Mandibular Fractures

1. Introduction

• Epidemiology
  • 2nd most common facial fracture
• Pathophysiology
  • Mechanism
    • Commonly due to assaults, motor vehicle crashes, falls and sports
    • Mandible more sensitive to lateral impact than frontal impact
    • Forced occlusions often results in fracture to condyle vs. mechanism of lateral blow results in fracture to body or angle
  • Pathoanatomy
    • Injury at the site of impact
    • Classic teaching: >2 sites fractured with second injury on opposite side of the ring
    • However, case study found 42% of mandibular fractures unifocal
  • Associated injuries
    • Intraoral, dental, tympanic, nerve, vessel

2. Classification

• One study reported location of mandibular fractures:

• Favourable vs. unfavourable
  • Depends if musculature reduces or opens fracture
  • Most fractures of the angle are unfavourable
  • Fractures of the coronoid alone usually no intervention

3. Presentation

• Symptoms
  • Dental malocclusion, trismus
  • Pain, worse with movement
  • Intraoral bleeding/deformity
  • Ear pain

• Physical Exam
  • Inspection
    • Swelling
    • Widened or displaced to one side
    • Intraoral examination
      • If blood in mouth or small breaks in mucosa, suspect open fracture
      • Sublingual or buccal ecchymosis considered pathognomonic for mandibular fracture
      • Examine for dental or alveolar ridge fractures
    • Examine tympanic membrane to rule out perforation or hemotympanum
  • Palpation
    • Irregular contours, step-off, along mandible
    • Crepitus
    • Tenderness intraorally and externally
    • Check for CN V3 function, leading to anesthesia/paresthesia to the lower lip, due to injury to the inferior alveolar or mental nerve
    • Palpate in and around the external auditory canal, while asking patient to open and close mouth, to palpate for condylar injury
  • Tongue blade test
    • Ability to maintain the bite on a tongue blade being twisted with enough force that it cracks
    • Negative predictive value of 95% for mandibular fracture
    • Positive if patient complains of pain before the depressor can be broken on either side

4. Investigations

• Radiographs
  • Initial imaging study for low clinical suspicion of injury
  • Simple radiographs less sensitive and tend to miss condyle fractures
  • If available, panorex radiographs good for isolated mandibular, dental or alveolar ridge fractures, but CT often preferred
• CT
  • 1st choice for all patients with suspected fracture
  • Obtain facial bone CT with coronal and axial sections and reconstructions
  • CT also helpful to assess associated injuries and with surgical planning
  • Interpretation requires close attention to bones, sinuses, orbital contents and soft tissue. Better handled by radiologists
• MRI
  • Not an optimal imaging choice as fractures better seen on CT

5. Treatment

• Consult Plastics/OMFS/ENT, especially if unstable
  • e.g. mobile bone segments, unable to open and close mouth effectively, significant pain and unable to eat
• Keep NPO until otherwise instructed by specialist
• Airway management
  • If tenuous airway due to mouth/tongue swelling, consult anesthesia. May require nasal intubation over flexible bronchoscope
  • If patient unconscious, remove material from mouth which can be aspirated (e.g. teeth, blood clots, road debris)
  • Frequent serial airway checks
• Stabilization
  • If stable airway, can place Barton bandage (ace wrap over top of head and underneath mandible) to help stabilize fracture and decrease pain

• Operative
  • Open fractures require admission for operative repair
  • For open mandibular fractures:
    • Antibiotics
      • Pen G 2-4 million units IV
      • If pen-allergic, Clindamycin 600-900mg IV
    • Tetanus booster
    • Analgesia
  • May require early splinting with arch bars, or “wiring the jaw”, to achieve interdental fixation by specialist
  • If adequate stabilization with closed fractures, elective operative repair can be done as an outpatient in 3-5 days
• Blunt cerebrovascular injury screening
  • CTA head & neck indicated for high-energy mechanism with complex mandibular fracture to rule out vertebral and carotid artery dissection
• May be appropriate to discharge patients home if closed, non-displaced fractures and reasonably aligned teeth. If so, discharge with:
  • Appropriate analgesia
  • Modified soft diet x 4-6 weeks
  • Outpatient follow-up with Plastics/OMFS/ENT

6. Complications

• Monitor for airway compromise from intraoral swelling or lack of tongue support in multi-focal fractures (flail mandible)
  • Less common in conscious patient, but may occur in unconscious patient
• If mechanism was due to forced occlusion, consider hyperextension injury to cervical spine for fracture or vascular injury
  • If high-energy transfer with complex mandibular fracture, consider screening for blunt cerebrovascular injury with CTA neck

7. Pediatrics

• In one study, 17-22% of pediatric patients aged 4-11 years old developed facial growth disturbances after a fractured mandible and later required operative correction.
• As a result, children with a blow to the chin and have trismus or tenderness in the TMJ should be assessed carefully with panorex imaging with appropriate referral