Material properties of human infant skull and suture at high rates

Clinicians are often faced with the challenging task of distinguishing between accidental and inflicted pediatric head trauma. There is currently a disparity in the anecdotal case study literature as to what kinds of injuries can occur in children from low height falls. There is also a paucity of material property data for pediatric skull and suture at rates similar to those expected in low height falls. We tested human infant (< 1 year old) cranial bone and suture from 23 calveria in three-point bending and tension, respectively, at rates ranging from 1.2-2.8 m/sec. Donor age was found to have the largest influence on the elastic modulus and ultimate stress of cranial bone, with an increase in age increasing both material properties. In adults, cranial bone and suture have similar properties and the adult calveria deforms very little prior to fracture. In contrast, pediatric cranial bone is 35 times stiffer than pediatric cranial suture. In addition, pediatric cranial suture deforms 30 times more before failure than pediatric cranial bone and 243 times more than adult cranial bone. The large strains in the pediatric bone and suture result in a skullcase that can undergo dramatic shape changes before fracture, potentially causing substantial deformation in the brain. The sizeable difference between pediatric bone and suture material properties also underscores the crucial role that sutures play in the unique response of the pediatric head to impact in low height falls. These data provide necessary information to enhance our understanding of mechanisms of head injury in young children.