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Dislocation, Mandible
Updated: Jan 14, 2009
Introduction
Background
Mandible dislocation is the displacement of the mandibular condyle from the articular groove in the temporal bone. Different types of dislocations can result from traumatic and nontraumatic processes. Most dislocations are managed and reduced in the emergency department with elective follow-up. However, some situations require immediate consultation with an oromaxillofacial surgeon. This article focuses primarily on the diagnosis and management of mandible dislocations in adults.
Anatomy
The temporomandibular joint.
The temporomandibular joint (TMJ) (see Media file 1) 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.1
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.
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.1
- 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 been reported.2
- 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.3
- 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.4,5,6
- 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.1,7
- Superior dislocations 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 and can result in facial nerve palsy, cerebral contusion, or deafness.
- Lateral dislocations are usually associated with mandible fractures.8,1 The condylar head migrates laterally and superiorly and can often be palpated in the temporal space.9
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.3 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.8,10,11
Mortality in cases of mandibular dislocation is usually a result of concurrent serious traumatic injuries and not from the dislocation itself.
Clinical
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.7,12
- 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.9
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.
- 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.13,9 Alonso et al and Schwab et al reported that the tongue blade test is 95% sensitive. It should be performed on both sides.
- 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.12
- 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.
Causes
Risk factors
- 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 tissue14,9,15
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References
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Further Reading
Keywords
jaw dislocation, mandible dislocation, temporomandibular joint dislocation, TMJ syndrome, temporomandibular joint syndrome, TMJ joint, traumatic mandible injury, TMJ dislocation, mandible dislocation types, mandibular dislocation, Marfan syndrome, Ehlers-Danlos syndrome
