Methods of fabricating stents with enhanced fracture toughness

• US 8,658,081 B2
• Filed: 07/28/2010
• Issued: 02/25/2014
• Est. Priority Date: 06/15/2006
• Status: Expired due to Fees

• Current Assignee: Advanced Cardiovascular Systems Incorporated (Abbott Laboratories)
• Original Assignee: Advanced Cardiovascular Systems Incorporated (Abbott Laboratories)
• Inventors: Gale, David C., Huang, Bin, Limon, Timothy, Gueriguian, Vincent J.
• Primary Examiner(s): Johnson, Christina
• Assistant Examiner(s): HUDA, SAEED M
• Application Number:
  US12/845,536
• Publication Number:
  US 20100289191A1
• Time in Patent Office: 1,308 Days
• Field of Search: 264/138, 264/400, 264/523, 264/534, 623/1.15, 623/1.16
• US Class Current: 264/534
• CPC Class Codes: A61F 2/90 characterised by a net-like or mesh-like structure
• 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 2/915 with bands having a meander structure, adjacent bands being connected to each other
• CPC Class Codes: A61F 2/9522 Means for mounting a stent or stent-graft onto or into a placement instrument
• CPC Class Codes: A61F 2002/91533 characterised by the phase between adjacent bands
• CPC Class Codes: A61F 2002/91558 connected peak to peak
• CPC Class Codes: A61F 2002/91566 connected trough to trough
• CPC Class Codes: A61F 2002/91583 by a bridge, whereby at least one of its ends is connected along the length of a strut between two consecutive apices within a band
• CPC Class Codes: A61F 2210/0004 bioabsorbable
• CPC Class Codes: A61F 2220/0016 with sharp anchoring protrusions, e.g. barbs, pins, spikes
• CPC Class Codes: A61L 31/06 obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds A61L31/041 takes precedence
• 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 31/148 Materials at least partially resorbable by the body
• CPC Class Codes: B29C 2049/7831 characterised by pressure values or ranges
• CPC Class Codes: B29C 2793/0009 Cutting out
• CPC Class Codes: B29C 2949/08 Preforms made of several individual parts, e.g. by welding or gluing parts together
• CPC Class Codes: B29C 35/045 using gas or flames
• CPC Class Codes: B29C 49/0005 characterised by the material
• CPC Class Codes: B29C 49/14 Clamps
• CPC Class Codes: B29C 49/4273 Auxiliary operations after the blow-moulding operation not otherwise provided for
• CPC Class Codes: B29C 49/4823 : with incorporated heating or cooling means
• CPC Class Codes: B29C 55/22 : of tubes B29C61/08 takes precedence
• CPC Class Codes: B29C 55/24 : radial
• CPC Class Codes: B29C 69/001 : a shaping technique combined with cutting, e.g. in parts or slices combined with rearranging and joining the cut parts for reinforced material B29C70/545; B29C49/4278, B29C51/268 take precedence
• CPC Class Codes: B29K 2067/00 : Use of polyesters or derivatives thereof, as moulding material
• CPC Class Codes: B29K 2067/046 : PLA, i.e. polylactic acid or polylactide
• CPC Class Codes: B29K 2105/258 : Tubular
• CPC Class Codes: B29K 2995/006 : Bio-degradable, e.g. bioabsorbable, bioresorbable or bioerodible
• CPC Class Codes: B29L 2031/7534 : Cardiovascular protheses
• CPC Class Codes: C08L 67/04 : Polyesters derived from hydroxycarboxylic acids, e.g. lactones C08L67/06 takes precedence
• CPC Class Codes: Y10T 156/1026 : with slitting or removal of material at reshaping area prior to reshaping

Abstract

Stents and methods of manufacturing a stents with enhanced fracture toughness are disclosed.

Claims

1. A method of making a stent comprising:

radially expanding a polymer tube to about 400% to 800% of a starting diameter of the tube to increase the radial stiffness of the tube, wherein the fracture toughness of the radially expanded tube is enhanced by heating the tube to a temperature such that the crystal nucleation rate is at least twice the crystal growth rate while the tube is being radially expanded; and

forming a plurality of rings from the radially expanded tube, wherein a ring forms a plurality of cells, each of the cells being defined by opposed ends separated by a circumferential distance and opposed bending elements extending between and connecting the opposed ends, and wherein an adjacent pair of rings are interconnected by a linking element.

2. The method of claim 1, the polymer having a glass transition temperature (Tg) and a melting temperature (Tm), wherein the tube has a temperature of about Tg+0.2(Tm−

Tg) when the tube is being radially expanded.

3. The method of claim 1,

wherein the tube is a poly (L-lactide) tube.

4. The method of claim 1, wherein the tube is a poly (glycolic acid) tube.

5. The method of claim 1, wherein the cell is a diamond shaped cell.

6. The method of claim 1, wherein a first cell and a second, adjacent cell share an end.

7. The method of claim 1, wherein the linking element is a longitudinal linking element.

8. The method of claim 1, wherein the linking element is connected to one of the ends that form the cell.

9. A method of making a stent comprising:

radially expanding a polymer tube at a temperature in which the crystal nucleation rate is at least twice the crystal growth rate to both increase radial stiffness and enhance fracture toughness in the polymer tube; and

forming a plurality of rings from the radially expanded tube;

wherein a ring includes a plurality of cells, each of which being defined by opposed ends separated by a circumferential distance and opposed bending elements extending between and connecting the opposed ends.

10. The method of claim 9, wherein the rings are interconnected by longitudinal linking elements.

11. The method of claim 10, wherein an end forms an end for each of two, adjacent cells of the ring.

12. The method of claim 11, wherein a longitudinal distance separating the opposed bending elements define a maximum width for the ring.

13. A method of making a stent comprising:

radially expanding an extruded poly (L-lactide) tube to increase its radial stiffness, wherein a temperature of the tube during the radial expansion is within a range where a crystal nucleation rate is higher than a crystal growth rate so as to provide at least a desired fracture toughness for the radially stiffened tube; and

forming the stent including forming a plurality of rings connected by linking elements from the radially stiffened tube;

wherein the stent is configured for being crimped to a balloon and then radially expanded within a body lumen by the balloon such that the inflated balloon induces plastic deformation of the stent to maintain the stent in an expanded state within the body lumen.

14. The method of claim 13 wherein the temperature during radial expansion is about Tg+0.2(Tm−

Tg).

15. The method of claim 14 wherein the stent is laser cut from the expanded poly (L-lactide) tube.