EPIPHYSEAL BONE-MARROW ABNORMALITIES AND RESTITUTION IN LEGG-CALVE-PERTHES-DISEASE - EVALUATION BY MR-IMAGING IN 86 CASES

Purpose: By means of MR imaging, to determine signal abnormalities in the femoral epiphysis; to determine their location, extent and restitu tion over time; and to correlate these findings to the Catterall radio logical classification. Material and Methods: A total of 247 MR images in 86 patients (101 hips) with Legg-Calve-Perthes disease were examin ed. The MR images were taken in the coronal plane, and the images thro ugh the center of the femoral head were used for this study. Results: TI-weighted images proved as good as T2-weighted images for the MR eva luation of the extent of the necrosis. In almost every case, the centr al-cranial part of the epiphysis showed a low initial signal. In Catte rall group I, the medial part was never involved. In Catterall III and TV, almost the entire epiphysis showed signal changes. In the period 3-6 years after diagnosis, we still found signal changes in the epiphy sis in some hips but there was no correlation with the Catterall class ification. 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 par t of the epiphysis became more enhanced over time and peaked in the pe riod 1-3 years after diagnosis. Conclusion: MR is a valuable modality for monitoring changes in the femoral epiphysis. We propose a new clas sification of the extent and pattern of epiphyseal bone-marrow abnorma lities based on the 4 zones most commonly observed in MR imaging.