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Effect of Vocal Fold Implant Placement on Depth of Vibration and Vocal Output
Journal article   Peer reviewed

Effect of Vocal Fold Implant Placement on Depth of Vibration and Vocal Output

Simeon L. Smith, Ingo R. Titze, Claudio Storck and Ted Mau
The Laryngoscope, Vol.130(9), pp.2192-2198
09/2020
DOI: 10.1002/lary.28365
PMCID: PMC7382902
PMID: 31643091
url
https://www.ncbi.nlm.nih.gov/pmc/articles/7382902View
Open Access

Abstract

Objective Most type 1 thyroplasty implants and some common injectable materials are mechanically stiff. Placing them close to the supple vocal fold mucosa can potentially dampen vibration and adversely impact phonation, yet this effect has not been systematically investigated. This study aims to examine the effect of implant depth on vocal fold vibration and vocal output. Study Design Computational simulation. Methods Voice production was simulated with a fiber‐gel finite element computational model that incorporates a three‐layer vocal fold composition (superficial lamina propria, vocal ligament, thyroarytenoid muscle). Implants of various depths were simulated, with a “deeper” or more medial implant positioned closer to the vocal fold mucosa and replacing more muscle elements. Trajectories of surface and within‐tissue nodal points during vibration were produced. Outcome measures were the trajectory radii, fundamental frequency (F0), sound pressure level (SPL), and smoothed cepstral peak prominence (CPPS) as a function of implant depth. Results Amplitude of vibration at the vocal fold medial surface was reduced by an implant depth of as little as 14% of the total transverse vocal fold depth. Increase in F0 and decrease in CPPS were noted beyond 30% to 40% implant depth, and SPL decreased beyond 40% to 60% implant depth. Conclusions Commonly used implants can dampen vibration “from a distance,” ie, even without being immediately adjacent to vocal fold mucosa. Since implants are typically placed at depths examined in this study, stiff implants likely have a negative vocal impact in a subset of patients. Softer materials may be preferable, especially in bilateral medialization procedures. Level of Evidence N/A Laryngoscope, 130:2192–2198, 2020
 injection laryngoplasty silastic implant Thyroplasty vocal fold injection vocal fold paralysis

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