Publication Date

8-2023

Date of Final Oral Examination (Defense)

5-1-2023

Type of Culminating Activity

Dissertation

Degree Title

Doctor of Philosophy in Biomedical Engineering

Department

Mechanical and Biomechanical Engineering

Major Advisor

Trevor J. Lujan, Ph.D.

Advisor

Clare Fitzpatrick, Ph.D.

Advisor

Gunes Uzer, Ph.D.

Advisor

Julia Oxford, Ph.D.

Advisor

Tracye Lawyer, M.D., Ph.D.

Abstract

The knee meniscus is a soft fibrous tissue with a high incidence of injury in older populations. Surgical treatments do not fully restore the functionality of the meniscus, and the meniscus lacks native healing capacity, leading to a 40% increase in the probability of developing osteoarthritis once torn. Meniscus injury prevention is thus paramount to reducing the onset of osteoarthritis. Despite the importance of the meniscus in joint health, its mechanical properties, and how these change with age, are poorly understood. In order to quantify these properties, and how they change with age, we performed uniaxial tensile tests on two age groups of human menisci: under 40 and over 65 years old. We found that tissue from the older donor groups had significantly reduced strength and toughness. We refined the data analysis techniques used in this work to build a free web application to provide to the scientific community to standardize the calculation of mechanical properties found in soft tissue tensile testing, and to provide a convenient tool to reduce the time to analyze data. We then used the mechanical testing data to build and validate a finite element model of tissue failures with continuum damage mechanics. This work showed that using von Mises stress to evolve damage produced excellent fits to the experimental data, and was able to mimic the failure behavior from the previous experiments. Finally, we performed biochemical analysis on the tissue in order to evaluate the changing structure-function relationship with age. This showed changes to the meniscus proteome with age, and that changes to collagen crosslinks correlated to changes to the strength of the tissue. Collectively, this work has detailed potential reasons as to how and why the meniscus becomes more susceptible to tears with age, detailed computational methods to analyze these tears, and provided a tool to further analyze tears of the meniscus and other soft tissues in a lab setting.

DOI

https://doi.org/10.18122/td.2121.boisestate

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