Silk-Hyaluronic Acid for Vocal Fold Augmentation: Safety Profile and Long-Term Voice Outcomes

Silk-hyaluronic acid (silk-HA) is a novel vocal fold augmentation material used in humans since July 2020. We aim to describe indications, voice outcomes, and longevity data for silk-HA injectable when used for vocal fold injection (VFI) augmentation in a large cohort of patients with longer-term follow-up than preliminary clinical studies.

Retrospective chart review of Silk-HA injections for glottic insufficiency (GI) and follow-up between July 2020 and November 2023. Subject demographics, diagnoses, volume of material injected, VHI-10 data, time from injection, need for reinjection, and complications were collected. Blinded perceptual voice analysis of randomly selected pre- and post-intervention voice samples for unilateral vocal fold paralysis patients was performed by three voice-specialized speech-language pathologists, and changes in VHI-10 determined at various time intervals up to 1year and beyond.

A total of 160 silk-HA injection procedures were performed: 59% female, with a mean age of 66± 13 (range 21-90) years. Ninety-four subjects had unilateral paralysis (58.4%); the remainder had scar, atrophy, paresis, or a combination thereof. Mean volume of silk-HA injected was 0.24± 0.14 cc. Major complications were rare, most notable for laryngoscopic evidence of hemilaryngeal edema (n = 6, 3.8%), with a readmission rate to hospital of 1.3% (n = 2). There was a statistically significant decrease in paired ΔVHI-10 and CAPE-V ratings for each of the postoperative follow-up intervals. A total of 24 (27.2%) repeat medialization procedures were recommended following silk-HA injection for unilateral paralysis.

This study demonstrates that silk-HA is a safe product for VFI augmentation, and effective injectable for the treatment of GI due to unilateral vocal fold paralysis. Based on the current data, it is reasonable to counsel patients that they should expect benefit for several months following the injection. If patients reach 1year from their injection with a stable and satisfactory outcome, the majority experience ongoing benefit without need for additional procedures, however, the final duration of clinical effect appears to be years, but it is yet to be determined.