Influence of mechanical behavior on the wear of 4 clinically relevant polymeric biomaterials in a hip simulator

The elastic and large-deformation mechanical behavior of 4 materials with k nown clinical performance was examined and correlated with the wear behavio r in a hip simulator. Acetabular liners of a commercially available design were machined from ultra-high molecular weight polyethylene (UHMWPE), high- density polyethylene (HDPE), polytetrafluoroethylene (PTFE), and polyacetal and wear tested in a multidirectional hip joint simulator. Elastic and lar ge-deformation mechanical behavior was directly measured from the wear-test ed liners using the small punch test. The finite element method was used to compute elastic modulus from the measured small punch test initial stiffne ss, and the contact stress for the liners was calculated using the theory o f elasticity solution. Positive, statistically significant correlations wer e observed between the hip simulator wear rate and the initial peak load, u ltimate load, and work to failure from the small punch test. Negative corre lations were observed between the wear rate and the elastic modulus and con tact stress. The results of this study support the hypothesis that the larg e-deformation mechanical behavior of a polymer plays a greater role in the wear mechanisms prevalent in total hip replacements than the elastic behavi or.