The Zygoma

The zygoma forms a large part of the anterolateral wall of the orbit, the lateral margin of the infraorbital rim and the anterior segment of the zygomatic arch. It articulates with the superior portion of the maxilla and the frontal, temporal and sphenoid bones.

Zygomaticomaxillary Complex (ZMC)

In the past the ZMC was frequently referred to as a tripod but functionally it is more correct to consider it as having four legs, like a four-legged stool. This analogy helps to understand the likely sites of fracture and displacement when the ZMC is struck by a direct blow.

The anatomical structures corresponding to the four legs of the stool:

• Lateral orbital rim
• Inferior orbital rim
• Zygomaticomaxillary buttress the thickened area of bone forming the lateral wall of the maxillary sinus
• Zygomatic arch

Zygomatic Arch

The zygomatic arch is predominantly formed by the zygomatic process of the temporal bone which articulates with the much smaller temporal process of the zygoma forming the arch. The temporalis muscle and coronoid process of the mandible lie beneath the arch and may become trapped in depressed fractures of the zygomatic arch.

Immediately below the infraorbital margin lies the infraorbital foramen, through which passes the infraorbital nerve (part of the maxillary division of the trigeminal nerve). The nerves location makes it very vulnerable to both direct injury, and involvement in ZMC fractures.