Blowout Fracture

A fracture of the thin orbital floor or medial wall caused by a sudden rise in orbital pressure from a direct blow to the globe or orbital soft tissues (fist, ball, elbow, dashboard, airbag), while the orbital rim stays intact (pure blowout) or is fractured as well (impure).

• Mechanisms: hydraulic theory (pressure transmitted through the globe and orbital fat to the weakest walls) and buckling theory (force transmitted along the rim to the floor).
• Sites: floor (most common, posteromedial to the infraorbital groove and canal), medial wall (lamina papyracea, thin and perforated by ethmoid air cells), or both.
• Contents may herniate into the maxillary or ethmoid sinus (fat, inferior rectus, inferior oblique, medial rectus) and become trapped.
• Associated ocular injuries in about 25 to 30 percent: hyphaema, angle recession, corneal abrasion, retinal tear, commotio retinae, choroidal rupture, traumatic optic neuropathy, and open globe.
• Children: trapdoor fracture with a "white eyed blowout", in which a pliable bone springs back and traps the muscle with ischaemia.

• Periorbital oedema, ecchymosis, subconjunctival haemorrhage, orbital emphysema (after nose blowing), epistaxis.
• Diplopia in upgaze and downgaze (vertical); limited elevation (inferior rectus entrapment) and sometimes limited depression; limited abduction and adduction in medial wall fractures; positive forced duction test.
• Infraorbital nerve hypoaesthesia (cheek, upper lip, upper teeth and gums), enophthalmos (delayed, as swelling resolves; above 2 mm is significant), hypoglobus, and lowered globe position.
• Pain on eye movement, nausea, vomiting, bradycardia and syncope (oculocardiac reflex), particularly in trapdoor fractures in children.
• Palpable step at the rim and crepitus in impure fractures.
• Visual loss in the presence of retrobulbar haemorrhage or optic nerve injury requires urgent attention.

• Complete eye examination first to exclude globe injury (acuity, pupils, pressure when globe is intact, dilated fundus examination); orthoptic assessment of binocular single vision field, Hess or Lees chart, forced duction test.
• CT of the orbits with thin axial slices and coronal and sagittal reconstructions: fracture site and size, herniated tissue, enlarged volume, rectus muscle position, haemosinus; "teardrop" sign of herniated tissue hanging in the maxillary sinus; trapdoor fractures may show only subtle linear defects.
• Exophthalmometry baseline and repeat (enophthalmos); infraorbital sensory testing.
• ECG monitoring in children with bradycardia.

• Initial: ice packs for 48 hours, head elevation, avoid nose blowing for 2 to 3 weeks, analgesia (paracetamol 1 g four times daily), decongestant spray (oxymetazoline 0.05 percent twice daily for 3 days), antibiotics when sinus communication or contamination exists (amoxicillin clavulanate 625 mg three times daily for 5 to 7 days; in penicillin allergy, clarithromycin 500 mg twice daily or doxycycline 100 mg twice daily), and oral prednisolone 40 to 60 mg daily for 3 to 5 days in selected patients with marked oedema or restriction.
• Emergency surgery within 24 to 48 hours: trapdoor fractures in children with muscle entrapment (limited motility with oculocardiac reflex, nausea and vomiting), and any entrapment with ischaemia.
• Elective surgery at 7 to 14 days (before fibrosis around 2 to 3 weeks), indicated for:
  • Persistent restrictive diplopia with confirmed entrapment.
  • Large floor defect (over 50 percent of floor or over 2 cm2) or medial wall defect with risk of enophthalmos.
  • Enophthalmos over 2 mm or hypoglobus.
  • Associated displaced fractures.
• Technique: transconjunctival, subciliary or transcaruncular approach, release of herniated tissue, restoration of continuity with a floor implant (porous polyethylene, titanium mesh, absorbable polydioxanone sheet, or autologous bone); forced duction test before and after; postoperative check for implant position and optic nerve function.
• Observation (when diplopia improves, motility is near full, enophthalmos is minimal, and defect is small), with reviews at 1, 2 and 4 weeks and 3 months.
• Late: persistent diplopia (prisms, strabismus surgery), lower lid retraction, implant infection or migration, enophthalmos (secondary orbital reconstruction), and infraorbital numbness (may persist for months).