title: Revision of metal-on-metal hip arthroplasty in a tertiary center: a prospective study of 39 hips with between 1 and 4 years of follow-up.
abstract: OBJECTIVE
  Operative findings during revision of metal-on-metal hip arthroplasty (MOMHA) vary widely and can involve massive soft tissue and bone disruption. As a result, planning of theater time and resources is difficult, surgery is challenging, and outcomes are often poor. We describe our experience with revision of MOMHA and provide recommendations for management.
  
  
  METHODS
  We present the findings and outcomes of 39 consecutive MOMHAs (in 35 patients) revised in a tertiary unit (median follow-up time 30 (12-54) months). The patients underwent a preoperative work-up including CT, metal artifact reduction sequence (MARS) MRI, and blood metal ion levels.
  
  
  RESULTS
  We determined 5 categories of failure. 8 of 39 hips had conventional failure mechanisms including infection and impingement. Of the other 31 hips, 14 showed synovitis without significant disruption of soft tissue; 6 had a cystic pseudotumor with significant soft tissue disruption; 7 had significant osteolysis; and 4 had a solid pseudotumor. Each category of failure had specific surgical hazards that could be addressed preoperatively. There were 2 reoperations and 1 patient (2 hips) died of an unrelated cause. Median Oxford hip score (OHS) was 37 (9-48); median change (ΔOHS) was 17 (-10 to 41) points. ΔOHS was similar in all groups-except those patients with solid pseudotumors and those revised to metal-on-metal bearings, who fared worse.
  
  
  CONCLUSIONS
  Planning in revision MOMHA is aided by knowledge of the different categories of failure to enable choice of appropriate personnel, theater time, and equipment. With this knowledge, satisfactory outcomes can be achieved in revision of metal-on-metal hip arthroplasty.
authors.affiliation: Department of Orthopaedic Surgery, Imperial College, Charing Cross Hospital, London, UK.
authors.forename: Alexander D
authors.initials: AD
authors.lastname: Liddle
authors.forename: Keshtra
authors.initials: K
authors.lastname: Satchithananda
authors.forename: Johann
authors.initials: J
authors.lastname: Henckel
authors.forename: Shiraz A
authors.initials: SA
authors.lastname: Sabah
authors.forename: Karuniyan V
authors.initials: KV
authors.lastname: Vipulendran
authors.forename: Angus
authors.initials: A
authors.lastname: Lewis
authors.forename: John A
authors.initials: JA
authors.lastname: Skinner
authors.forename: Adam W M
authors.initials: AW
authors.lastname: Mitchell
authors.forename: Alister J
authors.initials: AJ
authors.lastname: Hart
mesh_terms: D000328:Adult; D000368:Aged; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects / Q000379:methods*; D019544:Equipment Failure Analysis / Q000379:methods; D005260:Female; D005500:Follow-Up Studies; D006622:Hip Prosthesis; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008670:Metals; D008875:Middle Aged; D011446:Prospective Studies; D011474:Prosthesis Design; D011475:Prosthesis Failure; D016459:Prosthesis-Related Infections / Q000209:etiology; D012086:Reoperation / Q000379:methods; D013585:Synovitis / Q000209:etiology; D014057:Tomography, X-Ray Computed; D016896:Treatment Outcome
chemical_list: D008670:Metals