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Access Type

WSU Access

Date of Award

January 2012

Degree Type

Thesis

Degree Name

M.S.

Department

Biomedical Engineering

First Advisor

John M. Cavanaugh

Abstract

ABSTRACT

TENSILE PROPERTIES OF SPINAL NERVE ROOTS AT HIGH STRAIN RATES: AN IN VIVO STUDY

by

Joseph M. Yaldo

April 2012

Advisor: Dr. John M. Cavanaugh

Major: Biomedical Engineering

Degree: Master of Science

Spinal nerve roots are subject to tension in many traumatic and non-traumatic situations, such as motor vehicle accidents or disc herniation. These events may cause severe injuries and pain to the victims who are involved. By obtaining a better understanding of the biomechanical properties of spinal nerve roots, in particular in tension, better methods can be developed to help predict the amount of tension that may be applied to spinal nerve roots before causing serious injury to an individual.

For this study biomechanical properties of dorsal nerve roots at the L4 and L5 lumbar levels were determined at high displacement rates of 20, 200, and 800 mm/sec. The study was done using Sprague Dawley rats in vivo. Load and displacement data was obtained from the nerve roots as they were stretched to failure. Maximum load, maximum stress, and modulus of elasticity (E) values were calculated.

Maximum load values of 8.3 2.3g, 21.4 5.1g, and 26.3 4.2g were found for the 20, 200, and 800 mm/sec rates, respectively. Also, maximum stress and E values of 210.1 42.0 kPa and 1.1 0.3MPa, 511.5 85.2 kPa and 3.1 1.4MPa, and 687.9 120.6 kPa and 3.5 1.3MPa were obtained for the 20, 200, and 800 mm/sec rates, respectively. It was found that as the displacement rate increased, the maximum load, stress, and E values also increased. No significant difference was shown in the failure strain among the three displacement rates.

The results from the study demonstrated spinal nerve roots exhibit a strain rate dependency. These results help give a better understanding of how tensile properties of nerve roots are affected by different strain rates.