Principles and Components of Upper Limb Orthoses

Patient Goals and Outcomes

When considering orthotic recommendations for the upper limb, particular care must be taken to properly understand and address each of the patient's goals through a thorough interview process. This has added complexity and importance over lower limb interviews, because many of the available devices are designed and maintained for a specific set of grasping patterns or activities. Patient goals may include gross motor position of the arm and hand in space or may be more focused on fine motor movements of the hand, wrist, or fingers. Particular designs should drive toward independent completion of activities of daily living, eating, toileting, food preparation, and so on. Additional functional goals of the orthosis may be to reduce pain, reduce weight, or improve cosmesis. Because use of an upper limb orthosis can be obtrusive, or more conspicuous than its lower limb counterparts, care should be taken to understand the user's psychosocial well-being and overall “gadget tolerance.” For proper implementation, each goal should be discussed with the team to ensure alignment and agreement. The orthotist should then be able to interpret these goals and requirements to better understand and formulate the treatment plan.

Underlying Pathology

In addition to patient goals and outcomes, the therapeutic intent of the upper limb orthosis must be considered. Therapeutic intent can be further classified into the treatment of three principle factors. The efficacy of the orthosis may be measured by the reduction of the effects of the three Ps: paralysis, pain, and position.

Neurosensory Conditions

Partial or complete neurosensory deficits are common in this population and may manifest as pain, numbness, tingling, or complete sensory deficit. This poses unique functional challenges but may also have compounding concerns when considering the distribution of forces over the body by the orthosis. Additionally, upper limb segments often lack the benefit of underlying subcutaneous tissue, which would be used for padding and dissipation of forces in other areas of the body, including the lower limbs and torso. In each case, consideration must be given to protect the limb, reduce shear force across skin layers, and ensure even and broad distribution of forces when stabilization or loading is required.

Functional Deficits and Opportunities

In any case in which an upper limb orthosis is required, the patient has lost some degree of expected function compared with an unaffected limb segment. This loss of function forms the foundation of the orthotic prescription and subsequent treatment plan. Every effort is made to maximize function and opportunities for mobility and independence. Currently no orthoses perfectly mimic the complex movements of the nonaffected upper limb, so when considering orthotic management, clinicians and patients must prioritize function and activity in the context of the patient goals and expected outcomes. Well-designed orthoses restore, support, or augment the remaining function of affected joints or limb segments and position the limb to make better use of more distal segments such as the wrist and the hand. This is accomplished by encouraging the patient to use all available range of motion (ROM) and available muscle power, without limiting or impeding critical movements through the orthotic design. Functional deficits should be carefully and objectively quantified where possible through the use of validated outcome measures or other available clinical tools such as goniometers, length gauges, or other measurement devices. Validated clinical measures help the clinician to objectively quantify the current state and long-term efficacy of the prescribed treatment. Measures in this space can take multiple forms and formats and range from user-reported survey instruments through objective performance measures.

Upper Limb Biomechanics

Biomechanics is quite simply the application of forces and their effects on the biologic system. In the human body these are the effects of the application of forces to the human body. In the case of the upper limb this could include internal or external forces. Knowing and understanding the range of forces that are unique in the upper limb will help the health care team to appropriately create the intended design and treatment plan. In the case of the upper limb, muscles are typically attached close to joints, favoring efficiency, speed, and fine motor movements. For the most part, internal muscles of the upper limb such as the lumbricals, triceps, biceps, and flexor digitorum are optimized for fine quick movements over a larger ROM. Correctly designed orthoses should consider the internal forces of the limb segments being treated and the application of external forces that will be applied to the limbs as required by the patient's environment, chosen profession, or activities of daily living. See Chapter 11 for more detailed information on the topic of upper limb biomechanics.

Contralateral Function and Dominance

Occasionally clinicians become focused on maximizing or attempting to restore function of the affected segment without looking holistically at the entirety of upper limb function. In the case of unilateral involvement, users will often retrain their unaffected side for all activity and function. The design of an orthosis must ensure that orthotic care aids in this transition process. This often results in the orthosis being specifically designed to position the affected segments of the body to provide functional assistance to the now-dominant unaffected side.

Expected Prognosis and Rehabilitative Trajectory

Use of upper limb orthoses can range widely from acute to permanent use. In many conditions, use of the orthosis is expected to be time limited to aid the user in progressing through the appropriate stages of rehabilitation. In all but the most chronic conditions, experts in the field are beginning to look at orthoses as therapeutic devices that are designed to carry the patient to the next stage of the rehabilitative process, at which point devices should be modified or replaced to better position the patient for the subsequent rehabilitative milestone.

Nomenclature and Terminology

Orthoses can be described or presented based on a variety of different paradigms such as by pathology, segmentally by joint or segment treated, or by its objective. Modern convention and associated International Organization for Standardization (ISO) standards name orthoses by the joint segment or section of the limb that they interface with. Common abbreviations of upper limb orthoses are as follows:

• Finger orthosis (FgO)

• Hand orthosis (HdO)

• Wrist–hand orthosis (WHO)

• Elbow orthosis (EO)

• Shoulder orthosis (SO)

To remain consistent with ISO standards, this nomenclature will be used throughout the chapter when describing specific orthoses or designs. For the purposes of this chapter it would be difficult to catalog each of the recommended orthoses by the underlying pathology, as specific pathologies could present with very distinct functional deficits depending on severity or involvement. Where possible and when supported by the literature, examples of common, associated pathologies are provided. Furthermore, the devices are categorized as static or dynamic devices. For consistency, static orthoses in this text are defined as fixed positioning devices or static progressive devices. Static progressive devices allow manual manipulation of a joint angle to increase ROM, typically achieved through a ratchet or dial mechanism. When the orthosis is moved to a specific position, the joint mechanism is fixed and holds that position unless manually adjusted to an alternate joint angle. Although static orthoses are often fixed, they still provide significant utility and may be required to position the hand, wrist, elbow, or shoulder most optimally for the required task. Dynamic orthoses, on the other hand, create, assist, or resist specific movements. Dynamic orthoses are further subdivided based on the desired dynamic feature of the orthosis. Dynamic orthoses apply a constant load that may be graded based on the angle or intrinsic strength of the underlying musculature. Typical applications of dynamic orthoses include constant low-load stretching and coupled movements (in which force or excursion is transferred through gearing or levers from one joint to another). An additional category that is introduced near the end of this chapter is powered upper limb orthoses, typically controlled through myoelectric inputs, brain–machine interfaces, manual switches, or physical patient feedback. This burgeoning field often refers to these devices as robotic or exoskeletal.

In most cases of significant impairment, orthoses may be highly customized, with specific components designed for specific activities or function. Examples of these adaptations are discussed based on the motion that is created or resisted by these additions. Previous editions of this text have broken down orthoses further into functional or therapeutic parameters, but in looking at the expanded definition of these elements, there is general recognition that all orthoses should provide both a functional and therapeutic benefit to fulfill their intended purpose.

Components and Applications of Upper Limb Orthoses