Statistical analysis of biomechanical properties of the adult sagittal suture using a bending method in a Japanese forensic sample

• We assess the mechanical properties of the adult sagittal suture.
• Bending strength of the adult sagittal suture is significantly low.
• Bending strength of the middle sagittal suture increases with age only in females.
• Bending strength of the middle sagittal suture is higher in males than in females.
• Sex difference in bony interdigitation of the sutures during childhood may exist.

This study examined the mechanical properties of the adult sagittal suture compared with surrounding parietal bones using bending tests and investigated the association between the mechanical properties of the suture and age. We used the heads of 116 Japanese cadavers (76 male cadavers and 40 female cadavers) of known age and sex. A total of 1160 cranial samples, 10 from each skull, were collected. The samples were imaged using multidetector computed tomography, and the sample thickness at the center of each sample (ST) was measured. The failure stress of each sample (FS) was measured by a bending test, and the ratio of failure stress to the square of sample thickness (FS/ST2) was calculated. Statistical analyses revealed that the FS and FS/ST2 values were significantly lower at all suture sites than at all bone sites regardless of sex. There were not significant but slight positive correlations between age and FS and FS/ST2 values at any suture site in male samples. In female samples, age had significant positive correlations with FS and FS/ST2 values at the middle suture sites, whereas there were not significant but slight positive correlations between age and FS and FS/ST2 values at the edges of the suture. Statistical analyses also demonstrated that FS and FS/ST2 values were significantly greater in male samples than in female samples at the middle suture sites. These findings suggest that the bending strength of the adult sagittal suture is significantly lower than that of surrounding parietal bones. Therefore, avoiding direct impact on cranial sutures may be important for preventing skull fractures and severe complications that can cause death. The results of this study also revealed that the bending strength of the middle sagittal suture significantly increases with age in only female samples, whereas the bending strength is significantly higher in male samples than in female samples at the middle suture sites, indicating the possibility of sex difference in the bony interdigitation of the sutures during childhood.