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

University of British Columbia

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<0.01. When data from all locations were pooled (n=221), the correlation coefficient was r=0.55 and a regression line fitted to the data predicted stiffness from CECT measurements with an error of 20% of the stiffness range. However, correlations between stiffness and CECT attenuations in full-depth cartilage were substantially lower and not significant in half of the tested specimens. CECT identified regions of reduced cartilage stiffness and the expected depth dependent changes in GAG concentration. Conclusion: CECT of superficial cartilage using CA4+ provides a surrogate measure of compressive cartilage stiffness in intact joint surfaces.

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2016-02-29

Attribution-NonCommercial-NoDerivs 2.5 Canada

http://hdl.handle.net/2429/54580

Biomedical Engineering

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/2.5/ca/