Chapter 14 Upper Limb Orthotic Devices

Brian M. Kelly, Atul T. Patel, Carole V. Dodge

This chapter provides a guide for prescribing and the basic principles for using upper limb orthotic devices, commonly known as splints or braces. The word orthosis (derived from the Greek orthos, meaning to correct or make straight) encompasses the full spectrum of devices currently fabricated by therapists and orthotists.¹⁶ As defined by the International Standards Organization of the International Society for Prosthetics and Orthotics, an orthosis is any externally applied device used to modify structural and functional characteristics of the neuromuscular skeletal system.³⁰ Orthosis—or alternatively, orthotic device—is the preferred term.²¹ The terms splint and brace are less preferred because they imply mere immobilization and do not suggest either improved function or restoration of mobility. However, these terms remain common, and in this chapter we use the terms orthotic device and splint interchangeably.

Principles and Indications

The objectives of upper limb orthotic applications can be classified into three major areas: protection, correction, and assistance with function.

• Protection: Orthotic devices can provide compressive forces and traction in a controlled manner, protecting the impaired joint or body part. Restricting or preventing joint motion allows for corrective alignment and serves to prevent deformity. Protective orthoses can also stabilize unstable bony components and promote healing of soft tissues and bones.

• Correction: Orthoses help in correcting joint contractures and subluxation of joints or tendons, assisting in the prevention and reduction of joint deformities.

• Assistance with function: Orthoses can assist function by compensating for deformity, muscle weakness, or increased muscle tone.

Physicians prescribe orthotic devices based on their knowledge of diagnosis and preferred treatment. Other health professionals, including occupational therapists and orthotists, are involved in the design and application of these devices.

Classification

We use many different terms to describe upper limb orthotic devices. We call them by the joint they cover, the function they provide (e.g., immobilization), or the condition they treat. Some are named by their appearance (e.g., banjo or sugar tong), and still others bear the name of the person who designed them (e.g., Kleinert).²⁸

Most splints are known by their common names (Table 14-1)—names that have evolved over time. But such names are not fully informative, are not systematic, and are not even universally accepted. This lack of a universally accepted terminology often presents a communication barrier between the physician and other health professionals. Consequently, more systematic naming systems have been developed that classify orthotic devices according to anatomic region or to purpose and function. Table 14-1 compares the common names of several orthotic devices with those in three other naming systems.

Table 14-1 Nomenclature Systems in Current Use

The simplest naming system is that developed by the International Organization for Standards. It reports the anatomic region the orthotic device encompasses. A wrist-hand orthosis, for example, is called a WHO.³² This system, however, fails to define the purpose or function of the orthosis.

In 1991 the American Society of Hand Therapists (ASHT) published the ASHT Splint Classification System.¹ This system provides standard nomenclature for splints based on function. It classifies splints by characteristics (e.g., articular or nonarticular) and location of the body part covered. A humeral fracture brace, for example, is identified as a nonarticular splint—humerus. It also identifies the direction of the force applied, and whether the splint is for mobilization, immobilization, or restriction. In this system a long arm splint (Figure 14-1) is characterized as a 45-degree elbow flexion immobilization. The problem with the system is that one splint design can provide many different functions.¹⁰

FIGURE 14-1 Long arm splint used for cubital tunnel syndrome.

Biomechanical and Anatomic Considerations

Health care personnel involved in the fabrication and application of orthotic devices need a good understanding of biomechanics and anatomy as well as the physiologic response to tissue healing. They also need technical and creative skills that allow them to design and fabricate orthotic devices that can win the patient’s acceptance and satisfy the treatment goals. In the United States upper limb splinting is performed by occupational therapists, certified hand therapists, orthotists, and some physical therapists. Physicians ordering these devices need to understand the technical factors involved in fabrication and fitting. Some of these are listed here.

• The wrist will act as the keystone for hand positioning and outlines the basis for all splinting, except isolated digital splinting. The weight of the immobile hand, gravity, and resting muscle tension tend to pull the wrist into flexion, which increases tension in the extrinsic extensor tendons, pulling the metacarpophalangeal (MCP) joints into hyperextension. Concurrently, the tension of the extrinsic flexor is maintained while forcing the interphalangeal (IP) joints (which include the proximal interphalangeal [PIP] and distal interphalangeal [DIP] joints) into flexion. The metacarpal arch of the hand flattens and the thumb falls into adduction. This results in a “claw hand” that is not functional. Prevention of this deformity is one goal of hand splinting.

• The MCP (some experts refer to this as the MP) joint is the key for finger function. When MCP joints are hyperextended, the IP joints flex because of the tension of the flexors and the delicate balance between the finger extensors and flexors. Extension stability of the wrist is important for optimal function of the hand. The wrist should also be placed in slight extension to maintain flexor tendon length and to improve hand function (Figure 14-2). This position will place the MCP collateral ligaments on maximum stretch, preserve the anatomic arches of the hand and thus oppose the development of a “claw hand” deformity. This position is also referred to as the ”safe” or “intrinsic plus.”¹⁰ This position fosters the weaker intrinsic motions of the MCP flexion and IP extension that are difficult to obtain.

• The hand is used during functional activities through basic prehension patterns: to pinch, to grasp, or to hook objects. There are two basic types of hand grips: power and precision (which can be further subdivided). In power grip the wrist is held in dorsiflexion with the fingers wrapped around an object held in the palm (such as holding a screwdriver with a cylindrical grip). The spherical grip is useful for holding a ball. The hook pattern is useful for carrying heavy objects. In precision grip, the thumb is held against the tip of the index and middle finger. Functional hand splinting is typically aimed at improving pinch. There are three types of pinch: (1) oppositional pinch (three-jaw chuck), (2) precision pinch, and (3) lateral key pinch. It is best to splint towards oppositional pinch. This allows the best compromise between fine precision pinch and strong lateral pinch. No practical orthosis can substitute for or improve thumb adduction.¹⁰ When making a splint, the therapist should fabricate it in a position that enhances prehension and does not force the thumb into a position of extension and radial abduction. This position causes the rest of the arm to have to compensate for poor thumb positioning.¹⁰

• When increasing joint range of motion with splinting, the angle of pull needs to be perpendicular to the bony axis that is being mobilized.⁶ Otherwise the forces on the skin and underlying structures can be sufficient to cause injury through excessive pressure on the skin and deforming stresses on the underlying healing structures.

• The improvement in range of motion is directly proportional to the length of time a joint is held at its end range.¹⁸ This is referred to as the TERT principle and is used with static progressive splinting. The load should be low and the application long for effective tissue deformation. the clinically safe degree of force covers a very narrow range.

FIGURE 14-2 Hand and wrist are positioned to keep the metacarpophalangeal joints flexed and the interphalangeal joint extended with the wrist in slight extension. This is also known as the “safe” or “intrinsic plus” position.

Design Categories

Orthotic devices can be classified by the support (or forces provided) to improve motion or function. The categories of splint design are listed below.³⁴

Nonarticular

The nonarticular splint provides support to a body part without crossing any joints, and protects a bone or body part. For example, a humeral fracture splint provides circumferential support to the arm during fracture healing. Other examples are a sugar tong splint to immobilize a proximal radius fracture, or a gel shell splint (Figure 14-3) to exert pressure over a healing scar to prevent hypertrophic scarring.

FIGURE 14-3 Gel shell splint.

Static

The static splint provides static support to hold a joint or joints stationary. For example, a volar wrist splint for acute carpal tunnel syndrome reduces motion and rests injured tissues (Figure 14-4). Static splints can be used to protect healing structures (Figure 14-5), to decrease or prevent deformity, and to reduce tone in spastic muscles.

FIGURE 14-4 Wrist splint for carpal tunnel syndrome, with the wrist in a position of 0 to 5 degrees of extension; distal palmar crease free to allow for full metacarpophalangeal motion.

FIGURE 14-5 Hand-based static thumb splint with interphalangeal joint included for immobilization of a distal phalanx fracture.

Serial Static

The serial static splint is also static but is periodically changed to alter the joint angle at which the splint is positioned. The splints are applied with the tissue at its maximum length. For example, a wrist splint can be changed periodically to increase extension in a wrist with a flexion contracture after a wrist fracture. This serial repositioning provides a prolonged gentle stretch to involved structures, helping a stiff joint regain motion.

Static Motion-Blocking

The static motion-blocking splint permits motion in one direction but blocks motion in another. For example, a swan neck splint (Figures 14-6 and 14-7) is designed to allow flexion but block hyperextension of the PIP joint. (See the section on rheumatoid arthritis.)

FIGURE 14-6 Swan neck deformity with no splint support in place.

FIGURE 14-7 Swan neck splint: Oval 8 product of 3-Point Products; note that the deformity is reduced.

Static Progressive

The static progressive splint is the one most commonly used for regaining joint motion. Unlike the serial static splint, the orthosis is not remolded to increase joint motion. These splints differ from serial splints in that they use nonelastic components such as static lines, hinges, screws, and turnbuckles to place a force on a joint to induce progressive change. The MERiT static progressive component ³ (available commercially) decreases the static line length as it is turned, thereby increasing the range of joint motion (Figure 14-8).

FIGURE 14-8 Static progressive flexion splint using a MERiT component.

Dynamic

The dynamic splint provides an elastic force to help regain joint motion. An example of such an orthosis is a finger extension splint, which uses a spring coil or wire tension assist to increase extension in a PIP joint with a mild contracture (Figure 14-9).

FIGURE 14-9 LMB extension type of finger splint produces extension of the proximal interphalangeal or distal interphalangeal joints of the fingers and/or thumb.

Dynamic Motion-Blocking

The dynamic motion-blocking splint allows certain motions but blocks others. It uses a passive, elastic line of pull in the desired direction, but permits active motion in the opposite direction. An example is a Kleinert postoperative splint for flexor tendon repairs (Figure 14-10). It passively pulls the finger into flexion with an elastic thread or rubber band. It allows active digital extension, while parts of the splint block full extension of the MCP joint and the wrist.

FIGURE 14-10 Kleinert splint used for postoperative care for patients with flexor tendon injuries. It allows for passive flexion, holding digits flexed at rest.

Dynamic Traction

The dynamic traction splint offers traction to a joint while allowing controlled motion. An example is a splint for an intraarticular fracture. This a hand-based PIP extension splint with an outrigger (Figure 14-11), which gives constant longitudinal traction while the joint is gently flexed and extended.

FIGURE 14-11 Hand-based PIP extension splint with low-profile outrigger placing dynamic traction on the digit while allowing for passive range of motion.

(Courtesy Jeanne Riggs, OTR/L, CHT.)

Tenodesis

The tenodesis splint facilitates function in a hand that has lost motion because of nervous system injury. An example is the Rehabilitation Institute of Chicago tenodesis splint (Figures 14-12 and 14-13), which assists the patient with a C6 level of spinal cord injury to achieve a functional pinch. Active extension of the wrist produces controlled passive flexion of the fingers against a static thumb post through a tenodesis action.

FIGURE 14-12 Rehabilitation Institute of Chicago tenodesis splint, used for functional pinch during activities of daily living; pinching to thumb post.

FIGURE 14-13 The splint uses a cord or string running from the wrist piece, across the palm, and up between the index and ring fingers. The string is lax when the wrist is released and tightens with wrist extension, bringing the fingers closer to the immobilized thumb, creating three-jaw chuck prehension.

Continuous Passive Motion Orthoses

Continuous passive motion orthoses are electrically powered devices that mechanically move joints through a desired range of motion. This keeps the joints supple and maintains articular, ligamentous, and tendinous structure mobility during the healing phases after injury or surgery.

Adaptive or Functional Usage

Adaptive or functional usage devices promote functional use of the upper limb with impairment resulting from weakness, paralysis, or loss of a body part. An example is the universal cuff, which encompasses the hand and holds various small items such as a fork, a pen, or a toothbrush. This cuff allows patients to manipulate these items (known as activities of daily living tools), and enhances their degree of independence.

Diagnostic Categories and Splint Examples

There are many common clinical conditions for which orthotic intervention is appropriate. This section gives a brief overview of the features of specific diagnoses, followed by the type of splints commonly indicated for each diagnosis. This is not an all-inclusive list, and the reader is referred to comprehensive overviews of upper limb orthotic devices in splinting texts and other references.^∗

Musculoskeletal Conditions

Tendonitis, Tenosynovitis, and Enthesopathy

Tendonitis (inflammation of the tendon), tenosynovitis (inflammation of the tendon sheaths), and enthesopathy (inflammation at a muscle or tendon origin or insertion) can all result from excessive repetitive movement or external stressors. The upper limb tendons most commonly involved are the wrist extensors or the abductor pollicis longus and extensor pollicis brevis muscles of the thumb, commonly called de Quervain’s stenosing tenosynovitis. The goal of splints for these conditions is to immobilize the affected structures in order to facilitate healing and decrease inflammation. The thumb spica splint, forearm-based, immobilizes the wrist, the carpometacarpal (CMC) joint, and the MCP joint of the thumb. The IP joint of the thumb does not need fixation because the affected tendons do not move this joint (Figure 14-14).

FIGURE 14-14 Forearm-based thumb spica splint used for de Quervain’s stenosing tenosynovitis.

(Courtesy Jeanne Riggs, OTR/L, CHT.)

Lateral epicondylitis is a more common enthesopathy of the upper limb.34 It can be treated by a tennis elbow orthosis (Figure 14-15). This is a forearm band that changes the lever arm against which the wrist extensors pull. In essence, it puts the origin of the extensor muscles at rest and decreases the microtrauma from overuse. This orthotic device is placed approximately two fingerbreadths distal to the lateral epicondyle, and is a firm strap against which the extensors press against when contracting. A similar brace is used for medial epicondylitis (also known as golfer’s elbow). (See Chapter 38.)