Publication Date

12-2017

Date of Final Oral Examination (Defense)

11-9-2017

Type of Culminating Activity

Thesis

Degree Title

Master of Science in Mechanical Engineering

Department

Mechanical and Biomechanical Engineering

Major Advisor

Trevor Lujan, Ph.D.

Advisor

Gunes Uzer, Ph.D.

Advisor

Julia Thom Oxford, Ph.D.

Advisor

John F. Gardner, Ph.D.

Abstract

Ligament injuries are the most common sports injury in the United States. The current clinical practice for treating ligament injuries leaves many patients with significant pain and joint laxity for years following the initial injury. Controlled mechanical stimulation of the tissue after injury is necessary for robust healing, but the optimal mechanical environment for ligament healing is not fully understood. Alternative therapies, such as instrument assisted soft tissue mobilization (IASTM), offer a form of mechanical stimulation that is non-invasive and has shown promising clinical outcomes but the optimal dosage for IASTM treatments is unknown. The objective of this study was to develop in-vitro and in-vivo experimental devices that can help determine the specific mechanical loads that strengthen and accelerate ligament healing.

Two devices were developed. The in-vitro device is a novel multi-axis mechanical stimulation bioreactor that can accurately apply tensile and combined tensile/compressive stress states to 3D fibroblast seeded tissue constructs. The bioreactor consists of two independently controlled actuators, one tensile, one compressive, a tablet computer, and data acquisition hardware. The bioreactor was validated using gelatin constructs to simultaneously apply cyclic forces from 0 – 0.2N with an accuracy of approximately 0.01N, and a high degree of repeatability. The in-vivo device is a hand-held device to control the frequency and magnitude of applied force during IASTM treatments on rats after ligament transection. The device consists of a force sensor, tablet computer, and custom software to guide the application of user-specified loading parameters during IASTM treatments. The device accuracy was measured by applying a combination of force and stroke frequencies to rigid foam and was experimentally validated over a 3-week animal experiment. The device was demonstrated to apply forces between 0 – 5N at frequencies from 0 – 1Hz with a high degree of accuracy and repeatability.

The devices validated in this study provide a framework for future studies. The in-vitro device can provide insight into the mechanobiological effects of different loading configurations on fibroblast seeded constructs, including the simultaneous application of tensile and compressive loading, which is similar to IASTM treatment. The in-vivo device will be used to perform animal studies that can assess the effects of varying applied force and frequency parameters during IASTM treatments.

DOI

https://doi.org/10.18122/B2SM5V

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