The Zygomatic Bone
The zygomatic bone (also known as the zygoma) is one of the most irregular shaped bones of the skull. It consists of three different processes, varying in size and shape. Because the pair of them protrude laterally and form the eminences of the face ("cheek bones"), both are prone to fractures.
Several bones and joints surround the zygoma including the:
- frontal bone via the frontozygomatic suture, which creates the rounded form of the bony orbit
- zygomatic process of the temporal bone, linked by the temporozygomatic suture
- zygomatic process of the maxillary bone, articulated by the zygomaticomaxillary suture, which again, forms another aspect of the bony orbit.
As well as supporting the facial tissue and pronouncing it to form cheeks, the zygomatic bone also serves as a place of insertion for the masseter muscle, which is one of the four muscles of mastication.
The bone contains three main foramina which are strategically dotted about in the various processes.
- The zygomaticofacial foramen is located in the frontal process of the zygoma and contains the zygomaticofacial nerve and corresponding vessels.
- The zygomatico-orbital foramina are found in the frontal process, lateral to the bony orbit. Between the zygomaticofacial and zygomatico-orbital foramina runs a small canal connecting them. One side opens into the temporal fossa and the other opens into the malar part of the zygoma.
- The zygomaticotemporal foramen exists in the temporal process of the zygoma, while the maxillary process doesn’t contain any foramina.
The entire zygoma matures through a process known as intramembranous ossification.
The second most common area of fracture in the face is the zygoma, especially the left frontal process of the zygomatic bone, e.g. due to the impact of a car accident or a blow from a fist. Depending on the severity of the dislocation, the bone can either move slightly along its sutures or more severely in an anterior, medial, lateral or posterior direction.
Clinically, one should check for the following symptoms:
- a flattened cheek bone
- a subconjunctival hemorrhage
- bone displacement and mobility
- a lowered lateral portion of the palpebral fissure due to the downward displacement of the lateral canthal ligament and ecchymosis.