Hip resurfacing data from national joint registries: what do they tell us? What do they not tell us?

Current-generation metal-on-metal hip resurfacing implants (SRAs) have been in widespread global use since the 1990s, and in the United States, specific implants have recently been approved for clinical use. Many recent publications describe short-term survivorship achieved by either implant-designing surgeons or high-volume centers. National joint replacement registries (NJRRs) on the other hand report survivorship achieved from the orthopaedic community at large. We therefore reviewed SRA survivorship from national registry data and compared with that reported from individual centers. Additionally, we compared SRA survivorship reported by registries and compared prognosticators for failure with those of conventional total hip arthroplasty (THA). Although resurfacing was associated with an overall increased failure rate in comparison to THA (Australian registry 5-year cumulative revision rate [CRR], 3.7% and 2.7%, respectively), there were exceptions to this. Male patients younger than 65 years with primary osteoarthritis had equivalent results with SRA and THA (Australian registry 5-year CRR, 2.5% and 2.8%, respectively). Head size over 50 mm in diameter was a predictor of surface replacement arthroplasty survivorship and only females with a head diameter of 50 mm or greater (14% of females) had a comparable survivorship to males. Diagnoses other than primary osteoarthritis bear a higher risk of early revision of SRA as compared with THA. Revision of SRA does not lead to reproducible results with rerevision rates of 11% at 5 years. Given these predictors of failure, our review of data from the NJRR suggests stringent patient selection criteria might enhance the survival rates of SRA.