Giant cell tumors of the knee: subchondral bone integrity affects the outcome.

From January 1992 to July 2001, we treated 38 patients with giant cell tumour in the knee region. Seventeen tumours were located in the distal femur and 21 in the proximal tibia . Twenty patients were classified as Campanacci grade II, 15 as grade III, and three as grade I. Patients' mean age was 34.5 (19-65) years, and the mean follow-up was 52 (24-134) months. Operative procedures were chosen according to the extent of bone and soft-tissue involvement. In 28 patients, intralesional curettage and bone grafting was performed and in ten patients a wide resection. We defined subchondral bone of the knee to be affected when the distance to the tumour was less than 3 mm. We then measured the area of affected subchondral bone radiographically using plain radiographs, CT, and MRI. In patients initially treated with curettage and bone grafting, the mean area of initially affected subchondral bone was 18.6 (0-81)%. The mean Enneking functional score at follow-up was 88 (66.6-100). There was a linear trend showing that the larger the area of affected subchondral bone, the worse the functional score. Among patients initially treated with wide resection, the mean area of affected subchondral bone was 68.2 (41-100)%. There was, however, no significant association between affected subchondral bone area and functional score.