Unilateral laminotomy with bilateral decompression versus standard open bilateral decompression in patients with single-level lumbar spinal stenosis without instability: a single-center retrospective cohort study

Background and purpose Degenerative lumbar spinal stenosis is commonly treated surgically. Standard open bilateral decompression (SOBD) is established, whereas unilateral laminotomy with bilateral decompression (ULBD, “over-the-top”) aims to preserve posterior midline structures and contralateral musculature. We compared 3-year outcomes after ULBD and SOBD in patients with single-level stenosis without instability. Patients and methods In this single-center retrospective cohort study, consecutive patients operated between 2017 and 2020 for MRI-confirmed single-level lumbar stenosis without radiological instability were included. The primary outcome was the Oswestry Disability Index (ODI) assessed preoperatively and at 12, 24, and 36 months. Secondary outcomes were operative time, hospital stay, and complications. Between-group comparisons were exploratory and used the Mann–Whitney U test or Fisher's exact test. Longitudinal ODI analysis was limited by substantial missing baseline ODI data. Results Of 65 operated patients, 63 were included in the functional outcome analysis: 14 underwent ULBD and 49 underwent SOBD. ULBD patients were older than SOBD patients (mean 59.9 vs. 51.2 years; p = 0.011), while BMI did not differ significantly. Preoperative ODI was available for only 3/14 ULBD and 12/49 SOBD patients. ULBD was associated with shorter operative time (median 60 vs. 80 min; p < 0.001) and shorter hospital stay (median 4 vs. 5 days; p = 0.035). ODI was lower after ULBD at 12 months (median 4 vs. 6; p = 0.049), but not at 24 or 36 months. Complication comparisons were limited by low event numbers. Conclusion In this retrospective cohort, ULBD was associated with shorter operative time and hospital stay. Postoperative ODI was lower in the ULBD group at 12 months but not at 24 or 36 months. Because of non-randomized treatment allocation, substantial missing baseline ODI data, and the small ULBD cohort, comparative functional superiority cannot be established.