Experimental quantification of the vibrant soundbridge stapes head (SH-) coupler in human cadaveric temporal bones

The "floating mass transducer" (FMT) of the Vibrant Soundbridge was initially attached to the long process of the incus (LP). In patients missing an incus, coupling to the stapes head using the Vibroplasty CliP-coupler is used. Its main limitation is the height, leading to potential contact with the tympanic membrane. The new stapes head (SH)-coupler reduces the functional height but tilts the stimulation angle by 30°. We investigated the SH-coupler's magnitude and sound transmission quality compared to the LP-coupler.

Laser Doppler vibrometry was used on 10 cadaveric human temporal bones. Measurements of the stapes and round window motion were taken for electrical (FMT-) stimulation during application of both couplers.

At the round window, the SH-coupler showed a significantly higher gain magnitude than the LP-coupler (+ 13.4 dB over 1023-3577Hz). At low frequencies (382-500Hz), the SH-coupler gain was significantly lower (-9.9 dB). Total harmonic distortions >10% at 100 dB HLeq were recorded in 3.4% of the SH- and 7.4% of the LP-couplers above 500 Hz.

The SH-coupler's performance exceeds the LP-coupler in middle and high frequencies and is comparable to and a good alternative to the CliP-coupler, dependent on the individual anatomy.