Maternal trauma is the leading non-obstetric cause of maternal and fetal death. Because the anatomy of a pregnancy is distinct, and highly transient, the pregnant woman and her fetus are both susceptible to injuries which are not seen in the typical trauma patient. The pregnant uterus, the placenta, and the fetus are all relatively poorly supported, as compared with non-transient abdominal or thoracic organs, which can lead to injuries such as uterine rupture, placental abruption, and fetal trauma or death. The leading cause of maternal trauma is automotive collision, and other common causes include violence, falls, and other accidents. Automotive collision is often researched with more traditional physical experiments such as post-mortem crash testing, but this form of study is exceedingly difficult with the pregnant subject due to ethical and logistical issues. Computational simulations of automotive collisions have received much attention as a method of performing experiments without the use of physical specimens, and have been successful in modeling trauma. These simulations benefit from constitutive relationships which effectively describe the biomechanical and structural behaviors of biological tissues. Internal state variable models driven by microstructural data offer the potential for capturing a myriad of material behaviors intrinsic to many biological tissues. The studies presented include many advances in the existing research of maternal trauma. These studies include advanced biomechanical and microstructural characterization of the placenta, the organ commonly injured in maternal trauma, to capture stress state and strain rate dependencies, as well as microstructural evolution across stress states. The studies also describe the construction of a finite element mesh of a near-term pregnant woman and fetus from medical images. This finite element mesh was implemented in a simulation of maternal trauma based on one of the only post mortem studies of pregnant cadavers ever reported in the literature. The results are a significant advancement for trauma simulation research.

The tibia is a frequent site of injury in frontal automotive collisions. The bulk of experimental cadaveric studies on injury tolerance assume load is applied in line with the leg’s long axis, leaving non-standard postures largely uninvestigated. The purpose of this work was to study the effects of non-standard postures on the tibia’s injury tolerance. A pneumatic system was designed to facilitate impact testing. This system allows the user to fire a projectile of variable mass towards a specimen at a range of velocities by varying the supplied air pressure. Impact tests were performed using pairs of isolated cadaveric tibias. Within each pair of specimens, two postures were compared by varying the angle of the bone’s long axis relative to the direction of impact, representing knee extension and corresponding plantarflexion. It was found that the specimens held further from the axial posture sustained injury at lower forces. Two commonly-used Anthropomorphic Test Device legforms were impacted in these non-standard postures. New load limits were proposed for the use of these devices in off-axis impact testing. In order to compare directly with the loads measured by the legforms, it was necessary to measure forces and moments internal to the bone’s long axis. A non-invasive load estimation method was developed and tested using strain measured from the surface of four specimens. The method performed poorly under impact conditions, but may be refined in the future. Quantifying the effect of posture on injury risk in the tibia allows for the refinement of existing injury criteria. Ultimately, this can be used to enhance the design of protective devices to reduce the incidence of tibia fractures in automotive collisions. / Thesis / Master of Applied Science (MASc) / Fractures of the tibia (the shin bone) are common in automotive collisions, and often lead to long-term impairment. Experimental studies on these kinds of injuries are usually performed with the lower leg aligned with the direction of impact, which does not reflect the range of postures an occupant may assume during a crash. Cadaveric tibias were subjected to impact loading in two different postures. It was found that the specimens held further from an axial posture sustained fractures at lower forces. Two commonly-used crash test dummy legs were also impacted in these non-standard postures to test their performance. Suggestions were made for new load limits to be used with these devices in non-standard postures. The finding that leg posture has an effect on injury risk in the tibia can be used in the future to design and evaluate better protective devices and ultimately reduce the incidence of these injuries.