Radionuclide imaging in orthopedic infections.

In otherwise normal bone, Three Phase Bone Scintigraphy is sensitive and specific for osteomyelitis. In patients with underlying osseous abnormalities the specificity of the study is decreased. The four phase bone scan, bone/gallium scintigraphy, leukocyte imaging, leukocyte/bone and leukocyte/marrow studies have all been reported to increase specificity. The techniques, strategies, and limitations are discussed. No single study is equally useful in all situations. Labeled leukocyte imaging is of little value in vertebral osteomyelitis because this entity often presents as a nonspecific photopenic defect. The preferred technique for the spine is bone/gallium imaging. Intense uptake, on bone scintigraphy, in two adjacent vertebrae with loss of the disc space is highly suggestive of spinal osteomyelitis. Gallium not only enhances the specificity of the diagnosis but provides information about surrounding soft tissue infection. In the diabetic foot, labeled leukocyte imaging alone is sufficient to determine the presence of osteomyelitis in the fore--foot. In the midfoot and hindfoot it may be necessary to combine leukocyte scintigraphy with bone scintigraphy to precisely localize the infection. Labeled leukocytes accumulate in the uninfected neuropathic joint and preliminary data suggest that leukocyte/marrow imaging may be useful to determine the significance of such uptake. For the painful joint replacement, if infection is the primary concern, leukocyte/marrow scintigraphy should be performed initially. If any postoperative complication, regardless of type, is the concern, it is reasonable to begin with bone scintigraphy because a normal study rules strongly against any complication. An abnormal bone scan will require additional studies to more precisely determine the cause of that abnormality.