Determination of frictional conditions between electrode array and endosteum lining for use in cochlear implant models

Frictional conditions between the electrode array (in cochlear implants) and the endosteum lining covering the walls of the interior scala tympani structure strongly influence the sliding behaviour of the electrode array. Friction coefficients, determined by a simple but effective method based on the impending slippage model of electrode arrays sliding over the endosteum lining are reported in this paper. In this study, friction coefficients of the Nucleus standard straight and the Contour arrays have been determined with and without lubricants applied on the endosteum lining. In the absence of applied lubricants, friction coefficients were found to be 0.19 for the Nucleus standard straight array and 0.12 for the Contour array. Application of lubricants (glycerin and sorbelene) has the potential to lower the friction coefficient for Nucleus standard straight array (0.12 and 0.15) and for the Contour array (0.04 and 0.08). These results are used in finite element models to predict accurately the trajectories of electrode arrays and sliding contact pressures on cochlear structures to evaluate the likelihood of damage sustained during insertion.