3D CT Analysis of Soft Tissue Changes After Orthognathic Surgery for Prognathism and Facial Asymmetry
- Dr. Park
- Dec 31, 2024
- 4 min read
Introduction
I am Dr. Jong-Chul Park, a board-certified Oral and Maxillofacial Surgeon.
Today, I will discuss the soft tissue changes that occur after double jaw surgery (orthognathic surgery) for patients with prognathism (protruding lower jaw) and facial asymmetry, using 3D CT analysis data as a basis.
During consultations, many patients express concerns about nasal flaring, an upturned nose, or consider surgery to reduce the length of their midface. However, few people fully understand the actual changes in soft tissues, especially around the nose, philtrum, and lips after double jaw surgery for prognathism and facial asymmetry.
This posting aims to provide an objective examination of changes to the nose, philtrum, and lips after double jaw surgery through 3D CT data. We will address concerns about nasal flaring, upturned noses, and changes in philtrum and midface length.
Lip Shape Changes: Improvement of Facial Asymmetry
In cases of facial asymmetry, changes in lip shape can be observed more clearly. The following patient had their lower jaw deviated to the right, resulting in a tilted lip line.
After correcting the skeletal asymmetry through double jaw surgery, the corners of the mouth became level and symmetrical.
This is one of the key differentiating features of double jaw surgery compared to contouring surgery in improving facial asymmetry. Determining whether nasal flaring occurs is difficult to judge solely from frontal photos, so we will explain this further below.
Improvement of Nasolabial Folds: Forward Movement of the Nasal Area
Changes in the anteroposterior position of the soft tissues around the nose can be examined more closely in the lateral view. First, let's look at the skeletal changes using 3D CT.
The red arrow indicates the bending of the metal plate, showing the forward movement of the maxilla after LeFort I osteotomy. In other words, the bone around the nose has moved forward. This skeletal change is accompanied by the following soft tissue changes:
To clearly demonstrate changes in the soft tissues around the nose, we have placed a red square of the same size at the location of the red arrow. As you can see in the photo, the area around the nasolabial fold has moved forward.
Nose Upturning, Nasal Flaring, and Nose Height Changes: Effects of Inferior Nasal Bone Movement
Let's also look at the view from below.
The 3D CT analysis showed that the nose became slightly upturned. This can also be interpreted as an increase in nose height.
To better understand the pre- and post-operative changes in the nose, please refer to the following 3D CT video:
The shape of the nose inevitably changes with the movement of the underlying bone. Despite performing a Cinch suture to prevent nasal flaring in all patients who underwent surgery, it seems unavoidable that the shape of the nose will change due to the movement of the underlying bone.
If there were no soft tissue changes following skeletal movement, it would be impossible to improve soft tissue asymmetry caused by skeletal asymmetry.
It is believed that the degree of these soft tissue changes is related to the amount of bone movement in that area.
In other words, if the bone around the nose moves backward, nasal flaring does not occur.
Cases with Concurrent Anterior Segmental Osteotomy (ASO) for Maxillary Protrusion: Potential for Upturned Nose Without Flaring
The correlation between the direction of nasal bone movement and soft tissue changes can be better understood through the case of the following patient. This patient underwent concurrent ASO, resulting in the nasal bone being positioned more posteriorly than before the surgery.
We drew a yellow vertical line at the same location before and after surgery. The anteroposterior position of the soft tissue below the nose barely changed or moved slightly backward after surgery. When the upper jaw moves backward through ASO, the width of the nose does not change significantly. In other words, you can consider that there is almost no nasal flaring.
However, since the bone moved vertically, the nose may become upturned.
The changes are subtle and may be difficult to discern from photos alone, so we marked red vertical and horizontal lines at the same location before and after surgery. The areas indicated by the red and blue arrows moved upward after surgery, while the width of the nose indicated by the black arrow shows little difference before and after surgery.
Conclusion and Additional Considerations
Whether nasal flaring occurs after double jaw surgery is determined by the direction of movement of the bone supporting the nose.
If the supporting bone moves forward, the nose may widen or upturned, but if it moves backward, the width of the nose may remain the same.
Nose upturning is also affected by the direction of movement of the supporting bone. If the bone moves upward, the nose may become upturned, but backward movement alone may not cause an upturned nose.
Careful consideration is needed when reducing the length of the midface. When reducing midface length through double jaw surgery, it is important to ensure that the upper teeth are appropriately visible when the muscles around the lips are completely relaxed to maintain a natural appearance. Individuals whose upper teeth are not normally visible should carefully consider midface reduction through double jaw surgery.
In conclusion, the changes in soft tissues around the nose are subtle, so referring to 3D CT analysis and video materials may be helpful for understanding. I hope this posting helps you understand soft tissue changes after double jaw surgery for prognathism and facial asymmetry and provides objective information to those considering surgery.
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