The medical plaster that plays the role of fixation is generally cooked plaster. The main component of plaster is calcium sulfate, and the component of medical plaster is mainly anhydrous calcium sulfate, which is often referred to as cooked plaster, formed by forging calcium sulfate containing water. It is not harmful to people and does not cause any irritation to the skin. Plaster external fixation is a frequently used external fixation method in orthopedic clinics, which mainly makes use of the nature of plaster solidification after encountering water to play a role in fixing the human skeletal limbs. Because of the good plasticity of plaster, the soft tissues will be affected more evenly when the limb is fixed, and no adverse reaction will occur, so it is widely used in clinical practice. Patients who have been externally fixed in plaster must be relaxed and protected after 24-48 hours, mainly because the plaster will be completely solidified after 48 hours.