Relationship between magnetic resonance imaging and histologic findings by bone biopsy in nontraumatic osteonecrosis of the femoral head.

To attest the validity of magnetic resonance imaging (MRI) to evaluate the pathophysiology in nontraumatic osteonecrosis (ON) of the femoral head, we attempted to correlate the different MRI patterns with the histology in cases of early stages. We used not only the T1 and T2 pulse sequences, but also the T1 sequence after gadolinium-DTPA to demonstrate the presence of vascularization. Studying 24 core biopsies from 16 hips (9 patients), we explored the MRI presentations that corresponded to the main histologic findings of the different trabecular bone and bone marrow conditions. Histologic findings including trabecular bone necrosis and bone marrow necrosis represented by amorphous eosinophilic debris presented a low T1 signal intensity without enhancement after intravenous gadolinium injection and a low T2 signal intensity. Trabecular bone necrosis associated with mummified fat cells presented a normal T1 and T2 signal intensity. Trabecular bone necrosis with fibrosis filling the intertrabecular spaces had a low T1 signal intensity that was enhanced by gadolinium and had an intermediate T2 signal intensity. Bands of fibrosis without trabecular bone as seen in fracture zones showed a low T1 signal intensity that was enhanced by gadolinium with a high T2 signal intensity. Thickened trabecular bone with fibrosis as found in creeping substitution areas had also a low T1 signal enhanced by gadolinium, but the T2 signal intensity was low. Farther from the necrotic area, despite normal trabecular bone, we found some patchy necrosis of the bone marrow without any modification of the normal T1 and T2 MRI patterns.(ABSTRACT TRUNCATED AT 250 WORDS)