Prediction of femoral head collapse in osteonecrosis using 18F-fluoride positron emission tomography

We investigated the usefulness of (18)F-fluoride PET as a predictor of femoral head collapse in patients with osteonecrosis (ON) before radiographic changes occur.

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 (SUV(max)) in (18)F-fluoride PET and the Ficat classification. We evaluated the relationship between SUV(max) and the presence of femoral head collapse on plain radiography at 12 months after (18)F-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 SUV(max) and femoral head collapse on plain radiography in the 23 hips using a logistic regression model.

SUV(max) increased according to the progression of the Ficat classification stage. The mean SUV(max) was 12.3±5.9 in the collapse group and 4.9±1.3 in the noncollapse group (P<0.01). The cut-off SUV(max) of 6.45 (sensitivity: 0.80, specificity: 0.92) was used for the prediction of femoral head collapse. In the univariate analysis, SUV(max), type classification, and ring sign were related significantly to femoral head collapse.

We showed that the quantitative assessment of SUV(max) in (18)F-fluoride PET was useful to predict femoral head collapse in ON. (18)F-Fluoride PET might reflect accelerated bone metabolism because of microcollapse of the femoral head, which is undetectable on plain radiography.