Medical devices incorporating SIM alloy elements

• US 6,306,141 B1
• Filed: 06/07/1995
• Issued: 10/23/2001
• Est. Priority Date: 10/14/1983
• Status: Expired due to Term

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Jervis, James E.
• Primary Examiner(s): YU, JUSTINE ROMANG
• Application Number:
  US08/483,291
• Time in Patent Office: 2,330 Days
• Field of Search: 606/78, 606/60, 606/108, 606/62, 606/68, 606/200, 606/195, 606/198, 623/1
• US Class Current: 606/78
• CPC Class Codes: A61B 17/0642 for bones, e.g. for osteosynthesis or connecting tendon to bone
• CPC Class Codes: A61B 17/08 Wound clamps or clips, i.e. not or only partly penetrating the tissue suture bridges A61B17/0466; Devices for bringing together the edges of a wound
• CPC Class Codes: A61B 17/72 Intramedullary pins, nails or other devices A61B17/744 takes precedence
• CPC Class Codes: A61B 2017/00867 shape memory effect
• CPC Class Codes: A61B 2017/0647 having one single leg, e.g. tacks
• CPC Class Codes: A61B 2017/0649 Coils or spirals
• CPC Class Codes: A61C 2201/007 using shape memory effect
• CPC Class Codes: A61C 7/12 Brackets; Arch wires; Combinations thereof; Accessories therefor
• CPC Class Codes: A61F 2/01 Filters implantable into blood vessels
• CPC Class Codes: A61F 2/07 Stent-grafts
• CPC Class Codes: A61F 2/2409 Support rings therefor, e.g. for connecting valves to tissue annuloplasty rings A61F2/2442
• CPC Class Codes: A61F 2002/30092 using shape memory or superelastic materials, e.g. nitinol
• CPC Class Codes: A61F 2210/0019 operated at only one temperature whilst inside or touching the human body, e.g. constrained in a non-operative shape during surgery, another temperature only occurring before the operation
• CPC Class Codes: A61F 6/14 intra-uterine type
• CPC Class Codes: A61L 2400/16 Materials with shape-memory or superelastic properties
• CPC Class Codes: A61L 2430/02 for reconstruction of bones; weight-bearing implants
• CPC Class Codes: A61L 27/04 Metals or alloys
• CPC Class Codes: A61L 31/022 Metals or alloys

Abstract

Medical devices which are currently proposed to use elements made from shape memory alloys may be improved by the use of stress-induced martensite alloy elements instead. The use of stress-induced martensite decreases the temperature sensitivity of the devices, thereby making them easier to install and/or remove.

Claims

1. A medical device for insertion into a mammalian body, the device comprising

(a) a hollow placement device;

(b) a memory alloy element formed at least partly from pseudoelastic shape-memory alloy, the alloy displaying reversible stress-induced martensite at about body temperature such that it has a stress-induced martensitic state and an austenitic state, the memory alloy element having (i) a deformed shape when the alloy is in its stress-induced martensitic state and (ii) a different unstressed shape when the alloy is in its austenitic state; and

(c) a guide wire;

the memory alloy element being within the hollow placement device, and the placement device being guidable by the guide wire, the hollow placement device stressing the memory alloy element at a temperature greater than the A_s of the alloy so that the memory alloy element is in its deformed shape,

wherein the memory alloy element can be extruded from the hollow placement device by the guide wire at a temperature greater than the A_s of the alloy to transform at least a portion of the alloy from its stress-induced martensitic state so that the memory alloy element transforms from its deformed shape to its unstressed shape, and wherein the alloy is selected so that the transformation can occur without any change in temperature of the placement device or the memory alloy element.

2. The device of claim 1 wherein the memory alloy element is a stent.

3. The device of claim 2, including a guide wire for endarterial placement of the stent graft.

4. The invention of claim 1 wherein the transformation occurs without any change in the state of the placement device.

5. The device of claim 1, wherein the hollow placement device is a catheter.

17. The device of claim 1, 11, 15, or 16, wherein the mammalian body is a human body.

21. The device of claim 1, 15, 16, or 18, wherein the restraint is a catheter.

22. The device of claim 1, 11, 15, or 18 wherein the stent is a coil stent.

6. A medical device which comprises:

(a) a stent for endarterial placement within a human body so that the stent is substantially at human body temperature, the stent comprising a shape memory alloy which displays stress-induced martensite behavior at body temperature; and

(b) a restraint holding the stent in a deformed configuration at a temperature less than the body temperature of the human for endarterial positioning of the stent within the human body in its deformed configuration, the deformation occurring through the formation of stress-induced martensite;

wherein the stent is sufficiently deformed that when the stent is at human body temperature removal of the restraint from the stent, without change in temperature of the device, releases at least a portion of the stent from its deformed configuration.

8. A device as claimed in claim 6 or 7, in which the restraint is a catheter.

9. A device as claimed in claim 6 or 7, in which the stent has a transverse dimension and a longitudinal dimension, and wherein the stent is deformed by its transverse dimension being reduced, and wherein the restraint prevents transverse expansion of the stent.

10. The device of claim 6, wherein the shape memory alloy element is sufficiently deformed that removal of the restraint from the shape memory alloy releases at least a portion of the shape alloy element from its deformed configuration without change in state of the restraint.

7. A device as claimed in 6, in which the restraint is hollow, and the stent is positioned at least partially within the restraint.

11. A medical device suitable for placement within a mammalian body for treatment of the mammalian body, the device comprising:

(a) a stent formed at least partly from a pseudoelastic shape-memory alloy, the alloy having a reversible stress-induced martensitic state and an austenitic state, the memory alloy element having (i) a deformed shape when the alloy is in its stress-induced martensitic state and (ii) a different, unstressed shape; and

(b) restraining means engaging and stressing the stent at a temperature less than the body temperature of the mammal and greater than the A_s of the alloy for positioning the stent within the mammalian body while the stent is in its deformed shape;

wherein the alloy is selected so that removal of the restraining means from the stent at a temperature greater than the A_s of the alloy when the device is placed within the mammalian body, transforms at least a portion of the alloy from its stressed-induced martensitic state so that the stent transforms from its deformed relatively straightened shape towards its unstressed relatively coiled shape, without any change in temperature of the restraining means or the stent being required for the transformation of the alloy.

12. The device of claim 11, wherein the transformation of the alloy occurs without any change in state of the restraining means.

13. The device of claim 11 wherein the restraining means is a catheter.

14. The device of claim 13 wherein the stent is within the catheter.

19. The device of claim 6, 11, 15, 16 or 18, including a guide wire for endarterial placement of the stent.

15. A medical device for treatment of a mammalian body, the device comprising:

(a) a memory alloy stent formed at least partly from a pseudoelastic shape-memory alloy, the alloy displaying reversible stress-induced martensite at about the mammalian body temperature such that it has a stress-induced martensitic state and an austenitic state, the memory alloy stent having (i) a deformed relatively straightened shape when the alloy is in its stress-induced martensitic state and (ii) a different unstressed relatively coiled shape; and

(b) a hollow restraining member with the memory alloy stent being within the restraining member, the restraining member engaging and stressing the memory alloy stent at a temperature less than the body temperature of the mammal and greater than the A_s of the alloy for positioning the memory alloy stent within the human body while the memory alloy coil stent is in its deformed relatively straightened shape;

wherein the restraining member and the memory alloy stent are movable relative to each other to transform at least a portion of the alloy from its stress-induced martensitic state at a temperature greater than the A_s of the alloy so that the memory alloy element transforms from its deformed shape towards its unstressed relatively coiled shape, and wherein the alloy is selected so that the transformation can occur without any change in temperature of the restraining member or the memory alloy coil stent.

20. The device of claim 15, 16, or 18, wherein the transformation of the alloy occurs without any change in state of the restraint.

16. A medical device suitable for placement within a mammalian body for treatment of the mammalian body, the device comprising (i) a restraint, and (ii) a coil stent formed at least partly from a pseudoelastic shape-memory alloy,

the alloy displaying reversible stress-induced martensite by virtue of being above its A_s and above its M_s and below its M_d at about body temperature;

such that it has a stress-induced martensitic state and an austenitic state, the element having (i) a relatively straightened shape when the alloy is in its stress-induced martensitic state and (ii) a different relatively coiled shape;

wherein the restraint is (i) stressing the coil stent at a temperature less than the body temperature of the mammal for placement of the coil stent in its relatively straightened shape in the mammalian body and (ii) is capable of being at least partially removed from the coil stent while the coil stent is within the body at the body temperature and the coil stent is therefore at an operating temperature greater than the A_s and M_s and below the M_d of the alloy,

such removal of the restraint causing at least a portion of the alloy to transform from its stress-induced martensitic state to its austenitic state so that the coil stent spontaneously transforms from its relatively straightened shape towards its relatively coiled shape,

and such transformation can occur without a change in temperature of the restraint or of the coil stent from the operating temperature.

18. A medical device comprising:

(a) a wire stent formed at least partly from a pseudoelastic shape memory alloy, the alloy displaying reversible stress-induced martensite at about human body temperature such as it has a deformed shape when the alloy is in its stress-induced martensitic state and a different unstressed shape when the alloy is in its austenitic state; and

(b) a restraint stressing the wire stent at a temperature greater than the A_s of the alloy so that the wire stent is in its deformed shape,

wherein the stent can be disengaged from the restraint upon placement in a human so that the stent transforms from its deformed shape to its unstressed shape, and

wherein the alloy is selected so that the transformation can occur without any change in temperature of the restraint or the wire stent.