Changes in the position of the larynx relatively to the external base of the skull during some physiological movements of the head and neck

Abstract

Surgical interventions in the oropharyngeal zone and on the anatomical structures of the laryngeal entrance, especially its posterior sections, still present significant difficulties due to the difficult surgical access for performing the required volume of surgical manipulations. A large number of surgical approaches proposed for operating in this zone — transoral, various types of pharyngotomies, lateral and median mandibulotomy, resection of both jaws (bimaxillary resection) indicate the absence of a definitive solution to this surgical problem. Therefore, intraoperative physiological changes in the position of the patient’s head can contribute to improving the key parameters of surgical approaches to the oropharyngeal zone and the structures of the laryngeal entrance by increasing the working space when performing manipulations in the area of interest, and new information on the intravital positional anatomy of the larynx will become a source of development of surgery for diseases of this complex anatomical zone. Purpose of the study — to obtain information on lifetime changes in the position of the larynx relative to the external base of the skull during some physiological movements of the head and neck.
Materials and methods.
The material for the work was the data obtained as a result of anthropometric measurements and magnetic resonance imaging of the neck of 100 healthy, randomly selected individuals (55 women and 45 men) who agreed to participate in the research project. The lifetime topography of the larynx was studied in the standard anatomical position of the body, with a fully flexed (extended) neck and with head turns depending on the gender and constitutional characteristics of the subject.
Results.
When measuring in different positions the distances from the most lateral points of the upper edge of the thyroid cartilage on the right and left and from the center of the most medial point of the posterior surface of the cricoid arch to the reference point on the base of the skull (the most medial point of the foramen magnum), the following changes were revealed. During neck flexion, the distances from the most medial point of the foramen magnum edge to the most lateral points of the thyroid cartilage (on the right and left) decrease. The greatest changes were found in the group of dolichomorph males — by 26%. At the same time, during neck flexion, the distance from the reference point on the base of the skull to the center of the most medial point of the posterior surface of the cricoid cartilage arch increases in almost all examined groups. A more significant increase is observed in males with a mesomorphic body type — by 18.9%. Neck extension has different effects on the transformation of the distances from the base of the skull to the reference points on the main cartilages of the larynx. In most of our observations, the above intervals increase. The greatest increase in the length of the segment from the reference point to the center of the most medial point of the posterior surface of the cricoid cartilage arch was observed in women with a brachymorphic body type — by 10.6%. At the same time, the distance to the lateral part of the thyroid cartilage on the right in brachymorph males, on the contrary, decreases, by a maximum of 21.3%. Turning the head to the left and to the right in most of the examined groups leads to a decrease in all measured distances. When turning the head to the left, the greatest changes in the form of a decrease in the studied distances in relation to the left half of the thyroid cartilage were recorded in men with a brachymorphic body type — by 17.8%. When turning the head to the right in relation to the right half of the thyroid cartilage in the group of examined dolichomorph males, the decrease in the length of the studied distance was 25%.
Conclusion.
The intravital positional anatomy of the larynx was studied relative to the reference point on the outer surface of the base of the skull, depending on the gender and constitutional characteristics of the examined person, which significantly expands the information on the topographic anatomy of this organ and the anterior neck as a whole.