Date of Completion

9-4-2018

Embargo Period

9-4-2018

Keywords

Cartilage, Shear, Digital Image Correlation, Osteoarthritis

Major Advisor

David M. Pierce

Associate Advisor

Eric H. Jordan

Associate Advisor

Bin Feng

Associate Advisor

Ying Li

Associate Advisor

George Lykotrafitis

Field of Study

Mechanical Engineering

Degree

Doctor of Philosophy

Open Access

Open Access

Abstract

Cartilage covers the articulating bones in all synovial joints throughout the body, providing a wear-resistant, low-friction surface. Complex interactions of solid (collagen and proteoglycans) and fluid (water and dissolved ions) maintain the tissue’s load- bearing properties. Osteoarthritis burdens approximately 20% of the population in the United States, and its prevalence is projected to increase. With progressing disease, the tissue’s constituents alter in composition and structure, resulting in a downward cascade of degeneration. In this work we determined the location dependent multiaxial properties of human cartilage. We found strain dependent anisotropy and significant inter-joint variability in mechanical strength and energy dissipation in healthy human tissue. Subsequently we investigated the mechanical response of tissue harvested from patients undergoing total knee arthroplasty. We correlated mechanical metrics with tissue composition and structure, assessed biochemically and histologically. We found a significant reduction in mechanical strength with moderate disease and a reduction in anisotropy. More importantly, we observed a significant reduction in energy dissipation, preceding changes in tissue composition, in tissue representing the onset of the disease. A detailed analysis of the through-thickness shear strain distribution, obtained via digital image correlation, revealed significant changes in the depth-dependent mechanical response. Tissue deformation in the bottom 30% of the thickness reduces with mild structural remodeling and disease progression. Those changes in the mechanobiological environment of the tissue’s cell might further deregulate the cell response and progress the disease. We successfully measured depth-dependent multiaxial properties of cartilage undergoing large strains and identified two potential biomarkers for the early detection of osteoarthritis.

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