The darkening of the patient’s skin during a fracture is mainly related to blood circulation, and if a fractured patient is immobilized in a cast or splint after reduction and immobilization, the immobilization must be watched to see that it is not too tight. If it is too tight, the fracture end will be severely swollen or the skin will turn purple. After the skin turns purple, pigmentation sinks into the surface of the skin, and the iron from hemoglobin may stay in the skin to form pigmentation during the absorption period, so the skin is black during the recovery period, which is mainly caused by poor blood circulation. Generally one month after the fracture the healed tissue will be formed, you should go down to the ground as soon as possible to promote blood circulation, so as to have a better recovery and reduce the possibility of the skin becoming black. If the skin is black and there are no symptoms, no special treatment is needed. If it is serious, you need to go to the hospital to find out the cause before treatment.