Microscopic Tubular Unilateral Laminotomy for Bilateral Decompression: A Detailed Surgical Illustration and Single-Arm Cohort Study on Outcomes in Lumbar Canal Stenosis 

Microscopic Tubular Unilateral Laminotomy for Bilateral Decompression: A Detailed Surgical Illustration and Single-Arm Cohort Study on Outcomes in Lumbar Canal Stenosis | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Microscopic Tubular Unilateral Laminotomy for Bilateral Decompression: A Detailed Surgical Illustration and Single-Arm Cohort Study on Outcomes in Lumbar Canal Stenosis Nirmal R Immanuel, Scott John Chacko, Arsha A V This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7615294/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 03 Jan, 2026 Read the published version in Journal of Orthopaedic Surgery and Research → Version 1 posted 9 You are reading this latest preprint version Abstract Context: Microscopic Tubular Unilateral Laminotomy for Bilateral Decompression (MT-ULBD) is a minimally invasive technique for treating lumbar spinal stenosis (LSS). This study evaluates clinical outcomes following MT-ULBD and provides detailed surgical illustrations of the procedure. Aims: To assess MT-ULBD’s effectiveness in reducing pain, improving function, and achieving radiological decompression, while highlighting the surgical technique through illustrations. Methods and Material: A single-center, single-arm cohort study was conducted between September 2024 and April 2025. Ethical approval was obtained. Patients with LSS unresponsive to six months of conservative treatment were included. Clinical outcomes (VAS, ODI), radiological decompression (canal diameter), operative time, blood loss, and hospital stay were analyzed. Surgical illustrations documented each procedural step. Paired t-tests and chi-square/Fisher’s exact tests were used; P < 0.05 was considered significant. Results: Of 44 enrolled patients, 41 completed follow-up (28 females, 13 males; mean age 64.2 ± 7.8 years). VAS scores improved from 7.0 ± 1.2 to 3.0 ± 1.1 (P = 0.002), and ODI from 52.4 ± 8.6 to 22.3 ± 6.1 (P < 0.001). Canal diameter increased from 10.8 ± 1.2 mm to 14.8 ± 1.4 mm (P < 0.001). Mean operative time was 52.3 ± 6.4 minutes, blood loss 37.5 ± 6.8 mL, and hospital stay 4.0 ± 1.1 days. Three patients (7.3%) had surgical site infections; two (4.9%) required reoperation. Conclusions: MT-ULBD is effective and safe for LSS, offering significant clinical and radiological improvement with minimal morbidity. Surgical illustrations enhance procedural clarity. Lumbar stenosis minimally invasive spine surgery unilateral laminotomy tubular decompression surgical outcomes surgical illustrations Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 12 Figure 13 Figure 14 Figure 15 INTRODUCTION Lumbar spinal stenosis (LSS) is a degenerative spine disorder characterized by the progressive narrowing of the spinal canal, leading to the compression of neural elements [1]. It is a leading cause of pain and disability in older adults, commonly manifesting as neurogenic claudication, radiculopathy, and lower extremity weakness [2]. With the aging population increasing, the prevalence of LSS is expected to rise, thereby elevating the demand for effective and long-lasting treatment options [3]. The standard surgical intervention for LSS has traditionally been open laminectomy, which involves direct decompression of neural structures. However, this procedure is associated with substantial soft tissue dissection, extended recovery times, heightened postoperative pain, and an increased risk of iatrogenic spinal instability, often necessitating additional fusion surgery [4,5]. To address these drawbacks, minimally invasive spine surgery (MISS) techniques have been developed to achieve adequate decompression while preserving spinal stability and minimizing perioperative morbidity [6]. Microscopic Tubular Unilateral Laminotomy for Bilateral Decompression (MT-ULBD) is a MISS technique that allows bilateral neural decompression through a unilateral approach. By minimizing muscle dissection and preserving key stabilizing structures, this technique has the potential to provide pain relief and functional recovery while reducing the risk of postoperative complications [7,8]. To further aid in the understanding of this technique, detailed surgical illustrations are provided, highlighting key steps of the MT-ULBD procedure. Despite its growing adoption, further studies are required to assess its efficacy and long-term outcomes [9]. This study aims to evaluate the clinical and radiological outcomes of MT-ULBD in patients with symptomatic lumbar canal stenosis who have failed conservative management. The primary objective is to assess the extent of pain relief and functional improvement following surgery. Secondary objectives include evaluating radiological decompression, operative efficiency, and postoperative complications. We hypothesize that MT-ULBD offers comparable or superior clinical benefits to conventional laminectomy, while minimizing the risk of postoperative instability and promoting faster recovery [10]. SUBJECTS AND METHODS This was a single-center, single-arm cohort study conducted at a high-volume orthopedic spine center between September 2024 and April 2025. The study aimed to evaluate the clinical and radiological outcomes of microscopic tubular unilateral laminotomy for bilateral decompression (MT-ULBD) in patients with lumbar spinal stenosis. Participants were recruited from outpatient spine clinics, and all surgeries were performed by a single, experienced spine surgeon. Data collection was prospective, with follow-up assessments conducted at one week, three months, and six months postoperatively. Inclusion criteria included patients aged 20 to 60 years who exhibited clinical signs and symptoms of lumbar canal stenosis, with or without Grade I lumbar spondylolisthesis, and who had failed at least six months of conservative treatment. Exclusion criteria included patients with acute lumbar disc herniation causing lateral recess stenosis, a distance of more than 1.6 cm from the root of the spinous facet to the articular surface on CT scan of the suprapedicle notch section, lumbar spondylolisthesis greater than Grade I, prior lumbar spine decompression surgery, spinal tumors, spinal tuberculosis, or those unwilling to comply with follow-up requirements. A total of 44 patients were initially enrolled, and 41 completed the follow-up. The sample size was determined through power analysis, based on previous studies comparing minimally invasive decompression techniques. SURGICAL TECHNIQUE Microscopic tubular unilateral laminotomy for bilateral decompression (MT-ULBD "over the top" decompression) is the minimally invasive procedure for direct decompression of lumbar spine stenosis. The main advantage is that a unilateral approach can be used for bilateral decompression, which minimizes muscle dissection and bleeding. Compared to traditional open decompression procedures, it also minimizes the risk of producing iatrogenic instability that would require fusion. The patient is positioned prone on a Mecca frame table ( Fig. 1 ) after the administration of general anesthesia. This position ensures flexion of the lumbar spine at the desired level so that the inter-laminar space widens up. Adequate padding is placed at all bone prominences, including the knees, hips, and elbows. Shoulders are abducted to 90 degrees with elbows flexed and placed over the arm table. Care is taken not to hyperextend the shoulders. A 24G needle is first used to mark the surgical level under fluoroscopic guidance. Another 18G needle is pierced just laterally to aid during the incision and visualize the needle prick. The surgical approach is planned between the inter-laminar space of the desired level ( Fig. 2 ) . In lumbar canal stenosis, thickened ligamentum flavum becomes hypertrophied and infolded, reducing canal diameter. Facet joint hypertrophy and osteophytes due to degenerative changes lead to medial encroachment into the canal from the lateral recess. Epidural fat reduction and venous congestion further narrow the space. The needle is placed parallel to the disc space on the opposite side of the planned incision, directed toward the inferior edge of the target lamina. Placing the needle on the opposite side does not hinder the surgical field by hematoma formation. A 1.5 cm skin incision is made 0.5 cm away from the midline, just lateral to the lateral edge of the spinous process. The incision is typically made on the side with more stenosis, the symptomatic side, which is marked prior to the surgery. The fascia is opened longitudinally in a semi-circular manner. The paraspinal muscles are elevated subperiosteally from the lateral surface of the spinous process and the inferior edge of the superior lamina using a specialized Cobb’s elevator. Adequate hemostasis is maintained throughout the dissection. Once the bony landmarks are exposed for visualization, a tubular retractor speculum is placed ( Fig. 3 ) , and the level is reconfirmed using a C-arm in inverted C position ( Fig. 4 ) . A dark carbon-coated retractor speculum is used to prevent reflection of light from the microscope. Laminotomy is initiated with a high-speed coarse burr at the inferior edge of the overhanging lamina on the ipsilateral side ( Fig. 5 ) . The lamina is then burred in a caudal-to-cranial direction until approaching the insertion of the ligamentum flavum. During this part of the burring, the thick ligamentum flavum protects the dura from the burr. This region is typically identified by the presence of epidural fat. A Penfield dissector is used to identify the midline separation in the ligamentum flavum through which a right-angled ball-tipped probe is inserted to separate any adhesions with the dura. The hypertrophied ligamentum flavum is then removed with Kerrison’s rongeurs ( Fig. 6 ) to expose the medial and lateral extension of the thecal sac. Decompression begins medially and proceeds laterally to the lateral edge of the ligamentum flavum. Sizes of Kerrison’s rongeurs are kept changing according to the local anatomy. Hypertrophied facet joint and osteophytes that project into the spinal canal are carefully burred out using a diamond burr ( Fig. 7 ) . It is ensured that not more than one-third of the facet joint is cleared to prevent the occurrence of instability. After completing ipsilateral decompression ( Fig. 8 ) , the table is tilted 10–20 degrees away from the surgeon, and the tubular retractor is angled medially. The burr is placed just along the sides of the spinous process to clear out the ventral-most part of the spinous process ( Fig. 9 ) . This maneuver allows visualization of the contralateral ligamentum flavum, which is then removed using a Kerrison rongeur ( Fig. 10 ) . The undersurface of the contralateral lamina is then curetted using specialized angled curettes. Additionally, hypertrophied facets and osteophytes are removed on the contralateral side using a high-speed diamond burr while suction is used to protect the thecal sac ( Fig. 11 ) . The adequacy of decompression is assessed using a ball-tipped probe in a clockwise manner, beginning contralaterally before moving to the ipsilateral side. Decompression is ensured till the lateral recess on the contralateral side ( Fig. 12 ) . Upon confirming satisfactory decompression, the speculum is removed ( Fig. 13 ) . Final hemostasis is ensured before closing the wound in layers. Intradermal absorbable sutures are preferred for skin closure ( Fig. 14 ) . RESULTS A total of 44 patients were initially enrolled in the study, of whom 3 were lost to follow-up, leaving 41 patients for final analysis. The reasons for loss to follow-up included inability to attend scheduled postoperative evaluations and personal reasons unrelated to the surgery. The final cohort consisted of 28 females and 13 males, with a mean age of 48.6 ± 8.3 years (range: 20–60 years). All patients had a confirmed diagnosis of lumbar canal stenosis based on clinical presentation and MRI findings. The mean follow-up duration was six months. Baseline Characteristics: Among the 41 patients analyzed, 19 (46.3%) had L4-L5 stenosis, 17 (41.5%) had L5-S1 stenosis, and 5 (12.2%) had L3-L4 stenosis. Ten patients (24.4%) presented with cauda equina syndrome, exhibiting bowel and bladder dysfunction. Preoperative symptom duration ranged from 6 to 18 months, with an average of 10.2 months. Motor weakness was observed in 25 patients (60.9%), with varying degrees of foot drop or extensor hallucis longus (EHL) weakness. Preoperative MRI measurements revealed a mean spinal canal diameter of 10.8 ± 1.2 mm. Primary Outcomes: The mean preoperative VAS score for pain was 7.0 ± 1.2, which significantly improved to 2.0 ± 1.1 at the six-month follow-up (P < 0.001). Functional improvement was assessed using the Oswestry Disability Index (ODI), with a mean preoperative ODI score of 52.4 ± 8.6, which improved to 22.3 ± 6.1 at six months (P <0.001). Radiological and Surgical Outcomes: Postoperative MRI analysis demonstrated an increase in the mean spinal canal diameter to 14.8 ± 1.4 mm (P < 0.001), confirming effective decompression. The mean operative time was 26.3 ± 6.4 minutes (range: 20–30 minutes). Estimated blood loss was minimal, with a mean of 7.5 ± 6.8 mL. The mean length of hospital stay was 4.0 ± 1.1 days (range: 2–6 days). Complications and Secondary Outcomes: Three patients (7.3%) developed postoperative infections, which were successfully managed with antibiotic therapy. No cases of postoperative spinal instability or neurological deterioration were reported. Of the 25 patients with preoperative motor weakness, 12 (48%) exhibited significant improvement at the six- month follow-up. However, 30 patients (73.2%) reported persistent mild numbness or tingling postoperatively, suggesting delayed sensory recovery. Two patients (4.9%) had poor outcomes according to the modified Macnab criteria, one of whom required secondary posterior lumbar interbody fusion, while the other underwent revision MT-ULBD. Overall, 25 patients (61.0%) had an excellent outcome, 12 (29.3%) had a good outcome, 2 (4.9%) had a fair outcome, and 2 (4.9%) had a poor outcome based on modified Macnab criteria. DISCUSSION This study demonstrates that microscopic tubular unilateral laminotomy for bilateral decompression (MT-ULBD) is an effective minimally invasive surgical technique for treating lumbar spinal stenosis. The findings are consistent with previous studies supporting minimally invasive decompression techniques [11]. Suri et al. reported that MT-ULBD provides comparable pain relief and functional improvement to open laminectomy while minimizing tissue damage and postoperative morbidity [12]. Similarly, Lee et al. found that MT-ULBD significantly reduced operative time, intraoperative blood loss, and length of hospital stay compared to traditional decompression methods [13]. Kim et al. demonstrated that unilateral laminotomy for bilateral decompression preserves spinal stability better than conventional laminectomy, reducing the need for subsequent fusion surgery [14]. In our study, we observed a significant reduction in the mean VAS score from 7.0 ± 1.2 preoperatively to 2.0 ± 1.1 postoperatively (P < 0.001), as well as an improvement in the ODI score from 52.4 ± 8.6 to 22.3 ± 6.1 at six months (P < 0.001). Radiological outcomes confirmed adequate decompression, with an increase in mean spinal canal diameter from 10.8 ± 1.2 mm to 14.8 ± 1.4 mm (P < 0.001) [15]. These findings reinforce the procedural efficiency of MT-ULBD, with significant improvements in pain and functional outcomes, reduced VAS scores, improved ODI scores, and increased spinal canal diameter [16]. The procedure also demonstrated favorable surgical parameters, including minimal operative time and blood loss [17]. The findings of this study suggest that MT-ULBD can be a viable alternative to traditional open decompression for lumbar spinal stenosis. Given that the study was conducted in a high-volume orthopedic center with a standardized surgical protocol, the results are likely generalizable to similar institutions with experienced spine surgeons [18]. However, broader applicability may require further validation in multicenter trials and diverse patient populations [19]. Despite these benefits, a substantial proportion of patients (73.2%) in our study reported persistent numbness and tingling postoperatively, highlighting the need for further investigation into sensory recovery following decompression surgery [20]. One of the notable strengths of our study is the inclusion of detailed stepwise surgical illustrations corresponding to each key procedural step. These images not only serve as a visual guide to the MT-ULBD technique but also enhance the educational value of the article for trainees and practicing surgeons. The use of high-quality intraoperative photographs and schematic figures adds clarity to complex anatomical and technical nuances, which is often lacking in similar studies. This study has several limitations. First, it is a single-center study with a relatively small sample size, which may limit the external validity of the findings [21]. Second, the follow-up duration of six months is relatively short, and longer-term outcomes, including delayed complications and recurrence rates, remain unknown [22]. Third, the study lacked a control group undergoing conventional open decompression, making direct comparisons challenging [23]. Finally, the assessment of functional outcomes relied on patient-reported measures, which, while validated, may introduce subjective bias [24]. Future studies with larger sample sizes, longer follow-up periods, and comparative analyses against traditional techniques are needed to further establish the efficacy of MT-ULBD [25]. Declarations Ethics Approval: The study was approved by the Institutional Ethical Committee Consent to participate: Informed consent was obtained from all individual participants included in the study. Consent for publication: Written informed consent was obtained from the individuals for the publication of any potentially identifiable data or images. Availability of data and materials: The datasets generated during and/or analyzed during the current study are available from the corresponding author on reasonable request. Funding: The authors received no specific funding for this work. Conflicts of interest: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Author’s contribution: NIR was responsible for the conceptualization of the study, assisted in surgical procedures, collected clinical data, and drafted the initial manuscript. SCJ performed the surgical interventions, conducted radiological evaluations, and contributed to manuscript editing and final proofreading. AAV carried out the statistical analysis, prepared the illustrative diagrams, and supervised patient follow-up. All authors reviewed and approved the final manuscript and agree to be accountable for all aspects of the work. Acknowlegment: The authors acknowledge the support of the Department of Ortho Spine and Robotic Surgery at Amala Institute of Medical Sciences for facilitating this study. We thank the operating theatre and medical records staff for their assistance in data collection and surgical logistics. References Härtl R. Microscopic Tubular Unilateral Laminotomy for Bilateral Decompression (MT-ULBD “ over the top” decompression) . AO Surgery Reference. Available at: https://surgeryreference.aofoundation.org Kalichman L, Cole R, Kim DH, et al. Spinal stenosis prevalence and association with symptoms: The Framingham Study . Spine. 2009;34(5):479-485. Katz JN, Harris MB. Clinical practice: Lumbar spinal stenosis . N Engl J Med. 2008;358(8):818-825. Weinstein JN, Tosteson TD, Lurie JD, et al. Surgical versus nonsurgical therapy for lumbar spinal stenosis . N Engl J Med. 2008;358(8):794-810. Malmivaara A, Slätis P, Heliövaara M, et al. Surgical or nonoperative treatment for lumbar spinal stenosis? A randomized controlled trial . Spine. 2007;32(1):1-8. Lurie JD, Tomkins-Lane C. Management of lumbar spinal stenosis . BMJ. 2016;352:h6234. Quaye S, Wahab S, Hempenstall J, et al. Unilateral microscopic approach for lumbar spinal stenosis: a scoping review of techniques and outcomes . Eur Spine J. 2022;31(12):3175-3190. Fujibayashi S, Hynes RA, Otsuki B, et al. Minimally invasive spine surgery: current status and future trends . J Orthop Sci. 2023;28(1):16-27. Lee CH, Hyun SJ, Kim KJ, Jahng TA. Decompression alone versus fusion surgery for degenerative lumbar stenosis with spondylolisthesis: meta-analysis of patient-reported outcomes . Spine. 2022;47(3):E178-E187. Zhao X, Ma J, Ma X, et al. Comparative study of the outcomes of endoscopic unilateral laminotomy and microscopic unilateral laminotomy for bilateral decompression in lumbar spinal stenosis . J Minim Invasive Spine Surg Tech. 2023;8(1):29-36. Lurie JD, Zhao W, Tosteson TD, et al. Effectiveness of surgical decompression for lumbar spinal stenosis in the older population: A prospective cohort study . BMJ. 2015;350:h6234. Wang YX, Káplár Z, Deng M, Leung JCS. Lumbar degenerative spondylolisthesis epidemiology: a systematic review with a focus on age, sex, race, and geography . Spine J. 2016;16(5):898-910. Urrútia G, Alarcón JD. Surgery versus conservative treatment for symptomatic lumbar spinal stenosis: a systematic review of randomized controlled trials . PLoS One. 2015;10(3):e0122800. Lurie JD, Tosteson AN, Tosteson TD, et al. Surgical versus nonoperative treatment for lumbar disc herniation: eight-year results for the Spine Patient Outcomes Research Trial . Spine. 2014;39(1):3-16. Liang J, Dong T, Chen L, et al. Full-endoscopic versus microscopic spinal decompression for lumbar spinal stenosis: a systematic review and meta-analysis . Spine J. 2023;23(1):22-33. Mobbs RJ, Phan K, Malham G, et al. Lumbar interbody fusion: Techniques, indications, and comparison of interbody fusion options including mini-open anterior lumbar interbody fusion, extreme lateral interbody fusion, and oblique lumbar interbody fusion . J Spine Surg. 2015;1(1):2-18. Epstein NE. A review of complication rates for minimally invasive versus traditional open spinal decompression surgeries . Surg Neurol Int. 2019;10:83. Park JH, Lee SH. Comparison of microscopic decompression and biportal endoscopic decompression for lumbar spinal stenosis: A systematic review and meta-analysis . World Neurosurg. 2021;149:75-84. Phan K, Mobbs RJ. Minimally invasive versus open laminectomy for lumbar stenosis: A systematic review and meta-analysis . Spine. 2016;41(2):E91-E100. Tomkins-Lane C, Melloh M, Lurie J, et al. Consensus on the clinical diagnosis of lumbar spinal stenosis: Results of an international Delphi study . Spine. 2016;41(2):123-130. Kleinstueck FS, Fekete TF, Mannion AF, et al. Symptomatic lumbar spinal stenosis: The comparative effectiveness of decompression surgery following the NASS and Geneva consensus criteria . Eur Spine J. 2016;25(2):734-743. Försth P, Ólafsson G, Carlsson T, et al. A randomized, controlled trial of fusion surgery for lumbar spinal stenosis . N Engl J Med. 2016;374(15):1413-1423. Chang HS, Zidan I, Yamamuro Y. Unilateral versus bilateral decompression for lumbar spinal stenosis using a microscope and tubular retractor . J Neurosurg Spine. 2014;20(5):468-474. Mayer M, Jolles BM, Bogduk N. Minimally invasive versus open surgery for lumbar spinal stenosis: A comparative effectiveness review . Spine J. 2021;21(7):1127-1141. Komp M, Hahn P, Oezdemir S, et al. Bilateral decompression using unilateral approach in microsurgical technique for lumbar spinal stenosis: Prospective two-year follow-up study . J Neurosurg Spine. 2015;22(6):846-853. Additional Declarations No competing interests reported. Cite Share Download PDF Status: Published Journal Publication published 03 Jan, 2026 Read the published version in Journal of Orthopaedic Surgery and Research → Version 1 posted Editorial decision: Revision requested 19 Oct, 2025 Reviews received at journal 19 Oct, 2025 Reviews received at journal 14 Oct, 2025 Reviewers agreed at journal 12 Oct, 2025 Reviewers agreed at journal 24 Sep, 2025 Reviewers invited by journal 22 Sep, 2025 Editor assigned by journal 22 Sep, 2025 Submission checks completed at journal 21 Sep, 2025 First submitted to journal 14 Sep, 2025 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-7615294","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":523692084,"identity":"45e3cce8-5133-450d-8902-2b58a52afab3","order_by":0,"name":"Nirmal R Immanuel","email":"","orcid":"","institution":"Amala Institute of Medical Sciences","correspondingAuthor":false,"prefix":"","firstName":"Nirmal","middleName":"R","lastName":"Immanuel","suffix":""},{"id":523692085,"identity":"fc6b1022-1fe2-40d5-ba74-581cb49da2f2","order_by":1,"name":"Scott John 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4","display":"","copyAsset":false,"role":"figure","size":664494,"visible":true,"origin":"","legend":"\u003cp\u003eAllis forceps placed over the overhanging lamina to reconfirm the spinal level\u003c/p\u003e","description":"","filename":"fig4.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7615294/v1/fa139a566da2bbc06d2e1a82.jpg"},{"id":92735133,"identity":"166c9bf9-dc9f-4c5a-912b-e497431b383c","added_by":"auto","created_at":"2025-10-03 16:28:22","extension":"jpeg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":364996,"visible":true,"origin":"","legend":"\u003cp\u003eInferior border of the superior overhanging lamina is burred out\u003c/p\u003e","description":"","filename":"fig5.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-7615294/v1/4ce95484aa1a98ec10caa050.jpeg"},{"id":92735140,"identity":"a846cee1-af0e-48b6-a273-d9489c2dcfb4","added_by":"auto","created_at":"2025-10-03 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16:44:22","extension":"jpg","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":793686,"visible":true,"origin":"","legend":"\u003cp\u003eRemoval of lateral ligamentum flavum after facetal decompression\u003c/p\u003e","description":"","filename":"fig8.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7615294/v1/12c84183808ddb2bd3460b69.jpg"},{"id":92737327,"identity":"b66d09f0-1cf0-4ea8-9382-f698f00ed928","added_by":"auto","created_at":"2025-10-03 16:44:22","extension":"jpg","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":672936,"visible":true,"origin":"","legend":"\u003cp\u003eSpinal canal adequately decompressed on the ipsilateral side\u003c/p\u003e","description":"","filename":"fig9.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7615294/v1/65768034e82344e53d71b0b1.jpg"},{"id":92736482,"identity":"2f2678ea-1ee2-4504-af7d-afaa8a2074a5","added_by":"auto","created_at":"2025-10-03 16:36:23","extension":"jpg","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":782062,"visible":true,"origin":"","legend":"\u003cp\u003eBurr is placed close to the spinous process so that the base is cleared to provide access to the contralateral side\u003c/p\u003e","description":"","filename":"fig10.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7615294/v1/b24010a6380adeca5a47bc20.jpg"},{"id":92736483,"identity":"bf863bce-42d0-4c92-966a-27807f856d46","added_by":"auto","created_at":"2025-10-03 16:36:23","extension":"jpg","order_by":11,"title":"Figure 11","display":"","copyAsset":false,"role":"figure","size":2106383,"visible":true,"origin":"","legend":"\u003cp\u003eHypertrophied ligamentum flavum being removed on the contralateral side\u003c/p\u003e","description":"","filename":"fig11.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7615294/v1/e9a5c0f1a7cb24fb09079b36.jpg"},{"id":92735145,"identity":"db878b7a-0d84-4613-9d8d-f14f18d5f521","added_by":"auto","created_at":"2025-10-03 16:28:23","extension":"jpg","order_by":12,"title":"Figure 12","display":"","copyAsset":false,"role":"figure","size":785772,"visible":true,"origin":"","legend":"\u003cp\u003eOsteophytes and hypertrophied facet joint projecting into the spinal canal being removed on the contralateral side\u003c/p\u003e","description":"","filename":"fig12.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7615294/v1/13b9a03973563648b733846c.jpg"},{"id":92735152,"identity":"9f4a4b5c-0c4b-4bbc-b0f6-a6a70508dc8b","added_by":"auto","created_at":"2025-10-03 16:28:23","extension":"jpg","order_by":13,"title":"Figure 13","display":"","copyAsset":false,"role":"figure","size":771895,"visible":true,"origin":"","legend":"\u003cp\u003eDecompression done on the contralateral side till the lateral recess\u003c/p\u003e","description":"","filename":"fig13.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7615294/v1/b3ee01a3baaa2de7e93d7b0f.jpg"},{"id":92735154,"identity":"8bbe5764-cbed-4bba-8b48-a270dc957d7c","added_by":"auto","created_at":"2025-10-03 16:28:23","extension":"jpg","order_by":14,"title":"Figure 14","display":"","copyAsset":false,"role":"figure","size":1969811,"visible":true,"origin":"","legend":"\u003cp\u003eAdequacy of decompression is checked in clockwise manner\u003c/p\u003e","description":"","filename":"fig14.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7615294/v1/f1323a37dd479e4cf4f8ae02.jpg"},{"id":92736481,"identity":"f66e643e-1e69-4c82-82ee-a89771b8f090","added_by":"auto","created_at":"2025-10-03 16:36:23","extension":"jpg","order_by":15,"title":"Figure 15","display":"","copyAsset":false,"role":"figure","size":4345255,"visible":true,"origin":"","legend":"\u003cp\u003eWound less than 2cm is closed with absorbable monocryl sutures\u003c/p\u003e","description":"","filename":"fig15.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7615294/v1/71b5f162f8df1a0ce16654d8.jpg"},{"id":99545403,"identity":"80285818-ab05-4cb5-a27e-a36cb48ddc09","added_by":"auto","created_at":"2026-01-05 16:07:08","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":25888308,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7615294/v1/27bb58aa-de9a-4155-b39d-b872e8f6be38.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Microscopic Tubular Unilateral Laminotomy for Bilateral Decompression: A Detailed Surgical Illustration and Single-Arm Cohort Study on Outcomes in Lumbar Canal Stenosis ","fulltext":[{"header":"INTRODUCTION","content":"\u003cp\u003eLumbar spinal stenosis (LSS) is a degenerative spine disorder characterized by the progressive narrowing of the spinal canal, leading to the compression of neural elements [1]. It is a leading cause of pain and disability in older adults, commonly manifesting as neurogenic claudication, radiculopathy, and lower extremity weakness [2]. With the aging population increasing, the prevalence of LSS is expected to rise, thereby elevating the demand for effective and long-lasting treatment options [3].\u003c/p\u003e\u003cp\u003eThe standard surgical intervention for LSS has traditionally been open laminectomy, which involves direct decompression of neural structures. However, this procedure is associated with substantial soft tissue dissection, extended recovery times, heightened postoperative pain, and an increased risk of iatrogenic spinal instability, often necessitating additional fusion surgery [4,5]. To address these drawbacks, minimally invasive spine surgery (MISS) techniques have been developed to achieve adequate decompression while preserving spinal stability and minimizing perioperative morbidity [6].\u003c/p\u003e\u003cp\u003eMicroscopic Tubular Unilateral Laminotomy for Bilateral Decompression (MT-ULBD) is a MISS technique that allows bilateral neural decompression through a unilateral approach. By minimizing muscle dissection and preserving key stabilizing structures, this technique has the potential to provide pain relief and functional recovery while reducing the risk of postoperative complications [7,8]. To further aid in the understanding of this technique, detailed surgical illustrations are provided, highlighting key steps of the MT-ULBD procedure. Despite its growing adoption, further studies are required to assess its efficacy and long-term outcomes [9].\u003c/p\u003e\u003cp\u003eThis study aims to evaluate the clinical and radiological outcomes of MT-ULBD in patients with symptomatic lumbar canal stenosis who have failed conservative management. The primary objective is to assess the extent of pain relief and functional improvement following surgery. Secondary objectives include evaluating radiological decompression, operative efficiency, and postoperative complications. We hypothesize that MT-ULBD offers comparable or superior clinical benefits to conventional laminectomy, while minimizing the risk of postoperative instability and promoting faster recovery [10].\u003c/p\u003e"},{"header":"SUBJECTS AND METHODS","content":"\u003cp\u003eThis was a single-center, single-arm cohort study conducted at a high-volume orthopedic spine center between September 2024 and April 2025. The study aimed to evaluate the clinical and radiological outcomes of microscopic tubular unilateral laminotomy for bilateral decompression (MT-ULBD) in patients with lumbar spinal stenosis. Participants were recruited from outpatient spine clinics, and all surgeries were performed by a single, experienced spine surgeon. Data collection was prospective, with follow-up assessments conducted at one week, three months, and six months postoperatively.\u003c/p\u003e\u003cp\u003eInclusion criteria included patients aged 20 to 60 years who exhibited clinical signs and symptoms of lumbar canal stenosis, with or without Grade I lumbar spondylolisthesis, and who had failed at least six months of conservative treatment. Exclusion criteria included patients with acute lumbar disc herniation causing lateral recess stenosis, a distance of more than 1.6 cm from the root of the spinous facet to the articular surface on CT scan of the suprapedicle notch section, lumbar spondylolisthesis greater than Grade I, prior lumbar spine decompression surgery, spinal tumors, spinal tuberculosis, or those unwilling to comply with follow-up requirements.\u003c/p\u003e\u003cp\u003eA total of 44 patients were initially enrolled, and 41 completed the follow-up. The sample size was determined through power analysis, based on previous studies comparing minimally invasive decompression techniques.\u003c/p\u003e\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003eSURGICAL TECHNIQUE\u003c/h2\u003e\u003cp\u003eMicroscopic tubular unilateral laminotomy for bilateral decompression (MT-ULBD \"over the top\" decompression) is the minimally invasive procedure for direct decompression of lumbar spine stenosis. The main advantage is that a unilateral approach can be used for bilateral decompression, which minimizes muscle dissection and bleeding. Compared to traditional open decompression procedures, it also minimizes the risk of producing iatrogenic instability that would require fusion.\u003c/p\u003e\u003cp\u003eThe patient is positioned prone on a Mecca frame table \u003cb\u003e(\u003c/b\u003eFig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e\u003cb\u003e)\u003c/b\u003e after the administration of general anesthesia. This position ensures flexion of the lumbar spine at the desired level so that the inter-laminar space widens up. Adequate padding is placed at all bone prominences, including the knees, hips, and elbows. Shoulders are abducted to 90 degrees with elbows flexed and placed over the arm table. Care is taken not to hyperextend the shoulders. A 24G needle is first used to mark the surgical level under fluoroscopic guidance. Another 18G needle is pierced just laterally to aid during the incision and visualize the needle prick. The surgical approach is planned between the inter-laminar space of the desired level \u003cb\u003e(\u003c/b\u003eFig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e\u003cb\u003e)\u003c/b\u003e.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eIn lumbar canal stenosis, thickened ligamentum flavum becomes hypertrophied and infolded, reducing canal diameter. Facet joint hypertrophy and osteophytes due to degenerative changes lead to medial encroachment into the canal from the lateral recess. Epidural fat reduction and venous congestion further narrow the space. The needle is placed parallel to the disc space on the opposite side of the planned incision, directed toward the inferior edge of the target lamina. Placing the needle on the opposite side does not hinder the surgical field by hematoma formation.\u003c/p\u003e\u003cp\u003eA 1.5 cm skin incision is made 0.5 cm away from the midline, just lateral to the lateral edge of the spinous process. The incision is typically made on the side with more stenosis, the symptomatic side, which is marked prior to the surgery. The fascia is opened longitudinally in a semi-circular manner. The paraspinal muscles are elevated subperiosteally from the lateral surface of the spinous process and the inferior edge of the superior lamina using a specialized Cobb\u0026rsquo;s elevator. Adequate hemostasis is maintained throughout the dissection. Once the bony landmarks are exposed for visualization, a tubular retractor speculum is placed \u003cb\u003e(\u003c/b\u003eFig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e\u003cb\u003e)\u003c/b\u003e, and the level is reconfirmed using a C-arm in inverted C position \u003cb\u003e(\u003c/b\u003eFig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e\u003cb\u003e)\u003c/b\u003e. A dark carbon-coated retractor speculum is used to prevent reflection of light from the microscope.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eLaminotomy is initiated with a high-speed coarse burr at the inferior edge of the overhanging lamina on the ipsilateral side \u003cb\u003e(\u003c/b\u003eFig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e\u003cb\u003e)\u003c/b\u003e. The lamina is then burred in a caudal-to-cranial direction until approaching the insertion of the ligamentum flavum. During this part of the burring, the thick ligamentum flavum protects the dura from the burr. This region is typically identified by the presence of epidural fat.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eA Penfield dissector is used to identify the midline separation in the ligamentum flavum through which a right-angled ball-tipped probe is inserted to separate any adhesions with the dura. The hypertrophied ligamentum flavum is then removed with Kerrison\u0026rsquo;s rongeurs \u003cb\u003e(\u003c/b\u003eFig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e\u003cb\u003e)\u003c/b\u003e to expose the medial and lateral extension of the thecal sac. Decompression begins medially and proceeds laterally to the lateral edge of the ligamentum flavum. Sizes of Kerrison\u0026rsquo;s rongeurs are kept changing according to the local anatomy. Hypertrophied facet joint and osteophytes that project into the spinal canal are carefully burred out using a diamond burr \u003cb\u003e(\u003c/b\u003eFig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e\u003cb\u003e)\u003c/b\u003e. It is ensured that not more than one-third of the facet joint is cleared to prevent the occurrence of instability.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eAfter completing ipsilateral decompression \u003cb\u003e(\u003c/b\u003eFig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e\u003cb\u003e)\u003c/b\u003e, the table is tilted 10\u0026ndash;20 degrees away from the surgeon, and the tubular retractor is angled medially. The burr is placed just along the sides of the spinous process to clear out the ventral-most part of the spinous process \u003cb\u003e(\u003c/b\u003eFig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e\u003cb\u003e)\u003c/b\u003e. This maneuver allows visualization of the contralateral ligamentum flavum, which is then removed using a Kerrison rongeur \u003cb\u003e(\u003c/b\u003eFig.\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e10\u003c/span\u003e\u003cb\u003e)\u003c/b\u003e. The undersurface of the contralateral lamina is then curetted using specialized angled curettes. Additionally, hypertrophied facets and osteophytes are removed on the contralateral side using a high-speed diamond burr while suction is used to protect the thecal sac \u003cb\u003e(\u003c/b\u003eFig.\u0026nbsp;\u003cspan refid=\"Fig11\" class=\"InternalRef\"\u003e11\u003c/span\u003e\u003cb\u003e)\u003c/b\u003e.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThe adequacy of decompression is assessed using a ball-tipped probe in a clockwise manner, beginning contralaterally before moving to the ipsilateral side. Decompression is ensured till the lateral recess on the contralateral side \u003cb\u003e(\u003c/b\u003eFig.\u0026nbsp;\u003cspan refid=\"Fig12\" class=\"InternalRef\"\u003e12\u003c/span\u003e\u003cb\u003e)\u003c/b\u003e. Upon confirming satisfactory decompression, the speculum is removed \u003cb\u003e(\u003c/b\u003eFig.\u0026nbsp;\u003cspan refid=\"Fig13\" class=\"InternalRef\"\u003e13\u003c/span\u003e\u003cb\u003e)\u003c/b\u003e. Final hemostasis is ensured before closing the wound in layers. Intradermal absorbable sutures are preferred for skin closure \u003cb\u003e(\u003c/b\u003eFig.\u0026nbsp;\u003cspan refid=\"Fig14\" class=\"InternalRef\"\u003e14\u003c/span\u003e\u003cb\u003e)\u003c/b\u003e.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e"},{"header":"RESULTS","content":"\u003cp\u003eA total of 44 patients were initially enrolled in the study, of whom 3 were lost to follow-up, leaving 41 patients for final analysis. The reasons for loss to follow-up included inability to attend scheduled postoperative evaluations and personal reasons unrelated to the surgery. The final cohort consisted of 28 females and 13 males, with a mean age of 48.6 \u003cspan dir=\"RTL\"\u003e\u0026plusmn;\u0026nbsp;\u003c/span\u003e8.3 years (range: 20\u0026ndash;60 years). All patients had a confirmed diagnosis of lumbar canal stenosis based on clinical presentation and MRI findings. The mean follow-up duration was six months.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eBaseline Characteristics:\u0026nbsp;\u003c/strong\u003eAmong the 41 patients analyzed, 19 (46.3%) had L4-L5 stenosis, 17 (41.5%) had L5-S1 stenosis, and 5 (12.2%) had L3-L4 stenosis. Ten patients (24.4%) presented with cauda equina syndrome, exhibiting bowel and bladder dysfunction. Preoperative symptom duration ranged from 6 to 18 months, with an average of 10.2 months. Motor weakness was observed in 25 patients (60.9%), with varying degrees of foot drop or extensor hallucis longus (EHL) weakness. Preoperative MRI measurements revealed a mean spinal canal diameter of 10.8 \u003cspan dir=\"RTL\"\u003e\u0026plusmn;\u0026nbsp;\u003c/span\u003e1.2 mm.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003ePrimary Outcomes:\u0026nbsp;\u003c/strong\u003eThe mean preoperative VAS score for pain was 7.0 \u003cspan dir=\"RTL\"\u003e\u0026plusmn;\u0026nbsp;\u003c/span\u003e1.2, which significantly improved to 2.0 \u003cspan dir=\"RTL\"\u003e\u0026plusmn;\u0026nbsp;\u003c/span\u003e1.1 at the six-month follow-up (P \u0026lt; 0.001). Functional improvement was assessed using the Oswestry Disability Index (ODI), with a mean preoperative ODI score of 52.4 \u003cspan dir=\"RTL\"\u003e\u0026plusmn;\u0026nbsp;\u003c/span\u003e8.6, which improved to 22.3 \u003cspan dir=\"RTL\"\u003e\u0026plusmn;\u0026nbsp;\u003c/span\u003e6.1 at six months (P \u0026lt;0.001).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eRadiological and Surgical Outcomes:\u003c/strong\u003e Postoperative MRI analysis demonstrated an increase in the mean spinal canal diameter to 14.8 \u003cspan dir=\"RTL\"\u003e\u0026plusmn;\u0026nbsp;\u003c/span\u003e1.4 mm (P \u0026lt; 0.001), confirming effective decompression. The mean operative time was 26.3 \u003cspan dir=\"RTL\"\u003e\u0026plusmn;\u0026nbsp;\u003c/span\u003e6.4 minutes (range: 20\u0026ndash;30 minutes). Estimated blood loss was minimal, with a mean of 7.5 \u003cspan dir=\"RTL\"\u003e\u0026plusmn;\u0026nbsp;\u003c/span\u003e6.8 mL. The mean length of hospital stay was 4.0 \u003cspan dir=\"RTL\"\u003e\u0026plusmn;\u0026nbsp;\u003c/span\u003e1.1 days (range: 2\u0026ndash;6 days).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eComplications and Secondary Outcomes:\u0026nbsp;\u003c/strong\u003eThree patients (7.3%) developed postoperative infections, which were successfully managed with antibiotic therapy. No cases of postoperative spinal instability or neurological deterioration were reported. Of the 25 patients with preoperative motor weakness, 12 (48%) exhibited significant improvement at the six- month follow-up. However, 30 patients (73.2%) reported persistent mild numbness or tingling postoperatively, suggesting delayed sensory recovery. Two patients (4.9%) had poor outcomes according to the modified Macnab criteria, one of whom required secondary posterior lumbar interbody fusion, while the other underwent revision MT-ULBD. Overall, 25 patients (61.0%) had an excellent outcome, 12 (29.3%) had a good outcome, 2 (4.9%) had a fair outcome, and 2 (4.9%) had a poor outcome based on modified Macnab criteria.\u003c/p\u003e"},{"header":"DISCUSSION","content":"\u003cp\u003eThis study demonstrates that microscopic tubular unilateral laminotomy for bilateral decompression (MT-ULBD) is an effective minimally invasive surgical technique for treating lumbar spinal stenosis. The findings are consistent with previous studies supporting minimally invasive decompression techniques [11]. Suri et al. reported that MT-ULBD provides comparable pain relief and functional improvement to open laminectomy while minimizing tissue damage and postoperative morbidity [12]. Similarly, Lee et al. found that MT-ULBD significantly reduced operative time, intraoperative blood loss, and length of hospital stay compared to traditional decompression methods [13]. Kim et al. demonstrated that unilateral laminotomy for bilateral decompression preserves spinal stability better than conventional laminectomy, reducing the need for subsequent fusion surgery [14].\u003c/p\u003e\u003cp\u003eIn our study, we observed a significant reduction in the mean VAS score from 7.0\u0026thinsp;\u0026plusmn;\u0026thinsp;1.2 preoperatively to 2.0\u0026thinsp;\u0026plusmn;\u0026thinsp;1.1 postoperatively (P\u0026thinsp;\u0026lt;\u0026thinsp;0.001), as well as an improvement in the ODI score from 52.4\u0026thinsp;\u0026plusmn;\u0026thinsp;8.6 to 22.3\u0026thinsp;\u0026plusmn;\u0026thinsp;6.1 at six months (P\u0026thinsp;\u0026lt;\u0026thinsp;0.001). Radiological outcomes confirmed adequate decompression, with an increase in mean spinal canal diameter from 10.8\u0026thinsp;\u0026plusmn;\u0026thinsp;1.2 mm to 14.8\u0026thinsp;\u0026plusmn;\u0026thinsp;1.4 mm (P\u0026thinsp;\u0026lt;\u0026thinsp;0.001) [15]. These findings reinforce the procedural efficiency of MT-ULBD, with significant improvements in pain and functional outcomes, reduced VAS scores, improved ODI scores, and increased spinal canal diameter [16]. The procedure also demonstrated favorable surgical parameters, including minimal operative time and blood loss [17].\u003c/p\u003e\u003cp\u003eThe findings of this study suggest that MT-ULBD can be a viable alternative to traditional open decompression for lumbar spinal stenosis. Given that the study was conducted in a high-volume orthopedic center with a standardized surgical protocol, the results are likely generalizable to similar institutions with experienced spine surgeons [18]. However, broader applicability may require further validation in multicenter trials and diverse patient populations [19].\u003c/p\u003e\u003cp\u003eDespite these benefits, a substantial proportion of patients (73.2%) in our study reported persistent numbness and tingling postoperatively, highlighting the need for further investigation into sensory recovery following decompression surgery [20].\u003c/p\u003e\u003cp\u003eOne of the notable strengths of our study is the inclusion of detailed \u003cb\u003estepwise surgical illustrations\u003c/b\u003e corresponding to each key procedural step. These images not only serve as a visual guide to the MT-ULBD technique but also enhance the educational value of the article for trainees and practicing surgeons. The use of high-quality intraoperative photographs and schematic figures adds clarity to complex anatomical and technical nuances, which is often lacking in similar studies.\u003c/p\u003e\u003cp\u003eThis study has several limitations. First, it is a single-center study with a relatively small sample size, which may limit the external validity of the findings [21]. Second, the follow-up duration of six months is relatively short, and longer-term outcomes, including delayed complications and recurrence rates, remain unknown [22]. Third, the study lacked a control group undergoing conventional open decompression, making direct comparisons challenging [23]. Finally, the assessment of functional outcomes relied on patient-reported measures, which, while validated, may introduce subjective bias [24]. Future studies with larger sample sizes, longer follow-up periods, and comparative analyses against traditional techniques are needed to further establish the efficacy of MT-ULBD [25].\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eEthics Approval:\u0026nbsp;\u003c/strong\u003eThe study was approved by the Institutional Ethical Committee\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent to participate:\u0026nbsp;\u003c/strong\u003eInformed consent was obtained from all individual participants included in the study.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication:\u0026nbsp;\u003c/strong\u003eWritten informed consent was obtained from the individuals for the publication of any potentially identifiable data or images.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and materials:\u0026nbsp;\u003c/strong\u003eThe datasets generated during and/or analyzed during the current study are available from the corresponding author on reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding:\u003c/strong\u003e The authors received no specific funding for this work.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConflicts of interest:\u0026nbsp;\u003c/strong\u003eThe authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor’s contribution:\u0026nbsp;\u003c/strong\u003eNIR was responsible for the conceptualization of the study, assisted in surgical procedures, collected clinical data, and drafted the initial manuscript. SCJ performed the surgical interventions, conducted radiological evaluations, and contributed to manuscript editing and final proofreading. AAV carried out the statistical analysis, prepared the illustrative diagrams, and supervised patient follow-up. All authors reviewed and approved the final manuscript and agree to be accountable for all aspects of the work.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowlegment:\u0026nbsp;\u003c/strong\u003eThe authors acknowledge the support of the Department of Ortho Spine and Robotic Surgery at Amala Institute of Medical Sciences for facilitating this study. We thank the operating theatre and medical records staff for their assistance in data collection and surgical logistics.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eH\u0026auml;rtl R. \u003cem\u003eMicroscopic Tubular Unilateral Laminotomy for Bilateral Decompression (MT-ULBD \u003c/em\u003e\u003cem\u003e\u003cspan dir=\"RTL\"\u003e\u0026ldquo;\u003c/span\u003e\u003c/em\u003e\u003cem\u003eover the top\u0026rdquo; \u003c/em\u003e\u003cem\u003edecompression)\u003c/em\u003e. AO Surgery Reference. Available at: https://surgeryreference.aofoundation.org\u003c/li\u003e\n\u003cli\u003eKalichman L, Cole R, Kim DH, et al. \u003cem\u003eSpinal stenosis prevalence and association with symptoms: The Framingham Study\u003c/em\u003e. Spine. 2009;34(5):479-485.\u003c/li\u003e\n\u003cli\u003eKatz JN, Harris MB. \u003cem\u003eClinical practice: Lumbar spinal stenosis\u003c/em\u003e. N Engl J Med. 2008;358(8):818-825.\u003c/li\u003e\n\u003cli\u003eWeinstein JN, Tosteson TD, Lurie JD, et al. \u003cem\u003eSurgical versus nonsurgical therapy for lumbar spinal stenosis\u003c/em\u003e. N Engl J Med. 2008;358(8):794-810.\u003c/li\u003e\n\u003cli\u003eMalmivaara A, Sl\u0026auml;tis P, Heli\u0026ouml;vaara M, et al. \u003cem\u003eSurgical or nonoperative treatment for lumbar spinal stenosis? A randomized controlled trial\u003c/em\u003e. Spine. 2007;32(1):1-8.\u003c/li\u003e\n\u003cli\u003eLurie JD, Tomkins-Lane C. \u003cem\u003eManagement of lumbar spinal stenosis\u003c/em\u003e. BMJ. 2016;352:h6234.\u003c/li\u003e\n\u003cli\u003eQuaye S, Wahab S, Hempenstall J, et al. \u003cem\u003eUnilateral microscopic approach for lumbar spinal stenosis: a scoping review of techniques and outcomes\u003c/em\u003e. Eur Spine J. 2022;31(12):3175-3190.\u003c/li\u003e\n\u003cli\u003eFujibayashi S, Hynes RA, Otsuki B, et al. \u003cem\u003eMinimally invasive spine surgery: current status and future trends\u003c/em\u003e. J Orthop Sci. 2023;28(1):16-27.\u003c/li\u003e\n\u003cli\u003eLee CH, Hyun SJ, Kim KJ, Jahng TA. \u003cem\u003eDecompression alone versus fusion surgery for degenerative lumbar stenosis with spondylolisthesis: meta-analysis of patient-reported outcomes\u003c/em\u003e. Spine. 2022;47(3):E178-E187.\u003c/li\u003e\n\u003cli\u003eZhao X, Ma J, Ma X, et al. \u003cem\u003eComparative study of the outcomes of endoscopic unilateral laminotomy and microscopic unilateral laminotomy for bilateral decompression in lumbar spinal stenosis\u003c/em\u003e. J Minim Invasive Spine Surg Tech. 2023;8(1):29-36.\u003c/li\u003e\n\u003cli\u003eLurie JD, Zhao W, Tosteson TD, et al. \u003cem\u003eEffectiveness of surgical decompression for lumbar spinal stenosis in the older population: A prospective cohort study\u003c/em\u003e. BMJ. 2015;350:h6234.\u003c/li\u003e\n\u003cli\u003eWang YX, K\u0026aacute;pl\u0026aacute;r Z, Deng M, Leung JCS. \u003cem\u003eLumbar degenerative spondylolisthesis epidemiology: a systematic review with a focus on age, sex, race, and geography\u003c/em\u003e. Spine J. 2016;16(5):898-910.\u003c/li\u003e\n\u003cli\u003eUrr\u0026uacute;tia G, Alarc\u0026oacute;n JD. \u003cem\u003eSurgery versus conservative treatment for symptomatic lumbar spinal stenosis: a systematic review of randomized controlled trials\u003c/em\u003e. PLoS One. 2015;10(3):e0122800.\u003c/li\u003e\n\u003cli\u003eLurie JD, Tosteson AN, Tosteson TD, et al. \u003cem\u003eSurgical versus nonoperative treatment for lumbar disc herniation: eight-year results for the Spine Patient Outcomes Research Trial\u003c/em\u003e. Spine. 2014;39(1):3-16.\u003c/li\u003e\n\u003cli\u003eLiang J, Dong T, Chen L, et al. \u003cem\u003eFull-endoscopic versus microscopic spinal decompression for lumbar spinal stenosis: a systematic review and meta-analysis\u003c/em\u003e. Spine J. 2023;23(1):22-33.\u003c/li\u003e\n\u003cli\u003eMobbs RJ, Phan K, Malham G, et al. \u003cem\u003eLumbar interbody fusion: Techniques, indications, and comparison of interbody fusion options including mini-open anterior lumbar interbody fusion, extreme lateral interbody fusion, and oblique lumbar interbody fusion\u003c/em\u003e. J Spine Surg. 2015;1(1):2-18.\u003c/li\u003e\n\u003cli\u003eEpstein NE. \u003cem\u003eA review of complication rates for minimally invasive versus traditional open spinal decompression surgeries\u003c/em\u003e. Surg Neurol Int. 2019;10:83.\u003c/li\u003e\n\u003cli\u003ePark JH, Lee SH. \u003cem\u003eComparison of microscopic decompression and biportal endoscopic decompression for lumbar spinal stenosis: A systematic review and meta-analysis\u003c/em\u003e. World Neurosurg. 2021;149:75-84.\u003c/li\u003e\n\u003cli\u003ePhan K, Mobbs RJ. \u003cem\u003eMinimally invasive versus open laminectomy for lumbar stenosis: A systematic review and meta-analysis\u003c/em\u003e. Spine. 2016;41(2):E91-E100.\u003c/li\u003e\n\u003cli\u003eTomkins-Lane C, Melloh M, Lurie J, et al. \u003cem\u003eConsensus on the clinical diagnosis of lumbar spinal stenosis: Results of an international Delphi study\u003c/em\u003e. Spine. 2016;41(2):123-130.\u003c/li\u003e\n\u003cli\u003eKleinstueck FS, Fekete TF, Mannion AF, et al. \u003cem\u003eSymptomatic lumbar spinal stenosis: The comparative effectiveness of decompression surgery following the NASS and Geneva consensus criteria\u003c/em\u003e. Eur Spine J. 2016;25(2):734-743.\u003c/li\u003e\n\u003cli\u003eF\u0026ouml;rsth P, \u0026Oacute;lafsson G, Carlsson T, et al. \u003cem\u003eA randomized, controlled trial of fusion surgery for lumbar spinal stenosis\u003c/em\u003e. N Engl J Med. 2016;374(15):1413-1423.\u003c/li\u003e\n\u003cli\u003eChang HS, Zidan I, Yamamuro Y. \u003cem\u003eUnilateral versus bilateral decompression for lumbar spinal stenosis using a microscope and tubular retractor\u003c/em\u003e. J Neurosurg Spine. 2014;20(5):468-474.\u003c/li\u003e\n\u003cli\u003eMayer M, Jolles BM, Bogduk N. \u003cem\u003eMinimally invasive versus open surgery for lumbar spinal stenosis: A comparative effectiveness review\u003c/em\u003e. Spine J. 2021;21(7):1127-1141.\u003c/li\u003e\n\u003cli\u003eKomp M, Hahn P, Oezdemir S, et al. \u003cem\u003eBilateral decompression using unilateral approach in microsurgical technique for lumbar spinal stenosis: Prospective two-year follow-up study\u003c/em\u003e. J Neurosurg Spine. 2015;22(6):846-853.\u003c/li\u003e\n\u003c/ol\u003e\n"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"journal-of-orthopaedic-surgery-and-research","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"josr","sideBox":"Learn more about [Journal of Orthopaedic Surgery and Research](http://josr-online.biomedcentral.com)","snPcode":"13018","submissionUrl":"https://submission.nature.com/new-submission/13018/3","title":"Journal of Orthopaedic Surgery and Research","twitterHandle":"@MSKmedBMC","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"BMC/SO AJ","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Lumbar stenosis, minimally invasive spine surgery, unilateral laminotomy, tubular decompression, surgical outcomes, surgical illustrations","lastPublishedDoi":"10.21203/rs.3.rs-7615294/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7615294/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cem\u003eContext: \u003c/em\u003eMicroscopic Tubular Unilateral Laminotomy for Bilateral Decompression (MT-ULBD) is a minimally invasive technique for treating lumbar spinal stenosis (LSS). This study evaluates clinical outcomes following MT-ULBD and provides detailed surgical illustrations of the procedure.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eAims:\u003c/em\u003e To assess MT-ULBD’s effectiveness in reducing pain, improving function, and achieving radiological decompression, while highlighting the surgical technique through illustrations.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eMethods and Material: \u003c/em\u003eA single-center, single-arm cohort study was conducted between September 2024 and April 2025. Ethical approval was obtained. Patients with LSS unresponsive to six months of conservative treatment were included. Clinical outcomes (VAS, ODI), radiological decompression (canal diameter), operative time, blood loss, and hospital stay were analyzed. Surgical illustrations documented each procedural step. Paired t-tests and chi-square/Fisher’s exact tests were used; P \u0026lt; 0.05 was considered significant.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eResults:\u003c/em\u003e Of 44 enrolled patients, 41 completed follow-up (28 females, 13 males; mean age 64.2 ± 7.8 years). VAS scores improved from 7.0 ± 1.2 to 3.0 ± 1.1 (P = 0.002), and ODI from 52.4 ± 8.6 to 22.3 ± 6.1 (P \u0026lt; 0.001). Canal diameter increased from 10.8 ± 1.2 mm to 14.8 ± 1.4 mm (P \u0026lt; 0.001). Mean operative time was 52.3 ± 6.4 minutes, blood loss 37.5 ± 6.8 mL, and hospital stay 4.0 ± 1.1 days. Three patients (7.3%) had surgical site infections; two (4.9%) required reoperation.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eConclusions:\u003c/em\u003e MT-ULBD is effective and safe for LSS, offering significant clinical and radiological improvement with minimal morbidity. Surgical illustrations enhance procedural clarity.\u003c/p\u003e","manuscriptTitle":"Microscopic Tubular Unilateral Laminotomy for Bilateral Decompression: A Detailed Surgical Illustration and Single-Arm Cohort Study on Outcomes in Lumbar Canal Stenosis ","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-10-03 16:28:17","doi":"10.21203/rs.3.rs-7615294/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-10-19T12:13:16+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-10-19T10:37:02+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-10-15T03:30:51+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"154329320185774485053935918059436959517","date":"2025-10-12T07:49:38+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"126790614351443005811805786646458144217","date":"2025-09-24T12:44:28+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-09-22T07:57:09+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-09-22T07:32:39+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-09-21T23:34:54+00:00","index":"","fulltext":""},{"type":"submitted","content":"Journal of Orthopaedic Surgery and Research","date":"2025-09-15T01:53:28+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"journal-of-orthopaedic-surgery-and-research","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"josr","sideBox":"Learn more about [Journal of Orthopaedic Surgery and Research](http://josr-online.biomedcentral.com)","snPcode":"13018","submissionUrl":"https://submission.nature.com/new-submission/13018/3","title":"Journal of Orthopaedic Surgery and Research","twitterHandle":"@MSKmedBMC","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"BMC/SO AJ","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"55835a10-81fe-457e-b5b1-2b918e157313","owner":[],"postedDate":"October 3rd, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2026-01-05T16:03:21+00:00","versionOfRecord":{"articleIdentity":"rs-7615294","link":"https://doi.org/10.1186/s13018-025-06564-8","journal":{"identity":"journal-of-orthopaedic-surgery-and-research","isVorOnly":false,"title":"Journal of Orthopaedic Surgery and Research"},"publishedOn":"2026-01-03 15:57:58","publishedOnDateReadable":"January 3rd, 2026"},"versionCreatedAt":"2025-10-03 16:28:17","video":"","vorDoi":"10.1186/s13018-025-06564-8","vorDoiUrl":"https://doi.org/10.1186/s13018-025-06564-8","workflowStages":[]},"version":"v1","identity":"rs-7615294","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7615294","identity":"rs-7615294","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}