Surgery: light – thermal – and electrical application – Light – thermal – and electrical application – Electrical therapeutic systems
Reexamination Certificate
2000-01-25
2001-02-06
Evanisko, George R. (Department: 3762)
Surgery: light, thermal, and electrical application
Light, thermal, and electrical application
Electrical therapeutic systems
C607S048000
Reexamination Certificate
active
06185455
ABSTRACT:
BACKGROUND OF THE INVENTION
Muscles serve a number of functions, most of which are dependent upon their regular contraction, which is in turn dependent upon their strength and health. For example, in addition to the well known functions of supporting the skeleton and permitting movement, muscles serve to pad the force of bone protuberances against the skin, and they promote blood flow, particularly through deep blood vessels. In response to repeated contractions against a load, muscle fibers grow in cross-sectional area and develop more force, and in response to repeated contraction over a long period of time, the oxidative capacity and blood supply of the fibers is enhanced.
In normal individuals, muscles are activated to contract by electrical signals that are communicated from the brain and spinal cord by way of muscle nerves. Many medical diseases, physical disabilities and cosmetic disfigurements arise from abnormal or absent electrical signals to the muscles. Such abnormal or absent electrical signals may be pathological or may simply be due to prolonged immobility or confinement that restricts or prevents the voluntary movement of one or more muscles. Without normal, routine electrical stimulation, muscles atrophy, that is lose their normal size and strength. Also contributing to muscle atrophy may be a wide range of other pathophysiological mechanisms, including absence of sustaining hormones and other endogenous trophic substances.
Many situations exist in which voluntary muscle contraction cannot be used effectively to operate, condition or strengthen muscles. The most extreme loss of voluntary muscle function occurs when the brain or spinal cord is injured by trauma, the growth of tumors or cerebrovascular accidents. In patients suffering from these conditions, muscles become wholly or partially paralyzed because the electrical commands that are normally generated in the nervous system are no longer available to stimulate muscle contractions. Less extreme degrees of muscle weakness and atrophy can come about when some of the nerve fibers supplying a muscle are damaged by disease or injury or when the muscle is immobilized or voluntarily rested, for example by casting or bedrest, in order to recover from an injury or surgical intervention involving a nearby body part, or other prolonged confinement or immobilization.
With respect to prolonged physical confinement or immobilization, the affect of muscle non-use and atrophy frequently leads to two disorders that are particularly difficult to avoid and expensive to treat, pressure ulcers of the skin and subcutaneous tissues and retardation of the normal circulation of blood through deep vessels. Continual, unrelieved pressure on localized regions of skin can result in the development of pressure ulcers of the skin and subcutaneous tissues, also known as bed sores or decubitus ulcers. Pressure ulcers are thought to occur when tissues underlying a site of pressure are deprived of oxygen and nutrients because blood flow is impeded, and when the area is subjected to frictional and shearing forces associated with continuous rubbing and movement. Pressure ulcers vary in size and degree of damage from small regions of redness to deep craters of tissue erosion passing through skin, connective tissues, muscle and even bone that can threaten the life of a patient by providing portals of entry for pathogenic organisms. They are often exacerbated in chronically paralyzed or bedridden patients because of atrophy of the unused muscles that normally provide a degree of padding between the skin and underlying bony protuberances. The treatment of pressure ulcers often requires prolonged, intensive medical care and occasionally extensive surgery, usually entailing further restrictions in the posture of the patient, which may further complicate medical and nursing care and cause other complications.
As mentioned above, prolonged immobilization or physical confinement of a body part often also results in retardation of circulation of blood through deep vessels, particularly the veins in an around muscles. For example, the failure to contract muscles in the limbs at regular intervals, as occurs normally when walking or standing, is known to cause stasis of blood in some veins. Venous stasis is a predisposing factor in the formation of clots in the veins. Such deep venous thrombosis further compromises blood flow to the immobilized body part and can be the source of dangerous emboli to the heart and lungs. Thrombosed veins may also become chronically infected, posing a danger of septicemia. Examples of particular populations of patients that are especially at risk for development of pressure ulcers and venous emboli include comatose and obtunded patients, patients who are confined by paralysis to bed or wheelchairs, bedridden patients who have medical or surgical conditions that limit their activity, and elderly patients with limited mobility. To reduce complications in these patients, it is necessary to reestablish movement of the vulnerable body parts; however, these patients are either incapable of voluntary movement or severely restricted in their ability to voluntarily move. Therefore, therapists often spend considerable time manipulating the passive limbs of these patients, but this is expensive and relatively ineffectual because it is the active contraction of muscle that tends to pump blood through the veins and to maintain the bulk of the muscle.
It has long been known that muscle contractions can be elicited involuntarily by stimulating muscles and their associated motor nerves by means of electrical currents generated from electronic devices called stimulators. This has given rise to various therapies that seek to prevent or reverse muscle atrophy and its associated disorders by the application of electrical stimulation to the muscles and their nerves via these stimulators. For example, the field of research known as functional neuromuscular stimulation (FNS) or functional electrical stimulation (FES) has begun, which seeks to design and implement devices capable of applying electrical currents, in order to restore functional movement to paralyzed limbs. Similarly, therapies employing stimulators to regularly apply specific patterns of electrical stimulation to muscles in order to prevent or reverse atrophy are known.
Many of the earliest stimulators were bulky and relied upon the delivery of large current pulses through electrodes affixed to the skin, a procedure that requires careful positioning and fixation of the electrodes to the skin and frequently produces disagreeable cutaneous sensations and irritation of the skin. Additionally, such transcutaneous stimulation produces relatively poor control over specific muscles, particularly those that lie deep in the body. Thus, this procedure can be time-consuming, uncomfortable, and is generally useful only for muscles located immediately beneath the skin.
It is also possible to stimulate muscles more directly by passing electrodes through the skin into the muscles or by surgically implanting self-contained stimulators and their associated leads and electrodes in the body. These devices have many configurations, but most are large and have numerous leads that must be implanted and routed through the body to the desired muscles using complex surgical methods. Further, they are expensive to produce and the invasive procedures required for their implantation are impractical for most patients because they increase rather than decrease the required care and the danger of infection and other sources of morbidity in patients who are already seriously ill. Thus, such devices have been used primarily in patients with severe paralysis in order to demonstrate the feasibility of producing purposeful movements such as those required for locomotion, hand-grasp or respiration.
More recently a new technology has been described whereby electrical signals can be generated within specific tissues by means of a miniature implanted capsule, referred to as a “microstimulator”, that receives power and co
Loeb Gerald E.
Richmond Frances J. R.
Advanced Bionics Corporation
Evanisko George R.
Gold Bryant R.
Green Kenneth L.
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