Impact of mentorship on the learning curve of unilateral biportal endoscopic unilateral laminotomy for bilateral decompression in lumbar spinal stenosis: a cumulative sum analysis across 2 generations of surgeons.

Introduction: Unilateral biportal endoscopic unilateral laminotomy for bilateral decompression (UBE-ULBD) is a minimally-invasive yet technically demanding procedure for lumbar spinal stenosis. Aim: This study aimed to compare the learning curves of 2 generations of surgeons performing UBE-ULBD under a structured mentorship model. Materials and methods: We retrospectively analyzed 200 consecutive surgeries performed between January 2020 and June 2024. The first-generation surgeon (FGS) performed all procedures independently. The second-generation surgeon (SGS) assisted in 30 surgeries and then received on-site supervision for the first 15 independent cases. Data on operative time, blood loss, complications, and clinical outcomes, including the Visual Analog Scale and Oswestry Disability Index, were collected. Operative time-based cumulative sum analysis was used to evaluate the learning curves. Results: The FGS achieved proficiency after 37 and the SGS after 29 procedures. The SGS had significantly shorter mean (SD) operative time of 127.6 (13.2) vs 137.1 (19.3) minutes and lower blood mean (SD) loss of 49 (13.6) vs 57.7 (20.6) milliliters, as compared with his first-generation counterpart. Complications and clinical outcomes were comparable. After achieving proficiency, both surgeons showed improved efficiency without differences in safety or outcomes. Conclusions: Under the guidance of the FGS, the SGS achieved proficiency in UBE-ULBD more rapidly, as reflected in the shorter operative time. Moreover, once proficiency was reached, no notable differences were observed between the 2 surgeons in terms of postoperative complications or clinical outcomes.