Biomechanical effects of incremental resection of the lumbar superior articular process using an endoscopic approach

Abstract Purpose This study aimed to evaluate the biomechanical effects of progressively removing parts of the facet joint (mainly the superior articular process (SAP)) in cadaveric models via the typical endoscopic posterolateral route. Materials and methods Twelve spinal segments were biomechanically evaluated in a load-controlled study to assess the impact of the endoscopic trans superior articular process (transSAP) approach on segmental range of motion (ROM). ROM was compared between the native state and after the transSAP approach, using two drill hole sizes (4 mm and 8 mm). The segments were tested under various loading conditions: flexion-extension (FE), lateral shear (LS), lateral bending (LB), anteroposterior shear (AS), and axial rotation (AR). Results The ROM of the vertebral segments did not change significantly across most movement directions between the native, intact state, and the two endoscopic approaches. A significant increase in ROM was observed in AS compared to the native state: 1.3° (SD: 0.63) versus 1.34° (0.65; p = 0.007) for the 4 mm transSAP, and 1.4° (0.71; p = 0.04) for the 8 mm transSAP. Additionally, in FE, the 8 mm transSAP approach showed a 5% increase in ROM compared to the 4 mm approach ( p = 0.03). No significant differences were observed in the other loading conditions. Conclusion The transSAP approach, requiring substantial resection of the SAP and potentially parts of the inferior articular process (IAP), may be performed without necessarily compromising segmental stability and function.