[Metal/metal coupling in total hip arthroplasty. Progress or setback?]

It was about 1966 that the metal/metal coupling was introduced into clinical use by McKee and Watson-Farrar. The main arguments for the introduction of this hard/hard coupling were the low wear rates compared to polyethylene couplings and the long-term stability of the metal components. The metal/metal couplings of McKee and Watson-Farrar could not meet the requirements of corresponding long-term results (loosening rates of more than 50% in part). The reason was the inadequate manufacturing quality, but also the random combination of components of different manufacturers. Nevertheless, remarkable long-term results could be reported and they were the reason for introducing a modified metal/metal coupling into clinical use in 1999. This metal/metal coupling of the second generation is characterised by modified CoCrMo materials, but also by definitely excellent manufacturing technologies. The clinical results seem to be better due to improved material quality and manufacturing technique. However, the question remains whether the high Co and Cr level, which is often noticed, has any pathological relevance.