Tubular Metal Prosthesis and Method of Making It

Abstract

For welding a polished component of one metal to a polished prosthesis of another metal, ramp surfaces are used, to compensate for loss of precise dimensions of the two components at the surfaces that face each other at the weld interface, during the respective polishing procedures for the two metals.

Claims

1. A tubular metal stent, comprising: a stent body formed from a first material including: a first stent ring including struts connected by nodes positioned at a first end of the stent body, a plurality of shanks extending axially away from nodes on the first stent ring along a longitudinal axis of the stent body, each of the plurality of shanks having a head portion, each head portion including first and second polished ramp surfaces converging and meeting at a point axially away from the stent body; and a plurality of radiopaque markers formed from a second material different from the first material, each of the markers including an end recess having complementary polished third and fourth ramp surfaces that abut the polished first and second ramp surfaces when the head portion is inserted into the end recess.

2. The stent according to claim 1 wherein the end recess of each of the radiopaque markers includes axially aligned edges parallel to the longitudinal axis of the stent body adjacent the polished third and fourth ramp surfaces.

3. The stent according to claim 2 further comprising a second stent ring including struts connected by nodes positioned at a second end of the stent body opposite the first end of the stent body.

4. The stent according to claim 3 further comprising a plurality of shanks extending axially away from nodes on the second stent ring along a longitudinal axis of the stent body, each of the plurality of shanks having a head portion.

5. The stent according to claim 4 wherein each head portion includes first and second polished ramp surfaces converging and meeting at a point axially away from the stent body.

6. The stent according to claim 1 wherein the head portion polished first and second ramp surfaces and end recess complementary polished third and fourth ramp surfaces have an arcuate shape.

7. The stent according to claim 6 further comprising a second stent ring including struts connected by nodes positioned at a second end of the stent body opposite the first end of the stent body.

8. The stent according to claim 7 further comprising a plurality of shanks extending axially away from nodes on the second stent ring along a longitudinal axis of the stent body, each of the plurality of shanks having a head portion.

9. The stent according to claim 8 wherein each head portion includes first and second polished ramp surfaces converging and meeting at a point axially away from the stent body.

10. A tubular metal stent, comprising: a stent body formed from a first material including: a first stent ring including struts connected by nodes positioned at a first end of the stent body, a plurality of shanks extending axially away from nodes on the first stent ring along a longitudinal axis of the stent body, each of the plurality of shanks having a head portion, each head portion including first and second polished ramp surfaces converging and meeting at a point axially away from the stent body; and a plurality of radiopaque markers formed from a second material different from the first material, each of the markers including an end recess having complementary polished third and fourth ramp surfaces that abut the polished first and second ramp surfaces when the head portion is inserted into the end recess wherein the head portion polished first and second ramp surfaces and end recess complementary polished third and fourth ramp surfaces have an arcuate shape

11. The stent according to claim 10 further comprising a second stent ring including struts connected by nodes positioned at a second end of the stent body opposite the first end of the stent body.

12. The stent according to claim 11 further comprising a plurality of shanks extending axially away from nodes on the second stent ring along a longitudinal axis of the stent body, each of the plurality of shanks having a head portion.

13. The stent according to claim 12 wherein each head portion includes first and second polished ramp surfaces converging and meeting at a point axially away from the stent body.

14. The stent according to claim 13 wherein each of the radiopaque markers further comprises a cylindrical throughbore at an end of the recess.

15. A tubular metal stent, comprising: a stent body formed from a first material, including: a first stent ring including struts connected by nodes positioned at a first end of the stent body, a plurality of shanks extending axially away from nodes on the first stent ring along a longitudinal axis of the stent body, an arrow-shaped head extending from each of the plurality of shanks, each arrow-shaped head portion including first and second polished ramp surfaces; and a plurality of radiopaque markers formed from a second material different from the first material, each of the markers including an end recess having complementary polished third and fourth ramp surfaces that abut the polished first and second ramp surfaces when the head portion is inserted into the end recess.

16. The stent according to claim 15 further comprising a second stent ring including struts connected by nodes positioned at a second end of the stent body opposite the first end of the stent body.

17. The stent according to claim 16 further comprising a plurality of shanks extending axially away from nodes on the second stent ring along a longitudinal axis of the stent body, each of the plurality of shanks having a head portion.

18. The stent according to claim 17 wherein each head portion includes first and second polished ramp surfaces converging and meeting at a point axially away from the stent body.

19. The stent according to claim 18 wherein each of the radiopaque markers further comprises a cylindrical throughbore at an end of the recess.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] For a better understanding of the present invention, and to show how the same may be carried into effect, reference will now be made, be way of example, to the accompanying drawings, in which

[0014] FIG. 1 is a perspective view of a single welding interface between part of a tubular metal prosthesis and a component of a different metal to be welded to that prosthesis;

[0015] FIGS. 2 to 5 show, respectively, plan views of four variations on the design concept visible in FIG. 1;

[0016] FIG. 6 shows part of a ring of male portions that extends around the circumference of a tubular metal prosthesis; and

[0017] FIG. 7 shows (at slightly higher magnification) part of a ring of corresponding components of another metal, with female portions destined to be welded to the respective projecting male portions shown in FIG. 6.

DETAILED DESCRIPTION

[0018] Referring to FIG. 1, a stent 10 similar to the one shown in WO-A-02/15820 has, at each end, a ring of nodes 12 between adjacent struts 14, 15 of the strut matrix of the stent. A shank 16 extends axially away from each node 12 and the stent matrix as such, as far as the root 18 of an arrowhead shape 20 that lies between symmetrical and complementary ramp surfaces 22 and 24 that converge to a tip 26 of the arrowhead 20 to define a male portion that is approximated with a female portion of a tantalum marker spoon 30 that has an abluminal major surface 32 and (not visible in FIG. 1) an opposed luminal major surface 34 which faces the long axis of the stent tube so that the thickness or the tantalum spoon 30 lies within an annulus centered on the long axis of the stent.

[0019] The female portion chat receives the arrowhead 20 is provided by opposed symmetrical complementary ramp surfaces 36 and 38 which converge to the root or base 40 of what can be seen as a V-shaped recess to receive the ramp surfaces 22 an 24 of the arrowhead 20. At the base of the groove 40 there is a cylindrical throughbore 42 which is provided for reducing the risk of crack-initiation and propagation from the root of the V-shaped groove that receives the arrowhead 20.

[0020] In manufacture, the stent matrix (typically made of nickel titanium shape memory alloy) is electro-polished before it is approximated with the tantalum spoon 30. Likewise, the tantalum spoon 30, likely still part of a laser cut tube of tantalum and in the company of a plurality of other tantalum spoons that extends around the axis of the tubular workpiece (see the description in WO-A-02/15820) is also electro-polished and, after separate electro-polishing of the tantalum components and the nickel titanium components, the respective arrowhead male portions 20 can be brought into approximation with the corresponding female ramp surfaces of the respective tantalum spoons 30, ready for welding.

[0021] FIG. 1 does reveal a small welding gap between ramp surfaces 22 and 36, and surfaces 24 and 38. This is the gap that is filled with weld metal in consequence of the welding step of assembly of the tantalum spoons 30 to the stent prosthesis 10. If the amount of material removed from the respective ramp surfaces during respective electro-polishing is different form what was predicted, this need have no disturbing effect on the desired welding gap, provided that prior to welding there is a judicious relative axial movement of the male and female portions so as to bring about the desired optimal welding gap between the respective ramp surfaces.

[0022] Turning now to the remaining drawing figures, FIG. 2 is provided with reference numbers corresponding to those of FIG. 1 and, we think, needs no further text description. FIG. 3 differs only slightly from FIG. 2, in that the female ramp surfaces do not run as far as the marginal edge of the tantalum component. Rather, the ramp surfaces are set back from the edge 50, in that the ramp surface 36 continues as an unramped axially aligned edge 52 and, likewise, ramp surface 38 continues as an axially aligned straight edge 54, parallel to edge 52. Recessing the arrowhead inside the tantalum spoon avoids any adverse effects that might flow from having the acute angle between the arrowhead ramp surfaces 22 and 24 and the base 56 of the arrowhead lying outside the envelope of the tantalum spoon 30.

[0023] Turning to FIG. 4, there is shown, two further variations. First, the ramp surfaces are arcuate rather than straight, so the welding gap is not mathematically constant but nevertheless changes with relative axial movement of the ramp surfaces and, second, the arrowhead is gripped by re-entrant portions 60 that flank the shank 16. This engagement can be, as a matter of design preference, either resilient or of form-fit conception, with the arrowhead being introduced from radially inside or outside the female receiving portion in the component 30.

[0024] FIG. 5 reveals a further variation, and difference from FIG. 4, in that the arrowhead shape includes two terminal barbs 70 which can be resilient enough to locate the arrowhead with the cavity in the spoon 30. From FIGS. 6 and 7 it will be appreciated that a ring of male projections 20 can be located around the circumference of the prosthesis, and offered up to a corresponding ring of recesses, each with root 40, in respective components of another metal such as spoons 30. Just as in WO 02/15820 mentioned above, the ring of spoons can constitute a complete ring of material around the lumen of the prosthesis, with only laser cut gaps in between adjacent spoons.

[0025] In the case of welding a plurality of components (such as radiopaque markers) to a prosthesis, the components can be found all within a common workpiece, from which they are parted after welding, as described above. Alternatively, each component can be separate from the outset, then prepared individually, and then welded individually to the prosthesis.

[0026] It will be appreciated that the prosthesis needs to be polished to a high level and, generally speaking, the excellence and integrity of the polishing of the prosthesis overall should, if anything, be higher than the level of polishing of a radiopaque marker on the prosthesis.

[0027] The ramp surfaces that characterise the present invention can compensate for variations, prior to welding, in the weld surfaces of the prosthesis and component, respectively.