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Disease Entity

Disease

Zygomaticomaxillary Fractures (ICD 10: S02.40FK)

Etiology

Zygomaticomaxillary Complex (ZMC) fractures result from blunt trauma to the periorbital area (viz. malar eminence). ZMC fractures are also referred to as tripod, trimalar, tetrapod, quadripod, or malar fractures. Etiologies reported in the literature include high-risk activities, such as road traffic accidents, civilian warfare, assaults or falls (especially related to alcohol use), contact sports, missile injuries, and not wearing protective equipment (e.g. seat-belt, helmet) while riding in motorized transport. ZMC fractures are the second most common type of facial fracture, behind nasal fractures. ZMC fractures are commonly associated with other orbital fractures. See orbital roof fractures, Orbital Medial Wall Fractures, and orbital floor fractures for additional information.

Risk Factors

ZMC fractures appear more commonly in:

Young adult males
Engagement in high risk activities (listed above in Etiology)

General Pathology

ZMC fractures are usually caused by blunt force injury to the middle-third of the face.

Pathophysiology (Relevant Anatomy)

The most important anatomical consideration in ZMC fractures is the central portion of the ZMC, which is known as the malar eminence. The malar eminence is located ~2 cm inferior to the lateral canthus. ZMC fractures are classified along a spectrum: non-displaced fractures, fractures displaced at an isolated buttress, and severely comminuted fractures with bone loss. Even minimally displaced fractures of the ZMC-region can result in functional and aesthetic deformities.

ZMC fractures occur at four articulations with adjacent bones:

Zygomatic arch
1. Zygomaticomaxillary suture anteriorly
  1. Associated with V2 paresthesias
2. Zygomaticotemporal suture laterally
  1. Weakest point of zygomatic arch: 1.5 cm posterior to the zygomaticotemporal suture
Lateral orbital wall
1. Zygomaticofrontal suture superiorly
2. Zygomaticosphenoid suture posteriorly
Orbital floor
1. Near the infraorbital canal
2. Weakest point of ZMC: orbital floor
Lateral wall of the maxillary sinus

1. At the end of the lateral orbital wall

Primary prevention

ZMC primary prevention includes avoiding trauma to the face/periorbital area. Wearing activity specific protective goggles with polycarbonate lenses during higher risk activities (e.g. contact sports) is generally recommended along with other protective equipment.

Diagnosis

History

ZMC fractures typically occur in the setting of recent trauma to face, nose, and/or eye. Featured symptoms include facial bruising, facial paresthesias, facial pain, facial swelling, periorbital ecchymosis, loss of consciousness, headache, vertigo, soft tissue emphysema, epistaxis, trismus, altered mastication, diplopia, exophthalmos, enophthalmos, midface flattening, and ophthalmoplegia.

Physical examination

On exam, ZMC fractures can appear as a loss of cheek projection with increased width of the face. In addition, trismus is a common finding. Typically, the infraorbital nerve is injured, resulting in decreased sensation to the ipsilateral upper lip/cheek/gum/side of nose area. Associated periocular soft tissue injuries, such as eyelid/canalicular laceration/canthal tendon avulsion, may be present. Like other orbit fractures, potential ophthalmic injuries are broad and include globe rupture (corneal or scleral laceration), iritis, iridodialysis, lens instability, traumatic cataract, vitreous hemorrhage, commotio retinae, retinal hemorrhage, retinal detachment, choroidal rupture, and traumatic optic neuropathy. The most common concominant ocular finding is subconjunctival hemorrhage followed by hyphema.

In the setting of periocular trauma, a full eye evaluation is essential and includes measurement of visual acuity, extraocular muscle (EOM) movements, intraocular pressure (IOP), relative afferent pupillary defect, facial sensation, and color vision or red color desaturation. Dilated fundus examination allows for assessment of posterior segment involvement. Because globe position may change depending on the severity and location of ZMC fractures, repeat exophthalmometer measurements can help to evaluate for enophthalmos/exophthalmos, which may be masked due to early soft tissue swelling.

Typical presentations of ZMC-fracture associated ocular findings include traumatic enophthalmos (globe sinking, globe ptosis, superior sulcus deformity, and/or loss of upper/lower eyelid bulge), traumatic exophthalmos (typically secondary to retrobulbar hemorrhage presenting as painful proptosis, elevated IOP, and a decrease in vision), lateral canthal dystopia, and EOM restriction and less commonly entrapment (diplopia with/without an oculocardiac reflex: bradycardia/heart block, nausea, vomiting, and/or syncope).

Clinical diagnosis

ZMC fractures can be diagnosed based on history of ocular trauma and by radiologic confirmation, most commonly a non contrast maxillofacial CT scan. Other associated facial fractures occur in ~25% of patients who sustain ZMC fractures. Step-offs around the zygomatic arch are strong clinical indicators for ZMC fracture. Many authors have described ZMC classification schemes.

As described in 1992 by Markus Zingg, et. al., there are three injuries leading to ZMC fractures, which bear little clinical significance and are more useful in research/physician communication:

Type A:
1. Isolated fracture to one component of the tetrapod structure:
  1. Type A1: zygomatic arch
  2. Type A2: lateral orbital wall
  3. Type A3: inferior orbital rim
2. Least common of Types A, B, and C
Type B:
1. Involving all four components of the tetrapod structure
Type C:
1. Complex fractures with comminution of the zygomatic bone

indicates Zingg fracture types in which the orbital contents are at risk.

Understanding the classification scheme described by Rene Le Fort in 1991 is useful in evaluating ZMC fractures because Le Fort II and III fractures both have a ZMC fracture component. For completeness the Le Fort classification is as follows:

Le Fort I:
1. Low transverse maxillary fracture:
  1. Resulting from a downward force on the upper jaw
  2. Occuring at the alveolar ridge
  3. Not involving the orbit
2. Repaired with mandibular wiring
Le Fort II:
1. Pyramidal fracture:
  1. Resulting from a blow to the middle maxilla
  2. Extending from the nasal bridge
  3. Extending through the maxillary frontal process
  4. Extending through the lacrimal bone
  5. Extending through the medial orbital floor/rim
  6. Extending through the anterior wall of the maxillary sinus
  7. Extending through the pterygoid plates
Le Fort III:
1. Craniofacial disjunction fracture:
  1. Resulting from a blow to the upper maxilla or nasal bridge
  2. Separating the facial skeleton from the cranium
  3. Sparing the optic canal
  4. Involving the orbital floor

Diagnostic procedures

Computed tomography (CT) is the primary diagnostic tool in evaluating for ZMC/orbital fractures, EOM entrapment, or retrobulbar hemorrhage. In addition, CT of the head can help in assessing the size of fractures, surgical planning, and evaluation for associated intracranial bleeding. While X-rays provide limited utility in ZMC fractures, the submental-vertex view offers excellent resolution of the zygomatic arches.

Differential diagnosis

Periorbital ecchymosis/lacerations without fracture
Traumatic retrobulbar hemorrhage (orbital hemorrhage)
- Exophthalmos
Traumatic optic neuropathy
Traumatic choroidal rupture
Iridodialysis/Cyclodialysis
Intraorbital foreign body
Intracranial bleeding
Commotio retinae
EOM entrapment
Enophthalmos
Auricular hematoma
Dental trauma
Nasal septal hematoma
Globe rupture
Chorioretinitis sclopetaria
Other fractures:
- Orbital fractures:
  - Medial wall
  - Lateral wall
  - Floor (blowout)
  - Roof
- Mandible fracture
- Nasal fracture
- Skull fracture

Management

Non-surgical interventions

If the zygoma is not significantly displaced and there is no optic nerve impingement, extraocular muscle entrapment or ruptured globe, medical treatment for pain management may be sufficient. Surgical intervention is not taken unless a functional or aesthetic impairment is deemed unacceptable, such as in the case of reduced mouth-opening and cheek prominence depression. Contraindications to ZMC surgical intervention include medical instability and globe injuries.

Surgical interventions

When surgical intervention is indicated, the best results are obtained with timely open ZMC fracture reduction with bone screw-secured miniature metal plate(s) fixation. Sub-labial or buccal sulcus incisions allow for a surgical approach to precisely realign and stabilize the maxillary buttress. Intraoperative C-arm CT scanning allows for immediate visualization of fracture reduction but also increases the patient’s radiation exposure and surgical costs. Unless there is concern for orbital content entrapment in the ZMC fracture, orbital floor exploration is not always necessary. When orbital floor exploration is indicated, transmaxillary endoscopic evaluation can be employed to assess the integrity of the orbital floor. However, care must be taken to protect the globe and intraocular contents during any periocular surgery. When there is significant orbital floor involvement, a single surgery including addressing this defect can minimize the need for a second surgery. The orbital floor defect will be larger than it appears on initial radiographic evaluation. Once the maxilla is repositioned, moving it anteriorly and laterally, the orbital floor defect increases in size.

Complications

In general, the long-term prognosis after ZMC fracture surgical repair is very good, particularly in non-displaced fractures and fractures displaced at an isolated buttress. The rate of secondary correction for the following are greater in comminuted fractures: ZMC malreduction, secondary orbital floor reconstruction, and functional correction of diplopia via correction of the EOM. Postoperative infection rates are extremely low, and these infections nearly always resolve with oral antibiotics and local wound care. ZMC fractures can rarely cause globe displacement, cosmetic deformity, diplopia, and/or trismus (limitation of mandibular opening) due to fracture impingement on the coronoid process of the mandible. Furthermore, in comparison to isolated orbital floor fractures, ZMC fractures portended a worse long-term sensory outcome in cases of infraorbital nerve hypesthesia.

References

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