Question

Blow out fracture of the orbit involves the:

• A. Floor
• B. Medial wall
• C. Lateral wall
• D. Roof

Hint:

Thinnest wall over the infraorbital canal gives way first.

Answer 1

The Correct Option is A

Step 1: A blow out fracture is produced by a sudden rise in intraorbital pressure that fractures the thinnest part of the bony orbit.
Step 2: The orbital floor is the most common site. The infraorbital neurovascular bundle runs in the floor, and the bone over this canal is only about 0.23 mm thick, with the posteromedial floor about 0.37 mm thick.
Step 3: By contrast the lateral part of the floor averages about 1.25 mm, over five times thicker, so the fracture occurs at the very thin area over the neurovascular bundle.
Step 4: Because the floor is the weakest wall and the usual site, the answer is floor. The medial wall is also thin but the floor is the classic blow out site.