Investigation of the coupling quality of partial prostheses at the stapes head

The success of partial ossicular chain reconstructions in cases of conductive hearing loss depends on many factors. One important factor is the coupling between the prosthesis and the stapes head, which has not been explicitly investigated previously. Prostheses with different forms of attachment to the stapes are available, namely clip and bell type PORP. We present a standardized method to assess the quality of the prosthesis-stapes connection. The coupling quality of different prostheses is compared using measurements on a specimen model.

This study delineated six groups categorized by prosthesis types, employing 12 temporal bones to create a reconstructed ossicular chain model. The model comprised stapes and inner ear of the specimen, various prostheses and a standardized mechanical excitation at the prosthesis head. Multiple-points measurements were conducted using laser Doppler vibrometry along the sound transfer direction. This methodology enabled the assessment of vibrational magnitude loss and sound distortion from the prosthesis to the stapes.

All six groups showed uniformly good sound transmission, with low magnitude loss of < 10 dB and very low total harmonic distortion of < 1%.

The proposed measurement method enables an explicit and comparable examination of the prosthesis coupling to the stapes head. While the coupling mechanism may be important in terms of handling, stability or long-term robustness of the reconstruction, our results show no relevant differences between types in terms of sound transmission.