Robotic-Assisted Versus Manual Electrode Array Insertion

Electrode insertion force is a critical determinant of the degree/amount of intracochlear trauma caused by CI surgery. It is affected by the speed of electrode array insertion, with higher insertion speeds leading to greater insertion forces. In addition, rapid electrode array insertions with higher forces are associated with translocation of electrode arrays from the scala tympani into the scala media or vestibuli which leads to lower performance and higher rates of loss of residual hearing. Furthermore, variability in insertion force during electrode insertion can cause dramatic increases in intracochlear fluid pressure which appears to be traumatic. The recent FDA-approved iotaSOFT™ insertion system is designed to address these issues by controlling the speed of implant insertion (0.1-1.0 mm/sec) with reduced insertion force and variability. Use of the iotaSOFT™ insertion system significantly reduces the maximum insertion force, variation in insertion force and intracochlear pressure changes over time, which leads to decreased intracochlear trauma compared with manual insertion in cadavers. In addition, this robotics-assisted insertion system can be used with ECochG monitoring systems, which enables response dynamics that can dramatically reduce electrode array stopping distances (1-2 µm of further electrode array advancement) compared to the kinetics of human manual insertion (~1 mm) once a change in intraoperative ECochG response is detected. Theoretically, robotics-assisted electrode array insertion should result in better preserved structural and functional integrity of the peripheral auditory system due to reduced intracochlear trauma. However, this theoretical possibility has not been tested in human CI users.

To address this knowledge gap, the investigators propose to determine the functional benefits of using robotics-assisted electrode insertion in reducing intracochlear trauma. This will be achieved by comparing trauma to the cochlea from electrode insertion based on postoperative CT scans, electrode impedance, the functional status of the cochlea and the AN, as well as preservation of acoustic hearing in participants randomized to have the electrode array inserted manually or with the iotaSOFT™ insertion system. The investigators hypothesize that robotics-assisted electrode insertion will better preserve peripheral structural and functional integrity by reducing intraoperative trauma. The investigators expect that participants with robotics-assisted electrode insertions will show smaller trauma scores based on CT scans, lower electrode impedance, better functional statuses of the AN, higher ENI indices, less hearing loss, and improved speech perception scores than participants with manual electrode insertions.