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

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

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

Today, following up on that, I’ll explain the difference between lateral 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 outer cortex of the jawbone.

Cortical osteotomy surgery

There are several surgical methods, but the basic approach is to use a surgical instrument such as a saw or burr to score the cortex first, then separate only the lateral cortex.

The cortex removed from the square jaw

When cortical osteotomy is performed, this kind of bone is detached, reducing the width of the face.

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

However, because this is such an effective surgery, the risk is also inevitably quite high: ※risk of injury to the mandibular alveolar bone※

The mandibular alveolar bone is located in the medullary space between the outer cortex and the inner cortex of the mandible.

Mandibular alveolar nerve

In the CT image, the circled area shows the location where the nerve is situated.

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

But if you carefully examine the CT, there are quite a few patients whose nerves run closer to the outer cortex.

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

However, if too much of the medullary space is exposed, some patients may feel sensory abnormalities because the nerve is too close to the skin. In my case, if the cortex is very large, I perform cortical osteotomy, but in general cases, I perform lateral cortical shaving.

CT after lateral cortical shaving

As you can see on the CT, the thickness of the lateral cortex has been reduced.

On 3D CT,

CT before and after lateral cortical shaving

You can see that the protruding area circled in the image has been smoothly refined after surgery.

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

Before surgery

This patient came in because their face looked longer and their left jaw appeared larger.

Looking at the actual CT image,

CT before surgery

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

In such a case, lateral cortical shaving is performed on the right side, and cortical osteotomy is performed on the left side.

CT after surgery

In the 3D CT image after surgery, you can see that the cortex has been precisely detached.

In the patient’s photos after surgery as well,

After surgery

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

As such, it is true that osteotomy of the cortex can reduce a greater amount.

But while fully cutting and reducing the cortex may reduce it by about 1–2 mm more and produce better results, I prefer lateral cortical shaving, which is safer and can be performed without nerve damage. No matter how effective it is, it becomes a problem if it causes sensory abnormalities and discomfort.

Depending on the patient, if they want a greater reduction in the width of the cortex, cortical osteotomy can also be performed through consultation. So after getting a CT scan, it would be best to choose the surgical method that suits you.

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

Zygoma reduction surgery, square jaw surgery, cortical osteotomy, masseter muscle resection, chin surgery

Square jaw surgery, cortical osteotomy, masseter muscle resection

Zygoma reduction surgery, square jaw surgery, cortical osteotomy, chin surgery

Zygoma reduction surgery, square jaw surgery, cortical osteotomy, masseter muscle resection

Over the course of the previous post and today’s post, I explained the importance of lateral cortical osteotomy in square jaw surgery and what lateral cortical shaving is.

Please remember that square jaw surgery is never just about cutting the angle near the ear; it must be done together with cortical osteotomy to reduce the width of the mandible in order to achieve a frontal effect.

Thank you.