Pediatric head contours and inertial properties for ATD design

Child head trauma in the United States is responsible for 30% of all childhood injury deaths with costs estimated at $10 billion per year. The common tools for studying this problem are the child anthropomorphic test devices (ATDs). The headform sizes and structural properties of child ATDs are based on various anthropometric studies and scaled Hybrid III mass and center of gravity (CG) properties. The goals of this study were to produce pediatric head and skull contours, provide estimates of pediatric head mass, mass moment of inertia and CG locations, and compare the head contours with the current child ATD head designs. To that end, computer tomography (CT) scans from one hundred eighty-five children in twelve age groups were analyzed to develop three-dimensional head and skull contours. The contours were averaged to estimate head and skull contours for children aged 1-month to 10-years. Inertial properties were estimated from a small sample of post- mortem human subjects (PMHSs). This paper provides new equations for estimating the moments of inertia and anatomical landmarks in the head. There were reasonable agreement between the estimates for head masses obtained from analysis of the CT scans of the PMHS heads and the estimates obtained using the volumetric scaling rule used in ATD design work. The regression of the pediatric head sizes was found to be non-linear, with different regression slope for ages 1M to 18M and 18M to 120M. The 12M CRABI and 36M Hybrid III heads were found to be different by 10 and 18mm, respectively, from the average human CT contours due to the differences in the occipital condyle placement relative to the nasion.