Multimodality imaging of intraosseous ganglia of the wrist and their differential diagnosis.

Intraosseous ganglion (IOG) is the most frequently occurring bone lesion within the carpus and is often an incidental finding on radiographs obtained for other reasons. Two types of IOG have been described: an "idiopathic" form (or type I), the pathogenesis of which has not been completely clarified, and a "penetrating" form (or type II), caused by the intrusion of juxtacortical material (often a ganglion cyst of the dorsal soft tissue) into the cancellous bone compartment. The differential diagnosis for IOG is wide-ranging and complex, including lesions of posttraumatic (posttraumatic cystlike defects), degenerative (subchondral degenerative cysts), inflammatory [cystic rheumatoid arthritis, chronic tophaceous gout (CTG)], neoplastic (benign primary bone tumours and synovial proliferative lesions), ischaemic (Kienböck's disease or avascular osteonecrosis of the lunate) and metabolic (amyloidosis) origin. Multimodality imaging of IOGs is a useful diagnostic tool that provides complete morphological characterisation and differentiation from other intraosseous cystic abnormalities of the carpus. Thin-slice multidetector computed tomography (MDCT) can provide high-spatial-resolution images of the cortical and cancellous bone compartments, allowing detection of morphological findings helpful in characterising bone lesions, whereas magnetic resonance (MR) imaging can simultaneously visualise bone, articular surfaces, hyaline cartilage, fibrocartilage, capsules and ligaments, along with intra- and periarticular soft tissues.