Mandible Dislocation

Background

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. However, some situations require immediate consultation with a facial surgeon. This article focuses primarily on the diagnosis and management of mandible dislocations in adults.

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. Manual reduction is sufficient for acute dislocation; 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]}

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 two bones. The joint acts with a hinge as well as a gliding mechanism.^[5]

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The temporomandibular joint.

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.

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Pathophysiology

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.^[5]

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.

• 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.^[6]
• 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 resulting 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.^[7]
• Acute chronic dislocations result from a similar mechanism in patients with risk factors such as congenitally shallow mandibular fossa, loss of joint capsule from previous mandible dislocations, or hypermobility syndromes.
• Chronic dislocations result from untreated TMJ dislocations and the condyle remains displaced for an extended time period. Open reduction is often required.^{[8, 9, 10]}

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.^{[5, 11]}

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.^[12]

Lateral dislocations are usually associated with mandible fractures.^{[13, 5]} The condylar head migrates laterally and superiorly and can often be palpated in the temporal space.^[14]

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Epidemiology

Frequency

Mandibular dislocations are infrequent presentations to the emergency department. Lowery et al reported seeing 37 dislocations over a 7-year period in an emergency setting with approximately 100,000 annual visits.^[7] 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.^{[13, 15, 16]}

Mortality in cases of mandibular dislocation is usually a result of concurrent serious traumatic injuries and not from the dislocation itself.

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Prognosis

The prognosis for most isolated mandibular dislocations is good but varies based on the type of dislocation, as follows:

• Acute anterior mandibular dislocations carry an excellent prognosis with few cases that progress to recurrent dislocation.
• Lateral dislocations are often associated with fractures and require open reduction.
• Posttraumatic ankylosis is possible for dislocations with displaced condylar fractures.
• Posterior dislocations occasionally require fixation of the external auditory canal and may result in hearing deficits.
• Superior dislocations 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.
• 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.^[12]

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Patient Education

Patients should be instructed to avoid opening their mouths widely to prevent recurrent dislocation.

For patient education resources, see the Back, Ribs, Neck, and Head Center, Breaks, Fractures, and Dislocations Center, and Teeth and Mouth Center, as well as Temporomandibular Joint (TMJ) Syndrome, Broken Jaw, and Broken or Knocked-out Teeth.

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History

Most patients present with jaw pain and trismus after extreme mouth opening or after a direct blow to the jaw. In addition, patients describe difficulty with speaking or swallowing, and malocclusion.^{[11, 17]}

A history of previous dislocations, hypermobility syndromes, or injury to the TMJ joint should be elicited from patients.

In rare cases of multisystem trauma, head injuries, intoxication, or other causes of altered mental status, the patient may not be able to give a history suggestive of mandible dislocation.

Malocclusion is not unique to mandible fractures or dislocations, and maxillary fractures should be considered in the differential diagnosis in patients with malocclusion and pain.^[14]

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Physical

A thorough examination of the head, neck, and nervous system should be performed in patients with suspected mandible dislocation. Usually pain and difficulty with jaw movement is present in all patients with mandible injury.

Anterior mandible dislocations usually result in a visible and palpable periauricular depression from displacement of the condyle. Unilateral dislocations result in a deviation of the jaw away from the dislocation. When both mandibular condyles are dislocated anteriorly, the patient appears to have an underbite, or prognathia, with pain over both TMJ areas.^[17]

A thorough examination of the central nervous system, especially cranial nerves V and VII, should be performed in all patients with suspected jaw dislocations. This is vital, especially in cases of superior jaw dislocation.

External auditory canal should be inspected, and hearing should be assessed in patients with suspected posterior mandible dislocation.

The condylar head can sometimes be felt in the temporal space in cases of lateral dislocation.

Inspect the oral cavity for gingival lacerations, which may signal an open fracture.

A "tongue blade test" can be performed in subtle cases of jaw injury. A tongue blade is placed between the molars, and the patient is asked to bite down. If the patient can stabilize the tongue blade sufficiently for the examiner to twist it until it breaks, a mandibular fracture is unlikely.^{[18, 14]} Alonso et al and Schwab et al reported that the tongue blade test is 95% sensitive. It should be performed on both sides.

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Causes

Risk factors for mandible dislocation include the following:

• Shallow mandibular fossa
• Previous TMJ trauma or dislocation that disrupted the joint capsule
• Dystonic reactions
• Seizures
• Hypermobility syndromes, such as Marfan syndrome or Ehlers-Danlos syndrome, which predisposes the TMJ to dislocation due to increased laxity of surrounding connective tissue^{[19, 14, 20]}

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Laboratory Studies

No initial laboratory workup is necessary in a healthy patient with an isolated jaw injury and an otherwise normal examination and vital signs.

A pregnancy test may be indicated in women of childbearing age prior to imaging studies.

In patients with associated injuries, other comorbid illnesses, or those requiring open reduction, trauma radiographs and/or laboratory workup may be useful.

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Imaging Studies

Imaging studies should be obtained prior to reduction to identify any fractures. In rare cases of recurrent dislocations, imaging studies may be deferred, based on the discretion of the treating physician.

Fractures associated with nontraumatic anterior mandibular dislocations are rare. However, traumatic dislocations are often associated with mandibular fractures. Isolated trauma to the mandible can be evaluated by using an orthopanoramic radiograph and a mandible posteroanterior (PA) view with maximal mouth opening. This is an acceptable option for patients with chronic recurrent dislocations and a nontraumatic mechanism. However, certain fractures, such as nondisplaced mental fractures, may not be recognized on panoramic and PA radiographs because of the overlapping spine obscuring the image. In addition, restricted mouth opening can result in inadequate projection of the condylar process on the PA view, resulting in missed fracture of the mandibular ramus.

The use of CT scanning for mandible injuries is increasing because CT scan provides greater sensitivity in diagnosing mandibular abnormalities. The use of CT in traumatic mandible injuries is increasing.^[21] The ability to obtain reconstructed images along the sagittal and coronal plane and along the alveolar ridge to create panoramiclike images further contributes to improved visualization of the fractures and acceptability of CT as the initial imaging modality in stable patients with traumatic mandible injury.

Although MRI is not the first-line imaging modality in patients with mandible dislocations, it is useful in assessing the integrity of the TMJ joint, articular disks, and associated structures. MRI is also informative in patients with chronic recurrent dislocations while planning further long-term management. MRI is highly sensitive in detecting complications of mandibular injuries, such as pseudoarthrosis from fragment nonunion of traumatic fractures, ischemic necrosis of the condylar head, and traumatic damage to the articular disk. Both CT and MRI can be used to assess for posttraumatic osteomyelitis.^[21]

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Prehospital Care

No specific treatment of mandibular dislocation is indicated in the field. The decision regarding self-transport versus paramedic transport is based upon factors other than the mandibular dislocation (eg, presence of multiple trauma, patient's level of pain and distress).

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Emergency Department Care

A thorough assessment of the patient's airway, breathing, and circulation (ABCs) should be performed at presentation. If a complete history, physical assessment, and appropriate imaging study reveal an isolated mandibular dislocation, a decision is to be made if closed reduction in the emergency department is appropriate.

Oral maxillofacial surgery consultation is indicated for patients with dislocations associated with fractures and for chronic dislocations. Based on the degree and displacement of the fracture and damage to associated structures, many of these patients require open reduction in the operating room.

Providing analgesia and muscle relaxation prior to reduction is important. Several options are available including procedural sedation using a combination of intravenous sedatives and analgesics. Local anesthetics (eg, lidocaine) can be injected directly in the TMJ space at the site of the preauricular depression.^[22] A short-acting benzodiazepine, such as intravenous midazolam, can be used for muscle relaxation. In patients deemed high risk for procedural sedation, masseteric and deep temporal nerve block along with local analgesic infiltration of lidocaine into the TMJ joint can be considered to aid reduction. This technique has been reported to reduce both masseter and temporalis muscle spams and pain, resulting in successful reduction of the anterior jaw dislocation.^[23]

Several methods have been proposed and successfully used for reduction of anterior jaw displacement. Several case reports also suggest that eliciting a gag reflex may help spontaneously reduce anterior jaw dislocations.^[24] Also, see Joint Reduction, Mandibular Dislocation.

Classic reduction technique

The patient is placed in a sitting position, and the physician stands facing the patient (as shown in the image below).

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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 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.

The physician applies downward and backward pressure on the mandible using his or her thumbs while slightly opening the mouth. This helps disengage the condyle from the anterior eminence and reposition it back into the mandibular fossa.

There is a risk of injury to the thumbs of the physician as the mouth snaps closed with successful reduction. Therefore, it is recommended that the physician wrap both thumbs with gauze.^[5]

Recumbent approach

The patient is placed recumbent, and the physician stands behind the head of the patient (as shown in the image below).

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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 o....

The physician places his or her thumbs on the inferior molars and applies downward and backward pressure until the jaw pops back into place.^[25]

Wrist pivot method

The patient is placed in a sitting position, and the physician stands facing the patient (as shown in the image below).

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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....

The physician grasps the mandible at the apex of the mentum with both thumbs. The fingers are placed on the inferior molars. The physician applies cephalad force on the thumbs and caudad pressure with fingers. The wrist is then pivoted to reduce the dislocated mandibular condyle back into place.^[7]

Ipsilateral approach

This approach is composed of 3 maneuvers: external, intraoral, and then combined route.

The extraoral route is attempted first. The patient is placed in a sitting position, and the physician stands behind the patient (as shown in the image below). 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. The external approach has been reported to be successful in approximately 55% of cases of acute anterior mandible dislocation.^{[25, 26]}

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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 stabil....

If this method fails, the physician stands facing the patient and applies downward pressure intraorally on the ipsilateral lower molar teeth. A combined approach is then used if the first two approaches are unsuccessful. Intraoral downward force is applied on the molars as the other hand is used to apply extraoral downward pressure on the displaced condyle.^[25]

Successfully relocated mandible dislocations do not require any specific ongoing treatment, although the patient should be cautioned against opening the mouth wide, which could easily cause a recurrence.

A soft collar may be considered for support of the TMJ after reduction.

All patients with reduced mandible dislocations should be monitored by an appropriate specialist because of the possibility of jaw instability, ligamentous damage, and chronic TMJ pain.

Several methods have been successfully used in outpatient follow up to prevent recurrent dislocations. These include surgical alteration of the ligaments, muscles, and bones of the jaw, as well as immobilization of the mandible by maxillomandibular fixation.^[27] Intramuscular botulin injections to weaken the lateral pterygoid muscles have also been used to prevent recurrent dislocations.^[28]

In the rare cases of mandible dislocation that cannot be reduced by the methods described in Emergency Department Care, closed reduction under general anesthesia or open reduction may be required.

Dislocations associated with fractures of the mandible are best reduced by oral maxillofacial surgeons or otolaryngologists.

In many cases, relocation is simple to perform at the initial ED visit, and the patient can be referred for ongoing care at another facility, precluding the need for transfer.

Patients with dislocation of the mandible can be transferred providing no severe associated injuries are present, vital signs are stable, and the airway is patent.

A soft diet should be recommended for the first few days after reduction.

Patients should refrain from wide jaw opening for 1-2 weeks after reduction. Nonsteroidal anti-inflammatory drugs (NSAIDs) may be used to alleviate initial discomfort.^[11]

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Consultations

Superior dislocations, chronic old dislocations, open dislocations, dislocations associated with cranial nerve injury or fractures, or acute dislocations unreducible by a closed technique require emergent consultation with an oral maxillofacial surgeon.

Elective follow-up with an oral maxillofacial surgery is recommended for all dislocations managed and reduced in the emergency department.

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Complications

Complications from mandibular dislocation and reduction are rare.

Complications of dislocation include the following:

• Recurrent anterior dislocations can result in injury to the joint capsule and degenerative disease of the joint space.
• Injury to the external carotid and facial nerve can result.
• Posterior dislocations can injure the external auditory canal.
• Deafness can result from damage to the auditory canals and surrounding structures.
• Superior dislocations have been associated with cerebral contusion, CNS deficits, and seventh and eighth cranial nerve injury.

Complications of reduction include the following

• Iatrogenic fracture of the mandibular condyle may occur as it passes under the articular eminence.^[5]
• The physician's thumbs may be injured as a consequence of rapid jaw closure with reduction.
• In geriatric patients, the ridges of the mandible become atrophic with time, and the use of any method of reduction that exerts force on the mandible increases the risk of fracture of the mandible.^[29]

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Medication Summary

Sedation and analgesia are indicated if reduction is attempted. The componants of procedural sedation may be dictated by hospital setting. The medications traditionally used for this purpose are diazepam and morphine. Other conscious sedation protocols can be used providing the patient maintains an adequate gag reflex. Certain medications that can cause masseter spasm (eg, methohexital, chlordiazepoxide, phenothiazines) should be avoided because this complication would prevent relocation of the mandible.

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Morphine (Astramorph, Duramorph)

• Dosing, Interactions, etc.

Clinical Context:  DOC for analgesia due to reliable and predictable effects, safety profile, and ease of reversibility with naloxone.

Various IV doses are used; commonly titrated until desired effect obtained.

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Fentanyl citrate (Duragesic, Sublimaze)

• Dosing, Interactions, etc.

Clinical Context:  Potent narcotic analgesic with much shorter half-life than morphine sulfate. With short duration (30-60 min) and easy titration, an excellent choice for pain management and sedation. Easily and quickly reversed by naloxone.

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Class Summary

Pain control is essential to quality patient care. It ensures patient comfort, promotes pulmonary toilet, and aids physical therapy regimens. Many analgesics have sedating properties that benefit patients with injuries.

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Diazepam (Valium)

• Dosing, Interactions, etc.

Clinical Context:  Individualize dosage and increase cautiously to avoid adverse effects.

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Lorazepam (Ativan)

• Dosing, Interactions, etc.

Clinical Context:  Sedative hypnotic in benzodiazepine class that has short onset of effect and relatively long half-life. By increasing action of GABA, a major inhibitory neurotransmitter, may depress all levels of CNS, including limbic and reticular formation. Excellent medication for patients requiring sedation for >24h. Monitor BP after administering dose and adjust as necessary.

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Class Summary

Benzodiazepines have both anxiolytic and muscle relaxation properties.  Patients with painful injuries usually experience significant anxiety. Anxiolytics allow the clinician to administer a smaller analgesic dose to achieve the same effect.

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Lidocaine (Lidocaine CV, Lidopen)

• Dosing, Interactions, etc.

Clinical Context:  Lidocaine injections can be used for nerve blocks in mandible reductions.

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Class Summary

These agents are used to reduce pain and can be used for nerve blocks in mandible reductions.

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