title: Contrast enhanced computed tomography can predict the glycosaminoglycan content and biomechanical properties of articular cartilage.
abstract: OBJECTIVE
  An early hallmark of osteoarthritis (OA) is the progressive loss of glycosaminoglycans (GAGs), the extracellular matrix (ECM) component of articular cartilage that confers it with compressive stiffness. Our aim in this work is to establish the feasibility of using Contrast Enhanced Computed Tomography (CECT) with an anionic iodinated contrast agent - Cysto Conray II - as a minimally invasive tool to measure the changes in the GAG content as well as the compressive stiffness of articular cartilage.
  
  
  METHODS
  The GAG content of mated osteochondral plugs excised from bovine patello-femoral joints was progressively degraded using chondroitinase ABC. The mated plugs were then immersed in an anionic, tri-iodinated contrast agent, imaged using peripheral quantitative computed tomography (pQCT), subjected to an unconfined compressive stress relaxation test and the GAG content measured using 1,9-dimethylmethylene blue (DMMB) assay. Partial correlation analysis was performed to compare the variation in X-ray attenuation measured by pQCT to the variation in GAG content and in equilibrium compressive modulus.
  
  
  RESULTS
  The X-ray attenuation of cartilage exposed to an anionic, tri-iodinated, contrast agent measured by quantitative computed tomography (QCT) accounted for 83% of the variation in GAG content (r(2)=0.83, P<0.0001) and 93% of the variation in the equilibrium compressive modulus (r(2)=0.93, P<0.0001).
  
  
  CONCLUSIONS
  Using a mated osteochondral plug model to evaluate the biochemical composition and biomechanical properties of cartilage, this study demonstrates the interrelationships between X-ray attenuation, GAG content, and equilibrium compressive modulus, and that CECT can be used to monitor and quantify changes in the GAG content and biomechanical properties of articular cartilage.
authors.affiliation: Orthopedic Biomechanics Laboratory, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA 02215, USA.
authors.forename: P N
authors.initials: PN
authors.lastname: Bansal
authors.forename: N S
authors.initials: NS
authors.lastname: Joshi
authors.forename: V
authors.initials: V
authors.lastname: Entezari
authors.forename: M W
authors.initials: MW
authors.lastname: Grinstaff
authors.forename: B D
authors.initials: BD
authors.lastname: Snyder
mesh_terms: D000818:Animals; D002358:Cartilage, Articular / Q000737:chemistry / Q000000981:diagnostic imaging* / Q000473:pathology; D002417:Cattle; D019245:Compressive Strength / Q000502:physiology; D003287:Contrast Media / Q000493:pharmacokinetics; D004195:Disease Models, Animal; D006025:Glycosaminoglycans / Q000032:analysis*; D008751:Methylene Blue / Q000031:analogs & derivatives; D020370:Osteoarthritis, Knee / Q000000981:diagnostic imaging* / Q000378:metabolism / Q000503:physiopathology; D014057:Tomography, X-Ray Computed / Q000379:methods*
chemical_list: D003287:Contrast Media; D006025:Glycosaminoglycans; D008751:Methylene Blue; C016401:1,9-dimethylmethylene blue