Cricothyroid joint anatomy as a predicting factor for success of cricoid-thyroid approximation in transwomen.

Objectives/Hypothesis: Cricoid-thyroid approximation (CTA) performed to elevate the vocal pitch in transwomen fails in about one-third of the patients. The purpose of this study was to test the feasibility of predicting the likelihood of success of CTA by preoperative determination of the crico-thyroid joint (CTJ) type using three-dimensional (3-D) images derived from high-resolution computer tomography (HRCT). Study Design: Prospective cohort study of 18 transwomen who underwent CTA at our institution. Methods: All patients had a preoperative and a postoperative HRCT of the larynx, as well as pre- and postoperative measurements of the fundamental vocal pitch (F0). Results: Three-dimensional images showed type A CTJs in 11 patients and type B or C CTJs in seven patients (see below for the definition of these types). Cricoid-thyroid approximation raised the F0 on average by 76 Hz in patients with type A CTJs and by 45 Hz in patients with type B/C CTJs. Moreover, CTA produced a vocal fold elongation of 17% in larynges with type A joint but only of 3% in larynges with type B/C joints. Conclusion: Three-dimensional images allow the differentiation of type A versus type B/C CTJs but not the distinction between type B and type C CTJs. Both vocal pitch elevation and vocal fold elongation following CTA are significantly greater in patients with type A CTJs than in patients with type B/C CTJs. Based on these preliminary results, we recommend identifying the CTJ type on 3-D images and limiting CTA to patients with type A CTJs.