title: The outcome and prognostic factors in children with bilateral Perthes' disease: a prospective study of 40 children with follow-up over five years.
abstract: OBJECTIVE
  The aims of this study were to describe the course of non-operatively managed, bilateral Perthes' disease, and to determine specific prognostic factors for the radiographic and clinical outcome.
  
  
  METHODS
  We identified 40 children with a mean age of 5.9 years (1.8 to 13.5), who were managed non-operatively for bilateral Perthes' disease from our prospective, multicentre study of this condition, which included all children in Norway who were diagnosed with Perthes' disease in the five-year period between 1996 and 2000. All children were followed up for five years. The hips were classified according to the Catterall classification. A modified three-group Stulberg classification was used as an outcome measure, with a spherical femoral head being defined as a good outcome, an oval head as fair, and a flat femoral head as a poor outcome.
  
  
  RESULTS
  Concurrent, simultaneous bilateral Perthes' disease was seen in 23 children and 17 had the sequential onset of bilateral disease. The mean delay in onset for the second hip in the latter group was 1.9 years (0.3 to 5.5). The five-year radiographic outcome was good in 30 (39%), fair in 25 (33%) and poor in 21 (28%) of the hips. The strongest predictors of poor outcome were > 50% necrosis of the femoral head, with odds ratio (OR) 19.6, and age at diagnosis > 6 years (OR 3.3). Other risk factors for poor outcome were the timing of the onset of disease, where children with the sequential onset of bilateral disease had a higher risk than those with the concurrent onset of bilateral disease (p = 0.021, chi-squared test). Following a diagnosis of Perthes' disease in one hip, there was a 5% chance of developing it in the contralateral hip.
  
  
  CONCLUSIONS
  These results imply that we need to distinguish between children with concurrent onset and those with sequential onset of bilateral Perthes' disease, as the outcomes may be different. This has not been previously described. Children with concurrent onset of bilateral disease had a similar outcome to our previous series of those with unilateral disease, whereas children with sequential onset of bilateral disease had a worse prognosis. The increased risk of developing Perthes' disease in the contralateral hip in those with unilateral disease is important information for the child and parents.
authors.affiliation: Oslo University Hospital Rikshospitalet, Postboks 4950 Nydalen, 0424 Oslo, Norway.
authors.forename: O
authors.initials: O
authors.lastname: Wiig
authors.affiliation: Oslo University Hospital Rikshospitalet, Postboks 4950 Nydalen, 0424 Oslo, Norway.
authors.forename: S
authors.initials: S
authors.lastname: Huhnstock
authors.affiliation: Oslo University Hospital Rikshospitalet, Postboks 4950 Nydalen, 0424 Oslo, Norway.
authors.forename: T
authors.initials: T
authors.lastname: Terjesen
authors.affiliation: Oslo University Hospital Rikshospitalet, Postboks 4950 Nydalen, 0424 Oslo, Norway.
authors.forename: A H
authors.initials: AH
authors.lastname: Pripp
authors.affiliation: Sørlandet Sykehus, Arendal, Postboks 783 Stoa, NO-4809 Arendal, Norway.
authors.forename: S
authors.initials: S
authors.lastname: Svenningsen
mesh_terms: D000293:Adolescent; D001175:Arthrography / Q000379:methods*; D002648:Child; D002675:Child, Preschool; D005260:Female; D005270:Femur Head / Q000000981:diagnostic imaging*; D005500:Follow-Up Studies; D006621:Hip Joint / Q000000981:diagnostic imaging* / Q000503:physiopathology; D006801:Humans; D015994:Incidence; D007223:Infant; D007873:Legg-Calve-Perthes Disease / Q000000981:diagnostic imaging / Q000453:epidemiology / Q000628:therapy*; D008297:Male; D009664:Norway / Q000453:epidemiology; D019637:Orthopedic Procedures / Q000379:methods*; D011379:Prognosis; D011446:Prospective Studies; D015203:Reproducibility of Results; D012307:Risk Factors; D013997:Time Factors
keywords: Perthes disease; bilateral disease; hip; prognostic factors