Purpose of a Cast
A cast is a hard, protective covering made from plaster of Paris or fiberglass. It is applied to a broken bone (fracture) to keep it in the correct position while it heals. Proper care of your cast is essential to ensure successful healing and to avoid complications.
How is a cast put on?
The injured limb is positioned in a way that will hold the broken bone into the best position. The skin is then wrapped with soft material, similar to cotton wool. The plaster or fiberglass is then soaked in warm water to make it soft and flexible. It is then wrapped on top of the soft padding. A doctor or nurse may put some careful pressure on the cast material as it dries to ensure a snug fit.
What are casts made of?
The two most common materials used for casts are:
- Plaster Cast (Plaster of Paris): White in colour. Takes 24–72 hours to fully dry. Must be kept dry at all times.
- Fiberglass Cast: Comes in different colours. Lighter, more durable, dries faster, but still must be kept dry.
Types of casts
- Backslab: Plaster of Paris is applied to one side of the limb and wrapped up with a bandage. This allows for swelling of the limb
- Split Cast: If the limb is very swollen, or has the potential to swell, the cast may be split to allow for this swelling. Once the cast is dry, a special saw is used to cut the plaster along its length. Some airlines will want passengers to have their casts split before air travel
- Long Arm Cast: a cast that starts just below the shoulder and extends past the wrist with the elbow bent at 90 degrees
- Short Arm Cast: a cast that starts just below the elbow and extends past the wrist
- Bennett’s Cast: like a short arm cast but also extends up the length of the thumb
- Long Leg Cast: a cast that starts at the thigh and extends past the ankle to the toes. The knee will be almost straight
- Short Leg Cast: a cast that starts below the knee and extends past the ankle to the toes
Do's: How to care for your cast
Keep It Dry: Always cover the cast with a waterproof cover or plastic bag sealed with tape or rubber bands when bathing or showering.
Elevate Your Limb: Raise your arm or leg on pillows above heart level, especially for the first 48–72 hours, to reduce swelling.
Move Your Digits: Wiggle your fingers or toes gently every hour to maintain good blood flow and prevent stiffness.
Keep It Clean: Avoid dirt, sand, or powder near the cast. Clean the skin around the edges with a damp cloth and mild soap.
Watch for Odours: A mild odour is normal, but a strong or unpleasant smell may indicate infection.
Act on Damaged Casts: If the cast becomes broken or soft it may not be holding the broken bone securely. Seek advice from a healthcare professional.
Don'ts: What to avoid
Do Not Insert Objects: Do not put anything inside the cast to scratch.
Do Not Alter the Cast: Do not trim, cut, or break off any part of the cast.
Do Not Try to Remove Your Cast: Trying to remove your own cast may cause further injury
Do Not Get the Cast Wet: Avoid baths, swimming pools, hot tubs, or walking in the rain without protection.
Do Not Ignore Signs of Trouble: Changes in sensation, colour, or swelling may be serious and should be checked by a Health Care Professional
Do Not Walk on the Cast: If you are in a leg cast don’t walk on it unless you have been told you can by your Health Care Professional
Contact a Doctor Immediately if you Experience:
- Numbness, tingling or pins and needles
- Fingers or toes turning pale, blue, or cold
- Severe or increasing pain not relieved by elevation or medication
- Excessive swelling above or below the cast
- Wet or damaged cast
- Foul odour or discharge from the cast
- Fever over 38°C (100.4°F) or signs of infection
- Tightness or pressure that doesn’t go away after elevation
- The cast becomes loose
- The cast rubbing on your skin
- You feel burning or stinging under the cast
Is there a risk of blood clots if I am in a cast?
Clots are a risk in a limb, especially the leg, is immobilized. Your healthcare professional should assess your risk of clots by asking you questions about your health if they are going to place you in a cast. You may need some medication to help thin your blood to reduce the risk while you are immobilized. Please see our blog on blood clots for more information.
Cast drying time (for new plaster casts)
- Allow 24–72 hours to dry completely.
- During this time, avoid resting the cast on hard surfaces, support the cast with soft cushions or a sling, and avoid getting the cast wet or pressing it.
Skin care tips
- Do not apply lotions, creams, or powders near or inside the cast.
- After the cast is removed, wash the area gently with soap and water.
- Expect some stiffness, dry skin, or weakness — this is normal.
- Do stretching or strengthening exercises if advised.
Cast removal
Your cast will be removed with a specialized oscillating saw that vibrates to break the cast without harming the skin. It can look and sound quite scary, but it’s perfectly safe and won’t harm you.
Contact information
If you have questions or concerns, contact your GP or local fracture clinic.
