BIOMECHANICAL PERFORMANCE OF A MODIFIED DESIGN OF DYNAMIC CERVICAL IMPLANT COMPARED TO CONVENTIONAL BALL AND SOCKET DESIGN OF AN ARTIFICIAL INTERVERTEBRAL DISC IMPLANT: A FINITE ELEMENT STUDY

Most of the implants used for total disc replacement (TDR) surgery are designed as a ball and socket pair aimed at providing a three-dimensional unconstrained motion. However, one of the major concerns with ball and socket design is the wear of the implant which limits its life. In this study the biomechanical performance of two types of implant designs is compared - a conventional ball and socket type (Prodisc-C) and a modified design of dynamic cervical implant (DCI) using FE analysis. A 3-dimensional geometrical model of cervical spine (C1-T1) was developed using CT scan data of a middle-aged healthy male. Subsequently, using FE analysis, the ROM values were validated with the existing literature using a compressive load in combination with different physiological motions of the neck. Furthermore, FE analysis on the two implants, fitted at C5-C6 segment, showed a significant increase in the ROM of implanted segment using Prodisc and decrease in the ROM of inferior segment, but modified-DCI restored the motion of the implanted and adjacent segments. Analysis of average bone strains adjacent to the implant showed a possibility of stress shielding for Prodisc. However, higher stress distribution on the modified-DCI limited its clinical use.