U.S. patent application number 16/943093 was filed with the patent office on 2021-06-24 for stents with improved fixation.
The applicant listed for this patent is BVW Holding AG. Invention is credited to Lukas Bluecher, Michael Milbocker, Roel Trip.
Application Number | 20210186720 16/943093 |
Document ID | / |
Family ID | 1000005434640 |
Filed Date | 2021-06-24 |
United States Patent
Application |
20210186720 |
Kind Code |
A1 |
Bluecher; Lukas ; et
al. |
June 24, 2021 |
STENTS WITH IMPROVED FIXATION
Abstract
The present disclosure provides stents, particularly
self-expanding stents, useful for the GI tract, and more
particularly, useful for treating esophageal strictures. The stents
provided herein include a medial region and proximal and distal
cuffs having external diameters greater than the medial region
diameter when the stent is in the deployed state. The medial region
comprises an open weave wire construction. An elastomeric coating
circumscribes the medial region, while the may be an extension of
the wire construction or separate elements. Preferably, the cuffs
have a textured surface for contact with the esophageal wall tissue
to resist stent migration. The elastomer coated medial region
provides a barrier to tissue ingrowth, and has an enhanced radial
restoring force to maintain an open passageway in a body lumen.
Optionally, the stent includes an exterior sheath with a surface
pattern, to which the stent couples. A low durometer sleeve,
between the stent and body lumen, axial positioning of the stent
relative to the body lumen. Consequently, precision in stent
placement is provided without tissue damage that could result if
positioning motion occurred between the surface texture and the
body lumen.
Inventors: |
Bluecher; Lukas; (Eurasberg,
DE) ; Milbocker; Michael; (Holliston, MA) ;
Trip; Roel; (Atlanta, GA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
BVW Holding AG |
Cham |
|
CH |
|
|
Family ID: |
1000005434640 |
Appl. No.: |
16/943093 |
Filed: |
July 30, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15859440 |
Dec 30, 2017 |
10758380 |
|
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16943093 |
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62441087 |
Dec 30, 2016 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61F 2/90 20130101; A61F
2002/044 20130101; A61F 2250/0056 20130101; A61F 2250/0048
20130101; A61F 2002/075 20130101; A61F 2250/0039 20130101; A61F
2002/045 20130101; A61F 2002/072 20130101; A61F 2/88 20130101; A61F
2250/0051 20130101; A61F 2/07 20130101; A61F 2230/0065 20130101;
A61F 2250/0067 20130101; A61F 2250/0003 20130101; A61F 2250/0025
20130101; A61F 2250/0026 20130101; A61F 2210/0004 20130101 |
International
Class: |
A61F 2/88 20060101
A61F002/88; A61F 2/07 20060101 A61F002/07; A61F 2/90 20060101
A61F002/90 |
Claims
1. A device for fixation in a body lumen, comprising: a tubular
stent of open weave construction having a stent body having an
axial length, the stent body comprising first and second ends and a
medial region, the stent having a predetermined normal
configuration and being radially compressible to a reduced-radius
configuration; and a continuous elastomeric film disposed axially
along the stent, the continuous film circumscribing the stent over
substantially the entirety of the axial length to define a barrier
region of the stent to substantially prevent growth of tissue
through the stent along the barrier region; and wherein a portion
of the barrier region of the stent comprises a surface texture for
contact with the body lumen to provide a fixation region of the
stent for positively fixing the stent within the body lumen at the
treatment site, by radial expansion of the stent into a surface
engagement with a tissue wall segment defining the body lumen, and
wherein the surface texture contains at least one class of
hydrophobic regions on at least one spatial interaction dimension,
and at least one class of hydrophilic regions on one or more other
spatial interaction dimensions, wherein the ratio of any two
spatial dimensions is greater than 2.
2. The device of claim 1 wherein: the stent is flexible, thereby
assuming the reduced-radius configuration in response to the
application of an external force, and tending to assume the normal
configuration in the absence of the external force.
3. The device of claim 2 wherein the elastomeric film reinforces
the stent along the barrier region.
4. The device of claim 3 wherein the film comprises silicone.
5. The device of claim 3, wherein the fixation region of the stent
exerts a lower restoring force in its return toward the normal
configuration, relative to a non-textured region of the stent, upon
removal of an external force.
6. The device of claim 5, wherein the fixation region comprises an
inflatable annulus at each end of the stent.
7. The device of claim 5, wherein the fixation region comprises
elastic polymeric torus at each end of the stent.
8. The device of claim 7 wherein the polymeric torus comprises a
dry hydrogel.
9. The device of claim 1, wherein the surface texture is disposed
on a proximal cuff and a distal cuff.
10. The device of claim 9 wherein the surface texture is provided
in a segmented pattern on the proximal and distal cuffs.
11. The device of claim 1, wherein the barrier region has a
diameter less than the diameter of the fixation region when the
stent is in the deployed configuration.
12. The device of claim 1, wherein the elastomeric film reinforces
the stent along the barrier region.
13. The device of claim 1, further comprising a removable and a low
durometer delivery sleeve disposed on an outer surface of the
stent, the sleeve following the outer surface, wherein the sleeve
separates the body lumen from the fixation surface of the stent to
allow positioning of the stent within the body lumen without
engaging the fixation surface with the body lumen.
14. A device for fixation in a body lumen, comprising: a flexible
tubular stent having a predetermined normal configuration and being
radially compressible to a reduced radius configuration in response
to an external compression force; the stent radially expanding to
the normal configuration in the absence of the external compression
force, thereby fixing the stent within the body lumen; and an
elastically deformable reinforcement sleeve integral with the
stent, disposed axially along the stent and substantially
surrounding the stent to provide a reinforced region of the stent,
said reinforced region requiring at least one minute to return to
the normal configuration after removal of the external force;
wherein a portion of the stent is substantially free from the
reinforcement sleeve and comprise a surface texture, the surface
texture providing a fixation region of the stent, wherein the
fixation region radially expands with less restoring force than the
reinforced region upon removal of said external force; wherein the
fixation region comprises a surface texture comprising at least one
class of hydrophobic regions on at least one spatial interaction
dimension, and at least one class of hydrophilic regions on one or
more other spatial interaction dimensions, wherein the ratio of any
two spatial dimensions is greater than 2.
15. The device of claim 14, wherein: the elastic deformable
reinforcement sleeve comprises a polymeric film.
16. The device of claim 15, wherein the polymeric film is a
silicone film.
17. The device of claim 14, wherein, the fixation region is
disposed on proximal and distal cuffs, and the reinforced region
comprises a medial region of the stent between the proximal and
distal cuffs.
18. The device of claim 17, wherein the proximal and distal cuffs
have diameters larger than the diameter of the medial region when
the stent is in the normal configuration.
19. A device for fixation in a body lumen, comprising: a tubular
elastic stent of open weave construction having a predetermined
deployed configuration and being radially compressible to a reduced
radius configuration in response to the application of an external
force, the stent expanding to the deployed configuration in the
absence of the external force; and wherein a portion of the barrier
region of the stent is of greater radius than other portions; and
wherein a separable and a low durometer, fixation sleeve is placed
on the exterior surface of the stent, the sheath follows the outer
surface of the stent when the stent is placed under compression,
and follows the outer surface of the stent when it is deployed
within a body lumen, and wherein the fixation sleeve comprises an
external surface having a surface texture disposed thereon, the
surface texture comprising at least one class of hydrophobic
regions on at least one spatial interaction dimension, and at least
one class of hydrophilic regions on one or more other spatial
interaction dimensions, wherein the ratio of any two spatial
dimensions is greater than 2, and wherein the fixation sleeve
comprises an internal surface in contact with the stent.
20. The device of claim 19, wherein the fixation sleeve and the
stent are attached by at least one of a suture, a staple, or an
adhesive.
21.-32. (canceled)
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. application Ser.
No. 15/859,440 filed on Dec. 30, 2017, and claims benefit of U.S.
Provisional Application No. 62/441,087 filed on Dec. 30, 2016,
which are hereby incorporated by reference in its entirety.
TECHNICAL FIELD
[0002] The present disclosure provides stents, particularly
esophageal stents, comprising a micro-textured surface, and a
method of manufacturing thereof. The micro-textured surface
advantageously contacts esophageal surfaces and reduces or prevents
stent migration.
BACKGROUND OF THE INVENTION
[0003] The present disclosure relates to implantable treatment
devices, and more particularly to stents and other prostheses
intended for fixation in body lumens especially including the
esophagus
[0004] Stents are generally employed to open or keep open a body
lumen. For example, carcinomas in the esophagus lead to progressive
dysphagia, i.e. difficulty in swallowing, and the inability to
swallow liquids in the most severe cases. While surgical removal is
sometimes effective, the majority of patients have tumors that
cannot be surgically removed. Repeated dilations of the body lumen
of the esophagus provide only temporary relief.
[0005] Difficult or refractory cases often are treated by
intubation using open wire weave prostheses or stents. An example
of an open wire weave stent is provided in U.S. Pat. No. 4,800,882
(Gianturco), wherein is described such a device employed as an
endovascular stent. These prostheses are frequently subject to
migration. Self-expanding mesh stents also have been considered for
use as esophageal prostheses. U.S. Pat. No. 4,655,771 (Wallsten)
discloses a mesh stent as a flexible tubular braided structure
formed of helically wound thread elements. Mesh stents appear
unlikely to lead to pressure necrosis of the esophageal wall. The
inherent scalability of mesh stents, as compared to a rigid plastic
stents, makes them more easily inserted and the subsequent
implantation causes much less trauma to the patient.
[0006] A difficulty with self-expanding stents concerns their
accurate placement and deployment. Typically a tube surrounds the
self-expanding stent and radially compresses the stent into a
reduced-radius delivery configuration. With the stent positioned at
a treatment site, the outer tube is axially withdrawn, permitting
the stent to radially self-expand. However, the larger size of an
esophageal stent (as compared to biliary and vascular applications,
for example) gives rise to substantial friction at the stent/outer
tubing interface. As a result, it is difficult to precisely
maintain the position of the stent during deployment, and
practically impossible to retract the stent after partial
deployment.
[0007] Migration resistant stent designs include the addition of a
mechanically lumen-bonding surface to the outer surface of a stent.
U.S. Pat. No. 8,435,283 (Jordan et al) describes the addition of a
cross hatch pattern of pyramids to the outer surface of a stent.
The texture is intended to mechanically grasp tissue, and thereby
anchor the stent. Such stents suffer from the disadvantage that
dislocation by peristaltic motion causes inflammation of the inner
lining of the body lumen, leading to infection, necrosis and
possibly perforation.
[0008] Stenting of the esophagus has proven to be a particularly
challenging stent application. The esophagus is a muscular lumen
that is about ten inches long and extends from the hypopharynx to
the stomach. The esophageal lumen is subject to wavelike
contractions known as peristalsis, which pushes food down through
the esophagus to the stomach.
[0009] Conventional stents utilized for the esophagus have
significant drawbacks. Because the esophagus is very soft and
flexible compared to other lumina, preventing migration of the
stent is problematic. In particular, the esophagus frequently
changes size and position, which causes complications for typical
stents. For instance, a stent having a constant diameter along its
entire axial length will have a tendency to migrate as the
esophagus expands. The stricture is narrower than the lumen located
proximally and distally of the stricture, and the stent is longer
than the length of the stricture such that the portions of the
stent proximately and distally of the stricture do not help prevent
the stent from migrating. Therefore, there is an increased
possibility that the stent will migrate within the lumen.
[0010] Moreover, the esophageal lumen is muscular and its wavelike
contractions generally travel from its proximal end to its distal
end resulting from an impulse applied at one side of the lumen
wall. Due to the actions of the lumen, flexible stents have been
designed to mimic the movement of the lumen. However, flexible
stents may be prone to infolding or kinking, effectively occluding
one or both of the openings of the stent. Furthermore, providing
more rigid stents increases the risk of damage to the lumen of the
esophagus, such as by damaging the blood vessels lining the lumen.
Rigid stents are also typically more prone to migration.
[0011] A further difficulty with self-expanding esophageal stents
is that they can cause gastrointestinal reflux. To place the
self-expandable esophageal stent at a lesioned part of the stenosed
gullet, an operator primarily shrinks the stent so as to reduce the
cross section of the stent, installs the shrunken stent in a stent
insertion device, and inserts the stent into the stenosed part of
the gullet using the insertion device. After the stent reaches the
stenosed part of the gullet, the stent is pushed so that the stent,
usually fabricated from shape-memory alloy wires, is separated from
the insertion device and elastically expands and restores its
original shape, thus pushing the wall of the stenosed part outwards
in radial directions and thereby enlarging the size of the passage
of the stenosed part, making swallowing easier.
[0012] However, when the esophagus is stenosed near the stomach,
where the esophageal sphincter is located, the esophageal stent
must be placed in the lower end of the esophagus. Low end
esophageal placement can open the esophageal sphincter causing
gastrointestinal reflux. The presence of stomach acid in the
esophagus can significantly complicate an already pathologic
condition.
[0013] Accordingly, there is a need in the industry for a stent
that is capable of conforming to a lumen and maintaining the
opening through a stricture. In addition, there is a need for a
stent that reduces migration and the possibility of obstruction of
the stent openings.
BRIEF SUMMARY OF THE INVENTION
[0014] With these considerations in mind, the present disclosure
provides a stent device possessing an exterior (body lumen
contacting) textured surface to prevent stent migration. A further
object of the disclosure is to provide a radially self-expanding
stent including a freely radially self-expanding fixation region in
combination with a barrier region to inhibit tumor ingrowth.
[0015] Yet another object of the disclosure is to provide a stent
that is in a reduced cross section state prior to implantation, and
expands in the body to achieve a therapeutic state possessing
larger cross section.
[0016] Yet another object is to provide an esophageal prosthesis
deployable with reduced trauma to the patient, having more
resistance to migration, and providing a barrier to tumor
ingrowth.
[0017] Yet another object is to provide an esophageal prosthesis
with controllable expansion regarding both rate and final cross
section.
[0018] Yet another object is to provide an esophageal prosthesis
with the proximal end of minimal diameter, and not engaged in
preventing stent migration, so as not to affect the esophageal
sphincter.
[0019] Yet another object is to provide an esophageal stent wherein
the fixation region is detachable from the stent.
[0020] Yet another object is to provide a stent fixation region
that does not rely on mechanical bonding to the inner lumen
wall.
[0021] In particular, it is an object of the present application to
provide a luminal stent that is resistant to migration, minimally
damaging to the lumen lining, the contact with the lumen lining is
adjustable, and the contact with the lumen lining follows any
variations in the geometry or kinetics of the lumen lining.
[0022] The present invention is specifically directed to fixing or
preventing the migration of a stent once it has been placed in a
body lumen. And more specifically, to fixing region that employ a
Wenzel-Cassie effect to provide a shear force in opposition to
axial displacement of a stent.
[0023] The present disclosure the above needs and achieves other
advantages which can be understood by the example of providing a
stent for a lumen of the esophagus. The stent includes a tubular
member and fixation regions located on or in contact with the
tubular member. The fixation regions are configured to reduce
migration and infolding of the stent during changes in geometry of
the body lumen; for example, peristalsis.
[0024] Accordingly, the stent is capable of not only maintaining or
even expanding a target area within a lumen but also mimicking the
size and movement of the lumen. The present invention in some
embodiments utilizes a modification of the stent's outer surface
with microtextured features such as sinusoids, cylinders, ridges
and other surfaces geometries to provide a non-mechanical bonding
surface.
[0025] One embodiment of the present invention therefore relates to
a radially-expandable implant for implantation in a bodily
passageway, being at least partially expandable from an initial
unexpanded state to an expanded state, having an outer surface with
a geometric pattern covering said outer surface to minimize
migration after implantation. It should be appreciated this pattern
is extremely small in size, and in most cases undetectable by
touch. However, the pattern presents a surface of microscopically
and hierarchically arranged regions of varying hydrophilicity which
has the unexpected effect of fixing a prosthetic within the aqueous
and lubricious environment characteristic of most body lumens.
[0026] The stent is useable in various bodily passageways for
implanting a stent, including the gastrointestinal tract (e.g.,
bile ducts, colon, duodenum), esophagus, trachea, urinary tract
(e.g., urethra, prostate) and vasculature (e.g., aorta, coronary
blood vessels, peripheral blood vessels, intracranial blood
vessels).
[0027] According to one aspect of the present invention, the
expandable cylindrical body of the stent may comprise more than one
distal cuff in order to address the occurrence of a branch in the
body vessel. The expandable cylindrical body being either modular
or unibody in nature.
[0028] These and other features will be better understood through a
study of the following detailed description and accompanying
drawings.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0029] FIG. 1A-ID is a schematic diagram of an exemplary textured
surface useful in the stents of the present disclosure.
[0030] FIG. 2A depicts an exemplary stent having a microtextured
surface region, and FIG. 2B depicts the stent of FIG. 2A further
comprising a delivery sleeve.
[0031] FIG. 3 is alternative embodiment of a stent having a
microtextured surface region.
[0032] FIG. 4 is a schematic of an embodiment where the textured
regions are provided as bands.
[0033] FIG. 5 depicts a stent having a hydrogel coating disposed on
a cuffed or flared end of the stent.
[0034] FIG. 6 depicts a two-part stent comprising a stent and a
fixation sleeve.
[0035] FIG. 7 depicts a stent having a fixation region woven into
the stent.
[0036] FIG. 8 depicts a stent having a fixation region disposed on
flared regions, and further having a lubricious region on the stent
body. In this embodiment, the spring constant of the stent body may
be selected to match the spring constant of the esophagus in which
it is inserted.
[0037] FIG. 9 depicts a stent having a plurality of surface
textures regions disposed annularly about the stent body with a
selected spatial periodicity alternating with slip regions.
[0038] FIG. 10 depicts an embodiment of a stent wherein a first end
comprises a cuffed or flared region comprising a surface texture
and second end that is free floating within a body lumen. The free
end may comprises lubricious ribs axially oriented.
[0039] FIG. 11 depicts an esophageal stent comprising a surface
textured region. The stent body advantageously dilates in response
to a peristaltic wave from a body lumen.
[0040] FIG. 12 depicts a stent comprising dilated or flared regions
that are displaced with respect to the stent body centerline.
[0041] FIG. 13 depicts a stent comprising slip ribs and a surface
texture region. The surface texture region in this embodiment is
capable of engaging with an esophageal growth in the esophagus.
DETAILED DESCRIPTION OF THE INVENTION
[0042] The following description is an exemplification of the
principles of the present disclosure and is not intended to limit
the disclosure to the particular embodiments illustrated
herein.
[0043] Stents perform three functions: 1) stent or hold open a body
lumen, 2) prevent ingrowth into a body lumen, and 3) anchor or fix
functions 1 and 2 at a specific site within the body lumen.
[0044] Generally, there is no clinical requirement that the stent
part responsible for the anti-migration or fixation feature should
be fixed permanently to the stent part responsible for the radial
force component. In other words, the anti-migration function and
the stent function can be completely decoupled structurally. In
this disclosure, the stent is considered to be all components of a
lumen opening device implanted in a body.
[0045] Accordingly, the embodiments can be divided into three
categories: 1) fixation regions integral to the stent, 2) fixation
regions separable from the stent, and 3) fixation regions that are
both separable and integral to the stent. In the third category,
the fixation region provides the dual role of providing fixation
and blocking ingrowth.
Textured Surface Fixation
[0046] The textured surfaces responsible for the fixation or
gripping features of the stents of the present invention comprise
textures that initially create Cassie and Wenzel states when
exposed to a liquid environment in a mammalian body. These states
evolve in situ, and their evolution analogues differ from typical
Wenzel and Cassie states in that they involve a solid hydrophilic
phase, a liquid hydrophobic phase, and a liquid hydrophilic phase
or a solid hydrophobic phase, a liquid hydrophilic phase, and a
liquid hydrophobic phase. In these modified Wenzel and Cassie
states, the trapped phase analogous to the classical gaseous phase
is the liquid hydrophobic phase. Alternatively, a trapped gaseous
phase is preferentially replaced by a liquid hydrophobic phase.
[0047] The Cassie and Wenzel phenomena, occur when three phases are
in contact with one another. In the body, the respective states
lead to the formation and retention of an implant of a liquid
hydrophobic film in the Cassie state and retention of tissue
(containing lipids) in the Wenzel state. In a hybrid Cassie-Wenzel
state, where one texture scale is Wenzel and the other is Cassie,
the implant can be localizing to a tissue surface.
[0048] A scale of interaction is defined by the surface texture of
the present stent surfaces, and is typically hierarchical, and
characterized by at least two spatial scales, one on the order of
micrometers (microns) and another on the order of 10 to 100
microns. The surface texture may induce one state with a large
difference between preceding and receding contact angles (contact
angle hysteresis), or alternatively another state with a small
contact angle hysteresis. States of interest are known respectively
as Wenzel and Cassie states. Each of the hierarchical spatial
scales may induce separately a Wenzel or Cassie state, such that
combinations are possible on a multiplicity of spatial scales. It
is this combination of states that results in the surprising
non-traumatic gripping feature of the present stents.
[0049] Examples of geometrical structures having scales of
interaction include pillars, cubes, pyramids, or any feature with a
typical overall size. For example, in the case of a cube, the scale
of interaction would be the length of the cube. These surface
structures, characterized by a scale of interaction are typically
spaced apart, distance center to center, by a spatial frequency
known as pitch. For example 4 micron squares with pitch 8 microns
would mean the squares are separated on their surfaces by 4
microns. Typically the pitch is 1 to 10 times the scale of
interaction. Also typically regarding hierarchical arrangement of
different scales of interaction, the different scales of
interaction and the pitch are 1 to 10 times smaller than the next
hierarchical level. In many cases, one size of interaction is
located on a large size of interaction. For example 1 micron
pillars placed on the top surface of 10 micron pillars, with pitch
1 and 10 microns respectively.
[0050] These textures develop phenomena between hydrophobic and
hydrophilic components of a mixture disposed on a surface
interface. For example, the smaller interaction scales are
hydrophobic and the larger interaction scales are hydrophilic. A
hydrophobic surface attracts hydrophobic components in a
interfacial mixture, and repels hydrophilic components, and
conversely for hydrophilic surfaces.
[0051] The interaction of a solid textured surface with water in a
gaseous environment is described by the Cassie-Baxter model. In
this model, air is trapped in the microgrooves of a textured
surface and water droplets rest on a compound surface comprising
air and the tops of micro-protrusions. The importance of a fractal
dimension between multiple scales of texture is well recognized and
many approaches have been based on the fractal contribution, i.e.,
the dimensional relationship between different scales of texture.
However, regardless of the material (organic or inorganic) used and
geometric structure of the surface texture (particles, rod arrays,
or pores), multiple scales of texture in combination with low
surface energy has been required to obtain the so called
superhydrophobic surfaces.
[0052] Superhydrophobicity is variously reported as a material
exhibiting a contact angle with water that is greater than contact
angles achievable with smooth but strongly hydrophobic materials.
The consensus for the minimum contact angle for a superhydrophobic
substance is 150 degrees, so in this context most of the
embodiments of the present invention are not strictly
superhydrophobic, although this option is not excluded. The reason
for this is that a Wenzel-Cassie state lies in its hydrophobicity
between non-textured surfaces and surface that generate a
Cassie-Baxter interface. In optimizing the fixation of the stents
of the present invention superhydrophobicity is just one aspect of
a number of interesting texture controlled mechanisms, and in this
context the contact angle is less important than the contact angle
hysteresis.
[0053] A hydrophobic surface repels water. The hydrophobicity of a
surface can be measured, for example, by determining the contact
angle of a drop of water on a surface. The contact angle can be
measured in a static state or in a dynamic state. A dynamic contact
angle measurement can include determining an advancing contact
angle or a receding contact angle with respect to an adherent
species such as a water drop. A hydrophobic surface having a small
difference between advancing and receding contact angles (i.e., low
contact angle hysteresis) results in surfaces with low resistance
to in plane translation (low adherence). Water can travel across a
surface having low contact angle hysteresis more readily than
across a surface having a high contact angle hysteresis, thus the
magnitude of the contact angle hysteresis can be equated with the
amount of energy needed to move a substance.
[0054] A high surface area is achieved by superimposing multiple
structures one on top of the other in superposition. When these
multiple structures are sufficiently different in dimension then
the superposition of these structures is referred to as a
hierarchical structure or pattern. A subset of surfaces useful in
the present invention are characterized as superhydrophobic.
[0055] Surface textures useful in the stents disclosed herein
provide a gripping or fixation region when in contact with a body
lumen, such as a lumen of an esophagus. The surface texture can
comprise at least one class of hydrophobic regions on at least one
spatial interaction dimension, and at least one class of
hydrophilic regions on one or more other spatial interaction
dimensions, wherein the ratio of any two spatial dimensions is
greater than 2.
[0056] One embodiment of a surface texture useful in the present
stents is a biomimetic of the natural rose pattern. Referring to
FIG. 1, the pattern 100 comprises three structures: 1) a
two-dimensional sinusoidal pattern 102, 2) a first column pattern
104, and 3) a second column pattern 106 combined with a flute
pattern 108 disposed on second column 106. These structures have
characteristic dimensions. For example the amplitude 110 and pitch
112 of the sinusoidal pattern 102 is in the range of 50 to 500
microns or larger. The height 114, diameter 116 and pitch 118 of
the first column pattern is in the range 20-50 microns. The height
120, diameter 122 and pitch 124 of the second column pattern as
well as the height 126 and pitch 128 of the flutes are in the range
of 5-20 microns.
Fixation Integral to the Stent
[0057] In accordance with one embodiment of the present invention,
the stent can be manufactured by utilizing an injection molding
process. By utilizing this process, a particular surface texture of
the stent can be controlled by cutting the inverse surface texture
pattern into the inner diameter of the mold. The inner surface of
the mold can contain any of various geometrical patterns arranged
hierarchically and possessing different spatial dimensions such as
sinusoids, columns, pyramids or flutes, as shown in FIG. 1.
[0058] In some embodiments, low profile geometries on the exterior
wall of the stent will minimize migration while preventing tissue
damage in situ or upon removal. Additionally, these structures,
since they are arranged hierarchically allow fluids to flow between
the stent and body lumen. For example, fluids from either the
pancreatic duct or cystic duct can pass between the wall of the
bile duct and the outer surface of the stent, should the stent pass
over these ducts.
[0059] In one embodiment, the invention comprises a stent and, more
preferably, a stent suited for placement within the
gastrointestinal (GI) tract of an animal or a human. In a further
embodiment, the GI tract comprises the esophagus, the pancreatic
duct, cystic duct or common bile duct. In yet a further embodiment,
the outer surface of the implant comprises at least one surface
texture that provides a fixation region to assist in limiting the
potential migration of the implant within the body lumen. In
addition to its use as an esophageal prosthetic, the present
invention may be used in any bodily vessel, such as in the coronary
or peripheral vasculature, esophagus, trachea, bronchi, colon,
biliary tract, urinary tract, prostate, brain, as well as in a
variety of other applications in the body.
[0060] FIG. 2A depicts stent 200 of the present invention. In one
embodiment, stent 200 includes a stent body 202 having an axial
length 224. The stent 200 assumes the normal or relaxed
configuration, as depicted in FIG. 2, when it is not subject to any
external load or stress. The stent body 200 may be partly or fully
covered with an elastomeric membrane or film 204. The elastomeric
film 204 is defined by an exterior surface 206 and an inner surface
208. The film may be disposed axially along the stent to cover
substantially the entirety of the axial length of the stent. Stent
200 comprises an open weave construction of mesh segments 210. Mesh
segments 210 may be metal wire or a polymeric mesh, and provide a
flexible stent structure in some embodiments. Wires or segments 210
may be paired and helically wound.
[0061] Stent 200 includes several regions, including an
intermediate region 212, a distal end cuff region 214 and a
proximal end cuff region 216. The distal end cuff region 214 and
the proximal end cuff region 216 may be shaped so as to have a
wider cross-section than intermediate region 212, for example,
which may be useful as an esophageal prosthetic device. Distal end
cuff region 214 and proximal end cuff region 216 may include flares
or dilated regions having cross sections 218 and 220. The cuff
region and/or the flares have a diameter that is larger than the
diameter of the intermediate region and aid in fixation of the
stent when inserted in a body lumen.
[0062] The stent 200 further includes a surface texture disposed on
a portion thereof, the surface texture providing a fixation region
of the stent. As depicted in FIG. 2A, the surface texture 222 may
be disposed on the flare regions 218 and 220 in some embodiments.
The surface texture 222 can be a three dimensional geometric
structure depicted in FIG. 1, and may be integrally formed with the
elastomeric film 204. The surface texture 222 provides an
anti-migration effect to the prosthesis 200.
[0063] This embodiment provides improved stent fixation and is
particularly effective in resisting either proximal or distal
migration of the stent 200 upon insertion into a body lumen. Flared
cuffs 218, 220 may be designed with flexibility to readily conform
to changes in the body lumen wall during the transmittal of bodily
fluid or food. Alternatively, the present invention also envisions
a stent body having no flared end, or including one flared end.
[0064] In some embodiments, each end of the stent comprises a
fixation region. In some embodiments, the fixation region comprises
an inflatable annulus. In other embodiments, the textured region
comprises an elastic polymeric torus.
[0065] FIG. 2B depicts an embodiment of stent 200 having a delivery
sleeve 223 disposed around the exterior of stent body 200. The
delivery sleeve may be disposed around any area of the stent 200,
including at least one of the intermediate region 212, distal end
cuff region 214 and proximal end cuff region 216. The delivery
sleeve advantageously aids in the positioning and deployment of the
stent within the body lumen.
[0066] Generally, the exterior surface 206 of the stent 200 may be
designed to be fairly smooth. A surface texture 222, such as a
three dimensional geometric structure depicted in FIG. 1 may be
integrally formed with the elastomeric film 204. The surface
texture 222 provides an anti-migration effect to the prosthesis
200.
[0067] As depicted in FIG. 1, surface texture 222 may be a
three-dimensional geometric structure containing a relief feature
such as columns, sinusoids, or flutes. However, the surface texture
222 may encompass any projection or indents of shapes or other
complex geometries which comprise hierarchical and alternating
regions of differing hydrophilicity over the exterior surface 206.
When formed with the surface texture 222 disposed over the exterior
surface 206, the stent body 200 is given a wet surface gripping
functionality over all or a portion of the surface 206, which act
as fixation regions between the stent body 200 and the body lumen
into which the stent body 200 is disposed.
[0068] The surface texture 222 may be configured to accommodate
various tolerances in delivery systems which in some embodiments
are to be used with the stent body 200. For instance, a stent body
200 is depicted in its relaxed or normal configuration in FIG. 2.
As depicted, the intermediate region 212 may have a diameter of
about 15-20 mm, and the cuff of the proximal region 214 and/or the
cuff of the distal end region 216 may have a diameter of about
25-28 mm. In this particular embodiment, the wires 210 may have a
diameter of about 0.22 mm or less. The three-dimensional structure
222 may preferably have a cross section of less than approximately
1 mm. This tolerance ensures that the overall diameter increase of
the delivery device is kept, for instance, less than 2 mm (assuming
one three-dimensional structure 222 wraps around the stent).
However, the present invention is not limited by the exemplary
dimension tolerance. The total diameter may vary according to usage
of the particular delivery device in a particular vessel. For
instance, the dimensional tolerance for esophageal stent may be
different from a coronary stent.
[0069] FIG. 3 depicts yet another embodiment of the present
invention in which the surface texture layer 322 is not integrally
formed with the elastomeric membrane 304. As depicted in FIG. 3, a
thin discrete layer may be disposed on the exterior surface 306. In
one particular embodiment, the anti-migration structure layer 322
forms a pattern helically expanded about the exterior surface 304
of the intraluminal prosthesis 300. According to one embodiment of
the invention, the surface texture 322 may be formed from the same
material from the elastomeric membrane 304 is formed. In some
embodiments, the surface texture 322 may be in the form of bands
that span across a common longitudinal axis of the stent body
300.
[0070] In another embodiment, the stent body 300 may be provided
with the first set of anti-migration bands comprising surface
texture 322 having a common direction of winding but
circumferentially displaced relative to each other. In this
embodiment, the first set of anti-migration bands comprising
surface texture 322 may be configured to cross a second set of
anti-migration bands also circumferentially displaced relative to
each other but winding in substantially opposite direction. In this
embodiment, the stent body 300 is sufficiently configured to have
anti-migration properties, as provided by the anti-migration bands.
The directions of the bands for the present invention are not
limited by the above examples, and also may extend lengthwise or
perpendicular to the longitudinal axis. Further, the bands may
change direction at random locations, for example, they may be
curved or wavy at random locations along stent 300.
[0071] The device 300 of the present invention may include surface
textures 322 provided as bands configured to flex along certain
selective dimensions. For instance, the surface texture band 322
may include an anti-migration structure that is flexible in a
radially outward direction of the stent body 300. In addition, the
surface texture 322 may be rigid in the longitudinal direction at
certain locations.
[0072] Various methods of forming the stents are provided herein.
In one embodiment, during the fabrication process of the stent body
200, surface texture 222 may be added to the wires 210 after the
outer surface 206 is disposed on the wires 210. In an alternate
embodiment, the surface texture 222 may be provided as a layer
formed integrally with the wires 210. Instead of the layer
completely wrapping over exterior surface 206, bands of the surface
texture 222 may be interwoven with the wires 210. In this
embodiment, the surface texture 222 may partially or wholly
substitute the elastic membrane 204.
[0073] FIG. 4 depicts a portion of a stent body 200. The surface
texture 422 may be provided as anti migration bands 430 having
smaller width 432 than the distance 434 between wires 410. In an
alternate embodiment, the bands 436 may along exposed portions 438
have a width 440 larger than the distance 434 between wires 410.
Further, the stent 400 may be configured with a variety of bands
422 of different widths.
[0074] Yet another advantage of the surface texture being provided
as anti-migration bands 430 disposed on the elastomeric membrane is
that it may provide structural reinforcement along the stent body.
This reinforcement may enable the wires 410 to be constructed with
a reduced angle. As used herein, the angles between the wires 410
is measured based on their incline deviation from the axis 440 of
the stent.
[0075] In prior stents, an angle 436 of 45 degrees from the axis
440 may have been considered a lower practical limit for the angle
of a mesh or open weave wire stent 200. Employing the present
invention, however, may enable a reduction of the braid angle to as
low as 20 degrees from the axis 440. The advantage of a lower angle
for the wires 410 follows from the fact that the angle may
contribute to the ratio of stent axial shortening to its radial
increase structure. As the stent expands, either through use of
self-expanding materials or through the assistance of a balloon, a
lower angle facilitates greater radial expansion of the stent body
200. With a reduced braid angle, upon expansion, there may be less
axial shortening for a given radial expansion. Due to the reduced
axial shortening, the stent body 200 may be more accurately
positioned within the body lumens during its deployment. Thus, the
profile of a surface texture 422, in combination with the stent
200, may resist the extraneous stretching and assist in the precise
positioning of the stent inside a body lumen.
[0076] There are a multiplicity of arrangements of the
anti-migration layer that are clinically preferred, depending upon
the application. The possibilities are: full coverage of the stent,
spiral patterns formed using strips, checkerboard pattern of
squares or circles located on the crossing points of the wires, and
mainly on the end regions (flared) and in segments or a continuous
band.
[0077] In general, coating of the device with an elastomeric
membrane is designed to enhance lumen patency. In addition, the
tubular coating may resist tumor ingrowth. The thickness of the
elastomeric membrane may be in the range of 0.075-0.25 mm. However,
such elastomeric membrane may also be up to a range of 0.75-1.00
mm. In some embodiments, the elastomeric membrane may include a
silicone film layer. The elastomeric membrane 204 may be disposed
onto the outer surface of the stent body 200 by any desired means,
including by placing the elastomeric membrane onto the surface, by
extruding the elastomeric membrane onto the outer surface, or by
dipping or spraying the elastomeric membrane onto the outer
surface.
[0078] The elastomeric membrane of the prosthesis may also be
formed of polytetrafluoroethylene (PTFE/ePTFE). Considered alone,
the coating should provide an effective barrier to tissue ingrowth.
In addition, the elastomeric membrane may be elastic, and thus may
radially expand like the remainder of stent body. Thus, silicone
construction, in general, may be engineered to exert constant,
gentle pressure to help adapt to normal luminal patency, for
instance of esophageal peristalsis as its smooth inner surface
helps facilitate passage of fluid. Optionally, the ends of the
prosthesis may also be reinforced by continuous polymeric film to
help resist hyperplasia.
[0079] All of the components of the intraluminal device should be
made of biocompatible materials, including metals or polymeric
materials. Any materials may be used in the forming of these
elements. In one embodiment, the elastomeric membrane preferably
includes silicone, but other materials having elastomeric and
biocompatible characteristics are also envisioned by the present
invention. By way of example and not limiting the invention in any
manner, other materials for any or all of the components of the
device may include polyurethane, polyethylene,
polytetrafluoroethylene, or expanded polytetrafluoroethylene,
polyolefins such as high density polyethylene and polypropylene,
polyolefin copolymers and terpolymers, polyethylene terephthalate,
polyesters, polyamides, polyurethaneureas and polycarbonates,
polyvinyl acetate, thermoplastic elastomers including
polyether-polyester block copolymers, polyvinyl chloride,
polystyrene, polyacrylate, polymethacrylate, polyacrylonitrile,
polyacrylamide, silicone resins, combinations and copolymers
thereof, and the like.
[0080] Other useful coating materials include any suitable
biocompatible coating. Non-limiting examples of suitable coatings
include hydrophilic materials, hydrogels, and the like. Useful
hydrophilic coating materials include, but are not limited to,
alkylene glycols, alkoxy polyalkylene glycols such as
methoxypolvethylene oxide, polyoxyalkylene glycols such as
polyethylene oxide and its copolymers, polyethylene
oxide/polypropylene oxide copolymers, polvalkylene oxide-modified
polydimethylsiloxanes, polyphosphazenes, poly(2-ethyl-2-oxazoline),
homopolymers and copolymers of (meth) acrylic acid, poly(acrylic
acid), copolymers of maleic anhydride including copolymers of
methylvinyl ether and maleic acid, pyrrolidones including
poly(vinylpyrrolidone) and its derivatives, homopolymers and
copolymers of vinyl pyrrolidone, poly(vinylsulfonic acid), acryl
amides including poly(N-alkyl acrylamide), poly(vinyl alcohol),
poly(ethyleneimine), poly(carboxylic acids), methyl cellulose,
carboxymethylcellulose, hydroxypropyl cellulose, polyvinyl sulfonic
acid, water soluble nylons, heparin, dextran, modified dextran,
hydroxylated chitin, chondroitin sulphate, lecithin, hyaluronan,
combinations and copolymers thereof, and the like.
[0081] Other non-limiting examples of suitable hydrogels include
hydroxyethyl acrylate or hydroxyethyl(meth)acrylates; polyethylene
maleic anhydride, combinations and copolymers thereof, and the
like.
[0082] Other useful synthetic biocompatible polymeric materials
include, but are not limited to, polyesters, including poly methyl
acetates, naphthalene dicarboxylate derivatives, and silks. The
polymeric materials may further include a metallic, a glass,
ceramic or carbon constituent or fiber. Useful and non limiting
examples of bioabsorbable or biodegradable polymeric materials
include poly(L-lactide), poly(D,L-lactide), poly(glycolide),
poly(L-lactide-co-D,L-lactide), poly(L-lactide-co-glycolide),
poly(D,L-lactide-co-glycolide) (PLA/PGA),
poly(glycolide-co-trimethylene carbonate) (PGA/PTMC),
polydioxanone, Polycaprolactone, polyhydroxybutyrate,
poly(phosphazene) poly(D,L-lactide-co-caprolactone),
poly(glycolide-co-caprolactone), poly(phosphate ester) and the
like. Some other materials which may be used as the filament
include, but are not limited to polyether ether ketone, fluorinated
ethylene propylene, and polyimide, polybutylene terephthalate,
polyurethane rubber, and silicone rubber.
[0083] Any component of the prosthetic device, and particularly the
anti-migration structure layer, may also include a therapeutic
agent that may be released into the body. Useful therapeutic agents
or drugs include but not limited to, anti-platelets,
anti-thrombins, anti-tumor drugs, anti-hyperplasia agents,
anti-plaque building agents, cytostatic agents, and
anti-proliferative agents, or other drugs for a specific purpose.
This may also include agents for gene therapy. The therapeutic
agent or drug is preferably selected from the group of therapeutic
agents or drugs consisting of urokinase, dextro phenylalanine
proline arginine chloromethylketone, enoxaparin, angiopeptin,
acetylsalicylic acid, paclitaxel, 5-fluorouracil, cisplatin,
vinblastine, vincristine, sulfasalazine, mesalamine, sodium
heparin, low molecular weight heparin, hirudin, prostacyclin and
prostacyclin analogues, dextran, glycoprotein Ib/IIIa platelet
membrane receptor antibody, recombinant hirudin, thrombin
inhibitor, calcium channel blockers, colchicine, fibroblast growth
factor antagonists, fish oil, omega 3-fatty acid, histamine
antagonists, HMG-CoA reductase inhibitor, methotrexate, monoclonal
antibodies, nitroprusside, phosphodiesterase inhibitors,
prostaglandin inhibitor, suramin, serotonin blockers, steroids,
thiol protease inhibitors, triazolopyrimidine and other PDGF
antagonists, alpha-interferon and genetically engineered epithelial
cells, and combinations thereof. The foregoing list of therapeutic
agents is provided by way of example and is not meant to be
limiting, as other therapeutic agents and drugs may be developed
which are equally applicable for use with the present
invention.
[0084] Stents of the present disclosure may be manufactured from a
mold comprising a top portion and a bottom portion. The top portion
may comprise an inner and outer surface, wherein the inner surface
may be adapted to receiving material for the manufacture of the
stent according to the present invention. The stent may be formed
as a hollow structure, which may be etched, or may be formed as a
coiled structure resembling a coil spring. U.S. patent application
Ser. No. 10/683,314, filed Oct. 10, 2003, disclose suitable
materials and geometries for stents.
[0085] In another alternate method of manufacture, the stent may be
formed by molding the exterior surface modification onto a separate
layer of material, such as for example a non-textile material. As
used herein, the term "non-textile" and its variants refer to a
material formed by casting, molding, spinning or extruding
techniques to the exclusion of typical textile forming techniques,
such as braiding, weaving, knitting and the like. Non limiting
examples of useful polymeric materials for the non-textile
polymeric graft portions include polyesters, polypropylenes,
polyethylenes, polyurethanes, polynaphthalenes,
polytetrafluoroethylenes, expanded polytetrafluoroethylene,
silicone, and combinations and copolymers thereof. Desirably, the
polymeric material polytetrafluoroethylene, including expanded
polytetrafluoroethylene.
[0086] A stent can be formed in a variety of configurations and of
a variety materials known to one skilled in the art. In particular,
conventional esophageal stents can be used or readily modified for
use in the present invention. Such stents can be of the
non-expanding or expanding variety, including those typically used
in addressing problems of progressive dysphagia associated with
esophageal cancer. Expanding stents include those that are
deformable and that are typically expanded using, e.g., a balloon
catheter, as well as those that are resilient in nature and that
can be delivered in a compressed state and which can self-expand to
their original state. Preferably, the stents are of the radially
self-expanding variety for ease of deployment in the esophagus.
Typically, such stents are made of stainless steel or nitinol
(nickel-titanium alloy) and formed into e.g. knitted wire tube,
tubular mesh, coiled spring, and like configurations. Suitable
self-expanding esophageal metal stents include those sold under the
brand names Esophacoil.TM. (Medtronic/Instent, Eden Prairie,
Minn.). Ultraflex.TM. (Boston Scientific/Microvasive, Natick,
Mass.), Wallstent.TM. (Boston Scientific/Microvasive, Natick,
Mass.), and Z-stent.TM. (Wilson-Cook, Winston-Salem, N.C.).
Additional examples of such stents include those described in U.S.
Pat. Nos. 5,876,448 and 6,248,058, each of which is incorporated
herein by reference in its entirety. Length and diameter of the
stent can usually range from 6-15 cm (length) and 16-22 mm
(diameter) for most applications. The stents may further be coated,
either partially or completely, with e.g. a polymeric film such as
silicone.
[0087] Any stent can have a covering and the coverings are thus not
limited to nitinol stents. Moreover, the stent need not be covered
whatsoever, may be partially covered or may be fully covered. The
stent may also have a covering on the inside, the outside or
both.
[0088] Other suitable covering materials can be employed as well.
Examples of other suitable covering materials include, but are not
limited to, polyethylene, polypropylene, polyvinyl chloride,
polytetrafluoroethylene, including expanded
polytetrafluoroethylene, fluorinated ethylene propylene,
fluorinated ethylene propylene, polyvinyl acetate, polystyrene,
poly(ethylene terephthalate), naphthalene, dicarboxylate
derivatives, such as polyethylene naphthalate, polybutylene
naphthalate, polytrimethylene naphthalate and trimethylenediol
naphthalate, polyurethane, polyurea, polyamides, polyimides,
polycarbonates, polyaldehydes, polyether ether ketone, natural
rubbers, polyester copolymers, styrene-butadiene copolymers,
polyethers, such as fully or partially halogenated polyethers, and
copolymers and combinations thereof.
[0089] Alternatively, the stent may have a braided construction
with a flared proximal end. In this embodiment, the stent is an
esophageal stent. A stent may be formed of any suitable stent
material including metallic and non-metallic materials as well as
shape memory materials. Examples of suitable materials include, but
are not limited to, shape memory alloys such as Nitinol, other
metallic materials such as stainless steel, tantalum, titanium,
nickel-chrome, or cobalt-chromium alloys such as those sold under
the tradename of Elgiloy.RTM.. A stent may have a flared distal end
or flared proximal and distal ends as well.
Hydrogel Cushioned Stents
[0090] In FIG. 5, a hydrogel coated stent 500 is shown in its
expanded form. The hydrogel coated stent 510 comprises a proximal
cuff or flare 525, a main elongated body 520, a distal cuff or
flare 530. A hydrophilic polyurethane hydrogel 535 is disposed
about at least one of the proximal 525 and distal cuffs 530 of the
stent 510. Preferably, the proximal cuff 525 includes a hydrophilic
polyurethane hydrogel. According to another aspect of the present
disclosure, both cuffs 525 and 530 comprise the polyurethane
hydrogel.
[0091] When initially inserted into the body vessel, each of the
cuffs 525, 530 and the elongated body 520 are similar in diameter
and allow for continued fluid flow around the exterior of the stent
510. However, upon exposure to an aqueous environment (i.e., bodily
fluids) the polyurethane hydrogel expands so that the outer
diameter of the cuffs 525, 530 increases. This increase in diameter
causes the cuffs 525, 530 to exert a sealing force against the wall
of the body vessel. This sealing force stops the bodily fluid from
flowing between the cuffs 525, 530 and the vessel wall, thereby,
forcing all of the fluid flow to enter and exit through the stent
510.
[0092] The use of a hydrophilic polyurethane hydrogel can
potentially reduce the incidence of encrustation and the occurrence
of a complicating infection. However, if this polymer layer is a
polyurethane hydrogel, the polymer layer will enlarge or swell when
exposed to an aqueous environment, thereby, allowing the struts of
the stent-graft to bend more freely without kinking.
[0093] The polyurethane hydrogel layer represents a 3-dimensional
network of cross-linked hydrophilic macromolecules that can swell
and absorb about 20 to 90 percent by weight of water. The hydrogel
layer may be applied as or onto the cuff of a stent-graft by
coating, adhesive bonding, lamination, extrusion, or molding. The
application method used is selected to provide a layer of the
hydrogel having a substantially uniform thickness.
[0094] The stent may comprise an expandable or inflatable structure
embedded within a polymeric matrix or a solid polymeric matrix. In
both cases, the polyurethane hydrogel may be applied as a strip or
band disposed around the outer surface of the cuff, such as a torus
shape or an annulus.
[0095] After the hydrogel is disposed around the cuff of a stent,
it may be dried by any method known in the art, including but not
limited to conduction drying, convection drying, hot air
impingement, steam treatment, infrared irradiation, ultraviolet
irradiation, and microwave irradiation. Preferably, the hydrogel
coating is dried by the application of thermal energy.
[0096] Drying the hydrogel causes it to dimensionally shrink. A
stent whose hydrogel cuff is dried can be made to shrink to a cross
section ready for insertion into a body vessel. In this condition,
the hydrogel cuff can take about the same diameter as the elongated
body 520 of the stent 510. In some cases the act of drying the
polyurethane gel will cause the stent to be in collapsed state. If
the hydrogel is formed around a mesh, the gel will expand only in
the direction perpendicular to the mesh. The shape and ratio of
polyurethane to water is predetermined at the moment of
polymerization.
[0097] The migration resistant surface texture can be applied to
the hydrogel or elsewhere on the stent. If applied to the hydrogel,
the surface texture can be applied either in the hydrogel dry state
or wet state. In either case, the surface texture can be applied as
an elastomeric layer or a segmented layer, or formed in the
hydrogel itself.
Fixation Separate from the Stent
[0098] In some cases, once the stent is deployed, the position of
the stent may shift relative to its position in the body lumen
prior to deployment. After the stent is deployed, it can be
difficult to reposition the stent. In some cases, re-positioning of
the stent can be facilitated by decoupling the stenting function
from the fixation function.
[0099] Referring to FIG. 6, a two-part stent 610 comprises a
conventional wire stent 612 and fixation sleeve 614. Stent 610 is
shown in its deployed state. To deliver the stent, stent 610 is
collapsed. Once deployed, outer sleeve surface 616 with surface
texture 618 engages the inner wall of the body lumen. On initial
deployment, wire stent 612 can easily be relocated within sleeve
614 without moving the sleeve 614 relative to the body lumen.
[0100] Wire stent 612 comprises outer surface 620 and optionally a
fixation region 624. Alternatively, in the case where fixation
region 624 is absent, wire stent 612 can be fixed to sleeve 614 via
suture, staple or the like.
[0101] Preferably, fixation region 624 is a surface texture 622
coated with a water soluble material such that initially surface
texture 622 is smooth. Optionally, a second coated surface texture
may be placed on the inner surface 626 of sleeve 614. The coating
may be any material used in the pharmaceutical industry to delay
release of a drug.
[0102] After a predetermined time, the coating dissolves either
through irrigation or due to body fluids present in the body lumen.
Upon dissolution of the coating, wire stent 612 fixes to sleeve
614, and sleeve 614 is fixed to the inner wall of the body lumen,
thus fixing stent 610 within the body lumen.
Fixation both Separate and Integral to the Stent
[0103] In yet another embodiment, the fixation region can be woven
into the stent in a relatively loose configuration, which allows
repositioning of the stent without repositioning the fixation
region. After deployment, the loose configuration can be tightened
or fixed.
[0104] In one particular embodiment shown in FIG. 7, stent 700
comprises stenting body 710 and movable anchoring element 720 is in
the form of a strip of patterned silicone. Stent 710 may be coiled
or patterned as a braided or woven open network of wires, fibers or
filaments interwoven in a braided pattern to form a tubular stent
700,
[0105] In this embodiment, the movable anchoring element 720 may
extend in the direction of the longitudinal axis of the stent and
can be interwoven in the braided construction of the stent 710. The
anchoring elements 720 may be fixed at one end, both ends, or at
some point in between the distal and proximal portions of the
stent. The anchoring element may comprise a surface texture as
described herein.
[0106] Any number of strips can be employed. Suitably, a minimum of
two strips are positioned symmetrically about the circumference of
the stent 700 to provide uniform anchoring in a body lumen.
[0107] Additionally, a single circumferential ring of anchoring
elements may be positioned in the middle of the stent to prevent
stent "walking" which may occur if anchoring elements are
positioned at both ends of the stent.
[0108] With reference to FIG. 8, an esophageal stent 800 comprises
stent body 802 and dilated regions 804 where a surface texture 806
is disposed thereon, thereby providing a fixation region. A
lubricious region 808 is disposed on the middle of the stent body
802. The spring constant of the stent body 802 may be designed to
match the spring constant of a target esophagus.
[0109] With reference to FIG. 9, an esophageal stent 900 comprises
stent body 902 and dilated regions 904 where a surface texture 906
is provided as an annular band and disposed over the stent body 902
with a particular spatial periodicity. In this embodiment, the
wavelength of the target esophageal peristaltic motion is known.
For example, for the adult human esophagus the peristaltic
wavelength is approximately 5 cm. When stent 900 is placed in a
human esophagus, the surface texture 906 is placed at 1/2
wavelength intervals 908, such that esophageal peristaltic wave 910
is alternatingly slipping in regions 912 and gripping the
esophageal wall in regions 914. This arrangement of grip surfaces
allows the passage of the esophageal peristaltic wave without
displacement of esophageal stent 900 relative to the esophagus 916.
Alternatively, the spacing 908 may be one wavelength.
Alternatively, surface textures 918 may be disposed on cuff or
flared regions 904.
[0110] The slip regions of FIGS. 8 and 9 may comprise a lubricious
membrane, such as silicone, or a gel, such as a hydrogel.
[0111] With reference to FIG. 10, an esophageal stent 1000
comprises a stent body 1002 and one flared or cuff region 1004
where surface texture 1006 is disposed over the stent body 1002. In
this embodiment, one end 1008 is free floating within an esophagus.
Optionally, end 1008 may be configured with lubricious ribs 1010
oriented axially, such that the esophagus is induced to slip
axially without stent end 1008 displacement. Ribs 1010 may be of
sufficient height to prevent rotational displacement of stent end
1008. Optionally, hydrogels may be disposed on ribs 1010.
[0112] With reference to FIG. 11, an esophageal stent 1100
comprises a stent body 1102 and cuff or flare regions 1104 where
surface texture 1106 is disposed over the stent body 1102. Stent
body 1102 when compressed in direction 1108 by peristaltic wave
1110, stent body 1102 dilates in direction 1112, such that stent
body 1102 stays in contact and follows peristaltic wave 1110.
Optionally, stent body 1102 may be disposed with grip regions 1106
with peristaltic wave periodicity as illustrated in FIG. 9.
[0113] With reference to FIG. 12, an esophageal stent 1200
comprises a stent body 1202 and dilated regions 1204 where surface
texture 1206 is disposed over the stent body 1202. Cuff or flare
regions 1204 are displaced with respect to stent body centerline
1208. The displacements of the two cuff or flare regions 1204 are
ideally 180 degrees out of phase, such that one end is displaced
"up" and the other end is displaced "down". This configuration
induces the middle part of stent body 1202 to deflect in direction
1212 with respect to peristaltic wave 1210. Accordingly, stent body
1202 follows peristaltic wave 1210.
[0114] With reference to FIG. 13, an esophageal stent 1300
comprises a stent body 1302 and cuff or flare regions 1304 where
slip ribs 1306 are disposed over the stent body 1302. The primary
fixation region 1308 is designed to engage an esophageal growth
1310 on esophagus 1312. Optionally, region 1308 may be radially
reinforced, or stiffer than dilated regions 1304. Optionally one
cuff or flare region 1304 may be gripping, rather than
slipping.
[0115] Alternatively, some of the wires through which the strips
are woven can be separate from the stent construction, such that
when they are removed, the interwoven pattern is undone, and the
textured strips are released from the stent.
[0116] The description provided herein is not to be limited in
scope by the specific embodiments described which are intended as
single illustrations of individual aspects of certain embodiments.
The methods, compositions and devices described herein can comprise
any feature described herein either alone or in combination with
any other feature(s) described herein. Indeed, various
modifications, in addition to those shown and described herein,
will become apparent to those skilled in the art from the foregoing
description and accompanying drawings using no more than routine
experimentation. Such modifications and equivalents are intended to
fall within the scope of the appended claims.
[0117] All publications, patents and patent applications mentioned
in this specification are herein incorporated by reference in their
entirety into the specification to the same extent as if each
individual publication, patent or patent application was
specifically and individually indicated to be incorporated herein
by reference. Citation or discussion of a reference herein shall
not be construed as an admission that such is prior art.
[0118] Thus, although there have been described particular
embodiments of the present invention of a new and useful Stents
with Improved Fixation it is not intended that such references be
construed as limitations upon the scope of this invention except as
set forth in the following claims.
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