Blow-Out Fracture

Basics

Description

  • Defined as an orbital floor fracture that results from sudden blunt trauma to the orbital region
  • Orbital floor serves as roof to air-filled maxillary and ethmoid sinuses:
    • Communication between the spaces results in orbital emphysema
  • Orbit contains fat, which holds the globe in place:
    • Orbital floor fracture may result in herniation of the fat on the inferior orbital surface into the maxillary or ethmoid sinuses
    • Leads to enophthalmos owing to orbital volume loss and sinus congestion; fluid collection may occur secondary to edema and bleeding
  • Infraorbital nerve runs through the bony canal 3 mm below the orbital floor:
    • Injury may result in hypoesthesia of the ipsilateral cheek and upper lip
    • To distinguish facial hypoesthesia related to local swelling from nerve injury: Test for sensation on the ipsilateral gingiva, which is within the infraorbital nerve distribution
  • Inferior rectus and the inferior oblique muscle run along the orbital floor:
    • Restriction of these extraocular muscles may occur because of entrapment within the fracture, contusion, or cranial nerve dysfunction
    • Typically manifests as diplopia on upward gaze
    • Inability to elevate the affected eye normally on exam
  • Medial rectus located above the ethmoid sinus:
    • Less commonly entrapped
    • Diplopia on ipsilateral lateral gaze

Etiology

Caused by blunt trauma that strikes the orbit. The force is transmitted through the noncompressible structures of the orbit to the weakest structural point, the orbital floor, resulting in a blow-out fracture

Pediatric Considerations

  • Orbital floor fractures: Unlikely before age 7:
    • Orbital floor is not as weak a point in the orbit due to lack of pneumatization of the paranasal sinuses
  • Fractures can occur in children and may result in unrecognized entrapment of the rectus muscle labeled the “white-eyed” fracture:
    • Findings are subtle and there may be little associated soft tissue injury
    • These children may present with marked nausea, vomiting, bradycardia, headache, and irritability suggestive of a head injury that commonly distracts from the true diagnosis
  • Orbital roof fractures with associated CNS injuries more common in children

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