A comprehensive analysis of human cranial morphology: multiscale characterization and statistical analysis

Understanding the structure–property relationship of the human cranium is crucial for enhancing personalized head protection design and improving injury prevention criteria. This study presents a thorough spatial analysis of cranial morphology at both the macro- and micro-scale through micro-CT scanning. Two statistical quantifiers (i.e., Cortico-trabecular thickness (CoTb.Th) and Cortico-trabecular spacing (CoTb.Sp)) are defined here to characterize the micro-structural morphology in both the cortical and cancellous tables. A new adaptive layer segmentation method is proposed that considers the micro-structural variation to quantify the porosity threshold between the inner table, the diploë and the outer table. Then, statistical analysis was employed to investigate the interaction between donor information (e.g., age, sex, and sample extraction location) and structural characteristics (maximum and average porosity, CoTb.Th and CoTb.Sp). The morphological results revealed that the peak parallel porosity of 55 \(\,\pm \,\) $\pm$ 30% can be found in the diploë region, while the perpendicular porosity remained essentially stable and fluctuated between a range of 10–15%. Furthermore, the layer segmentation results demonstrated that the porosity threshold between the inner table and the diploë was 29.14 \(\,\pm \,\) $\pm$ 3.93%, and 46.50 \(\,\pm \,\) $\pm$ 4.80% between the diploë and the outer table. In addition, the statistical analyses indicated that age ( \(p<0.01\) $p<0.01$ ) and sex ( \(p<0.05\) $p<0.05$ ) were the most influential factors affecting maximum and average porosity. The novelty of this work stems from the comprehensive understanding of the morphological features of human crania, which is needed to advance the physical surrogate models of human skull, contributing to the mechanical testing of head protection devices and improvement of injury criteria.