Managed Care - August 2008 - (Page 48) TOMORROW’S MEDICINE New Gait Stimulation Devices Walk the Coverage Line As microprocessor-controlled devices are improved to help patients maintain freedom and function, insurers are divided on coverage Thomas Morrow, MD early everyone reading this column has “tripped over his own foot” at one time or another. For most of us, it happened because of our less-than-gold-medal-level athletic prowess. But foot drop is a permanent disability for a growing number of Americans due to a variety of age-related conditions. N Etiology Foot drop is a significant weakness in the muscles of the ankle and toe which control dorsiflexion; the tibialis anterior, extensor hallucis longus, and extensor digitorum longus. These muscles allow the body to lift the foot during the swing phase of walking, thus preventing a person from truly tripping over his own foot. Weakness in this group of muscles causes the foot to drop in an unsupported manner when the leg is lifted by the hip and knee muscles. Compensatory exaggerated flexion of the hip and knee must occur to prevent the toes from catching onto or dragging on the ground in order to safely walk. Therapy for foot drop depends on the etiology. Some patients are treated with surgical release of the pressure on the nerve, such as removing a herniated disc or releasing the pressure of a compartment syndrome. Others are treated to control the primary disease, such as diabetes or multiple sclerosis. If the foot drop does not respond to a medical or surgical therapy, an ankle foot orthosis (AFO) is often used. There are a variety of AFOs available, ranging from simple rigid plastic “braces” to articulated varieties. They are constructed of various materials ranging from leather and canvas to various plastics — and now even Kevlar and high Thomas Morrow, MD, is the immediate past president of the National Association of Managed Care Physicians. He has 23 years of managed care experience at the payer or health plan level. technology metals. Their primary function is to splint the ankle to keep the foot from dropping and thereby prevent tripping. An electrical stimulation device may offer people who still have a functioning common peroneal nerve a more useful solution. There are a number of third-generation devices marketed in the United States, the two latest being the WalkAide External Functional Neuromuscular Stimulator by Innovative Neurotronics and the NESS L300 Foot Drop System by Bioness. Both require a doctor’s prescription. The WalkAide has a tilt sensor embedded in the leg cuff that senses the movement of the tibia. The leg cuff is attached just below the knee with a hook-and-loop strap. When a specific angle of tilt has occurred, it fires the stimulator, which leads to contraction of the muscle. When another angle is articulated at the end of the stride, the firing ceases and the foot is allowed to drop to the ground to start the entire process again. The electrodes are positioned to fire the muscles that are not functioning normally. The entire device is programmed for each patient by a trained clinician who can make fine adjustments. Intensity controls The WalkAide is programmed for walking, but can be programmed to allow the patient to exercise while at rest to strengthen the muscles. The patient has intensity controls but cannot reprogram the system without the clinician. The NESS L300 uses a slightly different technology. It consists of three pieces: a leg cuff with adjustable electrodes placed over the peroneal nerve below the patella, a sensor, and a handheld control unit. The gait sensor is attached to the shoe near the ankle and uses radio waves to communicate with the stimulator on the leg cuff. 48 MANAGED CARE / AUGUST 2008
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