Comprehensive Learning Curve, Clinical Outcomes, and Radiological Evaluation of Modified Trans-Kambin Endoscopic Lumbar Interbody Fusion at over 1-Year Follow-Up.

Abstract

To evaluate the learning curve, clinical outcomes, and radiological results of modified trans-Kambin endoscopic lumbar interbody fusion. In this single-center retrospective study, 50 patients (66 segments) who underwent Kambin Torpedo endoscopic lumbar interbody fusion between January 2022 and April 2024 were assessed. Clinical outcomes included visual analogue scale (VAS) scores for back pain and ipsilateral and contralateral leg pain. Radiological measures included disc height, foraminal height and cross-sectional area, spinal canal area, segmental and lumbar lordosis, and adjacent segment motion. Fusion status was graded using the Bridwell classification system. The fusion rate was 99% (65/66 segments). VAS scores for back and leg pain improved significantly. Disc height was preserved in 97% of segments. Lumbar lordosis increased significantly, reaching the lower threshold of clinical relevance. Learning-curve analysis identified the 33rd patient as the threshold for shorter surgical duration, while outcome-based analyses showed cut-points of 23, 40, and 43 segments for graft volume, fusion grade, and VO, respectively. VO, observed in 35% of segments, was significantly associated with higher body mass index (BMI), male sex, and osteoporosis requiring pharmacological treatment. Greater graft volume correlated with better Bridwell grades. Heterotopic ossification occurred in 3 patients, with one presenting symptoms. Modified trans-Kambin endoscopic lumbar interbody fusion is effective and safe, with high fusion rates and significant pain relief. Greater graft volume improved fusion grades. VO was linked to high BMI, male sex, and osteoporosis treatment. A 40-case threshold was associated with improved outcomes, underscoring the importance of surgical experience.