ORCID Identifier(s)

0000-0002-2871-6006

Graduation Semester and Year

2021

Language

English

Document Type

Thesis

Degree Name

Master of Science in Biomedical Engineering

Department

Bioengineering

First Advisor

Jun Liao

Second Advisor

George Alexandrakis

Abstract

Rotator cuff tendon injuries and tear are caused by overuse, falling, or other accidents, and are often associated with old age. The severe injuries and tear can be debilitating and require nonsurgical treatment for partial tear and arthroscopic surgery for complete tear. The frequent location of injuries and tear are at the enthesis region, the interface where the tendon tissue gradually hardens and merges into the bone. Although aging has been identified as an important factor for rotator cuff tendon injuries and tear, how the mechanical properties of the bone-tendon complex evolve along with age is still a knowledge gap. Collaborating with the University of Nebraska Medical Centre, we have assessed the biomechanical properties of bone-rotator cuff tendon complex of male mice and female mice among various age groups (young: 2-3 months old, adult: 6-8 months old, and old: 15-18 months old). The failure stress, failure strain, and maximum tensile modulus were compared to reveal the overall trends among young, adult, and old groups, as well as female versus male. We found that, for failure stress (mechanical strength), no difference between young and adult mice was found, while old mice showed increased failure stress, especially the old male mice. The maximum tensile modulus represents the stiffness of the complex. An increasing trend was observed from young, to adult, to old mice, but only the difference between old male and young female groups was significant. No obvious trend exists in the failure strain, except the complexes of young females had larger failure strains (more extensible) compared with the young male and adult male groups. Lastly, the male mice had higher overall failure stress than the female mice in adult and old groups, and the male mice had larger overall maximum tensile moduli than the female mice in all three age groups. Our mechanical data showed an interesting observation. The failure stress in the old group, especially the old male group, increased significantly compared to the young and adult groups. The maximum tensile modulus also showed an increasing trend from the young to old groups. Our observation in the mouse model indicates that age alone might not be the dominant risk factor to predict rotator cuff injury rate, and other factors associated with the aging process, like overuse, accumulated tissue damages/injuries, and underlying chronic disease, might contribute to the vulnerability of the rotator cuff in the elderly populations. We further performed Micro-CT imaging on the bone- tendon complex and reconstructed its 3D geometrical model using MITK, Slicer, and MeshLab software . With the material parameters obtained from the biomechanical tests, we successful established a Finite Element Analysis model for the bone-rotator cuff tendon complex using ANSYS software and were able to simulate and demonstrate its age dependent mechanical behavior.

Keywords

Biomechanics, FEA simulation

Disciplines

Biomedical Engineering and Bioengineering | Engineering

Comments

Degree granted by The University of Texas at Arlington

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