U.S. patent application number 13/490225 was filed with the patent office on 2013-12-12 for apparatus, systems and methods for medical device expansion.
This patent application is currently assigned to ABBOTT CARDIOVASCULAR SYSTEMS, INC.. The applicant listed for this patent is Michael Lee Green. Invention is credited to Michael Lee Green.
Application Number | 20130327113 13/490225 |
Document ID | / |
Family ID | 49712788 |
Filed Date | 2013-12-12 |
United States Patent
Application |
20130327113 |
Kind Code |
A1 |
Green; Michael Lee |
December 12, 2013 |
APPARATUS, SYSTEMS AND METHODS FOR MEDICAL DEVICE EXPANSION
Abstract
A system and method for manufacturing a medical device. The
system can include a thermal chamber and an expander at least
partially positioned within the thermal chamber. The expander can
be configured to uniformly expand a medical device as the medical
device is advanced over the heated expander and heat set the
expanded medical device while the medical device is positioned on
the heated expander. The method can include forming a medical
device from a tube having a first diameter; uniformly expanding the
medical device from the first diameter to a second diameter at
which the medical device can be left within a body vessel, the
medical device being expanded from the first diameter to the second
diameter while being continuously positioned on an expander; and
heat setting the expanded medical device at the second diameter
while the medical device is positioned on the expander.
Inventors: |
Green; Michael Lee;
(Pleasanton, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Green; Michael Lee |
Pleasanton |
CA |
US |
|
|
Assignee: |
ABBOTT CARDIOVASCULAR SYSTEMS,
INC.
Santa Clara
CA
|
Family ID: |
49712788 |
Appl. No.: |
13/490225 |
Filed: |
June 6, 2012 |
Current U.S.
Class: |
72/342.7 |
Current CPC
Class: |
B21D 39/20 20130101;
A61B 2017/00526 20130101; B29C 55/24 20130101; A61B 2017/00867
20130101; A61F 2210/0019 20130101; A61F 2240/001 20130101; A61F
2/86 20130101; B29L 2023/007 20130101; A61F 2/915 20130101; B29C
71/02 20130101; A61F 2/91 20130101 |
Class at
Publication: |
72/342.7 |
International
Class: |
B21D 39/20 20060101
B21D039/20 |
Claims
1. A system for uniformly expanding and heat setting a medical
device, the system comprising: a thermal chamber; and an expander
at least partially positioned within the thermal chamber, the
thermal chamber maintaining the expander at a predetermined
elevated temperature, the expander being configured to: uniformly
expand a medical device as the medical device is advanced over the
heated expander; and heat set the expanded medical device while the
medical device is positioned on the heated expander.
2. The system of claim 1, wherein the expander extends
longitudinally between a proximal end and a distal end, the
expander having an outer surface with a plurality of transport
guides formed thereon that extend longitudinally from the proximal
end toward the distal end; and the system further comprises: a
transport assembly extending between a proximal end and a distal
end, the transport assembly comprising a plurality of transport
mechanisms each extending longitudinally between the proximal and
distal ends of the transport assembly, the distal ends of the
transport mechanisms being receivable within and slidable along the
transport guides, the transport assembly being configured to
receive a medical device thereon and position the medical device
radially over the expander, and the expander being configured to
radially expand the medical device while the medical device remains
on the transport assembly.
3. The system of claim 2, further comprising an axial guide that
longitudinally guides the transport assembly when the transport
mechanisms of the transport assembly are received within and slide
longitudinally along the transport guides.
4. The system of claim 3, wherein the expander has a guide opening
extending distally thereinto from a proximal end face, and the
axial guide is receivable within the guide opening to
longitudinally guide the transport mechanisms of the transport
assembly to the wire guides and to guide the transport mechanisms
as the transport mechanisms slide longitudinally along the
transport guides.
5. The system of claim 3, further comprising means for rotationally
aligning the axial guide and the expander.
6. The system of claim 5, wherein the means for rotationally
aligning the axial guide and the expander comprises: the axial
guide and the expander having mating shapes; or mating keys formed
on the axial guide and the expander.
7. The system of claim 2, wherein the expander has a tapered
portion positioned between the proximal and distal portions, the
tapered portion having a cross sectional area that transitions
between the cross sectional area of the proximal portion and the
cross sectional area of the distal portion.
8. The system of claim 2, wherein the transport guides are
circumferentially distributed about the outer surface of the
expander.
9. The system of claim 2, wherein the transport mechanisms and the
transport guides are configured so that the medical device is
physically separated from the expander when the medical device is
positioned radially over the expander and expanded by the
expander.
10. The system of claim 2, wherein the plurality of transport
mechanisms comprises a plurality of wires, the transport assembly
comprises an array of the wires, and the plurality of transport
guides comprises a plurality of wire guides.
11. A method of manufacturing a medical device, the method
comprising: forming a medical device from a tube having a first
diameter; uniformly expanding the medical device from the first
diameter to a second diameter at which the medical device can be
left within a body vessel, the medical device being expanded from
the first diameter to the second diameter while being continuously
positioned on an expander; and heat setting the expanded medical
device at the second diameter while the medical device is
positioned on the expander.
12. The method of claim 11, wherein heat setting the expanded
medical device comprises maintaining the expanded medical device at
the second diameter on the expander for a predetermined period of
time while the expander is maintained at a predetermined
heat-setting temperature.
13. The method of claim 12, wherein the expander is positioned
within a thermal chamber that maintains the expander at the
predetermined heat-setting temperature during the steps of
uniformly expanding the medical device and heat setting the
expanded medical device.
14. The method of claim 11, wherein the medical device is comprised
of a shape-memory material.
15. The method of claim 11, wherein the medical device is
physically separated from the expander when the medical device is
positioned on the expander.
16. The method of claim 11, further comprising: preheating the
medical device within a thermal chamber before uniformly expanding
the medical device; and maintaining heat on the medical device
within the thermal chamber during radial expansion of the medical
device.
17. A method of manufacturing a medical device, the method
comprising: positioning a medical device on a transport assembly
having a plurality of transport mechanisms, the transport
mechanisms being arranged generally parallel to a central
longitudinal axis; positioning a portion of the transport assembly
on an expander so that the medical device becomes positioned
radially over the expander; radially expanding the medical device
with the expander while the medical device is positioned on the
transport assembly; and heat setting the expanded medical device
while the medical device is positioned on the expander, the acts of
radially expanding the medical device and heat setting the expanded
medical device being performed while the medical device is
positioned in a heated thermal chamber.
18. The method of claim 17, wherein positioning the portion of the
transport assembly on the expander comprises: positioning ends of
the transport mechanisms of the transport assembly in transport
guides formed on the expander; and moving the transport assembly
longitudinally with respect to the expander so that the transport
mechanisms slide along the transport guides until the medical
device is positioned radially over the expander.
19. The method of claim 18, wherein positioning the portion of the
transport assembly on the expander further comprises: inserting an
axial guide into a guide opening extending longitudinally through
the expander, the transport assembly being attached to the axial
guide so as to move therewith, and wherein the steps of positioning
the ends of the transport mechanisms in the transport guides and
moving the transport assembly longitudinally are accomplished by
moving the axial guide along the guide opening.
20. The method of claim 17, wherein radially expanding the medical
device with the expander comprises moving the medical device
relative to the expander from a first position on a first portion
of the expander to a second position on a second portion of the
expander, the first and second portions of the expander
respectively having first and second cross sectional areas, the
second cross sectional area being greater than the first cross
sectional area, the medical device being radially expanded as the
medical device moves from the first position to the second
position.
Description
BACKGROUND OF THE INVENTION
[0001] I. The Field of the Invention
[0002] The present invention generally relates to the field of
medical devices. More specifically, the present invention relates
to methods, systems, and devices for manufacturing a self-expanding
medical device.
[0003] II. Related Technology
[0004] The use of intravascular devices to treat cardiovascular
diseases is well known in the field of medicine. The need for a
greater variety of devices to address different types of
circumstances has grown tremendously as the techniques for using
intravascular devices has progressed. One type of intravascular
device is a stent or scaffold. Stents and scaffolds are generally
cylindrically shaped intravascular devices that are placed within
an artery (or other vessel within the body) to hold it open. The
device can be used to reduce the likelihood of restenosis or
recurrence of the blocking of a blood vessel and can be placed
within an artery on a permanent basis, such as a stent, or a
temporary basis, such as a scaffold. In some circumstances, a stent
or scaffold can be used as the primary treatment device where it is
expanded to dilate a stenosis and left in place.
[0005] A variety of stent or scaffold designs have been developed.
Examples include coiled wires in a variety of patterns that are
expanded after being placed within a vessel on a balloon catheter,
helically wound coiled springs manufactured from expandable heat
sensitive metals, stents or scaffolds shaped in zig-zag patterns,
and self-expanding stents or scaffolds inserted in a compressed
state for deployment in a body lumen.
[0006] Stents and scaffolds can have various features. For
instance, a stent or scaffold can have a tubular shape formed from
a plurality of interconnected struts and/or legs that can form a
series of interconnected rings. In the expanded condition, the
stent or scaffold can have a cylindrical shape to expand in an
artery. One material for manufacturing self-expanding stents or
scaffolds is nitinol, an alloy of nickel and titanium.
[0007] The conventional approach to manufacture a self-expanding
stent or scaffold is to begin by laser cutting the design of the
stent or scaffold from a tube having a diameter that is
approximately equal to the desired diameter of the compressed
(i.e., unexpanded) stent or scaffold. The tube is then deburred to
clean any imperfections due to the cutting. Once the tube has been
deburred, the tube is then expanded to the desired diameter, which
is the diameter the stent will maintain when left within a body
vessel. The tube is then heat set at the desired expanded diameter
to maintain the tube at that diameter.
[0008] Conventionally, expanding the stent or scaffold to the
desired expanded diameter requires an iterative process: The tube
is positioned on a mandrel having a diameter that is slightly
larger than the diameter of the compressed tube, thereby expanding
the tube. Heat is applied to the tube while the tube is on the
mandrel to heat set the tube at the new diameter. The tube and
mandrel are allowed to cool to complete the heat setting, and the
tube is then removed from the mandrel. This process is then
repeated with a slightly larger mandrel to expand the tube further.
This iterative process of expanding the tube a little at a time is
repeated until the desired expanded diameter is attained.
[0009] Although the conventional manufacturing approach discussed
above generally yields acceptable self expanding medical devices,
the approach has some shortcomings. For example, it is cumbersome
and time consuming due, in large part, to the iterative heating and
cooling processes. In addition, a significant amount of energy is
used by heating and reheating the medical device and the mandrel
during each iteration. Another shortcoming is that, in many
instances, cracks are induced in the stent or scaffold during
conventional manufacturing due to undesired torque, tension,
expansion, and/or compression.
BRIEF SUMMARY OF THE INVENTION
[0010] Embodiments of the invention relate to the expansion of
medical devices including implantable medical devices such as
stents or scaffolds.
[0011] In one embodiment, a method of manufacturing a medical
device can include forming a medical device from a tube having a
first diameter; uniformly expanding the medical device from the
first diameter to a second diameter at which the medical device can
be left within a body vessel, the medical device being expanded
from the first diameter to the second diameter while being
continuously positioned on an expander; and heat setting the
expanded medical device at the second diameter while the medical
device is positioned on the expander.
[0012] In another embodiment, a method of manufacturing a medical
device can include positioning a medical device on a transport
assembly having a plurality of transport mechanisms, the transport
mechanisms being arranged generally parallel to a central
longitudinal axis; positioning a portion of the transport assembly
on an expander so that the medical device becomes positioned
radially over the expander; radially expanding the medical device
with the expander while the medical device is positioned on the
transport assembly; and heat setting the expanded medical device
while the medical device is positioned on the expander, the acts of
radially expanding the medical device and heat setting the expanded
medical device being performed while the medical device is
positioned in a heated thermal chamber.
[0013] In another embodiment, a system for uniformly expanding and
heat setting a medical device can include a thermal chamber and an
expander at least partially positioned within the thermal chamber.
The thermal chamber maintains the expander at a predetermined
elevated temperature. The expander is configured to uniformly
expand a medical device as the medical device is advanced over the
heated expander and heat set the expanded medical device while the
medical device is positioned on the heated expander.
[0014] In some embodiments of the invention, the medical device can
be placed over a transport assembly having a plurality of transport
mechanisms. The transport mechanisms can then be expanded with an
expander, thereby uniformly expanding the medical device. The
medical device can be expanded at any operable temperature. In some
embodiments, the medical device can be expanded while within a
temperature controlled zone. In some embodiments, the medical
device can be heat set while in the expanded state.
[0015] The transport mechanisms may engage with corresponding
transport guides, such as recesses, grooves, or channels, in the
expander that keep the transport mechanisms uniformly spaced
circumferentially around the expander, while the transport
mechanisms provide a separation between the medical device and the
expander body. As a result, the transport mechanisms can act as a
transport to reduce friction that may otherwise occur between the
medical device and the expander during expansion or manufacture of
the medical device. By reducing friction, the medical device can be
expanded with less susceptibility to adverse effects such as
compression, tension, fracturing, torquing, bending, uneven
expansion, and the like or any combination thereof.
[0016] A medical device can thus be expanded in one embodiment by
positioning the medical device over a transport assembly that
includes a plurality of transport mechanisms, such as wires. The
transport mechanisms can be arranged generally parallel to a
central longitudinal axis of the expander. Next, at least a portion
of the transport assembly and at least a portion of the medical
device can be positioned over an expander, such as a mandrel. Then,
at least a portion of the medical device can be radially expanded
with the expander.
[0017] The expander may have a central longitudinal axis and a body
having an outer surface. The outer surface may have a plurality of
longitudinal transport guides, such as wire recesses, grooves, or
channels defined therein. The longitudinal transport mechanisms can
be configured to be positioned at least partially within the
transport guides to guide the transport assembly for translation of
the transport assembly with respect to the expander, parallel to
the longitudinal axis. The expander may also have a portion with a
first diameter, a portion with a second larger diameter, and a
transition portion that transitions the expander from the first
diameter to the second diameter.
[0018] In one embodiment, the medical device can be expanded by
axially translating the expander relative to the medical device.
The transport mechanisms can transport the medical device by
reducing friction between the medical device and the expander as
the expander moves axially (or while the medical device moves
axially along the expander). During heat-setting of the medical
device, the medical device can be heat-set in the expanded
position, for instance.
[0019] In one embodiment, the transport assembly can comprise a
wire array and the transport mechanisms can comprise the wires that
make up the wire array. Correspondingly, the transport guides can
comprise wire guides arranged generally parallel to the central
longitudinal axis of the expander so as to receive and guide the
wires over the expander. The medical device can be expanded by
positioning the medical device over the wires of the wire array and
then moving the wire array toward the expander so that the wires
are received within the wire guides of the expander. Next, at least
a portion of the wire array and at least a portion of the medical
device can be advanced onto the expander. The medical device can
then be radially expanded by the expander as the medical device
moves with the wires within the wire guides.
[0020] These and other advantages and features of the present
invention will become more fully apparent from the following
description and appended claims, or may be learned by the practice
of the invention as set forth hereinafter.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] To further clarify the above and other advantages and
features of the present invention, a more particular description of
the invention will be rendered by reference to specific embodiments
thereof which are illustrated in the appended drawings. It is
appreciated that these drawings depict only typical embodiments of
the invention and are therefore not to be considered limiting of
its scope. In the drawings, like numerals designate like elements.
Furthermore, multiple instances of an element may each include
separate letters appended to the element number. For example two
instances of a particular element "20" may be labeled as "20a" and
"20b". In that case, the element label may be used without an
appended letter (e.g., "20") to generally refer to every instance
of the element; while the element label will include an appended
letter (e.g., "20a") to refer to a specific instance of the
element.
[0022] FIG. 1 illustrates an exploded view of a system for
expanding a medical device according to one embodiment;
[0023] FIG. 2 is a perspective view of the expander shown in FIG.
1;
[0024] FIGS. 3A, 3B, and 3C are cross sectional views of the
expander of FIG. 2, taken along section lines 3A-3A, 3B-3B, and
3C-3C, respectively, of FIG. 2;
[0025] FIGS. 4A-4C illustrate a method for expanding a medical
device using the system shown in FIG. 1, according to one
embodiment;
[0026] FIGS. 5A-5C illustrate a method for deploying a medical
device according to one embodiment;
[0027] FIGS. 6A-6B is a side view of an expander according to
another embodiment;
[0028] FIGS. 7A-7B are cross sectional views of an expander
according to another embodiment:
[0029] FIGS. 8A-8C illustrate a method for expanding a medical
device using the system shown in FIG. 1, according to another
embodiment;
[0030] FIG. 9 illustrates an exploded view of a system for
expanding a medical device according to another embodiment;
[0031] FIG. 10 is a end view of the integrated wiring guide shown
in FIG. 9;
[0032] FIGS. 11A-11B illustrate a method for expanding a medical
device using the system shown in FIG. 9, according to one
embodiment; and
[0033] FIGS. 12A-12B illustrate embodiments for rotationally
aligning an integrated wiring guide and an expander.
DETAILED DESCRIPTION
[0034] As used in the specification and appended claims,
directional terms, such as "top," "bottom," "up," "down," "upper,"
"lower," "proximal," "distal," and the like are used herein solely
to indicate relative directions and are not otherwise intended to
limit the scope of the invention or claims.
[0035] Methods and devices are provided herein for expanding a
medical device. The methods provided through the systems and
devices are repeatable and reduce the possibility of incorrectly
expanding medical devices during the manufacturing process.
Further, the methods provided herein reduce the possibility of
undesired torque, tension, expansion and compression of the stent
or scaffold during manufacture.
[0036] In at least one embodiment, a method for expanding a medical
device includes placing the medical device over longitudinally
oriented transport mechanisms, such as wires. The medical device is
then expanded while in place over the transport mechanisms. The
transport mechanisms can provide a bearing-type surface to allow
for even expansion while reducing the potential for deformation. In
at least one embodiment, the transport mechanisms can be positioned
on an expander with transport guides, such as recesses, grooves, or
channels, for maintaining a desired spacing between the transport
mechanisms. In at least one embodiment, the expander can cause the
medical device to expand without the expander itself expanding. In
other embodiments, the expander can be expanded with a separate
expanding mechanism that is inserted into the expander to expand
the expander, and thereby expand the transport mechanisms and the
medical device. Accordingly, a variety of methods, systems, and
devices can be used to expand a medical device over longitudinally
oriented transport mechanisms, as will be discussed in more detail
below.
[0037] Reference will now be made to figures wherein like
structures will be provided with like reference designations. It is
understood that the drawings are diagrammatic and schematic
representations of exemplary embodiments of the invention, and are
not limiting of the present invention nor are they necessarily
drawn to scale.
[0038] FIG. 1 illustrates one embodiment of a system 100 for
expanding a medical device 110, such as a vascular device,
extending between a proximal end 112 and a spaced apart distal end
114. For ease of reference, a coordinate system will be referenced
in discussing system 100 (and the other systems discussed herein)
that includes a central axis C. Elements that are generally
parallel to central axis C will also be described as being
longitudinally oriented relative to central axis C while elements
that are generally transverse or perpendicular to central axis C
will be described as being radially oriented relative to central
axis C. In addition, the direction indicated by arrow 102 that is
parallel to central axis C will be referred to as the "proximal"
direction and the opposite direction will be referred to as the
"distal" direction. As such, movement in the proximal and distal
directions may be referred to as proximal and distal movement,
respectively.
[0039] In the illustrated embodiment, system 100 includes a
longitudinally oriented transport assembly in the form of a wire
array 120 having a plurality of individual transport mechanisms in
the form of wires 125 extending from a proximal end 126 to a distal
end 128. The number of wires can vary, as discussed below. The
wires can be made of metals or alloys, such as, but not limited to,
stainless steel, titanium, tantalum, tungsten, or alloys thereof,
nickle chromium (commonly known as nichrome) quartz, glass, glass
thread, polymers, or other high temperature material. Using wires
that can sustain high temperatures allows the medical device to be
heat treated (e.g., such as shape set using heat).
[0040] Although reference has been made to the use of wires and a
wire array, respectively, as the transport mechanisms and transport
assembly, one skilled in the art will appreciate that other
structures can also perform the functions of the transport
mechanisms and transport assembly. For example, and not by way of
limitation, other structures that can be used as the transport
mechanisms include strips, ribbons, yarns, threads, rods, or other
structures having the desired strength and rigidity, with
associated flexibility and resiliency to allow the structure to i)
provide a bearing-type surface for the medical device, ii) separate
at least a portion of the medical device from an expander or
expander mechanism during a manufacturing process, or iii)
otherwise perform other functions described or identified from the
description contained herein.
[0041] Wire array 120 is configured to receive medical device 110
thereon. System 100 also includes an expander 130, which can also
be described as a mandrel in the present embodiment. Expander 130
includes features that are configured to guide and/or partially
receive wire array 120.
[0042] For example, expander 130 illustrated in FIG. 2 generally
includes a body 200 having an outer surface 202 extending between a
proximal end face 204 on a proximal end 200A and a distal end 200B.
Body 200 can have a first diameter D.sub.A at proximal end 200A
that transitions to a second diameter D.sub.B that is greater than
the first diameter D.sub.A. In at least one embodiment, the second
diameter D.sub.B is at distal end 200B, though it will be
appreciated that the first diameter D.sub.A can transition to any
number of varying diameters at any number of locations between
proximal end 200A and distal end 200B.
[0043] In at least one embodiment, proximal end 200A and distal end
200B can each be as long or longer than medical device 110 (FIG. 1)
which system 100 (FIG. 1) is configured to expand. Such a
configuration can provide support for medical device 110 both
before and after medical device 110 is expanded as the diameter of
the portion of body 200 is increased. As the diameter of body 200
increases, body 200 continues to support wire array 120 which, in
turn, supports and provides a bearing-type surface for medical
device 110 (FIG. 1).
[0044] In the illustrated embodiment, body 200 transitions from the
first diameter D.sub.A to the second diameter D.sub.B at a
transition portion 200C. The depicted transition portion 200C
includes a ramped profile with a shoulder portion 205A associated
with proximal end 200A and a shoulder portion 205B associated with
distal end 200B. As such, transition portion 200C is substantially
frustoconically shaped in the depicted embodiment. It will be
appreciated, however, that other shapes are possible and that
transition portion 200C and shoulder portions 205A, 205B can have
any profile, and that any number of transition portions can be
provided.
[0045] In the depicted embodiment, the diameters of proximal and
distal ends 200A and 200B remain substantially unchanged along the
lengths of the respective end. That is, the diameter D.sub.A of
proximal end 200A remains substantially unchanged along the entire
length of proximal end 200A and the diameter D.sub.B of distal end
200B remains substantially unchanged along the entire length of
distal end 200B. However, if desired the diameter of proximal end
200A and/or the diameter of distal end 200B can instead vary along
the length of the corresponding end. For example, in one
embodiment, the diameter D.sub.B of distal end 200B progressively
increases as distal end 200B extends distally away from transition
portion 200C. In that embodiment, distal end 200B can have a ramped
profile similar to transition portion 200C. That embodiment can be
used to expand and heat set medical devices into a tapered heat set
configuration, such as, e.g., a tapered stent.
[0046] To correspond to wires 125, transport guides in the form of
wire guides 210 are defined on outer surface 202 of body 200 and
are distributed circumferentially about outer surface 202. Each
wire guide 210 extends longitudinally between end face 204 at
proximal end 200A, through transition portion 200C, and toward
distal end 200B. Wire guides 210 are configured to receive wires
125 of wire array 120 (FIG. 1). Such a configuration can constrain
wires 125 and keep them in a particular spatial orientation during
expansion of medical device 110. As such, the number of wire guides
210 should be equal to or greater than the number of wires 125 in
wire array 120. Ideally, the number of wire guides 210 equals the
number of wires 125.
[0047] Further, wire guides 210 can control friction between
medical device 110 and body 200 of the expander 130 during
expansion. For instance, changing the depth of wire guides 210
changes the height of wires 125 extending above surface 202 of body
200 to function and provide a bearing-type surface upon which at
least a portion of medical device 110 (FIG. 1) rests. With more of
each wire 125 exposed above surface 202, there is a decreased
likelihood that a portion of medical device 110 (FIG. 1)
frictionally engages body 200 upon axial movement of medical device
110 (FIG. 1) relative to body 200, or vice versa.
[0048] This limits the possibility of unwanted frictional contact
that could damage medical device 110 (FIG. 1) due to the
application of undesired torque, tension, expansion, and/or
compression to medical device 110 (FIG. 1) during the manufacturing
processes. In one configuration, therefore, wires 125 extend
radially outward from wire guides 210 sufficiently to prevent
contact between medical device 110 (FIG. 1) and the body 200. In
another configuration, wires 125 extend radially outward from wire
guides 210 sufficiently to prevent contact that would be sufficient
to damage medical device 110 (FIG. 1).
[0049] Transition portion 200C may have a tapered configuration
with a slope that allows expansion of medical device 110 to proceed
smoothly without unduly expanding a portion of medical device 110
relative to an adjacent portion of the medical device. Further, the
cross sectional shape of expander member 130 is typically similar
in all portions and thus the expansion of medical device 110 can be
to the same shape. For example, as shown in FIGS. 3A-3C, the cross
sectional shape of expander 130 in the depicted embodiment is
generally circular for each portion.
[0050] In alternative embodiments, the portions of expander 130 may
have different cross sectional shapes. This may allow, for example,
a medical device to be expanded from a circular cross section to
some other cross-sectional shape, such as, but not limited to, an
oval cross section, a polygonal cross section, or some other
regular or irregular geometric cross section. In addition, the
expander 130 can be shaped to accommodate the shape of an
anticipated deployment site. As a result, the final cross sectional
area of the medical device can vary. Also, the cross sectional
shape can vary as well.
[0051] Expander 130 can be fabricated from a variety of different
materials. For instance, expander 130 can be made from metals,
alloys, plastics, polymers, composites, ceramics, or any
combinations thereof. Expander 130 can alternatively be made of
other materials, as desired, based upon the particular medical
device being formed and the temperatures and/or pressures that
expander 130 is to withstand during the manufacture of the medical
device. In another configuration, expander 130 can be plated with
another material, such as, but not limited to, a chromium coating
or a diamond chromium coating, such as Armoloy.RTM., or a
nickel-phosphor alloy, such as NEDOX.RTM. 10K.TM.-1 or MAGNAPLATE
HMF, both manufactured by General Magnaplate Corporation. In one
embodiment, expander 130 can be fabricated from stainless steel or
a nickel titanium alloy, such as nitinol. In various embodiments,
the materials forming expander 130 can withstand a temperature from
about 250.degree. C. to about 600.degree. C., from about
250.degree. C. to about 650.degree. C., from about 300.degree. C.
to about 600.degree. C., from about 300.degree. C. to about
550.degree. C., from about 450.degree. C. to about 600.degree. C.,
from about 450.degree. C. to about 550.degree. C., or some other
range known to one skilled in the art in view of the teachings
contained herein.
[0052] FIG. 3A illustrates a cross-sectional view of proximal end
200A of expander 130 taken along section line 3A-3A of FIG. 2, FIG.
3B illustrates a cross-sectional view of distal end 200B taken
along section line 3B-3B, and FIG. 3C illustrates a cross-sectional
view of transition portion 200C taken along section line 3C-3C of
FIG. 2.
[0053] As shown particularly in FIG. 3A, proximal end 200A has a
generally circular or tubular cross sectional profile with the
first diameter D.sub.A. A guide opening or lumen 320 can
longitudinally extend into expander 130 from proximal end face 204,
if desired, and extend at least partially through expander 130, as
shown in FIGS. 3A-3C, although this is not required. In at least
one embodiment, guide opening 320 is centered on central axis C of
the body. Guide opening 320 can be used to guide wire array 120 and
medical device 110 onto the expander 130, as discussed below.
[0054] Wire guides 210 are positioned circumferentially about outer
surface 202 of body 200 (FIG. 2) and about proximal end 200A. In at
least one embodiment, each wire guide 210 can include a profile
that is partially circular, although various other profiles are
possible which receive wire 125.
[0055] Wire guides 210 are separated by angular separations 310
relative to central axis C. In the depicted embodiment, the angular
separations between the individual wire guides are substantially
equal, but this is not required. In other embodiments, the angular
separations can be different and wire guides 210 can be arranged in
a manner that is partially symmetrical or asymmetrical.
[0056] Each wire guide 210 can have any desired depth and dimension
and shape. In at least one embodiment, each wire guide 210 can
include a recess, groove, or channel having a generally
hemispherical inner portion. In other embodiments, the recess,
groove, or channel can be square shaped, angular, and the like.
Further, each recess, groove, or channel can have an inner portion
having a central angle of any size. Finally, the arrangement of the
wire guides provides, in one embodiment, a spline-type geometry to
keep the wires uniformly spaced circumferentially around the
expansion member. For instance, adjacently positioned wire guides
210 can be separated by a portion of body 200 or a spline 212 as
illustrated in FIG. 3A.
[0057] For ease of reference, positions of wire guides 210 relative
to other elements will be described with reference to the central
portion of the recesses defining wire guides 210. It will be
appreciated that other reference points can be used to describe
relative positions. In at least one embodiment, wire guides 210 are
positioned about the perimeter of proximal end 200A such that
angular separations 310 are substantially equal.
[0058] As illustrated in FIG. 3B, distal end 200B of body 200 (FIG.
2) also has a generally circular or tubular cross sectional
profile, but with the second diameter D.sub.B. As previously
discussed, the second diameter D.sub.B is greater than the first
diameter D.sub.A. Further, at or near distal end 200B, wire guides
210 can be separated by angular separations 312. In at least one
embodiment, angular separations 312 can be substantially equal with
respect to distal end 200B. Further, in at least one embodiment
angular separations 312 can be substantially equal to angular
separations 310 between wire guides 210 on proximal end 200A (FIG.
3A). Accordingly, angular separations 312 can remain substantially
constant while the diameter of body 200 (FIG. 2) increases.
[0059] The diameter of body 200 increases from the first diameter
D.sub.A to the second diameter D.sub.B through transition portion
200C. As illustrated in FIG. 3C, transition portion 200C provides
an angular separation 314 that is substantially similar to angular
separations 310, 312 respectively associated with proximal end 200A
(FIG. 3A) and distal end 200B (FIG. 3B) while increasing the
diameter of body 200 (FIG. 2). Such a configuration can allow wire
guides 210 to maintain wires 125 (FIG. 1) of wire array 120 (FIG.
1) evenly distributed, which can evenly distribute forces exerted
by the wires during an expansion process.
[0060] Although the above-described embodiment includes evenly
distributed wire guides 210, one skilled in the art will appreciate
that in other configurations wire guides 210 may be unevenly
distributed along all or a portion of the length of body 200. For
instance, in another embodiment, the angle of angular separation
310 of wire guides 210 at at least a portion of proximal end 200A
can be smaller than the angle of angular separation 312 at at least
a portion of distal end 200B. Similarly, in another embodiment, the
angle of angular separation 310 of wire guides 210 at at least a
portion of proximal end 200A can be greater than the angle of
angular separation 312 at at least a portion of distal end 200B. It
will be understood that various other combinations of angular
separations are also possible and known to those skilled in the art
in view of the teaching contained herein.
[0061] Various methods of operation will be discussed below. It
will be appreciated that when discussing movement of elements with
respect to each other, either element can move while the other is
stationary, or both elements can move. For example, if element A is
said to move distally toward element B, this means that i) element
A can move in the distal direction while element B remains
stationary, ii) element B can move in the proximal direction while
element A remains stationary, or iii) both elements can move toward
each other.
[0062] FIGS. 4A-4C illustrate one embodiment of a method of
uniformly expanding medical device 110 using an axial guide 400 to
move wire array 120 with respect to expander 130. Axial guide 400
extends between a proximal end 402 and a distal end 404 and is
sized to be insertable into guide opening 320 in expander 130. As
such, axial guide 400 can have a substantially uniform cross
sectional shape along its length, if desired.
[0063] As with the other method embodiments described herein, while
an exemplary order of steps will be described in expanding the
medical device, it will be appreciated that the steps may be
performed in different orders, that additional steps may be
included, and/or that steps may be omitted.
[0064] Before expanding a medical device, the medical device must
first be initially cut out or otherwise formed. For example, the
medical device can be laser cut from a tube having a diameter that
is approximately equal to the desired diameter of the compressed
(i.e., unexpanded) medical device. The tube can then be deburred to
clean any imperfections due to the cutting. Other initial forming
methods may also be used.
[0065] As shown in FIG. 4A, the expansion process can begin by
positioning wire array 120 over axial guide 400. Thereafter,
medical device 110, such as, e.g., a stent or scaffold as shown in
the depicted embodiment, can be positioned over wire array 120,
and, consequently, over axial guide 400. In one embodiment,
proximal end 126 of wire array 120 is attached or otherwise coupled
to axial guide 400. In another embodiment, axial guide 400 includes
a stop portion (not shown) that extends radially outward so that
the proximal end 126 of wire array 120 butts up against the stop
portion, thereby causing wire array 120 to move axially as axial
guide 400 moves. In another embodiment, wire array 120 is not
attached to axial guide 400 and is moved independent of axial guide
400.
[0066] Once wire array 120 and medical device 110 are in position
over axial guide 400 as shown in FIG. 4A, medical device 110 can
then be positioned over proximal end 200A of expander 130. To do
this, expander 130 can be positioned on axial guide 400 by way of
guide opening 320. That is, axial guide 400 can be received into
guide opening 320 of expander 130 at proximal end face 204 so that
wire array 120 and medical device 110 can be advanced along axial
guide 400 in the distal direction, denoted by arrow 406, toward
expander 130. In one embodiment, wire array 120 and medical device
110 are moved distally by distal movement of axial guide 400. In
another embodiment, a separate pushing mechanism can be used to
advance medical device 110 and/or wire array 120 distally (see,
e.g., advancement mechanism 932 in FIG. 9).
[0067] As wire array 120 and medical device 110 are distally
advanced, distal end 128 of wire array 120 arrives at proximal end
face 204 of proximal end 200A of expander 130. Thereafter, distal
ends 128 of at least some of wires 125 can be positioned on wire
guides 210 formed on proximal end 200A of expander 130. Wire array
120 and medical device 110 can then be advanced further distally so
that wires 125 slide distally along wire guides 210.
[0068] As shown in FIG. 4A, medical device 110 can be positioned
within a thermal chamber 410, such as an oven, a refrigerator, or
any other device or apparatus configured to regulate thermal
chamber 410 at one or more desired temperatures. The desired
temperature(s) is/are whatever temperature(s) facilitate expansion
and heat setting of the medical device. This can be affected by the
material of the medical device among other factors. Thermal chamber
410 can be configured to maintain medical device 102 at a same
predetermined temperature throughout preheating, expansion, and
heat setting of medical device 102 or to heat medical device 102 to
different predetermined temperatures for two or three of the steps.
In one embodiment, the thermal chamber can be configured to heat
medical device 110 to between about 450.degree. C. to about
600.degree. C. Of course, other temperature ranges can also be
used.
[0069] Thermal chamber 410 can have an axial length that is
substantially equal to or slightly longer than medical device 110.
As such, thermal chamber 410 can remain axially aligned with
respect to medical device 110 (i.e., thermal chamber 410 can move
proximally or distally with medical device 110) so that the medical
device remains positioned within thermal chamber 410 as medical
device 110 and expander 130 are moved with respect to each other.
For ease of reference, thermal chamber 410 will be described herein
as a heating device that heats medical device 110 and expander 130
and is illustrated schematically and in cross-section.
[0070] In at least one embodiment, axial guide 400 can be supported
by supports 420 that maintain axial guide 400 and/or wire array 120
radially aligned relative to thermal chamber 410. Supports 420 can
allow axial guide 400 to move proximally and distally along central
axis C, thereby allowing the elements that axial guide 400 is
supporting to be moved into desired positions within thermal
chamber 410.
[0071] Supports 420 can allow axial guide 400 to proximally and
distally move medical device 110, wire array 120, and/or expander
130 into and out of thermal chamber 410. If required, supports 420
can be moved radially away from axial guide and/or wire array 120
during axial movement of wire array 120 and/or medical device 110
to allow wire array 120 and/or medical device 110 to pass.
[0072] Once wire array 120 and medical device 110 are positioned in
thermal chamber 410, medical device 110 can be preheated by thermal
chamber 410 to a desired temperature.
[0073] Once medical device 110 is preheated to the desired
temperature, the distal advancement of wire array 120 and medical
device 110 can continue until medical device 110 becomes positioned
on proximal end 200A of expander 130, as illustrated in FIG. 4B.
The shape and configuration of wire guides 210 help retain wires
125 in position relative to expander 130. This configuration can
allow wire guides 210 to guide wires 125 as wires 125 move distally
over expander 130.
[0074] As shown in FIG. 4B, thermal chamber 410 can move distally
with medical device 110 so that thermal chamber 410 remains
longitudinally aligned with medical device 110 and can continue
heating medical device 110.
[0075] With medical device 110 preheated to the desired
temperature, wire array 120 and medical device 110 can be advanced
further distally by axial guide 400. As shown in FIG. 4C, as wire
array 120 and medical device 110 advance distally, increasingly
larger diameters of transition portion 200C of expander 130 urge
wires 125, which are positioned within wire guides 210, radially
outward. As wires 125 are urged radially outward, wires 125, in
turn, urge medical device 110 uniformly radially outward beginning
with distal end 114 of medical device 110.
[0076] Wires 125 act as a bearing-type surface that supports and
guides medical device 110 while maintaining a separation between
medical device 110 and expander 130. In this manner, wires 125 help
reduce frictional engagement between medical device 110 and
expander 130. As a result, the likelihood is reduced of medical
device damage from excessive stresses associated with induced
torque, tension, compression and/or expansion of the medical device
during manufacture
[0077] As medical device 110 passes distally through transition
portion 200C of expander 130, distal end 114 of medical device 110
becomes supported on distal end 200B of expander 130. As medical
device 110 continues to move distally, proximal end 112 of medical
device 110 is also uniformly expanded by the cooperation of
transition portion 200C, expander 130, and wires 125 until proximal
end 112 also becomes supported on distal end 200B of expander 130,
as shown in FIG. 4C.
[0078] At this point, medical device 110 is fully expanded to the
second diameter D.sub.B (FIG. 3B) and is supported at that diameter
on distal end 200B of expander 130. In the expanded configuration,
medical device 110 generally takes on the shape of distal end 200B.
For example, in the depicted embodiment, distal end 200B is
substantially cylindrical, thereby causing medical device 110 to
also have a substantially cylindrical shape in the expanded
configuration. Alternatively, if a tapered medical device is
desired, an expander can be used in which the diameter D.sub.B of
distal end 200B progressively increases as distal end 200B extends
distally away from transition portion 200C, as discussed above.
Because of the changing shape of distal end 200B, medical device
110 is caused to have a tapered shape in the expanded
configuration. Other expanded medical device shapes can also be
obtained by using expanders having distal ends with corresponding
shapes.
[0079] As shown in FIG. 4C, thermal chamber 410 can continue to
move distally with medical device 110 so that thermal chamber 410
remains longitudinally aligned with medical device 110 when medical
device 110 is expanded and can continue heating medical device 110.
As discussed above, during expansion of medical device 110, thermal
chamber 410 can maintain medical device 110 at the same
predetermined temperature as during preheating, or can cause
medical device to be heated to a different predetermined
temperature.
[0080] Medical device 110 can remain within thermal chamber 410
after the expansion process, if desired. To do so, thermal chamber
410 can remain axially aligned with medical device 110 when medical
device 110 is in the expanded configuration, as shown in FIG. 4C.
In one embodiment, the expanded medical device 110 can remain
within thermal chamber 410 for a predetermined period of time to
heat set medical device 110 in the expanded configuration. As
discussed above, during heat setting of medical device 110, thermal
chamber 410 can maintain medical device 110 at the same
predetermined temperature as during preheating and/or expansion or
can cause medical device to be heated to a different predetermined
heat setting temperature.
[0081] In at least one embodiment, while in position on expander
130, wires 125 may extend only slightly above outer surface 202 of
body 200. Such a configuration may cause medical device 110 to
contact outer surface 202 of expander 130 as well as wires 125
during the expansion process. Alternatively, wires 125 may extend
sufficiently above outer surface 202 of body 200 so that only wires
125 contact medical device 110 during expansion while wires 125 are
held in place by wire guides 210.
[0082] By substantially limiting contact of medical device 110 to
only wires 125, frictional forces can be reduced compared to those
generated through contact between medical device 110 and expander
130. This reduces the likelihood that medical device 110 will
frictionally bind with expander 130 during heat setting or become
damaged due to excessive torque, tension, expansion, and/or
compression.
[0083] Further, the interaction between wires 125 and expansion
member 130 can help ensure that expander 130 tracks a path that is
generally parallel to central axis C as expander 130 expands
medical device 110. Tracking a generally parallel path can in turn
help provide even stress distribution of the stresses induced by
the interaction of medical device 110 and expander 130. This even
stress distribution also reduces the likelihood of medical device
damage due to excessive torque, tension, expansion, and/or
compression.
[0084] Once the heating and expansion process is complete, medical
device 110 can be removed from heating chamber 410 and expander 130
and wire array 120. In one embodiment, medical device 110 can be
removed from heating chamber 410 by essentially reversing the
process discussed above. That is, axial guide 400 can be axially
moved in the opposite direction (i.e., proximally), thereby moving
wire array 120 and medical device 110 away from expander 130 until
wire array 120 and medical device 110 are separated from expander
130. In one embodiment, the distal end 128 of wire array 120 can
remain engaged with expander 130 after the expanded medical device
110 has become separated from expander 130.
[0085] As discussed above, in at least one embodiment, medical
device 110 can be expanded and heat set using the method discussed
above. In this embodiment, because of the heating and expansion
process, the medical device is unconstrained in the expanded
position. The medical device can then be constrained prior to
deployment.
[0086] FIGS. 8A-8C illustrate another embodiment of a method of
uniformly expanding (and heat setting, if desired) medical device
110 using a wire array. The method illustrated in FIGS. 8A-8C is
similar to the method discussed above with respect to FIGS. 4A-4C.
However, in the alternative method, a thermal chamber 800 is used
having a different configuration than thermal chamber 410.
Specifically, instead of having an axial length substantially equal
to or slightly longer than medical device 110, thermal chamber 800
has an axial length that is substantially the same as or slightly
longer or shorter than expander 130, as shown in FIGS. 8B and
8C.
[0087] As a result, thermal chamber 800 can remain axially aligned
with respect to expander 130 (i.e., thermal chamber 800 can remain
fixed with expander 130 or move proximally or distally with
expander 130) instead of axially moving with medical device 110.
This allows expander 130 and medical device 110 to both remain
positioned within thermal chamber 800 when medical device 110 is
mounted on expander 130, even as medical device 110 advances on
expander 130.
[0088] In a similar manner to the method discussed above, the
process can begin by positioning wire array 120 over axial guide
400, then positioning medical device 110 over wire array 120 and
advancing axial guide 400 distally toward expander 130, as shown in
FIG. 8A. In a similar manner to the method discussed above, wire
array 120 and medical device 110 can be advanced distally on
expander 130 to pre-heat and then expand and heat-set medical
device 110, as shown in FIGS. 8B and 8C. Similar to the method
discussed above, medical device 110 can remain within thermal
chamber 800 during the expansion process and for a predetermined
period of time thereafter, if desired, to heat set the expanded
medical device. To do this, however, thermal chamber 800 does not
need to move with medical device 110, but can remain axially
aligned with expander 130 by remaining stationary as medical device
110 moves distally.
[0089] Whether one uses the shorter thermal chamber 410 or the
longer thermal chamber 800 is generally a matter of design choice.
In some aspects, longer thermal chamber 800 may provide some
benefits over shorter thermal chamber 410. For example, when using
thermal chamber 800, expander 130 can be maintained within thermal
chamber 800 during the entire expansion process. As a result, once
expander 130 is heated to a desired temperature by thermal chamber
800, the temperature of expander 130 can be maintained at a
substantially constant value, such as a predetermined heat setting
value of medical device 110, even between uses. Because of this, no
time is lost waiting for expander 130 to subsequently heat up each
time a different medical device 110 is to be expanded and heat
set.
[0090] In contrast, when using shorter thermal chamber 410,
different portions of expander 130 may cool and require a finite
amount of time to become re-heated each time a medical device needs
to be expanded and heat set due to the axial movement of thermal
chamber 410 with medical device 110. This can result in delays when
expanding and heat setting multiple medical devices. However,
thermal chamber 410 may require less energy than thermal chamber
810 due to the shorter length. It is appreciated that other lengths
can also be used for the thermal chamber, if desired.
[0091] FIG. 9 illustrates another embodiment of a system 900 for
uniformly expanding (and heat setting, if desired) medical device
110. Similar to system 100, system 900 includes a wire array 902
having a plurality of wires 904 configured to be advanced onto an
expander 906. However, instead of using a separate axial guide to
advance the wires, system 900 combines wire array 902 and an axial
guide 916 along with an advancement guide 908, to form an
integrated advancement guide assembly 910. System 900 also includes
an advancement mechanism 932 to aid in advancing medical device 110
over advancement guide assembly 910 and onto expander 906.
[0092] As shown in FIGS. 9 and 10, advancement guide 908 comprises
a rod or the like that extends distally to a distal facing end face
920. Similar to axial guide 400, axial guide 916 is sized to be
insertable into a guide opening within expander 906. Axial guide
916 extends distally from end face 920 of advancement guide 908 and
has a smaller cross sectional area than advancement guide 908, as
particularly shown in FIG. 10. Also as shown in FIG. 10, axial
guide 916 generally extends from the center of end face 920,
although this is not required. Axial guide 916 can be integrally
formed with advancement guide 908 or rigidly attached thereto, such
as by welding, adhesive, or any other attaching method known in the
art. In some embodiments, axial guide 916 can be omitted, if
desired.
[0093] As shown in FIG. 9, wire array 902 extends between a
proximal end 922, positioned at end face 920, and a distal end 924.
At proximal end 922, each wire 904 is welded or otherwise attached
to advancement guide 908 at end face 920 to form advancement guide
assembly 910. Alternatively, each wire 904 can be integrally formed
with advancement guide 908 at end face 920. The number of wires in
wire array 902 can vary. Although sixteen wires 904 are shown in
FIG. 10, other numbers of wires can alternatively be used. For
example, eight, ten, twelve, or any other number of wires can be
used. However, for each wire, a corresponding wire guide should be
found in the expander to receive the wire.
[0094] As shown in FIG. 10, wires 904 of wire array 902 can be
positioned radially about end face 920 so that the radially
outer-most edge of each wire 904 is axially aligned with the outer
surface of advancement guide 908 at end face 920. That is, the
diameter of wire array 902, taken at the radially outermost portion
of wires 904 can be substantially equal to the diameter of
advancement guide 908. By doing so, a smooth transition can be
formed between advancement guide 908 and wire array 902, allowing
easy passage between the two for medical device 110. Wires 904 can
also be configured to radially encircle axial guide 916, if axial
guide 916 is used. As such, wires 904 can longitudinally align with
wire guides 210 positioned on expander 906.
[0095] In the embodiment depicted in FIGS. 9 and 10, axial guide
916 is longitudinally longer than wire array 902 and thus extends
beyond distal end 924 of wire array 902. In other embodiments, wire
array 902 is longer than axial guide 916 and thus extends beyond
axial guide 916. In still other embodiments, axial guide 916 is not
included in advancement guide assembly 910. In one embodiment, the
axial guide projects from expander 906 to be received by
advancement guide assembly 910.
[0096] Advancement mechanism 932 can be used to advance medical
device 110 over advancement guide 908 and wire array 902 of
advancement guide assembly 910 and onto expander 906. As such,
advancement mechanism 932 can be substantially tubular, with an
inner diameter slightly greater than the diameter of advancement
guide 908 and wire array 902 such that advancement mechanism 932
can snugly fit onto and slide along advancement guide assembly 910.
The inner diameter of advancement mechanism 932 is also less than
the outer diameter of medical device 110 such that a distal end
face 934 of advancement mechanism 932 can contact proximal end 112
of medical device 110 to advance medical device 110 distally.
[0097] As shown in FIG. 9, expander 906 is similar to expander 130,
except that proximal end 200A of expander 130 is omitted from
expander 906. That is, expander 930 includes only transition
portion 200C and distal end 200B. As such, a proximal end face 926
is positioned at the proximal end of transition portion 200C.
Proximal end face 926 is substantially similar in structure and
size to proximal end face 204 discussed above and also includes the
opening to guide opening 320 that extends into expander 906.
Because expander 906 includes transition portion 200C and distal
end 200B, expander 906 also includes wire guides 210 formed
thereon. Wire guides 210 terminate at proximal end face 926.
[0098] FIGS. 11A-11B illustrate one embodiment of a method of
uniformly expanding (and heat setting, if desired) medical device
110 using advancement guide assembly 910. Similar to the method
illustrated in FIGS. 8A-8C, a thermal chamber 1000 is used that has
an axial length that is substantially the same as or slightly
longer or shorter than expander 906, as shown in FIG. 11B, and
remains axially aligned with expander 906 during the expansion
process. However, because expander 906 is missing proximal end
200A, thermal chamber 1000 can be substantially axially shorter
than thermal chamber 800.
[0099] Thermal chamber 1000 can be longer or shorter, if desired.
For example, thermal chamber 1000 can extend proximally beyond
expander 906 (as shown by dashed lines 1000' in FIG. 11A) to allow
medical device 110 to be pre-heated before being advanced onto
expander 906.
[0100] The process can begin by positioning medical device 110 over
wire array 902 and advancing advancement guide assembly 910
distally toward expander 906 so that axial guide 916 aligns with
guide opening 320 in end face 926 of transition portion 200C, as
shown in FIG. 11A. To position medical device 110 over wire array
902, advancement mechanism 932 can be used. Medical device 110 and
advancement mechanism 932 are first positioned onto the proximal
end of advancement guide 908. Then, advancement mechanism 932 is
advanced distally along advancement guide 908, causing distal end
face 934 to contact proximal end 112 of medical device 110 and
thereby push medical device 110 distally along advancement guide
908 and onto wires 904 of wiring guide 902. Medical device 110 can
be positioned on advancement guide assembly 910 before or after
axial guide 916 has been aligned with guide opening 320. If axial
guide 916 is not used or is shorter than wiring guide 902,
advancement guide assembly 910 can be positioned by aligning wires
904 with wire guides 210 on expander 906.
[0101] If desired, axial guide 916 and guide opening 320 can be
configured to require rotational alignment therebetween prior to
insertion of axial guide 916 so as to better align wires 904 with
wire guides 210. In one embodiment, axial guide 916 and guide
opening 320 can both have matching non-circular cross sectional
shapes. For example, axial guide 916 and guide opening 320 can each
have an oval cross section, a polygonal cross section, or some
other regular or irregular geometric cross section.
[0102] In another embodiment, shown in FIG. 12A, a key, such as
radial protrusion 928 can be formed on distal end 914 of axial
guide 916 and a mating key, such as notch 930, can be formed on
guide opening 320 of expander 906 so that advancement guide 908 can
only be inserted into guide opening 320 when the mating keys are
rotationally aligned.
[0103] By requiring rotational alignment before axial guide 916 can
be inserted into guide opening 320, wires 904 can be caused to be
aligned with wire guides 210 before wires 904 are advanced, thereby
avoiding potential wire advancement issues. It is appreciated that
other devices and methods for rotational alignment of advancement
guide assembly 910 and expander 906 can alternatively be used.
[0104] For example, an external alignment mechanism can be used to
ensure that advancement guide assembly 910 and expander 906 are
rotationally aligned. In one embodiment, advancement guide 908
and/or expander 906 can include one or more alignment engagers
which are engaged by corresponding external alignment devices to
align the two devices. Each external alignment device can comprise
a structure that mates with the alignment engager that is used and
that, when mated, can cause the advancement guide 908 and expander
906 to be rotationally aligned and secured with respect to each
other.
[0105] For example, as shown in the cross sectional view of FIG.
12B, advancement guide 908 can have a pair of flat spots 940 on
either side thereof. A pair of clamp arms 942 can be positioned on
both sides of advancement guide 908 so as to be aligned with flat
spots 940. Each clamp arm 942 can have a clamping surface 944 that
includes a flat section 946 corresponding to flat spot 940. As
such, when each clamp arm 942 is brought toward each other, as
indicated by arrows 948, flat sections 946 can press against flat
spots 940 to rotationally align advancement guide 908. Other
alignment engagers can be used, such as a bore, a channel, a
flange, or any other engager that can be engaged by corresponding
external alignment devices.
[0106] Returning to FIG. 11A, advancement guide assembly 910 can be
further advanced to cause axial guide 916 to be received within
guide opening 320 and distal ends 924 of wires 904 to be received
on wire guides 210 of transition portion 200C of expander 906.
Further distal advancement of advancement guide assembly 910 causes
axial guide 916 to continue through guide opening 320 and wires 904
to slide distally along wire guides 210 until medical device 110
becomes positioned adjacent the proximal end 926 of expander 906.
If thermal chamber 1000 extends proximally beyond expander 906,
such as shown in dashed lines 1000', medical device 110 can remain
positioned adjacent the proximal end 926 of expander 906 for a
pre-determined period of time to be pre-heated by thermal chamber
1000.
[0107] Further advancement of advancement guide assembly 910 can
cause wire array 902 and medical device 110 to be advanced distally
on expander 906 to uniformly expand and heat-set medical device 110
in a similar manner to the methods discussed above. That is,
further distal advancement of advancement guide assembly 910 causes
wires 904 of wire array 902 to advance distally along wire guides
210 in transition portion 200C and distal end 200B. This causes
medical device 110 to also be advanced distally on expansion
member/expander 902, and to expand as medical device 110 passes
over transition portion 200C to the final expanded configuration
when positioned on distal end 200B, as shown in FIG. 11B.
[0108] By integrating the wire array, axial guide, and advancement
guide into a single advancement guide assembly, several advantages
can be realized. For example, because the wire array, axial guide,
and advancement guide are all rigidly attached, there is no
possibility of the wires of the wire array binding within the wire
guides or otherwise not advancing when the advancement guide is
advanced. Furthermore, because the wires are rigidly attached to
the advancement guide, the advancement guide assembly can be
configured so that the wires will better align with the wire guides
on the expansion member/expander when in use. For example, as
discussed above, mating keys can be formed on the axial guide and
the guide opening of the expansion member/expander to force the
wires to be axially aligned with the wire guides before the wires
can be advanced. Other advantages may also be realized.
[0109] In the methods discussed above, medical device 110 and wire
arrays 120 and 902 are described as moving distally to engage
expansion member/expanders 130 and 906 and to expand medical device
110. However, it is appreciated that this movement is relative. As
such, the axial movement can be accomplished by any of the
following: i) the medical device and wire array can move distally
while the expansion member/expander remains axially stationary, ii)
the expansion member/expander can move proximally while the medical
device and wire array remain axially stationary, or iii) the
expansion member/expander, the medical device, and wire array can
all move axially, the medical device and wire array moving in the
opposite axial direction as the expansion member/expander.
[0110] In one embodiment, medical device 110 can include a material
made from any of a variety of known suitable materials, such as a
shape-memory material ("SMM") or superelastic material. For
example, the SMM can be shaped in a manner that allows for
restriction to induce a substantially tubular, linear orientation
while within a delivery shaft (e.g., delivery catheter or
encircling an expandable member), but can automatically retain the
memory shape of the medical device once extended from the delivery
shaft. SMMs have a shape-memory effect in which they can be made to
remember a particular shape. Once a shape has been remembered, the
SMM may be bent out of shape or deformed and then returned to its
original shape by unloading from strain or heating. SMMs can be
shape-memory alloys ("SMA") or superelastic metals comprised of
metal alloys, or shape-memory plastics ("SMP") comprised of
polymers.
[0111] An SMA can have any non-characteristic initial shape that
can then be configured into a memory shape by heating the SMA and
conforming the SMA into the desired memory shape. After the SMA is
cooled, the desired memory shape can be retained. This allows the
SMA to be bent, straightened, compacted, and placed into various
contortions by the application of requisite forces; however, after
the forces are released, the SMA can be capable of returning to the
memory shape. Examples of SMAs that can be used include, but are
not limited to: copper-zinc-aluminum; copper-aluminum-nickel;
nickel-titanium ("NiTi") alloys known as nitinol; and
cobalt-chromium-nickel alloys or cobalt-chromium-nickel-molybdenum
alloys known as elgiloy. The nitinol and elgiloy alloys can be more
expensive, but have superior mechanical characteristics in
comparison with the copper-based SMAs. The temperatures at which
the SMA changes its crystallographic structure are characteristic
of the alloy, and can be tuned by varying the elemental ratios.
[0112] For example, the primary material of the medical device 110
can be of a NiTi alloy that forms superelastic nitinol. Nitinol
materials can be trained to remember a certain shape, straightened
in a shaft, catheter, or other tube, and then released from the
catheter or tube to return to its trained shape. Also, additional
materials can be added to the nitinol depending on the desired
characteristic.
[0113] An SMP is a shape-memory polymer or plastic that can be
fashioned into medical device 110 in accordance with the present
invention. When an SMP encounters a temperature above the lowest
melting point of the individual polymers, the blend makes a
transition to a rubbery state. The elastic modulus can change more
than two orders of magnitude across the transition temperature
("T.sub.tr"). As such, an SMP can be formed into a desired shape of
medical device 110 by heating the SMP above the T.sub.tr, fixing
the SMP into the new shape, and cooling the material below
T.sub.tr. The SMP can then be arranged into a temporary shape by
force and then resume the memory shape after heating and following
removal of the force. Examples of SMPs that can be used include,
but are not limited to: biodegradable polymers, such as
oligo(.epsilon.-caprolactone)diol, oligo(.rho.-dioxanone)diol, and
non-biodegradable polymers such as, polynorborene, polyisoprene,
styrene butadiene, polyurethane-based materials, vinyl
acetate-polyester-based compounds, and others yet to be determined.
As such, any SMP can be used in accordance with the present
invention.
[0114] FIGS. 5A-5C illustrate one embodiment of a method for
deploying a medical device that has been expanded using any of the
methods and devices discussed herein. FIG. 5A illustrates medical
device 110 positioned within a deployment device 500 that can
include an outer housing 510 and an inner portion 520 positioned
within outer housing 510. Inner portion 520 can be operatively
associated with an actuation assembly (not shown) to advance inner
portion 520 relative to outer housing 510. In at least one
embodiment, the deployment method begins by positioning medical
device 110 within outer housing 510. Medical device 110 can be
positioned within outer housing 510 in any suitable manner, such as
through the use of a crimping device or other device that moves
medical device 110 from the expanded state to the pre-deployed
state shown in FIG. 5A.
[0115] After medical device 110 is positioned within outer housing
510, a distal end 512 of outer housing 510 can be positioned at a
deployment site 530, as shown in FIG. 5B. With the outer housing
510 in position at the deployment site 530, inner portion 520 can
be advanced distally relative to outer housing 510 to urge medical
device 110 from distal end 512 of outer housing 510.
[0116] In alternative embodiments, medical device 110 can be
constrained by a thin housing or sheath. Instead of urging the
medical device from within outer housing 510, the thin housing or
sheath can be pulled from medical device 110. At the same time,
deployment device 500 can be withdrawn and medical device 110 can
expand as the thin housing or sheath is removed.
[0117] Deployment of medical device 110 from the housing, whether
using outer housing 510 or a thin housing, can be accomplished
through one or more of: advancing a portion of deployment device
500 (e.g., inner portion 520), withdrawing a portion of deployment
device 500 (e.g., outer housing 510), and advancing a portion of
medical device 100, whether simultaneously or otherwise. One of
skill in the art can appreciate that other known deployment devices
and configurations can be used to deploy medical device 110.
[0118] In at least one embodiment, when medical device 110 is urged
from distal end 512 of deployment device 500, medical device 110 is
no longer constrained and can expand towards its expanded state, as
illustrated in FIG. 5C. In this manner, medical device 110 can be
deployed at deployment site 530.
[0119] As previously discussed, the method for forming medical
device 110 can reduce localized friction or other factors to
provide uniform expansion of medical device 110. Uniform expansion
of medical device 110 in turn can allow medical device 110 to be
deployed in the intended manner.
[0120] While various configurations have been described that
include expanders that are self expanding, it will be appreciated
that expanders can also be used that require separate expansion
mechanisms to become expanded.
[0121] For example, FIG. 6A illustrates an expansion system 600 for
expanding medical device 110 that includes an expansion mechanism
610 and an expander 620 positionable upon expansion mechanism 610.
The expander 620 can be configured to receive and support a wire
array 120', the cooperation of wire array 120' and expander 620
being usable to expand medical device 110. For simplicity, a
portion of expansion mechanism 610 is illustrated as being received
within expander 620 and a number of wires 125' of wire array 120'
have been omitted in FIG. 6A.
[0122] Expansion mechanism 610, illustrated in FIG. 6A, generally
includes a body 612 having a proximal end 616 and a distal end 618.
Body 612 can have a first diameter D.sub.A at proximal end 616 that
transitions to a second diameter D.sub.B that is greater than first
diameter D.sub.A. In at least one embodiment, the second diameter
D.sub.B is at distal end 618, though it will be appreciated that
the first diameter D.sub.A can transition to any number of varying
diameters at any number of locations between proximal end 616 and
distal end 618.
[0123] In the illustrated embodiment, body 612 transitions from the
first diameter D.sub.A to the second diameter D.sub.B at a
transition portion 612C. Transition portion 612C can include a
tapered or ramped profile with a shoulder portion 614A associated
with proximal end 616 and a shoulder portion 614B associated with
distal end 618. It will be appreciated that transition portion 612C
and shoulder portions 614A, 614B can have any profile and that any
number of transition portions can be provided. Expansion mechanism
610, expander 620, and medical device 110 will be described with
common central axis C.
[0124] Expander 620 can include a number of segmented portions 622,
illustrated in FIG. 6B, separated by slots 624. Segmented portions
622 are configured to interface with the inside diameter of medical
device 110, illustrated in phantom in FIG. 6A. In at least one
embodiment, segmented portions 622 have wire guides 210' defined
therein that are configured to at least receive a wire array 120'.
Segmented portions 622 are configured to interface with the
expansion mechanism 610 and to outwardly move as the diameters of
the expansion mechanism 610 increase. Wire guides 210' are defined
in segmented portions 622 and are aligned generally parallel to
central axis C.
[0125] As previously discussed, segmented portions 622 can be
supported by expansion mechanism 610. In particular, FIG. 6B
illustrates segmented portions 622 positioned over proximal end 616
of expansion mechanism 610. In this position, segmented portions
622 are separated by approximately the distance D.sub.A. Expansion
mechanism 610 can be advanced axially relative to expander 620 to
move first transition portion 612C and then distal end 618 into
engagement with expander 620. This is similar to the axial motion
of body 200 relative to medical device 110 in FIGS. 4A-4C.
[0126] As expander 620 moves into engagement with transition
portion 612C and distal end 618, segmented portions 622 and wires
125' move radially outward, in the direction of the arrows
illustrated in FIG. 6B, resulting in a separation of approximately
D.sub.B, as illustrated in phantom in FIG. 6B. The radially outward
movement of segment portions 622 and wires 125' uniformly expands
medical device 110 in a similar manner as described above. The
expanded medical device 110 can then be deployed by positioning the
medical device in a deployment device as described above.
[0127] Generally, expander 620 and/or the expansion mechanism 610
can be fabricated from a variety of different materials. By way of
example, expander 620 and/or expansion mechanism 610 can be made
from metals, alloys, plastics, polymers, composites, ceramics,
quartz, glass, combinations thereof, or other materials, as
desired, based upon the particular medical device being formed and
the temperatures and/or pressures that expander 620 and/or
expansion mechanism 610 are to withstand during the manufacture of
the medical device.
[0128] In one embodiment, expander 620 and/or expansion mechanism
610 can be fabricated from stainless steel or nitinol. In another
embodiment, the materials can withstand a temperature from about
250.degree. C. to about 600.degree. C., from about 250.degree. C.
to about 650.degree. C., from about 300.degree. C. to about
600.degree. C., from about 300.degree. C. to about 550.degree. C.,
from about 450.degree. C. to about 600.degree. C., or some other
range known to one skilled in the art in view of the teaching
contained herein.
[0129] FIGS. 7A-7B illustrate another embodiment of an expander
700. Expander 700 can include a rolled configuration in which
expander 700 includes a first end 704, a second end 706 and a
central portion 708. Wire guides 210'' can be formed in expander
700 between first end 704 and second end 706 and can receive wires
125''. In such a configuration, first end 704 and second end 706
are separated by at least one angular separation and central
portion 708 is curved to define a central lumen 702. In such a
configuration angular separation between first end 704 and second
end 706 can be increased. In particular, overlap between first end
704 and second end 706 can be described as negative angular
separation while a gap between first end 704 and second end 706 can
be described as positive angular separation.
[0130] Accordingly, a negative angular separation A.sub.A is shown
in FIG. 7A in which first end 704 and second end 706 overlap. The
angular separation A.sub.A shown in FIG. 7A can be established when
expander 700 is in engagement with a proximal end of an expansion
mechanism, such as expansion mechanism 610 described above, upon
insertion of expansion mechanism 610 within central lumen 702.
Axial movement of expansion mechanism 610 can expand expander 700
to change the angular separation between first end 704 and second
end 706 to a positive angular separation A.sub.B shown in FIG. 7B.
A wire array 120'', similar to the other wire arrays described
herein, can be positioned in wire guides 210'' such that as
expander 700 is expanded, wire array 120'' and expander 700 are
also expanded to allow expansion of a medical device as described
above.
[0131] Generally, expander 700 can be fabricated from a variety of
different materials. By way of example, expander 700 can be made
from metals, alloys, plastics, polymers, composites, combinations
thereof, or other materials, as desired, based upon the particular
medical device being formed and the temperatures and/or pressures
that expander 700 is to withstand during medical device
manufacture. In one embodiment, expander 700 can be fabricated from
stainless steel or nitinol. In one embodiment, the materials can
withstand a temperature from about 300.degree. C. to about
600.degree. C.
[0132] While one type of expansion mechanism has been provided for
expanding expanders 620 and 700, it will be appreciated that other
types of expansion mechanisms can be used in a process in which a
medical device is expanded with a wire array.
[0133] As noted above, although the embodiments discussed herein
employ wires as the transport mechanisms, it is appreciated that
other types of transport mechanisms can alternatively be used
according to the present invention. For example, strips, ribbons,
yarns, threads, rods, or other structures can be used as the
transport mechanisms, as long as those structures have the desired
strength and rigidity, with associated flexibility and resiliency
to allow the structure to i) provide a bearing-type surface for the
medical device, ii) separate at least a portion of the medical
device from an expander or expander mechanism during a
manufacturing process, or iii) otherwise perform other functions
described or identified from the description contained herein.
[0134] The present invention may be embodied in other specific
forms without departing from its spirit or essential
characteristics. For example, slight modifications of the mandrel
are contemplated and possible and still be within the spirit of the
present invention and the scope of the claims. The scope of the
invention is, therefore, indicated by the appended claims rather
than by the foregoing description.
* * * * *