Three-dimensional vocal fold structural change due to implant insertion in medialization laryngoplasty

Glottal insufficiency due to vocal fold paralysis, paresis, or atrophy often leads to degraded voice quality. One of the primary surgical intervention procedures to treat glottal insufficiency is medialization laryngoplasty, in which an implant is inserted through a lateral window on the thyroid cartilage to medialize the vocal folds. While the goal of medialization is to modify the vocal fold structure to restore normal phonation, few studies have attempted to quantify such structural changes of the vocal folds. The goal of this study is to quantify the three-dimensional structural changes of the vocal folds due to implant insertion in medialization laryngoplasty, and evaluate its potential effect on voice production. Medialization laryngoplasty were performed in excised human larynges using implants of different stiffness. Magnetic resonance images of the larynges were obtained with and without implant insertion. The results showed that implant insertion significantly changed the original body-cover structure of the vocal folds, with the implant taking over the large space used to be occupied by the original body layer and the vocal fold being stretched into a thin layer wrapped around the implant. The medial-lateral dimension of the vocal fold was significantly reduced from about 4 mm to 1 mm, and the vocal fold was stretched in the coronal plane by about 70%. It is hypothesized that use of implants with stiffness comparable to that of the vocal folds is beneficial because the degree of medialization can be adjusted without much negative effects on phonation frequency, phonation threshold pressure, or vibration amplitude.