Traumatic injuries are the leading cause of death of children aged one to nineteen in the United States. These unintentional injuries are principally caused by motor vehicle collisions, with the head being the primary region injured. The neck, though not commonly injured, governs head kinematics and influences head impact location and velocity. Vehicle design improvements necessary to reduce or prevent these injuries are evaluated using anthropomorphic testing devices (ATDs). The head and neck properties of the current pediatric ATDs were established by scaling adult properties using the size differences between adults and children. Due to the paucity and limitations of pediatric head and neck biomechanical research, computational models are the only available methods that combine all existing biomechanical data to produce injury-relevant biofidelity specifications for pediatric ATDs. The purpose of this study is to provide the first frontal impact biofidelity corridors for neck flexion response of six and ten year olds using computational models incorporating pediatric cadaveric data. These corridors are compared with response of the Hybrid III (HIII) ATD necks and the Mertz flexion corridors.

Our six and ten year old head and neck multibody models used pediatric biomechanical properties obtained from pediatric cadaveric and radiological studies. The computations included the effect of passive and active musculature, and were validated with data including 3 g dynamic frontal impact responses using pediatric volunteer tests. Because ATD pendulum tests are used to calibrate HIII neck bending stiffness, we simulated these tests to compare the pediatric model and HIII ATD neck bending stiffness, and to compare the model flexion bending responses with the Mertz scaled neck flexion corridors. Additionally, pediatric response corridors for both pendulum calibration tests and high speed (15 g) frontal impacts were estimated through uncertainty analyses on primary model variables. For the frontal impacts, adult boundary conditions and muscle activations, validated against 15 g volunteer tests, were applied to the pediatric models. Response corridors for each loading scenario were calculated from the average ± standard deviation response over 650 simulations.

We found that the models were less stiff in dynamic anterioposterior bending than the pediatric ATDs, as the secant stiffness of the six and ten year old models was 53% and 67% less than that of the HIII ATDs. At higher rotation angles the ATDs exhibited nonlinear stiffening while the models demonstrated nonlinear softening. Consequently, the models did not remain within the Mertz scaled flexion bending corridors, especially for rotations above 60 degrees of flexion. The more compliant model necks suggest an increased potential for head impact via larger head excursions. In contrast with the Mertz corridors, no interactions between the head and chest were modeled in these simulations since the loading conditions used (pendulum calibration testing) do not include chin-on-chest contact. The pediatric anterioposterior bending corridors developed in this study are extensible to any frontal loading condition through calculation and sensitivity analysis. Our corridors are the first based on pediatric cadaveric data and provide the basis for future, more biofidelic designs of six and ten year old ATD necks.