Mitchell Z. Abrams

Instrumented mouthguard systems (iMGs) are commonly used to study rigid body head kinematics across a variety of athletic environments. Previous work has found good fidelity for iMGs rigidly fixed to anthropomorphic test device (ATD) headforms when compared to reference systems, but few validation studies have focused on iMG performance in human cadaver heads. Here, we examine the performance of two boil-and-bite style iMGs in helmeted cadaver heads. Three unembalmed human cadaver heads were fitted with two instrumented boil-and-bite mouthguards [Prevent Biometrics and Diversified Technical Systems (DTS)] per manufacturer instructions. Reference sensors were rigidly fixed to each specimen. Specimens were fitted with a Riddell SpeedFlex American football helmet and impacted with a rigid impactor at three velocities and locations. All impact kinematics were compared at the head center of gravity. The Prevent iMG performed comparably to the reference system up to   60 g in linear acceleration, but overall had poor correlation (CCC = 0.39). Prevent iMG angular velocity and BrIC generally well correlated with the reference, while underestimating HIC and overestimating HIC duration. The DTS iMG consistently overestimated the reference across all measures, with linear acceleration error ranging from 10 to 66%, and angular acceleration errors greater than 300%. Neither iMG demonstrated consistent agreement with the reference system. While iMG validation efforts have utilized ATD testing, this study highlights the need for cadaver testing and validation of devices intended for use in-vivo, particularly when considering realistic (non-idealized) sensor-skull coupling, when accounting for interactions with the mandible and when subject-specific anatomy may affect device performance.

Motor vehicle accidents are the leading cause of death for young adults 18–29 years old worldwide, resulting in nearly 1 million years of life lost annually in the United States. Despite improvements in vehicle safety technologies, young women are at higher risk of dying in car crashes compared with men in matched scenarios. Vehicle crash testing primarily revolves around test dummies representative of the 50th percentile adult male, potentially resulting in these differences in fatality risk for female occupants compared to males. Vehicle occupants involved in fatal car crashes were matched using seating location, vehicle type, airbag deployment, seatbelt usage, and age. The relative risk for fatality (R) between males and females was calculated using a Double Pair Comparison. Young women (20s-40s) are at approximately 20% higher risk of dying in car crashes compared with men of the same age in matched scenarios. In passenger cars, 25-year-old female occupants in passenger car crashes from 1975–2020 exhibit R = 1.201 (95% CI 1.160–1.250) compared to 25-year-old males, and R-1.117 (95% CI 1.040–1.207) for passenger car crashes from 2010–2020. This trend persists across vehicle type, airbag deployment, seatbelt use, and number of vehicles involved in a crash. Known sex-based differences do not explain this large risk differential, suggesting a need for expanded test methodologies and research strategies to address as-yet unexplored sex differences in crash fatalities. These differences should be further investigated to ensure equitable crash protection.

Since 1975, the US has seen a decrease in vehicle crash fatalities, noticeably among recent model vehicles. However, a lack of requirement to test motor vehicles using anthropomorphic test devices representative of both the average male and the average female occupant may be driving a disparity in the risk of fatality in severe crash scenarios. The double pair comparison method, first developed by Evans, was applied to many different cross-sections of the US Fatality Analysis Reporting System to investigate sex-dependent differences in relative fatality risk in crashes. Despite a dramatic decline in fatalities over the reporting period, female vehicle occupants aged 20–30 years are 20–25% more likely to die as a result of a fatal crash than males in the same age range. The risk to females and males becomes similar as age increases to 60. These trends hold when looking at subsets of crashes in either rural or urban areas, when looking at vehicles manufactured since 2010, and when isolating by single, two- or multiple-vehicle crashes. The consistency of this age-dependent relative risk emphasises a need to further investigate sex differences in crash-related outcomes.

Motor vehicle crashes are a leading cause of death both in the United States and around the world. While research has showed younger females are at increased risk of fatality in fatal crashes, the underlying cause of this disparity is unclear. Data from the Fatality Analysis Reporting System (FARS), Mortality Multiple Cause of Death (MCOD), and National Automotive Sampling System Crashworthiness Data System (NASS-CDS) were used with the double-pair comparison method to identify relative risk of head injury and injury to other major body systems in motor vehicle crashes. FARS cases were linked to detailed cause of death records in MCOD. Young female occupants are at increased risk of fatal and severe head and abdominal injuries in motor vehicle crashes. This increased risk is pronounced for young females in both fatal crashes and non-fatal crashes with severe injuries. Along with previous research pointing to an increased overall fatality risk for young females in fatal crashes, these findings suggest a need to more carefully study biomechanical sex differences in car crashes.

Instrumented mouthguard systems are used to study rigid body head kinematics in vivo in a variety of athletic environments. Previous work has assessed these systems when rigidly attached to anthropomorphic test device (ATD) heads and found good fidelity compared with reference sensors. Here, we examine the fidelity of two instrumented boil-and-bite mouthguards (iMGs) in helmeted, human cadaver impact tests at three velocities and three impact locations. The Prevent Biometrics iMG correlates with reference linear acceleration up to approximately 60 g, underestimating impacts at higher magnitudes. The Prevent iMG correlates well with angular velocity, while underestimating angular acceleration past approximately 3,000 rad/s^2. The DTS iMG consistently overestimates angular acceleration and velocity, and transformed linear kinematics are not well-correlated to reference kinematics at the head centre of gravity (HCG) for these impact conditions. Future work should examine the influence of the mandible and subject-specific mouthguard fit on fidelity of impact kinematics. This study highlights the need for cadaver validation studies of wearable head impact instrumentation systems, particularly when considering realistic (non-idealised) sensor-skull coupling and accounting for interactions with the mandible.