Materials and MethodsThree patients (two women and one man, ages 44, 56, and 77 years, respectively) with the CT diagnosis of intraspinal synovial cyst in the lumbar spine were evaluated and treated by percutaneous injection of the adjacent facet joint. The initial CT examination was obtained

Sixteen patients with early and late stages of spontaneous osteonecrosis of the knee were studied to evaluate if MR imaging can be used to determine the prognosis of the disease. All patients had sequential conventional radiographs and clinical examinations, one or more 99mTc-methylene diphosphonate bone scintigrams, and an MR examination. The duration of the disease at the time of the MR examination ranged from 1 to 58 months (mean, 18 months). A relationship was identified between the pattern of bone marrow alteration noted on long TR/TE MR sequences and the scintigraphic stage and clinical course of the disease. The dimensions of the osteonecrotic region could be identified as well or better on the short TR/TE MR images than on the radiographs in all patients. MR imaging also afforded evaluation of the hyaline cartilage overlying the osteonecrotic lesion, revealing secondary osteoarthrosis in seven patients. We conclude that MR imaging in patients with spontaneous osteonecrosis of the knee may provide information of value for determining the prognosis of the disease.

In patients with rheumatoid arthritis, the presence of acute synovial inflammation is an indication of the activity of the disease. It is an important finding because it often influences therapeutic decisions. However, acute synovitis may be difficult to detect by clinical examination, especially if a joint effusion also is present. As gadolinium tetra-azacyclododecane tetraacetic acid (Gd-DOTA) can be expected to accumulate in areas of acute inflammation, we studied the value of Gd-DOTA-enhanced MR to determine the presence of acute synovitis. Nine patients with current knee symptoms underwent MR examination of the knee. Short and long TR/TE MR images were obtained with a 0.3-T magnet before and immediately after IV administration of Gd-DOTA. A 15-min delayed short TR/TE image also was obtained. Of eight patients with moderate to severe clinical evidence of acute synovitis, six had marked increase and two had moderate increase in signal intensity from synovial tissue on the short TR/TE image obtained immediately after administration of contrast material. In the ninth patient, who had minimal synovitis clinically, the signal from the synovium did not change after administration of contrast material. No difference was seen between the enhancement pattern on the immediate and the 15-min delayed images. These results suggest that Gd-DOTA is taken up by inflamed synovium and that Gd-DOTA-enhanced MR scans may be useful in detecting acute synovitis in patients with rheumatoid arthritis.

Clinically suspected primary osteonecrosis of the knee was studied in 40 patients with repeated plain radiography and scintimetry, and the patients were followed for 1-7 years. Thirty-three patients had typical scintimetric and radiographic signs of osteonecrosis of either one of the femoral condyles, whereas 7 patients had only typical scintimetric findings, but never developed an osteonecrosis based on plain radiography. Because the scintimetric findings were identical to the other 33 knees and because there is no other well-known localized disease in this region of the femoral condyle, we deemed that these 7 patients had probable osteonecrosis, but in an abortive form. The scintimetries were prognostic during the second half year after onset. Thirty knees had a poor outcome--29 because of development of arthrosis, of which eight were treated with a knee arthroplasty and four with a proximal osteotomy.

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