Ultrasonography of the hip for Perthes' disease.

The incidence of intracapsular hip-joint effusion in the initial stage of Perthes' disease is unknown. Recent experimental data demonstrated intracapsular hip-joint tamponade followed by necrosis of the femoral head. Ultrasonographic screening of children with "irritable hip syndrome" may reveal a ventral capsular distension as the decisive morphological criterion of hip-joint effusion. The patient is treated by aspiration of the effusion, bed rest, and nonsteroidal anti-inflammatory drugs. The noninvasive and nonionizing ultrasonographic technique permits the identification of a persisting hip-joint effusion by consequent serial follow-up. The suspicion of Perthes' disease can be confirmed by radiography, scintimetry, or, moreover, by magnetic resonance. On the other hand, hypertrophic synovial tissue stopping up the articular cavity and producing weak echos can be demonstrated in patients with a severe course of the disease. The importance of the sonographic diagnosis "ventral capsular distension along the femoral neck" for the prognosis and therapy of Perthes' disease should be investigated. Hips with intracapsular effusion should not be immobilized in extension and/or mild traction, as a relation between high intracapsular pressure and the position of the extended hip is known.