Human posterior cricoarytenoid muscle compartments. Anatomy and mechanics.

OBJECTIVE

To document the presence and functional significance of distinct anatomical compartments in the human posterior cricoarytenoid muscle (PCA).

DESIGN

Anatomic study of human cadaver larynges.

SUBJECTS

Seventeen fresh larynges, harvested at autopsy from 8 men and 9 women, with no history of laryngeal disease or surgery.

INTERVENTIONS

Twenty-three PCA muscles from 12 human cadaver larynges were dissected. Computed tomographic scanning and rigid body mechanical analysis were used to compute 3-dimensional motion with simulated individual contraction of PCA compartments in 5 fresh larynges.

RESULTS

Discrete medial and lateral bellies with different orientations of muscle fibers were found in every muscle. The 2 bellies insert on opposing aspects of the muscular process of the arytenoid. Very little linear translation was effected by either muscle. The axes of rotation attributable to the 2 bellies differed significantly, with the medial belly effecting rotation about a more vertical axis. The axis of rotation for the lateral muscle belly was nearer the anterior posterior axis than that of the medial belly.

CONCLUSIONS

These data indicate that PCA muscle contraction results in arytenoid rotation about a variable oblique axis without significant lateral gliding. There are 2 bellies within the human PCA muscle with differing mechanical actions on the cricoarytenoid joint.