Coupling of an active middle-ear implant to the long process of the incus using an elastic clip attachment

Abstract

The active middle-ear implant Vibrant Soundbridge© (VSB) is used to treat mild-to-severe sensorineural hearing losses. The standard surgical approach for incus vibroplasty is a mastoidectomy and a posterior tympanotomy, crimping the Floating Mass Transducer (FMT) to the long process of the incus (LPI) (standard crimped application). However, tight crimping increases the risk of necrosis of the LPI, resulting in reduction of energy transfer and loss of amplification.The aim of this study was to develop a new coupling device for the LPI, that does not require crimping, and to test its vibrational transfer properties in temporal-bone preparations.An extended antrotomy and a posterior tympanotomy were performed in ten fresh human temporal bones. As a control for normal middle-ear function, the tympanic membrane was stimulated acoustically and the vibration of the stapes footplate was measured by laser Doppler vibrometry (LDV). FMT-induced vibration responses of the stapes were then measured for the standard crimped application at the LPI and for the newly designed elastic long process coupler (LP coupler). For the LP coupler, velocity-amplitude responses in temporal-bone preparations showed increased mean amplitudes at around 1 kHz (∼10 dB) and a reduction between 1.8 and 6 kHz (13 dB on average for 2 ≤ f ≤ 5 kHz).In conclusion, attachment of the FMT to the LPI with the LP coupler leads to generally good mechanical and functional coupling in temporal-bone preparations with a notable disadvantage between 1.8 and 6 kHz. Due to its elastic clip attachment it is expected that the LP coupler will reduce the risk of necrosis of the incus long process, which has to been shown in further studies. Clinical results of the LP coupler are pending.