Role of magnetic resonance imaging in the evaluation of diabetic foot with suspected osteomyelitis

Purpose

This study evaluated Magnetic Resonance Imaging (MRI) in infected diabetic foot ulcers.

Materials and methods

Sixteen diabetic patients underwent foot MRI between January 2006 and September 2007 for suspected unilateral osteomyelitis. Three of 16 patients showed radiographic changes due to Charcot neuropathic osteoarthropathy. Twelve of 16 patients also underwent MR angiography of the lower limbs for the purpose of planning surgical or endovascular treatment. The musculoskeletal and vascular MRI studies were retrospectively reviewed by three radiologists.

Results

The final diagnosis, based on clinical, imaging, microbiological and histological findings, was osteomyelitis in 13/16 cases. Foot MRI allowed a correct diagnosis in 15/16 patients, with 1 false positive result demonstrated by computed tomography (CT)-guided bone biopsy. MR angiography of the lower limbs was considered nondiagnostic in 5/12 patients in the infrapopliteal region owing to venous contamination.

Conclusions

MRI has high sensitivity for the detection of osteomyelitis in the diabetic foot but lower specificity related to Charcot neuropathic osteoarthropathy. If diagnostic uncertainty persists, a bone biopsy is indicated. The inflammatory hyperaemia caused by the ulcer deteriorates the diagnostic quality of 40%–50% of MR angiography studies in the infrapopliteal region. In these cases, selective arteriography is appropriate, as it can be performed in the same session as angioplasty.