U.S. patent application number 13/795127 was filed with the patent office on 2014-09-18 for variable porosity intravascular implant and manufacturing method.
This patent application is currently assigned to DEPUY SYNTHES PRODUCTS, LLC. The applicant listed for this patent is DEPUY SYNTHES PRODUCTS, LLC. Invention is credited to Juan A. Lorenzo.
Application Number | 20140277397 13/795127 |
Document ID | / |
Family ID | 50280144 |
Filed Date | 2014-09-18 |
United States Patent
Application |
20140277397 |
Kind Code |
A1 |
Lorenzo; Juan A. |
September 18, 2014 |
VARIABLE POROSITY INTRAVASCULAR IMPLANT AND MANUFACTURING
METHOD
Abstract
A vascular occlusion device for effectively occluding blood flow
and pressure to a vascular defect while simultaneously not
occluding blood flow and pressure to adjacent vasculature is
provided. The vascular occlusion device can include a tubular
member that has variable porosity regions along its length. The
tubular member can be formed of a plurality of filaments that have
different cross-sectional shapes along their length that are
indexed to the variable porosity regions along the length of the
tubular member.
Inventors: |
Lorenzo; Juan A.; (Davie,
FL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
DEPUY SYNTHES PRODUCTS, LLC |
|
|
|
|
|
Assignee: |
DEPUY SYNTHES PRODUCTS, LLC
|
Family ID: |
50280144 |
Appl. No.: |
13/795127 |
Filed: |
March 12, 2013 |
Current U.S.
Class: |
623/1.39 ;
87/9 |
Current CPC
Class: |
A61F 2250/0036 20130101;
A61F 2/90 20130101; A61F 2/86 20130101; A61F 2002/823 20130101;
A61F 2230/0004 20130101; A61F 2250/0023 20130101; D04C 1/06
20130101 |
Class at
Publication: |
623/1.39 ;
87/9 |
International
Class: |
A61F 2/90 20060101
A61F002/90; D04C 1/06 20060101 D04C001/06 |
Claims
1. A vascular occlusion device, comprising: a tubular member formed
from a plurality of braided filaments that define an outer surface
having a mesh pattern with mesh openings defined by the braided
filaments, the tubular member having a first porosity region along
a first length portion of the tubular member and a second porosity
region along a second length portion of the tubular member, wherein
the first porosity region includes filaments having a different
shape than the filaments in the second porosity region and the
porosity of the first porosity region being less than the porosity
of the second porosity region, the tubular member having a constant
pick count throughout its length.
2. The device of claim 1, wherein braid angle is substantially
similar throughout the tubular member.
3. The device of claim 1, wherein the tubular member is an
intravascular stent.
4. The device of claim 2, wherein the intravascular stent is
radially compressible.
5. The device of claim 1, wherein the first length is at an
intermediate portion of the tubular member proximal to a distal end
of the tubular member and distal to a proximal end of the tubular
member.
6. The device of claim 5, wherein the second length portion is
adjacent to the distal end of the tubular member.
7. The device of claim 5, wherein the second length portion is
adjacent to the proximal end of the tubular member.
8. The device of claim 1, wherein the first porosity region
includes filaments having a flattened cross-sectional shape having
a length, a width, and a thickness wherein the width is greater
than the thickness and less than the length of the filaments in the
first porosity region having a flattened cross-sectional shape.
9. The device of claim 8, wherein the filaments in the first
porosity region are exclusively of a flattened cross-sectional
shape.
10. The device of claim 8, wherein the filaments in the first
porosity region include filaments with a flattened cross-sectional
shape and filaments with a round cross-sectional shape.
11. The device of claim 8, wherein the filaments in the second
porosity region have a round cross-sectional shape.
12. The device of claim 1, wherein the first length portion of the
tubular member extends over a distance in the range of about 5 mm
to about 25 mm.
13. The device of claim 8, wherein the width of the filaments
having a flattened cross-sectional shape is in the range of about
0.001 inches to about 0.05 inches.
14. The device of claim 8, wherein the thickness of the filaments
having a flattened cross-sectional shape is in the range of about
0.0003 inches to about 0.010 inches.
15. The device of claim 11, wherein the filaments having a round
cross-sectional shape have a diameter in the range of about 0.0005
inches to about 0.0100 inches.
16. The device of claim 1, wherein the mesh openings have a
polygonal shape.
17. The device of claim 1, wherein the mesh openings of the first
porosity region are smaller than the mesh openings of the second
porosity region.
18. The device of claim 16, wherein the mesh openings of the first
porosity region have an inscribed circle diameter in the range of
about 10 .mu.m to about 500 .mu.m.
19. The device of claim 16, wherein the mesh openings of the second
porosity region have an inscribed circle diameter in the range of
about 400 .mu.m to about 1000 .mu.m.
20. The device of claim 1, wherein the number of filaments forming
the tubular member is in the range of about 8 to about 288.
21. The device of claim 20, wherein the number of filaments forming
the tubular member is selected from the group consisting of 8, 16,
32, 48, 64, 72, 96, 120, 144, 192, and 288.
22. A method of manufacturing a tubular intravascular implant,
comprising: providing a plurality of supply spools, each having a
supply of a filament having a round cross-sectional shape;
advancing the filaments on each supply spool to a corresponding
collection spool; deforming a selected number of the filaments in a
selected region thereof at selected intervals between the supply
spools and the collection spools such that at least some of the
collection spools have filaments with a round cross-sectional shape
and a flattened cross-sectional shape; utilizing the filaments in
the collection spools in a filament braiding device to form a
tubular member with an outer surface defined by the braided
filaments, the tubular member having a length with regions of a
first, lower porosity and regions of a second, higher porosity.
23. The method of claim 22, further comprising the step of cutting
the tubular member to form a plurality of intravascular stents,
each sent having a first length region of a first, lower porosity
characterized by the presence of filaments having a flattened
cross-sectional shape.
24. The method of claim 23, wherein the intravascular stents each
have at least one second length region of a second, higher porosity
characterized by the presence of filaments having a rounded
cross-sectional shape.
25. The method of claim 22, wherein all of the collection spools
have filaments with a flattened cross-sectional shape.
Description
FIELD
[0001] The present disclosure relates generally to intravascular
implants and more particularly to occlusive devices such as
vascular stents.
BACKGROUND
[0002] Vascular disorders and defects such as aneurysms and other
arteriovenous malformations often occur near the junction of large
arteries, for instance at the base of the brain in the Circle of
Willis. As aneurysms develop they typically form as a saccular
aneurysm protruding from a wall of a vessel and have a neck and a
dome portion. Alternatively, aneurysms can form as fusiform
malformations that balloon a cross-section of the affected
vessel.
[0003] As an aneurysm develops, the arterial internal elastic
lamina disappears at the base of the neck portion, the media thins,
and connective tissue replaces smooth-muscle cells. As the aneurysm
is continually subjected to vascular blood pressure and blood flow,
the aneurysm will grow outwardly from the wall of the vessel, which
can cause pressure on the surrounding tissue as the sac or fusiform
contacts the surrounding tissue. When the malformation occurs in
the brain, this pressure can lead to serious mass effects, such as
cognitive impairment, loss of vision, and nerve palsies.
Additionally, as the aneurysm is subject to vascular blood pressure
and blood flow, the walls of the aneurysm weaken, usually in the
dome portion, which can eventually cause the aneurysm to tear or
rupture. Ruptured aneurysms are the most common cause of
subarachnoid hemorrhages, which have a mortality rate of
approximately 50%.
[0004] Aneurysms and other malformations are especially difficult
to treat when located near critical tissue or where ready access to
the malformation is not available. Both difficulty factors apply
especially to cranial aneurysms. Surgical methods have developed to
treat cranial aneurysms and generally include eliminating blood
flow to the aneurysm by placing a clip around the neck of a
saccular aneurysm or by blocking off a fusiform aneurysm by cliping
both ends of the fusiform and detouring blood flow around the
secluded fusiform through an implanted vessel graft. Due to the
sensitive brain tissue surrounding cranial blood vessels and the
restricted access, it is challenging and risky to surgically treat
defects of the cranial vasculature.
[0005] Alternatives to such surgical procedures include
endovascular delivery of an implantable device, such as a
stent-like device or embolic coil, through a microcatheter delivery
device. In one such procedure to treat a saccular-form cranial
aneurysm, the distal end of an embolic coil delivery catheter is
initially inserted into non-cranial vasculature of a patient,
typically a femoral artery in the groin, and guided to the
aneurysm. The aneurysm sac is then filled with embolic material,
such as platinum coils, that forms a solid, thrombotic mass that
protects the vessel walls from blood pressure and flow. This
treatment method is advantageous in that it only occludes blood
flow to the aneurysm leaving the surrounding portions of the vessel
unobstructed. However, it cannot treat fusiform aneurysms, and the
aneurysm volume is permanently maintained.
[0006] Another technique involving the use of an intravascular
implant delivers, by a microcatheter, an occlusive device in the
form of a tubular, stent structure. Stents can be braided, woven,
or wound from various filaments, such as a wire or wires, laser-cut
from metal, or made in various other ways. They can either be
self-expanding or can be expanded by another device such as a
balloon. What most have in common is radial symmetry, i.e., a
uniform porosity, meaning that they do not cover one portion, side,
or radial sector of the vessel more or less porously than other
sectors. Their symmetric construction, and therefore coverage of
vessel walls, is relatively homogeneous around any given transverse
slice or cross-section.
[0007] This homogenous structure can be disadvantageous in that
such stents not only occlude or block blood flow to the aneurysm,
but they also block blood pressure and flow along the entire length
of the stent, which often impedes flow into surrounding joined
vessels, such as perforator-type vessels branching off of the
parent vessel. The use of a non-discriminatory occlusive device in
this type of vessel can cause unintended harm to the patient if the
openings, or ostia, of the perforator vessels are blocked.
[0008] Some have developed selectively-occlusive devices that
discriminately block flow to an aneurysm while simultaneously
allowing flow to surrounding vessels. These attempts to create
discriminate occlusion devices have used multilayered devices,
varied the amount of filaments along the length of the
intravascular implant, or changed the picks per inch along the
length of the intravascular implant. But, generally, these devices
face difficulties in manufacturing and increased costs due to
difficulties in creating the multiple layers or variations in the
number of filaments to create the varied porosity regions.
[0009] Accordingly, there remains a need for a device that
effectively occludes a neck or fusiform of an aneurysm or other
arteriovenous malformation in a parent vessel without blocking flow
into perforator vessels communicating with the parent vessel that
is structurally sound and easily manufactured.
SUMMARY
[0010] A vascular occlusion device for effectively occluding blood
flow and pressure to a vascular defect while simultaneously not
occluding blood flow and pressure to adjacent vasculature is
provided. The vascular occlusion device can include a tubular
member that has variable porosity regions along its length. The
tubular member can be formed of a plurality of filaments that have
different cross-sectional shapes along their length that are
indexed to the variable porosity regions along the length of the
tubular member.
[0011] In some embodiments, the vascular occlusion device includes
a tubular member formed from a plurality of braided filaments. The
braided filaments can define an outer surface having a mesh pattern
with mesh openings defined by the braided filaments. The tubular
member can have a first porosity region along a first length
portion of the tubular member and a second porosity region along a
second length portion of the tubular member. The porosity of the
first porosity region can be less than the porosity of the second
porosity region. The first porosity region can include filaments
having a different shape than the filaments in the second porosity
region and the tubular member can have a constant pick count
throughout its length. In another embodiment the tubular member can
have a braid angle that is substantially similar throughout the
tubular member.
[0012] In some embodiments, the tubular member is an intravascular
stent, which can be radially compressible. The first length portion
is at an intermediate portion of the tubular member proximal to a
distal end of the tubular member and distal to a proximal end of
the tubular member. The second length portion can be adjacent to
the distal end of the tubular member and/or the proximal end of the
tubular member. The first length portion of the tubular member can
extend over a distance in the range of about 5 mm to about 25 mm.
The first porosity region can include filaments having a flattened
cross-sectional shape having a length, a width, and a thickness.
The width can be greater than the thickness and less than the
length of the filaments in the first porosity region having a
flattened cross-sectional shape. The width of the filaments having
a flattened cross-sectional shape is in the range of about 0.001
inches to about 0.05 inches. The thickness of the filaments having
a flattened cross-sectional shape is in the range of about 0.0003
inches to about 0.010 inches. The filaments having a round
cross-sectional shape can have a diameter in the range of about
0.0005 inches to about 0.0100 inches.
[0013] The filaments in the first porosity region can be
exclusively of a flattened cross-sectional shape, or can be a
mixture of filaments with a flattened cross-sectional shape and/or
round cross-sectional shape. The filaments in the second porosity
region can have a round cross-sectional shape. The mesh openings
formed from the braided filaments can have a polygonal shape and
the mesh openings of the first porosity region can be smaller than
the mesh openings of the second porosity region. The mesh openings
of the first porosity region can have an inscribed circle diameter
in the range of about 10 .mu.m to about 500 .mu.m and the mesh
openings of the second porosity region have an inscribed circle
diameter in the range of about 400 .mu.m to about 1000 .mu.m. The
number of filaments forming the tubular member can be in the range
of about 8 to about 288. For example, the number of filaments
forming the tubular stent can be selected from the group consisting
of 8, 16, 32, 48, 64, 72, 96, 120, 144, 192, and 288.
[0014] In another aspect, a method of manufacturing a tubular
intravascular implant includes providing a plurality of supply
spools, each having a supply of a filament having a round
cross-sectional shape. The method further includes advancing the
filaments on each supply spool to a corresponding collection spool
and deforming a selected number of the filaments in a selected
region thereof at selected intervals between the supply spools and
the collection spools. The filaments can be deformed such that at
least some of the collection spools have filaments with a round
cross-sectional shape and a flattened cross-sectional shape.
According to the method, the filaments in the collection spools are
utilized in a filament braiding device to form a tubular member
with an outer surface defined by the braided filaments. All of the
collection spools used in the braiding device can have filaments
with a flattened cross-sectional shape, or alternatively only a
portion of the collection spools used in the braiding device can
have filaments with a flattened cross-sectional shape.
[0015] The tubular member formed by the method can have a length
with regions of a first, lower porosity and regions of a second,
higher porosity. The method can also include the step of cutting
the tubular member to form a plurality of intravascular stents;
each sent having a first length region of a first, lower porosity
characterized by the presence of filaments having a flattened
cross-sectional shape. The intravascular stents can each have at
least one second length region of a second, higher porosity
characterized by the presence of filaments having a rounded
cross-sectional shape.
BRIEF DESCRIPTION OF DRAWINGS
[0016] This invention will be more fully understood from the
following detailed description taken in conjunction with the
accompanying drawings, in which:
[0017] FIG. 1 is a cross-sectional view of an exemplary vascular
occlusive device implanted within a vessel having a saccular
aneurysm;
[0018] FIG. 2 is a cross-sectional view of an exemplary vascular
occlusive device implanted within a vessel having a fusiform
aneurysm;
[0019] FIG. 3 is a partial cross-sectional view of an exemplary
vascular occlusive device;
[0020] FIG. 4 is a magnified view of a portion of the device of
FIG. 3;
[0021] FIG. 5 is a partial cross-sectional view of another
embodiment of an exemplary vascular occlusive device;
[0022] FIG. 6 is a top view of an exemplary filament for use in
forming a vascular occlusive device;
[0023] FIG. 7 is a cross-section view of the exemplary filament of
FIG. 6 at Section A-A;
[0024] FIG. 8 is a schematic view of an exemplary system for
forming exemplary filaments;
[0025] FIG. 9 is a schematic view of an exemplary braiding
system.
DETAILED DESCRIPTION
[0026] Certain exemplary embodiments will now be described to
provide an overall understanding of the principles of the
structure, function, manufacture, and use of the devices and
methods disclosed herein. One or more examples of these embodiments
are illustrated in the accompanying drawings. Those skilled in the
art will understand that the devices and methods specifically
described herein and illustrated in the accompanying drawings are
non-limiting exemplary embodiments and that the scope of the
present invention is defined solely by the claims. The features
illustrated or described in connection with one exemplary
embodiment may be combined with the features of other embodiments.
Such modifications and variations are intended to be included
within the scope of the present invention
[0027] Further, in the present disclosure, like-numbered components
of the embodiments generally have similar features, and thus within
a particular embodiment each feature of each like-numbered
component is not necessarily fully elaborated upon. Additionally,
to the extent that linear or circular dimensions are used in the
description of the disclosed systems, devices, and methods, such
dimensions are not intended to limit the types of shapes that can
be used in conjunction with such systems, devices, and methods. A
person skilled in the art will recognize that an equivalent to such
linear and circular dimensions can easily be determined for any
geometric shape. Sizes and shapes of the systems and devices, and
the components thereof, can depend at least on the anatomy of the
subject in which the systems and devices will be used, the size and
shape of components with which the systems and devices will be
used, and the methods and procedures in which the systems and
devices will be used.
[0028] To treat vascular disorders and defects, such as aneurysms
and other arteriovenous malformations, intravascular implants, such
as stents, can be implanted to span a length of vessel containing
the defect to occlude blood pressure and flow to the defect. For
instance, a stent can be delivered to the site of an aneurysm and
positioned in such a manner as to occlude blood pressure and flow
to the aneurysm walls. By occluding, i.e., blocking or obstructing,
blood flow to the aneurysm, the risk of the aneurysm rupturing is
reduced. But, in treating the vascular defect, it is important to
avoid unnecessary occlusion of blood flow and pressure to adjacent
vascular tissue, such as perforator vessels.
[0029] The present disclosure relates to a vascular occlusion
device, such as a variable porosity stent, that is configured to
occlude flow to a vascular defect while allowing flow to adjacent
vessel tissue. The device utilizes a tubular member formed from a
plurality of braided filaments. As explained below, the tubular
member can include an outer surface having a mesh pattern with mesh
openings defined by the braided filaments. The tubular member is
constructed such that the porosity varies at different regions
along the length of the member. For example, the tubular member can
have a first porosity region along a first length portion of the
tubular member and a second porosity region along a second length
portion of the tubular member. In some embodiments, the first
porosity region is a center portion of the tubular member. The
first porosity region can include filaments having a different
shape than the filaments in the second porosity region. By changing
the shape of the filaments at selected regions along the length of
the tubular member, the porosity of a given region can be altered
while maintaining a constant pick count throughout the length of
the stent. For example, the cross-sectional shape of the filament
in the first porosity region can be selected to be different than
the cross-sectional shape of the filament in the second porosity
region so as to have a lower porosity in the first porosity region
than the second porosity region. In this manner it is possible to
vary the porosity from the first region to the second region by
changing only the shape of the filaments, holding the other
structural characteristics of the tubular member substantially
constant along the length of the tubular member. That is, the
number of filaments, pick count, braid angle, or braid pattern is
the same in the first porosity region as in the second porosity
region.
[0030] FIGS. 1 and 2 illustrate embodiments wherein a variable
porosity stent 10 is placed within a vessel 12 so as to occlude or
obstruct blood flow and pressure to a vascular defect 14 while
simultaneously allowing substantially unimpeded blood flow and
pressure to adjacent vessel tissue, such as perforator vessels 16.
The vessel 12 can be any vasculature, for example a cranial blood
vessel such as those found in the Circle of Willis. As shown in
FIG. 1, the vascular defect 14 can be a saccular form aneurysm
having a neck 18 and a dome portion 20. As shown in FIG. 2, the
vascular defect 14 can be a fusiform aneurysm wherein a
cross-sectional portion 22 of the vessel 12 is ballooned in a
radial direction. In treating either the saccular aneurysm of FIG.
1 or the fusiform aneurysm of FIG. 2, the vascular occlusion device
is placed along the length of the defective vessel 12 to occlude
blood flow and pressure to the aneurysm walls 20, 22.
[0031] FIG. 3 illustrates one embodiment of a tubular stent 10 used
in treating the vascular defects 14 of FIGS. 1 and 2 according to
the present invention. The stent 10 can have a proximal region 24,
distal region 26, and center region 28, wherein the center region
28 is intermediate the proximal and distal regions 24, 26. In the
embodiment shown in FIG. 3, region 28 of stent 10 represents a
first porosity region having a porosity that is different (i.e.,
lower) than that of regions 24 and 26, which represent a second
porosity region. The difference in porosity is achieved by changing
the cross-sectional shape of the filaments 30 in region 28, as
explained below. The stent 10 can be a braided stent having one or
more filaments 30 of stent material woven, braided, or otherwise
formed into a desired tubular shape and pattern.
[0032] FIG. 4 illustrates the braided, mesh structure of the stent
10. As mentioned above, the stent can be formed of braided
filaments 30 that cross at junctions referred to as picks 32 to
form a mesh. The mesh density is a function of the degree of
spacing between the filaments 30 in the braid. Structures with more
closely spaced filaments have a higher mesh density than structures
with filaments that are less closely spaced. One measure of mesh
density can be determined based on the number of picks 32 per inch
of the material. A pick, as understood by a person skilled in the
art, is a point where filaments intersect.
[0033] Porosity is a measure of the tendency of a material or
structure to allow passage of a fluid therethrough. A material or
structure with higher porosity has a higher fluid flow across the
material than another material with lower porosity. The porosity of
a braided structure, such as a stent, can be a function of the mesh
density as well as the surface area of the filaments that form the
structure as well as the number of filaments, the number of picks
per inch, and the interstitial surface area between filaments as
discussed below.
[0034] As mentioned previously, according to the present invention
the cross-sectional shape of the filaments 30 can be selectively
altered in certain regions, before braiding, to produce a stent 10
having a region of lower porosity. By altering the cross-sectional
shape of the filaments 30, the interstitial surface area between
filaments 30 can be controlled.
[0035] The interstitial surface area between filaments can be
determined by measuring an inscribed circle diameter 36 (FIG. 4) in
the open spaces between the filaments 30. For a non-circular shape,
such as a triangle, square, or diamond, the inscribed circle
diameter 36 is the diameter of the largest circle that fits
entirely within the shape, i.e., the diameter of a circle that is
tangent to the sides of the shape. The lower porosity regions of
the stent 10 can have an inscribed circle diameter 36 in the range
of about 1 .mu.m to about 400 .mu.m, and more particularly about
100 .mu.m. For example, the inscribed circle diameter 36 of the
first porosity region 28 of the stent 10 shown in FIGS. 1-4 can be
about 100 .mu.m. The higher porosity regions, i.e., second porosity
regions 24, 26, of the stent 10 can have an inscribed circle
diameter 36 that is greater than about 400 .mu.m. For example,
second porosity regions 26, 24 of the stent 10 shown in FIGS. 1-4
can be in the range of about 400 .mu.m to about 1000 .mu.m.
[0036] To decrease the inscribed circle diameter 36 and thus
decrease porosity, the cross-sectional shape of the filament 30 can
be changed to increase the surface area of the filament 30 along
selected portions of the filament 30 length that will correspond to
the lowered porosity region(s) along the length of the stent 10.
For example, a substantially round filament 30 can be flattened
along a portion of the filament 30 that corresponds to the first
porosity region 28 (e.g., the center region) of the stent 10. As
shown in FIGS. 1-4 and 6, the first porosity region 28 is formed of
filaments 30 that have a substantially flattened cross-sectional
shape, sometimes referred to as a ribbon shape. Further, higher
porosity regions of the filaments used in forming the stent (i.e.,
regions 24 and 26) can have a substantially round cross-sectional
shape, which for example is the unaltered or natural shape of the
filament. It is understood that any initial or unaltered
cross-sectional shape can be utilized, so long as the shape allows
for alteration of the filament cross-sectional shape such that the
inscribed circle diameter 36 in regions of a stent formed with
shape-altered filaments can be smaller than the inscribed circle
diameter 36 in the regions formed of filaments that are not
shape-altered. By way of example substantially rectangular,
triangular, and round cross-sectional shapes can be used.
[0037] In some embodiments, the number of filaments 30 braided to
form the stent 10 is uniform along the entire length of the stent
10. Additionally, the filaments 30 forming the stent 10 are
continuous along the entire length of the stent 10, i.e., the
filaments 30 found in the first porosity region 28 of the stent 10
are the same filaments 30 found in the second porosity 24, 26. As
explained above, the only difference between the filaments in the
first porosity region 28 and the second porosity regions 24, 26 is
the cross-sectional shape of the filament 30.
[0038] In the embodiments of FIGS. 1-4 the first or lower porosity
region 28 is formed using filaments that are exclusively of an
altered, i.e., substantially flattened cross-sectional shape. One
skilled in the art will appreciate that the first of reduced
porosity region can alternatively be formed using some filaments
having an altered (such as flattened) cross-sectional shape
together with other filaments having an unaltered shape, such as a
rounded shape. FIG. 5 illustrates an example of such a stent where
only some of the filaments used in forming the first or lower
porosity region 28' of the stent 10' have an altered (e.g.,
flattened) cross-sectional shape. As is shown, the stent 10' has a
first filament type 38 that has an unaltered and substantially
constant cross-sectional shape along its length and a second
filament type 40 that has at least two cross-sectional shapes along
its length, an altered cross-sectional shape and an unaltered
cross-sectional shape. The proportion of filaments altered to
unaltered filaments in the first porosity region 28' can vary
depending upon porosity characteristics desired for the stent.
Generally, region 28' of stent 10' will have at least as many and
typically more filaments with an altered cross-sectional shape in
region 28'. For example, the filaments with an altered shape
typically comprise about 50 percent to about 99 percent of the
fibers in region 28'. More typically about 60 percent, about 70
percent, about 80 percent, or about 90 percent of the fibers in
region 28' are those having an altered cross-sectional shape.
Despite the stent 10' having filaments of different cross-sectional
shapes within first porosity region 28', as in other embodiments,
the number of filaments 38, 40 is uniform along the entire length
of the stent 10' and the filaments 38, 40 themselves are continuous
along the entire length of the stent 10', i.e., the filaments found
in the center portion 28' of the stent are the same filaments 38,
40 found in the end portions 24', 26'.
[0039] FIG. 6 illustrates an exemplary filament 30 used to form the
braided stent 10. The filament has a first portion 42 and a second
portion 44 having a rounded cross-sectional shape, which is the
unaltered filament shape. Another region of filament 30, shown as
middle portion 46 in FIG. 6, has an altered cross-sectional shape,
i.e., a flattened or somewhat oval cross-sectional shape. The
flattened portion 46 has a width 48 across the center of the
flattened portion 46 that is wider than the diameter 52 of the
adjacent round cross-section portions 42, 44. When a stent is
formed using filament 30, the region braided with portion 46 will
have a smaller inscribed diameter than regions braided with
portions 42 and 44. By way of example, the width 48 can be in the
range of about 0.001 inches to about 0.05 inches. FIG. 7
illustrates a cross-section of the filament 30 as viewed along line
A-A of FIG. 6. As is shown, the flattened portion 46 will have a
thickness 50 that is less than the diameter 52 of the round
cross-section. The thickness 50 can be any desired thickness, for
example the thickness 50 can be in the range of about 0.0003 inches
to about 0.010 inches. The diameter 52 of the round cross-sectional
portion of the filament can have any desired diameter, for example
the diameter 52 can be in the range of about 0.0005 inches to about
0.0100 inches. The flattened middle portion 46 can have feathered
ends 54 yielding a somewhat an oval shape when viewed from the top
as is shown in FIG. 6. When braided, the flattened middle portion
46 of the filament 30 can be indexed about the region of the stent
10 that is to form the first or lower porosity region. For example,
in the stent 10 shown in FIG. 3, the flattened portion 46 of the
filaments 30 form the center region of the stent, which is the
lower porosity region 28. The flattened middle portion 46 can have
a length that will yield a center, lower porosity region of the
stent that is large enough to cover the defect 14 to be treated but
not so large as to occlude blood flow unnecessarily to adjacent
vascular tissue.
[0040] One skilled in the art can readily determine the dimensions
of a stent as deemed appropriate for a given application. The stent
10 can have a length that is so dimensioned as to stretch across a
vascular defect 14. For example, the stent 10 length can be in the
range of about 10 mm to about 100 mm.
[0041] The stent 10 can be self-expanding and radially compressible
such that the stent 10 has a first, constrained diameter that is
smaller than a second, unconstrained diameter that the stent
assumes in its natural state. The unconstrained diameter should be
so dimensioned as to be sufficiently larger than the vessel within
which it is to be implanted to be safe and to maintain proper
position. Generally, vessel 12 diameters will range from about 2 mm
to about 5 mm and thus the stent 10 unconstrained outer diameter
can be in the range of about 2.5 mm to about 5.5 mm, but the stent
can have any desired diameter. The constrained diameter can be
dimensioned for endovascular delivery, for example the constrained
diameter can be in the range of about 0.01 inches to about 0.100
inches. Additionally, the stent 10 can be configured to provide
structural support to the vessel 12 once placed in the vasculature
in its expanded form. To aid in placement and blood flow, the ends
24, 26 of the stent 10 can be flared.
[0042] Self-expanding stents can be constructed from a variety of
filament materials known to those skilled in the art. These
materials include stainless steel, cobalt-chromium alloys, nickel,
titanium, nitinol, and polymeric materials. Polymeric materials
known to those skilled in the art can include, without limitation,
shape memory polymers, silicone, polyethylenes, polyurethanes,
polyethylene terephthalate (PET) polyesters, polyorthoesters,
polyolefins, polyvinyls, polymethylacetates, polyamides, napthalane
dicarboxylene derivatives, silks, polytetraflyouroethylenes, and
polyanhydrides. The filament material can also be bioabsorbable or
radio-opaque, for instance by having an inner core formed of gold,
platinum, iridium, or any other known radio-opaque material.
[0043] To effectively treat a defect, such as the aneurysms 14
shown in FIGS. 1 and 2, the stent 10 can have a variable porosity
along the length of the tubular stent 10. For example, first
porosity region 28 of the stent can be of a lower porosity than
other regions of the stent, such as second porosity regions 24, 26.
Although region 28 is shown to be disposed between regions 24 and
26, other arrangements of lower and higher porosity regions are
possible. Additionally, the stent 10 can have multiple regions of
lower porosity. For example, the stent 10 can have a distal region,
proximal region, first center region, second center region, and
third center region, wherein each region has a different porosity
than the others (not shown). In any event, the lower porosity
region can have a length that is sufficient to occlude flow to the
defect, for example the length of the lower or first porosity
region 28 can be in the range of about 5 mm to about 25 mm. In the
embodiments illustrated in FIGS. 1-3, the center region 28 is
configured to have a lower porosity and thus occlude blood flow to
the neck 18 or walls 20, 22 of the aneurysm 14 and the proximal and
distal regions 24, 26 are configured to allow blood flow and
pressure without any substantial occlusion thereof to the adjacent
perforator vessels 16.
[0044] The stent 10 can have a substantially constant number of
picks-per-inch count along the length of the stent 10. For example,
the picks-per-inch count in the region 24 can be the same as the
picks-per-inch count in the region 26, which is the same as the
picks-per-inch count in the region 28. For example, the
picks-per-inch can be in the range of about 20 picks-per-inch to
about 250 picks-per-inch.
[0045] As mentioned above, when braided, the filaments 30 forming
the stent 10 can intersect to create polygonal mesh openings. The
size of the polygonal mesh opening can then be measured by the
inscribed circle diameter as described herein. The stent 10 can be
formed so as to yield a first region having a first inscribed
circle diameter (i.e., a first or lower porosity region) and a
second region having a second inscribed circle diameter that is
larger than the first inscribed circle diameter (i.e., a higher
porosity region). Generally, the mesh openings of the first
porosity region can have an inscribed circle diameter in the range
of about 10 .mu.m to about 500 .mu.m and the mesh openings of the
second porosity region can have an inscribed circle diameter in the
range of about 400 .mu.m to about 1000 .mu.m.
[0046] FIG. 8 illustrates an exemplary manufacturing system 56 to
produce a filament 30 having alternating round and flat
cross-sectional shapes. A supply spool 58 is first provided. The
supply spool 58 should be wound with a supply filament 60 having a
round cross-sectional shape. This can be formed of a typical stent
filament material as described above and as is known in the art.
The supply filament 60 from the supply spool 58 is then fed to a
collection spool 62 configured to receive processed filament 30.
Intermediate the supply spool 58 and collection spool 60, the
supply filament 60 is fed through a press or stamping device 64,
such as a pneumatic press. The press 64 can have a die set 66 that
provides the means for altering (e.g., flattening) the filament 60.
The die set 64 can be adjusted to control the thickness and length
of the flattened section of filament 46 created by stamping the
round supply filament 60 as it moves through the press 64. The
press 64 can be configured to press any diameter of filament 60 and
the die length, die pressure, die shims that control the thickness,
and spool speed can be independently controlled and calibrated to
produce the desired dimensions of the processed filament 30. Using
this press 64, the supply filament 60 is pressed at set intervals
to produce a filament 30 having alternating round 42, 44 and flat
46 cross-sectional shapes. The processed filament 30 is stored on
the collection spool 62 once the filament is processed and ready to
be braided.
[0047] Braiding of filaments 30 includes the interlacing of at
least two sections of filament 30 such that the paths of the
filament 30 sections are substantially diagonal to the stent 10
delivery direction, forming a tubular structure. Generally, braided
stents can have a polygonal interstitial surface shape and can
include a diamond braid having a 1/1 intersection repeat, a regular
polygonal braid having a 2/2 intersection repeat, and a Hercules
braid having a 3/3 intersection repeat. Moreover, a triaxial braid
may also be used. A triaxial braid has at least one filament
section that typically runs in the longitudinal direction or axial
direction of the stent to limit filament movement. Moreover, an
interlocking three-dimensional braided structure or a multi-layered
braided structure can also be used. A multi-layered braided
structure is defined as a structure formed by braiding wherein the
structure has a plurality of distinct and discrete layers.
[0048] FIG. 9 illustrates an exemplary braiding device 68. The
braiding device 68 can have a spool loading mechanism 70 and a
braiding mandrel 72 is first loaded with the desired filaments
wound on spools 74 disposed in the spool loading mechanism 70. For
example, the collection spools 62 of processed filaments 30 can be
loaded into the braiding machine 68. The collection spools 62 used
in the braiding machine 68 can have filaments 30 with flattened
cross-sectional shapes as described above, filaments 60 with round
cross-sectional shapes, or combinations of both. If only collection
spools 62 having flattened cross-sectional shapes are utilized, the
resulting stent 10 can be of the form shown in FIGS. 1-4. If a
combination of collection spools 62 having flattened
cross-sectional shapes and spools having a round cross-sectional
shape are used, then the resulting stent 10' can be of the form
shown in FIG. 5. The collection spools 62 should be indexed in the
braid machine 68 so that any flattened portions 46 of the filaments
on the collection spools corresponds to a desired region of lower
porosity in the resulting stent 28. For example, the collection
spools 62 can be indexed so that the flattened portion is indexed
to an indexing line 76 such that the flat portion 46 of the
filament 30 corresponds to the center region 28 of the stent
intermediate the end portions 24, 26 of the stent. The braided
stent 10 can be cut to length distally of the braiding mandrel
72.
[0049] Alternatively, the region of lower porosity can have more
filaments or more picks per inch than the region of higher
porosity. But, by changing only the cross-sectional shape of the
filaments and keeping the number of filaments and picks per inch
uniform along the length of the stent, manufacturing can be
simplified as the braiding process is uncomplicated by changing the
number of filaments or braiding pattern during the braiding
process. Thus, a preferred embodiment is one that has a uniform
filament count and picks per inch along the entire length of the
stent.
[0050] As mentioned, the mesh density, and therefore the porosity,
can also depend on the braid angle. Generally, the braid angle is
defined as the angle between crossing filaments at a braid pick.
Typically three braid angles are relevant: the braid angle during
construction on a braiding machine, the braid angle when the stent
is unconstrained, and the braid angle when the stent is
constrained. The braid angle during construction is generally
larger than the unconstrained and constrained braid angle. The
braided structure is formed having a braid angle from about
30.degree. to about 150.degree. with respect to the longitudinal
axis of the braided structure.
[0051] When deploying the stent 10 into a vessel 12, the braid
angle is reduced as the stent 10 is compressed radially to fit into
the vessel 12. The braid angle then expands when the stent 10 moves
from the constrained position to its unconstrained position.
Preferably, the stent 10 will be formed such that the braid angle
is uniform along the length of the tubular member 10 when the
tubular member 10 is either entirely constrained or unconstrained,
such that the braid angle in the first length is the same as the
braid angle in the second length.
[0052] A person skilled in the art will appreciate that the present
invention has application in conventional minimally-invasive and
open surgical instrumentation as well application in
robotic-assisted surgery. While in many cases the description uses
cranial vasculature, aneurysms, and stents configured for the
treatment thereof as an exemplary delivery location and implant,
this is by way of illustration only. The methods and devices
described herein can be applied to virtually any vasculature,
defect, and intravascular implant.
[0053] The devices disclosed herein can also be designed to be
disposed of after a single use, or they can be designed to be used
multiple times. In either case, however, the device can be
reconditioned for reuse after at least one use. Reconditioning can
include any combination of the steps of disassembly of the device,
followed by cleaning or replacement of particular pieces and
subsequent reassembly. In particular, the device can be
disassembled, and any number of the particular pieces or parts of
the device can be selectively replaced or removed in any
combination. Upon cleaning and/or replacement of particular parts,
the device can be reassembled for subsequent use either at a
reconditioning facility, or by a surgical team immediately prior to
a surgical procedure. Those skilled in the art will appreciate that
reconditioning of a device can utilize a variety of techniques for
disassembly, cleaning/replacement, and reassembly. Use of such
techniques, and the resulting reconditioned device, are all within
the scope of the present application.
[0054] One skilled in the art will appreciate further features and
advantages of the invention based on the above-described
embodiments. Accordingly, the invention is not to be limited by
what has been particularly shown and described, except as indicated
by the appended claims. All publications and references cited
herein are expressly incorporated herein by reference in their
entirety.
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