Accessing the vocal folds by transcutaneous injection

This study tested three techniques and two approaches to access the vocal fold (VF) by transcutaneous injection using a cadaver model. The three techniques include an anatomically informed geometric technique, flexible laryngoscope (FL) guidance, and planned injection with use of computed tomography (CT). The two approaches for injection include the thyrohyoid membrane (THM) and the cricothyroid membrane (CTM). The hypothesis was that the VF is more reliably reached with techniques using technological visualization and the THM and CTM provides equal access to the VF. A geometric approach to the VF was developed and tested on seven formalin-fixed human cadavers with three injections of 0.5 ml pigmented acrylic polymer through the CTM and one through the THM. The FL-guided technique through the THM and the CTM was tested on eight formalin-fixed human cadavers and the CT informed technique on two subjects. All tests were inspected by dissection and results recorded. Pertinent measurements and characteristics of each technique were recorded. Data were analyzed for statistical significance for each approach and technique. A chi-square analysis revealed that a technology guided technique was more successful than anatomical knowledge alone (X² = 6.55, P = 0.01). The null hypothesis that the VF was equally accessed through the THM and the CTM was rejected (X² = 5.33, P = 0.02). We found that technology guided visualization is better than anatomical knowledge alone in accessing the VF. We also found that the CTM approach provides more reliable access to the entire length of the VF.