Oral Presentations

Best Paper Session

A001: Complications and Revision Rates in Robotic-Guided vs Fluoro-Guided Minimally Invasive Lumbar Fusion Surgery - A Report from the MIS Refresh Prospective Comparative Study

Andrew Cannestra¹, Samuel Schroerlucke², Michael Wang³, Christopher Good⁴, Jae Lim⁴, Victor Hsu⁵, Faissal Zahrawi⁶, Hunaldo Villalobos⁷, Thomas Sweeney⁸

¹Lyerly Neurosurgery, Jacksonville FL - United States ²Tabor Orthopaedics, Memphis - United States ³Univsersity of Miami, Miami - United States ⁴Virginia Spine Institute, Reston - United States ⁵Rothman Spine Institute, Abington - United States ⁶Florida Hospital, Celebration - United States ⁷Osceola Regional Medical Center, Orlando - United States ⁸Southeastern Spine Center, Sarasota - United States

Introduction: As robotic-guidance and minimally invasive approaches become more prevalent in spine surgery, there is a growing interest in high-level scientific evidence of their clinical value. MIS ReFRESH is the first prospective, comparative, multi-center study designed to assess differences in surgical complication and revision rates, and exposure to intra-operative radiation, in adult degenerative conditions, operated in a minimally invasive (MIS) approach in 1-to-3 level fusions. Materials and Methods: Multicenter data (9 sites) were prospectively collected from 379 adult patients indicated for fusion surgery, including demographics, complications, need for revision surgery and use of intra-operative fluoroscopy (in seconds). A single site randomized patients between arms, while other sites enrolled exclusively to one arm. We compared of incidence of revision surgeries and clinical complications (surgical and medical) through a logistic regression model (Cox) as well as intra-operative fluoroscopy use. Results: Altogether, 9 sites enrolled 379 cases: 287 in the robot-guided arm (RG), and 92 in the fluoro-guided arm (FG). One site randomized patients, 15 to RG and 11 to FG. Mean age of RG patients was 59.1 years vs. 62.4 for FG (p = 0.032) and BMI was 31.4 vs. 28.0, respectively (p < 0.001). Sex distribution was similar at 62.0% females in RG and 57.4% in FG (p = 0.468). Charlson Comorbidity Index was 0.5 ± 0.8 in RG vs. 0.3 ± 0.6 in FG (p = 0.022). There were 4.8 ± 1.2 pedicle screws per case in RG vs. 4.3 ± 0.9 screws in FG (p < 0.001). In RG 33% of cases were 2-levels and 5% 3-levels, while in FG 16% were 2-level fusions, and 1% were 3-level fusions. Use of fluoroscopy for the instrumentation phase was 3.8 ± 3.9 seconds/screw in RG vs. 16.9 ± 9.2 in FG (p < 0.001). Average follow up was 174 days in RG and 159 in FG. Within the first year of follow up there were 28 (9.7%) complications in RG vs. 35 (38.0%) in FG, and 4 (1.4%) revisions in RG vs. 4 (4.3%) in FG. When evaluated in a Cox logistic regression model that includes age, gender, BMI, Charlson Comorbidity Index and number of executed screws, the Relative Risk (RR) for a complication was 5.3 times higher in FG compared to RG (95% Confidence Interval (CI): 3.0-9.5, p < 0.001). RR for a revision surgery were 7.1 times higher for a fluoro-guided surgery compared to the robot-guided cases (95% CI 1.6-32.6, p = 0.012). Conclusion: We report our findings from a prospective, multi-center, comparative study of MIS lumbar fusions performed with robotic-guidance in 287 patients vs. fluoro-guidance in 92 controls. RR for a complication or a revision surgery was significantly higher in FG during the first year of follow-up compared to RG (5.3-fold and 7.1-fold, respectively). RG reduced fluoroscopy exposure time per case by 78%, or almost a minute, helping offset the patients’ exposure during the pre-operative CT scan required for planning the robotic procedure.

A002: Smart Neural Stem Cells to Degrade Scar and Optimize Regeneration After Spinal Cord Injury

Christopher Ahuja¹, Mohamad Khazaei², Priscilla Chan², Zijian Lou², Yao Yao², Jinil Bhavsar², Michael Fehlings²

¹Division of Neurosurgery, Department of Surgery, University of Toronto, Toronto - Canada ²Department of Genetics and Development, Krembil Research Institute, Toronto Western Hospital, University Health Network, Toronto - Canada

Introduction: Human induced pluripotent stem cell-derived neural stem cells (hiPS-NSCs) represent an exciting therapeutic strategy for traumatic spinal cord injury (SCI) as they can replace lost neural circuits, remyelinate denuded axons and provide local neurotrophic support. Unfortunately, over 95% of affected individuals are in the chronic phase of their injuries where dense deposits of chondroitin sulfate proteoglycan (CSPG) in the glial/CSPG scar impair neurite outgrowth and regenerative cell migration. Several scar-modifying enzymes have been shown to synergistically enhance NSC-mediated recovery, however, nonspecific intrathecal administration can produce off-target effects. We aimed to generate a genetically-engineered line of hiPS-NSCs, termed Spinal Microenvironment Modifying and Regenerative Therapeutic (SMaRT) cells, which are uniquely capable of expressing a scar-modifying enzyme within their local environment to enhance functional recovery. Material and Methods: A proprietary CSPG-degrading enzyme was genetically integrated into hiPS-NSCs using non-viral transposon technology. An constitutive EF1α promoter was placed upstream of the enzyme linked by a 2A cleavage peptide to a nuclear import tagged red fluorescent protein (RFP) reporter. A monoclonal line of resultant SMaRT human cells was generated by single-cell fluorescence activated cell sorting (FACS) and expanded. Enzyme expression and enzyme activity was extensively characterized in vitro by biochemical assays and antibody-based slot blots with a chondroitin sulfate (CS) or human CSPG substrate. Ex vivo injured rodent cervical cord sections were also incubated with conditioned media from wild-type hiPS-NSCs and SMaRT cells, followed by immunolabelling to assess in situ CSPG degradation. To assess in vivo efficacy, T-cell deficient RNU rats (N = 60) with translationally-relevant chronic C6-7 clip-contusion injuries were randomized to receive: (1) injury + vehicle, (2) injury + conventional hiPS-NSCs, (3) injury + SMaRT cells, or (4) sham surgery (laminectomy alone). Weekly neurobehavioural assessments of all animals include BBB open-field locomotor scoring, inclined plane test, forelimb grip strength and tail flick sensory test. CatWalk digital gait assessment is also being completed every 4 weeks. Results: The monoclonal SmaRT cell line uniformly expresses the RFP reporter and demonstrates key retained hiPS-NSC characteristics such as repeated neurosphere formation, a 46XY karyogram, nestin cytoplasmic staining and the capacity to differentiate along all three neuroglial lineages (neurons, oligodendrocytes and astrocytes). The enzyme expressed by SMaRT cells rapidly degrades CSPGs on WST-1 and DMMB biochemical assays and allows neurons to extend into scar mimicking CSPG-rich regions in vitro. Furthermore, unlike wild-type hiPS-NSC media, conditioned SMaRT cell media can degrade rodent CSPGs in ex vivo injured cord cryosections as assessed by CS-56 (intact long-chain CSPG) immunohistochemistry. While blinded in vivo sensorimotor behavioural assessments are ongoing with a long-term 40-week endpoint, interim histological analyses shows that grafted human cells are extending remarkably long (≥ 20 000 µm) axons along host white matter tracts in both the rostral and caudal directions. These processes extend from the cervicomedullary junction to below the mid-thoracic cord. Conclusion: This work provides exciting proof-of-concept data that genetically-engineered SMaRT cells can degrade CSPGs in vitro and that human NSC transplants can grow long axons in chronic cervical SCI to potentially form a bridge for sensorimotor signal transmission.

A003: Early Versus Delayed Rod Fracture in Adult Spinal Deformity Surgery Fused to the Sacrum Differ in Presentation and Revision Rates

Thamrong Lertudomphonwanit¹, Michael Kelly², Keith Bridwell², Lawrence Lenke³, Steve McAnany², Prachya Punyarat⁴, Jacob Buchowski², Lukas Zebala², Brenda Sides², Kalin Pearce⁵, Munish Gupta²

¹Department of Orthopaedic Surgery, Faculty of Medicine Ramathibodi Hospital, Mahidol University, Bangkok - Thailand ²Department of Orthopaedic Surgery, Washington University School of Medicine, St. Louis - United States ³Department of Orthopedic Surgery, Columbia University Hospital, New York, NY - United States ⁴Department of Surgery, Faculty of Medicine, Thammasat University, Pathumthani - Thailand ⁵Brown School of Social Work, Washington University School of Medicine, St. Louis, MO - United States

Introduction: Rod fracture (RF) is a challenging complication in adult spinal deformity (ASD) surgery. A detailed analysis of the patients correlating time of onset of RF after ASD surgery has not been previously described in the literature. We aimed to compare differences in incidence, contributing factors, revision rates and clinical outcomes between early rod fracture (ERF) and delayed rod fracture (DRF) patients. Material and Methods: A database of ASD patients undergoing long construct posterior spinal fusion by 2 senior surgeons at one institution from 2004 to 2014 was retrospectively reviewed. Inclusion criteria were age > 18, minimum 5 vertebrae fused to sacrum and minimum 2-year follow-up. Patients were stratified according to onset of RF. ERF occurred within 4 years and DRF occurred beyond 4 years after index surgery. Demographics, radiographic parameters, operative data and clinical outcomes were reviewed and compared between the two groups at baseline and at follow-up. Statistical analysis was performed using independent sample t-tests for continuous variables and chi-square or Fisher’s exact test for categorical variables. Results: Five hundred twenty-four patients out of 657 patients (average age 56.8 year-old, 87% female) met the inclusion criteria. Sixty-three patients (12%) developed ERF and 32 patients (6.1%) developed DRF. There were no differences in demographics. We found no differences in baseline radiographic parameters (SVA, PI, PT, PI-LL, Lumbar lordosis, thoracic kyphosis, thoracolumbar kyphosis and max coronal Cobb angle) and amount of correction between the group, all p > 0.05. The ERF group had more percentage of cobalt chromium (CoCr) rod use (59% vs. 28%; p = .010), smaller diameter (diameter < 6 mm) rod use compared to 6.35 mm rod (87% vs. 63%; p = .004) and used lower dose of rhBMP-2 (106 mg vs. 138 mg; p = .044). There were no differences in number of rods used, number of fused levels, number/type of osteotomies, interbody fusion, pelvic fixation and use of allograft, all p > 0.05. The DRF group had longer follow-up (6.7 years. vs 4.6 years; p < .001.) and longer survival time to RF (5.9 years. vs 2.1 years; P < .001.). The ERF group had higher postoperative major symptoms including persistent back pain, loss of correction and prominent implants (49% vs 28%; p = .049), and higher revision rate (49% vs 28%; p = .049). There were no significant differences in baseline, 1-year and latest follow-up in clinical outcomes as measured by ODI and SRS-30 between the groups. The overall improvement of ODI and SRS-30 compared to baseline was similar in both groups (all p > 0.05), however the ERF group showed a trend toward lower improvement of ODI at 1-year postoperatively (17.3 vs 24.6, p = 0.051). Conclusion: There are distinct differences between ERF and DRF. Use of smaller rod diameter, CC material and lower dose of rhBMP-2 is associated with ERF. Compared to DRF patients, ERF patients have greater symptoms, higher revision rates and tend to have lower improvements in clinical outcomes based on ODI at early postoperative period.

A004: Practice of Patient-Reported Outcome Measures in Spine Care

Asdrubal Falavigna¹, Diego Cassol Dozza², Alisson Teles³, Chung Chek Wong⁴, Giuseppe Barbagallo⁵, Darrel Brodke⁶, Abdulaziz Al-Mutair⁷, Zoher Ghogawala⁸, Daniel Riew⁹

¹University of Caxias do Sul - Brazil ²Department of Neurosurgery, São Vicente de Paulo Hospital. Fronteira Sul Federal University - Brazil ³Department of Clinical Neurosciences, Division of Neurosurgery, University of Calgary - Canada ⁴Sarawak General Hospital, Department of Orthopedic Surgery, Jalan Tun Ahmad Zaidi Adruce, Sarawak - Malesia ⁵Azienda Ospedaliero-Universitaria, Policlinico Neurosurgery, Catania - Italy ⁶Spine Service, University of Utah, Department of Orthopaedics, Salt Lake City – United States ⁷Alrazi Hospital, Ministry of Health / Kuwait Institute for Medical Specialization, Kuwait City - Kuwait ⁸Alan and Jacqueline Stuart Spine Center, Department of Neurosurgery, Lahey Hospital and Medical Center, Burlington - United States ⁹Department of Orthopedic Surgery, Columbia University, New York - United States

Introduction: The use of prospective clinical registries based on patient-reported outcome measures (PROMs) is an important component of medical care because it has the potential to narrow the gap between the clinician’s and patient’s view of clinical reality and help tailor treatment plans to meet the patient’s preferences and needs. PROMs are the most widely accepted means of measuring outcomes following spine procedures. In order to have the treating physician actively involved, it is necessary to recognize and overcome the barriers to the implementation of clinical registries, which may differ in different regions of the world. We sought to determine the current status of worldwide use of PROMs in Latin America (LA), Europe (EU), Asia Pacific (AP), North America (NA), and Middle East (ME) in order to determine the barrier to its full implementation. Material and Methods: A questionnaire survey was sent by e-mail to members of AOSpine to evaluate their familiarity and use of PROMs instruments, and to assess the barriers to their use in spine care practice in LA, EU, AP, NA, and ME Results: A total of 1,634 AOSpine members from LA, EU, AP, NA, and ME answered the electronic questionnaire. The percentage of spine surgeons familiar with the generic health-related quality of life (HRQoL) questionnaire was 71.7%. in addition, 31.9% of respondents did not routinely use any PROMs. The main barriers to implementing PROMs were lack of time to administer the questionnaires (57%) followed by lack of staff to assist in data collection (55%), and the long time to fill out the questionnaires (46%). The routine use of questionnaires was more frequent in NA and EU and less common in LA and ME (p < 0.001). Conclusion: We found that 31.9% of spine surgeons do not routinely use the PROMs questionnaire. This appears to occur because of lack of knowledge regarding their importance, absence of reimbursement for this extra work, minimal financial support for clinical research, the cost of implementation and lack of concern among physicians.

A005: Efficacy and Safety of Riluzole in Acute Spinal Cord Injury (Sci). Rationale and Design of AOSpine Phase III Multi-Center Double Blinded Randomized Controlled Trial (RISCIS)

Michael Fehlings¹, Branko Kopjar², Robert Grossman³

¹Department of Surgery, University of Toronto, Toronto - Canada ²Department of Health Services, University of Washington, Seattle - United States ³The Methodist Hospital, Houston - United States

Introduction: There is convincing evidence from the preclinical realm that the pharmacologic agent riluzole attenuates certain aspects of the secondary injury cascade leading to diminished neurological tissue destruction in animal SCI models. The safety and pharmacokinetic profile of riluzole have been studied in a multicenter pilot study in 36 patients. Efficacy of riluzole in acute human SCI has not been established. Material and Methods: This ongoing multi-center, international double-blinded phase III RCT will enroll 351 patients with acute C4-C8 SCI and ASIA Impairment Grade A, B or C randomized 1:1 to riluzole and placebo. Primary outcome is the change in ASIA Motor Score (AMS) between baseline and 180 days. Other outcomes include ASIA Upper and Lower Extremity MS; ASIA Sensory Score; ASIA grade; SCIM); SF-36v2; EQ-5D and GRASSP. Two-stage sequential adaptive trial statistical design has 90% power to detect 9 points difference in the ASIA Motor Score at one-sided alpha = .025. Results: A matched cohort analysis performed in the Phase I study showed that riluzole treated cervical SCI patients experienced an additional 15.5 points in AMS recovery at 90 days post injury. Although the phase I study was underpowered to investigate efficacy the current phase III study is poised to definitive address this question. To date, 98 subjects have been enrolled. Average age of the enrolled subjects is 48.0 (SD 16.4); 84% males. ASIA at arrival and Pre-Injury status, ASIA Grade A (48%), B (27%), C (25%). GRASSP 64.6 (SD 61.4), SF35v2 PCS 53.0 (SD 9.0) SF36v2 MCS 54.3 (SD 11.5). Conclusion: This is a Phase III study of riluzole in acute SCI.

A006: Perioperative Complications after Vertebral Column Resection (VCR) For Severe Pediatric Spinal Deformity

Lawrence Lenke¹, Munish Gupta², Brenda Sides², Burt Yaszay³, Patrick Cahill⁴, Michael Kelly²

¹Department of Orthopedics, Columbia University Medical Center, New York - United States ²Washington University School of Medicine Department of Orthopaedics, St. Louis - United States ³Rady Children’s Hospital, San Diego - United States ⁴Children’s Hospital of Philadelphia, Philadelphia - United States

Introduction: VCR is commonly performed for severe pediatric spinal deformity. Retrospective cohorts have reported intraoperative neuromonitoring changes and new neurological deficit rates of 27%. A prospective cohort of severe adult deformity has reported a new neurological deficit rate of 22%. No prospective cohort of severe pediatric deformity exists. Methods: Consecutive pediatric patients with severe spinal deformity were enrolled in a multi-center observational cohort. Patients undergoing VCR for management of the deformity were selected. Demographic data and perioperative data were collected. The prevalence of intraoperative and immediate postoperative complications was calculated. The relationships between intraoperative and postoperative complications were investigated with logistic regression. Results: 136 Patients were identified, Female 73(54%), Male 63 (46%), average age 15.3 ( ± 2.8). Most common diagnoses were congenital scoliosis (27(20%)) and congenital kyphoscoliosis (23(17%)). Mean maximum coronal Cobb was 66.1 (range: 0-161) degrees; mean maximum sagittal Cobb was 105.3 (R: 28-178). 62/135(46%) Sustained some intraoperative complication; excessive blood loss was the most common 39(29%). 39/136(29%) Sustained a postoperative complication; pulmonary system complications being the most common 17(12.5%). 22/136 (16%) Sustained a new neurological deficit intraoperatively (17/136) or postoperatively (5/136). Intraoperative complications were not associated with postoperative complications. Conclusion: Intraoperative and postoperative complications were not uncommon after VCR for severe pediatric deformity surgery; with an overall prevalence of 46% intraoperative and 29% postoperative complications. New neurological deficits developed in 16% of patients. Intraoperative complications were not related to postoperative complications.

Deformity - Thoracolumbar (Adult) - Kyphosis

A007: Clinical and Radiographic Results after Posterior Wedge Osteotomy for Thoracolumbar Kyphosis Secondary to Ankylosing Spondylitis: Comparison of Long and Short Segment Instrumentation

Mu Qiao¹, Bangping Qian¹, Yong Qiu¹

¹Department of Spine Surgery, Drum Tower Hospital, Nanjing University Medical School, Nanjing - China

Introduction: Although lumbar PSO with posterior instrumentation was widely used to correct thoracolumbar kyphosis secondary to AS, studies designed to investigate the selection of long or short segment instrumentation are rather scarce. The current study aims at comparing the efficacy of long and short segmental fusion following lumbar pedicle subtraction osteotomy (PSO) in the correction of thoracolumbar kyphosis caused by ankylosing spondylitis (AS). Materials and methods: Radiographic data of 64 consecutive AS patients who were surgically treated through lumbar PSO combined with posterior segment fusion were analyzed retrospectively. Patients were divided into two groups according to location of the uppermost instrumented vertebra (UIV): SSF group (n = 20) treated by short segment instrumentation (UIV below T10) and LSF group (n = 44) underwent long segment fusion (UIV at or above T10). Radiological parameters included global kyphosis (GK), lumbar lordosis (LL), sagittal vertical axis (SVA), angle of fused segments (AFS), osteotomized vertebral angle (OVA) and proximal junctional angle. The degree of ossification in the thoracolumbar region is assessed by the modified stoke ankylosing spondylitis spine score (mSASSS). Clinical assessment involved oswestry disability index (ODI) and visual analogue scale (VAS). Results: LSF group had significantly larger deformity correction in GK and LL than SSF group while both groups had similar magnitude of correction for SVA. No significantly different loss of correction in GK and LL was identified in LSF group when compared to SSF group (GK correction loss: 2.63º vs 3.84º; LL correction loss: 2.89º vs 4.30º). In terms of OVA and AFS, no significant difference was noted in both groups. Notably, significant higher mSASSS in the thoracolumbar region was noticed in the SSF group in comparison with LSF group. The Pearson correlation analysis demonstrated that mSASSS for thoracic and lumbar spine was significantly associated with sagittal alignment changes at the final follow-up, which explained 34.5% and 53.0% of the variability of correction loss in GK and LL, respectively. Improved ODI and VAS were found in both groups at the final follow-up (P < 0.05). Intraoperative vertebral subluxation at the osteotomy site was detected in 3 patients with long constructs. There were 2 patients developed with a proximal junctional kyphosis (PJK) and 1 patient with rod fracture in LSF group. Conclusion: Both long and short segment instrumentations could maintain sustained surgical outcomes for thoracolumbar kyphosis caused by AS. Short segment instrumentation is recommended for AS patients with bridging syndesmophytes in the thoracolumbar region. Long segment fixation is better indicated for patients without fully ossified anterior longitudinal ligaments. Nevertheless, extension for length of instrumentation might not prevent the complications such as PJK or rod fracture in patients without fully ossified spine.

A008: Clinical Results and Surgery Tactics of Spinal Osteotomy for Ankylosing Spondylitis Kyphosis: Experience with 448 Patients

Yan Wang¹

¹Department of Orthopedic, 301 Hospital, Beijing - China

Introduction: The aim of this study is to report the clinical results and surgical tactics of spinal osteotomy for severe AS kyphosis based on the experience of single spine center. Material and Methods: From January 2003 to January 2015, totally 448 patients suffering from AS kyphosis who underwent spinal osteotomy in our hospital were reviewed, and 428 patients had reach a 2-year minimum follow-up. Among them, Patients, with an average chin-brow vertical angle (CBVA) of 51.5° (range, 28° to 108.1°) and average global kyphosis (GK) of 59.6° (range, 32.4°-110.6°), were selected to underwent one or two-level pedicle subtraction osteotomy (PSO) or vertebral column decancellation (VCD), and the osteotomies were performed range from T12 to L3 according to the apex of kyphosis. Pre or postoperative radiological parameters were measured. Intraoperative, postoperative, and general complications were recorded. Results: All patients could walk with horizontal vision and lie on their backs postoperatively. The CBVA was improved from 68.3° to 8.2° (P = 0.000) in two-level group and from 46.2° to 4.2° (P = 0.000) in one-level group. The mean sagittal vertical axis (SVA) was improved from 29.4 cm to 8 cm (P = 0.000) in two-level group and from 18.0 cm to 4.3 cm (P = 0.000) in one-level group. The mean amount of correction was 27.8° at the superior site of the osteotomy and 42.1° at the inferior site of the osteotomy in two-level group and was 46.2° in one-level group. No major acute complications such as death or complete paralysis occurred. 32 patients suffered one or two complications including: CSF leaks (n = 21, 9 in two-level group and 12 in one-level group), transient neurological deficit (n = 3, in two-level group), vascular laceration bleeding (n = 1, in two-level group), infections (n = 2, 1 in two-level group and 1 in one-level group), postoperatively low back pain (n = 5, 2 in two-level group and 3 in one-level group), spinal rod broken (n = 3, 2 in two-level group and 1 in one-level group), distally pedicle screws pull out (n = 4, 2 in two-level group and 2 in one-level group), and non-fusion at osteotomy site (n = 4, 3 patients associated with Andersson’s lesion preoperatively). Conclusion: Spinal osteotomy, such as PSO and VCD, can improve the living quality of AS patients secondary to the correction of kyphotic deformities. VCD, a new technique of spinal osteotomy by make a ‘Y’ shaped osteotomy rather than ‘V’ shaped in PSO, can reduce the shorten distance of middle column and then decrease the neurological complication rate. One-level spinal osteotomy shows lower complications rate, while two-level spinal osteotomy is a relatively aggressive procedure which is more suitable to correct severe AS patients with hyperkyphosis in thoracolumbar spine in combination with the loss of lumbar lordosis.

A009: Outcomes of Complex Spine Surgery in Elderly Patients

John Ibrahim¹, Linda Racine², Daniel Beckerman², Shane Burch², Sigurd Berven²

¹Department of Orthopaedic Surgery, UC San Francisco, San Francisco - United States ²

Introduction: Spinal disorders are becoming increasingly prevalent among the elderly as they continue to comprise a larger proportion of the population. An increase has been observed in both the rate and complexity of spine surgeries for elderly patients. The goal of this study is to explore the appropriateness of complex spine surgery in elderly patients by analyzing the outcomes, risks, and benefits of surgery. Methods: Patients over age 70 who had 5 or more levels of fusion between January 2012 and December 2014 were identified from the UCSF spine database. A retrospective review identified predictive variables – including age, gender, ASA score, surgical indication, and extent of fusion – and outcome variables – including intraoperative and perioperative complications, hospital course, reoperations, and death. Change in health status was measured via pre-operative and > 2-years post-operative health related quality of life (HRQOL) surveys: VAS, EQ-5D, ODI, SF-12 and SRS-30. Results: 101 patients were included. The majority were female (73%) and the average age was 74.9 years (range 70–88). The mean BMI was 27.8 ± 5.8, ASA score was 2.4 ± 0.5, Charlson Comorbidity Index was 1.1 ± 1.4, and metabolic equivalents (METs) was 4.6 ± 1.4. The most common surgical indications were adult spinal deformity (53%) and lumbar spinal stenosis (21%), and 56% of all surgeries were revision surgeries. The average number of levels fused was 9.4 ± 3.5. Frequent complications included dural tears (17%), admission to the ICU (45%), an additional revision surgery within 2-5 years (23%), and death within 2-5 years (16%). The average improvement in health status from pre-operative to at least 2 years after surgery for VAS Back was 3.8 ± 4.3, EQ-5D was 0.11 ± 0.23, ODI was 10.6 ± 18.5, SF-12 Physical Component Score was 4.6 ± 14.6, SF-12 Mental Component Score was 1.8 ± 19.5, and SRS was 0.53 ± 0.63. 91% of patients reported improvement in at least one survey. The percentage of patients who reported a worse QOL and those who had an improvement greater than or equal to the MCID for each survey score, listed as [Survey: % worse vs % MCID improved (MCID value)] was VAS Back: 12% vs 69% (2), EQ-5D: 29% vs 41% (0.15), ODI: 23% vs 58% (10), SF-12 Physical Component Score: 26% vs 44% (5), SF-12 Mental Component Score: 26% vs 48% (5), and SRS: 23% vs 45% (0.4). Primary surgeries, as compared to revisions, were associated with significantly higher improvements in ODI (22 vs 7.2, p = 0.006) and surgeries requiring a future revision were associated with significantly lower EQ-5D improvement (0.02 vs 0.18, p = 0.039). Any surgical complication was associated with significantly lower improvement in EQ-5D (0.002 vs 0.154, p = 0.020) and ODI (1.6 vs 14.1, p = 0.047). Conclusion: Appropriate surgery is surgery in which the benefits of the intervention exceed the risk. In multilevel surgery in patients over age 70, complications are common, and most (51%) patients find clinically meaningful improvement. Patients undergoing revision surgery or those who develop a surgical complication are more likely to have lower improvement.

A010: The Preoperative and Intraoperative Management and Control of the Risks of as Patients Underwent Spinal Osteotomy

Guoquan Zheng¹, Zhijun Xin², Yan Wang¹, Xuesong Zhang¹

¹Department of Orthopaedics, Chinese People’s Liberation Army General Hospital (301 Hospital), Beijing - China ²Department of Spinal Surgery, Affiliated Hospital of Zunyi Medical College, Zunyi - China

Introduction: Spinal osteotomies, including pedicle subtraction osteotomy (PSO) and vertebral column decancellation (VCD), have been described as effective techniques to correct kyphotic deformity in patients with AS. However, only a few reports focus on the risks of those techniques, and seldom report described the prevention and management measures of those risks. Systematic review of the risks of spinal osteotomies for correction of kyphosis in Ankylosing Spondylitis (AS) at single spine center is help to ensure the successful perform of the procedures. Materials and Methods: 472 patients with AS who underwent spinal osteotomy at single spine center between January 2003 to June 2015 for correcting spinal kyphotic deformity were reviewed. Among them, 443 patients who underwent one or two-level PSO or VCD had reached a 2-year minimum follow-up. Risk factors including operative time, blood loss, and complications were recorded and analyzed for all patients. Radiographic and clinical data were documented before surgery and at 6-month follow-up. Results: All patients could walk with horizontal vision and lie on their backs postoperatively. 149 patients were performed with PSO and 294 patients performed with VCD. The average operation time was 290 minutes (range 208–422 minutes), average blood loss of 752 ml (range 180–2550 ml), and the average instrumented vertebral body was 6.8 (range, 5-10). Neither mortalities nor any major neurologic complications were occurred during the follow-up. However, 39 patients suffered one or two complications have been encountered, including CSF leaks (n = 25), transient neurological deficits (n = 4), vascular laceration bleeding (n = 1), infections (n = 3), post-operatively low back pain (n = 7), spinal rod broken (n = 4), pedicle screws loosening (n = 5), non-fusion at osteotomy site (n = 2), and the the total complication rate was 8.6%. Post-operatively radiographic parameters and clinical characteristics all improved significantly at 6-month follow-up. All patients were satisfied with the surgical results with an average follow-up of 2.3 years. Conclusions: Spinal osteotomies, such as PSO and VCD, can effectively correct spinal kyphotic deformity, restore sagittal balance, improve the visual field, and relieve back pain. Whereas, as a technically demanding and complication-fraught procedure, spinal osteotomy should be precise planning before operation, meticulous process during operation, and careful management after operation to achieve satisfactory results while avoiding unsatisfactory results occurred.

Keywords: ankylosing spondylitis, spinal deformity, risk factors, complications, vertebral column decancellation, pedicle subtraction osteotomy

A011: Surgical Strategy of Thoracolumbar Kyphosis Secondary to Old Osteoporotic Vertebral Compression Fracture

Yu Jiang¹, Zhaoqing Guo¹, Zhongqiang Chen¹, Yan Zeng¹, Qiang Qi¹, Weishi Li¹, Chuiguo Sun¹

¹Department of Orthopaedics, Peking University Third Hospital, Beijing - China

Introduction: To investigate the selection and strategy between posterior osteotomy and lateral anterior decompression and correction for thoracolumbar kyphosis secondary to old osteoporotic vertebral compression fractures (OVCF). Material and Methods: From May 2004 to April 2015, 40 cases received surgical treatment of thoracolumbar kyphosis secondary to old OVCF, consisted of 30 female and 10 male, the mean age was 63.9 years old (51 years to 76 years). 22 cases received posterior osteotomy correction surgery, including the pedicle subtraction osteotomy in 19 cases and the vertebral column resection in 3 cases. Lateral anterior decompression and correction were received in 18 cases. The angle of kyphosis, lumber lordosis (LL) and sagittal vertical axis (SVA) were measured before surgery, as well as the final follow-up. Kyphotic correction and loss of correction were compared between the two operation methods. The Oswestry Disability Index (ODI) and Japanese Orthopedic Association (JOA29 for life quality, Visual Analogue Scale were evaluated preoperatively and the final follow-up. The modified Frankel grading system was recorded for describing the neurological function of lower extremities. Results: The mean operative time of lateral anterior approach group was 204 min, mean blood loss was 819 ml. The mean operative time of posterior osteotomy group was 289 min, mean blood loss was 1692 ml. 40 cases were followed up from 3 to 108 months, 50.5 months in average. The angle of kyphosis of lateral anterior approach group was 24.8° ± 14° (11.6° ∼ 51.5°) in average preoperatively, the surgical correction was 9.8° ± 5.4° in average, the loss of correction was 4.6° ± 2.9° in average at final follow-up. The angle of kyphosis of posterior osteotomy was 39.8° ± 17° (9.1° ∼ 70.8°) in average preoperatively, the surgical correction was 31.2° ± 13.1° in average, the loss of correction was 3.8° ± 2.9° in average at final follow-up. A significant difference was found in surgical correction between two operation methods (P < 0.05), no significant difference was found in the loss of correction (p > 0.05). The average lumbar lordosis angle was 26.4° ± 19.9° in lateral anterior approach group before surgery and 28.9° ± 14.8° at final follow-up. Meanwhile, the average lumbar lordosis angle was 32.3° ± 22.6° in posterior osteotomy group before surgery and 29.1° ± 11.4° at final follow-up. 1 case from the lateral anterior approach group was still in sagittal plane imbalance postoperatively. 6 cases from the posterior osteotomy group were reconstructed in sagittal plane balance postoperatively. The average post-operative VAS, JOA29 and ODI improved significantly (p < 0.05). A significant difference of the ODI was found between lateral anterior approach group and posterior osteotomy group (p < 0.05). In the lateral anterior approach group, the modified Frankel grading were D1 in 4 cases, D2 in 2 cases, D3 in 1 case before surgery, and were D1 in 1 case, D2 in 2 cases, D3 in 2 cases, E in 2 cases at the final follow-up. In the posterior osteotomy group, D2 in 3 cases, D3 in 1 case were observed before surgery, and D3 in 3 cases, E in 1 case were observed at the final follow-up. Conclusion: In order to obtain decompression of nerve and restore spinal stability and alignment, both posterior osteotomy and lateral anterior decompression and correction can be effective treatments for the thoracolumbar kyphosis secondary to the old OVCF. The larger correction degrees was realized in the posterior osteotomy, and which ensured the restoration of the sagittal plane balance, meanwhile, the better ODI was recorded at final follow-up. The posterior osteotomy can be an optimum selection of single segment or several segments thoracolumbar kyphosis with larger degrees secondary to OVCF, especially for the trunk in spinal sagittal imbalance. The lateral anterior decompression and correction was suitable for single segmental thoracolumbar kyphosis with smaller degrees secondary to OVCF.

A012: Spinal Sagittal Realignment after Osteotomy on Old Thoracolumbar Osteoporotic Fracture-Related Kyphosis

Kai Cao¹, Junlong Zhong¹, Yiwei Chen¹, Zhimin Pan², Pingguo Duan¹

¹Orthopedics Department, The First Affiliated Hospital of Nanchang University, Nanchang - China ²Department of Neurosurgery, Spine and Spinal Cord Institute, Yonsei University College of Medicine, Seoul - Korea, Republic

Introduction: Old thoracolumbar osteoporotic fracture-related kyphosis is likely to develop into severe sagittal malalignment which permanently influences patients HRQoL. Few study reported the change of global spinal alignment and improvement of HRQoL after osteotomy in this scenario. This study is to investigate the effect of osteotomy on realign the global spine as well as the significant sagittal parameter associated with the improvement of HRQoL. Material and Methods: Consecutive old thoracolumbar osteoporotic fracture-related kyphosis patients underwent osteotomy with 2-year follow-up were included in this cohort. MRI, CT and upright X-ray of spine were taken pre- and postoperatively. Spinal sagittal alignment parameters including T2-T12 cobb angle (TK), T10-L2 cobb angle (TL), L1-S1 cobb angle (LL), T9 tilt, L1 tilt, sacral slope (SS), pelvic tilt (PT), SVA, pelvic incidence (PI) and sacral spinal angle(SSA) were measured. ODI, SF-36 PCS and SRS-22 were assessed pre- and postoperatively. Significant independent parameters associated with HRQoL were analyzed first by correlation analysis, and then by stepwise regression analysis. Results: Total 24 patients (17 female, 7male) were included with mean age of 66.5 ± 11.4. The mean BMI was 24.6 ± 5.15 and T-score was -2.67 ± 0.92. TK, TL, LL, T9 tilt, L1 tilt, SS, PT, SVA, SSA except PI were significantly improved after osteotomy (P < 0.05). ODI, SF-36 PCS and SRS-22 were significantly improved from 55.4 ± 14.3, 30.7 ± 10.7, 2.7 ± 1.1 to 30.2 ± 10.5 (P = 0.012), 39.6 ± 11.8(P = 0.001), 3.9 ± 0.8 (P = 0.003), respectively. Correlation analysis showed that the change of TK, TL, LL, T9 tilt, L1 tilt, PT, SS, SVA, PI-LL were associated with the improvement of ODI, SF-36 PCS and SRS-22. Stepwise regression indicated that the change of TL and PT were identified as parameters significantly associated with ODI, the change of TL and SVA were identified as parameters significantly associated with SF-36 PCS, the change of TL was identified as parameter significantly associated with SRS-22. Conclusion: Osteotomy can effectively correct the old osteoporotic thoracolumbar fracture-related kyphosis and realign the global spine. The realignment of TL was the independent parameter to improve the HRQoL.

Minimally Invasive Spine Surgery Endoscopic

A013: Percutaneous Endoscopic Thoracic Discectomy on Upper Thoracic Spine

Junseok Bae¹, Sang-Ho Lee¹

¹Neurosurgery, Wooridul Spine Hospital, Seoul - Korea, Republic

Introduction: Thoracic disc herniation is relatively uncommon. Considering the complexity of neural and vascular structure, surgical treatment of upper thoracic disc herniation (UTDH) is technically challenging. Although percutaneous endoscopic thoracic discectomy (PETD) has been introduced, technical feasibility and outcomes for UTDH have not been reported. The purpose of this report is to describe percutaneous endoscopic approach to remove disc herniation on upper thoracic spine via transforaminal approach. Material and Methods: Included patients were those who presented with symptomatic TDH on upper thoracic spine not responding to conservative treatments. Calcified disc herniation or concomitant OPLL were excluded. Under the local anesthesia and intravenous sedation, PETD was performed by 4.7 mm endoscope (TESSYS, Joimax GmbH, Germany) that introduced via transforaminal approach with foraminoplasty using reamer and bone-drill. Patients’ outcome was evaluated using VAS and ODI scores. Results: Eleven consecutive patients (mean 41.3 years old, 9 males) who underwent PETD from 2001 to 2017 were reviewed. Regarding surgical levels, there were 3 for T2-3, 4 for T3-4, and 4 for T5-6. At mean 52 months follow-up, all patients showed significant improvement of pain (6.8 to 2.3 for VAS and 53.5 vs. 16.8 for ODI, p < 0.05 for all). No serious complication has been reported during the follow-up. Conclusion: Percutaneous endoscopic thoracic discectomy for upper thoracic disc herniation is a safe and effective minimally invasive treatment with favorable clinical results.

A014: Percutaneous Transforaminal Endoscopic Discectomy for Lumbar Foraminal Stenosis

Youngha Woo¹, Heung-Tae Jung¹, In-Bo Kim¹, Woo-Seong Sun¹, Dong-Wook Jung¹

¹Department of Orthopaedic Surgery and Joint Center, Bumin Busan Hospital, Busan - Korea, Republic

Introduction: Spine degeneration is a natural process manifesting as spinal stenosis in the elderly population. Prolonged life span increases the prevalence of spinal stenosis. Classic operations for spinal stenosis are open laminectomy, foraminotomy, or fusion. However, in the elderly population factors such as comorbidity, age, surgical complications always needs to be considered and open surgery may cause more complications. Therefore, minimally invasive spine surgery has been increasingly gaining popularity in spinal management preserving the surrounding anatomical structures (muscles and ligaments). In the past, the indication for percutaneous endoscopic surgery was disc herniation and spinal stenosis was a contraindication. However, the indication has broadened to include spinal stenosis through the development of equipment and surgical techniques. Percutaneous endoscopic stenosis lumbar decompression (PESLD) is increasingly regarded as an effective alternative to open surgery. We report the surgical procedure and clinical results of PESLD technique using a uniportal approach for bilateral decompression of degenerative spinal stenosis. Materials and Methods: Uniportal bilateral PESLD was performed for decompression in patients with spinal stenosis. 44 patients underwent surgery from August 2015 to August 2016 and patients with neurogenic claudication with degenerative spinal stenosis where conservative treatment failed. All patients underwent preoperative and postoperative dynamic lumbar x-ray, magnetic resonance imaging, and computed tomography. To verify the efficacy of this technique, preoperative and postoperative cross-sectional area (CSA) of thecal sac was measured. Clinical results were evaluation using the MacNab classification. Results: There were 44 cases (20 men, 24 women). Mean age of the patients was 57.65 ± 4.36 years. Mean symptom duration was 24.48 ± 15.87 months. Follow-up period was 10.89 ± 4.23 months (range 12-24 months). The mean preoperative CSA was 69.5 mm² (range 30.3-85.1) and it increased to 199.2 mm² (range 176.4-218.5) postoperatively. According to the MacNab classification, 31 patients were excellent, 9 were good, and fair was 4 patients. Complications related to surgery did not occur. During the follow-up period from 3 months to 24 months postoperatively, lumbar lateral flexion extension radiography was performed and no postoperative instability was found. Conclusion: Uniportal bilateral PESLD is an effective surgical procedure that can adequately decompress degenerative spinal stenosis without causing spinal instability and risking complications in the elderly population.

A015: Minimally Invasive-Microscopic Assisted Stand-Alone Trans-Articular Screw Fixation (MIS-TAS) Without Gallie Supplementation in the Management of Mobile Atlanto-Axial Instability

Tarun Dusad¹, Vishal Kundnani¹, Mahendra Singh¹, Gaurav Mehta¹, Ankit Patel¹, Shumayou Dutta¹, Sameer Ruparel¹

¹Department of Spine Surgery, Bombay Hospital & Medical Research Centre, Mumbai - India

Introduction: Stand-alone Trans-articular screw fixation (TAS) provides excellent rotational and lateral bending C1-C2 stability but isn’t as effective in resisting flexion and extension loads. Good fusion rates are reported even when the posterior wiring construct fails. We hypothesize that the added stability provided by structural graft and wiring may not influence fusion rates in the clinical setting. If this is correct, a whole set of complications associated with wires and graft harvest can be avoided. Thus, this retrospective study was conducted to evaluate the clinico-radiological efficacy of stand-alone MIS-TAS (Minimal invasive trans-articular screw fixation) without supplemental Gallie fixation in the management of mobile C1-C2 instability. Methods: Patients with mobile Atlanta-Axial instability and > 2 years follow up were included and managed by stand-alone TAS fixation using Magerl’s technique and morsellised allograft without additional fixation. We mentioned our technique as Minimal invasive TAS (MIS-TAS) because of principles used to minimise the surgical trauma in every possible aspect by using smaller exposure with avoiding damage to C2-C3 interspinous ligament and C2-C3 capsule, allograft instead of autograft, avoiding use of wires. Patient demographics and Intra operative parameters were noted. Clinical parameters (VAS/ODI), neurology (mJOA) and radiological factors (Anterior Atlanto-Dens Interval- ADI & Space Available for Cord- SAC) were evaluated pre and post-operative. CT scan was obtained in those who did not show interspinous fusion on x-ray at 1 year to see intra-articular fusion. Statistical analysis done with SPSS-20.0 with Student t test and ANOVA to assess level of statistical significance [p < 0.05]. Results: 82 consecutive cases (M;F = 3;1, Mean age = 36.26 ± 5.78 years) were evaluated. Total of 163 Trans articular screws were placed. Significant improvement was noticed in clinical (mean pre operative/post operative VAS = 7.2 ± 2.19 / 3.3 ± 1.12, pre/post operative ODI = 78.3 ± 4.83 / 34.05 ± 3.26) and neurological features (mean pre operative/post operative mJOA = 14.73 ± 2.68 / 17.5 ± 2.21). Radiological evidence of fusion was noted in 97.5% cases at final follow up. 17 patients did not show inter-spinous fusion on X-Rays but CT scan revealed facet fusion in all of them except two. Inadvertent Vertebral artery injury was noticed in 3 cases. Two of them were managed with Tamponade with screw itself as the bleeding occurred while drilling the path of second screw. In one patient screw insertion was avoided and additional wire fixation had to be done. Conclusions: Stand-alone TAS fixation with morcellised allograft provides excellent radiological and clinical outcomes. Addition of a supplementary tension band and structural graft are not essential. This provides the opportunity to avoid the complications associated with graft harvesting and wiring.

A016: Incidental Dural Tears during Bi-Portal Endoscopic Spine Surgery for Degenerative Lumbar Spine Diseases

Dae-Jung Choi¹

¹Orthopaedics, Spine Center, Barun Hospital, Jinju - Korea, Republic

Introduction: Incidental dural tears (IDTs) occur in 3-16% of open spine surgeries spinal surgery and 1.7-4.3% of percutaneous endoscopic spine surgeries ^1-3). Preventive strategies are important and essential during the endoscopic procedure, since conversion to open surgery for repair must necessitate a wider dissection and laminectomy and, consequently, persistent back pain may occur. Analyzing association of IDTs with specific operative maneuvers during biportal endoscopic spine surgery (BESS) would help surgeons to formulate strategies for decreasing their incidence. Material and Methods: We retrospectively reviewed all BESSs performed for degenerative lumbar spine diseases, including lumbar disc herniation (LDH), recurrent LDH, spinal stenosis with/without degenerative spondylolisthesis, and spondylolytic spondylolisthesis, from December. 2014 to December. 2016. Retrospective review of the causes of IDTs and the associated operative maneuvers during BESS by three surgeons were analyzed to modify the pattern of the procedures and the operative plan to prevent un-hopeful IDTs. Follow-up magnetic resonance imaging examination was performed at postoperative 2 or 3 days, 1 week, and 1 month postoperatively to determinate the success of the treatment. Results: There were 16 cases (1.2%) of IDTs in a total of 1351 operations. Of these, 10 (62.5%) occurred within the first 6-months during the learning curve. The IDT locations included 7 cases at central and 9 cases at lateral side to the dura. The Small-sized tears (≤ 10 mm) occurred in 13 cases; (11 slit tears and 2 flap tears) while, the Large-sized tears ( > 10 mm) occurred in 3 cases; (2 slit tears and 1 flap tear). Specific maneuvers associated with IDTs included punching under blurred vision (6 cases, 37.5%), curetting for adhesiolysis (4), direct injury to the central folding of the dura (2), burring over the dura after flavectomy (1), imprecise handling of the muscle dilator (1), laminectomized sharp bone-edges (1), and blind procedures under the ligamentum flavum (1). The initial treatments included mechanical packing with Gelfoam (7), Fibrin glue (6), immediate open repair (2), and blood patching for unnoticed IDT (1). The Success rate of the compression technique without direct suturing for small-sized IDTs less than 10 mm was 92.3% (12/13). Conversion to open repair was needed in 3 cases of large tears and one 1 case of small tear after failure of blood patching. There were no progression instances to wound infection or pyogenic spondylitis. Conclusion: Maintaining a clear surgical field during BESS is very important to prevent IDTs while securing saline outflow and maintaining thorough control of small bleeds. Small IDTs (≤10 mm) may be treated successfully with the compression technique even without direct suturing. Large-sized IDTs and large flap tears were recommended to open repair. Practiced handling of the surgical instruments safely and a thorough understanding of the surgical anatomy under a saline-filled surgical field may reduce the risk of IDTs during BESS, especially during the initial learning curve.

A017: Postoperative Pain Assessment after Full-Endoscopic Interlaminar Approach Comparing With a Mini-Open Microsurgical Technique for the Treatment of Lumbar Disc Disease

Miguel Casimiro¹

¹Neurosurgery Department, Hospital da Luz, Lisbon - Portugal

Introduction: Full-endoscopic interlaminar approach (FEIA) is a minimally invasive procedure indicated for treatment of lumbar disc herniation (LDH). Its benefits, comparing with minimally invasive microsurgical technique (MMST), are not yet well defined. Short-term pain and functional outcome are prospectively compared between two groups of patients with LDH, treated with FEIA or open MMST. Methods: All consecutive LDH patients treated through FEIA, were prospectively followed for one month. Clinical outcome parameters (low back and leg numeric rating scale (NRS) and Quebec Back Pain Disability Scale (QDS)) were measured pre and postoperatively. Analgesics use after surgery, was quantified. Results were compared with a cohort of patients treated, in the same period, trough MMST. Decision on the surgical technique to use relied only on endoscope availability. Prism7 v.7.0b, for Mac OS-X was used for statistical analysis. Results: 26 patients were treated through FEIA and 18 through MMST. Baseline patient characteristics were comparable. Sciatic pain was treated in both groups. Postoperative back pain, was significantly lower in FEIA group (NRS: 1.5, 0.3 and 0.2 at one, two and four weeks after FEIA vs 3.6, 2.4 and 1.6 respectively after MMST). 61.5% of FEIA patients didn’t take any pain medication. The average number of painkillers taken within 30 days was 4.0 in FEIA group and 27.2 in MMST. The average QDS reduced from 57.7 to 25.0, 18.0 and 14.2 at one, two and four weeks after FEIA comparing with 58.8 to 41.1, 34.7 and 23.0 respectively in MMST group. No approach related complications were reported. Conclusions: With less use of analgesics, back and leg pain relieve in endoscopic treated patients, after one week, was only comparable to that achieved by the MMST group after one month. Moreover, that was also true for the overall ability to perform their daily activities.

A018: Strategies of Anesthesia in Percutaneous Endoscopic Lumbar Discectomy

Xiaofeng Lian¹, Bo Liang¹, Guowang Zhang¹, Jianguang Xu¹

¹Department of Orthopedics, Shanghai Sixth People’s Hospital, Shanghai - China

Purpose: To investigate the effect of different patterns of anesthesia on percutaneous endoscopic lumbar discectomy. Methods: We retrospectively analyzed the data of the patients with lumbar disc herniation and radiculopathy who were treated with percutaneous endoscopic lumbar discectomy in our hospital from March 2016 to March 2017. Totally 213 patients were enrolled in the present study, including 101 males and 112 females with an average age of 39.8(12-82). The patients were divided into four groups: group A, 151 patients who received percutaneous endoscopic transforaminal discectomy (PETD); group B, 33 patients who received percutaneous endoscopic interlaminar discectomy (PEID); group C, 18 patients who received PETD on two segments at the same time; group D, 11 patients who both received PETD and PEID on two different segments at the same time. The effect of anesthesia, as well as anesthesia and surgery related complications in four groups were evaluated. Results: For all 213 patients, local infiltration anesthesia was adopted for 191 patients (89.7%), general anesthesia was used for 22 patients (10.3%). In group A, there were 138 local infiltration anesthesia (91.4%) and 13 general anesthesia (8.6%). Among patients who received local infiltration anesthesia, 12 patients need extra intravenous-injected fentanyl to complete the surgery (9.4%), and 2 patients exhibited transient unconsciousness during the surgery (one 76 years old male and one 77 years old female), though, surgeries were completed after that. In group B, there were 5 general anesthesia (15.2%) and 28 local infiltration anesthesia (84.8%). Among objectives using local infiltration anesthesia, extra intravenous-injected fentanyl was demanded by 3 patients (10.7%). In group C, there were 2 general anesthesia (11.1%) and 16 local infiltration anesthesia (88.9%). In group D, here were 2 general anesthesia (18.2%) and 9 local infiltration anesthesia (81.8%). Among local infiltration anesthesia adopted ones, one patient need extra intravenous-injected fentanyl, and one patient’s surgery was ceased and transferred to general anesthesia due to intolerable pain. In total, in all 213 patients, excepted for one patient changed from local anesthesia to general anesthesia due to intolerable pain, surgeries were completed successfully on other 212 patients (99.5%). Two elder patients in group A exhibited transient unconsciousness during the surgery, but they recovered quickly and surgeries were continued and finished, and not any sequela was demonstrated. Complications such as nerve injury, cerebrospinal fluid leakage and infection were not seen in all patients. Conclusions: As for percutaneous endoscopic lumbar discectomy, around 90% could be completed under local infiltration anesthesia, and extra intravenous-injected fentanyl would be recommended if there were any intense pain during the surgery. For elder patients, general anesthesia was recommended. For PETD surgery, general anesthesia was safe and effective. For PEID, local infiltration anesthesia was effective and safe for most of the patients.

Degenerative Cervical 1

A019: Serum Biomarkers in Patients with Ossification of the Posterior Longitudinal Ligament (OPLL)

Yoshiharu Kawaguchi¹, Isao Kitajima², Masato Nakano¹, Taketoshi Yasuda¹, Shoji Seki¹, Kayo Suzuki¹, Yasuhito Yahara¹, Hiroto Makino¹, Kenji Kobayashi¹, Tomoatsu Kimura¹

¹Department of Orthopaedic Surgery, Toyama University, Toyama - Japan ²Department of Clinical Laboratory Medicine, University of Toyama, Toyama - Japan

Introduction: Ossification of the posterior longitudinal ligament (OPLL) is characterized by replacement of ligamentous tissue by ectopic new bone formation, causing myelopathy and/or radiculopathy. However, the pathogenesis of OPLL has not been fully elucidated. Previous study has demonstrated that the CRP level is increased in heterotopic ossification after total hip replacement. Thus, it is hypothesized that CRP might be increased, because of the ectopic bone formation in the spinal ligaments. The present study was prospectively designed to determine whether or not the serum CRP concentration, especially hypersensitive CRP (hs-CRP), and other biomarkers are altered in patients with OPLL in comparison with the age- and sex-matched controls. Further, if there is a difference in the serum hs-CRP concentration and/or other biomarkers, we analyzed the factors which were related to the difference. Material and Methods: 103 patients with OPLL were included in the patient group and 95 age- and sex-matched normal volunteers comprised the control group. 88 patients with OPLL who were available for more than 2 years follow up were checked for OPLL progression. Blood sample was obtained. Hs-CRP, and other routine data, including total protein (TP), albumin (ALB), lactate dehydrogenase (LDH), alkaline phosphatase (ALP), calcium (Ca), inorganic phosphate (Pi), white blood cell count (WBC), hemoglobin (Hb) and platelet (PLT), were checked. The data were compared between the patients with OPLL and the controls. Whole spine CT was obtained. The severity of the ossified lesions in the whole spine were evaluated by the ossification index (OS index) in patients with OPLL. The data were also compared between the patients with OPLL progression (the progression group) and the patients without OPLL progression (the non-progression group). Results: The mean hs-CRP in the OPLL group was higher than that in the controls (p = 0.047). The concentration of Pi in the OPLL group was lower than that in the control group (p = 0.02). A negative correlation was found between the Pi and the OS index (p < 0.001, r = -0.51). 88 patients could be followed more than 2 years. 32 patients (36%) out of 88 patients had OPLL progression during follow up period. The mean hs-CRP in the progression group was higher than that in the none progression group (p = 0.0013). The average length of the OPLL progression was 6.4 ± 4.2 mm, ranged from 2 to 21 mm. There was positive correlation between the average length of the OPLL progression per year and the hs-CRP (p = 0.045, r = 0.36). Conclusion: The occurrence of local inflammation might be suggested in OPLL and the inflammation might cause OPLL progression. Therefore, hs-CRP might be a useful marker to predict OPLL progression. The serum concentration of Pi was lower in the patients with OPLL and a negative correlation was found between the serum concentration of Pi and the severity of OPLL. These facts are important for understanding the pathogenesis of OPLL.

A020: Lateral Mass Screw Fixation in Cervical Spine: Introducing a New Technique

Sandip Chatterjee¹, Ariful Islam²

¹Department of Neurosurgery, Park Clinic, Kolkata, Kolkata - India ²Spine Fellow, Park Clinic, Department of Neurosurgery, Kolkata - India

Introduction: Lateral mass screw fixation is now one of the commonest surgeries performed in cervical spine. The objective of this study to find out an alternative technique of introducing lateral mass screws which utilizes the maximum possible dimension of the lateral mass and ensures the same safety standards provided by other techniques. Material and Methods: From Jan 2009 to August 2017, total 176 patients were recruited for this study. They were randomized to have lateral mass screws inserted by our technique or by classical Magerl technique. In study group of 88 patients, a total number of 664 screws were inserted by our technique and in control group of 88 patient, total 604 screws were inserted by classical Magerl technique. Intraoperative measurement was used to assess the bone screw interface length. Bicortical purchase was ensured in all cases. Post- operative x- ray and CT scans were used to assess the trajectory of the screws. Results: The average bicortical screw length in our study group was 19.77 at c3, 20.03 at c4, 20.11 at c5, and 19.93 at c6. The average screw length was 19.96 i.e. approximately 20 mm. this contrasted significantly with the average length of screws in patients we had inserted using the classical Magerl technique in the control group where we looked at the similar number of patient having average screws length at c3 was16 mm, at c4 17.4 mm at c5 17.31 and at c6 16.72. Conclusion: There is no doubt that a trajectory which involves an entry point in the posterior inferior medial angle of the lateral mass cuboid and which traverses a distance of around 20 mm to obtain a bicortical purchase in the diagonally opposite angle can provide a much better and firmer bony purchase in the lateral mass compared to conventional points of entry and conventional trajectories which achieve a much shorter screw length. Moreover the undoubted safety of this technique makes us recommend it to every surgeon desirous of inserting lateral mass screws.

A021: Cervical Hybrid Laminoplasty vs Laminectomy: Correlation Among the Extent of Posterior Spinal Cord Drifting, the Dural Sac Diameter, the Presence of C5 Palsy and Spinal Cord Alignment a Retrospective Comparative Study Between the Two Techniques

Michele Federico Pecoraro¹, Fabio Cofano¹, Federica Penner¹, Giovanni Vercelli¹, Nicola Marengo¹, Marco Ajello¹, Francesco Zenga¹, Alessandro Ducati¹, Diego Garbossa¹

¹Department of Neurosurgery, University of Torino, Torino - Italy

Introduction: The end point for treatment of multilevel spondylotic myelopathy is to adequately decompress the spinal canal with different posterior approaches (laminectomy or laminoplasty). Nevertheless it is difficult to predict the dorsal migration of the spinal cord during surgery and prevent possible clinical complications such as C5 palsy. It is well known from the literature that there are no significant differences in clinical outcome between the two techniques. Though, laminectomy procedure is associated to a higher incidence of C5 palsy probably caused by an excessive expansion of the spinal cord. In this study the extent of the spinal cord migration is evaluated by comparing the spinal cord shinft in laminectomy vs hybrid open door laminoplasty and its possible clinical implications on the surgical planning. Materials and Methods: A retrospective review of 40 consecutive patients, who had undergone cervical laminectomy (L) or hybrid laminoplasty (HLP) was performed. Three main radiological parameters were used to evaluate the position of the spinal cord after surgery: spinal cord shift at every single decompressed level, dural sac diameter and C3-C7 spinal cord lordosis angle (SCLA). To evaluate the clinical outcome, the Modified Japanese Orthopedic Association (mJOA) was used. Axial symptoms were evaluated by the 10-point visual analog scale (VAS). The number of C5 nerve root palsy (at least 1 grade on MMT) was recorded for both groups. Results: 20 patients had laminectomy (L) and 20 had hybrid laminoplasty (HLP). Average follow up was 1 year and minimum period of 3 months. There were no statistically significant differences between the L and HLP group in terms of age, gender, follow-up duration, pre-operative diagnosis and pre-operative JOA score. There were 3 cases of post-operative C5 palsy in L group compared to none in HLP. According to literature the dural sac diameter can be considered as a predictive factor for posterior cord shift. In this study there was a significant correlation between the spinal cord shift and the dural sac expansion for every level in both groups. A higher postoperative dural sac diameter was found in the laminectomy group where a larger posterior shift was obtained. Plotting the amount of posterior shift at C5 vertebral level, the 3 cases with C5 palsy or C5 symptoms had the largest posterior shift in the Laminectomy group. In comparing patients with post-operative C5 palsy with those who did not acquire C5 palsy in the L group, dorsal migration was found to be significantly greater in the C5 palsy group at the levels of C4 (3,16 ± 0.65 mm vs 1.17 ± 0,36 mm, p = 0.00), C5 (4.,43 ± 0.11 mm vs 1.72 ± 0,81 mm, p = 0.00) and C6 (3,4 ± 0.43 mm vs 1,29 ± 0,34 mm, p = 0.00) as compared to the non-C5 palsy group. The relationship between spinal cord alignment and posterior shift at C5 had a significant but weak correlation Conclusions: The posterior shift of the spinal cord after laminectomy has a tendency to shift more posteriorly than that observed after cervical laminoplasty. C5 palsy may be prevented if the expansion of dura mater, which is strongly correlated with the posterior shift, can be controlled. Laminoplasty seems to be the best surgical procedure for patients with multilevel spondylotic myelopathy due to the possibility to control the postoperative spinal cord position more precisely by controlling the opening of the laminae with different sizes of lamina plates. This would allow to obtain a better neurological outcome and reduce the incidence of C5 nerve root palsy caused by excessive posterior shift of the spinal cord. This study could also confirm the C5 nerve tethering as main palsy mechanism after spinal cord drifting. To the best of the authors’ knowledge, there are no radiological studies comparing the results of decompression and its relation with clinical results between hybrid laminoplasty and laminectomy.

A022: Risk of Spring-Back Closure in Skipped-Level Plating for Open-door Laminoplasty: An Insight of its Cost-saving Potential

Jason Pui Yin Cheung¹, Prudence Wing Hang Cheung¹, Amy Yim Ling Cheung¹, Darren Lui¹, Kenneth Man-Chee Cheung¹

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

Introduction: The open-door laminoplasty technique is a commonly adopted posterior approach to decompression for cervical spondylotic myelopathy (CSM). Spring-back phenomenon is a major concern as closure of the lamina opening can cause recurrence of symptoms. Plating has since reduced the risk of spring-back but incurs higher costs. Providing the most cost-effective treatment is necessary at current medicine practice. For laminoplasty, the need for plating at every level of lamina opening is unknown. Hence, the aim of this study is to determine whether skipped-level plating can still avoid the risk of spring-back closure while maintaining adequate neurological recovery. Materials and Methods: Patients with CSM treated by open-door laminoplasty with 2-year postoperative follow-up were recruited. All patients had opening from C3-6 or C3-7 and were divided into skipped-level or all-level plating groups. Japanese Orthopaedic Association (JOA) scores were obtained preoperatively, immediate (within 1 week) postoperatively, and at 2 weeks, 6 weeks, 3, 6 and 12 months postoperatively. Recovery rate was calculated using the formula: recovery rate(%) = (postoperative JOA-preoperative JOA) / (17[full score]-preoperative JOA)x100. Similarly, cervical spine radiographs at each time-point were measured by three independent readers for the canal diameter. Comparisons of measurement between time-points allow determining of any spring-back closure, defined as > 1 mm loss of initial expansion. Statistical analyses included intraclass correlation coefficient (ICC) for inter-rater and intra-rater reliability; chi-square test of independence, Mann-Whitney U test and paired t-test for comparative analysis. Receiver operating characteristic (ROC) analysis was utilized to determine cut-off values of canal expansion with which spring-back occurred. Results: A total of 74 subjects (24% females) were included with mean age of 66.1 ± 11.3 years at surgery. 32 underwent skipped-level plating and 42 underwent all-level plating. Good intra-rater reliability was shown in both pre-operative (ICC: 0.826-0.915, p < 0.05) and post-operative measurements (ICC: 0.878-0.936 and 0.855-0.884 with p < 0.001 for all-level and skipped-level plating respectively) of canal diameter at all vertebral levels. No significant differences existed between the two groups at baseline and follow-up. Spring-back closure was observed in up to 50% of the non-plated levels within 3 months postoperatively. The cut-off for developing spring-back closure was 7 mm canal expansion for C3-6, with an area under the curve of 0.795 to 0.889, a sensitivity and specificity of 80.0 to 84.6% and 75.0 to 83.3% respectively. No differences were observed in JOA scores (p = 0.294-0.850) and recovery rates (p = 0.189-0.864) between the two groups at all postoperative time points. Conclusion: This is a novel study that presents compelling data that highlights the non-inferiority of patients undergoing different combinations of skipped-level plating as compared with all-level plating for laminoplasty. No significant differences between groups were observed for spring-back closure at all levels from C3-7 without plating. This has tremendous impact on saving costs in CSM management as up to two plates per patient undergoing a standard C3-6 laminoplasty may be omitted instead of four plates to every level to achieve similar clinical and radiological outcomes. In addition, a threshold of at least 7 mm canal expansion can be proposed to avoid spring-back closure.

A023: Are There Relationship Between Hyper Thoracic Kyphosis and Occipital-Cervical Junctional Fused Joint in Patients With Ankylosing Spondylitis?

Nodoka Manabe¹, Yohan Robinson², Augusto Covaro³

¹Department of Orthopaedic Surgery, Gunma Spine Center (Harunaso Hospital), Takasaki, Gunma - Japan ²Uppsala University, Dept. of Surgical Science, Uppsala - Sweden ³Institut Universitari Dexeus, Barcelona - Spain

Background: Ankylosing spondylitis (AS) affects the axial skeleton and leads to progressive ankylosis of all spinal segments. However, the progress of the ankylosis in the upper cervical spine is not well-documented. The aim of this study is to describe radiographical features of the relationship between hyper thoracic kyphosis and the occipito-cervical (OC) junction in AS patients using a novel measure, the X-angle. Materials and Methods: Patients with AS treated in a single institution for a cervical spinal fracture were followed prospectively using the SWESPINE registry. The integrity of the C0-C1-C2 joints was determined and classified into fused and non-fused joints. By determining the angle between C0-C1 and C1-C2 joints in the coronal view of the CT-scan (X-angle) the progressive degeneration of these joints was described. Intra- and inter-observer reliability of this test was determined. Results: 86 patients with surgically treated cervical fracture related to AS had a complete facet joint ankylosis between C3 and T1 due to their pathology. The most common level of fracture was at C6. The C0-C1 fused joint patients had hyper thoracic kyphosis compared with non fused group (p = 0.00). The X-angle was 125 degree in not fused patients and 136 degree in fused patients (p = 0.00). The intra- and inter-class reliabilities for X-angle measurement were very high (ICC = 0.95, 0.98). Conclusions: Hyper thoracic kyphosis was highly related with fused OC junctional joint in patients with AS. With the X-angle OC joint changes could be described with exceptionally high inter-observer validity.

A024: The Clinical and Radiological Features of Familial Cervical Ossification of Posterior Longitudinal Ligament

Yu Sun¹

¹Department of Orthopaedics, Peking University Third Hospital, Beijing - China

Objective: To reveal the clinical and radiological features of familial ossification of the posterior longitudinal ligament (OPLL) of the cervical spine. Method: Retrospective study. During the period of 2011 to 2016, the in-patients of cervical OPLL were screened for familial aggregation by asking family history. The familial OPLL was identified if two or more family members had OPLL history. Six patients and their families were indentified finally and their clinical and radiological data were collected.

Result

Radiological features. The prevalence of radiological OPLL was 33%(The ratio of male to female was 0.99). The average age of radiological OPLL was 49.5 years old. The average number of involved segments was about 3.6;and the average number of male to female was 3.8:3.4

Clinical features. The prevalence of symptomatic OPLL of the cervical spine was about 24.5%(The ratio of male to female was 1.04). The average age of the patients with symptomatic OPLL was 52.8 years old and the average number of involved segments was 4.3 (male: female 4.6:4.0). The average age of onset of symptomatic OPLL was 47.2 years old, of which the average age of the male was 50 years old; the average age of women was 44 years old.

The corresponding number and average age of the radiological OPLL is: Focal type 5 cases (aged 38), Segmental type 3 cases (aged 53), Continuous type 4 cases (aged 50), Mixed type 7 cases (aged 56). Among them, the younger generation of cervical spine OPLL was all focal type.

By observing 19 OPLL individuals, OPLL of the cervical spine was most likely to occur in the C4-C6 vertebra. C5 had the highest frequency (21.7%), and decreased in the upper and lower directions.

69% of patients had neck pain and 31% had myelopathy as the first symptom.

The incidence of all symptoms, respectively, from high to low: upper limb pain and numbness, dizziness or headache, neck pain or stiff neck, limb numbness and pain, chest and abdomen girdle feeling, cotton feeling, upper limb strength disorders, lower limb strength disorders, sphincter dysfunction disorders.

Conclusion

The prevalence of familial cervical OPLL was significantly higher than that in the general population, and there was no significant difference in gender.

Familial cervical OPLL usually early onset as a focal type, and most often located near the C5 segment. With the increase of age, more segments gradually involved; at the same time, the continuous type and mixed type were more common in familial cases.

The average age of the onset of familial cervical ossification of the posterior longitudinal ligament was younger than that of the general population.

The familial symptomatic OPLL of the cervical spine had the feature of slow onset and gradual aggravation.

Neck pain or stiff is the major onset symptom of familial cervical OPLL. With the development of the disease, upper limb pain and sensory disturbance are the most common symptoms.

Keywords: Familial Aggregation, Cervical Ossification of Posterior Longitudinal Ligament (OPLL), epidemiology, Imaging Features, Clinical Symptom Features

Disc Degeneration 1

A025: Mesenchymal Stem Cell-Seeded High-Density Collagen Gel for Annulus Fibrosus Repair: 6 Week Results From in Vivo Sheep Models

Ibrahim Hussain¹, Christoph Wipplinger¹, Stephen Sloan², Rodrigo Navarro-Ramirez¹, Eliana Kim¹, Micaella Zubkov¹, Gernot Lang¹, Lawrence Bonassar², Roger Hartl¹

¹Department of Neurological Surgery, Weill Cornell Medical College, New York - United States ²Department of Biomedical Engineering, Cornell University, Ithaca - United States

Introduction: Our group has previously shown successful in vivo annulus fibrosus (AF) repair in rodents and sheep models using acellular high-density collagen (HDC) gel. This gel sealed defects and preserved AF lamellar organization and nucleus pulposus (NP) hydration greater than untreated controls. We hypothesize that loading cells into the HDC gel will achieve faster and more robust annular repair. The objective of this study was to determine the effects of seeding allogeneic mesenchymal stem cells (MSCs) into HDC gels for annular repair to prevent degeneration of injured intervertebral discs (IVDs) in an in vivo sheep model. Material and Methods: 15 lumbar IVDs from three skeletally mature sheep were exposed via a lateral retroperitoneal pre-psoas approach. IVDs were randomized into 4 groups: 1) intact (N = 3); 2) injury only (3x10 mm annulotomy+100 mg nucleotomy)(N = 4); 3) injury+acellular HDC gel treatment (N = 4); and 4) injury+MSC-seeded HDC gel treatment (10⁶ MSCs/mL)(N = 4). After 6 weeks sheep were sacrificed. Disc height index (DHI) and Pfirrmann grading were performed using X-ray and 3 T MR images, respectively. Quantitative MRI analyses was completed using a MATLAB algorithm to measure NP area and T2 relaxation time (T2-RT). Values were calculated as ratios standardized with normal controls from the same sheep. Statistical analysis for DHI and quantitative MRI analyses was performed using ANOVA with Tukey’s HSD. The Kruskal-Wallis test with Mann-Whitney test was used to analyze Pfirrmann Grades. Quantitative histologic assessment was also performed using the validated Han score based on cellularity and morphology of the AF and NP. Results: For injury only IVDs, IVDs treated with acellular HDC gel, and IVDs treated with MSC-seeded HDC gel, DHIs were 0.846, 0.874, and 0.96, respectively (P = 0.00 274). The MSC-seeded HDC group displayed similar DHI to intact controls and significantly greater height than the acellular HDC and injury only groups. Average Pfirrmann grades were 2.5, 2.5, and 1.75, respectively (P = 0.00 035). Average NP area ratios were 0.868, 0.926, and 0.894, respectively (P = 0.636). Average T2-RT ratios were 0.784, 0.835, and 0.909, respectively (P = 0.0154). Injured IVDs exhibited ∼80% T2-RT of intact controls, while the MSC-seeded and acellular HDC groups averaged ∼90% and ∼85% of intact controls, respectively. There were no statistically significant differences in T2-RT between the MSC-seeded HDC group and intact controls. Average Han degeneration scores were 11.5, 10, and 9.5, but differences did not reach statistical significance. Conclusion: 6 weeks post-injury, the MSC-seeded HDC groups demonstrated less degeneration than the acellular HDC groups and injury-only IVDs based on radiographic and histologic assessments. These results are promising that HDC gel with MSC-cell augmentation results in more robust annular repair and mitigation of IVD degeneration in a shorter period of time, validating results in a large animal model. Increasing the number of animals analyzed and longer end-point analyses to 16 weeks post-injury are ongoing and may potentially provide a stepping stone for trialing this technology in humans.

A026: Toll-Like Receptor2 Activation Induces Human Intervertebral Disc Degeneration

Emerson Krock¹, Derek Rosenzweig¹, Brooke Currie¹, Daniel Bisson¹, Jean Ouellet², Lisbet Haglund¹

¹Department of Surgery, McGill University, Montreal - Canada ²McGill Scoliosis and Spine Research Group, McGill University, Montreal - Canada

Introduction: Intervertebral disc is characterized by breakdown of the extracellular matrix (ECM) of the nucleus pulposus (NP), which is composed of mainly collagen type II and proteoglycans like aggrecan. Furthermore, catabolic proteases, such as matrix metalloproteinases (MMP), and proinflammatory cytokines, including IL-1β and TNFα, increase during degeneration and contribute to ECM breakdown and development of pain. Neurotrophins, such as nerve growth factor (NGF), which is strongly linked to back pain, also increase. The early stages of disc degeneration that lead to these catabolic changes are poorly understood. However, toll-like receptor 2 (TLR2) has recently been suggested to play a role in disc degeneration. TLR2 was originally characterized in innate immunity, but is also activated by endogenous ligands found in discs that are termed ‘alarmins’ , such as fragmented hyaluronic acid, aggrecan, and fibronectin. TLR2 is expressed by NP cells of non-degenerating discs and activation of TLR2 on disc cells increases cytokines, proteases and neurotrophins.^3,4 Therefore, TLR2 may contribute to the early progression of disc degeneration and throughout the course the pathology. We therefore hypothesize that activation of TLR2 is sufficient to induce disc degeneration. Material and Methods: Intervertebral discs lacking visual and radiographic signs of degeneration from organ donors were used for cell culture or ex vivo whole disc organ culture. For organ culture, discs were excised from the spine. 3 discs from the same spine (n = 6 spines) were isolated and injected once in the NP region with either PBS, Pam2CSK4 (TLR2/6 agonist) or 30 kDa fibronectin fragments (FN-f, TLR2 and TLR4 agonist).⁵ NP GAG content was assessed with DMMB assay and Safranin-O staining. Release of ECM components and proteases into the conditioned culture media was analyzed by mass spectrometry. MMP3 and MMP13 were also analyzed with ELISAs. Proinflammatory cytokine secretion into conditioned media was quantified using protein arrays. Data was analyzed using GraphPad Prism v7, p < 0.05 was considered statistically significant and data was analyzed using one-way repeated-measures ANOVAs with a Tukey post-hoc test. Results: Discs injected with TLR2/6 agonists or FN-f had decreased GAG in the NP compared to PBS injected discs from the same spine. Safranin-O staining was also weaker in agonist injected discs, further indicating TLR activation leads to GAG loss. Increased levels of GAG and ECM proteins, such as collagen type II, were released into conditioned culture media according to DMMB and mass spectrometry, further suggesting TLR activation leads to matrix degradation. TLR2/6 agonists and FN-f also increased secretion of several proteases including MMP3 and 13, HTRA1, and cathepsin-D into culture media compared to PBS injected discs. Proinflammatory cytokines, such as IL-1 and -5, IFNγ, TNF and CXCL1, were increased in conditioned culture media from TLR2/6 agonist and FN-f injected discs compared to PBS. Conclusion: The current study showed that TLR2 activation is sufficient to induce degenerative changes in human discs and thus may play a role in the early stages of disc degeneration. Inhibition of TLR2 during early stages of disc degeneration could potentially slow degeneration and prevent the development of chronic low back pain.

A027: Comparison of Inflammaging in Cervical and Lumbar Degenerated Intervertebral Discs: Analysis of Proinflammatory Cytokine and Trp Channel Expression

Aleksandra Sadowska¹, Ermioni Touli², Wolfgang Hitzl³, Helen Greutert¹, Stephen J. Ferguson¹, Karin Wuertz-Kozak¹, Oliver N. Hausmann²

¹ETH, Department of Health Sciences and Technology, Zurich - Switzerland ²Klinik St. Anna-Hirslanden, Neuro- and Spine Center, Luzern - Switzerland ³Research Office (Biostatistics), Paracelsus Medical University, Salzburg - Austria

Introduction: Disc degeneration (DD) is an age-related process that occurs early in life and is associated with low back pain with approximately ∼80% of the population suffering from it at some point in their lifetime [1]. Certain individuals experience age-related chronic inflammation of the intervertebral disc (IVD), termed “inflammaging”, which is characterized by up-regulation of proinflammatory cytokines such as interleukin-6 (IL-6) [2, 3]. Due to their putative role in pain-transduction and inflammation, Transient Receptor Potential (TRP) channels may contribute to DD and discogenic pain and hence be of mechanistic relevance in disc inflammaging [4-7]. The aim of this study was to investigate and compare the occurrence of inflammatory processes in the sites of disc degeneration in the lumbar and cervical spine and to investigate the mechanistic involvement of Transient Receptor Potential Channels TRPC6 and TRPV4. Material and Methods: A total of 51 disc samples were obtained after informed consent from 45 patients (18 men, 27 women, mean age = 52) undergoing elective spinal surgery in the cervical (n = 24) or lumbar (n = 21) region. The procedures were approved by the local ethical committee. Gene expression of inflammatory cytokines and TRP channels was analyzed for differences with regard to spinal level (lumbar vs cervical), pathology (disc herniation (DH) vs DD), Pfirrmann degeneration grade, Modic grade, age, sex, disc region (annulus fibrosus (AF) vs nucleus pulposus (NP)) and surgical extent. For statistical analysis, the Wilcoxon-matched pairs test, Mann-Whitney U test and Spearman correlation were used. All reported tests were two-sided, and p-values < 0.05 were considered as statistically significant. Results: Aside from genes with known implication in DD and DH, four previously unreported genes from the interferon and TRP families (IFNA1, IFNA8, IFNB1, TRPC6) could be detected. A correlation between gene expression and age (IL-15) as well as degeneration grade (IFNA1, IL-6, IL-15, TRPC6), but not Modic grade, was identified. Significant differences were detected between cervical and lumbar discs (IL-15), NP and AF (IL-6, TNF-α, TRPC6), single-level and multi-level surgery (IL-6, IL-8) as well as DD and DH (IL-8), while sex had no effect. Multiple gene-gene pair correlations, either between different cytokines or importantly also between cytokines and TRP channels, exist in the disc. Conclusion: Our study unveiled a potentially crucial role of Ca²⁺ permeable cation channels, specifically of TRPC6, in the disc inflammaging. Furthermore, we confirmed the presence of the pro-inflammatory cytokines IL-1B, TNF-α, IL-6 and IL-8 in degenerative disc disease and highlighted the expression and relevance of cytokines that have previously gained little or no attention in disc research (INFA1, IFNA8, INFB1, IL-15). Importantly, we were able to demonstrate that the expression of IL-15, INFA1, IL-6, IL-8 and TRPC6 was affected by central patient/tissue characteristics, such as the degeneration grade, age, spinal level and/or pathology. These molecules may hence constitute targets to modulate the process of disc degeneration and pain development.

References

1. Walker, B.F., The prevalence of low back pain: a systematic review of the literature from 1966 to 1998. J Spinal Disord, 2000. 13(3): p. 205-17.

2. Franceschi, C. and M. Bonafe, Centenarians as a model for healthy aging. Biochemical Society Transactions, 2003. 31: p. 457-461.

3. Musumeci, G., et al., Osteoarthritis in the XXIst century: risk factors and behaviours that influence disease onset and progression. Int J Mol Sci, 2015. 16(3): p. 6093-112.

4. Schumacher, M.A., Transient receptor potential channels in pain and inflammation: therapeutic opportunities. Pain Pract, 2010. 10(3): p. 185-200.

5. Flockerzi, V. and B. Nilius, Transient Receptor Potential (TRP) Channels 2006, Berlin: Springer.

6. Parenti, A., et al., What is the evidence for the role of TRP channels in inflammatory and immune cells? British Journal of Pharmacology, 2016. 173(6): p. 953-969.

7. Walter, B.A., et al., Reduced tissue osmolarity increases TRPV4 expression and pro-inflammatory cytokines in intervertebral disc cells. Eur Cell Mater, 2016. 32: p. 123-36.

A028: High Resolution Imaging With 9.4 T MRI and Complementary Specialised Microscopy Provides New Insights Into The Structure of the Intervertebral Disc

Idrees Sher¹, Mustafa Sher², Chris Daly³, David Oehme⁴, Peter Ghosh⁵, Alex Fulcher⁶, Ronil V. Chandra⁷, Julian Smith³, Tony Goldschlager⁸

¹Department of Neurosurgery, Melbourne - Australia ²Faculty of Medicine, Griffith University, Gold Coast - Australia ³Department of Surgery, Monash Medical Centre, Melbourne - Australia ⁴Department of Neurosurgery, St Vincent’s Hospital, Melbourne - Australia ⁵Proteobioactives Pty Ltd, Sydney - Australia ⁶Monash Micro Imaging, Monash University, Melbourne - Australia ⁷Department of Radiology, Monash Medical Centre, Melbourne - Australia ⁸Department of Neurosurgery, Monash Medical Centre, Melbourne - Australia

Introduction: The intervertebral disc is integral to the stability, flexibility and function of the spine. However, despite technological advances the common understanding of the anatomy of the intervertebral disc is that of a bi-layered structure consisting of the annulus fibrosus (AF) and nucleus pulposus (NP). Some groups have demonstrated a histological tri-layered structure with division of the AF into outer annular (OA) and inner annular (IA) segments. We performed a qualitative laboratory based animal study using 9.4 T MRI, light microscopy histology, immunohistochemistry and polarised microscopy revealing new insights into the microarchitecture of the intervertebral disc. We demonstrated five distinct regions with each layer possessing unique anatomical properties that underpin its physiological and biomechanical function in health and disease. Materials and Methods: 30 lumbar intervertebral discs from 6 mature ewes involved in a cellular regenerative study were acquired at necropsy. Lumbar discs L2/3, L3/4 and L4/5 in all ewes had been exposed to a validated injury model consisting of a 6 x 20 mm incision into the AF via an anterolateral retroperitoneal approach, whilst discs L1/2 and L5/6 served as uninjured controls. Disc degeneration had been allowed to progress naturally up to 3 months. 9.4 T MRI was applied to all discs followed by careful preparation for microanatomical analysis. 5 micron thick slides were acquired consisting of vertebral body-disc-vertebral body using a standard rotatory microtome and prepared for histological analyses, immunohistochemistry and polarised microscopy. Results: The 9.4 T MRI provided high resolution images of the intervertebral disc demonstrating exceptional anatomical detail that surpassed any previously demonstrated by radiological techniques. Radiological confirmation of sinuvertebral nerve and perforating artery penetration of the degenerate intervertebral discs was confirmed radiologically for the first time providing new insights into the physiological processes that take place during disc degeneration. Furthermore, we were able to radiologically demonstrate a collagenous structure to the NP. Early changes in the transitional zone (TZ) of control discs provides insight into possible early degenerative changes in this region in adjacent level degenerative disc disease. The 9.4 T MRI findings were complemented by histology and polarised birefringence microscopy demonstrating 5 discrete microanatomical regions of the intervertebral discs consisting of the OA, IA, TZ, and peripheral and central NP (pNP and cNP respectively). The lamellation of the TZ could be clearly distinguished from the IA and OA. The pNP consists of a proteoglycan rich matrix with distinct concentric collagenous sheets forming a lattice of linearly arranged chondrocytes and admixed notochordal cells. This structure is completely lost in the cNP, a region focally exposed to multidimensional forces. Conclusion: 9.4 T MRI in conjunction with modern histological techniques and polarised microscopy provide novel insights into the architecture of the intervertebral disc, defining 5 distinct regions that underpin it’s biomechanical and physiological properties.

A029: Identifying the Expression of Newly Defined Phenotype of Young Healthy Nucleus Pulposus Cells Under Normoxic and Hypoxic Culture Conditions

Arjun Sinkemani¹, Feng Wang¹, Zhi-Yang Xie¹, Lu Chen¹, Cong Zhang¹, Xiao-Tao Wu¹

¹Department of Spine Surgery, Zhongda Hosptial, Southeast University School of Medicine, Nanjing - China

Introduction: The intervertebral disc (IVD) is situated between the vertebras of the spinal column. It is composed of cartilaginous connective tissues, which transfers loads, absorbs shocks and allows the movement and flexibility of the spine. The IVD is an avascular structure which consists of three distinct components: the central gelatinous nucleus pulposus (NP), surrounded by annulus fibrosus (AF) and the cartilaginous endplates which separates intervertebral disc and is linked to the vertebral bodies at the top and bottom. The intervertebral disc is completely avascular in nature¹; so the nucleus pulposus cells within the IVD live in a hypoxic environment with poor nutrition². The aim of this study was to determine the expression of the recommended newly defined young healthy nucleus pulposus cells phenotypes³ under normoxia (Nx) and hypoxia (Hx) culture conditions. Material and Methods: Nucleus pulposus cells were isolated from the Sprague-Dawley rats and cultured in 20% and 2% oxygen for 3 days. Quantitative real-time PCR (qPCR), western blot and immunofluorescence microscopy were used to identify the expression of the recommended newly defined young healthy nucleus pulposus cells phenotypes (aggrecan, brachyury, carbonic anhydrase 3, carbonic anhydrase 12, shh, CD24, collagen II, Glut-1, Hif-1α, Hif-2α, Cytokeratin 8, Cytokeratin 18 and Cytokeratin 19) respectively. Results: qPCR, western blot and immunofluorescence microscopy results showed that the recommended newly defined young healthy nucleus pulposus cells phenotypes were expressed both in the normoxia and hypoxia culture conditions. The expression of aggrecan, brachyury, carbonic anhydrase 3, carbonic anhydrase 12, CD24, collagen II, Glut-1, Hif-1α, Hif-2α, cytokeratin 8, cytokeratin 18, cytokeratin 19 and shh were significantly higher in the hypoxia culture condition compared to the normoxia culture group. The results were analyzed by using unpaired students’ t-test and p-values < 0.05 were considered significant. Conclusion: Nucleus pulposus cells cultured under normoxia and hypoxia conditions, the expressions of these newly defined young healthy nucleus pulposus cells phenotypes were significantly higher in hypoxic group compared to the normoxic group. This study showed that nucleus pulposus cells can be adapted in hypoxic microenvironment where hypoxia conduces nucleus pulposus cells to maintain their specific phenotypes that the nucleus pulposus cells grow in a unique microenvironment. Furthermore, it is confirmed that these recommended newly defined young healthy nucleus pulposus cells phenotypes can be used as phenotypic markers of nucleus pulposus cells.

Keywords: Intervertebral disc, nucleus pulposus cells, phenotypes, normoxia, hypoxia, microenvironment

References

1. Nerlich AG, Schaaf R, Walchli B, et al. 2007. Temporo-spatial distribution of blood vessels in human lumbar intervertebral discs. European spine journal: official publication of the European Spine Society, the European Spinal Deformity Society, and the European Section of the Cervical Spine Research Society 16:547-555.

2. Urban JP, Smith S, Fairbank JC. 2004. Nutrition of the intervertebral disc. Spine 29:2700-2709.

3. Risbud MV, Schoepflin ZR, Mwale F, et al. 2015. Defining the phenotype of young healthy nucleus pulposus cells: recommendations of the Spine Research Interest Group at the 2014 annual ORS meeting. Journal of orthopaedic research: official publication of the Orthopaedic Research Society 33:283-293.

A030: Autologous Nucleus Pulposus Cell-Seeded Hydrogel Delivery to Isolated Human Intervertebral Discs in Dynamic Culture Promotes Tissue Repair

Lisbet Haglund¹, Jean Ouellet², Derek Rosenzweig¹, Rayan Fairag¹, David Eglin³, Thomas Seffen⁴

¹Department of Surgery, McGill University, Montreal - Canada ²McGill Scoliosis and Spine Research Group, McGill University, Montreal - Canada ³AO Research Institute Davos, Davos - Switzerland ⁴The Orthopaedic Research Laboratory, McGill University, Montreal - Canada

Introduction: Current treatment options for painful IVD degeneration are either physiotherapy and pain management or invasive surgical procedures to remove the painful degenerate disc. Over the past decade, several high-level in vitro and in vivo animal studies have paved the way for novel tissue engineering strategies to repair or reverse painful IVD degeneration. However, translation to human IVD repair has not been as rapid. We previously developed a whole disc organ culture system for physiological loading of human IVDs and showed feasibility of monitoring cell injection therapy. Here we use our unique platform for determining NP cell biocompatibility and matrix production within a hydrogel. We also assess human disc repair whereby intact lumbar IVDs are harvested from organ donors and cultured under physiological conditions in a bioreactor system. Isolated autologous nucleus pulposus cells suspended in a hyaluronic acid thermo-responsive hydrogel were implanted into IVDs, cultured for 5 weeks and are being evaluated and quantified for tissue repair by both a novel T1ρ MRI sequence and histology. Material and Methods: Human lumbar IVDs were isolated from spine segments of consented Organ Donors. NP cells were isolated from adjacent IVDs of the same individual. Cells were first tested for viability and matrix production within hydrogels in vitro in a custom bioreactors system for 3 weeks. Human discs were scanned sagittal and axial planes using a custom quadrature volumetric coil in a 7 T Bruker Biospec 70/30 with AVIII electronics MRI using Bruker an issued T1ρ pulse sequences. Discs were then injected laterally with ∼500 µL of either HA-pNIPAM hydrogel alone or hydrogel seeded with 2 x 10⁶ cells/mL and placed in the bioreactor with intermittent cyclic load of 0.1-0.6 MPa. Discs underwent follow-up MRI and were then sectioned and stained with safranin-O and antibodies against collagen types I and II. T1ρ image quantification was performed using MIPAV software (NIH). Statistical analysis was performed using paired t-tests in Microsoft Excel. Results: The initial in vitro physiological culture of human NP cells seeded in hydrogel showed high levels of viability in both loaded and unloaded conditions. The loaded constructs generated more proteoglycan formation than the unloaded controls (Figure 1). T1ρ scans of human lumbar IVDs revealed high quality images of tissue health status which also showed “hot spots” in the NP which we then aimed to treat with either hydrogel alone or NP cell-seeded hydrogel. After 5 weeks of culture, post-treatment scans revealed increased signal in the treated discs corresponding to injected regions (Figure 2A). Image quantification showed significant improvement in T1ρ values for cell seeded hydrogels. Histological analysis Conclusion: This study show feasibility of assessing cell and biological therapy strategies in ex vivo isolated human lumbar IVDs under dynamic culture conditions for 5 weeks. This study focused on implantation of autologous NP cells within an injectable thermoresponsive hydrogel. Increased matrix and proteoglycan was detectable within the hydrogels using T1ρ MRI scanning and histological analysis suggesting enhanced tissue repair over hydrogel alone. Our current work demonstrates that this unique culture platform provides a pre-clinical ex vivo model system in combination with novel T1ρ MRI, the bioreactor provides an experimental platform for pre-clinical screening in human intact discs, which enhances directives towards future in vivo work.

Deformity - Thoracolumbar (Adult) - Surgical Outcomes

A031: A Pilot Study on Posterior Polyester Tethers as an Anti-Pjk Device For Multilevel Spinal Instrumentation for Adult Spinal Deformity

Thomas Buell¹, Avery Buchholz², John Quinn³, Shay Bess⁴, Bret Line⁴, Christopher Ames⁵, Frank Schwab⁶, Virginie Lafage⁶, Christopher Shaffrey¹, Justin Smith¹

¹Department of Neurosurgery, University of Virginia, Charlottesville - United States ²Department of Neurosurgery, Medical University of South Carolina, Charleston - United States ³Department of Neurosurgery, University of Texas Houston, Houston - United States ⁴Denver International Spine Center, Denver - United States ⁵Department of Neurosurgery, University of California San Francisco, San Francisco - United States ⁶Department of Orthopedics, Hospital for Special Surgery, New York - United States

Introduction: Proximal junctional kyphosis (PJK) is a common problem after multilevel spine instrumentation. The purpose of this study was to determine the effect of posterior polyester junctional tethers on PJK for adult spinal deformity (ASD). Material and Methods: We performed a single-center, retrospective review of ASD patients who met the following criteria: age > 18 years, instrumented segmental posterior fusion at minimum > 6 motion segments, thoracic upper-most instrumented vertebrae (UIV), pedicle screw instrumentation without transitional rods or interlaminar hooks at the UIV, and minimum 3-month follow-up (majority of PJK occurs within 6 weeks of surgery). Patients were divided into 3 groups: no tether (NT), Mersilene tape only (MO; passed through base of UIV+1 and UIV-2 and tied securely), and Mersilene with crosslink (MC; passed through base of UIV+1 and tied to crosslink between UIV-2 and UIV-3). Proximal junctional angle (PJA) was measured from UIV inferior endplate to UIV+2 superior endplate. PJK was defined as PJA ≥ 10° and ≥ 10° greater than the corresponding preoperative measurement. Results: 184 (96%) of 191 consecutive patients met inclusion criteria and achieved minimum 3-month follow-up (mean = 20 months [range: 3-56 months]; mean age = 66 years; 67.4% female). There were no significant differences among NT, MO, and MC groups based on age (p = 0.944), gender (p = 0.895), body mass index (p = 0.144), number of instrumented vertebrae (p = 0.192), pelvic fixation (p = 0.136), use of 3-column osteotomy (p = 0.153), use of combined anterior-posterior approach (p = 0.252), and sagittal plane radiographic parameters. PJK rates were 45.3% (29/64), 34.4% (22/64), and 17.9% (10/56) for NT, MO, and MC, respectively. PJK rate for MC was significantly lower than NT (p = 0.001; OR = 3.81). MC tethers significantly reduced postoperative change in PJA compared to MO and NT (p = 0.011). Kaplan-Meier analysis showed a significant time-dependent reduction in PJK for MC compared to NT (log rank test, p = 0.010). There were no significant differences in time-to-PJK or revision surgery for proximal junctional failure among cohorts. No complications due to tether use were identified. Conclusion: Use of junctional tethers for long-segment posterior fusion for ASD significantly reduced the occurrence of PJK. This difference was progressive from NT to MO to MC cohorts, but only reached statistical significance for NT versus MC. These findings suggest potential benefit of junctional tethers to reduce PJK, and that future prospective studies with longer-term follow-up are warranted.

A032: The Safety and Efficacy of CT-Guided, Fluoroscopy-Free Vertebroplasty in Adult Spinal Deformity Surgery

Corinna Zygourakis¹, Anthony DiGiorgio², Clifford Crutcher³, Michael Safaee⁴, Fred Nicholls⁵, Cecilia Dalle Ore³, Vedat Deviren⁶, Christopher Ames³

¹Department of Neurosurgery, Johns Hopkins Hospital - United States ²Department of Neurosurgery, Louisiana State University Health Sciences Center - United States ³- ⁴Department of Neurosurgery, University of California, San Francisco - United States ⁵Department of Surgery, Division of Orthopaedic Surgery, University of Calgary - Canada ⁶Department of Orthopedic Surgery, University of California, San Francisco - United States

Introduction: Proximal junctional kyphosis (PJK) is one of the most common, morbid, and costly complications of adult spinal deformity surgery. The goal of this study is to analyze the safety and efficacy of a novel technique of CT-guided, fluoroscopy-free vertebroplasty as an adjunct to help prevent PJK in long-segment posterior spinal fusions. Material and Methods: We performed a retrospective analysis of 118 consecutive adult spinal deformity patients who underwent long-segment fusion with vertebroplasty augmentation from 2013-2016 at a single institution. For each patient, we collected demographics, surgical information (anterior/posterior versus posterior approach, use of interbody fusion device, use of ligamentoplasty augmentation, and whether or not decompression was performed), length of stay, discharge disposition, and complications, including reoperation, PJK, and PJK requiring reoperation. We reviewed all post-operative radiographs to assess for cement leakage from vertebroplasty. These patients were compared to a historical control of 253 patients who underwent adult spinal deformity surgery without vertebroplasty augmentation from 2004-2013 at our institution. Results: 118 patients (77 females, 41 males) underwent posterior spinal instrumentation with fluoroscopy-free vertebroplasty, the majority with ligamentoplasty, interbody fusion, and decompressions. More than half of the patients (52%) had no radiographic evidence of cement leakage, and none of the patients were symptomatic from this leakage. The PJK rate of 14% and the PJK requiring re-operation rate of 3% in this cohort of patients who underwent vertebroplasty-augmented fusion was significantly lower than that of the 253 historical controls at our institution who did not undergo vertebroplasty (40% PJK rate, 17% PJK-rate requiring re-operation; both p < 0.001). After controlling for patient and other surgical factors in multivariate analyses, vertebroplasty was significantly associated with lower rates of PJK and PJK requiring re-operation (p < 0.001 and p = 0.003). Conclusion: Our novel vertebroplasty technique is safe and eliminates the need for additional fluoroscopy in cases already utilizing the O-arm to verify screw placement. In addition, it is an effective technique for reducing PJK in adult spinal deformity surgery when compared to historical institutional controls.

A033: Assessing the Influence of Diabetes and Cardiopulmonary Disease on Patient Reported Outcomes: Pre- And Post-Operatively

Eli Bunzel¹, Darrel S. Brodke², Ashley Neese², Yue Zhang³, Jared C. Reese¹, Nicholas Spina²

¹School of Medicine, University of Utah, Salt Lake City - United States ²Department of Orthopaedics, University of Utah, Salt Lake City - United States ³Division of Epidemiology, University of Utah, Salt Lake City - United States

Introduction: Adult Spinal Deformity (ASD) negatively impacts quality of life, yet the surgical correction of ASD has been associated with major complication rates as high as 30-50%¹; the magnitude of these procedures and complication rates highlight the importance of shared decision making and managed expectations between patient and physician. To adequately inform patients, we must understand how certain pre-operative factors influence disease presentation and post-operative outcomes. Recently, PROMIS Physical Function (PF) Computer Adaptive Testing (CAT) has gained popularity in measuring the health state of a patient’s physical function². PROMIS PF CAT has been shown to outperform the Oswestry Disability Index (ODI), a spine specific legacy patient reported outcome measure (PROM), in patients with lumbar spine pathology. Yet little is known about how PF CAT will change with surgical intervention or with various comorbidities³. This study aims to assess the effect of ASD surgical correction on PF CAT scores as well as the influence of diabetes and cardiopulmonary comorbidities on these PROMs. Materials and Methods: A retrospective review of all patients undergoing surgical correction of ASD from 2013-Present was performed to identify those who underwent fusion of at least 4 levels or greater. Patients with a primary diagnosis of tumor, infection, or trauma were excluded. PF CAT scores were obtained pre-operatively and post-operatively at 3, 6 and 12-month time periods. Patients with Diabetes Mellitus type 1 and 2, Heart Disease (history of MI, percutaneous coronary intervention for CHF, previous coronary artery bypass grafting), and COPD were identified based on ICD-9 and 10 documentation within the patient medical record. Linear Mixed Effect Models were performed to compare outcome scores in four cohorts: healthy cohort, diabetes mellitus, COPD and heart disease. These models were adjusted for age, gender, and BMI. Results: 180 patients met our inclusion criteria. The mean age was 66.8; 79 (44%) were male and 101 (56%) were female. Patients who reported no COPD (healthy) improved 6 points from their pre-operative PF CAT score (43.6) at 12 months post-op, while COPD patients (n = 10) decreased by 1.7 points at 12 months (p = .400) from their pre-operative PF CAT score (41.1). Conversely, ODI improved in both healthy and COPD cohorts by 12 months (p = .726). At 3 months, patients with Heart Disease (n = 37) saw a decrease in pre-operative PF CAT (37.6) of 0.8, but an overall improvement at 12 months similar to the healthy cohort (p = 0.433). ODI for Heart Disease patients improved steadily through 12 months, with a slower rate compared to the healthy cohort (p = 0.395). PF CAT and ODI scores for Diabetes Mellitus patients (n = 51) improved at a similar rate to the healthy cohort, but with a slower improvement in PF CAT from 6 to 12 months (p = 0.490). Statistical significance was not achieved. Conclusions: There appears to be a trend towards an impact of medical comorbidities on PF CAT scores, unlike the ODI. This seems to suggest that PF CAT is more sensitive to the effects of these disease states on their physical function domain compared to ODI.

References

1. Uribe JS, Deukmedjian AR, Mummaneni PV, Fu KM, Mundis GM Jr, Okonkwo DO, Kanter AS, Eastlack R, Wang MY, Anand N, Fessler RG, La MF, Park P, Lafage V, Deviren V, Bess S, Shaffrey CI (2014). Complications in adult spinal deformity surgery: an analysis of minimally invasive, hybrid, and open surgical techniques. Neurosurg Focus 5: E15

2. Brodke DJ, Saltzman CL, Brodke DS. PROMIS for Orthopaedic Outcomes Measurement. J Am Acad Orthop Surg. 2016;24(11):744-749.

3. Robert G. Whitmore, James H. Stephen, Coleen Vernick, Peter G. Campbell, Sanjay Yadla, George M. Ghobrial, Mitchell G. Maltenfort, John K. Ratliff. ASA grade and Charlson Comorbidity Index of spinal surgery patients: correlation with complications and societal costs. The Spine Journal. 2014;14(1):31-38.

A034: Impact of Three Column Osteotomy on Health Related Quality of Life Measures in Patients With Adult Spinal Deformity: A Systematic Review and Meta-Analysis

Muralidharan Venkatesan¹, Jagdeep Singh², Dani Pasku¹, Sarang Sapare¹, Nasir Quraishi¹

¹The Centre for Spinal Studies and Surgery, Queen’s Medical Centre, Nottingham - United Kingdom ²Guru Gobind Singh Medical College, Faridkot - India

Introduction: Three-column osteotomies (3-CO) have gained popularity in the last decade as surgical intervention for adult spinal deformity (ASD). 3-CO in the form of either Pedicle subtraction osteotomy (PSO) or vertebral column resection (VCR) is required to achieve adequate correction for severe and rigid deformity. The aim of the 3-CO is to correct and provide a balanced spine thereby improving pain and function. Studies reporting improvement in health related quality of life with validated outcome measures after 3-CO surgery are sparse and currently consist of small series. We conducted systematic review and meta-analysis to evaluate improvement in health related quality of life measures following 3-CO for adult spinal deformity. Materials and Methods: Two independent reviewers conducted systematic review of English literature between period 1996 and 2016 for articles reporting outcome of 3-CO in patients with ASD. Review was conducted according to PRISMA (Preferred Reporting Items for Systematic reviews and Meta-Analyses) guidelines using a PRISMA checklist. Inclusion criteria were studies reporting patient reported outcome (ODI, SRS 22, SF36) after 3-CO surgery for adult spine deformity patients (18 years or older) with a minimum follow-up of 1 year. A random effect model was used for meta-analysis to combine the studies for each outcome and forest plots were prepared. Outcomes were expressed as mean difference (MD). Results: Eight studies with 364 PSO and 63 VCR were included for the meta-analysis. The pooled mean for ODI was -15.1 (95% CI: -18.1 to -12.5) with negative value indicating mean drop in ODI scores from the pre-operative to the post-operative state and the mean effect size for SRS-22 was 0.61 with 95% CI 0.49-0.73. Conclusion: Three-column osteotomy surgery improves quality of life in patients with adult spinal deformity.

A035: Interbody Impaction Grafting in Adult Spinal Deformity: 2-Year Fusion Outcomes

Stephen Lewis¹, Colby Oitment¹, Robert Ravinsky¹

¹University Health Network, University of Toronto, Toronto - Canada

Introduction: Interbody fusion is typically performed with a cage, providing a stable conduit for bone to form between adjacent vertebral endplates. In addition to being expensive, cages depend on normal endplate and disc space geometry, and host bone stock. Impaction grafting is an inexpensive alternative for achieving interbody fusion which does not rely on these factors. This paper reviews the outcomes of impaction grafting from a single institution with respect to achieving radiographic union. Materials and Methods: The demographic, surgical and radiographic data from patients undergoing open Posterior Lumbar Interbody Fusion (PLIF) were retrieved from a prospective database of surgical procedures, having taken place between January 1st, 2012 and December 31st, 2014. After endplate preparation through a PLIF approach, patients underwent impaction of 20 to 30 cc of corticocancellous radiated allograft bone graft that was placed in a bone mill and then impacted through a 10 mm funnel into the disc space. Disc heights were measured using lateral lumbar radiographs pre-and postoperatively and compared to measurements made with Computed Tomography (CT) scans. CT scans were used to assess resorption in the first 6 post-operative months. Both resorption and fusion were assessed between 6-18 and greater than 18 months postoperatively. Results: 103 PLIFs were analyzed among 75 patients with a mean age of 60.0 ( ± 14.8) years. The population was predominantly female (2:1). Disc height was stable over time in all groups and there were no differences in disc height between those that fused (N = 42, $\stackrel{\text{x}}{¯}$ = 10.8 ± 2.9 mm) and those that did not (N = 26, $\stackrel{\text{x}}{¯}$ = 10.6 ± 3.9 mm) (p > 0.05). CT scans showed an immediate total resorption of impaction graft bone in 10% of patients, and sub-total resorption in another 10% within the first six postoperative months. This rate of resorption increased over time to a final rate of 56% of discs showing some degree of resorption. Despite this, solid interbody fusion occurred in 72% of patients and posterior inter-facet fusion occurred in 89% of patients. Qualitatively the graft initially appears as a solid mass on XR and CT and over time follows a pattern of resorption, re-organization and remodeling to take on a spongy appearance. Conclusion: While our total fusion rates are comparable to the literature, overall interbody fusion rates are lower than what is reported in the literature. Despite absorption, a high fusion rate was observed in this series, with maintenance of the disc height, suggesting the grafts served a load sharing function. This is the first study to observe the resorption period of impaction grafts which appears to increase during the first postoperative year.

A036: Biomechanical Assessment of Multi-Rod Instrumentation Techniques Following Pedicle Subtraction Osteotomy: a Finite Element Study

Ardalan Seyed Vosoughi¹, Amin Joukar¹, Ali Kiapour¹, Anand Agarwal¹, Vijay Goel¹, Joseph Zavatsky²

¹University of Toledo, Toledo - United States ²Spine and Scoliosis Specialists, Tampa - United States

Introduction: One major complication of pedicle subtraction osteotomy (PSO) is rod fracture, usually at the level of the PSO, with reported rates as high as 31.6%. The addition of satellite rods has been shown to decrease the rate of rod fracture. We evaluated different multi-rod instrumentation techniques, in a PSO model, using finite element modeling. Methods: A validated T10-pelvis model was used to develop a 30° PSO at L3. In addition to standard rod instrumentation from T10 to pelvis, various satellite rod configurations including medially, laterally, and posteriorly affixed accessory rods, along with the short rod technique described by Gupta were simulated. In medially and laterally affixed multi-rod constructs, satellite rods were connected to the primary rods above the L2 and below the L4 pedicle screws. In the posteriorly affixed configuration, satellite rods were affixed to the L1 and L5 screws. In the short rod technique, two additional recessed short rods spanned the L3 PSO level from L2 to L4. Loads for the FE models were applied in all degrees of freedom. Results: Adding 2 satellite rods medially, decreased flexion, extension, and axial rotation by 15%, 16%, and 8%, respectively. Lateral satellite rods decreased flexion, extension, and axial rotation by 11%, 12%, and 6%, respectively. Adding accessory rods posteriorly, reduced flexion and extension by 36%, lateral bending by 17%, and axial rotation by 10%. Utilizing the short-rod technique resulted in 11%, 4%, and 49% reduction in flexion, extension, and lateral bending motions, respectively, while the axial rotation motion increased by about 31%. Adding satellite rods decreased the maximum von Mises stress at the PSO region on the rods in all configurations. Table 1 shows the magnitudes and locations of the maximum von Mises stress recorded on the rods. Adding medial, lateral, and posterior satellite rods reduced the force acting across the osteotomy site by 16%, 11%, and 37%, respectively, while the short-rod technique resulted in similar forces. Discussion: Satellite rods increase the moment of inertia, which result in lower stress on the standard rods at the PSO region. The location of the maximum von Mises stress on the rods occurred adjacent to the domino connectors when used. Greater maximum von Mises stresses occurred on the medially affixed satellite rods at the PSO region, while in the laterally affixed multi-rod construct, greater stress was located on the primary rods. These data suggest a benefit in supplementing medial vs. lateral satellite rods at the PSO, so that if rod failure occurs, it should occur on the medially placed satellite rods, which are more easily replaced vs. primary rods. The short-rod technique, obviates the need for acute rod contouring at the PSO, leading to a reduction in the von Mises stresses. Additionally, except for the short-rod technique, all other multi-rod constructs decrease the magnitude of load acting on the osteotomy site, which may cause a delayed or non-union at the osteotomy site.

Table 1.

Location and magnitudes of the maximum von Mises stress on the rods.

Minimally Invasive Surgery 1

A037: Single Incision Mini-Open TLIF – a Modified Minimally Invasive Technique Clinico - Radiological Comparison With Traditional Open TLIF a Prospective Randomized Study

Nagendra Palukuri¹, Pravin Gupta¹, Rupinder Singh Chahal¹, Shankar Acharya¹, Kalra K L¹

¹Dept. of Spine Surgery, Sir Ganga Ram Hospital, New Delhi - India

Introduction: Many techniques of TLIF have been reported in literature ranging from traditional open, mini-open, and minimally invasive techniques. The traditional open TLIF (TO-TLIF) technique is associated with longer operative time, blood loss, hospital stay and longer recovery period while minimally invasive technique (MIS- TLIF) require special retractors, instruments and an unfamiliar paraspinal approach and also higher expenditure. In our study single incision mini-open technique (MO-TLIF) was used to minimize the disadvantages of both the techniques. The aim of this study is to compare clinical and radiological outcomes of mini-open TLIF with traditional open TLIF. Material and Methods: A Prospective randomized cohort study was done in patients diagnosed with degenerative disc disease, degenerative spondylolisthesis and isthmic spondylolisthesis in a tertiary care center. Patients were randomly allocated in two cohorts, one of which underwent TO-TLIF and the other MO-TLIF. Both cohorts consisted 26 patients each. Data was collected regarding pre- operative Visual Analogue Scale (VAS) (Back & leg), Oswestry Disability Index (ODI), and SF-36. Duration of surgery and intraoperative blood loss was recorded. Post-op drain output, difference in Pre & post- operative Hemoglobin, duration of hospital stay was recorded. Patients were followed up at two weeks, eight weeks, six months, one year for clinical outcomes quantified with VAS, ODI, SF-36 and radiological evaluation done at eight weeks, six months, one year follow up. Complications and fusion was compared between both the groups. Results: The minimum follow-up was 12 months. The mean estimated blood loss was 170 ml in MO-TLIF group and 480 ml in TO-TLIF group (p < 0.01). No patient in MO-TLIF group needed blood transfusion while 61.5% patient in open group needed transfusion (p < 0.01). Mean duration of hospital stay was significantly less in MO-TLIF group. Both groups showed significant improvement in symptoms compared to preoperative. MO-TLIF group showed significantly better (p < 0.01) VAS, ODI, & SF-36 scores at 2 weeks, 8 weeks, and 6 months follow up but the difference was statistically not significant (p > 0.05) at one year follow up. However, MO-TLIF patients showed significant early return to work (p < 0.03). Complication rates were higher in MO-TLIF group during the perioperative period, but not statistically significant. However, overall complication rates were similar in both the groups. Conclusion: Mini-open TLIF is feasible option to gain the benefits of minimally invasive technique that is reduced blood loss and early return to work at the same time reducing the cost. Long-term results are comparable in both the groups. However, a steep learning curve associated with this technique predispose it to slightly higher complications in early period.

A038: Percutaneous Vertebroplasty for Vertebral Compression Fracture in Glucocorticosteroid-Induced Osteoporosis: A Case-Control Study

Haolin Sun¹

¹Peking University First Hospital, Beijing - China

Introduction: To investigate the clinical characteristics of vertebral compression fracture(VCF) in glucocorticosteroid-induced osteoporosis(GIOP) and risk of vertebral refracture after percutaneous vertebroplasty(PVP). Methods: 570 cases who received PVP as treatments of VCF from January 2010 to December 2013 were retrospective reviewed, 42 cases were GIOP and 21 cases were followed up as GIOP group, other 528 cases were primary osteoporosis and 391 cases were followed up, 84 cases of them were selected based on age and gender as Control group. Compared the fracture location, ratio of single segment fracture and multiple segments fracture in two groups. In final follow up, compared the reoperation rate for vertebral refractures by the Kaplan-Meier method in two groups. Results: Follow up period were 24.0 ± 13.1 months in GIOP group and 25.8 ± 14.4 months in Control group (P > 0.05). In GIOP group, there were 11 cases with one-segment fracture, 2 cases with two-segments fracture, 3 cases with three-segments fracture, 2 cases with four-segments fracture, 2 cases with five-segments fracture and 1 case with eight-segments fracture. In Control group, there were 67 cases with one-segment fracture, 12 cases with two-segments fracture, 3 cases with three-segment fracture, 2 cases with four-segments fracture. The ratio of single segment fracture in GIOP group was significantly lower than that in Control group (52.4% vs 79.8%, P = 0.01). There were 50 fracture segments in GIOP group and 109 fracture segments in Control group. The ratio of fracture segments located in thoracic segments (T1-T10), thoracolumbar segments (T11-L1) and lumbar segments (L2-L5) was 18%, 46% and 36% in GIOP group and 11.9%,58.7% and 29.4% in Control group (P > 0.05). The refracture rate in GIOP group was higher than that in Control group (23.8% vs 6.0%). The survival rate is lower in GIOP group than that in Control group (P < 0.01). Conclusion: Predilection site of VCF was similar in GIOP and primary osteoporosis (thoracolumbar segments > thoracic segments > lumbar segments). The risk of multiple segments VCF was higher in GIOP than in primary osteoporosis. The risk of vertebral refractures after PVP was higher in GIOP than in primary osteoporosis.

Keywords: Vertebral compression fracture; Percutaneous vertebroplasty; Percutaneous kyphoplasty; Glucocorticosteroid-induced osteoporosis

A039: Incidence of Cranial Facet Joint Violation in Open Versus Minimally Invasive Screw Placement in Single Level Lumbar Fusion - Analysis of Risk Factors

Anil Solanki¹, Aditya Banta², Sandeep Kesharvani², Saumyajit Basu², Amitava Biswas²

¹Department of Spine Surgery, Park Clinic, Kolkata - India ²Department of Neuroscience, Park Clinic, Kolkata - India

Introduction: Cranial facet joint violation (FJV) can lead to accelerated Adjacent Segment Degeneration (ASD) –we compared the incidence of FJV in minimally invasive and open pedicle screw placement in single level lumbar fusions and evaluated the risk factors by a matched cohort study. Material and Methods: 30 patients (60 screws) in each group of open and minimally invasive placement having single level lumbar fusion for degenerative conditions between January 2013 to December 2015 were selected. Data was retrieved from the hospital electronic medical records and PACS. They were matched with respect to age, sex, level of fusion. Postoperative CT scans were assessed by two fellowship trained spine surgeons and one radiologist and FJV was graded as per Seo classification (0 = no impingement; 1 = screw thread or head in contact/suspected to be in contact with facet joint, 2 = screw thread or head clearly invading the facet joint). Unpaired t-test was used to compare continuous variables between two groups to match the two cohorts and Chi square test was used to determine FJV with respect to surgical technique (open vs minimally invasive), the joint violated (L3/4 vs L4/5), age (< 60 vs & > +60) sex (male vs female) and BMI (< 30 vs > = 30). Inter observer reliability was determined. Results: Cranial FJV occurred in 38.33% in the minimally invasive group (23/60, Grade1 = 15, Grade 2 = 8) and 51.67% in the open group (31/60, all grade 1), which was significantly higher (p < 0.0001). On analysis of risk factors for facet joint violation, patients with BMI > = 30 (vs. < 30) (90% vs 60%) and Age < = 60years (vs. > = 60) (71.73% vs. 42.85%) showed significant association for increased cranial FJV (P < 0.05). Male vs Female sex (66.33% vs. 66.67%) did not show any association with cranial FJV (p = 0.787). However, L4/5 facet joint (vs L3/4) (56.8% vs 37.5%) showed a greater propensity towards cranial FJV. Inter-observer reliability was fair (k = 0.60 - 0.68). Conclusion: Higher rate of cranial FJV was found in the open group though grade 2 violations were commoner in the minimally invasive group. Patients with increased BMI, L4/5 facet joint (as opposed to L3/4) and Age < = 60 years were independent risk factors while sex had no correlation. Surgeons should be extra cautious to avoid this complication during surgery and do some modification in entry point and trajectory in patients more likely to have proximal FJV to avoid ASD.

A040: Early Return to Work in Working Age Population After Minimally Invasive Transforaminal Lumbar Interbody Fusion Does not Translate to Superior Outcomes - A Five-Year Follow-Up Study

Ming Han Lincoln Liow¹, Graham Seow-Hng Goh¹, William Yeo¹, Zhixing Marcus Ling¹, Wai-Mun Yue¹, Chang Ming Guo¹, Seang Beng Tan¹

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

Introduction: Minimally invasive (MIS) transforaminal interbody fusion (TLIF) has been associated with accelerated return to work, potentially improving workplace productivity and reduction of indirect costs borne by patients and employers. However, a subgroup of working age adults do not return to work (RTW) as quickly as desired. The perioperative factors which influence RTW in MIS-TLIF are not well understood. The aim of our study is to: (1) determine the factors which influence RTW in patients undergoing MIS-TLIF and, (2) determine if early RTW plays a role in subsequent functional, patient-reported (PROM), health-related quality-of-life (HRQoL) and satisfaction/expectation fulfilment. Material and Methods: Prospectively collected registry data of 907 patients who underwent MIS-TLIF at a single institution from 2004-2013 were reviewed. Of these, 110 working adults who underwent a single level MIS-TLIF and had complete preoperative and 5-year postoperative follow-up data were included in our study. Patients were stratified into Early RTW (≤60 days, n = 40) and Late RTW ( > 60 days, n = 70). All patients were assessed pre- and post-operatively at two and five years, with numerical pain rating scale (NPRS back and leg pain), Oswestry Disability Index (ODI), Short-form 36 Physical and Mental component scores (SF-36 PCS and MCS), North American Spine Society (NASS) score for neurogenic symptoms (NS), return to work (RTW), return to function (RTF) and satisfaction/expectation fulfilment. Length of operation, length of stay and comorbidities were also recorded. Student’s T-test and Chi-Square test was used to compare parametric and proportion-based outcomes respectively between groups. Results: Preoperative factors affecting RTW. The Early RTW group had significantly lower ODI, NASS NS, NPRS back and leg pain scores than the Late RTW group ( < 0.01). In addition, the Early RTW group had high SF-36 PCS scores, suggesting that the group had less functional impairment and bodily pain than the Late RTW group. Effect of Early RTW on 5-year functional, PROM, HRQoL outcomes. There were no significant differences in ODI, NASS NS, SF-36 PCS/MCS and NPRS between the Early and Late RTW groups at 2-year and 5-year follow-up. Both groups reported similar proportions that RTW and RTF at 2-years and 5-years. There were no significant differences in satisfaction/expectation fulfilment between the Early and Late RTW groups. Conclusion: Working adults who RTW early after MIS-TLIF have superior preoperative PROM and HRQoL indices. However, early RTW does not predict or translate into better outcomes or higher rate of satisfaction for this class of patients. Conversely, late RTW in the working adult does not necessarily lead to an inferior result. Surgeons should be cognizant that working adults with poorer preoperative function will tend to return to work later, but should reassure them that they will likely have similar outcomes and satisfaction when compared to patients who are able to return to work early.

A041: Lumbar Ganglion Cyst: Nosology, Surgical Management And Proposal of a New Classification Based on 34 Personal Cases and Literature Review

Maurizio Domenicucci¹, Alessandro Ramieri²

¹Neurosurgery Sapienza University, Rome - Italy ²Don Gnocchi Foundation, Milan - Italy

Introduction: Different terms were used in literature to identify lumbar extradural cysts, without proposing a common scientific terminology. To our knowledge, a morphological classification of this pathology, that could be useful for clinical and surgical purposes, has never been realized. So, to clarify nosology, propose a new classification and describe the best surgical approach to remove these cysts, we review our experience and the pertinent literature. Methods: We retrospectively reviewed 34 patients with symptomatic lumbar ganglion cysts treated with spinal canal decompression with or without spinal fixation. Microsurgical approach was the main procedure and spinal instrumentation was required only in case of evident pre-operative segmental instability. Results: The complete cystectomy with histological examination was performed in all cases. All patients presented an improvement of clinical conditions, evaluated by VAS and JOA scoring. Conclusion: Spinal ganglion cysts are generally found in the lumbar spine. The treatment of choice is the microsurgical cystectomy, which generally does not require stabilization. The need for fusion must be carefully evaluated: pre-operative spondylolisthesis or a wide joint resection, during the operation, are the main indications for spinal instrumentation. We propose the terms “ganglion cyst” to finally identify this spinal pathology and for the first time its morphological classification, clinically useful for all specialists.

A042: Unilateral Versus Bilateral Percutaneous Kyphoplasty for Osteoporotic Vertebral Compression Fracture: A Meta-Analysis

Yun-lin Chen¹, Wei-yu Jiang¹, Wei-hu Ma¹

¹Department of Spinal Surgery, Ningbo No. 6 Hospital, Ningbo, China

Introductions: Osteoporotic vertebral compression fractures (OVCFs) are common in the elderly. Traditional bilateral PKP approaches were regarded as safe and effective. Nevertheless, unilateral PKP approaches were accepted attribute to surgical time, safety, and less expense. We performed the meta-analysis to compare the unilateral and bilateral PKP for patients with OVCF in terms of the short- and long-term clinical outcomes and complications. Methods: Randomized or non-randomized controlled trials published up to Jul. 2017 that compared the unilateral and bilateral PKP for the treatment of OVCF were included by a comprehensive search in the Cochrane, PubMed, MEDLINE, EMBASE, Web of Science, and CNKI. The main measure outcomes included: the short- and long-term postoperative Visual Analogue Scale (VAS) scores, the short-term postoperative Oswestry Disability Index (ODI), operation time, restoration rate, cement dosage and leakage, and postoperative adjacent-level fractures. Results: A total of 17 studies involving 1344 patients were included in the meta-analysis. The mean operative time and cement dosage were less in the unilateral groups compared with the bilateral groups (p < 0.05). Unilateral PKP had a better degree of pain relief (visual analog scale) than bilateral PKP (p = 0.05) with short-term follow-up (within 4 weeks) after operation. However, Bilateral PKP approach has high restoration rate (P < 0.01). There was no significant difference in the long-term postoperative VAS scores between them (P = 0.13), the short-term postoperative ODI (P = 0.75), risk ratio of cement leakage (p = 0.07) and postoperative adjacent-level fractures (p = 0.97) between the two groups. Conclusion: In conclusion, our meta-analysis showed unilateral PKP was associated with shorter operative time, lower VAS in the short-term and less dosage of PMMA than bilateral PKP. However, Bilateral PKP approach has high restoration rate. There was no significative difference in the long-term clinical outcomes and complications between them. More high-quality randomized controlled trails should be required to make sure which method is better for the treatment of OVCF in the future.

Degenerative Cervical 2

A043: To Plate or Not is Not a Question. Results With Non-Anchored Stand-Alone Titanium Cage Compared to Cage-Plate Constructs in One or Two Level Anterior Cervical Discectomy at 2 Year Follow-Up

Ankit Patel¹, Vishal Kundnani¹, Tarun Dusad¹, Gaurav Mehta¹, Mahendra Singh¹

¹Department of Orthopaedics & Spine Surgery, Bombay Hospital, Mumbai - India

Introduction: To compare perioperative parameters, clinico-radiographic outcomes, and complication rates of Non-Anchored stand-alone TITANIUM cervical cage (NAC) with those of anatomic cages with a titanium plate (CP) for anterior cervical discectomy and fusion (ACDF) for the treatment of one or two level cervical degenerative disc disease (DDD). Material and Methods: Between October 2009 and JULY 2015, 242 consecutive patients [157 males and 85 females; mean age 51.0 years (range 28-67 years)] with cervical DDD, who underwent surgery and were followed for more than 2 years (mean 31.1 months, range 24–47 months), were enrolled in this study and divided into the NON-ANCHORED cage group (NAC) and Cage-Plate group (CP). Results: The clinical and radiologic results in both groups were satisfactory after a minimum 2-year follow-up. No significant differences between the NAC group and CP group in terms of improvement in the SF-36, VAS, NDI, and JOA scores, Disc Height Index (DHI), mean fusion time, fusion rate, adjacent segment degeneration, and restoration of cervical lordosis. The NAC group fusion rates were 95.5% (149/156) vs 97.6% (84/86) and the radiologic mean fusion time was 9.9 months. From 3 months after surgery to final follow-up the DHI showed a significant reduction comparing 1 week after surgery [p < 0.05; Subsidence in NAC 10.2% vs 3.4% in CP Group] with all cases of subsidence attaining fusion. The NAC group was associated with a lower risk of postoperative dysphagia, shorter operation time, less blood loss, less cost of index surgery, and relatively greater simplicity than the CP group. Conclusion: The Non-Anchored Titanium cage for ACDF is an effective, reliable, and safe alternate to conventional method for treatment of cervical DDD. However, there is no definitive evidence that NA cervical cage has better intermediate-term outcomes than the Anchored stand-alone cages or a titanium cage-plate for ACDF.

A044: Comparison of Dynamic Cervical Implant Arthroplasty Versus Anterior Cervical Discectomy and Fusion for the Treatment of Single-Level Cervical Degenerative Disc Disease: A Minimal Five-Year Follow-Up

Ce Zhu¹, Xi Yang¹, Yueming Song¹, Limin Liu¹

¹Department of Orthopedics Surgery, West China Hospital, Sichuan University, Chengdu - China

Introduction: To compare clinical and radiographic outcomes at 5 years after surgery using dynamic cervical implant (DCI) with anterior cervical discectomy and fusion (ACDF) in the treatment of single-level cervical degenerative disc disease (CDDD). Material and Methods: Forty-three patients with DCI were matched one-to-one with patients with ACDF based on age, gender, and operative segment. All patients had been followed up for more than 5 years. Radiological assessments included intervertebral height (IH) and the range of motion (ROM) of C2-7, functional spinal unit (FSU) and adjacent levels. Clinical parameters included Visual analogue scale (VAS), Japanese Orthopedic Association (JOA) scores, Neck Disability Index (NDI) and Short Form-36 scores (SF-36). Patients were also asked to rate their postoperative satisfaction at final follow-up. Results: The postoperative ROM of C2-7 and FSU in DCI group were higher than that in ACDF group. The ROM of FSU in DCI group maintained at 2-year postoperatively but decreased at final follow-up (10.7° vs 4.5°). The rate of heterotopic ossification (HO) in DCI group was 46.5% (20/43). The JOA, VAS, NDI, and SF-36 scores were comparable between two groups and improved postoperatively. However, the proportion of patients who reported their level of satisfaction as being very satisfied, or somewhat satisfied was larger in ACDF group than that in DCI group (95.3% vs 79.1%). Conclusion: DCI resulted in better ROM of C2-7 and FSU than ACDF. The clinical outcomes were similar between two groups. However, the ROM of FSU decreased at final follow-up in DCI group, which may lower the degree of patients’ satisfaction.

A045: Clinical and Radiographic Outcome of Unilateral Open-Door Laminoplasty With Alternative Levels Centerpiece Mini-Plate Fixation for Cervical Compressive Myelopathy: A Five-Year Follow-Up Study

Linnan Wang¹, Lei Wang¹, Yue-ming Song¹, Li-min Liu¹, Tao Li¹, Xi Yang¹

¹West China Hospital, Chengdu - China,

Introduction: To evaluate the five year clinical and radiographic outcome of unilateral open-door laminoplasty with alternative levels centerpiece mini-plate fixation for cervical compressive myelopathy. Materials and Methods: From August 2009 to June 2010, 56 patients with cervical compressive myelopathy underwent unilateral open-door laminoplasty with alternative levels centerpiece mini-plate fixation with a mean age of 64.8 years. Clinical results were investigated including Japanese Orthopedic Association (JOA) scores, Neck Dysfunction Index (NDI), occurrences of complications and neurological deterioration. Radiographic results including cervical alignments, cervical range of motion (ROM), spinal canal enlargement and spinal cord decompression were assessed on X-ray, three-dimensional CT and MRI. Results: The mean follow-up period was 59.2 months (range 53-64 months), and all patients achieved osseous fusion at hinge side at an average of 6.8 months after operation. The average cost from admission to discharge is $9817.9. Compared to previous all-level fixation, the cost decreased nearly 40%. During the follow-up, all patients showed a significant improvement in the JOA score and NDI score. A 23.2% incidence of axial neck pain were also observed; Significant enlargement of the spinal canal and spinal cord drift was achieved and well maintained, overall cervical ROM decreased by 27.1% (mean 12.9° loss) at the final follow-up and cervical lordosis decreased slightly in all patients without statistic difference. No instrumentation failure or lamina reclosure was observed in our study. Comparing mini-plate segments and suture segments, the mean AP diameter and Pavlov’s ratio at the final follow-up showed no statistic difference, only open angle at the final follow-up showed significant decrease. Conclusions: Unilateral open-door laminoplasty with alternative levels centerpiece mini-plate fixation is a safe, effective and economical surgical method for cervical compressive myelopathy and the five year result is satisfactory.

A046: Usefulness and Trouble of Mini-Open Open Door Laminoplasty

Kanji Sasaki¹

¹Spine Center, Seirei Hamamatsu General Hosp., Hamamatsu - Japan

Introduction: Cervical spinal stenosis (including cervical spondylotic myelopathy (CSM) and ossification of posterior longitudinal ligament (OPLL)) is major disease and the surgeries for these diseases are widely needed. For most of the cases, we surgeon required to widen the canal from C3-C7 because most of the stenosis is not segmental but whole cervical canal (mainly from C3/4 to C6/7). Thus mini-open is not so major procedure and we select conventional laminoplasty (Hirabayashi’s procedure, Kurokawa’s procedure, etc.). Although these conventional laminoplasty resulted good result, we are often troubled with severe nape pain after surgery. We underwent mini-open procedure (skin incision: under 0.1 feet) and this report is to certify this procedure reduce nape pain. Material and Methods: We selected eighty-four cases with open door laminoplasty (LP) into criteria. The criteria included fifty-six male and twenty-eight female and the average age was 66.0 years old. All cases were undergone surgical laminoplasty from C3-C7 by single surgeon. Diagnoses were 75 CSM and 9 OPLL. 56 cases, we underwent mini-open open door LP (C3-7 Using titanium plate and screw, skin incision 0.1 feet). To practise the procedure, our intention is only to keep neck position a little extended and to use two right angled Gelpi retractors. We could finish only with these intention for all cases. For comparative cases, 28 cases were conventional open door LP (modified Hirabayashi’s procedure: C3-7 using hydroxyapatite brock and strings, skin incision is 0.2-0.3 feet). Any orthotics were not used after surgery. We compared surgical times, nape pain after surgery (VAS score), recovery rate of neurological deficit (JOA score), hospitalized duration and trouble during surgery. Results: The recovery rate at 1 month after surgery did not significantly differ (Conventional LP: 46% and mini-open LP: 55%). There were no cases of C5 palsy and worsened neurological deficit by surgery. Surgical time of mini open LP (average 61 min.) was significantly superior to conventional (72 min.) Although hospitalized duration was 7.0 days (mini open) and 8.7 days (conventional), the nape pain of the mini open group at discharge (VAS score: 2.3) was significantly less than conventional (3.0). For one case of mini-open, we underwent repeat surgery 2 weeks after surgery because of the impingement of spinous peocess and muscle. Conclusion: To tie hydroxyapatite brock and widened lamina in small incision is difficult and it is easy way to shorten skin incision with using plate and screw to keep lamina widened. Furthermore using plate and screw can be rigider fixation than using hydroxyapatite brock and strings. It can be better way to shorten hospitalized duration and nape pain. Mini-open LP is easy and safe methods.

A047: A Comparison of Clinical Outcome Between Stand-Alone Zero-Profile Implant Versus Cervical Plate Fixation in Single and Multilevel Anterior Cervical Discectomy and Fusion: an Institutional Analysis of 166 Patients

Samuel Sommaruga¹, Joaquin Camara-Quintana¹, Aria Nouri², Justin Virojanapa¹, Xin Sun¹, Luis Kolb¹, Kishan Patel¹, Julio Montejo¹, Patrick Tomak¹, Khalid Abbed¹, Joseph Cheng²

¹Department of Neurosurgery, Yale University, New Haven - United States ²Department of Neurosurgery, University of Cincinnati College of Medicine, Cincinnati - United States

Introduction: The stand-alone (SA) zero-profile implant has become an attractive alternative to cervical plating (CP) in anterior cervical discectomy and fusion (ACDF) for the treatment of degenerative cervical myelopathy (DCM) and degenerative cervical radiculopathy (DCR). Results to date have been mixed at best. We undertook an ambispective study to investigate differences in operative factors, neurological recovery and dysphagia between DCM and DCR patients receiving SA or CP. Material and Methods: We conducted a retrospective analysis of a prospective cohort of consecutive patients with DCM and DCR who underwent ACDF with SA or CP from January 2013 to December 2016. Demographic information was collected. Outcome measurements included: Bazaz dysphagia score at 3 months, post-operative steroid use, and Nurick grade at last follow-up. Neurological outcome was dichotomized with the Nurick grade. Assessments of differences between outcomes were performed using the Fisher exact test for categorical variables and the Mann-Whitney U test for continuous variables. A p < 0.2 was used to select variables for inclusion in the multivariate logistic regression model. A multivariate logistic regression model was constructed using variables that reached the predetermined significance level in the univariate analysis. Results: Of the 166 patients (92 females and 74 males) ranging in age from 23 to 85 years (mean = 53 years), 84 (51%) presented with radiculopathy, 36 (21%) with myelopathy, 35 (21%) with myeloradiculopathy and 11 (7%) with intractable pain. From this group, 85 patients (51%) received surgical treatment at 1 level, 65 patients (39%) at 2 levels, and 16 patients (10%) at 3 levels. The average time of surgery was 150 ( ± 64) minutes, with a statistically significant (p-value = 2.5x10^-9) longer average time of 195 ( ± 70) minutes for CP vs. 127 ( ± 46) minutes for SA. The SA group had a statistically significant (p-value = 0.024) shorter length of stay (1.5 ± 1 day) than the CP group (2.1 ± 2 days), and the length of stay of the total population was (1.7 ± 1 days). At 3 months’ follow-up, 84 patients (51%) had a complete follow up, for dysphagia. Four patients reported mild dysphagia, and none reported moderate or severe dysphagia. However, all 4 patients recovered at their last follow-up. Baseline Nurick grade was 1 for 89 patients (54%), 2 for 63 patients (38%), 3 for 10 patients (6%), 4 for 3 patients (2%) and 6 for 1 patient ( < 1%). The Nurick grade at last follow-up was 0 for 131 patients (79%), 1 for 25 patients (25%), 2 for 7 patients (4%), 3 for 2 patients ( < 1%), and 6 for 1 patient ( < 1%). Nurick grade improved in 140 patients while 26 patients showed no change or worse Nurick grade. Multivariate analysis revealed no statistically significant independent predictors of outcome between SA or CP. Conclusion: This study is one of the largest studies comparing SA and CP. Our analysis demonstrated that there were no statistically significant differences in rates of dysphagia and neurological outcome between CP and SA. However, it has been shown here that length of hospital stay and the operative time was shorter in patients with SA.

A048: Is Stand-Alone Polyetheretherketone (Peek Cage) the New Gold Standard In Anterior Cervical Decompression And Interbody Fusion (acdf) for the Management of One and Two Levels of Degenerative Cervical Spondylotic Myelopathy

Ayush Sharma¹, Hari Kishor¹, Vijay Singh¹, Ahmad Shawk²

¹Department of orthopedic and Spine surgeries Dr B R Ambedker Central Railway Hospital, Mumbai - India ²Department of Spine Surgery, Helios Klinikum Erfurt, Erfurt - Germany

Introduction: Aim of the study was to compare the outcome of anterior cervical decompression and interbody fusion (ACDF) with stand-alone tricotical iliac crest auto graft verses stand-alone polyetheretherketone (PEEK Cage). Material and methods: Prospectively collected data of 60 patients in each group was compared. MJOA (Modified Japanese Orthopaedic Association) scoring and sequential follow-up radiographs was done pre-operatively and post-operatively at 3 months, 6 months and at 1 year to assess the functional outcome and fusion. Two independent authors blinded to clinical data did assessment for fusion and cage subsidence. The association between two variables was done with chi-square test. Comparison of mean between two fusion groups was done with unpaired t test and comparison of mean values of MJOA Scores at different time intervals was done with repeated measures ANOVA and multiple comparison within groups was done with sidak test. P value less than 0.05 was considered significant. Results: There was statistically significant improvement noted in post-operative MJOA follow up scores with comparison pairs of preoperative verses 6 months, preoperative verses 1 year, and 3 months verses 6 months, 3 months verses 1 year in both groups. But improvements in MJOA scores were statistically insignificant between 6 months and one year (P = .0639) for auto-graft group when compared to PEEK cage group (P = 0001*). The mean loss of segmental lordosis on follows up X-ray for auto graft group was (5. 89° ± 2.90°) which was significantly higher (1.88° ± 2.77°) than the mean loss seen in PEEK cage group (P = 0.01). This was most evident between six months and one year resulting in plateauing of the improvement in MJOA score between six months to one year in auto graft group. While there was no statistical difference between fusion rates between the groups for one and two levels overall fusion rates were significantly better for one level (95.74%) when compared to two levels ACDF (76.00%). Conclusion: Based on our study use of tricotical iliac crest and PEEK cage as stand-alone interbody graft for ACDF results in good functional outcome with statistically significant improvement in post-operative MJOA scores. But ACDF with PEEK is the fusion technique of choice for cervical spondylotic myelopathy with fewer complications and better functional recovery.

Disc Degeneration 2

A049: Intervertebral Disc Degeneration and Microglia: A Crosstalk in Promoting and Sustaining Neuroinflammation

Giovanni Marfia¹, Stefania Navone¹, Laura Guarnaccia¹, Matteo Beretta¹, Paolo Rampini², Chiara Cordiglieri³, Daniele Nicoli², Stefano Borsa², Roberta Gualtierotti⁴, Mauro Alini⁵, Laura Riboni⁶, Mauro Pluderi², Rolando Campanella¹

¹Laboratory of Experimental Neurosurgery and Cell Therapy, Neurosurgery Unit, Fondazione IRCCS Ca’ Granda Ospedale Maggiore Policlinico, University of Milan, Milano - Italy ²Neurosurgery Unit, Milano - Italy ³INGM, Istituto di Genetica Molecolare, Milano - Italy ⁴Division of Rheumatology, ASST Pini, Department of Clinical Sciences and Community Health, University of Milan, Milano - Italy ⁵AO Research Institute Davos, Davos, Switzerland, Davos - Switzerland ⁶Department of Medical Biotechnology and Translational Medicine, LITA-Segrate, University of Milan, Milano - Italy

Introduction: Low back pain (LBP) is a serious public health problem and the single most common cause of disability worldwide¹. Although LBP etiology is still not completely understood, it is typically associated with IVD degeneration (IDD). It has been established that the pathological inflammation during IDD is characterized by increased levels of several pro-inflammatory cytokines and chemokines². These pro-inflammatory mediators are produced by resident IVD cells, as well as by both circulating immune cells, e.g. macrophages, T- and B-cells, and natural killer cells^3-6 and microglia and astrocytes⁷ of dorsal root ganglia (DRG). Recently, it has been reported that IDD upregulates microglial activity leading to activation of these cells in the spinal dorsal horn, which directly correlates with radicular pain^7,8. Pathways of microglial activation during IDD are still not completely understood, although previous studies demonstrate a pivotal role of sphingolipids in the pathophysiology of numerous neuroinflammatory disorders where activation of microglia is involved^9-10. In this context, sphingolipids, and spingosine-1-phosphate (S1P) in particular, have proven to be strictly related to neuroinflammation, and a dysregulation of their metabolism can cause the release of pro-inflammatory mediators, responsible for degenerative microenvironment¹¹. Materials and Methods: Human NP from degenerated IVD (D-IVD) and adipose tissue (AT), as negative control, were collected from seven patients after written informed consent. Microglial cells were kept in culture for 48 h in wells with DMEM+10% Foetal bovine serum (FBS), the basal condition and with treatments: i) D-IVD, ii) D-IVD with S1P (200 nM), iii) AT, iv) AT with FTY720 (100 nM), a functional antagonist of S1P receptor. After co-incubation neuro-inflammatory activation was assessed in terms of migration, chemotaxis, nitrites production and cytokines released. Results: Degenerative condition stimulated more microglia proliferation than AT conditioned medium (AT-CM). Upon 48 h of co-incubation with microglia, degenerative condition induced microglia chemotaxis, migration and invasion in human D-IVD. Moreover, not only IVD-CM incubation lead microglia cells to increase nitrites production, but also induced an incremented release of proto-typical inflammatory mediators, such as RANTES, TGF-β1, and IP-10 with a significant increment respect to resting microglia and AT-CM. Interestingly, the co-administration of FTY720 with IVD-CM, significantly decreased the IVD-CM-induced chemotactic activity and migration of microglial cells, suggesting that S1P activity is required by IVD microenvironment to exert its growth promoting effect on microglia. Indeed, cell exposure to S1P, induced a potent chemotactic effect on microglia, even in presence of AT-CM, otherwise not influent in microglial chemotaxis by itself. Furthermore, the combined treatment with IVD-CM and FTY720 significantly decreased the expression levels of all the neuroinflammatory markers investigated, TNF-α, IBA1, iNOS, and CD68. Conclusion: In conclusion, to our knowledge, this is the first report demonstrating that IVD degenerative microenvironment can activate microglial cells, inducing chemotaxis, migration and secretion of pro-inflammatory cytokines. Moreover, the finding that S1P signalling is involved in IVD degeneration process, could be important in the identification of new treatment of IDD and related chronic pain. These results may be of relevance for a better understanding not only of microglia inflammatory properties but also of neurodegenerative disease pathogenesis.

Acknowledgements

The study was partially supported by a grant from the Italian Ministry of Health, Fondazione IRCCS Ca’ Granda Ospedale Maggiore Policlinico (RC2016) and by University of Milan.

Conflict of Interest

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

References

 1. Vos T, Flaxman AD, Naghavi M, et al. 2012. Years lived with disability (YLDs) for 1160 sequelae of 289 diseases and injuries 1990-2010: a systematic analysis for the Global Burden of Disease Study 2010. Lancet 380: 2163-2196.

 2. Navone SE, Marfia G, Giannoni A, et al. 2017. Inflammatory mediators and signalling pathways controlling intervertebral disc degeneration. Histol Histopathol 32: 523-542

 3. Shamji MF, Setton LA, Jarvis W, et al. 2010. Proinflammatory cytokine expression profile in degenerated and herniated human intervertebral disc tissues. Arthritis Rheum 62: 1974-1982

 4. Murai K., Sakai D., Nakamura Y., Nakai T., Igarashi T., Seo N., Murakami T., Kobayashi E. and Mochida J. (2010). Primary immune system responders to nucleus pulposus cells: evidence for immune response in disc herniation. Eur. Cell Mater. 19, 13-21

 5. Geiss A., Larsson K., Rydevik B., Takahashi I. and Olmarker K. (2007). Autoimmune properties of nucleus pulposus: an experimental study in pigs. Spine (Phila Pa 1976). 32 168-173

 6. Kokubo Y., Uchida K., Kobayashi S., Yayama T., Sato R., Nakajima H., Takamura T., Mwaka E., Orwotho N., Bangirana A. and Baba H. (2008). Herniated and spondylotic intervertebral discs of the human cervical spine: histological and immunohistological findings in 500 en bloc surgical samples. Laboratory investigation. J. Neurosurg. Spine 3, 285-295.

 7. Cho HK, Ahn SH, Kim SY, et al. 2015. Changes in the Expressions of Iba1 and Calcitonin Gene-Related Peptide in Adjacent Lumbar Spinal Segments after Lumbar Disc Herniation in a Rat Model. J Korean Med Sci. 30: 1902-1910.

 8. Cho HK, Kim SY, Choi MJ, et al. 2016. The Effect of GCSB-5 a New Herbal Medicine on Changes in Pain Behavior and Neuroglial Activation in a Rat Model of Lumbar Disc Herniation. J Korean Neurosurg Soc 59: 98–105.

 9. Davies L, Fassbender K, Walter S. 2013. Sphingolipids in neuroinflammation. Handb. Exp. Pharmacol 216: 421-430.

10. Gualtierotti R, Guarnaccia L, Beretta M, et al. 2017. Modulation of Neuroinflammation in the Central Nervous System: Role of Chemokines and Sphingolipids. Adv Ther 34: 396-420.

11. Riboni L, Viani P, Bassi R et al. 1997. The role of sphingolipids in the process of signal transduction. Prog Lipid Res 36:153-195.

A050: Association of Vitamin D Receptor Gene Polymorphisms With Disc Degeneration Endophenotpyes

Adam Biczo¹, Arpad Bozsodi¹, Iain McCall², Peter Pal Varga¹, Aron Lazary¹

¹National Center for Spinal Disorders, Budapest - Hungary ²Department of Diagnostic Imaging, The Robert Jones and Agnes Hunt Orthopaedic Hospital, Gobowen - United Kingdom

Introduction: Candidate gene and genome wide association studies have identified numerous genes and single nucleotide polymorphisms (SNPs) in the background of lumbar disc degeneration (LDD). However, most of these studies have been underpowered, definitions of LDD are not consistent and many of the findings have not been replicated. For instance, although Vitamin D receptor gene (VDR) has been reported to be one of the major candidate genes, studies about the possible role of VDR variants have led to contradictory results. Here, we aimed to analyse the association between the candidate VDR single-nucleotide polymorphisms (SNPs) and LDD characterized by different, well defined endophenotypes on the homogenous dataset of a large, international cohort. Materials and Methods: The international Genodisc database contains the clinical, radiological and genetic data of 2635 back pain patients from specialist spinal hospitals in four European countries. Four different degenerative endophenotypes (Pfirrmann grade, disc prolapse, Modic change, endplate defect) were scored by the same radiologist. DNA was extracted from venous blood or saliva samples. Seven candidate VDR SNPs were genotyped on a Sequenom MassArray platform. Statistical analyses were performed using the ‘SNPassoc’ and ‘haplo.stats’ R packages and THESIAS software. P-values less than 0.05 were considered significant. Results: Out of the 7 VDR SNPs, 6 were found to be associated with different degenerative endophenotypes. “CC” genotype of ApaI (rs7975232) was found to have a positive correlation with disc prolapse (OR = 1.13, p = 0.0458) and Pfirrmann grade (OR = 1.46, p = 0.0408). The “CC” genotype of TaqI (rs731236) (OR = 0.62, p = 0.0032) and the “AA” genotype of BsmI (rs1544410) (G/G-G/A; A/A, OR = 0.67, 95%CI = 0.49- 0.91, p = 0.01 005) were negatively associated with Modic change. “G” allele of DdeI (rs3782905) (OR = 1.38, p = 0.0064) and “AA” genotype of Cdx2 (rs10783215) (OR = 2.32, p = 0.0444) was associated with the presence of endplate defects. The “T/C” genotype of the FokI (rs2228570) was associated with both Pfirrmann grade (p = 0.04 458) and Modic change (p = 0.03 023). Haplotype analysis showed a significant (p < 0.05) association of the VDR 3’ UTR haplotype with different degenerative phenotypes. Conclusion: Clarification of the genetic background of LDD is crucial for improving understanding of its pathomechanism and for finding possible therapeutic targets. Discrepancies between the results of various genetic studies of LDD, could originate from the different definitions of degenerative disc disease.Therefore the use of simple, well defined phenotypes (endophenotypes) in such studies is strongly advised. Through applying this approach to a large, international cohort of patients, our findings support the role of association of different SNPS of VDR with specific LDD endophenotypes. Our study thus demonstrates the importance of phenotyping, by MRI or other means, for genetic studies of complex disorders such as disc degeneration. Large, homogenously assessed and analyzed cohort, are crucial for producing more reliable data on the genetic background of such a condition, which is not only multifactorial and polygenic, but also multidimensional in its phenotypic structure.

A051: Ca²⁺ and Po₄ Regulate Matrix Protein Synthesis in Intervertebral Discs

Yazeed AlSaran¹, Michael Grant¹, Laura Epure¹, John Antoniou¹, Fackson Mwale¹

¹Lady Davis Institute for Medical Research, McGill University, Montreal - Canada

Introduction: Degenerative disc disease (DDD) is a common cause of lower back pain. Calcification of the intervertebral disc (IVD) has been correlated with DDD, and is especially prevalent in scoliotic discs. The appearance of calcium deposits has been shown to increase with age, and its occurrence has been associated with several other disorders such as hyperparathyroidism, chondrocalcinosis, and arthritis. Trauma, vertebral fusion and infection have also been shown to increase the incidence of IVD calcification. Calcification is the product of free calcium (Ca²⁺) and phosphate (PO₄). Our preliminary data suggest that ionic calcium and P0₄ content are increased from [2.0 – 8.0 mM] and [1.0 – 4.0 mM], for mild, moderate and severe degenerative IVDs, respectively. The roles of these individual ions on IVD function and in the development DDD is unknown. In this study, we evaluated the effects of Ca²⁺, PO₄, and their combination on IVD nucleus pulposus (NP) and annulus fibrosis (AF) cells. Material and Methods: Bovine IVD cells were isolated from bovine caudal tails of 20-24-month-old steers. Cells were recovered from NP and AF tissue by sequential digestion with Pronase followed by Collagenase, and expanded in low glucose DMEM medium supplemented with 10% heat-inactivated FBS. Cells were expanded in flasks then prepared for 3D culturing in alginate beads at a density of 1*10⁶ cells/mL. Beads were cultured in medium containing increasing Ca²⁺ [1.0, 3.0, 6.0 mM], PO₄ [1.0, 2.0, 4.0 mM], or their combination and cultured for 12 days. A modified GAG assay was performed on the beads to determine proteoglycan content and Western blotting for type II collagen (Col II) synthesis. Cell viability was determined by counting live and dead cells in the beads following incubation with the Live/Dead Viability Assay kit. Cell numbers in beads at the end of the incubation period was determined using Quant-iT dsDNA Assay Kit. Bovine IVD organ culture model was performed as previously described. IVDs were cultured for 4 weeks in Ca²⁺ [1.0 and 6.0 mM] with and without PO₄ [4.0 mM]. Results: Using similar Ca²⁺ concentrations found in degenerate [1.8 – 6.0 mM], Ca²⁺ dose-dependently decreased matrix protein synthesis of proteoglycan and Col II in NP and AF cells (n = 4). Moreover, increasing PO₄, from 1 – 4 mM, further decreases in matrix protein synthesis was observed (n = 4). Interestingly, although cell viability was unaltered from higher PO₄ or Ca²⁺ concentrations, the combination of PO₄ and Ca²⁺ significantly affected cell proliferation (n = 3). IVDs cultured in increasing Ca²⁺ demonstrated decreased total proteoglycan content in both NP and AF regions. Western blotting for aggrecan in NP and AF tissues showed similar results. Histology and immunohistochemistry was performed to identify proteoglycan and nerve growth factor expression, respectively. Conclusion: Our results suggest that changes in the local concentrations of calcium and PO₄ are not benign, and that the combination of these ions affects IVD cell growth and matrix protein synthesis. Ca²⁺ and PO₄ may be a contributing factor in IVD degeneration and pain.

A052: Tungsten Induces Fibrosis and Upregulates Markers for Pain in the Intervertebral Disc Both in Vitro and in Vivo

Michael Grant¹, Alicia Bolt¹, Hsiang Chou¹, Laura Epure¹, Koren Mann¹, John Antoniou¹, Fackson Mwale¹

¹Lady Davis Institute for Medical Research, McGill University, Montreal - Canada

Introduction: Tungsten has been increasing in demand for use in manufacturing and recently, medical devices, as it imparts flexibility, strength, and conductance of metal alloys. Given the surge in tungsten use, our population may be subjected to elevated exposures. For instance, embolism coils made of tungsten used in the treatment of intracerebral aneurysms and dural fistulas have been shown to degrade in some patients resulting in elevated levels of tungsten in both serum and urine. Although tungsten toxicity is not well described, it was shown to induce cell death and genotoxicity in a human liver and renal cell line. In a recent report, tungsten was shown to rapidly accumulate in bone. Whether tungsten accumulates in other tissues and affects viability and/or function remains unknown. We recently determined that when mice are exposed to tungsten [15 ppm] in their drinking water it bioaccumulates in the intervertebral disc [∼3 ppm], equivalent to what is observed in bone. This study was performed to determine the toxicity of tungsten on the intervertebral disc. Material and Methods: Mice (C57BL/6) were given tap water or water supplemented with 15 ppm sodium tungstate for 4 weeks. Animals were sacrificed and spines were removed for histology. Discs were excised and analyzed for proteoglycan and collagen content. Bovine nucleus pulposus (bNP) and annulus fibrosus (bAF) cells were isolated from bovine caudal tails. Cells were expanded and prepared for 3D culturing in alginate beads at a density of 2*10⁁6 cells/mL. Beads were cultured in medium supplemented with increasing tungsten concentrations in the form of sodium tungstate [0, 0.5, 5, 15 ug/mL] for 12 days. A modified GAG assay was performed on the beads to determine proteoglycan content and the hydroxyproline assay was performed for collagen synthesis. Cell viability was determined by counting live and dead cells in the beads following incubation with the Live/Dead Viability Assay kit (Thermo Fisher Scientific). Gene expression of matrix proteins (ACAN, COL1A1, COL2A1), catabolic enzymes (ADAMTS4, ADAMTS5, MMP3, MMP13), and markers of inflammation (TNFalpha, IL-1beta) and pain (NGF, BDNF) were analyzed by qPCR. Organ culture of bovine IVDs was prepared using PrimeGrowth® media system and cultured in with 15 ppm sodium tungstate for 4 weeks. Proteoglycan and collagen contents were analyzed. Results: Tungsten dose-dependently decreased the synthesis of proteoglycan in both NP and AF cells reaching greatest significance in NP cells at 15 ppm (3.3 ug/ug DNA to 2.3 ug/ug DNA; p < 0.01; n = 4). Decreases in proteoglycan content were alos observed in organ cultures and in mouse IVDs (30.3 ug/mg to 19.5 ug/mg tissue; p < 0.01; n = 4). Furthermore, tungsten increased the synthesis of collagen in both discs cells, organ culture, and in vivo. Interestingly, in disc cells synthesis of COL2A1 was downregulated but COL1A1 was increased by 6-fold (p < 0.0001, n = 4). This increase in Col I was also observed in vivo. Upregulation of catabolic enzymes was also observed. Tungsten also upregulated NGF by 9-fold (p < 0.05, n = 4) and BDNF by 3-fold (p < 0.05, n = 4) in NP cells. This upregulation of NGF was confirmed upon histological examination of discs in mice. Conclusion: We provide evidence that tungsten affects matrix protein synthesis in IVD cells, possibly enhancing disc fibrosis, and may also play a role in pain.

A053: Single Nucleotide Variants of IL6 and COL1A1 are Associated With Intensity of Pain and Severity of Disability in Chronic Low Back Pain

Romain Perera¹, Upul Senarath², Harsha Dissanayake³, Lalith Wijayaratne⁴, Aranjan Karunanayake⁵, Vajira Dissanayake⁶

¹Department of Allied Health Sciences, Faculty of Medicine, University of Colombo, Colombo 08 - Sri Lanka ²Department of Community Medicine, Faculty of Medicine, University of Colombo, Colombo 08 - Sri Lanka ³Department of Anatomy, Faculty of Medical Sciences, University of Sri Jayewardenepura, Nugegoda - Sri Lanka ⁴National Hospital of Sri Lanka, Colombo 10 - Sri Lanka ⁵Department of Anatomy, Faculty of Medicine, University of Kelaniya, Ragama - Sri Lanka ⁶Human Genetics Unit, Department of Anatomy, Faculty of Medicine, University of Colombo, Colombo 08 - Sri Lanka

Introduction: Intensity of pain and severity of disability are the main clinical outcomes of chronic low back pain. Lumbar disc degeneration (LDD) weakly correlates with chronic low back pain. Variation in certain genes encoding proteins involved in pain pathways, structural components of the disc and their metabolic pathways may explain the varying degrees of pain/disability experienced by patients with LDD. Genetic variants which affect LDD may influence the clinical outcomes of the chronic low back pain. The aim of this study was to assess the relationship of single nucleotide variants (SNVs) which affect LDD with the intensity of pain and severity of disability. Material and Methods: A descriptive cross sectional study was carried out on 120 patients with chronic mechanical low back pain. Patients were selected based on the grades of disc space narrowing and anterior osteophytes in the lateral lumbar x-ray which were recorded by a consultant radiologist blinded to clinical details. Intensity of pain was assessed using the numeric rating scale and severity of disability was assessed using Modified Oswestry Disability Index. Twenty-six SNVs of seventeen genes (ACAN, ADAMTS5, CILP, COL1A1, COL9A1, COL9A3, COL11A1, COL11A2, COX2, HAPLN1, IL1A, IL1B, IL18RAP, IL18R1, IL6, NOS2 and VEGFA) associated with LDD were identified from the literature search. DNA was extracted from venous blood and genotyping was performed using Sequenom MassARRAY iPLEX platform. Multivariable linear regression analysis was carried out using PLINK 1.9 in accordance with additive genetic model. Age, gender, body mass index and grades of disc space narrowing and anterior osteophytes were used as covariates. Results: Mean age was 51.47 ± 10.43. 82 (68.3%) were females. 30 (25%) were obese. Mean intensity of pain was 45.18 ± 21.11 and mean severity of disability was 31.87 ± 14.04. All SNVs were in Hardy-Weinberg equilibrium. Minor allele frequency ranged from 0.05 to 0.5. Presence of each additional “C” allele of the rs1800795 variant of IL6 progressively reduced the intensity of pain (β = −0.29, p < 0.01). Furthermore, presence of each additional “A” allele of the rs1007086 variant and “T” allele of the rs2075555 variant of COL1A1 was associated with a progressive increase in the intensity of pain (β = 0.27, p < 0.01 and β = 0.25, p < 0.01, respectively) and severity of disability (β = 0.25, p < 0.01 and β = 0.28, p < 0.01, respectively). Conclusion: SNVs of IL6 and COL1A1 were associated with clinical outcomes of the chronic low back pain. More studies are needed to explore their effects on the interaction between LDD and clinical outcomes of chronic low back pain.

A054: Nose To Back: Nasal Chondrocytes Are a Potential Autologous Cell-transplant Source For Cell Therapy Based Treatment of Degenerative Disc Disease

Max Gay¹, Arne Mehrkens¹, Andrea Barbero¹, Ivan Martin¹, Stefan Schaeren¹

¹Department of Tissue Engineering & Department of Spinal Surgery, University Hospital Basel, Basel - Switzerland

Introduction: This project aims to determine whether nasal chondrocytes can be considered as an autologous cell source for cell therapy of disc degeneration by comparing them to MSCs and articular chondrocytes, two cells sources used in phase two clinical trials at the moment. Material and Methods: Cells are cultured in in vitro micromass culture conditions mimicking facets of a degenerated intervertebral disc, such as hypoxia, low glucose, inflammation, and acidity The production of the extra cellular matrix is evaluated by means of immunohistochemistry, quantative real time PCR, and biochemical analysis. Results: Our data demonstrates MSCs, ACs and NCs have a similar GAG and Collagen 2 production in response to in vitro conditions simulating singular facets of the IVD environment and the addition of TGFβ1. However, NCs synthesis more of these ECM components than MSCs or ACs when cultured in the same conditions without the addition of the growth factor. Furthermore, growth factor primed NCs maintain an exceeding production of GAG and Collagen 2 compared to both growth factor primed MSCs and ACs in harsher conditions, which combine different characteristics of the degenerated IVD environment. Interestingly, the indifference of ECM production of NCs in response to inflammation factors cannot be linked to the absence of gene expression of the respective receptors. Moreover, NCs as the only cell sources display gene expression of the transcription factor FoxF1, a marker for nucleus pulposus cells. Conclusion: In summary, NCs are more similar to nucleus pulposus cells than MSCs and ACs, as they can better produce ECM in an in vitro IVD environment and express the nucleus pulposus marker FoxF1. These findings encourage the assessment that employing NCs in a cell therapy treatment of degenerated disc disease could promote new matrix production in the disc, which could inhibit or delay further disc height loss if not even lead to disc height gain.

Deformity - Thoracolumbar (Adolescent) - Surgery 1

A055: Posterior Column Osteotomies in Restore Shoulder Balance in Lenke Type 1 Scoliosis Treated by Convex Manipulation

Leonardo Oggiano¹, Sergio Sessa¹, Cloe Curri¹, Guido La Rosa¹

¹Department of Surgery, Orthopaedic Unit, Bambino Gesù Children’s Hospital, Rome - Italy

Introduction: Shoulder balance is important for adolescent idiopathic scoliosis, which affects the patient’s appearance and satisfaction after scoliosis surgery. Concave derotation is the traditional correction maneuver in adolescent idiopathic scoliosis surgery. In order to reduce risks of neural damages, and ensure the same strenght of correction maneuvers, a convex manipulation through an all-level pedicle screws convex instrumentation can be performed. We report perioperative and 3-year results in terms of deformity correction and shoulder balance in a consecutive series of patients treated by convex manipulation through an all-level pedicle screws convex instrumentation. Material and Methods: From January 2013 to January 2016 we surgical treated 42 consecutive patients (37 F, 5 M, mean age 13 years) affected by single thoracic adolescent idiopathic scoliosis (Lenke type 1). Mean pre-operative Cobb angle was 56° ± 6°. Shoulder balance was evaluated by pre-operative measurement of clavicle angle and T1-tilt. We performed a posterior access only in all patients using polyaxial pedicle screws at each level on the convex side of the curve. Among this patients, we distinguished 2 groups: patients in which posterior column osteotomies (PCO) were performed at the apical level of scoliosis only on the convexity of the curve (10 patients), and patients in which PCO were not performed. All the correction maneuvers were performed on the convex prebent rod. In all cases motor-evoked potentials monitoring was used. Mean follow-up time was 36 months. Results: The average percentage of coronal correction was 76 ± 5% (mean post-operative Cobb angle 15° ± 4°), with no neurological complications. Concerning the post-operative kyphosis, we observed a slight decrease of mean values compared to pre-operative measurements (mean reduction of thoracic kyphosis 5° ± 2°). At 3-year follow-up no changes in coronal nor in sagittal plane were observed. Concerning post-operative shoulder balance, we reported a statistically significant change in clavicle angle and T1-tilt in patients operated with asymmetrical PCO respect to patients in which PCO were not performed. Conclusion: This case-series study shows the effectiveness and the safety of convex manipulation in Lenke type 1 scoliosis. The coronal correction obtained with this technique is comparable to that obtained with the traditional concave derotation. Concerning shoulder balance correction, PCO, providing a shortening and a higher mobilization of the convex side of the curve, allow a better management of the upper thoracic spine and, consequently, a better restore of shoulder symmetry.

A056: Sagittal Alignment After Surgical Treatment of Adolescent Idiopathic Scoliosis - Application of the Roussouly Classification

Søren Ohrt-Nissen¹, Tanvir Bari¹, Benny Dahl², Martin Gehrchen¹

¹Department of Orthopedic Surgery, Spine Unit, Rigshospitalet, Copenhagen - Denmark ²Department of Orthopedics and Scoliosis Surgery, Texas Children’s Hospital, Houston - United States

Introduction: How spinopelvic alignment is affected in patients with adolescent idiopathic scoliosis (AIS) is not well established. Roussouly et al proposed a classification based on the sagittal spinal profile and spinopelvic alignment that may have clinical utility in these patients. The objective of the study was to investigate spinopelvic alignment and spine shape in patients surgically treated for adolescent idiopathic scoliosis (AIS) and to assess the distribution and clinical applicability of the Roussouly classification. Material and Methods: A consecutive cohort of 134 surgically treated AIS patients were retrospectively included. Whole-spine standing lateral radiographs were analyzed preoperatively, one-week postoperatively and at two-year follow-up. Patients were categorized using the previously published modified Roussouly classification and analyzed for sagittal alignment. Primary emphasis was placed on the rate of proximal junctional kyphosis, pelvic anteversion and pelvic Incidence (PI) – lumbar lordosis (LL) mismatch. Results: Postoperatively, global thoracic kyphosis decreased by 2.6° and LL decreased by 6.2° (p ≤ 0.012) while pelvic tilt increased 1.4° (p = 0.024). At two-year follow-up, thoracic kyphosis and LL had returned to preoperative values (p ≥ 0.346) while pelvic tilt had decreased from preoperative 9.7 ± 7.6° to 7.0 ± 7.5° (p > 0.001). Proximal junctional angle increased from 8.4 ± 5.0° preoperatively to 12.8 ± 8.9 (p < 0.001). Preoperatively, Roussouly curve types were distributed equally apart from a lower rate of type 1 (12%). At final follow-up, 30% were categorized as type 3 with pelvic anteversion which is considerably higher than the normal adolescent population. Only three patients were type 1 at the final follow-up. Overall, we found a high rate of proximal junctional kyphosis (16%), PI-LL mismatch (60%) and pelvic anteversion (38%). In preoperative type 1 patients, the rate was 50%, 82% and 64%, respectively. Conclusion: We found that immediate postoperative changes in LL and thoracic kyphosis were reversed at final follow-up and found evidence of proximal junctional kyphosation and pelvic anteversion as the main compensatory mechanisms. Poor sagittal alignment was especially frequent in type 1 curves. Surgical decision-making such as rod contouring and fusion selection may need to be individualized according to the sagittal profile.

A057: What Decides Shoulder Levels in a Double Thoracic (Lenke 2) Adolescent Idiopathic Scoliosis?

Naresh-Babu J¹, Arun-Kumar Viswanadha¹

¹Department of Spine Surgery, Mallika Spine Centre, Guntur - India

Introduction: Preoperative directionality of shoulder tilting seems to be independent of the radiographic features of proximal thoracic (PT) curve in adolescent idiopathic scoliosis (AIS) patients. To date, no study had investigated the mechanisms underlying the variety of preoperative directionalities of shoulder tilting in AIS patients. The purpose of this study was to evaluate the differences of radiographic features between Lenke type 2 (double thoracic curve) AIS patients with different preoperative directionalities of shoulder tilting. Material and Methods: A total of 35 Lenke type 2 AIS patients were included in this study and were divided into 2 groups according to the value of radiographic shoulder height (RSH). There were 11 cases with RSH less than 0 cm in Group R (right elevated shoulder) and 24 cases with RSH equal to or more than 0 cm in Group L (level or left elevated shoulder). Preoperative standing anteroposterior X-ray films of the spine were obtained in all these subjects and were analyzed with respect to the following parameters: T1 tilt, PT Cobb angle, main thoracic (MT) Cobb angle, TL/L curve cobb angle, the apical level of PT curve, PT curve modifier, the apical level of MT curve and RSH. These parameters were compared between these 2 groups and the correlations between RSH and the other parameters were analyzed in all of these subjects. Results: Even though the mean PT, MT and TL/L curve cobb angles were similar, the sum total of left deviating curves (PT and TL/L) was significantly higher than the right deviating curve (MT) in Group L (6.5) compared to Group R (3.7). Similarly the ratio of MT curve to PT curve was more than 2 in Group R and less than 2 in Group L. Interestingly, the positive T1 tilt is present in only 45% of Group L and even 18% of Group R also demonstrated a positive tilt. The correlation analysis also demonstrated that the RSH was positively associated PT Cobb angle/MT Cobb angle ratio but negatively associated with MT Cobb angle (p < 0.05), However, the apex of PT curve, PT Cobb angle, T1 tilt, PT curve modifier, PT Curve apical rotation had no significant association with the preoperative RSH. Conclusion: The directionality of shoulder tilting is diverse in Lenke type 2 AIS patients. Not only the PT curve characteristics but also on the radiographic profile of MT and TL/L curves influence the directionality of shoulder.

A058: A Clinical Study of Correlation Between Coronal Imbalance and SRS Score in Patients With Adolescent Idiopathic Scoliosis - Preoperative CIB May Cause Postoperative Pain

Ryo Sugawara¹, Hideaki Watanabe², Hirokazu Inoue¹, Katsushi Takeshita¹, Ichiro Kikkawa¹

¹Department of Orthopedic Surgery, Jichi Medical University - Japan ²Department of Pediatric Orthopedics, Jichi Children’s Medical Center Tochgi - Japan

Introduction: Coronal imbalance (CIB) causes not only low back pain, but also the progression of scoliosis and accompanying thoracic deformity, as noted in congenital, syndromic and neuromuscular scoliosis. However, there are few reports focusing on the effects of coronal imbalance in patients with adolescent idiopathic scoliosis (AIS). This study investigated the negative effects of CIB in patients with AIS by using Scoliosis Research Society (SRS) questionnaire. Methods: A total of 54 patients with AIS that underwent posterior spinal fusion were retrospectively reviewed after a minimum follow-up of 1 year. Coronal balance, determined as the distance between C7 plumb line and central sacral vertebral line in the frontal radiograph of the whole spine in a standing position, was measured before surgery, and CIB was defined as a 20 mm and greater of lateral deviation of C7 plumb line. Clinical results were evaluated by using the SRS questionnaire preoperatively and 1 year postoperatively, and these questionnaire score (SRS score) were compared between the preoperative normal balance group and preoperative CIB group. Results: Preoperative CIB was seen in 22 patients (40.7%). The preoperative SRS scores in preoperative normal balance group and CIB group were, function: 4.47, 4.60, pain: 4.26, 4.48, self-imaging: 2.66, 2.80, mental health: 4.26, 4.39, satisfaction: 4.03, 4.50, total: 3.77, 3.97, respectively. The postoperative SRS scores were, function: 4.54, 4.44, pain: 4.09, 4.17, self-imaging: 4.00, 4.21, mental health: 3.76, 4.04, satisfaction: 3.76, 4.04, total: 4.20, 4.32, respectively. There was no statistical difference between the scores in the preoperative normal balance group and CIB group in all domain in the SRS questionnaire preoperatively and postoperatively. There were significant improvements at self-imaging, mental health, satisfaction and total domain in both groups. However, there was a significant deterioration at pain domain in preoperative CIB group from pre-to post operatively (p < 0.05). Conclusions: Preoperative CIB may cause postoperative pain in patients with adolescent idiopathic scoliosis.

Pediatric Deformity and Interventional

A059: CT-Guided Percutaneous Treatment of Lumbar Facet Joint Synovial Cysts in 29 Patients –Technique, Challenge and Clinical Outcome

Nurith Hiller¹, Masha Galiner-Ron¹, Anna Finkelstein¹, Josh Schroeder²

¹Departments of Radiology, Hadasash Medical Cener, Jerusalem – Israel

²Department of Orthopedic surgery, Hadassah Medical Center, Jerusalem - Israel,

Purpose: To evaluate the effectiveness of percutaneous CT-guided treatment of lumbar facet joint synovial cysts in patients with radicular pain. Methods: Consecutive patients treated for radiculopathy secondary to lumbar facet joint cyst from 3.2012–6.2016 were included. Patients were treated by direct cyst filling with diluted contrast medium using a percutaneous CT-guided intra-articular or translaminar approach. Cyst rupture was confirmed by visualization of contrast medium in the epidural space. Before needle retrieval, a corticosteroid-lidocain mixture was injected into the epidural space. Presenting symptoms, lumbar level and side, puncture method, complications, and immediate and long-term clinical outcome were assessed and prospectively recorded in an Excel file. The IRB Committee waived the requirement for informed consent. Results: 29 patients met inclusion criteria (12 males/17 females; mean age 67 years, range 48–85); 3 patients required a repeat procedure (32 procedures). Sciatic pain was right-sided in 16 patients (55%), left-sided in 12 (41%), and bilateral in 1 (4%). Side of radiculopathy correlated with cyst location in the spinal canal. Cysts were located at L4-L5 in 21 patients (73%), L5-S1 in 5 (17%), and L3-L4 in 3 (10%). Cyst-filling was performed via the intra-articular route in 17 patients (59%, 18 procedures), translaminar in 2 (7%), translaminar approach after failed transarticular approach in 7 (2.4%, 9 procedures), contra-translaminar approach in 2 cases (7%), and by direct puncture in 1 case of extra-foraminal cyst (3%). Cyst rupture with epidural steroid injection was successful in all 32 procedures. 25 patients (86%) reported marked relief of symptoms immediately after the procedure, 3 (10%) reported mild improvement, and 1 (3%) reported no change. Among 25 patients with 6-month follow-up, 12 (48%) were pain free, 7 (28%) reported clinical improvement, 7 (28%) showed no improvement, and 5 (20%) had undergone surgical removal of the cyst, including 1 who had undergone 2 percutaneous attempts. Complications included sepsis in 1 patient and septic facet arthritis in 1; neither had received prophylactic antibiotics. Transient urinary incontinence appeared in 1 patient after spinal and epidural injection, and 6 patients experienced mild transient leg weakness. Among 14 patients with MRI at 1–15 months follow-up, the cyst had almost disappeared in 6 (43%) and was unchanged in 8 (57%). Conclusion: In these patients, CT-guided percutaneous puncture of lumbar facet joint synovial cyst was a safe nonsurgical procedure that provided good pain relief. In patients with radiculopathy secondary to facet joint synovial cyst, therapeutic attempt with this procedure should be considered before surgical decision. Prophylactic antibiotic therapy is indicated.

A060: Hybrid Growing Rod Technique With Hemivertebrectomy and Short Fusion: An Alternative Option to Correction Long-spanned Kyphotic Congenital Scoliosis

Xu Sun¹, Zhonghui Chen², Zezhang Zhu¹, Yong Qiu¹

¹Department of Spine Surgery, Drum Tower Hospital, Nanjing University Medical School, Nanjing - China

Introduction: Hemivertebra (HV) resection with short segmental fusion for congenital scoliosis is a standard procedure for young children with localized deformity. However, such a technique might not best address the deformities with long-spanned kyphotic scoliosis secondary to HV. In these cases, a hybrid growing rod technique with hemivertebrectomy and short fusion may be the option. Therefore, the current study aimed to evaluate the clinical outcomes and complications of this hybrid technique. Materials and Methods: Thirteen patients who were treated with this hybrid technique were reviewed. There were 5 patients with single rod and 8 with dual rods after apical hemivertebra resection and short fusion. They had averagely 2.2 lengthening procedures with an average follow-up of 34.7 months. The magnitude of coronal/sagittal deformity and T1-S1 height were measured on the preoperative, postoperative, and last follow-up radiographs. The complications were recorded. Results: The average coronal Cobb angle of main curve was 74.8 degrees before the index surgery, 24.3 degrees after the index surgery, and 25.6 degrees at the last follow-up. The correction rate was 65.8%. The mean global kyphosis was corrected from 64.2 degrees to 34.3 degrees postoperatively and further improved to 28.3 degrees at the latest follow-up. The average height of T1-S1 was 238.4 mm before the index surgery, 270.5 mm after the index surgery, and 282 mm at the latest follow-up. The average growth rate was 12.8 mm per year. One case had rod breakage 8 months after the index surgery and was revised during the planned lengthening. One case exprenced superficial wound infection in 3 weeks after the index surgery and were successfully with debridement. Conclusion: The hybrid growing rod technique with hemivertebrectomy and short fusion is safe and effective in the treatment of congenital kyphotic scoliosis with a long curve. The technique is an alternative for young children with multiple anomalous vertebrae and a long curve to avoid early long fusion.

A061: High Rate Of Intraoperative Monitoring (IOM) Alerts in 176 Severe Pediatric Deformity Patients and its Relationship to the Deformity Angularity Ratio (DAR)

Munish Gupta¹, Lawrence Lenke², Jahangir Asghar³, Oheneba Boachie-Adjei⁴, Patrick Cahill⁵, Mark Erickson⁶, Sumeet Garg⁶, Peter Newton⁷, Amer Samdani⁸, Suken Shah⁹, Harry Shufflebarger³, Brenda Sides¹, Paul Sponseller¹⁰, Daniel Sucato¹¹, Michael Kelly¹, Fox Pediatric Spinal Deformity Study Group¹

¹Department of Orthopaedic Surgery, Washington University School of Medicine, St. Louis - United States ²Department of Orthopedic Surgery, Columbia University Hospital, New York, NY - United States ³Orthopedics, Nicklaus Children’s Hospital, Miami, FL - United States ⁴FOCOS Orthopaedic Hospital, Accra - Ghana ⁵Orthopaedic Surgery, Children’s Hospital of Philadelphia, Philadelphia, PA - United States ⁶Orthopedic Surgery, Children’s Hospital, Aurora, CO - United States ⁷Orthopaedic Surgery, Rady Children’s Hospital, San Diego, CA - United States ⁸Shriners Hospitals for Children, Philadelphia, Philadelphia, PA - United States ⁹Orthopaedic Surgery, Nemours Alfred I. duPont Hospital for Children, Wilmington, DE - United States ¹⁰Orthopaedic Surgery, Johns Hopkins University, Baltimore, MD - United States ¹¹Orthopaedic Surgery, Texas Scottish Rite Hospital, Dallas, TX - United States

Introduction: Severe pediatric deformity is technically challenging with higher complications. Intraoperative monitoring alerts occur frequently in severe pediatric deformity cases, especially with severe angular deformity. The surgical procedures from a prospective observational multicenter cohort study were analyzed in terms of neurologic safety. IOM alerts were common (43%) in this cohort of complex pediatric spinal deformity. Sagittal DAR is associated with any IOM and TCeMEP alerts; however, new permanent neurologic deficits are uncommon. Material and Methods: Patients with severe spinal deformity with a minimum curve of 100° or a planned VCR underwent operative treatment for their deformity and were followed for minimum 2 years. Logistic regression was used to evaluate associations of different procedures and radiographic parameters (VCR procedure, ant/post procedure, coronal C-DAR, sagittal S-DAR) with intraoperative neural monitoring alerts (SSEP, TCeMEP, and any IOM) and postoperative deficits. Results: 176/312 enrolled in the study met the inclusion criteria; we excluded patients with < 2 yrs FU. 76/176 (43%) patients had a VCR procedure and one patient had a PSO. 162 (92%) had a posterior only approach; 14 (8%) were treated with a combined ant/post-surgery. 75 patients had 114 total intraop monitoring alerts. S-DAR was associated with any intraop alerts (p = 0.04) and TCeMEP (p = 0.04). C-DAR was associated with SSEP alerts (p = 0.02). The 5 most common triggering events were correction maneuvers, 3-column osteotomy, implant and instrumentation placement, and hypotension. Some patients had multiple triggering events (N = 26). 161 were neurologically normal preop. 150 pts remained normal neurologically postop and 11 had new deficits. However at 2 years postop, only 1/11 still had a deficit. 14 pts had a neurologic deficit preop. Postop 4 pts improved to a normal neurologic status, 9 pts continued to have a deficit, and 1 pt had partial recovery neurologically. At 2 years, out of the 14 neurologically abnormal pts preoperatively, 11 totally recovered, 2 partially recovered and 1 deficit did not improve. Conclusion: Severe deformity pediatric patients have a high incidence of intraoperative neural monitoring alerts (43%); however, only 2 new permanent deficits were seen. 13 out of 14 patients improved or recovered from preoperative neurologic deficits. Sagittal DAR is associated with intraoperative monitoring alerts. Neural monitoring should be mandatory in these cases

A062: Trauma CT Scan of Spine in Children- are we Over Scanning?

Purnajyoti Banerjee¹, Azal Jalgaonkar¹

¹Department of Orthopaedics, Frimley Park Hospital, Camberley - United Kingdom

Introduction: NICE guidelines in UK suggest computed tomogram (CT) scanning for children with suspected trauma that fulfil the criteria of significant mechanism or focal spinal pathology. It is however a concern that CT scans can expose to radiation that might subsequently increase the risk of radiation induced cancer. Objective: We evaluated the CT scans undertaken in a secondary spine centre amongst children (0-17 years) for trauma and assessed the number of radiographs and CT scans they each received at presentation. The radiation exposure and risk of cancer were estimated. Material & Methods: All CT scans undertaken from August 2015 to July 2017 were reviewed retrospectively. Scans indicated for trauma were included. Further radiographs of spine obtained in the same episode were noted. Data was obtained from the formal radiology reports and case notes. Results: Thirty-five spine CT scans were obtained for trauma whereas 757 radiographs were undertaken. The mean age was 13.5 (SD: 3.3) years and M: F = 18:17.The commonest mechanisms were falls followed by sports injuries and road traffic accidents. Nine (25%) children had their spines scanned as a part of trauma series due to severe mechanism of injury. Thirty patients (85%) patients had spine radiographs before CT scans were obtained. Two patients (6%) had abnormalities in their radiographs prior to CT scans and rest were obtained to exclude injuries with negative radiographs. The mean radiation dose from CT scan was 20.3 (SD: 11.3) mSV. The relative risk of missing a spine fracture in a child with a normal radiograph was 1.14 (95% CI 0.3 to 4.3 and P = 0.8) and the number needed to treat (NNT) for detecting a spine fracture with a normal Radiograph with further CT scan was 56. The mean lifetime risk with CT scan in this group was 0.37%. Conclusion: It is unusual for a child to have a spine fracture detected with CT scan immediately after negative radiographs. Even in children undergoing a trauma series for significant mechanism, the yield of positive pathology after CT is very low. We recommend children with isolated spine tenderness with negative radiographs might be candidates for a magnetic resonance scan (MRI) to exclude further injuries. This will reduce the excess risk of CT related radiation and its associated hazards.

Medical Economics

A063: Racial Disparities in Perioperative Outcomes Following Lumbar Spine Fusion: an Analysis of the 2015 NSQIP Database

Abigale Berry¹, Emily Leary², Ruiqing Feng², Theodore J. Choma², Christina L. Goldstein²

¹Department of Orthopaedic Surgery, University of Missouri, - ²Department of Orthopaedic Surgery, University of Missouri, Columbia - United States

Introduction: Lumbar spine fusion is commonly used to treat a variety of spine pathology and can provide significant improvements in pain, function and health-related quality of life. However, these procedures are not performed without some element of risk, with reported complication rates after lumbar spine fusion range from 5.6% to 31.4%. These complications may impact discharge destination and lead to unplanned reoperations and readmissions. Multiple publications have examined the associations between patient and procedure-related variables and complication rates and perioperative outcomes following lumbar spine fusion. However, none have investigated the impact of race on perioperative outcomes of lumbar spine fusion. The purpose of this study is to examine the impact of race on discharge destination, complication rates, unplanned reoperation rates and readmission rates following lumbar spine fusion using a national quality improvement database. Materials and Methods: Using the 2015 American College of Surgeons National Surgical Quality Improvement Program (ACS-NSQIP) data, patients were limited to those undergoing lumbar spine fusion by Current Procedural Terminology (CPT) codes. Demographic, medical comorbidity, discharge and 30-day perioperative outcome data were extracted. Continuous and categorical variables were summarized, and complication, unplanned reoperation and unplanned readmission rates were calculated. Pearson’s chi-squared test was used to examine the impact of race on discharge destination, risk of experiencing at least one complication, unplanned reoperations and unplanned readmissions. SPSS and R were used to perform the statistical analysis and a p-value of 0.05 was determined to be statistically significant. Results: 11 021 patients with a mean age of 59.22 years were identified for study inclusion. Over half of the patients were women (53.57%) and in those in whom race was reported (n = 678), 88.70% were white and 11.30% were minority race. The two primary indications for spinal fusion were spinal stenosis (20.29%) and spondylosis/intervertebral disc degeneration (20.14%). The most commonly performed surgical procedures were posterior lumbar fusion (40.5%) or posterior including an interbody procedure with or without decompression (37.28%). More than 4 in 5 patients (81.44%) were discharged home following surgery. At least one complication was experienced by 14.97% of patients, 3.54% underwent an unplanned reoperation and 5.83% had an unplanned readmission. Minority race was positively associated with discharge from hospital to somewhere other than home (χ² = 32.422, df = 5, p < 0.001) and unplanned reoperation (χ² = 11.202, df = 5, p = 0.0475). Minority race was not associated with overall risk of experiencing at least one complication (χ² = 1.9944, df = 5, p = 0.8499) or unplanned readmission to hospital (χ² = 4.7752, df = 2, p = 0.0918). Conclusions: This examination of the interplay of race on perioperative outcomes of lumbar spine fusion in a national database demonstrates racial disparities in discharge destination and unplanned reoperation. These findings support further investigations into the specific surgical indications, fusion procedures and other sociodemographic variables which might inform resource allocation for minority patients undergoing these procedures, with the goal of optimizing their episode of care.

A064: Effect of Surgical Setting (Tertiary vs. Community Hospitals) on the Cost of Posterior Cervical Spine Procedures

Heath Gould¹, Joseph Tanenbaum¹, Kelsey Goon¹, Emily Hu¹, Colin Haines², Thomas Mroz¹, Michael Steinmetz¹, Don Moore¹

¹Cleveland Clinic, Cleveland, OH - United States ²Virginia Spine Institute, Reston, VA - United States

Introduction: Healthcare in the United States continues to strive toward a model of service that provides cost-effective care without sacrificing patient outcomes. Laminectomy with fusion (LF) has demonstrated clinical benefit for degenerative cervical myelopathy, but the impact of surgical setting on the cost of these procedures remains unclear. We sought to evaluate the cost of LF surgeries performed at a large tertiary-care hospital (TH) compared to those performed at smaller community hospitals (CHs). Methods: A retrospective cohort study was conducted among patients undergoing posterior cervical decompression between January 2014 and December 2015. Current Procedural Terminology (CPT) codes were used to identify all LF procedures performed in a single healthcare system during this time period. The primary outcome measure was the mean cost of performing LF at a TH compared to a CH. Secondary outcome measures included the mean length of stay (LOS) and the number of patients discharged to a facility postoperatively. Results: 209 patients were eligible for inclusion; 156 patients underwent LF at the TH (75%), while 53 underwent the same procedure at a CH (25%). There were no differences between the two cohorts with regard to age, gender, and marital status. However, a greater proportion of patients treated at the TH identified as Caucasian compared to those treated at a CH (84% vs. 65%; p < 0.05). Patients treated at the TH also had a significantly lower BMI (30.2 vs. 32.4; p < 0.05) and marginally lower Charlson Comorbidity Index relative to their CH-treated counterparts. Interestingly, the average cost of performing LF was still 123% higher at the TH compared to the CHs (p < 0.001). Similarly, the average LOS was significantly longer at the TH (6.12 vs. 4.21; p < 0.001), though this increase in LOS did not translate to any difference in discharge disposition between the two groups. Conclusions: Despite indications that patients undergoing surgery at the TH may have been healthier at baseline, the direct cost of LF was higher at the TH compared to the CHs in the same health system. The average LOS was also longer at the TH, indicating that institutional factors aside from preoperative health status may be contributing to this disparity in cost. We therefore conclude that surgical setting is a key determinant of the cost and hospital-reported outcomes associated with posterior cervical decompression.

A065: Racial Disparities in Perioperative Outcomes Following Lumbar Fusion for Spondylolisthesis: An Analysis of the 2011-2015 NSQIP Databases

Victoria Buescher¹, Emily Leary¹, Yinghua Cui¹, Theodore J. Choma¹, Christina L. Goldstein¹

¹Department of Orthopaedic Surgery, University of Missouri, Columbia - United States

Introduction: Lumbar spondylolisthesis is a common cause of back and leg pain, functional disability and impaired health related quality of life. Surgical intervention can effectively eliminate instability, relieve pain and improve quality of life, though these procedures are not performed without risk, A review of the Nationwide Inpatient Sample reported an 11% complication rate for spinal fusion for lumbar spondylolisthesis. These complications may prevent patients from being discharged home and may lead to unplanned reoperations and hospital readmissions. While patient and surgery-related risk factors for complications have been examined, race has never been studied as such. The purpose of this national database study is to examine the relationship between race and discharge destination, complication rates, and risk of unplanned reoperation and readmission in patients undergoing lumbar fusion for acquired and congenital spondylolisthesis. Materials and Methods: Using appropriate Current Procedural Terminology (CPT) and ICD-9 diagnostic codes, patients undergoing lumbar spine fusion for acquired or congenital spondylolisthesis were identified from the 2011 to 2015 American College of Surgeons National Surgical Quality Improvement Program (ACS-NSQIP) databases. Patient data pertaining to demographics, medical comorbidities, discharge destination and 30-day perioperative outcome were collected. SPSS and R were used to summarize continuous and categorical variables and calculate complication, unplanned reoperation and unplanned readmission rates. The impact of race on discharge destination, and the risk of experiencing at least one complication, an unplanned reoperation or an unplanned readmission was evaluated using Pearson’s χ² test. Odds ratios were calculated for significant findings. A p-value of 0.05 was considered statistically significant. Results: 6098 patients with a mean age of 60.20 years were included in this study. Almost two thirds of the patients were female (62.67%) with the majority being white (84.88%). Nearly three quarters of the patients underwent surgery for an acquired spondylolisthesis (73.53%). Posterior lumbar fusion was the most commonly performed surgery (40.10%), with the remaining patients undergoing anterior lumbar fusion, posterior interbody fusion and posterior interbody fusion with decompression in almost equal numbers (17.33%, 20.68% and 21.19% respectively). 82.75% of the patients were discharged home. At least one complication was incurred by 15.07% of patients, 2.98% underwent an unplanned reoperation and in those for whom data was reported (n = 5443), 5.29% had an unplanned readmission. Minority race was found to be positively associated with discharge from hospital to somewhere other than home (χ² = 3.9425, df = 1, p = 0.04 708, odds ratio = 1.20), but not with complications, unplanned reoperations or unplanned readmissions. Conclusions: This analysis of the interplay between race and perioperative outcomes of lumbar spine fusion for spondylolisthesis using a national database demonstrates racial disparities in postoperative discharge destination. This finding supports further investigations into the impact of this disparity on patient reported outcomes, as well as into the medical, social, economic and demographic factors that may contribute to the disparity. Future findings may subsequently inform resource allocation for minority patients undergoing spine fusion for lumbar spondylolisthesis with the goal of optimizing their episode of care.

A066: Misaligned Incentives for Lumbar Spine Surgery in the Bundled Payment for Care Initiative

Joseph Tanenbaum¹, Phillina Yee¹, Dominic Pelle¹, Edward Benzel¹, Michael Steinmetz¹, Thomas Mroz¹

¹Cleveland Clinic Center for Spine Health, Cleveland - United States

Background: Under the Bundled Payments for Care Initiative (BPCI), Medicare reimburses for lumbar fusion without adjusting for the patient’s underlying pathology. However, lumbar fusion is a widely used technique that can treat both degenerative and traumatic pathologies. In other surgical cohorts, significant heterogeneity exists in the intensity of hospital and post-acute care resource use when comparing emergent procedures for traumatic pathologies to elective procedures for degenerative pathologies. This difference has not been characterized in lumbar fusion surgery and BPCI does not distinguish between lumbar fusion for degenerative versus traumatic pathologies. If significant heterogeneity in hospital and post-acute care resource use exists among lumbar fusion patients, then BPCI would create a financial dis-incentive to treat specific patient populations. To study this question, we compared the hospital resource use of two lumbar fusion cohorts that BPCI groups into the same payment bundle for lumbar fusion: patients with spondylolisthesis and patients with thoracolumbar fracture. Methods: With bundled payments, hospitals are reimbursed for a lumbar fusion episode of care if patients are assigned diagnosis related group (DRG) 459 or 460. In the present study, national Inpatient Sample data from 2013 were queried to identify all patients that underwent lumbar fusion to treat a primary diagnosis of thoracolumbar fracture or spondylolisthesis and that were assigned DRG 459 or 460. Importantly, vertebroplasty and kyphoplasty are assigned different DRGs and are excluded from the typical bundled payment for lumbar fusion. Hospital resource use was measured using length of stay (LOS), direct hospital cots, and odds of discharge to a post- acute care facility. Multivariable linear and logistic regression were used to compare LOS, direct hospital costs, and odds of discharge to a post-acute care facility for thoracolumbar fracture patients and spondylolisthesis patients. All models adjusted for patient demographics, 29 comorbidities, and hospital characteristics. The complex survey design of the NIS was taken into account in all models. Results: After adjusting for patient demographics, insurance status, hospital characteristics, and 29 comorbidities, spondylolisthesis patients had a mean LOS that was 36% shorter (95% CI 26% - 44%, p < 0.0001), a mean cost that was 13% less (95% CI 3.7% - 21%, p < 0.0001), and had 3.6 times greater odds of being discharged home (95% CI 2.5 - 5.4, p < 0.0001) than thoracolumbar fracture patients. Conclusion: Under the proposed DRG-based bundled payment for care initiative, hospitals would be reimbursed the same amount for lumbar fusion regardless of whether a patient had spondylolisthesis or thoracolumbar fracture. However, compared with fusion for spondylolisthesis, fusion for thoracolumbar fracture was associated with longer LOS, greater direct hospital costs, and increased likelihood of being discharged to a post-acute care facility. Our findings suggest that the BPCI episode of care for lumbar fusion dis-incentivizes treatment of trauma patients.

Basic Science - Spinal Cord Injuries and Tumors

A067: Human Recombinant Erythropoietin Can Improve Motor Function in Cervical Myelopathy Rat Model

Takahiro Tanaka¹

¹Department of Neurological Surgery, Yokohama City University, Yokohama - Japan

Introduction: Erythropoietin (EPO) is a hematopoietic cytokine for red blood cell production in the bone marrow, and clinically used to treat chronic anemia. Recently, the neuroprotective effects of EPO have been reported in cerebral infarction, brain contusion and acute spinal cord injury. Here, we assessed neuroprotective effect of EPO in a rat chronic spinal cord compression model to explore the potential as a pharmacological treatment for cervical spondylotic myelopathy. Material and Methods: Male Wistar rats were used to produce chronic cervical compression model, a sheet of gradually expandable urethane compound polymer (size 2 x 6 x 0.7 mm) was inserted into sublaminar space of C5-C6. The motor functions (rotarod performance and grip strength) were evaluated once a week. In preliminary experiment, motor functions significantly declined 7 weeks after surgery, so recombinant human EPO (rhEPO) 5000 IU/kg, 500 IU/kg or normal saline (NS) was administered subcutaneously from 8 to 16 weeks after surgery two times a week. 16 weeks after surgery, cervical spinal cords were evaluated histopahologically. In another experiment, terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-biotin nick and labeling (TUNEL) stein was made to analyze apoptotic cell death and microvascular remodeling at 10 weeks after surgery. Results: In high dose rhEPO group, rotarod performance was improved from 9 to 15 weeks and grip strength was improved from 9 to 16 weeks after surgery significantly compared with low dose rhEPO group and NS group. Motor neurons in anterior horn were also preserved significantly in high dose rhEPO group. Apoptotic cells were significantly lower than another two groups. Conclusion: EPO preserves motor functions and anterior horn motor neurons in the rat chronic spinal cord compression model. EPO also improves motor function even in the progressive phase of compression myelopathy.

A068: The Effect of Neuropeptide ACTH4-10Pro8-Gly9-Pro10 on Caspase-3 on Spinal Cord Compression Injury

Eko Subagio¹, Ema Shofiana Azkia²

¹Dept. Neurosurgery Airlangga University, Surabaya - Indonesia ²Dept. Neurosurgery Rsud Prof Dr Margono Soekarjo, Purwokerto - Indonesia

Introduction: Spinal cord injury (SCI) is a clinical problem that has irreversible consequences, resulting in permanent loss of function and lifelong disability. The injury was related to the occurrence of apoptosis which occur after secondary insult. Some proteins are regarded as apoptotic regulatory molecules such as caspase-3 which has an important role in neuron cell apoptosis. This study was conducted to determine the effect of neuropeptide ACTH4-10Pro8-Gly9-Pro10 on caspase-3. Material and Methods: The subjects were divided into 9 groups of male Sprague Dawley rats. This research used an aneurysm clip which have compression power 20 gr for a mild compression group and aneurysm clip which have compression power 35 gr for the heavy compression group. First group (Negative control) was performed laminectomy and then terminated, the spinal cord was removed. Eight remaining groups were performed laminectomy. After laminectomy, 4 groups were given mild compression for 1 minute, and 4 groups were given heavy compression for 1 minute. One hour later 2 groups of mild compression were given 0.9% NaCl drops and 2 other groups were given nasal drops of ACTH4-10Pro8-Gly9-Pro10. The heavy compression group was treated equally. Moreover, half of these groups were sacrificed after 3 hours and after 6 hours. The sample would be fixed with formalin, then performed immunohistochemical examination and statistical analysis. Results: In the mild compression group, mild compression at 3 hours was found to significantly increase caspase-3 rate compared with the control group (7.00 vs 1.33; p = 0.000). Caspase-3 was also significantly larger at 6 hours measurement (13.67; p = 0.000). Moreover, the 6 hours SEMAX group had a significantly smaller number of caspase-3 compared with the 3 hours SEMAX group (12.67 vs 5.67; p = 0.000). Meanwhile, the heavy compression group also showed a significant increase in caspase-3 compared with the mild compression group. In the measurement of 6 hours of heavy compression group, there was also an increase of caspase-3 rate compared with 3 hours (25.33 vs 15.67; p = 0.000). In the treatment group, the 6 hours group had a significantly smaller number of caspase-3 compared with 3 hours observation (10.67 vs 13.67; p = 0.000). Conclusion: Both groups (mild and heavy compression trauma) have been proven to increase the number of caspase-3. While the addition of ACTH4-10Pro8-Gly9-Pro10 was able to decrease caspase-3 in spinal cord injury by compression.

A069: Comparative Analysis of Perioperative Blood Loss in Posterior Thoracolumbar Spine Surgery in Patients Taking Aspirin and Clopidogrel – A Prospective Matched Cohort Study

Aditya Banta¹, Saumyajit Basu¹, Amitava Biswas¹, Subhodeep Mandal¹, Anil Solanki¹

¹Neurosciences Division, Park Clinic, Kolkata - India

Introduction: Evidence based recommendations are available regarding continuation of Aspirin and Clopidogrel in patients listed for surgery who have had percutaneous transluminal coronary angioplasty (PTCA) for Ischemic Heart Disease (HD). However, for non-stented patients, conflicting reports are available in literature regarding the outcome of thoracolumbar surgery on continuation of Aspirin and Clopidogrel in perioperative period. The objective of this study is to assess whether continuation of these antiplatelet drugs in patients without PTCA are associated with increased perioperative blood loss, need for blood transfusion and perioperative complications, or not. Materials and Methods: In this study, 88 patients were selected with single and multilevel posterior thoracolumbar surgery and was classified into three groups: (A = 22) Aspirin only, (B = 22) Clopidogrel only and (C = 44) Control. These groups were matched with respect to age, sex and comorbidity status. The estimated blood loss (EBL), postoperative drain collection (PDC), differential hematocrit (DH) (Pre-op PCV – Postop Day 1 PCV) and transfusion related data were collected. This was then statistically analyzed. Results: There is no significant difference regarding EBL in single level surgery in patients taking Aspirin or Clopidogrel with Control [p = 0.1(A vs. C) and p = 0.06(B vs. C)] and in multilevel surgery [p = .38(A vs. C) and p = .5(B vs. C)]. No difference has been found in PDC in three groups; 'single level surgery [p = 0.06(A vs. C) and p = 0.06(B vs. C] and multilevel surgery [p = 0.31(A vs. C) and p = .22(B vs. C)]. Regarding differential hematocrit, no significant difference was found in these groups; single level [p = .48(A vs. C) and p = .21(B vs. C)] and multilevel surgery [p = .46(A vs. C) and p = .33(B vs. C)]. Conclusion: Continuation of antiplatelet therapy is not associated with increased perioperative blood loss and no significant change in hematocrit occurs. It is not associated with increase in transfusion need and enhanced morbidity.

A070: Early Tissue Effects of SBRT in Spinal Metastases: a Pilot Study in Humans

Jasper G. Steverink¹, Stefan M. Willems², Marielle E.P. Philippens³, Nicolien Kasperts³, Wietse S.C. Eppinga³, Joannes J. Verlaan¹

¹Department of Orthopaedics, University Medical Center, Utrecht - Netherlands ²Department of Pathology, University Medical Center, Utrecht - Netherlands ³Department of Radiotherapy, University Medical Center, Utrecht - Netherlands

Introduction: Stereotactic body radiotherapy (SBRT) is a clinically highly effective modality in the treatment of spinal metastases. Recent literature suggests effects of SBRT expanding beyond the traditional concept of DNA-damage. Anti-tumour immunity, vascular damage leading to tumour necrosis and increased rates of tumour apoptosis are implied, yet in-human evidence remains scarce. This study reports which aforementioned effects occur in spinal metastases within 24 hours after SBRT. Material and Methods: A total of 10 patients with spinal metastases secondary to several primary solid tumours (including relatively radioresistant melanoma and renal cell tumors) underwent 1x18 Gy followed by percutaneous fixation within 24 hours. Perioperative samples of vertebral metastases were obtained. Of 6 patients, a pre-SBRT biopsy was also available for comparison. Samples were immunohistochemically stained for T-cells (CD3+, CD4+, CD8+), NK-cells (CD56+), endothelium (CD31+) and apoptotic activity (Caspase-3). To assess tumour necrosis, mitotic activity and stromal reaction, HE-staining was performed. Results: Perioperative biopsies were obtained circa 6 hours (4.5-7.5 h) or 21 hours (18.5-22.5 h) after SBRT. Seven out of ten (70%) 21 h post-SBRT samples showed necrosis, compared to 0% necrosis in pre-SBRT and 6 h post-SBRT samples. Tumour cell apoptosis increased greatly as time after SBRT progressed. CD31+ endothelial cell counts decreased after SBRT. Both renal cell metastases displayed notable decreases in vessel density. Mitotic activity decreased after radiotherapy. Reactive stroma was visible in 4 out of 6 pre-SBRT samples compared to 10 out of 10 post-SBRT samples. T- and NK-cell counts were relatively unaffected. Conclusion: SBRT induces tumour necrosis and tumour apoptosis and a decrease in tumour vessel density within 24 hours, even in renal cell metastases, a tumour deemed relatively radioresistant. The role of immune cells is limited in this early phase. These first-in-man results imply vascular damage and DNA-damage as important mechanisms accounting for the clinical efficacy of SBRT.

Deformity - Thoracolumbar (Adolescent) - Surgery 2

A071: Do Photometric Parameters Changes With BMI and Cobb Angle in Adolescent Idiopathic Scoliosis? A Waist Asymmetry Research

Akay Kirat¹, Akif Albayrak¹, Ali Öner¹, Kutalmis Albayrak¹, Deniz Akbulut¹, Mehmet Akif Kaygusuz¹

¹Department of Orthopaedics and Traumatology, University of Health Sciences, Baltalimani Bone Diseases Education and Research Hospital, Istanbul - Turkey

Introduction: The most common cosmetic complaints in adolescent idiopathic scoliosis are lumbar asymmetry, hump and shoulder imbalance. Several photometric parameters have been defined to evaluate waist asymmetry. The aim of this study is to investigate how the body mass index and Cobb angle affecting these waist asymmetries related photometric parameters of the adolescent idiopathic scoliosis patients. Material and Methods: 68 AIS patients who applied to our spine clinic were included in the study. (14 M, 54 F). Mean age was 15.66 (10-30) years. We obtained a full X-ray of the spine and back clinical photography for all patients. On photographs, waist height angle (WHA), right/left waist angles and right/left waistline distance ratio were measured. Body/Mass indexes were calculated. Major Cobb angles were measured. Patients were divided into 2 groups according to their major Cobb angle (Group 1 < 45 degrees, Group 2 > 45 degrees). A correlation analysis between all variables was done using Pearson Correlations Coefficient. Results: In group 1, the mean major Cobb angle was 31.7 ± 8 degrees. In group 2 the mean major Cobb angle was 59.2 ± 11.8 degrees (p < 0.01). Average BMI was 21.5 ± 4.5 in group 1 and 19.7 ± 4.8 in group 2. There was a poor but significant inverse correlation between BMI and waist height angle (-0.24 p = 0.049). There was no significant correlation between BMI and the other photometric parameters. We found a significant correlation between Cobb angle and WHA (0.515, p < 0.01) and a poor correlation between Cobb angle and left waist angle (0.312, p = 0.01). There was no significant correlation between Cobb angle and the other photometric parameters. Conclusion: One of the common cosmetic complaints in adolescent idiopathic scoliosis is lumbar asymmetry. Correlation of waist height angle and Cobb meaningfulness was also shown in previous studies. We have found a significant inverse correlation between clinical WHA and BMI. We consider that these findings will be effective in giving decision of surgery in scoliosis patients who are operated mostly for cosmetic reasons today.

A072: Diagnostic Accuracy of Intraoperative Electromyography in the Positioning of Pedicle Screws in Adolescent Idiopathic Scoliosis Treatment: A Cross-Sectional Diagnostic Study

Raphael Pratali¹, Bruno Gavassi¹, Bernardo Batista², Carlos Eduardo Barsotti¹, Ricardo Ferreira²

¹Hospital Do Servidor Publico Estadual, Sao Paulo - Brazil ²Faculdade De Medicina Da Universidade De Sao Paulo, Sao Paulo - Brazil

Introduction: Pedicular screw has become the most popular device in spine surgeries, especially in treatment of Adolescent Idiopathic Scoliosis (AIS). This technique allows better curve correction in coronal, sagittal and rotational plans, shorter constructions and better pulmonary function, compared with other devices. Despite those advantages, this technique is potentially dangerous. Intraoperative neuromonitoring is frequently used to detect misplacement of screw and reverse possible neurologic complications. The aim of this study was to investigate the relationship between EMG thresholds during AIS surgery and the positioning of pedicle screws as evaluated by computed tomography (CT) in the postoperative period. Material and Methods: This is an observational, cross-sectional study, including 16 patients undergoing AIS surgical correction. All procedures were monitored with electromyography (EMG) of the inserted screws and the stimulation threshold of each screw was recorded. Those values were compared with the position of the screws, based on the postoperative CT-scan, according to a specific classification system. Every individual screw was assessed and classified in both medial and sagittal planes as: AT RISK FOR NERVE INJURY (ARNI), if presenting medial, superior or inferior cortical perforation, or NO RISK FOR NERVE INJURY (NRNI), if normally placed or presenting lateral cortical perforation. Diagnostic accuracy of EMG to predict screw position ARNI was investigated using a receiver operating characteristic (ROC) curve. Results: 226 pedicles, below T6, were considered on the EMG accuracy study. In the axial plane, 204 (90.3%) screws were considered as NRNI, 136 (60.2%) ideally positioned and 68 (30.1%) with lateral cortical perforation, and 22 (9.7%) as ARNI, with medial cortical perforation. In the sagittal plane, 183 (81%) pedicle screws were considered as NRNI while 43 (19%), that violated the inferior foramen superior foramen, were considered ARNI. We observed a statistically significant association between EMG responses and positioning of screws associated with risk for nerve injury. A 1 mA decrease in the EMG threshold was associated with an 12% increase in the odds of screw position ARNI (OR = 1.12; 95% CI = 1.06 -1.18; p < .001). Considering the ROC to evaluate the accuracy of EMG, the Positive Predictive Value of the EMG, as diagnostic method for screws ARNI, was very low, the highest of 18% for cutoff of 25 mA, but the Negative Predictive Value was moderate to high (78%-93%) for every cutoff analyzed. Conclusion: There was found a poor accuracy of the EMG as diagnostic test for screws at risk for nerve injury. However, the EMG has shown to be effective to minimize false-negatives screws, considering their position ARNI.

A073: Coronal Imbalance in Lenke5c Adolescent Idiopathic Scoliosis Relevant to The Lowest Instrumented Vertebrae Selection: Lower- End Vertebra Versus Lower-end Vertebra +1 in Posterior Fusion

Bowen Hu¹, Yueming Song¹, Xi Yang¹

¹Department of Orthopedics Surgery, West China Hospital, Sichuan University, Chengdu - China

Introduction: The choice for the distal fusion level of the posterior selective thoracolumbar or lumbar fusion in the lenke5c adolescent idiopathic scoliosis patients is highly associated with the coronal balance. Previous studies indicated that patients with LIV tilt > 25°could extend distal fusion to LEV+1 to avoid coronal imbalance. This study aimed to assess the potential risk factor of coronal imbalance in Lenke 5C scoliosis, and to discuss how to select lowest instrumented vertebra (LIV). Material and Methods: We reviewed 41 Lenke5c AIS patients in one institution with at least 2 years follow-up from 2011 through 2015. Preoperative radiographs, 3 months and 2 years postoperatively follow-up radiographs were measured specifically in a quite variety of measurements related to the coronal balance. Patients were categorized into 2 groups -the LEV group and the LEV+1 group. Results: Coronal imbalance at final follow-up was found in 4 of the 23 patients at theLEV+1 group patients and none of the 18 patients pf LEV group had coronal imbalance both in the first and final follow-up . 35 of the 41 patients have their C7PL shifted to the convex side of the CSVL, which included all of the 13 coronal imbalanced patients at the first follow-up .Patients fusion to LEV+1 with > 25° LEV tilt also showed poor result of coronal imbalance. Statistically speaking, the coronal balance at the final follow-up was correlated with the preoperative reduced lumbosacral hemi-curve(p = 0.019). Conclusion: With the distal fusion extension at LEV+1, it is more likely to get coronal imbalance both in the first and final follow-up, especially when the the reduced lumbosacral hemi-curve exceeds 15°. It should not choose the LEV+1 as lowest instrumented vertebra when the LEV is L4.

A074: Comparison of Flexibility Assessments in Adolescent Idiopathic Scoliosis (Flexis Study)

Kenny Yat Hong Kwan¹, Calgar Yiglor², Hui Yu Koh¹, Ahmet Alanay², Kenneth Cheung³

¹Department of Orthopaedics and Traumatology, The University of Hong Kong - Hong Kong ²Dep. of Orthopaedics and Traumatology, Acibadem University, Istanbul - Turkey ³

Introduction: The goals of surgical correction of adolescent idiopathic scoliosis (AIS) are to achieve a balance spine with a parallel fusion block. Preoperative curve flexibility assessment is integral in the radiographic evaluation and surgical decision making. The aim of this prospective study was to compare five radiographic techniques in flexibility assessment and correlate them to surgical correction. Material and Methods: A prospective comparative observational study was carried out in two academic institutions in Hong Kong and Turkey. Consecutive patients undergoing AIS surgical collections were recruited between June 2016 to August 2017. Preoperative radiographic evaluation included standing posteroanterior and lateral whole spine, supine, supine side bending, fulcrum bending (FB) in both sites; awake traction in Hong Kong; and supine traction under general anaesthesia (STUGA) in Turkey. Surgical correction and fusion levels were determined by the surgeons’ usual technique, and postoperative radiographs were taken. For each radiographic assessment, correction rate and flexibility percentages were calculated, and correction index was the correction rate as a percentage of the flexibility. Statistical differences were calculated. Results: 76 patients were recruited into the study, but 2 patients had anterior surgery and were excluded from analysis. 74 patients (65 females and 9 males) with an average age of 13.91 years (range, 11-18) at the time of operation. 51 patients had a thoracic major curve (34 cases Lenke 1; 10 Lenke 2; and 7 Lenke 3), and 23 patients had a thoracolumbar or lumbar major curve (21 cases Lenke 5 and 2 Lenke 6). For thoracic curves, mean preoperative standing frontal Cobb was 57.8^o (range, 34.3^o-79.7^o), and the mean postoperative Cobb was 15.5^o (range, 1-40.7^o) with a mean correction rate of 72.5% (range, 27.1%-97.9%). For lumbar curves mean preoperative Cobb was 50.3^o (range, 35^o-88^o), and the mean postoperative Cobb was 8.0^o (range, 0.1^o-22^o) with a mean correction rate of 84.5% (range, 59.1%-99.8%). The correction indices showed that the most predictive dynamic assessment for AIS correction was FB, compared with STUGA (p = 0.2), awake traction (p = 0.004), supine side bending (p = 0.003), and supine (p = 0.000) for thoracic curves. For lumbar curves, FB, STUGA and supine side bending were similar in prediction (p > 0.05), which were better than supine film (p = 0.000). Conclusion: Although correction rate can give an indication of the amount of correction achieved per case, it is inaccurate to compare between different cases as it does not take into account the intrinsic flexibility of the curve, and does not necessarily reflect on either the surgical technique or the instrumentation strategy. Correction index takes into account of the curve’s intrinsic flexibility, and the closer one gets to 100%, the more effective is the final surgical correction in taking up this flexibility. Our study showed that FB is most predictive in thoracic curves undergoing posterior instrumented fusion. In lumbar curves which are usually more flexible, no statistical significant difference was found amongst different dynamic radiographs in predicting surgical correction. An accurate flexibility assessment will allow improve pre-operative planning for the need of additional release and fusion level determination.

A075: Two Stage Front Back Fusion for Double Major Adolescent Idiopathic Scoliosis (AIS): Saving Lumbar Levels With Improved Derotation of the Lowest Instrumented Vertebra (LIV)

Lui Darren¹, Adam Benton¹, Hai Ming Yu¹, Alexander Gibson¹, Sean Molloy¹

¹Royal National Orthopaedic Hospital, London - United Kingdom

Introduction: Selective proximal lumbar fusion has clinical benefits to the patient. A supine bending radiograph (SBR) can be utilised to stratify the flexibility of the thoracolumbar (TL) and MT curves in double major adolescent idiopathic scoliosis (AIS). Utilising a two stage anterior/posterior fusion can save lumbar motion segments proximal to the Harrington Stable Zone (HSZ). We compared the distal LIV and the HSZ across a novel method of stratification into 4 categories of flexibility for double major curves. Materials and Methods: Retrospective Review: 2420 consecutive scoliosis deformity correcting surgeries from 2006 to 2012 with minimum 2 year follow up identifying all AIS with front / back two stage surgery and stratified by Kings Classification and Lenke. Preoperative demographics. Preoperative: standing radiograph Cobb, Harrington Stable Vertebra, Supine Bending Radiograph (SBR) Cobb. Postoperative radiographs: Correction Rate (CR), Supine Bend Flexibility (SBF) and Supine Bending Flexibility Index (SBFI), LIV intervertebral Cobb. Mean HSV. Results: Of the 2420 cases there were 54 two stage procedures for double major curves (21 King 1 and 35 King 2). There were 15 double curves (Lenke 1C) with 14 Lenke 3C, 7 Lenke 4C and 18 Lenke 6C curves. 58 anterior/posterior King 1&2 AIS (2.6%). 82% female, mean age 14.5y. Preoperative Cobb Main Thoracic (MT) 62.7°, Thoracolumbar (TL) 59.1°, Flexibility 31.8% (MT), 50.4% (TL). Postoperative CR was 68.6% (MT), 79.3% (TL). SCBI of 277.9% (MT), 177.9% (TL). The mean HSV 4.63, mean LIV 3.1. LIV intervertebral Cobb 4.57°. Quartiles for flexibility: 4th ( > 64%), 3 rd (53-64%), 2nd (39-53%), 1st (0-39%). Non parametric testing rejects the null hypothesis for postoperative parameters CR TL, SBCI TL and FTL and intervertebral cobb of LIV (p < 0.05) across all categories of flexibility. The null hypothesis is retained comparing the distribution of HSV (p = 0.744) and LIV (p = 0.548) across all categories of flexibility. Conclusion: We validated our novel approach to stratifying the flexibility of thoracolumbar curves by supine bending radiograph showing significant differences across stratification of flexibility. The HSV, LIV and mean numbers of level saved showed no significant difference comparing the stiffest curves to the most flexible. There was a mean saving of 1.53 levels in the lumbar spine with a Pedriolle derotation of 1.4 grades. This result shows the independent power of a two stage anterior/posterior procedure for correction of double major curves regardless of stiffness and saves lumbar levels whilst restoring radiographic parameters to more normal values.

A076: Posterior Spinal Surgery for Adolescent Idiopathic Scoliosis Does Not Induce Compensatory Increases in Adjacent Segment Motion: A Prospective Gait Analysis Study

Roderick M. Holewijn¹, Idsart Kingma², Marinus de Kleuver³, Noël L.W. Keijsers⁴

¹Department of Orthopedic Surgery, VU University Medical Center, Amsterdam Movement Sciences, Amsterdam - Netherlands ²Faculty of Human Movement Sciences, Vrije Universiteit Amsterdam, Amsterdam Movement Sciences, Amsterdam - Netherlands ³Department of Orthopedic Surgery, Radboud University Medical Center, Nijmegen - Netherlands ⁴Sint Maartenskliniek Research, Sint Maartenskliniek, Ubbergen - Netherlands

Introduction: It remains surprising to see how well adolescent idiopathic scoliosis (AIS) patients perform after spinal correction and fusion. It was previously hypothesized that mechanisms are at play during gait that compensate for the loss in motion of the fused spine. Still, previous studies could not identify such compensatory mechanisms in the lower body. This study aims to test the hypothesis of a compensatory increased motion of the distal unfused part of the spine during gait. Material and Methods: Twelve AIS patients were included. Sets of three VICON cluster markers were used to measure the 3D motion of the proximal (PFP, representing the fused and distal unfused spine) and distal part of the fusion (DFP, representing only the distal unfused spine) in relation to the pelvis. The range of motion (ROM) was measured during gait in the frontal, sagittal and axial planes. Measurements were performed prior to surgery and three and twelve months after surgery. Results: Surgery resulted in a decrease in PFP axial plane ROM (8.3° versus 5.9°, p = 0.006). Surprisingly, no compensatory increase in DFP range of motion could be identified. Actually, axial plane DFP decreased in a similar fashion (8.2° versus 5.6°, p = 0.0019). Additionally, no improvement over time was observed when comparing the 3 and 12 month postoperative measurements. Conclusion: Although the hypothesis of a compensatory increase in motion of the distal unfused segments after spinal fusion for AIS is a much researched and controversial topic, this study is the first to study it in such detail during gait, and could not demonstrate such increase. AIS patients possibly use multiple subtle compensatory techniques in the upper and lower body.

Spine Surgery and Complications

A077: Clinico-Radiological Outcome of Cervical Pedicular Screw Inserted by Free Hand Technique and Complications Related to Pedicle Wall Violation

Aditya Dahapute¹, Sandeep Sonone¹, Piyush Nashikar¹, Saurabh Muni¹, Sai Gautam¹

¹Dept of Orthopaedics, Seth G.S.Medical College and KEM Hospital, Mumbai - India

Introduction: Pedicle screw system is intended to provide immobilisation and stabilisation of spinal segments adjunct to bone graft healing and fusion mass development and /or to restore the integrity of spinal column even in absence of fusion for prolonged period for following acute and chronic instabilities of cervical spine. Pedicular screws in cervical spine have been shown to have significantly higher pull out strength and higher primary stability than lateral mass screws. Though appealing, this procedure is associated with inherent risk of vascular and neurological damage. Use of cervical lateral mass and pedicle screws entails the potential risk of vertebral artery, spinal cord and nerve root injury. Anatomic restrictions for pedicle screws include anomalies of the vertebral artery, varied and small size pedicles with restricted direction for screw insertion, and bone that precludes placement. Thus the present study will be conducted with the aim to investigate clinic-radiological outcome of cervical pedicular screws. Aim is to find out incidence of post operative complications of CPS fixation, radiological complications of CPS fixation and to correlate clinical and radiological outcome of CPS fixation. Material and Methods: It is a retrospective study. 22 patients underwent CPS (cervical pedicle screws) fixation using free hand technique by one surgeon at KEM Hospital during period of Jan 2011 to June 2016. Inclusion criteria for CPS: CPS can be done in patients including cervical segmental instabilities due to following reasons. 1. Trauma (spinal fractures and dislocations). 2. Instability and deformity. 3. Degenerative disease (intractable radiculopathy and/ myelopathy, discogenic arm and/ or neck pain confirmed by radiographic studies, degenerative disease of facets with instability and Occification of Posterior Longitudinal Ligament). In this study CPS done in cervicle myelopathy, cervical ossification of Posterior Longitudinal Ligament (OPLL), traumatic listhesis, atlanto-axial dislocation, spinal tumors and tuberculosis of cervical and upper dorsal region. Exclusion criteria for CPS: 1. Anomalies of vertebral artery on side of CPS insertion. 2. Small size pedicle with restricted direction for screw insertion. 3. Dysplastic pedicle. Post operatively CT scan with angiography of cervical spine and x ray of cervical spine was done for all patients selected for this study. Following parameters were studied on CT scan and xrays-medial angulation of pedicle screw, angle made by screw with superior end plate, incidence of sclerotic pedicles and violation of pedicle wall by screw and its clinical correlation. Post-operatively CT angiography was done to look for vertebral artery compression. Perforations were classified as: Cp (complete perforation): deviation of screw from pedicle by more than half of screw diameter; Pp (partial perforation): deviation less than half screw diameter; Np (no perforation): screw did not violate pedicle cortex. Results: In this study 22 patients were included. Age of patients was between 14yrs to 62 with mean 49 yrs and median 55 yrs. 92 cervical pedicular screws (CPS) were done in 22 patients that include c2 to c7 level. Of these 46 screws, 24 (52.2%) CPS were on left side and 22 (47.8%) on right side. C2 pedicle is significantly different from rest in relationship to vertebral artery and anatomical landmarks. For this reason only subaxial cervical vertebras are analysed separately. Mean screw size for subaxial CPS was 21.05 ± 3.493 mm with minimum of 16 mm & maximum of 28 mm being used. For c2 mean screw size for CPS was 20.50 ± 3.728 mm with minimum 16 mm and maximum of 25 mm being used. 3.5 mm diameter screws were used for all level of fixation. Mean angle of screw with end plate for subaxial pedicle was 4.4 ± 7.883 Degrees. Range of angles used in this study was -10 to 24 degrees. Mean angle of screw with sagittal axis of vertebrae was 23.43 ± 9.279 Degrees. Range of angle used was 6-40 Degrees. Perforation occur in 20 cps which is clinically insignificant (p value is 0.561). C3 (4 out of 8, 50%), c5 (6 of 22, 30%) and c4 (6 of 20, 27%) have maximum chances of perforation because the pedicle width and height are smaller in c3, c4 and c5. Perforations are more on left side 14 (70%) than on right side 6 (30%). Out of 20 perforations 4 (20%) were CP and 16 (80%) were PP. Most of the perforations were into lateral wall. There were no superior perforations. Medial perforation was present in 4 screws (20%), lateral perforation was present in 10 screws (50%), infero-lateral perforation was present in 4 screws (20%), infero-medial perforation was present in 2 screws (10%). 9.1% (2 of 22) of patients developed neurodeficit. Deficit was transient and patient recovered completely. 9.1% (2 of 22 patients) of patients had vertebral artery compression. None of the patient developed signs and symptoms of vertebral artery syndrome. Sclerotic pedicles were divided into broad sclerotic and narrow (hour glass) sclerotic. Sclerotic and broad pedicles were used for CPS fixation. Out of 80 pedicles 22 (26.1%) were broad and sclerotic. Out of 22, 6 were perforated (27.5%). There is increase in perforation rate of sclerotic pedicle (27.5%) compare to normal pedicle (72.5%) with p value 0.696. Conclusion: Not all perforations are associated with neurological or vascular complications. As many of the perforations remain asymptomatic, postoperative CT scan should be done to know the status of CPS. CT scan with vertebral artery angiography is mandatory before planning CPS fixation. For Indian population smaller diameter screw 3.5 mm can be used safely. Broad sclerotic pedicles can be used for CPS safely. Difficulty should be anticipated compare to those non sclerotic. Hour glass (narrow) sclerotic pedicles should be excluded during preoperative evaluation. As associated with complications this procedure should be done in highly selected patients, with selection of each vertebra on the basis of CT scan and vertebral artery angiography.

A078: Features of Patients Transferred to the ICU Due to Respiratory Failure Following Spine Surgery

Ryder Reed¹, Robin Carlson¹, Michelle George¹, John McClellan¹

¹Nebraska Spine Hospital, Omaha - United States

Introduction: Prolonged apneic periods and respiratory failure are among the most frequent serious complications postoperatively, often exacerbated in patients receiving narcotics. In the setting of spine surgery, pain management with opioids remains the standard. However, in recent years the adverse effects of opioid toxicity have taken center stage and have been the focus of several investigations. While patients develop tolerance to the intended analgesic effects of opioids, no tolerance is developed to their respiratory suppressive effects. Combine this phenomenon with patients that already have significant preexisting conditions and it may necessitate transfer to an ICU or a more well-equipped center of care, negatively affecting quality of care and patient outcomes. This investigation aims to characterize common features among patients transferred to the ICU with respiratory failure following spine surgery. Materials and Methods: A retrospective case study of the electronic medical records (EMRs) of 37 patients were inspected individually by an independent reviewer to extract the required data, including age, BMI, American Society of Anesthesiologists (ASA) Physical Status Classification score, cause of transfer to the ICU, complications, medications, and comorbidities. Data were compiled and grouped to describe features shared among transferred patients. Of the 2456 patients who underwent inpatient spine surgery between 2015 and 2017, 37 were transferred to the ICU and ranged in age from 32 - 83, with 16 being male and 21 females. Results: Of the 37 patients transferred to the ICU, 13 (35%) were transferred due to respiratory failure. Five of these patients were female and 8 were male, with an average age of 60.8 years and an average BMI of 33.4. Additionally, these patients had an average ASA Physical Status Classification score of 3.2, indicating a noteworthy level of morbidity prior to surgery. Indeed, all but three of the patients had a positive history of significant respiratory disease, including obstructive sleep apnea (5), COPD (4), and asthma (3). Furthermore, 10 of the 13 were either current or former smokers. Despite the morbidity of these patients, just 6 received a bronchodilating agent preoperatively. While all patients received narcotic analgesics, 4 of the patients received an intraoperative intrathecal injection of morphine and 5 of the patients were placed on patient-controlled analgesia hydromorphone. Of particular interest, 3 of the 4 patients who received intrathecal morphine were given naloxone during their postoperative course, indicating reasonable suspicion that the narcotic contributed to their respiratory suppression. Conclusions: Here we have described common features of patients suffering from respiratory failure necessitating transfer to the ICU following spine surgery. This study should draw attention to the importance of perioperative care in individuals with significant morbidity and higher levels of narcotic use. These results may prompt a closer investigation into possible preventative measures, such as closer monitoring of respiratory rate, airway patency, and narcotic use. Limitations of this study should be considered, since without a paired control group no claims can be made as to which conditions specifically increase the likelihood of transfer to the ICU.

A079: Predictive Factors Leading to Readmission Within 30 Days in Patients Undergoing Surgery for Spinal Metastases: A Multivariate Logistic Regression Analysis

Jay I. Kumar¹, Vijay Yanamadala¹, Ganesh Shankar¹, Bryan Choi¹, John Shin¹

¹Department of Neurosurgery, Massachusetts General Hospital and Harvard Medical School, Boston - United States

Introduction: Readmission within 30 days after complex spine surgery is considered a “never event” by Medicare but remains a reality in 30-35% of cases after surgical treatment of spinal metastases. We present a single-center experience of readmissions in 185 consecutive patients who underwent surgery for spinal metastases and assess predictive factors for readmission. Methods: Charts of 185 patients who underwent surgery for spinal metastases over five years from October 2011 through February 2017 were reviewed for unplanned readmission within 30 days and possible contributing factors. A multivariate analysis was performed for patient demographic and surgical parameters that predict readmission. Results: The rate of unplanned readmission within 30 days was 27%. The most common reason for readmission was pain, accounting for 25% of all readmissions. Medical factors accounted for 54% of readmissions: failure to thrive, 14%; fever, 12%; altered mental status, 12%; pulmonary embolism, 4%; and miscellaneous, 12%. Surgical factors accounted for 22% of readmissions: wound infection, 14%; new neurologic deficit, 6%; and miscellaneous, 2%. Age > 65, prior radiation, and multiple metastases were all predictive of readmission at a statistically significant threshold of p < 0.05. Conclusions: Surgery for spinal metastases is associated with a significant readmission rate. Pain and medical factors accounted for most of readmissions. Older age and advanced nature of disease are predictive factors for readmission and should be taken into account when deciding on discharge disposition for patients after surgery for spinal metastases. Enhanced coordination of post-operative care between surgical and medical teams may help reduce readmission rates.

A080: Slick Enough? Subaxial Cervical Spine Classification Systems: An External Agreement Validation Study

Michael Petrie¹, Angus Fong¹, Morgan Jones¹, Tobias Steadman¹, Michael Athanassacopoulos¹, Lee Breakwell², Neil Chiverton¹, Ashley Cole¹, Marcel Ivanov¹, Antony Rex Michael¹, James Tomlinson¹

¹Sheffield Spine Unit, Sheffield Teaching Hospitals NHS Trust, Sheffield - United Kingdom ²Spine Unit, Northern General Hospital, Sheffield - United Kingdom

Introduction: An effective classification system should be all inclusive, clinically relevant, a guide to subsequent treatment and reliable. In 2007, the Subaxial Cervical Spine Injury Classification (SLIC) system was introduced to clinical practice. In 2015, the AOSpine group developed a classification system (AO), with the intent of producing a “user friendly” classification system. The aim of the study was to assess the reliability of the SLIC system and the AO system amongst a number of orthopaedic surgeons working in a specialist spinal surgery unit. Material and Methods: All patients admitted to a UK Major Trauma Centre over a six-month period from February to August 2016 with a cervical spine fracture had their imaging reviewed and injuries classified using both the SLIC and AO systems. Clinical and radiographic data for 51 patients were reviewed by 9 spinal surgeons. Clinical management as suggested by SLIC score was also compared to actual patient management. Results: SLIC: The overall inter-rater Fleiss’ kappa (κ) coefficient was 0.87. Highest agreement was seen on grading neurologic status (0.97), with injury morphology and disco-ligamentous classification showing substantial correlation (0.65 and 0.64 respectively). AO: The overall inter-rater Fleiss’ kappa (κ) coefficient was 0.43, significantly lower than that seen for the SLIC system. Conclusion: The reliability of the SLIC system compares well with previously reported levels of inter-rater reliability from the authors’ own internal verification study, as well as from other published external studies. The AOSpine system may be useful as a research tool but the reliability values from this study suggest that more work needs to be done. SLIC has substantial agreement for inter-rater reliability for overall score, and in our experience, is a useful assessment tool to help guide clinical decision making - especially in the hands of trainees and non-specialist surgeons.

A081: Factors That Influence the Rate of Pedicle Screw System Sailure in Patients With Traumatic Injuries of a Lumbar Spine and Thoracolumbar Junction

Andrey Bokov¹, Sergey Mlyavykh¹, Anatoliy Bulkin¹, Marina Rasteryaeva¹

¹Department of neurosurgery of Privolzhskiy Federal Research Center, Nizhny Novgorod - Russian Federation

Introduction: Implant failure has a noticeable incidence in patients with altered bone quality, on the other hand surgical tactics may also influence implant stability, although the reported data remains controversial. The objective of this study is to determine risk factors that influence pedicle screws fixation stability in patients with traumatic injuries of a lumbar spine and thoracolumbar junction. Materials and Methods: This is a retrospective evaluation of 137 spinal instrumentations performed in cases of traumatic injuries of lumbar spine and thoracolumbar junction. Patients with A3, A4 and B2 injuries were selected for this study. Preoperatively patients underwent CT examination and bone radiodensity was measured in Hounsfield units (HU) at standard level of L3. Pedicle screws fixation was used either as a stand-alone technique or in combination with anterior interbody fusion. In cases with posttraumatic spinal stenosis a decompression of nerve roots and spinal cord were performed. Cases with implant malposition were excluded from this study. The duration of follow up was 18 months. Cases with screws loosening, screws and rod breakage were registered and general logistic regression model was used to assess the relationship between complication rate and potential risk factors. Results: Bone density measured in HU, number of fixed levels, presence of vertebra without screw insertion (fractured vertebra); bilateral facet joints removal and laminectomy performed for decompression, residual kyphotic deformity of more than 10° and anterior interbody fusion (ALIF) were taken into consideration as potential factors that affect pedicle screw fixation stability. It has been estimated that the rate of implant instability was growing with the decrease in bone radiodensity in HU. The detected risk factors for implant failure were laminectomy and residual kyphotic deformity of more than 10°. ALIF performed for augmentation of pedicle screw fixation was associated with a lower complication rate. The influence of other factors was insignificant. The parameters of regression model for complication rate were: B0 = −2675, p = 0,7416 (insignificant); B1 for bone density = 0,00 130, p = 0,0089, OR (odds ratio per unit change) = 10 131; B2 for residual kyphotic deformity = -11 838, p = 0,0140 OR = 0,3061; B3 for decompression with laminectomy = −0,9440, p = 0,0323, OR = 0,3891; B4 for augmentation with ALIF = 1,1983, p = 0,0092, OR = 3,3143. Goodness of fit of general logistic regression model: Chi-square = 24 806, p = 0,00 015. Classification of cases – 75,85% correctly predicted. Conclusion: Bone quality is significant contributing factor for implant stability that must be taken into account and radiodensity measured in HU may have an application in implant failure prediction. Surgical tactics may also influence a stability of pedicle screw fixation. The necessity of destabilizing decompression especially in groups ASIA E should be assessed thoroughly because laminectomy could be a significant contributing factor for implant instability development. Under restored alignment resulting in residual kyphotic deformity of over 10° is also a significant factor for implant failure development. Patients who are at risk of implant related complications may benefit from ALIF procedure by getting decreased load on pedicle screw system, nevertheless further studies with secondary effects assessment are required to work-up optimal strategy for traumatic injuries treatment.

A082: Lumbar Spinal Stenosis Treated by Conventional Microsurgical Laminotomy or Endoscopic Interlaminar Decompression: Cost-Analysis to Decision-Making

Prudence Wing Hang Cheung¹, Carlos King Ho Wong², Jason Pui Yin Cheung¹

¹Department of Orthopaedics and Traumatology, The University of Hong Kong, - Hong Kong ²Department of Family Medicine and Primary Care, - Hong Kong

Introduction: Lumbar spinal stenosis (LSS) is one of the commonest spine conditions worldwide especially in the over-65 age group.¹ Patients with LSS requiring operation generally have good clinical response after decompression surgery.^2-4 Two of the most commonly used techniques include endoscopic interlaminar decompression and conventional microscope assisted decompression, which have had comparative randomized controlled trials.^{5, 6} Both procedures however appear to have similar clinical and radiological outcomes. In this modern age, the raised accumulative costs to patients and healthcare infrastructure are of concerns for the successful implementation of certain newer surgical approach into routine practice by healthcare providers. This study aims to provide comparison of full-endoscopic interlaminar decompression (MIS) versus conventional microsurgical decompression for LSS via cost analysis. Material and Methods: A decision-tree model comparing MIS and conventional microsurgical decompression for patients with LSS over a one-year time horizon was conducted. All patients were subjected to risk of complication, and the respective complication rate for MIS and conventional surgery were taken from two prospective randomized controlled trials (RCTs) by Komp and Ruetten.^5,6 Re-operation only applied to the following complications: epidural hematoma, inadequate decompression or iatrogenic instability requiring fusion. Complications like infection or dural tear required only the respective use of antibiotics or dural patch. Relevant unit costs associated with each surgical procedure and each possible complication treatment were estimated from expert input by local orthopaedic surgeons and were retrieved from the Department of Orthopaedics and Traumatology at affiliated hospitals. Costs associated with radiology, hospitalizations, outpatient, and physiotherapy visits were based on the latest charges to non-entitled persons for use of health services in the public sector. Results: The average total costs for MIS and conventional microsurgical decompression were found to be HKD$56 459.0 and $52 802.0 respectively. With the general ward hospitalization, radiology and routine follow-up visits being of the same cost for both surgical approaches, the 6.5% (HKD$3657.0) difference in total cost was largely due to the difference at the unit cost of surgery, as well as in the treatment for any complication. For the unit cost at operating theater for surgery, MIS costs 8.1% (HKD$2690.0) higher than the conventional microsurgical decompression. Since the complication rates found in the large-scale RCTs were 10.6% and 3.1% for MIS and conventional decompression respectively, the calculated cost of treatment for complication was HKD$2673.0 for conventional decompression, being 26.6% less than that for MIS (HKD$3640.0). Conclusion: Health economic evaluation is a necessary component in guiding spine surgery decision-making nowadays. Debate between open procedures and minimally invasive procedures for LSS has been ongoing. Our findings indicate the average total cost is higher for MIS, due to both the higher unit cost with surgical procedure as well as the treatment required for any complication, especially for cases where inadequate decompression needing a wider laminectomy after the index surgery. Surgeons can effectively decide on either surgical procedure, taking into consideration the cost-analysis findings, in addition to difference in clinical outcomes if any. In view of the learning curve with endoscopic procedures, continued use of an open, conventional technique can still be justified.

References

1. Deyo RA, Mirza SK, Martin BI, et al. Trends, major medical complications, and charges associated with surgery for lumbar spinal stenosis in older adults. JAMA 2010;303:1259-65.

2. Malmivaara A, Slatis P, Heliovaara M, et al. Surgical or nonoperative treatment for lumbar spinal stenosis? A randomized controlled trial. Spine (Phila Pa 1976) 2007;32:1-8.

3. Weinstein JN, Tosteson TD, Lurie JD, et al. Surgical versus nonoperative treatment for lumbar spinal stenosis four-year results of the Spine Patient Outcomes Research Trial. Spine (Phila Pa 1976) 2010;35:1329-38.

4. Weinstein JN, Tosteson TD, Lurie JD, et al. Surgical versus nonsurgical therapy for lumbar spinal stenosis. N Engl J Med 2008;358:794-810.

5. Komp M, Hahn P, Oezdemir S, et al. Bilateral spinal decompression of lumbar central stenosis with the full-endoscopic interlaminar versus microsurgical laminotomy technique: a prospective, randomized, controlled study. Pain Physician 2015;18:61-70.

6. Ruetten S, Komp M, Merk H, et al. Surgical treatment for lumbar lateral recess stenosis with the full-endoscopic interlaminar approach versus conventional microsurgical technique: a prospective, randomized, controlled study. J Neurosurg Spine 2009;10:476-85.

Spine Infections

A083: Preoperative Antisepsis in Spinal Surgery: How Effective Are Routine Antiseptic Solutions Against the Specific Microbioma of the Back’s Skin?

Claudia Eder¹, Peter Landowski², Gerlinde Angerler¹, Julia Hahne¹, Sabrina Schildböck¹, Peter Metzger², Michael Ogon¹

¹Orthopaedic Hospital Speising, Vienna - Austria ²Krankenhaus Göttlicher Heiland, Vienna - Austria

Introduction: Surgical site infections (SSI) represent a major complication of spinal surgery, with the patient's physiological skin flora being the main reservoir. The local microbioma of the back is highly specific and differs significantly from other areas of the human body. As the predominant bacteria strains are not covered by the European Standard Specifications for antiseptic evaluation, little is known regarding the specific efficacy of routinely used antiseptics for spinal surgery procedures. Aim of the presented study is to evaluate the efficacy of different antiseptic solutions in a spinal surgery specific in vitro and in vivo setting. Materials & Methods: The bacterial spectrum causing SSI after spinal surgery in our department was analysed retrospectively for 2015. Representative bacterial cultures were harvested from wound swabs and cultivated in Lysogeny Broth. PVP-Iodine (Braunol^®), Hexetidin (Isozid^®), Propanol/Biphenyol (Kodan forte^®) and Octenidin (Octenisept^®) were evaluated. Bacterial proliferation was monitored by measuring medium turbidity at 600 nm prior to disinfection, immediately and after 1 and 3 hours to simulate the time course of a surgical procedure. Colony forming units were evaluated on agar plates. Additionally, swabs were taken in the OR from skin incision and the surgical blade after routine disinfection with Propanol/Biphenyol (n = 138) and after changing pre-operative skin preparation to Octenidin (n = 638) as a result of in vitro evaluation. Results: Bacterial spectrum: Staph. epidermidis was responsible for 37% of the SSIs, followed by Propionibacterium acnes (17%), Enterococcus faecalis (14%), and Proteus mirabilis respectively Staph. aureus accounting for 6% each. Staph. epidermidis, Enterococcus faecalis, Proteus mirabilis and Stap aureus could be cultivated from wound swabs and used for the subsequent evaluation. In vitro evaluation: The efficacy of the antiseptic solutions tested varied significantly: Octenidin demonstrated a significantly higher efficacy (p < 0,01) in vitro and was able to completely eradicate or test bacteria except for Proteus mirabilis, which was still reduced to 1% of the initial bacterial load. In contrast, 9% (Propanol/Biphenyol) resp. 2% (PVP-iodine), resp. 10% (Hexetidin) of the initial Staph epidermidis were still present after disinfection. Hexetidin showed the lowest remanent effect with Staph. epidermidis increasing to 21% of the initial bacterial load after 3 hours. In vivo evaluation: Following skin preparation with propanol/Biphenyol in the OR, 31% of the swabs taken resulted in positive bacterial testing. According to our in vitro results, pre-operative disinfection routine was changed to Octenidin (Octeniderm^®, as Octenisept^® is not licensed for surgical skin preparation). Subsequently, the number of positive swabs was reduced to 22% (p < 0,021). Most of the positive swabs derived from the surgical blade and contained Staph. epidermidis or P. acnes. Conclusion: Antisepsis does not automatically mean a total eradication of the local microbiome. Even under standardized in vitro conditions, a significant bacterial load could be detected after disinfection. The antiseptic solutions evaluated differed significantly regarding their efficacy. Octenidin demonstrated a significantly higher effectiveness on a spinal surgery specific microbioma in vitro and in vivo. While the test strains were reduced beyond the level of detection during in vitro evaluation, deeper layers of the skin, which are not reached by antiseptic treatment, may act as reservoir in vivo.

A084: The Infectious Etiology of Degenerative Disc Disease: Myth or Reality?

Peter Jarzem¹, Ahmed Aoude¹, Kyle Raasck¹, Michael Weber¹, Husam Almajed¹, Patrick Wang¹, Jean Ouellet¹

¹McGill Scoliosis and Spine Group, Montreal - Canada

Introduction: Lower back pain (LBP) is the world’s leading cause of disability, with over 632 million people affected worldwide. A major etiological factor contributing to LBP is the progressive degeneration of intervertebral discs (IVD), which leads to disc herniation. It has been postulated that this nutrient rich anaerobic environment makes the disc susceptible to opportunistic bacteria. A recent double blind randomized study demonstrated that antibacterial treatments significantly reduced lower back pain, but the relationship between bacterial infection and disc degeneration remains largely unexplored. The objective of this study is to determine if degenerative disc disease is associated with colonization of the disc with low virulence micro-organisms. Material and Methods: Disc cultures were carried out systematically in all of one surgeon’s patients undergoing spine surgery for degenerative disc disease at our institution. All patients with disc cultures sent to microbiology laboratories were analyzed and the species of micro-organism was documented. All patients included in the study provided consent for tissue donation for research. Patients without disc specimens, without cultures or with a known discitis were excluded. Results: We identified 61 patients undergoing undergoing spine surgery for degenerative disc disease, excluding known discitis or history of infections, between December 2015 and July 2016. The average patient age was 59 years and a total of 88 disc cultures were analyzed. In total, 12 patients (20%) had positive disc cultures, with 100% of patients undergoing revision fusions growing bacteria from the disc space (p < 0.05). Subgroup analysis indicated that disc hernias had the highest positive culture rate among all other etiologies, with 29% (p < 0.05) growing bacteria. Staphylococcus epidermidis was the most common organism (33%), though Propionibacterium acnes, Clostridium, Corynebacterium, Escherichia coli, Streptococcus and Staphylococcus species were also found to be present. Conclusion: This is the first study to sample intervertebral discs from a cohort of patients considered to have primary degenerative conditions of the spine. Our study demonstrates that degenerate discs are frequently co-infected with bacterial species. The highest infection rates were in disc hernias (29%) and revision fusions (100%). These preliminary data support the notion that bacterial infection may be a source of back pain in patients with degenerative discs, as there may be an infectious etiology in significant proportion (20%). Furthermore, the use of prophylactic antibiotics in revision fusions should be explored. Given the current surgical treatment for LBP is lumbar fusion – an invasive procedure which carries significant cost and risk – determining the microbiological validity of antibacterial use for lower back pain is of paramount importance. These results warrant further investigation, and a larger study is ongoing.

A085: A Retrospective Study of Operative Outcomes for Patients With Spinal Epidural Abscess

Leonard Keller¹, Joseph Tanenbaum¹, Vincent Alentado², Bryan Lee³, Amy Nowacki⁴, Thomas Mroz³, Edward Benzel³, Michael Steinmetz³

¹Case Western Reserve University, Cleveland - United States ²Indiana University Health, - United States ³Cleveland Clinic Foundation - Center for Spine Health, Cleveland - United States ⁴Cleveland Clinic Foundation - Department of Quantitative Health Sciences, Cleveland - United States

Introduction: A spinal epidural abscess (SEA) is a serious condition that can be treated with antibiotics alone or with decompression surgery combined with antibiotics. The objectives of this study were to assess the clinical outcomes of SEA after surgical management and to identify patient-level factors that are associated with outcomes following surgical decompression of SEA. Material and Methods: A retrospective analysis of 152 consecutive patients that presented to the Cleveland Clinic with SEA and that were treated with surgery between 2010 and 2015 was performed. Post-operative pre-discharge ASIA scores, 6-month follow-up encounter ASIA scores, more than one SEA surgery, and death during SEA surgery were the primary outcomes. Fisher’s exact and Wilcoxon rank-sum tests were used to determine the association between patient-level factors and outcomes. Results: 152 patients (mean age, 58 years) were treated using surgical decompression and antibiotics during the study period. The majority of patients were Caucasian (81%) and male (61%). None of the patients died during surgery to treat SEA. A second SEA surgery was required in 8% of patients. A comparison of the pre-operative ASIA and post-operative pre-discharge ASIA scores showed that 49% of patients maintained an ASIA score of E or improved while 45% remained at their pre-operative status and 6% worsened. Among a subset of patients (n = 36) for whom a 6 ± 2 month follow-up encounter occurred, 75% maintained an ASIA score of E or improved, 19% remained at their pre-operative status, and 6% worsened. Both the presence and longer duration of pre-operative paresis was associated with an increased risk of remaining at the same ASIA score or worsening at the post-operative pre-discharge encounter (both p < 0.001). Age, race, sex, BMI, smoking status, bladder or bowel dysfunction, C-reactive protein level, white blood cell count, diabetes status, erythrocyte sedimentation rate, location of abscess in a specific spinal region, and degree of thecal sac compression were not associated with an increased risk of remaining at the same or worsening ASIA score at the post-operative pre-discharge encounter. Conclusion: Surgical decompression as part of the management of SEA can contribute to improving or maintaining ASIA scores in most patients. The presence and duration of pre-operative paresis are prognostic for poorer outcomes and suggest that rapid surgical intervention before it develops may lead to improved post-operative outcomes.

A086: Does Topical Intrawound Application of Vancomycin Powder Reduce the Rate of Surgical Site Infection in Spinal Surgery: A Case-Control Study

Prashant Adhikari¹, Vugar Nabiyev¹, Selim Ayhan¹, Selcen Yuksel¹, Selcuk Palaoglu¹, Emre Acaroglu¹

¹ARTES Spine Center, Ankara - Turkey

Introduction: Surgical site infection (SSI) after spine surgery is debilitating with significant increase in health care costs, hospital stay and morbidities. Recent studies have suggested the application of topical intrawound vancomycin powder before surgical closure as a promising method for reducing the SSI rate after spine surgery. However, its use is controversial and ongoing research projects are focused on identifying its safety, efficacy and the potential patient population. The purpose of this single center study is to compare the SSI rates in spinal surgery with or without topical intrawound application of vancomycin powder in addition to standard IV antibiotic prophylaxis. Material and Methods: A retrospective case series review of 158 patients undergoing spinal surgery for indications other than infections from January 2015 to December 2016, was performed. Eighty-eight (55.7%) patients who had received intrawound vancomycin (V group) were compared to 70 (54.3%) matched historical controls who did not (No-V group). Data on demographics, surgical characteristics, possible risk factors for SSIs and the application of vancomycin powder were collected from the patients’ files and electronic health records. Infection rates were compared with Chi-square statistics. Results: The groups were similar with respect to demographic and surgical characteristics. Out of 158 patients, 4 (2.5%) patients acquired SSI. There were 3 (3.4%) patients with SSI in the V group compared to 1 (1.4%) patient in the non-V group (p = 0.43). All patients with SSI in both groups were found to have undergone more than three levels of instrumented fusion. The isolated microorganisms were Escherichia coli in two patients and Pseudomonas aeruginosa in one patient in the V group, whereas the non-V patient grew Morganella morganii and Staphylococcus epidermidis. Conclusion: This study has demonstrated that topical intrawound application of vancomycin powder does not reduce the risk of SSI in spinal surgery. Moreover, it may also affect the underlying pathogens increasing the propensity for Gram negative species.

A087: Proposal of a New Classification for the Treatment of Pyogenic Spondylodiscitis: Validation Study on a Population of 250 Patients With a Follow-Up of Two Years

Enrico Pola¹, Giovanni Autore¹, Virginia Pambianco¹, Massimo Fantoni², Roberto Cauda², Giulio Maccauro³

¹Spine Division, Department of Orthopaedics and Traumatology, A. Gemelli University Hospital, Catholic University of Rome, Rome - Italy ²Department of Infectious Diseases, A. Gemelli University Hospital, Catholic University of Rome, Rome - Italy ³Department of Orthopaedics and Traumatology, A. Gemelli University Hospital, Catholic University of Rome - Italy

Introduction: Pyogenic spondylodiscitis (PS) is an uncommon and potentially life-threating infectious disease. Previous studies estimated the annual incidence of pyogenic spondylodiscitis ranging from 0,4 to 2,4/100 000 inhabitants in Europe. However, several recent studies reported an alarming increase of incidence in the last 20 years. PS is still burdened by a high rate of orthopedic and neurological complications. Despite the rising incidence, the choice of a proper orthopedic treatment is often delayed by the lack of clinical data and guidelines. The aim of this study was to propose a clinical-radiological classification of pyogenic spondylodiscitis to define a standard treatment algorithm. Material and Methods: Based on data from 250 patients treated from 2008 to 2015, a clinical-radiological classification of pyogenic spondylodiscitis was developed. According to primary classification criteria (bone destruction or segmental instability, epidural abscesses and neurological impairment), three main classes were identified. Subclasses were defined according to secondary criteria (paravertebral and intramuscular abscesses). PS without segmental instability or neurological impairment were treated conservatively. When significant bone loss or neurological impairment occurred, surgical stabilization and/or decompression were performed. All patients underwent clinical and radiological follow-up at 1, 3, 6, 12, and 24 months. Results: Most common symptoms at diagnosis were localized spinal pain (236 patients; 94.40%) and fever (159 patients; 63.60%). 56 patients presented with neurological deficits at diagnosis (22.40%) and lumbar spine was the most commonly affected (184 patients; 73.60%). Type A PS occurred in 84 patients, while 46 cases were classified as type B and 120 as type C. Average time of hospitalization was 51.94 days and overall healing rate was 92.80%. 140 patients (56.00%) were treated conservatively with average time of immobilization of 218.17 ± 9.89 days. Both VAS and SF-12 scores improved across time points in all classes. Residual chronic back pain occurred in 27 patients (10.80%). Overall observed mortality was 4.80%. Conclusion: Standardized treatment of PS is highly recommended to ensure patients a good quality of life. The proposed scheme includes all available orthopedic treatments and helps spine surgeons to significantly reduce complications and costs and to avoid overtreatment.

A088: Predicting Factors for Residual Neurologic Deficit in the Patients With Spinal Epidural Abscess After Surgical Intervention of the Thoracic and Lumbar Spine

Shih-Tien Wang¹, Yu-Cheng Yao¹, Hsi-Hsien Lin¹, Po-Hsin Chou¹, Ming-Chau Chang¹

¹Department of Orthopedics, Division of Spine surgery, Taipei Veterans General Hospital, Taipei - Taiwan, Province of China

Introduction: Spinal epidural abscess (SEA) can cause neurologic deficits and need surgical intervention urgently. The percentage of residual neurologic deficits has been reported around 11 to 57.1% after surgical treatment. The predicting factors reported in previous studies included preoperative neurologic status, older age, diabetes and methicillin resistant Staphylococcus aureus (MRSA) infection. The predicting factors of magnetic resonance imaging (MRI) were less discussed and all reported by studies with small case numbers. This study was designed retrospectively trying to find out the predicting factors of residual neurologic deficit after surgical treatment for SEA of the thoracic and lumbar spine. Material and Methods: We retrospectively analyzed 53 consecutive patients (35 men, 18 women) with SEA of thoracic or lumbar spine between January 2005 and December 2014 in a single institution. The SEA was proved on culture or histopathological reports. Presence of epidural abscess was diagnosed based on the MRI. All patients had undergone surgical intervention. The indications for surgeries were progressive neurologic deficits, mechanical instability and failure of medical treatment. All surgeries were performed through posterior-only approach. Neurologic status was recorded using the Frankel classification and documented at preoperatively, postoperatively and at the latest two years follow up. Frankel A – D was defined as neurologic deficit and Frankel E was neurologic intact. Clinical factors and radiological factor based on MRI were recorded. Results: 53 patients were included in this study. The mean age was 68.4 (range, 30-86) years. There were 39 pyogenic SEAs and 14 tuberculous SEAs. Staphylococcus aureus was the most common pathogen in patients with culture positive pyogenic SEAs (51.9%). Culture positive rate was 77.3%. There were 35 in 53 patients (66%) with pre-operative neurologic deficits, and 22 in 53 patients (42%) with post-operative residual neurologic deficits. The neurologic status after the surgical intervention improved significantly (p < 0.001). The patients with postoperative residual neurologic deficits (Frankel A – D) were classified into group A. The remaining patients without residual neurologic deficits (Frankel E) were classified into group B. Factors included age ( > = 70 years), diabetes, presence of urinary incontinence, presence dorsal dural abscess, abscess/canal compression ratio, abscess/canal CSA ratio, abscess length, and abscess thickness were correlated with postoperative residual neurologic deficits significantly. In univariate logistic regression analysis, age, diabetes (OR: 4.67, CI: 1.43-15.87, p = 0.011), preoperative urinary incontinence (OR: 7.25, CI: 1.67-31.52, p = 0.008), dorsal dural abscess (OR: 7.25, CI: 1.67-31.52, p = 0.008), abscess/canal compression ratio (OR: 8.38, CI:1.67-42.1, p = 0.01), abscess length (OR: 3.82, CI: 1.19-12.23, p = 0.024), and abscess thickness (OR: 18, CI:4.18-77.58, p < 0.001) were significantly associated with postoperative residual neurologic deficits. In multivariate logistic regression analysis, three factors, age (OR: 15.17, CI: 1.17-196.34, p = 0.037), presence of urinary incontinence (OR: 13.4, CI: 1.02-175.86, p = 0.048), and abscess thickness (OR: 33.27, CI: 3.43-317.92, p = 0.002), maintained significance. Conclusion: Age, preoperative urinary incontinence, and abscess thickness were the most significant predicting factors for residual neurologic deficits in patients with spinal epidural abscess after surgical intervention.

Diagnostics

A089: Accuracy of Gene Xpert as Diagnostic Tool in Spinal Tuberculosis

Anil Solanki¹, Saumyajit Basu², Amitava Biswas², Aditya Banta²

¹Department of Spine surgery, Park Clinic, Kolkata - India ²Department of Neuroscience, Park Clinic, Kolkata - India

Introduction: Tuberculosis of the spine is one of the most common spine pathology in South-East Asia. In era of evidence base medicine, early diagnosis and management of spinal TB has special importance in preventing serious complications. Confirmation of Mycobacterium tuberculosis by positive culture takes 3 to 6 weeks. Xpert MTB/RIF assay (Gene Xpert) is rapid automated molecular test with high accuracy for pulmonary and various extra pulmonary samples of Tb such as CSF, urine, lymph node and other tissues. But data regarding sensitivity and specificity in samples collected from spinal tuberculosis is not available. Material and Methods: We tried to evaluate sensitivity, specificity of Gene Xpert in diagnosis of spinal tuberculosis by a prospective study. From January 2016 to July 2017, we prospectively studied 56 patients of clinical-radiological suspected spinal tuberculosis who underwent biopsy procedures by CT guided, percutaneous or open surgical procedures. All samples were tested for AFB stain, standard AFB culture, Histopathology and gene Xpert. Similarly a control cohort of 60 patients were studied, who were clinical-radiological non TB lesions who had similar investigations from a biopsy procedure. The results of Gene Xpert were analyzed in relation to histopathology and AFB culture report at 42 days. Results: This study included 116 specimens, all of which were sent to the same laboratory between January 2016 and July 2017. Among the 116 tissue samples, CT guided FNAC was done in 20 cases (TB-12, Non Tb-8), percutaneous wide bore needle biopsy in 48 cases (TB-17, Non Tb-21) and open surgical biopsy was done in 48 cases (TB-26, Non Tb-22). Out of 56 cases of spinal tuberculosis confirmed by Histopathology and/or AFB culture, in 50 cases Gene Xpert detected M. Tuberculosis (True positive: 50/56) and in 6 cases M.tuberculosis were not detected (False negative: 6/56). Gene Xpert was negative for all 60 cases that were clinical-radiological non-TB lesions (True negative: 60/60, False positive 0/60). Thus, sensitivity of gene Xpert for spinal tuberculosis in our series is 89.29%, specificity is 100%, positive predictive value is 100% and Negative predictive value is 90.90%). In statistical analysis considering p value < 0.05, method of sample collection CT v/s percutaneous v/s open, did not affect the result of gene Xpert significantly. In our series, only in one patient who had taken AKT for 1 month before procedure, gene Xpert was negative. But, there were 7 other patients of TB who were on AKT for more than one month (up to 6 month) before procedure and Gene Xpert was positive. Hence this test cannot be used for monitoring the response to treatment. Drug resistance detected by Gene Xpert was consistent with results of AFB culture. Conclusion: In spinal tuberculosis, gene Xpert clearly outperforms microscopy, AFB culture and Histopathology due to its high sensitivity and specificity apart from being rapid in diagnosis - allowing early evidence based treatment –it should be used as the initial diagnostic test but Histopathology and clinical-radiological criteria should also be used to supplement before excluding diagnosis of spinal tuberculosis.

A090: Performance Characteristics of a Novel Handheld Web-Based Device for 3D Topographical Detection and Assessment of Scoliosis

Kenny Yat Hong Kwan¹, Michael To¹, Horace Choi², Karen Yiu¹, Johnson Lau³, Lok Ting Lau⁴, Parker Tsang¹, L.H. Chu¹, Berry Cheung¹, Kenneth Cheung¹

¹Department of Orthopaedics and Traumatology, The University of Hong Kong - Hong Kong ²Department of Clinical Oncology, The University of Hong Kong - Hong Kong ³Avalon SpineCare, Hong Kong - Hong Kong ⁴Hong Kong Polytechnic University, Hong Kong - Hong Kong

Introduction: Current topographical assessment devices for scoliosis are based on one-dimension measurement. We have developed a 3D novel handheld web-based device, SpineScan3D™ based on a built-in gyroscope, for topographic assessment of the spine. The data is captured when rolled on a patient’s back in standing and forward bent position, allowing posture and 3D assessments. This data is directly uploaded to the cloud storage and allows prospective analyses and longitudinal follow-up. Additional clinical information such as health quality of life scores can be captured by the associated Smartphone application. A prospective observational study was performed to evaluate the reliability and validity of this device compared with the scoliometer, and it correlation with radiographic Cobb angle measurements. Material and Methods: All patients referred to our spine specialist outpatient clinic were consecutively recruited. Measurements of the back topography were done three times in the standing and forward bending positions. Intra-rater reliability was assessed by Cronbach’s alpha, and Pearson’s correlation was used to analyse its relationship with the Scoliometer. Standing whole spine posteroanterior and lateral views were taken as part of their routine follow-up assessments. Multivariable regression was performed to analyse correlation between the maximal tilt as detected by SpineScan3D™ and radiographic Cobb angle on the posteroanterior view. Results: 397 patients had Scoliometer and 89 had radiographic data for analyses. Data output were expressed as maximal lateral tilt to right (-ve) and to the left (+ve), as well as by region of the spine based on the spinal length scanned. High intra-rater reliability for the 3 scans performed in standing and forward bending positions with Cronbach’s alpha > 0.9. Pearson’s correlation analyses with angle of trunk rotation (ATR) on Scoliometer showed a correlation coefficient r = 0.39 for thoracic humps, and r = 0.531 for loin humps. Maximal regional tilt at the thoracic (2.97, 95% CI 1,92, 4.01; p < 0.001) and lumbar (−2.24, 95% CI -3.19, -1.28; p < 0.001) regions had good correlation with radiographic Cobb angle. Conclusion: SpineScan3D™ is a reliable assessment tool for a patient’s back topography, and provides valid measurements for patients’ ATR. SpineScan3D™showed good correlation with radiographic Cobb measurements in patients with scoliosis, with screening parameters for scoliosis (sensitivity and specificity) to be defined. If the performance characteristics are proven to be consistent and specific in a large scale validation study, this device can not only be used as a non-invasive screening tool for scoliosis, but a surrogate for radiographs in patients with known scoliosis undergoing longitudinal follow-up.

A091: Dynamic Magnetic Resonance Imaging: Preliminary Presentation of a Technique

Raphael Pratali¹, Marcello Nogueira-Barbosa², Bruno Ancheschi², Daniel Maranho², Carlos Fernando Herrero²

¹Hospital do Servidor Publico Estadual, Sao Paulo - Brazil ² Faculdade de Medicina de Ribeirao Preto - USP, Ribeirao Preto - Brazil

Introduction: Since dynamic factors contribute to the etiology and severity of cervical spondylotic myelopathy (CSM), dynamic (flexion-extension) magnetic resonance imaging (MRI) may be useful to better evaluate the canal narrowing and spinal cord condition. The aims of this study were to evaluate morphometric variations of the cervical spine in patients with CSM using a standard technique of dynamic MRI and to assess the inter- and intra-observer reliability of the parameters considered. Material and Methods: This is a prospective study including 18 patients with clinical signal and/or symptoms of CSM. Dynamic cervical MRI was obtained following a standard protocol with the neck in neutral position and in maximal flexion and extension confortable to the patients. The morphometric parameters considered were the anterior length of the spinal cord (ALSC), the posterior length of the spinal cord (PLSC), the diameter of the vertebral canal (DVC) and the diameter of the spinal cord (DSC). The parameters were analyzed independently by two observers, and the inter- and intra-observer reliability were assessed by the Intraclass correlation coefficient (ICC). Results: All the 18 patients completed the dynamic MRI protocol, with none experiencing severe pain or worse in symptoms. The ALSC and PLSC were significantly longer in flexion than in extension (P < 0.05). The DVC and the DSC were greater, but not significantly, in flexion than in extension and neutral position. All morphometric parameters presented excellent reliability (ICC > 0.8) both inter- and intra-observer. Conclusion: The dynamic MRI protocol presented was safe and allowed to evaluate more accurately morphometric variations in the cervical spine in patients with CSM. The morphometric parameters analysis presented excellent inter- and intra-observer reliability.

A092: Analysis of Spino-Pelvic Sagittal Alignment in Chinese Young Subjects in Standing Versus Sitting Positions

Zhuo Ran Sun¹, Wei Shi Li¹, Shuai Jiang¹

¹Department of Orthopaedic, Peking University Third Hospital, Bei Jing - China

Introduction: With the development of modern computer technology, the sitting position has become the most common posture in today’s workplace. Both the sitting and standing posture must be equally considered in understanding the pathogenesis of degenerative lumbar disease and determining the optimum position for spinal fusion. This project intends to analyze the spino-pelvic sagittal alignment of Chinese asymptomatic adults in standing versus sitting positions. Based on the characteristics of asymptomatic adults’ sagittal alignment in standing, the variation in sitting position and its relationship with standing will be studied. Materials and Methods: This is a prospective radiological analysis using full-spine standing and sitting lateral radiographs of Chinese volunteers. 86 volunteers (24 males, 62 females; mean age 23.3 years [range, 19-29 years]) participated. Pelvic and spinal parameters were measured. Using Student’s t test, the angular parameters will be compared between standing posture and sitting posture. The changes of sagittal alignment in sitting position from standing position will be discussed. Using Pearson’s correlation test according to different position, difference of relationship between spinal and pelvic parameters in standing versus sitting position will be discussed. Results: Average pelvic incidence (PI) was 46.2 ± 8.6 degrees. When moving from standing to a seated position, the spine lost nearly 24-degree lumbar lordosis (LL) (49.6 ± 9.8 VS 25.2 ± 10.8, P < 0.001). The sagittal vertical axis (SVA) also moved more anteriorly by 45 mm (−20.7 ± 20.8 VS 24.5 ± 29.5, P < 0.001). Regarding changes from the standing to sitting positions, average pelvic tilt (PT), lordosis tilt (LT), T₁-pelvic angle (T₁PA) were greater (P < 0.05), and thoracic kyphosis (TK), sacral slope (SS) were decreased (P < 0.05). In sitting position, the correlation between PI and LL was lost, but correlation between PI-SVA and LL-SVA were still remained. Conclusion: In sitting position, the majority of the changes occurred in the lumbar spine and pelvis alignment. Sitting significantly straightened the spine with decreased TK, LL, and SS. Lumbar alignment and SVA moved anteriorly. Pelvis rotation and lumbar hypolordosis were the mechanisms of adjusting the trunk sagittal balance in sitting position. This variation in sitting position and its relationship with standing should be fully understood in terms of long-term effects of the sitting position in patients with lumbar and thoracic fusion, and the pathogenesis of lumbar degenerative changes in young patients due to the most common posture of today’s work time.

A093: Predicting the Risk of Curve Progression by the Radius and Distal Ulna (DRU) Classification for Patients With Adolescent Idiopathic Scoliosis

Jason Pui Yin Cheung¹, Prudence Wing Hang Cheung¹, Dino Samartzis¹, Dip-Kei Keith Luk¹

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

Introduction: For patients with adolescent idiopathic scoliosis (AIS), having an accurate growth measure like skeletal maturity assessment tool is mandatory in predicting remaining growth potential, which is important for timely interventions to prevent poor outcomes [1]. Curve progression to 40 degrees may lead to adulthood progression, while progression to 50 degrees commonly requires surgery [2, 3]. This study aims to validate the role of the distal radius and ulna (DRU) classification in predicting the risk of curve progression in AIS, according to curve magnitude upon initial presentation. Material and Methods: AIS patients presenting with Risser 0-3 were recruited and followed until skeletal maturity or when surgery was offered at Cobb angle ≥ 50 degrees (°). Body height, arm span, Cobb angle, curve type, age at menarche, Risser sign, DRU grades, and any brace use were examined. Final Cobb angle at either skeletal maturity/surgical intervention and whether any progression were used as outcome measure. Statistical analysis was performed to testing any association between curve progression and various parameters. Logistic regression was used in determining the probabilities of curve progression to final Cobb angle thresholds of 40° and 50°, based on initial curve magnitude and DRU grading. Results: A total of 513 AIS patients were recruited, with follow-up duration of 4.7 ± 2.5 years. At initial presentation, patients were of a mean age of 12.5 ± 1.3 years, 50.2% were pre-menarche, 226 (44.1%) at Risser 0, 175 (34.1%) at radius grade 6, and 156 (30.4%) at ulna grade 5. Bracing was prescribed for 61.6% of patients, among these 32 eventually underwent surgery. Final curve progression to ≥ 40° and ≥ 50° were both found to be significantly correlated to initial curve magnitudes, modified Lenke curve types, menarche, Risser stages, radius and ulna grades (p < 0.05). Based on the prediction model, with R6/U5 at initial presentation, most curves progress with an initial Cobb of 25°; whereas an initial Cobb angle ≥ 35° had a high risk (∼50-75%) of progression to final 40° and 50°. Patients at R9 did not progress to ≥ 50° regardless of initial curve magnitudes. Conclusion: The significant relationship of initial curve magnitudes and DRU grades with final curve progression outcomes of 40° and 50° provided the basis for developing this predictive model. Cobb angle of 25° appeared to be the main cut-off for the likelihood of poor outcomes at peak height velocity (PHV) at R6U5, suggesting that bracing is required immediately for immature patients prior to/at PHV if the initial curve reaches ≥ 25°. With same skeletal immaturity, larger initial curves of ≥ 35° are predicted with higher risk to reach both unfavourable thresholds, hence a poor prognosis and likelihood of requiring surgery. Despite being near or at skeletal maturity, those with ≥ 35° are still at fair risk for progression to 50°. These patients are of priority for early brace intervention. By utilizing the DRU growth status and initial severity of deformity, the risk of curve progression to unfavourable outcomes is predicted. This can aid clinicians in deciding on monitoring, bracing or offering surgery, and whether and when bracing should be introduced at various stages of growth for AIS patients.

References

1. Busscher I, Wapstra FH, Veldhuizen AG: Predicting growth and curve progression in the individual patient with adolescent idiopathic scoliosis: design of a prospective longitudinal cohort study. BMC Musculoskelet Disord 2010, 11:93.

2. Weinstein SL, Dolan LA, Spratt KF, Peterson KK, Spoonamore MJ, Ponseti IV: Health and function of patients with untreated idiopathic scoliosis: a 50-year natural history study. Jama 2003, 289:559-567.

3. Weinstein SL, Ponseti IV: Curve progression in idiopathic scoliosis. J Bone Joint Surg Am 1983, 65:447-455.

A094: What is the Ideal Zoom [Magnification] for Printing Digital Lumbosacral Spine Flexion-Extension Radiographs so as to Detect Early Instability?

Yogesh Pithwa¹, Kelvin Sureja²

¹Consultant Spine Surgeon, Department of Spine Surgery, HOSMAT Hospital, Bengaluru - India ²Postgraduate Student, Department of Orthopaedics, HOSMAT Hospital, Bengaluru - India

Introduction: Lumbar spine radiographs taken in flexion and extension constitute the most routine investigation to detect instability in the spine. Digital radiography has allowed printing of these radiographs in varying zoom [magnification] percentages. Often, these are printed in zoom percentages smaller than 100% to cut down on the costs of a larger film! These films are often assessed in high-volume spine surgical units by surgeons who would screen patients for radiological instability by a cursory visual assessment to identify instability in the form of abnormal angulation and/ or translation. Less than 100% zoom might compromise this assessment, particularly in low grade spondylolistheses. The present study was carried out to assess whether the validity of cursory visual assessment for radiological lumbar instability tends to vary with varying levels of zoom percentages in digital radiographs in spondylolistheses not exceeding Meyerding grade I. Materials and Methods: After due IRB approval, patients presenting with complaints of low backache with/ without radiculopathy were prospectively included in the study. Patients with spondylolistheses greater than grade I, infections, trauma, as well as postoperative patients were excluded. Practising spine surgeons were identified to participate in the study. Pairs of flexion-extension radiographs of lumbar spine of all included patients were printed in 25%, 50%, 75% and 100% magnifications on digital radiographic films. These sets were then sent to the participants. Each week, a set of radiographs belonging to only one magnification level was sent. Names of patients were masked in the radiographs. A single set of flexion-extension radiograph belonging to a single patient was given a numbered code and these were randomized every week. Objective measurement of instability was done independently by another observer using White and Panjabi’s criteria to validate the cursory assessments. Statistical analysis was done using Graphpad Instat, version 3.10. Data following Gaussian distribution was analysed by parametric tests while those following non-Gaussian distribution was analysed by nonparametric tests. Significance was set at two-tailed p < 0.05. Results: Nineteen patients were included in the study. Ten practising spine surgeons participated in the study. Accuracy of assessment of instability was 53.4 ± 10.58%, 54.8 ± 10.95%, 60 ± 7.89% and 66.5 ± 10.23% in 25%, 50%, 75% and 100% zoom percentages, respectively. This difference was found to be statistically significant by repeated measures ANOVA [p = 0.01]. Individually comparing various zoom percentages, there was a statistically significant difference in the accuracy between 25% and 100% [p < 0.01], as well as between 50% and 100% [p < 0.05]. Conclusion: Though printing films in zoom percentages less than 100% may cut down on costs, it tends to significantly compromise cursory screening for lumbar radiological instability. This would be particularly relevant in high-volume surgical units wherein detailed objective assessment for every single patient may not be possible.

Deformity - Thoracolumbar Congenital Sclerosis Surgery

A095: Sacral Slanting, a Rarely Recognized Issue in Early-Onset Congenital Scoliosis With Lumbar Hemivertebra - Definition, Etiology and Surgical Strategy

Jianguo Zhang¹, Yanbin Zhang¹

¹Department of Orthopedics, Peking Union Medical College Hospital, Beijing - China

Introduction: Sacral Slanting in congenital scoliosis has never been reported despite of its high incidence. Great challenge remains in restoring coronal balance after hemivertebra resection with short fusion in cases with Sacral Slanting. The purpose of this study was to clarify its definition, etiology and surgical strategy. Material and Methods: From July 2004 to December 2014, clinical charts and radiographic data of patients with early-onset congenital scoliosis were reviewed. Posterior hemivertebra resection with short fusion was performed in all cases that met our critieria. Coronal and sagittal parameters, as well as Sacral slanted angle and UIV-Pelvis Angle, were measured. Sacral Slanting was defined as the angle of more than 5° and severe Sacral Slanting was thought to be more than 10°. Statistical analyses were performed. Results: 42 consecutive patients were included. The mean age was 4.0 years old with an average follow-up of 51.7 months. The mean segmental curve was 34.9° before surgery, 4.7° immediately postoperatively, and 8.7° at final follow-up. Trunk shift was 15.4 mm preoperatively, 16.9 mm immediately after surgery and 12.1 mm at final follow-up. Sacral slanted angle was measured as 7.2° before surgery. Sacral Slanting could be noticed in 26 patients with an incidence of 61.9%. Patients with hemivertebrae at or below L3 had higher incidence of Sacral Slanting than that with hemivertebrae above L3. Severe Sacral Slanting was noted in 11 patients with an incidence of 26.2%. Sacral slanted angle was corrected to 5.1° immediately after surgery. And at final follow-up, it was 4.5°. Postoperative UIV-Pelvis Angle was 3.9°. Postoperative UIVT was correlated positively with postoperative TS. Two independent risk factors were identified for postoperative proximal adding-on: larger postoperative Sacral Slanted Angle and larger postoperative UIV-Pelvis Angle. Conclusion: Sacral Slanting was rarely recognized despite its high incidence. The etiology may be congenital malformation and sacrum rotation. Segmental undercorrection and placing a more central and even UIV were wise strategies for congenital EOS with severe Sacral Slanting.

A096: Hemivertebra Resection After Age 3 Produces the Similar Results but With Less Complications Compared to Earlier Surgery

Yong Qiu¹, Zhonghui Chen¹, Xu Sun¹, Zezhang Zhu¹

¹Department of Spine Surgery, Drum Tower Hospital, Nanjing University Medical School, Nanjing - China

Introduction: The optimal timing for hemivertebra resection remains controversial. Early intervention before 3 years of age seems being able to get better correction and require less fusion segments. However, it was also found that early surgery might be associated with more complications. The current study aimed to investigate correction outcome and complications of delayed hemivertebra resection (between 3 and 5 years of age), in comparison to early surgery (before 3 years of age). Materials and methods: Patients who had undergone hemivertebra resection for single hemivertebra before 5 years of age and had a minimum 2-year follow-up were retrospectively reviewed. There were 13 patients with early resection of hemivertebra under 3 years of age, and 18 patients with delayed resection of hemivertebra between 3 and 5 years of age. Radiographs from the preoperative, immediate postoperative, and the most recent follow-up visits were reviewed to investigate the correction outcome. Correction results and complications were compared between the early and delayed groups. Results: The patients of the early group had less fusion segments (2.3 ± 0.6 vs. 3.1 ± 1.1, P = 0.014), less operation time (180.4 ± 20.6 min vs. 206.2 ± 30.4 min, P = 0.011) and blood loss (196.4 ± 48.2 ml vs. 236.4 ± 56.3 ml, P = 0.042) than the delayed group. Both groups had similar correction rates of scoliosis (83.5% versus 81.4%, P > 0.05), but the early group experienced slightly more correction loss (15.2% versus 8.6%). With regards to the sagittal plane, both groups has similar correction of segmental kyphosis (64.5% versus 71.2%) while higher correction loss was observed in the early group (24.4% versus 4.7%). Notably, the complication rate in the delayed group was lower than the early group (44.4% versus 57.1%). Conclusion: Hemivertebra resection resulted in the similar correction results in both age groups. However, the rate of complications was lower for the older age group than the younger age group. Thus, for non-kyphotic hemivertebra, surgery may be delayed till 3 to 5 years of age.

A097: Radiological Characteristics Associated With Successfully Outcome, After Boston Brace Treatment of Adolescent Idiopathic Scoliosis - A Retrospective Review

Ane Simony¹, Mikkel Osterheden Andersen¹, Steen Bach Christensen¹

¹Center for Spine Surgery & Research, Middelfart Hospital, Middelfart - Denmark

Introduction: Boston brace treatment has been used for conservative treatment of Adolescent Idiopathic Scoliosis, since the 1970'ies. The treatment has been shown to stop the progression of the deformity, and reduce the rate for surgical treatment. The purpose of this study was to examine the curve characteristics in the patients, who progressed during brace treatment. Material and Methods: 153 AIS patients were treated with Boston braces, at Rigshospitalet in Copenhagen from 1983-1990. A retrospective study was performed, of the radiological characteristics of the brace treated patients. Curves were classified according to the King Moe classification, and apical and distal vertebrae was recorded along with the apex of the curve. The curve magnitude was examined by Cobb measurement, The Harrington factor was calculated and the spinal rotation was described using Pedriolle. Results: 138/153 patient completed their brace treatment and was included in this study. Mean age when brace treatment was initiated was 14.1 y (+/- 1.6 y), Time in brace 2.6 y (+/- 1.0 y) and Mean Cobb before treatment 39° +/- 10°. Brace treatment did not alter the spinal rotation (p > 0.3), age at start Brace treatment (p > 0.8) or Age at menarche (p > 0.05) was not correlated with progression during brace treatment. The curve correction was significant better in curves, with apex between Th11 and L1 (p < 0.0001). A correlation was seen in between the in brace correction and Cobb angel during side bending films pre-treatment (p < 0.002). No patients with Cobb < 11° during side bending films progressed during Brace treatment and needed surgical treatment. The Harrington Factor seems to correlate with progression during brace treatment (p < 0.001) and no patients with a Harrington Factor less than 5° progressed during Brace treatment. Conclusion: Boston braces are effective in the conservative treatment of AIS. The risk of progression is very small if the apex is in the thoracolumbar area, and Harrington Factor is < 5°. Curves should be evaluated prior to brace treatment and close attention is recommended if risk factors are identified during the radiological evaluation.

A098: Posterior Hemivertebra Resection for Congenital Scoliosis Caused by Hemimetameric Segmental Shift

Qiunan Lyu¹, Chunguang Zhou², Yueming Song²

¹Department of orthopedics surgery, West China Hospital, Sichuan University, ChengDu - China ²Department of Orthopedics Surgery, West China Hospital, Sichuan University, Chengdu - China

Introduction: Hemimetameric segmental shift (HMMS) is a common finding in congenital scoliosis. It is defined as two or more hemivertebrae which exist on contralateral sides of the spine. The hemivertebrae are separated by at least one normal vertebra and often cause double or more scoliosis. Previous researches of HMMS have been mainly focused on its natural history, associated anomalies and morphology, whereas there is no research that has specially studied the surgical management of HMMS. We aimed to study the efficacy of posterior hemivertebra resection with pedicle screw instrumentation in the treatment of HMMS and to find out areas for potential surgical improvement. Material and Methods: From 2009 to 2015, 15 patients (4 males and 11 females) with congenital scoliosis caused by HMMS underwent posterior hemivertebra resection with transpedicular instrumentation at our department. The average age at surgery was 9.9 ± 4.8 years and the mean length of follow-up after spinal surgery was 38.5 ± 7.1 months. Clinical outcomes and related complications were assessed by reviewing medical records, operative notes, radiographic data and scores on the SRS-22 questionnaire. Results: In total, 28 balanced hemivertebrae were excised in the 15 patients. Two hemivertebrae were excised in 13 patients and only one hemivertebra was excised in 2 patients. The average segmental Cobb angle on coronal plane was corrected from 44.9 ± 10.8° preoperatively to 15.3 ± 7.6° at the latest follow-up. The average segmental Cobb angle on sagittal plane was corrected from 16.5 ± 14.1° preoperatively to 7.1 ± 9.1° at the latest follow-up. Both the cranial compensatory curve and caudal compensatory curve were significantly improved at the latest follow-up. Trunk balance was improved in both coronal and sagittal plane after surgery, and remained stable at the latest follow-up. Four domains of SRS-22, including the self-image, the mental health, the satisfaction and the pain, were significantly improved at the latest follow-up compared with preoperative status. Progression of kyphosis was observed in one patient. Conclusion: Posterior hemivertebra resection with transpedicular instrumentation can produce relatively satisfactory outcomes in the treatment of HMMS. Close attention should be paid to the growth potential on both coronal and sagittal plane when estimating the progression of deformity.

A099: The Efficacy of Posterior Hemivertebra Resection With Lumbosacral Fixation and Fusion in the Treatment of Congenital Scoliosis: A More Than 2-Year Follow Up

Qiunan Lyu¹, Chunguang Zhou², Yueming Song²

¹Department of orthopedics surgery, West China Hospital, Sichuan University, ChengDu - China ²Department of Orthopedics Surgery, West China Hospital, Sichuan University, Chengdu - China

Introduction: Hemivertebrae locating at lower lumbar or lumbosacral region often produce early trunk imbalance and long compensatory curves. Due to the biomechanic characteristics of lumbosacral junction, the rate of instrumentation failures has always been high at the region. The study aimed to evaluate the results of posterior hemivertebra resection with lumbosacral fixation and fusion in the treatment of congenital scoliosis and to make preliminary analysis of the possible risk factors for instrument failures. Material and Methods: From 2010 to 2015, 17 patients (7 males and 10 females) with congenital scoliosis underwent HV resection with lumbosacral fixation and fusion at our department. The mean age was 13.2 ± 4.4 years at the surgery and the mean follow-up was 37.6 ± 4.6 months. Clinical outcomes and related complications were assessed by reviewing medical records, operative notes, radiographic data and scores on the SRS-22 questionnaire. Results: The mean Cobb angle of the segmental curve was 37.5 ± 12.7° preoperatively, 7.9 ± 5.5° postoperatively, and 7.9 ± 5.3° at the latest follow-up. The mean Cobb angle of the cranial compensatory curve was 39.2 ± 17.2°, 9.1 ± 9.5°, and 9.5 ± 10.8°, respectively. Trunk balance was improved in both coronal (59.6%) and sagittal (58.6%) plane after surgery, and remained stable at the latest follow-up. Three domains of SRS-22, including the self-image, the mental health and the satisfaction, were significantly improved at the latest follow-up compared with preoperative status. Complications included one transient neurologic impairment, one superficial wound infection and two implant failures. Conclusion: Early posterior hemivertebra resection with short lumbosacral fixation and fusion is effective in the treatment of hemivertebrae locating at lower lumbar or lumbosacral region. Delayed surgical intervention may lead to longer fusion and fixation. A long lumbosacral construct using only S1 pedicle screws as distal anchors tends to accompany a high rate of implant failures.

A100: Is Radical Hemi-Vertebra Resection Really Necessary for Congenital Scoliosis Patients Without Kyphosis?

Zezhang Zhu¹, Zhen Liu¹, Xu Sun¹, Bangping Qian¹, Yong Qiu¹

¹Drum Tower Hospital Nanjing University Medical School, Nanjing - China

Introduction: There has been many reports on posterior hemivertebra resection. However, does it is necessary to undergoing radical hemi-vertebra resection for congenital scoliosis patients without kyphosis? AS far as we known, there were few articles in comparison between radical resection and partial resection in these patients. This is a clinical retrospective study to evaluate the efficacy of partial hemivertebra resection and to confirm whether it is necessary to take radical resection in young congenital cases without kyphosis. Materials and Methods: This retrospective study of a prospective collected database comprises a consecutive series of 72 congenital scoliosis due to lumbar hemivertebra treated by posterior hemivertebra resection with short segmental fusion, with at least a 1-year follow-up period (12-60 months). The patients were divided into radical resection group (R group) and partial resection group (P group) based on their pre- and post-operation CT three-dimensions constructions. There were 40 patients experienced radical resection with mean operation age 7 years and 32 patients experienced partial resection with mean operation age 10 years. Clinical charts and radiographs of spine were retrospectively reviewed to record complications and outcomes postoperatively and at the latest follow-up. Radiographic evaluation included measured changes in segmental scoliosis, lumbar lordosis, and trunk shift in coronal and sagittal planes. Results: Our results showed that the mean follow-up period was 32.1 months. The mean fusion level was 3.5 segments in R group and 4.6 segments in P group. The mean segmental scoliosis was 34.3 degress vs 42.4 degress in R and P group respective preoperatively, 8.1 degress vs 13.8 degress postoperatively (76.1% vs 67.6% correction rate), and 8.2 degress vs 14.5 degress (76.4% vs 66.0%) at the latest follow-up in R and P group. Trunk shift was significantly improved on both coronal (15.4 mm to 12.3 mm in R group and 17.6 mm to 14.9 mm in P group) and sagittal plane (30.7 mm to 26.4 mm in R group and 25.7 mm to 24.1 mm in P group) after the surgery, and kept stable during the follow-up. The mean operation time and the average blood loss in P group (215.1 min, 583.8 ml) were significantly less than R group (255.3 min, 686.7 ml). Conclusions: In summary, our results showed that both radical and partial one-stage HV resection and short segment fusion by a posterior approach could offer excellent scoliosis correction and trunk shift improvement without neurological complications. It is considerable to carry out partial resection with less operation time and blood loss for lumbar hemivertebra without kyphosis.

Minimally Invasive Surgery Navigation

A101: Total Navigation Based Minimally Invasive Transforaminal Lumbar Interbody Fusion (MIS-TLIF) - Feasibility, Technique and Preliminary Results

Sourabh Chachan¹, Wee Lim Loo¹, Shree Kumar Dinesh¹

¹Dept of Orthopaedics, Singapore - Singapore

Introduction: Minimal invasive surgery (MIS) techniques have revolutionized the TLIF procedure by decreasing approach related morbidity resulting in faster recovery, while giving clinical outcomes comparable to open technique. Introduction of intra-operative CT and image-guided navigation have significantly improved the accuracy of instrumentation while reducing radiation exposure at the same time. We describe here a technique of “Total Navigation” based MIS-TLIF. Material and Methods: The study includes 34 patients who underwent MIS TLIF using O-arm based navigation technique. The patients were position prone on Jackson table and reference array was docked at L2 spinous process. Intra-operative O-arm 3D scan was then acquired for all cases and images automatically transferred to the navigation system (S7). Navigation was utilized for all steps of procedure starting from surgical incision planning, probing of lumbar pedicles, placement of screws, docking of tubular retractors over the facet, estimation of disc space trajectory, assessing adequacy of decompression and interbody cage placement. All the cases were done with intra-op neuromonitoring. A final O-arm fluoroscopic image antero-posterior and lateral view was obtained at the end just before wound closure, to verify accuracy of implant placement. Results: There were 21 males and 13 females with a mean age of 53 years (range 33–71). MIS-TLIF was performed at one-level, two-level and three-level in 29 (85.3%), 4 (11.8%) and 1 (2.9%) cases, respectively. All the patients had low back pain and/or lower extremity pain and/or neurogenic intermittent claudication that were refractory to conservative treatment. Among one-level TLIF, 21 (72.4%) were done at L4-L5 level followed by 7 at L5-S1 (24.1%) and 1 at L3-L4 (3.4%). Among two-level TLIF, two were performed at L3-L5 levels and two at L4-S1 levels. The one case of 3 level TLIF was performed at L3-S1 levels. All the interbody cages were packed with a mix of allograft and autograft. Average duration of surgery for one-level TLIF was 173.8 minutes (range 115-235 minutes) with trend towards statistically significant decrease in surgery duration as the surgeon’s experience improved. Average surgery duration for first ten cases of one-level TLIF was 206 minutes, which improved to 157.7 minutes for next 10 cases (p value < 0.05) and further improved to 153.3 minutes for last 9 cases. Total of 148 pedicle screws were inserted with only one screw (incidence 0.7%) required intra-op revision due to grade 2 breach. None of the interbody cage placements required revision. There were no intra-operative complications of incidental durotomies, nerve or vascular injury. There was no software/hardware failure of navigation system. The multi-level TLIF cases required second intra-op 3D scan to update navigation after placement of interbody cages and before placement of pedicle screws, due to inter-segmental shifts in the spine. Conclusion: “Total Navigation” based minimally invasive TLIF is feasible, safe and accurate. One level TLIF cases can be successfully performed with only one intra-op 3D scan whereas multi-level cases require a second intra-op scan.

A102: Utilization of Spinal Intra-Operative Three-Dimensional Navigation by Canadian Surgeons and Trainees: A Population Based Time Trend Study

Daipayan Guha¹, Ali Moghaddamjou¹, Zaneen Jiwani², Naif Alotaibi¹, Albert Yee³, Victor Yang¹

¹Division of Neurosurgery, University of Toronto, Toronto - Canada ²Biophotonics and Bioengineering Laboratory, Sunnybrook Health Sciences Centre, Toronto - Canada ³Division of Orthopedic Surgery, University of Toronto, Toronto - Canada

Introduction: Computer-assisted navigation (CAN) is a useful adjunct to improve the accuracy of spinal instrumentation as well as for trainee education, but is not widely adopted by spinal surgeons due partly to lack of training, high capital costs, and workflow hindrances. Here, we characterize the spatiotemporal use of spinal CAN in a single-payer health care system, such as in Canada, and assess the impact of intra-operative CAN use on trainee proficiency. Material and Methods: A prospectively-maintained Ontario database of patients undergoing spinal instrumentation from 2005-2014 was reviewed retrospectively. Data was collected on treated pathology, spine region, surgical approach, institution type, surgeon specialty, the use of 2D or 3D-CAN, and revision surgeries within 2 years of the index procedure. Predictors of CAN usage as well as revision surgery were identified. Trainee comfort with CAN and its impact on technical proficiency were assessed using an electronic questionnaire distributed to all Canadian orthopedic surgical and neurosurgical trainees across 15 nationwide training programs. Results: 16.8% of instrumented fusions in our provincial cohort were CAN-guided, predominantly by 3D-CAN. Navigation was employed more frequently in academic institutions (15.9% vs. 12.3%, p < 0.001) and by neurosurgeons more than orthopedic surgeons (21.0% vs. 12.4%, p < 0.001). Revision surgery was required in 6.4% of patients undergoing instrumented fusion, more frequently for trauma and deformity cases, for cases performed at academic centers, and for cases performed without CAN guidance. 34.1% of residents reported being fully comfortable in the setup and use of spinal CAN, greater for neurosurgical than orthopedic surgical trainees (48.1% vs. 11.8%, p = 0.008). The use of CAN for thoracic instrumentation increased the mean self-reported proficiency rank across all trainees by 11.0% (p = 0.036), with orthopedic residents also reporting an increase in mean proficiency rank of 18.0% for atlantoaxial instrumentation (p = 0.014) with CAN guidance. Conclusion: In current practice, spinal CAN is employed most frequently by neurosurgeons and in academic centers. The use of CAN is associated with a significant decrease in associated revision surgeries. Most spine surgical trainees are not fully comfortable with the setup and use of intra-operative CAN, but do report an increase in technical comfort with CAN guidance particularly for thoracic instrumentation. Increased education in spinal CAN starting at the trainee level, particularly for orthopedic surgery, may improve adoption.

A103: Optical Topographic Imaging for Spinal Intra-Operative Three-Dimensional Navigation in Minimally-Invasive Approaches: Initial Pre-Clinical and Clinical Feasibility

Daipayan Guha¹, Raphael Jakubovic², Naif Alotaibi¹, Ryan Deorajh³, Michael Fehlings¹, Albert Yee⁴,

Victor Yang¹

¹Division of Neurosurgery, University of Toronto, Toronto - Canada ²Department of Biomedical Physics, Ryerson University, Toronto - Canada ³Biophotonics and Bioengineering Laboratory, Sunnybrook Health Sciences Centre, Toronto - Canada ⁴Division of Orthopedic Surgery, University of Toronto, Toronto - Canada

Introduction: Computer-assisted three-dimensional navigation may guide spinal instrumentation. A novel optical topographic imaging (OTI) system, developed in our laboratory, offers comparable accuracy and significantly faster registration relative to current navigation systems, in open posterior thoracolumbar exposures. Here, we explore the utility of OTI in minimally-invasive (MIS) spinal approaches. Material and Methods: Mini-open midline posterior exposures were performed in four human cadavers. Square exposures of size 25, 30, 35, and 40 mm were registered to a preoperative CT scan. Screw tracts were fashioned using a tracked awl and probe, and instrumentation placed. Navigation data were compared to screw positions on postoperative CT imaging, and absolute translational and angular deviations computed. In-vivo validation was performed in eight patients, with mini-open thoracolumbar exposures and percutaneous placement of navigated instrumentation. Results: For 37 cadaveric screws, absolute translational errors were (1.79 ± 1.43 mm) and (1.81 ± 1.51 mm) in the axial and sagittal planes, respectively; absolute angular deviations were (3.81 ± 2.91°) and (3.45 ± 2.82°), respectively (mean ± SD). Errors were similar across levels and screw types. The number of surface points registered by the navigation system, but not exposure size, correlated positively with the likelihood of successful registration (OR = 1.02, 95%-CI 1.009 -1.024, p < 0.0001). 55 in-vivo thoracolumbar pedicle screws were analyzed. Overall (mean ± SD) axial and sagittal translational errors were (1.79 ± 1.41 mm) and (2.68 ± 2.26 mm), while axial and sagittal angular errors were (3.63 ± 2.92°) and (4.65 ± 3.36°), respectively. There were no critical radiographic breaches, nor any neurovascular complications from any placed screws. Conclusion: OTI is a novel navigation technique previously validated for open posterior exposures, which has comparable accuracy for mini-open MIS exposures. The likelihood of successful registration is affected more by the geometry of the exposure than its size.

A104: The Effect of Thoracolumbar Anatomy on Pedicle Screw Accuracy

Kyle Raasck¹, Ahmed Aoude¹, Benjamin Beland¹, Alex Munteanu¹, Michael Weber¹, Jeff Golan²

¹McGill Scoliosis and Spine Group, Montreal - Canada ²Department of Neurosurgery, Jewish General Hospital, Montreal - Canada

Introduction: Pedicle screws have been used for posterior spinal fixation since the free hand technique was first reported in 1959. Multiple methods have since been developed to facilitate more accurate screw placement, such as stereotactic-guiding and intraoperative fluoroscopy, though they also increase radiation exposure and operative interval. Pedicle screws remain technically demanding to place. Aberrant screws can lead to serious neurovascular complications, including radicular pain, sensory loss, damage to great vessels, and damage to the pleural cavity. We propose that a predominant factor of pedicle screw breach is due to the inherent vertebral anatomy involved at a given spinal level. While it has been suggested that vertebrae morphology can influence breach incidence, there has never been a clear link made between isthmus size and the rate of pedicle screw breach. The study aims to investigate the inverse correlation between breach incidence and vertebral isthmus width. Material and Methods: We retrospectively reviewed the post-operative computed tomography (CT) scans of 91 patients who underwent thoracolumbar (T2-L5) surgery at the Jewish General Hospital. Average patient age was 62.9 years and the patients were 58% male and 42% female. Radiologically detectable breach incidence was computed and a Fisher exact test was performed. Each breach was also categorized as minor ( < 2 mm) or major ( > 2 mm). Clinical correlation was not a requirement for presence of breach. Isthmus width is defined as the narrowest portion of the pedicle in the mediolateral plan. The average isthmus width by spinal level, reported by Zindrick in 1986, was then compared to the collected breach incidences by spinal level. A regression analysis and Pearson’s correlation was performed. Results: A total of 656 pedicle screws were analyzed and 233 radiologically detectable breaches were found, though only 8 patients developed post-operative symptoms clinically relevant to the detected breach. The average incidence of breach was 35.5%, while the average incidence of major breach was 8.6%. Breach incidence was over two times higher in the thoracic than the lumbar spine while major breach incidence was three times higher (Fisher exact test, P < .0001). A lateral breach was three times less likely to occur than a medial breach, though it was twice as likely to be a major breach (Fisher exact test, P < .0001). The two spinal levels with the thinnest average isthmus width - T4 and T5 - had the highest breach incidence, whereas the two spinal levels with the thickest average isthmus width – L4 and L5 – had the lowest breach incidence. Breach incidence and isthmus width were shown to have a significant inverse correlation with an R squared of 0.7 (Pearson’s correlation, P < .0001). Conclusion: A thinner vertebral isthmus width significantly increases the pedicle screw breach incidence. The smaller size and complex pedicle morphology of the thoracic spine was breached over two times more frequently than the larger pedicles of the lumbar spine, which allow for more degrees of freedom. Despite the high incidence of cortical bone violation observed, there was little correlation with clinical symptoms and we were unable to conclude the absolute size of breach necessary for symptoms to develop. A breach is not automatically a clinical problem, provided the screw remains structurally sound and the patient symptomless. One must consider every case uniquely. Image-guided assistance may be most useful where breach incidence is highest and isthmus width is lowest, particularly between T3 and T6.

A105: Image Guidance in the Cervical Spine. An Essential Tool or a Distraction? A Consecutive Series of 175 Patients

John Duff¹, Sonia Plaza Wuthrich¹, Lukas Bobinski²

¹Clinical Neurosciences, CHUV, Lausanne - Switzerland ²Umea University Hospital, Umea - Sweden

Introduction: Cervical spine screw placement requires precise implant insertion into a bone corridor which is surrounded circumferentially by neural and vascular structures. While the use of image guidance has improved accuracy, there is currently no classification which provides sufficient precision to assess the navigation success of critical cervical screw placement. Multiple measurement methodologies have been used to assess implant precision with good success. Despite the use of image guidance in the cervical spine, the clinical benefit to the patients is unclear. We examine our experience in 175 consecutive cases to determine if technically challenging screw placements at the craniocervical junction and in the pedicles of the subaxial spines are feasible, safe and precise. Material and Methods: A retrospective medical record review of 175 patients undergoing posterior instrumentation of the cervical spine over a 10 year period was carried out. Inclusion criteria were 1) screw placement at the craniocervical junction, 2) subaxial pedicle screw placement, 3) image guidance (66/175 with CT stereotaxis, and 109/175 using 3D fluoroscopy). A total of 75 patients were included for CCJ fixation, and 100 patients for subaxial pedicle fixation. Two surgeons independently evaluated implant accuracy using the orthogonal view evaluation method (OVEM) on postoperative CT scans. This looks “down the barrel” of the narrowest portion of the bone target to assess cortical breeches. The grading system is as follows. Gr 1: no breech, gr 1a: outer diameter of the screw (ie thread) breeches the cortical bone, gr 2: inner diameter of the screw breeches the cortical bone, gr 3: neural or vascular injury. Grade 1 and 1a are considered acceptable navigated placements. Grade 2 and 3 are considered as navigational failures, some of which may also be clinical failures (complications). Results: A total of 756 screws were placed in the posterior cervical spine. 483 screws were gr 1 placements (63.9%), 159 (21%) were gr 1a, and 113 (14.97%) were gr 2 placements. There was 1 gr 3 placement (0.13%), which was reoperated and repositioned with complete resolution of symptoms. The overall navigational “success” was 84.9%. None of the gr 2 screw placements had any observed clinical complications. We were unable to demonstrate the superiority of one navigation technique (3D fluoroscopy) over the other (CT stereotaxis). The subaxial pedicles showed the lowest gr 1 & gr 1a screw placements (62.6%), reflecting the small bone target volumes at these vertebral levels. Conclusion: Image guided posterior cervical screw placement at the craniocervical junction and in the subaxial pedicles is feasible and is safe in our experience. Advantages using image guidance over freehand techniques have been suggested in published studies, and the main advantage of image guidance is probably in cases where the target bone volume is not much larger than the diameter of the screw, as is sometimes seen in the C2 pedicles and frequently in the subaxial pedicles.

A106: Comparative Prospective Study Reporting Intra-Operative Parameters, Pedicle Screw Perforation and Radiation Exposure in Navigation Guided MIS TLIF Versus Non-Navigated Fluoroscopy Assisted MIS TLIF

Vishal Kundnani¹, Mahendra Singh², Tarun Dusad¹

¹Dept of Orthopedics and Spine Surgery, Mumbai - India

Introduction: Poor reliability of fluoroscopy guided instrumentation and growing concerns about radiation exposure has led to innovation of navigation guided instrumentation techniques in MIS-TLIF. Literature comparing efficacy of Navigation guided MIS TLIF is scanty. Material and Methods: 87 patients underwent MIS-TLIF for symptomatic Lumbar/Lumbosacral spondylolisthesis with navigation and fluoroscopy guidance. Demographics, intra-operative parameters (Surgical time, blood loss), radiation exposure (Sec/mGy/Gy.cm2 - noted from C-arm as required to compare only) were recorded. CT scan was done in patients of navigated and non-navigated group at 12 months post-operative, reviewed by an independent observer to assess the accuracy of screw placement, perforation incidence, location, and grade (Mirza), critical vs non critical, neurological implications. Results: 27 patients (M/F = 11/16; L4-L5/L5-S1 = 9/18) were operated with navigation guided MIS-TLIF while 60 (M/F = 25/35; L4-L5/L5-S1 = 26/34) with conventional fluoroscopy. Use of navigation resulted in reduced fluoroscopy usage [Dose area product-0.47 Gy.cm2 vs 2.93 Gy.cm2] [Cumulative radiation exposure- 1.68 mGy vs 10.97 mGy], [Fluoroscopy time- 46.5 sec vs 119.08 sec] with p value < 0.001. 96.29% (104/108) of the pedicle screws in the navigated group were accurately placed (grade 0) (4 breaches- all grade I) compared to 91.67% (220/240) in the non-navigated group (20 breaches- 16 grade I + 4 grade II) (p = 0.114). None of the breaches resulted in a corresponding neurological deficit or required revision. Conclusion: Navigation guidance in MIS-TLIF reduced the radiation exposure, but the perforation status was not statistical different from fluoroscopic based technique. Thus navigation in non-deformity cases can be useful in terms of reducing radiation exposure significantly but its significance in reducing pedicle screw perforation with expert hands in non deformity cases is yet to be proved

Infections - Tubercolosis

A107: A Proposed Novel Classification Based on Surgical Treatment Strategies in Advanced Lumbosacral Tuberculous Spondylodiscitis

Aju Bosco¹, Nalli Ramanathan Uvaraj²

¹Center for Advanced Brain and Spine Surgery(CABSS), Tamilnadu Govt. Multi Superspeciality Hospital, Chennai - India ²Spine Surgery Unit, Department of Orthopaedics and Traumatology, Madras Medical College and Rajiv Gandhi Govt. General Hospital, Chennai - India

Introduction: Advanced tuberculosis with destruction of the lumbosacral spine results in spinal instability and loss of lumbar lordosis with altered lumbosacral biomechanics. Surgical reconstruction of lumbosacral junction is technically demanding due to its complex local anatomy, unique biomechanics, loss of sacral bone for implant anchorage and difficult fixation in the surrounding diseased bone. Currently, there are no defined guidelines on the surgical treatment of lumbosacral tuberculous spondylodiscitis with extensive destruction of lumbosacral spine. The aim of the study was to analyze the difficulties in surgical reconstruction of the lumbosacral junction with restoration of spinal stability and to describe an effective surgical strategy for tuberculosis with extensive destruction of lumbosacral spine. Material and Methods: We retrospectively reviewed 32 patients (17 males, 15 females) with advanced lumbosacral tuberculosis (L3 and lower levels) who underwent surgical reconstruction according to the following protocol. Patients with L5 tuberculous spondylitis (Type 1) were treated with posterior spinal instrumentation involving L3, L4, S1 (with supplemental iliac screws if anchorage in S1 was inadequate). In L5-S1 spondylodiscitis with extensive destruction of sacral promontory with disease free sacral ala (Type 2), lumbosacral spine was reconstructed by spinopelvic stabilization using alar screws with supplemental iliac screws. In extensive L5-S1 spondylodiscitis with destruction of both sacral promontory and sacral ala (Type 3), stability was achieved with spinopelvic stabilization using the only available option of iliac screws as distal anchors. Additional anterior reconstruction was performed in cases where there was a significant anterior column deficiency and additional restoration of lordosis within physiological limits was needed. Outcomes were analysed with respect to neurological improvement, VAS (Visual Analogue Scale) scores, functional outcomes [Oswestry Disability Index (ODI)], improvement in global lumbar lordosis (GLL), and bony fusion on radiographs. Results: Average follow-up was 35.2 ± 8.3 (26-64) months. All patients showed good bone healing at a mean of 9.5 ± 1.6 months, significant improvement in neurology, VAS scores, ESR and CRP, p < 0.05.Average gain of GLL was 11.3 ± 2.7 degrees.There was no neurological deterioration in any patient. ODI scores showed significant improvement at final follow-up (p < 0.05). Conclusions: There are no detailed studies on surgical strategies in advanced lumbosacral junctional tuberculosis. Surgery forms the mainstay of treatment in advanced lumbosacral tuberculosis. Spinopelvic fixation is a biomechanically stable option for surgical reconstruction in advanced lumbosacral disease. It helps withstand shear forces across the lumbosacral junction, prevents graft slippage and accelerates graft incorporation and fusion, thereby allowing early mobilisation and rehabilitation. In cases with extensive loss of anterior spinal column and its anterior load bearing function, anterior column reconstruction with a strut graft helps restore and maintain physiological lumbar lordosis and lumbosacral biomechanics. The proposed classification and the corresponding treatment strategies have proved to be effective in addressing the various scenarios of lumbosacral tuberculosis with extensive destruction of lumbosacral spine, in a systematic way. It helps reconstruct the lumbosacral spine, restore spinal stability and physiological lumbar lordosis as evidenced by the good radiological and functional outcomes at a mean follow-up of 35.2 ± 8.3 months.

Keywords: Tuberculosis, lumbosacral spine, lumbar lordosis, spinopelvic stabilization, classification

Source of Funding-NIL; Conflicts of interest-NIL.

A108: Does Preserving or Restoring Lumbar Lordosis Have an Impact on Functional Outcomes in Lumbosacral Tuberculous Spondylodiscitis?

Ajoy Shetty¹, Aju Bosco², S Rajasekaran³

¹Senior Spine Consultant, Dept of Orthopaedics, Ganga Hospital, Coimbatore - India ²Spine Fellow, Department of Orthopaedics, Ganga Hospital, Coimbatore - India ³Chairman, Dept of Orthopaedics, Trauma & Spine Surgery, Ganga Hospital, Coimbatore - India

Introduction: In lumbosacral tuberculosis loss of lordosis leads to altered lumbosacral biomechanics.All available studies have assessed treatment outcomes with respect to bone healing, neurological improvement and physical well-being. None have correlated functional outcomes with lumbar lordosis at end of treatment. We reviewed 63 patients with lumbosacral tuberculosis, with an attempt to analyse the impact of loss of global lumbar lordosis on functional outcomes. Materials and Methods: Sixty-three patients with lumbar and lumbosacral tuberculosis were treated conservatively (n = 33) or surgically (n = 30) from March 2007 to July 2013.Outcomes were analysed with respect to neurological improvement, VAS (Visual Analogue Scale) scores, functional outcomes, improvement in global lumbar lordosis (GLL), and bony fusion on radiographs.Average follow-up period was 35.2 ± 8.7 months. Correlation between the final post-treatment GLL and functional outcomes (Oswestry Disability Index) were analysed. Results: All patients showed good bone healing (at 8.4 ± 1.5 months), significant improvement in neurology, VAS scores, ESR and CRP, p < 0.05. Mean loss of lordosis in conservatively treated group was 6.4 ± 5.7 degrees, while lordosis was restored by 12.6 ± 7.9 degrees after surgery. Overall, 70% of patients had minimal disability at the end of treatment (conservative and operative). In patients with minimal disability (Oswestry Disability Index) at end of treatment, the final GLL was above 40 degrees. In all patients with severe disability and moderate disability, the average post-treatment GLL was below 40 degrees. Pearson’s correlation test showed a strong correlation between GLL and the degree of disability (r = -0.867, p < 0.001). Conclusion: The significant correlation between lumbar lordosis and functional outcomes has been proved by several studies on surgical management of degenerative diseases of lumbar spine. Ours is the first study which has shown that there exists a significant statistical correlation between the final post-treatment GLL and functional outcomes in infective pathology of lumbosacral spine. The study shows that GLL could be an independent determinant of functional outcomes in lumbosacral tuberculous spondylodiscitis. There exists a significant correlation between maintaining normal lumbar lordosis and good functional outcomes. Early disease with minimal loss of lordosis, can be managed conservatively, while in advanced disease with gross hypolordosis/kyphosis, posterior stabilization with or without global spinal reconstruction is essential to regain lumbar lordosis. The management of lumbosacral tuberculosis should aim at preserving or restoring the normal global lumbar lordosis to achieve good functional outcomes.

A109: Spinal Tuberculosis: A Challenging Diagnosis for Spinal Surgeons. Are Combined Approaches Always Necessary?

Tuna Pehlivanoglu¹, Turgut Akgul¹, Mehmet Demirel¹, Serkan Bayram¹, Murat Korkmaz², Cuneyt Sar¹

¹Istanbul University, Istanbul Faculty of Medicine, Department of Orthopedic Surgery and Traumatology, Istanbul - Turkey ²Istanbul Koc University, Medical Faculty, Department of Orthopedic Surgery and Traumatology, Istanbul - Turkey

Introduction: The most drastic osseous involvement of tuberculosis was reported to be the spine. The present study aimed to conduct a comparison of the results between the posterior surgery alone and the combined anterior and posterior surgery in the management of vertebral tuberculosis. Methods: With a diagnosis of spinal tuberculosis, 60 consecutive patients were operated between 1999 and 2014. Inclusion criteria was to have a type-A spinal deformity secondary to tuberculosis according to Rajasekaran classification. After excluding 29 patients, remaining 31 were included. Based on the implemented surgery, 31 patients with type-A xpinal deformity were retrospectively analyzed and divided into two groups: group A (16 patients: 9 males, 7 females), with posterior surgery alone and group B (15 patients: 7 males, 8 females), with the combined anterior and posterior surgery. The mean ages of group A/B were 56/60 years respectively; the average follow-ups of group A/B were 29 months/28 months respectively. The two groups were compared in terms of intraoperative blood losses, total durations of operations, duration of hospital stays, pre-and postoperative neurological status according to the American Spinal Injury Association impairment (ASIA) scale, spinal deformities and rates of fusion. The local angles of kyphosis were measured at the cephalad and caudal endplates of the affected vertebra as well as above and below on lateral plain X-rays of the spine. To assess the fusion, plain radiographs and computed tomography were used. Results: The average operation times of group A/B were 180.5 ± 21.5 / 361.3 ± 61.3 mins respectively p < 0.001); mean length of hospitalizations were 16.8 ± 4.8 / 27.3 ± 3.4 days (p = 0.03), respectively. Furthermore, the mean Intraoperative blood loss of group A/B were detected to be 463 ± / 573 ± 57 ml respectively (p = 0.027). In group A, angle of kyphosis decreased from 32.6° preoperatively to 25.9° postoperatively with a mean correction angle of 16.5 ± 13.6°. In group B, angle of kyphosis decreased from 25.9 ± 12.7° preoperatively to 10.8 ± 8.3° postoperatively with a mean correction angle of 14.4 ± 10.2°. At the final follow-up, while group A illustrated a mean kyphotic angle of 16.9 ± 9.5°, the mean kyphotic angle of group B was detected to be 12.3 ± 9.3°. Accordingly, loss of correction was calculated as 0.8 ± 0.5° in group A and 1.4 ± 1.4° in group B. All but one patient showed complete bony fusion. The average time until complete fusion was 10.5 ± 2.1 months in group A and 9.3 ± 3.1 months in group B (p = 0.027). In group A, preoperative neurological status according to ASIA scale was assessed as A in 1 patient, B in 1 patient, C in 5 patients, and D in 3 patients. Likewise, in group B, 1 patient was graded as A, 2 patients as C, and 1 patient as D preoperatively. At the latest follow-up all patients with neurological deficits were detected to have a neurological status of E (normal). Conclusion: This study concluded that spinal tuberculosis could be treated with only posterior approach safely and effectively by providing similar clinical efficacy and less morbidity, while combined anterior-posterior approaches might not always be necessary.

A110: Micro Organisms Trends in Infected Implant Removal After Posterior Decompression and Transpedicular Screw Fixation

Muhammad Farrukh Bashir¹

¹Department of Orthopaedic and Spine Surgery, Lahore - Pakistan

Background: Spinal implant infections provide unique diagnostic and therapeutic challenges. Implant removal because of pain and infection after posterior fusion in the thoracic and lumbar spine is a widely performed operation. Implant bulk, metallurgic reactions, and contamination with low-virulence microorganisms have been suggested as possible etiologic factors. The clinical symptoms include pain, swelling, redness, and spontaneous drainage of fluid. Complete instrumentation removal and systemic antibiotics is usually curative The main objective of this study was to determine the causative micro organisms in infected posterior spine implants and sensitivity of these micro-organisms to different antibiotics. Materials and Methods: This retrospective study was conducted at Department of orthopedics and spine centre Ghurki trust teaching hospital, Pakistan after approval from hospital ethical committee. 97 patients of any age and gender who underwent Removal of posterior spinal implants, previously operated either at our hospital or somewhere else, from Jan 2011 to Dec. 2016 due to infection were included in the study. Those patients whose record were incomplete were excluded from the study. The data was collected from departmental database. Patients demographic data as well as culture and sensitivity report of the pus were initially entered on preformed performa and later on entered on SPSS 17.0 version for data analysis. Results: Out of 97 patients, there were 54 (55.67%) males and 43 (44.33%) males with male to females ratio of 1.26: 1 and with mean age of 46.78 ± 9.54. Among all patients 54 (55.67%) patients having no co morbidity, 30 (30.93%) were diabetic, 10 (10.31%) were hypertensive, 8 (8.25%) having cardiac issue while 3 (3.12%) patients having some other co morbidity. 34 (35.05%) patients were non addict, 31 (31.96%) patients were smokers, 17 (17.53%) eat Pan, 6 (6.19%) were using domestic alcohol and 9(9.27%) some other types of addiction. 29(29.90%) patients having culture and sensitivity negative reports.The frequency of bugs were different. Most of the micro organisms were Gram +ive Cocci i-e 31(31.95%) followed by gram -ive rods i-e 24 (24.74%).Some samples showed growth of more one organism.The Gram -ive rods and Gram +ive cocci were found in 7 (7.21%) of the cultures and others 6 (6.18%). The different micro organisms were in different percentages. The most common were MRSA i-e 29 (29.89%) followed by Streptoccoci and MSSA with equal incidence i-e 21(21.65%).The fungal infection were found only in 2 (2.06%) of patients and few others micro organisms were 7 (7.21%). Vancomycin and Doxycyline were most common drugs sensitive against MRSA followed by Amikacin and fusidic acid. Proteus mirabilis, Klebsiella, Pseudomonas Aeroginosa and E.Coli were most sensitive to Amikacin.MSSA were mostly sensitive to Vancomycine. Streptococci showed most and equal sensitivity to amoxicillin and ampicillin. Conclusion: Vancomycin, Amikacin, Doxyclin and fucidine should be included among the empirical treatment whenever a patient with spinal infection come because of high sensitivity of these antibiotics to common bugs found in culture reports.

A111: A Novel One-Stage Surgical Treatment for Thoracic and Lumbar Tuberculosis By Internal Fixation, Limited Debridement and 270° Fusion Via Posterior-Only Approach

Tong Meng¹, Huabin Yin¹, Dianwen Song¹

¹Department of Orthopedics of Shanghai First Peoples Hospital, Shanghai - China

Introduction: Total tuberculosis incidence has increased all over the world, especially in developing countries. However, there are still controversies over surgical methods for spinal tuberculosis in the literature. In this study, we introduced a novel one-stage surgical treatment by internal fixation, limited debridement and 270° fusion via posterior-only approach, and investigate the clinical efficacy and feasibility of this method in treating thoracic and lumbar spinal tuberculosis. Methods: We enrolled patients with active spinal tuberculosis of the thoracic or lumbar spine who underwent surgical treatment between January 2013 and September 2014, and chose patients suitable for this surgical treatment. Then, the clinical efficacy was evaluated with Frankel Grade scores, Cobb angle, erythrocyte sedimentation rate and imaging examination preoperatively and postoperatively. Result: Twenty-one patients enrolled in this study with the method of limited debridement, effective fusion and posterior fixation, with a mean age of 47.9 (range, 24-73) years. All of them were followed up at least 12 months, with the mean bony fusion time 5.86 (median, 4-9) months. There were significant differences between preoperative group and postoperative group regarding the Cobb angle, ESR and Frankel Grade scores. Delayed wound healing affected one patient due to diabetes. No complication regarding to internal fixation and no tuberculosis recurrence were observed during follow-up. Conclusion: Combined with multiple anti-tuberculosis drugs, this method of limited debridement, effective fusion and posterior fixation can maintain spinal column integrity, improve neurological function, achieve satisfactory bony fusion, decrease postoperative complications and lead to effective recovery in the end.

A112: Atypical Infections of the Spine in the Context of HIV and TB Co-Infection

Fred U N Ukunda¹

¹Department of Orthopaedics, University of the Witwatersrand, Johannesburg - South Africa

Introduction: Sub-Saharan Africa (SSA), and South Africa in particular globally, is worst affected by Human Immunodeficiency Virus (HIV) and tuberculosis (TB) epidemics. So any infection in this setting must be viewed in the context of these 2 epidemics. Especially, up to 70% of adults with TB are infected with HIV. As access to resources is not always easy, It is not unusual for clinicians to initiate antituberculosis treatment on presumption of diagnosis alone when extra-pulmonary TB (i.e spine) is suspected. To demonstrate that presumption of diagnosis alone is not sufficient. Methods: This is a retrospective record-based study from a prospectively maintained database of orthopaedic spine unit. An audit of the histology results of all patients who underwent incisional (percutaneous core biopsy) and excisional (radical debridement) of spine, whenever the diagnosis of TB spine was suspected, between 2013-2017. Data were collected using case sheets of spine patients from the medical records, microbiology as well as histology results hard copy from the National Health Laboratories Services. Inclusion criteria are complete medical records, microbiology and histology results. Results will be interpreted in terms of percentage. Results: Of 217 patients on the database, were diagnosed with spine TB. The diagnosis was made histologically, with identification of Necrotising granulomatous inflammation; positive acid fast bacilli (AFB) microscopy staining and PCR (Polymerase Chain Reaction) using Gene Xpert testing. Mycobacterium xenopi osteomyelitis of spine (n = 1), Cryptococcal osteomyelitis of the spine (n = 2), Salmonella species (n = 1), Hydatid Disease of spine (n = 1), Sporothrix schenckii osteomyelitis of spine (n = 1), Blastomycosis cervical spine (n = 1), Aspergillus Spp of lumbar spine (n = 1). Surgical management was dependant was tailored to the patient. Conclusion: Biopsy is mandatory for all suspected cases of spine TB. Particularly, where HIV is so epidemic, with TB coinfection so endemic in the community, atypical mycobacterial or non-mycobacterial TB manifestations are possible. And do not forget other differential diagnosis.

Imaging

A113: Prevalence of Lumbar Disc Degeneration in Symptomatic Twenty to Thirty Year Olds - A Study of Over 850 MRI Scans

Uzair Ahmadje¹, Andrew James Berg², Harsha Haraluru Jayanna², Philip Saniville³, Vik Kapoor²

¹Faculty of Biology, Medicine and Health, Manchester, The University of Manchester, Manchester - United Kingdom ²The Spinal Unit, Stepping Hill Hospital, Stockport - United Kingdom ³Department of Radiology, Stepping Hill Hospital, Stockport - United Kingdom

Introduction: The prevalence of lumbar disc degeneration (LDD) in both the symptomatic and asymptomatic older population is well reported. There is however a paucity of data regarding the prevalence of disc degeneration in younger patients. We aimed to assess the prevalence of disc degeneration in a cohort of symptomatic patients aged between 20 and 30 years presenting to our institution. Material and Methods: All patients, between the ages of 20 and 30 years, who had undergone lumbrosacral Magnetic Resonance Imaging (MRI), at the authors' institution, between April 2008 and May 2017, were identified from hospital records. Imaging had been performed for investigation of low back pain and/or radicular symptoms. The MRI scan images were reviewed to assess for evidence of lumbar disc degeneration on a high resolution monitor using the GE Medical Systems Centricity Enterprise Web V3.0 platform. Results: 1010 patients who had undergone lumbosacral MRI during the study period were identified. 884 scans were available electronically and reviewed. The average age of subjects was 25.3 years (range 20-30 years). There were 521 females and 362 males. 472 (53.4%) patients had MRI evidence of lumbar disc degeneration. 54% of these had disc degeneration at a single level and the remaining 46% at more than one level. The most commonly affected level was L5/S1 with 72% exhibiting disc degeneration at this level followed by 58% at L4/5, 19% at L3/4, 8% at L1/2 and 7% at L2/3. Conclusion: This study is, to our knowledge, the largest to describe the prevalence of disc degeneration in a symptomatic younger age group. 53.4% of MRI scans performed on symptomatic 20-30 year olds had evidence of lumbar disc degeneration. 46% of these had evidence of multi-level degeneration. This study therefore highlights that there is a high prevalence of lumbar disc degeneration in a symptomatic young population. While we accept that the association between disc degeneration and symptoms is poorly understood, this study should encourage further research and awareness from surgeons of the evolving technologies, which may offer treatment options for symptomatic patients.

A114: A Novel Patient-Specific Virtual Reality Environment for Immersive Assessment and Surgical Planning

Gregory F. Jost¹, Benedikt Bitterli², Mathias Griessen², Maria Licci¹, Stefan Schaeren¹, Philippe C. Cattin²

¹Spine Surgery, University Hospital Basel, Basel - Switzerland ²University of Basel, Medical Image Analysis Center, Department of Biomedical Engineering, Allschwil - Switzerland

Introduction: The computer and gaming industry has come forward with exciting virtual reality (VR) equipment that is powerful and affordable. Elaborate programming i.e. Volume Rendering techniques allow using this equipment to visualise standard DICOM datasets and enabling surgeons to study a patient’s anatomy in an unforeseen immersive fashion. Material and Methods: A patient with a cervical deformity caused by ankylosing spondylitis was studied. The DICOM dataset of an angiography-enhanced computed tomography of the cervico-thoracic spine was reconstructed to be shown in a VR environment. The surgeons immersed into the VR environment by wearing a VR headset and studied the anatomy. Results: Three surgeons used the VR environment to study and familiarize themselves with the patient’s complex deformity. It was uniformly felt, that the unique possibility to “look and walk” around the pristinely reconstructed spine and arteries allowed the surgeons to quickly understand the elements of the deformity such as pseudarthrotic sites, tilting and rotation. Together with planning the surgery on multiplanar reconstructions, the VR environment enabled surgeons to optimize their preoperative 3D understanding of the case. Conclusion: Studying patients with complex spinal anatomy in a VR environment appears to significantly support the preoperative planning phase.

A115: Analysis of Factors Influencing Ligamentum Flavum Thickness in Lumbar Spine - A Radiological Study of 1070 Disc Levels in 214 Patients

Sudhir Ganesan¹, Vignesh Jayabalan¹, Karthik Kailash¹, Saikrishna Gadde¹

¹Department of Spine Surgery, Chennai - India

Introduction: Ligamentum Flavum Hypertrophy (LFH) is known for its strong association with spinal canal stenosis especially at L4-5. The pathomechanism & factors influencing hypertrophy of the Ligamentum flavum still requires a confident specificity. This is a retrospective observational study to analyse the association between various factors and Ligamentum Flavum Thickness (LFT) and also to investigate the major contributor for LFH at various levels in the lumbar spine. Materials and Methods: The following were evaluated at L1-L2, L2-L3, L3-L4, L4-L5 and L5-S1 levels in MRI of 1070 lumbar disc levels of 214 patients with chronic lower back ache: Pfirrmann’s grade of the disc, anterior disc height and posterior disc height, disc volume, facet tropism and Ligamentum Flavum Thickness. LFT > 0.4 cm was considered as hypertrophy. Correlation between LFT and other parameters was done and values with p < 0.05 was considered statistically significant. Results: 112 male and 102 female (average age-52.57 years) were included. There was an increase in the anterior disc height (0.98 cm to 1.50 cm), posterior disc height (0.84 cm to 0.96 cm), disc volume (7.17 cm³ to 14.6 cm³), facetal angle (Right side-42.6° to 58.8°, Left side-41.7° to 56.4°) and LFT (Right side-0.32 cm to 0.48 cm, Left side-0.31 cm to 0.44 cm) from L1-2 to L5-S1 levels. Highest frequency of LFT was seen at L4-5. Pfirrmann’s grade of the disc & Anterior disc height had a statistically significant positive correlation with LFT at L1-L2, L2-L3, L3-L4, L4-L5 levels whereas facet tropism was strongly associated with LFT at L5-S1 level. Conclusion: Higher Pfirrmann’s grade and decreased anterior disc height can lead to ligamentum flavum hypertrophy at L1-L2, L2-L3, L3-L4, L4-L5 levels. Whereas at L5-S1 level, it is the presence of facet tropism which can cause LFH. Hence, patients with the presence of above mentioned factors at those respective levels have higher preponderance to develop Lumbar canal stenosis.

A116: Changes in Thoracic Spinal Cord Movement and Sagittal Cord Diameter, A Kinematic MRI Analysis

Permsak Paholpak¹, Aidin Abedi¹, Rattanaporn Chamnan¹, Kunlavit Chantarasirirat¹, Koji Tamai¹, Zorica Buser¹, Jeffrey Wang¹

¹Department of Orthopaedic Surgery, Keck School of Medicine, University of Southern California, Los Angeles - United States

Introduction: The thoracic spine is considered as a semi-rigid region in human spine. Several studies have reported dynamic changes of the thoracic spine in terms of motion and cross-sectional area of the thoracic spinal cord. The movement of thoracic spinal cord within dural sac and the change in mid-sagittal diameter in correlation with positional changed is still unknown. The aims of this study were (1) to evaluate the dynamic change of anterior and posterior Space Available for Cord (SAC) of the thoracic spinal cord in the dural sac in three position, neutral, flexion, and extension, and (2) to evaluate the dynamic change of the thoracic spinal cord in mid-sagittal diameter in three positions. Materials and Methods: 118 patients (66 males and 52 females, mean age of 45.6 ± 10.6) who underwent thoracic spine kMRI were evaluated from T4/5 to T11/12 in flexion, neutral, and extension positions. The anterior SAC, posterior SAC, and mid-sagittal thoracic cord diameter were measure at the level of each intervertebral disc from T4-5 to T11-12. The anterior SAC is the distance from posterior borders of the disc to the anterior border of the thoracic cord. The posterior SAC is the distance from the posterior border of the thoracic cord to the anterior border of the posterior column at each level. The mid-sagittal cord diameter is the distance between anterior and posterior border of thoracic cord, and was measured in the mid-sagittal plane of the MRI. The Friedman’s test was used to test the statistical significance for each parameter in three positions, then Wilcoxon-signed-rank test was used for post-hoc analysis. P-value of less than 0.0167 was considered statistically significant after Bonferroni correction. Results: Between three positions, there were statistically significant differences in anterior SAC at levels T8-9 to T11-12 (p < 0.001 at T9-10 to T11-12, p = 0.001 at T8-9). The posterior SAC also showed statistically significant difference between three positions at T4-5, T7-8, T8-9 and T9-10 level. For mid-sagittal cord diameter, there were statistically significant differences between three positions at T4-5, T6-7, T8-9, T9-10, and T10-11 (p < 0.01). After post-hoc analysis, the anterior SAC in flexion position was significantly narrower than in the neutral and in the extension position at T8-9 to T11-12 level. The T8-9 level had significantly wider posterior SAC in flexion than in the neutral position. Thoracic spinal cord mid-sagittal diameter significantly increased in flexion position when compared to the neutral position at T8-9, T9-10, and T11-12 level. On the other hand, thoracic cord at T4-5 in extension position was significantly narrower than in the neutral position. Conclusions: Thoracic spinal cord changed in shape and position in the dural sac during positional changes. In flexion position, the thoracic cord at T8-9 and below tended to move anteriorly closer to posterior vertebral body and intervertebral disc. The thoracic cord, itself, increased in mid-sagittal diameter in flexion position at the levels below T8-9. In flexion position there is a higher chance of spinal cord compression if there are lesion in the anterior epidural space, especially at the levels below T8-9.

A117: Assessment of Accuracy of EOS Imagining Technology in Comparison to Computed Tomography in Determining Vertebral Orientation in Instrumented Spines in Adolescent Idiopathic Scoliosis

Fan Jiang¹, Leonardo Simoes², Jean Ouellet³, Neil Saran³

¹University Health Network, University of Toronto, Toronto - Canada ²Silvestre Hospital, Rio de Janeiro - Brazil ³McGill Scoliosis and Spine Research Group, McGill University Health Centre, Montreal - Canada

Introduction: EOS 3D imagining technology allows simultaneous orthogonal views of the spine to be captured in the weightbearing position while exposing the patients to low dosage of radiation. It has been shown that EOS is capable of generating radiographic images of good quality, good structural visibilities, and its measurement of spinopelvic alignment and curve measurement is comparable to that of conventional radiograph. Previous studies have demonstrated that in assessing the non-instrumented spine, vertebral shape and orientation generated by EOS are similar to that of computed tomography (CT). The goal of this study was to assess the validity of EOS in determination of vertebral rotations in the instrumented spine. Methods: Retrospectively 31 patents with adolescent idiopathic scoliosis (AIS) who underwent instrumented fusion and post operatively had CT scan of spine were identified in a single institution. 3D models of the instrumented spine were generated from the EOS image performed closest to the date of the CT scan within a 6 months period. Vertebral rotation of the apex vertebra, the uppermost (UIV) and lowermost (LIV) instrumented vertebra, the non-instrumented vertebra one level cranial to the UIV (UIV+1) and one level caudal to LIV (LIV +1) were determined using the EOS 3D morphological analysis. The same vertebral level rotation was also measured using the CT axial images. To account for the differences in plane of reference with respect to the two different imagining modalities, relative vertebral rotation changes were calculated for UIV to apex, UIV+1 to apex, LIV to apex, LIV+1 to apex, UIV to LIV and UIV+1 to LIV+1. Paired t-test was used to compare the relative vertebral rotation changes measured using the two different imagining modalities. For values where p > 0.05, the Bland-Altman plot was used to assess the agreement between the measures. Interclass correlation (ICC) was used to assess interobserver and intraobserver reliabilities of EOS and CT measurements. Results: EOS analysis of relative vertebral rotation were found to be significantly different to that of CT for UIV to apex (p 0.006) and UIV+1 to apex (p 0.003). No significant differences were found for LIV to Apex (p 0.06), LIV+1 to apex (p 0.06), UIV to LIV (p 0.59) and UIV+1 to LIV +1 (p 0.64). Though there is no difference by Bland-Altman between these methods for these measurements, variance was noted to be very high. ICC showed good interobserver and intraobserver reliability for EOS and very good intraobserver reliability for CT. Conclusion: EOS 3D morphological analysis of vertebral rotational changes in the instrumented levels of the spine of patients with AIS demonstrated significant difference and unacceptable variance in comparison to CT measurement. The presence of hardware obscures the proper assessment of images and thus introduces error in the precision of EOS analysis. The error is worse in the upper segments of the construct than the lower segments. Using EOS to quantify rotation in instrumented spines of patients with scoliosis is not precise.

A118: Is There Any Use? Validity of Rasterstereography Compared to EOS 3D Imaging in Patients With Degenerative Disc Disease

Lorenz Wanke-Jellinek¹, Christoph Mehren¹, Christoph J Siepe¹, Karsten Wiechert¹

¹Dept. of Spinal Surgery, Schoen Klinik Munich, Muncih - Germany

Introduction: The aim of the present study was to evaluate the validity of rasterstereography in patients with degenerative disc disease for frontal, sagittal, and transverse parameters. Previous studies comparing inter- and intraobserver reliability of rasterstereography exist in abundance and show a high intra- and interday reliability in healthy volunteers. However, there is lack of data comparing the validity of rasterstereography with conventional Xray imaging. We utilized the recently developed EOS imaging system (EOS Imaging, Paris, France) for accurate 3D spinal modeling and compared the measurement of spinal and pelvic parameters obtained by EOS to parameters obtained by rasterstereography. Material and Methods: Sixteen healthy individuals (female = 10) at the age between 25 and 88- yrs. with diagnosed degenerative disc disease were included. EOS Xray images were analyzed using the sterEOS software to determine the lumbar lordosis- (LL) and thoracic kyphosis (TK) angle as well as pelvic obliquity (PO) and pelvic axial rotation (PR). Patients received rasterstereographic measurements independently performed by a single operator on the same day as EOS imaging. Parameters obtained by EOS 3D imaging were compared to those obtained by rasterstereography. For data analysis we used Bland and Altman’s Limit of Agreement (LOA) as well as Pearson correlation coefficient to compare accuracy of rasterstereography vs. EOS imaging. Results: LOA as well as Pearson correlation did not show any significant correlation between the two modalities for Lumbar Lordosis (LL) (R = 0.26), Pelvic Obliquity (PO) (R = -0.14) and Pelvic Axial Rotation (PR) (R = 0.05). The Thoracic Kyphosis (TK) angle showed the strongest correlation of all parameters evaluated (R = 0.57). Conclusion: For assessment of the respective parameters, rasterstereographic systems are no reliable substitute for Xray based imaging systems. EOS imaging was previously shown to provide reliable and accurate spinal modeling in the measurement of spinal parameters while using substantially lower levels of radiation than conventional Xray based imaging. Based on our results rasterstereographic imaging should be used with caution for evaluating spinal parameters.

Minimally Invasive Surgery 2

A119: A Prospective Randomised Study to Analyse the Efficacy of Balanced Preemptive Analgesia in Spine Surgery

Soundararajan Dilip Chand Raja¹, Ajoy Shetty², Rishi Mugesh Kanna³, S Rajasekaran⁴

¹Spine Fellow, Department of Orthopaedics, Ganga Hospital, Coimbatore - India ²Senior Spine Consultant, Dept of Orthopaedics, Ganga Hospital, Coimbatore - India ³Associate Consultant, Dept of Orthopaedics, Ganga Hospital, Coimbatore - India ⁴Chairman, Dept of Orthopaedics, Trauma & Spine Surgery, Ganga Hospital, Coimbatore - India

Introduction: Surgical procedures of spine are known to cause moderate to severe postoperative pain. Inadequate management of acute pain in postoperative period results in higher morbidity, and consequently may end up in chronic pain due to central sensitization. The role of preemptive and intraoperative analgesia has gained importance over the recent years. Pathophysiology of postoperative pain in spine surgery is unique, as it is a combination of nociceptive, inflammatory and neuronal stimuli. This is the first randomized double blinded clinical trial to assess the efficacy of paracetamol (P), ketorolac (K) and pregabalin (PR) as preemptive multimodal analgesia, aimed to block or reduce all three stimuli in the perioperative period. Materials and Methods: After Institutional Review Board (IRB) approval, 100 consecutive patients requiring single or double level spinal fusion procedures were randomized into two groups- Preemptive analgesia (PE) and control (C). Both groups received esomeprazole (E) and domperidone (D) as preanaesthetic medication 8 hours prior to surgery, while the PE group alone received three drugs P, K and PR 4 hours before surgery, as preemptive analgesia. Both groups underwent identical anesthetic and postoperative pain management protocol. Demographic and surgical data, four hourly postoperative pain levels- Numeric Pain Intensity (NPI) scores, Ambulatory NPI scores, level of consciousness - Ramsay sedation scale (RSS), total amount of opioids consumed (TOC) through patient controlled analgesia (PCA), functional levels-Oswestry Disability Index (ODI), surgical satisfaction index-North American Spine Society Satisfaction Scale (NASSS), duration of hospital stay (DOH), and all complications were recorded and analyzed. Results: Both the groups had identical demographic and surgical profile. The average 48 hour NPI score in PE group was 2.7 ± 0.79 and less than 3.4 ± 0.98 in the C group (p < 0.001) and was much more significantly low in the first 12 hours following surgery. In addition the PE group had low consumption of opioids 3.02 ± 2.29 in comparison to 4.94 ± 3.08 (p < 0.001). Ambulatory NPI was significantly low in PE group during first and second postoperative days. The PE group was found to be more motivated and 95.7% compared to 30% in the C group were able to ambulate 50 meters on the first postoperative day. The duration of hospital stay was 4.17 ± 1.02 and 4.84 ± 1.62 days in the PE and C groups (p = 0.017). Dry mouth was the most common side effect noted irrespective of the groups, possibly due to domperidone. All patients had significant improvement in ODI with better results in PE group at first month of follow up.97.90% of PE group compared to 72% in C group (p = 0.002) were extremely satisfactory according to NASSS. Conclusion: Optimal postoperative pain management in spine surgery could be achievable, only if perioperative painful stimuli can be inhibited, which requires adequate blood levels of analgesic, anti-inflammatory and neuropathic drugs intraoperatively, and in the immediate postoperative period. Our strategy of administering three preemptive drugs, each having different mechanisms of action has, reduced the requirement of opioids, enabled early mobilization, reduced duration of hospital stay and has no additional complications. Thus this balanced analgesia administered preoperatively would address the complicated postsurgical pain.

A120: The Rates of Post-Operative Complications After Lumbar Discectomy in the Inpatient and Outpatient Setting

Permsak Paholpak¹, Ifije Ohiorhenuan¹, Christopher Wang¹, Jeffrey Wang¹, Zorica Buser¹

¹Department of Orthopaedic Surgery, Keck School of Medicine, University of Southern California, Los Angeles - United States

Introduction: Recently, the number of outpatient lumbar discectomy procedure has been increasing every year. Outpatient setting is considered safe and cost effective procedure for lumbar discectomy. However, outpatient spinal procedures have a higher risk of neurological complications from epidural and retropharyngeal hematoma. The aim of this study was to compare the rates of post-operative complications after lumbar discectomy between outpatient and inpatient settings. Materials and Methods: This is a retrospective study using Humana database from 2007-2016 (PearlDiver® Technologies). We evaluated patients who underwent lumbar discectomy at any level, from 2007 to the first quarter of 2016. The presence of re-operation at the same lumbar level within 1 year after index surgery, immediate post-operative lumbar nerve root injury, venous-thombotic event (VTE) within 1 year after surgery, surgical site and post-operative infection within 3 months were evaluated. The VTE were defined as deep vein thrombosis and pulmonary embolism. The post-operative infections were defined as surgical site infection, urinary tract infection, catheter related infection, and sepsis related infection. The surgical site complications were defined as wound disruption, hematoma or seroma at surgical wound, and non-healing surgical wound. The Chi-Square test was used to compare between two setting groups in each complication, the p-value, Odd-ratio (OR), and 95% Confidence Interval (95%CI) were calculated. The statistically significant difference level was set at a p-value of less than 0.05 Results: Over a nine-year period 23 832 patients underwent lumbar discectomy procedures. 69.23% (16 498) of patients received lumbar discectomy in outpatient setting. The outpatient setting showed significantly lower incidence of post-operative infection (p < 0.001, Odd Ratio (OR) 0.32, 95%CI 0.27-0.38), surgical wound related complications (p < 0.001, OR 0.57, 95%CI 0.49-0.66), and VTE (p < 0.001, OR 0.42, 95%CI 0.36-0.5). On the other hand, outpatients setting had a significant higher risk for re-operation at the same level within 1 year than inpatient setting (p < 0.001, OR 1.47, 95%CI 1.3 -1.66). There was no statistical significant difference in immediate post-operative lumbar nerve injury between the two procedural settings. Conclusion: Lumbar discectomy was performed more in the outpatient than inpatient setting. Inpatient procedures had a higher rate of surgical-wound related complications, post-operative infections, and VTE compared to the outpatient setting. At the same time the outpatient setting had a higher rate of re-operation at the same lumbar level than inpatient setting. The discectomy level identification and acute post-operative wound monitoring (such as hematoma) are crucial in outpatient procedure in order to reduce the rate of same level re-exploration.

A121: Post-Operative Single-Shot Epidural Fentanyl and Bupivacaine for Post-Operative Analgesia After Lumbar Decompression: A Prospective, Double-Blind Randomized Study

Mannuel Feliciano Alican¹, Miguel Rafael Ramos¹, Mario Ver¹, Lulu Joan Mamaril²

¹Institute of Orthopedics and Sports Medicine, St Luke’s Medical Center, Quezon City - Philippines ²Department of Anesthesia, St. Luke’s Medical Center, Quezon City - Philippines

Introduction: Despite the success of lumbar decompression in alleviating symptoms of sciatica, radiculopathy, and neurogenic claudication, transient back and buttock pain is still a common complaint in the immediate postoperative period. The purpose of this study was to evaluate the pre-emptive analgesic effects of a single, postoperatively administered epidural bolus of Fentanyl and Bupivicaine in patients that underwent lumbar decompressive surgery. Material and Methods: We performed a randomized, double-blinded, clinical trial. After approval from the institutional review board and local ethics committee, informed consents were obtained, and 45 patients scheduled for lumbar decompression from December 2015 to August 2017 were randomly assigned to receive a postoperative bolus of 10-mL solution of 50 mcg of Fentanyl, 0.125% Bupivacaine, and 0.9% saline solution via an intraoperatively placed epidural catheter immediately after wound closure, before dressing application. Facial pain scale scores (from 0 to 10) were measured at 3 time points after surgery (fully awake at recovery room, transfer to ward, first postoperative day). Postoperative need for oral analgesics, time to independent ambulation, associated adverse events, and time to hospital discharge were also evaluated. Results: Pain scores were noted to be significantly lower at all time points except upon transfer to recovery room in the epidural group (P < 0.05). In turn, they also received less on-demand oral pain medications (p = 0.000). The mean time to ambulation was 0.09 days in the epidural group and 0.91 days in the decompression-alone group (p = 0.000). Criteria for hospital discharge was usually met on Day 0 in the epidural and Day 1 in the control group (p = 0.000). No adverse events or complications related to Fentanyl use were observed. Conclusion: A postoperative bolus of Fentanyl and Bupivacaine is effective in reducing early postoperative pain without the related complications of opioid administration.

A122: Elastoplasty With Syilicone Purified for the Treatment of Spinal Lytic Lesions in Cancer Patients: A Retrospective Evaluation of 46 Cases

Stefano Telera¹, Francesco Crispo¹, Maddalena Giovannetti¹, Carmine Carapella¹, Isabella Sperduti¹, Laura Raus¹

¹Deparment of Neurosurgery, National Cancer Institute “Regina Elena”, Rome - Italy

Introduction: Balloon Kyphoplasty (BKP) for vertebral compression fractures (VCFs) in cancer patients is more challenging than for osteoporotic ones. Cord compressions are frequent and the incidence of complications is reported to be ten-fold greater. PMMA is the gold standard for BKP. However, PMMA has also some disadvantages: exothermic reaction, short working time, rapid solidification, absence of osteoconductive properties. A new purified silicon material has been recently introduced for BKP. It is a mixture of Dimethyl methylvinyl siloxane, Barium Sulphate and Platinum catalyst, it is adhesive to bone, it has no exothermic reaction leaving up to 30 minutes before solidification and is more elastic than PMMA. The surgical procedure called elastoplasty, is similar to a BKP. Material and Methods: To investigate the clinical results obtained with this new silicon material in pathological VCFs, we treated 46 cancer patients (80 vertebral bodies) with purified silicon, through percutaneous BKP, open BKP and augmentation procedures to implement dorso-lumbar stabilizations. Leakages and pulmonary embolism (PE) were evaluated with CT scans. Median follow-up was 14 months. Results: The average working time allowed by VK 100 was 30 minutes. The mean volume of silicon inserted in each vertebra was 3.8 cc. Complications included seven cases of leakages in 41 patients treated with BKP (17%), two asymptomatic PE (4.3%) and 3 postoperative adjacent fractures (7.3%). A significant improvement was observed in KPS, VAS and Dennis Pain Score (p < 0.0001). The 1-yr survival rate was 77.5 Conclusion: Elastoplasty appears a safe and effective palliative treatment of VCFs in oncologic patients. Major advantages over PMMA are the lack of exothermic reaction and the wider working window. The influence of biomechanical properties of silicon on reduction of adjacent level fractures requires further investigations.

A123: Direct Lateral Front Psoas Approach Lumbar Interbody Fusion

Kanji Sasaki¹

¹Spine Center, Seirei Hamamatsu General Hosp., Hamamatsu - Japan

Introduction: Oblique lumbar interbody fusion (OLIF) is new choice of lumbar fusion, superior to posterior fusion at the point of rigid fixation and no or less invasion of posterior column. However this technique has the possibility of some complications (e.g. injury of renal truct/ colon or aorta/ vena cava, segmental artery). On the other hands, direct lateral interbody fusion (DLIF) has less possibility of these complications, but invasive approach of psoas major cannot prevent the damage of ilioinguinal nerve or lumbar plexus. We hypothesized that the combination of direct approach and no psoas invasion is better than these two and we improved the approach. This study is to certify whether this approach is safe and easy or not. Material and Methods: Ninety-two cases of single or double level OLIF (male 47 and female 45; mean age: 68.2 years old) were investigated. Surgical levels were 13 cases of L3/4, 49 cases of L4/5 and 30 cases of L3/4/5 fusion. Surgical procedure was followings; Position: knee and hip bend more than 45 degree flexion (to soften the tension of abdominal muscles and psoas). Surgeons stand at the abdominal side. Approach: check the exact lateral view of X-ray (C-arm) and mark 3 cm incision on the skin at the front edge of vertebra. Tract: after tear the abdominal oblique muscle directly, to find transvers process of upper level above the transverse muscle by finger (No need to optical check). After finding, tear the transverse muscle on transverse process and go into retro peritoneal space (only one finger). To feel the fat pad and we can touch psoas major. To move finger into abdominal side, we can strike vertebra, and we can feel the disc space. Then check X-ray and place dilators and retractors, pushing psoas to back side with finger dilation. Retractor position is similar to direct lateral approach, and psoas is retracted over the center of vertebra. All the procedure underwent only with fingers, and without optical check of vessels, or neuro-monitoring. Results: Major complications occurred in 2 cases. One case was the herniation of right lateral pushed by implant insertion and one segmental artery injury. Tree patients suffered left leg pain for several days. 3 cases of implant sinking were occurred. There was one case of late infection. Surgical times were single level: 48 minutes, double level: 67 minutes. With this approach, we could avoid tract injury. For last 12 cases, intra-operative check were done to confirm whether the tracts were ideal or not by O-arm II. All the cases, no peritoneal injury found. Conclusion: We consider this approach safer than OLIF/DLIF. To find retroperitoneal space, this procedure is easy and usable than oblique. Furthermore we can reduce the troubles related to peritoneal injury (because renal tract, lymph vessels, et al exist on or inside of peritoneum) and complications related to lumbar plexus. The minimum invasive direct lateral approach with anterior psoas dilation (Direct-front psoas) may be considered to be main option of lateral approach.

A124: Changes of Segmental Lordosis, and Foraminal Height in Relation With the Position of Custom Made PMMA Spacer in Monosegmental TLIF. Minimum Two Years Follow up of a Prospective Randomized Study

Marton Ronai¹, Maria Puhl¹, Tibor Csakany¹, Peter Pal Varga¹

¹National Center for Spinal Disorders, Budapest - Hungary

Introduction: When performing TLIF there are different arguments to position the intervertebral spacer in different position (anterior or posterior). In a prospective randomized study we found non inferiority of a costum made PMMA spacer in monosegmental TLIF compared with standard, preformed PEEK spacer regarding the mechanical and clinical outcome. Preformed PEEK interbody spacers are often designed to be positioned in the anterior part of the intervertebral space, but PMMA spacer can be formed as well in the anterior, as in the posterior part of this space. In this prospective, randomized study we compare the segmental anatomical changes following the position of a custom made PMMA spacer in monosegmental TLIF. Material and Methods: 106 consecutive patients (18-65 y/o) to whom we suggested to perform single level TLIF were included into the study. The patients were randomised into three groups by the GraphPad QuickCalcs software. Group A is a control group, standard TLIF with PEEK spacer positioned in the anterior part of the intervertebral space. Group B is standard TLIF with PMMA spacer placed in the anterior part of the intervertebral space. Group C is standard TLIF with PMMA spacer formed in the posterior part of the intervertebral space. Patients with a high grade spondylolisthesis, metabolic bone desease, spinal infection, cancer, severe scoliosis (Cobb over 30°) were excluded from the study. We evaluated the changes in segmental, and overall lordosis and in the height of the neuroforamen according to the position of the spacer at each follow up. Results: 8 patients were excluded from the cohort, because the operating surgeon did not follow the randomization for some surgical reason (i.e. not enough place for a spacer, injury of the end plate, etc.). At this moment 5 of the 98 followed patients (4,9%) are lost from the study (did not come to the planned control) 93 patinets (94,9%) have at least 12 month follow up, and 85 completed the 24 month follow up (86,7%). From this 85 subjects, 32 are in Group A, 27 in Group B, and 26 in Group C. In groups A and B (anterior position) the segmental lordosis increased. The mean change was similar (3°and 3,5° consecutively). But in group C it decreased (mean change -1,5°). This difference in the change of lordosis between the groups is significant. The foraminal height increased in all three groups, the mean change was 3% in group A, 5% in group B and 7% in group C. This difference between the groups is not significant. Conclusion: Anterior position of the intervertebral spacer provides more possibility to correct lumbar lordosis in single level TLIF. There is no significant difference between the change of the foraminal height according to the position of an intervertebral spacer.

A125: Percutaneous Transforaminal Endoscopic Surgery (PTES) for Symptomatic Lumbar Disc Herniation

YuTong Gu¹

¹Department of Orthopaedics, Zhongshan Hospital of Fudan University, Shanghai - China

Introduction: Although nearly all kinds of disc herniations are accessible for TESS of outside disc-inside technique directly into spinal canal, complexity of C-arm guided orientation, difficulty to find the optimal trajectory for target and more steps of surgical manipulation leaded to much exposure of X-ray, long duration of operation, and steep learning curve. We designed an easy posterolateral transforaminal endoscopic decompression technique, termed PTES, for radiculopathy secondary to lumbar disc herniation. We found that the entrance point was located at the corner of flat back turning to lateral side, and as high as, or more cranially or slight more caudally than the horizontal line of target disc, which was similar to “All roads lead to Rome (herniated fragment)”. This has never been mentioned by other scholars, and we named this entrance point after “Gu’s Point”. In PTES, press-down enlargement of foramen could make it easy to advance the working cannula into the spine canal between the dura and disc even if the angle of puncture was 45° and to remove the fragments underneath the nerve root and the central dura, even the contralateral nerve root. The purpose of study is to describe the technique of PTES and evaluate the efficacy and safety for treatment of lumbar disc herniation including primary herniation, reherniation, intracanal herniation, and extracanal herniation; and to report outcome and complications. Materials and Methods: PTES was performed to treat 328 cases of 1-level intracanal or extracanal herniations with or without extruding or sequestrated fragment, high iliac crest, scoliosis or calcification including recurrent herniation after previous surgical intervention at the index level or adjacent disc herniation after decompression and fusion. Preoperative and postoperative leg pain was evaluated using visual analog scale (VAS) and the results were determined to be excellent, good, fair, or poor according to the MacNab classification at 2-year follow-up. Results: The mean frequency of intraoperative fluoroscopy was 5(3-14) times per level. The patients were followed for an average of 27.4 ± 3.2months. The VAS score of leg pain significantly dropped from 9(6-10) before operation to 1(0-3) (P < 0.001) immediately after surgery and to 0(0-3) (P < 0.001) 2 years after surgery. At 2-year follow-up, 97.0% (318/328) of the patients showed excellent or good outcomes, 1.8% (6/328) fair and 1.2% (4/328) poor. No patients had any form of permanent iatrogenic nerve damage and a major complication, although there were 1 case of infection and 2 case of recurrence. Conclusions: PTES for lumbar disc herniation is an effective and safe method with simple orientation, easy puncture, reduced steps and little X-ray exposure, which can be applied in almost all kinds of lumbar disc herniation, including L5/S1 level with high iliac crest, herniation with scoliosis or calcification, recurrent herniation, adjacent disc herniation after decompression and fusion. The learning curve is no longer steep for surgeons.

A126: Cryocompression Therapy After Elective Spinal Surgery for Pain Management: A Double Blind Study With Historical Control

Vugar Nabiyev¹, Prashant Adhikari¹, Selim Ayhan¹, Selcuk Palaoglu², Emre Acaroglu¹

¹Ankara ARTES Spine Center, Ankara - Turkey ²Özel Acibadem Ankara Hastanesi, Ankara - Turkey

Introduction: The acute recovery phase after spinal surgery is often complicated by severe pain, high narcotic and non narcotic analgesics consumption. Postoperative continuous-flow cryocompression therapy has been suggested to minimize these complications and to attenuate the inflammatory reaction in orthopaedic joint reconstruction surgery. The aim of this study is to analyse the analgesic efficacy of dynamic cryocompression (DC) after spinal surgery. Our hypothesis is that DC will decrease analgesic drug requirements and decrease pain severity while improving capacity for mobilisation. Material and Methods: This study was conducted on adult spinal disorders requiring surgery with or without instrumentation at lumbar region from a single spine center after ethical committee approval. DC was applied by using the ‘Game Ready system’ (GRS; CoolSystems Alameda, California) at every 6 hours for 30 minutes. A treatment period of 30 minutes has proved to be adequate to sustain the desired tissue temperature, with two cycles of 15 minutes on and 15 minutes off after the initial 30 minutes producing a significantly greater effect on decreased blood flow. Visual analogue scale (VAS) for surgical pain was measured at every 6 hours, for the first 3 days of hospital stay. Patients’pain medication needs were monitored using the PCA system as well as patient charts. Fifteen patients who had had DC therapy were compared to 15 controls who were matched for demographic as well as surgical variables. Results: Of the 30 patients, 15 recieved DC. In the post-anaesthesia recovery unit, the mean visual analog scale (VAS) back pain score was 5.87 (range: 4-7) in DC group and 6.95 (range: 5-8) in control group. The corresponding VAS values for DC vscontrol groups were 3.8 (range: 2-6) vs 5.2 (range: 4-6) at 6 hours postoperatively, and 2.7 (range: 2-4) vs 6.25 (range: 3-5) at discharge, respectively. Cumulative mean analgesic consumptions for paracetemol, tenoxicam and tramadol in DC group vs. control group were 3733.3 ± 562.7 mg vs 4633.3 ± 693.5 mg (p < 0.005), 53.3 ± 19.5 mg vs 85.3 ± 33.4 mg (p < 0.005) and 63.3 ± 83.4 mg vs 393.3 ± 79.9 mg (p < 0.0001), respectively. Conclusion: The results of this study demonstrate a positive correlation between the use of the DC and accelerated improvement in patients during early rehabilitation from adult spine surgery compared to patients who are treated with painkillers only.

A127: Unilateral Laminotomy and Bilateral Decompression Compared to Conventional Laminectomy: A Randomized Prospective Study

Nagendra Palukuri¹, Kalra K L¹, Rupinder Singh Chahal¹, Pravin Gupta¹

¹Dept. of Spine Surgery, Sir Ganga Ram Hospital, New Delhi - India

Introduction: Lumbar canal stenosis (LCS) is a common condition in elderly population. Patients with LCS usually present with numbness, leg & back pain. Patients who are not responding to conservative management or those patients who present with cauda-equina need surgical decompression. Conventional laminectomy (CL) involves extensive damage to paraspinal muscles and posterior spinal ligaments. CL is associated with high blood loss, longer hospital stay and high incidence of back pain. In our study Unilateral laminotomy and bilateral decompression (ULBD) technique was performed for decompression of spinal canal to minimize these complications. Aim of this study is to compare the intra-operative and clinical outcomes of ULBD with CL. Materials & Methods: A prospective randomized cohort study was done in a tertiary care spine centre. Patients were randomly allocated into two groups. Group A underwent ULBD, and group B underwent laminectomy. Group A consisted of 34 patients, while group B of 38 patients. Demographic parameters were recorded. Preoperative ODI and Neurogenic claudication outcome score (NCOS) was collected. Duration of surgery, blood loss, incidence of dural tear was recorded. Patients were followed up at 2 weeks, 8 weeks, 6 months and yearly there after. ODI and NCOS were recorded at every visit while radiographs were obtained at 6 months and yearly thereafter. Results: Minimum follow up period was 12 months. All patients in group A were mobilized same day and were discharged the day after. Duration of surgery was longer in group A. Both groups showed significant improvement in NCOS score. (p < 0.01) Group A showed significant improvement in ODI compared to group B. All group A patients were able to perform their daily activities, while only 76% in group B. Complication rates were similar in both the groups. 4 patients in group B needed posterior fixation. Conclusion: ULBD is an effective and safer alternative to conventional laminectomy for decompression of spinal canal in patients lumbar canal stenosis

Biomechanics

A128: Gravity Line and Sagittal Alignment are Both Risk Factors for Increased Rod Stresses in Long Lumbopelvic Fixation – A Biomechanics Study

Woojin Cho¹, Wenhai Wang², Brandon Bucklen²

¹Albert Einstein College of Medicine/Montefiore Medical Center, New York - United States ²Musculoskeletal Education and Research Center (MERC) a division of Globus Medical Inc., Audubon - United States

Introduction: Posterior lumbopelvic fixation with iliac screws is a method that is commonly used for reconstructing the spine. However, clinically significant failure of lumbopelvic fixation (11.9%) [1] and other complications such as pseudoarthrosis (observed in up to 50% of patients with rod failure) are possible, requiring revision surgery [2]. With high rates of implant failure, questions remain regarding mechanical risk factors, or if there is any relationship between implant type, spinopelvic parameters, and failure to achieve fusion. The purpose of this study is to identify if - and to what extent - spinal-pelvic parameters play a role in construct failure using an in-silico model. Materials and Methods: Finite element models (T10-pelvis) were created to match the average spinal-pelvic parameters (pelvic tilt, sacral slope, and lumbar lordosis) of two cohorts of patients reported in the literature [1], major-failure (defined as pseudoarthrosis or rod fracture above S1) and non-failure groups. In both groups, vertebral segments were modeled as three-dimensional solid elements. Intervertebral discs were structured as hyperelastic materials. The sacroiliac joint was modeled as articular cartilage contacts surrounded by six types of strong ligaments, depicted as spring elements. Pedicle screws with 5.5 mm diameters were modeled as titanium cylinders (yield strength = 795 MPa). A moment load was applied at the T10 superior endplate to simulate gravimetric loading in a standing position. Both non-failure and major-failure spines had a similar gravity line offset from the heels, as provided by literature [3]. Model validation was carried out to compare the range of motion of the intact spine with the experiments. Results: Despite a fixed gravity line position relative to the heels, differences in spinopelvic parameters resulted in a neutral sagittal alignment in the non-failure spine model, but produced a “sagittal forward” alignment of the major-failure spine model [3]. In order for the latter to maintain sagittal balance, pelvic retroversion was reported [3] and the major-failure spine was translated toward the heel by 10 mm to simulate that. As a result, the bending moment was approximately 17.3 Nm in the non-failure group and 20.7 Nm in the major-failure group. Differences in loads produced 14 mm translation and 4.9 degree rotation for the major-failure group — 18% and 14% higher than in the non-failure group (11.9 mm translation/4.3 degree rotation). Rod stresses were highest at L1-L2 and L4-L5. In the major-failure group, the maximum stress (138.3 MPa) was observed at the left rod between L4 and L5. In the non-failure group, the maximum stress (115.4 MPa) was at the left rod surface between L1 and L2. High stress (141.0 MPa) was also observed in right S1 screws in the major-failure group; it was 42% higher than the stress observed in the non-failure group. Conclusion: Due to compensatory differences in alignment of spinopelvic parameters between normal and failed spines, in the presence of a fixed gravity line, the major failure cohort in this study observed a 20% higher load and 18% greater instability. The higher load and instability further increased loading and mechanical demand on the posterior rods in the lower lumbar spine, further emphasizing the importance of proper sagittal alignment.

References

1. Cho W, Mason JR, Smith JS, et al. Failure of lumbopelvic fixation after long construct fusions in patients with adult spinal deformity: clinical and radiographic risk factors: clinical article. J Neurosurg Spine; 19:445-53.

2. Berjano P, Bassani R, Casero G, et al. Failures and revisions in surgery for sagittal imbalance: analysis of factors influencing failure. Eur Spine J; 22 Suppl 6: S853-8.

3. Schwab F, Lafage V, Patel A, Farcy JP. Sagittal plane considerations and the pelvis in the adult patient. Spine; 34:1828-33.

A129: Biomechanical Effects of Lumbar Disc Geometry on Rod Fracture Following L3 Pedicle Subtraction Osteotomy: A Finite Element Study

Ardalan Seyed Vosoughi¹, Amin Joukar¹, Ali Kiapour¹, Anand Agarwal¹, Vijay Goel¹, Joseph Zavatsky¹

¹University of Toledo, Toledo - United States ¹Spine and Scoliosis Specialists, Tampa - United States

Introduction: A common post-operative complication of pedicle subtraction osteotomy (PSO), is rod fracture, usually occurring at the level of the PSO often requiring revision surgery. The main objective of this project was to identify a threshold disc height that increases rod stresses placing them at higher risk for fracture. Additionally, the use of interbody spacers (IBS) were used to mitigate micromotion, to evaluate their effects on rod failure, using a finite element approach. Methods: A validated osseoligamentous 3D T10-pelvis spinopelvic model was used to develop a PSO at L3. Four 30° L3 PSO models were analyzed: healthy discs, and 3 degenerated disc (DDD) models. Compared to the normal healthy disc heights, the 3 degenerated disc models included disc height reductions of 20% (mild), 50% (moderate), and 80% (severe), respectively. All models were instrumented from T10-pelvis. The instrumented healthy disc PSO model was also supplemented with PEEK IBS above (L2-L3) and below (L3-L4) the PSO level. Results: With the increase in the disc degeneration, the L2-L4 global range of motion decreased in flexion, extension, lateral bending, and axial rotation. Increased DDD (decreased heights), decreased the maximum von Mises stresses on the rods at the PSO region in all loading modes (Table 1). Flexion force resulted in the greatest von Mises stresses on the rods, but these stresses were mitigated as disc heights decreased (339 321 267, and 224 MPa, in healthy, mildly, moderately, and severely degenerated discs, respectively). The greatest change (Δ -16.8%) in von Mises stress to the rods occurred with moderately degenerated discs (50% disc height reduction). Adding inter body spacers to the L2-L3 and L3-L4 levels, reduced the flexion, extension, lateral bending, and axial rotation motions by 22%, 21%, 4%, and 11%, respectively. Supplementing the instrumented PSO model with IBS decreased the maximum von Mises stress on the rods (4% reduction in extension, to 33% reduction in flexion). The use of IBS adjacent to the PSO increased the force magnitude acting on the PSO fracture site to 335.4 N. Discussion: Larger discs adjacent to the PSO lead to greater micromotion. Greater mobility adjacent to the PSO can result in a greater von Mises stress on the rods. Increased DDD (decreased disc heights), results in decreased stress values and risk of fracture to the rods. The greatest change (Δ -16.8%) in von Mises stress on the rods occurred with moderate DDD (50% disc height reduction) at L2-L3 and L3-L4, which translates to 4.92 mm and 4.99 in this model, respectively. Surgeons may consider performing IBS fixation in disc heights greater than 5 mm to increase stability and decrease the von Mises stresses on the rods, thereby reducing the risk of rod fracture. Additionally, greater DDD results in greater load across the osteotomy site, increasing forces required for successful fusion. Hence, adding interbody spacers above and below the L3 PSO can facilitate PSO union and decrease the risk of rod failure.

Table 1.

Location and magnitudes of the maximum von Mises stress on the rods for various grades of disc degeneration.

A130: Biomechanical Effects of Bone Cement Placed Near Endplates During the Vertebroplasty for Long Thoracolumbar Fusions- A Finite Element Study

Anoli Shah¹, Amey Kelkar¹, Manoj Kodigudla¹, Robert McGuire², Hassan Serhan³, Anand Agarwal¹, Koji Matsumoto¹, Vijay Goel¹, Joseph Zavatsky⁴

¹Department of Bioengineering, University of Toledo, Toledo - United States ²University of Mississipi Medical Center, Jackson - United States ³Depuy Synthes Spine, Raynham - United States ⁴Spine and Scoliosis Specialists, Tampa - United States

Introduction: Long segment fusion is often utilized in the treatment of symptomatic spinal deformity. Proximal junction kyphosis (PJK) (Kyphotic Cobb angle > 15 degrees) can lead to proximal junctional failure, and has revision surgery rates reported up to 27% within 6 months following primary surgery. As cited in our previous study, the use of a tapered dose of prophylactic bone in UIV (T10), UIV+1 (T9) and UIV+2 (T8) in an instrumented T10-S1 model, which eliminated fractures at T7 (supra adjacent to the augmented T8 vertebra). The tapered dose of bone cement and the disc spaces may buffer axial forces, allowing for a smoother load transfer through the segments. The optimal dose and configuration of the tapered dose of bone cement has also been cited in our previous study. In this current parametric study, we explore the effects of the bone cement placed near the upper and lower end plates and distributed vertically or horizontally in the adjacent proximal vertebrae. Material and Methods: A validated FE model from T6-pelvis was used for the analyses. An osteoporotic model was developed and modified by insertion of pedicle screws and rods from T10 to S1, therein simulating the standard surgical procedure in-silico. Polymethyl methacrylate (PMMA) bone cement was injected in the UIV (T10), UIV+1 (T9) and UIV+2 (T8). 2.5 cc of cement was injected in T10, 2 cc in T9 and 1 cc in T8 near the upper endplate, lower endplate, distributed in a vertical direction and a horizontal direction in the vertebrae. The load was applied to a metal bock 10 mm anterior to the center of the vertebra to simulate flexion moment and the pelvis was fixed. The stresses at the end plates from T7 to T10 were analyzed. Results: Except for 3.8% increase at the T7 inferior endplate for the bone cement placed near the upper endplates, lower stresses were observed when the cement was placed near the upper endplates as compared to placement near the lower endplates, ranging from 3% to 20.5% at the T9 superior endplate. Lower stresses were observed at all endplates for horizontal cement distribution as compared to vertical cement distribution. Conclusion: Our data suggests bone cement should be injected close to the upper endplates and not the lower endplates, to decrease endplate stresses and thus the risk of vertebral fractures. Additionally, as compared to vertically distributed cement, bone cement should be spread horizontally to reduce endplate stresses and thus reducing the risk of compression fractures.

A131: Off-Axis Rotation of the Sacroiliac Joint: An In-Vitro Study

Khalid Odeh¹, Ben Taylor², Connor Purviance², Gio Gajudo², Jeremi Leasure², Dimitriy Kondrashov¹

¹San Francisco Orthopaedic Residency Program, San Francisco - United States ²The Taylor Collaboration, San Francisco - United States

Introduction: Increasing attention has been given to the sacroiliac joint (SIJ) as a source of low back pain, despite a limited range of motion. Fusion of the SIJ seeks to minimize this movement as a possible pain generator. Our study aimed to develop a more comprehensive understanding of the native motion of the SIJ within the context of spinal kinematics and spinal implant evaluation. We sought to characterize the rotational motion in each axis utilizing standard flexion-extension (FE), lateral bending (LB), and axial rotation (AR) testing. Our hypothesis was that current descriptions do not fully describe SIJ motion. Methods and Materials: Eight human lumbosacral cadaver specimens (6 female, 2 male) were harvested from subjects aged 28-57 (mean age 46.8) with BMI 22-36 (mean BMI 30). Both ischia were potted in two separate blocks of epoxy resin, and the L4 endplate was secured in a cylindrical potting. Single leg stance was modeled by clamping the blocks on one ischium in a vise and letting the contralateral ischium hang freely. Pure moment loading was applied in FE, right/left AR, and right/left LB. Three preconditioning cycles were run and then a final cycle was applied a moment from 0 to 7.5 Nm in 1.5 Nm increments which data was collected from. Relative motions between the sacrum and iliac wings were collected with an Optotrak system and infrared markers. We defined resultant rotation as the Pythagorean sum of the three sub-component rotations, on-axis rotation as the component rotation in the same plane as the loading moment, on-axis rotation ratio as the on-axis rotation divided by the resultant rotation, and rotational deviation angle as the angle between the on-axis rotation plane and the plane of resultant rotation. Results: All eight specimens completed bilateral ROM testing. In FE resultant rotation measured 2.76 ± 1.77°, on-axis rotation measured 2.65 ± 1.71°, and the mean on-axis ratio was 0.96 ± 0.05. In AR resultant rotation measured 1.85 ± 1.26°, on-axis rotation measured 1.77 ± 1.25°, and the mean on-axis ratio was 0.95 ± 0.06. In LB resultant rotation measured 1.90 ± 1.93°, on-axis rotation measured 1.16 ± 1.16°, and the mean on-axis ratio was 0.75 ± 0.30. The on-axis ratio was significantly lower in LB than in FE (p = 0.012) and in AR (p = 0.017). The rotation deviation angle measured 13.9 ± 9.1° in FE, 17.1 ± 8.7° in AR, and 35.7 ± 25.7° in LB. In LB the rotational deviation angle is significantly higher than both FE and AR (p = 0.003 and p = 0.011, respectively). Conclusion: A non-trivial amount of rotation occurred out of the expected axis of motion in our in-vitro study. The largest amount of off-axis rotation was observed in LB. Our results indicate that rotation of the SIJ is not fully described with the in-plane metrics which are normally reported in evaluation of fusion devices. Future studies of the SIJ may need to consider including off-axis rotation measurements when describing SIJ kinematics.

A132: Do Zero-Profile Devices Affect Long-Term Stability in a Cervical Hybrid Decompression Model? A Biomechanical In-Vitro Study

Merritt Kinon¹, Samantha Greeley², Jonathan Harris², Yaroslav Gelfand¹, Reza Yassari¹, Jonathan Nakhla¹, Rafael De la Garza-Ramos¹, Pavan Patel³, Belin Mirabile⁴, Brandon Bucklen⁵

¹Department of Neurological Surgery, Montefiore Medical Center, Bronx - United States ²Musculoskeletal Education and Research Center, A Division of Globus Medical Inc., Audubon - United States ³School of Biomedical Engineering, Science and Health Systems, Drexel University, Philadelphia - United States ⁴Department of Mechanical Engineering, College of Engineering, University of Notre Dame, Notre Dame - United States ⁵Musculoskeletal Education and Research Center (MERC) a division of Globus Medical Inc., Audubon - United States

Introduction: A hybrid decompression model combining anterior cervical discectomy and fusion (ACDF) and anterior cervical corpectomy and fusion (ACCF) has been proposed in literature as a viable surgical alternative in the treatment of cervical spondylotic myelopathy. Surgeons have the option of using the traditional method utilizing an anterior plate, or may adopt a more modern method of using solely zero-profile devices. However, the initial and long-term stability of the aforementioned zero-profile constructions are unknown. The current study aims to evaluate the stability within a cadaveric cervical hybrid decompression model before and after simulated in vivo fatiguing. Methods: Twelve fresh frozen cadaveric spines (C2-C7) were divided into two groups of equal average bone mineral density (BMD) (n = 6). The groups were instrumented with either (1) a corpectomy spacer and an adjacent static spacer with an anterior plate (Hybrid-AP) or (2) a zero-profile corpectomy spacer with adjacent zero-profile ACDF (Hybrid-Z). A load control protocol ( ± 1.5º/s) tested the constructs in flexion-extension (FE), lateral bending (LB), and axial rotation (AR). After initial motion testing, specimens underwent cyclic loading of 1,000 cycles of FE, LB, and AR in consecutive order to simulate in vivo loading conditions and determine long-term stability. Motion was captured for (1) intact condition, (2) hybrid model pre-fatigue, and (3) hybrid model post-fatigue. Motion was normalized to intact, and analyses were performed to determine significant differences (p < 0.05). Results: The average BMD of the Hybrid-AP and Hybrid-Z groups was 0.6 g/cm² for both groups. The pre-fatigue hybrid construct reduced motion in FE, LB, and AR for Hybrid-AP and Hybrid-Z relative to intact (71%, 56%, and 51% vs. 38%, 60%, and 6%, respectively). Following simulated in vivo fatiguing, an increase in motion was observed for both groups in all planes, namely during Hybrid-Z post fatigue condition where motion increased relative to intact by 29%. Minimal significant differences were found between the Hybrid-AP and Hybrid-Z groups (p > 0.05). Three (50%) specimens in the Hybrid-Z group exhibited signs of implant migration from the inferior endplate during testing. Conclusion: The present study observed no significant differences in range of motion between the traditional anterior plate method and the use of zero-profile devices in a hybrid decompression model. All constructs reduced motion relative to intact except for the Hybrid-Z post-fatigue condition. However, half of the Hybrid-Z group exhibited signs of implant migration, suggesting that zero-profile reconstruction requires anterior plating to maintain long-term fixation. The high percentage of implant migration refutes the use of zero-profile implants for long-term stability in a cervical hybrid decompression model however further biomechanical investigation is necessary to determine the causes.

A133: Can a Transitional Cortical Screw Construct Provide the Same Amount of Stability as a Pedicle Screw Construct? A Finite Element Analysis

Wenhai Wang¹, Woojin Cho², Brandon Bucklen¹

¹Musculoskeletal Education and Research Center (MERC) a Division of Globus Medical Inc., Audubon - United States ²Albert Einstein College of Medicine/Montefiore Medical Center, New York - United States

Introduction: In a long spinal fusion construct that uses both pedicle screws (PS) and cortical screws (CS), it is necessary to bend the rod into a z-shape to adapt the trajectories of PS and CS at the transition level. The question remains as to whether such a construct can provide the same amount of the stability as the straight rod construct. This investigation compared the range of motion and rod stress in a functional spinal unit (FSU) with a construct consisting of (a) PS with straight rods, or (b) mix of CS and PS with z-shape rods (z-rod). Methods: The basic anatomical geometry of L4-L5 FSU was obtained from a computer-aided design model (Digimation, Lake Mary, Florida, United States). A stepwise validation was performed and the validated model was altered to simulate the following surgical interventions: a) L4/L5 pedicle screws and straight rod fixation; or b) a mix of L4 cortical screws and L5 pedicle screws with z-rod fixation. Range of motion (ROM) and rod stress were evaluated when applying a pure 10 nm moment to simulate flexion-extension, lateral bending, and axial rotation. Results: Both straight rod and z-rod constructed resulted in 1.4° ROM during flexion-extension. ROM dropped by 0.5 -1.0 degree during lateral bending and axial rotation; it was higher with z-rod fixation. During flexion-extension and axial rotation, maximum rod stress was higher in the z-rod construct (avg. = 120 MPa) than in the straight rod construct (avg. = 66 MPa). The highest rod stress was observed during lateral bending, which was also higher in the z-rod (178 MPa) than in the straight rod (91 MPa) constructs. Both were less than the material’s yield strength (841 MPa). Conclusions: Cortical/pedicle screw constructs provided similar stabilization in comparison to pedicle screw constructs in flexion-extension, but were more flexible during lateral bending and axial rotation. Rod stress was typically higher with z-rod constructs than straight rod constructs, and it was the highest in lateral bending. The results suggests that transitional cortical screws are a biomechanically viable option.

A134: Biomechanical Evaluation Examining the Importance of Posterior Fixation in a Cervical Hybrid Decompression Model Using Both Traditional Methods and Zero-Profile Devices

Merritt Kinon¹, Samantha Greeley², Jonathan Harris², Yaroslav Gelfand¹, Reza Yassari¹, Jonathan Nakhla¹, Rafael De la Garza-Ramos¹, Pavan Patel³, Belin Mirabile⁴, Brandon Bucklen⁵

¹Department of Neurological Surgery, Montefiore Medical Center, Bronx - United States ²Musculoskeletal Education and Research Center, A Division of Globus Medical Inc., Audubon - United States ³School of Biomedical Engineering, Science and Health Systems, Drexel University, Philadelphia - United States ⁴Department of Mechanical Engineering, College of Engineering, University of Notre Dame, Notre Dame - United States ⁵Musculoskeletal Education and Research Center (MERC) a division of Globus Medical Inc., Audubon - United States

Introduction: A hybrid decompression model combining anterior cervical discectomy and fusion (ACDF) and anterior cervical corpectomy and fusion (ACCF) has been proposed in literature as a viable surgical alternative in the treatment of cervical spondylotic myelopathy. The traditional method utilizes a corpectomy spacer, an adjacent static spacer, and an anterior plate to optimize decompression and fusion. While zero-profile devices have been found to be advantageous in their efficiency and reduced risk of dysphagia, there are potential shortcomings such as reduced stability and dislodgement. There are no biomechanical studies examining the stability of zero-profile devices in a hybrid decompression model. Therefore, the purpose of the current investigation is to evaluate the biomechanical efficacy of zero-profile devices in comparison to the traditional plate system in a hybrid decompression model. Methods: Twelve fresh frozen cadaveric spines (C2-C7) were divided into two groups of equal average bone mineral density (BMD) (n = 6). Groups were instrumented with either (1) an expandable corpectomy spacer and a static spacer with an anterior plate (Hybrid-AP) or (2) a zero-profile corpectomy spacer with adjacent zero-profile ACDF (Hybrid-Z). A load control protocol ( ± 1.5º/s) tested constructs before and after posterior fixation in flexion-extension (FE), lateral bending (LB), and axial rotation (AR). Motion was captured for the (1) intact condition, (2) a hybrid model prior to posterior fixation (w/o LMS), (3) a hybrid model with posterior lateral mass fixation (w/ LMS). Motion was normalized to intact and analyses were performed to determine significant differences (p < 0.05). Results: The average BMD of Hybrid-AP and Hybrid-Z groups was 0.6 g/cm² for both groups. Both the Hybrid-AP and the Hybrid-Z groups exhibited the greatest reduction in motion with posterior fixation in FE, LB, and AR (77%, 88%, and 82%, vs. 90%, 95%, and 66%, respectively). There were no significant differences found between the Hybrid-AP group and the Hybrid-Z group regardless of construct (p > 0.05). Three (50%) of the specimens in the Hybrid-Z group exhibited signs of implant migration from the inferior endplate during testing. Conclusions: The present study observed biomechanical equivalency between the traditional anterior plate method and zero-profile devices in a hybrid decompression model. However, dislodgement of the Hybrid-Z group prior to posterior fixation emphasizes the necessity for posterior fixation in a zero-profile cervical hybrid decompression model. The traditional method utilizing an anterior plate for supplemental fixation is biomechanically more favorable to stabilize the segment and prevent dislodgement.

A135: Shape Loss of Autoclaved, Machine-Bent Cobalt-Chrome and Titanium Spine Surgery Rods

Robert Wilson¹, Haitao Zhou², Sadanand Fulzele³, Sean Mitchell⁴, Brent Munroe⁴, Norman Chutkan⁴

¹Department of Orthopaedic Surgery, Howard University, Washington DC - United States ²Department of Orthopaedics, Univesity of Washington, Seattle - United States ³Augusta University Orthopaedics, Augusta - United States ⁴Department of Orthopaedic Surgery, University of Arizona, Phoenix - United States

Introduction: Shape loss of surgical spine rods have been implicated as a possible contributing factor leading to post-surgical loss of alignment correction. Previous literature has suggested that CPTi rods are prone to shape loss after autoclaving and manual bending. Comparison of these existing results to those of CoCr rods have not been clearly demonstrated in the literature. Obtaining this information may influence the choice of spine rods used by spine surgeons in instrumentation of the spine. The purpose of this study is to determine and compare the degree of shape loss in surgical spine rods of different composition being maintained under physiologic conditions that were machine-bent either before or after being autoclaved. Materials and Methods: 10 CoCr and 10 CPTi surgical spine rods were contoured using a machine press. All rods were autoclaved in adherence with surgical implant protocol. 5 CoCr and 5 CPTi rods were machine bent before being autoclaved (pre-bent group). 5 CoCr and 5 CPTi rods were machine bent after being autoclaved (intra-op bent group). All rods from both group were then immersed in a phosphate buffered saline (PBS) bath at body temperature (37.2 ^oC ± 2 ^oC) for a duration of 8 weeks. The radius of curvature was measured at different time interval over the 8 weeks course with a high-definition scanner and Adobe Photoshop. Results: Using the Mann-Whitney U-Test, all spine surgery rods demonstrated significant shape loss (1.37 mm - 9.4 mm) over the duration of the study (p < 0.01). Intra-op bent CPTi rods demonstrated the greatest amount of shape loss measured at 9.4 mm (p < 0.01). Pre-bent CPTi and intra-op bent CoCr rods underwent the least amount of shape loss, 1.37 mm and 1.86 mm respectively (p < 0.01). Conclusion: This study has suggested that careful consideration should be given to the use of CPTi spinal rods that must be bent intra-operatively as this may lead to considerable loss of alignment correction. In addition, our results further suggest that pre-bent CPTi and intra-operatively bent CoCr spinal rods may be a more ideal choice of implant to be used in alignment correct as they may provide more resistance to shape loss over time.

A136: Effect of Microdiscectomy on the Capsule Strains of the Lumbar Facet Joints

Sheri Imsdahl¹, Richard Bransford², Randal Ching¹

¹Department of Mechanical Engineering, University of Washington, Seattle - United States ²Department of Orthopaedics and Sports Medicine, Harborview Medical Center, Seattle - United States

Introduction: Microdiscectomy is the surgical standard of care for lumbar disc herniation. There are two methods of disc removal used in this procedure. In a partial microdiscectomy (PD), the herniated fragment is removed with minimal invasion of the disc space. This contrasts with a subtotal microdiscectomy (SD), in which the disc space is aggressively curetted after excising the herniated fragment. There are limited studies describing the effects of microdiscectomy on lumbar spine biomechanics. Furthermore, most of the existing studies have focused on parameters that characterize the biomechanics of the entire intervertebral joint. The goal of this study was to determine how PD and SD affect the strains in the facet joint capsules at the level of surgery. Material and Methods: Eight lumbar motion segments (three L2-L3, three L3-L4, and two L4-L5) were obtained from three human cadaveric spines. Unconstrained, pure moments were applied to the segments with a custom spine simulator. The segments were tested in their intact condition and after a PD and SD. Both procedures involved a left laminotomy (while leaving sufficient pars) and annular incision with a cruciate cut. For PD, a small piece of disc was excised, and for SD, 2 grams of material were removed from the disc space. Under each condition, the motion segments were tested to 15 Nm in ten loading modes: flexion, extension, right and left lateral bending, right and left axial rotation, and four combinations of flexion or extension with lateral bending. Throughout testing, a 3D digital image correlation system tracked the deformation of a random speckle pattern applied to the posterior surface of each capsule. The images were post-processed to obtain the full-field first principal strains in the capsules. For every loading mode, the maximum strain at 15 Nm was identified in each capsule for subsequent statistical analysis. The analysis was done with a linear mixed-effects regression model that tested for differences in strain by condition for each loading mode. A single model was run by combining the data from the right and left capsules according to symmetry, and the significance level was set to P < .05. Results: In four loading modes, the capsule strains were significantly greater after SD than what was measured in the intact and PD conditions. This was observed in: flexion (intact vs. SD, P < .01; PD vs. SD, P < .05), contralateral bending (intact vs. SD and PD vs. SD, P < .05), flexion with contralateral bending (intact vs. SD and PD vs. SD, P < .001), and flexion with ipsilateral bending (intact vs. SD and PD vs. SD, P < .001). After PD, there was no evidence that the capsule strains were significantly different from what was seen in the intact condition. Conclusion: Of the two procedures, only SD significantly increased the capsule strains. Neuroanatomical studies have shown that this ligament is innervated with mechanosensitive nociceptors that are activated by capsular strain due to joint motion. Patients who undergo a more aggressive microdiscectomy may therefore be at risk of experiencing pain that originates from the capsules.

Trauma Cervical

A137: Impact of Injury Severity on the Relationship Between Time to Surgical Decompression and Neurological Recovery and Functional Outcomes Following Traumatic Cervical Spinal Cord Injury

Wilson Jefferson¹, James Harrop², Bizhan Aarabi³, RG Grossman⁴, Blessing Jaja⁵, Michael G Fehlings⁶

¹Department of Surgery, University of Toronto, Toronto - Canada ²Division of Spine and Peripheral Nerve Surgery, Delaware Valley SCI Center, Thomas Jefferson University, Philadelphia - United States ³Department of Neurosurgery, University of Maryland School of Medicine, Baltimore - United States ⁴Department of Neurosurgery, Houston Methodist Hospital, Houston - United States ⁵Krembil Discovery Tower, Toronto Western Hospital, Toronto - Canada ⁶Spine Program, University of Toronto, Toronto, ON, Canada, Toronto - Canada

Introduction: Despite extensive research and newly developed practice guidelines, the optimal timing for surgery for traumatic spinal cord injury is still the subject of ongoing debate. Although the literature suggests that early decompression results to improved neurological and functional recovery, and a reduction in complication rates and health care resource utilization, it is uncertain whether such benefit is related to the injury severity—and specifically whether this approach is “worth it” for complete (AIS A) injuries. This study sought to investigate the relationship between time to surgical decompression and neurological and functional outcomes following traumatic spinal cord injury (SCI); and whether the effect of time to decompression, if any, differed between patients who have complete versus those with incomplete injury. Material and Methods: A pooled cohort from the North American Clinical Trials Network SCI Registry and the STASCIS trial was analyzed for the subset of patients with cervical SCI. The independent variable was time from injury to surgical decompression dichotomized as early (≤ 24 hrs.) versus delayed (> 24 hrs.). The outcomes were assessed at 6 months, and include AIS grade improvement (analyzed using ordinal regression); AIS motor score change, total score on the SCIM (analyzed using linear regression); and the SCIM sub scores for independent breathing and ambulation (analyzed using penalized maximum likelihood logistic regression). The likelihood ratio test was used to compare a model including time to decompression and AIS grade (categorized as Complete (grade A) versus Incomplete (grades B/D)) to a model extending the former to include the interaction term. Results: The study included 579 patients. We found patients who had early surgical decompression were significantly younger (42 vs. 52 years), more likely to have incomplete injury (AIS grade D: 44% vs. 17%), higher APACHE II score at admission, but lower motor score change at 6 months compared with patients who had delayed decompression. At 6-month follow up, patients who had early decompression were significantly more likely to breath independently (97% vs. 89%), ambulate independently (58% vs. 25%) and had a higher total SCIM score (96 vs. 48 points) than those who had delayed decompression. In adjusted analysis accounting for age, baseline AIS grade and APACHE II score at admission, early decompression was associated with a higher likelihood of AIS grade improvement (OR, 1.28; 95% CI: 0.55 – 2.99), independent breathing (OR, 2.05; 95% CI: 0.50 – 8.50) and ambulation (OR, 5. 07; 95% CI: 1.87 – 13.76) and a higher total SCIM score. The interaction term between time to surgical decompression and AIS grade at admission was not significant for any of the studied outcomes. Conclusion: This study has shown an association between early decompression and improved neurological and functional outcomes in traumatic cervical spinal cord injury. The benefit is seen in complete and incomplete SCI. When feasible, patients with complete spinal cord injury should have early surgical intervention as the benefit may be comparable to that in patients with incomplete injury.

A138: Evaluation of the Clinical Outcome of Facet Joints Distraction Following ACDF for Patients With Traumatic Cervical Spine Injury

Nathan Kirzner¹, Ali Humadi¹, Susan Liew¹

¹Department of Orthopaedics, Alfred Hospital, Melbourne - Australia

Introduction: Facet joint distraction after Anterior Cervical Decompression and Fusion (ACDF) for unstable traumatic cervical spine injury is a possible cause of chronic neck pain and poor functional outcome. Some surgeons treat recognized postoperative facet joint over-distraction with posterior cervical fusion. This study investigates the outcomes of facet joint distraction and posterior fusion after ACDF. Material and Methods: This is a retrospective epidemiologic cohort study of Alfred Hospital patients that received ACDF for cervical spine injury within the last 15 years (2000 to 2015) with a minimum of 2-years follow up. Functional outcomes were assessed by recording responses to the validated Neck Disability Index (NDI) tool. Radiological outcome assessment consisted of reviewing all existent postoperative x-rays to quantify the degree of facet joint distraction, classifying them as having < 3 mm or > 3 mm distraction compared to the above and below vertebrae. It was also recorded if the patient went on to have posterior fusion. Results: The results of the functional and radiological outcomes were correlated and analysed to assess whether distraction of the facet joint is associated with less favourable outcomes. A total of 239 received ACDF for traumatic cervical spine injury in the timeframe. 195 of these completed the NDI, the remainder being excluded due to being deceased or non-contactable. A total of 34 of these patients went on to have posterior fusion after the initial ACDF. Our results showed reduction in NDI and pain scores in patients who had < 3 mm facet joint distraction post ACDF compared to those with > 3 mm distraction. Furthermore, patients that went on to have posterior fusion had significantly worse outcomes. Conclusion: This study showed that facet joint over-distraction more than 3 mm after ACDF for traumatic cervical spine injuries contributes to less favourable clinical outcomes. Furthermore, additional posterior fusion surgery is associated with increased NDI and pain score.

A139: Optimal Mass Screw Placement in Jefferson-Fractures

Renate Krassnig¹, Paul Puchwein¹, Fanz Josef Seibert¹, Uldis Berzins¹, Gloria Maria Hohenberger¹

¹Medical University Graz, Graz - Austria

Introduction: Surgical stabilization of C1 ring fractures is usually favored in highly unstable fractures. Motion preserving techniques are increasingly used especially in young patients. Therefore lateral mass screws are inserted in the first vertebra and connected by a rod. Safe screw positioning is important to avoid harming the medulla oblongata or the vertebral arteries. Material and Methods: Images of the cervical spine of 50 patients (64-line CT scanner) were evaluated and virtual screws were positioned in both lateral masses of the first vertebra using 3D-reconstructions of CT-scans. The length of the screws, the insertion angles in two planes, the distance to the vertebral artery and the spinal canal were investigated. Descriptive statistics was used, gender depend differences were calculated using student-T-test. A diameter of 4 mm was chosen for the screws. Results: The mean screw length was 30.0 ± 2.3 mm on the right and 30.1 ± 2.1 mm on the left side. The arithmetic mean for the transverse angle was 16.4 ± 5.6° on the right and 15.6 ± 6.3° on the left, the sagittal angle averaged 8.3 ± 3.8° on the right and 11.0 ± 4.9° on the left side. The mean distance between screw and spinal canal has been determined on the right with 2.4 ± 0.7 mm and 2.2 ± 0.6 mm on the left side. The distance from the C1 lateral mass screw to the vertebral artery was on average 7.1 ± 1.5 mm on the right side (significant correlation with gender, p-value: 0.03) and 7.5 ± 1.4 mm on the left side. Conclusion: Due to the required high precision technique intraoperatively multiplanar 2 D or 3 D imaging is recommended to avoid harm to the vertebral artery or the spinal canal.

A140: Posterior Osteosynthesis With Monoaxial Lateral Mass Screw-rod System for Unstable C1 Burst Fractures

YinShun Zhang¹, JianXiang Zhang¹, Qingguo Yang¹, Wei Li¹, Hui Tao¹, Yun Cao¹, Cailiang Shen¹

¹Department of Spine surgery, the first affiliated hospital of Anhui Medical University, Hefei - China

Introduction: Surgical treatment for unstable atlas fractures has evolved in recent decades from C1-C2 or C0-C2 fusion to motion-preservation techniques of open reduction and internal fixation (ORIF). However, regardless of transoral or posterior approach, the reduction is still not satisfactory. This article describes and evaluates a new technique for treating the unstable atlas fractures by using a monoaxial screw-rod system. Material and Methods: From August 2013 to May 2016, 9 consecutive patients with unstable atlas fractures were retrospectively reviewed. All patients were treated with posterior ORIF by using a monoaxial screw-rod system. The medical records and the preoperative and postoperative radiographs were reviewed. The preoperative and postoperative computed tomography (CT) scans were used to specify the fracture types and to assess the reduction. Results: All 9 patients with a mean age of 50.3 years successfully underwent surgery with this technique, and a follow-up of 17.4 ± 9.3 months was performed. Transverse atlantal ligament (TAL) injury was found in 8 of the 9 patients: 1 of type I and 7 of type II. The preoperative lateral mass displacement averaged 7.0 ± 2.2 mm and was restored completely after surgery; all the fractures achieved bony healing without loss of reduction or implant failure. None of the patients had complications of neurological deficit, vertebral artery injury, or wound infection associated with the surgical procedure. Two patients complained of greater occipital nerve neuralgia after the operation, which gradually disappeared in 1 month. All patients had a well-preserved range of motion of the upper cervical spine at the final follow-up. Conclusion: Posterior osteosynthesis with a monoaxial screw-rod system is capable of almost anatomical reduction for the unstable atlas fractures. The TAL incompetence is not a contraindication to ORIF for C1 fractures, but the long-term effect of C1-C2 instability remains to be further investigated.

This article has been published on line on The Spine Journal )

A141: Anterior Surgeries for Fresh Flexion Distraction Injury of Lower Cervical Spine Facets and the Possible Affecting Factors of the Surgery

Zhiqi Zhang¹, Yang Lv¹, Fang Zhou¹, Yun Tian¹, Hongquan Ji¹, Zhishan Zhang¹, Yan Guo¹

¹Peking University Third Hospital, Beijing - China

Introduction: To explore (1) whether an anterior approach alone could achieve complete reduction, thorough decompression and final consolidation for fresh lower cervical facet dislocations; (2) whether the clinical outcomes of an anterior surgery are affected by whether the dislocation is (i) unilateral or bilateral, (ii) with or without fractures, or (iii) with or without spondylolisthesis or anterior vertebral damage; and (3) in what situations a posterior surgical approach may be a better initial surgical route. Material and Methods: From 2005 to 2015, a total of 112 patients diagnosed with fresh lower cervical spine facet dislocations and/or fractures were retrospectively reviewed. Patients who underwent anterior-only surgeries were divided into two groups according to the following factors: unilateral or bilateral facet joint dislocations, dislocations with or without fractures, dislocations with spondylolisthesis ≤ 50% or > 50%, and dislocations with or without anterior vertebral damage to investigate whether these factors impact the outcomes of anterior surgeries. Information regarding each patient’s general information, cause of trauma, surgical data, postoperative bone fusion time, pre-operative and post-operative neurological function, and implant and wound complications was collected and compared. Results: All patients underwent at least 15 months of follow-up. Two patients who underwent anterior cervical fusion and plating experienced re-subluxation and underwent reoperation with an anterior-posterior-anterior approach. Solid bony fusion at final follow-up was achieved in the other 110 patients. Ninety-four patients underwent anterior surgeries. Of them, significant differences were not observed between patients with unilateral and with bilateral dislocations, between patients with bilateral dislocations with fractures and with bilateral dislocations without fractures, and between patients with spondylolisthesis ≤50% and with spondylolisthesis ≤ 50%, regarding the patients’ general information, postoperative bone fusion time, neurological improvement and complications; the average operation time was significantly less in patients with unilateral dislocation with fractures than those without fractures (79.9 ± 25.4 minutes versus 111.0 ± 36.7 minutes, P = 0.004); the average blood loss was less in patients with unilateral dislocation with fractures than those without fractures but the difference was not significant (30 (10-200) ml versus 50 (0-450) ml, P = 0.096). The average operation time and average blood loss were significantly less in patients without anterior vertebral damage than in patients with anterior vertebral damage (82.4 ± 22.8 minutes versus 114.7 ± 30.5 minutes, P < 0.001; 50(0-2000) ml versus 100(20-700) ml, P = 0.001). Conclusion: For fresh cervical unilateral or bilateral facet joint dislocations, with or without fractures, and regardless of whether spondylolisthesis or anterior vertebral damage exists, anterior operations can result in satisfactory reduction and fixation and, to some extent, improved neurological function. For a unilateral dislocation, it is more difficult to restore and the surgical time is increased if the dislocation is accompanied with fractures. Potential reasons for choosing posterior surgeries as an initial choice are described below: (1) for facet dislocations with fractures or if large bone fragments can be seen in the spinal canal; (2) for patients with multi-segment dislocations or osteoporosis; (3) in patients with cervical stenosis; (4) complicated bilateral lateral masses or pedicle fractures which could result in a floating lateral mass.

A142: Modification of the AO Sub-Axial Cervical Spine Injury Classification (Slic) Algorithm: The Importance of the Erect C Spine X-Ray in Cervical Trauma

Ruben Thumbadoo¹, Jan Herzog¹, Niv Bhamber¹, Jason Bernard¹, Timothy Bishop¹, Darren Lui¹

¹Department of Trauma and Orthopaedics, St George’s University Hospital, London - United Kingdom

Introduction: In the management of a trauma patient with potential c-spine trauma, the need for accurate diagnostic imaging is paramount. ATLS guides that c-spine pain requires c-spine CT, with an obviously unstable fracture treated surgically. The AO SLIC score helps to determine if surgery is required. Through a systematic review we have identified a group of cases where the AO SLIC score may be deficient and the use of erect C Spine X ray can help identify instability. Methods: Systematic review of the literature to identify cervical spine injuries with low AO SLIC scores and erect c-spine x-ray indications. There is one paper by Humphrey et al which describes 4 cases of low scoring SLIC scores suggesting conservative management was satisfactory including 2 from our own series. Results: There were 6 cases identified in total. The mean AO SLIC score pre erect X-ray was 0.33 in contrast to the post erect x-ray mean AO SLIC score of 6. Using paired T-test the p-value was 0.00 004 which showed statistical significance. Conclusion: CT can propose instability only by suggesting ligamentous injury. Supine imaging eliminates the gravitational loads normally exerted on the c-spine. The Subaxial Injury Classification system (SLIC) can be used to guide management based on clinical and radiological evidence. A score of 4 may be treated either conservatively or surgically. We show 6 cases of assumed cervical stability based on CT who underwent erect cervical spine x-ray which increased their AO SLICS score above the surgical threshold. We suggest a modification to the AO SLIC algorithm and that a patient who scores 4 or less undergo erect c-spine x-ray to assess stability. During the erect x-ray the muscles and ligaments are under strain, therefore instability due to ligament damage can be demonstrated.

A143: Review of Subaxial Cervical Spine Injuries Presenting to a Tertiary Level Hospital in Nepal: Challenges In Surgical Management in a Third World Scenario

Gaurav Raj Dhakal¹, Ravi Bhandari¹, Siddhartha Dhungana¹, Santosh Paudel¹, Ganesh Gurung¹, Yoshiharu Kawaguchi¹, K.Daniel Riew¹

¹National Trauma Center, Kathmandu - Nepal

Introduction: While the results of treatment of Subaxial cervical injuries in first-world countries with modern hospitals has been reported, there are few studies describing the surgical outcome in resource-constrained regions.The purpose of this study was to describe the demographics, duration of presentation and timing to surgery, cause of surgical delay, short term neurological recovery and complications in surgically treated sub axial cervical trauma in a resource-poor third-world country. Material and Methods: 30 consecutive sub-axial cervical trauma patients presenting to a teaching hospital in Nepal between December 2015 and August 2017 were analyzed as retrospective cohort study. All patients had a fracture or dislocation with or without neurologic deficit sustained as a result of trauma. Patients were segregated into four groups based on the timing to surgery: within 2 day, 3-7 days, 8 – 30 days and > 31 days. Results: There were 27 male and 3 female patients with mean age 40 years.24 sustained fall injury and 27 patients were from outside Kathmandu. No patients were treated within the first 48 hours, only 7 were treated between 3-7 days, 16 were treated between 8 – 30 days and 5 were treated at greater than 1 month. In spite of the 40% who presented early, none of the patients were able to be treated surgically in the first 48 hours. The majority of the delay was due to financial reasons and operating room availability. The vast majority, 70% (21 out of 30), received their treatment at a period longer than 1 week. 13 patients had a C6C7 involvement followed by C5C6 in 6 patients. AO type C injury was present in 25 patients and a SLIC score of more than 6 in 28 patients. 7 had complete neurological deficit while 18 had incomplete deficit. Preoperative skull traction was applied in all AO C injuries. Anterior approach was performed in 18 patients and combined approach in 2 patients. Of the 30 patients enrolled, 43.33% (13) improved their impairment scale by one grade (5 in 3 – 7 days group and 7 in 8 -30 days group) in six months’ time. No neurological recovery was observed in complete deficit patients. Dysphagia was present in all patients operated anteriorly and one had an anterior wound infection. Hoarseness was observed in two patients while deep vein thrombosis and urinary tract infection appeared in one patient each. Conclusion: Managing cervical spine trauma in the third world is a challenge due to late presentation of the trauma victim, unavailability of the operating room, financial constraint and limited number of cervical spine surgeons in the periphery, all contributing to our findings that 70% were treated at longer than 1 week after injury, which would likely be considered unacceptable in most 1st world countries. As expected, the outcomes for many of these patients are far worse than reported in North American centers with early access to medical care and insurance. Despite this, nearly half of our patients improved neurologically following treatment hence surgery holds hope of some restoration of neurologic deficits.

A144: Treatment Strategy for Atypical Hangman Fractures Based on a New Classification

Guangzhou Li¹, Qing Wang², Hao Liu³, Song Wang²

¹Affiliated Hospital of Southwest Medical University, luzhou - China ²Department of Spine Surgery, Affiliated Hospital of Southwest Medical University, Luzhou - China ³Department of Orthopedics, West China Hospital, Sichuan University, Chengdu - China

Introduction: There is a paucity of literature focusing on treatment strategy for Atypical Hangman fractures (AHF). The purpose of the retrospective study was to introduce a comprehensive treatment strategy for AHF based on a new classification. Material and Methods: Sixty-seven patients with Hangman fractures were treated with a comprehensive treatment strategy: Firstly, Hangman fractures were classified as typical or atypical (AHF) lesions using computed tomography scans of the cervical spine; Secondly, AHF was divided into 1 of 4 types (type A1, A2, B1, and B2) devised by Li-Wang to clarify the feature of injury; Thirdly, the injury status of disco-ligamentous complex (intact/indeterminate/ruptured) was evaluated using magnetic resonance imaging, and it was stable lesion, conservative treatment or isolated direct screw osteosynthesis was recommended, or surgical treatment using anterior or posterior stabilization and fusion at C2-C3 level was used. Specifically, if posterior stabilization and/or fusion were chosen, each type lesion of the new classification had a key point to reduce fracture. Results: Forty-nine patients were identified with AHF, and according to Li-Wang’ classification, 29 patients were classified as type A1, 13 as A2, 5 as B1, and 2 as B2 lesions. Twenty patients were treated with nonoperative treatment, and 2 patients were treated with isolated direct screw osteosynthesis. And the remaining 27 underwent posterior stabilization and fusion at C2-C3 level (15 patients with posterior approach with screw-rod fixation and fusion, 10 with anterior approach by C2/3 discectomy and fusion, and 2 with anterior and posterior approach). The average follow-up period was 18 months (range, 12–36 months). Neck pain improved significantly at 3-month follow-up, and neurologic status improved at least 1 grade in 13 patients with neurologic deficits at final follow-up. Radiological valuation showed bony fusion in all patients at 12-month follow-up. Conclusion: The treatment strategy for AHF based on a new classification is helpful in managing such fractures, resulting in good clinical and radiological outcomes.

A145: Analysis of Spinal Movement and Dural Sac Compression During Emergency Airway Management in Case of Atlanto-Occipital Instability

Sven Vetter¹, Shiyao Liao¹, Niko R.E. Schneider², Erik Popp², Paul A. Grützner¹, Stefan Matschke¹, Michael Kreinest¹

¹BG Trauma Center Ludwigshafen, Department of Trauma Surgery, Ludwigshafen - Germany ²Heidelberg University Hospital, Department of Anesthesiology, Heidelberg - Germany

Introduction: Instable conditions of the upper cervical spine such as the atlanto-occipital dislocation (AOD) are devastating injuries with a high risk of tetraplegia and a high mortality. Because of possible restrictions on respiration, emergency airway management is frequently required in these patients. If the procedure of performing airway intervention in these patients is free of risk to exacerbate spinal cord injury is still unclear. Thus, the aims of the study are (i) to analyze the compression on the dural sac and (ii) to analyze the overall cervical spinal movement during performing different emergency airway interventions in case of AOD. Material and Methods: In six fresh cadavers ligamental AOD was prepared by posterior surgery. In each cadaver, airway management was performed using three airway devices: direct laryngoscopy, video laryngoscopy (King Vision® aBlade, Ambu, Bad Nauheim, Germany) and insertion of a laryngeal tube (LTS-D, Size 4, VBM Medizintechnik, Germany). The compression of the dural sac and the intervertebral angulation were recorded by myelography (Optiray, 300 mg/ml, Mallinckrodt, Germany) and video fluoroscopy (Veradius C-Arm, Philips, Netherlands) in stable condition of the upper cervical spine and in AOD condition. Overall 3D spinal movement were assessed by a motion tracking system (Xsens Technologies, Enschede, Netherlands). Sample size calculation and statistical analysis were performed with SPSS (IBM, USA). Results: Compared with a mean dural sac compression of 0.5 mm (range: 0.3 to 0.7 mm) in stable cervical spine condition, direct laryngoscopy caused a significantly increased dural sac compression of 1.6 mm (range: 0.6 to 1.9 mm; p = 0.028) in the case of AOD. No increased compression on dural sac was found using video laryngoscopy or the laryngeal tube (p = 0.116 and p = 0.173, respectively). Intervertebral angulation is not affected by emergency airway management in any case. But laryngoscopy (direct and video) caused greater overall 3D spinal movement than laryngeal tube insertion in both stable and unstable conditions. Conclusion: In case of AOD, using direct laryngoscopy for emergency airway management will cause movement in the cervical spine and exacerbates compression on the dural sac. It remains unclear if a compression on the dural sac of up to 1.9 mm at the atlanto-occipital level may cause damage to the spinal cord. Since there are great individual variations in subarachnoid space diameter ¹ and since the amount of tolerable compression of the dural sac is further reduced in the presence of an existing cervical spine injury ², secondary spinal cord damage caused by direct laryngoscopy could not be ruled out completely. The insertion of a laryngeal tube could serve as an alternative emergency airway device in these patients.

References

1. Zaaroor M et al. (2006) MIN 49:220

2. Batchelor PE et al. (2013) PLoS one 8: e72659

Tumor - Scoring System / Predictions

A146: Predicting Tumor Specific Survival in Patients With Metastatic Spine Disease: Which Scoring System is Most Appropriate?

A. Karim Ahmed¹, C. Rory Goodwin², Amir Heravi¹, Rachel Kim¹, Nancy Abu-Bonsrah², Eric W. Sankey², Rafael De la Garza Ramos³, Vikram Mehta², John Berry-Candelario², Zachary Pennington¹, Joseph Schwab⁴, Camilo Molina¹, Daniel M. Sciubba¹

¹Department of Neurosurgery, The Johns Hopkins University School of Medicine, Baltimore - United States ²Department of Neurosurgery, Duke University Medical Center, Durham - United States ³Department of Neurological Surgery, Montefiore Medical Center/Albert Einstein College of Medicine, New York - United States ⁴Department of Orthopedic Surgery Massachusetts General Hospital, Boston - United States

Introduction: Despite advances in spinal oncology, research into patient-based prognostic calculators for metastatic spine disease is lacking. Much of the literature in this area investigates the general predictive accuracy of scoring systems in a heterogeneous population. The aim of the current study was to compare the ability of widespread scoring systems to estimate both overall survival at various time points and tumor-specific survival for patients undergoing surgical treatment for metastatic spine disease in order to provide surgeons with information to determine the most appropriate scoring system for a specific patient and timeline. Material and Methods: Patients who underwent surgical resection for metastatic spine disease at a single institution were included. A pre-operative score for all 176 patients was calculated utilizing the SORG Classic Scoring algorithm, SORG Nomogram, Original Tokuhashi, Revised Tokuhashi, Tomita, Original Bauer, Modified Bauer, Katagiri, and van der Linden scoring systems. Univariate and multivariate cox proportional hazard models were constructed to assess the association of patient variables with survival. Receiver operating characteristic analysis (ROC) modeling was utilized to quantify the accuracy of each test at different end-points and for different primary tumor subgroups. Results: Among all patients surgically treated for metastatic spine disease, the SORG Nomogram demonstrated the highest accuracy at predicting 30-day (AUC 0·81), and 90-day (AUC 0·70) survival following surgery. The Original Tokuhashi was the most accurate at predicting 365-day survival (AUC 0·78). Multivariate analysis demonstrated multiple pre-operative factors strongly associated with survival following surgery for spinal metastasis. The accuracy of each scoring system in determining survival probability relative to primary tumor etiology and time elapsed since surgery was assessed. Conclusion: The findings of this study may guide surgeons in selecting the most appropriate scoring system for survival estimation at different postoperative time points for a given patient with known primary disease.

A147: The Refined Spine Oncology Study Group Outcome Questionnaire2.0 (SOSGOQ2.0) A Reliable And Valid Disease Specific Outcome Measure

Anne Versteeg¹, Arjun Sahgal², Laurence Rhines³, Daniel Sciubba⁴, James Schuster⁵, Michael Weber⁶, Peter Pal Varga⁷, Stefano Boriani⁸, Chetan Bettegowda⁴, Michael Fehlings⁹, Michelle Clarke¹⁰, Paul Arnold¹¹, Ziya Gokaslan¹², Charles Fisher¹³, AOSpine Knowledge Forum Tumor¹⁴

¹Department of Orthopedics, University Medical Center Utrecht, Utrecht - Netherlands ²Department of Radiation Oncology, Sunnybrook Odette Cancer Centre and University of Toronto, Toronto - Canada ³Department of Neurosurgery, Division of Surgery, The University of Texas MD Anderson Cancer Center, Houston - United States ⁴Department of Neurosurgery, Johns Hopkins University School of Medicine, Baltimore - United States ⁵Department of Neurosurgery, Hospital of the University of Pennsylvania, Philadelphia - United States ⁶Division of Surgery, McGill University and Montreal General Hospital, Montreal - Canada ⁷Spine Department, National Center for Spinal Disorders and Buda Health Center, Budapest - Hungary ⁸GSpine4 Spine Surgery Division. IRCCS Istituto Ortopedico Galeazzi, Milan - Italy ⁹Division of Neurosurgery, University of Toronto and Toronto Western Hospital, Toronto - Canada ¹⁰ Department of Neurosurgery, Mayo Clinic, Rochester - United States ¹¹Department of Neurosurgery, The University of Kansas Hospital, Kansas city - United States ¹²Department of Neurosurgery, The Warren Alpert Medical School of Brown University and Rhode Island Hospital and The Miriam Hospital, Providence - United States ¹³Division of Spine, department of Orthopaedics, The Combined Neurosurgical and Orthopaedic Spine Program at Vancouver Coastal Health, Vancouver - Canada ¹⁴Research department, AOSpine International, Davos - Switzerland

Introduction: The Spine Oncology Study Group Outcomes Questionnaire (SOSGOQ) was developed as the first spine oncology specific outcome measure. The purpose of this study was to evaluate the hypothesized structure and the clinical validity of the SOSGOQ. Materials and Methods: A prospective international multicenter observational study including patients with spinal metastases who underwent surgery and/or radiotherapy was conducted by the AOSpine Knowledge Forum Tumour. Data regarding patient demographics, primary tumour diagnosis and treatment were recorded. Health related quality of life (HRQOL) was evaluated at fixed time points using the SF-36v2, NRS pain, and the SOSGOQ. Multi-trait scaling analyses, confirmatory factor analyses (CFA) and correlation between the SF-36 domains and the SOSGOQ were used to evaluate the structure of the SOSGOQ. Reliability of the SOSGOQ was assessed with the cronbach alpha and in two centers a test-retest analysis at 12 weeks post-treatment and 4-9 days later (intraclass coefficient (ICC)) was performed. Results: A total of 153 patients had HRQOL data available at 12 weeks post-treatment. Multi-trait scaling analyses and CFA based on the original structure of the SOSGOQ demonstrated improper model fit. Revisions to the items and structure resulted in a refined SOSGOQ2.0 consisting of 4 domains, 4 single items and a revised scoring system. Correlation between the SF-36, NRS pain and the SOSGOQ2.0 showed high correlations confirming the validity of the refined measure. Reliability was evaluated in 36 patients at two centers and confirmed with an alpha between 0.74 and 0.85 and an ICC between 0.58 and 0.92. Clinical validity of the SOSGOQ2.0 was confirmed by the ability to discriminate between clinically distinct patient groups. Conclusion: The refined SOSGOQ2.0 is a valid and reliable measure to evaluate HRQOL in patients with spinal metastases who undergo surgical and/or radiotherapy treatment. Use of the SOSGOQ2.0 together with a generic HRQOL measure is recommended for a comprehensive HRQOL assessment.

A148: Predictors of Quality of Life Improvement After Surgery for Metastatic Tumors of the Spine: A Prospective Cohort Study

Ori Barzilai¹, Lily Mclaughlin¹, Mary Kate Amato¹, Anne Reiner², Shahiba Ogilvie¹, Eric Lis³, Yoshiya Yamada⁴, Mark Bilsky¹, Ilya Laufer¹

¹Department of Neurosurgery, Memorial Sloan Kettering Cancer Center, New York - United States ²Depratment of Epidemiology and Biostatistics, Memorial Sloan Kettering Cancer Center, NYC - United States ³Department of Radiology, Memorial Sloan Kettering Cancer Center, NYC - United States ⁴Deprtment of Radiation Oncology, Memorial Sloan Kettering Cancer Center, NYC - United States

Introduction: Surgical decompression and stabilization followed by radiosurgery represents an effective method for local tumor control and neurologic preservation for patients with metastatic epidural spinal cord compression. We have previously demonstrated improvement in HrQOL after this combined modality treatment (“hybrid therapy”). The current analysis focuses on delineation of patient-specific prognostic factors predictive of HrQOL change after combined surgery-SRS treatment of MESCC. Materials and Methods: This is a prospective, single-center, cohort study. One hundred and eleven patients with MESCC who underwent separation surgery followed by SRS were included. Prognostic factors associated with improved patient reported outcome (PRO) measures. PRO tools, i.e. Brief Pain Inventory (BPI) and MD Anderson Symptom Inventory – Spine Tumor (MDASI-SP), both validated in the cancer population, were prospectively collected. Numeric prognostic factors were correlated with PRO measures using the Spearman rank correlation coefficient. Categorical prognostic factors were correlated with PRO measures using the Wilcoxon two-sample test (for two categories) or the Kruskal-Wallis test (for three or more categories). All statistical tests were two-sided with a level of significance < 0.05 for correlation of prognostic factors with PRO constructs and a level of significance < 0.0014 for correlation of prognostic factors with PRO items. Statistical analyses were done in SAS (version 9.4, Cary, NC). Results: One hundred and eleven patients were included in this analysis. Patients with lower pre-operative Medical Research Council (MRC) motor scores experienced a greater decrease in symptom interference (BPI Interference construct (p = 0.03), and individual functional measures including general activity (p = 0.001), walking (p = 0.001) and normal work (p = 0.006)). Lumbar location was associated with better outcomes than cervical or thoracic as noted on the BPI pain experience construct (p = 0.03) and MDASI-SP interference (p = 0.01) and core symptom (p = 0.002) constructs. Patients with ASIA scores of C or D benefit more than those with ASIA E on BPI Interference construct (p = 0.04)). Patients with higher ECOG scores at presentation benefit more than those with low ECOG scores on MDASI-SP interference construct, (p = 0.03)). Women benefit more than men on BPI interference (p = 0.03) and pain experience (p = 0.04) constructs. Patients with prior spinal surgery at the current level of interest benefit less than those which are naïve surgical patients in MDASI-SP interference construct, (p = 0.04). Conclusions: Delineation of patient characteristics associated with HrQOL improvement provides crucial information for patient selection, patient education and setting treatment expectations. For patients with MESCC treated with hybrid therapy using surgery and radiosurgery, the presence of neurological deficits and diminished performance status, lumbar tumor level and female gender were associated with greater PRO improvement.

A149: Frailty Index to Determine Short-Term Outcomes Following Surgery for Primary Spinal Tumors

A. Karim Ahmed¹, C. Rory Goodwin², Nancy Abu-Bonsrah², Rafael De la Garza Ramos³, Zachary Pennington¹, John Berry-Candelario², Eric W. Sankey², Vikram Mehta², Camilo Molina¹, Daniel M. Sciubba¹

¹Department of Neurosurgery, The Johns Hopkins University School of Medicine, Baltimore - United States ²Department of Neurosurgery, Duke University Medical Center, Durham - United States ³Department of Neurological Surgery, Montefiore Medical Center/Albert Einstein College of Medicine, New York - United States

Introduction: The concept of ‘Frailty’, i.e. decreased physiologic reserve and increased vulnerability to stressors beyond what is expected for normal aging is associated with increased risk of morbidity and mortality. The objective of this study was to develop a preoperative frailty index (STFI) for patients undergoing surgery for primary spinal column tumors that predicts morbidity, mortality, and length of stay. Material and Methods: The Nationwide Inpatient Sample database from 2002 to 2011 was used to identify patients who underwent surgery for a primary spinal tumor. The STFI, consisting of nine items, was applied to each patient. Patients were characterized as “not frail” (0), “mildly frail”, “moderately frail (2), and “severely frail” ( ≥ 3). Results: A total of 1,589 patients met inclusion criteria. The overall major complication rate was 10.6%. Compared to patients without frailty, patients with mild (OR 3.83; 95% CI, 2.63– 5.58), moderate (OR 6.80; 95% CI, 4.10– 11.3), and severe frailty (OR 13.05; 95% CI, 6.34 – 26.87) had significantly increased odds of complication development (all p < 0.001). The mean length of stay was 6.4 ± 0.2 days, 9.8 ± 0.6 days, 14.4 ± 1.7 days, and 18.3 ± 2.6 days for patients without frailty, with mild frailty, with moderate frailty, and with severe frailty, respectively (p < 0.05 between all groups). Conclusion: Compared to patients without frailty, patients with mild, moderate, and severe frailty had significantly increased odds of developing post-operative complications. A systematic evaluation of pre-operative frailty should play a key role in decision-making for patients undergoing surgery for primary spinal tumors.

A150: Predictive Factors for Survival in a Surgical Series of Metastatic Epidural Spinal Cord Compression: A Prospective North American Multi-Centre Study in 142 Patients

Anick Nater¹, Lindsay Tetreault², Branko Kopjar³, Paul Arnold⁴, Mark Dekutoski⁵, Joel Finkelstein⁶, Charles Fisher⁷, John France⁸, Ziya Gokaslan⁹, Laurence Rhines¹⁰, Peter Rose¹¹, Arjun Sahgal⁶, James Schuster¹², Alexander Vaccaro¹³, Michael Fehlings¹

¹Department of Surgery, University of Toronto, Toronto - Canada ²Graduate Entry Medicine, University College Cork, Cork - Ireland ³Department of Health Services, University of Washington, Seattle - United States ⁴Department of Neurosurgery, University of Kansas Medical Center, Kansas City - United States ⁵The Core Institute, Sun City West - United States ⁶Division of Orthopaedic Surgery, Sunnybrook Health Sciences Center, Toronto - Canada ⁷Vancouver General Hospital and University of British Columbia, Vancouver - Canada ⁸West Virginia University, Morgantown - United States ⁹Department of Neurosurgery, Rhode Island Hospital, Providence - United States ¹⁰MD Anderson Cancer Center, University of Texas, Houston - United States ¹¹Mayo Clinic, Rochester - United States ¹²Department of Neurosurgery, Hospital of the University of Pennsylvania, Philadelphia - United States ¹³Thomas Jefferson University and Rothman Institute Orthopaedics, Philadelphia - United States

Introduction: Metastatic Epidural Spinal Cord Compression (MESCC) afflicts up to 10% of cancer patients. Few prospective studies have evaluated key preoperative clinical factors of survival such as scores on patient-assessed questionnaires, patient factors and tumor characteristics, using multivariable analysis in adult patients treated surgically for a single MESCC lesion. These results could help modify or develop new predictive scoring systems. Material and Methods: One hundred and forty-two surgical MESCC patients were enrolled in a prospective, multicenter, North American, cohort study and followed postoperatively for at least 12 months or until death. Cox proportional hazards regression was used following the assessment of the proportional hazards assumption. Non-collinear, preoperative predictors of survival with < 10% missing data, ≥ 10 events per stratum and p < 0.05 in univariable analysis were tested through a backward stepwise selection process. Results: The median survival was 7.5 months. A total of 88 patients died and 54 were censored. Seven factors were significant in univariable analysis: growth of primary tumor (Tomita tumor grade), sex, lymph node/other organ metastasis, body mass index, and SF-36v2 physical component, EQ-5D and Oswestry disability index (ODI) scores. Since the ODI*time term was significant, it was included in the multivariable model. Tomita tumor Grade II/III (HR: 2.767, 95% CI: 1.520-5.035, p = 0.0009), presence of lymph node/other organ metastasis (HR: 2.044, 95% CI: 1.259-3.319, p = 0.0038), and SF-36v2 physical component score (HR: 0.94 595% CI: 0.920-0.970, p < 0.0001) had an independent effect on survival. Conclusion: Slow growing tumor (Tomita tumor Grade I), absence of lymph node/other organ metastasis, and lower degree of preoperative physical disability, as reflected by a higher score on the SF-36v2 physical component questionnaire, are independent preoperative clinical factors associated with longer survival in patients treated surgically for a focal MESCC lesion.

A151: Correlation of the Spinal Instability Neoplastic Score (SINS) Individual Components and Indeterminate Subgroup Designation With Patient-Reported Outcomes Following Instrumented Surgical Stabilization

Ibrahim Hussain¹, Ori Barzilai¹, Anne Reiner², Natalie DiStefano¹, Lily McLaughlin¹, Shahiba Ogilvie¹, Mark Bilsky¹, Ilya Laufer¹

¹Department of Neurological Sugery, Memorial Sloan Kettering Cancer Center, New York - United States ²Department of Epidemiology and Biostatistics, Memorial Sloan Kettering Cancer Center, New York - United States

Introduction: The Spinal Instability Neoplastic Score (SINS) was developed to facilitate the diagnosis of instability in patients with spine tumors. It is comprised of six categories and cumulative scores are denoted as stable (0-6), indeterminate (7-12), or unstable (13-18). We have previously demonstrated that SINS correlates with pre-operative patient reported outcomes (PRO) and response to stabilization, with higher scores experiencing greater relief after surgery. However, there is a paucity of data demonstrating the extent to which each component contributes to PRO. Furthermore, treatment decisions for “indeterminate” SINS requires further elucidation. The objectives of our study were to determine how each SINS component correlates with pre- and post-operative PRO and to study the heterogeneity of the “indeterminate” group in order to further delineate instability. Material and Methods: SINS and PRO (10 pain, walking, and activity related items from the Brief Pain Inventory (BPI) and MD Anderson Symptom Inventory (MDASI)) were prospectively collected from 131 patients undergoing instrumented stabilization surgery for metastatic spinal disease. Association between individual SINS components with pre-operative symptom burden and symptom change after surgery was analyzed using Spearman Rank Correlation Coefficient (ρ). Correlation between SINS component scores and magnitude of pain relief was analyzed using the Kruskal Wallis test. Pre-operative SINS and association with pre-operative PRO scores were compared for two SINS categories within the indeterminate group (7-9 vs. 10-12) using the Wilcoxon two-sample test. The mean differences in post- and pre-operative PRO scores for these subgroups were compared using the Wilcoxon signed rank test. P-values less than or equal to 0.05 were considered statistically significant. Results: SINS metastatic location component significantly correlated with all pre-operative functional disability measures, including BPI activity (ρ = 0.27; P = 0.002) and MDASI walking (ρ = 0.33; P = 0.0002). Patients with higher location scores experienced a larger improvement in walking ability after surgery (BPI P = 0.04, MDASI P = 0.02). 8 out of 10 pre-operative PRO items significantly correlated with SINS mechanical pain component, including MDASI pain (ρ = 0.34; P < 0.0001) and activity (ρ = 0.31; P = 0.0003). This component also significantly correlated with improvement in BPI worst pain (ρ = −0.26; P = 0.01) and MDASI pain (ρ = −0.28; P = 0.04) following surgery. There was a significant association between lower SINS bone lesion quality component scores and improvement in BPI worst pain (P = 0.05) postoperatively, with sclerotic tumors (score = 0) experiencing greater relief compared to patients with lytic (score = 2) tumors. Following surgical stabilization, patients with low indeterminate SINS (7-9) demonstrated significant decreases in 3 out of 10 PRO, whereas those with high indeterminate SINS (10-12) demonstrated significant decreases in 8/10 PRO, including MDASI spine pain (-2.4; P = 0.001) and BPI activity (-2.4; P < 0.0001), and MDASI activity (-2.0; P = 0.0006). Conclusion: The presence of mechanical pain followed by metastatic location correlated most strongly with pre-operative functional disability measures and improvement in PRO following surgical stabilization to a statistically significant degree. Blastic rather than lytic bone lesions demonstrated a significantly stronger association with symptomatic pain improvement following stabilization. Patients with SINS 10-12 demonstrated markedly improved PRO nearly across the board compared to SINS 7-9 with stabilization surgery, suggesting that this group includes distinct populations.

A152: The Psychometric Properties of a Self-Administered, Open-Source, Web-Based Tool for Valuing Metastatic Spinal Cord Compression Health States

Markian Pahuta¹, Doug Coyle²

¹Departments of Orthopedic and Neurological Surgery, Henry Ford Health System, Detroit - United States ²Department of Epidemiology, University of Ottawa, Ottawa - Canada

Objectives: Internet market research panels are often used as a substitute for general population samples for ex ante utility valuation. Typically, custom utility valuation tools that have not undergone psychometric evaluation are used. This study aims to determine the psychometric properties of a customizable open-source internet-based self-directed utility valuation tool the (Self-directed Online Assessment of Preferences; SOAP) module for metastatic epidural spinal cord compression health states. Methods: Individuals accompanying patients to the emergency department waiting room were recruited into this study. Participants made SOAP metastatic epidural spinal cord compression health state valuations in the waiting room, and 48 hours later at home. Validity, agreement reliability, and responsiveness were measured by logical consistency of responses, Smallest Detectable Change, the Interclass Correlation Coefficient, and Guyatt's Responsiveness Index respectively. Results: Of 285 participants who completed utility valuations, only 113 (39.6%) completed the re-test. Of these 113 participants, 92 (81.4%) provided valid responses on the first test, and 75 (66.4%) provided valid responses on the test and re-test. Agreement for all groups of health states was adequate since their Smallest Detectable Change was less than the Minimally Clinically Important Difference. The mean Interclass Correlation Coefficient s for all health states were greater than 0.8 indicating at least substantial reliability. Guyatt's Responsiveness Indices all exceeded 0.80, indicating high level of responsiveness. Conclusions: The SOAP metastatic epidural spinal cord compression module is a valid, reproducible and responsive tool for obtaining ex ante utilities. This tool can now be used to obtain general population valuations of metastatic epidural spinal cord compression health states. Additional modules could be developed to facilitate decision making for other diseases.

A153: Biomarker Mutations Predict Survival in Patients With Metastatic Lung Cancer to the Spine

Bryan Choi¹, Ganesh Shankar¹, Laura Van Beaver¹, Kevin Oh¹, John Shin¹

¹Department of Neurosurgery, Massachusetts General Hospital, Boston - United States

Introduction: Spinal metastases are a major cause of morbidity. Molecular profiling strategies to characterize lung cancer have identified several biomarkers and gene expression signatures that may lead to more effective prognostication and personalized treatment. The aim of this study was to ascertain whether molecular phenotype in patients with advanced metastatic disease is associated with survival, when the disease has progressed to spinal metastases. Material and Methods: We retrospectively analyzed our database of 26 patients with metastatic lung cancer who had undergone treatment for spinal metastases between 2011 and 2017. Reports were reviewed for molecular phenotype. Survival time was calculated as the difference between treatment for spinal metastases and date of death. Analysis was performed using the Kaplan-Meier method and log-rank tests. Results: Median survival following surgery was 0.67 years. Median overall survival (OS) following diagnosis was 2.7 years. Survival times were not significantly different with respect to molecule phenotype for individual mutations in ALK, ROS1, EGFR, KRAS. However, when considered together, the presence of any molecular abnormality in patients with spinal metastases was significantly associated with increased OS (HR 0.38, 95% CI 0.12 -1.22, P = 0.03). Conclusion: Information gleaned from the molecular phenotype of metastatic disease provides prognostic insight for patients undergoing surgery for spinal metastases. The altered molecular markers studied here demonstrate an association with prolonged survival time when compared with wild-type counterparts. This is the first study to demonstrate a significant association between genetic mutational data and overall survival in this patient population. This study also represents the largest published series of patients (n = 26) with metastatic lung cancer to the spine for which genetic mutational data are reported. Future models estimating survival for patients with spinal metastases may be enhanced by inclusion of molecular phenotype criteria.

A154: The Surical Treatment of Upper Cervical Intraspinal Tumors: A Series of 24 Patients With Long-term Follow-up

Dechun Wang¹, Jianwei Wei¹, Longwei Chen¹

¹Qingdao Spine Center, Qingdao Municipal Hospital, Qingdao - China

Introduction: Due to the specific anatomical characteristics of the upper cervical spine, there are some difficulties for the surgical treatment of upper cervical intraspinal tumor. To evaluate retrospectively the clinical results of 24 cases of upper cervical intraspinal tumor who were surgically treated. Material and Methods: Twenty-four consecutive cases of upper cervical intraspinal tumor were surgically treated between January 2003 and March 2012. Data regarding age, sex, levels, initial symptoms, topographical locations, surgical results, and histological features were investigated. The Modified Japanese Orthopaedic Association (mJOA) score was used to evaluate the neurologic states pre and postoperatively. All patients were followed up for at least 38 months. Results: In our series of 17 men and 7 women aging 11 to 75, paresthesia of the upper extremities was the most common initial symptom. Tumors at C1-2 and C2-3 segments accounted for 70.83% of all. Total tumor resection was achieved in 22 patients (91.67%) and subtotal resection in 2 (8.33%). Histology indicated neurogenic tumors in 23 cases (95.83%), and hematoma in 1 case (4.17%). Oval (58.33%) and dumbbell-shaped (29.17%) tumors showed predominance. Excellent and good results were obtained in 83.33% of the patients. Recurrence was observed in 3 cases (12.50%). A 70-year old man died of pulmonary emboli (4.17%) after operation. Conclusions: The majority of the upper cervical intraspinal tumors were neurogenic. Distinct recognization of the location, shape and size of the tumor, as well as the spinal cord and vertebral artery with MRI, CT and CTA were required for the surgery. Total tumor resection showed satisfied surgical results.

Degenerative Lumbar 1

A155: Comparison of the Incidence of Fusion in ALIF Procedures Between BMP-2/Allograft and ILIAC Crest Autograft/Allograft

Ata Kasis¹, Rahul Dharmadhikari², Matthew Mawdsley¹, Cyrus Jensen¹

¹Department of Trauma and Orthopaedics, Northumbria Healthcare NHS Foundation Trust, Ashington - United Kingdom ²Department of Radiology, Northumbria Healthcare NHS Foundation Trust, Ashington - United Kingdom

Introduction: Bone Morphogenic Protein-2 (BMP-2) has been commonly used to increase spinal fusion rates. Prior to 2016, the authors used BMP-2 in combination with fresh frozen femoral head (FFFH) in Anterior Lumbar Interbody Fusion (ALIF) procedures with excellent results. Due to the significant shortage of BMP-2 in Europe in 2016, a new technique was developed to replace the BMP-2 with a core of iliac crest bone autograft in combination with FFFH. The original BMP-2/femoral head technique of inserting BMP-2 inside the FFFH was adopted from the Gold Coast Spine, Australia. In this study we compare the fusion rate between the two techniques using CT scanning. Material and Methods: One hundred consecutive patients (50 in each group) who underwent ALIF procedures between 2013-2017 at L4-S1 for degenerative pathologies were reviewed. The osteoinductive ± osteogenic bone graft (BMP-2 or iliac crest cancellous bone) was inserted in the middle of cancellous FFFH allograft into two drilled tunnels in the middle of the FFFH. When BMP-2 was used, a 2 mg piece was inserted into each drilled tunnel (4 mg per level). When an autograft was used, two cores of cancellous iliac crest bone graft were obtained through a stab incision using a cannulated vertebral biopsy 10 gauge needle (Stryker®). All patients had a routine CT scan performed at 4-5 months after surgery to check for fusion. CT scan imaging was reviewed by a consultant radiologist who was blinded to the type of bone graft used. Results: The were 50 consecutive patients in each group. There was no statistical difference in the age of the patients, the male/female ratio, the level of surgery or the indications for surgery. For the BMP-2 group, 8 were ex-smokers and the remainder had never smoked. The was radiological fusion in 49 patients (total of 53 levels) (98%). There was one non-union in this group in a non-smoker who had surgery for neuroforaminal stenosis. In the iliac crest group, there were 9 ex-smokers and the remainder had never smoked. There was also radiological fusion in 49 patients (total of 52 levels) (98%), and again non-union in one patient (DDD) who had never smoked. There were no complications from the donor bone graft site (pain, or infection or fracture) as one might have seen if the whole graft had been taken from the iliac crest, as opposed to using FFFH. Conclusion: There has been a huge amount of debate in the literature during the past decade regarding the potential risks associated with BMP-2 use, and so the use of bone core autografts in this way, removed these risks. The osteogenic properties of the Iliac crest bone core, in addition to its osteoinductive profile may give it a further advantage over BMP-2 (only osteoinductive) in achieving a solid fusion mass. The cost of using a core autograft was significantly less than using BMP-2. We used iliac crest bone core autografts as an alternative to BMP-2 in ALIF procedures using this well established technique, and found comparable fusion rates in the two groups.

A156: Preventing Implant Loosening Via Cortical Bone Trajectory

Kim Soon Oh¹, Hooi Ming Tan¹

¹Island Hospital Spine Centre, Penang - Malaysia

Introduction: Recent years have seen an increase in the adoption of the cortical bone trajectory (CBT) technique while instrumenting the osteoporotic lumbar spine. Such a practice finds relevance as more elderly patients require spinal surgery. We continued studying the effectiveness of our CBT cohort by focusing on the rate of screw loosening. Material and Methods: Our patient pool was collected from December 2012 till June 2015, when 180 adult women underwent lumbar spine decompression and instrumentation. Every other patient was treated using the CBT technique while the alternate patient received classical pedicle screw fixation. The entire series of surgery was performed by a single main surgeon and his assisting spinal team. All were post-menopausal women with ages ranging from 62 till 92 years old. All patients had evidence of abnormal bone density with T-score readings of worse than −1.0. Surgery was indicated for lumbar spine stenosis presenting with radiculopathy. The number of levels operated on ranged from one till three. Excluded from our study were patients with acute traumatic lesions, metastatic spine disease, infective spine lesions and spondylolisthesis greater than Grade 1. Thoracic spine involvement was not studied. CBT technique was effected in 86 patients and classical pedicle screw technique in 94. All patients had bilaminar decompression and at least one level of interbody fusion. These patients were then followed up for a minimum of 24 months. Of the 180 cases, 9 were lost to follow-up (3 CBT and 6 classical pedicle screw). Our monitoring of the incidence of implant loosening was performed with quarterly radiographs in the first year and twice annually in the second, with CT scans at 12 and 24 months. Radiographs were read and interpreted separately by the author and 2 radiologists, with statistical adjustment of inter-observer variation. Results: In the CBT arm, 8 patients suffered screw loosening, 5 of them having it at the sacral level and the remaining, on the cephalad last-instrumented vertebra. Loosening afflicted 17 of those receiving classical pedicle screws. The chronological incidence of loosening ranged from 3 months to 10 months after surgery. Conclusion: We conclude that compared to traditional pedicle screw constructs, cortical bone trajectory has shown significant impact in preventing implant loosening by virtue of its good cortical purchase. We suggest the adoption of this technique in the elderly osteoporotic lumbar spine.

Disclosure - Neither the author or any member of the studying team received funds or benefits in any kind pertaining to this subject during the conduct of this study.

A157: ABM/P-15 (I-Factortm) Versus Allograft in Non-Instrumented Lumbar Fusion Surgery - 1-Year Postoperative Intertransverse Segmental Fusion Rate. A Double-Blind RCT

Michael Kjaer Jacobsen¹, Andreas Kiilerich Andresen¹, Annette Bennedsgaard Jespersen¹, Leah Carreon¹, Soeren Overgaard², Mikkel Oesterheden Andersen¹

¹Department of Spine surgery and research, Middelfart - Denmark ²Department of ortopaedic surgery and traumatology, Odense - Denmark

Introduction: Lumbar spinal stenosis is the most common indication for spinal surgery and as a result of the demographic shift, caused by prolonged life expectancy in developed countries, the prevalence is expected to increase. In the elderly, due to poor bone stock, decompression supplemented with non-instrumented posterolateral fusion is often preferred in Scandinavia, when instability is present. The current gold standard fusion graft is harvested iliac crest bone. This procedure has many disadvantages with donor site pain being the most frequent complication. The use of allograft has inherent problems as the donor has to be tested several times for infectious diseases and the need for subzero storage. The presence of these factors justifies the necessity and use of the shelve bone graft substitutes. Bone grafts studies conducted in spinal surgery have a massive publication bias favoring BMP, which necessitate tests of different bone graft materials. Purpose: To evaluate the intertransverse segmental fusion rate in elderly patients suffering symptomatic lumbar spinal stenosis and concomitant degenerative listhesis undergoing decompression and posterolateral intertransverse non-instrumented fusion surgery. Clinical gov trials nr: NCT02895555 Approved by The Danish Ethics Committee file nr: 20 120 012. Material and Methods: From March 2012 to April 2013, 101 ASA 1+2 patients age 60+ referred to Lillebaelt Hospital, with lumbar spinal stenosis and degenerative listhesis verified on MRI and lateral standing radiographs, agreed to participate. All patients had completed a minimum of 3 month of non-operative therapy with little or no effect. Patients were randomized 1:1 to either i-FactorTM (mixed 50/50) or allograft bone (30 g/level), both mixed with local lamina autograft from the decompression, and underwent one-year postoperative evaluation. FUSION EVALUATION: Fine cut CT-scans (0,9 mm) with reconstructions were used to establish fusion. The CT-scans were evaluated independently by 3 reviewers. The reviewers were blinded to the treatment and evaluated digital films on PACS using axial cuts with sagittal and coronal reconstruction viewed simultaneously. The fusion was determined by consensus of 2 of the 3 reviewers as “fusion” or “non-fusion”. Results: During the 1-year follow-up period, 3 patients were excluded due to reoperation (2 ABM/P-15 and 1 allograft patient, non-significant) leaving 98 patients for fusion evaluation (49 in each group). Patient groups were comparable on all preoperative parameters (BMI, sex, diabetes, hypertension, grade of listhesis, amount of decompressed bone, p > 0.05). All patients were non-smokers. In the ABM/P-15 group, 14 patients had 2-level fusion and in the allograft group, 8 patients had 2-level fusion, leaving 126 and 114 intertransverse segments for evaluation, respectively. FUSION RATE: The overall intertransverse segmental fusion rate was 63/126 (50%) in the ABM/P-15 group versus 23/114 (20.2%) in the allograft group (p < 0.001). In 1-level listhesis patients, the fusion rates were 29/72 (40.28%) and 17/80 (21.25%) respectively (p = 0.011) and in 2-level patients 34/54 (62.96%) and 6/34 (17.64%) respectively (p < 0.001). Conclusion: Enhancing fusion rate in non-instrumented fusion surgery is a massive challenge in geriatric lumbar spinal surgery. This RCT showed that ABM/P-15 is significantly superior to allografted bone in enhancing intertransverse fusion in both one and two level patients. Follow-up studies on the clinical effect of fusion are warranted.

A158: Custom Made Pmma Spacer Performs Better in Single Level Tlif Than Preformed Peek Spacer. Minimum Two Years Follow Up of a Prospective Randomized Study

Marton Ronai¹, Tibor Csakany¹, Maria Puhl¹, Peter Pal Varga¹

¹National Center for Spinal Disorders, Budapest - Hungary

Introduction: The use of bone cement in spine surgery is more and more accepted world-wide not only for performing vertebro- or kyphoplasty, but also to fill open or percutaneosly the intervertebral space in advanced disc degeneration to stabilize the anterior column. In our Institut we also use PMMA as a spacer in TLIF procedures. In a previous retrospective analysis we reviewed are results with this kind of surgeries which led us to start a prospective randomized study. Here we present our results at a minimum of two years follow up. Material and Methods: 106 consecutive patients to whom we suggested to perform single level TLIF were included into the study. The patients were randomised into three groups by the GraphPad QuickCalcs software. Group A is a control group, standard TLIF with PEEK spacer positioned in the anterior part of the intervertebral space. Group B is standard TLIF with PMMA spacer placed in the anterior part of the intervertebral space. Group C is standard TLIF with PMMA spacer formed in the posterior part of the intervertebral space. Patients between 18-65 y/o were included. Patients with a high grade spondylolisthesis, metabolic bone desease, spinal infection, cancer, severe scoliosis (Cobb over 30°) were excluded. We evaluated the clinical results with standard questioners (ODI, VAS). Radiological evaluation was focused on the process of bony fusion, loosening of any instrument implanted (PMMA spacer or screws), osteolysis around the cement, subsidence. Results: 8 patients were excluded from the cohort, because the operating surgeon did not follow the randomization for some surgical reason (i.e. not enough place for a spacer, injury of the end plate, etc.). At this moment 5 of the 98 followed patients (4,9%) are lost from the study (did not come to the planned control) 93 patinets (94,9%) have at least 12 month follow up, and 85 completed the 24 month follow up (86,7%). From this 85 subjects, 32 are in Group A, 27 in Group B, and 26 in Group C. On CT scan 12 months after surgery we could observe complete fusion in 74% of the operated segments and the fusion rate was higher in the PMMA spacer group B, but the difference was not significant. The overall fusion rate at 24 months is 93%, and there was no difference between the groups. We found 14 subsidence (13%), 10 in the PEEK spacer group (A) meaning, that the subsidence rate was significantly higher in this group. We found a radiolucent zone around the implant (sign of loosening) in only 7 cases (6,6%), 5 in the A group, 1 in the B group and 1 in the C group. This difference was not significant. The overall clinical result was very good in 61%, good in 28% and poor in 11% of the cases without significant difference between the groups. Conclusion: This results show, that custom made PMMA spacer in TLIF performs better regarding the mechanical aim of the surgery than preformed PEEK spacer even in non-osteoporotic population. The clinical result is not inferior either, than with the use of PEEK spacer, but this technic has some advantages compared to preformed cages: it is cheaper; it requires smaller annular window to implant.

A159: Factors Affecting Lordosis Correction After TLIF With Unilateral Facetectomy

Christopher Martin¹, Shuo Niu², Emily Whicker², S. Tim Yoon²

¹Department of Orthopaedics, University of Minnesota, MInneapolis - United States ²Department of Orthopaedics, Emory University School of Medicine, Atlanta - United States

Introduction: Lordosis correction after TLIF is variable, with some authors reporting significant improvement and others reporting no improvement or even a slight increase in positive sagittal balance after the procedure. The purpose of the current study was to identify pre-operative radiographic features that are associated with increased lordosis correction. Material and Methods: We retrospectively reviewed the patients of a single surgeon to identify cases of single level TLIF performed at L4-5 for a diagnosis of spondylolisthesis between 2010 and 2015. All cases were performed with the same surgical technique involving unilateral facetectomy and insertion of a banana type cage. 108 cases were available with complete pre-and post-op plain radiographs, and 62 patients with a pre-op CT scan. We compared segmental lordosis correction between the pre-op and 6-week post-operative radiographs. Patients were divided into groups of those with or without more than 5 degrees lordosis correction. Radiographic features were then compared between the cohorts and a multivariate analysis was performed to identify the features most predictive of lordosis correction. Results: The mean lordosis correction of the entire cohort was 2.5 degrees (range of -9 to 16 degrees). The percentage of patients with a vacuum disc on the pre-op CT (40% v. 10%, p = 0.01) was higher in the group with greater than 5 degrees lordosis correction, whereas the mean pre-op segmental lordosis (14.3 v. 18.6 degrees), and the pre-op segmental disc angle (6.4 v 8.4 degrees), were both lower (p < 0.05 for each). The percentage of patients with a myerding grade of 2 or higher (28% v. 16%) trended higher but was not significant (p = 0.1). There was no significant difference in the mean BMI, patient age, pre-operative lumbar lordosis, disc space height, or segmental translation. Conclusion: Patients with a pre-operative vacuum disc sign on CT scan or those with a more kyphotic disc space on pre-operative radiographs were more likely to achieve significant lordosis correction after a TLIF procedure. This information may be useful in pre-operative planning for TLIF.

A160: Prospective, Comparative, Multicenter Trial of Surgical Outcomes for Degenerative Lumbar Spondylolisthesis

Mamoru Kawakami¹, Shigenogu Sato¹, Yoshiharu Kawaguchi¹, Seiji Ohtori¹, Hiroshi Miyamoto¹, Hideki Nagashima¹, Ryoji Yamasaki¹, Motoki Iwasaki¹, Takeshi Fuji¹, Hiroaki Konishi¹, Hideki Shigematsu¹, Hiroshi Yamada¹, Norio Kawahara¹

¹The AOSpine Japan Collaboration Research Consortium, Ito Gun - Japan

Introduction: There was no high evidence if spine fusion is effective in clinical outcomes for degenerative lumbar spondylolisthesis (DLS). The purpose of this prospective multicenter study was to compare clinical and radiological outcomes in patients with DLS treated using different surgical procedures. Material and Methods: This prospective observational cohort study included 20 institutes. The inclusion criteria were the presence of neurogenic claudication, single-level DLS. The exclusion criteria were previous spine operation, osteoporosis, degenerative scoliosis,, or psychological disorders. A total of 165 cases were registered from October 2013 to March 2016. Demographic data including age, gender, body mass index, smoking, bone mineral density, comorbidity, and duration of symptoms before surgery were recorded. The patient-reported outcomes (PROs) including a visual analogue scale (VAS) for low back pain, leg pain, and numbness, Zurich claudication questionnaire (ZCQ) and EuroQol 5 Dimension (EQ-5D) were used at 3, 6, and 12 months postoperatively. Slippage, lumbar lordosis, lumbar axis sacral distance, range of motion at each disc level, bony fusion, and disc degeneration according to the Schneiderman classification were examined radiologically. Twelve patients were excluded. Sixteen patients underwent posterior decompression only (D group), and 137 underwent decompression and fusion (DF group). In the DF group, 41, 78, and 18 patients had posterolateral fusion (PLF), posterior or transforaminal lumbar interbody fusion (IF), and another procedure, respectively. Operative time, estimated blood loss (EBL), and complications were recorded. We used propensity score matching and compared clinical and radiological outcomes between the D and DF groups and between the PLF and IF groups. A p-value < 0.05 was considered to be significant. Results: The 14 patients in the D and DF groups were matched. Operative time and EBL were significantly lower in the D group than those in the DF group (95.1 vs. 185.6 min, 67.3 vs. 308.6 ml, P < 0.05). At 3 months postoperatively, only VAS for leg numbness and ZCQ Physical function scale had improved significantly in the DF group, compared with the D group (11.8 vs. 34.5 mm, 6.9 vs. 9.6, p < 0.05). At 6 and 12 months, PROs did not differ between the groups. The 28 patients in the PLF and IF groups were matched using the propensity score. The operative time, EBL, complications and PROs at 3 months did not differ between the PLF and IF groups. The VAS for low back pain, EQ-5D score, and ZCQ patient satisfaction with treatment at 6 and 12 months were better in the IF group than in the PLF group (38.6 vs. 18.6 mm, 0.711 vs. 0.812 and 10.6 vs. 7.1, 8.7 vs. 6.2, respectively, p < 0.05). Radiological outcomes did not differ between the PLF and IF groups up to 12 months. Conclusion: We used propensity score matching to avoid bias related to confounding preoperative variables for patients with single-level DLS. The results of this prospective multicenter trial suggest that, compared with decompression only, decompression and fusion might improve clinical outcomes such as leg numbness and physical function at 3 months and that IF might result in better clinical outcomes up to 12 months postoperatively than PLF.

Surgical Complications - Proximal Junctional Kyphosis

A161: Learning Curve of Thoracic Pedicle Screw Placement in Typical Thoracic (T1-T10) Vertebrae Using Free Hand Technique in Non Scoliotic Spine

Tarun Dusad¹, Mahendra Singh¹, Vishal Kundnani¹

¹Dept of Orthopedics and Spine Surgery, Mumbai - India

Introduction: Thoracic pedicle screw insertion has a steep learning curve with high perforation rates with devastating complication . Literature evaluating learning curve is scanty. Understanding the learning curve and challenges in thoracic pedicle screw insertion may help design mentoring & workshop programs to reduce implant related complications. Material and Methods: Prospective cohort study, Single Surgeon, Single center. Post Operative CT scan images of consecutive 92 cases (2010-2015) of typical thoracic vertebrae (T1-T10 vertebrae) pedicle screw instrumentation (n = 735 screws). Perforation incidence, Location & Grade of perforation using Gertzbein et al criteria were assessed (three independent observers). 92 cases divided into 4 equal quartiles (23 cases/group q1, q2, q3, q4).Perforation rate compared over time using analysis of variance measures with each group serving control for prior. Learning curve assessed using logarithmic curve-fit regression analysis & ANNOVA test-comparison of variables in different quartiles (p Value = 0.05). Results: 735 typical thoracic pedicle screws (q1, n = 180; q2, n = 174; q3, n = 193 & q4, n = 188) were studied in 92 patients (53 M, 39F). 72 screws classified as perforated = 9.79%(medial, 25; lateral, 42; superior, 2, inferior = 3).T4 had most number (n = 14) of perforation with q1 = 5, q2 = 3, q3 = 3 q4 = 3. High thoracic (T1-T6) screws higher perforation (55/72, 76.38%) compared to lower levels (T7-T10 = 17/72). Majority was grade 2(46 perforation, 63.88%), Grade 3 = 4 & Grade 1 = 22 perforation. Perforation rates stratified by surgeon’s evolving experience; temporal decrease in overall perforation rate (q1 = 13.89%, q2 = 9.77%, q3 = 8.31% & q4 = 7.44%) with significant correlation (P value .023) between q1 & q2; Asymptote status achieved after first quartile. Statistical significance (p value .03) noted between first two quartiles for medial perforation rate with lesser medial perforation over time in sequential quartiles (q1 = 5.00%, q2 = 3.44%, q3 = 3.10% & 2.66%). Similar trends observed for lateral perforation rate, although statistical significance not obtained (q1 = 6.66%, q2 = 5.74%, q3 = 5.26%, q4 = 4.78%). Symptomatic perforation in one patient addressed by screw removal/Revision. Conclusion: Learning curve with reducing perforation rates can be mastered with experience and Thoracic pedicle Screw perforation reduces overt time including medial perforation and severity of grade of perforation. This study paves way for designing workshop and mentorship programs to reduce the pedicle perforation related complications.

A162: Risk Factors for Proximal Junction Kyphosis (PJK) in Scheuermann’S Kyphosis (SK)

Darren Lui¹, Haiming Yu², Adam Benton³, Sara Gargent⁴, Jesse Galina⁵, Stephen Wendolowski⁵, Sean Molloy³, Vishal Sarwahi⁵

¹Trauma and Orthopaedics, London - United Kingdom ²The Second Affiliated Hospital of Fujian Medical University, Fujian - China ³Royal National Orthopaedic Hospital, Stanmore - United Kingdom ⁴St. George’s University Hospital, London - United Kingdom ⁵Pediatric Orthopaedics, Cohen Children’s Medical Center, New Hyde Park - United Kingdom

Introduction: PJK has been well documented with pedicle screws in AIS patients. In Scheuermann’s kyphosis (SK), PJK has been reported with hybrid fixation in the presence of shorter fusions. The literature is deficient about PJK in SK with all pedicle screw constructs. Material and Methods: Xray and chart review of all SK patients operated with all pedicle screw (PS), hybrid fixation (HF), and anterior/posterior fusions with hybrid fixation (AP) were reviewed. Number of fusion levels, percent correction, UIV, LIV, pre and postop PJK, sagittal balance, and demographic data was collected. PJK was defined as more than 10 degrees. Fisher’s exact test, Kruskal-Wallis, Wilcoxon ranked sum test were used. Results: 84 total patients: PS (n = 29), HF (n = 24), and AP (n = 31). Median preop kyphosis was significantly higher in the AP compared to PS and HF (89 vs 77 vs 81.5, p < 0.001). Median postop kyphosis was significantly higher in the PS cohort (50.3 vs HF: 45.5 vs AP: 43, p = 0.048). Median percent correction was highest in the AP cohort (51.8 vs HF: 43.8 vs PS: 32.9, p < 0.001). Pre and post sagittal balance was similar across the three cohorts. Overall, at postop 47.6% of patients had PJK, and at final 70.2%. Immediate postop-PJK was significantly higher in PS 13.4 vs HF: 7.8 vs AP: 8, p = 0.008). However, final PJK was similar across the three groups (PS: 19 vs HF: 15 vs AP:14, p = 0.07). T2 was the most common UIV for AP (71%) and HF (71%) compared to T3 for PS (59%), p < 0.001). Overall, significantly higher postop-PJK was seen with UIV below T3 (13.7 vs 9.4, p = 0.043). Conclusion: Incidence of PJK appears to be higher in SK compared to that reported in AIS. Patients with pedicle screw fixation appear to be at the highest risk. UIV at T3 or proximally has significantly lower PJK.

A163: Dysphagia Following Cervical Spine Surgery

Timothy Woodacre¹, Tom Majoran¹, Lucy Maling¹

¹Ipswich Hospital, Ipswich - United Kingdom

Introduction: Dysphagia is a known risk following cervical spine surgery. It is however rarely assessed objectively, rather it is patient reported. Material and Methods: We objectively assessed the presence of dysphagia post elective cervical spine surgery within one tertiary referral spinal unit. All patients over a 3 month period completed an EAT-10 questionnaire pre-surgery, day 1 post-surgery and 8 weeks following surgery. Results were correlated with approach, complexity and duration of surgery, number of operated levels and presence of an anterior plate. Results: 30 patients underwent cervical spine surgery: 25 via an anterior approach, 4 via posterior and one combined. The overall initial rate of dysphagia following anterior surgery was 73% and 33% at 8 weeks. Posterior cervical surgery numbers were small but they demonstrated an initial dysphagia rate of 0%, rising to 20% at 8 weeks following one episode of re-operation. Multi-level surgery demonstrated a higher 6 week dysphagia rate of 50%. Revision surgery and cervical corpectomy also showed higher rates. Conclusion: We assessed dysphagia following cervical spine surgery via an objective method. We demonstrated rates comparable to the established literature. We have suggested that the complexity of anterior surgery correlates to dysphagia risk and that even posterior cervical surgery poses a potential problem.

A164: Complications in 214 Consecutive Cases of Anterior Lumbar Spine Access: Experience of a Single Institution

Francesco Caiazzo¹, Gloria Tresserras Gine¹, Bartolomé Fiol Busquets¹, Josep Cabiol Belmonte¹

¹Department of Neurosurgery, General Catalonia Hospital, Barcelona - Spain

Introduction: The purpose of the study was to investigate the adverse events in patients undergoing an anterior retroperitoneal approach to the lumbar spine, particularly neurological and biomechanical events. Material and Methods: A total series of 214 patients underwent anterior left retroperitoneal approach at our Institution, due to degenerative disc disease or deformity. One-level surgery was performed in 68% (n = 146) and two-level surgery in 32% (n = 68). Total disc replacement was performed in 40% (n = 85) of cases; 60% (n = 128) were ALIF (combined or not with posterior approach), in 20% (n = 42) of those an hyperlordotic cage was placed. A minimum period of follow-up of 4 months (36m-4 m) was established and clinical and radiological data were recorded intraoperatively and at first visit postoperative. We classified as major events (vascular injuries, bowel or bladder perforations, infections, deep venous thrombosis) and minor (radiculopathy, sensory deficits, neurovegetative conditions, sacroiliac syndrome, abdominal wall hematoma). Results: Total amount of adverse events was 20% (42 events in 37 patients). All minor deficits cleared along the follow-up period with full recovery. 6 major events: 1 iliac vein lesion (revision case), 2 deep venous thrombosis and 2 intestinal perforations (one managed conservatively), 1 prosthesis infection, were observed. No cases of retrograde ejaculation were recorded. Uni or bilateral radiculopathy, especially affecting S1 root were recorded like transient adverse event in 15 cases. Neurovegetative disorders, consist mainly in edema and temperature changes, along the left leg without motor deficit and with variable degrees of pain mimicking a sympathetic dystrophy, were observed in 5 cases. A total of 11 patients (8 of those were ALIF surgery) developed sacroiliac joint pain, which responded to repeat anesthetics blocks or thermal denervation. Conclusions: The anterior approach is generally safe and the amount complications is low. We point out the incidence of postoperative sacroiliac joint pain, transient radiculopathy and neurovegetative events as well, conditions not usually reported in the literature.

A165: Analysis of Risk Factors for Success in Lumbar Spinal Stenosis Surgery

Thiago Maia¹, Charbel Jacob Jr¹, Igor Machado Cardoso¹, José Lucas Batista Jr¹, Marcus Alexandre Novo Brazolino¹, Caroline Oliveira Bretas¹, Larissa Furbino de Pinho Valentim¹

¹Department of Orthopedics Santa Casa de Vitoria, Vitoria - Brazil

Introduction: The objective of this study was identify the patient profile that gets more improvement in clinic and quality of life after lumbar spinal stenosis surgery, comparing the results in the pre and postoperative periods. Materials and Methods: 37 patients with lumbar spine stenosis submitted to surgery were prospectively evaluated. Through the questionnaire 36-Item Short Form General Health Survey (SF-36), morbidities identification and Social Security Benefit it was made preoperative analysis. The SF-36 and a subjective questionnaire postoperative assessed surgical success six months after the surgery. Results: There was unfavorable outcome in patients who received social security benefits or had morbidity. At SF-36 score, the surgical result is better when the patient is not a smoker (p = 0.05), not hypertensive (p = 0.040), non-diabetic (p = 0.010) or not sedentary (p = 0.019) respectively the following domains mental health, pain, social aspects and general health. Conclusions: The patient profile that best benefit from the surgery is one that does not have the morbidity and has no security benefit.

Evidence Level II, Prospective Study.

A166: The Incidence and Risk Factors of Proximal Junctional Kyphosis During Growing-Rod Treatment for Early Onset Scoliosis: A Retrospective Case-Control Study

Aixing Pan¹, Yong Hai¹

¹Department of Orthopedics, Beijing Chaoyang Hospital, Beijing - China

Introduction: Proximal junctional kyphosis (PJK) is one of the most common reported postoperative complications. Until now, limited information about the prevalence and risk factors of PJK after growing-rod surgery in EOS can be achieved. This study aimed to evaluate the incidence and risk factors of proximal junctional kyphosis(PJK) after growing-rod surgery for early onset scoliosis (EOS). Materials and Methods: A retrospective case-control study was performed in a group of 50 children (24 males and 26 female) with EOS who received the treatment of growing-rod surgery. The demographic data, surgery strategy and radiographic parameters of preoperative and final follow up were recorded and analyzed to identify the PJK risk factors. Results: The mean age of initial operation was 8.6 ± 2.5 years old. The mean follow-up time was 33.5 ± 10.8 months. 28 of the procedures were single growing-rod surgery and 22 of them were dual growing-rod surgery. PJK developed in 14 of 50 (28%) patients. After the multi-factors regression analysis, UIV distal to T2 (HR = 5.474, p = 0.044) and postoperative UTS greater than 50°(HR = 1.049, p = 0.046) were confirmed as the independent risk factors of developing PJK. Conclusion: The incidence of PJK was 28% during growing-rod treatment in EOS. The independent risk factors of developing PJK were UIV distal to T2 and postoperative UTS greater than 50°.

Arthroplasty Cervical

A167: Cervical Artificial Disc Replacement With Prodisc-C: 10-Year Clinical and Radiographic Results of Prospective Observational Study in a Single Institute

Jung-Woo Hur¹, Kyeong-Sik Ryu¹, Jin-Sung Kim¹

¹Department of Neurosurgery, Seoul St. Mary’s Hospital, Seoul - Korea, Republic

Introduction: Cervical artificial disc replacement (ADR) is indicated for the treatment of severe radiculopathy permitting neural decompression and maintenance of motion. Previous reports of short and mid-term results have shown that cervical ADR using Prodisc-C is safe and effective in symptomatic CDD between C3 and C7. The objective of this study is to evaluate long-term clinical and radiologic results of ADR using the Prodisc-C in patients with single-level cervical disc disease (CDD) in minimum 10-year follow-up. Material and Methods: Data were collected through a prospective registry, with retrospective analysis performed on 79 consecutive patients treated with cervical ADR with the Prodisc-C device (DePuy Synthes, West Chester, PA, USA) in a single institution. All enrollees were evaluated pre- and post-operatively at regular intervals using both clinical and radiologic parameters. Clinical outcome measures included visual analogue scale (VAS) for neck and arm pain and Owestry disability index (ODI). Serial flexion-extension cervical radiographs and CT scans were performed to assess range of motion (ROM) of index segment, adjacent segment degenerations (ASD), implant-related complications (migration, subsidence, lucency) and heterotopic ossification (HO) using McAfee classification system. Results: Out of 79 patients enrolled, 79.7% (63/79) of patients continued regular outpatient visit at the 5-year follow-up period. However, after 10 years, only 22.9% (17/71) of patients remained with the study. Average follow-up was 10.7 years. After 5-year follow-up, neck and arm pain improved 68.6% and 86.8%, respectively, and ODI had an improvement of 85.7%. However, after the last visit, neck pain improvement decreased to 29.7%, whereas arm pain and ODI remained at 74.6% and 68.9%, respectively. Neurologic success rate was 82.3% after final assessment. There were no episodes of device failure except one case of subsidence. Mean ROM of the device decreased from 6.7° at 5-year to 5.4° at final assessment. Radiographic ASD developed in 58.8% of patients (mild; 29.4%, moderate; 23.5%, severe; 5.8%, respectively) and 58.8% demonstrated HO at the final follow-up, however, only 17.6% were symptomatic requiring second surgery. Conclusion: The Prodisc-C device for cervical ADR appears to be safe and effective for the treatment of CDD after long-term follow-up. Despite radiographic evidence of ASD and HO on final assessment, Prodisc-C ADR provided maintenance of segmental motion at the index level and good neurologic success rate.

A168: Cervical Disc Arthroplasty (CDA) Versus Anterior Cervical Discectomy and Fusion (ACDF) in Symptomatic Cervical Degenerative Disc Diseases (CDDDS): an Updated Meta-Analysis of Prospective Randomized Controlled Trials (RCTS)

Lin Xie¹

¹Wuhan Puai Hospital, Wuhan - China

Introduction: This meta-analysis of Randomized Controlled Trials (RCTs) aims to evaluate the efficacy and safety in cervical disc arthroplasty (CDA) and anterior cervical discectomy and fusion (ACDF) for treating cervical degenerative disc diseases (CDDDs). Material and Methods: The authors searched RCTs in the electronic databases (Cochrane Central Register of Controlled Trials, PubMed, EMBASE, Medline, Embase, Springer Link, Web of Knowledge, OVID and Google Scholar) from their establishment to march 2016 without language restrictions. We also manually searched the reference lists of articles and reviews for possible relevant studies. Researches on CDA versus ACDF in CDDDs were selected in this meta-analysis. The quality of all studies was assessed and effective data was pooled for this meta-analysis. Outcome measurements were surgical parameters (operative time, blood loss, and length of hospital stay), clinical indexes (neck disability index (NDI), neurological success, range of motion (ROM), Visual Analogue Score (VAS)), complications (the number of adverse events, adjacent segment disease (ASD), and reoperation). Subgroup analysis, sensitivity analysis, and publication bias assessment were also performed, respectively. The meta-analysis was performed with software RevMan 5.3. Results: 37 articles (20 RCTs) with a total 4123 patients (1762 in the CDA and 1472 in the ACDF) met inclusion criteria. Eight types of disc prostheses were used in the included studies. Patients were followed up for at least two years in all the studies. No statistically significant differences were found between CDA and ACDF for blood loss (SMD -0.02; 95% CI (−0.20, 0.17)), length of hospital stay (MD -0.06; 95% CI (−0.19, 0.06)). Statistical differences were found between operative time (MD 14.22; 95% CI (6.73, 21.71)), NDI (SMD −0.27; 95% CI (−0.43, −0.10)), neurological success (RR 1.13; 95%CI (1.08, 1.18)), ROM (MD 6.72; 95%CI (5.72, 7.71)), VAS of neck (SMD -0.40; 95%CI (−0.75, −0.04)), VAS of arm (SMD −0.55; 95%CI (-1.04, -0.06)), the rate of adverse events (RR 0.72 95% CI (0.53, 0.96)), the rate of ASD (RR 0.62; 95% CI (0.43, 0.88)), and reoperation (RR 0.50; 95% CI (0.39, 0.63)). Subgroup analysis stratified by different types of disc prostheses was also performed. Conclusion: CDA is associated with higher clinical indexes and fewer complications than ACDF, indicating that it is a safe and effective treatment for CDDDs. However, the operative time of CDA is longer than ACDF and NDI score of CDA is lower than ACDF. Because of some limitations, these findings should be interpreted with caution. Additional studies are needed. Large, definitive RCTs are needed.

A169: Stability and Clinical Performance of the Prodisc-C VIVO Cervical Total Disc Replacement: A Radiostereometric Assessment Study

Miranda van Hooff¹, Petra Heesterbeek¹, Maarten Spruit²

¹Department Research, Sint Maartenskliniek, Nijmegen - Netherlands ²Department of Orthopedic surgery, Sint Maartenskliniek, Nijmegen - Netherlands

Introduction: Cervical total disc replacement (CTDR) is promising in patients with cervical diseases [1,2]. Recently, a meta-analysis showed that CTDR was superior over anterior discectomy and fusion for the treatment of cervical disc disease in terms of success in clinical performance, patient satisfaction, and superior adjacent segment degeneration. However, concerns as implant migration and spontaneous fusion are described [1]. As the Prodisc-C Vivo is implanted without additional fixation, it is important to investigate the primary stability of the implant in the intervertebral disc space. Purpose: To evaluate the translational stability 6 months postoperatively of the Prodisc-C Vivo in the intervertebral disc space, with regard to the adjacent vertebrae, with model-based radiostereometric assessment (MB-RSA) and to describe its clinical performance in patients with single level C3-7 radiculopathy due to herniated disc, degenerative disc disease or spondylosis. Material and Methods: A cohort study, including 16 patients (9 women), aged 44 years (range 28-54), with single level C3-C7 radiculopathy due to degeneration, and preserved motion at symptomatic level, was performed. Main exclusion criteria: previous surgery at index level, disc height < 50%, comorbidities. RSA radiographs were obtained during hospitalization after surgery, at 6weeks, 3, and at 6months follow up (6moFU). Migration (total translation [TT]; mm) of both components of the implant was measured with MB-RSA (RSAcore, Leiden, the Netherlands) using CAD models of the implant components and marker models in the cervical vertebral bodies. At 6 weeks, double RSA radiographs were obtained to assess precision. Stability over time was analysed using the non-parametric Friedman test. Cervical mobility was assessed using maximum flexion-extension X-rays and digital vertebral corner assessment; the angle C2-C7 was measured. The difference between the angles of maximum flexion and extension was assessed (ROM; degrees) and maintenance of mobility was analysed. Clinical results were described with Neck Disability Index (NDI; 0-100), pain intensity (NRSneck, NRSarm; 0-10), satisfaction with symptoms neck (5-point Likert scale), and adverse events (AE). Results: Preliminary results show an acceptable reproducibility of the MB-RSA method; for both components the precision of translation was below 1 mm. At 6 moFU the median TT for superior component was 0.62 mm (range 0.03 -1.14) and for inferior component 0.53 mm (range 0.26 -1.30). Median migration (translation) of both components remain below ≤1 mm and translational stability is maintained over time (superior component X ²(2) = 1.500, p = 0.472; inferior component X ²(2) = 1.625, p = 0.444). Clinical results (n = 15) at 6moFU (median [range]): ROM (53.1 degrees [35.89-69.39]; 49.7 degrees [23.44-71.31]), NDI (43 [14-82]; 18 [0-62]), NRSneck (6 [1-10]; 1 [0-7]), NRSarm (6 [1-9]; 0 [0-7]), and 12/15 are satisfied with symptoms neck at 6months. In total, 3 AEs in 3/16 patients occurred (1 persistent pain in neck and arm; 1 postoperative hoarse; 1 increasing headache). Mobility was maintained at 6moFU (Z = 1.93, p = 0.230). Conclusion: Translation of the Prodisc-C Vivo with reference to the adjacent vertebrae can be measured accurately with MB-RSA. The translational migration over 6 months follow up of both components is below clinical threshold and cervical mobility is maintained. Clinical improvement seems as expected. Final study results will be presented at the conference.

References

1. Tu T, et al. Heterotopic ossification after cervical total disc replacement: determination by CT and effects on clinical outcomes. J Neurosurg Spine. 2011; 14:457-465.

2. Hu Y, et al. Mid- to Long-Term Outcomes of Cervical Disc Arthroplasty versus Anterior Cervical Discectomy and Fusion for Treatment of Symptomatic Cervical Disc Disease: A Systematic Review and Meta-Analysis of Eight Prospective Randomized Controlled Trials. PLOS One. 2016; February: 1-17.

A170: Functional Outcome and Patient Satisfaction Between Smokers and Non-Smokers With Cervical Artificial Disc Replacement: Analysis of a Spine Registry

Wen-Shen Lee¹, Maksim Lai², William Yeo², Seang Beng Tan², Wai Mun Yue², Chang Ming Guo², Mohammad Mashfiqul Arafin Siddiqui²

¹Department of Orthopaedic Surgery - Spine Service, Singapore General Hospital, Singapore - Singapore ²Department of Orthopaedic Surgery, Singapore General Hospital, Singapore - Singapore

Introduction: Smoking is a known predictor of negative outcome in most spinal surgeries. However, the evidence behind smoking as a predictor of outcome in cervical artificial disc replacement (ADR) is limited. An analysis of a spine registry at a major tertiary centre was performed to evaluate patient outcomes after ADR between smokers and non-smokers. Material and Methods: A retrospective analysis of a spine registry, consisting of patients with debilitating cervical radiculopathy or myelopathy treated with cervical ADR from 2004 to 2015 with a minimum of 2 years follow-up were included in the study. Patient function was assessed using Short Form-36 (SF-36), American Association of Orthopaedic Surgery (AAOS) cervical spine and Japanese Orthopaedic Association (JOA) scoring systems preoperatively and at 2 years post-operatively. Patients undergoing concurrent fusion surgery were excluded from the study. Incidence of further surgery on affected and adjacent segments was analysed as well. Results: 195 patients underwent ADR from 2004 to 2015, with 137 patients undergoing a minimum 2-year follow up, of which 60 patients presented with myelopathy and 77 with radiculopathy. There were 117 non-smokers and 20 smokers in total. The mean age in the smoker group was 42.6, compared to 46.4 in the non-smoker group (p < 0.01). Mean follow-up period was 2527 days in the smoker group and 2226 days in non-smokers. AAOS and SF-36 scores revealed statistical improvement in both groups, with no significant difference between groups at 2-years follow-up, and post-operative range of motion improved significantly in both groups. 84.2% of non-smokers and 87.5% of smokers reported as surgery having met their expectations. JOA scores in patients with cervical myelopathy significantly improved in both groups but did not statistically differ between smokers and non-smokers (p < 0.05). 6 out of 117 non-smokers (5.13%) and 3 out of 20 smokers (15%) needed revision surgery (p = 0.099). All smokers needed a fusion surgery, with 2 of them needing revision of ADR to fusion, and one needing adjacent segment fusion. 3 out of 6 of the non-smokers needed revision of ADR to fusion, of which 1 needed an adjacent segment fusion in addition. The remaining 3 surgeries consisted of an adjacent ADR, a laminoplasty and a posterior laminectomy. Smokers had a longer time to fusion (1335.6 days vs 1247.6 days). Conclusion: Our analysis indicates that there is no difference in functional outcome or patient satisfaction between smokers and non-smokers. Although there is a tendency for smokers to undergo revision surgery, it is not statistically significant. This may be due to the smaller number of smokers in our study. It can be concluded that smoking does not hold a significant negative impact on the outcomes of cervical ADR surgery.

A171: Risk Factors and Preventative Measures of Early and Persistent Dysphagia After Anterior Cervical Spine Surgery: a Systematic Review

Yong Hai¹, Jingwei Liu¹

¹Department of Orthopedics, Beijing Chao-Yang Hospital, Capital Medical University, Beijing - China

Introduction: Anterior cervical spine surgery (ACSS) is commonly used for the treatment of numerous cervical disorders, such as traumatic, degenerative and congenital diseases. Dysphagia is one of the most common complications after ACSS which easily occurred in the early postoperative stage with reported incidence of up to 88%, and its symptoms were particularly serious in the early phase. And persistent dysphagia troubled the patients for a long time. Knowing risk factors and preventative measures of early and persistent dysphagia after ACSS becomes an important work for the spine surgeons when doing the procedure. Methods: On 27th March 2017 we searched the database PubMed, Medline, EMBASE, the Cochrane library, Clinical key, Springer link and Wiley Online Library without time restriction. Selected papers were examined for the level of evidence by published guidelines as level I, level II, level III, level IV studies. We investigated risk factors and preventative measures of early or persistent dysphagia after ACSS from these papers. Results: The initial search yielded 515 citations. Fifty-nine of these studies met the inclusion and exclusion criteria. Three of them were level I evidence studies, twenty-nine were level II evidence studies, twenty-two were level III evidence studies, and three were level IV evidence studies. Preventable risk factors included prolonged operative time, use of rhBMP, endotracheal tube cuff pressure, cervical plate type and position, dC2-C7 angle, psychiatric factors, smoke, prevertebral soft tissue swelling, SLN or RLN palsy or injury of branches. Preventative measures included preoperative tracheal traction exercise, maintain endotracheal tube cuff pressure at 20 mm Hg, avoid routine use of rhBMP-2, use Zero-profile implant, use Zephir plate, use new cervical retractor, steroid application, avoid prolonged operating time, avoid overenlargement of cervical lordosis, decrease surgical levels, ensure knowledge of anatomy of superior laryngeal nerve and recurrent laryngeal nerve, to comfort always, patients quit smoking and doctors improve skills. Unpreventable risk factors included age, gender, multilevel surgery, revision surgery, duration of preexisting pain, BMI, blood loss, high level surgeries, preoperative comorbidities and surgical type. Conclusion: Adequate preoperative preparation of the patients, properly preventative measures during surgery, ensure knowledge of anatomy and skilled surgical technique are essential for preventing early and persistent dysphagia after ACSS.

A172: Effect of Novel Unconstrained-Type Artificial Disc in Hybrid Cervical Surgery in Terms of Adjacent Segment Degeneration and Motion Preservation

Jung-Woo Hur¹, Kyeong-Sik Ryu¹, Jin-Sung Kim¹

¹Department of Neurosurgery, Seoul St. Mary’s Hospital, Seoul - Korea, Republic

Introduction: Multi-level anterior cervical fusion results in greater risk of adjacent segment degeneration (ASD) with a substantially greater increase in longitudinal strain immediately adjacent to fused level. Hybrid surgery, consisting of artificial disc replacement (ADR) combined with anterior cervical discectomy and fusion (ACDF), has been reported with favorable results for 2-level cervical disease. Novel unconstrained-type artificial disc with variable center of rotation demonstrated physiologic facet-guided movement enabling better motion preservation. The purpose of this study is to compare the clinical and radiologic outcome of cervical hybrid surgery using conventional semi-constrained-type artificial disc and novel unconstrained-type artificial disc in patients with 2-level disc disease in terms of adjacent segment degeneration and motion preservation. Material and Methods: Between October 2013 and December 2014, 82 patients with 2 consecutive level cervical disc disease (CDD) between C3/4 and C6/7 underwent hybrid surgery were retrospectively reviewed. All operations were conducted with two surgeons with the same surgical protocols. In study group (44 patients), novel unconstrained-type artificial disc (ROTAIO Cervical Disc Prosthesis; SIGNUS Medizintechnik GmbH, Alzenau, Germany) was inserted in ADR level and in control group (38 patients), conventional semi-constrained type was used. Standard ACDF surgery was done at fusion level in both group. All patients were followed clinically and radiologically for a minimum of 24 months. Clinical outcomes were assessed by Neck Disability Index (NDI), visual analogue scale (VAS) scores for neck and arm pain, patients' overall satisfaction and the usage of postoperative analgesics. Additionally, radiological measurements including angular range of motion (ROM) of C2–C7 and adjacent segments and any radiological evidence of adjacent segment degeneration were recorded. Results: Both groups showed significant improvement in NDI and VAS scores postoperatively and continued improvements were observed in both groups until 2 years. Although no significant differences in NDI scores existed between 2 groups postoperatively, study group experienced a trend towards better results at 12 and 24 months (p = 0,333, 0.018 respectively). Over 95% of patients in both group showed good to excellent results at the last visit and a significant reduction of analgesic usage was observed (p < 0.001). The C2-C7 ROM was significantly limited immediately after surgery in both group and then gradually recovered. The study group showed more rapid and greater C2-C7 ROM recovery compared to control group at the final follow-up (30.1 ± 10.8° vs 24.2 ± 11.4°; p = 0.005). Although, superior adjacent segment ROM for both group remained hypo-mobile compared to preoperative value during the follow-up periods, the control group exhibited gradual increase from 12 month to final follow-up after the surgery (6.4 ± 3.2 vs 8.9 ± 4.2; p = 0.005, 6.8 ± 5.4 vs 10.5 ± 4.9; p = 0.005 respectively). Significantly increased ROM at inferior adjacent segments was observed in both groups compared with preoperative values at the final follow-up, but the compensatory ROM was less in study group without statistical significance. Adjacent disc space narrowing was observed equally in both groups. No new osteophyte formations and signs of prosthesis-related complication were recorded and in both group. There were low rate of complication and no secondary operation. Conclusion: The hybrid surgery may be a promising alternative to fusion surgery for CDD, but studies suggest still some degree of adjacent segment degeneration observed. In this study, hybrid surgery with novel unconstrained-type artificial disc demonstrated better neck pain improvement, C2-C7 ROM recovery and less impact at superior adjacent level compared to conventional semi-constrained-type. Variable center of rotation enabling physiologic facet-guided movement without joint gapping in unconstrained-type artificial disc may be a promising solution to eliminate unwanted adjacent segment degenerations.

Tumor - Metastatic Disease 1

A173: A Minimally Invasive Surgical Strategy for Thoracic Metastatic Tumor Accompanied With Neurologic Compression

YuTong Gu¹

¹Department of Orthopaedics, Zhongshan Hospital of Fudan University, Shanghai - China

Introduction: The neurological decompression, spinal tumor resection and stabilization with instrumentation should be performed either from an anterior, posterior, or a combined approach for spinal metastatic tumor accompanied with symptoms of neurologic compression. However, these operations have significant morbidity related to the surgical approach, potential blood loss, extensive dissection or biomechanical instability. The purpose of study is to evaluate the feasibility, efficacy and safety of minimally invasive pedicle screws fixation (MIPS) combined with percutaneous vertebroplasty (PVP), minimally invasive neurologic decompression and partial tumor resection for treating thoracic metastasis with epidural involvement and neurologic symptoms. Materials and Methods: Eighteen patients with a mean age of 53.2 years (range, 31-72 years), who sustained single-level thoracic vertebral metastasis and neurologic compression underwent the procedure of MIPS (The minimal-access in a paraspinalsacrospinalis muscle-splitting approach was performed to insert pedicle screws into the vertebrae under direct vision and two rods of the appropriate size were placed over the pedicle screws through subcutaneous soft tissues and muscles) combined with PVP, minimally invasive decompression and partial tumor resection through mini posterior midline approach. The mean prognostic score was 7 (6-7 points) according to Tomita scoring system. The pain intensity in the previously symptomatic region was evaluated with visual analog scale pain scores (VAS) and the severity of the neurologic deficit was assessed by using the ASIA impairment scale. Cobb angles, central and anterior vertebral body height were measured on the lateral radiographs before surgery and during the follow-up after surgery. Results: The mean duration of the operation was 204.7 ± 10.5 min. The mean length of the midline incision was 3.1 ± 0.3 cm. There was a mean blood loss of 150 ml (70-600 ml). The mean amount of cement injected was 5.8 ± 1.3 ml. The mean stay at the hospital was 6 days (4-7 days). Clinical follow-up was available for 17 patients in this study ranging from 12 to 16 months (mean time, 14.2 months) and other 1 patient died 8 months after surgery. There were no perioperative complications such as infection and no death due to complications of the procedure itself. The VAS score significantly dropped from 9 (7-10) before operation to 3 (2-4) (P < 0.001) immediately after the operation and to 1 (0 -1) (P < 0.001) at final follow-up. Improvement of paraplegia was observed after surgery in all of these patients. At 3-month follow-up, 3 of 5 patients with complete paraplegia improved from ASIA scale B to D, 10 of 13 patients with incomplete paraplegia from C or D to E. Ten of 17 surviving patients got ASIA scale E at the latest follow-up. Spine stability was observed in all of surviving patients at the latest follow-up. Conclusions: MIPS combined with PVP, minimally invasive decompression and partial tumor resection is a good choice of surgical treatment for thoracic metastatic tumor accompanied with neurologic compression.

A174: Steroids for the Management of Neurological Deficits in Patients Undergoing Surgical Treatment for Metastatic Spine Disease; A Prospective Case Series

Ahmed Aoude¹, Anne Versteeg², Michael Weber¹, Arjun Sahgal³, Peter Pal Varga⁴, Daniel Sciubba⁵, James Schuster⁶, Michelle Clarke⁷, Laurence Rhines⁸, Stefano Boriani⁹, Chetan Bettegowda⁵, Michael Fehlings¹⁰, Paul Arnold¹¹, Ziya Gokaslan¹², Charles Fisher¹³, AOSpine Knowledge Forum Tumor¹⁴

¹Division of Surgery, McGill University and Montreal General Hospital, Montreal - Canada ²Department of Orthopedics, University Medical Center Utrecht, Utrecht - Netherlands ³Department of Radiation Oncology, Sunnybrook Odette Cancer Centre and University of Toronto, Toronto - Canada ⁴Spine Department, National Center for Spinal Disorders and Buda Health Center, Budapest - Hungary ⁵Department of Neurosurgery, Johns Hopkins University School of Medicine, Baltimore - United States ⁶Department of Neurosurgery, Hospital of the University of Pennsylvania, Philadelphia - United States ⁷Department of Neurosurgery, Mayo Clinic, Rochester - United States ⁸Department of Neurosurgery, Division of Surgery, The University of Texas MD Anderson Cancer Center, Houston - United States ⁹GSpine4 Spine Surgery Division. IRCCS Istituto Ortopedico Galeazzi, Milan - Italy ¹⁰Division of Neurosurgery, University of Toronto and Toronto Western Hospital, Toronto - Canada ¹¹Department of Neurosurgery, The University of Kansas Hospital, Kansas city - United States ¹²Department of Neurosurgery, The Warren Alpert Medical School of Brown University and Rhode Island Hospital and The Miriam Hospital, Providence - United States ¹³Division of Spine, department of Orthopaedics, The Combined Neurosurgical and Orthopaedic Spine Program at Vancouver Coastal Health, Vancouver - Canada ¹⁴Research department, AOSpine International, Davos - Switzerland

Introduction: Patients presenting with metastatic epidural spinal cord compression (MESCC) causing neurological deficit are often initially treated with high dose corticosteroids prior to surgery and/or radiation. Although commonly administered, the evidence regarding the use of steroids in these patients and their effect is limited and historical. Therefore, we explored the effect of corticosteroid use on patient neurological and health-related quality of life (HRQOL) outcomes. Materials and Methods: A prospective case series from the international multicenter prospective observational cohort study on metastatic spine disease (EPOSO) was conducted. Patients were included if they underwent surgery between August 2013 and February 2017 for the treatment of spinal metastases and received steroids for (prevention or stabilization of) neurological deterioration. Data regarding demographics, diagnosis, treatment, neurological function, and HRQOL were evaluated. Results: A total of 101 patients received steroids as baseline, of these only 30 underwent surgery and received steroids for the treatment of neurological deficits and were included in the analysis. These patients had a mean age of 58.2 years (range: 28-74) at surgery. Half of the patients experienced progressive neurological deterioration, while 30% stabilized and 20% improved in neurological function. Lengthier steroid use did not correlate with improved or stabilized neurological improvement. Significant improvements in HRQOL were observed over time. Conclusion: This is the first study evaluating the effect of steroids on neurological function in surgically treated patients. Half of the patients either stabilized or improved in neurological function before surgery. Steroid use in this patient population would seem to be indicated, but further research defining their indication is needed.

A175: A General Population Utility Valuation Study for Metastatic Spinal Cord Compression

Markian Pahuta¹, Doug Coyle²

¹Departments of Orthopedic and Neurological Surgery, Henry Ford Health System, Detroit - United States ²Department of Epidemiology, University of Ottawa, Ottawa - Canada

Objectives: A particularly disabling consequence of cancer is metastatic epidural spinal cord compression (MESCC). Few prospective studies on the treatment of MESCC have collected quality-adjusted-life-year weights (termed “utilities”). Utilities are an important summative measure which distills health outcomes to a single number that can be used by healthcare providers to counsel patients and policy makers to make funding decisions. The primary objective of this study is to obtain utility valuations for the 31 unique MESCC health states from a Canadian general population perspective. The secondary objective of this study is to determine the relative importance of various aspects to quality-of-life in MESCC. Method: We recruited a sample of 822 adult Canadians from a market research company. Quota sampling was used to ensure that the participants were representative of the Canadian population in terms of age, gender, and province of residence. Participants were asked to rate 6 of the 31 MESCC health states using the validated SOAP tool. Results: Sixty-six percent of participants provided logical ratings (for example perfect health was rated higher than non-ambulatory health states). The regression model building exercise revealed that members of the general population value all attributes characterizing MESCC health states equally. Furthermore, dysfunction follows a pattern of diminishing marginal disutility). That is, each additional dysfunction affects a smaller incremental change in utility than the previous dysfunction. These results demonstrate that from the societal perspective, physical function is valued equal to other facets of well-being. Ambulation and continence, which are dysfunctions addressed by surgery, are no more important than other attributes evaluated (pain, other symptoms, and level of independence). Conclusions: We have provided utility estimates for metastatic epidural spinal cord compression health states. The utility values derived from this study can be used to help inform population level healthcare decision making, such as allocation of limited resources for specific treatments. Approximately 63.7% of participants completed, understood and engaged in the task. Thus self-administered utility valuation over the internet is feasible. This approach can serve as a model for deriving utilities for conditions for which quality-of-life data is not available.

A176: Minimal Access Surgery for Spinal Metastases: Prospectively Validated Treatment Algorithm Using Patient Reported Outcomes

Ori Barzilai¹, Lily Mclaughlin¹, Mary Kate Amato¹, Anne Reiner², Shahiba Ogilvie¹, Eric Lis³, Yoshiya Yamada⁴, Mark Bilsky¹, Ilya Laufer¹

¹Department of Neurosurgery, Memorial Sloan Kettering Cancer Center, New York - United States ²Depratment of Epidemiology and Biostatistics, Memorial Sloan Kettering Cancer Center, NYC - United States ³Department of Radiology, Memorial Sloan Kettering Cancer Center, NYC - United States ⁴Department of Radiation Oncology, Memorial Sloan Kettering Cancer Center, NYC - United States

Introduction: Minimal access surgery (MAS) allows early return to systemic and radiation therapy in patients with cancer leading to its increasing utilization in the treatment of spinal metastases. Systematic examination of surgical indications resulted in the development of an algorithm for implementation of MAS in the treatment of spinal metastases. The object of this study was to evaluate a spine tumor MAS treatment algorithm using patient-reported outcomes of pain experience and disease interference in cancer patients undergoing treatment of spinal metastases. Materials and Methods: This is a prospective cohort study. Patients who underwent spinal percutaneous instrumented stabilization with the addition of MAS cord or nerve root decompression and/or kyphoplasty when indicated at a tertiary cancer center between December 2013 and August 2016 were included. Validated Patient Reported Outcome (PRO) measures including the Brief Pain Inventory (BPI) and the MD Anderson Symptom Inventory – Spine module (MDASI-sp) were used as outcome measures. PROs were collected at baseline, 3 month and long-term follow up (4.5-12 months). PROs at 3 months of follow up and long-term follow up were compared to baseline measures using the Wilcoxon Signed-Rank test. Results: Fifty-one patients were included. MAS resulted in a statistically significant decrease in the severity of pain, and improved activity, ability to work and enjoyment of life (P < 0.001). The improvement was reported at the short- and long-term follow-up time points. Conclusions: We present our treatment algorithm for MAS implementation in the treatment of thoraco-lumbar spinal metastases. Prospectively collected data demonstrate that using this algorithm, MAS surgery for the treatment of spinal metastases results in significant decrease in pain severity and symptom interference with daily activities.

A177: Evidence From the Epidemiology, Process and Outcomes of Spine Oncology (EPOSO) Cohort: Surgical Versus Radiation Therapy for the Treatment of Cervical Metastases

Michael Bond¹, Anne Versteeg², Arjun Sahgal³, Peter Varga⁴, Daniel Sciubba⁵, James Schuster⁶, Michael Weber⁷, Michelle Clarke⁸, Laurence Rhines⁹, Stefano Boriani¹⁰, Chetan Bettegowda⁵, Michael Fehlings¹¹, Paul Arnold¹², Ziya Gokaslan¹³, Charles Fisher¹

¹Combined Neurosurgical and Orthopedic Spine Program, University of British Columbia, Vancouver - Canada ²Department of Orthopaedics, University Medical Center Utrecht, Utrecht - Netherlands ³Department of Radiation Oncology, Sunnybrook Odette Cancer Centre and University of Toronto, Toronto - Canada ⁴Spine Department, National Center for Spinal Disorders and Buda Health Center, Budapest - Hungary ⁵Department of Neurosurgery, Johns Hopkins University School of Medicine, Baltimore - United States ⁶Department of Neurosurgery, Hospital of the University of Pennsylvania, Philadelphia - United States ⁷Division of Surgery, McGill University and Montreal General Hospital, Montreal - Canada ⁸ Department of Neurosurgery, Mayo Clinic, Rochester - United States ⁹Department of Neurosurgery, Division of Surgery, The University of Texas MD Anderson Cancer Center, Houston - United States ¹⁰GSpine4 Spine Surgery Division. IRCCS Istituto Ortopedico Galeazzi, Milan - Italy ¹¹Division of Neurosurgery, University of Toronto and Toronto Western Hospital, Toronto - Canada ¹²Department of Neurosurgery, The University of Kansas Hospital, Kansas City - United States ¹³Department of Neurosurgery, The Warren Alpert Medical School of Brown University and Rhode Island Hospital and The Miriam Hospital, Providence - United States

Introduction: Cervical metastases have unique clinical considerations because of complex neighbouring anatomy, and the unique biomechanical regions within the cervical spine. The literature regarding cervical metastases is limited to retrospective studies without comparison of different treatment regimens. The purpose of this study was therefore to compare surgery (+/- radiation) with radiation alone for the management of cervical metastases in a prospective manner. Materials and Methods: Patients treated with surgery and/or radiotherapy for cervical metastases between August 2013 and February 2017 were identified from the Epidemiology, Process and Outcomes of Spine Oncology (EPOSO) observational cohort. Demographic, diagnostic, treatment and health related quality of life (HRQOL) (NRS Pain, EQ-5D, SF-36v2, and SOSGOQ2.0) measures were prospectively collected at baseline, 6 weeks, 3 months, and 6 months post-intervention. Results: Fifty-five patients treated for cervical metastases were identified: 38 underwent surgery (+/- radiation) and 17 received radiation alone. Surgically treated patients had higher SINS scores compared to the radiation-alone group (13.0 [SD 2.8] vs. 8.0 [SD 2.8], p < 0.001) and were more likely to have mechanical neck pain (89.5% vs. 37.5%, p < 0.001). Surgically treated patients presented with significantly higher NRS pain scores and lower HRQOL scores compared to the radiation alone group (p < 0.05). From baseline to 6 months post-treatment, surgically treated patients demonstrated significant improvements in NRS pain, EQ-5D and SOSGOQ2.0 compared to non-significant improvements in the radiotherapy only group. Conclusions: Surgically treated patients presented with significantly worse baseline pain and HRQOL scores compared to patients who underwent radiotherapy only. Preservation of pain and HRQOL was observed for patients treated with radiotherapy only compared to significant improvements for surgically treated patients at 6 months follow-up.

This study was funded by an Orthopedic Research and Education Foundation grant and by AOSpine International through the AOSpine Knowledge Forum Tumor.

A178: Metastatic Spinal Cord Compression Due to Unknown Primary Tumour: 5 Year Review

Sujay Dheerendra¹, Shreya Srinivas², Mark McGowan², Radu Popa², Sathya Thambiraj², Prokopis Annis², Marcus DeMatas²

¹Centre for Spinal Studies, The Robert Jones and Agnes Hunt Orthopaedic Hospital, Oswestry - United Kingdom ²Royal Liverpool University Hospital, Liverpool - United Kingdom

Introduction: Metastatic Spinal Cord Compression (MSCC) due to unknown primary tumour (UPT) poses challenges in diagnosis and appropriate management. The aim of our study was to assess the neurological and functional outcomes including survival compared to MSCC due to known primary tumours (KPT). Methods: The data was collected prospectively between September 2010 and September 2015. Results: There were 131 patients treated with MSCC during this period and 25 (19%) were due to UPT (M: F = 15:10, mean age of 65 (42 – 81) years). 10 (40%) patients were treated with surgical intervention and 13 (52%) with radiotherapy. The median Tokuhashi score was 8 for surgery group and 7 for radiotherapy group (p < 0.05). The median time to obtain an MRI scan from referral was 18.04 hrs with only 1 (4%) breaching the 24-hour target. The Frankel score improved in 85% of the patients who underwent surgery compared to 90% in the KPT. The mean survival for UPT group was 156.5 days (Surgery: 160.2, Radiotherapy: 154; p = 0.9) compared to KPT group of 126.7 days (p = 0.24). The primary was confirmed in 15 (60%) patients [Lymphoma (3), Lung (5), GI (5), Thyroid (1), Myeloma (1)]. Conclusions: The neurological outcomes and mean survival were similar in both the UPT and KPT groups. Interestingly there were no differences in survival or neurological outcome in patients who underwent surgery or radiotherapy in the UPT group. These patients present a conundrum in decision-making and our data would suggest a similar outcome on standardizing management for every MSCC.

Degenerative Lumbar 2

A179: Comparison of Minimally Invasive Transforaminal Lumbar Interbody Fusion and Open Transforminal Lumbar Interbody Fusion: A Meta-Analysis

Wei-hu Ma¹, Yun-lin Chen², Wei-yu Jiang¹

¹Deparrtment of Spinal Surgery, Ningbo No.6 Hospital, Ningbo - China

Introduction: Open-TLIF is a standard technique to achieve fusion in degenerative spinal disease. The previous studies showed minimally invasive-TLIF has better clinical and function outcomes when compared to open-TLIF. However, there were several limitations such as lower evidence level and lack of important information in some studies. We aimed to provide a meta-analysis to compare MIS-TLIF and open-TLIF. Methods: Studies that compared MIS-TLIF and open-TLIF were identified by searching Pubmed, Medline, Embase, Web of Science, Wanfang. The general data, operation time, blood loss, hospital stay, and ambulation time were compared between two groups. VAS-back pain and VAS-leg pain, Oswestry Disability Index (ODI) evaluation standards were applied to evaluate the clinical effects. The intervertebral fusion rates and complication rates were also compared. Results: Thirty studies (n = 2400 patients) were included in our meta-analysis. MIS-TLIF has less VAS-back pain (p = 0.02), VAS-leg pain (p = 0.01), ODI (p = 0.01), less blood loss (p < 0.00 001), shorter hospital stay (p < 0.00 001), and early ambulation (p < 0.00 001). However, there were no significant differences in the operation time (p = 0.75), fusion rate (p = 0.26) and complication rate (p = 0.17). Conclusion: MIS-TLIF is comparable with open-TLIF in terms of functional outcome and fusion rate, moreover, it has less blood loss, earlier rehabilitation and shorter hospitalization.

A180: Patient Reported Outcomes of Lumbar Decompression Surgery

Geriant Sunderland¹, Mitchell Foster¹, Sujay Dheerendra², Robin Pillay¹

¹The Walton Centre, Liverpool - United Kingdom ²Centre for Spinal Studies, The Robert Jones and Agnes Hunt Orthopaedic Hospital, Oswestry - United Kingdom

Background: Lumbar decompression surgery is a well-established surgical strategy with proven efficacy in numerous large-scale systematic reviews and meta-analyses. Patient Reported Outcome Measures (PROMs) based on core outcome sets are increasingly recognised as vital for surgeons and healthcare providers to appreciate effectiveness of interventions from a patient perspective as well as standardising assessment and promoting service improvement. The aim of the study was to assess the efficacy of lumbar decompression surgery based on PROMs. Methods: Between January 2012 and October 2016, Lumbar decompression surgeries were undertaken for degenerative lumbar spine disease on 2838 patients in a single centre. Data was collected routinely from patient-completed questionnaires at baseline, 3 months, 1 year and 2 years post-operatively on the Spine Tango registry. Median age of patients was 61 years (71-49). All primary (n = 1983) and revision (n = 855) decompression surgeries performed during this time period were included for analysis. Spine Tango international spine registry core outcome measures index (COMI) for low back pain 2011 version, a validated multidimensional questionnaire that investigates five dimensions in low back pain, Scored from 0 (best) to 10 (worst) was used. Patient demographics and surgical details were collected routinely in addition to patient questionnaires. Data was analysed using Microsoft Excel 2010 and GraphPad Prism 7. Results: Completion rate of questionnaires was 83%. The majority of surgeries were performed with peripheral pain relief as the patients’ stated goal (57%) followed by functional improvement (26.4%). The operation was rated as having ‘helped’ or ‘helped a lot’ by 71% of respondents at 3 months and 67% at both 1 year and 2 year follow up. Median COMI score (scored 0 - best to 10 - worst) was 8.3 at baseline, improving to 5.15 at 3 months (p < 0.001), 5.2 at 1 year (p < 0.001) and 4.9 at 2 years (p < 0.001). Mean leg pain/back pain scores (visual analogue score 0-10) improved significantly (p < 0.005) from pre-op to 3 months, 1 year and 2 years follow-up. Interestingly the percentage of patients reporting back pain doubled from pre-operative (20%) to 2-year (40%) follow-up (p < 0.005). Quality of life (QoL) rating improved post-operatively; 29% of patients rated QoL ‘moderate’, ‘good’ or ‘very good’ pre-operatively, improving to 74% at 3 months (OR = 0.142, 95%CI 0.125-0.161). This was maintained at 1 year (71%, OR = 0.165, 95%CI 0.15:0.187) and 2 year follow up (73%, OR = 0.153, 95%CI 0.133-0.176). 6.4% of patients had undergone revision surgery at the end of 2 years. All the results were significantly (p < 0.005) inferior in patients undergoing revision surgery compared to primary surgery. Conclusions: Lumbar decompression has impressive efficacy in the improvement of symptoms and QoL for patients with degenerative lumbar stenosis. As expected the outcomes were inferior in revision surgery. Much of the improvement a patient will experience will be present at 3 months and is sustained for at least 2 years. The number of patients reporting back pain as most troubling doubled at 2-year follow-up. PROMs are an extremely useful method for assessing treatment efficacy and demonstrate excellent patient satisfaction from this surgery and can be used as a tool in counselling prospective patients regarding surgery.

A181: The Effectiveness of Lumbar Spinous Process-Splitting Laminectomy Versus Conventional Laminectomy for Lumbar Spinal Stenosis

Hirokazu Inoue¹, Atsushi Kimura¹, Hideaki Watanabe¹, Teruaki Endo¹, Ryo Sugawara¹, Yasuyuki Shiraishi¹, Katsushi Takeshita¹

¹Department of Orthopaedics, Jichi Medical University, Shimotsuke - Japan

Introduction: Lumbar spinous process-splitting laminectomy is less invasive because of less paraspinal muscle damage and is becoming common as a minimally invasive surgery. But few papers have prospectively demonstrated the difference in patient satisfaction between lumbar spinous process-splitting laminectomy and conventional laminectomy for lumbar spinal stenosis. In this study, we researched the difference between lumbar spinous process-splitting laminectomy and conventional laminectomy, and focused on patient satisfaction. Material and Methods: Fifty-seven patients underwent spinous-splitting laminectomy or conventional laminectomy for lumbar spinal stenosis in Jichi Medical University hospital from August 2008 through March 2014. The exclusion criteria were: over 75 years old, rheumatoid arthritis, dialysis, over 20 degrees in Cobb angle, and any history of spinal surgery. We evaluated the numeric rating score (NRS) of low back pain, lower limb pain, lower limb numbness, Roland-Morris Disability Questionnaire (RDQ), and 36-Item Short Form Survey (SF-36). Results: The follow-up rate was 84% at 2-year follow-up. We excluded two patients who received reoperation during two years. In total there were 46 patients (29 male, 17 female) with a mean age of 66.7 years. Conventional laminectomy was performed on 25 patients, and spinous-splitting laminectomy on 21 patients. The spinous-splitting laminectomy group showed significantly higher NRS of low back pain and lower leg pain, RDQ at 2-year follow-up, baseline SF-36 scores in physical functioning, bodily pain, role-emotional, and role-physical at 1-year and 2-year follow-up than the conventional laminectomy group. Conclusion: Compared with conventional laminectomy, spinous-splitting laminectomy results in significant improvements in low back pain, lower limb pain, physical functioning, bodily pain, role-emotional, and role-physical at 2-year follow-up. We suggest this surgery is less invasive and provides high patient satisfaction.

A182: A New Score Predicting Clinical Outcome Following Lumbar Spine Surgery for Degenerative Disc Disease

Ehab Shiban¹, Angelika Kellersmann¹, Youssef Shiban², Bernhard Meyer¹

¹Department of Neurosurgery, Technical University of Munich, Munich - Germany ²Clinical Psychology and Psychotherapy, University of Regensburg, Regensburg - Germany

Introduction: This study was performed to create and validate a scoring system to predict unfavourable outcome following first-time elective lumbar spine surgery for degenerative disc disease Material and Methods: A Prospective cohort study of 150 patients was performed. 100 patients were assigned to a test group and 50 patients to a validation group. In the test group, 16 pre-treatment factors including age, gender, education level, relationship status, presents of previous psychiatric disorders, the Anxiety Sensitivity Index, State Anxiety Inventory, Trait Anxiety Inventory, Depression Scale, Berliner Social Support Scale, PTSS-10 for PTSD symptoms, SF-36 physical and mental composite scores, visual analogue scale for pain, EuroQOL-5D and Oswestry Disability Index (ODI) were prospectively analysed. Unfavourable outcome was defined as less than 15 points improvement of ODI one year postoperatively. Results: A multivariate logistic regression analysis identified age (p = 0.031), trait anxiety (p = 0.020), depression (p = 0.022) and SF-36 physical (p = 0.002) and mental composite scores (p = 0.004) and ODI (p = 0.049) as predictors of unfavourable outcome one year postoperatively. These factors were included in the score. The total risk score was the sum of the 6 factor scores and ranged from 0 to 12 points. Three prognostic groups were designed. Group A: 0-3 points for favourable outcome, Group B: 4-5 points for probable unfavourable outcome and group C: 6-12 points for unfavourable outcome. In the validation group 100%, 56% and 86% of patients in groups A, B and C were successfully predicted, respectively (p = 0.026). Conclusion: Clinical outcome following elective spine surgery for degenerative disease is influence by physical and mental factors. This newly developed score appears reproducible as most cases in the validation group were successfully identified. This new score can help identify possible patients with unfavourable outcome. Thereby concomitant psychosomatic treatment may me initiated.

A183: Two Levels Lumbar Disc Disease Treated by Hybrid PDL and ALIF Construct: A Prospective Series About 41 Patients

Stéphane Litrico¹, Antoine Gennari², Florent Pennes¹, Fabien Almairac¹, Serge Declemy³, Philippe Paquis¹

¹Neurosurgery, Spine Unit CHU Pasteur, Nice - France ² Institut de Biomécanique Humaine Georges Charpak, Paris - France ³Vascular Surgery CHU Pasteur Nice, Nice - France

Introduction: Surgical treatment of single level degenerative disc disease (DDD) is often purposed when conservative treatment failed. However, a part of patients with chronic low back pain presents two-level DDD. In these cases, surgical treatment is still discussed. Fusion may lead to adjacent segment disease while two-level arthroplasty seems to bring poor results. The aim of our study is to evaluate clinical and radiological efficiency of hybrid construct combining total disc arthroplasty at one level and anterior fusion at the other for treatment of two-level DDD. Material and Methods: We present a prospective observational monocentric study. Forty-one patients were included for surgical treatment of two-level DDD using hybrid construct between January 2008 and December 2016. Mean age was 41y/o (range 20-51). All patients were treated for L4L5/L5S1 DDD with total disc replacement (TDR) at L4L5 and anterior lumbar interbody fusion (ALIF) at L5S1. Ten patients had prior surgery at one level at least for disc herniation. All patients received conservative treatment including anti-inflammatory drugs and intensive rehabilitation for at least one year and failed to improve. Low back pain was the main symptom and patients with true radiculopathy were not included. Mean follow up was 3.8 years (1-9). Perioperative data were collected including complications. Primary functional outcome was assessed with Oswestry disability index (ODI) measured before and after surgery. Visual analog scale (VAS) for lumbar and radicular pain and SF-12 were also measured. Placement, centering and mobility of the prosthesis and quality of fusion of the ALIF were assessed with neutral and dynamic X-rays. Clinical and radiological measurements were performed before surgery and at 1, 3, 6 and 12 months postoperative and then annually. Results: Preoperative ODI was 43 with a significant improvement at 6 months (-15 pts), 1 year (-21 pts) and at the last follow-up (-22 pts). 70% of patients had an ODI improvement of more than 25% at 1 year. The preoperative lumbar VAS of 6.7 improved significantly from 3 months (-2.7 pts) and continues to decrease to 1 year (-3.7 pts). The preoperative radicular VAS of 3.8 decreased significantly to 1 year (-1.8 pts). Improvement of SF 12 is significant at 6 months. The overall lordosis (50° to 54°) and L4-S1 (31.4° to 37°) were increased but only the L5-S1 lordosis was significant (7.6° to 13.6°). The mean mobility of the prosthesis at one year was 6.8° (0-15). Only 2 prostheses had a centering failure > 4 mm. The fusion rate at L5S1 was 100% at 1 year. We didn’t observe any radiological or clinical adjacent segment disease at the last follow-up. The overall rate of complications was 14%. Conclusion: Hybrid construct combining TDR and ALIF for the treatment of two-level DDD seems to be a reasonable option with favorable clinical and radiological outcomes and a low rate of complications.

The improvement seems significant from 6 months with a continuation up to 1 year.

A184: A Potential Influence of a Screw Design on Loosening Rate in Patients With Degenerative Diseases of a Lumbar Spine

Andrey Bokov¹, Anatoliy Bulkin¹, Sergey Mlyavykh¹, Alexander Aleynik¹, Marina Kutlaeva²

¹Department of Neurosurgery of Privolzhskiy Federal Research Center, Nizhny Novgorod - Russian Federation ²Department of Roentgenology of Privolzhskiy Federal Research Center, Nizhny Novgorod - Russian Federation

Introduction: It has been reported that screws design may have an impact on pedicle screws fixation stability, however the data concerning potential clinical effect remain controversial. The objective of this study is to estimate potential effect of screw design on rate of screw loosening in patients with degenerative diseases of a lumbar spine. Materials and Methods: This is a retrospective evaluation of 215 spinal instrumentations performed in case of degenerative diseases of a lumbar spine. Preoperatively patients underwent CT examination and bone density was measured in Hounsfield units (HU). Pedicle screw fixation was used to treat patients either as a stand-alone technique or in combination with interbody fusion (patients with TLIF ALIF, DLIF were enrolled). If indicated, a decompression of nerve roots and spinal cord was performed. Patients with suboptimal placement of pedicle screws and interbody implants were excluded from this study. Patients who underwent degenerative deformity correction and pelviosacral fixation were not included in this study. The follow up period was 18 months; patients underwent CT at 6, 12, 18 months of a follow-up period. Criterion for screw loosening was a radiolucent zone of at last 1 mm around a screw. Cases with screws loosening were registered and logistic regression analysis was used to assess the relationship between complication rate and potential factors that potentially influence stability of screws. Results: The following factors were taken into account assessing potential impact on screws stability: external diameter of a screw, core diameter and difference between inner and outer diameter, conic versus cylinder design, standard versus buttress thread design and helical pitch. Non-implant related factors taken into account were bone density measured in HU, the extension of fixation (number of fixed levels), presence of segments without fusion within instrumented zone; bilateral facet joints removal and laminectomy to achieve decompression and type of fusion (TLIF versus broad cage with solid bone in case of D-LIF and ALIF). The rate of screw loosening was declining with greater bone radiodensity and bigger outer diameter of a screw conversely the rate of complication was growing with the increase in core diameter, greater helical pitch and greater extension of fixation. The influence of other factors was statistically insignificant. The parameters of general logistic regression for implant instability rate were: B0 = −33 071, p = 0,5341 (insignificant); B1 for bone density = −0,0311, p < 0,0001, Odds ratio per unit change (OR) = 0,9694; B2 for external screw diameter = −61 007, p = 0,0312, OR = 0,0022; B3 for number of fixed levels = 11 245, p < 0,0001, OR = 30 788; B4 for core diameter = 64 208, p = 0,0265, OR = 614,5056; B5 for helical pitch = 44 246, p = 0,0183, OR = 834 806. Goodness of fit of general model - Chi-square = 993 653, p < 0,0001. Correct classification of cases – 81,40%, specificity and sensitivity of estimated model achieve 88,97% and 68,35% respectively. Conclusions: The results of the analysis show that pedicle screws fixation depends not only on bone quality and specific features of surgical intervention but is also influenced by characteristics of the pedicle screws. Especial attention towards the choice of implants should be taken in patients who are at risk of implant instability development because screw design matters.

Surgical Complications - Avoidance

A185: Does Parkinson’s Disease Significantly Affect Immediately Post-Operative Outcomes in Patients Undergoing Elective Lumbar Surgery?

Andrew Chung¹, Sean Mitchell², Joshua Hustedt², Norman Chutkan²

¹Mayo Clinic, Department of Orthopedic Surgery, Phoenix - United States ²Department of Orthopaedic Surgery, University of Arizona, Phoenix - United States

Introduction: Parkinson’s disease is associated with osteoporosis, postural abnormalities and subsequent spinal deformities. While increased complication rates and poorer hospital outcomes have been reported in patients undergoing elective spine surgery in this growing population, the literature is limited to smaller studies. The purpose of this study is to assess inpatient outcomes in patients with Parkinson’s disease undergoing elective lumbar surgery for both deformity and degenerative lumbar diseases. Material and Methods: Patients with Parkinson’s disease undergoing elective lumbar spinal surgery for both thoracolumbar deformity and degenerative lumbar disease between 2001-2012 were identified in The National Inpatient Sample. Mean length of stay and all post-operative complications were recorded. Complications were categorized into major and minor complications. Major complications included cardiac complications, septic shock, stroke, and pulmonary embolism. Minor complications included deep vein thrombosis, pulmonary complications, surgical complications, post-operative anemia, and genitourinary complications. The number of transfers to a skilled facility was also recorded. 21 758 patients with Parkinson’s disease undergoing elective lumbar surgery for both deformity and degenerative lumbar disease were identified and compared to 2 765 766 patients without Parkinson’s disease undergoing the same surgeries. Results: Mean age of patients with Parkinson’s disease was 70.4 (SD = 8.3) compared to 57.9 (SD – 14.7) in patients without (p < 0.001). Major complications were increased in the Parkinson’s cohort (2.0% compared to 1.1%; p < 0.001). In the Parkinson’s cohort, mean length of stay was mildly increased (4.4 days, SD = 3.7 compared to 3.7 days SD = 3.1; p < 0.001), however, the rate of patients requiring transfer to a skilled facility after discharge was more than doubled (42.7% compared to 15.7%; p < 0.001). Conclusion: In the immediate post-operative period, Parkinson’s disease may be associated with an increase in immediate post-operative complications. A substantial increase in the need for transfer to a skilled facility post-operatively should be part of the pre-operative planning.

A186: Effect of Transfusing Red Blood Cells Stored More Than 28 Days on Spine Surgery Outcomes

Taylor Purvis¹, C. Rory Goodwin², Camilo Molina¹, Steven M. Frank³, Daniel Sciubba¹

¹Department of Neurosurgery, Johns Hopkins University School of Medicine, Baltimore, Maryland, - United States ²Department of Neurosurgery, Duke University Medical Center, Durham - United States,³ Department of Anesthesiology, Johns Hopkins University Medical Center, Baltimore, Maryland, - United States

Introduction: Despite retrospective studies that have shown that longer packed red blood cell (PRBC) storage duration worsens patient outcomes, randomized clinical trials have found no difference in outcomes. However, no studies have examined the impact of giving the oldest blood (28 days-old or more) on morbidity within spine surgery. Our objective in this study was to describe the association between storage duration of PRBCs and perioperative adverse events in patients undergoing spine surgery at a tertiary care center. Materials and Methods: The surgical administrative database at our institution was queried for patients transfused with PRBCs who underwent spine surgery between December 4, 2008 and June 26, 2015. Patients undergoing spinal fusion, tumor-related surgeries, and other identified spine surgeries were included. Patients were divided into two groups based on storage duration of blood transfused: exclusively ≤ 28 days’ storage or exclusively > 28 days’ storage. The primary outcome was composite in-hospital morbidity, which included: (1) infection, (2) thrombotic event, (3) renal injury, (4) respiratory event, and/or (5) ischemic event. Results: In total, 1,141 patients who received a transfusion were included for analysis in this retrospective study; 710 were transfused exclusively with PRBCs ≤ 28 days’ storage and 431 exclusively with PRBCs > 28 days’ storage. Perioperative complications occurred in 119 patients (10.4%). Patients who received blood stored for > 28 days had higher odds of developing any one complication (odds ratio [OR] = 1.82; 95% confidence interval [CI], 1.20-2.74; P = 0.005) even after adjusting for competing perioperative risk factors. Conclusion: Blood stored for > 28 days is independently associated with higher odds of developing perioperative complications in patients transfused during spinal surgery. Our results suggest that blood storage duration may be an appropriate parameter to consider when developing institutional transfusion guidelines that seek to optimize patient outcomes.

A187: Pre-Operative Functional Status and Comorbidity Burden are Risk Factors for Delay in Surgery in Patients Undergoing Elective ACDF

Andrew Chung¹, Sean Mitchell², Joshua Hustedt², Robert Waldrop³, Norman Chutkan², Dennis Crandall³

¹Mayo Clinic, Department of Orthopedic Surgery, Phoenix - United States ²Department of Orthopaedic Surgery, University of Arizona, Phoenix - United States ³Sonoran Spine, Phoenix - United States

Introduction: Anterior Cervical Discectomy and Fusion (ACDF) is well-tolerated by most patients and commonly necessitates only a short hospital admission. Surgical delay after hospital admission, however, may result in longer hospital stays, consequently increasing hospital resource utilization. The purpose of this study was to examine the incidence and risk factors for surgical delay after hospital admission in patients undergoing elective ACDF. Material and Methods: A retrospective analysis of the ACS-NSQIP data was performed between 2006-2013. Patients undergoing cervical spine surgery were selected using Current Procedural Terminology (CPT) codes. Emergency procedures, infections, tumor cases, and patients who were dialysis or ventilator dependent, were excluded to isolate a typical elective patient population. A surgical delay was defined as surgery that occurred one day or later after initial hospital admission. A total of 898 surgical delays were identified. Differences between the non-delayed and delayed cohorts were evaluated with univariate analysis. Multivariate logistic regression was then performed to identify risk factors for surgical delay. Results: There were a total of 898 (4.8%) surgical delays out of 18 596 patients undergoing elective ACDF between 2006-2013. Mean age was similar between the non-delayed and delayed cohort (53.4 compared to 54.4). Multivariate analysis found impaired functional status (OR 6.58; 95% CI 5.14 to 8.41; p < 0.001), coagulopathy (OR 2.92; 95% CI 1.97 to 4.31; p < 0.001), ASA class ≥ 3 (OR 1.68; 95% CI 1.45 to 1.95; p < 0.001), and chronic steroid use (OR 1.44; 95% CI 1.04 to 1.98; p = 0.027) as independent predictors of delayed surgery after hospital admission. A surgical delay was associated with a higher rate of post-operative major adverse events (8.4% compared to 2.1%; p < 0.001), death (1.1% compared to 0.2%; < 0.001) and a greater than three-fold increase in total length of stay (7.08 days compared to 1.65 days; p < 0.001). Conclusion: Impaired pre-operative functional status, and a higher comorbidity burden are significant risk factors for surgical delay following hospital admission in patients undergoing elective ACDF.

A188: Pre-Operative Functional Status and Comorbidity Burden are Risk Factors for Delay in Surgery in Patients Undergoing Elective Posterior Lumbar Fusions

Sean Mitchell¹, Andrew Chung², Joshua Hustedt¹, Robert Waldrop³, Norman Chutkan¹, Dennis Crandall³

¹Department of Orthopaedic Surgery, University of Arizona, Phoenix - United States ²Mayo Clinic, Department of Orthopedic Surgery, Phoenix - United States ³Sonoran Spine, Phoenix - United States

Introduction: The number of elective posterior lumbar fusions performed annually is increasing. A delay in surgery after hospital admission may result in increased hospital resource utilization. Limited data exists on the incidence and risk factors for surgical delay after hospital admission in patients undergoing elective posterior lumbar fusion. Material and Methods: A retrospective analysis of the ACS-NSQIP data was performed between 2006-2013. Patients undergoing lumbar surgery were selected using Current Procedural Terminology (CPT) codes. Emergency procedures, infections, tumor cases, revision surgeries, were excluded to isolate an elective patient population. A surgical delay was defined as surgery that occurred one day or later after initial admission. Out of 15 618 cases, a total of 338 surgical delays were identified. Differences between the non-delayed and delayed cohorts were evaluated with univariate analysis. Multivariate logistic regression was then performed to identify risk factors for surgical delay. Results: There were a total of 338 (2.2%) surgical delays between 2006-2013. Mean age was similar between the non-delayed and delayed cohort (60.6 compared to 61.3). Multivariate analysis identified impaired functional status (OR 5.73 95% CI 4.06 to 8.09; p < 0.001), weight loss > 10% in last 6 months (OR 3.85; 95% CI 1.43 to 10.38; p = 0.008), history of congestive heart failure (OR 3.58; 95% CI 1.19 to 10.76; p = 0.023), bleeding disorders (OR 2.51; 95% CI 1.46 to 4.33; p = 0.001), and ASA class ≥ 3 (OR 1.64; 95% CI 1.30 to 2.07; p < 0.001), as independent predictors of a delay in surgery after hospital admission. A surgical delay was associated with higher rate of post-operative major adverse events (8.3% compared to 4.8%; p = 0.005) and a greater than two-fold increase in total length of stay (9.25 days compared to 3.75; p < 0.001). Conclusion: Pre-operative optimization of comorbidities seems to be the most important factor in preventing surgical delay after hospital admission in patients undergoing elective posterior spinal fusion.

A189: Relative Decrease in Blood Hemoglobin Level is Associated With Morbidity in Spine Surgery Patients

Taylor Purvis¹, C. Rory Goodwin², Camilo Molina¹, Steven M. Frank³, Daniel Sciubba¹

¹Department of Neurosurgery, Johns Hopkins University School of Medicine, Baltimore, Maryland, - United States ²Department of Neurosurgery, Duke University Medical Center, Durham - United States ³Department of Anesthesiology, Johns Hopkins University Medical Center, Baltimore, Maryland, - United States

Introduction: Several studies in gastrointestinal and cardiac surgical fields have demonstrated the importance of considering delta hemoglobin (ΔHb) in the formula for appropriate perioperative blood transfusions, where ΔHb is the difference between a patient’s preoperative Hb and nadir Hb concentration during a hospital stay. In this study, we sought to determine the perioperative clinical outcomes associated with percent ΔHb as an independent factor among spine surgery patients. Materials and Methods: Patients who underwent spine surgery at our institution between December 4, 2008 and June 26, 2015 were eligible for this retrospective study. Patients undergoing the following procedures were included: atlantoaxial fusion, subaxial anterior cervical fusion, subaxial posterior cervical fusion, anterior lumbar fusion, posterior lumbar fusion, lateral lumbar fusion, excision of intervertebral disc, and excision of spinal cord lesion. Data on intraoperative transfusion were obtained from an automated prospectively collected anesthesia data management system. Data on postoperative hospital transfusions were obtained through a Web-based intelligence portal. Percent ΔHb was defined as: ((first Hb - nadir Hb)/first Hb) x 100. Clinical outcomes included in-hospital morbidity and length of stay associated with percent ΔHb. Results: A total of 3,949 patients who underwent spine surgery were identified. A total of 1204 patients (30.5%) received at least one unit of packed red blood cells (PRBC). The median nadir Hb level was 10.6 g/dL (IQR, 8.7-12.4 g/dL), yielding a mean percent ΔHb of 23.6% (SD = 15.4%). Perioperative complications occurred in 234 patients (5.9%) and were more common in patients with a larger percent ΔHb (P = 0.017). Hospital-related infection, which occurred in 60 patients (1.5%), was also more common in patients with a greater percent ΔHb (P = 0.001). Conclusion: Percent ΔHb is independently associated with a higher risk of developing any one perioperative complication and hospital-related infections. Our results suggest that percent ΔHb may be a useful measure to identify patients at risk for adverse perioperative events.

A190: The Effect of Lumbar Fusion With Instrumentation in Severely Osteoporotic Patients Using Teriparatide

Yutaka Nakamura¹, Masayoshi Kanai¹, Ken Mine¹, Satoshi Asano¹

¹Saitama Spine Center, Higashi-Saitama General Hospital, Saitama Satte - Japan

Introduction: Osteoporosis is one of the major risks in spinal instrumentation surgery. However, recently spinal instrumentation surgery for elderly patients with osteoporosis is increasing, because of an increase in degenerative scoliosis and kyphosis, and the spread of minimally invasive procedures along with improvements in implants such as percutaneous pedicle screws. Relevant to this trend, the efficacy of teriparatide for increasing vertebral bone mineral density (BMD) and for the promotion of bone union are well known, so the administration of teriparatide before and after lumbar spinal fusion is being tried for patients with severe osteoporosis. However, when lumbar spinal fusion is performed using spinal instrumentation, it is impossible to measure lumbar BMD after surgery so it is difficult to evaluate the effect of teriparatide. The purpose of this study is to retrospectively investigate the effect of the adjunctive administration of teriparatide in lumbar spinal fusion treatment for osteoporotic patients. Material and Methods: Of 251 lumbar fusion recipients between January 2010 and March 2016, 44 received teriparatide for bone mineral density (BMD) -3.3 SD or less (YAM < 62%). The 27 (6 males and 21 females) with minimum 1 year follow-up were studied. Cases included 12 with lumbar spondylolisthesis, 6 with degenerative scoliosis, 5 with post vertebral fracture kyphosis, 3 with lumbar spondylolysis and 1 postoperative adjacent segment disorder. We analyzed lumbar BMD, proximal femoral BMD, total serum type 1 procollagen N-terminal propeptide (P1NP), JOA scores, at 6 months and 1 year, non-union, loosening of Pedicle Screws (PS), early adjacent disc lesions, adjacent vertebral fractures and reoperations. Results: Average lumbar BMD (g/cm²) was 0.728 preop. Femoral BMD was 0.611 preop, 0.595 at 6Mos, and 0.597 at 1 yr. A total P1NP increase of 10 μg/ L or more from the baseline at one or three months after the commencement of teriparatide administration, considered the effect of teriparatide, was seen in 26 of 27 cases. The mean JOA score was 9pts (pre-op) and 20 and 20 at 6 and 12 months respectively. There were 2 nonunions at 6mos, and 2 at 1 yr, and 2 cases of PS loosening at 1 yr. As of final follow up, there was one adjacent disc degeneration, two adjacent vertebral body fractures, and one reoperation. Conclusion: In osteoporotic patients, where promotion of bone fusion is the key to the prevention of instrumentation failure, the effects of teriparatide have been reported BMD increase effect, fracture prevention effect, bone fusion promotion effect, screw holding strength enhancement effect. In this study of combined lumbar spinal fusion for severe osteoporosis patients, with the adjunctive administration of teliparatide, results were relatively good and were maintained after 1 year postoperatively. However the effect of teriparatide on bone metabolism is expected to be vary greatly between individuals. Increased P1NP at one month after administration, has been shown to predict an improved lumbar BMD after 12 months. In our study, P1NP was determined in 25 of 26 cases to be effective as an early indicator of the effect of teriparatide administration during the period before and after surgery.

Degenerative Cervical

A191: Surgical Technique for Cervical and Cervicothoracic Hemivertebrae Resection. One-Year Follow up of Seven Patients in an IV Level Orthopedics Children’s Institute

Carlos Montero¹, Fernando Alvarado¹, Wilmer Godoy¹, David Meneses¹, Viviana Vela¹, Carlos Marítnez¹

¹Department of Spine Surgery, Roosevelt Institute, Bogotá - Colombia

Introduction: The most frequent congenital malformation of the spine is hemivertebra; they could be segmented or unsegmented regarding its anatomical relation with adjacent intervertebral disc. Cervical spine anomalies are infrequent and they could appear as lone malformation or as part of a syndromatic entity but its prevalence is unknown. Surgical indication depends on the progression of the curve, the presence of hemivertebra producing sagittal imbalance and the progression risk. Hemivertebrectomy allows for redundant defect splitting and spine fixing; however it is much more challenging for the surgeon and more serious complications could emerge. Materials and Methods: A retrospective observational study comparing patients who underwent one-stage anterior plus posterior approach hemivertebrectomy with sublaminar hook fixation between 2008 and 2013 in a IV level orthopedics children institution were performed. A non-probabilistic sampling was obtain and sociodemographic, surgical and postoperative variables were analyzed. Results: Combined two-staged (anterior-posterior) surgery was performed in all patients. First, vertebral body is removed by anterior technique using an oblique approach through the neck choosing the side of the convexity. Five to seven days later, posterior approach is done under neurological surveillance. Laminectomy is performed preserving articular processes, and then pedicle is resected protecting vertebral artery and nerve roots. Finally, spine instrumentation is performed using sublaminar hooks in order to correct the deformity. Seven patients were found who met the inclusion criteria, three males and four females. Mean age at diagnosis was 4,3 years and for surgery 5,2 years old. Mean weight of the patients at surgery was 17,6 Kg. Preoperative frontal Cobb angle average was 27° and 13,7° for sagittal plain. Average measurements after procedure were 14,5° and 9° respectively. Correction was maintained in all patients in the one year follow up. It only appeared one transitory neurological complication because of median nerve palsy which resolved completely 3 months after with physical therapy. Conclusion: We described a new surgical approach to a challenging surgical problem. Using two-staged surgical management, cervical hemivertebrae were successfully removed and long-lasting correction achieved without major complications.

A192: A Novel Skull Clamp Positioning Device to Obtain Quantitative Cervical Sagittal Alignment During Posterior Cervical Surgery

Nodoka Manabe¹, Takachika Shimizu¹, Keisuke Fueki¹, Masatake Ino¹, Testu Tanouchi¹, Kanako Itoh¹, Masatoshi Ono¹

¹Department of Orhopaedic Surgery, Gunma Spine Center (Harunaso Hospital), Takasaki, Gunma - Japan

Introduction: A good, quantitative cervical sagittal alignment and axis during posterior cervical surgery is largely dependent on the positioning technique, because maneuver of the head-neck position is greatly influenced by the skill of the operator. Skull fixation system, for example mayfield and halo, is a standard tools for the posterior cervical surgery. However, it is difficult to get quantitative cervical alignment and axis using the such devices. We have developed a new skull clamp system to obtain intended head-neck position safely and quantitatively. The purpose of this study is to analyze the utility of the device for a quantitative cervical sagittal alignment during surgery. Material and Methods: This study included 55 patients (mean age, 65.6 ± 10.2 years) with cervical spondylotic myelopathy who underwent laminoplasty. The positioning device has a scale to adjust the head-neck position. Before surgery, the patient was placed in the prone position in accordance with preplanned head-neck sagittal alignment (position A). During surgery, the head was rotated sagittally and the head-neck position was changed to the military tuck position using our device to widen the interlaminar space (position B). After completing the decompression procedure, the head was rotated back to the initial preplanned position again (position C). The angles (C0-C1, C1-C2, and C2-C7) were measured on lateral radiographs taken at positions A, B, and C, respectively. The cervical range of motion from position A to B (dC0-C1, dC1-C2, and dC2-C7) was calculated and differences between each time point were compared using the paired t-test. Results and Discussion: Our proposed positioning device allowed us to obtain adequate, quantitative cervical sagittal alignment during posterior cervical surgery. The cervical range of motion for the C0-C7 angle (position A to B) was approximately 27° with a ratio of 1:1:1 for dC0-C1: dC1-C2: dC2-C7. There were no clinically significant differences observed between pre- and postoperative angles. Conclusions: Sagittal neck position was quantitatively changed during posterior cervical surgery using this device, enabling adequate final cervical sagittal alignment identical to the preplanned neck position.

A193: Return to Sport After Surgical Procedure Versus Conservative Treatment for Cervical Disc Herniation: A Systematic Review And Meta-Analysis

Muralidharan Venkatesan¹, Mutaz Yousef², Nasir Quraishi²

¹The Centre for Spinal Studies and Surgery, Queen’s Medical Centre, Nottingham - United Kingdom ²Guru Gobind Singh Medical College, Faridkot - India

Background: A cervical disc herniation (CDH) is the second most common intervertebral disc herniation, and it can lead an athlete to end their career because of this condition or its symptoms. Treatment possibilities are conservative or operative. This paper reviews the recent literature on return to sports (RTS) in professional athletes after a cervical disc herniation treated either conservatively or operatively. Materials and Methods: An electronic (computer-based) literature search of Cochrane, Medline, Ovid, PEDro, Science Direct, PubMed, Journal of Neurosurgery and Spine databases (from 1970 to August 7, 2017) was performed using keywords related to ‘cervical disc herniation’ and ‘return to sports or play.’ The guidelines for the Preferred Reporting Items for Systematic Reviews and Meta- Analyses (PRISMA) were used in the design of this systematic review. The Downs and Black scale (score 0-16) was used to assess the methodological quality of each included study. Results: The search strategy resulted in 6 articles. Four studies were rated as ‘moderate’ and 2 as ‘low quality.’ Three studies reported on RTS after surgery whilst the other 3 articles investigated RTS after surgical versus conservative treatments. Return to Sports in both surgical (N = 150) and non-surgical (N = 62) groups was high at 72.2%. However, the RTS rate in the surgical group (76.7%) was significantly higher than the conservative (61.2%; 95% CI 1.1 – 3.92; P = 0.029). Meta-analysis of the three studies that directly compared surgical versus conservative treatment revealed that the difference of odds of returning to sport did not reach statistical significance. When all six studies were pooled, it was observed that those undergoing surgery had approximately twice the odds (2.08 95% confidence interval 1.1-3.92) of RTP compared to those managed conservatively. This difference was statistically significant (p = 0.028 Chi-squared test). Conclusion: The comparison between surgical and non-surgical treatments for CDH in professional athletes showed significant differences regarding RTS favouring surgical treatment. This study would be useful to those treating professional athletes with cervical disc herniations and could help with prognostication of return to professional sports.

A194: Trends And Costs of Anterior Cervical Discectomy and Fusion: A Comparison of Inpatient and Outpatient Procedures

Christopher Martin¹, Anthony D’Oro², Zorica Buser², Jim Youssef³, Jong-Beom Park⁴, Hans-Jeorg Meisel⁵, S. Tim Yoon⁶

¹Department of Orthopaedics, University of Minnesota, MInneapolis - United States ²Department of Orthopaedic Surgery, University of Southern California, Los Angeles - United States ³Spine Colorado, Colorado - United States ⁴The Catholic University of Korea School of Medicine, Uijongbu - Korea, Republic ⁵Department of Neurosurgery, Bergmannstrost Hospital, Halle - Germany ⁶Department of Orthopaedics, Emory University School of Medicine, Atlanta - United States

Introduction: The safety and costs of outpatient discharge after single level anterior cervical discectomy and fusion (ACDF), relative to inpatient admission, have not been well established. Thus, our objective was to identify the trends in utilization of outpatient discharge for ACDF, between 2007 and 2014, and to compare the costs and incidence of complications against a cohort of inpatients. Material and Methods: We retrospectively reviewed 18 386 patients from the PearlDiver database from between 2007 and 2014. Discharge status was determined from billing codes. The total cost of all procedures and diagnostic tests, was determined for the global period from the time of diagnosis up until 90-days post-operatively, and the incidence of complications was recorded for 30-days. Results: The proportion of outpatient discharges was stable around 20% from 2007 to 2014 (range17-23%). The mean 90-day cost was lower for outpatients ($39 528 v. $47 330) but reimbursement fell nearly 1/3 from 2007-2014 for both groups, and the difference between the two narrowed over time ($13 745 difference in 2008, to $3,834 in 2014). Outpatients had a lower incidence of overall 30-day complications (9.5% v. 18.6%, p < 0.0001), but were also significantly less comorbid (mean Charlson comorbidity index 2.32 v. 3.85, p < 0.001). Older patient age, obesity, cardiac, renal, and pulmonary comorbidity were each more common in the inpatients (p < 0.05 for each). Conclusion: Outpatient discharge after ACDF is a viable treatment option with a reasonable safety profile and decreased costs relative to inpatient admission. Appropriate patient selection is key, and the standard of care nationally for the comorbid patient remains inpatient admission. The economic trends and epidemiologic data presented here should be useful for health policy decisions.

A195: Racial Disparities in Perioperative Outcomes Following Cervical Spine Fusion: An Analysis of the 2015 Nsqip Database

Julia A. Matera¹, Emily Leary¹, Kaiyi Chen¹, Theodore J. Choma¹, Christina L. Goldstein¹

¹Department of Orthopaedic Surgery, University of Missouri, Columbia - United States

Introduction: Spinal fusion treats many cervical spine disorders and has been shown to positively impact pain, function and health-related quality of life. However, both anterior and posterior cervical spine fusions are associated unique complications which may impact discharge destination, or lead to unplanned reoperations or readmissions. Complication rates following cervical spine fusion have been estimated to range from 11 to 38%. While prior investigators have examined the impact of patient and surgery-related variables on perioperative outcomes and complications following cervical spine fusion, none have included race in their analysis. The purpose of this study, therefore, is to examine the impact of race on discharge destination, complication rates, and unplanned reoperation and readmission rates following cervical spine fusion. Materials and Methods: Patients undergoing cervical fusion were selected from the 2015 American College of Surgeons National Surgical Quality Improvement Program (ACS-NSQIP) database using appropriate Current Procedural Terminology (CPT) codes. Data related to demographics, medical comorbidities, discharge destination and 30-day perioperative outcomes were extracted. Continuous and categorical variables were summarized, and complication, unplanned reoperation and unplanned readmission rates were calculated. Pearson’s χ² test was used to examine the impact of race on discharge destination and risk of experiencing at least one complication, an unplanned reoperation or an unplanned readmission. Statistical analysis was performed using SPSS and R, with a p-value of 0.05 set as the cutoff for statistical significance. Results: A total of 10 531 patients undergoing cervical spine fusion were identified. The patients had a mean age of 37.17 years and were equally divided between males and females (49.24% vs. 50.76%). Almost 80% of the patients were white with the remainder being minority race (20.24%). A disorder of the intervertebral disc with or without myelopathy was the most common indication for surgery (48.79%). 81.71% of the patients underwent anterior cervical fusion. Following surgery, 91.3% of the patients were able to be discharged home. At least one perioperative complication was experienced by 4.2% of the patients, the most common being pneumonia (0.98%) and urinary tract infection (0.72%). Unplanned readmission was required in 3.9% of the patients and an unplanned reoperation was performed on 2% of the patients. Minority race was found to be a predictor of being discharged somewhere other than home (p < 0.0001, OR = 1.988), developing at least one complication (p = 0.0001, OR = 1.526) and undergoing an unplanned reoperation (p = 0.0148, OR = 1.478). Race was not associated with unplanned readmission. Conclusions: This is an examination of the interplay of race on perioperative outcomes of cervical spine fusion. Despite an acceptable complication rate for cervical fusions, minority patients are more likely to experience them, as well as require unplanned reoperations and discharge to somewhere other than home. It may be that further investigations into the impact of other sociodemographic variables on complication development and postoperative care requirements would impact treatment decision making and resource allocation.

A196: The Impact of Outpatient Surgery on the Revision Rates After One Level Anterior Cervical Discectomy and Fusion

Koji Tamai¹, Pranay Patel¹, Christopher Wang¹, Permsak Paholpak¹, Zorica Buser¹, Jeffrey Wang¹

¹Department of Orthopaedic Surgery, Keck School of Medicine, University of Southern California, Los Angeles - United States

Introduction: Anterior cervical discectomy and fusion (ACDF) is one of the most commonly performed spine surgeries, and the frequency has been rapidly increasing as the aging population grows. Spine surgery in an outpatient setting is becoming a preferred option for both patients and providers. Multiple studies have demonstrated that ACDF can be safely performed on an outpatient basis. However, the impact of the outpatient setting on the revision rate following one level ACDF is still not well investigated. Materials and Methods: The Humana private insurance database was analyzed using the PearlDiver software. Patients who underwent one level ACDF from 2007-2015 were collected, and divided into two groups according to the surgical setting; outpatient or inpatient. The incidence of revision surgery (anterior or posterior) within a year was compared between two groups. Subsequently, subgroup analysis was performed based one the patient’s gender, body mass index (BMI), severity of comorbidity using Charleson Comorbidity index (CCI), the presence of mood disorders and the anxiety disorders. Chi-square test was used to calculate the crude Odds ratio (OR). Results: A total of 11 631 patients in the Humana database underwent cervical surgery between 2007 and 2015. Of those, 8728 patients (75.0%) were treated in inpatient and 2903 (25.0%) in outpatient setting. The revision rate using an anterior approach within one year was 3.7% in outpatient and 2.4% in inpatient group (cOR: 1.53, 95% Confidential interval (CI): 1.21 -1.94, p < 0.001). In contrast, the revision rate using a posterior approach was 1.6% in outpatient and 2.1% in inpatient setting (cOR: 0.76, 95% CI: 0.55 -1.05, p = 0.110). Sub-group analysis based on the patient’s BMI, cOR of the anterior revision rate between out- and inpatient subgroup was 2.44 (95%CI: 1.45-4.10, p = 0.002) in patients with BMI > 30, and 1.39 (95%CI: 1.06 -1.81, p = 0.010) in patients with BMI≤30. However, the cOR was similar between the subgroups based on gender (cOR: 1.55 in male, and 1.51 in female), age (cOR: 1.10 in the patients > 65 y.o., and 1.41 in ≤ 65 y.o.), comorbidity (1.77 in the patients with CCI > 2, 1.41 in CCI≤2), mood disorders (1.37 in the patients with mood disorders, 1.61 without mood disorders) and anxiety disorders (1.55 in the patients with anxiety disorders and 1.53 without anxiety disorders). Conclusion: The outpatient setting for one level ACDF negatively impacted the incidence of revision rate within one year when the anterior approach was used. Furthermore, the obesity was a factor contributing to higher odds ratios.

Tumor - Metastatic Disease 2

A197: The Results of Surgical Treatment of the Patients With Neurological Deficit due to Metastatic Lesion of the Cervical Spine Without Histological Verification of the Tumor

Alekandr Tatarintsev¹, Dmitrii Ptashnikov¹, Shamil Magomedov¹, Nikita Zaborovskii¹, Dmitrii Mikhaylov¹

¹Spinal Surgery and Oncology Service, R.R.Vreden Russian Research Institute of Traumatology and Orthopedics, Saint-Petersburg - Russian Federation

Introduction: Spinal metastasis is often accompanied by pathological fractures, which can lead to the development of neurological deficit. Progression of the neurological deficit especially in the cervical spine dramatically reduces the possibility of adjuvant therapy and worsens quality of life. The purpose of research considers the results of surgical treatment of the patients with neurological deficits due the metastatic lesion of the cervical spine without the histological verification of the tumor. Material and Methods: This retrospective study evaluated 120 patients with cervical spine metastasis and progressive tetraparesis without verification of the primary tumor. All patients were selected using the scale SINS and the scale ASIA. Surgery was performed by ablastic removal of the tumor in cases of the solitary metastasis. Patients with data about the multiple lessons was treated by decompression of the neural structures and stabilization of the spine. Preoperative and follow-up radiographic, heath related quality of life parameters (VAS, ODI, SF36), the index of survival Kaplan - Meier were evaluated. Results: After surgery 54% (n = 65, p > 0.05) evaluated complete regression of the neurological deficit and received complete courses of treatment. 32% (n = 38, p > 0.05) evaluated reduce of neurological deficits or they received incomplete courses of treatment. Tetraparesis retained at 14% (n = 17, p > 0.05). According to the results of histological verification was obtained metastases of breast cancer at 56%, lung cancer at 15%, stomach cancer at 8% and were able to receive anti-tumor therapy. The one-year survival rate of these patients is comparable to survival of patients with same pathology, but without pathological fractures and neurological deficit. Conclusion: Surgical treatment of the patients with neurological deficits due to metastatic lesion of the cervical spine without the histological verification of the tumor is reasonable and comparable the one-year survival rate.

A198: Non-Elective Surgery for Patients With Symptomatic Spinal Metastases as a Predictor for Clinical Outcome

Floris van Tol¹, David Choi², FC Oner³, Jorit-Jan Verlaan¹

¹Department of Orthopaedic Surgery, UMC Utrecht - Netherlands ²The National Hospital for Neurology and Neurosurgery, London - United Kingdom

Introduction: Approximately 20% of all oncological patients eventually develop spinal metastases which, if left untreated, often lead to pain and can cause neurological deficits. The extent of neurological symptoms is a known predictor for worse clinical outcome. Patients that are referred in an appropriate and timely fashion can generally undergo elective (planned) surgery, possibly leading to better clinical outcomes. In this study, we assess the influence of non-elective surgery versus elective surgery on clinical outcome measures. Material and Methods: All patients that received surgical treatment for symptomatic spinal metastases between March 2009 and June 2017 were included in the prospective ‘Global Spine Tumor Study Group’ database. Based on the presence of alarming symptoms at admission, patients were treated on an emergency basis (non-elective) or could be scheduled for surgery (elective) at the discretion of the treating spine surgeon. Clinical outcome measures between the two groups were compared. Results: In total, 176 patients received elective surgery and 86 received non-elective surgery. At presentation, the two groups did not differ significantly in age, gender, tumor-histology and the number of affected levels but did differ significantly in the extent of neurological symptoms and ASA-score. Within non-elective and elective patients, respectively, the percentage of percutaneous versus open interventions (12.8% vs 48.3%), median blood loss (400 cc vs 200 cc), median admission time (13 vs 8 days), the percentage of patients with complications (43.0% vs 25.0%) and the percentage of patients that were discharged home (45.1% vs 80.9%) differed significantly. Using multiple regression models this difference remained present independent of tumor prognosis, Karnofsky Performance Score, preoperative mobility and ASA-score. Conclusion: Non-elective surgery within this population leads to worse clinical outcome, independent of known prognostic factors. Improvements in referral patterns could potentially lead to more scheduled care, negating the negative effects of non-elective surgery.

A199: The Outcome of Operative Treatment Modalities in Patients With Spinal Metastases

Jude Cornelius Savarirajo¹, Nur Aida Faruk Senan¹, Boon Beng Tan², Yian Young Teo², Mohammad Zaki Mohd Amin², Chung Chek Wong¹

¹Department of Orthopaedics, Sarawak General Hospital, Kuching - Malaysia ²Department of Orthopaedics, University Malaysia Sarawak, Kota Samarahan - Malaysia

Introduction: Cancer is increasingly becoming a major health problem globally. It is one of the leading causes of medically certified death in the country¹. With an aging population, the numbers are set to rise. One of the complications of cancer is metastases. It is estimated that two thirds of patients will develop bone metastases, with 80% attributed to cancers of the breast, lung and prostate². An oncological study revealed that 29% of bone metastases occurred in the spine followed by 28% in the femur, ³making it one of the commonest complication of cancer. Spinal metastases can be debilitating, causing pain, instability and neurological injuries such as incontinence and paraplegia². Therefore, diagnosing and treating spinal metastases early is important, as well as ascertaining the prognosis. The modified Tokuhashi score has been proven accurate in determining the prognosis and need for palliative surgery⁴. The assessment of quality of life was done using the SF-36 survey, which is currently one of the most widely used quality of life measures⁵. The Karnofsky’s Performance Status was also used⁶. Material and Methods: All patients who presented to a single centre from July 2014 to July 2016 with spinal metastases were included. There were 31 men and 20 women with an average age of 55.1 (range 23 to 98). Each patient was scored using the modified Tokuhashi Score, SF 36 and Karnofsky’s Performance status upon admission. The patients or their next of kin were then interviewed 1 year from the time of admission or surgery. Results: Out of the 51 patients enrolled, 10 patients and their next of kin were uncontactable. The highest type of primary malignancy was breast carcinoma with 23.5%, followed by lung carcinoma at 21.6%. The modified Tokuhashi predicted survival rate of 60.8% for less than 6 months, 29.4% for 6 to 12 months and 9.8% for more than 1 year. The mean survival rates were 8.8 months for scores 0 to 8, 16.2 months for scores 9 to 11 and 18.3 months for scores 12 to 15. A total of 37 patients underwent a surgical procedure, 11 of which were biopsies. Among the procedures done were posterior instrumentation with laminectomy (12, 46.2%) and posterior instrumentation with vertebrectomy (10, 38.5%). The other 14 were treated conservatively. From those who underwent surgical palliation, 69.2% showed improved SF 36 and Karnofsky’s performance status, as compared to 27.3% among the biopsied patients and 21.4% from those treated conservatively. Those who underwent surgical palliation but deteriorated, was due to disease progression. Conclusion: Palliative surgery in patients with spinal metastases was associated with improved quality of life^8,9, as opposed to conservative management.

References

1. Lim GC. Overview of cancer in Malaysia. Japanese Journal of Clinical Oncology. 2002 Feb 1;32(suppl_1): S37-42.

2. Maccauro G, Spinelli MS, Mauro S, Perisano C, Graci C, Rosa MA. Physiopathology of spine metastasis. International journal of surgical oncology. 2011 Aug 10;2011.

3. Toma CD, Dominkus M, Nedelcu T, Abdolvahab F, Assadian O, Krepler P, Kotz R. Metastatic bone disease: A 36-Year single centre trend-analysis of patients admitted to a tertiary orthopaedic surgical department. Journal of surgical oncology. 2007 Oct 1;96(5):404-10.

4. Aoude A, Amiot LP. A comparison of the modified Tokuhashi and Tomita scores in determining prognosis for patients afflicted with spinal metastasis. Canadian Journal of Surgery. 2014 Jun;57(3):188.

5. Laucis NC, Hays RD, Bhattacharyya T. Scoring the SF-36 in orthopaedics: a brief guide. The Journal of bone and joint surgery. American volume. 2015 Oct 7;97(19):1628.

6. Hwang SS, Scott CB, Chang VT, Cogswell J, Srinivas S, Kasimis B. Prediction of survival for advanced cancer patients by recursive partitioning analysis: role of Karnofsky performance status, quality of life, and symptom distress. Cancer investigation. 2004 Jan 1;22(5):678-87.

7. Weigel B, Maghsudi M, Neumann C, Kretschmer R, Müller FJ, Nerlich M. Surgical management of symptomatic spinal metastases: postoperative outcome and quality of life. Spine. 1999 Nov 1;24(21):2240.

8. Falicov A, Fisher CG, Sparkes J, Boyd MC, Wing PC, Dvorak MF. Impact of surgical intervention on quality of life in patients with spinal metastases. Spine. 2006 Nov 15;31(24):2849-56.

9. Hirabayashi H, Ebara S, Kinoshita T, Yuzawa Y, Nakamura I, Takahashi J, Kamimura M, Ohtsuka K, Takaoka K. Clinical outcome and survival after palliative surgery for spinal metastases. Cancer. 2003 Jan 15;97(2):476-84.

A200: Wound Reoperations in Patients Undergoing Surgery for Metastatic Spine Tumors

John Berry-Candelario¹, Hannah Carl², A. Karim Ahmed², Nancy Abu-Bonsrah¹, C. Rory Goodwin¹, Rafael De la Garza Ramos³, Vikram Mehta¹, Eric W. Sankey¹, Zachary Pennington², Justin Sacks⁴, Ziya L Gokaslan⁵, Daniel M. Sciubba²

¹Department of Neurosurgery, Duke University Medical Center, Durham - United States ²Department of Neurosurgery, The Johns Hopkins University School of Medicine, Baltimore - United States ³Department of Neurological Surgery, Montefiore Medical Center/Albert Einstein College of Medicine, New York - United States ⁴Department of Plastic Surgery, The Johns Hopkins School of Medicine, Baltimore - United States ⁵Department of Neurosurgery, The Warren Alpert School of Medicine of Brown University, Providence - United States

Introduction: Surgical resection of metastatic spinal tumors can improve patients’ quality of life by addressing pain or neurological compromise. However, resections are often complicated by wound dehiscence, infection, instrumentation failures and the need for reoperation. Moreover, when reoperations are needed, the most common indication is surgical site infection and wound breakdown. In turn, wound reoperations increase morbidity as well as the length and cost of hospitalization. The aim of this study is to examine perioperative risk factors associated with increased rate of wound reoperations after metastatic spine tumor resection. Material and Methods: A retrospective study of patients at a single institution who underwent metastatic spinal tumor resection between 2003 and 2013 was conducted. Factors with a p-value < 0.200 in a univariate analysis were included in the multivariate model. Results: A total of 159 patients were included in this study. Karnofsky score Performance Status > 70, smoking status, hypertension, thromboembolic events, hyperlipidemia, increasing number of levels, and posterior approach were included in the multivariate analysis. Thromboembolic events (95% CI: 1.19-48.5; p-value: 0.032) and number of levels involved were independently associated with increased wound reoperation rates in the multivariate model. For each additional spinal level involved, the risk for wound reoperations increased by 21% (95% CI: 1.03 -1.43, p-value: 0.018). Conclusion: While wound complications and subsequent reoperations are potential risks for all metastatic spinal tumor patients due to adjuvant radiotherapy and other medical comorbidities, this study identified patients with thromboembolic events or those requiring a larger incision as being at the highest risk. Measures intended to decrease the occurrence of perioperative venous thromboembolism (VTE) and to improve wound care, especially for long incisions, may decrease wound-related revision surgeries in this vulnerable group of patients.

A201: Symptomatic Implant/Construct Failure in Metastatic Spine Tumour Surgery: Incidence, Categories, and Management

Naresh Kumar¹, Ravish Patel¹, Jonathan Tan¹, Barry Tan¹

¹Department of Orthopaedic Surgery, National University Hospital, Singapore - Singapore

Introduction: To evaluate the incidence and presentation of symptomatic implant/construct failures (SIF/SCF) following metastatic spine tumour surgery (MSTS) and to identify associated risk factors. To categorize SIF/SCF based on revision surgery in these patients. Methods: A retrospective analysis of 288 patients (246 for final analysis) undergoing MSTS between 2005 and 2015 was carried out. Demographic data, perioperative radiological and clinical features were included. Radiological criteria for SIF/SCF were defined. Early failures included patients presenting within 3 months from index surgery while late failures presented after 3 months. Results: A total of 14 failures (5.7%) were recorded in 246 patients and 10 patients underwent revision (4.1%). The median survival of the whole cohort was 13.4 months (range: 1-127 months). The mean age was 58.8 years (range: 21-87 years) and 48.4% were female. The median time to failure was 5 months (range: 1-60 months). Three groups were: a) SIF/SCF were primary implant was revised- five (35.7%) patients, b) peri-construct progression of disease requiring extension- five (35.7%) patients, c) SIF/SCF did not have revision- four (28.5%) patients. Four patients (28.5%) presented as early failures while 10 (71.5%) patients presented late. A trend of early failures was observed in ambulatory patients but this was not statistically significant. SIF/SCF were associated with a higher spinal instability neoplastic score (SINS > 7) (p, 0.005) and junctional fixations (p, 0.05). Conclusion: The incidence of SIF/SCF (5.7%) was low in patients undergoing MSTS. Patients with higher SINS score ( > 7) and fixation spanning junctional regions were at higher risk of SIF/SCF. About one third of the patients did not undergo any revision despite failure.

A202: Sacral Metastases: A Clinical Case Series From the Epidemiology, Process and Outcomes of Spine Oncology (EPOSO) Dataset

Raphaële Charest-Morin¹, Nicolas Dea², Anne L. Versteeg³, Arjun Saghal⁴, Peter Pal Varga⁵, Daniel M. Sciubba⁶, Michael H. Weber⁷, James M. Schuster⁸, Laurence D. Rhines⁹, Michelle J. Clarke¹⁰, Stefano boriani¹¹, Chetan Bettegowda¹², Michael G. Fehlings¹³, Ziya L. Gokaslan¹⁴, Paul M. Arnold¹⁵, Charles G. Fisher²

¹Department of Orthopaedic surgery, Laval University, Québec - Canada ²Combined Neurosurgical and Orthopedic Spine Program Department of Orthopedic Surgery University of British Columbia, Vancouver - Canada ³Department of Orthopedics, University Medical Center Utrecht & University Utrecht, Utrecht - Netherlands ⁴Department of Radiation Oncology, Sunnybrook Odette Cancer Centre and University of Toronto, Toronto - Canada ⁵National Center for Spinal Disorders and Buda Health Center, budapest - Hungary ⁶Department of Neurosurgery, Johns Hopkins University School of Medicine, Baltimore - United States ⁷Division of Surgery, McGill University and Montreal General Hospital, Montreal - Canada ⁸Department of Neurosurgery, Hospital of the University of Pennsylvania,, Philadelphia - United States ⁹Department of Neurosurgery, Division of Surgery, The University of Texas MD Anderson Cancer Center, Houston - United States ¹⁰Department of Neurosurgery, Mayo Clinic, Rochester - United States ¹¹Istituto Ortopedico Rizzoli, Bologna - Italy ¹²Department of Neurosurgery, Johns Hopkins University School of Medicine, baltimore - United States ¹³Division of Orthopedic surgery, University of Toronto and Toronto Western Hospital, toronto - Canada ¹⁴Department of Neurosurgery, The Warren Alpert Medical School of Brown University and Rhode Island Hospital and The Miriam Hospital, providence - United States ¹⁵Department of Neurosurgery, The University of Kansas Hospital, Kansas - United States

Introduction: Sacral metastases are rare and the literature regarding their management is sparse. This is a descriptive case series that reports on Health Related-Quality of Life (HRQOL) and pain in patients treated for sacral metastasis with surgery and/or radiation therapy (RT). Describing the adverse event (AE) profile and change in neurologic function were secondary objectives. Materials and Methods: Using the Epidemiology, Process and Outcomes of Spine Oncology (EPOSO) dataset, patients presenting with sacral metastasis were identified. Patients requiring surgery and/or RT between August 2013 and February 2017 were enrolled in this international multicenter prospective observational cohort study. HRQOL outcome measures including the Spine Oncology Study Group Outcomes Questionnaire 2.0 (SOSGOQ 2.0), the Short Form-36 version 2 (SF-36v2), and the EuroQol-5Dimension (EQ-5D) were documented at baseline, 6 weeks, 3 months, and 6 months post-treatment. Pain was assessed with the pain numeric rating scale (NRS). AEs, the American Spinal Injury Association motor score, and bowel and bladder function were recorded at baseline and follow-up. Results: We identified 23 patients with sacral metastasis: 8 patients underwent surgery ± RT and 15 patients underwent RT alone. Mean age was 59.3 years (SD 11.7) and 13 patients were female. At the 6-month follow-up, 3 (37.5%) surgical patients and 2 (13.3%) RT patients were deceased. For patients who received RT alone, 7 (46.7%) received stereotactic body radiotherapy and 8 (58.3%) conventional radiotherapy. There was a trend showing that patients treated surgically had worse baseline pain and HRQOL. Specifically, mechanical pain was more frequent at baseline in the surgical group. Pain NRS, EQ-5D, SOSGOQ, and the mental component of the SF-36v2 showed improvement in all patients, irrespective of treatment allocation. No statistical difference was observed between the treatment groups or between visits within the same group (p > 0.05). Ten AEs occurred in the surgical cohort, dominated by wound complications (n = 4). Two patients in the surgical group and one patient in the RT group experienced partial bowel and bladder loss. The lower extremity mean motor score was 48.4 (range 29-50) at baseline and marginally improved to 48.7 at the 3-month follow-up with a narrower range (40-50). Conclusion: Surgical treatment as well as RT are both valid alternatives for patients with symptomatic sacral metastases. Based on initial presentation, select patients may benefit from more aggressive treatment. Improvement in HRQOL can be expected with an acceptable AE rate. Neurologic deficits appeared to be stable over time with marginal improvement with treatment.

Funding

This study was funded by an Orthopedic Research and Education Foundation grant and by AOSpine International through the AOSpine Knowledge Forum Tumor.

Deformity - Thoracolumbar (Adolescent) - Scoliosis 1

A203: First Presentation Adolsecent Idiopathic Scoliosis in the UK. A Case for School Screening

Jan Herzog¹, Daniel Chan², Nimesh Patel², Jason Bernard¹, Tim Bishop¹, Oliver Stokes², Darren Lui¹

¹St. George’s University Hospital, London - United Kingdom ²Royal Devon and Exeter Hospital, Exeter - United Kingdom

Introduction: Currently the UK national screening committee does not recommend screening for adolescent idiopathic scoliosis (AIS). In two tertiary spinal centres serving two different but large geographical areas, we investigated first presentation of AIS and the potential impact that introducing a school prevention programme (SPP) may have. In light of evidence for bracing as well as new technology for the growing spine including vertebral body tethering there is a real need to re-explore school screening. Methods: Royal Devon and Exeter Hospital and St. George’s Hospital performed a retrospective case review of all new children referred over a 2-year period (2015-16) was performed, noting age at presentation, aetiology, curve magnitude, Risser grade, and intention to treat on first consultation. Four groups of patients were identified: early onset idiopathic ( < 10 years), syndromic (any age), adolescent patients with a potential to treat with a brace according to the SRS bracing criteria, or adolescents too skeletally mature or with curves beyond bracing criteria. Results: Of 488 cases, 286 were diagnosed with scoliosis (Cobb > 10°), 66% (n = 189) female. 26 with early onset scoliosis, mean Cobb angle of 37.7° and 37 patients in the syndromic group, mean Cobb of 44° respectively. We identified that of 57 patients with AIS and Risser grade 0-2 of which 11.1% (n = 32) were within bracing range, and 8.7% (n = 25) were beyond bracing magnitude. 58% (n = 166) with Risser grade 3-5. 30% (n = 87) curves too large to brace. Discussion: Fusion of the spine for scoliosis is an invasive treatment carrying significant morbidity. Only 11.1% of first presentation AIS fulfilled the SRS criteria for bracing. Following publication of level I evidence demonstrating that bracing is effective at altering the natural history of AIS and the results of this study give a good snapshot of current incidence, strongly supporting the need to introduce a school prevention programme in the U.K.

A204: Brain Tractography in Adolescent Idiopathic Scoliosis; New Findings

Francisco Ardura¹, Ruben Hernandez-Ramajo², David Noriega¹, Belen Garcia-Medrano², Jesus Crespo²

¹Department of Orthopedics, Clinical Hospital, Department of Surgery, School of Medicine, Valladolid - Spain ²Department of Orthopedics, Clinical Hospital, Valladolid - Spain

Introduction: Abnormal connections and brain alterations have been described in idiopathic scoliosis. Our aim was to study the possible relationship between adolescent idiopathic scoliosis and the findings of brain connectivity alterations comparing diffusion Magnetic Resonce Images (MRI) between a group of patients (P) and a group of healthy controls (HC). Material and Methods: We included healthy teenagers and idiopathic scoliotic adolescents. We obtained T1 weighted and diffusion 3 teslas MRIs. For diffusion acquisitions we used 32 gradient directions, b = 1000s/mm², a voxel size of 1.66x1.66x2 mm and a matrix of 144x144 with 140 slices covering the whole brain and cervical area. Data was analyzed building a connectivity matrix among 84 cortical and subcortical areas, using Freesurfer, FSL and MRTrix software. Two million lines of tractography were obtained per subject. Fractional Anisotropy was used to evaluate connectivity. We obtained 3570 connections. We chose for later statistical analysis, those with a minimum of 500 lines of tractography present in all subject analysis. For this analysis, we used general lineal model, and we have studied the influence of age, sex and scoliosis or control. Statistical significancy was established for p < 0.01. Results: We included 18 HC (8 women; mean age: 12.33 years DS 2.43) and 22 P (17 women; mean age: 14.73 years DS 3.03). Out of the initial 3570 connections, 159 were over the 500 minimum stablished and were selected for statistical analysis. Global connections after age and gender adjustment, were statistically significant different between HC and P. One by one connection comparison showed significant differences between caudal-middle-frontal cortex (left hemisphere) and superior-frontal cortex (left hemisphere). Same differences were found concerning the isthmus of the left cingulate turn, and also in the connections of the right cerebellum cortex. Conclusion: Our findings are still preliminar, but we found alterations in brain connectivity in scoliotic patients. This alterations may be involved in the genesis of the disease itself, as other researchers have already reported. Treatment strategies could benefit also from these findings. Former studies must be conducted in this line of investigation. Patients with idiopathic adolescent scoliosis in our study, showed alterations in brain white substance connections.

A205: Does Pedicle Screw Instrumentation Truly Cause no Negative Effect on Growth of Vertebrae? - A More Than 5-Year Follow-Up in Children Younger Than 5 Years Old

Jianguo Zhang¹, Yanbin Zhang¹

¹Department of Orthopedics, Peking Union Medical College Hospital, Beijing - China

Introduction: Concern remains over the effect of pedicle screw instrumentation on the growth of vertebral body and spinal canal in young children. There was a discrepancy between animal experiments and clinical studies in previous literatures. Our purpose was to investigate whether pedicle screw instrumentation could cause negative effects on the growth of immature spine in children younger than 5 years old. Methods: Individuals met our criteria were included. Parameters of instrumented vertebrae and adjacent non-instrumented vertebrae were measured on adjusted axial CT images before surgery and at final follow-up. Growth value and growth percentage of each parameter were calculated. Parameters of thoracic vertebrae and lumbar vertebrae were compared, respectively. Statistical analyses were performed. Results: 13 patients were enrolled. The mean age at surgery was 3.4 (range 2-5) years old with an average follow-up of 7.2 (range 5-11) years. Osteotomy and instrumentation with pedicle screws were performed. Total 69 segments were measured, including 43 instrumented vertebrae and 26 adjacent non-instrumented vertebrae. Significant increases of all parameters were noted at the final follow-up. Growth value and growth percentage of PL, CAP and AREA increased significantly, and those of VAP decreased significantly in IV group compared to NIV group. Similar results were noted in lumbar region. Shape-change phenomenon was found in NIV group and not apparent in IV group. Conclusion: Pedicle screw instrumentation may mainly slow down the growth of vertebral body, indirectly speed up the growth of spinal canal, and hinder the shape-change phenomenon of lumbar spinal canal. But the negative effects were quite tiny and significant developments did occur in instrumented vertebrae. So pedicle screw instrumentation was reliable and trustworthy in children younger than 5 years old.

A206: The Effect of Body Mass Index on Surgical Outcomes After Posterior Spinal Fusion for Adolescent Idiopathic Scoliosis

Rafael De la Garza Ramos¹, Jonathan Nakhla¹, Rani Nasser¹, Jacob F Schulz², Taylor Purvis³, Daniel Sciubba³, Merrit Kinon¹, Reza Yassari¹

¹Department of Neurosurgery, Montefiore Medical Center, New York - United States ²Department of Orthopaedic Surgery, Montefiore Medical Center, New York - United States ³Department of Neurosurgery, Johns Hopkins University School of Medicine

Introduction: Obesity is an increasing public health concern in the pediatric population. The purpose of this investigation was to examine the impact of body mass index (BMI) on 30-day outcomes after posterior spinal fusion for adolescent idiopathic scoliosis (AIS). Methods: The American College of Surgeons National Surgical Quality Improvement Program Pediatric database (2013 and 2014) was reviewed. Patients aged 10 – 18 who underwent fusion of 7 or more spinal levels for AIS were included. Thirty-day outcomes (complications, readmissions, and reoperations) were compared for patients based on their BMI per age- and gender-adjusted growth charts as follows: normal weight (NW; BMI < 85th percentile), overweight (OW; BMI 85 – 95th percentile), and obese (OB; BMI > 95th percentile). Results: There were 2,712 patients identified with a mean age of 14.4 ± 1.8 years; 80.1% female and 19.9% male patients. The average BMI for the entire cohort was 21.9 ± 5.0 kg/m²; 2,010 patients were classified as having NW (74.1%), 345 were OW (12.7%), and 357 were OB (13.2%). The overall complication rate was 36/2,712 (1.3%); 0.9% for NW, 0.9% for OW, and 4.2% for OB patients (p < 0.001). The 30-day readmission rate was 55/2,712 (2.0%) for all patients; 1.6% for NW, 1.2% for OW, and 5.0% for OB patients (p < 0.001). The 30-day reoperation rate was 2.1% (39/2,712 patients); based on BMI, this corresponded to 0.9%, 1.2%, and 4.8% for NW, OW, and OB patients, respectively (p < 0.001). After controlling for patient age, number of levels fused, and operative/anesthesia time on multiple logistic regression analysis, OB remained a significant risk factor for complications (OR 4.61), readmissions (OR 3.16), and reoperations (OR 5.33; all p < 0.001). Conclusion: Body mass index may be significantly associated with short-term outcomes after long-segment fusion procedures for AIS. Although NW and OW patients may have similar 30-day outcomes, OB patients exhibited a significantly higher wound complication rate, readmission, and reoperation rate, and longer lengths of stay compared to patients with NW. The findings of this study may help spine surgeons and patients for preoperative risk stratification and perioperative expectations.

Basic Science and Interventional

A207: Scoliosis Within the 22Q11.2 Deletion Syndrome

Jelle Homans¹, Vyaas Baldew¹, Tom Schlösser¹, Moyo Kruyt¹, René Castelein¹

¹Department of Orthopedic Surgery, University Medical Center Utrecht, Utrecht - Netherlands

Introduction: The 22q11.2 Deletion Syndrome (22q11.2DS) is the most common microdeletion syndrome with an estimated prevalence of 1:4000 new-borns. It is the cause of multiple conditions originally described clinically, e.g. DiGeorge syndrome and velocardiofacial syndrome. 22q11.2DS is characterized by a broad spectrum of clinical features, including scoliosis. The exact epidemiology of scoliosis within 22q11.2DS is unknown. This epidemiological study on prospective data identifies the prevalence, curve pattern and clinical risk factors associated with the development of scoliosis within 22q11.2DS. Material and Methods: A cross-sectional study based on prospective collected data was performed. Since 2014, all 22q11.2DS patients are radiographically screened for scoliosis in our specialized 22q11.2DS clinic. If there was no previous clinical suspicion a whole spine X-ray was performed once at the age of eight. The prevalence of scoliosis (≥ 10 degrees Cobb Angle) was calculated. The criteria defined by Spiegel et al. (2003) were used to divide curves into ‘typical’ (idiopathic-like) or ‘atypical’ curves. Furthermore, clinical characteristics that may be associated with the presence of a scoliosis, like a congenital heart defect with or without thoracotomy, were analyzed by means of logistic regression. Results: A total of 95 patients (mean age: 12.0 years) were included. The prevalence of scoliosis was 51% (n = 48) and four patients (4.2%) received scoliosis surgery. There were no baseline differences between the group with and without scoliosis. The median Cobb angle at first X-ray was 15 degrees (Interquartile Range: 13-19). 57% had a typical curve, 32% had an atypical curve and within one patient the curve type could not be determined. In the group of typical curves, the majority (63%) had atypical features (e.g. lumbar curve until L5). Four patients (4.2% of the whole cohort) received scoliosis surgery. Interestingly, within the current cohort, there was a trend (univariate analysis p = 0.085 and multivariate analysis p = 0.07) that a congenital heart defect irrespective of surgery was a risk factor for scoliosis. Conclusion: Scoliosis had a prevalence of 51% within our cohort of 22q11.2DS patients. This prevalence is probably higher for all patients, since many of the included patients were still growing. The majority of the patients had a typical curve pattern. Based on these insights we recommend regular scoliosis screening of the 22q11.2DS patients.

A208: Comparison of Transforaminal Steroid Versus Caudal Steroid Versus Combined Caudal and Transforaminal Steroid in the Treatment of Lumbar Disc Prolapse

Sudhir Ganesan¹, Vignesh Jayabalan¹

¹Department of Spine Surgery, Chennai – India

Introduction: Various techniques of epidural steroid injections have been described for treating intervertebral disc prolapse. Transforaminal nerve root injections are generally favoured because it directly targets the affected nerve root. We aimed to compare the short term and long term efficacy of transforaminal steroid, caudal steroid and combined transforaminal with caudal steroid injections in lumbar disc prolapse. Methods: 45 patients (average age of 52.2 years) with single level lumbar disc prolapse with failed conservative treatment were included in the study. They were divided into three groups: Group 1 received transforaminal root block, group 2 received caudal epidural block and group 3 were treated with caudal block along with transforaminal nerve root injection using triamcinolone acetate. Analysis was done using VAS and ODI before the procedure, immediately after the procedure, 3 months, 6 months and 1 year after the procedure. Results: All the patients had significant improvement in VAS and ODI after the procedure. Group 3 patients had a statistically significant improvement in VAS immediately after the procedure compared to Group 1 and 2. However there was no difference in VAS and ODI between the three groups at the end of one year. Conclusion: Our study revealed that all the three techniques had similar efficacy at the end of one year with no difference in the clinical outcome. However patients who received caudal block along with transforaminal nerve root injection had a better outcome in the short term.

A209: Delivery Of BMP-2 Via BMP-2 Binding Peptide Amphiphile Scaffolds Augments Spine Fusion at Sub-Therapeutic Doses

Ryan Lubbe¹, Mark McClendon², Adam Driscoll¹, Gurmit Singh¹, Karina Katchko¹, Kevin Chang¹, Meeraj Haleem¹, Sohaib Hashmi¹, Abhishek Kannan¹, Chawon Yun¹, Soyeon Jeong¹, Richard Pahapill¹, Stuart Stock³, Samuel Stupp², Erin Hsu¹, Wellington Hsu¹

¹Department of Orthopaedic Surgery, Northwestern University, Chicago - United States ²Simpson Querrey Institute for BioNanotechnology, Northwestern University, Chicago - United States ³Department of Cell and Molecular Biology, Northwestern University, Chicago - United States

Introduction: Advances in biologics, such as recombinant human bone morphogenetic protein-2 (rhBMP-2), have decreased the rate of pseudoarthorsis. In humans, rhBMP-2 applied onto an absorbable collagen sponge (ACS) has been shown to elicit high rates of fusion; however, supraphysiologic doses of rhBMP-2 required when delivered with ACS can lead to serious complications. These complications call for an ongoing need to develop a product that elicits high fusion rates with minimal adverse effects. In previous work from our group, we developed peptide amphiphile (PA) nanofiber scaffolds that contain a rhBMP-2 binding motif. This carrier is capable of localizing both exogenous and endogenous BMP-2, consequently reducing the requisite dose of exogenous growth factor for successful fusion. In this study, we evaluated the efficacy of the PA to elicit spine fusion with sub-therapeutic doses of rhBMP-2 in the rabbit posterolateral spine fusion (PLF) model. Materials and Methods: Female New Zealand white rabbits underwent bilateral PLF at L5-L6 with delivery of either 30μg or 60μg of rhBMP-2 per animal (15μg or 30μg of rhBMP-2 per side). rhBMP-2 was delivered using either an absorbable collagen sponge (ACS), PA/ACS, or PA/collagen slurry. Spine fusion was assessed using radiography, manual palpation-based fusion scoring, and microCT imaging. An established scoring system for fusion was used whereby 0 = no bridging bone, 1 = unilateral bridging, and 2 = bilateral bridging. Spines with an average score of ≥ 1 were considered successfully fused. One-way ANOVA with Tukey’s post-hoc was used to evaluate differences in fusion scoring among groups with continuous variables. Results: In both formulations of PA, the PA loaded with 30μg or 60μg of rhBMP-2 (per animal) elicited significantly higher fusion scores (2.00, p < 0.001 and 2.00, p < 0.01, respectively) relative to equivalently pre-loaded ACS alone (1.04). Successful fusion was seen in 100% of the rabbits treated with PA, regardless of rhBMP-2 dose or whether the PA was delivered on ACS or as a PA/collagen slurry. This was significantly higher than fusion rates in rabbits treated with 30μg (0%, p < 0.001) or 60μg rhBMP-2 (50%, p < 0.01) on ACS alone. PA delivered on ACS or with the collagen slurry elicited equally successful fusion rates regardless of exogenous growth factor dose (100% for both 30μg and 60μg rhBMP-2). Conclusion: Currently, ACS is the only FDA-approved carrier for rhBMP-2. Our data suggests that both iterations of the PA nanofiber scaffolds are better carriers for rhBMP-2 when compared to equivalently loaded ACS alone. Whether delivered on ACS or as a collagen slurry, the PA nanofibers are equally effective in promoting fusion at sub-therapeutic doses of 30μg and 60μg rhBMP-2. The success of this technology in the rabbit PLF model suggests that it may be robust enough for the clinical setting. Future studies will identify the lowest dose of exogenous growth factor required for successful fusion using these iterations of the PA nanofiber scaffold in the rabbit.

A210: Short Link N Promotes Repair of Disc Degeneration, But More May not be Better

Fackson Mwale¹, Koici Masuda², Michael Grant¹, Laura Epure¹, Peter Roughley³, John Antoniou¹

¹Lady Davis Institute for Medical Research, McGill University, Montreal - Canada ²Department of Orthopaedic Surgery, University of California, San Diego - United States ³Shriners Hospital for Children, McGill University, Montreal - Canada

Introduction: The degeneration of the intervertebral disc (IVD) is characterized by proteolytic degradation of the extracellular matrix, and its repair requires the production of an extracellular matrix with a high proteoglycan to collagen ratio characteristic of a NP-like phenotype in vivo. At the moment, there is no medical treatment to reverse or even retard disc degeneration. Here we evaluate the potential dose dependency of Short Link N (sLN) to promote extracellular matrix regeneration in a rabbit annular needle puncture model of IVD degeneration. Material and Methods: Thirty adolescent New Zealand white rabbits received an annular puncture in 2 noncontiguous discs with an 18-gauge needle to induce disc degeneration. Two weeks later, either saline (10 μL) or sLN (25 μg or 200 μg in 10 μL saline) was injected into the center of the nucleus pulposus. The effect on radiographic, biochemical and histologic changes were evaluated. Results: Following needle puncture, disc height decreased by about 25-30% over the next 2 weeks, and although this was partially restored by sLN injection, the 200 μg sLN injection was always less effective than the sLN 25 μg, indicating that increase in disc height does not correlate with sLN concentration. sLN injection at 25 μg or 200 μg led to an increase in GAG content 12 weeks post-injection in both the NP and AF. There was a trend towards maintaining control disc collagen content at 25μg sLN, whereas at 200 μg sLN, there was a significant increase in collagen content when compared to the non-punctured discs. The amount of collagen synthesized in the presence of 200ug sLN was higher than that with 25 μg sLN. For the 25 μg sLN treated groups, the GAG to collagen ratio in the NP increased when compared to the saline group to an average of 3.0:1. For the 200 μg sLN treated groups, the GAG to collagen ratio in the NP was on average 0.9:1. Conclusion: When administered to the degenerate disc in vivo, the 200 μg sLN injection leads to an increase in proteoglycan, but it also increases collagen content making it harder for the disc to swell. Hence, even though both the 25 μg and 200 μg sLN treatments eventually reach a similar disc height, the 200 μg treatment takes longer to achieve this even though it has more GAG. Thus, supplementation with the 25 μg sLN could be a better dose for treating disc degeneration as it leads to high GAG synthesis and swelling potential but minimizes fibrosis and the consequent delay in swelling rate. sLink N proves effective as a therapy in disc repair.

Arthroplasty - Lumbar and Adjacent Pathology

A211: Analysis of Lumbar Total Disc Replacement Removals/Revisions During a 17 Year Experience With 1,707 Patients

Scott Blumenthal¹, Jack Zigler¹, Richard Guyer¹, Donna Ohnmeiss²

¹Texas Back Institute, Plano - United States ²Texas Back Institute Research Foundation, Plano, TX - United States

Introduction: One concern expressed about lumbar total disc replacement (TDR) has been safety. One measure of safety is the need for subsequent surgery to removal or revise an implant. This may be of particular importance considering TDR removal/revision generally requires re-operation through the anterior approach with the corresponding increased risk of vascular injury. The purpose of this study was to analyze the incidence of, and reasons for, removal or revision of lumbar TDR devices. Methods: A consecutive series of 1,707 lumbar TDR patients, beginning with the first case experience in 2000, was reviewed to identify those undergoing re-operation for TDR removal or revision. Only patients who were at least 6 months post-operative were included. Among the 1,707 patients, the mean follow-up was 42.7 months with a median of 30 months and a maximum of 195 months. Six different devices were used in the series. For each case of device removal/revision, the reason, duration from index surgery, and procedure performed were recorded. Results: In the series of 1,707 patients, there were 17 patients who underwent TDR removal (0.99%) and 3 additional patients underwent TDR revision (0.17%). The rates based on the total number of 2,023 TDR devices implanted in the 1,707 patients, were 0.89% removals and 0.15% revisions. The reasons and timing of removal/revisions were analyzed. Removals included: 8 for migration and/or loosening, 3 developed problems after a trauma, 1 had vertebral body fractures (osteoporosis), 1 TDR too large and replaced with smaller device, 1 had ongoing pain, and 1 had an infection seeded from a chest infection at 146 month post-TDR. Revisions included 1 repositioning the core (technique error), 1 repositioned device after displacement, and 1 core replacement due to wear/failure. With respect to timing, 40% of removals/revisions occurred within one month after the index surgery, and a total of 85% occurred within 2 years. Of note, 40% of the revisions/removals occurred in the first 25 TDR cases performed by individual surgeons. There were no vascular complications causing clinical sequelae during the removal/revision surgeries. Discussion: In this large patient series, 1% of lumbar TDRs were removed/revised. Only one revision was related to device failure or wear. Many of the subsequent procedures were performed within a month of implantation. Also of note, many occurred within the first 25 TDR cases for individual surgeons, suggesting a learning curve. In cases of TDR removal/revision, as with any repeat anterior spine surgery, one should be acutely aware and prepared for vascular injury should it occur. The low rate of removal/revision in this large institutional experience over a 17 year period provides support for the safety of these devices.

A212: Seven Year Outcomes of Lumbar Total Disc Replacement Systems on Patient Lifestyle and Quality of Life

Scott Blumenthal¹

¹Texas Back Institute, Plano - United States

Introduction: Degenerative disc disease (DDD) is a potentially debilitating condition resulting in pain and decreased functional ability in patients. Lumbar total disc replacement (TDR) helps to alleviate this pain and dysfunction and potentially allows for a return to pre-injury activities. This is the first study to our knowledge reporting on post-surgical quality of life (QoL) assessments at 7 years post-surgery. Methods and Methods: As part of a large, multicenter clinical trial, eligible patients were randomly allocated (2:1) to treatment with an investigational TDR device (activL®, n = 218) or FDA-approved control TDR devices (ProDisc-L, n = 65 or Charité, n = 41). Follow-up occurred at 6 weeks and 3, 6, 12 and 24 months and every year thereafter up to 7 years post-surgery. Patient QoL was evaluated using the SF-36 questionnaire. Data were also collected on patient satisfaction, work status and use of pain medication at baseline and at 7 year follow-up. Results: At 7 years, 77% and 73% of activL and Control patients (respectively) showed improvements in mental component scores (MCS) for the SF-36 compared to baseline. Similarly, physical component scores (PCS) improved for 92% and 86% of activL and Control patients at 7 years post-surgery. Clinically significant improvements in MCS and PCS scores (≥ 15% improvement from baseline) occurred in approximately 44% (MCS) and 62% (PCS) of all TDR patients combined at 6 weeks, increased to 61% (MCS) and 80% (PCS) at 12 months and remained constant through to 7 years. Approximately 53% of all TDR patients returned to work without restriction by 12 months, which increased to 64% and 54% for activL and Control patients at 7 years. Most activL patients were able to return to the same workload as before their back injury at 7 years, whereas more Control patients worked in sedentary jobs at 7 years than before their back injury. Similar decreases in the proportion of patients utilizing pain medication were noted in both groups. At baseline, 90% and 92% of activL and Control patients were using medications for pain control, which decreased by half by 7 years. Patient satisfaction at 7 years post-surgery showed 97% of all TDR patients were “very satisfied” or “somewhat satisfied” with the procedure, and 93% indicated that they would “definitely” or “probably” undergo the procedure again for the same condition. 97% of activL and 89% of Control patients indicated that the treatment was “very” or “moderately” effective in eliminating their symptoms. Conclusions: The results of this analysis indicate that lumbar TDR is effective at helping to improve patient’s quality of life, potentially facilitating return to work, and reducing pain medication usage.

A213: A Novel Elastomer Lumbar Total Disc Replacement Device Affords Mechanics Similar to the Intact Spine: a Finite Element Study

Ali Kiapour¹, Kingsley R. Chin², Jake Lubinski², Vijay K. Goel¹, Joseph M. Zavatsky²

¹Engineering Center for Orthopaedic Research Excellence (E-CORE), Department of Bioengineering, Toledo, OH - United States ²LESS Institute, Fort Lauderdale, FL - United States

Introduction: Lumbar total disc replacement (TDR) devices are intended to preserve motion in the surgically treated segment, in an attempt to eliminate many of the shortcomings of traditional fusion techniques. Currently available TDR instrumentation does preserve motion in the treated spinal segment, but this motion does not exactly mimic natural spinal kinematics. This study investigates the biomechanics of novel polymer disc design using the finite element model. Methods: An experimentally validated FE model of a ligamentous L1-S1 lumbar spinal model was used and modified to simulate placement of FREEDOM total disc replacement device at L4-L5 level following removal of entire nucleus and ALL ligament and partial removal of annulus. Properties of titanium alloy and CarboSil 20 80A silicone rubber were assigned to the endplates and implant’s flexible component. The intact and instrumented spines were subjected to 400 N compressive follower load plus 10 Nm bending moments in anatomical planes (flexion/extension/left-right bending, left and right rotation). The range of motion, intra-discal pressure and facet loads were measured and compared for segments of intact and instrumented spines. Results Section: The kinematic data for index and superior adjacent levels are shown in Figure 1. At the index level, the instrumented model had range of motion equal to 88% and 80% of intact in extension and flexion motions, respectively. The ratios were 62% in left and right bending, and 86% in axial rotation. The extension-to-flexion center of rotation (COR) of the intact FE was very close to the in vivo COR reported by Pearcy et al. (Spine 1988). The motion at the superior adjacent segment increased slightly, following instrumentation at L4-L5. The increase in motion was not greater than 8% in flexion, and 20% in extension. The intra-discal pressure at the adjacent segment was very close in the instrumented and intact model with the difference not being greater than 12% in any of the loadings. Compared to the intact spine under extension loading, the loads at the facet joints at the index level increased by 1% in the instrumented model. However, in the instrumented model, adjacent level facet loads decreased approximately 5% with extension, compared to the intact spine. Discussion: This elastomer TDR did not result in significant alterations in spinal kinematics, quality of motion and biomechanics of the instrumented spine, as compared to the intact spine model. A study by Rohlmann et al. (Spine 2005) showed that ProDisc-L increased the ROM of the spine by 38% in Extension and decreased by 40% in Flexion. The elastomer disc resulted in change of motion not greater than 20% of intact in either motion. Also the elastomer disc had minimal effect on range of motion, intradiscal pressure and facet joint of at L3-L4 segment which is an indicative of lower risk of adjacent segment disc and facet degeneration in the long run.

Figure 1.

Range of motion at index and adjacent segments and Ext-Flex center of rotation at index level.

A214: Pain After “Successful” Lumbosacral Fixation - is it Adjacent Segment Pathology From SI Joint?

Arun-Kumar Viswanadha¹, Naresh-Babu J¹

¹Department Of Spine Surgery, Mallika Spine Centre, Guntur - India

Introduction: Lumbosacral fixations have been increasing over the past decade. However, post-operative back or leg pain is not infrequent. New onset buttock pain can be frequently observed in spite of relief of pre-operative symptoms with sacroiliac joint (SIJ) being one of the potential sources. Possible theory for occurrence of SIJ pain after fixation may be attributed to transfer of mechanical load to adjacent joints after lumbosacral fixations. Material and Methods: The study was conducted between January 2017 and July 2017 at our institution. 143 patients who underwent lumbosacral fixations with no previous S.I. joint pathology formed the study group. All cases (27 of 143) of new onset, post-operative S.I. joint dysfunction were treated by injecting 40 mg methylprednisolone into the joint under fluoroscopic guidance. Outcomes were assessed through VAS and ODI scores at 3 weeks, 3 months and 6 months. Results: The commonest presentation of post-operative pain was unilateral or bilateral buttock pain radiating to groin. Incidence of sacro-iliac joint dysfunction in post lumbosacral fixations is 18.8% (n = 27). Right S.I. joint (41%) is the most frequently involved side followed by bilateral (37%) and left sacro-iliac joint (22%). Majority of the cases developed S.I joint syndrome within 3 weeks from the index lumbosacral fixation (79%). Most of the cases improved significantly with single corticosteroid injection (62%). There was significant improvement in terms of VAS and ODI after corticosteroid injection both at 3 weeks and 6 months (p-value < 0.05). Conclusion: Post-operative buttock pain after successful lumbosacral fixations is not uncommon, posing diagnostic and therapeutic challenges. Its role should be particularly evoked when the postoperative pain distribution differs from the preoperative pattern. Awareness and prompt identification of SI joint dysfunction as a potential source of pain improves outcomes.

Infections 1

A215: Post Operative Deep Wound Infection in Posterior Dorso-Lumbar Fixation Surgeries: Does it Affect the Clinic-Radiological Outcome? Minimum 2 Years Follow-Up

Aditya Banta¹, Saumyajit Basu¹, Amitava Biswas¹, Anil Solanki¹

¹Neurosciences Division, Park Clinic, Kolkata - India

Introduction: Incidence of post operative deep wound infection (PODWI) after lumbar surgery varies from 2.1% to 6.7%. Studies looking into the effect of post operative infection on functional recovery of the patient have thrown conflicting. Aim of present study is to evaluate the 2 year functional and radiological outcome of patients with PODWI. Materials and Methods: A retrospective matched cohort study of 23 patients with acute PODWI ( < 3 months) after instrumented dorso-lumbar spinal fusion from 2005 to 2013. All patients were treated by wound reexploration and thorough debridement along with parenteral followed by oral antibiotics for 3 weeks duration each. Their pre-op and post op (6 m and 2 yrs) functional scores in the form of ODI (Oswestry Disability Index) and VAS (Visual Analogue Scale) were queried from the electronic database. Radiographs and CT scan was done in all patients to assess fusion at 2 years. A non infected control group (CG) was identified matching the ODI, CACI (Charlson Age-matched Co morbidity Index), indication, type and number of levels of fusion. Clinical and radiological outcomes were analyzed using Microsoft Excel Data Analyzer Tool pack. Results: Out of 23 patients 21 underwent posterior spinal fusion and 2 underwent additional anterior surgery. Mean lag time before diagnosis of infection was 4.6 weeks. Most common pathogenic organism was Staph Aureus (30.4%) followed by E-coli (26%). All patients except one had documented fusion at 2 year follow up. 4 patients developed discharging sinuses, one had delayed recurrence of infection. Implant removal had to be done in 3 patients; one had screw pullout and two persistent discharging sinuses. The mean ODI score difference at 6 month from baseline was higher in the CG (33) as compared to IG (19) (p < 0.0001). The score difference at 2 yrs from baseline was not statistically significant (p = 0.4), however it is significant when we compared score difference at 2 yr from 6 months. (p < 0.0001). No statistically significant difference was found in the VAS scores between the two groups. Small sample size and retrospective nature are the potential limitations of this study. Conclusion: This study demonstrates that patients with acute postoperative deep wound infections after instrumented spinal fusion who were treated by wound re-exploration and 6 week antibiotic regimen have comparable outcome measures to a patient with uneventful post-operative period in the long term, However initial temporary worsening in functional status in short term follow up was seen in patients with post operative deep wound infections. Fusion was a predictable outcome in all patients.

A216: Microorganisms Trends in Infected Implant Removal After Posterior Decompression and Transpedicular Screw Fixation

Muhammad Farrukh Bashir¹

¹Department of oOrthopaedic and Spine Surgery, Lahore - Pakistan

Background: Spinal implant infections provide unique diagnostic and therapeutic challenges. Implant removal because of pain and infection after posterior fusion in the thoracic and lumbar spine is a widely performed operation. Implant bulk, metallurgic reactions, and contamination with low-virulence microorganisms have been suggested as possible etiologic factors. The clinical symptoms include pain, swelling, redness, and spontaneous drainage of fluid. Complete instrumentation removal and systemic antibiotics is usually curative. The main objective of this study was to determine the causative micro organisms in infected posterior spine implants and sensitivity of these micro-organisms to different antibiotics. Materials and Methods: This retrospective study was conducted at Department of orthopedics and spine centre Ghurki trust teaching hospital, Pakistan after approval from hospital ethical committee.97 patients of any age and gender who underwent Removal of posterior spinal implants, previously operated either at our hospital or somewhere else, from Jan 2011 to Dec. 2016 due to infection were included in the study. Those patients whose record were incomplete were excluded from the study. The data was collected from departmental database. Patients demographic data as well as culture and sensitivity report of the pus were initially entered on preformed performa and later on entered on SPSS 17.0 version for data analysis. Results: Out of 97 patients, there were 54 (55.67%) males and 43 (44.33%) males with male to females ratio of 1.26: 1 and with mean age of 46.78 ± 9.54. Among all patients 54 (55.67%) patients having no co morbidity, 30 (30.93%) were diabetic, 10 (10.31%) were hypertensive, 8 (8.25%) having cardiac issue while 3 (3.12%) patients having some other co morbidity. 34 (35.05%) patients were non addict, 31(31.96%) patients were smokers, 17 (17.53%) eat Pan, 6 (6.19%) were using domestic alcohol and 9(9.27%) some other types of addiction. 29 (29.90%) patients having culture and sensitivity negative reports. The frequency of bugs were different. Most of the micro organisms were Gram +ive Cocci i-e 31(31.95%) followed by Gram –ive rods i-e 24 (24.74%). Some samples showed growth of more one organism. The Gram –ive rods and Gram +ive cocci were found in 7(7.21%) of the cultures and others 6 (6.18%). The different micro organisms were in different percentages. The most common were MRSA i-e 29 (29.89%) followed by Streptoccoci and MSSA with equal incidence i-e 21 (21.65%). The fungal infection were found only in 2 (2.06%) of patients and few others micro organisms were 7 (7.21%). Vancomycin and Doxycyline were most common drugs sensitive against MRSA followed by Amikacin and fusidic acid. Proteus mirabilis, Klebsiella, Pseudomonas Aeruginosa and E. Coli were most sensitive to Amikacin. MSSA were mostly sensitive to Vancomycine. Streptococci showed most and equal sensitivity to amoxicillin and ampicillin. Conclusion: Vancomycin, Amikacin, Doxyclin and fucidine should be included among the empirical treatment whenever a patient with spinal infection come because of high sensitivity of these antibiotics to common bugs found in culture reports.

A217: Anterolateral Decompression Revisited: Early Results of Lamina Sparing Decompression, Anterior Column Reconstruction and Instrumented Fusion in Thoracolumbar Spinal Tuberculosis

Pankaj Kandwal¹, Naveen Pandita¹, Prince Raina¹, Shobha Arora¹, Gagandeep Yadav¹

¹Department of Orthopaedics, AIIMS, Rishikesh, - India

Introduction: To study clinical, functional, radiological and neurological outcome following Lamina sparing decompression, anterior column reconstruction and instrumented fusion in Thoracolumbar Spinal Tuberculosis Material and Methods: Study period- Oct 2014 to march 2017. A total of 18 patients were included in study, one patient died and hence was excluded from the study. Inclusion criteria involve tuberculosis spine with dorsal or lumbar involvement and Single or multilevel involvement cases The outcomes were studied in terms of clinical improvement of VAS, neurological improvement in Frankel grading, improvement in ODI scoring and correction of segmental kyphosis. Average follow-up 18.33 mth. Results: A total of 17 patients underwent Lamina sparing decompression, anterior fusion and posterior instrumentation procedure. The mean age was 29.7 yrs (15-65 years). The average duration of surgery and blood loss was 280 ± 56.2 min and 625 ± 344 ml respectively. The VAS was improved from 8.5 ± 0.8 (pre-op) to 5 ± 0.9 & 3 ± 0.8 (p < 0.05) at one week and two week post-op respectively. ODI at last follow up was 37.2 ± 14.9 when compared to pre-op status of 70.2 ± 17.5. The neurological /Frankel grade improved in all patients. The mean kyphosis correction achieved was 58.5% (Pre-op 26.11 ± 12 & Post-op 15.3 ± 8). Anterior cage was used in 5 cases and graft in 12 cases. The average level of instrumentation was 5.38 ± 1.34 (range3- 8). Complications: One patient had deep infection requiring debridement. Conclusion: Posterior approach for dorsolumbar spine tuberculosis can be used for decompression and three column reconstruction. The modified decompression technique not only gives good neurological recovery and functional outcome (early pain relief and hence mobilization) but sparing the lamina apart form added stabilty, gives a larger area for posterior and posterolateral fusion. Posterior approach for dorsolumbar spine tuberculosis can be used for decompression and three column reconstruction. The modified decompression technique not only gives good neurological recovery and functional outcome (early pain relief and hence mobilization) but sparing the lamina apart form added stabilty, gives a larger area for posterior and posterolateral fusion.

A218: Complications Associated With Surgery for Spinal Metastases: A Multivariable Analysis

Jay Kumar¹, Vijay Yanamadala¹, Ganesh Shankar¹, Bryan Choi¹, John Shin¹

¹Department of Neurosurgery, Massachusetts General Hospital and Harvard Medical School, Boston – United States

Introduction: Metastases to the spine occur from a variety of primary malignancies. Surgery on these patients can be challenging with a substantial risk of complications. We present a single-center experience of 189 consecutive patients who underwent surgery for spinal metastases, and share our insights regarding complications. Methods: Charts of 189 patients who underwent surgery for spinal metastases over 5 years from October 2011 through February 2017 were reviewed for complications and possible contributing factors. A multivariate analysis was performed for patient demographic and surgical parameters that predict complications. Results: Complications were identified in 20% of all patients who underwent surgery for spine metastases. Medical complications included: urinary tract infection, 10%; deep vein thrombosis/pulmonary embolism, 5%; pneumonia, 3% and myocardial infarction, 1%. Surgical complications included: wound infection, 3%; and new neurologic deficit, 2%. Average thirty-day survival was 87%. Average ninety-day survival was 65%. Age > 65, prior radiation, and multiple metastases were all predictive of complications at a statistically significant threshold of p < 0.05. Conclusions: Surgery for spinal metastases is associated with a relatively high complication rate. Medical complications are more common than surgical complications. Age > 65, prior radiation, and multiple metastases were all predictive of complications. Optimization of co-morbid conditions by a multidisciplinary team may help reduce medical complications associated with surgery for spinal metastases.

Deformity - Thoracolumbar (Adolescent) - Scoliosis 2

A219: High-Grade High Dysplastic Spondylolisthesis in Children Treated With Complete Reduction and Monosegmental Fixation

Jan Stulik¹, Petr Nesnidal¹, Michal Barna¹, Kristina Kozelnicka¹

¹Department of Spinal Surgery, First Faculty of Medicine, Charles University and Teaching Hospital Motol, Prague - Czech Republic

Introduction: Prospective long-term moncentric radiographic and clinical study of pediatric patients with high-grade high-dysplastic (HGHD) spondylolisthesis treated by complete reduction and monosegmental fixation with Schanz screws technique. The aim of this study is to assess the efficacy of this technique in fusion rate, reduction of local deformity and correction of overall sagittal profile. Material and Methods: There are no clear guidelines for optimal technique for surgical treatment of HGHD spondylolisthesis due to the lack of high-level evidence. Complete reduction and monsegmental fusion for HGHD have been described previously. However, very few prospective long-term studies on complete HGHD reduction by the same team using the same strategy with no data loss have been reported. A total of 14 consecutive pediatric patients with HGHD spondylolisthesis of L5-S1 were treated with instrumented monosegmental complete reduction and 360° fusion of L5-S1 using a fixation system with Schanz screws. Each patient was prospectively followed up at a minimum of 1 year (mean follow-up was 61 months; range 12-115). Our group included 4 boys and 10 girls with the mean age of 13.2 years (range 11-18 years). Results: The mean forward slippage of the L5 vertebral body was 65.9% preoperatively, 5.6% postoperatively and 5.7% at the follow up with a complete bone fusion in all patients confirmed by CT scans. With a significance level of 0.05 a statistically significant variance in the difference of graphical values was present between the preoperative and postoperative values in variables Slip %, Slip mm, Slip angle, Lumbosacral Slip Angle (Dubousset), Lumbosacral Slip Angle (SDSG), Pelvic Tilt, Pelvic Incidence except for Sacral Slope. The VAS and ODI values showed significant improvement in clinical status (VAS from 6.3 to 1.2 at last follow up, P = 0.001 033, 95%; ODI from 39.9 to 9.4 at last follow up, p = 0.001 359, 95%. Conclusion: The technique of complete reduction by monosegmental instrumentation is a safe technique in children, provides a high rate of bone fusion and good clinical results, including a satisfactory improvement in lumbopelvic measurements. In comparison to other surgical techniques complications are not significant.

A220: Spinal Growth Tethering Around the Apical Vertebrae Leads to Asymmetric Growth as a Mechanism of Spinal Deformity Correction in Kyphosis and Scoliosis

Alaaeldin Ahmad¹, Loai Aker², Ahmad Ghanem³

¹Polytechnique University, Ramallah - Palestinian Territory, Occupied ²Arabi Hospital, Nablus - Palestinian Territory, Occupied ³Annajah Medical School, Nablus - Palestinian Territory, Occupied

Introduction: Spinal growth tethering through posterior approach around the peaked wedged vertebrae in early onset scoliosis and kyphosis is a new non- fusion method that aims to create growth in the vertebrae that results in gradual deformity correction Material and Methods: The study consisted of an institutional review board-approved, retrospective review of the X-rays and 3D CT scans of 17 patients (4 scoliosis, 11 kyphosis, 2 kyphoscoliosis) All patients were with early onset scoliosis, underwent posterior tethering proximal and distal to the peak of the deformity as an adjunct to distraction-based growth-friendly or the Shilla implants performed by the same surgeon. The rate of change was calculated for the wedged apical vertebrae at the concave and convex heights in scoliosis. Same parameters were taken for vertebrae outside the tethering effect as a control group. Cobb angle and spinal height was also calculated Results: Mean follow up time 50.8 months. Mean age at surgery is 61 months within the tether: average pre op concave vertebral length: 7.45 mm(range 3.55-11.8); average last follow up concave vertebral length: 12.41 mm. p < 0.005; average pre op convex vertebral length: 13.67 (7.44-25.5); average last convex vertebral length: 16.76…p < 0.005; average preop ratio: 0.55(0.35-0.74) while average last follow up ratio: 0.76.(0.46-0.92) p < 0.005. Outside the tether: average pre op concave vertebral length: 10.64. average last follow up concave vertebral length: 14.37. p < 0.005; average pre op convex vertebral length: 13.18. average last follow up convex vertebral length: 17.65. p < 0.005; average preop ratio: 0.80. average last follow up ratio: 0.82. p = 0.064 (not significant). The concave vertebral height within the tether increased by 79.6% from preop to last follow up, while convex side increased by 27.2%…the increase in ratio is 20%. The concave vertebral height outside the tether increased by 42.7% from preop to last follow up, while convex side increased by 37.3%…the increase in ratio is 1.8%. Scoliosis cobb angle pre op mean was 51 (20-100), and in last follow up 43.8(16-89) p = 0.057 (not significant). Kyphosis cobb angle pre op mean 56.1(27-81) and in last follow up became 21.5 (10-62) p < 0.005. Spine length in preo op was 250.1 mm(183.7-324) and in last follow up became 292.27 (229.4 -373.2) p < 0.005. Conclusion: Posterior tethering in EOS will asymmetrically modulate the apical vertebrae which will correct the deformity with non fusion technique.

A221: Comparative Analysis of Static and Dynamic Intraoperative Skull-Femoral Traction (Iosft) in Adolescent Idiopathic Scoliosis (AIS) Correction

Ravi Ghag¹, Yale Tang¹, Sameer Desai², Christopher Reilly¹, Firoz Miyanji¹

¹Department of Orthopaedic Surgery, BC Children’s Hospital and University of British Columbia, Vancouver - Canada ²Department of Orthopaedic Surgery, BC Children’s Hospital, Vancouver - Canada

Introduction: Limited literature exists comparing outcomes in AIS correction with intraoperative skull-femoral traction (IOSFT), however, current findings suggest it to be an effective, safe, and well-tolerated adjunctive technique for improving outcomes and reducing healthcare resource use in curves > 80º. Furthermore, previous studies highlight the utility of IOSFT for large and rigid deformities, yet it is becoming increasing popular for use on smaller curves. Various IOSFT techniques exist, but to date no studies have compared the safety and efficacy of different IOSFT methods. The aim of this study is to compare the intra- and post-operative neurologic safety and clinical efficacy of static IOSFT, which places a fixed traction force, and dynamic IOSFT, which entails hanging weight from bilateral femora. Material and Methods: A retrospective comparative case series was conducted. Static IOSFT is applied with a fixed traction force, whereas 96 consecutive surgical patients treated by two surgeons at a tertiary care facility with mean 1.6 year follow-up between 2011 and 2014 were identified. 63 patients received static and 33 patients received dynamic IOSFT. Each surgeon employed only one mode of traction. Primary outcomes included neuromonitoring (NM) changes, estimated blood loss (EBL), OR time, length of stay (LOS), percent curve correction, and complications. Descriptive statistics, t-tests and Fisher’s exact test for significance (α = 0.05) were calculated for analysis. Results: We found comparable safety and efficacy between the two common methods of traction; dynamic IOSFT, and static IOSFT. Demographic variables and curve characteristics were similar between static and dynamic groups. Levels fused (12.3 static vs. 12.1 dynamic), EBL (601 mL static vs. 508 mL dynamic), OR time (365 min static vs. 376 min dynamic), LOS (6 days static vs. 5.8 days dynamic), and curve correction (71.5% static vs. 69.5% dynamic) were not significantly different. Mean traction weight applied in the dynamic group was 12.1 lbs to the head and 23.3 lbs to bilateral legs. NM changes were not significantly different: 11 (17.5%) patients in the static group and 4 (12.1%) patients in the dynamic group. Specifically, MEP and SSEP changes occurred in 11 (17.5%) and 2 (3.2%) patients in the static group and 3 (9.1%) and 1 (3%) patient in the dynamic group. Mean number of osteotomies was significantly higher in the static group (p < 0.001). No significant differences in mean follow-up major cobb angle (18.4º static vs. 20.3º dynamic), mean percent correction (71.5% static vs. 69.5% dynamic), or complication rates between the groups were observed. Conclusion: IOSFT in AIS correction is a safe and effective adjunctive technique in curves < 80°, with no neurologic complications in this cohort and similar rates of NM changes regardless of static or dynamic application. Perioperative clinical outcomes and postoperative radiographic outcomes were comparable between dynamic and static IOSFT. Further research is required to quantify safe amounts of IOSFT.

A222: Management of Early Onset Scoliosis Using Growing Rods vs Veptr. A Comparative Study.

David Meneses¹, Fernando Alvarado¹, Carlos Montero¹, Wilmer Godoy¹, Gustavo Rozo¹, Diana Rosero¹, Alexander Tristancho¹, Keli Silva¹

¹Department of Spine Surgery, Roosevelt Institute, Bogotá - Colombia

Introduction: Early onset scoliosis (EOS) was first described in 1936 and since then, the concept had been evolving. Nowadays, EOS is used to depict a deviation of more than 10° in the frontal plain measured by Cobb’s method. Previous treatment options included premature spine fixation, leading to cardiopulmonary complications and short torso syndrome. The advent of new treatment choices has resulted in diminishing of those ancient complications and better quality of life for children. Two of the most popular systems are growing rods and Vertical Expandable Prosthetic Titanium Rib (VEPTR); however these new systems has its own complications such as infections, skin and neurological damage and high rate of surgical interventions. Materials and Methods: An observational cross sectional study comparing patients with EOS diagnosis, who underwent surgical correction using growing rods or VEPTR systems between 2010 and 2016 in an IV level Orthopedics children Institute were evaluated. A non-probabilistic sampling was performed. Statistical analysis was performed with STATA v14 Statistics program. Results: 54 patients met inclusion criteria. Mean age at intervention were 6.6 and 6 years old for rods and VEPTR groups respectively. Mean Cobb angle was 62.9 for rods group and 66.4 for VEPTR. Gender distribution was as follows 7:3 and 6.5:4.5 for Rods and VEPTR. The groups were matched for every variable. Regarding the correction of the spine deformity, both systems achieved a statically significant value (Growing Rods p < 0.00 001 VEPTR p < 0.01; however, when compared with each other, growing rods achieved the best correction with statistical significance p < 0.04. Mean time between consecutive elongation surgeries was 11 months. No difference was noted between primary outcomes, including complications and only important difference were found in secondary variables without the possibility of establishing the individual value. Conclusion: EOS is challenging for spine surgeon due to the complexity of patients and additional comorbidities. Nowadays elongations systems are the mainstay of treatment. Growing rods and VEPTR systems are the most widespread worldwide. Growing Rods appears to better correct deformity without increase in complications, making it a more efficient system. Current literature recommends surgery every 9-12 months in contrast with previous concept of every 6 months, obtaining same clinical outcome with lower complications rates.

A223: Hemivertebra Excision in Pediatric Patients: How Does the Operation Technique Influence on Outcomes?

Ekaterina Umenushkina¹, Alexandr Mushkin¹, Denis Naumov²

¹Pediatric Surgery and Orthopedics clinic, St. Petersburg Research Institute of Phthisiopulmonology, Saint-Petersburg - Russian Federation ²Pediatric Surgery and Orthopedic clinic, St. Petersburg Research Institute of Phthisiopulmonology, Saint-Petersburg - Russian Federation

Introduction: Principles of surgical correction for congenital scoliosis caused by hemivertebra (hemivertebra excision and instrumentation) are well-established and unchanging during last 25 years. How does the changes in surgical technique are influence on the operative time and blood loss? Patients and Methods: 32 hemivertebra excision with posterior instrumentation was performed in 30 patients between 2014 and 2017. The average age of patients was 3 years and 11 mns (min = 1yrs 4 mns; max = 13 yrs) at the time of surgery. All operations performed by one surgeon experienced (more than 25 years) in such operations. It was studied how does operative approach, age, tools for bone removal and level of abnormality are influence on the operative time and blood loss (in ml and per cent from circulating blood volume, CBV). Results: Hemivertebrae located in thoracic spine in 18 cases and in lumbar in 14. According to operative tool, three groups were compared: in group 1 (n₁ = 17) the surgery was performed from two approaches (anterior and lateral) with hemivertebra excision by high-speed drill; in group 2 (n₂ = 7) surgery was done from posterior approach only with the same technique for bone removal; in group 3 (n₃ = 8) the surgery was from posterior approach only with bone removal by ultra-sound bone scalpel. The operation time was 208 ± 72 min, 187 ± 54 min and 171 ± 34 min per group. The blood loss was 181 ± 39; 181 ± 53 and 142 ± 28 (ml) or 11, 5 ± 1; 9, 4 ± 1,1 and 13 ± 1,9 (% of CBV) per group. Despite the clear differences we didn’t find statistically significance between groups (p₁ = 0,502; p₂ = 0,229, p₃ = 0,234), perhaps, it could be associated with small number of patients. The operation time (209 min. ± 17 min. vs 176 min. ± 10 min.) and blood loss (202 ml. ± 38 ml. vs 132 ml. ± 22 ml.) were significantly higher in thoracic abnormalities than in lumbar spine (p₄ = 0,049). Correlation between patients age and operation time and blood loss didn’t find. Conclusion: Development of operation technique and surgical tools could decrease operation time and blood loss in patients with hemivertebra. It is statistically confirmed that the thoracic hemivertebra is a predictor for higher operation time and blood loss in compare with lumbar ones.

A224: How do Different Ultrasound Measurements of the Scoliotic Spine Relate To The Cobb Angle? A Ct Based Study

Isabel Tromp¹, Rob Brink¹, Jelle Homans¹, Tom Schlösser¹, Marijn van Stralen², Moyo Kruyt¹, Winnie Chu³, Jack Cheng⁴, René Castelein¹

¹Department of Orthopaedic Surgery, University Medical Center Utrecht, Utrecht - Netherlands ²Imaging Division, University Medical Center Utrecht, Utrecht - Netherlands ³Department of Imaging and Interventional Radiology, Prince of Wales Hospital, The Chinese University of Hong Kong - Hong Kong ⁴Department of Orthopaedics and Traumatology, Prince of Wales Hospital, The Chinese University of Hong Kong - Hong Kong

Introduction: Ultrasound imaging of the scoliotic spine has gained growing attention as a radiation free alternative for the conventional radiographic diagnosis of scoliosis. Within radiography the Cobb angle is used, which is based on the angulation of the vertebral endplates in the coronal plane. Ultrasound visualizes the spine in a plane more posterior than the endplates and therefore it is not possible to determine the Cobb angle using ultrasound imaging. However, both the spinous processes (SP) and transverse processes (TP) can be used for ultrasound coronal curve assessment. In other words, no standardized ultrasound equivalent for the Cobb angle exists. In this study 3D computed tomography (CT) scans, are used to provide important information about the in vivo anatomical relations between the angles of the SP, TP and vertebral endplates. The aim of this study was to investigate the relationship between the anatomical landmarks (SP and TP) and test the validity as compared to the coronal Cobb angle using reconstructed CT scans. Material and Methods: The local ethical review board approved this study. From an existing database, 105 CT scans of adolescent idiopathic scoliosis patients were included. The coronal Cobb, SP and TP angle were measured for main thoracic and (thoraco) lumbar curves on CT scans reconstructed for the relevant plane. Intraclass correlation coefficients (ICC) were used to asses intra- and interrater reliability. Absolute differences as well as correlations were used to test the validity of the measurements. Results: Both anatomical landmark angle measurements showed a high reliability (SP angle ICC ≥ 0.70-0.93, TP angle ICC ≥ 0.85-0.99). On average, the Cobb, SP and TP angle were 55°, 37° and 49° in the thoracic curves, and 34°, 26° and 31°, respectively, in the (thoraco) lumbar curves. Moderate to very good correlations were seen for the SP angle with the Cobb angle in both curves (R2 = 0.62-0.80) and very good correlations for the TP angle with the Cobb angle (R2 = 0.84). Conclusion: SP and TP angle measurements represent structures located more posteriorly than the vertebral bodies, for this reason they have different absolute values than the Cobb angle. Relatively, however, the SP and TP are valid and reliable anatomical landmarks for assessment of coronal curve severity in adolescent idiopathic scoliosis. Based on our analysis, the TP angle appears to be more reliable than the SP angle and should be favoured for practical ultrasound use.

A225: The Benefits of Two Stage Front Back Surgery for Scheuremann’s Kyphosis Disease

Hai Ming Yu¹, Lui Darren¹, Sara Khoyratty¹, Sean Molloy¹, Alexander Gibson¹

¹Royal National Orthopaedic Hospital, London - United Kingdom

Introduction: Scheuremann Kyphosis has been traditionally treated as two staged anterior/posterior fusion (APF) or more recently with single stage posterior only fusion only (POF). Previous reports showed no significant difference in spinal height between these two groups. We compared the two techniques. Our aim was to compare single stage posterior fusion only versus two stage anterior/posterior fusion in patients with Scheuermann kyphosis. Materials and Methods: Retrospective review of 62 patients with SKD: 30 patients underwent POF and 32 underwent APF. Followed for mean 2.9y consecutively between 2006-2014 from 4720 deformity procedures. The 2 groups were well matched according to average age (APF 18.84, POF 18.77), preoperative kyphosis (T4-12) APF 88.3°, POF 83.5°, flexibility index (APF 34%, POF 35%), posterior fusion levels (APF 13.25, POF 12.47) and pre-operative spinal height (APF 457.05, POF 457.14). Results: At surgery, operating time was significantly less in the POF group (207.7 min vs 302 min; p < 0.05). There was no difference in residual kyphosis of the PFO group averaged 42.3° at final follow-up versus anterior/posterior fusion group (39.6°) but by definition the APF group had returned within normal range of kyphosis (10-40°). Kyphosis correction rate in the POF group averaged 45.86% at final follow-up versus the APF group (52.97%, p < 0.05). Post-operative spinal height greater in the APF 539.66 mm vs POF 517.13 mm (p < 0.05) and as percentage height gain 17.14% (APF) vs 12.58% (POF). There’s a high incidence of radiographic proximal junctional kyphosis (PJK) 80% (POF) vs 71.9% (APF) and distal junctional kyphosis (DJK) 16.7% (POF) vs 28.1% (APF). The POF revision rate was 24.3% (PJK 10%, DJK 3.3% Pseudoarthrosis 6.7%, infection 3.3%) vs APF = 18.7% (Pseudoarthrosis 3.1%, infection 9.4%, hardware 6.3%). Conclusion: APF achieved normal kyphosis with a better CR. The APF group resulted in greater post-operative spinal height both percentage height gained and actual. Operative time was less in the PFO group by a mean of 95 minutes. Interestingly there is a high incidence of radiographic PJK and DJK in both groups. However only the PFO group required surgical revision for PJK (10%) or DJK (3.3%) but the APF group had higher incidence of infection 9.4%(APF) vs 3.3%(POF).

A226: Reciprocal Changes in Sagittal Parameters Following Strategic Pedicle Screw Fixation Surgery in Adolescent Idiopathic Scoliosis

Ajoy Shetty¹, Srikant Reddy Dumpa², Rishi Mugesh Kanna³, S Rajasekaran⁴

¹Senior Spine Consultant, Dept of Orthopaedics, Ganga Hospital, Coimbatore - India ²Spine Fellow, Department of Orthopaedics, Ganga Hospital, Coimbatore - India ³Associate Consultant, Dept of Orthopaedics, Ganga Hospital, Coimbatore - India ⁴Chairman, Dept of Orthopaedics, Trauma & Spine Surgery, Ganga Hospital, Coimbatore - India

Introduction: Strategic pedicle screw fixation achieves good coronal correction in comparison with All pedicle screw construct for deformity correction in Adolescent Idiopathic Scoliosis (AIS). However the effect on sagittal parameters are least studied. Hence we aimed to quantify the changes in regional, spinopelvic and global sagittal alignment parameters in AIS patients following Strategic posterior pedicle screw fixation. Material and Methods: A retrospective study was conducted in 92 AIS patients (82 girls and 10 boys). Inclusion criteria were LENKE curve type I-VI who underwent posterior surgery with pedicle screw fixation at strategic levels, absence of neurological deficit, normal spinal MRI and minimum of 2 year follow up. Radiographic parameters assessed are Coronal plane parameters: Coronal cobb angle, Coronal Imbalance (CI), Regional Sagittal parameters are C0-C2 and C2-C6 angles (CSA), T2-T12 kyphosis (TSA), T5-12 kyphosis (TK) and Lumbar Lordosis (LL), Spinopelvic parameters are Pelvic Incidence (PI), Pelvic Tilt (PT), Sacral slope(SS) and Global sagittal parameters such as Sagittal vertical axis (SVA), Sacrospinal angle (SSA), Spinal Tilt (ST). Curve flexibility and Pedicle screw density ratio are also calculated. Statistical analysis done in overall group (n = 92), subgroups (Lenke I, Lenke V) and based on thoracic sagittal modifiers (Hypokyphotic, normokyphotic and hyperkyphotic group) to determine significances between preoperative and 2 year follow up radiographic parameters. Results: Mean age of patients in the study are 15.7 years .In overall group with primary curve flexibility of 41% and pedicle screw density ratio is 0.68, 67% correction achieved in coronal Cobb angle (p < 0.0001) and significant changes are noted in spino pelvic parameters (PI, PT and SS) and global sagittal parameters SVA and ST (p < 0.001). No significant difference was observed for regional sagittal parameters CI, CSA, TSA, TK, LL (P > 0.05). Sub group analysis in Lenke I (n = 40) shows significant changes in coronal cobb angle, global spinal parameters (SVA, SSA, ST) and in Lenke V (n = 25) significant changes are observed in coronal cobb angle correction, coronal imbalance (CI), LL, SS, PT, SVA. Subgroup analysis based on Thoracic sagittal parameters show significant changes in Regional thoracic parameters (p < 0.001) in Hypokyphotic and hyperkyphotic group whereas pelvic parameters and global sagittal parameters in normokyphotic group. Conclusion: Strategic pedicle screw fixation achieves significant curve correction irrespective of curve type (∼67%). Significant changes occur in spinopelvic and global sagittal parameters in overall group and normokyphotic group. AIS patients had negative sagittal imbalance preoperatively which increases postoperatively with normalization of spinal tilt in overall group, Lenke I and normokyphotic subgroups. Hypokyphotic and hyperkyphotic thoracic curve is corrected to normokyphosis in hypokyphotic and hyperkyphotic group. Hypolordotic curve and coronal imbalance are significantly corrected in Lenke V group.

A227: Surgical Correction of Spinal Deformity at Patients With Spinal Muscular Atrophy: Multicenter Analysis of National Experience and Literature Analysis

Egor Filatov¹, Sergey Riabykh¹, Dmitry Savin¹, Anastasiay Tretyakova¹, Sergey Kolesov², Andrey Baklanov³, Svetlana medvedeva¹

¹Ilizarov Centr, Kurgan - Russian Federation ²Cito, Department 7, Moskva - Russian Federation ³Center of Spine Patologi, Moskva - Russian Federation

Introduction: Neuro-muscular diseases (NMD) is a large group of genetic heterogenic diseases, their main clinical signs are weakness and atrophy of different groups of muscles. Spinal muscular atrophies (SMA) are the most frequent diseases from this group. Deformities of axial skeleton on the background of neuro-muscular diseases are narrowly presented in the literature. Materials and methods: Multicenter retrospective cohort including 26 patients at the age from 6 to 25 years old. Inclusion criteria: patients with neurogenic scoliosis on the background of SMA, genetically confirmed SMA diagnosis of 2 and 3 types, deformity in frontal plane more than 60° according to Cobb, radiological archive availability. Results: Amount of scoliotic curve before surgery was within the scope from 40° to 135° (average value - 92°), after – from 10° to 92° (average value - 52°). Percentage of correction was varying within the scope 13-75% (average value – 40%). Correction of frontal balance – 23%. Correction of frontal pelvis tilt – 17%. Respiratory function – insignificant growth after surgery. Improvement of functional class according to GMFCS after surgery for one level at 31% of patients. Complications: 1 patient – death, 2 – hematoma formation with application of secondary sutures, 1 patient – incompetence of metal-construction. Conclusion: Patients with deformity of axial skeleton on the background of SMA fall under the category of extremely high risk and need preoperative multidisciplinary study and further peri-postoperative care of patient. Surgical correction is indicated in decompensated deformity more than 40°. Surgical rehabilitation reasonably improves the quality of self-service and life of patients and ambience.

Degenerative Lumbar

A228: Morphometric MRI Study of the Corridor for the Oblique Lumbar Interbody Fusion (OLIF) Technique At L1-L5

Jia Xi Julian Li¹, Kevin Phan², Ralph Mobbs²

¹Faculty of Medicine, University of New South Wales, Kensington - Australia ²NeuroSpine Surgery Research Group, Randwick - Australia

Introduction: Anterior lumbar interbody fusion and lateral lumbar interbody fusion are associated with approach-related disadvantages. Oblique lumbar interbody fusion (OLIF) is a proposed solution. There is a paucity of studies investigating the advantages of OLIF and the anatomical basis for this technique. This study aims to analyze the size and regional anatomy of the corridor used in the OLIF technique between levels L1 and L5 which may assist with surgical decision making and operative planning. Material and Methods: 200 MRI studies, 20 males and 20 females in each age group (20-29, 30-39, 40-49, 50-59, and 60-69) with features of lumbar degenerative disease were randomly selected. The oblique corridor was defined as the smallest distance between the psoas major muscle and aorta/inferior vena cava (or common iliac artery) and measured at the L1/L2, L2/L3, L3/L4 and L4/L5 disc levels on both the left and right on the axial image at the mid-disc level. Potential obstruction to the corridor trajectory was noted if a perpendicular drawn from the corridor measurement line intersected with major anatomical structures. Results: Mean distances of the oblique corridor on the left were L1/L2 = 18.90 mm, L2/L3 = 15.50 mm; L3/L4 = 12.75 mm and L4/L5 = 8.92 mm, and on the right were L1/L2 = 14.80 mm, L2/L3 = 5.50 mm, L3/L4 = 3.00 mm and L4/L5 = 1.46 mm. For both sides, the corridor size was not significantly affected by sex, increased with age and decreased at the inferior lumbar disc levels. The L1/L2 and L2/L3 levels may be obstructed by the ipsilateral kidney and renal vasculature on both sides, and the liver on the right. Conclusion: A left-sided OLIF approach is viable for both sexes. Oblique access to the L1/L2 and L2/L3 disc levels is feasible regardless of age, while the L3/L4 and L4/L5 levels may be more suitable in the elderly, especially for males. The right-sided approach is less likely to be effectively performed due to anatomical constraints.

A229: Lumbar Degenerative Disc Disease: Influence of Sagittal Balance

Elisabete Ribeiro¹, Filipa Carvalho², Bruno Direito Santos¹, Cecília Sá Barros¹, Mário Batista¹, Pedro Varanda¹, Rui Duarte¹

¹Department of Orthopaedics, Hospital de Braga (HB), Braga - Portugal ²School of Medicine, University of Minho (SM-UM), Minho - Portugal

Introduction: Sagittal balance is the result of a harmonious articulation of the spine and pelvis. Changes in these parameters may lead to imbalances on shear and compressive forces that increase the risk of spinal pathology. Underlying mechanisms that favor the onset and development of lumbar disc degenerative disc disease at early ages are poorly understood. However, it is know that mechanical stress to the spine might accelerate the development of disc degeneration and increases the risk of early disc herniation. Our aim was to evaluate the relationship between sagittal balance and lumbar degenerative disc disease in young adults. Material and Methods: From our spinal unit database, we selected 65 patients between 18 and 35 years old with potential lumbar degenerative disc disease referral and no other spinal conditions. Based on Magnetic Ressonance Images, a “control group” (23 patients, grade I-II of Pfirrmann classification) and a “disease group” (42 patients, grade III-V of Pfirrmann classification) were obtained and spinopelvic parameters (Sagittal Vertical Axis - SVA, Thoracic Kyphosis –TK, Lumbar Lordosis - LL, Pelvic Incidence - PI, Pelvic Tilt – PT, and Sacral Slope - SS) were measured on long-standing lateral radiographs. Statistical analysis was performed with using SPSS® statistical package 22 and GraphPad Prism 7.00. Results: The mean values of LL, SS and PI were significantly lower (ρ < 0.05) in the “diseased group” (55.19° ± 8.34, 35.08° ± 6.77 and 46.92° ± 9.17, respectively), when compared to the control one (62.91° ± 8.01, 41.26° ± 6.94 and 51.84° ± 10.30, respectively). In the former group, a statistically significant correlation regarding Pfirrmann grades was found for the LL angle (ρ = - 0.433) and for the SS angle (ρ = - 0.286). For a given PI, LL and SS values tended to be lower, and PT values tended to be higher. Conclusion: Present data suggest that we young patients with lumbar degenerative disc disease have significantly lower SS and LL angles, suggesting that more verticalized pelvis and flatter lumbar spine trigger higher Pfirrmann grades. Low PI values may appear as a predisposing factor for early development of the disease. These data overlap current literature. It seems the loss of lordosis observed in the “disease group” might lead to compensatory pelvic retroversion (PT increasing and SS decreasing), to achieve a new sagittal balance. In conclusion, according to our data, spinopelvic morphology characterization might appear as a valuable tool for better understanding the pathophysiology of lumbar degenerative disc disease.

A230: Modic Changes - Degenerative or Infective?? A Causative Study

Saurabh Singh¹ Siddalingeshwara G I², Alok Rai³, Prabhat Pandey⁴, Manikant Anand⁴

¹Associate Professor, Department of Orthopaedics, IMS, BHU, Varanasi - India ²Junior Resident, Department of Orthopaedics, IMS, BHU, Varanasi - India ³Senior Resident, Department of Orthopaedics, IMS, BHU, Varanasi - India ⁴Department of Orthopaedics, IMS, BHU, Varanasi - India

Introduction: Since long time Modic changes are believed to be degenerative process. But occurrence of such changes in young individuals led to further studies that linked Modic changes to infective origin. Although there are studies that show relation of Modic changes to infectious discitis there is no such study that has been done to quantify the inflammatory markers. Till date the studies that have been done are based on isolation of bacteria by culture method or the detection of raise in various pro inflammatory markers. As such the culture isolation is considered to be very poor in sensitivity and surrogate markers of inflammation are very much non specific. Therefore the present study was done to detect the presence of bacteria by extremely sensitive and specific technique: amplification by Polymerase Chain Reaction (PCR).This article is about the study that had been conducted to know whether there is correlation between Modic changes and the infection in the disc that might have led to vertebral end plate changes(Modic changes). Materials and Methods: The study involved 20 patients of both sex with age ranging from 20-65years.

Inclusion Criteria:

Back pain for at least one month.

Patients with Modic changes at Lumbar Spine level on Magnetic Resonance Imaging(MRI).

5 ml of venous blood was collected from each patient under aseptic conditions and sent for Complete Blood Count, Erythrocyte Sedimentation Rate, Quantitative C-Reactive Protein in their respective vials. Atleast 1 cc of intervertebral disc was collected from each patient under aseptic conditions in operation theatre during surgery and stored in sterile container containing sterile normal saline. This sample was sent to department of microbiology for PCR study. In the present study we have targeted the conserved gene of the bacteria i.e. 16 s Ribosomal DNA. We have used universal eubacteria nested amplification protocol which may detect as low as picograms of bacterial DNA. Result: Among the total cases of 20 patients who had low back pain and Modic changes in MRI, 10% cases showed raised Leucocytosis, 25% cases showed raised ESR, 75% cases showed raised Q- CRP and 90% showed presence of bacteria in PCR study. Conclusion: Thus we can conclude that Vertebral end plate changes (Modic changes) may have an infective etiology such as bacteria which may have led to local inflammatory process and raised levels of acute phase reactants. This local inflammation might have led to vertebral end plate changes which appear in the MRI as Modic changes.

A231: A Comparison of Patient Reported Outcomes Between a Universal and Multi-Tier Health Care System in Surgical Patients With Degenerative Spondylolisthesis

Tamir Ailon¹, Jin Tee¹, Nicolas Nicolas Dea¹, Hamilton Hall², Kenneth Thomas³, Y. Raja Rampersaud², Charles Fisher⁴

¹Department of Orthopaedics, Vancouver - Canada ²Department of Orthopaedics, University of Toronto, Toronto - Canada ³Department of Orthopaedics, University of Calgary, Calgary - Canada ⁴Department of Orthopaedics, University of British Columbia, Vancouver - Canada

Introduction: Canada has a national health insurance program with unique properties: it is single-payer, coverage is universal, and access to specialist care is triaged by the family primary care physician. The United States on the other hand is a multi-tier payer system with rapid access for insured patients to specialist care. Materials and Methods: Surgical DS patients treated between 2013 and 2015 were identified in the Canadian Spine Outcome Research Network (CSORN) database. This population was compared with the surgical DS arm of the Spine Patients Outcome Research Trial (SPORT) study. We compared baseline demographic, spine-related, and health-related quality of life (HRQOL) outcomes at 3-months and 1-year. Multivariate analysis was used to identify factors predictive of outcome in surgical DS patients. Results: At baseline, the CSORN cohort of 213 patients was compared to the SPORT cohort of 248 patients. Patients in the CSORN cohort were younger (mean age 60.1 vs. 65.2; p < 0.001), comprised less females (60.1% vs. 67.7%; p = 0.09), and more smokers (23.3% vs. 8.9%; p < 0.001). The SPORT cohort had more patients receiving compensation (14.6% vs. 7.7%; p < 0.001). The CSORN cohort consisted of patients with greater baseline disability (ODI scores: 47.7 vs. 44.0; p = 0.008) and had more patients with symptom duration of more than 6-months (93.7% vs. 62.1%; p < 0.001). Despite having greater baseline and 1-year postoperative Oswestry Disability Index (ODI) scores, the CSORN cohort showed greater satisfaction with surgical results at 3-months (91.1% vs. 66.1% somewhat or very satisfied; p < 0.01) and 1-year (88.2% vs. 71.0%, p < 0.01). Improvements in back and leg pain were similar between the cohorts. On multivariate analysis, duration of symptoms, treatment group (CSORN versus SPORT) or insurance type (public/Medicare/Medicaid vs. Private/Employer) predicted higher level of post-operative satisfaction. Baseline depression was associated with higher ODI at 1-year follow-up. Conclusions: Surgical DS patients treated in Canada (CSORN cohort) reported higher levels of satisfaction than those treated in the US (SPORT cohort) despite similar to slightly worse baseline HRQOL measures. Symptom duration and insurance type appeared to impact satisfaction levels. Improvements in other patient reported health-related quality of life measures was similar between the cohorts.

A232: The Association of Inflammatory Bowel Disease With Short-Term Outcomes Following Lumbar Fusion

Joseph Tanenbaum¹, Stephanie Kha¹, Edward Benzel¹, Michael Steinmetz¹, Thomas Mroz¹

¹Cleveland Clinic Center for Spine Health, Cleveland - United States

Introduction: The United States Centers for Disease Control (CDC) estimates the prevalence of inflammatory bowel disease (IBD) at over 3.1 million people. As diagnostic techniques and treatment options for IBD (including both Crohn’s disease and ulcerative colitis) improve, the prevalence of IBD is expected to increase. For spine surgeons, patients with IBD have a unique complication profile because IBD patients may present with poor nutritional status and because the medications used to manage IBD have been associated with poor vertebral bone mineralization. Presently, there are very limited data regarding perioperative outcomes among patients with IBD that undergo spinal surgery, largely because it is a relatively rare comorbidity. National databases are therefore uniquely positioned to fill this gap in the literature. The present study begins to address this gap by describing trends in lumbar fusion patients with IBD and by quantifying the association between IBD and immediate postoperative outcomes using a large, nationally representative database. Methods: The annual volume of primary lumbar fusion was obtained from the Nationwide inpatient Sample (NIS) from 1998-2011 and patients younger than 18 years of age were excluded. The prevalence of IBD in this population (both Crohn’s and ulcerative colitis) was determined using ICD-9-CM codes. Prevalence of IBD among lumbar fusion patients, surgical complications (neurologic complications, acute respiratory failure, implant related complications, incidental durotomy, hemorrhage or hematoma, and wound complications), medical complications (AMI, pulmonary embolism, pneumonia, acute renal failure, deep vein thrombosis, sepsis, and stroke), length of stay (LOS), and hospital costs (inflated to 2011 U.S. Dollars) were used as outcomes. Logistic regression models were estimated to determine the association between IBD and the odds of postoperative medical and surgical complications while controlling for patient demographics, comorbidity burden, and hospital characteristics. The complex survey design of the NIS was taken into account by clustering on hospitals and assuming an exchangeable working correlation using the discharge weights supplied by the NIS. We accounted for multiple comparisons using the Bonferroni correction and an alpha level for statistical significance of 0.0028. Results: The prevalence of IBD is increasing among lumbar fusion patients, from 0.21% of all lumbar fusion patients in 1998 to 0.48% of all lumbar fusion patients in 2011 (p < 0.001). The odds of experiencing a post-operative medical or surgical complication were not significantly different when comparing IBD patients to control patients without IBD after controlling for patient demographics, comorbidity burden, and hospital characteristics (p XYZ and ABC, respectively). Both the median length of stay and median costs were significantly/not greater for patients with IBD relative to control patients. Conclusions: Among lumbar fusion patients, IBD is a rare comorbidity that is becoming increasingly more common. Importantly, IBD patients were not at increased risk of immediate postoperative complications. Spine surgeons should be prepared to treat more IBD patients and should incorporate the present findings into preoperative risk counseling and patient selection.

A233: The Prevalence of Diffuse Idiopathic Skeletal Hyperostosis in Four Different Patient Cohorts: In Search of Pathogenesis Hypotheses

Jonneke Kuperus¹, Willem Paul Gielis¹, Joost van Herwaarden², Stan Buckens³, Cumhur Oner¹, Pim de Jong³, Jorrit-Jan Verlaan¹

¹Department of Orthopedics, University Medical Center, Utrecht - Netherlands ²Department of Vascular Surgery, University Medical Center, Utrecht - Netherlands ³Department of Radiology, University Medical Center, Utrecht - Netherlands

Introduction: Diffuse idiopathic skeletal hyperostosis (DISH) is an increasingly prevalent ankylosing condition that confers an increased risk of spinal fractures hypothetically as a result of biomechanical changes of the spine. The aim of this study was to analyze if biomechanical stress-shielding occurs in subjects with DISH by longitudinally measuring bone mineral density (BMD) in the vertebral body of subjects with and without DISH, and in the newly formed bone in subjects with DISH. Materials and Methods: Chest computed tomography (CT) scans of male subjects aged > 50 with two scans with an interval of at least 2.5 years were selected after approval by the medical ethical committee. The first and last CT scan of each subject was evaluated for the presence of DISH using the Resnick criteria. This resulted in a group with pre-DISH (no DISH at the first scan, DISH at the last scan), a group with definite DISH (DISH at both the first and last scan) and a control group. Mean Hounsfield units (HU) were measured in the new bone formation (if present) and in the anterior part and posterior part of the upper vertebral body (1/3 of the vertebral body, above the endplate). The HU values were collected in all levels of the control group and in the most cranial, middle and most caudal levels with DISH. To serve as internal control the HU values were measured in the vertebral body two levels above and below the bridging hyperostosis in the groups with DISH. The paired samples t-test and the independent samples t-test were used after careful assessment of the distribution of the data. Results: The BMD in the new bone formation significantly increased (mean ΔHU 137.5, p-values < 0.01) during a mean interval of 5 years at the cranial, middle and caudally involved vertebral segments for both DISH (pre- and definite) groups. The BMD of the vertebral bodies included in the ankylotic segments in the DISH group did not significantly differ from the non-ankylotic vertebral bodies in the same subject. In contrast to our hypothesis, the vertebral body HU value decreased more in the control group compared to the groups with DISH, however statistical significance was reached at one level only (p = 0.048). Conclusions: The new bone bridges in subjects with (pre-)DISH showed increasing BMD over time. However, our data suggests that vertebral BMD is not influenced by the presence of DISH. It can be hypothesized that increased spinal stiffness may be a more important factor than vertebral BMD when explaining the increased fracture risk and typical fracture patterns observed in individuals with DISH.

A234: Surgeon Management of Osteoporosis in Instrumented Spine Surgery: AO Spine Latin America Survey

Marcelo Molina Salinas¹, Samuel Pantoja Contreras¹

¹Departamento de Traumatología y Ortopedia Clínica Las Condes, Santiago - Chile

Introduction: StudyDesign: Surveystudy. Objective: To determine the impact of the osteoporosis (OP) in instrumented spine surgery among latin american spine surgeons. Material and Methods: A survey was sent to all members of Latin American AOSpine (AOSLA). The survey consisted of 16 questions designed to determine aspects related to: incidence and type of complications experienced, strategies used by surgeons to prevent intra-operative complications and finally prevention and treatment prior to surgery. The questions had a multiple choice answer format. Results: The survey was answered by 349 spine surgeons in Latin America. Approximately 80% recalled having had to manage complications directly related to OP and the 71% of responders referred having had to revise spine instrumentation because of OP-related complications. Techniques employed for prevention of intra-operative complications were varied; 65% extended instrumentation to incorporate additional segments and 63% performed vertebral body cement injection. Screening for OP prior to surgery was effected routinely by 19% of surgeons. For patients with risk factors pre-operative evaluation of BMD increased to 75%. A limit value of BMD for delay surgery was not established in 66.4% of respondents. Consultation for OP management was requested for a majority of cases (81%), mostly directed to endocrinology (56.3%). Interestingly, 19% of responding surgeons elected to personally manage their patient's OP. Most surgeons directly participate in managing their patient's OP, more frequently with Calcium, Vitamin D and diphosphonates (74.3%, 73.1% and 73.1% respectively). Conclusion: The management of patients subject to instrumented spine surgery with osteoporosis is controversial. There are no standardized guidelines on how to evaluate or treat patients undergoing instrumented spine surgery in the presence of OP. This study determines on a global perspective how latin american spine surgeons manage patients with osteoporosis. The reported incidence of adverse events associated to OP is very high. Evidence based recommendations are needed to improve the management of this challenging clinical scenario. Because current evidence is weak and limited, data based in prospective randomized trials are urgently needed to provide better recommendations.

Keywords: spine surgery, osteoporosis, complications, AOSpine, survey

A235: The Natural Course of Diffuse Idiopathic Skeletal Hyperostosis in the Thoracic Spine of Adult Males

Jonneke Kuperus¹, Stan Buckens², Jurica Šprem³, Cumhur Oner¹, Pim de Jong², Jorrit-Jan Verlaan¹

¹Department of Orthopedics, University Medical Center, Utrecht - Netherlands ²Department of Radiology, University Medical Center, Utrecht - Netherlands ³Image Science Institute, Utrecht - Netherlands

Introduction: Diffuse idiopathic skeletal hyperostosis (DISH) is characterized by flowing bony bridges typically on the right side of the thoracic spine. Knowledge on the growth and development of these spinal bridges is limited. A retrospective longitudinal computed tomography (CT) study was performed describing the natural course of DISH to bridge this gap and to support further research on the pathophysiology of DISH. Materials and Methods: Chest CT scans from elderly male subjects were collected from our database if two scans were available with an interval ≥ 2.5 years. All scans were evaluated for the presence of DISH using the Resnick criteria. If DISH developed during the interval subjects were allocated to the pre-DISH group. Subjects with DISH at both the first and last CT scan were assigned to the definite DISH group. A scoring system based on the completeness of a bone bridge (bridge score 0-3), extent of fluency (flow score 0-3) and location of the new bone was created to evaluate the progression of bone formation. Statistics were performed on the mean results of the three parameters of the new scoring system using a paired t-test after careful assessment of the distribution of the data. Results: In total 145 of 1367 subjects were allocated to the DISH groups (55 pre-DISH and 90 definite DISH). The interrater reliability of the various components of the scoring system was moderate to good (ICC 0.6 - 0.9). The prevalence of a complete bone bridge over all segments increased over time from 11.3% to 31.0% in the pre-DISH group and from 45.0% to 55.8% in the definite DISH group. The mean bridge score increased significantly in both the pre-DISH group (1.4 to 1.8; p < 0.001) and the definite DISH group (1.9 to 2.1; p < 0.001). The new bone gradually became more flowing and expanded circumferentially. Conclusion: Over the course of five years the new bone developed from incomplete, pointy bone bridges to more flowing complete bridges. This suggests an ongoing and measurable bone forming process that continues to progress also in established cases of DISH. The results of the present study can be used to create new consecutive criteria for DISH and to investigate if parameters such as age, BMI and/or specific biomarkers are related to the progression of DISH.

A236: Comparison of Four Rods Technique vs. Two Rods Technique With TLIF in Elderly Patients With Ads

Dmitry Ptashnikov¹, Sergey Masevnin¹, Nikita Zaborovskii¹

¹Department of Spine Surgery, Russian Research Institute of Traumatology and Orthopedics named after R.R. Vreden, St. Petersburg - Russian Federation

Summary: Adult degenerative scoliosis (ADS) is a common problem in the World, affecting mostly those over the age of 60. A retrospective study of 345 patients (age 60 - 83 years) with ADS. According to ODI, ASIA, SVA, VAS data, patients with ADS who underwent spinal fusion have different clinical and radiological outcomes in different operative techniques. Study Design: Comparison of two groups with different surgical techniques. The first group comprising of patients (n = 180) operated with four rods and the second (n = 165) comprising of patients with TLIF of all lumbar segments and two rods. Minimum of 2-years follow-up. Introduction: The stability of fixation after PSO, multilevel SPO and correction is a problem at the present stage. The failure of fusion has been found in a minimum of 20% of patients. Our study set out to compare clinical and radiological outcomes in patients with ADS treated surgically by four rods and TLIF of all lumbar segments and two rods. Methods: A retrospective study of 345 patients (age 60 – 83 years) with ADS. Mean follow-up period was 4 years (2-7 years). Inclusion criteria: age > 60 yrs, no prior surgery, and ADS (scoliosis ≥ 20 degrees, sagittal vertical axis (SVA) ≥ 6 cm, pelvic tilt (PT) ≥ 25 degrees, or thoracic kyphosis (TK) > 60 degrees). Demographic, radiographic and HRQOL data evaluated including Oswestry Disability Index (ODI), ASIA and VAS pain scale. Patients were divided into 2 groups depending on the applied surgical techniques: the first group included 180 cases with four rods, transpedicular screw fixation and multilevel SPO+PSO, the second group included 165 cases with transpedicular screw fixation, multilevel SPO+TLIF on all lumbar levels. There was no significant difference between pre-op age, VAS, ASIA and ODI in both groups. Results: In the both groups, a full restoration of the sagittal & coronal balance was achieved. At 4 years control showed, that the late complications include adjacent segment disease with spinal stenosis and proximal junctional kyphosis were in 5% in the I group and 6.2% in the second group (p = 0.2). Broken rods were noted only in 10% of patients in the II group in the level of PSO. Post-op ODI, VAS and ASIA improved in all groups with no significant differences between them (p = 0.3). Conclusions: Using the four rods technique allow good clinical outcomes to be achieved and reduce the number of complications.

Trauma

A237: Diffusion-Weighted MRI Assessment of Adjacent Disc Degeneration After Thoracolumbar Vertebral Fractures

David Cesar Noriega Gonzalez¹, Francisco Ardura¹, Ruben HernandeZ Ramajo¹

¹Orthopedic Department, Valladolid University, Valladolid - Spain

Introduction: The ageing process and those factors triggering degeneration of the intervertebral disc are still debated among spine surgeons in the field. The purpose of our study was to determine the water diffusion in the thoracolumbar discs adjacent to a previous vertebral fracture. By using the mean apparent diffusion coefficient (ADC), the aim of this work was to analyse if a relationship exists between disc ADC and MR findings of adjacent disc degeneration after thoracolumbar fractures treated by anatomic reduction using cement augmentation. Materials and Methods: A series of 20 non-consecutive voluntary patients treated because of vertebral fractures (mean age, 50.7 years; range, 45-56 years) were included in the study. There were 10 A3.1 and 10 A1.2 fractures (AO classification). Surgical treatment was applied in 14 cases, and conservative in 6 cases. The intention of the surgery was the anatomical restoration of the vertebral endplates by placement of expandable implants into the vertebral body through a minimally invasive transpedicular approach. MRI T2-weighted images and mapping of apparent diffusion coefficient (ADC) of the intervertebral disc adjacent to the fractured segment were performed after a mean follow-up of 32 months. A total of 60 discs, 3 per patient, were analysed: infra-adjacent, supra-adjacent and a control disc one level above the supra-adjacent. Results: There were no differences between patients surgically treated, and those following a conservative protocol regarding the average ADC values obtained in the 20 control discs analysed. Taken all cases together, the average ADC in the supra-adjacent level was lower than in the infra-adjacent (1.53 ± 0.06 versus 1.35 ± 0.12; P < 0.001). Average ADC values of the disc used as a control were similar to those at the infra-adjacent level (1.54 ± 0.06). As compared to surgically treated patients, discs at the supra-adjacent fracture level showed statistically significant lower values in cases treated orthopedically (p < 0.001). The variation in the delay of surgery had no influence on the average values of ADC at any of the measured levels. Conclusion: ADC measurements of the supra-adjacent disc after a mean follow-up of 32 months following thoracolumbar fractures showed that restoration of the vertebral collapse by minimally invasive vertebral reduction and augmentation prevent posttraumatic disc degeneration.

A238: Current Practice of Worldwide Steroid Prescription for Acute Spinal Cord Injury

Asdrubal Falavigna¹, Abdulaziz Al-Mutair², Giuseppe Barbagallo³, Darrel Brodke⁴, Daniel RIew⁵, Alisson Teles⁶, Chung Chek Wong⁷, Francine Quadros⁸

¹University of Caxias do Sul - Brazil ²Alrazi Hospital, Ministry of Health / Kuwait Institute for Medical Specialization - Kuwait ³Azienda Ospedaliero-Universitaria Policlinico Neurosurgery, Catania - Italy ⁴Spine Service University of Utah, Department of Orthopaedics, Salt Lake City – United States ⁵Department of Orthopedic Surgery, Columbia University, New York – United States ⁶Department of Clinical Neurosciences, Division of Neurosurgery, University of Calgary - Canada ⁷Sarawak General Hospital, Department of Orthopedic Surgery, Jalan Tun Ahmad Zaidi Adruce, Sarawak - Malaysia ⁸Laboratory of Clinical Studies and Basic Models of Spinal Disorders at Universidade de Caxias do Sul - Brazil

Introduction: Currently, routine use of MP for SCI is not recommended because of a higher incidence of complications and no evident efficacy. Nevertheless, MP is still used worldwide to treat acute SCI. To continue the line of the previous publication using steroid for acute spinal cord injury (SCI) by spine surgeon from Latin America (LA) and assess the current status of methylprednisolone (MP) prescription in Europe (EU), Asia Pacific (AP), North America (NA), and Middle East (ME) to determine targets for educational activities suitable for each region. Material and Methods: English version of a previously published questionnaire were used to evaluate opinions about MP administration in acute SCI in LA, EU, AP, NA, and ME. This internet-based survey was conducted by members of AOSpine. The questionnaire asked about demographic features, background with management of spine trauma patients, routine administration of MP in acute SCI and reasons for MP administration. Results: A total of 2,659 responses were obtained for the electronic questionnaire from LA, EU, AP, NA, and ME. The number of spine surgeons that treat SCI was 2,206 (83%). The steroid was used by 1,198 (52.9%) surgeons. The uses of MP were based predominantly on the National Acute Spinal Cord Injury Study (NASCIS) III study (n = 595, 50%). The answers were most frequently given by spine surgeons from AP, ME, and LA. These regions presented a statistically significant difference from North America (p < 0.001). The number of SCI patients treated per year inversely influenced the use of MP. The higher the number of patients treated, the lower the administration rates of MP were observed. Conclusion: The study identified potential targets for educational campaigns, aiming to reduce inappropriate practices of MP administration.

A239: Coccydynia, Outcome 1 Year After Surgical Treatment of 138 Consecutive Patients

Ane Simony¹, Stig Mindedahl Jespersen², Carsten Ernst³

¹Center for Spine Surgery & Research, Middelfart Hospital., Middelfart - Denmark ²Department of Spine Surgery, Odense University Hospital, Odense - Denmark ³Department of Spine Surgery, Silkeborg Hospital, Silkeborg - Denmark

Introduction: Pain related to coccyx is a common pain disorder after trauma, falling or sports related injury. Coccydynia is mostly reported in females, in the age 30-60 years. Patients suffer from pain in sitting position, pain during defecation and intercourse. Many treatment modalities have been suggested, including Doughnut pillows, steroid injections, special physiotherapy and pain medication. Surgical treatment has been used previously, but only very few case studies report the outcome after surgical treatment. The purpose of the study was to report the outcome and rate of complications, 1 year after surgically treatment. Material and Methods: 138 consecutive were included in this study. Patients were referred to surgical evaluation, 12-18 months after the trauma. All patients had received conservative treatment, including 3 steroid injections. Patients reported pain, VAS > 3 in sitting position and a complete relief of symptoms when standing or walking. Patients were included in the National clinical Database, Danespine prior to surgery, and received a variety of Questionnaires including SF36 and ODI 3 and 12 months after surgery. Data was analyzed using Stata version 1.2. Results: 138 consecutive patients were included in this study, and all patients were evaluated by the surgeon 3 and 12 months after surgery. Data was entered to the Database by a research nurse. 3 months after surgery, 40% of the patients were pain free in sitting position, 47% of the patients still experienced some degree of pain/ discomfort in sitting position, and 13% of the patients still reported pain. 1 year after surgery, 99 patients are satisfied with the results after surgey, 22 patients had some relief but are still suffering from symptioms and 17 patients reported unchanged symptoms. 32 patients developed infections, 2 patients deep infections which needed revision surgery and 2 patients were re operated due to rupture of the skin. Conclusion: Patients with severe coccydynia and a pain duration more than 12-18 months, despite conservative treatments, should be referred for surgical evaluation. Removal of the coccyx, is a safe procedure, with a satisfactional outcome in most patients.

A240: Early Decompression for Spinal Cord Injury: The Faster the Better

Bilal Qutteineh¹, Leon Kaplan¹, Amir Hasharoni¹, Eyal Itshayek¹, Schroeder Josh¹

¹Hadassah University Hospital, Jerusalem - Israel

Introduction: There is preclinical data indicating that early decompression in spinal cord injury (SCI) can improve outcome. Fehlings et al has shown in the STASCIS study the there is an advantage in decompression under 24 hours in cervical spine fractures. Our objective was to evaluate the relative effectiveness of surgery done under 12 hours from traumatic SCI. Material and Methods: A retrospective review of all patients admitted to a level one trauma center with SCI between 01/2006 to 02/2017, we included patients who were surgically treated within 48 hours of admission with 6 month or more follow up. Patients’ medical records were reviewed for location of vertebra fracture, presence of acute spinal cord injury, mechanism of injury, associated injuries, time to surgery (group A: less than 12 hours, group B: 12-24 hours, group C: 24-48 hours), length of hospital stay, ASIA impairment scale before surgery, after surgery, and at long term follow up. The neurological outcome was compared to the results present in the STASCIS study. Results: 49 patients (35 males: 14 females) with SCI were admitted and surgically treated within 48 hours of admission. Mean age at admission was 36 years (range 15-79 years). The mean follow up was 30 months (range 7-110 months). 50% were injured in motor vehicle accident while 48% due to falls. 37 were operated within 12 hours (average- 5.5 hours (range 1.5-11), 7 were operated between 12-24 hours and 5 were operated after 24 hours. At long term follow up after surgery, 55% of patients with acute spinal cord injury had been improved in their ASIA scale. After Surgery, in group A 67.5% of patients improved in their ASIA score (P = 0.06 when compared to under 24 hours in the STASCIS study) with 41% with a 2 grade or more improvement in their ASIA scores (P < 0.01 when compared to under 24 hours in the STASCIS study), in group B 44% of patients improved in their ASIA, while in group C only 40% of patients improved in their ASIA score (none of them had ≥ 2 grade improvement in their ASIA scores). Conclusion: Early surgical intervention should be advised for patients with acute spinal cord injury. Surgery under 12 hours from the trauma should be recommended at as it is associated with improved outcome.

A241: Incidence and Risk Factors for Infection After Operatively Treated Spinal Trauma – a Retrospective Review of 2,276 Patients From a Single Level I Trauma Institution

Richard Bransford¹, Brett Walker¹, Carlo Bellabarba¹

¹Department of Orthopaedics, Harborview Medical Center, Seattle - United States

Introduction: In the USA, it is estimated that 300 000-500 000 surgical site infections occur each year that are associated with increased healthcare related costs. Few studies have looked specifically at surgical site infections in spine trauma, however, rates in the literature suggest a 10-15% rate of post-operative wound infection. The purpose of our study was to examine a large group of patients who underwent surgical management of spine fractures to assess rates of infection and try to identify potential risk factors. Material and Methods: After obtaining IRB approval, patients were identified by searching specific CPT codes (22 851, 22 325, 22 326, 22 327) and linked ICD-9 codes (codes beginning with 8) from January 2005 to December 2015. From the larger group, we then identified patients with CPT codes 998.59 or 996.67 who required a secondary irrigation and debridement. We did not include patients who may have had a superficial infection managed non-operatively. Patients less than 18 years of age were excluded. A chart review of the identified patients documented a large set of demographics (age, sex, BMI, tobacco use, drug use, diabetes, fracture location, surgical approach, injury severity score (ISS), ICU stay, and overall length of stay to allow for comparison between those with infection and those without. Results: 2,276 adult patients underwent operative management of a spine fracture between January 2005 and December 2015. 637 (28%) were cervical injuries, 887 (39%) thoracic, and 752 (33%) lumbar with 6% undergoing an anterior approach, 92% a posterior approach, and 2% a combined anterior/posterior. Following index procedure, 64 patients (2.8%) required a secondary unanticipated return to the OR for irrigation and debridement secondary to infection. Anatomic location of injury (cervical, thoracic, lumbar) did not affect rate of infection in our study. Comparing those with infection to those without, there were no differences in age, BMI, or ISS. Smoking (p = 0.0009), drug use (p = 0.01) and ICU stay (p = 0.041) were all associated with higher rates of infection. Conclusion: This study in a single level I trauma institution shows a post-operative infection rate of 2.8% in patients undergoing operative management of spine fractures. Factors associated with increased infection rate included smoking, illicit drug use, and patients admitted to the ICU.

A242: Current Incidence and Management of Spine Trauma at A Large Referral Center in Tanzania

Andreas Leidinger¹, Eliana Eunhee Kim¹, Salim Rashidi Msuya², Rodrigo Navarro-Ramírez¹, Hamisi K. Shabani², Roger Härtl¹

¹Department of Neurosurgery, Weill-Cornell Brain and Spine Center, New York - United States ²Muhimbili Orthopaedic Institute, Dar es Salaam - Tanzania, United Republic

Introduction: Spine Trauma (ST) is a prevalent condition worldwide that can carry life-long devastating consequences for people and increased costs, especially in developing countries. Tanzania has no standard of care related to ST. The objective of this study is to report and analyze for the first time the demographics, clinical and surgical management and outcomes of patients presenting with ST in Tanzania. Methods: We prospectively collected data on ST patients in the only referral center for Spinal Trauma in Tanzania from October 2016 to the September 2017. We collected general demographics and the following information: distance from site of trauma to the center, neurological level of injury, ASIA score, time to surgery, steroid use, and mechanism of trauma (occupational, MVA accidents, violent blunt or penetrating trauma). Vertebral fractures were studied with the AOSpine classification. Details regarding treatment, in-patient and out-patient complications, and post-operative outcome were recorded during patients’ hospital stay. Follow-up was conducted via a questionnaire completed through phone interviews. We describe, for the first time, the general demographics and epidemiology of ST in Tanzania. We analyze surgical outcome and determine favorable predicting factors for positive outcome. Correlations between variables were studied using the Pearson Correlation Coefficient (PCC) and subgroup comparisons were done using Chi-square Analysis. Results: 115 patients were included and analyzed in this study. Patients were admitted from all regions of Tanzania (mean distance to MOI 303.7 km; Range 1.0-1378.0 km). Time to admission was on average 7.5 days after trauma. AIS Grade at time of admission was 46.5% complete and 53.5% incomplete. ST affected primarily young males 83.3% males versus 16.7% females. Mean age: 36 ± 13). Most common mechanisms of injury were MVA (40.3%) and falls from height (39.5%) mostly resulting from occupational accidents. 36.8% of admitted patients were treated surgically. Time to surgical attention after trauma was 41.3 ( ± 31.6) days on average. Among those patients that had surgery, 45.2% were classified as incomplete and 54.8% as complete. Nearly half of those patients that received surgical treatment for incomplete lesions improved in at least 1 grade on the AIS scale. Most common complications were pressure ulcers (26.8%) and wound infection (4.8%). At discharge, mortality rate was 8.8%. Factors correlated to favorable surgical outcome were: younger age, falling from low height < 3 m as mechanism of injury, and private insurance. Surgery correlated to outcome with statistical significance (-0.289, PCC. p < 0.01). Mean length of stay (LOS) was 33.6 days ( ± 22). Conclusion: Surgery, younger age, traumatic history of falls from less than 3 m of height, and private insurance are associated with favorable outcomes post ST in Tanzania. Education and occupational safety may need to be implemented in an organized fashion to observe changes in ST incidence. Reduction of time to admission and time to surgery could also drastically improve outcomes in ST patients in Tanzania.

A243: Non-Contiguous Spine Injuries - Can we Predict Them?

Angus Fong¹, Michael Petrie¹, Michael Athanassacopoulos¹, Lee Breakwell¹, Neil Chiverton¹, Ashley Cole¹, Antony Rex Michael¹, James Tomlinson¹

¹Sheffield Spine Unit, Sheffield Teaching Hospitals NHS Trust, Sheffield - United Kingdom

Introduction: With spinal trauma a common injury in high energy blunt trauma, it was previously reported 10% of these were non-contiguous. However, there were no up-to-date studies of this cohort in this country nor that of linking non-contiguous spinal fractures to systemic injuries. We aim to identify association of non-contiguous injury with ISS, systemic injuries and the propensity of the region of spinal fractures. Material and Methods: A retrospective study of all major trauma patients with spinal fractures over one year at a major trauma centre. Data is collected from TARN database. This is then cross-referenced with radiological imaging from PACS and operation details through electronic theatre management system ORMIS. Further assessment of regions of spine injuries was recorded. Statistical analysis was performed to identify any association with non-contiguous injuries. Results: 247 patients with spinal injuries are identified with 8 central cord syndromes excluded. Of the 239 patients, 64(27%) sustained non-contiguous multi-level spine trauma with another 64 being contiguous injury. 111(46%) sustained single level injury. 30% of the non-contiguous group underwent surgery vs 23% in the others. Severe trauma (ISS > 15) has only a PPV of 0.34 but a NPV of 0.79. The sensitivity and specificity of this is 0.56 and 0.59 respectively. Likelihood ratio of positive test and negative test is 1.39 and 0.74. Associated systemic injuries are not suggestive of pattern of spine injuries. There is a trend of thoracic spine injuries being involved in the non-contiguous group. Conclusion: Non-contiguous injuries are much more common than literature reported (27% vs 10%). There is no indication that a severely injured patient will more likely sustain a non-contiguous injury. However, if the patient has an ISS < 15, it is less likely that they will sustain NCSI. There is a high proportion of thoracic spine involvement in the non-contiguous group which is different from literature. A TARN/BSR collaboration would allow an ideal epidemiological study to understand these injuries further and predict likely injury associations.

A244: Craniocervical Trauma Above the Age of 90: Are Current Prognostic Scores Sufficient

Ehab Shiban¹, Bernhard Meyer¹, Anna Rienmüller¹, Paulina Rothlauf¹

¹Department of Neurosurgery, Technical University of Munich, Munich - Germany

Introduction: Aim was to identify variables that may predict early mortality in geriatric trauma patients over the age of 90. Material and Methods: A retrospective analysis of all patients over the age of 90, that were treated between January 2006 and December 2016 at out department was performed. Patient characteristics, type of injury and comorbidities were analyzed with regards to the 30-day mortality rate. Results: 179 patients were identified. Mean age 93 (range 90-102), 105 (59%) patients were female. 131 (73%) and 34 (19%) of patients presented with head and spinal trauma, respectively. 14 patients (8%) had a combined head and spine injury. 100 (56%) patients were treated operatively. Mean Charlson comorbidity index was 4.1 (range 0-18), mean diagnosis count was 6.2 (range 0-12), mean geriatric index of comorbidity (GIC) was 3.3 (range 1-4) and mean Barthel Index was 28 (range 0-100). The 30-day mortality rate was 30%. Multivariate cox regression analysis showed that head trauma had a 1.66 hazard ratio (p = 0.036) of dyeing within 30 days of Admission, whereas a higher Glasgow coma score and surgical treatment had a hazard ration of 0.88 (p = 0.0001) and 0.72 (p = 0.05) to reach the primary outcome. Conclusion: Standard geriatric prognostic scores seem less reliable to predict mortality for patients above the age of 90. Higher Glasgow coma score and surgical treatment were associated with a higher survival probability.

A245: Lag Screws in Vertebral Pincer-Fractures (AO A2) - First Biomechanical and Clinical Results

Marc Auerswald¹, Philipp Messer², Kay Sellenschloh², Jan Wahlefeld³, Klaus Pueschel⁴, Maximilian Faschingbauer¹, Michael M. Morlock², Gerd Huber²

¹Dep. of Traumatology, Orthopedics and Sports Traumatology, BGKH, Hamburg - Germany ²Institute of Biomechanics, Hamburg University of Technology, Hamburg - Germany ³Kernspinzentrum Hamburg-Süd, Hamburg - Germany ⁴Department of Legal Medicine, University Medical Center Hamburg-Eppendorf, Hamburg - Germany

Introduction: Vertebral pincer-fractures (AO A2) are rare injuries and still there is no consensus concerning their stability. According to Magerl et al. they are to be treated conservatively. However, due to a high nonunion rate they are frequently stabilized. In previous therapeutical concepts vertebral pincer-fractures were treated either by indirect stabilization, or corporectomy. The lag-screw principle has in spite of its low invasiveness no significance in spinal surgery so far. The aim of this study was to evaluate the lag screw principle in vertebral pincer-fractures biomechanically. Additionally, results of a 6-month follow-up of 8 patients who were treated with lag screws in combination with a dorsal instrumentation due to a pincer-fracture, are presented. Material and Methods: 18 bisegmental human specimen (Th11-L2) were assigned to three groups (cortical/ cancellous/ no bolting) after they underwent a CT-scan to find possible exclusion-criteria. Each of them was, under a 485 N axial preload, consecutively - native/ fractured/ stabilized - loaded with 10 cycles of extension/flexion, torsion and lateral bending. This was followed by a fatigue testing (15.000 cycles, 0.5 Hz). Prior to and after the fatigue testing a CT scan was conducted. With this the length of both the superior (SE) and inferior endplate (IE), the vertebral body length (mid-vertebral body) (VBL), the intervertebral space (IVS) and the fracture gap extent (mid-vertebral body) was determined. Radiographs of 8 patients with vertebral pincer-fractures were analyzed over a 6- month follow-up, to figure out healing rates. Results: In comparison to the native specimen, the non-stabilized specimen exhibited both during the 10 cycles testing and in the fatigue test significantly increasing values for SE, IE and VBL, while in the stabilized specimen, for the same data only little or even no increase was depicted. Besides this the width of fracture gaps also increased significantly in the non-stabilized (mean: 3.7 mm, SD: 2.16) compared to the stabilized specimen (mean: 0 mm) in the fatigue testing. The height of the intervertebral space decreased during the testing due to constant load. Results ranged from 4.4-10.6 mm (native specimen) to 1.4-7.5 mm (post fatigue testing specimen). The decrease in the stabilized specimen was significant lower. All patients with lag screws had their devices removed. No nonunions were revealed. Conclusion: It was elaborated, that by the use of transpedicular lag screws a narrowing of a fracture gap can be achieved in vertebral pincer fractures. Additionally the maintenance of the fracture’s retention by lag screws was revealed. Biomechanically the lag screw principle seems advantageous compared to the conservative treatment. It seems that in suitable fractures by using the temporary solution of a transpedicular lag screw osteosynthesis the risc of a vertebral nonunion is reducible. Possibly the treatment described has the potential to replace the dorso-ventral stabilization (360°) in the treatment of A2 fractures. Patients treated with lag screws were not in need of a ventral fusion. Clinical findings appear as encouraging as biomechanical results regarding a less invasive treatment of vertebral pincer fractures.

Infections 2

A246: Fungal Spinal Epidural Abscess: Characteristics and Differences From Bacterial Spinal Epidural Abscess

Huiliang Yang¹, Gi Hye Im², Akash A. Shah², Sandra B. Nelson³, Yueming Song¹, Joseph H. Schwab²

¹Department of Orthopaedics, Sichuan University, Chengdu - China ²Department of Orthopaedic Surgery, Harvard University, Boston - United States ³Department of Infectious Diseases, Harvard University, Boston - United States

Introduction: Fungal spinal epidural abscess (FSEA) is a rare entity, with few reports that describe its clinical features, diagnosis, treatment, and outcomes. Similarly, the characteristics of FSEA and the more common bacterial spinal epidural abscess (BSEA) have not been compared. Therefore, we describe the clinical features, diagnosis, treatment, and outcomes of FSEA and report differences from bacterial spinal epidural abscess (BSEA). Material and Methods: We reviewed the electronic medical records of patients with FSEA who were treated within our hospital system in the last 23 years. We compared our findings to all reported FSEA cases in the English-language literature from 1952 to 2017. We compared our FSEA cases to the BSEA cases in our database. Results: From a database of 879 patients, we identified nine patients with FSEA. Aspergillus fumigatus was isolated from 2 (22%) patients, and Candida species were isolated from 7 (78%). Local spine pain, neurologic deficit, and fever were demonstrated in 89%, 50%, and 44% of FSEA cases, respectively. Patients with FSEA had longer symptom duration ( > 2 weeks) prior to presentation than those with BSEA (p = 0.020). Fifty-six percent of FSEAs involved the thoracic spine, and 89% were located anterior to the thecal sac. Fifty-nine patients with FSEA were identified through literature review. Aspergillus and Candida were responsible for 60% and 29% of cases, respectively. FSEA was less likely to cause fungemia than BSEA was to cause bacteremia (p = 0.023). FSEA cases were more likely to have longer symptom duration ( > 2 weeks) prior to presentation than BSEA cases (p = 0.020). Additionally, FSEA cases had a higher probability of having concurrent immunosuppression, vertebral osteomyelitis, and a history of malignant tumor than BSEA cases (p = 0.029, p = 0.040, and p = 0.044, respectively). Finally, the rate of recurrence and mortality within 90 days in FSEA are higher than in BSEA (p = 0.033 and p = 0.018, respectively). Conclusion: The most common pathogens identified in FSEA are Aspergillus and Candida species. Empiric treatment for FSEA should cover these species while definitive identification is pending. The three most common symptoms for FSEA are local spine pain, neurologic deficit, and fever. The thoracic and lumbar regions of the spine are most likely to be involved. FSEA cases had a higher probability of having longer symptom duration prior to presentation, concurrent immunosuppression, vertebral osteomyelitis, and a history of malignant tumor than BSEA cases. Additionally, FSEA has a higher rate of recurrence and mortality than BSEA.

A247: A Classification Scheme for Epidural Spinal Cord Compression in Spinal Epidural Abscess

Huiliang Yang¹, Akash A. Shah², Gi Hye Im², Yueming Song¹, Joseph H. Schwab²

¹Department of Orthopaedics, Sichuan University, Chengdu - China ²Department of Orthopaedic Surgery, Harvard University, Boston - United States

Introduction: Magnetic resonance imaging (MRI) has been the most common method to diagnose spinal epidural abscess (SEA) and evaluate the degree of epidural spinal cord compression (ESCC). High-grade ESCC frequently serves as an indication for surgical decompression, while no consensus exists in the literature about the precise definition of this term in SEA. The advancement of treatment paradigms in patients with SEA requires a clear grading scheme of ESCC, as the degree of ESCC often serves as a major determinant in the decision to operation. The purpose of this study was to develop a classification scheme for ESCC in patients with SEA and to determine whether this scoring scheme is associated with neurologic deficit at admission, treatment, and outcomes. Material and Methods: We conducted a retrospective cohort study using electronic records in our hospital system. All patients were over 18 years old and had a clinically and radiologically documented cervical or thoracic SEA during the period 1995-2016. All patients had both sagittal and axial T2-weighted MR images prior to initiation of treatment. We developed a 5-point classification scheme of ESCC. Grade 1: epidural impingement, no deformation of thecal sac; grade 2: deformation of thecal sac, without cord abutment; grade 3: deformation of thecal sac, with cord abutment, without cord compression; grade 4: spinal cord compression, with CSF visible around cord; grade 5: spinal cord compression, no CSF visible. We analyzed association of ESCC grade with patients’ neurologic deficit at admission, treatment, and outcomes through univariate logistic regression. Results: The study included 351 patients with SEA. The most common degree of ESCC was grade 5 (39%), followed by grade 4 (26%), grade 3 (17%), grade 2 (15%), and grade 1 (3%). Compared to grades 1 and 2, patients with grade 5 compression were more likely to exhibit pre-treatment motor deficit (p < 0.001), sensory change (p < 0.001), and bladder or bowel dysfunction (p = 0.030). Similarly, patients with grade 4 compression were more likely to have motor weakness at presentation (p = 0.017). The presence of grade 5 compression was associated with an increased likelihood of undergoing surgical management (p < 0.001) as well as with presence of a residual motor deficit at follow-up (p = 0.002). Our scheme was not associated with recurrence or mortality. Conclusion: With a cohort of 351 patients, we provided a framework to describe the grade of spinal cord compression in SEA. High-grade ESCC was most common in our study as a result of the narrow spinal canal of the cervical and thoracic spine. More compression was associated with worse neurologic status due to severe myelopathy and spinal cord dysfunction. High-grade ESCC was associated with poor outcome of residual motor deficit at last follow-up. The grade of ESCC was not associated with other poor outcomes, e.g. mortality, recurrence.

A248: Comparison of Loss of Kyphotic Deformity Correction After 6 Years in Caries Spine Patients Undergone Anterior Decompression and Locally Made Cage Placement

Ammar Dogar¹, Haseeb Hussain¹, Ashfaq Ahmad¹, Amer Aziz¹, Shahzad Javed¹, Rizwan Akram¹

¹Dept of Orthopaedics and Spine Surgery, Ghurki Trust Teaching Hospital, Lahore - Pakistan

Introduction: 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 was to find out the immediate kyphosis correction and loss in correction after 6 years follow up. Materials and Methodology: This prospective study was conducted in the Department of Orthopaedics and Spine of Ghurki Trust Teaching Hospital, Lahore from Jan 2003 to Jun 2017. 1246 patients were totally operated during this interval. Out of which 600 patients were operated 6 years back and they were considered in the study. All patients underwent anterior decompression and placement of Inter body Titanium 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 and after 6 years. Boston brace was applied for at least 6 months. Data was analyzed using SPSS 17.0 Results: Out of 600 patients, 43 patients were lost in follow up. There were 557 patients in which 331 (60.18%) were males and 226 (40.57%) were females. The patients aged between 15-30 years were 242 (43.44%), those between aged 31-45 years were 127 (22.80%) and between 46-60 years there were 191 (34.30%). 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 6 years follow-up was 1.7° ± 0.7. Conclusion: Anterior decompression along with Titanium 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 6 years follow up. It is safe and cheap procedure as compared to other instrumentation especially for the poor patients of developing countries.

A249: A Staged Treatment Strategy for Pyogenic Spondylodiscitis in the Destructive Stage With Percutaneous Endoscopic Debridement and Following Spinal Reconstruction

Terufumi Kokabu¹, Manabu Ito¹

¹Department of Ophthalmology, National Hospital Organization, Hokkaido Medical Center, Sapporo - Japan

Introduction: Percutaneous endoscopic debridement and drainage (PED) has been reported to be effective for the early phase of pyogenic spondylodiscitis with minimal destructive changes. However, PED is not necessarily effective for pyogenic spondylodiscitis in advanced stages with severe destruction at the vertebral bodies due to the progression of local kyphosis after PED. We have been using PED as the first treatment for pyogenic spondylodiscitis which is followed by spinal reconstruction at 2 to 3 week interval. The hypothesis of this study is that the staged treatment with PED and following spinal reconstruction surgery is a safe and effective treatment strategy for active pyogenic spondylodiscitis with destructive changes. Material and Methods: Eleven patients (7 male, 4 female) with pyogenic spondylodiscitis in the destructive stage of the Griffiths’ classification were enrolled. These patients underwent the staged treatment protocol with PED and following spinal reconstruction surgery from April 2014 at March 2017 at a single institution. Staged reconstruction surgery using titanium implants included posterior-only approach in 3 patients and combined anterior and posterior approach in 8. The interval between PED and spinal reconstruction was 20 days in average. The transitions of CRP, pain score (NRS), local kyphosis on plain radiographs, perioperative complications needing reoperations were evaluated retrospectively. Results: CRP before PED and before staged reconstruction surgery was 5.10 and 1.75, respectively. There was a significant difference between the two phases (P < 0.01). Averaged CRP at 2 weeks after spinal reconstruction surgery was 1.13, showing that combination of PED and spinal reconstruction surgery succeeded in controlling spinal infection. Averaged local kyphosis angle before PED and reconstruction surgery was 0.9 degree and 5.6 degree, respectively. There was a statistical significant difference between two phases (P < 0.01). Local kyphosis showed significant improvement after reconstruction surgery (-8.6 degree, P < 0.01). Averaged NRS for back pain before PED was 6.7, before reconstruction surgery was 3.0 and after reconstruction surgery was 1.3. There were significant differences between the three phases (P < 0.01, P = 0.04). There were no surgery-related complications and no worsening of spinal infection during follow-up. Conclusion: Most patients with active pyogenic spondylodiscitis are ill with multiple medical comorbidities. It is difficult for surgeons to select invasive surgical treatment for those with high CRP and poor general conditions. Irrigation and drainage by PED made the patients’ general conditions better with minimal invasiveness, which created a better environment for following spina reconstruction surgery. After confirming that CRP showed continuous decrease after PED, surgeons are able to move on to spinal reconstruction surgery for pyogenic spondylodiscitis with severe destructive changes.

A250: Instrumented vs Non Instrumented Anterior Decompression in TB Spine: Long Term Outcome Analysis

Saurabh Singh¹, Alok Rai²

¹Associate Professor, department of orthopaedics, IMS, BHU, varanasi - India ²Senior Resident, Department of Orthopaedics, IMS BHU, Varanasi - India

Introduction: Treatment of tuberculosis of spine has various modalities ranging from medical to various surgical form including just drainage of pus to only decompression and decompression with instrumentation. The goals of surgery include radical debridement of the infective focus. In some cases, when surgery causes mechanical spinal instability, the question arises whether the risk of recurrent infection outweighs the benefits of spinal instrumentation and stabilization. Instrumentation helps in preventing progression of kyphosis and helps in maintaining the achieved correction. With the time treatment of tuberculosis of spine changed from preventing mortality to preventing and treating neurological deficit and now preventing and treating the kyphotic deformity also. Material and Method: Retrospective study was done on 93 patients, who were available for follow up of at least 18 months duration, who were divided in two groups. Group 1: Anterior decompression without instrumentation (50 patients). Group 2: Anterior decompression with instrumentation (43 patients). The patients had an average age of 40.80 years with the age ranging from 14 years to 72 years. The two groups [Group 1 and 2], were matched in reference to age (mean 39.48 vs. 42.34) in years, average number of vertebrae involved (2.6 vs. 2.13)), severity of deformity (26.08⁰ vs. 27.23⁰) and type of auto grafts used. The most common region of spinal vertebrae involved was thoracic (D7-D8) in all the groups. Statistical test of significance used was the student T test. The average follow up was 30 months [18 months to 42 months]. Result: In group 1, Postoperative local kyphosis correction was 9.8⁰ [mean] and the late loss of correction at last follow up of 1 year was 9.1⁰ [mean]. The local kyphosis correction at immediate postoperative period in group 2 was 18.12⁰ [mean] and the late loss of correction at last follow up of 1 years has been 1.21⁰. Late loss of correction in the instrumented group was lesser [p value: < 0.05] compared to uninstrumented group which is statistically significant. Correction of kyphosis at latest follow up is significantly more in group 2 as compare to group 1 (p < 0.05). There is significant correction of kyphosis in group 2 as compare to group 1 (p < 0.05). In group 1 we achieved 2.6% correction of kyphosis as compared to preoperative angle. In group 2 this correction was 62.76%. Concern to neurological recovery there is no significant difference between group 1 and group 2. There were no episodes of wound infection, development of new discharging sinuses and recurrence of the disease at the same or any other level in the spine in either of the 2 groups. Conclusion: Kyphosis can lead to persistent deformity, back pain, cosmetic issues. Progressive kyphotic deformity can lead to late onset of paraplegia and cardiopulmonary compromised state. Instrumentation will prevent kyphosis progression and its adverse effect.

A251: Surgical Infections in the Spine: Ten Year Epidemiological Analysis of a Trauma Hospital

Vicente Ballesteros¹, Javier Lecaros¹, Byron Delgado², Marcela Quintanilla³, Ignacio Cirillo¹, José Fleiderman¹

¹Department of Orthopaedic Surgery, Hospital del Trabajador, Universidad Andrés Bello, Santiago - Chile ²Emergency Department, Hospital del Trabajador, Santiago - Chile ³Intrahospital Infections Unit, Hospital del Trabajador, Santiago - Chile

Introduction: It is widely recognized that the surgical site infections (SSI) of the spine, significantly increase morbidity and mortality, length of hospital stay, and the health expenditure. Despite the progress in technologies for the treatment of these complications, the most helpful tool in the management of infections is prevention. It’s essential to know their epidemiological behavior, in order to improve strategies that minimize the risk of occurrence. The purpose of this study is to describe the epidemiology of spine surgery infections at Hospital del Trabajador in Santiago, Chile. Material and Methods: The databases of the Surgical Spine Team and the Intrahospital Infections Unit of Hospital del Trabajador were reviewed. These databases included patients that underwent surgery between 2008 and 2017. The data extracted was age, gender, month of the surgery, surgical time, diagnosis, instrumentation, surgical level, microorganism, among others. Results: A total of 2764 spinal surgeries were performed in the period between 2008-2017 [71% for degenerative disease, 20% for trauma and 9% for other cause – E.g. tumors, removal of material, etc.]. The years with the highest SSI incidence were, in descending order, 2016 [2.45%], 2015 [1.88%], 2008 [1.84%] and 2010 [1.24%]. During this decade, the 29 patients with ISQ (83% men and 17% women) showed a mean age of 43.17 ± 11.92 years. The diagnosis of infection was performed in a median time of 14.5 (4 - 78) days. The most affected spine segment was lumbar [52%], followed by thoracic [40%] and cervical [8%]. The incidence of infection in trauma surgeries was 3.6% and in surgeries due to degenerative disease was 0.4% [OR = 9.31 (95% CI: 3.93 - 24.41, p < 0.001)]. The most common isolated microorganism was S. aureus with 17.24%, and no microbiological etiology was identified in 27.6% of the cases. Conclusion: At Hospital del Trabajador, the incidence of infection in trauma surgeries was 9 times more often than the incidence in surgery due to degenerative pathology. Future analytical studies are necessary to determine the differentiating factors that make the spine surgery by traumatic pathology more vulnerable to SSI, and therefore define the possible risk factors of this population.

A252: Post Operative Discitis Following Lumbar Discectomy

Sujit Triparthy¹, Ashish Pattnaik², Mantu Jain¹

¹Department of Orthopedics, Bhubaneswar - India ²Department of Nerosurgery, Bhubaneswar - India

Introduction: Post operative discitis is a post procedural complication of spinal surgery. The diagnosis is mainly based on clinical findings supported by laboratory markers, and imaging modalities. Management includes biopsy and antibiotics and occasionally debridement and stabilization in nonresponsive cases Methods: 10 cases of postoperative Discitis were identified by clinical symptoms, laboratory investigations (ESR & CRP) radiological parameters (X-ray / CT-Scan/MRI) in AIIMS Bhubaneswar. All the patients were initially treated conservatively after diagnosis. Absolute bed rest in hospital for 3 weeks followed by gradual mobilization with a moulded LS Brace. Initial blood culture was sent. Empirical broad spectrum I.V Antibiotics were started and changed accordingly to C/S report for three weeks followed by oral antibiotics for another 3 weeks. Serial ESR/CRP and other radiological parameters were evaluated regularly. The patients who didn’t respond to conservative treatment for three weeks were offered Surgery. The patients were reviewed at 1 month and 3 monthly thereafter. They were assessed with ESR, CRP and radiological parameters. Results: The ten cases had a Male: Female = 7:3, Mean age = 38.8years (Range: 24 -56years), mean follow up of 14.2 months (Range: 9 m to 20). Mean interval b/w Discectomy and establishment of diagnosis = 4.8 weeks (Range 1 to 10 weeks). Blood culture was positive in 4 cases (n = 3 staphylococcus, n = 1 for pseudomonas). 8 cases responded well to conservative treatment. 2 cases (20%) failed to respond and were treated surgically. one was sterile in intraoperative material and other had pseudomonas culture positive that required two debridement and fusion. Conclusion: Early detection and aggressive treatment is the cornerstone in management of Postoperative Discitis. Majority of them respond to conservative treatment. Surgical management is reserved for those not responding to IV antibiotics in whom isolation of germ is required or those with abscess.

A253: Long Term Clinico-Radiological Outcome of Cost-Effective Composite Reconstruction in Dorsal Tuberculosis of Spine and Review of the Literature

Sudhir Srivastava¹, Nirmal Patil²

¹Department of Orthopedics, Seth GS Medical College, Mumbai - India ²Department of Orthopedics, TNMC and BYL Nair Hospital, Mumbai - India

Study Design: Retrospective case series. Purpose: To compare the outcomes of using Hartshill rectangle via versatile approach vs pedicular screw via transpedicular approach in treatment of tuberculosis of the thoracic spine and study the neurological and radiological outcomes. Methods: Group A consisted of 143 patients surgically treated using the “Versatile approach” and posterior fixation was performed using sublaminar wires and a Hartshill rectangle. Anterior reconstruction was accomplished using autologous rib, iliac crest, or fibula as a bone graft. Group B consisted of 80 patients, surgically treated via transpedicular approach and posterior fixation performed using pedicle screws. Anterior reconstruction was done using iliac crest bone graft or cage. Results: Group A patients had a mean follow- up of 60.23 ± 24.56 months and Group B patients, of 71.56 ± 29.44 months. Kyphosis improved from a 24.02 preoperatively to 10.25 postoperatively in Group A vs 31.5 preoperatively to 11.67 postoperatively in Group B. 99.18% of patients regained ambulatory power in Group A compared to 95.58% in Group B patients. No patient had deterioration of neurological status following surgery. Fusion was achieved in all cases. There was no statistically significant difference in the pre-op and last follow-up VAS scores between the two groups. In Group A, 8 patients had superficial macerations, which healed spontaneously. One had buckling of the anterior graft, one had implant breakage following road traffic accident and one patient did not improve neurologically. In Group B, 2 patients had superficial macerations, which healed spontaneously. One had recurrence of disease, one had exposed implant and 3 did not improve neurologically. Conclusions: Meticulous neural decompression, skilful preparation of oestrogenic bed, autologous strut grafting with additional only grafting and adequate stabilization of column gives excellent and long lasting results even with cost effective and biomechanically weaker implant in dorsal tuberculosis of spine.

A254: A Prospective Case Study of Outcome of Posterolateral Transpedicular Corpectomy and Instrumented Fusion in Thoracic Spine Cases

Srinath P¹, Ravi V²

¹Department of Orthopedics, Apollo Hospitals, Chennai - India ²Department of Spine Surgery, Apollo Hospitals, Chennai - India

Introduction: Patients requiring anterior-posterior thoracic spine stabilization and suffering from concomitant cardiopulmonary disease are at increased risk to develop procedure-related complications. In order to reduce cardiopulmonary complications, the efficacy of a posterolateral transpedicular approach for fusion was investigated. We evaluated the functional, neurological, and radiological outcome in patients with spinal infection and tumours operated through the transpedicular approach. For surgical treatment of thoracic spinal infection and tumours with required corpectomy, the combined anterior and posterior approach has been the most popular because it allows direct access to the infected tissue, thereby providing good decompression and stabilization. However, in anterior and posterior combined approach, operative time, blood loss and morbidity are high. Also the post op morbidity of patient is more. The transpedicular approach allows circumferential decompression of neural elements along with three-column reconstruction and fixation attained via pedicle screws and cage placement by the same approach. Material and Methods: A total of 45 patients were diagnosed with tuberculosis or malignancies or trauma of the thoracic spine from January 2013 to January 2016. 3 levels above and below the required level were usually exposed. Pedicluar screws kept 2 levels above and below. Spinal cord decompression was achieved by hemi laminectomy, facetectomy, the corresponding affected level and the below rib up to medial 1 inch were excised and corpectomy with subsequent posterior instrumented fusion using a screw-rod system was done. Patients were mobilized on 2nd post operative day. Antituberculosis therapy was given till signs of radiological healing were evident (9–16 months) for patients with TB-SPINE and patients with malignancies were transferred to oncologist for further management. Functional outcome (visual analogue scale [VAS] score for back pain), neurological recovery (Frankel grading), and radiological assessment was done preoperatively, immediate postoperatively, and at 3 months and 6 months. Results: Mean VAS score for back pain improved from preoperatively 3.4 to 0 at 6months follow-up. Frankel grading preoperatively was C (on average), which improved to E(on average) at the last follow-up. Radiological healing was evident in the form of reappearance of trabeculae formation, resolution of pus, fatty marrow replacement, and bony fusion in all patients. Number of people requiring ICU stay are very less, in our study it was 4 out of 45, 1 – unrelated to surgery, 3 – pleural tear which needed ICD. Length of hospital stay is significantly lower when compared with a open thoracotomy. Number of patients with complications were 3 patients with pleural tear requiring ICD. In our study we notied 3 patients in which cage subsidence was present but fusion was achieved in those cases without implant failure. Conclusion: The posterolateral transpedicular approach is a safe, less-invasive and efficient alternative to anterior-posterior fusion.

Degenerative Cervical - Myelopathy

A255: Prediction of Anterior vs. Posterior Surgical Approach for Degenerative Cervical Myelopathy Based on MRI Pathology: Analysis of a Global Cohort

Aria Nouri¹, Allan Martin², So Kato², Christopher Witiw², Anick Nater², Lindsay Tetreault², Carlo Santaguida³, David Gimbel¹, Rani Nasser¹, Joseph Cheng¹, Michael Fehlings²

¹Department of Neurosurgery, University of Cincinnati, Cincinnati - United States ²Division of Neurosurgery, University of Toronto, Toronto - Canada ³Department of Neurology and Neurosurgery, McGill University, Montreal - Canada

Introduction: Degenerative Cervical Myelopathy (DCM) involves extrinsic spinal cord compression (SCC) causing neurological impairment that is often progressive. Surgical treatment is frequently used, but in many cases the decision between an anterior or posterior approach as the optimal choice is controversial. To better understand the influence of imaging features on this decision, we analyzed data from two large multicenter prospective studies. Materials and Methods: MR images of 458 patients were analyzed for various pathological features, characteristics of SCC, sagittal alignment using the modified K-line, and signal changes on T1-weighted (T1WI) and T2-weighted images (T2WI). Clinical severity was measured with modified Japanese Orthopedic Association (mJOA) score. Fisher exact tests and multivariate logistic regression were used to assess relationships between clinical/MRI features and anterior (A), posterior (P), or combined (AP) surgical approach. Results: Operative approach was anterior (A) = 265, posterior (P) = 184, and Anterior and Posterior (AP) = 9. In univariate analysis, AP approach was more commonly selected in Europe and North America (p = 0.03) and with more levels of SCC (p = 0.04). Anterior surgery was favored with lower age, mJOA ≥ 15, single-level disc pathology, anterior-only SCC, and kyphosis, while posterior approach was favored in South America or with multilevel spondylosis, ligamentum flavum enlargement, spondylolisthesis, SCC at or above C4-5, SCC at or below C6-7, more levels with SCC, T2WI hyperintensity, and more levels with T2WI hyperintensity (all p < 0.05). In multivariate analysis, more levels with SCC (p < 0.001), age (p < 0.001), South American region (p < 0.001), mJOA ≥ 15 (p = 0.008), kyphosis (p = 0.02), and maximal SCC at or above C4-5 (p = 0.05) were significant independent predictors. Clinical factors alone predicted A vs. P approach with 77.8% accuracy, whereas clinical and MRI factors achieved 86.9% accuracy. Conclusion: The selection of surgical approach for DCM is significantly associated with several clinical factors (age, region, and neurological status) and imaging factors (number of compressed levels, kyphosis, and compression at rostral levels). Combined surgery is more common in Europe and North America, possibly due to resource availability. These results in a large global cohort compliment a recent international survey on surgical decision-making based on MRI features, providing insights into the selection of surgical approach in DCM that may lead to improved education and standardization of care.

A256: Quality of Life and Surgical Outcomes of Mild Degenerative Cervical Myelopathy

Jetan Badhiwala¹, Christopher Witiw¹, Farshad Nassiri¹, Muhammad Akbar¹, Alireza Mansouri¹, Jefferson Wilson¹, Michael Fehlings¹

¹Division of Neurosurgery, Department of Surgery, University of Toronto, Toronto - Canada

Introduction: There is controversy over the optimal treatment strategy for patients with mild degenerative cervical myelopathy (DCM), as reflected in recent clinical guidelines. In a prospective cohort of mild DCM patients undergoing surgical decompression, we sought to evaluate: 1) the degree of impairment in baseline quality of life as compared to population norms; and 2) functional, disability, and quality of life outcomes following surgery. Methods: We identified patients with mild DCM, defined by a modified Japanese Orthopaedic Association (mJOA) score of 15 to 17, enrolled in the prospective, multi-center AOSpine CSM-NA or CSM-I trials. All patients underwent surgical decompression by an anterior, posterior, or combined approach. Data pertaining to patient demographics, clinical presentation, operative treatment, and clinical outcomes were obtained. Baseline quality of life (SF-36v2) was compared to Canadian population normative data by the standardized mean difference (SMD). Outcomes, including functional status (mJOA, Nurick grade), disability (Neck Disability Index [NDI]), and quality of life (SF-36v2, SF-6D), were evaluated at baseline and 6 months, 1 year, and 2 years after surgery. We performed pairwise comparison of means using the Tukey adjustment for multiple comparisons to evaluate how the outcomes of mJOA score, Nurick grade, each of the eight domains and two composite scores of the SF-36v2, NDI, and SF-6D changed over time. Post-operative complications within 30 days of surgery were monitored. Results: 193 patients met eligibility criteria. Mean age was 52.4 years. There were 67 females (34.7%). Mean symptom duration was 26.7 months. The most common presenting complaint was numb hands (156; 80.8%) and the most common exam finding was hyperreflexia (135; 69.9%). Patients had significant impairment in all domains of the SF-36v2 compared to population norms, greatest for Social Functioning (SMD -2.33, 95% CI -2.48 to -2.18), Physical Functioning (SMD -2.31, 95% CI -2.46 to -2.16), and Mental Health (SMD -2.30, 95% CI -2.44 to -2.15). A significant improvement in mean score from baseline to 2-year follow-up was observed for all major outcome measures, including mJOA (0.87, 95% CI 0.42 to 1.33, P < 0.01), Nurick grade (-1.24, 95% CI -1.55 to -0.93, P < 0.01), NDI (-12.97, 95% CI -18.18 to -7.76, P < 0.01), SF-36v2 PCS (5.75, 95% CI 3.08 to 8.41, P < 0.01) and MCS (6.93, 95% CI 3.41 to 10.45, P < 0.01), and SF-6D (0.11, 95% CI 0.07 to 0.14). The most common complication was worsening of myelopathy, seen in 13 patients (6.7%), followed by worsening of axial neck pain in 12 (6.2%), and dysphagia in 11 (5.7%). Six patients (3.1%) developed a superficial wound infection, 6 (3.1%) had a malpositioned screw, and 4 (2.1%) developed a post-operative kyphotic deformity. Conclusion: Even “mild” DCM is associated with significant impairment in quality of life. Surgery results in significant gains in functional status, level of disability, and quality of life. It is perhaps time we recalibrate the way we think of the goals of surgery in this population to extend beyond preventing neurological deterioration, to improving function and quality of life, as stability may not be a “good” or acceptable outcome to patients.

A257: The Discrepancy Between Clinical Measures and Self-Reported Ratings of Health Status After Surgery for Degenerative Cervical Myelopathy: An Introduction to Response Shift

Lindsay Tetreault¹, Mary Zhu², Rachel Howard¹, Michael Fehlings³, Jefferson Wilson²

¹Graduate Entry Medicine, University College Cork,, Cork - Ireland ²Division of Neurosurgery, St. Michael’s Hospital, Toronto, Canada, Toronto - Canada ³Department of Surgery, University of Toronto, Toronto - Canada

Introduction: Surgery is increasingly recommended as the preferred treatment strategy for patients with degenerative cervical myelopathy (DCM), as it can halt neurologic deterioration and significantly improve functional impairment, disability and quality of life. Despite objective post-operative clinical improvements, experience dictates that a proportion of patients remain dissatisfied with their outcome. Discrepancies between clinical measures and self-reported ratings of health status after surgery, often referred to as response shift, can be due changes in patients’ internal standards of measurement, values and/or conceptualization of quality of life. This study aims to investigate the presence of response shift in functional outcomes in patients undergoing surgery for DCM. Material and Methods: Four hundred and seventy-nine DCM patients were prospectively enrolled in the AOSpine-CSM-International study at 16 global sites. Functional impairment, disability and quality of life were evaluated at baseline and 1-year following surgery. Patients were also asked to complete the SF-36 questionnaire and to rate their general health status compared to one year ago (much better, somewhat better, the same, somewhat worse, much worse). Descriptive analyses were conducted to evaluate the concordance between achieving a clinically important improvement (MCID) in function (modified Japanese Orthopedic Association (mJOA) scale) and self-reported ratings of health status. Concordance was defined as achieving a MCID and reporting general health as somewhat better or much better, whereas discordance was defined as achieving a MCID and reporting general health as the same, somewhat worse or much worse. Logistic regression analysis was used to determine important differences between patients with discrepancies between their clinical measures and self-reported ratings and those without. Results: Four-hundred-one patients had complete follow-up data at 1-year and were included in this analysis. Based on patient self-reports, 55 patients were somewhat or much worse than a year ago, 82 patients were the same and 264 patients were somewhat or much better. Thirty-one percent of patients who reported being somewhat or much worse achieved a MCID on the mJOA. In addition, 56% of patients who indicated their health status was the same as one year ago exhibited clinically meaningful improvements in functional impairment. Univariate analyses indicated that there is an increased likelihood of observing a discrepancy between functional outcomes and self-reported ratings if the patient (1) exhibited less improvement in mJOA upper extremity scores (p = 0.071), (2) was older (p = 0.0073), (3) was a smoker (p = 0.082) and (4) achieved lower total mJOA scores at 1-year (p = 0.087). Following multivariate analysis, the most important factors were age and improvement in mJOA upper extremity scores. Conclusion: A response shift in functional outcomes was detected in patients undergoing surgery for DCM. Older patients, as well as those with smaller improvements in postoperative upper extremity scores, tend to report worsened or unchanged general health status, in spite of experiencing clinically significant improvement in overall post-operative function.

A258: Outcomes of Surgical Decompression in Patients With Very Severe Degenerative Cervical Myelopathy

Branko Kopjar¹, Parker Bohm², Joshua Arnold³, Michael Fehlings⁴, Lindsay Tetreault⁵, Paul Arnold²

¹Department of Health Services, University of Washington, Seattle - United States ²Department of Neurosurgery, University of Kansas Medical Center, Kansas City - United States ³Public Health and Professional Degree Programs, Tufts University School of Medicine, Boston - United States ⁴Department of Surgery, University of Toronto, Toronto - Canada ⁵Graduate Entry Medicine, University College Cork, Cork - Ireland

Introduction: Although decompressive surgery has been evidenced as a safe and effective approach for patients with myelopathic deficiencies, studies have suggested residual disability following treatment in patients with more severe disease presentation. The aim of this study was to evaluate outcomes of decompressive surgery in patients with very severe Degenerative Cervical Myelopathy (DCM). Material and Methods: A prospective observational international study. Postoperative outcomes of 60 patients with very severe DCM (modified Japanese Orthopaedic Association Score (mJOA) ≤ 8) were compared to outcomes of 188 patients with severe DCM (mJOA 9-11). Post-imputation follow-up rate was 93.1%. Unadjusted and adjusted analyses were performed using two-way repeated measurest of co-variance. Results: The two cohorts were similar in demographics, length of duration of myelopathy symptoms, source of stenosis and surgical approaches used to decompress the spine. The very severe and severe cohorts differed in preoperative Nurick grades (4.97 vs. 3.91, respectively, P < .0001) and Neck Disability Index (NDI) scores (45.20 vs. 56.21 respectively, P = .0006). There were no differences in Short Form 36 (SF-36v2) Physical (PCS) and Mental (MCS) Component Summary Scores. Both cohorts improved in mJOA, Nurick, NDI, and SF-36v2 PCS and MCS scores. Despite the substantial postoperative improvements, patients in both cohorts had considerable residual symptoms. Two-thirds of the patients in the very severe cohort had severe (mJOA ≤ 11) or moderate (mJOA ≤ 14) myelopathy symptoms at 24-months follow-up. Longer duration of disease was associated with poorer treatment response. Conclusion: Decompressive surgery is effective in patients with very severe DCM, however, patients have significant residual symptoms and disability. The very severe subgroup (mJOA ≤ 8) of patients with DCM represents a distinct group of patients and their different clinical trajectory is important for clinicians and patients to recognize. Duration of symptoms negatively affects chances for recovery. Whenever possible, patients with DCM should be treated before developing very severe symptomatology.

A259: Predicting Quality of Life After Surgical Decompression for Mild Degenerative Cervical Myelopathy: A Principal Component Regression Analysis

Jetan Badhiwala¹, Christopher Witiw¹, Farshad Nassiri¹, Muhammad Akbar¹, Alireza Mansouri¹, George Ibrahim¹, Jefferson Wilson¹, Michael Fehlings¹

¹Division of Neurosurgery, Department of Surgery, University of Toronto, Toronto - Canada

Introduction: Predictors of outcome after surgery for degenerative cervical myelopathy (DCM) have been determined previously through hypothesis-driven multivariate statistical models that rely on a priori knowledge of potential confounders, exclude potentially important variables due to restrictions in model building, cannot include highly collinear variables in the same model, and ignore intrinsic correlations among variables. We sought to apply a data-driven approach, principal component analysis (PCA), to identify patient phenotypes that may predict outcomes after surgery for mild DCM using data from two related prospective, multi-center cohort studies. Methods: We identified patients with mild DCM, defined by a modified Japanese Orthopaedic Association score of 15 to 17, undergoing surgical decompression as part of the AOSpine CSM-NA or CSM-I trials. Patient outcomes were evaluated pre-operatively at baseline and at 6 months, 1 year, and 2 years after surgery. Quality of life was evaluated by the Neck Disability Index (NDI) and Short Form-36 version 2 (SF-36v2). A heterogeneous correlation matrix was created using a combination of Pearson, polyserial, and polychoric regressions among 67 baseline variables, which then underwent eigen decomposition. Scores of significant principal components (PCs) (with eigenvalues > 1) were included in multivariate logistic regression analyses for three dichotomous outcomes of interest: achievement of the minimum clinically important difference (MCID) in 1) NDI (≤ -7.5); 2) SF-36v2 Physical Component Summary (PCS) score ( ≥ 5); and 3) SF-36v2 Mental Component Summary (MCS) score ( ≥ 5). Results: A total of 154 patients met eligibility criteria and had complete data. Twenty-four significant principal components accounting for 75% of the variance in the data were identified. Two principal components were associated with achievement of the MCID in NDI. The first (PC 1) was dominated by variables related to surgical approach and number of operated levels; the second (PC 21) consisted of variables related to patient demographics, severity and etiology of DCM, comorbid status, and surgical approach. Both PC 1 and PC 21 also correlated with SF-36v2 PCS score, in addition to PC 4, which described patients’ physical profile, including gender, height, and weight, as well as comorbid renal disease; PC 6, which received large loadings from variables related to cardiac disease, impaired mobility, and length of surgery and recovery; and PC 9, which harbored large contributions from features of upper limb dysfunction, cardiorespiratory disease, surgical approach, and region. In addition to PC 21, a component profiling patients’ socioeconomic status and support systems and degree of physical disability (PC 24), was associated with achievement of the MCID in SF-36 MCS score. Conclusions: Through a data-driven approach, we identified several phenotypes associated with disability and physical and mental health-related QOL. Such data reduction methods may separate patient-, disease-, and treatment-related variables more accurately into clinically meaningful phenotypes that may inform patient care and recruitment into clinical trials.

A260: Rates and Predictors of Neurologic Progression in Patients Treated Conservatively for Degenerative Cervical Myelopathy

Lindsay Tetreault¹, Sukhvinder Kalsi-Ryan², Jetan Badhiwala², Allan Martin³, Jefferson Wilson⁴, Eric Massicotte², Michael Fehlings³

¹Graduate Entry Medicine, University College Cork,, Cork - Ireland ²Division of Neurosurgery, Toronto Western Hospital, Toronto - Canada ³Department of Surgery, University of Toronto, Toronto - Canada ⁴Division of Neurosurgery, St. Michael’s Hospital, Toronto, Canada, Toronto - Canada

Introduction: Degenerative cervical myelopathy (DCM) is a progressive degenerative spine disease and the most common cause of spinal cord dysfunction in adults worldwide. A recent systematic review of the literature indicated that 20-62% of patients with DCM will deteriorate by 1 or more points on the Japanese Orthopaedic Association (JOA) score by 3-6 years if not treated surgically. A 1-point drop on the JOA reflects a significant decline in functional status and may underestimate rates of disease progression. Furthermore, there is limited evidence whether certain clinical and imaging parameters can predict neurologic and functional impairment in patients managed conservatively. This study aims to clarify rates of progression in DCM patients treated non-operatively using a variety of outcome measures and to identify important risk factors of neurologic deterioration. Material and Methods: One hundred and fifty-eight patients with symptomatic DCM were prospectively enrolled at a single Canadian center and either treated surgically or conservatively. x Patients were evaluated at baseline and at 12-months follow-up using a variety of outcome measures, including the modified JOA (mJOA), the Graded Redefined Assessment of Strength, Sensibility and Prehension (GRASSP), the JAMAR handgrip dynamometer and the Berg Balance Scale (BBS). In patients treated conservatively, rates of decline were computed for each outcome assessment tool. For a sub-analysis, functional deterioration was defined as a decrease in mJOA scores by ≥ 1 point. Logistic regression analyses were used to determine important clinical and imaging predictors of deterioration. Results: Of the 158 patients enrolled in this study, 79 received surgical intervention and 79 were managed conservatively. Eight patients treated nonoperatively were classified as severe (mJOA < 12), 15 as moderate (mJOA = 12-14) and 55 as mild (mJOA ≥ 15); the mJOA of a single patient was not scored at baseline. The mean age was 55.98 ± 11.00. Follow-up data was available for 57 patients (72.15%) at 12-months following enrollment. Based on the mJOA, 14 (24.56%) patients improved, 19 (33.33%) remained the same and 24 (42.10%) deteriorated. A greater percentage of patients exhibited progression in lower (n = 22, 38.6%) and upper extremity (n = 16, 28.07%) function than in sensory function (n = 7, 12.28%). Based on the GRASSP, 20 (35.09%) patients experienced a decrease in their scores, 15 (26.32%) stayed the same and 22 (38.60%) improved. Finally, thirty (52.63%) patients demonstrated reduced grip strength in their dominant hand on the JAMAR, while 16 (29.09%) deteriorated on the BBS. Unfortunately, there was no association between disease progression and the following factors: presence of signal change, effacement of spinal cord, character of compression, neck pain, age, gender or duration of symptoms. Conclusion: Rates of progression ranged from 29.09% to 52.63%. No important predictors of deterioration were identified. Further investigation is required to explore key risk factors of neurologic decline in patients treated conservatively for DCM.

A261: High Resolution Diffusion Tensor Imaging in Cervical Spondylotic Myelopathy: A Preliminary Follow-Up Study

Xiaolong Chen¹, Yong Hai¹, Li Guan¹

¹Beijing Chao-Yang Hospital, Beijing - China

Objective: Diffusion imaging is a promising technique as it can provide microstructural tissue information and thus potentially show viable change in spinal cords. However, traditional single-shot imaging method is limited by various image artifacts. In order to improve the measurement accuracy, we used newly developed multi-shot, high resolution, diffusion tensor imaging (DTI) method to investigate diffusion metric changes and compare them with T2-weighted images before and after decompressive surgery for cervical spondylotic myelopathy (CSM) patients. Methods: T2 W imaging, single-shot DTI, and multi-shot DTI were employed to scan 40 patients with CSM before and 12 months after decompressive surgery. High signal intensities were scored using the T2 W images. DTI metrics including fractional anisotropy (FA), axial diffusivity (AD), radial diffusivity (RD) and mean diffusivity (MD) were quantified and compared pre- and post-surgery. In addition, the relationship between imaging metrics and neurological assessments was examined. The reproducibility of multi-shot DTI was assessed in 10 healthy volunteers. Results: Post-surgery, the mean grade of cervical canal stenosis was reduced from grade 3 to normal from after 12 months. Compared with single-shot DTI, multi-shot DTI provided better images with lower artifact levels, especially following surgery, as a result of reduced artifacts from metal implants. The new method also showed acceptable reproducibility. FA of high signal intensity level, FA of high signal intensity, AD and RD values from the new acquisition showed significant differences post-surgery (t = −2.8, P = 0.031; t = −4.4, P = 0.005; t = 4.04, P = 0.007; t = 5.40, P = 0.002). Their changes are consistent with neurologic assessments. In contrast, T2 W images did not show significant changes before and after the surgery. Maximum spinal cord compression (MSCC) and high signal intensity were not correlation with the JOA recovery, while FA, AD and RD were significant correlation, especially the FA. Conclusions: Multi-shot diffusion imaging showed improved image quality than single shot DWI, and presented superior performance in diagnosis and recovery monitoring for CSM patients than T2 W imaging. DTI metrics can reflect the pathologic conditions of spondylotic spinal cord quantitatively, and might serve as a sensitive biomarker for potential CSM management.

Keywords: cervical spondylotic myelopathy, spinal cord, high resolution diffusion imaging, multi-shot diffusion imaging, diffusion tensor imaging

A262: Multilevel Cervical Compressive Myelopathy: Comparison of Three Different Operative Techniques

Natarajan Muthukumar¹

¹Department of Neurosurgery, Devadoss Multispeciality Hospital, Madurai - India

Objective: To compare the outcome and complications of three different operative techniques viz: double door laminoplasty (DDL), open door laminoplasty (ODL) and laminectomy with lateral mass fusion (LMF) for multilevel compressive cervical myelopathy due to cervical spondylosis (CSM) and/or OPLL. Methods: Patients with multilevel CSM and OPLL were treated with DDL or ODL or LMF. All patients underwent neurological evaluation, plain radiographs, MRI preoperatively and plain radiographs and CT postoperatively. Axial neck pain was graded as mild, moderate & severe. Neurological improvement was assessed using Nurick’s grading. Complications were recorded. Mean follow up was 9 months. Results: 15 patients underwent DDL, 18 underwent ODL and 20 underwent LMF. Only the first 20 patients operated with LMF were included in the LMF group as they were operated during the same period. In the DDL group all patients improved by atleast one Nurick’s grade, inadequate radiological decompression was seen in 3 of 57 operated levels and there was two cases of postop C5 palsy. In the ODL group, all patients improved by atleast one Nurick’s grade, there was inadequate radiological decompression in 6 of 72 levels and there was no postop C5 palsy. 50% of patients in both groups had significant axial neck pain postoperatively. In the LMF group, all patients improved by atleast one Nurick’s grade, fracture of the lateral masses occurred in 4 of the140 lateral masses, there was no C5 palsy, screw pull out or breakage. Axial neck pain was not disabling in any patient. Conclusions: All the three posterior approaches lead to equal neurological improvement. However, laminectomy with lateral mass fusion is associated with lesser complications with equally good outcome.

A263: Correlation Of Radiographic Outcomes and Quality of Life for Multilevel Cervical Spondylotic Myelopathy

Heath Gould¹, Kelsey Goon¹, Emily Hu¹, Joseph Tanenbaum¹, Colin Haines², Don Moore¹, Thomas Mroz¹

¹Cleveland Clinic, Cleveland, OH - United States ²Virginia Spine Institute, Reston, VA - United States

Introduction: Posterior operative approaches have demonstrated clinical benefit for multilevel cervical spondylotic myelopathy (CSM). Prior investigations have independently reported the radiographic and quality of life (QOL) outcomes associated with posterior cervical surgery, but the relationship between radiographic metrics and QOL remains unclear. Methods: A retrospective cohort study was conducted among patients undergoing laminoplasty or laminectomy with fusion for the treatment of multilevel CSM. QOL and radiographic data were collected preoperatively and postoperatively between 2008 and 2015. The EQ-5D instrument served as a measure of overall QOL, while the PDQ measured disability and the PHQ-9 assessed mental health. Radiographic metrics included C2-C7 Cobb angle, C2-C7 sagittal vertical axis (SVA), and modified Ishihara index. Multivariable linear regression models were used to investigate the association between radiographic measurements and QOL, while controlling for the following variables: age, gender, marital status, type of surgical procedure, Body Mass Index, Charlson Comorbidity Index. Results: 125 patients were eligible for inclusion. Following multivariable linear regression, change in radiographic measurements – preoperative to postoperative – did not correlate with change in QOL (Table 1). Similarly, change in radiographic measurements was not associated with achieving a minimum clinically important difference (MCID) in any of the QOL instruments (Table 2). When preoperative radiographic measurements were compared to change in QOL, SVA was found to be a statistically significant predictor of improvement in EQ-5D (p = 0.03; β = 0.0004). All other preoperative radiographic metrics showed no correlation with change in QOL (Table 3). Conclusions: Cobb angle and Ishihara index were not associated with QOL. One statistical model revealed an association between preoperative SVA and improvement in EQ-5D; however, the small β coefficient indicates that this correlation is unlikely to be clinically significant. We therefore conclude that radiographic outcomes are a poor surrogate for QOL in patients undergoing posterior surgery for multilevel CSM.

Deformity - Thoracolumbar (Adolescent) Surgery 3

A264: The Association of Body Mass Index and Socioeconomic Status on COBB Angle Severity at Presentation in Adolescent Idiopathic Scoliosis

Eve Hoffman¹, Alysa Nash¹, Tuo Li¹, Colin Dunn¹, Daniel Gelb¹, Eugene Koh¹, Steven Ludwig¹, Kelley Banagan¹

¹Department of Orthopaedics, Spine Division, University of Maryland Medical Center, Baltimore - United States

Introduction: Adolescent idiopathic scoliosis (AIS) is a three-dimensional deformity of the spine present in 1% to 5% of the population. While etiology remains unknown, recent studies suggest a positive relationship between BMI and severity of curve on presentation. Additionally, it has been noticed by attending spine surgeons at a large tertiary referral center, that children who present with AIS from lower socioeconomic households and/or with higher body mass indices appear to have more severe curves at initial presentation. This study was undertaken to compare the severity of scoliosis at initial presentation to the spinal surgeon’s office between adolescents with varying ranges of BMI’s from different socioeconomic statuses. Material and Methods: Following IRB approval, a review of our university billing database was performed over a 10-year period (2006-2016). Inclusion criteria were patients ages 10-18 who received a diagnosis of adolescent idiopathic scoliosis in that time period. Patients were excluded if they had ever received a diagnosis of a form of scoliosis other than idiopathic (eg neuromuscular, congenital, and traumatic), or if they were deemed to have insufficient medical record documentation. Results: 491 patients (mean age 14.5 years, 25.8% male) were included in this study. Mean poverty rate, BMI, and presenting Cobb angle were 11.0%, 23.6, and 26.8°, respectively. There was no correlation between presenting Cobb angle and poverty rate (R = -0.05). Mean poverty rate for patients presenting with operative curves ( > 45°) was higher than patients presenting with non-operative curves ( < 45°), but this difference failed to reach statistical significance (12.4% vs 10.7%, p = 0.13). Mean presenting Cobb angle was higher for both female patients (27.2° vs. 25.2°, p = 0.28) and black patients (28.5° vs. 25.1°, p = 0.10), but these differences failed to reach statistical significance. However, the mean BMI of patients presenting with Cobb angles in the operative range was significantly higher than that of patients presenting with Cobb angles in the non-operative range (22.1 vs. 20.7, p = 0.045). Conclusion: In our study, there was no significant correlation between poverty rate and severity of scoliosis at initial presentation. According to our findings, patients presenting with curves in the surgical range are more likely to have a higher BMI than patients presenting with curves in the non-surgical range.

A265: Curve Progression Matching With Skeletal Growth in Adolescent Idiopathic Scoliosis Using the Distal Radius and Ulna (DRU) Classification

Prudence Wing Hang Cheung¹, Dip-Kei Keith Luk¹, Dino Samartzis¹, Jason Pui Yin Cheung¹

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

Introduction: For adolescent idiopathic scoliosis (AIS) patients, it is important to determine their peak growth velocity for timely treatment in preventing curve progression. The ability to predict when the curve progression risk is greatest is necessary to maximize benefits of any intervention. Currently, there was limited information regarding the period of bracing and timing of weaning with success of curve control, particularly in relation to growth. This study aims to determine if there is any relationship between skeletal growth rate and curve progression rate in AIS patients, and how the distal radius and ulna (DRU) classification is able to define these parameters. Material and Methods: Data collection was performed for the growth parameters and Cobb angle of AIS patients who presented at Risser 0-3 and followed to maturity at Risser 5. Standing body height (BH), arm span (AS), curve magnitude, Risser sign and the DRU classification were studied. For analysis of clean data free from the effects of interventions such as bracing or surgery, only data from initial presentation to commencement of intervention was recorded. Growth rate (based on BH and AS) and the curve progression rate were then calculated for each DRU grade. Statistical analyses included Spearman correlation coefficient and paired t-test. Results: A total of 318 AIS (74.2% females) patients with mean age of 12.3 ± 1.5 years were studied. Mean follow-up before commencing intervention/reaching skeletal maturity was 4.3 ± 2.3 years. Significant correlations were found between radius and ulna grades with both the growth and curve progression rates (p < 0.001), the curve progression rate also significantly but weakly correlated (p < 0.001) with growth rates. When comparing peak growth and peak curve progression, there were statistical significant difference (p < 0.001) for both radius and ulna grades at which these peaks occurred. The curve progression peaked consistently after peak growth by a significant difference of one radius and ulna grade. The peak rate of curve progression can occur up to 8.3 months after the peak growth spurt of both body height (BH) and arm span (AS). Reductions in growth and curve progression rates reached a plateau at R9 and U7 (DRU grades). Conclusion: By utilizing the DRU grading, this large-scale study illustrates that the maximal curve progression occurs after the peak growth spurt, suggesting that the curve should be monitored closely even after peak growth. Our findings also demonstrate the period of potential curve continuing progression beyond the peak curve progression phase until the end of impactful growth. It is crucial that that DRU grades are capable to define such close relationship between growth and curve progression. The clinical use of DRU allows observation of not only growth at the important period before skeletal maturity, but how that relates to scoliotic curve progression rate as well. This plays a role in clinical decision-making on the timing of any scoliosis interventions.

A266: Cervical Kyphosis in Patients With Lenke Type 1 Adolescent Idiopathic Scoliosis: The Prediction of Thoracic Inlet Angle

Ce Zhu¹, Xi Yang¹, Bangjian Zhou¹, Limin Liu¹, Yueming Song¹

¹Department of Orthopedics Surgery, West China Hospital, Sichuan University, Chengdu - China

Introduction: Several studies have explored cervical kyphosis (CK) in adolescent idiopathic scoliosis(AIS) patients. However, few studies have evaluated the cervical alignment in these patients according to their coronal curve type. The aim of this study was to analyze the radiological features of cervical sagittal alignment in Lenke 1 AIS patients before and after surgery. Material and Methods: This is a retrospective study enrolled 50 patients. Preoperative and postoperative standing full-length radiographs (at last follow-up after operation) were used to measure the coronal and sagittal parameters. Main sagittal parameters included C2-C7 angle, thoracic inlet angle (TIA), T1 slope, proximal thoracic kyphosis (PTK, T1-5 kyphosis) and thoracic kyphosis (TK, T5-12 kyphosis). Results: The TIA of patients with CK was significantly smaller than that of patients with CL (63.0° vs. 76.3°, p < 0.05) and the cutoff value was 71°. The TIA of patients with CK after surgery was significantly smaller than that of patients with CL postoperatively (62.5° vs. 74.6°, p < 0.05) and the cutoff value was 62°. In patients with postoperative CL, there was a significant increase in their PTK and a reduction in their TK, regardless of preoperative CL or CK. In patients whose CL deteriorated to CK after surgery, both their PTK and TK significantly decreased after surgery. Conclusion: Patients with TIA less than 71° were more likely to have CK. And patients with TIA less than 62° would lead to the postoperative uncorrected or new onset of CK. The increased PTK after operation could have a beneficial effect on the improvement of CL.

A267: Final Fusion in Patients Affected by EOS Treated by Magnetically Controlled Growing Rods (MCGR): Results and Complications

Cloe Curri¹, Leonardo Oggiano¹, Sergio Sessa¹, Guido La Rosa¹

¹Department of Surgery, Orthopaedic Unit, Bambino Gesù Children’s Hospital, Rome - Italy

Introduction: Magnetically controlled growing rods systems have been introduced over recent years as an alternative to conventional growing rods for management of EOS. To report our experience in the final fusion of patients affected by early onset scoliosis (EOS) treated by Magnetically controlled growing rod system (MCGR). Materials and Methods: In a population of 30 patients affected by EOS treated by magnetic growing rods we identified six patients (4 F-2 M, mean age 12,8 years) with various etiology, who underwent the conversion in definitive rods at the puberty. Magnetically controlled growing rods (MAGEC System, Ellipse technology) were maintained for a mean of 5 years. Radiologic data were collected and analyzed in terms of Cobb angle before MAGEC implant, Cobb angle at the end of MAGEC treatment, Cobb angle after final fusion. The current follow-up since positioning of definitive rods is 12 months. Results: The mean operative time was 4 hours with a blood loss of 500 ± 100 ml. Mean pre-operative Cobb angle before MAGEC instrumentation was 53,8°(range 45°-63°), mean Cobb angle was 39°(range 29°-57°) at the end of MAGEC treatment and the mean Cobb angle after the fusion was 20°(range 12°-25°) with no change in coronal nor sagittal correction at 12 months follow-up. Most of the patients showed loss of anatomical landmarks, five patients had metallosis around the actuator of MAGEC. In five patients we reported autofusion; in these patients we performed posterior column osteotomy (PCO) to improve correction. No neurological complications nor infection were reported. Conclusions: Early results show satisfactory Cobb curve reduction after fusion in a follow-up period of 12 months. The Cobb angle value after final fusion is lesser than the preoperative and pre-fusion Cobb angles. The most common complications were the loss of anatomic landmarks, metallosis and autofusion as reported in literature.

A268: “Less is More” – Signficant Coronal Correction of AIS Deformity Predicts Thoracic Hypokyphosis

Oded Hershkovich¹, Areena D’Souza¹, Paul R.P. Rushton¹, Onosi S. Ifesemen², Michael P. Grevitt¹

¹Centre for Spinal Studies and Surgery, Queen’s Medical Centre, Nottingham, Nottingham - United Kingdom ²University of Nottingham, AR UK Centre for Sports Exercise and Osteoarthritis, Nottingham - United Kingdom

Introduction: It is suggested that posterior approach with significant coronal plane correction of AIS deformity is associated with hypokyphosis and imbalance in the sagittal plain. Other factors such as the pre-operative coronal curve magnitude, use of hooks, the number of levels fused, pre-operative kyphotic posture, screw density and rod type have all been implicated. Maintaining the normal thoracic kyphosis is important as hypokyphosis is associated with proximal junctional failure and early onset of degenerative changes in the spine. Our aim in this work was to study the association between the coronal correction successes with the sagittal balance outcome in AIS patients after posterior surgical correction. Methods: Retrospective case series of patients with Lenke 1-2 surgically corrected via posterior approach using a standardized surgical technique with a minimum follow up of 2 years. Complete radiographical preoperative and postoperative were measured as well as the operative data including UIV (divided into two Categories – T4 and above or below T5), LIV (divided into two categories - L3 or below and above L3), metal density (%, number of instrumented pedicles vs total available) and thoracic flexibility (%, MT correction ≤ 50% and > 50% in bending films). We further analyzed the post-surgical coronal outcome (Group I <60% and Group II ≥60%) of our group and studied their association with the post-operative kyphosis in the sagittal plain. Univariate and multivariate logistic regression were performed. Results: In total, 95 cases were included in our study (87% females, average age 14), 68 cases had thoracic correction of more than 60% (72%). Most cases had metal density of less than 80% (97.8%) and thoracic flexibility of more than 50% was found in 29 cases (31%). Preoperative hypo-kyphosis ( < 20°) was found in 24 cases (25.3%). Post-operative thoracic hypokyphosis was 5 times more likely in patients with thoracic correction ≥ 60% [OR 5.16 (95% CI, 1.79 - 14.91; p = 0.002)], after adjusting for cofounding variables. This association was not affected by metal density, thoracic flexibility, LIV, UIV, age or sex. Conclusion: Our data confirms the ‘essential lordosis’ hypothesis of Roaf (1966) and Dickson (1992) i.e. that with greater ability to translate the apical vertebra towards the midline there is a commensurate lengthening of the anterior column due to the vertebral wedging. The lack of association with metal density or flexibility, etc. suggests that this is an anatomical derivation rather than surgeon related. This also implies that use of Smith-Peterson osteotomies to ‘lengthen’ the posterior column and restore kyphosis is a flawed concept. Preservation of ‘normal’ thoracic kyphosis may require less coronal correction in preference for a balanced spine.

References

 1. De Jonge, T., J.F. Dubousset, and T. Illés, Sagittal plane correction in idiopathic scoliosis. Spine, 2002. 27(7): p. 754-760.

 2. Petcharaporn, M., et al., The relationship between thoracic hyperkyphosis and the Scoliosis Research Society outcomes instrument. Spine, 2007. 32(20): p. 2226-2231.

 3. Upasani, V.V., et al., Analysis of sagittal alignment in thoracic and thoracolumbar curves in adolescent idiopathic scoliosis: how do these two curve types differ? Spine, 2007. 32(12): p. 1355-1359.

 4. Lonner, B.S., et al., Multivariate analysis of factors associated with kyphosis maintenance in adolescent idiopathic scoliosis. Spine, 2012. 37(15): p. 1297-1302.

 5. Yang, M., et al., Lumbar Lordosis Minus Thoracic Kyphosis: Remain Constant in Adolescent Idiopathic Scoliosis Patients Before and After Correction Surgery. Spine, 2016. 41(6): p. E359-E363.

 6. Bernhardt, M. and K.H. Bridwell, Segmental analysis of the sagittal plane alignment of the normal thoracic and lumbar spines and thoracolumbar junction. Spine, 1989. 14(7): p. 717-721.

 7. Fletcher, N.D., et al., Residual Thoracic Hypokyphosis After Posterior Spinal Fusion and Instrumentation in Adolescent Idiopathic Scoliosis: Risk Factors and Clinical Ramifications. Spine, 2012. 37(3): p. 200-206.

 8. Watanabe, K., et al., Vertebral derotation in adolescent idiopathic scoliosis causes hypokyphosis of the thoracic spine. BMC musculoskeletal disorders, 2012. 13(1): p. 99.

 9. Halanski, M.A. and J.A. Cassidy, Do multilevel Ponte osteotomies in thoracic idiopathic scoliosis surgery improve curve correction and restore thoracic kyphosis? Clinical Spine Surgery, 2013. 26(5): p. 252-255.

10. Sucato, D.J., et al., Restoration of thoracic kyphosis after operative treatment of adolescent idiopathic scoliosis: a multicenter comparison of three surgical approaches. Spine, 2008. 33(24): p. 2630-2636.

11. Roaf, R., The basic anatomy of scoliosis. Bone & Joint Journal, 1966. 48(4): p. 786-792.

12. Dickson, R., The etiology and pathogenesis of idiopathic scoliosis. Acta orthopaedica belgica, 1992. 58: p. 21-25.

13. Millner, P.A. and R.A. Dickson, Idiopathic scoliosis: biomechanics and biology. European Spine Journal, 1996. 5(6): p. 362-373.

A269: Severe Rigid Kyphoscoliosis in Kids – it’s Different!!! Clinico Radiological Efficacy of Apical Spinal Osteotomy in 32 Paediatric Cases Over Long Term Follow Up.

Ankit Patel¹, Vishal Kundnani¹, Sameer Ruparel¹, Tarun Dusad¹, Gaurav Mehta¹, Shumayou Dutta¹

¹Department of Orthopaedics & Spine Surgery, Bombay Hospital, Mumbai - India

Introduction: Current surgical options for pediatric severe rigid kyphoscoliosis involves an array of complex surgeries with substantial operative hours, blood loss and morbidity. Apical spinal osteotomy (ASO) gives excellent 3-dimensional deformity correction at apex with definitive advantages. Aim of the study was to evaluate clinico-radiological efficacy of Apical Spinal Osteotomy (ASO) in management of pediatric severe ( > 50°) rigid kyphoscoliosis due to varied etiologies at mid-term follow-up of 2 years. Material and Methods: Retrospective Study, Single Institute, Single surgeon. Between Nov 2009- August 2014, 32 patients (Age < 12yrs) with fixed Thoraco-lumbar Kyphoscoliosis and having sagittal imbalance were operated and were evaluated. Clinico-Radiographic assessment included Pain-VAS, Disability-ODI, Neurology- Frankel grading. Intra operative parameters were documented. Sagittal balance-SVA & Kyphosis, Scoliosis Cobb’s angles, were evaluated before & after surgery and at last follow-up (minimum 24 months). Results: 26 Patients (mean age 9 yrs, M: F = 18:8) of 32 who underwent ASO (mean surgical time = 244 mins; blood loss = 337 ml; hospital stay = 8 days) for varied etiologies (Congenital = 8, Post tuberculosis = 7, Neurofibromatosis = 5, Post traumatic = 3, Scheuermann’s kyphosis = 1, Adolescent Idiopathic Kypho-Scoliosis = 2) satisfied minimum follow up of 24 months (Mean = 28.3 months; 24-48 months) and were included for evaluation. Average kyphotic angle improved significantly (p < 0.005) from 96.5⁰ preoperatively to 30.7⁰ postoperatively, average correction 68.57%. At last follow-up, average kyphotic angle was 35⁰ (Mean correction 64.15%). Average Scoliosis Cobb’s angle improved significantly (p < 0.005) from 52.5⁰ preoperatively to 15.76⁰ postoperatively, average correction 68.79%. At last follow-up, average scoliosis angle was 19.42⁰ (Mean correction 60.95%). Sagittal plane balance significantly improved (Pre/Post SVA = 7.59/3.94 cm). Preoperatively, 9 patients had neurological deficits (Frankel C-5, B-3; A-1), with Frankel E (No neurology) in 17 patients which improved significantly at last follow-up (Grade E-22, Grade D-2, Grade B-1, Grade A-1). 1 patient developed new-onset Frankel A neurology which failed to recover at last follow-up. Significant improvement in the ODI/VAS scores were noted. Complications included neurological deterioration-2 cases, dural tear-2, superficial infection -1 and implant failure-1 case which needed revision. Conclusion: Satisfactory correction can be safely performed by Apical Spinal Osteotomy with a direct visualization of the circumferentially decompressed spinal cord. This technique is versatile and useful for the reliable and safe correction of rigid kyphoscoliosis of varied etiologies, the treatment of which to date has proved to be extremely difficult and hazardous even in experienced hands.

Keywords: Kyphoscoliosis, severe, rigid, pediatric, osteotomy

A270: Safety and Efficacy of Correction Surgery Treatment for Spinal Deformity Associated With Intro-Spinal Abnormalities

Yong Hai¹, Shuo Zhang¹

¹Department of Orthopedics, Beijing Chaoyang Hospital, Capital Medical University of China, Beijing - China

Introduction: Intro-canal abnormalities are not rare in scoliosis deformity and the reported incidence was 20-40%. For Scoliosis with symptomatic intro-canal abnormalities, corrective surgery was combined with procedures of intro-canal intervention in one or two stages. But for scoliosis with asymptomatic intro-canal abnormalities, whether prophylactic surgery should be done or not still remain controversial. In order to evaluate the safety and efficacy of correction surgery only for scoliosis with asymptomatic intro-canal abnormalities, an retrospective study was carried out. Methods: From 2011.1-2014.12 135 consecutive AIS patients (M 43, F 92, average age of 19.27 ± 8.29yrs, Cobb: Scoliosis 79.06 ± 22.99, Kyphosis 59.02 ± 33.22) and 38 consecutive patients with asymptomatic intro-canal abnormalities (M 16 F 22, average age of 17.14 ± 6.81yrs, Cobb: Scoliosis 81.53 ± 27.2, Kyphosis 60.35 ± 33.82). The asymptomatic intro-canal abnormalities were: Diastematomyelia in 22 pts, Syringomyelia in 24 pts and Tethered Cord in 15 pts. All patients were undergoing traction pre-operatively for 1-2 week in large weight, short time and interval traction. All patients underwent posterior corrective surgery only. The mean major curves preoperatively, operating time, blood loss, mean major curves correction rate postoperatively, correction loss after two years and complication rate were compared between two groups. Results: The mean major curves preoperatively, operating time, blood loss, mean major curves correction rate postoperatively, correction loss after at least two years of two groups have no statistical differences. 3 patients had neurologic complications in intro-spinal abnormalities group postoperatively, 1 of them was lower limbs motor dysfunction, 2 of them was lower limb sensory dysfunction, all of were recovered after conservative treatment in 3 month. In addition, one patient had superficial infection and one patient had rod fracture. No neurologic deteriorations in two groups were observed in last follow-up more than two years. Conclusion: Scoliosis with asymptomatic intro-canal abnormalities with one stage posterior correction only could be successfully carried out and prophylactic surgery for intro-canal intervention may not be needed. Same clinical outcome could be achieved without increasing the neurological risk. No neurological deficits and increased loss of correction occurred at least 2 years post-operatively.

A271: Thoracic Only Fusions for Double (Type 3) and Triple (Type 4) Major Curves in AIS at a Minimum 5 Year Follow-up: Are They Possible and Durable?

Lawrence Lenke¹, Ronald Lehman¹, Michael Kelly², Baron Lonner³

¹Department of Orthopedics, Columbia University Medical Center, New York - United States ²Washington University School of Medicine Department of Orthopaedics, St. Louis - United States ³Orthopaedic Surgery Mount Sinai Hospital, New York - United States

Introduction: The recommended fusion of Lenke Type 3 (Double) and Type 4 (Triple) Major AIS curves includes the structural lumbar curve. However, there is a subset of pts. with greater thoracic vs. lumbar radiographic deformities who are candidates for a thoracic-only fusion, thereby saving lumbar motion segments, but the long-term radiographic results for these pts. are unknown. Methods: 26 pts. with Lenke Type 3 or 4 curves (Preop Lumbar modifiers: A: n = 2, B: n = 8, C: n = 16) that had thoracic-only fusions using pedicle screw constructs with the LIV at T11 (n = 2), T12 (n = 10), or L1 (n = 14), thus saving the structural lumbar curve from fusion, were analyzed radiographically at a minimum 5 yr. f/u. Results: The preop mean Main Thoracic (MT) Cobb was 69 deg and 48 deg for the thoracolumbar/lumbar (TL/L) curve (MT: TL/L Cobb ratio of 1.4), while the MT apical vertebral translation (AVT) was 6.1 cm vs. 2.7 cm for TL/L AVT (MT: TL/L AVT ratio of 2.3). Postop, the MT and TL/L Cobb measurements at 5 yr f/u were nearly matched at 27 and 25 deg respectively (p = 0.21). Pre- and postop coronal balance (C7-CSVL) was 1.5 and 1.8 cm respectively (p = 0.16), thus demonstrating maintenance of overall coronal alignment. In the sagittal plane, the preop T10-L2 Cobb mean was 10.4 deg., and unchanged at 10.5 deg at 5 yr f/u (p = 0.97). None of the pts. have required revision surgery up to a minimum 5 yr. f/u. Conclusions: A select group of pts. with Type 3 (Double) and 4 (Triple) major AIS curves can successfully undergo a thoracic-only fusion resulting in satisfactory coronal and sagittal alignment. Preop, having a MT: TL/L Cobb ratio of > 1.2 (mean 1.4), MT: TL/L AVT ratio of > 1.2 (mean 2.3), and a lack of structural TL/L kyphosis (T10-L2 < 20 deg) is important. These pts. have all avoided fusion into the lower lumbar region thus retaining important lumbar motion segments, while maintaining a balanced spine free of any revision surgery at a min. 5 yr. f/u.

A272: Posterior Spinal Osteotomy Surgery is an Effective Method for the Correction of Progressive Thoracolumbar Kyphosis in Patients With Achondroplasia

Leilei Xu¹, Chao Xia¹, Yong Qiu¹, Zezhang Zhu¹

¹Department of Spine Surgery, Drum Tower Hospital, Nanjing University Medical School, Nanjing - China

Introduction: Progressive thoracolumbar kyphosis (TLK) is a common manifestation in patients with achondroplasia. To date, few papers have investigated the outcome of correction surgery for TLK in this type of patients. The current study aims at evaluating the outcome of posterior spinal osteotomy surgery for TLK in pediatric patients with achondroplasia. Materials and methods: 14 achondroplastic patients undergoing one-stage posterior surgery for progressive TLK were reviewed. The osteotomy procedures included Smith-Petersen osteotomy (SPO) in 12 patients and pedicle subtraction osteotomy (PSO) in 2 patients. Correction rate of kyphotic deformity, fusion levels, density of pedicle screw, surgical complications, and patient satisfactory index (PSI) were evaluated for each patient. Results: The mean age at surgery was 9.1 ± 2.9 years (range, 5-13), with an average follow-up period of 47.8 ± 16.3 months (range, 24-84). The mean preoperative kyphotic angle was 58.3° ± 17.1° (range, 42° - 91°), which was corrected to 14.7° ± 6.4° with a mean correction rate of 74.8%. The mean curve magnitude was 40.5° ± 16.7°, which was corrected to 11.5° ± 6.8° with a mean correction rate of 71.6%. The average percentage of apical vertebral wedging was improved from 49.4% ± 12.3% before surgery to 26.6% ± 6.7% at the final follow up. There was no case with significant loss of correction or neurological symptoms during the follow-up. 13 patients were satisfied with the surgical results with a PSI of 92.9%. The perioperative complications included one case of dural tear concomitant with transient neurologic impairment and one case of infection at the incision site. Conclusions: The one-stage posterior osteotomy surgery with segmental instrumentation is a safe and effective surgical option for progressive TLK in pediatric patients with achondroplasia. The wedged apical vertebral can be spontaneously improved in the long-term follow-up. We recommended that early surgical intervention in childhood should be performed for achondroplastic patients with progressive deformities.

Keywords:Thoracolumbar spinal deformity; Achondroplasia; Kyphosis; Osteotomy

Novel Technologies

A273: Functional Rehabilitation Using the Hybrid Assistive Limb Exoskeleton: A First Experience in the United States

Christian Fisahn¹, Ziadee Cambier², Kim Kobata³, Cameron Schmidt¹, Emre Yilmaz¹, Paul Lim³, Angeli Mayadev², Nate Coomer³, Daniel Norvell⁴, Jens Chapman¹

¹Swedish Neuroscience Institute, Swedish Medical Center, Seattle - United States ²Swedish Multiple Sclerosis Center, Seattle - United States ³Swedish Neurological Rehabilitation Medicine, Seattle - United States ⁴Spectrum Research, Inc., Tacoma - United States

Introduction: The Hybrid Assistive Limb (HAL, Cyberdyne, Japan) exoskeleton facilitates voluntary, user-driven gait patterns through an electromyography-triggered neuromodulatory feedback system. This allows for the repeated execution of physiological gait patterns, crucial to recovery in cases of neurologic motor deficit. In this series, we present the first three patients (3 additional patients will be finishing their follow-up within the next few weeks) in the United States to undergo HAL rehabilitation training. Materials and Methods: A case series of three patients participating in a single-center prospective, interventional pilot study, who were suffering neurologic motor deficits such as spinal cord infarct following a pulmonary embolism, multiple sclerosis, the surgical resection of a petroclival meningioma and spinal cord injuries. Inclusion criteria included patients who had achieved a stable non-progressive state in their motor neurologic deficit following (a) spinal cord injury with ASIA A through D functional status with thoracic and lumbar levels of paralysis (b) cervical spinal cord injury with incomplete injuries below C6, or (c) CVA, MS, or other neurodegenerative disorders that cause significant gait impairment. Patients on active medications for spasticity were required to be on a stable dose for at least three months prior to study entry. The patients underwent 60 sessions of Body Weight-Supported Treadmill Training (BWSTT) in the HAL exoskeleton over the course of 12 weeks. Measures of functional ambulation (10 meter walk test) were performed out of the HAL exoskeleton before and after each session, and at the 12-week and 6-month follow-up. Timed Up & Go (TUG) test was performed each week. Treadmill data (time, distance, blood pressure, heart rate) while in HAL was recorded at each session. Measures of endurance (six-minute walk test), risk of falling (TUG), balance impairment (Berg Balance Scale), and improvements in walking performance (Walking Index for Spinal Cord Injury II score (WISCI II)) were measured at baseline, 12-weeks training and 6-month follow-up. Results: All three patients completed 60 visits. All patients achieved markedly increased treadmill paces, increased WISCI II scores, increased distance in the six-minute walk test, and decreased TUG times at 6-month follow-up. In the 10 meter walk test, all patients achieved a significant decrease in time and steps, and showed improvements in the required assistance level to perform the test. Patients 1 and 3 showed improvement on the Berg Balance Scale while patient 2 had no change between baseline and 6-month follow-up. Only minor adverse effects were reported, including skin abrasions and irritation secondary to chaffing of the HAL unit and EMG electrodes. Conclusion: These data show that HAL training is both feasible and effective in the rehabilitation of patients suffering neurologic motor deficits secondary to trauma and/or pathological/neurodegenerative processes who have achieved a stable non-progressive state for three or more months A greater number of patients are required to meaningfully assess the effectiveness of this modality and determine if specific pathologies respond greater than others.

A274: Medical Consultation of Spinal Pathologies With Kinematics in Virtual Reality

Diane Villaroman¹, Bilwaj Gaonkar¹, Luke Macyszyn¹

¹Department of Neurosurgery, University of California Los Angeles, Los Angeles - United States

Introduction: Presently, spine professionals use a static image to assist in surgical planning and patient education. However, the spine is not a static object. While the soft tissue anatomy of the spine is well elucidated using magnetic resonance imaging (MRI), the flexible, dynamic nature of the spine is difficult to visualize and portray, especially to patients. Therefore, the goal of this study was to implement spine kinematics and common degenerative pathologies in an interactive virtual reality (VR) program and determine its efficacy in improving patient education and communication. Material and Methods: We developed a library of digital 3D models of spinal anatomy that can be visualized and manipulated within a virtual environment. A generic healthy model of the spine was created using the Autodesk Maya® modeling software. Kinematics parameters were informed using published literature [1]. Clinical cases depicting degenerative pathology were likewise modeled after patient examples. These models were animated and exported to a Unity Game Engine application, which was run on a Samsung Gear VR headset. IRB approval was obtained and patients seen at the UCLA Spine Center were provided with the headset during their consultation. A survey was administered at the conclusion of the visit to quantify patient satisfaction and gauge the patients’ understanding of the relevant discussed anatomy. Results: Spine professionals can easily guide and educate patients regarding spinal anatomy and degenerative pathologies in an immersive VR environment. The scenario’s that present foraminal stenosis and central canal stenosis due to disk bulging and ligament hypertrophy were reported to be most useful by patients. Likewise, the kinematic model of the spine allowing visualization of lumbar flexion and extension enabled physician to better explain these dynamic states of the spine to the patients. No adverse events were observed and preliminary data from surveys demonstrates high patient satisfaction with the educational content and experience. Conclusion: Unlike static 2D medical images, VR allows people to immerse themselves in an educational environment that is difficult to create in real life, such as the inside of a spinal canal. The visualizations included color-coded anatomy, animations, and interactive movement based on real patient information. Patients not only improved their understanding of the pathology, but the technology enabled patients to feel more confident overall about their diagnosis. Future work will determine if this understanding and confidence will translate to improved patient consent prior to surgical interventions, preparation for post-operation safety needs, and reduced readmissions [2, 3, 4]. Furthermore, our aim is to ultimately present patients with 3D VR models that are personalized with their pathology, which can then be used for surgical planning also by surgeons.

References

1. White, Augustus A., and Manohar M. Panjabi. Clinical biomechanics of the spine. Philadelphia: Lippincott, 1978. Print.

2. Labhardt, Niklaus Daniel et al. Provider–patient interaction in rural Cameroon—How it relates to the patient’s understanding of diagnosis and prescribed drugs, the patient’s concept of illness, and access to therapy. Patient Education and Counseling, Volume 76, Issue 2, 196 - 201

3. Cho, R. N., Plunkett, B. A., Wolf, M. S., Simon, C. E. and Grobman, W. A. (2007), Health literacy and patient understanding of screening tests for aneuploidy and neural tube defects. Prenat. Diagn., 27: 463–467. doi:10.1002/pd.1712

4. Bollschweiler, Elfriede; Apitzsch, Jonas; Obliers, Rainer; Koerfer, Armin; Mönig Stefan P.; et al. Improving Informed Consent of Surgical Patients Using a Multimedia-Based Program?: Results of a Prospective Randomized Multicenter Study of Patients Before Cholecystectomy. Annals of Surgery. 248(2):205-211, AUG 2008. doi: 10.1097/SLA.0b013e318180a3a7

A275: Using Ultrasound Scans to Measure Longitudinal Growth of Magnetically Controlled Growing Rods

Mohamed Mohamed¹, Philip Brown¹, Sudarshan Munigangaiah¹, Colin Bruce¹, JM Trivedi¹, NT Davidson¹

¹Indian Spinal Injuries Centre, OPP, Vasant Valley School, New Delhi - India

Background: Magnetically controlled growing rods (MCGR) are used in the management of early onset scoliosis. Unlike traditional spinal rods these can be extended in clinic negating the need for repeat surgery, unfortunately as a result this predisposed the growing child to repeat radiographs and ionizing radiation. However, we propose that ultrasound scans can be used to effectively measure the extension obtained thus reducing the number of radiographs required. Method: This is a retrospective review of all the patients who have had MCGR at Alder Hey Hospital. Standardised method was used to assess rod extension using ultrasonography and radiographs. Inter-observer and intra-observer assessment was performed. Patients were reviewed every 3. Magnetically controlled extension was undertaken at each follow up followed by ultrasonography and radiograph measurement. Result: 30 patients (16 female and 14 males) with average age 7.6 years (4-12) underwent MCGR surgery. 6 patients were excluded (1 fractured rod, 1 infection and 4 had recent surgery and did not have radiographs). Linear regressions analysis showed perfect fit between XR and US measurements at each time point (R² 0.723). The two measurements distribution was not different (p 0.001). Conclusion: Magnetically controlled growing rods can reduce the number of repeat surgeries for children and thus has a psychological benefit for the patient and family. Ultrasonography is comparable to radiographs in the assessment of magnetic rod extension and can be used instead to reduce the exposure to ionizing radiation. We use ultrasonography every 3 months to assess rod extension and only get radiographs every 9 moths for assessment of overall spinal position.

A276: The Comparison of the Clinical Outcome and HRQOL Between Patients who Utilized S2AI and is

Changchun Zeng¹, Zhen Liu¹, Yong Qiu¹, Zezhang Zhu¹

¹Department of Spine Surgery, Drum Tower Hospital, Nanjing University Medical School, Nanjing - China

Introduction: To compare the clinical outcome and health related quality of life(HRQoL)of degenerative scoliosis patient who underwent spino-pelvic fixation utilized second sacral alar-iliac (S2AI) with patient utilized traditional iliac screw (IS). Materials and Methods: Patients diagnosed as degenerative scoliosis who underwent spino-pelvic fixation utilized either S2AI screw or Iliac screw at Department of Spine Surgery of Drum Tower hospital from January 2010 to January 2016 were retrospectively analyzed. A total of 22 patients who meet the inclusion were recruit in this study, patients were divided into two groups: 14 patients utilized S2AI screw and 8 patients utilized iliac screw. Cobb’s angle, Coronal balance distance (CBD), Regional kyphosis (RK), Sagittal vertical axis (SVA) were recorded pre- and post-operation and at last follow up. The MOS item short from health survey (SF-36), visual analogue scale (VAS), Oswestry disability index (ODI) were recorded pre-operation and at last follow up. Five tests were administered to all patient at the last follow up to diagnose sacroiliac joint dysfunction, three tests resulting positive was regarded as dysfunction. χ2 test and t-test were used to analyzed enumeration data and measurement data, respectively. Results: There was no significant difference in age, gender, follow up time between two groups. The Cobb’s angle, Coronal balance distance (CBD), Regional kyphosis (RK), Sagittal vertical axis (SVA) at pre- and post-operation and last follow up, SF-36, ODI, VAS at pre-operation and last follow up showed no significant difference between two groups. Compared to preoperative, the Cobb’s angle (44.42° ± 14° vs 20.17° ± 7.2° vs 18.25° ± 7.07°), C7PL-CSVL (25.33 ± 16.03 mm vs 10.33 ± 5.74 mm vs 9.16 ± 4.15 mm), RK (22° ± 30.86° vs −14.25° ± 23.04° vs -13.17° ± 22.16°), SVA (31.5 ± 34.38 mm vs 12.08 ± 8.4 mm vs 10.92 ± 7.18 mm), SF36-PCS (39.83 ± 14.31 vs 68.23 ± 21.47), SF36-MCS (44.85 ± 14.84 vs 73.89 ± 19.89), ODI (37.71 ± 16.9 vs 19.79 ± 15.79), VAS (4.75 ± 2.1 vs 1.75 ± 0.94) were significantly improved postoperatively in S2AI group. In IS group, compared to preoperative, the Cobb’s angle (54.29° ± 18.25° vs 26.14° ± 13.24° vs 25.57° ± 18.25°), C7PL-CSVL (31 ± 15.95 mm vs 13.86 ± 6.96 mm vs 12.43 ± 6.6 mm), RK (38° ± 20.43° vs 3.29° ± 16.94° vs 1.43° ± 14.03°), SVA (27.14 ± 23.85 mm vs 13.14 ± 7.47 mm vs 13.57 ± 6.02 mm), SF36-PCS (29.71 ± 7.09 vs 61.14 ± 11.21), SF36-MCS (35.86 ± 7.06 vs 64 ± 11.06), ODI (48.57 ± 13.37 vs 19 ± 10.66), VAS (4.86 ± 1.8 vs 2.64 ± 1.25) were significantly improved postoperatively. There were two patients need revision surgery in IS group due to the rod fracture. None of the patient in S2AI group need revision surgery due to the complication. There were no instances of sacroiliac joint dysfunction in both groups at last follow up. Conclusions: Spino-pelvic fixation utilizing S2AI screw can provide similar correction rate to iliac screw and the sacroiliac joint penetration due to S2AI won’t affect the HRQoL in degenerative scoliosis patient utilized S2AI.

A277: Early Stage Evaluation and Life Quality Assessment of Patients Treated With Magnetically Controlled Growing Rods With the Diagnosis of Early Onset Scoliosis

Ismet Oral¹, Yasin Sahin¹, Muhammed Mert¹, Ali Oner¹, Deniz Kargin¹, Akif Albayrak¹, Mehmet Bulent Balioglu¹, Mehmet Akif Kaygusuz¹

¹Department of Orthopedics, University of Health Sciences; M.S Baltalimani Bone Diseases Hospital, Istanbul - Turkey

Introduction: Growth friendly therapy methods for patients with early onset scoliosis are rapidly improving in recent years. The newest member of these therapies is magnetically controlled grawing rod technique. Our aim in this study is to evaluate early radiological findings of patients operated in our hospital using magnetically controlled growing rod and to determine differences in quality of life of treated patients and their parents. Material and Methods: Total 20 patients, treated with magnetically controlled growing rods and received elongation with 3 months intervals, between August 2014 and August 2016 has been included in the study. Mean age at the time of operation is 7.9 years (4-10) and mean follow-up time is 14.9 months (6-30). Preoperative, early postoperative and last follow-up x-rays of all patients are obtained. On these x-rays, Cobb angle, thoracic kyphosis, spinal height, thoracic height, sagittal balance, coronal balance, shoulder balance and pelvic balance are measured. All patients received preoperative and last follow-up respiratory function tests and every patient filled the EBS-Q24 questioner. Results: Preoperative, early postoperative and last follow-up mean Cobb angles are 56,6 degrees (38-93), 30.5 degrees (13-80) and 33.5 degrees (14-86), respectively. These findings showed statistically significant improvement in Cobb angle (p < 0.05). Thoracic height also significantly increased; preoperative mean was 181 mm (123-224), early postoperative mean was 200 mm (164-245) and last follow-up mean was 212 mm (167-248) (p < 0.05). Measurements for spinal height also showed significant increase, preoperative, early postoperative and last follow-up values were 219 mm (213-366), 315 mm (260-402) and 338 mm (261-406), respectively (p < 0.05). Thoracic kyphosis measurements were 41 degrees (5-65) preoperatively and this value significantly decreased to 32.5 degrees (0-53) in last follow-up (p < 0.05). Our measurements showed no statistically significant differences in coronal and sagittal balance, pelvic balance and shoulder balance. There were no significant differences between preoperative and postoperative respiratory function tests. EBS-Q24 questionnaire evaluation showed us significant improvements in the mean of the points (p < 0.05). When different categories in questionnaire evaluated separately, there was no statistically significant differences between preoperative and last follow-up scores of general health, pain-discomfort, respiratory function, movement capability, physical function and daily life (p > 0.05). However exhaustion and energy levels, emotional state, effect of the disease on parents and patient and parent satisfaction scores showed significant increase when preoperative and last follow-up points compared (p < 0.05). Financial effect decreased significantly in last follow-up comparing to preoperative values (p < 0.05). Four patients developed revision needed complications and none of the patients developed infection which needed surgical intervention. Conclusion: Our study shows that magnetically controlled growing rod is a safe procedure for early onset scoliosis treatment in the terms of deformity adjusting and improvement in daily functions. This method decreases repetitive operations and possible complications which may develop during other treatments. As a result, it increases the patient satisfaction and facilitates the patient compliance to the treatment.

A278: When Giants Talk; Robotic Dialect During Spine Surgery

Saadit Sarah Houri¹, Leon Kaplan¹, Hananel Shear Yashuv¹, Avraham Soroka¹, Amal Khoury¹, Meir Liebergall¹, Joshua Schroeder¹

¹Department of Orthopedic, Hadassah University Medical Center, Jerusalem - Israel

Introduction: Robotic assisted spine surgery has been used for over a decade using navigation assistance robot. This system allows intraoperative drilling of trajectories based on preoperative CT scans merged with intraoperative fluoroscopy images. However in cases of vertebral fractures due to fragments motion, the level of accuracy may decrease during the procedure. Imaging robot allow high level live intraoperative imaging. The dialect between the two robots allows an increased level of patient safety. Methods: Patients were operated in a hybrid operating room. After patient positioning, a navigation assistance robotic star marker was placed on the patient’s spine and a 3D scan was performed by the imaging robot. The images were transformed to the navigation assistance robotic station and screw trajectories were planned. In order for this dialect to conform, several optimizations of both robots were needed. Data output had to be changed, and settings on the imaging robot scanner needed to be modified for complying with the navigation assistance robot requirements. Additionally, as navigation assistance robot utilizes planning software that allows multiple segments planning in one scan, the imaging robot capabilities were stretched to their fullest with larger ‘sutured’ scans being tested for compatibility with the navigation assistance system. Trajectories were executed and verified with another 3D scan. Hardware placement was performed in the routine manner. Results: Ten surgeries were performed in eight patients in 2017; six patients with traumatic spinal fractures and two patients with multi-level thoracolumbar compression fractures due to severe osteoporosis. Average age was 40 (range 12-67); 5 were male and 3 female. Average radiation time was 53.25 seconds for the whole case (range 24-114 seconds). A total of 66 trajectories were performed, all were accurate and the vertebral positioning were improved after the operations. Operated levels were between T4 and S2. There were no procedure related complications. Conclusion: The combination of surgical robots increases patient safety and increases surgeon and patient confidence in large, complex and percutaneous procedures. We believe this merging of technologies is a small step forward benefiting with our patients.

A279: Optimizing the Architecture and Geometry of a 3D-Printable Hyperelastic “Bone” Composite Scaffold Designed for Spinal Fusion

Meraaj Haleem¹, Adam Jakus¹, Adam Driscoll¹, Ryan Lubbe¹, Kevin Chang¹, Richard Pahapill¹, Karina Katchko¹, Gurmit Singh¹, Andrew Schneider¹, Soyoen Jeong¹, Chawon Yun¹, Jonghwa Yun¹, Ramille Shah¹, Stuart Stock¹, Wellington Hsu¹, Erin Hsu¹

¹Northwestern University, Chicago - United States

Introduction: Pseudarthrosis occurs in 10-15% of patients undergoing spine fusion. Recombinant human bone morphogenetic protein-2 (rhBMP-2) is a bone graft substitute (BGS) that elicits high rates of fusion but is associated with significant adverse effects. Demineralized bone matrix (DBM) and synthetic ceramics cannot serve as bona fide BGSs because of insufficient osteoconductivity, low structural strength and/or poor handling properties. With a goal to develop a recombinant growth factor-free BGS, we have developed a unique biomaterial ink consisting of hydroxyapatite (HA) and demineralized bone matrix (DBM) particles, which is 3D-printed into a Hyperelastic ‘Bone’ composite (HBC) scaffold. We previously established that HBC scaffolds promote efficacious spinal fusion in a posterolateral spinal fusion (PLF) rat model. In the current study, we sought to determine the most effective strut angle and average macropore size in the HBC scaffold for achieving successful spinal fusion in the rat. Methods: Sixty female Sprague-Dawley rats underwent L4-L5 PLF with placement of one of five HBC scaffold iterations (N = 12). Each scaffold consisted of 30 vol.% poly lactic-co-glycolic acid (PLGA)—a biodegradable polymer that served as an elastomer—and 70 vol.% bioactive particles, which was composed of HA and DBM particles in a 3:1 ratio. One treatment group received a “solid” scaffold containing no separated struts (ie, no macropores), whereas the remaining 4 treatment groups received scaffolds with varying combinations of strut angle and macropore size: 90°/1000 µm, 45°/1000 µm, 90°/500 µm, or 45°/500 µm. Spinal fusion was evaluated 12 weeks postoperatively using plain radiographs, manual palpation assessing for motion between segments, and microCT imaging. Fusion scoring was assessed by 3 blinded investigators using an established scoring system: 0 = no fusion, 1 = unilateral fusion, and 2 = bilateral fusion. Spines that received an average score ≥ 1.0 were considered successfully fused. Results: The 45°/1000 µm scaffold had the highest fusion score of 1.61. Both 90°/500 µm and 90°/1000 µm scaffolds scored 1.42 and the 45°/500 µm and solid scaffold implants resulted in an average fusion score of 0.917 and 0.333, respectively. Animals treated with the 45°/1000 µm and 90°/500 µm scaffolds had fusion rates of 100% (12/12 fused). The 90°/1000, 45°/500 µm and solid scaffolds had fusion rates of 83.3% (10/12) and 58.3% (7/12) and 16.7% (2/12) respectively. Conclusion: HBC may represent a bona fide bone graft substitute. HA/DBM scaffolds can elicit high rates of fusion while the PLGA imparts superior handling over currently available HA-based scaffolds. This study focused on the effects of scaffold strut angle and macropore size on spine fusion, and our results suggest that struts printed at angles of 45°/135° and with a macropore size averaging 1000 µm across (1 mm² 2D area) may be the optimal configuration. Further studies will compare the efficacy of the HBC composites with that of rhBMP-2 delivered on an absorbable collagen sponge in promoting bone regeneration and spinal fusion. In all, the hyperelastic “bone” – DBM composite scaffold represents a novel biomaterial whose success in promoting bone regeneration and spinal fusion in a clinically relevant rat model suggests that the HBC has significant potential as a bone graft substitute.

A280: Clinical and Radiographic Evaluation of Bioactive Glass in Posterior Cervical or Lumbar Spinal Fusion

Cedric Barrey¹

¹Hopital Werteimer, Hospices Civils de Lyon, Lyon - France

Introduction: Spinal fusion is commonly performed in treating degenerative, traumatic and scoliotic conditions. Successful outcome of fusion depends largely on obtaining a solid bridge of bone across the spinal segment instrumented. Autogenous bone graft has been the accepted gold standard for spinal fusion for more than 50 years. However, graft harvest may lead to donor site morbidity such as pain, infection, etc…Bioactive glass could be an alternative, as this synthetic resorbable material has a unique composition, with high amounts of minerals. Soluble silicon has notably demonstrated its role in up-regulation of collagen synthesis, osteoblastic metabolism, promotion of osteoinductive gene expression, and therefore faster bone formation. The goal of the present work was to report our experience of using bioactive glass for spinal fusion through a consecutive series of 26 adult patients. Material and Methods: All patients from January to October 2015 with indications for a posterior spinal fusion procedure were operated by the author (CB) and consecutively included in the study. Appropriate decompressive surgery was performed, with subsequent fixation using posterior instrumentation. Bioactive glass granules (45S5) were mixed with local autograft harvested from the surgical site and blood. Demographic data, co-morbidities, pre and post-operative pain levels and neurological status were recorded. Operative data included location and quantity of graft, intraoperative complications, blood loss, and duration of operation. Pre and post-operative data included pain evaluation, patient satisfaction, CT scans, at 6 and 12 months. Results: Average age at the time of surgery was 66 years old. 5 patients underwent 1 or 2 levels fusions, 9 patients underwent 3 to 6 levels fusions and 12 patients underwent 7 to 10 levels fusions. Operative data, such as the duration of operation, blood loss and GlassBone volume, are highly dependent of the number of levels to be treated. After surgery, 3 complications were reported, all for 9 levels fusions: there was no neurological complication, nor mortality. The 3 patients were re-operated, with successful results. For cervical procedures, fusion is acquired or in good progress for 3 patients (100%). No patient shows average fusion nor pseudarthrosis. Patient recovery is good for 3 patients (100%). For lumbar procedures, fusion is acquired or in good progress for 22 patients (96%). One patient shows pseudarthrosis: this patient showed late infection 3 months after operation. After hardware removal, pain was not significant. Patient recovery is excellent for 21 patients (91%) and average for 2 patients. Conclusion: This study confirms that the use of bioactive glass mixed with local autograft is an excellent alternative to autologous graft. No changes were required to the standard surgical techniques for either approach or fixation method, and the results at 6 and 12 months from this treatment of degenerative or trauma spine disorders with respect to pain, neurological status and function were highly encouraging. The imaging results supported the clinical picture of solid fusion. However, clinical and radiological outcomes need to be confirmed at long-term follow-up.

A281: Outcomes of Lateral Anchor Placement for Occipitocervical Fusion in Atlantoaxial Instability

Kevin Kwan¹, Shashank Gandhi¹, Timothy White¹, Julia Schneider¹, Justin Virojanapa¹, Salvatore Insinga¹, Harold Rekate¹

¹Department of Neurological Surgery, Manhasset - United States

Introduction: Occipitocervical (OC) fusion in patients with cranial cervical instability remains a challenge, especially because many of these patients have had prior posterior fossa decompressions. Stabilization of the OC junction in this subset of patients is complicated by the regional anatomy, lack of midline fixation, the need for strong bicortical fixation, and the need for a low occipital profile. Multiple bicortical fixation points to the occipital bone may be required to increase construct rigidity. The authors evaluated the outcomes and complications of using a bilateral occipital anchor construct and a U-shaped cobalt-chrome single rod in patients following posterior fossa decompression. Material and Methods: Retrospective review of records from 17 consecutive patients who had undergone OC fusion between 2015 and 2017 at Northwell Health using K2 M occipital anchor bolts and a single U-shaped rod construct. Results: The patients consisted of 15 females and 2 males with a mean age of 32.2 years (SD 7). All patients had a preoperative diagnosis of cranial cervical instability. 82.4% of patients underwent posterior fossa decompression, occiput-C2 instrumentation and bilateral C2 rhizotomy, with the remaining 17.6% undergoing occiput-C3 instrumentation. Grafton putty and Orthoblend were used in all cases. 24% of patients had prior OC surgery. 1 patient, who had evidence of prior surgery, was discovered to have an inferior wound dehiscence which was closed at bedside. This same patient had an intraoperative complication of cerebrospinal fluid leak of no clinical consequence following primary repair. Two patients (11.76%) underwent revision surgery for occipital bolt pseudoarthrosis, one of which had evidence of prior surgery. Average length of stay was 3.7 days (SD 1). Ten of seventeen patients had 6 to 12 months follow-up with mean MRS scores of 1.1 (SD 0.3). The remaining seven patients had up to 3 month follow-up with mean MRS scores of 1 (SD 0). Average lateral occipital cortical thickness, measured on computerized tomography, was 5.2 mm (SD 1.4) Conclusions: Data in this report confirms that usage of our novel OC construct in adults may be safely employed as a primary technique or salvage technique for patients with failed prior fusions. There was a notable pseudoarthrosis complication rate in this retrospective series, which adds necessity for further patient accruement and longer patient follow-up to add power to these findings.

Tumor

A282: Adverse Events Profile in EN Bloc Resection and Surgery for Primary Bone Tumor

Shreya Srinivas¹, Charles Fisher¹, Michael Boyd¹, Scott Paquette¹, Brian Kwon¹, Tamir Ailon¹, Raphaele Charest Morin², Marcel Dvorak¹, John Street¹, Nicolas Dea¹

¹Department of Spine Surgery, Vancouver General Hospital, Vancouver - Canada ²Department of Orthopaedics, University Afiiliated hospital Laval, Quebec - Canada

Introduction: En bloc resection is uncommonly performed in the spine. Available evidence on complications after oncological surgery is of very low quality, often from small retrospective series with inconsistencies in adverse events (AE) reporting. The purpose of this study is to determine the AE profile in the population of patients undergoing en bloc resection for spinal metastases or surgery for primary bone tumor of the spine. Materials and Methods: This is a prospective cohort study in a single quaternary care referral center. All consecutive patients who underwent surgery for metastases with a curative intent or surgical excision of a primary tumor of the spine between January 1, 2009 to July 31, 2017 were included. AE were collected on a standardized form (Spine AdVerse Events Severity System, version 2 [SAVES V2] forms) at weekly-dedicated morbidity and mortality rounds. Data collected included patient demographics, primary tumor histology, neurological status, surgical intervention details, marginal status, Enneking appropriateness and all AEs (perioperative and post-operative) Results: A total of 56 patients (34 males, 22females average age 57.6 years) met the inclusion criteria and had complete data. Of these, 51 patients had a primary bone tumor and 5 patients had a metastatic lesion (enbloc resection). In the primary tumors, surgical resection margins were wide or marginal in 40, intralesional in 8 and indeterminate in 3 patients. There was at least 1 AE observed in 38 patients (68%) and there were no deaths seen. Of these 11 patients (20%) had Intraoperative AEs and common surgical complications seen were dural tear (20%), visceral or neuro vascular injury (18%), massive blood loss in excess of 2 L (14%), and implant/hardware malposition(12%). Predominantly AE was seen in the post- operative period in 33 patients (59%) and usually due to either a systemic infection (UTI/pneumonia) in 41% or a cardiac event (39%). Incidence of thromboembolic events (DVT/PE) was 12%. Implant failure or non-union was less common (5%) and neurological deterioration was seen only in 4 patients.(7%). AE occurred in patients who underwent wide/marginal resection (n = 35; 87.5%) rather than intralesional resection (n = 4; 50%). There was also significant wound related complication seen in 34% of the patients. This was more commonly seen in those who had surgical resection performed for lesions around the sacrum (88%) as compared to tumour location in the rest of the spine (7%). Conclusion: Surgery for primary bone tumors is associated with high incidence of AE. This should be of significant consideration when counselling these patients for surgical intervention and should be confronted to the curative intent of the procedure. A better understanding of this AE profile will benefit the surgeon and oncologist in developing preventative strategies in this patient cohort.

A283: Monitoring Disease Status in Chordoma Using Released Tumor DNA

Chetan Bettegowda¹, Dan Sciubba¹, Jean-Paul Wolinsky¹, Ziya Gokaslan¹

¹Johns Hopkins University School of Medicine, Baltimore - United States

Introduction: Chordoma is the most common primary spinal column neoplasm and is treated with maximal safe surgery and radiation. Despite ongoing efforts to improve outcomes, the median survival is approximately seven years. Imaging is currently the only approach to monitor disease status and evaluate for residual or recurrent tumor. We and others have demonstrated that many neoplasms will release tumor DNA into the circulation (rtDNA). These molecules of rtDNA can be detected, quantified and used as a personalized biomarker of disease. rtDNA can be distinguished from the background normal DNA by the presence of disease defining somatic mutations. To date, no one has studied whether chordoma sheds rtDNA into the circulation. Materials and Methods: After quality assurance, we isolated match tumor and normal DNA from fifteen patients undergoing surgical resection of spinal chordoma. We performed whole exome sequencing on matched chordoma tissue and lymphocyte cell pellet to identify somatic driver mutations within the tumor. We then queried for levels of rtDNA based on the mutation discovered via whole exome sequencing. rtDNA levels were quantified using droplet digital PCR and correlated with clinical measures of disease burden. Results: We performed whole exome sequencing on all fifteen cases and discovered that 47% percent of cases had a mutation in PBRM1, ARID1A or ARID1B. Twelve of fifteen (80%) pre-operative plasma samples tested had detectable levels of ctDNA with an average mutant allele fraction of 0.73%. In all ten patients where longitudinal samples were available, rtDNA levels correlated with disease status as measured by imaging. Conclusions: While some in the literature suggest a paucity of recurrent alterations in chordoma, we demonstrate recurrent somatic mutations in the epigenetic machinery of chordomas in nearly half of cases tested. We applied this genetic understanding of chordomas to detect rtDNA in the plasma. Eighty percent of chordomas shed detectable levels of rtDNA into the blood and the levels correlate with disease status. rtDNA appears to be a promising non-invasive biomarker for individuals with chordoma and future studies are required to further elucidate its role in the management of patients.

A284: Surgery of Intramedullary Spinal Cord Tumors Focusing on Preservation of Spinal Cord Function

Hidetoshi Murata¹, Takahiro Tanaka¹, Mitsuru Sato¹, Ryohei Miyazaki¹, Ryo Matsuzawa¹, Taishi Nakamura¹, Kensuke Tateishi¹, Tetsuya Yamamoto¹

¹Department of Neurosurgery, Yokohama City University Graduate School of Medical Sciences and School of Medicine, Yokohama - Japan

Introduction: It’s ideal to resect intramedullary spinal cord tumor (IMSCT) completely without any damage of spinal cord function. However, it’s sometimes difficult, especially for huge or malignant tumors. The adequate approach and elaborate surgical technique is inevitable for resection, but concrete procedure hasn’t been described well. We introduce our procedures for resection of IMSCT focusing on preservation of spinal cord function. Material and Methods: Since November 2006, we operated 86 cases of IMSCT and non-neoplastic lesions including ependymoma 26, hemangioblastoma 21, astrocytoma 9, cavernous malformation 2, intramedullary schwannoma 4, lipoma 2, metastatic tumor 2 and others 20. We gave a specific attention to preservation of spinal cord pial vessels, wide myelotomy enough to resect the tumor safely and avoidance of direct manipulation for spinal cord parenchyma. In addition, we resected them with the following four procedures. 1) Approach from both side; we resected the tumor from not only one-way side but also the opposite side. 2) Thin bioabsorbable patty; we covered a dissection plane with thin polyglactin mesh (Vicryl mesh) (thickness of 0.1 mm) to protect the spinal cord parenchyma and secure adequate surgical field. 3) Aspirating traction and dissection technique; for adhesive and invasive tumor, we elevated the tumor using fine aspiration tube, and coagulated and fragmented the base of tumor with bipolar coagulators, and resected it piece by piece. Eventually, the tumor was resected as much as spinal cord function was preserved. 4) Staged surgery: we adopted the staged surgery for huge IMSCT to make the dissection plane clearer through cerebrospinal layer. We accessed removal rate of tumor and neurological status in modified McCormick Scale (MMS) {Grade1 (good/normal)-Grade 5 (poor/severe deficit)} based on our procedures. Results: We achieved gross-total removal in 67 cases of 72 IMSCTs. We stayed at biopsy or partial removal in non-neoplastic lesions. In neurological status, MMS showed 2.4 preoperatively and 2.3 postoperatively, which did not indicate significant neurological deterioration. Subtotal resection was achieved even in the tumor with malignant component (WHO grade 3 or 4). Overall survival in malignant tumor was mean 3.2 years with subsequent radiochemotherapy. Conclusion: This resection procedure can achieve both preservation of spinal cord function and high removal rate for IMSCT. Further advanced antitumor therapy was desirable for malignant IMSCT.

A285: Systematic Review of Recurrent Sacral Chordoma

John Berry-Candelario¹, Daniel Kerekes², A. Karim Ahmed², C. Rory Goodwin¹, Nancy Abu-Bonsrah¹, Eric W. Sankey¹, John Berry-Candelario¹, Vikram Mehta¹, Zachary Pennington², Daniel M. Sciubba²

¹Department of Neurosurgery, Duke University Medical Center, Durham - United States ²Department of Neurosurgery, The Johns Hopkins University School of Medicine, Baltimore - United States

Introduction: Sacral chordomas are rare, primary tumors of the spine, best treated with en bloc resection. The purpose of this study was to assess the literature for resected sacral chordoma, and to quantify the prevalence of, risk factors for, and treatment outcomes of local and distant recurrence therein. Material and Methods: We searched five online databases from Jan 1980 to May 2016, to find articles that report survival, recurrence outcomes, and/or prognostic factors for the resected sacral chordoma patient population. Characteristics and clinical outcomes of the pooled cohort are reported. Fisher exact tests, unpaired t-tests, and one-way ANOVA were used to investigate patient- and treatment-associated prognostic factors for local and distant recurrence. Survival analyses were performed for time to local recurrence and death. The protocol’s PROSPERO ID is CRD42015024384. Results: Fifty-seven studies, with 1235 unique sacral chordoma patients, were included in this review. Local and distant recurrence occurred in 42.6% and 22.4% of patients with adequate follow-up, respectively. Kaplan-Meier overall median survival for patients with and without recurrence were 98 and 209 months after surgery, respectively. Wide surgical margin was associated with a lower rate of local recurrence; and wide surgical margin, female sex, and patient age ≥ 65 years were associated with lower rates of distant recurrence. Conclusion: While surgical margin remains the most significant prognostic factor for local and distant recurrence, combined surgical approach may be associated with local recurrence. Male sex and age < 65 may be associated with distant recurrence. Patients with risk factors for recurrence should undergo close monitoring to maximize survival.

A286: Extramedullary Foramen Magnum Tumors: Decision Making and Surgical Outcome

Sachin Borkar¹, Shashank Kale¹, Raghu Samala¹

¹Department of Neurosurgery AIIMS New Delhi, New Delhi - India

Introduction: Treatment of foramen magnum tumors is surgically challenging in view of their location and their critical relationship with vital neurovascular structures. Ideal approach to these tumors is a controversy in this modern era. We present our surgical experience of treating these tumors at AIIMS, New Delhi. Materials and Methods: This retrospective study includes 50 consecutive patients (mean age 37.5 years, M: F = 1.7:1) of extramedullary tumors at the surgical foramen magnum, operated at AIIMS, New Delhi, from 2012 to 2016. Results: Their mean duration of symptoms was 28.3 months. A major portion of the patients presented with motor symptoms (quadri/paraparesis, n = 36, 72%) followed by sensory symptoms like tingling/numbness (n = 17, 34%) and neck pain with/without suboccipital radiation (n = 13, 26%). Nerve sheath tumors (n = 24, 48%) and meningiomas (n = 15, 30%) were the most commonly encountered histologies in our series. Chordoma (2,4%), chondrosarcoma(1, 2%) and osteochondroma (1, 2%) were least common histopathologies observed in our study. Nineteen patients improved immediately after surgery and 8 patients worsened. Operative mortality and morbidity were 2 and 20%, respectively. Mean follow-up duration is of 48 months. Conclusion: Most of the foramen magnum tumors are amenable to surgical excision and most of the tumors can be excised by posterior approach alone except tumors which are anteriorly located which are better approached by far lateral approach.

A287: Factors of Influence on Outcomes in Intradural and Extramedular Tumors - A Focus on Surgical Access

Davi Jorge Fontoura Solla¹, Roger Schmidt Brock¹, Alberto Capel Cardoso¹, Manoel Teixeira Jacobsen¹, Igor Araújo Ferreira da Silva²

¹Department of Neurology, University of São Paulo, São Paulo - Brazil

Introduction: Approximately two-thirds of the intrarectal tumors are intradural and extramedullary. The most common are schwannomas, meningiomas and ependymomas of filum, which are benign tumors in which surgical treatment is required, therefore it is important to choose between minimally invasive and conventional accesses. We aimed to compare the minimally invasive versus conventional accesses, with the primary outcomes of immediate preoperative and postoperative degree of resection and neurological status, in order to characterize clinical, radiological and histopathological factors to aid in the choice of surgical access. Materials and Methods: We included all patients operated between June 2008 and January 2016 at our institution for intradural and extramedullary tumors, counting 107 patients with 119 surgical accesses. We obtained data from medical records and images. After classical univariate descriptive and inferential statistics, binary logistic regression was used to verify the characteristics associated with the degree of resection (total or partial) and ordinal logistic regression to identify the predictors of worsening or improvement in the pre-and postoperative Frankel scale Results: Of the 107 cases, 48 were men and 59 women. The mean age was 42 (2-82) years. We had 119 accesses for each lesion, being 36 (30%) cervical, 42 (35%) thoracic, 11 (9%) thoracolumbar, 30 (25%) lumbar. Of all the lesions, 60 (50%) were Schwannomas, 20 (16.8%) Meningiomas, 14 (11.7%) Ependymomas and 12 (10) Neurofibromas. The foraminal extension (27.1 vs 78.8%, p < 0.001) was a predictor of partial resection. The degree of resection did not have a statistically significant difference between the conventional accesses, 64.0% vs 79.5% minimally invasive, p = 0.075. The patients who presented functional improvement to the axial dimension of the average cut were 13.6 mm, maintained the same neurological status with dimensions 14.7 mm and neurological worsening with 21.0 mm (p = 0.030); respectively, for the mean sagittal dimension we had 28.4, 41.2 and 70.3 mm (p = 0.088). The type of surgical access and the position in the medullary canal did not influence both the preoperative and postoperative functional status and degree of resection of the patients. Conclusion: Minimally invasive access is safe and effective for total resection and maintenance of neurological status for all intradural and extramedullary tumors. We still found that the foraminal extension was a predictor of difficulty in achieving total resection for both accesses. In addition, the dimensions in the axial plane of 21 mm correlated with neurological worsening and smaller than 13.6 mm with improvement.

A288: Spinal Neurofibromatosis Type 1: A Cross-Sectional Study

Gayathri Suresh¹, Joshi George², Mueez Waqar², Calvin Soh³, John Ealing⁴, Tina Karabatsou²

¹University of Manchester, Manchester - United Kingdom ²Department of Neurosurgery, Salford Royal NHS Foundation Trust, Manchester - United Kingdom ³Department of Neuroradiology, Salford Royal NHS Foundation Trust, Manchester - United Kingdom ⁴Department of Neurology, Salford Royal NHS Foundation Trust, Manchester - United Kingdom

Introduction: Spinal abnormalities are common in neurofibromatosis type 1 (NF1). Spinal NF1 (SNF1) describes an NF1 subgroup with extensive spinal neurofibromas and limited cutaneous findings. The literature surrounding SNF1 is currently sparse. The aim of this single-centre study was to describe spinal findings in a large cohort of NF1 patients with and without SNF1. Methods: Review of referrals to a national NF1 referral centre (May 2016 to April 2017). Inclusion criteria: adults ( ≥ 17 years) with NF1 and at least one spinal abnormality detected on an MRI spine. SNF1 was defined as the presence of bilateral spinal neurofibromas involving the cervical, thoracic and lumbosacral spine, with limited cutaneous findings. Results: 149 patients with abnormalities on spinal MRI were included. The median age was 37 years (range 17-78 years) with no gender discrepancy (M: F, 77:72). Majority of patients (64.43%) had spinal tumours, of which a small proportion had SNF1 (27.08%). The remaining patients had spinal abnormalities in the absence of tumours. Back pain (52%), the most commonly reported symptom, was significantly associated with abnormal spinal curvature (p = 0.048). Dural ectasia (28.20%) was most commonly present in the lumbosacral spine (51%). Cord compression was associated with neurological symptoms (p = 0.022) and the presence of SNF1 (p < 0.001). There was also significant association between spondylolisthesis (18.60%) and SNF1 (p = 0.037). Scoliosis (65.60%) of the thoracic spine (71.10%) was the most common abnormal curvature present. Majority of the tumours were foraminal in the cervical (56.10%), thoracic (55.95%) and lumbar spine (53.23%). C2 had the highest proportion of intradural tumours (87.10%). Moreover, intradural tumours were significantly associated with SNF1 (p < 0.001). Surgical debulking of tumour (67.86%) was the most common surgical procedure performed. Conclusions: Patients with SNF1 have a high incidence of mechanical spinal column dysfunction and neurofibroma related complications. This cohort therefore requires close surveillance.

Keywords: Neurofibromatosis; NF1; neurofibromatosis type 1; Von-Recklinghausen’s disease; spinal neurofibromas; spinal neurofibromatosis; spinal NF1; SNF1

A289: The Results of Surgical Treatment for Patients With Recurrent Spinal Chondrosarcoma

Olga Lapaeva¹, Dmitry Ptashnikov², Evgeniy Levchenko³, Evgeny Slugin³, Dmitrii Mikhaylov², Sergei Masevnin²

¹Neurosurgery Department, North-Western State Medical University named after I.I. Mechnikov, Saint Petersburg - Russian Federation ²Spine Surgery Research and Clinical Departments, R.R. Vreden Russian Research Institute of Traumatology & Orthopaedics, Saint Petersburg - Russian Federation ³Department of Thoracic Surgery, N.N. Petrov National Medical Research Center of Oncology, Saint Petersburg - Russian Federation

Introduction: Aim of the surgical treatment of spinal chondrosarcoma is preserving or even recovering of neurologic function and relieving pain syndrome, promising a prolonged survival. Surgical treatment of spinal chondrosarcoma is particularly difficult as most of the tumors adhere to nerve roots and vessels. Surgical treatment of locally recurrent chondrosarcoma is especially challenging because of the altered anatomy and scarring from the previous surgery, which may result not only in the compromise of the surgical margin but also in significant morbidity of the patient. But despite the difficulties surgical excision of local recurrences can be beneficial and prolong survival. The aim of this study was to define justified of aggressive surgery as radical resection in this cases. Materials and Methods: Between 2012 and 2017, 12 patients with recurrent chondrosarcomas grade 2 or grade 3 were retrospectively reviewed. There were 66% males. Mean age was 41 years (range 35-61). Mean follow-up was 24 months (range 12-36 months). Localization of tumor was in the thoracic or lumbar part of the spine. 5 patients had the pulmonary metastasis, appearing synchronously with the local recurrence. The radical resection of the tumor with multilevel spondyloectomy and thoracoplastic was done in all cases. There were en-bloc wide excision with negative margins (R0) in 12 cases. 5 patients with pulmonary metastasis underwent thoracotomy and resection of metastasis at the moment. Overall survival was calculated. Quality of life was evaluated using ODI 3, 6, 12, 24 months postoperative follow-up. Results: There were no patients with repeated local recurrence after surgery. 3 patients with a pulmonary metastases had generalisation of the process during 12 months after surgery. Another 8 patients are still alive without evidence of disease at last follow-up. Low quality of life during first 3 months were in 5 cases, because of the aggressive surgery, but then quality of life parameters were improved for all patients. Conclusions: Radical resection of the tumor with multilevels spondyloectomy and thorocoplasty for patients with local recurrence chondrosarcoma is justified. An aggressive approach is also acceptable for patients with pulmonary metastases, because of improving of quality of life.

A290: Referral Patterns in Patients Surgically Treated for Spinal Metastases

Floris van Tol¹, FC Oner¹, Jorit-Jan Verlaan¹

¹Department of Orthopaedic Surgery, UMC Utrecht, Utrecht - Netherlands

Introduction: Spinal metastases occur in approximately 20% of all oncological patients. If left untreated, these metastases can lead to irreversible neurological deficits. In this study, we assess referral patterns for factors contributing to delay in both diagnosis and treatment in patients suffering from symptomatic spinal metastases. Material and Methods: Data was collected on all patients within our tertiary facility that received surgical treatment for symptomatic spinal metastases between the period of March 2009 until June 2017. Based on medical records, for each patient a timeline was created from the onset of symptoms until definitive treatment. Results: In total, 73 untimely and 107 timely referred patients were identified. On average, the time between the onset of symptoms and first medical consultation was 77 days, between first medical consultation and definitive diagnosis 11 days and between the diagnosis and referral to the definitive health-care provider 19 days. The presence of a malignancy in patients’ medical history did not significantly change any of these intervals. Also, no difference in these intervals was observed for timely and untimely referred patients. Conclusion: The largest contributor to total delay is patient-delay. Remarkably, the interval between diagnosis and referral to the definitive health-care provider (referral-delay) was larger than the interval between the first medical consultation and the diagnosis (diagnosis-delay). This suggests that caregivers are insufficiently aware of the urgency and correct referral of patients with symptomatic spinal metastases to their definitive health-care provider. It is also striking that a previously diagnosed malignancy did not seem to have an accelerating effect on the referral.

Trauma - Thoracolumbar

A291: Does MRI Affect the Surgical Plan in Patients With Thoracolumbar (T10-L1) Burst Fractures and Incomplete Spinal Cord Injuries?

Jason Pittman¹, Quynh Nguyen², Carlo Bellabarba³, Richard Bransford³

¹Department of Orthopaedic Surgery, Birmingham - United States ²Department of Radiology, University of Washington, Seattle - United States ³Department of Orthopaedic Surgery, University of Washington, Seattle - United States

Introduction: The initial imaging of patients with thoracolumbar burst fractures and incomplete spinal cord injuries often starts with obtaining a CT scan. While surgical intervention is often recommended¹, obtaining an MRI prior to going to the operating room is at the discretion of the treating surgeon. MRI has been shown to be useful in determining the extent of soft-tissue damage in spinal trauma, but each study did not distinguish whether or not a spinal cord injury was present.^2-4 Material and Methods: A survey of 127 spine surgeons was conducted to determine whether or not operative treatment plans were directly changed by the availability of MRI imaging studies in patients who had thoracolumbar burst fractures (T10-L1) and incomplete spinal cord injuries. The patients for this study (n = 10) were identified by searching the Department of Radiology’s diagnosis database for the diagnosis of burst fracture and both CT and MRI studies that were obtained prior to any surgical interventions. The admission history and physical exam for each of these patients was also reviewed to determine whether or not an incomplete spinal cord injury was present at the time of initial evaluation. The axial and sagittal CT studies as well as the initial history and physical for each of these 10 patients were deidentified and presented to the surgeons participating in the survey. Each participant was then asked to formulate a surgical plan. Once a surgical plan was formulated based on the CT scan, they were asked whether or not an MRI was desired and why. The axial and sagittal T2 MRI scan images were then presented. The surgeons were then asked whether or not this altered their initial surgical plan. Results: Of those surveyed, 66% were practicing as Orthopaedic and 34% as Neurosurgery trained spine surgeons. The majority (66%) of those responding to the survey have been in practice greater than 10-years. In the patient population presented, after reviewing the initial CT scan, 41% of respondents stated that they would like to obtain an MRI before proceeding to the operating room. This was desired to evaluate for discoligamentous injuries adjacent to the fractured segment, to determine if anterior only treatment is sufficient or due to suspicion of adjacent bony injury not evident on CT scan. After reviewing the MRI, 19% of all respondents stated that their previous surgical plan had been changed. Out of the 41% of respondents that desired a MRI scan after evaluating the CT scan, 45% stated that they had changed their surgical plan. Conclusion: The majority of the time (59%), respondents did not feel that an MRI was necessary for operative planning. Eighty-one percent of the time, MRI made no difference in planned treatment. The MRI was most often desired due to it being the standard protocol of the treating institution or to evaluate the posterior ligamentous complex. In conclusion, the operative treatment of patients with thoraco-lumbar burst fractures is changed in 1 out of 5 patients by imaging the injured levels with an MRI.

A292: Conservative vs. Operative Treatment of Stable Thoracolumbar Burst Fractures in Neurologically Intact Patients. Is There any Difference Regarding the Clinical and Radiological Outcomes?

Tuna Pehlivanoglu¹, Turgut Akgul¹, Serkan Bayram¹, Emre Meric¹, Murat Korkmaz², Cuneyt Sar¹

¹Istanbul University, Istanbul Faculty of Medicine, Department of Orthopedic Surgery and Traumatology, Istanbul - Turkey ²Koc University, Medical Faculty, Department of Orthopaedic Surgery, Istanbul - Turkey

Introduction: There is an ongoing controversity regarding the treatment of thoracolumbar burst fractures (A3, A4 according to AOSpine classification) in neurologically intact patients. Surgical treatment as well as conservative treatment methods are advised to this specific group of patients by many studies. The aim of this study was to compare the clinical and radiological results of neurologically intact patients diagnosed with thoracolumbar burst fractures and treated surgically and conservatively with the aim to optimize their management. Material and Methods: Between 2010-2016, 24 neurologically intact patients with thoracolumbar burst fractures (A3 or A4) were admitted to our clinic. Among them, 10 patients with a mean age of 35.5 and mean follow-up period of 25.3 months were treated surgically with short segment fixation using polyaxial pedicle screws (group 1), while 14 patients with a mean age of 52.43 and a mean follow-up period of 27.43 months were treated conservatively (group 2) with TLSO orthesis. Radiological outcome parameters included segmental kyphosis (SK) degrees, vertebral wedge angles (VWA), degree of the loss of kyphosis at the final follow-up and loss of anterior and posterior vertebral body height. Clinical outcome parameters included VAS, ODI, JOA and to asses the qualities of life SF-36 scores were assessed and compared between the two groups. Patients were evaluated annually following their initial treatment. Results: At the one year follow-up, group 1 had a mean SK of 2.49°, while group two had a mean SK of 6.9° (p = 0.03). At the final follow-up group 1 had a mean SK of 4.09°, while group two had a mean SK of 11.65° (p = 0.027). The mean loss of kyphosis of group one was 2.04°, while group two had 4.03° as the mean loss of kyphosis (p = 0.038). Mean loss of anterior/posteior vertebral body height of group 1 and was %12.89/%2.84 respectively; while group two had %17.94/%7.62 as the mean loss of anterior/posteior vertebral body height (p = 0.027/p = 0.03). At the final follow-up, group one and two had a mean JOA score of (16.6/16.75) (p = 0.198), ODI score of (%19/%18) (p = 0.25), VAS score of (1.9/2.3) (p = 0.3), SF-36 PCS of (56.74/56.67) (p = 0.25), SF-36 MCS of (55.47/55.5) (p = 0.3) respectively. Conclusion: While there was a controversity about the management of stable thoracolumbar burst fractures in neurologically intact patients in the literature, the results of this study showed that surgical management of stable burst fractures in neurologically intact patients provided better radiological outcomes. However clinical outcomes including JOA, NDI, VAS scores and SF-36 scores failed to show any statistically significant difference between surgically and conservatively treated patients. It was concluded that conservative treatment might yield equally good clinical outcomes as compared to surgical treatment, even if the radiological outcomes of surgical treatment remained superior as compared to conservative treatment.

A293: Thoracolumbar Burst Fractures: The Need for a Complementary Anterior Approach

Vicente Ballesteros¹, Javier Lecaros¹, Celmira Martínez²

¹Department of Orthopaedic Surgery, Hospital del Trabajador, Universidad Andrés Bello, Santiago - Chile ²Department of Orthopaedic Surgery, Hospital del Trabajador, Santiago - Chile

Introduction: The treatment of thoracolumbar burst fractures (TLBF) remains controversial. Since current literature does not offer a gold standard, recommendations lack robust scientific support. Regarding surgical procedures for these lesions, the anterior approach allows anatomical reconstruction, removal of damaged discs, and the option of a better decompression of the spinal cord for the surgical management of these fractures. However, the posterior approach is the preferred pathway by most spinal surgeons for the acute treatment of this type of injuries. Given this, for those cases where the posterior fixation is insufficient, the anterior approach has been considered as a complementary procedure. Despite this perspective, there are no clear criteria to define when the complementary anterior approach (CAA) is necessary. The purpose of this study is to identify the risk factors of the loss of reduction or failure of posterior bisegmental instrumentation that need a CAA in the treatment of thoracolumbar burst fractures. Material and Methods: The study was carried out in two phases, an initial descriptive phase, in which the patients who were given a CAA were identified, as well as the determining factors of the medical indication; and a case-control analysis, to determine the risk factors associated to the failure that determined the need for an anterior approach. The study cases were patients with objective indication of the anterior approach and the controls were patients that didn’t require complementary surgery. Chi-squared test was used to determine associations with risk factors and a logistic regression was performed later to determine which of these factors predicts the need for a CAA. Results: 48 patients with TLBF were treated surgically and 13 of those patients required a CAA. It was identified that burst fractures with a predominant coronal split fracture (PCSF) are significantly associated to a CAA (p = 0,022). There was also a strong significant association between the need of CAA and overdistraction of the proximal adjacent disc (OPAD) (equal to or greater than 1.4 times the height of the adjacent lower segment) after posterior approach (p < 0,01) and the presence of intracorporal gas (ICG) also showed a tendency to favor reduction loss obtained in the posterior approach (p = 0.06). In the logistic regression analysis, an area under the ROC curve of 0.7611 (95% CI 0.59 824 to 0.92 403) was identified for the presence of PCSF and ICG at the affected level for the need for a CAA. Neither age, McCormack score, nor the presence of intradiscal gas were associated with the need for a CAA (p > 0.05). Conclusion: The presence of a ICG added to PCSF in the affected vertebra predicts by 76.11%, the need for a CAA for TLBF previously operated by an isolated posterior approach.

A294: Timing and Risk Factors for Secondary Subsidence of Conservatively Treated Compression Fractures of the Thoracolumbar Spine in Elderly Patients

Chantal Fimian¹, Gregory F. Jost¹, Stefan Schaeren¹

¹Spine Surgery, University Hospital Basel, Basel - Switzerland

Background: Thoracolumbar compression fractures deemed stable at baseline can be followed and will usually heal without surgical intervention. However, a minority of patients will experience secondary subsidence of the fracture which may lead to delayed pain and possibly surgery. This study analyzed the timing and risk factors for secondary subsidence in elderly patients. Methods: X-rays and charts of all patients over 65 years, that were enrolled for conservative management of fractures between T10 and L5 in the years 2013 to 2016 were analyzed. Pelvic incidence, pelvic tilt, lumbar lordosis, fracture characteristics at baseline and follow-up, demographic data and comorbidities were retrieved from patient charts. Results: 109 patients were enrolled (mean age 79 ± 7). Secondary fracture subsidence between baseline and follow-up appointments was noted in 42% (n = 46) and diagnosed at an average of 30 ± 26 days (median 21 days) after trauma. 83% (n = 38) of subsiding fractures were diagnosed at the first follow-up. Only 4% (n = 2) of these had progressed at the second follow-up. Pelvic incidence - lumbar lordosis mismatch (PI-LL) was similar between the subsidence (6.9 ± 9.3°) and the non-subsidence (7.3 ± 13.6°) group. Multiple and logistic regression analysis revealed lower pelvic tilt as risk factor for secondary subsidence. Sex, age, obesity, smoking, vitamin D deficiency, prior vertebral fractures, pelvic incidence, and lumbar lordosis were not associated with subsidence. Osteoporosis was associated with less subsidence. Delayed operative fixation was significantly more often indicated for patients with secondary subsidence than patients without subsidence (32%, n = 15 versus 8%, n = 5; p < 0.05). Discussion: In this analysis both the subsidence and non-subsidence group had low PI-LL mismatches, suggesting that there was reserve to adjust the pelvic tilt for fracture-induced positive sagittal balance. However, within this range, lower pelvic tilt appears to be a risk factor for secondary subsidence of thoracolumbar compression fractures which had been classified stable at baseline and lined-up for conservative treatment. From the results it is speculated, that a higher pelvic tilt in a compensated sagittal balance shifts the axial load posteriorly thereby protecting the fractured vertebra from further subsidence. In elderly patients with known osteoporosis, compression fractures deemed stable at baseline (no change of height from supine to upright position) do not fare worse than similar compression fractures in patients without diagnosed osteoporosis. Conclusion: In elderly patients with low PI-LL mismatch, higher pelvic tilt appears to protect from secondary subsidence of compression fractures that were eligible and selected for conservative treatment. Subsidence happens mostly within the first four weeks and is associated with delayed surgery.

A295: Robotic Assisted Percutaneous Pedicle Screw Fixation for Thoracolumbar Spine Fractures

Leon Kaplan¹, Hananel Shear Yashuv¹, Josh Schroeder¹

¹Spine Unit, Department of Orthopedic Surgery, Hadassah Medical Center, Jerusalem - Israel

Scientific Background: Percutaneous fluoroscopy assisted pedicle screw fixation for thoracolumbar spine fractures is associated with preservation of posterior musculature, less blood loss, shorter operative time, lower infection risk, less postoperative pain, shorter rehabilitation time as well as shorter hospital stay when compared to open surgery, but with increased radiation exposure for the surgical team and patients. Robotic assisted spine surgery is an emerging field of surgery that has been shown to reduce radiation exposure with high level of safety. The purpose of this study is to evaluate the outcome of robotic assisted percutaneous pedicle screw fixation with for thoracolumbar spine fractures. Methods: A ambispective review of all patients with thoracolumbar fractures who were managed with robotic assisted percutaneous transpedicular screw fixation(Renaissance, Mazor robotics) at a level one traumal center between July 2014 and July 2017. Demographic data, accuracy rates, post-operative alignment, radiation exposure were evaluated. Results: Thirty two patients (22 males and 10 females) underwent robotic assisted percutaneous transpedicular screw fixation between July 2014 and July 2017 for type A and B (AO) thoracolumbar fractures. The average age was 37.8 years (range 14-82). Fifteen cases were due to falls from height, 7 for MVA, 3 extension type injuries, one gunshot injury, and six from other mechanisms. Six of the patients were poly trauma patients, eight had rib fractures and three others had calcaneus fractures as well. 216 screws were placed in total. Levels operated ranged from 2-7 levels, with 4 to 13 screws were used per case. In three cases cemented fenestrated screws were used. Mean total case radiation time per screw was 4.7 seconds (ranged 1.8-6.9 including registration, screw and rod placement). Only one screw was removed and inserted again manually (0.46%) because of malplacement. There were no treatment-related complications. There were no revision surgeries. Discussion: Robotic assisted percutaneous pedicle screw fixation for thoracolumbar spine fractures is a safe method for screw placement for thoracolumbar trauma cases. It allows restoration of the sagittal alignment with satisfactory clinical results even for geriatric patients and poly trauma patients with reduced radiation to the patient and surgeon when compared to free hand techniques. The non-fusion screw fixation allows removal of the screws if needed after healing has set.

A296: Minimally Invasive V Open Thoraco-Lumbar Fracture Fixation – a Comparative Audit of 62 MIS Cases and 135 Open Cases in a Single Centre

Jonathan Wasserberg¹, Robert Veres¹, Milan Urbansky¹

¹Dept of Neurosurgery, Mafraq Hospital, Abu Dhabi - United Arab Emirates

Introduction: Minimally invasive screw fixation (MIS) for thoraco-lumbar fractures is gaining in popularity compared to the gold standard of open fixation. We have previously presented our results of 135 open cases of fracture fixation showing that the majority of thoraco-lumbar fractures can be managed successfully by posterior open surgery¹. After introducing MIS into our practice, the indications for MIS have been expanded to cases previously treated by open surgery. We now present our results of 62 cases of minimally invasive pedicle screw fixation in a group of patients with a similar injury profile to those previously presented. The purpose of this audit was to determine if the results of our minimally invasive treatment is equivalent to open surgery. Material and Methods: We reviewed our MIS experience of thoraco-lumbar fractures treated at our institution from January 2016- June 2017. Following institutional ethics committee approval, a retrospective audit was carried out using the hospital electronic medical record system (Cerner, USA). All surgical cases were identified from the operating theatre records. Only fractures from T1 to L5 were included. Imaging was reviewed using the hospital PACS system and classified according to the AO TL classification system. Neurological deficit was classified according to the ASIA scale. Surgical blood loss, operating time and surgical complications were recorded. Post-operative images were reviewed and levels of fixation recorded. Pre and post-operative kyphotic angle was measured. Screw placement accuracy was assessed and neurological status and length of stay was recorded. Results: There were 62 MIS treated thoracolumbar fractures. In all cases the Longitude (Medtronic, USA) minimally invasive screw system was used. Two cases also had anterior reconstruction. Screw placement was monitored using intra-operative fluoroscopy combined with neuro-monitoring. Reduction of kyphosis with improvement in the kyphotic angle was achieved in all cases. There were 4 cases of complete paraplegia ASIA A and 12 cases which had a partial neurological deficit ASIA B-D. All cases of ASIA B, C and D showed improvement after surgery but only 2 of 4 cases of ASIA A improved to ASIA D after surgery. There were no cases of neurological worsening after surgery which is similar to our results with open surgery. Screw placement was classified according to Zdichavsky et al, grade 1- 96%, grade 2- 4% and grade 3- zero, which did not differ significantly from the open series². A mini open decompression was used in 16 cases to decompress the dural sac with direct impaction of the retropulsed fragment. There were no post-operative infections in the minimally invasive group compared with 3/135 (2.2%) in the open group. There was significantly less blood loss in the MIS group and operative times were similar. Conclusion: We have demonstrated that compared to open procedures, minimally invasive surgery produces equally effective spinal stabilization after reduction and fixation. This comparison of the early results of the two techniques demonstrates that minimally invasive pedicle screw fixation is an effective technique for the treatment of thoracolumbar fractures with some advantages in comparison to open reduction.

References

1. Surgical Results of 135 Thoraco-Lumbar Fractures Treated with Open Posterior Multi-level Segmental Fixation: A Single center experience. Global Spine Journal, First Published March 24 2017, s-0036-1 582 673 https://doi.org/10.1055/s-0036-1 582 673

2. Zdichavsky M et al, Accuracy of Pedicle Screw Placement in Thoracic Spine Fractures: Part II: A Retrospective Analysis of 278 Pedicle Screws Using Computed Tomographic Scans. Eur J Trauma 2004; 30: 241-7

A297: Spinal Canal Stenosis Treatment, Following AO Classification Type A3 and A4 Thoraca-Lumbar Traumatic Fracture, by Use of Ligamentotaxis-Analysis of Results With a New Quantitative Method

Árpád Viola¹, András Gati¹, Balázs Bölöni¹

¹Department Of Neurosurgery, Péterfy S. Hospital and Accident Centre, Budapest - Hungary

Introduction: The fracture of the thoracic and lumbar vertebra is the most common, between spine fractures. Unfortunately, many cases may result in permanent neurologic deficit. Because of the ageing population the number of fractures has increased, the evolution of medical technology has led to new dorsal transpedicular stabilization methods, hence the need to analyze their rate of success and effectiveness. Material and Methods: During a 21 month period, between November 2015 and July 2017, we analyzed the CT scan findings of 218 patients who were treated on our ward for thoraco-lumbar spine fracture, affecting only one vertebra, and who had absolute operative indication. Out of the mentioned number of patients 63 matched our criteria. The group consisted of patients who underwent dorsal transpedicular fixation in a classical “open” or minimal invasive manner. In these cases, posterior decompression was not used, the dislocated bone fragments were repositioned by use of ligamentotaxis alone. We measured the pre- and post-operative height, width of the affected vertebra, the diameter of the spinal canal and a number of other parameters. The results are as follow. Results: The average preop diameter of the spinal canal was 11.04 mm, or 69.67% (5.54%-96.48%) of the expected diameter, following operation it increased to 86.35% (53.73%-113.11%) p = 0.028 considered significant. We found no significant relation between the surgery type (Open vs MIS) and postoperative spinal canal diameter p = 0.38. Conclusion: The use of ligamentotaxis proves more benefic to the patient compared to the posterior decompression, not only by reducing the blood loss, the surgery time, but by excluding the possibility of dura lesions, or extended, postoperative, wound closing abnormalities. Furthermore, the combination of ligamentotaxis and minimal invasive approach, exponentially decreases the mentioned complications, in accordance with the new surgical viewpoint, which is the use of minimal invasive techniques.

A298: Thoraco-Lumbar Fractures With Traumatic Aortic Injury (TAI) in Adult Patients: Classification and Management

Giorgio Santoro¹, Alessandro Ramieri², Maurizio Domenicucci³

¹Neurosurgery Sapienza University, Rome - Italy ²Don Gnocchi Foundation, Milan - Italy ³Neurosurgery Sapienza University, Rome - Italy

Introduction: Traumatic fracture of the thoraco-lumbar spine with a concomitant TAI is a rare condition but potentially a fatal association. Comprehension of spinal damage and vascular injury could be crucial to avoid death. Methods: Based on 39 cases culled in detail from the literature and 5 personal cases, our purpose was clarify: -morphology of spinal fractures; -type of vascular injury related to fracture; -basic diagnostic procedures; - decision making process related to the best treatment options for spine and vessels. Results: Almost all fractures were at the T11-L2 junction and neurological. According to the AO classification, the most frequent type was C, followed by Chance Type B fractures. The most common vascular damage was the intimal flap, the most rare pseudoaneurysm. Vascular injury often required an open or endo surgical repair that preceded spinal fixation in all patients, except one who subsequently died. Combined vascular and spinal treatments obtained a full recovery in most cases, while 7 deaths were recorded. In our cases, 4 with neurological deficits, distraction forces developed an aortic intimal damage, flexion-distraction a lumbar artery pseudoaneurysm and rotation-torsion the rupture of a renal artery. The angio-TC was our examination of choice to detect the lesion, followed by conventional angiography. All unstable vertebral lesions were fixed by posterior instrumented surgery, while vascular surgery was not performed in 2 cases due to their stable hemodynamic conditions. Conclusions: Concomitant post-traumatic thoraco-lumbar fracture and TAI is a rare, but terrible event. In the adult, it is almost exclusively related to the thoraco-lumbar junction and the abdominal aorta. Biomechanics always highlights a spinal distraction mechanism, sometimes pure in Chance fractures, more often combined with shear forces in type C fractures with dislocation and/or rotation, realizing the condition for traction of the aorta and its vessels. In our experience, all spine injuries associated with vascular damage were type C. Therefore, observing an osteo-ligamentous injury of the thoraco-lumbar spine due to distraction-dislocation, an angio-CT could be recommended. Failure to recognize and classify these vertebral injuries could results in the patient’s death due to internal hemorrhage. In fact, priority must be given to the vascular reconstructive treatment, regardless of the neurological disorders detected.

A299: Influence of Blood Supply on Fracture Healing of Vertebral Bodies

Ludovit Hajnovic¹, Vladimir Sefranek¹, Ludwig Schütz¹

¹Zdravotnícka Univerzita Bratislava, Limbová ul., Bratislava - Slovakia

Introduction: The relevance of blood supply for bone fracture healing has been discussed throughout the literature, using scaphoids as the most refererred to. But, there is virtually nothing known about the relevance of blood supply for the vertebral fracture healing and even the guidelines of AO do not deal with this issue. Material and Methods: A prospective cohort study of 107 patients was run from January 2016 - December 2016, with 54 male and 53 female patients, who were treated for traumatic vertebral fractures of thoracolumbar spine using posterior stabilization only. The average age was 67 years and the follow-up 12.3 weeks. The total number of vertebrae was 129. We analysed the fracture morphology, and measured the vertebral bodies in all three dimensions, with five reference planes. The progress of vertebral deformity in time, measured before and after the surgery, was correlated with the potential damage of the main vascular canal in the rear of each vertebral body. The bone-pattern and morphology were analysed in detail as well. Pathological fractures were not taken into our consideration. We used Bias 11.1 program for the statistics. Results: The overall deformity progression of vertebral bodies in the fractures with morphologically damaged blood-supply was in all measured dimensions significantly higher than in the fractures with supposedly maintained perfusion. The osteoporosis played its role as well, but only with medium effect-size compared with strong effect-size of the vessel-canal damage (Cohen). The combination of the both factors (damage to the vessel-canal together with osteoporosis) showed also a strong correlation with a relevant deformity-progression (Evans), but not much different from the vessel-canal damage alone. With regards to the relevant changes of the verterbal body dimensions / volume we found relevant changes in 52% of all fractures (SD 0.5017) generally, for the subgroup with the canal damage in 84% (SD 0.3691), with strong correlation (Evans, 0.7721). In the group of fractures with maintained perfusion we found such changes in only in 5% of fractures (SD 0.2333). Conclusion: The damage of the vascular canal or of its relevant portion and thus supposedly compromised blood-supply should be taken into surgical consideration for eventual anterior surgery, since a significant deformity progression despite the posterior stabilisation in our patient group was observed.

Deformity - Thoracolumbar (Adult) - Surgical Treatment - Predicting Outcomes

A300: Lumbosacral Reconstruction Improves Postoperative Coronal Balance in Degenerative Lumbar Scoliosis - A Matched Cohort Analysis

Zhen Liu¹, Yong Qiu¹, Zezhang Zhu¹

¹Drum Tower Hospital Nanjing University Medical School, Nanjing - China

Introduction: To study the effect of lumbosacral reconstruction strategy including 360° release of fractional curve from the convex side and a transforaminal lumbar interbody fusion (TLIF) from the convexity of fractional curve on leveling the lower lumbar vertebra. In addition, the postoperative coronal balance (CB) and clinical outcomes in adult degenerative lumbar scoliosis (DLS) patients with preoperative coronal imbalance (CIB) were evaluated. Materials and Methods: 152 DLS patients with preoperative CIB who received posterior fusion surgery were reviewed retrospectively. Of these, 76 DLS patients that underwent spinal fusion procedures from the thoracic spine to the sacrum fulfilled the inclusion criteria. 12 patients (Group 1) with preoperative CIB who underwent lumbosacral reconstruction (L5/S1 TLIF) were included in this study. 24 DLS patients were matched to patients without lumbosacral TLIF for sex, age, curve magnitude, and preoperative CIB type (Group 2). The average age of the 36 DLS patients was 61.3 ± 7.2 years. The mean Cobb was 34.7 ± 10.3° preoperative. The coronal parameters including Cobb angle and distance between C7 plumb line and center sacral vertical line, as well as the oblique angle of L5 and S1, were measured preoperatively, postoperatively, and at the last follow-up. The Short Form-36 Health Survey (SF-36), Oswestry Disability Index, and Visual Analogue Scale (VAS) were fulfilled preoperatively and at follow-up. The clinical and radiographic parameters were compared between both groups. Results: The average follow-up period was 50.4 ± 11.2 months without significant differences (P = 0.55) in sagittal vertical axis between both groups. Preoperative L5 tilt existed in both groups of patients (P = 0.102), also similar preoperative and postoperative lumbar curve correction was noted (P = 0.63). Significant differences in the correction of L5 tilt (a1) postoperatively (P < 0.001) and at the last follow-up (P < 0.001) were observed between DLS patients with or without TLIF. Coronal balance distance of TLIF group (G1)at the postoperative follow-up was significantly less than the group without TLIF (G2, P < 0.001). Patients in Group 1 had a considerably higher fusion rate than those in group 2, also less postoperative complications were found in Group 1. Furthermore, an improvement was observed regarding Short Form-36 Physical Component Score and VAS for back pain (P = 0.061 and 0.037, respectively) in Group 1. Conclusion: Lumbosacral reconstruction strategy including 360° release of the fractional curve from convex side and a TLIF from the convexity of the fractional curve could restore the horizontal level of L5 and S1, thereby reducing the risk of postoperative CIB in DLS patients.

A301: Predicting Clinical Outcomes Following Adult Spinal Deformity Surgery

Akshay Sharma¹, Joseph Tanenbaum², Olivia Hogue³, Syed Mehdi², Sagar Vallabh², Emily Hu², Edward Benzel¹, Michael Steinmetz¹, Jason Savage²

¹Department of Neurosurgery, Cleveland Clinic - United States ²Center for Spine Health, Cleveland Clinic - United States ³Center for Neurologic Restoration, Cleveland Clinic - United States

Introduction: Deformity reconstruction surgery has been shown to improve quality of life in cases of adult spinal deformity (ASD), but is associated with significant morbidity. We sought to create a preoperative predictive nomogram determine which patients would likely benefit from surgery. Material and Methods: All patients aged 25-years and older with radiographic evidence of ASD and quality of life data that underwent thoracolumbar fusion between 2008 and 2014 were identified. Demographic, radiographic, and clinical parameters were obtained. The EuroQol five dimensions questionnaire (EQ-5D) was used to measure health-related quality of life (HRQoL) preoperatively and at 12 months postoperative follow-up. A preoperative to postoperative decline of .10 or greater was used to indicate the presence of clinically relevant decline in HRQoL. Logistic regression of preoperative variables was used to create the prognostic nomogram. Results: Our sample included data from 191 patients. 51% of patients experienced clinically relevant postoperative improvement in HRQoL. Seven variables were included in the final model: preoperative EQ-5D score, sex, preoperative diagnosis (degenerative, idiopathic, or iatrogenic), previous spinal surgical history, obesity, and a sex-by-obesity interaction term. Preoperative EQ-5D score independently predicted the outcome. Sex interacted with obesity: obese men were at disproportionately higher odds of improving than non-obese men, but obesity did not affect odds of the outcome among women. Female sex was also shown to be a predictor of postoperative improvement but only among non-obese patients. Model discrimination was good, with an optimism-adjusted c-statistic of 0.739. Conclusion: Lower preoperative EQ-5D scores were associated with a clinically significant increase in postoperative EQ-5D scores and sex was found to interact with obesity when predicting post-operative EQ-5D scores. The predictive nomogram that we developed using these data can improve preoperative risk counseling and patient selection for deformity correction surgery.

A302: Reliability of Pre-Operative Surgical Planning Software in Predicting Postoperative Alignment in Patients Undergoing Minimally Invasive Multilevel Anterior Column Reconstruction for Positive Sagittal Balance Deformity

Robert Lee¹, Michael Mokawem¹

¹Spinal Surgery Unit, Royal National Orthopaedic Hospital, Stanmore - United Kingdom

Introduction: Patients can present with an obvious increase in Sagittal Vertical Axis (SVA) or have a hidden sagittal balance problem with a normal SVA but high pelvic tilt (compensated balance). Sagittal realignment in adult deformity surgery is crucial. Surgical correction of positive sagittal balance can be performed via multilevel minimally invasive lateral and anterior cages. Careful choice of cage angle size at each lumbar level enables restoration of good sagittal alignment. Software is available to not only measure patient alignment parameters but also to simulate the operation. There is often difficulty in executing the preoperative plan with techniques such as osteotomies. Anterior column reconstruction using multiple anterior cages inserted via a minimally invasive lateral or anterior technique may provide a reliable way of executing the pre-operative plan. This study shows that surgical planning using software (Surgimap) in anterior column reconstruction can accurately predict the eventual radiological outcome. Material and Methods: A retrospective review of prospectively collected data of a single surgeon case series of 40 patients with positive sagittal balance (both compensated and uncompensated). All patients had erect pre-operative and post-operative whole spine radiographs including C7 and both femoral heads. Images were loaded onto Surgimap. Surgimap was then used to measure the following parameters: Lumbar lordosis (LL), Pelvic Incidence - Lumbar Lordosis mismatch (PI-LL), SVA and Pelvic Tilt (PT). Surgery was simulated using multilevel lateral or anterior cages. Pelvic tilt was then adjusted to normal values for each pelvic incidence to determine the predicted SVA. Predicted parameters were then compared to the final outcome Results: There were 26 degenerative scoliosis cases, 2 spondylolisthesis cases, 8 iatrogenic flat back cases and 12 cases with proximal level degeneration. Surgimap planning was accurate to within 15.13 mm for SVA, 4 degrees for LL, 4 degrees for PI-LL and 6 degrees for PT. Conclusion: Surgical planning software, Surgimap, provides an accurate and reliable way of predicting alignment outcomes in anterior column reconstruction surgery. Surgimap is therefore a powerful tool in pre-operative planning, guiding the use of specific implants in order to achieve the optimal correction of sagittal balance, and has the potential to significantly narrow the variability of radiological outcomes in this complex group of patients.

A303: Inter- and Intra-Rater Reliability and Agreement of the Roussouly Classification System in Patients With Adult Spinal Deformity

Tanvir Johanning Bari¹, Dennis Winge Hallager¹, Niklas Tøndevold¹, Lars Valentin Hansen¹, Benny Dahl², Martin Gehrchen¹

¹Department of Orthopaedic Surgery, Spine Unit, University Hospital of Copenhagen, Copenhagen - Denmark ²Department of Orthopedics and Scoliosis Surgery, Texas Children’s Hospital, Houston, Texas - United States

Introduction: The Roussouly Classification System was developed to describe the variation in sagittal spine shape in normal individuals. The authors found the sagittal profile of the spine to follow the orientation of the pelvis. As sacral slope increases so does the lower arc of lordosis and the global lordosis. A recent study suggests that patients' spine types could influence the outcome following spinal surgery. The utility of a classification system depends largely on its reproducibility. The objective of the current study was to provide the inter- and intra-rater reproducibility of the Roussouly Classification System in a single-center consecutive cohort of patients referred for Adult Spinal Deformity (ASD). Material and Methods: All patients referred for evaluation of ASD at our tertiary institution for spine surgery between August 1st 2013 and March 30th 2014 were assed for inclusion. The inclusion criteria were: referral for ASD, age ≥ 18 years and sufficient radiographs. Sufficient radiographs were defined as: high quality standing images in both the lateral and antero-posterior plane, including both femoral heads and visible vertebrates from C7 – S1 on the lateral images. Patients were standing with “fists-on-clavicles”. Patients were excluded if there was a history of previous instrumentation, spinal fracture or neuromuscular disease. The study was carried out in a blinded test-re-test setting using digital radiographs. All ratings were performed by 4 spine surgeons with different levels of experience. There was a 14-day delay between the two reading sessions. Inter- and intra-rater reproducibility was calculated using Fleiss Kappa (κ) and crude agreement percentages. Results were classified as significant at p < 0.05. All confidence intervals (CI) are provided as 95% CI. Results: A total of 803 patients were screened, of which 74 fulfilled inclusion criteria. Of these, 10 cases were used for training purposes leaving 64 for final ratings. We found moderate inter-rater reliability (κ = 0.60, CI = 0.53–0.66) and substantial intra-rater reliability (κ = 0.68, CI = 0.61-0.75). The most experienced rater had significantly higher intra-rater reliability (κ = 0.78, CI = 0.65–0.90) compared to the least experienced rater (κ = 0.57, CI = 00.41-0.72). The two most experienced raters had the highest crude agreement percentage; however, also had a significant difference in distribution of spine types. In 47% of cases all raters agreed on the spine type. The agreement percentage was the same for both ratings. The most frequently occurring Roussouly type across all 8 ratings was Type 2. Conclusion: The current study presents moderate inter-rater and substantial intra-rater reliability of the Roussouly Classification System. These findings are comparable to previous results of reproducibility for a classification system in patients with ASD. Additional studies are requested to validate these findings as well as to further investigate the impact of the classification system on outcome following surgery.

A304: An Algorithm for the Choice of Minimally Invasive Posterior Spine Surgical Treatment of Adult Spinal Deformity

Masaaki Chazono¹, Shoshi Akiyama¹, Yoshio Kumagae¹, Takaaki Tanaka¹

¹Department of Orthopaedic Surgery, Utsunomiya National Hospital, Utsunomiya, Tochigi - Japan

Introduction: To avoid surgical morbidity and complications, minimally invasive surgery (MIS) approaches to the treatment of adult spinal deformity (ASD) have been gaining in popularity. Recently, a new algorithm of the choice of MIS for ASD (The MISDEF algorithm: Mummaneni, 2014) has been proposed. However, the proportion of population ratio that is > 65 years of age now accounts for 28% of the population in Japan, leading to a super-aging society. Therefore, we need a Japanese version of the algorithm for MIS and have created it based on our own surgical data and named it MISDEF-J. The aim of this study was to evaluate the MISDEF and MISDEF-J algorithms in our patient series and to verify the efficacy of the MISDEF-J algorithm by comparison with some formulae to target the optimal lumbar lordosis (LL). Material and Methods: Subjects included 24 patients (2 male, 22 female) with a Cobb angle > 20 degrees in TL/L scoliotic curves, who underwent the two-stage surgery: minimally invasive lateral access surgery (LLIF) followed by minimally invasive posterior surgery (MIS-PSF). MIS-PSF was performed using a scoliotic rod that could be rotated 90 degrees within the screw extender slots using a handle, thus correcting the scoliosis and creating lumbar lordosis simultaneously once the rod is subfascially into the screw head after placing the parafascial pedicle screws. Mean age of the patients at the time of surgery was 69 years. The mean preoperative Cobb angle was 38 degrees. According to the SRS-Schwab classification, there were 18 cases with TL/L only and 6 cases with no major coronal deformity. They were divided into two groups: PI-LL (MIS-PSF) < 15 degrees and PI-LL (MIS-PSF) > 15 degrees and differences between the groups were then assessed by constructing 2 x 2 tables using a Fisher exact test in the MISDEF and MISDEF-J algorithm. The reproducibility of the MISDEF-J algorithm was additionally verified in the same manner as a threshold of 5-degree difference of LL calculated using the Hamamatsu formula (FoH), Dokkyo formula (FoD), and Niigata formula (FoN) minus LL (MIS-PSF). Results: There was a distribution with 4 cases of Class 2 and 20 cases of Class 3 in the MISDEF algorithm. The Fisher exact test found p = 0.11, indicating no significant relationship between the MISDEF algorithm and PI-LL (MIS-PSF). However, there were 11 cases of MIS-PSF category and 13 cases of Open category in the MISDEF-J algorithm. The test found p = 0.004, indicating a significant relationship between the MISDEF-J algorithm and PI-LL (MIS-PSF). Furthermore, there was a significant difference of p < 0.05 between the MISDEF-J algorithm and each LL formula (FoH, FoD, and FoN) – LL (MIS-PSF). Conclusion: The present study shows that the MISDEF-J algorithm is a reproducible and reliable instrument. Careful patient selection and evaluation with the algorithm was helpful to select patients with ASD who were appropriate candidates for MIS. Not all cases of deformity can be appropriately treated with MIS, but our algorithm offers a reliable method for the patient selection for ASD using MIS-PSF or Open surgery.

A305: Does Preoperative Distal-Apex Alignment Affect the Selection of Osteotomy Segment in Pedicle Subtraction Osteotomy for Thoracolumbar Kyphosis Secondary to Ankylosing Spondylitis?

Weiyi Diao¹, Bangping Qian¹, Yong Qiu¹

¹Department of Spine Surgery, Drum Tower Hospital, Nanjing University Medical School, Nanjing - China

Introduction: To investigate the correlations between preoperative sagittal distal-apex alignment and the selection of osteotomy level in one-level pedicle subtraction osteotomy (PSO) for correction of thoracolumbar kyphosis secondary to ankylosing spondylitis (AS). Materials and Methods: A retrospective study of consecutive AS patients with thoracolumbar kyphosis underwent one-level PSO was performed. Patients with lordotic distal-apex alignment were assigned to group A, while others with kyphotic distal-apex alignment were assigned to group B. The preoperative and postoperative radiologic parameters included global kyphosis (GK), thoracic kyphosis (TK), lumbar lordosis (LL), sagittal vertical axis (SVA), pelvic incidence (PI), pelvic tilt (PT) and sacrum slope (SS) were measured and compared. Correction efficient of PSO at different levels was compared. Perioperative and long-term complications were reviewed. Results: Patients in group A and group B had the mean age of 35.9 and 35.0 years, respectively. The thoracolumbar kyphosis was corrected from a mean preoperative GK of 67.8° to 35.9° in group A and from 72.0° to 38.3° in group B, and LL was corrected from -21.0° to -54.0° and from 2.3° to -43.3°, respectively. No obvious loss of GK correction (3.2°/ 3.9°) was observed in both groups at the final follow-up. Statistically significant differences were found for preoperative and correction of LL and SVA between group A and B. The correction of LL and SVA showed a strong increasing tendency as the PSO level went down from L1 to L3. Conclusions: Satisfactory correction of LL, SVA and SS was achieved in both groups, with no obvious loss of correction at the latest follow-up. For patients with lordotic distal-apex alignment, PSO at L1 or L2 is appropriate. As the preoperative LL still remains, great correction of LL is unnecessary. PSO at L2 or L3 is recommended for patients with kyphotic distal-apex alignment, as lower lumbar vertebra could provide more correction of LL and SVA.

A306: Optimum Pelvic Incidence Minus Lumbar Lordosis Value After Operation for Patients With Adult Degenerative Scoliosis

Xiangyao Sun¹, Yong Hai¹

¹Department of Orthopedics, Beijing Chaoyang Hospital, Capital Medical University of China, Beijing - China

Introduction: Schwab classification for adult degenerative scoliosis (ADS) concluded that health-related quality of life was closely related to curve type and three sagittal modifiers. It was suggested that pelvic incidence minus lumbar lordosis value (PI-LL) should be corrected within -10°∼+10°. However, recent studies also indicated that ideal clinical outcomes could also be achieved in patients without the ideal PI-LL mentioned above. This study evaluated the relation between the clinical outcomes and the PI-LL of Chinese patients with ADS who received long posterior internal fixation and fusion. Materials and Methods: This was a single-center retrospective comparative study of patients treated by long posterior internal fixation and fusion in our hospital between 2010 and 2014. Inclusion criteria were age > 45 years at the time of surgery, Cobb angle of lumbar curves ≥ 10°, long posterior internal fixation and fusion ≥ least 3 motion segments, follow-up ≥ 2 years, complete preoperative and postoperative radiographic data, and functional evaluation results. Exclusion criteria were history of previous lumbar spine surgery, other kinds of scoliosis, history of severe spinal trauma, spinal tumor, ankylosing spondylitis, and spinal tuberculosis. Seventy-four patients were enrolled in this study. Operative parameters included intraoperative blood loss, duration of surgery, length of hospital stay, number of fusion levels, and decompression. The radiological measurements included Cobb angle of the curves and PI-LL. Clinical outcomes were evaluated by the Japanese Orthopedic Association score, Oswestry Disability Index (ODI), visual analog scale, and Lumbar Stiffness Disability Index (LSDI). In addition, the complications of surgery were also collected. One-way analysis of variance, Student t test, Kruskal-Wallis test, Pearson chi-square test, and curve estimation were calculated for variables. All the patients were divided into Group 1 (long instrumentation and fusion to L5) and Group 2 (long instrumentation and fusion to S1). Operative parameters, radiological measurements, clinical outcomes, and complications of surgery were compared between two groups to confirm whether distal fusion level could influence therapeutic effect. Then patients were divided into PI-LL < 10° (Group A), 10°≤PI-LL≤20° (Group B), PI-LL > 20° (Group C). Operative parameters, radiological measurements, clinical outcomes, and complications of surgery were compared between each of the two groups. Curve estimation was performed to evaluate the relationship between postoperative PI-LL and clinical outcomes. Results: No difference was found between Group 1 and Group 2 in all postoperative parameters (p > .05). There were significant differences in final ODI (p < .001) and final LSDI (p < .001) among Group A, Group B, and Group C. Cubic curve model fitted the relationship between PI-LL and final ODI better than other models (R = 0.379, p < .001). Cubic curve model fitted the relationship between PI-LL and final LSDI better than other models (R = 0.691, p < .001). There was a significant difference in proximal junctional kyphosis (PJK) among groups (p = .038). No significant difference was found in other parameters. Conclusion: Optimal PI-LL value may be achieved between 10° and 20° in Chinese patients with ADS after long posterior instrumentation and fusion surgery with excellent clinical outcomes and a lower PJK occurrence.

A307: Does Spinopelvic Parameters Abnormality After Short Segment Lumbar Fusion Cause Adjacent Segment Degeneration?

Novan Krisno¹

¹Department of Neurosurgery, Seobandi General Hospital, Jember - Iceland

Introduction: Adjacent Segment Degeneration (ASD) is one of the complication following Lumbar Fusion Surgery. Its incidence it varies and the background factors has not been described clearly. The spinopelvic parameters has been helping the surgeon to predict the outcome of spinal surgery, but for the short fusion the surgeon usually didn’t care to much with this parameters. Material and Methods: This is a retrospective study, we assessed patients who undergone short segment Lumbar Fusion operation (one to three level) in our Hospital between January 2005 until December 2015 with one year minimum follow up. The variables for the study from the medical records are Pelvic Tilt (PT), Sacral Slope (SS), Lumbar Lordosis (LL), Pelvic Incidence (PI) all is measured before and after operation, age, gender, Osteoporosis state, discus change in MRI according Pfirrmann Grade. All of the variables will be categorized with the Schwabb Classification (normal PT < 20^o, normal PI-LL < 10^o), and analyze by Chi Square analysis. Results: From 117 patient we reviewed, 28 patient suffering ASD (23.85%), mean follow up 30.45 months, mean age 64.11 years old. No statistically significant difference, between the ASD and non ASD group in Gender, Age, Pelvic Tilt (PT) preoperation and postoperation also the PI-LL preoperation, Osteoporosis state and Pfirrmann Grade. But there is statistically significant difference in PI-LL postoperation with the P value 0.008. Conclusion: It is important to achieve harmony PI-LL even in short segment fusion to reduce the incidence of ASD in the future

A308: Adjacent Segment Disease Preventing in Patients With Pelvic Incidence-Lumbar Lordosis Mismatch After Lumbar Fusion

Dmitry Ptashnikov¹, Sergei Masevnin¹, Dmitry Michailov¹, Nikita Zaborovskii¹

¹Department of Spine Surgery, Saint Patersburg - Russian Federation

Introduction: Spinal segment arthrodesis has become a widely accepted treatment for degenerative disorders of the lumbar spine. However spinal fusion alters the normal biomechanics of the spine and eliminates mobile segments causing overload of adjacent segments. In recent years, increasing importance in degenerative decompensation of the adjacent segment after lumbar fusion is attached to spino-pelvic malalignment. At the same time, according to some authors, the overload of the adjacent segment in conditions of a PI-LL parameter mismatch exceeding 11° leads to the ASD development. Material and Methods: This prospective study evaluated 86 patients who were treated from 2011 to 2013 for lumbar canal stenosis with TLIF. All patients had preop PI-LL mismatch greater than 11° with no other global balance disturbance (SVA < 4 cm, PT < 20°). All patients had one level fusion with pedicle screws and TLIF with interbody PEEK cage. Patients were divided into two groups depending on the operative technique. First group consisted of 42 patients with minimal invasive bilateral facet joint resection, pedicle screw fixation and TLIF. Second group included 44 patients with operational technique aimed at the lumbar lordosis increasing. These patients were treated with Smith-Peterson osteotomy and TLIF with the most anterior cage position. The average follow-up was 44 months (36-62 months). Results: There were no statistically significant differences in operative time, blood loss and postop pain level between two groups. Comparison of the pre- and postoperative values within the groups showed significant differences in the second group for lumbar lordosis (p = 0.037). Summary in the I group symptomatic ASD was found in 14 cases (33.3%) during all follow-up period with 85.7% frequently of revision surgery. In the II group symptomatic ASD was identified in 2 patients (4.5%), one of them needed revision surgery. Conclusion: The described technique of operative treatment allows to achieve an increase in lumbar lordosis up to 10 degrees on one segment without increasing surgery trauma. This technique has shown a statistically significant (p = 0.012) prevention of ASD development in patients with PI-LL mismatch.

Minimally Invasive Surgery 3

A309: Myoglobin and Creatine Kinase Blood Levels as a Symptom of Perioperative Muscle Injury During Mini-Invasive and Open Stabilization of Thoracic and Lumbar Spine Fracture

Jiri Matejka¹, Tomas Matejka¹, Jaroslav Belatka¹, Jaroslav Zeman¹, Petr Zeman¹, Jaroslav Racek²

¹Department of Orthopaedics and Locomotor Apparatus Traumatology, Faculty of Medicine in Pilsen, Charles University, Czech Republic, Pilsen - Czech Republic ²Department of Clinical Biochemistry and Hematology, Faculty of Medicine in Pilsen, Charles University, Czech Republic, Pilsen - Czech Republic

Introduction: In this randomized prospective study, we monitored and compared perioperative changes in skeletal muscle enzymes in classical, i.e. open and mini-invasive stabilization of thoracolumbar spine fractures. The established hypothesis was to confirm higher levels of muscle enzymes in open stabilization. Material and Methods: The prospective randomized study included patients with isolated, type A and B fracture of the thoracolumbar spine. A total of 38 injured patients with 27 type A and 11 type B fractures, with the mean age of 46.4 years (18-68), were enrolled in the study. Of these, 28 were men and 10 women. 19 injuries were managed in an open procedure and 19 procedures were mini-invasive. The USS Fracture (DePuy-Synthes, Switzerland) was used for the open method of stabilization and the USS Fracture MIS (DePuy-Synthes, Switzerland) was used for the mini-invasive procedures. Venous blood was taken intermittently at short intervals to determine the levels of skeletal muscle enzymes, i.e. at least 16 samples in the first 3 postoperative days, in fracture stabilization and implant extraction. The catalytic concentration of creatine kinase (CK, EC 2.7.3.2) was determined via an enzymatic UV-test, and the concentration of myoglobin via electro-chemiluminescent immunoassay (ECLIA). Roche Diagnostics sets were used for both analytes; the Cobas 8000 analyser system was used for the measurements – creatine kinase on module c702, myoglobin on module e602 by Roche Diagnostics (Basel, Switzerland). Enzyme levels were processed statistically. The Wilcoxon test (equivalent to the Mann-Whitney test) was used. Results: The median increase in the values of both enzymes is higher in the mini-invasive method than in the open method in both the surgery phase for the injury and in the extraction phase. The median increase in the values of both enzymes is higher in both methods for the primary procedure phase compared to the extraction phase. All results are statistically significant at p of < 0.05. All tests were calculated using the MATLAB Statistics Toolbox. Conclusion: Analysis of biochemical changes in open and mini-invasive surgery to stabilize fracture of the thoracolumbar spine did not confirm the hypothesis that levels of creatine kinase and myoglobin enzymes increase especially in open stabilization. On the contrary, they were statistically significantly higher in mini-invasive procedures, both at the primary procedure after the injury and the extraction of the implant.

A310: Fallen From Height but Favourable Function? A Two Year Prospective Outcome Study on Extreme Lateral Lumbar Inter-Body Fusion and Foramina Heights

Keng Meng Jeremy Goh¹, Ming Han Lincoln Liow¹, Sheng Xu¹, Marcus Ling¹, William Yeo¹, Chang Ming Guo¹

¹Singapore General Hospital, Orthopaedic Surgery, Singapore - Singapore

Introduction: Extreme Lateral Inter-body Fusion (XLIF) is a minimally invasive (MIS) lateral access surgical technique used in the treatment of adult spinal deformity. Cage subsidence has been widely described in lumbar inter-body fusion procedures and may theoretically diminish the potential indirect decompression benefit through associated neuroforamina narrowing. However, the relationship between postoperative neuroforaminal height maintenance and Health-related Quality-of-Life (HRQoL) measures remains unclear. Objectives: The aim of this study is to determine if changes in neuroforaminal height affects patient outcomes and HRQoL at 2 year follow-up. Material and Methods: From Aug 10 to Nov 14, 45 patients with adult spinal deformity (13 male:32 female, mean age 65 ± 6.6 years) were prospectively recruited and underwent XLIF by a single surgeon. Mean foramina height improvements postoperatively and foramina height maintenance at 2 years were recorded. The cohort was divided into 2 groups, namely (1) maintenance and (2) reduction in foramina height. All patients were assessed pre- and post-operatively (6 months, 1 year and 2 years) with numerical pain rating scale (NPRS back and leg pain), Oswestry Disability Index (ODI), Short-form 36 scores (SF-36) and the North American Spine Society (NASS) score for neurogenic symptoms (NS) and patient-rating for overall result of surgery and expectations met for surgery. Radiological fusion was assessed with the Bridwell fusion classification. Results: All patients had a minimum of two years follow-up. The average pre-op mean foramina height was 16.9 ± 3.5 mm and the average post-op foramina height was 20.1 ± 3.4 mm. Of the 45 patients, 25 showed maintenance of foramina height at 2 years postoperatively whilst 20 patients had a decrease in foramina height. There was no difference in Bridwell fusion grade between groups, with all patients achieving Grade 1 fusion at 2 years. When comparing the PROM/HRQoL outcomes for the 2 groups, there was no significant difference in NPRS, ODI, NASS-NS or SF-36 scores (p > 0.05). In addition, there was no significant difference in the physical and mental component scores of SF-36. 92% of the group 1 and 85% of group 2 patients reported good/excellent satisfaction and attained fulfilment of expectations. For the overall cohort, there was significant improvement at 2 years post-op from pre-operative scores (p < 0.05) in VAS back pain (6.0 ± 3.0 to 1.8 ± 3.1), VAS leg pain (5.0 ± 4.0 to 1.3 ± 2.9), ODI (58.1 ± 17.1 to 16.5 ± 18.4), NASS-NS(43.1 ± 23.2 to 11.9 ± 17.7) and SF-36 PCS(51.3 ± 16.8 to 75.3 ± 19.1) and MCS (51.3 ± 16.8 to 75.3 ± 19.1). Conclusion: Despite an initial increase in foramina heights after XLIF, 45% (20/45) of patients had foramina height reduction at 2 years. However, foramina height reduction did not appear to affect clinical outcomes in the short-term. Future research should focus on identifying the critical foraminal height that predicts poorer outcomes in XLIF.

A311: Intraoperative Assessment of Adjacent Segment Foraminal and Central Canal Volume Changes After Cage Implantation During Lateral Trans-Psoas Surgery (XLIF)

Rodrigo Navarro-Ramirez¹, Ana Luís¹, Joshua Adjei¹, Christoph Wipplinger¹, Eliana Kim¹, Roger Härtl¹

¹Weill Cornell Brain and Spine Center, New York - United States

Introduction: Lumbar Spinal fusion using indirect decompression through extreme lateral trans-psoas surgery (XLIF) has been one of the most popular options for spinal fusion over the past decade. This procedure is now widely used to treat not only degenerative disc disease and spinal stenosis but also adult deformity and scoliosis. Furthermore, there is no question about the clinical benefits of indirect decompression or about better radiological outcomes associated with larger and wider implants. However, with the recent introduction of novel imaging tools such as the latest generation of fan-beam intraoperative CT scanners (FBiCT), multiple questions can be further studied. For instance, what is the immediate effect of XLIF over adjacent segment volumes after cage insertion? Fan-beam iCT possesses high soft tissue resolution capacity. Using these images, we have been able to accurately assess radiological outcomes of the index level and the adjacent segment (AS) as well, making this study the first to account for the intraoperative effects of XLIF on adjacent segment foramina and central canal volumes. Materials and Methods: This study was retrospectively conducted in a single-center on patients with symptomatic single or multilevel lumbosacral degenerative disorders who underwent FBiCT-guided XLIF between 2014 and 2016. We collected information regarding: Number of patients, age at time of surgery, gender, indexed level, incidence of adjacent level degeneration (ASDeg), incidence of symptomatic disease (ASDis), time to follow-up, and bilateral foramen volume for the indexed and the adjacent segments. Results: A total of 19 patients and 21 levels were analyzed in the present study. Mean age at surgery was 69 [67-80] years; 12 patients were males (57%) and 9 were females (42.9%). BMI at surgery was 26.8 [25.2;29.3]. 47.% of the indexed levels were L3-L4; 28.6% at L2-L3; 14.3% L1-L2; and 9.5% L4-L5. Radiological Outcomes (RO): Indexed level: Central Canal Volume (CCV) Pre 1.0 cm³ [0.85 -1.37] Post 4.8 cm³ [4.01-6.23]. Right foraminal volume (RFV) Pre 0.09 cm³ [0.08-0.13] Post 0.44 cm³ [0.42-0.59]. Left foraminal volume (LFV) Pre 0.09 cm³ [0.07-0.13] Post 0.51 cm³ [0.38-0.57]. AS Above(a): aCCV Pre 4.44 cm³ [3.03-6.26] Post 1.34 cm³ [1.23 -1.93] aRFV Pre 0.44 [0.41-0.58] Post 0.11 cm³ [0.09-0.13]. bLFV Pre 0.47 cm³ [0.35-0.58] Post 0.12 cm³ [0.10-0.15]. AS Below(b): bCCV: Pre 4.28 cm³ [3.00-5.52] Post 1.10 cm³ [1.01 -1.44] bRFV: Pre 0.47 [0.41-0.66] Post 0.11 cm³ [0.09-0.14]. bLFV: Pre 0.50 cm³ [0.39-0.59] Post 0.10 cm³ [0.09-0.14]. Despite a decreasing trend on the adjacent segment volumes, there was no statistically significant difference between preoperative and postoperative. Also, there was no direct correlation between the size of the cage and the volumes recorded. Conclusions: Indirect decompression decreases central canal and foraminal volume on the adjacent segments to the indexed XLIF level. Further studies with larger samples are needed to confirm these results.

A312: Which Peri-Operative Factors Influence Post-Operative Satisfaction After Lateral Access Surgery?

Sheng Xu¹, Lincoln Liow¹, Jeremy Goh¹, Yeo William¹, Seang Beng Tan¹, Marcus Ling¹, Reuben Soh¹, Chang Ming Guo¹

¹Department of Orthopaedics Surgery, Singapore General Hospital, - Singapore

Introduction: Lateral access surgery is a minimally invasive (MIS) lumbar fusion technique which has been shown to be reproducible, biomechanically stable and clinically efficacious. However, there is a paucity of literature describing the preoperative factors which influence the postoperative satisfaction and expectation fulfilment after lateral access surgery. The aim of our study is to identify the perioperative factors that may influence postoperative satisfaction and expectation fulfilment. Material and Methods: From 1st August 2010 to 30th November 2014, 52 patients with adult spinal deformity (16 male: 36 female, mean age 64.0 ± 8.7 years) were prospectively recruited and underwent lateral access surgery by a single surgeon at our institution. All patients were assessed pre- and post-operatively at two years with numerical pain rating scale (NPRS back and leg pain), Oswestry Disability Index (ODI), Short-form 36 scores (SF-36), North American Spine Society (NASS) score for neurogenic symptoms (NS) and patient satisfaction of overall result of surgery and expectation met. Plain lumbar spine radiographs were performed pre- and post-operatively at two years and Cobbs angles, global lumbar lordosis, disc heights (DH), and adjacent disc heights (ADH) were measured. Fusion rates based on the Bridwell grading and subsidence classified by the Marchi grading system were assessed at 2 years. Length of operation and stay were recorded. Multiple linear regression was performed with satisfaction as the dependent variable to identify predictive independent variables. Results: Lower preoperative SF36 general health scores (p = 0.03), higher NPRS leg pain scores (p = 0.04), and longer surgical duration (p = 0.02) were significant predictors of lower satisfaction rates (p < 0.05) and expectation fulfillment (p < 0.05). Mean duration of operation was 208.0 ± 85.1 minutes, mean length of stay was 5.0 ± 2.7 days. Overall, VAS back and leg pain decreased 80.3% (6.1 ± 3.0 to 1.2 ± 2.69) and 83.0% (4.7 ± 4.0 to 0.0.8 ± 2.3) respectively. ODI improved by 76.2% (51.9 ± 16.6 to 14.9 ± 18.4). NASS NS score improved by 75.9% (41.5 ± 24.0 to 10.0 ± 16.1). Significant improvements in SF36 health related quality of life scores were experienced by the patients, with 90% of patients satisfied and 88% had their expectations fulfilled. There was significant correction in postoperative Cobbs angle (9.1° to 6.0°, p = 0.023) and maintenance of Cobbs and global lumbar lordosis angles at 2 years. Significant increase in mean DH was observed postoperatively (6.9mm ± 2.2 to 11.3mm ± 2.0 postoperatively and 10.6mm ± 2.3mmm 2 years, p < 0.001) and there was no significant difference in mean ADH at 2 years (p = 0.05). 98% patients achieved mean Bridwell Grade 1 fusion, however approximately 70% had cage subsidence (Grade I to III) at 2 years. No visceral, vascular or neurological complications were noted. Conclusion: Lateral access surgery is a viable treatment for adult spinal deformity with significant improvement in clinical outcomes and high satisfaction rates. However, surgeons should be cognizant that lower preoperative SF36 general health, higher NPRS leg pain scores and longer surgical duration are predictors of lower satisfaction in patients undergoing lateral access surgery. These findings highlight the need for careful patient selection and counselling for patients considering lateral access surgery.

A313: Isthmic Approach for Transforaminal Percutaneous Endoscopic Lumbar Discectomy at the L5-S1 Level

Junseok Bae¹, Sang-Ho Lee¹

¹Neurosurgery, Wooridul Spine Hospital, Seoul - Korea, Republic

Introduction: Percutaneous endoscopic lumbar discectomy (PELD) is a minimally invasive procedure for symptomatic disc herniation not responding to conservative treatment. Transforaminal PELD at the L5-S1 level is difficult in high iliac crest or narrow foraminal dimension. The upper flexible part of neural foramen, bordered by lateral to isthmus and cranial to superior articular process offers safe and feasible way into the Kambin’s triangle. We introduce technical feasibility and case series of transforaminal PELD via isthmic approach at the L5-S1 level Material and Methods: Twenty-eight consecutive patients (mean age 48.2 years old, 25 males) with symptomatic lumbar disc herniation at the L5-S1 level treated by PELD via isthmic approach between 2015 and 2016. In posterolateral approach, the trajectory was intended to pass between cranial to the superior articular process and lateral to the isthmus. Further foraminoplasty was performed with progressive dilation using bone-drill (Joimax GmbH, Karlsruhe, Germany). A 7 mm beveled working cannula was placed and spinal endoscope was inserted. The herniated disc and fibrotic scar tissues were released and removed with discectomy forceps under the direct visualization. Results: At mean 12 months follow-up, VAS for back and leg pain was significantly improved after PELD. Mean operation time was 36 minutes and length of hospital stay was 1.2 days. There was no surgery related complication such as exiting nerve injury, incomplete decompression, dura tear. One patient has recurred disc herniation. Conclusion: PELD via isthmic approach is safe and effective in high iliac crest and small neural foramen that is difficult for conventional transforaminal approach.

A314: Anterior Column Reconstruction in Primary Adult Degenerative Scoliosis Correction Surgery: Restoring Lordosis and Achieving Indirect Decompression With Minimally Invasive Anterior Cages

Robert Lee¹, Michael Mokawem¹

¹Spinal Surgery Unit, Royal National Orthopaedic Hospital, Stanmore - United Kingdom

Introduction: Patients with degenerative scoliosis often present with leg pain, back pain and issues with sagittal balance. Complications following open correction surgery can be high and sagittal balance correction poor using a posterior only technique. We present a case series demonstrating that multiple anterior cages inserted via a minimally invasive lateral or anterior technique is an effective way of correcting the coronal deformity and restoring sagittal balance in these patients. Additionally, it provides indirect decompression of neural structures. Material and Methods: Retrospective review of prospectively collected data in a single surgeon case series of 48 patients with adult degenerative scoliosis. Previous spinal fusion surgery excluded patients. Surgery: Anterior cages inserted via a minimally invasive lateral or anterior technique (via a single or multiple stage approach). Outcome measures: (i) Radiographic. Pre and post-operative parameters: Lumbar lordosis (LL), Pelvic Incidence-Lumbar Lordosis mismatch (PI-LL), Sagittal Vertical Axis (SVA), Pelvic Tilt (PT) and Cobb angle. (ii) Patient reported outcome measures. Visual Analogue Scale (VAS) for Back pain, VAS for Leg pain, EuroQol- 5 Dimensions (EQ-5D), EQ-5D VAS, Oswestry Disability Index (ODI), Roland Morris Disability Score (RMD). Minimum follow-up: 6 months. Results: 48 Adult patients with degenerative scoliosis (30 females and 18 males). Average age: 67.0yrs (54.9yrs - 83.4yrs). Positive sagittal balance in 31 patients. 42 Cases purely MIS and 6 cases hybrid with open posterior fusion. A total of 128 lateral cages were inserted with 1 level in 7 patients, 2 levels in 14 patients, 3 levels in 15 patients and 4 levels in 12 patients. Distribution of levels: L1/2- 12 cages, L2/3 – 34 cages, L3/4 – 44 cages, L4/5 - 38 cages. Average post-operative radiographic outcomes showed improvement of SVA 90.1 to 35.3 mm, PI-LL 26 to 2 degrees and Cobb angle 23 to 5 degrees. Average 6 month patient reported outcome scores were: VAS back 8 to 3, VAS leg 8 to 2, EQ-5D 0.257 to 0.720, EQ-5D VAS 44 to 74, ODI 64 to 28, RMD 16 to 11. These scores were maintained in patients reaching 1 year and 2 year follow-up marks. Conclusion: The use of minimally invasive anterior cages in primary adult degenerative scoliosis surgery is an effective surgical strategy with very good radiographic outcomes (achieving restoration of lordosis and correction of scoliosis) and very good patient reported outcomes (achieving improvement in leg and back pain).

A315: Contralateral Radiculopathy After Minimally Invasive Oblique Lumbar Interbody Fusion

Nisarg Parikh¹, Amit Jhala², Manish Mistry²

¹Spine Fellow, Chirayu Fracture and Orthopeadic Hospital, Ahmedabad - India ²Consultant Spine Surgeon, Chirayu Hospital, Ahmedabad - India

Introduction: Minimally Invasive Oblique Lumbar Interbody Fusion is an effective means of indirect decompression in degenerative lumbar spine disease with its various approach related complications. Although many of them have been described in literature, there is lack of sufficient data on contralateral radiculopathy in OLIF. Here we have analyzed incidence and probable etiology of contralateral radiculopathy in our series. Materials and Methods: This is a retrospective study. Oblique lumber interbody fusion was carried out in 49 segments of 38 patients over the period of 16 months from May 2016 to August 2017. Patients with degenerative lumbar spine disease were included whereas patients with Infection, trauma, lumbar disc prolapse, severe bony canal stenosis, lysthesis of grade 3 or more were excluded. So we have assessed 45 segments of 34 patients. All patients were operated from left side by minimally invasive oblique lumbar inter body fusion with cage. Indirect decompression by distraction was achieved in all patients. No direct decompression was carried out. No neuromonitioring was carried out. Per operative and perioperative complications were noted up-to 6 weeks and among them patients with contralateral radiculopathy were assessed. Results: In the patients assessed, overall complication rate was 42%. That include per operative complications like rupture of iliolumbar vein in 1 (2.94%), breach of peritoneum and fracture of superior endplate of inferior vertebrae in 2 (5.88%). Post-operative complications neurological deficit in 1 (2.94%), graft site pain in 21 (61.76%), Graft site fracture of the anterior superior iliac spine in 2 (5.88%), ipsilateral psoas weakness & pain in 11 (32.35%), superficial/deep infection in 1 (2.94%). Incidence of contralateral radiculopathy with sensory or motor deficit was present in 6 (17.64%) patients (13.33% segments) who had in total 7 segments (2 in 1 patient & 1 in 5 patients) fused. 5 of them had sensory deficit with radicular pain whereas 1 had neurological deficit (weakness grade 2/5) as well. 2 patients recovered fully within 1 month. 1 patient with neurological deficit recovered partially at the follow-up of one month. 3 patients(8.82%) required direct decompression of the nerve root involved. Analysis for the mechanism of contralateral sensorimotor involvement showed fracture of the superior endplate on contralateral side due to cage preparation, cage malposition leading to direct nerve root compression or contralateral far disc prolapse, translational correction of spondylolisthesis leading to nerve root compression and nerve root stretching and neuropraxia due to distraction. Conclusion: This is the largest series reported on contralateral radiculopathy in Minimal Access OLIF. Being an approach related complication; its avoidance requires careful execution of surgical steps and patient counselling.

A316: The Changes of Volume of Psoas Muscle After Oblique Lateral Interbody Fusion L4-5 for Treatment of Degenerative Lumbar Disease: The Observation of the Effect on Atrophic Changes and Correlation With Clinical Outcomes

Hyunjin Jo¹, Jin-Sung Kim¹

¹Catholic University of Korea, St. Mary’s Hospital, Seoul - Korea, Republic

Introduction: Recently, minimally invasive lateral lumbar interbody fusion has gradually increased popularity as substituted method of conventional lumbar fusion. There are two methods of DLIF (direct lateral lumbar interbody fusion) and OLIF (oblique lateral interbody fusion) in lateral lumbar interbody fusion. In MIS-DLIF, blunt retroperitoneal and trans-psoas dissection poses a risk of injury to the psoas muscle and lumbar plexus, especially at lower lumbar level. As an alternative, MIS-OLIF uses a window between the prevertebral venous structures and psoas muscle, and gets an access to the target disc obliquely. Theoretically, MIS-OLIF preserves psoas muscle with reducing the complication of direct lateral approach. However, in most case, some psoas muscle violation can not be avoided during the OLIF. So, the purpose of this study was to evaluate the changes of psoas muscle volume after OLIF and also to analysis whether there is a correlation between the change of psoas volume and clinical outcomes Material and Methods: From July 2013 to May 2016, 30 consecutive patients underwent multi-level OLIF that included L4-5 or L4-5 single level OLIF for the treatment of L2-5 level degenerative disease were identified and retrospectively reviewed with prospectively acquired records. Degenerative disc disease and Spinal stenosis with/without spondylolisthesis of L2∼5 were included. For clinical outcomes, self-reported measures including visual analogue scale (VAS), Oswestry disability index (ODI) and total time of daily walk were used. The psoas muscle volume was obtained by measuring the cross sectional area of both psoas muscles at the middle point of L4-5 disc height. Results: Mean age of the patients included in this study was 65.4 ± 8.0 (52-83, Sex M: 8, F: 22) and preoperative diagnoses were Spinal stenosis / DDD in 14 patients (47%), Spondylolisthesis in 14 patients (47%) and HNP in 2 patients (6%). single level OLIF (L4-5) was performed in 23 patients (77%) and more than 2 level OLIF (include L4-5) was performed in 7 patients (23%). There was statistically significant improvement of clinical outcomes (VAS (back, leg), ODI, walking time for 1 day, all of them p < 0.001). The volume of psoas muscle was significantly increased from preoperative to last follow up (right: p = 0.004, left: p = 0.027). Also, the mean variation (92.92 mm²) of a between preoperative and postoperative 12 months was confirmed, and It was divided into group 1, which had a larger value than mean variation, group 2, which had a smaller value than mean variation and there was no significant difference in VAS (back, leg), ODI, total time of daily walk between two groups before surgery (VAS back, ODI, total time of daily walk p = 1.000, VAS leg p = 0.21), but group 1 was significantly lower than group 2 after post operative time (VAS back, VAS leg, ODI post op 6 months and 12 months p < 0.001, total time of daily walk 6 months p < 0.001, 12 months = 0.007). Conclusion: MIS-OLIF is a relatively safe procedure without definite atrophic change or reduction of volume of psoas muscle at the first follow after surgery and Overall, the volume of the psoas muscle at L4-5 significantly increased postoperatively, especially in the group with good clinical outcomes.

A317: Perioperative Complications of Minimally Invasive Oblique Lumbar Interbody Fusion in Degenerative Lumbar Spine Disease

Nisarg Parikh¹, Amit Jhala², Manish Mistry²

¹Spine Fellow, Chirayu Fracture and Orthopeadic Hospital, Ahmedabad - India ²Consultant Spine Surgeon, Chirayu Hospital, Ahmedabad - India

Introduction: Different approaches are used for lumbar interbody fusion in degenerative spine disease. Each of them has their own set of complications. Anterior approaches carry risk for vascular and neurological injuries. In this study we have assessed perioperative complications of minimally invasive oblique lumbar interbody fusion. Methods: This is a retrospective study. Oblique lumber interbody fusion was carried out in 49 segments of 38 patients over the period of 16 months from May 2016 to August 2017. Inclusion criteria were patients having degenerative disc disease, lumbar spinal stenosis, lytic or degenerative spondylolisthesis. Patients with Infection, trauma, lumbar disc prolapse, severe bony canal stenosis, lysthesis of grade 3 or more were excluded. So we have assessed 45 segments of 34 patients. All patients were operated from left side by minimally invasive oblique lumbar inter body fusion with cage. 30 patients had posterior and 4 had anterior fixation. Auto graft was used in 21 (31 segments) patients and artificial bone graft was used in 13(14 segments) patients along with cage. Indirect decompression by distraction was achieved in all patients. None of the patients had direct decompression done. No neuromonitioring was carried out. Per operative and perioperative complications were noted up-to 6 weeks. Results: Out of 34 patients 11 were male and 23 were female. Age was from 40 to 82 years with average age of 63 years. Diagnosis was Disc degeneration in 3 patients, degenerative listhesis in 20 patients, lytic listhesis in 2 patients, Lumbar stenosis in 4 patients, and adjacent segment degeneration in 5 patients. Single segment fusion was done in 24 patients, 2 segment fusion in 9 patients and 3 segment fusion was done in 1 patient. Average follow up was 4 months. All were benefited with indirect decompression & none required direct decompression post operatively due to persistent symptoms. Per operative complications included rupture of iliolumbar vein in 1 (2.94%) patient, breach of peritoneum and fracture of superior endplate of inferior vertebrae in 2 (5.88%) patients. Auto graft was used in 21 (61.76%) patients; all had postoperative graft site pain. Graft site fracture of the anterior superior iliac spine occurred in 2 (5.88%) patients which got healed after rest period of 3 weeks. The most common post-operative complication was ipsilateral psoas weakness & pain which was seen in 11 (32.35%) patients. However, all the patients recovered from it within 2-8 weeks with average recovery time of 3 weeks. 1 (2.94%) patient had superficial and 1 (2.94%) had deep infection which got healed after IV/Oral antibiotics. 6 (17.64%) patients had contralateral radiculopathy with sensory deficit in 5 & motor deficit in 1 patient. 3 (8.82%) of them had to undergo direct decompression due to persistent symptoms. Conservatively managed patients recovered partial to fully within 1 month. 1 (2.94%) patient had numbness in area distribution of left genitofemoral nerve. None had ureteric or lumbar sympathetic plexus injury. Overall complication rate was 40.12%. Conclusion: Oblique lumbar interbody fusion is safer approach with low incidence of permanent perioperative complications especially neurological complication. Most of them were recovered with varied time interval. Although we had low incidence of vascular complications, it does carry a higher risk in this approach.

Surgical Complications

A318: Postoperative Complications in Adult Spinal Deformity Patients With a Mental Illness Undergoing Thoracic Spine Surgery

Ishan Shah¹, Nick Jain¹, Christopher Wang¹, Zorica Buser¹, Jeffrey Wang¹

¹Department of Orthopaedic Surgery, Keck School of Medicine, University of Southern California, Los Angeles - United States

Introduction: Surgical correction for adult spinal deformity has been increasing in popularity due to the growing bed of literature supporting its efficacy on improving patient outcomes. Previous studies have found an association between mental illness and poor outcomes in spinal surgery, but not much is known about its effect on the adult spinal deformity population. In addition, most previous studies have focused only on the lumbar degenerative spine and have had limited patient sample sizes. The aim of the study is to investigate whether adult spinal deformity patients with depression and/or anxiety have an increased risk for postoperative complications and reoperation following posterior thoracolumbar deformity correction spine surgery. Materials and Methods: Adult spinal deformity patients undergoing any posterior thoracolumbar spine procedure between 2007 and 2015 Q2 were identified retrospectively using the Pearl Diver patient record database (Pearl Diver Technologies, West Conshohocken, PA, USA) containing records of approximately 18 million patients across the United States. Identified patients were then divided into two cohorts: a cohort with a preexisting diagnosis of depression and/or anxiety (N = 662) and a control group of patients without depression or anxiety (N = 1078). The diagnosis of depression and/or anxiety must have been made within 6 months of the operation date to be included in the mental illness cohort. Patients were identified using ICD-9 and ICD-10 diagnosis codes (International Classification of Diseases 9th-10th edition). 90-day and 1-year complication rates and reoperation rates were analyzed. Results: The mental illness cohort had significantly increased rates of many complications at the 90-day and 1-year intervals including: urinary tract infection (90-days: OR 1.733, P < 0.0001; 1-year: OR 1.978, P < 0.0001), pseudoarthrosis (90-days: OR 1.928, P = 0.001; 1-year: OR 2.22, P < 0.0001), osteomyelitis (90-days: OR 2.441, P < 0.0001; 1-year: OR 2.579, P < 0.0001), pneumonia (90-days: OR 1.641, P = 0.008; 1-year: OR 1.617, P = 0.003), incision and drainage (90-days: OR 2.214, P = 0.001; 1-year: OR 2.376, P < 0.0001), cardiac complications (90-days: OR 2.402, P = 0.027; 1-year: OR 2.625, P = 0.009), nervous system complications (90-days: OR 1.981, P < 0.0001; 1-year: OR 2.256, P < 0.0001), respiratory complications (90-days: OR 1.551, P < 0.0001; 1-year: OR 1.617, P < 0.0001), and surgical device complications (90-days: OR 2.497, P < 0.0001; 1-year: OR 2.782, P < 0.0001). Significantly increased rates of infection at 30 days (OR 1.812, P = 0.001) and 90 days (OR 2.161, P < 0.0001) and hematoma at 90 days (OR 1.577, P = 0.027) were seen in the mental illness cohort as well. The mental illness cohort also had significantly increased rates of reoperation at 1 year for all causes (OR 1.966, P < 0.0001). Conclusion: Patients with adult spinal deformity and pre-existing depression and/or anxiety treated with a posterior thoracolumbar spine deformity correction surgery have a significantly elevated risk of postoperative complications and reoperation when compared with patients without recently diagnosed mental disorders.

A319: Effect of Peri-Operative Goal-Directed Fluid Therapy on Orthopaedic Surgery Outcomes: A Systematic Review

Rakan Bokhari¹, Eunice Linh You², Oliver Lasry², Gabriele Baldini³, Michael Weber⁴

¹Division of Neurosurgery, King Abdelaziz University, Jeddah, Saudi Arabia, McGill University, Montreal, Quebec - Canada ²McGill University, Montreal - Canada ³Department of Anesthesia, Montreal General Hospital, Montreal, Quebec - Canada ⁴Department of Orthopaedic Surgery, Montreal General Hospital, Montreal, Quebec - Canada

Introduction: Hemodynamic stability in major surgery is a critical determinant of postoperative outcome. The risk of insufficient fluid delivery, leading to inadequate tissue perfusion, must be carefully balanced with the risk of edema from fluid overload. Intraoperative goal-directed fluid therapy (GDFT) is based on the objective assessment of hemodynamic of fluid responsiveness with minimally invasive cardiac output monitoring and may lead to better patient outcomes, fewer adverse events and shortened hospital stays, particularly in high-risk surgical cases. This systematic review aims to determine the effect of GDFT on post-operative outcomes following major orthopaedic and spine surgery. Material and Methods: MEDLINE, Embase and the Cochrane Library databases were searched for randomized clinical trials and observational studies that compared patients who received intraoperative GDFT during major orthopaedic and spine surgery against those who received the institution’s standard of care, and reported post-operative outcomes. Our primary outcomes were hospital length of stay (LOS) and our secondary outcomes were organ-related complications and 30-day mortality. Results: In total, 11 different studies were included for our analysis for a total of 992 patients: 493 patients receiving GDFT and 499 patients who received the standard of care. GDFT was associated with a significant reduction in post-operative complications ([RR] 0.77, 95% CI [0.67, 0.88], p = 0.0002). There do not appear to be a significant reduction in hospital length of stay (mean difference -0.69 days, 95% confidence interval [−1.67, 0.30], p = 0.17) or mortality (risk ratio [RR] 0.81, 95% CI [0.33, 2.01, p = 0.65]). Conclusion: GDFT may be of benefit to patients undergoing major orthopaedic surgery by reducing the rate of post-operative complications.

A320: Risk Factors and Management for Dural Tears in Anterior Surgery for Cervical Ossification of the Posterior Longitudinal Ligament

Wan-Ru Duan¹, Yueqi Du¹, Fengzeng Jian¹

¹Department of Neurosurgery, Xuanwu Hospital, Capital Medical University, Beijing - China

Introduction: Ossification of the posterior longitudinal ligament (OPLL) of the cervical spine is a condition of abnormal calcification of the posterior longitudinal ligament and a common cause of cervical myelopathy and radiculopathy. Anterior procedures decompress directly and usually achieve satisfactory results. However, when the dura matter become ossified or fused with the ligament, complete resection of the ossified PLL may result in unintentional dural lacerations, cerebrospinal fluid leaks or other complications. We reviewed a series of OPLL patients who underwent anterior surgery to investigate the incidence, risk factors and outcomes of dural tears, and to develop a cogent perioperative management algorithm for dural tears in anterior surgery for OPLL. Material and Methods: We reviewed 90 patients diagnosed with OPLL who underwent anterior surgical decompression (ACDF and ACCF) of the cervical spine between January 2014 and December 2016, Operating microscope was routinely used and dural laceration occurred in 12 patients. Demographic, clinical data, radiologic findings, intra- and postoperative management, and complications were retrospectively collected and analyzed. The risk factors of occurrence of dural tears were assessed using univariate and multivariate logistic analyses. A treatment algorithm was identified based on these findings and experience of the authors. Results: The prevalence of dural tear in our study is 13.3%(12/90). Univariate and multivariate analysis identified that moderate and severe myelopathy (JOA scores≤12), C sign, K-line (-) and broad base OPLL (base ratio ≥ 60%) were significant risk factors for dural tears. Broad base was the strongest risk factor (OR 31.14, 95%CI 1.87-518.36, P = 0.017), followed by moderate and severe myelopathy (OR 19.09, 95%CI 1.49-244.91, P = 0.023), K-line (-) (OR 14.15, 95%CI 1.10-182.27, P = 0.042), and C sign (OR 10.87, 95%CI 1.04-114.04, P = 0.047). Of the 12 patients, dural tears were noted in 11 of them and 9 was confirmed CSF leaks intaoperatively. All the tears noted during operation (11/12) were repaired during the operation using an onlay graft of gelatin sponge, autogenous fascia or artificial dura patch without suture or seal. Lumbar drains were placed during or immediate after surgery in all patients and kept for 5-7 days. One patient (1/12) was identified dural tears and CSF leaks 3 days after surgery with an asymptomatic neck mass, a lumbar CSF drainage catheter was placed and kept for 8 days. The treatment was successful in all dural tears and outcome measures including postoperative JOA scores and JOA improvement rates did not differ compared with the no dural tear group. No patient developed complications associated with dural tears and CSF leaks at the latest follow-up. Conclusion: Broad base OPLL (base ratio ≥ 60%), moderate and severe myelopathy (JOA scores≤12), K-line (-) and C sign were significant risk factors for dural tears. Intraoperative repair with onlay grafts combined with postoperative lumbar CSF drains were safe and effective strategies for dural tears or CSF leaks in the anterior surgery for OPLL.

A321: Factors Influencing Post-Operative Urinary Retention Following Elective Lumbar Spine Surgery - A Prospective Study

Siddharth Aiyer¹, N Ajit Kumar², Rishi Mugesh Kanna³, Ajoy Shetty⁴, S Rajasekaran⁵

¹Senior Registrar, Dept of Orthopaedics, Ganga Hospital, Coimbatore - India ²Spine Fellow, Department of Orthopaedics, Ganga Hospital, Coimbatore - India ³Associate Consultant, Dept of Orthopaedics, Ganga Hospital, Coimbatore - India ⁴Senior Spine Consultant, Dept of Orthopaedics, Ganga Hospital, Coimbatore - India ⁵Chairman, Dept of Orthopaedics, Trauma & Spine Surgery, Ganga Hospital, Coimbatore - India

Introduction: Postoperative urinary retention (POUR) following elective lumbar spine surgery can lead to prolonged hospital stay and increased morbidity. POUR often requires catheterisation thereby increasing the risk of urinary tract infections, catheter related complications and sepsis. The incidence and risk factors associated with POUR in lumbar spine surgery have not been well established.Recommendations for urinary catheterization in the perioperative setting vary widely and areinfluenced by numerous factors including surgical procedure, type of anaesthesia, co-morbidities, local policies, and personal preferences. The aim of the study was to determine the incidence of POUR in patients undergoing elective posterior lumbar spine surgery and to identify risk factors associated with development of POUR. Material and Methods: A prospective, consecutive analysiswas conducted in patients that underwent elective posterior lumbar surgery in the form of lumbar discectomy, lumbar decompression and single level lumbar fusions duringa six monthperiod. Patients with acute spine trauma, preoperative neurological deficit, history of previous urinary disturbance/symptoms, multiple level fusion and, those catheterized pre-operatively were excluded from the study. The patients that developed POUR (group A) were assessed for possible risk factors and compared with patients that did not develop any urinary retention (group B) during the study period.The patients with POUR were compared with the group without POUR during the study period to assess the risk factors. Univariate analysis and a multiple logistical regression analysis were performed. Results: A total of 687patients were operated for elective lumbar spine surgeryduringthestudyperiod. Based on the inclusion and exclusion criteria 370 patients were included in the final analysis. There were 61 patients that developed POUR and 309 patients formed the control group. Only one patient was discharged with an indwelling urinary catheter which was removed at 3 weeks. In the univariate analysis, significant risk factors for POUR were older age (p = 0.03); higher BMI ( < 0.0001); longerduration of surgery (p < 0.0001); largervolumeofintraoperativefluid administration (p < 0.001); surgical procedure of lumbar fusion versus discectomy/decompression (p = 0.001) and higher postoperative pain scores (p < 0.0001). Factors which did not show a significant association included sex (p = 0.54); diabetes (p = 0.06); type of inhalational agent used during anaesthesia (p = 0.2) (Isoflurane versus Sevoflurane). A multiple logistical regression analysis including age, BMI, duration of surgery, intraoperative fluid administration, type of surgical procedure and postoperative pain scores showed apredictive value of 93% overall and 97% in the POUR group. Conclusion: The occurrence of POUR was associated with older age, higher BMI, longer duration of surgery, larger volume of intraoperative fluid administration and higher postoperative pain scores. The multiple logistical regression analysis showed significant contribution of post operative pain scores in the prediction of POUR. This suggests that adequate pain relief in the post operative period is a key factor which can help prevent POUR.

A322: Evaluation of the Effectiveness and Efficiency of Two Hemostatic Utilization Strategies in Cervical and Lumbar Fusion Procedures

Manuel G. Ramirez Lopez De Nava¹, Harel Deutsch², Nitin Khanna³

¹Director, Global Market Access, BioSurgery, Deerfield - United States ²Associate Professor of Neurosurgery, Chicago - United States ³Assistant Clinical Professor of Orthopedics, Munster - United States

Introduction: Bleeding is an anticipated consequence of surgical procedures. In spine surgery the need for effective and rapid bleeding control is critical in maintaining the surgeon’s ability to visualize the field and avoid complications such as nerve injury and dural tears. During the past few decades, cervical and lumbar fusion procedure rates have escalated rapidly and now constitute 52% and 39%, respectively, of the 470 000 spine fusion procedures performed in 2011 (http://www.hcup-us.ahrq.gov/nisoverview.jsp). Given the high prevalence of cervical/lumbar procedures and the escalating costs of healthcare, there is increasing pressure on stakeholders to improve the efficiency of care and achieve cost containment through reductions in surgical time, transfusion need/utilization, hospital days, and perioperative morbidity. Hemostatic agent(s) selection is based on a number of factors with surgeons’ often choosing between a flowable agent such as Floseal only (FO) or in combination with gelatin and thrombin (F+G/T). Specifically, some tend to utilize FO while others utilize other hemostatic agents initially and reserve their use of Floseal as a “last line of defense” when other agents fail to provide adequate hemostasis. Across a broad list of ICD-9 coded spine surgeries, a recent large retrospective database analysis of 15 105 propensity score-matched cases found significant clinical and economic advantages to the use of FO as compared to F+G/T (Ikeme et al. 2017). Data subanalyses were performed to identify the potential clinical and economic implications of these findings in cervical/lumbar procedures. Material and Methods: Cervical or lumbar fusion procedures (ICD 81.00, 81.02, 81.03, 81.30, 81.32, 81.33, 81.04-0.8, 81.34-38) performed between October 2010 and September 2015 with charges for FO or F+G/T were identified from the Premier’s United States Perspective Hospital Database. Propensity-score match (1:1) was performed to match each F0 subject with a F+G/T subject and minimize treatment bias. Data were extracted to compare outcome variables of blood product administration (ie, intra-, peri-, and post-operative transfusion, pure blood/packed red blood cell transfusions), complication outcomes (ie, blood loss-related, severe, or other complications), and healthcare resource utilization (ie, hospital length-of-stay [LOS], surgery time, hemostat volume). Results: 14 021 cervical/lumbar FO and F+G/T matched pairs were compared. The FO compared with the F+G/T cohort exhibited significantly (p < 0.0001) lower rates of intraoperative transfusion (1.3% vs. 2.4%), perioperative transfusion (1.5% vs. 2.8%), postoperative transfusion (1.6% vs. 3.0%), and pure-blood/pRBC transfusion (2.2% vs. 4.3%). No between-cohort differences were observed in blood-loss complications, severe complications, or other complications. Healthcare resource utilization was significantly (p < 0.0001) lower in the FO vs. F+G/T cohort, with a mean reduction in hospital stay of 0.5 days, a 38-minute reduction in surgery time, and a 12-mL reduction in hemostat volume. Conclusion: In cervical/lumbar fusion cases, these findings indicate that the use of Floseal alone as compared to its use with Gelatin/Thrombin is associated with significant clinical benefits including less transfusion utilization and economic benefits of reduced hospital length-of-stay, surgery time, and hemostat volume use. These findings have significant implications for patient outcomes and healthcare cost, hence the need for well-controlled, clinical and cost-consequence studies to further elucidate these preliminary findings is necessary.

A323: Risk Factors & Associated Complications for Postoperative Urinary Retention After Lumbar Surgery for Lumbar Spinal Stenosis

Joshua Golubovsky¹, Haariss Ilyas², Jinxiao Chen³, Joseph Tanenbaum⁴, Thomas Mroz², Michael Steinmetz⁵

¹Center for Spine Health, Cleveland Clinic, Cleveland Clinic Lerner College of Medicine, Cleveland, OH - United States ²Center for Spine Health, Cleveland Clinic, Department of Orthopaedic Surgery, Cleveland, OH - United States ³Department of Epidemiology and Biostatistics, Case Western Reserve University Cleveland, OH - United States ⁴Center for Spine Health, Cleveland Clinic. Department of Epidemiology and Biostatistics, Case Western Reserve University School of Medicine, Cleveland - United States ⁵Center for Spine Health, Cleveland Clinic, Department of Neurological Surgery, Cleveland, OH - United States

Introduction: Postoperative Urinary Retention (POUR) is a very common post-operative complication of all surgeries (5-70%) that leads to complications such as urinary tract infection (UTI), bladder over-distention, autonomic dysregulation, and increased postoperative length of stay (LOS). Within the field of spine surgery, the reported incidence of POUR is highly variable (5.6-38%). Lack of clear stratification of surgical level, spinal pathology, and inadequate sample size is a major limitation of available studies concerning POUR following spine surgery that may lead to inconsistency in the incidence of POUR and the ability to model its occurrence and consequences. Additionally, limited data is available on the post-operative complications of POUR. Therefore, this study aims to study the incidence, predictive factors, and complications of POUR in patients undergoing elective posterior lumbar decompression with or without fusion for lumbar stenosis. Materials and Methods: A retrospective consecutive cohort analysis of all patients undergoing posterior lumbar decompression with or without fusion for lumbar stenosis with claudication from January 2014 through December 2015 was performed. Patients under the age of 18 and patients with spinal malignancies or infections were excluded. POUR was defined as re-insertion of a Foley catheter, use of straight catherization post-operatively, or by a clear medical diagnosis with pharmacological treatment. Statistical analysis was performed in RStudio. Multiple variable selection techniques were used to determine appropriate variables for regression models, and logistic models were fit to the development of POUR and post-operative complications, while a linear regression model was used for LOS. Results: Data was collected on 1592 consecutive patients. Among the sample population, the mean age at surgery was 67 (SD 10.1) and 45% of patients were female. The incidence of POUR was 17.1% (273/1592). Increased age (OR 1.037 (1.022, 1.052), p < 0.001), benign prostatic hyperplasia (BPH) (OR 1.898 (1.310, 2.748), p < 0.001), previous acute kidney injury (AKI) (OR 3.318(1.124, 9.393), p = 0.024), and previous UTI (OR 1.707 (1.254, 2.316), p < 0.001) significantly increased the probability of developing POUR. In an adjusted analysis, male gender, presence of neurodegenerative conditions, and surgical blood loss did not demonstrate increased risk for developing POUR. With respect to complications, POUR was found to be associated with development of UTI (OR 4.502 (3.148, 6.439), p < 0.001), sepsis (OR 4.073 (1.166, 13.619), p = 0.021), increased LOS (p < 0.001), increased likelihood to be discharged to a skilled nursing facility (p < 0.001), and increased risk for readmission within 90 days of the index surgery (OR 1.511 (1.048, 2.154), p = 0.024). Development of POUR did not increase the risk of developing AKI (p = 0.060) or a surgical site infection (p = 0.422). Conclusions: Overall, POUR was a significant risk factor for the development of UTI, sepsis, increased LOS, discharge to a skilled nursing facility, and readmission within 90 days. Surgeons and anesthesiologists should take preventative measures against POUR in individuals with increased age, BPH, and AKI and UTI within 90 days prior to surgery, as these factors were found to significantly increase the risk of POUR.

A324: Subacute Combined Degeneration of the Spinal Cord Following Nitrous-Oxide Anesthesia: A Systematic Review of the Literature

Kishan Patel¹, Juan Carlos Mejia Munne², Nitish Gunness³, Nabeel Alshafai³, Denise Hersey⁴, Joseph Cheng², Aria Nouri²

¹Department of Neurosurgery, Yale School of Medicine, New Haven - United States ²Department of Neurosurgery, University of Cincinnati College of Medicine, Cincinnati - United States ³Department of Neurosurgery, University of Toronto, Toronto - Canada ⁴Cushing/Whitney Medical Library, Yale School of Medicine, New Haven - United States

Introduction: Vitamin B12 (cobalamin) deficiency can lead to a form of myelopathy known as subacute combined degeneration (SCD), which is characterized by damage to the dorsal and lateral columns of the spinal cord. Nitrous oxide is an inhaled anesthetic which irreversibly oxidizes the cobalt ion of vitamin B12, interfering with its function as a key coenzyme. Although a number of individual case reports have described the development of SCD following nitrous oxide anesthesia, it is unknown what factors predispose patients to SCD or are predictive of long-term recovery. In this study, we conduct a systematic literature review of reported cases of SCD following nitrous oxide anesthesia. Materials and Methods: A medical librarian performed a comprehensive search of multiple databases after consultation with the lead authors and a Medical Subject Heading (MeSH) analysis of key articles provided by the research team. The final searches retrieved a total of 339 references, which were pooled in EndNote and de-duplicated to 148. 4 further studies were identified by examining the reference lists of all included articles. Two separate screeners (KP and AN) evaluated the titles, abstracts, and full texts of the eligible articles in a standardized manner. The following data were extracted from each eligible article: patient characteristics, the duration of nitrous oxide anesthesia, neurological findings, laboratory values, imaging factors, treatment, and recovery. Mann-Whitney U tests, Independent T-tests, and Chi Square tests were performed, with significance considered at p < 0.05 and trends considered at p < 0.15. Results: Our systematic search identified 152 unique articles. After screening these articles by title, abstract, and full-text, a total of 32 studies, reporting a total of 39 cases of nitrous oxide-induced SCD, were deemed relevant. These cases included 22 male patients and 17 female patients, with an average age of 51.3 years (SD 17.6). An etiology for subclinical deficiency, including pernicious anemia, atrophic gastritis, intestinal metaplasia, ileal resection, Crohn’s Disease, and nutritional deficiency, was determined in 31 reports, while there was no evidence of pre-operative deficiency in 8 reports. Duration of nitrous oxide exposure was described in 19 reports, and ranged from 30 minutes to 11 hours. Univariate analysis failed to find any association between post-operative recovery and age (p = 0.41), sex (p = 0.48), positive MRI findings (p = 0.42), and post-operative serum B12 (p = 0.96). However, there was a tendency of post-operative high Hemoglobin (p = 0.09) and post-operative high Mean Corpuscular Volume (p = 0.14) to relate with worse neurological recovery. Conclusions: Given the high prevalence of subclinical B12 deficiency and the potential for relatively short exposures to nitrous oxide to precipitate SCD, it is imperative that surgeons remain aware of this process. In patients with postsurgical myelopathy, the physician should evaluate serum B12 and consider the possibility that nitrous oxide could cause a subclinical B12 deficiency to become overt. Further, we recommend screening patients undergoing surgery for risk factors or signs of B12 deficiency to avoid post-operative myelopathy. Since we were limited by a small cohort in this study, the trends identified here will be important to study further with larger patient populations.

A325: The Incidence of Venous Thromboembolism in Patients Undergoing Anterior Lumbar Interbody Fusion. A Proposed Thromboprophylactic Regime

Ata Kasis¹, Helen Vint¹, Matthew Mawdsley¹, Cyrus Jensen¹

¹Department of Trauma and Orthopaedics, Northumbria Healthcare NHS Foundation Trust, Ashington - United Kingdom

Introduction: Deep vein thrombosis (DVT) and pulmonary embolism (PE) are recognised complications after spine surgery, with rates in the literature ranging from 0.7-5%. Pharmacological thromboprophylaxis can cause post-operative bleeding and haematomas which can result in neural compromise and wound complications. Anterior lumbar spine surgery involves the handling and compression of major abdominal vessels during surgery and this adds to the risk of venous thromboembolism (VTE). Herein we evaluate the incidence of VTE after Anterior Lumbar Interbody Fusion (ALIF) using a combination of mechanical and pharmacological thromboprophylaxis pre- and post-operatively. This regime was adopted from Gold Coast Spine, Australia. Material and Methods: A retrospective review of 160 consecutive patients who underwent ALIF for degenerative conditions 2013-2017. All patients had Low Molecular Weight Heparin (Tinzaparin) 4500 units subcutaneously on the evening before surgery, then daily for 3 to 5 days (whilst an in-patient) and then Aspirin 150 mg daily for 4 weeks after surgery. All patients wore Thrombo-Embolic Deterrent Stockings (TEDS) for a total of 6 weeks from the time of surgery. All patients had intermittent pneumatic compression of their calves and thighs (Flotron) intra-operatively and for 24 hours post-operatively. Patients were mobilised the morning after surgery. All patients were reviewed in the outpatient clinic at 2, 6, 24, and 52 weeks. The records of all patients were reviewed for the incidence of VTE. All patients were contacted by telephone to enquire if they had undergone any VTE investigations or treatments, in case patients had a VTE in between clinic appointments or in other hospitals. Results: 160 consecutive patients were included, with an average age of 44.8 (28-70.3) years. 93 patients were female. The ALIF was performed at L5/S1 in 82 patients, L4/5 in 65 patients, L4/5 and L5/S1 in 11 patients, one patient had revision of ALIF at L5/S1 and one patient had L3/4, L4/5 and L5/S1. 37 patients had surgery for spondylolisthesis, 13 for revision of posterior non-union, 27 for recurrent disc prolapse after discectomy, 48 for loss of disc height and neuroforaminal stenosis and 35 for degenerative disc disease. There was no incidence of any symptomatic VTE in the any of the 160 patients. There was no incidence of wound haematoma or bleeding, and no symptomatic retroperitoneal hematoma requiring intervention. There were 2 superficial wound infections treated with oral antibiotics, one of which required a Negative Pressure Wound Therapy (PICO) dressing for 10 days. Conclusion: The proposed VTE prophylactic regime is effective in preventing the incidence of symptomatic VTE in patients who underwent an ALIF procedure. Clearly, routine post-operative vein imaging would be needed to confirm the complete absence of VTE using this technique; however we have shown that it led to a reduction in the symptomatic VTE rate following ALIF surgery as compared with the general reported rates in the ALIF literature. In addition to the VTE prophylaxis, we think that minimising the time the abdominal vessels are under tension plays a role in reducing the incidence of VTE, however this was not investigated in this trial.

A326: Pre-Operative Dehydration Does Not Increase The Risk of Complications Following Elective Lumbar Surgery

Sean Mitchell¹, Andrew Chung², Joshua Hustedt¹, Robert Waldrop³, Norman Chutkan¹, Dennis Crandall³

¹Department of Orthopaedic Surgery, University of Arizona, Phoenix - United States ²Mayo Clinic, Scottsdale - United States ³Sonoran Spine, Phoenix - United States

Introduction: Pre-operative dehydration has long been associated with an increased risk of post-operative complications including deep vein thrombosis, wound infection, as well as general patient discomfort. Resultant longer lengths of stay following surgery have been reported. The effect of pre-operative dehydration on patients undergoing spine surgery has not been well-studied. Methods: A retrospective analysis of the ACS-NSQIP data was performed between 2006-2013. Patients undergoing elective lumbar surgery were selected using Current Procedural Terminology (CPT) codes. Emergency procedures, infections, tumor cases, revision surgeries, and patients with pre-existing renal disease were excluded. Dehydration was defined as a BUN/Creatinine ratio greater than 20. Outcomes assessed included post-operative complications, need for re-operation, lengths of stay, and rates of re-admission. Results: The incidence of pre-operative dehydration was 34.5% (4698 patients). Dehydration was common in the elderly (52.4% of patients greater than 80 years old compared to 17.6% in patients 18-49 years of age). Univariate analysis suggested that dehydration was associated with an increased risk of deep vein thrombosis, urinary tract infection, and need for transfusion. However, based on multivariate logistic regression models, pre-operative dehydration was not an independent risk factor for these complications (p < 0.05). Additionally, pre-operative dehydration was not associated with a longer length of stay post-operatively (p < 0.05). Conclusion: Pre-operative dehydration does not appear to be associated with poorer outcomes following elective lumbar spine surgery. Diligent peri-operative management of patient comorbidities should remain the priority.