Nanostructural and nanomechanical properties of synostosed postnatal human cranial sutures

Craniosynostosis represents a heterogeneous cluster of congenital disorders and manifests as premature ossification of one or more cranial sutures. Cranial sutures serve to enable calvarial growth and function as joints between skull bones. The mechanical properties of synostosed cranial sutures are of vital importance to their function and yet are poorly understood. The present study was designed to characterize the nanostructural and nanomechanical properties of synostosed postnatal sagittal and metopic sutures. Synostosed postnatal sagittal sutures (n = 5) and metopic sutures (n = 5) were obtained from craniosynostosis patients (aged 9.1 +/- 2.8 months). The synostosed sutural samples were prepared for imaging and indentation on both the endocranial and ectocranial surfaces with the cantilever probe of an atomic force microscopy. Analysis of the nanotopographic images indicated robust variations in sutural surface characteristics with localized peaks and valleys. In 5 x 5 mum scan sizes, the surface roughness of the synostosed metopic suture was significantly greater (223.6 +/- 93.3 nm) than the synostosed sagittal suture (142.9 +/- 80.3 nm) (P < 0.01). The Young's modulus of the synostosed sagittal suture at 0.7 +/- 0.2 MPa was significantly higher than the synostosed metopic suture at 0.5 +/- 0.1 MPa (P < 0.01). These data suggest that various synostosed cranial sutures may have different structural and mechanical characteristics.