The WalkAide® Functional Electrical Stimulation System
Figure 1: Options for Treatment of Foot Drop AB
Figure 2: The WalkAide System Delivering Electrical Stimulation to the Common Peroneal Nerve and Produces Timed Contraction of the Dorsiflexor Muscles
A: A traditional ankle foot orthosis; B: The WalkAide Functional Electrical Stimulation System.
the knee (see Figure 1B). The device includes tilt sensors, with accelerometers and inclinometers to measure the speed and position of the lower leg to trigger stimulation, and a pulse generator and self-adhesive electrodes to deliver the electrical current. The entire device is powered by a single AA battery. With the WalkAide, low intensity pulses of electrical current, of sufficient duration and amplitude to produce action potentials in peripheral nerves, are delivered from the generator to transcutaneous self-adhesive electrodes placed over the common peroneal nerve near the fibular head (see Figure 2). The stimulated action potentials are transmitted orthodromically to the superficial and deep peroneal nerves, and thence to the neuromuscular junctions of the muscles of the lateral and anterior compartment of the leg. This causes acetylcholine release at the neuromuscular junctions and muscle contractions to produce active ankle dorsiflexion. The tilt sensors trigger the electrical current pulses to start just as the patient enters the swing phase of gait and to end when swing ends. This produces dorsiflexion throughout swing phase, minimising or entirely eliminating foot drop and normalising the gait pattern.
Features and Advantages of the WalkAide Functional Electrical Stimulation System FES has a number of advantages over an AFO for treatment of foot drop (see Table 1). The active contraction produced by FES can help to prevent the muscle atrophy and range of motion loss associated with passive support offered by an AFO. In addition, the active muscle contractions and joint motion stimulate muscle spindles, Golgi tendon organs and joint proprioceptors, increasing sensory awareness and input to the CNS. This sensory input improves motor output, including the quality and control of movement patterns, the degree of reflex activity and the balance of muscle tone. The repetitive active movement stimulated by FES-facilitated gait also contributes to motor learning and neuroplastic changes in the CNS.18
By establishing and
promoting active motion in patients with foot drop, FES fosters long-term improvements in motor control, balance of muscle activation and quality and efficiency of gait. Unique features of the WalkAide FES System make it particularly well suited to the treatment of foot drop. The WalkAide is the only device on the market that uses tilt sensors to detect the angular velocity of the leg during gait
EUROPEAN NEUROLOGICAL REVIEW
and to use this information to determine when to trigger stimulation, and thus muscle contraction, during the gait cycle.19
Most other
devices use a heel-sensor-triggered switch to detect the beginning and end of swing phase. Since heel switch devices stimulate whenever the heel is off the ground, stimulation may occur when the heel, but not the toes, are raised. This can promote inefficient walking
19
Figure 3: The WalkAide System Has the Unit and Cuff in a Single Component and Can Be Used Without Shoes
Table 1: Comparison of Benefits of Funtional Electrical Stimulation and Ankle Foot Orthosis for Foot Drop
Reduces foot drop Improves gait mechanics
Prevents loss of passive ROM Prevents loss of active ROM Active muscle contraction Slows muscle atrophy Increases input to muscle
spindles, GTOs, proprioceptors Promotes motor learning
Promotes neuroplastic changes
FES Yes Yes Yes Yes Yes Yes Yes
Yes Yes
AFO Yes Yes Yes No No No No
No No
AFO = ankle foot orthosis; FES = functional electrical stimulation; GTO = Golgi tendon organ; ROM = range of motion.
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