title: Obesity is no longer a risk factor for dislocation after total hip arthroplasty with a double-mobility cup.
abstract: OBJECTIVE
  Dislocation is one of the most feared complications after total hip arthroplasty (THA). This risk is greater in obese patients compared with the general population.
  
  
  METHODS
  We performed a retrospective cohort study in which the main objective was to compare the dislocation rate between obese patients (BMI > 30 kg/m²) (exposed group) and non-obese patients (BMI ≤ 30 kg/m²) (unexposed group) after primary THA with a double-mobility acetabular cup. The patients had a minimum follow-up of 24 months.
  
  
  RESULTS
  The 'obese' group consisted of 77 THA cases and the 'non-obese' group of 425 cases; the two groups were similar in terms of age, gender and ASA score. After a mean follow-up of 58.3 ± 27 months (range 27-159), 43 patients had been lost to follow-up and 56 had died; the two groups had similar mean values. One patient in the 'obese' group had suffered a dislocation due to a fall 16 months after the THA. One patient in the 'non-obese' group had suffered a dislocation after a periprosthetic femur fracture with stem subsidence two months after the THA procedure. Both patients underwent surgical revision where the double-mobility cup was preserved; there were no further dislocation events as of the last follow-up. The dislocation rate in the two groups was similar (1.3 % versus 0.23%, p > 0.05). No cases of loosening were found. Revisions were secondary to deep or superficial infection (n = 22), periprosthetic femur fracture (n = 10) or haematoma (n = 3).
  
  
  CONCLUSIONS
  These findings imply that double-mobility cups are a reliable way of reducing the risk of dislocation in obese patients after primary THA.
authors.affiliation: Orthopaedic and Trauma Surgery Department, Hôpital Pierre Paul Riquet, Centre Hospitalier Universitaire de Toulouse, Toulouse, France.
authors.forename: Paul
authors.initials: P
authors.lastname: Maisongrosse
authors.forename: Benoit
authors.initials: B
authors.lastname: Lepage
authors.forename: Etienne
authors.initials: E
authors.lastname: Cavaignac
authors.forename: Régis
authors.initials: R
authors.lastname: Pailhe
authors.forename: Nicolas
authors.initials: N
authors.lastname: Reina
authors.forename: Philippe
authors.initials: P
authors.lastname: Chiron
authors.forename: Jean-Michel
authors.initials: JM
authors.lastname: Laffosse
mesh_terms: D000328:Adult; D000368:Aged; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects / Q000379:methods*; D015331:Cohort Studies; D005260:Female; D005500:Follow-Up Studies; D006617:Hip Dislocation / Q000453:epidemiology / Q000209:etiology / Q000601:surgery*; D006622:Hip Prosthesis / Q000009:adverse effects; D006801:Humans; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000150:complications*; D011183:Postoperative Complications; D012086:Reoperation; D012189:Retrospective Studies; D012307:Risk Factors