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S26 Active middle ear implants II
Alternative inner ear stimulation with the Cochlear™ Codacs™ Direct Acoustic Cochlear Implant
Großöhmichen M. , Salcher R.B. , Schwab B. , Schuon R.A. , Lenarz T. , Maier H.
Hannover Medical School, Department of Otolaryngology, Hannover, Germany
Background: The working principle of the Cochlear™ Codacs™ Direct Acoustic Cochlear Implant System is the
stimulation of the inner ear via a standard K-Piston through the stapes footplate (SFP) after a stapedotomy.
Alternatively the stapes head (SH) or SFP can be used as possible stimulation sides. Here the Codacs actuator
efficiency in these alternative applications was investigated.
Methods: All experiments were performed with the Codacs actuator in cadaveric human temporal bones in
analogy to ASTM standard F2504-05. Prior to the standard K-Piston application (N = 9), the SH was stimulated
with a “Bell prosthesis” (N = 9) and the SFP with an “Omega connector” (N = 8). The axial coupling force in the
alternative coupling conditions was adjusted to ~ 5 mN, whereas the K-Piston application uses ~ 0 mN static
loading force. The displacement of the round window (RW) membrane served as reference for output
determination and was measured with a Laser Doppler Velocimeter for the three conditions.
Results: In all conditions, the average outputs had a plateau range below ~ 2 kHz (≤ actuator resonance
frequency) and a drop-off at higher frequencies (Figure 1). The outputs of both alternative stimulation modes
using the SH and the SFP as input site were similar and both significantly more efficient than the K-Piston
application. Calculated as equivalent sound pressure output levels [eq. dB SPL] using the RW displacement as
reference, the mean (0.5, 1, 2, 3, 4 kHz) outputs at 1 V RMS input voltage were 133 dB SPL (Bell), 134 dB SPL
(Omega) and 115 dB SPL (K-Piston).
Conclusions: Both investigated alternative coupling conditions provided significantly higher output than the KPiston standard application, when the stimulation was performed at controlled axial force. Based on the results,
the Codacs actuator generates sufficient output at alternative stimulation sites, provided that experimental
conditions are adapted to the “real” situation, including geometric adaptations and providing a constant axial
coupling force.
Funding: This project was funded by Cochlear Ltd.