A cast is a rigid support structure designed to immobilize a fractured bone or injured limb, providing the stability necessary for proper healing. Most traditional casts are not designed to be submerged or saturated with water. Understanding the specific materials used is key to properly caring for the cast and protecting the injured limb. Moisture completely disrupts the delicate balance between supporting the bone and maintaining skin health underneath the cast.
Standard Cast Materials and Water Exposure
Traditional casts are primarily constructed from Plaster of Paris or fiberglass. Plaster of Paris casts, made from calcium sulfate hemihydrate, are highly susceptible to water damage. When wet, the material undergoes hydration, reverting to gypsum and causing the cast to soften and lose its structural integrity. This softening compromises the cast’s ability to hold the bone fragments in their correct position.
Fiberglass casts have a water-resistant outer shell made from a resin-impregnated synthetic material, but they are still not fully waterproof. The issue is the undercast or padding immediately next to the skin. This padding is typically cotton or a synthetic blend designed to absorb sweat and provide cushioning. Once this absorbent material gets wet, it retains moisture against the skin inside the cast’s hard shell.
Risks Associated with Wetting a Traditional Cast
Introducing water into a traditional cast creates two main risks: compromising the cast’s structure and creating a health hazard for the skin and underlying tissue. For plaster casts, water directly weakens the material, potentially causing it to crumble, crack, or become misshapen. This degradation means the cast may no longer effectively immobilize the fracture, putting the healing bone at risk of movement or re-injury.
The primary concern with any wet cast is the effect on the skin beneath the padding. Trapped moisture leads to skin maceration, where the skin softens, wrinkles, and breaks down, making it vulnerable to infection. The dark, damp, and warm environment is an ideal breeding ground for bacteria and fungi. This can result in severe itching and skin infections like cellulitis or osteomyelitis. Additionally, a wet cast can swell, causing it to rub or chafe the skin and increasing the risk of pressure sores.
Specialized Waterproof Cast Options
Modern orthopedic care offers specialized cast options designed to address water exposure. These options utilize a standard fiberglass outer shell but replace traditional cotton padding with a synthetic waterproof liner. Materials like Gore-Tex, expanded polytetrafluoroethylene (PTFE), or other synthetic open-knit paddings are used. These liners do not absorb water, allowing it to drain out and the limb to dry quickly through evaporation.
This type of cast allows the patient to shower, bathe, and even swim in pools with healthcare provider approval. Getting the cast wet daily is often recommended to help flush out debris and reduce odor and irritation. However, these specialized casts are generally applied only after initial swelling has subsided (one to two weeks post-injury). They are not suitable for all types of fractures or if there are open surgical wounds due to increased infection risk.
Protecting a Non-Waterproof Cast
Patients with a traditional plaster or fiberglass cast must prevent any contact with water. The most reliable method is to purchase a specialized, reusable waterproof cast cover. These covers are typically durable plastic or rubber sleeves with a vacuum seal or a tight, self-sealing neoprene opening. They fit snugly above the cast, creating a barrier that prevents water from seeping in during showering or bathing.
For temporary protection, a thick plastic bag or garbage bag can be pulled over the cast and sealed tightly at the top with medical tape or a rubber band. Ensure the seal is completely watertight, and never submerge the cast, as these makeshift solutions only protect against splashing. When showering, keeping the affected limb elevated and completely outside the shower stream is necessary, and a shower chair can help manage this process safely.