Williams K R, Blayney A W, Lesser T H
Department of Basic Dental Science, University of Wales College of Medicine, Cardiff, UK.
Clin Otolaryngol Allied Sci. 1995 Feb;20(1):36-44. doi: 10.1111/j.1365-2273.1995.tb00009.x.
In this work, the natural frequencies of vibration of two different stapes prosthesis replacement reconstructions have been analysed using the finite element method. Prosthesis 1 was constructed of fine stainless steel wire and a Teflon base, while prosthesis 2 was made entirely of Teflon. The results have indicated that generally, the first natural frequency of vibration falls as the prostheses become larger and more bulky. However, the fall in the first natural for prosthesis 1 was modest when compared with that of the isolated tympanic membrane. An important variable influencing frequencies and mode of vibration of the reconstruction was the tightness of fit of the prostheses within the remaining ossicular chain. The tightness of fit in this work was modelled as a range of spring constants applied at the stapes pseudo footplate, together with a series of joint elements at the incus tip/prosthesis head for the Teflon implant. When these spring constraints were below approximately 10 N/mm, the reconstruction exhibited normal mode 1 vibration behaviour, but at larger spring values, an abnormal mode 1 became established resembling the normal mode 2 vibration characteristics. The formation of new geometries and surfaces following reconstruction, introduces new constraints between umbo and stapes footplate particularly at the natural/artificial interfaces. These unnatural constraints may inhibit and modify the natural movements normally occurring at the stapes footplate leading to abnormal modes of vibration.
在这项工作中，使用有限元方法分析了两种不同镫骨假体置换重建的振动固有频率。假体1由细不锈钢丝和聚四氟乙烯基座构成，而假体2完全由聚四氟乙烯制成。结果表明，一般来说，随着假体变得更大、更笨重，第一振动固有频率会下降。然而，与孤立的鼓膜相比，假体1的第一固有频率下降幅度较小。影响重建振动频率和模式的一个重要变量是假体在剩余听骨链内的贴合紧密程度。在这项工作中，贴合紧密程度被建模为施加在镫骨假底板上的一系列弹簧常数范围，以及针对聚四氟乙烯植入物在砧骨尖端/假体头部处的一系列关节元件。当这些弹簧约束低于约10N/mm时，重建表现出正常模式1的振动行为，但在更大的弹簧值时，会形成一种类似于正常模式2振动特征的异常模式1。重建后新几何形状和表面的形成，在鼓膜脐和镫骨底板之间引入了新的约束，特别是在天然/人工界面处。这些不自然的约束可能会抑制和改变通常在镫骨底板处发生的自然运动，从而导致异常的振动模式。
