Square Jaw Surgery: The Difference Between Cortical Osteotomy and Lateral Cortical Shaving

Hello, this is Dr. Jo Hyun-woo of 3D Plastic Surgery.

In the previous column, I explained in detail the importance of cortical osteotomy in square jaw surgery.

Today, following on from last time, I will explain the difference between cortical osteotomy and lateral cortical shaving.

The basic way to reduce the thickness of the lateral cortex is cortical osteotomy.

As shown in the photo below, this is a surgery that removes the lateral cortex of the lower jaw bone, shown in blue.

Marked area for cortical osteotomy in square jaw

There are several surgical methods, but the basic method is to use a surgical instrument such as a saw or burr to create a groove in the cortex and then separate only the lateral cortex.

Cortex separated from the square jaw

When cortical osteotomy is performed, the bone shaped like this comes off, reducing the width of the face.

For people with a thick lateral cortex, there are cases where it is about 5 mm per side, so the effect of cortical osteotomy can be said to be quite significant.

Because it is such an effective surgery, the risk is also inevitably quite high.

※Risk of damage to the inferior alveolar bone※

The inferior alveolar bone is located in the medulla between the lateral cortex and the inner cortex of the mandible.

Marked location of the inferior alveolar bone

In the CT image, the circled area is where the nerve is located.

Of course, in most patients, the nerve is very close to the inner cortex, so even if lateral cortex osteotomy is performed, there is no risk or concern about nerve damage.

However, if you look closely at the CT scan, there are quite a few people whose nerves run close to the lateral cortex.

If this is accurately identified and surgery is performed, the operation can be carried out without nerve damage.

But if the medulla is exposed too much, the nerve is too close to the skin, so some patients occasionally feel sensory changes.

In my case, if the cortex is extremely large, I perform cortical osteotomy, but in general cases, I perform lateral cortical shaving.

CT after lateral cortical shaving

In the CT scan, you can see that the thickness of the lateral cortex has been reduced. In the 3D CT scan,

CT before and after lateral cortical shaving

You can see that the protruding part circled has been smoothly refined after surgery.

However, if the cortex is too thick, cortical osteotomy may be more effective as long as the nerve is running safely.

Before surgery

In this patient, you can see that the left jaw bone is protruding. In such cases, when looking at the CT scan,

CT before surgery

You can see that the left cortex is bulging like this.

In this case, only shaving is done on the right side, and cortical osteotomy is performed on the left side.

CT after surgery

In the 3D CT images after surgery, you can see that the cortex has been removed precisely. In the patient's photo after surgery as well,

After surgery

It was not corrected perfectly 100%, but you can see that the left-right difference has improved a lot.

As such, it is true that removing the cortex can reduce more volume.

But I prefer lateral cortical shaving, which is performed safely and without nerve damage, even though completely removing the cortex and reducing volume would probably make the result 1–2 mm smaller and more effective.

No matter how good the result is, if sensory changes occur and cause discomfort, that becomes a problem.

Depending on the patient, if you want to significantly reduce the width of the cortex, cortical osteotomy can also be performed through consultation.

Therefore, I think it is best to have a CT scan and choose the surgical method that is right for you.

Then I will show you photos of a patient whose facial width was reduced through cortical osteotomy.

How does it look to you?

Before and after zygoma reduction surgery and square jaw surgery with cortical osteotomy

Before and after zygoma reduction surgery, square jaw surgery, cortical osteotomy, and masseter muscle resection

Before and after zygoma reduction surgery, square jaw surgery, cortical osteotomy, and masseter muscle resection

Over the course of last time and today, I explained the importance of cortical osteotomy in square jaw surgery and what lateral cortical shaving is.

Please keep in mind that square jaw surgery is not simply a surgery that cuts only the angle of the jaw by the ear, but rather a procedure that must be done together with cortical osteotomy to reduce the width of the mandible in order to be effective.

Thank you.