What are the commonly used surgical approaches for facial bone plastic surgery? What are their respective advantages and disadvantages?
For zygomatic bone reshaping, the commonly used approach is an intraoral incision; while for mandibular angle osteotomy, there are two approaches as follows:
**Intraoral Approach**: The greatest advantage of this method is that it leaves no visible surgical traces. However, the difficulty of the surgery significantly increases, along with a higher risk. The recovery period is also relatively longer.
**Extraoral Approach**: The advantage of this method lies in its simplicity, good exposure, precise osteotomy, and faster recovery. The biggest drawback is the visible surgical scar on the face. For the correction of mandibular protrusion and reduction of zygomatic bones, both usually adopt the intraoral incision approach, which is relatively simple to operate and yields reliable results.
1) **Temporal Augmentation**
Generally, there are two methods: injection and implantation, with the latter being safer and more convenient.
**Implantation Method**: An incision within the hairline is made to place a silicone implant under the deep temporal fascia. After the operation, compression bandaging is applied, and a negative pressure drainage tube is usually placed for 3 days, with sutures removed after about 7 days.
2) **Zygomatic Bone Reshaping**
There are two commonly used methods: osteotomy and grinding.
**Osteotomy**: L-shaped osteotomy of the zygomatic bone is performed through an incision in the gingivobuccal groove from tooth 6-3│3-6. Subperiosteal dissection exposes the anterior wall of the maxilla, the zygomatic buttress, the zygomatic body, and the anterior portion of the zygomatic arch. According to preoperative design, an "L"-shaped osteotomy line is marked on the lateral side of the zygomatic buttress, below the infraorbital margin, and at the junction of the zygomatic arch and the orbital outer edge. After drilling through the bone plate with a fissure bur, a chisel is used to remove the bone block between the zygomatic buttress and the zygomatic bone. A straight-angle chisel is then used to break the oblique osteotomy line. The zygomatic bone is pressed inward and downward to create a "greenstick" fracture at the root of the zygomatic arch. The width of the zygomatic arch is narrowed and the high point of the zygomatic prominence is reduced. The bone ends are brought together and fixed with small titanium plates, and the bone edges are smoothed.
**Grinding**: This method is relatively simpler, where the corresponding high and convex parts of the zygomatic bone are ground according to the condition. Post-surgical reactions are also milder, and it is currently quite popular!
3) **Mandibular Angle Osteotomy**
There are also two methods: osteotomy and grinding.
**Osteotomy**: The incision starts from the anterior border of the mandibular ramus at the occlusal plane and extends 5mm buccally along the vestibular groove to the first mandibular premolar. The mucoperiosteum is incised. Using the "degloving" technique, subperiosteal dissection exposes the middle and lower portions of the mandibular ramus, the mandibular angle, and the posterior part of the mandibular body. Preoperative designs are marked with a small round bur, and arcuate osteotomies are performed using a long-handled round bur and reciprocating saw. The remaining bone connections are broken with a curved chisel. The medial attachments of the medial pterygoid muscle are separated, and the excised mandibular angle is completely removed. The osteotomy lines are smoothed and adjusted to ensure smoothness.
**Grinding (also known as milling)**: The incision design and periosteal stripping are similar to the previous method. A milling head is used to grind the external and inferior sides of the mandible into a wedge shape. Therefore, the effect of this surgery differs considerably from the previous method. The former shows obvious changes both visually and by touch, while with this method, the mandible may still feel square when touched post-surgery, but without visible symptoms externally, thus achieving significant surgical effects. It is currently quite popular!
4) **Chin Reshaping**
For microgenia, chin augmentation or chin bone reshaping can be used to achieve corrective purposes.
**Chin Bone Reshaping**: An incision is made between the first premolars in the bilateral gingivobuccal groove, and subperiosteal dissection is performed while preserving the soft tissue attachment of the inferior border as much as possible. Electric drills are used to create three vertical alignment marker lines in the midline symphysis mentis and on both sides, with the horizontal osteotomy line set 10-15 mm above the inferior border of the mandible. Reciprocating saws cut through the outer plate and part of the inner plate, and the remaining bone connections are broken with a chisel. According to the preoperative design, the bone segment is moved and fixed with small titanium plates. Bone gaps are filled with the trimmed mandibular angle or outer plate. If the shortening of the chin is mild, the excised mandibular angle or outer plate can be directly trimmed and transplanted to the chin, fixed with titanium screws.
**Chin Augmentation**: The incision and dissection method are the same as above. Appropriately carved prostheses are implanted subperiosteally, and sutures are generally removed after 7 days.
5) **Masseter Hypertrophy Treatment**
1. Generally speaking, by changing the attachment points and area of the masseter muscle, the muscle begins to undergo reconstructive atrophy 3 months post-surgery, and the contour and curve of soft and hard tissues stabilize around 6 months.
2. Partial masseter removal can also be performed simultaneously with osteotomy.
3. Drugs can also slim the face: Besides surgical partial resection, a simple and effective method is injecting botulinum toxin type A into the masseter muscle. The procedure takes only a few minutes, and its principle of action is to cause partial atrophy of the masseter muscle without affecting its basic physiological function. The optimal effect appears 1-3 months after injection, and the effect lasts 1-2 years.