The present study was undertaken to determine whether a correlation exists between localized magnetic resonance image (MRI) signal behavior and specific histopathologic features of femoral head osteonecrosis. Contiguous, 5-mm coronal MRI sections were compared with corresponding histologic sections from six surgically excised femoral heads. After identifying specific areas of interest on the images, signal intensity was evaluated, both subjectively and objectively, and T1 and T2 relaxation times were calculated. Mean values for these data were compared among the following histologic categories: normal bone, unrepaired dead bone and marrow, unrepaired dead bone with marrow replaced by amorphous debris, and zones of repair. For each type of tissue, MRI signal intensity on T1- and intermediately T2-weighted images behaved in a distinctive fashion. Active repair tissue could be differentiated from both necrotic bone and normal bone by a tendency for the signal to increase in intensity on intermediately T2-weighted images. These findings suggest that MRI may provide a noninvasive means of quantitatively analyzing the volume and spacial distribution of repair tissue in osteonecrotic femoral heads. In clinical practice, such analysis may lead to improvements in disease staging and treatment planning.
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