Poskiluun

Poskiluu, or zygomatic bone, is a paired skull bone that forms the cheekbone and part of the orbit. It lies on each side of the face, anterior to the temporal bone, and contributes to the cheek’s contour as well as to the lateral wall and floor of the eye socket. The poskiluu articulates with four bones: the frontal bone superiorly, the maxilla medially, the sphenoid posteriorly, and the temporal bone laterally via the zygomatic arch. The bone has three processes: a frontal process that helps form the orbital rim, a maxillary process that contributes to the floor of the orbit and the zygomaticomaxillary suture, and a temporal process that participates in the zygomatic arch.

The body of the poskiluu is curved, giving the facial contour. The bone features an orbital surface that contributes to the orbital rim and floor and a lateral surface that forms part of the cheek’s prominence. During development the poskiluu forms by intramembranous ossification.

Functionally, the poskiluu provides structural support for the orbit and face and serves as an attachment site for facial muscles, including zygomaticus major and minor, which influence expressions, and for the masseter muscle via the zygomatic arch.

Clinical significance: Fractures of the zygomatic bone — commonly part of zygomaticomaxillary complex injuries — can cause flattening of the cheek, orbital symptoms such as diplopia, and numbness if the infraorbital nerve is affected. Diagnosis relies on imaging; treatment may involve reduction and fixation with plates.

See also: Zygomatic bone, ZMC fracture.