U.S. patent application number 11/945939 was filed with the patent office on 2008-04-17 for stent fabrication method.
Invention is credited to Jacob Richter, Ira Yaron.
Application Number | 20080091258 11/945939 |
Document ID | / |
Family ID | 24984781 |
Filed Date | 2008-04-17 |
United States Patent
Application |
20080091258 |
Kind Code |
A1 |
Richter; Jacob ; et
al. |
April 17, 2008 |
Stent Fabrication Method
Abstract
A stent and a method for fabricating the stent are disclosed.
The stent has an originally flat pattern and connection points
where the sides of the flat pattern are joined. The method includes
the steps of a) cutting a stent pattern into a flat piece of metal
thereby to produce a metal pattern, b) deforming the metal pattern
so as to cause two opposing sides to meet, and c) joining the two
opposing sides at least at one point. Substantially no portion of
the stent projects into the lumen of the stent when the stent is
expanded against the internal wall of a blood vessel.
Inventors: |
Richter; Jacob; (Tel Aviv,
IL) ; Yaron; Ira; (Jerusalem, IL) |
Correspondence
Address: |
CADWALADER, WICKERSHAM & TAFT LLP
ONE WORLD FINANCIAL CENTER
NEW YORK
NY
10281
US
|
Family ID: |
24984781 |
Appl. No.: |
11/945939 |
Filed: |
November 27, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10682865 |
Oct 14, 2003 |
7314482 |
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11945939 |
Nov 27, 2007 |
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09624067 |
Jul 24, 2000 |
6660019 |
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10682865 |
Oct 14, 2003 |
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09191513 |
Nov 13, 1998 |
6156052 |
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09624067 |
Jul 24, 2000 |
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08742422 |
Oct 30, 1996 |
5836964 |
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09191513 |
Nov 13, 1998 |
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08330625 |
Oct 27, 1994 |
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08742422 |
Oct 30, 1996 |
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Current U.S.
Class: |
623/1.16 |
Current CPC
Class: |
A61F 2002/91558
20130101; A61F 2230/0054 20130101; A61F 2/915 20130101; A61M 29/02
20130101; A61F 2/91 20130101; A61F 2002/91541 20130101 |
Class at
Publication: |
623/001.16 |
International
Class: |
A61F 2/82 20060101
A61F002/82 |
Claims
1-63. (canceled)
64. An expandable stent, comprising: a plurality of portions
connected, after removal of a plurality of temporary bridges, by a
plurality of flexible compensating members, the flexible
compensating members projecting from an external surface of the
stent when the stent is in an unexpanded condition and configured
to be in circumferential registry with remaining portions of the
stent when the stent is in an expanded condition.
65. The stent of claim 64, wherein the stent is expandable from a
first diacter to a second diameter so the flexible compensating
members project from the external surface of the stent when the
stent is at the first diameter and are configured to be in
circumferential registry with remaining portions of the stent when
the stent is at the second diameter.
66. An expandable stent, comprising: a plurality of portions
connected, after removal of a plurality of temporary bridges, by a
plurality of flexible compensating members, wherein substantially
no portion of the stent projects into a longitudinal lumen of the
stent when the stent is expanded from a first diameter to a second
diameter.
67. The stent of claim 66, wherein the second diameter is greater
than the first diameter.
Description
FIELD OF THE INVENTION
[0001] The present invention relates generally to methods of
fabricating stents.
BACKGROUND OF THE INVENTION
[0002] Stents are known in the art. They are typically formed of a
cylindrical metal mesh which can expand when pressure is internally
applied. Alternatively, they can be formed of wire wrapped into a
cylindrical shape.
[0003] As described in U.S. Pat. No. 4,776,337 to Palmaz, the
cylindrical metal mesh shape is produced by laser cutting a thin
walled metal tube. The laser cuts away all but the lines and curves
of the mesh.
[0004] The method of U.S. '337 is applicable for relatively large
mesh shapes and for meshes whose lines are relatively wide.
However, for more delicate and/or intricate shapes, the spot size
of the laser is too large.
SUMMARY OF THE PRESENT INVENTION
[0005] It is, therefore, an object of the present invention to
provide a stent fabrication method which can produce stents with
relatively intricate and/or delicate designs.
[0006] The method involves first creating a flat version of the
desired stent pattern from a piece of thin sheet metal. The flat
pattern can be produced through any suitable technique, such as
etching the design into the sheet metal, or by cutting with a very
fine laser, should one become commercially available or by any
other technique.
[0007] Once the sheet metal has been cut, it is deformed so as to
cause its edges to meet. To create a cylindrical stent from a flat,
roughly rectangular metal pattern, the flat metal is rolled until
the edges meet. The locations where edges meet are joined together,
such as by spot welding. Afterwards, the stent is polished, either
mechanically or electrochemically.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] The present invention will be understood and appreciated
more fully from the following detailed description taken in
conjunction with the drawings in which:
[0009] FIG. 1 is a flow chart illustration of the stent fabrication
method of the present invention;
[0010] FIGS. 2A, 2B and 2C are illustrations of three alternative
stent patterns to be etched, in accordance with the method of FIG.
1, into a flat sheet of metal;
[0011] FIG. 3 is an isometric illustration of a stent being
deformed, useful in understanding the method of FIG. 1;
[0012] FIG. 4 is an isometric illustration of a stent formed from
the method of FIG. 1;
[0013] FIGS. 5A and 5B are side and top view illustrations,
respectively, of one connection location of the stent of FIG.
4;
[0014] FIG. 6 is a side view illustration of one connection
location of the stent of FIG. 4 which is connected in a nail-like
manner;
[0015] FIG. 7 shows a piece of sheet metal with a plurality of
patterns made in accordance with the invention;
[0016] FIG. 8 shows a detailed view of one of the patterns shown in
FIG. 7;
[0017] FIG. 9 shows a detailed view of a pair of engagement troughs
shown in FIG. 8;
[0018] FIG. 10 shows a detailed view of a pair of engaging
protrusions shown in FIG. 8;
[0019] FIG. 11 shows the engagement troughs and engagement
protrusions of FIGS. 9 and 10 in the engaged position;
[0020] FIG. 12 shows a welding run practiced in accordance with the
invention;
[0021] FIG. 13 is a detailed view of the welding run shown in FIG.
12;
[0022] FIG. 14 is a detailed view of a cell of a stent made in
accordance with this invention;
[0023] FIG. 15 is a detailed view of a cell made in accordance with
this invention;
[0024] FIG. 16 shows a cell of a stent made in accordance with this
invention;
[0025] FIG. 17 is an enlarged view of the cell shown in FIG.
16;
[0026] FIG. 18 is a cross-sectional view of a longitudinal member
of a stent constructed in accordance with this invention;
[0027] FIG. 19 is a cross-sectional view of a stent constructed in
accordance with this invention;
[0028] FIG. 20 is a perspective view of a stent constructed in
accordance with this invention;
[0029] FIG. 21 is a cross-sectional front view of an unexpanded
stent made in accordance with the invention;
[0030] FIG. 22 is a cross-sectional front view of the stent shown
in FIG. 21 after it has been expanded;
[0031] FIG. 23 is a cross-sectional front view of an unexpanded
stent made by cutting a pattern in a tube; and
[0032] FIG. 24 is a cross-sectional front view of the stent shown
in FIG. 23 after expansion.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
[0033] Reference is now made to FIG. 1 which illustrates the stent
fabrication method of the present invention and to FIGS. 2A, 2B,
2C, 3 and 4 which are useful in understanding the method of FIG.
1.
[0034] In the stent fabrication method of the present invention, a
stent designer first prepares a drawing of the desired stent
pattern in a flat format (step 10).
[0035] FIGS. 2A, 2B and 2C illustrate three exemplary stent pattern
designs. The pattern of FIG. 2A has two types of sections 20 and
22. Each section 20 has two opposing periodic patterns and each
section 22 has a plurality of connecting lines 24. The pattern of
FIG. 2A can be formed of any size; a preferable size is to have
each section 20 be between 1 and 6 mm wide and each section 22 have
connecting lines 24 of 1-6 mm long. At such sizes, the pattern of
FIG. 2A cannot be cut using a laser cutting system.
[0036] The pattern of FIG. 2B is similar to that of FIG. 2A in that
it also has sections 20 of opposing periodic patterns. The pattern
of FIG. 2B also has connecting sections, labeled 30, which have a Z
shape.
[0037] The pattern of FIG. 2C has no connecting sections. Instead,
it has a series of alternating patterns, labeled 32 and 34.
[0038] The patterns of FIGS. 2A, 2B and 2C optionally also have a
plurality of small protrusions 38 which are useful in forming the
stent, as described herein below.
[0039] Returning to FIG. 1, in step 12, the stent pattern is cut
into a flat piece of metal ("sheet metal"). The metal can be any
type of biocompatible material, such as stainless steel, or a
material which is plated with a biocompatible material. The cutting
operation can be implemented in any of a number of ways, such as by
etching, or by cutting with a fine cutting tool, or by cutting with
a very fine laser, should one become commercially available.
[0040] If step 12 is implemented with etching, then, the process is
designed to cut through the sheet metal. This process is known;
however, for the purposes of completeness, it will be briefly
described herein below.
[0041] The drawing of the pattern is reduced and printed onto a
transparent film. Since it is desired to cut completely through the
metal, the drawing is printed onto two films which are joined
together in a few places along their edges. The sheet metal is
covered, on both sides, with a layer of photoresist and placed
between the two transparent, printed films. The structure is
illuminated on both sides which causes the portions of the
photoresist which receive the light (which are all the empty spaces
in the pattern, such as spaces 26 of FIG. 2A) to change
properties.
[0042] The sheet metal is placed into acid which eats away those
portions of the photoresist which changes properties. The sheet
metal is then placed into an etching solution which etches away all
material on which there is no photoresist-removing solution which
removes the photoresist, leaving the metal having the desired stent
pattern.
[0043] In step 14, the metal pattern is deformed so as to cause its
long sides (labeled 28 in FIGS. 2A, 2B and 2C) to meet each other.
FIG. 3 illustrates the deformation process. For cylindrical stents,
the deformation process is a rolling process, as shown.
[0044] If the protrusions 38 have been produced, after deformation
of the metal pattern, the protrusions 38 protrude over the edge 28
to which they are not attached. This is illustrated in FIG. 5A.
[0045] In step 16, the edges 28 are joined together by any suitable
process, such as spot welding. If the protrusions 38 were made, the
protrusions 38 are joined to the opposite edge 28, either by
welding, adhesive or, as illustrated in FIG. 6, with a nail-like
element 40. FIG. 5B illustrates the connection of the protrusion to
the opposite edge 28. Since protrusion 38 is typically designed to
extend the width of one loop 39, the pattern in approximately
preserved. This is seen in FIG. 5B.
[0046] Alternatively, the edges 28 can be brought together and
joined in the appropriate places.
[0047] FIG. 4 illustrates a stent 31 formed by the process of steps
10-16 for the pattern of FIG. 2A. It is noted that such a stent has
connection points 32 formed by the joining of the points 30.
[0048] Finally, the stent 31 is polished to remove any excess
material not properly removed by the cutting process (step 12). The
polishing can be performed mechanically, by rubbing a polishing
stick having diamond dust on its outside inside the stent 31.
Alternatively, an electropolishing unit can be utilized.
[0049] FIG. 7 shows an alternative embodiment of the invention in
which a plurality of patterns 120 are etched and cut into the sheet
metal 121 as previously discussed. FIG. 8 is an enlarged view of
one of the plurality of patterns 120 shown in FIG. 7.
[0050] FIG. 9 is an enlarged view of one pair 127 of the plurality
of engagement troughs 128 and 129 shown in FIG. 8. FIG. 10 is an
enlarged view of one pair 130 of the plurality of engagement
protrusions 131 and 132 shown in FIG. 8. The sheet metal 121 and
each of the patterns 120 is provided with a plurality of alignment
apertures 122 and 122' adapted to receive sprockets (not shown) for
precisely moving and maintaining the precise alignment of the sheet
metal 121 and the patterns 120 during the various stages of
manufacturing. Each pattern 120 has a first long side 123 and a
second long side 124, a first short side 125, and a second short
side 126. The first long side 123 is provided with a plurality of
pairs 127, 127' and 127'' of engagement troughs 128 and 129 (shown
in greater detail in FIG. 9). Each pair 127, 127' and 127'' of
engagement troughs has a first engagement trough 128 and a second
engagement trough 129. The second long side 124 is provided with a
plurality of pairs 130, 130' and 130'' of engagement protrusions
(shown in greater detail in FIG. 10). Each pair 130, 130' and 130''
of engagement protrusions is provided with a first engagement
protrusion 131 and a second engagement protrusion 132. The pairs of
engagement protrusions 130, 130' and 130'' are disposed
substantially opposite the pairs of engagement troughs 127, 127'
and 127''.
[0051] The engagement troughs 128 and 129 are disposed and adapted
to receive and engage the engagement protrusions 131 and 132 so
that the alignment of the stent is maintained when the pattern 120
is deformed and the flat sheet metal is rolled so that the first
long side 123 and the second long side 124 meet each other to form
a tube as shown in FIGS. 19 and 20.
[0052] A bridge 133 of material is disposed between each pair 127,
127' and 127'' of engagement troughs 128 and 129. This bridge 133
imparts additional stability and facilitates alignment during
manufacturing and imparts additional strength to the welds of the
finished stent as discussed below.
[0053] After the sheet has been rolled into a tubular stent and the
engagement troughs 128 and 129 have received the engagement
protrusions 131 and 132, means (not shown) are utilized to maintain
the alignment and the bridge 133 is cut to leave two substantially
equal parts. The bridge 133 may be cut in a variety of ways well
known to those skilled in the art, however, in a preferred
embodiment, a laser is utilized. Engagement trough 128 is welded to
engagement protrusion 131 and engagement trough 129 is welded to
engagement protrusion 132 as shown in FIGS. 12 and 13. This may be
accomplished in a variety of ways well known to those skilled in
the art, however, in a preferred embodiment a plurality of spot
welds are utilized. In an especially preferred embodiment, about
five spot welds are used in each weld run as shown in FIGS. 12 and
13. The heat produced by the welding melts the cut bridge 133
material and the material is drawn towards the engagement trough
128 or 129 to which the material is attached and is drawn into the
welded area between the engagement trough and the engagement
protrusion where the additional bridge material becomes part of and
imparts additional strength to the weld. The stent may then be
finished as previously discussed.
[0054] FIG. 13 is an enlarged view of the welded area shown in FIG.
12. In a preferred embodiment, the weld run is offset from the
point where the engagement trough and the engagement protrusion
contact each other. In an especially preferred embodiment, the weld
run is offset about 0.01 mm.
[0055] FIG. 14 is a detailed view of the pattern shown in FIG. 8.
As shown in FIGS. 14 and 20, Applicants' invention can also be
described as an expandable stent defining a longitudinal aperture
80 having a longitudinal axis or extension 79 and a circumferential
axis or extension 105, including a plurality of flexible connected
cells 50 with each of the flexible cells 50 having a first
longitudinal end 77 and a second longitudinal end 78. Each cell 50
also is provided with a first longitudinal apex 100 disposed at the
first longitudinal end 77 and a second longitudinal apex 104
disposed at the second longitudinal end 78. Each cell 50 also
includes a first member 51 having a longitudinal component having a
first end 52 and a second end 53; a second member 54 having a
longitudinal component having a first end 55 and a second end 56; a
third member 57 having a longitudinal component having a first end
58 and a second end 59; and a fourth member 60 having a
longitudinal component having a first end 61 and a second end 62.
The stent also includes a first loop 63 defining a first angle 64
disposed between the first end 52 of the first member 51 and the
first end 55 of the second member 54. A second loop 65 defining a
second angle 66 is disposed between the second end 59 of the third
member 57 and the second end 62 of the fourth member 60 and is
disposed generally opposite to the first loop 63. A first flexible
compensating member or flexible link 67 having a first end 68 and a
second end 69 is disposed between the first member 51 and the third
member 57 with the first end 68 of the first flexible compensating
member or flexible link 67 communicating with the second end 53 of
the first member 51 and the second end 69 of the first flexible
compensating member or flexible link 67 communicating with the
first end 58 of the third member 57. The first end 68 and the
second end 69 are disposed a variable longitudinal distance 70 from
each other. A second flexible compensating member 71 having a first
end 72 and a second end 73 is disposed between the second member 54
and the fourth member 60. The first end 72 of the second flexible
compensating member or flexible link 71 communicates with the
second end 56 of the second member 54 and the second end 73 of the
second flexible compensating member or flexible link 71
communicates with the first end 61 of the fourth member 60. The
first end 72 and the second end 73 are disposed a variable
longitudinal distance 74 from each other. In a preferred
embodiment, the first and second flexible compensating member or
flexible links 67 and 71 are accurate. The first and second
flexible compensating member or flexible links 67 and 71 are
differentially extendable or compressible when the stent is bent in
a curved direction away from the longitudinal axis 79 of the
aperture 80. (Shown in FIG. 20.) The first member 51, second member
54, third member 57, and fourth member 60 and the first loop 63 and
the second loop 65 and the first flexible compensating member or
flexible link 67 and the second flexible compensating member or
flexible link 71 are disposed so that as the stent is expanded the
distance between the first flexible compensating member or flexible
link 67 and the second flexible compensating member or flexible
link 71 increases and the longitudinal component of the first
member 51, second member 54, third member 57 and fourth member 60
decreases while the first loop 63 and the second loop 65 remain
generally opposite to one another, the ends 68 and 69 of the first
flexible compensating member or flexible link 67 and the ends 72
and 73 of the second flexible compensating member or flexible link
71 open so as to increase the variable longitudinal distance 70
between the first end 68 and the second end 69 of the first
flexible compensating member or flexible link 67 and so as to
increase the variable longitudinal distance 74 between the first
end 72 and the second end 73 of the second flexible compensating
member or flexible link 71. This compensates for the decreasing of
the longitudinal component of the first member 51, second member
54, third member 57, and fourth member 60 and substantially lessens
the foreshortening of the stent upon its expansion. Upon expansion,
the first flexible compensating member 67 and the second flexible
compensating member 71 impart support to the lumen being
treated.
[0056] FIG. 15 shows the dimensions of an especially preferred
embodiment of this invention. The deflection points, i.e., the
first and second loops 63 and 65 and the first and second
compensating members 67 and 71, are made wider than the first,
second, third, and fourth members 51, 54, 57 and 60 so that the
force of the deflection is distributed over a wider area upon the
expansion of the stent. The deflection points can be made wider
than the first, second, third and fourth members in differing
amounts so that the deflection will occur in the narrower areas
first due to the decreased resistance. In a preferred embodiment,
the first and second compensating members are wider than the first,
second, third and fourth members and the first and second loops are
wider than the first and second compensating members. One of the
advantages of sizing the first and second loops so that they are
wider than the first and second compensating members is that the
stent will substantially compensate for foreshortening as the stent
is expanded. In the embodiment shown in FIG. 15, the first, second,
third and fourth members 51, 54, 57 and 60 have a width of about
0.1 mm. The first and second loops 63 and 65 have a width of about
0.14 mm. The first and second compensating members 67 and 71 are
provided with a thickened portion 75 and 76 having a width of about
0.12 mm. Thus, in this especially preferred embodiment, the first
and second loops have a width that is about 40% greater and the
first and second compensating members have a width that is about
20% greater than the width of the first, second, third and fourth
members.
[0057] FIGS. 16 through 20 show details of a stent constructed in
accordance with this invention.
[0058] Yet another advantage of Applicants' invention is shown in
FIGS. 21 to 24. For the sake of clarity, the dimensions and the
degree of displacement of the components of the stents shown in
FIGS. 21 to 24 has been intentionally exaggerated.
[0059] FIG. 21 is a cross-sectional front view taken along line A-A
of the unexpanded stent made in accordance with applicants
invention shown in FIG. 20. The unexpanded stent 200 of FIG. 21 is
shown disposed in the lumen 202 of a blood vessel 201 prior to
expansion. As previously discussed, this stent is made by first
cutting the stent pattern into a flat piece of sheet metal and then
rolling the sheet metal into a tube to form the tubular stent. As
shown in FIG. 21 after rolling, the first and second flexible
compensating members 67 and 71 of the unexpanded stent tend to
"flare out" in a direction away from the longitudinal axis or lumen
of the stent. Thus, the flexible compensating members 67 and 71
define outer diameters which are larger than the outer diameters
defined by the remaining portions of the stent. FIG. 22 shows the
stent of FIG. 21 after it has been expanded in the lumen and
against the internal wall of the blood vessel. As shown in FIG. 22,
upon expansion of the unexpanded stent toward the wall of the blood
vessels, the walls of the blood vessel imparts a mechanical force
to the first and second flexible compensating members 67 and 71 and
the compensating members move toward the longitudinal axis or lumen
of the stent until they are substantially in registry with the
remaining portion of the stent. Thus, the lumen of the expanded
stent is substantially circular when viewed in cross section with
substantially no portion of the expanded stent projecting into the
lumen or towards the longitudinal axis of the expanded stent.
[0060] FIG. 23 is similar to FIG. 21 except that the pattern has
been cut into a tubular member using conventional methods of making
stents. As shown in FIG. 23, the flexible compensating members do
not flare out away from the longitudinal axis of the unexpanded
stent 203. Upon the expansion of the stent shown in FIG. 23 toward
the walls of the blood vessel 201, the flexible compensating
members 67' and 71' tend to "flare in" and project into the lumen
204 of the expanded stent 203.
[0061] FIG. 24 shows the stent 203 of FIG. 23 after it has been
expanded in a lumen 204 of a blood vessel 201. The flexible
compensating members 67' and 71' are not in registry with the
remaining portions of the stent and define a diameter smaller than
the diameter of remaining portions of the stent. These projections
into the lumen of the stent create turbulence in a fluid flowing
through the longitudinal axis of the expanded stent and could
result in clot formation.
[0062] It will be appreciated by persons skilled in the art that
the present invention is not limited to what has been particularly
shown and described hereinabove. Rather the scope of the present
invention is defined only by the claims which follow.
* * * * *