Resident, PGY-4 San Antonio Military Medical Center Converse, Texas
Background/Objectives: Composite vocal fold (VF) biomechanical data are lacking for commonly employed augmentation materials for recurrent laryngeal nerve (RLN) injury. We hypothesize atrophy from RLN injury decreases VF stiffness and augmentation restores native VF biomechanics.
Methods: Twenty-two Yorkshire Crossbreed swine underwent excision of 2cm of the left RLN near the cricothyroid joint. Animals were divided into observation, carboxymethylcellulose (CMC), or calcium hydroxyapatite (CaHa) augmentation groups at 14 days, then observed for 28, 56, or 84 days. Biomechanical measurements (normal force, structural stiffness, and displacement at 1.96mN) were calculated using automated microindentation mapping with a grid overlay. Fixed specimen slides were matched to measurement points. Thyroarytenoid (TA) muscle cross sectional area was quantified. Comparisons were made with two-way ANOVA with Tukey’s post hoc test.
Results: Across the VF mid-section, structural stiffness (mean, SEM) on the right (53.2mN/mm, 5.04) was greater than the left (25.5mN/mm, 5.04) after 28 days (p=0.003). After 28 days, increased left VF stiffness was seen with augmentation with CMC (64.1mN/mm, 9.9, p=0.049) and CaHa (66.7mN/mm, 8.1, p=0.020) compared to no intervention. Stiffness after CMC or CaHa augmentation was similar to uninjured VFs (p>0.84). Left TA muscle area decreased by 57.3% at 28 days and 45.5% at 84 days and did not vary between study groups.
Conclusions: VF biomechanical properties with CMC or CaHa augmentation were comparable to native VFs in this RLN injury model. No significant differences were found between augmentation materials. These data suggest VF augmentation restores native VF biomechanics and variable materials result in similar outcomes.