Thomas S. Rau received the Diploma degree in mechatronics and doctoral degree (Dr.-Ing.) in biomedical engineering from the Technical University Ilmenau, Germany, in 2005 and 2014, respectively. In 2006, he joined the Department of Otolaryngology, Hannover Medical School as a research assistant in the research group “Computer-Aided Surgery (CAS) and Electrode Development”. Since 2016 he is the head of this group. His current research interests include image-guided surgery, microstereotactic frames, insertion force measurement and automation in cochlear implantation surgery as well as improving the electrode array of the cochlear implant system with special focus on the intracochlear implant-tissue interaction and self-bending mechanisms.
Is the shape memory effect a feasible mechanism to enable intracochlear position shift?
Thomas S. Rau, Tim Ehmann, M. Geraldine Zuniga, Thomas Lenarz
A straight cochlear implant electrode array (EA) featuring an intrinsic mechanism to adopt a perimodiolar position after insertion may combine the best of two worlds: while straight electrodes show lower rates of tip fold-over and scalar translocation, a position shift toward the modiolus will provide benefits due to the increased proximity to the spiral ganglion neurons. Utilizing the shape memory effect (SME) provided by special materials (e.g. Nitinol) is being discussed since the late 1990’s but clinical use is still lacking.
Material and Methods
In an iterative development process, an EA with an embedded Nitinol wire was developed. To test the SME concept, a “passive” activation was planned, i.e. solely by body temperature without artificial heat generation inside the EA. Considering premature curling as the main challenge for the insertion, different prototypes were tested in an artificial cochlea model while simulating local hypothermia.
We are presenting an EA prototype featuring the SME which can be inserted without premature curling. This became possible because of the minute adjustments of the material properties of the Nitinol wire in combination with local hypothermia as a suitable cooling strategy.
We present evidence that the SME triggered solely by body temperature is a feasible mechanism to enable a post-insertion position shift toward the modiolus.