The objective of the work was validation of the findings obtained by three-phase scintigraphy of the skeleton in the differential diagnosis of infection and loosening of total endoprostheses (TEP). As infection the authors classified abnormally enhanced cumulation of the radiopharmaceutical preparation in the area of the endoprosthesis in all three phases of the examination: aseptic loosening was defined as abnormal increase of osteoblastic activity on the delayed scan without hyperaemia in the arterial and blood pool stage. The scintigraphic finding was tested in 53 patients (in 38 by surgical revision and in 15 by long-term follow up). Of the 38 revised patients surgery verified loosening in 34 (15 infectious and 19 aseptic loosening). Loosening was not found in 19 of the examined patients and 15 patients were evaluated as normal (small probability of infection or loosening). Of 15 patients with confirmed infection 3-phase bone scintigraphy was positive in all phases in 10 patients, in two patients increased bone formation in the delayed phase was found and in two inflammation of soft tissues, and one patient with a TEP of the knee had increased bone formation only in the patella. Of 38 patients without infection 35 did not suffer from hyperaemia in the early phase. The diagnostic accuracy for detection of infection was 85% (45/53). The results indicate that three-phase bone scintigraphy can be a valuable examination for contemplations of the surgeon as regards the necessity of intervention and selection of a therapeutic strategy in patients with TEP.

        Key words: hip and knee prostheses - three-phase bone scintigraphy - infection - aseptic loosening