The mechanical and microstructural properties of the pediatric skull.

The pediatric skull differs drastically from the adult skull in terms of composition, rigidity, and structure. However, there is limited data which quantifies the mechanical properties of the pediatric skull. The lack of mechanical data may inhibit desired pediatric craniofacial surgical outcomes as current methodologies and materials employed for the pediatric population are adapted from those used for adults. In this study, normally discarded parietal bone tissue from eight pediatric craniosynostosis surgery patients (aged 4 to 10 months) was collected during reconstructive surgery and prepared for microstructural analysis and mechanical testing. Up to 12 individual coupon samples of fresh, never frozen tissue were harvested from each specimen and prepared for four-point bending testing to failure. The microstructure of each sample was analyzed using micro-computed tomography before and after each mechanical test. From this analysis, effective geometric and mechanical properties were determined for each sample (n = 68). Test results demonstrated that the pediatric parietal skull was 2.0 mm (±0.4) thick, with a porosity of 36% (±14). The effective modulus of the tissue samples, determined from the initial slope of the sample stress-strain response using Euler beam theory and a nonlinear Ramberg-Osgood stress-strain relationship, was 4.2 GPa (±2.1), which was approximately three times less stiff than adult skull tissue reported in the literature. Furthermore, the pediatric skull was able to bend up to flexural failure strains of 6.7% (±2.0), which was approximately five times larger than failure strains measured in adult skull. The disparity between the measured mechanical properties of pediatric skull tissue and adult skull tissue points towards the need to reevaluate current surgical technologies, such as pediatric cranial surgical hardware, so that they are more compatible with pediatric tissue.