Legg-Calvé-Perthes disease: detection of cartilaginous and synovial change with MR imaging.

T1-weighted spin-echo magnetic resonance (MR) images were obtained of 20 patients with Legg-Calvé-Perthes disease (19 unilateral, one bilateral). Measurements of acetabular and femoral head cartilage provided evidence of a statistically significant increase in thickness in affected hips. The mean increase over normal varied from 1.8 to 3.9 mm, depending on the location within the joint. Loss of containment of the femoral head within the acetabulum was identified in most cases but with variability in degree. A frondlike structure seen adjacent to the inferomedial joint space in seven cases may have represented villous hypertrophy of the synovium within the iliopsoas recess of the hip capsule. MR imaging provides a means of evaluating the acetabular and epiphyseal cartilage of the hip affected by Legg-Calvé-Perthes disease, allowing assessment of femoral head containment, congruity of the acetabular and femoral articular surfaces, and intracapsular soft-tissue irregularities.