Medical devices incorporating at least one element made from...

Electricity: conductors and insulators – Conduits – cables or conductors – Conductor structure

Reexamination Certificate

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Details

Type

Reexamination Certificate

Status

active

Patent number

06191365

Description

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates broadly to medical devices incorporating elements having a low modulus of elasticity. More particularly, this invention relates to medical devices incorporating one or more cable elements made from a plurality of twisted and drawn wires.
2. State of the Art
Wires are utilized throughout the medical arts. In many medical devices a particularly desirable feature for the wires is high elasticity. For example, in baskets and snares high elasticity may be the most important property of the wires used. The elasticity of the wires comprising snares and baskets is a factor in the extent to which each may be compressed for insertion to the surgical site and yet still be able to expand upon use. In addition, higher elasticity permits the baskets and snares to be contracted about smaller radii.
The need for highly flexible self-expanding stents is also well-known. Flexibility not only permits proper stent deployment, but also enables the stent to better conform to the vascular walls.
In endoscopic instruments, a control wire is often coupled between a proximal handle and a distal end effector. The control wire is used to translate movement of the handle into operation of the end effector. The wire must be able to easily bend through the tortuous paths through which endoscopic instruments are guided.
Wire flexibility is also important in numerous other medical devices. For that reason, the medical arts have recently had much interest in nickel-titanium alloy (Nitinol) wires which exhibit superelastic characteristics. However, Nitinol is relatively expensive, and alternatives to Nitinol offering comparable advantage in the medical device arts are desired.
In addition, with respect to many medical devices, the art has gone to great lengths and expense to provide radiopaque materials to the distal end of Nitinol elements (see, e.g., U.S. Pat. No. 5,520,194 to Miyata et al.). This is particularly required in devices using very fine (i.e., small diameter) Nitinol wires which cannot easily be seen during fluoroscopy. However, radiopaque materials are difficult to attach to the Nitinol components owing, in part, to their dissimilarity with the Nitinol material. Moreover, it is preferable in certain applications to have an elastic component which conducts electricity sufficiently to permit cautery functions or to permit the component to function as an electrical lead. However, nickel-titanium alloys are not particularly good conductors.
SUMMARY OF THE INVENTION
It is therefore an object of the invention to provide a variety of medical devices which utilize one or more multifilament twisted and drawn cables that exhibit excellent elasticity characteristics.
It is another object of the invention to provide medical devices with a radiopaque elastic element.
It is also object of the invention to provide medical devices which include a conductive elastic element.
It is a further object of the invention to provide medical devices which include a radiopaque, conductive, and elastic element.
In accord with these objects, which will be discussed in detail below, medical devices are provided which utilize a highly flexible cable of two and preferably three or more strands of wire, which are twined to form a wire rope which is drawn through successive dies to reduce its diameter until the outer surface of the cable is substantially smooth. Where the resulting cable is made from strands of a single material, the cable is provided with improvement elasticity and torqueability over of a wire of the same material having the same diameter as the cable. The cable is used in medical devices in which increased elasticity of a wire-like element is desired at a more reasonable cost than nickel-titanium wires. Twisted and drawn cables incorporating at least one strand of a radiopaque metal or alloy may be used in devices in which radiopacity of an elastic portion of the device is desired. Twisted and drawn cables incorporating at least one strand of a highly electrically conductive metal or alloy may be used in devices in which electrical conductivity of an elastic portion of the device is desired. Twisted and drawn cables incorporating at least one strand of a radiopaque metal or alloy with at least one strand of a highly electrically conductive alloy may be used in devices in which radiopacity of an electrically conductive elastic portion of a device is desired.
Additional objects and advantages of the invention will become apparent to those skilled in the art upon reference to the detailed description.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The invention will be described by first introducing the concept of cables formed from multistrand twisted and drawn wires. Then, examples will be provided illustrating how such cables can be substituted for conventional wires (e.g., stainless steel wires and nickel-titanium alloy wires) in medical devices to achieve the beneficial results of the invention.
The invention is the improvement of a variety of medical devices by utilizing therein a cable of two and preferably three or more strands of wire which are twined to form a wire rope. The wire rope is drawn through successive dies to reduce its diameter until the outer surface of the cable is substantially smooth, the cross section of the cable is substantially circular, and the overall diameter of the wire rope is reduced by 20-50%. The cable is then annealed to remove the effects of cold working.
The resulting cable has been found to have an improved flexibility (i.e., a lower modulus of elasticity) relative to a single wires of the same diameter and same constituent metals or alloys. Moreover, such cables have high torqueability and exhibit strong radial strength.
In addition, a twisted and drawn cable including one or more strands of a radiopaque material, e.g., gold, silver, or platinum-iridium, will exhibit both elastic and radiopaque properties. In accord with the invention, the cable so formed may be used in devices in which radiopacity of a flexible portion of a medical device is desired, e.g., for viewing the flexible portion during fluoroscopic procedures.
Also, a cable including one or more strands having high conductance, e.g., platinum, gold, silver, copper, or aluminum strands, will exhibit desirable elastic and electrical conductance properties. In accord with the invention, the cable so formed may be used in devices in which high electrical conductivity of a flexible portion of a medical device is desired.
Moreover, in accord with the invention, cables incorporating at least one strand of a radiopaque metal or alloy, and at least one strand of an electrically conductive metal may be used in devices in which a radiopaque, conductive, and flexible portion of the device is desired. It will be appreciated that the radiopaque strand and strand having high conductance may be the same strand, e.g., a gold or silver strand.
Furthermore, it will be appreciated that cables may be formed from particular ratios of materials by selecting the number and relative diameter of the wire strands of each material used in the manufacture of the cable. Such ratios permit the selection of varying degrees of elasticity, radiopacity, and conductance according to a particular application.
Particular cables, their manufacture, and their properties are described in detail in previously incorporated co-pending U.S. application Ser. Nos. 08/856,571 to Avellanet et al., 08/843,405 and 08/963,686 to Avellanet, 09/044,203 and 09/087,476 to Avellanet et al., 09/048,746 to Bales et al., and 09/060,969 to Avellanet. From reference to the respective disclosures, it will be appreciated that any particular cable composition described herein may be made by one skilled in the art. The following are examples of uses of twisted and drawn cables in medical devices.


REFERENCES:
patent: 3131469 (1964-05-01), Glaze
patent: 3261908 (1966-07-01), Roche et al.
patent: 3620212 (1971-11-01), Fannon, Jr.
patent: 4027677 (1977-06-01), Schulman et al.
patent: 4037324 (1977-

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