Biomechanical affect of percutaneous transforaminal endoscopic discectomy on adjacent segments with different degrees of degeneration:a finite element analysis

Abstract

To investigate the biomechanical affect of percutaneous transforaminal endoscopic discectomy(PTED) on adjacent segments with different degrees of degeneration and related risk of adjacent segment diseases (ASD) caused by this operation. A healthy male adult volunteer was selected, and the lumbosacral vertebra image data was obtained by CT scan, and the external contour of the bone structure was reconstructed. On this basis, the external contour of the bone structure was fitted by using the smooth curve in 3D-CAD software, and the complete three-dimensional finite element modelof the non degenerate L3-S1 segment and the degenerative models of the L3-L4 and L5-S1 segment were drawn forward. In L4, L5 segment simulating PTED surgery through the removal of right part of articular process and nucleus pulposus and anulus fibrosus. After PTED was simulated in the L4-L5 segment and the risk of ASD has been evaluated by six changes of biomechanical indicators in flexion, extension, left and right lateral bending, left and right axial rotation conditions. In the finite element model without adjacent segmental disc degeneration, the annulus fibrosus von Mises stress and intradiscal pressure of the PTED model showed only a slight increase under most stress conditions, and a slight decrease in a few conditions, and there was no significant change trend before and after surgery. In the original degenerated adjacent segment disc model, the biomechanical indicators related to disc degeneration in the pre- and post-PTED model showed significant deterioration, leading to an increased risk of potential adjacent spondylopathy. PTED surgery will not lead to the significant deterioration of postoperative biomechanical environment of non-degeneration adjacent intervertebral discs, and the original degeneration of adjacent intervertebral discs is a important risk factor for ASD.