U.S. patent application number 10/219979 was filed with the patent office on 2004-02-19 for covered stents with degradable barbs.
Invention is credited to Sherry, John.
Application Number | 20040034407 10/219979 |
Document ID | / |
Family ID | 31714843 |
Filed Date | 2004-02-19 |
United States Patent
Application |
20040034407 |
Kind Code |
A1 |
Sherry, John |
February 19, 2004 |
Covered stents with degradable barbs
Abstract
The present invention is directed at a removable stent for
providing reinforcement to a selected region of a selected body
lumen including a resilient cylindrical layer, including at least
one bioresorbable extrusion exterior from the resilient cylindrical
layer for resisting migration of the removable stent when the
removable stent is positioned in the selected region of the
selected body lumen. The present invention also includes a
temporary implantable endoprosthesis which includes a tubular,
radially compressible and axially flexible structure, including at
least one bioresorbable extrusion exterior from the resilient
cylindrical layer for resisting migration of the removable stent
when the removable stent is positioned in the selected region of
the selected body lumen.
Inventors: |
Sherry, John; (Needham,
MA) |
Correspondence
Address: |
Steven M. War
FULBRIGHT & JAWORSKI L.L.P.
Market Square
801 Pennsylvania Avenue, N.W.
Washington
DC
20004-2623
US
|
Family ID: |
31714843 |
Appl. No.: |
10/219979 |
Filed: |
August 16, 2002 |
Current U.S.
Class: |
623/1.15 |
Current CPC
Class: |
A61F 2002/8483 20130101;
A61F 2210/0004 20130101; A61F 2/848 20130101; A61F 2220/0016
20130101; A61F 2/90 20130101; A61F 2/07 20130101 |
Class at
Publication: |
623/1.15 |
International
Class: |
A61F 002/06 |
Claims
1. A removable stent for providing reinforcement to a selected
region of a selected body lumen including a resilient cylindrical
layer, the improvement which comprises: at least one bioresorbable
extrusion exterior from the resilient cylindrical layer for
resisting migration of the removable stent when said removable
stent is positioned in said selected region of said selected body
lumen.
2. The removable stent of claim 1 wherein said extrusion is a
barb.
3. The removable stent of claim 1 that is radially
self-expandable.
4. The removable stent of claim 1 wherein said selected body is
composed of a non-bioresorbable material.
5. The removable stent of claim 1 wherein said removable stent and
said at least one extrusion are part of a unitary design.
6. The removable stent of claim 1 wherein said removable stent is a
covered stent.
7. The removable stent of claim 1 wherein said removable stent is a
ePTFE covered removable stent.
8. The removable stent of claim 1 wherein said at least one
bioresorbable extrusion is composed of material selected from the
group consisting of PGA, PLA, PEO, nylon and polyester
urethane.
9. A temporary implantable endoprosthesis including a tubular,
radially compressible and axially flexible structure, the
improvement which comprises: at least one bioresorbable extrusion
exterior from the resilient cylindrical layer for resisting
migration of the stent when said stent is positioned in said
selected region of said selected body lumen.
10. The temporary implantable endoprosthesis of claim 9 wherein
said extrusion is a barb.
11. The temporary implantable endoprosthesis of claim 9 that is
radially self-expandable.
12. The temporary implantable endoprosthesis of claim 9 wherein
said temporary implantable endoprosthesis is made of
non-bioresorbable material.
13. The temporary implantable endoprosthesis of claim 9 wherein
said removable stent and said at least one extrusion are part of a
unitary design.
14. The temporary implantable endoprosthesis of claim 9 wherein
said removable stent is a covered stent.
15. The temporary implantable endoprosthesis of claim 9 wherein
said removable stent is a ePTFE covered removable stent.
16. The temporary implantable endoprosthesis of claim 9 wherein
said at least one extrusion is composed of material selected from
the group consisting of PGA, PLA, PEO, nylon and polyester
urethane.
17. A method of reducing migration of a removable stent comprising
the steps of: constructing said removable stent including a
resilient cylindrical layer; placing at least one bioresorbable
extrusion exterior from the resilient cylindrical layer of said
removable stent on said removable stent; positioning said removable
stent in a body lumen; expanding said removable stent within said
body lumen; and resisting migration of said removable stent by
interaction between said at least one bioabsorbable extrusion and
said body lumen.
18. The method of claim 17 wherein said step of placing at least
one bioresorbable extrusion is performed when the removable stent
is constructed as a unitary removable stent.
19. The method of claim 17 wherein said step of placing at least
one extrusion is performed after the resilient cylindrical layer of
said removable stent is completed.
20. The method of claim 17 wherein said step of expanding said
removable stent is accomplished by including self-expanding
material in the construction of said removable stent.
21. The method of claim 17 wherein said step of resisting migration
is performed by forming said at least one extrusion in the shape of
a barb.
22. The method of claim 17 wherein said step of resisting migration
is performed by said at least one extrusion interacting with the
wall of said body lumen.
23. The method of claim 17 further comprising the step of:
weakening said at least one extrusion by forming said extrusion of
a bioabsorbable material.
24. The method of claim 23 wherein the step of weakening said at
least one extrusion is accomplished by forming the extrusion of
material selected from the group consisting of PGA, PLA, PEO, nylon
and polyester urethane.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is related to an application entitled
"Disintegrating Stent and Method of Making Same," Ser. No.
09/592,413, by Jonathan Stinson, filed Jun. 13, 2000, the entire
contents of which is hereby incorporated by reference.
BACKGROUND
[0002] 1. Field of the Invention
[0003] The present invention relates generally to implantable
medical prostheses which incorporate an anchoring mechanism to
reduce or eliminate migration of the prostheses.
[0004] 2. Description of Related Art
[0005] Medical prostheses frequently referred to as stents are well
known and commercially available. These devices are used within
body vessels of humans for a variety of medical applications.
Examples include intravascular stents for treating stenoses, stents
for maintaining openings in the urinary biliary, tracheobronchial,
esophageal, and renal tracts, and vena cava filters. Stents may
also be used by physicians for malignant tumors. Benign tumors are
seldom stented with metal platforms.
[0006] Typically, a stent is delivered into position at a treatment
site in a compressed state using a delivery device. After the stent
is positioned at the treatment site, the delivery device is
actuated to release the stent. Following release of the stent,
self-expanding stents are allowed to self-expand within the body
vessel. Alternatively, a balloon may be used to expand other types
of stents. This expansion of the stent in the body vessel helps to
retain the stent in place and prevent movement or migration of the
stent. Stents are typically composed of stent filaments.
[0007] Stents may be categorized as permanent, removable or
bioresorbable. Permanent stents are retained in place and
incorporated into the vessel wall. Removable stents are removed
from the body vessel when the stent is no longer needed. A
bioresorbable stent may be composed of, or include, biogradable
material or bioresorbable material which is broken down by the body
and absorbed or passed from the body when it is no longer
needed.
[0008] Commonly used materials for known stent filaments include
Elgiloy.RTM. and Phynox.RTM. metal spring alloys. Other metallic
materials that may be used for stents filaments are 316 stainless
steel, MP35N alloy and superelastic Nitinol nickel-titanium.
Another stent, available from Schneider (USA) Inc. of Minneapolis,
Minn., has a radiopaque clad composite structure such as shown in
U.S. Pat. No. 5,630,840 to Mayer. Stents can also be made of a
titanium alloy as described in U.S. Pat. No. 5,888,201.
[0009] Bioabsorbable implantable endoprostheses such as stents,
stent-grafts, grafts, filters, occlusive devices, and valves may be
made of poly(alpha-hydroxy acid) such as poly-L-lactide (PLLA),
poly-D-lactide (PDLA), polyglycolide (PGA), polydioxanone,
polycaprolactone, polygluconate, polylactic acid-polyethylene oxide
copolymers, modified cellulose, collagen, poly(hydroxybutyrate),
polyanhydride, polyphosphoester, poly(aminoacides), or related
coploymers materials, each of which have a characteristic
degradation rate in the body. For example, PGA and polydioxanone
are relatively fast-bioabsorbing materials (weeks to months) and
PLA and polycaprolactone are a relatively slow-bioabsorbing
material (months to years).
[0010] Stents may also be covered with various materials to
encourage or inhibit tissue attachment to the stent. Covered stents
are gaining, favor for biliary applications because they more
effectively inhibit tissue attachment, intrusion, and constriction
of the tract than bare stents. For example, polytetrafluoroethylene
(PTFE) covered stents are desirable for removable stents because
tissue attachment or in-growth is reduced in comparison to bare
stent or a stent covered with textile (polyester) material.
Laminated ePTFE may also be used to cover stents.
[0011] As stents are covered with material to aid in their removal,
stent migration from the treatment site increases. There remains a
continuing need for covered stents which include characteristics to
maintain the stent in position at the treatment site. For example,
stents covered with ePTFE, such as Precedent, are easily removed
after a given time period, such as six months, but may not provide
sufficient fixation to prevent the risk of migration during the six
month period.
SUMMARY
[0012] The present invention relates to a removable stent for
providing reinforcement to a selected region of a selected body
lumen including a resilient cylindrical layer. The improvement to
the stent is the inclusion of at least one bioresorbably extrusion
exterior from the resilient cylindrical layer for resisting
migration of the stent when the stent is positioned in the selected
region of the selected body lumen.
[0013] Another embodiment of the present invention includes at
least one bioresorbable extrusion exterior from a resilient
cylindrical layer of a temporary implantable endoprosthesis. The
bioresorbable extrusion exterior to the resilient cylindrical layer
resists migration of the stent when the stent is positioned in a
selected region of a selected body lumen.
[0014] The present invention also includes a method of reducing
migration of a removable stent which includes the steps of
constructing a removable stent including a resilient cylindrical
layer and placing at least one bioresorbable extrusion exterior
from the resilient cylindrical layer on the stent. The removable
stent is then positioned and expanded within a body lumen.
Migration of the stent is resisted by the interaction between the
at least one biosorbable extrusion and the body lumen.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] We first briefly described the drawings.
[0016] FIG. 1 is an isometric view of an example of a braided
nitinol stent, comprised of 0.25 mm single filament strands that
incorporates bioresorbable extrusions of the present invention;
[0017] FIG. 2 is a simplified representation of a braided tubular
stent of the type illustrated in FIG. 1 incorporating bioresorbable
extrusions of the present invention;
[0018] FIG. 3 illustrates another stent incorporating another
bioresorbable extrusion of the present invention;
[0019] FIG. 4 is an isometric view of an example of a metal spring
alloy stent comprised of a single helical coil that a bioresorbable
extrusion of the present invention may be used in connection
with;
[0020] FIG. 5 is an isometric view of a rolled film or sheet-type
bioabsorbable stent that may be used in connection with the
bioresorbable extrusion of the present invention;
[0021] FIG. 6 is an isometric view of a solid extruded or molded
tube-type stent that may be used in connection with the
bioresorbable extrusion of the present invention;
[0022] FIG. 7 is an isometric view of a knitted or woven polymer
filament-type stent that may be used in connection with
bioresorbable extrusion of the present invention;
[0023] FIG. 8 is a side view of a delivery device with the sent
shown in FIG. 1 loaded thereon;
[0024] FIG. 9 is a detailed view of the portion of the delivery
device encircled at "FIG. 9" in FIG. 8;
[0025] FIG. 10 is a detailed view of the portion of the delivery
device encircled at "FIG. 10" in FIG. 8;
[0026] FIGS. 11-14 are partial cross-sectional side views of the
distal portion of the delivery device and stent shown in FIG. 8 at
various stages during a stent deployment operation in a body
vessel; and
[0027] FIG. 15 is a side view of a pusher-type delivery device.
DETAILED DESCRIPTION
[0028] The present invention improves the fixation characteristics
of removable stents by incorporating bioresorbable or bioabsorbable
barbs onto the removable stent or a covered stent to anchor the
stent during the service life of the stent.
[0029] An implantable prosthesis or stent 101 according to a
preferred embodiment of the present invention is illustrated
generally in FIGS. 1 through 3. Each of these figures includes a
removable stent body with bioresorbable exterior extrusions added
which, when placed in a body lumen, resist migration of the stent.
FIG. 4 shows an alternative embodiment of the invention according
to which the removable stent is comprised of a single helical coil
of a metal spring alloy and the bioresorbable exterior extrusion is
in the shape of a barb, angled to prevent migration of the stent
once placed in a body lumen. FIG. 5 shows an alternative embodiment
of the invention according to which the removable stent is
comprised of a rolled film or sheet and the bioresorbable exterior
extrusions are positioned circumferentially around the exterior of
the stent. FIG. 6 shows an alternative embodiment of the invention
according to which the removable stent is comprised of a solid
extruded or molded tube and the bioresorbable exterior extrusions
are triangular in shape to resist migration of the stent in any
direction. FIG. 7 shows an alternative embodiment of the invention
according to which the removable stent is comprised of knitted or
woven metal filaments and the bioresorbable exterior extrusions are
in the shape of barbs curved towards the ends of the stent.
Removable stent bodies of the type illustrated in FIGS. 4-7,
(without the bioresorbable exterior extrusions) are generally
well-known in the art and may be manufactured according to
well-known methods. The bioresorbable exterior extrusions may be
added to the removable stents after the body of the removable stent
is constructed or may be manufactured as part of the removable
stent body. Any of the removable stents according to the
embodiments of FIGS. 1-7 may be made using biostable material such
as Elgiloy.RTM. or Phynox.RTM. metal spring alloys, 316 stainless
steel, MP35N alloy, superelastic Nitinol nickel-titanium or similar
non-bioresorbable materials.
[0030] Referring again to the preferred embodiment of FIGS. 1
through 3, removable stent 101 is a tubular device formed from two
sets of oppositely-directed, parallel, spaced-apart and helically
wound elongated strands or filaments 102. The removable stent body
of FIGS. 1 and 2 is described in more detail in U.S. patent
application Ser. No. 08/904,967, filed Aug. 1, 1997. In particular,
the sets of filaments 102 are interwoven in an over and under
braided configuration intersecting at points such as 103 to form an
open mesh or weave construction. Methods for fabricating the body
of removable stents 101 are generally known and disclosed, for
example, in the Wallsten U.S. Pat. No. 4,655,771 and the Wallsten,
et al. U.S. Pat. No. 5,061,275.
[0031] Removable stent 101 is shown in its expanded or relaxed
state in FIGS. 1 and 2, i.e., in the configuration it assumes when
subject to no external loads or stresses. The filaments 102 are
resilient, permitting the radial compression of removable stent 101
into a reduced-radius, extended-length configuration or state
suitable for delivery to the desired placement or treatment site
through a body vessel (i.e., transluminally). Removable stent 101
may also be self-expandable from the compressed state, and axially
flexible. Bioresorbable exterior extrusions 104 are also resilient
permitting bioresorbable exterior extrusions 104 to be contained
within a delivery device when removable stent 101 is in a
compressed state but expanded to the relaxed state as shown in
FIGS. 1 and 2. Bioresorbable exterior extrusions 104 are also
inflexible enough, so that when in the expanded state in a body
lumen, bioresorbable exterior extrusions 104 prevent migration of
removable stent 101 within body lumen. According to one embodiment
of the invention, at least one and preferably all bioresorbable
extrusions is composed of one or more commercially available grades
of polylactide, poly-L-lactide (PLLA), poly-D-lactide (PDLA),
polyglycolide (PGA), polydioxanone, polycaprolactone,
polygluconate, polylactic acid-polyethylene oxide copolymers,
modified cellulose, collagen, poly(hydroxybutyrate), polyanhydride,
polyphosphoester, poly(amino acids), poly(alpha-hydroxy acid) or
related copolymers materials.
[0032] According to one embodiment of the invention, removable
stent 101 may be a radially and axially flexible tubular body
having a predetermined diameter that is variable under axial
movement of the ends of the body relative to each other. Removable
stent 101 may be composed of a plurality of individually rigid but
flexible and elastic thread elements or filaments 102, each of
which may extend in a helix configuration along a longitudinal
center line of the body as a common axis. The filaments 102 may
define a radially self-expanding body. The body may be provided by
a first number of filaments 102 having a common direction of
winding but axially displaced relative to each other, and crossing
a second number of filaments 102 also axially displaced relative to
each other but having an opposite direction of winding.
Bioresorbable exterior extrusions 104 are flexible in the axially
direction of removable stent 101, but rigid in the longitudinal
direction. The flexibility of bioresorbable exterior extrusions 104
in the axial direction allows removable stent 101, including
bioresorbable exterior extrusions 104 to be compressed into a
delivery device. The rigidity of bioresorbable exterior extrusions
104 in the longitudinal direction of removable stent 101 ensures
that, once removable stent 101 is positioned in a body lumen,
bioresorbable exterior extrusions 104 will resist migration of
removable stent 101 within the body lumen.
[0033] Bioresorbable exterior extrusions 104 may take a variety of
shapes. Bioresorbable exterior extrusions 104 of FIG. 1 are in the
shape of a barb with the concave surface of the barb towards the
center of removable stent 101. Alternatively, bioresorbable
exterior extrusions 201 of FIG. 2 may be triangular in shape and
rigid in the longitudinal direction of removable stent 202 to
resist migration in a longitudinal direction once removable stent
202 is positioned within a body lumen.
[0034] Removable stent 301 of FIG. 3 includes a plurality of
individually rigid but flexible and elastic thread elements or
filaments 302, each of which may extend in a helix configuration
along a longitudinal center line of the body as a common axis. The
filaments 302 may define a radially self-expanding body. The body
may be provided by a first number of filaments 302 having a common
direction of winding but axially displaced relative to each other,
and crossing a second number of filaments 305 also axially
displaced relative to each other but having an opposite direction
of winding. Bioresorbable exterior extrusions 304 are flexible in
the axially direction of removable stent 301, but rigid in the
longitudinal direction. The flexibility of bioresorbable exterior
extrusions 304 in the axial direction allows removable stent 301,
including bioresorbable exterior extrusions 304 to be compressed
into a delivery device. Filaments 302 and filaments 305 may be
configured to alternate at intersections. For example, at one
intersection filament 302 may be exterior to filament 305 as shown
at 303. Alternatively, filament 305 may be exterior to filament 302
at other intersections as shown at 306. FIG. 3 also shows that a
number of bioresorbable exterior extrusions may be included in an
embodiment to further resist migration of removable stent 301 when
placed within a body lumen.
[0035] FIGS. 3 through 7 show other embodiments of the placement of
bioresorbable exterior extrusions on various removable stent
configurations. Notably, FIG. 5 depicts bioresorbable exterior
extrusions 502 along an outer circumference of removable stent 501.
Note that many orientations and configurations of bioresorbable
exterior extrusions may be configured to resist migration of the
stent within a body lumen.
[0036] Note also that bioresorbable exterior extrusions of the
present invention may be used to resist migration of other types of
removable stents. Other stent structures and features may be
include, for example, stents having features which enhance or
cooperate with the tubular and self-expandable structure or which
facilitate the implantation of the structure. One example is the
inclusion of radiopaque markers on the structure which are used to
visualize the position of the stent through fluoroscopy during
implantation. Other examples include collapsing threads or other
structures to facilitate repositioning of the stent.
[0037] Note that the use of bioresorbable exterior extrusions on a
removable stent would help ensure the proper position of the
removable stent during its in service, or in the lumen, time. By
selection of the proper bioresorbable materials, when the time to
remove the removable stent has arrived, the bioresorbable exterior
extrusions have been absorbed into, or broken down by the body,
allowing for easy removal.
[0038] Note also that a non-bioresorbable exterior extrusion
attached to the removable stent body with bioabsorbable material
may also be used in the implementation of the present
invention.
[0039] FIGS. 8 through 10 are illustrations of a delivery device
801 for delivering removable stent 101 to a treatment site in a
body vessel. As shown, removable stent 101 is carried by the distal
portion 809 of delivery device 801, and is placed on the delivery
device in a radially contracted or compressed state. The proximal
portion of delivery device 801 generally remains outside of the
body for manipulation by the operator.
[0040] Delivery device 801 includes an elongated, inner tube 802,
preferably having an axially extending lumen therethrough. The
distal portion 809 of inner tube 801 is flexible and can be made
from nylon or other suitably flexible biocompatible polymeric
material. At its distal end, inner tube 801 is provided with a head
805. Head 805 serves to facilitate the insertion of delivery device
801 through a narrow opening in a body vessel. The proximal portion
of inner tube 802 is preferably formed from stainless steel or
other suitably rigid metal alloy. The proximal end of the distal
portion of inner tube 802 is bonded to the distal end of the
proximal portion of the inner tube in any conventional manner such
as by using a standard adhesive.
[0041] A proximal tube 804 surrounds the proximal portion of inner
tube 802 in coaxial fashion. Proximal tube 804 is preferably formed
from polyurethane. The proximal end of tube 804 is connected to a
valve body 803 having a side port 806. An extension tube 807
extends from side port 806 to an opening 808. This arrangement
allows fluid to be injected through extension tube 807 and between
proximal tube 804 and inner tube 802.
[0042] A moveable hose 901 surrounds the distal portion of inner
tube 802. Hose 901 is rolled over itself to form a double-walled
section. The proximal end of inner wall 1001 of a double-walled
section is connected directly to inner tube 802. The proximal end
of the outer wall 1002 of the double-walled section is connected to
the outer surface of the distal portion of proximal tube 804. These
connections can be achieved by any conventional means such as by a
standard adhesive. This arrangement allows hose 901 to be rolled
off removable stent 101 and placed on the distal portion of inner
tube 802. By moving valve body 803 in the proximal direction, outer
wall 1002 of hose 901 slides proximally over inner wall 1001. This
causes inner wall 1001 to "roll back" off of removable stent 101.
To facilitate movement of hose 901 off of removable stent 101, at
least that portion of inner wall 1001 that contacts outer wall 1002
in the area where hose 901 is rolled over to form the double-walled
section should be lubricious. The lubricious characteristic can be
achieved by adding a lubricious substance to this surface of hose
901, injecting a lubricious liquid between inner wall 1001 and
outer wall 1002 or forming hose 901 from a naturally slippery
material such as Teflon coating.
[0043] At least the surfaces of inner wall 1001 and outer wall 1002
that face each other in the double-walled section are coated with a
lubricious hydrophilic coating. In one embodiment the hydrophilic
coating is 2018-M material available from Hydromer Inc. of
Whitehouse, N.J. Other materials that can be used are polyethylene
oxide and hyaluronic acid. When wet, the hydrophilic coating
becomes lubricious and thus reduces friction between inner wall
1001 and outer wall 1002 of the double-walled section of hose 901
as outer wall 1002 moves past inner wall 1001. This facilitates the
removal of the double-walled section of hose 901 from removable
stent 101. Hydrophilic material may be added to hose 901 during the
assembly of delivery device 801. To enable the hydrophilic material
to adequately bond to hose 901, the material used to manufacture
hose 901 should be matched to the hydrophilic material used. It has
been found that polyurethane works well as a material for hose 901.
In particular, a blend of 65D and 75D polyurethane provides
sufficient flexibility to allow hose 901 to roll over itself yet
still be soft enough and compatible with the hydrophilic material
that it can be properly coated. In one embodiment, the blend is
formed of 50% 65D polyurethane and 50% 75D polyurethane. During the
assembly of delivery device 801, one side of hose 901 is coated
with the hydrophilic material after the outer wall 1002 of the hose
has been connected to proximal tube 804. Isopropyl alcohol is first
applied to one side of hose 901 to clean the surface and remove the
waxy film resulting from the plasticizers in the polyurethane. The
same side of hose 901 is then coated with the hydrophilic material.
The surface of hose 901 should be flushed with alcohol for about
thirty seconds. Similarly, the surface of hose 901 should be
flushed with the hydrophilic coating for about thirty seconds. It
has been found that this technique deposits sufficient hydrophilic
material on inner wall 1001 and outer wall 1002 to allow hose 901
to be rolled back with minimal friction when the hydrophilic
material is wet.
[0044] After delivery device 801 has been assembled and is ready
for use, the hydrophilic coating is wetted with physiological
saline solution by injecting the solution through extension tube
807, past proximal tube 804 and into the space between inner wall
1001 and outer wall 1002 of the double-walled section of hose 901.
Excess fluid exits from the hole 902 formed toward the distal end
of the double-walled section of hose 901. In this same manner, a
lubricious fluid such as polyethylene glycol can be injected into
the space between inner wall 1001 and outer wall 1002 of the
double-walled section to provide the lubricious characteristic of
hose 901 in place of adding a lubricious hydrophilic material
through hose 901 as described above.
[0045] The manner by which delivery device 801 is operated to
deliver removable stent 101 to a treatment site in a body vessel or
lumen including curved sections is illustrated in FIGS. 11-14. As
shown, removable stent 101 is placed in a radially compressed state
in a surrounding relationship to the outer distal end of inner tube
802. Removable stent 101 is constrained on inner tube 802 by the
double-walled section of hose 901. It is important that removable
stent 101 not be confined too tightly on inner tube 802. Hose 901
should apply just enough force to removable stent 101 to hold
removable stent 101 in place. The double-walled section of hose 901
can be removed from around removable stent 101 by pulling valve
body 803 and proximal tube 804 in a proximal direction. The
double-walled section "rolls" off removable stent 101. No sliding
movements take place between removable stent 101 and inner wall
1001 which contacts removable stent 101. Along with the movement of
the double-walled section in a proximal direction, the distal end
of removable stent 101 will be exposed in a radial direction to
engagement against the wall of the body vessel. As the
double-walled section of hose 901 continues moving proximally, more
of removable stent 101 expands in a radial direction until the
entire length of removable stent 101 is exposed and engages the
wall of a body.
[0046] A lumen is used to enable delivery device 801 to follow a
guide wire (not shown) previously inserted percutaneously into the
body vessel. The lumen of inner tube 802 can also be used to
introduce a contrast fluid to the area around the distal end of
delivery device 801 so the position of delivery device 801 can be
detected (e.g., through the use fluoroscopy or X-ray
techniques).
[0047] In FIG. 15 there is shown another embodiment of a delivery
device which may be used to position stents including the present
invention within a body lumen.
[0048] This assembly constitutes a flexible instrument intended to
introduce the tubular body in contracted state into for example a
blood vessel and then to expand the body when located therein. The
parts of the instrument consist of an outer flexible tube 1501 and
a concentric also flexible inner tube 1502. At one end of the outer
tube an operational member 1503 is arranged. Another operational
member 1504 is attached to the free end of inner tube 1502. In this
manner the inner tube 1502 is axially displaceable in relation to
the outer tube 1501. At the other end of inner tube 1502 a piston
1505 is attached which when moving runs along the inner wall of
outer tube 1501.
[0049] When the instrument is to be used the tubular expansible
body 1506 in contracted state is first placed inside tube 1501, the
inner tube 1502 with the piston 1505 being located in the rear part
1507 of outer tube 1501. The starting position of piston 1505 is
shown by dashed lines at 1508 in FIG. 15. In this manner part of
tube 1501 is filled with the contracted tubular body 1506 in the
starting position.
[0050] During implantation the flexible tubular part of the device
is inserted to the location of a blood vessel intended for
implantation. Member 1504 is then moved in the direction of arrow
1509, the contracted body 1506 being pushed out through end 1510 of
tube 1501, the part of the tubular body 1506 leaving tube end 1510
expanding until in its expanded position 1511 it is brought to
engagement with the interior of vascular wall 1512. The tubular
body 1506, 1511 is for sake of simplicity shown in FIG. 15 as two
sinus-shaped lines. To the extent that the expanded body 1506 comes
into engagement with vascular wall 1512 tube end 1510 is moved by
moving member 1503 in the direction of arrow 1513. The contracted
body 1506 is moved by the piston 1505 pushing against one end of
the body. Thus, the implantation takes place by simultaneous
oppositely directed movements of members 1504 and 1503, the
displacement of member 1504 being larger than that of member 1503.
When the contracted body 1506 has been fully removed from the tube
1501 the expansion is terminated and the instrument can be removed
from the location of the operation.
[0051] The delivery system according to FIG. 15 has the great
advantage that the constructional details are quite simple and can
be operated with high reliability. The instrument shown is also
suitable for implantation of helices with very small diameters. As
an example there may be mentioned that experiments have been
performed with a tubular expansible body consisting of crossing
thread elements, the contracted diameter of the body being only 2
mms and the expanded diameter 6 mms. It is also fully conceivable
to implant expanded bodies with even smaller diameter. The
instrument according to FIG. 15 may also advantageously be used for
implantation of bodies in the form of grafts of a very large
diameter.
[0052] In implantation of long bodies it is conceivable that the
resistance in displacing same in tube 1501 becomes too high. In
this case it may be suitable to replace piston 1505 at the front
end of tube 1502 with movable jaws or latches which operate in such
a manner that when tube 1502 is brought forward in the direction of
arrow 1509 the latches engage the inner side of body 1506, the body
being brought forward. When tube 1502 is brought back in the
direction of arrow 1513 the latches are released. In this manner
body 1506 can be moved forwardly by a pump-like motion of tube
1502.
[0053] Many embodiments of the different members shown in FIG. 15
are, of course, conceivable. Thus, it is possible for example to
simplify implantation for the surgeon by controlling the relative
motion between members 1503 and 1504 in a mechanical manner.
[0054] The stents of the present invention may be delivered by
alternative methods or using alternative devices. For instance, the
device described in Heyn et al. U.S. Pat. No. 5,201,757 may be
utilized.
[0055] Although the present invention has been described with
reference to preferred embodiments, those skilled in the art will
recognize that changes can be made in form and detail without
departing from the spirit and scope of the invention.
[0056] It will be evident from considerations of the foregoing that
the devices of the present invention may be constructed using a
number of methods and materials, in a wide variety of sizes and
styles for the greater efficiency and convenience of a user.
[0057] The above described embodiments of the invention are merely
descriptive of its principles and are not to be considered
limiting. Further modifications of the invention herein disclosed
will occur to those skilled in the respective arts and all such
modifications are deemed to be within the scope of the invention as
defined by the following claims.
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