Purpose: By means of MR imaging, to determine signal abnormalities in the femoral epiphysis; to determine their location, extent and restitution over time; and to correlate these findings to the Catterall radiological classification. Material and Methods: A total of 247 MR images in 86 patients (101 hips) with Legg-CalvC-Perthes disease were examined. The MR images were taken in the coronal plane, and the images through the center of the femoral head were used for this study. Results: T1-weighted images proved as good as T2-weighted images for the MR evaluation of the extent of the necrosis. In almost every case, the central-cranial part of the epiphysis showed a low initial signal. In Catterall group I, the medial part was never involved. In Catterall III and IV, almost the entire epiphysis showed signal changes. In the period 3–6 years after diagnosis, we still found signal changes in the epiphysis in some hips but there was no correlation with the Catterall classification. After 6 years, the epiphysis showed normal signal intensity in MR imaging. In T1-weighted images, Gd-enhancement occurred in the peripheral regions in the early stages of the disease. The central part of the epiphysis became more enhanced over time and peaked in the period 1–3 years after diagnosis. Conclusion: MR is a valuable modality for monitoring changes in the femoral epiphysis. We propose a new classification of the extent and pattern of epiphyseal bone-marrow abnormalities based on the 4 zones most commonly observed in MR imaging.
