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Care of your synthetic cast - Information for children’s fracture clinic patients

How long does the cast take to dry?

The cast will set in two to three minutes but takes about 20–45 minutes to dry completely.

Do not try to speed up the process by using a hairdryer or other appliance. During this time please take extra care to protect the cast, do not rest it on a hard surface or write on it until it is dry.

What should you look out for?

The cast becoming too tight. If this happens you may notice:

  • Swelling of the fingers/toes
  • Numbness or pins and needles in the fingers/toes
  • Pain
  • White or blue discolouration of the fingers/toes and possible coldness

Remember—if the cast is hurting it needs attention!

The first thing to do is to raise the limb.

  • Arm cast: Rest the cast on a pillow/cushion so that the hand is higher than the elbow.
  • Leg cast: Rest the cast on a pillow/cushion so that the foot is higher than the hip.

If symptoms do not improve after one or two hours then please return to us or your nearest A&E Department.

Do not attempt to remove the cast yourself. Wherever possible do rest the cast in this way to avoid swelling.

What should you look out for?

The cast becoming too loose, cracked or soft. Under normal circumstances you should not be able to move the cast up, down or around your limb.

It should feel comfortable and should not be cracked at any point. If you notice any of these things, and the Fracture Clinic is unable to see you, please go to your nearest A&E Department.

Important precautions:

  • Never use anything to scratch under the cast. The slightest scratch could develop into a serious infection.
  • Never trim or cut down the length of the cast yourself, or attempt to tuck in extra padding.

Can the cast get wet?

No! You should never allow the cast to become wet.

Can the cast be walked on?

Only if the doctor says it is okay and the cast is dry.

Can exercise continue?

Yes, exercise should continue in order to avoid stiffness in unaffected joints. We recommend the following gentle movements every couple of hours during the day.

Arm cast:

  • Wiggle your fingers
  • Bend and straighten the elbow joint (only if cast is below elbow)
  • Rotate the shoulder very gently

Leg cast:

  • Wiggle the toes
  • Bend and straighten the knee (only if the cast is below the knee)
  • Gently clench the muscles in the back of the calf and thigh to improve blood flow.

Taking care of the cast will help the injury heal properly.


The risks of having a cast are Deep Vein Thrombosis (DVT), Compartment Syndrome and pressure sores.

By following advice given in this leaflet and by your doctor, these risks can be reduced.


The benefits of having a cast will have been discussed with your doctor during consultation. The main benefit of having a cast is to immobilise the limb to prevent further damage and to promote healing.

After your cast has been removed

You may find that the arm/leg is thin and feels strange. Some stiffness and discomfort may also be felt. Don’t worry, this is normal and will improve as soon as the muscles get stronger.

The skin may be flaky, dry and itchy. A gentle wash or bath, followed by a moisturising cream, will help.

A tubigrip (elasticated stocking) may have to be worn to give support to the arm/leg. This also helps to prevent swelling. This needs to be removed at night.

Remember the arm/leg needs to be raised when sitting and rings should not be worn if the hand is swollen.

Contact sports should not be played until the doctor says it is safe to do so. However swimming is recommended in nearly all cases. Your doctor will advise you about this.

If there is a problem with the cast please call the Fracture Clinic on 020 3315 5204 or your GP. Alternatively, go to your nearest A&E Department.

If you are not registered with a GP, we would advise you do so as soon as possible:

  • Go to
  • Click GPs under the heading ‘Services near you’
  • Enter your home postcode in the box and click Find GP practices —this will provide you with a list of GPs close to your home

If you do not have internet access, your local pharmacy will be able to give you a list of GPs in your area.

This leaflet has been written by staff working in the Children’s Fracture Clinic at Chelsea and Westminster Hospital. We hope it answers some of your questions.

If after reading it you have any further questions, please speak to your GP or contact the Fracture Clinic.

Contact information

Fracture Clinic

Chelsea and Westminster Hospital

369 Fulham Road, London, SW10 9NH

T: 020 3315 5204


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