Anterior dislocation of the mandible: causes, symptoms, diagnosis, treatment

Depending on the direction of displacement of the head of the lower jaw, dislocations are divided into anterior (the head is displaced forward) and posterior (the head is displaced backward), unilateral and bilateral. Anterior dislocation of the lower jaw occurs more often. Displacement of the head inward or outward is observed very rarely, only when dislocation is combined with a fracture of the condylar process (fracture-dislocation).

Dislocations of the lower jaw account for 1.5 to 5.7% of all dislocations; they occur more often in women aged 20 to 40 years, since the ligamentous apparatus of their joints is not strong enough, and the mandibular fossa of the temporal bone has a shallow depth.

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What causes anterior mandibular dislocation?

Depending on the frequency of occurrence, dislocations are divided into acute and habitual.

The occurrence of accidental (acute) anterior dislocations is facilitated by:

1. relaxation of the ligament-capsular apparatus;
2. deformation (hypertrophy) of articular elements;
3. changes in the shape, size and structure of the interarticular disc.

Habitual dislocations of the lower jaw are caused by some deformation of the jaws, anomalies in the closure of the teeth (for example, progenia with loss of molars).

Anterior dislocation of the lower jaw usually occurs as a result of excessive opening of the mouth during yawning, screaming, vomiting, tooth extraction, biting off a large piece of food, and is sometimes observed during gastric probing, tracheal intubation, and under anesthesia during tracheobronchoscopy.

Traumatic dislocation of the lower jaw usually occurs as a result of a blow to the lower jaw: with a sagittal blow to the lowered chin, a bilateral dislocation occurs, and with a blow from the side, a unilateral dislocation occurs on the side where the blow was delivered.

Symptoms of anterior dislocation of the lower jaw

Anterior dislocation of the lower jaw is characterized by the forward displacement of the head of the lower jaw in relation to the articular tubercle of the temporal bone, as a result of which the mouth is open (especially wide - in bilateral dislocation), the chin is displaced downwards and forwards (in bilateral dislocation), the patient experiences more or less severe pain. Speech is difficult, chewing is impossible, saliva flows from the mouth, and it is difficult, and sometimes impossible, to close the lips. In case of unilateral dislocation of the lower jaw, the chin with the central incisors and the frenulum of the lower lip is displaced to the healthy side; the mouth is half-open, it is possible to close the lips. Movements of the lower jaw are possible only downwards, and the mouth opens even more. A depression is determined in front of the tragus of the ear, and a protrusion is determined under the zygomatic arch in front of the articular tubercle of the temporal bone due to the displacement of the head of the lower jaw into the infratemporal fossa. The posterior edge of the branch of the jaw takes on an oblique direction, the angle of the jaw is brought closer to the mastoid process of the temporal bone.

A lateral X-ray of the temporomandibular joint shows that the dislocated head of the lower jaw is located in front of the articular tubercle of the temporal bone.

Outcomes and complications of anterior dislocation of the mandible

If the reduction and subsequent immobilization of the jaw are performed in a timely manner (within the next few hours after the dislocation), no complications are observed. Only in some cases is pain during chewing observed for a long time, which is eliminated by physiotherapy. If the reduction is not performed in a timely manner, the treatment of the dislocation of the lower jaw is a more difficult task.

Outcomes and complications of chronic anterior dislocation of the lower jaw

The outcomes of chronic dislocations of the lower jaw are usually favorable. If mechanotherapy is not used sufficiently after surgery, contracture of the lower jaw may develop.

Differential diagnosis of anterior dislocation of the lower jaw

Unilateral anterior dislocation of the lower jaw must be differentiated from a unilateral fracture of the lower jaw, in which there is no symptom of the chin moving forward and to the healthy side.

Bilateral anterior dislocation of the mandible must be distinguished from bilateral fracture of the condylar processes or branch of the mandible with displacement of fragments. In this case, it is recommended to consider the following seven signs:

1. In both cases the bite is open, but in case of dislocation the chin and the entire frontal group of teeth are pushed forward, and in case of fracture they are displaced backwards. In case of dislocation the patient's face is prognathic, and in case of fracture it is prognathic.
2. A patient with a fracture has a greater range of jaw movement, and the limitation of mouth opening is due to pain. In the case of a dislocation, only some additional opening of the mouth is possible, although the patient does not experience significant pain when trying to move the lower jaw.
3. In case of a fracture, the posterior edges of the branch of the lower jaw are located more vertically and distally than in case of a dislocation.
4. When palpating the upper part of the posterior edge of the jaw branch, its deformation and localized pain (at the site of the bone fracture) can be detected, which is not present in patients with dislocation.
5. In case of fracture and dislocation of the lower jaw, there is no sensation of mobility of the heads of the lower jaw when palpating them through the external auditory canals; however, in case of fracture (without dislocation of the articular head), there is no depression in front of the tragus.
6. Radiographically, in the case of a fracture not accompanied by dislocation, the head of the lower jaw is in its usual place, and in the case of dislocation, it comes out of the glenoid fossa and is located in front of the articular tubercle.
7. In case of a fracture of the lower jaw, unlike a dislocation of the lower jaw, the shadow of the fracture gap is visible on the radiograph.

The prognosis for acute dislocation is favorable, since it is easy to diagnose and treat in most patients.

Complications of acute dislocation of the lower jaw most often include relapses and habitual dislocations.

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Correction of anterior dislocation of the lower jaw

Hippocratic Method

The patient is seated on a low chair or stool with his back to the back of the chair or to the wall (so that the occipital region of the head has a solid support). In this case, the patient's lower jaw should be slightly higher (up to 10 cm) than the level of the lowered upper limbs of the doctor standing in front of the patient. Compliance with this condition allows the doctor to achieve complete relaxation of the patient's masticatory muscles with minimal effort.

Facing the patient, the doctor wraps the thumbs of both hands in gauze napkins or the ends of a towel and places them on the right and left chewing surfaces of the molars (if they are absent, on the alveolar processes); with the other four fingers he grasps the dislocated jaw from below. Gradually and carefully pressing with the thumbs downwards and with the rest upwards (on the chin), the doctor achieves fatigue and relaxation of the masticatory muscles and forcibly pushes the heads of the lower jaw downwards - slightly below the level of the articular tubercles. After this, he smoothly shifts the jaw back so that the articular heads are immersed in the glenoid fossae. The return of the heads to their normal position is accompanied by a characteristic clicking sound (due to their rapid sliding from the tubercles into the glenoid fossae) and a reflex clenching of the jaws.

Therefore, when moving the jaw backwards, the doctor must simultaneously quickly move the thumbs of both hands toward the cheeks (into the vestibular space) to avoid biting them. In case of bilateral dislocation, both heads are reduced simultaneously or first on one side and then on the other.

The Hippocratic Method - P. V. Khodorovich

Since thumbs wrapped in a napkin become bulky and the sense of touch becomes dull, P. V. Khodorovich suggested inserting the thumbs into the vestibule of the mouth and placing them not on the large molars, but on the outer oblique lines of the lower jaw at the level of the large molars in such a way that the nail phalanges occupy the retromolar fossae (triangles) and rest with their ends on the anterior edges of the branches of the jaw. The index fingers grasp the corners, and the rest - the body of the jaw. When inserting the heads of the lower jaw into the glenoid fossae, the doctor's thumbs in this case cannot get pinched between the patient's teeth, because they remain in the retromolar fossae until the end of the manipulation.

If, in the process of eliminating a bilateral dislocation, only one articular head of the lower jaw is reduced, and the position of the other remains incorrect (dislocated), the doctor must continue to reduce it as with a unilateral dislocation.

It is important to take into account that the better the patient is physically developed or the more excited he is, the longer it takes for the chewing muscles to become fatigued and the more time is required to reset the lower jaw.

In case of severe pain in the stretched joint capsules, ligamentous apparatus and masticatory muscles, it is quite difficult to set the lower jaw. In such cases, regional anesthesia should be performed according to Berchet-M. D. Dubov, and if this cannot be done, then the heads of the jaw should be slowly pushed back, distracting the patient's attention.

After the dislocation has been eliminated, the lower jaw should be immobilized for 10-15 days using a sling-like bandage or a standard plastic sling with elastic traction to the head cap. During this period of immobilization, the patient should eat chopped food.

Method of G. L. Blekhman-Yu. D. Gershuni

The essence of G. L. Blekhman's method is that the doctor presses with his index fingers on the coronoid processes of the lower jaw protruding (during dislocation) in the vestibule of the mouth in the direction backwards and downwards. The resulting pain leads to a reflex relaxation of the masticatory muscles; the jaw is repositioned within a few seconds.

Yu. D. Gershuni modified the method of G. L. Blekhman in the following way. By palpation through the skin of the cheeks, slightly below the zygomatic bones, the position of the tops of the coronoid processes of the lower jaw is determined and pressure is applied to them with the thumbs in the backward and downward direction. This eliminates the need for great physical force, there is no need for an assistant, and the reduction can be carried out in any position of the patient and under any conditions. This method can be quickly taught not only to medical workers, but also to relatives of patients. An important point is that the reduction is carried out without inserting fingers into the patient's mouth. This method is especially appropriate for elderly and senile people.

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Elimination of chronic anterior dislocation of the lower jaw

It is often very difficult or impossible to correct a chronic anterior dislocation of the lower jaw in the same way as a fresh one. Dislocations of the lower jaw that repeatedly recur over long periods of time may also be irreducible. In such cases, an attempt should be made to correct the lower jaw using the Popesku method, which is as follows. The patient is placed on his back, the mouth is opened as wide as possible, and tightly rolled bandage rollers with a diameter of 1.5-2 cm are inserted between the molars; continuously pressing the chin with the hand from the bottom up, the heads of the lower jaw are lowered. Then press on the chin from front to back.

After the heads have been repositioned, an immobilizing circular bandage or sling is applied for 2-3 weeks, and then dosed and gradual mechanotherapy is prescribed.

In patients with chronic dislocation, the jaw is usually reduced under general anesthesia or under potentiated local anesthesia (according to Berchet-M. D. Dubov). In the treatment of difficult-to-reduce chronic dislocations, short-acting muscle relaxants (listenone, ditilin) are used intravenously in combination with general anesthesia. If such an attempt is unsuccessful, reduction is usually performed surgically, exposing the edge of the lower jaw notch with a 2-2.5 cm incision along the lower edge of the zygomatic arch. Grasping the branch of the jaw by the semilunar notch with a strong hook, pull it down, and then, pressing on the chin, shift the head of the jaw back and thereby install it in the mandibular fossa. If a deformed articular disc prevents reposition, it is removed. After the head of the jaw is reduced, the wound is sutured layer by layer.

If such reduction is impossible to perform due to gross cicatricial changes around the joint and in the joint cavity itself, the head of the lower jaw is resected and immediately after the wound has healed, active and passive mechanotherapy is prescribed, using standard devices for this purpose.

For reduction of difficult to reduce and chronic dislocations of the lower jaw, a method is proposed based on the possibility of using a device used in the treatment of fractures of the condylar processes of the lower jaw, since this device allows for the lowering of the dislocated head of the branch of the jaw. It is described above. For reduction of the dislocation of the lower jaw, one of the fixing hooks is inserted under the zygomatic arch, and the other hook-lever is rested against the edge of the notch of the lower jaw. After this, the adjusting screw is used to lower the branch of the jaw, which leads to separation of the contact of the posterior surface of the articular head with the anterior surface of the articular tubercle and the location of the upper point of the articular head below the lower point of the articular tubercle. The reduction is completed by tilting the supporting rod of the device, leading to the movement of the head towards the mandibular glenoid fossa with subsequent lifting of the branch and insertion of the head into the fossa. The device allows for gradual, measured force lowering of the jaw branch, which prevents rupture and damage to the articular ligaments.

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