title: The value of FDG-PET in patients with painful total knee arthroplasty.
abstract: OBJECTIVE
  The purpose of this study was to evaluate 18F-fluorodeoxyglucose (FDG) uptake in patients with painful total knee arthroplasty and to relate FDG uptake to the location of soft tissue pain.
  
  
  METHODS
  Twenty-eight patients with painful total knee arthroplasty had a clinical examination, standard radiographs, CT measurement of rotation of the femoral component and FDG-PET (18 PET/CT, 10 PET). The diagnosis of infection was based on microbiological examinations of surgical specimens (n=12) or clinical follow-up for at least 6 months (n=16), 99mTc-labelled monoclonal antibody scintigraphy and joint aspiration.
  
  
  RESULTS
  Twenty-seven of 28 patients presented with diffuse synovial FDG uptake. Additional focal extrasynovial FDG uptake was observed in 19 knees. Twenty-four of the 28 patients had a diagnosis of internal femoral malrotation. The remaining four patients showed no rotation (0 degrees) and 3 degrees, 4 degrees and 7 degrees of external rotation, respectively. Three patients presented with the additional diagnosis of an infected total knee replacement. Pain was described as diffuse (n=10) or focal (n=18). In two knees a relationship between pain location and FDG uptake was observed. Of ten patients with a severe internal femoral component rotation (>6 degrees), seven had focal uptake, four in the femoral periosteum and three in the tibial periosteum. The difference between knees with severe malrotation and the remaining knees was not significant (p=1.000, Fisher's Exact Test).
  
  
  CONCLUSIONS
  Diffuse synovial and focal extrasynovial FDG-PET uptake is commonly found in patients with malrotation of the femoral component and is not related to pain location. The information provided by FDG-PET does not contribute to the diagnosis and management of individual patients with persistent pain after total knee replacement.
authors.affiliation: Department of Medical Radiology, Division of Nuclear Medicine, University Hospital, Zurich, Switzerland.
authors.forename: Katrin D M
authors.initials: KD
authors.lastname: Stumpe
authors.forename: Jose
authors.initials: J
authors.lastname: Romero
authors.forename: Oliver
authors.initials: O
authors.lastname: Ziegler
authors.forename: Ehab M
authors.initials: EM
authors.lastname: Kamel
authors.forename: Gustav K
authors.initials: GK
authors.lastname: von Schulthess
authors.forename: Klaus
authors.initials: K
authors.lastname: Strobel
authors.forename: Juerg
authors.initials: J
authors.lastname: Hodler
mesh_terms: D000368:Aged; D018771:Arthralgia / Q000000981:diagnostic imaging* / Q000209:etiology; D019645:Arthroplasty, Replacement, Knee / Q000009:adverse effects*; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D007593:Joint Instability / Q000000981:diagnostic imaging* / Q000209:etiology; D007719:Knee Joint / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D049268:Positron-Emission Tomography / Q000379:methods*; D011475:Prosthesis Failure; D016459:Prosthesis-Related Infections / Q000000981:diagnostic imaging* / Q000209:etiology; D019275:Radiopharmaceuticals; D016896:Treatment Outcome
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18