Casting Techniques

Introduction

Immobilization in a cast has been the standard of care for spinal and upper and lower extremity injuries and fractures in children. Techniques were first described in antiquity and used a variety of hardening agents. Until the 1900s, plaster-impregnated bandages were used. Today’s more common casting material is fiberglass in various forms; it shares some of the same properties of plaster of Paris but is an improvement in other respects.

Casting techniques have evolved over the years. Unfortunately, complications still do occur but can be avoided with careful attention to detail.

Some variation of a body jacket can be used to treat spinal fractures in children, of which the most common is a flexion injury treated with a hyperextension cast. Spica hip casting can be used to treat pelvic or femoral fractures. Long arm and short arm casts are routinely used to treat upper extremity fractures from the elbow to the wrist, and long leg and short leg casts are used for fractures of the lower extremities.

General Cast Principles

Adequate cast padding is three to five layers thick.
Extra layers should be applied on bony prominences.
The cast should be molded to fit the anatomy.
Warm water should be used during application.
A stretch–relaxation technique should be used for fiberglass casting materials.
Three-point molding is necessary for long bone fractures.
The joint should be immobilized in a position to help hold the reduction.

Body Jackets

The use of fiberglass body jackets has dwindled with the increasing use of patient-specific molded braces (thoracic–lumbar–sacral orthoses [TLSOs]) in the treatment of spinal fractures in children. Stable burst fractures, bony Chance fractures, and other stable injuries of the spine in children can typically be treated with body casts and hyperextension molds. These are best applied on a Risser table, which allows total access to the torso for casting. As with all casting techniques, attention to padding over the bony prominences is important for prevention of pressure ulcers. The typical fiberglass jacket has cutouts for the abdomen to allow abdominal distention after eating, as well as molding over the iliac crests to prevent the cast from moving up and down on the patient. Curved cutouts to allow the thighs to flex on the abdomen to at least 90° are also created and well padded. All edges of the body jacket are padded with moleskin, moleskin-like material, or folded stockinette that covers the skin ( Fig. 3-1 ).

Spica Casting

Hip spica casting continues to be a mainstay of treatment for fractures of the femur from the hip joint to the knee joint. It is commonly used for fractures that are amenable to closed treatment, but an occasional indication is for fractures that have been treated operatively but require additional immobilization. Spica cast treatment has been used in the operating room and the emergency department successfully.

With the child adequately sedated or fully anesthetized, an underliner of either polypropylene (e.g., Gore-Tex, W.L. Gore Co., Newark, Delaware) or cotton tubular stockinette is applied; two different diameters of stockinette are used. The larger diameter stockinette is pulled up onto the torso above the nipple line and extended down to midthigh. Appropriate trimming of the stockinette allows the hips to flex as desired. Stockinette of a smaller size is then placed on the extremity to be immobilized. A single leg spica ( ) or double leg spica cast requires one or both legs to be incorporated in the cast. These can extend down past the knee and even out to the toes as deemed necessary for the fracture. Once the stockinette has been applied, the patient is placed on a pediatric spica table, which allows the chest and upper torso to be supported separately from the lower body. The buttocks and pelvis are positioned on a thin, midline extender that attaches to a perineal post, against which gentle traction can be applied by the assistant holding the legs. Placing the table in reverse Trendelenberg position or having a second assistant apply caudally directed, longitudinal pressure on the shoulders helps to keep the child positioned appropriately.

During application of the padding, one or two folds of operative towels are placed underneath the cast padding on the abdomen to allow room for expansion of the abdomen after eating. Synthetic padding material is applied while the limbs are held in the desired position to maintain reduction of the fracture. Moving the extremity after the padding is placed should be avoided so that “binding” by the circumferential padding is prevented. Three to four layers of padding are desired. Bony prominences should be protected with extra strips of padding, where needed.

Depending on the fracture type, hip flexion can be incorporated as desired. In general, the more proximal a fracture of the femur, the more hip flexion needed to affect reduction. Once the patient is on the fracture table, fiberglass is applied. The spica cast itself may be applied in one of two ways: proximal-to-distal or distal-to-proximal. Both require coordination between the holder and the individual placing the cast. In the proximal-to-distal technique, the cast is wrapped by incorporation of the torso first and then extension down on to one or both legs. In the distal-to-proximal technique, a long leg cast is applied first, supportive traction is applied to the long leg cast, and then the cast is extended proximally onto the torso. As a note of caution, one should avoid using a short leg cast to apply traction before wrapping the upper portion of the spica because this technique has been associated with compartment syndrome.

Three to four layers of overlapping fiberglass are typically appropriate, depending on the size of the child. Heat generated by the cast can be reduced with the use of lukewarm water and dissipated further by massaging the water into the pores of the casting material as it hardens. Carefully molding over the iliac crest, the greater trochanters, and the femoral condyles customizes the fit and allows the best chance for maintenance of fracture reduction. Once the fiberglass has hardened, the cast can be trimmed in the adductor region of the hips and along the buttocks to the top of the gluteal cleft to allow access to the perineum for diapering, toileting, and hygiene. If stiffness of the cast between the leg and torso is a concern, a fiberglass bar can be manufactured from a broomstick or a twisted roll of 3-inch fiberglass and then positioned and overwrapped to span the legs either obliquely from the thigh to the leg or transversely at the level of the distal femur ( Fig. 3-2 ).

Upper Extremity Splinting and Casting

Fractures of the upper extremities are often treated by closed reduction and initial splinting, casting, or both. The initial swelling that occurs with early fracture care will dictate which type of immobilization is used. A sugar-tong splint is a safe and effective way to temporarily immobilize fractures of the forearm. Ten thicknesses of plaster of Paris or five thicknesses of 3-inch fiberglass are typically adequate for immobilization of most children’s forearm fractures ( Fig. 3-3 ).

Definitive casting is performed in the acute setting or once swelling has resolved. A long arm cast ( ) is applied with the elbow incorporated for immobilization of forearm fractures. Tubular stockinette is placed at the upper end of the long arm cast and at the wrist and first web space or continuously from top to bottom. If a single continuous piece of stockinette is used, the stockinette should be cut across the antecubital fossa so that the stockinette can layer rather than wrinkle. Rolls of cast padding are then used in three to four layers circumferentially. Fiberglass long arm casting material is then applied with three to four thicknesses of fiberglass. Careful molding is performed at the forearm, flat dorsal to volar, to match the shape of the forearm and interosseous membrane. The ratio of dorsal:volar to radial:ulnar distance is the cast index. This should be less than 0.7 in the forearm. The upper arm is molded flat over the triceps and gently shaped triangularly toward the biceps. A recommended method for obtaining this shape is as follows: with the cast hardening and the elbow flexed appropriately, the patient’s arm should be slid onto the bed to allow the upper arm to lay flat on the table, forearm to the ceiling, so that the mold will be flat over the triceps. If swelling is anticipated, the cast padding should be split from the wrist to the upper arm. Noncircumferential layers of padding are placed over the split. The cast is then split and spread over the same area where the cast padding has been split, which then prevents circumferential constriction of either the cast padding or the fiberglass. All sharp edges of the cast are then either covered in folded down stockinette or petaled with moleskin with an adhesive backing ( Fig. 3-4 ).