Zygomatic Arch and Orbital Fractures

See also Eye Trauma.

The zygoma forms part of the floor and lateral wall of the orbit and the zygomatic arch is an important feature in the structure and appearance of the face. High impact, blunt trauma to the cheek causes zygomatic fractures; they are easy to overlook and, if displaced, require treating within 10 days.¹ Failure to treat risks cosmetic deformity or limited mandibular movement.

Usually, a displaced fracture involves the orbitozygomatic complex:

• The inferior orbital rim and orbital floor
• The zygomatico-frontal suture
• The zygomatico-maxillary buttress
• The zygomatic arch

Occasionally, a direct blow can produce an isolated depressed fracture of the arch only. (For normal anatomy, see ²)

After the nasal bone the zygoma is the second commonest bone of the face to be fractured. The group at highest risk are young males. Aetiology is usually blunt trauma to the cheek, such as involved in:

• Assault
• Road traffic accidents
• Contact sports (less common)

History

Always review the mechanism of injury.

• Diplopia occurs in about 30%. This can be due to entrapment of a muscle, neural injury or a haematoma in an external ocular muscle.
• Infraorbital/upper lip numbness on the affected side (involving maxillary, central, lateral and/or canine teeth) is present in 70-90% patients.¹
• Trismus is spasm of masseter and it makes chewing difficult and painful.
• The mucosa of the maxillary sinus may be lacerated and cause epistaxis on that side.

Examination

• It is essential to ascertain that the airway is not compromised, especially in multiple trauma.
• Examine the eye, including checking for damage to the globe. Eye injury is very common in midface trauma and may be present in as many as 30%. Look for:¹
  • Lacerations
  • Extraocular motility
  • Visual acuity
  • Visual fields
  • Pupillary light reflex
  • Diplopia
  • Opthalmoplegia
  • Hypoglobus (lowered pupillary level)
  • Enopthalmos (sunken eye)
  • Proptosis
  Even without a true orbital 'blowout' fracture, entrapment of orbital contents, enophthalmos, and diplopia with restriction of eye movement may occur because of the contributions of the zygomatic bone to the orbital floor. Where the eye is closed by swelling, check for the integrity of the optic nerve by asking the patient to confirm presence/absence of light over the closed eye. Check also for impairment of sensation below the eye.
• Periorbital and subconjunctival haemorrhage occur in around 50%.
• Fracture of the zygoma may or may not be painful to palpation and running a finger along the zygomatic arch may give a feel of a depressed fracture or a small dimple. The cheek may appear flattened: compare symmetry with the opposite side from behind the patient's head - this is most obvious immediately following trauma or several days later once swelling has subsided.
• Posterior displacement of the fractured fragment may impair movement of the mandible causing difficulty with chewing. Look for decreased range of mouth opening (normal should be >30 mm).
• Forceful nose blowing can produce subcutaneous emphysema as shown by crepitation or proptosis and visual loss from orbital emphysema.

• A plain x-ray of the skull is basic - standard views are occiptomental and submento vertical. Interpretation may be difficult, systematically check for:¹
  • The orbital outline
  • The sinus outline (any opacification or fluid level in the maxillary sinus is suggestive of a fracture)
  • An 'elephant's trunk' (follow the zygomatic line laterally and the maxillary line medially)
  • The coronoid processes (should be equidistant from the maxillary line bilaterally)
• CT is very useful to indicate more about distorted anatomy. A CT scan facial series is often essential to planning surgery.⁴ CT may also show intracranial injury that may be present in about half of patients. In about 75% of cases the fracture is displaced inferiorly, posteriorly and medially. Displaced ZMC fractures may increase orbital volume due to angulation of the zygomaticosphenoid suture or orbital floor blow out.⁵
• Ultrasound is sometimes used for visualisation of the zygomatic arch and anterior wall of the frontal sinus, particularly following reduction to avoid further radiation exposure.⁶
• MRI is inferior to CT scanning for demonstrating orbital floor fractures, but may have an adjunctive role for demonstrating soft tissue herniation.⁷

• A conservative approach is normal where there is no displacement of the fracture or minimal displacement without other complications. Stable, undisplaced fractures should be observed weekly. Patients must be under strict instruction to avoid blowing their nose.
• Where surgery is necessary, timing of intervention should aim to allow oedema to start to subside whilst not waiting for adhesion of displaced bone or the formation of dense scar tissue.
• Where a patient has multiple injuries or is severely unwell, surgery is often delayed. Damage to the globe takes precedence for repair.
• Closed reduction techniques have largely been abandoned as they give more unsatisfactory cosmetic and ophthalmological results but they may still be used where displacement is minimal.
• If displacement is more than minimal or if other structures are involved, an open technique is used, possibly involving plates to stabilise bone. The precise approach will depend upon the injuries seen on the CT film and open surgical reconstruction may be also have to be undertaken.⁸
• A multidisciplinary approach may be required in complex cases, using expertise from plastic surgery, facio-maxillary surgery, ENT and neurosurgery, depending upon other associated injuries.
• A soft diet is usually required.
• Attention should be payed to providing good analgesia. Antibiotics are normally prescribed with complex fractures and a short course of steroids may be used to reduce inflammation.
• Careful follow up is required to ascertain that there is good functional recovery including the ability to eat and chew, eye position and normal facial anatomy.

• Blindness
• Persisting diplopia
• Malposition of the globe
• Infection causing orbital cellulitis
• Infra-ocular nerve damage
• CSF leakage, especially in repair to the medial wall

Good prognosis is suggested by:

• Union of bones
• Lack of any deformity
• Full range of mandibular movement

• Seat belts are important in reducing injuries in road traffic accidents.⁹ It is possible that seat belts appear to increase facial injuries because those who do not wear them suffer more severe injuries and die. A Brazilian study looking at the relationship between facial injuries and seatbelt wearing suggested that:¹⁰
  • The driver position shows the highest incidence of facial fractures and was not effectively protected against this by the use of a seat belt.
  • The wearing of seat belts seems to protect against facial fractures in front-seat passengers.
  • There was a high incidence of facial fractures among rear-seat passengers but it was not possible to evaluate the effect of seat belt use in this group.
• Alcohol and binge-drinking are major contributory factors to assaults and facial injury. Many argue for harm-reduction measures such as the use of plastic glasses and bottles in licensed premises, controlling drinks prices and targeted policing¹¹ but there is little good quality evidence supporting the efficacy of interventions in the alcohol server setting.¹²
• Appropriate protective equipment may reduce sports-related injuries but the evidence is again of poor quality.¹³