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Overview of the Causes, Treatment, and Orthotic Management of Lower Limb Spasticity

Dulcey Lima, C.O., OTR/L

Introduction

Millions of adults and children world-wide have disabling physical conditions which are manifested by spasticity. Orthotists have been managing spasticity since the earliest days of the profession. The high frequency of upper motor neuron disorders such as cerebral vascular accidents, cerebral palsy, multiple sclerosis, and other diseases which produce spasticity of varying degrees, have filled orthotists' caseloads.

Unfortunately, little formal training is provided in the field to enhance the orthotist's understanding of the factors underlying spasticity and methods to control it. Spasticity is well documented in the literature of other health professionals, such as occupational and physical therapists. Anatomists, physiatrists, neurologists and orthopedists have also contributed to the body of knowledge. Presently these professionals are taking an active role in orthosis design for spasticity management and have begun to experiment using low temperature materials. In search of long-term definitive solutions to their patients' problems, these allied professionals have sought the expertise of orthotists who have a strong background in biomechanical principles and material application. The collaboration of the allied health professions is beginning to produce new and improved orthotic designs and a shift in traditional orthotic management. The orthotist who has a balanced knowledge base can co operate with other team members to produce the orthosis which will achieve maximum results. This overview of literature regarding spasticity management will review the writings of orthotists and other team members and will provide a foundation for spasticity management.

Reflexes of the Foot

In 1960, William Duncan, an orthopedic physician from Seattle, Washington, wrote an article entitled, "Tonic Reflexes of the Foot," which was published in the Journal of 13one and Joint Surgery. Duncan studied the reflexes which exist in the foot, how they are elicited, and at what age these reflexes appear and disappear. Since he knew that spinal cord injured patients and children with cerebral palsy often exhibited these reflexes pathologically, he felt that an understanding of the etiology of reflex induced deformities would be essential to understanding how to manage these problems.'

Duncan found that four tonic movements of the foot can be elicited in normal infants in the first year and in some older children with cerebral palsy. The tonic movements are: (1) toe grasp reflex; (2) inversion reflex; (3) eversion reflex; and (4) dorsiflexion reflex. Through vibratory stimulation, Duncan determined that the reflexes were stimulated in particular reflexogenous areas. These reflexes, if unopposed, can cause deformity. He suggested that these slow, tonic reflexes are distally located trigger mechanisms that initiate balance reactions in normal infants. Duncan found that he could extinguish the reflex three ways. The first way was to temporarily block the reflexogenous area with procain or ethylchloride spray. The second method was to perform a neurectomy of the cutaneous nerve supply in the area or to perform a tenotomy of the prime mover. The third way, and the one which is most related to orthotic management of spasticity, is to stimulate the reflex that is antagonistic to the deforming reflex.

Specifically, Duncan found that stimulation of particular reflexogenous areas of the foot had an effect on more proximal musculature. When the medial border of the foot near the head of the first metatarsal is stimulated it triggers the anterior and posterior tibial muscles with associated activity in the internal hamstring. When the lateral border of the foot near the head of the fifth metatarsal and base of the little toe is stimulated, primary muscle activity is in the peroneals, especially the peroneus brevis. More proximally, the vastus lateralis and tensor fascia latae were brought in. The dorsiflexion reflex was elicited in response to stimulation of the central portion of the plantar surface of the heel (Figure 1) . The tibialis anterior was facilitated and the vastus medialis also responded. Duncan found that all four reflexes are intensified by the upright position and are absent in sleep. The deforming potential is the dominance of a single reflex causing dynamic muscle imbalance.

The Basis of Spasticity

In 1977, Bishop wrote a series of articles related to spasticity documenting the effects of spasticity. "The spastic patient practices' involuntary unwanted motor responses... This repetitive neural activity may result in relatively permanent changes in neural function."² The abnormal joint positioning, postures, and unequal distribution of muscle activity imposed by spasticity can produce profound and lasting changes in joints and muscles. Hyperactive muscles hypertrophy and grow stronger.

In a separate article, Bishop wrote that spasticity occurs because the inhibition normally provided by the suppresser areas of the brain is not present.³ Brain lesions disrupt the linkages and upset the balance between suppresser and facilitory areas of the brain. The major consequence of the disruption of the balance is the excess facilitation of gamma motor neurons resulting in hypersensitive muscle spindles. This results in hyperactive phasic stretch reflexes, hyperactive tonic reflexes, and clonus.

Treatment

A variety of sources are reporting a number of treatments which are being utilized for spasticity management. Centrally acting drugs such as valium, dantrium and baclofen are used to depress the lateral reticular formation and work to control gamma motor neurons. Drug treatment is sometimes contraindicated in patients who become lethargic and drowsy or who experience a loss of voluntary muscle strength when taking the medication. There are a number of surgical procedures used to reduce spasticity. Among them are peripheral neurectromy, tenotomy/tendon transfers, rhizotomy, and myelotomy or cordotomy. Alcohol blocks are sometimes used at the muscle/motor point, peripheral nerve, or nerve root. Physical therapists utilize a variety of media including cooling, vibration of the antagonist, biofeedback, re-education, and postural righting reactions. Proprioceptive neuromuscular facilitation is another technique which has been used for many years, especially in the treatment of stroke patients.⁴

Therapists generally incorporate weight bearing into their treatment program for patients with spasticity. In a 1981 study done in Sweden, it was found that weight bearing, even in a plantar flexed position, resulted in a reduction and an inhibitory effect on pathological muscle tone.⁵ The best results were obtained, however, when the patient bore weight with feet dorsiflexed, which put stretch on the plantar flexors of the feet. Standing in this posture showed a marked reduction of the passive restraint to dorsiflexion of the foot.

Neurodevelopmental treatment is an approach taught by Berta Bobath. Bobath states that since a lesion "in effect cuts off higher integrated activity and produces a short circuit, then an attempt should be made to change the motor output by giving the patient more normal sensations of tonus and movement. "6 The patient must be helped gradually to gain control over his abnormal reflex activity, to bypass the "short circuit" into abnormal patterns, and so to enable more normal patterns to be estab- lished again. Bobath sees the need for orthoses when there is great sensory loss combined with medial-lateral instability and paralytic equinus. Generally, Bobath sees orthoses as having the following disadvantages:

• The orthosis which does not allow plantar flexion also prevents extensor activity at the knee and hip. The hip remains in some flexion and is unstable. To stabilize the knee, the patient locks it into hyperextension.
• Balance at the ankle cannot develop because activity and sensation of ankle movement is limited with resultant muscle wasting.
• Ankle clonus can be produced when stretch reflexes are stimulated.

An article written by Bevery Cusick, P.T. in December 1988, draws from many sources to delineate the goals of orthotic management. Although her points are addressed to the management of children, her goals apply to many adults with spasticity. Cusick's goals of orthotic management are:

• Prevention of deformity.
• Correction of soft tissue deformity.
• Control of undesirable motions while permitting motion which occurs normally.
• Protection of weak muscle.
• Control of deviations associated with tonus abnormality.
• Enhancement of experience for those patients who can experience upright posture with the support of biomechanical support devices.

Orthotic Management

For many years, the metal double upright AFO has been used to control plantar flex-ion resulting from moderate or severe spasticity or to control a flaccid extremity. This AFO provides stability in the saggital plane, promotes medial-lateral stability, and can be used to correct varus or valgus by incorporating an ankle control strap. By using a double adjustable ankle joint, the orthosis accommodates changes throughout the patient's rehabilitation process.

With the arrival of high temperature plastics, orthotists began fabricating more cosmetic and lightweight ankle-foot orthoses. These orthoses allowed for greater control of the foot/ankle complex because they could be custom-molded and did not stretch out like a shoe. Unfortunately, plastic orthoses lacked the versatility of the double adjustable ankle joint and were generally set rigid ly at 90° or in slight plantarflexion to compensate for shoe heel height.

Coinciding with the movement toward plastic orthoses, therapists began experimenting with plaster and low temperature splinting materials. Articles appeared in the physical therapy literature in the 60s and 70s about the benefits of serial and inhibitive casting. Casting used plaster which was readily available and was inexpensive. Often, tone was observed to be reduced throughout the entire body when even one extremity was casted. In a 1979 article by Sussman and Cusick, the authors stated that "enhanced mobilization is possible with tone reduction achieved by inhibiting the positive support response and plantar flexion reflex.

In 1975, Rosenthal, in conjunction with William Miller, C.O., and William Schumann, C.P., developed a below-knee plastic orthosis to control genu recurvatum. The polypropylene orthosis was generally set in 5° of dorsiflexion, had a solid ankle, and because of the ankle position it prevented stimulation of the spastic calf muscles. The ground reaction force was transmitted to the knee through the orthosis which prevented knee hyperextension and forward thrust of the tibia in mid-stance.¹⁰

In the early 80s, several therapists began touring the United States teaching other therapists how to make their particular variety of tone effecting orthoses. Beverly Cu-sick taught normal and abnormal development of the child's foot and discussed indications for a number of orthoses including solid below-knee serial casts and tone-reducing AFOs (TRAFOS), which were removeable cast boots with specific components intended to alter abnormal muscle tone and facilitate more normal alignment. ¹¹ She also designed an aquaplast orthosis which was an AFO that allowed plantarflexion, but resisted dorsiflexion by using an anterior stop.

Nancy Hylton, R.P.T., taught courses on how to fabricate footplates for dynamic AFOs. These footplates were initially incorporated into a bivalved cast boot that the child could ambulate in. Hylton then experimented with the design of each child's cast boot by adjusting the trimlines to allow free dorsi or plantar flexion. When Hylton was satisfied with the optimum design for a particular child, she teamed up with Don Buth orn, C.O., to produce a definitive orthosis which could be adapted in a variety of ways to limit or allow motion and facilitate more normalized movement. Hylton discovered that tone could be effected more proximally by using key points of contact on the plantar surface of the foot and wrapping the foot medially and laterally to get total contact (Figure 2) . ¹²

Jan Utley and Isabelle Boehman incorporated orthosis design into their neurodevelopmental treatment lectures and developed the Utley Foot Orthosis (UFO). They stressed the importance of not interfering with normal postural tone, and not inhibiting transitional movements. ¹³

In 1982, Lehmann et al. evaluated a number of plastic AFO designs to determine criteria for their application to patients. They found that it was desirable to have a plastic orthosis which could be modified to provide varying degrees of dorsiflexion resistance. These requirements varied from patient to patient and the orthotist could modify the plastic orthosis by changing the trimlines. ¹⁴

In 1985, Britell, Margo Williams, C.O., and John Hayes, C.P., teamed up to design the Denver "T" ankle foot orthosis. This orthosis was designed to provide medial/lateral stability while allowing mild to moderate dorsiflexion assist without resisting plantarflexion at heel strike. They found it to be most useful with patients with some dorsiflexors or patients who fatigued over time or distance. These patients may also have equinovarus or ankle instability in stance.¹⁵

In 1986, Ford, Grotz, and Joanne Klope Shamp, C.P.O., designed an AFO which incorporated the teachings of Bobath, Utley, Duncan, and Mott. This orthosis, called the Neurophysiological AFO (NPAFO), uses a biomechanical and a neurophysiological approach to the problem of spasticity (Figure 3) . It allows normal movement of the pelvis and knee over the foot-a feature absent in rigid AFOs and promotes the development of a "propulsive pushoff." It uses key points of control in the foot and ankle to stimulate straight plane dorsiflexion, control calcaneal varus, and facilitate eversion.¹⁶

The Quigley varus/valgus control AFO is still another method of addressing the need for medial/lateral control (Figure 4) . The orthosis is designed with the option of a solid ankle or a more flexible design allowing varying degrees of plantar flexion resistance. The control strap is vacuum-formed over the cast providing total contact over the maalleoli.¹⁷

Coddington, Burleson, Rogers, and Gilbreath designed the Chattanooga articulating AFO (Figure 5) . The orthosis has an anterior section which is effective with many spastic diplegic children who sink into excessive ankle dorsiflexion and corresponding knee flexion. It has also been effective with stroke patients and others with heel cord/ hamstring tightness. It provides another alternative to the "floor reaction" AFO for many patients with spasticity. ¹⁸

Conclusion

Orthotists, therapists, and physicians throughout the United States are involved in a collaborative effort to look at the orthotic management of spasticity in a new way. The traditional method of treating patients with a solid ankle-foot orthosis is still valid and in many cases it is the orthosis of choice. It is apparent, however, that many allied health professionals are involved in a process which is generating new innovative designs and fresh ways of providing more options for the patients we serve.

Dulcey Lima, C.O., OTR/L is with Oakbrook Orthopedic.

References:

1. Duncan, W., "Tonic Reflexes of the Foot," Journal of Bone and Joint Surgery, July 1960, pp. 15-23.
2. Bishop, Beverly, "Spasticity: Its Physiology and Management," Part II, Neurophysio/ogy of Spasticity: Current Concepts, Physical Therapy, 57(4), April 1977, pp.377-384.
3. Bishop, Beverly, "Spasticity: Its Physiology and Management," Part I, Neurophysiology of Spasticity: Classical Concepts, Physical Therapy, 57(4), April 1977, pp.371-376.
4. Bishop, Beverly, "Spasticity: Its Physiology and Management," Part 1V: Current and Projected Treatment Procedures for Spasticity, Physical Therapy, 57(4), April 1977, pp.396-400.
5. Odien and E. Knutsson, "Evaluation of the Effects of Muscle Stretch and Weight Load in Patients with Spastic Paraplegia," Scandinavian Journal of Rehab. Med., 131, 1981, pp.117-121.
6. Bobath, B., Adult Hemiplegia: Evaluation and Treatment, 1978.
7. Cusick, B., "Managing Foot Deformity in Children with Neuromotor Disorders," Physical Therapy, 68(12), December 1988, pp.1903-1911.
8. American Academy of Orthopaedic Surgeons, Atlas of Orthotics Biomechanical Principles and Application, 2nd Edition, 1985, pp.277- 279.
9. Sussman, M.D., and B. Cusick, Report: Role of Short-Leg Tone Reducing Casts as an Adjunct to Physical Therapy of Patients with Cerebral Palsy," John Hopkins Medical Journal, 145, 1979, pp.112-114.
10. Rosenthal, Deutsch, Miller, Schumann, and Hall, "A Fixed-Ankle Below the Knee Orthosis for the Management of Genu Recurvatum in Spastic C.P.," Journal of Bone and Joint Surgery, 1975, pp.545-546.
11. Cusick, Lecture Notes, University of Virginia Medical Center, March 1984.
12. Hylton, N., P.T., "Dynamic Orthotics," Lecture Notes and Personal Correspondence, 1986.
13. Utley and Boebman, Lecture Notes, "Neurodevelopmental Theory," Rehab. Institute of Chicago, 1988.
14. Lehmann, Esselman, Ko, Smith, de Lateur, Dralle, "Plastic Ankle-Foot Orthoses: Evaluation of Function." Arch. Phys. Med. Rehabil., 64, 1983, pp.402-407.
15. Britell, M.D., Hayes, C.P., Sherbon, Williams, C.O., "The Denver 'T' Ankle-Foot Orthosis: A Unique Orthotic Approach in Selected Hemiplegic Patients," Orthotics and Prosthetics, 39, pp.26-29.
16. Ford, Grotz, Shamp, "The Neurophysiological Ankle-Foot Orthosis," Clinical Prosthetics and Orthotics, 10(1), 1986, pp.15-23.
17. Quigley, J. and M. Quigley, C.P.O., ley Varus/Valgus Control AFO," Clinical Prosthetics and Orthotics 1989.
18. Coddington, Burleson, Rogers, and Gilbreath, "Useful Modifications of the Plastic AFO," Presented to American Academy of Orthopedic Surgeons 55th Annual Meeting, 1988.