Dobrev Ivo, Sim Jae Hoon, Aqtashi Baktash, Huber Alexander M, Linder Thomas, Röösli Christof
Department of Otorhinolaryngology, Head and Neck Surgery, University Hospital Zürich, Switzerland; University of Zürich, Zürich, Switzerland.
Department of Otorhinolaryngology, Head and Neck Surgery, University Hospital Zürich, Switzerland; University of Zürich, Zürich, Switzerland.
Hear Res. 2018 Jan;357:1-9. doi: 10.1016/j.heares.2017.11.002. Epub 2017 Nov 10.
Intra-operative quantification of the ossicle mobility could provide valuable feedback for the current status of the patient's conductive hearing. However, current methods for evaluation of middle ear mobility are mostly limited to the surgeon's subjective impression through manual palpation of the ossicles. This study investigates how middle ear transfer function is affected by stapes quasi-static stiffness of the ossicular chain. The stiffness of the middle ear is induced by a) using a novel fiber-optic 3-axis force sensor to quantify the quasi-static stiffness of the middle ear, and b) by artificial reduction of stapes mobility due to drying of the middle ear.
Middle ear transfer function, defined as the ratio of the stapes footplate velocity versus the ear canal sound pressure, was measured with a single point LDV in two conditions. First, a controlled palpation force was applied at the stapes head in two in-plane (superior-inferior or posterior-anterior) directions, and at the incus lenticular process near the incudostapedial joint in the piston (lateral-medial) direction with a novel 3-axis PalpEar force sensor (Sensoptic, Losone, Switzerland), while the corresponding quasi-static displacement of the contact point was measured via a 3-axis micrometer stage. The palpation force was applied sequentially, step-wise in the range of 0.1-20 gF (1-200 mN). Second, measurements were repeated with various stages of stapes fixation, simulated by pre-load on the stapes head or drying of the temporal bone, and with severe ossicle immobilization, simulated by gluing of the stapes footplate.
Simulated stapes fixation (forced drying of 5-15 min) severely decreases (20-30 dB) the low frequency (<1 kHz) response of the middle ear, while increasing (5-10 dB) the high frequency (>4 kHz) response. Stapes immobilization (gluing of the footplate) severely reduces (20-40 dB) the low and mid frequency response (<4 kHz) but has lesser effect (<10 dB) at higher frequencies. Even moderate levels of palpation force (<3gF, <30 mN), regardless of direction, have negative effect (10-20 dB) on the low frequency (<2 kHz) response, but with less significant (5-10 dB) effect at higher frequencies. Force-displacement measurements around the incudostapedial joint showed quasi-static stiffness in the range of 200-500 N/m for normal middle ears, and 1000-2500 N/m (5-8-fold increase) after artificially (through forced drying) reducing the middle ear transfer function with 10-25 dB at 1 kHz.
Effects of the palpation force level and direction, as well as stapes fixation and immobilization have been analyzed based on the measurement of the stapes footplate motion, and controlled application of 3D force and displacement.
术中对听小骨活动度进行量化可为患者传导性听力的当前状况提供有价值的反馈。然而，目前评估中耳活动度的方法大多局限于外科医生通过手动触诊听小骨获得的主观印象。本研究调查了听骨链镫骨准静态刚度如何影响中耳传递函数。中耳的刚度通过以下方式诱导：a）使用新型光纤三轴力传感器量化中耳的准静态刚度；b）通过中耳干燥人为降低镫骨活动度。
中耳传递函数定义为镫骨足板速度与外耳道声压之比，在两种情况下用单点激光多普勒测速仪（LDV）进行测量。首先，使用新型三轴PalpEar力传感器（Sensoptic，瑞士洛索内）在镫骨头沿两个平面内方向（上下或前后）以及在砧镫关节附近的砧骨豆状突沿活塞方向（内外）施加受控触诊力，同时通过三轴测微计台测量接触点的相应准静态位移。触诊力按顺序逐步施加，范围为0.1 - 20 gF（1 - 200 mN）。其次，在通过对镫骨头预加载或颞骨干燥模拟的镫骨固定的不同阶段，以及通过镫骨足板粘贴模拟的严重听小骨固定的情况下重复测量。
模拟镫骨固定（强制干燥5 - 15分钟）会严重降低（20 - 30 dB）中耳的低频（<1 kHz）响应，同时增加（5 - 10 dB）高频（>4 kHz）响应。镫骨固定（足板粘贴）会严重降低（20 - 40 dB）低频和中频响应（<4 kHz），但在较高频率下影响较小（<10 dB）。即使是中等水平的触诊力（<3gF，<30 mN），无论方向如何，都会对低频（<2 kHz）响应产生负面影响（10 - 20 dB），但在较高频率下影响较小（5 - 10 dB）。砧镫关节周围的力 - 位移测量显示，正常中耳的准静态刚度在200 - 500 N/m范围内，在通过强制干燥人为降低1 kHz处的中耳传递函数10 - 25 dB后，刚度增加到1000 - 2500 N/m（增加5 - 8倍）。
基于对镫骨足板运动的测量以及三维力和位移的受控应用，分析了触诊力水平和方向以及镫骨固定和固定的影响。
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