Volumetric analysis of osteonecrosis of the femur. Anatomical correlation using MRI.

We tested the accuracy of MRI for the precise quantification of the volume of osteonecrosis in 30 hips (stage III). The values were compared with direct anatomical measurements of the femoral heads obtained after total hip replacement. When the area of osteonecrosis was determined visually, and manually outlined on each slice, the accuracy of the measurement of volume was satisfactory, and the mean absolute deviation between MRI and anatomical measurements was similar to that between two MRI data sets. For ten of the hips which were measured by MRI, both before and after collapse, the volume did not appear to change significantly. Our findings suggest that the volume of osteonecrosis can be determined with accuracy by MRI, both before and after collapse.