Cranial defects have become more and more common in our life, and many people suffer from cranial defects due to some trauma, traffic accidents or diseases. Cranial defects can cause many uncomfortable symptoms, such as dizziness and nausea, which seriously affects the life and health of patients, so once the problem of cranial defects occurs, it is important to save health by doing cranial repair surgery. A few days ago, a patient consulted with me, saying that he had a cranial defect left behind by traumatic brain injury surgery, and there was no special discomfort, but his head was sometimes puffed up and sometimes collapsed. He was advised to have a repair surgery, but he wanted to know what exactly this surgery would do? The treatment of cranial defects is to perform cranioplasty, but the timing, method and materials used, as well as the indications and contraindications for surgery must be carefully considered, especially the purpose of the patient’s request to repair the cranial defect and what problems he wants to solve. This is because the outcome of simple cranioplasty is unpredictable for the treatment of functional symptoms, mental disorders and traumatic epilepsy manifestations after traumatic brain injury. Usually, skull defects less than 3 cm in diameter are asymptomatic, and after performing temporal muscle decompression or suboccipital decompression, there are thick muscles and fascia covering and forming a tough fibrous healing layer in the defect area, which can play a protective role of the original skull on the brain, and there is no symptom in the clinic, and usually no skull repair is needed. Defects with a diameter of more than 3 cm, especially those located in the frontal area, which are aesthetically and safely disfiguring, often have one or more symptoms, such as dizziness, headache, local tenderness, irritability, restlessness, etc.; or patients have fear of the pulsation, expansion, wall subsidence of the defect area, fear of sunlight, fear of vibration and even fear of loud noises, often have poor self-control, concentration and memory loss; or have depression, fatigue, reticence and self-consciousness, The patient’s skull is severely deformed due to large skull loss, which directly affects the physiological balance of intracranial pressure, collapses when standing upright, bulges when lying down, concave in the morning and convex at night; or the atmospheric pressure acts directly on the brain tissue through the defect area. Over time, this will inevitably lead to local brain atrophy and aggravate the symptoms of brain damage, and at the same time, the ventricles on the affected side will gradually expand and expand or deform to the defect area. In this case, repair surgery should be considered. In addition, the cranial defect of pediatric patients can become larger with the development of brain tissue, and the edges of the defect will turn outward, and the protruding brain tissue will gradually show progressive atrophy and cystic degeneration, so pediatric patients need a complete cranium to ensure normal brain development. Currently, the recognized indications for surgery are: skull defects larger than 3 cm in diameter, defects that are aesthetically displeasing and cause long-term dizziness, headache and other symptoms that are difficult to relieve, meningeal-brain scar formation with epilepsy (canker resection must be performed at the same time), severe mental burden affecting work and life. For patients with incomplete initial debridement, local infection, intracranial lesions and increased intracranial pressure, skullplasty should not be performed for the time being. In addition, some patients with poor general condition, serious neurological deficit and unable to take care of themselves, or those with thin scalp and large scar in the deficient area should not be repaired urgently, and can be temporarily protected by a local helmet, and then considered for the surgery when the conditions are mature. Currently, PEEK material is the ideal material for skull repair because it has excellent histocompatibility and does not produce rejection, and PEEK material has good radiation transmission and does not affect postoperative medical examinations. In addition, PEEK is an ideal material for cranial repair because it is comparable to human cranial bone in terms of elasticity, strength, thermal insulation, and stability.