The annular ligaments (cricotracheal and intertracheal ligaments) are the fibroelastic membranes connecting adjacent tracheal cartilaginous rings, allowing the trachea to lengthen during neck extension and shorten during neck flexion. The cricotracheal ligament connects the cricoid cartilage to the first tracheal ring. Between the subsequent tracheal rings, the fibroelastic annular ligaments (membranous portions) allow approximately 4-5 cm of tracheal elongation during neck extension.
Connect adjacent tracheal cartilages, allowing accordion-like tracheal length changes during neck movements; provide the elastic recoil that maintains tracheal patency as the intraluminal pressure falls below atmospheric during inspiration.
The annular ligaments are the structures incised in tracheotomy (between the second and third tracheal rings) and in emergency cricothyrotomy (the cricotracheal ligament or the cricothyroid ligament above). Tracheal resection for stenosis or tumour removes one or more tracheal rings including their annular ligaments; the maximum safe resection is approximately 4 rings (4-5 cm) before tension on the anastomosis exceeds safe limits. Neck flexion during tracheal anastomosis approximates the cut ends by shortening the trachea, a manoeuvre (Montgomery's technique) that allows resection of a longer tracheal segment.
Tracheal stenosis or tumour requiring resection of more than 4-5 cm (approximately 4 tracheal rings including their annular ligaments) produces anastomotic tension that exceeds the safe limit; release manoeuvres including suprahyoid laryngeal release and neck flexion during closure utilise the annular ligament elasticity to gain additional tracheal length for primary anastomosis.
