Transcutaneous injection laryngoplasty through the cricothyroid space in the sitting position: anatomical information and technique.

A variety of approaches have been introduced to perform injection laryngoplasty under local anesthesia. Among these reported methods, transcutaneous injection through the cricothyroid space offers many advantages, but it possesses some technical difficulties during access to the vocal fold. The aim of this study was to assess the anatomic references related to transcutaneous injection laryngoplasty through cricothyroid space using 3-dimensionally reconstructed computed tomography to provide guidelines and to achieve higher efficacy during the procedure. The study group consisted of 14 patients (7 male, 7 female) with unilateral vocal fold paralysis and who had undergone multi-detector array computed tomography (MDCT) between January 2004 and December 2005. Assumption was made that transcutaneous injection is approached from the surface at lower margin of the thyroid cartilage and 7 mm lateral to the midline through the cricothyroid membrane and spot at the posterior 1/3 of true vocal cord is the target for injection laryngoplasty. From the surface of the injection point to the target, a line was drawn. Its length and the angle formed between it and the approach direction of needle was measured. Based on these measurements, 15 patients (8 male, 7 female) with unilateral vocal fold paralysis received 15 trials of transcutaneous injection laryngoplasty through the cricothyroid space. The average length from the surface of the injection point (7 mm lateral to the midline) to the posterior 1/3 of the true vocal cord (target of the injection) was 15.75 mm in men and 13.91 mm in women. The average of the angle in medial direction at the surface needed to reach the target of the injection was 10.57 degrees in men and 12.71 degrees in women, and in superior direction was 47.57 degrees in men and 47.43 degrees in women. Injection laryngoplasty performed under acquired reference measurements were successful in 14 trials (93.3%) out of 15 trials in 15 patients. We suggest that knowledge of the anatomic references regarding the transcutaneous injection laryngoplasty through cricothyroid space will provide guidelines for beginners and improve the understanding of the procedure, eventually leading to easier and more precise access to the vocal cord.