Learning Curve Analysis: Impact of Ligamentum Flavum Removal Methods on Unilateral Biportal Endoscopic Laminectomy for Lumbar Spinal Stenosis

Objective: Despite the increasingly widespread adoption of unilateral biportal endoscopic (UBE) decompressive laminectomy for lumbar spinal stenosis, the learning curve for surgeons new to endoscopic techniques remains a significant barrier. This study aimed to quantify this learning curve and identify strategies to expedite proficiency, focusing on reducing operative times and complications.Methods: The cumulative summation test was used to evaluate the learning curves for both the operative time and the degree of intraoperative dural tear occurrence. Moreover, clinical outcomes and postoperative complications were compared between the cranial and caudal approaches, depending on the direction of ligamentum flavum removal.Results: In total, 54 patients were included, with 22 in the cranial group and 32 in the caudal group. The operative time was notably shorter in the caudal group (cranial group, 110.86±32.63 minutes; caudal group, 79.56±24.21 minutes; p<0.01), and the complication rate was considerably lower (cranial group, 40%; caudal group, 15%; p=0.04). Twenty-six patients and 29 patients were needed to overcome the learning curves for operative time and intraoperative dural tear occurrence, respectively.Conclusion: Although UBE surgery has a short learning curve, a considerable number of cases (26 and 29, respectively) were needed to achieve competency in terms of operative time and intraoperative dural tear occurrence. We highlight the caudal-to-cranial direction of ligamentum flavum dissection and removal as a way to decrease the number of dural tears and shorten the operative time.