Radionuclide evaluation of spontaneous femoral osteonecrosis.

Spontaneous osteonecrosis of the femoral condyle in 40 knees was followed by sequential radiographs and three-phase bone scans using 99mTc-methylene diphosphonate. The characteristic bone scan appearance of focal increased uptake by the medial femoral condyle in blood flow, blood pool, and delayed images helped to make the specific diagnosis in 11 knees that had no characteristic radiographic findings at the time of presentation. The three phases of the bone scan demonstrated a pattern that was useful in determining the activity of the process. There was a gradual loss of hyperemia as healing progressed. Late bone scans were normal or showed nonspecific findings. Radionuclide bone scans were able to confirm or exclude this disease and were superior to radiographs in demonstrating the disease in the acute phase.