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What is a Fiberglass Cast?

By Mona D. Rigdon
Updated Mar 03, 2024
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A cast is one of the preferred techniques to immobilize the bone of a limb that has been injured by fracture, dislocation or break. A fiberglass cast is a lighter, synthetic alternative to the more traditional plaster version. It is created by padding the extremity with cotton or waterproof padding material, followed by wrapping several layers of knitted fiberglass bandages impregnated with a water-soluble, quick-setting resin. It is lighter and more durable than plaster, so fiberglass has quickly become the preferred type of casting with many patients and medical care providers.

Fiberglass has many advantages over a plastic cast. The first thing most patients notice is that the cast weighs less and is more comfortable. It is made of water-activated polyurethane resin combined with bandaging materials, so this material offers greater strength and less time for setting, as well. Casts made of this material require less maintenance than those made with plaster and often are used after the healing process already has begun.

The fiberglass bandages on the outside of the cast are waterproof, but typically, most of the padding materials inside the cast are not. Waterproof materials have been developed to replace this inside padding with a waterproof alternative. This offers an option that would allow patients the ability to bathe or shower, wash hands, do chores and even swim while wearing a cast. The material also is reported to cut down on odor and itching by helping to wick moisture away from the skin under the cast.

As with any type of cast, fiberglass has its drawbacks. It sets quickly, so a less-experienced medical care provider has less time to properly wrap the injured extremity. Many opponents to the use of fiberglass casts claim that synthetic materials leave less room for swelling. They are not always appropriate for more complex fractures where the bone is out of position. Plaster is more moldable than the knitted fiberglass and resin bandages, so a more comfortable fit can sometimes be achieved with plaster. Further, plaster is smoother and less likely to snag clothing or to rub skin raw.

Medical professionals advise patients wearing fiberglass casts to report any rough spots that snag clothing or chafe skin immediately to their medical care facility for repair. Cracks are easily repaired but are not very likely to occur. Experts also encourage patients to report any foul odor or damage to the padding of the cast.

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Discussion Comments
By anon998277 — On May 07, 2017

@Pastanga They almost never use fiberglass in emergency rooms.

They do use half open plaster casts to allow for swelling.

In a week (doctor appointment) you get a closed fiberglass cast in most of the times.

If you haven't life threatening injuries in ER, you won't get the best care because they are short of doctors there and professionals in particular areas.

You will have to make an appointment with a professional anyway.

By anon345695 — On Aug 21, 2013

@Pastanga: That does sound weird about the emergency staff saying that. I went to the emergency room (on a Friday) for two broken bones and they said they weren't going to put me in a cast either (due to anticipated swelling) and it did swell over the weekend. However, they did tell me to contact my doctor and to get a referral to "ortho". The following Monday, my doctor saw me and referred me to an ortho, where I had a cast placed on my arm.

By bythewell — On Jun 30, 2012
@pastanaga - It is a patient's right to ask for a second opinion, of course, but do bear in mind that there are reasons behind what most doctors do. I can see that fiberglass is going to be the preferred cast material in most cases, but as it says in the article, it's not always the best thing to use.

If your doctor says that you'd be better off with plaster and explains why, then I think you should go with his or her advice. And if you go to a second doctor and get the same advice there, you should definitely do it. Don't go from doctor to doctor looking for the one that's going to agree with you rather than do what's right for your health.

By pastanaga — On Jun 29, 2012

It's interesting how different doctors can recommend different treatments for the same injury. I had a friend whose 4 year old boy managed to break his arm around the elbow. The people at the emergency room told her that he couldn't wear a cast at all, because he was too young and a cast might make the elbow set badly.

So, she was stuck with an active 4 four old, with no cast to hold his break in place.

Needless to say, that didn't last very long. He quickly managed to jar his arm even worse and she went to her own doctor who was horrified that the emergency room didn't put on a cast. He used a fiberglass cast, because it was light enough for a 4 year old and said there should be no problem with his elbow or anything.

So, if you really aren't happy with your doctor's decision, like perhaps they are insisting on a plaster cast, make sure you ask for a second opinion just in case they are giving you the run around.

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