Understanding the role of sutures in cranial mechano-morphogenesis
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The general purpose of this study was to perform finite element analysis (FEA) on 2D and 3D models of the cranium to determine the stress distribution and the stress components at the bone/suture interface. Two-dimensional and 3D models of the cranium were built using ALGOR (Pittsburgh, PA) and PROENGINEER WILDFIRE (CAD software). Linear and nonlinear analyses were performed on the models, mimicking various conditions that exist in craniosynostosis. The distribution of the stresses at the bone/suture interface was obtained by plotting the stress values along the length of the suture. To help elucidate the internal stress states at the bone/suture interface, 2D and 3D Mohr’s circles were constructed at peak and valley locations along the sagittal suture. The 2D models revealed that at the peak locations where there are high shear stresses and biaxial tension and compression, bone resorption may occur and at the valley location where there are small shear and tensile stresses bone growth may occur. The stress distribution along the bone/suture interface in the 3D model of the cranium indicates that there is high tensile stress in the upper layer of the suture, and high compressive stress in the inner layer. This nature of stress distribution explains why the pattern of interdigitation on the outer surface of the sutures is different from that on the inside, and offers an explanation as to why suture fusion starts from the inside surface of the cranium.