Non-Invasive Imaging of Complicated Osteomyelitis: The Added Value of Scintigraphic Techniques

F.      Gemmel; N.      Dumarey; C.   J.   Palestro

Abstract

Diagnosing osteomyelitis is clinically challenging. Laboratory tests are of limited utility, and other than isolation of the offending organism, diagnostic imaging tests are of paramount importance. There are a myriad of scintigraphic tests from which to choose, and no single test is optimal for all indications. With an accuracy of more than 90%, bone scintigraphy is the radionuclide test of choice for diagnosing osteomyelitis in unviolated bone. The test is less useful in violated bone conditions. Gallium-67 citrate imaging has been used in conjunction with the bone scan to improve test specificity. The overall accuracy of bone/gallium imaging, which is usually reserved for spinal osteomyelitis, is about 65%-80%. Except in the spine, combined radiolabeled leukocyte-marrow imaging is the radionuclide procedure of choice for diagnosing complicated osteomyelitis. The accuracy of the test is about 80%-90%. The in-vitro labeling procedure is a significant drawback to the test, and despite numerous attempts, no satisfactory in vivo labeling method is available. Recent work indicates that FDG PET is useful in the diagnosis of osteomyelitis. This tracer has shown promise for detecting acute and chronic infection in the axial and peripheral skeleton and has been reported to be highly accurate in suspected implant- (except prosthetic joint) associated infections. Increased FDG uptake, however, also is associated with inflammatory arthritis, acute fractures, normally healing bone and degenerative changes. Much investigation is still needed to determine the precise role of this procedure in musculoskeletal infection. Radiolabeled antibiotics and antimicrobials, which should in theory be highly specific for infection, have been investigated but are not in routine clinical use. It is important to recognize that no single tracer is equally efficacious in all regions of the skeleton and the selection of the appropriate study should be governed by the clinical question posed.

Keywords: Complicated osteomyelitis, bone scan, gallium scan, leukocyte scan, marrow scan, FDG-PET

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