Mandibular and Temporomandibular Joint Injuries

Author: Jonathan D Whittaker / Editor: Jonathan D Whittaker / Reviewer: Shanthi Siva, Pragya Mallick / Codes: C3AP1d, MaC4, MaP4, SLO4, SLO5Published: 09/06/2021

Fractures of the mandible are the second most common facial fractures seen in the ED, after nasal fractures. In one large series, they accounted for 45% of all facial fractures. Interpersonal violence is the most frequent cause of mandibular 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. The most common cause found in one survey was excessive mouth opening whilst yawning (3).

The mandible is a U shaped bone comprising of 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. Some patients may have concurrent other maxillofacial and non-maxillofacial fractures [4]. The most common site of fracture was the angle accounting for one third of the fractures, followed by the parasymphysis area and the condyles [4].

Learning Bite

It is good practice to look for other facial fracture sites in those with mandibular fractures.

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:

  • yawning
  • laughing
  • shouting
  • eating
  • 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 traps the dislocated condyle.

Clinical assessment

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).

Learning Bite

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)

Follow the system of “look, feel and move used in musculoskeletal examination;

Look

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 may indicate an 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

Learning Bite

Bleeding from the ear in addition to other causes, may arise from a fall onto the chin and an associated tympanic plate fracture.

Feel

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. Always assess and clearly document IAN status when examining patients with mandibular fractures [18].

Move

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.

Special Tests

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.

Learning Bite

The tongue blade test is useful in ruling out a mandibular fracture when combined with other clinical findings.

Risk Stratification

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;

  • Malocclusion
  • Trismus
  • Pain with mouth closed
  • Broken teeth
  • Step deformity

The authors report that its use could reduce the number of x-rays done in mandibular trauma by 30% and that it outperformed clinicians’ diagnostic ability.

The Manchester Mandibular Fracture Decision Rule (9)

Learning Bite

The use of a decision rule for mandibular trauma is highly sensitive and may reduce the number of x-rays done by 30%.

Investigation Strategies

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.

Learning Bite

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.

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 patient’s 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.

Learning Bite

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, the thumbs should be positioned behind the patient’s last molars. Thick gloves must be worn to ensure protection against a human bite occurring when the mouth snaps close due to muscle spasm. A bite block may also be used.

Learning Bite

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.

There are blog posts and videos available for revision, linked in the reference section [19, 20].

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)
  • Fracture of the mandible is the second most common facial fracture seen in the ED and some patients may have 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. This is a recognised 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 done 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)
  1. Boole JR, Holtel M, Amoroso P, Yore M. 5196 mandible fractures among 4381 active duty army soldiers, 1980 to 1998. Laryngoscope. 2001 Oct;111(10):1691-6. PMID: 11801927.
  2. Lowery LE, Beeson MS, Lum KK. The wrist pivot method, a novel technique for temporomandibular joint reduction. J Emerg Med 2004;27:167-170.
  3. Ugboko VI, Oginni FO, Ajike SO, et al., A survey of temporomandibular joint dislocation: aetiology, demographics, risk factors and management in 96 Nigerian cases. Int J Oral Maxillofac Surg. 2005 Jul;34(5):499-502. PMID: 16053868.
  4. Rashid A, Eyeson J, Haider D, van Gijn D, Fan K. Incidence and patterns of mandibular fractures during a 5-year period in a London teaching hospital. Br J Oral Maxillofac Surg. 2013 Dec;51(8):794-8. PMID: 23735734.
  5. Hung YC, Montazem A, Costello MA. The correlation between mandible fracture and loss of consciousness. J Oral Maxillofac Surg 2004;62:938-94.
  6. Chong VFH, Fan YF. External auditory canal fracture secondary to mandibular trauma. Clin Radiol2000;55:714-6.
  7. Malhotra R, Dunning J. The utility of the tongue blade test for the diagnosis of mandibular fracture. [accessed 2nd June 2008].
  8. Schwab RA, Genners K, Robinson WA. Clinical predictors in mandibular fractures. Am J Emerg Med1998;16:304-5.
  9. Charalambous C, Dunning J, Omorphos S et al. A maximally sensitive clinical decision rule to reduce the need for radiography in mandibular trauma. Ann R Coll Surg Engl 2005;87:259-263.
  10. Begum P, Jones S. Radiological diagnosis of mandibular fracture. [accessed 2nd June 2008].
  11. Nair MK, Nair UP. Imaging of mandibular trauma: ROC analysis. Acad Emerg Med 2001;8:689-695.
  12. Luyk NH, Larsen PE. The diagnosis and treatment of the dislocated mandible. Am J Emerg Med1989;7:329-335.
  13. Roth FS, Kokoska MS, Awwad EE et al. The identification of mandible fractures by helical computed tomography and panorex tomography. J Craniofac Surg 2005;16:394-9.
  14. Andreasen JO, Jensen SS, Schwartz O et al., A systematic review of prophylactic antibiotics in the surgical treatment of maxillofacial fractures. J Oral Maxillofac Surg 2006;64:1664-8.
  15. Totten VY, Zambito RF. Propofol bolus facilitates reduction of luxed temporomandibular joints. J Emerg Med1998;16:467-470.
  16. Shun TA, Wai WT, Chui LC. A case series of closed reduction for acute temporomandibular joint dislocation by a new approach. Eur J Emerg Med 2006;13:72-5.
  17. Chen YC, Chen CT, Lin CH et al., A safe and effective way for reduction of temporomandibular joint dislocation. Ann Plast Surg 2007;58:105-8.
  18. Boffano P, Roccia F, Gallesio C, et al.Inferior Alveolar Nerve Injuries Associated with Mandibular Fractures at Risk: A Two-Center Retrospective Study. Craniomaxillofacial Trauma & Reconstruction. 2014;7(4):280-283.
  19. Toles K, Trick of the Trade: Extra-oral reduction technique of anterior mandible dislocation. ALiEM, 2016.
  20. Core EM, TMJ Dislocation Reduction Techniques. 2016.

5 Comments

  1. van der westhuizenp6264 says:

    Concise

  2. Dr. Ahmed Ali says:

    good article

  3. Dr. Javaid Iqbal says:

    extremely beneficial article about TMJ and mandibular fracture & dislocation
    ALL Ed clinicians should read it

  4. Dr Askari Hasan Syed Reza says:

    good read, concise

  5. Dr. Yusuf Dala Gali says:

    Great Information

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