Parasymphysis fracture with a brief loss of consciousness

The order is dictated by trauma life support, not by the jaw:

1. Airway and cervical spine. He has no stridor or dyspnoea now, but a displaced mandible plus a chin laceration means the airway can deteriorate with swelling or a haematoma. Sit him up, keep suction and intubation equipment available, and keep cervical precautions until formally cleared.
2. Head injury. A witnessed loss of consciousness, even two minutes, mandates observation and a neurosurgical opinion. A patient who is GCS 15 with no vomiting is low risk, but he cannot be assumed safe, and elective surgery under general anaesthesia is deferred while this is unresolved.
3. Secondary survey. Rule out other injuries before treating the face; the facial fracture is not life-threatening.
4. Wound care and analgesia, tetanus prophylaxis, and intravenous antibiotics for the compound fracture (amoxicillin–clavulanate).
5. Provisional immobilisation with arch bars and light guiding elastics if the occlusion permits, to control pain and reduce the mobile segment.
6. Definitive fixation - ideally within 24–72 hours once the head injury is cleared and swelling allows.

Definitive fixation comes last because an unrecognised intracranial injury, an expanding haematoma or an unprotected airway kills the patient, whereas a mandible fixed at 48 hours instead of 6 has essentially the same functional outcome.

Left parasymphysis (displaced). Open reduction and internal fixation through an intraoral vestibular incision with a lower border incision only if needed. After applying arch bars and establishing the occlusion, I would fix with two 2.0-mm miniplates (or a single load-bearing plate plus a tension band) placed with at least 5 mm between screws and the fracture line. Anatomical reduction restores the contour and decompresses the inferior alveolar nerve.

Right angle (undisplaced). No indication for open reduction. It is managed closed with the same arch bars and 3–4 weeks of guiding elastics and a soft diet, with review radiographs at 1 and 3 weeks to confirm it stays undisplaced.

Teeth 31 and 41 in the fracture line:

• Retain if they are not grossly mobile, have no root fracture, are not preventing reduction, and the bone can be plated around them. Retained teeth preserve alveolar bone and the chance of vitality; they are pulp-tested at 2 weeks, 4–6 weeks and 3 months, and root canal treated if they become necrotic.
• Extract if they are grossly mobile, have a fractured root or non-restorable crown, or physically block reduction of the fragments. Given that both are mobile here, the deciding test is whether reduction can be achieved with them in place - if not, they come out at the time of fixation.

Assessment. Document the distribution and severity: light touch with cotton wool, pinprick, and two-point discrimination over the left lower lip, chin and buccal mucosa, compared with the normal right side. Record it in the notes before surgery, because a deficit that is present pre-operatively cannot be attributed to the operation.

Interpretation. The numbness follows the line of the fracture through the mandibular canal and is almost certainly a neuropraxia from displacement or haematoma rather than transection. The single most useful intervention is anatomical reduction of the fracture, which relieves traction on the nerve.

What I would do and say:

• Do not explore the nerve in the absence of a displaced fragment impinging on it or a documented transection.
• Explain that most such injuries recover over weeks to months, but that recovery can be incomplete and can take 6–12 months; the lip may feel altered long after the bone has healed.
• Warn him about biting the numb lip and about burns from hot food and drinks.
• Review sensation at each post-operative visit and refer for microneurosurgical assessment if there is no improvement at 3 months or if the deficit worsens.