U.S. patent application number 12/713988 was filed with the patent office on 2010-12-16 for reinforcing ring.
This patent application is currently assigned to William A. Cook Australia Pty. Ltd.. Invention is credited to David Ernest Hartley, Edward Graham Mills.
Application Number | 20100316830 12/713988 |
Document ID | / |
Family ID | 40935101 |
Filed Date | 2010-12-16 |
United States Patent
Application |
20100316830 |
Kind Code |
A1 |
Hartley; David Ernest ; et
al. |
December 16, 2010 |
REINFORCING RING
Abstract
A reinforcing ring (10) for a fenestration (32) of a stent graft
which can be surface treated such as by passivation and/or
electropolishing. The reinforcing ring has several turns of a
substantially inextensible resilient wire (12) in a circular two
dimensional planar shape and terminal ends (14) at each end of the
wire. The terminal ends each comprising a loop (14) and a tail
(16). The tail is folded back and extends around the circular
shape. Each of the tails of the terminal loops can have an enlarged
end. The reinforcing ring can be straightened out for surface
treatment such as passivation and/or electropolishing with
substantially no part of the circular shape, the loops or tails
touching each other.
Inventors: |
Hartley; David Ernest;
(Wannanup, AU) ; Mills; Edward Graham; (Gordon
Park, AU) |
Correspondence
Address: |
COOK GROUP PATENT OFFICE
P.O. BOX 2269
BLOOMINGTON
IN
47402
US
|
Assignee: |
William A. Cook Australia Pty.
Ltd.
Brisbane
IN
Cook Incorporated
Bloomington
|
Family ID: |
40935101 |
Appl. No.: |
12/713988 |
Filed: |
February 26, 2010 |
Current U.S.
Class: |
428/64.1 |
Current CPC
Class: |
A61F 2/07 20130101; A61F
2220/0075 20130101; Y10T 428/21 20150115; A61F 2002/061 20130101;
A61F 2/89 20130101; A61F 2002/075 20130101 |
Class at
Publication: |
428/64.1 |
International
Class: |
B32B 3/02 20060101
B32B003/02 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 10, 2009 |
AU |
2009202301 |
Claims
1. A reinforcing ring for a fenestration of a stent graft, the
reinforcing ring comprising a plurality of turns of a substantially
inextensible resilient wire in a circular two dimensional planar
shape and terminal ends at each end of the wire, the terminal ends
each comprising a loop and a tail, the tail being folded back and
extending around the circular shape.
2. A reinforcing ring as in claim 1 wherein the substantially
inextensible resilient wire comprises a superelastic wire.
3. A reinforcing ring as in claim 1 wherein the wire comprises a
nickel titanium alloy.
4. A reinforcing ring as in claim 1 wherein there are approximately
two circular turns of the wire.
5. A reinforcing ring as in claim 1 wherein the terminal loops at
each end of the wire overlap.
6. A reinforcing ring as in claim 1 wherein there are two complete
circular turns of the wire and the loops extend further around the
circular shape.
7. A reinforcing ring as in claim 1 wherein the terminal loops at
each end of the wire extend out of the plane of the circular shape
at approximately right angles thereto.
8. A reinforcing ring as in claim 1 wherein each of the tails of
the terminal loops comprises an enlarged end.
9. A reinforcing ring for a fenestration of a stent graft, the
reinforcing ring comprising a plurality of turns of a substantially
inextensible resilient wire in a circular two dimensional planar
shape and terminal ends at each end of the wire, the terminal ends
each comprising a loop and a tail, the tail being folded back and
extending around the circular shape, each of the tails of the
terminal loops comprises an enlarged end and the wire comprising a
passivated/electropolished surface.
Description
TECHNICAL FIELD
[0001] This invention relates to a medical device and more
particularly to a reinforcing ring used in stent graft device.
BACKGROUND OF THE INVENTION
[0002] Stent grafts are used to bridge a defect in the vasculature
of a patient and can be deployed into the vasculature
endovascularly. This requires that the device can be constrained
into a small delivery device and be able to expand or be expanded
when release within the vasculature.
[0003] Where there are side branches to the vasculature it may be
necessary to provide an aperture in the stent graft, known as a
fenestration, to enable access from a deployed stent graft to that
side branch. Such a fenestration may be reinforced with a
peripheral circular ring stitched to the graft material around the
fenestration. It is also desirable in some situations to provide a
side branch stent graft extending through the fenestration and into
the side branch.
[0004] PCT Publication WO 2005/034808 entitled "Fenestrated Stent
Graft" describes the use of resilient reinforcing rings in stent
grafts and the teachings therein are incorporated herein in their
entirety.
[0005] To obtain a good seal of the branch stent graft within the
fenestration an inflatable balloon can be used to expand the branch
stent graft into the fenestration and for this purpose the
reinforcing ring must be able to resist expansion of its diameter.
At the same time the ring must be resilient so that it can be
distorted into its deployment configuration but when released
expand back to its circular configuration. In this specification
the term resilient when used in relation to a wire used to
manufacture a reinforcing ring refers to a wire which is
substantially inextensible but which has a spring function so that
when distorted and released returns to its original
configuration.
[0006] This invention will be discussed in relation to the
application of a reinforcing ring to a fenestration but such a ring
may have greater applicability.
[0007] Generally such a reinforcing rings is manufactured from a
metal known as a superelastic metal such as, but not restricted, to
a nickel titanium alloy known as Nitinol. To form a ring of a
superelastic metal the desired final shape is formed from a wire on
a former and then the wire on the former is heated above a
temperature which sets the wire in the new shape. Upon cooling the
ring holds it formed shape and can be distorted and resiliently
returns to the formed shape.
[0008] The reinforcing rings discussed in PCT Publication WO
2005/034808 mentioned above when formed from a resilient wire each
have substantially circular loops at the terminal ends of the wire.
These loops prevent the sharp end of the wire puncturing the
vasculature into which the stent graft is deployed. When it is
desired to electropolish rings incorporating these prior art loops
it is necessary to straighten out the ring but the prior art loops
do not permit efficient electropolishing because parts of the loops
touch the wire of the ring.
SUMMARY OF THE INVENTION
[0009] In one form therefore the invention is said to reside in a
reinforcing ring for a fenestration of a stent graft, the
reinforcing ring comprising a plurality of turns of a substantially
inextensible resilient wire in a circular two dimensional shape and
terminal ends at each end of the wire, the terminal ends each
comprising a loop and a tail folded back and extending around the
circular shape whereby the reinforcing ring can be straightened out
for subsequent surface treatment with substantially no part of the
circular shape, the loops or tails touching each other.
[0010] The substantially inextensible resilient wire can be a
superelastic wire such as a wire formed from a nickel titanium
alloy such as Nitinol.
[0011] The forming of the loop provides an end which is less likely
to potentially damage the vasculature or a graft material. The
provision of the tail which is folded back and extending around the
circular shape enables the subsequent surface treatment to be
carried out on all of the surfaces of the wire after it has been
straightened out in a substantially linear manner.
[0012] Preferably there are substantially two circular turns of the
wire.
[0013] In preferred embodiments the terminal loops at each end of
the wire can overlap or be spaced apart either past each other or
nearly reaching each other.
[0014] In one embodiment there are two complete circular turns of
the wire and the loops extend further around the circular
shape.
[0015] In one embodiment the terminal loops at each end of the wire
can extend out of the plane of the circular shape at approximately
right angles thereto.
[0016] In one embodiment each of the tails of the terminal loops
comprises an enlarged end. The enlarged end can be in the form of a
ball of solder or the like.
[0017] The subsequent surface treatment such may be polishing,
passivation or coating. The polishing may be electropolishing,
mechanical polishing or chemical polishing. According to the
present invention these processes can be carried out on the entire
surface of the reinforcing ring of the present invention because
when it is straightened out no part of the loops or tails touch
each other.
[0018] The process of passivation in relation to a nickel titanium
alloy is intended to provide a protective nickel-depleted titanium
rich oxide layer for good biocompatibility. Passivation also
improves the corrosion resistance of the surface.
[0019] Electropolishing, also referred to as electrochemical
polishing, is an electrochemical process that removes material from
a metallic workpiece. It is used to polish, passivate and deburr
metal parts. It is often described as the reverse of
electroplating. It differs from anodizing in that the purpose of
anodizing is to grow a thick, protective oxide layer on the surface
of a material (usually aluminum) rather than polish.
[0020] For electropolishing typically, a metal work piece is
immersed in a temperature controlled bath of electrolyte and
connected to the positive terminal of a DC power supply, the
negative terminal being attached to an auxiliary electrode. A
current passes from the anode where metal on the surface is
oxidized and dissolved in the electrolyte. At the cathode, a
reduction reaction, normally hydrogen evolution, takes place.
Electrolytes used for electropolishing are most often concentrated
acid solutions having a high viscosity such as mixtures of sulfuric
acid and phosphoric acid. Other electropolishing electrolytes
reported in the literature include mixtures of perchlorates with
acetic anhydride and methanolic solutions of sulfuric acid. To
achieve electropolishing of a rough metal surface, the protruding
parts of a surface profile must dissolve faster than the recesses.
This behavior (referred to as anodic leveling) is achieved by
applying a specific electrochemical condition, most often involving
a mass transport limited dissolution reaction. A second condition
for achieving polishing is that surface heterogeneities due to
crystal orientation in a polycrystalline material are suppressed
and that no pitting occurs. These conditions, often associated with
surface brightening, are usually fulfilled with the above mentioned
polishing electrolytes and with proper process control. Anodic
dissolution under electropolishing conditions deburrs metal objects
due to increased current density on corners and burrs.
[0021] Hence in the present invention, the reinforcing ring after
it has been formed and suitably heat treated, as discussed above,
so that it will return to its circular ring shape can be stretched
out into a linear form so that no part of the ring touches another
and then can be electrochemically polished or have some other
surface treatment applied. Upon being released from its
straightened out condition the ring will return to its circular
ring shape.
BRIEF DESCRIPTION OF THE DRAWING
[0022] This then generally describes the invention but to assist
with understanding reference will now be made to the accompanying
drawings which show preferred embodiments of the invention.
[0023] In the drawings:
[0024] FIG. 1 shows a first embodiment of a reinforcing ring of the
present invention;
[0025] FIG. 2 shows an alternative embodiment of a reinforcing ring
of the present invention;
[0026] FIG. 3 shows an alternative embodiment of a reinforcing ring
of the present invention;
[0027] FIG. 4 shows a reinforcing ring according to the embodiment
shown in FIG. 2 stitched into a portion of graft material;
[0028] FIG. 5 shows a reinforcing ring according to the embodiments
shown in FIGS. 1 to 3 stretched out for electropolishing;
[0029] FIG. 6 shows a stent graft incorporating fenestrations and a
reinforcing ring according to the present invention;
[0030] FIG. 7 shows an alternative embodiment of the invention;
and
[0031] FIG. 8 shows a leg extension stent graft incorporating a
ring reinforcement of the embodiment of FIG. 7.
DETAILED DESCRIPTION
[0032] Now looking more closely at the drawings and in particularly
the embodiment shown in FIG. 1 it will be seen that the reinforcing
ring 2 is formed into a two dimensional circular shape of a
superelastic wire 4. The ring has a diameter of from 5 to 15 mm
when it is used as a reinforcing ring for a fenestration and from
10 to 40 mm when it is used as an end reinforcement for a tubular
stent graft. The ring 2 is formed from a superelastic metal wire
such as a nickel titanium alloy such as Nitinol. The wire can have
a diameter of from 0.1 mm to 1 mm and preferably a diameter of from
0.15 mm to 0.3 mm.
[0033] The ring has nearly two turns of the wire 4 and each end of
the wire terminates in a loop 6 and a tail 8. The loop 6 is
generally of a diameter through which can be passed a needle during
stitching of the reinforcing ring into a graft material. Typically
the loops may have a diameter of from 1 mm to 2 mm. The tail 8
extends back around the periphery of the reinforcing ring and when
the wire is stretched out for passivation and/or electropolishing
the tails are slightly spaced away from it (see FIG. 5). After
electropolishing or other surface treatment and when the
reinforcing ring is stitched into a stent graft there is no problem
with the parts of the ring touching each other.
[0034] Each of the tails 8 ends in an enlarged end 9. The enlarged
end 9 can be for instance in the form of a ball formed from solder,
fused material of the ring of the like. The enlarged end is
provided to protect the fabric of a stent graft unto which the
reinforcing ring is mounted from the sharp points at the ends of
the wire and to assist the sewing of the end of the wire as a
stitch can be added next to the ball which stitch can engage
against the enlarged end or ball and prevents the wire from being
pulled in one direction.
[0035] FIG. 2 shows an alternative embodiment of reinforcing ring
according to the invention. The reinforcing ring 10 is formed into
a two dimensional circular shape of a superelastic wire 12. The
ring 10 has two turns of the wire 12 and each end of the wire
terminates in a loop 14 and a tail 16. The loops 14 overlap each
other. The tails 16 extend back around the periphery of the
reinforcing ring and when the wire is stretched out for passivation
and/or electropolishing the tails are slightly spaced away from it
(see FIG. 5). Each of the tails 16 ends in an enlarged end 17.
[0036] FIG. 3 shows an alternative embodiment of reinforcing ring
according to the invention. The reinforcing ring 20 is formed into
a two dimensional circular shape of a superelastic wire 22. The
ring 20 has two complete turns and a little more of the wire 22 and
each end of the wire terminates in a loop 24 and a tail 26. The
tails 26 extend back towards each other. The tails 26 extend back
around the periphery of the reinforcing ring and when the wire is
stretched out for passivation and/or electropolishing the tails are
slightly spaced away from it (see FIG. 5). Each of the tails 26
ends in an enlarged end 27.
[0037] FIG. 4 shows a reinforcing ring according to the embodiment
shown in FIG. 2 stitched into a portion of graft material. The
graft material 30 has a fenestration 32 and around the fenestration
is a reinforcing ring 10 retained in place by blanket type
stitching 36. In this embodiment the reinforcing ring 10 is of the
type shown in FIG. 2 and the loops 14 overlap and two of the
stitches of the stitching pass through the loops 14. These extra
stitches 37 are provided into the loops 14 and through the graft
material. The tails 16 are also retained within the stitches 36. It
will be noted in particular that the stitch 36a engages against the
enlarged end or ball 17.
[0038] FIG. 5 shows a reinforcing ring according to the embodiments
shown in FIGS. 1 to 3 stretched out for passivation and/or
electropolishing. The wire 40 is stretched essentially by pulling
upon the tails 42 at each end out so that no portion of the rings,
loops or tails touch another. It will be particularly noted that
when stretched out the tail 42 does not touch the wire 40 thereby
ensuring good electropolishing all over the wire.
[0039] FIG. 6 shows a stent graft incorporating fenestrations and a
reinforcing ring according to the present invention. A stent graft
50 comprises a tubular wall body portion 53. The tubular wall body
portion is a biocompatible graft material such as Dacron, Thoralon,
expanded PTFE material or a naturally occurring biomaterial, such
as an extracellular matrix, such as small intestinal submucosa or
other suitable material.
[0040] Gianturco style zig zag Z stents 55 are provided inside the
graft material at each end and on the central tubular wall body
portion Gianturco style zig zag Z stents 57 are provided on the
outside of the graft material. There may be further Gianturco style
zig zag Z stents than those illustrated depending upon the overall
length of the stent graft 50. Other forms of stent may also be
used.
[0041] In the tubular wall body portion 53 there are two
substantially circular fenestrations or apertures 59 on the tubular
wall of the stent graft. In this embodiment there are two
fenestrations being one for each of the two renal arteries when
this embodiment is deployed into the aorta. Other numbers of
fenestrations may also be used where the placement of the stent
graft involves the possibility of occluding other branch vessels
such as the superior mesenteric artery and the celiac artery. The
fenestrations 59 are substantially circular. Radiopaque markers 61
are provided at each end of the fenestration 59 to assist a
physician to locate the fenestration 59 in respect to a side vessel
extending from a main vessel. The radiopaque markers 61 may be gold
or other convenient material.
[0042] A reinforcement ring 62 of the present invention is provided
around the periphery of the fenestration 59 to give good
dimensional stability to the fenestration 59. The reinforcing ring
is manufactured from Nitinol wire. In an alternative arrangement
the ring 62 may be formed from stainless steel or any other
convenient material. Stitching 63 is provided to retain the ring 62
around the periphery of the fenestration 59.
[0043] Also in FIG. 6 there is shown a scalloped fenestration 65
which opens to the end 67 of the stent graft.
[0044] FIG. 7 shows an alternative embodiment of the invention. In
this embodiment the reinforcing ring 70 has nearly two full turns
of Nitinol wire 72 and each end of the wire terminates in a loop
74. Each of the loops extend out of the plane of the circular shape
at approximately right angles thereto. The tails 76 of the loops
extend around the periphery of the circular shape and each of the
tails 76 ends in an enlarged end 78.
[0045] The reinforcement ring of this embodiment is useful as a
reinforcing ring at the end of a tubular body of graft material
such as an arm or leg of a stent graft where the ring is stitched
around the end of the tubular body and the loops at right angles to
the plane of the ring extend along the tubular body and can be
stitched thereto.
[0046] FIG. 8 shows a leg extension stent graft incorporating a
ring reinforcement of the embodiment of FIG. 7. In FIG. 8 the leg
extension 80 has a tubular body 82 of a graft material and a
reinforcement ring 70 at its proximal end 84.
[0047] The ring has loops 74 which extend out of the plane of the
circular shape of the ring at approximately right angles and along
the side of the tubular body. Stitching 86 fastens the ring to the
tubular body and also some of the stitches pass through the loops
74 and over the tails 76.
[0048] Throughout this specification various indication have been
made as to the scope of the invention but the invention is not
limited to any one of these but may reside in more than one
combined together. The example and embodiments are given for
illustration only and not for limitation.
* * * * *