中耳机械模型的建立及听骨赝复物传音特性的研究

目的探讨对人工听骨赝复物传音功能进行评价的客观方法，以及钛金属人工听骨赝复物不同质量和不同顶盘面积在中耳机械模型中对传音功能的影响。方法用两块圆形的弹性膜分别代替鼓膜和前庭窗，两膜之间放置人工听骨，在人工外耳道侧给予纯音刺激，同时记录其声强，在前庭窗膜处用激光测振仪测量前庭窗膜的振动速度，通过比较振动速度的大小来比较人工听骨的传音特性；将质量不同和面积不同的2组钛人工听骨分别安放于中耳机械模型中测量其传音特性。结果模型感觉阈曲线和正常人听阈曲线对比，两者走势基本相同。钛听骨顶盘面积较小的听骨在1500-4000Hz其传音特性优于顶盘面积较大的听骨；质量小的听骨在高频区传音好，质量大的听骨在低频区传音比较好，但总体上质量小的听骨传音特性较好。结论中耳机械模型是检验人工听骨传音特性并进行人工听骨赝复物客观评价的理想工具之一；钛人工听骨的质量和顶盘的面积对其传音特性均有影响，在设计人工听骨时或手术要同时考虑到质量和顶盘面积对传音的影响。

Establishment of mechanical middle ear model and the study of the acoustic characteristics of different ossicular prostheses

OBJECTIVE: To design a tool for evaluating the sound transmission function of ossicular prosthesis and explore the impacts of ossicular prosthesis bead area and the effects of the mass of ossicular prosthesis on the sound transmission function in mechanical middle ear model. METHODS: Two latex membranes were used to represent the tympanic membrane and oval window membrane. The ossicular prosthesis was fitted between the artificial tympanic membrane and oval window membrane during the test. Pure tune signals were used to stimulate the vibration of tympanic membrane. The vibration of oval window membrane was recorded by a laser Doppler vibrometer. The ossicular transmission function was evaluated by comparing the vibration velocities of oval window membrane. Two groups of titanium ossicular prosthesis with different head area and mass respectively were fitted into a mechanical middle ear model to evaluate their sound transmission functions. RESULTS: The feeling threshold curve of mechanical middle ear model (MMEM) was similar to the hearing threshold curve of normal person. The transmission function of the prosthesis with small head area was better than that of prostheses with large head area at frequencies 1500-4000 Hz. The small-massed prostheses functioned better at higher frequencies and the large-massed prostheses functioned better at lower frequencies. But small-massed prostheses functioned better as a whole. CONCLUSIONS: The MMEM was an idea tool to evaluate the transmission functions of different ossicular prostheses. Both the head area and prosthesis mass had an influence on the transmission function of ossicular prosthesis. So while designing the ossicular prosthesis or performing ossiculoplasty, both the head area and prosthesis mass should he taken into consideration.