Stents of enhanced biocompatibility and hemocompatibility

• US 5,690,670 A
• Filed: 06/06/1995
• Issued: 11/25/1997
• Est. Priority Date: 12/21/1989
• Status: Expired due to Fees

• Current Assignee: James A. Davidson
• Original Assignee: James A. Davidson
• Inventors: Davidson, James A.
• Primary Examiner(s): Buiz, Michael Powell
• Assistant Examiner(s): TRUONG, KEVIN THAO
• Application Number:
  US08/468,258
• Time in Patent Office: 903 Days
• Field of Search: 606/198, 606/191, 606/192, 606/194, 606/195, 606/197, 623/2, 623/12, 604/96, 604/104
• US Class Current: 606/198
• CPC Class Codes: A61B 17/58 for osteosynthesis, e.g. bone plates, screws , setting implements or the like A61B17/14, A61B17/16 take precedence
• CPC Class Codes: A61B 17/72 Intramedullary pins, nails or other devices A61B17/744 takes precedence
• CPC Class Codes: A61B 17/7275 with expanding cylindrical parts
• CPC Class Codes: A61B 17/746 the longitudinal elements coupled to a plate opposite the femoral head
• CPC Class Codes: A61B 17/80 Cortical plates , i.e. bone plates; Instruments for holding or positioning cortical plates, or for compressing bones attached to cortical plates
• CPC Class Codes: A61B 17/8061 specially adapted for particular bones A61B17/70 and A61B17/74 take precedence
• CPC Class Codes: A61B 17/86 Pins or screws or threaded wires; nuts therefor A61B17/72 take precedence
• CPC Class Codes: A61B 17/866 Material or manufacture
• CPC Class Codes: A61B 2017/22038 with a guide wire
• CPC Class Codes: A61C 7/12 Brackets; Arch wires; Combinations thereof; Accessories therefor
• CPC Class Codes: A61C 8/0012 characterised by the material or composition, e.g. ceramics, surface layer, metal alloy use of specific materials A61K6/00
• CPC Class Codes: A61F 2/0077 Special surfaces of prostheses, e.g. for improving ingrowth A61F2/30767 takes precedence
• CPC Class Codes: A61F 2/06 Blood vessels
• CPC Class Codes: A61F 2/07 Stent-grafts
• CPC Class Codes: A61F 2/24 Heart valves ; Vascular valves, e.g. venous valves; Heart implants, e.g. passive devices for improving the function of the native valve or the heart muscle; Transmyocardial revascularisation [TMR] devices; Valves implantable in the body
• CPC Class Codes: A61F 2/2403 with pivoting rigid closure members check valves with hinged closure members in general F16K15/03
• CPC Class Codes: A61F 2/2406 without fixed axis
• CPC Class Codes: A61F 2/2421 with non-pivoting rigid closure members
• CPC Class Codes: A61F 2/2424 Ball valves
• CPC Class Codes: A61F 2/2442 Annuloplasty rings or inserts for correcting the valve shape; Implants for improving the function of a native heart valve
• CPC Class Codes: A61F 2/2448 : D-shaped rings
• CPC Class Codes: A61F 2/30767 : Special external or bone-contacting surface, e.g. coating for improving bone ingrowth
• CPC Class Codes: A61F 2/367 : Proximal or metaphyseal parts of shafts trochanteric devices connected to said proximal parts A61F2/30739
• CPC Class Codes: A61F 2/38 : for elbows or knees
• CPC Class Codes: A61F 2/3859 : Femoral components
• CPC Class Codes: A61F 2/389 : Tibial components A61F2/3868 takes precedence
• CPC Class Codes: A61F 2/91 : made from perforated sheet material or tubes, e.g. perforated by laser cuts or etched holes
• CPC Class Codes: A61F 2/958 : Inflatable balloons for placing stents or stent-grafts
• CPC Class Codes: A61F 2002/30677 : Means for introducing or releasing pharmaceutical products, e.g. antibiotics, into the body
• CPC Class Codes: A61F 2002/30922 : Hardened surfaces
• CPC Class Codes: A61F 2002/3631 : with an integral complete or partial peripheral collar or bearing shoulder at its base
• CPC Class Codes: A61F 2002/368 : with lateral apertures, bores, holes or openings, e.g. for reducing the mass, for receiving fixation screws or for communicating with the inside of a hollow shaft
• CPC Class Codes: A61F 2250/0067 : Means for introducing or releasing pharmaceutical products into the body
• CPC Class Codes: A61F 2310/00023 : Titanium or titanium-based alloys, e.g. Ti-Ni alloys
• CPC Class Codes: A61F 2310/0058 : Coating made of diamond or of diamond-like carbon DLC
• CPC Class Codes: A61F 2310/00592 : Coating or prosthesis-covering structure made of ceramics or of ceramic-like compounds
• CPC Class Codes: A61F 2310/00616 : Coating made of titanium oxide or hydroxides
• CPC Class Codes: A61F 2310/00634 : Coating made of zirconium oxide or hydroxides
• CPC Class Codes: A61F 2310/0064 : Coating made of niobium oxide or hydroxides
• CPC Class Codes: A61F 2310/00658 : Coating made of tantalum oxide or hydroxides
• CPC Class Codes: A61F 2310/00748 : Coating made of titanium carbide
• CPC Class Codes: A61F 2310/00766 : Coating made of zirconium carbide
• CPC Class Codes: A61F 2310/00772 : Coating made of niobium carbide
• CPC Class Codes: A61F 2310/0088 : Coating made of titanium nitride
• CPC Class Codes: A61F 2310/00892 : Coating made of zirconium nitride
• CPC Class Codes: A61F 2310/00898 : Coating made of niobium nitride
• CPC Class Codes: A61L 2430/36 : for embolization or occlusion, e.g. vaso-occlusive compositions or devices
• CPC Class Codes: A61L 27/06 : Titanium or titanium alloys
• CPC Class Codes: A61L 27/50 : Materials characterised by their function or physical properties , e.g. injectable or lubricating compositions, shape-memory materials, surface modified materials
• CPC Class Codes: A61L 27/507 : for artificial blood vessels apparatus for applying cells on a blood vessel prosthesis A61F2/062
• CPC Class Codes: A61L 31/022 : Metals or alloys
• CPC Class Codes: A61L 31/14 : Materials characterised by their function or physical properties , e.g. injectable or lubricating compositions, shape-memory materials, surface modified materials
• CPC Class Codes: A61L 33/022 : Metal or alloys
• CPC Class Codes: A61M 2025/0062 : having features to improve the sliding of one part within another by using lubricants or surfaces with low friction
• CPC Class Codes: A61M 2205/32 : with radio-opaque indicia
• CPC Class Codes: A61M 25/09 : Guide wires
• CPC Class Codes: A61M 60/148 : in line with a blood vessel using resection or like techniques, e.g. permanent endovascular heart assist devices
• CPC Class Codes: A61M 60/178 : drawing blood from a ventricle and returning the blood to the arterial system via a cannula external to the ventricle, e.g. left or right ventricular assist devices
• CPC Class Codes: A61M 60/196 : replacing the entire heart, e.g. total artificial hearts [TAH]
• CPC Class Codes: A61M 60/43 : using vacuum at the blood pump, e.g. to accelerate filling
• CPC Class Codes: A61M 60/446 : the axis of both movements being parallel, e.g. roller screw actuators or cylindrical cam transmissions
• CPC Class Codes: A61M 60/867 : using position detection during deployment, e.g. for blood pumps mounted on and driven through a catheter
• CPC Class Codes: A61N 1/05 : for implantation or insertion into the body, e.g. heart electrode A61N1/06 takes precedence
• CPC Class Codes: A61N 1/056 : Transvascular endocardial electrode systems
• CPC Class Codes: C22C 14/00 : Alloys based on titanium
• CPC Class Codes: C22C 30/00 : Alloys containing less than 50% by weight of each constituent

Abstract

Cardiovascular and other medical implants fabricated from low-modulus Ti-Nb-Zr alloys to provide enhanced biocompatibility and hemocompatibility. The cardiovascular implants may be surface hardened by oxygen or nitrogen diffusion or by coating with a tightly adherent, hard, wear-resistant, hemocompatible ceramic coating. The cardiovascular implants include heart valves, total artificial heart implants, ventricular assist devices, vascular grafts, stents, electrical signal carrying devices such as pacemaker and neurological leads, defibrillator leads, and the like. It is contemplated that the Ti-Nb-Zr alloy can be substituted as a fabrication material for any cardiovascular implant that either comes into contact with blood thereby demanding high levels of hemocompatibility, or that is subject to microfretting, corrosion, or other wear and so that a low modulus metal with a corrosion-resistant, hardened surface would be desirable.

Claims

1. An expandable stent for supporting a blood, urinary, or gastrointestinal vessel from collapsing inward, the stent having enhanced hemocompatibility, comprising:

(a) a radially outwardlly expandable stent body for insertion in a tubular conduit of a living body, said stent body having outer surfaces and a longitudinal bore therethrough for receiving a means for expanding said stent body radially outwardly; and

(b) anchoring means on said outer surfaces for engaging said tubular conduit and anchoring said stent body in a radially outward expanded position thereby supporting said tubular conduit from collapsing inward;

the stent at least partially fabricated from a biocompatible and hemocompatible low elastic modulus metal alloy comprising;

(i) titanium; and

(ii) from about 10 wt. % to about 20 wt. % niobium or from about 35 wt. % to about 50 wt. % niobium;

wherein the alloy is free of toxic elements, except such amounts of said toxic elements as may occur as impurities in the alloy and as contaminants as a result of an alloying process.

2. The stent of claim 1, wherein said alloy further comprises an amount of zirconium sufficient to retard the transformation of beta.

3. The stent of claim 2, wherein the metal alloy comprises from about 0.5 to about 20 wt. % zirconium.

4. The stent of claim 2, further comprising a hardened outer surface layer on at least a portion of the stent, said layer formed on the stent by a process selected from the group consisting of oxygen diffusion hardening, nitrogen diffusion hardening, physical vapor deposition, and chemical vapor deposition.

5. The stent of claim 2, wherein the metal alloy comprises about 74 wt. % titanium, about 13 wt. % niobium, and about 13 wt. % zirconium.

6. The stent of claim 2, wherein the metal alloy comprises titanium, from about 10 to about 20 wt. % niobium, and up to about 20 wt. % zirconium.

7. The stent of claim 2, wherein the metal alloy comprises titanium, from about 35 to about 50 wt. % niobium, and up to about 20 wt. % zirconium.

8. The stent of claim 1, further comprising a hardened outer surface layer on at least a portion of the stent, said layer formed on the stent by a process selected from the group consisting of oxygen diffusion hardening, nitrogen diffusion hardening, physical vapor deposition, and chemical vapor deposition.

9. The stent of claim 1 or claim 2 or claim 8 or claim 4, wherein surfaces of the stent that come into contact with body tissue or fluid are at least partially coated with a composition selected from the group consisting of anticoagulants, antimicrobial agents, antibiotics, and medicaments.

10. The stent of claim 1 or claim 2 or claim 8 or claim 4, further comprising a lower friction wear-resistant outer surface layer on at least a portion of the stent, said lower friction wear-resistant outer surface layer produced by a process selected from the group consisting of boronation and silver doping.

11. An expandable stent for supporting a blood, urinary, or gastrointestinal vessel from collapsing inward, the stent having enhanced hemocompatibility, comprising:

(a) a radially outwardlly expandable stent body for insertion in a tubular conduit of a living body, said stent body having outer surfaces and a longitudinal bore therethrough for receiving a means for expanding said stent body radially outwardly; and

(b) anchoring means on said outer surfaces for engaging said tubular conduit and anchoring said stent body in a radially outward expanded position thereby supporting said tubular conduit from collapsing inward;

the stent at least partially fabricated from a biocompatible and hemocompatible low elastic modulus metal alloy comprising;

(i) titanium; and

(ii) niobium and tantalum, wherein the combined wt. % of niobium and tantalum is from about 10 wt. % to about 20 wt. % or from about 35 wt. % to about 50 wt. %;

wherein the alloy is free of toxic elements, except such amounts of said toxic elements as may occur as impurities in the alloy and as contaminants as a result of an alloying process.

12. The stent of claim 11, wherein said alloy further comprises an amount of zirconium sufficient to retard the transformation of beta.

13. The stent of claim 12, wherein the metal alloy comprises from about 0.5 to about 20 wt. % zirconium.

14. The stent of claim 12, further comprising a hardened outer surface layer on at least a portion of the stent, said layer formed on the stent by a process selected from the group consisting of oxygen diffusion hardening, nitrogen diffusion hardening, physical vapor deposition, and chemical vapor deposition.

15. The stent of claim 11, further comprising a hardened outer surface layer on at least a portion of the stent, said layer formed on the stent by a process selected from the group consisting of oxygen diffusion hardening, nitrogen diffusion hardening, physical vapor deposition, and chemical vapor deposition.

16. The stent of claim 11 or claim 12 or claim 15 or claim 14, wherein surfaces of the stent that come into contact with body tissue or fluid are at least partially coated with a composition selected from the group consisting of anticoagulants, antimicrobial agents, antibiotics, and medicaments.

17. The stent of claim 11 or claim 12 or claim 15 or claim 14, further comprising a lower friction wear-resistant outer surface layer on at least a portion of the stent, said lower friction wear-resistant outer surface layer produced by a process selected from the group consisting of boronation and silver doping.