Biomechanical effects of upper articular process resection proportion on lumbar after transforaminal endoscopic spine system surgery

Transforaminal endoscopic spine system resection of upper articular process with different proportions often has different effects on lumbar spine biomechanics. Therefore, finite element method was used to explore this problem in this study. The Finite Element (FE) model constructed and validated in this study was a 3D heterogeneous model of the L1-S1 lumbar spine. Nine groups of models with different resect proportions were constructed and compared in six physiological movements. Following the experiment, we reached the following main results. The peak Von Mises stress of the left upper articular process of L5 increased most significantly when the resection proportion increased from 40% to 50% under flexion-extension and bending conditions, with an increase value of 6.04-11.47 MPa. When the resection proportion increased from 70% to 80% under rotation conditions, the peak Von Mises stress of the left articular process of L5 increased most significantly, with an increase value of 26.89 and 37.43 MPa. When the resection proportion increased from 70% to 80% under rotation conditions, the peak Von Mises stress of L4-L5 disc increased by 0.69 and 1.84 MPa. The stress concentration area was mainly located in the junction area of articular process and articular cartilage. Based on the above results, we draw the following conclusions. The resection of 50% of the upper articular process is the critical value of lumbar spine biomechanical change. Especially when the proportion of upper articular process resection exceeds 80%, lumbar instability and postoperative pain may occur during rotation. The postoperative pain is related to the stress concentration stimulation of the articular process and articular cartilage junction.