Background:

Parameters related to cochlear trauma, such as insertion forces, gained more and more importance, especially in regard to preservation of residual hearing. The impact of lubricants on the insertion forces has not been systematically examined yet.

Methods:

Nucleus 24 Contour Advance electrodes were inserted into an artificial model of the human scala tympani filled with glycerin, sodium hyaluronate (Healon), and water or soap solution of 10% Bathox and 90% distilled water. A specially designed insertion protocol was applied so as any remains of the lubricants in the scala tympani model or on the electrodes' surface could be completely removed. Force measurements were performed by a force measurement system equipped with a 10 N load cell. Average (AF) and maximum (MF) insertion forces were recorded for every lubricant.

Results:

The highest values were documented with water (AF= 0.139 N, MF= 0.367 N) and the lowest with the soap solution (AF= 0.065 N, MF= 0.148 N). Application of Healon and glycerin resulted in low, comparable values between each other.

Conclusion:

The application of lubricants affects significantly the electrode insertion forces. As soap solution is not usable, for the time being, in human cochlear implantation, low insertion forces combined with the antiadhesive features of Healon make it a proper lubricant for intracochlear application. Because of the low recorded forces, soap solution represents an ideal experimental model for in vitro electrode-mechanics studies.