The effects of polyethylene cup thickness on wear of total hip prostheses.

The wear rate of the ultrahigh molecular weight polyethylene cups in combination with a 28 mm alumina femoral head was measured on the radiographs of patients without any complications, and on cups retrieved due to slight loosening of the prosthesis or due to late infection between bone and components. The wear rate on the radiographs did not include the initial wear, but the wear rate on the retrieved cups did include the initial wear. The wear rate on the retrieved cups was higher, by 50%, than that measured on the radiographs. In both cases, the thicker the polyethylene cups, the lower was the wear rate measured. The average wear rate of the 7 and 8 mm thick cups was about twice that of cups 10 and 11 mm thick. From these results, we conclude that polyethylene cups more than 11 mm thick should be used.