Development of New Criteria for Assessing the Risk of KTH Injury in Frontal Impacts Using Hybrid III Femur Force Measurements

Injury patterns in real-world frontal crashes and the forces predicted in computational simulations of knee impacts suggest that the risk of hip injury is higher than the risk of knee/distal femur injury in most frontal crashes that are similar in severity to those used in FMVSS 208 and NCAP. However, the knee-thigh-hip (KTH) injury criterion that is currently used with Hybrid III femur forces in FMVSS 208 and NCAP only assesses the risk of knee/distal femur injury. As a first step to developing new KTH injury assessment criteria that apply to hip and knee/distal femur injury, a one-dimensional lumped-parameter model of the Hybrid III ATD was developed and validated. Simulations were performed with this model and a previously validated lumped-parameter model of the cadaver to explore relationships between peak force at the Hybrid III femur load cell and peak force at the cadaver hip over the range of knee-loading conditions that occur in FMVSS 208 and NCAP crash tests. Results of these simulations indicate that there is not a singular relationship between peak Hybrid III femur force and peak force at the cadaver hip or at the knee/distal femur. Because of the complex relationship between femur force measured in the Hybrid III femur load cells and forces and injury risks in the human KTH, a new injury assessment criterion has been developed for the KTH that uses peak force and impulse calculated from force histories measured by the Hybrid III load cell to determine if the probability of KTH injury exceeds a specified value. The use of impulse allows the new injury assessment criterion to identify the high-rate, short duration loading conditions that are likely to produce knee/distal femur fractures and the slower loading rates and longer durations that are more likely to produce hip fracture/dislocation. The full text of this paper may be found at: http://www-nrd.nhtsa.dot.gov/pdf/esv/esv21/09-0306.pdf For the covering abstract see ITRD E145407.