Zygomatic Arch Fracture

Zygomatic arch fracture is an isolated fracture of the arch, the bony bridge formed by the zygomatic and temporal bones, without involvement of the orbital rim or the zygomaticomaxillary buttress. It is a result of a blow to the side of the face.

The usual pattern is a V-shaped or three part fracture with inward displacement of a central fragment, or comminution. It is common in assault and contact sport.

Pathophysiology. The arch is thin and exposed, and an inward displacement of the fragment pushes on the coronoid process of the mandible and the temporalis muscle, limiting jaw movement.

The temporal fascia and the temporalis give some stability, and the fracture is often stable after reduction. The facial nerve branches lie nearby, and injury is uncommon.

A hollow or depression in front of the ear over the arch, which can be masked by swelling, pain over the arch, trismus from coronoid impingement, difficulty chewing, and local bruising. There is no diplopia or infraorbital numbness in an isolated fracture.

Absent orbital signs separate it from the complex fracture. Ask about the mechanism, head injury and other facial injury.

Visual change, diplopia, infraorbital numbness, cerebrospinal fluid leak or altered consciousness suggest other injuries.

• Clinical diagnosis from palpation of the arch, depression and trismus.
• CT of the facial bones (the preferred test) or a submentovertical radiograph (jug handle view), which shows the arch.
• Opening range in millimetres, and eye movement and sensation to exclude orbital and complex fractures.
• Cervical spine and head injury assessment depending on the mechanism.
• Tetanus status.

Differential diagnosis.

• Zygomaticomaxillary complex fracture
• Coronoid process or condylar fracture
• Temporomandibular joint injury and haemarthrosis
• Soft tissue haematoma and contusion
• Orbital fracture
• Masticatory muscle spasm
• Parotid injury

• Undisplaced fractures without trismus or deformity: conservative care with soft diet, analgesia, and avoiding pressure on the arch (no sleeping on the affected side, with protection of the area in sport) for 4 to 6 weeks.
• Displaced fractures with trismus or contour deformity: elevation (reduction) within 7 to 10 days, up to 3 weeks, before fibrous union:
  • Temporal approach (a 2 cm incision in the hair bearing temporal region, an elevator passed under the temporal fascia and deep to the arch to lift the fragments).
  • Intraoral approach through an upper buccal sulcus incision behind the zygomatic buttress.
  • Percutaneous hook or screw elevation as an alternative.
• Fixation is rarely required, and a stability test after reduction guides the decision. Comminuted or unstable fractures need a plate.
• Antibiotics are not routine for closed fractures. For surgery, a single dose of cefazolin 2 g intravenously (3 g if over 120 kg), or clindamycin 600 mg intravenously in penicillin allergy.
• 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) for contaminated wounds 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.
• Jaw exercises after healing to restore opening. Complications: persistent trismus, facial asymmetry, nerve injury (temporal branch of the facial nerve in surgery), and malunion.

Monitoring. Review at 1 week, 2 weeks, 6 weeks and 3 months for opening range, symmetry and nerve function, with imaging at 6 weeks if the contour is abnormal.

Referral and escalation. Refer to oral and maxillofacial surgery for displaced fractures or trismus. Urgent referral for associated orbital signs, visual change or head injury.