Improvements and Validation of an Existing LS-DYNA Model of the Knee-Thigh-Hip of a 50th Percentile Male Including Muscles and Ligaments

A detailed review of an existing LSDYNA finite element (FE) model of the Knee-Thigh-Hip (KTH) of a 50th percentile male was accomplished. The main scope was to refine some aspects of the model for obtaining a more appropriate and biofidelic tool for injury mechanics investigation of the KTH in frontal car crashes. Detailed reviews of this model were performed with regards to material properties of the bone models used for representation of the pelvis, femur and patella. To investigate bone fracture mechanisms due to impact, the erosion material failure method was abandoned in favor of the adoption of a more realistic detection of failure locations using stress contour plots. Qualitative validations of the pelvis and femur bones of the new model were performed against cadaveric specimen tests conducted at University of Michigan Transportation Research Center. In addition, quantitative validations were performed with use of the Roadside Safety Verification and Validation Program (RSVVP), developed to validate numerical models in roadside safety. The approach for these validations was also different. Earlier work had compared the finite element results to the physical test corridors whereas this work used a direct comparison of each finite element validation simulation to a specific corresponding test. Validation of the bone models were based on comparison of the impact forces from contact between the dashboard and knee region of the KTH model. For each case, force simulation results were in good agreement with experiment outcomes, and FE fracture locations matched failure modes from cadaveric tests. Quantitative results indicate that the test and FE time histories can be considered to be the same, and they therefore represent the same impact event. A new validated dynamic representation of ligaments was adopted for prediction of avulsion ligament injuries in high speed frontal automotive collisions when lower extremities are subjected to high strain rates. FE results from ligament avulsion agreed with test data and injury criteria recommended from literature. A different model of the knee patellar tendon was implemented with use of material SEATBELT and the introduction of slip-rings to constrain the patellar tendon to the biomechanically correct line of action. This refined LSDYNA finite element model of the KTH resulted in a more biofidelic representation of the human KTH and represents a suitable and reliable tool for exploration of KTH fracture mechanisms resulting from frontal vehicle crashes.

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