Mikhasev Gennady, Ermochenko Sergey, Bornitz Matthias
Department of Bio- and Nanomechanics, The Belarusian State University, 4 Nezavisimosti Avenue, 220030 Minsk, Belarus.
Math Med Biol. 2010 Dec;27(4):289-312. doi: 10.1093/imammb/dqp020. Epub 2009 Nov 25.
The reconstructed middle ear (RME) consists of a thin annular plate made from cartilage, the intact stapes and a T-like prosthesis replacing the malleus-incus chain and interposed between the stapes and the reconstructed eardrum. Inserting the prosthesis leads inevitably to an initial pretension in the reconstructed ear. A high pretension can lead to a stiffening of the ligaments and a significant shift of the eigenfrequency spectrum of the middle-ear system. Only a weak pretension is required for satisfactory sound transmission. This paper presents a static model of the RME permitting one to estimate the initial strain-stress state of the sound-conducting system after insertion of a prosthesis. Several positions of the prosthesis with respect to the eardrum are considered. The anisotropic stiffness of the stapes annular ligament is represented by a fully occupied stiffness matrix. The equilibrium of the modelled system is described by four vector equations. In the case of small eccentricity of attachment of the prosthesis plate to the eardrum, the perturbation method and the Fourier series are used for solving the plate equation. Otherwise, the finite-difference method is applied. The influence of the geometrical dimensions of the inclined prosthesis and its position on the stresses in the prosthesis-stapes coupling as well as on the pretension of the annular ligament are analysed. Analysis of the calculations performed allows one to conclude that in order to avoid high pretensions and exclude possible luxation of the stapes, the prosthesis should be positioned as close to the centre of the reconstructed eardrum as possible.
重建中耳（RME）由一块由软骨制成的薄环形板、完整的镫骨以及一个T形假体组成，该假体取代了锤骨-砧骨链，并置于镫骨和重建鼓膜之间。插入假体不可避免地会导致重建耳产生初始预张力。高预张力会导致韧带变硬以及中耳系统特征频谱发生显著偏移。仅需较弱的预张力就能实现令人满意的声音传输。本文提出了一种RME的静态模型，可用于估计插入假体后传声系统的初始应变-应力状态。考虑了假体相对于鼓膜的几个位置。镫骨环形韧带的各向异性刚度由一个完全占据的刚度矩阵表示。建模系统的平衡由四个矢量方程描述。在假体板与鼓膜连接的偏心距较小时，采用摄动法和傅里叶级数求解板方程。否则，应用有限差分法。分析了倾斜假体的几何尺寸及其位置对假体-镫骨连接处应力以及环形韧带预张力的影响。对所进行计算的分析表明，为了避免高预张力并排除镫骨可能的脱位，假体应尽可能靠近重建鼓膜的中心放置。
