Focus On An update on outcomes following revision surgery for adverse reaction to metal debris

Over one-million patients worldwide have received metal-onmetal (MoM) hip replacements (hip resurfacing (HR) and total hip replacement (THR)).1 Good to excellent ten-year outcomes have been reported with certain HR devices by both designing and independent centres.2-4 However high short-term failure rates have been observed with other HR devices and stemmed MoM THRs.5-7 Adverse reaction to metal debris (ARMD) is the sequelae of large amounts of metal debris released from MoM hip bearings due to wear and corrosion.8 The subsequent local tissue reactions seen in ARMD often results in the formation of destructive soft-tissue masses, termed pseudotumours, which may require revision surgery.9 Theoretically all MoM hips are at risk of failure due to ARMD. This risk appears to increase with time since implantation, with ARMD appearing more common in MoM THR compared to HR due to the additional metal wear debris that can be generated at the trunnion-head interface in THRs and other modular junctions.5-7 In the light of MoM hips developing ARMD in recent years the Medical and Healthcare products Regulatory Agency (MHRA) have issued guidance with regard to the investigation and management of these reactions, and the market withdrawal of certain devices with unacceptably high failure rates.10,11 The high short-term morbidity reported in a previous study12 has led to the MHRA and orthopaedic experts recommending early revision surgery for ARMD.11,13 Of concern, in England, Wales and Northern Ireland the prevalence of ARMD revision surgery is increasing with ARMD accounting for 13.2% (n=1,330) of all revisions performed in 2012.14 Since these recommendations for early revision were made, a number of studies have been published which report outcomes of patients following revision surgery for ARMD. The present article provides an update on outcomes following ARMD revision surgery and assesses prognostic factors of outcome.