Biofidelity and Limitations of Instrumented Mouthguard Systems for Assessment of Rigid Body Head Kinematics.

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.

Investigating the Impact of Blunt Force Trauma: A Probabilistic Study of Behind Armor Blunt Trauma Risk.

Evaluating Behind Armor Blunt Trauma (BABT) is a critical step in preventing non-penetrating injuries in military personnel, which can result from the transfer of kinetic energy from projectiles impacting body armor. While the current NIJ Standard-0101.06 standard focuses on preventing excessive armor backface deformation, this standard does not account for the variability in impact location, thorax organ and tissue material properties, and injury thresholds in order to assess potential injury. To address this gap, Finite Element (FE) human body models (HBMs) have been employed to investigate variability in BABT impact conditions by recreating specific cases from survivor databases and generating injury risk curves. However, these deterministic analyses predominantly use models representing the 50th percentile male and do not investigate the uncertainty and variability inherent within the system, thus limiting the generalizability of investigating injury risk over a diverse military population. The DoD-funded I-PREDICT Future Naval Capability (FNC) introduces a probabilistic HBM, which considers uncertainty and variability in tissue material and failure properties, anthropometry, and external loading conditions. This study utilizes the I-PREDICT HBM for BABT simulations for three thoracic impact locations-liver, heart, and lower abdomen. A probabilistic analysis of tissue-level strains resulting from a BABT event is used to determine the probability of achieving a Military Combat Incapacitation Scale (MCIS) for organ-level injuries and the New Injury Severity Score (NISS) is employed for whole-body injury risk evaluations. Organ-level MCIS metrics show that impact at the heart can cause severe injuries to the heart and spleen, whereas impact to the liver can cause rib fractures and major lacerations in the liver. Impact at the lower abdomen can cause lacerations in the spleen. Simulation results indicate that, under current protection standards, the whole-body risk of injury varies between 6 and 98% based on impact location, with the impact at the heart being the most severe, followed by impact at the liver and the lower abdomen. These results suggest that the current body armor protection standards might result in severe injuries in specific locations, but no injuries in others.

Facial Fracture Injury Criteria from Night Vision Goggle Impact.

INTRODUCTION: Military personnel extensively use night vision goggles (NVGs) in contemporary scenarios. Since NVGs may induce or increase injuries from falls or vehicular accidents, biomechanical risk assessments would aid design goal or mitigation strategy development.METHODS: This study assesses injury risks from NVG impact on cadaver heads using impactors modeled on the PVS-14 NVG. Impacts to the zygoma and maxilla were performed at 20° or 40° angles. Risks of facial fracture, neurotrauma, and neck injury were assessed. Acoustic sensors and accelerometers assessed time of fracture and provided input variables for injury risk functions. Injuries were assessed using the Abbreviated Injury Scale (AIS); injury severity was assessed using the Rhee and Donat scales. Risk functions were developed for the input variables using censored survival analyses.RESULTS: The effects of impact angle and bone geometry on injury characteristics were determined with loading area, axial force, energy attenuation, and stress at fracture. Probabilities of facial fracture were quantified through survival analysis and injury risk functions. These risk functions determined a 50% risk of facial bone fracture at 1148 N (axial force) at a 20° maxillary impact, 588 N at a 40° maxillary impact, and 677 N at a 20° zygomatic impact. A cumulative distribution function indicates 769 N corresponds to 50% risk of fracture overall.DISCUSSION: Results found smaller impact areas on the maxilla are correlated with higher angles of impact increasing risk of facial fracture, neck injuries are unlikely to occur before fracture or neurotrauma, and a potential trade-off mechanism between fracture and brain injury.Davis MB, Pang DY, Herring IP, Bass CR. Facial fracture injury criteria from night vision goggle impact. Aerosp Med Hum Perform. 2023; 94(11):827-834.

Giant coronary artery aneurysms in a Japanese octogenarian - The oldest case of Kawasaki Disease?

Kawasaki disease (KD) is a leading cause of non-atherosclerotic coronary artery aneurysms and, less commonly, peripheral artery aneurysms. We report an 81-year-old Japanese man from Hawaii with a history of an abdominal aortic aneurysm, bilateral iliac aneurysms, and an ambiguous right atrial cystic mass. The patient developed new-onset atrial fibrillation during lithotripsy. Angiography and magnetic resonance imaging revealed giant coronary artery aneurysms of the right coronary artery (RCA) and left anterior descending artery, and a thoracic aortic aneurysm. The RCA aneurysm was greater than 2 inches in diameter at the time of operation. Although we cannot confirm whether the patient had KD during childhood, this is the most likely diagnosis in the absence of a connective tissue disorder, systemic vasculitis, or atherosclerotic risk factors. This patient may represent the oldest case of KD, predating the earliest known case by more than 20 years. This case sheds light on the historical epidemiology of KD and its clinical course, especially regarding late vascular sequelae.

Transient left ventricular apical ballooning syndrome (takotsubo cardiomyopathy) as a complication of permanent pacemaker implantation.

BACKGROUND: Takotsubo cardiomyopathy is a rare and newly described clinical entity characterized by transient left ventricular apical ballooning and left ventricular apical dyskinesis in the absence of angiographic evidence of significant coronary vessel disease found predominantly in post-menopausal women. It was first documented in the USA in 2004, and it has previously been described only in Japanese and Caucasian patients. CASE REPORT: A 77-year-old Native Hawaiian woman was admitted to the hospital for severe bradycardia. To the best of our knowledge, this is the first time that normal ventricular function has been documented by echocardiography just prior to the development of the syndrome of transient left ventricular apical ballooning. METHODS: Retrospective review of the reported patient's medical record, cardiac angiography and ventriculography, echocardiography, and ECGs. DISCUSSION: The patient reported manifested all of the diagnostic criteria for transient left ventricular apical ballooning syndrome proposed by the Mayo Clinic. The finding of normal cardiac morphology and contractility by echocardiography two days prior to diagnosis shows that this syndrome develops rapidly. The case reported here is the first time that transient left ventricular apical ballooning syndrome has been documented in a Native Hawaiian patient in a tropical location, suggesting that transient left ventricular apical ballooning likely occurs across all ethnic and geographical lines.