Zirconia as a sliding material: histologic, laboratory, and clinical data.

Zirconia ceramics have been introduced in orthopaedic surgery as prosthetic femoral heads to solve the critical issue of femoral head fractures sometimes observed with alumina ceramics. In addition to outstanding mechanical properties, zirconia ceramics have, similar to other surgical grade ceramics, a high biocompatibility and a high resistance to scratching. The radioactivity of zirconia ceramic, which has been the subject of contradictory data, now is well understood and managed with appropriate standards. The long-term stability of zirconia ceramics recently has been studied extensively and precise models allow a good prediction of their long-term behavior. In vitro wear tests against polyethylene and clinical data confirm the low wear rate associated with the use of ceramic femoral heads. The use of zirconia femoral heads in ceramic-on-ceramic total hip prostheses also has been investigated and now is clinically effective.