Wear of retrieved ceramic THA components--four matched pairs retrieved after 5-13 years in service

Retrieval analyses of alumina-alumina THA components are conducted in order to investigate in vivo wear of implants and provide guidance to material and design improvements. The contribution of the present study consists of the examination, by digital recording of spherical profiles and scanning electron microscopy, of four matched pairs of ceramic THA implants retrieved after 5, 11, 13, and 13 years in service because of mechanical loosening. Maximum wear depth values on measured surfaces ranged between 10-325 microm for heads and 25-784 microm for cups, while grossly worn areas varied between 240 and 1510 mm(2) for heads and 250 and 1570 mm(2) for cups. The greatest wear characteristics were demonstrated by the pair that served for 5 years, that is, on the cup that was found in a 65 degrees inclination. Quantitative topographical study of the results provided concrete evidence of a cascade of detrimental wear events of changing geometry, intensity, and progression associated with gradual cup tilting. Microscopy findings support previously recognized wear mechanisms.