Cheekbone
Os Zygomaticum
location_on Lateral face, forming the prominence of the cheek and lateral orbital wall
The zygomatic bone forms the bony prominence of the cheek and the lateral and inferior margins of the orbit. It bridges the maxilla to the temporal bone via the zygomatic arch, creating a bony bar that protects the temporalis muscle and transmits forces of mastication. The bone is frequently fractured in facial trauma due to its prominent position.
Key Anatomical Features
- Zygomatic arch is formed with the temporal process and transmits masticatory forces
- Orbital surface forms part of the lateral wall and floor of the orbit
- Zygomaticofacial foramen transmits the zygomaticofacial nerve to the cheek
- Temporal surface contributes to the temporal and infratemporal fossae
- Frontal process articulates with the frontal bone at the lateral orbital rim
Muscle Attachments
| Muscle | Attachment | Action |
|---|---|---|
| Masseter | Inferior border and medial surface of zygomatic arch | Elevates the mandible |
| Zygomaticus major | Lateral surface of zygomatic bone | Draws the angle of the mouth superolaterally (smiling muscle) |
| Zygomaticus minor | Anterior surface of zygomatic bone | Elevates the upper lip |
| Temporalis | Passes deep to the zygomatic arch | Elevates and retracts the mandible |
Joints and Articulations
| Joint | Type | Connects to |
|---|---|---|
| Zygomaticomaxillary suture | Fibrous suture | Maxilla |
| Zygomaticotemporal suture | Fibrous suture | Temporal bone |
| Frontozygomatic suture | Fibrous suture | Frontal bone |
Common Pathologies
Tripod (trimalar) fracture
Fracture of the zygomatic bone at its three sutural attachments (frontozygomatic, zygomaticomaxillary, and zygomaticotemporal). Causes flattening of the cheek and infraorbital nerve numbness.
Zygomatic arch fracture
Isolated fracture of the arch from a direct blow, causing a depressed cheekbone and difficulty opening the mouth if fragments impinge on the coronoid process.
Orbital floor blowout (involvement)
The zygomatic bone's orbital surface can be involved in orbital floor fractures, leading to enophthalmos, diplopia from extraocular muscle entrapment, and infraorbital numbness.
Clinical Relevance
Zygomatic fractures are the second most common facial fracture after nasal fractures. Clinical signs include flattening of the cheek, subconjunctival hemorrhage, infraorbital numbness (from injury to the infraorbital nerve), and trismus if the arch impinges on the coronoid process. Examination should always include assessment of extraocular movements and ocular integrity.
Development and Ossification
The zygomatic bone ossifies intramembranously from a single center appearing around the 8th fetal week. Occasionally, a horizontal suture divides the bone into upper and lower parts, a variant called os japonicum found in about 1-3% of individuals.
Did You Know?
- The word zygomatic comes from the Greek zygon meaning yoke, as the arch resembles the wooden yoke used on oxen
- The zygomaticus major is called the smiling muscle because it pulls the corner of the mouth upward
- High cheekbones are actually a result of the zygomatic bone being positioned more anteriorly and superiorly
Scan this bone yourself
Download Osteo+ and identify the cheekbone instantly with your camera. Get all the details above and more from a single photo.