Radiologic Mimics of Osteomyelitis and Septic Arthritis: A Pictorial Essay

Figure 5

A 30-year-old systemically well man with chronic osteomyelitis who initially presented with an enlarging mass in the posterior thigh. The planning CT (a) showed femoral shaft sclerosis, periosteal thickening, and cortical expansion which is worse medially. A lucent tract at the inferior border of the abnormal bone extends from the medulla to the cortex, consistent with a sinus tract (arrow). Sagittal T1 (b) demonstrating the extent of the osteomyelitis with sequestrum posteroinferiorly (arrow). Axial PDFS (c) and T1FS postcontrast (d) MRI shows the new bone formation or involucrum attempting to envelop the infection. A cloaca or sinus tract involving the posterolateral thigh discharges into the subcutaneous plane, accounting for the presentation (C arrow).

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