Knowledge of internal fixation of fractures is highly advanced, with diverse fracture fixation systems available to all veterinary surgeons; however, a definitive therapeutic role remains for coaptation devices. We must not neglect the “art” of constructing a proper splint. Rigid materials such as fiberglass, plaster, and splint rod provide the mechanical strength and stiffness required in external coaptation, but these may also endanger the splinted limb if used improperly. In choosing between the various types of bandages, splints, and casts, it is important to consider the somewhat conflicting basic principles of orthopedic bandaging versus external coaptation. The challenge is to balance a patient’s needs for soft bandaging with the strict requirements for bone splinting.
External casts, splints, and bandages are often called “coaptation fixation devices,” the word “coapt” meaning to approximate. This is accomplished by
simply immobilizing muscles, as with a bandage, or by transmitting compression forces to the bony structures by means of the interposed soft tissues, as with casts and splints. Such pressure must be uniformly distributed throughout the cast or splint to avoid circulatory stasis and swelling.
Casts are generally considered to be molded tubular structures that, if removed, would form a mold from which a casting of the limb could be made. A splint is something less than a full cast and typically is molded only to one aspect of the limb. A wire frame structure such as the Schroeder-Thomas splint is a special case, using soft bandage materials to suspend the limb within the wire frame.
As a general rule, molded casts and splints are more efficient stabilizers of the bones and joints than premade ones or the Schroeder-Thomas splint, although good use can be made of both latter methods. The advantage of molded devices is that they custom-fit the animal perfectly and therefore cause fewer soft tissue problems and are better tolerated by the patient. For many years, plaster of Paris was the only moldable material available, but many such materials have become available. Of these, two types have proved especially useful, the thermomoldable and the fiberglass/resin materials. X-Lite (AOA Kirschner Medical Corporation, Marlow, Okla) and Vet-Lite (Jorgensen Laboratories, Loveland, Colo) are thermo- moldable plastic materials, impregnated onto an open-mesh fabric. When heated to 160⬚ to 170⬚ F, the material becomes very soft and self-adherent and then hardens within a few minutes as it cools to room temperature. It is available as precut splints or rolls in 3-, 4-, and 6-inch widths. These materials are most useful in small animal patients for making splints. Veterinary Thermoplastic (VTP) (IMEX Veterinary Inc., Longview, Texas) is similar in application but is a solid, homogenous material rather than an open mesh; it is also available in rolls of varying widths. Because these mate- rials are self-adherent, they can be made as stiff as necessary by adding layers to effect.
Fiberglass materials have a resin-binding material impregnated into the roll of knitted fiberglass tape. They are popular because of ease of application and rela- tively few complications. The resin is activated by a 10- to 15-second immersion in water of room temperature, after which the material cures and hardens within a few minutes at room temperature. Fiberglass has proved very useful for full-cylinder casts, although it can also be used for splints. Cast-cutting saws are essential for removing cylinder casts. All these products are lightweight, strong, and waterproof. Because wider width material generally makes stronger casts, use the widest roll consistent with the animal’s size.18 To obtain maximal usefulness, use them with
polypropylene or other synthetic stockinet and cast padding, both of which shed water. Because these materials all “breathe” and do not retain water, there are few soft tissue problems such as maceration of skin. Pressure sores are still possible when casts are incorrectly applied, but even this problem occurs less frequently than when cotton padding materials are used. Synthetic orthopedic felt used over bony prominences will do much to reduce pressure sores. In general, the middle and distal phalanges of the middle toes should be left exposed to monitor swelling. Often the cast, once hardened, is cut longitudinally in two places (bivalved) to create two half-shells and to facilitate future cast changes. The two halves are secured to each other with non-elastic adhesive tape.
Owners should be instructed to observe the protruding toes twice daily, looking for signs that the toenails are spreading apart. Such a sign indicates swelling and requires that the cast be removed immediately to prevent pressure necrosis. Reapplication of the cast with less pressure can follow immediately, or the limb can be placed in a Robert-Jones bandage for a few days to allow swelling to be resorbed. The animal should be kept indoors to minimize damage to the external fixation device.
2—Fractures: Classification, Diagnosis, and Treatment 51 If taken outside for elimination in wet or damp conditions, a plastic bag
or similar impervious material should be temporarily placed over the foot to keep the cast/splint or bandage material clean and dry. An electric hair dryer can be applied to hasten drying in case the cast becomes wet. The owner should be instructed to have the device checked regularly at 7- to 10-day intervals or at any sign of foul odor, drainage, loosening, chafing, instability, or obsessive licking or chewing on the appliance. Such signs are indications for removal of the device and evaluation of the soft tissues, with appropriate treatment. Reapplication of the cast/splint may require some revision to prevent recurrence of the problem. The thermomoldable materials are reheated and reapplied as originally. Do not remove a cast or splint simply because a certain amount of time has elapsed and you are curious to see the soft tissues; if the animal is tolerating the device well and it is still functional, it should be left undisturbed until the appropriate time for removal.
Because of the pain created by manipulating broken bones and the muscular relaxation needed for most reductions, general anesthesia is almost always indicated when applying these devices.
Indications for Coaptation
Consider the forces acting on the bone and how well the proposed immobilization will neutralize them: angulation or bending, rotation (shear), shortening or overrid- ing (shear), and distraction. The following indications generally fall within the range of casts and splints:
1. Closed fracture below elbow or stifle. In Figure 2-20, a′, b′, c′, and d′ indicate the length of cast/splint needed for fractures in zones a, b, c, and d.
2. Fractures amenable to closed reduction, as previously discussed.
3. Fractures in which the bone will be stable after reduction relative to shortening or distraction; classified above as type A or B fractures (see Table 2-1).
4. Fractures in which the bone can be expected to heal quickly enough that the cast/splint will not cause severe joint stiffness and muscle atrophy (fracture disease).
5. Specific indications follow: • Greenstick fractures.
• Long-bone fractures in young animals in whom the periosteal sleeve is mostly intact.
• Impaction fractures. Long-Leg Cylinder Cast
A long-leg cast is one that extends from the toes to the axilla or groin (Figure 2-21). Plaster of Paris or fiberglass/resin tape are the most commonly used materials. A variety of casting tapes made of knitted fiberglass substrate and impregnated with various resins are now available and utilized in much the same manner as plaster of Paris. These products are strong, lightweight, waterproof, and porous but cannot be molded as perfectly as plaster. These casts must be removed with a cast-cutting oscillating saw whether they are made of plaster of Paris or fiberglass.
The cast can be bivalved after it has hardened for ease of inspection and redress- ing. To prevent the padding from sticking to the resin, it is covered with a sheet of thin polyethylene film (as used for food storage) while the cast material is applied. After hardening of the resin, the cast-cutter saw is used to split the cast into halves along either the sagittal or the frontal plane. The plastic film is removed after sepa- rating the two halves, which are then reapplied and held together with nonelastic white tape. Future cast changes are accomplished by cutting the tape, removing the
half shells, repadding the limb, and reapplying the half shells. Care must be taken to apply the same amount and type of padding as was used originally to prevent either undue pressure or looseness when the cast is reapplied.
Indications. Immobilization of the elbow and stifle, the radius and ulna, and the tibia and fibula.
Short-Leg Cylinder Cast
A short-leg cast extends only to the proximal tibia or radius (Figure 2-22). The elbow and stifle joints are free to move normally. The casts must be distal enough (1-2 inches below the humeral epicondyle or tibial tubercle) so that there is no binding during flexion/extension. Limb swelling under a cast may lead to disastrous sequelae.
Indications. Immobilization of the carpus and metacarpus and the tarsus and metatarsus. As a general rule, short-leg casts are used primarily in large, active ani- mals to provide more stabilization than short-leg splints.
Spica Splint—Foreleg
Although this splint can be constructed with wood, rigid plastics, or aluminum, the molded splint is better tolerated and gives better immobilization (Figure 2-23). The spica splint is named for the method of attaching it to the body by a “spica” (figure-of-8) bandage. In the dog the bandage is modified to be only half a figure- of-8. It can be applied to the hip, but bandaging in this region is very difficult, especially in the male dog, and ambulation is awkward.
Indications. Immobilization of the shoulder, humerus, and elbow.
a a′
b b′
c c′
d d′
A B C D
FIGURE 2-20. Optimal splint or cast length for fractures in the dark-shaded areas are shown by the length of the light-shaded areas.
A B C
D E F
FIGURE 2-21. Long-leg cylinder cast extends from the toes to the axilla or groin. Application here is to the forelimb with fiberglass material. A, Adhesive tape stirrups are applied to the lower limb and extend several inches beyond the toes. B, Polypropylene stock- inet is applied to the limb. The material should be long enough to extend distally beyond the toes and well into the axilla proximally. C, Two or three layers of polypropylene cast padding are applied to the limb starting at the toes and proceeding proximally. D, After the fiberglass tape is immersed in water at room temperature for 12 to 15 seconds and gently squeezed of excess water, the roll of fiberglass is spiraled onto the limb; rubber or vinyl (as recommended by the manufacturer) gloves are used to protect the hands. This material should be rolled on smoothly using even pressure, which is facilitated by rolling continuously around the limb in a spiral fashion and not raising the roll away from the skin. Two layers of cast material are produced by overlapping the spirals by half the width of the roll. The distal end of the cast should be at the level of the base of the distal phalanx of the middle toes. E, A longitudinal splint is applied to both the medial and lateral sides. This material is cut from the roll and applied over the spiraled material. Mechanical testing has revealed that these splints add more strength to fiberglass casts when applied cranially and caudally.18 F, A second spiral layer is applied over the splints, resulting in four spiraled layers plus the medial and lateral splints. Very large breeds may require six layers.
I J H G
FIGURE 2-21. Continued G, Hand lotion or lubricating jelly is used to treat the gloves to prevent them from sticking to the fiberglass resin. Some products do not require the use of lotion. H, After use of the lotion or jelly on the gloves, it is possible to smooth the fiberglass and conform it to the limb. The material begins to harden in 4 to 5 minutes under average temperature conditions. I, After hardening of the fiberglass, the ends of the cast are dressed by folding the stockinet over the end of the fiberglass. At the distal end, the tape initially applied to the skin is folded over the end of the cast. This tape and the stockinet are secured with circular wraps of tape. The proximal end of the cast is similarly taped. J, The completed cast. Note that both the elbow and the carpus have been maintained in moderate flexion.
2—Fractures: Classification, Diagnosis, and Treatment 55
FIGURE 2-22. Short-leg cylinder cast is made in the same manner as the long-leg cast but does not cover the elbow or the stifle. In this case the cast has been applied to the forelimb and ends just distal to the elbow joint, leaving the two middle toenails exposed for daily monitoring. To ease redressing, after hardening, the cast may be cut mediolaterally or craniocaudally (bivalving) and retaped.
A B
FIGURE 2-23. Spica splint for the foreleg. A, Precut X-Lite splints are laid over the limb, and the area of overlap is noted. Veterinary Thermoplastic can be applied in one piece, since it comes in long rolls. Three to six thicknesses are used, depending on the size of the animal and the degree of rigidity required. B, The limb has been padded with two or three layers of polypropylene cast padding to the axilla, and sheet cotton is placed over the proximal humerus, shoulder joint, and scapula. This padding should extend dorsally to the midline.
E F
C D
FIGURE 2-23. Continued C, The distal splints have been heated by immersion in water at 170° F and are being placed over the lower limb, then molded by hand. D, Conforming gauze is used to hold the softened splint material against the limb while it hardens. The proximal end of the splint is left exposed for attachment to the upper splints. E, The upper splints have been heated and are placed over the shoulder and onto the more distal splints. The material will adhere to itself and form a continuous splint. These splints are then molded by hand to conform to the limb. F, Conforming gauze has been rolled proximally to the axilla to com- plete molding of the proximal splints. The upper end of these proximal splints can be molded over the shoulder by hand pressure until sufficiently cooled to harden.
2—Fractures: Classification, Diagnosis, and Treatment 57
G H
I J
FIGURE 2-23. Continued G, Conforming gauze is used to attach the splint to the chest wall. This gauze creates a half figure-of-8 around the splinted limb but is carried behind the opposite axilla. H, Bandaging has been completed. I, The bandage is covered with wide elastic tape, applied in a pattern similar to that of the gauze. If short-term immobilization is contemplated, white tape can be substituted. J, Bandaging has been completed.
Long Lateral Splint
This splint is shorter than a spica splint, but otherwise the long lateral splint is constructed and attached similarly from the axilla or groin distally (Figure 2-24).
Indications. Immobilization of the elbow and stifle joints. Schroeder-Thomas Splint
This versatile splint has been widely used for immobilization of fractures (Figure 2-25). Considerable artistry is required to construct a functional, well- tolerated, and effective Schroeder-Thomas splint. Widely used in the past,19 it has
been largely superseded by molded splints and casts. Nevertheless, it remains useful for those versed in its application.
Indications. Immobilization of the elbow, stifle, carpus, and tarsus; the radius and ulna; and the tibia and fibula. The Schroeder-Thomas splint may be the most effective device for immobilization of the stifle joint at a functional angle. Care must be taken to keep the splint as short as possible to allow active weight bearing; this is accomplished by placing all joints at functional (standing) angles.
Short Lateral Splint—Hindleg
Although this type of molded splint (Figure 2-26) can be applied to any surface of the lower hindlimb, the lateral surface has resulted in fewer soft tissue injuries.
Indications. Immobilization of the tarsus and metatarsus. Short Caudal Splint—Foreleg
This splint (Figure 2-27) replaces the preformed rigid plastic and metal “spoon” splints in wide use. Such splints are not suitable for long-term use because of the incidence of soft tissue problems and poor immobilization. The only way a curved limb can be put in a straight premolded splint is with copious padding, and this destroys rigid immobilization. A properly made molded splint can often be left on for 6 weeks with no soft tissue problems.
Indications. Immobilization of the carpus and metacarpus. Phalangeal Splint
This bivalved splint (Figure 2-28) is designed to protect the toes while leaving the antebrachiocarpal or tarsocrural joints free to move normally.
Velpeau Sling
This bandage is generally well tolerated by most animals (Figure 2-29). In addition to its main use for shoulder and scapular injuries, the Velpeau sling can serve as a substitute for hard casts or splints when the objective is simply to prevent weight bearing of the foreleg, although the carpal flexion bandage is much easier to apply.
Carpal Flexion Bandage
The flexion bandage is intended solely to discourage weight bearing while maintaining passive motion of the shoulder and elbow joints. It is useful after lateral shoulder lux- ation, supraspinatus, and biceps brachii surgery. The carpus is less than fully flexed while two or three layers of wide white tape are applied from the distal third of the radius/ulna to the metacarpal region. Narrower tape is used in the middle to keep
2—Fractures: Classification, Diagnosis, and Treatment 59
A B
C D
FIGURE 2-24. Long lateral splint applied to the hindlimb. A, The lower limb is padded with two or three layers of polypropylene cast padding to the level of the stifle, and sheet cot- ton is applied from the stifle to the level of the hip joint. The cast padding overlaps the lower end of the sheet cotton to help fix it in place. B, Overlapping precut X-Lite splints or full- length Veterinary Thermoplastic splints are applied proximally and distally, with three to six thicknesses, depending on the size of the animal and the rigidity required. The splints will stick together where they overlap, and the splints are initially molded by hand to conform to the limb. C, The softened splints are covered with conforming gauze bandage to hold the splints conformed to the limb while they harden. D, After hardening, the splint material is covered with wide elastic tape to complete the splint.
the bandage from slipping off the leg. Although usually well tolerated when applied as illustrated in Figure 2-30, some animals will develop skin irritation on the cranial surface of the antebrachium and must have cast padding applied between the skin and tape.
Ehmer Sling
Primarily used to partially immobilize and stabilize the hip joint (Figure 2-31), this bandage can also be used to prevent weight bearing of any joint of the hindlimb.
A B C
G F
E D
FIGURE 2-25. Fabrication of modified Thomas splint. A, After the diameter of the thigh is