Casting is useful for immobilization, control of position, correction of deformity, and sometimes to ensure compliance with treatment. Cast treatment is relatively safe, inexpensive, and well tolerated by children. Casts may be made of plaster or fiberglass. Plaster casts are least expensive and readily molded. Fiberglass casts are expensive, lightweight, water-resistant, radiographically transparent, and less messy, and provide many color and decorating options. Sometimes the materials are combined in treating deformities such as clubfeet.
Categories of Casts
Casts are remarkably versatile and take many forms. They may be circumferential or applied as splints.
Cast Problems for Children
When applying casts for children, keep in mind the unique problems that may be encountered.
Compliance Children are less compliant than adults. They may not hold still for cast application, may allow the cast to become wet, or damage the cast in play.
Communication Infants or young children may not be able to communicate the pain that precedes the development of pressure sores over bony prominences.
Sensation The child with myelodysplasia or cerebral palsy has poor sensation and is at risk for pressure sores.
Positioning First, make certain the child is comfortable and the limb is held in the position desired after the cast is completed. For cylinder casts or body jackets, the child should be standing. For long-leg casts, it is helpful to apply the short-leg section first; after it has hardened, extend it to the thigh. Include the toes in children’s casts to provide protection. Apply the cast only when the patient is comfortable and the limb immobile. Make certain the assistant holding the limb maintains the proper position until the cast has hardened.
Padding Apply at least two layers of padding. The first is the tubular stockinette that allows a neat trim for the cast edges. The material is usually cotton or dacron. The second layer is the actual padding. Apply extra padding over bony prominences if the child is likely to move during cast application.
In applying the cast, start at one end and proceed in an orderly fashion to the other end of the cast. Apply with a 50% overlap by rolling rather than pulling on the material. The techniques for application of plaster versus fiberglass are different. Tucks are taken in plaster casts to make a neat application.
Fiberglass application Fiberglass rolls must be guided to maintain control of direction. When applying fiberglass, free a segment of material from the roll, then apply it smoothly and without tension. Whereas, plaster has a definite time of crystallization and hardens rather abruptly, fiberglass hardens slowly. The ideal thickness of most casts is three layers. Apply extra layers over sites of greater stress, such as the hip in spica casts or the knee and ankle in long-leg casts.
Early Cast Care
Bivalving Bivalving or splitting casts may be by degree. Be aware that padding is often not elastic and may create as much compression as cast material. For complete relief of pressure, it is necessary to divide all layers of the cast on both sides.
Pressure relief If sensation is poor or communication limited, consider relieving pressure over bony prominences. Cut a rectangle of cast or cut an X over the site for relief. Elevate the cast edges and leave the padding intact. To make the child in a spica cast more comfortable, consider flaring the thoracic edges and creating a stomach hole.
Trim cast edges To save operating room time, consider trimming the cast in the recovery room. Provide a generous amount of space around the perineum.
When the child bathes or plays in the rain, have the parent cover the cast with a plastic bag to keep it dry. Even fiberglass casts are uncomfortable when wet. In infants, spica casts pose a special problem. Instruct staff and parents to change the infant’s diapers frequently and to avoid tucking the diaper under the cast. Skin irritation is best managed by exposure to air and light. Avoid criticizing the child for the appearance of the cast. Often a worn cast is evidence of success in incorporating the treatment in the play activity.
Cast removal is often the most risky phase of cast treatment. Cast saws can cut the skin if contact is made under pressure. Cast saw lacerations are most likely over bony prominences such as the malleoli. Plaster casts may be soaked off by the parents prior to the clinic visit. The crying, struggling child is at special risk.
Reassurance Try to reassure the child by placing the moving blade gently against your arm to show that it only vibrates and normally does not cut skin. Compare the saw noise to an airplane. Have the parent comfort the child as well.
Technique Use consecutive in-and-out movements to cut the cast. Try to avoid cutting directly over the bony prominences. Insist that the inexperienced assistant learn to remove casts on adolescents or adults and not infants or children.
Hair grows more rapidly under casts. The adolescent girl is often shocked by the amount of hair on her leg following cast removal. Reassure her that in a month or so the hair growth will return to normal.
Spica Cast Application
Spica casts are the most difficult casts to apply. Some general points may be helpful to keep in mind during application.
The infant or child should be supported in the correct position during the cast application. The hammock, spica boxes, or frames are variously used in hospitals. Some means of stabilizing the arms is helpful. A custom spica support can secure the arms.
For children with neuromuscular problems such as cerebral palsy or myelodysplasia, plan to supplement the usual padding with extra felt over bony prominences—sacrum, trochanters, patella, malleoli, and heels. Once the patient is positioned, apply the liner that will be used to trim the cast. Place the padding and folded towel for the chest. Some extra padding at the trim ends of the cast will be helpful. Trim the cast with the saw, turn back the liner and apply an additional layer of cast material to create a smooth padded edge. Skin irritation is a common problem in infants. Special liners may be useful, but often the problem exists if the cast remains wet. Encourage the parent to avoid tucking in the diaper, to change diapers frequently, and to allow the cast to air dry without a diaper should irritation be present.
Spica Cast Types
Double spica casts are often necessary following procedures in cerebral palsy. Sometimes the foot can be left out. This reduces the risk of pressure sores over the malleoli and heel. Incorporating a cross-bar in the cast adds strength with little extra weight. Be sure to support the end of the cast on a pillow to unweight the heel. An abdominal window provides comfort. For additional comfort, divide the cast at the upper margin of this window (red arrow) to relieve the sense of compression about the thorax. Be prepared for the toddler to stand in the spica cast. A child in a single hip spica cast may be ambulatory. Flex the knee about 20° to keep the cast from sliding down, and add extra padding about the knee and lower edge of the cast for comfort.