Abstract
Outcomes following metal-on-metal hip replacement (MoMHR) revision surgery for adverse reactions to metal debris (ARMD) have been poor, and inferior compared with non-ARMD revisions. Subsequently, surgeons and worldwide authorities widely recommended early revision for ARMD, with a lower surgical threshold adopted. However, the impact of early surgery for ARMD is unknown. We compared the rates of adverse outcomes following MoMHR revision surgery in matched ARMD and non-ARMD patients.
We performed a retrospective observational study using data from the National Joint Registry for England, Wales, Northern Ireland and the Isle of Man. All MoMHR patients subsequently undergoing revision surgery for any indication between August 2008 and August 2014 were eligible. ARMD and non-ARMD revisions were matched one-to-one for multiple potential confounding factors using propensity scores. Adverse outcomes following revision surgery (intra-operative complications, mortality, re-revision surgery) were compared between matched groups using regression analysis.
In 2,576 matched MoMHR revisions (ARMD=1,288 and non-ARMD=1,288), intra-operative complications were similar between ARMD (2.4%) and non-ARMD (2.5%) revisions (odds ratio=0.97, 95% CI=0.59–1.60; p=0.899). All-cause mortality rates were lower following ARMD revision compared with non-ARMD revision (hazard ratio (HR)=0.43, 95% CI=0.22–0.86; p=0.018). All-cause re-revision rates were lower following ARMD revision compared with non-ARMD revision (HR=0.52, 95% CI=0.36–0.75; p<0.001). Compared with ARMD revision (5-years=94.3%), MoMHR revisions for infection (5-years=81.2%) and dislocation/subluxation (5-years=81.9%) had the lowest implant survival rates.
Contrary to previous observations, MoMHRs revised for ARMD have approximately half the risk of re-revision and death compared to non-ARMD revisions. We suspect worldwide regulatory authorities have positively influenced outcomes following ARMD revision by widely recommending that surgeons exercise a lower revision threshold.
Our findings suggest the threshold for ARMD revision surgery need not be lowered further. The high risk of failure following MoMHR revision for infection and dislocation is concerning.
