An LS-DYNA Finite Element Parametric Study for Relation of Out- of-Position Failure Modes of the Lower Extremity to Abbreviated Injury Scale Level 2+ and 3+ Chiara Silvestri Malcolm H. Ray Civil Engineering Department Worcester Polytechnic Institute 100 Institute Road Worcester, 01609 - MA – USA Abstract. Lower extremity injuries due to frontal car crashes can have long lasting physical and psychosocial consequences, other than having a huge impact on the societal costs. In the past years their percentage increased significantly, but still this problem was not addressed appropriately to ensure safety to the lower part of the body. This research aimed to investigate the relationship between different seated positions of a car passenger with the rank of potential injury occurring to the lower extremities during a frontal car crash. A better understanding and prediction of injuries allows deriving thresholds to theoretically define values at which injuries potentially occur, with the ultimate purpose of guiding engineers in the design of safer vehicles. A validated Knee-Thigh-Hip (KTH) finite element model of a 50th percentile male was used with the code LSDYNA: axial frontal impacts to the KTH joint were simulated at different angles of thigh flexion, adduction and abduction, and combinations of both. Abbreviated Injury Scale (AIS) level 2+ and 3+ were calculated from the peak femur force obtained from the FE simulations. Results show that the failure mechanism and the probability of AIS level 2+ and 3+ of the lower limb can significantly depend on the occupant position prior to impact. It appeared that a higher probability of KTH bone fracture occurs when the thigh is initially abducted, rather than adducted. It seemed also that a lower probability of KTH bone fracture occurs when the thigh is initially flexed, rather than in a neutral position. When considering combinations of adduction and flexion, results showed that the probability of KTH bone fracture is not greatly affected by the angle of thigh flexion. On the other hand, it appeared that it is more likely to have a lower probability of KTH bone injury when the thigh is either adducted or abducted to a relative high angle. Keywords: Knee-Thigh-Hip; Finite Element; injury mechanisms; Abbreviated Injury Scale; impact; out-of-position KTH fracture modes.
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