MRI of the abnormal pediatric hand and wrist with plain film correlation.

Based on a pool of 24 selected cases of nontraumatic pathology of the hand and wrist in patients under the age of 18 years, collected from three pediatric hospitals, the authors have illustrated a number of congenital, inflammatory, and infectious conditions as well as tumors of bones and soft tissues, utilizing MRI with plain film correlation. Due to different MR signal characteristics, the etiology of macrodactyly may be recognized, e.g., vascular and/or fatty versus neurofibromatosis, etc. In septic arthritis, MR has shown abnormal marrow signal in adjacent bones denoting osteomyelitis, often unexpected from the plain film appearance. Tenosynovitis has a specific MR appearance: Fluid in the tendon sheath gives high signal on T2-weighted imaging. In arthritis--because of the associated hyperemia--there is definite synovial enhancement easily visible immediately after Gd-chelate injection. Gd also helps identify viable tissues postinfection as well as viable tumor tissue (versus scar or necrotic tissue) in tumors. Plain radiography is the imaging method of choice for diagnosis and differential diagnosis of most cases of bone cysts, tumors, and tumor-like conditions, e.g., simple and aneurysmal bone cysts, enchondroma, and osteoid osteoma. In the study of masses, MRI gives excellent detail regarding tumor staging and the extent of soft tissue tumors as well as the soft tissue component of bone tumors. In the hand and wrist, aneurysmal bone cysts are usually confined within a metacarpal or carpal bone, showing high signal intensity on T2-weighted imaging, often with fluid/fluid levels. If ganglion cysts are excluded, the most commonly encountered soft tissue masses are the vascular malformations. MR angiography can demonstrate the vascularity of the lesion. Some benign soft tissue lesions have a characteristic MR appearance, e.g., ganglion cysts, lipomata, and accessory muscles.