Orbital Fractures

Fracture Patterns and Anatomy

The orbital floor is the most commonly fractured orbital wall in a "blowout" fracture. It is formed by the thin maxillary bone over the infraorbital canal, and this structural weakness relative to the thicker orbital rims is exactly why it gives way preferentially under blunt impact — a sudden rise in intraorbital pressure is transmitted to the weakest surrounding wall rather than the rim itself.

The medial orbital wall (lamina papyracea) is the other common fracture site. Medial wall fractures can entrap or injure the medial rectus muscle, producing restricted abduction and adduction — a horizontal motility deficit, unlike floor fractures, which more classically limit vertical gaze through inferior rectus involvement.

Orbital roof fractures are less common but carry a distinct danger: because the roof separates the orbit from the anterior cranial fossa, a roof fracture with pulsatile proptosis should raise concern for injury to the dura mater, with possible CSF leak or pneumocephalus. This finding mandates neurosurgical evaluation rather than being managed as a routine orbital fracture.

Complex Craniofacial Fractures

Beyond isolated orbital wall fractures, two named complex fracture patterns extend well beyond the orbit. The zygomaticomaxillary complex ("tripod") fracture classically disrupts the zygomatic arch, the orbital floor/rim, and the zygomaticofrontal suture, causing depression and rotation of the zygoma — the name reflects the three points of bony disruption around the cheekbone.

Le Fort III represents true craniofacial disjunction, the most severe of the Le Fort classification. The fracture line traverses the frontozygomatic and nasofrontal sutures along with the orbital floor and ethmoid bones, effectively separating the entire facial skeleton from the skull base.

Clinical Findings

An orbital floor fracture frequently injures the infraorbital nerve, which runs along the orbital floor. This produces hypoesthesia of the cheek, upper lip, gums, and lateral nose — a numb cheek and lip after blunt orbital trauma should prompt a floor fracture on the differential even before imaging.

Enophthalmos is a delayed but classic finding after blowout fracture. Fracture and outward displacement of the orbital walls increases the bony orbital volume, allowing orbital fat and soft tissue to prolapse into the adjacent sinus — which produces enophthalmos as the globe settles posteriorly within a now larger bony compartment.

Orbital emphysema — air trapped within the orbital soft tissues — occurs when a fracture communicates with an adjacent paranasal sinus, allowing air to track into the orbit, often worsened by nose-blowing. It's a useful confirmatory sign of sinus communication, though not itself an indication for urgent surgery.

Imaging and Entrapment

CT of the orbits, with thin coronal and axial cuts, is the gold-standard imaging study for diagnosing suspected orbital wall fractures — it is the standard of choice for evaluating bony fracture patterns, herniated contents, and muscle entrapment.

On coronal CT, a rounded or teardrop deformity of the inferior rectus muscle — herniating into the fracture site — strongly suggests entrapment and requires prompt surgical evaluation. Clinically, the finding most concerning for entrapment is restricted forced ductions: physically moving the eye during forced duction testing detects the mechanical restriction from a trapped muscle directly, independent of what imaging shows.

The Pediatric Trapdoor Fracture

Children's orbital bones are more pliable than adults', which produces a distinctive and dangerous fracture pattern: the "trapdoor" fracture, where the bone springs back into position after the impact, trapping the inferior rectus muscle within the fracture line and causing severe restriction of ocular motility, especially upgaze.

Entrapped tissue in a trapdoor fracture can trigger the oculocardiac reflex — a vagal response to extraocular muscle traction producing bradycardia, nausea, and vomiting on attempted eye movement. This combination is a genuine surgical emergency: it signals ongoing muscle traction and risks both muscle ischemia and cardiac complications if not released promptly.

Management and Repair

The most common indication for surgical repair of an orbital floor fracture is persistent diplopia with confirmed muscle entrapment. In adults without an emergent indication — such as entrapment causing the oculocardiac reflex — repair is typically performed within about two weeks of injury, allowing initial swelling to resolve while still preventing fibrosis and permanent restriction from developing.

Surgical reconstruction of the floor defect uses an orbital floor implant, made of materials such as titanium mesh, porous polyethylene, or resorbable sheets, placed to restore the bony floor and prevent recurrent herniation of orbital contents.

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