Radiologic outcomes of bilateral and unilateral perthes disease: A comparative cohort study

Introduction: This study was undertaken to compare the radiologic outcomes of bilateral and unilateral Perthes disease and also to evaluate the outcome of synchronous and metachronous bilateral Perthes disease. Methods: Of 353 children with Perthes disease followed up from presentation to healing during the last 10 years, 37 had bilateral involvement (11 synchronous and 26 metachronous onset). The radiologic outcomes of each hip of children with bilateral disease were compared with outcomes of 148 children with unilateral disease who were matched for age, sex, and treatment. Children with unilateral or bilateral diseases were treated with a proximal femoral varus derotation osteotomy if they fulfilled the criteria for surgery. The primary outcome measure was the shape of the femoral head at healing assessed by the Sphericity Deviation Score (SDS). Results: The children with bilateral disease were younger than those with unilateral disease (6.2 vs. 7.03 y; P < 0.001), and they had a longer duration of the disease. All other characteristics of bilateral and unilateral cases were similar. The SDS values of unilateral and bilateral disease were comparable, as were the SDS of synchronous and metachronous bilateral disease. The effect of early surgery on the evolution of the disease in bilateral cases was similar to that reported in unilateral disease. The age of onset of the disease alone influenced the SDS in bilateral cases. Conclusion: The age at onset of the bilateral disease is lower, the duration of the disease longer than that of unilateral disease, but the disease outcome is similar.