title: Treatment of recurrent THR dislocation using of a cementless dual-mobility cup: a 59 cases series with a mean 8 years' follow-up.
abstract: BACKGROUND
  Instability is one of the most feared complications following total hip replacement (THR). In France, dual-mobility cups are widely used in acetabular revision for instability; few studies, however, have focused on this type of implant.
  
  
  OBJECTIVE
  The gain in stability provided by the dual-mobility implant allows the risk of dislocation to decrease by the sole revision of the acetabular component in case of recurrent instability.
  
  
  OBJECTIVE
  This hypothesis was tested over medium-term follow-up of a series of cementless dual-mobility cups implanted during isolated acetabular revision for recurrent dislocation.
  
  
  METHODS
  A series of THR revision for instability was analyzed retrospectively. Inclusion criteria were: recurrent THR dislocation treated by cementless dual-mobility cup, between 1995 and 2001. Radiological analysis used Imagika™ software. Fifty-nine patients were included; nine died before radioclinical follow-up could be performed; none of the survivors were lost to follow-up. Mean follow-up was 8 years (range, 6-11 years).
  
  
  RESULTS
  There was one early dislocation without recurrence; the dislocation rate was 1.7%. At follow-up, mean PMA score was 16.5 (12-18) and mean Harris score 86.7 (49-99). Radiologically, there was no loosening or migration, but 19% of X-ray views showed less than 1mm wide peri-acetabular radiolucency. With dislocation as censoring criterion, 8-year survivorship was 98% (95% CI: 95-100%).
  
  
  CONCLUSIONS
  The dislocation rate (1.7%) and clinical results were better than in most series of revision by constrained cup for recurrent dislocation. The high rate of peri-acetabular radiolucency would seem to relate to the external coating of the cup: aluminum oxide in the Novae-1 implant and aluminum oxide/hydroxyapatite in the Novae-E.
  
  
  CONCLUSIONS
  The use of dual-mobility cups to treat THR instability gave satisfactory results. We recommend dual-mobility cups with hydroxyapatite surface treatment over a porous metallic substrate, rather than with an aluminum oxide or an aluminum oxide/hydroxyapatite bilayer coating.
  
  
  METHODS
  Level IV. Retrospective Study.
authors.affiliation: Orthopedics Department, Amiens University Hospital, place Victor-Pauchet, 80054 Amiens, France. lwfred@gmail.com
authors.forename: F
authors.initials: F
authors.lastname: Leiber-Wackenheim
authors.forename: B
authors.initials: B
authors.lastname: Brunschweiler
authors.forename: M
authors.initials: M
authors.lastname: Ehlinger
authors.forename: A
authors.initials: A
authors.lastname: Gabrion
authors.forename: P
authors.initials: P
authors.lastname: Mertl
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects*; D005500:Follow-Up Studies; D006617:Hip Dislocation / Q000209:etiology / Q000601:surgery*; D006622:Hip Prosthesis; D006801:Humans; D008297:Male; D008875:Middle Aged; D011474:Prosthesis Design; D011475:Prosthesis Failure; D012008:Recurrence; D012189:Retrospective Studies; D013997:Time Factors; D016896:Treatment Outcome