Why is plaster of Paris used in fracture casting?

A fracture needs protection while the body builds new bone. Plaster is applied over padding and shaped to support the injured area, often including the joints above and below it. Once set, the cast reduces bending and twisting that could disturb the fracture position. It can also provide a stable environment after the bone has been aligned.

The clinician may use a temporary splint first when swelling is expected, then replace it with a complete cast. Follow-up examinations and imaging help determine whether the limb remains aligned and when support can change. A cast does not speed every fracture in the same way, so treatment depends on the injury.

Keep the cast dry, elevate the limb as advised, and move free fingers or toes gently unless told otherwise. Never cut, heat or pad the cast yourself. Do not put powders or objects inside it for itching. Attend reviews and use crutches or a sling according to the weight-bearing instructions you were given.

Get urgent advice if pain or swelling is increasing, fingers or toes become numb, cold, pale or blue, movement becomes difficult, or the cast feels dangerously tight. A cracked, wet, loose or foul-smelling cast also needs assessment. Seek emergency help for severe uncontrolled pain or sudden loss of circulation.

Ask whether you have a splint or full cast, how much weight the limb can take, when repeat imaging is planned, and which changes require same-day help. You can explore [Plaster of Paris](/materials/plaster-of-paris/) and [Fracture Casting](/treatments/trauma-and-fracture-care/fracture-casting/).