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

描述（由申请人提供）：中耳的作用是将来自环境的压力波传递到充满液体的耳蜗。非哺乳动物的中耳通常是用一根相对简单的活塞状骨头来实现的，而哺乳动物的中耳是独特的，因为它包含三个不同的骨头（听骨）——锤骨、incus和镫骨，它们通过韧带和肌腱悬浮在中耳腔内。在人类和其他哺乳动物中，这些小听骨通过两个滑膜关节连接，每块肌肉分别与锤骨和镫骨相连。由于这种中耳设计在简单的听骨屈曲之外引入了额外的灵活性，因此可以期望它传递的振动更少

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.