Research On The Influence Of Congenital Malformation Of External And Middle Ear On The Performance Of Round-Window Stimulation

Due to the difficulty in wearing hearing aids and poor output gain,foreign researchers had developed traditional middle ear implant(MEI),which was a mechanical excitation ossicular chain to compensate patients for hearing impairment of the implantable hearing aid device.However,the implantation of traditional middle ear implant requires the patient's ossicular chain to be intact.And many clinical patients with sensorineural hearing loss and congenital malformation of ossicular chain who cannot provide a complete ossicular chain for the MEI,so that the MEI can not be implanted.For this reason,in recent years,foreign scholars have proposed the method that can avoid the ossicular chain,using actuator to direct excitation of the round window(RW)to compensate for the hearing loss.This method of excitation of the RW provides a new treatment for patients with mixed hearing loss and congenital malformation of ear.However,clinical studies have reported that individual differences are large after the surgery of RW.The individual differences are not caused by the actuator itself coupled to patient's ear,but also are effected by the congenital malformation of ear.In order to improving the hearing compensation performance of round window middle ear implant(RW-MEI)and reducing differences in individual performance after postoperative,this paper systematically studied the influence of congenital malformation of external and middle ear on the RW excitation.The specific work in this paper is summarized as follows.Firstly,the geometric model of the external ear canal and middle ear was established by using micro-computed tomography(Micro-CT)and technique of reverse engineering.The geometric model of the cochlea was established by using three-dimensional software.The geometric model of middle ear and inner ear were coupled by Boolean operation,and the solid model of human ear was obtained eventually.To ensure the reliability and accuracy of our constructed human ear FE model,five groups of comparison i.e.the cochlear input impedance,between our model-predicted results and the experimental reports were performed.The corresponding model-predicted results were calculated under sound pressure stimulation exerted at the ear canal sentrance.Secondly,based on the finite element model of human ear,the effects of common clinical CM of the external and middle ear on the hearing compensation performance of the RW-S MEI were systematically explored.The impacts of CM of the external and middle ear on RW stimulation performance were studied,and the results pointed out that it is essential to specifically improve the output stimulating force of RW-S MEI to make its actual gain being consistent with the theoretical expectancy after implantation.The experimental bench which was used to testing the dynamic performance of the selected piezoelectric actuator was tested.The middle ear models were printed by 3D printing technology and the physical models of the middle ear were constructed,By utilizing these models,the effect of the common clinical CM of the middle ear on the round window stimulation performance,which was obtained by calculating the finite element model of human ear,was verified.