title: A comparison of explanted Articular Surface Replacement and Birmingham Hip Resurfacing components.
abstract: The Articular Surface Replacement (ASR) hip resurfacing arthroplasty has a failure rate of 12.0% at five years, compared with 4.3% for the Birmingham Hip Resurfacing (BHR). We analysed 66 ASR and 64 BHR explanted metal-on-metal hip replacements with the aim of understanding their mechanisms of failure. We measured the linear wear rates of the acetabular and femoral components and analysed the clinical cause of failure, pre-revision blood metal ion levels and orientation of the acetabular component. There was no significant difference in metal ion levels (chromium, p = 0.82; cobalt, p = 0.40) or head wear rate (p = 0.14) between the two groups. The ASR had a significantly increased rate of wear of the acetabular component (p = 0.03) and a significantly increased occurrence of edge loading (p < 0.005), which can be attributed to differences in design between the ASR and BHR. The effects of differences in design on the in vivo wear rates are discussed: these may provide an explanation as to why the ASR is more sensitive to suboptimal positioning than the BHR.
authors.affiliation: Imperial College London, Department of Musculoskeletal Science, Charing Cross Hospital, London W6 8RF, UK.
authors.forename: R
authors.initials: R
authors.lastname: Underwood
authors.forename: A
authors.initials: A
authors.lastname: Matthies
authors.forename: P
authors.initials: P
authors.lastname: Cann
authors.forename: J A
authors.initials: JA
authors.lastname: Skinner
authors.forename: A J
authors.initials: AJ
authors.lastname: Hart
mesh_terms: D000328:Adult; D000368:Aged; D019644:Arthroplasty, Replacement, Hip / Q000295:instrumentation* / Q000379:methods; D002857:Chromium / Q000097:blood; D003035:Cobalt / Q000097:blood; D019544:Equipment Failure Analysis; D005260:Female; D006622:Hip Prosthesis / Q000706:statistics & numerical data*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011474:Prosthesis Design; D011475:Prosthesis Failure; D012189:Retrospective Studies; D055815:Young Adult
chemical_list: D002857:Chromium; D003035:Cobalt