Correlation between bone marrow edema and collapse of the femoral head in steroid-induced osteonecrosis

OBJECTIVE. The purpose of this study was to clarify whether bone marrow ede ma is detectable on initial MR imaging of steroid-induced osteonecrosis of the femoral head. SUBJECTS AND METHODS. Forty-eight hips with osteonecrosis were examined con secutively with MR imaging and radiography, In a previously reported screen ing program, osteonecrosis was diagnosed on MR imaging when subchondral ban ds of abnormal signals were present, In the screening program, the MR image s of 200 hips of 100 patients receiving high-dose steroid therapy were exam ined prospectively. Subchondral bands were detected in 48 hips at a mean of 14 weeks after the initiation of steroid therapy. RESULTS. On follow-up MR imaging of 47 hips tone hip excluded) bone marrow edema was initially observed in 13 hips after the onset of hip pain. MR ima ging of the remaining 34 hips did nor reveal bone marrow edema and the pati ents were all asymptomatic. MR imaging of 31 of the 34 hips continued to sh ow subchondral bands and MR imaging of the other three hips indicated that the subchondral bands had disappeared. When bone marrow edema was detectabl e, abnormal findings on radiography were slight but 11 (85%) of the 13 hips progressed to advanced osteonecrosis. Bone marrow edema was highly correla ted with the subsequent collapse of the femoral head (p < 0.0001). CONCLUSION. Bone marrow edema was not present on initial MR imaging of oste onecrosis, Bone marrow edema should be considered a marker for potential pr ogression to advanced osteonecrosis, and careful examinations for osteonecr osis are necessary when bone marrow edema is seen.