Fractures of the Mandible

Introduction

There are numerous causes of mandibular fractures including assault, motor vehicle accidents, projectile missiles, and pathologic fractures. Multiple studies have shown motor vehicle accidents and interpersonal assaults as the leading causes for mandibular fractures. When a mandible fracture is suspected, careful evaluation of other injuries must be ruled out. A recent study reported a 64.8% association with life-threatening injury such as closed head injury, skull fracture, and body cavity trauma. In the setting of isolated fractures to the maxillofacial skeleton, cervical spine injury ranged from 4.9% to 8.0%.

The mechanism of trauma can provide valuable information to the clinician on the potential injury patterns and locations to the mandible ( Fig. 185.1 ). An anterior impact typically causes a symphyseal fracture with or without condylar involvement, whereas lateral impacts typically result in body or angle fractures. Interpersonal assaults have a high predilection for mandibular angle fractures. The majority of mandibular fractures occur in males in the 25- to 34-year-old age group. Nearly 25% of mandible fractures in women are due to falls, and the practitioner should be wary of and evaluate for non-accidental trauma.

The classification of fractures by location can be further described by the fracture pattern as open (compound), closed (simple), comminuted, green stick, complex, and/or multiple. Open/compound fractures communicate through the skin or mucosa with the external environment. Comminuted fractures include multiple segments of bone that are crushed or splintered. Complex fractures are either an open or closed fracture that are associated with significant soft tissue injury.

Key Operative Learning Points

• Understanding the basic principles of dental occlusion is necessary to ensure optimal fracture repair.

• Displacement of fracture segments is defined as either favorable (stable) or unfavorable (unstable) given the biomechanics exerted on the fragments by muscle pull ( Fig. 185.2 ).

  

• Understanding the interaction of these forces is essential during reduction of fractures as excessive interfragmentary motion during fracture healing interrupts proper bone formation at the histologic level.

• Temporary reduction of significantly displaced fracture segments that include the dentition can be achieved by placement of a bridal wire, which assists in control of flail segment(s) or hemorrhage ( Fig. 185.3 ).

  

• Intubation is made challenging in cases of flail mandible fractures.

• A prospective cohort study found that inferior alveolar nerve injury was four times more likely in posterior mandibular fractures (56.2%) than in anterior mandibular fractures.

• A unilateral subcondylar fracture often presents with a contralateral open bite with deviation of the mandible to the ipsilateral side upon opening. Bilateral condylar fractures may present as an anterior open bite with premature contact of any posterior teeth.

• In contrast to bicortical fractures, greenstick fractures of the mandible are often difficult to identify by physical exam ination alone. Careful history with focus on mechanism of injury and force of impact are critical for further workup and evaluation in those with a high suspicion for mandibular trauma.

• In mandibular body fractures, masticatory forces create strain or tension above the mandibular canal. Below the canal, compression forces along the inferior border promote bony contact under an occlusal load. Fixation is necessary to neutralize this force.

• Angle fractures are shown to have the highest rate of complication compared with other mandibular fractures partly due to its proximity to the inferior alveolar nerve and masseteric and facial vessels.

• Regardless if a transoral or extraoral approach is used, rigid internal fixation for an angle fracture is necessary to neutralize the tension, compression, and torsional forces encountered at the angle due to the opposing forces of mandibular elevators and depressors in the region.

• A third molar in the line of fracture may be left in place if it does not interfere with reduction, while its removal at time of repair has been shown to increase the risk of infection.

• The marginal mandibular nerve and cervical nerve are 2 cm below the inferior border of the mandible 80% of the time.

• Condylar fractures account for 11% to 16% of all facial fractures and nearly a third of mandibular fractures. Management of these fractures remains highly controversial; many surgeons favor nonsurgical treatment because it results in satisfactory function and esthetics.

• Al-Moraissi and Ellis determined open reduction and rigid internal fixation (ORIF) for subcondylar fractures provided superior functional clinical outcomes compared to maxillomandibular fixation (MMF) when considering maximal incisal opening, laterotrusive movement, protrusive movement, malocclusion, pain, and chin deviation.

• Absolute indications for ORIF of condyle fractures: (1) displacement into the middle cranial fossa; (2) difficulty establishing dental occlusion with closed treatment alone; (3) lateral extracapsular displacement of the condyle; (4) presence of a foreign body; and (5) open fracture with potential for fibrosis

• Coronoid fractures occur in less than 2% of all mandible fractures and are typically due to lateral impact at the level of the zygomatic-maxillary complex. Treatment for coronoid fracture is typically unnecessary.

• Some have recommended that open treatment of atrophic mandible fractures be avoided due to the risk of compromised blood supply over the fracture.

• Atrophic fractures can be classified by the following: Class I—15 to 20 mm of bone height; Class II—10 to 15 mm; and Class III—<10 mm of bone height.

• More rigid fixation is necessary in mandibles with <15 mm of bone height. Fixation must be rigid enough to allow for load-bearing and ideally load-sharing under function.

• When multiple mandible fractures exist, rigid fixation on at least one side is necessary to decrease the chance of a complication.

Preoperative Period