Regional variability in craniofacial stiffness: a study in normal and Crouzon mice during postnatal development.

Craniosynostosis (CS) is the premature closure of craniofacial joints known as sutures. Typically, this condition is treated by numerous invasive surgical interventions. Previously we investigated the level of mechanical strain induced due to frontal bone loading on a mouse model of this condition in light of a minimally invasive cyclic bone loading, showing success in retaining coronal suture patency in the Crouzon mouse model. Here we expanded on the previous investigations and characterised the response to external loading on the anterior part of the parietal bone, posterior part of the parietal bone and interparietal bone in addition to the previously investigated frontal bone loading. The results highlighted the significantly higher deformation of the skull and cranial joints during loading of the posterior skull compared to anterior skull loading. These results suggest that loading-based treatment requires different loading regimes depending on location. Additionally, the response of the coronal suture was investigated directly at postnatal day 7 (P7) in both mutant and wild-type animals. The wild-type mice exhibited significant deformation of the coronal suture across all loading locations, whereas no significant deformation was observed in the mutants. Finally, the experimental results were utilised to develop and analyse computational models of WT mice at three ages: P7, P14, and P21. This underscored the challenges in accurately capturing the highly variable response of the mouse craniofacial system to external loading. In summary, this work provided more details on the mechanics of the mouse craniofacial system and its variable overall stiffness across the different anatomical regions of the skull.