Ischemic necrosis of the femoral head. Correlation of magnetic resonance imaging and histologic sections.

Magnetic resonance (MR) images were correlated with matched histologic sections of a resected ischemic necrotic femoral head and neck. Preoperative radiographs had revealed Stage 3 ischemic necrosis. Preoperative MR images disclosed foci of abnormally low signal intensity alternating with normal-appearing foci of high signal intensity. Surgical resection of the femoral head and neck was followed by MR imaging and pathologic sectioning, fixation, and staining, enabling the individual sections to be compared with the postoperative MR slices. A subchondral focus of diminished signal intensity was shown to represent saponified fat and consisted of a transudate of proteinaceous material with probable calcifications. The subjacent region of normal, high signal intensity represented "mummified" fat. The next lower stratum of diminished signal intensity was composed of fibrous and vascular tissues and histiocytic infiltrates that had extensively or completely replaced the fatty marrow.