title: A survey on the prevalence of pseudotumors with metal-on-metal hip resurfacing in Canadian academic centers.
abstract: BACKGROUND
  Metal-on-metal bearings for hip arthroplasty have been in clinical use for over twenty years with excellent clinical results reported worldwide. A small percentage (<1%) of patients have developed an inflammatory response, and a more severe inflammatory response termed pseudotumor has been more recently reported. The primary purpose of this study was to determine the prevalence of pseudotumor following metal-on-metal hip resurfacing in Canadian academic centers.
  
  
  METHODS
  Nine of the fourteen centers that perform metal-on-metal hip resurfacings were surveyed. The number of metal-on-metal hip resurfacing arthroplasties performed at each center was determined, as was the number of patients who presented with a pseudotumor and subsequently required revision hip surgery between 2002 and December 2008.
  
  
  RESULTS
  At the nine centers, 3432 hip resurfacing arthroplasties were performed; 76.9% of the patients were male, the mean age was 51.2 years (range, sixteen to eighty-three years), and the mean body-mass index was 28.1 (range, 17 to 55). The mean length of follow-up was 3.4 years (range, two to nine years). A pseudotumor developed after four of the 3432 arthroplasties, for a prevalence of 0.10%.
  
  
  CONCLUSIONS
  Although pseudotumors remain a concern after metal-on-metal hip resurfacing, the prevalence at short to midterm follow-up is very low in this multicenter survey. Continued close monitoring is required to determine what clinical factors are involved with the uncommon pseudotumor formation.
authors.affiliation: Division of Orthopaedic Surgery, University of Ottawa, Ottawa, 501 Smyth Road, CCW 1646, Box 502, Ottawa, ON K1H 8L6, Canada.
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects*; D002170:Canada / Q000453:epidemiology; D005260:Female; D005500:Follow-Up Studies; D005549:Foreign-Body Reaction / Q000453:epidemiology* / Q000601:surgery; D006104:Granuloma, Plasma Cell / Q000453:epidemiology* / Q000601:surgery; D006622:Hip Prosthesis / Q000009:adverse effects*; D006801:Humans; D008297:Male; D008670:Metals; D008875:Middle Aged; D015995:Prevalence; D012086:Reoperation; D013499:Surface Properties
chemical_list: D008670:Metals