Kirschner pin is also known as bone round needle,stainless steel needle with uniform thickness and diameter before and after.Its diameter has thick and fine, according to the needs of the time to choose different diameters.It acts as a temporary fixation,allowing different small bone pieces to be threaded together.However,its anti-rotation ability and stability are not good,and it generally plays a temporary fixed or auxiliary fixed.Generally,the needle tail on one side can be left outside the skin and can be pulled out directly about six weeks after surgery.There is also a common supracondylar fracture of the humerus in children,and the use of steel plates is easy to damage the epiphyseal line,so it is generally used for cross fixation.The patella is also composed of a tension band with Kirschner's pin and steel wire to hold the fractured end of the patella together.The Kirschner pin is similar to the screws used in ordinary times,but it is more flexible and convenient.