The outcome and prognostic factors in children with bilateral Perthes' disease: a prospective study of 40 children with follow-up over five years.

AIMS: 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. PATIENTS AND 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. CONCLUSION: 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.

The acetabulum in Perthes' disease: a prospective study of 123 children.

PURPOSE: We assessed the radiographic changes of the acetabulum during the course of Perthes' disease and investigated whether they were associated with femoral head sphericity 5 years after diagnosis. METHODS: We studied 123 children with unilateral Perthes' disease, femoral head necrosis more than 50 % and age at diagnosis 6 years or older. Pelvic radiographs were taken at onset, 1 year and 5 years after diagnosis. Sharp's angle, acetabular depth-to-width ratio (ADR) and lateral acetabular inclination were measured. RESULTS: Compared to the unaffected hips, the Perthes' hips developed significantly higher Sharp's angles (p < 0.001) and a higher proportion with an upward-sloping lateral acetabular margin (Perthes' hips: 49 %, unaffected hips 1 %). The mean ADR values were significantly lower on the affected side at all stages (p < 0.001). ADR values at diagnosis were associated with a more spherical femoral head at the 5-year follow-up [odds ratio (OR) 1.012, 95 % confidence interval (CI) 1.002-1.022, p = 0.016]. None of the other acetabular parameters were significantly associated with the femoral head shape 5 years after diagnosis. CONCLUSION: The acetabulum developed an increasingly dysplastic shape in the course of Perthes' disease. Early dysplastic changes of the acetabulum were not associated with a poor radiological outcome 5 years after diagnosis. Routine measurement and monitoring of acetabular changes in plain radiographs were of little prognostic value and can, therefore, hardly be recommended in clinical practice.