Evaluation and Refinement of the CRABI-6 Anthropomorphic Test Device Injury Criteria for Skull Fracture

Only sparse experimental pediatric tissue tolerance data are available for the development of pediatric surrogates and associated injury reference values. The objective of this study is to improve the efficacy of the CRABI series anthropometric test devices by increasing the foundational data used for head injury and skull fracture. To accomplish this, this study evaluated and refined the CRABI-6 injury assessment reference values (IARV) associated with skull fracture by correlating the test device response with the detailed fracture results of 50 infant cadaver drop studies reported by Weber in 1984 and 1985. Using the CRABI-6 test device, four 82-cm height free fall impacts were performed onto each of four different impact surfaces: concrete, carpet, 2-cm foam mat, and an 8-cm thick camel hair blanket. Average and standard deviation of peak head linear acceleration and HIC₃₆ (Head Injury Criteria) were computed for each impact surface. The average CRABI impact response was mapped to the Weber fracture outcomes for corresponding impact surfaces and logistic regression was performed to define a skull fracture risk curve based on exposure. The 5%, 25%, 50%, 75%, and 95% risk for skull fracture correlated with a CRABI-6 peak linear head acceleration of 50, 70, 82, 94, and 114 g’s and a HIC36 of 87, 214, 290, 366 and 493, respectively. This study made use of the most extensive set of controlled infant cadaver head impact and fracture data currently available. Previous head IARVs for the CRABI-6 are given by Melvin (1995) and by Klinich et al. (2002). Based on a review of pediatric tissue experiments, scaling of adult and child dummy IARVs, and sled tests, Melvin suggested a HIC₂₂ of 390 and a limit on peak head acceleration of 50 g’s. Klinich et al. reported the results of three reconstructions of airbag-related infant head injuries and three additional reconstructions not associated with head injury. They estimated the 50% risk of minor skull fracture to be 85 g’s and 220 HIC₁₅. These previously reported estimates appear to be in agreement with the results reported from this study for CRABI-6 IARV of 50% risk of skull fracture at 82 g’s and 290 HIC₃₆.