Investigation of Different Coupler Designs for Round Window Cochlea Stimulation

Introduction Established coupler designs used in round window stimulation through the Floating Mass Transducer (FMT) of the Vibrant Soundbridge (VSB) present rounded contact surfaces to the round window membrane with varying performance. Flat contact surfaces adapted to round window membrane anatomy could have positive effects on coupling quality.

Materials and methods The FMT of the MED-EL VSB was inserted into the drilled round window niche of five human temporal bones under 5mN pretension using three different couplers: (1) MED-EL RW-Soft Coupler, (2) cartilage, (3) a 3-D printed prototype. The prototype consists of elastic polymer in the form of a slanted cylinder. The flat contact surface was modelled after the average shape of the round window membrane. Footplate volume velocities were measured via Laser-Doppler-Vibrometry and used for comparison of coupling qualities.

Results Volume velocities using the prototype compared to RW-Soft Coupler are lower by an average of –5,3 dB ± 7,8 dB (p=0,501) (mean ± standard deviation; p-value) in the range of 100–1500 Hz, while performing better by +7,1 dB ± 7,3 dB (p=0,382) in the range of 1500–10000 Hz. Volume velocities using cartilage are not significantly different from that using the RW-Soft Coupler (+2,6 dB ± 3,9 dB; p=0,748) in the entire frequency range.

Conclusion  Coupling quality with the prototype is worse below 1500 Hz and better above. The prototype represents a potential effective alternative to the RW-Soft Coupler. Further optimization steps are necessary to ensure optimal and reliable coupling.

Publication History

Article published online:
12 May 2023