WO2015085107A1

WO2015085107A1 - Wire and method of making

Info

Publication number: WO2015085107A1
Application number: PCT/US2014/068648
Authority: WO
Inventors: Thomas R. MOLZ; Robert A. Kiefer
Original assignee: Us Biodesign, Llc
Priority date: 2013-12-04
Filing date: 2014-12-04
Publication date: 2015-06-11

Abstract

Flattened wires and devices made therefrom are disclosed herein. Methods of using the wires to make the devices are disclosed as well. The wires can have cross-sectional aspect ratios of greater than 1:1 and less than 3:1. Implantable medical devices, such as vascular filters, can be wound or braided from the wires.

Description

TITLE OF IN VENTION

WIRE AND METHOD OF MAKING

CROSS-REFERENCE TO RELATED APPLICATION

{0001] This application claims priority to U.S. Provisional Application No. 61/911.964. filed Dec. 4, 2013, which is incorporated by reference herein in its entirety.

BACKGROUND

[0002] Braiding of fine wires is a common manufacturing process used to make certain medical devices, such as the braided occlusion device of PCT Pub. No. WO 2011/147784, filed May 23, 2011, which is incorporated by reference herein in its entirety, other braided vascular filters such as pulmonary embolism thrombectomy baskets or filters, braided tubing (incl uding reinforcement within the wall of an otherwise non-braided element (e.g.. embedded or inside of catheter walls), or combinations thereof,

[ 0003] The current trend in these devices is to have higher radial stiffness and more wire coverage without adding more wire mass to the device. Figure 1 illustrates braided implantable device 1, such as a stent or vascular filter, having a low braid angle, such as 30°, Figure 2 illustrates a higher braid angle, such as 75°.

[0004] The braiding process imparts a large amount of cyclic bending stress into each of the wires. For example, during high braid angle braiding the wire may be cycled as high as 300 times during manufacturing. The higher braid angles impart significantly more cycles of stress into the wires during manufacturing, as compared to lower braid angles,

[0005] When braiding, for example metal wire, there are two types of wire commonly available: round cross section (typically down to .0005" diameter) and rectangular cross sections (typically down to .0003" thick).

[0006] When braiding comple structures that could be used for filtration purposes (temporary or permanent implants), it may be necessary to use the very fine wire (above) in order to reduce the catheter size of the procedure (down to approximately .015" diameter). As the braid geometry needs to be dense enough to successfully filter out particles in the bloodstream, or become a barrier to blood in the patient's cardiovascular system, it becomes very challenging to braid relativel y small diameter wires. As the density of the

I wire increases, and the braid pore sizes decrease, it is necessary to increase the tension of the wire daring the braiding process. This increase in tension may exceed the tensile strength of the wire and cause the wire to break durirta the braiding process,

{0007] One possible solution to this is to use wire with a rectangular cross section - this has been done for many years. This may be useful in some applications, but typically the aspect ratio of rectangular cross section wire that is coramerciaHy available is too large to be useful in some applications (typically aspect ratios of widthrthickness of 6; 1 to 10: 1 }. Other wire flattening techniques in the art tend to flatten wires to an aspect ratio in the range of about 10: 1 -3 : 1. SUMMARY OF THE INVENTIO

[0008] Wires partially flattened to have cross-sectional aspect ratios from about 1.05: 1 to about 3: 1, more narrowly from about 1.1 : 1 to about 2: 1 , yet more narrowly from about 1 , 1 : 1 to about 1.3:1, even more narrowly from about 1.1:1 to about 1.2: 1 are disclosed, Medical devices, such as those listed herein, and elements thereof can be made by braiding the wires,

[0009] An implantable medical device is disclosed. The device can have a vascular filter comprising a braided wire having a longitudinal axis. A cross-section of the wire transverse to the longitudinal axis can have a first curved side diametrically opposite to a second curved side, and a first flat side diametric lly opposite to a second flat side. The cross -section of the wire can have has an aspect ratio as disclosed herein.

[0010] An implantable raedicai device is disclosed that can have a braid comprising a wire. The wire can ha ve a perpendicular transverse cross-section with an aspect ratio as disclosed herein. The wire can have a first curved side diametrically opposite to a second curved side, and a first flat side diametrically opposite to a second flat side.

[0011] A method for making a vascular filter device is disclosed herein. The method can include forming a wire having a longitudinal axis and a circular cross-section. The method can further include flattening the wire. Flattening can include flattening a top side and a bottom side of the wire. Flattening can reduce the aspect ratio of the cross-section from 1:1 to the aspect ratios disclosed herein. The method can further include winding the wire to form at least part of the filter device. Winding can include braiding the wire. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figures 1 and 2 are illustrations of braided medical tubes having lower and higher braid angles, respectively,

f 0013] Figures 3 is a cross-sectional view of a variation of an unfiattened wire, not the invention.

[0014| Figures 4 and 5 are cross- section views of variations of partially-flattened wires.

[0015] Figure 6 illustrates a fi nite element stress analysis of a variation of an unfiattened wire in a braid.

[00161 Figure 7 illustrates a finite element stress analysis of a variation of a partial!y- flattened wire in a braid.

[0017 j Figure 8 i llustrates a variation of a method of making the partially- flattened wire. DETAILED DESCRIPTIO

[0018 j Slightly flattening the wires might not significantly reduce the mechanical properties of the final braided construct but can allow for much higher braid angles and higher densities of wire per unit length of braid.

[0019] Figure 3 illustrates that an unfiattened wire 2 having a circular cross-section transverse to the longitudinal axis of the wire can have a height 4 equal to the width 6. The height 4 and width 6 of the unfiattened circular cross-section are equal to the diameter. The aspect ratio of the unfiattened circular wire is 1 : 1 (i.e., ratio of height to width).

[0020] Figures 4 and 5 illustrate that the wire can have a partially flattened top and bottom (the orientation of the flattening is merely stated as top and bottom for explanatory purposes, but can be in any orientation with flattening occurring on diametrically opposite sides of the cross-section). The diametrically opposite sides of the wire adjacent to the flattened top and bottom can remain curved with the same curvature of the pre-flattened wire, or the curvature can increase due to deformation of the wire. The aspect ratio of the flattened wire can be 1.1 : 1 _s as shown in Figure 4, and 1.2: 1 as show in Figure 5. The width of the flattened wires can increase slightly compared to the original circular cross- section wire.

[0021] Figure 6 shows the amount of bending stress creating in wire during current art braiding of round wires (i.e., wires with circular cross-sections, such as shown in Figure 3).

[0022] Figure 7 shows the bending stress within the wires when a slightly flattened wire ··· such as those shown in Figures 4 or 5 - is used. This analysis shows a reduction in bending stress of 1 .3% compared to the bending stress of the unfiattened wire of Figure 6. [0023] Radial force the partially flattened wire can increase from about 20% to about 100% over convention round wire. Wire coverage in a braid ranges increase from about 40% coverage to about 80% coverage with the partially flattened wire. Braid angles from 140 degrees max with round wire to as high as 170 degrees with slightly flattened wire.

[0024] The current available flattened wires have flattening ratios in excess of 1 :2. We are claiming that a slight flattening of wire using ratios of 1 : 1.01 to ! : 1.5, will allow for a much higher densi ty of braid during fabrica tion but does not have any appreciable l oss in final construct mechanical properties. METHOD OF MAKING

[0025] A wire having a circular cross-section can be rolled between two metal rollers 10, as shown in Figure 8. To make a partially flattened wire as described herein (e.g., compared to a flattened wire with an aspect ratio known in the art), spacers can be placed between the rollers. For example, spacers ca support the bearings of the axles holding the rollers. The spacers can space the axles 12 farther apart than during wire rolling performed under dimensions previously used in the art for manufacture of wire for medical devices, |O026] When the wire 2 is rolled through the rollers 10, the rollers 10 ca deliver the same amount, of pressure as the rollers 10 would deliver without the spacers, but the rollers 10 can be spaced apart so as to only flatten the wire 2 to the desired dimension. Thus, the wire can have a pre-rolled height 4a that can be greater than a post-rolled height 4b.

j0027] The wire's cross section can provide the following possible exemplary advantages for the braiding of such fiber:

[002 1 1. Less drag a t the crimp interchange point of the braid;

[0029] 2. Minimize the bending fatigue of the wire (one pick requires the braider carrier to go around the entire circumference of the machine ···· about 40' for a 288-carrier braider);

[0030] 3. The partially flattened shape of the wire disclosed herein can allow for higher densities— higher braid angles and picks/inch. Slightly flattened wire 2 can increase braid angles by as much as 30 degrees, and increase the density by as much as 60% coverage of the surface of a braid compared to the use of wire having a circular cross section .

[0031] 4. Due to higher densities, the pore sizes will be smaller - may be important for various filtration end uses.

[0032] 5. Changing the cross sectional shape helps due to a phenomenon known as "second moment of inertia", which is a propert of a geometric shape. A second moment of inertia indicates how a shape resists bending. Typically, the thinner the wire., the easier the wire is able to bend, but if the wire is too thin, the aspect ratio becomes too large to be useful.

[0033] The terms "partially flattened" and "slightly flattened" wire refer to the aspect ratios of flattened wire described herein in the Summary of the Invention and Detailed

Description sections, not including descriptions of known art.

[003 1 The wire described herein can he used to make other medical devices, such as the filters described in U.S. Patent No. 7,862,577, issued January 4, 20j 1 ; U.S. Patent No. 5,725,552, issued March 10, 1998; OS8398670 , issued Mar 19, 20 i 3, all of which are incorporated by referenc herein in their entireties, or combinations thereof.

[ 035j It is apparent to one skilled in the art that various changes and modifications can be made to this disclosure, and equivalents employed, without departing from the spirit and scope of the invention. Elements shown with any variation are exemplary for the specific variation and can be used on other variations within this disclosure. Any elements described herein as singular can be plura!ized (i.e... anything described as "one" can be more than one). Any species element of a genus element can have the characteristics or elements of any other species element of that genus. The above-described configurations, elements or complete assemblies and methods and their elements for carrying out the invention, and variations of aspects of the invention can be combined and modified wit each other in any combination.

Claims

CLAIMS We claim:

1. An implantable medical device comprising:

a vascular filter comprising a braided wire having a longitudinal axis, wherein a cross-section of the wire transverse to the longitudinal axis has a first curved side diaraetricaHy opposite to a second curved side, and a first flat side diametrically opposite to a second flat side.

2. The device of claim 1 , wherein the cross-section of the wire has an aspec t ratio from 1 .05: 1 to 2: 1.

3. The device of claim 2, wherein the aspect ratio is from 1 .1 :1 to 1 .9: 1. 4, The device of claim 3. wherein the aspect ratio is from 1.1 : i to 1.3: 1 , 5. The device of claim 1 , wherein the aspect ratio is from 1.1 : 1 to 1 ,2 : 1. 6. An implantable medical device comprising;

a braid comprising a wire, wherein the wire has a perpendicular transverse cross- section with an aspect ratio from 1.05: 1 to 2: 1, 7. The device of claim 6, wherein the wire has a first curved side diametrically opposite to a second curved side, and a first flat side diametrically opposite to a second fiat side. 8. The device of claim 6, wherein the aspect ratio is from 1.1 : 1 to 1 ,9: 1. 9. The device of claim 6, wherein the aspect ratio is from 1.1 : 1 to 1.3: 1. 10. The device of claim 6, wherein the aspect ratio is from 1.1 : 1 to 1.2:1. 1 1. The device of claim 6, wherein the medical device comprises a catheter. 12. The device of claim 6, wherein the medical device comprises a vascular filter. 13, A method for making a vascular filter device comprising:

forming a wire having a longitudinal axis and a circular cross-section;

.flattening the wire, wherein flattening comprises .flattening a top side and a bottom side of the wire, and wherein the flattening reduces the aspect ratio of the cross-section from 1 : 1 to from 1 ,05: 1 to 2: 1 ; and

winding the wire to form at least part of the filter device. 14. The method of claim 13, wherein the flattening reduces the aspect ratio of the cross- section from 1 1 to from 1.1 : 1 to 1 ,9; 1. 15. The method of claim 13, wherein the flattening reduces the aspect ratio of the cross- section from 1 : 1 to from 1.1 :1 to 1.3: 1. 16. The method of claim .13, wherein the flattening reduces the aspect ratio of the cross- section from 1 ; 1 to from 1.1 : 1 to 1.2: 1. 17 , The method of claim 13, wherein the winding comprises braiding the wire.