Design of an Elastic Arthroplastic Disc Optimized under Different Loads

Introduction: Due to limitations of current treatments for degenerative disc disease, arthroplastic methods to repair the diseased disc have been proposed. The artificial disc is a mobile implant for degenerative disc replacement that attempts to lessen the degeneration of the adjacent elements following interbody fusion procedures. Because the success of artificial disc replacement depends on maintenance or restoration of the mechanical function of the intervertebral disc, it is useful to study the initial mechanical performance of the disc after implantation in the spine.   Materials and Methods: A three-dimensional finite element model of the L3–L4 disc was analyzed. The model took into account the material nonlinearities and it imposed different loading conditions. In this study, we validated the model by comparison of its predictions with several sets of experimental data; we determined the optimal Young’s modulus as well as the Poissan ratios for the artificial disc under different loading conditions. Results: The artificial disc was subjected to three loading conditions: 1) compression, 2) bending and 3) torsion. In each case, optimum elastic parameters were determined. Then, by using the root mean square method, optimum parameters for all loading conditions (and therefore minimum error) were calculated. Discussion and Conclusion: The results of this study suggest that a well-designed elastic arthroplastic disc preferably has Young’s modulus values of 18.63 MPa and 1.19 MPa for the annulus and nucleus sections, respectively. Elastic artificial disc with such properties can then achieve the goal of restoring the disc height and mechanical function of a normal disc under different loading conditions.