U.S. patent application number 12/882606 was filed with the patent office on 2011-01-06 for atraumatic gastrointestinal anchor.
Invention is credited to Andy H. Levine, John C. Meade, David A. Melanson.
Application Number | 20110004230 12/882606 |
Document ID | / |
Family ID | 35610001 |
Filed Date | 2011-01-06 |
United States Patent
Application |
20110004230 |
Kind Code |
A1 |
Levine; Andy H. ; et
al. |
January 6, 2011 |
Atraumatic Gastrointestinal Anchor
Abstract
The present invention relates to methods and articles for
anchoring within a natural bodily lumen. An anchor is adapted to
provide differing radially-outward forces along its length, a
securing force and a transitional force. Production of these forces
can be controlled by varying a physical property of the anchor,
such as its stiffness, thickness, or shape. For example, the
stiffness of an elongated anchor can be varied from a relatively
soft value at its proximal and distal ends to a relatively stiff
value at its center by varying the diameter of wire forming the
anchor, thereby tailoring it to an intended application. Such force
tailoring can be combined with external barbs and used to reliably
anchor other instruments, such as feeding tubes and intestinal
sleeves.
Inventors: |
Levine; Andy H.; (Newton,
MA) ; Meade; John C.; (Mendon, MA) ; Melanson;
David A.; (Hudson, NH) |
Correspondence
Address: |
HAMILTON, BROOK, SMITH & REYNOLDS, P.C.
530 VIRGINIA ROAD, P.O. BOX 9133
CONCORD
MA
01742-9133
US
|
Family ID: |
35610001 |
Appl. No.: |
12/882606 |
Filed: |
September 15, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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11229352 |
Sep 16, 2005 |
7815591 |
|
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12882606 |
|
|
|
|
60611038 |
Sep 17, 2004 |
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Current U.S.
Class: |
606/153 |
Current CPC
Class: |
A61F 2002/9534 20130101;
A61F 2002/828 20130101; A61F 2220/005 20130101; A61F 2002/072
20130101; A61F 2220/0075 20130101; A61F 2220/0058 20130101; A61F
2210/0076 20130101; A61F 2/07 20130101; A61F 2/915 20130101; A61F
2002/8483 20130101; A61F 2250/0037 20130101; A61F 2/90 20130101;
A61F 2/86 20130101; A61F 2002/045 20130101; A61F 2/89 20130101;
A61F 2002/075 20130101; A61F 2220/0016 20130101; A61F 2/91
20130101; A61F 2/04 20130101; A61F 2250/0036 20130101; A61F
2220/0066 20130101; A61F 5/0076 20130101; A61F 2/06 20130101; A61F
2/82 20130101 |
Class at
Publication: |
606/153 |
International
Class: |
A61B 17/00 20060101
A61B017/00 |
Claims
1. An intraluminal implant comprising: an anchor configured to be
implanted within a natural bodily lumen, the anchor comprising a
plurality of wave-shaped anchoring elements, at least one of the
plurality of anchoring elements comprising at least one external
barb configured to penetrate muscular tissue of the natural bodily
lumen, the respective anchoring element expanding against the lumen
and configured to hold the barb against the muscular tissue; and a
flexible, elongated sleeve coupled at its proximal end to the
anchor, the sleeve configured to extend distally beyond the anchor
within the natural bodily lumen.
2. The intraluminal implant of claim 1, wherein the anchor
comprises two of the wave-shaped anchoring elements.
3. The intraluminal implant of claim 1, wherein the anchor
comprises three of the wave-shaped anchoring elements.
4. The intraluminal implant of claim 3, wherein at least one
external barb extends from a central anchoring element and the
central anchoring element is stiffer than two end anchoring
elements.
5. The intraluminal implant of claim 1, wherein the sleeve is
floppy.
6. The intraluminal implant of claim 1, wherein the external barb
is a bi-directional barb, comprising a first barb segment
configured to oppose proximal movement and a second barb segment
configured to oppose distal movement.
7. The intraluminal implant of claim 1, wherein the elongated
sleeve is configured to be anchored in the proximal duodenum, the
sleeve extending distally within the intestine.
8. The intraluminal implant of claim 1, wherein the elongated
sleeve is thin-walled, collapsing upon itself.
9. The intraluminal implant of claim 1, wherein the anchor is
coupled to the sleeve between overlapping layers of the sleeve.
10. The intraluminal implant of claim 1, wherein the anchor is
radially collapsible for endoscopic insertion.
11. The intraluminal implant of claim 1, wherein the waves of the
wave-shaped anchoring elements do not overlap axially.
12. A method for anchoring a flexible, elongated sleeve within a
natural bodily lumen, the method comprising: providing an anchor
fixed to a proximal end of the flexible, elongated sleeve, the
sleeve extending distally into the natural bodily lumen, the anchor
comprising a plurality of wave-shaped anchoring elements, at least
one of the plurality of anchoring elements comprising at least one
external barb; providing a radially-outward securing force from the
anchor acting upon the natural bodily lumen; and piercing muscular
tissue of the natural bodily lumen with at least one external barb
of the plurality of anchoring elements, the radially outward
securing force driving the at least one barb into the muscular
tissue.
13. The method of claim 12, further comprising inhibiting movement
in either direction along the natural bodily lumen using the at
least one external barb.
14. The method of claim 12, further comprising at least partially
radially collapsing the anchor for insertion of the anchor into the
natural bodily lumen.
15. The method of claim 12, further comprising at least partially
radially collapsing at least a portion of the anchor for removal of
the anchor from the natural bodily lumen.
16. The method of claim 12, wherein the anchor comprises two of the
wave-shaped anchoring elements.
17. The method of claim 12, wherein the anchor comprises three of
the wave-shaped anchoring elements.
18. The method of claim 17, wherein at least one external barb
extends from a central anchoring element and the central anchoring
element is stiffer than two end anchoring elements.
19. The method of claim 12, wherein the sleeve is floppy.
20. The method of claim 12, wherein the external barb is a
bi-directional barb, comprising a first barb segment configured to
oppose proximal movement and a second barb segment configured to
oppose distal movement.
21. The method of claim 12, comprising anchoring the sleeve in the
proximal duodenum and extending the sleeve distally within the
intestine.
22. The method of claim 12, wherein the sleeve is thin-walled,
collapsing upon itself.
23. The method of claim 12, wherein the anchor is coupled to the
sleeve between overlapping layers of the sleeve.
24. The method of claim 12, wherein the waves of the wave-shaped
anchoring elements do not overlap axially.
Description
RELATED APPLICATIONS
[0001] This application is a continuation of U.S. application Ser.
No. 11/229,352, filed on Sep. 16, 2005, which claims the benefit of
U.S. Provisional Application No. 60/611,038, filed on Sep. 17,
2004.
[0002] The entire teachings of the above applications are
incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0003] Anchors are used in the treatment of patients to secure
devices at a desired location within a natural bodily lumen. For
example, anchors can be used to secure tubes within the digestive
tract, such as intestinal sleeves. For example intestinal sleeves
anchored within the gastrointestinal tract are described in U.S.
application Ser. No. 10/339,786 filed on Jan. 9, 2003, claiming
priority to U.S. Provisional Application No. 60/430,321 filed on
Dec. 2, 2002; 10/858,852 filed on Jun. 16, 2004, claiming priority
to U.S. Provisional Application Nos. 60/528,084 filed on Dec. 9,
2003 and 60/544,527 filed on Dec. 14, 2004, incorporated herein by
reference in their entirety.
SUMMARY OF THE INVENTION
[0004] This invention is generally related to articles and methods
for anchoring within a natural bodily lumen, and particularly to
articles and methods for anchoring atraumatically.
[0005] Unfortunately, stiff anchors can traumatize surrounding
tissue. This is particularly true in biological applications in
which the anchor operates against softer bodily tissues. A stiff
anchor may be used within a bodily lumen, such as the intestine to
prevent a medical device (e.g., a sleeve) from migrating therein.
In some applications, the anchor includes barbs adapted to pierce a
portion of the lumen. For the barbs to be effective, at least some
of them must engage the tissue at all times. To accomplish this
continued engagement, anchors provide a sufficient securing force
adapted to maintain the barbs within the tissue. As this securing
force can be substantial, tissue damage at the proximal and distal
ends of the anchor are likely to occur.
[0006] To anchor within a lumen, anchors generally apply at least
some outward force directed toward the inner walls of the lumen.
Depending upon the application, the anchoring force can vary from a
minimal force (e.g., to hold hooks in position) to a more
substantial force (e.g., forming an interference fit). In
biological applications the inner walls of a lumen typically
contain tissue that is soft and particularly vulnerable to
irritation. Thus, in these applications a greater force increases
the risk that the anchor will lead to trauma by way of irritation
or even tissue damage.
[0007] Such irritation and tissue damage are particular concerns
for anchors adapted for use within the intestine. Unfortunately,
the high mobility of the intestine and the nature of the forces
acting on material within the intestine (i.e., peristalsis)
complicate anchoring there. Thus, a more substantial force is
typically required to secure an intestinal anchor in place.
[0008] The present invention relates to an intraluminal anchor
adapted for implanting within a natural bodily lumen. The
intraluminal anchor includes an elongated anchor having a
longitudinal axis adapted for alignment with the natural bodily
lumen. The elongated anchor includes a primary anchoring region
adapted to expand against the lumen. The anchor also includes
secondary anchoring regions disposed along either side of the
primary anchoring region. The secondary anchoring regions are also
adapted to expand against the lumen with the primary anchoring
region expanding to a greater extent than the outer ends of the
secondary anchoring regions.
[0009] The intraluminal anchor also includes an elongated anchoring
member that, when implanted, provides at least two different radial
forces at respective positions along its length. These different
radial forces act differently upon respective portions of the
natural bodily lumen when the device is implanted therein. Namely,
at least one of the radial forces is primarily a securing force
adapted to anchor within the natural bodily lumen. The other radial
force is a transitional force adapted to mitigate damage to the
natural bodily lumen. Further, when implanted, the intraluminal
anchor defines an interior lumen allowing for continued functioning
of the natural bodily lumen.
[0010] The elongated anchoring member can include plural anchoring
elements each providing a respective radial force, at least one of
the elements providing a different radial force from the others. By
positioning each of the plural anchoring elements at a respective
position along the length of the intraluminal anchor, the
respective radial forces, including the different radial force, are
disposed at different lengths along the natural bodily lumen.
[0011] The different radial force can be provided by forming one or
more of the anchoring elements from a different material than the
other anchoring elements. Preferably, the different materials
provide different compliance values that produce different radial
forces when implanted. Alternatively, or in addition, the different
anchoring elements can be formed from the same material but in a
different configuration, such as its shape or thickness.
[0012] At least some of the anchoring elements can be coupled to
each other. For example, in some embodiments at least one joining
member is coupled between adjacent anchoring elements, the joining
member coupling two or more anchoring elements together.
[0013] In some embodiments having plural anchoring elements, at
least one of the anchoring elements can be formed from an elongated
wire. The elongated wire can be formed in any suitable shape, such
as a helix or an oscillating (i.e., wave-shaped) pattern. The
wave-shaped pattern distributes the respective radial force over
the length of the anchoring element while also improving
performance of the anchoring element's respective radial expansion
and contraction.
[0014] To further enhance its anchoring performance, the
intraluminal anchor can include at least one external barb adapted
to penetrate tissue of the natural bodily lumen. The external barb
is located at a predetermined position along the length of the
intraluminal anchor, the corresponding radial force acting to press
the barb into the tissue. For example, in a multi-anchoring element
embodiment, the at least one external barb can be coupled to one of
the anchoring elements. The force of the coupled anchoring element
then acts to hold the barb within the tissue.
[0015] In some embodiments, the external barb can be a
bi-directional barb. Bi-directional barbs are particularly well
suited for applications in which the intraluminal anchor is
subjected to external forces acting in either direction along the
natural bodily lumen. Generally, the bi-directional barb includes a
first barb segment adapted to oppose proximal movement and a second
barb segment adapted to oppose distal movement. Such barbs are well
suited to gastrointestinal applications in which the device is
subjected to the substantial axial forces of peristalsis.
[0016] Preferably, the anchor is radially collapsible for
endoscopic insertion. The intraluminal anchor can also include a
drawstring to facilitate repositioning and/or removal. The
drawstring, for example, can be provided at a proximal end of the
device and be adapted for engagement by a removal device, such as a
hook. The drawstring, when engaged, can be pushed or pulled by the
removal device, in opposition to the stationary intraluminal
anchor, to at least partially collapse at least part of the
intraluminal anchor. With a reduced diameter, the device can be
removed through, or repositioned within, the natural bodily lumen.
In some embodiments, at least a portion of the device is drawn into
a retrieval hood, sheath, or overtube prior to removal.
[0017] In some embodiments, the intraluminal anchor is coupled to
an elongated tube at a proximal end of the tube, the tube being
adapted to extend distally within the natural bodily lumen. The
elongated anchoring element can be coupled to the elongated tube in
any of a number of different ways. For example, the anchoring
element can be mechanically fastened using sutures, staples, or the
like. Alternatively or in addition, the anchoring element can be
bonded to the tube, using a chemical adhesive and/or heat welding.
In some embodiments the tube is thin-walled, and flexible. For
example, the tube can be formed as a sleeve having extremely thin
and floppy walls, the sleeve tending to collapse upon itself. The
anchoring element can secured between at least two overlapping
layers of the sleeve. The overlapping layers can then be attached
to each other using any available fastening technique including
bonding together at least a portion of the overlapping layers of
the sleeve.
[0018] In other embodiments, the elongated anchoring element can be
formed from a homogeneous hollow tube. The thickness of the tube
can be altered (i.e., tapered) along the length of the tube, such
that different portions of the tube provide different spring
forces. When implanted within a naturally bodily lumen, the tapered
tube provides different forces along its length and therefore
different forces along the bodily lumen according to the thickness
of the tube. In some embodiments, the tapered tube can be further
modified using known techniques (e.g., laser cutting) to promote
radial expansion and contraction of the device.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] The foregoing and other objects, features and advantages of
the invention will be apparent from the following more particular
description of preferred embodiments of the invention, as
illustrated in the accompanying drawings in which like reference
characters refer to the same parts throughout the different views.
The drawings are not necessarily to scale, emphasis instead being
placed upon illustrating the principles of the invention.
[0020] FIG. 1A is a schematic diagram illustrating a prior art
intraluminal anchor implanted within a natural bodily lumen.
[0021] FIG. 1B is a schematic diagram illustrating an embodiment of
an intraluminal anchor according to the principles of the invention
implanted within a natural bodily lumen.
[0022] FIG. 2 is a schematic diagram illustrating an embodiment of
an intraluminal anchor.
[0023] FIG. 3 is a schematic diagram illustrating an embodiment of
a bendable, intraluminal anchor.
[0024] FIG. 4A is a schematic diagram illustrating an alternative
embodiment of the intraluminal anchor shown in FIG. 1.
[0025] FIG. 4B is an exemplary radial-force profile for the
intraluminal anchor of FIG. 4A.
[0026] FIGS. 5A and 5B are schematic diagrams illustrating
alternative embodiments of the intraluminal anchor shown in FIG. 2
having cross-linking members.
[0027] FIG. 6 is a schematic diagram illustrating an alternative
embodiment of the intraluminal anchor shown in FIG. 4A having
multiple coupled wave elements.
[0028] FIG. 7 is a schematic diagram illustrating a cross-sectional
view of an embodiment of the intraluminal anchor device shown in
FIG. 2 attached to a tube and implanted within a natural bodily
lumen.
[0029] FIG. 8 is a schematic diagram illustrating a cross-sectional
view of the intraluminal anchor device shown in FIG. 7 implanted
within the proximal duodenum.
[0030] FIG. 9A is a schematic diagram illustrating an embodiment of
a shaped tube. FIG. 9B is a schematic diagram illustrating an
embodiment of an intraluminal anchor formed from the shaped tube
shown in FIG. 9A.
[0031] FIG. 9C is an exemplary radial-force profile for the
intraluminal anchor of FIG. 9B.
DETAILED DESCRIPTION OF THE INVENTION
[0032] A description of preferred embodiments of the invention
follows.
[0033] An anchor is adapted for anchoring within a natural bodily
lumen while allowing continued functionality of the lumen and
providing minimal trauma to the surrounding anatomy. Such an anchor
provides a securing force acting upon the surrounding anatomy to
hold the anchor fast, even in the presence of anticipated
biological forces. For example, the securing force would hold a
gastrointestinal anchor in position even in the presence of
peristalsis. Anchoring against such forces, however, may require
substantial securing force that could otherwise damage the
surrounding tissue.
[0034] A cross-section of a natural bodily lumen 20 including an
anchor 10b' is illustrated in FIG. 1A. Generally, the lumen defines
a natural diameter, D.sub.1, that may vary over time. The anchor
provides a radially-outward securing force directed against the
luminal walls. Depending upon the structure of the anchor 10b' and
the compliance of the luminal walls, the anchor 10b' when implanted
can increase the intraluminal diameter (i.e., D.sub.2) as shown.
The sharp transition from the anchored region to the unsupported
adjacent region applies a strain to the tissue, particularly at the
ends of the anchor 25. As shown, tissue stretching can occur over a
first distance .DELTA..sub.1. Such a strain can lead to irritation
of the tissue or even damage over time.
[0035] To offset the possibility of damage due to the securing
force, the anchor also provides a transitional force that is
different from the securing force and acts upon an adjacent region
of the surrounding anatomy. As shown in FIG. 1B, an anchor 10b''
providing a securing force is surrounded on either side by another
anchoring element 10a-, 10c'' providing a lesser, transitional
force. The transitional force allows for a more gradual decrease in
anchoring force from a central region along the length of the
anchor and thus less trauma. Thus, the transition from an expanded
diameter D.sub.2 to the natural luminal diameter D.sub.1 occurs
over a second distance .DELTA..sub.2, that is greater than first
distance .DELTA..sub.1. By transitioning from unsupported tissue to
anchored tissue using a softer anchoring element, the strain to the
tissue is reduced, thereby reducing the likelihood of tissue
irrigation and damage.
[0036] By applying different forces at different lengths along the
natural bodily lumen, the securing force can be applied, or focused
where needed, while the transitional force can distribute the
pressure loading to the surrounding anatomy. In particular, the
transitional force is a lesser force than the securing force,
providing a gradual transition from the luminal region subjected to
the securing force, to adjacent, unsupported luminal regions.
Preferably, the anchor can be used in combination with another
instrument, such as a feeding tube or a gastrointestinal sleeve, to
secure the instrument at a predetermined location within the bodily
lumen.
[0037] FIG. 2 schematically illustrates an exemplary embodiment of
an intraluminal anchor 100. The anchor 100 has an overall
axial-length `L` measured length-wise with respect to the lumen and
defines an interior channel 115 configured to allow continued
operation of the lumen when implanted therein. For example, the
anchor 100 can have a generally cylindrical shape, having a length
`L`, a diameter `D`, and defining an interior channel 115. When
implanted, the anchor provides a radially-outward spring force
directed against the adjacent walls of the natural bodily lumen
(i.e., the anchor includes an annular, radial spring providing a
force corresponding to a displacement of the spring along its
radius). The radial force includes a securing force, sufficient to
secure the anchor 100 in place under anticipated bodily forces. In
particular, the outward radial force is varied along the length of
the anchor to provide a transitional force, reducing the likelihood
of damage to surrounding tissue. When implanted within a natural
bodily lumen, the anchor provides a transition along the lumen from
soft tissue, to a low compliance region (i.e., transitional force),
to a higher compliance region (i.e., securing force), again to a
low compliance region, and ultimately back to unsupported, soft
tissue.
[0038] Generally, the anchor includes a spring providing the
desired securing force. The force produced by the spring is defined
by an associated spring rate relating to its compliance or
stiffness. The spring rate can be determined by one or more anchor
features including its type of material, material thickness,
dimensions, and shape. As a radial spring, a greater force results
from a greater radial displacement. For intraluminal applications,
such a radial spring preferably has a relaxed diameter (i.e., no
load diameter) that is greater than the largest anticipated
intraluminal diameter. Thus, the implanted anchor is always
subjected to a compressive force causing radial compression and
leading to an opposing securing force. Compliant anchors are
described in U.S. application Ser. No. 11/147,992 filed on Jun. 8,
2005, incorporated herein by reference in its entirety.
[0039] In many applications the anchor remains sufficiently
compliant, when implanted, to conform to the walls of the lumen
over a full range of motion. For example, an anchor implanted
within the proximal duodenum of an adult human may experience
intraluminal diameter variations from about 25-millimeters or less,
to greater than 50-millimeters.
[0040] As suggested by FIG. 2, the anchor 100 can provide a varied
force by using plural anchoring elements. For example, the anchor
100 can include three or more different anchoring elements 110a,
110b and 110c (generally 110), as shown. Each of the anchoring
elements 110a, 110b and 110c can be annular, as shown, and occupy a
respective axial sub-length `l.sub.1,` `l.sub.2,` and `l.sub.3.`
Further, each of the anchoring elements 110 can be separated from
its neighboring anchoring element by a respective distance
`s.sub.1,` `s.sub.2.` In some embodiments, the one or more of the
distances can be negative, suggesting that the elements overlap.
The overall length of the anchor 100 is determined as the sum of
the sub-lengths of the anchoring elements and any distances
provided therebetween. Each of the annular anchoring elements 110
can be sized and shaped to conform to the walls of the surrounding
lumen with its opening collinearly aligned with a luminal axis.
[0041] In some embodiments, the anchoring elements 110 are coupled
together using a respective cross-linking, or joining member 120a,
120b (generally 120), as shown. The joining member 120 can be a
rigid member or strut, such as a wire or rod. Use of rigid struts
can reduce or substantially eliminate axial compression of the
device. Alternatively or in addition, the joining member 120 can be
flexible, such as a wire, tape, or thread (e.g., a suture). Such
flexible members can permit axial compression but not expansion, so
the length can be less than or equal to a maximum length. If axial
compression and expansion is desired, the joining members 120 can
include elastic elements. Such flexibility can be beneficial to
both patient comfort and anchoring effectiveness. In some
embodiments, the joining members 120 are formed integrally to the
anchoring elements 110 themselves.
[0042] An embodiment of a flexible elongated anchor 200 is
illustrated in FIG. 3. The elongated anchor 200 can include more
than one anchoring element 210a, 210b, 210c, each capable of
independent movement with respect to the other elements. The anchor
200 may include joining members 220a, 220b, but they are selected
and positioned to allow a desired flexibility. For example, rigid
joining members can be aligned along one side of the anchor 200,
allowing the anchor to bend towards that side.
[0043] An alternative embodiment of an intraluminal anchor 300 is
illustrated in FIG. 4A. The anchor 300 includes multiple anchoring
elements 310a, 310b, 310c in a collinear arrangement with adjacent
elements 310 abutting. A corresponding force-versus-distance graph
for the anchor 300 is illustrated in FIG. 4B. In particular, the
graph illustrates the different radially-outward forces provided by
each of the anchoring elements 310 (FIG. 4A) versus its respective
distance as measured along a central axis of the anchor 300. As
shown for the exemplary embodiment of FIG. 4A, the greater radial
force is provided by the central element 310b, having a
representative force of F.sub.2. The corresponding force can be
substantially constant across the axial length subtended by the
second anchoring element 310b (i.e., from L/3 to 2L/3, assuming all
three elements are of equal length L/3). Similarly, forces F.sub.1
and F.sub.3 provided by the adjacent first and third anchoring
elements 310a, 310c are lesser forces, as shown in the graph (e.g.,
at region 320). The greater force F.sub.2 corresponds to a securing
force to hold the anchor in place when implanted; whereas, the
lesser forces F.sub.1 and F.sub.3 correspond to transitional forces
lessening the likelihood of damage to surrounding tissue.
[0044] In some embodiments, however, the structure of the anchoring
elements 310 allows the elements to provide different forces along
their respective sub-lengths. As the anchoring elements 310 are
radial springs, they have an associated spring constant. The radial
force provided by the anchoring element 310 is thus a result of the
spring constant and the amount of radial compression. Anchoring
element configurations that allow for varied compression along the
anchor sub-length will lead to a corresponding varied radial force.
For example, if the outer anchoring elements 310a, 310c are each
coupled at one end to the central anchoring element 310b, they may
have a different diameter on each end. As the central anchoring
element 310b is stiffer, it may have a greater diameter than a less
stiff element. In general, there is no limit to the number of
anchoring elements that can be provided or to the particular
stiffness profile desired.
[0045] The securing force produced by the anchor can include a
radial component directed outward and pressing against the walls of
the surrounding lumen. The securing force can also include an axial
component provided by a barb. The magnitude of the securing force
preferably depends on the intended application being selected to
sufficiently secure the anchor without being excessive. Limiting
the maximum force is important as substantial forces acting against
the luminal walls are more apt to traumatize the surrounding
tissue.
[0046] In some embodiments, the radially-outward force of an anchor
is varied by varying the stiffness (or compliance) of the anchor
along its length. Such a feature provides for greater flexibility
in tailoring the anchor to its intended delivery location. For
example, the thickness of the anchor member can be varied to
control the desired stiffness, such that a portion of the anchor is
relatively stiff, whereas another portion of the anchor is
relatively soft. In this manner, the stiffer portion of the anchor
can be used to distend that portion of the bodily lumen within
which it is implanted. To reduce irritation, the stiffness is then
reduced towards the proximal and distal ends of the anchor to
reduce any trauma to the tissue of the bodily lumen. For example, a
side view of a flexible intraluminal anchor 400' is illustrated in
FIG. 5A. By using different anchoring elements 410a', 410b', 410c',
interconnected by joining members 420a', 420b' (generally 420') as
shown, the anchor 400' is allowed to flex and bend. The joining
members 420' are not necessary for embodiments in which the
elements 410 are each coupled to the same tube or sleeve. The
anchoring elements 410' are each formed from a respective
continuous wire fashioned into the oscillating, wave-shaped pattern
shown. Viewed along an axis (not shown), the anchor 400' would
appear as an open circle or hoop. Wave-shaped anchors and related
matters are described in U.S. application Ser. No. 10/858,852 filed
on Jun. 1, 2004 and claiming priority to U.S. Provisional
Application Nos. 60/528,084 filed on Dec. 9, 2003 and 60/544,527
filed on Dec. 13, 2004. The entire teachings of these applications
are incorporated herein by reference in their entirety.
[0047] In one embodiment, the central anchoring element 410b' is
formed from a relatively thick wire, such as a 0.023 inch diameter
Nitinol wire. The additional anchoring elements 410a', 410c' are
formed from a thinner wire, such as a 0.014 inch diameter Nitinol
wire. Using wires formed from the same material, the thicker wire
results in a greater stiffness than the thinner wire. Thus, the
central anchoring 410b 'element provides a greater radially-outward
force when compressed than either of the two surrounding anchoring
elements 410a', 410c'. The spring rate can also be varied by
altering the axial length of a wave-shaped anchoring element,
shorter elements being stiffer than longer ones. Also, the spring
rate can be varied by altering the number of oscillations for a
give anchoring element, elements with more oscillations being
stiffer.
[0048] The wires can be formed from any suitable material, such as
metals, metal alloys (e.g., stainless steel and Nitinol), and/or
synthetic materials (e.g., plastic). Preferably, the material is
bio-compatible, although it is possible to use non bio-compatible
material that is coated or encapsulated in a bio-compatible
material. Anchoring can be accomplished using an interference fit
between the intraluminal anchor and the inner walls of the lumen.
Alternatively or in addition, anchoring can be accomplished using
other means including sutures, staples, surgical adhesives and/or
barbs or hooks. In the exemplary embodiment, at least one external
barb 425' is be attached to the central anchoring element 410b'.
When implanted, the barb 425' is held in place within muscular
tissue by the stiffness and corresponding radially-outward force of
the 0.023 inch diameter wire. The central anchor element 410b
provides a substantial force to keep the barb 425' inserted into
the surrounding tissue. Without the first and third anchoring
elements 410a', 410c', the securing force provided by the middle
anchoring element 410b' could lead to tissue irritation or even
damage at the ends of the element 410b'.
[0049] The anchoring elements described above can be formed into
any number of different shapes. In some embodiments, each of the
anchoring elements is formed in a wave shape. Thus, a linear
element (i.e., a wire) is contoured into an oscillating manner
along a cylindrical surface at a distance (i.e., a radius) from a
central axis. Such a wire form can be shaped on a cylindrical
mandrel. The two ends of the wire are joined together (e.g.,
crimped, soldered, or chemically or thermally bonded) forming a
continuous structure. An anchoring element thus formed provides a
relatively small surface area in contact with the natural bodily
lumen, while allowing the anchor to provide a relatively large
diameter (e.g., 25 to 50 or more millimeters for gastrointestinal
applications). The oscillations result in relatively straight
segments 412a, 412b (generally 412) interconnected at nodes 414a,
414b (generally 414). When compressed in a radial direction, the
nodes 414 flex allowing the relatively straight segments 412 to
become more aligned with respect to each other. Thus, the diameter
of the anchor 400' can be reduced substantially to allow for its
insertion and/or removal through a relatively small diameter. For
example, in some intestinal applications, a 50-millimeter diameter
device is adapted to be inserted through a 12-millimeter diameter
catheter. When released, the anchor 400' expands with spring force
against the walls of the bodily lumen.
[0050] The anchoring elements 410a', 410b', 410c' may be separated
by respective distances s.sub.1, s.sub.2 as shown, or one or more
of the elements may be adjacent or even overlapping. An alternative
embodiment of a wave-shaped wire anchor 400'' is illustrated in
FIG. 5B. The anchoring 400'' also includes multiple anchoring
elements 410a'', 410b'', 410c'' that may or may not be
interconnected by joining members 420a'', 420b''. As shown, one or
more of the anchoring elements 410a'', 410b'', 410c'' can overlap
another anchor element to varying degrees. At least one advantage
of such an overlap is a reduction in the overall length of the
anchor 400''. Such an overlap can also be used to achieve a desired
force-versus-distance profile of the anchor 400'', leading to a
more gradual transition of the forces distributed along the
axis.
[0051] A side view of an alternative embodiment of an intraluminal
anchor 500 is illustrated in FIG. 6. The anchor 500 includes
multiple anchoring elements 510a, 510b, 510c, again shown as
wave-shaped elements for illustrative purposes, that are
interconnected to each other. The anchoring elements 510a, 510b,
510c can be interconnected by mechanical fasteners, chemical
adhesives, thermal bonding, welding, soldering, and/or weaving. The
interconnection may be fixed, or in the case of a weave, capable of
longitudinal compression.
[0052] As described above, the intraluminal anchor can be used to
anchor an elongated tube within a natural bodily lumen. An
exemplary device 600 including an intraluminal anchor, similar to
the one described above in reference to FIG. 5A, and coupled to the
proximal end of an elongated tube 615 is illustrated in FIG. 7. The
tube 615 may be rigid, semi-rigid or flexible. Gastrointestinal
sleeves and related matters are described in U.S. application Ser.
No. 10/339,786, filed Jan. 9, 2003, which claims the benefit of
U.S. Provisional Application No. 60/430,321, filed Dec. 2, 2002;
and U.S. application Ser. No. 10/726,011, filed on Dec. 2, 2003,
which claims the benefit of U.S. Provisional Application No.
60/512,145 filed Oct. 17, 2003. The entire teachings of all of
these applications are incorporated herein by reference.
[0053] The anchoring elements 610a, 610b, 610c (generally 610) can
be bonded to the tube (e.g., chemically bonded using an adhesive,
or thermally bonded). The anchoring elements 610 can also be
mechanically coupled to the elongated tube 615. For example, the
anchoring elements 610 can be coupled using a suture, a surgical
staple, and/or by threading the anchoring element itself through
perforations in the elongated tube.
[0054] In some embodiments, the anchoring elements 610 are
encapsulated within the elongated tube 615. For example, the
elongated tube 615 can be formed as a sleeve. A portion the sleeve
can then be used to encapsulate the anchoring elements by folding
one end of the sleeve back upon itself to cover both the interior
and exterior of the anchoring elements 610. The portions of the
elongated tube forming the overlapping portion 617 can then be
coupled together, thereby capturing the anchoring elements 610 and
securing them in place with respect to each other and with respect
to the elongated tube 615. For example, the overlapping portions of
the tube 617 can be bonded together (e.g., chemically bonded using
an adhesive, or thermally bonded). Alternatively or in addition,
the overlapping portions of the tube 617 can be mechanically
fastened together. For example, the overlapping portions of the
elongated tube 617 can be coupled together using sutures, staples,
clasps, or any other suitable mechanical fastener.
[0055] As shown, the anchor 600 can include barbs 620 that protrude
externally from the anchor 600 to penetrate the surrounding tissue.
For illustrative purposes, the device 600 as implanted within a
portion of an animal's intestine 630 illustrated in cross section.
Shown are the intestinal wall 630 including an inner mucosal layer
632 in communication with the anchor 600 and a surrounding layer of
muscular tissue 634. Preferably, the barbs 620 are adapted to
penetrate the mucosal layer 632 and into the muscular tissue 634 of
the intestine 630. In some embodiments, the barbs 620 actually
penetrate the outer walls of the intestine 630. Thus, the barbs 620
provide an axial securing force component, with the anchoring
element 610b providing a securing force adapted to maintain the
barbs into engagement with the muscular tissue 634.
[0056] To ensure that the barbs 620 remain secured to the muscular
tissue during implantation, the anchoring element to which the
barbs 620 are coupled should be relatively stiff. Thus, the
stiffness of the supporting anchoring element 610b maintains a
radial force ensuring that the barbs 620 are driven into the
tissue. In some embodiments, the stiffness is sufficient to force
the supporting anchoring element 610b through the mucosal layer
632, abutting it to the layer of muscular tissue 634.
[0057] In some applications, however, the stiffness of the
anchoring element 310b can lead to irritation and possibly damage
to the surrounding tissue. To reduce the possibility of such
irritation or damage, additional anchoring elements 610a, 610c are
provided on either side of the anchoring element 610b. Preferably,
the additional anchoring elements 610a, 610c are less stiff (i.e.,
softer) than the central anchoring element 610b. In this manner,
the transition between unanchored portions of the lumen and the
stiff anchoring element 610b is spread over a larger surface area
to achieve the desired anchoring force at the barbs 620 in a
gradual manner. Thus, the additional anchoring elements 610a, 610c
provide a strain relief on both sides of the stiff anchoring
element 610b to minimize trauma to the tissue, as shown in FIG.
1B.
[0058] An exemplary embodiment of an intraluminal anchor anchoring
an elongated flexible sleeve within the intestine of an animal is
illustrated in FIG. 8. A lower portion of the stomach 700 is shown
terminating in a pyloric sphincter 705. Distal to the sphincter 705
is the proximal duodenum 715, sometimes referred to as the duodenal
bulb. The device of FIG. 7 is implanted with the anchor being
situated distal to the pyloric sphincter 705, preferably within the
duodenal bulb 715. The sleeve 600 can extend through the duodenum
710 and into the jejunum 720.
[0059] As described above in reference to wire anchoring elements,
the radial force, or stiffness can be controlled by varying a
physical property of the anchoring element. This approach can also
be extended beyond wire examples. For example, the elongated
anchoring element can be formed from a tapered tube. To vary the
radial force, or stiffness, the tube can be shaped to vary its wall
thickness. The axial taper can be accomplished by injection
moulding to a desired shape and/or by removing material from a
solid elongated tube. The result in either case is an anchoring
element having differing thicknesses along its central axis. FIG.
9A illustrates a cross-sectional view of an exemplary tube 800
after having both ends tapered from a thicker middle section. Thus,
the thinner ends 810 are achieved by removing extra material 820.
For example, a stainless steel or alloy (e.g., Nitinol) tube 800
can be shaped by grinding it and/or turning it on a lathe to
selectably remove material along its length. As shown, the tube 800
can be tapered from a relatively thick portion along the tube
middle, to a relatively thin portion at the tube's ends (with this
approach, any conceivable profile is possible). The shaped tube
800, once tapered, can be further processed to form an expandable
anchor. For example, referring to FIG. 9B, apertures 920 can be cut
into the shaped tube 900 walls using a laser. The remaining
portions of the shaped tube 910, once cut, can form a continuous
structure such as the interconnected network of struts 910 shown,
or even a wave structure as described above. Again, the resulting
structure provides an interior lumen 915, while also being radially
compressible. A corresponding force-versus-distance profile for the
exemplary tube 900 is illustrated in FIG. 9C.
[0060] As will be appreciated by those of skill in the art, there
are many potential variations to these methods and articles. Those
variations are encompassed by this invention.
[0061] While this invention has been particularly shown and
described with references to preferred embodiments thereof, it will
be understood by those skilled in the art that various changes in
form and details may be made therein without departing from the
scope of the invention encompassed by the appended claims.
* * * * *