Unilateral biportal endoscopy (UBE) technique is widely used in the treatment of lumbar disc herniation and lumbar spinal stenosis. By analyzing the learning curve of this technique, this study aims to inform the implementation and learning process of such surgical modalities.

Patients with lumbar spinal stenosis who underwent UBE between June 2021 and December 2023 in the Department of Spine Surgery, Orthopaedic Center, Beijing Friendship Hospital, Capital Medical University, were retrospectively analyzed. Baseline information, operative time, blood loss, complications, and subjective scores were collected from all patients. The learning curve was evaluated using the cumulative sum (CUSUM) method.

A total of 122 patients who underwent single-segment UBE-ULBD were included. The mean follow-up time was (10.51±2.44) months (8-20 months), and the operated segments included L_2/3 (3 patients), L_3/4 (13 patients), L_4/5 (85 patients), and L₅/S₁ (21 patients). Based on the results of surgical time curve fitting, the patient cohort was divided into groups according to different levels of mastery proficiency. Namely, the learning phase group (1-38 cases) and the mastery phase group (39-122 cases). The learning stage group had a longer operative time than the mastery stage group (153.3±44.0 min与129.2±34.5 min, t=2.978, P<0.05), higher blood loss than the mastery stage group (62.4±42.3 min与53.1±31.5 min, t=1.209, P>0.05), but lower hidden blood loss than the mastery stage group (207.1±140.5 min与211.2±110.9 min, t=-0.160, P>0.05). There was more drainage in the learning stage group than in the mastery stage group (64.1±43.1 min与29.4±34.4 min, t=-4.752, P<0.05). ANOVA with repeated measures design at preoperative, immediate postoperative, and final follow-up showed no statistically significant difference in ODI scores between the two groups (F=3.502, P=0.062), statistically significant difference between different time points (F=347.190, P=0.000), and no interaction between group and time point (F=0.071, P=0.931); For VAS scores for low back pain a statistically significant difference was found between groups (F=32.691, P=0.000), between time points (F=866.102, P=0.000) and no interaction between groups and time points (F=0.665, P=0.862). In terms of VAS scores for leg pain a statistically significant difference was found between different groups (F=24.980, P=0.000), between different time points (F=693.920, P=0.000), and no interaction between groups and time points (F=1.986, P=0.139).

As an effective minimally invasive spinal endoscopic technique for the treatment of lumbar spinal stenosis, the UBE-ULBD procedure requires approximately 38 cases to overcome the learning curve. If the learning curve can be successfully overcome, the technique will have the advantages of minimally invasive surgery, flexible and efficient operation, and fast postoperative recovery.