Epiphyseal bone-marrow abnormalities and restitution in Legg-Calvé-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 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-Calvé-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.