Long-term outcome of nonoperative treatment of Perthes' disease : only 19% total hip arthroplasty at a mean follow-up of 48 years.

AIMS: The outcome in Perthes' disease deteriorates with increasing follow-up, ending with total hip arthroplasty (THA) in patients with severe complaints. The purpose of this study was to assess the prevalence of THA according to length of follow-up and to define risk factors for THA.

METHODS

Patients were recruited from the radiological archive at Oslo University Hospital HF. In total, 229 patients (244 hips) were included in the study (184 males). The mean age at diagnosis was 6.2 years (2.1 to 13.7). A total of 105 hips (43%) were classified as spherical, 93 (38%) as ovoid, and 46 (19%) as flat. The mean time from diagnosis to follow-up was 48 years (27 to 72). Inclusion criteria were patients with nonoperative treatment for Perthes' disease and ≥ 25 years' follow-up. Sphericity of the femoral head at the healing stage was classified with the modified Stulberg method, which is a three-group classification based on the shape of the femoral head: spherical, ovoid, or flat. Information regarding THA was provided by the Norwegian Arthroplasty Register.

RESULTS

Overall, 47 hips (19%) had undergone THA at a mean patient age of 46 years (22 to 72). The most important prognostic factors for THA were femoral head sphericity and age at onset. The frequency of THA was 3% in hips with spherical femoral heads, 25% in ovoid heads, and 46% in flat heads. Age ≥ six years was associated with THA more frequently than age < six years (28% and 10%, respectively). Kaplan-Meier survival analysis showed a survival rate at 50 years' follow-up of 99% (95% CI 96 to 100) in spherical hips, 76% (95% CI 66 to 86) in ovoid hips, and 48% (95% CI 29 to 67) in flat hips.

CONCLUSION

After a mean follow-up of 48 years, 47 of 244 nonoperatively treated hips had undergone THA (19%). The results indicate that the aim of treatment should be to obtain a spherical femoral head.