Mandibular Fractures

Anatomy and Sites of Fracture

1. Condylar neck - most common
2. Angle of the mandible
3. Region of the mental foramen (parasymphysis)

• Parasymphysis + angle fracture (contralateral sides)
• Parasymphysis + condylar fracture (contralateral sides)

Clinical Features

• Pain and tenderness at the fracture site
• Malocclusion - the most important functional sign; altered dental occlusion results from muscle forces on fracture fragments
• Paraesthesia of the lower lip and chin - due to injury to the inferior alveolar (mental) nerve running within the mandibular canal; must be specifically documented on examination
• Trismus, difficulty chewing, and restricted mouth opening
• Step deformity palpable along the inferior border or at the dental occlusal plane
• Ecchymosis in the floor of the mouth (pathognomonic of mandibular fracture)
• Sublingual haematoma

Classification

• Class I: Normal occlusion - mesial buccal cusp of maxillary first molar occludes in the intercuspal groove of mandibular first molar
• Class II: Mesial (anterior) positioning of maxillary teeth relative to mandibular
• Class III: Distal (posterior) positioning of maxillary teeth

Investigations

• Orthopantomogram (OPG/Panorex) - first-line imaging for most mandibular fractures; provides good overall visualization of the entire mandible
• Mandibular series plain films - supplementary
• High-resolution CT with reformats (coronal, sagittal, 3D) - now the standard for complex injuries; 1-mm helical CT has 100% sensitivity vs 86% for OPG. CT is especially useful for comminuted fractures, condylar fractures, and to assess the extent of displacement
• Both OPG and CT are complementary - CT can miss posterior mandibular fractures that OPG identifies; OPG misses comminution visible on CT

Anesthesia for Reduction and Fixation

• Mandibular branch of the trigeminal nerve - anesthetized near the foramen ovale
• Maxillary division of the trigeminal nerve - in the pterygopalatine fossa near the foramen rotundum
• Superficial branches of the cervical plexus

Treatment

Non-operative (Conservative)

• Undisplaced or minimally displaced fractures
• Preserved pre-traumatic occlusal relationship
• Normal range of motion
• No significant soft tissue injury

Operative - Open Reduction and Internal Fixation (ORIF)

• Antibiotics on admission followed by surgical fixation
• Titanium miniplates and screws are the standard implants (Fig. 31.9 - postoperative OPG showing angle + parasymphyseal fixation)
• Ideally performed within 24-48 hours of injury
• For heavily displaced fractures where delay is anticipated, a bridal wire around the teeth can temporarily reduce the fracture, alleviating pain and facilitating oral intake

• Simple fractures: two 2-mm monocortical screws on each side of the fracture - these are load-sharing plates (fracture reduced, load shared between bone and plate)
• Complex/comminuted fractures: heavy reconstruction plates with bicortical screws as load-bearing fixation
• Angle and body fractures: single plate along the line of maximal tension (Champy technique)
• Parasymphyseal fractures: two plates placed 5 mm apart to resist the torsional forces of the anterior mandibular musculature
• Angle fractures: transbuccal approach (small cheek incision) allows screw placement perpendicular to plate and bone

• Arch bars are applied to maxillary and mandibular teeth and wired together to establish and stabilize dental occlusion before fracture fixation
• Alternatives: bone screws placed in maxilla and mandible serving as posts for spanning wires
• Must be released as early as possible post-operatively to prevent TMJ ankylosis

1. AO/ASIF (Association for Osteosynthesis) - rigid fixation
2. Champy technique - less rigid but functionally stable fixation

Condylar / Subcondylar Fractures

• Most condylar fractures are treated conservatively with closed reduction, IMF elastic guidance, soft diet, and analgesia
• Displaced condylar neck fractures with significant loss of mandibular height are increasingly treated with ORIF (transparotid retromandibular approach is most common; endoscopic-assisted fixation is an emerging option)
• Subcondylar fractures (just below the condyle) - typically minimal displacement due to reduced muscle forces and limited bone available for fixation; most often treated with MMF alone

Severely Comminuted Fractures

Complications

Key Teaching Points (Bailey & Love Summary Box 31.5)

• Always look for a second mandibular fracture - contralateral fractures are common
• Document mental nerve sensation (lower lip/chin paraesthesia) pre- and post-operatively
• Most mandibular fractures are treated with ORIF using titanium miniplates and screws, ideally within 24-48 hours of injury

Classification of Mandibular Fractures

1. Classification by Anatomical Location

• The angle is weakened by an unerupted wisdom tooth (partially erupted 3rd molar), which acts like a stress riser
• The parasymphysis is weakened by the long root of the lower canine
• The condylar neck is weakened by its slender anatomy
• Fractures are frequently multiple - when one is found, always look for a second (usually contralateral): e.g., parasymphysis + opposite condyle, or parasymphysis + opposite angle

2. Classification by Relationship to External Environment

3. Classification by Displacement: Favorable vs. Unfavorable

• Masseter - pulls the ramus superiorly and medially
• Medial pterygoid - pulls the ramus superomedially
• Lateral pterygoid - pulls the condylar fragment anteromedially
• Mylohyoid, geniohyoid, genioglossus - pull the anterior mandible inferiorly and posteriorly

Note: Cummings Otolaryngology states that the favorable/unfavorable classification is no longer considered helpful in determining the treatment plan and offers no communication or documentation advantages - it is now of historic significance only.

4. Classification by Dentition Status

• Dentulous - teeth present (arch bars can be applied directly)
• Edentulous - no teeth (requires bone screws, Gunning splints, or circummandibular wires)
• Atrophic edentulous - extremely thin, osteoporotic mandible; at high risk of pathological fracture and nonunion; may need reconstruction plates

5. Angle's Classification of Occlusion (Guides Management)

6. Condylar Fracture Sub-classification

Summary Table

Fracture of the Body of the Mandible

Definition and Anatomical Extent

A fracture involving the mandible between the mental foramen anteriorly and the anterior border of the masseter muscle (or angle) posteriorly.

• Anterior boundary: The mental foramen (where the mental nerve exits)
• Posterior boundary: The anterior border of the angle of the mandible / anterior attachment of the masseter muscle

• Parasymphysis/symphysis fractures - which lie anterior to the mental foramen, between the two canines
• Angle fractures - which begin at or posterior to the 3rd molar region, behind the dentition
• Ramus fractures - which lie entirely posterior to the angle

Anatomical Basis of Vulnerability

1. Inferior alveolar canal runs through the body, thinning the medullary bone and creating a stress concentration point
2. Tooth roots of the premolars and molars extend deeply, creating further areas of reduced bone stock between the roots and the inferior border
3. The body transmits the full bending moment of masticatory forces; during trauma, forces applied to the chin or parasymphysis are distributed around the curved mandible and concentrate at the body
4. A common mechanism is high-velocity direct impact (motor vehicle collisions, assault with a weapon), as opposed to fist blows which more commonly fracture the parasymphysis or symphysis

Structures at Risk Within the Extent of the Body Fracture

Because the mandibular body is covered by gingival mucosa and is tooth-bearing, virtually all body fractures are presumed open until intraoral examination proves otherwise.

Clinical Features Specific to Body Fractures

• Step deformity - palpable externally along the inferior border, or intraorally along the occlusal plane
• Malocclusion - asymmetry of the dental arch; the patient reports the bite "feels wrong"
• Anaesthesia / paraesthesia of the lower lip, chin, and lower teeth on the affected side - from injury to the inferior alveolar or mental nerve
• Pain and paradoxical movement - crepitus on manual distraction of the two fragments
• Sublingual/buccal haematoma - blood-stained saliva; haematoma in the floor of the mouth or buccal sulcus
• Intraoral laceration at the fracture site
• Missing or fractured teeth at the fracture line - always check for aspirated teeth

Displacement: What Moves and Why

Association with Contralateral Fracture

• A mandibular fracture should be considered bilateral until proven otherwise
• All imaging must survey the entire mandible, including both condyles

Imaging

• Dental panoramic tomogram (OPG/Panorex) - first-line; demonstrates the body fracture and the tooth-to-fracture-line relationship clearly

• PA mandible radiograph - paired with OPG as standard
• High-resolution CT (1 mm cuts) with 3D reformats - now preferred for displaced, comminuted, or complex fractures; 100% sensitivity vs 86% for OPG

Treatment

Non-displaced / Stable Body Fractures

• MMF (maxillomandibular fixation) alone with a liquid diet for 4-6 weeks
• Patient loses ~10-20 lbs on liquid diet during fixation period

Displaced Body Fractures - ORIF

• ORIF is the standard; performed ideally within 24-48 hours
• Approach: intraoral (transoral) or transcervical (submandibular) incision
  • Submandibular incisions must be placed sufficiently below the lower border of the body to protect the marginal mandibular branch of the facial nerve
• Titanium miniplates and screws are applied:
  • Single plate along the line of maximal tension (superior/outer cortex) for body fractures - the Champy technique
  • Alternatively, two plates may be used for greater stability in comminuted fractures
  • Monocortical screws (load-sharing) for simple fractures
  • Bicortical reconstruction plates (load-bearing) for comminuted or bone-loss fractures
• The fracture line and tooth roots constrain screw placement - monocortical screws are placed to avoid root damage

Tooth in the Fracture Line

• May act as a lever to aid reduction if it has a good periodontal status - keep it
• Should be extracted if it is mobile, non-restorable, infected, or impedes reduction - leaving an infected tooth dramatically increases infection and nonunion risk
• The molar in the line of an angle fracture often needs extraction if it prevents posterior fragment control (as shown in Scott-Brown's Fig. 107.8)

Postoperative Care

• Chlorhexidine mouthwashes 3-4 times daily
• Soft diet for 4-6 weeks
• Antibiotics (penicillins, cephalosporins, or clindamycin to cover oral organisms)
• Early release from MMF once fixation is confirmed - to prevent TMJ ankylosis

Summary