Materials Used to Make a Cast

After a bone is broken it needs rest and support to heal properly. Orthopedic doctors use casts to support and protect injured bones. A cast is a supportive bandage that is solid and wraps all the way around the extremity.

Casts come in many shapes and sizes, but the two most common types of cast material used are plaster and fiberglass. While casts can be uncomfortable and cumbersome, they are an effective and efficient method to treat fractures.

Little girl with an arm cast
igor kisselev / Getty Images


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 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 healthcare provider if you are interested in a "waterproof" cast.


Casts can also be differentiated from splint materials. A splint is often referred to by other names such as a soft cast or temporary cast.

Splints are often used when more rigid immobilization is not needed, or in the early 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. Splints can be made of many materials

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 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 healthcare providers don't want to risk a complication and will, therefore, use a splint to ensure there is adequate room for swelling. 

3 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Cleveland Clinic. Casts and splints.

  2. American Academy of Ortopaedic Surgeons. Care of casts and splints.

  3. American Academy of Orthopaedic Surgeons. Compartment syndrome.

By Jonathan Cluett, MD
Jonathan Cluett, MD, is board-certified in orthopedic surgery. He served as assistant team physician to Chivas USA (Major League Soccer) and the United States men's and women's national soccer teams.