Håkansson Bo, Woelflin Fausto, Tjellström Anders, Hodgetts William
Department of Electrical Engineering, Chalmers University of Technology, Gothenburg, Sweden.
Department of Communication Sciences and Disorders, University of Alberta, Edmonton, Canada.
Med Devices (Auckl). 2020 Sep 24;13:293-313. doi: 10.2147/MDER.S260732. eCollection 2020.
The mechanical skull impedance is used in the design of direct bone drive hearing systems. This impedance is also important for the design of skull simulators used in manufacturing, service, and fitting procedures of such devices.
The skull impedance was measured in 45 patients (25 female and 20 male) who were using percutaneous bone conduction implants (Ponto system or Baha system). Patients were recruited as a consecutive prospective case series and having an average age of 55.4 years (range 18-80 years). Seven patients were treated in Gothenburg, Sweden, and 38 patients in Edmonton, Canada. An impedance head (B&K 8001), driven by an excitation transducer with emphasized low-frequency response, was used to measure the mechanical point impedance with a swept sine from 100 to 10k Hz.
The skull impedance was found to have an anti-resonance of approximately 150 Hz, with a median maximum magnitude of 4500 mechanical ohms. Below this anti-resonance, the mechanical impedance was mainly mass-controlled corresponding to an effective skull mass of 2.5 kg at 100 Hz with substantial damping from neck and shoulder. Above the anti-resonance and up to 4 kHz, the impedance was stiffness-controlled, with a total compliance of approximately 450n m/N with a small amount of damping. At frequencies above 4 kHz, the skull impedance becomes gradually mass-controlled originating from the mass of the osseointegrated implant and adjacent bone. No significant differences related to gender or skull abnormalities were seen, just a slight dependence on age and major ear surgeries. The variability of the mechanical impedance among patients was not found to have any clinical importance.
The mechanical skull impedance of percutaneous implants was found to confirm previous studies and can be used for optimizing the design and test procedures of direct bone drive hearing implants.
机械颅骨阻抗用于直接骨驱动听力系统的设计。这种阻抗对于此类设备制造、维修和适配过程中使用的颅骨模拟器的设计也很重要。
对45例使用经皮骨传导植入物（Ponto系统或Baha系统）的患者（25例女性和20例男性）进行了颅骨阻抗测量。患者作为连续的前瞻性病例系列招募，平均年龄为55.4岁（范围18 - 80岁）。7例患者在瑞典哥德堡接受治疗，38例患者在加拿大埃德蒙顿接受治疗。使用由具有强调低频响应的激励换能器驱动的阻抗头（B&K 8001），通过100至10kHz的扫频正弦波测量机械点阻抗。
发现颅骨阻抗在约150Hz处有一个反共振，最大幅度中值为4500机械欧姆。在这个反共振频率以下，机械阻抗主要受质量控制，对应于100Hz时有效颅骨质量为2.5kg，颈部和肩部有显著阻尼。在反共振频率以上直至4kHz，阻抗受刚度控制，总柔顺性约为450nm/N，阻尼较小。在4kHz以上的频率，颅骨阻抗逐渐受质量控制，这源于骨整合植入物和相邻骨的质量。未发现与性别或颅骨异常相关的显著差异，仅对年龄和主要耳部手术有轻微依赖性。未发现患者之间机械阻抗的变异性具有任何临床重要性。
经皮植入物的机械颅骨阻抗证实了先前的研究结果，可用于优化直接骨驱动听力植入物的设计和测试程序。
