Pelvic musculoskeletal infection in infants -- diagnostic difficulties and radiological features.

Musculoskeletal infection involving the pelvis has rarely been reported in infants. When such infections involve the pelvic muscles they are generally believed to result from secondary spread from adjacent structures. We report five cases of primary pelvic musculoskeletal infection affecting infants <1 year, all of which presented during a 1-year period. In two patients the infection appeared to arise primarily in muscle. Clinical features were generally non-specific and often misleading, mimicking hip (4/5) or vascular (3/5) pathology; as a result, diagnosis was delayed in four patients. Radiological investigation was required to make the diagnosis and delineate the extent of the lesion in all cases. Magnetic resonance imaging (MRI) was the most useful imaging technique, accurately identifying the infection and its extent in all cases in which it was used. However, plain films, ultrasound (US), scintigraphy and computed tomography (CT) were all useful in individual cases and have a role in the primary investigation of these difficult infections. The clinical presentation of pelvic musculoskeletal infection in infants and the role of the various radiological investigations in its diagnosis is discussed.