IMAGING THE DIABETIC FOOT

Early and accurate diagnosis of infection or neuropathy of the diabeti c foot is the key to successful management. Angiopathy leads to ischem ia which, in combination with peripheral neuropathy, predisposes to pe dal skin ulceration, the precursor of osteomyelitis. Chronic hyperglyc emia promotes production of glycosylated end products which accumulate on endothelial proteins, causing ischemia of the vasa nervorum. When combined with axonal degeneration of the sensory nerves, the result is hypertrophic neuroarthropathy. Should the sympathetic nerve fibers al so be damaged, the resultant loss of vasoconstrictive impulses leads t o hyperemia and atrophic neuroarthropathy. Plain radiography, although less sensitive than radionuclide, magnetic resonance (MR), and comput ed tomographic examinations, should be the initial procedure for imagi ng suspected osteomyelitis in the diabetic patient. If the radiographs are normal but the clinical suspicion of osteomyelitis is strong, a t hree-phase Tc-99m-MDP scan or MR imaging is recommended. An equivocal Tc-99m-MDP scan should be followed by MR imaging. To exclude osteomyel itis at a site of neuroarthropathy, a In-111 white blood cell scan is preferable. To obtain a specimen of bone for bacteriological studies, percutaneous core biopsy is the procedure of choice, with the entrance of the needle well beyond the edge of the subjacent ulcer.