Date of Completion

5-12-2019

Embargo Period

4-24-2019

Advisors

David M. Pierce, George Lykotrafitis, Anna Tarakanova

Field of Study

Mechanical Engineering

Degree

Master of Science

Open Access

Open Access

Abstract

Articular cartilage is a soft tissue that facilitates joint movement and protects bone contact surfaces. Human articular cartilage sees a range of temperatures in vivodepending on external thermal conditions. Researchers recently demonstrated that cartilage dissipates energy during physiological loading to elevate the temperature to enhance cell viability. Despite these important insights, researchers often consider the knee isothermal, thus the large deformation mechanical response under transient thermal conditions remains largely unknown. We aimed to quantify the mechanical responses at 24°C, 40°C, 70°C, and 24°C repeated, and apply our data to determine whether the mechanical responses of cartilage vary within the range of temperatures relevant in vivo, and the effects of superphysiological temperatures on cartilage’s mechanical responses both during and after thermal treatments. We prepared a total of 36 cubic specimens from medial and lateral femoral condyles of female and male human patients. We applied large simple shear displacements parallel to the local alignment of the collagen network at 10% and 15% of the specimens thickness. Our results suggest the mechanical response does depend on temperature in the in vivo range and is strongly influenced by super-physiological temperatures, shown by a significant reduction in the peak-effective shear modulus and peak-to-peak stress. Furthermore, given the reduction in strain-energy dissipation in the human knee with the increase of temperature, it may be a sufficient mechanism for elevating the temperature of chondrocytes to their optimal metabolic condition. These additional insights to the mechanics of cartilage may suggest new treatment targets for damaged or osteoarthritic tissues.

Major Advisor

David M. Pierce

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