title: FDG and FDG-labelled leucocyte PET/CT in the imaging of prosthetic joint infection.
abstract: OBJECTIVE
  The demand for arthroplasty is rapidly growing as a result of the ageing of the population. Although complications such as heterotrophic ossification, fracture and dislocation are relatively rare, differentiating aseptic loosening, the most common complication of arthroplasty from infection, is a major challenge for clinicians. Radionuclide imaging is currently the imaging modality of choice since it is not affected by orthopaedic hardware. Whereas FDG PET/CT imaging has been widely used in periprosthetic infection, it cannot discriminate aseptic from septic inflammation. In this study we aimed to evaluate the role of FDG PET/CT and FDG-labelled leucocyte PET/CT in the diagnosis of periprosthetic infection.
  
  
  METHODS
  Of 54 patients with painful joint arthroplasty who were imaged by FDG PET/CT for diagnosis of periprosthetic infection examined, 46 (36 women, 10 men; mean age 61.04 ± 12.2 years, range 32-89 years) with 54 painful joint prostheses (19 hip, 35 knee) with grade 2 (above liver uptake) FDG accumulation on FDG PET/CT were included in the study and these 46 patients also underwent FDG-labelled leucocyte PET/CT. Final diagnoses were made by histopathological-microbiological culture or clinical follow-up.
  
  
  RESULTS
  The final diagnosis showed infection in 15 (28%) and aseptic loosening in 39 (72%) of the 54 prostheses. FDG PET/CT was found to have a positive predictive value of 28% (15/54). Since patients with no FDG uptake on FDG PET/CT were excluded from the study, the sensitivity, specificity, negative predictive value and accuracy could not be calculated. The sensitivity, specificity, and positive and negative predictive values of FDG-labelled leucocyte PET/CT were 93.3% (14/15), 97.4% (38/39), 93.3% and 97.4%, respectively.
  
  
  CONCLUSIONS
  Since FDG is not specific to infection, the specificity of FDG PET/CT was very low. FDG-labelled leucocyte PET/CT with its high specificity may be a useful method and better than labelled leucocyte scintigraphy in periprosthetic infection imaging.
authors.affiliation: Department of Nuclear Medicine, Cerrahpasa Medical Faculty, University of Istanbul, Aksaray, Istanbul, Turkey, sbr_ylmz@yahoo.com.
authors.forename: Sabire Yılmaz
authors.initials: SY
authors.lastname: Aksoy
authors.forename: Sertac
authors.initials: S
authors.lastname: Asa
authors.forename: Meftune
authors.initials: M
authors.lastname: Ozhan
authors.forename: Meltem
authors.initials: M
authors.lastname: Ocak
authors.forename: M Sait
authors.initials: MS
authors.lastname: Sager
authors.forename: Melih Engin
authors.initials: ME
authors.lastname: Erkan
authors.forename: Metin
authors.initials: M
authors.lastname: Halac
authors.forename: Levent
authors.initials: L
authors.lastname: Kabasakal
authors.forename: Kerim
authors.initials: K
authors.lastname: Sönmezoglu
authors.forename: Bedii
authors.initials: B
authors.lastname: Kanmaz
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D019788:Fluorodeoxyglucose F18 / Q000493:pharmacokinetics; D006801:Humans; D007595:Joint Prosthesis / Q000382:microbiology*; D007962:Leukocytes / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D064847:Multimodal Imaging; D049268:Positron-Emission Tomography; D016459:Prosthesis-Related Infections / Q000000981:diagnostic imaging*; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18