Types of Orthoses for Mobilization
Orthoses for mobilization are divided into three basic categories (Table 11-1):
- Dynamic orthoses
- Static progressive orthoses
- Serial static orthoses
Dynamic orthoses typically incorporate elastic components and/or coils or springs to put tension on a joint in order to increase ROM or act as a substitute for weak or absent muscles. Dynamic mobilization orthoses can have a variety of uses and functions (Figure 11-1). For example, they are often used to aid in functional activities, as with peripheral nerve injuries where muscles are weakened or paralyzed. The springs and/or coils of a mobilization orthosis can help substitute for the weak or paralyzed muscles as in cases of radial nerve palsy or ulnar nerve/median nerve palsy. The outriggers can also be used to mobilize stiff joints or pull fingers into better alignment.
STATIC PROGRESSIVE ORTHOSES
Static progressive orthoses are a type of mobilization orthosis that incorporate nonelastic components to apply force to a joint to hold it in its end-range position in order to improve joint PROM. Examples of these static components are string, turnbuckles (devices that allow for regulation of tension), gears, monofilaments, fishing lines, and Velcro (Velcro BVBA) hook and loop tape (Figure 11-2). Static progressive orthoses allow progressive changes in joint position as the PROM of the involved joint changes and improves over time.
SERIAL STATIC ORTHOSES
The use of serial static orthoses is a method of holding a stiff joint in its end-range position in order to increase PROM. Every few days, or even once per week, the practitioner removes the orthosis for additional treatment of heat, stretching, and exercise of the stiff or contracted joint before applying a new orthosis to the client in a new end-range position. Serial static orthoses are very useful in the treatment of stiff joints, such as a proximal interphalangeal (PIP) joint flexion contracture; the wrist following fractures or trauma due to extrinsic tightness; or a tight first web space, which can also occur after trauma or fractures (Figure 11-3).
When comparing the construction of dynamic and static progressive orthoses, it is apparent that both types of mobilization orthoses start with an immobilization base and have an outrigger attachment. Dynamic orthoses use dynamic components for force application, such as rubber bands, elastic, coils, and springs. Dynamic orthoses help to mobilize joints and allow movement within the orthosis. Conversely, static progressive orthoses are typically constructed with nonelastic components for force application, such as Velcro, static line, screws, gears, and turnbuckles. Static progressive orthoses are used to increase PROM. In the static progressive orthosis, as the tissue length changes, the client is able to readjust tension to a new maximum tolerable length and hold this tension on the stiff joint in its end-range position.
Box 11-1. Goals of Orthoses for Mobilization
- Remodel longstanding, dense, mature scar tissue
- Elongate soft tissue contractures
- Increase PROM
- Substitute for weak or absent muscle function
- Provide resistance for exercise
- Maintain intra-articular fracture reduction (a special type of dynamic orthosis places tension across the PIP joint when there is an intra-articular fracture; the orthosis helps to keep the fragments of bone in place)
Goals for Use of Orthoses for Mobilization
Goals for using orthoses for mobilization are presented in Box 11-1.
Depending on the client’s condition, the practitioner might fabricate either a dynamic, static progressive, or serial static orthosis to regain tissue length and joint ROM. For clients with nerve palsies or weakened muscles, a dynamic orthosis is the proper choice because these can be functional as well as corrective and allow the client to move his or her joints while wearing the orthosis.
Biomechanical Concepts of Orthoses for Mobilization
The connective tissue in the body is capable of being stretched due to its viscoelastic qualities. While under tension, it can respond by reaching an either elastic or plastic deformation state. Elastic deformation means that the tissue reverts back to its original length when the force on it is removed. Plastic deformation means the tissue will maintain its new length even without the force. Orthoses can be used to apply this force to the tightened or shortened tissue to promote tissue growth and lead to tissue remodeling.
There are two types of loading conditions with the application of mobilizing orthoses: creep and stress relaxation. In creep-based loading, the force applied is constant and the displacement of the limb varies. The specific tension is applied through rubber bands or elastic thread, exerting a variable force on the body part. Dynamic orthoses may need to be worn for 6 to 12 hours daily in order to be effective.
In stress relaxation loading, the displacement is constant and the applied force varies. This is the principle of static progressive orthoses where clients are instructed to constantly adjust and readjust the tension on their stiff joints. The tissue reaches the plastic deformation state more quickly and the effects will last longer. The force from the static progressive orthosis holds the shortened tissue at its maximum tolerable length. As this tissue length changes, the design of the orthosis also allows for changes and adjustments over time.
Low-load prolonged stretch (LLPS), applied over a long duration to a stiff joint, has been shown to be more effective than a high load of stress applied to a stiff joint for a short duration. The increase in PROM gained from exposure to LLPS is directly proportional to the amount of time the joint is held in its end-range position. This concept is known as total end range time (TERT).
One additional concept of orthoses for mobilization is the application of torque. Torque is the extent to which a force tends to cause rotation of an object around an axis, such as a bone around a joint. Torque can be defined simply as an equation: torque = amount of force × length of the lever arm (Figure 11-4). Torque is maximized by a long lever arm; the longer the lever arm, the less force required to generate sufficient torque to move or influence the joint. The amount of torque depends on the distance between the joint axis and the point of attachment of the mobilization assist as well as the amount of force applied to the body part. A longer lever arm means less torque or force is required to mobilize the body part. Less force on a stiff body part means a more comfortable or tolerable orthosis for the client, and hopefully increased compliance with the wearing protocol (Figure 11-5).
Indications and Contraindications for Orthoses for Mobilization
This section will cover the indications and contraindications for the use of orthoses for mobilization in clinical practice.
The indications for any of the three types of orthoses for mobilization include the following complex, and even not-so-complex, injuries: crush injuries, multiple fractures, scar tissue, stiffness, or any trauma that might occur resulting in joint stiffness. As the practitioner assesses the client’s overall condition and prognosis, it might be apparent that orthoses for mobilization will be an important and beneficial intervention for regaining ROM and function in the future. First, one must consider in what stage of healing the injured extremity presents before it is appropriate to apply any type of force to correct stiffness or decreased joint ROM. Orthoses for mobilization can be part of the overall treatment plan. The correct choice of orthoses depends significantly on the stage of healing the client’s tissue presents in at the time. Wounds of the body typically heal in a set pattern, known as the three main stages of healing (Box 11-2).
In stage 1, the inflammatory phase, initially all wounds and injuries cause an inflammatory reaction where edema and white blood cells invade the wound. This initial stage of healing can last less than 1 week but may take longer to resolve depending on the client’s general health and the presence of complicating factors such as infections, number of tissues involved, and mechanism of injury. The first phase of healing requires protection and proper positioning for best healing of the injured part. The correct and most appropriate orthotic approach is typically immobilization to allow for rest and resolution of the edema.
During stage 2, the fibroplasia phase, the predominate cell type is the fibroblast, the cell that contributes to the collagen production for wound healing. The wound is full of new vascular growth and granulation tissue. This is laying the groundwork for the synthesis of new collagen tissue. The collagen tissue begins to synthesize and becomes stronger and more abundant. This phase of healing usually lasts about 4 to 6 weeks, with a reduction in edema and pain and the beginning of restoration of movement and function in the involved extremity. Orthoses that apply a low load of force or stress on involved joints to improve PROM may be applied during this phase.
Stage 3, the last phase of healing, termed the scar maturation phase or remodeling phase, is where the scar collagen fibers increase and mature and reorganize. It is in this phase that mobilization orthoses are most effective. However, take care to avoid the overly aggressive use of mobilizing forces and orthosis that go too far in terms of force application and positioning, which can lead right back to a renewal of the inflammatory process. The connective tissue of the body responds to low loads of prolonged stress. Practitioners can help to influence and promote the reorganization of this tissue to accommodate this stress and allow for patterns of joint motion critical to function.
A practitioner considering using an orthosis for mobilization for any client must use sound clinical reasoning and a very careful assessment of the client’s particular situation. There are some significant contraindications to applying orthoses for mobilization to a client. Of critical importance is the recognition and acknowledgement of the continued period of acute edema or inflammation, in which the tissue is still indicating it is not ready or able to tolerate any kind of stress or force. This must be resolved before any type of mobilization orthosis can be applied. Specific treatment protocols, such as for Dupuytren’s disease, have not shown any real benefit to the use of any type of mobilization orthoses prior to surgical intervention. The practitioner must also recognize other client factors that may influence the effectiveness of a mobilization orthosis, such as client appropriateness. These include factors such as the sensory status of the hand and the client’s ability to follow directions and understand the principles involved.
Box 11-2. Stages of Healing
- Increased blood flow to area of injury; signs of inflammation, including erythema, heat, edema, and pain
- Use of orthoses to protect, support, position, and reduce pain and edema
PROLIFERATION OR FIBROPLASIA PHASE
- Formation of new granulation tissue with collagen and network of blood vessels; wound closure
- Active exercises and possibly light functional activities to help decrease edema and regain mobility
MATURATION OR REMODELING PHASE
- Final phase of wound healing when wound has closed; involves remodeling of collagen fibers to allow motion and gliding of tissues
- May need increased stretching and orthotic intervention to regain full ROM when limited by scar and shortening of soft tissue
Selecting the most appropriate mobilization orthosis for your client is an important decision that should be based on sound clinical reasoning and supporting evidence. The following information may help the practitioner make a decision in selecting an orthosis to help a client regain functional ROM in a stiff joint.
SOFT END FEEL VERSUS HARD END FEEL
When a client has a stiff joint or limited joint ROM, the practitioner can subjectively determine whether the specific joint has a soft end feel or a hard end feel. End feel is defined as the type of resistance that is felt when passively moving a joint through the end ROM. End feel is evaluated by applying pressure to the joint at the end of the available PROM. A soft end feel means the soft tissues give way with a small amount of pressure, whereas a hard end feel means firm pressure is required to mobilize the joint further than the limitation.
|CHANGE IN PROM||RECOMMENDED ORTHOSIS|
|About 20 degrees||No orthosis needed|
|About 15 degrees||Static orthosis|
|About 10 degrees||Dynamic orthosis|
|About 0 to 5 degrees||Static progressive orthosis|
Adapted from Flowers, K. (2002). A proposed decision hierarchy for splinting the stiff joint, with an emphasis on force application parameters. Journal of Hand Therapy, 17(3), 158-162.
The soft end feel can be described as a joint with immature scar tissue in the joint structures, and the limitations in motion can be addressed with any type of mobilization orthosis. The hard end feel can be described as a joint with mature scar tissue that might respond best to serial static or static progressive orthoses, described earlier in this chapter.
TORQUE ANGLE CURVE
The amount of force directed to the stiff joint by the practitioner can be measured quantitatively through the use of a torque gauge and the results of the joint movement plotted on a graph, called the torque angle curve (Figures 11-6 and 11-7).
The torque angle curve graph will display one of two variations of slopes, either indicating a rapidly rising slope where a large amount of force is needed to mobilize the joint, or a slowly rising slope where a small amount of force elicits movement of the stiff joint. The gentle slope describes tissue that is more compliant, and a steeper slope describes tissue that is stiffer and noncompliant. This is a more objective measure of joint stiffness than the assessment of hard versus soft end feel of a joint.
THE MODIFIED WEEKS TEST
The modified Weeks test is an assessment done prior to orthotic fabrication to help clarify what type of mobilization orthosis may be most appropriate for the client. A cold reading is taken of the stiff joint’s PROM. Then the client’s stiff joint is placed in a heated modality, such as a fluidotherapy unit or a heated whirlpool, so that the joint can be mobilized for 20 minutes. Afterward, the stiff joint is placed at its end-range position, with a tolerable overstretch and heat applied for another 10 minutes. The preconditioned reading is the PROM measurement taken immediately after these 30 minutes of heat and mobilization. The preconditioned reading is then compared with the cold reading.
The difference between the two PROMs can influence the orthotic selection according to the guidelines outlined in Table 11-2.
Clinical Conditions and Wearing Schedules
A growing body of literature and clinical trials support the use of mobilization orthoses for limitations of ROM and decreased function of the upper extremity (UE). In order to use an evidence-based approach when working with a client, before proceeding with a similar orthotic intervention, the practitioner should also compare his or her client with the clients and diagnoses described in the clinical trials to see if those conditions and symptoms match those of the client. The practitioner must also discuss the intervention and findings on clinical outcomes with the client.