[Sonography for evaluation of containment in perthes disease: a comparison with magnetic resonance imaging]

The objective of the present study was to investigate whether the sonographic visualization of lateralization of the femoral head is comparable to magnetic resonance imaging (MRI) and would therefore be able to contribute to the diagnosis of containment in patients with Perthes disease.

46 patients with unilateral Perthes disease (age: 5.9 +/- 2.3 years) of Catterall group III/IV were evaluated at first presentation by means of ultrasound (US) and MRI of both hip joints to evaluate the morphology of the acetabular lip (LA) and the epiphysis (EP). The diagnosis of containment was performed in MRI as well as in US by the protrusion and deformity of the epiphysis of the femoral head with cranialization of the labrum. The evaluation of the sonographic and MRI findings was carried out independently by three observers (high experience: 1, 2, low experience: 3). Statistical analysis was performed using Cohen's non-weighted kappa kappa (kappa > 0.75 very high level of correlation). The study was conducted in accordance with the recommendations of the local ethics committee that approved our study.

There was a high to very high agreement of the morphology of the LA and EP between observers 1 and 2 (MRI: LA: kappa = 0.87; EP: kappa = 0.90; US: LA kappa = 1.0; EP: kappa = 0.57). The comparison of observers 1 and 2 with observer 3 showed only a poor to acceptable level of agreement. US agreed well with MRI in the evaluation of the containment of the femoral head (1: kappa = 0.79; 2: kappa = 0.70, 3: kappa = 0.72).

The results of our study suggest that US is a reliable examination method for monitoring the containment of the femoral head in Perthes disease. The evaluation of both methods depends on the experience of the observer.