Development of Measurement method of Stapes Mobility

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It is important to evaluate the stapes mobility in tympanoplasty because it largely affects the degree of the prognostic hearing level. However, the practical objective measurement method of the stapes mobility has not been well established. Within the present study, the sensor was made to measure the displacement and reaction force of the stapes. The stapes mobility of guinea pigs and rabbits with normal and artificially fixed stapes were measured using this sensor, and the objective diagnosis method was discussed. Moreover, an attempt was made to measure the stapes mobility with the sensor held in hand for clinical use. The results could be drawn as follows :1. The reaction force increases linearly in the small displacement region, but nonlinearly in the large displacement region. The stiffnesses of the normal stapes of guinea pigs and rabbits in small displacement region were 16 【minus-plus】 7N/m and 115 【minus-plus】 25N/m, respectively.2. The significant difference was found between the stiffness of the normal and artificially fixed stapes, which as confirmed to be similar to realistic fixation by the CM measurement. These results indicated that this measurement system could be used for diagnosis of the stapes fixation.3. Although the stapes mobility was measured within 0.02 sec with the sensor held in hand, the stiffness curves well agreed with those in static measurement. The measurement of the stapes mobility within 0.02 sec did not be affected by the viscosity of the cochlea and ligament and the hand trembling.After this, a smaller device for clinical use will be made using micromachining technique.