Concern has been growing about the use of metal on metal hip implants. In its 2011 report, the National Joint Registry for England and Wales identified problems including higher revision rates compared with more traditional ceramic or polyethylene implants (BMJ 2011;343:d5977). A BMJ investigation by Deborah Cohen asked why it took so long for one metal on metal implant, the ASR, to be withdrawn, highlighting denials and delays by the manufacturer and failings in the regulation of medical devices (BMJ 2011;342:d2905).

This week we publish a systematic review of research into the safety and effectiveness of hip implants. Art Sedrakyan and colleagues conclude that the evidence is inadequate, but what …