An ex vivo porcine model of the anterior glottoplasty for voice feminization surgery

Abstract

Objective Perceived gender identity is correctly assigned when a combination of physical and vocal attributes become congruent. Several voice feminization procedures have gained popularity, but current evidence of their impact on vocal feminization is limited to case series. This study establishes an ex vivo porcine phonatory model to evaluate the ideal extent of anterior glottic web formation in relation to frequency elevation and airway patency. Methods Six fresh porcine larynges were obtained and fitted with arytenoid adduction sutures. Compressed air was passed through the larynges, and the vocal folds were adducted to induce phonation. Vocal fold length, posterior glottic width, fundamental frequency, and sound pressure intensity were measured as the vocal folds were progressively shortened as per the anterior glottic web surgical technique. Results The average fundamental frequency prior to web formation was 109.7 Hz. The maximum frequency achieved after web formation was 403.7 Hz, and the web proportions varied from 11.8% to 61.0% of the length of the membranous vocal folds. The glottic cross‐sectional area showed an expected inverse linear relationship to the length of the glottic web. Creation of an anterior glottic web caused consistent elevation of pitch, but there was a gradual plateau of effect with increased length of the web. Conclusion The ex vivo porcine larynx is demonstrated as an effective, available, and low‐cost model for further study of vocal pitch elevation surgical techniques. We demonstrate that in addition to progressively reducing the cross‐sectional area of the airway, additional benefit from increased web length is limited. Level of Evidence NA Laryngoscope, 130:E206–E212, 2020

Vocal Tradeoffs in Anterior Glottoplasty for Voice Feminization

“…7). This deviation from the string law was also noted by Rohlfing et al 20 This deviation could be explained by the fact that the vocal fold is made up of layers of tissue, each with its own material properties. The vocal fold is more aptly conceptualized as layers of strings coupled in the transverse direction (as opposed to a single string), with the coupling modeled as fibers immersed in a gel 23 .…”

“…Rohlfing et al 20 measured f o as a function of anterior glottic webbing in a porcine excised larynx phonation model. Consistent with their findings, the present data showed a general trend of increasing f o with greater extents of anterior glottic fixation.…”

“…Our examination and reanalysis of the excised larynx phonation data did not necessarily support a plateauing effect. The plateau and slight downward shape of the curve in Rohlfing et al 20 reflected the use of a second‐order polynomial fit. A linear regression fit to the aggregate data would have produced a slightly positive slope (percent f o increase per percent anterior fixation increase) that is very similar to the trend seen in the simulated human larynx data.…”

“…This discrepancy in the surgical literature begs the question whether the surgery is performed based on physical principles that govern pitch control and raises the possibility that the failure to include the ligament in anterior glottic suturing may account for some of the variability in outcomes. In all discussions of the Wendler glottoplasty, the theoretical basis of its effect on f o largely relied on treatment of the vocal fold as a vibrating string (e.g., Rohlfing et al 20 ). This simplified analogy, however, does not take into account factors such as variation of the ligament thickness in the anterior–posterior direction, bending stiffness of the ligament, and the ligament behaving more like a bundle of strings rather than a single string 11,12 .…”