MRI of Osteonecrosis of the Femoral head

Kang, C S; Song, K S; Kang, C H; Lee, S H

Abstract

Early diagnosis of osteonecrosis of the femoral head is very important because it leads to early treatment and a better chance of saving the femoral head. The conventional X-ray, bone scan, SPECT and Magnetic resonance imaging (MRI) can detect early AVN. Radionuclide bone imaging has been utilized to diagnose osteonecrosis at an early stage, however, poor sensitivity, poor specificity and a lack of anatomic detail have been reported. Mitchell et al reported that MRI is the most sensitive imaging technique for early diagnosis of avascular necrosis. MRI is therefore of value in evaluating osteonecrosis of the femoral head, especially as it provides high sensitivity and excellent anatomic detail. In our studies, MRI of 71 hips of 40 patients who visited the Keimyung University Dong San Hospital were analyzed and compared with conventional radiographs and technetium diphosphonate bone scans. The results are as follows: l. Of the 40 patients with osteonecrosis of the femoral head, 37 cases were male, 3 cases were female, 9 cases were unilateral and 31 cases had bilateral hip involvement. 2. Nine of thirteen (69%) stage 0 lesions of modified Ficat & Arlet were Class A and four (31%) were Class B. Classes C and D were not found. 3. Six of sixteen (38%) stage II were Class A, five (31%) were Class D. 4. Only six of thirty-six (17%) lesions in stage III-IV were Class A, while twentysix (72%) were Class D. 5. The MRI was useful in determining the extent, volume and detailed anatomic location of femoral head necrosis. This information leads to early surgical treatment and prevents progression of femoral head collapse and saves the femoral head. 6. Because of the risk factor in patients with a unilateral nontraumatic osteonecrosis of the hip, the MRI may be useful in detecting an early stage of osteonecrosis of the femoral head on the opposite side.