title: Dual mobility cup in revision total hip arthroplasty: dislocation rate and survival after 5 years.
abstract: BACKGROUND
  Dislocation is a common complication of total hip arthroplasty (THA), particularly when performed as revision surgery. Dual mobility cups (DMCs) minimize the risk of instability when implanted during primary THA. However, their usefulness and survival in revision THA remain unclear. We therefore conducted a retrospective study to assess DMC stability and survival at a minimal follow-up period of 5years after revision THA.
  
  
  OBJECTIVE
  The dislocation rate associated with DMCs for revision THA is similar to that seen after primary THA.
  
  
  METHODS
  Cup exchange with implantation of a DMC was performed in 71 patients (74 hips) between 2000 and 2007, for the following reasons: recurrent dislocation (n=22), aseptic loosening (n=38), and infection (n=14). The DMCs were cemented in 47 cases and cementless in 27 cases. The clinical variables (Merle d'Aubigné-Postel score and Harris Hip Score) and radiological findings were collected retrospectively from the medical records and compared with those obtained at the last follow-up visit.
  
  
  RESULTS
  Of the 74 cases, 2 were lost to follow-up. At last follow-up, the mean Merle d'Aubigné-Postel score was 15.2 (11-18) and the mean Harris Hip Score was 80.4 (51-98). Of the 8 failures, 2 (2/72, 2.7%) were related to mechanical factors (1 case each of aseptic loosening and dislocation) and 6 were changed because of infection (recurrent infection, n=4). Mechanical failure was not linked to a specific reason for revision THA. A radiolucent line was visible in 4 cases but this finding was not associated with clinical manifestations. When failure was defined as cup revision for any non-infectious complication, 5-year implant survival was 99% (95% confidence interval, 93-100%).
  
  
  CONCLUSIONS
  Use of a DMC in revision THA was associated with a slightly higher dislocation rate (1/72, 1.4%) than in primary THA, whereas 5-year survival was comparable. Cemented DMCs were not associated with a greater risk of loosening.
  
  
  CONCLUSIONS
  DMCs are useful to decrease the risk of dislocation in revision THA performed for any reason. The low rate of loosening indicates that DMCs do not result in high stresses at the bone-implant interface.
  
  
  METHODS
  IV, retrospective study.
authors.affiliation: Services d'orthopédie 1 et 2, CHU de Tours, avenue de la République, 37044 Tours cedex 09, France; Université François-Rabelais de Tours, PRES Centre-Val de Loire Université, 37020 Tours, France.
authors.forename: E
authors.initials: E
authors.lastname: Simian
authors.affiliation: Services d'orthopédie 1 et 2, CHU de Tours, avenue de la République, 37044 Tours cedex 09, France; Université François-Rabelais de Tours, PRES Centre-Val de Loire Université, 37020 Tours, France.
authors.forename: R
authors.initials: R
authors.lastname: Chatellard
authors.affiliation: Services d'orthopédie 1 et 2, CHU de Tours, avenue de la République, 37044 Tours cedex 09, France; Université François-Rabelais de Tours, PRES Centre-Val de Loire Université, 37020 Tours, France.
authors.forename: J
authors.initials: J
authors.lastname: Druon
authors.affiliation: Services d'orthopédie 1 et 2, CHU de Tours, avenue de la République, 37044 Tours cedex 09, France; Université François-Rabelais de Tours, PRES Centre-Val de Loire Université, 37020 Tours, France.
authors.forename: J
authors.initials: J
authors.lastname: Berhouet
authors.affiliation: Services d'orthopédie 1 et 2, CHU de Tours, avenue de la République, 37044 Tours cedex 09, France; Université François-Rabelais de Tours, PRES Centre-Val de Loire Université, 37020 Tours, France. Electronic address: philippe.rosset@univ-tours.fr.
authors.forename: P
authors.initials: P
authors.lastname: Rosset
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019644:Arthroplasty, Replacement, Hip; D005260:Female; D005500:Follow-Up Studies; D006622:Hip Prosthesis / Q000009:adverse effects*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011474:Prosthesis Design; D011475:Prosthesis Failure; D012086:Reoperation; D012189:Retrospective Studies
keywords: Dislocation rate; Dual mobility cup; Survivorship; Total hip replacement; Total hip revision