Effects of Skin Thickness on Cochlear Input Signal Using Transcutaneous Bone Conduction Implants

Area of Science:

• Audiology and Otolaryngology
• Biomedical Engineering
• Medical Device Technology

Background:

• Transcutaneous bone conduction implants (TCBCIs) are emerging alternatives to direct-connect bone conduction implants (DCBCIs).
• Clinical data suggest TCBCIs may have higher high-frequency thresholds than DCBCIs.
• The impact of skin thickness on the cochlear input signal with TCBCIs remains under-investigated.

Purpose of the Study:

• To quantify intracochlear sound pressures and ossicle velocities with magnet-based TCBCIs.
• To compare TCBCI performance against DCBCIs.
• To evaluate the effect of varying soft tissue flap thicknesses on the cochlear input signal.

Main Methods:

• Seven cadaveric heads were used to measure intracochlear sound pressures and stapes/round window/promontory velocities.
• Implant fixtures were connected to either DCBCI or TCBCI systems.
• Soft tissue flaps of varying thicknesses (0-9 mm) were placed between the implant and sound processor to assess signal transmission.

Main Results:

• Direct-connect bone conduction implants (DCBCIs) yielded the highest response magnitudes.
• Transcutaneous bone conduction implants (TCBCIs) demonstrated frequency-dependent reductions in sound pressure and velocity with increasing soft tissue thickness.
• Increased flap thickness led to a steeper phase slope at higher frequencies, indicating a longer group delay.

Conclusions:

• Optimizing the cochlear input signal necessitates careful soft tissue management in TCBCI recipients.
• Patient selection for TCBCIs should consider the impact of skin thickness on cochlear response magnitudes.
• Understanding these effects is vital for maximizing the efficacy of TCBCI devices.