Cochlear Implant Insertion with a Mechatronic Tool

Cochlear implants are routinely manually inserted, with limited control of insertion forces. Controlling the quality of insertion during cochlear implantation, should reduce trauma to inner ear structures to enhance preoperative residual hearing preservation. This could participate to improvement of speech performances of implanted patients. We have set up a test bench comprising, artificial and anatomical models of scala tympani with cochlear implant insertion force measurements. Three intracochlear lesion sites have been identified: entry point into cochlea, 180° region corresponding to first turn, and the end of the first turn. We have shown that manual insertion could generate peaks and jolts, contrary to motorized insertion which has smoother and a more predictable insertion profile. Insertion force analysis allows detecting abnormal insertions. In case of array progression blocking, or tip fold-over, a sudden rise of insertion forces is observed at the beginning of the insertion (<10 mm) and its final peak is higher (0,3 to 0,6 N vs 0.15 N for a normal insertion).These results have led to the conception of a mechatronic tool allowing a force controlled cochlear array insertion. This tool embeds a linear actuator and a force sensor in serial. It could be an additional tool to help the surgeon to perform a less traumatic surgical procedure to enhance rehabilitation of neurosensory deafness with cochlear implants.