Author(s)
Joseph J Pearson1
Alexandra S. Ortiz2
Sergio A Montelongo1
Charles B Simpson3
Teja Guda1
Gregory R Dion2
Affiliation(s)
1University of Texas at San Antonio; TX;2University of Texas Health Science Center at San Antonio; TX;3Brooke Army Medical Center; TX
Abstract:
Objective: In-office or operative injection laryngoplasty requires precise needle motion for accurate material placement. To date, there are no reports comparing injection forces based on needle gauge, bends, length, material type, or material temperature. We hypothesize that these factors alter injection forces and impact clinical use.Method: Swine larynges were placed in a compression testing machine. Calcium hydroxylapatite loaded syringes were affixed to a stabilizing crossbeam. Straight needles (25G 2-inch; 27G 1.25-inch; or 25cm malleable shaft 16G transoral with 24G 1cm needle tip) were inserted into the swine vocal folds to create realistic tissue resistance pressure. Compressive loading was conducted at 40mm/min until steady state force was achieved. Tests were completed with various bends in percutaneous and transoral needles and compared to carboxymethylcellulose, hyaluronic acid, and temperature effect data from our laboratory (n=3/group, Two-way ANOVA, Tukey’s post-hoc). Results: Needle size, shape, and length altered injection force mechanics. Steady state injection force was highest with the transoral needle at a mean of 44.5N compared to 26.4N and 29.8N in the 25G and 27G percutaneous needles, respectively (p<0.001). Stiffness rate (initial increasing force vs distance to initiate injection) ranged from 19.8N/mm (transoral) to 22.1N/mm (25G) to 24.6N/mm (27G), p=0.875. Adding multiple bends to the transoral needle increased stiffness rate to 25.0N/mm (p=0.035), while the 25G needle stiffness rate remained unchanged (p=0.941) with the stiffness rate decreasing in the 27G needle with increasing bends (p=0.033).Conclusion: Needle caliber, length, and bends impact steady state forces and stiffness rates during vocal fold injection.