Abstract:
This paper presents a computational method using finite element (FE) analysis to compare the biomechanical behavior and potential failure modes of prosthetic joint implants, with a focus on the thumb carpo-metacarpal (CMC) joint. The research aims to understand in-vivo failure, particularly wear and cracking of ultra-high molecular weight polyethylene (UHMWPE) components, which is often caused by high contact stresses. The study created 3D volumetric meshes of three distinct thumb implant designs: a congruent saddle-shaped implant, a ball-and-socket joint, and a one-piece silicone implant.
Using the nonlinear, implicit FE code NIKE3D, the researchers modeled the large deformation dynamics of the implants under uniaxial loading conditions representative of physiological forces (up to 500 lbs). The simulations were performed under two scenarios: perfect implant alignment and slight misalignment, to mimic both ideal and realistic surgical placement. The analysis focused on calculating the resulting contact stresses on the polyethylene articulating surfaces. The results showed that under physiological loads, the models could identify concentrated regions of high stress that exceeded the failure limits of polyethylene, representing potential "danger zones." This work establishes a valuable computational framework for evaluating and comparing the mechanical performance of different implant designs before clinical use, and can be extended to include surrounding biological tissues for more comprehensive in-vivo simulations.
