title: The withdrawn ASR™ THA and hip resurfacing systems: how have our patients fared over 1 to 6 years?
abstract: BACKGROUND
  The Articular Surface Replacement™ (ASR™) metal-on-metal hip arthroplasty system (DePuy Orthopaedics, Inc, Warsaw, IN, USA) reportedly has a higher than anticipated early failure rate leading to a voluntary recall. This prompted us to evaluate all ASR™ components implanted at our center.
  
  
  OBJECTIVE
  In all ASR™ components, we reported (1) revision rate, (2) blood metal ion levels, and (3) intraoperative findings for revisions related to adverse reaction to metal debris (ARMD).
  
  
  METHODS
  We retrospectively reviewed all 172 patients (190 hips) who underwent THA (149 hips) or hip resurfacing (41 hips) with the ASR™ system. We determined failure rates. We obtained blood metal ion concentrations from 93 patients at last followup. We evaluated MRI studies and intraoperative histopathology. Minimum followup was 12 months (mean, 40 months; range, 12-74 months).
  
  
  RESULTS
  At latest followup, we had revised 24 of 190 hips (13%): in 18 patients with THA and five patients with resurfacing. Mean time to revision was 45 months (range, 12-75 months). Mean blood concentrations were 13 μg/L (range, 0-150 μg/L) for cobalt and 6 μg/L (range, 0-87 μg/L) for chromium. Mean prerevision blood metal ion levels were higher in the revised group (cobalt: 48 μg/L; chromium: 18 μg/L) than in the nonrevised group (cobalt: 5 μg/L; chromium: 2 μg/L). ARMD was present in 14 of the 24 hips revised in this study.
  
  
  CONCLUSIONS
  Surgeons must have a low threshold for concern for ARMD in patients with ASR™ systems. Blood metal ion levels and MRI can be used to evaluate patients with underperforming implants. Intraoperative histopathologic analysis and joint fluid cytology can help diagnose ARMD at the time of revision.
  
  
  METHODS
  Level III, therapeutic study. See Instructions for Authors for a complete description of levels of evidence.
authors.affiliation: Department of Orthopaedic Surgery, Duke University Medical Center, Box 3269, Durham, NC 27710, USA. kevin.hug@gmail.com
authors.forename: Kevin T
authors.initials: KT
authors.lastname: Hug
authors.forename: Tyler S
authors.initials: TS
authors.lastname: Watters
authors.forename: Thomas P
authors.initials: TP
authors.lastname: Vail
authors.forename: Michael P
authors.initials: MP
authors.lastname: Bolognesi
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D019644:Arthroplasty, Replacement, Hip / Q000379:methods*; D002857:Chromium / Q000097:blood; D003035:Cobalt / Q000097:blood; D005260:Female; D006621:Hip Joint / Q000601:surgery*; D006622:Hip Prosthesis; D006801:Humans; D008297:Male; D057052:Medical Device Recalls; D008875:Middle Aged; D015207:Osteoarthritis, Hip / Q000601:surgery; D011474:Prosthesis Design; D011475:Prosthesis Failure; D012086:Reoperation; D012189:Retrospective Studies; D016896:Treatment Outcome
chemical_list: D002857:Chromium; D003035:Cobalt