Effects of Implant Stiffness, Shape, and Medialization Depth on the Acoustic Outcomes of Medialization Laryngoplasty

Abstract

Objective Medialization laryngoplasty is commonly used to treat glottic insufficiency. In this study, we investigated the effects of implant stiffness (Young’s modulus), medialization depth, and implant medial surface shape on acoustic outcomes. Study Design Basic science study using ex vivo laryngeal phonation model. Methods In an ex vivo human larynx phonation model, bilateral medialization laryngoplasties were performed with implants of varying stiffness, medial surface shape (rectangular, divergent and convergent), and varying depths of medialization. The subglottal pressure, the flow rate, and the outside sound were measured as the implant parameters were varied. Results Medialization through the use of implants generally improved the harmonic-to-noise ratio (HNR) and the number of harmonics excited in the outside sound spectra. The degree of acoustic improvement depended on the implant insertion depth, stiffness, and to a lesser degree implant shape. Varying implant insertion depth led to large variations in phonation for stiff implants, but had much smaller effects for soft implants. Conclusions Implants with stiffness comparable to vocal folds provided more consistent improvement in acoustic outcomes across different implant conditions. Further investigations are required to better understand the underlying mechanisms.

Effects of thyroplasty implant stiffness on glottal shape and voice acoustics

“…Its stiffness was previously measured using an instrumented indentation system . The softer implants were made by combining the two components of a silicone liquid polymer (Ecoflex 0030; Smooth On Inc, Easton, Pennsylvania) with a silicone thinner solution at different ratios to achieve varying degrees of stiffness as previously published . The two silicone components and the thinner solution were combined at a ratio of 1:1:1 (21.6 kPa, I2), 1:1:2 (9.3 kPa, I3), and 1:1:3 (5.5 kPa, I4) (Table ).…”

“…During medialization thyroplasty, both glottal contour and vocal fold body stiffness are altered concurrently by the implant shape and stiffness. However, the roles of implant stiffness and medial surface shape in optimizing phonation remain unclear and unexplored . The difficulty in visualizing the medial surface shape and measuring tissue stiffness in vivo has contributed to a poor understanding of these parameters and their effects.…”

“…The objectives of this study are to analyze the effects of thyroplasty implants of varying stiffnesses on glottal channel shape and acoustics. We chose to study soft implants because previous studies suggested that softer implants, which more accurately reflect the stiffness of native tissue, may result in improved acoustics . Still, the mechanism by which softer implants affect acoustics remains unclear.…”

Impact of medialization laryngoplasty on dynamic nanomechanical vocal fold structure properties

“…Because phonation is a dynamic process dependent on the appropriate production of a mucosal wave propagating from the conus elasticus through the free edge of the true VF, we hypothesize that investigation regarding the viscoelastic VF properties have substantive clinical relevance. Despite intense interest in the varying viscosities of compounds used in injection medialization laryngoplasty, only one review and a single study investigated the effects of implant stiffness on dynamic outcomes following medialization . In that study, Zhang et al investigated the effect of three silicone implants of varying rigidity on acoustic function in excised human VFs …”

“…Despite intense interest in the varying viscosities of compounds used in injection medialization laryngoplasty, only one review and a single study investigated the effects of implant stiffness on dynamic outcomes following medialization . In that study, Zhang et al investigated the effect of three silicone implants of varying rigidity on acoustic function in excised human VFs …”