A large number of experiments and clinical studies have shown that autologous fat transplantation should follow the principle of “three low and three multi”, i.e. low pressure aspiration, low speed centrifugation, low volume injection; multi-tunnel, multi-plane and multi-point injection. The current methods of fat grafting include syringe method, injection gun method, spiral injection method, thread injection method, pneumatic injection method, electric injection method, etc. Each method has its own characteristics, and the key is how to inject to ensure the survival of the transplanted fat. I. Syringe direct injection method The traditional, basic, commonly used, human-powered injection method. The syringe is connected to a fat injection needle of the corresponding diameter, and the needle is inserted into the skin and travels forward at the target level, puncturing reciprocally to form multiple radial tunnels, and after no return blood is drawn back at the distal end of the filled area, the fat particles are injected slowly while withdrawing the needle to form an even distribution. After the overall injection is completed, the surface can be gently rubbed with a flat gauze to make it as flat as possible, and be careful not to squeeze hard so that the fat particles do not overflow from the injection eye. Advantages: simple, applicable, can be used for various types of syringes, injecting various parts. Disadvantages: strength is not easy to grasp, once encountered resistance, easy to increase the push injection pressure, instantaneous injection, and the local accumulation of tissue. Second, the injection gun method fat injection gun is a precise device for fat injection, easier to control than unarmed injection. 1.Ratchet gun A fat injection device with a gear-driven piston that can gently graft fat particles to the appropriate site. The advantage of this device is that a specific dose of fat can be injected with each pull of the trigger, making precise injections possible. If the area to be treated is large, the injection needle is placed in the same position and the trigger is pulled several times to complete the injection. The disadvantage of this device is that additional devices are required and the piston of the injection gun needs to be replaced according to the size of the injection volume. 2.Lin’s injection gun Designed and made by Dr. Lin Cai Min from Taiwan according to the concept of fine autologous fat transplantation. The volume of fat pushed in each time is constant, consistent in size and precise and accurate. At the same time, its injection needle output port can be adjusted in 360° in multiple directions, so that the physician can easily change the injection direction without turning his wrist during operation. Third, the threaded injection method uses a LeVeen syringe (BostonScientificCorp.) or a threaded syringe with a 16- or 18-gauge fat injection needle (15cm), and two people work together to complete the fat injection. The operator holds the needle and the assistant rotates the threaded plunger to precisely control the injection volume according to the operator’s requirements. The amount of injection by rotating one frame depends on the volume of the syringe and the intended threaded frame. The spiral injection method is similar to the threaded injection method, which also requires two people to work together. The device includes a syringe body and a crank. The syringe body consists of a syringe barrel and a spiral rod, which is located in the syringe barrel, with a piston connected to one end and a crank connected to the other end. When used, the crank drives the screw rod according to a certain spacing and provides a large enough thrust to distribute fat particles evenly, which is suitable for large-capacity injections such as breast augmentation without frequent syringe changes, improving injection efficiency and saving time. V. Gear push injection method The device is connected to a specific disposable 1mL syringe, the syringe is put into the holder, and the syringe piston is connected to a series of reduction gears and positioners. When injecting, the holder and syringe as a whole are inserted forward into the tissue with the needle to form a tunnel, and the locator can fix the skin when backing up, pushing the holder and syringe piston forward to inject fat particles through the gear connection. After pushing, the positioner starts to contract and return to the original position, and the next round of injection begins. Sixth, air pressure push injection method With the help of foot switch control, air pressure is used to push the weight piston and special syringe to complete water injection, liposuction, separation and purification, and injection in one step, and the operation process is operated under vacuum, which eliminates contact with air and reduces external infection comprehensively. The syringe has automatic oil separation technology (weight piston), which maximally protects the integrity of fat cells. This method is suitable for a large number of autologous fat injections, such as buttock augmentation and breast augmentation, but it is not suitable for implementing fine fat injections. Seven, electric push injection method 1, fat tissue injector A sterile disposable battery-charged handheld device. It can be used together with the commonly used syringe, the trigger is adjusted to the infusion state, and the trigger is triggered to inject the pre-infused fat into the tissue, while the fat in the syringe is automatically replenished into the pump, which can be “point shot” or “continuous shot”. 2.Constant pressure and constant volume minimally invasive uniform booster This device is designed and developed by Lanzhou General Hospital of Lanzhou Military Region independently, based on the first generation of technical improvements to overcome its large size and cumbersome operation and other defects, and is a handheld electric precision fat injection grafting device developed for fine facial transplantation. The device consists of housing, syringe slot, push cylinder and speed and reset button. When the injection is completed, the syringe is replaced and the reset button is pressed to quickly return the slider to its original position. The device uses built-in battery, which is safe, sterile, lightweight and ergonomic in shape; the biggest advantage of the device is constant pressure, constant volume, minimally invasive and uniform speed, as well as easy operation and slight pain during injection.