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Bones & Muscles

When Your Child Needs a Cast

Broken bones, or fractures, are a common hazard of childhood. And although a bone can break in a split-second fall off the jungle gym or a quick collision on the soccer field, the healing process takes a bit longer.

In most cases, a child who breaks a bone will need a cast. A cast is a big, hard bandage made of fiberglass or plaster that keeps bones in place while they heal. Depending on the age of the child and type of fracture, a cast can be on for as little as 4 weeks or as long as 10 weeks.

For minor fractures, a splint may be all that is needed. A splint supports the broken bone on one or two sides and is adjustable; a cast encircles the entire broken area and needs to be removed by a doctor when the bone is healed.

Types of Breaks

A doctor might be able to tell whether a bone is broken simply by looking at the injured area. But the doctor will order an X-ray to confirm the fracture and determine what type it is.

Because their bones are softer and more likely to bend than break in half, kids are more likely to have incomplete fractures (fractures that go partially through the bone). Common incomplete fracture types include:

  • buckle or torus fracture: one side of the bone bends, raising a little buckle, without breaking the other side
  • greenstick fracture: a partial fracture in which one side of the bone is broken and the other side bends (this fracture resembles what would happen if you tried to break a green stick)

Mature bones are more likely to break completely. A stronger force will also result in a complete fracture of younger bones. A complete fracture is one that extends completely through the bone and sometimes causes the bone to break into several pieces. Types of complete fractures include:

  • closed fracture: a fracture that doesn’t break the skin
  • open (or compound) fracture: a fracture in which the ends of the broken bone break through the skin (these have an increased risk of infection)
  • non-displaced fracture: a fracture in which the pieces on either side of the break line up
  • displaced fracture: a fracture in which the pieces on either side of the break are out of line (which might require the doctor to realign the bones or require surgery to make sure the bones are properly aligned before casting)

Other common fracture terms include:

  • hairline fracture: a thin break in the bone
  • single fracture: the bone is broken in one place
  • segmental: the bone is broken in two or more places in the same bone
  • comminuted fracture: the bone is broken into more than two pieces or crushed

Also common among kids are growth plate fractures. These are breaks through the growth plate alone or through the growth plate and the area around it. Growth plate fractures are seen in kids until they reach late adolescence. At this point the growth plates close and cannot be fractured. These fractures range from mild to serious and require treatment by an orthopedic specialist.

Before Getting a Cast

For displaced fractures, the bone will need to be set, or realigned, before a cast is put on so that it will heal in a straighter position. To set the bone, the doctor will put the pieces of the broken bone in the right position so they can grow back together into one bone (this is called a closed reduction).

A closed reduction involves the doctor realigning the broken bone so that it heals in a straighter position. The child is given sedation, which is a medicine, usually through an intravenous line (IV) during the closed reduction. Realigning the bones is a painful procedure, so sedation is given so the child won’t feel it. A cast is then put on to keep the bone in position. You can expect another X-ray to be taken immediately after the procedure to make sure the bones are in good position after the realignment is done.

If the fracture is complicated or more serious, an open reduction might be necessary. Open reduction is a surgical procedure in which an incision is made in the skin and metal pins and plates are attached to the broken bone fragments to better stabilize the break while it heals. This is done under general anesthesia.


Casts usually are made of either:

  • plaster of paris: this heavy white powder forms a thick paste that hardens quickly when mixed with water. Plaster of paris casts are heavier than fiberglass casts and don’t hold up as well in water.
  • synthetic (fiberglass) material: these casts come in many bright colors and are lighter and cooler. The fiberglass (a kind of moldable plastic) covering is water-resistant, but the padding underneath is not. You can, however, sometimes get a waterproof liner. The doctor putting on the cast will decide whether your child should get a fiberglass cast with a waterproof lining.

Having a cast put on is a relatively simple process. First, several layers of soft cotton are wrapped around the injured area. Next, the doctor or orthopedic technician wraps a layer of plaster or fiberglass around the soft first layer. The outer layer is damp but will dry to a hard, protective covering. Doctors sometimes make tiny cuts in the sides of a cast so that there is room for swelling if it occurs.

There are many types of casts, for all types of breaks. The most common casts are:

  • short arm casts, which are placed from the knuckles of the hand to just below the elbow. These types of casts are used for forearm and wrist breaks and after some surgeries.
  • long arm casts, which go from the upper arm to the knuckles of the hand. These casts are generally used for upper arm or elbow fractures, but can also be used in forearm breaks.
  • short leg casts, which run from just below the knee to the bottom of the foot. These are usually used for ankle and lower leg breaks or surgeries.
  • long leg casts, which are applied from the upper thigh down over the foot. These casts are used to heal breaks or fractures of the knee, lower leg, or ankle.
  • short leg hip spica casts, which go from the chest to the knees and are used to keep hip muscles and tendons in place after surgery.

Sometimes splints are worn for a few days (usually between 3 to 7) before a cast is made. This allows for swelling to subside so that the cast can provide the best fit for your child.

Splints are usually held in place by fabric fasteners, velcro, or tape, but they should not be rewrapped or removed, even if a child is experiencing some discomfort. Only a doctor or orthopedic technician should adjust a splint.

Short-Term Cast Care

The area around the break will probably be a little sore and swollen for a few days, so the doctor may recommend acetaminophen or ibuprofen to help ease any pain.

The doctor might also recommend raising the body part with the fracture. Use something soft, like a pillow, to raise the injured arm or leg above heart level to reduce swelling and pain.

If the cast or splint is on an arm, the nurse or technician will give your child a sling to help support it. A sling is made of cloth and a strap that loops around the back of the neck and acts like a special sleeve to keep the arm comfortable and in place. A child with a broken leg who is mature enough and of adequate height probably will get crutches to make it a little easier to get around.

Sometimes a “walking cast” (a foot or leg cast with a special device implanted in the heel to allow for walking) can be used, though your child shouldn’t walk on it until it’s dry.

Long-Term Cast Care

For bones to heal properly, certain steps must be taken to make sure the cast can do its job. These tips can help keep a cast in good shape:

  • Keep non-waterproof casts dry. Many casts are not waterproof, so keeping them dry for the whole time the cast is in place is very important. It is preferred that your child take baths, not showers. The doctor will tell you to cover the cast with a plastic bag or special cast protector for baths. The cast area should be propped up on something like a milk crate during the bath to keep it completely out of the water. Children under age 5 years should be sponge bathed.
  • Keep out foreign objects or substances. At some point, the skin inside the cast will probably become itchy. Your child should not insert anything into the cast to relieve itching, as this could scrape the skin and lead to infection. You also should not pour baby powder, creams, or oils into the cast.

    To relieve itching, tapping on the outside of the cast or using a cool blow dryer to blow air in around the edges of the cast may help.

    Young children should be watched closely because they may place small toys or food inside their cast.

  • Check for cracks. Be sure to check the cast regularly for cracks, breaks, tears, or soft spots. If you notice any of these things, contact your doctor.
  • Don’t alter the cast. Decorating the cast and having friends and family sign it is OK, but things like pulling out the cotton lining or breaking off parts are not.
  • Sharp edges. If a sharp edge develops on the cast and is irritating the skin, put tape or moleskin on the edge to protect the skin from the rough surface.

When to Call the Doctor

When splints and casts are applied properly and care instructions are followed, complications are rare. Sometimes sores can occur if the splint or cast is loose fitting and rubs the skin. These sores can become infected. Tight fitting splints or casts can cause fingers or toes to turn bluish — this can be relieved by fixing the cast or splint.

Contact your doctor if you notice any of the following:

  • increased pain that isn’t better with raising the casted part and/or pain medication
  • extreme tightness that leads to the hand or foot feeling numb or tingly
  • fingers or toes turning white, purple, or blue
  • trouble moving toes or fingers
  • a blister developing inside the cast
  • any unusual odor or drainage coming from inside the cast
  • a break in the cast or the cast becoming loose
  • a wet cast
  • skin around the edges of the cast gets red or raw
  • fever

Cast Removal

Once the bone is healed, the cast will be removed with a small electrical saw. The saw’s blade isn’t sharp — it has a dull, rounded edge that vibrates from side to side. This vibration is strong enough to break apart the fiberglass or plaster but won’t hurt skin. Don’t attempt to remove the cast on your own.

Once the cast is off, the injured area will probably look and feel different to your child. The skin will be pale, dry, or flaky; the hair will look darker; and the muscles in the area will look smaller or thinner. This is all temporary. Over time, with some special exercises recommended by the doctor or a physical therapist, the bone itself, and muscles around it, will be back in working order.

Reviewed by: Yamini Durani, MD
Date reviewed: October 2012