WO2009140719A1

WO2009140719A1 - Fabricating a stent

Info

Publication number: WO2009140719A1
Application number: PCT/AU2009/000610
Authority: WO
Inventors: Zoran Milijasevic; Richard J. Parkinson
Original assignee: Neustent Pty Ltd
Priority date: 2008-05-23
Filing date: 2009-05-15
Publication date: 2009-11-26

Abstract

A stent (10) includes a first tubular member (12) which is at least partly foraminous, the first tubular member (12) having a first, upstream end and a second, downstream end (16), the downstream end (16) being formed into a predetermined shape. The stent (10) includes at least one further, at least partly foraminous, tubular member (14) having a first, upstream end (28) and a second, downstream end, the upstream end (28) of the at least one further tubular member (14) being formed into a predetermined shape and the shaped ends (16, 28) of the tubular members (12, 14) being secured together so that the at least one further tubular member (14) projects at a desired angle from the first tubular member (12) and the tubular members (12, 14) form a one-piece, integral unit.

Description

"Fabricating a stent" Cross-Reference to Related Applications

The present application claims priority from Australian Provisional Patent Application No 2008902599 filed on 23 May 2008, the contents of which are incorporated herein by reference in its entirety.

Field of the Invention

This invention relate, generally, to the field of stents and, more particularly, to a method of fabricating a stent and to a stent fabricated in accordance with the method.

Background to the Invention

The use of stents to treat lesions caused by the build up of plaque in a patient's vascular system is known. However, a lesion often occurs at a bifurcation in the vascular system. The treatment of such lesions is complex. In the past, two separate stents have been used where one of the stents is passed through an aperture in a side wall of the other stent. In addition, a clinician has to manoeuvre multiple guide wires and stents which often presents additional challenges.

The use of two separate stents can also increase the risk of impeding blood flow, especially to the branch artery. Another problem associated with the use of a separate stent branching from a primary stent is the effect of the stent in the side branch protruding into the main vessel increasing the risk of thrombosis.

Due to the complexity of using two separate stents, some clinicians take the chance of ignoring side branch stenosis. In addition, since lesions rarely occur exactly at the bifurcation but may occur above or below the bifurcation another problem is the effect of dislodging the plaque as a result of insertion of the stent or a balloon from one bifurcated vessel into the other.

It is therefore desirable to have a device specifically designed for treating lesions at bifurcations in the vasculature.

Summary of the Invention

According to a first aspect of the invention, there is provided a method of fabricating a stent which includes providing a first, at least partially foraminous, tubular member; providing at least one further, at least partially foraminous, tubular member; shaping those ends of the tubular members which are to be mated together so that, after mating, the at least one further tubular member projects at a desired angle from the first tubular member; and securing the mated ends together to form a one-piece, integrated unit.

Preferably the method includes providing at least two further tubular members to form a Y-shaped stent. The method may then include shaping the ends of the two further tubular members so that they mate with each other as well as with the end of the first tubular member.

The first tubular member may have a first, upstream end and a second downstream end and the method may include shaping the downstream end of the first tubular member. Each further tubular member may have a first, upstream end and a second, downstream end and the method may include shaping the upstream end of each further tubular member.

The method may include shaping the downstream end of the first tubular member by chamfering the downstream end. The chamfering of the downstream end may include forming a first chamfer from a first side of the first tubular member and forming a second chamfer from a diametrically opposed side of the tubular member. It will be appreciated that, where the chamfers are the same, which may not necessarily be the case, the chamfers meet on a longitudinal axis of the tubular member. Preferably, the chamfers have the same angle as each other as measured relative to a plane orthogonal to a longitudinal axis of the tubular member. The angle may be from about 5° to about 30°, preferably from about 10° to about 20° and, optimally, about 15°.

Similarly, the method may include shaping the upstream end of each further tubular member by chamfering the upstream end. Once again, the chamfering of the upstream end of each further tubular may include forming a first chamfer from a first side of the further tubular member and forming a second chamfer from a diametrically opposed side of the further tubular member. However, an angle of the second chamfer may be greater than an angle of the first chamfer. The angle of the first chamfer of each further tubular member may be from about 5° to about 30°, preferably from about 10° to about 20° and, optimally, about 15°. Once again, the angle of the first chamfer may be measured relative to a plane orthogonal to a longitudinal axis of the tubular member. The angle of the second chamfer of each tubular member may be from about 15° to about 40°, preferably from about 20° to about 30° and, optimally, about 25°. The angle of the second chamfer may be measured relative to a plane parallel to a longitudinal axis of the tubular member. It ^■will be appreciated that the further tubular members are mirror images of each other and are secured together so that their chamfers of greater angle mate with each other with the chamfers of lesser angle mating with the chamfers of the first tubular member.

The method may include securing the tubular members together by welding.

Further, the method may include forming each tubular member of a resiliently flexible bio-compatible material. Preferably, the material is a shape memory alloy material such as a nickel-titanium alloy (Nitinol).

Each tubular member may be formed from a sheet of the material which is worked, for example, by laser cutting to form foramens in the sheet and then forming the sheet into a cylindrical form. In another embodiment, the method may include providing a plurality of wave shaped members and securing the wave shaped members together out of phase with each other so that a peak of the wave in a first direction of one member is in register with the peak of a wave in an opposite direction of an adjacent member. The method may then include forming the joined wave shaped members into a cylindrical form. Instead, the method may include forming each of the wave shaped members into an annular element, with the peaks extending parallel to an axis of rotation of the annular element, and securing the annular elements together to form the tubular members.

According to a second aspect of the invention, there is provided a stent which includes a first tubular member which is at least partly foraminous, the first tubular member having a first, upstream end and a second, downstream end, the downstream end being formed into a predetermined shape; and at least one further, at least partly foraminous, tubular member having a first, upstream end and a second, downstream end, the upstream end of the at least one further tubular member being formed into a predetermined shape and the shaped ends of the tubular members being secured together so that the at least one further tubular member projects at a desired angle from the first tubular member and the tubular members form a one-piece, integral unit.

The stent preferably comprises at least two further tubular members to form a bifurcated stent, the two further tubular members having their upstream ends secured together as well as to the downstream end of the first tubular member as a one-piece, integrated unit. Brief Description of Drawings

Embodiments of the invention are now described by way of example with reference to the accompanying drawings in which: -

Fig. 1 shows a perspective view of an embodiment of a stent;

Fig. 2 shows, on an enlarged scale, the circled portion, labelled ¹A', of the stent of Fig. 1;

Fig. 3 shows a front view of the stent;

Fig. 4 shows, on an enlarged scale, the circled portion, labelled ¹B', of the stent of Fig. 3;

Fig. 5 shows a side view of a first tubular member used in the fabrication of the stent of Figs. 1-4;

Fig. 6 shows a side view of at least one further tubular member used in the fabrication of the stent of Figs. 1-4;

Fig. 7 shows, on a reduced scale, a front view of a sheet of material from which the tubular members of Figs. 5 and 6 are made;

Fig. 8 shows a side view of a tubular member fabricated from the sheet of Fig. 7;

Fig. 9 shows a perspective view of the tubular member; and

Fig. 10 shows, on an enlarged scale, the circled portion, labelled 'C", of Fig. 8.

Detailed Description of Exemplary Embodiments

In the drawings, reference numeral 10 generally designates a bifurcated stent made in accordance with an embodiment of a method of fabricating a stent. The stent 10 comprises a first, or primary, tubular member 12 and a pair of further, secondary tubular members 14. The tubular members 12, 14 are made of a biocompatible, resiliency flexible, foraminous material. For example, the tubular members 12, 14 are made of a shape memory alloy, more particularly, a nickel-titanium alloy such as Nitinol. This enables the stent, in use, to be inserted in a collapsed form into a patient's vasculature and, at the desired site, to be allowed to expand radially within the vasculature. The secondary tubular members 14 are secured, via their upstream ends, to a downstream end of the primary tubular member 12 to form a substantially Y-shaped, or bifurcated, stent. Thus, in the embodiment illustrated, the secondary tubular members 14 project at the same angle as each other from a longitudinal axis of the tubular member 12. It will, however, be appreciated that the tubular members 14 need not extend at the same angle as each other and could form a non-symmetrical Y-shaped stent in circumstances where such a device is desirable.

In the fabrication of the stent 10, the primary tubular member 12 is provided. As illustrated more clearly in Fig. 5 of the drawings, a downstream end 16 of the primary tubular member 12 is shaped into a predetermined form. The shaping of the downstream end is effected by chamfering the downstream end from diametrically opposite sides 18, 20 of the primary tubular member 12. In the illustrated embodiment, because the secondary tubular members 14 are to project at the same angle as each other from the primary tubular member 12, the chamfers 22 formed at the downstream end 16 are formed at the same angle. More particularly, each chamfer 22 is formed to have an angle of from about 5° to about 30°, preferably from about 10° to about 20° and, optimally about 15°. Thus, as illustrated, an included angle between the chamfers 22 is about 150°.

It is to be noted that the primary tubular member 12 has foramens 24 which are oblong in the direction of the longitudinal axis of the primary tubular member 12. Further, as illustrated in Fig. 6 of the drawings, each secondary tubular member 14 similarly has foramens 26 which are oblong in the direction of a longitudinal axis of the secondary tubular member 14.

Two such secondary tubular members 14 are provided which are mirror images of each other, only one being illustrated in Fig.6 of the drawings.

Each secondary tubular member 14 has an upstream end 28. Once again, the method of fabricating the stent 10 includes shaping the upstream end 28 of the secondary tubular member 14 into a desired shape. More particularly, the method includes chamfering the upstream end. In the case of each secondary tubular member, a first chamfer 30 of the upstream end 28 of each secondary tubular member 14 has an angle of from about 5° to about 30°, preferably from about 10° to about 20° and, optimally about 15°. This angle is measured in a plane orthogonal to a longitudinal axis of the secondary tubular member 14.

A second chamfer 32 at the upstream end 28 of each secondary tubular member 14 has an angle from about 15° to about 40°, preferably from about 20° to about 30° and, optimally, about 25°. The angle of the chamfer 32 is measured relative to a plane extending parallel to the longitudinal axis of each secondary tubular member 14. Thus, when measured relative to the plane orthogonal to the longitudinal axis of the secondary tubular member 14, the chamfer 32 has an angle of approximately 65°. In fabricating the stent 10, the secondary tubular members 14 are joined together by mating their chamfers 32 to each other. The chamfers 30 of the secondary tubular members 14 are then mated to the chamfers 22 at the downstream end 16 of the primary tubular member 12 as shown in greater detail in Figs. 2 and 4 of the drawings. The chamfers 22, 30 and 32 are joined together by welding to form a one-piece, integrated unit. In one embodiment, each tubular member 12, 14 is formed from a sheet 34 of the biocompatible material. The sheet 34 is worked to render it foraminous. More particularly, the sheet 34 is laser cut to form the foramens 24, 26, as the case may be. Opposed edges 36, 38 of the sheet 34 are secured together to form a tubular member 40 as shown in Figs 8 and 9 of the drawings. The tubular member 40 is used to form the secondary tubular members 12, 14 by shaping the upstream or downstream end of the tubular member 40, as described above.

In another embodiment, each tubular member 40 is formed by providing a length of biocompatible wire and shaping the length into a substantially sinusoidal wave shape as shown at 42 in Fig. 10 of the drawings. Each of a plurality of the wave shaped lengths is formed into an annulus. A plurality of the annuli are secured together so that a peak 44 of a wave in a first direction of one annulus is in register with the peak of a wave in an opposite direction of an adjacent annulus. This forms the foramens 24, 26 of the tubular member 40. It will be appreciated that, instead, the wave shaped lengths of wire can be secured together before being formed into annuli and, after being joined together, the joined wave shaped lengths are formed into the cylindrical tubular member 40.

It is an advantage of the invention that a one-piece stent is provided. This overcomes the potential disadvantages of trying to drive a secondary stent through a side aperture in a primary stent at a bifurcation in the patient's vasculature. By driving a secondary stent through the aperture, there is a risk of dislodging plaque in the patient's vasculature which can have serious consequences. The provision of a one- piece stent obviates this problem to a large extent. In addition, because the stent is a one-piece stent 10, the transition between the primary tubular member 12 and the secondary tubular members 14 is substantially smooth and without protrusions. This facilitates placement of the stent 10 at a bifurcation in the patient's vasculature and minimises the potential for trauma to vessels of the patient's vasculature.

It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the invention as shown in the specific embodiments without departing from the scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.

Claims

CLAIMS:

1. A method of fabricating a stent which includes providing a first, at least partially foraminous, tubular member; providing at least one further, at least partially foraminous, tubular member; shaping those ends of the tubular members which are to be mated together so that, after mating, the at least one further tubular member projects at a desired angle from the first tubular member; and securing the mated ends together to form a one-piece, integrated unit.

2. The method of claim 1 which includes providing at least two further tubular members to form a Y-shaped stent.

3. The method of claim 2 which include shaping the ends of the two further tubular members so that they mate with each other as well as with the end of the first tubular member.

4. The method of claim 2 or claim 3 in which the first tubular member has a first, upstream end and a second downstream end and in which the method includes shaping the downstream end of the first tubular member.

5. The method of claim 4 in which each further tubular member has a first, upstream end and a second, downstream end and in which the method includes shaping the upstream end of each further tubular member.

6. The method of claim 5 which includes shaping the downstream end of the first tubular member by chamfering the downstream end.

7. The method of claim 6 in which the chamfering of the downstream end includes forming a first chamfer from a first side of the first tubular member and forming a second chamfer from a diametrically opposed side of the tubular member.

8. The method of any one of claims 5 to 7 which includes shaping the upstream end of each further tubular member by chamfering the upstream end.

9. The method of claim 8 in which the chamfering of the upstream end of each further tubular includes forming a first chamfer from a first side of the further tubular member and forming a second chamfer from a diametrically opposed side of the further tubular member.

10. The method of any one of the preceding claims which includes securing the tubular members together by welding.

11. The method of claim 10 which includes forming each tubular member of a resiliently flexible bio-compatible material.

12. The method of any one of the preceding claims which includes forming each tubular member from a sheet of the material which has been worked to form foramens in the sheet and then forming the sheet into a cylindrical form.

13. The method of any one of claims 1 to 11 which includes providing a plurality of wave shaped members and securing the wave shaped members together out of phase with each other so that a peak of the wave in a first direction of one member is in register with the peak of a wave in an opposite direction of an adjacent member and then forming the joined wave shaped members into a cylindrical form to form the foraminous tubular members.

14. The method of any one of claims 1 to 11 which includes forming each of the wave shaped members into an annular element, with the peaks extending parallel to an axis of rotation of the annular element, and securing the annular elements together to form the tubular members.

15. A stent which includes a first tubular member which is at least partly foraminous, the first tubular member having a first, upstream end and a second, downstream end, the downstream end being formed into a predetermined shape; and at least one further, at least partly foraminous, tubular member having a first, upstream end and a second, downstream end, the upstream end of the at least one further tubular member being formed into a predetermined shape and the shaped ends of the tubular members being secured together so that the at least one further tubular member projects at a desired angle from the first tubular member and the tubular members form a one-piece, integral unit.

16. The stent of claim 15 which comprises at least two further tubular members to form a bifurcated stent, the two further tubular members having their upstream ends secured together as well as to the downstream end of the first tubular member as a one- piece, integrated unit.