Author: Jonathan D Whittaker / Editor: Jonathan D Whittaker / Reviewer: Shanthi Siva / Codes: C3AP1d / Published: 03/11/2017
Fractures of the mandible are the second most common facial fracture seen in the ED after nasal fracture. In one large series, they accounted for 45% of all facial fractures. Interpersonal violence is the most frequent cause of mandibular fracture accounting for over half of all fractures, with falls and road traffic accidents as the other common causes (1).
Dislocation of the temporomandibular joint (TMJ) is an infrequent presentation to the ED(2). Approximately 90% of all cases are bilateral and anterior and the most common cause found in one survey was excessive mouth opening whilst yawning(3).
The mandible is a U shaped bone comprising two hemimandibles which are completely fused at the symphysis by the age of two years. The mandible articulates with the mandibular fossa of the temporal bone forming the temporomandibular joints.
Basic anatomy of the mandible
The shape of the mandible and the stability of the temporomandibular joints, leave the mandible particularly susceptible to direct lateral force (4). The mandible may fracture at the site of impact but also at another point within the ring of bone formed by the mandible and skull over half of all mandibular fractures involve more than one fracture (1). The site of fracture is localised to three main areas; the body accounts for approximately one third of fractures, the condylar head and neck and coronoid process another third and the final third the ramus and other areas (1).
In over half of all mandibular fractures, there are at least two separate fracture sites.
The temporomandibular joint is split into two sections by an articular disc (or meniscus), a fibrocartilagenous structure that enables a greater range of movement of the joint.
The anatomy of the temporomandibular joint
Temporomandibular dislocations may be unilateral or bilateral and occur in anterior, posterior, lateral and superior positions. The anterior is by far the most common, the others all being associated with a fracture of either the mandible or base of the skull. Anterior dislocation may be traumatic or atraumatic; in trauma it is normally caused by direct downward force to a partially opened mouth. In predisposed patients with shallow mandibular fossae or underdeveloped mandibular condyles, certain repeated activities may initially sublux, then dislocate, the mandible. The most common mechanism relates to excessive opening of the mouth due to:
- during dental work
Connective tissue disorders such as Marfans and Ehlers-Danlos syndrome increase likelihood of dislocation. Once the mandible has dislocated anteriorly, spasm of the masseter and pterygoid muscles occurs which further trap the dislocated condyle.
All facial injuries, including mandibular fractures, are commonly associated with injury elsewhere (1) particularly to the head and neck. Also certain mandibular injuries may compromise the airway needing urgent attention. Any assessment must therefore start by following standard ATLS principles.
The mechanism of injury may point towards the site of injury:
- In children a fall onto the point of the chin may fracture the mandibular condyle(s)
- A lateral blow common in interpersonal violence is associated with mandibular body or ramus fracture
- A downward blow to the partially opened mouth may dislocate the TMJ
Almost 1 in 5 mandibular fractures are associated with a witnessed loss of consciousness (5).
Head injury commonly accompanies mandibular fracture and must be separately assessed and investigated.
If a TMJ dislocation is suspected, find out about prior TMJ symptoms, including previous dislocations or presence of a connective tissue disorder.
Examine the rest of the face as well as the mandible and TMJs as 25% of patients with mandibular fractures were found to have a fracture to at least one other facial bone (1)
Following a the system of look, feel and move used in musculoskeletal examination;
External examination of the face will reveal areas of swelling, bruising and wounds overlying a fracture. A tilted or asymmetrical position of the mandible may indicate a displaced mandibular fracture or unilaterally dislocated TMJ. A bilaterally dislocated TMJ is indicated by an open mouth that the patient is unable to close.
It is important to look inside the mouth, if trismus allows, for swelling, bruising and fractured or missing teeth. Haematoma in the sublingual space is indicative of a mandibular fracture. Lacerations to the gum mucosa almost always indicate an open fracture of the mandible.
Gum laceration and displacement indicating open mandibular fracture
Finally look for evidence of bleeding from the ear. Falls onto the point of the chin, often accompanied by a wound to the underside of the chin, may fracture the tympanic plate of the temporal bone (6) and tear the auditory canal membrane, producing bleeding from the ear. Mandibular condyle fractures are also associated with this mechanism of injury.
Other causes for bleeding from the ear must also be considered:
- basal skull fracture
- tears of the canal mucosa from foreign body insertion
- rupture of the tympanic membrane
Bleeding from the ear in addition to other causes, may arise from a fall onto the chin and an associated tympanic plate fracture.
Both the external mandible and TMJ and internal surface of the mandible must be palpated with a gloved finger. Gentle palpation of the TMJ can also be achieved by insertion of the gloved little finger in the external auditory meatus.
Sensation should be checked over the lower lip and chin. This area is supplied by the mental nerve, a branch of the inferior alveolar nerve, which is vulnerable to injury as it exits through the mental foramen.
Movements of the mandible at the TMJs are commonly reduced in both fracture and dislocation and may be due to:
- muscle spasm
- effusion in the TMJ
- depression of the zygomatic arch obstructing movement of the coronoid process of the mandible
If the patient is able to close the mouth they should be asked to bite down and to indicate whether the teeth fit correctly . Malocclusion may indicate either a fracture or unilateral dislocation of the mandible.
Martini MZ, Takahashi A, de Oliveira Neto HG, de Carvalho Jnior JP, Curcio R, Shinohara EH. Epidemiology of mandibular fractures treated in a Brazilian level I trauma public hospital in the city of So Paulo, Brazil. Braz Dent J. 2006;17:2438. 
The tongue blade test has been described and mainly utilised in the United States as an aid to the diagnosis of a mandibular fracture. In this examination a wooden spatula is held between the patients teeth on each side of the mandible and the examiner applies a twisting force, in some descriptions, a force large enough to break the blade.
A positive test is one where the patient is unable to hold the blade whilst pressure is applied. A BestBets review of the test concluded it may be useful in ruling out a fracture as the combined sensitivity was 95% although confidence intervals were wide (7). The tongue blade test should therefore be used in combination with other clinical findings.
The tongue blade test is useful in ruling out a mandibular fracture when combined with other clinical findings.
A number of clinical findings have been identified to correlate with the presence of a mandibular fracture. In one study, malocclusion, trismus, facial asymmetry or a positive tongue blade test were all strongly associated with a fracture (8). A clinical decision rule for radiography in mandibular trauma has also been developed (9). The presence of any of five factors produced a 100% sensitive rule for x ray.
The factors are;
- Pain with mouth closed
- Broken teeth
- Step deformity
The authors report that use of such a rule could reduce the number of x rays taken in mandibular trauma by 30% and that it outperformed clinicians diagnostic ability
The Manchester Mandibular Fracture Decision Rule (9)
The use of a decision rule for mandibular trauma is highly sensitive and may reduce the number of x rays taken by 30%.
Once the decision has been made to investigate the patient with mandibular trauma or suspected TMJ dislocation, the next step is to decide which x ray views should be used. In the UK, two techniques are used; the orthopantomogram (also known as OPG or panoramic radiograph) and the standard mandibular series (AP, reverse Townes and two lateral obliques). A number of comparisons have been made of the two techniques in mandibular fracture. A BestBets review concluded that the OPG is the most accurate technique and consequently the best initial film for screening but should be followed by additional views if clinical suspicion remains (10).
A more recent analysis agreed with this conclusion but noted greater diagnostic accuracy if the OPG was combined with an AP view of the mandible (11).
The OPG is also the best initial screening radiograph for TMJ dislocation (12) , although specific TMJ views may also demonstrate the dislocation.
The OPG is the best x ray technique for accurate diagnosis of mandibular fracture and TMJ dislocation. Its accuracy in mandibular fracture is even greater when combined with an AP view of the mandible.
Unfortunately, the OPG requires the patient to be seated and remain still for a period of time. These factors may alter the x ray technique used in multiple trauma and intoxicated or uncooperative patients.
Top OPG bilateral undisplaced fractures of the mandible.
Bottom OPG undisplaced fracture left side of the body of the mandible.
Recent comparisons of standard x ray techniques with CT scanning have found that a helical CT scan of the mandible offers equivalent sensitivity to an OPG, decreased interpretation error and greater interphysician agreement in the identification of mandibular fractures (13). Therefore, CT scan is an accurate method of diagnosis if x rays are technically impossible or CT scanning is required for other reasons.
A chest x ray may also be rarely required in an obtunded patient where a tooth has been avulsed and cannot be located.
Specific management of mandibular fracture is complex and it is therefore recommended that all patients are discussed with a maxillofacial surgeon.
Factors which will influence the further management include:
- Presence of other injuries
- Location and orientation of the fracture
- Open fractures
- Potential for airway compromise
With bilateral mandibular body fractures (a flail segment), anterior tongue support is lost resulting in posterior displacement of the tongue which occludes the airway. In this situation the patients airway must be protected by intubation as soon as possible. As a temporary measure, ask the patient to lean forwards or place them in the recovery position. If this is not possible due to other injuries, the flail segment should be grasped and pulled anteriorly, pulling the tongue forwards and an oropharyngeal airway inserted.
Flail fracture of the mandible may occlude the airway in an obtunded patient. It may require emergency manual reduction of the fracture to pull the tongue forwards, thereby clearing the airway.
Patients with an open mandibular fracture should be given a broad spectrum antibiotic whilst in the ED. A systematic review of antibiotic prophylaxis in the treatment of open mandibular fracture found that short term antibiotic therapy (<48 hours) reduces infection rates three fold (14).
The standard intraoral technique for reduction of the anteriorly dislocated TMJ is designed to push the mandible inferiorly and posteriorly back into the mandibular fossa. This can be done from either an anterior or posterior approach.
When manipulating the mandible with an intraoral technique it is important to wear strong gloves and position the thumbs behind the last molars to ensure protection against a human bite occurring when the mouth snaps closed due to muscle spasm. A bite block may also be used.
The operator must protect themselves against a human bite occurring whilst reducing an anterior dislocation of the mandible.
To facilitate reduction, it is common practice to administer an opioid analgesic and sedative agent such as midazolam although reduction using propofol bolus has also been described (15).
Other techniques have also been described if the standard technique fails involving intra-articular injection of local anaesthetic (12), extraoral techniques (16,17) and a wrist pivot method (2). On rare occasions general anaesthesia may be required using either a closed or open reduction.
Dislocations to the posterior, medial or lateral side are usually associated with a fracture of the mandible and should be referred to a maxillofacial surgeon for reduction.
Once the mandible has been relocated the patient must have a repeat x ray to confirm position and to exclude a fracture occurring on reduction. Discharge advice must include;
- Eat a soft diet in the first few days to minimise stress on the TMJ
- Avoid wide mouth opening for the next two weeks and support the mouth with the hand if yawning or laughing.
An encircling bandage (Barton bandage) to support the mandible is usually unnecessary unless the patient is unable to understand or comply with discharge advice.
All patients should be followed up by a maxillofacial specialist.
- Fracture of the mandible is the second most common facial fracture seen in the ED and in over half of all patients there is more than one fracture site. (level of evidence 4)
- One in five patients sustaining a mandibular fracture have a witnessed loss of consciousness and formal head injury assessment must take place in addition to assessment of the mandibular injury. (level of evidence 4)
- A fall onto the chin may fracture the mandibular condyle and the tympanic plate of the temporal bone and is a recognized cause of bleeding from the ear. (level of evidence 5)
- The tongue blade test is a useful clinical test which in combination with other clinical findings, is useful in excluding a mandibular fracture. (level of evidence 4)
- A decision rule for mandibular trauma is more accurate than clinicians in predicting fracture and may reduce the number of x rays taken by 30%. (level of evidence 2b)
- The OPG is the radiological technique of choice in both mandibular fracture and TMJ dislocation. In mandibular fracture, its accuracy can be improved by addition of an AP mandible view. (level of evidence 4)
- A broad spectrum antibiotic should be administered to patients with an open fracture of the mandible as post-injury infection rates are reduced three fold. (level of evidence 3a)
- Reduction of a dislocated mandible carries a high risk of human bite and the operator must take sufficient steps to protect themselves from this risk. (level of evidence 5)
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