Practice Essentials
Mandible dislocation is the displacement of the mandibular condyle from the articular groove in the temporal bone. Most dislocations are managed and reduced in the emergency department with elective follow-up. Some situations require immediate consultation with a facial surgeon. The management of temperomandibular joint dislocation depends on the underlying cause. Hypermobility or subluxation can be managed by the use of autologous blood, sclerosing agents, and capsulorrhaphy. Mandible dislocations are rare and often isolated events usually managed by manual reduction at the bedside. However, chronic protracted and chronic recurrent dislocations are among the most difficult to manage, and surgical intervention may be required to treat such cases. [1, 2, 3, 4, 5, 6, 7]
Area of dislocation
The mandible can dislocate in the anterior, posterior, lateral, or superior position. Description of the dislocation is based on the location of the condyle in comparison to the temporal articular groove. [8, 9, 10]
Anterior dislocations are the most common and result in displacement of the condyle anterior to the articular eminence of the temporal bone. These dislocations are classified as acute, chronic recurrent, or chronic, as follows:
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Acute dislocations can be seen after trauma or dystonic reactions, but they are usually a result of extreme mouth opening such as with yawning, general anesthesia, dental extraction, vomiting, or seizures. Anterior dislocations after endoscopic procedures have also been reported. [11]
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Anterior dislocations are usually secondary to an interruption in the normal sequence of muscle action when the mouth closes from extreme opening. The masseter and temporalis muscles elevate the mandible before the lateral pterygoid muscle relaxes, which results in the mandibular condyle being pulled anterior to the bony eminence and out of the temporal fossa. Spasm of the masseter, temporalis, and pterygoid muscles causes trismus and keeps the condyle from returning into the temporal fossa. These dislocations can be both unilateral and bilateral. [12]
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Chronic recurrent dislocations are marked by multiple recurrent dislocations as a result of everyday activity. They can case significant disruptiion in everyday life and may require minimaly invasive or surgical treatment. [3]
Posterior dislocations typically occur secondary to a direct blow to the chin. The mandibular condyle is pushed posteriorly toward the mastoid. Injury to the external auditory canal from the condylar head may occur from this type of injury. [10, 19]
Superior dislocations, also referred to as central dislocations, can occur from a direct blow to a partially opened mouth. The angle of the mandible in this position predisposes upward migration of the condylar head. This can result in fracture of the glenoid fossa with mandibular condyle dislocation into the middle skull base. Further injuries from this type of dislocation can range from facial nerve injury, to intracranial hematomas, cerebral contusion, leakage of cerebrospinal fluid, and damage to the eighth cranial nerve resulting in deafness. [20]
Lateral dislocations are usually associated with mandible fractures. [21, 10] The condylar head migrates laterally and superiorly and can often be palpated in the temporal space. [22]
Risk factors
Risk factors for mandible dislocation include the following:
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Shallow mandibular fossa
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Previous TMJ trauma or dislocation that disrupted the joint capsule
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Dystonic reactions
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Hypermobility syndromes, such as Marfan syndrome or Ehlers-Danlos syndrome, which predisposes the TMJ to dislocation due to increased laxity of surrounding connective tissue [23, 22, 24]
Anatomy
The temporomandibular joint (TMJ) (see the image below) is the articular surface between the mandibular condyles and the temporal bone. Synovial membranes line the space between the 2 bones. The joint acts with a hinge as well as a gliding mechanism. [10]
The temporomandibular ligament, sphenomandibular ligament, and capsular ligament support the joint. Blood supply is from the superficial temporal branch of the external carotid artery. Branches from the auriculotemporal and masseteric divisions of the mandibular nerve innervate the joint.
Closing of the mandible is performed by the masseter, temporalis, and medial pterygoid muscle. The jaw opens at the temporomandibular joint by traction on the mandibular neck by the lateral pterygoid muscle.
Epidemiology
Frequency
Spontaneous anterior TMJ dislocations are infrequent presentations with a reported incidence of 5.3 per 100,000 emergency department visits. [25] Anterior mandible dislocations are most common and often result from nontraumatic causes.
Mortality/Morbidity
Significant morbidity associated with isolated mandible dislocations is rare. However, fractures of the mandible, maxillofacial, or orbital bones are often seen with traumatic TMJ dislocations.
Mandibular dislocations may be associated with chronic recurrent dislocations, ischemic necrosis of the condylar head, traumatic damage to the articular disk, and mandibular osteomyelitis. Chronic untreated dislocations can result in permanent malocclusion. [21, 26, 27]
Mortality in cases of mandibular dislocation is usually a result of concurrent serious traumatic injuries and not from the dislocation itself.
Prognosis
The prognosis for most isolated mandibular dislocations is good but varies based on the type of dislocation, as follows:
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Acute anterior mandibular dislocations carry an excellent prognosis with few cases that progress to recurrent dislocation.
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Lateral dislocations are often associated with fractures and require open reduction.
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Posttraumatic ankylosis is possible for dislocations with displaced condylar fractures.
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Posterior dislocations occasionally require fixation of the external auditory canal and may result in hearing deficits.
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Superior dislocations, dislocations associated with a fracture, and those unreducible by a closed technique require emergent consultation by an oromaxillofacial surgeon and should be assessed for damage to the surrounding cranial nerves and cerebral structures.
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Slight facial asymmetry and lack of development of the mandibular ramus have been reported in long-term follow-up of a case of pediatric superior mandible dislocation. [20]
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The temporomandibular joint.
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Classic reduction technique. The physician places gloved thumbs on the patient's inferior molars bilaterally, as far back as possible. The fingers of the physician are curved beneath the angle and body of the mandible.
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Recumbent approach. The patient is placed recumbent, and the physician stands behind the head of the patient. The physician places his or her thumbs on the inferior molars and applies downward and backward pressure until the jaw pops back into place.
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Wrist pivot method. The patient is placed in a sitting position, and the physician stands facing the patient. The physician grasps the mandible at the apex of the mentum with both thumbs. The fingers are placed on the inferior molars.
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Ipsilateral approach - extraoral route. The patient is placed in a sitting position, and the physician stands behind the patient. The physician stabilizes the patient's head with his or her nondominant hand and uses the dominant hand to apply downward pressure on the displaced condyle that is palpated just inferior to the zygomatic arch.
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Syringe technique - a syringe is placed between the posterior molars and the patient is asked to bite down and try to roll the syringe back and forth.
