Primary Blast Traumatic Brain Injury in the Rat: Relating Diffusion Tensor Imaging and Behavior

The incidence of traumatic brain injury (TBI) among military personnel is at its highest point in U.S. history. Experimental animal models of blast have provided a wealth of insight into blast injury. The mechanisms of neurotrauma caused by blast, however, are still under debate. Specifically, it is unclear whether the blast shockwave in the absence of head motion is sufficient to induce brain trauma. In this study, the consequences of blast injury were investigated in a rat model of primary blast TBI. Animals were exposed to blast shockwaves with peak reflected overpressures of either 100 or 450 kPa (39 and 110 kPa incident pressure, respectively) and subsequently underwent a battery of behavioral tests. Diffusion tensor imaging (DTI), a promising method to detect blast injury in humans, was performed on fixed brains to detect and visualize the spatial dependence of blast injury. Blast TBI caused significant deficits in memory function as evidenced by the Morris Water Maze, but limited emotional deficits as evidenced by the Open Field Test and Elevated Plus Maze. Fractional anisotropy, a metric derived from DTI, revealed significant brain abnormalities in blast-exposed animals. A significant relationship between memory deficits and brain microstructure was evident in the hippocampus, consistent with its role in memory function. The results provide fundamental insight into the neurological consequences of blast TBI, including the evolution of injury during the sub-acute phase and the spatially dependent pattern of injury. The relationship between memory dysfunction and microstructural brain abnormalities may provide insight into the persistent cognitive difficulties experienced by soldiers exposed to blast neurotrauma and may be important to guide therapeutic and rehabilitative efforts

Biomechanical Tolerance of Whole Lumbar Spines in Straightened Posture Subjected to Axial Acceleration

Quantification of biomechanical tolerance is necessary for injury prediction and protection of vehicular occupants. This study experimentally quantified lumbar spine axial tolerance during accelerative environments simulating a variety of military and civilian scenarios. Intact human lumbar spines (T12‐L5) were dynamically loaded using a custom‐built drop tower. Twenty‐three specimens were tested at sub‐failure and failure levels consisting of peak axial forces between 2.6 and 7.9 kN and corresponding peak accelerations between 7 and 57 g. Military aircraft ejection and helicopter crashes fall within these high axial acceleration ranges. Testing was stopped following injury detection. Both peak force and acceleration were significant (p \u3c 0.0001) injury predictors. Injury probability curves using parametric survival analysis were created for peak acceleration and peak force. Fifty‐percent probability of injury (95%CI) for force and acceleration were 4.5 (3.9–5.2 kN), and 16 (13–19 g). A majority of injuries affected the L1 spinal level. Peak axial forces and accelerations were greater for specimens that sustained multiple injuries or injuries at L2–L5 spinal levels. In general, force‐based tolerance was consistent with previous shorter‐segment lumbar spine testing (3–5 vertebrae), although studies incorporating isolated vertebral bodies reported higher tolerance attributable to a different injury mechanism involving structural failure of the cortical shell. This study identified novel outcomes with regard to injury patterns, wherein more violent exposures produced more injuries in the caudal lumbar spine. This caudal migration was likely attributable to increased injury tolerance at lower lumbar spinal levels and a faster inertial mass recruitment process for high rate load application. Published 2017. This article is a U.S. Government work and is in the public domain in the USA

Consensus Head Acceleration Measurement Practices (CHAMP): Origins, methods, transparency and disclosure

The use of head kinematic measurement devices has recently proliferated owing to technology advances that make such measurement more feasible. In parallel, demand to understand the biomechanics of head impacts and injury in sports and the military has increased as the burden of such loading on the brain has received focused attention. As a result, the field has matured to the point of needing methodological guidelines to improve the rigor and consistency of research and reduce the risk of scientific bias. To this end, a diverse group of scientists undertook a comprehensive effort to define current best practices in head kinematic measurement, culminating in a series of manuscripts outlining consensus methodologies and companion summary statements. Summary statements were discussed, revised, and voted upon at the Consensus Head Acceleration Measurement Practices (CHAMP) Conference in March 2022. This manuscript summarizes the motivation and methods of the consensus process and introduces recommended reporting checklists to be used to increase transparency and rigor of future experimental design and publication of work in this field. The checklists provide an accessible means for researchers to apply the best practices summarized in the companion manuscripts when reporting studies utilizing head kinematic measurement in sport and military settings

Level- and Region-Specific Properties of Young Human Lumbar Annulus

ABSTRACT The objective of this study was to determine the material properties of the human lumbar intervertebral disc annulus as a function of anatomical region and spinal level. Samples from minimally or nondegenerated spines were extracted from young post mortem human subjects and tested in tension. Statistically significant differences were found based on anatomical region. Trends appear to indicate spinal level dependency, although additional samples are required to attain statistical significance. It is possible to use finite element models incorporating these region-and level-specific properties to quantify internal load-sharing and delineate the mechanism of disorders such as herniation

Whiplash Affects Cervical Spine Biomechanics

Whiplash injuries affect millions of people around the world each year. These injuries are most commonly the result of low velocity automotive rear impacts. While an extraordinary body of literature exists documenting clinical, epidemiological, and experimental studies, the exact cause and location of the injury and factors affecting the severity remain enigmatic. Clinical and experimental literature repeatedly highlighted influencing factors to include gender, impact severity, spinal degeneration (abnormal curvature), and occupant awareness of the impending collision. The present research quantified the effects of these issues on the biomechanics of the cervical spine using experimental and computational models. The experimental intact head-neck complex model was used to determine gender differences in cervical spine kinematics, and the head-neck computational model was used to investigate ligament elongations as a function of spinal level, impact severity, occupant awareness, and spinal degeneration. Chapter 1 introduces the whiplash topic through a description of epidemiology, including incidence and societal costs, and various theories of the whiplash injury mechanism. Chapter 2 gives a brief outline of the anatomy of the cervical spine, the likely region(s) affected by whiplash injury, and provides a background of the literature on the factors listed above. Chapter 3 describes the experimental investigation of the effects of gender, impact severity, and spinal level using the intact head-neck cadaver model. Chapters 4 through 7 describe the computational model. In particular, Chapter 4 describes the head-neck model and validation using experimental results from this research (Chapter 3) and other literature findings. Chapter 5 discusses effects of spinal level and impact severity. Chapters 6 and 7 describe the effects of occupant awareness in the form of cervical muscle contraction and spinal degeneration in the form of abnormal spinal curvatures. Conclusions are presented in Chapter 8

Whiplash affects cervical spine biomechanics

Whiplash injuries affect millions of people around the world each year. These injuries are most commonly the result of low velocity automotive rear impacts. While an extraordinary body of literature exists documenting clinical, epidemiological, and experimental studies, the exact cause and location of the injury and factors affecting the severity remain enigmatic. Clinical and experimental literature repeatedly highlighted influencing factors to include gender, impact severity, spinal degeneration (abnormal curvature), and occupant awareness of the impending collision. The present research quantified the effects of these issues on the biomechanics of the cervical spine using experimental and computational models. The experimental intact head-neck complex model was used to determine gender differences in cervical spine kinematics, and the head-neck computational model was used to investigate ligament elongations as a function of spinal level, impact severity, occupant awareness, and spinal degeneration. Chapter 1 introduces the whiplash topic through a description of epidemiology, including incidence and societal costs, and various theories of the whiplash injury mechanism. Chapter 2 gives a brief outline of the anatomy of the cervical spine, the likely region(s) affected by whiplash injury, and provides a background of the literature on the factors listed above. Chapter 3 describes the experimental investigation of the effects of gender, impact severity, and spinal level using the intact head-neck cadaver model. Chapters 4 through 7 describe the computational model. In particular, Chapter 4 describes the head-neck model and validation using experimental results from this research (Chapter 3) and other literature findings. Chapter 5 discusses effects of spinal level and impact severity. Chapters 6 and 7 describe the effects of occupant awareness in the form of cervical muscle contraction and spinal degeneration in the form of abnormal spinal curvatures. Conclusions are presented in Chapter 8