Influence of assigned material combination in a simulated total cervical disc replacement design on kinematics of a model of the full cervical spine: A finite element analysis study.

BACKGROUND

Although cervical total disc replacement (TDR) is becoming popular, there are no finite analysis (FEA) studies involving a model of the full spine cervical (C1-C7) and determination of the influence of materials assigned to different parts of a specified TDR design on biomechanics of the model when TDR implantation is simulated.

OBJECTIVE

To determine the influence of assigned material combination, for a given cervical TDR design, on the kinematics of a model of the full cervical spine.

METHODS

A three-dimensional solid model of the full cervical spine was constructed, a finite element mesh was obtained (INT Model), after which FEA was used to determine range of motion (ROM) at each of the intersegmental positions under three clinically-relevant loadings. INT model was then modified by simulated implantation of a notional endplates-and-mobile insert TDR design, at C5-C6 (TDR Model), and six clinically-relevant applied loadings were applied. Four variants of TDR Model were used, the difference between them being in the materials assigned to the endplates and the mobile insert. Under each of the loadings, principal motions at each of the intersegmental positions were determined and compared to counterpart motions when INT Model was used.

RESULTS

Comparison of ROM results of INT Model with relevant experimental results reported in the literature showed that the model was validated. With TDR Model, the smallest overall mean of the absolute values of the % change in principal intersegmental motions (relative to corresponding results in INT Model) was when the material assigned to both the endplates and the mobile insert was poly(ether-ether-ketone).

CONCLUSION

In a simulated implantation of a notional endplates-and-mobile-insert TDR design in a model of the full cervical spine, material combination assigned to the parts of the design exerts a marked influence on the kinematics of the model.