Imaging modalities of the diabetic foot

Abstract

Charcot osteoarthropathy is a devastating process that occurs in the diabetic foot. It must be distinguished from other conditions, such as osteomyelitis, with efficiency and accuracy. The prognosis and treatment depends on it. Charcot progresses along four radiographically identifiable stages; therefore, plain films should be the first step in the evaluation. When osteomyelitis is suspected, a three-phase bone scan may allow clear enough anatomic detail to diagnosis bony involvement compared with soft tissue in the forefoot. In the midfoot, a three-phase bone scan alone is not specific enough to distinguish between Charcot and osteomyelitis. Enhancing the bone scans by adding an additional phase (four-phase) or tracer (gallium) does not appear to improve specificity significantly. Computerized bone flow studies may be more helpful in making the distinction, particularly in acute presentation. A CT scan is not indicated because the MR image will better define the anatomic extent of the process for preoperative planning. The combined WBC scans and sulfur colloid marrow scans show improved specificity and can distinguish between Charcot and osteomyelitis. Combined leukocyte scan with bone marrow imaging is superior to leukocyte and bone scan alone or in combination for detecting infection in the neuropathic foot. The combined leukocyte scan and bone marrow imaging is the current gold standard for evaluating the presence of diabetic foot infection versus osteoarthropathy, and MR imagine is the anatomic gold standard that may be used to define the extent of the process.