Dimensions of the cricoid cartilage and the trachea

Important dimensions of the cricoid cartilage and trachea have been studied. Knowledge of size, variations in size, and configuration of these structures is important when tracheal intubation, stenting, endoscopy, and transplantation are to be performed.

In 34 male and 27 female adult human specimens, 1,861 measurements of the cricoid cartilage and trachea were performed.

The smallest dimension was found in the frontal plane. The mean inner diameter of the cricoid in this plane with mucous membrane in situ was in women 11.6 mm (range, 8.9-17.0 mm) and in men 15.0 mm (range, 11.0-21.5 mm). The configuration varied more than expected. For example, the angle between the longitudinal axes of the cricoarytenoid joint facets ranged from 42 degrees to 74 degrees in women and from 37 degrees to 75 degrees in men. The mean distance between these joint facets was 10.3 mm (range, 7.4-13.0 mm) in women and 12.6 mm (range, 8.0-18.2 mm) in men. The cross-section of the trachea varied much in configuration, the smallest frontal diameter being as little as 9.9 mm in women and 12 mm in men.

In some women the inner diameter of the cricoid ring does not permit passage of a standard-size (7 mm, internal diameter [ID]) tracheal tube or a standard-size rigid endoscope through the larynx without mucosal damage. The small distance between the cricoarytenoid joints in many women and some men is the basis for of the clinical observation that women, especially, receive pressure necroses at the medial sides of the arytenoid cartilages attributable to tracheal intubation with standard tubes. The large difference in almost all sizes and shapes of the cricoid cartilage and trachea makes it impossible to standardize the rigid stents used in these organs. When transplantation to the larynx is planned, this variation of the anatomy must be considered.