4. The low-wear prosthesis

4.1 Prosthesis concept

The use of a friction couple involving two hard surfaces, and therefore less prone to wear than contact involving a soft polymer, predates the Charnley prosthesis. McKee-Farrar prostheses, featuring a CoCrMo alloy femoral head in contact with an acetabular cup of the same material, were implanted as early as the late 1950s. Despite the rapid failure of some of these prostheses, mainly due to insufficient clearance between head and cup, some of these implants showed a remarkable longevity of 20 to 30 years