Hip Resurfacing and Large Diameter Metal on Metal Hip Replacement. Is There a Difference in the Clinical Outcome After Revision Surgery

Introduction Metal on metal hip arthroplasty continues to be controversial. Emerging evidence suggests that there are multiple modes of failure, and that the results of revision surgery are influenced by host and implant factors. Methods This study compares a single surgeon series of hip resurfacings (Birmingham Hip Resurfacing {BHR}) and large diameter metal on metal total hip replacements (LDMOMTHR). Primary outcome measures included survival rates, failure secondary to histologically identified Adverse Reaction to Metal Debris (ARMD), and patient reported outcome measures (Oxford Hip Score {OHS}) following revision. Between 1999 and 2005, 458 BHR and 175 LDMOMTHR were performed. At latest review 43 BHR9s (9.4%) and 28 LDMOMTHR9s (14%) have been revised. Results Failure secondary to ARMD was significantly greater in LDMOMTHR compared to BHR failures (89% and 16% respectively). Histology demonstrated a higher Aseptic Lymphocytic Vascular and Associated Lesions (ALVAL) score in the LDMOMTHR failures than the BHR failures (8.6 LDMOMTHR, 6.3 BHR). Patient reported outcomes were better following revision for failed BHR compared to LDMOMTHR. There was no difference between the revision cohorts for cup inclination, metal ion levels and gender. Failure of the BHR has predominantly been due to those causes unique to resurfacing such as avascular necrosis and fracture. In our series, aggressive ALVAL was unusual and clinical outcome following revision was superior compared to LDMOMTHR failures. The likely mechanisms that are responsible for the differences in outcome and the clinical implications will be discussed.