BLOW-OUT FRACTURES

CT can fairly accurately determine the size of the fracture and its relationship to the orbital soft tissues. Computed tomography (CT) scanning has become an integral factor in the diagnosis and treatment of blow out fractures. CT provides excellent detail of the bones and the relationship with the extraocular muscles and orbital tissues. Coronal views can help distinguish whether the muscle itself is entrapped, which can be difficult to evaluate on clinical examination.

Blowout fractures mainly involve orbital floor and medial wall. When an external force is applied to the globe, intraorbital pressure increases to the point that one or more of the thin-walled bones of the orbit “blow-out” or fracture. The most common bone fractured is the maxillary bone which comprises the floor of the orbit. The orbital contents can be significantly displaced inferiorly after orbital blowout fracture.

A > B i.e. Floor > Medial wall

Blow out fracture most frequently involves the floor of orbit along the thin bone covering the infraorbital canal (i.e. posteromedial wall of floor)Q. Occasionaly the medial wallQ may also be fractured. After h/o trauma from relatively large often rounded object (e.g. tennis ball, first) patient presents with periorbital oedema and blood extravasation in & around orbit, emphysema of eyelid, parasthesia & anaesthesia of infraorbital nerve, I/L epistaxis, proptosis, enopthalmos, diplopia (with forced duction test) Q. Water’s (nose-chin) view show hanging drop or tear drop sign Q

Blow Out Fracture

Occur when a blunt (non penetrating) force applied to anterior periorbital region compresses the orbital contents & causes a sudden increase in intraorbital pressure. This force is transmitted outward to the weakest orbital segment along with bone fragment & orbital content (eg fat). Severe ocular injury is rare as this is a nature’s way of protecting globe. It generally occurs after trauma to orbit by a large round object eg cricket ball or human fist.

These are isolated comminuted fractures of orbital floor (most common) & medial wallQ. Although lamina papyracea is truly thinner than the orbital floor, it is actually buttressed by perpendicular elements of ethmoid sinus bony lattice and therefore fractures less often than orbital floor. Orbital emphysema is most common in medial wall fractures.

Clinical features

• Periorbital oedema and blood extravasation in and around the orbit (such as subconjunctival ecchymosis)
• Emphysema of eyelid (mostly with medial wall fractures and made worse by blowing of nose)
• Parasthesia & anaesthesia in the distribution of infraorbital nerve (lower lid, cheek, side of nose, upper lip & upper teeth)
• Ipsilateral epistaxis
• Proptosis due to orbital oedema
• Enopthalmos after about 10 days as the oedema decreases, the eyeball sinks backward & inferiorly. It is due to

– Enlargement or orbit

Escape (herniation) of orbital fat into maxillary sinus Q

– Backward traction due to entrapped inferior rectus

• Diplopia Q in both up & down gaze (double diplopia)
• The presence of muscle restriction Q can be confirmed by a ‘positive forced duction test’ Q
• Restriction movements occur due to entrapment of inferior rectus & inferior obliqueQ
• Severe ocular damage is rare as this is a nature’s way of protecting globe. 

B i.e. Inferior wall

Blow out fracture mainly involve orbital floor (inferior wall) & medial wall Q. It presents with hanging drop or tear drop sign Q.

A i.e. Diplopia; B i.e. Tear drop sign; C i.e. Forced duction test

Blow out fracture is fracture of orbital floor or medial wall Q. It presents with emphysema of lid, subconjunctival ecchymosis, diplopia & forced duction test Q (due to entrapment of muscle), epistaxis, proptosis, enopthalmos & parasthesia in distribution of inferior alveolar nerve. X ray shows tear drop or hanging drop sign Q

Ans. Exophthalmos

1. A blow out fracture of the orbital floor is typically caused by a sudden increase in orbital pressure by a striking object which is greater than 5 cm in diameter, such as a fist or tennis ball.
2. The bones of the lateral wall and the roof are usually able to withstand such trauma, the fracture most frequently involves the floor of the orbit along the thin bone covering the infra orbital canal.
3. Occasionally, the medial orbital wall may also be fractured.
4. The floor consists of three bones: Zygomatic, Maxillary and Palatine.
5. The posteromedial portion of the maxillary bone is relatively weak and may be involved in a ‘blow out’fracture.
6. Therefore it is not the posterior wall of the floor of the orbit which is involved in the ‘blow out’ fracture of the orbit.
7. Fracture of the Roof of the orbit is caused by minor trauma such as falling on a sharp object or a blow to the brow or forehead, are caused by major trauma with associated displacement of the orbital rim. These are generally known as ‘blow in’ fractures.
8. Most medial wall orbital fractures are associated with floor fracture

Ans. Posteromedial floor of orbit

Ans. Medial wall and floor or orbit