In recent years, more and more parents have asked me about the early treatment of first and second parotid arch syndrome. Due to the different medical regions where the patients live, the medical information available varies greatly, and most parents are often in a hurry but lack clear treatment guidance, so much so that some parents travel to and from major medical centers across the country with their very young children, causing unnecessary mental and financial burdens. As a maxillofacial plastic surgeon who has been engaged in the research and treatment of this disease for nearly two decades, I feel obliged to communicate with parents in depth about the early comprehensive treatment of this type of deformity. 1, diagnostic name, causes and incidence of the problem: First, two cheek arch syndrome, also known as hemifacial short deformity, ear – mandibular dysplasia, mandibular – facial dysplasia, unilateral facial dysplasia, etc., is second only to cleft lip and palate of the most common congenital craniofacial deformity, the more accurate name should be hemifacial short deformity (English generic name for Hemifacial Microsomia). Its incidence is about 1/3500~1/5600 of born babies, therefore, it is a common congenital malformation. Familiality is not obvious and there is no clear heritability. There is no significant difference between male and female incidence and left and right side incidence. To date, the cause of the pathogenesis is still unclear, and the pathogenesis is mostly thought to be due to an abnormality in the development of the first and second parotid arches during the embryonic period and in the developmental migration of the neural crest. The malformation mostly occurs unilaterally, but individually it can involve both sides. Clinical manifestations: The first and second parotid arch syndromes vary in severity, and the scope and degree of involvement are also different. In the mildest cases, the only symptoms are the presence of an appendage in front of the ear and bilateral facial symmetry. In severe cases, the patient may have a shortened face, weak subcutaneous soft tissue, skewed chin, facial nerve hypoplasia, transverse facial cleft, different degrees of external ear deformity, and atresia of the ear canal. In severe cases, the maxilla, zygoma, zygomatic arch and craniotemporal bones are involved, among which mandibular dysplasia is the most common and most important. 3.Diagnosis and typing problems: Because of the diverse manifestations of the first and second parotid arch syndrome, which can be very mild or very serious, these malformations are a group of congenital malformations with different degrees of severity, different ranges of involvement and diverse manifestations. There are several classification methods, but the simpler and more practical one is Pruzansky’s classification based on mandibular malformation, which is briefly described as follows: Type I: Mild dysplasia of the ascending branches and body of the mandible. Type II: Short mandibular condyle and ascending branches, flat condyle, absent articular fossa, possible absence of coronoid process, condyle attached to a slightly depressed bone surface at the temporal skull base. It can be divided into type IIA and type IIB. Type IIA: The size and morphology of the ascending branch of the mandible and the condyle are different from normal, but the connection between the condyle and the articular fossa is still preserved, the position of the articular fossa is still normal, and the function of the temporomandibular joint can almost reach normal. Type IIB: The condyle of the mandible is obviously displaced, and the function of the temporomandibular joint on the affected side is basically lost, and the balance of bilateral activities cannot be maintained. Type III: Only a thin layer of bone remains in the ascending branch of the mandible, or even completely absent, and the temporomandibular joint does not exist. 4.Treatment problems 4.1 Treatment principles and surgical plan for hemifacial short deformity Because hemifacial short deformity involves facial organs, soft tissues and craniofacial skeleton, the severity varies, and the deformity can be aggravated progressively with growth and development after birth, so the treatment becomes a systematic project with different treatment plans at different stages, and the correction of deformity cannot be achieved overnight. Parents need to understand the characteristics of the deformity and the complexity and long-term nature of the treatment. The treatment plan at different ages is as follows: (1) Up to 1 year of age At around 1 year of age, preauricular oophorectomy is feasible. Children with transverse facial cleft (also known as macroglossia) can undergo macroglossia correction at the same time to improve facial appearance and restore the child’s sucking function. Correction of external ear and mandibular deformities is not considered during this period. Some experts advocate that the above surgery can be done at the age of 3 months, but my personal opinion is that it is better to do it at the age of about 1 year, because the child’s tolerance for surgery and anesthesia is stronger at this time, and the surgery will be safer, and the anatomical structure of the child’s mouth becomes clearer at this time, and the surgical revision will be more accurate. (2) 6-14 years old At the age of 6-14 years old, the patient is in the mixed dentition period. If there is an external ear deformity and obvious facial deviation and asymmetry, this is the best time for mandibular traction osteogenesis and external ear reconstruction surgery. Some scholars suggest that mandibular lengthening can be performed after the age of 2 years. We believe that it is more appropriate after the age of 6 years because the mandible has developed to a certain extent at this time, which facilitates surgical operation, and at the same time, the cooperation of the child can be obtained during this period, which can ensure the smooth implementation of treatment. However, in cases of severe bilateral mandibular dysplasia affecting the child’s breathing and sleep, mandibular lengthening should be performed at the age of 2 years to improve the respiratory function of the child. Selection of surgical options: ① Patients with open Pruzansky I, because the degree of deformity is mild, mostly not accompanied by inclination of the occlusal plane, no significant facial deviation, and the open and closed mouth movement bilateral mandibles are in a balanced and symmetrical state, should be observed and bony reconstruction surgery should be postponed until adulthood, when orthognathic surgery can be used to correct minor facial asymmetries. ②Patients with moderate to severe shortage of the height of the ascending mandible (Pruzansky type II), mandibular lengthening is feasible. Retraction of the osteogenesis not only lengthens the mandible in all directions, but also accompanies the lengthening of the soft tissues and masticatory muscles, thus reducing recurrence. In addition, the lengthened ascending mandible and condyle are closer to the normal anatomical shape, position and size. (iii) In patients with Pruzansky type III (absence of the ascending branch, condyle and temporomandibular fossa), mandibular ascending branch reconstruction should be performed at about 6 years of age. The traditional method mostly uses rib-cartilage for the reconstruction of the mandibular ascending branch, but due to the disadvantages of low success rate and complications, it has been gradually replaced by the anastomotic vascularized fibular flap graft reconstruction method. In the future, the reconstructed ascending branch can be extended if necessary according to the growth and development of the reconstructed ascending branch. (3) After 14 years of age 14 years of age is the maturity of the skeleton. After 14 years of age, further growth changes of the craniofacial bone are very minimal. The indications for surgical reconstruction during this period are: ① the growth rate of the affected area after surgical reconstruction and the affected area is not as fast as the normal side, and there is a bony deformity. (ii) poor craniofacial appearance due to soft tissue defects; and (iii) previously untreated patients. Any soft tissue defects and poor facial contour present at this stage can be considered for improvement using autologous fat injection filling. 4.2 Early intervention treatment of our children with hemifacial short deformity The growth potential of the affected facial bones in patients with hemifacial short deformity is lower than normal, and the deformity further worsens with growth and development, with the mandibular deformity being the earliest and most pronounced, which not only represents the severity of the deformity but also predicts the degree of progressive development of the deformity with growth and development, and the deformed mandible affects the maxilla The deformed mandible can interfere with the normal downward growth of the maxilla, leading to secondary midface deformities, inclination of the occlusal plane and inclination of the orbital plane. Early treatment of the deformed mandible can prevent and reduce the formation and extent of secondary deformities and promote coordinated development of the craniofacial skeleton. When treated early, the facial deformity is not yet complex, the surgery is relatively simple, and most patients can avoid larger, more complex surgeries in adulthood, such as surgery on the maxilla and orbital bone. Moreover, if the mandibular deformity can be corrected before school age, so that the period is in the period of tooth replacement, the bite and jaw relationship can be better improved through self-adjustment when permanent teeth erupt. In addition, early treatment is also beneficial to the psychological development of the child. The aim of surgery is to restore the normal anatomical position of the deformed mandible, i.e., the downward, forward and midline rotation of the affected mandible. In patients with external ear deformity, external ear reconstruction and mandibular lengthening can be combined in an organic and rational way, which not only shortens the number of surgeries, reduces the pain and economic cost of the child, but also significantly improves the surgical results. (1) Preoperative measurement and surgical design Through digital surgical technology, we analyze the characteristics and severity of the deformity of the child’s hemifacial hypoplasia, simulate osteotomy and bone traction, determine the precise osteotomy line and the fixation position of the extender, and find the most suitable surgical plan. In some patients, a surgical template was designed before surgery, and the alignment of the inferior alveolar vascular-neural bundle in the lateral bone cortex was marked on the template so that the osteotomy line would avoid these easily damaged structures. (2) Surgical method The first stage of surgery: the child undergoes a submaxillary incision under general anesthesia, the osteotomy line is designed according to the preoperative design of the osteotomy direction and the placement of the retractor, the mandibular retractor is placed, and the extension rod at the end of the retractor is extended in the direction of the extension to the skin incision. For patients with microtia, a soft tissue expander for the postauricular skin can be placed at the same time. Traction lengthening and dilator injection are started 5~7 days after surgery. Traction is ended when the mandibular traction reaches the preoperative design position or is slightly overcorrected. Phase II surgery: The outer ear reconstruction surgery can be performed 1 month after the dilator water injection is completed, and the lengthener is maintained in its original position for about 6 months to ensure the maturation of the new bone. Third stage surgery: The revision of the reconstructed ear is performed and the mandibular extender is removed. (3) Adjustment of occlusal relationship after mandibular traction in children For children with hemifacial short deformity, the purpose of mandibular traction is to increase the height of the ascending branch on the affected side, and through accurate preoperative simulation of osteotomy design, the skewed jaws return to the midline position after mandibular traction is completed, and the face tends to be symmetrical. The misalignment of the jaws. Because of the strong growth potential of the maxillofacial bone in children, this temporary misalignment can be self-adjusted by the downward growth of the maxilla and the eruption of the teeth. Therefore, it is not necessary to be overly preoccupied with occlusion problems during traction therapy. After the permanent teeth have fully erupted, the occlusal relationship can be further adjusted through orthodontics. Pre- and post-operative orthoptic photos of mandibular traction lengthening and external ear reconstruction during the same period of short facial deformity Pre- and post-operative oblique photos of occlusal plane and crooked mouth angle Pre- and post-operative comparison photos