Influence of simulated adverse events of the floating mass transducer in a mechanical middle ear model.

Abstract

Background: The Vibrant Soundbridge Implant provides multiple options for coupling the Floating Mass Transducer (FMT) to the ossicles. A parametric evaluation in clinical trials is difficult.

Aims/objectives: We studied the vibratory output of the FMT with three couplers-short process, former long process, and current long process-in an acoustic-mechanical middle ear model (AMEM) under simulated impaired coupling conditions.

Materials and methods: The AMEM, with life-sized ossicles, was tested via acoustic and electrical (FMT-) stimulation. Simulated impairments included accidental bone-contact, cable tension, and insufficient connection. Stapedial footplate vibrations were measured using Laser Doppler.

Results: Acoustic stimulation generally fulfilled the ASTM standard. With normal coupling, SP- and LP-couplers performed comparable to temporal bone data. Impaired coupling led to various effects: bone-contact reduced the transmission up to 20 dB, cable tension minimally affected SP and current LP couplers but reduced the sound transmission for the former LP coupler. Connecting the SP-coupler with only two of four titanium legs caused a single frequency dip without affecting overall magnitude, whereas off-axis LP fixation reduced the output by 15-20 dB around 1000 Hz.

Conclusions and significance: The AMEM generated reproducible, ASTM-compliant measurements. SP and current LP couplers showed resilience to potential FMT implantation impairments in most frequencies.