Benign exostoses and exostotic chondrosarcomas: evaluation of cartilage thickness by CT.

Computed tomograms of 16 benign exostoses and 15 exostotic chondrosarcomas were generally accurate in delineating anatomy for purposes of planning surgery, but they were inaccurate in the detection and measurement of the cartilage caps of the lesions. CT studies of 14 of the benign exostoses failed to show any cartilage cap, although the maximum cartilage thickness of these 14 lesions ranged from 0.1 to 2.5 cm pathologically. CT did demonstrate thick cartilage in 14 of the 15 chondrosarcomas, but the CT measurements of maximum thickness often were imprecise. Altogether, 15 CT studies failed to show any cartilage cap; 14 of these lesions were benign. CT did not reliably detect cartilage caps less than 2.5 cm in maximum thickness, and CT measurement of cartilage thickness was imprecise when the cartilage was 1.5 to 2.5 cm thick. For this reason, CT did not solve the difficult problem of distinguishing between benign exostoses with relatively thick cartilage caps and exostotic chondrosarcomas with relatively thin cartilage.