Alien Registration- Quarrington, Lydia A. (Portland, Cumberland County)

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Towards Understanding the Injury Mechanics and Clinical Outcomes of Traumatic Subaxial Cervical Facet Dislocation and Fracture-Dislocation

Despite potentially devastating outcomes, the injury mechanisms of traumatic subaxial cervical facet dislocation (CFD) and fracture-dislocation (CFD+Fx) are not well understood and have not been reliably produced in biomechanical testing. In particular, bilateral CFD (BFD) with concomitant facet fracture (BFD+Fx) has not been produced experimentally, possibly due to a lack of neck muscle replication. Muscle activation may impose intervertebral compression and anterior shear during injury, increasing loading of the facets and preventing isolated dislocation via intervertebral separation – such separation has been observed during inertially-produced CFD. The mechanical behaviour of the facets during these scenarios, and the effect of axial distraction on the risk of facet fracture or dislocation, have not been investigated. The aim of this thesis was to improve understanding of the epidemiology, clinical outcomes, and injury mechanisms of CFD and CFD+Fx, and to investigate the biomechanics underlying the injury. In Study 1, a large-cohort medical record and radiographic review of subaxial cervical subluxations, dislocations, and fracture-dislocations presenting at an Australian tertiary hospital over the decade to 2014 was performed. Two primary injury causations were identified: motor vehicle accidents in younger adults, and falls in the elderly. BFD frequently caused spinal cord injury (SCI) and concomitant facet fracture was common. The C6/C7 vertebral level was most commonly involved, and injury to this level most often caused SCI. In Study 2, the bilateral inferior facets of 31 isolated human cadaver subaxial cervical vertebrae (6×C3, C4, C5, and C7, 7×C6) were loaded quasi-statically in simulated supraphysiologic anterior shear and compressive-flexion directions using a materials testing machine – these motions are thought to be associated with BFD. Facet stiffness and failure load were significantly greater in the simulated compressive-flexion loading direction, and sub-failure deflection and surface strains were higher in anterior shear. Facet tip fractures occurred during anterior shear loading, while failure through the pedicles was most common in compressive-flexion. In Study 3, the effect of intervertebral axial separation on human cadaver C6 inferior facet biomechanics during non-destructive anterior shear, axial rotation, flexion, and lateral bending motions of twelve C6/C7 functional spinal units (FSUs) was investigated. Axial compression generally increased facet deflection and strains, when compared to intervertebral distraction. In Study 4, a method was developed to reliably apply 20 mm of constrained anterior shear motion with superimposed intervertebral axial compression or distraction to twelve human cadaver cervical FSUs in a materials testing machine. The effect of superimposed axial compression vs distraction on the type of fractures observed was assessed for the subset of specimens that successfully achieved 20 mm of anterior shear. BFD+Fx was produced in five of 12 specimens, of which three had axial compression superimposed. The mechanical behaviour of the C6 inferior facets at the point of initial anatomical failure did not appear to be affected by intervertebral axial separation. This thesis presents the first large-cohort clinical investigation of CFD and provides quantitative information about the biomechanical response of the subaxial cervical facets to simulated traumatic loading. Axial compression generally increased facet surface strains and deflections when superimposed on intervertebral motions, and constrained intervertebral anterior shear can produce BFD+Fx. It is anticipated that this thesis will inform the development of improved preventative measures and provide data for the validation of models of cervical trauma.Thesis (Ph.D.) -- University of Adelaide, School of Mechanical Engineering, 201

Tensile properties of human spinal dura mater and pericranium

Autologous pericranium is a promising dural graft material. An optimal graft should exhibit similar mechanical properties to the native dura, but the mechanical properties of human pericranium have not been characterized, and studies of the biomechanical performance of human spinal dura are limited. The primary aim of this study was to measure the tensile structural and material properties of the pericranium, in the longitudinal and circumferential directions, and of the dura in each spinal region (cervical, thoracic and lumbar) and in three directions (longitudinal anterior and posterior, and circumferential). The secondary aim was to determine corresponding constitutive stress–strain equations using a one-term Ogden model. A total of 146 specimens were tested from 7 cadavers. Linear regression models assessed the effect of tissue type, region, and orientation on the structural and material properties. Pericranium was isotropic, while spinal dura was anisotropic with higher stiffness and strength in the longitudinal than the circumferential direction. Pericranium had lower strength and modulus than spinal dura across all regions in the longitudinal direction but was stronger and stiffer than dura in the circumferential direction. Spinal dura and pericranium had similar strain at peak force, toe, and yield, across all regions and directions. Human pericranium exhibits isotropic mechanical behavior that lies between that of the longitudinal and circumferential spinal dura. Further studies are required to determine if pericranium grafts behave like native dura under in vivo loading conditions. The Ogden parameters reported may be used for computational modeling of the central nervous system.Sacha Cavelier, Ryan D. Quarrington, Claire F. Jone

Food loss and Waste Reduction as an Integral Part of a Circular Economy

One-third of food produced for human consumption is lost or wasted globally, which amounts to about 1.3 billion tons per year. An updated review of global food loss and waste (FLW) is presented, as well as the related environmental, social and economic impacts, based on existing data and peer-reviewed literature. The authors reflect on the different food waste patterns and challenges faced by diverse regions around the world. The scale of FLW throughout the food value chain is analyzed, from agricultural production down to household consumption and disposal. FLW represent a waste of resources used in each production stage, such as land, water and energy; FLW also contributes to unnecessary increase of greenhouse gas (GHG) emissions. The environmental and socio-economic impacts of FLW are analyzed based on reviewed life cycle assessments. Providing insights into key concepts around FLW, this article highlights the scale of the problem at a global and regional level. It also reflects on the main challenges for implementing strategies to reduce FLW and the implications for policy-making

A review of the compressive stiffness of the human head

Published 12 November 2022Synthetic surrogate head models are used in biomechanical studies to investigate skull, brain, and cervical spine injury. To ensure appropriate biofidelity of these head models, the stiffness is often tuned so that the surrogate’s response approximates the cadaveric response corridor. Impact parameters such as energy, and loading direction and region, can influence injury prediction measures, such as impact force and head acceleration. An improved understanding of how impact parameters affect the head’s structural response is required for designing better surrogate head models. This study comprises a synthesis and review of all existing ex vivo head stiffness data, and the primary factors that influence the force–deformation response are discussed. Eighteen studies from 1972 to 2019 were identified. Head stiffness statistically varied with age (pediatric vs. adult), loading region, and rate. The contact area of the impactor likely affects stiffness, whereas the impactor mass likely does not. The head’s response to frontal impacts was widely reported, but few studies have evaluated the response to other impact locations and directions. The findings from this review indicate that further work is required to assess the effect of head constraints, loading region, and impactor geometry, across a range of relevant scenarios.Darcy W. Thompson-Bagshaw, Ryan D. Quarrington, and Claire F. Jone