Micro-CT Evaluation of Robot-Assisted Insertion of CI632 Implant in Human Cadaveric Temporal Bones

To evaluate the surgical accuracy and intracochlear positioning of robot-assisted insertion of slim modiolar cochlear implant electrode arrays (CI632) using the RobOtol system in human cadaveric temporal bones.

A total of 14 fresh-frozen adult cadaveric temporal bones underwent cochlear implantation using RobOtol robot-assistance. Standard mastoidectomy, posterior tympanotomy, and round window exposure were performed. CI632 electrode arrays were robotically inserted at a speed of 0.1 mm/s. Postoperative micro-computed tomography (micro-CT) was performed to assess electrode scalar position, angular insertion depth, modiolar proximity (intracochlear position index), and frequency-to-place mismatch.

Robot-assisted insertion of all 22 electrodes was successfully achieved in 14 specimens. Micro-CT analysis confirmed scala tympani placement without evidence of translocation. A total of 13 arrays demonstrated correct perimodiolar positioning, while one was misplaced along the lateral wall. Mean insertion angle of the 13 correctly placed arrays was 406° ± 25° (351°-441°), and mean intracochlear position index was 0.5 ± 0.05. One array (7%) was mispositioned with lateral wall placement, which occurred in a cochlea with a large cochlear duct length (36.4 mm) and a wide basal turn at 90° (4.6 mm). Frequency-to-place mismatch varied across specimens, with a mismatch of 2637 ± 663 Hz (1973-4077 Hz) for the 8th electrode, and 1246 ± 317 Hz (899-1948 Hz) for the 16th electrode, corresponding to approximately one octave.

Robot-assisted insertion of slim modiolar electrode arrays was feasible and reproducible in human cadaveric temporal bones. One case of mispositioned array occurred in a cochlea with large dimensions, underscoring the importance of preoperative anatomical assessment.

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