PITFALLS AND COMPLICATIONS ENCOUNTERED WITH USE OF ORTHOSES

Unnecessary Bracing and the Importance of Follow-up

The importance of avoiding unnecessary bracing or overbracing has already been reviewed. After bracing, the patient should be followed by the physician for an extended period to assess any changes in bracing needs, especially for conditions that are not static. A patient who develops foot drop due to radiculopathy or peroneal palsy, for example, may recover enough dorsiflexion to obviate the need for the orthosis. It is not uncommon for patients to use heavy braces for several years until a physician or other health-care provider discovers that it is no longer needed. By avoiding unnecessary bracing and providing frequent follow-up, such occurrences can be prevented . Of course, it may also be discovered that more aggressive bracing is needed, particularly with progressive conditions.

Skin Breakdown

Patients with severely impaired sensation, significant edema, spasticity, deformity, or contractures are at particular risk for skin breakdown and require extra attention in the design of the brace and subsequent follow-up. The navicular tubercle, the malleoli, and the area of the trim lines of the orthosis are particularly likely problem points. Extra-soft lining, extra-depth footwear, use of more accommodating materials, and patient education reduce the incidence of breakdown, although the extra lining will increase the bulk of the brace.

When discomfort, erythema, or actual skin breakdown occurs, a particularly useful technique is to mark the affected area with a transferable medium such as lipstick and to have the patient don the brace. Areas of higher pressure will have more of a mark, and this information can be used to determine exactly how to modify the brace and where to relieve pressure. It is important to realize, however, that breakdown is not always an indication that the brace is too tight but may result from dynamic biomechanical gait abnormalities. For example, if theAchilles tendon is too tight, the patient may pronate in the brace, substituting subtalar motion for ankle motion and resulting in pressure and friction in the navicular area. In such a case, the solution may be a heel lift to accommodate the deformity rather than flaring of the brace.

Problems Resulting from Limitation of Ankle Range of Motion

Certain problems may arise when ROM at the ankle is severely limited either by disease or by a solid, semisolid, or metal upright AFO. In normal gait, the foot rapidly plantar flexes upon heel strike, controlled by eccentric contraction of the anterior compartment musculature to stabilize the knee. A fixed ankle will prevent this response, and the tibia will continue forward abruptly to achieve foot flat, forcing the knee and hip into excessive flexion. The quadriceps, which may already be weak due to underlying neuromuscular disease, are thus under an increased demand to prevent buckling of the knee. One solution is to cushion or bevel the heel of the shoe so as to move the ground reaction force further anterior and thus diminish the flexion moment at the knee. Because this moves the ground reaction force anterior to the ankle as well, it aids weak ankle dorsiflexor muscles by decreasing the plantar flexor moment. Derived from prosthetics jargon, the cushion heel is often referred to as the SACH, or the solid ankle cushion heel. Patients with mild hyperextension of the knee or genu recurvatum can be treated with a small heel lift placed under the AFO or external to the shoe. A heel lift places the ankle in plantar flexion and may result in an increased extension moment at the knee.

A rocker sole added to an orthopedic shoe mimics the action of the ankle and metatarsophalangeal (MTP) joints and aids in roll off, push off, and unweighting of the metatarsal heads, simulating ankle dorsiflexion. Use of a rocker sole requires a stiff sole and an additional elevation of one-quarter to one-half inch to the heel on the rocker side and to the heel and sole on the contralateral side to avoid a resulting leg length discrepancy. The combined use of a SACH heel and rocker sole in the shoe simulates dorsiflexion and plantar flexion in the gait cycle, even though the ankle is relatively fixed. This SACH plus rocker combination can be used whenever there is minimal or no motion at the ankle, as for example because of fusion, fracture, cast immobilization, orthosis design, pain, or arthritis.

Bilateral bracing poses a particular challenge. When rigid ankle AFO are used bilaterally, the contralateral limb is prevented from compensating, thus compounding the difficulties. Consequently, patients seldom tolerate bilateral solid AFO, and hinged or flexible joints should be used.

A solid ankle affects the patient during transitional movements. Normally, when rising from a chair, for example, the ankle is dorsiflexed to move the center of gravity anteriorly; thus, with a solid ankle, alternative strategies must be used. This is also true for movements such as bending or climbing up stairs. Because the ankle is locked, balance adjustments must be made at the hip or by stepping, which can be awkward.

Cane and Crutch Palsy

Those who depend heavily on their canes, such as poliomyelitis patients, should be informed of the possibility of developing secondary compression neuropathies in the hand. This is particularly true for elderly patients as they become more reliant on assistive devices for ambulation or for those who prematurely abandon their AFO or KAFO, causing them to lean on their canes excessively.

The syndrome of cane palsy is due to a lesion at the palm of the hand distal to the carpal and ulnar tunnels. It results in ulnar and median intrinsic muscle weakness and wasting with minimal sensory loss due to involvement of the terminal motor branches of the deep palmar branch of the ulnar and recurrent branch of the median nerves. There are treatment options to reduce pressure on these nerves, including use of a KAFO contralateral to the affected hand, weight control, or use of platform crutches, a walker, or a wheelchair.

Crutch palsy results from compression of the radial nerve at the fascial edge of the latissimus dorsi muscle by axillary crutches. Unlike the Saturday night radial nerve palsy or posterior interosseous nerve entrapment syndrome, there is weakness of the triceps muscle. As with cane palsy, therapy is aimed at reducing pressure on the nerve with the temporary use of platform crutches instead. The lesion is usually a neurapraxic one, and the prognosis for full recovery is good. Axillary artery thrombosis can rarely follow prolonged use of axillary crutches (13).

Other Compression Neuropathies

Carpal tunnel syndrome occurs in patients who use canes and crutches, whereas ulnar neuropathy at the elbow occurs in those who use wheelchairs. Better padding of the handle and armrest of the wheelchair reduces the latter complication.

Unauthorized Alteration

Braces that are altered by patients, often beyond repair, necessitate the fabrication of a new one. Those patients likely to engage in this activity should be educated as to the importance of leaving modifications to the appropriate professionals. It is particularly helpful to provide good communication and access to the orthotist so that patients can resolve problems before becoming frustrated and attempting to solve them themselves.

MANAGEMENT OF SPECIFIC ISSUES

Upper Motor Neuron Disorders

The spasticity and clonus of a UMN disorder may be exacerbated by a solid AFO. Even patients with moderate ankle clonus, however, can do well with a dorsiflexion assist brace, sometimes even a PLSO, without aggravating the clonus. When spasticity is severe, a solid AFO is indeed appropriate. If ataxia is present, bracing can be detrimental; in some cases, however, weighting of the extremity can improve gait, and in these patients bracing may be beneficial.

Dropped Head Syndrome

This syndrome is due to focal weakness of extensor neck muscles in association with inflammatory myopathy, myasthenia gravis, or motor neuron disease (14-16). A lightweight cervical orthosis that assists extension while providing firm support may be more beneficial than traditional restrictive cervical orthoses. Two such braces are pictured in Fig. 6 and are designed to allow for tracheostomy care.

Amyotrophic Lateral Sclerosis

The braces of a patient with amyotrophic lateral sclerosis should be supportive, minimally restrictive, and lightweight. For dorsiflexion weakness at the ankle, a PLSO is preferable to a heavier brace. A lightweight cervical orthosis should be considered if significant extensor neck weakness is present.

Loss of Sensation and Balance

Although it is commonly stated that patients with diminished sensation tolerate plastic braces poorly due to decreased proprioceptive input, however, when an AFO bridges the affected areas, as for example in stocking-and-glove neuropathies, the orthosis may actually transmit vibratory and position stimuli proximally to less affected areas. This can provide important feedback, allowing more physiologic and therefore more functional ambulation (11). Whenever orthoses are used in patients with decreased pain and light touch sensation, there should be frequent inspection of the insensate skin, particularly with plastic orthoses because they make intimate contact with the skin.

Charcot-Marie-Tooth Disease

Charcot-Marie-Tooth disease patients do well with plastic AFO because of their lighter weight. In general, a custom-made brace is appropriate due to diminished sensation and significant foot deformities. Patients with distal sensory and proprioceptive loss may shift their weight at the ankle or knees in an attempt to sense the supporting surface at more proximally placed Joints where proprioception is intact. Similarly, with severe sensory loss, a cane augments balance by transmitting proprioceptive input to the upper extremity.

The development of a cavus deformity is probably hastened by substitution of toe extensors for weak dorsiflexor muscles and thus may be delayed by early bracing. Dorsiflexion weakness is best managed with a lightweight spring-loaded dorsiflexion-assist orthosis such as a custom-made PLSO with accommodative footwear. When the deformity is severe, posterior tibial transfer, osteotomy, or tarsal arthrodeses may be necessary.

Polio and the Post-Polio Syndrome

Bracing in poliomyelitis and the PPS is often successful because of the spotty nature of the weakness, lack of spasticity, and intact sensation. The continued use of orthoses and adaptive devices is often indicated in these patients despite their ability to get by without them. Frequently, patients with poliomyelitis will have spent decades with minimal or no bracing, and with advancing age and possibly weakness due to PPS, more aggressive means are often needed for safe ambulation to prevent degenerative changes, improve stability, and prevent malalignment of affected Joints. Assistive devices such as canes, crutches, wheelchairs, and scooters are often useful as well. Cane palsy may occur in PPS due to increased reliance on assistive devices.

Acute Inflammatory Demyelinating Polyneuropathy or the Guillain-Barré Syndrome

Most patients with Guillain-Barré syndrome recover significant motor function. Nonetheless, an important consideration is to prevent contractures and to reduce overuse fatigue during recuperation. If contractures develop, they will usually be more detrimental to overall function than the residual neuropathy, and heavy bracing should be avoided.

Neuropathic Foot Drop due to a Compartment Syndrome

The anterior tibial compartment syndrome is frequently caused by trauma or fracture and complicated vascular surgery and often results in ischemic peroneal neuropathy. Early weight bearing and ambulation are necessary to prevent plantar flexion contracture. In addition to standing and stretching in the tilt table, early application of a dorsiflexion-assist AFO should be contemplated. An open fasciotomy wound does not preclude bracing, because an effective dorsiflexion-assist AFO can be designed to minimize pressure on the wound. The surgeon should be informed of the extreme importance of preventing contractures even if this interferes with closure of the wound.

Myopathies

The use of orthoses in myopathies is limited. These diseases typically affect proximal muscles more than distal, and orthotic control of proximal Joints such as hips, trunk, and shoulders is highly unsatisfactory. Myotonic muscular dystrophy, inclusion body myositis, and facioscapulohumeral dystrophy can present with quadriceps weakness and foot drop, requiring bracing.

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Fig. 6. Headmaster collar (above, and Canadian collar (below).