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Case 5 - Mandibular Fractures

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As I mentioned in the Yousem literature and experience, nasal bone fractures

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are the most common of the facial bone fractures followed by orbital fractures.

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In the maxillofacial literature, they say that mandibular fractures are

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more common than orbital wall fractures. When the mandible fractures, there's

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different portions of the mandible that will fracture and they include:

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The condyle, most commonly; the mandibular body, 21%; the symphysis, which

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is the frontal portion, in 14%; and then you have the less common

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sites, the angle, the ramus, the alveolar ridge and the coronoid process.

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Now, remember that the mandible is a ring

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and, therefore, if you have a fracture on one side of the mandible,

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it is highly likely that there is a fracture on the other side

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of the mandible, but not necessarily the same portion. So it's not unusual

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for us to see a symphysis fracture in association with a contralateral condyle

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fracture, or a body fracture and a ramus fracture. So it's not a

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symmetric fracture that tends to occur. The importance of mandibular fractures

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is that there are a lot of different complications that could occur including:

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Loss of the teeth because of a fracture that crosses the neurovascular bundle;

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mal union or non union of the fracture; avascular necrosis, and this tends

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to occur with neck fractures with avascular necrosis of the distal portion,

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that being the mandibular condyle; mirror displacement or deformity and

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malocclusion are fairly common, if it's not reduced appropriately;

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secondary temporomandibular joint ankylosis or degenerative change; and

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of course, whenever you have a fracture that may communicate with the oral

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cavity, you can have infection. I just want to point out the parts

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of the mandible. The symphysis being that frontal portion,

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the body just off the midline, and then we have the angle of

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the mandible where it starts to turn upward,

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the ramus, the coronoid process, and then the condylar fracture which leads

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to the mandibular condyle being separated here. Those that are occurring

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at the neck or sub condylar portion are the ones that have the

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highest risk of avascular necrosis. And here you see a few examples on

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slides of fractures that involve the symphysis and body on the right side,

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and a relatively subtle fracture which is occurring at the angle and ascending

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ramus of the left side of the mandible. Here's a different fracture

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coming across the symphysis. Here's an angle of the mandible fracture on

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coronal images. So this is all part of that ring where we may

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have fractures on both sides of the mandible but not necessarily symmetric

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ones. By mandibular ring, I'm not talking about cosmetic rings that some

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people will use to puncture their mandible or their tongue or their floor

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of the mouth. Here's another example of a fracture, this is in a

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child, where the fracture, as you can see, is involving the ascending ramus

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of the mandible with displacement of the fracture fragments. Always be careful

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with the mandibular fractures that there's no compromise of the oral airway

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because loss of an airway in a child or an adult with an

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associated fracture can lead to, obviously, hypoxic ischemic injury. As

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you can see with this case, you may also lose some of the

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teeth. In this case, this is the un erupted mandibular molar tooth on

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the right side. Here, we've lost that tooth. It's not extracted;

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it's been lost in the patient's mouth. And sometimes you may even find

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the tooth as something that the patient may aspirate into the airway.

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Fractures that involve the mandibular nerve canal, which is this structure

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right here that you follow down into the mandibular alveolus, may also lead

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to decrease or numbness in the soft tissues anterior to the mandible.

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Here, you can see a fracture which is going across the root of

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the tooth. Here is the same fracture on the sagittal reconstruction with

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comminution and, again, the tooth has been lost, either spit out or into

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the patient's airway or swallowed. Three dimensional reconstructions are

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really useful in the display of the mandibular fractures, particularly as

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the surgeons contemplate the reduction of the fracture into a normal alignment.

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So we like doing these 3 D recons to better display those displacements

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when the fracture is either comminuted or medial or laterally displaced.

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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