In Vivo Tribological Performance of 231 Metal-On-Metal Hip Articulations

231 cobalt-chromium metal-on-metal (METASUL design) retrieved articulations (297 retrieved components) were examined for their in vivo wear behaviour. A running-in period of about one year is observed where the in vivo wear rate for the whole articulation is approximately 35 μm/year. After this running-in period, the measured in vivo wear rate of the whole articulation decreases to about 5 μm/year. The metal-on-metal articulation can be considered as a very low wear articulation system. The combination of the specially designed components is mandatory to assure this low wear behaviour. In case of a mismatched bearing (stainless steel head – cobalt-chromium inlay), large amount of wear was measured.