Explore the Pattern of Biomechanical Alterations in Vocal Fold Scar and Its Objective Quantitative Assessment Method

This research aims to discern the evolving nature of the biomechanical properties of vocal fold scarring by calculating Young's modulus for the vocal fold cover layer, the body layer, and the structure as a whole. The study also investigates the potential of diffusion tensor imaging (DTI) for determining these biomechanical characteristics quantitatively.

A total of six adult female Beagles were divided into two groups (A and B groups) for the creation of unilateral vocal fold scar models, each group containing three subjects. Five months postmodel creation, larynxes were excised and placed within a 9.4T BioSpec MRI system (Bruker, Germany) for scanning. Subsequently, the vocal folds were segregated from the larynx. In A group of Beagles, the vocal fold cover layer and body layers were separated, whereas in B group they remained intact. All samples were then subjected to cyclic tensile testing using an Instron MicroTester 5948, with Young's modulus computed for the vocal fold cover layer and body layers in the A group and for the intact vocal fold in the B group. Differences in the overall Young's modulus between the vocal fold scarred side and the healthy side were analyzed, and a Pearson correlation analysis was performed between DTI parameters and the outcomes of the stress-strain experiments.

A statistically significant discrepancy in the overall Young's modulus was identified between the scar and healthy sides of the vocal fold (P = 0.0401). The Young's modulus also displayed a significant difference between the scar and healthy sides of the vocal fold cover layer (P = 0.0241). No meaningful divergence was observed in the elastic modulus between the scar and healthy sides of the vocal fold body layer (P > 0.05). Postseparation, Young's modulus for both the cover and body layers of the scarred vocal fold were less than that of the same layers on the healthy side. However, Young's modulus of the entirety of the vocal fold on the scar side was greater than that of the whole vocal fold on the healthy side. The fractional anisotropy (FA) of the vocal fold cover layer had a significant correlation with the elastic modulus (r = 0.812, P = 0.050), as did the Tensor trace (r = -0.821, P = 0.045). The FA of the vocal fold body layer showed no significant correlation with the elastic modulus (r = -0.725, P = 0.103), while the Tensor trace demonstrated a significant correlation (r = 0.911, P = 0.012).

Biomechanical alterations in vocal fold scars demonstrate a closer association with adhesion bands, thus emphasizing the importance of adhesion band loosening for the restoration of vibratory function within vocal fold scarring. DTI emerges as a potent noninvasive quantitative instrument for assessing these biomechanical changes, as well as for quantitatively gauging the severity of vocal fold scarring.