Magnetic resonance evaluation of "metaphyseal" changes in Legg-Calvé-Perthes disease.

Twenty involved hips in 16 patients with Legg-Calvé-Perthes disease (LCP) were studied with both plain radiographs and magnetic resonance imaging (MRI) scans to better evaluate the existence of "metaphyseal" changes. Thirty-four sets of radiographs and MRI scans were reviewed in a blinded fashion and compared for the presence and location of these changes. Of 23 hips with plain radiographic metaphyseal changes, 11 showed no such changes on MRI scans (48%). Twelve hips did show MRI changes located in the anterior metaphysis. One hip studied three times had a discrete cystic change located in the central metaphysis. Of 11 hips with no plain radiographic changes in the metaphysis, five showed metaphyseal changes on MRI. Metaphyseal changes in LCP remain poorly understood. Even with use of MRI, fine distinction between physis and metaphysis still proved difficult. It appears that most metaphyseal changes are physeal and epiphyseal irregularities. A few hips have truly metaphyseal lesions. The significance of these "cysts" is unclear.