title: What factors predict failure 4 to 12 years after periacetabular osteotomy?
abstract: BACKGROUND
  The goal of periacetabular osteotomy (PAO) is to delay or prevent osteoarthritic development in dysplastic hips. However, it is unclear whether the surgical goals are achieved and if so in which patients. This information is essential to select appropriate patients for a durable PAO that achieves its goals.
  
  
  OBJECTIVE
  We therefore (1) determined hip survival rates; (2) determined how many preserved hips were functionally unsuccessful after PAO; and (3) identified demographic, clinical, and radiographic factors predicting failure after PAO.
  
  
  METHODS
  We retrospectively reviewed 316 patients (401 hips) who had PAO between December 1998 and May 2007. We evaluated radiographic parameters of dysplasia and osteoarthritis and obtained WOMAC scores. Through inquiry to the National Registry of Patients, we identified conversions to THA. Risk factors for conversion to THA were assessed. Minimum followup was 4 years (mean, 8 years; range, 4-12 years).
  
  
  RESULTS
  The overall Kaplan-Meier hip survival rate was 74.8% at 12.4 years. A WOMAC pain score of 10 or more, suggesting clinical failure, was observed in 13% of preserved hips at last followup. Higher age, preoperative Tönnis grade of 2, incongruent hip, postoperative joint space width of 3 mm or less, and postoperative center-edge angle of less than 30° or more than 40° predicted conversion to THA.
  
  
  CONCLUSIONS
  PAO preserved three of four hips with most functioning well at 4- to 12-year followup. When planning surgery, surgeons should attempt to achieve hip congruence and a center-edge angle of between 30° to 40° to improve the durability of PAO.
  
  
  METHODS
  Level II, prognostic study. See Instructions for Authors for a complete description of levels of evidence.
authors.affiliation: Orthopaedic Research Unit, Aarhus University Hospital, Tage-Hansens Gade 2, Building 10A, 8000 Aarhus C, Denmark. hartig@dadlnet.dk
authors.forename: Charlotte
authors.initials: C
authors.lastname: Hartig-Andreasen
authors.forename: Anders
authors.initials: A
authors.lastname: Troelsen
authors.forename: Theis Muncholm
authors.initials: TM
authors.lastname: Thillemann
authors.forename: Kjeld
authors.initials: K
authors.lastname: Søballe
mesh_terms: D000077:Acetabulum / Q000601:surgery*; D000328:Adult; D019644:Arthroplasty, Replacement, Hip; D005260:Female; D006618:Hip Dislocation, Congenital / Q000000981:diagnostic imaging / Q000601:surgery*; D006621:Hip Joint / Q000000981:diagnostic imaging* / Q000601:surgery; D006801:Humans; D008297:Male; D015207:Osteoarthritis, Hip / Q000000981:diagnostic imaging* / Q000517:prevention & control / Q000601:surgery; D010027:Osteotomy; D011859:Radiography; D012189:Retrospective Studies; D013997:Time Factors; D017211:Treatment Failure; D055815:Young Adult