title: Lamellated hyperintense synovitis: potential MR imaging sign of an infected knee arthroplasty.
abstract: OBJECTIVE
  To determine the sensitivity and specificity of lamellated hyperintense synovitis for infection following knee arthroplasty and to determine the inter- and intraobserver variability of this sign at magnetic resonance (MR) imaging.
  
  
  METHODS
  The purpose of the retrospective case control study was approved by the hospital's institutional review board. MR images from 28 patients with proved infected total knee arthroplasty and 28 patients with noninfected arthroplasty were reviewed by two musculoskeletal radiologists for the presence of lamellated hyperintense synovitis. Cases were rereviewed 2 weeks later by each reader. The sensitivity and specificity were calculated with the initial reads. The κ statistic was used to assess inter- and intraobserver reliability.
  
  
  RESULTS
  The sensitivity of lamellated hyperintense synovitis for infection was 0.86-0.92 (95% confidence interval [CI]: 0.75, 0.97) and the specificity was 0.85-0.87 (95% CI: 0.74, 0.94). There was almost perfect interobserver agreement (κ = 0.82; 95% CI: 0.72, 0.93; P < .001) and intraobserver agreement (for reader 1, κ = 0.89 [95% CI: 0.78, 1.00; P < .001] and for reader 2, κ = 0.89 [95% CI: 0.77, 1.00; P < .001]) in the classification of the synovial pattern.
  
  
  CONCLUSIONS
  In this selected series of patients, the presence of lamellated hyperintense synovitis at MR imaging of knee arthroplasty had a high sensitivity and specificity for infection. This sign had high inter- and intraobserver reliability.
authors.affiliation: Department of Radiology and Imaging, Hospital for Special Surgery, 535 E 70th St, New York, NY 10021, USA. Plodkowski@yahoo.com
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Plodkowski
authors.forename: Catherine L
authors.initials: CL
authors.lastname: Hayter
authors.forename: Theodore T
authors.initials: TT
authors.lastname: Miller
authors.forename: Joseph T
authors.initials: JT
authors.lastname: Nguyen
authors.forename: Hollis G
authors.initials: HG
authors.lastname: Potter
mesh_terms: D000368:Aged; D019645:Arthroplasty, Replacement, Knee / Q000009:adverse effects*; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000473:pathology* / Q000601:surgery; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D016459:Prosthesis-Related Infections / Q000209:etiology* / Q000473:pathology*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013585:Synovitis / Q000209:etiology* / Q000473:pathology*