LASER DOPPLER VIBROMETRY DATA OF THE CLIP PISTON MVP

Introduction: A new malleus handle prosthesis for malleo-vestibulopexy and revision stapedotomy has been used successfully for the last two years. A CliP*-mechanism facilitates attachment to the malleus handle and a ball joint provides easy position adjustment intra-operatively. The present study was devised to determine if the ball joint of the CliP Piston MVP specially developed by Haeusler causes a loss of sound transfer from the malleus grip to the vestibulum. Methods: A middle ear model was set up, consisting of a vibrator normally used in an active implantable hearing device with a metal arm in the shape and size of an actual malleus handle, where the CliP Piston MVP was attached with the ball joint bent to an angle of about 120 degrees. The piston was dipped into the hole of a plastic container filled with water, simulating a piston hole in the footplate. A second hole served as the round window. The excitation level was more than 110 dB SPL for frequencies between 100 Hz -10000 Hz. The movements were picked up at different spots above and below the ball joint with a laser Doppler vibrometer. Vaseline simulated slight fibrosis around the piston in a second measurement. Results: The overall characteristics of sound transfer were virtually identical above and below the ball joint (difference < 3dB). Additionally, biphasic resonance peaks (5-10 dB) were observed around 1000 Hz. Discussion: Our results show very stable transfer properties over the frequency band. The resonance peaks of 5-10 dB are very probably below a level of significance in clinical pure tone audiometry. This is in accordance with our clinical practice experience. Conclusion: The ball joint of the CliP Piston MVP has good transfer characteristics with virtually no loss.