甲状軟骨形成術における声帯前交連の位置と甲状軟骨の関係

Precise localization of the anterior commissure (AC) as projected onto the external thyroid cartilage is critical during chondrolaryngoplasty to prevent inadvertent vocal fold (VF) detachment. This study aims to describe intraoperative methods for identifying the level of AC and to determine a safe inferior limit of thyroid cartilage excision during chondrolaryngoplasty.

Anterior thyroid cartilage length and anatomical AC position was measured in 105 transgender women who underwent feminization laryngoplasty [FemLar] between April 2022 and March 2025. In this retrospective review, 35/105 patients had a prior chondrolaryngoplasty performed elsewhere. The remaining 70 underwent FemLar for combined voice feminization and neck profile improvement.

The AC was attached internally most commonly at 8 mm from the inferior thyroid border in (36%, 38/105), followed by 10 mm (25%, 26/105) and 9 mm (22%, 23/105). Among 70 patients without prior surgery, the AC was at the midpoint in 30%, 1 and 2 mm below midpoint in 43% and 19% respectively and 1 mm and 2 mm above the midpoint in 3% and 4% respectively. Vocal fold detachment was verified in 29% of patients with prior chondrolaryngoplasty where the cartilage had been removed to or inferior to the level of AC.

The location of AC varies within a range of 2 mm above and below the midpoint or 6-10 mm from the inferior thyroid cartilage border. If not localizing the AC with endoscopy, a 2-3 mm safety margin above the estimated AC level should be considered during chondrolaryngoplasty.