Zygomaticomaxillary Complex (ZMC) Fracture

Figures 1 & 2: Axial CT images show displaced fractures of the anterior and posterior walls of the right maxillary sinus (arrows), subtle fracture of the right zygomatic arch (short arrow) and a slightly angulated fracture of the lateral wall of the orbit (arrowhead).
Figure 3: 3D CT image shows a complete look of a ZMC fracture, including the fracture of the maxillary walls, zygomatic arch (arrow) and lateral orbital wall at the zygomaticosphenoid suture (arrowheads).

Facts: ZMC Anatomy

• The zygomaticomaxillary complex is a quadrupled structure, meaning that it relates to 4 different bones of the skull: temporal bone, maxilla, frontal bone and skull base
• Paired zygomas each have two attachments to the cranium and two to the maxilla.
• Two major 'buttresses' of the ZMC are: upper transverse maxillary (across zygomaticomaxillary and zygomaticotemporal sutures) and lateral vertical maxillary (across zygomaticomaxillary and zygomaticofrontal sutures).
• In fact, zygoma also relates posteriorly with the sphenoid bone of the skull base

Facts: ZMC Fractures

• Fractures involving this quadrupled structures: anterior maxillary wall, posterolateral maxillary wall, zygomatic arch and lateral orbital wall
• If fracture at the lateral orbital wall is angulated, it often increases orbital volume resulting in enophthalmos)
• If fracture at the zygoma is comminuted, it often requires fixation via a scalp incision to fix the loss of cheek projection and increase facial width
• Frequently missed ZMC fracture is at the temporal bone portion

Imaging Descriptions

• Describe alignment of the zygoma and sphenoid at the lateral orbital wall fracture; angulation here reflects rotation deformity and increased orbital volume that needs to be fixed
• Describe if the fracture along the zygomaticomaxillary suture traverses the infraorbital nerve foramen
• Degree of comminution of zygomatic arch
• Don't forget to look at the temporal bone portion of the ZMC for a fracture

Reference:

Hopper RA, Salemy S, Sze RW. Diagnosis of midface fractures with CT: what the surgeon needs to know. Radiographics 2006;26:783-793.