Corrosion in modular femoral hip prostheses: a study of 22 retrieved implants

Retrieved modular hip prostheses were examined to determine the mechanism of corrosion at the Co-Cr alloy head, Ti-alloy neck taper junction. The corrosion at the neck was consistently more severe in the posterior medial distal region, and the specimens with the highest corrosion score all had a head-neck extension. Fretting, pitting and etching-type attacks were detected, and the corrosion product was predominantly a thin layer composed of Ti, Cr and Mo. The authors' findings suggest that the corrosion is due to the cumulative effect of an acidic crevice environment and micro motion at the interface during weight bearing causing breakdown of the passive layers.