Femoral head osteonecrosis. Detection by magnetic resonance imaging versus single-photon emission computed tomography.

Magnetic resonance imaging (MRI) and single-photon emission computed tomography (SPECT) examinations were compared for detection of femoral head osteonecrosis. Of 29 hips with clinical and roentgenographic evidence of osteonecrosis (18 histologically confirmed), 15 were Stage II, three transitional, six Stage III, and five Stage IV. MRI identified osteonecrosis in all 29 cases (100% sensitivity), and there were no false-positives (100% specificity). Of 24 osteonecrotic hips with technically adequate examinations, SPECT identified 14 (sensitivity 58%), and there were four false-positives (78% specificity). If Stages III and IV were eliminated, SPECT correctly identified ten of 15 (67% sensitivity).