Date of Award

2016

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Graduate Group

Bioengineering

First Advisor

Susan S. Margulies

Abstract

Traumatic brain injury (TBI) is the most prominent cause of death and disability in infants. Extra-axial hemorrhage (EAH) is a common finding among infants diagnosed with abusive head trauma, but is confounded by similar findings in accidental injuries. We conducted detailed biomechanical studies to determine whether the kinematics of vigorous shaking could rupture the parasagittal bridging veins (BVs), one cause of EAH. We performed BV mechanical property tests, in situ and in vivo rapid head rotation animal experiments, infant surrogate head kinematic studies, and finite element (FE) model simulations of the neonatal porcine and infant human heads to reveal whether BV rupture may occur due to vigorous shaking. Under longitudinal tension, we found that BV mechanical properties and behavior do not depend on age, but vary with species, stretch rate, and a history of cyclic loading. In situ brain-skull displacements in the neonatal porcine head under rapid nonimpact sagittal rotations are lower than those observed in axial rotations, and altering BV properties yielded no appreciable difference in FE model brain-skull displacement. We correlated FE-predicted BV element failures during sagittal rapid nonimpact head rotations in the piglet with EAH pathology from corresponding animal studies, and identified and independently validated a threshold of 6 failed BV elements in our model were associated with detectable EAH. Finally, using this threshold and human infant BV mechanical properties in a human infant head FE model, we determined a response corridor for BV rupture, and found that rotational acceleration influences BV rupture. Our results suggest that it may be possible to generate a combination of sagittal head kinematics during vigorous shaking that could produce EAH in the human infant. Prior to legal application, additional analyses are required to validate these predictions of BV rupture against real-world data, such as torn BVs at autopsy in cases of admitted shaking without impact. Together, the integrated studies presented in this dissertation illuminate biomechanical factors that may cause BV rupture in the infant.

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