Angles of needle insertion for true vocal fold access via the thyrohyoid and cricothyroid membranes of the Larynx

Abstract

Objective: This study aims to provide an analysis of the cricothyroid and thyrohyoid membrane approaches for laryngeal injections in cadaveric vocal cords. The primary objective is to determine the optimal techniques, needle trajectories, and anatomical landmarks for accessing different regions of the vocal cords percutaneously. Materials and methods: The study was conducted on 23 adult cadavers, consisting of 8 females and 15 males. The cadaveric larynges were mounted vertically to ensure proper anatomical positioning. Both the cricothyroid and thyrohyoid membrane approaches were utilized for reaching the vocal cords. Measurements were taken for needle trajectories, angles, and distances to determine the optimal approach for accessing the anterior, middle, and posterior thirds of the vocal cord. Results: Through the thyrohyoid membrane approach, the anterior, middle, and posterior thirds of the vocal cords can be accessed with the optimal needle insertion coronal angles of 15.46 ± 7.86°, 16.52 ± 7.15° and 18.29 ± 14.46°, and sagittal angles of 126.01 ± 9.65°, 116.67 ± 8.04° and 111.02 ± 8.86° respectively at a lateral distance of 1.92 ± 1.62 mm from the midline and 8.48 ± 2.73 mm below the vertical line. From the cricothyroid membrane approach, optimal coronal and sagittal insertion angles of the anterior, middle, and posterior thirds of the vocal cord were respectively: 158.95 ± 9.3°, 156.09 ± 11.59°, 152.4 ± 14.46°, 11.5 ± 7.77°, 21.83 ± 12.47° and 32.91 ± 12.59°. Conclusion: This analysis of the cricothyroid and thyrohyoid membrane approaches in cadaveric larynges provides valuable insights for clinicians and researchers in the field of laryngology. The findings serve as a reference for optimizing laryngeal injection techniques, enhancing patient outcomes, and minimizing complications.