Vulnerable Locations on the Head to Brain Injury and Implications for Helmet Design

Abstract

In studying traumatic brain injury (TBI), it has been long hypothesized that the head is more vulnerable to injury from impacts in certain directions or locations, as the relationship between impact force and the resulting neurological outcome is complex and can vary significantly between individual cases. Many studies have identified head angular acceleration to be the putative cause of brain trauma, but it is not well understood how impact location can affect the resulting head kinematics and tissue strain. Here, we identify the susceptibility of the head to accelerations and brain strain from normal forces at contact points across the surface of the skull and jaw using a three-dimensional, 20-degree-of-freedom rigid-body head and cervical spine model. We find that head angular acceleration and brain tissue strain resulting from an input force can vary by orders of magnitude based on impact location on the skull, with the mandible as the most vulnerable region. Conversely, head linear acceleration is not sensitive to contact location. Using these analyses, we present an optimization scheme to distribute helmet padding thickness to minimize angular acceleration, resulting in a reduction of angular acceleration by an estimated 25% at the most vulnerable contact point compared to uniform thickness padding. This work gives intuition behind the relationship between input force and resulting brain injury risk, and presents a framework for developing and evaluating novel head protection gear.

Head Impact Kinematics and Brain Deformation in Paired Opposing Youth Football Players

“…In regard to sport safety interventions, these findings underscore the importance of considering distribution of brain strain in development of the optimal helmet padding. 40 Previous studies have identified the struck player as having higher accelerations on average compared to the striking player. 12,42,43 In this study, players who were struck had greater peak rotational acceleration and brain strain metrics, on average, but players in the striking position had greater mean peak linear acceleration.…”

“…Impacts to the side of the head tend to produce both axial and coronal rotation. 40 It has been found that lateral motion of the falx caused by axial and coronal rotation is associated with corpus callosum trauma in sports-related concussions. 41 Taken together with our findings, impacts to the side of the head pose an increased risk for tissue level injury.…”

Neurotrauma Prevention Review: Improving Helmet Design and Implementation

“…Further examination of impact location can inform optimization of padding placement to minimize rotational angular acceleration in more vulnerable locations. 100 For example, Fanton et al 100 found mandibular impacts to be the most significant. Now that rotational acceleration is becoming a vital consideration of helmet testing, further testing and models to correlate head kinematics (particularly rotational acceleration) with brain strain will be important.…”

Neurotrauma Prevention Review: Improving Helmet Design and Implementation

“…More testing of the different rotational damping helmets is necessary to see which provides the most effective protection against concussions in different settings and at different impact locations. Further examination of impact location can inform optimization of padding placement to minimize rotational angular acceleration in more vulnerable locations [ 99 , 101 ]. For example, Fanton et al [ 101 ] found mandibular impacts to be the most significant.…”