A simulation study of spine biofidelity in the hybrid-III 6-year-old ATD

Because of the lack of pediatric biomechanical data, Hybrid-III (HIII) child anthropomorphic test devices (ATDs) are essentially scaled from the mid-size male ATD based on the geometric considerations. These ATDs inherit a rigid thoracic spine from the adult HIII ATDs, which has been criticized as unrealistic. Therefore, the objective of this study was to explore possible design modifications for improving the spine biofidelity of the HIII 6-year-old ATD.

A previously developed and validated HIII 6-year-old MADYMO ATD model was used as the baseline model to investigate the effects of design modifications on the spine biofidelity of the current ATD. Several sets of child volunteer and cadaver test data were considered as the design targets, including child volunteer low-speed crash test data, pediatric cadaver cervical spine tensile test data, and child cadaver crash test data. ATD design modifications include adding an additional joint to the thoracic spine region and changing the joint characteristics at the cervical and lumbar spine regions. Optimization techniques were used to match simulation results to each set of test results.

The results indicate that the translational characteristics of the cervical and lumbar spine in the current child ATD need to be reduced to achieve realistic spine flexibility. Adding an additional joint at the thoracic spine region with degree of freedom in both flexion/extension and tension would significantly improve the ATD biofidelity in terms of predicting the overall spine curvature and head excursion in frontal crashes.

Future ATD spine modification should focus on reducing the neck and lumbar tension stiffness and adding additional flexibility both in flexion/extension and tension at the thoracic spine region. The child ATD model developed in this study can be used as an important tool to improve child ATD biofidelity and child restraint system design in motor vehicle crashes.