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Case 2 - Orbital Blow Out Fractures

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What do we mean when we refer to orbital

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blow out fractures? Generally,

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this is a situation where there has been acute

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increase in the pressure in the orbit by either

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something hitting the globe or the orbital

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structures via the baseball in this case,

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or a fist, whatever it may be.

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And with that increasing pressure,

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something has to give.

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And usually it's the orbital floor or the

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medial orbital wall, which are the most vulnerable.

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The orbital floor potentially because of the

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presence of the infraorbital foramen,

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which is a weakness in the orbital

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floor, and the medial orbital wall,

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because as we talk about it,

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the lamina papyracea refers to papyracea,

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which means paper thin. Papyracea

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paper, paper thin medial orbital wall.

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So it's not unusual to see a fracture of the orbital

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floor when you're hitting the eye or the medial

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orbital wall, lamina papyracea.

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You notice in both of these examples, the

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inferior rectus muscle is crossing the plane

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of the fracture along with orbital fat.

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And here, you can make out the medial rectus muscle

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crossing the plane of the fracture

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along with orbital fat.

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These are going to be the risk factors that we as

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normal radiologists will evaluate

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as likely causing entrapment.

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So when you have an orbital floor fracture,

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assess that inferior rectus muscle for its

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shape and position to assess the fascial

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sling of the globe if round,

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if rounded and inferior located and / or the

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fat, that's more likely to be an indicator

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of entrapment. In children,

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you can have these little flaps that occur or trap

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door fractures that also may entrap the muscles.

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With regard to the medial orbit,

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again, high rate of diplopia,

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usually either because of edema of the medial rectus

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muscle or because of entrapment of the

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medial rectus muscle. Both of them,

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because there is an orbital tissue which is

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exiting the orbit and going into the paranasal

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sinuses may lead to enophthalmos, the eye

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actually sinking in compared to the

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contralateral eye from the involvement. I mentioned

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in the case discussion about the importance of

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mentioning whether or not the

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orbital rim is involved. Now,

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the orbital rim is the very anteriormost

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portion of the orbital floor.

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And you see that both on the axial scan as well as

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the anterior most image of the coronal imaging.

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And these lead to what are called impure fracture.

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These impure fractures involve

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orbital rim, often need need emergent realignment

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of the floor because of the attachments

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of the muscle and leading to decreased extraocular

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motility. If the lateral wall is involved,

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and I've only shown you one case

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where the lateral wall is involved,

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you have to think about the potential

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for a trimalleolar or a tripod fracture,

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and we'll refer to these as ZMC

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fractures in just a moment.

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So look elsewhere for the attachment

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of the zygoma to the frontal bone,

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the maxillary bone and the sphenoid

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bone. Roof fractures,

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I showed an example of lots of potential

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intracranial complications because of the potential

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communication with the subarachnoid space

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leading to potentially meningitis.

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If you have infection from that fracture,

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it may also lead to an extra axial

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collection of purulent material,

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usually manifesting as an epidural abscess.

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As I mentioned,

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coronal reconstructions are key. If you don't get

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them routinely from your technologists

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or from the scanner,

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make your own from the thin-section axial scans,

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so that way you have the greatest resolution

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for detecting these fractures.

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Beware retrobulbar hematoma

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and the orbital apex fractures,

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because they can lead to encroachment on the optic

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nerve, leading to an ischemic optic neuropathy,

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leading to blindness due to the optic nerve being

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injured. And finally, another pearl, as I said,

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was look for any little droplets of air.

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Wherever you see a droplet of air,

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try to explain it with an adjacent fracture.

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So here are just to make the points,

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orbital floor fracture with orbital

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emphysema on the right side.

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Here we have lamina papyracea fracture

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with little droplets of air nearby.

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Here we have air fluid levels indicative of

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potential hemorrhage from orbital floor fractures.

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Here we see fracture involving the infraorbital

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foramen, but as importantly,

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this is the anterior orbital rim.

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So this is an impure fracture involving the

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orbital rim. And finally, as I mentioned,

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the presence of air fluid levels that will indicate

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whether or not there is a fracture.

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So in this case,

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looking at the infraorbital foramen and a fracture

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that went right through the infraorbital foramen,

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and compare that to the normal side.

Report

Faculty

David M Yousem, MD, MBA

Professor of Radiology, Vice Chairman and Associate Dean

Johns Hopkins University

Tags

Neuroradiology

Head and Neck

Emergency

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