Most of the skull defects are caused by open craniocerebral injuries or firearm penetrating injuries, and some patients have residual bone defects due to surgical decompression or resection of diseased skulls. In recent years, due to heavy craniocerebral injury, high brain pressure cases, the prevalence of decompression of the bone flap method, and thus artificial huge skull defects are also quite a few, in fact, a considerable portion of these patients do not need to carry out large bone flap decompression surgery, most of them are in the operation of the creation of the urgency to make the decision, is not not improper. Therapeutic measures: the treatment of cranial defects is the implementation of cranioplasty, but the timing of the operation, method and choice of materials, as well as indications and contraindications must be carefully considered, in particular, the patient asked to repair the purpose of the cranial defects, hope to solve what problems. This is because the effectiveness of cranioplasty alone in treating functional symptoms, psychiatric disorders, and manifestations of traumatic epilepsy after traumatic brain injury is unpredictable. Currently, there are two types of repair materials available for cranioplasty: autologous tissues and allogeneic materials, the former using the patient’s own ribs, iliac bone, or cranial bone, and the latter implantable materials such as polymers and metals. Due to the different methods of repair, they can be divided into inlay method and covering method. Currently, the latter method is used more and more. The timing of cranial defect repair should depend on the patient’s systemic and local conditions, such as in the simple depressed fracture for collapsed bone piece removal, can be completed in the same period of a surgical repair operation. However, for open craniocerebral injuries resulting in skull defects, cranioplasty should be considered after the initial debridement and wound healing for 3~6 months. If the open wound has become infected, repair surgery should be delayed until the wound has healed for at least six months. Currently recognized indications for surgery are: 1. Cranial defects larger than 3cm in diameter. 2. 2. The defect is aesthetically displeasing. 3, cause long-term dizziness, headache and other symptoms difficult to relieve. 4, Meningeal-brain scar formation with epilepsy (need to perform epileptic foci resection at the same time). 5.Serious mental burden affecting work and life. Cranioplasty should not be performed on patients with incomplete initial debridement, local infection, intracranial lesions and increased intracranial pressure. In addition, some patients with poor general condition, serious nerve defects, and those who cannot take care of their own life; or those who have large scar in the defective area with thin scalp, should not be rushed to repair, and can be covered with a partial helmet for temporary protection, and then consider cranioplasty when the conditions are ripe. Regarding the material for repairing the skull, there are many kinds of materials, each with its own advantages and disadvantages. Although the autologous bone tissue reaction is small, but need to be in the bone donor area and bone grafting area in two places of surgery, increase the patient’s pain and plastic effect is poor. Some people will be a large bone flap decompression of bone embedded in the abdominal subcutaneous, as a future repair, due to the need for two surgeries, and the bone is often absorbed into small loose concave, the use of allogeneic bone and due to refrigeration in the bone bank, increasing the chances of contamination, the foreign reaction is also larger, so they are already less used. Metal cranial bone forming sheet such as stainless steel plate and mesh, tantalum plate or titanium alloy plate and mesh have strong compressive properties, histocompatibility is also good, but because of thermal conductivity, sharp edges are easy to penetrate the scalp and have the disadvantage of affecting the X-ray examination, has yet to be improved; flat plate of Plexiglas heated and shaped as a repair material, has the advantage of convenient and easy to carry out, but for the plastic requirements of the orbital area of the higher, the root of the nose is less effective, at the same time, the stamping strength is poor and easy to use. However, the effect is not good for places with high plastic requirements such as the eye socket and the root of the nose. By the polymer material methyl methacrylate and styrene copolymer powder plus methyl methacrylate monomer water mixed with each other made of plasticity self-coagulation material, both good plasticity, but also self-coagulation to form a solid and stable permanent implant, with appropriate strength, good tissue compatibility, not easy to degrade, does not affect the advantages of X-ray examination. In recent years, some people have added a pore-making agent to the above two-component materials, and developed plasticized microporous artificial cranial bone materials. After implantation into the body, fibroblasts can grow into the micropores of the implant, so that the implant is integrated with the tissue, and there is a tendency of calcification and ossification, which can be regarded as an ideal cranial bone repair material. In addition, the new cranial surface implant made of silicone rubber cranial plate, hydroxyapatite or ceramic material reinforced with mesh also has better performance. Surgical method: Under local or general anesthesia, the scalp incision is curved, and the blood supply to the base of the flap is fully guaranteed. When separating the scalp, do not damage the deep surface of the dura mater, so as to avoid postoperative fluid accumulation. When the covering method is used, the periphery of the bone defect area does not need to be trimmed, and the bone coat does not need to be cut, so the defect area is covered with an implant that is slightly larger than the defect, and the periphery is fixed to the bone coat with a thick silk thread. However, it is necessary to use strong, good texture, thin peripheral material to match the shape and curvature of the skull. If the inlay method is used, the bone coat should be cut along the edge of the bone defect and trimmed, and then the appropriately cut implant should be inlaid in the bone defect, and the peripheral holes should be drilled and fixed to the bone edge with a thick wire. Care should be taken not to open the frontal sinus when repairing the inlay in the forehead to avoid infection. After surgery, the scalp should be sutured in layers without drainage and appropriate pressure bandage. Clinical manifestations: usually cranial defects less than 3cm2 are mostly asymptomatic; temporalis muscle decompression or suboccipital decompression surgery, hypertrophic muscle and fascia cover and in the defective area can form a tough fibrous healing layer, play a role in the original skull on the brain’s protective effect, clinically there are no symptoms. Clinical manifestations of cranial defects: defects with a diameter of more than 3cm, especially those located in the frontal region, which hinder the aesthetics and safety, often have this or that symptom, such as dizziness, headache, localized tenderness, irritability, uneasiness and other manifestations; or the patient’s fear of throbbing, bulging, and collapsing of the defect area, fear of the sun, fear of vibration and even fear of the sound of the noises, and often have poor self-control, poor concentration and memory. Decrease; or have depression, fatigue, reticence and low self-esteem; or due to a large area of missing skull caused by the patient’s skull serious deformity, directly affecting the physiological balance of intracranial pressure, collapsing when standing upright, bulging when lying down, concave in the morning, convex at night; or due to the atmospheric pressure directly through the defect area acting on the brain tissue, which will inevitably lead to local cerebral atrophy, aggravate the symptoms of cerebral wastage, and at the same time, the ventricles on the affected side are gradually expanding or distorting to the defect area. At the same time, the ventricle on the affected side gradually expands or deforms to the defective area. In addition, pediatric cranial defects can become larger with the development of brain tissue, the edge of the defect turns outward, and the protruding brain tissue gradually shows progressive atrophy and cystic degeneration, so children need a complete cranium to ensure the normal development of the brain.