Etiology and epidemiology
- Mandible fractures are common facial fractures (second only to nasal fractures).
- Leading cause in developed countries is interpersonal violence followed by motor-vehicle accidents (MVAs)
- Occur most frequently in males in the third decade
- Fractures secondary to violence often occur at the angle of the mandible (King, Am J Otolaryngol, 2004).
- Fractures secondary to MVAs most often result in multiple injury sites; most commonly involving the condyle, body, and parasymphysis (King, Am J Otolaryngol, 2004).
- The majority of fractures occur at more than one site, often bilaterally (Ogundare, JOMS 2003; Kubilius, Stomatologija 2009)
- Fall to chin = bilateral condylar fractures
- Blow to mandible = ipsilateral parasymphyseal fracture + contralateral angle fracture
- 45% occur in conjunction with other injuries; 10% are lethal (Haug, JOMS, 1990).
- Substance abuse
- Mechanism of injury
- Concurrent injury
- Cervical spine
- Other facial fractures
Anatomy (Figure 1):
- Symphysis/parasymphysis (17–22%) (Figure 2)
- Alveolar (2–4%)
- Body (16–29%)
- Angle (25–31%)
- Ramus (2–4%)
- Condyle (26–29%)
- Subtypes: head, neck, subcondylar
- Coronoid (1–2%)
- Important muscles — determine dislocation of mandible after fracture:
- Masseter: elevates mandible
- Origin: zygomatic arch
- Insertion: mandibular angle/ramus
- Temporalis: elevates and retracts the mandible
- Origin: temporal fossa of the temporal bone
- Insertion: coronoid process
- Lateral pterygoid: protrude/depress mandible; excursive movements
- Superior head — origin: greater wing of the sphenoid
- Inferior head — origin: lateral surface of the lateral pterygoid plate
- Insertion — condyle/TMJ medial pterygoid: protrude/elevate mandible; excursive movements
- Superficial head — origin: tuberosity of maxilla
- Deep head — origin: medial surface of lateral pterygoid plate/palatine bone
- Insertion: medial surface of ramus and angle of mandible
- Anterior digastric: depresses mandible, elevates/retrudes tongue
- Geniohyoid/mylohyoid: depresses mandible and protrudes/extrudes tongue
- Mentalis: elevates the lower lip
- Depressor labii inferioris: depresses lower lip
- Mental nerve:
- Sensory somatic nerve: supplies the anterior chin, lip, buccal gingiva of mandibular anterior and premolar teeth
- Typically exits apical and inferior to the 1st and 2nd premolar roots
- Distal-most/terminal end of the mandibular nerve (V3)
- The mandibular nerve passes through the skull base through the foramen ovale into the inferotemporal fossa, where it gives rise to motor branches that innervate the muscles of mastication and sensory branches, including the inferior alveolar nerve
- Inferior alveolar nerve is the largest sensory branch of the mandibular nerve
- It enters, at the lingula, into the mandibular canal and exits between the first and second premolar roots at the mental foramen
- Teeth (Figure 3):
- Surface: Labial (surface toward lip for anterior teeth); Buccal (surface toward buccal mucosa for posterior teeth); Lingual (faces the tongue for lower teeth); Palatal (toward the palate for the upper teeth); Mesial (direction toward the anterior midline of the dental arch); Distal (direction toward the last tooth in each quadrant of the dental arch)
- Numbered 1–32:
- Right-upper 3rd molar is 1.
- Right-lower 3rd molar is 32.
- Names (Figure 3):
Fracture classification and clinical description:
- Anatomic location
- Fracture terminology
- Simple: External Skin and Mucosa are Intact
- Compound (open): Laceration of Skin or Mucosa present or passes through tooth root/periodontal ligament
- Comminuted: multiple fragments of bone
- Greenstick: involves only one cortex
- Pathologic fracture: occurs through bone weakened by preexisting disease
- Atrophic fracture: occurs from bone atrophy by loss of supporting alveolar bone in edentulous mandibles
- Favorable: reduced by muscle pull
- Unfavorable: fractures distracted by muscle pull; require greater fixation
- Dentition status
- Dentulous (with teeth)
- Edentulous (without teeth)
- Stability — favorable versus unfavorable fracture:
- Muscles of mastication and suprahyoid muscles lead to instability of the mandible and fracture displacement, requiring greater fixation.
- Example 1: Mandibular angle fractures are almost always unfavorable due to instability; vertical pull due to masseter, medial pterygoid, and temporalis muscles. (Figure 4)
- Example 2: In symphysis and parasymphysis fractures, masseter muscle pull will cause lingual displacement and rotation of the teeth. Distraction of the fracture site will result in lingual splay.
Sites of weakness of the mandible:
- Fractures tend to occur in areas of greatest tension
- Third molar (especially if impacted) correlated with angle fractures (Figure 5)
- Canine roots
Figure 1. Anatomy of the mandible and fracture sites. The mental foramen (orange) is found between the first and second premolars (orange). Coronoid process (blue). Condylar process (red). Angle (purple). The ramus and body are labeled. Lingual (green). Alveolus (yellow).
Figure 2. A teenage girl who sustained bilateral parasymphyseal fractures after being bucked from her horse. IMF was established using her existing braces. An intraoral approach was used to expose the bilateral fracture. Note 2-point fixation with 1 miniplate and 1 reconstruction plate. The mental nerve is indicated by the green arrow.
Figure 3. Numbering and names of teeth. Numbering starts with the right upper (maxillary) 3rd molar as number 1 and continues to the left, so that the left 3rd upper (maxillary) molar is number 16. The numbering continues to the left lower 3rd (mandibular) molar as number 17 and then through the right 3rd (mandibular) molar as number 32.
Figure 4. Favorable versus unfavorable fractures. Upper left shows a mandibular fracture proximal to the angle. This is a favorable fracture. Lower right shows an unfavorable fracture of the mandibular angle with forces resulting in an unstable fracture.
Figure 5. Panorex of angle fracture. Demonstrating a weak point at the 3rd molar root resulting in an angle fracture.
- Acute management
- Secure airway (tongue falling back)
- Blood clots (submandibular hemorrhage)
- Fractured teeth, broken fillings, dentures
- Identify soft- tissue lacerations
- Management of food and fluid
- Occlusal abnormality
- External exam looking for changes in facial bony architecture and lacerations
- Lacerations under the chin are common in symphysis fractures
- Tenderness or step-offs with palpation along the inferior border of the mandible
- Tenderness of palpation in preauricular area can indicate condylar fracture
- Hemorrhage from external auditory canal (EAC) is frequently seen in condylar fracture (due to laceration of the cartilaginous EAC)
- Limitation of jaw movement/mandibular range of motion
- Lateral deviation on opening to the side of the fracture (condylar fractures), inability to chew, loss of opening of jaw due to muscle splinting, trismus, joint dysfunction, coronoid impingement by zygomatic fractures.
- Anesthesia, hypoesthesia, paraesthesia of lower lip, teeth, gingiva (V3 inferior alveolar nerve damage); damage to the lingual nerve causing temporary or permanent anesthesia to the ipsilateral tongue
- Intraoral bruising
- Bruising of the floor of mouth might indicate a symphysis/parasymphysis/body fracture
- Gingival laceration
- Sublingual hematoma
- Fractures of teeth
- Occlusal derangement of teeth (document preexisting malocclusion)
- Angle class I: normal anteroposterior relationship of mandible and maxilla; mesiobuccal cusp of the maxillary first molar occludes within the buccal groove of the mandibular first molar.
- Angle class II: posterior relationship of the mandible to the maxilla; mesiobuccal cusp of the maxillary first molar occludes mesial to the buccal groove of the mandibular first molar.
- Angle class III: anterior relationship of the mandible to the maxilla; mesiobuccal cusp of the permanent maxillary first molar occludes distal to the buccal groove of the mandibular molar.
- Imaging modalities
- Panoramic tomography (Panorex) (Figure 6)
- View of entire mandible
- Patient has to be able to sit upright.
- Valuable for postoperative assessment
- Maxillofacial CT without contrast (1‑mm cuts)
- 3D reconstruction (Figure 7)
Figure 6. Panorex image showing Erich arch bars, a 2-plate technique for a parasymphysis fracture (bottom right) and a Champey technique (left).
Figure 7. 3D CT reconstruction of mandible fractures. Left to right: angle, subcondylar, body, symphysis/parasymphysis.