We examined stainless-steel, cobalt-chrome, titanium and alumina and zirconia ceramic femoral heads retrieved at revision surgery. All the heads had articulated against ultra-high-molecular-weight-polyethylene (UHMWPE) acetabular cups. We studied the simulation of third-body damage and the wear of UHMWPE against the various materials used for the heads. The surfaces of the retrieved heads were analysed using a two-dimensional contacting profilometer. Third-body damage was characterised by the mean height of the scratches above the mean line (Rpm). The alumina ceramic and zirconia ceramic retrieved heads were found to have significantly less damage. In laboratory studies the ceramics were also more resistant to simulated third-body damage than the metal alloys. We studied the wear of UHMWPE against the damaged counterfaces in simple configuration tests. The damaged ceramics produced less polyethylene wear than the damaged metal counterfaces. The wear factor of UHMWPE against the damaged materials was dependent on the amount of damage to the counterface (Rp). Our study has shown the benefit of using the harder and more damage-resistant ceramic materials for femoral heads.

We examined stainless-steel, cobalt-chrome, titanium and alumina and zirconia ceramic femoral heads retrieved at revision surgery. All the heads had articulated against ultra-high-molecularweight-polyethylene (UHMWPE) acetabular cups. We studied the simulation of third-body damage and the wear of UHMWPE against the various materials used for the heads. The surfaces of the retrieved heads were analysed using a two-dimensional contacting profilometer. Third-body damage was characterised by the mean height of the scratches above the mean line (R pm ).The alumina ceramic and zirconia ceramic retrieved heads were found to have significantly less damage. In laboratory studies the ceramics were also more resistant to simulated third-body damage than the metal alloys. We studied the wear of UHMWPE against the damaged counterfaces in simple configuration tests. The damaged ceramics produced less polyethylene wear than the damaged metal counterfaces. The wear factor of UHMWPE against the damaged materials was dependent on the amount of damage to the counterface (R p ). Our study has shown the benefit of using the harder and more damage-resistant ceramic materials for femoral heads.J Bone Joint Surg [Br] 1998;80-B:894-9. Received 23 December 1997 ; Accepted after revision 3 July 1998Although there has been gradual improvement in the materials, design and surgical techniques for total hip replacement (THR) over the last decade, many problems still remain. In particular, for the long-term success of THR, factors which cause high rates of wear must be identified in order to reduce the amount of wear debris produced. The clinical importance of these problems has increased since THR has become available to younger and more active patients who are themselves demanding a better quality of life. Implants now require to have a low coefficient of friction, resistance to third-body damage and wear, the generation of small amounts of wear debris, and low cellular reactions to such wear debris.Many studies, including wear tests, scratch tests, measurements of explanted prostheses and analysis of wear debris, have been performed in order to understand the mechanism of wear of ultra-high-molecular-weight polyethylene (UHMWPE) in implants. Polyethylene debris produces a foreign-body-connective-tissue reaction in the form of osteolysis and the formation of granuloma along the implant-bone interface. This reaction often progresses to late aseptic loosening.1-3 The surface topography or roughness of the counterface which rubs against the UHMWPE is one of the most important factors controlling the rate of wear of the polymer. 4 In laboratory tests, a single scratch 2 m deep on a metal counterface has been shown to produce a dramatic increase in the wear of UHMWPE. 5The roughening of the femoral counterface can also increase the number of wear particles generated. Clinically, damage to metal femoral heads can be caused by third bodies: bone-cement particles, 6,7 bone particles 8 and metal debris. 9 In laboratory simulator studies little diffe...

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