Angle Fracture of the Mandible

Angle fracture of the mandible is a fracture in the region between the distal part of the second molar and the insertion of the masseter and medial pterygoid, at the angle. It makes up about 20 to 30% of mandibular fractures, and is a frequent result of interpersonal violence.

An impacted or partly erupted lower third molar weakens the angle and raises the risk of fracture, and it carries the highest infection rate of all mandibular fractures.

Pathophysiology. The angle is thin, with a change in cross-section and a third molar socket, so it fails under a blow. Fractures may be favourable or unfavourable depending on the direction of the fracture line relative to the pull of the masseter, medial pterygoid and temporalis.

Unfavourable fractures displace the proximal fragment upward and medially, and need stronger fixation. A contralateral parasymphyseal or condylar fracture is often associated.

Pain, swelling and bruising over the angle, trismus, malocclusion with a step in the occlusion, a mobile fragment, numbness of the lower lip and chin from the inferior alveolar nerve, sublingual haematoma and bleeding from the gingival tear. Bad taste and halitosis with infection.

Check the airway, associated injuries and other mandibular and facial fractures. Open (compound) fractures through the gingiva or into the socket are common.

Airway compromise, head or neck injury, multiple fractures, and a wound with heavy contamination or infection need urgent care.

• Panoramic radiograph and posteroanterior view. CT of the facial bones when the fracture is complex, multiple, or when other facial fractures are suspected.
• Position of the third molar, the line of fracture and displacement.
• Sensory testing of the lower lip and chin.
• Occlusion assessment.
• Assess cervical spine and head injury using the trauma assessment.

Differential diagnosis.

• Fracture of the body or ramus
• Parasymphyseal or condylar fracture
• Pathological fracture through a cyst or tumour
• Mandibular dislocation
• Soft tissue contusion with haematoma
• Third molar pericoronitis with trismus
• Osteomyelitis with a pathological fracture

• Stabilise and treat life threatening injuries first. Temporary stabilisation with a bandage or intermaxillary fixation if airway permits.
• Open reduction and internal fixation is usual for displaced fractures: an intraoral approach with a single miniplate on the superior border (the ideal line of osteosynthesis), with the option of a second plate on the inferior border or a reconstruction plate for comminuted or unstable fractures. Temporary intermaxillary fixation for occlusion.
• Undisplaced, favourable fractures: closed management with soft diet and elastics, or a short period of intermaxillary fixation of 3 to 4 weeks.
• Third molar in the line of fracture: remove it if infected, mobile, decayed or interfering with reduction, and retain it if it is stable and helps the reduction.
• Antibiotics: amoxicillin with clavulanic acid 1.2 g intravenously every 8 hours as the first dose before surgery and for 24 hours, then no routine continuation beyond 24 hours after fixation unless infection exists, when 625 mg orally three times daily is used for 5 to 7 days. Clindamycin 600 mg intravenously every 8 hours in penicillin allergy. Reduce the dose of amoxicillin with clavulanic acid when eGFR is under 30.
• Tetanus toxoid 0.5 mL intramuscularly if vaccination is incomplete or the last dose was over 10 years ago, with tetanus immunoglobulin 250 IU intramuscularly (500 IU after 24 hours or heavy contamination) when status is unknown or incomplete.
• Analgesia: paracetamol 1 g every 6 hours (maximum 4 g daily) with ibuprofen 400 mg every 8 hours with food when appropriate. Chlorhexidine 0.2% mouthwash 10 mL twice daily.
• Soft diet for 4 to 6 weeks, oral hygiene, and smoking cessation.
• Complications: infection (about 5 to 20%), plate exposure, malunion, nonunion, malocclusion and inferior alveolar nerve dysfunction. Treat infection with drainage, antibiotics and plate removal if needed.

Monitoring. Review at 1 week, 2 weeks, 6 weeks and 3 months for occlusion, wound, infection and sensation, with a radiograph at 6 weeks.

Referral and escalation. Refer to oral and maxillofacial surgery. Urgent referral for airway threat, infection, wound breakdown or multiple fractures.