We investigated the usefulness of 18F-fluoride PET as a predictor of femoral head collapse in patients with osteonecrosis (ON) before radiographic changes occur.
Patients and methods
Sixty-six hips of 42 patients diagnosed with ON of the femoral head were included in this study. We evaluated the relationship between the maximum standardized uptake value (SUVmax) in 18F-fluoride PET and the Ficat classification. We evaluated the relationship between SUVmax and the presence of femoral head collapse on plain radiography at 12 months after 18F-fluoride PET in 23 hips of 18 patients with Ficat classification stage 1 or 2. A receiver operating characteristic analysis was carried out to calculate the cut-off SUVmax for the prediction of femoral head collapse. We analyzed the relationship between SUVmax and femoral head collapse on plain radiography in the 23 hips using a logistic regression model.
SUVmax increased according to the progression of the Ficat classification stage. The mean SUVmax was 12.3±5.9 in the collapse group and 4.9±1.3 in the noncollapse group (P<0.01). The cut-off SUVmax of 6.45 (sensitivity: 0.80, specificity: 0.92) was used for the prediction of femoral head collapse. In the univariate analysis, SUVmax, type classification, and ring sign were related significantly to femoral head collapse.
We showed that the quantitative assessment of SUVmax in 18F-fluoride PET was useful to predict femoral head collapse in ON. 18F-Fluoride PET might reflect accelerated bone metabolism because of microcollapse of the femoral head, which is undetectable on plain radiography.