Skeletal complications in pediatric oncology patients.

Pediatric oncology patients are at risk for the development of numerous skeletal complications, and radiologic studies are important in the identification and evaluation of these conditions. Methotrexate osteopathy manifests as osteopenia, dense provisional zones of calcification, pathologic fractures, and sharply outlined epiphyses. Hypertrophic osteoarthropathy may occur with nasopharyngeal carcinoma or tumors of the lungs or pleura and manifests as cortical thickening, lamellar periosteal new bone formation, and soft-tissue swelling. Biomechanical abnormalities are often seen at bone scintigraphy in patients who have undergone surgery for bone tumors. Growth plate injury may manifest as marked deformity, sclerotic metaphyseal bands, metaphyseal fraying, and longitudinal striations. Radiation "osteitis" is seen as an initial decrease in bone density with subsequent development of a mixed radiolucent and sclerotic appearance. Ischemic necrosis of the femoral heads is best demonstrated at magnetic resonance (MR) imaging and has low signal intensity on T1-weighted images and a high-signal-intensity rim on T2-weighted images. Bone infarcts are seen as well-demarcated, often ring-shaped areas of decreased signal intensity on T1-weighted MR images and as areas of increased signal intensity on short-inversion-time inversion recovery images. Radiographic signs of infection include bone destruction, periosteal new bone formation, and sclerotic changes. Short-inversion-time inversion recovery MR imaging is particularly useful in evaluating posttherapy changes in bone marrow. Osteochondroma may demonstrate a cartilaginous cap at MR imaging, whereas the most important finding in radiation-induced sarcoma is a soft-tissue mass. Radiologists who work with children with cancer need to be familiar with these complications and their imaging appearances.