Imaging orthopedic implant infections.

The diagnosis of infections associated with orthopedic implants is based on a combination of clinical signs, laboratory findings and imaging studies. There is no gold standard imaging technique: conventional radiography is indispensable, although 50% of the time the radiograph is normal. Computed tomography (CT), magnetic resonance imaging (MRI) and ultrasonography are valuable to detect soft tissue abnormalities. Bone scintigraphy (BS) rules out active infection. For infections involving the peripheral skeleton, labeled white blood cell (WBC) scintigraphy coupled with colloid scintigraphy is the reference technique, whereas a gallium scan is always necessary for imaging the spine or pelvis. To confirm or rule out infection, needle aspiration with analysis of aspirated fluid is the cornerstone of the diagnostic algorithm.