Self-expandable shape memory alloy stent and method for fabricating the same

Abstract

A self-expandable shape memory alloy stent includes first and second wires made of super-elastic shape memory alloy. The first wire extends downwardly from the top to the bottom of the stent without interlocking with itself but extends upwardly from the bottom to the top of the stent while interlocking with itself to leave a multiplicity of rhombic spaces. Similarly, the second wire extends downwardly from the top to the bottom of the stent without interlocking with itself but extends upwardly from the bottom to the top of the stent while interlocking with itself, in such a manner as to divide the rhombic spaces formed by the first wire into four small rhombic spaces. The first wire and the second wire are woven with each other in such a manner that the second wire passes alternately below and above the first wire at intersection points.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the present invention will become apparent from the following description of preferred embodiments given in conjunction with the accompanying drawings, in which:

FIG. 1 is a perspective view showing a base jig used for the purpose of embodying the present invention;

FIG. 2 is a top view of the base jig shown in FIG. 1, with a portion thereof illustrated in a microscopically exaggerated condition;

FIGS. 3 a through 3e are development views illustrating a process of producing a first stent member;

FIGS. 4 a through 4e are development views illustrating a process of forming a second stent member woven with the first stent member;

FIG. 5 is a schematic front view showing a self-expandable stent in accordance with the present invention;

FIGS. 6 a and 6b are partially enlarged views showing certain portions of the stent illustrated in FIG. 5, wherein FIG. 6a shows the stent in a normal expanded condition but FIG. 6a illustrates the stent in a diametrically contracted condition;

FIG. 7 is a conceptual view illustrating a process of installing the stent of the present invention into a blood vessel of a living body; and

FIGS. 8 and 9 are state-of-use views of the stent in accordance with the present invention.

Claims

1. A method for fabricating a self-expandable shape memory alloy stent, comprising the steps of: providing a base jig including a cylinder and a plurality of radially outwardly projecting pins, the cylinder having a plurality of circumference dividing lines (a0, a1, a2, a3 . . . and a19) and a plurality of length dividing lines (b0, b1 b2, b3 . . . and b26) defined by equally dividing a circumference W and a length L of the cylinder, the circumference dividing lines intersecting the length dividing lines to form a plurality of wire transition points at their intersections, the projecting pins implanted to the cylinder at the transition points;fabricating a primary stent member by extending a first shape memory alloy wire downwardly from a first top starting point to a projecting pin of a first primary transition point disposed at an uppermost position of the cylinder, then diagonally downwardly from the projecting pin of the first primary transition point to a projecting pin of a second primary transition point by a first diagonal length, then diagonally upwardly from the projecting pin of the second primary transition point to a projecting pin of a third primary transition point by a second diagonal length one half time smaller than the first diagonal length, then diagonally downwardly from the projecting pin of the third primary transition point to a projecting pin of a fourth primary transition point by a third diagonal length multiple times greater than the second diagonal length, then diagonally upwardly from the projecting pin of the fourth primary transition point to a projecting pin of a fifth primary transition point by the second diagonal length, and then diagonally downwardly by the first diagonal length from the projecting pin of the fifth primary transition point to a projecting pin of a sixth primary transition point disposed at a lowermost position of the cylinder, extending the first wire in zigzag from the projecting pin of the sixth primary transition point along a circumferential direction of the cylinder to form a lowermost cylindrical zigzag part, extending the first wire upwardly from the lowermost zigzag part in such a manner as to form a plurality of middle cylindrical zigzag parts and an uppermost cylindrical zigzag part, the lowermost, middle and uppermost zigzag parts being interlocked with one another to leave a plurality of rhombic spaces therebetween; andfabricating a secondary stent member by extending a second shape memory alloy wire downwardly from a second top starting point to a projecting pin of a first secondary transition point disposed at an uppermost position of the cylinder, then diagonally downwardly from the projecting pin of the first secondary transition point to a projecting pin of a second secondary transition point by a first diagonal length, then diagonally upwardly from the projecting pin of the second secondary transition point to a projecting pin of a third secondary transition point by a second diagonal length one half time smaller than the first diagonal length, then diagonally downwardly from the projecting pin of the third secondary transition point to a projecting pin of a fourth secondary transition point by a third diagonal length multiple times greater than the second diagonal length, then diagonally upwardly from the projecting pin of the fourth secondary transition point to a projecting pin of a fifth secondary transition point by the second diagonal length, and then diagonally downwardly by the first diagonal length from the projecting pin of the fifth secondary transition point to a projecting pin of a sixth secondary transition point disposed at a lowermost position of the cylinder, extending the second wire in zigzag from the projecting pin of the sixth secondary transition point along a circumferential direction of the cylinder to form a lowermost cylindrical zigzag part, extending the second wire upwardly from the lowermost zigzag part in such a manner as to form a plurality of middle cylindrical zigzag parts and an uppermost cylindrical zigzag part, the lowermost, middle and uppermost zigzag parts of the second wire being interlocked with one another to leave a plurality of rhombic spaces therebetween,wherein the second wire of the secondary stent member is arranged to intersect the first wire of the primary stent member at a multiplicity of intersection points and wherein the first wire and the second wire are woven with each other in such a manner that the second wire passes alternately below and above the first wire at the intersection points.

2. The method as recited in claim 1, wherein the first diagonal length is equal to 2 the second diagonal length is equal to and the third diagonal length is equal to 24 where the l denotes the distance between two diagonally neighboring transition points.

3. The method as recited in claim 2, wherein the lowermost, middle and uppermost zigzag parts of each of the first and the second wires are joined to one another by primary and secondary connecting wire parts each extending the first diagonal length between the adjoining zigzag parts in a diagonally upward direction.

4. The method as recited in claim 1, wherein the first top starting point from which the first wire of the primary stent member begins to extend is diametrically opposite to the second top starting point from which the second wire of the secondary stent member begins to extend.

5. The method as recited in claim 1, wherein the first wire of the primary stent member has a distal end fixedly secured to itself in the vicinity of the first top starting point, and the second wire of the secondary stent member has a distal end fixedly secured to itself in the vicinity of the second top starting point.

6. A self-expandable shape memory alloy stent comprising: a first wire made of a super-elastic shape memory alloy, the first wire extending downwardly from a first top starting point to a first primary transition point disposed at an uppermost position of the stent, diagonally downwardly extending from the first primary transition point to a second primary transition point by a first diagonal length, diagonally upwardly extending from the second primary transition point to a third primary transition point by a second diagonal length one half time smaller than the first diagonal length, diagonally downwardly extending from the third primary transition point to a fourth primary transition point by a third diagonal length multiple times greater than the second diagonal length, diagonally upwardly extending from the fourth primary transition point to a fifth primary transition point by the second diagonal length, and then diagonally downwardly extending by the first diagonal length from the fifth primary transition point to a sixth primary transition point disposed at a lowermost position of the stent, the first wire extending in zigzag from the sixth primary transition point along a circumferential direction of the stent to form a lowermost cylindrical zigzag part, the first wire extending upwardly from the lowermost zigzag part in such a manner as to form a plurality of middle cylindrical zigzag parts and an uppermost cylindrical zigzag part, the lowermost, middle and uppermost zigzag parts being interlocked with one another to leave a plurality of rhombic spaces therebetween; anda second wire made of a super-elastic shape memory alloy, the second wire extending downwardly from a second top starting point to a first secondary transition point disposed at an uppermost position of the stent, diagonally downwardly extending from the first secondary transition point to a second secondary transition point by a first diagonal length, diagonally upwardly extending from the second secondary transition point to a third secondary transition point by a second diagonal length one half time smaller than the first diagonal length, diagonally downwardly extending from the third secondary transition point to a fourth secondary transition point by a third diagonal length multiple times greater than the second diagonal length, diagonally upwardly extending from the fourth secondary transition point to a fifth secondary transition point by the second diagonal length, and then diagonally downwardly extending by the first diagonal length from the fifth secondary transition point to a sixth secondary transition point disposed at a lowermost position of the stent, the second wire extending in zigzag from the sixth secondary transition point along a circumferential direction of the stent to form a lowermost cylindrical zigzag part, the second wire extending upwardly from the lowermost zigzag part in such a manner as to form a plurality of middle cylindrical zigzag parts and an uppermost cylindrical zigzag part, the lowermost, middle and uppermost zigzag parts of the second wire being interlocked with one another to leave a plurality of rhombic spaces therebetween,wherein the second wire is arranged to intersect the first wire at a multiplicity of intersection points and wherein the first wire and the second wire are woven with each other in such a manner that the second wire passes alternately below and above the first wire at the intersection points.

7. The self-expandable shape memory alloy stent as recited in claim 6, wherein the first diagonal length is equal to 2 the second diagonal length is equal to and the third diagonal length is equal to 24 where the denotes the distance between two diagonally neighboring transition points.

8. The self-expandable shape memory alloy stent as recited in claim 7, wherein the lowermost, middle and uppermost zigzag parts of each of the first and the second wires are joined to one another by primary and secondary connecting wire parts each extending the first diagonal length between the adjoining zigzag parts in a diagonally upward direction.

9. The self-expandable shape memory alloy stent as recited in claim 6, wherein the first top starting point from which the first wire begins to extend is diametrically opposite to the second top starting point from which the second wire begins to extend.

10. The self-expandable shape memory alloy stent as recited in claim 6, wherein the first wire has an end point fixedly secured to the first wire in the vicinity of the first top starting point, and the second wire has an end point fixedly secured to the second wire in the vicinity of the second top starting point.

11. A self-expandable shape memory alloy stent comprising: a first wire made of a super-elastic shape memory alloy, the first wire extending downwardly from a first top starting point of the stent toward a bottom end of the stent without interlocking with itself to form a downward extension part, the first wire extending in zigzag from the bottom end of the stent toward a top end of the stent while forming a lowermost cylindrical zigzag part, a plurality of middle cylindrical zigzag parts and an uppermost cylindrical zigzag part, the lowermost, middle and uppermost zigzag parts of the first wire being interlocked with one another to leave a plurality of rhombic spaces therebetween; anda second wire made of a super-elastic shape memory alloy, the second wire extending downwardly from a second top starting point of the stent lying diametrically opposite from the first top starting point toward a bottom end of the stent without interlocking with itself to form a downward extension part, the second wire extending in zigzag from the bottom end of the stent to a top end of the stent while forming a lowermost cylindrical zigzag part, a plurality of middle cylindrical zigzag parts and an uppermost cylindrical zigzag part, the lowermost, middle and uppermost zigzag parts of the second wire being interlocked with one another to leave a plurality of rhombic spaces therebetween;wherein the second wire is arranged to intersect the first wire at a multiplicity of intersection points and wherein the first wire and the second wire are woven with each other in such a manner that the second wire passes alternately below and above the first wire at the intersection points.