With ZMC fractures, displacement in the posterior direction was found to be the most frequent, while displacement in the superior-inferior direction was rare. These results coincide with those of Toriumi et al. [3] that indicated that displacement around the superior-inferior axis is the most frequent in ZMC fractures. In the natural condition, the zygoma arch breaks first when tripod fractures occur because it is the thinnest and the most fragile support of the zygoma. When this occurs, the zygoma remains supported at three sites: the frontal process, the inferior orbital rim, and the zygomaticomaxillary buttress. They hypothesized that fracture patterns are largely determined by which of these three remaining sites breaks first under trauma [3].
In this study, reduction results obtained using a transconjunctival approach were statistically superior to those obtained using an intraoral approach, a Gillies approach, or a lateral canthotomy approach for posterior displacement. Ellis et al. have shown that rotation of the entire complex along its vertical axis was noted, despite the presence of bone plates at the frontozygomatic and zygomaticomaxillary areas [1]. To prevent rotation of the entire complex, the sphenozygomatic area should be examined during surgery.
Karlan and Cassisi reported that the masseter muscle contributed significantly to the forces of mastication, which range from 11.25 to 90.00 kg. With ZMC fractures, when fixed at the zygomatic frontal suture, the fracture was found to rotate downward and backward with a masseteric force of less than 2.25 kg [11]. Hanemann et al. reported that the zygomaticofrontal suture seemed to be most affected by the action of the masseter [12].
Karlan and Cassisi showed that, geometrically, the three-point (frontozygomatic suture, infraorbital rim, and lateral maxillary buttress) alignment of zygoma fractures resulted in a more exact orientation of the zygomatic pyramid. Their abstract model as well as their analysis using moiré topographic maps of the skull demonstrated that downward, backward, and medial rotation of the fractured segment may still occur, despite a one-point or two-point alignment of the fractured segment [11].
Some surgeons have stated that a one-point fixation at the zygomaticomaxillary buttress is sufficient [13] for fixation in ZMC fractures. However, assessment of the orbital floor by using a transconjunctival approach is essential for repairing associated blowout fractures. Exposure of the lateral orbital wall also helps in identifying the alignment of the greater wing of the sphenoid bone [14].
Even when considering the limitations of the technique, Jo and Kim showed that treatment of zygomatic fractures by using a transconjunctival approach and an intraoral approach was advantageous, as it did not result in any incision scars and achieved favorable and stable anatomic and anthropometric outcomes. This approach could serve as a novel alternative for socially active young male or female patients who are sensitive to esthetic changes [14].
Davidson et al. have proposed that a two-point fixation using a miniplate alone conferred a degree of stability comparable to most three-point fixation methods, regardless of the site in which the miniplates were applied [15]. Based on this, Lee et al. asserted that a two-point miniplate fixation at the infraorbital rim and zygomaticofrontal suture would suffice in non-comminuted ZMC fractures [16].
The presence of diastasis in the zygomaticofrontal suture plays an important role when determining whether this portion should be exposed. Surgeons generally prefer to perform accurate reduction under full exposure, using a lateral brow incision. All patients in the present study had zygomaticofrontal suture displacement, although this displacement was not particularly severe [14].
We re-classified ZMC fracture displacement using the maximum projection coordinate of the zygoma as the classification criterion and assessed whether a specific approach for particular displacement of a ZMC fracture would enhance the esthetic results. However, we did not consider the severity of the ZMC fracture in this study. More complicated ZMC fractures require more approaches and fixations. A study considering fracture severity is therefore required for a more accurate analysis.