Does Human Ossicular Joint Flexibility Filter Damaging Input to the Cochlea?

描述（由申请人提供）：中耳的目的是将压力波从环境传输到充满液体的耳蜗中。虽然非哺乳动物的中耳通常使用单个相对简单的活塞状骨来实现这一点，但哺乳动物的中耳是独特的，因为它包含三个不同的骨（听小骨）-锤骨，砧骨和镫骨-通过韧带和肌腱悬挂在中耳腔中。在人类和其他哺乳动物中，这些听小骨通过两个滑膜关节连接，并且每个肌肉都连接到锤骨和镫骨。由于这种中耳设计除了听小骨的简单弯曲之外还引入了额外的灵活性，因此可以预期其传递的振动更少 比一个融合的系统更有效。那么，为什么人类会进化出这种复杂而灵活的中耳结构呢？对中耳灵活性的深入了解将进一步加深科学知识，并为量化中耳病变的影响提供基础。它还将为改进的中耳假体的设计奠定框架，特别是因为目前的许多柱状装置消除了健康人类中耳中存在的大部分灵活性。这里提出的中心假设是，人中耳中的移动的关节赋予的灵活性通过减少来自脉冲刺激的对耳蜗的峰值输入以及通过允许两个中耳肌肉在持续噪声期间减少对耳蜗的传输来保护耳蜗结构，并且这种灵活性的优点不会以对通过中耳到耳蜗的正常声音传输的过度不利影响为代价。将通过以下方式对该中心假设进行检验：1）将正常人听骨链的3D运动测量结果与由于融合一个或两个听骨关节或由于植入市售的柱型假体而导致柔韧性降低的改良版本的测量结果进行比较，以及2）使用新的、实验验证的人中耳关节和肌肉的计算模型。完成后，这一建议将有助于我们对人类耳朵灵活性保护作用的科学理解，并将提供一个新的中耳计算模型。 除了研究中耳灵活性的有用性外，该模型还将有利于未来的研究工作，例如为设计更有效的中耳假体和手术干预提供测试平台。

DESCRIPTION (provided by applicant): The purpose of the middle ear is to transmit pressure waves from the environment into the fluid-filled cochlea. While non-mammalian middle ears typically achieve this using a single relatively simple piston-like bone, the mammalian middle ear is unique in that it contains three distinct bones (ossicles)-the malleus, incus, and stapes-suspended within the middle-ear cavity by ligaments and tendons. In humans, among other mammals, these ossicles are connected via two synovial joints, and one muscle each is attached to the malleus and the stapes. Since this middle-ear design introduces additional flexibility beyond simple flexion of the ossicles, it might be expected to transfer vibrations less efficiently than a fused system. Why, then, have humans evolved this complicated and flexible middle-ear structure? An in-depth understanding of middle-ear flexibility will both further scientific knowledge and provide a basis for quantifying the effects of middle-ear pathologies. It will also lay a framework for the design of improved middle-ear prostheses, especially since many of the current columella-like devices remove much of the flexibility present in the healthy human middle ear. The central hypothesis proposed here is that the flexibility imparted by mobile joints in the human middle ear protects cochlear structures by reducing the peak input to the cochlea from impulsive stimuli and by allowing the two middle-ear muscles to reduce transmission to the cochlea during periods of sustained noise, and that this flexibility advantage does not come at the cost of an excessive adverse effect on normal sound transmission through the middle ear to the cochlea. This central hypothesis will be tested by 1) comparing 3D motion measurements of the normal human ossicular chain against measurements of modified versions with reduced flexibility due to fusing one or both ossicular joints or due to implanting a commercially available columella-type prosthesis, as well as through 2) the use of new, experimentally validated computational model of the human middle-ear joints and muscles. When completed, this proposal will contribute to our scientific understanding of the protective role of flexibility in the human ear, and will provide a new computational model of the middle ear. In addition to its usefulness for studying middle-ear flexibility, this model will also benefit futre research efforts, such as by providing a test bed for the design of more-effective middle-ear prostheses and surgical interventions.