Alternative Fixation of an Active Middle Ear Implant at the Short Incus Process

Abstract

Introduction: Since 1996, the preferred approach for positioning the active middle-ear implant Vibrant Soundbridge© is a mastoidectomy and a posterior tympanotomy. With this device, placement of the floating mass transducer (FMT) on the long incus process is the standard method for treatment of mild-to-severe sensorineural hearing loss in the case of normal middle-ear anatomy. The aim of this study was to determine the vibrational effectiveness of FMT placement at the short incus process. Materials and Methods: An extended antrotomy and a posterior tympanotomy were performed in 5 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 and the round-window (RW) membrane were (sequentially) measured by laser Doppler vibrometry. Vibration responses for coupling of an FMT to the long incus process (standard coupling) were compared to those for coupling to the short incus process. Results: Apart from narrow frequency bands near 3 and 9 kHz for the stapes footplate and RW membrane, respectively, the velocity responses presented no significant differences between standard coupling of the FMT and coupling to the short incus process. Conclusion: Coupling the FMT to the short incus process may be a viable alternative in cases where the surgical approach is limited to an extended antrotomy. A reliable technique for attachment to the short incus process has yet to be developed.

Standardized Active Middle-Ear Implant Coupling to the Short Incus Process

“…The mean and the standard deviation of the ear canal pressure to stapes velocity transfer function were almost identical with our previous results (13,18), and the mean value falls within the mean values of previous temporal bone studies as summarized by Rosowski et al (19). One temporal bone (TB 5) showed velocity amplitudes clearly below the confidence range for intact preparations as defined by Rosowski et al (19).…”

“…For the standard FMT attachment, the curves show the same general behavior as in our previous results (13,18). The low-frequency amplitude response increases with slope of approximately 18 dB/oct, attaining a broad passband with amplitudes of 1.5 to 3 mm/s/V between 1.5 and 4 kHz.…”

“…In a recently published human temporal bone study, the fixation of the FMT at the short incus process showed slight reduction around 3 kHz, but at other frequencies, there were no significant differences compared with placement of the FMT on the long incus process (13). This alternative fixation would limit the surgical approach to an extended antrotomy accompanied by reduced surgical risks (facial nerve palsy, lesion of chorda tympani) and shortened time of surgery.…”

Comparison of Alternative Coupling Methods of the Vibrant Soundbridge Floating Mass Transducer

“…Other regularly performed attachments of the FMT are to the short incus process [Schraven et al, 2014;Mlynski et al, 2015b], the stapes head via clip vibroplasty [Beleites et al, 2011;Hüttenbrink et al 2011], the "power stapes" [Dumon, 2007;Venail et al, 2007;Kontorinis et al, 2011], a combination of the FMT on the long incus process and a stapes prosthesis (stapedotomy), and the third window stimulation into the scala tympani Yang et al, 2014].…”

Sound Transfer of Active Middle Ear Implants

“…SPL of 90 to 130 dB at 1 to 6 kHz with 3.5 V rms (rootmean-square voltage) driving voltage. Schraven and colleagues 29 attached the FMT to the short incus process and compared this position with the standard attachment at the long incus process. They observed on average about a 5-dB loss in AMEI-TF at the short incus process with standard deviation between 5 and À20 dB.…”