Evaluation of the inflammatory activity in chronic osteomyelitis. Contribution of the scintigraphy with polyclonal antibodies

Active chronic osteomyelitis or complicating osteomyelitis (superimposed on diseases that changes the normal bone structure fractures, post-surgery, prosthesis) can be difficult to diagnose by anatomic radiological imaging modalities, like plain radiograph and CT. These diseases frequently cause also increased bone remodeling, leading to nonspecific uptake of Tc-99m-bone scan agents and gallium-67. New radiopharmaceuticals with greater inflammation/infection avidity and specificity are being developed, including the nonspecific polyclonal immunoglobulin (IgG) labeled with technetium-99. Tc-99m-IgG may be available as a ready to use kit, with no reported side effects, low patient absorbed radiation dose and low cost. The mechanism of IgG uptake at the inflammation site has not been fully elucidated yet. Specific (receptor linking, physico-chemical immunoglobulin properties) and nonspecific mechanisms (enhanced vascular permeability and macromolecular exudate) has been suggested. IgG scintigraphy results are affected by the isotope, labeling procedure adopted and characteristics of the inflammatory focus. Nineteen patients with suspected osteomyelitis (active chronic osteomyelitis or violated bone osteomyelitis) were studied by Tc-99m-IgG scintigraphy (directly labeled polyclonal immunoglobulin, Sandoglobuilina - Sandoz). All patients also underwent standard three-phase bone scintigraphy using methylene diphosphonate (Tc-99m-MDP), gallium-67 scintigraphy and plain radiographs. Infection was found in 8 sites. Sensitivity and specificity for Tc-99m-MDP, gallium-67 and Tc 99m-IgG scintigraphy were, respectively, 88 and 36%, 75 and 73%,88 and 82%. All patients with false positive IgG scintigraphies had previous surgery. Other current scintigraphic procedures used in the diagnosis of osteomyelitis are also reviewed. (author)