Development of hand-guided measurement device of stapes mobility using the micromachining technique

听骨链由锤骨、砧骨和镫骨组成，在听觉力学中起着重要作用。如果听小骨的某些部分变得固定，就会发生听力损失。为了提高听力水平，用假体代替固定的部分。这个手术被称为“鼓室成形术”。在鼓室成形术中，镫骨活动度的评估是非常重要的，因为它直接影响听力水平改善的预后。然而，镫骨移动性的客观测量尚未实现。本研究基于Wada et al.（2000）的方法，通过装配小型力传感器和高精度执行器，研制了一种临床上有用的镫骨可动性测量装置，并通过在豚鼠身上测量镫骨可动性来评估其临床适用性。可以得出以下结论。采用小型电容式力传感器和带有柔性线圈杆和导线的液压微机械臂，实现了装置的小型化。由于这项技术，镫骨的活动性在手术过程中是可测量的，而不影响灵敏度和可重复性。豚鼠正常镫骨的等效刚度为17±3 N/m （N = 5）。正常镫骨与人工固定镫骨的僵硬程度有明显的区别，这与耳硬化的症状相对应。因此，本研究开发的新仪器将有助于镫骨固定的诊断。

The ossicular chain, consisting of the malleus, incus and stapes, plays an important role in auditory mechanics. If some part of the ossicles becomes fixed, hearing loss occurs. In order to improve the level of hearing, the fixated part is replaced with a prosthesis. This surgery is called "tympanoplasty." It is important to evaluate the stapes mobility during the tympanoplasty, because it affects the prognosis of improvement of the hearing level. However, objective measurement of stapes mobility has not yet to be achieved.In this study, an apparatus which is clinically useful for measuring the stapes mobility based on the method of Wada et al. (2000) was developed by assembling a small-sized force sensor and a high-precision actuator, and its clinical applicability was evaluated by measuring stapes mobility in the guinea pig. The following conclusions can be drawn.1. Miniaturization of the apparatus was realized by the use of a small-sized capacitive force sensor and a hydraulic micromanipulator with a flexible coil rod and wires. Owing to this technology, the stapes mobility is measurable during surgery without impairing the sensitivity and repeatability.2. The equivalent stiffness of the normal stapes in guinea pigs was 17±3 N/m (N = 5).3. The difference between the stiffness of the normal stapes and that of the artificially fixed stapes which corresponds to the symptom of otosclerosis was clearly distinguished. Therefore, the new apparatus developed in this study would be helpful for diagnosing stapes fixation.