Open Treatment of Mandible Fractures

Joseph Baylan

H. Peter Lorenz

ANATOMY²^,³

The mandible is a U-shaped bone composed of thick buccal and lingual cortices with a thin medullary canal.
The mandible is divided into paired condyle, coronoid, ramus, angle, body, parasymphysis areas with a single midline symphysis, and tooth-bearing alveolus (FIG 1).
Blood supply to the mandible comes from the inferior alveolar artery and direct muscular attachments.
The inferior alveolar nerve traverses the mandible in the medullary canal, exiting at the mental foramen which is located inferior to the second premolar.
Muscles inserting on the mandible (FIG 2):
- Muscles of mastication
  - Masseter
  - Temporalis
  - Medial pterygoid
  - Lateral pterygoid:
- Suprahyoid muscles
  - Digastric
    
    FIG 1 • Bony anatomy of the mandible.
  - Stylohyoid
  - Mylohyoid
  - Geniohyoid

PATHOGENESIS

Two most common causes of mandible fractures are assault and motor vehicle collisions.
Additional causes include gunshot wounds, falls, and sports injuries.
Most common location of fractures²^,³:
- Condylar (36%)
- Body (21%)
- Angle (20%)
- Symphysis (14%)
- Alveolar ridge (3%)
- Ramus (3%)
- Coronoid fractures (2%)
Displacement of fracture segments commonly occurs from differing forces of inserting muscles³:
- Muscles of mastication displace posterior segments superiorly.
- Suprahyoid muscles displace anterior segment inferiorly.
- The lateral pterygoid displaces condylar head medially.
Favorable mandible fractures³:
- Nondisplaced by muscular pull.
- Most rami fractures.
  
  FIG 2 • Muscle attachments of the mandible.
Unfavorable mandible fractures³:
- Horizontal angle fractures that extend posteriorly and downward tend to be displaced by muscles of mastication.
- Vertical symphyseal and parasymphyseal fractures are displaced downward by suprahyoid muscles.
- High condylar fractures are displaced medially by the lateral pterygoid muscle.

PATIENT HISTORY AND PHYSICAL FINDINGS

Focused history and physical exam:
- Mechanism of injury.
- Full intraoral and dental examination.
  - Evaluate for anterior or posterior open bite in centric occlusion.
  - Evaluate for deviation of the mandible upon opening.
  - Palpate condyles in preauricular area and external auditory canal during opening to assess translation and tenderness.
- Evaluate for mental nerve paresthesias.
- Tips.
  - Use tongue blade intraorally for complete soft tissue evaluation.
  - Gingival lacerations are typically present at fracture sites.
  - Ecchymosis on the floor of the mouth is indicative of mandible fracture.
  - Chin deviation suggests condylar fracture.
- Concomitant injury evaluation:
  - 2.6% of patients with facial fractures will have cervical spine injury.³

IMAGING

Panorex plain films may be used to diagnose mandible fractures.
CT imaging is superior to plain films for diagnosing and evaluating mandibular fractures.
Noncontrast maxillofacial CT, with three-dimensional (3D) reconstruction if available, is useful for determining fracture patterns, identifying concomitant injuries, and planning repair.²^,³

NONOPERATIVE MANAGEMENT

The majority of mandible fractures will require operative intervention.
Nondisplaced, stable fractures with normal occlusion can be treated with soft diet and close follow-up.
Greenstick-type fractures or minimally displaced fractures in children with normal occlusion can also be treated nonsurgically.³^,⁴
In the case of edentulous mandibles, minimally displaced fractures can be treated nonoperatively.³

SURGICAL MANAGEMENT

The main goal of operative intervention for mandible fractures is to restore preinjury occlusion and restore mandibular form and function.²
Timing of surgery has no correlation to complication rates.²^,⁵
Antibiotics:
- All patients with mandible fractures should receive prophylactic antibiotics from the time of injury until the fracture is treated.
  - This practice has been shown to reduce postoperative infection from 50% to 6%.²
  - Penicillin-based antibiotic is preferred or clindamycin for patients with penicillin allergy.
- Postoperative antibiotics have been shown to have no effect on infection rates.²
Fracture patterns to consider:
- Symphysis and parasymphysis: fracture is located in the anterior mandibular portion between the canine teeth.
- Body: fracture is located between canine and distal last molar.
- Angle or ramus: fracture is located posterior to the second molar and triangle between the horizontal and ascending ramus and often involving the third molar.
- Condylar and subcondylar fracture: fracture is located superior to the ramus and is classified according to levels.
Indications for open reduction and internal fixation (ORIF):
- Severely displaced fractures
- Bilateral fractures
- Open fractures
- Comminuted fractures
- Multiple fracture sites
- Panfacial fractures
- Infected fractures
- Uncooperative patients
- Patients with relative contraindication to MMF secondary to medical conditions (seizures, malnutrition, etc.)
Indications for external fixation⁶:
- Bridge until ORIF
- Large segmental defect
- Severe comminution
- Infection present
Indications for removal of the teeth:
- Grossly mobile teeth with periapical pathology or advanced periodontal disease
- Teeth preventing fracture reduction
- Fractured tooth root
- Exposed root apices