The jaw angle of the face is the key to determine the width and shape of the lower part of the face. An enlarged jaw angle leads to a wide lower part of the face, a square face or even a trapezoidal face. The melon face and oval face are the face shapes admired by women in China and even in East Asian countries, in line with traditional aesthetic standards. In the Oriental population, the incidence of jaw angle hypertrophy is relatively high. With the increasing demand for beauty, changing the face shape has become a key item in plastic surgery in recent years. Facial reshaping is the application of craniomaxillofacial surgical osteotomy techniques or bone surface grinding to improve the contours of the face. These procedures are usually performed on normal aesthetic candidates, not on people with facial injuries whose main claim is to treat a disease. Since the main goal is cosmetic, it is quite normal for the candidate to carry certain psychological expectations, but this also raises the difficulty of the procedure. Here is my summary of some of the complications that are likely to occur after facial reshaping surgery and ways to avoid them: I. Bleeding and hematoma: The area near the angle of the jaw is rich in blood vessels, and the operating space and field of view of the intraoral approach are narrow, so intraoperative misinjury is the main cause of bleeding. It is common to see bleeding from the inferior alveolar nerve vascular bundle, facial artery and posterior mandibular vein, followed by bleeding from resection of occlusal muscle or removal of buccal fat pad, bleeding from the osteotomy surface and bleeding from the injured muscle during periosteal stripping, and severe hemorrhage can also lead to death. Prevention methods: Preoperative familiarity with the alignment of the mandibular canal can effectively avoid injury to the inferior alveolar nerve vessel bundle. Injury to the inferior alveolar nerve vessel bundle may result in bleeding like a tidal wave at the osteotomy site. The treatment of intraoperative bleeding is mainly internal filling, external pressure, negative pressure drainage, etc. Blind repeated clamping electrocoagulation is not only not easy to achieve the purpose of hemostasis, but also will expand the bleeding point causing hemorrhage or even life-threatening. The facial artery enters the face at the anterior edge of the occlusal muscle at the lower edge of the mandible, and the injury of the facial artery branch can be seen as a blood spraying point, so the bleeding point can be found and ligated to stop bleeding; if the bleeding point cannot be found, the bleeding situation can be observed after gauze filling. Bleeding from the osteotomy surface and bleeding from damaged muscles during periosteal stripping can be completely prevented from forming hematomas as long as proper pressure is applied during bandaging. With the help of endoscopic technology, some hidden parts of the operation can be completed to improve the safety of the operation. Poor morphology: 1. Asymmetrical deformity: Since the operation is performed intraorally, the operation field is small and the site is deep, the mandibular osteotomy is mostly performed under blind or semi-blind vision, and the amount of osteotomy is derived from the experience and preoperative design of the main surgeon, so it is inevitable that the amount of osteotomy on both sides is inconsistent. To prevent this complication, blind osteotomy must be avoided. Surface tomography of the mandible and spiral 3D CT reconstruction are visual and clear guidelines for determining the osteotomy, osteotomy shape and osteotomy volume, which can improve the safety and accuracy of the surgery. Because the outer plate of the mandible is harder than the inner plate, improper use of the chisel when splitting the outer plate can cause the osteotomy line to be skewed and unconsciously bring down part of the inner plate, which is also the cause of asymmetry. 2, the appearance of the second jaw angle: the second jaw angle refers to the lower edge of the jaw after the jaw angle osteotomy angles appear, some visible to the naked eye, and some will feel it when touched. Although this problem has little impact on health, it will inevitably cause dissatisfaction among the candidates. This problem is related to the surgical approach and the proficiency of the surgeon. The main reason for this is the lack of skill of the surgeon, and if a second jaw angle is evident, it can only be surgically repaired again. In order to avoid the appearance of the second jaw angle, the straight line osteotomy is changed to arc osteotomy, and the range is extended from the jaw angle to the jaw body and even the chin, which not only improves the facial shape, but also preserves the natural soft lines of the jaw angle. Third, nerve injury: The number of important nerves in the mandibular angle area is small, but the consequences of injury are serious. The chin nerve is pierced from the chin hole, and its nerve is thick and easily discernible to the naked eye. During mandibular angle surgery, in order to protect the chin nerve, it is often exposed under direct vision when the periosteum is stripped to facilitate protection and avoid injury. The causes of injury to the chin nerve are: excessive intraoperative pulling, accidental injury by high-speed rotating grinding head, and accidental truncation of the osteotomy line too far forward. Numbness of the mouth, lips and chin appears early after the injury of the chin nerve, which can generally recover on its own in 3-6 months. In case of accidental amputation, anastomosis of the severed end is feasible. The mandibular rim branch of the facial nerve is easily injured in the extra-oral approach, and its injury often results in ipsilateral lower lip droop deformity and orofacial skew deformity. If overstretched or slightly injured, the motor function can be restored after surgery, but the symptoms are often irreversible after dissection. The intraoral incision can avoid the facial nerve branches because the dissection is performed under the periosteum, so facial nerve injury rarely occurs. Perioral injury and scar formation: The scar of the extraoral approach is obvious, and the intraoral approach has a small field of view, especially for those who have a small cleft of the mouth and a deeper inward angle of the jaw, excessive pulling can easily lead to perioral strains, and the high speed power saw axis contacting the mouth and lips can also lead to thermal burns of the mucosa of the mouth and lips. During the operation, oil and grease can be applied at the corners of the mouth to lubricate the patient, and wet gauze can be placed at the pulling hook or polyethylene film sleeve can be used for protection, which can effectively protect the perioral area from injury. If found in time after surgery, it should be protected with the candidate oil ointment, but need to pay attention to timely cleaning to avoid drug scabs affect the healing. V. Fracture: Fracture occurs commonly because of unreasonable design of osteotomy line, rough operation, and offset of osteotomy line, which is easy to occur in the vertical line of condylar neck and sigmoid notch. Therefore, if a fracture is found intraoperatively, strong internal fixation is required after repositioning, and postoperative treatment such as mouth opening training is also required. To prevent fracture, the design of the osteotomy line should not be too high, and the horizontal osteotomy line should be 1 cm below the sigmoid notch when splitting the outer plate, and the direction of force splitting should avoid upward and forward; the bone at the upper end of the osteotomy line is thick, and the oscillating saw needs to cut through the whole layer of bone before chiseling, and to ensure even force, the assistant of the surgeon in charge needs to hold the mandibular angle outward. Some candidates have unerupted third molars, making the bone in the mandibular angle fragile, and the bone in the mandibular angle is even weaker after the osteotomy, so fractures are likely to occur when extracting teeth, so preventive extractions should be done before surgery. Osteotomy generally does not cause mandibular fracture. Restriction of mouth opening: In the early postoperative period, because of pain and swelling, painful mouth opening and small mouth opening angle may occur. However, after the swelling subsides, when the pain is not obvious, it is still impossible to open the mouth normally, which needs to draw the attention of the candidates. On one hand, it may be due to the atrophy of the occlusal muscles after jaw angle removal and the change of muscle attachment points, resulting in muscle balance disorders, which can be restored through mouth opening exercises; on the other hand, it may be due to the disorder of the temporomandibular joint function and temporary mouth opening restriction, which may be caused by the intraoperative pulling of the temporomandibular joint. If the degree of mouth opening restriction is serious, the candidate should be examined by X-ray for condylar fracture, and once it is determined, immediate surgical repositioning and strong internal fixation are required, along with post-opening training. VII. Infection: Because of the rich blood supply in the jaw, the probability of infection in the surgery itself is not high. However, poor suturing of the incision, poor oral care, prolonged placement of drains and postoperative hematoma may increase the chances of infection, and large hematoma should be removed in time, and bone wax should be used sparingly or not after osteotomy. Once the infection is formed, submaxillary abscess is easily formed, and it is necessary to promptly remove the infected foci, local irrigation and drainage, and parallel anti-infection treatment to prevent and control the occurrence of skeletal infection. Tips: In clinical work, plastic surgeons have done a lot of exploration in order to improve surgical results and reduce the occurrence of complications. For example, endoscopic assisted mandibular osteoplasty can effectively reduce the occurrence of complications; however, in clinical practice, plastic surgeons mostly use endoscopes from other departments, and special endoscopes still need to be developed. Under “CT navigation”, the operation of mandibular osteoplasty is well planned, making it increasingly minimally invasive and effective in avoiding related complications, but its popularity will take time. That said, the core of deciding the effect of surgery is the medical staff, whose aesthetics as well as their surgical skills and clinical experience largely determine the effect of surgery.