Materials

Fiberglass is lighter, more rigid per unit of weight, and relatively water resistant compared to traditional plaster of Paris (POP, gypsum plaster, calcium sulfate hemihydrate). It is rarely available in austere environments, whereas POP is universally available, in rolls of different sizes. It can be of uneven quality, depending on the amount of plaster/roll, age of the roll, and manufacturer. In hot, humid environments, plaster’s half-life may be limited depending on how and where it is stored. It is bulkier, takes longer to set and to dry (up to 48 h), and softens if wet. If fiberglass is available, but only in limited quantities, it can be used as a strengthening outer layer over POP, lessening the cast’s weight and making it more durable.

Casting Technique

Stockinette should be used under the cast when available. It protects the skin and hair and helps prevent saw blade cuts or burns on cast removal. Leave excess stockinette at both ends of the cast. Avoid wrinkles or creases at joints by cutting the stockinette tube transversely and overlapping the cut edges.

Specialty undercast padding of cotton or synthetic may be available, but occasionally there are only large rolls of cotton batting. These are more difficult to use, as the layers must be separated before use and the cotton tears more easily and more unevenly. Cast padding should be rolled firmly but without tension, usually from distal to proximal, overlapping the previous layer by half its width, to achieve a uniform 6–8 mm layer—better slightly too thick than too thin. Extra cotton is used over prominences such as the fibular head or the malleoli; over areas particularly sensitive to pressure sores, such as the posterior heel; and under weight-bearing areas. The padding, like the cast itself, should be applied with all the joints in the desired position, to avoid creases and bunching that can cause pressure areas. Chinese finger traps or clove hitch loops of bandage to help immobilize and hold an extremity can prove useful to the unassisted surgeon (see Fig. 20.​2).

Completely submerge a roll of plaster in a container of skin-temperature water. When bubbling has ceased, gently squeeze it to the point where it is barely, but still, dripping. Pressure at each end of the roll will prevent “bananaing,” and if the leading edge of the roll is first folded back on itself, it is easier to find when wet, saving time. Cast heating problems can occur if the water is too warm and with certain types of quick-drying plaster, excessively thick plaster layers, or when a damp cast is placed directly on the plastic covers of pillows and mattresses and covered with a thick blanket.

The plaster is rolled in a manner similar to the cast padding, holding the roll against the patient with gentle tension but not pulling the roll away from the limb or bunching the padding. Unroll the plaster using the thenar side of the palm, smoothing each turn of the roll to remove air bubbles that lead to delamination. Take small tucks when moving between different circumferences and crossing over flexed joints. The desired thickness of the cast will vary according to patient age, anatomical site of the injury, and proposed usage, but it should be uniform. Reinforcement slabs can be applied over areas of high stress such as the front and back of the knee, the sole of the foot and ankle, and the elbow.

After the penultimate roll has been smoothed, mold the plaster to conform to the anatomical contours, e.g., a forearm or leg cast should be oval, not round. Three-point pressure is gently applied with the moving palms, never the finger tips, to maintain fracture reduction until the plaster is set. Trimming excess plaster can usually be done with scissors, cast saw, or a scalpel blade. Take care that the plaster does not dig into the first web of the thumb and the distal palmar flexion crease is visible, allowing finger MP flexion. The dorsum of all toes, including the fifth, should be free of plaster to the MTP joints to prevent sores caused by rubbing on the plaster with toe dorsiflexion. Turn the stockinette or remaining cotton over the plaster edges with a last layer of POP to give the cast a finished appearance.

When no assistant is available, it is easier to apply long-leg casts by completing the below-knee part first and proceeding with the above-knee section after the lower leg and ankle molding have been completed and the plaster has semi-set enough to maintain its position. Make sure the junction between the two cast segments is well padded and smooth with no sharp or bent edges to dig into the skin. Unless contraindicated, plaster the knee in 20–30° of flexion. With enough knee flexion it is difficult—even for the most noncompliant patient—to bear weight. The cast can be bivalved after it has reached a leathery state and the two halves secured with an ace wrap before discharge. In spite of all precautions, many patients will come back with broken, wet, or a foul-smelling cast or painful pressure points under the cast. Do not disregard patients’ complaints. It is better, albeit time-consuming, to redo a cast than to have potential limb-threatening complications of a poorly applied POP (Fig. 13.6).

Off-the-shelf cast boots are not readily available. Rubber sandals or flip-flops can be fashioned into a POP-protecting shoe (Fig. 13.7). Hospital workshops can make rubber or wood and rubber platforms that can be incorporated onto the POP as a “walking rubber” to save the cast’s planter integrity and give a nonslip surface for weight-bearing (Fig. 13.8).

Wedging Casts (Gypsotomy)

Depending on the age of the injury, some malalignment or loss of reduction can be corrected with POP wedging or gypsotomy, most often without anesthesia. Because fewer fractures in HICs are treated nonoperatively, cast wedging is becoming a lost art but is a useful technique for salvaging angulated forearm and tibial fractures in all ages and femur fractures in the pediatric population managed in spicas [3].

Opening wedges are made on the concave side of the deformity. They present fewer possibilities of pinching the skin than closing wedge gypsotomies on the convex side. Whether wedging a plaster of Paris or fiberglass cast, the principles are the same: identify the apex of the deformity; mark the proposed cutting line on the cast, making sure it covers more than half the circumference.

Identifying the site where the cast needs to be cut for wedging is made easier by taking an x-ray with a metallic marker (paperclip) taped on the cast at the presumed site before the gypsotomy (Fig. 13.9). If on first applying the cast you think it might need future wedging, tape the metal marker on for the first post-reduction x-ray, and mark this with a sharpie for later wedging when the plaster is set or after the fracture has become sticky.

Prepare precut wood, cork, or plaster spacers. Start by making ±10 cm perpendicular cuts at both extremities of the proposed wedge to prevent crack propagation. Then proceed with the gypsotomy. With one hand above as counter pressure, firmly and gradually apply distal pressure to open the plaster cut. Once in the proposed corrected position—usually calculated at 1 mm opening for each degree of desired correction, though one seems to always need a wider opening than anticipated—insert the spacer without allowing it to touch, or put pressure on the underlying skin, or curl the cut cast edges, and take the appropriate x-rays. More manipulation may be indicated, using a larger spacer, or the cast can be closed by applying a few rolls of material over the wedged area. Sequential wedging over several days to a week for progressive correction is possible, by using progressively bigger spacers and closing the cast when the desired correction is achieved.

Special Casts

Hip Spica

Hip spicas are uncomfortable and unwieldy for adults but are useful to rest the extremity after removal of a femoral ex-fix when a patient cannot be admitted for traction or in salvage situations. In most cases the patient will be able to stand during application while supported by two drip stands or crutches with the casted leg resting on a stool or box while applying a single-leg cylinder cast with a waist band. Pointers: cast the hip slightly abducted and flexed about 30–45°, to allow ground clearance. Knee flexion will depend on the weight-bearing status of the injury. Reinforce the connection between the pelvis and leg with extra plaster or fiberglass, and pad well sacral and other bony prominences. Hip spicas do not do well on obese patients.

Hip spicas for femur fractures are standard treatment and better tolerated in the pediatric population—up to about 25 kg body weight—whether applied as the initial post-fracture treatment or after a period of traction to allow early stabilizing callus (Fig. 13.10). Most hospitals have management protocols based on bed availability, personality of the fracture, proximity of the patient to the hospital, ease of transportation, and the philosophy of the local doctors. Variations include as follows: the type and length of traction, timing to spica application, type of spica—1.5 or single leg—where the spica is applied (i.e., OPD, OR, cast room), and type of anesthesia used.

When available, fiberglass is preferred as it is lighter, but the edges are sharp and should be covered with felt or extra cotton after trimming to allow rollback to produce rounded edges before the last rolls are applied. Spicas look neater and the edges wear better if stockinette is used. Prominences, especially around the sacrum, should be well padded.

A frame is usually available on which the child’s buttock can rest and allow easy access for cast application (Fig. 13.11). If not, a makeshift one can be assembled with boxes, pillows, an upturned medicine cup, or the OR table’s arm board. Place a small bag of IV fluid, folded towel, or sheet between the stockinette and the skin of the abdomen for chest expansion. One or two people, depending on the size of the child, need to hold the legs and maintain proper joint positions. This is particularly important after hip surgery, and a designated person (preferably the surgeon) is responsible to keep the limb in the desired position at all times throughout the casting.