The Role of Elastic and Large-Strain Mechanical Behavior on the Wear of UHMWPE, HDPE, PTFE, and Polyacetal Evaluated by a Hip Simulator

Abstract

Abstract The elastic and large deformation mechanical behavior of four materials with known clinical performance was examined and correlated with the wear behavior in a hip simulator. Acetabular liners of a commercially-available design were machined from UHMWPE, HDPE, PTFE, and polyacetal and wear tested in a multidirectional hip joint simulator. Elastic and large-deformation mechanical behavior was directly measured from the wear-tested liners using the small punch test. The inverse finite element method was used to compute elastic modulus from the measured small punch test initial stiffness, and the contact stress for the liners was calculated using the theory of elasticity solution. Positive, statistically-significant correlations were observed between the hip simulator wear rate and the initial peak load, ultimate load, and work to failure from the small punch test. Negative correlations were observed between the wear rate and the elastic modulus and contact stress. This results of this study support the hypothesis that the large deformation mechanical behavior of a polymer plays a greater role in the wear mechanisms prevalent in total hip replacements than the elastic behavior.