Thermoplastic materials are elastic, plastic, a combination of plastic and rubberlike, and rubberlike [North Coast Medical 2006]. Thermoplastic materials that are elastic based have some amount of memory. (Memory is addressed in the properties discussion of this section.) Typically, elastic thermoplastic has a coating to prevent the material from adhering to itself. (Most thermoplastics have a nonstick coating, but there are a few that specify they do not.) Elastic materials have a longer working time than other types of materials and tend to shrink during the cooling phase.

Thermoplastics with a high plastic content tend to be drapable and have a low resistance to stretch. Plastic-based materials are often used because they result in a highly conforming splint. Such plastic requires great skill in handling the material (e.g., avoiding fingerprints and stretch) during heating, cutting, moving, positioning, draping, and molding. Thus, for novice splinters positioning the client in a gravity-assisted position is best to prevent overstretching of the material.

Thermoplastic materials described as rubbery or rubberlike tend to be more resistant to stretching and fingerprinting. These materials are less conforming than their drapier plastic counterparts. Therapists should not confuse resistance to stretch during the molding process with the rigidity of the splint upon completion. Materials that are quite drapey become extremely rigid when cooled and set, and the opposite is also true. In addition, the more contours a splint contains the more rigid it will be.

Some LTT materials are engineered to include an antimicrobial protection. Splints can create a moist surface on the skin where mold and mildew can form [Sammons et al. 2006]. When skin cells and perspiration remain in a relatively oxygen-free environment for hours at a time, it is conducive to microbe growth and results in odor. Daily isopropyl alcohol cleansing of the inside surface of the splint will effectively combat this problem. Splinting materials containing the antimicrobial protection offer a defense against microorganisms. The antimicrobial protection does not wash or peel off.

Each type of thermoplastic material has unique properties [Lee 1995] categorized by handling and performance characteristics. Handling characteristics refer to the thermoplastic material properties when heated and softened, and performance characteristics refer to the thermoplastic material properties after the material has cooled and hardened.

Perforations

Theoretically, perforations in material allow for air exchange to the underlying skin. Various perforation patterns are available (e.g., mini-, maxi-, and micro-perforated) [PSR 2006]. Perforated materials are also designed to reduce the weight of splints. Several precautions must be taken if one is working with perforated materials [Wilton 1997]. Perforated material should not be stretched because stretching will enlarge the holes in the plastic and thereby decrease its strength and pressure distribution. When cutting a pattern out of perforated material, therapists should attempt to cut between the perforations to prevent uneven or sharp edges. If this cannot be avoided, the edges of the splint should be smoothed.

Finish, Colors, and Thickness

Finish refers to the texture of the end product. Some thermoplastics have a smooth finish, whereas others have a grainy texture. Generally, coated materials are easier to keep clean because the coating resists soiling [McKee and Morgan 1998].

The color of the thermoplastic material may affect a person’s acceptance and satisfaction with the splint and compliance with the wearing schedule. Darker-colored splints tend to show less soiling and appear cleaner than white splints. Brightly colored splints tend to be popular with children and youth. Colored materials may be used to help a person with unilateral neglect call attention to one side of the body [McKee and Morgan 1998]. In addition, colored splints are easily seen and therefore useful in preventing loss in institutional settings. For example, it is easier to see a blue splint in white bed linen than to see a white splint in white bed linen.

A common thickness for thermoplastic material is inch. However, if the weight of the entire splint is a concern a thinner plastic may be used—reducing the bulkiness of the splint and possibly increasing the person’s comfort and improving compliance with the wearing schedule. Some thermoplastic materials are available in thicknesses of 1/16, 3/32, and 3/16 inch. Thinner thermoplastic materials are commonly used for small splints and for arthritis and pediatric splints, whereas the 3/16-inch thickness is commonly used for lower extremity splints and fracture braces [Melvin 1989, Sammons et al. 2006]. Therapists should keep in mind that plastics thinner than inch will soften and harden more quickly than thicker materials. Therefore, therapists who are novices in splinting may find it easier to splint with -inch-thick materials than with thinner materials [McKee and Morgan 1998].Table 3-1 lists property guidelines for thermoplastic materials. (See also Laboratory Exercise 3-1.)

Laboratory Exercise 3-1 Low-temperature Thermoplastics

Cut small squares of different thermoplastic materials. Soften them in water, and experiment with the plastics so that you can answer the following questions for each type of thermoplastic.

Name of thermoplastic material:______________________________________________

Table 3-1

Thermoplastic Property Guidelines ^*

^*Not all-inclusive.

Courtesy Serena Berger, Smith & Nephew Rolyan, Inc., Germantown, Wisconsin, and North Coast Medical, Inc., San Jose, California.

Process: Making the Splint

Splint Patterns

Making a good pattern for a splint is necessary for success. Giving time and attention to the making of a well-fitting pattern will save the splintmaker’s time and materials involved in making adjustments or an entirely new splint. A pattern should be made for each person who needs a splint. Generic patterns rarely fit persons correctly without adjustments. Having several sizes of generic patterns cut out of aluminum foil for trial fittings may speed up the pattern process. A standard pattern can be reduced on a copy machine for pediatric sizes.

To make a custom pattern, the therapist traces the outline of the person’s hand (or corresponding body part) on a paper towel (or foil), making certain that the hand is flat and in a neutral position. If the person’s hand is unable to flatten on the paper, the contralateral hand may be used to draw the pattern and fit the pattern. If the contralateral hand cannot be used, the therapist may hold the paper in a manner so as to contour to the hand position. The therapist marks on the paper any hand landmarks needed for the pattern before the hand is removed. The therapist then draws the splint pattern over the outline of the hand, cuts out the pattern with scissors, and completes final sizing.

Fitting the Pattern to the Client

As shown in Figure 3-1, moistening the paper and applying it to the person’s hand helps the therapist determine which adjustments are required. Patterns made from aluminum foil work well to contour the pattern to the extremity. If the pattern is too large in areas, the therapist can make adjustments by marking the pattern with a pen and cutting or folding the paper. Sometimes it is necessary to make a new pattern or to retrace a pattern that is too small or that requires major adjustments. The therapist ensures that the pattern fits the person before tracing it onto and cutting it out of the thermoplastic material. It is well worth the time to make an accurate pattern because any ill-fitting pattern directly affects the finished product.

Figure 3-1 To make pattern adjustments, moisten the paper and apply it to the extremity during fitting.

Throughout this book, detailed instructions are provided for making different splint patterns. One should keep in mind that therapists with experience and competency may find it unnecessary to identify all landmarks as indicated by the detailed instructions. Form 3-1 lists suggestions helpful to a beginning splintmaker when drawing and fitting patterns.

FORM 3-1 ^*Hints for Drawing and Fitting a Splint Pattern

Explain the pattern-making process to the person.

Ask or assist the person to remove any jewelry from the area to be splinted.

Wash the area to be splinted if it is dirty.

If splinting over bandages or foam, cover the extremity with stockinette or a moist paper towel to prevent the plastic from sticking to the bandages.

Position the affected extremity on a paper towel in a flat, natural resting position. The wrist should be in a neutral position with a slight ulnar deviation. The fingers should be extended and slightly abducted.

To trace the outline of the person’s extremity, keep the pencil at a 90-degree angle to the paper.

Mark the landmarks needed to draw the pattern before the person removes the extremity from the paper.

For a more accurate pattern, the paper towel can be wet and placed on the area for evaluation of the pattern, or aluminum foil can be used.

Folding the paper towel to mark adjustments in the pattern can help with evaluation of the pattern.

When evaluating the pattern fit of a forearm-based splint on the person, look for the following:

• Half the circumference of body parts for the width of troughs

• Two-thirds the length of the forearm

• The length and width of metacarpal or palmar bars

• The correct use of hand creases for landmarks

• The amount of support to the wrist, fingers, and thenar and hypothenar eminencies

When tracing the pattern onto the thermoplastic material, do not use an ink pen because the ink may smear when the material is placed in the hot water to soften. Rather, use a pencil, grease pencil, or awl to mark the pattern outline on the material.

^*See Appendix B for a perforated copy of this form.

Tracing, Heating, and Cutting

After making and fitting the pattern to the client, the therapist places it on the sheet of thermoplastic material in such a way as to conserve material and then traces the pattern on the thermoplastic material with a pencil. (Conserving materials will ultimately save expenses for the clinic or hospital.) Pencil lines do not show up on all plastics. Using an awl to “scratch” the pattern outline on the plastics works well. Another option is to use grease pencils or china pencils. Caution should be taken when a therapist uses an ink pen, as the ink may smear onto the plastic. However, the ink may be removed with chlorine.

Once the pattern is outlined on a sheet of material, a rectangle slightly larger than the pattern is cut with a utility knife (Figure 3-2). After the cut is made, the material is folded over the edge of a countertop. If unbroken, the material can be turned over to the other side and folded over the countertop’s edge. Any unbroken line can then be cut with a utility knife or scissors.

Figure 3-2 (A) A utility knife is used to cut the sheet of material with the pattern outline on it in such a way that the thermoplastic material fits in the hydrocollator or fry pan. (B) The score from the utility knife is pressed against a countertop.

Heating the Thermoplastic Material

Thermoplastic material is softened in an electric fry pan, commercially available splint pan, or hydrocollator filled with water heated to approximately 135° to 180°F (Figure 3-3). (Some materials can be heated in a microwave oven or in a fry pan without water.) To ensure temperature consistency, the temperature dial should be marked to indicate the correct setting of 160°F by using a hook-and-loop (Velcro) dot or piece of tape. When softening materials vertically in a hydrocollator, the therapist must realize the potential for problems associated with material stretching due to gravity’s effects. If a fry pan is used, the water height in the pan should be a minimum of three-fourths full (approximately 2 inches deep).

Figure 3-3 Soften thermoplastic material in (A) an electric fry pan or (B) a hydrocollator.

Adequate water height allows a therapist to submerge portions of the splint later when making adjustments. If the thermoplastic material is larger than the fry pan, a portion of the material should be heated. When the material is soft, a paper towel is placed on the heated portion and the rest of the material is folded on the paper towel. A nonstick mesh may be placed in the bottom of a fry pan to prevent the plastic from sticking to any materials or particles. However, it can create a mesh imprint on the plastic. When the thermoplastic piece is large (and especially when it is a high-stretch material), it is a great advantage to lift the thermoplastic material out of the splint pan on the mesh. This keeps the plastic flat and minimizes stretch.

Cutting the Thermoplastic Material

After removing the thermoplastic material from the water with a spatula or on the mesh, the therapist cuts the material with either round- or flat-edged scissors (Figure 3-4). The therapist uses sharp scissors and cuts with long blade strokes (as opposed to using only the tips of the scissors). Scissors should be sharpened at least once each year, and possibly more often, depending on use. Dedicating scissors for specific materials will prolong the edge of the blade. For example, one pair of scissors should be used to cut plastic, another for paper, another for adhesive-backed products, and so on. Sharp scissors in a variety of sizes are helpful for difficult contoured cutting and trimming. Splinting solvent or adhesive removers will remove adhesive that builds up on scissor blades.