LeFort type Ⅱ osteotomy and advancement of the maxilla

Maxillary LeFort II osteotomy is used for surgical correction of maxillary deformities. The maxilla and blood supply. The LeFort II osteotomy is a more complicated type of orthognathic surgery. In addition to the maxilla, the osteotomy range includes the nasal bone and part of the iliac crest in the middle of the face, so that the whole bone is tapered at the sieve and the skull base, and can be moved to the desired position to correct the jaw. deformity. If necessary, often supplemented with other operations, such as bone grafting. Treating diseases: maxillary retraction Indication The maxillary LeFort II osteotomy is suitable for patients with congenital or acquired (such as post-traumatic) facial mid-maxillary dysplasia or retraction deformity. The deformity range includes the maxillary alveolar process, the nasal bridge and the base of the nose. Contraindications 1. The general condition is not good, it is not suitable for patients under general anesthesia. 2. Only the maxilla and the nose are sunken, but there is no deformity of the maxillary alveolar process, and the bite relationship is normal. Preoperative preparation There are many types of dental malformations, and the situation is different. The deformity may be simple or complicated. Patients often have a variety of mental and psychological states. Therefore, there are many factors to consider before surgery, and various preparations should be made according to the specific situation. 1. As with general surgery, detailed medical history enquiries, records, and comprehensive physical examinations are required before orthognathic surgery, including: general and partial examinations. The whole body examination focuses on the situation of important organs. Local examinations include facial examinations, oral and dental model examinations, and X-ray examinations (cephalometric measurements, full-mouth curved torsions, and dental fragments). Based on the above results, a definitive diagnosis is made and a question table is listed as a basis for developing a treatment plan. The final treatment plan should be able to solve all or most of the problems listed in the table. 2. Determining the preoperative prediction of the therapeutic effect before performing orthognathic surgery. The most common methods are: photo cutting and pairing, cephalometric X-ray film tracing, cutting and cutting (paper-cut surgery) and dental model surgery. The latter two are more important. Through the preoperative prediction, comprehensively judge the effect of the design surgery, and if necessary, make corrections. In recent years, scholars have used computers, graphic digitizers, cameras, scanners, etc. to acquire and input images, and perform fixed-point, measurement, analysis, and surgical simulations to predict postoperative morphology of the patient's side. Recently, computer-aided three-dimensional surgical design simulation systems and computer-aided three-dimensional skull models have been established to create more precise conditions for the design and prediction of orthognathic surgery. (1) Cephalometric Prediction Tracing with Cutting and Piecing together: cephalometric measurement, cutting, or cutting. It is an important means of preoperative prediction of orthognathic surgery. The specific method is as follows. 1 Place the cephalometric X-ray film on the viewing box (or the viewing light), and draw the trajectory map on the transparent tracing paper. A total of two images are drawn. 2 Take a well-drawn trajectory map and cut the bone segment ready for osteotomy and movement. For example, this example is intended to be a maxillary LeFortI osteotomy and upward movement. 3 Place the cut piece of paper (such as the maxilla in this case) on another complete trajectory map so that it is in the desired position of movement (as in this case, up). 4 Place the remaining part of the jaw of the first trajectory (such as the remaining mandible in this case) on the complete trajectory to fit the piece of paper that moves the bone. This is the expected general position of the jaw after orthognathic surgery. 5 Then draw a soft tissue outline on the outer circumference of the bone to obtain a general outline of the postoperative shape. This is one of the main references for predicting the outcome of surgery. (2) Model Surgery: referred to as model surgery. On the tooth model (usually on the shelf), simulate the design of the operation, saw the model, and move the block in the desired position, fixed with sticky wax. Observe and measure the changes of the model to judge and predict the effect of the operation. It is a three-dimensional template, and the paper-cutting surgery is a three-dimensional simulation. One of the commonly used preoperative prediction methods. 1 First take the mold, pour out the tooth model, and transfer the to the shelf through the facial arch to obtain the relationship between the mouth and fix it. And draw a horizontal and vertical reference baseline on the model. 2 If necessary, draw a longitudinal baseline in the medial side of the temporal side; between the canines to the canines, between the first molars and the first molars, cross the ankles as a baseline. 3 Remove the single jaw model, and use the model saw to saw the tooth model according to the surgical design and divide it into several pieces (such as the maxillary segmental osteotomy in this case). 4 On the mandible model on the rack, place the cut tooth model blocks in the desired position. 5 After each model is in place, the model blocks are connected by sticky wax and fixed on the frame, which is the postoperative condition. Observe the original baseline position on the model, measure and calculate the distance after the movement, which can be used as a reference for surgical design. 3. For patients with major orthodontic surgery requiring orthognathic surgery, it is often necessary to combine preoperative and postoperative orthodontic treatment to achieve the desired results. The main contents of preoperative orthodontic treatment include: correcting a few misplaced teeth, removing interference or blocking, aligning the dentition, adjusting the shape or width of the dental arch, and coordinating the upper and lower dental arches so that the upper and lower dentition can obtain a wide occlusion during the operation. Contact relationship; it is also important to remove the compensation of the teeth and adjust the inclination of the teeth so that the bone segments can be moved to the desired position after the osteotomy. 4. When the surgical plan is determined, a occlusal guide (ply plate) should be made on the model that has completed the model surgery. If you are preparing for the simultaneous osteotomy of the upper and lower jaws, it is often necessary to make two occlusal guides. One is a transitional (intermediate) occlusal guide; the other is a maintenance occlusal guide (final guide), that is, the guide is finally worn during the operation to maintain the ideal position of the upper and lower jaws, and then fixed between the jaws. 5. Prepare the fixation device for the bone segment several days before surgery (such as dental arch splint, adhesive bracket or external fixation device). 6. Do oral care, treat dental disease, and cure if necessary. 7. Prepare for general anesthesia and prepare for general anesthesia. It is estimated that blood transfusion is required, and blood is reserved. 8. Finally, there is an important point in preparing the patient's mind and conducting the necessary psychological counseling. All the designs and the results obtained at the end should be told to the patient in detail, and their opinions should be solicited so that the doctor and the patient can find the unity of both the subjective and the objective. In this way, it is possible to obtain the patient's postoperative cooperation and achieve the desired effect, and finally obtain a satisfactory postoperative effect. Otherwise, subjective and objective inconsistency, although the expected surgical results have been achieved, still can not meet the patient's excessively high non-conformity requirements, backfired. Surgical procedure Incision This procedure requires two paths from the extraoral incision and the intraoral incision to enter, expose and osteotomy. The extraoral incision can be a coronal incision or a paranasal (lateral) incision. The method steps for a coronary incision refer to the content of craniofacial surgery. Nasal (lateral) incision: through the oblique incision of the skin on the surface of the maxillary frontal prominence on both sides of the nose, the inner half of the nasal bone, the medial side wall and the sacral floor can be accessed. If necessary, the middle and outer sides of the inferior border can be exposed. section. The incision is from below the medial malleolar ligament, obliquely downward and outward, below the inferior temporal margin. 2. Separate and expose the bone surface The incision is deep to the surface of the maxilla and the periosteum in front of the maxilla is dissected to reveal the maxilla. Separate under the periosteum, expose the infraorbital nerve and protect it, and sneak along the surface of the maxilla to descend to the vestibular groove, carefully separate under the periosteum, reveal the nasal bone and the medial side wall until the front and back parts of the tear are visible. And tears. Do not disturb the medial malleolus ligament and its attachment. The periosteum of the inner wall of the fundus was turned up, and the nasal tears were dissected and separated. Before reaching the nasal tears, it is often seen that a small nodule is raised at the lower edge of the ankle, and there is a small piece of muscle attached to the iliac crest, which can be used as a marker to identify the edge of the nasolacrimal sulcus. Separate around the nasolacrimal duct, and carefully insert a small separator behind the nasolacrimal duct, peel off the periosteum of the medial side wall and nasal bone, and separate the periosteum of the anterior medial side of the nasolacrimal membrane to the nasal bone. The contralateral bone surface was separated in the same manner. After the bone surfaces on both sides are separated, the periosteum of the nasal bone surface can be completely turned up. An subperiosteal tunnel is formed from one side to the opposite side under the periosteum on the surface of the nasal bone. 3. Osteotomy The osteotomy of the nasal bone can be performed first, and the osteotomy line must be placed below the plane of the sieve plate. In the tunnel under the subperiosteal sneak separation of the nasal bone, the soft tissue is pulled up with a narrow hook for protection, and the complex saw or crack drill extends along the inner side wall of the iliac crest under the inner iliac crest, and crosses the upper part of the puncture for transverse osteotomy. . When osteotomy, it is often necessary to pull the lacrimal sac to the outside. For the front of the maxilla and the ankle osteotomy. The deep hook is pulled down from the nasal incision to reveal the front of the maxilla. An osteotomy is performed on the inside of the infraorbital nerve with a split or a cutting drill. Then, the osteotomy line passes through the infraorbital margin, to the outside of the lacrimal sac (note the protection) and reaches the inner wall of the sac. The osteotomy line of the upper part of the maxilla and the ankle is connected to the transverse osteotomy line of the nose. If necessary, use a small hook to pull the lacrimal sac to the inside, gently sculpt with a small and sharp bone knife, cut the bone behind the nasolacrimal duct, complete the nasal osteotomy, and the bone that has not been completely separated. Cut and connect the osteotomy line to complete the upper part of the bone incision. Beginning the osteotomy of the lower part of the maxilla from the mouth. The basic steps are like the LeFort I osteotomy. A mucosal incision was made from the maxillary canine to the anterior sulcus of the second molar in the mouth, revealing the lateral aspect of the maxilla, showing the vertical osteotomy line in front of the maxilla completed from the top of the nose. Continue to make subperiosteal separation backwards, to the back of the maxillary nodule, the groove in front of the wing. Fully expose the maxilla with a deep hook, along the vertical bone cut line in front of the existing maxilla, continue down to the underside of the maxillary process, and then cut the osteotomy line to the lateral shape, 4 to 5 mm above the root tip. Drill or come back for horizontal osteotomy, to the back of the maxillary nodule. Finally, an arcuate osteotome is placed between the maxillary nodules and the underside of the flaps to be inserted inwardly to separate the maxillary nodules from the flaps. The final step in osteotomy is to separate the nasal septum from the skull base. Insert a curved bone knife (with its curved shape downwards) through one side of the nasal incision, insert it from the transverse osteotomy line of the nose, and gently dig it in the downward and slightly posterior direction to make the vomer and nasal septum Disconnected from the base of the skull. At this point, the osteotomy has been completed. 4. Move the bones and put them in place After the osteotomy is completed, the entire bone of the maxilla is fully moved with a bone knife and technique. Wear a pre-made and sterilized occlusal guide on the lower jaw to move the maxilla bone block so that the occlusal relationship with the occlusal guide plate is completely suitable. Placed in a position where the occlusion relationship coincides, and is fixed between the jaws. This is the expected position of the maxilla. 5. Bone graft and bone fixation If the entire maxilla is moved forward and in place, if the resulting gap is too large, bone grafting is often needed to reduce recurrence and promote bone healing. Bone grafts are often taken from the humerus (see patella). The bone graft is placed in the interosseous space and can be ligated with a micro titanium plate or a wire to simultaneously fix the bone graft and the maxilla bone. If necessary, the upper jaw suspension or the external bracket should be fixed. 6. Stitching The paranasal skin incision and the intraoral vestibular sulcus mucosa incision were used for intermittent suture. complication Orthognathic surgery may have complications during and after surgery. The surgeon should perform the operation in a serious and responsible spirit, abide by the surgical requirements, operate correctly, carefully and carefully, observe the condition closely after the operation, and timely handle the abnormal situation to prevent various complications. Airway obstruction Acute obstruction of the respiratory tract and even suffocation are the most serious complications. During general anesthesia, due to vomiting aspiration, secretion obstruction, improper position, tongue fall, tracheal edema after tracheal intubation, and subsequent local tissue edema, plus intermaxillary fixation and other factors may cause respiratory obstruction. Measures should be taken to prevent it from happening. Close observation of the condition and elimination of factors that may cause acute obstruction of the respiratory tract. If signs of dyspnea appear (such as nasal agitation, three concave signs, etc.), it should be treated in time to prevent the occurrence of asphyxiating complications. 2. Bleeding Intraoperative injury to larger blood vessels can cause more serious bleeding, such as the maxillary LeFortI osteotomy when the internal maxillary artery or the aorta is injured, and the mandibular ascending branch is used to damage the inferior alveolar artery. Therefore, in the LeFortI type osteotomy, the osteotome can not be placed too high during the process of breaking off the distal end of the maxilla and the wing, and the direction of the incision cannot be upward to prevent damage to the internal artery of the jaw. When cutting the inner wall of the maxillary sinus, care should be taken to avoid damage to the aorta near the posterior end. It is often possible to use a bone knife to cut the bone and not to reach the trailing edge while retaining part of the bone to avoid accidental injury to the aorta. After the maxilla is broken down by the technique and the instrument, the posterior bone is trimmed. When the mandibular ascending branch is sagittal and osteotomy, the osteotome should not be too deep to avoid damage to the inferior alveolar artery. After the ascending branch is opened by the "cracking" method, the bone piece is opened and the bone piece is opened. Deeply repair the bone under direct vision. When the mandibular ascending longitudinal osteotomy (vertical or oblique osteotomy) is performed, the osteotomy line should remain behind the mandibular hole to prevent damage to the inferior alveolar artery. 3. Nerve damage For example, the mandibular nerve may be accidentally injured in the sagittal split osteotomy of the mandibular ascending branch. Precautions during osteotomy are the same as prevention of damage to the inferior alveolar artery. When the osteotomy and the moving bone segment are completed for fixation, care should be taken to avoid the occurrence of postoperative nerve injury symptoms caused by the compression of the inferior alveolar nerve by the bone segment. 4. Segmental necrosis The reason is mostly caused by excessive peeling of soft tissue or damage to the supply of blood vessels. Therefore, the separation and exposure of the bone surface should not be too large, especially in the distal heart segment (the bone segment near the gingival direction), the surface soft tissue should not be excessively separated, but the soft tissue should be kept as much as possible to maintain blood circulation and ensure bone. Healing. 5. Damaged root tip and pulp necrosis The root is simultaneously cut off because the transverse osteotomy line is too low (too close to the cutting edge or face). Therefore, the possible position of the root tip should be judged. The method includes: preoperative photographing of the X-ray film to detect the position and length of the root, and referring to the data of the normal normal root length, the intraoperative observation shows that the alveolar bone surrounded by the root has a slight elevation. After estimating the root length and the position of the root tip, a transverse osteotomy line is designed in the telecentric direction of the root tip of 4 to 5 mm (the maxilla is above the apex of the maxillary root and the mandible is below the root tip of the mandible). 6. Unconnected bone or poor bone healing Mainly due to poor fixation, insufficient contact of the bone segment, and poor blood supply. Therefore, the bone must be well fixed during and after surgery. Generally, inter-bone fixation (ligation fixation or micro-plate strong internal fixation) is used, supplemented by intermaxillary fixation, suspension fixation, and external stent fixation. In addition, the osteotomy design should consider maximizing the contact wounds when the bone segments (blocks) are connected, and prevent excessive peeling of the soft tissue and the like during the operation.