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Influence of Bonebridge screw fixation on the cochlear activation
Irina Wils1, Tobias Mair1, Ivo Dobrev1
1Department of Otorhinolaryngology, Head and Neck Surgery, University Hospital Zurich, University of Zurich, Switzerland.
Hearing Research
|November 21, 2025
Summary
Secure screw fixation for Bonebridge implants is crucial for optimal hearing. Loosening screws significantly reduces cochlear activation and audio quality, impacting the auditory benefit for bone conduction hearing implant recipients.
Area of Science:
- Biomedical Engineering
- Otolaryngology
- Biomechanics
Background:
- Effective mechanical coupling of bone conduction implants to the skull is vital for auditory stimulation.
- The Bonebridge implant uses cortical screws for fixation, but the impact of screw attachment quality on cochlear activation is not fully understood.
Purpose of the Study:
- To investigate the biomechanical consequences of varying screw fixation quality on cochlear activation and audio fidelity in Bonebridge implants.
Main Methods:
- Evaluated five fixation conditions (both screws fixed, superior/inferior screw fixed, skin tension, loose screws) in five Bonebridge implantations.
- Measured intracochlear pressure changes and utilized laser Doppler vibrometry for 3D velocity measurements on the implant, skull, and cochlear promontory.
Main Results:
- Reduced screw fixation, particularly the superior screw, led to significant decreases (5-25 dB above 3 kHz) in intracochlear pressure, promontory, and skull motion.
- Total harmonic distortion increased from 2% to 18% as screw fixation loosened, indicating worsened audio quality.
Conclusions:
- Suboptimal screw fixation weakens mechanical coupling, diminishing cochlear activation and audio quality for Bonebridge recipients.
- A firm attachment of both cortical screws during surgery is recommended to maximize auditory benefit.
