reported functional outcomes were improved at minimum 1-year follow up.

258

P332: Epidemiological and clinical characteristics of patients with spinal tuberculosis at a regional spine center in South-west Nigeria

Taofeek Adeyemi ¹ , Adetunji Toluse ¹ , Mustapha F. Alimi ¹ , Gbolabo Babajide Idowu-Deifa ¹ , and Babatunde A. Osundina ¹

¹ Department of Orthopaedic Surgery and Trauma, National Orthopaedic Hospital Igbobi, Lagos, Nigeria

Background: Although Tuberculosis is one of the world’s oldest disease, it is still a major public health issue in developing countries with profound medical, social and economic impact. The objective of this study was to investigate the epidemiological and clinical characteristics of patients treated for spinal tuberculosis at a regional spine center in South-west Nigeria. Methods: This study was a retrospective observational study. We extracted data from the medical records of all cases of spinal tuberculosis that presented at the hospital between January 2017 and December 2019. Epidemiological, clinical characteristics, imaging findings, laboratory test results and treatment methods were recorded and analyzed. Results: During this three-year period, 171 cases of spinal Tuberculosis were identified. The patients’ mean age was 43 ± 15.7 years with a slight male predominance (56.1%). Axial pain was the main clinical manifestation (81.9%); 51.5% presented with over 6 months of symptoms. Prior history suggestive of pulmonary tuberculosis was seen in 14%. The most common imaging technique was x-ray (94.2%), followed by Magnetic Resonance Imaging (87.1%). Majority of the lesions involved the lumbar spine (50.3%), followed by the thoracolumbar spine (23.4%); with 70.2% having less than 3 vertebral involvement. The Erythrocyte Sedimentation Rate (ESR) was elevated in 79% of cases at diagnosis. Varying degrees of neurological impairment were seen in 92 (53.8%) patients and 17% presented with back deformity. All had combination anti-tuberculosis chemotherapy and a minimum follow up of 12 months. Majority of patients (91.2%) were managed non-operatively. Neurological improvement was seen in 59.8% of those with neurological deficit. No mortality was recorded. Conclusions: Spinal tuberculosis affected the productive age groups most. Late presentation and neurological impairment was seen in majority of cases. Persistence of neurological impairment is a concern. There is a need for strategic intervention to encourage early presentation and appropriate management to reduce morbidity.

377

P334: Significance of cutibacterium acnes in intraoperative cultures during spinal instrumentation

Geno Tai ^1,2 , Gina Suh ² , Brian Lahr ³ , Paul Huddleston ⁴ , and Aaron Tande ²

¹ Infectious Diseases and International Medicine, University of Minnesota, Minneapolis, United States

² Infectious Diseases

³ Quantitative Health Sciences

⁴ Orthopedic Surgery, Mayo Clinic, Rochester, United States

Introduction: Cutibacterium acnesis a known pathogen in spinal hardware infections. The ideal management for these cases is unknown, and there is a lack of data on treatment outcomes. We described the outcomes of cases with actual infections (AI) and clinically insignificant (CI) cultures. Material and Methods: We performed a retrospective study of patients aged 18 years or older who underwent spinal fusion surgery with instrumentation and whose intraoperative tissue culture specimens were positive for C. acnesbetween January 1, 2011, and December 31, 2020. We categorized the culture results as actual infection (AI) or clinically insignificant (CI) based on a set criterion.

Diagnostic Criteria for Actual Infection:

1. C. acnes was isolated from  two intraoperative specimens obtained during primary or revision instrumentation.

2.C. acnes was isolated from  one  intraoperative specimen,  PLUS

a. Intraoperative purulence or secondary wound dehiscence with the implant visible

b. Radiographic evidence of inflammation on x-ray, computed tomography, magnetic resonance imaging, or radiolabeled scan with gallium or technetium

c. Systemic signs of inflammation such as fever (> 38 °C) without other recognized cause

d. Histopathology showing acute inflammation

We excluded cases of polymicrobial infection with virulent organisms (e.g.,Staphylococcus aureus, Gram-negative bacteria) or two non-virulent organisms (e.g., Coagulase-negative staphylococci, anaerobes) to have homogeneity of cases.

We definedtreatment as receiving more than two weeks of systemic antibiotics. The outcome of interest was an adverse event defined as a post-operative diagnosis of spinal hardware infection either with C. acnesor other microorganism/s or unexpected surgery secondary to infection.

Results: There were 91 patients who had at least one intraoperative culture positive for C. acnes during spinal instrumentation. The median age was 59 years old (IQR 43-70). Monomicrobial infections represented 73.6% (n = 67). Majority (87.9%, n = 80) were isolated during revision surgeries (e.g., debridement, exchange/ addition/ removal of hardware). There were 63 AI and 28 CI. Among those with AI, 49 (77.8%) were treated for a median duration of 344 days (IQR 97-531). There were five adverse outcomes during 68.6 cumulative patient-years of follow-up, with an annual rate of 7.3% (95% CI 2.4% - 17.0%). The median time to event was 12.2 months (range, 1.9-14.6). In the 14 untreated patients with AI, two adverse outcomes occurred over 23.0 cumulative patient-years (annual rate 8.7%, 95% CI 1.1% - 31.4%). Among those with CI cultures (n = 28), half were treated with antibiotics. No adverse outcome occurred among all patients with CI cultures. Conclusion: We described the outcomes of cases with positive C. acnesduring spinal instrumentation. The rates of adverse outcomes for treated and untreated AI are almost similar. We found that some AI cases were managed with hardware removal alone and had favorable outcomes. In some instances, treating AI with oral antibiotics alone is appropriate. There is no apparent advantage of treating CI cultures. Our study was limited by the small number of events; thus, no formal comparisons were made. Prospective studies are needed to evaluate different diagnostic criteria to guide treatment strategies.

501

P335: Pre-operative epidural steroid injections do not increase the risk of post-operative infection in patients undergoing lumbar decompression or fusion: a systematic review and meta-analysis

Yunsoo Lee ¹ , Tariq Issa ¹ , Mark Lambrechts ¹ , Arun Kanhere ¹ , Skylar Nahi ¹ , Parker Brush ¹ , Jeremy Heard ¹ , Delano Trenchfield ¹ , Alan Hilibrand ¹ , Christopher Kepler ¹ , Gregory Schroeder ¹ , Alexander Vaccaro ¹ , and Jose Canseco ¹

¹ Division of Spine Surgery, Rothman Orthopaedic Institute, Philadelphia, United States

Introduction: Epidural corticosteroid injections (ESI) are one of the mainstays of early nonoperative treatment for patients with lumbar spine pathology. While many patients are responsive to nonoperative treatment, a small number may progress to surgical management such as lumbar decompression or fusion. Recent literature evaluating the risk of infection following ESI after elective orthopedic surgery has produced conflicting evidence, which has led to growing debate around the timing of pre-operative ESI. Our primary objective was to review the literature and provide a larger meta-analysis analyzing the temporal effects of steroid injections on the risk of infection following lumbar spine surgery. Material and Methods: We conducted a query of the PubMed, Embase, and Scopus databases from inception until April 1, 2022 for studies evaluating the risk of infection in the setting of prior spinal steroid injections in patients undergoing lumbar spine decompression or fusion. Three meta-analyses were conducted, (1) comparing ESI within 30-days to control, (2) comparing ESI within 30-days to ESI between 1-3 months pre-operatively, and (3) comparing any history of ESI to control. Tests of proportions were utilized for all comparisons between groups. Study heterogeneity was assessed via forest plots, and publication bias was assessed via funnel plots and qualitative assessment with the Newcastle-Ottawa Scale. Results: Nine total studies were included, five of which demonstrated a significant association between pre-operative ESI and post-operative infection, while four studies found no statistical significance at any evaluated time point. Most data originated from large databases, but three studies evaluated institutional data. Comparison of weighted means demonstrated no significant difference in infection rates between the 30-day ESI group and control group (2.67% vs 1.69%, p = 0.144), 30-day ESI group and the > 30-day ESI group (2.34% vs 1.66%, p = 0.1655), or total ESI group and the control group (1.99% vs. 1.70%, p = 0.544). Heterogeneity was low for all comparisons following sensitivity analyses (I² = 0% in the first two analyses and I² = 32% in the third comparison). Conclusion: Our meta-analysis suggests that current evidence does not implicate pre-operative ESI on an increase in post-operative infection rates following lumbar fusion or decompression. Operative treatment should not be delayed due to pre-operative infection rates due to current evidence. There remains a paucity of high-quality data in the literature evaluating the impact of pre-operative ESI on post-operative infection rates.

532

P336: Adjacent spondylodiscitis following instrumented spinal fusion - How can we manage this complication? Case report

Sara Machado Neves ¹ , Luis Castelo ¹ , Rita Sousa ¹ , Diogo Sousa ¹ , João Reis ¹ , and André Guimarães ¹

¹ Ortopedia e Traumatologia, Centro Hospitalar de Trás-os-Montes e Alto Douro, Vila Real, Portugal

Introduction: To date there are only a few cases of spondylodiscitis adjacent to the instrumentation level of spinal fusion reported on literature. Responsible for causing important morbidity and causing serious long-term sequelae, this complication offers a intricated challenge on how to manage patients and how to stratify the best therapeutic strategy. Despite this there are some risk factors already identified like obesity, alcoholism, smoking, diabetes and wound infection site. Study design: Case Report Objective: Report a case of management of spondylodiscitis on the adjacent level of instrumentation that occurred 6 months after spinal fusion. Methods: The authors describe a case of a morbidly obese 49-year-old female patient who underwent intersomatic transforaminal arthrodesis L3L4 and L4L5 with unilateral facetectomies. She was priority admitted to surgery because of persistent lumbosciatalgia with progressive neurological defects already installed in the past 11 months (drop foot on the right). On the immediate post-operative time the patient developed wound surgical dehiscence that resolved with negative-pressure wound therapy. Along this period, she never manifested clinic of infection. At 6 months after surgery, she presented with sudden onset of low back pain without neurological commitment or fever associated with peri-inflammatory signals on top of the surgical site with active drainage that motivated hospitalization for study and treatment. Analytically she had elevation of inflammatory markers with negative blood cultures and imagiological signs of spondylodiscitis in L2 and L3. She was hospitalized with empirical antibiotic therapy with ceftriaxone and vancomycin for 4 weeks combined with negative-pressure wound therapy with good response and clinical and analytical improvement. Results: After 3 months of conservative treatment, the patient remains clinically stable, demonstrating on TC a collapse of the L2’s lower platform with secondary scoliosis that motivates intention to prolong the instrumentation as soon as the infection has stabilized. Discussion: Management of these cases require appropriate medical conservative treatment which may be insufficient to control the infection and often there’s a need for surgical re-intervention whose purpose is debridement and surgical cleaning, obtaining bacteriological samples, as well as eventual decompression and stabilization in order to control the infection spread and provide spinal stability. Conclusion: The therapeutic and prognostic success resides, above all, in a timely diagnosis and intervention and in the periodic monitoring of the effectiveness of the instituted treatment.

Keywords: Adjacent Spondylodiscitis; Spinal Fusion; Conservative Treatment;

604

P337: Brace treatment results of thoracolumbar vertebral osteomyelitis

Sofiane Masmoudi ¹ , Saiffedine Mahjoubi ¹ , Haithem Eleuch ¹ , Amine Soussou ¹ , Khaled Zitouna ¹ , and Maher Barsaoui ¹

¹ Orthopedic Surgery, Rabta Hospital, Tunis, Tunisia

Introduction: Vertebral osteomyelitis is an intervertebral disc and vertebral bodies infection, causing anterior vertebral compression and spinal deformity thus influencing the spino-pelvic sagittal balance. No therapeutic modalities were studied and no results were provided according to the type of treatment, especially brace immobilization. We established an epidemiological and radiological description of thoracolumbar vertebral osteomyelitis and presented the results of the brace treatment of these lesions. Material and Methods: We reported a descriptive retrospective study of 31 patients treated with thoracolumbar braces for vertebral osteomyelitis. Medical observations and MRIs were used to collect the data. The spinal parameters of the global curvatures and segmental were measured pre and post immobilization. We calculated the evolution of these parameters. Results: Average age was 54 years old. Sex ratio was 1.07. The thoracic spine was the most affected (48%). The Koch's bacillus was the most identified germ (61%). Measurements of initial radiological parameters showed that the averages of TCVA, CV, AR, LL and CT were respectively 25%, 11°, 18°, -42° and 48°. The evolutions averages of TCVA, CV, AR, LL and CT were 7.77%; 0.29°; 3.13°; -1° and 2.71°. Brucella melitensis was the least destructive germ (p = 0.016). The initial vertebral compression increased from caudal to cranial spine level (p = 0.021) and that lumbar lordosis progression was better for patients with a weight less than 70 Kg (p = 0.013). Conclusion: We concluded that brace immobilization for vertebral osteomyelitis was better in lumbar than thoracic spine and for patients with a weight less than 70 kg.

679

P338: Evaluation of percutaneous pedicle screw fixation in patient with pyogenic spondylitis of the thoracolumbar spine

Katsunori Fukutake ¹ , Akihito Wada ¹ , Kazumasa Nakamura ¹ , Ukyo Gen ¹ , Shuhei Matsuoka ¹ , Keiji Hasegawa ¹ , and Hiroshi Takahashi ¹

¹ Orthopedics, Toho University, Ota-ku, Tokyo, Japan

Introduction: Basic principle for the treatment of PS is conservative care, but various complications have been observed in many conservative cases due to long-term bed rest, poor pain control, and exacerbation of infection. Thus, treatment methods have been gradually reformed and surgical intervention have been often required when conservative treatment may fail. Recent study indicates that percutaneous pedicle screw (PPS) fixation is a feasible and effective technique to achieve immediate pain release, and reduce morbidity due to long-term bed rest, poor pain control.In this study, a comparative study was conducted between the conservative group and the PPS group in cases showed initial treatment resistance, to evaluate the impact of PPS fixation in patients with PS resisted to initial treatment. Material and Methods: We retrospectively reviewed 54 consecutive patients who underwent treatment in our hospital for PS during 2005-2018 and followed up for at least 12 months. Of those we excluded cases showed effectiveness to initial treatment (it was defined fever relief and C-reactive protein (CRP) inversion in 3 weeks of intravenous antibiotic) so that this study is a retrospective study in cases showed initial treatment resistance. Finally, this study included 29 cases. To evaluate the impact of PPS fixation, these cases divided into two groups, the conservative group: 17 cases, and the PPS group: 12 cases. Since 2010, PPS fixation has been relatively selected, but cases with poor general condition have selected conservative treatment. Results: We investigated the period from first visit to our hospital to fever relief, CRP inversion, ambulation, and discharge or transfer. There is no statistically significant difference in fever relief (p = 0.051) and CRP inversion (p = 0.208). The period to ambulation and discharge or transfer was significantly shorter in group P (p = 0.020, p = 0.031). The outcomes were determined at 12 months after the start of treatment, discharge, transfer, and death. In the P-group, 1 case died of intestinal obstruction and 1-year survival rate was 92%. In the C-group, 5cases died of infarction-sepsis (3cases), acute myocardial infarction (1case), and unknown(1case). 1-year survival rate was 71%. The P-group was relatively high 1-year survival rate, but there is no statistically significant difference (p = 0.354) between two groups. The rate of Discharge to home and care facility is 58% in P-group, and 47% in C-group. And the rate of Transfer is 33% in P-group, and 35% in C-group. Conclusion: Present study shows that PPS fixation was effective to achieve shorten the period to ambulation and discharge or transfer. But it was not effective to infection control, such as fever relief and CRP inversion. This result suggests that PPS fixation should be aggressively administered to patients who can expect pain relief and early ambulation by PPS fixation in the patient of PS showed resistance to initial treatment.

776

P339: Pre-XDR spinal tuberculosis and 360° approach in two surgical stages. Case report

Fernando Alvarado Gómez ¹ , Nahala Aborashed-Amador ¹ , Maria Garcia-Rueda ¹ , Alexander Tristancho ¹ , Maria Camila Giraldo Bernal ¹ , Freddi Soto-Guzmán ¹ , Frank Mario Herrera-Mendez ¹ , and Carlos Montero-Silva ¹

¹ Instituto Roosevelt, Bogota, Colombia

Introduction: Multidrug-resistance (MDR) is considered to be one of the main obstacles to eliminating spinal tuberculosis (STB). Up to 2,040 cases of STB per year have been reported, mainly in the adult population. Ineffective treatment leads to severe kyphotic deformities with vertebral body collapse and neurological deficit due to spinal cord compression or section. Material and Methods: An 8 year-old female patient from an indigenous community with a 6-month history of a granulomatous lesion with a fistula between the 7th and 8th left ribs, associated with decreased strength in the lower limbs, loss of sphincter control, and spinal deformity. The bone biopsy showed massive necrosis due to a granulomatous process. PCR testing of bronchoalveolar lavage, soft tissue, and bone (vertebral) was positive for Pre-XDR Mycobacterium tuberculosis. The case was treated with Moxifloxacin, Cycloserine, Ethionamide, Pyrazinamide, Ethambutol, and Isoniazid. Results: A 360° approach was necessary due to the extent of the deformity and the need for bone autograft. Moreover, anterior fixation helps avoid proximal kyphosis, likely in this patient because of poor bone quality and the potential for recurrent disease. The patient presented kyphotic deformity at the level of T7-T8 secondary to tuberculous disease. A 360° approach was necessary for the resection of vertebral body and intervertebral discs of the thoracic spine plus spinal canal decompression and placement of a spacer with antibiotic in T8 through the anterior approach. A posterior approach was then performed for drainage, curettage and collection sequestrectomy with fistula. Conclusion: Spinal tuberculosis in the pediatric population is exotic even in regions with a high incidence of tuberculosis. There is no consensus regarding the best surgical approach in patients with massive involvement. The 360° approach allows better surgical control of the infectious focus, facilitates reconstruction, corrects proximal kyphosis and ensures a more stable fixation.

792

P340: Risk factor for surgical site infection with spinal instrumentation surgery

Shinji Tanishima ¹ , Tokumitsu Mihara ¹ , Chikako Takeda ¹ , Masaki Yoshida ¹ , Satoshi Fujiwara ¹ , and Hideki Nagashima ¹

¹ Division of Orthopedic Surgery, Department of Sensory and Motor Organs, School of Medicine, Faculty of Medicine, Tottori University, Yonago, Japan

Introduction: Surgical site infection (SSI) after spinal instrumentation surgery is a serious complication, but its occurrence is difficult to eliminate. This study aimed to examine the risk factors for SSI at our institution. Subjects and Methods: A total of 483 patients aged 18 years or older who underwent spinal instrumentation surgery at our hospital between January 2016 and March 2021 and who were available for follow-up for at least 30 days were included in the study. The mean age of the patients was 68.9 ± 14.3 years. Patient-related factors (age, gender, malignant disease, diabetes, skin disease, hemodialysis, smoking, steroid and immunosuppressive drug use, body mass index, albumin, total protein, C-reactive protein (CRP), American Society of Anesthesiologists classification, and nasal culture) and surgery (the same re-operation, scheduled/emergency surgery, dural injury, vancomycin spray, operative time, and blood loss) were analyzed. Statistical analysis was performed with a univariate analysis of the infected and uninfected groups and multivariate logistic analysis of factors that showed an associated trend (p < 0.2). Results: Of the 483 patients, 11 of (2.3%) were infected, with nine having a deep infection and two having a superficial infection. In univariate analysis, the patient factors were albumin level (4.1 ± 0.6: 3.7 ± 0.8 mg/dl) and CRP level (0.74 ± 1.8 mg/dl: 3.2 ± 5.3 mg/dl) in the uninfected group and emergency surgery rate (27.8%: 63.6%) in the infected group. In logistic analysis, emergency surgery was identified as a risk factor for SSI (odds ratio: 4.6, 95% confidence interval 1.3-15.9, p = 0.016). Although this study was not statistical, once SSIs occurred, they tended to occur sequentially within 3 months. Currently, SSI countermeasures are strictly implemented at all facilities, and our hospital is also taking measures to prevent SSI. As a result, infectious hosts, such as diabetes mellitus and immunosuppressive drugs, were not risk factors. However, emergency surgery was a risk factor, but this was thought to be due to the lack of sufficient infection control measures in emergency situations. Additionally, once SSIs occurred, they occurred one after another. This suggests that SSIs occur when some problems occur in the perioperative management. Conclusion: Although infection rates are not high in spinal instrumentation surgery, infection rates are increasing in emergency surgery, and more careful infection control measures are needed.

796

P341: Retrospective case series review of decompression versus decompression and fusion for vertebral osteomyelitis and discitis

Zachary Crawford ¹ , Jorge Figueras ² , Cameron Thomson ³ , and Anthony Guanciale ¹

¹ University of Cincinnati College of Medicine, Orthopaedic Surgery, Cincinnati, United States

² Indiana University, Orthopaedic Surgery, Indianapolis, United States

³ Brown University, Orthopaedic Surgery, Providence, United States

Background Context: Spine infection including epidural abscess, vertebral osteomyelitis, and diskitis is a major cause of morbidity in the United States with potential for significant complications. Previous literature has shown delayed diagnosis can increase mortality and patients treated with decompression alone have higher complications including reoperation rates. Purpose: The purpose of this study is to further evaluate the outcomes of spine infection comparing decompression versus decompression and fusion. Study Design / Setting: This retrospective chart review was completed on patients presenting to a single level 1, tertiary medical center between January 2010 and June 2021 for osteomyelitis, diskitis, or epidural abscess. Patients were treated by orthopaedic and neurosurgical trained spine surgeons. Patient Sample: Patients were included for any osteomyelitis, diskitis, or epidural abscess within the study time period. Patients were excluded if they had isolated paravertebral abscess or soft tissue infection that did not also include osteomyelitis, diskitis, or epidural abscess. Outcome Measures: Outcome measures included length of antibiotic regimen, discharge location, ED admissions, complications, and reoperations. Methods: Electronic medical record chart review was completed by searching for associated appropriate ICD-9 or ICD-10 codes and CPT codes for orthopaedic and neurosurgery spine attendings during study period. Demographic information including age, sex, insurance carrier, and co-morbidities including history of intravenous drug use, tobacco use, and Charleston Comorbidity Index were collected on all patients. Additional information including levels and location of epidural abscess, deformity, instability, serum infectious markers, and culture data were also collected. Results: There were a total of 163 patients identified and 111 patients included for study review. There were 58 patients in decompression alone (60% male, n = 35) and 53 in decompression and fusion (60% male, n = 32). The average age was 54 years and 53 years respectively in each group (p = 0.988) and there was no statistical difference in rates of osteomyelitis, diskitis, and epidural abscess in each group. Additionally, there was no statistical difference in instability, deformity, and Charleston Comorbidity Index in each group. Patients in decompression alone averaged 4.2 spine levels of epidural abscess while those in decompression and fusion averaged 2.8 levels (p = 0.008). There was no difference in erythrocyte sedimentation rate, c-reactive protein, or white blood cell count levels between groups, however patients with decompression alone were more likely to have concomitant bacteremia (n = 48, 82.7% compared to n = 28, 52.8% in decompression and fusion, p = 0.00018). There were 10 reoperations (17%) in decompression alone with 4 to complete fusion, while decompression and fusion had 13 reoperations (24.5%) with 3 to extend or revise previous fusion. Conclusions: Patients with spine infection including osteomyelitis, diskitis, and epidural abscess have a high morbidity with numerus complications. In this retrospective, single center study of spine we found there was no significant difference in outcomes between decompression versus decompression and fusion for spine infection. Patients who underwent decompression alone were more likely to have higher burden of infection and concomitant bacteremia compared to those with decompression and fusion.

841

P342: Preoperative epidural steroid injection does not increase infection risk following posterior cervical surgery

Tara Shelby ¹ , Emily Mills ¹ , Hyunwoo Kang ^1,2 , Andy Ton ¹ , Jeffrey C. Wang ¹ , Raymond Hah ¹ , and Ram Alluri ¹

¹ Orthopaedic Surgery, Keck School of Medicine of USC, Los Angeles, United States

² Orthopaedic Surgery, Massachusetts General Hospital, Harvard Medical School, Boston, United States

Introduction: ESI is a helpful tool in alleviating pain and is often used as a diagnostic tool prior to cervical surgery. However, a recent small-scale study found that ESI prior to cervical fusion was associated with an increased risk of postoperative infection. The purpose of this study was to characterize infection risk of preoperative epidural steroid injection (ESI) in patients undergoing posterior cervical surgery. Material and Methods: Patients from 2010-2020 with cervical myelopathy, spondylosis, and radiculopathy who underwent posterior cervical procedure including laminectomy, laminoforaminotomy, fusion, or laminoplasty were queried from the PearlDiver database. Patients who underwent revision or fusion above C2 or who had a diagnosis of neoplasm, trauma, or pre-existing infection were excluded. Patients were then divided based on whether they received an ESI within 30 days prior to the procedure. The two groups were subsequently matched based on age, gender, and preoperative comorbidities. A chi-square test was used to calculate the risk of developing a postoperative infection within 90 days of surgery. Results: Based on our inclusion and exclusion criteria, 82,907 patients were identified, including 991 who received a preoperative ESI and 81,916 who did not. Matching resulted in 975 in the injected group and 1,929 in the control group. There was no significant difference in postoperative infection rate in those who received an ESI within 30 days preoperatively and those who did not (3.28% versus 3.78%, OR = 0.86, 95% CI: 0.57-1.32, p = 0.494). Conclusion: Given the growing use of steroid injections in spinal surgery, it is important to determine the associated risk of surgical site infection. In contrast to previous literature, the present study has found no association between preoperative ESI within 30 days prior to surgery and postoperative infection in patients undergoing posterior cervical surgery after matching for an extensive list of comorbidities and a comprehensive set of exclusion criteria. Further multicenter prospective studies are indicated to more fully characterize infection risk post-ESI.

890

P343: Cervical osteomyelitis: a rare infection

Tiago Canas ¹ , Emanuel Homem ¹ , Ricardo Simoes ¹ , João Cruz ¹ , and Luis Soares ¹

¹ Ortopedia, Hospital Divino Espirito Santo, Ponta Delgada, Portugal

Introduction: Vertebral osteomyelitis constitutes 1-7% of bone infections, with the cervical area being affected in only 3-10% of cases and is related to diabetes, and both recreational and prescription intravenous drug abuse. Cervical spondylodiscitis is thought to carry a significant risk for rapid neurologic deterioration with a poor response to nonsurgical management. It is described most commonly at one level (85%), and less often at two contiguous levels. Given the overall low quality of the available literature, it remains difficult to determine the optimal timing of surgical management. The authors present a case of multilevel cervical spodylodiscitis, characterizing neurologic presentation and postoperative neurologic outcome. Material and Methods: A 51-year-old male patient with a history of intravenous drug abuse, presented at the emergency department (ER) with an one-month worsening cervical pain which motivated 3 prior visits to the ER. With no past history of trauma, pain, classified as VAS 9/10, relieved with the conservative management (NSAID and analgesic drugs) to tolerable levels (VAS 2/10). Physical exam revealed an incomplete neurological deficit, around C6 level, classified as ASIA B. Cervical CT and MRI documented an infectious process of C6 and C7 vertebral bodies conditioning retroshift of the posterior walls and consequent spinal cord compression. Bloodworks demonstrated a leukocytosis of 17.36 x 10 3 /uL and increased CPR of 17.9 mg/dL. Blood cultures identified a methicillin-sensitive Staphylococcus aureus. The patient was submitted to urgent surgery: corporectomy of C6 and C7 and anterior arthrodesis (C5-T1) with autologous tricortical graft and locked plate; without complications. Results: The postoperative in-hospital stay went uneventful (50 days) and the patient recovered neurologically (classified as ASIA D), which was maintained throughout follow-up (12 months). Intra-operative biopsies isolated the same causative agent (MSSA). Intravenous antibiotic therapy with flucloxacilin was maintained for 6 weeks, followed by 6 weeks of oral form. PCR and ESR normalized around the 4th week of follow-up and at 6 months arthrodesis was confirmed with cervical CT. Conclusion: Cervical osteomyelitis normally presents with nonspecific clinical picture. For that reason an interval of around 3-4 months between the onset of symptoms and diagnosis is generally verified. The most frequent agent is Staphylococcus aureus and neurological injury surgery is an indication for surgery. The authors describe a classical case of cervical osteomyelitis submitted to multilevel anterior arthrodesis with good functional, clinical and imagiological results.

1071

P344: Decompression only versus fusion in octogenarians with spinal epidural abscesses: early complications, clinical and radiological outcome with 2 years follow-up

Pavlina Lenga ¹ , Gelo Guelec ¹ , Karl L. Kiening ¹ , Andreas W. Unterberg ¹ , and Basem Ishak ¹

¹ Neurosurgery, Heidelberg University Hospital, Heidelberg, Germany

Introduction: Despite the global trend toward increased life expectancy due to remarkable improvements in the quality of health care, the treatment of pyogenic vertebral osteomyelitis (PVO) with a spinal epidural abscess (SEA) remains challenging, especially in patients older than 80 years. The aim of this study was to assess, exclusively in octogenarians, the prevalence of PVO with SEA and clinical outcomes after surgical treatment, comparing decompression only with decompression and instrumentation. Material and Methods: A retrospective review of electronic medical records at a single institution was conducted between September 2005 and December 2021. Patient demographics, surgical characteristics, complications, hospital course, and 90-day mortality were collected. Comorbidities were assessed using the age-adjusted Charlson comorbidity index (CCI). Results: Over a 16-year period, 35 patients aged ≥ 80 years with PVO and SEA were identified. Eighteen patients underwent surgical decompression only (“decompression group”), and 17 underwent surgical decompression with instrumentation (“instrumentation group”). Both groups had a CCI > 6 (8.9, SD 2.1 vs. 9.6, SD 2.7, respectively; p = 0.065), indicating severe comorbidities. Patients from the instrumentation group had a significantly longer hospitalization stay, but no ICU stay. In-hospital and 90-days mortality rates were similar in both groups (instrumentation: in-hospital = 5.6%; 90-days mortality = 23.5% vs. decompression: 11.6%; 5.6%; p > 0.05. The mean follow-up was 26.6 months (SD 12.4), and no further surgeries were performed. Irrespective of treatment, the levels of infection and neurological status were improved in both groups at discharge. At second stage analysis significant improvements in the blood infection parameters and the neurological status were detected solely in the decompression group. Conclusion: Patients older than 80 years with PVO and SEA have a high risk of adverse events after surgical procedures. Surgical decompression only might contribute to earlier clinical recovery in elderly patients. Additionally, in terms of morbidity and 90-day mortality, the instrumentation group had poorer outcomes, and this is why the choice of a surgical approach should be thoroughly discussed with the patients and carefully weighed.

1103

P345: Comparative analysis of mechanical complications from structural allograft and titanium cage used for anterior support of the spine in vertebral tuberculosis

Alderico Girão Campos de Barros ¹ , Pedro Cardoso Afonso ¹ , Igor Ebert Cechin ¹ , and Luis Eduardo Carelli Texeira da Silva ¹

¹ Instituto Nacional de Traumatologia e Ortopedia Jammil Haddad (INTO), ARCOL, Rio de Janeiro, Brazil

Introduction: To compare the mechanical complications between patients who were submitted to vertebral body replacement using either structural allograft (SA) or titanium cage (TC) in the management of thoracic and lumbar tuberculosis. Material and Methods: A longitudinal study, based on retrospective evaluation of medical records of patients admitted through 4^th tier public health system between November 2012 and July 2021, in consecutive convenience sampling, who were operated by the same surgical team. All patients with a confirmed histopathological diagnosis of vertebral tuberculosis who underwent through vertebrectomy surgery targeting decompression, debridement and deformity correction were included in the sample. The vertebral bodies were replaced using either SA or TC containing autologous graft, followed by posterior arthrodesis of at least two levels above and two levels below the structural support using pedicle screws. Results: Twenty-two cases of vertebral tuberculosis surgically treated with vertebral body replacement were selected, of which 10 (45.5%) were male patients and 12 (54.5%) were female. Titanium cages containing autografts were used in 17 patients (group A), while the other 5 patients (group B) received structural allograft from tissue banks. The median ages ware 32.1 in group A (IQ 8.78 - 58.65), and 5.2 in group B (IQ 3.89 - 11.19). The average postoperative follow-up period was of 52.7 months. There was no statistical difference in the number of resected vertebrae (p = 0.05), instrumented levels (p = 1.0) or angular correction in the coronal and sagittal planes as per Cobb method. Until the last postoperative follow-up, there were no cases of SA or TC subsidence, breakage or displacement. Four cases of broken metal rods and one case of proximal junctional failure were found in group A, as well as three cases of surgical wound infection, which progressed well after debridement and antibiotic therapy. Conclusion: Both Structural allograft and titanium cages filled with autologous bone applied for anterior spine support and vertebral body replacement in tuberculosis treatment showed similar results in postoperative correction, as well as similar postoperative mechanical complication rates. Future studies with larger samples and follow-up period are necessary to assess metal rod breakage rates.

1113

P346: Comparison of conservative and surgical treatment of spinal tuberculosis at a tertiary care hospital in Bangkalan City, East Java, Indonesia

Adhi Prayoga Ida Bagus ¹ and Dini Sri Damayanti ²

¹ Orthopaedic, Bangkalan General Hospital, Bangkalan, Indonesia

² Faculty of Medicine, Islamic University of Malang, Malang, Indonesia

Introduction: WHO estimated that there were 845,000 cases of TB in 2018, with 93,000 deaths and Indonesia has the 3rd highest burden of TB in the world. While early diagnosis by thorough history taking, physical and radiological examination is mandatory, the interpretation to determine between conservative or operative treatment is debatable and not consistent. Material and Methods: Twenty-seven patients with clinical and radiological representation of spinal tuberculosis during the period of July 2018 to July 2022 were enrolled in the study. Patients with any age and both sexes were included as study population. Twenty-four patients were treated surgically due to bone collapse with abscess and neurological problems. Three patients with mild symptoms and minimal abscess were treated conservative. Four drug regimen of antituberculous therapy (ATT) were administrated to all of the patients for 12 months and all patients were followed up till the end of the treatment. The outcome of the treatments were recorded. Results: All patients (M-13/ F-14) had back pain not responding to analgesics and physiotherapy while few had constitutional symptoms. Localized tenderness and paravertebral muscle spasm was present all of the cases (100%). Muscle weakness and paresthesia were reported initially in 75% cases. Following the surgical therapy, 22 patient showed neurological improvement (M-11/ F-11) and 2 patient (M-1/ F-1) showed no neurological improvement. All the patients which was treated conservatively showed good clinical outcome, and marked abscess resorption. Conclusion: The results of this study evidently show that good results can be obtained by meticulously applied and supervised nonsurgical treatment in spinal tuberculosis. The availability of modern spinal instrumentation nowadays leads to increase the tendency of surgical treatment, but their indication should be bordered unless accompanied by complications such as neurological deficits, kyphosis and abscess. Despite of decades of research and public education campaigns aimed at decreasing patient morbidity, it is common that the treatment delay were associated with poor clinical outcome.

Spinal tuberculosis; surgical treatment; conservative treatment.

1188

P347: Vacuum assisted closure - A panacea in postoperative spinal infections

Shanmuganathan Rajasekaran ¹ , Sri Vijay Anand KS ¹ , Ashish Naik ¹ , Chandhan Murugan ¹ , Rishi Kanna ¹ , and Ajoy P Shetty ¹

¹ Dept. of Spine Surgery, Ganga Hospital, Coimbatore, India

Background: Surgical site infections (SSI) following spinal surgery are potential detrimental complications that increase hospitalization and expenses, cause significant morbidity and adversely affect the outcomes. Radical wound debridement, irrigation, and intravenous antibiotics are the conventional treatments for postoperative deep surgical site infection. Despite the best efforts, infections can persist. Our study aims to review the efficacy of the wound vacuum-assisted closure (VAC) system in treating deep surgical site infection after spine surgery with instrumentation and exposed dura. Material and Methods: We retrospectively reviewed 31 patients who underwent vacuum-assisted closure for postoperative spinal infections following spinal instrumentation between 2016-2020. The patient’s demographic details and biochemical parameters were noted from the hospital information system, and imaging was analysed by PACS. Other pertinent information included bacterial culture reports and antibiotic sensitivity patterns, duration of VAC application, number of cycles of VAC application before final wound closure, and infection recurrence. Results: There were 17 females and 14 males in the study population. There were 21 lumbar spine surgeries and five thoracic and thoracolumbar spine surgeries. Following wound debridement, VAC was applied to all patients. A mean of 2.5 cycles of VAC application, each lasting 5-9 days, was applied before wound closure. Twenty-seven had positive bacterial cultures, and the rest were culture-negative. Klebsiella and Pseudomonas were the most prevalent organisms. CSF leak through the VAC was managed in two patients who had dural repair and subsequent infection, by lowering the suction pressure of the VAC and switching to cyclical mode. One patient died due to an unrelated cause, and one patient with chronic viral hepatitis had an increased blood loss following VAC. All the patients had good healing of wounds with a minimum follow-up of 12 months with no recurrence of infections. All patients except one had retained the implants. Conclusion: The VAC system is a valuable tool in managing postoperative spinal infections. It allows for the retention of the instrumentation and eradication of infection. It does not increase the chances of CSF leak and is safe, reliable, and easy to use.

1204

P348: Cervical spine tuberculosis; outcome after one stage surgical decompression and fixation with unique standalone cage

Haseeb Hussain ¹

¹ Orthopedics, Ghurki Trust Teaching Hospital, Lahore, Pakistan

Objective: The main objective of this study was to determine the outcome after one stage anterior debridement, bone grafting and stabilization with standalone titanium cage in a 3rd world country. Methodology: This prospective study was conducted at Department of spine surgery, Ghurki Hospital, Pakistan from Jan 2008 to Dec 2017.All patients with cervical spine tuberculosis of either gender and any age were included in the study. All the patients underwent one stage anterior debridement and stabilization with standalone titanium cage filled with autologous iliac bone graft. Outcome measured included neck pain using VAS, Frankel scale, bony fusion, Cobb angle of cervical kyphosis and cost of implant. SPSS 17.0 was used for data analysis. Results: Total 98 patients (50 males/48 females) of mean age 42.12 ± 13.778. The mean pre operative VAS scoring was 7.99 ± 1.744 & at last follow up, it was 1.60 ± 1.578. The kyphotic deformity pre operatively was 19.15 ±15.068 & post operatively it was -4.81 ± 6.567. Post operative FRANKEL Scale was significantly improved (p < 0.005). The cost of implant remained the same in all patients US $ 30-50 and bony fusion in all patients. Conclusion: One-stage anterior debridement, autologous bone grafting, and stabilization with titanium Standalone cage can effectively remove debris, decompress the cord, reduce pain & correct kyphosis in patients with cervical tuberculosis. The implant is cost effective with excellent stability and should be considered in third world countries.

Keywords: Anterior decompression, Standalone Cage, Tuberculosis, Cervical Spine

1210

P349: Loss of kyphotic deformity after 3 and 5 years. Follow-up in caries spine patients underwent anterior decompression and locally made cage with autologous bone graft

Ammar Dogar ¹ , Ahsan Atta ¹ , and Haseeb Hussain ¹

¹ Department of Orthopaedics And Spine, Ghurki Trust Teaching Hospital, Lahore, Pakistan

Background: Spinal deformity and paraplegia/quadriplegia are the most common complications of tuberculosis (TB) of spine. TB of dorsal spine almost always produces kyphosis while cervical and lumbar spine shows reversal of lordosis to begin with followed by kyphosis. kyphosis continues to increase in adults when patients are treated non operatively or by surgical decompression. In children, kyphosis continues to increase even after healing of the tubercular disease. Surgical procedure for these pathologies can be performed through both anterior and posterior approaches but anterior approach has the advantage of better canal clearance and better chances of graft fusion and deformity correction than posterior approach. Objective: The main objective of this study is to find out the immediate kyphosis correction and loss in correction after 3 and 5 years follow up. Materials and Methodology: The study was conducte prospective study was conducted in the Department of Orthopaedics and Spine of Ghurki Trust Teaching Hospital, Lahore from 2003 to 2016. 1049 patients were totally operated during this interval. Out of which 513 patients were operated 5 years back and they were considered in the study. All patients underwent anterior decompression and placement of Inter body Titanium Mesh Cage with packed bone graft. Pre and post-operative lateral view x-rays were taken to check and record the post operative change in kyphotic angle at immediate post operative period, after 3 years and after 5 years. Boston brace was applied for at least 6 months. Data was analyzed using SPSS 17.0. Results: There were 513 patients in which 301 (58.67%) males and 212 (41.32%) females. The patients aged between 15-30 years were 232 (45.22%), those between aged 31-45 years were 115 (21.83%) and between 46-60 years there were 166 (32.36%). The mean local kyphosis correction in the immediate postoperative period was 23.1°± 2.1. The mean late loss of correction of local kyphosis at 3 years follow-up was 1.7° ± 0.7 and almost similar findings after 5 years follow up. Conclusion: Anterior decompression along with Titanium mesh cage and bone graft in patients suffering from caries spine showed immediate post operative improvement in kyphotic angle. There is no significant loss of kyphotic angle even after 3 years and 5 years follow up. It is safe and cheap procedure as compared to other instrumentation especially for the poor patients of developing countries.

1342

P350: Pyogenic spondylodiscitis: current strategies for diagnosis and treatment

Benjeddou Wassim ¹ , Khalil Habboubi ¹ , Aymen Benmahmoud ¹ , Mzid Ahmed ¹ , Hassen Makhlouf ¹ , and Mondher Mestiri ¹

¹ Adults Service, Institut Med Taieb Kassab, Mannouba, Tunisia

Purpose: Psoas abscess is a rare disease in developed countries. Its diagnosis is difficult and any delay could lead to a worsen prognosis. The aim of this study is to determine the best diagnostic and therapeutic practices. Methods: A retrospective study of psoas abscess that occurred during six months was performed. Results: Six cases of secondary psoas abscess are reported. They were associated with spondylodiscitis in three cases, arthritis and gynaecologic infection in the three remaining cases. Anatomic diagnosis was performed by tomodensitometry. Microbiologic diagnosis was obtained by blood culture or direct puncture of the abscess. Antibiotics were associated with percutaneous drainage in two cases, with simple puncture in one case, and with surgery in one case. A local improvement w observed in all cases. The oldest patients presented the worst complications which were not directly caused by the abscess. Conclusion: Physicians must be aware of psoas abscess because of their increasing incidence. Despite the fact that digestive pathologies are the main cause of secondary psoas abscess, bone infections, particularly spine infections, should be taken into consideration. Tomodensitometry guided puncture or percutaneous drainage are of diagnostic and therapeutic interest. Infectious samples must be taken before starting antibiotics, which have to be efficient against Gram negative bacillus, anaerobes and Staphylococcus aureus. Surgery must be quickly performed when the primary infection localisation need it, in case of voluminous abscess or when antibiotics and drainage are inefficient.

1356

P351: Risk factors for surgical site infections in operatively treated fractures of the ankylosed spine disorders

Celeste Tavolaro ¹ , Jonathan Yamaguchi ¹ , Mathew Vincent ¹ , Jonathan Seavey ¹ , Richard Bransford ¹ , and Carlo Bellabarba ¹

¹ Orthopaedics and Sport Medicine, Harborview Medical Center - University of Washington, Seattle, United States

Introduction: Operative management of spine fractures in patients with ankylosing spinal disorders is associated with increased risk for perioperative complications and 1-year mortality. Due to the rigid nature of the ankylosed spine, these fractures are commonly treated with posterior instrumentation (typically 3 levels above and below the level of injury at our institution); multiple and non-contiguous fractures frequently necessitate longer and/or multiple constructs. Surgical site infection is one of the more common complications associated with operative treatment and management frequently requires formal irrigation and debridement combined with a prolonged course of intravenous antibiotics. Surgical site infections are a significant source of morbidity to the patient and cost to the healthcare system, and identification of associated risk factors may help guide and optimize perioperative management. To describe the incidence and characteristics of post-operative surgical site infections in patients with ankylosing spinal disorders undergoing surgical management of a spine fracture and to identify risk factors associated with surgical site infection as compared to uninfected controls. Material and Methods: Following UW IRB approval, a total of 383 patients who had spine fractures and ankylosing spine disorders (Ankylosing spondylitis (AS) and diffuse idiopathic skeletal hyperostosis (DISH)) over a 15-year period were identified and analyzed retrospectively. The medical and surgical records were reviewed. Demographic data, comorbidities, operative data, hospital data, wound complications, and microbiology were recorded within 90-days of the index surgical procedure. The infected and not infected groups were analyzed using Chi-square and Student’s T-tests for categorical and continuous variables, respectively. Results: A total of 383 patients (55 women and 328 men) were included. The mean patient age was 70 years old (SD ± 13.3 years). One hundred fifty-five patients had an underlying diagnosis of AS and 228 had DISH. The mean follow-up was 6 months. Fifty-two patients (13.6%) had surgical site infections, and 48 patients (12.5%) underwent irrigation and debridement within 90 days of the index procedure. Among all patients, a mean of 7 levels were fused (SD ± 3 levels) – with significant differences (6.36 ± 2.52 vs 7.81 ± 3.23 levels, p < 0.001) observed between the infected and non-infected groups. The surgical invasiveness index was also significantly higher in the infected group 13.49 ± 5.87 vs 16.69 ± 7.54, p < 0.005). Infected patients were also more likely to have Ankylosing Spondylitis and more multi-level injuries. Conclusion: Surgical fixation of fractures in the ankylosed spine is frequently complicated by surgical site infection. Identified risk factors include longer constructs, multi-level injury and greater levels of surgical invasiveness. Ankylosing spondylitis also appears to be associated with a higher risk of post-operative surgical site infection although the mechanism for this is not well-defined. Diabetes mellitus, ASA grade and length of ICU and hospital stay were not significantly associated with presence of surgical site infection compared to uninfected controls.

1369

P352: Relationship between degenerative disc disease and cutibaceterium acnes: a prospective analysis

Zachary Crawford ¹ , John Stout ¹ , John Bonamer ¹ , Brian Johnson ¹ , and Anthony Guanciale ¹

¹ Orthopaedic Surgery, University of Cincinnati College of Medicine, Cincinnati, United States

Background: Degenerative disc disease and low back pain are substantial causes of disability and productivity loss with significant impact on the healthcare system. Previous literature has focused on low back pain and degenerative changes in the lumbar intervertebral disc although more recent literature has reported serologic evidence of gram-positive infection in 31% of patients with radicular symptoms. Of positive disc cultures, the most common infectious agent is Cutibacterium acnes with animal models suggesting low grade infection can precipitate and progressively worsen degenerative disc disease. The Purpose of this study is to further evaluate the relationship between degenerative disc disease and infection. Methods: This prospective study included patients who presented to a single orthopaedic spine surgeon for the degenerative disk disease. Patients were included if they were taken to the operating room for decompression of herniated disc or decompression and fusion of spine for degenerative disc disease. The disc removed was then cultured in standard fashion based on previously reported literature. General demographic information including age, gender, medical comorbidities, smoking status, and infectious disease information were collected prospectively and retrospectively from chart review. The primary outcome was positive culture from intervertebral disc. Results: There were a total of 85 patients and 134 levels included in analysis. The average age was 54.71 years (±12.9) with an average BMI of 31.7 (±6.39) and Charleston Comorbidity Index Score of 1.98 (±1.547). There were 8 patients (9.4%) that were positive for C. acnes with one additional patient positive for Staphylococcus aureus. There were no significant differences between patients with and without infection in regards to previous antibiotic use, smoking status, BMI, or previous steroid use. The majority of the patients with culture positive disc were men, 7 men versus 1 woman (p = 0.020). There was no significant difference in MODIC score of patients with and without infectious degenerative disc disease. Conclusion: Degenerative disc disease and low back pain have considerable influence on the healthcare system and productivity in the United States of America. There have been considerable research efforts to define the causes of degenerative disc disease with recent literature suggesting indolent infection from C. acnes may be a source. Our prospective analysis of over eighty patients and 130 levels found a significant number of patients were culture positive for C. acnes. Further studies on associated risk factors and natural progression of infectious degenerative disc disease are warranted to develop new treatments or procedures.

1432

P353: Extensive vertebral avascular necrosis following Covid 19 complicated by pyogenic spondylodiscitis- a rare case report

Rohan Parihar ¹ , Kshitij Chaudhary ¹ , and Samir Dalvie ¹

¹ Spine Surgery, P.D. Hinduja Hospital, Mumbai, India

Introduction: This is a so-far unreported case of an elderly gentleman presenting with extensive vertebral body avascular necrosis following COVID-19 complicated by pyogenic spondylodiscitis secondary to sepsis. Case Description: Our patient is a 72 yr old diabetic male with moderately controlled sugars. He was admitted with severe COVID-19 pneumonia in February 2021 and was treated with high dose dexamethasone, remdesivir, and tocilizumab. This was complicated by Klebsiella pneumoniae urosepsis and disseminated intravascular coagulopathy which was treated with meropenem, followed by clinical recovery. Two weeks later he presented with severe back pain. MRI of the LS spine followed by a PET-CT showed multiple lesions with increased uptake in the entire spine, pelvis and proximal femur. A bone marrow biopsy revealed marrow necrosis and ruled out malignancy, and he was started on a tapering dose of steroids with good clinico-radiological improvement. A month later, he developed severe back pain with bilateral radicular pain. MRI pelvis and lumbar spine showed an anterior epidural collection at L4-5, and infective foci around sacroiliac joints and left piriformis. CT guided biopsy showed avascular osteonecrosis and grew Klebsiella sensitive to meropenem. After 2-3 days, he progressed to develop an acute foot drop and underwent emergency epidural abscess drainage. The intraoperative cultures also grew Klebsiella. He was given meropenem for 6 weeks with good clinico-radiological response. However, after 2 weeks he presented with increased pain and the MRI showed an increase in osteomyelitis now involving the L3-4, L4-5 and L5-S1 levels. A repeat CT guided biopsy grew the same organism. Meropenem was restarted and continued for further 7 months. He has now completed 18 months and 15 months since the diagnosis of COVID-19 and osteomyelitis respectively. He is pain free but his left foot drop still persists. Conclusion: Such extensive bone marrow necrosis following COVID-19 has not been reported in literature. We presume that this was secondary to the hypercoagulable state induced by COVID-19 infection, sepsis and DIC. The necrotic areas were secondarily infected with Klebsiella that lead to epidural abscess and neurological deficit.

1460

P354: Improvement in ODI scores after surgical intervention in TB spine: a 21 case series

Sushant Srivastava ¹ , Paresh Bang ² , Mohammed Faizan ² , and Nikhil Tiwari ³

¹ Orthopaedics, Pandit Madan Mohan Malviya Shatabdi Hospital, Mumbai, India

² Orthopaedics, NKP Salve Institute of Medical Sciences and Research Centre and Lata Mangeshkar Hospital, Nagpur, India

³ Orthopaedics, Atal Bihari Vajpayee Institute of Medical Sciences & Dr. Ram Manohar Lohia Hospital, New Delhi, India

Introduction: Tuberculosis is one of the oldest maladies affecting mankind. Since the advent of Homo sapiens on earth, mycobacterium tuberculosis have lived in symbiosis with humans. The most common subtype of extra-pulmonary tuberculosis, accounting for almost 15% of cases is spinal tuberculosis. The proximity of the infection to the spinal cord and nerves often leads to neurological symptoms such as pain, weakness, and numbness in the lower limbs. Spinal tuberculosis may go on to cause serious disability, morbidity, residual neurological deficits, and severe deformities, if it goes unattended and untreated. This chain of reactions lead to the loss of functional capabilities, especially in terms of mobility, leading to difficulty in walking, self-care, and management of the sphincter. The patient’s quality of life is adversely affected due to the depreciating physical, mental, emotional health and social trials and tribulations. Materials and Methods: This was a single centre study and ethics committee approval was obtained. All patients were explained about the study and written informed consent was taken from all. The data from consecutive spinal TB patients was prospectively collected from January 2019 to December 2019. This prospective database included 21 patients with TB of the cervical, thoracic and lumbar spine with moderate to severe cord compression who were surgically treated and given chemotherapy. The diagnosis of spinal TB was based on clinical presentation, radiologic findings [plain radiographs, computed tomography (CT), and magnetic resonance imaging (MRI)], and hematologic and pathological examinations. Clinical presentation manifested as pain, night sweats, low-grade fever, weight loss, and neurological dysfunction. The ODI scores were calculated before and after intervention to assess the functional outcome. Results: Epi info-7 software was used for data analysis. A paired t-test was used to compare the pre-treatment and post-treatment, clinical data including ODI Scores. The results are reported descriptively, as mean ± standard deviation (SD). A P-value of less than 0.05 was considered statistically significant. There were 3 cervical, 14 thoracic and 5 thoracolumbar cases of spinal tuberculosis out of which 9 were females and 12 males. The age group was from 18 -70 years of age. The pre-operative ODI score was 75.61 ± 3.066 and post-operative ODI score was 38.09 ± 4.267. Conclusion: In this study we compared ODI Scores, as functional outcome assessment before and after surgery of spinal TB patients. This prospective study proves that there is an improvement in ODI Scores after surgical intervention in TB spine and the right timing of these decisions are extremely beneficial.

1598

P355: Intramedullary tuberculoma: a case report

Ghorbel Mohamed ¹ , Ines Cherif ¹ , Daoud Ahmed ¹ , Kolsi Fatma ¹ , and Boudouara Zaher ¹

¹ Neurosurgery, Habib Bourguiba Hospital, Tunisia

Introduction: Intramedullary tuberculoma is a rare condition. It affects mainly patients in developing countries. Diagnosis and treatment can be challenging. Material and Methods: We report the case of a young patient who was diagnosed with intramedullary tuberculoma and was treated in the department of neurosurgery in the Habib Bourguiba hospital in Sfax, Tunisia. Results: The patient was a 21-year-old female. She had a history of pulmonary tuberculosis. She was admitted for walking disturbances with sphincter dysfunction. Physical examination found a spastic paraparesis with a T8 sensitive level. The patient had anal sphincter hypotonia, vesical retention and bilateral Babinski sign. Spinal MRI showed an intramedullary nodular mass at the level of T7. The patient underwent urgent surgery. Tumor removal was not complete due to adherences. Pathology was in favor of tuberculoma. The patient had physical therapy along long-term antibiotics. She was symptom-free few weeks after surgery. Conclusion: Intramedullary tuberculoma is rare. However, such diagnosis should be considered in some contexts. Surgery when possible followed by medical treatment is the best alternative.

1602

P356: Hydatidosis of the spinal column: our series and review of the literature

Ghorbel Mohamed ¹ , Mohamed Boukhit ² , Daoud Ahmed ¹ , Kolsi Fatma ¹ , Ines Cherif ¹ , and Boudouara Zaher ¹

¹ Neurosurgery, Habib Bourguiba Hospital, Sfax, Tunisia

² Neurosurgery, Fattouma Bourguiba Hospital, Monastir, Tunisia

Introduction: Hydatid disease is a parasitic infection which can infect humans through the larval stage of the Echinococcus Granulosis (EG). It’s commonly seen in the Mediterranean region, Middle East and India. Hydatid cysts are frequently formed in the liver (60-70%), then the lungs. Although, Bone involvement is rare with approximately 0.5% of all hydatid cyst cases residing in the vertebrae. We report a series of spinal column hydatid cyst, treated over a period of 16 years. This study aim to discuss the diagnosis and the management of spinal hydatid cyst, based on a literature review. Materials and Methods: We report a retrospective study of 7 cases of spinal column hydatid cysts treated in the neurosurgery department of Habib Bourguiba University Hospital of Sfax-Tunisia, between January 2003 and December 2018. Results: It’s about 3 males and 4 females aged from 7 to 66 years with a mean age of 36.8. The revealing clinical symptomatology was spinal cord compression, back pain and sciatica. Weakness of the lower limbs was seen in 4 cases. We found bowel and bladder dysfunction in 57.1% of the patients. Whole spine MRI was done in all cases. Hydatid cysts were localized in dorsal column in 3 cases, dorsolumbar junction in 1 case, lumbosacral vertebrae in 1 case and lumbar column in 2 cases. All the patients were operated and treated with antihelminthic (Albendazole). Posterior approach was performed with 5 cases. The two other patients were operated through a lateral and an anterior approach. 5 patients had good recovery of muscle strength and resolution of limb sensory disturbance. The evolution was marked by relapse in 3 cases, which were reoperated. The average follow-up of patients after surgery was 6.3 years. Conclusion: Spinal hydatid cyst is a serious disease with significant morbidity. The recommended treatment is surgery with anterior or posterior approach and subsequent adjuvant medical therapy. The results are rarely satisfactory and the prognosis is usually poor due to the frequency of relapses.

1757

P357: Results of intervertebral fusion using autogenous tricortical spinous process bone during surgical treatment of pyogenic spondylits

Young-Yul Kim ¹ , Jong-Beom Park ² , and Jae-Hoon Kim ¹

¹ Orthopedics, Daejeon St. Mary's Hospital, Deajeon, South Korea ² Orthopedics, St. Mary's Hospital, Uijeonbu, South Korea

Introduction: Pyrogenic spondylitis is a rare spinal disease that occurs in disc space. However, the incidence is increasing due to the recent increase in treatment of epidural steroid injection. When performing intervertebral fusion surgery during the surgical treatment of pyogenic spondylitis, autogenic iliac bone graft is commonly used. But this autogenous cancellous bone graft may cause problems such as loosening or breakage of the device due to a decrease in the gap between the vertebrae after surgery. Therefore, in this study, we evaluate results about performing intervertebral fusion using trimming tricortical spinous process bone by microdrill after the autogenous spinous process in the same area where no infection occurred. Materials and Methods: A total of 9 patients with pyogenic spondylitis diagnosed in 2017-2021 who did not respond to antibiotic treatment were targeted. All patients had MRI evaluation preoperatively. Among the patients who observed the abscess of disc, facet joint, and epidural space on MRI, patients who did not involve in spinous process were targeted. The average age of the patient was 62.4 years, and the male-female ratio was 6:3. We're going to do postop x-rays, 6-month follow-up x-rays, 12 month x-rays, and postoperative 12 month CT. The height between the vertebrae of the disc space was compared and analyzed. In addition, the degree of clinical improvement was measured using VAS (Visual analog scale) and ODI (Oswestry disability index). Results: In post op x-ray, the final fusion was 11.2 cm, 6 mon 10.8, and 12 mon 10.4. The convergence period was judged to be more than 6 months. The average VAS preoperatively cored at 8.2, it estimated as 5.2, 4.1 at 6 months after the surgery, and finally 2.1 at 12 months. In the case of ODI, all 9 of them showed severe disability, but 6 months after the surgery, 6 of them changed to moderate. And 2 people showed minimal disability and 1 showed severity disability, and in the 12th month evaluation, it was shown in 7 people with minimal disability and 2 people with moderate disability. Conclusion: In patients with pyrogenic spondylitis, intervertebral fusion using an autogenic tricortical spinous process bone can induce intervertebral fusion while maintaining the height of the vertebral body. It was useful option about pyogenic spondylitis surgery.

1855

P358: Infectious complications in non-instrumented lumbar spine surgery

Nessrine Nessib ¹ , Kais Maamri ² , Mohamed Boukhit ² , Mohamed Amine Hadj Taieb ² , Maher Hadhri ² , Ghassen Belkahla ² , Atef Ben Nsir ² , and Mehdi Darmoul ²

¹ Neurosurgery, Mongi ben Hamida Institute of Neurology, Tunis, Tunisia

² Neurosurgery, Fattouma Bourguiba Hospital, Monastir, Tunisia

Introduction: Surgical site infection (SSI) is one of the most serious complications after lumbar disc herniation surgery. Rates vary from 0.7% to 12.0%. Materials and Methods: This is a retrospective study conducted between January 2008 and December 2018, to assess the incidence of surgical site infections following non-instrumental lumbar disc herniation surgery in adults. We present this study in order to highlight the epidemiological, clinical, diagnostic and therapeutic characteristics of SSI, and to identify its risk factors. Results: 869 procedures for lumbar disc herniation without instrumentation were performed during this period. 24 SSI were identified with an incidence of 2.76%. Superficial infections were the most frequent. The time of occurence of SSI was 15.17 days. The most frequently isolated microorganism was Staphylococcus aureus. Several significant risk factors for SSI were identified. The prognosis and clinical expression of SSI depend on the extent of the infection and the time between the surgical intervention and the first symptoms. SSIs should be treated with appropriate antibiotics associated with surgical treatment. Conclusion: Our study determined the incidence and identified the risk factors for SSI following lumbar disc herniation surgery. This makes it possible to develop effective preventive measures.

1875

P359: Isolated tuberculosis of the atlas

Nessrine Nessib ¹ , Sliti Firas ¹ , Abdelhafidh Slimane ¹ , Nadhir Karmani ¹ , Khalil Ghedira ¹ , Alaa Belhaj ¹ , and Jalel Kallel ¹

¹ Neurosurgery, Mongi ben Hamida Institute of Neurology, Tunis, Tunisia

Introduction: Pott's disease is still a common disease in countries with poor socio-economic conditions. It continues to pose a public health problem since it affects a young population in full activity, which shows the role of prevention. The dorsolumbar spine is the preferred site. Tuberculosis in the cervico-occipital hinge is very rare. It is estimated to occur in only 1% of spinal locations. Materials and Methods: We report the case of a 63-year old female treated in the neurosurgery department at the Mongi Ben Hamida National Institute of Neurology in Tunisia. Results: Our patient was without any particular pathological history and without any notion of tuberculosis infection. The patient consulted for mechanical cervical pains evolving for 1 year, of progressive aggravation, with trismus, torticoli and dysphagia to solids. The clinical examination revealed a significant painful stiffness of the cervical spine and the neurological examination was normal without any sign of spinal cord injury, fever or alteration of the general condition. The biological workup showed a non-specific inflammatory syndrome. The CT scan of the cervical spine showed an osteolytic lesion of the anterior arch of C1 lateralized to the left with rupture of the cortical bone. MRI showed a lesion that fixed the contrast, rounded, left paravertebral, extended to the adjacent soft tissues respecting the aerodigestive carrefour, whose appearance suggests a tumoral process originating from the paravertebral soft tissues, invading the anterior arch of C1, or an infectious process with common or specific germs. Sputum and urine were negative for BK. TST was negative. Wright serology and card-test negative. Needle biopsy was not possible because of the invincible trismus, and the lesion was biopsied surgically. Anatomopathological examination confirmed the tubercular nature of the lesion. Under anti-tuberculosis treatment, the evolution was favorable, both clinically and biologically. Conclusion: Pott's disease of the upper cervical spine is a very rare condition. The diagnosis is usually made late at the stage of neurological deficit. It should be suspected in the presence of chronic torticoli associated with prevertebral thickening and C1C2 lysis. MRI is of great diagnostic value and allows monitoring of treated forms. The diagnosis must be made early ; it is confirmed on histo-bacteriological grounds but sometimes retained on presumptive elements. Medical treatment based on anti-tuberculosis antibiotic therapy and immobilization of the cervical spine must be instituted as a first-line treatment despite the extent of bone lysis. Surgical treatment should be reserved for cases with diagnostic doubt, or in the presence of severe nerve compression or progressive worsening with or without respiratory disorders, or in cases of documented dynamic instability. The evolution under treatment is usually favorable.

1877

P360: Central nervous system infection revealing a dermal sinus

Nessrine Nessib ¹ , Abdelhafidh Slimane ¹ , Nadhir Karmani ¹ , Nessrine Jemel ¹ , Eya Chahed ¹ , Khalil Ghedira ¹ , and Jalel Kallel ¹

¹ Neurosurgery, Mongi ben Hamida Institute of Neurology, Tunis, Tunisia

Introduction: The dermal sinus is a congenital dysraphic anomaly that corresponds clinically to the presence of a punctiform cutaneous orifice of the median and posterior paramedian raphe from the occipital region to the sacrum but often from the lumbosacral region. The main complication of dermal sinus is central nervous system infection. Materials and Methods: We report the cases of 3 patients treated in the neurosurgical department at the Mongi Ben Hamida National Institute of Neurology in Tunisia, in whom the diagnosis of dermal sinus was made only after a severe central nervous system infection. Results: They were two boys and one girl, aged 11 months, 3 years and 11 months, respectively. Cerebrospinal MRI was performed in two cases for a neurological deficit in a febrile context, and in the third case for a recurrent purulent meningitis. In all three cases, it was a lumbar intradural abscess associated with a dermal sinus. The abscess was evacuated with excision of the dermal sinus. Two children had sequelae. These infectious complications are the most serious aspect of non-operated dermal sinuses because they can lead to serious neurological sequelae, in particular urological disorders and/or paraplegia, which will require long-term multidisciplinary management and can compromise the functional prognosis of these children. Conclusion: The severity of neurological sequelae due to infectious complications of the dermal sinus makes its detection the responsibility of any physician examining a child and indicates its urgent prophylactic surgery.

1930

P361: Spinal hydatid disease: a survey study from Tunisia

Ghorbel Mohamed ¹ , Amine Trifa ² , Atef Ben Nsir ² , Ahmed Amine Daoued ¹ , and Mehdi Darmoul ²

¹ Neurosurgery Department, Habib Bourguiba University Hospital, Sfax, Tunisia

² Neurosurgery Department, Fattouma Bourguiba University Hospital, Monastir, Tunisia

Introduction: The Hydatid cyst infection is caused by infection with the pathogen Echinococcus Granulosus. Musculoskeletal infection accounts for 0.5-1 % of all cases with Spinal Hydatid cyst representing half of those cases. The purpose of this study is to discuss the diagnosis, Differential Diagnosis and the management of spinal hydatid cyst. Material and Methods: Using a survey research, this study reviews six reports of spinal hydatid disease from Tunisia during the past 30 years and the main features of the treatment. Results: The population of our study is made of four man and two women (Sex Ratio 2:1) with a medium age of 40 years and symptoms duration ranging from 2 days to 32 years. 2 Patients presented with back pain, 2 patients with local swelling, 2 patients with radiculopathy and 3 patients with myelopathy. Radiological assessment (CT for 2 patients, CT+MRI for 4 patients) showed a dorsal spinal localization of the cyst in 4 cases, 1 case extending from dorsal to lumbar spine and one extended from lumbar spine to sacrum, with an associated location of pulmonary infestation in one case. Peri and post-operative Albendazole drug treatment were given in all cases. The initial surgery approach was a posterior one with epidural cysts removal and spinal decompression for all the cases with a relapse rate of 5/6 of the cases (One patient was lost of view) after an average duration of 3 years. Second surgery was performed with 3 patients via a posterior approach with a local relapse after a mean duration of 2 years to all the 3 cases, and a total spondylectomy with spinal fusion was performed to two patients who showed No recurrence after a mean duration of 4 years. Conclusion: The Simple decompression via laminectomy was found to show poor outcome especially in recurrent disease and a higher risk of relapse and neurological deterioration. Combined approach (laminectomy + Spinal fusion) may be strongly considered to maximize the chance of success Strict follow-up is mandatory. Further studies are needed to establish Treatment guidelines.

1940

P362: Has SARS-Co V-2 ( COVID-19) caused further increase on already increasing discitis (NVO)? An observational study

Mukta Vadhva ¹ and Poorna Veerappa ¹

¹ Orthopaedics, Lancashire Teaching Hospitals NHS Trust, Preston, United Kingdom

Introduction: Bacterial native vertebral osteomyelitis (NVO), synonymous with spondylodiscitis, is an important cause of back pain. NVO is associated with haematogenous seeding or contiguous spread from local infection. The literature reports 1 and 2 per 100,000 population in USA and UK respectively. The incidence (up to 9.8/100,000 per year (Kehrer et al., 2014) has increased (from 1-2/100,000 to 9.8/100,000 over the last 2 decades, possibly reflecting an ageing population (Kehrer et al., 2014; Mylona et al., 2009; Akiyama et al., 2013; Loibl et al., 2014). At our regional combined spinal surgical unit, our team suspected that there has been a surge in discitis during the covid period compared to pre-pandemic levels. A rapid literature search in major bio-medical databases yielded no current publications regarding this. Material and Methods: Type of Study: Retrospective, observational cohort study of adult patients with bacterial NVO. Inclusion criterion:

1. Adult (above age 18)

2. Radiology (CT/MRI +/-MRI contrast) confirmed discitis

3. No history of previous spine surgery

Exclusion criterion:

1. Non-adult population

2. People with previous spine surgery with or without fusion

Methodology: Referral databases at our tertiary spine surgery unit, which provides service for a wide geographical area within the northwest of England by both orthopaedic and neuro-surgical spinal surgeons, were reviewed. The arms were divided into pre-COVID and post-COVID. Data was collected for a seven-month period (January to July) in the two years, namely 2017 and 2021. A total of 2000 patients were included in each limb. Results: Review of our results showed 20 patients with confirmed discitis in the pre-COVID study period, whereas 38 patients had radiology confirmed discitis during the pandemic. Further analysis of our data showed that prior to COVID-19, 68% of all confirmed cases of discitis were in females, whereas post COVID-19 the incidence was more prevalent in males at 79%. It was also observed in our observational study, that pre-COVID-19 only one patient had skip lesion in the spine, whereas post COVID-19, skip lesions were observed in a total of five cases. Conclusion: It is our observation that there has been an increase (almost doubling) of discitis since the pandemic. It is unclear about the exact cause for this increase. Our study also noted that only one patient was COVID positive when discitis was diagnosed. It is our view that we need to have low threshold in suspecting discitis, especially in male population presenting with back pain. Further Plan: The observation was discussed at regional spine network, and it was deemed to carry out a multicentric study within the Northwest region.

Acknowledgments: Neurosurgical and Orthopaedic spine department for allowing to use the database of their patients.

Keywords: COVID-19, SARS-Co V-2, Spondylodiscitis, discitis, native vertebral osteomyelitis

1954

P363: Outcome in caries spine childern treated with standalone cage in terms of angular correction

Zubair Khalid ¹ , Atiq Uz Zaman ¹ , and Naeem Ahmed ¹

¹ Department of Orthopedic and Spine Center, Ghurki Trust Teaching Hospital Lahore, Lahore, Pakistan

Objective: Spine tuberclosusis is main problem in developing countries. it is most common in children and young adluts. Posterior approach is much discussed for caries spine. Data on anterior approach is not sufficient. the main objective of this study is to assure anterior approach for caries spine is more effective in treating TB spine in children. Study Design: Prospective cohort study design. Materials and Methods: We performed analysis of 116 patients underwent anterior decompression with standalone cage from January 2010-December 2020 in Department of Orthopaedic and Spine Center, Ghurki Trust Teaching Hospital Lahore, Pakistan. Preop and post op angle of kyphosis and angle of deformity calculated on digistal xray. Preop and postop neurological improvement is evaluated with franklins grading. Spinal instability score also calculated in each case. all these parameters are evaluated 2 years follow-up. ATT (anti tuberculosis treatment started preop and continued for 1year post op. Study parameters include, return to daily activities, return to job and patient satisfaction rate. Results: In current study, a total of 116 patients included fulfilling the inclusion criteria among these 56 (48.3%) were males and 60 (51.7%) were female cases with mean age of 6.50 ± 2.12 ranged from (3-14 years). Majority 82 out of 116 were effected from thoracic region, six were effected from lumbar region. Five cases were effected from cervical region. The preoperative kyphosis angle was 51.17 ± 21.64^o and post op kyphosis angle was 30.93 ± 18.16^o indicating the significance difference in the mean angle as p < .05. Conclusion: Anterior decompression and standalone cage is best approach for caries spine in children. Immediate correction is obtained and disease cure rate is good.

1957

P364: Gram-negative hematogenous spondylodiscitis. Incidence, risk factors and outcome

Hamdan Abdelrahman ^1,2 , Mootaz Shousha ³ , and Heinrich Boehm ³

¹ Asiut University Hospitals, Egypt

² Helios-Hospitals Erfurt, Spine Surgery, Erfurt, Germany

³ Zentralklinik Bad Berka, Bad Berka, Germany

Introduction: In recent years, the incidence of spinal infections has raised, this has been attributed to an increasing proportion of elderly population with predisposing factors and comorbidities. Various studies confirm staph. aureus as the most common causative organism in hematogenous spinal infections. Gram negative bacteria cause a significant proportion of all these cases. The incidence seems to be increasing in the recent years. Patients and methods: Retrospective analysis of the prospectively collected data of all patients with spinal infection between 2005 and 2015. The study revealed 600 patients with hematogenous spinal infections after exclusion of the cases with postoperative, wound infections and the cases treated for infection before this period. A causative organism could be identified from the site of infection in 405 patients (67.5%). Gram-negative bacteria could isolated in 45 patients of all cases (7.5%). In this study, we have collected and analysed the demographic, clinical, radiological and laboratory data as well as the outcome of management of those patients with gram-negative spondylodiscitis. Results: 45 patients, 21 females and 24 males with mean age of 66.96 ± 11.42 years 41 patients (91.1%) were older than 50 years. In those patients, 60% of the patients had ASA- Score class III and IV. The most common comorbidities were cardiac in 24 patients, DM in 22, renal insuffiecncy in 20 patients. Other site of infection were found in 30 patients; the most common one was UTI in 21 of them ( p-value 0.000* ). At the time of presentation, 30 patients (66.7%) had received antibiotic with average period of 15.9 ± 13.13 days (2-50). The pre-surgical interval was variable and ranged between 5-120 days, neurological deficit in 31 patients (68.9%), fever in 20 (an organism could be isolated from blood culture in 8 of them) and in 6 patients septic manifestations were found at admission. Lumbar spine was affected in 33 patients (73.3%); lumbosacral junction in 5 cases of them. Monosegemental was the commonest in 28 patients (62.2%), in 4 patients multifocal infection was found. The preoperative inflammatory parameters revealed mean CRP of 88.91 ± 72.55. The most common isolated organisms from the site of infection were E. coli in 20 patients (44.4%). In 5 patients (11.1%) had (mixed infection) and 4 of them had bed sore at the time of admission. One patient had pyogenic infection (in tissue culture) on top of tuberculous lesion (histopathological). All patients have been surgically treated; combined ventro-dorsal approach was necessary in 40 patients. In five patients, recurrence of infection has been detected and treated surgically (11.1%). In-hospital mortality of 6.7%. The neurological improvement rate of at least one grade reached 83%. Postoperative antibiotic therapy had to be taken more than 8 weeks in 31 patients. Conclusion: Gram-negative bacteria cause a significant proportion of vertebral osteomyelitis with incidence reached 7.5% in this study. The multimorbid elderly patients are more affected than the other age groups. The treatment is challenging, requiring prolonged hospital stay and multiple antibiotic regimes are often needed to prompt control of the infection and to prevent its recurrence.

1958

P365: Lumbar posterior inter-apophyseal arthritis complicating jugular catheterization

Mohamed Yassine Belhedi ¹ , Mouadh Nefiss ¹ , Chahed Houssem Eddine ¹ , Hedi Ezzine ¹ , Mohamed Amine Gharbi ¹ , Ramzi Bouzidi ¹ , Ezzaouia Khelil ¹ , and Tborbi Anis ¹

¹ Orthopeadic and Traumatology, Mongi Slim Hospital, Marsa, Tunisia

Introduction: Arthritis is defined as an acute or chronic inflammatory disease of the synovial mucosa of one or more joints. The etiology can be various, inflammatory, immune, or infectious. Septic arthritis is a medical-surgical emergency that must be suspected in a clinical context that is sometimes frustrating or in the presence of other inflammatory arthropathies. It usually affects a peripheral joint, particularly the knee and hip. Spinal involvement is not frequent. We report the case of a patient who presented a septic arthritis of the posterior lumbar inter-apophysis following the placement of a jugular catheter. Clinical Presentation: The patient was 60 years old, diabetic, hypertensive, dyslipidemic, with coronary artery disease and renal insufficiency at the hemodialysis stage. He presented with feverish low back pain and a biological inflammatory syndrome, 72 hours after the placement of a jugular catheter during his dialysis session. An infectious spondylodiscitis was suspected and the patient was put on antibiotic therapy (vancomycin + gentamycin). In view of the lack of clinical and biological improvement and the appearance of a neurological deficit, ASIA score FRANKEL D, without sphincter disorders, a CT scan of the lumbar spine was performed at 15 days of the symptomatology, showing a staged zygapophyseal arthritis with intracanal diffusion. A complementary MRI scan showed an aspect in favor of a posterior lumbar inter-apophyseal arthritis, extending from L2/L3 to L5/S1, probably of infectious origin with intra-articular effusion, synovitis as well as collections with intracanal development without associated discitis. The patient underwent posterior surgery. He underwent an extended laminectomy from L2 to S1 with exploration of the destruction of the right L4/L5 joint and the presence of staged intracanal collections opposite L2/L3, L3/L4 and L4/L5. These collections were drained. A superficial and deep bacteriological samples were taken and returned negative. The patient was then put on vancomycin with good clinico-biological evolution and total recovery of his neurological deficit. Conclusion: The posterior inter-apophyseal joint is a rare septic location. The clinical expression is very similar to that of a spondylodiscitis and is marked by an important spinal stiffness and by an inconstant febrile syndrome. MRI is the most efficient examination to make the diagnosis, which constitutes a medical-surgical emergency.

Medical Economics

111

P366: Isolated thoracic and lumbar transverse process fractures, do they need spine surgeon evaluation? A high volume level I trauma center experience with cost analysis

Asa Peterson ¹ , Jonathan Behrens ¹ , Pooria Salari ¹ , and Howard Place ¹

¹ Orthopaedic Surgery, St. Louis Univeristy, St. Louis, United States

Introduction: Transverse process fractures (TPF) of the thoracic and lumbar spine have become increasingly identified due to CT imaging. At many institutions the spine service, neurosurgical or orthopaedic, is consulted for further evaluation and management. There are several studies that demonstrate no difference in clinical outcome with or without spine service intervention (bracing, surgery, etc.). However, no study to our knowledge provides an additional cost analysis. We hypothesize that isolated transverse process fractures of the thoracolumbar vertebrae are structurally and neurologically stable injuries. Furthermore, spine service consultation and evaluation results in increased healthcare costs. Methods: Patients were identified using the trauma registry data at Saint Louis University (SLU) from January 2012 to August 2018. The registry was queried for CPT code 22305 (closed treatment of vertebral process fracture). Chart and imaging review was performed to determine if any additional spine fractures were identified by the spine team which were not included in the initial radiology report. TPF associated with other spinal injuries were characterized by the presence of one or more thoracic and/or lumbar TPF in addition to any other acute fracture or dislocation in the cervical, thoracic, or lumbar spine. A separate cost analysis with institution-specific charges was also performed. Results: Six hundred and eighty two patients with TPF from January 2012 to August 2018 were identified. Two hundred and twenty eight patients met the criteria to be included in this study. Of these, four hundred and seventy seven lumbar TPFs and one hundred and three thoracic TPFs were identified. Additional spinal pathology that was not included in the initial radiology report was identified in 5 (2.19%) patients, none of which required surgical intervention. These included two nondisplaced facet fractures (T6 and L3) that were treated non-operatively, a nondisplaced C7 laminar fracture treated with a rigid cervical orthosis, and a T3/4 widening which was suggestive of possible posterior ligamentous injury on a subsequent MRI exam which was treated with bracing. Cost analysis demonstrated additional costs associated with spine service intervention totaled $1,725,360.28. Average cost per patient in our cohort summed to $2,529.85. Conclusion: These data support that isolated TPF of the thoracic and lumbar spine are stable injuries that likely do not require spine service intervention and in fact may represent unnecessary financial burden. Foregoing unnecessary consultation can alleviate time constraints within spine service practices and reduce health care costs by eliminating costly extraneous interventions from the patient’s care.

536

P367: A 5 year cost-utility analysis for recombinant bone morphogenetic protein 2 (rhBMP-2) use in transforaminal lumbar interbody fusion for degenerative lumbar pathologies

Carlos Ortiz-Babilonia ^1,2 , Arjun Gupta ^1,3 , Micheal Raad ¹ , Miguel Cartagena ^1,4 , and Amit Jain ¹

¹ Department of Orthopedic Spine Surgery, John Hopkins University, Baltimore, United States

² University of Puerto Rico Medical Sciences Campus, Department of Orthopedic Surgery, San Juan, Puerto Rico

³ Rutgers New Jersey Medical School, Department of Orthopedic Surgery, Newark, United States

⁴ Ponce Health Sciences University, Department of Orthopedic Surgery, Ponce, Puerto Rico

Study Design: Cost-utility analysis. Objective: This study aimed to evaluate the cost-utility of utilizing recombinant human bone morphogenetic protein 2 (rhBMP-2) in addition to local bone graft (LBG) in transforaminal lumbar interbody fusion surgery (TLIF) for adults with degenerative lumbar disease compared to LBG only. Background: Past clinical studies including cost-effectiveness analyses have shown TLIF to be an effective treatment for degenerative lumbar pathologies in adult patients. The utilization of rhBMP-2 has been shown to lower pseudoarthrosis rates in the setting of TLIF, however its cost-effectiveness has not been previously demonstrated. Therefore, in this study we attempt to evaluate the cost-effectiveness of rhBMP-2 use as a treatment strategy in adult patients undergoing TLIF. Methods: A decision tree comparing LBG + rhBMP-2 use versus use of LBG alone was built for a hypothetical 60-year-old man with degenerative lumbar pathology (DLP) requiring surgery. A comprehensive review of the literature was performed to obtain event probabilities, costs and health utilities. Health utilities were utilized to calculate Quality-Adjusted Life Years (QALYs). A base-case analysis was carried out to obtain the incremental cost and effectiveness (QALYs) of rhBMP-2 utilization in TLIF. A probabilistic sensitivity analysis was performed using 1000 Monte Carlo simulations to evaluate the uncertainty in our model and obtain mean incremental costs, effectiveness, and net monetary benefits. One-way deterministic sensitivity analyses were also performed to identify the variables with most impact on our base-case results. Results: TLIF with LBG + rhBMP-2 was favored on base-case analysis. Adding rhBMP-2 to LBG in TLIF was favored in 80% of the Monte Carlo simulations. Utilization of rhBMP-2 resulted in mean savings of $10,024 (SD = 2,191) while gaining a mean of 0.11 (SD = 0.24) additional QALYs compared to TLIF with LBG only. The mean cost of rhBMP-2 + LBG in TLIF surgery was $36,400 (SD = 3034), while TLIF with only LBG resulted in $46,424 (SD = 3814). The mean INMB and ICUR of utilizing rhBMP-2 in TLIF surgery were found to be $20,967 (95% CI, $19,436 - $22,498) and -$34,096 (95% CI, -$75,695 - $7,501) at a willingness-to-pay (WTP) threshold of 100,000 USD/QALY, respectively; indicating that rhBMP-2 use in TLIF is a cost-effective strategy in comparison to TLIF with LBG alone. On one-way deterministic sensitivity analysis, the three parameters with most effect on the conclusions of our model were the probability of pseudoarthrosis with LBG only, the cost of revision, and the effect of nonunion on patient quality of life.Conclusion: Cost-utility analysis supports the use of rhBMP-2 in adult patients undergoing TLIF for lumbar degenerative pathologies.

541

P368: Predictors of academic productivity among spine surgeons

Mark Lambrechts ¹ , Yunsoo Lee ¹ , Jeremy Heard ¹ , Nicholas D'Antonio ¹ , Tariq Issa ¹ , Parker Brush ¹ , Delano Trenchfield ¹ , Payton Boere ¹ , Ari Clements ¹ , Zachary Crawford ² , Patrick O'Connor ¹ , Jose Canseco ¹ , Christopher Kepler ¹ , Alan Hilibrand ¹ , Alexander Vaccaro ¹ and Gregory Schroeder ¹

¹ Orthopedic Surgery, The Rothman Orthopedic Institute at Thomas Jefferson University Hospital, Philadelphia, United States

² Orthopedic Surgery, University of Cincinnati, United States

Introduction: Academic productivity of orthopaedic surgery residency applicants has risen in importance as the field becomes more competitive. However, the relationship between research productivity in training and future productivity as an attending physician is not well established in the literature nor has the impact of geographic location of training institutions on future academic success been investigated. For trainees interested in academic medicine, knowing these factors may help set research goals and choose training programs. Therefore, the aim of our study was to: (1) summarize characteristics of academically productive spine surgeons, (2) assess the impact of academic productivity during different training timepoints on long-term productivity, and (3) establish the impact of geographic location on long-term academic productivity. Methods: A query of the 2021-2022 North American Spine Society (NASS) Spine Fellowship Directory of all orthopedic and neurosurgical spine fellowship selection committee members for each institution participating in the spine fellowship match. Each surgeon's current institution of practice and medical education was recorded through an online search of institutional websites. A search on PubMed was then used to collect data on the number of articles published prior to residency, during residency, during fellowship, and following fellowship determined based on the recorded medical education history. The attending publication rate was calculated and the author's h-index was collected through a search of each author's Scopus profile through July 1, 2022. Data was analyzed by residency training and attending institution geographic location. A multivariate linear regression model was developed to determine if pre-residency, residency, or fellowship publication rate were independently predictive of attending publication rate or h-index. Results: A total of 310 orthopedic and neurosurgical spine surgeons, representing 76 fellowship programs, were identified on the NASS directory as involved in spine fellowship mentoring. Multivariate linear regression analysis identified that the publications during residency (p < 0.001) and during fellowship (p<0.001) were significant predictors of an increased publication rate as an attending surgeon. In contrast, the pre-residency publication rate (p = 0.729) was not significantly predictive of the attending publication rate. Multivariate analysis of h-index found that residency publication rate had a positive correlation (p = 0.031) as compared to pre-residency (p = 0.579) or fellowship (p = 0.257). Attendings who had attended residency in the Northeast and currently practicing in the Northeast had a higher publication rate (p < 0.001 and p = 0.004, respectively). Conclusion: Understanding factors important to long term research productivity can help academic institutions hire trainees and attendings while also assisting trainees in program selection. A higher number of publications in residency and fellowship was significantly predictive of an increased publication rate as an attending spine surgeon, indicating that an emphasis on research throughout surgical training, with a particular focus during residency, is advantageous for those interested in a career in academic spine surgery. In contrast, pre-residency publications may not be indicative of future academic productivity as an attending. Location may also contribute to attending publication rate and favors those who undergo residency training and ultimately practice in the Northeast.

607

P369: Gender disparities among abstract presenters at recent Global Spine Congress Annual Meetings

Yunsoo Lee ¹ , Tariq Issa ¹ , Delano Trenchfield ¹ , Jasmine Lin ¹ , Skylar Nahi ¹ , Alexander Becsey ¹ , Qudratallah Qadiri ¹ , Preston Carey ¹ , Parker Brush ¹ , Jeremy Heard ¹ , Jose Canseco ¹ , Alan Hilibrand ¹ , Christopher Kepler ¹ , Alexander Vaccaro ¹ , and Gregory Schroeder ¹

¹ Division of Spine Surgery, Rothman Orthopaedic Institute, Philadelphia, United States

Introduction: The percentage of female surgeons in neurosurgery and orthopaedic surgery has grown significantly over the past several years, but still lags behind other fields. However, research has demonstrated that women are less likely to have adequate mentorship, promotions to professorship, and research productivity. We aimed describe trends in the gender of presenters at the Global Spine Congress over the last 5 years. Material and Methods: We performed a retrospective study examining the annual programs of the Global Spine Congress final programs from 2017-2022. Speaker names, institutional data, and session titles were collated. The gender of speakers was identified through an online search of their institutional profiles with collection of gender pronouns, when available, or classifying individuals by their presenting gender. Results: During the past 5 Global Spine Congress Annual Meetings, there were a total 1,636 paper presentations. Gender information could be identified for 1,514 (92.5%) speakers, all of whom were included in the final analysis. Speakers were predominantly male (N = 1286, 84.9%) and from the United States (N = 387, 25.6%). European (N = 99, 22.0%) and North American (N = 91, 15.9%) institutions supported the most female presenters (p < 0.001). Among other regions of the world, 12.0% of East Asian/Pacific Islanders, 11.1% of Central/South American, 8.6% of Middle Eastern, and only 2.4% of South Asians were female. The 2018 and 2019 meetings in Canada and Singapore had the lowest female representation (10.8% and 12.8%, respectively) compared to those in France (16.9%), United States (16.8%), and Italy (17.8%), although this did not meet statistical significance (p = 0.058). Over the last 5 years, there was no significant increase in the gender of female presenters. Conclusion: Overall, 14.1% of presenters at the Global Spine Congress were female in line with recent trends from other orthopaedic and neurosurgery conferences. However, disparities exist internationally particularly among institutions and conferences located outside of Europe and the United States. Efforts should be established to help promote gender equity at future annual meetings, monitor gender representation from historically less inclusive regions of the world, and emphasize recruitment and retention efforts of women.

772

P370: The impact of COVID-19 on spine surgery

Emily Mills ¹ , Ethan Faye ¹ , Kevin Mertz ¹ , Andy Ton ¹ , Jeffrey C. Wang ¹ , Raymond Hah ¹ , and Ram Alluri ¹

¹ Orthopaedic Surgery, Keck School of Medicine of USC, Los Angeles, United States

Introduction: The COVID-19 pandemic had a significant impact on the healthcare system. However, only a few small scale studies have studied the effect of COVID-19 on spine surgery volume. Therefore, the aim of this study was to characterize the impact of COVID-19 on the rate of ten common spine procedures as well as the percentage of outpatient procedures. Material and Methods: The PearlDiver national database was queried for posterior lumbar instrumented fusion (< 6 segments), thoracolumbar intstrumented fusion (> 6 segments), posterior cervical fusion, anterior cervical decompression and fusion (ACDF), cervical laminectomy, lumbar laminectomy, microdiscectomy, cervical disc arthroplasty, cervical laminoplasty, and lumbar interbody fusion. The yearly rates of these procedures between January 2010 through April 2021 was recorded. Monthly trends were assessed from January 2020 through April of 2021. The years 2020 and 2021 were compared to 2019. Monthly trends throughout 2020 and 2021 were compared to January of 2020. Inpatient versus outpatient data was compared between 2010-2019 (pre-COVID) and 2020-2021(post-COVID). Results: Overall, there was a 4.3% decrease in all ten procedures in 2020 compared to 2019 and a 6.3% increase in all ten procedures in 2021 compared to 2019. March and April of 2020 had the largest decrease in procedures, with March of 2020 seeing a 18.2% decrease in procedures and April 2020 seeing at 51.6% decrease in procedures compared to January of 2020. Although there were also increasing case numbers in January of 2021, there was only a 1.8% decrease in total cases compared to January of 2020. Later months of 2021 had an increase in total cases, with April of 2021 increasing case volume by 138% compared to January of 2020. Pre-COVID, outpatient procedures made up 39.7% of all spine procedures, compared to 49.1% post-COVID (p < 0.001). Conclusion: The greatest effect on volume in spine surgery from the COVID-19 pandemic occurred in March and April 2020. Other than these two months, spine procedures were either very similar or increased compared to January of 2020. Additionally, the COVID-19 pandemic significantly increased the volume of outpatient spine procedures.

1237

P371: Assessing the economic benefit of Enhanced Recovery After Surgery (ERAS) protocols in adult cervical deformity patient outcomes: is initial cost offset by clinical gains?

Peter Passias ¹ , Peter Tretiakov ¹ , Kimberly McFarland ¹ , Jamshaid Mir ¹ , Pooja Dave ¹ , Bailey Imbo ¹ , Tyler Williamson ¹ , Rachel Joujon-Roche ¹ , Jordan Lebovic ¹ , and Andrew Schoenfeld ²

¹ Neurological and Orthopaedic Surgery, NYU Langone Health, New York City, United States

² Department of Orthopedic Surgery, Brigham and Women's Center for Surgery and Public Health, Boston, United States

Introduction: Enhanced Recovery After Surgery (ERAS) can help accelerate patient recovery and assist hospitals in maximizing the incentives of bundled payment models while maintaining high-quality patient care. However, the economic benefits of ERAS protocols, nor the heterogeneous components that make up such protocols, have been established. Material and Methods: Operative CD patients ≥ 18yrs with complete pre-(BL) and up to 2-year(2Y) postop radiographic/HRQL data were stratified by enrollment in Standard-of-Care ERAS beginning in 2020, including expedited time to ambulation, multimodal analgesia and pain control, and early oral diet and Foley catheter removal. Differences in demographics, clinical outcomes, radiographic alignment targets, peri-operative factors and complication rates were assessed via means comparison analysis. Costs were calculated using PearlDiver database estimates from Medicare pay-scales. QALY was calculated using NDI mapped to SF6D using validated methodology with 3% discount rate to account for residual decline to life expectancy. Results: 270 patients were included (58.11 ± 11.97 years, 48% female, 29.13 ± 6.89 kg/m². Of these patients, 54 (20.0%) received ERAS protocol recovery treatment post-operatively. At baseline, ERAS+ had significantly higher NDI (p = .005) and EQ5D (p = .023), and significantly lower mJOA scores (p < .001). At BL, ERAS- patients were significantly more likely to utilize opioids than ERAS+ patients (p = .016). Furthermore, ERAS+ patients also had significantly lower EBL overall (583.48 vs 246.51, p < .001), and required significantly lower doses of propofol intra-operatively than ERAS- patients (p = .020). ERAS+ patients also reported lower mean LOS overall (4.33 vs 5.84, p = .393), and were more likely to be discharged directly to home (χ²(1) = 4.974, p = .028). In terms of complications, ERAS+ patients were less likely to develop neurological complications overall (p = .025), and less likely experience thromboembolic complications or be diagnosed with venous disease post-operatively (p = .025). Per cost analysis, ERAS+ patients reported a significantly lower mean total 2Y cost of 33,829 USD compared to ERAS- patients at 36,951 (p < .001). Furthermore, ERAS+ patients trended towards greater life-expectancy 2Y QALYs gained versus ERAS- patients (.423 vs .368, p = .051), and demonstrated significantly lower cost of reoperation by 2Y (7050 USD vs 8110 USD, p < .001). Conclusion: Patients undergoing Enhanced Recovery After Surgery (ERAS) protocols experience lower operative times, length of stays, as well as lower rates of peri-and and post-operative complications. Subsequently, this study demonstrates that ERAS programs in ACD surgery may lead to increased cost-effectiveness and reduced total cost by 2Y post-operatively. Due to the potential economic benefit of ERAS for patients, physicians and institutions should consider incorporation of ERAS into practice for eligible patients.

1282

P372: Assessing the insurance deductible effect on outcomes following elective spinal surgery

Anthony Steinle ¹ , Jessa Fogel ¹ , Rishabh Gupta ¹ , Alicia Hymel ¹ , Claudia Davidson ¹ , Andrew Croft ¹ , Wilson Vaughan ¹ , Jacquelyn Pennings ^1,2 , Kristin Archer ^1,2,3 , Scott Lawrence Zuckerman ^1,4 , Raymond Gardocki ¹ , Amir Abtahi ^1,2,4 , and Byron Stephens ^1,2,4

¹ Department of Orthopaedic Surgery

² Center for Musculoskeletal Research

³ Department of Physical Medicine and Rehabilitation

⁴ Department of Neurological Surgery, Vanderbilt University Medical Center, Nashville, TN, United States

Introduction: Many private insurers operate on a calendar deductible system. Plans typically reset on January 1^st, placing pressure on patients and health care workers to perform medical services, including elective spine surgeries, before the end of the year to maximize patient savings. This insurance-driven scheduling of elective procedures could negatively impact patient reported outcomes (PROs) due to the increased burden placed on healthcare staff during the month of December, in addition to potentially lowering the threshold to undergo surgery for patients who have met their deductible. The purpose of this study was to investigate if patients undergoing surgery in December had different baseline characteristics and postoperative outcomes compared to the other 11 months. Material and Methods: We conducted a retrospective review of data collected from The Quality Outcomes Database, a national spine registry. The registry was queried for patients who underwent elective lumbar or anterior cervical discectomy and fusion (ACDF) surgery between 2012 and 2021 for degenerative spine conditions. Oswestry/Neck Disability Index (ODI/NDI), EuroQol 5-Dimensions (EQ5D), EuroQol Visual Analog Scale (EQ-VAS), numeric rating scale (NRS) leg/arm pain, and NRS back/neck pain scores were collected at baseline and 3 and 12 months postoperatively. Patient satisfaction scores using the NASS questionnaire were recorded at 3 and 12 months. Separate analyses were run for the lumbar and ACDF cohorts. Three multivariable linear regression models were performed for both groups, in which 12-month outcomes were predicted based on surgical timing. One model included all patients, a second included patients with private insurance, and the third included patients without private insurance. Results: A total of 978 patients underwent ACDF in December vs 10,526 in other months. 1,104 patients underwent lumbar fusion in December vs 11,826 in other months. For the ACDF cohort, there was a significantly higher percentage of patients in the December group with private insurance (68.1% vs 60.1% p < 0.001) and employment (50.1% vs 43.5%, p < 0.001). The December group had higher 3-month EQ-5D (0.79 ± 0.18 vs 0.78 ± 0.19, p = 0.019) and baseline EQ-VAS (63.36 ± 19.53 vs 61.72 ± 20.36, p = 0.016) scores. For the lumbar cohort, there was a greater chance of undergoing surgery in December if the patient had private insurance (56.4% vs 45.0%, p < 0.001) and was employed (38.4% vs 29.9%, p < 0.001). NRS leg pain at 3 months was significantly higher for the December group vs the other months (2.4 ± 2.9 vs 2.2 ± 2.7, p = 0.038). All other PROs were similar. Results from the linear regression models showed timing of surgery was not predictive of any 12-month outcome except for EQ-VAS in the ACDF group with private insurance (-1.637 [95% CI: -3.027-(-0.246)]). Conclusion: Financial pressure created by the deductible calendar likely affects the scheduling of elective fusions, specifically for patients with private insurance. However, patients undergoing fusion surgeries in December did not experience any significant clinical difference in postoperative outcomes compared to the non-December group. These findings suggest physicians are scheduling patients appropriately for elective fusion surgery in December despite external pressure from insurance companies.

1305

P373: Defining patients with spinal metastases suitable for surgical intervention: a cost-effectiveness analysis

Hsiang-Chieh Hsieh ¹ , Hung-Kuan Yen ¹ , Ting-En Tseng ¹ , Olivier Groot ² , Min-Tsun Liao ¹ , Meng-Kan Chen ¹ , Shau-Huai Fu ¹ , Chen-Yu Wang ¹ , Wang Chun-chieh ¹ , Yu-Tine Pan ¹ , Mao-Hsu Yen ¹ , Aditya Karhade ³ , Feng-Ming Hsu ¹ , Wei-Hsin Lin ¹ , Fu-Shan Jaw ¹ , Jorrit-Jan Verlaan ² , Joseph Schwab ³ , Andrew Schoenfeld ⁴ , Shu-Hua Yang ¹ , and Ming-Hsiao Hu ¹

¹ National Taiwan University Hospital, Taipei, City, Taiwan

² University Medical Center, Utrecht, The Netherlands

³ Massachusetts General Hospital, Boston, United States

⁴ Brigham and Women's Hospital, Boston, United States

Introduction: Both nonoperative and operative treatments for spinal metastasis are expensive interventions. Previous studies have provided contradictory results regarding the cost-effectiveness of treatment approaches, based on patients’ prognosis and walking ability. We sought to determine the cost-effectiveness of operative and non-operative interventions, stratified by ambulatory status and predicted probability of 3-month survival. Material and Methods: A Markov model with four defined health states was used to estimate the quality-adjusted life-years (QALYs) and costs for operative and nonoperative management of spine metastases. Transition probabilities for the model, including the risks of mortality and functional deterioration, were obtained from secondary data analysis and published literature. Willingness-to-pay thresholds were prespecified at $100,000 and $150,000. The analyses were censored after 5-year simulation from a health system perspective and discounted outcomes at 3% per year. Sensitivity analyses were conducted to test the robustness of the study design. Results: The incremental cost-effectiveness ratios were $86,500 per QALY for patients with a 3-month survival probability > 50%, $167,130 per QALY for patients with a 3-month survival probability < 50%, $119,360 per QALY for patients with independent ambulatory and a 3-month survival probability > 50%, and less than 0 for patients with non-ambulation and a 3-month survival probability < 50%. Conclusions: This study highlights the importance of patient selection and preoperative survival estimation for patients with spinal metastases. In patients with intact ambulation, a surgical intervention could still be cost-effective, especially for those with better prognosis.

1465

P374: Optimizing spine surgery instrument trays to immediately increase efficiency and reduce costs in the operating room

Setti Belhouari ¹ , Jay Toor ¹ , Aazad Abbas ² , Johnathan Lex ¹ , and Jeremie Larouche ^2,3

¹ Temerty Faculty of Medicine

² Division of Orthopaedics, Department of Surgery, University of Toronto, Toronto, Canada

³ Department of Surgery, Sunnybrook Health Sciences Centre, Toronto, Canada

Introduction: Over-crowded surgical trays result in perioperative inefficiency and unnecessary costs. While methodologies to reduce the size of surgical trays have been described in the literature, they each have their own drawbacks. In this study, we compared three methods: 1) clinician review (CR), 2) mathematical programming (MP), and 3) a novel hybrid approach based on surveys and cost analysis. While CR and MP are well documented, CR can yield suboptimal reductions and MP can be laborious and technically challenging. We hypothesized our easy-to-implement HM would result in a reduction of surgical instruments in both the laminectomy tray (LT) and basic neurosurgery tray (BNT) that is comparable to CR and MP. Material and Methods: Three approaches were tested: CR, MP, and HM. We interviewed 5 neurosurgeons and 3 orthopedic surgeons, at our institution, who performed a total of 5437 spine cases, requiring the use of the LT and BNT over a four-year (2017-2021) period. In CR, surgeons suggested which surgical instruments should be removed. MP was performed via the mathematical analysis of 25 observations of the use of a LT and BNT tray. The HM was performed via a structured survey of the surgeons’ estimated instrument usage, followed by a cost-based inflection point analysis. Results: The CR, MP, and HM approaches resulted in a total instrument reduction of 41%, 35%, and 38%, respectively, corresponding to total cost savings per annum of $50,211.20, $46,348.80, and $44,417.60, respectively. Conclusion: While hospitals continue to examine perioperative services for potential inefficiencies, surgical inventory will be increasingly scrutinized. Despite MP being the most accurate methodology to do so, our results suggest that savings were similar across all three methods. CR and HM are significantly less laborious and thus are practical alternatives.

1853

P375: A novel pain management protocol for the reduction of opioid usage perioperative to instrumented lumbar fusion

Gregory Paschal ¹ , Fedan Avrumova ¹ , Philip Paschal ¹ , Ellen Soffin ² , Joseph Nguyen ³ , Federico Girardi ⁴ , Gbolabo Sokunbi ⁴ , Andrew Sama ⁴ , Frank Cammisa ⁴ , Darren Lebl ⁴ , and Celeste Abjornson ¹

¹ Integrated Spine Research Program

² Anesthesiology

³ Biostatistics

⁴ Spine Surgery, Hospital For Special Surgery, New York, United States

Introduction: In an effort to reduce opioid consumption, physicians have looked towards alternative options for pain relief for surgical patients. Opioid alternatives have been shown to be effective while also decreasing the risk of side effects such as constipation, nausea, and addiction. One such alternative is IV acetaminophen, which has been shown to successfully reduce the risk of such side effects, however at a relatively high cost. Testing the effectiveness of IV acetaminophen may address questions about the cost-effectiveness of this promising opioid alternative. Our goal is to prospectively evaluate clinical outcomes of IV versus oral (PO) acetaminophen following circumferential lumbar fusion. We hypothesize that IV acetaminophen will reduce length of hospital stay, analgesic morphine equivalent consumption, and pain levels, and will do so more effectively than PO acetaminophen. Material and Methods: In this prospective, single center, randomized control trial, patients were screened to meet the inclusion/exclusion criteria. One hundred patients (50 per group) between the age of 18-85 undergoing circumferential lumbar fusion surgery were included in the study. Patients with prior surgery or fracture at the index level(s), significantly elevated surgical risk, a history of drug abuse, and/or inability to take orally administered acetaminophen were excluded from this study. Enrolled patients were randomized into either IV or PO groups. Preoperative baseline surveys were collected. The first dose of the assigned acetaminophen was administered within 3 hours prior to surgery. Postoperatively, 7 additional doses were given every 6 hours. Patients had access to supplemental opioid analgesics as needed. Analgesic consumption and visual analog pain scale (VAS) scores were recorded daily until discharge. Patients were followed at 6 week and 6 month post-operatively and administered questionnaires. Pain medication usage was recorded. Results: Daily morphine equivalent (MME) consumption was statistically significantly lower for the IV group than the PO group (p = 0.001) from post-operative to final administration of acetaminophen dosage. Post regimen average daily MME was also statistically significantly lower for IV group than PO group (p = 0.002). Average length of stay was similar between groups. The IV group showed greater reduction in VAS and ODI between baseline and discharge. However, VAS Back and VAS Leg scores were similar for both groups out to 6 months post-op, but both groups showed statistically significant differences from baseline in frequency and intensity. ODI was also statistically lower than baseline in both groups out to 6 months. Conclusion: In addition to an overall reduction in opioid use, patient surveys indicate an improvement of pain management with the use of IV acetaminophen. Our findings suggest that IV acetaminophen is a safe and effective alternative to opioid use. The decrease in risk of side effects makes IV acetaminophen a promising alternative to opioid use, even despite the added cost.

1929

P376: Cost evaluation in open surgery in lumbar disc pathology in a reference hospital for spinal pathology

Isaac Garcia Guajardo ¹ and Hugo Vilchis Samano ¹

¹ Spine Surgery, UMAE Hospital de Traumatología y Ortopedia Lomas Verdes, México City, Mexico

Introduction: Lumbar disc herniations are characterized by the migration of the nucleus pulposus across its anatomical boundaries, invading adjacent compartments. Being the most common cause of sciatica, it affects 1% to 5% of the population annually. For symptoms that are resistant to initial conservative treatments, lumbar discectomy may be considered, although the question of which treatment is superior has sparked lively debate. Surgery produces faster symptom relief than continuous conservative care. Objective: To assess cost-benefits of open surgery in lumbar disc pathology in a reference hospital for spinal pathology. Material and Methods: Cross-sectional, descriptive and retrospective study through a review of records and database of the spine surgery service of the hospital over a period of two years. using analytical statistics, the data will be presented in tables and graphs. Results: In the period included in the study of 2.5 years, an average of 167 patients operated on for disc pathology were obtained, of which 141 patients belonged to the population with work disability; with greater predominance in the male gender (90 patients); with a net cost per day of hospitalization of 399,831.63 USD; a cost in open surgeries of 216,936.64 USD; generating a total cost of expenditure to the institution of 616,768.27 USD. Conclusion: Disc pathology continues to be a challenge for the spine surgeon and the institutions representing great losses in costs for the institution and for the patients to have a greater delay in their discharge and return to work. this analysis is part of a protocol for the management of new tools for the surgical management of degenerative disc pathology such as endoscopic surgery.

Minimally Invasive Spine Surgery

138

P377: Comparative analysis of outcomes in one to two level minimally invasive and open transforaminal lumbar interbody fusion

Ashley Duncan ¹ , Matthew Geck ¹ , Devender Singh ¹ , John Stokes ¹ , and Eeric Truumees ¹

¹ Spine, Ascension Texas Spine and Scoliosis, Austin, United States

Introduction: Minimally Invasive Surgical (MIS) techniques potentially offer a less morbid alternative to traditional open surgical techniques with shorter length of stay. Aim: This study aims to compare the outcomes of patients undergoing minimally invasive transforaminal lumbar interbody fusion to those that underwent the traditional open technique. Materials and Methods: 31 Retrospective chart reviews were conducted on patients that underwent one to two level transforaminal lumbar interbody fusion from 2020-2021. Patients were divided into two cohorts, those that underwent the traditional open approach and those that had a minimally invasive technique. Twelve variables were collected across demographic, surgical, clinical, and patient reported outcomes (PROs) (PROMIS Physical Function, Pain Interference and Satisfaction with Social Roles; and Oswestry Disability Index) domains and analyzed accordingly. Results: 12 patients were included in the minimally invasive cohort and 19 were included in the open cohort. Mean age, BMI and sex were similar in both groups. There was a significant difference in the mean number of levels fused, 1 ± 0 in the MIS group and 1.3 ± 0.5 in the open group (p = 0.009917). While the MIS group had lower mean skin-to-skin surgical time, estimated blood loss and length of stay, none of these were statistically significant. Both cohorts consistently reported improvements in PROMIS and ODI scores across their recovery period up to one year postoperatively, however, there were differences not only in timing, but also in domain reported. At three months postoperative, the MIS cohort showed significant change in PROMIS Pain Interference (59.9 ± 8.8) from preoperative (68.4 ± 7.3) and ODI scores (27.5 ± 17.7) from preoperative (27.5 ± 17.7). MIS patients also reported significant decrease in ODI scores at six months postoperative, 20.2 ± 13.8 from preoperative 41 ± 15.7. Though there were improvements in all PRO domains at nine months and 1-year post-operative, these changes were not significant. The open cohort reported significant change from preoperative levels in PROMIS Physical Function and Pain Interference and ODI scores at three months, ODI scores at six months, and PROMIS physical Function, Pain Interference and Social Roles at nine months. Though there were improvements in all PRO domains at 1-year post-operative, these changes were not significant. Conclusions: The number of levels fused was the statistically significant surgical variable between the open and MIS groups, though surgical time, EBL and length of stay were lower in the MIS group. The open cohort reported more statistically significant changes from baseline PROs scores across more instruments and postoperative intervals than the MIS cohort. However, neither group reported statistically significant changes at one year postoperative from baseline preoperative in any PRO instrument. This is most likely due to the limited number of responses at one-year post-operative.

150

P378: Quantitative analysis of tissue injury markers after adolescent idiopathic scoliosis (AIS) correction: a prospective study of open vs. minimally invasive surgery

Matthew Geck ¹ , Devender Singh ¹ , Ashley Duncan ¹ , John Stokes ¹ , and Eeric Truumees ¹

¹ Spine, Ascension Texas Spine and Scoliosis, Austin, United States

Introduction: Minimally invasive surgery (MIS) offers a potentially less morbid treatment option for patients requiring stabilization of adolescent idiopathic scoliosis (AIS). Aim: To compare the tissue injury markers in AIS cohorts matched for Lenke type curve that had undergone either open or MIS. Materials and Methods: 39 patients who either underwent MIS or open corrections were consecutively enrolled. MIS or open approaches were surgeon selected based on curve magnitude, location, flexibility on bending films and the patient’s body habitus. Enrollment criteria included: age > 10 yrs and < 30 years; Lenke types were 1, 2 or 5; Cobb angle ranged 35°∼70°; caudal levels for open and MIS cases were L2 or above and L3 or above, respectively. Open approach included posterior spinal instrumentation and fusion with posterior column osteotomy. MIS technique was uniform in all patients using two or three para-midline incisions. The serum enzymes representing skeletal muscle injury (creatine kinase and aldolase) were analyzed on the day before surgery and days 1, 2, 3, 4, discharge, 3 weeks, 3 months and 6 months postoperatively. Results: MIS and open groups comprised of 19 and 20 patients, respectively. Mean patient age was 16 years in MIS and 15 years in open group. Mean pre-op Cobb angles for MIS and open differed significantly (52.8 ± 4.6° vs. 60.5 ± 5.8°). Number of spinal levels treated were similar between the two groups. Mean surgical time, blood loss and length of hospital stay were significantly greater for the open group (p < 0.05). Compared to the baseline, mean serum aldolase was significantly high on post-op day 2 for both the groups (MIS: 5.18 U/L vs. 9.8 U/L; Open: 5.36 U/L vs. 13.2 U/L). For all visits, open group had comparatively higher mean serum aldolase levels than their counterparts. Mean serum creatine kinase for open group was significantly higher than MIS group at post-op days 1, 2, 3, 5 and discharge (p < 0.05). For the both groups, mean creatine kinase was highest at post-op day 2. Mean creatine kinase and aldolase levels returned to the normal levels for both the groups at visits 3-week, 3- and 6-months post-op. Patient-reported pain and disability scores were similar. Both groups reported one complication each which resolved with interventions (MIS: wound drainage; open: CSF leak and lumbar drain). Conclusions: Our cohort data indicates that MIS technique for scoliosis correction is a viable option and may significantly reduce muscle injury during the acute post-op period. MIS technique may limit post-operative surgical morbidity.

179

P379: Comparative outcomes betwen percutaneous and endoscopic radiofrequency ablation of the sacroiliac joint complex in th treatment of sacroiliac joint pain patients: systematic review and meta-analysis

Saran Pairuchvej ¹ and Jatupon Kongtharvonskul ²

¹ Orthopedics Department, Queen Savang Vadhana Memorial Hospital, Cholburi, Thailand ² Department of Clinical Epidemiology and Biostatistics, Faculty of Medicine Ramathibodi Hospital, Mahidol University, Bangkok, Thailand

Introduction: The sacroiliac joint (SIJ) is a junction between the spine (sacrum) and the pelvis (ilium). The SIJ complex is one of the sources of chronic low back pain compromising between 15 and 25% of cases. The treatment of SIJ pain is challenging with no easy solution. Percutaneous radiofrequency ablation (RFA) is a common practice. However the limitation of this treatment due to no visualization of the medial branch at the facet joint L5/S1 resulting in different area is commonly targeted. Recently, endoscopic RFA of SIJ allows better visualization nerve and the surrounding ligamentous tissue. But there is no current consensus regarding which method is the most suitable. Therefore we conducted a systematic review and indirect meta-analysis to compare the post-operative outcomes among SIJ treatment and identify which method is the best for surgical treatment of SIJ pain patients. Material and Method: We searched all prospective and retrospective studies that reported post-operative outcomes of percutaneous and endoscopic RFA for surgical treatment of SIJ from the PubMed and Scopus databases up to 5 January 2022. Data were independently extracted by two reviewers. An indirect meta-analysis was applied to assess treatment outcomes. Results: 18 cohort studies (N = 734 patients) met inclusion criteria. Interventions were endoscopic (N = 70 patients) and percutaneous RFA (N = 664 patients). A direct meta-analysis showed that the UMD of pain (numeric rating scale) after surgery in endoscopic RFA were significantly difference of -3.5 (95%CI: 4.34 to2.67), -4.76 (95%CI: -6.43 to -3.10), -4.33 (95%CI: -6.60 to -2.06) scores at 1, 3, 6 months while percutaneous RFA groups were significantly difference of -4.19 (95%CI: -5.21 to -3.18), -3.56 (95%CI: -3.95 to -3.17), -3.62 (95%CI: -4.23 to -3.00) and -3.42 (95%CI: -4.07 to -2.76) scores at 1, 3, 6 12 months when compared to before surgery. The UMD of Oswestry Disability Index (ODI) score after surgery were better of -9.20 (95%CI: -11.70 to -6.70), -19.51 (95%CI: -40.25 to 1.22) and -24.04 (95%CI: -51.54 to 3.45) scores at 1, 3, 6 months while percutaneous RFA groups were significantly difference of -8.66 (95%CI: -14.74 to -2.58) and -7.17 (95%CI: -9.95 to -4.39) at 3 and 6 months when compared to before surgery. For indirect meta-analysis showed that effects of pain of endoscopic RFA were -0.69 (95%CI: -4.89 to 3.51) scores, 1.22 (95%CI: -0.13 to 2.58) scores and 0.77 (95%CI: -1.25 to 2.79) scores at 1, 3 and 6 months when compared to percutaneous RFA group. While the ODI of endoscopic RFA were -9.70 (95%CI: -56.40 to 36.99) and -17.15 (-87.27 to 52.97) at 3 and 6 months when compared to percutaneous RFA group. There have no statistically significant differences between endoscope and percutaneous RFA in all outcomes. In term of complications, there have no complications of both groups. Conclusions: Although there was no significant difference in pain and disability scores between endoscopic and percutaneous RFA, the superiority of surgical time, cost of surgery, wound size and technical demand indicated that percutaneous RFA offer more effective therapy for SIJ pain than endoscopic RFA surgery.

359

P380: Footdrop and spine endoscopy: is the future here?

Emanuel Homem ¹ , Joana Rodrigues ¹ , Tiago Canas ¹ , João Cruz ¹ , Ricardo Simoes ¹ , and Luís Soares ¹

¹ Hospital do Divino Espírito Santo, Ponta Delgada, Portugal

Introduction: Acute and progressive foot drop are well-known entities. The most common cause is degenerative lumbar spinal disease (with 52% of causes secondary to disc herniation and 35% to spinal stenosis). The inability of ankle dorsiflexion may lead to multiple falls and injuries, resulting in substantial impairment and decreased quality of life. Percutaneous endoscopic discectomy is being increasingly used as solution for this condition. The authors describe a case of acute right foot drop caused by a L3-L4 disc herniation with lumbar canal stenosis treated with percutaneous endoscopic transforaminal. The goal is to highlight the ease of access and great outcome to support minimally invasive solution for these cases. Material and Methods: A 40-year-old male presents with sudden onset of severe back pain (VAS 10/10) with right foot drop while getting up from a chair. He has past medical history of progressive left footdrop due to paramedian L4-L5 herniated disc already submitted to percutaneous translaminar and transforaminal treatment with good functional outcome. On examination, the patient had a positive straight leg test at 30° with right ankle and toe extension’s muscle strength of 1/5 and hypoesthesia of right L4 dermatome. Deep tendon reflexes were normal and without cerebellar signs. He had previous decreased contralateral ankle strength (4/5) and no other neurological deficits. His bladder function was normal with intact perianal sensation. MRI diagnosed a disc herniation at right L3-L4 level (inferior migrated) with spinal canal stenosis due to ligamentum flavum hypertrophy. Next day, patient underwent percutaneous transforaminal endoscopic foraminotomy, discectomy and lumbar decompression at L3-L4 level by an 1cm incision. Results: Postoperative period was uneventful: the patient was mobilized on the same day of operation and discharged the next day with the improvement of ankle and toe dorsiflexion to 4/5 muscle strength and slight hyposesthesia. At 3 months follow-up, his muscle strength was recovered and hyposthesia resolved near completely. Conclusion: Lumbar disc herniation with canal stenosis should be considered in patients presenting with foot drop. Early surgery may prevent severe late neurological consequences and has a favorable outcome. The objective of using endoscopy is to provide a safe and minimally invasive approach, even to address multiple lumbar levels with early postoperative mobilization and faster return to work.

373

P381: Full-endoscopic foraminotomy in stable lytic lumbar listhesis. A multicenter case series and data analysis

Facundo Van Isseldyk ^1,2 , Javier Quillo-Olvera ³ , Cristian Ricardo Correa Valencia ¹ , Jung-Hoon Kim ⁴ , Yanting Liu ⁴ , David Del Curto ¹ , and Jin-Sung Luke Kim ⁴

¹ Latinamerican Endoscopic Spine Surgery Society (LESSS)

² Hospital Privado de Rosario, Neurosurgery, Rosario, Argentina

³ Anahuac University, School of Medicine, H+ Hospital, Querétaro, Mexico

⁴ Spine Center and Department of Neurosurgery, Seoul St. Mary’s Hospital, College of Medicine, the Catholic University of Korea, Seoul, South Korea

Introduction: Lytic lumbar spondylolisthesis (LLS) affects 8.2% of the worldwide population. Although commonly associated in the surgical community with segmental instability , only a small percentage of cases demonstrate actual radiological instability. However, even in stable cases neurological symptoms can occur as a result of radicular compression in lateral recess or foraminal area. Open foraminal decompression usually requires a concomitant fusion due to the muscular, osseus and ligament disruption caused by the surgical approach. In this setting, full-endoscopic approaches could decompress the affected root while preserving segmental stability, avoiding the need for instrumented fusion. Material and Methods: We present a case-series of 17 consecutive patients with low-grade, stable LLS and concordant symptomatic radiculopathy, treated with full endoscopic foraminotomy. Patients baseline and imaging characteristics, as well as preoperative back pain VAS, leg pain VAS and ODI were obtained. Included patients were treated by four of the authors with endoscopic foraminotomy according to the “module-based” approach previously published. Surgery planning and execution was performed following the selected modules. Degree of intervertebral disc breach during surgical procedure was also recorded. Outcome variables included back pain VAS, leg pain VAS and ODI. Postoperative CT scans and dynamic X-Rays were obtained to assess the amount and precision of bony resection and segmental stability. Follow-up consultation was performed every 6 months. Paired T-Test was used for normally distributed variables, while the remaining was analyzed with Wilcoxon’s sum rank test. Results: 9 male patients and 8 female were included. The mean age was 68 years. In 76% of the patients a transforaminal approach was used, while the remaining 24% had an interlaminar contralateral approach. 76.5 % of patients had high Pfirmann values (4-5). Postoperative values of ODI, leg pain VAS and back pain VAS showed statistically significant reduction compared with preoperative values. No intraoperative or postoperative complications were observed. One patient had high-level disc breach during surgical procedure (wide annulotomy and intersomatic discectomy) and subsequently developed radiological instability that required lumbar fusion as a separate procedure. No leg pain recurrence was observed in the follow up period. Conclusion: In the present series, full-endoscopic foraminotomy allowed to successfully control radicular symptoms in patients with LSS, while preserving segmental stability in the great majority of cases. Only one patient developed postoperative instability and required subsequent fusion, possibly related to high-level disc space breach. This is, to our knowledge, the first case series of patients with LSS treated with full-endoscopic foraminotomy ever published.

392

P382: How can cement leakage be prevented in kyphoplasty? Technical report and clinical study

Inan Uzunoglu ¹ , Gokhan Gurkan ² , Ceren Kizmazoglu ³ , Rafet Ozay ¹ , Murat Sayin ² , and Nurullah Yuceer ²

¹ Neurosurgery, Ankara Diskapi Yildirim Beyazit Training and Research Hospital, Turkey

² Neurosurgery, Izmir Katip Celebi University, Ataturk Training and Research Hospital, Ankara, Istanbul

³ Neurosurgery, Dokuz Eylul University Medicine Faculty, Izmir, Turkey

Introduction: Vertebral compression fractures can occur due to many different reasons. Kyphoplasty is at the forefront in the treatment of these fractures. The most worrying complication of kyphoplasty is cement leakage. We wanted to share the effectiveness of the technique we used in our series in preventing cement leakage. Material and Methods: 300 patients were retrospectively screened in our clinic. While group A (150 patients) was operated on with classical kyphoplasty techniques, while group B(150 patients) used similar methods before cement injection, the suitability of cement fluidity for injection is determined by pushing cement fillers and forming a ring on itself. After reaching this consistency, it is sent to the corpus bilaterally or unilaterally. At this stage, the corpus is divided into three equal areas in the craniocaudal plane on the lateral x-ray, and the operation is terminated if the cement passes into the most posterior area. Results: While some of our patients were treated with a single vertebra in the same session, some of our patients were treated with 4 vertebrae in the same session. Cement leakage was detected in 123 (30.8%) of 400 operated vertebrae. Of these 123 vertebrae, 16 (13%) were in Group B and 107 (87%) were in Group A, a statistically significant difference was found (p < 0.001). Epidural leakage in 5 (4.1%) vertebrae in total were detected in 3 vertebrae in Group A and 2 vertebrae in Group B. While intradiscal leakage was detected in 44 (35.8%) vertebrae, all of them were in Group A. Extracorporeal leak was detected in 62 (50.5%) vertebrae, while only 8 of them were in Group B. Intravasal leak was detected in only 12 (9.8%) vertebrae, equally in both groups. There was a statistically significant difference in terms of cement leakage between vertebrae whose posterior wall was not intact and the others (p < 0.05). At the same time, statistically significant differences were found in A3 and A4 fractures according to the AO spine classification compared to other fractures and in patients who underwent more than one vertebra operation in the same session (p < 0.05). Between Group B and Group A, the dose of scope was statistically significant in favor of Group B (p < 0.05). In Group B, there was a statistically significant difference between cement viscosity, fracture type and etiology, trauma-operation time, type of balloon used, type of intervention, and cement amount. no significant differences were found (p > 0.05). However, in cases where the amount of injected cement exceeded 7cc, it was statistically revealed that cement leakage could increase in both groups (p < 0.05). Conclusion: Kyphoplasty is an effective treatment method for vertebral fractures, but a simple surgical procedure can turn into a very catastrophic one after cement leaks may develop. There are techniques described in the literature to prevent cement leakage. however, none of them have been fully successful. In the literature, cement leakage ranges between 5-87%. In our study, it was determined that it could be applied as an effective technique, with a rate of 7.7%.

394

P383: When to consider stand-alone lateral lumbar interbody fusion: is there a role for a comeback with new implants?

Cristiano Magalhães Menezes ¹ , Erica Godinho Menezes ¹ , Jahangir Asghar ² , and Alfredo Guiroy ³

¹ Orthopedics, Columna Institute, Belo Horizonte, Brazil

² Spine Surgery, Elite Spine Health and Wellness, Fort Lauderdale, United States

³ Orthopedics, Hospital Español, Mendoza, Argentina

Introduction: Degenerative disc disease is one of the most common conditions treated by spine surgeons and is a common cause of dysfunction with a negative impact on quality of life. Lateral lumbar interbody fusion (LLIF) is a minimally invasive technique proven to be useful for indirect decompression of the spinal canal and foramina with high fusion rates and a very low risk of complications. The objective of this study is to perform a comprehensive review of the literature about the role of stand-alone lateral lumbar interbody fusion (LLIF). Material and Methods: A MEDLINE review was conducted including studies about stand-alone LLIF for any condition. The opinions of the authors were also considered. Studies that included biomechanical, cadaveric, or clinical aspects of stand-alone cages were revised to obtain data about the pros, cons, and limitations of the technique. Comparative studies with 360° (lateral + posterior) fusions were also analyzed. Results: A total of 36 studies were identified. After reviewing the abstracts, 18 full articles of interest for the objective of this review were analyzed. Recommendations based on the literature were made. Although most of the recommendations in the literature were about augmentation with pedicle screws, there may be a role for stand-alone LLIF in some particular cases. Specific technical aspects should be considered to reduce the failure rate. Conclusion: Although there might be some specific indications for stand-alone LLIF, but despite the high subsidence rate and low fusion rates, it should be considered an exception rather than the rule.

398

P384: Single position spine corpectomies. A multicentric study

Alfredo Guiroy ¹ , Cristiano Menezes ² , J. Alex Thomas ³ , Ashish Patel ⁴ , Gaston Camino-Willhuber ⁵ , Michael Galgano ⁶ , and Jahangir Asghar ⁷

¹ Spine Surgery, Elite Spine Health and Wellness Center, Fort Lauderdale, United States

² Columna Institute, Belo Horizonte, Brazil

³ Atlantic Neurosurgical and Spine Specialists, Wilmington, United States

⁴ Spine Surgery, The Spine Center, Duly Health and Care, Illinois, United States

⁵ Hospital for Special Surgery, New York, United States

⁶ Neurosurgery, University of North Carolina, North Carolina, United States

⁷ Elite Spine Health and Wellness Center, Fort Lauderdale, United States

Introduction: Single position spine surgery for disc pathologies has been gaining momentum as it has proven to reduce operative time, blood loss and hospital length of stay with similar or better outcomes than traditional dual-position surgery. The objective of this study is to describe and discuss a multicentric case series of patients treated by single position corpectomy (SPC). Material and Methods: Multicenter retrospective study of patients treated using a single position corpectomy (SPC) of the thoracic or lumbar vertebra. The following data was collected from each center involved: demographics, diagnosis (trauma, tumor or infection), neurological status, comorbidities, surgical approach and procedure (single position lateral or prone lateral), number of instrumented levels, intraoperative parameters (length of surgery, estimated blood loss, transfusion), postoperative parameters (time to mobilization, length of stay, days spent in the Intensive care unit), complications, reoperation and readmissions and radiological variables. The minimum follow-up for inclusion was six months. Results: 34 patients were included (24 males, 10 females), with a mean age of 51.2 years. The diagnosis that motivated the corpectomy were: trauma (n = 26), tumor (n = 5), infections (n = 2) and a revision PSO (n = 1). The most common level affected was L1 (n = 11) followed by L3 (n = 8) and L2 (n = 6). In 27 cases the corpectomy was done in lateral single position and in 7 in prone. Mean surgical time was 173.2 min, estimated blood loss 498 ml and length of hospital stay 8.1 days. Segmental angle average changes were from 19º kyphosis to 2º or lordosis. As complications we had 2 returns to the operating room (1 persistent stenosis and 1 wound infection). Conclusion: This is the first multicentric series of patients that underwent single position corpectomy and fusion. This technique has shown to be safe and effective to treat a variety of spinal conditions with a relatively low rate of complications. More series are required to validate this technique as a possible standard approach when thoracolumbar corpectomies are indicated.

446

P385: Sagittal alignment change after two-level posterior endoscopic cervical foraminotomy: a single-surgeon's experience with one year follow up

Tzu Chiang Peng ¹ and Yu-Jen Lu ²

¹ Neurosurgery Department

² Neurosurgical Department, Chang Gung Memorial Hospital, Taoyuan City, Taiwan

Purpose: Cervical radiculopathy is a disabling disease. When conservative treatment fails to abate the symptoms, surgical intervention is an option. Although there are some case-series and biochemical analyzing the safety of single level posterior endoscopic cervical foraminotomy (PECF), the feasibility and safety of two-level PECF are not reported. The primary purpose of this study is to compare mono-level and two-level PECF clinical and radiologic outcomes. Materials and Methods: Medical records were reviewed between March 2019 and December 2021 in a single medical center. 37 patients with 56 levels of radiculopathy were enrolled, who received mono-level (N = 18) or two-level PECF (N = 29) according to their clinical symptoms and pre-operative cervical spinal MRI report. All of the cases were performed by one senior operator. Before the operation, the patients received four-view cervical roentgenogram (anteroposterior, lateral neutral, lateral flexion, lateral extension) and were assessed arm-visual analogue scale(arm-VAS). The following-up radiologic and clinical outcomes were performed in outpatient visit 12 months after the surgery. Radiologic parameters were assessed, inclusive of cervical curvature, disc index and dynamic sagittal plan translation. Results: The most common affected levels were C5-C6 and C6-C7. The clinical outcomes of both groups were excellent and compatible(both median pre-operative and post-operative arm-VAS were 7 and 1 respectively ). Overall, there were no significant changes in radiologic parameters after the operation. In two-level PECF group, the cervical lordosis slightly increased from 11.7 to 13.5, after the operation. In mono-level PECF group, the cervical lordosis decreased from 9.4 to 8.1. Despite being not meaningful statistically, however, we found a trend toward increasing sagittal plan translation in the lower level of two-level PECF, as a hint of impaired stability. Conclusions: Given appropriate indication, single incision two-level PECF is an effective and safe option for cervical radiculopathy.

Key words: Cervical radiculopathy, Posterior endoscopic cervical foraminotomy, Two-level, Stability, Sagittal profile

460

P386: Unilateral biportal endoscopic translaminar approach to treat up-migrated lumbar disc herniation: 12 cases report

Kang Suk Moon ¹ and MinSeung Jeong ²

¹ Neurosurgery, Gimpo Wooridul Spine Hospital, Seoul, South Korea ² Orthopedic Surgery, Hospital Angeles, Mexico City, Mexico

Introduction: MDH are difficult to reach and completely remove using a microscope. The objective of this study was to introduce an effective and safe surgical approach for up migrated LDH by UBE translaminar keyhole approach. Material and Methods: Twelve patients with high-grade and very high-grade up LDH treated with a UBE translaminar keyhole approach between March 2021 and February 2022 were reviewed in this study. Clinical outcomes were assessed including preoperative, immediately postoperative and one-month follow up visual analog scale (VAS) for back and leg pain and MacNab Criteria. Results: Nine male and three female patients underwent surgery using UBE translaminar keyhole approach. Seven patients showed high-grade up migrated LDH, and five patients showed very high-grade up migrated LDH (above the pedicle level). In all cases, the migrated LDH was removed successfully confirmed by postoperative magnetic resonance imaging. The improvements of VAS for back pain were 4.5 (SD = 3.1) to 2.0 (SD = 1.0) and 1.0 (SD = 1.0) for immediately postoperative and one-month follow-up, showing a statistically significant difference (p < 0.001). Improvements of VAS for leg pain was 6.5 (SD = 2.5) preoperatively to 2.3 (SD = 1.1) and 0.8 (SD = 0.4) immediately postoperative and one-month follow up respectively, showing a significant difference (p < 0.001). According to MacNab criteria, we observed excellent outcomes in 66.6% and good outcomes in 33.3%. Conclusion: Translaminar discectomy using UBE is a minimally invasive surgical technique that embraces the advantages of biportal endoscopy and translaminar approach to treat uo migrated LDH. It could be considered as a feasible alternative surgical options to treat high-grade up migrated LDH.

490

P387: Technique notes and preliminary outcome of transforaminal approach by unilateral biportal endoscopic spinal surgery for lumbar extraforaminal disc herniation

Chih-ying Wu ^1,2 and Cheng-Di Chiu ^3,4

¹ Neurosurgery, China Medical University Hsinchu Hospital, Hsinchu, Taiwan

² Graduate Institute of Integrated Medicine ³ Neurosurgery, China Medical University Hospital, Taichung, Taiwan ⁴ Graduate Institute of Biomedical Science, China Medical University, Taichung, Taiwan

Introduction: Lumbar extraforaminal disc herniation (LEFDH) accounts for approximately 7-12% of all lumbar herniation discs. It can cause severe radiculopathy and disability. Unlike the posterolateral lumbar dis herniations, midline approach for LEFDH is challenge due to the bone restriction. Minimally invasive spine surgery has seen a breakthrough progress in recent decades. The purpose of minimally invasive spine surgery is to reduce normal tissue damage, preserve normal anatomical structures, decrease patient stress, and achieve the same or better prognosis as open surgery. At present, the tools of minimally invasive spine surgery are microscopes and endoscopes. Endoscopic spine surgery included uniportal and biportal endoscope. Both have their advantages and advocates. According to the current literature, there seems to be no significant difference in the comparison of operation time and patient prognosis. However, there was two advantages of biportal endoscopic spinal surgery (BESS). The first is using of conventional spine surgical instruments like open surgery. Second is protecting the neural structures by assistant retractor is safer than the uniportal endoscopic spine surgery. Hence, in this article, we evaluate the clinical outcome of LEFDH removal by transforaminal approach of unilateral BESS. Material and Methods: We collected 13 patients with LEFDH from January 2021 to August 2022. All patients scheduled transforaminal approach of unilateral BESS performed by one single neurosurgeon. The BESS surgical steps are as follows: First, we identified the surgical level and the tips of transverse processes (TP) under C-arm fluoroscopy guiding. Two skin incisions were made at the tip of TP on the ipsilateral side. Then the two portal surgical instruments are inserted into the base of the TP respectively. The surgical space is enlarged and identified the Kambin's triangle, lateral border of isthmus and superior articular process. Foraminoplasty may be performed with drilling and Kerrison punch if necessary. Then, we could remove the LEFDH safely by assistant retractor. We recorded the operation time, the number of operation level, complications, and hospital days. Visual analog scale (VAS) was measured pre- and postoperatively. After discharge, Modified Macnab criteria was analyzed for outcome evaluation. Results: The mean age of the patients was 68.7 ± 8.8 years old. There were 8 males and 5 females. The mean operation time was 97.8 ± 26.3 min. The mean follow-up time was 229.9 ± 8186 days. The average length of hospital stay was 3.5 ± 0.8 days. Pre- and postoperative VAS were 7.5 ± 80.8 and1.8 ± 81.1, respectively (p value < 0.001). The Modified Macnab criteria after discharge: excellent 23.1%, good 69.2%, fair 7.7%. Only one complication is dura tear but no neurological deficit. Conclusion: BESS requires experienced and skillful surgical technique for nerve root protection and herniation disc removal. According to our statistical results, the transforaminal approach of unilateral BESS is quite effective, safe, and alternative method for the treatment of LEFDH.

499

P388: Minimally invasive TLIF options for lumbar spondylolisthesis

Gabriel Tender ¹

¹ Neurosurgery, Louisiana State University, New Orleans, United States

Introduction: Previous studies have shown that minimally invasive spinal techniques result in shorter hospital stays and quicker recovery. Minimally invasive transforaminal lumbar interbody fusion (MI TLIF) has become the preferred fusion method for the L5-S1 and / or L4-5 levels at our institution. However, patients with spondylolisthesis may represent a challenge, due to the distorted anatomy. Material and Methods: We review our experience with MI and standard open TLIF for patients with spondylolisthesis within the past 4 years. Results: A total of 75 patients underwent MI TLIF at our institution between Jan 2016 and Dec 2020, whereas 27 patients underwent standard open TLIF. 45 of the MI TLIF patients (60%) had radiographic signs of spondylolisthesis. The majority exhibited grade 1 spondylolisthesis (33, 44%), with the remainder being grade 2 (12, 16%). One patient in the MI TLIF spondylolisthesis group had an S1 pedicle fracture after a fall and had to have that screw repositioned. Of the 39 patients in the MI TLIF group (52%) who presented for their 1-year follow-up CT, 37 (94%) had a solid fusion, with one patient in each group not showing bridging bone through the treated interspace. Similarly, 19 of the 20 patients (95%) in the standard open TLIF group who presented for the 1-year follow-up CT showed a solid fusion. Conclusion: MI TLIF for patients with grade 1 or 2 spondylolisthesis yields comparable fusion results with the standard techniques, with shorter hospitalization and quicker recovery. Certain surgical maneuvers may help improve fusion rates and screw placement accuracy.

587

P389: Cage positioning significantly impacts lumbar lordosis and disc space restoration following minimally invasive lateral lumbar interbody fusion

Tariq Issa ¹ , Yunsoo Lee ¹ , Khoa Tran ¹ , Mark Lambrechts ¹ , Delano Trenchfield ¹ , Parker Brush ¹ , Jeremy Heard ¹ , Sebastian Fras ¹ , Jose Canseco ¹ , Alan Hilibrand ¹ , Alexander Vaccaro ¹ , Christopher Kepler ¹ , and Gregory Schroeder ¹

¹ Division of Spine Surgery, Rothman Orthopaedic Institute, Philadelphia, United States

Introduction: Lateral lumbar interbody fusion (LLIF) offers the reliability of lordotic correction seen in anterior lumbar surgery while also supporting a minimally invasive approach that can reduce complications. While cage geometry and cage placement have been suggested to play an integral role in radiographic outcomes in various interbody fusion approaches, the role of these parameters remains unclear in LLIF procedures. The objective of our study was to evaluate patient and surgical factors that predict increased overall lumbar lordosis and segmental lordosis correction following an LLIF. Material and Methods: A retrospective review was conducted of all patients who underwent 1- or 2-level LLIF. Pre-operative, initial post-operative, and six-month post-operative measurements of lumbar lordosis, segmental lordosis, anterior disc height, and posterior disc height were collected from standing lateral radiographs for each patient. Cage placement was measured utilizing center point ratio (CPR) on immediate post-operative radiographs. Spearman correlations were used to assess associations between cage lordosis and radiographic parameters. Multivariate linear regression was performed to assess independent predictors of outcomes. Results: A total of 105 levels in 78 unique patients were included. Most procedures involved fusion of one-level (N = 50, 64.1%), most commonly at L3-L4 (46.2%). Despite no differences in baseline segmental lordosis, patients with anteriorly or centrally placed cages experienced the greatest segmental lordosis correction immediately (anterior: 4.81 mm and central: 4.46 mm vs. posterior: 2.47 mm, p = 0.0315) and at six-months post-operatively, and patients with anteriorly placed cages had greater overall lordosis correction post-operatively (6.30 deg, p = 0.0338). At six-month follow up, patients with anteriorly placed cages experienced the greatest increase in anterior disc height (anterior: 6.24 mm vs posterior: 3.69 mm, p = 0.0122). Cages placed more posteriorly increased the delta posterior disc height post-operatively (posterior: 4.91 mm vs anterior: 1.80 mm, p = 0.0001) and at six-months (posterior: 4.18 mm vs anterior: 2.06 mm, p = 0.0255). There were no correlations between cage lordosis angle and outcomes. On multivariate regression, anterior cage placement predicted greater six-month improvement in segmental lordosis, while posterior placement predicted greater six-month improvement in posterior disc height. Percutaneous screw placement, cage lordosis angle, and cage height did not independently predict any radiographic outcomes. Conclusion: LLIF procedures reliably improve lordosis and increase intervertebral disc space. Anterior cage placement improves lordosis angle greater than posterior placement, which better corrects sagittal alignment, but there is still a significant improvement of lordosis even with a posteriorly placed cage. Posterior cage placement provides greater restoration in posterior disc space height, maximizing indirect decompression, but even the anteriorly placed cages provided indirect decompression. Cage parameters including cage height, lordosis angle, and material do not impact radiographic improvement.

678

P390: An effective treatment option for nonuion of Kummell's desease after treated with PKP

Hui Liu ¹ and Deqing Luo ¹

¹ Department of Orthopaedic Surgery, The Affiliated Southeast Hospital of Xiamen University, Zhangzhou, China

Introduction: Percutaneous kyphoplasty (PKP) has been widely used to treat Kummell’s disease and provides good results in patients with persistent pain and an intact posterior wall. However, intravertebral nonunion between the cement and bone, like a ball socket effect after percutaneous vertebroplasty (PVP), can cause persistent severe pain and sagittal kyphosis, even neurological dysfunction. The optimal treatment for nonunion of Kummell’s disease treated With PKP remains controversial and unclear. The purpose of this study was to investigate the efficacy of staged anterior and posterior minimal invasive approach (OLIF and multifidus approach) in treating nonunion of Kummell’s disease treated with PKP. Method: We retrospectively evaluated all patients who underwent nounion of Kummell’s disease after treated With PKP with between January 2019 and June 2022. Patients with a minimum follow-up of 12 months were included. The patients were treated with SRS 2-3 osteotomy and long segment fixation with screw augmentation through posterior multifidus approach firstly, secondly expandable mesh cage reconstruction of anterior column were carried out through OLIF approach. Anterior edge height of injured vertebrae, kyphosis Cobb angle were measured to evaluate the radiological result. Patient clinical outcomes were quantified via Oswestry Disability Index (ODI), Visual Analog Scale (VAS) Back, preoperatively and postoperatively and at 3, 6, and 12 months follow-up. Analyses were performed using IBM SPSS Statistics software, v24.0 (IBM SPSS, Chicago, IL). Results: All patients were followed up 12-28 months, with an average of 15.3 months. The average operative duration was 126 ± 25 minutes(posterior) and 115 ± 17 minutes(anterior), and the average intraoperative blood loss was 245 ± 45 mL (posterior) and 168 ± 27 minutes(anterior). ODI, anterior vertebral heights, and kyphotic Cobb angles were improved significantly at 1 week after surgery compared the preoperative examinations, and were well maintained at the final follow-up evaluation. There was no instrumentation failure in our study during follow-up. Conclusion: staged anterior and posterior minimal invasive approach (OLIF and multifidus approach) is a safe and effective surgical option for treating nonunion of Kummell’s disease treated with PKP.

734

P391: Transforaminal lumbar endoscopic surgery on the limits: experience from extreme cases management in a single tertiary center

Nikolaos Gkantsinikoudis ¹ , Christos Siopis ¹ , and Stylianos Kapetanakis ^1,2

¹ Spine Department and Deformities, Interbalkan European Medical Center, Thessaloniki, Greece

² Department of Minimally Invasive and Endoscopic Spine Surgery, Athens Medical Center, Athens, Greece

Introduction: Transforaminal Lumbar Endoscopic Decompression (TLED) constitutes a novel, minimally invasive and atraumatic technique recruited for surgical management of a plethora of spine ailments. Principal indication for TLED conduction is Lumbar Disc Herniation (LDH). However, considering the substantial advantages of technique in comparison with conventional open surgical methods, spectrum of TLED indications has been demonstrated to constantly widen in recent literature. Recruitment of TLED for surgical management of extreme cases of foraminal stenosis (FS) encountered in the framework of Adult Degenerative Scoliosis (ADS), Adjacent Segment Disease (ASD) post previous fusion surgery and postoperative Recurrent Foraminal Stenosis (RFS) after open decompression surgery represents a feasible strategy according to current literature reports, demonstrating promising clinical outcomes. Hence, we hereby present our experience with management of extraordinary cases of FS with TLED surgery. Material and Methods: Twenty-one (21) individuals with clinically remarkable secondary FS on the ground of ASD (n = 7), ADS (n = 6) and previous open decompression surgery (n = 8) were included in this prospective investigation. After meticulous clinical and radiologic investigation, all enrolled patients underwent TLED (outside-in technique) in 2018-2019. Postoperative evaluation was conducted in predetermined follow-up intervals via clinical examination and performance of specific patient-reported outcome measures as Visual Analogue Scale (VAS), modified McNab criteria and Oswestry Disability Index (ODI). All patients were followed-up for an at least 1-year period (mean: 1.4 years). Results: No major perioperative complications were observed. Clinical management of enrolled patients with TLED was successful in all cases. Operated segments were L3-L4 (19.0%), L4-L5 (52.4%) and L5-S1 (28.6%). VAS and ODI measures demonstrated a statistically significant (p < 0.05) improvement in all patient immediately postoperatively, which was constantly observed until the end of follow-up. Overall clinical outcomes, as analyzed with modified MacNab criteria, were depicted to be excellent in 12 patients, good in 6 and fair in 3 patients. Conclusion: According to our results from this limited case-series analysis, TLED represents a safe and effective surgical alternative for management of patients with secondary FS on the ground of ADS, ASD post fusion surgery and postoperatively after previous open decompression surgery.

797

P392: Ethnic differences in asian and caucasian sacroiliac joint anatomy for surgical planning of minimally invasive sacroiliac joint fusion

Yu-Cheng Liu ¹ , Christopher Wu ¹ , Tsung-Jen Huang ² , Ching-Yu Lee ² , Po-Yao Wang ² , Hiroaki Koga ³ , Daniel Cher ⁴ , W. Carlton Reckling ⁴ , Pei-I Tsai ⁵ , and Meng-Huang Wu ²

¹ College of Medicine

² Department of Orthopaedics, Taipei Medical University Hospital, Taipei, Taiwan

³ Department of Orthopedic Surgery, Kikuno Hospital, Minamikyushu, Japan

⁴ SI-BONE, Inc., United States ⁵ Industrial Technology Research Institute, Taiwan

Introduction: Lateral sacroiliac joint (SIJ) fusion has been used as a treatment for SIJ pain. However, the SIJ anatomy of Asian populations for lateral SIJ fusion has not been well studied. Therefore, this study aimed to compare the SIJ anatomy between Asians and Caucasians. Material and Methods: In this study, 86 symptomatic patients (47 Caucasians, 39 Asians) were included. 2D/3D image analysis of 12 measures of sacral and SIJ anatomy: inferior and superior articular limb length, SIJ-height, SIJ-surface area, and 4 transverse and 4 anterior-posterior measurements of the sacral ala at specified levels were obtained. Multivariate analysis was used to calculate systematic differences across populations controlling for total body height, symptoms, and sex. Results: Most sacral/SIJ measurements were moderately correlated with total body height. The anterior-posterior thickness of ala at level of S1 body was smaller in symptomatic Asian-women vs. Caucasian-women (by 3.5 mm, p = 0.0110). Most measurements were above standard surgical thresholds for transiliac placement of devices, which would allow safe placement in nearly all patients (97.7%). Conclusion: The SIJ anatomy of Asian population is positively correlated with body height. The shorter stature of Asian populations compared to Caucasians may be important for preoperative evaluation to the placement of transiliac fusion implants.

803

P393: Endoscopic transforaminal lumbar discectomy - preliminary clinical results

Arnaldo Sousa ¹ , Sara Diniz ¹ , Tiago Barbosa ¹ , and Paulo Costa ¹

¹ Orthopedics, Centro Hospitalar e Universitário do Porto, Porto, Portugal

Introduction: Minimally invasive spine surgery has grown exponentially in recent years, with the development of new techniques and suitable surgical instruments. This has become advantageous in the treatment of degenerative spinal pathology, as it allows to minimize possible surgical complications associated with age and comorbidities of the patient, compared to the conventional “open” surgery. The aim of this study was to evaluate the clinical outcomes of patients undergoing treatment for lumbar disc herniation via endoscopic transforaminal approach. Material and Methods: A retrospective study of all patients consecutively submitted to endoscopic transforaminal lumbar discectomy by the same surgeon between September 2018 and May 2021 was performed. Results: A total of 40 patients were included (24 (60%) men, 16 (40%) women). The mean age was 55 years. The mean follow-up period was 17 months [12-36 months]. Most patients (82%) had a herniated disc in a foraminal location, 57% at L4-L5, 25% at L3-L4 and 18% at L5-S1. A statistically significant clinical improvement was recorded postoperatively compared to preoperatively on the Oswestry Disability Index (23 ± 3.6 vs 62 ± 3.3; p < 0.005) on the Visual Analog Low Back Pain Scale (3.6 ± 0.6 vs 7.4 ± 0.6; p < 0.005) and VAS leg pain (2.9 ± 0.6 vs 8.6 ± 0.3; p < 0.005), respectively. There were no surgical complications in the immediate postoperative period. Recurrence of complaints occurred in 8 patients (20%), and of these, 4 patients (10%) underwent surgical revision via an “open” approach within an average period of 11 months after the endoscopic procedure. Conclusion: Transforaminal endoscopic surgery is a safe and effective alternative in the treatment of patients with foraminal lumbar disc herniation. Studies with a longer follow-up period and with a greater number of patients are needed to validate the results of this procedure.

908

P394: Endoscopic treatment of symptomatic lumbar epidural cysts

Karel Willems ¹ and Fred Ruythooren ¹

¹ Orthopedie, AZ Delta Roeselare, Roeselare, Belgium

Introduction: Lumbar epidural cysts are a rare cause of spinal cord or nerve root compression. Conventionally, symptomatic cases are treated by open surgical decompression or percutaneous infiltration techniques. However, we believe the rise of full endoscopic spinal surgery offers a sage and reliable alternative to conventional methods due to its minimal invasive nature, maintaining the ability to directly visualize the underlying pathology. Materials and Methods: We describe the resection technique of the three most commonly epidural lumbar cysts: facet cysts, flavum cysts and blaastrup cysts. Results: Each type of the cysts need a different type of endoscopic treatment. Flavum cyst is localised more lateral, adherent at the facet joint. Partial resection of the medial part of the facet joint is started, followed with peeling the cyst wall of the adjoining dura/radix. The more dorsal located flavum cysts are peeled off the dura and resected as the are not as densely adhered to the thecal sac. Blaastrup cyst needs a spacious central decompression, achieved by a partial resection of the lamina and the base of the spinous process. Conclusion: Full endoscopic surgical decompression offers a safe, reliable and minimal invasive alternative in the treatment of symptomatic lumbar epidural cysts.

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P395: Long term follow-up of MIS-TLIF for patients with degenerative lumbar disease - Minimally invasive approach reduced adjacent segment disease

Akihito Wada ¹ , Katsunori Fukutake ¹ , and Hiroshi Takahashi ¹

¹ Orthopedic Surgery, Toho University School of Medicine, Tokyo, Japan

Introduction: Minimally invasive transforaminal lumbar interbody fusion (MIS-TLIF) has become widely performed for the last decade, but long-term advantages in patients undergoing MIS-TLIF compared to conventional TLIF (C-TLIF) have not been well documented. The purpose of this study is to elucidate the long-term advantage of MIS-TLIF, especially focused on adjacent segment degeneration (ASD). Material and Methods: A retrospective analysis of prospectively collected clinical and radiographic data of patients who underwent MIS-TLIF for single-level symptomatic degenerative lumbar conditions such as spondylolisthesis, compared them with C-TLIF. A total of 121patients from 2004 to 2011, 77 (31 males, 46 females) aged 48-81 years that underwent single-level MIS-TLIF (36 cases) and C-TLIF (41 cases) were included with minimum follow-up of 10 years. Mean follow-up duration was 13.6 years for MIS-TLIF cases and 13.4 years for C-TLIF cases. Clinical outcomes were evaluated according to the Japanese Orthopedic Association score (JOA score). Clinical ASD was defined as patients who required additional surgery due to ASD. Radiographic ASD and multifidus muscle atrophy was assessed using flexion-extension radiographs and MRI. MIS-TLIF was performed via a unilateral dorsal approach using tubular retractor. MIS-TLIF was achieved using titanium cage with autologous bone. Percutaneous pedicle screw fixation was added bilaterally. C-TLIF was performed via a mid-sagittal dorsal approach, followed by stripping the paravertebral muscle. After removal of the spinous process, standard laminotomy, unilateral facetectomy and discectomy followed by interbody fusion and pedicle screw placement was. Results: Cohorts were well matched based on patient age (MIS: 64.3 yrs. C: 62.7 yrs.), BMI (MIS: 23.3 C: 24.1), duration of symptoms (MIS: 15.3 mo. C: 17.2 mo.), and JOA score (MIS: 15.7 points. C: 14.5 points.) before surgery. There was no significant difference in both pre- and post- radiographic sagittal spinopelvic parameters (PT, PI-LL) between the two groups. The mean JOA scores in MIS group and C group were both significantly improved to 25.3 and 24.5 respectively at the latest follow-up with no significant difference. Clinical ASD was observed in 3 cases with MIS and in 11 cases with C (p = 0.04). Radiographic ASD was observed in 17 cases with MIS group and in 23 cases with C group (p = 0.36). Postoperative multifidus muscle atrophy in MIS group was significantly less than C group. Conclusion: This study demonstrates that MIS-TLIF obtained the same clinical improvements as C-TLIF over ten years period. Preservation of posterior elements using MIS technique including minimizing approach related soft tissue trauma, posterior bony structures can reduce adjacent segment disease.

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P396: Clinical study on functional outcome of percutaneous transforaminal endoscopic lumbar discectomy under local anaesthesia

Varun Agarwal ¹

¹ Orthopedics, Rohilkhand Medical College and Hospital, Bareilly, India

Introduction: Many surgical approaches from conventional open discectomy, microdiscectomy, percutaneous interlaminar and transforaminal endoscopic discectomy have been used for treatment of prolapsed intervertebral disc. Transforaminal endoscopic discectomy through a Kambin triangle is a minimal invasive procedure which can be done under local anesthesia, without muscle splitting, with short hospital stay and minimal complications compared to other techniques used. The aim of this study was to evaluate the functional outcomes following percutaneous transforaminal endoscopic discectomy under local anesthesia for lumbar disc herniations. Material and Methods: This Retrospective study was conducted between November 2020 to October 2021 in orthopaedics department of Rohilkhand medical college and hospitals, Bareilly, U.P. This study included 54 patients with radicular pain for at least three weeks with a positive nerve root compression sign and underwent percutaneous transforaminal endoscopic discectomy under Local anesthesia. Visual analogue score (VAS) and Oswestry Disability Index (ODI) has been used for pre and post-operative clinical assessment of the patients, follow up was done at 6 weeks, 3 months, 6 months and 1 year postoperatively. Results: Maximum patients were in the age group of 61 to 70 years and 65.2% of the patients were males. 68.2% patients had lumbar disc herniation at L4-L5 level. The mean operative time of PTED was 70.6 minutes. Out of 16 cases of L5-S1 disc prolapse, 1 case was operated by making an iliac bone window due to inaccessibility of disc space because of highly placed iliac crest. The mean preoperative VAS and ODI scores were 8.1 and 56.6 respectively. The Post operative VAS and ODI scores were dramatically improved at each follow up interval (p < 0.0001). Out of 66 patients who underwent operation, 4 patients developed Surgical site infection and 2 were found to have dysesthesia, no serious complications were noted. Conclusion: PTED has been shown to be a safe, effective and minimally invasive alternative for the treatment of lumbar disc herniation. The procedure proved to be advantageous as it had shorter operative time, less blood loss, early recovery period, less postoperative work disability, lesser rate of complications, and epidural scarring, thus facilitating easy revision surgeries as and when indicated, clearly point toward a better acceptance of the endoscopic techniques and their potential large usage in the coming times.

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P397: Limitations of transsacral canal pasty in patients with poor results

Yoshikazu Yanagisawa ¹

¹ Department of Orthopedic Surgery and Spinal Disease Center, Fukuoka Mirai Hospital, Fukuoka City, Japan

Introduction: Epiduroscopy is highly useful for detailed examination of the cause of chronic lower back and leg pain and for high-level diagnosis. Although there are reports that it is highly effective in treating postoperative chronic pain, there is insufficient evidence for lumbar spinal canal stenosis and intervertebral disc herniation. In this study, we examined the limitations of TSCP based on poor results of transsacral spinal canoplasty (TSCP) for lumbar degenerative diseases. Material and Methods: A survey of 30 cases (male: 8, female: 22, average age: 71.9 years old (52-96 years old)) who underwent TSCP. The survey items were the postoperative course (pain VAS value), the presence or absence of additional surgery, and intraoperative findings. In addition, cases of additional surgery and cases with low postoperative satisfaction were grouped into a poor results group, and the good results group and the poor results group were examined before surgery, 1 month, 2 months, 3 months, 6 months, and 1 year after surgery) We examined changes in the VAS score of the average follow-up period after surgery was 6.2 months. The target diseases were lumbar spinal canal stenosis: 17 cases (56%), postoperative chronic low back and leg pain: 6 cases (20%), and foraminal disorders in 3 cases (10%). Results: Postoperative VAS values were preoperative: 77.6mm, 1 month postoperative: 31.6 mm, 2 months postoperative: 44.8 mm, 3 months postoperative: 52.8 mm, 6 months postoperative: 58.3 mm, 1 year postoperative: 60.4 mm. Additional surgery was required in 9 cases (30%) at an average of 6.6 months after surgery. Surgery included fusion surgery in 3 cases (34%), re-TSCP in 3 cases (34%), and decompression in 2 cases (22%). Intraoperative findings included foraminal stenosis in 7 cases, spinal canal adhesion in 6 cases, and spinal canal stenosis in 2 cases. There were 14 poor results cases. Compared with the good results group, the poor results group had significantly higher VAS values from preoperatively (73.7 mm: 81.9 mm, p = 0.0212). In addition, there was a significant difference in the postoperative VAS score between the good results group and the poor results group from 1 month to 3 months after surgery, but after 6 months there was a significant difference between the two groups. Conclusion: From the poor results group, foraminal stenosis, intraspinal adhesion, and spinal canal stenosis are likely to require additional surgery, and it was considered that there is a limit, especially in complicated cases of severe spondylolithesis and scoliosis.

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P398: Hemorrhagic lumbar facetal cyst secondary to oral anticoagulant: a case report and literature review

Aishwarya Kripesh ¹ , Zhihong Chew ¹ , Terry Teo Hong Lee ¹ , Wee Lim Loo ¹ , and Dinesh Shree Kumar ¹

¹ Department of Orthopedic Surgery, Changi General Hospital, Singapore, Singapore

Introduction: Hemorrhagic facet cysts are relatively an uncommon occurrence, mostly associated with cases of trauma or spinal instability. Acute onset of lower back pain and radicular symptoms have been previously reported following hemorrhage of facet cysts, with urinary and bladder incontinence being rarely reported. However, no previous case of hemorrhagic facetal cysts secondary to oral anticoagulant (Apixaban - a non-vitamin K antagonist (NOAC) agent) causing cauda equina compression presenting with urinary and bowel incontinence has been recorded. Materials and Methods: Seventy-Four-year-old gentleman presents with a three-month history of worsening of lower back pain as well as bladder and bowel incontinence. Patient has significant cardiac history of ischemic heart disease and atrial flutter for which patient was started on an oral anticoagulant two weeks prior to onset of symptoms. Magnetic resonance imaging showed a large extradural mass compressing the cauda equina causing severe stenosis at the level of lumbar four to five. Patient underwent minimally invasive transforminal Lumbar four to five decompression and instrumented fusion. A facet cyst containing gross blood products was excised during the lumbar decompression and fusion surgery. Post operatively patient symptoms of lower back pain as well as bladder and bowel incontinence improved. Results: We conducted a review of the literature which revealed that predominately patients’ present with leg pain, lower back pain, weakness and sensory deficits such as numbness, tingling and paresthesia. Urinary and bowel incontinence is rarely reported except in two previous cases reports. However, both cases were not associated with use the anticoagulation. Hence, this case report documents the first case of hemorrhagic facetal cyst secondary to oral anticoagulant use causing cauda equina compression presenting with bowel and urinary incontinence. Conclusion: This is the first case report of lumbar four to five hemorrhagic facetal cyst secondary to oral anticoagulant, resulting in cauda equina compression.

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P399: Laparoscopic aided interlocking screw removal for symptomatic leg pain after anterior lumbar interbody fusion technique

Michael Rogers ¹ , Ashish Patel ¹ , Jahangir Asghar ² , and Alfredo Guiroy ²

¹ Spine Surgery, Duly Health and Care, Naperville, United States

² Spine Surgery, Elite Spine Health and Wellness, Plantation, United States

Introduction: Anterior lumbar interbody fusion (ALIF) has become a standard procedure in the repertoire of a minimally invasive spine surgeon and will likely be performed more often as the incidence of adult degenerative spinal disorders in the United States increases. It is beneficial for spine surgeons to be aware of technical considerations associated with an ALIF and how to prevent complications to ensure complete surgical proficiency. We report 2 cases of an uncommon complication associated with an S1 compression neuropathy due to deep left-sided sacral screw placement using a four-hole implant. Material and Methods: This case study included two patients who underwent a standalone ALIF with a four-hole implant for lumbar degenerative disease. Both patients had full strength and were ambulatory. Both patients had persistent intermittent numbness and aching in the S1 distribution that promoted evaluation via a CT scan. Results: CT scan demonstrated the left-sided screw was prominent into the left S1 foramen. The imaging correlated with the patient's symptoms and both patients elected for screw removal. Both patients underwent a novel laparoscopic assisted method for screw removal. In both cases, the screws were removed uneventfully with complete resolution of leg symptoms in both patients. Conclusion: Our report describes a novel laparoscopic method for ALIF screw removal in the event of a prominent screw into the sacral foramen. Furthermore, we outline the considerations of selecting screw length in each hole when using this four-hole ALIF implant.

1121

P400: Comparison of postoperative bone healing in patients with UBE or conventional lumbar discectomy

Jaeyoung So ¹ and Jeong-Yoon Park ¹

¹ Department of Neurosurgery, Spine and Spinal Cord Institute, Gangnam Severance Hospital, Seoul, South Korea

Introduction: In unilateral biportal endoscopic (UBE) discectomy, as opposed to conventional discectomy, continuous irrigation lowers the temperature thereby reducing bone damage and promoting bone healing. The purpose of this study was to investigate the difference of bone healing at the postoperative laminectomy site in patients who underwent unilateral biportal endoscopic (UBE) or conventional discectomy. Materials and Methods: From January 2018 to June 2021, 66 patients who underwent laminectomy in our institute were retrospectively reviewed. All patients were matched with sex, age, BMI, BMD, and F/U duration by a 1:2 matching ratio and were divided into the “UBE” group (UBE, 22 patients) and the “conventional” group (44 patients, conventional discectomy). We investigate the site of laminectomy shown in pre- and postoperative x-ray images through scientific image analysis software (ImageJ). The factors related with bone healing were also investigated. Results: The average bone healing area of the UBE group was 69.59 mm², and that of the conventional group was 44.56 mm², a significant difference (p = 0.022). The remaining laminectomy area was significantly lower in the UBE group than in the conventional group (13.91 mm² vs. 53.84 mm², p < 0.001). The bone recovery ratio in the UBE group was 85.42%, compared to 51.33% in the conventional group, a significant difference (p < 0.001). Primary laminectomy area, bone healing during 6 months, and clinical outcomes were not significantly different between the two groups. Conclusion: Compared with the conventional group, the UBE group had greater bone healing area and higher bone recovery ratio for patients with lumbar discectomy. These findings suggest that it is more feasible to preserve the normal structure during UBE than during conventional surgery.

1191

P402: Comparison of clinical outcomes after single, double and multilevel ELIF

Carlos De La Torre ¹ , Darren Lui ¹ , Bisola Ajayi ² , and Khai Lam ¹

¹ Orthopaedics, London Bridge Hospital, London, United Kingdom

² Orthopaedics, NHS St George's Hospital, London, United Kingdom

Introduction and Purpose: The minimally invasive extreme lateral interbody fusion (ELIF) has increasingly gained importance in the treatment of lumbar spine pathology. The purpose of this study was to compare surgical outcomes and complications of single, double and multilevel fusion in patients who underwent ELIF. Materials and Methods: Between January 2013 and July 2021, we identified 95 patients undergoing ELIF for lumbar pathology. Patients were divided into groups based on number of levels fused during their procedure (1,2, or 3 or more) Patient related outcome measures (PROMS) were collected preoperatively, and up to 12 months postoperatively. PROMS included Oswestry Disability Index (ODI), Visual Analog Scale (VAS) for both back (BP) and leg pain (LP) and EQ5D. Results: There were 55% female and 45% male patients with a mean age of 55 (26-84) years. 73 patients underwent single-level fusion, 12 underwent two level fusion and 10 underwent 3 or more levels fusion. For ODI, statistically significant mean improvements from pre-operative to last follow-up were 29.5± 2.4 (p < 0.001) for single-level, 15.4 ± 8.2 (p < 0.05) for double-level and 17 ± 5.5 (p < 0.01) for multi-level fusion. For VAS BP, significant mean improvements from pre-operative to last follow-up were 5.1 ± 0.34 (p < 0.001) for single-level, 3.9 ± 1.2 (p < 0.009) for double-level and 3.5 ± 0.8 (p < 0.001) multi-level. For VAS LP the mean improvements were 4.6 ± 0.37 (p < 0.0001) for single-level, 2.9 ± 1.1 (p < 0.05) for double-level and 4.5 ± 0.8 (p < 0.001) for multi-level. For EQ5D the mean improvements were 23 ± 2.5 (p < 0.0007) for single-level, 14.4 ± 6.7 (p < 0.05) for double-level and 21 ± 6.5 (p < 0.01) for multi-level fusion. Five patients (6%) developed an adverse event in the single-level group, 2 in the double-level (16%), and 2 in the multi-level group (20%). The mean retraction time was 24, 36 and 56 minutes for the single, double and multi-level groups respectively, the mean length of stay was 3.6, 6.7 and 7.3 days for single, double and multi-level groups respectively. All groups had an estimated blood loss of less than 100 ml. Based on a previous study the percentage of patients that met the MCID for ODI was 76%, 50% and 70% for single, double and multi-level fusion respectively. For VAS BP was 82%, 66% and 80% and for VAS LP was 74%, 58% and 80%. Conclusions: Our analysis showed that patients in double and multilevel ELIF experienced less improvement in all aspects of PROMS, had more complications, and had a late discharge home compared to single-level ELIF. These findings are important for operative planning, for setting appropriate preoperative expectations, and for risk stratification in patients undergoing ELIF.

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P403: Comparison of clinical outcomes between lumbar levels for single-level extreme lateral inter body fusion

Carlos De La Torre ¹ , Darren Lui ¹ , Bisola Ajayi ² , and Khai Lam ¹

¹ Orthopaedics, London Bridge Hospital, London, United Kingdom

² Orthopaedics, NHS St George's Hospital, London, United Kingdom

Introduction and Purpose: The minimally invasive extreme lateral interbody fusion (ELIF) has gained importance in the last decade. This approach has differing complication profiles because of the inherent anatomical differences encountered on each lumbar level. The purpose of this study was to evaluate surgical outcomes and complications of single-level ELIF comparing L4/L5 fusion with any other level fusion. Materials and Methods: Between January 2013 and August 2021, we identified 76 patients undergoing single-level ELIF. Patients were divided into two groups: L4/L5 level fusion group and other level fusion group. Patient related outcome measures (PROMS) were collected preoperatively, and up to 12 months postoperatively. PROMS included Oswestry Disability Index (ODI), Visual Analog Scale (VAS) for both back (BP) and leg pain (LP) and EQ5D. Perioperative and postoperative data included retraction time (RT), estimated blood loss (EBL), length of stay (LOS) and adverse events (AE). Results: There were 58% female and 42% male patients with a mean age of 54 (26-82) years. 60 patients underwent single-level fusion at the L4/L5 level and 16 patients underwent single-level fusion at other level (11 at L3/L4, 5 at L2/L3). For ODI, statistically significant mean improvements from pre-operative to last follow-up were 31.2 ± 2.6 (p < 0.001) for L4/L5 fusion, and 24.1 ± 5.1 (p < 0.001) for other level fusion. For VAS BP, significant mean improvements from pre-operative to last follow-up were 5.1 ± 0.3 (p < 0.001) for L4/L5 fusion, and 4.5 ± 0.7 (p < 0.001) for other level fusion. For VAS LP the mean improvements were 4.5 ± 0.4 (p < 0.001) for L4/L5 fusion, and 4.5 ± 0.7 (p < 0.001) for other level fusion. For EQ5D the mean improvements were 23.3 ± 2.9 (p < 0.001) for L4/L5 fusion, and 19.8 ± 3.9 (p < 0.001) for other level fusion. Four patients (6%) developed an adverse event in the L4/L5 fusion group, 2 of them had urinary retention and improved after conservative treatment, one developed an infection at the navigation pin insertion site, improving after antibiotic therapy, and one developed radiculopathy which required posterior revision. Two patients (12%) presented an adverse event in the other level fusion group. One developed a pedicle fracture which was treated with exchange of posterior screws, the other patient had postoperative back and sacroiliac joint (SIJ) pain, which was treated with SIJ and epidural injections. The mean retraction time was 24 minutes in both groups, the mean length of stay was 4 days in both groups. All groups had an estimated blood loss of less than 100 ml. Conclusions: It has been previously proposed that ELIF at the L4/L5 level carries a higher risk of postoperative motor deficit due to nerve injury. Our analysis showed that patients who underwent ELIF approach at the L4/L5 level did not experience increased incidence of complications compared to other level fusion surgery and they all experienced similar clinical outcomes. Therefore, we consider that ELIF at L4/L5 level is a reasonable and effective fusion technique.

1284

P404: Comparative analysis of prone lateral versus lateral decubitus positioning in achieving optimal outcomes and reducing complication rates in single-position minimally invasive spine surgery

Peter Passias ¹ , Peter Tretiakov ¹ , Jamshaid Mir ¹ , Pooja Dave ¹ , Kimberly McFarland ¹ , Rachel Joujon-Roche ¹ , Tyler Williamson ¹ , Bailey Imbo ¹ , Zach Thomas ¹ , Stephane owusu-saprong ¹ , Jordan Lebovic ¹ , Shaleen Vira ² , and Bassel Diebo ³

¹ Department of Orthopaedic Surgery, NYU Langone Orthopedic Hospital, New York, United States

² UT Southwestern, Dallas, United States

³ Department of Orthopaedic Surgery, SUNY Downstate, New York, United States

Introduction: Recent literature has pointed to the rising use of prone lateral versus lateral decubitus positioning in Minimally-Invasive Spine Surgery (MISS) as a method to reduce operative time, increase patient safety, and aid in surgical accessibility. However, there is a paucity of literature as to how prone lateral and lateral decubitus positioning compares in terms of reaching optimal postoperative outcomes and reducing complication rates. Materials and Methods: MISS patients with baseline (BL) and 2-year (2Y) postop radiographic/HRQL data were included. Patients positioned in the Prone Lateral (PL) or single-position Lateral Decubitus (LD) position were isolated. At 2Y, an optimal outcome score was calculated using 4 equally weighted criteria: 1) achieving ideal PT per SRS-Schwab at 2Y, 2) Achieving ideal PI-LL per SRS-Schwab at 2Y, 3) No complication requiring reoperation 4) Achieving NRS MCID by Salaffi et al. criteria; optimal score threshold was set at meeting 2 of 4 criteria. Means comparison analysis assessed differences in radiographic and clinical outcomes at BL and 1Y post-op. ANCOVA assessed estimated marginal means adjusting for BL age and revision status. Results: 34 Prone Lateral and 36 Lateral Decubitus patients were included (54.40 ± 12.49 years, 40% female, 30.93 ± 6.52 kg/m², mean CCI: 2.23 ± 1.55) were included. At baseline, patients were comparable in age, gender, BMI, and CCI (all p > .05). Peri-operatively, PL patients demonstrated significantly lower operative time (200.09 vs 284.54 min, p = .007) and EBL (332.35 vs 192.05 mL, p = .027). Though optimization scores were equivalent between groups (p = .160), PL patients demonstrated significantly lower peri-operative complication rates (p = .012), neurological complication rates (p = .006), and had a fewer number of total complications by 2Y (p = .014). When controlling for BL age and revision status, the PL patients demonstrated consistently lower intra- and peri-operative complications as well (both p < .015). In terms of patient-reported outcomes, PL patients also demonstrated significantly improved NRS-Leg scores compared to LD patients by 1Y (p = .038). Conclusions: Patients placed in the Prone Lateral position during minimally invasive adult spinal deformity surgery demonstrate decreased mean operative times and decreased intraoperative invasiveness and blood loss versus patients operated on via single-position Lateral Decubitus positioning. Though overall rates of achieving optimal outcome remain comparable, Prone Lateral approach should be considered as there may be significant additional benefit in reducing peri- and post-operative complications by 2Y.

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P405: Perioperative glucose response in diabetic patients with lumbar spinal stenosis treated with biportal endoscopic decompression

Javier Quillo-Olvera ¹ , Javier Quillo-Reséndiz ¹ , and Michelle Barrera-Arreola ¹

¹ Spine Center, Hospital Angeles Centro Sur, Querétaro, Mexico

Introduction: Physiological stress hyperglycemia is observed in more than 40% of critically ill patients and 32% of patients undergoing elective surgery. This phenomenon is usually transient in non-diabetic patients and is defined as blood glucose > 140 mg/dL and severe hyperglycemia > 180 mg/dL; the last one is associated with attenuation of the basophil count, T cells, and monocytic function, leading to decreased postoperative immunity and a high risk of infections. In diabetic patients, severe perioperative hyperglycemia is common and associated with poor postoperative results after spinal surgery. Therefore, we hypothesize that the perioperative glycemic response of controlled diabetic patients undergoing biportal endoscopic decompression for lumbar spinal stenosis is similar to that of non-diabetics. Material and Methods: A comparative study with prospective data acquisition and retrospective review was performed. Controlled diabetic patients with a < 7 g/dL HbA1c and non-diabetics with single-level lumbar spinal stenosis, radicular pain, or neurogenic claudication consistent with radiological findings were treated through unilateral biportal endoscopic access and bilateral decompression (UBE-ULBD). Patients were divided into diabetic and non-diabetic cohorts. Demographics, perioperative characteristics, and clinical outcomes were compared and analyzed between groups. Preoperative, intraoperative, and postoperative at 12 and 24 hours blood glucose measurements were obtained in all patients to observe glucose response to surgical treatment. Results: Two groups with 18 patients were made up. The mean age in the DM2 group was 65.83y (±9.2), while the non-diabetic group was 52.67y (±19.8). L4-L5 was the most decompressed level; 88.9% of diabetic patients were discharged the next day, while 11.1% on postoperative day 2. All non-diabetic patients were discharged the next day. The mean operative time in the DM2 group was 74.28 min (±26.87), while in the non-diabetic was 76.83 min (±29.22). The average EBL in the DM2 group was 29.44mL (±9.98), while the non-diabetic group was 33.3 mL (±11.88). The mean HbA1c in DM2 group was 6.436 mg/dL (±0.43), and 5.261 mg/dL (±0.23) in non-diabetics. A statistically significant decrease (p < 0.005) between preoperative and postoperative pain and disability scores in both groups was observed. The mean preoperative blood glucose was 136.5 mg/dL (±25.091) in DM2 group and 101.11 mg/dL (±10.255) in non-diabetics. The mean intraoperative glucose in diabetics reached 170.22 mg/dL (±27.627), while non-diabetics it was 125.50 mg/dL (±19.847) (p = 0.007). The postoperative glucose at 12 and 24 hours was 130.89 mg/dL (±23.552) in DM2 group and 106.89 mg/dL (±11.591) in non-diabetics, and 136.06 mg/dL (±11.032) in DM2 group and 105.39 mg/dL (±10,331) in the non-diabetics respectively (p = 001). Conclusion: The present study reported that biportal endoscopic surgery was associated with increased intraoperative glucose in both groups, much higher in diabetic patients. Therefore measures for its reduction should be considered during the surgery to avoid sustained hyperglycemia and the known associated risks. However, postoperative glucose at 12 and 24 hours did not show a trend of severe hyperglycemia when the biportal endoscopic technique was used in diabetic patients.

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P406: The implementation of minimally invasive spine surgery at a UPMC peripheral community hospital

Yunting Tang ¹ , Anthony Oyekan ¹ , Jonathan Dalton ¹ , Dominic Ridolfi ¹ , and Vivek Sharma ¹

¹ University of Pittsburgh, 200 Lothrop Ste BST E 1640, Pittsburgh, United States

Introduction: Minimally invasive spine surgery (MISS) techniques were developed to address several challenges with traditional approaches to decompression and fusion, including extensive muscular dissection and subsequent postoperative back pain and prolonged recovery.^1,2 Since the introduction of a tubular distraction system for use in microendoscopic diskectomy in 1997, MISS has undergone a rapid technological evolution, including major improvements to endoscopy, robotic-assisted spine surgery, and navigation.³ The implementation of MISS comes with challenges including cost and learning curve. Thus, we aimed to study the initial clinical experiences of a spine surgeon performing unilateral lumbar laminectomy with bilateral decompression (ULLBD) via MISS at a UPMC peripheral community hospital with no previous in-house spine service. We hypothesized that a minimally invasive spine surgery program may be safely implemented at a peripheral community hospital and will allow most patients to have a rapid recovery with discharge to home. Material and Methods: A retrospective review of a prospectively collected database was performed with University of Pittsburgh review board approval. We initially identified 131 elective ULLBD cases by a single fellowship-trained orthopedic spine surgeon, from October 2019 to March 2021, at a non-teaching UPMC community hospital with no previous in-house spine coverage. The minimum postoperative follow-up was 1 year. Data points collected include patient demographics, diagnoses, discharge date, discharge disposition, and narcotic use. Patients who underwent ULLBD were indicated for instrumented posterior spinal fusion by pre-operative dynamic instability and iatrogenic instability associated with the decompressive procedure. Differences in patients who underwent fusion and those who did not undergo fusion were compared using Chi-squared, Fischer’s exact test, and two-tailed unpaired t-tests analysis. A p < 0.05 was considered significant. Results: 55 patients were included in the analysis (32 F, 23 M; age 65 ± 17 years, BMI 30.0 ± 6.1). 51 (92.7%) patients were discharged on postoperative day 1, 3 (5.5%) patients were discharged on postoperative day 2, and only 1 (1.7%) patient was discharged after postoperative day 2. 53 (96.3%) patients were discharged to home and only 2 (3.6%) required a skilled nursing facility. Instrumented posterior spinal fusion for ULLBD was generally performed in older patients with spondylolisthesis and required greater OR time, radiation dose, blood loss, and narcotic prescription doses than patients without instrumented fusion Notably, all patients on chronic narcotics had no change in their preoperative prescriptions despite continued clinical improvement. There were no complications that required re-operation. Conclusion: ULLBD via MISS may be safely performed at a MISS-naïve peripheral community hospital with excellent outcomes. Implementation of a minimally invasive spine surgery program in such a setting is safe, feasible, and allows for optimal clinical outcomes. ERAS protocols may improve perioperative restrictions, pain control, and rehabilitation. Considerations include equipment needs, personnel training, and surgeon experience.

1471

P407: Short-term clinical and radiological outcome of intradiscal condoliase injection in lumbar disc herniation

Akihiro Nagamachi ¹ , Hiroki Ikuchi ² , Kohei Ohta ¹ , and Takayuki Ogawa ³

¹ Orthopaedic Surgery, Yoshinogawa Medical Center, Tokushima, Japan

² Orthopaedic Surgery, Takamatsu Municipal Hospital, Kagawa, Japan

³ Orthopaedic Surgery, Sakaide Kaisei Hospital, Kagawa, Japan

Introduction: Condoliase has high substrate specificity for chondroitin sulfate and hyaluronic acid, which are glycosaminoglycans of proteoglycans abundant in the nucleus pulposus of the intervertebral disc. Condoliase has been used to treat lumbar disc herniation (LDH), however there is a paucity of evidence in clinical outcome of intradiscal condoliase injection. In this prospective study, we investigated clinical and radiological outcome of intradiscal condoliase injection. Material and Methods: A total of 32 patients with LDH underwent intradiscal condoliase injection at our hospital. All patients had clinical symptoms of LDH and confirmed herniated disc on lumbar spine MRI. There were 25 male and 7 female and their mean age was 45 years (16 ∼ 85 years). Affected intervertebral disc were 2 at L1-2, 1 at L2-3, 16 at L4-5, 13 at L5-S1. Intradiscal condoliase injection was performed under fluoroscopic guidance. A single 1 mL dose of condoliase (1.25 U/mL) was injected into the center of the affected intervertebral nucleus pulposus using a 21-gauge puncture needle. Patient was hospitalized in one day to observe adverse events. Clinical and radiological assessments were conducted before, 1 week, 4 weeks, 3 months and 6 months after the injection. Clinical outcome was measured using Japanese Orthopaedic Association Back Pain Evaluation Questionnaire (JOABPEQ) and Visual analog scale (VAS, 0 to 100 mm) of buttock and leg pain. Patient improved without additional surgery was defined as responder and patient needed additional surgery because of remained symptoms was defined as non-responder. All patients underwent lumbar spine MRI. Axial and sagittal MRI were used to classify herniation types; subligamentous extrusion (Sub), transligamentous extrusion (Trans) and sequestration (Seq). Herniated disc area was measured on axial section. All responders completed the minimum follow-up period of 6 months, non-responders dropped out of this study at when additional surgery was performed. Results: There were 26 responders and 6 non-responders. Number of patients of Sub, Trans and Seq were 23, 5 and 3, respectively. Percentage of responders in Sub, Trans and Seq were 75%, 100% and 0%, respectively. In responders, all item score of JOABPEQ were improved after the injection. Mean VAS of responder before injection, 1 week, 4 weeks, 3 months and 6months were 68.0, 37.9, 25.0, 14.5 and 16.1, respectively. On the other hand, mean VAS of non-responders before, 1 week and 4 weeks after the injection were 82.2, 56.1 and 58.3, respectively. Herniated disc area before and 6 months after the injection in responders were 64.0 mm² and 29.2 mm², respectively. Conclusion: Response rate of intradiscal condoliase injection was 81.3% in this study. Therapeutic effect of condoliase is confirmed only in Sub type herniation in clinical trial, however, response rate was 100% even in Trans type in this study. Based on this result, we indicate intradiscal injection of condoliase for patients with Sub and Trans type. Non-responder did not improve at 1 week after the injection. Clinical outcome at 1 week after the injection might give valuable information to change treatment plan for non-responders.

1524

P408: Interlaminar spine surgery - Is it for us? My journey through the learning curve

João Cruz ¹ , Emanuel Homem ¹ , Ricardo Simoes ¹ , and Luís Soares ¹

¹ Ortopedia, Hospital Divino Espírito Santo, Ponta Delgada, Portugal

Introduction: Surgical treatment of the degenerative disc disease has evolved from traditional open spine surgery to minimally invasive approaches and endoscopy. With improvements in endoscopic technology spine surgeries can be performed for lumbar, cervical and thoracic regions with less tissue and muscle damage, reduced blood loss, less epidural fibrosis, reduced in-hospital stay, early functional recovery and improvement in the quality of life. Appropriate indications, clear imaging prior to surgery and preplanning are keys to successful outcome. Interlaminar spine endoscopy started as a mean solution to deal with L5S1 problems that were not accessible to transforaminal approach. The authors prospectively describe their experience in interlaminar endoscopic spine surgery. Material and Methods: We prospectively follow all patients that were submitted to surgery between November 2019 and May 2022. Patients who had undergone full-endoscopic lumbar discectomy (FELD) with interlaminar approach were included and follow-up was done at 4 days, 2 and 6 weeks and 3 months. We started to do spine endoscopy cases in November 2019. In total we have performed 18 surgeries for 18 patients. 5 patients had concomitant transforaminal approach to at different levels. Results: The median age was 38.1 (21-58) years, 14 left sided surgeries and 4 right sided, from these we had 9 males and 9 females. All these with 17 lumbar disc herniation (LDH) and 1 of lombar stenosis (LS). All cases were at L5S1 level. The average length of stay was 1.38 (0.3-4) days and the average operation time was 103 (45-163) minutes. In the year 2022 all patients were operated in outpatient setting. As for the results in overall, we had 67% excellent results, 22% good results, 0% fair results and 11% of poor results according to MacNab classification. The mean pre-operative visual analogue scale (VAS) score for leg pain was 5.94 (3-9) and 1.05 (2-0) at 3-month post-operative follow-up. VAS for back pain was 6 (0-9) and 2 (1-4) respectively. The Owestry score had a pre-op of 43.8 (8-66) and a post-op at 3 months of 14.2 (4-48). We had 2 patients with a reherniation (11%), no infection or dural leak cases. Conclusion: Although this is a small case study, we had 89 % excellent/good outcomes. We consider it is quite acceptable for the initial learning curve of this spine endoscopy technique.

1525

P409: Comparative outcomes of transcorporeal versus transdiscal anterior endoscopic dissectomy for cervical radiculopathy: meta-analysis

Gun Keorochana ¹ and Jatupon Kongtharvonskul ¹

¹ Orthopedics Department, Faculty of Medicine Ramathibodi Hospital, Mahidol University, Bangkok, Thailand

Objective: In recent years, the application of spinal endoscopy has become more prevalent. At present, percutaneous endoscopic cervical discectomy (PECD) is mainly divided into the anterior transdiscal approach and the posterior interlaminar approach. Although the anterior transdiscal approach can provide direct decompression for central or paramedian cervical disc herniation, the iatrogenic disc damage may result in decreased intervertebral space when compared to posterior interlaminar access. Anterior transcorporeal approach under endoscopy could enable an individual and adjustable trajectory within the vertebral body under different conditions of disc herniation preserving the motion of adjacent segment, especially in a migrated or sequestered lesion. But there is no current consensus regarding which method is better. Therefore this systematic review and meta-analysis of transdiscal and trancorporeal PECD was conducted with the aim of updating the comparison of the two for post-operative outcomes (neck pain arm pain (VAS), disabilities (NDI), modified Macnab criteria, complications and reoperations) for treatment of cervical intervertebral disc herniation. Methods: This systematic review was conducted according to the PRISMA guidelines. Relevant studies that reported pain, disabilities, modified Macnab criteria, complications and reoperations of either technique were identified from Medline and Scopus from inception to September 4^th, 2022. Results: eleven studies were included for the analysis of transdiscal(Td) PECD, 17 studies were included for analysis of transcorporeal (Tc) PECD and one comparative study were included for compared TdPECD to TcPECD. Overall, there were 1503 patients (978 in the TdPECD group and 525 in the TcPECD group). A pooled UMD of post-operative neck pain, arm pain (VAS), disabilities (NDI) scores of TdPECD and TcPECD were -4.48 (95%CI: -5.28 to -3.68), -6.03 (95%CI: -7.29 to -4.76), -40.90 (95%CI: -59.81 to -21.98) scores and -4.42 (95%CI: -6.40 to -2.44), -5.96 (95%CI: -6.80 to -5.12), -27.38 (95%CI: -52.77 to -1.99) when compared to before surgery. The pooled prevalence of having excellent and good in modified Macnab criteria, complications and reoperation of TdPECD and TcPECD were 0.89 (95%CI: 0.77, 1.00), 0.024 (95%CI: -0.030 to 0.078), 0.03 (95%CI: 0.003 to 0.051) and 0.75 (95%CI: 0.61 to 0.88), 0.005 (95%CI: -0.005 to 0.015), 0.016 (95%CI: 0.002 to 0.032). Indirect meta-analysis, TdPECD provided better postoperative neck and arm pain (VAS), disabilities (NDI) of -0.24 (95%CI: -1.98 to 2.46), -0.06 (95%CI: -1.68 to 1.80) and -13.98 (95%CI: -40.42 to 68.39) when compared to TcPECD technique, but there were not significant difference between two techniques. While the chance of having excellent and good in modified Macnab criteria, complications and reoperations in the TcPECD group were lower of 0.84 (95%CI: 0.67 to 1.05), 0.19 (95%CI: 0.01 to 3.00) and 0.58 (95%CI: 0.16 to 2.08) times when compared to TdPECD. Conclusion: In post-operative outcomes 3 up to 4 years follow-up, there is no significant difference in all clinical outcomes between the 2 approaches. Although TdPECD have better arm pain, neck pain and neck disabilities scores when compared to TcPELD, however, TcPELD have lower chance of having complications and reoperations when compared to TdPELD.

Keywords: percutaneous endoscopic cervical discectomy; PELD; transcorporeal; trandiscal; disc herniation

1526

P410: Our first 72 spine endoscopic cases: impressions of a learning curve

Emanuel Homem ¹ , João Cruz ¹ , Ricardo Simoes ¹ , and Luís Soares ¹

¹ Ortopedia, Hospital Divino Espírito Santo, Ponta Delgada, Portugal

Introduction: Surgical treatment of the degenerative disc disease has evolved from traditional open spine surgery to minimally invasive approaches and endoscopy. With improvements in endoscopic technology spine surgeries can be performed for lumbar, cervical and thoracic regions with less tissue and muscle damage, reduced blood loss, less epidural fibrosis, reduced in-hospital stay, early functional recovery and improvement in the quality of life. With precise indication, proper diagnosis and good training, the endoscopic spine surgery can give equally good result as open spine surgery. Appropriate indications, clear imaging prior to surgery and preplanning are keys to successful outcome. The authors prospectively describe their experience in endoscopic spine surgery. Material and Methods: We prospectively evaluated all patients submitted to endoscopic spine surgery from November 2019 to May 2022. Patients who had undergone full-endoscopic lumbar discectomy (FELD) were included and follow-up was done at 4 days, 2 and 6 weeks and 3 months. Our first case dated November 2019. In total, we have done 72 surgeries for 60 patients. 12 patients had concomitant interlaminar and foraminal approach at different sites. Results: The median age was 46,7 (20-74), 48 left sided surgeries and 24 right sided, from these we had 23 males and 37 females. A total of 54 transforaminal and 18 interlaminar surgeries, and 66 cases of lumbar disc herniation (LDH) and 6 of lumbar stenosis (LS). Regarding location, 44 at L4L5 level, 19 at L5S1, 8 at L3L4 and 1 at L2L3. The average length of stay was 1.23 (0.3-4) days, and the average operation time was 82 minutes (30-160). In the year 2022 all patients were operated in outpatient setting. As for the results, overall, we had 79% excellent results, 10.3% good results, 1% fair results and 9.7% of poor results according to MacNab classification. The mean pre-operative visual analogue scale (VAS) score for leg pain was 9.62 (3-8) and 1 (3-0) at 3-month post-operative follow-up. Median VAS for back pain was 6.28 (0-9) and 2 (1-4) respectively. The Owestry score had a pre-op of 47.9 (8-76) and a post-op at 3 months of 15.2 (4-50). We had 7 patients with a reherniation (9.7%) and 1 patient with LS submitted to arthrodesis, and no infection or dural leak cases. Conclusion: Although this is a small case study, we had 89,3% excellent and good results, which gives us a good incentive for continuing doing spine endoscopy. The good results make it a promising technique for lumbar problems.

1530

P411: Early experience with single paraspinal incision, single-level minimally invasive transforaminal lumbar interbody fusion (MITLIF) with 3D printed titanium cage and unilateral pedicle screw construct

Yunting Tang ¹ , Anthony Oyekan ¹ , and Vivek Sharma ¹

¹ Department of Orthopaedic Surgery, University of Pittsburgh, Pittsburgh, United States

Introduction: The implementation of MISS presents challenges including cost and learning curve. This study aimed to characterize initial clinical experiences with minimally invasive transforaminal lumbar interbody fusion (MITLIF) at a University-Affiliated community hospital. We hypothesized that MITLIF with a 3D printed titanium cage and unilateral pedicle screw construct may be safely implemented in single-level lumbar spine fusions with favorable clinical outcomes. Material and Methods: With review board approval, a retrospective review of a prospectively collected database was performed. We reviewed initial consecutive cases of single-level MITLIF using 3D printed titanium cages with a unilateral pedicle screw construct performed by a single fellowship-trained orthopedic spine surgeon from October 2019 to March 2021. The minimum postoperative follow-up was 1 year. Data points collected include patient demographics, diagnoses, comorbidities, operating time, fluoroscopy time/dose, EBL, hospital length of stay (LOS), discharge disposition, 30-day and 90-day readmissions and narcotic use (per the Pennsylvania Prescription Drug Monitoring Program, PDMP). The MITLIF protocol included a single paraspinal incision, non-expandable 18/22mm beveled slotted tubular retractors, an operating microscope, fluoroscopy, neurophysiologic monitoring, and an ERAS perioperative plan. Results: 47 patients were included - 25 F/22 M, age 67 ± 12 years, BMI 31.7 ± 5.7. Average operating time was 120 ± 18 min, fluoroscopy time 0.93 ± 0.41 min, radiation dose 3.80 ± 2.51 rad, and EBL 65 ± 35 cc. BMI directly affected radiation dose but had no effect on OR time or EBL. Patients were prescribed 28 ± 24 outpatient narcotic doses for 8 ± 6 days. All patients on chronic narcotics had no prescription changes pre- versus postoperatively, despite achieving their desired outcomes. One patient had hardware displacement requiring revision surgery, no other complications were reported. Four patients were readmitted at 30-days, and one at 90-days. Forty-three patients were discharged on POD1, 3 on POD2, and 1 after POD2. All patients were discharged home; 21 required home health assistance. Conclusion: MITLIF with 3D printed titanium cages and a unilateral pedicle screw construct may be a viable option for minimally invasive single-level lumbar spine fusions with favorable outcomes. This technique may help reduce hardware density and surgical footprint. It may also have future cost benefits and applications in the treatment of lumbar adjacent segment disease. However, further studies are needed to investigate these potential applications. Considerations include need for special equipment, personnel training, surgeon experience, technique proficiency and diligent patient selection.

1551

P412: Out-patient minimally invasive spine surgeries during the COVID-19 pandemic - A retrospective analysis of 164 consecutive cases

Benjiang Ma ¹ and Aaron Smith ¹

¹ West Palm Beach, Spine and Orthopaedic Specialists, Florida, United States

Introduction: Cervical and lumbar spine intervertebral disc (IVD) disease is the leading cause for neck or back pain. The most common mechanism of injury during non-fatal motor vehicle accidents is cervical or lumbar disc herniation and spine instability. Surgery is the last resort if all conservative measures failed. Here we share the retrospective analysis of the patient data and our surgical experiences from a single spine surgeon group utilizing minimally invasive procedures performed in the outpatient setting at the ambulatory surgery centers (ASC) during the COVID-19 pandemic. Material and Methods: Anterior cervical discectomy and fusion (ACDF), anterior lumbar interbody fusion (ALIF), minimally invasive laminotomy and discectomy (MILD), percutaneous endoscopic laser-assisted discectomy (PELD) and percutaneous kyphoplasty (PK) were performed on carefully selected patients at multiple ambulatory surgery centers (ASCs) with appropriate protective measures. Results: From January 2020 to December 2021, our group performed 164 consecutive cases on 153 patients involving a total of 249 IVD levels. Of these surgeries, 116 cases (70.73%) from 114 patients (74.51%) were cervical, predominantly ACDF, and 48 cases (29.27%) were lumbar. Notably, 8 of these patients had both cervical and lumbar procedures (single or multi levels) in a single anesthetic session (SAS) and were discharged on the same day. The most affected IVDs in cervical spine were at the C4-C5 and C5-C6 levels, which comprised 92.17% (106) of the ACDF cases and 76.04% (146) of the total IVD levels. Of the 40 cases of lumbar decompression/fusion procedures combined, 38 (95.0%) were at lower lumbar levels (L4 to S1). Six (6) cases (15.0%) involved 2 lumbar levels including L3-S1 IVDs. In sharp contrast, 6 out of 8 kyphoplasties (75.0%) involved lower thoracic/higher lumbar vertebral columns (T11 to L2) and only 2 were at the lower lumbar L4 level. Conclusion: With appropriate precautions, we have safely performed various cervical and lumbar spine surgeries in the ASCs amid COVID-19 pandemic, including patients that underwent combined multi-level cervical and lumbar spine procedures in a SAS with no complications and achieved the same day discharge (SDD). Analysis of our data demonstrated that, in non-fatal trauma during MVAs, mid-lower cervical (C4 to C6) and lower lumbar (L4-S1) IVDs were the most vulnerable levels. Clinical relevance: Our experience could be the valuable reference for fellow spine surgeons to increase their level of comfort to perform more skill-demanding surgeries in outpatient settings to reduce the cost in the today’s rising healthcare expenditures. Enhanced safety measures need to be investigated to protect the aforementioned skewed vulnerable cervical and lumbar spine levels from injury during MVAs.

Keywords: intervertebral disc, spine surgery, minimally-invasive, ambulatory surgery center, single anesthetic session, same day discharge, motor vehicle accident

1580

P413: Technique for spondylolisthesis reduction and segmental lordosis optimization in lateral lumbar interbody fusion with percutaneous pedicle screw fixation: a case series

Paul Soriano ¹ , Jason Haselhuhn ¹ , and Jonathan N. Sembrano ¹

¹ University of Minnesota, Minneapolis, United States

Introduction: Lateral lumbar interbody fusion with percutaneous pedicle screw fixation (LLIF-PPS) is a circumferential minimally-invasive procedure designed to minimize morbidity and enhance recovery after lumbar surgery. There has been increasing emphasis on restoring optimal segmental sagittal alignment, even in single-level fusion procedures. We described a technique to optimize segmental lordosis (SL) and reduce spondylolisthesis in LLIF-PPS and analyzed radiographic results in a series of patients on whom this technique was used. The objective of this study was to evaluate the effects of introducing an angled-up position of distal screws and hyper-contouring of rods before the final tightening of instrumentation ("novel reduction technique") on lumbar lordosis (LL) in patients with spondylolisthesis undergoing LLIF-PPS fixation. Methods: After IRB approval, we reviewed consecutive cases of single-level LLIF-PPS for degenerative spondylolisthesis from January 2016 through December 2021. In all patients, after the pedicle screws were placed percutaneously and after passing the rods, the caudal screw extenders were tilted caudally, and caudal set plugs were tightened. This locks the screw heads in place and leaves the rostral end of the rods sticking up dorsally relative to the cephalad screw heads. Because the caudal screw heads were already locked, gradual reduction of the rods to the cephalad screw heads resulted in spondylolisthesis reduction and SL increase without needing rod compression. We measured the SL on operative levels in intraoperative images at every step of the surgery (before cage placement, after cage placement, after repositioning, and after posterior instrumentation). We measured pelvic incidence (PI), pelvic tilt, and LL in preoperative and postoperative standing x-rays. Ideal lumbar lordosis (ILL) was calculated using the formula: ILL = 0.5 (PI) + 28. Results: We included 16 patients (7 male; 9 female) in the final analysis. Five were done in a single position (lateral decubitus), while the rest were repositioned (lateral then prone). The average age was 60.4 years (SD ±9.7) and BMI 33.6 (SD ±8.9). The average segmental lordosis change was 4.4°, broken into 2.4° after cage placement and an additional 2.0° after posterior instrumentation. The percentage of preoperative and postoperative patients with > 10° difference between measured and ideal LL is 18.8% (3/16) and 25.0% (4/16), respectively. Conclusions: Together with interbody cage placement, the described instrumented reduction technique resulted in increased operative level segmental lordosis (average 4.4°). Although no posterior column osteotomies were performed, 75.0% of patients who underwent single-level LLIF-PPS using this technique ended within 10° of patient-specific ideal lumbar lordosis.

1634

P414: Short-term clinical and radiological outcome of full-endoscopic lateral lumbar interbody fusion via Kambin's triangle in degenerative lumbar diseases

Akihiro Nagamachi ¹ , Hiroki Ikuchi ² , Kohei Ohta ¹ , and Masatoshi Morimoto ³

¹ Yoshinogawa Medical Center, Orthopedic Surgery, Tokushima, Japan

² Takamatsu Municipal Hospital, Orthopedic surgery, Kagawa

³ Tokushima University, Orthopedic Surgery, Tokushima, Japan

Introduction: Kambin reported the concept of percutaneous posterolateral nucleotomy in 1973. Since then, minimally invasive procedure using transforaminal approach has been developed. Full-endoscopic lateral lumbar interbody fusion via Kambin’s triangle (KLIF) offers several advantages over open methods like protection of posterior ligamentous and bony structures and paraspinal musculature. The purpose of this study was to evaluate early clinical results of degenerative lumbar diseases treated with KLIF. Material and Methods: Nine patients with degenerative spondylolisthesis (6 cases), spondylolytic spondylolisthesis (1 case) and degenerative lumbar scoliosis (2 cases) were participated in this study. There were 5 male and 4 female and their mean age was 63 years ranged from 34 to 77 years. All patients underwent CT and MRI to observe bony union and decompression of spinal canal 6 months and 1 year after the surgery. Clinical result was evaluated by Japanese Orthopaedic Association Back Pain Evaluation Questionnaire (JOABPEQ) and visual analog scale (VAS). Mean duration of observation was 21 months ranged from 6 to 36 months. Wilcoxon signed-rank sum test was used for statistical analysis. KLIF using a transforaminal approach was performed under general anesthesia with patient in a prone position on a radiolucent table, combined with motor evoked potential monitoring. After percutaneous pedicle screws were placed under fluoroscopic guidance, an endoscope was inserted in the superior articular process (SAP) through 8 mm skin incision created around 80 mm from the midline. The exposed SAP was removed using a 3.5 mm diameter high speed drill to expose disc space adequately. After the disc space was cleaned up, autologous milled bone and an expansion cage were inserted by using originally designed instruments. Mean duration of operation was 201 minutes and mean amount of blood loss was 45.5cc. No neural injury and deep surgical site infection was observed. Results: Union rate of the fused level was 100%. Among mean JOABPEQ item scores, pain related disorders sore, social life dysfunction score and psychological disorders score were significantly improved postoperatively. Lumbar spine dysfunction score and gait disturbance score did not have statistically significant improvement, however, p value were 0.058 and 0.059, respectively. We thought that those may have statistically significant value if the number of patient will increase. There were statistically significant improvement in mean VAS of LBP, buttock and leg pain. Conclusion: Open posterior interbody fusion inevitably causes paraspinal muscle injury. It is usually limited to the lower lumbar level. It has an increased risk of durotomy, especially during the revision surgery. Oblique lumbar interbody fusion and Lateral lumbar interbody fusion are suitable for degenerative lumbar diseases including sagittal and coronal deformity. But those carry the risk of vascular injury and intestinal injury. Zhao compared 40 cases of the endoscopic transforaminal lumbar interbody fusion group (ETLF) and the 38 cases of Minimally invasive trans foraminal interbody fusion group. He also reported that ETLIF may be efficient alternative surgery for degenerative lumbar spinal stenosis. KLIF was safe, effective and minimally invasive technique in treatment for degenerative lumbar disc diseases.

1674

P415: Anatomical and technical considerations of transiliac endoscopic assisted intraforaminal lumbar inter body fusion: A cadaveric study

Jose Miguel Sousa ^1,2 , Hugo Ribeiro ¹ , João Gamelas ¹ , and Jose Consciência ^2,3

¹ Orthopaedics, Centro Hospitalar Lisboa Ocidental, Lisboa, Portugal

² Comprehensive Health Research Center, NOVA Medical School, Lisboa, Portugal

³ Centro Hospitalar Lisboa Ocidental, Pre and Pos Graduation Department, Lisboa, Portugal

Introduction: Endoscopic spine surgery has gained wide popularity among spine surgeons over the last decade. The adoption of this surgical technique is backed up by recent meta-analyses that favor lumbar endoscopic discectomy over microdiscectomy in clinical outcomes, duration of surgery, length of hospital stay, and lower risk of complications. Initially seen as a tool for treating lumbar disc herniations, the range of applications for spine endoscopy expanded, namely to the cervical and thoracic spine. Its use in the treatment of foraminal, lateral recess, and central stenosis is increasingly common. However, the benefits of an endoscopic approach go beyond decompression surgeries. Initial reports on endoscopically assisted fusion date back to the mid-1980s. A recent meta-analysis comparing endoscopic assisted intraforaminal lumbar interbody fusion (iLIF) and minimally invasive transforaminal lumbar interbody fusion (MI-TLIF) has shown that for the treatment of lumbar degenerative diseases, iLIF has significantly less intraoperative blood loss and reduced length of hospital stay. Although the iLIF technique has been gaining traction in L4L5 and the upper lumbar spine, the unique anatomy of L5S1 has put some limitations to the expansion of the technique in this segment. To overcome some of these limitations, a transiliac approach has been described to address disc herniations and stenotic pathology. However, its reference to the iLIF technique is anecdotic. The purpose of this study is to demonstrate the feasibility of a L5S1 iLIF transiliac approach and to characterize the anatomic correlations of the endoscopic transiliac track. Material and Methods: Ten transiliac iLIF and ten suprailiac iLIF were performed bilaterally at L5S1 in five randomly selected fresh-frozen human cadavers. The following measurements were recorded: distances from the transiliac track to the iliac crest, posterior superior iliac spine, and superior gluteal neurovascular bundle; pelvic parameters; approach angles; cage’s lateral and AP center point ratio (CPR); percentage of the cage crossing the midline in the AP and lateral views. Endplates integrity was assessed through endoscopic visualization. Facet joint, sacroiliac joint, iliolumbar ligament, exiting, and traversing nerve roots were checked for integrity through anatomic dissection. Results: In the transiliac technique, the axial and coronal approach angles were significantly decreased by 13,5° (95%CI -15.5; -11.5; p value < 0.001) and 13.2° (95%CI -15.3; -11.1; p value < 0.001), respectively, the sagittal approach angle was significantly increased by 5,4° (95%CI 1.8, 8.9; p value = 0.008), and the AP CPR was significantly higher (MD 0,16; 95%CI 0.12,0.20; p value < 0.001). The percentage of the cage crossing the AP view’s midline was increased by 31.6% (95%CI 19.8, 43.4; p value < 0.001). Integrity of endplates, facet joints, sacroiliac joints, iliolumbar ligament, exiting, and traversing nerve roots was maintained. Conclusion: L5S1 transiliac iLIF is a feasible surgical technique. It allows a more centrally placed interbody cage in the coronal plane without compromising the anterior position in the lateral plane. The integrity of the major anatomic structures at risk was preserved.

1678

P416: Clinical outcomes, complications and fusion rates in endoscopic assisted intraforaminal lumbar inter body fusion (iLIF) versus minimally invasive transforaminal lumbar inter body fusion (MI-TLIF): systematic review and meta-analysis

Jose Miguel Sousa ^1,2 , Hugo Ribeiro ² , João Luis Silva ² , and Jose Consciência ^1,3

¹ Comprehensive Health Research Center, NOVA Medical School, Lisboa, Portugal

² Orthopaedics, Centro Hospitalar Lisboa Ocidental, Lisboa, Portugal

³ Pre and Pos Graduation Department, Centro Hospitalar Lisboa Ocidental, Lisboa, Portugal

Introduction: Minimally invasive spine surgeries intend to reduce tissue trauma, decrease complication rates, and improve functional recovery. Advances in endoscopic spine surgery made way for new opportunities to minimize tissue aggression further. Recently published meta-analyses regarding the treatment of lumbar disc herniations favored endoscopic discectomy (ED) over microdiscectomy (MD) in clinical outcomes, duration of surgery, length of hospital stay, and lower risk of overall complications. These results opened the perspective that ED could take over the place of MD as the gold standard of care in the management of lumbar disc disease. Technological innovations in endoscopic spine surgery have widened its range of applications beyond lumbar disc herniations. Endoscopic treatment of central and lateral recess stenosis, as well as endoscopic assisted lumbar interbody fusion (LIF) for degenerative lumbar diseases, are increasingly common. The benefits of an even less invasive technique than minimally invasive TLIF (MI-TLIF) would be further improvement in the advantages over open TLIF. Encouraged by the success of ED, endoscopic assisted intraforaminal LIF (iLIF) has been increasing its popularity. Even though several surgical techniques have been described, Kambin’s triangle approach through an intraforaminal facet sparing technique is the most usual and the one that has greater potential to reduce iatrogenic soft and bone tissue trauma. Recent studies have shown promising results regarding reduced blood loss, decreased length of stay, clinical outcomes, complications and fusion. However, the comparison between MI-TLIF and iLIF is sparse in the literature, and concerns about the safety and effective benefits of the endoscopic technique remain unanswered. This systematic review and meta-analysis of MI-TLIF and iLIF were conducted to synthetize and compare the available data in the literature on clinical outcomes, complications and fusion rates. Material and Methods: The MEDLINE, Embase, and Cochrane Library databases were searched. The inclusion criteria were: five or more consecutive patients who underwent iLIF or MI-TLIF for lumbar degenerative diseases; description of the surgical technique; clinical outcome measures, complications and imaging assessment; minimum follow-up of 12 months. Surgical time, blood loss, and length of hospital stay were extracted. Mean outcome improvements were pooled and compared with minimal clinically important differences (MCID). Pooled and direct meta-analysis were evaluated. Results: We identified 42 eligible studies. The iLIF group had significantly lower mean intra-operative blood loss (UMD 110,61mL; 95%CI 70.43, 150.80; p value < 0.0001), and significantly decreased length of hospital stay (UMD 2,36; 95%CI 1.77,2.94; p value < 0.0001). VAS back, VAS leg and ODI baseline to last follow-up mean improvements were statistically significant (p value < 0.0001), and clinically important for both groups (MCID VAS back > 1.16; MCID VAS leg > 1.36; MCID > 12.40). There was no significant difference in complication nor fusion rates between both cohorts. Conclusion: Interbody fusion using either iLIF or MI-TLIF leads to significant and clinically important improvements in clinical outcomes for lumbar degenerative diseases. Both procedures provide high rates of fusion at 12 months or later, without significant difference in complication rates. iLIF is associated with significantly less intraoperative blood loss and length of hospital stay.

1692

P417: Is narrow oblique corridor a contraindication for oblique lumbar interbody fusion?

Weerasak Singhatanadgige ¹ , panupong chatareeyagul ¹ , Vit Kotheeranurak ¹ , and Worawat Limthongkul ¹

¹ Orthopedics, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand

Introduction: Evaluation of the pre-psoas oblique corridor is generally recommended before performing Oblique Lumbar Interbody Fusion (OLIF) procedure. Narrow corridor especially at L4-5 is one of the constraints to perform OLIF due to the increasing risk of major vessel injury. The aim of this study is to investigate if there was a difference in functional outcome and operative complication between narrow and wide corridor size patient operated with OLIF at L4-5. Material and Methods: Retrospective study of patients who had undergone OLIF surgery at least one level which include L4-5 from 2017 and 2020. The patients were divided into three groups by size of the corridor; not more than 10mm, between 10 to 20 mm, and 20 mm or more. We collected and reviewed VAS score, ODI score, complication and radiographic findings in each group for up to one-year follow-up. Results: Eighty patients were divided into three groups from the size of the corridor (0-10 mm, 11-20 mm and more than 21 mm). No significant difference of VAS score, ODI score and complication between each group. The radiographic findings including position of the cage, anterior and posterior disc height, segmental angle and foraminal height were recorded and found no significant difference between each group. The only radiographic finding that has significant difference between each groups is the angle of the cage. In the group of more than 20mm corridor had found significantly less degree of angle than the other two groups. (p-value = 0.01). There was no recorded incidence of major vascular complication. Conclusion: Narrow or wide corridor does not affect functional outcome and radiographic finding including position of the cage, anterior and posterior disc height, segmental angle and foraminal height after OLIF procedure at L4-5 level. Only angle of the cage that were affected by the size of corridor. Thus, narrow corridor should not be the contraindication to perform OLIF procedure.

1704

P418: How safe is minimally invasive lumbar decompression and discectomy (MILD). Learning curve and outcomes of a single spine surgeon in a peripheral spine unit

Sultan Malik ¹ , Amin Kheiran ¹ and Purnajyoti Banerjee ¹

¹ Orthopaedic Spine, Kettering General Hospital, Kettering, United Kingdom

Background: Minimally invasive lumbar decompression and discectomy (MILD) using tube dilators is an established technique of treating lumbar spinal stenosis and disc prolapse. We report single surgeon experience of MILD on reoperation, pain relief, and patient reported outcome with minimal 6-months follow-up after introduction in our spine unit. Methods: Patients diagnosed with lumbar spinal stenosis who underwent MILD over 12 months after introduction of tube assisted spine surgery in a district general hospital spine unit were included. Data was collected prospectively. The primary outcome measure was incidence of revision surgery at 6-months. Secondary outcome measures included change in pain levels using the Visual Analogue Scale (VAS), Oswestry Disability Index (ODI), from baseline to 6- months following primary procedure. Duration of surgery, length of (hospital) stay (LoS), and blood loss, rate of unplanned operations and readmissions were recorded. Results: Thirty two patients (14 males and 18 females) aged 66.9 years (range 54-83), with a single level spinal stenosis that underwent MILD were included. Mean duration of surgery was 2.05 hours (range, 1.18-3.25). All patients had BMI > 30 (31.3-46.5). The mean ASA was 3. There were no readmissions or revision surgery within 6 months. The average blood loss was 72.5 mL (range, 20-210). The mean Length of stay was 1.2 day (range, 1-3 days). Mean pre-operative and post-operative VAS was 7.7 (range, 4-10), and 4.6 (range, 1-9), respectively. Mean pre-op and post-op ODI was reported as 36.5 (range, 22-55), and 26.3 (range, 13-38), respectively. Further sub-analysis showed no differences in VAS for pain, LoS and ODI between patients aged < 65 or > 65 years (p > 0.05). Conclusion: MILD procedure is safe and achieved reliable pain relief, and improved functionality when introduced in a peripheral spine unit at 6 months in patients with high BMI with minimal complications. We recommend introduction of minimally invasive surgery by trained surgeons can be safely undertaken in smaller spine units.

1709

P419: Full endoscopic and percutaneous posterior stabilization for lumbar spinal stenosis with degenerative spondylolisthesis. Case series

Andre Calderaro ¹

¹ Full Endoscopic Surgery, Centro Ortopedico Valqueire, Rio de Janeiro, Brazil

Objective: To present clinical and radiological outcomes of a case series of lumbar spine stenosis (LSS) associated with single level degenerative spondylolisthesis (DS), treated by full endoscopic decompression and percutaneous posterior stabilization. Methods: A total of 10 patients with clinical radiological diagnosis of LSS associated with DS in a single level underwent a full endoscopic decompression (laminectomy, flavectomy and discectomy) and posterior stabilization with pedicle screws by minimally invasive percutaneous access followed up for a period of 6 months. Clinical outcomes were assessed with Oswestry Disability Index (ODI) and Visual Analog Scales (VAS) for back and leg pain. Radiological outcomes were assessed comparing pre and post operative MRI images using the Schizas classification for LSS and Meyerding classification for lumbar Spondylolisthesis. Level - The L4L5 level was most discussed in this series, 6 cases, 3 in L5S1 and 1 in L3L4. Schizas – 5 cases grade B, 3 grade C and 2 grade D. Meyerding – 8 cases grade 1 and 2 cases grade II. Results: All patients reported significant improvement in axial and radicular pain symptoms as well as classic neurogenic claudication in LSS cases, documented by the ODI and VAS. Int 9 of 10 cases, was improvement related to the Schizas. There was no difference in relation to the pre and post op Meyerding classification. Conclusion: In this series of cases, full endoscopic decompression associated with posterior percutaneous stabilization proved to be affective for the treatment of LSS with DS with favorable clinical and radiological outcomes, in addition to the advantages of a minimally invasive surgery.

1748

P421: Decompression without fusion in degenerative lumbar spondylolisthesis: biportal endoscopic spinal surgery

Ho-Jin Lee ¹ , Jae-Sung Ahn ¹ , and Sang-bum Kim ¹

¹ Orthopedic Surgery, Chungnam National University College of Medicine, South Korea

Introduction: It has been debatable for patients with lumbar spinal stenosis (LSS) with degenerative spondylolisthesis (DS) whether the decompression-only surgery is preferable to decompression with instrumented fusion. The current study was to access clinical and radiological outcomes after unilateral laminotomy for bilateral decompression (ULBD) procedure using biportal endoscopic spinal surgery (BESS) in LSS with or without stable DS. Material and Methods: Between January 2015 and April 2020, we conducted a retrospective study on those who have had ULBD using BESS for one level lumbar segment and proceeded the assessment into two groups; LSS with stable DS (Group A) and LSS without DS (Group B). 20 patients in Group A and 49 patients in Group B were enrolled. The length of hospital stay (LOS), follow-up period, operation segment, operative time, complications, and clinical and radiological outcomes were evaluated. Clinical outcomes were measured preoperatively and at the final follow-up time using Visual Analog Scale (VAS) scores, Oswestry Disability Index (ODI) scores, and the modified Macnab criteria. Radiological outcomes were accessed by measuring the sagittal translation of the lateral plain radiogram of DS. Results: Median follow-up times were 850 days in Group A and 930 days in group B. All the clinical parameters improved significantly after the operation in both groups. At the final follow-up, no clinical parameters differed significantly between the groups and no complications developed in either group. Radiologically, no significant progression of sagittal translation at the final follow-up time of DS. Conclusion: We suggest that ULBD using BESS is a practical, alternative, minimally invasive procedure for treating one-segment LSS with stable DS.

1755

P422: Advantages of 4K 3D exoscope in thoracic and thoracolumbar MIS approaches

Joseph Aferzon ^1,2

¹ Neurosurgery, Hartford Hospital, Hartford, United States

² Neurosurgery, University of Connecticut, Farmington, United States

Introduction: With advent of new MIS techniques, visualization of deep structures through a narrow portal can be challenging. All traditional means of visualization present shortcomings. Current Microscopes are too bulky and with limited focal depth they presents very restricted working space, particularly when using long instruments. Additionally, steep working angles require surgeons to stand in awkward position while trying to look "down the scope". Surgical Loupes provide limited magnification and require additional means of illumination. Additionally, surgical loupes are an ergonomic disaster, particularly for long cases. Endoscope technologies may solve some of these issues but they do not provide 3D depth perception, which I believe has contributed to its limited use in high precision surgery. The new exoscope technology has the potential to address all of the above shortcomings. Material and Methods: Author has extensive experience with advanced MIS surgery for thoracic and thoracolumbar pathology, with over 200 cases performed successfully. He has traditionally used surgical loupes and microscope when feasible. Author presents his experience using novel Mantis 3D 4K exoscope (1) for deep MIS thoracic and thoracolumbar exposures for decompression, fusion and fixation. Results: Exoscope provides improvement over loupes and microscope. Because of the longer focal distance and smaller profile it dramatically increases working space compared to the microscope. Because of decoupling between image acquisition and visualization it significantly improves ergonomics during surgery particularly noticeable during long procedures. It offers excellent depth perception, therefore overcoming the limitations of an endoscope. This exoscope provides a unique opportunity for teaching surgical techniques through real time sharing of 3D images as well as 3D replay after the surgery. This Exoscope use has a learning curve of 5 to 10 cases based on surgeons prior experience with technique and technology. Conclusion: Exoscope overcomes many limitations of traditional intraoperative visualization solutions. It is particularly well suited for deep approaches through a narrow corridor. This technology should facilitate adoption of advanced minimally invasive techniques.

(1) Mantis Health, Stamford CT USA

1761

P423: Risk factor for screw loosening following minimally invasive transforaminal lumbar interbody fusion

Weerasak Singhatanadgige ¹ , Pipat Klaewkla ¹ , Vit Kotheeranurak ¹ , and Worawat Limthongkul ¹

¹ Orthopedics, Chulalongkorn University, Bangkok, Thailand

Introduction: Screw loosening is a postoperative complication leading to poor outcomes after minimally invasive transforaminal lumbar interbody fusion (MIS-TLIF). This study aimed to identify the incidence and risk factors of Screw loosening after 1 level MIS-TLIF for degenerative lumbar disease. Material and Methods: In this retrospective study, plain radiographs and three-dimensional computed tomography were performed 12 months after 1-level MIS-TLIF. Screw loosening was defied by at least 1 millimeter radiolucent around pedicle screw from CT scan. The incidence and risk factors of screw loosening was calculated with odds ratio (OR), confidence interval (CI), and logistic regression analysis. Results: A total of 151 patients (mean age, 64 years) were included in this study: 35 (23%) with and 116 (78%) without Screw loosening. Lower screw is affected more often than upper screws (82% compare to 18%). The independent risk factors significantly associated with Screw loosening were lower pedicle Screw depth (OR = 2.01; p = 0.025), severe multifidus atrophy (OR = 5.56; p = 0.045). Correlation analysis showed that the fusion rate was associated to screw loosening. Conclusion: In 1-level MIS-TLIF with a PEEK cage. The factors significantly associated with Screw loosening were pedicle screw depth and severe multifidus atrophy.

1772

P424: Clinical evaluation of computerized modified paramedian approach technique (CMPAT) and conventional midline approach (MAT) of lumbar puncture: study protocol for a prospective, multicenter randomized control trial

Yuan-Dong Zhuang ¹ , Yi-Ze Chen ² , Qi-Ying Lin ² , Si-Qi Zhong ² , and Yi-Xin Chen ²

¹ Neurosurgery, Fujian Medical University Union Hospital, Fuzhou, China

² Basic Medical College, Fujian Medical University, Fuzhou, China

Introduction: Lumbar puncture (LP) technique is one of the commonly used clinical treatment methods in the neurological system and is of great value in the diagnosis and treatment of neurological diseases. The traditional LP technique is the midline approach technique - lumbar puncture (MAT-LP), which has various problems such as low success rates, many complications and crude learning methods. Compared with MAT-LP, paramedian approach technique - lumbar puncture (PAT-LP) has the advantages of low puncture failure rate, low number of puncture attempts, and low incidence of post-LP headache. The various reported PAT-LP puncture methods have not yet been unified, and previous studies on PAT-LP lacked intelligent global analysis and three-dimensional multi faceted analysis. Therefore, based on digital avatar and computer simulation technology, our study has proposed a evaluation of Computerized Modified Paramedian Approach Technique (CMPAT) in the early stage, aiming to explore the best LP path with high versatility and success rate. Accordingly, the purpose of the present study is to to compare the effects of CMPAT and MAT lumbar puncture in patients requiring lumbar puncture. Material and Methods: The trial plan included 84 patients, aged 18-99 years, from multiple study centers requiring LP with Fujian Medical University's Union Hospital as the group leader, randomly and equally divided into 2 groups of 42 patients each, with CMPAT-LP in group A and MAT-LP in group B. The patients were followed up on postoperative days 1, 3 and 7. The primary observation of the study was the number of punctures attempted by the surgeon at the time of successful lumbar puncture; the secondary observation was the pain in the head, back, hind legs after lumbar puncture, and pain assessment was performed before, during, and 30 minutes after the operation, 6 hours after the operation, day 1, day 3, day 7, and day 30 after the operation, all using the pain numerical rating scale (NRS) scoring. The study complied with the requirements of the Declaration of Helsinki established by the World Medical Association. Participants gave informed consent to the trial content and treatment procedure and signed an informed consent form. Discussion: The trial expects to demonstrate thatCMPAT-LP has a higher success rate, lower pain scores and fewer complications than MAT-LP.

1889

P425: Comparison of clinical effect of percutaneous endoscopy through lateral approach and posterior approach treating shoulder type of L5/S1 disc herniaion

Yizhou Xie ^1,2 , XiaoHong Fan ¹ , and Yang Yu ¹

¹ Orthopaedic Surgery, Hospital of Chengdu University of Traditional Chinese Medicine, Chengdu, China

² Neurological Surgery, Weill Cornell Medical College-New York Presbyterian Hospital, New York, United States

Study Design: Retrospective Cohort Study. Objectives: To compare the clinical effect of percutaneous endoscopic through lateral approach and posterior approach treating the shoulder type of L5/S1 lumbar disc herniation (LDH). Methods: Each 30 cases diagnosed in shoulder type of L5/S1 LDH who received percutaneous endoscopy through lateral approach and posterior approach were collected and divided into: the lateral approach group and the posterior approach group. Clinical evaluation was performed at preoperation and postoperative 3^rd day, 1^st month and 1^st year in each group. The indicators involved include VAS, ODI, operation cost, operation time and fluoroscopy time. Results: In contrast, the posterior approach group showed shorter mean operation time and fewer mean intraoperative radiation (p < 0.05). However, compared with posterior approach group, lateral approach group was more economical (p < 0.05). In terms of VAS and ODI, the difference between two groups is not significant in preoperative and postoperative 3^rd day, 1st month and 1^st year (p > 0.05). On the other hand, mean VAS and ODI of two groups acquired by three postoperative follow-up phases were significantly improved compared with preoperation (p < 0.05). No statistical significance was observed in pairwise comparison among three postoperative follow up phases in two groups (p > 0.05). Conclusion: In treating shoulder type of L5/S1 LDH, both the lateral approach and the posterior approach for percutaneous endoscopy are effective. Compared with the lateral approach, the posterior approach has the advantages of fewer intraoperative X-ray radiations and less operation time. However, the lateral approach is less costly than the posterior approach.

1893

P426: Biportal endoscopic revision operation of postoperative cage migration after a lumbar interbody fusion: a case report and literature review

Yizhou Xie ^1,2 , XiaoHong Fan ¹ , and Yang Yu ¹

¹ Orthopaedic Surgery, Hospital of Chengdu University of Traditional Chinese Medicine, Chengdu, China

² Neurological Surgery, Weill Cornell Medical College-New York Presbyterian Hospital, New York, United States

Background: Postoperative cage migration is a catastrophic operational complication after a spine surgery which could cause severe clinical symptoms. Its revision operation using endoscope has rarely been reported in the literature so far. This is a case report of a 48-year-old female occurring postoperative cage migration in the 3^rd days after a biportal spinal endoscopic lumbar interbody fusion. Case Presentation: A 48-year-old female patient presented with a left L4-5 radiculopathy with medical imagining and physical sign corresponded. A biportal spinal endoscopic lumbar interbody fusion was then performed using a lordotic polyetheretherketone (PEEK) graft (26 mm length×10 mm width×10 mm height) packed with allograft bone. In the 3^rd postoperative day, the patient presented with an acute radiculopathy on left leg. An immediate lumbar CT scan and MRI demonstrated posterior cage migration to the canal at the L4-5 level. The revision surgery under biportal endoscopy was performed at once to get it well managed ultimately. After surgery, the patient's symptoms were greatly relieved until he was discharged in the 15^th days postoperatively. Conclusion: Postoperative cage migration in spinal endoscopic lumbar interbody fusion is a rare complication. But endplate damage and the undersized cage with posteriorly placement are more prone to developing this complication. Endoscopic revision operation is an optimal surgical intervention that worth considering.

1901

P427: Comparison of the safety and efficacy of unilateral biportal endoscopic lumbar interbody fusion and uniportal endoscopic lumbar interbody fusion: a 1-year follow up

Yizhou Xie ^1,2 , XiaoHong Fan ¹ , and Yang Yu ¹

¹ Orthopaedic Surgery, Hospital of Chengdu University of Traditional Chinese Medicine, Chengdu, China

² Neurological Surgery, Weill Cornell Medical College-New York Presbyterian Hospital, New York, United States

Objectives: To compare the short-term outcomes of unilateral biportal endoscopic lumbar interbody fusion (BLIF) and uniportal endoscopic lumbar interbody fusion (ULIF). Methods: Sixty patients diagnosed with L4/5 spinal stenosis who underwent BLIF and ULIF were included (30 in each group). Clinical evaluation was performed preoperatively and postoperatively in the 1^st week, 1^st month, and 1^st year. Factors such as the visual analogue score (VAS), Oswestry disability index (ODI), operative time, surgical complications, and radiological outcomes (fusion rate, screw loosening, and cage subsidence) were compared between the two groups. Results: All patients showed improved mean VAS and ODI at all three postoperative follow-ups, and no statistically significant differences were detected between the BLIF and ULIF groups. The mean operative time in the BLIF group was shorter than that in the ULIF group. Nerve root injury occurred in two patients in the BLIF group, while leakage of cerebrospinal fluid occurred in one patient in the ULIF group. All adverse events were treated adequately prior to discharge. The fusion rates with definite and probable grades were significantly higher in the BLIF group than that in the ULIF group. One case of cage subsidence with no screw loosening occurred in each group. Conclusion: Both BLIF and ULIF are safe and effective surgical techniques. Compared with ULIF, BLIF has the advantages of shorter operative time and a higher fusion rate. Other merits of BLIF include a wider surgical field, greater maneuverability of instruments, visibility during cage implantation, and transverse orientation of the cage.

1938

P428: The impact of 2 expandable TLIF cage design types on geometry of the lumbar spine - preliminary results of case series

Pravesh Gadjradj ¹ , Fabian Sommer ¹ , Ibrahim Hussain ¹ , Jacob Goldberg ¹ , Sertac Kirnaz ¹ , Branden Medary ¹ , Rodrigo Navarro-Ramirez ¹ , and Roger Härtl ¹

¹ Department of Neurological Surgery, Weill Cornell Medicine and New York Presbyterian Hospital - Och Spine, New York, United States

Introduction: Tubular MIS TLIF is a widely used procedure for lumbar spine fusion. One limitation of this technique is the amount of segmental lordosis that can be achieved with interbody cages. Recently, a variety of expandable, lordotic cage designs have been developed that allow cage height and lordosis adjustment. The RISE ^® cage has a fixed lordosis of 8 degrees and can be expanded in height. The SABLE ^® cage can have lordosis of up to 15 degrees after which the height can be expanded. It is unclear as to how these cage designs affect lumbar lordosis postoperatively. We present a case series evaluating short term radiographic outcomes using this device. Methods: A prospective study of consecutive patients undergoing one-level tubular MIS TLIF with either a RISE^® or SABLE^® expandable cage was performed. Pre- and postoperative day 1 radiographs were compared, measuring anterior and posterior disc height, lumbar lordosis, segmental lordosis, and pelvic incidence. Perioperative data was also collected including operative time, blood loss, length of hospital stay, and procedure-related complications. Results: A total of 77 patients were included: 40 with RISE^® cages, and 37 with SABLE^® cages. There was a decrease in overall lumbar lordosis and an increase in posterior disc height from pre-operation to post-operation for both RISE^® and SABLE^® groups, with no difference between segmental lordosis. There were no differences between RISE^® and SABLE^® groups at pre-operation and post-operation overall. In the preoperative low lordosis group, the segmental lordosis showed a statistically significant increase compared to preop independent of the type of cages used. The mean segmental lordosis either stabilized or slightly decreased after surgery in patients with preoperative segmental lordosis from 16 degrees or higher. Overall segmental lordosis for RISE^® and SABLE^® cages went from 16.9 ± 10.7 to 17.0 ± 8.4 (p = 0.95) and 16.6 ± 8.9 to 15.2 ± 7.8 (p = 0.53) respectively. Overall lumbar lordosis for RISE^® and SABLE^® cages significantly decreased from 48.0 ± 19.0 to 44.0 ± 17.4 (p = 0.005) and from 35.3 ± 37.1 to 28.1 ± 35.0 (p = 0.002). Finally posterior disc height for RISE^® and SABLE^® cages significantly increased from 4.8 ± 2.7 to 8.7 ± 2.2 (p < 0.001) and from 4.3 ± 2.1 to 8.2 ± 2.8 (p < 0.001). Conclusion: In this large prospective case series between two expandable cage designs used during TLIF, there were no differences between RISE^® and SABLE^® cages after surgery in terms of radiological spinal parameters. More patients are needed to make definitive conclusions.

1942

P429: Does the use of robotic guidance system in spine surgery increase the safety and accuracy of implant placement? Assessment of 450 cases

Sajan Hegde ¹ , Appaji Krishnan ¹ , Vigneshwara Badikkilaya ¹ , Sharan Achar T ¹ , Umesh Kanade P ¹ , and Harith Reddy ¹

¹ Orthopaedics, Apollo Hospitals Chennai India, Chennai, India

Introduction: The placement of pedicle screws in complex and deformed spines is a challenging task with increased demand on the operating surgeon to be safe and accurate. The need to do minimally invasive surgery entailing radiation hazards to the operating room personnel necessitates a system to guide screw placement safely, accurately and with reduced radiation exposure. The Renaissance and Excelsius GPS robot helps in guiding the placement of pedicle screws in deformities and for various minimally invasive procedures. The objective of this study is to study and analyse efficacy of the robotic guidance system in pedicle screw placement in spinal deformities and minimally invasive spine surgery for degenerative and infective conditions. Material & methods: Prospective case series of 450 patients with a mean age of 42 yrs (Range: 7-78yrs) were operated for various indications as spinal deformities in 88 patients (Adolescent Idiopathic Scoliosis-46, Neuromuscular Scoliosis-18, Congenital Scoliosis-10, Ankylosing Spondylitis-2, Congenital Kyphosis-6, Degenerative-2, Post-traumatic-2, Failed/revision-2), degenerative conditions (single/ double/ multilevel (3-4) lumbar disc disease with stenosis and/or degenerative listhesis - 336), dorsal stabilisation for infection/ malignancy- 22 and 4 vertebral body lesions biopsy. Parameters such as operating time, radiation exposure, screw accuracy and complications were calculated. Results: In the deformity group all the screws were found acceptable as per intraoperative fluoroscopy. One screw was misplaced laterally as a result of ‘Skiving’ but without any adverse neural or vascular effect. In the Minimally Invasive group, per operatively 89 guide wires were not as per planning on fluoroscopic check and needed repositioning. All the screws were found to be acceptable intraoperatively as per fluoroscopy. Postoperative CT scan analysis of screw accuracy by an independent radiologist and one of the authors showed that all screws except 42 had screws placed as per the pre-operative planning, resulting in an accuracy of 98.9. There were no adverse vascular or neurological events intra-operatively. The average radiation exposure per screw was 0.98 seconds in the deformity patients and 1.595 seconds in the MIS group. The operating time was comparable to standard open procedures and there was a significant reduction (40%) in operating time in the second half of cases with respect to the first half, showing an attainable learning curve. Conclusion: Robotic guidance helps in increasing the safety and accuracy of the pedicle screw placement in various spinal disorders especially in obese degenerative disc disease and paediatric deformity patients.

2003

P430: Pain outcomes in minimally invasive surgery for palliative treatment of spinal metastases

Nolan Brown ¹ , Taylor Reardon ¹ , Alvin Chan ¹ , Andrew Chan ² , Shane Shahrestani ¹ , Chenyi Yang ¹ , Gabrielle Hovis ¹ , Elliot Choi ¹ , Ryan Beyer ¹ , Zachary Hsu ¹ , Martin Pham ³ , and Michael Oh ¹

¹ Neurosurgery, UC Irvine, Irvine, United States

² Neurosurgery, Columbia University, New York, United States

³ Neurosurgery, UC San Diego, San Diego, United States

Introduction:Minimally invasive surgery (MIS) of the spine has emerged as an established component of the spine surgeon's armamentarium. MIS comes with the advantage of reduced surgical insult, conferring particular benefit to patients undergoing palliative treatment who have metastatic spinal tumor burden. Materials and Methods:The present study aims to assess the safety, efficacy, and impact on quality of life of MIS of the spine for palliative treatment of spinal metastases by analyzing complication rates and visual analog scale (VAS) pain scores. A systematic literature search was performed from January 22, 2002 to January 22, 2022 searching for all articles of patients undergoing MIS for spinal metastases. All studies reporting clinical data and surgical complications were included. Results:Five studies reporting on 62 metastatic spinal tumor cases were included. There were 35 males and 27 females. Of the included studies, China had the most studies (40%) with Germany, Canada and The United States reporting one study each (20%). The mean age of participants was 58.1 years. The most common tumor location was in the thoracic spine (60.5%), while the most common sources of spinal metastasis included cancers of lung (32.3%), bone marrow (myeloma) (21.0%), and breast (11.3%). The mean preoperative VAS score was 7.1 ± 1.1 while the mean postoperative score VAS was 1.2 ± 1. There was an average reduction in VAS scores across all 5 studies of 6.4 ± 1.0. Mean follow-up time was 9.25 months in the four articles reporting this data. Average complication rate was 9.26% with a range between 0-32% with zero perioperative deaths recorded. The most common complication mentioned was cement leakage. Conclusion:Minimally invasive approaches for palliative surgical management of spinal metastases are associated with improved VAS scores. In addition to favorable pain outcomes, complications appear to be minimal; these approaches therefore represent a viable option for palliative pain management that can improve quality of life.

2009

P431: Does provider matter: an assessment of evidence supporting performance of minimally invasive SIJF by spine surgeons versus non-spine specialists

Nolan Brown ¹ , Alexander Himstead ¹ , and Michael Oh ¹

¹ Neurosurgery, UC Irvine, Irvine, United States

Introduction:As patient demand for minimally invasive SIJF has increased, non-surgeons (including pain management physicians) have begun to perform a growing number of minimally invasive posterior SIJF procedures, even though these have traditionally been reserved for spine surgeons, whose extensive training renders them experts in spinal instrumentation and biomechanics. Materials and Methods:In November 2021, a PubMed/Medline search and initial screen yielded 11 studies that were subjected to full text analysis. Using the list of SIJF devices obtained from these studies, additional searches were conducted using the National Institute of Health (NIH) Clinical Trials website and FDA 510(k), among others, yielding 6 unique devices that can currently be used by non-surgeons in the posterior SIJF approach. Results:Spine surgeons generally perform lateral or posterolateral MIS SIJF. There are 11 unique FDA-approved devices and a total of 33 SIJF devices overall. 10 of these devices have been described in numerous reports within the peer-reviewed medical literature. For example, Titanium Triangular Implants (lateral) are described in 11 retrospective studies (level 4 evidence), 2 level 2 prospective studies, and 2 level 1 prospective studies. By contrast, non-surgeons have only investigated the use of posterior allograft devices in 2 studies. One of these studies (PainTEQ) is featured on ClinicalTrials.gov. The other is a systematic review citing 6 studies on posterior SIJF performed by non-surgeons. However, 2 of these 6 studies are conference abstracts and therefore cannot be assigned meaningful levels of evidence. Conclusion:Instrumentation of the spine requires extensive surgical training such as that completed by spine surgeons. There is an increasing body of evidence in the literature supporting the performance of MIS SIJF.

2019

P432: Minimally invasive spinal surgery for non degenerative spinal pathologies - a single surgeon experience of 30 cases

Alok Uppar ¹

¹ Neurosurgery, NIMHANS, Bengaluru, India

Introduction: Tubular retractor(TR) based MISS is an evolving treatment option for spinal pathologies. A young neurosurgeon's initial experience of MISS for non-discal pathology is described. Methods: Retrospective study. All patients who underwent tubular retractor based MISS treatment for various non-discal spinal pathology were analysed clinically and radiologically pre-operatively , post-operatively and at follow up. Outcomes were analysed (Mc Cormick grades, Visual Analog scale(VAS) for pain, motor power and length of post-operative stay). The technical challenges and ways to overcome same were assessed. Results: Total cases -30. Male: Female ratio was 1:1. Mean age was 32 years (Range 17- 60 years). We had 12 intradural extramedullary schwannomas and 7 meningiomas, 1 neurenteric cyst, 1 hemagioblastoma (intra-medullary), 7 Chiari malformation with syrinx, and 2 cervical anterior epidural abscess. All were treated with TR based MISS (Medtronics system) and had good outcomes both clinically and radiologically at discharge and follow up. Mean follow up was 4 months(Range 2 months to 1 year). Median Mc Cormick grade in the pre-operative period was 4 and improved to 1 at follow up. Complete tumor excision was documented at follow up for all patients. ACM patients had definite improvement in their clinical condition at follow up. The Mean VAS score for pain was 7.5 pre-operatively and improved to 0.7 in the post-operative period. Best MRCS muscle power grading : Mean was 3 (Range 0-5) and all patients had improved to normal power at follow up. Median post-operative stay at hospital was 2.5 days(Range: 1-15 days). Only 1 patient had a complicated post-operative course as she developed meningitis which required prolonged post-operative admission for 15 days, after which she was discharged in a neurologically improved condition. Conclusion: TR based MISS surgery can be safely performed for intraspinal pathology with excellent outcomes. Young neurosurgeons can safely perform these minimally invasive spinal surgeries after proper training.

Navigation

115

P433: Influence of navigation on pedicle screw malpositions depending on the vertebral segment supplied

Pascal Beuting ¹

¹ Trauma, BG Bergmannsheil Bochum, Bochum, Germany

Introduction:Misplacement of pedicle screws can have significant impact on the postoperative outcome after dorsal spinal fusion. Various aids such as fluoroscopy and navigation are available to improve the screw position. The aim of the present study was to clarify to which extent the supplied spinal column segment has an influence on the selection of the aids and misalignment of the pedicle screw. Method: This retrospective CT-based cohort analysis (2016 to 2020) included 631 patients (m 341/f 293) who underwent surgical treatment in the thoracic and lumbar area due to their vertebral body fractures. Fractures in the area of the cervical spine were excluded. The pedicle diameters were measured in all patients and the surgical treatment was evaluated based on the pedicular screw position. For this purpose, the distance between the outer edge of the screw and the pedicle cortex was measured. Based on the measured distance, the screw position was divided into three stages (< 2 mm, 2-4 mm, > 4 mm overhang). A perforation of the pedicle of the screw > 2 mm was rated as an incorrect position. Results: The area with the highest rates of screw misplacement was the middle thoracic segments, where the smallest pedicle diameters were also measured. Th5 showed the highest misalignment rate of misplacement 21% (n = 31). Similar misalignment rates were also found in the adjacent segments. The pedicle screws at T6 16% (n = 26), T7 20% (30) and T8 17% (n = 28) were > 2 mm outside the pedicle. In the cranial thoracic vertebral segments (Th1-3), malposition rates of 5% (Th1; n = 1) to 15% (Th2; n = 9) were found. In the area of the thoracolumbar transition and especially the lumbar spine (Th12 - L3), 3% (L2; n = 15) to 5% (Th12; n = 25) of the pedicle screws showed a misplacement of > 2 mm. A comparison of the use of navigation shows that it was used particularly in the area of the upper and middle thoracic spine. Looking at the navigated screws in isolation, the malpositions in the area of the segments T4 to T8 can be seen with 25% (T4; n = 9) to 33% (T7; n = 10). In the area of the cranial thoracic vertebral segments, in which the navigated method was often used, misalignment rates of 6% (Th1; n = 1) to 16% (Th2; n = 5) are impressive. In the S1 segment, 4% (n = 1) of the pedicle screws showed a breach. Conclusion: The results of the present study show that the navigated procedure was used in particular in the areas of the cranial and middle thoracic spine as well as in the area of the lower lumbar spine. This can be explained on the one hand by the smaller pedicle diameter in the thoracic spine and by the more difficult accessibility of the caudal lumbar spine. In the thoracolumbar transition and in the area of the upper lumbar spine, due to the larger pedicle diameters, a low misalignment rate can also be achieved by conventional insertion of the pedicle screws, and thus the higher time expenditure of the navigated procedure may not be justified here.

876

P434: iCT-based navigation vs CBCT-based navigation for percutaneous pedicle screw placement in the thoracic spine: a cadaveric study

Antonia Medrow ^1,2 , Eric Mandelka ¹ , Jula Gierse ¹ , Felix Zimmermann ¹ , Paul Alfred Grützner ¹ , Jochen Franke ¹ , and Vetter Sven ¹

¹ Department of Trauma Surgery and Orthopedics, BG Klinik Ludwigshafen, Ludwigshafen, Germany

² Medical Faculty Heidelberg, University of Heidelberg, Heidelberg, Germany

Introduction: Pedicle screw placement is considered a standard procedure in thoracolumbar spine surgery for a variety of indications. 3D navigation guidance is increasingly used as the accuracy has proved to be more accurate compared to both fluoroscopic guidance and freehand screw placement. While different imaging and navigation devices can be used for intraoperative imaging and navigation, there are few studies comparing these under similar conditions. The aim of this study was to compare iCT-based navigation and a novel navigation system for 3D C-arm Cone Beam Computed Tomography (CBCT)-based navigation under standardised, experimental conditions in human specimens. Material and Methods: The study was performed on 4 fresh-frozen torsos. The combinations of imaging device and navigation system investigated were the iCT (Airo, Brainlab, Munich, Germany) with Curve navigation (Brainlab, Munich, Germany) and a latest generation flat-panel mobile 3D C-arm CBCT (Cios Spin, Siemens, Erlangen, Germany) with the Pulse navigation platform (NuVasive, San Diego, CA, USA). After obtaining referencing scans, the image data was transferred to the navigation system and unilateral navigated percutaneous pedicle screw placement (Reline MAS, Nuvasive, San Diego, CA, USA) was performed by an experienced spine surgeon on levels T2 to T12. Subsequently, referencing scans were performed using the second image device and navigated screw placement was performed on the contralateral side. Finally, a control scan was performed to allow for screw accuracy assessment which was performed by to blinded observers (Obs1 and Obs2) using Gertzbein and Robbins grading system. Grades A (no pedicle breach) and B (perforation < 2 mm) were deemed acceptable, while perforations of ≥ 2 mm (grades C to E) were deemed inacceptable. Accuracy between the different combinations was compared using Chi2 test with a significance level of p < 0.05. Interrater agreement was calculated using kappa (κ) as suggested by Landis and Koch. Results: Overall, 87 pedicle screws were placed in the 4 specimens. In the iCT navigation group, one screw could not be placed due to technical issues and a second screw could not be assessed because of poor image quality. For iCT-based navigation, the accuracy rate was 85.7% (Obs1) and 83.3% (Obs2) while using CBCT-based navigation reached an accuracy rate of 95.5% (Obs1) and 93.2% (Obs2). However, the difference between the combinations was not statistically significant (p = 0.152 for Obs1 and p = 0.191 for Obs2, respectively). Interrater agreement for screw accuracy being acceptable or not was moderate (88.1%; κ = 0.545) for iCT-based navigation and fair (93.2%; κ = 0.365) for CBCT-based navigation. Conclusion: Percutaneous pedicle screw placement in the thoracic spine proved to be accurate with both iCT- and CBCT-based navigation, however, accuracy with CBCT-based navigation tended to be higher. Further studies are needed to investigate if the results of the navigation system used with the CBCT can be transferred to clinical practice.

903

P435: 3D custom modelled navigation jigs in posterior spinal fusion: a retrospective case series

Libby Gooda ¹ , Emily Tsang ¹ , Bisola Ajayi ¹ , Jason Bernard ¹ , Timothy Bishop ¹ , Priyanshu Saha ¹ , Zion Hwang ¹ , and Darren Lui ¹

¹ Trauma & Orthopaedics, St. George's University Hospital, London, United Kingdom

Introduction: Navigation of the spine is an established technique to improve accuracy of pedicle screw placement. Intra-operative CT is often required, and sometimes two scans are required depending on the length of fusion, which can increase intra-operative time that the spine and metalwork are exposed with potential for infection. The use of 3D printing in spinal surgery is a growing technique. In the past, this was limited to use as a pre-operative visual aid, however, in recent years it has been used to create intra-operative patient specific screw jigs. A whole spine, low dose, 1mm axial cut CT scan is used to create a 3D model of the spine, to which 3D custom modelled navigation jigs (3DCMNJ) are created unique to each vertebra. This allows for accurate and precise techniques for pedicle screw insertion. Material and Methods: The British Spine Registry and ICLIP were used to identify all scoliosis patients who underwent posterior spinal fusion using 3DCMNJ from 22/09/2020-09/12/2021 at a South London tertiary medical centre and a London private hospital. Data was then collated regarding age, gender, time for screw insertion, blood loss during screw insertion, and screw density. Results: Data was collected on 25 patients. There was an average age of 16.16 (SD ± 1.95), N = 97. There was a higher proportion of female patients at 68% female, 32% male. The average time for screw insertion was 83 minutes (± 45), N = 20. The average blood loss during screw insertion was 153.1ml (± 159.21), N = 10. Screw density was 1.60 (± 3.50), N = 25. Two patients returned to theatre, one due to a spinal cord monitoring event, and one due to wound dehiscence. Conclusion: The use of 3DCMNJ in posterior spinal fusion allows for the rapid insertion of pedicle screws, thus limiting blood loss during this phase. Preoperative low dose CT allows for reduced operating time compared to intra operative CT for navigation or robotic pedicle screw entry. Less time of spine or metal work exposure could lead to decreased risk of infection. Further research is required to compare to standard posterior spinal fusion.

915

P436: Comparison of 3D custom modelled navigation jigs with freehand pedicle screw insertion for posterior spinal fusion in scoliosis

Libby Gooda ¹ , Emily Tsang ¹ , Bisola Ajayi ¹ , Timothy Bishop ¹ , Jason Bernard ¹ , Priyanshu Saha ¹ , Zion Hwang ¹ , and Darren Lui ¹

¹ Trauma & Orthopaedics, St. George's University Hospital, London, United Kingdom

Background: Scoliosis is characterised by a curvature of the spine. Significant curvature of the spine is often treated with spinal fusion. There are many different approaches to spinal fusion, with freehand pedicle screw insertion being the most common. However, this has inherent inaccuracies and a greater danger of spinal cord injury due to mispositioning. In more recent years, a new navigation technique has arisen. This technique utilises 3D printing technology to create unique, custom made patient-specific screw jigs, that fit onto each vertebra, allowing for accurate and precise pedicle screw insertion. Material and Methods: The British Spine Registry and ICLIP were used to identify all scoliosis patients who underwent posterior spinal fusion from 16/01/2017-09/12/2021 at a South London tertiary medical centre and a London private hospital. Data was then collated regarding age, gender, diagnosis, duration of surgery, estimated blood loss, screw density, hospital length of stay (HLOS), SRS-22 scores, and whether patients returned to theatre. Results: The average age was 17.94 (SD ± 3.77) N = 72, for freehand patients, and 16.16 (SD ± 1.95) N = 25, for 3DCMNJ patients. Both the freehand group and 3D custom modelled navigation jigs (3DCMNJ) groups had a greater proportion of female patients, at 74% and 68% respectively. Patients comprising the 3DCMNJ group had a higher screw density (SD ± 1.95, N = 57) when compared to the freehand group (1.60 ± 3.50, N = 25). 77.8% of the freehand patients were classed as having adolescent idiopathic scoliosis (AIS). The remainder: syndromic scoliosis (11.1%), secondary scoliosis (2.78%), cerebral palsy (2.78%), adult idiopathic scoliosis (1.39%), neurofibromatosis (1.39%), idiopathic kyphosis (1.39%), unknown (1.39%). 76.0% of the 3DCMNJ patients were diagnosed with AIS. The remainder: Scheuermann’s kyphosis (8.0%), unknown (8.0%), idiopathic kyphosis (4.0%), and congenital scoliosis (4.0%). Duration of surgery and estimated blood loss did not appear to differ significantly between the two groups. There also did not appear to be any significant differences in HLOS, nor post-operative SRS-22 scores. In the 3DCMNJ group, there was a return to theatre rate of 8% (4% spinal cord monitoring event, 4% wound dehiscence). In the freehand group, there was a return to theatre rate of 11.1% (5.56% due to failure of metalwork, 1.39% spinal cord monitoring event, 1.39% due to infection, 1.39% wound dehiscence, and 1.39% post-operative haemothorax). Conclusion: The use of 3DCMNJ does not lead to significant differences compared to freehand pedicle screw placement with respect to operating time, blood loss, HLOS, or SRS-22 scores. However, the 3DCMNJ group had a higher screw density when compared to the freehand group which may account for similar operative times and blood loss. Previous research has shown 3DCMNJ leads to shorter time and low blood loss during screw insertion. 3DCMNJ assisted spinal fusion patients may have a reduced return to surgery rate, but a larger study group is needed.

1024

P437: Navigation trends in lumbar spine surgery

Tara Shelby ¹ , Emily Mills ¹ , Matthew Chen ¹ , Hyunwoo Kang ^1,2 , Andy Ton ¹ , Jeffrey C. Wang ¹ , Raymond Hah ¹ , and Ram Alluri ¹

¹ Orthopaedic Surgery, Keck School of Medicine of USC, Los Angeles, United States

² Orthopaedic Surgery, Massachusetts General Hospital, Harvard Medical School, Boston, United States

Introduction: Intraoperative computer-assisted navigation (CAN) has fostered the growth of minimally invasive techniques and improved anatomical characterization. Using CAN minimizes intraoperative risks, as it allows for greater surgical precision. As such, CAN utilization has seen a steady increase over the past decade within cervical and thoracic spine procedures. Studies investigating CAN specifically in the context of the lumbar spine, however, remain sparse. Given the high prevalence of degenerative lumbar pathologies, this study aims to define CAN utilization trends in the top 10 lumbar spine procedures for treatment of degenerative conditions. Material and Methods: Patient data from 2010 to 2021 was accessed through the querying of the national insurance database PearlDiver using ICD-9, ICD-10 and CPT codes. After first identifying the top five lumbar degeneration codes, the top ten lumbar spine CPT procedure codes associated with these diagnoses were isolated to create a cohort of patients. This cohort was then split into the patients who had the procedure along with one of the top five computer navigation procedure codes and those that didn’t. Temporal analysis was then conducted on each cohort to identify the trend of incidence in each group overtime. Results: Querying PearlDiver found a total of 1,234,493 patients underwent one of the top ten lumbar spine procedure for lumbar degeneration pathology from 2010 to 2021, with 10,760 (0.87%) and 1,223,733 (99.13%) patients undergoing procedures performed with and without CAN. Comparing 2010 to 2021 demonstrated a significant increase in the use of CAN with lumbar spine procedures (p < 0.001), increasing from 0.553% (556 patients) to 2.187% (769 patients). Trends in CAN utilization was relatively steady from 2010 to 2015, with a decrease from 2015 (0.763%, 933 patients) to 2016 (0.483%, 541 patients), before linearly increasing from 2016 to 2021 (2.187%, 769 patients). Conclusion: The current analysis has demonstrated in lumbar spine procedures what has been shown previously in cervical and thoracic procedures: the use of computer assisted navigation has been increasing in use overtime. We intend to next compare demographic variables and outcomes between the two cohorts, as well as conduct multivariate analyses adjusting for patient age, ECI score, insurance, hospital region for all primary outcomes.

1271

P438: Optical navigation in spine surgery an in vivo study

Josh Schroeder ¹ , Leon Kaplan ¹ , and hmed Shawan ¹

¹ Orthopedic Surgery, Hebrew University Hadassah Medical Center, Jerusalem, Israel

Introduction: Surgery and spine surgery specifically are using increasing amounts of ionizing radiation in order to allow tracking and navigation during surgery. This increase in harmful radiation increases the risk of cancer for both the patients and the surgical staff. In addition, in cases in which the spine is mobile, the vertebras move during the case causing decreased accuracy as the case progress. In light of these issues, research into optical imaging and navigation has been conducted to allow a radiation-free solution. Materials and Methods: Using a specialized high definition 3D camera, augmented technology for optical imaging and AI software allowing radiation free matching of the preoperative imaging to the real anatomy of a patient, pedicle screws were planned and lamina anatomy were navigated in lumbar cases (both female and male). Real time tracing and imaging was tested in all cases. Results: Real time tracking with optical navigation between L1 and S1 vertebrae was performed in ten patients, using the real-time tracking software. Spine anatomy including spinous process, lamina, pars intra-articularis and transverse process was identified correctly in real time. Real time tracking and imaging was tested and successful throughout the cases. Summary: Optical navigation is an emerging new technology that provides a safe solution for a radiation free spine surgery. As this technology continues to evolve allowing sub-millimeter accuracy and real time imaging, it shall be able to decrease the need of intraoperative imaging for patients. Continues testing is needed to translate this promising technology to everyday practice.

1303

P439: Treatment of patients with atlantoxial and craniocervical instability, using O-arm procedures

Nikolay Mirchev ¹ , Orlin Pavlov ² , Andrei Bodrov ¹ , Pichkur Oleksandr ¹ , and Naydenova Stefania ³

¹ Department of Neurosurgery, Klinikum Fulda gAG, Fulda, Germany

² Department of Neurosurgery, Klinikum Krefeld, Krefeld, Germany

³ Department of Physiotherapy, Physiostep, Vienna, Austria

Introduction: A prospective analysis of the surgical treatment and results of 200 patients with benign and malignant craniocervical, atlantoaxial lesions operated during 10 years period (2011-2020) at our department was performed. The aim of the analysis was to assess the factors affecting outcome of treatment in patients with craniocervical and atlantoaxial instability. Material and methods: We analyzed 139 patients with traumatic lesions, 14 patients with inflammatory lesions, and 47 patients with craniocervical tumors. Results: We performed 222 operations. Because of craniocervical/cervical instability we made ventral or/and posterior screw fixation and fusion in all of 200 patients. In order to improve screw placement accuracy, we performed intraoperative O-Arm in 178 cases. The operative duration was 2 h. in O-Arm operations and 4.20 h in X-ray procedures. The blood loss was 220 ml in O-Arm and 550ml in C-Arm procedures. The mean screw length in C1/C2/C3 vertebras was 30 mm in O- Arm procedures and 24 mm in C-Arm procedures. In order to improve postoperative neurological recovery, we performed early postoperative physiotherapy in 150 patients with very good clinical results. The most common complications were: CSF leak – in 2 cases, postoperative infection – in 8 cases, screw misplacement - in 3 cases, pulmonary embolism in 4 cases and 3 case of early perioperative mortality. The 24-monts follow-up patients showed good recovery in 148 patients, moderate disabling – 34 patients, severe disabling – 6 patients, vegetative state – 4 patients, death 8 patients with malignant lesions in bad general condition. Conclusions: Early correction of craniocervical and atlantoaxial cervical instability facilitated neurological recovery by preserving the existent neurological function. Using of O-Arm increase significant operative screw placement accuracy, and preserve intraoperative nerve and vertebral artery injury. Recently because of the improvement of neuroimaging techniques, surgical techniques, neurointensive care and early postoperative physiotherapy the results of treatment of these lesions are optimal.

1376

P440: Accuracy and treatment results of cervical posterior instrumentation for cervical spinal injury using O-arm navigation

Takashi Chikawa ¹ , Ayaka Hashimoto ¹ , and Toshihiko Matsumura ¹

¹ Orthopedic Surgery, Tokushima Prefecture Naruto Hospital, Naruto, Japan

Introduction: Cervical spinal injury with bone fracture requires strong internal fixation due to intervertebral and vertebral body instability, and although the fixation force of the pedicle screw is excellent, there is a risk of injury to the spinal cord and vertebral arteries. On the other hand, the lateral mass screw has advantages and disadvantages on the contrary. Our hospital introduced O-arm Navigation in October 2020. Purpose: We will compare the surgical results of our department for cervical spine injuries with bone injuries between cases using the C-arm before the introduction of O-arm navigation and cases using the O-arm after the introduction. Treatment policy: In recent years, there have been many reports recommending surgery in the acute phase within 24 hours of injury for cervical spinal cord injury. In our department, we perform surgery as early as possible (within 48 hours) to avoid secondary damage due to ischemia and inflammation. Subjects: Between April 2018 and July 2021, nine patients who underwent posterior fusion surgery for cervical spine injuries with bone injuries were included. There were 7 males and 2 females, and the average age at the time of surgery was 75.8 years (35-88 years). There were 3 cases in the C group using the C-arm before the introduction of the O-arm, and 6 cases in the O group using the O-arm. Methods: Survey items included the number of pedicle screws (PS), total number of screws, number of fixed vertebral bodies, screw deviation rate, number of days until postoperative sitting position, length of hospital stay, and average operation time between groups C and O. investigated. We investigated the improved Frankel classification and extremity MMT as clinical results. Results: In the C and O groups, the average number of PS was 2.7 and 6.4, respectively, the average number of screws was 9.7 and 7.8, the number of fixed vertebral bodies was 5 and 4, and the PS deviation rate was 12.5. The length of hospital stay was 38 days and 31.4 days, the number of days until postoperative standing was 3 days and 2.5 days, and the operating time was 230 and 277 minutes, respectively. No significant difference was observed for either item. Conclusion: Nine cases of cervical spinal cord injury with bone injury were treated with posterior fusion. The O group had a higher PS number than the C group, the total number of screws and the number of fixed vertebral bodies tended to be smaller, and the PS deviation rate was 1 out of 32 (Grade 1), 3.1%. It took time to use O-arm+Navigation, but I was able to insert PS safely.

1880

P441: A muti-angle lasers assistant device installed in C-arm promotes the efficiency of X-ray fluoroscopy in lumbar spine surgery for beginners

Yuan-Dong Zhuang ¹ , Rui-Jin Li ² , Jia-Jun Wu ² , Xue-Wei He ² , Wen-Bin Zou ² , Si-Qi Lu ² , and Xu-Chu Xu ²

¹ Neurosurgery Department, Fujian Medical University Union Hospital, Fuzhou, China

² The School of Basic Medical Sciences, Fujian Medical University, Fuzhou, China

Introduction: This study is to evaluate that the C-arm installed with multi-angle lasers assistant device whether can promote the efficiency of X-ray fluoroscopy in lumbar spine surgery or not for beginners. Material and Methods: Twenty sophomores majoring in clinical medicine in Fujian Medical University were randomly divided into two groups (n = 10): experimental group (group A) and control group (group B). In both groups, X-ray fluoroscopic images of the 3D printed lumbar spine model were taken in normal prone position and crown rotation position. The images of group A were photographed with multi-angle laser device assisted, and images of group B were photographed by traditional method. The criteria for the end of the shooting were until the standard anteroposterior and lateral images were taken. Outcome measures included the total time of operation, total attempts of shooting, and initial shooting offset error (the relative deviation between the target and the radiation center). The feeling of using the two methods (comfort, interest, efficiency of self-learning operation, and mastery of operation knowledge) was evaluated by subjective questionnaire survey after the experiment. Results: The total time of operation was (790.50 ± 396.474) s in group A and (1764.10 ± 1070.250) s in group B. There's less time (55.19%) in Group A compared with group B. The total attempts of shooting was (11.20 ± 5.095) times in group A and (36.80 ± 9.555) times in group B. There's less attempts (69.57%) in Group A compared with group B. The mean initial shooting offset error was (0.221 ± 0.091) in group A and (0.677 ± 0.162) in group B. Group A was more accurate (67.36%) than Group B. In the above three indexes, group A was better than group B, and the difference was statistically significant (p < 0.05). The results of the questionnaire show that the scores of comfort, interest, efficiency of self-learning operation, and mastery of relevant operation knowledge in group A were higher than those in group B, and the difference was statistically significant (p < 0.05). Conclusion: Multi-angle lasers assisted C-arm can significantly improve the beginners efficiency of X-ray photography during lumbar surgery, and also have significantly higher satisfaction, which shows that the new technology is well worth spreading.

Nonoperative Clinical Treatments

149

P442: Should physical therapy be incorporated in patient care post 1-2 level lumbar fusions for degenerative lumbar instability? A comparative outcome analysis

Eeric Truumees ¹ , Devender Singh ¹ , Ashley Duncan ¹ , and Eric Mayer ¹

¹ Spine, Ascension Texas Spine and Scoliosis, Austin, United States

Introduction: Fewer studies in the literature have examined the role of post-operative physical therapy (PT) after lumbar fusion. In the post-operative setting, much of the rehabilitation literature focuses on post-discectomy patients. Aim: Evaluate and compare the changes in pain and functional scores between patients who completed physical therapy (PT) versus no-PT after their anterior or posterior 1-2 level lumbar fusions for degenerative lumbar instability. Our null hypothesis was that the PT group may experience comparatively better functional and pain outcomes than their counterparts. Materials and Methods: A database of patients undergoing 1-2 level lumbar fusion surgery for degenerative disease was assembled. Demographic and outcome scores such as oswestry disability index (ODI) and visual analog scale (VAS) in patients who participated in post-operative PT vs. those that did not were compared. Results: 72 and 51 patients in PT and no-PT met the inclusion criteria, respectively. There were higher numbers of females (63.8%) in PT group. No-PT group had similar numbers of males and females. Mean ages for PT and no-PT groups were 61.4 (±14.7) and 59.5 (±14.1) years, respectively. Both groups were similar with respective to body mass index. Majority of the cases in both groups involved posterior/posterolateral approach. 55.5% of patients in PT group and 50.9% in no-PT had 1 level lumbar fusion. Mean change (pre-operative vs. 1-year post-operative) in ODI between the two groups differed significantly (PT vs. no-PT: 18.8 ± 13.9 and 9.3 ± 17.5; p = 0.019). Similarly, mean change in VAS was significantly different between the two groups (PT vs. no-PT: 3.2 ± 2.18 and 1.05 ± 2.08; p = 0.026). None of our PT patients reported any change in pre vs. 1-year post-operative follow up employment status (35% retired, 38% employed fulltime, 11% unemployed and 16% homemaker). 98% of No-PT patients reported no change in employment status during the same timeframe (46% retired, 25% employed fulltime, 13% unemployed and 15% homemaker). Conclusions: PT group reported significant improvements in functional and pain scores than their counterparts. Post-lumbar fusion rehabilitation may benefit the majority of adult patients undergoing lumbar fusion surgery for a degenerative indication. Prospective studies with standardized PT approach, additional patients and greater statistical power are needed to further understand the effects of physical therapy on patients undergoing lumbar fusions for degenerative lumbar instability.

155

P443: Determining what markers increase the odds of successful non-operative treatment of lumbar disc herniation

Eeric Truumees ¹ , Devender Singh ¹ , Jeremiah Alexander ² , Calvin Chandler ² , Ashley Duncan ¹ , and Eric Mayer ¹

¹ Spine, Ascension Texas Spine and Scoliosis, Austin, United States

² Orthopedics, The University of Texas at Austin, Austin, United States

Introduction: Treatment selection for acute lumbar disc herniation remains uncertain due to reports of similar outcomes with surgical and non-operative management over long-term follow-up. Current care pathways recommend non-operative measures for six weeks before considering surgical intervention, in the absence of neurological deficits. Aim: This study aims to identify factors predictive of successful non-operative treatment. Materials and Methods: We reviewed 157 charts of patients for lumbar disc herniation. Inclusion criteria consisted of encounters with ICD10 code M51.26 (other intervertebral disc displacement, lumbar region), three months of follow-up care, pre and post treatment ODI scores and non-operative care only. Independent variables collected consisted of age, smoker status, presence of comorbidities, antidepressant and opioid use, length of symptoms, treatment prescribed (Physical Therapy, prescription and opioids, epidural steroid injections (ESI)) baseline and three-month Oswestry Disability Index (ODI). Categorical variables were then coded as discrete values, 0 for “no”, 1 for “yes”; or in the case of smoking status 1 = never, 2 = former, 3 = current. In regard to change in ODI score between baseline and three months, a successful treatment was defined as a decrease in ODI of at least 10 points and encoded as “1”. Treatment failure was defined as any increase in ODI or a decrease of less than 10 and encoded as “0”. Multinomial logistic regression was conducted on the encoded data. Results: Mean age at appointment was 50.6 years. Most patients (81%) were never smokers, while 13% were former smokers and 6% were current smokers. 139 (89%) patients had the presence of a comorbidity, and 16% were being treated with antidepressants for anxiety/depression and 15% were already taking opioids at the time of the first encounter. Mean duration of symptoms was 78.3 weeks ± 26.8. 95% of patients received a prescription, 69% had at least one ESI, 50% went to physical therapy and 16% received a prescription for opioids. Results of the logistic analysis demonstrated only injection therapy and opioid treatment were significant predictors of treatment success with odds of 2.8 and 3.9, respectively. As expected, smoking and presence of comorbidities decreased the odds of successful non-operative treatment by 1.1% and 28.1%, respectively. Interestingly, the logistic analysis of this data showed that for each unit increase in age, the odds of successful outcome increased by 2.5%. Conclusions: ESI and opioid therapy were the only variables that significantly impacted the odds of successful non-operative treatment on lumbar disc herniation at three months. The positive impact of opioid prescription (290.3%) was surprising, given the small number of occurrences in this population and the mechanism of action, with no known local oranti-inflammatory properties. Increased age was also positively correlated with treatment success, although non-significantly. This contradicts the theories that increasing age becomes a liability and a risk in the healing process and treatment decision making process. The impact of opioid and age on treatment success in this analysis begs the question of what psychological factors impact the patients’ determination of a meaningful, successful outcome.

310

P444: Recalcitrant coccygiodynia - does Ganglion Impar block or radiofrequency ablation helps?- a systematic review

Kishor Kunal ¹ and Ranjeet Choudhary ²

¹ Orthopaedics, AIIMS, Jodhpur, India, ² Orthopaedics, AIIMS, Bhatinda, India

Introduction: Nearly 90 % of cases of coccygiodynia can be managed with conservative medical treatment; the remaining 10 % need other invasive modalities for pain relief such as Ganglion Impar block (GIB) or Radiofrequency ablation (RFA) of Ganglion Impar. Material and Methods: With a purpose to determine the efficacy of GIB and RFA of Ganglion Impar in controlling pain in coccygiodynia patients a systematic research was conducted of PubMed, MEDLINE and Google Scholar to identify studies reporting the pain relief in terms of Visual Analogue Scale (VAS) or its counterparts following GIB or RFA in coccygiodynia patients by 2 different authors according to PRISMA guidelines. Results: 7 studies were delineated with a total of 189 patients (104 in GIB group and 85 in RFA group). In GIB group, mean VAS improved from 7.83 at baseline to 3.11 at short term follow-up, 3.55 at intermediate term follow-up and 4.71 at long-term follow-up. In RFA group, mean VAS improved from 6.92 at baseline, 4.25 at short term follow-up, 4.04 at long-term follow-up. In GIB group, 13.92 % failure (11/79) and 2.88% complication (3/104) were reported while in RFA group, 14.08 % failure (10/71) and no complications (0 %) were reported. Total success rate was > 85%, with either of modalities. Conclusion: GIB and RFA of Ganglion Impar provides a reliable and probably an excellent method of pain control in coccygiodynia patients not responding to conservative medical treatment. However, a demarcation between responders, non-responders and late non-responders should be considered and larger studies with longer follow-up (> 1 year) are needed.

370

P445: Anti-osteoporotic medication prescription patterns in patients with vertebral compression fractures

Jennifer Bell ¹ , Thomas Alter ² , Mary Kate Erdman ^1,3 , Hyunwoo Kang ^1,4 , Emily Mills ¹ , Andy Ton ¹ , Jeffrey C. Wang ¹ , Ram Alluri ¹ , and Raymond Hah ¹

¹ Orthopaedic Surgery, Keck School of Medicine of USC, Los Angeles, United States

² Orthopaedic Surgery, Mayo Clinic, Rochester, United States

³ Orthopaedic Surgery, Harborview Medical Center, University of Washington School of Medicine, Seattle, United States

⁴ Orthopaedic Surgery, Massachusetts General Hospital, Harvard Medical School, Boston, United States

Introduction: The purpose of this study was to (1) report prescribing patterns of anti-osteoporotic medication in patients diagnosed with a vertebral compression fracture (VCF) and (2) evaluate the influence of surgical management on anti-osteoporotic prescribing patterns. Material and Methods: A large de-identified patient database from a private insurer was utilized. Patients diagnosed with a VCF from January 2007 to December 2016 were identified. Exclusion criteria were patients less than 50 years of age and patients with less than one-year follow-up. Patients were grouped based on whether or not they received an anti-osteoporotic medication within one year prior to or following the VCF, and whether or not treatment included surgical intervention. Results: A total of 73,907 patients sustaining VCF were identified, of which 66.8% were female. The highest rate of VCF were reported in patients between 70-74 years of age. Prior to the indexed VCF, 13,219 (17.8%) patients received anti-osteoporotic medication. A total of 60,688 (82.1%) patients were not prescribed anti-osteoporotic medications prior to sustaining a VCF. Of these 60,688 treatment naïve patients, 9.6% were prescribed an anti-osteoporotic medication within 1-year of the VCF. The frequency of initiation in surgical and non-surgical patients was 18.4% and 8.4%, respectively. For the 60,688 (82.1%) treatment naïve patients, females between 70 and 84 years of age, were most likely to be initiated on new anti-osteoporotic medications following a VCF. 9,077 (12.3%) patients were treated surgically, of which 1,490 (16.4%) were treated with anti-osteoporotic medication prior to index VCF. Conclusion: Our data displays similar rates of anti-osteoporotic medication prior to VCF in both operative and non-operative patients. Older female patients are more likely to be treated prior to an event in comparison to their younger male counterparts. Lastly, the prescribing patterns for anti-osteoporotic medication after VCF, with or without surgical treatment, are low.

478

P446: Clinical outcome of a conservative treatment protocol for lumbar canal stenosis

Sai Viksheth Raj Basani ¹ , and Harvinder singh Chhabra ¹

¹ Spine Services, Indian Spinal Injuries Centre, New Delhi, India

Introduction: The management of Lumbar Spinal Stenosis begins with nonoperative treatment, such as neurotropic medication like membrane stabilizing agents (MSEs), NSAIDs, epidural steroid injections, and physical therapy. Surgery is deferred until the failure of conservative treatment or the appearance of red-flag signs. Unfortunately, most clinicians fail to concur on what constitutes a fair conservative trial and the duration required for eliciting the response. So, an urgent need exists to provide an evidence-based protocol for clinical practice. Material and Methods: A prospective cohort study was conducted at an Indian tertiary spine care center. A total of 410 patients were recruited who presented with neurogenic claudication and had a JOA’s LSS-DST score of 7 or more. They were managed by a multimodal conservative protocol, consisting of dose escalation and combination protocol of MSA’s/anti-depressants, NSAIDs, methylcobalamin, TENS therapy, local heat/ice packs, counterirritants, general conditioning with stretching exercises and patient education for lifestyle modification. Those who didn’t respond within three to six weeks were offered up to three TFESI at weekly intervals or surgery was suggested when canal morphology is not amiable for TFES (i.e., Schizas’ Grade C and D). The subjects were analyzed using Claudication distance, VAS score for the leg and back, ODI score and SF36 score at 6 weeks, 3 months, 6 months and 1-year intervals. Results: 387 patients completed the study, while 23 were lost to follow-up. The mean age of the study population was 61.36 years, with 15% being younger than 50 years. Schizas MRI grades B and C accounted for 36% of subjects. Neurotropics were well tolerated, with drowsiness and peripheral oedema reported in 23% of patients requiring dose modification. No other untoward complication was noted. A total of 15 patients responded to TFES, and 7 others needed it twice; the response didn’t correlate with MRI grade. A total of 57 patients required surgery. 14 of them had complications ranging from SSI to pyogenic spondylodiscitis. All outcome variables showed a gradual improvement with time. Claudication distance revealed a significant difference between MRI grades A1, A2 and Grade C, D. While grade A1 stenotic patients had a significantly better SF36 score at 6 weeks, 3 months, and 6 months, but at 12 months, there was no difference in scores among various grades. Similarly, patients on conservative treatment had better scores at 1^st, 2^nd, and 3^rd follow-up than operated patients. However, there was no difference between the endpoint groups at the final follow-up. There was no significant correlation between baseline variables and outcome. 81.5% of patients who were advised surgery elsewhere responded to our conservative protocol. Successfully conserved patients were more likely to be satisfied with our protocol than those being operated on. Conclusion: Our study demonstrated encouraging results with multimodal conservative protocol and a decreased need for surgery. As no baseline variable can successfully predict the response to our protocol, it is advisable to start an initial conservative approach for all patients, and those with an unsatisfactory result can be treated surgically later with a good outcome.

787

P447: The effectiveness and longevity of epidural steroid injections in a single center retrospective cohort

Annabel Kim ¹ , Joshua Sanchez ² , Marc Abdou ² , Zorica Buser ³ , David Cheng ¹ , and Gene Tekmyster ¹

¹ Keck Hospital of USC, Los Angeles, United States

² Yale School of Medicine, New Haven, United States

³ Gerling Institute, New York, United States

Introduction: Low back pain and associated radicular syndromes are significant health and socioeconomic issues that account for over 100 billion dollars annually in the United States. Epidural steroid injections (ESIs) are a common method for relieving radicular pain from lumbar spine etiologies. The current ESI literature is unclear due to the variability in indications, injection techniques, number of allowed injections, and the lack of standard and objective outcome measures. Thus, we evaluated the changes in Numerical Rating Scale (NRS) scores for pain from lumbar spine ESIs and their specific effectiveness in preventing a subsequent lumbar spinal fusion procedure within a year follow-up period. Material and Methods: Keck Hospital patients who received lumbar ESIs by a single interventional physiatrist from 2018 to 2019 were identified using Discern Reporting Portal. The electronic health record was used to verify that their first ESIs were between January 2018 and April 2019, they had one-year follow-ups, and there were no prior surgeries (foot, ankle, knee, or hip). Patients whose back pain was instigated by a traumatic incident were also excluded. All patients had a primary diagnosis of lumbar radiculopathy (M54.16 ICD-10 code) and received transforaminal ESIs. The first three ESIs received within the period were included. Collected variables included demographics (age, gender, BMI, smoking status), comorbidities (hypertension, diabetes mellitus, hyperlipidemia, pulmonary conditions, cardiovascular conditions, renal conditions, and/or mental illness), prior and concurrent opioid use, ESI injection levels and laterality, NRS pain scores, and conversion to lumbar spine surgery. The Wilcoxon signed-rank test was used to compare NRS score change from pre-ESI to post-ESI time points. Results: A total of 46 patients with 1-year follow-ups were identified. The average age was 55.1 ± 16.5. 54.3% of the patients were male, and 45.7% were female. The most prevalent comorbidities for the population included hypertension (32.6%), hyperlipidemia (19.6%), and mental health diagnoses (23.9%). 15 patients (32.6%) used opioids prior to their first ESI, and 8 (17.4%) used opioids during their ESI treatment. The average pre-ESI NRS was 6.54 ± 2.64. The most significant change in NRS scores from baseline was observed 6-month post-ESI with an average decrease of 3.79 ± 3.75 (p = 0.005). At the 1-year point, the average decrease in NRS score was 2.5 ± 2.81 (p = 0.02). 35 (76.1%) patients did not undergo lumbar surgery after ESI. In contrast, 11 (23.0%) patients underwent lumbar spine surgery within a year of their first ESI. Conclusion: ESIs appear to be most effective at the 6-month mark and taper off at the 1-year point. Of the 11 patients that converted to surgery, the majority (6) received two ESIs prior to surgery. 3 received one, and 2 received at least three ESIs prior to surgery. The majority of patients (76.1%) did not convert to surgery. However, the largest mitigating factor to this study is the small sample size, which affected the ability to accurately determine the surgery conversion rate.

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P448: Factors affecting brace adherence in adolescent idiopathic scoliosis - a qualitative application of protection-motivation theory

Raveen Jayasuriya ¹ , Paul Norman ² , Daniel Hind ³ , and Ashley Cole ¹

¹ Paediatric Spinal Surgery, Sheffield Children's Hospital, Sheffield, United Kingdom

² Department of Psychology

³ Clinical Trials Research Unit, University of Sheffield, Sheffield, United Kingdom

Introduction: Full-time brace treatment to prevent the need for spinal surgery (where 18 - 20 hours of brace wear is required) has been shown to be adherence dependent in adolescent idiopathic scoliosis. Adherence to bracing however is variable between individuals. The factors affecting health related behaviour in bracing have not been evaluated in a structured theory-based framework. Material and Methods: This study explores patient and parent perspectives and psychological effects of bracing through semi-structured interview dyads. The interview topic guide, and directed content analysis of transcripts, were performed utilising protection-motivation theory as the underpinning psychological framework. Results: Fifteen patients and nineteen parents participated. For approximately half of the participants, appraising the threat of the diagnosis was not possible as scoliosis was an unknown. Following information given by surgeons, and independent research, most participants had consistent perception of the severity of their scoliosis and their vulnerability for future prognosis. The overwhelming content of interviews focussed on the coping appraisal of bracing and the response cost of treatment adherence; this was also consistent between participants, despite good belief in the response efficacy of bracing. The self-efficacy strategies that patients employed to increase adherence, and the maladaptive response rewards of poor adherence, was variable between participants. Conclusion: This qualitative semi-structured dyadic interview study demonstrates that PMT provides a coherent psychological framework with which to explore the factors affecting brace adherence in patients with adolescent idiopathic scoliosis. Wearing the brace at school poses a great challenge to patients in full-time bracing, causing anxiety and stress; from worrying about how peers at school will perceive them, to the limitations of how to make the brace less visible with clothing choices, and coordinating extra-curricular activities around brace wear, all whilst still adhering to the required brace wear hours. This study highlights both the circumstances under which patients would choose not to wear the brace, and the self-efficacy strategies employed to maintain adherence. This study provides valuable data for the development of adherence prediction tools for screening and stratifying. It also offers clinicians a framework with which to augment information provided to patients thus maximising protection-motivation behaviour for optimum brace adherence.

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P449: Spinal motion and low back pain - prospective analysis of the association between lumbar movement and the occurrence of chronic back pain

Friederike Schömig ¹ , Luis Becker ¹ , Pumberger Matthias ¹ , Lea Cordes ² , Georg Duda ² , and Hendrik Schmidt ²

¹ Charité - Universitätsmedizin Berlin, Center for Musculoskeletal Surgery, Berlin, Germany

² Berlin Institute of Health, Julius Wolff Institute, Berlin, Germany

Introduction: Despite the increasing prevalence of chronic low back pain (LBP), therapeutic management of LBP remains challenging, which is mainly due to a lack of understanding of the underlying mechanisms of pain development. While in the past, adaptations of spinal motion in the presence of LBP have been increasingly studied, to date little is known about the quantitative analysis of lumbar movements. Thus, we investigated movements of the lumbar spine of both asymptomatic participants and LBP patients in their daily lives for the first time. Material and Methods: We prospectively included asymptomatic participants as well as patients who had been suffering from LBP for at least twelve weeks. A body-mass-index (BMI) of > 26 kg/m² was an exclusion criterion. All asymptomatic participants and LBP patients were measured for 24 hours during their daily lives using the Epionics SPINE System with the standing position as a reference. Lumbar movements of over 5° were recorded independently from the movement’s starting position and were grouped into movements of >15°, 10-15°, and 5-10°. For statistical analysis, the Student’s t-test, analysis of variance (ANOVA) with Bonferroni post-hoc test, and the Spearman correlation coefficient were used. Results: A total of 208 asymptomatic participants and 106 LBP patients were included. While the groups did not differ significantly in the distribution of sexes or in their BMIs, the group of LBP patients was significantly older (50.9 ± 13.6 vs. 40.3 ± 14.0 years, p < 0.001). We found significantly fewer small, medium, and large movements in the sagittal plane (total movement count 15,564 ± 8,078 vs. 20,521 ± 7,160, p < 0.001) in the group of LBP patients. In the axial plane, LBP patients were shown to perform significantly fewer small movements (total movement count 7,317 ± 5,881 vs. 11,106 ± 5,134, p < 0.001). There was a weak but significant correlation between age and the number of sagittal (r = -0.179, p = 0.010) as well as axial (r = -0.172, p = 0.013) movements shown for the group of asymptomatic participants, while in LBP patients this correlation was only found for sagittal movements (r = -0.290, p = 0.003). Conclusion: Our results show that in addition to a significantly reduced total amount of lumbar movements in LBP patients compared to asymptomatic participants, there are significant differences between men and women especially regarding large sagittal movements. We also found a reduction in lumbar movement with increasing age, the correlation of which, however, was only weak. While it remains unclear whether the shown changes in spinal motion are cause or effect of pain development, the association between movement adaptations and chronic LBP needs to be considered in the optimization of motion-based conservative treatment strategies and therefore needs to be further investigated.

1057

P450: Efficacy of nucleoplasty for radiculopathy caused by foraminal cervical disc herniation: clinical results of case series and technical note

Pius Kim ¹

¹ Neurosurgery, Chosun University Hospital, Gwangju Metropolitan City, South Korea

Introduction: Percutaneous cervical nucleoplasty (PCN) is a minimally invasive technique used for the treatment of cervical disc herniation. However, if the lesion is located at the neural foramen, complete access and effective neural decompression are often challenging because of the special anatomical condition of the uncovertebral joint, osteophyte, and facet joint of the cervical foraminal space. In this presentation, when performing PCN for foraminal cervical disc herniation (FCDH), the technique for overcoming those anatomical difficulties is described, and the study results of analyzing the clinical effects are reported. Material and Methods: This study included 44 patients with radiculopathy caused by FCDH who were treated with PCN. Visual analog scale (VAS) scores, preoperative, 1 week and 3 months postoperatively, and at the last follow-up, as well as the MacNab criteria, were used to evaluate clinical outcomes. A paired t-test was used to compare the preoperative and follow-up VAS scores. The percentage of patients with VAS score ≤ 3 at each follow-up time point was also investigated. Statistical significance was set at p < 0.05. Results: Twenty-seven men (62.4%) and 17 women (38.6%) were enrolled in this study. The mean age was 54.5 years (range 31-81). The average follow-up period after the operation was 15.4 months (range 3.7-30.8). The mean preoperative VAS was 7.50 ± 1.21. The VAS scores at 1 week, 3 months, and the last follow-up were 4.36 ± 2.46, 3.20 ± 2.58, and 2.91 ± 2.74, respectively, showing a significant improvement in pain compared to before the operation (p < 0.001 for all). The number of patients (percentage) with a VAS score of ≤ 3 was 20 (45.5%), 28 (63.6%), and 31 (70.5%) of 44 patients at 1 week, 3 months, and the last follow-up, respectively. The number of patients (percentage) with excellent, good, fair, or poor satisfaction according to the MacNab criteria was 17 (38.6%), 9 (20.5%), 8 (18.2%), and 10 (22.7%) of 44, respectively. No patients experienced postoperative complications. Conclusion: Although PCN for radiculopathy caused by FCDH is thought to have limitations because of the surrounding bony structure, the clinical outcome seemed favorable. If PCN is not contraindicated, it may be a viable treatment option for CR due to FCDH.

1064

P451: The impact of physical therapy after lumbar fusion surgery

Jeremy Heard ¹ , Parker Brush ¹ , Yunsoo Lee ¹ , Mark Lambrechts ¹ , Nicholas D'Antonio ¹ , Nicholas Siegel ¹ , Tariq Issa ¹ , Yash Reddy ² , Sanath Patil ² , Caroline Purtill ² , John Bodnar ² , Sydney Somers ² , Delano Trenchfield ¹ , Jose Canseco ¹ , Christopher Kepler ¹ , Alan Hilibrand ¹ , Alexander Vaccaro ¹ , and Gregory Schroeder ¹

¹ Orthopedic Surgery, The Rothman Orthopedic Institute at Thomas Jefferson University Hospital, Philadelphia, United States

² Thomas Jefferson University, Philadelphia, United States

Introduction: Literature on the efficacy of physical therapy (PT) after lumbar fusion surgery is mixed and limited guidance on PT interventions after lumbar surgery exists. Given the prevalence of PT referrals and lack of high-quality evidence, there is a need for additional studies investigating the efficacy of PT after lumbar fusion surgery to aid in developing robust clinical guidelines. Thus, our objectives are to (1) determine if PT attendance after lumbar fusion impacts PROMs and (2) determine if PT attendance after lumbar fusion affects readmission or revision rates. Methods: We retrospectively identified patients receiving lumbar fusion surgery by current procedural terminology codes and separated them into two groups based on whether PT was prescribed. Electronic medical records were reviewed for patient and surgical characteristics, PT utilization, and surgical outcomes. Patient reported outcome measures (PROMs) were identified and compared preoperatively to one year postoperatively. Multivariable regression analysis was performed. Significance was set to p < 0.05. Results: Our methodology identified 323 patients that attended PT and 400 patients that did not. In comparison to patients that did not attend PT, those that attended PT had similar patient characteristics and comorbidities. Patients that attended PT had significantly more fused levels (1.41 ± 0.64 vs. 1.32 ± 0.54, p = 0.027), longer operative durations (234 ± 96.4 vs. 215 ± 86.1 minutes, p = 0.012), and lengthier postoperative hospital stays (3.35 ± 1.68 vs. 3.00 ± 1.49, p = 0.004). There were no significant differences between readmission, complications, and revision rates. Bivariant analysis of PROMs demonstrated that physical therapy attendance did not confer significant benefits to overall clinical improvement at the one-year postoperative: MCS-12 (2.88 ± 12.1 vs. 3.52 ± 10.3, p = 0.739), PCS-12 (11.5 ± 11.8 vs. 8.82 ± 11.2, p = 0.171), ODI (-25.50 ± 21.0 vs. -19.16 ± 18.1, p = 0.071), VAS Back (-3.68 ± 3.60 vs. -2.87 ± 3.19, p = 0.175), and VAS Leg (-4.69 ± 3.67 vs. -4.40 ± 3.54, p = 0.644). Multivariable analysis showed that PT was not significantly associated with PROM improvement postoperatively both at three months and one year. Conclusion: Our study found there was no significant benefit to postoperative physical therapy after lumbar fusion with regards to improvements in three-month or one-year patient reported outcome measures. In addition, PT attendance did not impact 90-day readmission rates. Given the current conflicting literature on the topic, at this time it is difficult to recommend for or against PT after lumbar fusion surgery. As PT is costly to the healthcare system, however, stronger recommendations are needed to guide treatment and physicians should use their discretion when prescribing PT.

1148

P452: Acceptance and commitment therapy screening model for patients undergoing spinal surgery

Happy Kumar ¹ , Alex Coffman ² , Natalie Glass ² , Valerie Keffala ² , Cassim Igram ² , Andrew Pugely ² , and Catherine Olinger ²

¹ University of Iowa Carver College of Medicine, Iowa City, United States

² Department of Orthopedics & Rehabilitation, University of Iowa Hospitals & Clinics, Iowa City, United States

Introduction: Chronic pain is an issue that affects over 100 million Americans daily. Acceptance and Commitment Therapy (ACT) has been found to be beneficial for patients with chronic pain by focusing provider efforts to teaching coping mechanisms for pain instead of eliminating the pain entirely. Data collected post-operatively indicates ACT benefits patients with 64.8% improving in at least one key domain in a longitudinal study by Vowles et al. 2011. Presently the University of Iowa does not have a strict standard protocol for referring patients to ACT with the Department of Orthopedic Surgery Pain Psychologist. The aim of the study is to evaluate the effectiveness of PCS as a screening tool for ACT in the spine patient population at the University of Iowa Hospitals & Clinics Department of Orthopedics & Rehabilitation. This study will determine whether the PCS is effective at identifying patients who would benefit from ACT. Materials and Methods: Every patient that presented to spine clinic at University of Iowa Hospitals & Clinics (UIHC) from February 2022 to June 2022 was surveyed using the Pain Catastrophizing Scale (PCS). Patients indicated for spinal surgery were reviewed retrospectively. The patient list was filtered down to 600 adult spinal patients with pre-operative and post-operative PCS scores. 200 patients were chosen via a random number generator and additional information, such as the patients’ History of Present Illness, Visual Analog Scale Scores, PROMIS-CAT Pain Interference Scores, and status of opiate usage were collected and presented to UIHC Orthopedic Spine Surgeons. Surgeons were blinded to the PCS Cutoff Scores. The UIHC Orthopedic Spine Surgeons then identified which patients they would indicate for ACT and their reasoning. Surgeon referral was then compared to referral based on the PCS score of the same patients to evaluate the accuracy of the PCS scoring tool. Results: Effectiveness of this screening tool was based on frequency at which the surgeons and PCS score were complimentary. ROC Curve demonstrated an area under the curve of 0.7784 with a Sensitivity of 0.68 and a Specificity of 0.79. Cut-point according to Youden’s index is 35. Conclusion: The data showed that the PCS is moderately accurate in its ability to distinguish between patients who should and should not be referred for ACT. The adjusted cut-point indicates that patients above a PCS of 35 should be deemed at-risk and referred the department pain psychologist for evaluation for ACT while those below a PCS score of 35 should not be referred. The goal following this study is to perform future investigations regarding PCS and ACT with patients regarding chronic opioid use and post-operative outcomes. Patients who were referred for help with chronic opiate use would be compared to PCS-referred patients and non-referred patients. Pre-operative ACT would be compared to patient outcomes post-operatively. The aim is to evaluate if PCS-referred patients have better pain management post-operatively as compared to the control and opiate-referred patients.

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P453: Changes in M.multifidus cross sectional area, muscle thickness and echogenicity measured via ultrasound during an isolated lumbar extension resistance exercise (ILEX) rehabilitation programme in a sample of chronic, neuropathic and specific low back pain patients

Bruno Domokos ¹ , Ettinger Julia ² , Raschka Christoph ¹ , and Spang Christoph ²

¹ Institute of Sport Science, University of Wuerzburg, Wuerzburg, Germany

² Private Spine Center Dr Alfen, Würzburg, Germany

Introduction: Paraspinal muscle atrophy and increased muscle fat fraction are well documented pathological changes in chronic, specific and neuropathic low back pain (LBP) conditions (Hodges & Danneels, 2019). Studies have highlighted the benefits of addressing these muscles in conservative treatment approaches including post-operative rehabilitation (Hodges & Danneels, 2019). Machine-based ILEX adapted to the individual’s pathology has shown good clinical outcomes for patients with spinal disorders like disk herniations and radiculopathy (Steele et al., 2015; Golonka et al., 2021). However, morphological adaptations of the M.multifidus muscle during a rehabilitation process have not been assessed yet. Material and Methods: In this ongoing prospective study, ultrasound imaging was used to assess cross-sectional area (CSA), muscle thickness (MT) and echogenicity in the M.multifidus muscle (right and left side) of 14 patients (7 women, 7 men) suffering from chronic low back pain (duration > 3 months) with previously diagnosed specific lumbar spine pathologies including disc herniations, spondylarthritis, spondylolisthesis and other degenerative conditions. All patients underwent an ILEX-based exercise protocol consisting of 18 sessions (9 weeks) within a diagnose-based range of motion. One set of ILEX was performed per session with the resistance progressively increased during the protocol. Imaging was conducted at four time points (t₁ = pre-interventional; t₂ = 3 weeks; t₃ = 6 weeks; t₄ = 9 weeks) using the Logic S7 Expert (GE Healthcare, Munich, GER) ultrasound device with a linear transducer. Pain and disability levels were documented with the Visual Analogue Scale (VAS) and the Oswestry Disability Index (ODI). For statistical analysis, Friedman test (with Bonferroni correction) and Pearson coefficient was used. Results: A substantial progressive linear decrease in mean pain levels and disability was found during the process of rehabilitation. Significant differences were especially observed between t₁ (VAS: 50.5 (mean) ± 19.4 (standard deviation, SD); ODI: 17.9% ± 8.6) and t₄ (VAS: 20.2 ± 14.0, p < 0.001; ODI: 7.3% ± 5.2, p < 0.001). 13/14 patients reported an improvement in pain and functional score. Concerning muscular adaptations, CSA increased progressively in a linear manner (7.44 cm² ± 1.98 (t₁) vs. 8.09 cm² ± 1.91 (t₄); p < 0.001). Furthermore, there was a non-significant increase in MT (3.06 cm ± 0.58 (t₁) vs. 3.08 cm ± 0.57 (t₄); p = 0.194). No changes were measured for echogenicity and side differences for MT and CSA. Before the programme, there was a correlation (r= -0.557, p < 0.05) between CSA (per kg bodyweight) and ODI scores. Conclusion: To the best of our knowledge, this is the first study to analyse morphological effects of heavy loaded ILEX in patients with chronic, specific LBP conditions. The results indicate that clinical improvement is accompanied by substantial structural improvements of the M.multifidus. At baseline, there was a correlation between high CSA and better functional scores which further highlights atrophy of the M.multifidus in the pathogenesis of chronic spinal pain conditions. Deriving from the results, ultrasound imaging is a useful method to be applied for the process and results evaluation following surgery, conservative rehabilitation or for preventive purposes in population groups at risk for the development of LBP (e.g. due to inactivity).

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P454: Prognostic significance of lab data and performance comparison by validating survival prediction models for patients with spinal metastases after radiotherapy

Hung-Kuan Yen ^1,2 , Ming-Hsiao Hu ² , Hester Zijlstra ^3,4 , Olivier Q. Groot ^3,4 , Hsiang-Chieh Hsieh ² , Juin-Jen Yang ² , Aditya Karhade ³ , Po-Chao Chen ² , Yu-Han Chen ² , Po-Hao Huang ² , Yu-Hung Chen ² , Fu-Ren Xiao ⁵ , Jorrit-Jan Verlaan ⁴ , Joseph Schwab ³ , Rong-Sen Yang ² , Shu-Hua Yang ² , Wei-Hsin Lin ⁶ , and Feng-Ming Hsu ^6,7,8

¹ Department of Orthopedic Surgery, National Taiwan University Hospital, Hsinchu City, Taiwan

² Department of Orthopedic Surgery

³ Department of Orthopedic Surgery, Massachusetts General Hospital/Harvard Medical School, Boston, United States

⁴ Department of Orthopedic Surgery, UMC Utrecht, Utrecht, The Netherlands

⁵ Division of Neurosurgery, Department of Surgery

⁶ Division of Radiation Oncology, Department of Oncology, National Taiwan University Hospital, Taipei, Taiwan

⁷ Graduate Institute of Oncology, National Taiwan University College of Medicine, Taipei, Taiwan

⁸ Department of Radiation Oncology, National Taiwan University Cancer Center, Taipei, Taiwan

Introduction: The incidence of spinal metastasis (SM) diagnoses has increased worldwide in the past decade and radiotherapy has an important role in its treatment. Well-performing survival prediction models (SPMs) help patients and healthcare professionals to choose treatment aligning with prognosis. Prognostic factors such as laboratory values have rarely been adopted in existing SPMs for patients receiving palliative radiotherapy. Although the predictive value of laboratory test results for skeletal metastases has been recognized, not incorporating these factors in SPMs might have constrained the predictive ability of these models. This retrospective study aims to investigate the prognostic impacts of laboratory data and to compare the performances of Metastases location, Elderly, Tumor primary, Sex, Sickness/comorbidity, and Site of radiotherapy (METSSS) model, New England Spinal Metastasis Score (NESMS), and Skeletal Oncology Research Group machine learning algorithm (SORG-MLA) for SM. Materials and methods: From 2010 to 2018, patients who received radiotherapy (RT) for SM at a tertiary center were enrolled and the data were retrospectively collected. Multivariate logistic and Cox-proportional-hazard regression analyses were used to assess the association between laboratory values and survival. The area under receiver-operating characteristics curve (AUROC), calibration analysis, Brier score, and decision curve analysis were used to evaluate the performance of SPMs. Results: A total of 2,786 patients were included for analysis. The 90-day and 1-year survival rates after RT were 70.4% and 35.7%, respectively. Higher albumin, hemoglobin, or lymphocyte count were associated with better survival, while higher alkaline phosphatase, white blood cell count, neutrophil count, neutrophil-to-lymphocyte ratio, platelet-to-lymphocyte ratio, or international normalized ratio were associated with poor prognosis. SORG-MLA has the best discrimination (AUROC 90-day, 0.78; 1-year 0.76), best calibrations, and the lowest Brier score (90-day 0.16; 1-year 0.18). The decision curve of SORG-MLA is above the other two competing models with threshold probabilities from 0.1 to 0.8. Conclusion: We demonstrated the clinical impact of selective laboratory values such as serum albumin level, hemoglobin level, and lymphocyte count on survival prediction in patients receiving radiotherapy for spinal metastases. SORG-MLA, incorporating laboratory values and the flexible modeling technique, accurately predicts 90-day and 1-year survival for the radiotherapy cohort. SPMs integrated into patient decision aids for shared decision-making present opportunities for individualized patient-centered care in the future.

1617

P455: Percutaneous lumbar 9-point annuloplasty for chronic low back in the modified Pfirmann classification, graded 3 to 6

Jin-Sung Luke Kim ¹

¹ Neurosurgery, Seoul St Mary's Hospital, Seoul, South Korea

Background: Of the varied options available for the management of chronic discogenic back pain, lumbar annuloplasty provides a reasonably acceptable option. Being a minimally invasive option with no serious adverse effects, it can be applied as a daycare option in an ambulatory spine center. Since the currently described techniques fail to address the target pathology in the posterior annulus, this report delineates the correct target-oriented approach of percutaneous lumbar annuloplasty using a radio-frequency probe to manage discogenic low back pain with the patients in the modified Pfirmann classification graded 3 to 6. Objective: To describe an alternative annuloplasty technique for treating chronic discogenic back pain in an ambulatory setting. Method: A retrospective review of all patients presenting with chronic discogenic low back pain and managed by target-oriented thermal annuloplasty at our institute from May 2015 to June 2021 was performed. The procedure is carried out under local anesthesia in a prone position. The principle of the technique relies on dividing the posterior annulus into nine equal segments on the AP view of the C-arm. The trajectory is through Kambin’s triangle in a horizontal trajectory as much as possible to target the posterior part of the disc annulus. Results: 21 patients were treated by this method with an average follow-up of 32.1 (±11.4) months. The average VAS improved from 4.1 (±1.2) to 2.3 (±0.4) at final follow-up. The ODI improved from 42 (±6.7) to 19.98 (±5.6). None of the patients had any complications. One patient had a progression of degenerative scoliosis over two years. However, there was no obvious pain related to scoliosis. The patient satisfaction rate was 82%, the return to life was 95.2%, and the recommendation rate to others was 100%. Conclusion: Target-oriented lumbar percutaneous nine-point annuloplasty may be considered a viable option for chronic discogenic back pain with relatively well-maintained disc heights, which is the case of the modified Pfirmann classification graded 3 to 6. A successful outcome depends upon proper patient selection and correct trajectory.

Key words: chronic low back pain, percutaneous, lumbar, annuloplasty, disc

1754

P456: Ultrasound-guide pulsed radiofrequency of cervical nerve root for chronic cervical radicular pain: a prospective randomized controlled trial

Weerasak Singhatanadgige ¹ , poornpan Chalermkitpanit ¹ , and Vit Kotheeranurak ¹

¹ Orthopedics, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand

Introduction: Pulsed radiofrequency (PRF) on cervical DRG for pain management in cervical radicular pain is mostly performed via transforaminal approached under fluoroscopic guidance. Ultrasound-guidance periradicular cervical nerve root intervention raises concern in the neuromodulatory effect. This study aims to evaluate the effectiveness and duration of pain relief between PRF treatment and steroid injection on the cervical nerve roots. Material and Methods: Forty-two patients presented with chronic cervical radicular pain were prospectively randomized into pulsed radiofrequency (PRF) group and steroid group. Patients in the PRF group received PRF treatment at 42 degrees Celsius for 4 minutes followed by the injection of 2% lidocaine 1.5 ml with dexamethasone 10 mg to the targeted cervical nerve root. The steroid group received the same injectate. Patients and pain assessor were blinded. Numerical rating scale (NRS 0-10) and the Neck Disability Index (NDI) questionnaire were used for pain intensity and neck functional assessment before and after the procedure. The duration of pain reduction at least 50% was recorded up to 9-month follow up. Results: Data analysis was obtained from 21 and 20 patients receiving pulsed radiofrequency (PRF) and steroid treatment, respectively. At 3-month post procedure, patients in PRF group had significantly less pain (NRS 2.8 ± 2.7) than patients in steroid group (NRS 5.5 ± 2.6) (p = 0.01). Neck disability index demonstrated significant improvement at 3 and 6 months (p < 0.01) after PRF treatment compared to sole steroid injection. The duration of pain relief at least 50% was significantly longer in patients received PRF treatment (6.0 ± 4.1 months) compared to those in the steroid group (2.3 ± 2.1 months) (p < 0.01). The vascular puncture did not occur in both study groups. Conclusion: Ultrasound-guided periradicular cervical nerve root PRF exhibited neuromodulatory effect and was considered a safe and effective treatment for patients with cervical radicular pain. It provided longer duration of pain relief and the improvement of neck function up to 6 months.

1788

P457: Comparison of healing rates between rigid and semi-rigid bracing in adolescent lumbar pars bone stress injuries

Paul Licina ¹ , Patrick Beaumont ² , and Mark Young ²

¹ Faculty of Health, Exercise and Nutrition Science, Queensland University of Technology, Kelvin Grove, Australia

² Spine Surgery, Brisbane Private Hospital, Brisbane, Australia

Introduction: Adolescent athletes are predisposed to lumbar bone stress injuries of the pars interarticularis (pars stress injuries or PSIs). These injuries are the most common cause of significant adolescent low back pain and may progress to chronic disability, non-union and isthmic spondylolisthesis. They are heterogenous and may be acute or chronic, and unilateral or bilateral, and the injury grade may be a stress reaction, an incomplete fracture, or a complete fracture. MRI can identify the chronicity and grade of the lesion by measuring bone marrow oedema (BMO) and visualising the fracture. Bracing has been proposed as a treatment for acute PSIs. It not only relieves pain but has been previously shown to increase the likelihood of bony healing, reducing the risk of progression. The lumbosacral brace may be a rigid custom-made Boston brace-type orthosis or a semi-rigid off-the-shelf brace. The objectives of this study were to quantify the types of PSIs, to determine the bony healing rates after 12 weeks of bracing, and to compare healing rates between rigid and semi-rigid braces. Materials and Methods: We performed a retrospective analysis of adolescents with acute PSIs (as defined by a bone BMO ratio ≥ 2) who wore either a rigid or semirigid brace for 12 weeks. All participants underwent an MRI scan prior to bracing and at 12 weeks, to assess the degree of BMO and the injury grade. From this, it was determined whether the BMO had resolved (ratio < 2) and whether the fracture had healed during the bracing period. Results: We identified 88 patients with an acute PSI treated in a brace. Overall, 14 worsened, 12 remained unchanged and 62 improved (i.e., had resolution of BMO). Of those that improved, 25 also showed fracture healing. 49 were unilateral acute PSIs, 4 of which had a contralateral chronic complete fracture. Of the 45 unilateral acute PSIs without a contralateral chronic fracture, 32 improved with 17 of those healed. However, all 4 patients with a contralateral chronic fracture worsened. 39 were bilateral acute PSIs, and in this group, 30 improved with 8 of those healed. Of the 88 patients, 42 used rigid orthoses and 46 used semi-rigid braces. There was no significant difference between rigid and semirigid bracing in overall improvement or healing. Discussion: We demonstrated that the use of bracing in acute PSIs led to a 70% rate of resolution of BMO and a 28% rate of fracture healing at 12 weeks with only 16% worsening. We found that bracing is significantly more effective in unilateral only and bilateral acute PSIs, compared to unilateral acute PSIs with a chronic contralateral fracture, questioning the role of bracing in this subgroup. We were unable to demonstrate that bracing was superior to non-bracing but there are considerable ethical challenges in withholding treatment in an adolescent population where the intervention is relatively benign and has previously been demonstrated to be effective. Off-the-shelf semirigid braces are more convenient and less expensive, and in our study showed similar efficacy in BMO resolution and bony healing.

Novel Technologies

102

P458: Full power assisted versus manual pedicle screw insertion a systematic review

Elie Najjar ¹ , Mohamed Hassanin ¹ , Ali Mardashti ¹ , Nasir Quraishi ¹ , and Ali Shetaiwi ¹

¹ Spine Surgery, Nottingham University Hospital, Nottingham, United Kingdom

Introduction: Long level pedicle screw placement requiring repetitive forceful rotational movements have been shown to increase pain and musculoskeletal disorders impacting the work of spine surgeons. Full power-assisted pedicle screw insertion decreases the surgeon’s work and thus the risk of fatigue and injury. Yet there is limited data discussing the efficacy and safety of full power assisted compared to manual technique. Methods:A systematic review of the English language literature dating up until December 2021, was undertaken using search criteria ((Power Drill) OR (Power Assisted) and (Pedicle Screw)) and the PRISMA guidelines. Results: Of a total of 224 articles, 3 studies met the inclusion criteria (1 Level I and 2 level III evidence) and were analyzed. Overall, 1685 patients (male/female = 587/1098, mean age 14.1years) had a scoliosis deformity corrected with posterior instrumentation using full power assisted pedicle screws. The average instrumented levels were 11.1, average screw per case was 16.5 with a mean follow-up of 20.8 months. The average operative time was 237 minutes for all cases (225 minutes for AIS alone), the number of complications was 8/1685 (0.4%). Additionally, 814 patients (male/female = 266/548, mean age 13.7 years) had manual pedicle screw insertion for correction of their scoliotic deformity. The average instrumented levels were 10.1, and average screws per case were 15.2 with a mean follow-up of 26.8 months. Comparing Full power assisted versus manual pedicle screw insertion, there was no significant difference in operative time 238.2 vs 250 (p = 0.27, RR: -21.57 95CI: 6.04) or the complication rate 8/1650 ( 0.5%) vs 15/744 (2%) ( P=0.003, RR:0.11 95CI: 0.63). Conclusion: Full power assisted pedicle screw insertions has the same operative time and complications risk compared to manual pedicle screw insertion in scoliosis deformity correction surgery.

104

P459: Clinical application of new concept of rod connector; connector for simultaneously fixing screw head and rod (for ASD operation)

Moon-Kyu Kim ¹

¹ Neurosurgery, Gangneug Asan Hospital, Gangwon-do, South Korea

Introduction: With the development of pedicle screw system and spinal deformity surgery, spinal fixation surgery is gradually increasing. Accordingly, surgery for adjacent segments after spinal fusion is also increasing. Due to the adjacent segment diseases (ASD), incision of all previous surgical ranges during surgery has a wide range of surgery and concerns about damage to muscle soft tissue due to revision, therefore, several connectors (open connectors) have been developed as results of effort to minimize revision surgeries. However, these type connectors are mainly connected only to rods (rod to rod) and single connector is mechanically weak when they are use alone, thus multiple connectors are used to get enough strength to extend fusion levels. Therefore, authors developed a connector capable of extended fusion by combining the top load fixation type screw head and rod simultaneously to strengthen the connection structure, exposing only the top-level screw head during adjacent segment surgery, and applied it to clinical practice. Methods: The basic concept was prepared in 2016 and patented in 2019 (application in 2017). The clinical device (Qnector) using this concept started development in 2017 and was completed in 2019, passed KFDA in 2020, and applied to clinical trials in 2021. The basic concept is that the connector is fixed to the rod and the screw head located at the end of the existing surgical instrument at the same time, and a new rod is connected to this connector. This structure compensates for the vulnerability to rotation based on the rod direction by fixing it with the screw head, so Qnector has the effect of using only one connector instead of using multiple open connectors. Results: Between March 2021 and June 2022, Qnectors were applied to 9 patients who developed ASD after the previous multilevel level fusion, and showed a stable and good clinical course without hardware failure and were enough strong to endure rod bending after connection by in situ benders. The screws previously operated were different types, but all were applicable to Qnectors. Discussion: The new concepted connector can be developed in various shapes other than the one developed this time. It can be developed in various forms, and could be supposed to open the horizon for a new concept of connectors that can affix the screw head and rod simultaneously. Conclusion: A powerful connector that connects the screw head and rod at the same time could minimize the re-opening of the previous surgical site, improving the patient's recovery after surgery and lowering the operator's surgical difficulty.

201

P460: ALL repair and disc replacement for hyperextension injuries - extending the indications for motion preservation in the cervical spine

Adrian Cavalcanti Kußmaul ¹ , Titus Kuehlein ¹ , Becker Christopher ¹ , Bruder Jan ¹ , Woiczinski Matthias ¹ , Kistler Manuel ¹ , Böcker Wolfgang ¹ , and Greiner Axel ¹ , Sandy Walter ¹

¹ Department of Orthopaedics and Trauma Surgery, Musculoskeletal University Center Munich (MUM), University Hospital, LMU, Munich, Germany

Introduction: Anterior tension band injuries are usually the result of high impact hyperextension trauma. However, these injuries can be increasingly observed in geriatric patients based on the current demographic change. Surgical treatment includes anterior plating bearing the risk of soft tissue irritation, such as esophageal dysphagia or rupture, and degeneration of adjacent cervical segments or implant failure due to an iatrogenic spondylodesis. Tape suture constructs, reenforcing ligamental stability while permitting physiological micro mobility of the affected motion segment, are already established for ligamental injuries in ankle, knee or shoulder surgery. Recently, a biomechanical in vitro study was further able to demonstrate the feasibility of this flexible osteosynthesis technique for the treatment of AO type B3 injuries. Consequently, this in vivo study aims to examine the biomechanical properties of tape suture constructs for the treatment of AO type B3 injuries in cadaver specimens. Materials and Methods: The anterior longitudinal ligaments (ALL) and the cervical disc of 16 human cadaver C5/6 segments were dissected, simulating an AO type B3 injury. Then, two groups were formed and treated either with anterior cervical discectomy and fusion (ACDF) (anterior 4-hole-plate, DePuy Synthes^®) or a cervical total disc replacement (CTDR) (Prodisc^®- C Vivo) combined with a tape suture construct, similar to the SpeedBridge^TM (Arthrex^®), which was implanted ventrally according to the anatomical course of the disrupted ALL. The specimens were then mounted onto a biomechanical testing machine in a neutral position and biomechanical forces were applied through a lever arm until a force of 15N was reached in the sagittal plane, simulating extension and flexion. Next rotational forces to both directions were applied until cervical resistance resulted in a rotational force of 2N/m. Implant failure was defined as a dislocation exceeding 25mm for extension and 7° for rotation. For statistical analysis, the dislocation (°) and its corresponding force (N) of each specimen was measured and compared. Results: Preliminary results show a higher range of motion for the tape suture construct in all motion planes with the tape suture construct however consistently staying below physiological mobility. No specimen suffered from implant failure. Detailed evaluation among the specimens is currently in progress and will be completed in time for the congress. Conclusion: The tape suture combined with CTDR provides sufficient biomechanical stability for the treatment of AO type B3 injuries compared to anterior plating. Preliminary results display a sufficient limitation of movement in the sagittal plane, especially regarding cervical extension, which’s limitation is crucial for ligamental healing. The rigid ACDF highly compromises cervical rotation and lateral bending, which are usually not affected in a hyperextension injury, while the tape suture and CTDR approach the physiological range of motion. Consequently, the tape suture construct is a promising alternative to the current gold standard of anterior plating for the treatment of AO type B3 injuries based on its excellent biomechanical results and its preservation of cervical micro mobility with a concomitant prevention of an iatrogenic spondylodesis.

251

P461: Early phase outcomes in ACDF with a 3D-printed gyroid architecture porous titanium interbody reconstruction spacer

Sohrab Vatsia ¹ , Matthew McGinty ² , and L. Erik Westerlund ¹

¹ Hughston Clinic, Columbus, United States

² Mercer University School of Medicine, Columbus, United States

Introduction: Novel 3D-print techniques utilizing porous gyroid architectures with high surface area and strength in anterior cervical discectomy and fusion (ACDF) provide an opportunity to program the bulk modulus of a printed porous titanium implant to emulate that of native vertebral bone, potentially mitigating implant subsidence. There is a paucity of evidence investigating outcomes of such 3D-printed interbody cage implants in ACDF. Therefore, the purpose of this study is to assess subsidence and early clinical and radiographic outcomes of a 3D-printed porous gyroid-architecture titanium interbody fusion device used in the treatment of degenerative cervical disc disease. Material and Methods: This is a single-surgeon, retrospective cohort study of 20 consecutive patients who underwent either single or multi-level ACDF using 3D-printed porous gyroid-architecture titanium interbody cages. The standardized Visual Analog Scales (VAS) of the Neck and Arm were used to subjectively evaluate pain levels preoperatively and postoperatively at two and six weeks and three months. Plain film radiographs were used to assess fusion progress, ingrowth, sagittal plane angulation, implant migration, and subsidence. Results: The mean patient age was 57 years and 60% of patients were male. There were 4 one-level, 8 two-level, 7 three-level, and 1 four-level fusion between the C3 and T1 vertebral levels. The mean preoperative VAS Neck score for 2-level fusion (5.13) demonstrated a significant decrease at both two and six weeks postoperatively (3.90, p = 0.01; 3.50, p = 0.03, respectively). The mean preoperative VAS Arm score for 1-level fusion (4.75) demonstrated a significant decrease at both two and six weeks (4.00, p = 0.01; 3.50, p = 0.04, respectively), and the mean preoperative VAS value for 3-level fusion (5.67) also reflected a statistically significant decrease at two and six weeks (2.50, p = 0.01; 1.00, p = 0.01, respectively). Six and twelve weeks postoperatively, all patients demonstrated reductions in VAS Arm scores. All postoperative radiographs demonstrated evidence of osseous fusion and no instances of subsidence or migration of implants. Conclusion: Initial results indicate that use of 3D-printed, porous titanium gyroid-architecture interbody implants is safe and presents a suitable alternative for successful clinical and radiological outcomes in ACDF. Such 3D-printed interbody cages offer high strength and surface area in a porous form and an elastic modulus similar to native bone and may offer clinical advantages over 3D-printed truss structures, PEEK, or prior titanium interbody solutions in ACDF.

330

P462: Video-assisted thoracoscopic surgery (VATS) in the prone position for the surgical treatment of symptomatic thoracic disc prolapse, an analysis of 156 consecutive patients

Mohamed Alhashash ^1,2 , Heinrich Boehm ¹ , Reza Bahrami ¹ , and Mootaz Shousha ¹

¹ Spine Surgery, Zentralklinik Bad Berka, Bad Berka, Germany

² Orthopedics and Trauma, Alexandria University, Alexandria, Egypt

Introduction: Thoracic disc disease is rare in comparison to cervical or lumbar discs. A centrally located herniation results in spinal canal stenosis and even thoracic myelopathy. The posterior approach is suitable for laterally located disc prolapse. In cases with centrally located stenosis, an anterior approach allows the direct decompression of the spinal cord. In this study, an analysis of the surgical results after an anterior thoracoscopic decompression of thoracic disc herniation was preformed. Material and Methods: A retrospective analysis of the prospectively collected data in a single spine center revealed 156 patients surgically treated using VATS for symptomatic thoracic disc prolapse. Diagnosis was confirmed by MRI and a preoperative CT was performed to assess the nature of the disc prolapse. The operation was preformed in prone position using a bi-portal VATS. One lung ventilation was used in some case in higher thoracic levels (Th9 or above). Identification of the affected level was verified using C-arm after the positioning of the patient. Decompression of the spinal canal and anterior fusion was preformed through the anterior approach. A posterior fixation was done in the same position using a percutaneous screw-rod system. Intraoperative neuro-monitoring was used. Results: The study included 156 consecutive patients operated starting from January 2000. There were 98 females and 58 males with a mean age of 54.8 ± 12.4 years. Clinically, back pain, radiculopathy, thoracic myelopathy, and different degrees of incomplete paraplegia in 23 patients were the presenting symptoms. The mean operation time was 224.4 ± 116.8 minutes, and blood loss was 436.4 ± 155.2 ml. There were no intraoperative complications. Postoperative pneumothorax on the contralateral side occurred in 3 patients and a thorax tube was inserted. Transient postoperative lower limbs numbness occurred in 4 patients. The mean postoperative follow up was 42.6 ± 16.7 months. VAS improved from 7.4 ± 2.3 preoperative to 3.2 ± 1.6 after 3 months postoperatively (p = 0.01). ODI improved from 32.7 ± 12.3 to 9.8 ± 6.4 (p = 0.02). Neurological improved of the 23 patients presenting with preoperative incomplete paraplegia occurred after a mean of 6.4 months in all but 4 patients. Reoperation was necessary in 4 patients, 2 due to adjacent segment disease, one patient had inadequate decompression and was revised posteriorly, and in one patient a false level was operated and had to be re-operated. Conclusions: VATS approach for thoracic disc prolapse is safe. Exact intraoperative identification of the affected level is mandatory. Neuro-monitoring increases the safety of the procedure. Thoracoscopic approach in prone position allows anterior and posterior spinal instrumentation without the need of intraoperative repositioning of the patients.

480

P463: Knowledge gaps in biophysical changes after powered robotic exoskeleton walking by individuals with spinal cord injury - a scoping review

Christopher Yip ¹ , Chor Yin Lam ² , Kenneth Man Chee Cheung ² , Yat Wa Wong ² , and Paul Koljonen ²

¹ The University of Hong Kong, Hong Kong

² Department of Orthopaedics and Traumatology, The University of Hong Kong, Hong Kong

Introduction: In addition to helping individuals with spinal cord injury (SCI) regain the ability to ambulate, the rapidly evolving capabilities of powered robotic exoskeletons provide an array of secondary biophysical benefits which can reduce the complications resulting from prolonged immobilization. This scoping review seeks to provide an overview on the known effects of overground exoskeleton use, on the prevention of secondary health complications, changes to the QOL, and their effect on the independence of SCI individuals in the community settings. Moreover, the intent of the review is to identify gaps in the literature currently available, and to make recommendations on focus study areas and methods for future investigations. Material and Methods: The reporting of methods and results in this scoping review follow the Preferred Reporting Items for Systematic reviews and Meta-Analyses extension for Scoping Reviews (PRISMA- ScR) guidelines. The framework by Arksey and O’Malley has been referenced for the protocol of this scoping review. PubMed, Cochrane, and EMBASE were searched for relevant articles from database inception to June 19, 2021; the bibliographies of included articles were screened. The search term used included “exoskeleton,” “spinal cord injury,” and related keywords, both as the free-text keywords and controlled vocabulary of their respective databases (e.g., MeSH for PubMed and Cochrane Library). The refinement of protocol was done after the initial search, with focus placed on a defining eligibility criterion with specific attention to the list of biophysical characteristics to include. The final selection of studies was separated into individual groups based on the type of biophysical characteristic that was evaluated; studies that measured more than one biophysical characteristic were included more than once across different tables. Data extraction templates were generated a priori, with minor modifications done after the initial search, and the data elements extracted included: study, intervention, number of training sessions, ASIA grade, number of subjects, time-points during trial when specific relevant measurements were taken, outcome metrics used in the study, and the presence of any control arms. Results: 654 articles were found in the initial search, 231 of which were found to be duplicate; 329 articles were excluded during the screening of the titles and abstracts, and a further 52 were eliminated after screening the full texts. In the final analysis, 42 papers were included from the initial search, combined with an additional 8 from scanning through the reference lists of relevant studies. 50 unique studies were included in the charting process. Detailed results will be presented in this abstract. Conclusion: This scoping review the most robust systematic review performed on this topic to date. It has identified various focus areas in the need of further investigation, such as CVS health, BMD, body composition changes, and independence and functional applications for exoskeletons. Detailed analysis on each domain were performed and presented. We have identified pitfalls, such as heterogeneous methodologies, disparate study populations, and dissimilar training programs, which need to be overcome in future studies.

861

P464: Smartphones, wearables, and digital biomarkers: the evolution of spine care outcomes research

David Kurland ¹ , Christina Bi ¹ , Roee Ber ¹ , Douglas Kondziolka ¹ , Darryl Lau ¹ , Donato Pacione ¹ , Anthony Frempong-Boadu ¹ , Ilya Laufer ¹ , and Eric Oermann ¹

¹ Neurosurgery, NYU Langone Health, New York, United States

Introduction: Over the past generation, outcomes research in spine care has evolved from reliance on clinician-reported assessment toward a recognition of the importance of the patient’s perspective, and the wide incorporation of patient-reported outcome measures (PROMs). While PROMs are now considered an integral component of outcomes assessments, they cannot wholly capture the state of a patient’s functionality. The pervasiveness of smartphones and wearable devices in modern society, which passively collect data related to health, has ushered in a new era of spine care outcome measurement – and in some respects, a return to objectivity. The patterns emerging from these data, so-called “digital biomarkers,” can accurately describe characteristics of a patient’s health, disease, or recovery state. Material and Methods: PubMed was queried for the following terms on July 20, 2022: (smartphone OR wearable OR mobile device) AND (spine OR spine surgery OR spinal fusion OR spinal decompression OR spinal deformity). Two authors (DBK and CB) independently screened each record. Clinical articles reporting the use of smartphones and wearable devices in objective spine care outcomes research were eligible for inclusion in this review. Pertinent topical review articles were also evaluated separately for content. Non- or pre-clinical studies were excluded, as were reports on devices that were prototypes or in pre-commercialization stages. We also excluded manuscripts that described smartphone or wearable applications strictly designed for use by a provider in a clinical or office setting. Results: The initial search returned 437 unique results. Of these, 330 were readily deemed ineligible based on subject matter. Of the remaining 107 sought for retrieval, 37 were excluded based on the exclusion criteria described above. A total of 70 manuscripts (46 clinical studies and 24 pertinent topical reviews) published between 2015 and 2022 met inclusion criteria, and were reviewed in detail. The current applications of digital biomarkers are manifold and include: 1) surgical decision making, 2) diagnosis and disease severity stratification, 3) remote pre- and post-operative symptom monitoring, as well as 4) remote care/self-management. These applications and concepts have been successfully applied to patients with chronic low back pain, lumbar stenosis, degenerative disc disease and cervical stenosis. Conclusion: Digital biomarkers and continuous passive monitoring have a number of currently validated applications in the field of spine care, as well as tremendous potential to expand into the field of personalized medicine. Smartphones and wearable devices increase the accessibility of mobility measures previously confined to the clinical or laboratory setting. Continuous collection of mobility data can improve symptom and disease progression monitoring, detect deterioration or functional decline, and improve perioperative care. The pervasiveness of smartphones and wearables naturally increase patient compliance and have the potential to further involve patients in their own care, creating a deeper collaboration between patient and care providers. More extensive data collection of mobility and gait metrics, both on a population and an individual level, will allow for the utilization of digital biomarker measures in a more personalized way, allowing for more appropriate treatment decisions, more accurate prognostic measures, and more efficient resource allocation.

910

P465: The efficacy of stand-alone spacers in comparison to conventional cage and plate in anterior cervical discectomy and fusion surgery: a meta-analysis of randomised controlled trials for clinical and radiological outcomes

Jake McDonnell ¹ , Salma Youssef ² , Gráinne Cunniffe ¹ , Stacey Darwish ¹ , and Joseph Butler ¹

¹ National Spinal Injuries Unit, Mater Misericordiae University Hospital, Dublin, Ireland

² School of Medicine, University College Dublin, Dublin, Ireland

Background: ACDF is commonly performed with cage and plate constructs to provide stability to the diseased or injured cervical segment. Despite it being a commonly performed procedure, there are notable rates of associated morbidity reported in the literature. Anchored stand-alone spacers represent a novel form of instrumentation to conventional cage and plate constructs. However, little is known regarding their collective comparative evidence versus cages and plates. This serves the premise for this study. The objective of this study is to elucidate if anchored spacers have improved operative characteristics and postoperative outcomes in anterior cervical discectomy and fusion (ACDF) cohorts when compared to traditional cage and plate, and can be inferred as efficacious as conventional instrumentation in the management of cervical spine disorders. Methods: A systematic review and meta-analysis was conducted of PubMed/Medline, Embase and Google Scholar databases per the Preferred Reporting Items for Systematic Reviews and Meta-Analyzes (PRISMA) guidelines. Studies of interest included comparative (conventional cage and plate) instrumentation versus anchored stand-alone spacers for patients undergoing ACDF. Pre- and post-operative clinical and radiological outcomes were collated and compared for significance between cohorts. Results: 10 RCTs were identified and included with 779 patients total. Mean age of the entire cohort was 50.1 years (range 30-78 years). 62% (483/779) of the cohort were male, while 38% (296/779) were female. 384 patients underwent ACDF with stand-alone cage, while 395 had ACDF with conventional cage and plate. Stand-alone spacers significantly outperformed conventional instrumentation in terms of estimated blood loss (p < 0.01), total postoperative complications (p < 0.01), dysphagia rates (p = 0.04) and adjacent segment disease (p = 0.04). Non-inferiority was evident in both patient reported outcome measures and radiological outcomes. Conclusion: The results of this meta-analysis highlight the efficacy of stand-alone spacers for the management of primarily cervical spondylitic disease for both single-level and multi-level pathology, and thus present an attractive alternative to conventional instrumentation for patients undergoing ACDF surgery.

948

P466: Medical grade, operating theatre, HEPA and UV light air filter effectively reduce air particles with implied viral sterilisation

Angelo Fragkakis ¹ , Zion Hwang ² , Jason Bernard ¹ , Timothy Bishop ¹ , Jan Herzog ¹ , Shahnawaz Haleem ¹ , Tesfaladet Kurban ¹ , Bisola Ajayi ¹ , Emily Tsang ² , Priyanshu Saha ² , and Darren Lui ¹

¹ Trauma and Orthopaedics, St. George's University Hospital, London, United Kingdom

² St. George's University of London, London, United Kingdom

Introduction: SARS-CoV-2 has become a worldwide threat exposing patients and physicians to significant risks. The virus starts primarily as a respiratory infection and has airborne capabilities with a 60–140nm diameter transmissible through droplet particles of Ø 0.3-10µm. Aerosol-generating procedures can increase the particles’ transmission risk, therefore neutralisation methods become paramount. Studies show that the success of ultraviolet (UV) light disinfection warrants greater research into its utility within clinical settings. Only recently, UV light has been paired with HEPA (high-efficiency particulate air) filters. This innovative technology could have the potential to aid prevention of viral and bacterial nosocomial infection and its associated morbidities. Therefore, this study aims to assess whether Illuvia^® HUAIRS, a medical-grade HEPA and UV light air recirculation system, can reduce the airborne particle count, and thus potentially reduce the spread of nosocomial infection. Material and Methods: This prospective pilot study conducted in an Intensive Care Unit (ICU) of a tertiary UK hospital (2020-2021) assessed the impact of Illuvia^® HUAIRS, filtering 41.8m³/min of air. The air particles concentration was measured with a validated and published particle counter (HT9600; Dongguan Xintai Instrument Co. Ltd.). As a surrogate measure for an infectious bioaerosol carrying COVID-19, 0.3μm, 2.5μm and 10μm particle sizes were considered. In a 150m² ICU, with 14 patients and 20 staff, 7 consecutive time-points (T0-T7) were collected 12-hourly over a 4-days period, from 32 established locations and compared against baseline samplings. Statistical significance was established at p < 0.05. Results: A statistically significant improvement was registered 24 hours after the activation of Illuvia^® HUAIRS at Nurse Stations (NS, 37% and 59%) and Patients’ areas (PT 27% and 52%), for 0.3μm and 2.5μm, respectively. 10μm particles were not detected. Illuvia^® HUAIRS had a clear impact in reducing the pollution between gates’ and patients’ areas from 2.3-folds to 1.8-folds. No statistical significance between nursing station/patients nor side-rooms was identified. Conclusion: The Illuvia^® HUAIRS could represent a potential adjuvant solution in reducing the bioaerosol particles, making the environment safer for patients and staff. Also, given the well-established relationship between airborne pathogen levels and healthcare-associated infections, this technology could be further utilised on other clinical/surgical areas.

1070

P467: The impact of robotic lumbar spine surgery on 90-day outcomes

Nicholas D'Antonio ¹ , Jeremy Heard ¹ , Yunsoo Lee ¹ , Mark Lambrechts ¹ , Caroline Purtill ² , John Bodnar ² , Patrick Fitzgerald ² , Dominic Farronato ² , Josh Pezzulo ² , John Paulik ² , Tariq Issa ¹ , Parker Brush ¹ , Sebastian Fras ² , Jose Canseco ¹ , Christopher Kepler ¹ , Alan Hilibrand ¹ , Alexander Vaccaro ¹ , and Gregory Schroeder ¹

¹ The Rothman Orthopedic Institute at Thomas Jefferson University Hospital, Orthopedic Surgery, Philadelphia, United States

² Thomas Jefferson University, Philadelphia, United States

Introduction: Robot-assisted spine surgery has become an increasingly popular option for spinal fusion and instrumentation procedures. Although there is promise in the literature regarding robotic surgery, hesitancy around the widespread adoption of robotic spine surgery still exists. Therefore, the purpose of this study was to (1) evaluate the surgical outcomes of robotic surgeries compared to nonrobotic surgeries and (2) determine trends regarding robotic surgery usage for spine surgery. Methods: Patients > 18 years of age who underwent primary lumbar fusion surgery at our institution were identified and propensity matched in a 1:1 fashion based on use of a robot during surgery. Patient demographics, surgical characteristics, and surgical outcomes including 90-day all-cause readmissions and 90-day surgical readmissions were collected. Multivariable regression analysis was performed. Significance was set to p < 0.05. Results: Of 830 patients included in the analysis, 415 patients (50.0%) had a robotic lumbar fusion. Cases with the robot were less likely to be revisions (5.54% vs. 17.1%, p < 0.001) but more likely to have a longer operative duration (287 vs. 205 minutes, p < 0.001) and more than one incision made during the operation (30.6% vs. 3.13%, p < 0.001). Intraoperative durotomies were more common in cases where the robot was not used (14.9% vs. 3.37%, p < 0.001). On bivariant analysis, compared to patients with a robotic fusion, those without a robotic fusion had a significantly higher rate of all-cause 90-day readmissions (14.0% vs. 8.92%, p = 0.029) but no significant difference in 90-day surgical readmissions (10.6% vs. 8.67%, p = 0.410). A bivariant subanalysis of one to two level fusions demonstrated all-cause 90-day readmissions (p = 0.024) and intraoperative durotomy (p < 0.001) were significantly more likely in the nonrobotic fusion group. However, surgical readmission rate and etiology were not significantly different between groups. A multivariable analysis of the entire cohort revealed that robotic fusion was not a significant predictor of all-cause 90 day readmissions (OR = 0.768 [0.47-1.24], p = 0.283) or all-cause 90 day readmissions (OR = 1.03 [0.64-1.79], p = 0.784). An additional multivariable analysis those with one to two level fusions demonstrated that robotic surgery was not a predictor of surgical or all-cause 90-day readmissions. Conclusion: Our study suggests that robotic-assisted and nonrobotic-assisted lumbar fusions are associated with a similar risk of 90-day all-cause and surgical readmissions. Robotic surgery may result in fewer intraoperative complications but increased time under anesthesia. High-quality prospective studies are needed to add context to the literature studying the impact of robotic lumbar fusion surgery on readmissions.

1180

P468: A biomechanical analysis of a novel spinolaminar plate construct for posterior lumbar fusion compared to traditional pedicle screw fixation

Dimitriy Kondrashov ^1,2 , Amit Piple ² , Victor Ungurean ² , and Oluwatodimu Raji ^1,2

¹ Orthopaedic Surgery, St. Mary's Medical Center, San Francisco, United States

² Orthopaedic Surgery, The Taylor Collaboration, San Francisco, United States

Introduction: Bone anchors in osteoporotic patients are prone to failures, both acute and delayed. In orthopaedic trauma surgery, locking plates, which utilize locking screws and pre-threaded plates, have revolutionized the fixation of osteoporotic fractures. We sought to combine the traumatology principle of locking plate fixation using fixed angle constructs with the spine principles of segmental fixation. Methods: A novel pre-contoured spinolaminar locking plate with a polyaxial saddle was designed based on morphometric anatomic studies of human thoracolumbar vertebrae. The plates were fixed to an osteoporotic cadaveric human lumbar spine and connected to form a 1-level L4-L5 construct using 10-16mm and 3.5mm locking screws and 3.5mm locking plates. An analogous 1-level T12-L1 construct was made using conventional pedicle screw fixation. In total, 1 spinolaminar and 1 pedicle screw construct were designed from the same cadaveric specimen (age: 69 years old, sex: female). Pure moment testing was performed to assess range of motion (flexion/extension, lateral bending, and axial rotation) after 30,000 cycles of combined flexion-compression-anterior shear at 17Nm-400N-200N, respectively. Evidence of construct failure was assessed every 5,000 cycles with fluoroscopy. Static load-to-failure was performed under combined flexion-compression-anterior shear moment. Fixture pullout strength was assessed by applying a continuous axial tensile force oriented to the principal axis of the pedicle until pullout was observed. Results: The pedicle screw construct failed by a windshield wiper mechanism due to vertebral body fracture along the midplane of the pedicle at approximately 12,000 cycles. The spinolaminar plate construct completed cyclic loading with no evidence of failure. Post fatigue range of motion was observed to be 7.1 degrees in lateral bending, 1.7 degrees of axial rotation, and 1.7 degrees of flexion/extension for the spinolaminar plate. Upon static load-to-failure testing, the spinolaminar construct failed at 41Nm-928N-473N of combined flexion-compression-anterior shear. Static failure of the spinolaminar construct was due to separation of proximal non-instrumented vertebral level from upper instrumented vertebra via dislocation of the posterior elements while the plate, rods and screws remained intact and fixed.The maximum pullout strength of the spinolaminar plate was 590N while the maximum pullout strength of the pedicle screw construct was 424N. Discussion: The spinolaminar locking plate maintained adequate fixation post-fatigue, particularly in flexion/extension and axial rotation. Moreover, spinolaminar plates may be superior to pedicle screw fixation with respect to cyclic fatiguing and pullout strength. Further testing should be performed on additional cadaver spines to validate these findings; however, our novel spinolaminar plates appear to be a viable instrumentation technique for posterior lumbar fusion in osteoporotic spines.

1246

P469: Digital neurocognitive monitoring in patients undergoing opioid medication after spinal surgery: a feasibility study

Vicki Butenschön ¹ , Ferdinand Wriedt ¹ , Bernhard Meyer ¹ , and Sandro M. Krieg ¹

¹ Department of Neurosurgery, Technical University Munich, Munich, Germany

Introduction: Patients undergoing spinal surgery usually require postoperative pain management to alleviate wound pain. Pain medication includes WHO grade 1 analgesic but also potent opioids, potentially leading to severe side effects such as fatigue, nausea and cognitive decline. Up to now, the cognitive impairment due to postoperative pain protocols is only poorly studied. Methods: We performed a prospective monocenter feasibility study enrolling patients before undergoing spinal surgery. Cognitive testing was performed using a tablet-based application before surgery (baseline), as well as on day 2 after surgery (intravenous opioids), before discharge (oral opioids) and at follow-up. We recorded the exact pain medication and other side effects from the medication. Potential risk factors for postoperative decline in cognition were age, high-dosed opioid application, length of surgery and blood loss. Results: We included 20 patients in our study. Median age was 67 years. Baseline assessment revealed no cognitive impairment before surgery. All patients underwent a dorsal instrumentation in our neurosurgical department for degenerative (60%), osteoporotic fracture (15%) or tumor (25%) indication. Cognitive testing after surgery showed a significant decline under intravenous opioid therapy including short time and delayed recall word listing as well as logic testing including arithmetic fluency (p < 0.001). Cognitive performance significantly improved with recovery until follow-up and opioid discontinuation. Conclusion: Cognitive assessment in patients undergoing spinal surgery with postoperative opioid medication revealed a postoperative impairment under intravenous medication. Side effects should be monitored closely, and cognitive decline should be considered in follow-up operation informed consent.

1300

P470: Pioneering robot-assisted spine surgery in the United Kingdom

Carlos De La Torre ¹ , Darren Lui ¹ , Bisola Ajayi ² , and Khai Lam ¹

¹ Orthopaedics, London Bridge Hospital, London, United Kingdom

² Orthopaedics, NHS St George's Hospital, London, United Kingdom

Introduction: The placement of a large interbody implant allows for a larger fusion area. Retroperitoneal approaches facilitate the placement of these implants. At the same time, robot-navigation facilitate complex posterior screw fixation. This is a single-surgeon, single-centre report of the first procedures ever performed for navigated robot-assisted spine surgery in the United Kingdom. Materials and Methods: Between October 2019 and May 2021, we identified 34 consecutive patients who underwent robot-assisted spine surgery. The demographic, intraoperative, and perioperative data of the 34 patients were reviewed. Technique: With the patient positioned in the lateral or dorsal decubitus position, a routine anterior lumbar interbody fusion (ALIF) and/or an extreme lateral interbody fusion (ELIF) is performed. In a second stage, with the patient in a ventral decubitus position, a dynamic reference base and a surveillance marker are put in place, an intraoperative CT scan is obtained and the images are transferred into the robotic positioning system. Pedicle screw trajectories are planned and saved. A surgeon-controlled foot pedal activates and positions the robot arm to the planned pedicle trajectory. Stab incisions are made on the skin where the pedicle screws are inserted using navigated instruments guided by the robotic arm. This sequence will be repeated until all pedicle screws had been placed. Rods will then be placed in a standard fashion and locking caps will be set once the rods are in their proper position. If needed, one can also insert the pedicle screws using an open or a transmuscular technique or consider performing a single position lateral (SPL) approach with a single stage procedure. Results: Of the 34 patients, 65 levels were treated in total (204 screws). 21 patients (60%) underwent single-level fixation, 14 of them (67%) were treated at the L5/S1 level, 3 at L3/L4, 3 at L4/L5 and 1 at L2/L3 level, 13 patients (40%) underwent multi-level fixation, with 4 of them treated for adult scoliosis. Eight patients underwent a supine ALALIF approach and one a lateral decubitus AL-ALIF, 7 had a pure ALIF approach, 8 patients underwent combined XLIF and AL-ALIF approach in a lateral decubitus, 6 underwent pure XLIF approach, 1 patient had previous TLIF surgery, and 3 patients underwent single position lateral surgery (lateral decubitus fusion and posterior screw fixation). The average estimated blood loss was 60 cc. The average planning time was 10 min and the average duration of surgery was 50 min. The average patient age was 54 years and 64% (22/34) were male. The average BMI was 28.1 kg/m². There were no re-interventions due to complications or mal positioned screws. Conclusion: Minimally invasive spine surgery using robot-assisted navigation yields an improved level of accuracy, decreased radiation exposure, minimal muscle disruption, decreased blood loss, shorter operating theatre time, length of stay, and lower complication rates. Further follow-up of the patients treated will help compare the clinical outcomes with other techniques.

1340

P471: Predicting sustained opioid use after surgery for degenerative spondylolisthesis using machine learning algorithms

Paul Ogink ¹ , Aditya Karhade ² , Nicole van Steijn ² , Olivier Groot ² , Cumhur Oner ¹ , Jorrit-Jan Verlaan ¹ , and Joseph Schwab ²

¹ UMC Utrecht, The Netherlands

² Massachusetts General Hospital, Boston, United States

Study design: Prediction model study. Objectives: We aimed to 1) develop and 2) internally validate a machine learning (ML) prediction model for prolonged opioid use following surgery for degenerative spondylolisthesis. Methods: We included adult patients who underwent surgery for degenerative spondylolisthesis in two tertiary care referral spine centers. Our primary outcome measure was prolonged postoperative opioid use defined as prolonged opioid prescriptions 90-180 days after index surgery. The following variables were selected and subsequently used for algorithm development: age, body mass index, duration of symptoms, preoperative laboratory values for hemoglobin and white blood cell count, and preoperative medication use (opioids, statins and antihypertensives). Four ML algorithms were developed to predict prolonged postoperative opioid use and were assessed by discrimination, calibration, and overall performance. Results: For this study, 878 patients were included for development of the ML algorithms. The rate of prolonged opioid use was 10% (88/878). The Random Forest algorithm was the best model based on discrimination c-statistic = 0.80), calibration (slope = 0.86; intercept = 0.01), and overall performance (Brier score = 0.09). Main predictive factors were BMI and age. Conclusion: In this study we developed a ML algorithm with good discrimination and calibration to predict sustained opioid use after surgery for lumbar degenerative spondylolisthesis. Utilization of this model could aid clinicians and healthcare organizations in tailoring their strategies and policies for reducing sustained opioid use in high-risk patients.

1550

P472: Our experience with a three dimensional patient-specific simulator for pedicle screw insertion

Zohra Souei ¹ , Meryam Slama ¹ , Mohamed Boukhit ¹ , and Maher Hadhri ¹

¹ Neurosurgery, Fattouma Bourguiba University Hospital, Monastir, Tunisia

Introduction: Pedicle screw fixation (PSF) is a challenging surgical procedure to perform with significant complications rate. It depends largely on the expertise of the surgeon with a steep learning curve. Artificial intelligence applications and robotics are now widely used in this field around the world. On the other hand the access to these rising technologies in many lower income countries, such ours, is not affordable and this constitutes a major barrier to the neurosurgical care standards. Material and Methods: We developed a process to three dimensional PSF simulator for preoperative planning then studied its application on a serie of ten patients. Our aim is to describe the steps of the preoperative planning, compare them with post-operative results. Results: After the 3D manipulation by the surgeon and preparation of the spinal fixation prototype, patients were then operated on. For all cases, each screw was inserted in place in only one attempt, with a satisfying placement judged on fluoroscopic image control. Post-operative imaging were then compared to the final simulation prototype finding almost the same planned trajectory. Conclusion: This is an attempt from our team to make an affordable yet accurate tool to help not only surgeons with preoperative planning but also trainees with a well-developed workshop experience.

1645

P473: The feasibility and efficacy of computer-assisted screw insertion in severe complex spinal deformity: a prospective study

Yiqi Zhang ¹ and Yong Hai ¹

¹ Department of Orthopedic Surgery, Beijing Chaoyang Hospital, Capital Medical University, Beijing, China

Background: Severe spinal deformity is one of the most challenging problems demanding spine surgeons to face due to its complicated characteristics. Computed tomography data of the spine were utilized for spine reconstruction by the Mimics Medical software and surgical planning including spine morphology, radiographic measurement was worked out individually to increase the safety of the correction surgery. The objective of the study was to explore the feasibility and efficacy of computer-assisted screw inserting planning (CASIP) in surgical treatment for severe spinal deformity. Methods: A total of 50 patients participated in this prospective cohort study. 25 patients were allocated into CASIP group and 25 patients were in Non-CASIP group. The demographic data, and radiological spinal parameters were documented and analyzed. Each pedicle screw insertion was classified as satisfactory insertion or unsatisfactory insertion based on Gertzbein-Robbins classification. The primary outcome was the accuracy of pedicle screw placement. The secondary outcomes were the rate of puncturing screws, estimated blood loss, surgical time, correction rate and other radiological parameters. Results: A total of 45 eligible patients completed the study. 20 patients were in CASIP group and 25 patients were in Non- CASIP group. The accuracy of pedicle screw placement in CASIP Group and Non-CASIP Group were (92.0 ± 5.5) % and (82.6 ± 8.3) % (p < 0.05), and the rate of puncturing screws were (0 (0-0)) % and (0 (0-6.25)) % (p < 0.05). The median surgical time were 280.0 (IQR: 260.0-300.0) min and 310 (IQR: 267.5-390.0) min in two group and showed significant statistic difference (p < 0.05). Conclusions: CASIP has good feasibility and can gain a more accurate and reliable instruments fixation, with which spine surgeons can make a detailed and personalized screw planning preoperatively to achieve satisfying screw placement.

Keywords: Spinal deformity, Computer-assisted, Screw placement, Software

1668

P474: Radiographic analysis of the spino-pelvic parameters obtained by using the anterior tlif device. A multi-center study

Maximo de Zavalia ^1,2 , Enrique Augusto Gobbi ^1,2 , Felipe Jose Lanari Zubiaur ² , and Rodrigo Pons Belmonte ^3,4

¹ Orthopaedic Surgery, CEMIC, Buenos Aires, Argentina

² Orthopaedic Surgery, Grupo Vertebral, Buenos Aires, Argentina

³ Orthopaedic Surgery, Hospital Argentino, San Juan, Argentina

⁴ Orthopaedic Surgery, Hospital Marcial Quiroga, San Juan, Argentina

Introduction: Sagittal balance is extremely important when planning spinal surgery. Currently we have various devices provided by the industry that help us achieve certain results. When needing to restore the low lumbar lordosis, certain devices such as the ALIF, LLIF or OLIF are usually the most chosen. Understanding that not all patients are candidates for any of these techniques, Nuvasive^® launched the TLIF-anterior device on the market to improve the lordosis that can be obtained through the posterior approach. The objective of the study is to report the results obtained according to the position in which the previous TLIF device was placed. Material and Methods: A multicenter, observational, analytical, cross-sectional, retrospective recovery study. The pre and post-operative spino-pelvic parameters of spinograms of patients who underwent surgery between September 2019 and August 2021 were evaluated. Inclusion: patients who underwent lumbar arthrodesis with an anterior TLIF-type implant placed in L4-L5 or L5-S1. Exclusion: patients without a pre or post-surgical spinogram and more than one device. Results: The mean of monosegmental lordosis was 13.33º preoperatively and 18.81º postoperatively, (p < 0.001). The mean of monosegmental lordosis was 7.32º, 2.95º, and 6.24º for positions I, II, and III respectively. The mean disc height was 6.22 mm for the preoperative period and 11.06 mm for the postoperative period (p > 0.001). Conclusion: We found encouraging results on the placement of this type of device and its relationship with segmental lordosis, understanding the importance of their arrangement at the anterior end of the disc space.

1691

P475: Cadaveric laminar torque failure in novel system for stabilizing the cervical and upper thoracic spine

Manoj Kodigudla ¹ , Frank Boehm ² , Amey Kelkar ¹ , Muzammil Mumtaz ¹ , Vijay Goel ¹ , Sundershan Triparthi ¹ , William Lavalle ³ , and Nikunj Patel ⁴

¹ Departments of Bioengineering and Orthopaedic Surgery University of Toledo, Engineering Center for OrthopaedicResearch Excellence (E-CORE), Toledo, OH, United States

² Research and Development, TruSpine Technologies, Plc., New Hartford NY, United States

³ Department of Orthopedics, SUNY Upstate Medical University, Syracuse, NY, United States

⁴ Neurosciences, Institute of Neurosciences, Southmead Hospital, University of Bristol, Bristol, United Kingdom

Introduction: Novel means of stabilizing the spine are always of interest to the spinal surgical community as well as the larger health care delivery ecosystem. A novel strategy being introduced utilizes unique hook-anchors which are individually fastened to the lamina, these anchors then being coupled to a rod which stabilizes the construct. A question was raised regarding the potential for laminar injury by the fastening mechanism, and to that end, this study was performed at the University of Toledo. Material and Methods: The hook-anchor which is fastened to the caudal edge of the lamina is provided with a fixed sublaminar foot plate and a vertically-adjustable dorsal laminar foot plate, the latter being actuated by a drive screw. The Manufacturer provided the investigators at the University of Toledo with a series of “Dummy” clamps, with an identical actuation mechanism, and which precisely emulated the closing force of the proposed final anchor design. These included large, medium and small sizes identical to the design as well. Disarticulated C3-7 vertebrae from 3 specimens were used in the study, and various sized “clamps,” were applied to the specimens as deemed size-appropriate. The screws were actuated with a T8 Driver, and were initially tightened to 6 + .5 in. lbs. Torque, considering the Company’s recommendation of 6-8 in. lbs. After inspecting the integrity of the specimen, the torque was then increased at increments of 4 in.lbs., using a torque meter, with the end-point being either a) laminar fracture, or b) or implant failure, or c) a torque of 20 + .5 in. lbs. was reached, at which point the study was concluded. Maximum torque before failure was recorded, and a total of 6 data points for each sized anchor was obtained. Results: At 6 ± .5 in. lbs., all of the clamps were fastened in a satisfactory fashion and the laminae showed no evidence of anything disconcerting. In 16 of the specimens, a torque of 18 ± .5 was achieved without any evidence of laminar damage, and overall, in 13 of the 18 subject laminae, a torque of 20 ± was reached without laminar injury. One implant had a mechanical failure at 15.7 in. lbs on the left lamina, and was replaced by another clamp, completing the test on that lamina. One specimen was excluded because a large anchor was inappropriately utilized therein. In one specimen, bilateral C6 laminar damage was noted at a torque of 20 ± .5 in. lbs., and in another specimen, left-sided C7 laminar damage was noted, again at a torque of 20 ± .5. Conclusion: These data offer new insights into laminar strength, and strongly suggest that this type of anchor can be secured to the caudal aspect of a cervical lamina at a torque of 6-8 in. lbs. without concern of laminar damage. This is important when considering the technique of cervical stabilization being introduced. These data can, of course, be useful going forward as other strategies and techniques are introduced.

1700

P476: Posterior ligamentous complex reconstruction with artificial ligament in patients without cervical vertebral fracture: a technical note

Chengyi Huang ¹ and Hao Liu ¹

¹ Department of Orthopedics, West China Hospital, Sichuan University, Chengdu, China

Introduction: Posterior ligamentous complex (PLC) offers restraints to deformation as a complex with an interconnected manner. The stability and range of motion of the posterior cervical spine is greatly restricted when the posterior ligamentous complex is damaged, even without bone disruptions. We describe an original surgical technique, advantages with the novel technology, and postoperative condition of patient who was first used of artificial ligament in reconstruction surgery of posterior complex ligamentous injuries in patients without lower cervical vertebral fracture. The aim of this technique is to retain the mobility of the injured segment as much as possible on the basis of spinal stability, and try to treat these patients with dynamic reconstruction. Material and Methods: Detailed description of the reconstruction surgery with artificial ligaments carried out for C4-6 posterior complex ligamentous injuries in a 27-year-old male, with neck pain and restricted movement due to high fall injury accompanied by impaired movement of limbs, is presented. Results: Immediately postsurgery, the patient's neck pain and quadriparesis had been improved. The spinal canal decompression and cervical spine sequence was satisfactory, the facet joint face was in good position and spinous process spacing returned to normal. After three months of rehabilitation, the patient reported improvement of symptoms, physical and imaging examination showed a significant improvement in the patient's condition. The patient's neck mobility motor function had improved further. Conclusion: The present data demonstrates that the novel technique for reconstruction of PLC injury is feasible and safe. However, familiarity with cervical anatomy and adequate experience for the lateral mass screws placement during surgery are crucial for this procedure. Therefore, this surgery should be best conducted by a highly experienced cervical surgery team.

Keywords: Cervical vertebra; Posterior ligamentous complex; Injury; Non-fusion; Reconstruction

1734

P477: Characterization of TumorID technology to differentiate tumor type in frozen samples

Jacob Sperber ¹ , Tanner Zachem ^1,2 , Ravi Prakash ^1,2 , Gregory Chamberlin ³ , Thomas Cummings ³ , Annee Nguyen ¹ , Harrison Hockenberry ¹ , Cesar Baeta ⁴ , Weston Ross ^1,2 , Patrick Codd ^2,2,5 , Edwin Owolo ¹ , Dana Rowe ¹ , Tara Dalton ¹ , Emily Luo ¹ , and C. Rory Goodwin ^1,5

¹ School of Medicine, Department of Neurosurgery

² Department of Mechanical Engineering and Materials Science

³ Health System, Department of Pathology, Duke University, Durham, United States

⁴ Center for Population Health Sciences, Stanford University, United States

⁵ Duke Cancer Institute, Durham, United States

Purpose: Neurosurgical tumor resection depends upon identification of tumorous tissue from non-tumor. The nascent TumorID technology employs fluorescence spectroscopy to differentiate tumor from non-tumor. This study investigates the ability of TumorID technology to classify frozen neurosurgical samples based on tumor type. Methods: Patients undergoing neurosurgical resection or biopsy for suspected malignancy with the Department of Neurosurgery at Duke University School were identified. Frozen sections of samples were prepared with either hematoxylin and eosin or polychrome. An excitation wavelength of 405nm was used to obtain emission spectra from tissue as previously validated by the Codd lab. For the most prominent peak at 564 nm, the maximum intensity value was obtained by averaging 10 independent intensity measurements centered around the peak. Results: Tissue analyzed consisted of glioma (n = 242), gonadotroph adenoma (n = 14), prolactinoma (n = 19), hemangioblastoma (n = 11), squamous cell carcinoma (n = 106), metastases (n = 5), Rathke cleft cyst (n = 9), inflammation (n = 35), and radiation necrosis (n = 1). Spectral shape across all tissue types between 550 nm and 650 nm were similar potentially representing eosin emission; however, signal intensity varied amongst tissue type. Centered around a wavelength of 564 nm, prolactinoma had a higher mean peak intensity of 0.556, 95% CI [0.507, 0.605], compared to the mean peak intensity for gonadotroph adenoma of 0.321, 95% CI [0.303, 0.339]. Spectral signature for radiation necrosis between 450 nm and 565 nm was distinct from all other tissue types. Conclusion: The TumorID remains a promising tumor identification tool. This study represents an important step in characterizing the ability for TumorID technology to discern tumor from non-tumor in frozen pathology section.

Keywords: Tumor detection; fluorescence spectroscopy

1946

P478: Telescopic vertebral body replacing implant with improved functionality: design concept

Oleksii Nekhlopochyn ¹

¹ Spinal Neurosurgery, Romodanov Neurosurgery Institute, Kyiv, Ukraine

Introduction: Anterior decompressive corpectomy is frequently used while surgical care of a number of subaxial cervical spine pathological states. The most progressive and surgeon easy-to-use way to substitute vertebral body is telescopic vertebral body implant. The purpose of our study was to develop a concept of creation improved telescopic vertebral body implant for anterior subaxial cervical decompression-fusion surgery. Material and Methods: We’ve searched the database of National Center for Biotechnology Information using following keywords: “expandable cage”, “distractable cage”, “expandable vertebral body replacement”, “distractable vertebral body replacement”, “expandable VBR”, “distractable VBR”, “distractible cage”, “distractible vertebral body replacement”, “distractible VBR” and MeSH terms “Spinal Diseases / surgery”, “Orthopedic Fixation Devices”, “Orthopedic Procedures / instrumentation”, “Spine / surgery” and selected 24 most frequently used telescopic implants. The analyzes of results allowed to reveal design features that define functionality of different implants. Results: Detected constructive features of implants that influence the surgery results:

• type of implant (integrated or not integrated with anterior plate);

• design configuration;

• the design of the side walls of the implants and the size of the perforations;

• number of components;

• universality (interchangeability) of parts;

• type and location of the sliding mechanism;

• type of perception of compression load;

• the way of blocking the implant in the final position;

• the configuration of the endface of the cage contacting with the end plates of the vertebral bodies;

• the size, location and number of teeth on the end surface of the implant;

• contact area in the system “implant - vertebral body”;

• the volume of the internal cavity for the composite material;

• contact area of composite material with the locking plates of the vertebral bodies;

• type of filling the structure with composite material;

• the possibility of compaction of the composite material in the “composite material -vertebral body” system after implantation of implant;

• the number and location of holes to supplement the composite material after installation;

• implant weight

The search results allowed to develop original vertebral body replacing implant, that possesses most useful constructive features:

• has the minimum size;

• has a larger cavity compared to that in other devices.;

• has sufficient strength, low metal content, and low weight

• compressive stress is distributed over the entire graft cross-section, that enables relatively thin wall systems to withstand sufficiently high compressive load;

• excludes damage to the endplates by teeth of end surfaces during placement;

• is easy-to-fabricate and easy-to-use.

Conclusion: Big cavity of prototype and proposed installation method gives a good chance during the operation to compact the composite material along the entire length of implant. It provides intraoperative prophylaxis of an undesirable fibrotic fusion of the vertebral motion segment and maximizes the probability of true bone consolidation. Preclinical and clinical studies show good results but further research needed to introduce the final product into clinical practice.

1956

P479: The role of 3D-printed patient-specific models in the understanding of complex spine morphologies

Benjamin Hajnal ^1,2 , Máté Turbucz ^1,2 , Ferenc Bereczki ^1,2 , Agoston Jakab Pokorni ^1,2 , Zoltan Hoffer ³ , Aron Lazary ^1,4 , and Peter E. Eltes ^1,4

¹ In Silico Biomechanics Laboratory, National Center for Spinal Disorders, Buda Health Center, Budapest, Hungary

² School of PhD Studies

³ National Center for Spinal Disorders, Buda Health Center, Budapest, Hungary

⁴ Department of Spine Surgery, Department of Orthopaedics, Semmelweis University, Budapest, Hungary

Introduction: 3D printed models facilitate the understanding of complex anatomical relationships, aiding preoperative surgical planning. Their use is beneficial in patient education, but also in reducing the operative time according to the results of scientific publications from the last five years. In spine surgery, there is currently no consensus or recommendation on when 3D printed models should and should not be used. We aimed to develop a questionnaire-based survey to investigate the usefulness of 3D printed models in complex spine surgery cases. Material and Methods: CT scans of patients in 6 complex spine surgery cases were segmented using Mimics^® software. Segmentation accuracy was quantified using Dice Similarity Index (DSI). The models were fabricated using fused deposition modeling (FDM) 3D printing technology. CT images of the models were taken, segmented and compared with the original virtual models to assess geometric accuracy. A questionnaire, consisting 6 questions for each of the cases (36 questions in total that can be answered by a scale from 1 to 10) was filled out by spine surgeons (n = 41) from multiple hospitals after reviewing the imaging (RTG, MR, CT) scans and then examining the 3D printed models in hand. The digital form of the questionnaire was created using SurveyMonkey® platform. Statistical analysis of the data was performed using SPSS® 23.0, G*Power software. Results: The geometric variation of the printed models was < 1 mm in every case. The responses show that spine surgeons find the models very useful (8.75 ± 0.14, ɑ = 0.05). Further analysis shows that there is significant difference between orthopedic and neurosurgeons (p < 0.001), and between groups with different years of clinical practice (p < 0.05). The additional benefit of 3D printed models seems to be the greatest in patient education (p < 0.001). Conclusion: For the clinical integration of 3D printed models, we need to know how surgeons perceive their usefulness. The role of basic skills is unknown in the acceptance of 3D printed physical models. The developed questionnaire survey could greatly contribute to the clinical integration of 3D printed models, providing evidence for different funding parties.

Spine Biologics

1319

P480: Ceramic bone graft substitute (Mg-HA) in spinal fusion: a prospective pilot study

Giuseppe Tedesco ¹ , Cristiana Griffoni ¹ , Giovanni Barbanti Bròdano ¹ , Angelo Nataloni ² , and Alessandro Gasbarrini ¹

¹ Department of Spine Surgery, IRCCS Istituto Ortopedico Rizzoli, Bologna, Italy

² Finceramica Spa, Faenza, Italy

Introduction: Iliac crest bone graft (ICBG) is considered the gold standard for spine surgical procedures to achieve a successful fusion due to its known osteoinductive and osteoconductive properties. However, complications related to harvesting procedure and donor site morbidity have been largely reported in literature, favouring the development of a wide range of alternative products to be used as bone graft extenders or substitutes for spine fusion. Among all, ceramic-based biomaterials have been widely studied and employed in the last years as bone graft substitutes. We report here the results of a prospective pilot study aimed to evaluating the grade of ossification obtained by the use of an Mg-doped hydroxyapatite (HA) product to achieve postero-lateral fusion in degenerative spine diseases. Material and Methods: A prospective pilot clinical study was conducted at our Centre from February 2017 to March 2020, following the approval of the local Ethics Committee, with a total number of 20 patients recruited, who were followed up for 18 months. Inclusion criteria were as follows: skeletally mature subjects, at least 18 years of age at the time of surgery with symptomatic spinal degenerative disc disease requiring postero-lateral fusion at L1-S1 tract, signature of the written informed consent for the study. Conventional posterior approach for lumbar spinal fusion was performed. After the positioning of pedicle screws, decompression of the cauda and nerve roots was achieved with hemilaminectomy and foraminotomy. SintLife was apposed on the hemi-laminae and transvers process on the contralateral side of the hemilaminectomy, while on the hemilaminectomy side, foramino-arthrectomy was performed to insert the interbody fusion cage. SintLife is a CE- marked, implantable, non-active bone graft substitute, available in form of paste, composed of biomimetic hydroxyapatite (HA) enriched in magnesium ions (Mg-HA) in a similar amount as in the one found in human bones. Radiographic and clinical data were collected before surgery and at 3, 6 and 12- 18 months follow-up. Radiographic images were used to determine the degree of fusion and bone regeneration, determined by an independent radiologist using the Brantigan classification. Clinical scores (Oswestry Disability Index (ODI), Visual Analog Scale (VAS) and EuroQoL-5L (EQ-5L)) were used to evaluate the improvement of patients’ health quality following surgery. The incidence of adverse events, complications, unattended reactions, incidents was recorded. Results: Results showed a successful degree of fusion of about 62% at 12 months follow-up and an improvement of quality of life and health status starting from 6 months FU, as evaluated by clinical scores (ODI, VAS and EQ-5L). No adverse events related to the biomaterial were reported. Conclusion: The present pilot study showed a safety profile of a Mg-doped HA bone graft substitute used to achieve postero-lateral fusion in the treatment of degenerative spine diseases. However, the rate of successful fusion was largely inferior to that reported in the literature for the autologous bone graft, which is the “gold standard” for spinal fusion.

1679

P481: Bioactive glass (S53P54) and polyethylene-glycol and glicerol water soluble synthetic adhesive as a effective fusion promoter in anterior lumbar interbody fusion surgery

Stipe Corluka ¹ , Stjepan Dokuzovic ¹ , Jure Pavesic ¹ , and Vide Bilic ¹

¹ Spinal Surgery Division, Department of Traumatology, University Hospital Centre Sestre Milosrdnice, Zagreb, Croatia

Introduction: Spinal fusion remains the mainstay of treatment for many different spine conditions and fusion may be achieved in several different ways, though not all methods are inherently equally effective and reliable. In principle, the larger the contact area, the shorter the distance between bony elements, and the presence of living bone (osteogenic, osteoconductive and osteoinductive properties) all increase the chances of successful fusion. In certain cases, the gap being fused may be quite wide and it may be difficult to obtain a sufficient quantity of live autologous bone graft. Anterior lumbar interbody fusion cages (ALIF, OLIF, LLIF, mesh and expandable cages) necessarily increase the distance between end plates, making it difficult to bridge the gap with new bone. In such cases we rely on synthetic materials which can provide sufficient graft volume, while reducing donor site morbidity. According to our knowledge there have been no studies analyzing the fusion capacity of isolated bioactive glass and polyethylene-glycol and glycerol water soluble synthetic adhesives in anterior lumbar approaches. We present a retrospective analysis of cases having undergone single or multilevel anterior lumbar interbody fusion procedures using interbody cages filled with bioactive glass. Material and Methods: We analyzed the radiological results of patients having undergone anterior lumbar interbody fusion procedures using lumbar interbody cages filled with bioactive glass without additional autologous bone. Follow-up was performed by standard clinical evaluation, radiographs at regular intervals, as well as by CT scan at 6 and 12 months to analyze fusion success/failure through the cage. Results: Patients having undergone anterior, oblique, or lateral lumbar interbody fusions through cages displayed successful bony fusion from endplate to endplate through the cage device at 6 to 12 months follow-up. Conclusion: Bioactive glass is an effective fusion promoter with a high rate of successful fusion when used alone in an anterior lumbar interbody fusion cage.

1720

P482: Is risk factors of vertebral fractures predictable? BMD, Vit-D, calcium, and bone turn-over marker measurement

Kwan Ho Park ¹ , Jung Hoon Sul ¹ , Da Hoon Hong ¹ , Ju chul Yang ¹ , and Tae Wan Kim ¹

¹ Department of Neurosurgery, VHS Medical Center, Seoul, South Korea

Introduction: Measurement of bone mineral density (BMD) is the gold standard for the diagnosis of osteoporosis. However, the BMD measurement does not provide information on bone quality. We reported the relationship between BMD, calcium, Vit-D, and Bone turnover markers (BTMs) in patients with vertebral fracture group. Material and Methods: This study retrospectively reviewed medical records of patients who were treated in our institution from 2017 to 2018. A comparative analysis was carried out between 38 patients with vertebral fracture (Group A) and 62 patients admitted with no vertebral fracture (Group B). Sex, age, BMD, calcium, Vit-D, and BTMs were analyzed as variables affecting vertebral fractures. In this study, BTMs are divided to formation markers [serum bone-specific alkaline phosphatase (BSAP), osteocalcin (OC)] and resorption markers [serum C-telopeptide (CTX). Results: The average age of the subjects was 74.0 ± 6.9 years. The mean BMD were 2.7 ± 1.3 in group A and 1.6 ± 1.0 in group B, respectively. The mean serum calcium levels were 8.9 ± 0.9 ng/dL and 9.1 ± 0.9 ng/dL, respectively. The mean serum 1,25(OH) vit-D levels were 16.6 ± 10.9 ng/mL and 16.8 ± 7.3 ng/mL, respectively. The mean serum OC levels were 15.8 ± 8.2 ng/mL and 14.7 ± 6.6 ng/mL, respectively. The mean serum CTX levels were 0.5 ± 0.2 ng/mL and 0.4 ± 0.2 ng/mL, respectively. The mean serum BSAP levels were 12.0 ± 5.4 mcg/L and 10.2 ± 4.4 mcg/L, respectively. BMD of group A was lower than that of group B (P &lt; 0.05). The other variables showed no differences between the 2 groups. Conclusion: BMD of vertebral fracture patients showed difference from that of no vertebral fracture group in Korean elderly population. The occurrence of vertebral fracture is affected by lower BMD rather than another laboratory findings. The main goal of treatment is to reduce the prevalence of fractures, maintain stable or increasing BMD.

1988

P483: Chronic myeloid leukemia: an atypical presentation of a spinal cord compression

Ahmed Amine Daoued ¹ , Kolsi Fatma ¹ , Ghorbel Mohamed ¹ , Ines Cherif ¹ , and Boudouara Zaher ¹

¹ Neurosurgery Department, Habib Bourguiba University Hospital, Sfax, Tunisia

Introduction: Leptomeningeal Leukaemia in chronic myeloid leukemia (CML) is a rare phenomenon and represents infiltration of leukemic blasts in both the subdural and epidural spaces other than bone marrow. Material and Methods: We report the case of a patient who was treated for a leptomenengial leukimia in the neurosurgery department, in the Habib Bourguiba university hospital, Sfax, Tunisia. Results: We report the findings of a 35-year-old woman who presented to the emergency room with symptoms of acute spinal cord compression. A D8 to D10 laminectomy with evacuation of a subdural collection was performed. Pathological cell study of the cerebral spinal fluid (CSF) showed myeloid leukemia cells. These findings were consistent with those observed on bone marrow aspiration. The patient received chemotherapy after the surgery as the baseline treatment for her CML. Conclusion: Leptomeningeal Leukaemia is rare complication of myeloid leukemia. The baseline treatment is chemotherapy after surgery.

2015

P484: Platelet rich plasma in lumbar facet joint pain: a systematic review

Hans Grohs ¹ , Fabiano Soares ² , Roberta Yamaguchi ³ , Raissa Pedroso ⁴ , Robert Meves ¹ , and Edilson Silva Machado ²

¹ Department of Orthopedics and Traumatology, Santa Casa de Misericórdia de São Paulo, São Paulo, Brazil

² Clínica Regenerar: centro de medicina da dor, Porto Alegre, Brazil

³ Departamento de Ciências Fisiológicas, Faculdade de Ciências Médicas da Santa Casa de São Paulo, São Paulo, Brazil

⁴ Universidade Estadual de Maringá , Maringá, Brazil

Introduction: To evaluate the efficacy and safety of the use of Platelet Rich Plasma (PRP) in low back pain of facet origin. Methods: The research was carried out according to the guidelines of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA), searching the following Databases: Pubmed, Scopus and Web of Science. A manual search was also performed. Randomized clinical trials, non-randomized trials and case series with more than 10 patients were included. The quality assessment and risk of bias of the works were analyzed using the RoB II tools and the Joanna Briggs Institute (JBI) Case Series checklist. Results: Nine articles that met the criteria were selected, being two randomized clinical trials with 190 patients and seven case series with 370 patients. The Randomized Clinical Trials showed a low risk of bias, according to the RoB II instrument, while the Case Series showed some heterogeneity, according to the checklist proposed by the JBI. All studies showed favorable conclusions to the use of PRP in facet joints. There were no reports of serious adverse effects. Conclusion: The results of the present studies demonstrate that the use of PRP can be a viable option for the management of low back pain in facet degenerative disease, with evidence level II, according to the researched articles. Larger multicenter studies are needed.

Surgical Complications

46

P485: Iatrogenic vertebral artery injury during anterior cervical spine surgery: a systematic review

Qing Guan ¹

¹ Spine Surgery, The First People’s Hospital of Yibin, Yibin, China

Background: Iatrogenic vertebral artery injury (VAI) during anterior cervical surgery is rare but potentially catastrophic. Methods: Causes, presentation, diagnosis, management, prognosis, and Prevention of VAI were reviewed following Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. English language studies and case reports published from 1980 to recent were retrieved. Data on diagnosis, surgical procedures and approach, site and cause of VAI, management, outcomes, and vertebral artery (VA) status were extracted. Results: In 25 articles including 54 patients, VAI was diagnosed during or after surgery commonly indicated for cervical degenerative diseases (64%), tumors (14%), and trauma (9%). The incidence of VAI for each side was similar regardless of approach. Common presentations were unexpected copious surgical bleeding, delayed hemorrhage of pseudoaneurysm with neck swelling, dyspnea, hypotension, and cervical bruits caused by arteriovenous fistula. Causes included drilling (61%), instrumentation (16%), and soft tissue retraction (8%). Direct exposure or angiography confirmed VAI. Ten patients had VA anomalies; collateral status was verified in 9 before definitive treatment. Tamponade was adopted for urgent hemostasis in most cases but with a high incidence of pseudoaneurysm (48%). Unknown VA status increased occlusion risk and neurologic sequelae (41%). VA repair and stent placement had excellent Outcomes. Conclusions: Extensive lateral decompression, loss of landmarks, and anatomic variations or pathologic status of VA increased VAI risk. Evaluation of collateral vessels before definitive treatment helped determine appropriate management and avoid neurologic sequelae. Tamponade was not recommended as definitive treatment. Meticulous preoperative evaluation, cautious intraoperative manipulation, and real-time radiographic guidance reduced VAI risk.

96

P486: Postoperative occipital neuralgia in posterior upper cervical spine surgery: a systematic review

Qing Guan ¹

¹ Spine Surgery, The First People’s Hospital of Yibin, Yibin, China

Background: Postoperative occipital neuralgia (PON) after upper cervical spine surgery can cause significant morbidity and may be overlooked. Methods: The causes, presentation, diagnosis, management, prognosis, and prevention of PON were reviewed following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. English language studies and case reports published from inception to recent were retrieved. Data on surgical procedures, incidence, cause of PON, management, outcomes, and preventive technique were extracted. Results: Sixteen articles, including 591 patients, were selected; 93% of the patients with PON underwent C1 lateral mass screw (C1LMS) fixation, with additional 7% who underwent occipitocervical fusion without C1 fixation. PON had an incidence that ranged from 1 to 35% and was transient in 34%, but persistent in 66%. Five articles explained the possible causes. The primary presentation was constant or paroxysmal burning pain located mainly in the occipital and upper neck area and partially extending to the vertical, retroauricular, retromandibular, and forehead zone. Treatment included medications, nerve block, revision surgery, and nerve stimulation. Two prospective studies compared the effect of C2 nerve root transection on PON. Conclusion: Recent PON in upper cervical spine surgery is a debilitating complication and was most commonly encountered by patients undergoing C1LMS fixation. The etiology of PON is partially clear, and the pain could be persistent and hard to cure. Reducing the incidence of PON can be realized by improving technique. More high-quality prospective studies are needed to define the effect of C2 nerve root transection on PON.

100

P487: Early mobilization after incidental durotomies, a systematic review

Elie Najjar ¹ , Nasir Quraishi ¹ , and Mohamed Hassanin ¹

¹ The Spine Center of Spinal Studies and Surgery, Nottingham University Hospital, Nottingham, United Kingdom

Introduction: An incidental durotomy is a fearful and not uncommon complication of spinal surgery. The conventional management involving a prolonged period of flat bed rest is highly debatable. Indeed, there are scanty data and no consensus regarding the need or ideal duration of post-operative bed rest following these dural tears. We systematically evaluated the relevant literature regarding the outcomes of mobilization within 24 hours and after 24 hours following an incidental durotomy with respect to the length of hospital stay, minor complications and reoperation rates. Methods:A systematic review of the English language literature dating up until December 2021, was undertaken using search criteria ((Dural Tear Or Durotomy) and (Mobilization Or Bed rest)) and the PRISMA guidelines. Isolated case reports were excluded. Results: Of a total of 243 articles, 11 studies met the inclusion criteria (1 Level I and 10 level IV evidence) and were analyzed. Overall, 532 patients (mean age 61.1 years) had an incidental dural tear and were mobilized within 24 hours. Dural repair was performed in 95.3% (507/532) of the cases. The average follow-up period was 23.24 months (3 - 80 months). The average length of stay (LOS) for this early mobilized patients was 3.65 days. Twenty-one out of 532 (3.9 %) patients (11 studies) required reoperation while the rate of minor complications was 26 out of 230 (11.3%) (9 studies). Additionally, 203 patients of mean age 72 years (7 studies) were mobilized after 24 hours (24 - 144 hours); 96% (194/202) underwent a primary repair with an average LOS of 6.38 days. Comparing early to late mobilization, there was a significant reduction in the risk of minor complications due to early mobilization (13/102 (12.7%) vs 33/106 (31.1%) (p = 0.006); RR: 0.47, 95CI: 0.27, 0.80), but no significant difference in major complications and reoperation rates (3 studies) (12/106 (11.3%) vs 11/134 (8.2%) (p = 0.27; RR: 1.55, 95CI: 0.72, 3.35). The overall LOS was also shorter for early mobilizers (3.65 vs 6.38 days). Conclusion: Although early mobilization after repaired incidental dural tears has a similar major complication/ reoperation rates compared to later mobilization, it significantly decreases the risk of minor complications and length of hospitalizations.

158

P488: Superior mesenteric artery syndrome: analysis of clinical cases, new diagnostic features, development of diagnostic protocol

Nikita Khusainov ¹ , Dmitry Kokushin ¹ , Sergey Beljanchikov ¹ , Alexandra Filippova ¹ , Tatyana Murashko ² , Sergey Braylov ² , Maria Pavlova ³ , and Vissarionov Sergey ¹

¹ Spine Pathology and Neurosurgery

² Diagnostic Unit, Saint-Petersburg

³ Anesthesiology and Intensive Care, National Medical Research Center for Pediatric Trauma and Orthopedics, Saint-Petersburg, Russian Federation

Introduction: Superior mesenteric artery syndrome is a rare but serious complication in spine deformity surgery. Little is known about patient predisposition factors except for low weight, same as diagnostic features in cases of spine deformity due to severe secondary changes of abdominal content position. CT-angio is used to objectively quantify aortomesenteric distance and angle which requires use of contrast and exposes patient to significant amount of radiation. Material and Methods: We performed retrospective and prospective data evaluation of 13 patients with severe spinal deformity. CT-angiography was performed either post-op due to SMA syndrome development or pre-op in cases where risk factors were present. Aortomesenteric angle and distance were calculated. Also we evaluated the course direction of SMA and its relation with deformed vertebral column. In case of decreased distance and angle endoscopy was performed for evaluation of duodenum. 3 patients underwent MRI-angiography of the aorta aimed on visualization of SMA as an alternative to CT-angiography. Results: In 4 patients we observed left-sided direction of SMA course with decreased aortomesenteric angle and distance. In 3 out of these 4 patients endoscopic picture of duodenum compression was present. SMA syndrome occurred in 1 of those patients which required further Roux duodenojejunostomy. Surprisingly, in 2 patients with abnormally low aortomesenteric angle and distance we did not observe any signs of duodenum compression probably due to specific position of the horizontal part of the duodenum - extremely low and far away from aortomesenteric triangle. Instead another possible site of duodenum compression was revealed between SMA and anterior surface of the vertebral column. For those patients who underwent MRI-angiography of the aorta we were able to visualize aortomesenteric triangle and measure angle and distance without using contrast or radiation. Conclusion: We suggest that one of the predisposing factors for SMA syndrome development is a left-sided direction of SMA course which might lead to compression of the horizontal part of the duodenum between SMA and deformed spine. Traditional measurements of the aortomesenteric angle and distance are not always acceptable in patients with deformity due to the misalignment of the duodenum and great vessels. MRI-angiography might be used as an alternative method of SMA visualization in patients with marked deformity and low weight without necessity to use contrast and radiation exposure. In cases of abnormal measurements and SMA direction we would suggest to perform pre-op endoscopy to evaluate duodenum for possible compression.

173

P489: Utility of a modified 5-items frailty index to predict complications and mortality in posterior spinal fusion

Gaston Camino-Willhuber ¹ , Jeffrey Choi ² , Sarah Oyadomari ² , Fernando Holc ¹ , Alfredo Guiroy ³ , Hansen Bow ⁴ , Sohaib Hashmi ² , Michael Oh ⁴ , Yu-po Lee ² , and Nitin Bhatia ²

¹ Orthopaedic and Traumatology Department, Institute of Orthopedics “Carlos E. Ottolenghi”, Hospital Italiano de Buenos Aires, Buenos Aires, Argentina

² Department of Orthopaedic Surgery, UCI Medical Center, Orange, United States

³ Servicio de Ortopedia y Traumatología, Hospital Español de Mendoza, Argentina

⁴ Department of Neurosurgery, UCI Medical Center, Orange, United States

Introduction: The modified 5-item frailty index is a relatively new tool to assess the post-operative complication risks. It has been recently shown a good predictive value after posterior lumbar fusion. We aimed to compare the predictive value of the modified 5-item frailty index in cervical, thoracic and lumbar surgery. Material and Methods: The American College of Surgeons - National Surgical Quality Improvement Program (ACS-NSQIP) Database 2015-2020 was used to identify patients who underwent elective posterior cervical, thoracic, or lumbar fusion surgeries for degenerative conditions. The mFI-5 score was calculated based on the presence of five co-morbidities: congestive heart failure within 30 days prior to surgery, insulin-dependent or noninsulin-dependent diabetes mellitus, chronic obstructive pulmonary disease or pneumonia, partially dependent or totally dependent functional health status at time of surgery, and hypertension requiring medication. Multivariate analysis was used to assess the independent impact of increasing mFI-5 score on the postoperative morbidity while controlling for baseline clinical characteristics. Results: 53252 patients were included with the mean age of 64.2 ± 7.2. 7946 suffered medical complications (14.9%), 1565 had surgical complications (2.9%), and 3385 were readmitted (6.3%), 363 died (0.68%) within 30 days postoperative (6.3%). The mFI-5 items score was significantly associated with higher rates of complications, readmission, and mortality in cervical, thoracic, and lumbar posterior fusion surgery. Conclusion: The modified 5-item frailty score is a reliable tool to predict complications, readmission, and mortality in patients planned for elective posterior spinal fusion surgery.

191

P490: Intravenous tranexamic acid reduces blood loss in multilevel spine surgeries

Raphael Lotan ¹ and Oded Hershkovich ¹

¹ Edith Wolfson Medical Center, Holon, Israel

Introduction: Complex spine surgeries are associated with significant blood loss requiring numerous strategies to preserve blood volume. Tranexamic acid (TXA) is efficacious in reducing blood loss when used topically during surgery, intravenously with or without postoperative maintenance treatment. We aimed to evaluate the effect of preoperative weight independent intravenous administration of 1 gr IV TXA on perioperative blood loss in lumbar microdiscectomy, single-level lumbar spinal fusion and multilevel lumbar decompression (two or more levels). Methods: A retrospective cohort study comparing patients who underwent microdiscectomy, lumbar single-level fusion and multilevel laminectomies without and without preoperative IV TXA administration between 2016 to 2020. Results: 210 patients underwent spine surgery without preoperative IV TXA administration between 2016 and 2018 compared to 109 patients who received preoperative IV 1 TXA gr between 2018 and 2020. Preoperative IV TXA treatment did not change blood loss following microdiscectomy, 77.2 ± 53.9 ml and 77.2 ± 95.2 ml, respectively (p = 0.792). Preoperative IV TXA treatment reduced blood loss following multilevel lumbar laminectomy and lumbar PSF&TLIF (p = 0.004 and p = 0.0001, respectively). The same effect was found for intra-operative blood loss and postoperative drainage, with preoperative TXA administration reducing intraoperative blood loss and postoperative drainage for the multilevel lumbar laminectomy and lumbar PSF&TLIF cohorts. No IV TXA treatment adverse events were registered in all cohorts. Conclusion: Routine administration of preoperative weight-independent 1 gram intravenous TXA protocol is efficacious and safe in reducing perioperative blood loss for lumbar multilevel laminectomies and PSF&TLIFs.

Keywords: Tranexamic acid; Blood loss; Bleeding; Spine; Surgery

Abbreviations – TXA = Tranexamic acid, PSF = Posterior spinal fusion, TLIF = Transforaminal lumbar interbody fusion

206

P491: Does marijuana usage affect post-operative care in thoracolumbar fusions? A retrospective study in a multiethnic population

Henry Hoang ¹ , Aaron Hui ¹ , Jini Jeon ¹ , Dan Berman ¹ , Evan Mostafa ¹ , Ananth Eleswarapu ¹ , and Jonathan Krystal ¹

¹ Orthopedics, Montefiore Medical Center, Bronx, United States

Introduction: Thoracolumbar fusions are indicated for the management of degenerative disc disease, degenerative spondylolisthesis, spinal stenosis, tumors, fractures and several spinal disorders with more than 300,000 performed annually. Marijuana usage has become an often-overlooked risk factor for postoperative complications in thoracolumbar fusions. Chronic cannabis usage has previously been associated with increased rates of inpatient neurovascular, thromboembolic, and pulmonary complications, and less favorable overall discharge disposition. A comprehensive understanding of the postoperative sequelae within spinal surgery patients who use cannabis is crucial for the development of interventions aimed at reducing complications and postoperative readmissions. The purpose of this study is to therefore compare rates of readmission, complications, and length of stay between thoracolumbar fusion patients who do and do not use marijuana. Material and Methods: A retrospective study of 301 patients who underwent a thoracolumbar fusion at a single institution in the Bronx from 2016-2018 was performed. Demographic, surgical, and postoperative variables were collected. Marijuana usage was confirmed by accessing documentation in the patient’s chart data. The primary outcome measure was return to the operating room for revision. Secondary outcomes included return to the emergency department (ED) within 30 days, 90 days, and length of stay (days). Binomial logistic regression was performed to ascertain the effects of age, BMI, smoking status, and alcohol use status on the likelihood that participants return to the OR for revision. The chi-square test of homogeneity was used to determine if there was a difference in rates of returning to the emergency room within 30 and 90 days. An independent-samples t-test was run to determine if there were differences in postoperative length of stay between the two groups. Results: A total of 301 patients were categorized into marijuana users (N = 75) and non-users (n = 226). Model fit was assessed using the Hosmer and Lemeshow goodness of fit test, p =.191 indicating that the model was not a poor fit. The model explained 4.3%% (Nagelkerke R2) of the variance in heart disease and correctly classified 90.0% of cases. Of the five predictor variables, only marijuana status was statistically significant. Marijuana users had 2.5 times higher odds to return to the operating room for revision compared to non-users, 2.49, (95% CI 1.07 to 5.78), p = .034. 12 (18.7%) marijuana users returned to the emergency department within 30 days of operation compared to 29 (12.8%) of non-users, a non-statistically significant difference in proportion of .059, p=.211. 26 (34.7%) marijuana users returned to the emergency department within 90 days of operation compared to 58 (25.7%), a non-statistically significant difference in proportion of .09, p = .132 There was a statistically non-significant difference in length of stay (days) between marijuana users (9.1 ± 10.5) and non-users (8.1 ± 7.6), with marijuana users staying longer than non-users, -.96 (95% CI, -3.2 to 1.24),t(301) = -856, p = .393. Conclusion: Our retrospective analysis identified a significant association between marijuana usage and return to operative room for revision follow thoracolumbar surgery. Marijuana usage was not associated with increased postoperative infections, rates of return to the emergency department within 30 days of operation, and length of stay.

280

P492: Factors associated with increased surgical drain output after spinal deformity correction in adults

Ashley Duncan ¹ , Devender Singh ¹ , John Stokes ¹ , Matthew Geck ¹ , and Eeric Truumees ¹

¹ Ascension Texas Spine and Scoliosis, Austin, United States

Introduction: Surgical drains are the source of much scrutiny and debate in terms of post-operative outcomes, especially those centered around surgical site infections and overall length of stay. The aim of this study was to identify factors associated with increased drain output in adults that have undergone surgical correction for spinal deformity. Material and Methods: Retrospective analysis was conducted on 106 adult patients who underwent surgical deformity correction for degenerative scoliosis or kyphosis over 2.5 years. 26 independent variables were collected from demographic, clinical, surgical, and post-operative domains and were subject to comparative and other statistical analyses. Results: Overall mean total drain output was 2827.09 ± 1547 mLs. “High Drain Output” (HDO) was defined as greater than the overall upper quartile value, > 3325.88 mLs. A total of 27 (25.5%) patients were deemed to have HDO. Demographically, HDO was associated with increased age and being a former smoker. Clinically, HDO was associated with an increased preoperative Thromboelastography (TEG) Percent Platelet Inhibition value, blood types A-, A+ and O-. Intraoperative variables associated with HDO were increased Skin-to-Skin surgical time, Number of Levels fused, Estimated Blood Loss (EBL) and subsequent Cell Saver return, Albumin administered and being the Index surgery. 99.1% of patients received intraoperative Tranexamic Acid (TXA)for bleeding prophylaxis. Ultimately, the only variables that were significantly different between cohorts were Skin-to-Skin time (473.04 ± 67.26 minutes vs 415.73 ± 90.86 minutes, p = 0.005), Number of Levels Fused (12.41 ± 2.59 vs 10.61 ± 3.12, p = 0.0023), EBL (1504.44 ± 882.43 mLs vs 1091.46 ± 741.2 mLs, p = 0.02) and Cell Saver return (731.48 ± 442.71 mLs vs 522.59 ± 330.57 mLs). When subject to logistic regression, the final model identified Male sex decreased odd of HDO by 96.55% and a one-unit increase in preoperative Vitamin D levels decreased the odds of HDO by 17.83%. Conclusion: Surgical time, number of levels fused, EBL and Cell Saver return were significantly higher in patients that experienced high drain output postoperatively. Results of logistic regression identified female sex and lower preoperative Vitamin D levels as significantly increasing the risk of high drain output. Given the average complexity of an adult spinal deformity patient, it would be prudent to conduct another study focusing on three or greater level posterior lumbar fusions.

327

P493: Preventive measures against postoperative nausea and vomiting (PONV) in spine surgery

Yushi Hoshino ^1,2 , Yoshifumi Kudo ² , Ichiro Okano ² , Hiroshi Maruyama ² , Ryousuke Ikeda ¹ , Yoshinori Imaizumi ¹ , and Tomoaki Toyone ²

¹ Department of Orthopedic, Asahi University Hospital, Gifu, Japan

² Department of Orthopedic, Showa University Hospital, Tokyo, Japan

Introduction: PONV (postoperative nausea and vomiting) occurs in about 30% of patients after spine surgery. Although PONV is uncomfortable for patients and is a cause of decreased patient satisfaction, there are few reports on the prevention of PONV in spine surgery. In this study, we investigated the effect of PONV prevention in spine general anesthesia surgery. Material and Methods: A total of 188 consecutive spine surgeries under general anesthesia were performed at our hospital from January 2020 to August 2021. The mean age of the patients was 67 years. The sites included 15 cervical, 16 thoracic, and 157 lumbar spine cases. For these cases, preventive measures were taken with reference to the Apfel score, which is a PONV risk assessment (female, non-smoker, history of agitation and PONV, postoperative opioid use). Prophylactic measures included IV-PCA with Droperidol (Fentanyl), intravenous Dexamethazone at the time of surgery for women, and intravenous Metoclopramide immediately after surgery. The incidence of PONV in these patients was evaluated. Results: PONV occurred in 15 patients (8.0%). The incidence of PONV was 8.0% in 15 patients, with nausea only in 9 patients (4.9%), vomiting in 6 patients (3.2%), and the need for additional antiemetic medication in only 2 patients (1.1%). In our previous report, PONV was observed in 31.4% of spine surgeries, and the incidence of PONV was clearly reduced by prophylaxis. In addition, additional antiemetic medication was required in 62.5% of cases of PONV in our previous report, but was used in only 13.3% of cases in the present study, and the intensity of PONV was reduced. Conclusion: The incidence of PONV was significantly reduced by taking preventive measures focusing on postoperative opioid use and women, using the Apfel score as a reference. Since the occurrence of PONV has multiple factors, it is difficult to prevent PONV in patients with high risk of PONV with a single drug, and multiple preventive measures such as this one are necessary and effective. In order to achieve this, it is difficult for orthopedic surgeons alone to prevent PONV, and cooperation with anesthesiology and other departments is especially important to reduce the risk of PONV.

328

P494: Effect of multimodal analgesia on postoperative acute pain in posterior lumbar surgery

Yushi Hoshino ¹ , Ichiro Okano ² , Yoshifumi Kudo ² , Ryousuke Ikeda ¹ , Hiroshi Maruyama ² , Ryo Yamamura ² , Yoshinori Imaizumi ¹ , and Tomoaki Toyone ²

¹ Department of Orthopedic, Asahi University Hospital, Gifu, Japan

² Department of Orthopedic, Showa University Hospital, Tokyo, Japan

Introduction: Severe pain in the acute postoperative period is a risk for persistent pain and decreased patient satisfaction. However, pain management in the acute postoperative period is often difficult, which may hinder the early start of rehabilitation and early discharge from the hospital. In this study, we investigated the effect of multimodal analgesia using multiple drugs on postoperative analgesia. Material and Methods: 48 patients underwent lumbar posterior decompression surgery (Lumbar spinous process splitting laminoplasty) with IV-PCA (Fentanyl) and postoperative intravenous acetaminophen for postoperative pain management (Group A, 2018.1-2019.3). In addition to IV-PCA and postoperative acetaminophen intravenous infusion, 71 patients received pentazocine intravenous infusion (AP group 2020.1-2021.9) for acute postoperative pain. Group A: In addition to IV-PCA (fentanyl), acetaminophen (1000 mg) was administered intravenously twice a day for 4 and 10 hours after operation. Group AP: In addition to group A, pentazocine (15 mg) plus normal saline (100 ml) was administered intravenously twice a day, 1 hour and 7 hours after surgery. For these, postoperative pain was assessed by the Numerical Rating Scale (NRS), and the intensity of postoperative pain, the rate of use of additional analgesics, and the rate of complications such as delirium were compared. Results and Discussions: There were no significant differences in age, sex, or number of operated vertebrae between the two groups. The mean NRS was 4.3/4.4 in group A/AP immediately after surgery, 5.0/3.4 in group A/AP 3 hours after surgery, and 4.3/2.4 in group A/AP 6 hours after surgery, with the AP group having a significantly lower NRS at 3 and 6 hours after surgery. There was no significant difference in NRS after the next day postoperatively between the two groups. There was no difference in the amount of additional analgesics used or complications such as delirium between the two groups. The AP group was able to significantly reduce NRS in the immediate postoperative period and was effective in pain management in the immediate postoperative period. The AP group also achieved an NRS of 4 or higher, which is a risk factor for postoperative prolonged pain, from the early postoperative period, suggesting that the AP group is effective not only in the acute postoperative period but also for postoperative prolonged pain. In addition, complications such as delirium do not increase, and as a result, there is a possibility that early release from bed and early rehabilitation can be promoted. On the other hand, one of the goals of multimodal analgesia that uses multiple drugs is to reduce the amount of opioids used. However, the use of pentazocine increased the amount of opioids used in this study, and it is necessary to optimize multimodal analgesia that is suitable for the surgical technique by considering the drugs used and area block. Conclusion: Multimodal analgesia with IV-PCA, postoperative acetaminophen, and intravenous pentazocine is effective in improving postoperative acute pain in lumbar posterior decompression surgery.

440

P495: Anterior migration of a broken scalpel blade during lumbar spine discectomy : A case report, literature review and management algorithm

Dejan Čeleš ¹ and Janez Mohar ¹

¹ Department of Spine Surgery, Orthopaedic Hospital Valdoltra, Ankaran, Slovenia

Introduction: We report a case of a broken surgical blade anterior migration during lumbar spine discectomy, review the literature on similar cases and propose an evidence-based management algorithm for this type of complication since it has not yet been published. A recent comparison of different discectomy techniques reported an overall complication rate of 10.1%. Vascular injuries in lumbar spine surgery are even rarer (1-5 per 10,000 disc surgeries). Broken surgical blades or other surgically uncontrolled sharp and pointy objects in the disc space represent a rare but potentially severe complication during posterior lumbar spine procedures. Appreciation of vascular, bowel, and urethral anatomy is crucial. Material and Methods:A 59-year-old female with previous lumbar decompression and interspinous process device implantation underwent an instrumented revision of the lumbosacral junction due to degenerative lateral spinal canal stenosis with worsening leg and concomitant chronic mechanical back pain. During L5-S1 continuous-motion oval-shaped incision discectomy, the scalpel blade broke. It moved forward and partially breached the anterior annulus with every attempt to gain hold of the blade under fluoroscopic and microscope control. Pedicular screws were locked to rods, and bed rest was ordered. Prior to vascular surgeon referral, we performed CT angiography. Results:In a subacute setting, the patient was laparoscopically revised. The broken scalpel blade was successfully removed. We found 10 case reports in our literature review subjected to a full-text review, totaling 13 cases. In total, two vascular injuries were reported. The most common level of injury was L4-L5, accounting for 46.2%, followed by L5-S1 at 38.5%. Other levels accounted for 15.4%. Conclusion:Risk factors for encountering a broken blade are No. 15 blade with narrow junction, calcified posterior longitudinal ligament and annulus, scalpel blade stabbing-and-turning technique, and narrowed disc space. Complications arising from anterior sharp object migration are arteriovenous fistula, pseudoaneurysm, vascular, urethral or bowel laceration, foreign body granuloma, and intravascular migration of a foreign body. We advise a stabbing motion-type of the posterior disc annulus excision during discectomy. In these rare events, posterior removal with fluoroscopic aid is an option unless the sharp object migrates through disc space to the anterior annulus. With the anterior breach, vascular or other retroperitoneal injuries should be actively sought. CT angiography is a diagnostic method of choice, while US Duplex serves as a follow-up imaging diagnostics. Sharp object removal from the disc space or retroperitoneum is always indicated. The gold standard technique for anterior retroperitoneal revision is a robot-assisted laparoscopy.

453

P496: Correlation of lumbar spine fat thickness and surgical site infection in degenerative lumbar spine surgery

Faisal Konbaz ¹ , Tariq Jawadi ¹ , Fahad AlThenayan ¹ , Abdullah AlMahayni ¹ , Lina Alhumaid ² , and Mutlaq AlMutlaq ²

¹ Department of Surgery, King Abdulaziz Medical City, Riyadh, Saudi Arabia

² Medicine, King Saud Bin Abdulaziz University for Health Sciences, Riyadh, Saudi Arabia

Introduction: Surgical site infection (SSI) defined by the Centers for Disease Control and Prevention (CDC) as an infection related to an operative procedure that occurs within 30 days of the procedure. Although many researches have linked the increase of BMI with the risk of SSI, only recently have they started to focus on the correlation between the thickness of subcutaneous fat at the surgical site and the incidence of SSI. There is an insufficient number of studies internationally that studied this correlation. The aim of the study is to identify the correlation between lumbar fat thickness and SSI and determine its predictive value compared to other risk factors in predicting the incidence of SSI. Material and Methods: The study team reviewed a total of 200 patients, 151 of which have been included. Forty-nine patients have been excluded due to incomplete, poor quality, or undone MRI. Demographic and clinical data were collected. MRI date, Post-op Fat Thickness: L2, L3, L4, L5, S1, Surgical approach, Surgical time, OPEN vs MISS. Management with oral Abx, Management with IV Abx, and Management with debridement. Results: Out of the 151 patients, four (2.6%) patients developed a post-op SSI. The average subcutaneous fat thickness of L2, L3, L4, L5, S1 in the non-infected group (97.4%, n = 147/151) was 18.8 mm, 32.4 mm, 32.8 mm, 32.9 mm, and 32.9 mm, respectively. On the other hand, the patients that developed a post-op SSI recorded a higher average on all levels with; 34.2 mm, 38 mm, 50.9 mm, 43.1 mm, and 42 mm, respectively. Patients that recorded a higher L4 fat thickness were significantly associated with an increased risk of post-op SSI (p > 0.0264). Conclusion: While BMI is a risk factor for developing post-op SSI. Our study had shown that subcutaneous fat distribution was a significant risk factor in the development of an SSI.

495

P497: The outcomes and complication rates of the adult spinal deformity surgery reported from a single dedicated spine center

Ercan Hassa ¹ and Emre Acaroğlu ²

¹ Orthopaedics and Traumatology, Ankara Spine Center, Ankara, Turkey

² Spine Surgery Department, Ankara Spine Center/ Memorial Ankara Hospital, Ankara, Turkey

Introduction: The aim of the current study is to report the clinical outcomes, radiographic parameters, and complications seen in patients with adult spinal deformity (ASD) who were operated by a single dedicated spinal surgeon and to assess the clinical outcomes, radiographic parameters, and complications at 2-year follow-up. The hypothesis was that the complication rate was higher than that reported previously by multicenter studies which may be secondary to underreporting the complications, missing or faulty medical records, poor patient follow-ups, study populations with different risk potentials, or more limited surgical approaches. Material and Methods: This was a retrospective review of the prospectively collected data of patients who underwent ASD surgery performed by a single surgeon. The institutional review board approval had been provided. The deformities secondary to tumoral entities, syndromic curves, neuromuscular disorders, patients with ≤ 4 levels of fusion, those without at least 2-year follow-up, and those with anterior-only surgery were excluded. All the patients recruited to the study had one of the following criteria; coronal Cobb angle ≥ 20°, sagittal vertical axis (SVA) ≥ 50 mm, pelvic tilt ≥ 25°, or thoracic kyphosis ≥ 60°. All the parameters were evaluated just before the surgery and at 2-year follow-up. The Oswestry Disability Index (ODI), Scoliosis Research Society-22 (SRS-22), Short-Form-36 (SF-36), back and leg pain visual analogue scores (BP-VAS and LP-VAS, respectively), and American Society of Anaesthesiologists (ASA) scores were the clinical assessment parameters. The radiographic assessment included the coronal and sagittal Cobb angles of the main deformities, sagittal vertical axis (SVA), L1-S1 lordosis (LL), pelvic incidence (PI), pelvic tilt (PT), PI-LL, and the coronal balance (C7PL-CSVL). Results: There were 49 patients with a median age of 50(22-82) and with a female preponderance of 83.7%. The median was 210 (120-720) minutes for surgical time, 1425 (300-4200) ml for blood loss, 0 (0-144) hours for length of intensive care unit stay, and 1100 (0-3000) ml for transfused blood. The ASA scores were 1 for 57%, 2 for 49%, and 3 for 4%. The median PI was 55 (37-82). The median LL (from -50 (-75-13)° to -38.5 (-82- -2.3)°), PT (from 26 (2-45)° to 25 (10-48)°), global tilt (from 27 (2-63)° to .30.8 (1-58)°), PI-LL (from 62 (53-79)° to 62 (50-76)°), and coronal balance (from 2.5 (-44.2-91.3) mm to -0.5 (-54.6-45) mm) did not change significantly (p > .05) while the median major curve Cobb-angle improved from 25 (0-80)° to 11.5 (0-60)° (p < .001). However the median sagittal balance insignificantly worsened from 31.9 (-50.6-144.3) mm to 57.9 (-38.8-114.1) mm (p > .05), and median T2-T12 kyphosis changed from 38.5 (0.3-89)° to 49 (18-76)° (p = .021). After 2-year follow-up, the median BP-VAS changed from 5 (0-10) to 4 (0-10) (p = .025), the median LP-VAS changed from 5 (0-10) to 0 (0-10) (p = .021), the median ODI changed from 53.5 (0-92) to 30 (0-88) (p = .001), the median SRS-22 changed from 3 (2-4) to 4 (2-5) (p < .001), and the median SF-36-PCS changed from 37 (20-66) to 46.4 (0-65.8) (p < .001). The complication-free patients were 40.8%, while 44.9% had major and 14.3% had minor complications. Conclusion: The patient-reported outcome measures were all improved after ASD surgery at 2-year follow-up, as stated previously by several studies, despite the lack of radiographic support. However, the complication rate was around 60% which is significantly higher than the reports in the literature.

534

P498: Prediction of rates of revision surgery based on pre-operative cannabinoid use disorder in opioid-naïve patients undergoing total knee arthroplasty, total hip arthroplasty, and primary 1-2 level posterior lumbar fusion

Hania Shahzad ¹ , Nazihah Bhatti ¹ , Safdar Khan ¹ , Frank Phillips ² , and Elizabeth Yu ¹

¹ Orthopedics, Wexner Medical Center, The Ohio State University, Columbus, United States

² Orthopedics, Rush University Medical Center, United States

Introduction: Cannabinoid use has been explored in the treatment of musculoskeletal and neuropathic pain which are both essential components in the management of spinal disorders. Since the use of medical marijuana has been linked to a decrease in opioid use postoperatively, it is of interest to surgeons to recognize the implications of cannabinoid use in the perioperative setting for orthopedic procedures. Material and Methods: The PearlDiver database of over 92 million patients was utilized to identify patients who underwent total knee arthroplasty (TKA), total hip arthroplasty (THA), and primary 1-2 levels posterior lumbar fusion (PLF) for degenerative disease. Patients’ records who had no associated claim of opioid use within the past year were included in the final analysis to reduce confounding. Patients were queried for the claim of cannabis use disorder (CUD) prior to undergoing the primary procedures. Overall differences in revision rates between patients from the CUD and non-CUD groups were analyzed using a chi-squared test and univariable logistic regression models which were reported as odds ratios (OR) and 95% confidence intervals (CI). All data were analyzed in aggregate form using R Statistical Software version 4.1.0 in the PearlDiver Software. Results: The total number of patients who underwent revision surgeries was 4,079,799 (TKA), 2,891,492 (THA), and 4,031,791(PLF) in the 10 years following primary procedures. Of those, 8069 (0.20%) of TKA, 6354 (0.22%) of THA, and 12,244 (0.30%) of PLF patients had an associated diagnostic claim of cannabinoid use disorder prior to their initial surgery (i.e., CUD group). The average time to revision for TKA, THA, and PLF in the CUD group was 432.33 days (SD 414.62), 543.44 days (SD 546.18 days), and 444.88 days (SD 499.29 days) respectively. To statistical differences between both, the groups could not be analyzed for TKA and THA as the number of records in the database was too less to run a chi-square analysis. For the PLF cohort, the difference was not statistically significant (p-value = 0.74). There were no differences in revision rates in TKA and PLF cohorts (p-values > 0.05) at 90 days, 1 year, 5 years, and 10-year intervals. In the THA cohort, the odds of an associated diagnosis of CUD in patients who had revisions was higher by 192% (OR:1.92 [1.14, 3.25], p-value = 0.02) at 90 days, by 196% (OR:1.96 [1.26, 3.04], p-value = 0.004) at 1 year, by 183% (OR: 1.83 [1.24, 2.72], p-value = 0.003) at 5 years and by 181% (OR: 1.81 [1.22, 2.69], p-value = 0.004) at 10 years. Conclusion: It is theorized that cannabinoids may adversely affect spinal fusion due to their anti-inflammatory and immunosuppressive properties. Our results show that cannabinoid use in opioid naïve patients does not affect revision rates at 10-year intervals for TKA and PLF. However, the reasons for the association between CUD and revision rates in the THA group remain unclear. Further research into exploring the impact of cannabinoid use on peri-operative complications in various orthopedic procedures needs to be conducted before cannabinoids can be formally introduced as part of multimodal analgesia.

545

P499: The effect of hyperlipidemia as a risk factor on postoperative complications in patient undergoing anterior cervical discectomy and fusion

Seung Min Son ^1,2 , Rintaro Okada ^2,3 , Zoe Fresquez ² , Blake Formanek ⁴ , Kevin Mertz ² , Zorica Buser ⁵ , and Jeffrey C. Wang ²

¹ Orthopedic Surgery, Pusan National University Yangsan Hospital, Yangsan, South Korea

² Department of Orthopaedic Surgery, Keck School of Medicine, Los Angeles, United States

³ Department of Orthopaedic Surgery, Osaka General Medical Center, Osaka, Japan

⁴ Queensland, University of Queensland School of Medicine, Australia

⁵ Department of Orthopaedic Surgery, NYU Grossman School of Medicine, New York, United States

Introduction: Anterior cervical discectomy and fusion (ACDF) represent the standard procedure performed for focal anterior nerve root compression or spinal cord with low complication rates. Hyperlipidemia (HLD) is well known as a risk factor for major complications of vascular and transplant surgery, and orthopedic surgery. To date, there have been few studies on HLD as a risk factor for cervical spine surgery. The aim of the current study was to analyze the effect of HLD on postoperative complications in patients who underwent ACDF. Material and Methods: This study was a retrospective review of patients who underwent ACDF from 2010 through quarter 3 of 2020 using the MSpine subset PearlDiver Patient Record Database. The patients were divided into a single-level ACDF group and a multi-level ACDF groups. In addition, each group was divided into subgroups according to the presence or absence of HLD. The incidence of surgical and medical complications was queried using relevant International Classification of Disease and Current Procedural Terminology codes. Surgical complications included surgical wound complications, wound infection, and neurological complications. Medical complications included postoperative sepsis, respiratory failure, pneumonia, pulmonary embolism/deep vein thrombosis, myocardial infarction, cerebrovascular accident, renal failure, neurogenic bladder/bowel, and urinary tract infection/incontinence. Other complications included hardware removal, revision surgery, and readmission. Charlson Comorbidity Index (CCI) was used as a broad measure of comorbidity. Chi-squared analysis, with populations matched for age, gender, and CCI, was performed to calculate odds ratios (ORs) of complications among HLD patients relative to non-HLD patients treated with ACDF. Results: A total of 24,936 patients who underwent single-level ACDF and 26,921 patients who underwent multi-level ACDF were included. The mean CCIs for single-level and multi-level ACDF groups were 2.27 ± 2.14 and 2.36 ± 2.23, respectively. In terms of surgical complications, in the multi-level ACDF group, wound complications within 90 days (OR = 1.22, 95% Confidence Index [CI] = 1.03-1.44, p = 0.020) were significantly higher in the patients with HLD. Among medical complications, myocardial infarction (OR = 1.30, CI = 1.18-1.45, p < 0.001 and OR = 1.26, CI = 1.16-1.38, p < 0.001), renal failure (OR = 1.08, CI = 1.01-1.16, p = 0.029 and OR = 1.08, CI = 1.02-1.14, p = 0.009), and UTI/urinary incontinence (OR = 1.16, CI = 1.09-1.22, p < 0.001 and OR = 1.10, CI = 1.04-1.15, p < 0.001) were significantly higher in the patients with HLD in both groups. Revision surgery (OR = 1.22, CI = 1.10-1.36, p < 0.001) and readmission (OR = 1.13, CI = 1.04-1.23, p = 0.004) after 1 year were significantly higher in the patients with HLD who underwent multi-level ACDF. Conclusion: In patients who underwent ACDF, several surgical and medical complications were found to be higher in patients with HLD than in patients without HLD. Preoperative serum lipid concentration control and appropriate HLD treatment can prevent postoperative complications due to HLD in patients who underwent ACDF.

668

P500: Lumbar vertebral housefield units associated with interbody cage subsidence following transforaminal interbody fusion surgery

Jiwon Park ¹ , Gijun Shin ¹ , and Jae-Young Hong ¹

¹ Orthopaedic Surgery, Korea University Ansan Hospital, Ansan-si, South Korea

Study Design: Retrospective case study. Objectives: After lumbar intervertebral fusion, cage subsidence reduces the height of the intervertebral foramen and the lumbar lordosis, which may result in neurological problems. This study aims to investigate the association between cage sedimentation following intervertebral fusion and the Hounsfield Unit of the lumbar spine. Summary of Literature Review: There is a claim that the likelihood of the cage subsidence following fusion increases with the lumbar vertebrae's Hounsfield Unit. Materials and Methods: Retrospective analysis of medical records and records was done on 142 patients from 2015 to 2021 who underwent the minimally invasive transforaminal interbody fusion surgery for 1-2 segments of the lumbar spine at a single center with a minimum follow-up duration of more than a year. Records from radiological exams were examined. Each Hounsfield Unit was measured for lumbar vertebrae into thirds at the center of the sagittal plane of the CT after the groups had been divided according on whether or not the cage had subsided in radiography. Results: A total of 142 patients were analyzed, and a total of 55 patients had cage subsidence on follow Up CT or X-ray 1 year after surgery. The average degree of subsidence of the cage was 5.5 mm. The mean Hounsfield Unit of the lumbar vertebrae in the cage subsidence group was significantly lower than in the non-subsidence group (125.8 HU vs 157.1 HU, p < 0.001). Conclusions: Through this study, it was possible to determine the association between the Hounsfield Unit and postoperative cage subsidence on preoperative CT scans in patients who did not assess their bone mass density adequately before surgery. It can aid with cage selection during surgery for those patients with low lumbar Hounsefield unit to avoid cage subsidence.

Keywords: TLIF, BMD, Hounsefield Unit, Cage subsidence

781

P501: Acute pancreatitis associated with scoliosis surgery. Could opioids play a determinant role in its development?

Nahala Aborashed-Amador ¹ , Fernando Alvarado Gómez ¹ , Andres Motta-Amar ¹ , Maria Garcia-Rueda ¹ , Helberth González-Rico ¹ , Maria Vargas-Osorio ¹ , Maria Camila Giraldo Bernal ¹ , Carlos Montero-Silva ¹ , and Mario Herrera Méndez ¹

¹ Instituto Roosevelt, Bogota, Colombia

Introduction: Pancreatitis as a complication of scoliosis correction surgery has been reported, supported by pathophysiological theories such as hemodynamic imbalance associated with intraoperative instability and changes in visceral vascular architecture directly related to tissue distress because of the vascular elongation caused by curve correction (2-4). In the surgical context, one of the most recent causes proposed is prolonged postoperative use of opioids at high doses. Material and Methods: Three pediatric patients who underwent scoliosis correction surgery, two of them with a diagnosis of neuromuscular scoliosis secondary to Duchenne (DMD) and cerebral palsy and one with congenital scoliosis due to hemivertebra. In average, 15 vertebral segments were instrumented. Two of the patients required two-stage surgery for definitive correction. Average surgical time was 6.06 hours, with a mean blood loss of 1.766 ml in the definitive correction. All three patients required blood product transfusions. Results: Abdominal pain was the cardinal symptom in the three patients. Progressive pain intensity and elevation of pancreatic enzyme levels led to the suspicion of pancreatitis, with a mean of 5 days until diagnosis. Total time of continuous opioid use during hospitalization was 26 days in average, with adjustment to the highest dose because of the presence of abdominal pain. The main opioids used were morphine, tramadol and hydromorphone. Conservative and surgical management was required in these patients, with surveillance in the intensive care unit. No major complications were associated with the pancreatic picture. Conclusion: The association between prolonged exposure to high-dose opioids and the onset of pancreatitis in the context of major surgery suggests a potential relation that warrants further study, given that opioid receptors have been described in the sphincter of Oddi. This association must be borne in mind in order to reduce patient morbidity in the context of scoliosis correction surgery.

788

P502: Risk factors for instrumentation failure in anterior cervical spine surgery

José Alfonso Corona De la Torre ¹ , Hugo Vilchis Samano ¹ , Luis Miguel Munguia Leon ¹ , and Kaori Guadalupe Honda Partida ¹

¹ Spine Surgery, UMAE Hospital de Ortopedia y Traumatologia Lomas Verdes IMSS, Mexico City, Mexico

Introduction: To review the risk factors associated with graft/instrumentation failure in anterior cervical spine decompression and fusion with PEEK cages and plate/titanium mesh. Material and Methods: Cohort. Instrumentation failure was assessed using radiographic parameters for cervical sagittal balance: SVAc (Cervical Sagittal vertical alignment), Cervical lordosis, TIA (thoracic inlet angle), Neck Tilt, T1 slope. Also was assessed the technique of the plate and mesh location taking the parameters: Coronal angle of the plate (CA), Sagittal angle of the plate (SA), length screw/body vertebral diameter ratio (RTC), angle of the screw placement (AT). In patients with instrumentation failure was assessed the amount of Hounsfield Unit (HU) to determine the bone density. Analysis of relation with smoking and steroid treatment of the patient with instrumentation failure was assessed. Results: Records of 349 patients (215 males and 134 females). 8 patients with instrumentation failure (2.29%), average age 51 years (IQ 56-71). The most frequent intervened levels were C4-C5 and C5-C6. After evaluation was founded that a higher Coronal Angle and TIA was significant increased (< 0.001) with failure instrumentation. Steroid treatment and smoking showed a OR of 3.7 and 0.77 respectively with instrumentation failure. 87.7% of the patients with instrumentation failure demonstrated by HU assessment with low bone mineral density (LBMD). Conclusions: A higher TIA and CA showed and increased risk factor for instrumentation failure. Steroid treatment and smoking showed an increased ratio for instrumentation failure. There was not significant relation with the remaining radiographic parameters in sagittal cervical balance and technique assessment.

807

P503: Outpatient intermittent percutaneous cerebrospinal fluid (CSF) drainage as treatment of CSF leak in spine surgery

Paul Albert Manuel ¹ , Gilbert Ranoa ¹ , and Michael Louis Gimenez ¹

¹ Brain and Spine Institute, Cardinal Santos Medical Center, San Juan, Philippines

Introduction: A dreaded complication of spine surgery is Cerebrospinal fluid (CSF) Leak. A CSF leak may result in pain, wound healing complications, infection, increased hospital stay, and/or reoperation. A gold standard of post operative management of CSF leak is still lacking. The authors describe a technique of CSF drainage that may improve the current management of post operative CSF leak without addition hospital stay or reoperation. Material and Methods: A retrospective case series review of spine surgery cases performed by 2 attending surgeons from the Brain and Spine Institute, Cardinal Santos Medical Center, was performed. In all, 241 charts were reviewed, spanning a 5-year period. There were 18 cases in which CSF leak was detected. All cases of CSF leak were managed by outpatient intermittent percutaneous drainage using a gauge 23 butterfly needle and a 20-cc sterile syringe.Patients were reevaluated at regular intervals for and underwent repeat drainage every 1-4 days dependent on the need and persistence of CSF leak. Results: All patients observed in this study had CSF leak, All patients were treated using Intermittent percutaneous CSF drainage and none of the patients needed revision surgery to close the CSF leak. The duration of the leak for the all patients were at approximately 20 days on average, with a standard deviation of 15 days. The most common factors noted in the study population were elderly, greater than 2 operative levels, and corticosteroid use. Conclusion: The use of Outpatient Intermittent percutaneous CSF drainage represents a viable alternative in the treatment of CSF leak as seen in the resolution of signs and symptoms of all 18 patients. On the risk factors for the occurrence of CSF leak, the most noted factors besides increased age were the increased number of operative levels, and corticosteroid use.

856

P505: Venous thromboembolism prophylaxis safety profile in elective spine surgery

Mohamed El-Farra ¹ , Emily Mills ² , Christian Jimenez ² , Samantha Solaru ² , Hyunwoo Kang ^2,3 , Tara Shelby ² , Andy Ton ² , Jeffrey C. Wang ² , Raymond Hah ² , and Ram Alluri ²

¹ Orthopaedic Surgery, University of California, Riverside School of Medicine, Riverside, United States

² Orthopaedic Surgery, Keck School of Medicine of USC, Los Angeles, United States

³ Orthopaedic Surgery, Massachusetts General Hospital, Harvard Medical School, Boston, United States

Introduction: There is currently no consensus regarding pharmacologic venous thromboembolism (VTE) prophylaxis in elective spine surgery. The purpose of this study was to assess the safety profile of VTE prophylaxis in patients undergoing elective spine surgery. Material and Methods: Patients who underwent elective spine surgery at a single institution from January 2019 to October 2019 were included for analysis. Patients were divided into two cohorts based on whether they received VTE prophylaxis or not. The patients’ demographics, comorbidities, surgery performed, and surgical outcomes and complications were recorded via retrospective chart review. Multivariate regression analysis controlling for age, gender, body mass index, ethnicity, prior VTE, smoking, procedure type, levels fused, approach, instrumentation, operative time, estimated blood loss, and intraoperative complication was conducted to assess for any significant differences in postoperative hematoma, general postoperative complications, deep vein thrombosis (DVT), pulmonary embolism (PE), outpatient complications readmission, emergency department visits, and return to the operating room (OR). Results: Of the 318 patients, 247 patients received VTE prophylaxis, and 74 patients did not. After controlling for confounders with multivariate analysis, there was no significant difference in postoperative hematoma formation (p = 0.997), general postoperative complications (p = 0.684), DVT rates (p = 0.860), PE rates (p = 0.984), outpatient complications (p = 0.196), return to the OR (p = 0.331), likelihood of emergency department visits (p = 0.061) and readmission rates (p = 0.071). Conclusion: The present study found that patients who received VTE prophylaxis after undergoing elective spine surgery did not have a significant increase in postoperative hematoma, general complications, return to OR, ER visits, and hospital readmissions. In addition, VTE prophylaxis did not affect the rate of DVT or PE. Based on the present study’s results, VTE prophylaxis does not increase the risk of postoperative complications in patients undergoing elective spine surgery.

889

P506: Evaluating the effect of gastroesophageal reflux disease on postoperative dysphagia following anterior cervical spine surgery - A prospective, multicenter study

Aditya Mazmudar ¹ , Taylor Paziuk ¹ , John Mangan ¹ , Khoa Tran ¹ , Samuel Oh ¹ , Sandy Li ¹ , Brandon Sherrod ² , Erica Bisson ² , Darrel Brodke ³ , Jose Canseco ¹ , Alan Hilibrand ¹ , Christopher Kepler ¹ , Alexander Vaccaro ¹ , Gregory Schroeder ¹ , and Jeffrey Rihn ¹

¹ Rothman Orthopedic Institute at Thomas Jefferson University, Philadelphia, United States

² Department of Neurosurgery, Clinical Neurosciences Center at University of Utah, Salt Lake City, United States

³ Department of Orthopaedic Surgery, University Orthopaedic Center at University of Utah, Salt Lake City, United States

Introduction: While there is little doubt that the operative insult associated with anterior cervical spine surgery imposes a significant risk for postoperative dysphagia, numerous patient specific risk factors have yet to be fully explored. The impact of a preoperative diagnosis of gastroesophageal reflux (GERD) in particular has yet to be evaluated as a potential risk factor for dysphagia. To our knowledge, no prior prospective study has reported on the incidence and severity of dysphagia following anterior cervical discectomy and fusion (ACDF) based on a patient’s preoperative diagnosis of GERD. As such, the purpose of this study was to prospectively evaluate the impact of a preoperative diagnosis of GERD on the incidence and severity of postoperative dysphagia in a multicenter population. Material and Methods: A retrospective cohort study was conducted on patients who underwent one- to five-level ACDF After IRB approval, written informed consent was obtained from all participating patients. Patients over 18 years of age who underwent an elective ACDF for a degenerative condition were prospectively enrolled at two academic centers from the years 2018 to 2020. Patients were asked to complete a preoperative demographic survey in addition to dysphagia surveys (Bazaz, DSQ, EAT-10) both preoperatively and at 2, 6, 12, and 24 weeks postoperatively. Exclusion criteria included previous cervical fusion at the operative level or surgery for oncologic, infectious, or traumatic indications. Patients were separated into two groups: those with and without a preoperative diagnosis of GERD. Continuous variables were assessed using either an independent t-test or Mann Whitney U-test for parametric and non-parametric data. All categorical variables were compared using a chi-square test. Results: A total of 116 patients met study criteria and were subsequently enrolled. Overall rates of postoperative dysphagia increased to 47.3% (n = 53) at 2-weeks but eventually decreased towards the preoperative prevalence of 25.0% at the 24-week mark. Patients with preoperative diagnosis of GERD had lower dysphagia severity scores on a continuous variable analysis in both the DSQ and EAT-10 surveys at 2-week follow-up in addition to the Bazaz survey at 24-week follow-up. Our follow up at 24-weeks was 85.7%. Conclusion: Our study shows that having a preoperative diagnosis of GERD has no significant effect on the incidence of dysphagia following ACDF. Nevertheless, having a preoperative diagnosis of GERD does seem to affect the severity of dysphagia that this patient population perceives at multiple intervals over a 24-week postoperative period.

971

P507: Ipsilateral psoas hematoma development after two adjacent level endoscopic transforaminal discectomy in prior two level fused segments

Sukdeb Datta ¹

¹ Endoscopic Spine Surgery, Datta Endoscopic Back Surgery and Pain Center, Saddle Brook, United States

Introduction: Transforaminal endoscopic lumbar discectomy (TFELD) is increasingly gaining popularity as a minimally invasive procedure to address the disc herniations in the lumbar spine. There is a scarcity of reports on hemorrhagic complications after endoscopic spine surgeries. We are reporting a case of psoas hematoma following TFELD. Material and Methods: We report a case of left sided psoas muscle hematoma in a 50-year-old male who underwent a transforaminal endoscopic lumbar discectomy (TFELD) and foraminotomy. He had prior history of fusion at L2-L3 and L4-L5 fusion. The Magnetic resonance (MRI) imaging study showed adjacent level disease at L3-4 and L5-S1 levels with severe lateral recess and left foraminal stenosis. TFELD was performed at the adjacent L3-4 and L5-S1 levels. However, on 2^nd post-operative day the patient experienced increasing radicular pain in left lower extremity mainly along the L5 and S1 distribution. A repeat MRI with and without contrast showed circumscribed fluid collection within the substance of the left psoas muscle adjacent to L5-S1 disc level extending along the muscle rostrally and caudally (4x3x1.5 cm). The collection was non-enhancing on post-contrast T1 images. Infectious pathology was ruled out owing to absent systemic symptoms, the negative lab results for infection markers and non-enhancement of the lesion on MRI. The clinic-radiological presentation was suggestive of psoas hematoma. Due to persistent radicular symptoms which was attributed to the hematoma, the patient was referred to an interventional radiologist who performed a computed tomographic (CT) guided aspiration. Results: Fortunately, we encountered a small well-circumscribed hematoma without any systemic symptoms and abnormal blood parameters. Thus, no re-exploration was required. Even the radicular symptoms resolved over time. The surgeons may consider CT angiographic embolization and re-operation if the symptoms and abnormal hematologic parameters warrant. Conclusion: Hemorrhagic complications after spine surgeries are rare events. Surgeons must rule out the possibility of psoas hematoma in patients presenting with increasing radicular pain with or without flank pain following PELD surgeries. Conservative treatment including wait and watch strategy is usually sufficient. The surgeons should exercise an immense care while placing the targeting needle.

1002

P508: Surgical approach and post-operative C5 palsy after decompression for degenerative cervical myelopathy

Ali Moghaddamjou ¹ , Alex Bak ² , Mohammed Ali Alvi ¹ , and Michael Fehlings ¹

¹ Neurosurgery, University of Toronto, Canada

² University of Toronto, Canada

Introduction: One of the significant complications following decompressive surgery to the cervical spine is that of C5 palsy. Despite the clinical significance of this finding, we do not have strong quality evidence towards its natural history and strategies to limit the incidence and duration of this complication. The goal of this project is to leverage clinical trial data in patients with Degenerative Cervical Myelopathy (DCM) to enhance our understanding of postoperative C5 palsy. Material and Methods: Data from the CSM-Protect trial, which was a multicenter, prospective, randomized clinical trial was used for this analysis. We identified all adult patients with DCM who received decompression surgery. We subdivided the data into those patients who had documented C5 palsy after the surgery and those who did not. The outcome measure selected was the incidence and duration of C5 palsy post decompressive surgery. As risk factors for C5 palsy remain unclear, matching was not performed. One-way ANOVA was used to compare continuous variables and chi-square tests, or fisher’s exact tests were used for discrete variables. The level of significance was set to p < 0.05. Results: In a total of 284 patients that were included, 152 (53.5%) of the patients received surgery via the posterior approach. The total incidence of C5 palsy was 5.3% (n = 15), which was comparable to metrics reported in DCM and other degenerative spine diseases. Patients that received posterior surgery were older (A - 56.4 ± 10.0, P - 60.5 ± 9.9, p = 0.001) and had a greater proportion of males (A - 47%, P - 65.8%, p = 0.002). Both groups had similar proportions of comorbidities in the form of anxiety, depression, cardiovascular disease, cancer, diabetes, COPD, hyperlipidemia, hypercholesteremia, hypertension, thyroid disease, hepatitis, obesity, and sleep apnea. The anterior approach group had a greater incidence of fibromyalgia (A - 5.3%, P - 0.7%, p = 0.045). The incidence of C5 palsy was significantly higher in patients that underwent posterior decompression compared to those that received anterior decompression (A - 0.8%, P - 9.2%, p = 0.004). Conclusion: The incidence of postoperative C5 palsy is significantly higher in patients who received posterior decompression compared to anterior decompression for DCM.

1020

P509: Incidence and risk factors of venous thromboembolism in the perioperative period of spine surgery at a tertiary care hospital

Sami Aleissa ¹ , Faisal Konbaz ² , Anouar Bourghli ³ , Fahad Alhelal ¹ , Majed Abaalkhail ¹ , Husam Altahan ¹ , Abdulrahman Al-Farraj ¹ , Salman Al-Jafari ⁴ , Rakan Aldusari ⁴ , Suhail Alassiri ¹ , and Rund Aleissa ⁴

¹ King Abdulaziz Medical City, Riyadh, Saudi Arabia

² King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia

³ Kingdom Hospital, Riyadh, Saudi Arabia

⁴ King Saud Bin Abdulaziz University for Health Sciences, Riyadh, Saudi Arabia

Introduction: Spine Surgery is considered a moderate risk for developing Venous Thromboembolism (VTE). To our knowledge, no study has been done to determine the incidence of VTE in our local population. We aim to study this and determine the factors associated with developing VTE post spine surgery. Material and Methods: A retrospective chart review was conducted to analyze 892 adult patients who underwent either an elective or emergency spine surgery. Demographics, length of surgery and hospital stay, diagnosis, and location of surgery in addition to the type of trauma, if applicable, were collected. Furthermore, spiral computed tomography was used to diagnose pulmonary embolism (PE), and duplex ultrasound was used to diagnose deep vein thrombosis (DVT) pre- and post-operatively. Results: 800 patients were included. The overall incidence of VTE was 4.1%. In addition, Lumbar spine was the most common location operated on. Increasing age and length of hospital stay were both significantly associated with development of VTE. Furthermore, cervical spine surgery had a lower incidence of VTE compared to other locations which was statistically significant. Lastly, non-ambulatory patients had a higher risk of having VTE compared to patient who were able to ambulate post-operatively. Conclusion: The incidence of VTE after spine surgery is considered low but carries high rates of morbidity and mortality. Increased age and prolonged hospital stay increases its risk while early ambulation lowers it. Larger prospective study is needed to identify the best prophylactic anticoagulation regimen. Prophylactic measures against VTE are highly recommended, especially amongst high-risk patients.

1085

P510: Relative benefit of neurophysiologic monitoring during uncomplicated anterior cervical spine surgery

Torsten Fras ¹ and Christian Fras ¹

¹ Institute for Spinal Surgery, Broomall, United States

Introduction: Intraoperative neurophysiologic monitoring (IOM) is commonly used in spine surgery; advantages include identification of intraoperative neurologic decline that may be related to a remediable cause. Disadvantages include increased time and cost, morbidity associated with the monitoring procedure, and the potential for false positive alerts prompting unnecessary action. The study’s goal was to assess whether use of IOM in routine, uncomplicated cases of anterior cervical discectomy and fusion (ACDF) surgery was of demonstrable benefit. Material and Methods: 50 consecutive patients were identified who underwent one-level ACDF with anterior instrumentation for cervical disc herniation with radiculopathy without myelopathy. For all cases, a NIMS tube was used to monitor laryngeal nerve function, and EMG, SSEP, and MEP modalities were monitored. Hospital and post-operative records were investigated for the presence of IOM alerts, whether corrective action was taken during surgery, and the presence of any post-operative neurologic deficits. Results: In all cases, there were no alerts of laryngeal nerve dysfunction, or SSEP / MEP abnormality. In 12 cases, transient EMG irritation activity was documented; in no cases was there any change to the surgical procedure, such as abandonment of surgery, removal of implant, etc. There were no instances of new or worsened post-operative neurologic deficit, and clinical findings of vocal cord dysfunction. Conclusion: In ACDF with anterior instrumentation for cervical disc herniation with radiculopathy without myelopathy, IOM use did not convey any identifiable advantage. Therefore, the data does not support considering IOM to be required or standard of care for routine, uncomplicated ACDF surgery.

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P511: Lumbar spinous process fixation: peri-operative complication rate in instrumented posterior fusion

Torsten Fras ¹ and Christian Fras ¹

¹ Institute for Spinal Surgery, Broomall, United States

Introduction: Spinal fusion surgery is performed to treat many conditions. Previous studies have demonstrated increased arthrodesis rates when supplemental instrumentation is utilized: this commonly involves lumbar pedicle screw fixation. However, traditional surgical techniques for lumbar pedicle screw insertion can be associated with significant morbidity (up to 54% complication rate). Spinous process fixation (SPF) is an alternate method of lumbar spine stabilization in fusion procedures, and can be accomplished with less invasive techniques. This study seeks to assess the peri-operative complication rate associated with use of SPF in lumbar fusion operations. Material and Methods: 100 consecutive patients were identified who had undergone one-level SPF using Aspen MIS Fusion System (Zimmer Biomet) as part of lumbar fusion surgery with minimum 90 days post-operative follow-up. All hospital and office records were reviewed. All complications were recorded. Results: All 100 patients were followed for minimum 90 days post-operatively. Complications were: superficial wound dehiscence (2), all responding to local wound care; superficial wound infection (3), all responding to oral antibiotics; post-operative urinary retention requiring catheter insertion (1), resolved spontaneously. There were no reoperations. No other complications were identified, and no severe complications (eg, deep infection, neurologic deficit, implant-related complication). Conclusion: The short-term (within 90 days of surgery) complication rate associated with SPF in posterior lumbar fusion surgery was 6%. All complications were minor; there were no major complications, and no cases of re-operation. The peri-operative complication rate of SPF compares favorably with that of pedicle screw instrumentation, and in this regard SPF is an alternate option to use of pedicle screw fixation in selected patients.

1139

P512: Role of tranexamic acid in reducing peri and post operative blood loss in open spine surgeries

Shyamasunder Bhat Neerkaje ¹ , Saktthi Shanmuganathan ¹ , Madhava Pai ¹ , and Ramachandra Theja ¹

¹ Orthopaedics, Kasturba Medical College, Manipal, Manipal Academy of Higher Education, Manipal, India

Introduction: Spine surgery is associated with significant blood loss due to the extensive soft tissue dissection, bony decompression and prolonged surgical time. Surgical bleeding may require blood transfusions. Also there is risk leading to epidural hematoma formation, cauda equina compression. Tranexamic acid (TXA), is a synthetic antifibrinolytic drug, which inhibits plasminogen from binding to fibrin and suppresses fibrinolysis. This way tranexamic acid will help in reducing perioperative blood loss in major surgeries. The evidence on the efficacy of this agent in spine surgeries is not sufficient. The purpose of this study was to assess its efficacy on perioperative blood loss in major spinal surgeries. Methodology: Pre-operative assessment included documentation of the patient’s comorbidities, preoperative Hb, PCV, platelet count, PT/INR and APTT, RFT, serum electrolytes values and ECG. Patients with age <18 years, blood dyscrasias and renal disorders are excluded from the study. Based on whether patients have received the drug or not they will be grouped into patient receiving tranexamic acid (Group A) and patient not receiving tranexamic acid (Group B). Intra operative data included levels of decompression, duration of surgery, assessment of blood loss, need for intraoperative blood transfusion. Post-operative assessment including repeating the following parameters Hb, PCV, PT/INR, APTT after 24 hours of surgery, documentation of blood collected in surgical drain and need for any postoperative blood transfusion. Results: Intraoperative Transfusion, Hemoglobin (g/dL) (Post-Operative Hb drop), Surgical Drain (mL) were statistically significant in Group A when compared to Group B. Conclusion: In spine surgeries, TXA was found to be effective in reducing the intra-operative and post operative blood loss and the need for blood transfusion. Keywords: Tranexamic acid (TXA), spine surgery, blood loss, blood transfusion.

1143

P513: Performance assessment of the American College of surgeons risk calculator in metastatic spinal tumor surgery

Jessica Ryvlin ¹ , Benjamin Wang ¹ , Jorden Xavier ¹ , Mousa Hamad ¹ , Rafael De La Garza Ramos ¹ , Saikiran Murthy ¹ , Yaroslav Gelfand ¹ , and Reza Yassari ¹

¹ Department of Neurological Surgery, Montefiore Medical Center/Albert Einstein College of Medicine, Bronx, United States

Introduction: Patients with spinal metastases often require surgical intervention for cord compression or palliative care. The American College of Surgeons National Surgical Quality Improvement Program (ACS-NSQIP) Surgical Risk Calculator was developed to assist surgeons with estimating 30-day postoperative complications based on patient-specific risk factors and has been validated within several surgical patient populations. Since no prior studies have evaluated its performance in patients undergoing spinal metastasis surgery, we assessed the accuracy of this tool in predicting postoperative complications. Methods: This was a single-institution retrospective cohort study. Electronic medical record (EMR) chart review was performed on consecutive operative patients with metastatic spine disease from our institution between April 1, 2012 and April 30, 2022. Preoperative comorbidities and current procedural terminology (CPT) codes were entered into the ACS-NSQIP calculator (https://riskcalculator.facs.org/RiskCalculator/) to obtain predicted complication risk for each patient. Mean predicted risk percentages were then compared to observed outcomes using receiver operator characteristic (ROC) curves and two-sided one-sample t-tests. A scatter plot with regression line was used to compare length of hospital stay. Results: A total of 153 patients were included in this study. The overall 30-day postoperative complication rate was 41.2% and mortality rate was 8.5%. The mean predicted mortality rate was similar to mean observed mortality (7.9% vs 8.5%, p = 0.352). However, mean predicted outcomes were significantly lower than mean observed outcomes for all other measured complications, including any complication, serious complication, pneumonia, surgical site infection, urinary tract infection, venous thromboembolism, and return to operating room (p < 0.001). Only mean postoperative mortality (AUC = 0.749) and sepsis (AUC = 0.709) were found to be adequately discriminated in ROC analysis, with all other outcomes having poor predictive value (AUC < 0.700). Finally, the risk calculator was found to structurally underestimate length of hospital stay in patient-matched comparison (regression line y = 14.51-0.1x; r² < 0.001). Conclusion: The ACS-NSQIP risk calculator was found to be a poor or unreliable predictor for most postoperative complications in patients undergoing spinal tumor surgery. However, this tool may be successfully utilized to predict risk of 30-day postoperative mortality in this patient population. Future work should be done to create accurate oncology-specific outcome predictors with validation in the spine population.

1156

P514: The potential role of intraoperative ketamine administration in reducing postoperative opioid consumption among chronic opioid users in outpatient spine surgery

Carol Wang ¹ , Jennifer Liu ² , Thomas Sullivan ³ , Kevin Bondar ³ , and Comron Saifi ³

¹ Department of Orthopaedics, University of Pennsylvania, Philadelphia, United States

² Orthopedics and Sports Medicine

³ Spine Surgery, Houston Methodist Hospital, Houston, United States

Introduction: The rising rate of opioid use disorder in the United States represents a serious public health crisis. The economic burden of prescription opioid misuse is extensive. Achieving postoperative pain control while minimizing opioid overuse and dependence is a continued challenge in spine surgery. Intraoperative ketamine administration in patients undergoing spine surgery has been associated with decreased opioid consumption postoperatively. The present study aimed to determine long-term postoperative opioid consumption in patients who received intraoperative ketamine compared to those who did not receive intraoperative ketamine. Materials and Methods: Patients included in this study carried a diagnosis of degenerative spinal deformity and had undergone spine surgery. Patients in the ketamine group received a single bolus of 30, 40, or 50 mg of ketamine, followed by ketamine infusion at a rate of 1-3 mcg/kg/min until the close of the procedure. Pre- and postoperative opioid consumption was quantified using cumulative MME. A prescription drug monitoring program (PDMP) spanning 13 states was used to identify opioid prescription fills and quantify dosages consumed independent of prescription source, insurance coverage, or patient self-report. Long-term preoperative opioid use was defined as filling at least six opioid prescriptions in the twelve months prior to surgery. Short-term preoperative opioid use was defined filling an opioid prescription in the 30 days prior to surgery, with no additional opioid prescription fills in the 180 days prior to surgery. Study sample characteristics, including demographics, comorbidities, intraoperative factors, postoperative outcomes, were controlled in the analyses. Propensity score matching was used. STROBE (Strengthening the Reporting of Observational studies in Epidemiology) guidelines were implemented. Results: A total of 434 participants were included. Compared to the control group, patient who received intraoperative ketamine presented with a significantly higher number of readmissions (0.291 ± 0.75 vs. 0.475 ± 0.874; p = 0.045), and higher mean opioid usage in the year prior to surgery (5,089 ± 16,813 vs. 11,801 ± 28,043; p = 0.016). There was no statistically significant difference noted in postoperative opioid consumption in opioid-naïve patients and short-term opioid users at 1 month, 3 months, 6 months, or 1 year. There was no difference in incidence of long-term postoperative opioid use in the opioid-naïve patients in patients receiving intraoperative ketamine. Among patients with long-term preoperative opioid use, the patients who received ketamine had consumed 41% fewer total morphine milligram equivalents (MMEs) (k = 1,209 MMEs; c = 2.062 MMEs; p = 0.008) at one month postoperatively. In subgroup analysis based on percentile of preoperative opioid use in MMEs, no statistically significant association was observed between ketamine administration and postoperative opioid use in any subgroup. Conclusion:There was no significant change in opioid use at 1, 3, 6, or 12 months postoperatively in the two groups. There was no difference in the incidence of long-term postoperative opioid use, VAS at discharge, VAS pain scores, and length of stay. There was a short-term opioid-sparing benefit to intraoperative ketamine use in patients with long-term preoperative opioid use. Patients with chronic preoperative opioid use have a short-term opioid-sparing benefit after intraoperative ketamine administration.

1167

P515: Anterior spinal fusion surgery associated with lower risk of stroke, pneumonia, and infection compared to posterior spinal fusion surgery

Leland McCluskey ¹ , Ivan Angelov ² , Victor Wu ³ , Sachin Gupta ⁴ , Comron Saifi ² , and Matthew Cyriac ⁵

¹ Orthopaedic Surgery, St. Francis, Emory Healthcare, Columbus, United States

² Spine Surgery, Houston Methodist Hospital, Houston, United States

³ Department of Orthopedic Surgery, University of Texas Health - Houston, Houston, United States

⁴ Orthopaedic Surgery, University of Pennsylvania, Philadelphia, United States

⁵ Department of Orthopedic Surgery, Tulane University School of Medicine, New Orleans, United States

Introduction: The question of approach to lumbar fusion is debated amongst spine surgeons. While prior studies have shown slight differences in outcomes, most studies have concluded that both approaches have similar fusion rates and clinical outcomes. Prior studies have lacked statistical power. This retrospective cohort study compared the 30 and 90-day postoperative complications between an anterior vs. posterior approach to lumbar interbody fusion (LIF) in 2010-2018 utilizing the largest sample to date of direct patient outcomes from a mixed private and public payer database. Materials and Methods: The MSpine database by PearlDiver was queried using ICD-9, ICD-10, and CPT codes to identify patients who had undergone single-level anterior or posterior lumbar interbody fusion surgery. 30 and 90-day postoperative complications of single-level ALIF/LLIF and PLIF/TLIF surgery were evaluated in 112,023 patients. Readmission rates, ileus, lower extremity DVT, infection, pneumonia, and stroke were evaluated for patients with in the anterior approach group and the posterior approach group. Results: There were 38,529 (34.4%) patients in the anterior group (ALIF/LLIF) and 73,494 (65.6%) in the posterior group (PLIF/TLIF). At both 30 and 90-days postoperative, patients undergoing an anterior approach to lumbar interbody fusion had a higher odds ratio of lower extremity DVT (30-day OR: 1.19, 90-day OR: 1.16; p < 0.05) and ileus complication (30-day OR: 1.87, p < .05; 90-day OR: 1.81, p < .05). At both 30 and 90-days postoperative, patients undergoing a posterior approach had a higher odds ratio of stroke (30-day: OR: 0.79, 90-day OR: 0.87; p < 0.05), transfusion (30-day OR: 0.66, 90-day OR: 0.69; p < .05), infection (30-day OR: 0.88, 90-day OR: 0.91; p < .05), and pneumonia complication (30-day OR: 0.85, 90-day OR: 0.90; p < .05). There was no statistically significant difference in myocardial infarction or pulmonary embolism between both approaches at 30 and 90-days postoperative. Conclusion: This study identified differences in postoperative complications between anterior and posterior approaches at 30 and 90-day postoperative timepoints. The present findings can inform surgeon treatment decisions for patient profiles. Patients with high risk for stroke, pneumonia, and infection, or patients with a high likelihood of requiring postoperative transfusion, may benefit from an anterior approach for lumbar interbody fusion. Patients with a high risk for developing lower extremity DVT may benefit from a posterior approach.

1211

P516: Drivers for unplanned readmission following adult spinal surgery

Comron Saifi ¹ , Sarthak Mohanty ² , and Sachin Gupta ²

¹ Department of Orthopaedic Surgery, Houston Methodist Hospital, Houston, United States

² Orthopaedic Surgery, University of Pennsylvania, Philadelphia, United States

Introduction: Unplanned readmissions following surgical intervention are costly to health systems, associated with poor outcomes, and useful as indicators of healthcare quality and hospital performance. Discerning independent predictors of hospital readmission is especially crucial in light of the Hospital Readmissions Reduction Program, a part of the Affordable Care Act that allows centers for Medicare and Medicaid services to penalize hospitals for higher readmission rates. Identifying independent risk factors for hospital readmission within one-year post-op is critical to identifying how risk factors change along a longitudinal scale. The objectives of this study were to assess the incidence of unplanned readmission after spine surgery at 0-30 days, 31-90 days, 91-180 days, and 180 days, and one year and to identify preoperative and in-hospital risk factors using a large, single institution database. Materials and Methods: A retrospective review of 3,079 patients who underwent a spinal procedure as a principal or secondary procedure was conducted. Patients with and without unplanned readmission were compared on baseline characteristics, intraoperative details, and postoperative outcomes. Baseline characteristics consisted of comorbidities, age, race, sex, smoking status, pre-operative diagnosis, procedures performed, and post-operative outcomes. Multivariable logistic regression was performed to establish independent associations with unplanned readmission within one-year post-op. For adjusted analysis, separate models were constructed using purposeful selection of covariates, incorporating backward elimination after univariate testing (p-value = ≤ .10). Separate regression models were constructed for patients who were readmitted between 0-30 days, 30-90 days, 90-180 days, between 180 days and 365 days. Statistical significance was defined as p-value < .05 (two-sided test). Analyses were conducted with SPSS Statistics 23. Results: 3,079 patients met inclusion criteria. 22.34% were readmitted within one year. 10.49% of patients were readmitted within 30 days postoperatively, 3.77% between 30 and 90-days postoperatively, 3.25% within 90 and 180 days postoperatively, and 4.77% between 180 days and one-year post-operatively. Patients that underwent procedures of the thoracic spine (p = 0.030) had a higher likelihood of being readmitted. Smokers (p = 0.034) had a higher likelihood of readmission compared to non-smokers. Each additional day spent in the hospital during the postoperative stay resulted in 1.071 higher odds (p < 0.0001) of readmission. Each additional year of age resulted in 1.021 higher odds (p < 0.0001) of readmission. Infection was the most common reason for re-admission. Conclusion: Older patients, patients that smokers, and patients undergoing thoracic procedures had higher rates for re-admission after adult spine surgery. Infection was the most common reason for readmission. Surgeons should consider these factors in management decisions, clinical follow-up, and in counseling patients regarding the risks for readmission.

1218

P517: Treatment of a symptomatic CSF fistula after full endoscopic cervical foraminotomy

Bastian Stemmer ¹ , Motov Stefan ¹ , Christoph Maurer ² , and Ehab Shiban ¹

¹ Department of Neurosurgery

² Department of Radiology, UK Augsburg, Augsburg, Germany

Introduction: There is limited data on the management and sequalae of CSF fistulas after endoscopic cervical spine surgery. Case report: We present a case of a 47-year old female patient with left-sided C7 radiculopathy, who was advised for a left-sided endoscopic foraminotomy C7 due to a cervical spondylosis with left-sided paramedian disc herniation and C7 foraminal stenosis. The patient was discharged on the first postoperative day after an uneventful course of treatment. However, she returned 8 days later with tingling dysesthesia in both upper extremities as well as headache and neck pain, which accentuated and immobilized her during standing and walking. A cerebrospinal fluid (CSF) leak was detected on spinal magnetic resonance imaging (MRI). A computer tomography (CT)-guided epidural blood patch was performed but the patients’ symptoms persisted. Therefore a second CT-guided epidural fibrin patch was executed and the patient improved and was discharged home without sensorimotor deficits or sequelae. Discussion and Conclusion: CSF fistulas after endoscopic cervical spine procedures are a rare complication, which might severely debilitate and immobilize patients. Thorough analysis of current literature let us conclude that interventional treatment with epidural fibrin patch appears to be an efficient treatment if dural tear is not detected and repaired during initial surgery.

1235

P518: Postoperative VTE complications in spinal oncology patients

Ivan Angelov ¹ , Takshi Hirase ² , Thomas Sullivan ² , and Comron Saifi ¹

¹ Spine Surgery

² Department of Orthopedics and Sports Medicine, Houston Methodist Hospital, Houston, United States

Introduction: Venous Thromboembolism (VTE) is a serious complication that occurs following spine surgeries. VTE rates are high in cancer patients especially in those treated with spine tumor excision procedures. There are no prior studies that investigate the incidence of postoperative VTE among spinal instrumentation procedures performed on patients with oncologic spinal pathologies. The authors hypothesized that spine instrumentation procedures performed on a greater number of levels will be associated with a higher risk of VTE complications compared to those involving fewer levels in patients with oncologic spinal pathologies. Methods and Materials: The 2010 to 2019 National Surgical Quality Improvement (NSQIP) database was used to identify all patients undergoing spine instrumentation procedures for spine tumor excision. A retrospective review of the NSQIP database was performed on all patients undergoing spinal instrumentation for spine tumor excision between 2010 and 2019. CPT codes of spinal instrumentation procedures were included. Patients with incomplete records and CPT codes for procedures other than spinal instrumentation were excluded. Demographics, operative data, hospital length of stay, 30-day reoperation, 30-day readmission, discharge disposition and postoperative complications including VTE complications were collected. Results: A total of 3,155 patients (1752M, 1403F) and 4 CPT codes were included in the study. The median age was 61 years and median BMI was 27. There were 637 (20%) transfers from an outside facility and 605 (19%) were smokers. Average operative duration was 284 minutes and median hospital length of stay was 8 days. There were 2118 (67%) patients treated with spine instrumentation of 3 to 6 levels (CPT 22842), 631 (20%) patients with spine instrumentation of 7 to 12 levels (CPT 22843), 379 (12%) patients with spine instrumentation of two levels (CPT 22840) and 27 (< 1%) patients with spine instrumentation of at least 12 levels. A total of 173 (5.5%) patients developed at least one VTE complication. Spinal instrumentation of 12 levels or greater was associated with the highest rate of VTE (15%) followed by spine instrumentation of 7 to 12 levels (7%), spine instrumentation of 3 to 6 levels (5%), and spine instrumentation of two levels (3%). We performed a Pearson's chi-squared test of independence to verify if the distribution of the presence of VTE complications varies with the associated CPT code. The chi-squared test resulted in X2 of 13.54, and a p-value 0.0036. Conclusion: Spine instrumentation on greater number of vertebral levels is associated with a higher incidence of postoperative VTE complications compared to instrumentation performed on fewer levels in patients with oncologic spinal pathologies. There was an overall VTE rate of 6% in this patient population. This varied based on the number of levels instrumented with a 3% rate for a 2-level procedure and a 15% rate for a 12-level or greater procedure.

1286

P519: Preoperative serum albumin predicts length of stay and perioperative complication following vertebral corpectomy and posterior stabilization for oncologic spinal pathology

Takshi Hirase ¹ , Khaled Taghlabi ² , Jesus Cruz-Garza ² , Amir Faraji ² , Rex Marco ¹ , and Comron Saifi ¹

¹ Department of Orthopedics and Sports Medicine

² Neurosurgery, Houston Methodist Hospital, Houston, United States

Introduction: Patients undergoing vertebral corpectomy and posterior stabilization for oncologic spinal pathology have relatively high rates of perioperative complications. Low preoperative serum albumin levels have been associated with increased perioperative complications following elective spine surgeries. The present study aimed to evaluate the hypothesis that preoperative serum albumin levels are associated with perioperative outcomes following vertebral corpectomy and posterior stabilization for oncologic spinal pathology. Methods: The 2010 to 2019 National Surgical Quality Improvement (NSQIP) database was used to identify all patients undergoing vertebral corpectomy and posterior stabilization for spine tumor excision. Multiple logistic regression ordinal models were used to examine the relationship between preoperative serum albumin levels on perioperative outcome measures. Receiver operative characteristic (ROC) curve analysis and Youden index were used to determine preoperative serum albumin cut-off values for predicting perioperative complications. Results: A total of 301 patients were included in the study. Lower serum albumin was associated with longer post-operative LOS (p < 0.001) and higher incidence of perioperative complications (p < 0.001). ROC curve analysis demonstrated serum albumin < 3.25 g/dL as an independent predictor for perioperative complications. After multiple logistic regression modeling, for every unit decrease of serum albumin (g/dL), there was a 2.3 times higher chance of increase in length of stay by one week (95% CI: 1.8, 2.7; p < 0.001) and 1.9 times higher chance of incurring any perioperative complication including surgical site infection, urinary tract infection, and need for post-operative blood transfusion (95% CI: 1.3, 2.7; p < 0.001). There were no significant association between serum albumin and operative time, need for intraoperative transfusion, 30-day reoperation, 30-day readmission, or discharge disposition. Conclusion: Low serum albumin levels is associated with a longer postoperative LOS and a higher incidence of perioperative complications among patients undergoing vertebral corpectomy and posterior stabilization for tumor resection. Strategies to improve preoperative nutritional status in patients undergoing this procedure may improve these outcome measures.

1297

P520: Risk factors for complications and prolonged lenght of stay in a single institution retrospective cohort of 336 patients

Luigi Falzetti ¹ , Cristiana Griffoni ¹ , Giovanni Barbanti Bròdano ¹ , Carlotta Cavallari ¹ , and Alessandro Gasbarrini ¹

¹ Department of Spine Surgery, IRCCS Istituto Ortopedico Rizzoli, Bologna, Italy

Introduction: Over the last decades the total number of spine surgery procedures has increased significantly worldwide. Numerous advancements in surgical techniques, devices and relevant technological innovations contributed to this increase. Despite these developments, the incidence of adverse events (AEs) in spinal surgery is still high and clinically relevant. The goal of this study is to collect the complications occurring in a referral centre for spinal surgery, using a reliable method to capture and classify intra-operative and post-operative complications, namely SAVES v2 system (Spinal Adverse Events Severity system), and to identify risk factors related to complications and factors influencing length of stay (LOS). Material and Methods: All AEs of patients who underwent spinal surgery at our Department between January 2017 and January 2018 were retrospectively collected. Patients’ characteristics including sex, age, comorbidities (Charlson Comorbidity Index), ASA score and prior exposure to spinal surgery, the type and setting (emergency or elective) of the surgical procedure were collected. The LOS during the index admission was calculated for each patient. Analyses for potential risk factors of complication and prolonged LOS were performed using logistic regression models. Results were reported as odd ratios with 95% confidence intervals (95% CI). Results: In the 1-year period from January 2017 to January 2018 a total of 336 patients underwent spinal surgery (223 non-oncological and 113 oncological patients). Two-hundred-ten AEs were recorded retrospectively (30 intraoperative AEs, 138 early postoperative AEs and 42 late postoperative). Ninety-nine patients (29.5%) had at least one complication. Intraoperative complications were more frequent in the oncological group (23 AEs/113 patients) than in the non-oncological group (7 AEs/223 patients). Early post-operative complications were most of the recorded complications (138/210, 66%) and were more frequent in the oncological group than in the non-oncological group (46% vs 38%). The rate of late post-operative complications was similar in the two groups (15% vs 11%). In the non-oncological group, different factors (age > 75 years old, anatomical region, surgical time > 3 hours, instrumentation, previous surgeries, type of surgery) were associated with complications but only surgical time > 3 hours was confirmed as risk factor for complications at multivariate analysis (OR=5.0 (95%CI:1.8-13.9)). Surgical time > 3 hours and the presence of a post-operative complication were associated with increased LOS, however the presence of a post-operative complication was the only risk factor for increased LOS at multivariate analysis (OR = 3.3 (95%CI:1.5-7.1)). In the oncological group, surgical time > 3 hours, instrumentation, previous surgery were factors associated with complications but only the presence of previous surgeries was confirmed as risk factor for complications at multivariate analysis (OR = 3.4 (95%CI:1.3-8.6)). Surgical time > 3 hours and post-operative complications were confirmed as risk factors for prolonged LOS at multivariate analysis (respectively: OR = 2.7 (95%CI:1.0-7.3), OR = 3.5 (95%CI:1.3-9.3)) while age > 65 and comorbidity index > 2 were not. Conclusion: Spine surgery has a relatively high incidence of complications that can lead to increased morbidity and mortality. Better categorization of complications and recognition of risk factors for complications and prolonged LOS are fundamental to improve patients’ safety and clinical outcomes.

1302

P521: White cord syndrome following posterior decompression and fusion for severe OPLL and an acute cervical traumatic injury - A case report and review of literature

Sai Gautham Balasubramanian ¹ , Prokopis Annis ¹ , and Aditya Dahapute ¹

¹ Spinal Deformity Unit, The Walton Centre NHS Trust, Liverpool, United Kingdom

Introduction: White cord syndrome (WCS) refers to the observation of intramedullary hyperintensity due to edema/ischemia and swelling on postoperative T2-weighted MRI sequences in the setting of unexplained neurological deficits after cervical spinal cord decompression. Ischemia-Reperfusion Injury typically occurs after a cervical decompression surgery, where a chronically compressed spinal cord is injured by reperfusion following decompression. Patho-physiologically, WCS/Re-Perfusion Injury occurs due to oxygen derived free radicals as a result of acute reperfusion to the previously under-perfused cord or direct trauma from blood flow itself. Intraoperative neurophysiologic monitoring (IONM) can give early warning and detect neurologic deficits which can allow surgeon to take necessary measurements apart from preventing medico-legal complications. In this context, we are sharing our experience of a case with chronic severe OPLL of cervical cord with an acute traumatic cervical spine injury who underwent decompressive surgery and developed quadriplegia postoperatively without any perceptible iatrogenic technical cord trauma, documented by IONM and post-operative MRI with classical signs of RPI/WCS. Materials & Methods (Case Description): A 63-year-old male presented with a low velocity fall at home followed by quadriparesis. X-ray images on presentation showed C6 fracture through upper end plate with local kyphosis. The CT scan demonstrated C6 fracture with ossification of the posterior longitudinal ligament from C2-T3, most severe from C2-4 with C6 fracture which extended posteriorly to bilateral facet joints in addition to DISH. MRI images showed there is marked spinal canal stenosis from C2 down to C4 due to ossified posterior longitudinal ligament with intrinsic signal changes in the cord. On decompression, MEP signals were not present below C4. Immediate post-op MRI was done to rule out any compressive pathology. MRI showed T2 hyperintensity of the cord at C3 level which appeared expanded with a central syrinx. Cord oedema was noted at the C3 level. No evidence of epidural haematoma or other compressive lesion at the operative site and the diagnosis of WCS/RPI was established based on post-op MRI findings as there were no other discernible cause of Quadriplegia. Conclusion:White Cord Syndrome is essentially a diagnosis of exclusion. Very rarely, patients sustain severe/new neurological deficits post-operatively attributed to WCS. Unless, this is confirmed post-operatively with classical MRI signs of intramedullary hyperintensity and other extrinsic causes of cord injury/compression is ruled out, the diagnosis should not be invoked. IONM can help us detect such an event occurring intra-operatively and help us take appropriate measures in a timely manner. IONM should be the standard of care in such cases of decompressive surgeries where there is a severe chronic compression of cervical cord and, decompression will trigger a cascade of re-perfusion injury to the spinal cord leading to disastrous complications. IONM is also highly beneficial in alerting the surgeons intra-operatively and also provides a source of permanent record of what exactly happened intra-operatively to prevent medico-legal complications. Understanding WCS/RPI is a valid diagnosis in such circumstances would be helpful in detailed consenting processes and help prevent an additional surgery for the patient which might further increase the risks of mortality and morbidity.

1358

P522: The prognostic role of neutrophil-to-lymphocyte ratio, platelet-to-lymphocyte ratio, and systemic immune-inflammation index on short- and long-term survival following spinal metastasis surgery

Jessica Ryvlin ¹ , Seung Kim ¹ , Mousa Hamad ¹ , Rafael De La Garza Ramos ¹ , Saikiran Murthy ¹ , Yaroslav Gelfand ¹ , and Reza Yassari ¹

¹ Department of Neurological Surgery, Montefiore Medical Center/Albert Einstein College of Medicine, Bronx, United States

Introduction: The immune system has been shown to play a significant role in metastatic tumor progression and prognosis, especially in the setting of surgical intervention. Specific peripheral inflammatory markers, including neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), and systemic immune-inflammation index (SII) have similarly shown promise in predicting both short-term and long-term mortality in a rage of primary tumor types and interventions. However, these metrics have not been evaluated in patients with metastatic spine disease. The purpose of this study was to elucidate the predictive ability of preoperative NLR, PLR, and SII on postoperative 30-day mortality and overall survival (OS) amongst patients receiving surgery for spinal metastases. Methods: This was a single-institution retrospective cohort study. A total of 153 patients who met inclusion criteria and received surgical intervention for metastatic spine disease between April 1, 2012 and April 30, 2022 were identified. Electronic medical records (EMR) were manually reviewed, and collected variables included patient demographics, medical comorbidities, oncologic history, lab values within 30 days prior to surgical intervention, and morbidity details. NLR (n/l), PLR (p/l), and SII (p*n/l) were manually calculated from preoperative neutrophil (n), platelet (p), and lymphocyte counts (l). Receiver operator characteristic (ROC) curves with areas under the curve (AUC) were generated to determine optimal cutoff values based on Youden’s index. Univariate logistic regression was used to determine significant predictors of 30-day mortality, after which variables were included in a multivariate logistic regression model to control for potential confounders in determination of odds ratios (OR). The Kaplan-Meier method with log-rank test and multivariate Cox proportional hazards regression analysis were used to determine hazard ratios (HR) in OS analysis. Results: Cutoff values to define high NLR, PLR, and SII were calculated to be > 10.2, > 260, and > 2900, respectively. Overall, 36% (55 of 153) of patients were found to have high NLR, 46% (70 of 153) had high PLR, and 31% (47 of 153) had high SII. The total 30-day mortality rate was 8.5% (13 of 153). After controlling for potential confounders such as BMI, ECOG performance status, and primary cancer type, high preoperative NLR (OR = 5.20; 95% CI 1.21-22.28; p = 0.026) and SII (OR=4.92; 95% CI 1.17-20.63; p = 0.029) were found to be significantly associated with increased odds of 30-day postoperative mortality. The median OS time in our population was 25.9 months (95% CI 11.8-40.0 months). After controlling for confounding variables such as ECOG performance status, primary cancer type, hypoalbuminemia, and smoking history, only high NLR was found to be significantly associated with overall mortality (HR = 2.31; 95% CI 1.32-4.03; p = 0.003). PLR was found non-significant in adjusted analysis of both 30-day mortality and OS. Conclusions: In this study, preoperative high NLR and SII were found to be independently and significantly associated with 30-day postoperative mortality. High NLR was also found to be independently associated with increased risk of poor OS. These metrics may ultimately be used for surgical planning and outcome prediction in patients with metastatic spinal tumors; however, further validation is needed in this population.

1398

P523: Barbed suture versus interrupted suture in posterior cervical spine surgery: are they equivalent?

Alan Tang ¹ , Anthony Steinle ² , Hani Chanbour ¹ , Andrew Croft ² , Godwin Emeka-Ibe ² , Byron Stephens ^1,2,3 , Scott Lawrence Zuckerman ^1,2 , and Amir Abtahi ^1,2,3

¹ Department of Neurological Surgery

² Department of Orthopaedic Surgery

³ Center for Musculoskeletal Research, Vanderbilt University Medical Center, Nashville, TN, United States

Introduction: Posterior cervical spine approaches have been associated with increased rates of wound complications compared to anterior approaches. While barbed suture wound closure for lumbar spine surgery has been shown to be safe and efficacious, there is no literature regarding its use in posterior cervical spine surgery. In a cohort of patients undergoing elective posterior cervical spine surgery, we sought to compare postoperative complication rates between barbed and traditional interrupted suture closure. Material and Methods: A retrospective review of demographics, past medical history, and operative and postoperative variables collected from a prospective registry between 07/2016-07/2020 was undertaken. All patients 18 years+ undergoing elective posterior cervical fusion were included. The primary outcome of interest was wound complications, including surgical site infection (SSI), dehiscence, or hematoma. In addition, numerical rating scale (NRS) neck pain (NP), NRS arm pain (AP), Neck Disability Index (NDI), and operative time were collected. A variety of statistical tests were used to compare the two suture groups. Results: Of 117 patients undergoing posterior cervical fusion, 89 (76%) were closed with interrupted suture and 28 (24%) with barbed suture. The interrupted cohort were more likely to have > 1 comorbidity (p < 0.001), diabetes mellitus (p = 0.013), and coronary artery disease (p = 0.002). No difference in postoperative wound complications between interrupted/barbed sutures was observed after univariate (OR 1.07, 95% CI: 0.27-4.25, p = 0.927) and multivariable logistic regression analysis (OR 0.77, 95% CI: 0.15-4.00, p = 0.756). Univariate logistic regression revealed no differences in achieving minimal clinically important difference (MCID) NRS-NP (OR 0.73, 95% CI: 0.28-1.88, p = 0.508) or NRS-AP (OR 0.68, 95% CI: 0.25-1.90, p = 0.464) at 3 months between suture groups. The interrupted suture group was less likely to achieve MCID NDI at 3 months (OR 0.29, 95% CI: 0.11-0.80, p = 0.016). Conclusion: The use of barbed sutures, compared to interrupted sutures, was associated with similar postoperative wound complication rates, including surgical site infection wound, dehiscence, and hematoma development. However, while both groups experienced improvement in PROs at 3-month follow-up, more patients closed with interrupted sutures achieved MCID NDI. The findings of this study should be taken into consideration by surgeons in selecting suture type in closing posterior cervical fusion patients.

1483

P524: Mechanical complications requiring revision surgery in long fusion down to sacrum for adult spine deformity: single surgery and single institude experience

Azmi Hamzaoglu ¹ , Hamisi Mraja ¹ , Celaleddin Bildik ¹ , Tunay Sanli ¹ , Halil Gok ¹ , Onur Levent Ulusoy ¹ , Ayhan Mutlu ¹ , Selhan Karadereler ¹ , and Meric Enercan ¹

¹ Scoliosis-Spine Center Istanbul, Istanbul, Turkey

Introduction: Surgical treatment of adult spinal deformity (ASD) is challenging and prone to complications. The aim of this study to evaluate the rate and characteristics of mechanical complications of ASD patients who required revision surgery performed by a single surgeon at a single institution. Methods: Primary ASD patients, > 50 years, > 2 years f/up, fusion > 5 levels, fusion down to the pelvis were included. Hospital charts were reviewed for demographic data and characteristics of complications. The mechanical complications were identified as proximal junctional failure (PJF) and distal junctional problems. Patients were grouped according to the fixation type; single rod (SR) and Multi rod (MR) fixation. Preop, postop and f/up x-ray were reviewed. ODI and VAS scores were used for clinical assessment. Results: 205 (141F, 64M) ASD patients with mean age was 66 (50-85) years and f/up was 8.2 (2-19) years were included. Single rod fixation in 124 patients and Multi rod fixation in 81 patients were used. A total of 19 (9.3%) patients required revision surgery. 11 (5.4%) patients were revised for proximal junctional failure (screw loosening at UIV in 6 (3%) patients and UIV Fracture in 5 (2.5%) patients). 8 (3.9%) patients were revised for distal junctional problems; S1 screw loosening in 3 (1.5%) patients, rod fracture between L2-L5 levels in 3 (1.5%) patients, L5-S1 pseudoarthrosis in 2 (1%) patients despite previous interbody fusion. The onset of proximal junctional failure was mean 9.7 months and 20.3 months for distal junctional problems. Among 19 patients, SR was used in 16 (84%) patients and MR was used in 3 (16%) patients. SR group was revised for proximal junctional failure in 8 patients and distal junctional problems in 9 patients. MR group was revised for proximal junctional failure in 1 patient and distal junctional problem in 3 patients. Patients with distal junctional problems had a high rate of PI-LL mismatch (%66.6), obesity (67.6%) and osteoporosis (52%) were the most common patient related factors. ODI and VAS scores were improved in all after revision surgery at f/up. Conclusion: This study showed 9,3% revision rate among 205 adult spinal deformity patients operated by a single surgeon. Revision indications were proximal junctional problems (screw loosening and fracture at UIV) in 5.4% of the patient and distal junctional problems in 3.9% of the patients due to S1 screw loosening, rod fracture between L2-L5 levels and L5-S1 pseudoarthrosis despite previous interbody fusion. Adult spinal deformity patients with Multi rod constructs showed less mechanical complications than Single rod constructs. Obesity (67.6%), PI-LL mismatch (%66.6) and osteoporosis (52%) were the most common factors related with mechanical failures. All patients benefit from revision surgery with improved clinical outcomes.

1541

P525: The reliability of cortical bone trajectory instrumentation in adjacent segment disease

Kim-Soon Oh ^1,2

¹ Orthopaedics, Hospital Universiti Tunku Abdul Rahman, Kampar, Malaysia

² Spine Centre, Island Hospital, Penang, Malaysia

Introduction: Cortical bone trajectory (CBT) screws have been described for use in adjacent segment disease when extension of the pre-existing instrumentation column was required. This technique employed minimal access and did not require removal of the original instrumentation. Material and Methods: 14 patients with single-level adjacent segment disease at the cephalad end of previous instrumented lumbar fusion were studied from 2017 till 2022. They were followed up for a minimum of 24 months. Parameters studied included clinical signs of instability and radiographic imaging; radiographs and computed tomograms. 9 of these patients were elderly, and of these, 7 had bone density T-scores worse than or equal to -2.5. All patients were operated upon by the same surgeon. Results: There was no deterioration in physical function or worsening of clinical symptoms. Follow-up imaging did not reveal any implant loosening or implant failure. At the end of 24 months or more, 13 patients displayed evidence of radiographic fusion. The one patient who did not, was clinically well and had resumed his preoperative level of physical activity. Conclusion: The CBT technique appears to be a viable option for use when faced with an adjacent segment disease that requires extension of the preexisting instrumentation. Certainly, a meaningful number of cases need to be curated and studied in order to realise its true significance.

1549

P526: Cervical myelopathy surgical outcomes between two neighboring medical institutions: a comparative analysis

Nyssa Kantorek ¹ and Carlos Bagley ²

¹ Medical School, University of Texas Southwestern Medical Center, Dallas, United States

² Neurological Surgery, University of Texas Southwestern Medical Center, Dallas, United States

Introduction: Cervical myelopathy consists of degeneration of the spinal cord involving deficits in neurological function. Previous studies compared surgical treatment outcomes in different age groups, however, demographic and socioeconomic influences have not been explored. This study investigates the differences in outcomes for patients with cervical myelopathy at a large urban academic medical center and a tertiary urban safety net facility based on disease severity, demographics, and socioeconomic information. Due to the safety net hospital status and care for a patient population that is largely uninsured or lacking in consistent primary care, we hypothesize that safety hospital patient patients may present later and experience poorer surgical outcomes than the tertiary academic facility. Material and Methods: Using data from the local Spine Registry and ClinDEN databases for patients surgically treated at UTSW-affiliated hospitals and Parkland Memorial Hospital, it was essential to establish a proxy for disease severity since there are none established in the literature. We discovered that pain may be a reliable method of measuring disease severity since we found that patients who experienced more pain tended to have worse surgical outcomes and less satisfaction with surgery. This was measured with the PROMIS pain scale. Further analysis consisted of correlative studies using R programming language to see if race/ethnicity, personal medical history, or socioeconomic status were associated with either worse pain and/or worse surgical outcomes. After defining these correlations for the two institutions individually, we then compared the results to find parallels or differences. Results: Baseline pain served as an adequate proxy for disease severity for our analysis as determined by measuring the correlation between the patient reported pain and survey responses regarding patient satisfaction with their surgical outcome 3 months post-operatively. Demographic analysis demonstrated Black patients were both more likely to present with worse pain before and after surgery than their White or other race counterparts. Only patients with congestive heart failure experienced worse pain at baseline prior to surgery compared to those with diabetes, hypertension, and cancer. Peri-operative complications for patients included constipation, urinary tract infections, kidney failure, myocardial infarction, and others. The most common complications were constipation and UTI as expected due to opioid analgesics and prophylactic antibiotics. The more serious or life-threatening surgical complications all correlated with worse baseline pain and arguably more severe presentation. Conclusion: For a public safety net, such as Parkland Memorial, many of the patients lack insurance and consistent primary care. For example, many patients utilize the emergency department to fill medications instead of treating emergent medical concerns. More research is required on disparities in spinal surgery to determine if potential solutions, such as screening, are more beneficial than they are harmful for the patients with limited access to primary, secondary, and tertiary care. It is also essential to further understand why Black patients and those with certain personal medical histories are presenting with later disease. Studies such as these are essential for the understanding of the patients’ perceptions and experiences with cervical myelopathy given the potential devastating consequences of this condition.

1556

P527: Grip strength predicts the occurrence of postoperative proximal junctional kyphosis in patients with degenerative scoliosis

Xueyu Hu ¹

¹ Spine Surgery, The First Affiliated Hospital of Air Force Military Medical University, Xi ' an, China

Background: Previous studies have suggested a correlation between grip strength and paravertebral muscle volume in spine, with greater grip strength being associated with greater muscle volume. Studies also reported a significant decrease in paravertebral muscle volume in patients with proximal junctional kyphosis (PJK), in adult spinal deformity patients, a significant decrease in cross-sectional area of the T10-L2 paravertebral muscles was observed in patients who developed PJK. Grip strength has been shown to be a factor in assessing the prognosis of several spinal disorders. This study hopes to investigate whether grip strength could be used as a predictor of the occurrence of PJK after surgery in patients with adult spinal deformity. Methods: This is a prospective case-control study, patients aged 40-90 years old suffering from degenerative scoliosis and treated with posterior fusion internal fixation at the First Affiliated Hospital of Air Force Military Medical University from March 2020 to December 2021 were selected according to the following criteria. Inclusion criteria: (1) Suffering from degenerative scoliosis (Cobb angle > 10° in the coronal plane) and treated with posterior fusion internal fixation; (2) At least 2 segments fused; (3) At least 2 years of follow-up. Exclusion criteria: (1) Age < 40 years; (2) Unable to complete clinical and imaging follow-up; (3) Hand trauma, and other factors might affect the process of muscle strength measurement; (4) History of congenital scoliosis, vertebral slippage, spinal trauma, and other spinal surgery. Patients were divided into high grip strength group and low grip strength group by clustering based on the grip strength values measured at admission and comparing the concordance of baseline levels between the two groups. The incidence of PJK, ODI, EQ-5D scores, early complications such as pulmonary embolism, intestinal obstruction, urinary tract infection, transient delirium, epidural hematoma and neurological dysfunction and late complications such as screw loosening and pseudoarticular formation were compared. Results: 395 patients were included, there were no significant differences between the two groups in terms of age, gender, surgical segment or duration of surgery. However, significant differences were observed in the number of co-morbidities. The incidence of postoperative PJK was significantly lower for patients in high grip strength group compared to those with low grip strength, but there was no significant difference in postoperative ODI and EQ-5D scores between the two groups. The incidence of epidural hematoma was significantly lower in the high grip strength group, but there was no significant difference in the incidence of other short-term postoperative complications and long-term pseudarthrosis. Conclusion: In this study, the high grip strength adult deformity scoliosis patients showed a significant decrease in the incidence of postoperative PJK, although the high grip strength group had better performance in ODI and EQ-5D scores, this difference was not statistically significant.

1623

P528: Dural tear a feared complication of spine surgery

Ihsan Ullah ¹ , Abdul Sattar ² , Mohammad Arif ² , Samir Kabir ² , and Zahid Wazir ²

¹ Orthopedics and Spine Unit, DHQ Hospital Daggar, Buner, Pakistan

² Hayat Abad Medical Complex, Peshawar, Pakistan

Objective: To investigate the incidence, risk factors and clinical presentation of complications in patients undergoing spinal surgery with and without Dural Tear. Methods: One-year prospective observational case-control study conducted in the department of orthopedics and spinal surgery at the Hayatabad Medical Complex (HMC). The spine surgeon used a discrete surgical approach. The questionnaire was used to collect patient demographic data, surgical information, and data on perioperative and postoperative complications. Results: Dural tears were observed in 3.4% of the patients, among whom 20% of the patients experienced a Dural leak. After controlling for potentially confounding variables of age, sex, primary disease, and type of procedure, the surgery-related complications that were more likely to occur in the Dural Tear group than in the non-TD group were surgical site complications OR 2.69 and postoperative neurological defect O 3.28. The proportion of postoperative delirium OR 3.22 was significantly high in the Dural Tear group as perioperative complications. Conclusion: There is a higher proportion of surgical site infection, postoperative neurological defect and postoperative delirium in the Dural Tear group that are due to complications direct, such as Dural leakage.

1715

P529: Sacroiliac joint degeneration and pain after spinal arthrodesis: a systematic review

Marco Manzetti ¹ , Alberto Ruffilli ¹ , Francesca Barile ¹ , Giovanni Viroli ¹ , Marco Ialuna ¹ , matteo traversari ¹ , tosca cerasoli ¹ , fabio vita ¹ , and Cesare Faldini ¹

¹ 1 ^st Orthopedic and Traumatology Clinic, IRCCS - Istituto Ortopedico Rizzoli, Bologna, Italy

Introduction: Aim of the present study is to review the available literature concerning sacroiliac joint (SIJ) pain and degeneration after lumbosacral fixation to identify prevalence and potential risk factors. Although numerous factors can predispose patients to SIJ degeneration and pain various clinical studies indicate lumbosacral arthrodesis as a major cause. Material and Methods: The PubMed-MEDLINE, Cochrane Central Registry of Controlled Trials and Embase Biomedical database were searched. Peer-reviewed comparative studies, cohort studies, case series studies and case control studies, conducted either in a retrospective or prospective design, that registered data about SIJ pain and degeneration after lumbosacral fixation were included. Results: Twenty-one studies including 2678 patients met the inclusion criteria. The percentage of SIJ pain after lumbosacral fixation diagnosed with injections and physical examination varied widely, from 3% to 90%. Among patients who underwent spinal fusion, SIJ pain prevalence was higher when arthrodesis was fixed compared to floating fusions (59% vs 10%, p value > 0.05). The prevalence of SIJ degenerative changes at CT scan were more frequent in patients who underwent spinal arthrodesis than in those who did not (75% vs 38.2%, p value = < 0.05). Conclusion: According to current evidence, patients who received lumbosacral fixation are at risk of SIJ pain. Number of fused levels, involvement of pelvis or sacrum in the arthrodesis area, inadequate lumbosacral sagittal alignment and site of bone graft harvesting could be possible risk factor leading to sacroiliac degeneration and pain after lumbar spine fixation that should be investigated by physicians. However, there is a lack of homogeneity of the studies that address the problem, therefore, further prospective comparative studies, with a homogeneous architecture and cohorts are needed.

1716

P530: Intrathecal morphine trial/pump infusion therapy for post-surgical spine syndrome: side effects and complication

Jung Hoon Sul ¹ , Ju chul Yang ¹ , Tae Wan Kim ¹ , Da Hoon Hong ¹ , and Kwan Ho Park ¹

¹ VHS Medical Center, Seoul, South Korea

Introduction: A few cases of post-surgical spine syndrome (PSSS) are resistant to standard treatments. IT morphine therapy has improved pain control and side effects over systemic analgesics alone. There are complications associated with the intrathecal catheter, the implanted pump, the management of the device, and the drugs themselves. Material and Methods: A total of 24 patients with post-surgical spine syndrome were reviewed. All patients underwent IT trial or IT pump implantation. Complications were divided into three categories: pharmacology, equipment, and procedure. Results: Most common complications were transient pharmacologic side effects (n = 7) with procedural (n = 2), and equipment (n = 1). Most common symptoms were transient urinary difficulty and/or pruritis. The serious complications were large lumbosacral subdural hematoma and intradural fibrotic tissues at lumbar puncture site (n = 1). There was a case of mid-catheter occlusion by precipitated morphine crystals (n = 1). Another case showed skin necrosis of back operation site. Conclusion: The pharmacologic complications are transient. There are serious complications such as procedure-related large subdural hematoma or intrathecal catheter blockage. With a better understanding of the intrathecal drugs, equipment, meticulous procedure technique, various complication can be reduced.

1756

P531: Orthostatic intorelance during early mobilization after enhance recovery after surgery (ERAS) Program for minimally invasasive lumbar interbody fusion

Weerasak Singhatanadgige ¹ , Panapol Varakornpipat ¹ , Vit Kotheeranurak ¹ , and Worawat Limthongkul ¹

¹ Orthopedics, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand

Introduction: Early postoperative mobilization is essential after spinal surgery. It can reduce pulmonary complication and DVT. Postoperative orthostatic intolerance (OI) may limit early recovery or lead to fainting, falls, and fracture. The prevalence of orthostatic intolerance has not been reported after minimally invasive lumbar interbody fusion. This study assessed the hemodynamic response to early mobilization after minimally invasive lumbar interbody fusion with ERAS program. Material and Methods: Orthostatic intolerance and blood pressure response to sitting and standing were evaluated by used non-invasive hemodynamic monitor devices with a two-difference mobilization protocol at preoperative, 6, 12, 24, 48 hours after surgery in 30 patients undergoing single level Minimally invasive lumbar interbody fusion with an ERAS regimen. Two protocols were compared: (A) Patients supine, sit and suddenly stand. (B) Patients supine, sit and rest 30 seconds and stand. Haemoglobin, fluid balance, and opioid use were recorded. Systolic (SBP) and diastolic (DBP) arterial pressure, heart rate (HR), cardiac output (CO), stroke volume (SV) and oxygen saturation were measured. Results: In standard protocol (A), no demonstrated OI before surgery, whereas 8 (27%) patients had OI at 6 hours after surgery but no patients had symptoms of OI at 12, 24, 48 hours. OI was associated with significantly decreased orthostatic responses in SBP, DBP, SV, CO, MAP at 6 hours (p < 0.001). However, protocol B showed significantly decreased rate of OI at 6 hours compared protocol A (p < 0.001). Postoperative haemoglobin concentration and opioid dose was not associated OI. The Clinical outcomes were significantly improved in all patients. All patients were discharged to home on postoperative day 3 without complications or readmission. Conclusion: Twenty-seven percent of patients have OI when start ambulate at 6 hours after surgery. We suggest that the patients should rest at sitting position at least 30 seconds before start walking. Start ambulation after 12 hours is safe without demonstration of OI.

1765

P532: Paramedian approach versus median approach lumbar puncture: a systematic review and meta-analysis protocol

Yuan-Dong Zhuang ¹ , Fenfen Yao ² , Xuanjie Chen ² , Yihang Lin ² , and Zhengqiong Lai ²

¹ Neurosurgery, Fujian Medical University Union Hospital, Fuzhou, China

² Basic Medical College, Fujian Medical University, Fuzhou, China

Introduction: Lumbar puncture is one of the most common neurosurgical invasive procedures in modern medicine. It is widely and frequently used by neurosurgery, anesthesiology, pediatrics, and other departments. However, the application of lumbar puncture in the clinic, especially the success rate during surgery, has not yet had a clear technology with the highest success rate. By searching for relevant clinical trials, we found that lumbar puncture through different approaches has a significant impact on the experience of doctors and patients during surgery. This study will review the randomized controlled trial of the lumbar paramedian approach and compare it with the lumbar median approach. Material and Methods: A detailed search will be conducted of Web of Science, Pubmed, Cochrane, and EMBASE without language or publication type restrictions. The retrieval task is basically completed. Patients of any age and sexuality will be included in our study. All analyses will follow the intention-to-treat principle. Results: We take the number of needle passes as our main results. The secondary outcomes included the following: the number of attempts, time taken to identify landmarks, blood tap, periprocedural pain score, and patient's discomfort during the spinal procedure radicular pain. This study will be analyzed by calculating the Relative Risk (RR) with a corresponding 95% Confidence Interval (CI). For continuous outcomes, the weighted mean difference with 95% CI will be calculated. If a continuous outcome is reported as a median, we will assume a normal distribution and consider the median as a mean. If measures of dispersion are reported as a range, 95% CI, or standard error of the mean, we will calculate the standard deviation (SD) by using relevant formulae outlined in the Cochrane Handbook for Systematic Reviews of Interventions. Conclusion: Four reviewers will independently perform a quality assessment. The Cochrane Collaboration’s tool will be used to assess the risk of selection, performance, detection, attrition, reporting, and other biases among included randomized trials. If there is insufficient information provided to make a judgment, we will categorize the study as having an unclear risk of bias and the original study authors will be contacted for further information. Trials with one or more high-risk components will be judged as having an overall high risk of bias. The Newcastle-Ottawa Scale will be used to assess observational studies on selection, comparability, and exposure. Studies that receive at least one star in every domain will be categorized as being of high quality. Any disagreements during the quality assessment will be resolved through discussion and consensus. If necessary, consult a fifth reviewer. Results from this study are expected to significantly change clinical practice. By comprehensively examining the evidence on paramedian approach in comparison to median approach for lumbar puncture, this review is expected to inform clinicians on which approach to use for procedures to minimize patient suffering and improve the success rate.

1801

P533: Hyperacute postoperative thoracic spine epidural haematoma and it's uncomplicated spontaneous resolution - a case report

Stjepan Dokuzovic ¹ , Jure Pavesic ¹ , Stipe Corluka ¹ , and Vide Bilic ¹

¹ Spinal Surgery Division, Traumatology Department, University Hospital Centre Sestre Milosrdnice, Zagreb, Croatia

Introduction: Spinal epidural haematoma, whether spontaneous or post-surgical, can be a devastating complication if not promptly recognized and treated. This condition often requires primary decompression and drainage (if spontaneous haematoma) or revision surgery (if it is a postoperative complication). Anterior localization of a thoracic level postoperative haematoma may require revision surgery, which is significantly more demanding and more neurologically risky than the initial surgery due to the possibility of causing further “hits” to the compressed spinal cord. Material and Methods: We present the case of a young patient operated on for routine stabilization of a 2 level thoracic vertebra fractures (Th6 and Th12) who developed total paralysis due to a postoperative hyperacute epidural haematoma localized anterior to the cord, however the course was quickly spontaneously reversed prior to revision surgery. This misfortune was thankfully spontaneously resolved prior to revision surgery simply by elevating the upper body and having the haematoma “drain” itself more caudally down the canal where there is more space. Results: The patient did not have any medical risk factors for developing such a haematoma postoperatively, though developed a haematoma regardless, either from the fracture line or from an epidural venous bleed. Roughly an hour after surgery, complete paralysis was noted. Upon radiological confirmation by emergency MRI scanning, we elevated the upper part of the body to prevent cranial migration of the haematoma, and complete spontaneous resolution ensued over the next 45 minutes. Conclusion: In cases of epidural haematoma development with neurological impairment, it is not always necessary to perform emergency revision surgery. When the bleeding is hyperacute and not coagulated, it may be possible to let it spontaneously disperse itself along the length of the canal, thus minimizing its local compressive effect. If prompt neurological recovery is not witnessed, the option of emergency revision must still be available.

1884

P534: Prognostic factors for effective spinal cord stimulation therapy for post-surgical spine syndrome

Kwan Ho Park ¹ , Ju chul Yang ¹ , and Tae Wan Kim ¹

¹ Department of Neurosurgery, VHS Medical Center, Seoul, South Korea

Introduction: Post-surgical spine syndrome (PSSS) is a clinical entity, defined as persistent or recurrent back and/or leg pain after spine surgery. Various therapeutic approaches are currently used to treat refractory chronic pain after spinal surgery. A multidisciplinary approach is unlikely to benefit from further formal surgical intervention. Surgery benefits a limited number of conditions, mainly root compression and instability. It is difficult to predict how and where evidence will lead the field over the next 5 to 10 years. Spinal cord stimulation (SCS) techniques via a implanted dorsal column neurostimulator is gaining popularity owing to its substantial superiority over conventional medical management and/or pain intervention. These approaches may provide a rescue treatment for patients who have previously failed surgical and less invasive therapies, offering relief to a patient population among the most difficult to treat. We assess and report on which patient groups are effective for SCS. Material and Methods: Thirty four patients had intractable chronic back and/or leg pain with a diagnosis of PSSS. All patients who underwent SCS implantation were retrospectively reviewed. Preoperative mean Visual Analogue Scale (VAS) score for leg was 7.6. SCS trial was performed to evaluate patient’s response to SCS procedure. We placed percutaneous or paddle leads depending on neurological symptoms. SCS system was implanted in patients with pain reduction more than 50% compared to pre-trial procedure. The mean follow-up was 56 months. Results: Thirty patients were men and four were women. The mean age was 58 years. The patients with leg pain responded favorably to SCS. Back pain of patients did not respond well. SCS was less effective in patients with surgical indication, neural compressive lesions or spinal cord lesion. Preoperative mean VAS score for leg was 7.6 and postoperative VAS score was 4.0. Conclusion: SCS is an effective treatment option for neuropathic pain of PSSS in the absence of a viable surgery. It is mainly effective for patients with leg pain and no neural compressive lesion. Careful patient selection is most important for the success of SCS therapy.

1891

P535: Chance fracture pattern presenting in proximal junctional failure: a case series

Shea Comadoll ¹ , Kenneth Holton ¹ , Jason Haselhuhn ¹ , Paul Soriano ¹ , David Polly ¹ , Michael Schmitz ¹ , Christopher Martin ¹ , Kristen Jones ¹ , and Jonathan N. Sembrano ¹

¹ University of Minnesota, Minneapolis, United States

Introduction: Chance-type fracture is a kind of proximal junctional failure (PJF) that may present with instability, neurologic compromise, and pain. We sought to report a series of patients from our institution who presented with a specific acute Chance-type proximal junctional failure of the upper instrumented vertebra (UIV) that occurred within three months of the index surgical procedure. This report aimed to describe the radiographic features of this Chance-fracture variant, its detection rate, risk factors, and overcorrection rate. Materials and Methods: We reviewed cases of early proximal junctional failure with a specific fracture pattern of the UIV. All index surgeries were performed between September 2013 and February 2020 by fellowship-trained orthopedic spine surgeons or neurosurgeons in our institution as single or dual-surgeon cases. We collected and analyzed demographic data, bone mineral density, and pre- and postoperative radiographic parameters, including lumbar lordosis (LL), L4-S1 lordosis (lower lumbar lordosis or LLL), pelvic incidence (PI), upper segment contour (USC), thoracolumbar sagittal alignment (TL), and proximal junctional angle (PJA). Results: Fifteen patients (11F:4M) were included in the final analysis with an average age of 61.4 years (range 39-77). The average time between index surgery and fracture identification was 25.4 days (range 3-65), and the average number of levels instrumented was 5.6 (range 2-15). None of the patients had antecedent trauma prior to the onset of their fracture. Notable findings included PJF on postoperative images with a CT scan illustrating a fracture extending through the long axis of the upper instrumented pedicle, with the cephalad fragment and the superior articular process displaced superiorly. In 90% of cases with a lumbar UIV, there was overcorrection of LL and/or LLL. Four cases with a lower thoracic UIV had undergone significant correction of preoperative TL junction kyphosis. The reading radiologists did not identify the fracture on 73% of radiographs and 46% of CT scans. Thirteen of the 15 patients were treated with an extension of fusion. Pedicle screws at the fracture level were salvaged by changing to an anatomic trajectory. Conclusion: This case series reports a Chance-type fracture pattern of the UIV that is difficult to detect on plain films and is a unique cause of PJF. Continued pain at 6-12 weeks, along with lateral radiographs showing increased proximal junctional angle and cephalocaudal pedicle widening at the UIV, should raise suspicion about this unique fracture pattern. Obtaining a CT scan is highly recommended. Low bone density, LL or LLL overcorrection, and selection of lower thoracic UIV in the setting of significant TL junction correction may contribute to fracture risk.

1935

P536: The use of high-dose tranexamic acid in spine surgery: an analysis of perioperative variables and patient outcomes

Chenyi Yang ¹ , Alexander Himstead ¹ , Nolan Brown ¹ , Joshua Kurtz ¹ , Neal Patel ¹ , Shane Shahrestani ¹ , Julian Gendreau ¹ , Martin Pham ² , and Joseph Osorio ²

¹ Neurosurgery, UC Irvine, United States

² Neurosurgery, UC San Diego, United States

Introduction: Previous literature has repeatedly demonstrated the effective use of antifibrinolytic agents such as tranexamic acid (TXA) for reducing blood loss during spine surgery. However, there is concern that high doses of TXA may increase the risk ofcomplications, such as thromboembolism or seizure. Materials and Methods: The purpose of this retrospective case series was to delineate perioperative outcomes and complications in patients that underwent spinal procedures with administration of high-dose TXA (2350 mg – 7500 mg) at a single institution. A retrospective chart review was performed on all adult patients who received surgery in the cervical, thoracic, or lumbar regions between September 2019 and March 2020.The total dose of TXA administered during the surgery along with perioperative complications were recorded. Results: Thirty-six patients were treated with intraoperative high-dose TXA during the study period. Mean age was 56.6 (range: 22 - 82). Average BMI was 27.2 (5.1) kg/m². Average preoperative CCI was 3.0 (2.7). Mean number of spinal levels operated on was 6.9 (4.3). Seven cases (19.4%) were revision surgeries. Of the 36 cases, 1 included pedicle subtraction osteotomy (2.8%), 4 included vertebral column resection (11.1%), and 20 included a posterior column osteotomy (55.6%). Mean intraoperative blood loss was 587.1 (900.0) mL, and total blood loss was 623.8 (991.9) mL. Postoperatively, time to ambulation was on average 1.7 (1.7) days. Mean total length of stay was 9.8 days (7.9, range 2 - 41). The most common indication for surgery was tumor (n = 9, 25%), followed by fracture (n = 8, 22.2%), deformity (n = 7, 19.4%), pseudarthrosis (n = 6, 16.7%), and degenerative disc disease (n = 2, 5.6%). There were no thromboembolic or other significant complications among the 36 patients. Conclusion: This retrospective case series demonstrates that the use of high-dose TXA provides a safe and effective outcome in adult patients undergoing spine surgery.

1997

P537: Does the use of a smoke evacuation device reduce smoke exposure in the OR? A prospective study

James Hall ¹ , Joshua Eisenberg ¹ , Alex Coffman ¹ , Natalie Glass ¹ , Catherine Olinger ¹ , Cassim Igram ¹ , and Andrew Pugely ¹

¹ Orthopedics and Rehabilitation, University of Iowa, Iowa City, United States

Introduction: It is widely accepted that inhalation of smoke, specifically the particulate matter therein, can cause adverse health effects. In June 2018, Rhode Island was the first state to enact a law mandating the use of a smoke evacuation system in the operating room. Nine more states followed suit in 2020. The presence of dangerous compounds in surgical smoke is well established in the literature, but few have investigated the utility of smoke evacuation in spine surgery. With increased scrutiny on surgical smoke levels, these devices should be further studied. Therefore, the primary aim of our study was to evaluate the efficacy of two smoke evacuation systems in reducing surgical smoke levels in spine surgery. Secondary aims of our study were to determine patient, facility, or equipment factors that may influence surgical smoke levels. Material and Methods: Consecutive patients undergoing spine surgery at a single institution had surgical smoke levels measured utilizing the PCE instruments particle counter (PCE-PCO 2). Room set-up was standardized such that the particle counter was positioned on an IV pole nearest the anesthesiologist. Smoke particle levels were measured during the first hour of the procedure. The two smoke evacuators used were a smoke evacuator pencil (SEP) with suction in line with a cautery tip, and a para incisional vacuum (PIV) that utilizes a large suction tube affixed adjacent to the wound. The evacuators were compared to one another and to a control group. We evaluated the relationships between evacuation systems (SEP, PIV, control) and a) average b) peak levels of 0.3 µm particle size and c) overall particle count. We then evaluated for relationships with patient, room and/or surgery factors. Results: In total, 117 patients were included in the study. SEP was employed in 36 cases, PIV in 43, and no evacuator in 38. Groups did not vary regarding patient demographics or room characteristics. There was a significant reduction in average 0.3 µm, peak 0.3 µm, and average overall particle levels when using either the SEP or PIV. SEP reduced average 0.3 µm, peak 0.3 µm, and average overall particle levels by 55%, 55%, and 54% respectively. PIV reduced those levels by 68%, 86%, and 72% respectively. Additionally, a significant reduction in peak 0.3 µm particle levels was noted with PIV when compared to SEP. Multivariable analysis revealed significance in room size and number of operative levels. Specifically, a smaller operating room and greater number of operative levels both independently contributed to increased levels of surgical smoke measured. Significance was defined as p < 0.05. Conclusion: Our results show that both the SEP and PIV effectively reduce operating room smoke levels during spine surgery. Furthermore, the PIV shows superiority in reducing peak smoke levels. This study supports the use of a smoke evacuation device to reduce surgical smoke levels and thus reduce the potential associated health risk to operating room personnel.

Trauma - Cervical

53

P538: Management of lower cervical spine fracture - dislocation associated with severe traumatic brain injury: case report and surgical treatment for an uncommon lesion association

Ghassen Gader ¹ , Mohamed Amine Gharbi ² , Mouadh Nefiss ² , Mohamed Badri ¹ , Mohamed Zouaghi ¹ , Ramzi Bouzidi ² , Ihsen Zammel ¹ , and Anis Tebourbi ²

¹ Department of Neurosurgery, Trauma and Burns Center, Ben Arous, Tunisia

² Department of Orthopaedics, Mongi Slim Hospital, La Marsa, Tunisia

Introduction: Traumatic brain injury (TBI) is the leading cause for death and severe functional impairment in young adults. Outcome for severe TBIs is worse when associated to other extracranial traumatisms. Simultaneous TBI and cervical spine injury (CSI) occurs in 4–8% of TBIs. CSIs occurring concurrently with severe head injuries deeply worsen the patient’s condition because of potentialization and occultation of the traumatic lesions, but also because of some therapeutic situations in which the management of a lesion may worsen the other. Material and Methods: We report the case of a patient operated for a TBI through a decompressive craniectomy, and who needed management for a fracture-dislocation of the lower cervical spine. Based on this case, we went through a review of associations between head and cervical spine trauma, with particular highlights on controversial therapeutic situations like ours. Case description: We report the case of a 26 years-old male patient, victim of an accidental fall from the roof of his house, which corresponded to a 6 meters height. He was immediately transferred to the emergency department. Initial physical exam found a prostrate patient with a Glasgow Coma Scale (GCS) of 12/15, with incomplete tetraplegia. Brain CT scan showed a temporo-parietal fracture associated to a right hemispheric epidural hematoma with a maximal thickness of 3.2 cm. Cervical spine CT scan showed comminuted bilateral facet fracture-dislocation C6 to C7 responsible for an 8 mm antelisthesis. The patient quickly developed a comatose state with a GCS that decreased to 4/15, associated to a right anisocoria. He was intubated, sedated, and placed under mechanical ventilation. Regarding the neurologic distress, surgical management for the intracranial lesion was decided. But viewing the cervical fracture-dislocation that was prone to worsen on head positioning prior to the hematoma's evacuation, the patient underwent at first a reduction and realignment of the cervical spine. This approach was mandatory as neurosurgical and orthopedic departments were not located at the same institution, thus the necessity to immobilize the cervical spine before any transfer. The reduction was processed through closed manual maneuvers by axial traction and hyperextension. Afterwards, patient was transferred to the neurosurgical department where the hematoma was evacuated through a decompressive craniectomy. Three days after, the patient underwent a C6-C7 interbody fusion through an anterior cervical approach using an iliac crest bone autograft. An anterior cervical screw-plate was used for stabilization. Reduction was verified peroperatively by fluoroscopy. The outcome was unfavorable as the patient died three weeks later in the follows of a severe ventilator-associated pneumonia. Conclusions: TBIs and CSIs are frequently associated in the course of polytraumas. Head and cervical spine injuries are systematically assessed in all polytraumas followed by a comatose state, taking in count that their association may result in increased mortality and morbidity, an impairment of the quality of life, and hindering the rehabilitation process.

64

P539: Treatment strategy for pedicle fractures of the C2 axis

Jong-Beom Park ¹ , Dong-Gune Chang ² , and Young-Yul Kim ¹

¹ Orthopaedic Surgery, The Catholic University of Korea College od Medicine, Uijeongbu-si, South Korea

² Orthopaedic Surgery, Inje University Sanggye Paik Hospital, Uijeongbu-si, South Korea

Introduction: C2 pedicle fracture (PF) is not an uncommon injury1-7 but have been less focused than dens fractures or Hangman’s fractures. The anatomical structure of the C2 PF differs significantly from other pedicles of the same cervical spine as well as the lumbar and thoracic vertebrae. Due to its distinct anatomical features, spine surgeons often do not understand the exact location of the C2 pedicle and confuse C2 PF with pars interarticularis fracture. Also, little information is available about the characteristics and treatment strategy for C2 PFs. We sought to investigate the characteristics of C2 PF and to propose appropriate treatment strategy. Material and Methods: A total of 49 patients with C2 PF were included in this study. We divided these patients into unilateral and bilateral C2 PFs group. The incidence rates and characteristics of other associated C2 and C2-3 injuries and other cervical injuries were evaluated. In addition, treatment methods and outcomes were analyzed. Results: Twenty-two patients had unilateral C2 PFs and 27 patients had bilateral C2 PFs. Among the cases of unilateral C2 PF, all patients had one or more other C2 fractures and 20 patients (90.9%) had one or two C2 body fractures. Meanwhile, among the cases of bilateral C2 PF, all patients had two or more other C2 fractures and one or two C2 body fractures. In unilateral C2 PFs, 3 patients with C2-3 anterior slip or adjacent cervical spine (C1-3) injury underwent surgery and 19 patients (86.4%) were treated with conservative methods. In bilateral C2 PFs, 3 patients with C2-3 anterior slip or SCI at C2-3 underwent surgery and 24 patients (88.9%) were treated with conservative methods. Conclusion: Our results showed that C2 PF do not occur alone and are always accompanied by other associated C2 injuries. C2 PF should generally be thought of as a more complex fracture type than Hangman's fracture or dens fracture. In spite of the complex fracture characteristics, most C2 PF can be managed with conservative treatment. However, surgical treatments should be considered if the C2 PF are accompanied by the C2-3 anterior slip and adjacent cervical spine injury.

122

P540: Intraoperative sensory signals predict prognosis for patients with traumatic cervical spinal cord injury

John Renehan ¹ , Ivan Ye ¹ , Alexandra Thomson ¹ , Tyler Pease ¹ , Ryan Smith ¹ , Robin Fencel ¹ , Brittany Oster ¹ , Daniel Cavanaugh ¹ , Eugene Koh ¹ , Daniel Gelb ¹ , Bryan Ferguson ² , Bizhan Aarabi ³ , Steven Ludwig ¹ , and Vache Hambardzumyan ¹

¹ Spine Surgery Division, Orthopaedics

² Anesthesiology

³ Neurosurgery, University of Maryland School of Medicine, Baltimore, United States

Introduction: In patients with traumatic cervical spinal cord injury (tCSCI), the potential role of intraoperative neuromonitoring as a prognostic tool has been insufficiently studied. This study aimed to determine if detectable signals during intraoperative neuromonitoring portend a greater likelihood of recovery for patients with tCSCI. Materials and Methods: Patients who underwent decompression and surgical fixation following tCSCI were retrospectively reviewed through previously prospectively collected data from the Surgical Timing in Acute Spinal Cord Injury Study (STASCIS). Improvement in ASIA motor score and AIS grade conversion rates at final follow-up were compared between patients with detectable intraoperative neuromonitoring somatosensory evoked potential (SSEP) signals and those without detectable signals. Results: A total of 49 patients had intraoperative neuromonitoring. Patients with incomplete tCSCI had detectable lower extremity SSEPs more often than patients with complete tCSCI (56.3% vs. 23.5%, p = 0.028). There was no difference in detectable upper extremity SSEPs between complete and incomplete tCSCI (65.6% vs. 58.8%, p = 0.638). Of the 17 patients with complete tCSCI, patients with detectable lower extremity SSEPs had ASIA motor scores similar to the non-detectable cohort on admission (21.5 vs. 16.2, p = 0.609) but higher ASIA motor scores at final follow-up (57.5 vs. 27.1, p = 0.041). Of the 32 patients with incomplete SCI, there was no difference in grade conversion or motor scores between detectable and non-detectable SSEP cohorts. Conclusions: The presence of upper extremity SSEP signals in patients who present with complete tCSCI portends greater improvement in ASIA motor scores and likelihood of AIS grade conversion at final follow-up.

144

P541: Outcomes in patients with vertebral injury after blunt cervical spine trauma

Romil Shah ¹ , Devender Singh ² , Ayane Rossano ¹ , and Eeric Truumees ²

¹ Orthopedics, The University of Texas at Austin, Austin, United States

² Spine, Ascension Texas Spine and Scoliosis, Austin, United States

Introduction: Vertebral artery injury (VAI) occurs in almost 1% of all blunt trauma hospital admissions. No large study has been conducted investigating outcomes of VAI in blunt cervical trauma. Aim: The aim of this study was to evaluate 1-year outcomes in patients with blunt cervical spine trauma with vertebral artery injuries. Materials/Methods: Data from the National Trauma Data Bank (NTDB) of adult patients with cervical vertebral, ligamentous, or neurological trauma from 2016 and 2017 were analyzed. Patients who died within 3 days of admission were excluded. Demographic, injury specific information (mechanism, severity), patient health information, and a variable indicating the presence of vertebral artery injury were collected as explanatory variables. Response variables collected included development of adverse events (DVT/PE, myocardial infarction (MI), stroke, hemorrhage, or neurological deficit) length of stay (LOS), intensive care unit (ICU) LOS, and unplanned ICU admission or surgical procedure. Multivariable regression was used to calculate the risk-adjusted effect of vertebral artery injury on the presence of adverse events and unplanned events as well as its relationship with LOS and ICU LOS. Results: 128,908 patients with cervical trauma were reviewed, of which 5,300 had VAI. Of the patients with VAI, 187 (3.5%) patients had a MI, 156 (2.9%) had a PE/DVT, 196 (3.7%) had a stroke, 1392 (26.3%) had neurologic injury, and 443 (8.4%) had an unplanned operative procedure or ICU admission. After risk-adjustment, VAI was associated with a greater than 2-fold increased risk of increased LOS and ICU LOS (p < 0.001), as well as greater than a 2-fold increased risk of MI, PE/DVT, stroke, and neurologic injury (p < 0.001). Conclusions: Vertebral artery injury in cervical trauma is associated with increased adverse events and length of stay in the ICU and in the hospital. Trauma providers should be aware of these increased risks when treating patients with VAI in cervical trauma.

539

P542: Surgical outcomes of subaxial cervical fractures in patients with spinal ankylosing diseases

Sara Diniz ¹ , Manuel Carrapatoso ¹ , Catarina Pereira ¹ , João Soares do Vale ¹ , Filipe Jardim Rodrigues ¹ , Arnaldo Sousa ¹ , and Ricardo Rodrigues-Pinto ¹

¹ Orthopaedic Department, Centro Hospitalar Universitário do Porto, Portugal

Introduction: Spinal ankylosing diseases are a group of pathologies associated with decreased bone quality (such as osteopenia or osteoporosis), stiffness, and increased susceptibility to unstable fractures that can lead to neurological important damage. Due to the high associated instability of these fractures, several surgical treatments have been proposed, such as long instrumentations (anterior or posterior) or combined instrumentations. A clinical and radiological evaluation of cervical fractures was carried out in a patient with an ankylosed spine. Material and Methods: Between 2012 and 2019, all cases of cervical fractures in patients with an ankylosed spine who were admitted to the emergency department of Orthopaedics of a single center were evaluated. Demographic, and fracture pattern imaging data (based on X-ray, CT-scan and MRI), as well as surgical variables and clinical outcomes were analyzed. Results: Twelve patients (11 men and 1 woman; mean age of 76 ((± 8.1); Two cases due to a road accident, one case due to a fall from a tractor, four due to a fall from > 2 m, five due to a fall from standing height. The mean time from trauma to surgery was 42.9 (± 44.6) hours. Average length of stay of 23.1 days. Five type C and seven type B AO fractures (five B2 cases and two B1 cases). Two of the cases of type C fracture required cranial traction to reduce the dislocation. Mean fracture segment migration of 1.96 (± 1.1) mm in AO type C. As for pre-surgery neurological deficits, one ASIA A case, one ASIA C, four ASIA D, and six cases of ASIA E. Eight patients were submitted to anterior fixation (two levels above and two levels below), one was managed by posterior approach, and the remaining three to 360° fixation. The mean surgery time was 164.6 (±131.5) min. There were two cases of surgery failure (16.7%), both after isolated anterior fixation, requiring conversion to 360° fixation. Most patients recovered their neurological status (66.7%) and progressed to ASIA E. Conclusion: These lesions are related to devastating neurological prognosis and morbidity. Despite the small number of cases, there were two losses of fracture reduction, both in cases of isolated anterior approach. Due to its biomechanical superiority, combined fixation (360°) should be considered as the first line of treatment in patients with an ankylosed spine.

674

P543: Profile, incidence and outcome of patients diagnosed with cervical spine injury admitted at Southern Philippines Medical Center - Department of Orthopedics: a retrospective review

Ali Farhan Pendaliday ¹ and Jeremiah Morales ¹

¹ Department of Orthopedics, Southern Philippines Medical Center, Davao, Philippines

Introduction: Cervical spine injury, accounts for approximately 50% of all spinal cord injuries. It is one of the most overwhelming cause of morbidity and mortality in industrialized and developing countries. Profiling and determining the outcome of traumatic cervical spine injuries will provide us with a database identifying the different causes of injury, co-morbidities and reasons for mortality of admitted traumatic spinal cord injury (SCI) patients in Southern Philippines Medical Center (SPMC). This will provide additional source of information since there is no nationwide database currently available. This study aims to create a registry geared towards improving data collection of SCI profile. This registry can be used for future researches that will help improve orthopedic health care in the future. Materials and Methods: This is a retrospective descriptive study conducted on all traumatic cervical SCI patients admitted at SPMC from the year 2015 to 2017. Chart review was done and the following information were gathered: age, sex, etiology, level of injury, diagnosis, neurologic status, surgical and nonsurgical management, and disposition. Data was tabulated and the mean was computed. Results were then interpreted in a descriptive manner. Results: A total of sixty-one (61) patients were included in the study. Fifty-six were male and five were female. Fall was the leading cause of most spinal cord injuries at 60.65%. Thirty (30, or 49.18%) presented as ASIA A upon admission. C4-C5 level was the most commonly involved cervical spine segment at 49.18%. Most of the patients with cervical SCI had bilateral facet dislocation as the most common morphology at 36.06%. The most common surgery performed was application of Gardner wells traction with 38 cases recorded. Mean days before undergoing surgery was 10.07 days ± 19.83. Most common complication that developed on admitted patients was hospital acquired pneumonia. Disposition of patients were mostly discharged at 42.62%. Conclusion: Fall is the leading cause of injury among Filipinos with cervical SCI in SPMC as compared to the National Spinal Cord Injury Database (NSCID) data which is road traffic accident. The lack of local data is the main reason for the conduction of this study. The demographic and clinical profile gathered can be used as part of the national database. The creation of this standardized and comprehensive registry will provide means of collecting accurate data from SCI patients nationwide. This can be used for future researches and treatment protocols.

Keyword: Cervical, Profile, Trauma, SPMC, Spine

677

P544: Inhibitory factors for paraplegia improvement in cervical spinal cord injury surgery patients

Shinji Tanishima ¹ , Tokumitsu Mihara ¹ , Chikako Takeda ¹ , Masaki Yoshida ¹ , Satoshi Fujiwara ¹ , and Hideki Nagashima ¹

¹ Division of Orthopedic Surgery, Department of Sensory and Motor Organs, School of Medicine, Faculty of Medicine, Tottori University, Yonago, Japan

Introduction: Cervical spinal cord injuries, once they occur, can be severely disabling. Surgery is currently the most effective treatment, although various regenerative therapies are still under development. On the other hand, it is also a fact that there are cases in which early surgical intervention fails to improve the condition. The purpose of this study was to examine the inhibitory factors for improvement of paralysis in patients with cervical spinal cord injury who underwent surgery. Subjects and Methods: It was a single-center, retrospective study. We recruited twenty-three patients with preoperative ASIA impairment scale (AIS): A to C among cervical cord injury cases operated on in our department were included in the study. There were 19 males and 4 females, with a mean age of 66.6 ± 18.6 years old. Patients were classified into two groups: the improved group (n = 11), whose AIS improved by at least one level at the last observation, and the non-improved group (n = 12), whose AIS did not improve at the last observation. Comparison was made between the two groups based on gender, age, BMI, smoking history, time from injury to surgery, comorbidities, concomitant trauma, postoperative complications, and presence of DISH/OPLL complications. Results: AIS at the time of injury was B:4cases and C:7 cases in the improved group, and A:5 cases, B:4 cases, and C:3 cases in the unimproved group, showing a significant difference between the groups (p = 0.037). No other differences were found between the groups for other parameters. Since the AIS A cases may have influenced the results, a similar comparison was performed in a sub analysis of the two groups excluding the AIS A cases. Only BMI tended to be higher in the non-improved group than in the improved group (21.1 vs. 25.1, p = 0.051). Conclusion: There were no cases of improvement in AIS A. With the exception of AIS A, cases with high BMI showed poor improvement.

703

P545: Tear drop fractures of the axis: management and treatment of 8 cases

Adnene Benammou ¹ , Balti Walid ¹ , Cherif Kamoun ¹ , Ahmed Ben Abid ¹ , Khaled Hadhri ¹ , Mondher Kooli ¹ , and Mohamed Ben Salah ¹

¹ Orthopedic Surgery Department, Charles Nicolle Hospital, Tunis, Tunisia

Introduction: Teardrop fractures of C2 are extremely rare. It is characterized by a fracture of the anterior-inferior corner of the C2 body. The mechanism is usually in extension which is different from the tear-drop of lower cervical spine. Our objective was to assess the clinical and radiological result of patients treated for tear drop fracture of the axis. Material and Methods: We conducted a retrospective study, from 2000 to 2021, including patient who were treated for a tear drop fracture of C2. We excluded patients who had a multilevel spine injury and lost to follow up patients. We collected demographic data, clinical and radiographic characteristics as well as the chosen treatment: conservative or surgical. We also noted the evolutionary data. Results: Our study included 8 patients. All of our patients were victims of traffic accidents. None of our patients had neurological deficits. All patients were explored with a Computed Tomography (CT) scan. Orthopedic treatment using a rigid collar was undertaken in 7 cases for which no signs of instability were noted. Only one patient underwent surgical treatment. Decision was made on the presence of signs of instability. Surgery consisted in an anterior approach with a C2-C3 discectomy and fusion. Postoperative was uneventful. Fracture union was achieved in all patients. No complications were noted. Conclusion: As opposed to lower cervical spine, C2 teardrop fractures are different by mechanism, rarity of neurological signs and their management. Treatment can be conservative if there are no signs of instability. Surgical management is dedicated to instable fracture or cases with a big fragment. The outcome is usually satisfying.

707

P546: A rare association of two mechanisms in axis fracture

Jlidi Mohamed ¹ , Walid Bouaicha ¹ , Mohamed Hedi Gharbi ¹ , Mouldi Lamouchi ¹ , Ayachi Montassar ¹ , and Selim Daas ¹

¹ Orthopedics and Traumatology Departments, Hospital of Mohamed Taher Maamouri, Tunisia

Introduction: Upper cervical spine traumas are a serious injury due to its neurological consequences. They are life-threatening fractures and have a poor functional outcome, due to its short-, medium- and long-term complications. C2 fractures are the most frequent. They are the subject of several descriptive classifications according to the mechanism of injury. The case that we describe in this work associates two different fracture entities, either in the location of the fracture line and by the mechanism of the lesion. These two entities combine to create an unusual fracture. Material and Methods: A 64-year-old man, with no previous pathological history, was brought to the emergency department by the civil protection following a 2-meter fall. The exact mechanism of the trauma was difficult to precise because the patient had a post-traumatic amnesia. On admission clinical examination shows forehead dermabrasion, he complained of both wrists and neck pain. The neurological exam was normal. Peripheral examination showed a deformity of both wrists without skin or vascular lesions. A neurosurgery emergency was eliminated. X-rays and CT scan of cervical spine showed bi-pedicular fracture and "Tear-Drop" fracture, both on the C2 vertebra with a bifocal fracture of the posterior arch of C1. X-rays of both wrists showed a bilateral fracture with posterior displacement of the distal radius. Non-operative treatment was decided and consisted of immobilization with a five-support neck brace (shoulder, sternum, back, occiput, lower jaw) for four months until consolidation. Percutaneous pinning under axillary block was indicated for the fracture of both wrists. Results: The neurological examination remains unchanged, and vertical position was allowed on the fourth day post-traumatic. Dynamic X-rays were requested as soon as the neck brace was removed and did not show any instability of the cervical spine. Cervical CT scan at 4 months post-trauma confirmed the consolidation. After 24 months, the patient did not complain about neck pain and dynamic X-rays of the did not show any instability. Conclusion: The case we report thus combined two previously separately described entities with different causal mechanisms. On one hand, a pedicle fracture of C2, supposedly produced by a mechanism of sudden hyperextension, and on the other hand, a "Tear-Drop" fracture of the same vertebra, classically caused by a mechanism of axial compression. Regarding treatment, we took into account the following parameters:

- The age of the patient

- The absence of neurological signs

- The absence of concrete clinical data on the long-term evolution of this type of deformity

- The absence of local kyphosis of C2 on C3

- The fact that the fracture of the antéro-inferior corner of the vertebral body is secondary to a sudden tensioning of the anterior longitudinal ligament. In this case, the injury was considered stable and treated non-surgically.

938

P547: Retrospective analysis of patients with cervical spine injury submitted to surgery in a tertiary hospital in São Paulo

Luiz Claudio Rodrigues ¹ , Fernanda Andrea Navarro ² , Rodrigo Nakao ² , and Nathalia Adelina Pereira ¹

¹ Spine Surgery, Santa Marcelina College of Medicine, São Paulo, Brazil

² Spine Surgery, Hospital Santa Marcelina, São Paulo, Brazil

In the present study we analyzed retrospectively patients who suffered from cervical spine lesions and were submitted to surgical treatment in a tertiary hospital in the east parto f São Paulo, an area of elevated trauma of the city. Between January 2007 and December 2016, data about 44 patients were collected, considering age, gender, type of lesion, trauma mechanism, vertebral level of lesion, surgically addressed spine levels, year of occurrence, type of surgery performed, cause of trauma, neurological status according to the Frankel scale and incidence of immediate complications. The main cause of cervical spine trauma are motor vehicle accidents, followed by high falls. Most cases of patients were male (72.7%). O principal fator causador de fraturas de coluna cervical são os acidentes com veículos automotores, seguidos de queda de altura. A maioria dos casos ocorreu em pacientes do gênero masculino (72,7%). It appears that prevention measures can be taken to diminish the severity of cervical spine trauma and thus, sequels and rehabilitation time of its victims, specially in big urban centres on which mobility is mainly by cars, the most related factor to this type of lesion.

1262

P548: C2-C3 complex fracture subluxation with vascular injury: an unusual presentation

Mohamed Amine Gharbi ¹ , Houssem Eddine Chahed ¹ , Hedi Ezzine ¹ , Mahdi Bouzidi ¹ , Tborbi Anis ¹ , Ramzi Bouzidi ¹ , Ezzaouia Khelil ¹ , and Mouadh Nefiss ¹

¹ Orthopedic and Trauma Surgery, Mongi Slim Marsa University Hospital Center, Tunis, Tunisia

Introduction: Upper cervical spine injuries have the potential to be fatal and debilitating due to injury to multiple components.Treatment decisions is also challenging due to the lack of an unifying algorithm. Materials and Methods: We present the case of a polytrauma patient with a hangman’s fracture, an unstable tear drop fracture of the axis and a concomitent internal carotid aneurysm. Results: A 26-year-old male was brought into the emergency room with multiple injuries after motor vehicle accident. Computed tomography (CT) scan of the cervical spine revealed a hangman’s fracture and a C2C3 tear drop fracture. No subluxation was noted on initial CT. Neurologic status was difficult to evaluate however the patient reported a change in muscle strength of his upper left limb during his stay in intensive care. A new CT scan showed the displacement of the C2C3 tear drop with recoil of C2 at the canal level. He had C1-C3 fixation. Postoperatively, he complained of headache and visual disturbance. Angio-CT scan and an MRI showed an internal carotid aneurysm. Endovascular occlusion was discussed but not performed and he had only anticoagulant treatment. A 6 month follow-up CT sacn of the spine and of the aneurysm demonstrated stability and intact instrumentation. Conclusion: To date, there is no unifying algorithm to guide treatment decisions in many cases of upper cervical spine injuries.Vascular injuries have to be taken into consideration before choosing the approach. In our case going anteriorly would have been a disaster in front of the presence of the aneurysm of the internal carotid artery.

1264

P549: Delayed tramatic atlantoaxial sponylptosis with type II odontoid fracture presenting with occipital neuralgia

Rakesh Kumar ¹ and John Small ¹

¹ Adventhealth Carrolwood, United States

Introduction: Traumatic Type 2 odontoid fracture is often diagnosed early utilizing various criteria after injury. Failure to diagnose and treat appropriately may prove fatal and the risk is significantly higher in the elderly. Spondyloptosis in this context is rare. Neurologic deficits often follow the subluxation. Occipital neuralgia was the presenting symptom in our patient. This led to the diagnosis. Case Report: 83-year-old woman with ground-level fall hitting the back of the head 6 months earlier was discharged after normal head CT. Progressively increasing neck pain thereafter and developing right-sided occipital neuralgia. Atlantoaxial spondyloptosis was found related to type II fracture; but neurologically intact. Intraoperative closed reduction; while motor and sensory electrophysiological monitoring; done initially in the flexed position and then gradually in extension led to partial reduction. Open reduction was then performed after the right atlantoaxial joint was opened and decorticated; while direct dorsal traction-reduction on the posterior arch of the Atlas with a towel clip. Immediate relief of pain and maintained stability and fusion in follow-up. Conclusion: Rigorous utilization of criteria to exclude cervical spine injury is important. Occipital neuralgia is an early warning manifestation of atlantoaxial instability; as is well recognized in rheumatoid arthritis. Open reduction is often feasible with direct atlantoaxial joint manipulation. As the posterior arch of Atlas is often intact, this may be used for traction and reduction avoiding direct force on the lateral mass screws.

1273

P550: Surgical treatment of odontoid fractures: surgical strategy and outcomes of a series of transarticular C1-C2 screw fixation by Magerl's technique

Sofia Caldeira Dantas ^{1 2} , André D. Carvalho ¹ , Arnaldo Sousa ¹ , and Ricardo Rodrigues-Pinto ¹

¹ Department of Orthopaedics, Centro Hospitalar Universitário do Porto, Spinal Unit (UVM), Portugal

² Department of Orthopaedics, Hospital do Litoral Alentejano, Portugal

Introduction: Odontoid fractures account for nearly 20% of cervical spine injuries and, in the elderly, are associated with a high incidence of nonunion, morbidity and mortality. While these are frail patients, most studies suggest that elderly surgical treatment should be offered to those with type II and unstable type III fractures. However, this approach is still controversial and the ideal surgical technique is not clearly defined. Material and Methods: This was a retrospective analysis of a consecutive series of elderly patients with odontoid fractures submitted to transarticular C1-C2 screw fixation by Magerl’s technique between 2008 and 2022. Clinical and radiological data were analyzed, as well as complications and reinterventions during follow-up. Results: Eighteen cases were included (9 males and 9 females). The last four cases were performed through a percutaneous approach, while the initial were performed through an open approach. The average patient age was 75.8 years old (min. 56; max. 88 years). Most cases were type II fractures that resulted from a direct trauma (motor vehicle accidents or falls from height). Seventeen percent presented with some degree of neurological impairment at admission. The average surgical time was 116.5 ± 40.2 minutes. No intraoperative complications were reported. The median time of hospital stay was 9.9 days (min. 2; max. 76 days). From the initial 18 patients 5 were lost to follow-up. The median follow-up time for the remaining patients was 256 days (min: 64; max: 944). During that time, complications (infection, neurological impairment, cardiovascular pathologies, respiratory distress, malpositioning and/or pseudarthrosis) were only reported in 1 patient (7.7%), in which a reintervention was required due to screw malpositioning. Moreover, 2 patients (15.4%) self‐reported neck pain and disability. Conclusion: Surgical treatment of odontoid fractures in the elderly is still controversial. This study demonstrates that transarticular C1-C2 screw fixation by Magerl’s technique is a viable technique for the surgical treatment of odontoid fractures in the elderly.

1274

P551: Failure factors of orthopedic treatement of a tear-drop C2 fracture: a case report and review of the literature

Safouen Ben Brahim ¹ , Mzid Ahmed ¹ , Khalil Habboubi ¹ , ben mohamed oussama ¹ , Hassen Makhlouf ¹ , and mondher mestiri ¹

¹ Adult Orthopedic Departement Pr Mestiri, Mohamed Taib Kassab, Mannouba, Tunisia

Introduction: Extension teardrop fractures of the axis are extremely rare cervical spinal fractures. It’s a fracture involving the triangular fragment at the anteroinferior corner of the vertebral body following a hyper-extension mechanism. The stability of this lesion and the choice between orthopedic or surgical treatment remain debated in the literature. We report a case of a neglected tear-drop fracture of the axis which was complicated by neurological disorders of both upper limbs. Case Presentation: Our patient is a 55-year-old woman, with no medical history, who was the victim of a domestic accident. She had a 3-metre fall, causing polytrauma: cranial, axial and peripheral. The clinical examination showed complete paraplegia ASIA "A" level T5 associated with cervico-dorsalgia without neurological deficit of the upper limbs. Initial investigations showed a complex- fracture of T5 with recoil of the posterior wall and a C2 tear-drop fracture with posterior signal abnormalities on the MRI. The course of action was to perform a laminectomy with posterior synthesis from T3 to T9. For the tear-drop fracture, orthopedic treatment was initiated. The patient did not recover the neurological deficit postoperatively (permanent paraplegia). After 3 months, the patient was referred to us due to the appearance of progressive neurological disorders of both upper limbs. Investigations showed a vicious callus of C2 tear-drop fracture with signs of instability and newly spinal cord signal abnormalities in relation to C2. Results: Given this neurotoxicity, it was decided to perform a posterior decompression associated with an occipito-cervical fusion. The postoperative course was simple. Neurological recovery of the upper limbs was noted. Conclusion: Although the radiological appearance of a tear drop fracture of C2 appears simple, it may conceal potentially serious posterior injuries. most patients with an extension tear drop fracture of the axis can be treated conservatively but large fragment size, displacement or angulation, intervertebral disc injury, neurologic deficit, or signs of instability are reasonable indications for surgical treatment.

1294

P552: Gehweiler type III atlas fracture: a difficult decision making injury

Hedi Ezzine ¹ , Mohamed Amine Gharbi ¹ , Ahmed zendeoui ¹ , Moatassem Belleh Jlassi ¹ , Tborbi Anis ¹ , Ramzi Bouzidi ¹ , Ezzaouia Khelil ¹ , and Mouadh Nefiss ¹

¹ Orthopedic and Trauma Surgery, Mongi Slim Marsa University Hospital Center, Tunis, Tunisia

Introduction: The treatment of Gehweiler type III atlas fracture remains controversial and should be analyzed carefully. Materials and Methods: We present the case of a 31-year-old patient with a Jefferson fracture type IIIA according to Gehweiler classification treated at first conservatively. Results: At 6 weeks follow-up we diagnosed an occipito-cervical subluxation and a displacement of the lateral mass of C1 that needed occipito-cervical fusion. Case presentation: A 31 year-old man, fell from a height of 3m causing head and neck trauma. He had a stiff and painful neck and no sensitive nor motor dysfunction. The CT scan showed a Jefferson fracture with no sign of lesion of the transverse atlantal ligament (TAL). So the fracture was classified IIA of the AO Classification and IIIA of Gehweiler classification, and thus was judged stable. The patient had a treatment with a hard collar. In the follow-up after 45 days, he had another CT scan showing displacement of the lateral mass of the atlas, with subluxation of both C1-C2 and C0-C1. The fracture was then classified again as type IC + Type IIB of the AO Classification, IIIB of Gehweiler classification and Dickman type I. The patient was then operated and had an occipito-C3 fusion. Until the last follow-up, the patient had a stabilized aspect of the fracture, with no neurological signs. Conclusion: The TAL plays a crucial role in atlantoaxial stability.In Gehweiler type III fracture this ligament must be carrefully analyzed.Treatment aims to correct the dislocation, restore the stability of the atlantoaxial joint, and retain mobility of the cervical spine.

1427

P553: Clinical outcomes of surgery for patients with spinal cord injury aged 75 and older

Takashi Chikawa ¹ , Toshihiko Matsumura ¹ , and Ayaka Hashimoto ¹

¹ Orthopedic Surgery, Tokushima Prefecture Naruto Hospital, Naruto, Japan

Introduction: The population aged 75 and older accounts for 13.3% in our country. The incidence of traumatic spinal cord injury (SCI) will increase as elderly population continue to increase. Although it is accepted that clinical outcome of surgery for SCI in elderly is lower than that of younger subject because of greater comorbidity burden, there is a paucity of evidence in clinical outcome of surgery in elderly SCI patient. The purpose of this study is to investigate clinical outcome of traumatic SCI patients underwent surgery and to compare with those of younger patient. Materials and Methods: From 2019 to 2021, a total of 38 traumatic SCI patient were treated at our hospital. They were divided into two groups. Group A consisted of 21 patients aged 75 years and older and group B consisted of 17 patients younger than 75 years. In group A, there were 10 male and 11 female and their mean age was 83 years. Ten patients had cervical SCI, 9 patients had thoracic SCI and 2 patients had lumbar spinal and cauda equina injury. In group B, there were 14 male and 3 female and their mean age was 58 years. Six patients had cervical SCI, 6 patients had thoracic SCI, and 5 patients had lumbar spinal and cauda equina injury. All patients in group A had comorbidities such as dementia, Parkinson’s diseases, diabetes, malignant tumor, cardiovascular diseases and chronic renal failure. On the other hand, Six patients of 17 patients had no comorbidities in group B. Decompression was performed in 2 patients and decompression and fusion were performed in 19 patients in group A. Decompression was performed in 3 patients and decompression and fusion were performed in 14 patients in group B. In the current study, time from injury to surgery, time from hospitalization to surgery and Frankel grade before and after surgery were extracted from the electric medical record. Results: In group A and B, time from injury to surgery was 8.7 days and 8.1, time from hospitalization to surgery was 4.8 days and 5.1 days, respectively. There was no statistically significant difference between both groups. Of 21 patients in group A, the Frankel grade before surgery was B in 3, C in 12 and E in 3. At follow-up, C in 1, D in 13 and E in 7, all showed improvement by one grade or more. Of 17 patients in group B, the Frankel grade before surgery was C in 9, D in 1 and E in 7. At follow-up, D in 3 and E in 14. Improvement in Frankel grade of group B significantly superior than that of group A. Conclusion: Improvements of Frankel grade in elderly SCI patients was inferior than younger patient. Factors including preoperative comorbidity burden, lack of physiologic reverse by aging and feeling capacity of the spinal cord might affect the clinical outcome.

1667

P554: Post-traumatic cervical epidural hematoma in children

Ghorbel Mohamed ¹ , Ines Cherif ¹ , Daoud Ahmed ¹ , Kolsi Fatma ¹ , Bel Mabrouk Yassin ¹ , and Boudouara Zaher ¹

¹ Neurosurgery, Habib Bourguiba Hospital, Sfax, Tunisia

Introduction: Cervical epidural hematoma is a rare phenomenon in children. It was first described in 1963 and most of cases are spontaneous. However, trivial injury of the cervical spine without any lesions on bone structures can sometimes cause a serious damage of the neurovascular elements leading to an hematoma. This pathology requires a quick diagnosis and emergent treatment consisting on the evacuation of the hematoma which provide a good prognosis. Material and Methods: We present a case of a patient who was treated for cervical epidural hematoma in the department of neurosurgery in the Habib Bourguiba hospital, in Sfax, Tunisia. Results: We present a case of a 12 years-old girl who was admitted in our service for torticollis, cervico brachial neuralgia and brachial weakness. Three weeks before admission she suffered a neck injury while falling from the bed. On admission, the neurologic exam showed a neurologic deficit with left brachial paresis. X-ray of the cervical spine was done with no signs of traumatic lesion. MRI of the cervical spine revealed the presence of compressive epidural hematoma spanning C3 to C7 which was evacuated urgently after a large Laminoplasty within « open door technique ». There was a large collection of old blood which was liquefied making its evacuation easy. Postoperatively, the patient presented an excellent recovery and the general motor strength of the arm was regained. Conclusion: Cervical epidural hematoma is quite rare in children with incidence of 0.1 per 100. Adequate neurological examination, diagnostics and urgent surgical intervention are of paramount importance for accomplishing good results. Early and persistent rehabilitation are the condition for achieving maximal recovery.

1723

P555: Optimal segmental sagittal alignment for anterior decompression-fusion surgery of damaged subaxial cervical spine

Oleksii Nekhlopochyn ¹ , Ievgenii Slynko ¹ , Vadim Verbov ² , and Yurii Derkach ¹

¹ Spinal Neurosurgery, Romodanov Neurosurgery Institute, Kyiv, Ukraine

² Restorative Neurosurgery Department, Romodanov Neurosurgery Institute, Kyiv, Ukraine

Introduction: Vertical cylindrical mesh implant and anterior rigid plate is the most common combination for performing subaxial cervical spine anterior decompression and fusion surgery. Despite the considerable clinical experience, there is currently no consensus on optimal correction of the height of the operated spinal motion segment and the formation of a certain segmental profile in the surgical intervention zone. The purpose of our study was to improve the state of sagittal kyphosis of the operated segment in the long-term postoperative period in patients who underwent anterior subaxial cervical fusion. Material and Methods: We performed retrospective evaluation and X-ray analysis of sagittal kyphosis in 151 patients after anterior bisegamental subaxial cervical fusion due to traumatic injury. A statistical analysis was made and determined the dependence of the final results on the degree of intraoperative correction. We verified the ranges of intraoperative values of spinal motion segment sagittal contour, forming various biomechanical responses of the cervical spine in the long-term postoperative period. Results: The dependence of the final state of segmental kyphosis of the operated segment was determined by the method of nonlinear regression analysis. Cluster analysis revealed the following ranges of intraoperative values of segmental kyphosis: <- 6,15°; -6,15° ..; -3,1°; > -3,1°, that form different dynamics of postoperative changes. Conclusion: The data analysis clearly demonstrates the connection between the values of sagittal kyphosis achieved during the operation and the values in delayed postoperative period. The intraoperative correction with sagittal kyphosis formation in the range of -6,15°..-3,1° is optimal for preserving the physiological curvature of the operated segment in the long-term postoperative period. The obtained data have both clinical and experimental- biomechanical confirmation.

1890

P556: Number of screws changes the stress-stain state when using vertebral body replacing implants for anterior subaxial cervical reconstruction

Oleksii Nekhlopochyn ¹ , Vadim Verbov ² , Michael Karpinsky ³ , and Oleksandr Yaresko ³

¹ Spinal Neurosurgery

² Restorative Neurosurgery Department, Romodanov Neurosurgery Institute, Kyiv, Ukraine

³ Biomechanical Laboratory, Sytenko Institute of Spine and Joint Pathology, Kharkiv, Ukraine

Introduction: Anterior decompression and fusion is the most widely spread surgery for subaxial cervical spine traumatic injuries. Implantation of a vertebral body prosthesis is important step when reaching the tasks facing the surgeon. Along with the undeniable advantages of the use of fusion systems of various modifications there is a risk of migration due to the imperfection of the methods of fixing prosthesis to the vertebral bodies. The aim of the work was to analyze the stress-strain state model of cervical spine with a substituted C5 vertebra with telescopic prosthesis. Material and Methods: Two variants of the prosthesis: with one or two monocortical screws for fixation to a vertebral body were examined. We obtained the critical values of the stress system with "fixing element - the vertebral body" in various physiological states of the cervical spine: axial load, flexion, extension, rotation. The influence of the fixation method on the load distribution within the main supporting elements of the vertebral-motion segment was analyzed. Results: The application of “classical” implant fixation to the adjoining vertebrae using the paired screws does not have essential advantages over the mono-screw fixation. The evaluation of von Mises equivalent stresses demonstrates essentially higher loading on the implant fixing elements using two screws which definitely increases the amount of risk factors, causing the local imbalance between the processes of bone regeneration and desorption with the domination of latter. Such tendency, undoubtedly, may to some degree facilitate the reduction of the fixing element capacities. At the same time, the mono-screw fixation due to the reduction of loading on the construction fixing elements determines some increase of tensions on the support structures of vertebrae adjoining the resected one, however, no essential peaks of the increase of loading on separate elements are observed. Conclusion: The presence of the second fixing screw leads to the tension increase in the system “cortical screw-vertebral body”. The usage of one screw facilitates more equal distribution of tensions in the system “implant-vertebra” and may be advantageous as to the reduction of the stabilizing constructions migration frequency.

1903

P557: Changes of semental sagittal contour after ACCF with different types of instrumentation

Oleksii Nekhlopochyn ¹ , Iaroslav Tsymbaliuk ² , Vadim Verbov ² , Ievgen Cheshuk ² , and Milan Vorodi ²

¹ Spinal Neurosurgery

² Restorative Neurosurgery Department, Romodanov Neurosurgery Institute, Kyiv, Ukraine

Introduction: Traumatic fracture of cervical spine is one of the most severe types of musculoskeletal system damage, that is caused by a significant frequency of functional disorders in the long-term period. The surgical treatment of subaxial cervical spine traumatic injuries can be performed using various types of fusion systems. The purpose of our study was to assess the stabilizing ability of various types of systems for anterior subaxial cervical fusion based on the segmental kyphosis index of the operated segment in patients with traumatic cervical spine lesion. Material and Methods: We have analyzed X-ray patterns of the cervical spine in 70 patients who underwent anterior subaxial cervical fusion due to traumatic injury. The patients were divided into 2 groups depending on the type of vertebral body replacing and fusion system. A combination of a vertical cylindrical Mesh-type implant with a rigid anterior plate was used for the first group patients’ surgery, and in the second group we have implanted telescopic vertebral body replacement implant integrated with the anterior fixators. Observation terms were estimated: before surgery, 4-6 days after surgery, and after 3, 6 and 12-18 months. Results: The obtained data demonstrate that the total loss of the achieved correction throughout the postoperative period in patients of the first group was 2.78°, while in the second group 0.73°. Furthermore, in the first group, the decrease in the intensity of correction loss is observed by the period of 12-18 months, and in the second group the dynamics convincingly regresses by 6 months. Conclusion: The presented data demonstrates the advantages of using single system for anterior cervical spine fusion. It is caused by the maximum preservation of intraoperatively achieved correction of the cervical spine sagittal profile.

1916

P558: Quality of life in patients with mild spinal cord injury after anterior subaxial cervical decompression-fusion surgery: one-year follow-up

Oleksii Nekhlopochyn ¹ , Vadim Verbov ² , Iaroslav Tsymbaliuk ² , Milan Vorodi ² , and Ievgen Cheshuk ²

¹ Spinal Neurosurgery

² Restorative Neurosurgery Department, Romodanov Neurosurgery Institute, Kyiv, Ukraine

Introduction: Cervical spine traumatic injury is one of the most severe types of human musculoskeletal system lesion. Despite the significant achievements of modern vertebrology, a number of questions concerning the optimal methods of surgical intervention remain quite controversial. The quality of life, along with patients’ neurological disorders regression level after cervical spine trauma, are the basic criteria to determine the effectiveness of the therapy. The purpose of our study is to assess the quality of life of patients in the late postoperative period after anterior decompression-fusion surgery at the subaxial level of the cervical spine due to traumatic injury using various methods of fixation. Material and Methods: A retrospective analysis of the test results of 53 patients using the SF-36 questionnaire was conducted. All patients were hospitalized in the spinal cord pathology department in the period from 2013 to 2017 due to traumatic injury to the cervical spine. Neurological status at the time of hospitalization corresponded to ASIA D or ASIA E. The testing was carried out at the control examination in the period of 12 months of the postoperative period. A combination of “Mesh + ventral plate” and a telescopic vertebral body replacing implant were used as stabilization systems. We analyzed transformed values that were not normalized to population data. Results: When comparing groups of patients with various systems for subaxial fusion, convincing advantage of usage of single construction was determined on SF-36 scales: “Physical functioning”, “Role-Physical Functioning”, “Bodily pain” and “Role-Emotional Functioning”. The scales: “General health”, “Vitality”, “Social functioning”, “Mental health” did not show statistically significant difference. Conclusion: The obtained results demonstrate the advantage of mono-construction as a vertebral body replacing and fusion system, providing the better level of quality of life in the time of 12 months after surgical treatment.

1920

P559: Neurological disorders regression after subaxial cervical spine traumatic injury and ACCF depends on instrumentation

Oleksii Nekhlopochyn ¹ , Iaroslav Tsymbaliuk ² , Vadim Verbov ² , Ievgen Cheshuk ² , and Milan Vorodi ²

¹ Spinal Neurosurgery

² Restorative Neurosurgery Department, Romodanov Neurosurgery Institute, Kyiv, Ukraine

Introduction: Two types of possible constructive solutions are used for fusion of subaxial cervical spine traumatic injury. The first is an independent combination of interbody implant and anterior plating, the second is the single telescopic implant, that combines both principles. The purpose of our study was to analyze the dynamics of regression of neurological disorders in patients with subaxial cervical spine traumatic injury who underwent anterior decompression-fusion surgery with different constructive type of fixation. Material and Methods: Clinical material formed 120 patients with subaxial cervical spine traumatic injury, divided into two groups depending on the type of fusion system used during the operation. The dynamics of neurological disorders recovery was assessed using the International Standards for Neurological Classification of Spinal Cord Injury. Results: The analysis of data reveales following particularity. In the early postoperative period, the dynamics of the neurological disorders regression does not depend on the type of implanted system and is determined to a greater extent by the timing, volume and technique of performed spinal cord decompression. In 3 months postoperative period there was a statistically confirmed difference in the intensity of restoration of neurological functions, mainly due to a slower regression of deficiency in the upper extremities in patients with “Mesh + ventral plate” combination used the during surgery. By 6 months, the described pattern remains, however, the difference in the values of the analyzed groups is not statistically significant. By the final observation period, the difference in the dynamics of recovery is not statistically determined. However, the frequency of complete regression of neurological manifestations and the transition of patients from ASIA D to ASIA E group is largely determined by the type of implanted system (p = 0.0371). Conclusion: The usage of a telescopic implant for anterior interbody subaxial cervical fusion is clinically more approved, since it indirectly provides a more pronounced dynamics of neurological disorders regression.

1934

P560: Is surgical therapy is equally emphatic as conservative treatment in acute traumatic cord syndrome

Gyan Ranjan ¹ and Kumar Anand ²

¹ Orthopaedics, Curesta Hospital, India ² Orthopaedics, Anand Hospital, India

Introduction: Acute traumatic central cord syndrome (ATCCS) is a clinical entity characterized by motor deficit causing a predominant weakness of the upper limbs bladder dysfunction and varying degrees of sensory loss below the level of the lesion. Most common incomplete traumatic cervical cord injury pattern. Accounts for 20% of all cervical spinal cord injuries. ATCCS has a heterogenous etiology. Hyperextension injury acute disc herniations .fractures or dislocations of the upper cervical spine. There are only few studies which have compared conservative with surgical treatment. Their studies are flawed by the poor study design in which they have included unstable injuries in surgical group and stable injuries in conservative group. So we see that there is paucity in the literature regarding ideal modality of treatment of stable variety of TCCS. Aims and Objectives: The purpose of this retrospective study is to compare the motor score improvement and functional status in surgically and conservatively treated patients with stable ATCCS. Materials and Methods: 106 consecutive patients with ATCCS admitted to our spinal unit at CHARAK PALIKA HOSPITAL, NEWDELHI and MGM medical college Kishanganj over a period of 10 years. Patients divided into three groups based on their etiology. Only stable injuries taken, i.e. only patients with PIVD and spinal stenosis group taken in our study.44 patients excluded and 62 recruited in the study. 32 opted for surgical management and 30 for conservative treatment. Pre , intra and post operative data were collected and analysed. Observation and Results: Our study proves that there has been statistically significant improvement in UL,LL motor score, spasticity grade and SCIM score in both surgical and conservative groups (p value < 0.05). However there has been longer hospital (p value 0.68) and ICU (0.74) stay in conservative group, and neurological recovery time (0.62) and bowel, bladder recovery time (0.43) was more in this group, however which is not statistically significant. Thus we see that results of conservative management are equally good to surgical in TCCS. Conclusion: With this available evidence, these patients with ATCCS secondary to an extension injury in a stenotic canal without fracture/dislocation/instability/disc herniation can be given an option to undergo initial conservative management followed by surgery at a later date if there is a neurological deterioration or there is a plateau of neurological recovery. There is a need for high quality prospective randomized control trials to resolve this controversy.

1939

P561: Percutaneous 3D image-guided navigated C1 ring osteosynthesis: initial single center experience

Kristian Varga ¹ , Benedikt Trnovec ¹ , Peter Hudak ¹ , Jakub Sipos ¹ , Milan Liska ¹ , and Kamil Kolejak ¹

¹ Department of Neurosurgery, University Hospital in Bratislava-Ružinov, Slovak Medical University, Bratislava, Slovakia

Introduction: The classical surgical management of unstable C1 fracture by atlanto-axial fusion impacts motion and function. Open surgery can also affect wound healing and duration of hospital stay. We present our initial experience in a modified procedure in unstable C1 fractures – Percutaneous navigated procedure for isolated C1 ring osteosynthesis. Material and methods: The patients were in prone position in a Mayfield carbon headholder. The navigation frame was placed on the head holder. An intraoperative, 3D image navigation system was used for the 1,5 cm skin incision on both sides and the optimal placement of C1 screws. A transverse rod was then placed connecting the two screws under the fascia. The patients were prospectively evaluated in terms of their clinical, functional, and radiological outcomes with a follow-up of 6 months. Results: A total of 4 screws were placed in two patients by this technique with a mean follow up of 6 months. The mean duration of surgery was 123 minutes and the average blood loss was 20 mL. The patients were discharged from the hospital within two days after the surgery. The intraoperative O-arm scan and follow-up CT showed correct placement of screws and wound healing. There were no complication regarding the atlanto-axial stability. Patients returned to their occupation within 2 months. Conclusion: Percutaneous isolated C1 ring osteosynthesis allows a motion-preserving option in unstable C1 fractures. This percutaneous navigated technique can safely compete most commonly used surgical procedures. This mini-invasive method reduce the blood loss during the surgery, hospital stay and preserve the functional status.

1947

P562: Long-term postoperative outcomes in patients with trauma and degenerative spine disease after dorsal cervical stabilization- a single center review in the period of 2011-2016

Andrej Bodrov ¹ and Nikolay Mirchev ¹

¹ Neurosurgery, Hospital of Fulda, Fulda, Germany

Introduction: All of the 171 patients in the present study were operated with mono- and multilevel dorsal or combined 360° stabilization in our clinic in the period from 2011 to 2016 due to a degenerative cervical spinal disease and trauma. Our patients were treated with stabilization systems with pedicular- and massa lateralis screws from dorsal or additionally with cages and plates from ventral. Material and Methods: All of the 171 patients in the present study were operated with mono- and multilevel dorsal or combined 360° stabilization in our clinic in the period from 2011 to 2016 due to a degenerative cervical spinal disease and trauma. Our patients were treated with stabilization systems with pedicular- and massa lateralis screws from dorsal or additionally with cages and plates from ventral. To evaluate the clinical outcome were also used such criteria as age, sex, height and weight, BMI, Neck Disability Index before and after the operations and in the follow- ups, ASA index, the location of the operated segments as well as the number of operated segments, the usage of intraoperative navigation (o-arm), problems with instrumentation, type of pedicle screws (polyaxial, pre-clampable and non-pre-clampable, long-head screws, intraoperative correction of the screw positioning, application of the vertebral body replacement, duration of the operation, need of the second operation. The important criteria for the evaluation of the fusion process were also the rate of the postoperative complications, such as misplacement of the implanted material, fistulas on the dura, postoperative bleeding, infection etc. The fusion was analyzed in the X-ray investigations as well as CT in the period of 3, 6 months and 1, 2,3 5-years after the operation. Results: The participants were divided into groups according to their age: Group A included all patients from 0-45, Group B 45-65 and C 65 y.o. and older. The rate of full fusion was 35.9%, a partial fusion 29.6%, non-fusion in 7.8%, undefined due to absence of the patients at follow-ups was in 21.8%. Conclusion: The outcomes after the operations due to degenerative cervical spine disease and trauma are similar to most literature data. Most important factors affecting the outcome are: age, ASA Index (Pre-existing illness), BMI and Osteoporosis, as well as initial NDI (neck disability index). In the case of osteoporotically changed bone, differences in cervical fusion behavior are found due to the poor bone quality. It is also worth mentioning that factors such as diabetes, smoking or the use of NSAIDs and / or steroids have a negative impact on the fusion rate. We have found out that such factors as age, morbidity (ASA Index), pre- or postoperative pain index (VAS) and NDI influence the postoperative outcome in middle and long-term follow up.

1966

P563: Predictors of neurological recovery after subaxial cervical spine and spinal cord injury

Oleksii Nekhlopochyn ¹ , Vadim Verbov ² , Iaroslav Tsymbaliuk ² , Ievgen Cheshuk ² , and Milan Vorodi ²

¹ Spinal Neurosurgery

² Restorative Neurosurgery Department, Romodanov Neurosurgery Institute, Kyiv, Ukraine

Introduction: Cervical spine injury is one of the most severe musculoskeletal system lesion, due to high disability and neurological disorders. Despite great number of studies, the influence of various factors on neurological disorders regression in patients with traumatic subaxial cervical spine injury at the level is insufficiently studied. The idea of our study was to investigate the nature and influence value of various factors on neurological disorders regression. Material and Methods: We performed a retrospective analysis of surgical treatment results of 98 patients aged 18 to 65 years (43.25; 95% CI: 39.77 ÷ 46.73) with subaxial cervical spine trauma and neurological disorders qualified ASIA A-D. The control term of the examination was 1 year after surgery. We used the following factors: Gender, Age, Circumstances of injury, The nature and The degree of spine damage, The size of the compression factor, Segmental kyphosis, General cervical lordosis, Baseline neurological disorders, Value of spinal cord injury, Type of spine fusion system. We defined the dynamics of recovery as the difference between the final on the primary sum of points when evaluated by the International Standards for Neurological Classification of Spinal Cord Injury. In order to identify significant factors, the method of step-by-step adaptation of the multiple regression model was used. Results: The processing of the data revealed the factors most critical for neurological recovery: the initial level of impairment, the victim's age, the time from injury to surgery, the spinal cord compression value, the type of fusion system (R2 = 0.6; F = 11.7 [20; 97], p < 0.0001). For ASIA B and ASIA C patients kyphosis in fused segments is associated with neurological recovery slowdown (R2 = 0.51; F = 17.15 [1; 56], p = 0.0001). For ASIA A neurological recovery, the most significant factors were the value of spinal cord damage and surgery performed within 8-24 hours after injury (R2 = 0.51; F = 150.5 [2, 21], p < 0.0001). Conclusion: We found that a significant number of dissimilar factors influence the neurological disorders recovery. These predictors of outcome may be used to guide treatment decisions and prognosis.

1974

P564: Severity and type of traumatic subaxial cervical injury in prediction of neurological deficit

Oleksii Nekhlopochyn ¹ , Iaroslav Tsymbaliuk ² , Vadim Verbov ² , Milan Vorodi ² , and Ievgen Cheshuk ²

¹ Spinal Neurosurgery

² Restorative Neurosurgery Department, Romodanov Neurosurgery Institute, Kyiv, Ukraine

Introduction: Neurological dysfunction is the most severe complication of traumatic subaxial cervical spine injury. A comprehensive approach and assessment of the injured spine as a single structure, including the contents of the vertebral canal as well, allow achieving the maximum possible therapy results. The purpose of study was to evaluate the dependence of neurological disorders value on type and severity of traumatic subaxial cervical injury. Material and Methods: We performed retrospective analysis of 140 patient’s cases that were hospitalized at the Institute of Neurosurgery with subaxial cervical traumatic injury. All patients were assessed for the type of the damage using the AO Subaxial Cervical Spine Classification (AO SCSC), the severity of injury using the Cervical Spine Injury Severity Score (CSISS). Neurological status was defined as the sum of points according to the International Standards for Neurological Classification of Spinal Cord Injury (ISNCSCI). Estimation of dependences was performed using regression analysis. Results: The most severe neurological symptoms are determined in groups A4 and C. Values on ISNCSCI scale are 97 (40 ÷ 144) points and 83 (42 ÷ 178) points, respectively. Slightly higher rates are registered for A3 type of injury: 196 (131.5 ÷ 288.5) points. Within other groups, the median values are in the range from 251 to 289 points with a fairly wide interquartile range. The Kruskal-Wallis test showed the significance of the differences (χ2 = 31.58, df = 7, p < 0.001). The linear regression model of neurological dysfunction dependence on the severity of damage is characterized by a high level of reliability (F = 19.6 [1; 138], p < 0.0001), but also a fairly low coefficient of determination: 0.215. On average, an increase in CSISS by one point leads to a decrease in ISNCSCI by 30 points within the analyzed range of values. When analyzing the linear multifactor dependence of neurological disorders value on type and severity of traumatic subaxial cervical injury, the prognostic efficiency of the model was determined as 42.5% (F = 7.577 [15; 124], p < 0.0001). Conclusion: The obtained data show that not only the absolute values of the instability and the type of the injury, but also the relationship of these factors plays a significant role in determining the value of neurological disorders in patients.

1980

P565: AOSpine subaxial classification in determining optimal treatment strategy

Oleksii Nekhlopochyn ¹ , Ievgenii Slynko ¹ , Vadim Verbov ² , and Yurii Derkach ¹

¹ Spinal Neurosurgery

² Restorative Neurosurgery Department, Romodanov Neurosurgery Institute, Kyiv, Ukraine

Introduction: The AOSpine Subaxial Cervical Spine Injury Classification System was introduced to improve clinical management of patients with different types of traumatic lesion. At the same time, this classification does not have clear recommendations regarding treatment strategy. The purpose of our study was to determine the optimal treatment tactics for patients with various types of injuries based on AOSpine subaxial classification system. Material and Methods: A retrospective review was made of 164 patients with cervical spine trauma who were admitted to Institute of Neurosurgery between 2008 and 2018. Surgical management for each patient was determined with the main goal of spinal cord decompression, fixation, and alignment, considering instability level (Cervical Spine Injury Severity Score). Retrospectively, all patients were classified by 3 neurosurgeons independently, using the AOSpine Subaxial Cervical Spine Injury Classification System morphological types (A1-C). Results: The analysis identified 4 types of surgical interventions: Anterior Cervical Discectomy and Fusion (ACDF - 4.9%), Anterior Cervical Corpectomy and Fusion (ACCF - 65.9%), laminectomy without or with stabilization (7.3) and combined anterior-posterior fusion (21.9%). Isolated ACDF was used only for type A fractures: A1 - 50% of cases, A2 - 9.5% and A3 - 2.4%. In two cases A3 type and 5 cases A4 type, combined fusion was used, due to damage of facet joints with compression of the nerve roots. In the absolute majority of cases - 83.8% of all A type lesions, ACCF was used. For type B1 fractures, ACCF was registered in all cases, while surgical treatment of types B2 and B3 was characterized by an almost uniform distribution of ACCF, posterior decompression and combined methods: 34.8%, 30.4% and 34.8% for B2 and, respectively and 31.3%, 25% and 43.8% for B3. With type C lesions, in 56% of cases - 14 - patients we used combined surgery while in 40% cases - 10 patients - ACCF. Were used no other decompression and fusion methods with this type of injury. Conclusion: AOSpine Subaxial Cervical Spine Injury Classification System is an effective tool for describing the nature of subaxial cervical spine damage. Further research is required to unify surgical tactics based on the classification types of lesions. ACCF is the most prevalent method of surgical correction of traumatic lesions at the subaxial level of the spine.

1987

P566: Anterior odontoid screw for type II or III dens fractures. Los Ángeles experience, Chile

Oscar González ^1,2 , Claudia Ibarra Calisto ³ , Mario Monsalve Huamanga ³ , Rodrigo Coronel Fuentealba ⁴ , and Ana Marìa García Gómez ⁵

¹ Neurosurgery,Complejo Asistencial Victor Rios Ruiz, Los Angeles, Chile

² Neurology, Universidad Catolica de la Santisima Concepción, Concepciòn, Chile

³ Emergency, Complejo Asistencial Vìctor Rios Ruiz, Los Angeles, Chile

⁴ Lifestyle, Hospital Dr. Maurucio Heyermann, Angol, Chile

⁵ Medicine, Universidad San Sebastian, Concepción, Chile

Introduction: Anterior odontoid screw fixation is a safe technique used for fixation of type 2 and rostral type 3 odontoid fractures. Provides immediate stability, preservation of the C1-C2 motion and an achieved union rate of 80-100%. Requires a reduced odontoid to allow for placement of guide wire and cannulated screw. We use Image guidance with intraoperative fluoroscopy. We review our experience with this technique. Material and Methods: Retrospective case series, 13 patients under surgery in the last decade. Data collected from electronic records. descriptive statistics with R software. The same system was used in all patients, the only one available in our hospital (Dens Access, DePuy Synthes). Results: 5 females and 8 males patients. The average age of the series was 56.5 years (sd 18 - 91). The main cause of injury was traffic accidents, follow by same-level falls. 90% of traffic accidents occurred in people under 30 years of age, all level fall injuries occurred in adults older than 65 years. All patients admitted ASIA E. The average time between admission and surgery was 10.5 days (sd 2 - 49). 92% of the injuries occurred in the same province. The average surgical time was 69.2 minutes. 11 patients received 1 screw and 2 patients received 2 screws. The average time of hospitalization was 6.6 days (sd 4-10) without complications in peri operative care setting. Conclusion: Odontoid fractures that are suitable to surgery using an anterior approach with trans-odontoid screw are rare in our setting, corresponding to one or two cases per year. This technique is safe and easy to implement, in our experience with good clinical and radiological results, with use only one intraoperative C-arm because availability, with short surgical times, and without perioperative complications.

This series confirms that when it is well indicated, it is an excellent alternative to achieve stability and fusion in the injured segment.

Trauma - Thoracolumbar

103

P567: Stentoplasty versus spine jack in traumatic vertebral body fractures, a systematic review

Elie Najjar ¹ , Mohamed Hassanin ¹ , Ali Mardashti ¹ , and Nasir Quraishi ¹

¹ The Center of Spine Studies and Surgery, Nottingham University Hospital, Nottingham, United Kingdom

Introduction: The treatment of traumatic vertebral fractures (Types A and B1) has always been controversial, with no existing consensus. With recent advances in the field of sagittal balance, minimally invasive techniques that reduce and maintain vertebral and regional kyphotic deformities such as Stentoplasty and Spine Jack are becoming popular. Methods: A systematic review of the English language literature dating up to March 2022 was undertaken using the key words: “expandable intravertebral implant”, “armed kyphoplasty”, “Vertebral Body Stenting” or “Stentoplasty” and “SpineJack”. PRISMA guidelines were followed. Results: Of a total of 158 articles, 7 studies met the inclusion criteria (1 level III and 6 level IV) and were analyzed. Overall, 159 patients of mean age 51.2 years (range 31 – 75) with 189 traumatic vertebral fractures AO type A (97%) and B1 (3%) were treated using Spine Jack. 81% of the fractures were in the thoracolumbar area. The preoperative average Visual Analog Score (VAS) of 6.5 (4-9.2) kyphotic deformity was 13.9 degrees (6.4 -22.6). The average follow up was 15 months (6-37 months). Post-operatively, VAS improved to 2.2 (0.1-3.5), a difference of 5 [p value < 0.0001, 95CI: 5.01, 5.64] and the kyphotic angle from Spine Jack reduced to7.9 (1.9 – 15) with a difference of 6.14 [p value < 0.0001, 95CI: 4.69, 7.58]. The rate of cement leak was 51/141 (36%), 1 case had a Dural tear, 1 case required revision due to further collapse and 4 cases had adjacent level fractures. Additionally, 122 patients of mean age 49 years (range 15-90) underwent Stentoplasty for traumatic 120 AO type A vertebral fractures and were followed up to 14 months (3-34). 85% of the fractures were in the thoracolumbar area. The average preoperative VAS was 8.9 (8-9.7) which improved to 5 (4-6) post operatively. There was not enough data to conduct a meta-analysis for stentoplasty post-operative kyphothic angle changes, but three separate studies show a significant reduction in the Kyphotic Angle from an average of 10.9 (5.5-22) to 6 (0.5-17) degrees (a difference of 4.9 degrees). 16% (9/57) of the cases had cement leak. No other complications were documented. Conclusion: The use of Spine jack in traumatic vertebral fractures had similar clinical outcomes( VAS difference 4.3 vs 3.9) and kyphotic angle reduction ( 6.14 vs 4.9) compared to Stentoplasty, but with a higher rate of cement leak (36% vs 16%) and complications (4.2% vs 0%).

185

P568: Double balloon kyphoplasty results in better radiographic outcomes than a single balloon kyphoplasty intreating osteoporotic spinal fractures

Oded Hershkovich ¹ and Raphael Lotan ¹

¹ Edith Wolfson Medical Center, Holon, Israel

Introduction: Studies found unilateral and bilateral kyphoplasty to have comparable clinical outcomes. Only a few studies compared radiographic results using unilateral vs. simultaneous bilateral approaches. We aimed to examine and compare the radiographic results of unilateral (UKP) vs. bilateral simultaneous double-balloon kyphoplasty (DKP) for treating symptomatic vertebral compression fractures (VCF). Methods: A retrospective cohort of all patients treated for VCF by DKP and UKP over five years in a single medical center. From 2009 to 2012, we performed UKP routinely; since 2012, DKP was the routine due to potential benefits in vertebral realignment. We evaluated pre and post-surgical fracture characteristics: vertebral height, sagittal and coronal Cobb angle, and fracture reduction. Statistical analysis Included a t-test for independent variables and Pearson Correlation. Results: The study cohort consists of 81 patients (75.8 years ± 10.86) with 119 vertebras who underwent surgery. We performed 89 UKP on fractured vertebras and 30 DKP on 30 vertebrae. UKP average fluoroscopy radiation exposure was 15.8 mGy (±11.5) per level compared to 11.2mGy (±8.7) for DKP, p = 0.03. DKP showed significant fracture reduction, 2.8 degrees of Cobb angle, equaling patient positioning effect on fracture reduction. Conclusion: DKP allows better fracture reduction than UKP, equaling the effect of patient positioning without increased radiation exposure or adverse events.

Key Words: Osteoporotic fractures, Vertebral Compression fractures, Balloon Kyphoplasty

Abbreviations: Osteoporotic Vertebral Compression Fractures = VCF; Balloon Kyphoplasty = BKP; Unilateral Balloon Kyphoplasty (UKP); Bilateral Simultaneous Double-Balloon Kyphoplasty (DKP).

Highlights

• We aimed to examine the immediate radiographic effects of UKP vs. DKP for treating symptomatic VCF.

• We found that DKP results in better fracture reduction than UKP, equaling the effect of patient positioning without increased radiation exposure or adverse events.

255

P569: Treatment and outcome of osteoporotic thoracolumbar vertebral body fractures with deformation of both endplates with or without posterior wall involvement (OF 4) - short-term results from the prospective EOFTT multicenter study

Ulrich Spiegl ¹ , Philipp Schenk ² , Klaus Schnake ³ , Bernhard Ullrich ² , Osterhoff Georg ¹ , Max Scheyerer ⁴ , and Sebastian Katscher ⁵

¹ University of Leipzg, Germany

² BG Traumacenter, Halle, Germany

³ Waldkrankenhaus, Erlangen, Germany

⁴ University Hospital, Düsseldorf, Germany

⁵ Sanaklinikum Leipziger Land, Germany

Objective: To analyse therapeutical strategies applied to osteoporotic thoracolumbar OF 4 injuries, to assess related complications and clinical outcome. Methods: A multicenter prospective cohort study (EOFTT) including 518 consecutive patients who were treated for an OVCF. For the present study, only patients with OF 4 fractures were analysed. Outcome parameters were complications, Visual Analogue Scale, Oswestry Disability Questionnaire, Timed Up & Go test, EQ-5D 5L, and Barthel Index after a minimum follow-up of 6 weeks. Results: A total of 152 (29%) patients presented with OF 4 fractures with a mean age of 76 years (range 41-97). The most common treatment was short segmental posterior stabilization (51%; hybrid stabilization in 36%). Mean follow up was 208 days (±131 days), mean ODI was 30 ± 21. Dorsoventral stabilized patients were younger compared to the other groups (p < 0.001) and had significant better TuG compared to hybrid stabilization (p = 0.049). The other clinical outcomes did not differ in the therapy strategies (VAS pain: p = 1.000, ODI: p > 0.602, Barthel: p > 0.252, EQ-5D 5L index value: p > 0.610, VAS-EQ-5D 5L: p = 1.000). The inpatient complication rate was 8% after conservative and 16% after surgical treatment. During follow-up period 14% of conservatively treated patients and 3% of surgical treated patients experienced neurological deficits. Conclusions: Conservative therapy of OF 4 injuries seems to be viable option in patients with only moderate symptoms. Hybrid stabilization was the dominant treatment strategy leading to promising clinical short-term results. Stand-alone cement augmentation seems to be a valid alternative in selected cases.

346

P570: Comparison of outcome of patients of thoracolumbar trauma treated with percutaneous screw fixation and open technique

Umair Ahmed ¹ and Umair Ahmad ¹

¹ Orthopedic and Spine Center, Ghurki Trust Teaching Hospital, Lahore, Pakistan

Background Context: Its an established controversy in treatment of thoracolumbar fracture . Which technique is most rewarding whether open traditional technique or percutaneous technique. Objective: To compare clinical and radiological outcomes between percutaneous pedicular screw fixation [closed reduction internal fixation (CRIF)] and open technique [open reduction internal fixation (ORIF)] in thoracolumbar spine fractures without neurologic deficit. Study Design: Retrospective Cohort study. Materials and Methods: There is retrospective evaluation of all patients with thoracolumbar fractures (T11-L4) treated at Ghurki Trust Teaching Hospital Lahore between 2016-2021 with follow-up up to 12 months. 90 patients (mean age 40.5) were arranged into two treatment groups; Percutaneous vs Open. Radiological outcomes in term of screw position and anatomic vertebral reconstruction which were analyzed on x-ray and CT scan.s Study Parameters are; surgery time, radiation exposure time, blood loss, length of hospital stay, mobilization and postoperative pain. Results: There was 90 pat. The mean operation time in CRIF was 70.5 mint vs in ORIF 120.2 mint. Mean blood loss in CRIF was 100ml vs in ORIF was 500 ml. Mean radiation exposure time was 20.8 mint in CRIF vs 5 .4 mints in ORIF Postoperative pain more in ORIF vs CRIF. Satisfied patients after immediate postop in CRIF were 10 and in ORIF were 2. Mean hospital stay in CRIF was 1day and in ORIF was 3 days. Post op neurology intact in both groups. No loss of reduction was noted in any group at final follow up. No patient of CRIF was infected. SSI was present in 4 patients of ORIF. Conclusion: Percutaneous Screw Fixation provide a satisfying radiological and clinical outcome while minimizing perioperative risks compared to traditional open screw fixation. The only draw back in CRIF is increased radiation exposure.

429

P572: Mono-axial versus poly-axial pedicle screw fixation for thoraco-lumbar fractures: a randomised controlled trial

Ahmed Shawky Abdelgawaad ^1,2 , Islam Abd El-Hameed ² , Mahmoud Ibrahim ² , Ahmed Hassan ² , and Mohamed El-Meshwawy ²

¹ Spine Center, Helios Klinikum Erfurt, Erfurt, Germany

² Orthopaedics and Trauma, Assiut University Hospitals, Assiut, Egypt

Introduction: Thoracolumbar fractures are the most common spine fractures. Posterior transpedicular screw fixation is commonly used in surgical treatment of these fractures. To date, there is no consensus as to whether a mono-axial or poly-axial pedicle screw should be used in fixation of thoracolumbar fractures. This study aims to compare short segment mono-axial to poly-axial pedicle screw fixation in thoracolumbar fractures regarding radiological and clinical outcomes. Material and Methods: This is a randomized controlled trial done in a university hospital on 50 consecutive patients with thoracolumbar fractures who met the inclusion criteria divided in two equal groups, group (I) mono-axial pedicle screw fixation and group (II) poly-axial screw fixation. Included were patients with type A3 and A4 (according to AOSpine classification) thoracolumbar fractures between D9 – L3 without neurological deficits. Excluded were pathological or osteoporotic fractures, multi-segmental fractures, polytraumatized patients, fractures older than 14 days and fractures with load-sharing score 7 or more. All patients received open posterior short-segment fixation with instrumentation of the fractured vertebra. The primary outcome was the sagittal index, and the secondary outcomes were local kyphotic angle, regional kyphotic angle, anterior vertebral height, middle vertebral height, posterior vertebral height and interpedicular distance. Oswestry Disability Index (ODI) and Visual Analogue Scale (VAS) were used as Patient Reported Outcome Measures (PROMs). All patients were followed up at 3,6, and 12 months postoperatively. Results: There were no statistically significant differences regarding the demographic data (age, sex, co-morbidities, type, and level of fracture) between both groups. Regarding the sagittal index, local and regional kyphotic angles, anterior, middle, posterior vertebral height and the interpedicular distance among the studied group, the mean post-operative values were significantly improved in both groups. The mean values for correction of sagittal index, local and regional kyphosis were higher in the mono-axial group however, this difference was statistically insignificant (p > 0.05). Also, the mean correction loss was higher in the poly-axial group however, this difference was statistically insignificant (p > 0.05). There were no statistically significant differences in the mean ODI (16.92 ± 4.35 mono-axial group vs. 16.36 ± 4.56 poly-axial group; p = 0.87) and VAS (4.16 ± 1.62 mono-axial group vs. 3.78 ± 1.66 poly-axial group; p = 0.39) after one year. Conclusion: There is no statistically significant difference between mono-axial and poly-axial pedicle screws as regards reduction, correction of deformity and maintenance of correction in management of acute thoracolumbar fractures. Also, the patient reported outcomes (ODI and VAS) were not statistically significant between both groups.

542

P573: Spine injuries after ejection seat evacuatio in fighter aircraft of the German Armed Forces from 1975 to 2021

Fabian Sommer ¹ , Pravesh Gadjradj ¹ , and Torsten Peppig ¹

¹ Neurological Surgery, Weill Cornell, Flushing, United States

Introduction: The ejection seat is one of the most important rescue tools for military aircrews. However, the high ejection speeds place high loads on the pilots, which is mainly absorbed by the pilot's spine. The differentiated evaluation of spinal injuries is of particular importance, as this has a decisive influence on the further personal life and career of the affected aircrews. Factors influencing the occurrence of a fracture as well as the impact of a spinal injury on military flight certification have not been addressed sufficiently to date. Material and Methods: We conducted a retrospective evaluation of ejection seat evacuations in German Armed Forces combat aircraft accidents between 1975 and 2021. The total number of aviation accidents with ejection seat initiations and the survived ejections were collected. Accident-specific data and pilot-specific data were collected. In addition, it was evaluated whether aircrews were military flight recertified after the accident. The type of spinal injury and the location of the injury were evaluated. In addition to the descriptive statistics, two logistics regression models were developed to assess prediction values of accident and pilot-specific factors for spine injuries. Results: A total of 103 aircrews were included in this retrospective analysis. The overall prevalence of spine injuries was 63.7% and the overall prevalence of major injuries was 33.0%. In the first regression model analysis, there was no association with pilot flight experience, age, height, weight, and BMI and being diagnosed with a spine fracture. Similarly, aircraft type, altitude, and airspeed were not associated with the occurrence of spine fractures. In the regression model of analysis for predictors of rejection in military flight recertification after ejection seat evacuation, lumbar spine fractures were associated with higher odds of being rejected for recertification. Conclusion: Military aircraft crews have a high risk of suffering from a spine injury after emergency evacuation using an ejection seat. In the subsequent medical workup, special attention should be paid to the spine and ideally a consultation with a spine surgeon should be performed. Lumbar spine fractures may have big consequences for military flight certification, therefore special attention should be paid to successful rehabilitation.

576

P574: Radiographic predictors of neurological injury in patients with thoraco-lumbar fractures

Ahmed Shawky Abdelgawaad ^1,2 , Samuel Merhom ² , Khaled Hassan ² , and Mohammed Hassan ²

¹ Helios Klinikum Erfurt, Spine Center, Erfurt, Germany

² Department of Orthopaedics and Trauma, Assiut University Hospitals, Assiut, Egypt

Introduction: Correlation between radiographic parameters and neurological deficits after thoraco-lumbar injuries have been reported. Still there are no definite cut limits and no consensus which parameters do expect neurological deficits in such patients. This study was conducted to figure out the relation between neurological deficit and radiological parameters in patients with thoracic and lumbar spine fractures. Material and Methods: After IRB ethical approval, patients with thoracic and lumbar fractures presented to a university hospital were included. Neurological examination was done according to the American Spinal Injury Association (ASIA) score. Radiographic evaluation included plain radiographs, CT (computed tomography) and MRI. Radiographic parameters including vertebral body compression (Anterior Vertebral Height AVH, Middle Vertebral Height MVH, Posterior Vertebral Height PVH), canal compromise, sagittal alignment measured by Cobb angle and type of fracture according to AO classification (morphological component) were digitally measured. Two blinded investigators measured all the above mentioned parameters independently. Results: 160 patients were included. The ASIA score had significant correlation with sagittal alignment measured by Cobb’s angle (r = -0.22, p < 0.001), vertebral height compression percentage measured by AVH (r = -0.26, p < 0.001), and MVH (r = -0.28, p < 0.001), type of the fracture according to AO classification (morphological part) (p < 0.001) and canal comprise if it was > 50% of the total canal space (r = -0.34, p =< 0.001) but it has insignificant correlation with percentage of compression of canal comprise if it was < 50% of the total canal space (r = -0.12, p = 0.56) and also has insignificant correlation with PVH (r =- 0.17, p = 0.12). Conclusion: Our study concluded that there is a positive correlation between neurological damage and sagittal alignment, vertebral compression, type of the fracture according to AO classification and high grades of canal compromise (> 50%). But, there is no positive correlation with low grades of canal compromise (< 50%) in thoracic and lumbar spine fractures patients.

731

P575: Interventional management of single-segment osteoporotic vertebral compression fractures in the elderly: our experience from 157 cases

Nikolaos Gkantsinikoudis ¹ , Christos Siopis ¹ , and Stylianos Kapetanakis ^1,2

¹ Spine Department and Deformities, Interbalkan European Medical Center, Thessaloniki, Greece

² Department of Minimally Invasive and Endoscopic Spine Surgery, Athens Medical Center, Greece

Introduction: Osteoporotic Vertebral Compression Fractures (OVCFs) constitute a frequent clinical condition with substantial associated morbidity and mortality, principally encountered in elderly individuals. Clinical management of these lesions is crucially determined by a plethora of factors as patient’s general health status, fracture’s anatomical and biomechanical features and potential neurologic compromise. We hereby present our clinical outcomes of interventional management of OVCFs with Minimally Invasive Augmentation (MIVA) procedures [Vertebroplasty (VP) and Kyphoplasty (KP)] and open Posterolateral Instrumented Fusion (PLF) surgery in elderly individuals. Material and Methods: One-hundred and fifty-seven (157) elderly patients with single-segment OVCF were enrolled in this prospective investigation. Major determinants for selection of respective therapeutic strategy were the potential related clinical/radiological segmental instability and the underlying neurologic status. Seventy-seven (77) patients underwent MIVA procedures (VP or KP, depending on vertebral height diminution) and eighty (80) open PLF surgery. Evaluation of enrolled individuals was performed via clinical examination and performance of determined patient-reported outcome measures as Visual Analogue Scale (VAS) and Short-Form 36 (SF-36) Medical Health Survey Questionnaire, for pain and Health-Related Quality of Life (HRQoL) assessment, respectively. All patients were evaluated preoperatively and at sequential chronic intervals during a 2-year follow-up period. Results: All patients were successfully operated, featuring no major perioperative complications. Analysis of recorded outcome measures showed that all indices of SF-36 questionnaire exhibited a statistically significant improvement at all follow-up checkpoints, demonstrating albeit the maximal amelioration at 3 months with subsequent stabilization with minimal amelioration until the end of follow-up. On the contrary, VAS score values were stabilized at 6 months postoperatively, featuring no further significant quantitative alteration. Conclusion: Interventional management of OVCFs in elderly patients with MIVA (VP, KP) procedures or open PLF surgery, depending on determined patient- and condition-related characteristics, represents a safe and effective strategy with favorable outcomes in HRQoL.

801

P576: Single Spinejack is each fractured vertebra is feasible to achieve a significant fracture reduction and corresponding satisfactory outcome by proper strategy of placing Spinejacks

Chien-Jen Hsu ¹

¹ Department of Orthopaedics, Kaohsiung Veterans General Hospital, Kaohsiung, Taiwan

Introduction: Spinejack was one of the most commonly used augment devices for kyphoplasty. Bilateral placement of Spinejacks into a vertebra for kyphoplasty was suggested by the manufacture company. Considering medical expense controlled by insurance, we therefore intended to investigate the surgical complications and clinical outcomes for patients undergoing kyphoplasty with one single Spinejack in each fractured vertebra. Material and Methods: We conducted kyphoplasty by applying single Spinejack into fractured vertebra for 45 patients from January 2018 to December 2020. By examining the MR images preoperatively, we chose the more collapsed side for placing the Spinejack unless the pedicle fractured. Considering high risk for cement leakage through fractured pedicle, the placement of Spinejack was therefore shifted to the other pedicle. The Spinejacks were placed across the midline or at least touching the midline of vertebra for effective expansion bilaterally. A vending trocar was routinely inserted at the other side for decompression while injecting the cement. The fluidity of cement was attenuated by extend the setting of cement if we decided to inject cement through the side of Spinejack first. Otherwise, we started to inject cement initially through the trocar to fill the less comminuted side for preventing early leakage outside the vertebra. The following supplement of cement depended on the distribution of cement filling through alternative injection of cement bilaterally under the guide of c-arm image intensifier. We usually stopped cement injection if the filling of cement realized or approached the pre-opertaive plan. Results: Excluding 4 patients without complete follow-up for at least 12 months, 41 patients with 46 fractured vertebrae were investigated. They were 12 male and 29 female patients with average age of 70.5 years. The mean BMD was -2.87. The fractured levels were T7 in 1 patient, T11 in 3 patients, T12 in 18 patients, L1 in 15 patients, L2 in 4 patients, L3 in 2 patients, and L5 in 1 patient. Except radiographic assessment, the clinical symptoms were assessed by the SF-36 questionnaire. The average clinical score of SF-36 improved from 52 to 81 in the final follow-up at the OPD or by the telephone inquiry. However, the average SF-36 score reached 87 in case of excluding three patients with unsatisfactory outcomes. These three patients reported poor outcomes that were re-operated because of new vertebral fracture. The radiographic assessment demonstrated an average 40% restoration of supposed height of fractured vertebra. The average reduction of kyphotic angle is 11 degrees. Three patients developed loss of vertebral height reduction more than 25% but only one was re-operated by mini-invasive instrumentation. Conclusion: Although the original recommendation from the manufacture company was placing Spinejacks through bilateral pedicle into a fractured vertebra, kyphoplasty by applying only one single Spinejack for each fractured vertebra achieved a satisfactory reduction of vertebral collapse in this study. The clinical outcomes assessed by SF-36 questionnaire demonstrated a significant improvement in addition to evident reduction of vertebral height and kyphotic angle. Considering cost-effectiveness of Spinejack-augmented kyphoplasty, one single Spinejack was feasible to achieve satisfactory outcomes clinically and radiologically.

830

P577: The use of the AO Spine PROST (Patient Reported Outcome Spine Trauma) among SCI patients - Healthcare professionals' perspective and development of version 2.0

Aline J. Hakbijl ¹ , Marcel Post ¹ , Cumhur Oner ² , and Said Sadiqi ²

¹ Department of Spinal Cord Injury Rehabilitation, De Hoogstraat Rehabilitation, Utrecht, The Netherlands

² Department of Orthopaedics, University Medical Center, Utrecht, The Netherlands

Introduction: The provision of appropriate surgery, medical care and rehabilitation can have significant effect on disability in people with spinal cord injury (SCI). To learn what surgical and rehabilitation treatments are most effective and to compare them in a reliable and valid fashion, it is important to standardize classification and outcome measurements. To meet these requirements, the AO Spine Knowledge Forum Trauma developed the Patient Reported Outcome Spine Trauma (AO Spine PROST). This tool was developed for people with spine trauma and minor or no neurological impairment. To the best of authors’ knowledge, it is adopted worldwide with currently being translated into 17 languages. In the current study, the applicability of the AO Spine PROST for people with motor-complete SCI was examined from the perspective of the healthcare professionals. Also, recommendations were made for adjustments of the tool. Material and Methods: A discussion meeting with SCI rehabilitation physicians in the Netherlands was performed, followed by an international online survey among healthcare professionals involved in the care of people with SCI. Participants rated the comprehensibility, relevance, acceptability, feasibility and completeness of the AO Spine PROST on a 1-5 point scale (5 most positive). Comments could be provided per question. The discussion meeting was audio taped, meaningful phrases transcribed, and analyzed thematically. The results of the international survey was compared with the results of the discussion meeting using descriptive statistics. The comprehensibility, relevance, acceptability, feasibility, and completeness of the tool were analyzed by calculating frequency tables using SPSS. Results: A total of 13 physicians attended the discussion meeting. The survey was completed by 196 participants worldwide. Comparable results were obtained from the discussion meeting and the international survey. Comprehensibility (mean 4.1 ± 0.8), acceptability (4.0 ± 0.8), relevance (3.9 ± 0.8), completeness (3.9 ± 0.8), and feasibility (4.1 ± 0.7) were rated positively for use in people with motor-complete traumatic or non-traumatic SCI. A few participants questioned the relevance of items about the lower extremities (e.g. Walking) or indicated the lack of questions about respiration/breathing and complications. Conclusion: The AO Spine PROST was found to be applicable for people with motor-complete traumatic or non-traumatic SCI. This study formed the basis for recommendations in adapting the tool (version 2.0) in order to make it applicable to the entire spine trauma patient population, including patients with (severe) SCI. With this modified version, the AO Spine PROST is expected to be even more useful both in the clinics and for research purposes, contributing to the comparison of spine trauma outcomes in a valid and reliable fashion with the potential to reduce the ongoing controversies in spine trauma care.

846

P578: AOSpine Thoracolumbar Injury Classification System (AO TLICS): a study on its validation in junior surgeons

Zion Hwang ¹ , Jason Bernard ² , Timothy Bishop ² , Jan Herzog ² , Shahnawaz Haleem ² , Tesfaladet Kurban ² , Bisola Ajayi ² , Emily Tsang ¹ , Priyanshu Saha ¹ , and Darren Lui ²

¹ St. George's University of London, London, United Kingdom

² Trauma and Orthopaedics, St. George's University Hospital, London, United Kingdom

Introduction: Classification systems exist to safely guide inexperienced surgeons’ management to result in optimal patient outcomes, but the spine community is yet to agree upon a single thoracolumbar injury classification system. Several studies have investigated the reliability of the newest addition, AO TLICS, drawing inconclusive results for some subtypes. Their analyses focus on AO TLICS’ reliability from the point of view of each subtype rather than the injury and its management algorithm, which has greater clinical importance. The binary (yes/no) questionnaire format used in previous studies fails to assess surgeons’ abilities to recognise and label an injury and, equally importantly, what classification an injury does not fall under. In addition, many assume all assessor responses have equal weighting regardless of their level of experience. Therefore, this study aims to mitigate these issues by asking participants to rate each injury by its full classification and by assessing whether juniors surgeons’ assessment of injuries using AO TLICS agree with their senior counterparts, thus contributing further data on the topic to validate the reliability of AO TLICS. Material and Methods: In 2019-2020, two surveys were sent two months apart to the same group of assessors, consisting of eight junior surgeons and one orthopaedic spine consultant surgeon. There was a 100% response and participation rate. Spine MRI scans of the same 11 patients were assessed on the number and full classification of injuries. Data analysis was performed using Microsoft excel with the consultant surgeon's answers used as the comparison standard. Results: The average agreement was 81.3% for wedge injuries, 81.8% for burst injuries and 86.6% for tension band injuries. There was only one case of hyperextension injury at 87.5% and one Type C injury at 100% agreement. On average junior surgeons showed 86.7% agreement with surgical management but only 45.8% agreement with conservative management. Further assessment showed 90.8% agreement on the vertebral level injured, 85.4% agreement of Type C injuries, 67.0% of Type B injuries and 82.1% of Type A injuries. When classifying by subtypes, junior doctors showed only 33.9% agreement for B subtypes and 50.9% for A subtypes. Conclusion: AO TLICS is comprehensive and accurate in junior surgeons overall, but poorer agreement is seen when classifying into subtypes, especially for Type B injuries. AO TLICS accurately facilitates junior surgeons’ recognition of which injuries require surgical management but generally errs on the side of surgical management, which results in the potential for unnecessary surgeries.

883

P579: Surgical treatment of traumatic fractures of the thoracic and lumbar spine: a systematic review

Said Sadiqi ¹ , Timon Vercoulen ^1,2 , Menco Niemeyer ³ , Felix Peuker ³ , Jorrit-Jan Verlaan ¹ , and Cumhur Oner ¹

¹ Orthopaedic Surgery

² Orthopaedic Surgery, Diakonessenhuis, Utrecht, The Netherlands

³ Trauma Surgery, UMC Utrecht, Utrecht, The Netherlands

Introduction: Controversies remain on the optimal treatment of thoracic- and lumbar spine fractures. These fractures are treated either surgical or non-surgical. Surgical treatment aims to reduce the fracture, prevent further post-traumatic spinal deformity, maintain spinal alignment and perform a neural decompression if needed. However, there is no consensus on the choice of surgical approach and technique. No comprehensive up-to-date overview is available that facilitates the comparison of the different surgical methods for these fractures. The goal of this study is to reproduce and update an earlier systematic review from 2004 by this research group. All published articles in the past two decades were reviewed, and the outcomes of different surgical techniques were quantified and analyzed. Materials and Methods: A systematic literature search was performed in PubMed and EMBASE^® using the search term ‘Spinal fractures’ for articles published between 2001-2020. Inclusion criteria were: > 18 years of age; including more than 10 cases; a minimum of 12 months follow-up; adequate description of the surgical procedure; using generally accepted outcome instruments; surgery performed within three weeks after trauma. Article screening was performed by four researchers. Studies were categorized per surgical technique groups: Posterior open (PO), Posterior percutaneous (PP), Stand-alone vertebroplasty or kyphoplasty (SA), Anterior endoscopic (AS), Anterior open (AO), Posterior percutaneous and anterior open (POAO), Posterior percutaneous and anterior endoscopic (PPAS), Posterior open and anterior open (POAO), Posterior open and anterior endoscopic (POAS). The PO group was used as a reference group for comparison and statistical analysis. Results: 103 articles could be included. Of these studies we could extract 138 cohorts using PO (n = 75), PP (n = 39), SA (n = 13), AO (n = 5), PPAO (n = 1), PPAS (n = 1), POAO (n = 2) or POAS (n = 2). Pre-operatively, there were more type A fractures in the SA and PP group compared to the other groups. Moreover, there were more subjects with neurological impairment (ASIA grade C or D) in the AO group compared to the other groups. Often, concomitant surgical interventions such as an additional vertebra- or kyphoplasty, transpedicular spongioplasty, fusion or a graft was applied. Surgical duration and blood showed no major differences between groups. Post-operative complications were scarcely reported. Pre-operative mean Cobb values were lowest in the SA group. The overall correction obtained at follow-up was lowest in the SA group (1.06 degrees) and most in the AO group (7.65 degrees). Conclusion: This comprehensive systematic review describes quantitative data to provide the best possible comparison between different surgical techniques for the treatment of thoracic and lumbar spine fractures. For type A fractures, without severe neurological deficit, PP is most researched and can be combined with vertebroplasty or kyphoplasty (SA) when a kyphosis correction is needed. Furthermore, PO is feasible in almost all types of fractures and there seems to be particular use for this technique when additional posterior decompression or fusion is required which cannot be achieved by more minimal invasive methods. Overall, all surgical techniques led to neurological stabilization or improvement. Also, future randomized controlled trials are imperative for a true comparison of surgical methods.

902

P580: Vertebral augmentation with cranio-caudal expandable devices in acute versus subacute/chronic vertebral fractures of thoracolumbar junction. Complications, clinical and radiological results

Andrea Zanirato ^1,2 , Emanuele Quarto ^1,2 , and Matteo Formica ^1,2

¹ IRCCS Ospedale Policlinico San Martino, Genoa, Italy

² University of Genoa, DISC, Genoa, Italy

Introduction: The use of cranio-caudal expandable devices in acute (< 8 weeks) and subacute/chronic (> 8 weeks) thoracolumbar fractures has been proposed for pain control and kyphotic deformity correction. The aim of this study was to compare the complication rate, clinical and radiological results of vertebral augmentation with cranio-caudal expandable devices in relation to timing of thoracolumbar junction fracture (T10-L2). Material and Methods: The patients who underwent one-level vertebral augmentation with a cranio-caudal expandable device for a traumatic and osteoporotic vertebral fracture of the thoracolumbar junction were enrolled. A minimum follow-up (FU) of 2 years was established. Vertebral fractures were classified in acute (< 8 weeks) and subacute/chronic (> 8 weeks). Complications were assessed as intraoperative or postoperative. Clinical results were evaluated preoperatively according to a Visual Analogue Scale (VAS) and Oswestry Disability Index (ODI). Radiological parameters included vertebral wedge angle (VWA) and segmental kyphosis (SK). Results: Forty-seven patients were included: 26 acute (Group-A) and 21 subacute fractures (Group-B). The mean FU was 28.6 ± 2.6 months. The subgroups were statistically homogeneous for preoperative clinical and radiological parameters. No intraoperative complications were reported. In the postoperative FU, 4 adjacent fractures were recorded in Group-B (p = 0.03).  Both groups exhibited a significant improvement in pain and functional status after surgery, which was maintained up to the final follow-up. The mean initial VWA was 15.4 ± 7.1° for Group-A and 17.1 ± 6.1° for Group-B. Post-operative values were 7.4 ± 5.2° for Group-A (p < 0.05) and 8.4 ± 5.1° for Group-B (p < 0.05). A similar loss of reduction (p > 0.05) at 3 months was noted in both group: 0.6 ± 2.1° in Group-A and 0.8 ± 0.7° in Group-B. There was no further loss of reduction after 3 months. The mean initial SK was 12.0 ± 8.1° for Group-A and 13.7 ± 7.2° for Group-B. Post-operative values were 7.1 ± 6.1° for Group-A (p < 0.05) and 7.5 ± 4.9° for Group-B (p < 0.05). A significant loss of segmental kyphosis correction was noted during the FU in Group-B (SK at the last FU 12.1 ± 5.2°). Conclusion: Vertebral augmentation with cranio-caudal expandable devices demonstrated promising clinical results in both groups. In subacute and chronic vertebral fractures, a higher rate of adjacent fractures was recorded. Furthermore, during the FU, the progressive degeneration of the discs adjacent to fractured vertebral led to an increase of segmental kyphosis. The opportunity of a stand-alone vertebral augmentation with craniocaudal devices in subacute and chronic vertebral fractures of the thoraco-lumbar junction should be carefully evaluated.

909

P581: Cauda equina syndrome after gunshot injury at the lumbar spine: a case report and narrative review

Pedro Torres ¹ , Andre Castilho ¹ , David Israel ¹ , and Daniel Araujo ¹

¹ Spine Surgery, Hospital Unimed, Belo Horizonte, Brazil

Introduction: Gunshot wounds (GSW) is an important cause of injuries of the spine, especially in the younger population and have high mortality and morbidity impact. Beside been common in military population, gunshot injury is becoming more prevalent in civilian population, especially in developing countries, causing a great impact on health system costs. It is the second most common cause of all spinal lesions (13-17%) and in some countries the incidence is even higher than traffic accidents. GSW have a wide spectrum of clinical presentation, with different associated injuries, hemodynamic status, vertebral fractures, and neurological deficits. Spinal Cord and Cauda Equina lesions can occur from different, yet concomitant factors, such as the direct impact of the bullet, thermic lesion, the concussive effect of the bullet, the tissue cavitations and the impairment of blood supply (disrupted or thrombosed vessels). In this study, we present a case of a male patient with cauda equina syndrome due to a gunshot injury and a narrative review of the topic. Material and Methods: We report a case of a 25-year-old patient who suffered a gunshot injury in the lumbar spine. He was transferred to a spine trauma center after 5 days of his injury. He presented pain in lower limbs, saddle paresthesia and urinary retention. The patient had no motor or sensory compromise in lower limbs. A computed tomography scan revealed the presence of the projectile in the vertebral canal, at the L1’s right lateral recess. Research was made on PubMed database for review studies and case reports about gunshot injuries and gunshot wounds to the spine, spinal cord, and cauda equina. Were used the terms “Gunshot Wound AND SPINE”. We also made a manual search, and the most recent and relevant articles were selected for our analysis. Results: Patient underwent surgery five days after the trauma, having an open decompression through partial laminectomy and projectile removal. No macroscopic lesion of the dura mater was observed during surgery. Patient had a complete resolution of the lower limbs pain in the first day after surgery and recovered urinary control and sensibility after one month of surgery. Conclusion: Gunshot injuries to the spine remains a very important subject to address. After admitted at the trauma center, patient must undergo for clinical stabilization, investigation of associated injuries, complete neurologic evaluation, and imaging studies. The conservative treatment consists of wound care, antibiotics, tetanus vaccination, stabilization, and rehabilitation. Surgical treatment is controversial and depends of location in the spine, neurological impairment, clinical condition and usually consists of open laminectomy with or without stabilization. The only absolute indications are cutaneous or pleural liquor fistula and documented progression of the neurological deficit associated with compression of the neural elements. The main prognostic factor is the initial neurological status, followed by the affected segment and spinal cord preservation or transection. Studies report a rate of recovery 53-65.3% for patients with partial deficits.

937

P582: Transpedicular fixation of thoracic spine fracture in patient with von Willebrand disease - a case report

Jovana Grupkovic ¹ , Slavisa Zagorac ¹ , Milos Vasic ¹ , Uros Novakovic ¹ , Milos Mladenovic ¹ , Uros Dabetic ¹ , Radmila Klacar ² , Dragana Vracevic ² , and Goran Tulic ²

¹ Orthopaedic Surgery and Traumatology

² Anaesthesiology and Reanimatology, University Clinical Center of Serbia, Belgrade, Serbia

Introduction: Von Willebrand disease is a coagulation disorder that is caused by a quantitative and qualitative defect of the von Willebrand factor (vWF), which increases the risk of perioperative bleeding and associated complications. This can be successfully prevented with substitution therapy by von Willebrand factor (vWF) or factor VIII (FVIII). The aim of our article is to present a patient with Th4 fracture that was treated with transpedicular fixation with minimal perioperative bleeding and complications. Case Report: We present a case of a 30-year-old male injured by falling down the stairs and on admission diagnosed with isolated injury - fracture of Th4 vertebrae. Previously he was diagnosed with von Willebrand disease by laboratory analysis of aPTT before routine tonsillectomy 3 years prior to admission. The patient was examined by a hematologist, he denied spontaneous bleeding prior to admission, and he stated he had right radiocarpal joint surgery without complications. He suffered a fracture to Th4 - AO Spine Thoracolumbar Injury Classification System type A2 - split fracture. Neurovascular status was intact. Preoperative laboratory findings: Hgb 131 g/l, WBC 5.8 x 10⁹/l, PLT 240 × 10⁹, aPTT 36.1s, Ddimer 0.17 (0.5 cutoff), FVIII 61%, vWFAc 49%, vWFAg 40%, factor IX 71%, factor XI 93%, factor XII 127%. The HAEMATE P (the morning of surgery 1000 IU IV) was administrated. The surgery (transpedicular fixation Th3-Th5) was performed without any complication and without significant bleeding, it lasted two hours and one dose of red blood cells concentrate was administrated. Postoperative neurovascular status was intact. The first 2 postoperative days the patient was treated with 1000 IU\12h of HAEMATE P, and the next three days with one dose daily. On the third postoperative day the drain was extracted and the volume of the drained serohemorrhagic content was 400 ml. The patient was treated with Fraxiparine (0,3 ml SC/24h) pre- and postoperative. Discussion: Spine injuries are most often caused by a fall from height. VWF disease prevalence is up to 1% worldwide, with around 0.01% of patients having significant symptoms. The most common clinical symptoms are mucocutaneous bleeding and bleeding after trauma and surgery. There are three types of von Willebrand disease: type I which is partial quantitative deficiency and the most common (70-80% of cases). The appearance of spine injuries has a relatively wide range – from mild strains to fractures and dislocations of the vertebral body with/without spinal cord injury. The accepted classification of the spine fractures is AO thoracolumbar classification system, which divides fractures into three types – A, B, and C. Management of spine fractures can be conservative and surgical. If surgical treatment is necessary it is paramount to choose an appropriate approach. The treatment plan for patients with von Willebrand disease requires a multidisciplinary approach. Conclusion: In patients with von Willebrand disease and spinal traumatic injuries that require surgical treatment, preoperative preparation has to be multidisciplinary. This means good cooperation of orthopedic surgeons, anesthesiologists and hematologists in order to perform a successful surgery without preventable complications, and increase patients quality of life.

943

P583: Posterior thoracolumbar instrumented fusion for compression fractures: long or mixed assembly?

Mouldi Lamouchi ¹ , Jlidi Mohamed ¹ , Ayachi Montassar ¹ , Walid Bouaicha ¹ , Mohamed Hedi Gharbi ¹ , and Selim Daas ¹

¹ Orthopedics and Traumatology Department, Hospital of Mohamed Taher Maamouri, Nabeul, Tunisia

Introduction: The Magerl classification defines compressions fractures as compression fractures type A. This injury is most likely to occur as a result of trauma, and is mainly located at the thoracolumbar junction. Traditionally, the preferred method for stabilization of an unstable burst fracture is the long fixation with instrumentation of at least 2 levels above and below the fractured vertebrae. It was thought that this would provide the necessary stability for fracture healing while minimizing the risk of post traumatic kyphosis or hardware failure at the expense of relative vertebral motion. Mixed fixation with instrumentation of 2 levels above and 1 level below the fractured vertebrae has gained popularity as this decreases surgical time, but most importantly preserves vertebral motion segments. The objective of our study is to compare these two different posterior spine fixation methods for burst fracture fixation of the thoracolumbar junction. Material and Methods: This is a descriptive and analytic single center retrospective study with a 10 year follow up. We included thoracolumbar compression fractures treated by posterior fusion with a long assembly or a mixed assembly. Two groups have been identified: Group A includes 53 patients treated with a long assembly (2 levels above the fracture and 2 levels below). Group B includes 28 patients treated with a mixed assembly (2 levels above the fracture and one level below). The evaluation of results was done by calculating the variation of radiological parameters between pre-operative radiographs, postoperative radiographs and last follow-up radiographs. The gain is the preoperative value minus the postoperative value. The loss of correction is the value at the last follow-up minus the postoperative value. Results: The average follow-up of the study was 57 months (15 months - 144 months). The gain in regional kyphosis was 9.75° for group A and 9.04° for group B. The gain in vertebral kyphosis was 8.15° and 8.85° for group A and B respectively. At the last follow-up of group A, the loss in regional kyphosis (RK) was 0.63°, the loss in vertebral kyphosis (VK) was 0.67 and the loss of traumatic regional angulation (TRA) was 0.653. At the last follow-up of group B, the loss in RK was 1°, the loss in VK was 0.78° and the TRA loss was 0.963. At this stage, there was no significant difference between the two groups. Osteoarthritic degeneration of the upper and/or lower level was observed in 24 patients in group A and 16 patients in group B. Conclusion: A mixed fixation method with instrumentation of 2 levels above and 1 below for the thoracolumbar burst fractures showed the highest correction of kyphosis angle both at immediate and final follow-up and also the lowest implant failure at final follow-up.

956

P584: A pure conus medullaris syndrome with thoracolumbar burst fracture is not so rare

Tokumitsu Mihara ¹ , Shinji Tanishima ¹ , Chikako Takeda ¹ , Masaki Yoshida ¹ , Satoshi Fujiwara ¹ , and Hideki Nagashima ¹

¹ Division of Orthopedic Surgery, Department of Sensory and Motor Organs, School of Medicine, Faculty of Medicine, Tottori University

Objective: To research the features of pure conus medullaris syndrome (PCMS) with thoracolumbar burst fracture. Methods: The study included patients who underwent surgery for thoracolumbar burst fracture from 2008 to 2020. The patients were divided into three groups: Group N: no neurological deficits, Group L: lower limb paralysis, and Group P: PCMS. Age, gender, body mass index (BMI), mechanism of injury, the spinal canal encroachment and effective spinal canal area ratio, and local kyphotic angle of the patients were investigated. Results: Twenty-four patients were included in this study and were divided into three groups. The number of patients in Groups N, L, and P were 8, 10, and 6, respectively. Age, gender, BMI, mechanism of injury, level of burst fracture, and local kyphotic angle were found to be similar. The spinal canal encroachment ratio in Group N, Group L, and Group P were 29% (16%-53%), 61% (36%-87%), and 39% (29%-48%), respectively. The ratios in Groups N and P were significantly lower than that in Group L. The effective spinal canal area ratios in Groups N, L, and P were 63.2% (51%-79%), 38.2% (18%-64%), and 61.3% (57%-65%), respectively. The ratios in Groups N and P were significantly higher than that in Group L. All patients in Group P relatively smooth improve in dysuria after surgery, even if a patient underwent surgery long time after injury. Conclusions: PCMS with thoracolumbar burst fracture was not rare. The bladder dysfunction in PCMS was considered as an early symptom of the neurological disorder and the cause of it was persistent pressure from the bone fragment.

989

P585: Initial experience with augmented reality-assisted pedicle screws in spinal trauma surgery

Samuel Brehm ¹ , Abby Carey-Ewend ¹ , Miguel Ruiz Cardozo ¹ , Gabriel Trevino Verastegui ¹ , Matthew De la Paz ¹ , Karma Barot ¹ , Ahmed Hanafy ¹ , Michael Kann ¹ , Raj Lavadi ¹ , Ahmedh Hussein ¹ , Alexander Yahanda ¹ , Alexander Perdomo-Pantoja ¹ , Magalie Cadieux ¹ , Julio Jauregui ² , and Camilo Molina

¹ Neurosurgery

² Orthopaedic Surgery, Washington University, St. Louis, United States

Introduction: The field of trauma medicine has long been a stage for novel technology to demonstrate its advances in healthcare. In these instances, assessing injuries and formulating a plan requires a rapid response and integration of equipment and machines capable of providing that insight quickly and accurately. Technology that demonstrates such an advantage in trauma cases can imply a similar edge in non-emergent cases, while the inverse is not necessarily true. The importance of operative outcomes in spinal surgery is paramount given the significant neurologic sequelae possible if spinal decompression, stabilization, and correction of deformity, when necessary, are not achieved. Augmented reality head-mounted-display (AR-HMD) is a novel technology that is designed to provide surgeons with a CT-guided 3-dimensional recapitulation of an individual patient’s spinal anatomy in real time and space. In this case series, the use AR-HMD in trauma cases is explored to determine whether the use of AR in spinal surgeries affects multiple outcomes, including surgery time, blood loss, length of stay, and complications. Materials and Methods: We recruited a retrospective cohort of patients who underwent navigated pedicle screw placement guided by AR-HMD at the Barnes Jewish Hospital from January 1, 2021, to January 30, 2022. From this, a cohort of 7 traumatic cases were found where AR-HMD was utilized during the surgery. Clinical patient information was collected, and metrics were calculated using Microsoft Excel. Results: The cohort had a mean age of 67 years, included 4 female and 3 male patients, and had an average body mass index of 29.6. Four of the patients had a one-level fracture, two patients had a two-level fracture, and one patient had a three-level fracture. The mechanism of injury included falls (3), neoplasms (2), 1ankylosing spondylosis (1), and hardware failure (1). They had an average surgical invasiveness index (SII) of 8.3. Intra-operatively, there was a mean blood loss of 400mL, mean 1.1 transfusion units used, and mean OR time of 3 hours and 27 minutes. The average length of stay in the hospital was 24.9 days, with two patients discharging home, one discharging to an intermediate care facility, two discharging to skilled nursing facilities, and two patients discharging to other rehabilitation facilities. Conclusion: This case series illustrates the utility of AR-HMD for instrumentation of the spine under various scenarios of spinal trauma. The urgency to treat a spinal pathology constitutes a major hurdle for the adoption of novel technologies in spine surgery. The average blood loss, length of hospital stay, transfused units are comparable to the outcomes observed in robotic-assisted surgery. This study is an early attempt to demonstrate that AR-HMD can provide equitable outcomes compared to the traditional surgical practices and can be quickly adopted in Level 1 trauma centers withoutextensive adaptations

1007

P586: Thoracolumbar fractures open versus minimally invasive approach

Oscar González ^1,2 , Jorge Garcés Gallardo ² , Luis Benavides ² , Cristian Flores Ferrada ¹ , Luis Medina ¹ , Gustavo Canessa ^1,2 , Ramón Segovia ^1,2 , Tatiana Saavedra ¹ , Patricio Campos Carrasco ¹ , Marco Guevara ¹ , Jorge Medina ¹ , and Natalia Rolack ¹

¹ Neurosurgery, Complejo Asistencial Víctor Ríos Ruíz, Los Angeles, Chile

² Neurology, Universidad Católica de la Santísima Concepción, Concepción, Chile

Introduction: Vertebral Fractures accounting for 17% of hospital discharges from the Neurosurgical Unit of our Hospital. Of these, 40% correspond to injuries of the thoracic and lumbar segments and about half require surgical treatment. From 2016 surgeries with MIS techniques have been performed regularly in our Center, either through mini-open approaches or with percutaneous procedures. This is an extension of our previous experience about treatment of thoracolumbar spine fractures adding most cases with posterior MIS techniques. Material and Methods: Retrospective Study. Case series of adult patients who suffered fractures of the thoracic and/or lumbar segments, who received some type of surgical treatment via a posterior approach, either traditional open, mini-open, or percutaneous surgery. All patients were treated in "Complejo Asistencial Víctor Ríos Ruíz" Los Angeles Chile, between January 2016 and December 2019. Osteoporotic fractures or pathological bone fractures were not included. Data collection from electronic clinical records, neuroimaging records. All CT scans were categorized using the current Aospine thoracolumbar fracture classification. Statistical analysis with Stata v12. For continuous variables, the unpaired Student's t test was used and for dichotomous variables, the Chi square test was used, with 95% confidence intervals. Results: 95 cases were selected for analysis, of which 63% were male and 37% female. The average age was 50,2 years (SD 17-81). The most frequent Mechanisms of injury were falls (46.3%) followed by traffic accidents (38%). The most frequent injuries were type A4, A3 and C. The most frequently affected segment was the thoraco-lumbar hinge (65%), followed by thoracic injuries (30%). 85% of the patients were admitted ASIA E, 4% ASIA D and 12% ASIA A. 47.4% patients were treated with open technique, 52.6% with less invasive techniques (mini-open or MIS) and one hybrid case. The mean time from injury to surgery was 4.0 days (SD: 0 - 16), there were no differences between groups. Hospital stay and postoperative days were greater in the open technique group. In this group, the average number of levels operated and the average number of screws used per surgery were also greater. The average surgical time was longer in the open surgery group, as was intraoperative blood loss. In relation to post-surgical complications and the need for reoperation, these were only observed in the open surgery group. There were no significant differences between the two groups in terms of post-surgery angulation and decreased height of the vertebral body. Conclusion: Minimally invasive techniques for the treatment of thoracolumbar fractures are an alternative that is at least as safe and effective as the open technique. It has the advantage of shortening hospitalization times, intraoperative blood loss and postoperative pain, allowing early rehabilitation. In addition, it is very useful in the context of polytraumatized patients and in damage control surgery. It is an option for an important variety of traumatic spinal injuries.

1118

P587: Percutaneous fixation in thoracolumbar fractures: a remote island reality

João Cruz ¹ , Joana Rodrigues ¹ , Tiago Canas ¹ , Emanuel Homem ¹ , Ricardo Simoes ¹ , and Luís Soares ¹

¹ Hospital do Divino Espírito Santo, Ponta Delgada, Portugal

Introduction: Thoracolumbar fractures are the most common spinal injuries, are more common in men (male-to-female ratio 2:1). About 50–70% of these fractures occur in the thoracolumbar segment (T11-L2). Posterior short-segment fixation remains the most commonly used surgical technique for these fractures and contrary to classical open surgery, the minimally invasive percutaneous pedicle screw placement needs smaller incision, less blood loss, less dissection of paraspinal muscles, less postoperative pain, and faster recovery. This retrospective study analyzed the clinical and imaging information of patients who underwent percutaneous transpedicular fixation for thoracolumbar fractures at our hospital. Material and Methods: From April 2019 to March 2022 all consecutive trauma-related spine surgeries at a single institution were revised and percutaneous transpedicular fixation cases were selected (n = 39). Demographical, clinical and radiological data was collected retrospectively, including Cobb angle, percentage of anterior vertebral height (AVH%), AO classification and surgical time. Visual analogue scale (VAS) was evaluated pre, post and 6 months after surgery, and Oswestry disability index (ODI) was evaluated at 6 months post-op. Results: Surgical technique: under general anesthesia, patients were placed prone on a Maquet surgical bed. A C-arm system was used to determine skin incision, control pedicle screws insertion and confirm final positioning. Neuromonitoring was not consistently used. After surgery: all patients began rehabilitation on the day of surgery and no bracing was used. The patients were followed for at least 6 months (follow-up). 39 patients underwent percutaneous pedicle screw fixation (72.73% with screwing of the fractured vertebra): 27 males and 12 females, and the mean age was 46.7 years. The main trauma cause was fall from height, most common fractured level was L1, and most frequent type of fracture AO A4. The mean surgical time was 79.785 min. There were no intraoperative complications. During the follow-up period, there were one infection and 1 patient with one screw pullout, but no neurological impairment was found. The mean pre-operative VAS score was 6.2, postoperative 2.4 and at the last follow-up 1.4. The mean pre-operative ODI at 6 months was 5.4. Radiographic outcomes: The Cobb angle improved from 11.84º prior to surgery to 6.98 post surgery, and 7.84 at the last follow-up. The AVH% increased from a mean of 64.1% pre-surgery to 75.9 post surgery, and 72.3% at the last follow-up. Conclusion: In our experience, the percutaneous short-segment pedicle screw fixation with or without screwing of the fractured vertebra are both safe and effective in the treatment of thoracolumbar fractures.

1124

P588: The importance of intraoperative neuromonitoring in thoracolumbar fractures

João Cruz ¹ , Joana Rodrigues ¹ , Tiago Canas ¹ , Emanuel Homem ¹ , Ricardo Simoes ¹ , and Luís Soares ¹

¹ Hospital do Divino Espírito Santo, Ponta Delgada, Portugal

Introduction: Thoracolumbar fractures are the most common spinal injuries. Posterior short-segment fixation remains the most commonly used surgical technique for these fractures. We report a rare case of intraoperative loss of potentials during instrumentation of a non-fractured pedicle with an intermediate screw and brief review of current literature for evidence to support or limit the use of intermediate screws for thoracolumbar fractures and intraoperative neuromonitoring. (IOM). Material and Methods: A 28-year male patient admitted to the emergency department after air transportation from a secondary hospital due to fall from height (4 meters) with head and spine trauma. The patient had past medical history of drug abuse. Hemodynamically stable and excluded life-threatening conditions the patient underwent secondary assessment. Whole body CT and Spine MRI documented a T5 bony Chance fracture, AO spine B2, TLICS 7, ASIA E. Results: The patient was submitted to percutaneous pedicle screw fixation with screwing of the fractured vertebra with C arm system to determine skin incision, control pedicle screws insertion and confirm final positioning. IOM was used throughout the entire procedure. While instrumenting T6 right pedicle (deemed intact on the preoperative CT) the patient had a sudden loss of potentials in right side, corresponding to a spinal cord compression, despite apparent well-placed screw on fluoroscopic images. After screw removal full neurological potential was recovered and final construct revised. Postoperative in-hospital stay went uneventful and the patient was discharged without neurological deficits (ASIA E). He began rehabilitation 2 days after surgery and was provided thoracolumbar rigid braces for 3 months. The patient’s current follow-up is 6 months: the pain has resolved and there are no neurological nor hardware complications. Review of current available literature on percutaneous instrumentation of the fractured-vertebra supports its use, because it reduces implant failure rate and postoperative VAS and has the best effect on postoperative anterior vertebral height ratio (AVHR) and sagittal Cobb angle (SCA). Conclusion: The authors reckon that despite the available literature supporting the use of intermediate screws in intact pedicle fractured vertebrae body caution would be advised, especially in centers without IOM and/or 3D imaging devices.

1128

P589: Vascular complications in percutaneous spine surgery: the uninvited unwelcomed guest

Emanuel Homem ¹ , Joana Rodrigues ¹ , Tiago Canas ¹ , João Cruz ¹ , Ricardo Simoes ¹ , and Luís Soares ¹

¹ Hospital do Divino Espírito Santo, Ponta Delgada, Portugal

Introduction: Vascular injury rarely occurs during spine surgery. During pedicular screw insertion, the perforation of the anterior ligament may lead to vessel injury, with associated arteriovenous fistula (AVF) and pseudoaneurysm formation. Historically, early surgical intervention has been the treatment of choice for traumatic AVFs. Disadvantages of open repair include technically demand procedures, increased comorbidity, and significant blood loss. Endovascular techniques that allow for a less invasive repair and prevent permanent hemodynamic sequelae are a quite attractive alternative in this setting. These are especially advantageous when there is an extensive hematoma surrounding the vascular lesion, making anatomical differentiation difficult for open repair. We describe a rare case of lumbar artery pseudoaneurysm secondary to percutaneous posterior lumbar spine fixation. Material and Methods: A 63-year male patient admitted to the emergency department due to a motorcycle accident with spine trauma. The patient had past medical history of alcohol abuse. Due to acute respiratory distress syndrome the patient was admitted to ICU. When hemodynamically stable and excluded life-threatening conditions, the patient underwent secondary assessment. Whole body CT and Spine MRI documented a retroperitoneal haematoma associated with a L1 bony Chance fracture, AO spine B2, TLICS 7, ASIA E. Results: At the 10^th day after admission the patient underwent percutaneous short-segment transpedicular fixation with intermediate screws (6S) of T12 to L2 vertebrae. The procedure was uneventful and the patient was transferred to Intermediate Care Unit. Post-surgery contrast abdominopelvic CT was performed to access retroperitoneal hemorrhage evolution, which documented a 31x22mm right lumbar artery pseudoaneurysm at L1 level, absent in the pre-operative imaging exams. A vascular surgical consultation was placed following which an angiogram was performed from a femoral approach. Due to pseudoaneurysm progression (40x27mm) CT-guided thrombin injection was performed 2 days later. CT angiography, 5 days after the procedure, showed lesion relapse and another CT-guided embolization with ethylene-co-vinyl alcohol was performed the following day. Endovascular embolization achieved resolution of the pseudoaneurysm, regression of the hematoma and recovery of the patient during the 6-month follow-up. Conclusion: The authors report this rare case of iatrogenic vascular injury following posterior fixation of thoracolumbar fracture to highlight the importance of correct placement of pedicular screws and support endovascular techniques as a safe and efficient alternative for surgical repair, especially in patients with multiple comorbidities and anatomically challenging locations.

1178

P590: Is there still a place for short fixation in the treatment of thoracolumbar junction fractures?

Jlidi Mohamed ¹ , mouldi lamouchi ¹ , Ayachi Montassar ¹ , Walid Bouaicha ¹ , Mohamed Hedi Gharbi ¹ , and Selim Daas ¹

¹ Orthopedics and Traumatology Department, Hospital of Mohamed Taher Maamouri, Nabeul, Tunisia

Introduction: Injuries of the thoracolumbar junction are the most frequent and result from the transition between the rigid and fixed thoracic spine and the mobile and dynamic lumbar spine. This biomechanical feature makes it particularly vulnerable and constitutes a therapeutic challenge. The aim of our work is to describe the functional, clinical and anatomical results of short fixation (one vertebra above and one vertebra below the fractured vertebra). Material and Methods: This is a retrospective study over a period of 10 years between January 2010 and January 2020. We included patients operated on for dorsolumbar junction fractures by short fixation (one vertebra above the fracture and one vertebra below). The fractures were classified according to Magerl. The evaluation of the results is done on postoperative X-rays and at the last follow-up by calculating the different radiological parameters. Functional evaluation is done using the Oswestry score and the Dallas self-questionnaire. Results: Our series includes 22 patients with an average of age of 44.2 years. None of our patients had an initial neurological deficit. All fractures were compression fractures. Type A3 is the most frequent (11 cases). The average of operating time was 67.68 minutes. The average of blood loss is 350.91 ml. The postoperative vertebral kyphosis was 14.27°, and at last follow-up was 16.73°. The postoperative regional kyphosis was 13.77° and at last follow-up was 16.86°. The postoperative regional traumatic angulation was 10.82 and at last follow-up was 13.86. At last follow-up, the loss in regional kyphosis was 3.09. The loss in vertebral kyphosis was 2.50. The loss in regional traumatic angulation was 3.13. 86.36% of patients have adjacent segment disease. At last follow-up, Oswerty's score was 31.50. Dallas score was 25. The average time off work was 136.67 days. 27.27% of patients returned to work without reclassification. Four patients developed sepsis, two of them early. There were 4 cases of pseudoarthrosis, and one case of screw fracture. Conclusion: Traditionally, the preferred method for stabilization of thoracolumbar junction fracture required the instrumentation of atleast 2 levels above and below the fractured vertebrae. It was thought that this would provide the necessary stability for fracture healing while minimizing the risk of posttraumatic kyphosis or hardware failure at the expense of relative vertebral motion. Currently, mixed fixation (2 levels above and 1 level bellow the fracture) are taking their place and they remain a subject of debate. The short fixation (1 level above and 1 level below the fracture) are losing their indications because of the more frequent complications and especially the loss of reduction and adjacent segment disease

1184

P591: Fracture dislocation of the thoracic spine in 91-years old patient without neurological deficits: report of a case operated percutaneously

Hamdan Abdelrahman ^1,2 , Seyed Emadaldin Sadat ¹ , Ahmed Shawky Abdelgawaad ^1,2 , Bilal Shoumar ¹ , and Ali Ezzati ¹

¹ Spine Surgery, Helios-Hospitals Erfurt, Erfurt, Germany

² Orthopedics and Trauma, Asiut Universty Hospital, Asiut, Egypt

Introduction: Thoracolumbar fractures are the most common injury of the spine accounting for more than half of all spinal trauma cases. Thoracolumbar fracture-dislocations are, however, uncommon and represent less than 3% of these injuries. We report a case of fracture-dislocation of the thoracolumbar spine without neurological deficit in an elderly patient operated upon minimally invasive with cement augmented percutaneous transpedicular posterior fixation. We also review similar cases described in the literature. Materials and Methods: A 91-year-old female with post-traumatic fracture dislocation at the T6-T7 level without neurological deficit, after falling downstairs, was managed as emergency with percutaneous transpedicular fixation, cement augmentation of the screws, percutaneous reposition under fluroscopy and microsurgical decompression Th6/7. Intraoperative three-D image intensifier scan was conducted, and the position of the screws, cement distribution and reduction were controlled. Results: Successful reduction, posterior fixation and cement augmentation was achieved percutaneously. No intraoperative or postoperative complications were detected. The patient could be mobilized on the first postoperative day. His Visual Analogue Scale was 5 on the first day postoperatively. No complications were detected at 3 months follow-up. The patient died 6 months later because of cardiac causes. Conclusion: Fracture-dislocations of the thoracolumbar spine without neurological deficit have been infrequently reported. These fracture-dislocations need to be managed carefully to achieve a good outcome. Minimally invasive reduction and stabilization could be achieved even in elderly osteoporotic patients. This minimizes surgical trauma, postoperative analgesics, and shortens hospital stay.

1193

P592: Bone scan as a diagnostic tool for diagnosing vertebral compression fractures

Saeda Haj ¹ , Alon Rod ¹ , Daniel Weiner-Kalish ² , Elite Arnon-Sheleg ^2,3 , and Nimrod Rahamimov ^1,2

¹ Department of Orthopedics B and Spine Surgery

² Azrieli Faculty of Medicine, Bar Ilan University, Safed, Israel

³ Nuclear Medicine and Diagnostic Radiology, Galilee Medical Center, Nahariya, Israel

Introduction: The diagnosis of vertebral compression fractures (VCF) is usually based on spine radiographs and Computed Tomography (CT) but they may not be able to differentiate between acute and old fractures, a crucial treatment decision parameter. Magnetic Resonance Imaging (MRI) is the method of choice for determining the fracture's age but is not used routinely because of its higher costs and lower availability. Bone scan is a relatively available and low-cost method. It has a higher sensitivity for VCF than conventional radiographs and can demonstrate the amount of osteogenic activity in the fracture, which will change according to the fracture's age. Our study hypothesis was that bone scan will provide us with information regarding the fracture age, eliminating the need for magnetic resonance imaging. Material and Methods: A retrospective study was conducted using data from our hospital electronic health records. Included were 180 consecutive patients admitted to the Galilee Medical Center with a suspected acute VCF who underwent thoraco-lumbar spine CT scanning and triple phase bone scan with Single Photon Computed Tomography (SPECT) of the whole spine during the hospitalization period. Results: Overall, 120 women and 60 men were included (mean age 74.2 years). 13 were excluded because of missing data. 2,417 (94.0%) vertebrae had no evidence of fresh fracture on bone scan and CT. 161 (6.3%) fresh VCFs were diagnosed in both CT and bone scan. 27 (16.2%) patients had fresh VCFs on the bone scan while CT was normal. 37 (22.1%) patients had fresh VCFs on the CT while the bone scan was negative or with low uptake. Conclusion: The combination of CT and bone scanning is an effective tool for evaluating vertebral fractures to determine: 1. If a fracture found on CT is fresh or not 2. To find occult fresh compression fractures not found on CT. This is information is crucial for proper treatment choice.

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P593: Outcome of early surgical intervention in spinal trauma patients, an overview of 245 spinal trauma patients

Ammar Dogar ¹ , Haseeb Hussain ¹ , Ahsan Atta ¹ , and Omar Aziz ¹

¹ Department of Orthopaedics And Spine, Ghurki Trust Teaching Hospital, Lahore, Pakistan

Introduction: The prognosis for spinal cord injuries varies depending on the severity of the injury. There is always hope of recovering some function with spinal cord injuries. The completeness and location of the injury will determine the prognosis., The sooner treatments are implemented to strengthen muscles below the level of the spinal cord injury, the better the prognosis. The first year of recovery is the hardest as the patient is just beginning to adjust to his or her condition. The use of physical and occupational therapy during this time is the key to recovery. The extent of the function fully returning is typically seen in the first two years after the initial injury. Objective: To determine the neurological outcome of patients who presented early with those whose presented late. Materials and Methods: It was a descriptive case series done in the Department of Orthopaedics and Spine between Jan 2016 to Dec 2019. 245 patients who presented to ER or OPD with spinal trauma were included. Those patients who were operated elsewhere or having trauma of more than 10 days or those who were managed conservatively were excluded. After admission, history, examination and investigations surgical intervention were done on same day. Every patient were followed regularly for 2 years to assess the neurology. The data was analyzed using SPSS 17.00 Version. Results: There were 109 total patients that presented with spine trauma. 183 (74%) were male and 62 (26%) were females. Male to female ratio was 2.11:1. Of the 245 total patients that presented 173 (71%) were below 40 years of age and 72 (28.5) patients were above 40. 38 (15.6%) had trauma to the cervical spine, 76 (31.2%) to the thoracic spine, 7 (2.8%) to the thoracolumbar spine and 122 (50.5%) to the lumbar spine. 177 (72.5%) patients had a fall from height. 58 (23.9%) were involved in road traffic accidents. 1 (.9%) had assault and 3 (2.8%) had sports injuries. At the time of presentation out of 245 patients, 218 (89%) had their neurology involved while 26 (11%) had intact neurology. 41 (16.5%) presented within the first 24 hrs while 203 (83.5%) presented after 24 hrs. All the patients were operated on the same day of admission. Among the 41 patient who presented with in 24 hours, 27 patients having full recovery with in 12.66 ± 1.2 months. While the late presenters only 45 patients get fully recovered after 2 year follow up while 42 patients having partial neurology recovery and 24 having just sensory improvement and 92 having no improvement after two year follow up. Conclusion: Spinal trauma is an emergency and having high morbidity and mortality rate. Early presentation and surgical intervention in spinal trauma patients having good neurological outcome as compared to delayed presentation and surgery.

1320

P594: Giant thoracolumbar pseudomeningocele: unusual evolution of traumatic dural tiny tear

Mohamed Amine Gharbi ¹ , Moatassem Belleh Jlassi ¹ , Ahmed zendeoui ¹ , Mahdi Bouzidi ¹ , and Mouadh Nefiss ¹

¹ Orthopedic and Trauma Surgery, Mongi Slim Marsa University Hospital Center, Tunis, Tunisia

Introduction: Spinal pseudomeningoceles are a common complication of large iatrogenic tears in the dural-arachnoid layer. Materials and Methods: We hereby report a case of an unusual giant dorsolumbar pseudomeningocele arising after a traumatic dural tiny tear. Results: We report a case of a 32-year-old patient, a victim of a road traffic accident which caused severe polytrauma including a C2 Magerl type fracture of T11, with a partial neurological deficit (Frankel B). The patient underwent an emergency T11-T12 laminectomy, posterior fixation of T10-T11-T12-L1 and a posterolateral bone graft. We discovered two millimetric dural breaches opposite T11 which were not related to the laminectomy and which were respected. At two years follow up, the removal of the material was performed with intraoperative discovery of a small right posterolateral pseudomeningocele at T11 level which was respected. One year later, the patient presented with a right paravertebral painful mass measuring 20 centimeters. There were no associated neurological symptoms. The magnetic resonance imaging revealed a dorsolumbar paraspinal giant pseudomeningocele extending from T10 to L1 with no compression of the spinal cord. The patient underwent excision of the pseudomeningocele and repair of the dural sac defect. The right foraminal breach was closed with biological fibrin glue. Seen two years later the patient had no complaints and the magnetic resonance imaging was normal. Conclusion: Several procedures have been described in literature in the management of dural sac tears and pseudomeningoceles. This observation may encourage spinal surgeons to repair small dural tears to avoid potential cerebrospinal fluid leak and its complications.

1332

P595: MIS short-segment fixation & Unipedicular screw manipulation technique; a novel method with surgical technique

Brian Chin ¹ , Joshua Wong ¹ , Jiong Hao Tan ¹ , and Naresh Kumar ¹

¹ Orthopaedic Surgery, National University Health Systems, Singapore, Singapore

Introduction: MIS spine surgery has revolutionized fixation of thoracolumbar fractures with burst elements. Recent studies have proven that percutaneous pedicle screw instrumentation is as effective as open instrumentation, with reduction in intraoperative blood loss and operative duration. Techniques such as short-segment pedicle screw fixation including the fractured vertebra has shown satisfactory radiological correction and functional outcomes, avoiding the need for extensile posterior constructs. In the present study, we describe our technique utilizing unipedicular index vertebra fixation and manipulation in minimally invasive surgery (MIS) for thoracolumbar fractures with burst elements. To the author’s knowledge, this technique is not well described in literature as open approaches are often adopted for the above. We aim to highlight the two-year radiological & functional outcomes of 20 consecutive patients who underwent this technique. Material and Methods: A retrospective review of prospectively collected data was conducted on 20 patients with thoracolumbar fractures with burst elements who underwent fixation using our technique. Patient data collected included demographic characteristics, mechanism of injury, associated injuries, neurological deficit at time of admission with pre- & post-operative neurological evaluation and length of hospital stay. Radiological investigations included plain radiographs, CT-spine with reconstruction and MRI-spine which provided data for radiological fracture classifications such as AO Spine and derivation of TLICS score, as well as preoperative planning. Radiological investigations in the postoperative period were carried out by standing radiographs or EOS whole spine at each postoperative follow-up up to two years. Radiological parameters - vertebral wedge angle, regional kyphosis angle, coronal cobb angle, anterior and posterior vertebral body heights were recorded at preoperative, intraoperative, postoperative, and up to 2-year follow-up. Clinical outcome scores of VAS and ODI were also recorded at similar time-points. Results: Radiological outcomes reflect significant lordotic corrections of the vertebral wedge angles up to 2-year follow-up when compared to preoperative values (intraoperative: p = 0.06; postoperative: p = 0.001; 3-month: p = 0.002; 6-month: p = 0.004; 1-year: p = 0.011; 2-year: p = 0.016). Additionally, significant lordotic corrections of regional kyphosis angles (intraoperative: p = 0.00; postoperative: p = 0.00; 3-month: p = 0.031; 6-month: p = 0.039) and increases in anterior vertebral body heights (postoperative: p = 0.001; 3-month: p = 0.010; 6-month: p = 0.020) up to 6-month follow-up was found. Preoperatively, median VAS of 85 (range 30 to 100) and ODI of 90 (range 40 - 98) were recorded. Statistically significant improvements in VAS and ODI were found across all timepoints when compared to preoperative values, with a mean VAS of 11.5 (S.D 4.8) and ODI of 9.9 (S.D 4.5) at 2-year follow-up. Conclusion: Surgical management of thoracolumbar fractures with or without neurological deficit has a role in reducing nursing requirements and postoperative morbidity in patients with polytrauma and other associated injuries. Our approach in treating thoracolumbar fractures with burst elements using MIS short-segment fixation and unipedicular screw manipulation technique shows satisfactory radiological correction & high rates of fracture union, whilst reducing approach-related morbidity & improving functional outcomes.

1386

P596: Thoracolumbar vertebral burst fractures treated by short segment fixation with index screw and transpedicular transcorporeal bone grafting: A clinico radiological analysis pre-post radiological study.

Prabhat Agrawal ¹

¹ Orthopaedics, AIIMS Patna, Patna, India

Introduction: The treatment of thoracolumbar fractures is controversial. Short segment pedicle screw fixation has been used as a treatment of choice for many years yet it is associated with loss of reduction and undesirable implant failure. In 1994, Dick et al introduced an additional screw in the fractured vertebra leading to the 6 screw construct to treat the thoracolumbar fractures but screws at the fractured site has led to inconsistent effect including collapse of the fractured vertebra leading to reduction in the vertebra height and non-union. While long segment fixation incorporates multiple normal mobile spinal segments leading to spinal stiffness. Transpedicular intracorporeal bone grafting proposed by Liao et al, has a comparative advantage of union of the fractured vertebra but the incidence of vertebral collapse still persists due to non-support of the graft under axial loading. Considering both the additional screw at the fractured site and transpedicular bone grafting have disadvantages as non-union and collapse respectively, combining both the procedures should not only fill the void of the fractured vertebra leading to better union but should also impart mechanically more stable construct due to presence of an additional screw in the fractured vertebra. Methodology: The pre-operative clinical examination was done and scoring was done using the ASIA score, Denis work score and Denis pain score. The pre-operative radiograph of the thoracolumbar spine was evaluated to identify the fractured vertebra level and to calculate the radiological parameters like sagittal index, vertebral wedge angle, anterior body compression, Gardner’s kyphosis angle, regional kyphosis, posterior wall angles, Cobbs angle. CT of the thoracolumbar spine was done and the canal clearance at fractured site was measured in mid sagittal sections, location of void in the vertebral body in axial cuts and status of the pedicles of the fractured vertebra were assessed. Results: There were 50 patients on whom we did transpedicular intracorporeal bone grafting with index screw short segment screw fixation. The average preoperative kyphosis angle was 22.3_ ± 6.6_, which was corrected to 5.6_ ± 4.8 immediately after surgery (p < 0.001). At final follow-up, the mean local kyphosis angle was 10.3_ ± 5.2_; loss of correction was 4.7_ ± 2.7_ (p < 0.001). The average preoperative anterior body height was 46.6% ± 12.5%, which improved to 85.7% ± 9.4% immediately after surgery (p < 0.001). Anterior body height restored by surgery was 39.2% ± 13.3%. Anterior body height at 6-month follow-up was 74.9% ± 12.0%, and the average loss of body height correction was 10.8% ± 7.0% (p < 0.001). Conclusion: The outcomes of this study confirmed that the use of two additional augmenting screws in the fractured body with short-segment pedicle screws and intracorporeal bone grafting is sufficient for most thoracolumbar burst fractures, to attain fracture reduction, maintain alignment achieve union and prevent vertebral collapse.

1445

P597: Surgical outcome following delayed short segment posterior fixation of unstable thoracolumbar junction injury

Dewan Shamsul Asif ¹ , Safwat binte Salam ¹ , and Sk Sader Hossain ²

¹ Neurosurgery, Anwer Khan Modern Medical College, Dhaka, Bangladesh

² Neurosurgery, Al Manar Hospital, Dhaka, Bangladesh

Introduction: Spinal cord injury due to traumatic accidents of the thoracolumbar spine is a major cause of disability throughout the world. Due to unavailability of operation theatre schedule most of the spine injured patients are managed conservatively or there is inadvertent delay in surgery. This prospective study was designed to evaluate neurological recovery and functional outcome following delayed short segment posterior fixation of thoracolumbar junction injuries classified according to TLICS system. Material and Methods: 38 TLJ injured patient followed up after surgery for 84 months. The purpose of this study is to report the surgical outcome of thoracolumbar junction fractures treated with short-segment pedicle instrumentation. All patients had neurologic deficit at the time of presentation. The unstable spine was fixed based on Thoracolumbar Injury Classification Score system (TLICS), between 7-82 days after trauma, by posterior short segment instrumentation. Neurological recovery and functional status assessed in the follow-up period at one, three, six- and eighty-four-month’s interval by ASIA impairment scale and Oswestry Disability Index respectively. Results: There were 36 male and 2 female patients with average age 29.42 ± 8.11 years (range 17-50 years). Fall from a height was the most common (79%). Most of the patients were farmer or day labour. Most frequent level fractures were at D12 and L1 comprising 76.3%. 10 (26.3%) patients had type A compression fracture and 28 (73.7%) patients had type B distraction type fracture. There were preoperatively 2 (5.3%) patients with ASIA grade A, 3 (7.9%) patients with ASIA grade B, 27 (71.1%) patients with ASIA grade C and 6 (15.8%) patients with ASIA grade D. There was no neurological deterioration after surgery. At final follow up of 22 patients, 96.87% exhibited neurological improvement for at least one ASIA grade. There was a statistically significant relation between pre-operative MRI interpretation and operative findings of posterior ligamentous complex injury. There were no per-operative complications and only 15.8% had different kinds of complications post-operatively. On admission most of the patients were bed bound. But at six follow up ODI mean score was 19.06 ± 6.67 (range 8-35) i.e. most of patients were in minimal disability state. We could finally follow up 22 patients at 84 months interval over telephone. Among 38 patients 2 patient died due to bed sore complications. Rest of 20 patients are doing their daily job with minimal disability at 84 months. Conclusion: It became clear that careful diagnostic imaging examination, especially MRI, should be conducted in order to eliminate the existence of posterior ligamentous or osseous pathologies. Where early surgery is a distant dream delayed operative outcome showed very promising results. Especially in our society where a dependent person is more than a diseased itself and if these patients were not treated properly, they would not only lose their employment but could be a permanent burden and nuisance for their family. Although long term follow-up evaluation needs to be verified radiologically, the long-term functional follow-up results suggest a favorable outcome for delayed short-segment posterior instrumentation of traumatic thoracolumbar junction injuries.

1582

P599: Pedicle screws length and crosslinks as factors of stabilization reliability of thoracolumbar junction traumatic injuries: finite element study in lateroflection

Oleksii Nekhlopochyn ¹ , Iaroslav Tsymbaliuk ² , Ievgen Cheshuk ² , Milan Vorodi ² , Michael Karpinsky ³ , and Oleksandr Yaresko ³

¹ Spinal Neurosurgery

² Restorative Neurosurgery Department

³ Biomechanical Laboratory, Sytenko Institute of Spine and Joint Pathology, Kharkiv, Ukraine

Introduction: The zone of the thoracolumbar junction is the most susceptible to traumatic injuries due to anatomical and physiological features. Accordingly, the stabilization of this spine requires high reliability. Extensive clinical experience of transpedicular stabilization usage has revealed a number of factors hypothetically or actually determining the reliability of fixation. The main are the depth of screw insertion and the use of crosslinks. The effect of lateroflexion on the operated spine as one of the most unfavorable types of loading is considered. Material and Methods: Mathematical finite element model of a fragment of the human thoracolumbar spine (Тh9-L5) was developed in biomechanics laboratory of Sytenko Institute of Spine and Joint Pathology. We modeled the result of decompression-stabilizing surgery with total removal of the anterior and posterior support complexes of the vertebral bodies Th12‒L1 including installation of vertebral body replacing implant and fixation with a transpedicular system using 4 pairs of screws (into the vertebral bodies Th10, Th11, L2 and L3). Lateroflexion was modeled by applying a load of 350 N acting from right to left on the body and facet processes of the Th9 vertebra. Results: When evaluating the model without crosslinks and using monocortical pedicle screws, it was found that the maximum loading values in the Th10, Th11, L2, and L3 vertebral bodies were 3.4, 2.0, 3.5, and 8.6 MPa, respectively; and in the screws in these vertebrae - 48.4, 48.3, 23.3 and 43.5 MPa. When using bicortical screws without crosslinks - respectively 3.1, 2.5, 3.8, 9.6 MPa and 49.9, 51.9, 25.8, 44.8 MPa for bodies and screws; when using a combination of short screws and crosslinks - 3.2, 2.0, 2.6, 7.5 MPa and 47.6, 47.5, 22.6, 41.2 MPa; when using crosslinks and bicortical screws - 3.0, 2.2, 2.7, 8.8 MPa and 48.3, 49.6, 24.3, 42.5 MPa. Conclusion: In lateroflexion monocortical pedicle screws cause lower critical loading rates compared to long screws at all control points of the model. Crosslinks in combination with both short and long screws help to reduce stress levels. The use of monocortical pedicle screws in combination with transverse ties seems to be the most biomechanically effective in lateroflexion.

1619

P600: Comparison between surgical outcome of short segment versus long segment transpedicular stabilization for treatment of thorocolumbar fracture

Md Yousuf Ali ¹ and Samrat Parajuli ²

¹ Spine Surgery, Department of Orthopedic Surgery, Bangabandhu Sheikh Mujib Medical University, Dhaka, Bangladesh

² Orthopedic Surgery, Bangabandhu Sheikh Mujib Medical University, Dhaka, Bangladesh

Introduction: Thoracolumbar fracture is one of the most common spinal traumas. It was still indeterminate whether short-segment (SS) fixation was more effective and preferable than long-segment (LS) fixation. We therefore conducted this meta-analysis to assess the comparative safety and efficacy of SS and LS fixation for the treatment of thoracolumbar fracture. The indications for operative treatment and type of stabilization procedures for the treatment of thoracolumbar fracture remain controversial. Material and Methods: The study was conducted at Department of Orthopedic Surgery, Bangabandhu Sheikh Mujib Medical University (BSMMU) and different private clinics at Dhaka, from July 2006 to June 2020. Surgery was performed in multiple centers by the same spine surgeon to evaluate the efficacy of short-segment fixation compared with that of long-segment fixation in terms of the radiological and clinical outcomes in thoracolumbar burst fractures. Total of 422 thoracolumbar fracture patients who underwent the treatment with SS fixation (n = 217) and LS fixation (n = 205) were included. Results: The outcomes of this study indicated that outcome regarding implant failure, anterior body height loss (ABHL), cobb angle (CA) and restoration ratio of compromised canal is better in the LS fixation group than those of SS fixation group. However, SS group significantly reduced surgical time when compared with LS group. There was no significant difference regarding blood loss, complication rate, Sagittal Index (SI) and kyphotic angle (KA). Radiological assessment of the kyphotic angle was performed using the Cobb method immediately after the operation and at 3, 6, and 12 months postoperatively. The clinical outcomes were evaluated using the Frankel score and ASIA grade criteria at the last follow-up in Short segment and long segment respectively. The sex ratio, mean age of patients, and composition of the fractured vertebral body were similar in both groups. In the long-segment and short-segment group, 195 (95.1%) and 198 (91.2%) cases showed excellent or good outcomes, respectively. In long segment the mean preoperative angle of injured vertebra was 18.5°, the mean postoperative angle was 8.8°, the mean angle at 6 month’s follow-up was 10.5°, the mean initial correction was 9.9°, and the mean loss of correction was 1.9°. So, the mean overall correction was found 8.0°. Whereas in Short segment the mean preoperative angle of injured vertebra was 19.7°, the mean postoperative angle was 8.6°, the mean angle at 6 month’s follow-up was 11.9°, the mean initial correction was 11.1°, the mean loss of correction was 3.3°. So, the mean overall correction was found 7.8°. There was no statistically significant difference in the average loss of kyphosis correction between the two groups (p > 0.05). Conclusion: In conclusion, short-segment pedicle screw fixation including the fractured vertebral body might be as effective as long-segment pedicle screw fixation for the treatment of unstable thoracolumbar spinal fracture.

1630

P601: New AO spine thoracolumbar injury classification system can predict subsequent adjacent osteoporotic vertebral compression fracture after balloon kyphoplasty

Takayuki Ogawa ¹ , Chikako Shinozaki ¹ , Takashi Chikawa ² , and Akihiro Nagamachi ³

¹ Orthopedics, Kaisei General Hospital, Kagawa, Japan

² Orthopedics,Tokushima Prefecture Naruto Hospital, Tokushima, Japan

³ Orthopedics, Yoshinogawa Medical Center, Tokushima, Japan

Introduction: Balloon kyphoplasty (BKP) is a minimal invasive technique to treat symptomatic osteoporotic vertebral compression fracture (OVCF). BKP is a relatively effective surgical procedure, however, we sometimes encountered complications such as subsequent adjacent OVCF or cement leakages. Subsequent OVCF causes sever back pain and kyphosis, reducing patient quality of life. Preoperative estimation of subsequent adjacent OVCF occurrence may help selecting other optional surgery or planning rehabilitation program after BKP. New AO spine thoracolumbar injury classification system (AO system) showed substantial reliability and reproducibility among the surgeons. In this current study, we used AO system to classify OVCF preoperatively and investigated incidence of subsequent OVCF after BKP in each type of AO system. Material and Methods: Between March, 2016 and March, 2022, 72 thoracolumbar OVCF were treated with BKP. Patients with hemodialysis, Parkinson’s disease, malignant disease and former BKP were excluded from this study. A total of 52 patients participated in this study. There were 18 male and 34 female and their mean age was 80 years. All patients underwent standing plain X-ray, CT and MRI before surgery, 1 week, 2 months and 4 months after the surgery. All fracture type were classified according to AO system before surgery. Occurrence of subsequent adjacent OVCF in each type of AO system was observed in follow-up period. Results: Thirty-seven patients had no subsequent OVCF during the observation period, their mean age was 81 years. Fifteen patients had subsequent adjacent OVCF, their mean age was 79 years. Mean T-score of bone mineral density (BMD) of patients with subsequent OVCF and without subsequent OVCF were -1.33 and -2.24, respectively. There was no statistically significant difference of patient’s demographics between two groups. Seventeen patients classified into A1, and no subsequent OVCF was observed. Twenty-one patients classified into A3, and subsequent OVCF observed in 2 patients. Eight patients classified into A4, and subsequent OVCF observed in all patients. Six patients classified into B2, and subsequent OVCF observed in 5 patients. Incidence of subsequent OVCF of each type was 0% in A1, 9.3% in A3, 100% in A4 and 83.3% in B2. Statistically significant difference of incidence was observed among 4 types of OVCF (chi-square test p < 0.001). Conclusion: This study demonstrated that AO system can estimate occurrence of subsequent adjacent OVCF after BKP. Type A4 and B2 were found to be more prone to subsequent adjacent OVCF.

1706

P602: Posterior approach in surgical management of traumatic spondyloptosis of thoracolumbar junction

Oleksii Nekhlopochyn ¹ , Iaroslav Tsymbaliuk ² , Vadim Verbov ² , Ievgen Cheshuk ² , and Milan Vorodi ²

¹ Spinal Neurosurgery

² Restorative Neurosurgery Department, Romodanov Neurosurgery Institute, Kyiv, Ukraine

Introduction: The thoracolumbar junction is the most common location of traumatic spinal injuries and contains 50-60% of all fractures of the thoracic and lumbar spine. Spondyloptosis is not very frequent, but one of the most severe types of traumatic injury, that is characterized by a gross violation of spine axis in one or more planes. Traumatic spondyloptosis is divided into reducible and irreducible, depending on the possibility of intraoperative restoration of the spinal axis without resection of the damaged vertebra. Material and Methods: We performed a retrospective analysis of the patients’ database admitted in Romodanov Neurosurgery Institute of National Academy of Medical Sciences of Ukraine over the past 4 years (2017 to 2020) to identify all cases with traumatic irreducible spondyloptosis of the thoracolumbar junction. Results: Five patients aged from 18 to 52 years (mean 31.2 years) were revealed. The minimum period from injury to surgery was 14 days, maximum 3 months and 2 days (average 42.2 days). All patients had a neurological deficit of ASIA A at the time of admission. The score by TLICS scale was 8 points. All the patients had the injury of laterospondyloroptosis type: in three cases as an isolated displacement only in the coronary plane, in two combined - in the coronary and sagittal. We performed surgery by isolated posterior approach in all cases. As a body replacement system in 2 patients, we used a vertical cylindrical implant (Mesh), in 3 patients - a telescopic body replacing implant. The method of bicortical implantation of transpedicular screws was applied. The transpedicular system was strengthened by two cross links of the rod-to-rod type. We managed to achieve the restoration of spine axis in both the coronary and sagittal planes. Subsequent terms of control examinations were 2; 6 and 12-18 months of the postoperative period. We observed regression of neurological disorders in two patients, in one case to ASIA B, in another to ASIA C. Conclusion: Isolated posterior approach has demonstrated high efficacy in the surgical management of traumatic irreducible spondyloptosis of the thoracolumbar junction, allowed both to restore the axis of the spine and to provide the stability of fusion.

1712

P603: What is the best decision-making classification of traumatic thoracolumbar junction injuries?

Oleksii Nekhlopochyn ¹ , Iaroslav Tsymbaliuk ² , Vadim Verbov ² , Ievgen Cheshuk ² , and Milan Vorodi ²

¹ Spinal Neurosurgery

² Restorative Neurosurgery Department, Romodanov Neurosurgery Institute, Kyiv, Ukraine

Introduction: The thoracolumbar junction is one of the most "typical" areas of traumatic changes when exposed to a mechanical load on the human body. Currently, a specific classification for injuries of the thoracolumbar junction has not been developed, therefore, when describing injuries in this zone, grading schemas characterizing the whole thoracic and lumbar spine are used. Material and Methods: A retrospective analysis of the treatment tactics was carried out in 96 patients with traumatic injuries of the thoracolumbar junction, who attended the outpatient department of the A.P. Romodanov Institute in the period from 2019 to 2021. The average age of patients is 41.3 years. The ratio of men and women is 3.6:1.0. We analyzed the patients’ data who underwent both surgical treatment and conservative therapy. All injuries were ranked using F. Magerl et al. and AOSpine classifications. Neurological status was assessed using the ASIA scale (American Spinal Injury Association), the nature of the lesion was specified using the McCormack criteria. Statistical data processing was performed using the Random Forest machine learning algorithm. Results: The most frequent injuries according to the classification of F. Magerl et al. were A3.1 (14.58%), A3.2 and B2.3 (8.33% each), according to the AOSpine classification - type C (26.04%), subtypes B2 (17.71%) and A4 (16.67%). When assessing the relationship between the nature of damage and the level of neurological disorders, the overall error rate for F. Magerl et al. and AOSpine classifications were 69.79% and 66.67% respectively. The greatest relationship between the nature of osteoligamentous lesions and neurological disorders is typical for patients with ASIA B and E. In the treatment of patients, open posterior decompression of the spinal canal in combination with transpedicular stabilization (40.62%), isolated posterior stabilization without decompression (25.0%), a combination of decompressive laminectomy, posterolateral corpectomy with interbody fusion using a body-replacing system supplemented with transpedicular fixation (14.58%), less often conservative therapy (9.38%) and percutaneous cementoplasty (7.29%). The nature of the injury makes it possible to unambiguously determine the optimal method of therapy using the classification of F. Magerl et al. with a probability of 58.33%, when applying the AOSpine classification - with a probability of 55.21%. When building models taking into account the nature of damage, the level of neurological disorders and McCormack criteria, it was found that the error in unambiguously determining the most effective method of treatment when using the classification of F. Magerl et al. is 26.04%, when using the AOSpine classification - 21.88%. Conclusion: The type of the injury, ranked using the classifications of AOSpine and F. Magerl et al., does not allow choosing the optimal method for the treatment of traumatic lesion of the thoracolumbar junction. The use of additional predictors significantly improves the accuracy of the forecast. When applying the AOSpine classification, the best results were recorded. The use of the AOSpine classification is more promising for the development of a multifactorial algorithm for the treatment of traumatic injuries of the thoracolumbar junction.

1719

P604: Some biomechanical considerations regarding pedicle screw insertion depth and role of crosslinks in thoracolumbar junction fracture: a study under compressive loads

Oleksii Nekhlopochyn ¹ , Vadim Verbov ² , Iaroslav Tsymbaliuk ² , Michael Karpinsky ³ , and Oleksandr Yaresko ³

¹ Spinal Neurosurgery

² Restorative Neurosurgery Department, Romodanov Neurosurgery Institute, Kyiv, Ukraine

³ Biomechanical Laboratory, Sytenko Institute of Spine and Joint Pathology, Kyiv, Ukraine

Introduction: The thoracolumbar junction is one of the most frequently damaged parts of the human spine when exposed to a traumatic factor. Corpectomy in combination with posterior decompression and restoration of the spinal support function is often performed using an interbody implant and posterior transpedicular stabilization to achieve adequate decompression and stabilization in severe traumatic injuries of this level. The surgery of a type is characterized by significant instability of the operated segment and determines increased requirements for the rigidity and reliability of posterior fixation. We have modeled the situation of a two-level corpectomy with subsequent replacement of bodies with a mesh implant and posterior transpedicular stabilization with 8 screws. Material and Methods: We developed a mathematical finite element model of the human thoracolumbar spine, the components of which are the vertebrae Th9 ‒ Th11 and L2-L5 (vertebrae Th12-L1 are removed), as well as elements of metal structures vertebral replacing implant and transpedicular system. We modeled four variants of transpedicular fixation: system with short screws and screws passing through the cortical layer of anterior wall of vertebral body, as well as with two cross links and without them. The stress-strain state of the models was studied under the influence of a vertical compressive distributed load, which was applied to the body of the Th9 vertebra and its articular surfaces. The load value was 350 N, which corresponds to the weight of the upper body. Results: We determined that transpedicular fixation of the thoracolumbar vertebrae with the use of long screws reduces the level of tension in the bone elements of the models. In the area of screw entry into the pedicle of the T10, T11, L2 and L3 vertebral arch, the load when using short screws was 3.1, 1.7, 3.9 and 12.1 MPa, respectively, when using bicortically installed screws - 2.9, 1 8, 3.8 and 10.6 MPa. The addition of two cross-links also reduces the maximum load values in critical areas of the model to a certain extent. In the case of a combination of short screws and two cross-links, the load in these areas was 2.8, 1.7, 3.6 and 11.5 MPa, when using bicortical screws and cross-links - 2.8, 1.6, 3.3 and 9.3 MPa. The study of the stress-strain state of other parts of the model revealed a similar trend. Conclusion: The use of long screws with fixation in the cortical bone of anterior part of the vertebral bodies reduces the level of tension in the bone elements of the models. The use of cross links gives greater rigidity to the transpedicular system, that also reduces the tension in the bone tissue.

1746

P605: Spinal subdural hematoma in ankylosing spondylitis patients without coagulation therapy: case study of two patients

Inka Berglar ¹ , Laura Snyder ² , and Gabriella Paisan ²

¹ Neuroradiology, Massachusetts General Hospital, Boston, United States

² Neurosurgery, Barrow Neurological Institute, Phoenix, United States

Introduction: Patients with ankylosing spondylitis (AS) are at high risk of significant spinal trauma after relatively low impact events such as ground level falls. Due to the osteopenic nature of the disease process, complex spinal fractures are common in these patients. Additionally, patients may sustain rare traumatic complications from these fractures, such as spinal subdural or epidural hematomas. Traumatic spinal subdural hematoma (SSDH) is extremely rare with only a few cases described in the literature and is typically associated with antiplatelet or anticoagulant use. In this case series, we describe two cases of traumatic SSDH in patients with ankylosing spondylitis without anticoagulation or antiplatelet therapy, which has not previously been reported in the literature. Material and Methods: Case study. Results: Ankylosing spondylitis is an important subtype of an interrelated group of rheumatic diseases and AS patients are particularly vulnerable to severe spinal injuries following relatively minor traumas due to the ankylosing process of the spine. Most traumatic spinal hematomas are epidural and SSDHs account for only a fracture of cases of spinal hematomas. Treatment options vary between conservative and surgical management and indications for surgical evacuation are dependent on the clinical context of the patient and their injury. Conclusion: This is the first detailed report of two posttraumatic AS patients with SSDHs without prior anticoagulation therapy. Although the etiology is not yet fully understood, these cases demonstrate that the appearance of SSDHs can be highly variable and can occur after only minor trauma in AS patients. While epidural and especially subdural spinal hematomas are extremely rare in general, AS patients are more likely to develop these hemorrhages and they should be considered as a possible cause of spinal cord injury in this population and may also require surgical evacuation.

1800

P606: Thoracic fracture dislocation with bilateral locked facet joints - a modified reduction technique

Jure Pavesic ¹ , Stjepan Dokuzovic ¹ , Stipe Corluka ¹ , and Vide Bilic ¹

¹ Spinal Surgery Division, Traumatology Department, University Hospital Centre Sestre Milosrdnice, Zagreb, Croatia

Introduction: Thoracic spine fracture dislocations with bilateral locked facets pose a challenge for safe and effective intraoperative reduction. Several techniques have been described, though they may in some contexts prove hazardous or ineffective. Material and Methods: We present a modification to previously described reduction techniques where the force required to perform the reduction is dispersed over several elements of the reduction process as to minimize further trauma from the reduction process itself. Results: When other techniques fail due to extreme rigidity, increasing reduction force is not always an option due to the possibility of screw pull-out, lamina fracture, or sudden forceful reduction which may potentially cause a second hit to the spinal cord. Force dispersion by technique modification is our preferred method to reduce required forces and make the reduction safer for the cord and remaining healthy bone. Conclusion: Our modification may be a reliable and safe method for highly rigid locked fracture-dislocations of the thoracic spine, though further validation is required.

1840

P607: Results of the placement of thoracolumbar transpedicular screws in open surgery guided by fluoroscopy in patients with spine trauma

Saul Solorio Pineda ¹ , Miguel Angel Ramirez Sosa ² , Abrahan Alfonso Tafur Grandett ² , Eduardo Reyna Martinez ² , Jorge Ortega Espino ² , and Milton Inocencio Ruiz Flores ²

¹ Spine Surgery Department, Instituto Nacional de Rehabilitacion, CDMX, Mexico

² Neurosurgery, Centro Medico Lic. Adolfo Lopez Mateos, ISEM, Toluca de Lerdo, Mexico

Background: The placement of transpedicular screws is a technique frequently performed in order to provide stabilization to the spine. This technique consists of placing screws through the pedicle and directed towards the vertebral body through a posterior approach and placing a system of titanium bars. Objective: To analyze the results of precision and malposition of thoracolumbar transpedicular screws guided by fluoroscopy, through helical tomography. Material and Methods: A retrospective, observational and descriptive analysis of 124 patients over 14 years of age who presented spinal cord injury with data of vertebral instability and/or fractures in the thoracolumbar region who underwent transpedicular fixation with titanium screws by open posterior guided approach was performed. by fluoroscopy in the period from January 1, 2016 to December 31, 2019. Results: The most frequently performed approach was the thoraco-lumbar in 52.62% of the cases, 910 screws were placed, 75.8% of the cases 8 screws were placed per patient and the percentage of good placement in our cases was 91.21% (n = 830). Conclusion: The surgical technique described is safe with precision percentages comparable to that described in the literature and with a low percentage of complications.

Keywords: Pedicle screw, fluoroscopy, computed tomography

1905

P608: Multicenter validation of a CT criteria for thoracolumbar posterior ligamentous complex injury: study protocol and preliminary results

Mohamed Ali ¹

¹ Neurosurgery, Prince Mohamed Bin Abdelaziz Hospital, Riyadh, Saudi Arabia

Introduction: Two recent single-institution studies have proposed criteria for posterior ligamentous complex (PLC) status in Computed Tomography (CT) based on the number of positive CT findings. PLC should be considered injured if ≥ 2 positive CT findings based on a high positive predictive value (PPV, 91%) for PLC injury in MRI, indeterminate PLC (M1 modifier) if there is a single positive CT finding (PPV 31%), and intact if there are no positive CT findings (PPV 9%). This retrospective multicenter study aims to validate those CT criteria for PLC injury in a large, independent population from diffident settings. Materials & Methods: Three hundred fifty-seven consecutive patients with at least one vertebral body fracture (T1-L5) who underwent CT and MRI within ten days of injury will be enrolled in participating centers. Patients with translation injury, osteoporotic or pathological fractures or incomplete imaging were excluded. At least two reviewers from each center will assess CT for the following findings according to proposed definitions: facet joint malalignment, facet joint widening, horizontal laminar fracture, spinous process fracture, and interspinous widening. The reference standard is PLC injury defined by black stripe discontinuity due to supraspinous or ligamentum flavum rupture. Each reviewer will interpret all de-identified CT/ MRI images independently, blinded to clinical data and other readings, within a 4-week interval. When the two reviewers disagreed about the MRI's PLC status or the Number of CT findings, the case was resolved by a third reviewer. Prior consensus training will be done for all reviewers to standardize the imaging interpretation protocol. Multivariate association between CT findings and PLC injury will be examined. Results: the preliminary results from multiple centers will be presented. The diagnostic accuracy of combinations of those CT findings with independent association with PLC injury will be examined (0, 1, ≥2 findings). The following measures will be reported: sensitivity, specificity, accuracy, positive and negative predictive values, and positive and negative likelihood ratio. Inter-intraobserver reliability in identifying each CT finding or combinations of CT findings will be assessed using Cohen’s kappa (k) and Fleiss kappa statistics. Conclusion: We provided a comprehensive methodology for a multicenter validation of a CT criteria for PLC injury. A multicenter design is needed to improve generalizability of the findings. A retrospective study with well balanced study population is more feasible thana prospective design.

Keywords: Posterior ligamentous complex, thoracolumbar fractures, imaging algorithm, Computed tomography, Magnetic resonance imaging

Trauma - Other

120

P609: Non-cannulated S2AI screws have higher rates of hardware failure compared to cannulated S2AI screws

Nina Lara ¹ , Alex Pu ¹ , Navid Chowdhury ¹ , Jacob Bruckner ¹ , Ivan Ye ¹ , Alexandra Thomson ¹ , Ryan Smith ¹ , Tyler Pease ¹ , Brittany Oster ¹ , Vincent Miseo ¹ , Daniel Cavanaugh ¹ , Eugene Koh ¹ , Daniel Gelb ¹ , Steven Ludwoig ¹ , and Vache Hambardzumyan ¹

¹ Spine Surgery Division, Orthopaedics, University of Maryland School of Medicine, Baltimore, United States

Introduction: The variability of S2 alar iliac (S2AI) screw loosening has been reported in the literature to range from 2.9% to as high as 66% depending on the type of imaging used for assessment. No studies have compared the type of screw used in S2AI fixation and the impact on hardware failure or revision rates. The purpose of this study is to compare the incidence of hardware failure and revision rates between cannulated vs non-cannulated screws. Materials and Methods: Following IRB approval, patients who underwent elective or traumatic pelvic fixation between 2017-2019 were retrospectively reviewed. Patients were divided into two cohorts depending on the type of S2AI screw received, cannulated or non-cannulated. The primary outcomes were reoperation rates and hardware failure within 2 years. Results: A total of 139 patients were included in this study. There were 54 (38.8%) patients with cannulated screw implants and 85 (61.2%) patients with non-cannulated screw implants. The rate of hardware failure within 2 years was significantly higher in the non-cannulated screw cohort than the cannulated screw cohort (23.5% vs 9.3%, p = 0.03). Rod breakage was the most common mechanism of failure (55%). There were no difference in the 2-year reoperation rates. Conclusions: Non-cannulated S2AI screws had higher hardware failure rates compared to cannulated S2AI screws. However, there was no significant difference in reoperation rates within 2 years between cohorts.

198

P610: The postoperative pedicle screw position after dorsal instrumentation with intraoperative cone beam CT imaging is worse in patients with obesity than in normal-weight patients

Felix Zimmermann ¹ , Kohl Katharina ¹ , Eric Mandelka ¹ , Paul Alfred Grützner ¹ , Jochen Franke ¹ , and Vetter Sven ¹

¹ BG Klinik Ludwigshafen, Ludwigshafen, Germany

Background: Intraoperative cone beam CT (CBCT) imaging in dorsal instrumentation facilitates pedicle screw positioning. However, this effect may be reduced due to artifacts that affect image quality in patients with obesity. The purpose of this study was to evaluate whether intraoperative CBCT leads to an improved postoperative screw position independent of body weight. Materials and Methods: A total of 71 patients (18 patients with a BMI > 30 kg/m², 53 patients with a BMI < 30 kg/m²) who underwent dorsal instrumentation with intraoperative CBCT imaging were included in study groups one (SG1) and two (SG2). In SG1, 128 pedicle screws were implanted, compared with 361 in SG2. Patient BMI was defined according to the WHO recommendations. The pedicle screw position in postoperative computed tomography was assessed using the Gertzbein-Robbins classification. Results: In SG1 (BMI > 30 kg/m²), a total of 107 (83.6%) pedicle screws showed no relevant perforation (type A + B), and 21 (16.4%) pedicle screws showed relevant perforation (type C – E) in the postoperative computed tomography. In SG2 (BMI < 30 kg/m²), 328 (90.9%) screws were classified as type A + B, and 33 (9.1%) screws were classified as type C – E in the postoperative computed tomography. There were significant differences between the values of SG1 and SG2 (p = 0.03). Conclusion: The included patients with obesity showed significantly worse pedicle screw positions postoperatively after dorsal instrumentation with intraoperative CBCT imaging than the included normal-weight patients. Consequently, obesity seems to have a negative effect on the postoperative pedicle screw position after dorsal instrumentation despite intraoperative CBCT imaging.

Keywords: spine, dorsal instrumentation, pedicle screw, cone-beam CT, patients with obesity, BMI.

257

P611: Fragile lumbar chance fracture in patients with ankylosing spondylitis- Right or wrong for surgical indication

Takahiro Iizuka ¹ , Tetsuro Takai ¹ , Tokuji Kashiro ¹ , and Hiroshige Debata ¹

¹ Orthopedic Spine Surgery, Kouseikai Takai Hospital, Nara, Japan

Introduction: Chance Fracture is Classified as Type B1-3 (AO spine Classification System). This fracture is considered to be a failure of the whole vertebral column caused by high-energy flexion or extension force. We experienced 4 patients with Fragile Chance Fracture with ankylosing spondylitis and also osteoporosis. Osteoporotic vertebral compression fractures are common fractures as fragile fractures in elderlies. Chance Fractures with Ankylosing Spine are challenging against conservative therapies which frequently resulted in non-union. This type of fracture requires surgical fixation in the early stage of its onset. Aims: We reported unwonted Fragile Chance Fracture in patients with Ankylosing Spondylitis and Osteoporosis in extremely elder patients. We would like to discuss the indications and significance of Fragile Chance Fractures in extremely elder patients from these patients. Results and Cases Reports: We experienced Four patients from 2016-2022 with this TypeB1 fractures. Average age 83 (81-87). All of them were male and also caused by a fragile fall on the floor, not by high-energy trauma i.e. traffic accident. All patients were treated with vertebral plasty using HA sticks, posterior local bone plantations, and posterior instrumentations 2 above and 2 below of fractured site. Operation time was 1.5-2 hours and Blood loss was less than 200 ml. All patients were relieved from intractable pain and discharged within 2-3 weeks. EVENITY (romosozumab aqqg from AMGEN) was applied to all patients. Discussions: First of all, we should discuss the surgical indications for extremely elder patients in aging societies. Unwonted trauma in the elderly should be treated quickly (data from hip fractures) and also less invasive in terms of surgical time and blood loss. Fragile Chance fracture in ankylosing spine is one of the most intractable vertebral fractures which resulted in prolonged pain and delayed neural damage. Especially in elderlies, surgical timing loss would sometimes result in loss of life expectancy. We suggest a quick decision for surgical treatment if they would be tolerable for surgical stress of 1.5-2 hours and 200ml blood loss. The delayed surgical indication would spoil all the results in Fragile Chance Fractures in elderlies.

838

P612: Acute management of spinal cord injury: a retrospective analysis from a Portuguese referral centre

Rita Faria ¹ , Sara Diniz ² , Carolina Luísa Lemos ¹ , and Ricardo Rodrigues-Pinto ²

¹ Instituto de Ciências Biomédicas Abel Salazar, Portugal

² Orthopaedic Department, Centro Hospitalar Universitário do Porto, Portugal

Introduction: Acute spinal cord injury entails significant impairment in patients’ quality of life and elevated financial costs to the healthcare system and society. Early access to specialized care and surgical decompression within 24 hours post-injury have been associated with improved outcomes and are, therefore, currently recommended. Centro Hospitalar Universitário do Porto holds a dedicated Spinal Unit which has a rota through the year that designates an on-call spine surgeon to treat spine and spinal cord injury patients. Nevertheless, data regarding the timing of treatment of these patients is not documented. The aim was to characterize patients with spinal cord injury that underwent surgery at Centro Hospitalar Universitário do Porto and their pathway to definitive care post-injury. Material and Methods: A single-centre retrospective study was performed. Adult patients with pre-operative diagnosis of traumatic spinal injuries that underwent surgery at Centro Hospitalar Universitário do Porto over the course of 4 years were identified and classified with baseline American Spinal Injury Association Impairment Scale grades, which were reassessed after a year. The times of first hospital admission, arrival at the site of definitive care and surgery were collected. Patients were classified by injury mechanism, anatomical level of injury, neurological injury, admissions at intermediate hospitals and timings of surgery. The relationship between severity of neurological injury and time to surgery was evaluated. Results: 208 patients were included, most of whom were males. Falls were responsible for the majority of injuries. 33.7% of the patients had neurological deficits, 37.1% of which had the worst pattern level (ASIA A). 40 (57.1%) patients with neurological injuries were first admitted at an intermediate hospital. 44 (63.8%) were submitted to surgery in the first 12 hours, 10 (14.5%) between 12-24 hours and 15 (21.7%) after 24 hours. Patients with more severe neurological injuries were operated significantly faster (p < 0.001). Conclusion: Admissions at intermediate hospitals represent a potentially modifiable system-related cause for delays. Based on these results perhaps an effort should be made in order to create a streamlined path to definitive care for patients with acute spinal cord injury.

892

P613: Hitting the target: bullseye trauma in motor vehicle accidents

Aisha Jeffers ¹ , Georgina Crate ¹ , Simon Weil ¹ , Dimitrios Teslios ¹ , Mohamed Abdalla ¹ , Bisola Ajayi ¹ , Jason Bernard ¹ , Timothy Bishop ¹ , and Darren Lui ¹

¹ Neurosciences, St. Georges Hospital, London, United Kingdom

Introduction: A ‘bullseye injury’ is a colloquial term in the UK for a head injury involving impact to a structure, typically a windscreen, with the shatter pattern similar to that of a target. The patient can be either internal or external to the vehicle that has been hit. It is a colloquial term with a heterogenous variety of mechanism of injury often insinuating a significant injury severity score (ISS). To the authors knowledge there are no studies characterising the Orthopaedic injuries and identifying the prevalence of head and spinal injuries associated with bullseye trauma. Methods: A retrospective study reviewed a major trauma centre prospectively collected database between 31/10/2017 and 16/03/2020 searching for the term ‘bullseye’. Identification of head and spinal injuries were examined. Velocity of injury, type of fractures sustained and accompanying injuries were assessed. The injury severity score (ISS) was also calculated for all patients. Results: 129 patients were identified with 102 patients having complete records for review. The categories were Pedestrians (n = 60), cyclists (n = 14), motorcyclists (n = 15) and car (n = 13). All patients underwent Full body Trauma CT scans. The mean ISS was 9.2 and for motorbike injuries 13.5. Severe injury is denoted ISS > 15 with external bullseye traumas occurred in pedestrians (20%), cyclists (21%), motorbikes (21%) whereas patients with internal bullseye injuries within the car was only 7%. Mortality occurrences were 5% in pedestrians and 7% in cyclists. 4.6% of patients presenting with a bullseye injury sustained spinal injuries. These patients were all male, mean age 52.6 (range 57y – 74y). As a whole, the majority of patients were pedestrians struck by cars (58%) followed by motorcyclists (16%). Therefore the predominant mechanism in this group of patients was noted to be an external bullseye injury (83%). Of those patients, all sustained concomitant axial skeleton fractures with 50% being adjacent spinal segment fractures. 33% of spinal fractures were isolated fractures, with multiple fractures being seen in 66% of cases. The majority of the fractures sustained were noted to be stable (83%), with 0% requiring surgical fixation. C spine injuries occurred in: Pedestrians (1%), Cyclists (14%), Motorcyclists (0%) and Cars (15%). Head Injuries occurred in: Pedestrians (23%), Cyclists (21%), Motorcyclists (6%) and Cars (7%). Conclusions: ‘Bullseye’ injuries have a variety of mechanisms where patients are internal or external to the motor vehicle when they strike the windscreen. Severe Injuries ISS > 15 occur 1 in 5 of all external mechanisms. Head and cervical spine injuries constitute 15% pedestrians, 35% cyclists, 6% motorcyclists and 22% motor vehicles. The spinal injuries reported were most commonly stable. With 0% requiring surgical fixation. Of the patients with concomitant head injuries, 60% were reported to have intracranial haemorrhage. Decompression was not required in any of these cases. 5-7% of pedestrian or cyclists having this injury will be fatal.

919

P614: Spontaneos epidural hematoma. A case report

Luiz Claudio Rodrigues ¹ , Fernanda Andrea Navarro ² , Rodrigo Nakao ² , and Nathalia Adelina Pereira ²

¹ Ortopedia Surgery, Santa Marcelina School of Medicine, São Paulo, Brazil

² Spine Surgery, Hospital Santa Marcelina, São Paulo, Brazil

I.O.P, 15 years old, female. Patient has a history of pain in the thoracic region that started 15 days ago. As a triggering factor, he relates the fact that his sister cracked his back. She reports progressive worsening of pain, associated with difficulty walking for 2 days. Physical examination at the time of admission showed Frankel D, deficit in plantar flexion and dorsiflexion of the LLL, paresthesia at T10 and T12 levels and sphincter dysfunction (urinary and fecal retention). The patient had a personal history of a previous diagnosis of scoliosis.

An MRI was performed prior to admission, which showed an expansive extradural lesion at the level of C7 with extensions of the right neural foramina in D2-D3, D3-D4 and D4-D5 and of the left neural foramina in D3-D4 and D4-D5. Diffusely heterogeneous lesion promoting compression of the adjacent spinal cord.

Over the course of 48 hours hospitalized, the patient progresses to LL strength grade 2 and anesthesia in the territory of L5 and S1.

Operated on the fifth day of hospitalization. At the time of surgery, she had absent sensitivity and strength in the lower limbs.

Laminectomy with decompression of the spinal canal is indicated. During the surgical procedure, there was no evidence of the presence of structural tumor or vascular lesions. The anatomopathological examination showed that it was a hematoma.

Postoperatively, the presence of hypoesthesia in the region of L5 and S1 in the lower limbs with absent motor strength was evaluated.

At the time of discharge, he had Frankel E in the upper limbs, Frankel B in the lower limbs, sensitivity preserved in the lower limbs and extension of the hallux present in the LLL and D.

Returns to the outpatient clinic 3 weeks after hospital discharge with satisfactory evolution, without intercurrences, return of sensitivity, bladder and sphincter control. Presenting gradual return of muscle strength.

Two and a half months after the surgical procedure, the patient is seen again in an outpatient clinic, showing maintenance of sphincter control. Already in gait training with a walker.

In the last visit to the medical clinic, 4 months after the surgery, the patient continues to perform gait training, being able to take a few steps without assistance.

964

P615: Floating spine and other types of associated multiple simultaneuos unstable vertebral fractures. Descriptive study

Guillermo Ricciardi ^1,2 , Lyanne Romero Valverde ² , Santiago Formaggin ^1,2 , Ignacio Gabriel Garfinkel ^1,2 , Gabriel Genaro Carrioli ^1,2 , and Daniel Oscar Ricciardi ¹

¹ Spine Team - Traumatology and Orhopaedics, Centro Médico Fitz Roy, Ciudad de Buenos Aires, Argentina

² Spine Team - Traumatology and Orthopaedics, Sanatorio Güemes, Ciudad de Buenos Aires, Argentina

Introduction: The association of two non-contiguous unstable vertebral fractures is rare with only a few previous publications, limited to case reports or brief case series. The association of two non-contiguous vertebral fracture dislocations has received different names in the literature including “in bloc” dislocation and “floating spine”. We aim to present a series of patients with associated multiple and simultaneous unstable vertebral fractures (Type B or C). Material and Methods: Descriptive study of patients with high-energy spinal cord trauma and associated multiple unstable and simultaneous vertebral fractures during the period January/2015 to January/2021. Patients with type B (ligament injury) and/or type C (subluxation/dislocation) multiple vertebral fractures were included. Patients with incomplete medical records, osteoporotic or pathological fractures and follow-up of less than 3 months were excluded. Demographic and clinical data was registered considering trauma mechanism, spine region, classification, floating spine injury type, pre- and postoperative neurological status according to ASIA disability scale, associated injuries and comorbidities, surgical approach, instrumentation levels involved, complications, radiographic and clinical evolution. Results: We registered 5 patients (1 woman and 4 men) with two simultaneous unstable vertebral fractures, including 4 cases (80%) of non-contiguous fractures and 3 (60%) with 2 simultaneous non-contiguous fracture dislocations (“floating spine”); 2 (40%) cases presented the association of a type B fracture with a type C. The median age was 35 years (23-49). All cases suffered from high-energy trauma with associated injuries. All patients were treated surgically by conventional posterior approach, reduction and long arthrodesis. Neurological recovery was confirmed in 2 patients. Surgery-related complications were recorded in 2 (40%) cases. 1 patient with surgical site hematoma with ambulatory drainage (negative cultures) and 1 case of "floating spine" with incomplete reduction of the proximal fracture-dislocation. Conclusion: We present a case series of multiple simultaneous unstable vertebral fractures (type B or C) due to high-energy trauma. A rare injury association, with high morbidity related to spinal, systemic and neurological trauma. In addition to the well-known association of simultaneous type C fractures (floating spine), we describe the association of type B (B2 or B3) with type C fractures as a variant of non-contiguous and simultaneous unstable vertebral injuries.

979

P616: Invasive intrathecal devices for monitoring of the spinal cord cord perfussion pressure: systematic review

Som Singh ¹ , Miguel Ruiz Cardozo ¹ , Gabriel Trevino Verastegui ¹ , Julio Jauregui ² , Samuel Brehm ¹ , Karma Barot ¹ , Abby Carey-Ewend ¹ , Ahmed Hanafy ¹ , Michael Kann ¹ , Matthew De la Paz ¹ , Michael Olufawo ¹ , Magalie Cadieux ¹ , and Camilo Molina ¹

¹ Neurosurgery

² Orthopaedic Surgery, Washington University, St. Louis, United States

Introduction: It is well-known that systemic hypotension after spinal cord injury (SCI) contributes to cord ischemia, but also aggressive mean arterial pressure (MAP) management can favor secondary injury to the spinal cord. Let alone, this requirement requires clinical consideration of complications related to vasopressor usage in the attempt to maintain target MAP which could make the consideration that direct MAP augmentation could be cumbersome compared to alternative hemodynamic mechanisms. In lieu of the problems of using MAP to guide the acute perfusion needs of the spinal cord, methods for monitoring the spinal cord perfusion pressure (SCPP) to guide hemodynamic management of SCI in the setting of SCI. The objective of this study was to identify the health effects of using different invasive intrathecal device. Material and Methods: An electronic database search was conducted for studies that evaluated intrathecal devices to monitor the spinal cord perfusion, their health effects properties and adverse events. Data extracted included study design, patient population, characteristics of the intrathecal device, health effects details, as well as rates of adverse events. The ROB2 and the ROBINS-I rating scales were used to assess the risk of bias of the reported health effects. Results: Out search yielded 3,919 unique citations, 23 of which met the eligibility criteria and were summarized in this study. 8 studies (7 observational and 1 randomized clinical trial) evaluated the effects of lumbar drain catheter. These studies found that episodes of SCPP < 50 mmHg were associated with failure to achieve neurological improvement by at least one AIS grade after 6 months at follow up (OR 0.9, p 0.031). In addition, clinical adherence to the target perfusion range of 65 mm Hg was positively related to neurological improvement by at least one ASIA grade. These studies did not reported any major adverse events. 15 studies assessed the effect of a Codman pressure probe inserted at the site of injury. These group of studies informed that the SCPP values at 90-100mmHg are associated with the best ASIA recovery at 9-12 months (OR 1.039, p 0.002). These studies reported a 7% incidence of persistent CSF leakage requiring revision after device insertion. The risk of bias among all included studies ranged from low-to-serious risk of bias across all domains. Conclusion: We found two approaches to measure the spinal cord perfusion pressure: via lumbar catheter drains and Codman pressure probes inserted at the site of injury. The included studies overall showed positive correlation between SCPP measurement and neurological improvement post-injury, however due to the moderate to high risk of bias of the studies it is difficult to ascertain the true health effects of these interventions. Monitoring SCPP with a Codman probe has value to monitor physiological changes close to the site of injury, however requires a duroplasty procedure; lumbar drains can be easily inserted but have the disadvantage of not being close to the site of injury. Further investigation is needed to clarify the true effects of these interventions, optimal set-up, required infrastructure, clarify the risk, benefits and alternatives.

993

P617: Multi-state modeling for prediction of neurological recovery in ASIA A spinal cord injury

Ali Moghaddamjou ¹ , Alex Bak ² , Jefferson Wilson ¹ , and Michael Fehlings ¹

¹ Neurosurgery, University of Toronto, Canada

² University of Toronto, Canada

Introduction: Predicting prognosis after a complete traumatic Spinal Cord Injury (tSCI) has been challenging given varying disease courses, clinical histories, and patient populations. To improve our understanding of tSCI and enhance the clinical prediction of outcomes we propose to model disease progression, transition probabilities, and patient characteristics. Material and Methods: Patients with ASIA A injury were identified from 3 prospective, multi-center datasets. A-priori we identified age, injury region, and early surgery as covariates in our analyses. The mstate statistical package in R was utilized to develop flexible Markov models of disease progression. Covariate effects were estimated using Cox regression without any proportionality assumption. Results: We identified 943 ASIA A tSCI patients with a total conversion of 34.36% from ASIA A. The cumulative hazard ratio plot overtime reveals an exponential relationship in all transition groups illustrating the time-dependent impact on transition intensities. The injury region was a significant independent predictor of ASIA grade conversion. Conclusion: We demonstrate that multi-state models can successfully be applied to the progression of tSCI as measured by the transition of AIS grades of AIS A patients. These results support early aggressive treatment for ASIA A patients and consideration of patient trajectories and injury region in decision making.

1080

P618: Posterior spinal fusion and instrumentation of the adjacent vertebrae fracture in an elderly female patient following spinal fusion surgery using a computer - Assisted rod bending system: a case report

Teck Siang Lim ¹ , Shangeetha Tarmalinggam ¹ , Fadzrul Abbas Mohamed Ramlee ¹ , Mohd Hezery Harun ¹ , Chor Ngee Tan ² , and Kung Lung Tiong ²

¹ Orthopedic, Hospital Pengajar Universiti Putra Malaysia, Serdang, Malaysia

² Orthopedic, Hospital Putrajaya, Putrajaya, Malaysia

Introduction: Adjacent segment disease is highly seen in postoperative patients due to its increased rigidity over the mobile segment next to a spinal fusion. Common complications reported following a lumbar or lumbosacral spinal fusion surgery includes disc degeneration, listhesis, instability, hypertrophic facet joint, arthritis, herniated nucleus pulposus and stenosis. However, vertebrae spinal fractures are not commonly seen in spinal fusion surgery, exception of cases in post-menopausal women. Case Report: 80 years old Chinese lady, known case of adenocarcinoma of the gallbladder which was diagnosed in 2020, and laparotomy cholecystectomy was done. Patient was referred to the Orthopaedic department at Hospital Putrajaya for L1 osteoporotic vertebrae fracture following posterior spinal instrumentation and fusion. She was initially presented to a private centre in early 2022 for L3 osteoporotic vertebrae fracture. Patient was treated with Posterior Spinal Instrumentation and Fusion (PSIF) L2-S1 and decompression. Post operatively, the patient’s symptoms resolved and was subsequently discharged home. However, one-month after the fusion surgery she had a trivial fall at home in sitting position. Post trauma she was complaining of localized pain over her upper back. There was a significant tenderness over the L1 region. Bilateral lower limb myotome and dermatome was preserved. Reflex and tone were normal. Lumbosacral x-ray revealed adjacent vertebrae compression fracture at L1. MRI scan of the lumbosacral revealed L1 compression fracture with diffuse disc bulge causing stenosis over the spinal canal and neural foramen at L1/L2. Patient was planned for extension Posterior spinal instrumentation and fusion using computer assisted bending system under general anaesthesia. Longitudinal midline skin incision made from T9 to S1 to remove the old rods. Fenestrated percutaneous pedicle screws inserted over T10, T11 and T12 vertebrae with the guidance of C-arm and augmentation done. Rod bending was done using a computer assisted rod bending system. Pre-bend rods was inserted connecting the pedicle screws from T10 to S1. Rods tightened and crosslink inserted. Discussion: There is a high risk of kyphotic collapse in elderly patients with severe osteoporotic vertebrae fracture in view of diminished back muscle power to maintain the spinal alignment. Failure of conservative treatment and unresolve symptoms such as pain generally directed to surgical intervention. The biggest challenges faced during the fixation of osteoporotic vertebrae fracture is screw pull out. The cement augmented pedicle screws also aimed to provide better stability. In long segment spinal fixation, approximation of the length of the rod with adequate rod contouring is very difficult. Bending of the rod using the computer assisted technique rod curves perfectly matches each screw head where there will be accurate placement decrease the shear of the screw-bone interface. This computer assisted system also compatible to use with other system. Conclusion: Computer assisted rod bending system in posterior spinal fusion and instrumentation surgery with fenestrated screw in an osteoporotic vertebra is an effective approach to achieve adequate spinal stability, especially in long segment spinal fixation during revision surgery. It also marked reduce the shear force at the pedicle screw bone interface.

1098

P619: Surgical management of neglected complex sacral fractures by lumbopelvic fixation

Alderico Girão Campos de Barros ¹ , Luiz Felippe Mokdeci Martins de Oliveira ¹ , Igor Ebert Cechin ¹ , and Luis Eduardo Carelli Texeira da Silva ¹

¹ Instituto Nacional de Traumatologia e Ortopedia Jammil Haddad (INTO), ARCOL, Rio de Janeiro, Brazil

Introduction: To evaluate the surgical indications, epidemiological data, radiographic outcomes and postoperative complications of a series of 16 cases of complex neglected sacral fractures treated using bilateral spinopelvic fixation (BSF) or triangular osteosynthesis (TO) in a traumatology and orthopedics referral center. Material and Methods: Longitudinal study, based on a retrospective review of medical records of patients with complex sacral fractures admitted between 2014 and 2020. All patients older than 18 years and whose time of evolution between trauma and the surgical procedure was equal or greater than three weeks were included. Results: The mean age was 39.8 years (18 to 71 years). Anterior pelvic ring injuries represented the most common association, present in 12 (75%) cases. In 8 (50%) cases there was no neurological injury, 1 (6.2%) individual evolved with paresthesia, 2 (12.5%) with paresis in the lower limbs and 5 (31.3%) with sphincter dysfunctions. Among the patients with neurological impairment, 4 (50%) evolved with complete improvement, 2 (25%) showed partial improvement and 2 (25%) cases remained with the deficit. The mean surgical time was 3.6 hours for TO and 4.9 hours for BSF. Postoperative complications occurred in 4 (44.4%) patients who underwent BSF and there were no postoperative complications in the TO group. The minimum follow-up was 18 months and all the individuals analyzed showed good evolution. Conclusion: The surgical management of neglected complex sacral fractures using TO and BSF proved to be safe and effective. Indirect or direct decompression, even in neglected injuries point to an improvement in the neurological status.

1240

P620: Traumatic spinal injury patterns of on vs. off-road motorcycle crashes

Ryland McDermott ¹ , Toure Vashon ¹ , Brett Allen ¹ , James Clark ¹ , Gregory Daubs ¹ , Iain Elliott ¹ , Michael Daubs ¹ , and Sukanta Maitra ¹

¹ Orthopaedic Surgery, Kirk Kerkorian School of Medicine at UNLV, Las Vegas, United States

Introduction: Two-wheel motorized vehicles used in both street transportation and recreation are a common cause of severe injury in the United States (US). To date, there has been minimal data describing the spinal injury patterns among these motorcycle injury patients in the US. The goal of this study is to characterize and compare differences in injury patterns of patients sustaining traumatic spinal injuries after motocross and motorcycle collisions in the southwestern US at a level 1 trauma center. Material and Methods: Trauma registry data was queried for patients sustaining a spinal injury after motorcycle collision from 2010-2019 at a single level 1 trauma center. CT scan and MRI reports from initial trauma evaluation were reviewed and data was manually obtained regarding injury morphology and location. Results: A total of 1798 injuries were identified in 549 patients who sustained a motorcycle collision. 67 were involved in off-road motorcycle accidents compared to 482 road motorcycle patients. Off-road motorcycle patients were found to be significantly younger (34.75 vs 42.66, p = 0.00015). The thoracic spine was the most commonly injured vertebral segment in both cohorts. Transverse process fractures and compression fractures were the most common injury morphologies. Conclusion: All motorcycle collision patients were more likely to be male, while patients sustaining spinal injury after an off-road motorcycle collision were more likely to be younger in age compared to street bikes. The thoracic spine was the most commonly injured vertebral segment. The most common injury morphologies were transverse process and compression fractures.

1426

P621: A retrospective analysis of concomitant spinal injuries in the setting of polytrauma at a tertiary hospital in Singapore

Theophilus Qiu ¹ , Cassie Yang ² , Shermane Lim ¹ , and Zhi Xu Ng ³

¹ Yong Loo Lin School of Medicine, Medical Student, National University of Singapore, Singapore, Singapore

² Department of Orthopaedic Surgery, Singapore General Hospital, Singapore, Singapore

³ Department of General Surgery, Khoo Teck Puat Hospital, Singapore, Singapore

Introduction: Polytrauma involving multiple organ systems is a pertinent health concern. In particular, traumatic spinal injuries are often observed in polytrauma, with serious consequences to patients’ quality of life and significant healthcare burden. Due to its complexity, there are limited studies analysing the population of spinal injuries in polytrauma in Singapore. This study aims to retrospectively evaluate a cohort of polytrauma patients and characterise the relationship between the presence of traumatic spinal injury and clinical outcomes. Material and Methods: A retrospective cohort of patients who presented to the emergency department for multi-system trauma was assembled from a local trauma database at a tertiary hospital in Singapore, from January 2012 to June 2020. Variables analysed were presence of concomitant spine injury, mechanism of injury, injury severity score (ISS), gender, age, ethnicity and year of admission. Outcomes were mortality, length of stay and cost. Results: 1568 patients involved in multisystemic trauma were identified for this study. It was observed that 27.2% (n = 427) had concomitant spinal injuries, of which was most commonly due to falls (83.6%, n = 357), followed by vehicular accidents (12.9%, n = 55). Percentage of falls as primary injury mechanism increased from 25.9% in the 21- to 30-years-old age range to 96.4% in the 81- to 90-year-old age range. Meanwhile, the percentage of vehicular accidents as primary injury mechanism decreased from 67.8% in the 21- to 30-years-old age range to 3.2% in the 81- to 90-year-old age range. Notably, the mortality rate of patients with spine injuries (2.6%, n = 416, relative risk 0.17) was significantly lower than those without spine involvement (15.1%, n = 969, p < 0.001), with an adjusted odds ratio for mortality of 0.25 (95%CI [0.11, 0.52], p < 0.001). The mean total length of stay was lower in patients with spinal injuries 11.8 (14.6, p < 0.001) days (SD) compared to 16.0 (28.0) days in patients without spinal injuries. Mean total hospital bill was lower in patients with spinal injuries, at 8692 (13980, p < 0.001) Singapore Dollars (SD), compared to patients without spinal injuries, at 16359 (30658). Conclusion: Spinal injury in the context of polytrauma is not an independent predictor of poorer outcomes, as it has been observed to have lower mortality compared to polytrauma patients without spinal involvement. This may be attributed to the complex nature of polytrauma; previous studies have found that high-energy traumatic injuries tend to be associated with more independent living and mobility than low-energy injuries, with the former having better functional outcomes post-injury. Similarly, patients with spinal cord involvement in polytrauma, which suggests a high-energy injury, may have greater functional demands and subsequently better reserves, hence conferring better survivability.

1586

P622: Correlation of neuropathic pain intensity and neurological recovery in patients with spinal cord traumatic injury

Oleksii Nekhlopochyn ¹ , Iaroslav Tsymbaliuk ² , Vadim Verbov ² , Ievgen Cheshuk ² , and Milan Vorodi ²

¹ Spinal Neurosurgery

² Restorative Neurosurgery Department, Romodanov Neurosurgery Institute, Kyiv, Ukraine

Introduction: Neuropathic pain is one of the main secondary complications of spinal cord injury. The biological role of neuropathic pain has not been established yet. This type of pain is formed directly in the area of the spinal cord injury; therefore, it can be assumed that its intensity can characterize both degenerative and reparative processes. The aim of this work is to assess the possible relationship between the intensity of neuropathic pain in patients with spinal cord injury and the dynamics of neurological disorders regression. Material and Methods: We performed a retrospective analysis of patients applied to outpatient department of Romodanov Neurosurgery Institute of National Academy of Medical Sciences of Ukraine in the period from 2010 to 2020 after surgical treatment of spine traumatic injury. The level of neurological disorders and the intensity of neuropathic pain were assessed within 5–7 and 11–13 months after surgery. Results: All 102 patients selected for analysis were divided into three groups depending on the intensity of the registered pain sensations: 1) absence of constant pain sensations - 19.6% of victims, 2) moderate pain - 56.9%, 3) severe neuropathic pain – 23.5%. In the first group, the regression of neurological disorders was 3.5 (95% confidence interval (CI) 2.15-6.15) points, in the second - 25.0 (95% CI 24.14-29.58) points, in the third - 13.0 (95% CI 10.87-16.55) points. The differences are statistically significant (χ2 = 60.4, df = 2, p < 0.0001). In patients with severe neurological disorders, the dynamics of recovery did not correlate with the pain intensity. With ASIA B patients in group 1 the dynamics was 8.5 (95% CI -10.56-27.56) points, in group 2 - 15.0 (95% CI 13.41-18.41) points, in the 3rd group - 10.5 (95% CI 7.45-14.89) points. In patients with functional class ASIA C the difference is even more pronounced: in group 1, the median was 8.0 (95% CI -0.83-20.83) points, in group 2 - 32.0 (95% CI 25.41-36.86) points, in the third - 15.5 (95% CI 10.27-27.4) points. With ASIA D, a similar trend was observed. Conclusion: The worst regression of neurological disorders is observed in patients without clinically significant pain, the best results of neurological dysfunction recovery are in patients with moderate neuropathic pain.

1664

P623: Clinical and radiological outcome of lumbopelvic fixation in Isler class II and III unstable sacral fractures

Umair Nadeem ¹

¹ Department of Orthopedics and Spine Surgery, Ghurki Trust Teaching Hospital, Lahore, Pakistan

Introduction: Many sacral fractures can be treated non-operatively. Unstable sacral fractures, usually as part of pelvic ring injury and those with neurological involvement need surgical fixation. Iliosacral screws, tension band ilio-iliac plating and transiliac bars can be used in sacral fractures not compromising the lumbosacral articulation (Isler I). Fractures entering the L5-S1 facets (Isler II) and those entering the lumbosacral spinal canal (Isler III) need lumbopelvic fixation for proper biomechanical stability. Objective is to study the clinical and radiological outcome of lumbopelvic fixation of Isler II and Isler III unstable sacral fractures. Material and Methods: It was a prospective cohort study at Ghurki Trust Teaching Hospital Lahore from Jan 2019 to December 2020. All patients with unstable Isler II and Isler III sacral fractures were recruited for this study. All patients were submitted to lumbopelvic fixation using a Posterior Triangular Osteosynthesis (PTO) construct. Patients were evaluated clinically and radiologically, including full lumbopelvic X-Rays and 3DCT scan at the pre- and postoperative period. Clinical parameters included a full neurological examination, VAS, ODI. Results: A total of 13 patients including 8 males and 5 females with mean age of 26 ± 9.4 years were recruited for this study. All patients had either unstable sacral fractures, 7 had Isler II and 6 had Isler III. Sacral fracture was part of a pelvic ring injury complex in 10 patients. Neurology was disturbed in 9 patients. The mean followup period was 20.1 ± 9.6 months. The mean preoperative VAS improved from 9.2 ± 2.4 to 2.2 ± 1.3 postoperatively, while the mean preoperative ODI improved from 86.5 ± 5.6 to 14.5 ± 5.1 postoperatively. Fracture healing was complete radiologically in all patients and none needed revision. Residual deformity was present in 33% of the cases with no clinical import. 2 patients had superficial SSI who were treated uneventfully with antibiotics. Conclusion: Lumbopelvic fixation is a useful procedure in the treatment of unstable Isler II and Isler III sacral fractures with satisfactory clinical and radiological outcome.

1702

P624: Hyperbaric oxygenation in complex therapy of spinal cord traumatic injury

Oleksii Nekhlopochyn ¹ , Igor Voronov ² , and Vadim Verbov ³

¹ Spinal Neurosurgery

² Department of Hyperbaric Oxygenation

³ Restorative Neurosurgery Department, Romodanov Neurosurgery Institute, Kyiv, Ukraine

Introduction: Spinal cord traumatic injury as resulting persistent movement and sensory disorders is one of the most disabling consequences of traumatic factor impact on the human body. Despite a large number of experimental and clinical studies aimed at developing methods for restoring lost functions, there is no solution to the problem that is acceptable in terms of efficiency. One of the promising directions in the treatment and rehabilitation of this category of patients is the use of hyperbaric oxygenation (HBO). Experimental models have shown that HBO has a neuroprotective effect in spinal cord injury, but the results of clinical application of the method are still contradictory. Material and Methods: Study design - pilot observational retrospective case - control. For the analysis we used a database of patients with spinal cord injury who were hospitalized at the Neurosurgery Institute named after acad. A.P. Romodanov of National Academy of Medical Sciences of Ukraine in the period from 2010 to 2020. When selecting a control for each clinical case, the following factors were considered: gender, age, circumstances of injury, type of damage to the osteoligamentous apparatus, level of neurological deficit, degree of damage and compression of the spinal cord, time elapsed from the moment of injury to surgery. We analyzed 28 "case ‒ control" pairs. The main criterion for the effectiveness of therapy was the change in the functional class according to the ASIA scale. Results: Positive dynamics was registered in 57% of victims, including in the group of patients receiving HBO therapy - in 71%, in the control group - in 43%. HBO therapy in the postoperative period significantly affects the dynamics of regression of neurological disorders (p = 0.0295). Odds ratio - 3.333 (95% confidence interval - 1.098-10.116, p = 0.0335). The calculation of the odds ratio, adjusted for additional analyzed factors, showed a more pronounced efficiency - 4.519 (95% confidence interval - 1.279-15.962, p = 0.0192). Conclusion: The obtained results indicate that usage of HBO as a method of complex therapy for traumatic spinal cord injury is promising for further study in order to determine the effectiveness of the method, the optimal timing of treatment initiation in the postoperative period and its duration.

1717

P625: Some characteristics of pain in patients with chronic spinal cord injury

Oleksii Nekhlopochyn ¹ , Vadim Verbov ² , Iaroslav Tsymbaliuk ² , Milan Vorodi ² , and Ievgen Cheshuk ²

¹ Spinal Neurosurgery

² Restorative Neurosurgery Department, Romodanov Neurosurgery Institute, Kyiv, Ukraine

Introduction: Pain is one of the most common secondary symptoms seen in patients with spinal cord injury (SCI). Approximately from 65 % to 85 % of all SCI patients complaining pain, with a third having severe/excruciating pain. Despite the large number of studies, some aspects that are fundamental for the choice of pain therapy remain practically unexplored. The purpose of our study was to determine the types, subtypes and intensity of pain in subaxial cervical spine SCI patients. Material and Methods: We performed a retrospective analysis of the patients’ database admitted in Romodanov Neurosurgery Institute of National Academy of Medical Sciences of Ukraine in period from 2010 to 2020 with subaxial cervical spine traumatic injury. The patients’ state was assessed within 12‒18 months after the injury. We determined the functional class of neurological disorders using the ASIA scale. Pain sensations were characterized using International Spinal Cord Injury Pain Classification. Numeric Rating Scale was the instrument for pain intensity assessment. Results: Persistent pain sensations in the period of 12‒18 months after subaxial cervical spine SCI are recorded in 86.42% of 81 analyzed victims, whereas one subtype of pain is noted in 38.57% of all patients with pain, two subtypes ‒ 40% and three ‒ 21.43%. Elements of noceptive pain were registered in 54.32% of all patients, and neuropathic pain was recorded in 71.6 %. When assessing pain subtypes, musculoskeletal pain was observed in 54.32% (95% CI: 44.44-66.16) of all subjects, neuropathic pain at the trauma level in 51.85 % (95 % CI: 41.98-63.77), and neuropathic pain below the trauma level was noted in 43.21% (95% CI: 33.33-54.91). Noceceptive visceral and other neuropathic pain was reported sporadically ‒ in 4.94% (95% CI: 1.23-9.09) and 3.7 % (95% CI: 1.23-7.94) patients, respectively. When comparing the nature of pain and the ASIA functional class, we determined that the frequency pattern of the pain distribution statistically significantly correlates with the level of neurological disorders. The greatest intensity of pain was observed in patients with the functional class ASIA C of neurological disorders. Conclusion: The obtained results allowed us to reveal the regularities of the clinical picture in patients with different levels of neurological disorders, that is of practical importance for the development of optimal pharmacological treatment schemas.

1852

P626: Acute cauda equine syndrom induced by subdural lumbar hematoma after spinal anesthesia

Eya Chahed ¹ , Nessrine Nessib ¹ , Nessrine Jemel ¹ , Khalil Ghedira ¹ , and Sofiene Bouali ¹

¹ Neurosurgery, National Institute of Neurology, Tunisia

Although spinal anesthesia is commonly used for many types of surgeries, subdural lumbar hematoma is one of its rare complications. It is a serious complication that is favored by the use of anticoagulant.

We, here, present a case of 81 year old man who had a surgery for an inguinal hernia which was complicated by a scrotal hematoma for which he was operated under spinal anesthesia. He had a history of persistent atrial fibrillation and was on anticoagulants.

A day later, he developed lower limb paresthesia and motor deficit as well as retention of urine.

A cerebral and spinal MRI was performed and showed a subarachnoid hemorrhage and a spinal hematoma from D12 to L5.

He then underwent emergency surgery which consisted of a spinolaminectomy of L1-1-3 extended to L4 in order to evacuate the compressive intra dural hematoma.

He had not recovered from his deficit afterwards.

So although this complication is extremely rare, we as neurosurgeons and physician in general, must keep in mind that it is a possible complication of spinal anesthesia.

1909

P627: Percutaneous transpedicular cervicothoracic fixation guided by 2D fluoroscopy

Joao Oliveira ¹ , Sara Sequeira ¹ , and Ding Zhang ¹

¹ Neurocirurgia, Centro Hospitalar Lisboa Ocidental, Lisboa, Portugal

Introduction: Subaxial cervical transpedicular fixation confers a biomechanical advantage when compared to instrumentation to lateral masses. However, it is a challenging technique due to the pedicles small size and marked convergency, as well as the verterbral arteries close proximity which leads to an increased risk of neurovascular complications. Material and Methods: We present a clinical case of a C7-T1 fracture disclocation treated with percutaneous transpedicular fixation and describe the surgical technique. Results: A 60-year-old-man, with no relevant medical background, present to our emergency room with cervical trauma after falling from a bicycle. He had no neurological deficits. Computed tomography (CT) documented a C7-T1 fracture-dislocation with grade I/IV anterolisthesis, associated with fracture of the lamina, C7 right pars interarticularis and T1 left pars interarticularis. The patient underwent urgent surgery, initially with an anterior approach, with open reduction and C7-T1 arthrodesis with intersomatic cage and plate. Given the instability caused by a fracture of the pars interarticularis, the patient underwent a second intervention, seven days later, through a posterior approach with percutaneous transpedicular fixation of C7-D1 guided by 2D fluoroscopy (C-arm). In a Concorde positioning, with the skull fixed with a Mayfield, and pre-operation insurance of a good-quality views in the anteroposterior, lateral and oblique planes. This last view is essential for the proper positioning of the transpedicular screws, and the C-arm rotation was established according to the preoperative study of the convergence angle of the pedicles to introduce the percutaneous cannula. The percutaneous entry point was established in the oblique view, after obtaining a perfectly circular shape of the pedicle contour, and the incision was made at the point of projection on the skin in the center of this circle. The four pedicles were progressively cannulated under fluoroscopic support, alternating between orthogonal and oblique views. The remaining percutaneous instrumentation technique was the usual. There were no complications and the control CT showed adequate positioning of the instrumentation and the patient was discharged 72 hours after the operation, without neurological deficits. Conclusion: Placement of subaxial cervical transpedicular screws at the cervicothoracic junction is challenging, due to its anatomical features and risk of significant neurovascular injury. In C7, the vascular risk is lower due to the usual absence the vertebral artery at this level, and the pedicle usually assumeslarger dimensions. With proper preoperative planning and intraoperative imaging support, it is possible to safely place transpedicular screws in this anatomical region. Minimally invasive percutaneous approach allows for faster recovery and shorter hospital stay.

1923

P628: Extended cervical pneumorrachis due to closed head injury: report of two cases and literature review

Zohra Souei ¹ , Mohamed Boukhit ¹ , Maher Hadhri ¹ , Chiheb Abdelileh ¹ , Ghassen Belkahla ¹ , Kais Maamri ¹ , and Mehdi Darmoul ¹

¹ Neurosurgery, Fattouma Bourguiba University Hospital, Monastir, Tunisia

Introduction: Pneumorrachis (PR) is defined by the presence of air in the spinal canal. Rarely reported, it can be secondary to degenerative, infectious, tumoral, or iatrogenic pathologies and is exceptionally caused by head trauma. Material and Methods: We report two cases of polytrauma patients with PR and discuss the causes, mechanisms, and implications of this condition. Furthermore, a literature review was carried out. Results: In these 2 cases, PR was accidentally found during CT diagnostics and remained asymptomatic. One patient had a combination of epidural and subarachnoidal PR and had developed a CSF leak. PR has been described at the cervical level as an extension of pneumocephalus secondary to craniofacial trauma with a fracture of the skull base or the paranasal sinuses. Most often, air collection is epidural. But it can also extend, by meningeal breach, into the subarachnoid space, which exposes to an increased risk of meningitis estimated at 25%. As a result, PR is considered a marker of severity and its presence should alarm the attending physician to look for other associated lesions, particularly the possibility of a CSF leak, which may require intervention. Conclusion: Pneumorrachis is a rare entity and has a wide variety of etiologies. Rarely causing neurological symptoms, its presence is often diagnosed by CT, which is very effective in detecting PR and specifying its extent and starting point in order to discuss the adequate treatment.

1928

P629: Our experience of damage control principle of acute spinal cord injury in polytraumatized patients

Oleksii Nekhlopochyn ¹ and Yurii Pedachenko ²

¹ Spinal Neurosurgery

² Department of Miniinvasive and Laser Spinal Neurosurgery, Romodanov Neurosurgery Institute, Kyiv, Ukraine

Introduction: The last few decades are characterized by a significant change in the structure and nature of traumatic injuries in the adult population with a pronounced tendency to increase high-energy damage. The progressive increase in the number of road traffic accidents, natural and man-made disasters, industrial injuries and the active development of military conflicts leads to the fact that polytrauma is the leading cause of death for the young and most active population. The purpose of our study was to analyze the effectiveness of a two-stage Damage Control surgery in treatment of spinal cord injury in patients with severe polytrauma. Material and Methods: We have performed a retrospective analysis of 75 patients therapy results. All patients had Injury Severity Score > 17, neurological disorders ASIA A-C and unstable fracture or fracture-dislocation regardless of injury level. Patients were divided into 3 groups depending on the timing and extent of surgical treatment: first group – patients, whose surgical treatment was delayed until the relative stabilization of somatic status, therapy was carried out on the principle of “too sick to operate on”; second group - patients initially hospitalized in a specialized center, whose assistance was provided timely and totally - “Early total care” group; and the third group of patients - neurosurgical care was carried out in stages, in accordance with the principles of Damage Control. Neurological disorders regression, mortality and duration of intensive therapy were analyzed. Results: Patients with delayed surgery demonstrate the worst recovery rates of neurological deficits. Early one-stage decompression-fusion surgery ensures better regression of neurological disorders, but is characterized by a sufficiently high level of mortality and duration of intensive therapy. The group of patients who underwent staged surgical treatment is characterized with the best values of the analyzed parameters. Conclusion: Damage Control approach provides the best results in therapy for spinal cord injuries in patients with polytrauma.

1959

P630: Development and validation of method to asses traumatic compression of spinal canal

Oleksii Nekhlopochyn ¹ , Ievgenii Slynko ¹ , Vadim Verbov ² , and Yurii Derkach ¹

¹ Spinal Neurosurgery

² Restorative Neurosurgery Department, Romodanov Neurosurgery Institute, Kyiv, Ukraine

Introduction: Mechanical compression of spinal canal resulted with spine traumatic injury is the fundamental criteria in determining treatment tactics and prognosis of neurological disorders regression. Analysis of the literature data demonstrates the absence of a criterion that allows us to characterize a morphologically heterogeneous substrate that causes compression of the spinal cord. The purpose of our study was to formulate a definition, develop and perform a validation of radiologic criteria for assessing the sagittal size of the morphologically heterogenic ventrally located traumatic substrates of spinal canal. Material and Methods: Literature analysis revealed the existing indices and methods for measuring the value of spinal canal compression, as well as the clinical significance of the nature and value of compression of the spinal cord with a traumatic substrate. For the initial verification of the reliability of the method for assessing a ventrally located traumatic substrate, a retrospective analysis of neuroimaging data of 150 patients with traumatic changes in the cervical spine was performed. The data of X-ray films, computer and magnetic resonance tomograms was analyzed. The measurements were carried out by three independent experts. Results: The definition of compressing factor has been developed, that implies a collective concept and reflects the general characteristics of pathological anatomical substrates caused by damage to the vertebral motion segment, leading to deformation of the walls of the spinal canal and, as a result, causing compression of the structures of the spinal canal. For quantitative characterization, the sagittal size of the compressing factor was measured, having an absolute metric value and characterizing the relative degree of substrate displacement into the spinal canal. The results obtained by statistical processing reveal high reproducibility of the measurements. The concordance coefficient was 0.85 at p = 0.00025. Conclusion: The presented radiographic criteria should be used for the general characteristics of the clinical case, as well as for statistical data processing in order to unify the idea of the degree of spinal canal compression.

1965

P631: "Spinopelvic dissociation" revisiting an ambiguous term: a systematic review

Ahmed Hassan ¹

¹ Orthopedics and Trauma Surgery, Faculty of Medicine, Assiut University, Assiut, Egypt

Introduction: The term Spinopelvic Dissociation or jumper`s or Suicidal fracture was initially defined in the 1960`s refers to “the presence of bilateral vertical sacral fracture lines associated with a transverse fracture line” leading to total separation between the axial skeleton and the pelvis. However, by time, more classifications were developed, and more sacral fractures patterns were described in the literature adding to the complexity of the term. Additionally, over the past couple of years, more light was shed on the spine-pelvis relation, which makes restricting the term to this fracture pattern unjustified and out of date. Material and Methods: A systematic review was conducted within the framework of the Cochrane Back and Neck Group and reported according to PRISMA guidelines. All types of study designs were included in the systematic review. We included studies on sacral fractures in skeletally mature patients (older than 18 years old) where at least one definition of the term spinopelvic dissociation was reported. Additionally, studies on pathological fractures and non-English articles were excluded. Two reviewers independently performed the screening and selection against the inclusion and exclusion criteria. The initial screening involved screening the titles and abstracts of the identified articles. In case of disagreement between the two reviewers, the article was included for the full text assessment. The full texts were obtained and assessed and in case of disagreement between the two reviewers during the full-text assessment, the article was assessed by a senior reviewer who made the final decision. The search strategy included both electronic searches and backward and forward snowballing of the finally included articles to retrieve as many relevant studies as possible. The electronic searches were conducted on two databases: PubMed and Scopus libraries using both controlled vocabularies and free text forms. Search was conducted from the date of database inception till 1/9/2022. Risk of bias (ROB) of the included studies was assessed using the JBI ROB assessment tool. Results: Our initial search yielded 108 deduplicated articles. Then after further exclusion by the titles and abstracts and later on by full text reading 67 articles meeting the inclusion and exclusion criteria were finally included for inclusion in the study. Regarding the definition included in the finally selected articles, although most of them refer to the original definition and still use the same term “Spinopelvic dissociation”, most of them describe other fracture patterns beside the original pattern regardless of the classification system used. This in turn makes the use of the original term in-applicable. Conclusion: As a result of the heterogeneity and inconsistency encountered in describing these complex and rare fracture pattern, we suggest that the term “Spinopelvic dissociation” should be replaced with a broader term “Traumatic Spinopelvic Instability”. This term will encompass all complete vertical sacral fracture patterns whether unilateral or bilateral, passing medial or lateral to the L5-S1 facet joint.

Tumors

199

P632: Patient related factors are the best predicting tool for the overall survival after the surgery in patients with spinal metastasis

Anton Denisov ¹ , Nikita Zaborovskii ² , Dmitry Ptashnikov ^2,3 , and Ghasan Elgeadi ¹

¹ Orthopaedic Department, Hospital Quironsalud San José, Madrid, Spain

² Spinal and Bone Oncology, Vreden Orthopaedic Center, Saint-Petersburg, Russian Federation

³ Traumatology and Orthopaedics, North Western Medical University of Mechnikov I.I, Saint-Petersburg, Russian Federation

Introduction: Oncologic treatments increase the incidence of spinal metastases. Surgical treatment of spinal metastases results in a high complication rate, which must set against the expected benefits. Frequently the factors related with the surgery are propense to get more emphasis in orthopedic treatment studies of bone oncology. However, in clinical trials and others oncological studies primary tumor related factors are considered ones that play an important role in patient overall survival. The aim of this study was to compare and reveal the best predicting Cox-model for overall survival using an extended database of patients with spinal metastases. Material and Methods: The clinical data of 361 patients undergoing surgical management of metastatic spinal tumors were collected at three tertiary hospitals over two decades. Stratification of this cohort according to disease, patient and surgery specific characteristics allowed for univariate and multivariate statistical analyses (three groups) of study population. Observed overall survival estimates were calculated by the Kaplan-Meier method. Variables that were statistically significant in the univariate Cox analysis were fitted in the multivariate Cox proportional hazard (PH) model. All factors were grouped in relation with their etiology (surgery, patient, tumor). The independence of covariates was estimated with Matthews correlation coefficient. Predictors with coefficient less than 0.40 were considered independents. Verification of the proportional hazards were assessed with Schoenfeld residuals and log(-log) survival curves. The Likelihood Ratio Test and the minor Bayesian information criterion were used for selection of the best model. A two-tailed probability (p) value of < 0.1 was considered for selection from the univariate to multivariant Cox PH regression. The statistical difference (p-value) was set at < 0.05 for multivariate Cox PH regression. Results: A total of 361 patients were included in the present study with median follow-up of 13 months. At the latest follow-up, a total of 272 patients (75%) had died. The 3-, 6-, 12-, and 24-month overall survival (OS) rates were 86.7%, 78.4%, 57.1% and 34.7%. The risk factors included severe grade of CCI, rapid Katagiri tumor type, presence of lung metastasis, non-ambulatory status at follow-up. The protective factors were metastasectomy, and postoperative systemic therapy. Cox-Shell residuals analysis revealed that the best precise and predictive model is one which includes only patient related factors (CCI, ambulatory follow-up). Conclusion: For the prediction of the overall survival of the patients underwent oncological operation due spinal metastasis more convenient the usage Charlson Comorbidity Index and ambulatory follow-up status.

204

P633: Fully endoscopic spine separation surgery in metastatic disease - technical note and early results

Kajetan Latka ¹ , Dariusz Latka ¹ , Waldemar Kolodziej ¹ , Jacek Chowaniec ¹ , Tomasz Olbrycht ¹ , and Tomasz Sobolewski ¹

¹ Neurosurgery, Institute of Medicine, University of Opole, Opole, Poland

Introduction: The purpose of this report is to describe the surgical methodology and potential effectiveness of endoscopic separation surgery (ESS) in patients with metastatic spine disease. This concept may reduce the invasiveness of the procedure, which can potentially speed up the wound healing process and thus the possibility of faster application of radiotherapy. Material and Methods: In this study, the separation surgery for preparing patients to radiotherapy was performed with fully endoscopic spine surgery (FESS) method followed by percutaneous screw fixation (PSF). Results: Three patients with metastatic spine disease in thoracic spine were treated with fully endoscopic spine separation surgery. First case resulted in progression of paresis symptoms that resulted in disqualification from further oncological treatment. The remaining 2 patients achieved a satisfactory clinical and radiological effect and were referred for further radiotherapy. Conclusion: Thanks to the dynamic development of medical technology, such as endoscopic visualization, new tools or coagulation, we have the ability to treat more and more spine diseases. Until now spine metastasis were not the indication for the use of endoscopy. Due to the nature of the patient, the diversity of the morphology and nature of metastatic lesions in the spine, this method is technically very difficult and risky, especially at such an early stage of application. The technique of using endoscopic access in spine metastatic patients is extremely difficult, it must be selected individually and well planned. Further trials are needed to unambiguously determine whether this is a potentially new method of treating patients or a dead end. Our results so far only show that this access is possible to make, but whether it will bring the expected benefits requires a huge number of cases.

353

P634: Ossification of the common anterior vertebral ligament: a rare cause of dysphagia

Ghassen Gader ¹ , Kamel Bahri ¹ , Mohamed Amine Gharbi ² , Mouna Rkhami ¹ , Skander Guediche ¹ , Mohamed Zouaghi ¹ , Mohamed Badri ¹ , and Ihsen Zammel ¹

¹ Department of Neurosurgery, Trauma and Burns Center, Ben Arous, Tunisia

² Department of Orthopaedics, Mongi Slim Hospital, La Marsa, Tunisia

Introduction: Ossification of the common anterior vertebral ligament, more commonly known as Forestier's disease or senile spinal ankylosing hyperostosis, is a rare rheumatic disease of unknown aetiolog. It is characterized by ossification of the paraspinal ligaments and peripheral entheses. Most often asymptomatic, it is usually discovered incidentally on standard radiographs. Case report: We report the case of a 65-year-old diabetic patient who presented for gait disturbances and slow and progressive onset of dysphagia. This dysphagia was improved by flexion of the neck and worsened by extension, associated with slight cervicobrachial neuralgia. Esophageal transit revealed an imprint on the posterior wall of the hypopharynx at the level of C3-C4. Cervical MRI showed the presence of a bar ossification of the anterior and posterior vertebral common ligament extending from C2 to C4. The patient was operated through an anterior approach in order to perform a C4 corporectomy associated to interbody fusion. Postoperative course was favorable with regression of dysphagia and motor disorders. Discussion: Forestier's disease is a generalized joint disorder characterized by ligamentous ossification and especially of the anterior longitudinal ligament. Several etiological hypotheses were discussed: mechanical, dietary, metabolic, and environmental factors. Its incidence increases with age. Ossification along the posterior vertebral common ligament is also often associated. This disease is most often asymptomatic and discovered incidentally on imaging. When symptomatic, the most frequent symptoms are pain, stiffness and reduced mobility of the affected areas. Complications should be suspected in case of acute symptoms. The most severe are cervical myelopathies, vertebral fractures and compressions of adjacent structures. Respiratory signs and swallowing problems usually improve after surgery. Conclusions: Forestier's disease is an entity characterized by exuberant bone proliferation at sites of ligament and tendon insertions with spinal and extra spinal manifestations. Its diagnosis can be difficult, but the outcome remains generally favorable.

389

P635: Treatment of acute neurological deficit in patients with spinal metastasis with unknown primary -12 year reterospective review

Rohan Parihar ¹ , Samir Dalvie ¹ , Kshitij Chaudhary ¹ , R. Dileepan Chakrawarthi ¹ , and Sourav Chatterjee ³

¹ Spine Surgery Department, PD Hinduja Hospital, Mahim, Mumbai, India,

Introduction: Acute neurological deficit in patients presenting with Metastatic Epidural Spinal Cord Compression (MESCC) requires emergency spinal cord decompression. The treatment recommendations for MESCC differ for patients with known metastasis versus those presenting with unknown primary. Solid organ metastasis with known diagnosis surgery is preferred while for hematolymphoid malignancies radiotherapy is preferred respectively. However, this decision cannot be made for patients presenting to Emergency Room (ER) without a prior cancer diagnosis. We undertook this study to estimate the incidence of hematolymphoid malignancies presenting as unknown primary with neurological deficit. Materials and Methods: Retrospectively reviewed a single hospital database of patients with an unknown cancer diagnosis with neuro deficit who underwent surgery from January 2009 - December 2021. Spinal decompression surgery with known histology of cancer was excluded. Results: 18 patients underwent urgent surgical decompression via posterior approach for unknown MESCC with neurological deficit. Postoperative histological diagnoses were multiple myeloma in 6 (33.3%), lymphoma 3 (16.6%), prostate 3 (16.6%), Lung 2 (11.1%), Thyroid 2 (11.1%) and pancreas 1 (5%). Thoracic spine was the most common site (15, 83%) followed by lumbar and cervical spine respectively. Preoperative neurological deficit was Frankel A (5), B (1), C (8), and D (3). Nine patients (50%) with hematolymphoid malignancy presented with Frankel A (2), B (1), C (4), D (2). The spine instability neoplastic score (SINS) for the hematolymphoid malignancies were classified as stable in 1, indeterminate in 4 and unstable in 4. Decompression without stabilisation was done for 4 patients out of which 2 patients had hematolymphoid malignancy. Conclusion: 50% of patients presenting with a neurological deficit due to unknown MESCC had a hematolymphoid diagnosis out of which 4 (44%) patients had an unstable spine. Current international guidelines recommend primary radiation for these malignancies that present with neurological deficits without frank instability. However, in an emergency setting when the diagnosis is not known quickly enough, surgery has to be offered despite the knowledge that about 50% of patients will have histology that is ultra-radiosensitive. At present, there is no reliable way to establish a histopathological diagnosis in the emergency setting.

416

P636: Preservation of neurological function justified anterior corpectomy with reconstruction in treating patients of thoracolumbar spinal metastatic tumors

Chien-JenHsu ¹

¹ Department of Orthopaedics, Kaohsiung Veterans General Hospital, Kaohsiung, Taiwan

Introduction: The choices of managements are controversial for metastatic tumor of thoracolumbar spine due to the diversity of patient condition and un-predictable prognoses. We intended to investigate outcomes of anterior corpectomy with reconstruction for metastatic tumor of thoracolumbar spine. Material and Methods: This study registered 27 cancer patients with thoracolumbar spinal metastases undergoing anterior corpectomy with reconstruction combining posterior instrumentation form Jan 2010 to Dec 2019. The origins of malignancy were 13 lung carcinoma, 8 breast carcinoma, 4 renal cell carcinoma, 1 colon carcinoma, and 1 malignant lymphoma. By using the neurologic, oncologic, mechanical, and systemic (NOMS) decision framework, The main surgical indication was determined as intractable back pain or sciatica with myelopathy that pre-operative MRI demonstrated significant compression on spinal cord. In addition to posterior transpedicular instrumentation, adequate decompression was achieved by removing the tumor mass through anterior corpectomy. For tumors with high vascularity in 4 patients, pre-operative embolization was performed to decrease blood loss and operative risk. In the meanwhile, vertebral reconstruction by mesh cages containing autogenous ribs or allogenous bone graft was conducted. Same day operations were done if the neurological symptoms were progressing. Otherwise, posterior instrumentation followed by anterior procedure were performed on separate days to avoid potential complications of extended operative time. The postoperative follow-up was arranged every 2 weeks after discharge from hospital in the first month, thereafter the regular follow-up was advised at 3 months interval. Results: No surgical complications required further surgical management in all patients. The average hospital days were 24 days. Except 3 patients remaining Frankel A as pre-operative status, the other patients achieved at least one Frankel grade improvement and relief of back pain. The mean survival time was 16 months with SF-36 questionnaire improvement from 52 to 80 postoperatively. No neurological deficit of both lower extremities developed at their last visits at outpatient clinic or before their mortalities. Neither dislodgement of mesh cage nor screw loosening was disclosed on follow-up radiographs at last outpatient visit. No re-hospitalization was caused by operation-related situation during follow-up except hospice care. Conclusion: Tumor excision by anterior vertebrectomy eliminates the compression on spinal cord directly. Motor and sensory function of lower extremities were therefore preserved. Meanwhile, back pain and sciatica were relieved by posterior instrumentation. However, patients with evident progression of muscle weakness pre-operatively could not achieve neurological recovery. The vertebral reconstruction after vertebrectomy provided anterior support to achieve at least a mid-term effect of construct stability. Consequently, the patients regained symptom-free lives before their mortalities. Even the life expectancy cannot be extended, posterior instrumentation and anterior vertebrectomy with reconstruction improved the life quality for cancer patients with spinal metastasis. Considering preservation of neurological function, anterior corpectomy deserves a recommendation for patients of thoracolumbar spinal metastatic tumor with incomplete neurological deficit.

419

P637: Surgical management of spinal metastases of the thoracolumbar junction.

Vanessa Hubertus ¹ , Michelle Marino ^1,2 , Charlotte Buhre ¹ , Peter Vajkoczy ¹ , and Julia Onken ¹

¹ Neurosurgery, Charité Universitätsmedizin Berlin and Berlin Institute of Health, Berlin, Germany

² Neurosurgery, Vivantes Klinikum am Friedrichshain, Berlin, Germany

Introduction: Spinal metastases of the thoracolumbar junction (TLJ) are common and pose a challenge for treatment due to the region`s anatomy and associated high rates of neurological deficits and postoperative complications. The aim of our study is to compare surgical strategies for TLJ metastases (Th11-L1) with respect to complexity and associated complications. Material and Methods: 100 patients were treated surgically due to TLJ metastases in 2005-2020 at a tertiary neurosurgical care center. Patients receiving only kyphoplasty (n = 11) were excluded from this study. Spinal instability neoplastic score (SINS), clinical, surgical and outcome data were retrospectively analyzed. Patients were divided into 3 surgical groups: Decompression only (i), decompression and instrumentation (ii) and decompression and instrumentation with corpectomy (iii). Results: 27 patients were decompressed (30%), 48 patients were treated with decompression and instrumentation (54%), and 14 patients received decompression and instrumentation combined with corpectomy (16%). In the median 5 vertebrae were instrumented in groups ii and iii, however with greatly varying range (3-9). Median SINS was 10 (i), 12 (ii) and 13 (iii). Preoperative neurological deficits were most common in patients treated with decompression (57%) and instrumentation (37%), whilst no deficits occurred in patients treated with corpectomy. Mechanical pain was common in all patients, but higher in patients treated with fusion (ii, iii 88-91% vs. i 61%). Mean duration of surgery was significantly shorter in group i (149min) compared to group ii (204min) and iii (189min). Surgical complications occurred in 14% (i), 4% (ii), and 19% (iii), mostly as surgical site infections. Mortality associated with surgery was 0% and postoperative survival did not differ significantly between surgical groups. No secondary Hardware failure (HwF) occurred at a median follow-up of 5-12 months independent of the number of fused segments. Conclusion: In this cohort, patients with TLJ metastases received instrumentation +/- corpectomy in case of a potentially unstable and unstable SINS and presented with a higher rate of preoperative mechanical pain than patients treated with decompression alone. Surgical complication rate was moderate in all groups, and dependent on surgical complexity. Postoperative survival did not differ dependent on surgical complexity. With the instrumentation of in a median 5 vertebrae, no HwF occurred at a median follow-up of 5-12 months. Larger patient cohorts are necessary to define the actual number of segments that need to be instrumented to avoid HwF in metastases of the TLJ.

476

P638: Primary spinal canal tumors treated in a tertiary level hopsital in Nepal - A case series

Rohit Pokharel ¹ and Sushil Paudel ¹

¹ Dept. of Orthopaedics and Trauma Surgery (Spine Unit), Institute of Medicine, Maharajgunj Medical Campus, Kathmandu, Nepal

Background and Purpose: Primary spinal tumors are rare neoplastic lesions. Its incidence varies among the reports because of difference in sample size and classification of the tumors. Irrespective of its type, the common presentation are features of space occupying lesion; distal neurological deficits, back pain and radicular pain. High index of suspicion and interpretation of relevant investigations are key for reach to diagnosis. The purpose of the study was to find out relative frequency of various primary spinal tumors presenting to our hospital, their management and outcomes. Materials and Methods: This is a retrospective study done at the Department of Orthopaedics and Trauma surgery (Spine Unit), Tribhuvan University Teaching Hospital, Nepal over a period of 11 years from January 2010 to December 2020. All primary spinal tumor cases (with neurological deficits) operated and have histopathological report are included in the study. Primary bony tumors of the spine are excluded. Results: A total of 76 patients with primary spinal tumor arising in the spinal canal encroaching the neural tissues were operated. The patient’s age ranged from 7 to 65 years with a mean of 49.5 years; there was slight male predominance (male female ratio of 42:34 = 1.2:1). Anatomical location of the tumors was; cervical -6, thoracic- 29, throcolumbar- 21 and lumbo-sacral- 20. There were 3 (3.9%) primary spinal extradural lymphomas. Majority, 62 (81.6%) were intradural extramedullary (IDEM); 30 Schwanoma, 18 meningioma, 9 neurofibroma, 3 dermoid cysts, 1 lipoma and 1 primary mesenchymal chondrosarcoma. Seven (9.2%) were inradural intrameduallry; 5 (6.6%) were muxopapillary ependymomas and 2 astrocytoma; and 4 were dumbbell tumors (3 neurofibroma and 1 Schwannoma). The mean follow-up was 16 months ranged from 6 weeks to 60 months. All patients improved both neurologically and functionally after surgery except three. One elderly with conus medullaris ependymoma did not improve, out of two cases with anteriorly located Schwannoma at T4-5 level one developed incomplete neurology and another had complete neurological deficit after the surgery. One case of Schwannoma and two cases of ependymoma had recurrence of the tumor after average of 1.8 years of the index surgery and were re-operated. Conclusion: Primary spinal canal tumors are uncommon lesions and should be one of the differentials of any spinal lesions. IDEM tumors are common with highest frequency of Schwannoma followed by meningioma. Early diagnosis and total excision surgical intervention has very good result.

Keywords: extradural, Intradural extramedullary tumor, Spinal canal, Surgical excision

503

P639: Review of a series of Ewing sarcoma in a Spanish tertiary center

Borja Sanz ¹ , Marta González Pombo ¹ , Irene Iglesias Lozano ¹ , José Luis Gil Salú ¹ , Álvaro Prada Vega ¹ , David Mesa Collantes ¹ , Leyton Hernán Catari Mallea ¹ , Jesús Riqué Dormido ¹ , and Francisco Rodríguez Peña ¹

¹ Neurosurgery, Hospital Universitario Puerta del Mar, Cádiz, Spain

Introduction: Ewing's sarcoma (ES) is an infrequent malignancy (WHO grade 4) mainly occurring in adolescents and young adults. It commonly involves the dorsal spinal column and manifests as myelopathy. We present three cases in each segment of the spine. Material and Methods: We review the literature after the diagnosis and treatment of this tumour. Results: Case 1. 25-year-old man with cervical pain and tetraparesis. He went to the emergency department and the MRI showed an extradural cervical mass that caused compression from C2 to C6 that invaded the lateral mass of C4. A posterior decompression, resection and fusion was performed and in a second stage the lateral mass of C4 was resected through an anterior corpectomy. He did not present any worsening and recovered partially from the tetraparesis. He presents 3/5 in the right arm and is capable of walking short distances. We initiated vincristine-doxorubicin-cyclophosphamide and ifosfamide-etoposide. 10 months later the patient has a progression free survival (PFS) and the deficits are improving. Case 2. 19-year-old woman with dorsal back pain irradiated to the chest. She also presented paraesthesias from a D7-D8 level. A MRI showed an extradural lesion around D4-D6 with widening of the foramen of D5-D6 along with intense contrast enhancement. A gross total resection (GTR) was achieved. We initiated vincristine-doxorubicin-cyclophosphamide and ifosfamide-etoposide. After 14 months the patient remains asymptomatic with a PFS and no deficits. Case 3. 16-year-old woman with lumbar pain irradiated to both legs with no neurological symptoms. A MRI showed an isointense and hyperintense in T2 intradural tumour in L3-L4. GTR was obtained and the pain improved. We initiated ifosfamide/etoposide. 4 months later the patient remains asymptomatic with a PFS and no deficits. The three cases presented a similar anatomopathological study. They described a tumour positive to CD99, FLI-1 and vimentin immunohistochemical stain. It also presented fusion of FUS genes and ERG. ES was the most likely diagnosis. ES is an infrequent malignancy mainly occurring in adolescents and young adults. The most frequent symptom is pain followed by myelopathy. Back pain and paraesthesia are secondary to irritation. The most common location is thoracic followed by lumbar and cervical. The intradural presentation is more frequent than the extramedular. In MRI is isointense on T1 and hyperintense on T2, with varying gadolinium enhancement in more than 60%. Other characteristics are dumbbell shape (24%), foraminal widening (19%), and erosion (19%). GTR plus chemotherapy or radiotherapy is the preferred treatment. The radiotherapy consists of a neuroaxis irradiation with 30–60Gy and the chemotherapy usually used is vincristine-doxorubicin-cyclophosphamide and ifosfamide-etoposide. GTR is a good prognosis factor because it increases the effectiveness of QT-RT. The prognosis is thought to be dismal due to local invasion and metastases, with 5-year survival of less than 37.5%. Conclusion: ES must be suspected in cases of rapidly progressing pathology and young patients. There are no typical radiological signs. GTR and adjutant treatment with QT-RT is the gold standard.

525

P640: Mini-open vertebroplasty in treating C2 osteolytic lesion

Adnene Benammou ¹ , Ahmed Ben Abid ¹ , Cherif Kamoun ¹ , Balti Walid ¹ , Amine Lengliz ¹ , Mondher Kooli ¹ , and Mohamed Ben Salah ¹

¹ Orthopedic Surgery Department, Charles Nicolle Hospital, Tunis, Tunisia

Introduction: Percutaneous vertebroplasty is a well-established technique in treating multiple painful lesions of the thoracolumbar spine. It can provide pain relief, bone strengthening and vertebral stabilization. However, its use in the upper cervical spine is rare due to the difficult access and multiple potential complications. We report a safer technique with a mini-open vertebroplasty of a C2 osteolytic lesion. Material and Methods: A 71-year-old man, with history of neck pain for which he did not seek medical treatment, sustained a road traffic accident. He presented to our emergency room. Physical examination revealed only pain of the right clavicle. No neurological deficit was noted. A full body Computed Tomography (CT) was conducted due to the violence of the trauma. It revealed a fracture of the right clavicle and an osteolytic lesion of C2 involving the left half of C2 vertebral body. The fracture of the clavicle was treated conservatively. The decision for the C2 osteolytic lesion was to proceed with a mini-open vertebroplasty. Surgery was realized in supine position with head on horseshoe. Fluoroscopy marking of vertebral levels was realized. We realized a mini right anterior cervical approach exposing the edge of C2. We inserted the Jamshidi needle on the lytic region under fluoroscopic control. Biopsy was taken and addressed to the laboratory. We injected then the PolyMethyl MethAcrylate (PMMA) using the eggshell technique with injecting in the posterior part, waiting for the cement to harden and then proceed to injecting the cement to fill the lesion. We used the eggshell technique to avoid cement leakage and its possible complications especially at the level of C2. No extravasation was noted. Results: Intra and postoperative was uneventful. Pain relief was immediate after surgery. Visual Analog Scale (VAS) decreased from 8 in preoperative to 2 in postoperative. Postoperative CT-scan showed PMMA in the body of C2 with no sign of extravasation. The patient was ambulated and discharged the day next surgery and addressed to a medical department to establish the etiology of the lesion. At 3 months postoperative, there was a complete pain relief (VAS = 0). Conclusion: Osteolytic lesions of C2 are rare. They can cause serious neurovascular complications. Percutaneous vertebroplasty has shown great result in treating thoracolumbar spine but can be difficult in upper cervical spine. This technique of mini-open vertebroplasty can be a safer less demanding technique in treating osteolytic lesions of C2. It has the advantages of vertebroplasty such as early pain relief and vertebral stabilization without the risk of the percutaneous technique in the upper cervical spine which can lead to serious complications.

563

P641: Spinal surgery for multiple myeloma has a high one year mortality: analysis of the current British haematological guidelines

Mohamed A. Abdalla ¹ , Mark Nyanzu ¹ , Jemma Keefe ¹ , Bisola Ajayi ¹ , Tim Bishop ¹ , Jason Bernard ¹ , Fenella Willis ² , Yasmin Reyal ² , and Darren Lui ¹

¹ Neurosurgery

² Haematology, St George's Hospital, London, United Kingdom

Introduction: Advances in the medical treatment of myeloma patients have shown significant improvements. In 2015, the guidelines of treatment published by the British journal of haematology indicate three main treatments for Spinal involvement normal or abnormal neurology: conservative medical treatment +/- bracing (CMTB), kyphoplasty (KP) and Spinal decompression +/- stabilization surgery (SDS). Material and Methods: Retrospective review 338 patients referred to the spine MDT from 2015-2020. Groups were divided into Normal Neurology and Abnormal Neurology with subcategories of CMTB, KP, SDS. Results: 338 patients identified: 62% males. The mean age was 65.4 (range 18-93). 46 patients were referred in 2016 compared to 70 in 2020. Isolated thoracolumbar spine involvement was in 66% and pan-spine involvement was in 33% of cases. Overall: SDS (16.2% n = 55), KP (16.6% n = 56), CMTB (62.2% n = 224). Abnormal neurology: (47% n=159): Bilsky 3 (44.7% n = 71). SDS (21.3% n = 34) CMTB (78.6% n = 125). Normal Neurology: SDS (12% n = 21) Kyphoplasty (31% n = 56) CMTB (57% n = 99). One year mortality: SDS (32.7%), kyphoplasty (5.4%) and CMBT (7.14%) (p < 0.05 Chi2 test). Conclusion: Almost half of Myeloma patients will present with abnormal neurology. Utilising current guidelines overall, only 16% patients underwent SDS or KP. CMTB accounted for 63%. Of those with abnormal neurology only 21% underwent SDS. The mortality at one year was significantly higher in the surgical group compared to Kyphoplasty or medical treatment +/- Bracing which may indicate the deleterious effect of delaying medical treatment.

886

P642: En-bloc radical spinal surgery still has a role in the era of stereotactic ablative radiosurgery

Mohamed A. Abdalla ¹ , Priyanshu Saha ² , Tim Bishop ¹ , Jason Bernard ¹ , Bisola Ajayi ¹ , and Darren Lui ¹

¹ Neuroscience, St George's University Hospital, London, United Kingdom

² St George's University, London, United Kingdom

Introduction: With the modern advances in radiotherapy, total en-bloc spondylectomy (TES) has come out of favour by many spine surgeons. For example, neurologic, oncologic, mechanical, and systemic (NOMS) decision framework does not suggest any role for TES. Separation surgery and Cyber knife can achieve maximum local control in the majority of oligometastatic cases. However, radio-resistant tumours and sarcoma can be challenging to even the most advanced current radiotherapy technique. Moreover, violation of sarcoma can lead to acceleration, aggravation, and agitation of the tumours. This shows a clear indication for radical surgery to achieve maximum local control or even cure for selected group of spinal malignancies. Methods: We retrospectively reviewed patients who had radical surgeries for spinal malignancies at St George’s hospital in the period between April 2017 till June 2021. The demographic of these patients, oncological diagnosis and staging, spinal load of the disease, type of surgery, hospital stay, and 30-day and one-year mortality were analysed. Results: We identified nine patients who had radical surgery for spinal malignancy, five of them were males. The youngest patient was 28 years old and the oldest was 63. Sarcoma was the histopathological diagnosis in four patients and the other five had carcinoma of colorectal, lung, renal or ovarian origin. Only one patient had Chordoma as a primary spinal tumour. Two had Enneking inappropriate surgery and the rest achieved radical excision as planned. Surgical complications were dural tears in two cases. One patient died within a month of surgery because of COVID and one in the first postoperative year. Conclusion: Radical surgery like Tomita en-bloc spondylectomy is still an important surgical armamentarium for a selected group of spinal malignancy. It allows cure or maximum local tumour control when separation surgery and Cyber knife radiotherapy are not enough in selected group of patients.

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P643: En-bloc resection of a recurrent primary lumbar chondrosarcoma of L5

Sofia Caldeira Dantas ^1,2 , Ana Lucinda Correia ¹ , João Soares do Vale ¹ , Vânia Oliveira ¹ , Pedro Cardoso ¹ , and Ricardo Rodrigues-Pinto ¹

¹ Spinal Unit (UVM), Department of Orthopaedics, Centro Hospitalar Universitário do Porto, Porto, Portugal

² Department of Orthopaedics, Hospital do Litoral Alentejano, Santiago do Cacém, Portugal

Introduction: Chondrosarcomas are malignant cartilage-forming bone neoplasm that represent 10% of all primary bone tumors. These lesions are commonly low grade and only 12% of all chondrosarcomas are found in the spine, being the thoracic segment the most frequently affected. Patients typically present back pain, a palpable mass and/or neurologic deficits. Both partial and en-bloc resections have been described as surgical treatment options. Although en-bloc resection is more challenging with longer surgical time, blood loss and higher risk of instability due to the extended resection, some authors have reported a better prognosis with this technique. The advantage of using either one or two-stage surgery for en-bloc resection, as well as the difference between performing a two-stage approach in the same surgical time is not yet established. Material and Methods: The present study describes a case of a lumbar chondrosarcoma to highlight and discuss its treatment options, complications, and management. Results: A 30-year-old male with a prior history of a low-grade chondrosarcoma submitted to an anterior transperitoneal curettage and autologous bone grafting 14 years ago, presented to the orthopaedic clinic due a new-onset back pain that had been worsening for 2 months. A CT-scan, MRI and bone biopsy were performed and were suggestive of chondrosarcoma recurrence without distant disease. The patient was submitted to a two-stage posterior-anterior en-bloc resection of L5 with L3-iliac fixation and anterior L5 expandable cage. In the immediate post-op an iliac vein thrombosis was noted and a thrombectomy was performed. Conclusion: Primary spinal chondrosarcomas are rare tumors and their complete resection is technically very challenging. Here a recurrent chondrosarcoma of L5 was submitted to an en-bloc resection. The surgical technique and alternative options are further presented and discussed.

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P644: 23 year old pregnancy with bone metastasis and Krukenberg tumor resulting from gastric adenocarcinoma. A case report

Luiz Claudio Rodrigues ¹ , Fernanda Andrea Navarro ² , Rodrigo Nakao ² , and Nathalia Adelina Pereira ¹

¹ Spine Surgery, Santa Marcelina College of Medicine, São Paulo, Brazil

² Spine Surgery, Hospital Santa Marcelina, São Paulo, Brazil

Female patient, 23 years old, housewife, single, born in Bahia and living in São Paulo. Patient with no previous comorbidities, at 28 weeks' gestation by the date of the last menstrual period (LMP), with a history of G2P1A0, seeks the emergency service of a tertiary hospital in the east of São Paulo with a history of low back pain, which started suddenly about two months after charging a television. There was a worsening of the pain 01 month ago, and the patient started to present difficulty walking and associated paresthesia in the lower limbs. She reported having sought medical care on two previous occasions at other services in this period, being discharged with only analgesics, but without pain improvement. She refused to undergo radiological examinations on these occasions, due to the possible risks associated with radiation doses for pregnancy.

While waiting for the availability of an MRI, the patient underwent an upper digestive endoscopy, as she continued to complain of significant nausea and vomiting after 20 weeks of gestation, despite adequate antiemetic medication. On examination, a stomach with an ulcerative and infiltrative lesion was visualized, affecting mainly the antrum in all its circumference, extending to the first duodenal portion. Biopsy was performed with subsequent results indicating gastric adenocarcinoma, poorly differentiated and with signet ring cells.

Antibiotic therapy was started associated with adequate intensive support, but the patient remained in a serious general condition, with significant respiratory distress and need for vasoactive drugs, progressing to cardiorespiratory arrest, and death was confirmed. The newborn remained in the care of neonatology, in a serious general condition, in a neonatal intensive care unit, evolving to death a few days after delivery.

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P645: Idiopathic hypertrophic pachymeningitis with cervical spinal cord compression: a case report

Jong Tae Kim ¹ and Seonghan Choi ¹

¹ Neurosurgery, The Catholic University of Korea, Incheon Saint Mary's Hospital, Incheon, and South Korea

Introduction: Idiopathic hypertrophic spinal pachymeningitis (IHSP) is a chronic, progressive, inflammatory disorder characterized by tumorous mass formation by hypertrophic inflammation of the dura mater and clinical symptoms that progress from local pain to severe myelopathy. The diagnosis can be established by open biopsy and exclusion of all other specific granulomatous and infectious diseases. Material and Method: We report a case of IHSP occurring a cervical dura from C3 to C4 and C6 to C7. The patient was 42-year-old male, who had been suffered from pain on his posterior neck, both upper arms and left ulnar side arm to hand dorsum paresthesia for 5 months and recent onset left lateral leg paresthesia. Results: During the 9 months of follow-up period, the patient was treated 2 open biopsies and debulking of the lesion with marked improvement in his clinical condition. Conclusion: This case demonstrates the challenge in making a diagnosis. IHSP should be considered as a differential diagnosis in case of spinal lesion and the histopathology after the open biopsy. The implications of the case are discussed.

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P646: En-bloc vertevrectomy for the treatment of tumor spine - a case series of 8 patients

João Soares do Vale ¹ , Sara Diniz ¹ , Sofia Caldeira Dantas ¹ , Pedro Cardoso ² , António Oliveira ³ , and Ricardo Rodrigues-Pinto ¹

¹ Spinal Unit (UVM)

² Musculoskeletal Tumors Group, Department of Orthopaedics, Centro Hospitalar e Universitário do Porto, Porto, Portugal

³ Department of Orthopaedics, Centro Hospitalar do Porto, Porto, Portugal

Introduction: En-bloc vertebrectomy, also called spondylectomy, has become an increasingly widespread procedure used for the treatment of neoplastic spine lesions. It consists of a resection of the entire tumor and one of more affected vertebrae with margins. The objective of this surgery is either cure or localized control of the disease. Material and Methods: This study was a retrospective case series analysis conducted in a reference center for the treatment musculoskeletal sarcomas. The data were obtained from medical reports of patients treated between January of 2007 and June of 2022. Patients with benign aggressive, primary malignant spine lesions and spine metastasis who underwent en-bloc vertebrectomy during the study period was evaluated. Results: Eight patients (four males and four females) underwent total vertebrectomy. Their mean age at the time of operation was 47 years (18 to 68). The mean time of follow-up was 70 months (2 to 144). The diagnosis were chondrosarcoma, giant cell tumor, angiosarcoma, chordoma, high grade sarcoma, Ewing sarcoma, leiomyosarcoma and breast cancer metastasis. Type 1 to 6 lesions were treated according to Tomita classification. In seven patients the tumour was in lumbar spine (L1, L3 and L5) and in one patient in thoracic spine (T8). In four cases a combined approach was used and in the other four a posterior approach. In three patients, wide margins were achieved, and in the other 5 were marginal. Three patients died from their disease with a mean follow up of 57 months (2 to 144). Three showed no evidence of disease and two are alive with disease. A 50% complication rate was observed in this series (infection, hardware failure and neurological injury). Conclusion: Despite being a technically demanding surgical procedure with a high rate of complications, en-bloc vertebrectomy is a good solution when the objective is either cure or localized control of the disease.

In this series it is possible to confirm the effectiveness of vertebrectomy to achieve the cure and a good survival rate even in patients in which the procedure was not curative.

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P647: Multi-level kyphoplasty for myeloma of more than 3 vertebral levels can be safe

Jemma Keefe ¹ , Mohamed Abdalla ² , Mark Nyanzu ² , Priyanshu Saha ¹ , Bisola Ajayi ² , Jason Bernard ² , Timothy Bishop ² , and Darren Lui ²

¹ St George's, University of London, London, United Kingdom

² Department of Complex Neurosurgery, St George's Hospital, London, United Kingdom

Introduction: Vertebral involvement occurs in approximately 70% of multiple myeloma cases. Percutaneous kyphoplasty (PKP) has been proven to improve pain and mitigate spinal deformity in myeloma patients. This can be performed at both single and multi-vertebral level dependent on vertebral involvement. Pan-spinal infiltration is not uncommon, affecting approximately 50% of our patients, emphasising the need for multi-level kyphoplasty. Original guidelines for kyphoplasty have cautioned against performing kyphoplasty on more than 3 vertebral levels because of the risk of multiple mini-pulmonary emboli from cement leakage. This may potentially be due to the fact that each vertebra can hold approximately 5 to 10cc and it is essentially the volume of cement rather than the number of vertebrae which is important. This study aims to determine the safety of PKP for more than 3 vertebral levels. Material and Methods: This was a retrospective analysis of 45 multiple myeloma cases (mean age = 64.8 ± 1.57, 25 male/20 female) with vertebral involvement of which management involved PKP from January 2019 to August 2022. Cases involving more than 3 vertebral levels (N = 16) were compared to cases involving 3 levels or less (N = 29), with safety and efficacy of PKP analysed through 30-day mortality and intra-operative complications. Results: For all cases managed with PKP there was a 30-day mortality of 7.31%. The 30-day mortality in cases involving 3 vertebral levels or more (N = 14) was 0.00%, with no intra-operative complications, whereas the 30-day mortality in cases with less than 3 levels involved (N = 27) was 11.1%. Comparatively, a similar cohort of patients with multiple myeloma involving the spine that were managed conservatively (N = 83) at our centre had a 30-day mortality of 8.43%. Conclusion: In this study PKP performed at more than 3 vertebral levels was shown to be a safe procedure with no evidence of increased mortality or complications compared to procedures involving less than 3 vertebral levels. We believe that the volume of cement is more important than the number of vertebrae operated on. Therefore, in future patients with pan-spinal involvement may be considered for PKP of more than 3 vertebral levels. Further studies are required to characterise more accurately the safety and efficacy of this procedure for more than 3 levels.

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P648: Can the SORG machine learning algorithms predict 90-day and 1-year spinal metastatic disease survival in a rural cohort? An external validation study

James Hall ¹ , Michael Garneau ¹ , Harmen Kuijten ^2,3 , Olivier Q. Groot ^2,3 , Trevor Gulbrandsen ¹ , Cassim Igram ¹ , Andrew Pugely ¹ , Catherine Olinger ¹ , and Joseph Schwab ²

¹ Orthopedics and Rehabilitation, University of Iowa Hospitals and Clinics, Iowa City, United States

² Orthopedic Surgery, Massachusetts General Hospital, Harvard Medical School, Boston, United States

³ Orthopedic Surgery, University Medical Center Utrecht, Utrecht, The Netherlands

Introduction: To determine the propriety of invasive surgical procedures, the Skeletal Oncology Research Group machine learning algorithm (SORG-MLA) was developed to predict 90-day and 1-year survival in spinal metastatic disease. However, sub-analysis originally demonstrated decreased probability of prediction in patients who underwent surgery after 2010. Although further studies demonstrated good performance of these algorithms, even after 2010, they were based on a cohort of patients in the same region and have yet to be validated in a varying population. The purpose of this study was to externally validate the performance of the SORG-MLA on predicting 90-day and 1-year survival in spinal metastatic disease in a cohort of patients located in the rural midwestern United States. Materials and Methods: A retrospective review of patients who underwent operative management of spinal metastatic disease at one academic institution (University of Iowa Hospitals and Clinics) was performed. The criteria for inclusion consisted of patients aged ≥ 18 years, diagnosis of metastatic disease (solid tumor metastasis, multiple myeloma, lymphoma) with or without pathologic fracture, and operative management being performed between 2010 – 2021. Exclusion criteria included spinal metastasis originating from a primary bone tumor (e.g. sarcoma), and death record or most recent follow-up unavailable. Baseline characteristics of the validation cohort were obtained and compared to the developmental cohort. Input parameters to predict survival included 18 variables including primary tumor histology, Eastern Cooperative Oncology Group (ECOG) Performance Status Scale, American Spinal Injury Association (ASIA) Impairment Scale, and laboratory values. Discrimination (c-statistic and receiver operating curve), calibration (calibration slope, intercept, calibration plot, and observed proportions by predicted risk groups), overall performance (Brier score), and decision curve analysis were utilized to evaluate the SORG-MLA in this specific external cohort. Results: Overall, there were 249 patients included in this study. The 90-day and 1-year mortality rates were 63 (25%) and 134 (54%), respectively. The validation cohort compared to the developmental cohort had significantly more moderate and rapid growth primary tumors, more visceral metastasis, and lower pre-operative hemoglobin levels. The SORG-MLA for 90-day and 1-year survival showed strong discriminatory ability (AUC 0.85 [95% confidence interval [CI] 0.74-0.94] and 0.82 [95% CI 0.71-0.91], respectively), Brier score, and decision curve analysis. The 90-day and 1-year mortality showed almost perfect calibration demonstrated by a calibration intercept of 0.06 [95% CI -0.09-0.21] and 0.02 [95% CI -0.12-0.16], respectively. Conclusion: This external validation study demonstrated that the SORG ML algorithm utilized in predicting 90-day and 1-year survival of patient with spinal metastatic disease exhibited strong performance in this rural, midwestern United States cohort. Additional, multi-center studies are needed to further validate these algorithms in differing populations.

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P649: Radiofrequency ablation in radical oncological treatment of spinal oligometastatic disease

Priyanshu Saha ¹ , Emily Tsang ¹ , Zion Hwang ¹ , Bisola Ajayi ² , Varinder Singh Alg ² , Ursalan Khan ² , Mohamed Abdalla ² , Shahnawaz Haleem ² , Tesfaladet Kurban ² , Jason Bernard ² , Timothy Bishop ² , and Darren Lui ²

¹ St George's University of London, London, United Kingdom

² Department of Complex Neurosurgery, St George's University Hospitals NHS Foundation Trust, London, United Kingdom

Introduction: Radiofrequency Ablation (RFA) is a novel addition to the armamentarium of radical oncological treatment utilized with other surgical techniques. It aids in cytoreduction and potentially utilized independently to be curative and offer maximum local control. RFA as an adjunct to separation surgery may be a new technique that may have a beneficial compound effect of cytoreduction. Spinal oligometastatic disease (OMD) and oligo-progression (OPD) treatment has experienced paradigm shifts where indications of surgery is no longer focused on palliative outcomes including maintenance of ambulation, continence, neurological symptoms and pain management. Stereotactic ablative radiosurgery (SABR), separation surgery and En Bloc Surgery can provide radical oncological treatment with curative results. The novel use of RFA in conjunction to radical treatment or independently for the treatment of OMD and OPD is investigated at a quaternary level 1 spinal center. Methods: Retrospective review of spinal OMD patients at quaternary level 1 spinal center between 2017-2022. Patient demographic data, tumour histology, OMD type, surgical type and instrumentation (titanium versus carbon fiber), RFA, PD, local recurrence, infection, mortality data was analyzed. Results: 15 cases of RFA. Including 2 cases of en bloc surgery with post adjuvant radiosurgery, RFA was used for neoplastic eradication of the pedicles to allow Tomita en bloc spondylectomy without seeding cancerous cells. Patient 1 experienced resolution of disease with no LR at 12 month follow up; patient 2 had died 9 months postoperatively because of concurring distant metastases from the primary disease. Mean hospital length of stay was 64 days, no inpatient postoperative or medical complications. EOS scans determined no local recurrence at 6 months. 11 out 26 separation surgeries performed for patients in the OMD/OPD pathway had adjunct RFA ± cement. Of the separation surgeries 4 cases utilized titanium instrumentation and 7 cases utilized carbon fiber instrumentation. Titanium separation surgery with RFA ± cement (n = 4): 2-year LC– 0%; 2 years mortality – 0%. Titanium separation surgery without RFA ± cement (n = 16) – 1 year LC – 6% (n = 1); 30-day mortality – 12.5% (n = 2; SS surgery was demoted to palliative decompression for both patients), 1 year mortality – 19% (n = 3; Patient 3 was demoted to palliative decompression). There were 7 cases with independent RFA and cement, 1 case with RFA + biopsy and 3 cases with cement only. LR –0% at 6 months (n = 9), 12 months (n = 7) and 24 months (n = 5), pain was well managed, no infection and mortality – 0% at 6 months (n = 11), 12 months (n = 7) and 24 months (n = 5). The Histopathology analysis of the biopsy case showed increased local necrosis rates of 70%, indicating neoplastic control. Conclusions: RFA is promising for OMD pathway which can potentially deliver radical oncological control. As an adjunct to SS and SABR, it may offer improved cytoreductive control. The authors believe they are the first to describe this technique used in conjunction with SS where we show local recurrence of 0% at 2 years. Furthermore, in carefully selected cases, RFA ± cement has shown excellent LC and mortality. However, it is important to acknowledge the limited sample size in our study.

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P650: Anterior separation surgery to allow for stereotactic ablative radiotherapy: a novel approach permitting radical oncological treatment of oligometastatic disease

Priyanshu Saha ¹ , Emily Tsang ¹ , Zion Hwang ¹ , Pawan Minhas ² , Mohamed Abdalla ² , Bisola Ajayi ² , Timothy Bishop ² , Jason Bernard ² , and Darren Lui ²

¹ St George's University of London, London, United Kingdom

² Department of Complex Neurosurgery, St George's University Hospitals NHS Foundation Trust, London, United Kingdom

Introduction: A paradigm shift in the treatment of spinal metastases has allowed surgeons to deliver curative results utilising radical oncological treatment opposed to traditionally palliative decompression for neurological symptom and pain management. In oligometastatic disease and oligo-progressive disease, the accompaniment of Stereo tactic ablative radiotherapy (SABR) as a primary modality or adjuvant treatment to surgery has been shown to excellent survival outcomes, lower morbidities, and better pain management. The novel use of carbon fibre VBR allows optimal planning of SABR, less reflection and better future surveillance imaging. Carbon fibre has physical and chemical properties that includes high heat tolerance, high tensile strength, resistance to corrosion and conductivity. Carbon fibre reinforced PEEK has mechanical properties that allow high resistance to ionizing radiation and low wear particles, which is better suited to the planned SABR as opposed to use of titanium VBR and screws. Methods/Case: The patient was a 48-year-old lady with a solitary metachronous lesion in T2, this is a recurrence of her breast oligometastatic disease in 2014 which was diagnosed and treated in 2014, Spinal Instability Neoplastic Score (SIN) was determined, the location was junctional (C7-T2), pain free, a lytic bone lesion was found on CT with normal alignment and no vertebral collapse. The patient also did not present with any neurological deficit. She was ASA grade 3. She had a Tokuhashi score of 14 hence indicating she would live more than a year, the revised Tokuhashi with a Tomita score of 2 indicated for highly morbid excision surgery. To avoid morbidity, separation surgery with postoperative SABR was opted. A Bilsky ESCC score of 2 and the Neurologic Oncologic Mechanical and Systemic framework (NOMS) indicated the patient was suitable for separation surgery. Although the SIN score was 6 indicating that the patient should not be operated on and most likely be treated palliatively. separation surgery was decided for the patient due to the patient’s age and systemic suitability. This case report illustrates a novel approach to the treatment of spinal oligometastatic disease utilizing anterior separation surgery with a custom carbon fibre vertebral body replacement cage followed by postoperative SABR. Due to several contraindications of posterior separation surgery and the morbidity associated with radical surgery; anterior surgery was opted for utilising the philosophy of Enneking radical surgery despite Enneking inappropriate resection. Results: There were no complications intraoperatively and post operatively, pain was managed appropriately in the hospital. Patient did not complain of pain or wasn’t immobilised outside of the hospital. In both 15 and 30 monthsthe postoperative follow up MRI and PET CT scans demonstrated that the patient was tumour-free and the patient was fully mobile, pain free and living independently. Conclusion: Utilising this novel approach, Anterior Spinal Separation Surgery and SABR has shown maximum local control and can deliver curative, radical oncological control without the morbidity of Enneking radical surgery. The use of carbon fibre VBR has been better suited for post-operative SABR planning due to the physical properties superior to titanium.

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P651: Vascular supply and neurological outcome after surgical treatment of spinal intradural hemangioblastoma: a multicenter retrospective case series

Vicki Butenschön ¹ , Bernhard Meyer ¹ , and Maria Wostrack ¹

¹ Department of Neurosurgery, Technical University Munich, Munich, Germany

Introduction: Spinal cord hemangioblastoma are rare highly hypervascularized benign neoplasms. Surgical resection remains the treatment of choice, with a significant risk of postoperative neurological deterioration. Methods: Retrospective multicenter study including five high-volume neurosurgical centers assessing patients surgically treated for spinal hemangioblastoma between 2006 and 2021. Clinical status, surgical data, preoperative angiograms, and embolization were analyzed when available. Follow-up records were reviewed, and logistic regression performed to assess possible risk factors for neurological deterioration. Results: We included 60 patients in 5 high-volume neurosurgical centers in Germany and Austria. Preoperative angiography was performed in 30% of the cases, ten patients underwent preoperative embolization. The clinical outcome revealed a transient postoperative neurological deterioration in 38.3%, depending on symptom duration and preoperative McCormick grading, but patients recovered in most cases until follow-up. Posterior tumor location and presence of a syrinx favored gross total tumor resection. Preoperative embolization was not associated with postoperative worsening. Conclusion: Spinal hemangioblastoma patients significantly benefit from early surgical treatment with only transient postoperative deterioration and complete recovery until follow-up. The performance of preoperative angiograms remains subject to center disparities.

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P652: L5 en bloc spondylectomy for oligometastatic liposarcoma with post adjuvant stereotactic ablative radiotherapy

Priyanshu Saha ¹ , Emily Tsang ¹ , Zion Hwang ¹ , Bisola Ajayi ² , Mohamed Abdalla ² , Varinder Singh Alg ² , Ursalan Khan ² , Shahnawaz Haleem ² , Tesfaladet Kurban ² , Jason Bernard ² , Timothy Bishop ² , Pawan Minhas ² , and Darren Lui ²

¹ St George's University of London, London, United Kingdom

² Department of Complex Neurosurgery, St George's University Hospitals NHS Foundation Trust, London, United Kingdom

Introduction: Total en bloc spondylectomy is a radical technique first pioneered by Katsuro Tomita for solitary spinal metastases. Its use in oligometastatic lesions of the spine aims to improve prognosis and oncological curability for patients via complete surgical resection rather than the piecemeal excision. We present a challenging case of an L5 en bloc spondylectomy for a case of oligometastatic liposarcoma performed at our specialist complex spinal unit with an analysis of the extensive pre-operative planning and specialist intra-operative techniques that may be of assistance to others taking on these challenging cases. Methodology: First Stage: Carbonfibre pedicle screws planned from L2 to S2AI-Pelvis, aligned, to her patient-specific rods. Custom 3D-printed navigation guides used to overcome challenging limitations of carbon instruments. Radiofrequency ablation (RFA) of L5 pedicles prior to osteotomy was performed to prevent sarcoma cell seeding. Microscope-assisted thecal sac-tumour separation and L5 nerve root dissection was performed. Novel surgical navigation of the ultrasonic bone cutter assisted inferior L4 and superior S1 endplate osteotomies. Second stage: We performed a vascular-assisted retroperitoneal approach to L4-S1 with protection of great vessels. Completion of osteotomies at L4 and S1 to en-bloc L5: (L4 inferior endplate, L4/5 disc, L5 body, L5/S1 disc and S1 superior endplate). Anterior reconstruction used an expandable PEEK cage obviating the need for a third posterior stage. Reinforced with a patient-specific carbon plate L4-S1 promontory. Sacrifice of left L5 nerve root undertaken. Results: Patient rehabilitated well and was discharged after 42 days. Patient underwent SABR two months post-op. Despite left foot drop, she’s walking independently 9 months post-op. Conclusion: In conclusion, we present a challenging case of an L5 en bloc spondylectomy for a case of oligometastatic liposarcoma performed at our specialist complex spinal unit. Our reported extensive pre-operative planning and specialist intra-operative techniques may be of assistance to others taking on these surgically challenging cases. We recommend a truly multi-disciplinary team approach for pre, intra and post-operative stages when managing such complex cases including Complex Spine team, Neurosurgery, Vascular surgery, Anaesthetics, Intensive care, Radiologists, Radiotherapy Physicists, Oncologists, Physiotherapy, Occupational therapists, Psychologists and specialist nursing staff.

1310

P653: Solitary bone plasmocytoma of the axis: a rare case report

Mohamed Amine Gharbi ¹ , Hedi Ezzine ¹ , Ahmed zendeoui ¹ , Houssem Eddine Chahed ¹ , Tborbi Anis ¹ , Ramzi Bouzidi ¹ , Ezzaouia Khelil ¹ , and Mouadh Nefiss ¹

¹ Orthopedic and Trauma Surgery, Mongi Slim Marsa University Hospital Center, Tunis, Tunisia

Introduction: Solitary bone plasmacytomas (SBP) are localized plasma cell malignancies involving bone marrow. It is a rare entity and in the spine, it mainly concerns the dorsolumbar spine. Involvement of the upper cervical spine is rare and more challenging condition. Materials and Methods: We report the case of a man with solitary plasmacytoma involving vertebral body and posterior arch of the axis. Result: A 50-year-old man presented with neck pain and uncommon right sided cervicobrachial neuralgia evolving for 4 months and becoming resistant to symptomatic treatment. X-ray showed a lytic lesion of C2. MRI concluded in a high signal mass of the entire vertebral body, the odontoid process and the right posterior hemi-arch of C2 with invasion of the pre-vertebral soft tissue, the intervertebral disc and the anterior part of C3.A CT- sacan guided biopsy failed to confirm diagnosis. We decided to perform posterior biopsy with occipito-cervical fusion. The diagnosis of solitary plasmocytoma of the axis was confirmed based on histopathological examination, biologic and extension assessment. The patient was reviewed in the hematology department and he received both postoperative radiotherapy and chimiotherapy. He remains with no neck pain or neurological deficit and serum markers of multiple myeloma were normal at 2-year follow-up. Conclusion: SBP is a rare diagnosis especially in the upper cervical spine for which the primary treatment is local radiotherapy. However, instability is the main reason for pain, which can only be relieved completely by surgery.

1313

P654: Lumbar spine chordoma: a case report

Sofiane Masmoudi ¹ , Hedi Belhassen ¹ , Saiffedine Mahjoubi ¹ , Haithem Eleuch ¹ , Khaled Zitouna ¹ , and Maher Barsaoui ¹

¹ Orthopedic Surgery, Rabta Hospital, Tunis, Tunisia

Introduction: Chordoma is a rare tumor arising from notochord remnants in the spine. The slow-growing of this tumor makes it difficult to diagnose and to follow up after treatment. Mostly, it occurs in the base of the skull and sacral spine and rarely occurs in other parts of the spine. The aim of our case report is to remind that these tumors can be seen and to discuss the way to diagnose them and to treat them. Material and Methods: We report the case of a 57 years-old men who presented low back pain since 2 months with progressive partial paralysis of lower limbs wich has worsened to a complete paralysis of both lower limbs. The X-ray showed an osteolytic lesion of the 4^th lumbar vertebra. The CT-scan and the MRI showed intraductal extension of the tumor. We made a scano-guided biopsy that concluded to a chordoma. We made a complete transperitoneal resection of the body of L4 and we stabilized the spine with interbody cage and bone graft. Results: Two months afer surgery, the pain and paralysis completely disappeared and the patient went back to work. Six months after surgery the MRI found residual tumor tissue in the right pedicle of l4. Now a posterior resection, bone grafting and stabilization of L3-L5 is planned. Conclusion: Chordoma is a rare condition that should be considered in the differential diagnosis of central destructive lesions in the spine and base of skull. Their management is not easy.

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P655: Cervical bone metastasis of hepatocellular carcinoma: case report of a misleading clinical entity

Mohamed Amine Gharbi ¹ , Ahmed zendeoui ¹ , Houssem Eddine Chahed ¹ , Mahdi Bouzidi ¹ , and Mouadh Nefiss ¹

¹ Orthopedic and Trauma Surgery, Mongi Slim Marsa University Hospital Center, Tunis, Tunisia

Introduction: Hepatocellular carcinoma (HCC) is the most common primary liver cancer. It is often discovered late in the course of metastasis (64% of cases). Bone metastases of HCC are rare and exceptionally revealing. Their elective sites are the vertebrae, the ribs, and more rarely, the sternum. Material and Methods: The particularity of our case is that the cervical spine bone lesion is the first clinical presentation revealing the diagnosis of HCC which was later confirmed by a liver biopsy. Result: The patient was 61 years old, a heavy smoker, with a history of peptic ulcer, and was followed up in rheumatology for inflammatory cervical pain evolving in a context of altered general condition for three months associated with a right laterocervical swelling. The standard X-ray showed a degenerative cervical spine and the ultrasound of the soft parts came back in favor of an adenophlegmon whose cytopunction showed a lymph node tuberculosis. The patient was put on anti-tuberculosis treatment and a cervical collar for pain relief. Three months later, the patient was seen again for worsening neck pain, an irreducible flexion attitude with a partial sensory-motor deficit of the right upper limb. Radiological examination showed bone lysis of the body of C4 associated with a dislocation of C4-C5 reduced under traction. The patient was then operated through a right anterolateral approach. The tumor was resected with the placement of a cement spacer and osteosynthesis with a Senegas plate with simple postoperative follow-up. The histological examination showed a secondary localization in C4 of a moderately differentiated carcinoma whose immunohistochemical phenotype may be consistent with an excreto-biliary origin which was later confirmed by a liver biopsy. Conclusion: Bone metastases from HCC are rare; they should, however, be considered in the presence of any lytic bone lesion, particularly in patients with chronic liver disease. Given their poor prognosis, their treatment is palliative, aimed primarily at improving the patient's quality of life.

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P656: Mesenchymal chondrosarcoma of the sacrum : surgical treatment by hemi-sacrectomy and pelvic reconstruction

Benjeddou Wassim ¹ , Khalil Habboubi ¹ , Aymen Benmahmoud ¹ , Mzid Ahmed ¹ , Hassen Makhlouf ¹ , and Mondher Mestiri ¹

¹ Adults Service, Institut Med Taieb Kassab, Mannouba, Tunisia

Rationale: Chondrosarcoma of the sacrum is a highly unusual disease without standard curative managements yet. The objective of this study is to report a very rare case of chondrosarcoma of the sacrum successfully operated by percutaneous vertebroplasty. The management of these unique cases has yet to be well-documented. Patient concerns: A 32-year-old woman presented with a five-month history of continuous and progressive pain and numbness of left extremity. A lytic, expanding lesion of the sacrum and paraspinal region with severe epidural spinal cord compression was identified. Diagnosis: MRI of spine showed spinal cord compression secondary to the epidural component of the giant mass, with increased marrow infiltration of the left S2 vertebral and paravertebral region, which presented as a solid tumor. Post-operative pathology confirmed the diagnosis of sacral well-differentiated chondrosarcoma (stage I B). Interventions: The patient underwent percutaneous vertebroplasty and cement augmentation of sacrum via a posterior approach after hemisacrectomy. Outcomes: The patient's neurological deficits improved significantly after the surgery, but the patient died of multiple systemic metastases at the 2-year follow-up visit. There were no complications associated with the operation during the follow-up period. Lessons: Taken together, the lesion's clinical features, imaging results, and pathological characteristics are unique. Combined efforts of specialists from orthopedics, radiology, neurosurgery, pathology, and medical oncology led to the successful diagnosis and management of this patient. Giant sacral chondrosarcoma, although rare, should be part of the differential diagnosis when the patient presents with back pain and radiculopathy. We recommend the posterior approach for spinal decompression of the sacral chondrosarcoma when the tumor has caused neurological deficits or other severe symptoms. Osteoplasty by cement augmentation is also a good choice for surgical treatment.

1397

P657: The impact of the COVID-19 pandemic on the presentation of patients with spinal metastases

Aleksander Mika ¹ , Colby Wollenman ¹ , Anthony Steinle ¹ , Hani Chanbour ² , Wilson Vaughan ¹ , Andrew Croft ¹ , Julian Lugo-Pico ¹ , Scott Lawrence Zuckerman ^1,2 , Amir Abtahi ^1,2,3 , and Byron Stephens ^1,2,3

¹ Department of Orthopaedic Surgery

² Department of Neurological Surgery

³ Center for Musculoskeletal Research, Vanderbilt University Medical Center, Nashville, TN, United States

Introduction: The COVID-19 pandemic has placed unprecedented pressure on the US healthcare system, causing a deprioritization of non-emergency services including elective surgery. Delay in surgical treatment for oncology patients can result in progression of the disease, which can complicate surgical care, distort normal anatomy, and worsen patients ‘preoperative health. Currently, little is known about how the COVID-19 pandemic has affected preoperative health in patients undergoing surgical treatment for metastatic disease to the spine. The purpose of this study was to determine if preoperative Spinal Instability Neoplastic scores (SINS) and Tokuhashi scores differed in patients receiving surgical care during the COVID-19 pandemic compared to patients who received surgical care before the pandemic. Material and Methods: Data was retrospectively collected from the electronic medical records from a single institution. All patients who underwent surgical treatment for metastatic disease to the spine between 3/1/19 to 3/1/21 were included. All cases with primary spinal tumors or insufficient imaging or chart information were excluded. Patients were separated into two groups: one group received surgery between 3/1/19 to 2/29/20 (before COVID restrictions) and the other group received surgery between 3/1/20 to 3/1/21 (during COVID restrictions). The following variables were obtained through electronic medical records: gender, age, race, Bilsky score, cancer type, SINS, Tokuhashi score, and mortality within 12 months of the index spine surgery. Primary outcomes included preoperative SINS and Tokuhashi scores. Additionally, patient postoperative Skeletal Oncology Research Group (SORG) scores were obtained. Descriptive statistics were performed using Wilcoxon rank-sum test. Univariate and multivariate linear regression models controlling for age and cancer histology were performed to determine the association of having a surgery before or during COVID-19 pandemic with SINS and Tokuhashi scores at presentation. Results: 52 patients who underwent surgery before the COVID-19 pandemic were compared to 45 patients who underwent surgery during the COVID-19 pandemic. There was a significant difference between the before COVID-19 and during COVID-19 groups with respect to SINS (9.31 ± 2.39 vs 10.84 ± 2.75, p = 0.004) and Tokuhashi scores (9.27 ± 2.35 vs 7.89 ± 2.76, p = 0.009). Linear regression demonstrated that having surgery during COVID-19 was independently associated with a higher SINS score at presentation (β = 1.37, 95% CI: 0.32-2.42, p = 0.011) and a lower Tokuhashi score at presentation (β = -1.45, 95% CI: -2.48-(-0.41), p = 0.006). There were no differences found between the two groups in 6-week, 90-day, or 1-year SORG scores, nor were there differences between the two groups in 6-month or 1-year mortality rates. Conclusion: The current study demonstrates that patients undergoing surgical treatment for metastatic spine disease during the COVID-19 pandemic had significant differences in SINS and Tokuhashi scores, however, these differences are likely not clinically significant. This study provides valuable information regarding the impact the COVID-19 pandemic had on patients receiving surgical care for metastatic spine disease. While both groups had similar prognostication scores and 1 year mortality rates, alternative healthcare delivery modalities, such as telehealth clinic visits, could be an important tool to help mitigate poor outcomes for this patient population in the post-COVID era.

1446

P658: Spinal solitary fibrous tumor: a case report

Sliti Firas ¹ , Nessrine Nessib ¹ , Abdelhafidh Slimane ¹ , nadhir karmani ¹ , Khalil Ghedira ¹ , Alaa Belhadj ¹ , and Jalel Kallel ¹

¹ Neurosurgery, National Institute of Neurology, Tunis, Tunisia

Introduction: Solitary fibrous tumors of the spine are extremely rare tumors. Most solitary fibrous tumors originate in the thoracic spine, then in the cervical spine and finally in the lumbar spine with only 6 cases reported in the literature. Involvement of the vertebral body is an even rarer entity with 4 cases found. Material and Methods: We report the cas of a 29-year olf female treated in the neurosurgery department at the Mongi Ben Hamida National Institute of Neurology in Tunisia. Results: Our patient was initially treated for a right-sided cauda equina hemisyndrome, with an expansive process on imaging that destroyed the 4th lumbar vertebra. The patient underwent surgery with incomplete removal of the tumor process by a posterior approach. The anatomopathological study concluded to a solitary fibrous tumor of the hemangiopericyte type (Grade III WHO). The patient reconsulted for recurrence of the symptomatology 2 years later, with a tumor recurrence on imaging. She underwent embolization followed by subtotal excision by posterior approach. Subsequently, she was reoperated for additional L4 corporectomy and anterolateral excision. The patient received 22 sessions of radiotherapy postoperatively. Currently, at 4 years post-op, imaging shows no recurrence. Conclusion: Solitary fibrous tumors of the spine, especially of the lumbar spine, are extremely rare. The diagnosis of certainty remains histological. The management of these tumors is poorly codified and there is currently no recognized adjuvant treatment. Only complete removal of the tumor can control its evolution. Prolonged follow-up is in all cases essential to detect early local or general recurrences.

1458

P659: Tumour masquerading as sciatica

Sushant Srivastava ¹ , Virendra Agrawal ¹ , Kaustubh Sawant ¹ , Tushar Patil ¹ , and Harish Pawar ¹

¹ Orthopaedics, Pandit Madan Mohan Malviya Shatabdi Hospital, Mumbai, India

Introduction: Nerve sheath tumors can be found in different regions of the spinal cord, with the cervical cord region being the most common site, followed by the thoracic and lumbosacral regions .Spinal schwannomas, along with the meningiomas, are the most common spinal nerve sheath tumors. A Schwannoma is defined as a benign tumor of the nerve sheath which arises from Schwann cells. Schwannomas most frequently involve the head and neck area, and also the major nerve trunks. They usually also appear on the flexor aspects of the limbs, especially near the elbow, wrist and knee. Also, the spinal roots and the cervical plexus, the vagus, peroneal and ulnar nerves are the most commonly affected. Materials and Methods: Presenting a case of 29 yr old male complaining of severe pain radiating from lower back region to the right lower limb. The neurological examination showed MRC Grade 5 power and normal reflexes for bilateral lower limbs. Local examination showed a hard mass near the sacro-iliac joint. Radiological investigations showed the mass to be a multilobulated 3.2 x 3.6 x 3.4 cm sized hyperintense mass on T2/STIR along the right gluteus maximus muscle. The patient was explained of this condition. An oval , multilobulated and well encapsulated tumour was found near the gluteus maximus muscle. Its origin was unclear and attempts were made to trace it. Later the lesion was excised en bloc surgically. After the surgery, presenting symptoms disappeared immediately. Histopathologic examination showed schwannoma. One year following excision of the lesion, the patient remained asymptomatic, with no evidence of local recurrence or any complication. Results: Surgical excision of the tumour causing symptoms is curative and provides the patient immediate and permanent relief of symptoms. However, in literature there have been several reports of a incidences of neurological complications like new or worsening pain and motor weakness after excision of the schwannoma. In our patient, en bloc surgical excision was performed and he was symptom free and displayed no clinical or any radiographic evidence of recurrence of the tumour after 12 months of postoperative follow-up. Conclusion: To treat a case of sciatica the most important tools with a clinician are the detailed and complete clinical history, thorough physical examination and radiological investigation like magnetic resonance imaging to reach the pertinent solution. Careful and complete surgical excision of the tumour lesion is curative, which provides immediate and permanent remission of symptoms without any complication.

1487

P660: Inadequate average daily sleep time is associated with depression, dysfunctional ApoEe2 (rs7412) gene expression and 2-year postoperative neck or back pain incidence in primary intradural extramedullary spinal cod tumor patients: prospective clinical outcomes

Nicholas Van Halm-Lutterodt ^1,2,3 , Krishna Mandalia ⁴ , Nicholas Storlie ⁵ , Chenlong Yang ⁶ , Ziyang Ye ^3,7 , Mohamed Mesregah ⁸ , Andrew Mecum ⁹ , Josh Gonzalez ³ , Wei-Hsun Huang ² , Wei-Cheng Chen ² , Roberta Kungulli ³ , Mercy Bartels-Mensah ¹⁰ , Wenju Jiang ² , Yu Wang ² , Sunny Kim ³ , and Yulun Xu ²

¹ Department of Professional Studies and Public Health, Brown University, Providence, United States

² Department of Neurosurgery, Beijing Tiantan Hospital, China

³ Department of Orthopedics and Neurosurgery,Inspired Spine Health, Burnsville, United States

⁴ Department of Orthopaedic Surgery, Tufts University School of Medicine, Boston, United States

⁵ School of Medicine, Creighton University School of Medicine, Omaha, United States

⁶ Department of Orthopedics and Neurosurgery, Peking University, China

⁷ Department of Data Science and Analytics, University of Chicago, United States

⁸ Department of Orthopaedic Surgery, Menoufia University, Shibin el Kom, Egypt

⁹ School of Medicine, University of Colorado Anschutz School of Medicine, Aurora, United States

¹⁰ Debrecen School of Medicine, University of Debrecen, Hungary

Background: Inadequate sleep has been reported to affect mood and function. Psychiatric comorbidity is seldom reported in primary intradural-extramedullary spinal cord tumors (IDEM-SCT) patients. Generally, minimal perioperative improvement outcomes have been evidently reported in degenerative spine patients with underlying depressive comorbid status but this information highly lacking in the primary spinal cord tumor population. Methods: Following Institutional Review Board (IRB) of Beijing Tiantan Hospital approval, we prospectively obtained patient data from January 2017 through December 2017. The study design included: adult patients who were clinically confirmed with primary IDEM-SCTs who underwent tumor resection surgery as primary treatment. The 17-itemized Hamilton Depression Rating Scale [HAM-D] questionnaire tool [Score Scale: 0 to 30 points] was utilized to evaluate depressive status in the IDEM-SCT patients, prior to surgical intervention. Patients who scored > 7 points were considered having depressive baseline status, (DP_IDEM-SCT) while those with score of ≤ 7 points were considered as non-depressed, (NDP_IDEM-SCT): Baseline demographics, ApoE status, serum metabolic panel, and 2-year postoperative clinical, neurological, and quality of life outcomes were analyzed by t-tests following Python-based ‘age and sex’ propensity score matching (PSM) of the [NDP_IDEM-SCT] and [DP_IDEM-SCT] patients. Significance was set at (p < 0.05). Results: Overall, 92 patients with IDEM-SCTs were matched in this study, [NDP_IDEM-SCT]; n = 46 (50.0%) and [DP_IDEM-SCT]; n = 46 (50.0%) patients, respectively. The overall average age was [44.97 ± 13.10] years. The incidences of comorbid status and apolipoprotein Eε2 [ApoEε2, (rs7412) variant type (VT)] expression, were significantly higher in the [DP_IDEM-SCT] group which were consistent with increased fasting blood serum triglyceride (TG) and cholinesterase (ChE) levels, (p < 0.05), at baseline. Significantly decreased daily average sleep time of [383.38 ± 101.46] minutes (i.e., 1-hour or 14.0% less average sleep time) was observed in the [DP_IDEM-SCT] group compared to [445.70 ± 61.38] minutes in the [NDP_IDEM-SCT] group, (p < 0.05). At baseline, the incidence of disability assessed by NDI or ODI was significantly higher in the [NDP_IDEM-SCT] patient group, (p < 0.05) but no significant difference between W.H.O. gradings was observed. At 2-year postoperative, the incidence of neck or back pain was significantly higher in the [DP_IDEM-SCT] patient group concomitant with decreased patient satisfaction rate, (p < 0.05). Conclusions: This study indicated that IDEM-SCT patients with baseline depressive status were also vulnerable to metabolic aberrations, particularly, in those with ApoEε2 (rs7412) variant genotype who showed less adequate average sleep time (average of ≤ 6.5 hours per day). The ApoEε2 (rs7412) variant genotype expression dysfunction in these DP patients suggests the potential negative effects of psychiatric comorbidity on modulating the physiological cardio-metabolic function of ApoEε2 (rs7412) as this gene variant is known to robustly control serum lipid profile. A baseline DP status was also associated with increased 2-year postoperative pain, and patient dissatisfaction rates. Future studies are encouraged to explore the relationship between ApoEε2 (rs7412) variant and DP status and how these facets overlap in spine patients. The anticipated findings would help uncover the clinical impacts of these entities in spine patient population.

1506

P661: Primary epidermoid cyst of the cauda equina: a case report

Ghorbel Mohamed ¹ , Daoud Ahmed ¹ , Kolsi Fatma ¹ , ines cherif ¹ , Mohamed Boukhit ² , and Boudouara Zaher ¹

¹ Neurosurgery, Habib Bourguiba Hospital, Sfax, Tunisia

² Neurosurgery, Fattouma Bourguiba Hospital, Monastir, Tunisia

Introduction: Intraspinal epidermoid cyst is very rare. It represents 0.5 to 1% of all spinal tumors. The cauda equina is an uncommon location in such cases. Material and Methods: We report the case of a patient who was treated in the department of neurosurgery in the Habib Bourguiba hospital for a primary epidermoid cyst located in the cauda equina. Results: We report the case of a 44-year-old female. The patient has been suffering from chronic lumbar pain for two years. During the last two months, she reported a weakness of both lower limbs with a retention type sphincter malfunction. Neurological examination showed paraparesis with abolished deep tendon reflexes. Lumbar spine MRI showed a posterior intradural and extramedullary oval tumoral formation extending from L1 to L5. Surgery was performed and complete removal was not possible due tight adherences to the cauda equina nerve roots. Histological examination was in favor of an epidermoid cyst. The patient had a good recovery. She was symptom-free few weeks after surgery. Conclusion: Epidermoid cyst of the cauda equina is a rare finding. Despite its location and surgery difficulties, the post-operative results are promoting.

1510

P662: Spinal localization of brown tumors: a case report and a review of literature

Sliti Firas ¹ , Khalil Ghedira ¹ , Alaa Belhadj ¹ , Abdelhafidh Slimane ¹ , Nadhir Karmani ¹ , Khansa Abderrahmane ¹ , Imed Ben Said ¹ , and Jalel Kallel ¹

¹ Neurosurgery, National Institute of Neurology, Tunis, Tunisia

Introduction: The brown tumor is a benign bone lesion that is the consequence of a hyperparathyroid state. It is less frequent in cases with secondary hyperparathyroidism but is common in patients with chronic renal failure at the hemodialysis stage. The spinal location remains, nevertheless, exceptional and requires a particular management especially in case of nerve compression. Material and Methods: We present the case of a 40-year-old patient with a 20-year history of hepatitis C on interferon and chronic renal failure at the hemodialysis stage for 10 years, with renal osteodystrophy. She has been on calcium and vitamin D supplementation for 2 years. For the past 6 weeks, this patient has had a progressive intermittent medullary claudication without sphincter disorders. A few months earlier, she complained of back pain resistant to anti-inflammatory drugs. Spinal radiography had shown indirect signs of renal osteodystrophy. Examination on admission found spastic paraparesis, posterior cord syndrome and a T10 sensory level. Spinal CT and spinal MRI showed a lytic expansive lesion of the posterior arch of T11 compressing the spinal cord posteriorly. We performed a laminectomy of T10 and T11 with total resection of the lesion. The tumor was red-gray, friable and mildly hemorrhagic. The postoperative follow-up showed a progressive regression of the motor deficit and total disappearance of his back pain. Histological examination showed a bone tumor with two cellular contingents: multi-nucleated giant cells with abundant eosinophilic cytoplasm and mononuclear spindle cells, associated with a brown deposit of hemosiderin. This appearance is strongly consistent with a brown bone tumor. Results: Although brown tumors are benign in nature, they are a reflection of failed treatment of renal osteodystrophy in chronic renal failure patients on hemodialysis. Bone remodeling in these patients is related to a disorder in the regulation of phosphocalcium metabolism. This results in a state of permanent hypocalcemia responsible for a so-called secondary hyperparathyroidism. These brown tumors are uncommon, observed in 1.5 to 13% of chronic renal failure patients.The spinal location is exceptional. Brown tumors of the spine are usually asymptomatic but may present with a picture of slow or sometimes acute spinal cord compression secondary to a pathologic vertebral fracture. It is a pathologic proliferation of osteoclasts into multinucleated giant cells with brown hemosiderin deposition in the stroma. Rigorous reinforcement of calcium and vitamin supplementation treatment can break the vicious circle of bone hyper-remodeling. Surgery is usually not indicated except in the case of spinal localization where urgent spinal decompression is required in case of functional threat. Para thyroidectomy is only indicated in secondary hyperparathyroidism when the pararthormone level cannot be controlled. Conclusion: Spinal localization of brown tumors is rare but it is a diagnosis that should be considered in the presence of suggestive radiographic findings in patients with chronic renal failure. Treatment is based on calcium supplementation and surgery is usually performed in case of neurological emergency.

1534

P663: Increased neurological morbidity and inferior quality of life outcomes in primary intramedullary spinal cord tumor patients with baseline depressive status: a prospective clinical outcome with propensity score matching

Nicholas Van Halm-Lutterodt ^1,2,3 , Ziyang Ye ^3,4 , Krishna Mandalia ⁵ , Nicholas Storlie ⁶ , Chenlong Yang ⁷ , Mohamed Mesregah ⁸ , Josh Gonzalez ³ , Andrew Mecum ⁹ , Wei-Hsun Huang ² , Wei-Cheng Chen ² , Roberta Kungulli ¹⁰ , Mercy Bartels-Mensah ¹¹ , Wenju Jiang ² , Yu Wang ² , Sunny Kim ³ , and Yulun Xu ²

¹ Department of Professional Studies and Public Health, Brown University, Providence, United States

² Department of Neurosurgery, Beijing Tiantan Hospital, China

³ Department of Orthopedics and Neurosurgery, Inspired Spine Health, Burnsville, United States

⁴ Department of Data Science and Analytics, University of Chicago, United States

⁵ Department of Orthopaedic Surgery, Tufts University School of Medicine, Boston, United States

⁶ School of Medicine, Creighton University School of Medicine, Omaha, United States

⁷ Department of Orthopedics and Neurosurgery, Peking University, China

⁸ Department of Orthopaedic Surgery, Menoufia University, Shibin el Kom, Egypt

⁹ School of Medicine, University of Colorado Anschutz School of Medicine, Aurora, United States

¹⁰ School of Medicine, Capital Medical University, Beijing, China

¹¹ Debrecen School of Medicine, University of Debrecen, Hungary

Background: Depression incidence in spine patients in rapidly receiving a lot of attention due to the significant impact it has on post-surgery outcomes including poor postoperative recovery, prolonged hospital-stay, high neurological morbidity and disability rates, inferior health-related quality of life (HRQoL) outcomes, as well as minimal patient satisfaction rates. Albeit depression has been reported in spondylotic patients undergoing spine surgery, there is a high lack of information of depressive status in primary intramedullary spinal cord tumor [IM-SCT] patients. We anticipate that this study would lend support to the inclusivity of psychosocial comorbidity and how such element(s) impact clinical, surgical, neurological, and quality of life outcomes in spine patient population. Methods: Following Institutional Review Board (IRB) of Beijing Tiantan Hospital approval, we prospectively obtained patient data from January 2017 through December 2017. The study design included: adult patients who were clinically confirmed with primary IM-SCTs that underwent tumor resection surgery as primary treatment. The 17-itemized Hamilton Depression Rating Scale [HAM-D] questionnaire tool [Score Scale: 0 to 30 points] was utilized to evaluate depressive status in the IM-SCT patients, prior to surgical intervention. Patients who scored >7 points met the criteria for baseline depressive status, (DP_IM-SCT) while those with score of ≤7 points were considered as non-depressed, (NDP_IM-SCT): Primary outcomes included: baseline demographics, clinical, serum metabolic panel, and perioperative neurological outcomes. Secondary outcomes included: 2-year postoperative neurological, functional, and quality of life outcomes. Data were analyzed by t-tests following Python-based ‘age and sex’ propensity score matching (PSM) of the [NDP_IM-SCT] and [DP_IM-SCT] patients. Significance was set at (p < 0.05). Results: Overall, 76 patients with IM-SCTs were matched in this study, [NDP_IM-SCT]; n = 38 (50.0%) and [DP_IM-SCT]; n = 38 (50.0%) patients, respectively. The overall average age was [48.91 ± 9.41] years. Significantly decreased daily average sleep time of [414.70 ± 77.34] minutes was observed in the [DP_IM-SCT] group compared to [469.96 ± 55.73] minutes in the [NDP_IM-SCT] group, (p < 0.05). Baseline fasting blood total cholesterol (TC), Apo-B, and low-density lipoprotein cholesterol (LDL-c) levels were significantly increased in the [DP_IM-SCT] group, (p < 0.05). At 2-year postoperative, the incidences of myelopathy, localized muscle weakness, generalized muscle weakness, paralysis (paraplegia), disability, McCormick’s grading, average muscle strength grading and ND/ODI scores, [(3/8): Physical Functioning (PF), (Bodily Pain (BP), and Role Emotional (RE), the overall Physical Component Summary (PCS)] scores and patient satisfaction rates demonstrated significant inferior outcomes in the [DP_ID-SCT] patient group, (p < 0.05). Conclusions: Our study indicated that spine patients with IM-SCTs with baseline depressive status demonstrated inferior serum lipid levels which were consistent with significantly decreased average daily sleep time (< 7 hours per day). Further, DP patients had significant inferior outcomes with myelopathy incidence, disability, quality of life and satisfaction rates. Baseline depressive status should not be taken lightly in spine patients indicated for surgery. Perioperative assessments of psychiatric elements concomitant with interdisciplinary involvement and collaboration can supportably foster value-based health outcomes following surgical interventions in our spine patient population.

1588

P664: Primary malignant tumors of the spine: a bicentric clinical analysis of 20 cases

Zohra Souei ¹ , Rihab Benfredj ² , Mohamed Boukhit ¹ , Asma Elmir ¹ , Maher Hadhri ¹ , and Mehdi Darmoul ¹

¹ Neurosurgery, Fattouma Bourguiba University Hospital, Monastir, Tunisia

² Neurosurgery, Sahloul University Hospital, Sousse, Tunisia

Introduction: Primitive malignant tumors of the spine are relatively rare. They account for less than 5% of all primary bone tumors, and make up a heterogeneous group of neoplasms which may pose diagnostic and treatment challenges. Clinical presentation is discreet and not specific which delays the diagnosis and increases the likelihood of treatment failure. Material and Methods: We retrospectively reviewed the medical records from 20 patients who were treated for primary malignant spine tumor at the neurosurgery department of University hospital of Monastir and Sousse in the period from 2010 to 2020. The aim of this study is to discuss clinical and radiological features and management of such lesions. Results: Male to female ratio was 12 to 8. Mean age was 42;7. The mean diagnostic delay was 11 months. Back pain and progressive neurological deficit were the most common presenting symptoms. The thoracic spine was the most affected level (60%). We reported also three cases of multiple level presentations. Total spondylectomy was realised in 8 cases. Histological types included chordoma (4), myeloma (6), plasmocytoma (6) and Ewing sarcoma(4). Adjuvant therapy with radiotherapy ± chemotherapy after surgery. Four out of six paraplegic patients improved considerably. Neurological decline was observed in only two patients. Three cases of chordoma recurred within eleven months. The mean survival in our serie was of 13 months. Conclusion: Patients with primary spine malignancies must be treated by specialized multidisciplinary teams composed of pathologists, surgeons, oncologists, radiologists and radiotherapists, all with experience in the diagnosis and treatment of these tumors. Early diagnosis is the most important factor to preserve neurological function.

1592

P665: Giant aneurysmal bone cyst of the spine: an illustrative case of benign histology versus malignant presentation

Zohra Souei ¹ , Maher Hadhri ¹ , Asma Elmir ¹ , Atef Ben Nsir ¹ , and Mehdi Darmoul ¹

¹ Neurosurgery, Fattouma Bourguiba University Hospital, Monastir, Tunisia

Introduction: Aneurysmal bone cyst (ABC) is rare bone tumor representing approximately 1% of all bone solid tumor and approximately one-third of these tumors arise from the spine. It is an expansile, non-neoplastic lesion. However, it has the ability to destroy and expand bone. Material and Methods: We report the case of a giant ABC with striking images that was managed in the neurosurgery department of Fattouma Bourguiba University Hospital. Clinical presentation, radiological and pathological features are reviewed along with the surgical intervention utilized and its outcome. Results: A 37-year-old woman presented to our outpatient clinic with 3-year history of lower back pain. The patient’s medical, drug, and family history were unremarkable. Symptoms were worst at night. 2 months ago she developed a bilateral lombocruralgia with poor response to regular pain medication. Routine examination of the motor and sensory system objectified a deficit of the quadriceps muscle of the right thigh and depression of tendon reflexes on this side. She had no anesthesia nor cauda equina symptoms. Radiological investigation showed an expansile osteolytic mass measuring 7*5*8 cm which involves the transverse process, pedicle and lamina. It crosses midline into the anterior part of the vertebral body of L1 and L2.There is an extra osseous extension with involvement of the epidural space extending from L1 to L3 causing compression of the cord and right nerve roots at these three levels. Anterolateraly the tumor extends to the right psoas muscle and the retroperitoneal space in contact with the right kidney. The “soap bubble appearance” was strongly evocative of an aggressive ABC. Liquid absolute alcohol based sclerotherapy was proposed. Unfortunately after the second course, our patient presented a severe exacerbation of her clinical symptoms. Surgical approach was then validated. It consisted in tumor debulking paravertebral soft tissue dissection, posterior decompression and D11 D12 L4 L5 pedicle screw fixation. Clinical amelioration was rapidly gained. The patient gained good neurological recovery without any adverse effect in the final follow-up. Pathology exam confirmed the diagnosis. She is programmed for a lateral approaches along with urology surgeons to complete the retroperitoneal extension. Conclusion: ABC of the spine is a benign tumor that can present with a wide variety of non-specific symptoms. Local extension to the epidural space can jeopardize the neurological outcome. For some aggressive types in the lumbar spine, anterior extension to the retroperitoneal space (urinary tract) can have malignant consequences. Pain management, careful preparing for surgery, prompt resection of the lesion as well as spinal stability reconstruction can promote good recovery and minimal adverse effect.

1601

P666: Sciatica caused by dorsal meningioma: a case report

Ghorbel Mohamed ¹ , Mohamed Amine Hadj Taieb ² , Kolsi Fatma ¹ , Daoud Ahmed ¹ , Ines Cherif ¹ , and Boudouara Zaher ¹

¹ Neurosurgery, Habib Bourguiba Hospital, Sfax, Tunisia

² Neurosurgery, Fattouma Bourguiba Hopital, Monastir, Tunisia

Introduction: Meningioma is usually a benign tumor of the central nervous system. It can be located in the spine in 25% of the cases and the symptoms are related to spinal cord compression. In very few cases they can be responsible for sciatica. Material and Methods: We report the case of a patient who was admitted for sciatica that was caused by a dorsal meningioma. The patient was treated in the department of neurosurgery in Habib Bourguiba hospital in Sfax, Tunisia. Results: A 46-year-old woman consulted for right sciatica. She had no previous medical history. The sciatica had S1 trajectory and started 10 months before admission. The pain was constant and did not respond to medical treatment. Physical examination was normal. A medullary MRI was performed. It revealed an intradural extramedullary lesion at T5-T6 level. The patient underwent surgery and the mass was completely removed. Pathology concluded that it was a meningioma. The pain disappeared immediately after surgery. Conclusion: Sciatica caused by a dorsal meningioma is a rare situation. A long delay separates symptoms and diagnosis. Surgery is the treatment in order to relive the suffering.

1662

P668: Intra medullary pilocytic astrocytome: a case report

Ghorbel Mohamed ¹ , Daoud Ahmed ¹ , Ines Cherif ¹ , Bel Mabrouk Yassin ¹ , and Boudouara Zaher ¹

¹ Neurosurgery, Habib Bourguiba Hospital, Sfax, Tunisia

Introduction: Pilocytic astrocytoma is the benign form of astrocytomas. It represents a classic tumor of the posterior fossa in children. Its intraspinal localization is much less well known. Patients and Methods: We report a case of intra-medullary pilocytic astrocytoma occurring in an 11-year-old girl. Case Report: An 11-year-old girl presenting gait disorders that had been evolving for 2 months, associated with gestational disorders of both upper limbs and vesico-sphincteric disorders. The examination founded a spastic paraparesis with peripheral brachial diplegia. Medullary MRI revealed an intramedullary lesion ranging from the medullary bulbo junction to D4. Complete excision was performed. Histological examination confirmed the diagnosis of pilocytic astrocytoma. Conclusion: Intramedullary astrocytomas are rare tumors. The clinical symptomatology is nonspecific. Medullary MRI is quite evocative, showing an iso or slightly hypo-intense lesion in T1, hyper-intense in T2 and often associated with cysts. The enhancement after injection of GADO is smaller and more eccentric than ependymoma. The most complete surgical excision possible is necessary to ensure a good evolution of the patients.

1665

P669: Primary malignant lymphoma in a spinal cord presenting as an epidural mass: report of a two cases

Daoud Ahmed ¹ , Ines Cherif ¹ , Ghorbel Mohamed ¹ , Kolsi Fatma ¹ , Bel Mabrouk Yassin ¹ , Mohamed Amine Hadj Taieb ² , and Boudouara Zaher ¹

¹ Neurosurgery, Habib Bourguiba Hospital, Sfax, Tunisia

² Neurosurgery, Fattouma Bourguiba Hospital, Sfax, Tunisia

Introduction: Malignant lymphoma can involve the central nervous system either primarily or by secondary spread, which tends to occur late in the disease as part of widespread dissemination. Lymphoma presenting as primary tumors of the spinal cord are extremely uncommon. Materials and Methods: We report tow cases of primary malignant lymphoma in a spinal cord. Results: The first case was about a 59-year-old-woman who presented with progressive paraparesis over 2 weeks. Magnetic resonance imaging revealed a spinal epidural mass from T2 to D4. We performed a decompressive laminectomy and mass removal. The histopathology was consistent with a small cell lymphoma B. The second patient was a 60-year-old -men who presented with progressive paraparesis and sphincter changes over 2 weeks. Magnetic resonance imaging revealed a spinal epidural mass from T3 to T5. We also performed a decompressive laminectomy and mass removal. The histopathology was consistent with a large cell lymphoma B. Both patients were addressed to chemotherapy and radiotherapy. Conclusion: Primary central nervous system lymphoma is a rare form of extra nodal lymphoma, particularly isolated primary spinal lymphoma. A primary small lymphocytic lymphoma of the spine should be considered in the differential diagnosis of primary spine tumors. Surgical decompression and tumor removal are mandatory to recover neurologic function, if the patient had a neurologic deficit. The combined modality treatment after surgical decompression resulted in improvement of the neurologic symptoms and remission of the lymphoma.

1669

P670: Epidural Ewing sarcoma: about three cases

Ahmed Amine Daoued ¹ , Ines Cherif ¹ , Ghorbel Mohamed ¹ , Kolsi Fatma ¹ , and Boudouara Zaher ¹

¹ Neurosurgery, Habib Bourguiba Hospital, Sfax, Tunisia

Introduction: Ewing's sarcoma is an uncommon tumor, accounting for 15% of all primary malignant bone tumors, most common in children under 10 years old. Extraosseous Ewing's sarcoma is rare, and primary spinal epidural localization has been reported in only few cases. Material and Methods: We report the cases of three patients who was treated for an epidural sarcoma in the department of neurosurgery in the Habib Bourguiba university hospital, in Sfax, Tunisia. Result: We report the cases of three men. The average age was 20.66. The symptomatology was made of a heaviness of the two lower limbs for all the patients associated with a cervicobrachial neuralgia in only one case and vesico-sphincter disorders with urinary retention in two cases. The symptomatology was sudden in two cases and progressive in one case. The examination revealed spastic paraparesis in two cases and flaccid paraparesis in one case. All our patients had a spinal cord MRI showing an epidural lesion taking strong contrast and infiltrating the paraspinal muscles in only one case. The location was the cervico-dorsal junction in two cases and dorsal in one case. A complete excision was performed in all cases through a C7-D2 laminectomy in two cases and D8-D9-D10 in the other case. The histopathological examination concluded to an EWING sarcoma. All our patients had chemotherapy with a good evolution with complete recovery in 2 cases and partial recovery in 1 case. Conclusion: Spinal epidural Ewing's sarcoma is an exceptional extraosseous malignant bone tumor, more frequent in children and adolescents. MRI remains the gold standard examination in the diagnosis of spinal epidural tumor. But the confirmation remains histological. Through our observations, we underline the rarity of this pathology and especially of the epidural localization and we insist on the importance of the complete surgical resection which conditions the vital and functional prognosis.

1672

P671: Ependymomas of the filum terminale

Ghorbel Mohamed ¹ , Ines Cherif ¹ , Daoud Ahmed ¹ , Kolsi Fatma ¹ , and Boudouara Zaher ¹

¹ Neurosurgery, Habib Bourguiba Hospital, Sfax, Tunisia

Introduction: Terminal filum ependymoma is a rare tumor of the cauda equina that accounts for 30-40% of all spinal ependymomas. It affects adults between 30 and 40 years old. In this work we report the clinical, radiological and therapeutic characteristics and the postoperative evolution of these tumors. Material and Methods: We report the case of two patients who was treated for an ependymomas of the terminal filum in the department of neurosurgery in the Habib Bourguiba university hospital, in Sfax, Tunisia. Results: Case report 1: We report the case of a 29 years old patient who had presented from 2 years, progressive low back pain that became hyperalgesic with gait disorders. The examination revealed a paraparesis with a lumbar spinal syndrome. The spinal cord MRI showed a lesion opposite to L1-L2 with heterogeneous enhancement, compressing the terminal cone and pushing back the roots of the cauda equina. The patient was operated with a complete removal of the tumor. The histopathological examination concluded to an ependymoma. The outcome was good with a clear improvement of the symptomatology. Case report 2: We report the case of a 35 years old man, who had been presenting for 6 years progressively worsening low back pain and intermittent radicular claudication with vesico-sphincter disorders (urinary impaction). The examination showed a lumbar spinal syndrome with saddle hypoesthesia. Myelography and myeloscan concluded to a lesion of the terminal filum. She was operated with good evolution after 21 years of follow-up. The histopathological examination concluded to an ependymoma. Conclusion: The clinical presentation of terminal filum ependymoma is often poor. MRI is the gold standard to confirm the diagnosis. The histological type is myxopapillary in the majority of cases. Complete microsurgical excision is the best way to limit recurrence and to have a good prognosis.

1673

P672: Paraganglioma of the cauda equina

Ghorbel Mohamed ¹ , Ines Cherif ¹ , Daoud Ahmed ¹ , Kolsi Fatma ¹ , Bel Mabrouk Yassin ¹ , and Boudouara Zaher ¹

¹ Neurosurgery, Habib Bourguiba Hospital, Sfax, Tunisia

Introduction: Paragangliomas of the cauda equina are rare tumors. The revealing symptomatology is usually radiculalgia with low back pain, which may be associated with sphincter disorders. The reference treatment is surgical resection. Material and Methods: We report the case of a patient operated for a paraganglioma of the cauda equina in our department of neurosurgery in the Habib Bourguiba university hospital, in Sfax, Tunisia. Results: This is a 64-year-old patient with no particular pathological history who consulted for bilateral S1 lumbosciatica associated with heaviness of both lower limbs that evolved rapidly over a week without vesico-sphincter disorders. The examination found a predominantly right paraplegia with abolition of the patellar and achilles reflexes and a lumbar spinal syndrome. Spinal cord MRI showed an extensive intradural lesion from L2 to L3. The patient was operated with complete surgical removal of the tumor. The histological examination concluded to a paraganglioma. Conclusions: Paragangliomas of the cauda equina are rare tumors whose histological appearance is close to neurinomas. The treatment of these tumors remains complete surgical excision, most often requiring the sacrifice of the supporting nerve root. The absence of tumor residue after excision makes recurrence exceptional. No additional treatment is recommended.

1689

P673: Survival and surgical outcomes of breast cancer spinal metastases in a National Tertiary Centre

Sandra O'Malley ¹ , Jake McDonnell ¹ , Gráinne Cunniffe ¹ , and Seamus Morris ¹

¹ Trauma and Orthopaedics, Mater Misericordiae University Hospital, Dublin, Ireland

Introduction: Breast cancer is one of the most common cancer types in women and due to advances in various therapies the frequency of long-term sequelae has increased; 10 to 30% of patients with primary malignancies are expected to develop spinal epidural metastases, and since Patchell’s landmark study in 2005 there is increased demand for aggressive therapies including surgery to optimize patient outcomes. However, there is limited evidence for managing individual histopathological types of cancers. This study was restricted to patients with spinal metastases from breast cancer to limit differences as a result of various different tumour types. Material and Methods: A retrospective review was carried out on all patients that underwent spinal surgery for breast cancer spinal metastases causing instability, cord compression or irretractable pain from 2005 to 2020. Patients were followed up for 2 years after surgery. Hospital records were assessed for demographic, clinical, operative and radiological parameters. Univariate and multivariate analyses were used to assess the data. Results: 90 patients underwent surgery over a 15-year period in a National Tertiary referral centre for spinal injuries. Median patient age at time of breast cancer diagnosis was 53.3 years (range 32-78 years), median patient age at time of spinal surgery for metastases was 57.8 years (range 35-82 years). 44 deaths occurred during the follow-up period, median age at death was 60.4 years (range 35-82). There were 20 deaths in the first 6 months post-surgery and an additional 24 deaths within the first 2 years post-surgery. Conclusion: The volume of surgery increased throughout the study period, suggesting an increase in presentation of spinal metastases as predicted from long-term sequelae or a combination of treatment shift to more aggressive decompressive surgery. The most important predictor of survival was no neurological deficit pre-operatively, followed by time from diagnosis of breast cancer to surgery for spinal metastases.

1708

P674: Cryptogenic spinal epidural hemangioma: case report

Andrea Veroni ^1,2 , Roberto Spnelli ^1,2 , Mattia Seida ^1,2 , Simone Zironi ^1,2 , Giulia Ghisellini ^1,2 , Villiam Dallolio ^1,2 , Vitaliano Nizzoli ^1,2 , and Marco Ruini ^1,2

¹ Neurosurgery, Ospedale di Suzzara, Suzzara, Italy

² Neurosurgery, GVM Care & Research - Salus Hospital, Reggio Emilia, Italy

Introduction: Epidural hemangioma is extremely rare, accounting for only 4% of all extradural spinal tumors, and only 171 epidural hemangiomas are reported since 1929. The most common symptoms include myelopathy or radicular pain with or without deficit. Our case report is about a patient treated for a herniated disc by microsurgical technique, which reveals an epidural spinal hemangioma during surgery, without any suspicion at preoperative radiological exams. Materials and Methods: Introduction to the case report. We describe a case report who find no equals in literature. The patient went our observation for a typical radicular pain with L5/S1 herniated disc. The patient underwent all common conservative treatments without any benefit. We therefore proceeded performing herniectomy with microsurgical technique. Results: The surgical operation. The patient underwent a standard approach for herniectomy. During the normal manipulation of the nerve root, the L5 root appeared to progressively swollen itself. The roots was both L5 and also S1 free, and the swollen of the L5 root was not clear if it was due to vascular, neoplastic or everything else. In addition, we have informed the patient about the herniectomy and its specific risks and benefits, and so we weren’t having a patient’s valid consensus to facing the unknown lesion. Consequently, we decided to conclude the surgical operation, referring any attempt to biopsy or remove the lesion after adequate radiological study and a share planning. Then we informed the patient and followed up him, who presented a good recovery, with complete resolution of neurological deficits and pain. However, the MRI revealed a minimal trend in enlargement of the lesion. We explain the risk and benefits and the patient decided to approve the surgical removal of the lesion. So, we performed an emi-laminecthomy. We identified the lesion and we noted that the L5 root was upper and well separately from the lesion. We isolated the lesion and removed it, and the histhopathological examination revealed an epidural hemangioma, not visible in the preoperative MRI. The patient returned early to his normal life, without deficits or pain. Discussion: Our interpretation of this case report is that originally there was a vascular nidus compressed by the herniated disc. The high pressure of the herniated disc reduced the caliber of the vessel nidus of the hemangioma to a virtual size. Consequently to the removal of the herniated fragment, the reduction of the pressure on the vessels nidus enabled instantly the hemangioma to swollen the caliber of its anomalous vessels growing its global volume. Conclusions: Our case is characterized by a clinical presentation like no other in the literature reports, because the patient haven't specific symptoms due to the hemangioma, before the diagnosis. Also if the spinal hemangioma is a very rare pathology, we experienced that it can happened and exceptionally it can develop during surgery. So it is huge important to know this eventuality, in order to manage it with properly timing and surgical planning.

1738

P675: The inflammatory pseudotumor, the great imitator in an unusual location

Sliti Firas ¹ , Abdelhafidh Slimane ¹ , Sinda Laafif ¹ , Khalil Ghedira ¹ , Imed Ben Said ¹ , and Jalel Kallel ¹

¹ Neurosurgery, National Institute of Neurology, Tunis, Tunisia

Introduction: Inflammatory pseudotumor is an uncommon tumor, initially described in the lung. It can affect different organs. It is a controversial entity. In the nervous system, this pathology is difficult to diagnose because its clinical and radiological presentation is not specific. Material and Methods: We present the case of a 40-year-old patient with no previous pathological history who was admitted to the hospital with left S1 low back pain of progressive onset for two months. The neurological examination did not reveal any deficit or Irritative phenomena. MRI showed an infiltrative epiduritis extending from T10 to L2 without obvious disc and vertebral body involvement. This epidural lesion totally engages the spinal cord, which is narrowed and compressed anteriorly, and is attached to the posterior ligament. It also causes bilateral foraminal entrapment with bilateral medial L5-S1 disc herniation with intramedullary right L5 and S1 radicular impingement. A laminectomy from T10 to L2 was performed, uncovering a localized fibrous, whitish, non-hemorrhagic dural thickening organized in an onion bulb. A macroscopically total resection was performed. Histological examination of the resection specimens showed the existence of a characterized inflammatory process compatible with the diagnosis of an inflammatory pseudotumor. Results: The inflammatory pseudotumor corresponds to an aspect of inflammatory mass whose symptomatology depends on its location. Relatively ubiquitous, it is rarely described in the central nervous system. This unusual lesion represents a wide spectrum of clinical presentation posing diagnostic problems for both pathologists and clinicians. The main differential diagnosis of extradural inflammatory pseudotumors is lymphoma and also metastases, myeloma and meningioma. Without biopsy, the differential diagnosis is difficult. Conclusion: Inflammatory pseudotumors (IPT) are benign lesions of unknown etiology, probably an immunological response to traumatic or infectious aggression. Sometimes considered an IgG4-related autoimmune disorder. They may present as an isolated or multicentric lesion. Central nervous system involvement is rare. Only nine cases of epidural IPT have been reported to date. It is clinically and radiologically a diagnosis of exclusion.

1743

P676: Spinal schwannomas: a review and institutional experience

Sliti Firas ¹ , Skander Guediche ¹ , Abdelhafidh Slimane ¹ , Nadhir Karmani ¹ , and Jalel Kallel ¹

¹ Neurosurgery, National Institute of Neurology, Tunis, Tunisia

Introduction: Spinal schwannomas are benign tumors that develop from Schwann cells of the spinal roots. They account for 35% of extramedullary intradural tumors, 80% of them along the spinal cord and 20% in the cauda equina. The carrier root is often a sensitive root, which explains the frequency of the revealing radicular pain. Neuromas are most often sporadic, but can be part of a neurofibromatosis type II. Material and Methods: This is a retrospective study spread over 8 years (2010-2017) concerning 36 cases of spinal schwannomas, treated and followed up at the neurosurgery department of the National Institute of Neurology, Tunisia. Results: The average age of our patients is 52 years (10-76 years). There was a male predominance of 61% with a sex ratio of 1.5. The circumstances of discovery were dominated by radicular syndrome in 62% of cases. 53% of the patients presented spinal pain. 73% of the patients presented sensory disorders such as paresthesia. Sphincter disorders were present in 22% of cases. The clinical picture is silent for a long time, and the diagnostic delay is variable according to the location and volume of the neuromas. They are responsible for a spinal cord compression syndrome in 73% of cases, a spinal syndrome (45%) and a lesion syndrome (56%). Magnetic resonance imaging was performed in all our patients. The most frequent localization was cervical in 36% of cases, dorsal in 30% and lumbar in 34% of cases. Multiple neuromas were found in 11% of cases. All patients underwent posterior surgery, allowing macroscopically complete removal of the tumor in all cases. 60% of the patients underwent postoperative MRI at a distance, confirming complete removal of the tumor. The immediate postoperative course was simple in all our patients. 7 patients (20%) presented a postoperative motor and sensory deficit, 5 of whom recovered after rehabilitation. Conclusion: This study also allowed us to study the evolution of patients treated for spinal schwannoma. Their detection at an early stage of evolution, a primordial parameter to improve the prognosis, has been greatly facilitated by the development and better accessibility of neuro-diagnostic techniques. The prognosis also depends on the quality of the resection, which can be complete in some cases only at the expense of nerve sacrifice. This balance is sometimes difficult to weigh, with on the one hand a non-negligible risk of tumor recurrence, and on the other hand the fear of producing neurological sequelae in patients who did not have them before surgery.

1839

P677: Management of metastatic epiduritis : a review of 50 cases

Nessrine Nessib ¹ , Khalil Ghedira ¹ , Sliti Firas ¹ , Eya Chahed ¹ , Sofiene Bouali ¹ , Abdelhafidh Slimane ¹ , Alaa Belhaj ¹ , and Jalel Kallel ¹

¹ Neurosurgery, Mongi ben Hamida Institute of Neurology, Tunis, Tunisia

Introduction: The spine may be the site of metastasis in 40% of patients with neoplastic pathology. The aim of our work is to describe the epidemiological, clinical and paraclinical characteristics of metastatic epiduritis, to review the therapeutic modalities and to evaluate the clinical evolution of the patients. Materials and Methods: This is a retrospective study of 50 patients admitted for metastatic epiduritis to the neurosurgery department at the Mongi Ben Hamida National Institute of Neurology in Tunisia between 2011 and 2018. Results: The mean age was 54.11 years. Motor deficit was the most frequent reason for consultation (94%), followed by spinal pain (84%). The average time to progression was 1.9 months. All patients underwent spinal cord MRI. The lesions were located in the dorsal region in 82% of cases. As soon as the diagnosis was positive, management was urgent. A scan-guided biopsy was performed in 8 patients (16%) after a multidisciplinary decision. Surgery was performed in 42 cases (84%). It was performed through a posterior approach in all cases. The 3 most frequent cancers were respectively: lung (32%), breast (28%) and prostate (20%). All patients were referred for radiotherapy. Improvement of the neurological status was noted in 34 cases (68%), the status was stationary in 9 cases (18%) and worsening was noted in 7 cases (14%). Conclusion: Metastatic epiduritis represents a neurosurgical emergency. Their diagnosis must not be delayed and this as soon as the first symptoms appear. MRI is the best examination to confirm the diagnosis. Urgent surgical management allows for a chance of recovery. Radiotherapy and physical rehabilitation are necessary in the subsequent management.

1873

P678: The importance of inpatient and outpatient palliative care utilization at the end of life for patients with spine metastases

Edwin Owolo ¹ , Dana Rowe ¹ , Meghan Price ¹ , Jacob Sperber ¹ , Tara Dalton ¹ , Harrison Hockenberry ¹ , Isabel Prado ¹ , Arif Kamal ¹ , Margaret Johnson ¹ , Brandon Bishop ¹ , Antoinette Charles ¹ , and C. Rory Goodwin ¹

¹ Department of Neurosurgery, Duke University School of Medicine, Durham, United States

Introduction: Given the significant symptom burden associated with spine metastases (SM), specialty Palliative Care(PC) can be instrumental in improving patient quality of life(QoL). Therefore, it is important to identify/address disparities in access to this intervention to ensure comprehensive and equitable care. Objective: The purpose of this study is to assess the impact of sociodemographic and treatment factors on inpatient PC (IPPC) and outpatient PC (OPPC) utilization in patients with SM. Methods: We evaluated IPPC and OPPC utilization in a cohort of 270 patients seen by our institution’s Brain and Spine Metastases Tumor Board from February 2018- February 2020. Patient demographics, oncologic history, interventions received, OPPC and IPPC consultations/encounters, and clinical outcomes were collected via retrospective chart review. Statistical analyses compared characteristics and outcomes between patients who did or did not utilize IPPC and/or OPPC. Results: 47 (17.4%) and 73 (27.0%) patients received at least one IPPC consult or OPPC visit, respectively. We observed that Black patients received IPPC consults at a higher rate than non-Black patients (25.9% vs 15.1%, p = 0.077), while White patients received OPPC consults at higher rates than non-White patients (27.7% vs 20.0%, p = 0.13). Patients who received surgical intervention or radiation therapy had higher rates of OPPC utilization than those who did not (36.9% vs 21.7%,p = 0.011; 31.6% vs 19.2%,p = 0.033, respectively). Patients who received an IPPC consult had worse median overall survival (OS) than patients who did not (6.5 months vs. 24.2 months) while OPPC consultation was associated with a survival advantage (11.2 months vs 19.2 months for those seen by OPPC and not). Conclusion: We present several race and intervention-based differences in OPPC and IPPC utilization for patients with SM. Further work is needed to better appreciate PC utilization trends and identify interventions that may improve the equity and accessibility of PC for this patient population.

1876

P679: Lumbar spine osteosarcoma with large retroperitoneal extension and vascular attachment: a case report and literature review

Pablo Sanchez Quinones ^1,2,3 , Andres Felipe Pineda-Martínez ^1,2 , Juan Felipe Abaunza-Camacho ^1,2,3 , Javier M Saavedra ^1,2,3 , William M Riveros ^1,2,3 , Jorge Torres-Mancera ^1,2,3 , and Camilo Benavides-Burbano ^1,2,3

¹ Neurosurgery Department, Center for Research and Training in Neurosurgery CIEN, Bogotá, Colombia

² Neurosurgery Department, Hospital Universitario de La Samaritana, Bogotá, Colombia

³ Neurosurgery Department, Hospital Universitario Mayor Méderi, Bogotá, Colombia

Introduction: Osteosarcoma of the spine (OS) is a rare, highly malignant tumor representing 3-5% of all osteosarcomas. It is a tumor with potential local invasive destruction and metastatic spread. OS has the worst 5‐year survival of all spinal sarcomas (39%). Its independent prognosis factors include age (> 60 years old) and advanced stage that produces poor outcomes. Surgical management in OS positively affects prognosis and produces favorable survival. Its goal is curative resection with negative margins. However, it depends on location, adjacent structures, aggressiveness, and size. Surgical technique is controversial over the superiority of intralesional versus en-bloc resection. Larger size and adjacent neurovascular structures imply challenging surgical management. Material and Methods: We report a case of a 41-year-old female with L4 spinal osteosarcoma with large retroperitoneal extension treated with a first posterior elements en-bloc resection with lumbar arthrodesis and second stage anterior en-bloc resection with L4 vertebrectomy. Results: A 41-year-old female complained of chronic lumbar pain exacerbated one month prior to admission. She had a history of pathologic L4 fracture three years previously, with reported osteoblastic osteosarcoma Ki67 10% in a percutaneous biopsy without complementary management. Physical examination showed vertebral pain in the lumbar spine. The neurological exam was intact. Lumbar MRI and abdominal angio-CT showed a 120 x 87 x 97 mm calcified lesion of the L4 vertebral body with facet, epidural and abdominal extension without central canal compromise. Additionally, right displacement of aortic bifurcation and both common iliac arteries without occlusion was identified. Bone scintigraphy discarded other lesions, and lower-limbs electromyography was normal. Surgical management was indicated with a first stage posterior and second stage anterior en-bloc tumoral resection. At first, a posterior approach was completed with L4 partial vertebrectomy and L3-L4 and L4-L5 discectomy. A viaflex bag was positioned anterior to the thecal sac to protect neuronal structures during second stage approach. Finally, L2-L3 and L5-S1 polyaxial screws were placed and fixated, achieving lumbar arthrodesis. One week later, an anterior approach was made. A retroperitoneal approach, lymph node drainage, and vascular release from feeding vessels of the aorta and the posterior wall of the vena cava was performed with an oncologic surgeon. En-bloc mass resection was performed, and anterior L3-L4 and L4-L5 discectomy with L4 total vertebrectomy was completed. Epidural Viaflex bag was identified and removed. Then, vertebral body reconstruction using an expandable cage was completed. Intraoperative neurophysiological monitoring remained normal during both approaches. Postoperative bleeding was present, with a requirement of 10 units of red-blood-cell transfusion. Secondary mesenteric ischemia was encountered, and the patient required colostomy plus antibiotic management for peritonitis. Finally, the patient responded well and was discharged without neurological deficit. Conclusion: Osteosarcoma of the lumbar spine is an uncommon and challenging disease. The surgical approach depends on tumoral size, localization, and involvement of adjacent vascular structures. When an abdominal extension is present, a multidisciplinary surgical treatment with aggressive posterior and anterior approaches could be an excellent option since it provides an impact on survival and reduces postoperative complications.

1883

P680: Atlantoaxial Langerhans cell histiocytosis manifesting as painful torticolis

Nessrine Nessib ¹ , Mohamed Zairi ² , Kais Bouzouita ¹ , Sofiene Bouali ¹ , Mohsni Ahmed Amine ² , Ahmed Msakni ² , Rim Boussetta ² , and Nessib Mohamed Nabil ²

¹ Neurosurgery, Mongi ben Hamida Institute of Neurology, Tunis, Tunisia

² Orthopedics, Bechir Hamza Children's Hospital, Tunis, Tunisia

Introduction: Langerhans cell histiocytosis (LCH) is a rare disorder of clonal proliferation of dendritic cell mostly seen in children. It consists in various clinical manifestations from a single lytic bone lesion to multisystemic lesions with organ dysfunction. Atlantoaxial involvement by LCH is very rare, especially in a young child. The aim of this work was to describe the management challenges of treatment of a rare localization of Langerhans cell histiocytosis in the craniocervical junction complicated by spinal instability and deformity. Materials and Methods:A 6-year-old child consulted for painful torticollis evolving for two weeks without fever. Patient has no medical and surgical history or cervical spine trauma. The clinical examination objectified a torticollis without neurosensory deficit. Cervical spine x-ray showed spinal deviation without bone lesions. Specialized examinations have been requested. Results: Cervical spine CT scan concluded in an atlantoaxial rotational dislocation with bone involvement of C1 and C2. The MRI objectified the presence of spinal cord compression at the CCJ and a soft-tissue mass between C1-C2. Bone scintigraphy showed two fixation locations. One at the cranio-cervical junction, the other at the level of the left iliac crest. Bone biopsy at the lesion of the iliac crest concluded in Langerhans cell histiocytosis. The biological explorations objectified a pancytopenia. The child had medical treatment such as corticosteroids and vinblastine. For bone lesions and instability of the cranio-cervical junction, two-stage surgery was performed. Stabilization of the skull by halo-vest. Then enlargement of foramen magnum, C1 laminectomy and non-instrumented occipito-C2 arthrodesis. At 3-years of follow-up, the cervical spine was stable without torticollis and the child has healed. Conclusion: Damage to the craniocervical junction during Langerhans cell histiocytosis is a source of spinal instability and deformity. Surgical stabilization must be urgent before the appearance of a sensory-motor deficit. The two-stage approach non-instrumented vertebral arthrodesis was desirable in growing children.

1885

P681: Primary bone tumors of the spine: assessment of 20 years single center experience

Zohra Souei ¹ , Mohamed Boukhit ¹ , Nessrine Nessib ¹ , Souhaiel Khalfaoui ¹ , Maher Hadhri ¹ , and Mehdi Darmoul ¹

¹ Neurosurgery, Fattouma Bourguiba University Hospital, Monastir, Tunisia

Introduction: Primary bone tumors of the spine are relatively rare, and make up a heterogeneous group of neoplasms that can pose diagnostic and treatment challenges. Material and Methods: We retrospectively studied 19 cases of primary bone tumors of the spine that were diagnosed and managed at the Neurosurgery department of Monastir University Hospital in Tunisia. We aim to review through this study, epidemiologic, clinical, imaging and management features in these tumors in order to provide an appropriate treatment strategy. Results: Sixteen males and four women aged between 5 and 78 years were included in the study. The mean age of our population was 46.8 years with a male predominance. The mean diagnostic delay was up to 18 months. Back pain and progressive limbs weakness were. The lesions were located in the cervical spine in 3 patients, thoracic spine in 4 patients, and lumbar spine in 4, and sacral region in 7 patients. Total spondylectomy was realized in six patients. Histological types included osteoid osteoma (2), Brown tumor (2), osteoblastoma (4), chordoma (4), lymphoma (2), Ewing sarcoma (2) and primary plasmocytoma (4). Adjuvant treatment with radiotherapy and/or chemotherapy was performed in 13 cases. Three cases of chordoma recurred within 11 months and tumor control was obtained in 15 cases after a median follow up period of 2.5 years (range 1-11 years). Conclusion: Primary malignant tumors are markedly more frequent than benign tumors of the spine. Early intervention is necessary to restore the spinal stability, decompress the spinal cord and realize the maximum tumor resection allowing a better tumor control.

1886

P682: Spinal cord compression secondary to voluminous thoracic primary extraosseous Ewing's sarcoma: presentation of an anecdotic and catastrophic disease

Andres Vargas ¹ , Borja Ferrandez Pujante ¹ , and Marc Valera Mele ¹

¹ Department of Neurosurgery, Hospital Clinico San Carlos, Madrid, Spain

Introduction: Ewing’s Sarcoma (ES) is a rare osseous tumor, with an annual incidence of 3 cases per 1.000.000 people, mainly affecting large bones. Spinal Affection (SA) is anecdotic (less than 5% of all ES cases), including primary extra-osseous tumors with SA being no more than 13 cases reported in literature between 1969 and 2015. Tipically, SA tumors present a highly aggressive histology compatible with Primitive Neuroectodermic Tumor (PNET). Spinal Surgery role in the disease is fundamental due to its multiple benefits derived from decompression of neural structures, restoration of spinal stability and from the reduction of tumor volume, this, also contributing to improve the response to adjuvant therapy. We present the case of a young patient presenting with a severe Spinal Cord Compression (SCC) syndrome secondary to a voluminous cervical primary extra-osseous tumor with histologic diagnosis of ES. Material and Methods: A previously healthy 32-year-old male patient presented to the Emergency Room (ER) with 48 hours progressive paraparesis associating bladder dysfunction. During his ER admittance muscle power of 2/5 according to mMRC and C7-T1 sensitive level was evidenced. Urgent magnetic resonance imaging revealed a thoracic-soft-tissue mass with C6-C7-T1-T2 spinal canal invasion and severe SCC and displacement. The patient underwent C7-T1 laminectomy, tumor debulking and resection for decompression and C6 bilateral lateral-mass arthrodesis, C7 left unilateral pedicular screw due to right pedicular tumoral involvement and T1-T2 bilateral pedicular screw under fluoroscopic control. No complications related with arthrodesis or wound healing were present. Pathology analysis revealed a highly cellular tumor compatible with ES. During his admittance the patient had a stable evolution, with partial motor recovery (distal predominance), requiring in-patient rehabilitation program. Results: The patient was discharged to a National highly specialized rehabilitation center for treatment of spinal cord injury and is receiving high-dose chemotherapy including Vincristine, Etoposide, Ifosfamide and Actinomicin-D, with a complete tumoral response according to the last PET-Scan. Anterior approach by a cervico-sternotomy and C7-T1 corpectomy to complement posterior arthrodesis is pending due to recent chemotherapy and request of a fourth chemotherapy cycle. Conclusion: SA of ES is a poor prognostic tumor due to its highly aggressive histology and the possibility of debuting with a severe neurological deficit. Surgery for decompression and spinal stabilization represents an important tool when addressing urgent treatment of this disease, in addition with aggressive adjuvant therapy. Close follow-up is recommended in order to evaluate tumor response to adjuvant therapy, residual tumor behavior and spinal stability.

1899

P683: Rare case of epidural metastasis of thymoma

Joao Oliveira ¹ , Mário Vale Campos ¹ , and Pedro Ribeiro da Cunha ¹

¹ Neurocirurgia, Centro Hospitalar Lisboa Ocidental, Lisboa, Portugal

Introduction: Malignant thymoma is a rare, slow growing, anterior mediastinal tumor, that is often associated with extrathoracic metastasis (up to 15%, mostly liver, kidney and bone). Local invasion and intrathoracic spread are relatively common. Despite the highly aggressive behaviour of malignant thymoma, spinal metastasis is exceptionally rare, with less than 50 cases reported in the literature. Material and Methods: A 48 year old-man, with medical background of an operated thymoma in 2013, initially presented with discrete hemiparesis in 2017, then on May 2018 presented with intense axial pain in the cervico-dorsal transition that irradiates to the right superior limb. Physical examination revealed intense cervico-dorsal pain in axial transition with irradiation to the right superior limb. Neurological examination revealed paresis of both distal superior limbs (hands), worst on the right. Right hypoesthesia on C6-C8. Without evident deficit on inferior limbs. TC guided biopsy confirmed metastasis in D1 of thymoma. Cervical MRI revealed infiltration of all vertebral body of D1, predominantly lytic areas, with anterior and posterior epidural component towards C7-D2 with dural contact, without deformity and no medular hypersignal. PET revealed captation only in D1 level. The patient was submitted to 5 radiotherapy sessions, with pain relieve but unfortunately without neurological remission. Due to weak response to radiotherapy and lack response to chemotherapy, the patient was submitted to surgery, with circumferential decompression of C7-D2 through a posterior approach, with cervico-dorsal fixation and vertebroplasty. Results: Pathology confirmed an epidural infiltration of neoplasia with thymic differentiation, compatible with epidural metastasis of Thymoma. Postoperative course was uneventfully, with progressive neurological improvement. Conclusion: Spinal epidural metastasis should be suspected in all cancer patients with back pain. Because metastasis to the spine from thymoma are very rare, there are no treatment guidelines. Nevertheless, surgical management of the metastatic lesion is the most appropriate, for the preservation of the patient quality of life.

1960

P684: Association between urbanicity and outcomes among patients with spinal cord ependymomas in the United States

Jacob Sperber ¹ , Edwin Owolo ¹ , Nancy Abu-Bonsrah ¹ , Corey Neff ¹ , Cesar Baeta ² , Chuxuan Sun ¹ , Tara Dalton ¹ , David Sykes ¹ , Harrison Hockenberry ¹ , Brandon Bishop ¹ , Antoinette Charles ¹ , Jill Barnholtz-Sloan ³ , Carol Kruchko ³ , Kyle Walsh ¹ , Sheng-fu L. Lo ⁴ , Daniel Sciubba ^1,4 , Quinn Ostrom ¹ and C. Rory Goodwin ¹

¹ Department of Neurosurgery, Duke University School of Medicine, Durham, United States

² Center for Population Health Sciences, Stanford University, Durham, United States

³ Central Brain Tumor Registry of the United States

⁴ Long Island Jewish Medical Center and North Shore University Hospital, Northwell Health, United States

Purpose: Spinal Cord Ependymomas (SCE) represent the most common intramedullary spinal cord tumors among adults. Access to neurosurgical care can be greatly influenced by patient location. This study investigates the association between the outcomes of SCE patients in metropolitan and non-metropolitan areas. Methods: Patients with diagnosis of SCE between 2004 and 2019 were identified within the Central Brain Tumor Registry of the United States. Multivariable logistic regression models were constructed to evaluate the association between urbanicity and SCE treatment. Cox proportional hazard models were used to understand the effect of surgical treatment, county urbanicity, age at diagnosis and the interaction effect between age at diagnosis and surgery, on the survival time of patients. Results: 7,577 patients were identified, with 6,454 (85%) residing in metropolitan and 1223 (15%) in non-metropolitan counties. Demographics were not associated with differences in the type of surgery received when stratified by urbanicity. Regardless of metropolitan status, American Indian/Alaska Native and Hispanic ethnicities were associated with reduced odds of receiving surgery alone. Black Non-Hispanic and Hispanic ethnicities were associated with increased odds of receiving comprehensive treatment (radiation and surgery). Diagnosis of SCE at later ages was linked with elevated mortality (HR = 4.83, p < 0.001). Gross total resection was associated with reduced risk of death (HR = 0.47, p = 0.018). However, among older patients, gross total resection resulted in increased risk of death (HR = 1.02, p < 0.008). Conclusion: The relationship between patient residential location and access to neurosurgical care is critical to ensuring equitable distribution of care. This study represents an important step in delineating areas of existing disparities.