Zygomatic Arch Fracture

Etiology

Zygomatic arch fractures tend to result from high-energy impact trauma, such as interpersonal violence, motor vehicle accidents, or sporting injuries (see Image. Zygoma Fracture). In a 2020 study published by Cohn et al, assault was the most common cause of ZA fractures (55%), followed by falls (27%), and motor vehicle accidents (18%). In contrast, a 2012 study performed by Ungari et al reported equal rates of ZA fractures between assaults and motor vehicle accidents (29%), with sports injuries following (16%), then falls (14%), domestic accidents (9%), and work accidents (5%).[3]

Epidemiology

Most zygomatic arch fractures occur in males (~80%) in the third to fourth decades of life.[4][5] Zygomaticomaxillary complex fractures are common, and estimates suggest that ZMC fractures account for 25% of facial fractures.[5] African Americans appear to be affected most commonly (61%-64%), with Caucasians second (18%-25%), Hispanic patients third (7%-12%), and Asians fourth (5%-7%).[4]

History and Physical

History

When evaluating patients with zygoma fractures, it is crucial to ascertain the mechanism and timing of the injury. Determining whether the injury was caused by blunt or penetrating trauma is also essential, as penetrating trauma is more likely to involve deeper neurovascular structures.[5] A history of prior facial trauma or facial surgeries may complicate fracture repair and should be ascertained preoperatively.

Physical Examination

As with any patient with trauma, it is important to begin the examination by evaluating the "ABCs." Ensuring the patient has an adequate airway, is breathing spontaneously, and has any bleeding under control is critical. Evaluating the cervical spine for any associated injury, as high-energy impacts to the face or head are also liable to affect the spine, is crucial. The face should be inspected, noting any obvious asymmetry, lacerations, and ecchymosis. Ipsilateral epistaxis is common and may require packing if severe. An ophthalmologic examination should include visual acuity, visual field assessments, and extraocular movement evaluation. In a patient with a ZMC injury, depression of the malar eminence may cause facial flattening and may be apparent from a "bird's eye" view. However, facial flattening may be obscured by overlying soft tissue edema in the acute phase. Applying cold compresses may alleviate the edema and facilitate a more detailed physical examination. The clinician should also note the position of the globe; enophthalmos may be visible from a "worm's-eye" 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 particular attention to facial movement and sensation.

Evaluation

After a comprehensive history and physical examination, imaging is necessary for a suspected zygomatic arch or ZMC fracture see Image. Zygomatic Arch). Historically, the Waters view plain film x-ray was used to evaluate facial fractures, although a submentovertex view provides better visualization for evaluating zygomatic arch fractures. A computed tomography (CT) scan is now the gold standard imaging modality, typically performed using fine cuts (<1 mm) without contrast (see Image. Face CT, Tripod Fracture). Three-dimensional reconstruction is beneficial for preoperative planning (see Images. Zygomatic Bone in 3D and 3D Reconstructions of Left ZOMC.). There may also be a role for intraoperative CT scanning to assess the adequacy of fracture reduction, but there is not strong evidence to support its use on a routine basis.[6]

Classification of ZMC Fractures

Various classification systems have been used to categorize ZMC fractures. Below is a system proposed by Zingg et al in 1992:

Type A: an incomplete zygomatic fracture that involves one articulation of the zygoma

• A1: zygomatic arch fracture
• A2: lateral orbital wall fracture
• A3: infraorbital rim fracture

Type B: all 4 articulations are fractured (a complete tetrapod fracture), with the zygomatic bone itself remaining intact

Type C: a multi-fragment zygomatic fracture, wherein all 4 articulations are fractured, and the body of the zygoma is fractured as well [7]

Treatment / Management

Managing ZMC fractures can be broadly classified into 3 categories: medical management, closed reduction, and open reduction internal fixation. Further, managing ZMC fractures is controversial and requires an individual approach to each case.

Medical Management

Zygoma fractures are usually manageable by observation alone 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 for patients with upper and midface fractures. However, some surgeons prescribe a 5- to 7-day course of antibiotics, particularly if communication exists with the maxillary sinus. If prescribed, antibiotics should cover sinonasal flora, eg, amoxicillin-clavulanate.[8] Additionally, a soft diet is usually recommended to prevent the distraction of fractures by muscle contraction.

Operative Management

The indications for operative management of zygomatic arch (ZA) and ZMC fractures are to restore the form and function of the midface. Fractures of the ZMC or ZA can often lead to unsightly malar depression, which should be corrected to restore normal facial contour and symmetry. Zygomaticomaxillary complex fractures can also cause significant functional issues, including trismus, enophthalmos, diplopia, and paresthesias of the infraorbital nerve. A suspected globe injury is a contraindication to operative management of ZMC fractures and should be addressed before any other surgical intervention is performed in the facial skeleton.

A key principle of facial fracture repair is a reduction with the fixation of fractures that involve the facial buttresses to restore the structural integrity of the midface. Several methods have evolved to repair ZA and ZMC fractures. However, closed reduction may be adequate for simple, low-velocity injuries of the ZA (see Type A1 below) that are nondisplaced or minimally displaced and remain stable after initial reduction.[5] Open reduction and internal fixation (see Image. ORIF of ZOMC Fracture) should be the approach of choice for fractures that are comminuted or are likely to be unstable after reduction. Typically, low-profile titanium mini-plates are used to fixate the fractured bone segments, working to repair fractures from laterally to medially and from stable to mobile segments. Absorbable plates may also be used for fixation in cases where follow-up is unlikely, but such plates should not be routinely used because absorbable plates are biomechanically weaker than titanium plates.[9] In any case, the conventional sequence of events involves surgical exposure of the displaced fracture site(s) as described below, reduction of the fractured bone segment(s), confirmation of alignment by direct visualization via the exposure obtained initially, and finally, rigid fixation. It is common practice among trauma surgeons to plate the zygomaticofrontal (ZF) suture first, then the zygomaticomaxillary (ZM) buttress or the infraorbital, and lastly, to repair the orbital floor, if necessary.

Management algorithm based on Zingg's classification system of ZMC fractures as described above (see Evaluation):[10]

• Type A1 (zygomatic arch fracture): Nondisplaced fractures of the ZA are often managed conservatively. In contrast, displaced fractures of the ZA require reduction, which is possible via a Gillies approach using a temporal incision, a transcutaneous Carroll-Girard screw directly over the depressed fracture site, or a Keen approach via an intraoral incision in the maxillary vestibule. Isolated arch fractures that are unstable after reduction can be splinted externally with steel wires or heavy sutures or plated via a coronal incision.[11]
• Type A2 (lateral orbital wall fracture): Reduction and fixation of this area are best accomplished via a lateral brow incision or an upper blepharoplasty incision. Mini-plates provide adequate stabilization of these fractures.
• Type A3 (infraorbital rim): The infraorbital rim should be reduced and plated to restore its normal contour and approached via either a transconjunctival or a subciliary lower eyelid incision.
• Type B (tetrapod fracture): Mildly displaced tetrapod fractures may occasionally be reduced via a Gillies or Keene approach. Most tetrapod fractures, however, remain unstable after such reduction attempts and ultimately require open reduction and internal fixation with single-point fixation (zygomaticomaxillary or zygomaticofrontal suture), 2-point fixation (ZM and ZF sutures), or 3-point fixation (ZM and ZF sutures, and infraorbital rim). Finally, the ZA can be plated via a coronal incision or pre-existing lacerations as the fourth point of fixation if necessary.
• Type C (comminuted tetrapod fracture): These fractures constitute absolute indications for open reduction and internal fixation (ORIF). Treatment is similar to that used for type B fractures, with ORIF of the ZM buttress, infraorbital rim, ZF suture, zygomaticotemporal suture, and zygoma fragments as necessary. 

Orbital Floor Exploration and Repair

Indications for repair of the orbital floor remain controversial. Generally, if greater than 50% of the floor is disrupted or the defect is ≥1 cm² in area, the orbital floor should be repaired. Additional indications include non-resolving oculocardiac reflex, diplopia in primary gaze, >3 mm of enophthalmos, and entrapment of extraocular muscles. Different materials may be used to reconstitute the orbital floor, including titanium mesh, porous polyethylene, vinyl or polydioxanone sheeting, dura, split calvarium, or temporalis fascia.[10] After repair, a forced duction test should be performed to ensure normal mobility of the globe (see Video. Forced Duction Testing).

Maxillary Sinus Fracture Management

Many maxillary sinus fractures may be managed conservatively, particularly if there is no more than minimal displacement and none of the facial buttresses or the orbital floor is involved. Frequent saline irrigation to decrease the risk of sinusitis and avoidance of nose blowing to prevent soft tissue pneumatosis are recommended, as they are for any patients with fractures involving the nasal cavity (including those with orbital fractures). The addition of antibiotics to the regimen remains controversial, as there is no clear advantage to their routine use.[12][13] For significantly displaced or comminuted fractures that do require fixation, the approach is typically made via a gingivolabial sulcus incision, which provides excellent exposure of the anterior face of the maxillary sinus. The bone fragments may then be fixated with plates and screws, mesh, or resorbable foils. Bone grafts may be employed as well, such as split calvarium, if large gaps persist after fragment reduction. More recently, minimally-invasive approaches employing endoscopic maxillary antrostomy, Foley catheter balloons, and fibrin glue to reduce and fixate the fragments without the need for an incision have been described.[14][15] One group additionally reported successful use of intraoperative ultrasound imaging to confirm appropriate bony reduction.[16]

Number of Fixation Points

No consensus exists on 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, and most surgeons will typically place at least two screws in each plate on each side of a fracture line to prevent rotation of the bone fragments around the screws. A 2019 meta-analysis published by Jazayeri et al suggested that 3-point fixation reduced fracture instability and orbital dystopia at three months post-operatively compared to 2-point fixation, but the quality of evidence was low.[17] The zygoma and its articulations should be palpated after fixation to determine if additional fixation points are needed, and an intraoperative or postoperative CT scan should be used to visualize the articulations of the zygoma and verify adequate reduction.(A1)

Order of Plating

There is no universally accepted plating order for multipoint fixation of ZMC fractures. During single-point fixation, the ZM suture is usually plated. The ZF suture can also be plated, although most surgeons would argue that the intraoral incision used to plate the ZM buttress is less morbid than the external incision needed to access the ZF suture. When performing two-point fixation, the ZF suture should be plated first, followed by the ZM buttress. During 3 or 4-point fixation, the ZF requires plating first, then the ZM buttress, then the infraorbital rim. If one plans to plate the ZA 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 been reduced, as mobilizing the zygoma often affects the configuration of the orbital floor; if the zygoma is impacted significantly, reducing it into its anatomical position will frequently increase the size of the defect by distracting the bone segments of the orbital floor.

Soft Tissue Suspension

If the lateral canthal tendon has been avulsed, it requires resuspension with suturing to the tubercle of Whitnall. The malar soft tissue may also require suspension to the periosteum of the zygoma to prevent ectropion or scleral show in the long term.

Summary of Surgical Approaches

• Existing lacerations are utilized to approach fixation sites (if possible)
• Zygomaticofrontal suture 
• Lateral brow incision
• Upper blepharoplasty incision
• Transconjunctival incision with lateral canthotomy and cantholysis
• Coronal or hemicoronal incision
• Zygomaticomaxillary suture
• Intraoral gingivolabial sulcus incision
• Infraorbital rim and orbital floor 
• Subciliary or subtarsal incision
• Transconjunctival incision
• Zygomatic arch
• Percutaneous stab incision for placement of Carroll-Girard screw: requires a conspicuous scar and theoretically puts the facial nerve at risk 
• Temporal incision (Gillies): conceals the scar in the hairline. Facial nerve can be preserved by dissecting deep into the temporalis fascia during dissection
• Intraoral incision (Sheen): conceals the scar in the mouth and avoids facial nerve injury. Careful, watertight closure of intraoral incision can prevent plate exposure in the mouth and oroantral fistula formation to maxillary sinus
• Coronal or hemicoronal incision

Timing of Repair

Fracture repair should take place as quickly as possible before scarring and setting of bony fragments into their posttraumatic positions begins. Because significant facial edema disguises aesthetic deformities and increases exposure difficulty, fracture repair should ideally be performed within 2 to 3 days of the initial injury. Fracture repair from 2 to 6 weeks post-injury is more difficult due to fibrosis and scarring. Fracture repair beyond 6 weeks is challenging but possible using intraoperative imaging and navigation. If orbital floor repair is necessary, it should ideally be performed within 2 weeks of injury.[10]

Differential Diagnosis

The zygoma contributes a significant portion of the inferior and lateral orbital walls. Any zygoma fracture warrants evaluating possible fractures or injury of the orbit, particularly open globe injuries. Cervical spine injury must be ruled out, as well as concomitant facial fractures, including frontal sinus, nasal, midface (eg, Lefort, naso-orbito-ethmoid), and mandible fractures. Midface trauma may result in nasal septal hematoma formation, which should be assessed and managed as necessary to avoid septal necrosis and perforation or saddle nose deformity. Lastly, malocclusion may result from mandibular or midfacial trauma and should be evaluated and addressed as well.

Prognosis

Comminuted fractures of the ZMC have worse outcomes than non-comminuted fractures, with a 33% higher rate of corrective surgery.[18] Some (5%-9%) patients, including those with non-comminuted fractures, will require a second operation due to inadequate fracture reduction.[18][19] Indications for revision surgery include persistent enophthalmos, diplopia, facial contour irregularity, and temporomandibular joint dysfunction.[18][20] Some degree of postoperative asymmetry occurs in 20% to 40% of patients, with major asymmetry occurring in 3% to 4%. Paresthesia may be persistent in the long term for 22% to 65% of patients.[21]

Complications

Complications from ZMC fractures can be related to the initial injury or operative management and can include:

• Pain
• Wound infection
• Facial asymmetry
• Scarring
• Bleeding (epistaxis)
• Hardware failure (exposure, palpability)
• Infraorbital nerve paresthesia
• Temperature sensitivity
• Facial paresis or paralysis
• Poor cosmetic result
• Trismus [18][22]

Orbital complications (usually related to concomitant orbital floor fracture):

• Blindness
• Decreased visual acuity
• Ectropion/entropion/lid malposition
• Corneal exposure/abrasion
• Ptosis
• Epiphora
• Enophthalmos/orbital dystopia
• Diplopia
• Superior orbital fissure syndrome