A‐P positioning of medialization thyroplasty in an excised larynx model

Abstract

Hypothesis Posterior positioning of medialization thyroplasty provides the best acoustic and aerodynamic outcomes. Study Design Ex vivo excised canine larynx. Methods Unilateral thyroplasty windows were cut in the thyroid cartilages of 10 excised canine larynges. Each larynx was mounted on an artificial lung and the vocal fold opposite the thyroid window was adducted by medializing its arytenoid cartilage. Then, medialization thyroplasty was simulated with a probe placed anterior, central, and posterior in the thyroid window. The glottal area, airway reduction, medialization force, phonation threshold pressure and flow, aerodynamic power, intensity, efficiency, jitter, shimmer, and signal-to-noise ratio (SNR) were measured at each medialization position. Results Posterior medialization probe placement minimized the glottal area, provided the best voice as determined by perturbation measures and SNR, reduced the work of phonation, and increased efficiency. Anterior and middle probe placement minimized the work of phonation but provided only modest gains in sound quality and decreased sound intensity. Medializing the vocal fold with posterior probe placement required twice as much force as central and anterior probe placement. Conclusions The results suggest that posterior medialization provides the greatest improvement in acoustic parameters and efficiency in patients who can tolerate the airway reduction. Middle and anterior medialization can decrease work of phonation, but in this experiment objective improvement in sound quality was limited. Subtle changes in displacement shim contour, especially in middle and anterior locations, have a substantial impact on voice outcome, affirming the value of intraoperative voice assessment.

Multiparameter comparison of injection laryngoplasty, medialization laryngoplasty, and arytenoid adduction in an excised larynx model

“…Doing so in a controlled excised larynx setting with easily repeatable conditions decreased potential variability that may arise when conducting research on human subjects. Both ex vivo and in vivo canine larynges have been used previously to study interventions for vocal fold paralysis 35, 36, 38. There are several anatomical differences between the human and canine larynx.…”

“…2A, Fig. 3A) allowed for adduction of one vocal fold, simulating UVFP in the unadducted vocal fold, as in Czerwonka et al36 and Inagi et al37 Methodological consistency was maintained by always adducting the contralateral arytenoid (simulated normal) to the midline. Micrometer positioning remained across sets of trials within the same larynx.…”

Multiparameter Analysis of Titanium Vocal Fold Medializing Implant in an Excised Larynx Model

“…Through the insertion of one 3-pronged micrometer in the arytenoid cartilage ipsilateral to the dissected thyroid cartilage (Figure 2A), only one vocal fold was adducted, simulating unilateral VFP with the unadducted vocal fold, as in Czerwonka et al . (35). The level of the adducted vocal fold was adjusted before the first trial by moving the moicrometer in the superior and inferior directions until it was in the same plane as the unadducted vocal fold.…”

“…Additionally, the canine model has recently been used to model unilateral vocal fold paralysis by Czerwonka et al . (35). By taking measurements of these parameters in a controlled environment, the potential human variability that may be present in clinical studies was eliminated.…”

Optimal arytenoid adduction based on quantitative real‐time voice analysis

“…11 A metal pull clamp was used to stabilize the trachea to a tube connected to a pseudolung which served as a constant pressure source. Insertion of one 3-pronged micrometer in the arytenoid cartilage ipsilateral to the dissected thyroid cartilage allowed for adduction of one vocal fold, simulating UVFP in the unadducted vocal fold as in Czerwonka et al, 13 Witt et al, 14 and Hoffman et al 10 An additional 3-pronged micrometer was placed against the contralateral thyroid lamina for stability without providing vocal fold adduction. Methodological consistency was maintained by always adducting the contralateral arytenoid (simulated normal) to the midline.…”