Mandibular Fractures

See related article Temporo-mandibular joint dislocation.

Fractures of the mandible were described in ancient Egypt around 1650 BC. Hippocrates described facial injuries around 400 BC.¹

• The problem of occlusion was addressed in Italy in 1180, but fixation of the fractured mandible was first recorded in 1492.
• The First and Second World Wars saw improvements in radiology and management of airways and other injuries.
• The advent of CT allowed a much more detailed picture of the injured area to assess injury and plan treatment.
• Better anaesthetic and supportive techniques have permitted a more aggressive approach to reconstruction.

When a blow to the mandible causes a fracture there are often other fractures too and these must be sought:

• Trauma to one side often produces an ipsilateral body fracture and a contralateral subcondylar fracture.
• A heavy blow to the symphysis produces a symphyseal fracture and bilateral subcondylar fractures.
• It is also important to exclude damage to the cervical spine and to ascertain that the airway is not compromised.

The most commonly fractured sites are:

• Condyle 29%
• Angle 24%
• Symphysis 22%
• Body 16%
• Ramus 1.7%
• Coracoid 1.3%

The average number of fractures in a mandible is between 1.5 and 1.8 with 10% of patients having more than 2 fractures.

The cause of the injury may be road traffic accidents, assault, falls, industrial or sports injuries but the relative number of each varies considerably between countries and areas.

• Under the age of 25, dental trauma accounts for more lost teeth than caries or gum disease.^2,3
• In terms of violence, young males are most at risk with alcohol an aggravating factor.
• Women and children are much less at risk, but can be from domestic violence.
• There is a male preponderance of about 3:1 in adults and 3:2 in children.

History

The history may indicate the site and direction of force, the possible presence of other injuries, especially to the neck and other relevant features such as loss of consciousness and head injury.

Examination

• Note any abnormality in facial contour and shape of the mandible as well as tenderness, swelling, redness, lacerations or haematoma.
• Check movements of the mandible and malocclusion.
• Loose and fractured teeth should be evaluated and counted.
• If teeth are missing, and unaccounted for, consider CXR in case of inhalation.

• If the mucosa is intact, clinical findings may be limited to bruising. If the mandibular branch of the trigeminal nerve (the inferior alveolar or mental nerve) has been injured, there will be paraesthesia or anaesthesia of the chin. Documenting this and any damage to the marginal mandibular nerve branch of the facial nerve is important before surgery.
• Spasm of the muscles of mastication can produce trismus that impairs a proper oral examination. The pull of muscles may reduce or distract a fracture. Facial oedema, erythema, and pain may also occur.
• Some fractures can result in the posterior displacement of the tongue and lead to airway compromise. The airway obstruction requires immediate attention.

• There are a number of views of plain x-rays that give a good picture of the mandible, teeth and their roots. A panoramic view is especially useful.
• CXR may also be required if teeth are unaccounted for.
• CT gives excellent detail and is very helpful in planning management.

Teeth that may be loose or knocked out require immediate referral to a dentist if other injuries do not over-ride that consideration.⁴

• A conservative approach is permissible if there is little or no displacement.
  • This may be acceptable for children with a greenstick fracture or the elderly edentulous patient with minimal displacement.
  • Support to the jaw may relieve discomfort.
  • Chewing should be minimised or avoided with a liquid or puréed diet.
• A surgical approach is often advocated nowadays where a conservative line may have been acceptable before.
  • Closed reduction may be achieved or open reduction permits direct inspection and mechanisms to stabilise the fracture.
  • Wire tends to be reserved for children and titanium plates and screw fixation are often used in adults.
• Pre-operative antibiotics reduce the frequency of infection considerably.
• Mandibulo-maxillary fixation (MMF) may be required.
  • Children have MMF for 4 weeks, adults for 6 weeks, but the elderly may require 8 weeks.
  • Patients with condylar fractures must have MMF removed by 2 weeks, and aggressive physiotherapy is required to prevent ankylosis.
  • MMF requires tube feeding of a liquid or purée diet and attention to oral hygiene.
• Implants may be used to correct deformity.^5,6 Teeth on the fracture line rarely need removal.⁷

Complications may be related to the trauma to the mandible or related trauma.

• Delay in fixing the fractured mandible increases the risk of complications, but neurological complications or other problems such as airway compromise may make this inevitable.
• If there is bilateral fracture of the body of mandible, parasymphyseal, or condylar fractures, there is risk of airways impairment as the muscular action pulls the distal mandibular segment backwards, allowing the tongue to obstruct the oropharynx.
• There may also be nerve damage.
  • In neuropraxia, function takes 4 to 6 weeks to return, but in neurotmesis, function takes around 18 months to return if it returns.
• Infection increases complications including malunion or non-union.
• Ankylosis can result in poor ability to open the mouth.
• The psychological implications of facial trauma are such that the risk of post traumatic stress disorder is increased in this condition.^8,9

• Mouth guards in sport reduce the incidence of trauma to the mandible.^10,11
• They do not have an adverse effect on aerobic performance.¹²
• The mouth guard needs to be appropriate to the individual and the sport.^13,14