Faculty Bibliography

Osteomyelitis underlies the majority of diabetic foot ulcers, and it is usually not detected clinically. Leukocyte scanning with indium oxyquinoline has greater sensitivity than radiographs, bone scans, and MR imaging in diagnosing osteomyelitis in diabetic foot ulcers. All ulcers that expose bone, and perhaps moderately deep ulcers as well, should be treated for osteomyelitis because of the high prevalence of this infection (100% and 82%, respectively). Osteomyelitis should be evaluated for in shallow ulcers by radiographs, followed by leukocyte scans if the former tests are negative. Bone biopsies should be performed if possible because cultures may guide antibiotic treatment

OBJECTIVE--To compare the accuracies of MRI and leukocyte scanning in diagnosing clinically unsuspected osteomyelitis in diabetic foot ulcers. RESEARCH DESIGN AND METHODS--A prospective study of 16 diabetic foot ulcers in 12 patients, including both ambulatory and hospitalized patients, was performed at a university medical center. Pedal images were obtained by leukocyte scanning with [111In]oxyquinoline and MRI. Definitive diagnosis of osteomyelitis then was determined by bone biopsy for culture and histology. RESULTS--Biopsy-proven osteomyelitis was present in 7 (44%) of the 16 foot ulcers. The diagnosis was suspected clinically in 0%. Leukocyte scanning was 100% sensitive, whereas MRI was only 29% sensitive in diagnosing osteomyelitis in diabetic foot ulcers. Specificities were 67 and 78%, respectively. The positive and negative predictive values (70 and 100%, respectively) for the leukocyte scan also were greater than those of MRI (50 and 58%, respectively). CONCLUSIONS--Leukocyte scanning is superior to MRI in detecting clinically unsuspected osteomyelitis in diabetic foot ulcers