Force measurement of insertion of cochlear implant electrode arrays in vitro: comparison of surgeon to automated insertion tool

Conclusions: We have demonstrated that an automated insertion tool (i.e. a robot) can be used to duplicate a complex surgical motion in inserting cochlear implant (CI) electrode arrays via the 'advance-off-stylet' (AOS) technique. As compared with human operators, the forces generated by the robot were slightly larger but the robot was more reliable (i.e. less force maxima). Objectives: We present force data collected during CI electrode insertion by human operators and by an automated insertion tool. Materials and methods: Using a three-dimensional, anatomically correct, translucent model of the scala tympani chamber of the cochlea, CI electrodes were inserted either by one of three surgeons (26 insertions) or by the robotic insertion tool (8 insertions). Force was recorded using a load beam cell calibrated for expected forces of <0.1 Newtons (N). The insertions were also videotaped to allow correlation of force with depth of penetration into the cochlea and speed of insertion. Results: Average insertion force used by the surgeons was 0.004 +/- 0.001 N and for the insertion tool it was 0.005 +/- 0.014 N (p <0.00001, Student's t test). While the average insertion force of the automated tool was larger than that of the surgeons, the surgeons did have intermittent peaks during the AOS component of the insertion (between 120 and 200 degrees).