Prosthesis is a medical device that can be used to replace a certain tissue, organ or limb of the body. According to whether it is implanted into the body or not, it is divided into two kinds: implantable prosthesis and extracorporeal prosthesis. I. Implantable prosthesis: 1. Medical prosthesis: mainly including artificial joints, artificial heart valves, artificial tendons, etc. Artificial joints are mainly composed of metal alloys, polymers, ceramics, etc.; 2. Plastic surgery prosthesis: according to the different parts of the body, there are mainly rhinoplasty prosthesis, breast augmentation prosthesis, etc. In plastic surgery, there are mainly silicone prosthesis, breast augmentation prosthesis and other prostheses. In plastic surgery prosthesis, silicone gel prosthesis and expanded body are more commonly used, silicone gel is mostly used for breast augmentation, rhinoplasty. Silicone gel is stable in nature and is not prone to infection, inflammation or adhesion, but the disadvantage is that it is highly mobile and easily permeable to light. Expanded body, also known as polytetrafluoroethylene, is characterized by easier shaping, the material contains microporous, cells and blood vessels can enter the microporous growth, not easy to shake, the disadvantage is that it is more difficult to remove the expanded body. Second, extracorporeal prosthesis: through the prosthesis instead of a part of the body or function, such as dentures, prosthetics, etc. 1, dentures: mainly porcelain teeth, metal dentures, plastic dentures, etc., characterized by higher stability, not easy to age, deformation, etc.; 2, prosthetics: mainly composed of resin and alloy, or sets of silicone sets, more advanced “myoelectricity prosthetics “, can do more subtle movements to meet the needs of the human body; 3, others: such as prosthetic eyes, cochlear implants, prosthetic eyes are mainly polymer prosthetic eyes, crystal prosthetic eyes, glass prosthetic eyes, etc., of which polymer prosthetic eyes are more commonly used. Cochlear implant is an implantable electronic prosthesis, including straight electrode, curved electrode, half-ring electrode, full-ring electrode and other different types.