title: Dual-mobility cups for revision due to instability are associated with a low rate of re-revisions due to dislocation: 228 patients from the Swedish Hip Arthroplasty Register.
abstract: OBJECTIVE
  Revision total hip arthroplasty (THA) due to recurrent dislocations is associated with a high risk of persistent instability. We hypothesized that the use of dual-mobility cups would reduce the risk of re-revision due to dislocation after revision THA.
  
  
  METHODS
  228 THA cup revisions (in 228 patients) performed due to recurrent dislocations and employing a specific dual-mobility cup (Avantage) were identified in the Swedish Hip Arthroplasty Register. Kaplan-Meier survival analysis was performed with re-revision due to dislocation as the primary endpoint and re-revision for any reason as the secondary endpoint. Cox regression models were fitted in order to calculate the influence of various covariates on the risk of re-revision.
  
  
  RESULTS
  58 patients (25%) had been revised at least once prior to the index cup revision. The surgical approach at the index cup revision was lateral in 99 cases (44%) and posterior in 124 cases (56%). Median follow-up was 2 (0-6) years after the index cup revision, and by then 18 patients (8%) had been re-revised for any reason. Of these, 4 patients (2%) had been re-revised due to dislocation. Survival after 2 years with the endpoint revision of any component due to dislocation was 99% (95% CI: 97-100), and it was 93% (CI: 90-97) with the endpoint revision of any component for any reason. Risk factors for subsequent re-revision for any reason were age between 50-59 years at the time of the index cup revision (risk ratio (RR) = 5 when compared with age > 75, CI: 1-23) and previous revision surgery to the relevant joint (RR = 1.7 per previous revision, CI: 1-3).
  
  
  CONCLUSIONS
  The risk of re-revision due to dislocation after insertion of dual-mobility cups during revision THA performed for recurrent dislocations appears to be low in the short term. Since most dislocations occur early after revision THA, we believe that this device adequately addresses the problem of recurrent instability. Younger age and prior hip revision surgery are risk factors for further revision surgery. However, problems such as potentially increased liner wear and subsequent aseptic loosening may be associated with the use of such devices in the long term.
authors.affiliation: Department of Orthopaedics, Institute of Surgical Sciences, Uppsala University Hospital, Uppsala, Sweden. nils.hailer@surgsci.uu.se
authors.forename: Nils P
authors.initials: NP
authors.lastname: Hailer
authors.forename: Rüdiger J
authors.initials: RJ
authors.lastname: Weiss
authors.forename: André
authors.initials: A
authors.lastname: Stark
authors.forename: Johan
authors.initials: J
authors.lastname: Kärrholm
mesh_terms: D000077:Acetabulum / Q000601:surgery; D000367:Age Factors; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects* / Q000379:methods; D016009:Chi-Square Distribution; D016001:Confidence Intervals; D005260:Female; D005500:Follow-Up Studies; D006622:Hip Prosthesis; D006801:Humans; D015994:Incidence; D007593:Joint Instability / Q000209:etiology / Q000601:surgery*; D053208:Kaplan-Meier Estimate; D008297:Male; D016016:Proportional Hazards Models; D011474:Prosthesis Design; D011475:Prosthesis Failure; D012042:Registries; D012086:Reoperation / Q000379:methods / Q000706:statistics & numerical data*; D012189:Retrospective Studies; D018570:Risk Assessment; D012737:Sex Factors; D013548:Sweden; D013997:Time Factors; D016896:Treatment Outcome