After the fracture, if the external fixation of the cast, how to determine the cast loosening: First, if there is obvious loosening after the cast, there will be an obvious gap in the cast fixation, and can move the cast in a small way, if the width of two fingers are stretched into the cast gap, consider re-fixing the cast to avoid triggering the displacement of the fracture end. Secondly, the patient’s self-perception, commonly speaking, the cast is like wearing shoes and clothes, if the patient feels loose, he or she will have obvious feelings, if this external fixation method does not play a role in protecting the fracture end, it is possible that the slight activity will trigger severe pain at the fracture end. These methods can determine whether the cast is loose or not. It is very normal for the cast to loosen during the later fixation process, because the affected limb is abnormally swollen during the acute phase, and with the later treatment, the swelling of the affected limb subsides, leading to the loosening of the cast, which needs to be replaced in time.