Adaptive Therapy and Bracing in CMT (continued)

Page 5 of 5

ADAPTIVE EQUIPMENT

Ambulation aids such as canes, crutches, and walkers are technically upper extremity orthoses that provide increased stability and safety. They can reduce the load on one or both lower extremities and improve sensory feedback by transmitting information to the upper extremity. They also alert the public that the user needs special consideration. The use of these devices requires functional upper extremities and adequate strength.

Canes

A cane is the most basic adaptive device and supports up to 25% of body weight (17). In unilateral conditions, it is used on the opposite side of the impairment to reduce the load on the affected lower extremity, but they can also be used bilaterally. Wide-based canes are most stable and consist of a platform with three or four legs connected to a shaft and handle, with variable base widths. Although heavier and clumsier than a standard cane, they stand by themselves so that it is not necessary to lean or hook them when not in use. When a cane is used for a prolonged period of time, a functional grip cane, as opposed to the standard C-cane, improves comfort and minimizes the risk of developing problems from excessive pressure to the palm. When fitting a patient for a cane, the top should come up to the level of the greater trochanter, resulting in 20 to 30° of elbow flexion.

Crutches

Crutches are indicated when the impairment is more severe and requires greater support. Whereas a cane conveys balance and sensory feedback, crutches allow the transfer of a significant amount of weight to the upper extremities. This may be problematic, however, in neuromuscular diseases when there is accompanying upper extremity weakness. Bilateral axillary crutches transfer 80% of body weight away from the lower extremities. Although they are commonly padded, this should be avoided because it may encourage increased axillary weight bearing and lead to compression neuropathy of the radial nerve in the axilla. The crutch handle should measure similar to a standard cane, and because it is oriented obliquely to the floor, the total length of the crutch should be about 3 to 5 cm longer than the distance from the anterior axillary fold to the bottom of the heel.

Nonaxillary crutches are less cumbersome and can transfer 40 to 50% of body weight. The most common of these, Lofstrand crutches, consists of an adjustable aluminum shaft with a molded hand piece and an adjustable forearm piece with an open cuff. This design allows the user to release the hand piece while retaining the crutch, thus freeing the hands for other activities. The wooden forearm orthosis, or Kenny Stick, is basically an axillary crutch with shortened proximal end at the level of the forearm and a closed forearm cuff. For patients with distal weakness, they are even easier to retain than Lofstrand crutches (18). Canadian crutches are similar to Lofstrands with longer uprights and a second half cuff that extends above the elbow. The crutch tips for patients with triceps weakness should be checked routinely for wear. Special tips are available for use in the rain, ice, and snow. Patients that cannot bear weight along the forearm or those with wrist or hand weakness due to arthritis, fractures, and neuromuscular diseases should consider platform crutches.

Walkers

A walker should be used when maximum stability is needed, particularly in disorders of balance and coordination. They require good bilateral grasp and arm strength and result in a slowed and more awkward gait. As with crutches, a platform can be added when weight bearing through the forearm is problematic. Although they provide less stability, rolling walkers allow for a more natural gait pattern and require less upper extremity coordination. They are particularly useful in patients with Parkinson disease because they minimize starts and stops. These ambulatory aids may be unsafe if the user is unable to keep themselves within the base of support of the walker. Newer lightweight walkers are more efficient for patients with neuromuscular disease.

Wheelchairs

A wheelchair is indicated when walking becomes unsafe, impossible, or impractical, even with the use of the above devices. Quite commonly, the patient and their family see the failure to ambulate as a defeat. The physician must emphasize that their wheelchair allows safer and more efficient mobility. Some patients are able to ambulate indoors or even limited distances outdoors but require a wheelchair for longer distances to improve their safety and level of independence. A standard wheelchair is inappropriate for patients who spend most of the day in them. A great variety of lightweight designs and different cushions, seat backs, headrests, armrests, and other components are available. Complex wheelchairs should be prescribed with the input of a multidisciplinary team, including the physiatrist, other physicians, therapists, and the equipment vendor. Concomitant with the cessation of ambulating, complications due to underlying disease and increased immobility, including scoliosis, pressure ulcers, deconditioning, and contractures, can rapidly arise, requiring additional attention.

A manually powered wheelchair is preferable to a motorized chair because they are more durable, lighter in weight and therefore easier to transport, less expensive, and allow greater access in confined spaces. They are often the only significant exercise that a patient may receive. A motorized wheelchair or scooter should only be considered when a patient is unable to propel themselves independently, when greater mobility is required for independence at work or school, and to avoid undue strain upon already weakened limbs. Prescription considerations are similar to those for manual chairs; numerous control devices are available to accommodate various impairments.

UPPER EXTREMITY ORTHOSES

Upper extremity orthoses are primarily used to prevent or minimize contractures and to improve function in patients with neuromuscular diseases. There are two basic types, static and dynamic, with the former being a fixed or rigid device and the latter allowing some movement. The term functional is sometimes applied to a splint designed to directly increase function, as opposed to resting splints, which are designed to prevent or stretch contractures.

As with lower extremity bracing, it is important to keep in mind the purpose of the orthosis and whether it is likely to be used. In functional bracing, patients are only likely to continue to use orthoses if this enables them to do things that they otherwise could not. A patient with bilateral deficits is more likely to use a functional orthosis because the other hand may not be able to compensate. With resting splints, comfort and ease of donning and doffing are paramount. Cosmesis is much more of an issue with upper extremity orthoses given the visibility of the hand and another reason why an upper extremity orthosis may be rejected. Orthoses that cover the volar aspect of the hand can be problematic because they interfere with sensation, which is a primary function of the hand. Sometimes, this can be alleviated by a dorsal design, minimizing the impact on sensory feedback. Orthoses that hinder sensation can be used at rest, whereas a less cumbersome one can be used during activities.

Wrist-Hand Orthoses

These are the most common types of upper extremity orthoses and usually consist of a volar support with dorsal forearm straps. When indicated, variations are available with the support applied to the dorsal surface and ventral straps.

Resting Hand Splint

This widely used volar splint is designed to prevent contractures by maintaining the hand in a functional position, preserving the balance between extrinsic and intrinsic muscles. It also provides joint protection and is applicable to UMN conditions that result in increased tone.

Tenodesis Splints

The fingers normally flex somewhat with wrist extension and extend with wrist flexion. So-called tenodesis is enhanced by orthoses that use a hinged parallelogram design to approximate the thumb and fingers when the wrist is extended. The patient should be prepared and trained before the brace is ordered, and the finger flexors should be left to develop mild contractures so that with passive wrist extension, the distal and proximal interphlangeal langeal joints flex, aiding in tenodesis. The classic indication for these is a C6 tetraplegia, although they can also be used in other conditions in which hand weakness is significant.

Wrist Cock-up Splint

This static splint supports the wrist in a functional position of about 20 to 30° of extension and improves grip by placing a slight stretch on the finger flexors (tenodesis) providing protection and functional improvement when there is weakness of wrist extension and grip. For good leverage, it should begin about two thirds the way up the forearm and should extend no further than the distal palmar crease. This splint is often used in carpal tunnel syndrome, in which case a more neutral wrist position of 0 to 20° of extension is preferable.

Balanced Forearm Orthosis

This orthosis can be attached to a supporting structure such as a wheelchair or pelvic band and consists of a ball-bearing hinge joint at the elbow with a forearm trough. It is configured to support the forearm and allow for flexion and extension at the elbow along the horizontal plane, essentially eliminating the effect of gravity. In cases of proximal weakness, including the shoulder with relative sparing of the hand, it can increase independence in the activities of daily living, but elbow strength should be grade 2 or more. An overhead sling arrangement can also be used for trial purposes. When shoulder strength is adequate but elbow weakness is a problem, a dynamic flexion-assist orthosis can be made by using arm and forearm cuffs connected by a spring joint. Elbow extension can usually be substituted by gravity (19). In cases of complete paralysis, tendon transfer may be beneficial.

Shoulder Slings

The basic shoulder sling is known to virtually everyone. It positions the arm in adduction and internal rotation with the elbow flexed. By limiting motion at the shoulder, it contributes to contractures, and minimizes opportunities for the patient to reincorporate use of the extremity into the activities of daily living; it and should therefore only be used acutely or for protection during transfers. A sling with a humeral cuff and chest straps that support the humerus and reduce subluxation while interfering much less with shoulder motion should be used for shoulder subluxation resulting from paralysis.

SUMMARY

The judicious use of orthoses and adaptive equipment can greatly benefit the patient with a neuromuscular disease. A thorough knowledge of the biomechanics of ambulation and upper extremity function and the capabilities and limitations of bracing are necessary to prescribe orthoses correctly. The physician should focus on function, maintenance of ROM, and joint preservation, although the patient will often be more concerned about cosmesis, comfort, and ease of donning and doffing them. If the patient agrees with a chosen orthosis or brace, compliance will be best when the goals of both the patient and physician are suitably addressed.

ACKNOWLEDGMENT

Lynn Nichols, CO, J-V-Prosthetics & Orthotics Inc. for providing information and samples oforthoses.

REFERENCES

An extensive reference list can be found in Motor Disorders, edited by David S. Younger, MD, Lippincott Williams & Wilkins, 1999, pgs. 466-467.