Radiologic Mimics of Osteomyelitis and Septic Arthritis: A Pictorial Essay

Figure 10

Metastases. Axial T1 (a) pelvis at the level of the hip joint of a 47-year-old female with metastatic breast cancer involving the right acetabulum. Ill-defined acetabular cortex is consistent with cortical breach of tumour and intraarticular extension (arrow). Tumour exhibits mass-effect that is usually readily apparent on MRI. Tumour is usually hyperintense in fluid-sensitive sequences which can mimic infection. Coronal PDFS (b) at the anterior acetabular margin with fluid-hyperintensity of the tumour breaching the acetabular cortex (arrow). Periosteal extension lateral pelvis (dotted arrow). A separate metastatic deposit also presents in the proximal right femoral shaft which helps clinch the diagnosis (dash). Axial T1 (c) and coronal STIR (d) and axial fat-saturated postcontrast T1 (e) of the right foot of a 38-year-old man with AIDS-related Kaposi sarcoma. The fungating, partially necrotic/enhancing mass (e) is centred in the forefoot, particularly involving the second metatarsal (arrow). The signal intensity of the involved bone mimics that of osteomyelitis, although infection should not be infiltrative and mass-forming (dotted arrows).

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