Biomechanical effects of incremental resection of the ligamentum flavum and lumbar facet joint using a contralateral endoscopic approach

Purpose This study aimed to evaluate the biomechanical effects of progressively removing ligamentous structures and the facet joint using a contralateral endoscopic approach. Materials and methods Twenty spinal segments were biomechanically evaluated in a load-controlled study to assess the impact of resection of the yellow ligament and stepwise resection of facet joint (1/3 and 2/3) using a contralateral endoscopic approach on segmental range of motion (ROM). ROM was compared between the native state and after stepwise resection of contralateral structures. The segments were tested under various loading conditions: flexion-extension (FE), lateral shear (LS), lateral bending (LB), anteroposterior shear (AS), axial rotation (AR), and axial compression/decompression (AC). Results The ROM of the vertebral segment increased significantly across all movement directions following stepwise resection, compared to the native intact state, with the greatest effect observed after partial resection of the contralateral facet joint. The most significant increases were seen in LS, AS and AC after two-thirds of the contralateral facet joint was resected: LS increased by 18.5% (1.24° vs. 1.43°, p = 0.03), AS by 22.8% (1.27 mm vs. 1.78 mm, p = 0.0009), and AC by 20.2% (0.39 mm vs. 0.45 mm, p = 0.006). Conclusion The contralateral endoscopic approach should be performed with caution, limiting resection of the facet joint. Excessive removal of the contralateral facet joint can compromise segmental stability and function.