Clinical experience with ceramics in total hip replacement

As part of a search for better articulation in total hip prostheses, the de crease in the thickness of the socket in different total hip prostheses was measured in vivo. The wear rates of (1) RCH 1000 (molecular weight, 10(6)) socket gamma-irradiated with 100 Mrad articulating with a crude COP (stain less steel containing 20% cobalt and 0.01% phosphorous) metal femoral head; (2) RCH 1000 socket nonirradiated articulating with a crude COP femoral he ad; (3) RCH 1000 socket irradiated with 100 Mrad articulating with an alumi na femoral head; (4) ultra high molecular weight polyethylene (molecular we ight, 5-6 X 10(6)) socket articulating with an alumina femoral head; and (5 ) ultrahigh molecular weight polyethylene socket articulating with a stainl ess steel femoral head (T-28) were 0.06, 0.30, 0.06, 0.10 and 0.25 mm/year, respectively, in the authors' clinical cases. Alumina femoral heads were e ffective in decreasing wear of the polyethylene socket. However, the wear r ates of gamma-irradiated sockets articulating with alumina and with metal f emoral heads wear very low and were not different from each other. Regardin g the relationship between wear rate and the thickness of the ultra high mo lecular weight polyethylene socket articulating with a 28 mm alumina femora l head, on radiographs, average wear rates of socket thicknesses of 7, 8, 9 , 10 and 11 mm were 0.14, 0.15, 0.12, 0.06, and 0.08 mm/year, respectively. On measuring retrieved prostheses, average wear rates of 7, 8, 9 and 11 mm thickness sockets were 0.2, 0.19, 0.14, and 0.1 mm/year, respectively. The wear of sockets has been proven to be minimal in alumina femoral heads art iculating with ultrahigh molecular weight polyethylene sockets thicker than 10 mm.