X-Ray Versus Magnetic Resonance Imaging in Diabetic Foot Osteomyelitis: A Clinical Comparison.

OBJECTIVE Radiographic imaging is an important diagnostic tool in diabetic foot osteomyelitis (DFO). It is unknown whether DFO cases diagnosed with conventional X-ray versus positive Magnetic Resonance Imaging (MRI) differ regarding epidemiology and treatment outcome. Theoretically, signs of inflammation on MRI without bone lesions might be easier to treat and predominate among selected clinical variables. METHODS Our clinical pathway for diabetic foot infections discourages the use of MRI for the diagnosis of DFO. We compared the epidemiology and therapy of non-amputated DFO with positive features on conventional X-ray, MRI, or both. Radiology specialists interpreted the images. The intraoperative aspect of bone during amputation and the results of bone cultures were considered gold standard for DFO diagnosis. RESULTS We prospectively followed 390 DFO episodes in 186 adult patients for a median of 2.9 years and performed 318 conventional X-rays (median costs 100 Swiss Francs; 100 US$) and 47 (47/390; 12%) MRI scans (median 800 Swiss Francs; 800US$). Among them, 18 episodes were associated with positive MRI findings but lacked bone lesions on X-ray. After debridement, the median duration of systemic antibiotics was 28 days for MRI-only episodes and 30 days for X-ray-positive cases (Wilcoxon-ranksum-test; p=0.26). The corresponding median numbers of surgical debridements were 1 and 1; and remission was achieved in 25% and 27%, respectively. In multivariate logistic regression analysis, MRI-only episodes did not alter remission rate (odds ratio 0.5, 95%CI 0.1-5.2). CONCLUSIONS According to our clinical pathway, DFO episodes with positive MRI findings only did not differ epidemiologically and did not influence the choice of therapy nor remission rate.