Arm ectropion may be congenital arm ectropion, elbow joint fracture, poor fracture repositioning and other reasons, as follows: 1, congenital arm ectropion: under normal circumstances, the elbow joint carrying angle is in the 10-15 degrees or so, in some cases, such as congenital mutation, it can be significantly greater than 15 degrees, for example, to reach 20 degrees or 30 degrees or so; 2, elbow joint fracture: due to the fracture in the Fracture in childhood can cause the growth potential of the epiphyseal plate at the fracture site to be damaged, which may make the local growth too fast, and thus cause the elbow joint to be ectopia; 3. Poor fracture reset: it may be due to the fracture caused by the adult, and the fracture is poorly aligned, poorly aligned, and not accurately reset, which may also cause the arm to be ectopia.