title: Cartilaginous defects of the femorotibial joint: accuracy of coronal short inversion time inversion-recovery MR sequence.
abstract: OBJECTIVE
  To retrospectively assess the diagnostic performance of the short inversion time inversion-recovery (STIR) magnetic resonance (MR) sequence for depiction and classification of articular cartilaginous lesions in femorotibial joint, with arthroscopy as reference standard.
  
  
  METHODS
  Institutional review board did not require approval and informed consent for review of patients' records or images. All patients (and parents of underage patients) agreed to use of their data. Two musculoskeletal radiologists independently analyzed femorotibial cartilage on coronal STIR images from 84 knee MR examinations in 83 patients (48 male patients [49 knees], 35 female patients; mean age, 39.5 years). Slightly modified Outerbridge classification was used: grade 0, normal cartilage; grade 1, softening or swelling; grade 2, partial-thickness defect; grade 3, fissuring to the level of the subchondral bone; and grade 4, exposed subchondral bone. Arthroscopy performed within 15 weeks was the standard of reference. Classification for arthroscopy differed only in definition of grade 1 (softening or swelling of cartilage). Sensitivity, specificity, accuracy, positive and negative predictive values, and weighted kappa values were calculated to assess interobserver reliability.
  
  
  RESULTS
  At arthroscopy, 212 (63%) of 336 surfaces were classified as grade 0 (normal); 37 (11%), as grade 1 abnormalities; 30 (9%), as grade 2 lesions; 25 (7%), as grade 3 lesions; and 32 (10%), as grade 4 lesions. Grades 0 and 1 were considered normal; grades 2-4, as abnormal. For detection of contour defects of the cartilaginous surface, coronal STIR MR imaging had sensitivity values of 77% and 76%, specificity values of 96% and 89%, accuracy values of 91% and 85%, positive predictive values of 86% and 70%, and negative predictive values of 92% and 91% for readers 1 and 2, respectively. Weighted kappa value was 0.63.
  
  
  CONCLUSIONS
  Contour defects of femorotibial cartilage can be detected with reasonable accuracy with routine STIR sequence.
authors.affiliation: Department of Radiology, University Hospital Balgrist, Forchstrasse 340, CH-8008 Zurich, Switzerland.
authors.forename: Karl-Peter
authors.initials: KP
authors.lastname: Jungius
authors.forename: Marius R
authors.initials: MR
authors.lastname: Schmid
authors.forename: Marco
authors.initials: M
authors.lastname: Zanetti
authors.forename: Juerg
authors.initials: J
authors.lastname: Hodler
authors.forename: Peter
authors.initials: P
authors.lastname: Koch
authors.forename: Christian W A
authors.initials: CW
authors.lastname: Pfirrmann
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001182:Arthroscopy; D002357:Cartilage Diseases / Q000175:diagnosis*; D002358:Cartilage, Articular / Q000473:pathology*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007719:Knee Joint / Q000473:pathology*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D012680:Sensitivity and Specificity