title: MRI-based extended ordered values more efficiently differentiate cartilage loss in knees with and without joint space narrowing than region-specific approaches using MRI or radiography--data from the OA initiative.
abstract: OBJECTIVE
  The sensitivity to change of quantitative analysis of cartilage in knee osteoarthritis using magnetic resonance imaging (MRI) is compromised by the spatial heterogeneity of cartilage loss. We explore whether extended (medial-lateral) "ordered values" (OVs) are superior to conventional approaches of analyzing subregional cartilage thickness loss and to radiography, in differentiating rates of progression in knees with and without joint space narrowing (JSN).
  
  
  METHODS
  607 Osteoarthritis Initiative (OAI) participants (308 without and 299 with baseline JSN at baseline) were studied over 12 months. Subregional femorotibial cartilage loss was determined in all knees, and changes in minimum joint space width (mJSW) in a subset of 290 knees. Subregional thickness changes in medial and lateral tibial and femoral cartilages were sorted in ascending order (OV1-16). A Wilcoxon rank-sum test was used to compare rates of change in knees with and without JSN.
  
  
  RESULTS
  JSN-knees displayed greater cartilage loss than those without JSN, with minimal P-values of 0.008 for femorotibial subregions, 3.3×10(-4) for medial OV1, and 5.4×10(-7) for extended (medial and lateral) OV1. mJSW measurements (n=290) did not discriminate between longitudinal rates of change in JSN vs no-JSN knees (P=0.386), whereas medial OV1 (P=5.1×10(-4)) and extended OV1 did (P=2.1×10(-5)).
  
  
  CONCLUSIONS
  Extended OVs showed higher sensitivity to detecting differences in longitudinal rates of cartilage loss in knees with and without baseline JSN than anatomical (sub)regions and radiography. The OV technique also circumvents challenges of selecting particular regions "a priori" in clinical trials and may thus provide a powerful tool in studying risk factors or treatment efficacy in osteoarthritis.
authors.affiliation: Chondrometrics GmbH, Ainring, Germany. wolfgang.wirth@pmu.ac.at
authors.forename: W
authors.initials: W
authors.lastname: Wirth
authors.forename: R
authors.initials: R
authors.lastname: Buck
authors.forename: M
authors.initials: M
authors.lastname: Nevitt
authors.forename: M P H
authors.initials: MP
authors.lastname: Le Graverand
authors.forename: O
authors.initials: O
authors.lastname: Benichou
authors.forename: D
authors.initials: D
authors.lastname: Dreher
authors.forename: R Y
authors.initials: RY
authors.lastname: Davies
authors.forename: J H
authors.initials: JH
authors.lastname: Lee
authors.forename: K
authors.initials: K
authors.lastname: Picha
authors.forename: A
authors.initials: A
authors.lastname: Gimona
authors.forename: S
authors.initials: S
authors.lastname: Maschek
authors.forename: M
authors.initials: M
authors.lastname: Hudelmaier
authors.forename: F
authors.initials: F
authors.lastname: Eckstein
mesh_terms: D000368:Aged; D002358:Cartilage, Articular / Q000000981:diagnostic imaging* / Q000473:pathology*; D018450:Disease Progression; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000000981:diagnostic imaging* / Q000473:pathology*; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000000981:diagnostic imaging* / Q000473:pathology*; D011859:Radiography; D012680:Sensitivity and Specificity