DOS 2019

166 · DOS Abstracts FDG-PET/CT has poor diagnostic accuracy in diagnosing shoulder periprosthetic joint infection Thomas Falstie-Jensen, Jeppe Lange, Henrik Daugaard, Anne Katrine Belling Sørensen, Bo Zerahn, Janne Ovesen, Mikkel Vendelbo, Lars Christian Gormsen Department of Orthopedic Surgery, section for shoulder and elbow surgery, Aarhus UniversityHospital; Department of Orthopedic Surgery, Regional Hospital Horsens; Department of Orthopedic Surgery, Gentofte Hospital; Department of Orthopedic Surgery, section for shoulder and elbow surgery, Herlev Hospital; Department of Clinical Physiology, Herlev Hospital ; Department of Nuclear Medicine & PET Centre, Aarhus University Hospital; Department of Nuclear Medicine & PET Centre, Aarhus University Hospital Background: Chronic low-grade periprosthetic joint infection (PJI) of a shoul- der replacement can be challenging to diagnose. 18F-FDG PET/CT is suggested as a modality to diagnose lower limb PJI, but no studies on shoulder replace- ments exist. Purpose / Aim of Study: The aim of this study was to determine the diag- nostic accuracy of 18F-FDG PET/CT in diagnosing chronic PJI of the shoulder. Materials and Methods: Patients evaluated for a failed shoulder replacement during a 3-year period were prospectively included in the study. All patients un- derwent pre-operative 18F-FDG PET/CT and were evaluated for signs of infec- tion by three independent reviewers using newly developed shoulder-specific criteria. Interrater-agreement was calculated between the reviewers. If the pa- tient was revised, biopsy specimens were obtained and cultured with bacterial growth in the cultures serving as gold standard of infection. Findings / Results: A total of 86 patients were included in the study. Nine patients were 18F-FDG PET/CT positive for infection; with only 3 true posi- tive. Using the gold standard, infection was diagnosed after revision-surgery in 22 cases. All infections were chronic and caused by low-virulent microbes. The sensitivity of 18F-FDG PET/CT was 0.14 95%CI(0.03-0.36), specificity 0.91 95%CI(0.81-0.97), positive predictive value was 0.40 95%CI(0.15-0.71) and negative predictive value 0.71 95%CI(0.67-0.75). The interobserver agree- ment was 0.56 (Fleiss’ kappa) indicating moderate agreement of the visual FDG-PET evaluation using the shoulder-specific criterion. Conclusions: 18F-FDG PET/CT has poor diagnostic accuracy in diagnosing low-grade PJI of the shoulder. 18F-FDG PET/CT cannot be recommended as a part of the preoperative workup to diagnose low-grade infection of a shoulder replacement. 122.