Assessment of stiffness in intact cartilage using contrast-enhanced computed tomography (CECT)

Introduction: Osteoarthritis (OA) is the most prevalent joint disease in Canada, affecting millions of people. OA begins with softening of cartilage and is characterized by progressive loss of the tissue resulting in joint impairment. Because cartilage’s primary function is mechanical, and because OA disrupts cartilage’s mechanical function, there is a substantial need for a non-invasive method to assess cartilage mechanics. Contrast-enhanced computed tomography (CECT) using charged contrast agents is an imaging method developed to quantify Glycosaminoglycan (GAG) content of cartilage. Since GAG is a key determinant of cartilage compressive stiffness, CECT measurements may be correlated with cartilage stiffness. The objective of this study was to determine whether CECT using a novel cationic contrast agent (CA4+) is correlated with cartilage stiffness in intact human joint surfaces. Methods: Six human femoral condyle compartments with intact healthy cartilage (ICRS grade 0 or 1) were used. Cartilage stiffness was measured across the surface in a Mach-1 testing system (Biomomentum, Montreal) using an indentation test. The samples were then immersed in CA4+ solution for 48 hours and then scanned at 41μm resolution in a hr-pQCT scanner (Xtreme CT, Scanco, Zurich). The averages of CECT attenuations at the sites of the indentation tests were computed for both superficial cartilage (600μm depth) and for the full thickness of cartilage. Correlations between stiffness and CECT attenuation were assessed with scatter plots and Pearson’s correlation coefficient. Results: A significant and positive correlation was observed between stiffness data and mean CECT attenuations in superficial cartilage across all samples, with correlation coefficients ranging from r=0.4 to 0.72, and p