A cast is a rigid support structure designed to immobilize a fractured bone or damaged joint, ensuring proper alignment during the healing process. Casts are typically constructed from plaster of Paris or fiberglass, wrapped over soft, protective padding. While fiberglass is more water-resistant than plaster, the cotton or synthetic padding beneath the hard shell is not waterproof and must be kept dry. Maintaining a completely dry cast environment is essential for successful treatment and the health of the underlying skin.
The Critical Importance of Cast Dryness
Keeping a cast dry is necessary not only to preserve the structural integrity of the outer shell but also for skin health. Water exposure causes plaster casts to soften and lose the rigidity needed for proper immobilization. Although the fiberglass shell resists water, the inner padding retains moisture like a sponge, which is detrimental to skin health.
A damp environment inside the cast leads to maceration, where the skin softens and breaks down due to prolonged moisture exposure. Macerated skin is fragile and highly susceptible to injury. This moist, warm setting creates an ideal breeding ground for bacteria and fungi, significantly increasing the risk of skin irritation and infection. Dampness compromises the healing environment and may require the cast to be removed and replaced.
Daily Strategies for Waterproofing
Preventing water exposure requires consistent, careful planning for all daily activities, especially those involving water like bathing and showering. The most effective method for waterproofing a cast is the use of specialized, medical-grade cast protectors. These commercial products are typically made of durable vinyl or rubber and feature a tight, waterproof seal designed to create a vacuum barrier, offering superior protection against water penetration.
If a commercial protector is unavailable, a reliable do-it-yourself method involves using heavy-duty plastic bags, such as large trash bags, to cover the cast completely. Secure the bag opening tightly above the cast edge, preferably over the stockinette liner and not directly on the skin. Multiple layers of plastic should be secured with waterproof tape, like duct tape, or a wide rubber band to form a watertight seal.
Taking a shallow sponge bath is generally safer than showering, as it allows for better control over water placement and keeps the casted limb completely out of the water zone. If showering, position the casted limb completely outside the shower enclosure, resting it on a stool or the edge of the tub, to avoid accidental splashes or direct spray. Never submerge the cast in water, even when covered, as the seal may fail under water pressure.
Waterproofing also extends to environmental protection during daily life, not just hygiene routines. The cast should be protected from rain, snow, or splashes that occur during outdoor activities or household chores like washing dishes. Covering the cast with a plastic bag or a coat sleeve when going outside can prevent small exposures that lead to moisture retention. Consistency in covering the cast is the best defense against compromise.
Emergency Steps If the Cast Gets Wet
If a cast accidentally becomes damp or wet, immediate action is required to prevent serious complications. Assess the extent of the dampness by looking for visible water marks, a change in the plaster texture, or a musty odor. A persistent foul smell strongly indicates that the inner padding is wet or that a serious infection has begun.
For minor dampness, thoroughly dry the cast using a hairdryer set exclusively to the cool or fan-only setting. Directing cool air over the wet area and into the cast openings helps evaporate moisture from the inner padding. Never use the hot setting on a hairdryer, as concentrated heat can cause internal burns to the skin, which is impossible to treat under the cast.
Position the limb to maximize air circulation around the cast to aid drying. Promote airflow by elevating the limb and avoiding covering the cast with clothing or blankets. Never attempt to stick any object, such as a hanger or pencil, inside the cast to scratch an itch or dry the padding, as this can tear the skin and introduce bacteria.
Contact a healthcare provider immediately if the cast feels soggy, if the foul odor persists after drying, or if there is a noticeable increase in pain or tightness in the limb. These signs suggest that the cast’s structural integrity or underlying skin health has been compromised. The doctor can determine if the cast needs replacement to prevent delayed healing or severe infection.