Journal Club: Retrospective study of Soundbridge round window vibroplasty implanted between 2006-2021.

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Today's journal article

Knölke N, Knölke N, Busch S, Lenarz T, Maier H. Vibrant Soundbridge Round Window Vibroplasty: Safety, Coupling Efficiency, and Speech Outcome of the Most Common Coupling Modalities. 

Why I picked this article

The Vibrant Soundbridge is an active middle ear implant technology developed by MED-EL, Gmb, Austria. The Vibrant Soundbridge is designed to drive sound through a "floating mass transducer". When the floating mass transducer is coupled to a part of the cochlea,  it enables “reverse stimulation” of the cochlea. The idea is to use this concept to restore hearing in patients with conductive or mixed hearing loss when other treatments, such as ossicular reconstruction, are not feasible. 

The floating mass transducer of the Vibrant Soundbridge can be targeted to various sites such as on the stapes, oval window, or round window. Although the variability of the round window can pose a challenge, targetting of the round window has been demonstrated to be feasible by previous studies. 

This research is a clinical study that systematically compared several coupling techniques used in clinical practice and reported long-term outcomes up to five years post-implantation, focusing on the safety, patient's hearing, and speech perception. Understanding which coupling options preserve residual hearing and maintain speech performance over time is critical for improving surgical and audiological results using this technology. 

Some of the research findings

Model and cohort:
  • Retrospective analysis of 111 round window vibroplasties performed at Hannover Medical School between 2006–2021 (102 ears, 95 patients)
  • Audiological follow-up at activation (6–8 weeks), 2 years, and 5 years post-surgery.
  • Coupling methods were:
    • direct or indirect contact between FMT and RWM
    • via Fascia 
    • Toutopatch
    • round window coupler (RWC)
    • round window soft (RWS), or 
    • Hannover coupler version 2 (HCV2).
Safety, residual hearing and speech recognition:
  • Among 79 ears with preoperative bone conduction data, the overall adverse event rate was 29.1%.
  • Mean bone-conduction pure-tone average (BC PTA4; 0.5~4 kHz) declined slightly in RWS (-7.6 dB, p = 0.022) and HCV2 (-8.8 dB, p ≤ 0.001) groups at 2 years.
  • Word recognition score (Freiburg monosyllable test, 65 dB SPL) improved significantly across all groups.
  • Overall mean WRS = 81.1% at 2 years, highest in HCV2 = 90.8% (p ≤ 0.001 vs. activation).
  • Coupling efficiency "Ceff" (in-situ – BC PTA4) remained <25 dB in most groups.
  • In the RWC group, Ceff improved significantly by +9.9 dB between activation and 5 years, reaching 16.8 dB (p ≤ 0.001).

Haruna's takeaway

I found this article after searching for research related to the round window. I had not heard much about this technology before. Effective coupling of the device through the round window or other location sounds challenging, given that everyone's cochlear geometry can differ slightly, and the middle ear can also be quite variable. I'm interested to see more about how it works, so I might go back on the trail for publications related to this. 

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This is Haruna's 57/100 of the 100-day challenge to post a science blog article every day! I love inner ear biology & cochlear physiology.