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Al-Salehi, Loay

University of British Columbia

Catastrophic spine and spinal cord injuries remain a public health concern. The largest share of these injuries is attributed to motor vehicle crashes, e.g., headfirst impacts in vehicle rollovers, and this share has remained stable, despite advancements in vehicle safety. To improve our understanding of the underlying injury mechanisms, this dissertation comprised an epidemiological study, two in vivo experiments, and the design of a novel rollover test device for future human subject experiments. In the epidemiology study, we examined how different types of cervical spine injuries vary with different occupant-related factors, and compared rollovers to non-rollovers. We found that all types of cervical spine injuries were 3.4–6.5 times more likely to occur in rollovers compared to non-rollovers, and the frequent occurrence of vertebral fractures suggests that countermeasures focused on preventing fractures will effectively prevent most cervical spinal cord injuries. In our first in vivo experiment, we exposed eleven human subjects to headfirst freefalls that simulated an impending headfirst impact. We quantified head and cervical spine posture before and at the end of the freefalls, and head kinematics and muscle activation during the freefalls. We confirmed our hypothesis that a 312.5 ms freefall is sufficiently long for an individual to significantly change their head-neck posture and muscle activation states prior to an impending headfirst impact. Subjects consistently moved their necks anteriorly and inferiorly, increased their neck’s anterior eccentricity, and rotated their cervical spines and heads in the flexion direction. Subjects used a variety of muscle activation patterns to achieve this consistent head and neck rotation response, and muscles were activated well before the end of the freefall duration. Finally, to increase fidelity to a real-world rollover, we designed and tested a novel rollover test device that simulates the yaw, trip and first half roll of a vehicle rollover with a high repeatability, that is safe for human subject use, and that enables the collection of human subject kinematic and muscle activation data throughout the rollover. The findings of these studies will improve our understanding of cervical spine injury mechanisms, and represent an incremental step towards their prevention.

Text

2025-04-23

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/90721

Mechanical Engineering

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/