BLOW-OUT FRACTURES

BLOW-OUT FRACTURES

• Caused by direct trauma to the globe.
• Causes an increase in intraorbital pressure & decompression via fracture of the ornital floor (ot its wall).
• They are usually due to blunt trauma caused by a large object such as a cricket ball, human fist etc.

Site of fracture

• Most commonly the orbital floor blows, but it can also affect the medial wall of the orbit.
• M/c site is posteromedial aspect of the orbital floor, medial to the infraorbital neurovascular bundle where the maxillary bone is very thin.
• Lamina papyracea is also thin & the medial orbital wall is also prone to fracture.
• The orbital floor overlies the maxillary sinus without reinforcement, therefore is weaker & more blowouts tend to occur here.
• Especially in the posteromedial floor (near the infraorbital groove), where it is the weakest area.
• Fracture of the floor causes the orbital contents to collapse into the the maxillary sinus, causing enopthalmos & entrapment of the inferior rectus muscle. 

Blowout fractures are divided into pure & impure

1. Pure orbital blowout  fracture:

• Used to describe a fracture of the orbital floor, the medial orbital floor or both.

2. Impure orbital blowout fracture is when such fractures occur in combination with a fracture of the orbital rim.

CLINICAL FEATURES

• Periorbital edema & blood extravasation e.g. Subconjunctival ecchymosis.
• Emphysema of eyelids (in medial wall fracture).
• Paraesthesia & anaesthesia in the distribution of infraorbital nerve i.e.

1. lower lid
2. cheek
3. side of nose
4. upper lip & teeth

• Ipsilateral epistaxis
• Proptosis (exophthalmos) of variable degree occurs initially due to orbital edema & haemorrhage.
• Later there is enophthalmos & mechanical ptosis as the edema subsides & eyeball sinks backward & downward.
• Enophthalmos is more characterstic of blowout fracture, not exophthalmos.
• Diplopia in both up & down gaze (double diplopia) due to entrapment of soft tissue structures.
• The presence of muscle restriction can be confirmed by a positive forced duction test.
• Plane X-ray: Water’s view is best. It shows-

1. Fragmentation & irregularities of orbital floor

2. Depression of bony fragments

3. Hanging drop opacity (Tear drop sign) because of herniation of orbital content into superior part of maxillary antrum.

TREATMENT

• Small cracks & fractures involving less than half of the orbital floor with little or herniation & improving diplopia do not require treatment unless more than 2mm endophthalmos develop.
• Fractures involving half or more orbital floor with entrapment of orbital contents & persistent diplopia in the primary should be repaired within 2 weeks by using synthetic material such as a silicon, teflon, or supramid.

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