Metal-on-metal failures—in science, regulation, and policy

Worldwide there is dissatisfaction and fear among patients because commonly used implantable devices such as hip and breast implants, or defibrillator leads, fail. Metal-on-metal implants used for hip resurfacing or replacement are at the epicentre of the controversy because weaknesses in regulatory systems for medical devices have been exposed.

^, 

Initially the Australian and England and Wales registries reported failures associated with ASR (Articular Surface Replacement), a specific metal-on-metal device for hip replacement.

^, 

Subsequent reports highlighted common failures associated with large-head metal-on-metal implants in evidence from registries and comparative studies.

^, 

^, 

In The Lancet, Alison Smith and colleagues

now strengthen and extend the evidence that large-head metal-on-metal failure is not implant specific—it is a class effect. By use of data from the National Joint Registry of England and Wales, Smith and colleagues were able to assess more than 400 000 primary hip-replacement procedures, of which 31 171 employed stemmed metal-on-metal prostheses that were commonly used between 2003 and 2011. There was a 5-year revision rate of 6·2% (95% CI 5·8–6·6) in patients who had received metal-on-metal prostheses, substantially greater than that with other types of device and more elevated for prostheses with larger head sizes. Although the risk estimates are slightly smaller than those reported by the Australian Registry the follow up is also shorter within the National Joint Registry, which explains the difference.