Avci Ersin, Nauwelaers Tim, Hamacher Volkmar, Kral Andrej
1Cluster of Excellence Hearing4all, Institute of AudioNeuroTechnology and Department of Experimental Otology, Ear, Nose, and Throat Clinics, Hannover Medical University, Hannover, Germany; and 2Advanced Bionics, European Research Center, Hannover, Germany.
Ear Hear. 2017 May/Jun;38(3):e168-e179. doi: 10.1097/AUD.0000000000000394.
To preserve the acoustic hearing, cochlear implantation has to be as atraumatic as possible. Therefore, understanding the impact of the cochlear geometry on insertion forces and intracochlear trauma might help to adapt and improve the electrode insertion and reduce the probability of intracochlear trauma.
The study was conducted on 10 fresh-frozen human temporal bones. The inner ear was removed from the temporal bone. The bony capsule covering the scala vestibuli was removed and the dissected inner ear was mounted on the three-dimensional (3D) force measurement system (Agilent technologies, Nano UTM, Santa Clare, CA). A lateral wall electrode array was inserted, and the forces were recorded in three dimensions with a sensitivity of 2 μN. Afterwards, the bones were scanned using a Skyscan 1173 micro-computed tomography (micro-CT). The obtained 3D force profiles were correlated with the videos of the insertions recorded through the microscope, and the micro-CT images.
A correlation was found between intracochlear force profiles measured in three different directions with intracochlear trauma detected with micro-CT imaging. The angle of insertion and the cochlear geometry had a significant impact on the electrode array insertion forces and possible insertion trauma. Intracochlear trauma occurred frequently within the first 180° from the round window, where buckling of the proximal part of the electrode carrier inside the cochlea, and rupturing of the spiral ligament was observed.
The combination of the 3D force measurement system and micro-CT can be used to characterize the mechanical behavior of a CI electrode array and some forms of insertion trauma. Intracochlear trauma does not always correlate with higher force amplitudes, but rather with an abrupt change of force directions.
为了保留听觉，人工耳蜗植入必须尽可能减少创伤。因此，了解耳蜗几何形状对插入力和耳蜗内创伤的影响，可能有助于调整和改进电极插入方式，并降低耳蜗内创伤的可能性。
本研究对10个新鲜冷冻的人类颞骨进行。将内耳从颞骨中取出。去除覆盖前庭阶的骨膜，将解剖后的内耳安装在三维（3D）力测量系统（安捷伦科技公司，纳米万能材料试验机，加利福尼亚州圣克拉拉）上。插入一个侧壁电极阵列，以2微牛的灵敏度记录三个维度的力。之后，使用Skyscan 1173微型计算机断层扫描（微型CT）对骨头进行扫描。将获得的3D力分布与通过显微镜记录的插入视频以及微型CT图像进行关联。
在三个不同方向测量的耳蜗内力分布与微型CT成像检测到的耳蜗内创伤之间发现了相关性。插入角度和耳蜗几何形状对电极阵列插入力和可能的插入创伤有显著影响。耳蜗内创伤在前180°圆窗范围内频繁发生，在此处观察到电极载体近端在耳蜗内弯曲以及螺旋韧带破裂。
3D力测量系统和微型CT的组合可用于表征人工耳蜗电极阵列的力学行为和某些形式的插入创伤。耳蜗内创伤并不总是与较高的力幅值相关，而是与力方向的突然变化相关。
