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Zygomatic Arch Dislocation – Complete Medical Guide

Overview

The zygomatic arch (also called the cheekbone or malar process) is the bony ridge that forms the lateral border of the eye socket and connects the zygomatic bone to the temporal bone. A zygomatic arch dislocation occurs when this arch is displaced from its normal position, usually after a high‑impact blow to the face. The injury is most commonly seen as a fracture that results in a “step‑off” deformity rather than a true dislocation, but the term is used clinically to describe any loss of the normal continuity of the arch.

Who it affects:

• Young adults (18‑35 years) – the age group most involved in contact sports and high‑energy trauma.
• Male individuals – accounting for roughly 70‑80 % of cases, likely due to higher participation in risk‑taking activities.
• Patients with pre‑existing facial bone conditions (e.g., osteogenesis imperfecta) may be more susceptible.

Prevalence: Isolated zygomatic‑arch injuries represent ~5‑10 % of all facial fractures, with an estimated 1–2 per 100,000 persons per year in the United States (CDC, 2022). They are more common in regions with high rates of motor‑vehicle collisions or combat‑related injuries.

Symptoms

The presentation can range from mild discomfort to severe facial deformity. Typical signs include:

• Visible flattening or depression of the cheek contour on the affected side.
• Swelling and bruising (often spreading to the periorbital area).
• Pain on palpation of the arch, especially when the jaw is opened or side‑to‑side.
• Difficulty opening the mouth (trismus) due to involvement of the temporalis muscle attachment.
• Clicking or grinding sensation when moving the jaw.
• Numbness or tingling in the cheek or lateral lower eyelid (possible infra‑orbital nerve involvement).
• Vision changes – double vision or diplopia if the orbital floor is also compromised.
• Hearing changes – rare, but a basal skull fracture can affect the ear.
• Loss of facial symmetry that becomes more apparent when smiling or grimacing.

Causes and Risk Factors

Traumatic events are the primary cause:

• Direct facial impact*: sports collisions (football, boxing, martial arts), bicycle or motorcycle accidents, falls from height.
• Indirect forces*: a blow to the jaw that transmits energy to the zygomatic arch.
• Penetrating injuries*: gunshot or shrapnel wounds.

Risk factors that increase susceptibility include:

• Engagement in high‑impact or contact sports without appropriate protective gear.
• Alcohol or drug use that impairs judgment and coordination.
• Pre‑existing bone weakness (osteoporosis, metabolic bone disease).
• Congenital facial skeletal anomalies.
• Previous facial fractures that have left the arch structurally compromised.

Diagnosis

Prompt and accurate diagnosis is essential to restore facial aesthetics and function.

Clinical Examination

• Inspection for asymmetry, bruising, and step‑off deformity.
• Palpation for mobility of the arch, tenderness, and crepitus.
• Assessment of ocular function (extra‑ocular movements, visual acuity) and infra‑orbital nerve sensation.
• Evaluation of jaw range of motion to detect trismus.

Imaging Studies

• CT scan (computed tomography) – the gold standard. Thin‑slice axial and coronal images show fracture lines, displacement, and any associated injuries (orbital floor, maxillary sinus).
• 3‑D reconstruction – helpful for surgical planning and patient counseling.
• Panoramic radiograph (OPG) – may reveal gross displacement but lacks detail for complex injuries.
• MRI – rarely needed, only if soft‑tissue (muscle or nerve) injury is suspected.

Classification

Most clinicians use the Le Fort classification system for mid‑facial fractures. Isolated zygomatic‑arch injuries are often described as “Zygomaticomaxillary complex (ZMC) Type I” when no other facial bones are involved.

Treatment Options

Treatment goals are to restore bony alignment, protect ocular structures, and preserve facial nerve function.

Non‑Surgical Management

• Closed reduction: In mild, nondisplaced fractures, manual repositioning under local anesthesia may be sufficient.
• Analgesia: NSAIDs (ibuprofen 400–600 mg q6‑8h) or acetaminophen; avoid aspirin in patients with coagulopathy.
• Cold compresses: 15 minutes on/off for the first 48 hours to reduce swelling.
• Soft diet: For 1‑2 weeks to minimize jaw stress.
• Follow‑up imaging: Repeat CT in 5–7 days if symptoms persist.

Surgical Intervention

Indicated for displaced fractures, facial asymmetry, or associated orbital injury.

• Open reduction and internal fixation (ORIF):
  • Incision placed either intra‑oral (sub‑labial) or extra‑oral (temporal) depending on surgeon preference.
  • Reduction of the arch by levering the fragment back into place.
  • Stabilization using titanium plates and screws (usually 2‑point fixation).
  • Typical operative time: 45‑90 minutes.
• Bone grafting: Rarely required, reserved for comminuted fractures with bone loss.
• Adjunctive procedures: If the orbital floor is involved, a separate repair with porous polyethylene or titanium mesh may be performed.

Post‑Operative Care

• Antibiotic prophylaxis – e.g., amoxicillin‑clavulanate 875/125 mg PO BID for 5 days (or clindamycin if allergic).
• Analgesics – continue NSAIDs as tolerated; prescribe short‑course opioids only if needed.
• Stitches removal – usually 5–7 days post‑op.
• Physical therapy – gentle jaw opening exercises after 1 week to prevent trismus.
• Sun protection – limit direct UV exposure for 6 weeks to prevent hyperpigmentation of scar tissue.

Living with Zygomatic Arch Dislocation

Recovery generally takes 4–6 weeks for minor injuries and up to 3 months for complex fractures.

• Nutrition: Soft, high‑protein foods (e.g., smoothies, yogurts, scrambled eggs) support healing.
• Oral hygiene: Use a soft‑bristled toothbrush; rinse with saline or an alcohol‑free mouthwash after meals.
• Sleep positioning: Elevate the head with an extra pillow to reduce edema.
• Activity modification: Avoid contact sports, heavy lifting, or anything that raises intrathoracic pressure (e.g., straining during bowel movements) for at least 6 weeks.
• Emotional health: Facial changes can impact self‑image; consider counseling or support groups if distress persists.

Prevention

Many zygomatic‑arch injuries are preventable with simple measures:

• Wear approved face shields or full‑face helmets during high‑risk activities (motorcycling, cycling, equestrian sports).
• Use mouthguards in contact sports to limit the transmission of forces to the mid‑face.
• Practice proper technique and adhere to safety rules in sports and workplace environments.
• Limit alcohol consumption, especially when operating vehicles or engaging in potentially hazardous activities.
• Maintain good bone health: adequate calcium (1,000 mg/day) and vitamin D (600–800 IU/day); engage in weight‑bearing exercise.

Complications

If untreated or improperly managed, a zygomatic‑arch injury can lead to:

• Persistent facial asymmetry – may require secondary corrective surgery.
• Chronic pain or neuralgia from infra‑orbital nerve injury.
• Trismus due to temporalis muscle entrapment, limiting mouth opening.
• Orbital complications – diplopia, enophthalmos (sunken eye), or globe rupture if the orbital floor is involved.
• Infection of the fracture site or sinusitis secondary to maxillary sinus involvement.
• Non‑union or malunion of the bone causing long‑term functional deficits.
• Psychological impact – self‑esteem issues related to altered appearance.

When to Seek Emergency Care

References

• Mayo Clinic. “Zygomatic bone fracture.” 2023. mayoclinic.org
• Centers for Disease Control and Prevention (CDC). “Traumatic Brain Injury & Facial Fractures.” 2022.
• National Institutes of Health (NIH) – National Institute of Dental and Craniofacial Research. “Facial Trauma.” 2021.
• Cleveland Clinic. “Facial bone fractures: Diagnosis & treatment.” 2023.
• World Health Organization. “Injury prevention and safety.” 2020.
• J. J. Ellis et al., “Open reduction and internal fixation of zygomatic arch fractures: Outcomes in 124 patients,” *Journal of Oral and Maxillofacial Surgery*, vol. 78, no. 4, 2020.

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