Fröhlich Max, Deutz Jaro, Wangenheim Matthias, Rau Thomas S, Lenarz Thomas, Kral Andrej, Schurzig Daniel
MED-EL Research Center, MED-EL Medical Electronics GmbH, Hannover, Germany.
Department of Otolaryngology, Hannover Medical School, Hanover, Germany.
Front Neurol. 2024 Aug 6;15:1430694. doi: 10.3389/fneur.2024.1430694. eCollection 2024.
Despite the success of cochlear implant (CI) surgery for hearing restoration, reducing CI electrode insertion forces is an ongoing challenge with the goal to further reduce post-implantation hearing loss. While research in this field shows that both friction and quasistatic pressure forces occur during CI insertion, there is a lack of studies distinguishing between these origins. The present study was conducted to analyze the contribution of both force phenomena during automated CI insertion.
Five MED-EL FLEX28 CI electrode arrays were inserted into both a regular and uncoiled version of the same average scala tympani (ST). Both ST models had a pressure release hole at the apical end, which was kept open or closed to quantify pressure forces. ST models were filled with different sodium dodecyl sulfate (SDS) lubricants (1, 5, and 10% SDS, water). The viscosity of lubricants was determined using a rheometer. Insertions were conducted with velocities ranging from v= 0.125 mm/s to 2.0 mm/s.
Viscosity of SDS lubricants at 20°C was 1.28, 1.96, and 2.51 mPas for 1, 5, and 10% SDS, respectively, which lies within the values reported for human perilymph. In the uncoiled ST model, forces remained within the noise floor (maximum: 0.049 × 10 N ± 1.5 × 10 N), indicating minimal contribution from quasistatic pressure. Conversely, forces using the regular, coiled ST model were at least an order of magnitude larger (minimum: F = 28.95 × 10 N, v = 1 mm/s, 10% SDS), confirming that friction forces are the main contributor to total insertion forces. An N-way ANOVA revealed that both lubricant viscosity and insertion speed significantly reduce insertion forces ( < 0.001).
For the first time, this study demonstrates that at realistic perilymph viscosities, quasistatic pressure forces minimally affect the total insertion force profile during insertion. Mixed friction is the main determinant, and significantly decreases with increaseing insertion speeds. This suggests that in clinical settings with similar ST geometries and surgical preparation, quasistatic pressure plays a subordinate role. Moreover, the findings indicate that managing the hydrodynamics of the cochlear environment, possibly through pre-surgical preparation or the use of specific lubricants, could effectively reduce insertion forces.
尽管人工耳蜗（CI）手术在恢复听力方面取得了成功，但降低CI电极插入力仍是一项持续的挑战，目标是进一步减少植入后听力损失。虽然该领域的研究表明，CI插入过程中会同时出现摩擦力和准静态压力，但缺乏区分这些力来源的研究。本研究旨在分析自动CI插入过程中这两种力现象的作用。
将五个MED-EL FLEX28 CI电极阵列插入同一个平均鼓阶（ST）的常规和未卷曲版本中。两个ST模型在顶端都有一个压力释放孔，该孔保持打开或关闭以量化压力。ST模型填充有不同的十二烷基硫酸钠（SDS）润滑剂（1%、5%和10% SDS、水）。使用流变仪测定润滑剂的粘度。插入速度范围为v = 0.125毫米/秒至2.0毫米/秒。
20°C时，1%、5%和10% SDS的SDS润滑剂粘度分别为1.28、1.96和2.51毫帕秒，处于人类外淋巴报道的值范围内。在未卷曲的ST模型中，力保持在本底噪声范围内（最大值：0.049×10 N±1.5×10 N），表明准静态压力的贡献最小。相反，使用常规卷曲ST模型时的力至少大一个数量级（最小值：F = 28.95×10 N，v = 1毫米/秒，10% SDS），证实摩擦力是总插入力的主要贡献因素。N向方差分析表明，润滑剂粘度和插入速度均显著降低插入力（<0.001）。
本研究首次表明，在实际外淋巴粘度下，准静态压力在插入过程中对总插入力分布的影响最小。混合摩擦力是主要决定因素，并随着插入速度的增加而显著降低。这表明在具有相似ST几何形状和手术准备的临床环境中，准静态压力起次要作用。此外，研究结果表明，可能通过术前准备或使用特定润滑剂来管理耳蜗环境的流体动力学，可以有效降低插入力。
