Introduction:
Since four decades, cochlear implants are used as state of the art treatment for sensorineural hearing loss. The implantation typically involves a manually performed mastoidectomy. As this procedure is limited in terms of tissue preservation and operation time, a fast and minimally-invasive implantation technique is indicated to overcome these limitations.
Material and Methods:
A facial recess approach was performed in 12 human cadavers by drilling a single tunnel through the temporal bone using a novel stereotaxic operation system. A stereotaxic frame was mounted with boneanchors on the cadaver skull and a cone beam computed tomography (CBCT) was performed to identify the facial recess in respect to the position of the mounted frame. Following this, the optimal position of the drill path was defined and an individual drilling jig was manufactured fitting to the stereotaxic frame. Using this, the drill tunnel was developed and the drill accuracy was evaluated using a coordinate-measuring machine, a post-operative CBCT scan, and microscopically.
Results:
The calculated drill pathways were successfully conducted in each cadaver. No injuries of the facial nerve or the chorda tympany was observed. An average deviation of 0.27 ± 0.05 mm from the planned drill path was achieved, being lower than the required safety distance (> 0.4 mm) to preserve the nerves at the facial recess level.
Conclusion:
Good agreement between the calculated and the measured drill path positions was achieved, indicating the feasibility to perform a safe and reliable cochlear surgery with the presented minimally-invasive operation approach. Accordingly, we aim to overcome the limitations of the conventional surgery in order to increase the patient safety and to decrease the operation time and costs.
