Materials Used to Make a Cast

Cast Material Used for the Treatment of a Broken Bone

cast bone
Fiberglass cast material is applied to a broken wrist.. jacus / Getty Images

After a bone is broken it needs rest and support to heal properly. Orthopedic doctors use casts to support and protect injured bones. While casts can be uncomfortable and cumbersome, they are an effective and efficient method to treat fractures.

Casts come in many shapes and sizes, but the two most common types of cast material used are plaster and fiberglass. A cast is a supportive bandage that is solid, and wraps all the way around the extremity.

  • Plaster
    While fiberglass material is newer, many casts used today are still made from plaster. Plaster casts are most often used when a fracture reduction (repositioning of the bone) is performed. The reason plaster is used after repositioning the bone is that plaster can be well molded to the patient, and therefore it can support the bone more precisely. When a bone was out of position, and is manipulated back into position, plaster may be used to help hold the bone in the proper position.

    The problem with plaster is that it is heavy and must remain dry. Plaster casts are a burden for the patient because of their bulky and heavy material. Furthermore, water will distort the cast shape and can cause problems for healing should the cast get wet.

  • Fiberglass
    Fiberglass casts are usually fitted when the bone is not out of position, or if the healing process has already started. Fiberglass casts are lighter weight, longer wearing, and more breathable than plaster. The fiberglass casts are sturdier than the plaster and require less maintenance.  The vast majority of casts used today are fiberglass.  The other advantage of fiberglass that is appealing to many (not just kids) is that it comes in many colors and is easy to 'dress up.'

    Both plaster and fiberglass casts are wrapped over a few layers of cotton that serve to protect the skin. Keeping this cotton clean and dry will be of utmost importance for your comfort. There is a special type of padding material that can be used under fiberglass casts to allow the cast to get wet.

    Ask your doctor if you are interested in a "waterproof" cast.


    Casts can also be differentiated from splint materials.  Splints are often used when more rigid immobilization is not needed, or in the early stages after a fracture has occurred.  A splint is often referred to by other names such as a 'soft cast' or 'temporary cast.'

    Splints can be made of many materials.  One of the common uses of a splint is in the earliest stages after a fracture has occurred.  For example, seldom do patients leave a hospital emergency room in a cast.  Instead, after their fracture is diagnosed, they are typically splinted.  The advantage of the splint in this setting is that there is more room for swelling.  A potentially devastating complication of cast treatment after a fracture is a compartment syndrome.  This condition occurs when too much pressure builds up inside the body, and can occur after a fracture when swelling occurs in a space confined by a cast.  While compartment syndrome typically causes severe pain, this can be difficult to distinguish from normal fracture pain after a broken bone, and therefore most doctors don't want to risk a complication and will therefore use a splint to ensure there is adequate room for swelling.


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