What to know about a plaster cast for a broken arm

The cast is moulded to limit movement at the fracture. Some fractures are realigned before casting, while unstable or open injuries may need a different treatment. Follow-up checks confirm that the bones remain acceptably positioned as swelling changes.

Early swelling can make a cast feel snug, while later reduction in swelling may make it feel loose. A cast should support the arm without causing burning, increasing pressure, numbness or restricted finger movement. Loose padding, cracks or softened plaster can reduce control of the fracture.

A plaster cast is heavier and takes longer to dry than many fibreglass supports, but it can be shaped closely around an injured limb. The chosen material depends on the injury, swelling and the clinician's treatment plan.

Keep the cast away from water and allow newly applied plaster to dry in open air. Lift it with your palms rather than fingertips while it is setting to avoid dents. Do not trim the edges, remove padding or insert objects to scratch the skin.

Raise the arm on pillows during the early swollen phase and move uncovered fingers as instructed. Check their colour, warmth, feeling and movement each day. Attend arranged imaging and cast appointments even when pain has improved, because comfort alone cannot confirm alignment.

Contact the treating service if the cast becomes wet, cracked, soft, very loose, foul-smelling or painful at one spot. Increasing swelling, pain that is not settling, fluid from inside the cast, fever, or skin rubbing at an edge also merits prompt review.

Obtain urgent help if the fingers turn pale or blue, become cold or numb, cannot move normally, or severe tight pain continues despite elevation. These changes can signal pressure on circulation, nerves or tissues.

Confirm which joints and fingers you should move, whether a sling is needed, and what activities could shift the fracture. Ask when the next examination or image is due, what happens when the cast comes off, and whether stiffness or weakness will require physiotherapy.