Mechanical Properties of Calvarial Bones in a Mouse Model for Craniosynostosis

Abstract

The mammalian cranial vault largely consists of five flat bones that are joined together along their edges by soft fibrous tissues called sutures. Premature closure of the cranial sutures, craniosynostosis, can lead to serious clinical pathology unless there is surgical intervention. Research into the genetic basis of the disease has led to the development of various animal models that display this condition, e.g. mutant type Fgfr2C342Y/+ mice which display early fusion of the coronal suture (joining the parietal and frontal bones). However, whether the biomechanical properties of the mutant and wild type bones are affected has not been investigated before. Therefore, nanoindentation was used to compare the elastic modulus of cranial bone and sutures in wild type (WT) and Fgfr2C342Y/+mutant type (MT) mice during their postnatal development. Further, the variations in properties with indentation position and plane were assessed. No difference was observed in the elastic modulus of parietal bone between the WT and MT mice at postnatal (P) day 10 and 20. However, the modulus of frontal bone in the MT group was lower than the WT group at both P10 (1.39±0.30 vs. 5.32±0.68 GPa; p<0.05) and P20 (5.57±0.33 vs. 7.14±0.79 GPa; p<0.05). A wide range of values was measured along the coronal sutures for both the WT and MT samples, with no significant difference between the two groups. Findings of this study suggest that the inherent mechanical properties of the frontal bone in the mutant mice were different to the wild type mice from the same genetic background. These differences may reflect variations in the degree of biomechanical adaptation during skull growth, which could have implications for the surgical management of craniosynostosis patients.

Salicylic acid (SA)‐eluting bone regeneration scaffolds with interconnected porosity and local and sustained SA release

“…This range is relatively wide because the bone mechanical properties and load‐bearing requirement vary widely in vivo . As the modulus of the scaffolds presented herein is on the lower end of the range of bone, they may be more suitable for mandibular or calvarial bone regeneration, which does not require high mechanical loading …”

Predicting calvarial growth in normal and craniosynostotic mice using a computational approach

“…), therefore the baseline value of 150 MPa was altered within the range from 1 to 1500 MPa; (iii) suture properties: our previous experimental measurements (Moazen et al. ) showed a large standard deviation for the suture properties, therefore the baseline value of 30 MPa was varied between 3 and 300 MPa.…”

“…This was based on extrapolation of the frontal and parietal bone properties measured in mice at P10, P20 and P70 (Moazen et al. ). Sutures and undeveloped areas of bone were assigned an elastic modulus of 30 MPa (Henderson et al.…”

“…; Moazen et al. ) and brain (the ICV) was modelled with an elastic modulus of 150 MPa. A Poisson's ratio of 0.3 was used for all the materials, except 0.48 for the brain (Claessens et al.…”

An Overview of Modelling Craniosynostosis Using the Finite Element Method

“…It must be noted that while increasing the complexity of FE models is possible, further studies are required to investigate how much complexity is needed to develop a validated model of craniosynostosis, whereby, the outcome of different reconstructions can be reliably predicted; (4) material properties -our understanding of changes in mechanical properties of calvarial bones and other related tissues such as dura mater during the development is still limited. Few studies have quantified such changes during the development [e.g., McPherson and Kriewall, 1980;Margulies and Thibault, 2000;Henderson et al, 2005;Coats and Margulies, 2006;Wang et al, 2014;Moazen et al, 2015]. Clearly, soft tissues involved in the calvarial development are viscoelastic materials, and their properties change during the development.…”