Mechanical stress in lumbar total disk prostheses — A finite element study

Total disk prosthesis is a medical device used to treat back pain by replacing the damaged intervertebral disk and by restoring height and mobility of the spinal segment. The purpose of this paper was to create finite element models of total disk prostheses made-up different materials and to analyze the mechanical stress which occurs in these devices in physiological movements of extension, flexion and lateral bending. We have considered the artificial disks made off three pieces: two endplates and a core. And then, we have worked four finite element models: Model 1 - with metallic endplates and polymeric core, Model 2 - with metallic endplates and metallic core, Model 3 - with metallic endplates and ceramic core, Model 4 - with ceramic endplates and ceramic core. The lowest mechanical stress was detected in Model 1; in this case, a hard material (Cobalt-Chromium-Molybdenum alloy - Co-Cr-Mo) was in direct contact with a soft material (ultra high molecular weight polyethylene - UHMWPE). The last three models indicated similar mechanical stress.