A medical cast is a rigid shell used to immobilize a fractured or injured limb, providing the necessary support for the bone to heal in the correct alignment. The process is performed by a healthcare professional, but the hands-on application itself is generally quicker than many people expect. While time is spent in the clinic for preparation and observation, the direct time spent applying the cast is relatively brief and methodical.
The Average Time for Cast Application
The active phase of applying a cast typically lasts between 10 and 30 minutes. This range represents the hands-on time the medical professional spends preparing the limb and wrapping the casting material. For a simple wrist fracture requiring a short arm cast, application may be closer to 10 minutes. Conversely, a larger, more complex long leg cast will require more time, sometimes extending to 30 minutes or slightly longer. This duration focuses only on the wrapping and molding, distinct from the time spent waiting for the cast to fully harden. Fiberglass casts, the more common type today, allow for a faster application due to their material properties.
Step-by-Step: The Casting Process
The application begins with preparing the skin and the limb to ensure comfort and prevent complications. The medical professional first applies a thin, soft, and stretchy fabric sleeve called a stockinette directly over the injured area, extending beyond the planned edges of the cast. This layer provides a breathable barrier against the hard casting material. Following the stockinette, a layer of cotton or synthetic padding is carefully rolled over the limb, and extra material is added over bony areas for additional protection.
Once the inner layers are in place, the casting material, either fiberglass or plaster, is prepared by immersing it in water. Fiberglass comes pre-coated with a resin that is activated by the water. The professional then quickly and evenly wraps the moistened material around the limb, overlapping each turn by about half the roll’s width. During this phase, the limb must be held in the specific position required for healing, such as a wrist being placed in slight extension.
The molding phase occurs as the material is wrapped, with the professional shaping the cast to the contours of the limb while it is still pliable. Proper molding is necessary to ensure the cast provides an exact, snug fit. The stockinette is then folded back over the raw edges of the cast to create a smooth, comfortable finish. After wrapping, the professional maintains the correct limb position until the material hardens sufficiently to hold its shape, typically about 10 to 15 minutes.
Variables That Affect Application Duration
The time required for cast application depends on several factors related to the injury and the materials used. The location of the injury plays a large role, as a cast covering a larger area, such as a long leg cast, requires more material and wrapping time than a short arm cast. A non-displaced fracture, where the bone fragments are correctly aligned, allows for a faster application than a displaced fracture. If the fracture is displaced, the professional must first perform a procedure called reduction, or realignment, before the cast can be applied, which adds significant time to the overall process. The choice of casting material also influences the duration, though modern fiberglass is often preferred for its speed. While plaster is easier to mold, it requires a longer working time and more careful handling to prevent issues like thermal injury from the exothermic setting reaction. The experience level of the casting technician can also be a factor, as a more experienced professional can complete the wrapping and molding process more efficiently.
Understanding Setting and Curing Time
The time it takes to apply the cast is separate from the time it takes for the cast to become fully hard. This post-application period is divided into two phases: setting and curing. Setting time is the initial period when the cast hardens enough to retain its shape and is no longer pliable. For a fiberglass cast, this typically occurs within 10 to 15 minutes after application. Curing time is the extended period required for the cast to reach its maximum strength and durability. While a fiberglass cast may be strong enough to bear weight about 30 minutes after application, it continues to cure for several hours. Plaster casts set initially within about 15 minutes, but they require a much longer curing time, often taking 24 to 72 hours to dry completely and achieve full strength. During this initial setting and curing period, it is important to handle the cast with the palms of the hands and avoid placing pressure on it that could cause dents or deformities.