Modeling And Biomechanical Analysis Of The Stapes, Cochlea And Organ Of Corti

In order to obtain the elastic parameters of the organ of Corti(OC)of the unfixed fresh basilar membrane for biomechanical analysis,the atomic force microscopy (AFM)and liquid-contact measurement method were used.The force curves of six different parts,which were equivalent to the Hensen's cells,outer hair cells,pillar cell,inner hair cells,inner phalangeal cell and the tectorial membrane,of the OC were got.According to the Hooke's law and referring to Jan Domke's method,we have analyzed the elastic parameters of these six parts.The results showed that the Young's modulus of these tissues,which were situated along the basilar membrane in radial direction,were significantly different.It is concluded that measuring and analyzing the Young's modulus of tissues on the entire basilar membrane could reflect their physiological elastic characteristics more accurately.Our studies suggest that the measurement method with AFM could provide accurate elastic parameters for the finite element modeling and analysis of the OC.The temporal bone containing the middle and inner ear was scanned with a high-resolution Micro-CT and the high-quality scan data were acquired.The 3D models of the human stapes,cochlea and the guinea pig's cochlea were reconstructed. After data format transformation for finite element analysis,the models could be used for the three-dimensional morphological measurement and the biomechanical analysis.Meanwhile,referring to electron microscopic images of the OC,the 3D simulation model of the OC was created with the help of the advanced modeling methods in 3Ds Max software.The complex structural constitutions of the OC and their spatial relationships were reproduced in the 3D model,which laid the foundation for developing a further mechanical model.In the numerical simulation work,the finite element method was applied in modal analysis of the intrinsic motions of stapes.The analyzing results were validated using the experimental method of the Laser Doppler Vibrometer(LDV).The flow fields of two simplified cochlear models with straight canal and spiral canal,respectively, were analyzed and compared by the finite element method.The results suggested that the flow velocity distribution and pressure distribution were quite different between these two models.After a 2D geometric model of the OC was constructed,its finite element model with necessary simplification and reasonable assumption was also built.With this model,both static and dynamic analyses of the OC responding to lymph flow are done.The results showed that the arcuate zone and the middle part of the pectinate zone flexed when the basilar membrane vibrated,and the flexion could bring on the deflection of the stereocilia on the top of the hair cells.It was also found that the entire OC turned around the foot of the inner pillar.In the study of the relationship between the tectorial membrane(TM)and the inner hair cell(IHC) stereocilia(St),the interaction between them in the condition of vibration of the OC was investigated.Two 2-D finite element models with coupled and non-coupled between TM and St were built based on the electron microscopic images of the guinea pig's OC.When approximate Couette flow was loaded,Von Mises stress was all higher on Tip Link(TL)and Rootlet and the characteristics of modal frequencies were quite similar on the two models.The St has a larger angular displacement in the non-coupled manner.The results suggested that the St is excited easily when it doesn't contact TM.In addition,the dynamic behaviors of the St of the outer hair cells with the different open angles were analyzed.The results showed that the first row of St with the largest open angle was easy to bend,and the third row of St with the smallest open angle was not easy to bend and had a maximum bending stiffness. Our studies explained more clearly the physiological effect of vibration of the OC conduced by sound wave.In this thesis,several methods for modeling of the cochlea and OC and for their elastic parameters measurement were developed.The vibration characteristics of the basilar membrane and the relationship between the tectorial membrane and hair cell were analyzed using the 2D finite element method.It was found that the entire OC turns around the foot of the inner pillar when the basilar membrane vibrates,and the St is excited easily when it doesn't contact TM.Using 3D finite element method,the flow fields of two simplified cochlear models and the force state of the St were analyzed and compared.The St with different open angles has different bending properties.This finding may help explain the reason why the first row of the St is prone to transposition or lodging.The results obtained in this work are instructive and may be helpful for clinical diagnosis and treatment of ear diseases.This research will contribute to a better understanding of the dynamic behaviors of the stapes and organ of Corti,and to the exploring micro-biomechanical method.It is hoped that this study will provide a virtual analytic platform for the inner ear sensorineural mechanism.