Magnetic Resonance Imaging in Legg-Calve-Perthes Disease.

We carried out a Magnetic Resonance Imaging (MRI) study in fourteen patients with unilateral Legg-Calve-Perthes Disease. The purpose of this study was to show the process of deformation of the femoral head in this disease. In the early stage, the perichondral ring of the affected head was thicker than the unaffected hip in all cases and hypertrophy of this cartilage produced lateralization of the femoral head on plain roentgenograms.With progression of the disease, a high signal area appeared around the physis corresponding with the perichondral ring. Although this area extended proximally, the subchondral region near the sumit of the epiphysis remained as a relatively low signal area for a long time. This difference in reparative activity between the base and near the top of the epiphysis produced the typical residual deformity of Legg-Calve-Perthes Disease, the coxa magna and the coxa plana.We also measured the width of the hypertrophied cartilage on MRI films taken in the initial stage and discussed the relationship between the degree of width and final results. The thicker the cartilage was, the poorer the result. The measurement of articular cartilage in the early stage could predict the future of this disease.