Wear Prediction of UHMWPE Cup Against Commercially Pure Titanium Hip Implant with the Nonlinear Load and Contact Area Wear Equation

Abstract

Hip implants are prostheses designed for severe hip arthritis patients. One of its components, acetabular cup is mostly made from ultra-high molecular weight polyethylene (UHMWPE). This polymer has a wear problem. Its debris would cause osteolysis followed by implant failures. Numerical studies of this problem were commonly used a linear contact pressure wear equation. Recently it was found not suitable to model the polymer wear in hip implants. This study used a nonlinear equation to predict the UHMWPE volumetric wear. It states a nonlinear relation between wear, load and contact area. The computation model was a biaxial rocking motion hip simulator assembly with UHMWPE acetabular cup sliding on commercially pure titanium femoral head. Multidirectional pin on disc experiments conducted to obtain wear factor and coefficient of friction data for the computations. Commercial finite element software calculated the other parameters. Predicted volumetric wear has a good agreement with the experimental data. Lowest numerical error was found 0.53 %.