Prediction of skull fracture risk for children 0–9 months old through validated parametric finite element model and cadaver test reconstruction

Abstract

Skull fracture is one of the most common pediatric traumas. However, injury assessment tools for predicting pediatric skull fracture risk is not well established mainly due to the lack of cadaver tests. Weber conducted 50 pediatric cadaver drop tests for forensic research on child abuse in the mid-1980s (Experimental studies of skull fractures in infants, Z Rechtsmed. 92: 87-94, 1984; Biomechanical fragility of the infant skull, Z Rechtsmed. 94: 93-101, 1985). To our knowledge, these studies contained the largest sample size among pediatric cadaver tests in the literature. However, the lack of injury measurements limited their direct application in investigating pediatric skull fracture risks. In this study, 50 pediatric cadaver tests from Weber's studies were reconstructed using a parametric pediatric head finite element (FE) model which were morphed into subjects with ages, head sizes/shapes, and skull thickness values that reported in the tests. The skull fracture risk curves for infants from 0 to 9 months old were developed based on the model-predicted head injury measures through logistic regression analysis. It was found that the model-predicted stress responses in the skull (maximal von Mises stress, maximal shear stress, and maximal first principal stress) were better predictors than global kinematic-based injury measures (peak head acceleration and head injury criterion (HIC)) in predicting pediatric skull fracture. This study demonstrated the feasibility of using age- and size/shape-appropriate head FE models to predict pediatric head injuries. Such models can account for the morphological variations among the subjects, which cannot be considered by a single FE human model.

Infant skull fracture risk for low height falls

“…Coats et al [ 23 ] validated the fracture behavior of their 1.5-month-old infant head model with a single simulation of Weber’s infant cadaver drops onto stone and a single real-world fall onto the carpet [ 24 ]. Li et al [ 25 ] simulated all 50 of Weber’s cadaver drops and subsequently developed pediatric skull fracture risk curves for 0–9 month-old infants using six different biomechanical parameters. As detailed earlier, lack of specifics regarding the tissue sample harvest and preservation methods may compromise the value of using the cadaver data obtained in Weber’s study for fracture threshold assessment.…”

The importance of nonlinear tissue modelling in finite element simulations of infant head impacts

“…2007), while other studies chose to simplify infant skull modelling as an isotropic material (Li et al. 2013a, b, 2015a, b, 2016; Roth et al. 2010), taking from Coats and Margulies (2006) as the equivalent Young’s modulus.…”

“…2013a), 6-month-olds (2013b, 2016), as well as other ages from 0- to 9-month-olds were developed (Li et al. 2015b), morphed from a baseline FE mesh of a 6-month-old. …”

“…Further, infant skull bones are often simplified as isotropic material (Li et al. 2013a, b, 2015a, b, 2016; Roth et al. 2010), despite the fact that the grain fibre patterns are clearly visible to naked eyes in newborns (Coats and Margulies 2006), causing a much larger stiffness in the fibre direction confirmed by mechanical tests (Kriewall 1982; McPherson and Kriewall 1980).…”

Height of head centre of gravity predicts paediatric head injury severity in short-distance falls

“…This study addressed the effects from fall conditions extensively, which is valuable, but only limited subject characteristics (age and sex) were considered. The weight, height, developmental stage and specific head anatomy vary significantly in infants or young children even of the same age3 and may significantly affect the head injury outcome as well 4. Future studies on the relationship between more subject characteristics and head injuries in paediatric falls are needed.…”