Infection of the appendicular skeleton.

In relation to the clinical course, infection in bone can be divided into acute, subacute and chronic osteomyelitis. The diagnosis of acute osteomyelitis is often challenging but can best be made by correlating radiography, bone scintigraphy and MRI with clinical information. Radiography should routinely be supplemented by sonography in the newborns and infants, if applicable. Brodie's abscess, which is clinically a subacute form of osteomyelitis, is best diagnosed by the combination of radiography and MRI. Chronic osteomyelitis is divided into primary haematogenous forms and exogenous, mostly post-traumatic, osteomyelitis. In the majority of patients, post-traumatic osteomyelitis is a clinical diagnosis; however, in a number of patients only the correlation of clinical findings, blood tests and imaging reveals the correct diagnosis. Often, MRI and scintigraphic methods, such as scanning with labeled leucocytes, together establish the diagnosis. Chronic recurrent multifocal osteomyelitis may mimic bacterial osteomyelitis but is a distinct disease probably associated with the SAPHO syndrome.