The Clinical Utility of MRI in Evaluating for Osteomyelitis in Patients Presenting with Uncomplicated Cellulitis.

Magnetic resonance imaging (MRI) is vital in the diagnosis of osteomyelitis (OM) in patients presenting with cellulitis. Typically, cellulitis is treated with oral antibiotics; however, patients with concomitant OM may require long-term intravenous antibiotics or surgical intervention. We reviewed lower extremity MRIs in patients presenting with cellulitis and clinical concern for OM. We found 488 patient examinations spanning 5 years (2011 to 2016); 47 patients were excluded (final N = 441). Each MRI was interpreted by a radiologist to determine the rate of OM, abscess, ulceration, and imaging diagnosis of cellulitis. Concurrent assessment of the electronic medical record was performed to review patient demographics, the presence of abscess and/or ulceration, and comorbidities such as diabetes, hyperlipidemia (HLD), atherosclerotic disease, and peripheral vascular disease. Of the 441 lower extremity MRIs included, 170 (39%) were diagnosed with OM, 236 (54%) had ulcers, and 66 (15%) had abscesses. Age, laterality, and reporting physician were not statistically significant independent variables in the rate of reported OM. Diabetes and HLD/atherosclerotic disease were both statistically significant variables with regard to OM rates. Clinical documentation and MRI diagnosis of ulceration were both statistically significant variables in the rate of OM. Regression analysis determined that body part, ulceration, HLD/atherosclerosis, and sex were independent predictors of OM. In our study, of the population of patients with a high clinical suspicion for OM, 39% had OM diagnosed on MRI. However, the incidence of OM in uncomplicated cellulitis was only 11.8% compared with 43.9% in complicated cellulitis. When considering the forefoot alone, patients with ulceration at MRI were 5.6 times more likely to have underlying OM than those without.