title: Cup size and risk of dislocation after primary total hip arthroplasty.
abstract: We evaluated the relationship between cup diameter and dislocation risk in patients undergoing primary total hip arthroplasty (THA) with a 28-mm head. There were 50 dislocations, 28 of which occurred in 2221 (1.3%) THAs with a cup diameter smaller than 56 mm and 22 in 513 (4.3%) with a cup diameter of 56 mm or larger. Dislocation risk varied between 0.6% and 2.4% in the smaller cup group and between 4.1% and 5.2% in the larger cup group. The risk was substantially higher in the large cup group (unadjusted odds ratio, 3.5; 95% confidence interval, 2.0-6.2). Multivariable logistic regression revealed an adjusted odds ratio of 2.4 (95% confidence interval, 1.2-4.9). Patients with THA (28-mm head) had more than twice the risk of dislocation with cup size of 56 mm or higher compared to patients with smaller cups.
authors.affiliation: Division of Orthopaedics and Trauma Surgery, University Hospitals of Geneva, Geneva, Switzerland.
authors.forename: Robin
authors.initials: R
authors.lastname: Peter
authors.forename: Anne
authors.initials: A
authors.lastname: Lübbeke
authors.forename: Richard
authors.initials: R
authors.lastname: Stern
authors.forename: Pierre
authors.initials: P
authors.lastname: Hoffmeyer
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D019644:Arthroplasty, Replacement, Hip / Q000295:instrumentation* / Q000379:methods*; D015331:Cohort Studies; D005260:Female; D005270:Femur Head / Q000473:pathology / Q000601:surgery*; D006617:Hip Dislocation / Q000453:epidemiology*; D006621:Hip Joint / Q000601:surgery*; D006622:Hip Prosthesis; D006801:Humans; D015994:Incidence; D016015:Logistic Models; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D015207:Osteoarthritis, Hip / Q000601:surgery; D011446:Prospective Studies; D011474:Prosthesis Design; D011475:Prosthesis Failure; D012189:Retrospective Studies; D012307:Risk Factors; D016896:Treatment Outcome