Comparative Analysis of Robotics-Assisted and Manual Insertions of Cochlear Implant Electrode Arrays

Abstract

Hypothesis: Robotics-assisted cochlear implant (CI) insertions will result in reduced intracochlear trauma when compared with manual, across multiple users.

Background: Whether intracochlear trauma and translocations are two factors that may contribute to significant variability in CI outcomes remains to be seen. To address this issue, we have developed a robotics-assisted insertion system designed to aid the surgeon in inserting electrode arrays with consistent speeds and reduced variability. This study evaluated the effect of robotics-assisted insertions on the intracochlear trauma as compared with manual insertions in cadaveric cochleae in a simulated operative environment.

Methods: Twelve neurotologists performed bilateral electrode insertions into cochleae of full cadaveric heads using both the robotics-assisted system and manual hand insertion. Lateral wall electrodes from three different manufacturers (n = 24) were used and randomized between surgeons. Insertion angle of the electrode and trauma scoring were evaluated using high-resolution three-dimensional x-ray microscopy and compared between robotics-assisted and manual insertions.

Results: Three-dimensional x-ray microscopy provided excellent resolution to characterize the in situ trauma and insertion angle. Robotics-assisted insertions significantly decreased insertional intracochlear trauma as measured by reduced trauma scores compared with manual insertions (average: 1.3 versus 2.2, device versus manual, respectively; p < 0.05). There was no significant difference between insertion angles observed for manual and robotics-assisted techniques (311 ± 131° versus 307 ± 96°, device versus manual, respectively).

Conclusions: Robotics-assisted insertion systems enable standardized electrode insertions across individual surgeons and experience levels. Clinical trials are necessary to investigate whether insertion techniques that reduce insertional variability and the likelihood of intracochlear trauma also improve CI auditory outcomes.

FIG. 1.

Diagram of robotics-assisted CI insertion system. The robotic system comprises two basic components—a sterile, disposable drive unit, which interfaces with the electrode array (outlined in blue), and a reusable control console/footpedal (outlined in green), which allows the user to control the speed of insertion in a “hands-free” manner. In brief, the robotics-assisted cochlear implantation was accomplished in three basic steps after the mastoidectomy. First, the drive unit was aligned with the facial recess and attached to the skull using the self-tapping screws. Next, the surgeon loaded the drive unit with the assigned electrode array and achieved the desired trajectory through manipulation of a movable head. Then, using the control console and footpedal, the electrode array was inserted into the cochlea at a desired speed. Lastly, the drive unit was detached from the electrode array and the skull, and the surgeon glued the electrode in place before explanation of the cochlea. CI indicates cochlear implant.

FIG. 2.

Demonstrative images of 3-D x-ray microscopy. Image (A) demonstrate a scala tympani robotics-assisted insertion with associated 3-D and 2-D composite reconstructions. B, shows a manual scala tympani CI insertion with tip fold-over on similar composite reconstructions. CI indicates cochlear implant; 2-D/3-D, two/three-dimensional.

FIG. 3.

Trauma scoring. The distribution of scored trauma grades between groups is plotted as the absolute number of grades assigned. The mean group trauma score is plotted on the right-hand side. The manual insertion group had a significantly greater mean trauma grade compared with the robotics-assisted group. “*” denotes significant differences (p < 0.05).