Zygomatic Complex Fracture

A zygomatic complex fracture is also known as a tripod, tetrapod, quadrupedmalar, or trimalar fracture that involves the zygoma and its surrounding bones. The typical lines of a zygomatic complex fracture are A fracture emanating from the inferior orbital fissure superiorly along the sphenozygomatic suture to the frontozygomatic suture where it crosses the lateral orbital rim. The zygomatic bone articulates with the sphenoid bone, maxilla, frontal bone, and temporal bone to form the lateral wall of the floor of the orbit, part of the temporal and infratemporal fossa, and the prominence of the cheek.

The zygoma is a bone that provides vital contributions to both the structure and aesthetic of the midface and articulates with several bones of the craniofacial skeleton. The zygoma and its articulations comprise the zygomaticomaxillary complex (ZMC). Fractures of the zygomatic arch (ZA) or any of its bony articulations can cause significant functional and cosmetic morbidity. The management of the zygomatic arch and ZMC fractures should be patient-specific but range from simple observation to open reduction with internal fixation (ORIF).

These complexes are referred to as the zygomaticomaxillary complex. The upper and transverse maxillary bone has the zygomaticomaxillary and zygomaticotemporal sutures, while the lateral and vertical maxillary bone has the zygomaticomaxillary and frontozygomatic sutures. Zygomatic bone also called cheekbone, or malar bone is diamond-shaped bone below and lateral to the orbit, or eye socket, at the widest part of the cheek. It adjoins the frontal bone at the outer edge of the orbit and the sphenoid and maxilla within the orbit.

Anatomy

The zygoma is the most anterolateral projection of the midface. It plays a key role structurally as it absorbs and dissipates forces away from the cranial base. The zygoma also comprises a significant portion of the inferior and lateral orbital walls; thus, fractures of the zygoma warrant investigation into fractures of the orbit.

The zygoma has four articulations, referred to as the ZMC complex:

  1. Zygomaticotemporal (ZT) suture – The temporal process of the zygoma articulates with the zygomatic process of the temporal bone to form the anterolaterally projected zygomatic arch (ZA)
  2. Zygomaticomaxillary (ZM) suture and the infraorbital rim (IOR)
  3. Zygomaticofrontal (ZF) suture
  4. Zygomaticosphenoidal (ZS) suture

NOTE: Fractures of the ZMC complex may be mistakenly referred to as “tripod fractured,” though the correct terminology is, in fact, “tetrapod fracture,” given the four articulations of the zygoma as stated above.

Neuroanatomy

Paresthesia of the face is a common sequela of a ZMC fracture given its proximity to sensory nerves such as the infraorbital nerve, the zygomaticofacial nerve, and the zygomaticotemporal nerve (all branches of cranial nerve V2).

  • The infraorbital nerve exits the maxilla via the infraorbital foramen, medial to the articulation of the maxilla, and the zygoma. The infraorbital nerve detects sensory input from the cheek, upper lip, nose, and anterior maxillary dentition.
  • The zygomaticofacial and zygomaticotemporal nerves transmit sensory input from the lateral cheek and anterior temporal area, respectively. They are branches of the zygomatic nerve, which arises in the pterygopalatine fossa and enters the orbit via the inferior orbital fissure, and travels along the lateral orbital wall. The zygomaticofacial and zygomaticotemporal branches then exit via identically named foramina in the zygoma.

Severe ZMC fractures may also result in ipsilateral facial palsy since the facial nerve is intimately associated with the zygomatic arch. The facial nerve’s frontal branch emerges from the parotid gland within the parotid-masseteric fascia and crosses superficial to the zygomatic arch in the innominate fascia deep to the superficial muscular aponeurotic system (SMAS). The frontal branch then transitions to the undersurface of the temporoparietal fascia where it travels to innervate the frontalis muscle.

Muscular Anatomy

The temporalis originates along the temporal line of the parietal and frontal bones and travels medially to the zygomatic arch to insert on the coronoid process of the mandible. It also has attachments to the zygoma.

The masseter originates on the inferior aspect of the zygoma and zygomatic arch and inserts on the angle of the mandible.

The zygomaticus major and minor are muscles of facial expression that originate on the zygoma and insert near the corner of the mouth to assist with commissure elevation.

You Might Also Read  Physical Examination of Ankle

Other landmarks

Tubercle of Whitnall: The attachment site of the lateral canthal tendon located on the medial surface of the frontal process of the zygoma.

Causes

The fracture complex results from a direct blow to the malar eminence and results in three distinct fracture components that disrupt the anchoring of the zygoma. Additionally, the fracture components may result in impingement of the temporalis muscle, trismus (difficulty with mastication) and may compromise the infraorbital foramen/nerve resulting in hypoesthesia (numbness) within its sensory distribution

The zygomaticofacial foramen is a small foramen in the mid-lateral surface of the zygomatic bone that transmits the zygomaticofacial nerve (a branch of the zygomatic nerve from the maxillary division of the trigeminal nerve) and zygomaticofacial vessels.

Fractures of the zygoma are almost always the result of high-impact trauma. The most common mechanisms are assault, motor vehicle collisions, falls, and sporting injuries.

The cause is usually a direct blow to the malar eminence of the cheek during the assault. The paired zygomas each have two attachments to the cranium, and two attachments to the maxilla, making up the orbital floors and lateral walls. These complexes are referred to as the zygomaticomaxillary complex. The upper and transverse maxillary bone has the zygomaticomaxillary and zygomaticotemporal sutures, while the lateral and vertical maxillary bone has the zygomaticomaxillary and frontozygomatic sutures.

The formerly used ‘tripod fracture’ refers to these buttresses, but did not also incorporate the posterior relationship of the zygoma to the sphenoid bone at the zygomaticosphenoid suture.

There is an association of ZMC fractures with naso-orbito-ethmoidal fractures (NOE) on the same side as the injury. Concomitant NOE fractures predict a higher incidence of postoperative deformity.

Symptoms

On physical exam, the fracture appears as a loss of cheek projection with increased width of the face. In most cases, there is loss of sensation in the cheek and upper lip due to infraorbital nerve injury. Facial bruising, periorbital ecchymosis, soft tissue gas, swelling, trismus, altered mastication, diplopia, and ophthalmoplegia are other indirect features of the injury.[1] The zygomatic arch usually fractures at its weakest point, 1.5 cm behind the zygomaticotemporal suture.[2]

Diagnosis

History

It is crucial to ascertain the mechanism and timing of the injury. Note whether the injury was caused by blunt or penetrating trauma, as penetrating trauma is more likely to involve deeper-lying neurovascular structures. One should ask about prior facial trauma or facial surgeries, which may make fracture repair more difficult.

Physical

As with any trauma patient, it is important to start the examination with an evaluation of the “ABCs.” Ensure the patient has an adequate airway, is breathing spontaneously, and that any bleeding is under control. It is also vitally important to “clear” the cervical spine for any associated injury. Inspect the face, noting any obvious asymmetry, lacerations, and ecchymosis of the skin. Ipsilateral epistaxis is common and requires controlling if severe. An ophthalmologic exam should be performed, including visual acuity, visual fields, and extraocular movements. In a patient with a ZMC injury, the facial flattening may be apparent from a birds-ey view, which is caused by depression of the malar eminence; however, the facial flattening may get obscured by overlying soft tissue edema. The clinician should note the position of the globe. Enophthalmos may be visible from a worms-ey view. The face should be palpated, noting any bony step-offs or mobility of the underlying craniofacial skeleton. A comprehensive cranial nerve examination should be completed, paying special attention to facial movement and sensation.

Evaluation

After a comprehensive history and physical examination, imaging is almost always necessary if a zygomatic arch or ZMC fracture is suspected. Historically, the Waters view plain film was used to evaluate ZMC fractures. A computed tomography (CT) scan is now the gold standard imaging modality. The 3-dimensional reconstruction is particularly useful for preoperative planning. There may also be a role for the intraoperative use of CT to assess the adequacy of fracture reduction, but there is no strong evidence to support the routine use of this practice.

You Might Also Read  Physical Examination of Back Spine

Classification of ZMC Fractures

Various classification systems have been used to categorize ZMC fractures further. Below is a widely used system proposed by Zingg:

  • Type A: an incomplete zygomatic fracture that involves one pillar
    • 1: zygomatic arch fracture
    • 2: lateral orbital wall fracture
    • 3: infraorbital rim fracture
  • Type B: all four pillars are fractured (a complete tetrapod fracture) with the zygoma remaining intact
  • Type C: a multi-fragment zygomatic fracture, wherein all four pillars are fractured plus the body of the zygoma is fractured

Treatment

Management of ZMC fractures can broadly classify into three categories: medical management, closed reduction, and open reduction with internal fixation (ORIF). Management of ZMC fractures is controversial and requires tailoring to each case.

Medical Management

Zygomatic fractures are usually observable if there is minimal or no displacement of fracture segments. Additionally, medical management may be the choice if other comorbidities preclude safe surgery. No strong evidence supports the use of prophylactic antibiotics in upper and midface fractures, though some surgeons prescribe a 5 to 7-day course of antibiotics, particularly if a communication exists with the maxillary sinus. If prescribed, antibiotics should cover sinonasal flora.

Operative Management

The indications for operative management of zygomatic arch and ZMC fractures are to restore the form and function of the ZMC. Fractures of the ZMC or zygomatic arch can often lead to unsightly malar depression, which should be corrected to restore a normal facial contour. ZMC fractures can also cause significant functional issues, including trismus, enophthalmos and/or diplopia, and paresthesias of the infraorbital nerve. A suspected globe injury is a contraindication to operative management of ZMC fractures and should be diagnosed/addressed before any surgical intervention to repair the zygomatic arch or ZMC fracture sites.

A principle of facial fracture repair includes the ability to reduce and/or fixate fractures that involve the facial buttresses to restore the structural integrity of the midface. Several methods exist to repair zygomatic arch and ZMA fractures, though closed reduction may be adequate for simple, low-velocity injuries of the zygomatic arch (see TYPE A1 below) that are non-displaced or minimally displaced and remain stable after initial attempts of reduction. ORIF should be the choice for fractures that are comminuted or are likely to be unstable after reduction. Typically, profile titanium mini-plates are commonly used to fixate the fracture sites, working in a manner to repair fractures from laterally to medially and from stable to non-stable segments. Absorbable plates may also be used for fixation in cases where follow-up is unlikely, but such plates should not be routinely used as absorbable plates are structurally weaker in biomechanical studies.

Herein we summarize a management algorithm based on Zingg’s classification system of ZMC fractures as described above (see EVALUATION:

  • Type A1 (zygomatic arch fracture) – Nondisplaced fractures of the zygomatic arch are often observable, whereas displaced fractures of the zygomatic arch require reduction, which is possible via a Gillies approach via a temporal incision, a transcutaneous Caroll-Girard screw directly over the depressed fracture site, or a Keen approach via a transoral incision in the maxillary vestibule. Isolated arch fractures that are not stable after reduction can be splinted externally with cardiac wires, or plated via a coronal incision.
  • Type A2 (Lateral orbital wall fracture) – Reduction and fixation of this area are best via a lateral brow incision or a blepharoplasty incision. Small mini-plates provide adequate stabilization of such fractures.
  • Type A3 (Infraorbital rim) – The infraorbital rim (IOR) should be reduced and plated to restore its normal contour, and the optimal approach is via a transconjunctival incision or lower eyelid incision.
  • Type B (Tetrapod fracture) – Mildly displaced tetrapod fractures may occasionally be reducible via a Gillies or Keene approach. Most tetrapod fractures, however, remain unstable after such reduction attempts and ultimately require ORIF with single point fixation (zygomaticomaxillary buttress or the zygomaticofrontal suture), two-point fixation (the ZM buttress and the zygomaticofrontal suture), and three-point fixation (the IOR). Finally, the zygomatic arch can be plated via a coronal incision or pre-existing lacerations as the fourth point of fixation if necessary.
  • Type C (Comminuted tetrapod fracture) – comminuted tetrapod fractures are an absolute indication for ORIF (after excluding an orbital injury). Treatment is similar to a type B fracture, with ORIF of the ZM buttress, IOR, zygomaticofrontal suture, and zygomaticotemporal suture.

Orbital Floor Exploration and Repair

You Might Also Read  Peroneal Muscular Atrophy - Causes, Symptoms, Treatment

Indications for the repair of the orbital floor are controversial. Generally, if greater than 50% of the floor is involved or the defect is 1 to 2 cm^2 or larger, the orbital floor should be repaired. Additional indications include a non-resolving oculocardiac reflex, primary diplopia, enophthalmos, and entrapment of extraocular muscles. Many different materials can be used, including titanium mesh, dura, temporalis fascia, and other allogeneic implants. After repair, a forced duction test should be performed to ensure normal mobility of the globe.

Number of Fixation Points

There is no consensus as to how many fixation points are necessary when treating ZMC fractures. In general, the more comminuted or unstable a fracture is, the more fixation points will be needed to ensure a good result. A recent meta-analysis suggested that three-point fixation had less fracture instability and orbital dystopia at three months post-operatively as compared to two-point fixation, but the quality of evidence was low. An intraoperative CT scan is used to visualize the articulations of the zygoma and verify adequate reduction. The zygoma and its articulations can also be palpated after fixation to determine if additional fixation points are needed.

Order of Plating

There is no universal order of plating in multipoint fixation. In single-point fixation, the ZM buttress usually gets plated. The zygomaticofrontal suture can also get plated, though most would argue that the intraoral incision used to plate the ZM buttress is less morbid than approaches to the ZF suture. In two-point fixation, the zygomaticofrontal suture should be plated first, followed by the ZM buttress. In three or four-point fixation, the ZF requires plating first, then the ZM buttress, then the IOR followed by the zygomatic arch if necessary. If one plans to plate the zygomatic arch from the outset, it can often be plated first to ensure adequate projection of the ZMC. If concomitant repair of the orbital floor is necessary, it should take place after the zygoma has had a reduction performed.

Soft tissue suspension

If the lateral canthal tendon has suffered disruption, it requires resuspension with suturing to the tubercle of Whitnall. The malar eminence can be suspended to prevent ectropion or scleral show.

Summary of Surgical Approaches

  • If possible, existing lacerations are utilized to approach fixation sites.
  • Zygomaticofrontal suture

    • Lateral brow incision
    • Upper blepharoplasty incision
    • A transconjunctival incision with lateral canthotomy
    • Coronal incision
  • ZM suture

    • intraoral incision
  • IOR and orbital floor

    • Subsidiary or subtarsal incision
    • Transconjunctival incision
  • Zygomatic Arch

    • Percutaneous stab incision for placement of Caroll-Girard screw – requires a conspicuous scar and theoretically puts the facial nerve at risk
    • Temporal incision (Gillies) – conceals the scar in the hairline; NOTE: the facial nerve can be preserved by staying deep to the temporalis fascia (e.g., the superficial layer of deep temporal fascia) during dissection
    • Intraoral incision (Sheen) – conceals the scar in the mouth and avoids facial nerve injury; NOTE: a careful, watertight closure of the intraoral incision can prevent plate exposure in the mouth and oroantral fistula formation to the maxillary sinus
    • Coronal or hemicoronal incision

Timing of repair

Fracture repair should take place as quickly as possible before scarring, and healing of bony fragments begins. Because significant facial edema guises aesthetic deformities and increases exposure difficulty, fracture repair should ideally take place within 7 to 10 days of the initial injury. Fracture repair from 2 to-6 weeks post-injury is possible, but usually more difficult due to ensuing fibrosis and scarring. Fracture repair past six weeks is extremely challenging, but the surgeon can facilitate it by the use of intraoperative imaging and navigation. If orbital floor repair is necessary, it should ideally occur within two weeks of the injury.