Comparative analysis of the biomechanics of the adjacent segments after minimally invasive cervical surgeries versus anterior cervical discectomy and fusion: A finite element study

Purpose: Percutaneous full-endoscopic anterior cervical discectomy (PEACD) and posterior cervical foraminotomy (PCF) as alternatives to anterior cervical discectomy and fusion (ACDF) are extensively used in the treatment of patients with cervical spondylotic radiculopathy. The possibility of avoiding the risk of accelerated degeneration of the adjacent segments caused by fusion is claimed to be the theoretical advantage of these approaches; however, there is a paucity of supportive evidence from biomechanical data. Therefore, this study investigated and compared the effects of PCF, PEACD, and ACDF on the adjacent segments and operative segments of the cervical spine from a biomechanical standpoint. Method: A normal and intact three-dimensional finite element digital model of C4-C7 was constructed and validated, and the finite element models of PEACD, PCF, and ACDF were obtained by modifying the C4-C7 model. All models were exposed to identical conditions of load during flexion, extension, axial rotation, and lateral bending. We calculated the range of motion (ROM), intervertebral disc pressure (IDP), and facet joint contact force (FJCF) of the operative segment and the adjacent segment in different motion conditions. Result: The conventional ACDF had a remarkable influence on the ROM and IDP of the operative segment and the adjacent segments. In the PEACD model, the change of ROM was not noticeable; the IDP of the operative segment was significantly smaller, whereas the change of IDP of the adjacent segment was insignificant. In the PCF model, the ROM and IDP of all segments remained unaffected.During extension, the facet joint contact force changed significantly after ACDF, and it changed slightly after PECAD and PCF. Conclusion: By comparatively analyzing the biomechanical changes of the cervical spine after PCF, PEACD, and ACDF using the finite element method, we suggested that PCF and PEACD were more suitable for surgical intervention of cervical spondylotic radiculopathy than ACDF from a biomechanical point of view and PCF may outperform PEACD.