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Fractures of the mandible can occur in one or more of the following regions: the
symphysis, body, angle, ramus, and condyle ( Fig. 107.2 ). The mechanism of
injury often determines the site of potential fracture in patients with trauma to the
mandible. Motor vehicle collisions and falls tend to cause fractures of the
condyles and symphysis because the force is directed against the chin, whereas
assaults tend to result in injuries to the body or angle of the mandible at the point
of impact. Patients with parasymphyseal fractures resulting from falls often have
an associated fracture in the contralateral subcondylar region. Pain and difficulty
opening the mouth are typically present with mandibular fractures. Numbness of
the lip and chin may also suggest a mandibular fracture because the inferior
alveolar nerve courses through the center of the mandible, from the middle of the
ramus, to its exit at the mental foramen. Mandibular fractures may result in
airway obstruction due to hemorrhage either from the floor of the mouth or from
a disruption in the bony support structure for the tongue.
Powerful muscles of mastication apply distracting forces to the fractured
mandibular segments, often resulting in bony displacement and occlusal
disharmony. The growth center for the mandible is located in the area of the
condyle, and damage to this area from a fracture can cause significant growth
disturbances, especially if sustained before the age of 3 years. Therefore, the
clinical evaluation of any chin laceration should include palpation of the
mandible, particularly the condyles. Malalignment of the lower central incisors
(i.e., step off in dentition) suggests a mandibular fracture at the symphysis.
Unilateral condyle fractures will most often result in the deviation of the jaw
toward the side of the fracture upon mouth opening.

FIGURE 107.2 Anatomy of the mandible. Common sites of fracture include the condyle and
subcondylar region, as well as the angle, body, and symphysis of the mandible.