[Paper Review] What Matters More in Zygoma Reduction Than Double or Triple Fixation

Hello, I am Dr. Jo Hyun-woo, director of Ipche Plastic Surgery.

These days, when I consult with patients about zygoma reduction surgery, many of them come in having researched the surgical methods in great detail.

In the past, they often asked questions such as, “How much will my cheekbones be reduced?” and “Will my 45-degree cheekbones also be reduced?”

These days, however, I also hear questions like, “At how many points are the cheekbones fixed?” and “Is it double fixation or triple fixation?”

In fact, wouldn’t fixing the bone at two points obviously be stronger than fixing it at one point, and fixing it at three points stronger than fixing it at two?

I was also curious about this, so I looked for relevant papers and found a particularly interesting study.

Today, I will explain in simple terms a paper published in 2023 that compared fixation methods for zygoma reduction surgery.

In this paper, the researchers created several fixation methods for zygoma reduction surgery on a computer and compared how much the zygoma moved and where forces were concentrated when actual chewing forces were applied.

They digitally reproduced zygoma surgery using the CT scan of an actual 26-year-old woman.

The zygomatic body was osteotomized in an L-shape, and the zygomatic arch was also osteotomized before the zygoma was moved inward.

The researchers then compared various fixation methods while the osteotomy surfaces of the zygomatic body remained in contact with each other.

Figure 1. Zygoma fixation methods compared in the paper

As shown in the figure, the four methods at the top involved fixation at relatively high positions on the zygoma, while the two methods at the bottom used large plates placed along the long, lower osteotomy line of the zygoma. The zygomatic arch was also fixed separately using three different methods.

In total, the researchers compared 18 combinations by combining six methods for the anterior zygoma with three methods for the posterior zygomatic arch.

This was the first result that stood out in the study.

The first finding was that fixation at the upper part was more stable than fixation at the lower part.

Overall, the methods that fixed the zygoma at a somewhat higher position showed less force and movement than the method that placed a large plate along the long, lower osteotomy line of the zygoma.

The paper explains that fixation at a higher position—particularly closer to the bone outside the eye—may be more advantageous.

Why was there such a difference?

The authors focused on the force of the masseter muscle pulling the zygoma downward and the orientation of the fixation device.

The long plate placed along the lower part was positioned in a direction similar to the direction in which the masseter pulls the zygoma downward. Therefore, it may be more effective to brace across that force rather than extending the fixation in a similar direction. In other words, a larger plate with more screws is not automatically stronger.

Here is the second finding.

Even with the same L-shaped plate, the results differed depending on its orientation.

The researchers compared two methods that used identical L-shaped plates but placed them in different directions.

In one method, the short section was placed on the mobile zygomatic side; in the other, the short section was placed on the nonmobile maxillary side.

Figure 2. The results differed depending on the orientation of the same plate.

The method that placed the short section on the nonmobile maxillary side was more stable.

The paper’s authors explain that, with this method, stress and displacement in the zygomatic bone were approximately 50% lower than when the plate was placed in the opposite direction.

The reason is relatively easy to understand as well.

When the short section of the plate is placed on the nonmoving bone, the screws can better resist the force that tries to rotate the zygoma, and the plate itself is positioned more favorably against the force pulling the zygoma downward.

This means that even when the same single plate is used, stability can vary depending on where it is placed and in which direction it is oriented.

Based on this result alone, simply asking, “How many points are used for fixation?” may not be enough.

The third finding was that two long screws produced better results than a large plate.

One of the methods that showed particularly good results in this study was fixation of the zygoma with two long screws.

Rather than placing a large plate, this method fixed the zygoma by inserting long screws at two separate points.

It produced good results when combined with a structure in which the posterior zygomatic arch bones interlocked with each other.

Figure 3. The combinations that showed the least and greatest zygomatic movement

In terms of the average movement of the zygomatic bone itself, the combination of two long screws and posterior bony interlocking showed movement of 0.037 mm under average chewing force and 0.187 mm under maximum chewing force.

By contrast, among the combinations using a large plate along the long, lower osteotomy line, the one with the greatest movement showed 0.244 mm under average chewing force and 1.135 mm under maximum chewing force. Under maximum chewing force, this represents a difference of approximately six times.

The stress placed on the zygomatic bone was also lowest with the combination using two long screws, at 149.73 → 748.66.

This suggests that using a large plate and many screws is not automatically more stable; properly securing two separate points may be more effective.

This is relatively easy to understand.

If the zygomatic bone is secured at only one point, a force may develop that tries to rotate the bone around that fixation point.

However, securing two points that are separated from each other can prevent not only downward movement but also rotational forces.

The paper’s authors describe this as “double bridge fixation,” or a method that supports the bone like a bridge at two points.

They interpreted this two-point fixation as contributing to zygomatic stability.

I think this concept is more important than the numbers we commonly refer to as “double fixation” or “triple fixation.”

Then, would it be better to secure the posterior zygoma with a plate as well?

This study also compared three methods for the posterior zygomatic arch.

One method allowed the bones to interlock with each other, another used a small three-hole plate, and the third used short screws.

The results were different from what one might expect.

There were no statistically significant differences in stress, strain, or displacement among the three fixation methods for the posterior zygomatic arch.

In other words, adding another plate to the posterior side did not automatically make the entire zygoma much more stable.

Instead, in this study, where and in what direction the anterior zygomatic body was secured appeared to be the more important variables.

Figure 4. Movement was differentiated by color according to the zygoma fixation method.

A large plate was not automatically better either.

In the paper, the combination that showed the highest stress used a square plate on the lower part of the zygoma and a three-hole plate on the posterior side.

The stress on the zygomatic bone was highest, measuring 604.1 under average chewing force and 2934.6 under maximum chewing force.

This does not mean that large plates are bad.

It means that, under the conditions of this study, the position and orientation of the plate may have been relatively disadvantageous for resisting the force of the masseter muscle.

Ultimately, the results are difficult to explain based only on plate size or the number of screws.

Then, are two long screws always the best method?

Numerically, the method using two long screws showed fairly good results.

The authors also explained that, when there is sufficient bone, this method may be highly recommendable.

They also mentioned advantages such as good resistance to rotation, being less palpable than a plate, having a lower likelihood of migration, and costing less.

In fact, zygomatic movement was less than 2.5 mm in all combinations.

However, the paper’s final conclusion was that all 18 fixation combinations demonstrated sufficient basic stability.

This means that although all of the methods fell within a stable range, there were differences in the degree of force concentration and movement among them.

Let us return to the initial question.

This paper did not directly compare double and triple fixation. Instead, it emphasized and explained that the more important factors were where and in what direction the bone was fixed, and how effectively the separated fixation points restrained zygomatic rotation.

When the orientation of the same single plate was changed, the results differed by nearly 50%, and the method using a large plate was not always more stable than the method using two long screws.

Using one additional plate on the posterior zygomatic arch also did not result in statistically greater stability.

Therefore, although it is fine for patients to ask, “How many points are used for fixation?” I think a slightly more important question is, “Where and how is the bone fixed?”

There are three things I felt were important after reviewing this paper.

The first is to fix the bone at a high position whenever possible.

Fixation at a high position close to the bone outside the eye produced better results than the method that secured the long, lower osteotomy line.

The second is to consider the direction of the force when determining the fixation method.

If the masseter pulls downward and outward, it is important to fix the bone in a direction that can efficiently resist that force.

The third is to properly secure the zygoma at two or more separated points so that it does not rotate.

This means that simply adding another screw is not what matters; what matters is the actual role played by each fixation point.

This paper suggests that, when evaluating zygoma surgery, we need to consider together where the osteotomies were made, whether the bone surfaces are making sufficient contact, where the fixation was placed, from which direction the masseter’s pulling force is being resisted, and whether the force that tries to rotate the zygoma is also being adequately controlled.

For this reason, I believe that good fixation in zygoma surgery is less about using more fixation points and more about properly securing the necessary locations.

However, this was a computer simulation study rather than a study involving long-term follow-up of actual patients.

Because bone thickness, bone quality, the amount of zygomatic movement, and the force of the masseter differ from person to person, the authors also state at the end that longer-term clinical studies involving actual patients are needed.

Therefore, I think the most appropriate way to understand the significance of this paper is: “In zygoma surgery, we should not look only at the number of fixation points; we should also consider their position and orientation, as well as how effectively they control rotation.” I hope today’s content was helpful.

Thank you.