Processes for making crush recoverable polymer scaffolds

• US 9,642,730 B2
• Filed: 04/01/2016
• Issued: 05/09/2017
• Est. Priority Date: 09/23/2010
• Status: Active Grant

• Current Assignee: Abbott Cardiovascular Systems Incorporated (Abbott Laboratories Incorporated)
• Original Assignee: Abbott Cardiovascular Systems Incorporated (Abbott Laboratories Incorporated)
• Inventors: Ngo, Michael H., Trollsas, Mikael, Papp, John E., Nguyen, Hung T., Jayasinghe, Dudley, Farnbach, Ron, Orr, Gregory C., Smith, Joshua, Xie, Yongjin, Ku, Yu-Chun
• Primary Examiner(s): Johnson, Christina
• Assistant Examiner(s): LIU, XUE H
• Application Number:
  US15/089,392
• Publication Number:
  US 20160278952A1
• Time in Patent Office: 403 Days
• Field of Search: 264280
• CPC Class Codes: A61F 2/844 folded prior to deployment
• CPC Class Codes: A61F 2/89 the wire-like elements comprising two or more adjacent rings flexibly connected by separate members
• 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 2/958 Inflatable balloons for placing stents or stent-grafts
• CPC Class Codes: A61F 2002/91566 connected trough to trough
• CPC Class Codes: A61F 2002/91575 connected peak 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 2002/9583 Means for holding the stent on the balloon, e.g. using protrusions, adhesives or an outer sleeve
• CPC Class Codes: A61F 2210/0071 thermoplastic
• CPC Class Codes: A61F 2230/0054 V-shaped
• CPC Class Codes: A61F 2230/0056 W-shaped, e.g. M-shaped, sigma-shaped
• CPC Class Codes: B23K 2103/42 Plastics B23K2103/16 takes precedence
• CPC Class Codes: B23K 2103/50 Inorganic material, e.g. metals, not provided for in B23K2103/02 – B23K2103/26
• CPC Class Codes: B23K 26/361 for deburring or mechanical trimming B23K26/351 takes precedence
• CPC Class Codes: B23K 26/362 Laser etching
• CPC Class Codes: B23K 26/402 involving non-metallic material, e.g. isolators
• 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 49/071 Preforms or parisons characterised by their configuration, e.g. geometry, dimensions or physical properties
• CPC Class Codes: B29C 49/08 : Biaxial stretching during blow-moulding
• CPC Class Codes: B29C 55/26 : biaxial
• CPC Class Codes: B29K 2067/046 : PLA, i.e. polylactic acid or polylactide
• CPC Class Codes: B29L 2031/753 : Medical equipment; Accessories therefor bloodbags, medical bags B29L2031/7148; artificial eyes B29L2011/0008
• CPC Class Codes: B29L 2031/7534 : Cardiovascular protheses
• CPC Class Codes: Y10T 156/1002 : with permanent bending or reshaping or surface deformation of self sustaining lamina

Abstract

Methods for making scaffolds for delivery via a balloon catheter are described. The scaffold, after being deployed by the balloon, provides a crush recovery of about 90% after the diameter of the scaffold has been pinched or crushed by 50%. The scaffold structure has patterns that include an asymmetric or symmetric closed cell, and links connecting such closed cells.

Claims

1. A method for making a medical device, comprising:

forming a scaffold from a tube made from a polymer;

crimping the scaffold to a balloon, wherein the scaffold is plastically deformed to have a crimped state; and

fitting a removable sheath over the scaffold and balloon following crimping to limit recoil of the crimped scaffold;

wherein the scaffold has an expanded diameter when plastically deformed from the crimped state by the balloon; and

wherein the scaffold attains greater than 90% of the expanded diameter after being crushed by an amount equal to at least 33% of the expanded diameter.

2. The method of claim 1, wherein the scaffold is heated to a temperature below a glass transition temperature of the polymer when the scaffold is being crimped to the balloon.

3. The method of claim 1, wherein the polymer is poly (L-lactide) (PLLA), a polymer made from at least 80% L-lactide, a block copolymer with a PLLA block, or a copolymer of PLLA.

4. The method of claim 1, wherein the scaffold has a pre-crimp diameter prior to crimping and a wall thickness, and a ratio of the pre-crimp diameter to the wall thickness is between 20 and 45.

5. The method of claim 1, wherein the scaffold is crimped to a balloon of a balloon-catheter having a distal end, wherein the sheath includes a distal end that extends beyond the catheter distal end, and wherein the sheath includes flaps that are folded to enable the flaps to be gripped and pulled apart when removing the sheath from the scaffold.

6. The method of claim 1, wherein the scaffold includes rings having crowns and the crowns form crown angles, wherein during crimping a ring is reduced in diameter by plastic deformation resulting in an articulation of struts about crowns;

and

wherein prior to crimping

the scaffold has an outer diameter of 8 to 10 mm, the crown angles for the rings are between 90 and 115 degrees, and the scaffold has a wall thickness of at least 0.008 in.

7. The method of claim 1, wherein the tube has a crystallinity of between about 30% and 40%.

8. The method of claim 1, wherein the tube is made from a polymer comprising a copolymer of poly (L-lactide) (PLLA) and polycaprolactone (PCL).

9. A method for making a medical device, comprising:

forming a scaffold from a tube made from a polymer, the scaffold having a first diameter;

crimping the scaffold to a balloon by plastic deformation of the scaffold,

wherein

the scaffold is crimped from the first diameter to a second diameter, thereby forming a crimped state of the scaffold,

the first diameter is greater than a nominal inflation diameter for the balloon, and

the scaffold has an expanded diameter when plastically deformed from the crimped state by the balloon; and

wherein the scaffold is capable of regaining more than 90% of the expanded diameter after being crushed by an amount equal to at least 33% of the expanded diameter.

10. The method of claim 9, wherein the scaffold has an 8 mm inner diameter that is the first diameter and the balloon has a nominal inflated diameter of 6.5 mm.

11. The method of claim 9, wherein the scaffold has a network of interconnected elements including struts joined at crowns to form rings and links connecting the rings, the plastic deformation causes an articulation of struts about crowns, and

wherein an aspect ratio (AR) of a width to a wall thickness of a strut or link is between 0.4 and 1.4.

12. The method of claim 11, wherein the AR is between 0.4 and 0.9.

13. The method of claim 11, wherein the AR is between 0.8 and 1.4.

14. The method of claim 9, wherein the scaffold has a ratio of the first diameter to a wall thickness of between 20 and 60.

15. The method of claim 14, wherein the ratio of the first diameter to the wall thickness is between 20 and 45.

16. The method of claim 14, wherein the ratio of the first diameter to the wall thickness is between 30 and 60.

17. A method, comprising:

forming a scaffold from a tube, the scaffold comprising rings, each ring having crowns and struts,

crimping the scaffold to a balloon by plastic deformation of the scaffold and while the scaffold is heated to an elevated temperature below a glass transition temperature (Tg) of the polymer, wherein

the scaffold is crimped from a first diameter to a second diameter, and

the first diameter is greater than a nominal inflation diameter for the balloon, and

the crimping further including the step of performing a dwell of the scaffold after reducing the scaffold to the second diameter, wherein the second diameter is less than a minimum crimped diameter (MCD) satisfying either of equations 1 or 2;

MCD =(Σ

Swi +Σ

Crj +Σ

Lwk) *(π

)<sup>−

1</sup>+2*WT 

 

(equation

     1)

MCD =(Σ

Swi +Σ

Crj +Σ

Lwk) *(π

)<sup>−

1</sup> 

 

(equation

     2)

such that

Σ

Swi (i=1. . . n) is the sum of n ring struts having width Swi;

Σ

Crj (j=1. . . m) is the sum of m crown inner radii having radii Crj (times

     2);

Σ

Lwk (k=1. . . p) is the sum of p links having width Lwk; and

WT is a ring wall thickness.

18. The method of claim 17, wherein the tube is made from a polymer comprising a copolymer of poly (L-lactide) (PLLA) and polycaprolactone (PCL).

19. The method of claim 17, wherein the scaffold has a wall thickness and a ratio of the first diameter to the wall thickness is between 20 and 45.

20. The method of claim 19, wherein an aspect ratio (AR) of a width of a strut to the wall thickness is between 0.8 and 1.4.