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Lower leg injuries commonly occur in frontal automobile collisions, and are associated with high disability rates. Accurate methods to predict these injuries must be developed to facilitate the testing and improvement of vehicle safety systems. Anthropomorphic test devices (ATDs) are often used to assess injury risk by mimicking the behavior of the human body in a crash while recording data from sensors at discrete locations, which are then compared to established safety limits developed by cadaveric testing. Due to the difference in compliance of cadaveric and ATD legs, the force dissipating characteristics of footwear, and the lack of direct measurement of injury risk to the foot and ankle, a novel instrumented insole was developed that could be applied equally to all specimens both during injury limit generation and during safety evaluation tests. An array of piezoresistive sensors were calibrated over a range of speeds using a pneumatic impacting apparatus, and then applied to the insole of a boot. The boot was subsequently tested and compared to loads measured using ankle and toe load cells in an ATD, and found to have an average error of 10%. The sensors also provided useful information regarding the force distribution across the sole of the foot during an impact, which may be used to develop regional injury criteria. This work has furthered the understanding of lower leg injury prediction and developed a tool that may be useful in developing accurate injury criteria in the future for the foot and lower leg.

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Ballistic shields are used by military and police members in dangerous situations to protect the user against threats such as gunfire. When struck, the shield material deforms to absorb the incoming kinetic energy of the projectile. If the rapid back-face deformation contacts the arm, it can potentially impart a large force, leading to injury risk, termed Behind Armour Blunt Trauma (BABT). This work characterized the loading profiles due to the contact between the deforming back-face of the shield and the arm using a modified upper extremity Anthropomorphic Test Device (ATD). This ATD measured forces at the hand, wrist, forearm, and elbow to compare the locational effects of the force transfer for future investigations of fracture risk. Two composite ballistic shields, both with the same ballistic protection rating, were investigated and had statistically different responses to the same impact conditions, indicating a further need for shield safety evaluation. Additionally, ballistic force curves were compared among stand-off distance, defined as the distance between the back-face of the shield and the front of the force sensor, where the peak impact force significantly decreased with increased stand-off. This study presents the first highly instrumented ATD upper limb capable of evaluating BABT and characterization of these loading profiles. This work demonstrates the importance of realistic boundary conditions as loading varies by anatomical location. Stand-off distance is an effective method to reduce loading and should be considered in future shield design iterations and standards that are developed using this device.

Foot injuries as a result of automotive collisions are frequent and impactful. Anthropomorphic Test Devices (ATDs), used to assess injury risk during impact scenarios such as motor vehicle collisions, typically assess risk of foot/ankle injuries by analyzing data in tibia load cells. The peak axial force (Fz) and the Tibia Index (TI) are metrics commonly used to evaluate risk of injury to the lower extremity but do not directly account for injury risk to the foot, or the risk of injury associated with out-of-position loading. Two ATDs, the Hybrid III lower leg and the Military Lower Extremity (MIL-Lx), were exposed to axial impacts at seven different ankle postures. An array of piezoresistive sensors located on the insole of a boot was employed during these tests to assess the load distribution variations among postures and between ATD models on the plantar surface of the foot. Both posture and ATD model affected the load distribution on the foot, highlighting the need for regional injury risk assessments in this vulnerable anatomical region. The increase in forefoot loading during plantarflexion was not reflected in the standard industry metrics of Fz or TI, suggesting that increased fracture risk to the forefoot would not be detected. The variations in load distribution between the models could also alter injury risk assessment in frontal collisions based on differences in attenuation. These data could be used for regional foot injury assessment and to inform the design of an improved ATD foot.