Introduction The likeliness of intracochlear trauma is correlated to forces acting during the
insertion of cochlear implant (CI) electrode arrays (EA). Most research on parameters
affecting these forces focuses on artificial cochlea models (ACM), which are transparent
and thus allow easy control of the insertion process. However, such experimental results
need to be validated using ex vivo specimens. These provide more realistic tissue
properties, but require methods to control the individual insertion trajectory and
for intracochlear imaging due to their opaqueness.
Material and Methods We devised design requirements for a test bench from the target application, aiming
to allow for force measurement, insertion trajectory adjustability, controlling of
insertion speed and exchangeable types of EAs. The test bench was validated by inserting
EAs into porcine specimens and performing CBCT scans of the inserted EAs within the
specimens.
Results The test bench utilizes an image-guided method to accurately position and align the
specimen. Furthermore, a two-axis goniometer is integrated to allow adjustments of
the insertion trajectory. A precision linear actuator performs the insertion of variable
EA types. The validation experiments showed that insertions from different trajectories
are feasible and precisely adjustable. The CBCT scans were undistorted by artefacts
from the test bench and enabled analysis of the intracochlear EA position.
Discussion and Conclusion As a singular CBCT scan can only capture a static state, continuous fluoroscopy could
provide additional information. The precise investigation of parameters influencing
insertion forces in specimens rather than ACMs can help to optimize surgical techniques
with respect to hearing preservation for CI recipients.
German Federal Ministry of Education and Research, Project: OtoTrak, Grant no.: 13GW0367B;
Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under Germany’s
Excellence Strategy, Cluster of Excellence EXC 2177/ “Hearing4all”, Project ID: 390895286
