Novel Anatomic Characteristics of the Laryngeal Framework: A Computed Tomography Evaluation.

ABSTRACT

OBJECTIVE: The thyroid cartilage (TC) in men has a more prominent thyroid notch and a narrower interlaminae angle (ILA) as compared with women. Anatomy textbooks classically stipulate that the ILA is 90° in men and 120° in women. Our observation, based on thyroid chondroplasty operations, of a much narrower angle led to the current investigation. STUDY DESIGN: Cohort imaging study. SETTING: Tertiary academic referral center. SUBJECTS AND METHODS: Computed tomography angiography neck images of adult patients were studied. The ILA was measured on 2 axial planes at the level of the vocal processes (and the upper portion of thyroarytenoid muscles) and 5 mm superior and parallel to the former. The anterior projection of the TC and the vertical dimensions of the midline cricothyroid membrane (CTM) were also measured. RESULTS: A total of 126 patients were included in the study. The average ILAs were 63.5°±20.6° and 93.3°±16.6° for men and women, respectively (P < 10(-14)), and were significantly narrower at the upper level in comparison with the vocal process level (P < 10(-7) for men, P = .004 for women). The anterior projection of the TC in men was more prominent as compared with women (P = .0003) and significantly correlated with the ILA (P = .0159). The length of the midline CTM was 11.1±2.3 mm in men and 10.3±1.7 mm in women (P = .0355). CONCLUSIONS: The ILA is narrower than that reported in the classic anatomy textbooks. In male patients, the upper part of the TC becomes narrower and projects anteriorly like a "jug's spout." The mean vertical dimension of the midline CTM was 10 to 11 mm.