Date of Award

Summer 2008

Document Type

Thesis - Restricted

Degree Name

Master of Science (MS)

Department

Biomedical Engineering

First Advisor

Stemper, Brian D.

Second Advisor

Ropella, Kristina

Third Advisor

Baisden, Jamie L.

Abstract

Female susceptibility to traumatic spinal injury has been identified in automotive and clinical literature. The gender disparity is most clearly demonstrated in terms of whiplash injuries resulting from low speed rear impacts. These injuries carry a substantial economic and societal impact. Based on previous research, the female spine undergoes greater kinematics under static and dynamic loading, however, a fundamental biomechanical explanation behind this is lacking. Although not conclusive, recent investigations reported spinal ligament contents differ between genders. This may lead to fundamental spinal biomechanical differences between genders. However, a comprehensive investigation of biomechanical gender differences in spinal segments has not been reported. Motivation behind characterizing differences in structural and material properties of isolated spinal segments between genders stems from clinical and engineering interests. From an engineering perspective, analytical modeling and human surrogates are used to understand injury mechanisms and help mitigate injuries. Over the last forty years, characterization of the biomechanical properties of post mortem human testing has lead to the development and validation of instrumented surrogates called anthropometric test devices (ATDs), or commonly: crash dummies and high level computer models. Modeling allows iterative parametric analysis that decreases the amount of physical testing resources. Characterizing gender differences will increase the biofidelity of these models and help explain differing injury susceptibility between men and women. Coupled with the effect of gender is the biomechanical influence of age. Ageing induces fundamental changes in spinal geometry and material properties that has been shown to affect biomechanical response of spinal segments. However, due to gender-specific hormonal changes with age, there is evidence to indicate that ageing may affect men and women differently. Therefore, age will also be accounted for in the following research. Present results indicate that several mechanical properties may be affected by gender, including intervertebral disc compressive stiffness, annulus compressive stiffness, intact compressive elastic modulus, intact tensile elastic modulus, and intervertebral disc tensile elastic modulus. Parameters unaffected by gender included intact tensile stiffness, intervertebral disc tensile stiffness, annulus tensile stiffness, intact compressive stiffness, annulus tensile elastic modulus, intervertebral disc compressive elastic modulus, and annulus compressive elastic modulus. Age was found to affect all parameters except annulus tensile stiffness. Parameters were unaffected by spinal level. Based on these results, it can be concluded that gender may affect the material properties of the isolated thoracic disc segment.

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