18F FDG-PET/CT has poor diagnostic accuracy in diagnosing shoulder PJI
Chronic low-grade periprosthetic joint infection (PJI) of a shoulder 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 replacements exist. The aim of this study was therefore to determine the diagnostic accuracy of 18F-FDG PET/CT in diagnosing chronic PJI of the shoulder.
Patients evaluated for a failed shoulder replacement during a 3-year period were prospectively included in the study. All patients underwent pre-operative 18F-FDG PET/CT, and were evaluated for signs of infection by three independent reviewers using shoulder-specific criteria. Interrater-agreement was calculated between the reviewers. If the patient had revision surgery, biopsy specimens were obtained and cultured with bacterial growth in the cultures serving as gold standard of infection.
A total of 86 patients were included in the study. Nine patients were 18F-FDG PET/CT positive for infection, with only three true positive. 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 inter-observer agreement was 0.56 (Fleiss’ kappa), indicating moderate agreement of the visual FDG-PET evaluation using the shoulder-specific criteria.
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 routine preoperative workup to diagnose low-grade infection of a shoulder replacement.
KeywordsFDG-PET PJI Infection Shoulder Periprosthetic joint infection
Radiologic Department, Aarhus University Hospital, Aarhus, Denmark
TFJ conceived the study, collected data, analyzed data, and drafted the manuscript. JL participated in conceiving the study, and revised the manuscript. HD revised the manuscript. MHV reviewed images. BZ reviewed images and revised the manuscript. JOV collected data and revised the manuscript. KS participated in conceiving the study, and revised the final manuscript. AKS collected data and revised the manuscript. LCG participated in conceiving the study, reviewed images, and revised the manuscript. All authors read and approved the final manuscript.
Compliance with ethical standards
Conflict of interest
Author T Falstie-Jensen declares that he has no conflict of interest. Author J Lange declares that he has no conflict of interest. Author H Daugaard declares that he has no conflict of interest. Author MH Vendelbo declares that he has no conflict of interest. AKB Sørensen declares that she has no conflict of interest. Author B Zerahn declares that he has no conflict of interest. Author J Ovesen declares that she has no conflict of interest. Author K Søballe declares that he has no conflict of interest. Author LC Gormsen declares that he has no conflict of interest.
(T Falstie-Jensen) has received a grant from Aarhus University (no grant no.) covering part of the fee for the PhD training program. Furthermore, corresponding author has received a research grant from A. P. Møllers og Hustru Chastine Mc-Kinney Møllers Fond til almene Formaal (no grant no.) covering study expenses related to the PhD. The two institutions have not in any way been involved in data collection, data analysis, preparation of, or editing of the manuscript.
All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and national research committee (ref. no. 1–10–72-229-15) and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards.
Informed consent was obtained from all individual participants included in the study.
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