ABSTRACT

Prosthetic joint replacement surgery has became a more frequently used procedure worldwide. Although occurring infrequently, most serious complication of prosthetic joint replacement is infection. Differentiating prosthetic joint infection from aseptic loosening, which is the most common cause of prosthetic failure, is very important because the treatment of these two entities is different. Despite the detailed patient history, physical examination conventional diagnostic tests, differentiating prosthetic joint infection from aseptic loosening is difficult. The imaging modalities such as radiographs, computed tomography (CT) and magnetic resonance imaging are neither sensitive nor spesific and because of hardware induced artefacts. Radionuclide imaging technics display functional changes rather than anatomical changes, which is not obstacled by the presence of a metallic joint prosthesis. There is no consensus about the gold standard imaging technique since the presence of several drawbacks and limitations of conventional techniques. The mostly used radionuclide imaging modalities for diagnosis of joint prosthesis infection are galyum citrate scintigraphy, bone scintigraphy, radiolabelled leucocyte scintigraphy (in vitro and in vivo), monoclonal antibody scintigraphy (against spesific targets on the leukocytes) and F-18 fluorodeoxyglucose (F-18 FDG) imaging. Bone scintigraphy is sensitive for the discrimination of aseptic loosening, however it can not distinguish prosthesis infection from other conditions such as post-surgical changes, aseptic loosening and healing fractures. The combined imaging modalities such as bone/ gallium scintigraphy, bone/labelled leucocyte scintigraphy, or bone marrow/labelled leucocyte scintigraphy offers more information for diagnosing orthopedic prosthetic infections. Radiolabelled leucocyte scintigraphy is still the gold standard technique for diagnosing neutrophil-mediated processes. Currently, combined in vitro labelled leucocyte/bone marrow scintigraphy, with an accuracy of about 90%, is the imaging method of choice for diagnosing orthopedic prosthetic infections. Significant limitations using in vitro labelled leucocytes led to noticable trials to develop alternative radiopharmaceuticas, such as radiolabelled HIGs, liposomes, antigranulocyte antibodies and radiolabelled antibiotics, antimicrobial peptides, bacteriophages and thymidine kinase. On the other hand, positron imaging radiopharmaceuticals such as F-18 FDG, F-18 FDG labelled leucocyte and F-18 fluoride are still being investigated and used increasingly for diagnosis of orthopedic prosthetic infection. However, this excellent tomographic tecnique will receive full acceptance when spesific PET radiopharmaceuticals are developed. The hybrid imaging modality consisting single-photon emission computed tomography and PET with CT may be useful for more accurate evaluation of orthopedic prosthesis complications. The aim of this review is to define the principles and the role of molecular imaging methods in the management of orthopedic prosthesis infections.