Three-phase scintimetry in osteonecrosis of the knee

Three-phase scintimetry with 99mTc MDP was analyzed in 40 patients with a clinical history of spontaneous onset of knee pain and a focal static isotope uptake in the femoral condyle indicating osteonecrosis. A strong correlation was found between pool-phase ratios and the static ratios. The pool-phase study did not add to the information obtained from the flow phase and static studies. There was a characteristic change of the pattern of the early flow-phase curves with the duration since the onset of symptoms indicating hyperemia early in the disease. A persistent high flow-phase and static-uptake ratio 6-12 months after the onset of symptoms correlated positively with a poor clinical and radiographic outcome. The 10 patients with a good prognosis had, as a group, a more rapid decrease in isotope uptake after 6 months. There was a positive correlation between a high static uptake ratio and the size of the lesion, and subsequently with the clinical and radiographic outcome. 30 patients developed arthrosis and/or severe clinical symptoms. Five of the 10 patients who did not develop arthrosis never developed radiographic evidence of osteonecrosis.