zygomaticomaxillary complex fracture
Zygomaticomaxillary complex (ZMC) fractures, also known as tripod, tetrapod, quadripod, malar or trimalar fractures, are seen in the setting of traumatic injury to the face. They comprise fractures of the:
- zygomatic arch
- inferior orbital rim, and anterior and posterior maxillary sinus walls
- lateral orbital rim
They can account for ~40% of midface fractures. They are the second most common facial bone fracture after nasal bone fractures.
The fracture complex results from a direct blow to the malar eminence and results in three distinct fracture components that disrupt the anchoring of the zygoma. Additionally, the fracture components may result in impingement of the temporalis muscle, trismus (difficulty with mastication) and may compromise the infraorbital foramen/nerve resulting in hypoesthesia within its sensory distribution.
On radiographic evaluation, typically with dedicated CT imaging with multiplanar reformats, the following three fracture components are generally identified:
- fracture of the zygomatic arch and/or diastasis of the temporozygomatic suture
- fractures of the inferior orbital rim and anterior and posterior maxillary sinus walls and/or diastasis of the zygomaticomaxillary suture
- fracture of the lateral orbital rim and/or diastasis of the frontozygomatic suture