A PARAMETRIC INVESTIGATION OF THE EFFECTS OF CERVICAL DISC PROSTHESES WITH UPWARD AND DOWNWARD NUCLEI ON SPINE BIOMECHANICS

Abstract

This work aimed at investigating the influence of Baguera and Discocerv cervical disc prostheses, with mobile downward center of rotation (COR) and fixed upward COR, respectively, on the biomechanical behavior of C4–C6 cervical spine. For this purpose, using computed tomography (CT) data, a parametric nonlinear finite element (FE) model of intact C4–C6 spinal segments was developed, and an artificial disc was implanted at C5–C6 level. To assess the influence of implants on the biomechanics of cervical spine, the FE models were analyzed in flexion, extension, lateral bending, and axial rotation, and the results were presented in the range of motion (ROM) curves, and torsional stiffness. Results of this study, in agreement with the literature, suggested that both Baguera and Discocerv implants might be able to preserve the motion, and limit the alteration of the biomechanics of adjacent levels. Except for the possible confliction of adjacent vertebrae at the implanted level with Baguera implant in lateral bending, results of this study also indicated that the movability and downward COR of Baguera disc prosthesis caused ROMs of the implanted segment to be more similar to the intact model than Discocerv implant. Moreover, the upward COR of Discocerv implant may result in over-distraction on facets in the maximal flexion, with the ratio of 1.22 versus 1.36, and consequently facet syndrome during extension for Bageura and Discocerv disc prostheses, respectively.