title: A comparative and retrospective study of three hundred and twenty primary Charnley type hip replacements with a minimum follow up of ten years to assess whether a dual mobility cup has a decreased dislocation risk.
abstract: OBJECTIVE
  Mid- and long-term follow-up of Charnley total hip arthroplasty (THA) demonstrated good functional results with 85 % survivorship at 25-year follow-up. However, dislocation still remains an unsolved problem. Dislocation may occur throughout the patient's and implant's life. The aim of this study is to answer the question: does a dual mobility cup (DMC) decrease the dislocation risk?
  
  
  METHODS
  We report comparative results at ten years of follow-up of two groups of primary cemented Charnley-type THA, one with a standard polyethylene cup (group 1, n = 215) and the other one with a DMC (group 2, n = 105).
  
  
  RESULTS
  In group 1, 26 dislocations (12.9 %) occurred. In group 2 only one dislocation (0.9 %) occurred. This dislocation was successfully reduced by closed reduction, without any recurrence. This difference was statistically significant (p = 0.0018). In group 1, the reason for revision was recurrent dislocation in 21 cases. Five patients were revised for other reasons. The global revision rate was 12.9 %. In group 2, two patients needed revision surgery for aseptic loosening. The global revision rate was 2.1 %. This difference was statistically significant (p = 0.054). The goal was reached for the patients of group 2 who had more risks factors for dislocation (age, aetiology, American Society of Anesthesiologists and Devane scores) than those of group 1.
  
  
  CONCLUSIONS
  When using a DMC, we observed a low rate of dislocation in primary THA (0.9 %). This surgical choice seems to be a safe and effective technique in Charnley-type THA, especially in a high-risk population.
authors.affiliation: Clinique Emilie de Vialar, 116 rue Antoine Charial, 69003, Lyon, France, caton.jacques@wanadoo.fr.
authors.forename: Jacques H
authors.initials: JH
authors.lastname: Caton
authors.forename: Jean Louis
authors.initials: JL
authors.lastname: Prudhon
authors.forename: André
authors.initials: A
authors.lastname: Ferreira
authors.forename: Thierry
authors.initials: T
authors.lastname: Aslanian
authors.forename: Régis
authors.initials: R
authors.lastname: Verdier
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D019644:Arthroplasty, Replacement, Hip / Q000295:instrumentation*; D002484:Cementation; D005260:Female; D005500:Follow-Up Studies; D006617:Hip Dislocation / Q000517:prevention & control*; D006621:Hip Joint; D006622:Hip Prosthesis; D006801:Humans; D007592:Joint Diseases / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies
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