The skull is an important part of the human skeleton. Once a skull injury occurs, it not only affects the aesthetics, but also brings insecurity to the patient, and even causes a variety of adverse consequences such as cranial defect syndrome, brain atrophy, and traumatic epilepsy. Cranial defect is a common disease in craniomaxillofacial surgery. There are many causes of cranial defects, and the most common cause is trauma. Cranial defects are often accompanied by fractures of the zygoma, maxilla, mandible, nasal bone or even multiple craniofacial fractures, which are difficult to repair. For example, the British teacher Gavin? Rees and Liu Hailuo, the host of the Phoenix TV program in China, both had cranial defects of varying degrees due to trauma. Cranial tumor resection and debridement decompression surgery are also causes of cranial defects. In I. The purpose of cranial repair 1. improve the blood circulation of brain tissue; 2. improve the cerebrospinal fluid circulation of brain tissue; 3. release the adhesions of brain tissue at the cranial defect; 4. keep the stable pressure of brain tissue from changing with the external changes of air pressure; II. Indications for cranial repair 1. those whose bone defect range exceeds 3cm in diameter. 2.There are obvious self-conscious symptoms, such as headache, dizziness or pain at the edge of bone defect. 3.Phobia and insecurity about skull defect, such as fear of vibration, fear of trauma, etc. 4. The presence of epileptic source in the cranial defect area. 5. Cranial defect with hydrocephalus, cranial bone should be repaired at the same time of shunt operation. Contraindications for cranial repair: 1. Infection at the wound, or infection has healed but less than six months. 2, there is still an increase in intracranial pressure. 3.Open cranio-cerebral injury is not completely cleared, and there are still foreign bodies remaining. 4.Severe neurological and psychiatric disorders 4.The time of cranial repair For patients with cranial defects after craniocerebral injury surgery, it is generally believed that the repair time is 3 months to half a year after the first surgery and then cranial repair is more appropriate, and those with infection should be extended to more than half a year. Cranial repair is not a very difficult procedure in the field of neurosurgery (because it does not involve the brain) and the risk factor is not very high, but the appropriateness of this type of surgery for each patient should be determined on a patient-by-patient basis. If the site of skull depression is only 3 cm, the site is protected by temporal muscles in the temporal region, and the patient is elderly, the amount of movement is small and the possibility of re-trauma is small, and there is always a certain risk of surgery, so it is not necessary to perform another skull repair surgery. The head circumference of children under 5 years old grows faster, so cranial repair is not advocated under 5 years old. 5-10 years old head circumference growth has been slow, can be repaired, but should leave room, cranial replacement material should generally exceed the bone edge by 0.5 cm. after 10 years old head circumference no longer increases, so it is best to put this kind of surgery after 10 years old. In addition, it should be taken into account that children have a greater capacity for membrane ossification and some of them may not require secondary surgery due to new bone formation. Nowadays, many scholars advocate early repair according to the patient’s general condition, the degree of cranial injury, intracranial pressure changes and whether to use bone flap autologous subcutaneous embedding, in order to reduce or eliminate a series of symptoms caused by prolonged cranial defect. V. Repair materials of cranial defective plastic surgery At present, there are many materials used in clinical cranioplasty, including organic glass, silicone rubber polyester wire mesh, bone cement and titanium alloy, and titanium alloy material is getting more and more attention because of its non-toxic, good biocompatibility and good rigidity. The ideal cranial repair material must have the following conditions: (1) easy to shape and fix; (2) small tissue reaction and non-toxic; (3) chemically stable, not corroded, absorbed and aged in the tissue; (4) able to pass through X-rays; (5) non-heat transfer and non-conductive; (6) light in texture and sufficient mechanical strength. Currently applied cranial bone repair materials can be summarized into four types: (a) autologous bone graft: generally applied to iliac bone, rib bone and cranial outer plate, etc., because this kind of autologous bone without foreign body stimulation, small reaction, good postoperative healing process, and a certain curvature, in line with the physiological requirements, but its disadvantage is to increase a surgery, shaping is not ideal, the appearance is not good. (b) Allogeneic bone grafting: often using bone from other people or cadavers stored in bone banks, foreign body stimulation is mild, and the healing process is still good, but because of the storage relationship, it can increase the chance of infection. The above two methods are rarely applied. After 6 months post-transplantation both graft bone is absorbed and gradually replaced by new bone, so some people think that substitutes are preferable. (c) Allogeneic bone graft: animal bone, animal horn, ivory, etc. are used, but such materials often fail due to resorption or infection. Therefore, it has been abandoned. (d) foreign body graft: foreign body graft can be divided into two categories, namely non-metallic foreign body and metal foreign body, non-metallic materials: commonly used polymethacrylate (i.e., organic glass) commonly used metal tantalum (tantalum), titanium (titanium) alloy plate or stainless steel wire mesh, both domestic and foreign have been used, its convenient shaping, light tissue reaction, good appearance, in recent years, with three-dimensional reconstruction With the development of imaging technology, computer-aided design and manufacturing technology, titanium alloy personalized repair body has come into being. Doctors first obtain three-dimensional and complete imaging information of the patient’s skull through three-dimensional CT scan of the skull, then construct the morphology of the defect area according to the curvature of the skull around the defect and the morphology of the healthy side of the skull, especially the defect morphology of complex structures such as the brow arch and orbital cavity, and repeatedly deduce the shape and size of the patch and its relationship with the surrounding anatomical structures. Then, based on the measured data, a personalized cranial repair body is made for the patient by rapid molding and precision casting with titanium alloy as the material. Compared with traditional repair materials and methods, the titanium personalized repair has the following three advantages: 1) shorter operation time and lower risk, especially for patients with complex craniofacial fractures. Patients need to undergo a cranial CT examination before surgery, and a repair body is carefully designed after 2 to 4 weeks. The procedure is simple: the defect is exposed, the repair is inserted and fixed and the wound is closed. For the average patient with a skull defect, the procedure takes 30 to 90 minutes and the hospital stay is about 10 days. For patients with larger defects, the time may be slightly longer. 2.The post-operative repair form is perfect. The use of computer for personalized restoration design can make the curvature and edge form of the repair body fit perfectly with the skull, which can provide the patient with a perfect repair form. 3.The implant is made of pure titanium and titanium alloy, which is several times firmer than titanium mesh and autologous cranial bone, and is sufficient to provide reliable support and protection for brain tissue. Several issues need to be noted in the application of cranioplasty personalized design: 1. 1-2mm layer of cranial CT scan is appropriate, so that more edge parameters are obtained and the final design of the restoration is more compatible with the defect area; 2. It is better to apply two-dimensional titanium plate when making personalized repair, but not three-dimensional titanium plate, because the reshaping of three-dimensional titanium plate may cause its strength to decrease; 3. 3. A model should be made for the abnormal osteophytes, and the osteophytes above the skull surface should be marked for targeted removal during surgery; 4. That is, one point at the top of the defect area, and one point fixed at the front and back of the inferior temporal area, so that the fixation is the most solid, and the final fixation relies on the temporal muscle and the muscle column and scar tissue formed below the flap through the hole in the titanium plate. Individualized design of cranioplasty has been studied abroad, but there are disadvantages of expensive and long design period.