Plaster of Paris: Uses, Properties and Patient Care

Plaster of Paris is a mouldable medical casting material that supports and protects a limb while bones or soft tissues heal.

Plaster of Paris is a powder-based material mixed with water to form a paste. A clinician shapes the wet paste around padding and a bandage, where it sets into a firm shell. The cast limits movement so a bone, joint or corrected foot can remain in the position selected by the orthopaedic team.

The cast is fitted to the body part rather than applied as a loose hard covering. Padding protects the skin, while the outer layers provide support. It may be used as a temporary cast soon after an injury, when swelling can change, or as part of a planned correction.

When water is added, Plaster of Paris can be moulded closely to body contours before it hardens. This makes it useful where a personalised fit matters. The finished cast is rigid, but it can be shaped or removed by a trained clinician with the appropriate tools.

Orthopaedic teams use Plaster of Paris to support some fractures, maintain a correction during staged treatment, and protect an area after a procedure. The choice depends on the injury, the body region, swelling, expected healing and whether the cast needs to stay in place for a short or longer period.

For a broader explanation of a cast used to support a broken bone, see Fracture Casting. Plaster casts can also be part of staged treatment for a corrected foot; Clubfoot Casting explains that context.

Depending on the clinical goal, a team may choose a fibreglass cast, a removable brace, a splint or another support. These options differ in weight, moulding, water resistance, adjustability and how easily the skin can be checked. A splint may be preferred while swelling is changing; a removable support may be suitable only when the body part does not need continuous immobilisation.

Keep the cast dry unless your clinician has given different instructions, and do not push objects inside it to scratch. Elevate the limb when advised, move the fingers or toes that remain free, and follow the team’s instructions about walking or using the limb. Never trim, loosen or pad the cast yourself.

Contact the treating service promptly if pain is worsening, the cast feels unusually tight, fingers or toes become numb, pale, blue or cold, or swelling prevents normal movement. A wet, cracked, soft or foul-smelling cast also needs clinical advice.

A Plaster of Paris cast is intended for the treatment period chosen by the clinical team, not for indefinite wear. It may need review when swelling changes, the cast becomes loose or the planned stage of healing is reached. Removal should be carried out by a trained professional so the skin and the healing area can be checked safely.