High-resolution real-time sonography and MR imaging in assessment of osteocartilaginous exostoses

High-resolution real-time ultrasonography (US) and MR imaging, using both spin-echo (SE) and gradient-echo (GE) sequences, were performed prospectively in 14 patients with solitary osteocartilaginous exostoses to assess cartilage cap thickness and bursa formation. Results were compared to surgical and histopathologic findings in all cases. Both US and MR imaging were useful in evaluating exostotic cartilage cap thickness, which is supposed to be the most reliable sign of malignant transformation. Hyaline cartilage matrix had distinctive features in US and MR imaging caused by its specific histologic composition. The formation of bursae over the protruding exostoses, which results in pain and clinically could raise the suspicion of growth and malignant transformation, was demonstrated best using GE sequences. MR imaging was thus superior to US in the detection of bursa formation.