Investigation of the Influences of Biomechanical Force on the Ultrastructure of Human Sagittal Craniosynostosis

Abstract

This study presents comparisons of the ultrastructure of synostotic and open portions of synostotic sagittal sutures using histomorphometry, scanning electron microscopy, and microcomputed tomography. By using stereologic and histomorphometric analysis, this study proposes to demonstrate evidence of the influence of biomechanical force on the suture during the process of sagittal craniosynostosis. Finally, we propose to link the pathologic changes transforming normal suture fusion to craniosynostosis with concurrent changes in the polarity of suture fusion initiation. Seven infants (four boys and three girls) with sagittal craniosynostosis, ranging in age from 1.4 to 4.8 months (mean = 3.0 months), underwent sagittal synostectomies. The synostotic bone specimens were sectioned into three regions: an open suture, partial synostosis, and complete synostosis. Microcomputed tomographic and scanning electron microscopic scanning as well as histomorphometry was performed on all specimens to obtain detailed qualitative and quantitative information regarding the trabecular microarchitecture of the synostosed suture. Microcomputed tomographic analysis determined the bone volume fraction, trabecular thickness, trabecular separation, bone surface to bone volume ratio, and anisotropy for all specimens. Our results showed significant differences in all of these quantitative measurements when comparing the complete synostotic suture with the open portion of the synostotic sutures (p < 0.05). Microcomputed tomographic stereologic analysis showed evidence of the influence of biomechanical force on the synostotic and open portions of the synostotic sutures. Results of scanning electron microscopy show a definite qualitative difference in the trabecular pattern of the partial and complete synostotic suture when compared with the open portion of the synostotic sagittal suture. In this study, we performed both qualitative and quantitative comparisons of the ultrastructure of the complete synostotic and nonsynostotic sagittal sutures using stereologic and histomorphometric techniques. We also demonstrated evidence of the influence of biomechanical force on the synostotic sagittal suture. Finally, we established a link between the pathologic changes transforming normal suture fusion to craniosynostosis and concurrent changes in both the vector and direction of suture fusion initiation.

Fusion patterns of craniofacial sutures in rhesus monkey skulls of known age and sex from Cayo Santiago

“…Many genetic and epigenetic factors including biomechanical elements may play a role in the fusion of sutures (Ozaki et al, 1998;Kent and Carr, 2001;Sidor, 2001;Brunner, 2002;Brunner et al, 2004;Byron et al, 2004Byron et al, , 2006. Feeding mechanics may have played a similar role in the evolution of sutural fusion in mammal-like reptiles.…”

“…Over time, these species exhibited a reduction in the number of cranial bones (suggesting a higher incidence of early sutural fusion), which may be associated with the evolution of mastication in this clade (Sidor, 2001;Sidor et al, 2004), or to \reinforce the skull against the forces of subduing large prey" (Rubidge and Sidor, 2001). In human babies with premature fusion of the sagittal suture, the trabecular bone adjacent to and across the area of fusion displayed more organized trabecular orientation than in regions adjacent to the sagittal suture in normal individuals, suggesting a role for mechanical forces in remodeling trabecular structures in the cranial vault (Ozaki et al, 1998). Fig.…”

The Global Impact of Sutures Assessed in a Finite Element Model of a Macaque Cranium

“…This variation may be due to variation in growth potentials (Massler and Schour, 1951;Ozaki et al, 1998;Opperman, 2000;Sun et al, 2004;Carmody et al, 2008;Wang et al, 2007a), dietary adaptations (Byron, 2009), genetic patterning (Wang et al, 2006a), aging processes (Gross, 1961;Milch, 1966;Miroue and Rosenberg, 1975;Kokich, 1976), fusion patterns (Wang et al, 2006c), and ontogenetic changes in material properties along with cortical bones (Wang et al, 2010a). How these variables might affect the biomechanical behavior of sutures warrants further investigation.…”

Scanning Electron Microscope and Micro-CT Evaluation of Cranial Sutures in Health and Disease

“…1 Since then, investigations into structure and function have been undertaken using immunohistochemistry, 2 autoradiography, 3 and more recently conventional CT 4 and micro-CT scans. 5 However, most of these earlier studies had used animal models including mice, rats and rabbits. 2Y4 The underlying causes of both normal suture fusion in adulthood and premature fusion in craniosynostosis remain unclear.…”

“…While underlying genetic mutations have been identified in the common craniosynostosis syndromes 6 the causes of non-syndromic craniosynostosis remain uncertain but are thought to be multi-factorial with mechanical, genetic and hormonal factors all implicated. 2 Since the initial recognition that the cranial sutures could be studied using micro-CT, 5 there have been no further published reports. This is regardless of the development of improved technology producing enhanced image resolution with the current generation of scanners.…”