Material Selection

When fabricating orthoses and prostheses, the material selection is the first consideration of the process. There are multiple types of thermoplastics, metals, carbon fiber composites, and interface materials to choose from. Each type of material will have certain desirable characteristics or properties that will best suit each patient’s needs. Body weight, activity level, amount of rigidity needed, flexibility of material, energy storing properties, amount of cushioning required, and patient strength are all variables to consider when selecting fabrication materials (Table 26-3).

Plastic

Plastics used in orthoses and prostheses are copolymer, thermoplastic polyethylene, polypropylene, and acrylics. Plastics used for custom orthoses such as ankle-foot orthoses (AFOs), knee-ankle-foot orthoses (KAFOs), and upper extremity bracing are chosen for thermal properties and level of rigidity or flexibility and weight of material. When fabricating a lower extremity brace, a thicker, stronger plastic should be chosen over a thin plastic that may be used for an upper extremity splint. The heaviness, strength, and rigidity necessary for supporting one’s body weight would not be necessary for an upper extremity brace.

Metal

Metals most commonly used in orthoses are aluminum and steel alloys, titanium, copper, and bronze. These metals are used when designing and fabricating short leg braces or AFOs and KAFOs, and for pylons in prostheses. They are strong, lightweight, and noncorrosive. Metals are also used in knee orthoses and casings for prosthetic knees and torsion units.

Carbon Fiber Composites

Carbon fiber composites are being used more commonly in custom and prefabricated orthoses. Floor reaction, anterior tibial shell AFOs, foot plates, knee bracing, and KAFOs all use varying layers and pattern designs of carbon composites. The patterns create varying degrees of strength, flexibility, weight, and energy storing properties. This advancement has been beneficial to all users: the ability to provide a support that is lightweight and conserves energy. Reduced energy output for ambulation during the day is a tangible benefit. The potential of wearing a less cumbersome device under clothing is a cosmetic advantage, and also provides a more optimal, intimate fit of the device. Lastly, the energy storing property provides each patient with the ability to work and walk for longer periods of time, thus resulting in a more productive and happier individual. This same technology of layering carbon fiber in multiple, pattern specific directions is utilized in the production of prostheses feet in order to produce the same lightweight, yet strong, energy return benefit.

Interface Material

Interface material is used for cushioning an orthosis or prosthesis for comfort and fit, and for fabricating custom arch supports. Varying durometers of firmness, as well as multiple thicknesses and color options (which is a bonus when working with children) make obtaining the best option available possible. Plastazote, PPT, and pelite are some of the most commonly used interface materials. These product properties include vacuum molding, closed or open cell, and whether the material is subject to packing out, will resist packing out, or will not pack out. Packing out is what happens to the material over time and use, and the result is the material compresses and eventually collapses.

Fingers, hand, and wrist

A splint for the fingers and hand should only support the affected joint or joints and allow the unaffected joints free ROM. There are single joint splints for the fingers available, such as proximal interphalangeal (PIP) and distal interphalangeal (DIP) splints which maintain or promote active range of motion (AROM) in the phalanges after sprains, fractures, or contractures. Some splints maintain or hold the joint in a fixed position, whereas dynamic splints that are spring-loaded allow the patient some movement of flexion or extension while applying constant force in the desired direction (Fig. 26-1). One particular type of wrist-hand-finger orthosis (WHFO) is the Thomas suspension splint. The function of this splint is to apply tension to the wrist joint and thumb in order to dorsiflex the wrist for diagnoses such as radial palsy. The long opponens splint is often used for flexion contractures, nerve or tendon damage due to traumatic accidents, or rheumatoid arthritis. These splints offer dynamic finger extension and allow the patient to use flexors needed for gripping.

Another example of a functional custom fabricated WHFO is the tenodesis splint (also known as a wrist action splint) (Fig. 26-2). This splint is used to increase functional levels and independence mainly for quadriplegia. The design is ultra lightweight and uses the available ability to flex the wrist to accentuate the natural movement of opposition for gripping objects by using the three-jaw chuck pinch position. The wrist-driven wrist/hand orthosis employs the flexor hinge principle. The fingers and thumb are stabilized in the position of function. A small amount of wrist extensor strength will create flexion motion in the metacarpal phalangeal (MP) joints to produce adequate pinch for a variety of daily activities. Because it is custom fabricated, this style of splint requires a cast of the hand and forearm and measurements for fabrication.

There are multiple orthotic options available when supporting the hand and wrist, depending on the diagnosis and desired limitations for movement. For diagnoses such as carpal tunnel syndrome, tendonitis, or a sprain, a cock-up wrist splint, which holds the wrist in a neutral position is the most common choice (Fig. 26-3, A). This splint is a prefabricated brace that is readily available in varying sizes. For diagnoses such as a contracture secondary to a cerebral vascular accident (CVA) or rheumatoid arthritis (RA), a prefabricated malleable wrist-hand-finger orthosis will suffice. This orthosis is progressive in design because the wrist joint and finger platform is easily flexed or extended to accommodate gains made by stretching protocols in physical therapy sessions. These prefabricated, lightweight splints are called platform or resting splints and provide static positioning (Fig. 26-3, B). Some of the soft versions of these splints are more skin-friendly because they offer the option of a cover that can be removed and washed, which promotes good hygiene.

Elbow

Fitting choices for elbow orthoses can usually be prefabricated. A lateral epicondylitis splint (a band with a silicone or air pocket), is used to disperse the pressure placed on the tendon caused by use over a greater area, thus decreasing the point of high stress and pain (Fig. 26-4). ROM splints that limit AROM or provide pressure to increase ROM can also be purchased as prefabricated orthoses. The Flex POP Elbow Orthosis by RCAI (St. Petersburg, Fla.), for example, provides rehabilitation for joint stiffness and contractures, instabilities, strains, sprains, and ligament repairs. This ROM elbow orthosis offers flexion/extension stop sets at 5-degree increments, which allows changes to be made in therapy sessions as the patient progresses. Dynamic elbow splints can be used when the function desired is to gain ROM by applying a constant stretch to the elbow joint tendons and muscles. Protocols are set for wear time and when the tension placed upon the joint can be increased. Static splints can be set to a designated degree of flexion or extension and depending upon the style or brand, may or may not be adjustable. The physician’s prescription, rehabilitation protocols, and the patient’s level of compliance and tolerance all contribute to the decision-making process when fitting these types of elbow splints. Elbow contractures can be caused by a variety of injuries or diseases, such as cerebral palsy and CVA.

Shoulder

Shoulder splinting for immobilization can use a sling and swath or a shoulder immobilizer that will support the shoulder joint. One commonly used design utilizes a chest band, upper arm cuff, and a forearm cuff that is adjustable and positions the arm securely against the body (Fig. 26-5). If the required position is abduction, then an airplane splint can be fitted.

Specialized orthoses for the upper extremity

ADLs require a multitude of orthoses to promote independence for individuals who have suffered a stroke or debilitating injury. There are hand and wrist splints that are used to assist with feeding oneself, holding an ink pen, using a brush, and so on (Fig. 26-6). There are many types of foam available to place around utensils and items with handles to increase their circumference, therefore decreasing the grip strength and ROM needed to hold and use such items.

Fracture splinting uses a compression method for stabilization of the fracture site. The compression of fluid and soft tissue around the fracture site is key when providing a femoral, humeral, radial, or ulnar splint. These splints can be modified to a custom fit by heating and/or adding a soft interface material to provide added comfort. The fracture splint is a bivalve, two-piece orthosis and uses adjustable hook and loop strapping (Fig. 26-7). The splint will allow movement of the unaffected joints such as elbow and wrist for the ulnar fracture. The technique and principles used in splinting for upper extremity fractures is the same for lower extremity fractures.

Spine and Trunk

Cervical spine

Cervical orthoses are fitted for the purpose of supporting the cervical muscles; limiting rotation, flexion, and extension; or immobilization of the cervical spine. A soft cervical collar can be fitted for lesser injuries such as sprains and strains. The soft collar is a prefabricated orthosis made of foam with a cotton cover and has a hook and loop closure in the back (Fig. 26-8). They are available in different heights and lengths. A cervicothoracic orthosis is a semirigid, two-piece brace that can be fitted for whiplash, degenerative joint disease, arthritis, and presurgical or postsurgical repairs. These collars are adjustable in height, circumference, and rigidity, but, as with all bracing, the therapist must always check pressure points to make sure that there is no skin breakdown.