Friction Force Measurement During Cochlear Implant Insertion: Application to a Force-controlled Insertion Tool Design

Hypothesis: The aim of the study was to evaluate force profiles during array insertion in human cochlea specimens and to evaluate a mechatronic inserter using a 1-axis force sensor.

Background: Today, the surgical challenge in cochlear implantation is the preservation of the anatomic structures and the residual hearing. In routine practice, the electrode array is inserted manually with a limited sensitive feedback.

Materials And Methods: Hifocus 1J electrode arrays were studied. The bench test comprised a mechatronic inserter combined to a 1-axis force sensor between the inserter and the base of the array and a 6-axis force sensor beneath the cochlea model. Influence of insertion tube material, speed (0.15, 0.5, and 1.5 mm/s) and lubricant on frictions forces were studied (no-load). Different models were subsequently evaluated: epoxy scala tympani model and temporal bones.

Results: Frictions forces were lower in the plastic tube compared with those in the metal tube (0.09 ± 0.028 versus 0.14 ± 0.034 at 0.5 mm/s, p < 0.001) and with the use of hyaluronic acid gel. Speed did not influence frictions forces in our study. Insertion force profiles provided by the 1- and 6-axis force sensors were similar when friction forces inside the insertion tool (no-load measurements) were subtracted from the 1-axis sensor data in the epoxy and temporal bone models (mean error, 0.01 ± 0.001 N).

Conclusion: Using a sensor included in the inserter, we were able to measure array insertion forces. This tool can be potentially used to provide real-time information to the surgeon during the procedure.