The hyoid bone is an odd, medium-sized, completely symmetrical bone that is located in the anterior part of the neck. Its main characteristic is the absence of joints with any other bone. It has the shape of a semicircle with the concavity of the bone towards the back.
Its body is arcuate and has structures called horns on each side, in which its major and minor handles can be seen. Its location in the anterior and upper part of the neck - at the level of the third and fourth cervical vertebrae - relates it below to the larynx, above to the tongue, and above and anterior to the mandible.
The hyoid bone divides the neck into two regions; a suprahyoid region and an infrahyoid region. In the suprahyoid region are the digastric, stylohyoid, mylohyoid, and geniohyoid muscles, which attach to the superior portion of the hyoid bone.
In the infrahyoid region are the sternocleidohyoid, omohyoid, sternothyroid, and thyrohyoid muscles, which attach to the lower portion of the bone.
This bone develops embryologically from the second and third branchial arches, begins its chondrification in the fifth week and is completed in the fourth month of intrauterine life.
Features
By serving as an insert for 8 pairs of muscles, its function is to act as a support point for the performance of the specific functions of each muscle.
Thus, when the suprahyoid muscles contract, they lower the mandible, but for the hyoid bone to serve as support for this action, the infrahyoid muscles must fix it firmly.
This “lever” function allows mobilization of the lower jaw and both temporal bones.
Due to its position, it partially protects the larynx and serves as a support point for the tongue and larynx.
The hyoid is part of the so-called stomatognathic system, as part of the organs, tissue and structures that allow the functions of swallowing, phonation and breathing, as well as some facial expressions, such as kissing or sucking.
Related diseases
Little is known about the pathologies that could be related to the hyoid bone, since specific studies are not carried out on its anatomy in the presence of diseases that compromise swallowing, phonation and breathing.
Some authors consider it a lack of judgment not to devote the necessary attention to a bone that is part of such important processes, and they do not justify the lack of information about the conditions of the hyoid bone in the presence of some general pathologies.
However, more by chance, differences in the bony conformation of the hyoid bone have been described: from horns of different sizes to fusions of the same, even cartilaginous fusions between the thyroid cartilage and the hyoid horns.
- In some literatures the hyoid bone is spoken of as an ossification of 5 different bone structures, weaker in children and whose rigidity increases as age increases.
- In adulthood, a sychondrosis is evidenced between the lateral processes and the body of the hyoid, and in rare cases the dislocation of its parts has been evidenced by violent contractions of the neck muscles.
- An anterior dislocation of the body of the hyoid has been described, in cases in which the dislocation is produced by forces that come from the inside out (such as when swallowing a piece of food without chewing), and a posterior dislocation of the body of the hyoid, when the force comes from the outside in (as in trauma).
For this reason, ossification not only of the hyoid bone, but also of the stylohyoid ligament, has been evidenced in the elderly, which prevents the achievement of sufficient range of motion of the hyoid bone to allow swallowing and phonation.
Possible fractures
Hyoid bone fractures are exceptionally rare, about 0.002% of all fractures; This is probably due to the non-fusion of the bony parts of the hyoid bone, which gives it a certain protective power against trauma.
Isolated hyoid bone fractures have been described, as well as those associated with mandibular fractures, most of them due to traffic accidents such as winding.
Some cases of isolated hyoid bone fractures have been described in cervical hyperextension due to "whiplash syndrome" in road accidents, as well as in cardiopulmonary resuscitation or endotracheal intubation maneuvers due to inadequate cervical hyperextension.
Hyoid bone fractures have been identified in cervical trauma caused by manual strangulation, specifically in the synchondrosis between the greater horn and the body of the hyoid.
In most cases, the fracture of the hyoid bone does not represent a risk to the life of the patient and usually manifests itself clinically by acute dysphagia or acute respiratory obstruction secondary to pharyngeal hemorrhages.
Usually, the treatment for this type of isolated hyoid fractures consists of keeping the patient under observation to monitor the airway and oral tolerance, with functional limitation with a soft collar.
Pharmacologically recommended the use of corticosteroids and analgesics. The use of oral or intravenous antibiotic therapy will be individualized for each patient.
References
- Jorge Carrillo Rivera. Hyoid bone fracture. Clinical case and bibliographic review. Mexican Association of Oral and Maxillofacial Surgery, Mexican College of Oral and Maxillofacial Surgery, AC Vol 5 Num 2. May-August 2009. Págs. 68-71. Recovered from: medigraphic.com
- Jose Frank. Internal pathology. Volume XIV. Encyclopedia of Medicine, Surgery and Pharmacy. Chapter XXXII. P. 49-64 Recovered from: books.google.pt
- Edwin Ernest. Hyoid Bone Syndrome. Practical Pain Management. Vol. 6. Issue N 8. Recovered from: practicalpainmanagement.com
- Henry Gray. The Hyoid bone. Anatomy of the human Body. Recovered from: bartleby.com
- The Ruiz Liard card. Human anatomy. 4th Edition Volume I. Editorial Médica Panamericana. P. 112-113