We went together, the med student and I, to check the eye complaint of a man who had been assaulted a few hours before. The student quickly decided we needed a facial CT to rule out a fracture. I asked him what kind of fracture he suspected; an orbital blowout fracture, he said.
I asked the patient to look toward his nose, and a prominent lateral subconjunctival hemorrhage popped prominently into view. This is truly a red flag for a more complex midface fracture. Finding zygomatic arch tenderness, I wondered aloud if our patient had a zygomaticomaxillary complex fracture.
There seems to be little need to have a framework to consider mid-face fractures these days. Most of us have ready access to a CT scanner, and a radiologist gives us our answer. I grew up medically in the era of plain facial films, however. We needed to have a mental schema to consider the bony blunt force injury to the face. I divide the face into thirds:
- Upper third: Above the eyebrows; rarely fractured in blunt trauma.
- Lower third: The mandible; often fractured, but clinical cues are helpful: two areas of pain, step off of teeth, inability to bite down on a tongue depressor.
- Middle third: Upper teeth to eyebrows; often fractured in simple and complex ways.
Simple and complex can be defined as:
- Simple: Nasal fractures, blowout fractures (medial and inferior), and isolated zygomatic arch fractures
- Complex: LeFort fractures and zygomaticomaxillary complex fractures
Zygomaticomaxillary complex (ZMC) fractures involve multiple midface bones including the zygomatic arch, the inferior orbital rim, the maxillary sinus walls, and the lateral orbital rim. Essentially, there is a free-floating chunk of bone inferior and lateral to the orbit. These fractures have been known by many other names, including tripod, trimalar, tetrapod, and quadripod fractures. Clinically one might note trismus from impingement on the muscles of mastication, inferior orbital numbness from a traumatized inferior orbital nerve, or a lateral subconjunctival hemorrhage.
I opened up the bony reconstruction to see if the images matched my imagination ... and clinical suspicion. There it was, as if I were reading a textbook: a ZMC fracture (or tripod, as I had called it in training a quarter century ago).
Tip to Remember: Think ZMC fracture when you see a lateral subconjunctival hemorrhage.
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