When Physics Meets Biology: Low and High-Velocity Penetration, Blunt Impact, and Blast Injuries to the Brain

Abstract

The incidence of traumatic brain injuries (TBI) in the US has reached epidemic proportions with well over 2 million new cases reported each year. TBI can occur in both civilians and warfighters, with head injuries occurring in both combat and non-combat situations from a variety of threats, including ballistic penetration, acceleration, blunt impact, and blast. Most generally, TBI is a condition in which physical loads exceed the capacity of brain tissues to absorb without injury. More specifically, TBI results when sufficient external force is applied to the head and is subsequently converted into stresses that must be absorbed or redirected by protective equipment. If the stresses are not sufficiently absorbed or redirected, they will lead to damage of extracranial soft tissue and the skull. Complex interactions and kinematics of the head, neck and jaw cause strains within the brain tissue, resulting in structural, anatomical damage that is characteristic of the inciting insult. This mechanical trauma then initiates a neuro-chemical cascade that leads to the functional consequences of TBI, such as cognitive impairment. To fully understand the mechanisms by which TBI occurs, it is critically important to understand the effects of the loading environments created by these threats. In the following, a review is made of the pertinent complex loading conditions and how these loads cause injury. Also discussed are injury thresholds and gaps in knowledge, both of which are needed to design improved protective systems.

Combination therapies for neurobehavioral and cognitive recovery after experimental traumatic brain injury: Is more better?

“…Following up on previous studies evaluating EE as one of the key therapies in the combination approach (Kline et al, 2007, 2010, 2012), Young et al (2015) provided EE and NGF, alone and in combination, to adult male rats following a moderate CCI injury over the forelimb sensorimotor cortex. After surgery, the rats were randomized to groups receiving EE or STD housing and intranasal administration of NGF (0.1 mg/mL in phosphate buffered saline) or vehicle once every other day for 7 days post-injury.…”

“…Motor vehicle accidents and falls resulting in a blow to the head are the typical causes of TBI in the general population, whereas blasts and shrapnel from improvised explosive devices are the leading causes for military personnel in active war zones (Ling et al, 2009; Cernak and Noble-Haeusslein, 2010; Young et al, 2015). Brain traumas range from mild to severe with the former being the case in the majority of occurrences (Sosin et al, 1996) and generally not displaying marked behavioral symptoms, while the latter occurs less often, but presents significant motor and/or cognitive dysfunction that can have perpetual adverse consequences on the quality of life (Binder, 1986; Millis et al, 2001).…”

Analysis of Geometric Relation between Cerebral Contusion and Site of Impact in Traumatic Brain Injury Patients

“…Two main mechanisms are identified as the the reason behind contrecoup injury in this study, namely cavitation and inertial injury. 12 Cavitation theory describes the contact effect of an impact where impact force would create an area of positive pressure (compression) underneath the site of impact (coup) and negative pressure (tension) opposite to it (contrecoup). 13 When the brain returns to its normal state, compression may change into tension or vice versa.…”

Hybridized composite architecture for mitigation of non-penetrating ballistic trauma

“…While previous helmets were designed to decelerate and resist penetration of fragmentary and handgun rounds within the 20 mm spacing, the demand for even lighter helmet materials and higher threats will push performance requirements into a regime where penetration resistance is possible, however doing so in the confines of the system spacing will not be possible. There are no definitive medical criteria for correlation of armor deformation to blunt trauma in the event of a non-penetrating impact in where the deformation strikes the wearer's skull [9]. This is primarily because these mechanisms are not well under-stood to begin with.…”

“…However, the link between the amount of ballistic, blunt or blast insult and the physiological injury caused by those forces are not well known at this time. Therefore, there is a large impetus for not only developing physiologically based criteria for helmet blunt trauma [9], but also developing physics-based helmet materials solutions that work to mitigate the extent of forces reaching the Soldier's head during impact.…”