Mandibular Fracture

Mandibular fracture is a break in the continuity of the mandible, the most commonly fractured facial bone after the nasal bones, accounting for about 40 to 60 percent of facial fractures requiring admission. Causes in Kenya are road traffic injuries (especially motorcycle crashes), assault, falls, sports injuries and firearm injuries. The male to female ratio is about 4 to 1, with peak incidence in the age group 20 to 40 years.

Because of its horseshoe shape, the mandible commonly fractures at two sites: the site of impact and the opposite weak point. Sites by frequency: condyle (25 to 35 percent), angle (20 to 30 percent), body (15 to 25 percent), symphysis and parasymphysis (15 to 20 percent), ramus, coronoid. The direction of muscle pull (masseter, temporalis, medial pterygoid, and digastric) determines whether the fracture is favourable or unfavourable (displaced).

Fractures through tooth bearing areas are open (compound) into the mouth. Complications: infection (osteomyelitis 5 to 15 percent), malocclusion, nonunion, malunion, nerve injury, temporomandibular joint ankylosis in condylar injury, and airway compromise.

• Pain on jaw movement, swelling and bruising of the face, trismus.
• Malocclusion (a patient states "my bite is off"), step deformity of the dental arch, mobile segments, bleeding and haematoma in the floor of the mouth, sublingual ecchymosis.
• Numbness of the lower lip and chin (inferior alveolar nerve injury).
• Condylar fracture: preauricular pain, deviation of the chin to the injured side on opening, anterior open bite on the opposite side in bilateral fractures, blood in the external auditory canal.
• Airway compromise: tongue fall back in bilateral parasymphyseal fractures, bleeding and swelling.
• Associated injuries: cervical spine, head injury, other facial fractures.
• Red flags: airway obstruction, uncontrolled bleeding, loss of consciousness, cervical spine injury, open comminuted fractures, and signs of infection.

• Primary survey (airway with cervical spine protection, breathing, circulation); then facial examination: palpation along the lower border of the mandible, intraoral examination for lacerations and teeth, occlusion check, mouth opening, bimanual manipulation to test mobility, and sensation over the chin.
• Tongue depressor test (patient bites on a depressor; inability to hold or pain on twisting the blade suggests fracture: sensitivity about 95 percent).
• Imaging: panoramic radiograph (orthopantomogram) and posteroanterior mandible view; CT facial bones with 3D reconstruction (gold standard, especially for condylar and comminuted fractures); CT head and cervical spine when indicated.
• Blood tests as per trauma: full blood count, group and save.
• Exclude other facial fractures, dental injury, temporomandibular joint dislocation, and soft tissue injury.

• Airway, breathing and circulation first: control airway with suction, jaw thrust, nasopharyngeal airway, intubation or tracheostomy for obstruction or bilateral parasymphyseal fractures; control bleeding with pressure and packing; cervical spine immobilisation.
• Analgesia: paracetamol 1 g intravenously every 6 hours, ibuprofen 400 mg orally every 8 hours with food (after bleeding has settled), morphine 0.05 to 0.1 mg/kg intravenously every 4 hours as needed.
• Antibiotics for open fractures: amoxicillin clavulanate 1.2 g intravenously every 8 hours (or benzylpenicillin 1.2 g every 6 hours with metronidazole 500 mg every 8 hours) given within 1 hour of presentation and continued for 24 to 48 hours postoperatively if fixed within 24 to 72 hours; extend to 5 to 7 days for delayed treatment or contaminated or comminuted fractures; clindamycin 600 mg intravenously every 8 hours for penicillin allergy. Tetanus prophylaxis: tetanus toxoid 0.5 mL intramuscularly if not immunised in the last 5 years.
• Closed reduction with maxillomandibular fixation (arch bars, intermaxillary fixation screws) for 4 to 6 weeks for undisplaced or favourable fractures, and non-compliant or paediatric patients.
• Open reduction and internal fixation with miniplates and screws (titanium 2.0 mm monocortical plates along Champy lines of ideal osteosynthesis for angle fractures; two plates for symphysis, locking reconstruction plate for comminuted or atrophic mandibles); intraoperative teeth in the fracture line are removed only if loose, infected or interfering with reduction; operate within 3 to 7 days when swelling subsides.
• Condylar fractures: closed treatment with early mobilisation in most; ORIF for displaced fractures with dislocation, loss of ramus height, bilateral fractures with malocclusion, or foreign body.
• Postoperative: chlorhexidine 0.12 to 0.2 percent mouthwash 10 mL twice daily for 2 weeks, soft diet, high calorie liquid diet, oral hygiene, jaw exercises begin at 1 to 2 weeks after ORIF.
• Complications and management: infection (drainage, antibiotics, plate removal if loose), nonunion or malunion (revision with bone graft), malocclusion (orthodontic adjustment), inferior alveolar nerve paraesthesia (observe), TMJ ankylosis (early physiotherapy).
• Follow up: review at 1 week, 2 weeks, 6 weeks (check occlusion and union), and 3 months; radiograph at 6 weeks and 3 months.
• Counselling: no contact sport or heavy chewing for 6 to 8 weeks; road safety (helmet use), seat belts.