*2.2. Types of Device and Electrode Arrays*

Both patients had chosen the Advanced Bionics cochlear implant and the same type of electrode array was inserted: HiFocus™ Mid-Scala electrode array. This pre-curved electrode array has an active length of 15.5 mm and 16 electrodes.

#### *2.3. Robot-Assisted Electrode Array Insertion*

The surgeries were performed with the use of RobOtol® (Collin, Bagneux, France). The RobOtol® arm was controlled by the surgeon using a SpaceMouse® (3DConnexion, Waltham, MA, USA). The speed of the robotic arm could be switched between three gears (high speed: 10 mm/s; medium speed: 2 mm/s; low speed: 0.1–1 mm/s). Before the robot-assisted procedure, RobOtol® was sterile covered, moved into the optimal surgical position and then the Boglock sterilized connector (Collin, Bagneux, France; AB Mid-Scala: RBT-0406) was set on the arm. The internal coil of CI was inserted into the subperiosteal

pocket and the transducer was positioned in the bone bed and fixed with surgical thread. Then Mid-Scala array was positioned on the insertion tool previously attached to the dedicated connector and the prepared set was coupled to the robot arm by Boglock.
