What Is Cast Application?
A cast is used to hold a fractured bone in place while it heals. It is a noninvasive option for immobilizing a broken bone.
When to Use a Cast
A cast is used when the two ends of a fractured bone can be realigned (reduced) without surgery, which is called a closed reduction. In some cases–if the bone is badly misaligned, sticking through the skin or broken into three or more pieces–surgery is necessary to realign the bone. This is called an open reduction.
In cases of an open reduction, other immobilization techniques such as external fixation or the insertion of plates, screws or rods will be necessary. Certain types of fractures, such as hip fractures, are known to heal poorly or with increased risk of complications without surgery, so a cast is usually inappropriate for those cases as well.
Types of Casts
Casts are generally made from one of two materials: plaster or fiberglass. Fiberglass is lighter, more durable and more comfortable due to superior air flow. It is also easier to take effective X-rays through a fiberglass cast. Plaster is less expensive and more easily shaped.
How Cast Application Is Done
Whether fiberglass or plaster, cast application is performed the same way. First, a loosely knitted piece of fabric called a stockinette is placed over the fracture area. Next, a layer of padding is added. Both of these layers act as a buffer between the skin and the cast to reduce irritation.
Both plaster and fiberglass come in rolls. Strips are cut from these rolls, moistened, applied over the fracture site and left to dry. Plaster and fiberglass harden into a tight, stiff encasement that prevents the fractured area from moving and allows the broken ends of the bone to heal together.
It is normal for swelling to increase in the first few days after a cast goes on. To counteract this:
- Elevate the affected limb above the heart. This will reduce swelling and fluid buildup.
- Move the fingers and toes below the cast. If it is difficult to move the fingers or toes, see the doctor immediately.
- Apply ice to as much of the cast as possible.
Keep all casts clean and dry unless otherwise instructed. A light splash may be dried with a hair dryer, but a wet cast should be replaced. To keep skin healthy, do not put any creams, powders, or sharp objects inside the cast. Do not bear any weight on the cast unless specifically instructed by a doctor.
Call a doctor if:
- The cast is too loose or too tight; a tight cast may feel better with a period of elevation of the affected limb
- The cast becomes wet or damaged
- There is new tingling or numbness, or poor circulation (cold, numbness, very dark or very white) in the affected fingers or toes
The cast must be worn until the fractured bone has knit itself together and the affected limb can bear weight. When it’s time for the cast to be removed, the doctor will use a cast saw to cut it off. A cast saw vibrates but does not rotate, and will not damage the tissue underneath the cast.
Weight bearing and cast removal are not necessarily related. The cast can be removed when the fracture has healed with enough stability to hold its position with the cast off.
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