A cast is a rigid dressing used to immobilize a fractured bone or soft tissue injury. It is made of strips impregnated with plaster or fiberglass material. The injured area is first covered with a layer of padding made of cotton or synthetic materials to protect the skin from irritation.

A protective shell of fiberglass, plastic, or plaster, and bandage that is molded to protect broken or fractured limb(s) as it heals. Casts are supportive devices used to help keep an injured bone in place while it heals. A cast holds a broken bone (fracture) in place and prevents the area around it from moving as it heals. Casts also help prevent or decrease muscle contractions and help keep the injured area immobile, especially after surgery, which can also help decrease pain.