Observations on the structure and the biomechanics of the cricothyroid articulation.

We examined quantitatively the ventrodorsal gliding occurring along a sagittal plane in the cricothyroid articulation. For this purpose we used 10 fresh excised human larynges taken at autopsy. Furthermore we examined the morphology, the hydroxyproline content and collagen types of the ligaments and the articular capsule of the cricothyroid articulation. This articulation appeared to be a synovial joint, supported by two ligaments: the lateral and posterior ceratocricoid ligament and articular capsule. The ligaments and the capsule contained both type I and type III collagen fibres and they were rich in elastin fibres 1-2.5 microns in diameter. Ventrodorsal gliding was generally possible when the joint was not rotated to its extremes. The marked individual variation was not essentially affected by sex or age. The collagen content of the lateral ceratocricoid ligament showed a statistically significant negative correlation with the gliding. The articular facet of the cricoid cartilage, which was not usually well-shaped, limits the gliding. A force of +/- 1.0 N caused on the average a change of +/- 1.0 mm in the length of the vocal cord. Further research is needed to evaluate the physiological importance of these findings.