The zygomaticomaxillary complex (ZMC) is a component of the facial skeleton, consisting of the prominent cheekbone (zygoma) and its connection to the upper jaw (maxilla). This structure determines the mid-face’s contour and width, providing the prominence of the cheeks. Its integration with other skull bones establishes the face’s architectural framework, supporting soft tissues and shaping a person’s appearance.
Anatomy of the Zygomaticomaxillary Complex
The zygomaticomaxillary complex acts as a structural buttress, connecting the middle portion of the face to the cranium. The two principal bones forming this complex are the zygoma and the maxilla. The zygoma is a thick, resilient bone that absorbs and distributes forces applied to the face. This complex is anchored to the skull through four connections that give it stability.
- The zygomaticofrontal suture connects the zygoma upward to the frontal bone of the forehead.
- The zygomaticotemporal suture extends backward, joining the zygoma to the temporal bone and forming the zygomatic arch.
- Medially, the zygomaticomaxillary suture fuses the zygoma with the upper jawbone or maxilla.
- A deeper connection, the zygomaticosphenoid suture, links the zygoma to the sphenoid bone within the orbit.
Function of the Zygomaticomaxillary Complex
Aesthetically, the ZMC defines the projection of the cheeks, a feature that influences facial harmony. The ZMC also serves a protective purpose for the structures within the orbit by absorbing and dissipating energy from impacts to the side of the face. This complex is also integral to the proper function of the eyes.
The zygoma forms a substantial portion of the floor and the lateral wall of the orbit, the bony socket that contains the eyeball and its muscles. This support is necessary for maintaining the correct position of the globe. The ZMC provides an attachment point for the masseter muscle, one of the primary muscles of mastication, which enables the powerful forces required for chewing.
Zygomaticomaxillary Complex Fractures
ZMC fractures are common facial injuries resulting from direct, blunt force trauma. Common causes include motor vehicle accidents, physical altercations, falls, and sports-related impacts. An injury can result in a “tripod fracture,” involving breaks at multiple anchor points, which can push the entire complex inward and downward.
The signs of a ZMC fracture are distinct. A visible flattening of the cheek prominence is an indicator, accompanied by significant pain and swelling. Other signs include:
- Bruising that appears around the eye on the affected side.
- Numbness affecting the cheek, side of the nose, upper lip, and gums from disruption of the infraorbital nerve.
- Visual disturbances like double vision (diplopia) if the fracture alters the shape of the orbital floor.
- Difficulty or pain when opening the mouth if the fractured zygomatic arch impinges on the mandible.
Diagnosis and Treatment of Fractures
Diagnosing a ZMC fracture begins with a physical examination, where a clinician will palpate the facial bones for tenderness or step-offs, which are palpable discontinuities along the bony rims. The definitive diagnostic tool is a computed tomography (CT) scan. A CT scan provides detailed, cross-sectional images, allowing surgeons to visualize the fracture lines, assess bone displacement, and evaluate the orbit’s integrity.
If the bones are not displaced or only minimally moved, the fracture may be managed non-surgically. This approach involves a soft diet to avoid stress from chewing, pain management, and careful observation. Patients are also advised to avoid blowing their nose, which can force air from the sinuses into the soft tissues around the eye.
For significantly displaced fractures, surgery is necessary. The standard procedure is Open Reduction and Internal Fixation (ORIF). During ORIF, surgeons reposition displaced bone fragments into their correct anatomical alignment (reduction) and secure them with small, medical-grade titanium plates and screws (fixation).
Recovery and Potential Complications
After surgical repair, swelling and bruising are expected, peaking within the first few days before gradually subsiding over several weeks. A soft diet is required for four to six weeks to allow the bones to heal without the stress of forceful chewing. Activities that could result in a blow to the face, such as contact sports, are restricted for an extended period.
While surgical outcomes are successful, potential complications can arise. Infection at the incision sites or around the implanted hardware is a risk. Persistent numbness in the cheek and lip area can occur if the infraorbital nerve was severely damaged in the initial injury or during surgery. The hardware may also become palpable or cause irritation, requiring a subsequent procedure for removal.
If the bones heal in an incorrect position, a condition known as malunion, it can result in cosmetic asymmetry or persistent functional problems like double vision or difficulty chewing. Surgeons work to prevent these issues by ensuring precise anatomical reduction during the operation. Long-term visual problems can also persist if the orbital volume is not perfectly restored.