Electrode insertion force measurements in porcine cochlea specimens.

In the process of cochlear implant electrode array development and characterization the measurement of insertion forces in a cochlea bench model is a standard procedure for estimating trauma. Bench models made of various materials, like PTFE, glass, acrylic, epoxy, etc. in combination with various lubricants, are commonly used for these measurements. The question is if these materials are a valid model in respect to the frictional properties in comparison to a live patient. The measurement of insertion forces in a live patient is not possible at the moment and therefore we decided to use fresh never frozen temporal bones. As fresh never frozen human temporal bones are not easy to obtain, we decided to work with fresh never frozen animal temporal bones in this initial study. The cochlea of a pig was chosen because of its similar proportion to the human. Furthermore it provides straightforward surgical access and is readily available. For the insertion force measurement an automated insertion tool was used and a single axis load cell was equipped with the cut down fresh never frozen porcine temporal bone specimens. Dummy electrodes based on the Cochlear Slim Straight electrode were inserted in the porcine cochlea to a depth of approximately 15 mm or one turn. The measurements could be repeated in each bone. Based on the corresponding DVT scans of the porcine specimen a Teflon bench model was built matching the dimensions of the porcine cochlea. This bench model was also used for insertion measurements in the same automated setup with using the similar dummy electrodes based on the Slim Straight electrode. The obtained insertion forces of both sets of measurements were compared to check the accuracy of the bench model. [ABSTRACT FROM AUTHOR]