Blown out

Blowout fracture

An injury resulting in an increase in intra-orbital pressure has ‘blown out’ the floor of the left orbit with the displacement of fragments into the maxillary sinus.

There are at least two theories explaining this mechanism:

• the ‘hydraulic theory‘ — the force of the impact is transmitted from the globe to the orbit, which fractures at its weakest point: the floor.
• the ‘buckling theory‘ — the orbital floor buckles and fractures due to a direct blow to the orbital rim.

On the Waters view:

• The depressed fragment appears as an oblique line or ‘trapdoor‘ near the roof of the maxillary sinus.
• prolapsed soft tissue classically gives rise to the ‘tear drop‘ sign.
• Maxillary sinus opacification is seen with an air-fluid level.
• Inferior orbital rim and lateral wall of the maxillary sinus should be intact.
• Sometimes orbital emphysema is the only radiographic evidence that can be seen.
• Overlying soft tissue is a nonspecific finding.

History:

• mechanism of injury — typically blowout fractures result from an injury that increases the intraorbital pressure such as a blow from a fist or a small ball striking the eye/orbit at high speed.
• symptoms — pain (especially on vertical movement), local tenderness, diplopia (especially on vertical gaze), eyelid swelling and crepitus after nose blowing

Examination:

• epistaxis, ptosis, localised tenderness
• restricted eye movements, particular on vertical gaze, resulting in diplopia
• complete eye examination looking for evidence of ocular injury, e.g. hyphema, subconjunctival hemorrhage, retro-orbital hemorrhage, retinal detachment and vitreous hemorrhage.
• check for infraorbital nerve involvement — anesthesia of the affected cheek, and the upper teeth and gums on the affected side. this nerve passes along the floor of the orbit and be stretched or otherwise damaged.
• palpate the eyelid for crepitus
• there may be no other significant facial injury.

A CT scan of the orbits and brain may be required depending on the mechanism and associated injuries. However, the Caldwell (occipitofrontal) and Waters (occipitomental) facial radiographic views are often sufficient.

Early treatment includes:

• nasal decongestants for 1 week
• prophylactic antibiotics, e.g. cephalexin 500mg qid po
• instruct the patient to avoid nose blowing and valsalva maneuvers; and to avoid driving until diplopia resolves.
• apply an ice pack to the orbit for 1-2 days

• Ophthalmology referral is required for suspected orbital floor fractures (Maxillofacial surgeons manage these cases in some centres).
• Follow up in 1 week post-trauma to check for persistent diplopia or enophthalmos. Entrapment may resolve with the resolution of edema.
• Surgical repair is usually performed 1-2 weeks after the injury if required

This suggests the presence of traumatic optic neuropathy, vitreous hemorrhage, retinal detachment or intracranial injury (e.g. asymmetric damage to the optic chiasm).

Traumatic optic neuropathy may result from:

• compressive optic neuropathy — retrobulbar hemorrhage, orbital foreign body or orbital emphysema
• optic nerve sheath hematoma
• optic nerve head avulsion
• optic nerve laceration

and result from either direct or indirect mechanisms:

• direct — e.g. apical orbital fracture
• indirect — e.g. deceleration injury (e.g. head versus steering wheel) resulting in shearing of pial vessels to the optic nerve

Emergent ophthalmologist consultation is warranted.

Orbital fractures may be classified as:

• affecting the orbital rim
• affecting the orbital walls
• part of more complex midface fractures

Those affecting the orbital walls include:

• apical fractures —  usually involve severe and potentially lethal forces, and associated with involvement of the optic canal and traumatic optic neuropathy.
• superior wall fractures — herniatiation into the frontal sinus is rare but there may be extension to the posterior  wall of the frontal sinus and a CSF leak.
• medial wall fractures — associated with more extensive midface and nasal injuries. There may be soft tissue herniation into the ethmoid sinuses through the lamina papyracea (medial wall). Diplopia and exophthalmos are characteristic.
• fractures involving multiple walls of the orbit — associated with extensive midface fractures. There is no universally accepted classification system

Transverse section of CT Face showing a right medial orbital wall fracture. Although the lamina papyracea is the thinnest part of the orbital wall, it is not the weakest part as it is buttressed by the ethmoid air cells.

• Ehlers JP, Shah CP, Fenton GL, Hoskins EN. The Wills Eye Manual: Office and Emergency Room Diagnosis and Treatment of Eye Disease Lippincott Williams & Wilkins
• NSW Statewide Opthalmology Service. Eye Emergency Manual — An illustrated Guide. [Free PDF]