Plaster of Paris has clearly been the standard material for cast construction over the last 150 years. Exponential improvement in the texture, “rollability,” and “moldability” of synthetic materials has made them the cast material of choice for most modern orthopedic surgeons. Patients like them because they are light-weight and durable. We now use synthetics for all pediatric orthopedic casts, except for serial corrective foot casts used to treat clubfoot (Ponseti casts). However, some orthopedists still prefer the moldability of traditional plaster of Paris for reducing and maintaining acute fractures.

Although synthetic cast materials are more expensive than plaster of Paris, in assessing overall expense one must consider the costs in time, labor, materials, and repetitive visits to cast rooms by children who have inadvertently soaked or damaged a plaster cast.

Efficient rolling of the plaster or synthetic material requires experience. Appropriate rolling technique, including the placement of tucks to allow smooth wrapping over a conical structure, is a slowly learned art. This is most important for plaster casts in which the material will not stretch. Orthopedic residents need instruction in this art, followed by supervised practice. Often their opportunities for learning are blunted by the current trend toward having orthopedic technicians apply most casts in many training hospitals. The sad tradition of lumpy, formless, inefficient casts applied at “Elsewhere General” continues, applied by both inadequately trained surgeons and technicians.

Great care must be taken to avoid making casts too tight. This is a particular problem with synthetic-material casts: They are often wrapped in the same manner that one applies an elastic (Ace) bandage, with stretching to accommodate limb shape change rather than placing tucks (which makes the cast less tight). This is possible because the underlying “cloth” is stretchable (in contrast to the “stiff” muslin in plaster of Paris). The result is a cast that is often too tight, particularly when applied in the operating room following surgery. In circumstances where any swelling whatsoever is anticipated, synthetic cast materials should be applied with tucks, just as would be done with ordinary plaster. This makes a less restrictive cast.

Casts in the operating room should be applied after the tourniquet has been deflated to normalize limb volume (by allowing the blood to return to the limb). The cast is then applied loosely, using the tuck technique. Then in most cases the cast should be immediately split to allow further swelling, with the cast re-tightened 3-7 days later.

Proper cast molding assures good cast fit, thereby decreasing the chance for cast sores (Fig. 5-5). A cast should fit the limb contours and be thought of in the sculpting sense; that is, if the cast were removed and filled with plaster or wax, the result would be a “casting” identical to the patient’s limb. Careful molding around bony prominences is required to achieve excellent fit. The calcaneus is at great risk in the lower extremities; the molding must be focused on the soft tissues above the tip of the calcaneus, leaving a recess for the heel prominence. If you fail to provide this recess, a skin ulceration over the posterior calcaneus is a near certainty in a vigorous child.

The concept of a well-molded cast contrasts with the terminology of applying a “plaster dressing” after surgery. Many surgeons prefer a bulky “Robert Jones” dressing after surgery, followed by application of a well-molded cast once the swelling has subsided. We rarely do this in children because we can achieve the same effect applying the cast in the operating room and splitting and spreading the cast immediately postoperatively, with later tightening. This avoids post-operative cast changes, which children detest.

Cast edge trimming is time-consuming, but it can be avoided by careful planning when the cast material is rolled. For instance, at the distal end of a leg cast, the plaster should be rolled at a 30 degrees angle, keeping the lateral side short so that subsequent trimming in the area of the fifth toe and metatarsal head are not required. We perhaps exaggerate by stating that no cast should ever have a final “transverse end.” Whether in the foot, the popliteal fossa, the groin, or the proximal humeral area, casts predictably immobilize better, require less trimming, and fit better if they end obliquely. Learning to wrap casts with oblique ends greatly decreases the labor required to trim and finalize the cast. By avoiding trimming, few sharp edges remain (a particular problem with synthetic cast material).

Traditional training suggested that any cast requiring splitting be split completely to the skin, including the cast padding. We have no argument with the “always split to the skin” philosophy for hospitals with little supervision of patients casted following fracture reduction or operations. An edict issued by the “commanding officer” to split all casts to the skin is likely the best insurance against cast complications, compartment syndromes, etc., in these circumstances. Although some
orthopedists prefer a bivalve (double) split in all casts, with the use of spacers to maintain the separation, we have been able to use single splits in most cases—including synthetic casts (Fig. 5-6).

Although some insist on “always split to the skin” or “always bivalve,” we advise a more refined approach for an orthopedic office, or in a high-quality teaching hospital that provides close patient monitoring. This can be safe, economical, and, most importantly, less distressing to children.

Synthetic-material casts require special methods because even though the cast is split longitudinally (univalved), the resilience of the material will not allow the cast to stay separated. Special commercially available spacers are needed.

Graded splitting of casts following fracture reduction or orthopedic operations requires good orthopedic judgment. Limited splitting can provide great economic advantage to the hospital and surgeon without placing the patient at increased risk. Our policy of graded splitting according to risk is as follows:

Level 1. Only modest swelling anticipated (e.g., following simple limb surgery or reduction of simple distal radius fracture). Level 1 splitting includes a single longitudinal split in the cast, combined with spreading and placing a spacer but without cutting the underlying cast padding. In our children’s hospital environment, 95% of cast splits are level 1. This percentage must be interpreted within the context that we split nearly all postoperative casts and most fracture reduction casts.

Note that synthetic cast splits will not remain open unless spacers are placed. Several manufacturers produce small plastic spacers of varying sizes that are inserted to keep the cast separated. These are removed in 4-7 days after swelling has subsided, with the cast then tightened with tape (upper limb), or another roll of cast material (lower limb).

Level 2. For children with significant swelling anticipated (e.g., fracture with potential for vascular problems; postoperative triple arthrodesis; other similar cases). The single longitudinal split includes both the cast material and the underlying cast padding down to the skin, allowing wide spreading of the cast. Once the cast padding has been split, window edema can develop; therefore, thin strips of cast padding should be packed longitudinally into the split and should be over-wrapped with an elastic bandage. A cast with a level 2 split can still be repaired (pulled together) once swelling has subsided, although care must be taken to avoid “bunching” of the cast padding (we rarely perform a level 2 split—most are level 1, a few level 3).

Level 3. Used for cases with marked swelling anticipated (e.g., tibial fracture in which compartment syndrome is suspected). This includes a medial and lateral complete split of both the cast material and the underlying cast padding down to the skin. The anterior panel of the cast can then be removed for complete inspection of the limb and palpation of the compartments.

Cast removal remains an often traumatic event for a child. Potential complications can be minimized with continued education. Shore et al. identified three primary risk factors for cast saw injuries when removing a cast: provider inexperience, patient sedation, and poor cast blade condition. Although somewhat obvious, quality, dedicated training in regard to the application and removal of casts as well as rigorous maintenance of cast removal equipment is the first line of defense in preventing cast saw cuts and burns.

A variety of methods/techniques can make cast removal easier and safer. Traditional cast shears can be used for small plaster casts (Fig. 5-7). Current cast-removal saws are loud, aggressive, somewhat terrifying to children. No amount of conversation or playful application of the vibrating cast blade to one’s own hand to demonstrate that it “won’t cut” will placate a properly suspicious child.

Orthopedic technicians and orthopedists who deal with children can apply many special techniques to minimize cast-removal trauma. Empathy is the first step. All orthopedic residents and fellows should have a synthetic-material cast applied on their own limb and then removed by a fellow resident (see how they jump!). This greatly increases sensitivity for the child’s plight. We do a cast application-removal session with each new group of residents and fellows when they rotate through our hospital.

The correct mechanics of cast-saw use must be mastered. Techniques include placing the thumb and/or fingers on the cast as a stabilizing guide, with careful reciprocal “up and down” movement (Fig. 5-8) rather than long dragging movements of the blade along the cast increases the risk for skin injury (cut or burn). Also avoid using the cast saw over bony prominences (medial malleolus, etc.). Also pull the cast away from the skin as you begin the cut.