A cast is a hard, protective cover wrapped around a broken bone (fracture) to hold it in place while the bone heals. Once the bone is held still by the cast, it should heal by itself. After the cast has been put on, it's important to look after it. Here are some tips on how to take the best care of a cast.
Putting the cast on
- First, a healthcare professional will wrap the injured area in soft cotton or a bandage.
- Then an outer layer of plaster of Paris or fibreglass material is applied. It is soaked in water then wrapped around the inner layer, where it will dry to form a hard, protective shell.
- A full cast wraps around the whole limb. A ‘back slab’ or half cast, which wraps halfway around your limb and is held in place with a bandage.
- Sometimes the healthcare professional will make cuts in a full cast or cut it in half lengthwise. This is because the limb may swell for the first day or so and they want to make sure the cast is not too tight.
Taking the cast off
Once the bone is healed, the cast is taken off using a special saw. The saw’s vibrations break the cast, not a spinning blade, so it doesn’t hurt or damage the skin. You should never try to take off a cast yourself.
How long will I have a cast for?
The cast usually stays on for 6 weeks as this is how long it takes for the bone to heal. During that time, you'll need to go back to the hospital or clinic to check the condition of your cast and see how the bone is healing.
Taking care of your cast
- If you have a plaster of Paris cast (plaster cast), rest for a couple of days after the cast has been put on to make sure it fully dries.
- Keep the injured limb elevated for the first 2 days, as this will help stop swelling and your cast becoming too tight.
- Regularly move your fingers and toes to keep circulation flowing.
- If your cast is not water resistant, don’t get it wet. Put 1 or 2 plastic bags around it and seal with a rubber band or duct tape when having a bath or shower.
- If you have a water-resistant cast, you may be able to get it wet but check with your healthcare professional first. Once wet, rinse it with clean water and drain from both ends by changing the position of the cast.
- Keep the inside of the cast clean by keeping dirt, food, powders, lotions and sand away from it.
- Don’t put foreign objects inside the cast, including objects used to scratch the skin. They can cause a rash or infection.
- Don’t cut or try to change the shape of the cast. If it's too tight or rubbing, go back to your doctor or hospital.
- If the cast is on your foot, don’t walk directly on it. Use a plaster boot and crutches, if you have been given them.
- Follow any other cast-care instructions you receive from your healthcare professional.
Problems to watch out for
Contact your doctor or hospital straight away if you experience:
- a fever
- tingling or numbness in your toes or fingers, or if they won’t move or feel very cold
- your fingers or toes swelling or changing colour to white or blue
- a burning feeling, stinging, pins and needles or persistent pain under the cast
- your cast feeling too tight or too loose
- a bad smell coming from inside your cast
- blisters, a rash, red or raw skin around the edges or inside the cast
Go back to your doctor or hospital within 24 hours if your plaster cracks, breaks or goes soft.
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Last reviewed: May 2020