Is there evidence of metal-on-metal bearing failure in modern total wrist arthroplasty?

Given the well-publicised issues around metal-on-metal (MOM) hip replacements there has been a great deal of scrutiny around the same bearing when used in total wrist arthroplasty (TWA). There are several case series and reports in the literature of metallosis following MOM TWA which have implicated the MOM bearing as the cause of the issue with some authors advocating that the MOM bearing should be avoided. As the MOM version of one of the current TWA is widely used, this potentially represents a problem. This article discusses the issues of MOM articulations as they relate to both hip and wrist replacements and critically analyses the literature to see if there is indeed any evidence of issues with MOM bearings in modern TWA. While metallosis has been reported in TWA, frequently this has been due to failure of the polyethylene bearing or unintended impingement between arthroplasty components. In such cases, titanium debris has been released and, while not benign, such debris lacks the known toxicity associated with the cobalt and chromium of MoM hips. These findings, together with those from explant analysis of MOM articulations, suggest that metallosis seen with the MOM TWA is extra-articular in origin and there is no evidence to suggest an issue with the bearing itself.