Anatomical Observation Of The Cranial Suture And Finite Element Analysis Of Its Mechanical Behavior

Objective:The study is to improve the anatomical data of the cranial suture in Chinese adults and provide a reference basis for the treatment of related diseases by manipulation.A three-dimensional finite element model of the Chinese adult cranial and brain with cranial sutures was developed to provide a model and tool for studying the mechanical effects of cranial sutures.To investigate whether the different morphologies of the cranial suture can affect its mechanical behavior.Methods:1.Anthropological nonmetric observation and craniometry were used to study 285 dry skull specimens of Chinese adults.We observe and study the anatomical manifestations and characteristics of cranial suture closure,parietal foramen,metopism,wormian bones,and pterion in the skull of Chinese adults.2.The model was constructed and validated using Mimics,Geomagic,Solidworks,and Ansys software.3.Based on the different morphologies of the cranial suture,six group finite element models of the bone-suture-bone composite structure were constructed.An impact load of 50 kPa and a tensile load of 98 N on each side were applied to each model to analyze the changes of Mises stress and total deformation of each group under impact and tensile loads.Results:1.(1)The detection rate of closed extracranial sutures was 31.93%;the highest degree of closure was found in the sagittal suture;the coronal suture,and the lambdoid sutures’ closure were mostly symmetrical on lateral.In unclosed cranial sutures,the bone surfaces on both sides of the cranial suture were rough and embedded with each other,making it difficult to move.(2)The detection rate of the parietal foramen was 82.86%,with a single foramen type being the most frequent,mainly located on one or both sides of the sagittal suture;the rate of intracranial and extracranial communication was 39.97%.(3)The detection rates of metopism and wormian bones(WBs)were 10.18%and 63.86%,respectively.The different locations of WBs have different distribution and morphological characteristics.The metopism always accompanies WBs,but the WBs do not necessarily accompany metopism.(4)The morphological types of the pterion in Chinese adults were sphenoparietal-suture,epipteric,frontotemporal-suture,and stellate types,and they are mainly distributed bilaterally symmetrically.The distance from the center of the pterion to the relevant intracranial and extracranial markers is slightly longer on the right than on the left and more prolonged in males than in females.2.This study constructed a three-dimensional finite element model of the Chinese adult cranial and brain with cranial sutures based on CT and MRI images.The model consisted of anatomical structures such as the scalp,skull,dura mater,cerebrospinal fluid,cerebral falx,cerebellar curtain,brain tissue,and artificially delineated cranial sutures.The model construction was proved successful after verification by comparison with cadaveric data.3.(1)The presence of the cranial suture delayed the appearance time of the peak Mises stress while increasing the range and magnitude of the peak stress in the composite structure.This change does not depend on the straightness or flexion of the cranial suture morphology and the number of the waveform.It was related to the area and complexity of the bone-suture contact surface.The Mises stresses in the suture area are mainly concentrated on the bone surfaces on both sides of the cranial suture.(2)The cranial suture groups’ total deformation was only about 0.2 μm under impact loading and about 11 μm under tensile loading.The total deformation variation of the composite structure was related to the presence or absence of the cranial suture and not to the morphology of the cranial suture,but the deformation of the suture area was related to its morphology.Conclusions:We observed the cranial suture closure,parietal foramen,metopism,wormian bones,and pterion in the skull of Chinese adults and summarized their characteristics.The anatomical characteristics of the cranial suture dictate that manipulation cannot push the cranial suture at will.The cranial suture has a shock buffering effect related to the complexity of the cranial suture morphology but not to the straightness or flexion of the cranial suture or the number of waveforms.The tensile load can cause small deformation of the composite.The change of total deformation is not related to the cranial suture morphology.The recommended force of craniosacral therapy cannot push the cranial suture.