Where Do we Stand with Metal-on-Metal Bearings?

In this issue we have published advice from a collaborative group of experts representing several societies in relation to the current status and safety of metal-on-metal bearings in hip arthroplasty. Over the last decade, our journal has documented benign and encouraging results following the use of metal-on-metal (MoM) bearings, either in the form of total hip arthroplasty or hip resurfacing, both in relation to tribology and potential metal dissemination (including trans-placental passage) (1–8). The literature, at least in the period from 1990-2004, concentrated mainly on technical details relating to the procedures. Recent awareness of adverse reaction to metal debris combined with the potential effect of metal toxicity have radically altered the climate in relation to this discussion, and have highlighted the more encouraging results of small-bearing MoM total hip arthroplasty (< 32 mm) as well as hip resurfacing in larger males (9–11).

While some implant designs are particularly implicated, particularly in relation to large head metal-on-metal total hip arthroplasty, caution should be exercised in relation to all metal-on-metal bearings. Some countries have issued specific guidelines, such as the MHRA requirements for surveillance in the United Kingdom (12). Recent evidence from the Netherlands suggests the acuity of screening may become more intense in the years ahead (13).

The guidelines produced in the collaborative statement in the following pages may act as a framework in those countries in which specific recommendations have not yet been produced at a national level. This is an area of constantly evolving knowledge, and therefore new information will probably result in modification of these guidelines in the coming years.