Finite element (FE) models of the infant human head may be used to discriminate injury patterns resulting from accidents (e.g. falls) and from abusive head trauma (AHT). Existing FE models of infant head impacts are reviewed. Reliability of the material models is the major limitation currently. Infant head tissue properties differ from adults (notably in suture stiffness and strain-to-failure), change with age, and experimental data is scarce. The available data on scalp, cranial bone, dura, and brain are reviewed. Data is most scarce for living brain. All infant head model to date, except one, have used linear elastic models for all tissues except the brain (viscoelastic or Ogden hyperelastic), and do not capture the full complexity of tissue response, but the predicted whole-head response may be of acceptable accuracy. Recent work by Li, Sandler and Kleiven has used hyperelastic models for scalp and dura, and an orthotropic model for bone. There is a need to simulate falls from greater than one metre, and blunt force impacts.

There is much debate within the forensic community around the indications that suggest a head injury sustained by a child resulted from abusive head trauma, rather than from accidental causes, especially when a fall from low height is the explanation given by a caregiver. To better understand this problem, finite element models of the paediatric head have been and continue to be developed. These models require material models that fit the behaviour of paediatric head tissues under dynamic loading conditions. Currently, the highest loading rate for which skull data exists is 2.81 ms -1 . This study improves on this by providing preliminary experimental data for a loading rate of 5.65 ± 0.14 ms -1 , equivalent to a fall of 1.6 m. Eleven specimens of paediatric cranial bone (frontal, occipital, parietal and temporal) from seven donors (age range 3 weeks -18 years) were tested in three-point bending with an impactor of radius 2 mm. It was found that prompt brittle fracture with virtually no bending occurring in all specimens but those aged 3 weeks old, where bending preceded brittle fracture. The maximum impact force increased with age (or thickness) and was higher in occipital bone. Energy absorbed to failure followed a similar trend, with values 0.11 and 0.35 mJ/mm 3 for age three-weeks, agreeing with previously published static tests, increasing with age up to 9 mJ/mm 3 for 18-year-old occipital bone. The preliminary data provided here can help analysts improve pediatric head finite element models that can be used to provide better predictions of the nature of head injuries from both a biomechanical and forensic point of view.

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