Orthotics: Evaluation, intervention, and prescription

Abstract:

After reading this chapter the student or therapist will be able to: (1) Identify and analyze the force systems produced by the use of an orthosis. (2) Comprehend the prescription rationale gained from an orthotic evaluation for individuals with neuromuscular dysfunctions. (3) Identify and differentiate the variables considered by the rehabilitation team to optimize outcomes during orthotic intervention.

Keywords:

ankle-foot orthosis (AFO), knee-ankle-foot orthosis (KAFO), thoracolumbosacral orthosis (TLSO), lever arms, three-point pressure systems

Objectives

After reading this chapter the student or therapist will be able to:

1.

Identify and analyze the force systems produced by the use of an orthosis.
2.

Comprehend the prescription rationale gained from an orthotic evaluation for individuals with neuromuscular dysfunctions.
3.

Identify and differentiate the variables considered by the rehabilitation team to optimize outcomes during orthotic intervention.

Overview

An orthosis is an external device that produces a force that biomechanically affects the body to correct, support, or stabilize the trunk, the head, and/or an extremity. Orthoses are named by the sections of the body to which they are applied. For example, an orthosis that controls and covers the ankle and foot is called an ankle-foot orthosis (AFO). The abbreviations for the device are used by professionals in clinical documentation. Orthotic use varies from temporary application to permanent use based on patient care goals. Careful evaluation is used to determine whether a prefabricated, custom-fit, or custom-made orthosis is most appropriate for the patient. A prefabricated orthosis is one that is available in “off-the-shelf” sizing and is intended for temporary use. Commonly used prefabricated items are often kept in stock by the orthotic provider. Custom-fit orthoses are customizable devices that can be modified to optimize the fit to an individual patient. These devices are intended for use on a more definitive basis and are often appropriate when the patient has adequate sensation and normal anatomy. Custom-made orthoses require very specific measurements or models of the patient to be obtained for the most specific fit and to accommodate any deformity. These devices are time and labor intensive and are worn definitively when the patient’s condition is permanent or when his or her condition or anatomy does not facilitate fitting of a more basic device.

Orthoses are primarily designed on three simple biomechanical concepts: pressure, force, and the lever arm principle. The pressure principle simply means that pressure applied by the orthotic device is equal to the total force per unit area covered by the device. Because an orthosis is an external device that comes in contact with a part of the body, it has the ability to apply pressure based on the surface area it covers. If pressure is to be minimized, the surface area in contact with the device has to be maximized and vice versa. For example, a total contact orthosis will distribute pressure more evenly than a device that contacts the patient only at several points. The force principle is often used in designing orthoses that work on the three-point force system or the four-point force system. In a three-point force system, the orthosis is designed such that central components of the orthosis are able to apply force in one direction while the two terminal end parts provide a counterforce in the opposite direction, and the sum of all the three forces equals zero. For example, a knee orthosis designed to correct genu varum would consist of a central force directed medially at the lateral border of the knee joint and the terminal points of the orthosis applying laterally directed forces on the femur and tibia. This way an orthosis is effectively used to permit angular change or provide control over a joint. Similarly, a four-point force system can be used to provide translational control of adjacent segments and prevent displacement of one segment over another. For example, a knee brace to prevent knee hyperextension and anterior tibial translation would consist of two parallel forces equal in magnitude and opposite in direction applied at different points on the femur to facilitate femoral flexion and two other parallel forces of equal magnitude and opposite in direction applied at different points on the tibia to facilitate tibial extension. ^, Finally, the lever arm principle is important in designing orthoses to determine the force at the segment of interest based on the height/length of the orthosis. As per the lever principles, the longer the orthosis, the greater the moment arm and therefore lesser will be the magnitude of force required to produce the desired effect at the joint of interest. ^, For example, an elbow orthosis that is just proximal and distal to the joint area will apply a greater force to immobilize the elbow, compared with an orthosis that extends to closer to the wrist and axilla. The longer orthosis will require less force to provide the same outcome of elbow immobilization.

In addition to the basic biomechanical principles involved in designing an orthosis, many factors enter into the decision regarding use and type of orthosis. It is essential that the most functional, least complicated, and most cost-effective orthosis be applied to the patient. The rehabilitation team must build a priority list of desired outcomes and accept that sometimes all of the items on the list may not be achieved by either the orthosis or the patient-team combination. It is important to be aware that care may need to be attempted in stages because the patient’s condition changes or if other medical concerns may arise. Effective coordination and communication between health professionals in development of patient goals are essential during the evaluation process. For instance, placing a loop closure on the side of their body that a patient cannot reach will prohibit the use of the orthotic device. A sound understanding of biomechanical and orthotic principles, as well as skilled patient management techniques, must be used to be successful with patients who require orthoses.

There are similarities in orthotic management of orthopedic and neurologically impaired patients; however, the neurological population presents additional factors that challenge prescription criteria and outcomes for the rehabilitation team. Lack of proprioception, impairments in sensation, and spasticity are some of these special considerations. Concurrent medical issues, problems with communication, and caregivers may complicate patient management.

The advancements in and access to medical technology have had a profound impact in the field of orthotics. The evolution of plastic, composite, and metals fabrication technology has dramatically improved the ability to control, support, and protect all areas of the human body. Currently, patients are fit for custom and prefabricated orthotic devices that provide a variety of functions in both a timely and cost-effective manner. These factors have led physicians to routinely prescribe orthoses for a wide range of medical conditions, whereas historically lack of availability and shortage of experienced orthotists restricted patient access and narrowed the use of orthoses. Orthoses are important considerations for postoperative management, acute fracture management, and adjunct treatment in addition to more traditional uses. For many, the proliferation of the prefabricated orthosis signaled a dilution of quality orthotic care, but in reality it has had the opposite effect. These readily available, cost-effective orthoses have not taken orthoses out of the hands of the orthotist but rather have moved them into the minds of treating professionals. There has been continued growth of new and improved orthoses and expansion into other areas of treatment previously lacking in orthotic management. For example, positional and corrective orthoses can be used for premature and newborn infants, and a wide range of sizes of orthoses that previously were made only in adult sizes have become available for pediatric patients. As with any new technological advancement, there has been incorrect application and use. It is not that many of these prefabricated orthoses are difficult to apply; rather, there has been lack of a clear understanding of the indications, contraindications, and limitations these devices present to the rehabilitation team and patient caregivers.

Identifying patient functional goals and familiarity with the current state of evidence-based care for specific patient populations and diagnoses are critical in providing optimal patient care and achieving the desired clinical outcomes. In that spirit, a broad overview of the evaluation, prognosis, and intervention of orthotic devices in neurological rehabilitation is presented.

Basic orthotic functions

Alignment

Anatomical and functional alignment of the extremities and spine is a common reason for an orthotic prescription. The orthosis can provide either temporary or permanent function. A thoracolumbosacral orthosis (TLSO) may be prescribed for stabilizing alignment after spinal fusion or for non-operative management off an unstable spinal cord injury (SCI; refer to Chapter 14 ). A supramalleolar orthosis (SMO) is commonly prescribed to hold the foot in proper alignment in multiple planes. When the goal of orthotic intervention is to correct alignment to a position well tolerated by the overlying soft tissue and/or the malalignment is a result of a muscle weakness, the new position should stabilize the joint. Clinicians need to remember that aligning one joint may result in the proximal or distal joint being placed in malalignment. An example of this is a patient with correctable genu valgum of the knee. Although this coronal plane deformity can be orthotically corrected, changes in knee alignment result in adjustments by the other joints up and down the kinetic chain. If the patient lacks inversion/eversion range of motion (ROM) at the ankle, placing the knee in a more vertical alignment will cause the patient to weight bear on the lateral border of the foot and possibly create instability at the ankle joint. Considerations such as the subtalar joint’s mobility into pronation and supination must be accounted for when designing an orthosis that will provide coronal control at the knee.

Stability

Stability is often required for the patient with neurological deficits. These patients frequently lack the muscle control and strength necessary to maintain trunk balance or to ambulate. Patients with muscular dystrophy benefit from TLSOs to help maintain trunk stability, achieve sitting balance, and perform safer transfers. However, the orthotic prescription must be guided by the knowledge that maximum stability cannot compromise or restrain thoracic expansion for breathing capacity. An AFO that limits both dorsiflexion and plantarflexion can stabilize the ankle and the knee for the patient who has had a cerebrovascular accident (CVA). Although this patient may require both coronal and sagittal plane ankle stabilization, controlling the lever arms at the ankle can also provide knee stability and prevent future knee impairments created by excess coronal (varus/valgus) or sagittal (hyperextension/hyperflexion) motion at the knee. The orthosis functions in the sagittal plane by maintaining ground reaction force anterior to the knee during the stance phase of gait. Most patients requiring this type of stabilization have a foot-flat gait instead of a normal initial heel-strike pattern.

Contracture reduction

Contracture reduction is the goal for many orthotic applications in patients with neurological involvement. The increase in the use of these types of orthoses has been dramatic because even slight increases in contractures can make the difference between nonambulatory status and ambulatory community participation. Increased awareness and proactive use of prefabricated orthoses have become routine during periods of inactivity, associated surgical procedures, and “sound side” prevention. These types of orthoses can be either dynamic or static and are used in conjunction with various therapeutic modalities to reduce the contracture. Dynamic contracture-reducing orthoses use a spring-type mechanism that applies a low force to a joint over an extended period of time to gain range of motion (ROM). Static-type orthoses range from serial casts in which a manual stretch is placed over the joint for extended periods of time, to custom-made cylindrical devices designed to spread force over larger areas, to custom-fit devices with some type of quick adjustability. Dynamic-type orthoses are usually contraindicated for patients with neurological disorders that create tone and spasticity. Low-tension stretch can trigger spasticity and create skin breakdown because of the high pressure on localized skin areas. The exception for this would be individuals with lower motor neuron impairments and residual hypotonicity. Any type of tension orthosis needs to be monitored when there is sensory loss, regardless of the cause. To achieve results in contracture reduction, one must be cautiously aggressive because the amount of force required to improve ROM often threatens the soft tissue’s ability to tolerate the pressure of the orthosis. Experience, frequent sessions, and close communication with other members of the rehabilitation team and the family and patient are critical factors in the success of the use of orthotic devices.

Evaluation

The examination and evaluation of the neurologically impaired patient must be comprehensive. One must not read a diagnosis and assume a total clinical picture. The diagnosis should alert the evaluator to movement patterns associated with the impairment, and these should be used to confirm potential findings. Complete patient evaluations do not end with determination of ROM, muscle test findings, assessment of proprioception, skin sensitivity evaluation, or assessment of the integrity of the affected limb or spine. The rehabilitation team must assess the total picture to determine what limitations orthotic care may impose on other important functions and activities, and patient participation in life. The evaluation must include a patient management assessment. What is the patient’s or caregiver’s motivation? How much equipment can the patient tolerate, and with how much can he or she function? What functional potential does the patient have once they have left the clinical or acute setting? How significant are the risks associated with orthotic intervention? As stated, the total evaluation of the patient and the patient’s environment is important in developing the treatment plan, as is the communication among the physical therapist, occupational therapist, and orthotist. Whether done together or (more realistically) at separate sites, the details of the treatment plan must be discussed. The patient with neurological impairment often presents a series of complex issues: biomechanical, communication, visualization, and so on. Incomplete information or a lack of effort at communication among these professionals will not lead to a comprehensive treatment plan and ultimately optimal outcomes.

During evaluation, review of the diagnosis and gathering of patient history are extremely valuable. A complete medical diagnosis will indicate important information to the team. For example, for a patient with poliomyelitis, the orthotist is aware that it is a lower motor neuron lesion and that proprioception is intact (see Chapter 15 ). These patients have the benefit of skeletal balance in standing and ambulation and therefore require durable orthotic construction. Compare this to a patient with T12 paraplegia with similar muscle strength. T12 level paraplegia. Assuming this is a complete lesion, patients affected at this level lack proprioception. They require other means to get feedback about standing balance and require a lightweight orthosis because they rarely use orthoses as a major means of locomotion. Although gathering patient history is a vital part of the evaluation, it is, more importantly, an opportunity to establish a productive patient management environment. Patients and family members have important information regarding the initial injury, previous medical care, reasons they sought additional care, and desired outcomes of new treatment. Most of this information can be gathered efficiently as either the therapist or the orthotist begins other professional evaluations. These are important patient and family management skills. One must hear from the patient or caregivers why they came to see the health care professional and their expectations of care. The therapist should not assume the family’s goals without asking, because often patient and family goals are higher than the clinicians’ expectations. Communicating at a level that is understandable is vital and demonstrates to the patient and family that the therapist is a concerned professional, thereby engendering trust and confidence. Complete and timely documentation of these findings is vital to the evaluation and treatment plan. Whether communicating with others on the rehabilitation team, insurance carriers, or legal professionals, documentation and building medical justification are essential in treating all patients.

Evaluation of the spine

Each area of the spinal column presents various combinations of motion and function. Beginning at the lumbar level as the base for upright position, the spinal column (1) protects vital organs, (2) serves as a supporting structure for the lungs to expand, (3) provides a base for the upper extremities to reach from, (4) acts as a scaffold for objects to be carried, (5) protects the central nervous system pathways, and (6) controls the upright position and motions of the head. The individual segments of the spine have relatively few complicated orthotic challenges. However, it is rare that only one segment is involved in the patient with neuropathic impairments. It is more common for two or more segments of the spine to be involved when there is a need for orthotic control. For example, supporting the head in a functional position is a major goal of orthotic intervention, but to accomplish this the orthosis must encompass the thoracic as well as the cervical spine to distribute the forces to minimize skin pressures.

When evaluating the cervical spine and head, one must (in addition to muscle testing) determine past what angulations the upright position of the head cannot be recovered. Limiting the head from assuming nonfunctional positions such as extreme extension is an easier orthotic function than holding the head upright. Many patients with neurological problems may have the strength to move in a 15- to 20-degree range of flexion and extension, lateral bend, and rotation but do not have the strength to recover the head from greater angles. Even the most pressure-tolerant soft tissue around the head does not tolerate long-term pressure from an orthosis; intermittent control and relief are a critical part of the design. Pressure directly on the ear is not tolerated at any time.

When the orthosis is desired to limit cervical motion due to unstable fractures or postoperative management, selecting the most appropriate design depends on how much motion is acceptable. Upper cervical motion is controlled with a Halo orthosis ( Fig. 32.1 ) when complete immobilization is desired. If more motion is acceptable, or for lower cervical control, a collar is more acceptable to both the treating team and the patient. Many types of cervical collars exist to optimize patient fit and control ( Fig. 32.2 ).

The thoracic and lumbar spine are almost always treated concurrently with an orthosis in the patient with a neurological deficit. The major reasons for orthotic intervention in this area are to stabilize the trunk for balance, to protect surgical correction or stabilization, and to maintain respiration. The pelvis is generally used as a base to prevent distal migration of the orthosis when the patient is sitting or standing. One must closely evaluate the degree of deformity, prominence of bony structure, skin sensation, and condition of soft tissue coverage. Many neurologically impaired patients also have other medical issues that need to be considered in orthotic design, such as a colostomy, gastrointestinal (GI) tubes, pressure sores, and other factors. Scoliosis and kyphosis are common biomechanical impairments within this patient group. Balance between correcting the spinal deformity to maintain respiratory function by use of a tightly fitting TLSO and the skin pressure it creates must be reached by the rehabilitation team. The evaluation of the spine and potential need for orthotic intervention would not be complete without recognizing the effect the desired orthosis may have on the extremities, whether the patient is ambulatory or non–weight bearing. What movements of the spine are present during ambulation, and would immobilizing the spine significantly affect the patient? Will the orthosis restrict needed shoulder elevation and arm movements? Variation in materials used for fabrication of a spinal orthosis can often significantly improve the desired outcome, increase the wear time, ease the donning process, and improve skin care. From a patient and family management standpoint, one must consider many variables in potential design of the orthosis. Can the patient or family properly don the orthosis and remove it when appropriate? Do they understand potential areas of pressure? Do they know what to do if any issues arise with fitting or skin integrity?

Evaluation of the upper extremities

Evaluation of the upper extremities requires multiple inputs from health care professionals, patients, family, and teachers because of the wide range of specific functions an individual performs daily. Unique to the upper extremity, multiple functions generally require multiple orthotic devices for activities of daily living (ADLs). Typical functions of orthoses of the upper extremity include maintenance of functional wrist and hand position, reduction of contracture or tone, transfer of force available in one area to another, and support of subluxations resulting from denervation. It is common for the neurologically impaired patient to require several orthoses with different functions for use throughout the day. Strength, ROM, condition of soft tissues, and sensation are all important evaluation factors. In addition, ambulatory status, bilateral or unilateral condition, status of vision, and condition of the spine and head must be factored into the indications and contraindications in assessment of the orthotic needs of the patient. Much more critical muscle tests must be performed in the upper extremity as opposed to the lower extremity, because minor increases or decreases in strength will dramatically alter orthotic need. For example, the C5 quadriplegic has the ability to function with a wrist-hand orthosis by providing enough wrist extension to use the tenodesis effect, which can produce a three-jaw-chuck type of grip. The difference between a functioning and nonfunctioning orthosis is minor, not only because there is limited muscle strength, but also because minor inefficiencies in the tenodesis splint (from friction or malalignment) could reduce function to unacceptable levels. Patients with unilateral involvement have far different needs than the bilaterally involved. The patient post-CVA with unilateral involvement may use a positional wrist-hand orthosis to prevent contracture and injury and a supportive shoulder orthosis to prevent shoulder subluxation ( Fig. 32.3 A–C). In these cases the other extremity becomes dominant, and there is little need to fabricate complex orthoses for use by the affected extremity.

The patient with bilateral involvement presents a much different picture. Consideration for grooming, feeding, mobility, and so on must be factored into the desired expectation during evaluation. The case of the patient with neurological impairments who requires orthotic intervention is complex because this patient typically has involvement of the trunk, head, and lower extremity. These patients require specialized wheelchairs and seating systems. Evaluation is most effective with all rehabilitation team members present to establish a treatment plan. Orthotic treatments maximize what limited muscle strength and ROM the patient may have. Orthoses that are used during the day to maximize function are often replaced with positional orthoses at night to preserve gains and prevent decline in ROM. The occupational therapist provides most of the functional and positional orthoses for the upper extremity. In the current rehabilitation environment, many occupational therapists work directly with orthopedic hand specialists and trauma physicians. They use low-temperature materials to mold custom devices specifically designed for protecting surgical reconstruction or promoting or maintaining ROM or for use as assistive devices.

Evaluation of the lower extremities

Evaluation of the lower extremity offers additional challenges owing to the role of ambulation and its value to independence for the patient and caregivers. ROM, strength, existing deformity, proprioception, muscle tone, soft tissue condition, and sensation must all be evaluated. Where appropriate, weight-bearing evaluation and gait analysis are completed. Patient and family assessment as it relates to the ability to comprehend and follow instructions is extremely important because the potential for injury may outweigh the benefit of orthotic intervention to transform a patient from being non–weight bearing to having limited ambulation. Lack of ROM at the hip and knee will significantly decrease the duration of potential ambulation or may totally inhibit ambulation. Lack of ROM at the hip and knee is more critical than lack of strength. In the foot and ankle, the need for normal ROM is even more critical for efficient standing balance and ambulation. Orthoses of the lower extremity provide a combination of force lever arms acting about a joint axis at the knee, hip, or ankle. These joints are significantly compromised by the lack of ROM. Using the lever arm principles within the lower extremities substitutes for the lack of strength. For example, by blocking dorsiflexion of the ankle, the ground reaction force provides a posteriorly directed force in the sagittal plane during stance that stabilizes the knee. If the patient lacks the ability to get the ankle to a neutral alignment due to a plantarflexion contracture, this dorsiflexion limitation provides its own lever arm, which will result in a variety of undesirable forces and actions. Genu recurvatum, foot or ankle varus, a shortened stride length on the unaffected side, and the heel rising out of the shoe are common signs of this problem. These issues are further complicated when poor proprioception, spasticity, and lack of sensation are present. Lack of ROM at the ankle creates many symptoms in the lower extremity but is often overlooked during evaluation as the cause of these problems.

Genu varus and genu recurvatum are common deformities of the patient with neurological impairments. A number of factors create these problems. In addition to the ankle ROM limitations, leg length differences, lack of quadriceps strength, and lack of proprioception can create deformities about the knee. The patient with a history of poliomyelitis may have both a short extremity and weak knee extensors, which lead to genu recurvatum along with coronal plane deformity. However, reducing the genu recurvatum without protecting against instability created by undesirable knee flexion would be a mistake. Patients with lower motor neuron disease have excellent proprioception, which is the reason they protect the unstable knee by hyperextending it. They may even use force from their upper extremity by pushing posteriorly on the femur with the hand to increase knee stability. Allowing some knee hyperextension in the orthotic design may be necessary to stabilize the knee during gait. Polio survivors are closely attuned to the amount of knee extension that is necessary to maintain stability, and the orthosis can be designed around this angulation. A patient with upper neuron impairments, such as a patient who has had a CVA, has a similar knee alignment in gait. However, the typical cause of this patient’s deformity is different. The upper motor neuron impairment often causes reduced proprioception even when there is adequate strength to stabilize the knee. Hemiplegic patients may present with knee hyperextension due to poor proprioception and reduced ankle ROM. An orthotic design for this population may need to have a heel lift to accommodate the plantarflexion contracture, and this will also help to limit knee extension in gait.

Reduced strength and ROM limitations about the hip limit effective ambulation and leave a patient much more reliant on trunk stability and upper-extremity ambulatory aids. Hip flexors are more critical than hip extensors because they serve to advance the limb in reciprocal gait, whereas lack of hip extensors is compensated for by the strong hip ligaments, which tighten for stability in extension. Limited ROM to at least neutral extension about the hip creates major challenges for the patient, even if the patient has excellent upper-extremity strength. This lack of ROM will not allow stability in standing once force is removed from the upper-extremity ambulatory aids (cane or walker). The patient with a hip flexion contracture will have difficulty standing from a seated position and will stand with excess hip flexion, knee flexion, and lumbar lordosis. Once standing, they will have difficulty advancing the involved side to initiate a step as the hip flexors are already shortened and are at a mechanical disadvantage. It is difficult for the patient with a hip flexion contracture to stand without support because this alignment creates a hip and knee flexion moment that will pull them into a sitting position. Maintaining hip ROM is an important goal for the rehab team, and encouraging the patient to perform stretching exercises while supine and limiting time seated with excess hip flexion is helpful. Creating hands-free standing balance is a highly desirable outcome of orthotic intervention. The patient is then able to use both upper extremities for ADLs.

Orthotic evaluation

In addition to the comprehensive assessment of the patient which involves assessment of the patient’s ROM, muscle strength, skin condition, and spasticity, it is essential to determine appropriateness of the orthotic device being prescribed for the patient. This involves both a static and dynamic evaluation. Static evaluation consists of observing fit of the orthosis on and off the patient and dynamic evaluation consists of observation of weight-bearing alignment, gait, and functional activities both with and without the orthosis and determining whether the design meets the expectations and goals for which it was prescribed. Table 32.1 summarizes some of the key aspects of this evaluation. It is imperative to work closely with an orthotist for critical adjustments or modifications to optimize the fit and function of the device to best meet the goals of the patient and the rehabilitation team.

TABLE 32.1

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