Three-dimensional analysis of cricoarytenoid joint motion.

The normal motion of the cricoarytenoid joint was characterized and analyzed in this study using seven fresh cadaver larynges mounted rigidly in an external fixator apparatus after radiopaque markers were attached to laryngeal landmarks. Fluoroscopic imaging and recording was performed of top, front, and side views while the arytenoid cartilages of each larynx were manipulated through the full range of motion from adduction to abduction. Computer video capture was performed of the recordings and editing of still frames accomplished to generate three-dimensional plots of cricoarytenoid joint motion, which are shown in the manuscript. Selective and varying sequential disconnection of muscular and ligamentous structures to the arytenoid cartilage was achieved to determine their contributions to cricoarytenoid joint motion limitations and stability. The vocalis ligament, cricoarytenoid ligament, and conus elasticus are most important in controlling abduction, whereas the posterior cricoarytenoid muscle and conus elasticus are crucial in limiting adduction. The vocalis ligament prevents posterior displacement of the vocal process, while the cricoarytenoid ligament and a newly described ligament, the posterior capsular ligament, restricts anterior vocal process migration. Another ligament, the anterior capsular ligament, is described, which limits backward arytenoid cartilage tilting and lateral movement of the arytenoid cartilage on the cricoid cartilage facet. Section of the vocalis ligament with underlying conus elasticus produced reducible lateral arytenoid cartilage subluxation. Confirmation of cricoarytenoid joint facet relationships in full adduction and abduction was accomplished by fixation of the cricoarytenoid joints of one larynx in the two positions with adhesive, and subsequent exposure of the joint surfaces. Review of literature detailing human laryngeal embryological development shows that the glottis and arytenoid cartilages are formed in adduction, which explains how cricoarytenoid joint ligaments collaborate to achieve accurate vocal process approximation in adduction despite side-to-side asymmetries of the cricoarytenoid joint structures in the same larynges.