MR-IMAGING OF AVASCULAR NECROSIS AND TRANSIENT MARROW EDEMA OF THE FEMORAL-HEAD

The value of high spatial resolution and contrast material-enhanced ma gnetic resonance (MR) imaging was assessed in 69 patients with either femoral head avascular necrosis (AVN) or transient bone marrow edema l esions. An AVN lesion was typically a well-demarcated epiphyseal area of variable signal intensity. A transient bone marrow edema lesion app eared as an ill-delimited low-signal-intensity epiphyseal area on T1-w eighted images that converted to a high-signal-intensity area on T2-we ighted images. T1- and T2-weighted spin-echo images helped distinguish from AVN lesions some transient lesions apt -to simulate the segmenta l pattern of AVN lesions. T2-weighted images also helped detect necrot ic tissue in some unusual AVN lesions that mostly showed ill-delimited edemalike marrow changes. In some cases, contrast-enhanced MR images may increase diagnostic confidence by showing homogeneous hypervascula rization in bone marrow edema lesions and by depicting hypovascular ma rrow areas in AVN lesions. The authors believe sequential MR imaging i s valuable in the assessment of equivocal femoral head lesions.