Plaster casts are commonly placed around a broken bone soon after the injury. These casts are padded with bulky cotton and wrapped in ace bandages to make them comfortable to the patient. The reason plaster is used initially after the injury is that plaster casts can be easily fitted to allow for swelling of the extremity beneath the cast. If this were not accounted for, swelling could impair circulation in the arm or leg and cause further problems. 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 swelling has subsided. These casts are lighter weight, longer wearing, and more breathable than plaster. The fiberglass casts are sturdier than the plaster and require less maintenance. Usually, after breaking a bone, you will be placed in a plaster cast for a few days or a week.