The hyoid bone – structure, functions, diseases, treatment. Fracture of the hyoid bone

Proven content

The hyoid bone is a small bone located in front of the neck. It is located between the chin and the thyroid cartilage and plays a key role in swallowing and tongue movement. The hyoid bone is unique to the human skeleton for many reasons. First, it is mobile. This means that beyond the site of attachment to the discoid cartilage (which is part of the larynx) it rises. You can even move the hyoid from side to side by gently touching either end and then alternating lightly pushing. Secondly, it has an unusual horseshoe-like shape.

Hyoid bone – structure

The hyoid bone (lat. the hyoideum) is located in front of the neck, between the jaw bone (Latin maxillary bone) and the thyroid cartilage (Latin. cartilago thyroidea) and is firmly attached to the discoid cartilage by ligaments.

It is located at the level of the third cervical vertebra, attaching indirectly with tendons to the muscles of the tongue, floor of the mouth and the front of the neck. Although it is small, it is rare for the hyoid bone to break. This is due to its location, which generally protects the bone from all but direct injuries.

The hyoid bone consists of a shaft (Latin corpus ossis hyoidei), a pair of greater horns (Latin cornua maiora) and a pair of smaller horns (Latin cornua minora). The stem is formed by a central quadrilateral wide hyoid segment. The pair of larger horns is larger and longer than the pair of smaller horns. The stem and the greater horns appear to give the hyoid bone a U shape, where it is the pair of greater horns that form the “U” tips on either side of the stem. The larger and smaller horns usually connect to the hyoid shaft through a fibrous tissue or joint proper. With age, there is a physiological progression of stiffness of the joints connecting the larger and smaller horns with the hyoid bone shaft.

The hyoid bone provides attachment space for some of the front muscles of the neck. Muscles that attach to the hyoid bone include, but are not limited to:

1. the sternophilic muscle (Latin. sternohyoid muscle);
2. the hyoid-mandibular muscle (lat. musculus mylohyoideus);
3. the scapulo-hyoid muscle (lat. musculus omohyoideus);
4. the bicuspid muscle (lat. digestive muscle).

These and other muscles in the front of the neck play a role in swallowing and can be affected in the event of neck injuries or misalignment.

The hyoid bone is above the Adam’s apple (in men) and below the tonsils and epiglottis.

While not technically part of the larynx, at the top, the two structures are very close to each other. The hyoid bone is the site of the attachment of the muscles that control the movements of the larynx.

See also: Skeletal system – structure and functions

Hyoid bone – muscles

The hyoid bone functions as an anchor for the suprahyoid muscles (lat. suprahyoid muscles), which include:

1. the bicuspid muscle (lat. digestive muscle);
2. the styloid-hyoid muscle (lat. musculus stylohyoideus);
3. the hyoid-mandibular muscle (lat. musculus mylohyoideus);
4. the hyoid-hyoid muscle (lat. musculus geniohyoideus).

And the subglass muscles (lat. infrahyoid muscles), which in turn include:

1. the sternophilic muscle (Latin. sternohyoid muscle);
2. the scapulo-hyoid muscle (lat. musculus omohyoideus);
3. the sternothyroid muscle (lat. sternothyroid muscle);
4. thyroid-hyoid muscle (lat. musculus thyrohyoideus).

The styloid ligament suspends the hyoid bone in the styloid process (Latin. styloideus process) on both sides. It is limited by ligamentous attachments located at the top of the discoid cartilage (Latin. cartilago thyroidea) through the thyroid-hyoid membrane (Latin. membrana thyrohyoidea). In addition, the hyoid bone is attached to the cervical spine at the back through the cervical fascia (lat. cervical fascia).

Suprarenal muscles

The suprahyoid muscles attach the hyoid bone to the lower jaw, tongue, and skull. The bicuspid muscle has two abdomens, a posterior and an anterior one. The anterior abdomen comes from the bipartite fossa of the mandible, while the posterior abdomen comes from the nipple notch of the temporal bone. Both bellies are connected by an intermediate tendon (Latin. having intermediary), attached to the hyoid bone.

The styloid muscle begins at the styloid process of the temporal bone and ends at the hyoid bone. It accompanies the posterior belly of the bicuspid muscle, running more superficially. It is a thin and long muscle that sits parallel to the posterior abdomen of the bicuspid muscle. The hyoid muscle stretches between the mandibular-hyoid line of the mandible and the hyoid bone.

Above is the hyoid muscle and the sublingual gland. It is a thin muscle that supports and forms the bottom of the mouth. The hyoid muscle is a narrow and short muscle that runs from the mental spine of the mandible to the hyoid bone. It is the highest located among the suprahyoid muscles, covered from below by the mylohyoid muscle.

Subglass muscles

The subglass muscles are four pairs of muscles located at the front of the neck. The sternohyoid muscle attaches to the handle of the sternum, the sternal end of the clavicle, and also between these bones, on the capsule of the sternoclavicular joint. The final attachment is on the hyoid bone. The sternum-thyroid muscle attachments are: the handle of the sternum and the first costal cartilage, as well as the oblique line of the discoid cartilage of the larynx.

The scapulo-hyoid muscle has two bellies, an upper and a lower one (lat. waiting superior, lower abdomen), separated by an intermediate tendon (Latin. having intermediary). This tendon passes posteriorly behind the sternocleidomastoid muscle. The inferior abdomen of the scapulohyoid muscle divides the lateral triangle of the neck into a scapulo-clavicular triangle and a scapulo-trapezoidal triangle. The thyroid-hyoid muscle is stretched between the oblique line of the thyroid cartilage and the hyoid bone (it attaches more to the side than the sternohyoid and scapio-hyoid muscles).

Other muscles related to the hyoid bone

The hyoid-lingual muscle (lat. hyoglossus muscle) and the middle sphincter muscle (lat. middle pharyngeal constrictor muscle; musculus hyopharyngeus) come from the hyoid bone. These muscles do not form the hyoid muscle group mentioned above.

The muscles that raise the hyoid bone

The biceps, stylohyoid, mandibiothy and hyoid muscles are responsible for lifting the hyoid bone.

Muscles that lower the hyoid bone

The sternohyoid, sternothyroid, scapiohyoid and thyroid-hyoid muscles are responsible for lowering the hyoid bone.

Hyoid bone – physiological variants

The hyoid bone shows a wide range of anatomical changes, most likely due to the asymmetry of the greater and lesser horns. Therefore, the hyoid bone is considered one of the most polymorphic parts of the human body.

The most common variety of the hyoid bone occurs in the process of stiffening the joints between the horns (greater and lesser horns) and the hyoid shaft. Human ethnicity, sex, age, height and weight contribute to morphological changes. These differences can occur unilaterally, on both sides, and there can be many variations in the same person.

Surprisingly, the absence of the hyoid bone has been reported in a male newborn who was also teratoma, had a jaw cleft, and suffered from respiratory failure. These anomalies correlate with some clinical conditions such as micrognation, Pierre Robin syndrome, and cleft lip and palate. Symptoms caused by these abnormalities include dysphagia, restriction of neck movement, and a foreign body sensation in the throat.

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Hyoid bone – functions

Since the hyoid bone acts as an attachment point for the larynx, it is involved in every function the larynx is involved in.

The larynx is the area above our trachea that helps protect us from choking on foreign bodies. Perhaps the most famous example of this is when we feel we have choked.

The larynx fulfills its main function of preventing choking by quickly closing the opening to the trachea as a foreign body tries to enter. Let us not forget that the trachea is constructed in such a way as to allow air to pass, not food. Another thing the larynx does is make sounds. The larynx is also responsible for coughing, which is part of the anti-choking function mentioned above. The larynx also serves several other purposes, including playing a role in ventilation and functioning as a sense organ.

The second function of the hyoid bone is to provide a base from which the tongue can move. Finally, the hyoid bone is involved in breathing, plays a role in keeping the airway open. This is important not only for breathing, but also for sleep and sleep disorders such as sleep apnea. Moreover, the hyoid bone maintains the position of the head due to the complex connection it establishes between the lower jaw and the cervical spine.

See also: Foreign bodies in the respiratory tract

Hyoid bone – proper development

The second pair of gill arches (Latin. pharyngeal arch) forms the minor horn and the upper part of the hyoid body, while the greater horn and the lower part of the body are derived from the third pair of gill arches. This embryonic development of the hyoid bone remains controversial. Ossification of the greater horns occurs at the end of the normal gestation period of the fetus; this is followed by ossification of the hyoid bone shaft shortly after birth.

Ultimately, ossification of smaller horns occurs in the first or second year after birth. Later in adulthood, the horns usually connect to the stem, but this may not be the case in all individuals. The hyoid bone is located in the infancy before the second and third cervical vertebrae, and eventually, in adulthood, it descends to the level of the fourth and fifth cervical vertebrae. Descent occurs simultaneously with other functionally important structures, including the epiglottis and larynx.

Hyoid bone – surgery

The hyoid bone and blood vessels

The tip of the greater horn of the hyoid bone is a significant landmark in mid-neck surgery. Carotid bifurcation (lat. carotid artery), the upper thyroid artery (lat. arteria thyroidea superior) and the lingual artery (Latin. lingual artery) are closely related to the apex of the greater corner. The tip of the greater horn is a useful landmark in locating these arteries during surgery.

The bifurcation of the carotid artery is below and behind the tip of the greater horn. The origin of the superior thyroid artery, which is the first branch of the internal carotid artery, is also below the level of the greater horn. The lingual artery is one of the structures closely related to the hyoid bone and branches from the external carotid artery above the level of the greater horn.

Hyoid bone and nerves

The sublingual nerve (lat. nervus hypoglossus) and the superior laryngeal nerve (lat. superior laryngeal nerve) are closely related to the tip of the horn of the greater hyoid bone. The tip of the greater horn helps the surgeon locate these nerves during surgery. The sublingual nerve lies higher than the tip of the horn of the greater hyoid bone. The superior laryngeal nerve divides into outer and inner branches going around the greater corner, with the outer branch deeper than the inner one.

The hyoid bone and obstructive sleep apnea syndrome

Obstructive sleep apnea is a chronic breathing disorder related to sleep. This best describes the repeated narrowing and obstruction of the pharyngeal airways during sleep. The condition is caused by the collapse of the throat, which in turn is caused by a loss of wakefulness and changes in neuromuscular control.

Several factors contribute to a sagging throat; one of these factors is the position of the hyoid bone. An imbalance between the suprahyoid and subhyoid muscles can lead to a reposition of the hyoid bone, thus affecting the airway patency and causing the pharynx to become more collapsed. Clinical symptoms include lack of refreshing sleep, daytime sleepiness, fatigue, nocturia, irritability, and morning headache. If left untreated, it can lead to many complications, including cardiovascular disease, cognitive impairment, and decreased productivity and concentration, which can lead to road accidents.

The treatment option is continuous positive airway pressure (a device used to treat sleep apnea), if it does not bring the desired results, another option is positional therapy and upper airway surgery, such as genioglossus advancement or myotomy displacement. the hyoid muscles (hyoid myotomy).

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Hyoid bone – diseases

Hyoid tendinitis

Hyoid tendinitis is also known as hyoid bone syndrome. Patients describe the condition as neck pain that worsens with swallowing and neck movement. The pain is characteristically dull or sharp, radiating to the temporal area, the posterior wall of the pharynx, the sternocleidomastoid muscle, the ear and the supraclavicular area.

Palpation shows tenderness over the greater corner of the hyoid bone. The condition is diagnosed primarily through an interview and physical examination. Imaging can be used to rule out other differential diagnoses. Medical therapy is an initial treatment. It includes topical and systemic NSAIDs, local anesthetics, and steroid injections. If medical therapy fails, surgery is the next consideration.

Calcification of the stylohyoid ligament and Eagle’s syndrome

It is important to discuss Eagle’s syndrome here in the context of calcification of the stylohyoid ligament that joins the minor horn of the hyoid bone to the tip of the styloid, causing a similar symptomatology. The literature describes cases of unilateral and bilateral styloid ligament calcification. Partial or complete calcification of the stylohyoid ligament may occur. Accidental calcification of the stylohyoid ligament also occurs in asymptomatic individuals.

There are two types of eagle syndrome. The first type is classic Eagle’s syndrome, usually seen after tonsillectomy as pharyngodynia in the tonsil fossa, sometimes associated with odynophagia, dysphagia, foreign body sensation, excessive drooling, and rarely transient voice changes. All of these symptoms occur when the tense tonsil scar tissue moves along the tip of the elongated styloid through functional movements.

The second type is the carotid artery syndrome, associated with irritation of sympathetic fibers running in the wall of the carotid arteries by an elongated styloid process. The main symptoms are eye pain, visual disturbances, hemiphasic pain, migraine headaches and, in extreme cases, fainting. Other symptoms include dizziness and earache. Therefore, patients with these symptoms may visit ENT, dental, neurosurgical or ophthalmic clinics with various ailments. Additionally, as described above, this syndrome may be the result of calcification of the stylohyoid ligament.

The differential diagnosis of this syndrome includes temporomandibular joint disease, temporal arteritis, glossopharyngeal, spheno-palatal, or trigeminal neuralgia, mastoiditis, toothache, bursitis, cluster headache, and migraine.

Imaging is critical to the diagnosis of Eagle’s syndrome as elongated styloid is the most common symptom. The styloid is considered elongated if its length is more than 5 centimeters.

Treatment options include drug and surgical treatment. Treatment includes antihistamines, neuroleptics, vasodilators, sedatives, antidepressants, steroid injections, and local anesthetics. Surgery is considered a secondary method of treatment because relapses are reported after surgery.

Hyoid bone – fractures

Fracture of the hyoid bone is extremely rare and accounts for 0,002% of all human fractures. This is because it is well protected by its position in the neck behind the lower jaw and in front of the cervical spine, and by its mobility. It is estimated that 91,3% of the hyoid bone fractures occur in men. It is commonly associated with asphyxiation and rarely occurs in isolation. A fracture of the hyoid bone can be related to a gunshot, car accident, or vomiting. In 50% of asphyxiation and 27% of suffocation, the hyoid bone fractures.

The main symptoms of a hyoid fracture are pain when a person twists their neck, trouble swallowing (dysphagia), and painful swallowing (odynophagia). Other symptoms may include cracking or tender bones, breathlessness when sticking out the tongue, shortness of breath, dysphonia, and emphysema. During laryngoscopy, wounds on the throat, bruises, swelling, and / or fragments of the hyoid bone are visible. If the hyoid bone is broken, there is a high probability of damage to the larynx, pharynx, mandible and / or the cervical spine.

Diagnosis can be made by clinical examination, laryngoscopy, and / or radiographs.

Treatment options vary from very conservative to aggressive. Conservative options include rest, observation, pain control, diet change, use of a nasopharyngeal or oropharyngeal tube, and antibiotic therapy. More aggressive options include surgical repair of the hyoid bone and / or tracheotomy. In a meta-analysis from 2012, surgical treatment was used in 10,9% of cases.

Hyoid bone – rehabilitation

The hyoid bone is small and acts as an attachment point for many of the muscles involved in swallowing, jaw movement, and breathing.

Swallowing function may be impaired due to problems such as stroke, neck injuries, or tumors of the jaw and neck. In this case, it may be helpful to work with a specialist, such as a speech therapist.

Our speech therapist can perform certain exercises to help us swallow better, and these may include getting to know the hyoid bone. Exercises for the swallowing function may include:

1. Mendelsohn’s maneuver;
2. Supraglottic swallowing;
3. Epiglottic swallowing.

A specialist can also teach us how to mobilize the hyoid bone and stretch or strengthen the muscles around it.