title: Migration pattern of a cobalt-chrome monoblock acetabular component after metal-on-metal hip resurfacing.
abstract: OBJECTIVE
  The purpose of this study was to study the initial fixation and migration pattern of a monoblock acetabular component used for a metal on metal hip resurfacing using Einzel Bild Roentgen Analyse (EBRA).
  
  
  METHODS
  99 patients with a mean age of 49.6 years (range 28.5-66.3 years) of whom 14 were bilateral underwent a hip resurfacing (Conserve Plus®, MicroPort, Memphis, TN) for a total of 113 resurfacings. Acetabular component orientation was noted with 35 of the 113 components (31.0%) having a lucency &gt;2 mm on the immediate postoperative radiograph.
  
  
  RESULTS
  The mean follow-up for our cohort of 113 hips is 50 months (2-79 months). When examining the 2-year migration mark, 37 of the 113 hips exceeded the threshold of 0.5 mm/year with a median total migration of 1.40 mm (range 1.02-4.24). 6 resurfacings underwent revision surgery for aseptic loosening of the acetabular component at a mean time of 43.6 months. Presence of initial lucency (OR 2.29, p = 0.05) was the only significant predictor of migration over threshold at 2-years. Those that had migrated over the threshold (1.0 mm) at 2 years were at significantly greater risk of continued migration at 4 years.
  
  
  CONCLUSIONS
  The migration pattern of this component raises concerns about long term performance, with postoperative lucencies representing a significant factor for future migration.
authors.affiliation: University of Ottawa, Division of Orthopaedic Surgery, The Ottawa Hospital, Ontario - Canada.
authors.forename: Richard
authors.initials: R
authors.lastname: Roda
authors.affiliation: University of Ottawa, Division of Orthopaedic Surgery, The Ottawa Hospital, Ontario - Canada.
authors.forename: Paul M
authors.initials: PM
authors.lastname: Whittingham-Jones
authors.affiliation: University of Ottawa, Division of Orthopaedic Surgery, The Ottawa Hospital, Ontario - Canada.
authors.forename: Joshua
authors.initials: J
authors.lastname: Lee
authors.affiliation: University of Ottawa, Division of Orthopaedic Surgery, The Ottawa Hospital, Ontario - Canada.
authors.forename: Jae-Jin
authors.initials: JJ
authors.lastname: Ryu
authors.affiliation: University of Ottawa, Division of Orthopaedic Surgery, The Ottawa Hospital, Ontario - Canada.
authors.forename: Paul E
authors.initials: PE
authors.lastname: Beaulé
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects* / Q000379:methods; D002858:Chromium Alloys / Q000009:adverse effects; D015331:Cohort Studies; D005260:Female; D005500:Follow-Up Studies; D005548:Foreign-Body Migration / Q000000981:diagnostic imaging / Q000601:surgery*; D006622:Hip Prosthesis; D006801:Humans; D016015:Logistic Models; D008297:Male; D061825:Metal-on-Metal Joint Prostheses / Q000009:adverse effects*; D008875:Middle Aged; D011475:Prosthesis Failure; D012086:Reoperation / Q000379:methods; D012189:Retrospective Studies; D018570:Risk Assessment; D012737:Sex Factors; D013997:Time Factors; D014057:Tomography, X-Ray Computed / Q000379:methods; D016896:Treatment Outcome
chemical_list: D002858:Chromium Alloys