Abstract
Study design
A prospective nonrandomized observational cohort study.
Objective
To compare the clinical efficacy of arthroscopic-assisted uniportal spinal surgery combined with unilateral laminotomy bilateral decompression (AUSS-ULBD) and minimally invasive transforaminal lumbar interbody fusion (MIS-TLIF) in the treatment of single-segment stable degenerative lumbar spondylolisthesis (DLS).
Methods
A total of 168 patients (AUSS-ULBD n = 86, MIS-TLIF n = 82) with single-segment stable DLS were included. The patients were followed up for at least 2 years. The primary outcome was Oswestry disability index (ODI). Other perioperative indicators, clinical, and radiological outcomes were also compared.
Results
For ODI, the adjusted mean differences (AUSS-ULBD minus MIS-TLIF) were 1.20 (95% CI −0.85 to 3.25) at 3 months, −1.74 (−3.65 to 0.17) at 12 months, and −0.68 (−2.79 to 1.43) at 24 months. The excellent and good rates of efficacy for the AUSS-ULBD and MIS-TLIF groups were 90.7% and 93.9%, respectively. AUSS-ULBD group had a higher reoperation rate than MIS-TLIF group (difference 4.7%, 95% CI −2.7% to 11.4%, P > .05). The operation time, blood loss, incision length, and hospital stay in the AUSS-ULBD group were lower than those in the MIS-TLIF group (P < .001). At 24 months, lumbar lordosis and slippage improved significantly after MIS-TLIF (P < .05), but not after AUSS-ULBD (P > .05).
Conclusions
In single-level, stable DLS, AUSS-ULBD offered advantages in operative morbidity, while achieving 2-year improvements in pain and disability that were comparable to those of MIS-TLIF. By contrast, MIS-TLIF showed better radiographic correction and lower reoperation rate that did not reach statistical significance.
Keywords
Introduction
Degenerative lumbar spondylolisthesis (DLS) is defined as the slippage of the upper vertebra in relation to the lower vertebra due to lumbar degenerative disorders. 1 It is frequently associated with neural canal and spinal stenosis, leading to symptoms such as low back pain, radiating leg pain, and intermittent claudication. 2 For patients who do not respond well to conservative treatment and are accompanied by neurological dysfunction, surgery represents an important treatment approach. The primary aim of DLS surgery is neural decompression, and there is currently a significant controversy regarding whether fusion is necessary following decompression.3-5
Posterior laminectomy directly decompresses the central canal, lateral recess, and intervertebral foramen by removing part or all of the lamina. Kgomotso et al demonstrated that the clinical efficacy of decompression alone was not inferior to that of decompression combined with instrumented fusion. 6 However, some scholars believe that decompression without fusion may compromise spinal stability and exacerbate lumbar spondylolisthesis. 7 The purpose of fusion is to maintain segmental stability, and correct spondylolisthesis and kyphotic deformity. 8 Kleinstueck et al showed that the improvement rates in terms of intermittent claudication, low back pain, and radiating leg pain were significantly higher in the decompression and fusion group compared to the decompression alone group. 9 In summary, the clinical effects of decompression alone or decompression combined with fusion in the treatment of DLS still warrant further investigation.10-12
With the widespread adoption of the minimally invasive concept, various minimally invasive decompression and minimally invasive fusion techniques have been extensively utilized in lumbar spine surgery due to their advantages, such as less trauma, faster recovery, and ease of operation. We previously proposed a novel spinal endoscopic technique, arthroscopic-assisted uni-portal spinal surgery (AUSS), also known as uni-portal non-coaxial spinal endoscopic surgery (UNSES). 13 This technique combines the unilateral dual-channel double holes of unilateral biportal endoscopy into a single hole, enabling the operator to independently manipulate the endoscope and instruments within the single hole. 14 A 30° arthroscope is employed to expand the observation field of view, and the available operating space is compatible with a variety of spinal surgery instruments.15,16 Therefore, using the AUSS technique for unilateral laminotomy bilateral decompression (ULBD) may represent an ideal lumbar decompression strategy. Additionally, minimally invasive surgery transforaminal lumbar interbody fusion (MIS-TLIF) is the most commonly used decompression fusion surgery, and its clinical efficacy has been widely demonstrated.17-19 However, whether there are differences in the efficacy of AUSS-ULBD and MIS-TLIF in the treatment of DLS remains unclear.
We conducted a prospective study to compare the surgical trauma, clinical, and radiological outcomes of AUSS-ULBD and MIS-TLIF in the treatment of single-segment DLS. The primary hypothesis was that AUSS-ULBD would achieve 2-year improvements in pain and disability that are comparable to those of MIS-TLIF and within clinically important margins. The secondary hypotheses were that AUSS-ULBD would yield a more favorable perioperative profile, whereas MIS-TLIF would achieve greater radiographic correction and a lower reoperation rate. This study aimed to contribute to the debate on whether fusion is necessary after DLS decompression and provide an alternative for surgical strategies.
Methods
Study Design and Population
This is a prospective cohort study. Initially, 180 patients (n = 90 per group) with single-segment DLS who underwent surgical treatment in our hospital from January 2020 to January 2023 were enrolled. This study was conducted in accordance with the guiding principles of the Declaration of Helsinki and written informed consent was obtained from each patient. The study was approved by the Ethics Committee of the Second Affiliated Hospital of Xi’an Jiaotong University (IRB approval: No. 2019521).
The inclusion criteria were as follows: (1) aged between 18 and 80 years; (2) typical leg-dominant lower-limb symptoms, including radicular pain, numbness, motor weakness, or neurogenic claudication; patients whose primary complaint was disabling mechanical low-back pain suggestive of frank instability were not included; (3) Meyerding grade 1-2, accompanied by central spinal canal stenosis and/or lateral recess stenosis, consistent with clinical symptoms and signs; (4) radiographic segmental stability on preoperative standing flexion–extension lateral radiographs (Δtranslation <3 mm and change in segmental angulation <10° at the index level)20-23; (5) ineffective conservative treatment, including physical therapy and non-steroidal anti-inflammatory drug intervention for more than 3 months. The exclusion criteria were as follows: (1) presence of severe cardiorespiratory dysfunction, hepatic and renal insufficiency, and other surgical contraindications; (2) existence of other lumbar diseases such as tumors, infections, and congenital malformations; (3) multi-segment lumbar diseases or a history of surgery at this segment.
Surgical Technique
This was a nonrandomized, preference-based cohort. After standardized counseling on the indications, benefits, and risks of AUSS-ULBD and MIS-TLIF, patients selected their preferred procedure, subject to confirmation of technical feasibility by the surgeon. All surgeries were performed by experienced spinal surgeons from the same team.
AUSS-ULBD
A longitudinal incision approximately 1.5 cm long was marked at the level of the responsible interspace along the line connecting the lateral margins of the upper and lower pedicles. A 4-mm diameter 30° arthroscope and sheath (Shenyang Shenda Endoscopy Co, Ltd, Shenyang, China) were inserted into the operation channel. Part of the ipsilateral lamina and the medial margin of the facet joint were removed. The hypertrophied ligamentum flavum was resected to fully expose the dural sac and nerve roots. When necessary, the hypertrophied posterior longitudinal ligament and free nucleus pulposus tissue were treated. The tissue at the base of the spinous process was resected, and contralateral recess decompression was performed. After bilateral decompression, the decompression effect of the spinal canal and the bilateral nerve roots was examined, and good pulsation of the dura mater and relaxation of the bilateral nerve roots were observed (Figure 1). The surgical procedure of the AUSS-ULBD for a 57-year-old woman at the L4–L5 level. (A-D) Preoperative anteroposterior, lateral, flexion, and extension lumbar spine X-rays. Standing flexion–extension lateral views demonstrated 1.3 mm of dynamic sagittal translation and 5.3° of change in segmental angulation at L4–L5. (E-F) Sagittal and axial preoperative lumbar spine MRI. (G) Axial preoperative lumbar spine CT. (H-M) Endoscopic decompression process, successively exposing the ligamentum flavum, ipsilateral intervertebral disc, ipsilateral nerve root decompression, contralateral intervertebral disc decompression, contralateral nerve root decompression, and full decompression of the dural sac. (N-O) Immediate postoperative three-dimensional reconstruction and axial lumbar spine CT. (P) Axial lumbar spine CT at 2 years postoperatively. (Q-R) Sagittal and axial lumbar spine MRI at 2 years postoperatively
MIS-TLIF
An incision approximately 3 cm long was made along the line connecting the lateral margins of the pedicles on the affected side. Positioning needles were inserted along the muscle interval for localization. A working channel was established to expose the facet joint. Part of the facet joint was resected, and the removed bone was used for interbody bone grafting. The ligamentum flavum was resected to expose the ipsilateral dural sac, nerve roots, and intervertebral disc. The intervertebral space was cleared, the cartilage endplate was scraped, and a suitable Cage was inserted into the intervertebral space. Percutaneous pedicle screws were inserted, and a connecting rod was placed. Fluoroscopy was performed again, and the position of the fusion device, screws, and connecting rod was found to be satisfactory (Figure 2). The surgical procedure of the MIS-TLIF for a 53-year-old man at the L4–L5 level. (A-D) Preoperative anteroposterior, lateral, flexion, and extension lumbar spine X-rays. Standing flexion–extension lateral views demonstrated 2.8 mm of dynamic sagittal translation and 7.4° of change in segmental angulation at L4–L5. (E-F) Sagittal and axial preoperative lumbar spine MRI. (G-H) Exposing the intervertebral disc and inserting the interbody cage. (I-J) Immediate postoperative anteroposterior and lateral lumbar spine X-rays. (K-L) Anteroposterior and lateral lumbar spine X-rays at 2 years postoperatively. (M-N) Sagittal and axial lumbar spine MRI at 2 years postoperatively. (O) Sagittal lumbar spine CT at 2 years postoperatively
Postoperative Management
Postoperatively, routine treatments such as pain relief, radicular edema control, and neurotrophic support were carried out. Radicular edema control comprised oral horse chestnut seed extract (150 mg) twice daily for 1-2 weeks; a short rescue course of corticosteroids was permitted only for marked radicular inflammation. After AUSS-ULBD, patients were encouraged to perform bed activities early (6-12 h after surgery) and gradually transition to short-distance walking within 24 h with the support of a lumbar brace. After MIS-TLIF, patients were strictly bedridden for 24-48 h and wore a lumbar brace for 8-12 weeks.
Outcome Assessment
Patients were followed up in the outpatient clinic at 3 months, 12 months, and 24 months after surgery. The visual analog scale (VAS) score for back and leg pain was recorded to evaluate the postoperative pain, and the Oswestry disability index (ODI) score was used to evaluate the postoperative lumbar function. At the last follow-up, the functional recovery effect was evaluated according to the modified MacNab criteria.
In addition, perioperative indicators were recorded, including operation time, estimated blood loss, incision length, hospital stay, intraoperative and postoperative complications. Lumbar lordosis and slippage rate were measured by lumbar X-ray preoperatively and 24 months after surgery. Radiographic fusion in MIS-TLIF group was assessed at 24 months by CT. Bridwell grades I-II were defined as fusion; 2 blinded spine surgeons graded the images with adjudication of discrepancies.
Statistical Analysis
Data analysis was performed using SPSS 25.0 statistical software. Continuous variables were first examined for normality using the Shapiro–Wilk test and Q–Q plots. The normally distributed variables were presented as mean ± standard deviation and were compared between groups using independent-samples t-tests, whereas skewed variables (eg, symptom duration) were presented as median (interquartile range) and were compared using the Mann–Whitney U test. Categorical variables were presented as counts (percentages) and were compared using the χ2 test.
For repeated measures (ODI and VAS), preliminary comparisons of unadjusted means between groups were performed using two-way repeated-measures ANOVA, and within-group pre- and post-operative changes were assessed using paired t-tests. The primary longitudinal analyses of between-group differences were then conducted using a Mixed-Effects Model for Repeated Measures (MMRM). Fixed effects included group, time, and their group-by-time interaction. A random intercept for each patient was specified to account for within-subject correlation. The age, sex, BMI, symptom duration, baseline ODI, and lumbar lordosis entered as covariates, which were chosen a priori based on clinical judgment and observed baseline imbalances. An unstructured covariance matrix and restricted maximum likelihood estimation were used. Model assumptions were assessed by visual inspection of residual Q–Q plots to check normality and residual-versus-fitted plots to check homoscedasticity and linearity. The primary effect size was expressed as the adjusted mean difference between groups defined as AUSS-ULBD minus MIS-TLIF, together with 95% confidence intervals (CI).
The primary endpoint was ODI. An 8-point difference in ODI was prespecified as a clinical interpretive margin corresponding to the minimal clinically important difference (MCID) and was used to aid interpretation of the adjusted between-group differences and their 95% confidence intervals.24,25 VAS-back and VAS-leg were prespecified as key secondary endpoints and were analyzed using the same MMRM. An interpretive clinical margin of 1.2 points (back pain) and 1.6 points (leg pain) was prespecified. 26 Sample size was based on the primary endpoint using two-sample mean-difference formulas (one-sided α = 0.025, 80% power), with an 8-point between-group difference in ODI as clinically important, an assumed common SD of 18, and 1:1 allocation.
Results
Baseline Characteristics
Baseline Patient Characteristics
AUSS, arthroscopic-assisted uniportal spinal surgery; ULBD, unilateral laminotomy bilateral decompression; MIS-TLIF, minimally invasive transforaminal lumbar interbody fusion; BMI, body mass index.
Postoperative Pain and Functional Scores
Adjusted Mean Differences of ODI and VAS Scores
MD was defined as AUSS-ULBD minus MIS-TLIF. Adjusted MD was calculated used Mixed Model for Repeated Measures (MMRM). The age, sex, BMI, symptom duration, baseline ODI, and lumbar lordosis entered as covariates. The overall group-by-time interaction was tested by a likelihood-ratio test under maximum likelihood estimation.
VAS, visual analog scale; ODI, Oswestry disability index; MD, mean difference; CI, confidence interval.
According to the modified Macnab criteria, the excellent and good rates of efficacy for the AUSS-ULBD and MIS-TLIF groups were 90.7% and 93.9%, respectively (difference −3.2%, 95% CI −14.7% to 8.7%, P > .05). At the last follow-up, 4 patients (4.7%) in the AUSS-ULBD group underwent reoperation, and there were no cases of reoperation in the MIS-TLIF group (difference 4.7%, 95% CI −2.7% to 11.4%, P > .05). Reoperation was undertaken for low back pain or radicular symptoms attributable to recurrent stenosis, progression to instability, or inadequate initial decompression. All cases were converted to instrumented fusion, with favorable postoperative recovery.
Perioperative Parameters
Perioperative Parameters of Patients
AUSS, arthroscopic-assisted uniportal spinal surgery; ULBD, unilateral laminotomy bilateral decompression; MIS-TLIF, minimally invasive transforaminal lumbar interbody fusion; MD, mean difference; CI, confidence interval.
Imaging Parameters
Imaging Parameters of Patients
AUSS, arthroscopic-assisted uniportal spinal surgery; ULBD, unilateral laminotomy bilateral decompression; MIS-TLIF, minimally invasive transforaminal lumbar interbody fusion; MD, mean difference; CI, confidence interval.
*P < .05 vs preoperative data.
Discussion
Whether decompression alone or decompression with fusion is preferable for DLS remains debated.27-30 In this prospective observational comparative cohort restricted to single-level, dynamically stable DLS, we comprehensively compared AUSS-ULBD and MIS-TLIF with respect to perioperative morbidity, radiographic parameters, and 2-year patient-reported outcomes. The results demonstrated that AUSS-ULBD was associated with less surgical trauma but achieved less radiographic correction and showed a higher—though not statistically significant—reoperation rate. More importantly, 2-year functional and pain scores were comparable between groups. These findings suggest that, in appropriately selected, dynamically stable DLS, motion-preserving decompression can yield clinical outcomes comparable to fusion while minimizing operative morbidity.
Most DLS patients are elderly and may be accompanied by various medical conditions. 31 Minimal surgical trauma and anesthesia time are crucial for patients. Our findings showed that the operation time, intraoperative blood loss, incision length, and hospital stay in the AUSS-ULBD group were significantly lower than those in the MIS-TLIF group, indicating that the AUSS-ULBD technique has the advantages of minimal trauma and accelerated recovery. 32 These advantages likely owes to AUSS-ULBD causing less paraspinal and facet disruption.
Notably, we noticed that AUSS-ULBD achieved less radiographic correction yet yielded similar functional outcomes to MIS-TLIF, suggesting that radiographic improvement may not always translate into better patient-reported outcomes.33,34
In stable single-level DLS with radiculopathy-predominant symptoms, adequate neural decompression may yield good clinical outcomes without large gains in alignment. Thus, AUSS-ULBD may reduce peri-operative burden at the expense of less radiographic correction and a modestly higher revision risk. 35 However, radiographic correction likely matters most for mechanical back pain, progression of instability, or long-term maintenance of sagittal balance. MIS-TLIF restores disc height and enables coronal/sagittal correction at the cost of motion loss and implant-related risks. Therefore, patients with overt or progressive segmental instability, greater deformity, or a need for alignment restoration may benefit more from fusion.
Försth et al compared the effects of decompression alone and decompression fusion in the treatment of DLS. 36 The results showed that the treatment effects of the two surgical methods were comparable, but the operation and hospital stay were shorter in the decompression-alone group. Hua et al. compared the clinical efficacy of ULBD under lumbar endoscopy and MIS-TLIF in the treatment of single-segment lumbar spinal stenosis. 32 Their study showed shorter operative time, less blood loss, and a shorter hospital stay with ULBD than with MIS-TLIF, with no significant differences in VAS or ODI. These results are consistent with those of our study. 37
In recent years, with the development of the minimally invasive concept and endoscopic technology, minimally invasive techniques have become increasingly important in the treatment of DLS.38,39 Our team previously proposed a novel endoscopic technique, namely AUSS/UNSES, which has the advantages of minimal trauma, clear vision, and flexible operation, and has been proven to be effective in the treatment of lumbar disc herniation, lumbar spinal stenosis, and other diseases.13,16,40,41 In the future, the AUSS technique may have more applicable scenarios to meet the needs of more lumbar spine surgeries.
This study has some limitations. First, as a nonrandomized, preference-based observational cohort, the study is susceptible to selection bias; despite covariate adjustment, residual and unmeasured confounding may remain. Second, this study only compared AUSS-ULBD and MIS-TLIF, which limits the generalizability of the conclusions. Finally, the patients included in this study had single-segment DLS and lumbar stability. Whether decompression alone is feasible for multi-segment or lumbar unstable patients still needs further study.
Conclusion
In single-level, dynamically stable DLS, AUSS-ULBD offered advantages in operative morbidity and recovery, while achieving 2-year improvements in pain and disability that were comparable to those of MIS-TLIF and within the prespecified clinically important margins. By contrast, MIS-TLIF achieved superior radiographic correction and lower reoperation rate, though difference of reoperation rate was not statistically significant. Longer-term follow-up and randomized trials are needed to confirm these findings.
Supplemental Material
Supplemental Material - Uni-Portal Spinal Surgery vs MIS-TLIF for Single-Level Stable Degenerative Lumbar Spondylolisthesis: A Prospective Cohort Study
Supplemental Material for Uni-Portal Spinal Surgery vs MIS-TLIF for Single-Level Stable Degenerative Lumbar Spondylolisthesis: A Prospective Cohort Study by Fang Wang, Jie Li, Chengyi Zhang, Bo Zhang, Jizheng Li, Kening Sun, Dong Wang, Xijing He, En Song, and Fengtao Li in Global Spine Journal.
Footnotes
Consent to Participate
Informed consent was obtained from all individual participants included in the study.
Author Contributions
Conceptualization: En Song and Fengtao Li; Methodology: Fang Wang, Jie Li, Chengyi Zhang; Writing - original draft preparation: Fang Wang and Jie Li; Writing - review and editing: Bo Zhang, Jizheng Li, Kening Sun, Dong Wang, and Xijing He. All authors read and approved the final manuscript.
Funding
The authors disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This work was supported by the Natural Science Basic Research Program of Shaanxi (2024JC-YBMS-702), the Key Research and Development Program of Shaanxi (2024SF-YBXM-382), the Yunnan Revitalization Talent Support Program, and Yunnan health training project of high level talents (H-2024084), and UNSES Multi-Omics Cooperative Technology Promotion Project of CHPF(2025-SRXY-0216).
Declaration of Conflicting Interests
The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Data Availability Statement
The datasets used during the current study are available from the corresponding author on reasonable request.
IRB Approval
The study was performed according to the Helsinki Declaration and approved by the Ethics Committee of the Second Affiliated Hospital of Xi’an Jiaotong University (No. 2019521).
Supplemental Material
Supplemental material for this article is available online.
Appendix
References
Supplementary Material
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