Primary osteonecrosis in the knee evaluated by histopathology and specimen scintimetry related to clinical radiography, scintimetry and MR.

Arthroplasty for primary osteonecrosis of the femoral condyle of the knee was performed in 5 patients and the resected pieces of bone were studied histologically. The patients had been given 99 mm-Tc-MDP preoperatively and the scintimetric uptake in the resected bone pieces was determined. All patients had changes typical for osteonecrosis preoperatively on radiographs and scintimetry. In one case MRI investigation was performed. The histological investigation showed necrotic bone with empty lacunae and fatty degeneration corresponding to the osteonecrosis center. A reparative bone formation, osteoblastic activity, cartilage formation and bands of fibrovascular granulation tissue were observed at the borders to intact bone. The scintimetric uptake of the resected bone pieces showed a high uptake corresponding to the osteonecrosis center. The MR examination showed a well demarcated osteonecrotic region. The findings emphasize the localized nature of the osteonecrosis disease.