Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Arterial prosthesis
Reexamination Certificate
1996-12-26
2003-09-16
Low, Christopher S. F. (Department: 1653)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Arterial prosthesis
C623S001110, C623S001120, C623S001140, C623S001150, C623S001210, C623S001250, C606S194000, C606S195000, C526S255000, C428S422000, C428S304400, C428S398000
Reexamination Certificate
active
06620190
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to polytetrafluoroethylene (hereinafter PTFE) materials which, after being radially expanded, retain their the structural integrity.
More particularly, the invention relates to extruded, stretched, sintered tubular PTFE materials suited for use in the medical field as liners and covers for. expandable stents.
BACKGROUND OF THE INVENTION
The use of expandable endovascular stents to open and support aortic blood vessels is well known in the art. Such stents, which are typically made from stainless steel, are thrombogenic and tend to occlude due to growth of tissue through the stent into the blood vessel. The length of such stents is also limited because of their rigidity. Consequently, liners and covers have been sought for use in conjunction with metallic stents in order to shield the stent and to extend the length of anatomy which can be treated with the stent. The development of acceptable stent liners or covers has been slow because the liners or covers preferably must (1) expand with the stent, (2) be non-thrombogenic, (3) be biocompatible, (4) be inert, (5) have a low profile with the ability to expand up to about four times its original dimension, (6) be expandable at low pressures of less than five to ten atmospheres to reduce the risk of injury to the patient, (7) retain its physical properties and structural strength after being expanded, (8) generally not alter its length after being expanded, (9) be impervious to blood at physiological pressures, (10) conform to host anatomy when expanded, (11) resist the growth of bodily tissue therethrough, (12) be able to carry radiopaque markings for location during fluoroscopy.
Paste-formed, extruded tubular PTFE products are well known, as are paste extrusion and paste forming manufacturing processes for producing such products. During such manufacturing processes, a PTFE resin is mixed with a liquid lubricant. A preformed resin—lubricant charge is then produced and extruded through an annular orifice to produce an unsintered PTFE tube. The extruded tube is heated to remove the lubricant and produce a porous, unsintered PTFE tube. The tube typically has a density of from 1.5 to about 1.75 gm/cc and accompanying porosities of 39% to 26%. If the unsintered tube is sintered by heating the tube to a temperature above its crystalline melting temperature, a nonporous tube results. See U.S. Pat. Nos. 3,953,566, 3,962,153, 4,110,392, 4,187,309, 4,283,448, 4,385,093, 4,478,665, 4,482,516, 4,877,661, and 5,026,513.
In the medical field, PTFE products are used as replacement veins and arteries. PTFE is inert, is non-thrombogenic, and has other characteristics desirable for a stent cover or liner. Commercially available PTFE medical tubular products have, however, significant radial strength and are not readily dilated. Conventional PTFE tubes typically have a high radial strength and rapidly lose their tensile strength and become weak and thin after being dilated by only small amounts.
Accordingly, it would be highly desirable to provide improved PTFE products which can be readily expanded and which, after being expanded, substantially retain their tensile strength and other physical properties which make the use of PTFE in the body desirable.
Therefore, it is a principal object of the invention to provide improved PTFE products which are amenable to use as liners and covers for expandable stents.
A further object of the invention is to provide improved tubular PTFE products which substantially retain their structural integrity after the products are radially expanded.
Another object of the invention is to extend the length of anatomy which can be treated with an expandable
SUMMARY OF THE INVENTION
I have discovered new PTFE products and a process and composition for producing the same. The new PTFE products can be significantly expanded to configurations which retain their structural integrity and which substantially retain their tensile strength and other desirable physical properties. As discussed in detail in the examples below, the new PTFE products have an unusually low REC (Radial Expansion Coefficient) and RER (Radial Expansion Ratio) which function to permit thin-walled PTFE tubes to expand about 50% to 400% before, the tubes lose their structural integrity and suffer a rapid decline in tensile strength.
The following examples are presented to illustrate the presently preferred embodiments of and practice of the invention and not by way of limitation of the scope of the invention.
DETAILED DESCRIPTION OF THE INVENTION
Examples 1-17, below, concern expandable PTFE material formed as a result of stretching and subsequent sintering.
EXAMPLE 1
One hundred grams of FLUON CD123 resin produced by ICI Americas, Inc. was sifted through a No. 10 sieve and then blended at room temperature with twenty-five grams of ISOPAR M solvent produced by Exxon Corporation to produce a preform blend. Other lubricants well known in the art includes VM&P NAPHTHA (boiling point (bp) 118-130° C.), ISOPAR (Registered trademark of Exxon Corporation), ISOPAR 3 G (bp 159-174° C.), ISOPAR H (bp 176-189° C.), Low Odor Paraffin Solvent (bp 191-246° C.), and SHELLSOL (Trademark of Shell Oil) K.
The resulting preform blend was allowed to sit for over eight hours before being re-sifted through a No. 10 sieve. The lubricant level (LL) equals the weight of solvent used divided by the weight of resin used, which means the lubricant level utilized in this Example 1 was 25%. In the practice of the invention the lubricant level is normally in the range of 16% to 35%, and is presently preferably in the range of about 18% to 25%.
REFERENCES:
patent: 3008187 (1961-11-01), Slade
patent: 3260774 (1966-07-01), Harlow
patent: 3389201 (1968-06-01), Alsup et al.
patent: 3391221 (1968-07-01), Gore et al.
patent: 3953566 (1976-04-01), Gore
patent: 3962153 (1976-06-01), Gore
patent: 4025679 (1977-05-01), Denny
patent: 4104394 (1978-08-01), Okita
patent: 4110392 (1978-08-01), Yamazaki
patent: 4187390 (1980-02-01), Gore
patent: 4229838 (1980-10-01), Mano
patent: 4250138 (1981-02-01), Okita
patent: 4277429 (1981-07-01), Okita
patent: 4283448 (1981-08-01), Bowman
patent: 4332035 (1982-06-01), Mano
patent: 4385093 (1983-05-01), Hubis
patent: 4478665 (1984-10-01), Hubis
patent: 4482516 (1984-11-01), Bowman et al.
patent: 4496507 (1985-01-01), Okita et al.
patent: 4560374 (1985-12-01), Hammerslag
patent: 4576869 (1986-03-01), Malhotra
patent: 4598011 (1986-07-01), Bowman
patent: 4733665 (1988-03-01), Palmaz
patent: 4743251 (1988-05-01), Barra
patent: 4776337 (1988-10-01), Palmaz
patent: 4826725 (1989-05-01), Harlow
patent: 4830062 (1989-05-01), Yamamoto et al.
patent: 4876051 (1989-10-01), Campbell et al.
patent: 4877661 (1989-10-01), House et al.
patent: 4922905 (1990-05-01), Strecker
patent: 4973609 (1990-11-01), Browne
patent: 5024671 (1991-06-01), Tu et al.
patent: 5026513 (1991-06-01), House et al.
patent: 5061276 (1991-10-01), Tu et al.
patent: 5071609 (1991-12-01), Tu et al.
patent: 5078726 (1992-01-01), Kreamer
patent: 5098625 (1992-03-01), Huang et al.
patent: 5108424 (1992-04-01), Hoffman, Jr. et al.
patent: 5110527 (1992-05-01), Harada et al.
patent: 5122154 (1992-06-01), Rhodes
patent: 5123917 (1992-06-01), Lee
patent: 5217483 (1993-06-01), Tower
patent: 5219355 (1993-06-01), Parodi et al.
patent: 5238618 (1993-08-01), Kinzer
patent: 5258020 (1993-11-01), Froix
patent: 5308664 (1994-05-01), House et al.
patent: 5316023 (1994-05-01), Palmaz et al.
patent: 5360443 (1994-11-01), Barone et al.
patent: 5383928 (1995-01-01), Scott et al.
patent: 5389106 (1995-02-01), Tower
patent: 5425765 (1995-06-01), Tiefenbrun et al.
patent: 3918736 (1990-12-01), None
patent: 0 221 570 (1987-05-01), None
patent: 0 232 543 (1987-08-01), None
patent: 0 267 719 (1988-05-01), None
patent: 0 269 449 (1988-06-01), None
patent: 0 335 341 (1989-10-01), None
patent: 0 461 791 (1991-12-01), None
patent: 0 551 179 (1993-07-01), None
patent: 1 506 432 (1978-04-01), None
patent: 61-17648 (1955-04-01), None
patent: 58-44378 (1979-02-01), None
patent: 6-1143 (1980-0
Impra, Inc., a subsidiary of C.R. Bard, Inc.
Low Christopher S. F.
Mohamed Abdel A.
Morrison & Foerster
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