Effect Of Cervical Rotatory Manipulation On Biomechanics Of Carotid Atherosclerotic Plaque:A Finite Element Analysis

Background:Cervical rotatory manipulation（CRM）,as a effective therapy,is common used to treat the neck pain and headaches.But it might cause serious diseases such as stroke,transient ischemic attack,paralysis and shock in the atherosclerotic patient.The safety of CRM for the carotid atherosclerosis need be researched.Nowadays,the most of studies about CRM on the atherosclerosis emphasize on the hemodynamics of the carotid and vertebral artery,but not the biomechanics of the atherosclerotic plaque.Finite element analysis（FEA）,a computational mathematics which could simulate the real physical system,is a brand new method to analyze the biomechanics of the body-tissue.Therefore,FEA could be used to study the biomechanical changes of carotid atherosclerotic plaque proceeding CRM,it might be a new screening method for the atherosclerosis before CRM.Objective:The purpose of this research is to reconstruct the FEA models of carotid atherosclerosis and analyze the effect of CRM on biomechanics of carotid atherosclerotic plaqueMethod:①Eight patients with carotid atherosclerotic plaque were recruited for this study.Two kinds of examinations had been done during the recruitment to acquire patient’s database.One was magnetic resonance imaging（MRI）,the another was Doppler ultrasound.In the ultrasound,the patients were measured in two positions,the neutral position and the end range of motion（ROM）,for the datum of the velocities and the wall thickness of carotid arteries,etc.All models were established and verified in Ansys14.5.②To simulate of the carotid artery change during CRM,the CFD models were grouped and stretched in 7%and 16%respectively.The normal group was no-stretched represented the neck in a neutral position.And the 7%stretched group represented the mean stretched of carotid artery during CRM,the 16%was on behalf of the maximum stretched.The Fluent in Ansys14.5 was used to compute the hemodynamic parameters,including the average wall shear stress（AWSS）,the maximum wall shear stress（Max_WSS）,the average maximum wall shear stress（Max_AWSS）,the blood velocity on the region of the plaque and the blood flow vectorgraph,etc.③Through the CFD model,the hemodynamic parameters of the individual model in two positions were obtained.Combined the parameters of the ROM position with the individual model,the FSI model was to simulate the stretch of carotid artery which was proceeding two spinal manipulations,the high-speed,low-amplitude spinal manipulation and CRM.2%,6%,7%,12%,16%stretched deformations were proceeded in the model respectively.Biomechanical parameters were acquired in all deformations,including wall shear stress（WSS）,the maximum plaque wall stress（PWS）,wall tensile stress（Von mises stress,VWTS）and strain.Result:①Effective computational fluid dynamics（CFD）models and the precise individual fluid-structure interaction（FSI）models were established.②The AWSS and Max_WSS of the plaque,as well as the WSS on the upstream of the plaque,were enlarged significantly,but others were not.③The flow mass shear stress（FMSS）was larger than the rupture threshold.The WSS and PWS were enlarged following the deformation magnification.Only the VWTS in 16%stretched was higher than the rupture threshold.Conclusions:①Based on the MRI images,the FEA models of carotid atherosclerosis could be built effectively.②The 16%stretched would enlarged the WSS of the plaque that lead the endothelium of the plaque region to be vulnerable.③Large stretched deformation（16%）would influence the stability of the plaque.The risk of plaque rupture increases with the larger deformation.CRM in the patients with carotid atherosclerosis may damage atherosclerotic plaque.It may cause the plaque to be more vulnerable,or even rupture.Therefore,the patients with carotid atherosclerosis should be carefully treated with cervical rotatory manipulation.