Cast Care (cont.)
How Casts Are Applied
Many different sizes and shapes of casts are available depending on what body part needs to be protected. A doctor decides which type and shape is best for each person.
- Before casting material is applied (plaster or fiberglass), a "stockinette" is usually placed on the skin where the cast begins and ends (for example, at the hand and near the elbow for a wrist cast). This stockinette protects the skin from the casting material.
- After the stockinette is placed, soft cotton padding material (also called cast padding or Webril) is rolled on. This cotton padding layer provides both additional padding to protect the skin and elastic pressure to the fracture to aid in healing.
- Next, the plaster or fiberglass cast material is rolled on while it is still wet.
- The cast will usually begin to feel hard about 10 to 15 minutes after it is put on, but it takes much longer to be fully dry and hard.
- Be especially careful with a plaster cast for the first 1 to 2 days because it can easily crack or break while it is drying and hardening. It can take up to 24 to 48 hours for the cast to completely harden.
- A plaster cast is made from rolls or pieces of dry muslin that have starch or dextrose and calcium sulfate added.
- When the plaster gets wet, a chemical reaction happens (between the water and the calcium sulfate) that produces heat and eventually causes the plaster to set, or get hard, when it dries.
- A person can usually feel the cast getting warm on the skin from this chemical reaction as it sets.
- The temperature of the water used to wet the plaster affects the rate at which the cast sets. When colder water is used, it takes longer for the plaster to set, and a smaller amount of heat is produced from the chemical reaction.
- Plaster casts are usually smooth and white.
- Fiberglass casts are also applied starting from a roll that becomes wet.
- After the roll is wet, it is rolled on to form the cast. Fiberglass casts also become warm and harden as they dry.
- Fiberglass casts are rough on the outside and look like a weave when dry. Fiberglass are available in many colors.
Ice and Elevation for Cast Care
A doctor may want the person to use ice to help decrease the swelling of the injured body part. (Check with a physician before using ice.)
To keep the cast from becoming wet, put ice inside a sealed plastic bag and place a towel between the cast and the bag of ice.
Apply ice to the injury for 15 minutes each hour for the first 24 to 48 hours.
Try to keep the cast and injured body part elevated above the level of the heart, especially for the first 48 hours after the injury occurs.
Elevation will help to decrease the swelling and pain at the site of the injury.
Propping the cast up on several pillows may be necessary to help elevate the injured area, especially while asleep.
Medically Reviewed by a Doctor on 11/20/2017
Jennifer L Brown, MD, FACEP
Scott H Plantz, MD, FAAEM
Francisco Talavera, PharmD, PhD
Must Read Articles Related to Cast Care
Broken bones (also called fractures) in the foot are very common. A learn more >>