Development of a test bench for insertion force measurements with precise orientation of specimen using a stereo optical navigation system

During development and evaluation of new cochlear implant electrode arrays (EAs) and their insertion technique, insertions are conducted in human temporal bone samples including insertion force measurements, as automated insertions provide the necessary standardization. The EA has to be positioned in a highly accurate manner to the basal turn of the cochlea and the force sensor to achieve valuable measurements. A new test bench and corresponding software was developed to fit into the very small measuring volume of the highly accurate stereo optical measuring system (CamBar B1, Axios3D).

First, the specimen was glued into a small pot, mounted into a half-shell and scanned. The insertion axis within the basal turn of the cochlea and the direction of its rotation were determined based on that scan. Registration spheres on the half-shell were touched with a pointertool to transfer the plan onto the real position of the specimen. Retro-reflective markers were attached to both, pointertool and half-shell, to ensure traceability by the stereo camera. The tracked location of insertion axis and specimen were used by the software to show the position deviation between specimen and plan. To adjust the rotational degrees of freedom, the specimen's half-shell can be manually moved within another bigger half-shell through levers. After adjustment, the half-shell with the specimen was glued onto a plate under which the force sensor (KD24 s, ME-Messsysteme) was mounted.

The developed test bench provides easy and fast handling, as well as a favourable pressure relief for the force sensor during adjustment of the specimen. Further experiments serve for quantitative determination of the achievable accuracy.

Publication History

Publication Date:
23 April 2019 (online)