Surgery: light – thermal – and electrical application – Light – thermal – and electrical application – Thermal applicators
Reexamination Certificate
2000-01-20
2002-08-20
Peffley, Michael (Department: 3739)
Surgery: light, thermal, and electrical application
Light, thermal, and electrical application
Thermal applicators
C607S002000, C607S050000, C607S088000, C607S100000, C607S101000
Reexamination Certificate
active
06436129
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to methods and apparatus for enhancing nerve regeneration and growth, and more particularly relates to a method and apparatus for stimulating axon and dendrite extension across a severed nerve section.
2. Description of Related Art
The peripheral and autonomic nervous system are formed by nerve cell bodies and processes, i.e., axons and dendrites forming bundles, innervating the skin, skeletal muscles, glands and related structures. The nerve cell bodies are situated in the brain, spinal cord or in ganglia. Each myelinated nerve fiber is enveloped by Schwann cells. In the case of unmyelinated fibers, several axons are enclosed in each Schwann cell. The Schwann cells are enveloped by a basement membrane, an extracellular matrix and an endoneurial mesenchymal sheath. Many such units form a nerve, which is limited by a perineurium of collagen, fibroblasts and related cells. An epineurium encloses the entire nerve, mostly comprising several nerve fascicles. A blood-nerve barrier prevents plasma proteins and many other substances from unrestricted penetration among the nerve fascicles. Motor and sensory nerves have the same structure but differ with regard to the axon and myelin dimensions. This means that in a mixed peripheral nerve it is not possible by the morphological characteristics to state whether a single axon is afferent or efferent. Autonomic nerve fibers, sympathetic and parasympathetic, are accompanying the sensory and motor nerve fibers as well as blood vessels.
Nerve cells and their supporting neurological cells are derived from the neuroectoderm. Although originally having a common embryonic origin, the nerve cells at an early state differentiate and obtain their structural characteristics. About four decades ago Hamburger and Levi-Montalcini demonstrated that the development of neurons are dependent on their target structures in order not to degenerate after differentiation. They provided direct evidence that neurons may die during normal development if not gaining synaptic contacts. This is true both for the central, peripheral and autonomic nervous systems.
The nerve cells in the central and peripheral nervous system reach their final number at about birth in mammals. The regenerative capacity present for peripheral and autonomic nerves during childhood is reduced with increasing age. This means that no new nerve cells are formed after birth, although axons and dendrites may regenerate to a limited extent. The autonomic system has a much higher regenerative capacity than the peripheral nervous system.
Injury to peripheral and autonomic nerves results in degeneration of the distal parts of the axons and dendrites. After dissection, Wallerian degeneration results in hypertrophy and hyperplasia of the Schwann cells lining the distal nerve. The proximal end of the injured axons retract to a variable extent, and, after a short lag period, the repair processes of the nerves begin.
Sprouts with finger-like extensions form a leading part of the outgrowing cell processes, the path of which is guided by the reactive Schwann cells. In most systems the rate of regeneration is in the range of 1-2 mm/day. Higher values have been documented for the autonomic nervous system. However, after about a month, depending on the test system examined, the rate of regeneration begins slowing down and eventually ceases. Little is known about the mechanisms which regulate the rate of regeneration. Detailed mechanisms of the regenerative process remain unknown.
Nerve crush is an injury of moderate severity, mostly resulting in complete recovery of the structure and function of injured axons and dendrites. It has been established that continuity of the basement membrane as well as early reestablishment of the microcirculation in peripheral nerves after crush injury is a prerequisite for complete recovery. Discontinuities in the basement membrane or even limited persistent blood vessel damage delay or impair the recovery.
Sectioning of a nerve results in discontinuity of the epi-, peri- and endoneuriums, as well as of the basement membrane enveloping the supporting Schwann cells with the enclosed axons and dendrites. Extensive vascular damage occurs as well. In the latter cases nerve regeneration starts after a delay of a few days in most clinical and experimental systems using peripheral nerves. Even meticulous microsurgery, almost reestablishing continuity of each nerve fascicle to each corresponding nerve fascicle by approximation, is not sufficient to gain any major improvement of the regeneration. Removal of the peri- and/or epineurium neither improves the extent of nerve regeneration, structurally or functionally. Most techniques used result in limited improvement as compared to if the nerve ends remained opposed. For example, further complications which occur in cases of sectioned peripheral nerves are the formation of neuroma and fibrous scar tissue starting after about a week. This eventually results in formation of neuroma and a permanent deficient function of the nerves. In the case of physical separation of peripheral nerves, the severed distal segment begins the process of Wallerian Degeneration soon after severing if microcirculation and reapproximation of the severed segment does not occur.
Adequate function of the target innervated by peripheral and autonomic nerves seems to be a prerequisite for maintenance of the function of the peripheral and autonomic neurons. Hamburger, et al. established that neurons depend on their targets for their survival. This means that damage to skeletal muscle cells, integumentum or glands result in disconnection of synapses from the target organ and more or less extensive degeneration of at least the distal parts of axons and dendrites. The degeneration may be of such extent that even neurons are lost. Recovery of the target organ may result in recovery of function after appropriate regeneration. Even in such cases, continuity of the fascicles, at least to the close vicinity of the target organs, and adequate microcirculation seems to be a prerequisite for successful regeneration.
As described in detail above, nerves are vital to the basic operation and function of the human body. Injury to a nerve can result in a partial or total loss of the sensation, control, or use of a member or portion of the body. Although methods currently exist for surgically repairing nerve tissue, such methods are not always possible and are commonly not completely successful in achieving a restoration of sensation, control, and use of the affected portion of the body.
One method for repairing served nerve involves the use of very fine sutures (multiple microsutures) to sew the severed nerve ends together. Such microsurgical procedures are typically conducted with the use of a microscope, which is tedious and time-consuming. Further, such microsurgical procedures are often not very successful, particularly in view of the large amount of time which typically transpires before surgery can be completed, as well as in view of the amount of manipulation which is required while the ends of the injured nerve are being meticulously sewn together using these microsurgical techniques. In addition, the improvement may be limited in spite of careful microsurgical reestablishment of connections between the nerve ends, presumably because reestablishment of close contact of severed nerve ends is not enough for successful nerve regeneration.
Where substantial nerve injury has occurred, it is often physically impossible to suture the severed nerve ends together. Thus, for more extreme nerve injuries, nerve grafts are often used as a nerve replacement. However, suture techniques and/or grafting have not always been sufficient for repair of a severe defect. Furthermore, suture under tension, gap reduction by stretching, mobilization, flexion of a joint, or rerouting may compromise sensitive intraneuronal vascularity, and autografts induce a second surgical site with requisite risks and complications. Mor
Sharkey Hugh
Strul Bruno
Fish & Richardson P.C.
Oratec Interventions, Inc.
Peffley Michael
Vrettakos Pete J
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