Vibrant Soundbridge Round Window Vibroplasty: Safety, Coupling Efficiency, and Speech Outcome of the Most Common...

Introduction: The floating mass transducer (FMT) of the Vibrant Soundbridge (VSB) is successfully used for reverse stimulation of the round window membrane (RWM) since 2005, enabling the treatment of conductive and mixed hearing loss. The FMT can be placed directly to the RWM or indirectly by using an interposed material such as fascia and Tutopatch, or a coupler, e.g., the round window coupler (RWC), the round window soft (RWS) coupler, or the custom-made Hannover coupler version 2 (HCV2). The aim of the study was to retrospectively evaluate the long-term outcome of the most common VSB round window (RW) coupling modalities in our clinic with regard to (1) safety and preservation of residual hearing, (2) coupling efficiency (C_eff), and (3) speech outcome.

A total of 111 RW vibroplasties, a surgical procedure including the implantation of the VSB, in 102 ears (95 patients) performed at the Hannover Medical School between 2006 and 2021 were analyzed. Seventy-nine RW vibroplasties in ears with available preoperative bone conduction pure tone average (BC PTA₄) were included in the safety analysis, focusing on adverse events (AEs). Furthermore, the audiological outcomes were evaluated in 56 ears (52 patients, 4 bilateral implanted) preoperatively, at initial activation (6-8 weeks), 2 years, and 5 years, including BC PTA₄ (at 0.5, 1, 2, 4 kHz), C_eff (in situ measurement - BC PTA₄), effective gain (BC PTA₄ - sound field threshold), and monosyllable word recognition score (WRS; Freiburg monosyllable test at 65 dB SPL).

The safety analysis showed a total mean AE rate of 29.1%. A statistically significant decline over time in BC PTA₄ was found in groups RWS and HCV2 by 7.6 dB and 8.8 dB (paired t test, p = 0.022 and p ≤ 0.001, respectively), at 2 years. The WRS improved over time in all groups, resulting in an overall mean score of 81.1% in the range 70.0% to 90.8% at 2 years, with a statistically significant improvement between IA and 2 years and the best mean WRS of 90.8% at 2 years in group HCV2 (paired t test, p ≤ 0.001). While the C_eff was stable and below 25 dB at all time points in most groups, it improved statistically significantly in group RWC by a total of 9.9 dB between IA and 5 years to 16.8 dB (paired t test, p ≤ 0.001).

The RW vibroplasty is a safe surgery, though complex and challenging. All investigated coupling modalities provided effective treatment for conductive and mixed hearing loss. Patients in group RWC and HCV2 tended to perform noticeably better in terms of aided speech understanding and C_eff than those in the other groups.