Evaluation of Coupling Efficiency in Round Window Vibroplasty With a New Handheld Probe

A handheld measuring probe was developed that analyzes the vibration characteristics of the stapes footplate after backward stimulation of the cochlea in round window vibroplasty. In temporal bone experiments, the measuring accuracy of the probe was tested.

In round window vibroplasty, the effectiveness of the transmitted vibrations into the inner ear is provided with limited visual and tactile information. Currently, there is no objective measuring tool available.

In five unfixed temporal bones, a floating mass transducer was coupled to the round window membrane. During the excitation with different voltage levels (0, 5, 25, 100, 300 mV root mean square) corresponding to 0, 80, 94, 106, and 116 dB equivalent ear canal sound pressure respectively, the deflections of the footplate were recorded in parallel by laser Doppler vibrometry and the measuring probe.

The probe allowed for differentiation of the coupling efficiency. The measured footplate vibrations from the excitation levels of 106 dB (and 116 dB) were statistically significant compared with the testing without excitation. The footplate deflections determined in parallel by laser Doppler vibrometry showed comparable results.

In principal, the newly developed measuring probe allows for measuring the quality of retrograde cochlear excitation in a round window vibroplasty by detecting footplate vibrations. Further developments are directed for its application in clinical, intraoperative procedures.