U.S. patent application number 09/862068 was filed with the patent office on 2001-10-18 for entraining biological calculi.
Invention is credited to Dretler, Stephen P., Geragotelis, Paul D..
Application Number | 20010031971 09/862068 |
Document ID | / |
Family ID | 23364376 |
Filed Date | 2001-10-18 |
United States Patent
Application |
20010031971 |
Kind Code |
A1 |
Dretler, Stephen P. ; et
al. |
October 18, 2001 |
Entraining biological calculi
Abstract
A medical device for entraining biological stones during medical
procedures for the fragmentation of urinary, biliary, pancreatic,
and other biological calculi and safely removing them from the
body. The device includes a guidewire having a
longitudinally-extending wire core. A portion of the wire core more
adjacent the distal end thereof than the proximal end thereof is
wound to form a helical coil which tapers in diameter from a larger
diameter end at the proximal end thereof to a smaller diameter end
at the distal end thereof. At least a portion of the core forming
said helical coil is made of a super-elastic deformable material
which collapses upon retraction into a tubular sheath and which
reforms into a coil upon deployment from the sheath.
Inventors: |
Dretler, Stephen P.;
(Wayland, MA) ; Geragotelis, Paul D.; (Sharon,
MA) |
Correspondence
Address: |
HALE AND DORR, LLP
60 STATE STREET
BOSTON
MA
02109
|
Family ID: |
23364376 |
Appl. No.: |
09/862068 |
Filed: |
May 21, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09862068 |
May 21, 2001 |
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09347591 |
Jul 1, 1999 |
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Current U.S.
Class: |
606/127 |
Current CPC
Class: |
A61B 17/221 20130101;
A61B 2090/3925 20160201; A61B 2017/00867 20130101 |
Class at
Publication: |
606/127 |
International
Class: |
A61B 017/22 |
Claims
What is claimed is:
1. A medical device comprising a generally longitudinally-extending
wire core, a portion of said core more adjacent the distal end
thereof than the proximal end thereof being wound to form a helical
coil which tapers in diameter from a larger diameter end at the
proximal end thereof to a smaller diameter end at the distal end
thereof, at least the portion of said core forming said helical
coil being made of a super-elastic deformable material.
2. The medical device of claim 1, including a wrapped helical
spring surrounding a longitudinally-extending portion of said
core.
3. The medical device of claim 2, wherein said spring surrounds a
major fraction of the overall length of said core.
4. The medical device of claim 2, wherein the distal and proximal
ends of said spring are attached to said core.
5. The medical device of claim 2, wherein said spring includes a
first spring portion surrounding a first longitudinally-extending
portion of said core and a second spring surrounding a second
longitudinally-extending portion of said core, said second
longitudinally-extending portion including said helical coil, said
portions being adjacent to one another, and adjacent ends of said
spring portions being attached to each other and to said core in a
region proximal of said helical coil.
6. The medical device of claim 5, wherein the first spring portion
and said second spring portion comprise wires of different
diameters.
7. The medical device of claim 2, wherein the spring comprises
stainless steel.
8. The medical device of claim 2, wherein a layer of a polymeric
material substantially covers the outer surface of said spring.
9. The medical device of claim 8, wherein the polymeric material
comprises a fluorinated polymer.
10. The medical device of claim 9, wherein the fluorinated polymer
is polytetrafluoroethylene.
11. The medical device of claim 4, wherein the distal and proximal
ends of said spring are attached to said core by a weld or
braze.
12. The medical device of claim 5, wherein the adjacent ends of
said first and second spring sections are attached to each other
and to said core by an epoxy.
13. The medical device of claim 12, wherein the epoxy comprises
epoxy which cures upon exposure to ultraviolet radiation.
14. The medical device of claim 1, wherein said core comprises a
super-elastic deformable material.
15. The device of claim 1, wherein said super-elastic deformable
material is an alloy comprising nickel and titanium.
16. The device of claim 15, wherein the alloy consists of nickel,
titanium, and chromium.
17. A medical device comprising: a generally
longitudinally-extending wire core, a portion of said core more
adjacent the distal end thereof than the proximal end thereof being
wound to form a helical coil which tapers in diameter from a larger
diameter end at the proximal end thereof to a smaller diameter end
at the distal end thereof, at least the portion of said core
forming said helical coil being made of a super-elastic deformable
material; and, a pair of wrapped helical springs surrounding the
wire core, one of said springs extending distally from a point
adjacent the proximal end of said core, the other of said springs
extending proximally from a point adjacent the distal end of said
core to a point proximal to said helical coil, one end of one of
said springs being connected one end of the other of said springs
and to said core, and the other end of each of said springs being
connected to the core.
18. A medical device comprising: a guidewire including a
longitudinally-extending wire core, a portion of said core more
adjacent the distal end thereof than the proximal end thereof being
wound to form a helical coil which tapers in diameter from a larger
diameter end at the proximal end thereof to a smaller diameter end
at the distal end thereof, at least the portion of said core
forming said helical coil being made of a super-elastic deformable
material; and, a flexible tubular sheath surrounding a portion of
and being movable axially relative to said guidewire, the sheath
having an inner diameter that is greater than the diameter of the
guidewire other than a portion of said guidewire forming said
helical coil, such that said coil deforms into a configuration
having a maximum diameter not more than the inner diameter of said
sheath upon retraction into the sheath and returns to a coil
configuration having a maximum diameter greater than the outer
diameter of said sheath upon withdrawal from the sheath.
19. The device of claim 18, wherein said guidewire includes one or
more wrapped helical springs surrounding a longitudinally-extending
portion of said core, and a polymeric material covering a major
fraction of the outer surface of said springs.
20. A medical procedure comprising the steps of: providing a
medical device according to claim 18 in a configuration in which
the helical coil of the guide wire of said device is retracted into
the tubular sheath of said device; introducing the device in said
configuration into a desired pathway within a body; positioning the
device in a desired location within said pathway; moving the
helical coil portion of the guidewire relative to the sheath such
that the helical coil portion of the guide wire is withdrawn from
the sheath and returns to a coil configuration and in which the
coil engages the inner surface of the pathway.
21. The procedure of claim 20, wherein a biological calculus is
within said pathway and said procedure includes fragmentation of
the calculus, including the steps of: locating the biological
calculus within the pathway; placing at least a portion of the
sheathed guidewire beyond the location of the calculus; and moving
the guidewire relative to the sheath such that the helical coil
portion thereof is exposed from the distal end of the sheath and
reforms into a helical coil configuration distally of the
calculus.
22. The procedure of claim 20, wherein the procedure further
comprises the step of fragmenting a biological calculus located in
a desired location in said pathway and distally to the coil that
has engaged the inner surface of the pathway, using
lithotripsy.
23. The procedure of claim 22, wherein the lithotripsy comprises
one of electrohydraulic, pneumatic pulse, acoustic shock wave, and
laser lithotripsy.
24. The medical device of claim 1, wherein at least a portion of
the device includes a layer of radiopaque material.
25. The medical device of claim 24, wherein the radiopaque material
comprises gold, platinum, tantalum, tungsten, iridium, rhodium,
rhenium, or an alloy of two or more radiopaque materials.
26. The medical device of claim 18, wherein at least a portion of
the flexible tubular sheath comprises a layer of a radiopaque
material.
27. The medical device of claim 26, wherein the radiopaque material
comprises gold, platinum, tantalum, tungsten, iridium, rhodium,
rhenium, or an alloy of two or more radiopaque materials.
28. The medical device of claim 17, wherein a portion of the coil
is covered with a radiopaque material.
Description
FIELD OF THE INVENTION
[0001] This invention relates to medical treatments for biological
concretions and more specifically, to devices and methods for
entraining and extracting these concretions such as urinary,
biliary, and pancreatic stones, and other calcified material or
debris from the body.
BACKGROUND OF THE INVENTION
[0002] Urolithiasis, or kidney stone disease, is a significant
health problem in the United States. It is estimated that between
2-5% of the general population will develop a urinary calculus
during their lifetime. Since being introduced in the 1980s,
minimally invasive procedures such as lithotripsy as well as
ureteroscopy have become the preferred methods for treatment in a
majority of cases of stones in the ureter, and have a potential for
application to concretions that develop in other parts of the body
such as the pancreas and the gallbladder.
[0003] Lithotripsy is a medical procedure that uses energy in
various forms such as acoustic shock waves, pneumatic pulsation,
electrical hydraulic shock waves, or laser beams to break up
biological concretions such as urinary calculi (e.g. kidney
stones). The force of the energy, when applied either
extracorporeally or intracorporeally, usually in focused and
continuous or successive bursts, comminutes a kidney stone into
smaller fragments that may be extracted from the body or allowed to
pass through urination. Applications to other concretions formed in
the body, such as pancreatic, salivary and biliary stones as well
as the vascular system, are currently underway in several research
laboratories across the United States and Europe.
[0004] With the help of imaging tools such as transureteroscopic
videotechnology and fluoroscopic imaging, the operator of the
lithotripter device can monitor the process of the procedure and
terminate treatment when residual fragments are small enough to be
voided or grasped and removed. Currently, more than 2000
extracorporeal lithotripter devices and thousands of intracorporeal
lithotripter devices are in operation around the world and over
five million treatments have been performed.
[0005] Although these promising new techniques and instrumentation
have improved the treatment of kidney and other biological stones,
some problems remain. For example, stones in the ureter which are
treated by intracorporeal methods of fragmentation may become
repositioned closer to the kidney, and it then becomes necessary to
prevent retrograde, i.e. cephalad or upward, migration of the stone
fragments toward the kidney. It is also desirable to be able to
extract such fragments from the body with the same instrument,
preventing the need for successive instrumentation.
[0006] The prior art teaches several types of stone extraction
devices which are designed to extract biological concretions
without the necessity of major open surgery. However, each of these
devices suffers from limitations. Most of these devices comprise
curved wires which form a cage or basket; see, e.g., U.S. Pat. Nos.
2,943,626, 3,472,230, 4,299,225, 4,347,846, and 4,807,626. The cage
or basket-like configuration entrains a single stone within the
wire frame; but these prior art devices have rigid frames that lack
the maneuverability and flexibility to engage and disengage a stone
repeatedly without causing harm to the surrounding tissue, and the
entraining portion of these prior art devices are often rigid and
are either not collapsible into a smaller configuration or require
mechanisms for opening or closing the basket. If the basket or cage
of the device itself has become trapped within the ureter, a second
device often must be deployed to retrieve the first basket from the
body; and if the basket or coil structure has entrained a stone
which is too large to be extracted without further fragmentation,
it also may be difficult to disengage the stone without a
significant amount of manipulation.
[0007] Another prior art device comprises one or two inflatable
balloon catheters that are manipulated so that the arrested stone
is caught between one or more of the balloons. The balloon is
slowly withdrawn from the body, and if there are two balloons, the
lower balloon acts as a dilator of the ureteral wall and the upper
balloon pushes the stone downward towards the bladder. See, e.g.,
U.S. Pat. No. 4,295,464. The balloons of such devices are difficult
to manipulate and failure to maintain the balloons in the
correct-spatial position may result in loss of the stone. Further,
if a stone is caught in a narrow passageway during the extraction
process, the balloon catheters cannot move the stone away from the
exit direction to dislodge it from the passageway; and if the stone
is caught in between the lining of the ureteral wall and the
balloon, the pressure of the balloon may push the stone into the
lining, causing significant damage to the lining. Also, soft
air-inflated balloons are easily punctured when used in conjunction
with most types of stone fragmentation procedures.
[0008] There is a particular need, therefore, for a guidewire
device that prevents upward migration of stone fragments generated
during a stone fragmentation procedure, and which safely and
efficiently extracts fragments from the body. Thus, a device
possessing the following abilities is desired: ability to act as an
energy-absorbing barrier that prevents fragments from migrating
toward the kidney; ability to "sweep" one or multiple smaller
fragments downward and out of the body; the ability to engage and
disengage the stone repeatedly, and the ability to disengage the
stone for repositioning for further fragmentation if the entrained
stone is too large to pass from the body.
SUMMARY OF THE INVENTION
[0009] Accordingly, it is an object of the present invention to
provide a flexible, form-fitting device which prevents upward
migration of biological stones and fragments of stones generated
during medical procedures for stone fragmentation. It is another
object of the invention to provide a device in which the entraining
configuration may be collapsed and redeployed repeatedly as
required during a stone fragmentation procedure.
[0010] A further object of the invention is to provide a device
which can safely guide the one or multiple stone fragments from the
body, sweeping it downward and which as a safety feature,
disengages itself from a stone that is too large to pass a specific
path in the body by a simple pulling motion.
[0011] The invention features a device comprising a wire core at
least a portion of which is comprised of a super-elastic deformable
material wound to form a helical coil which tapers from a larger
diameter proximal end to a smaller diameter distal end. Because the
coil portion of the core is formed of a super-elastic material,
preferably a nickel titanium alloy such as nitinol, the coil has
the ability to uncoil into a relatively straight configuration when
retracted into a tubular sheath or pulled against an obstruction,
and reform into a coil configuration when deployed, e.g. withdrawn
from, a tubular sheath. In preferred embodiments, a continuous
super-elastic wire core is surrounded by a wrapped helical spring,
typically having two sections which are attached to each other and
to the core at a midjoint proximal to the tapered helical coil.
Another preferred embodiment features a layer of polymeric material
covering the surface of at least a portion of the device, as well
as a layer of radiopaque material which covers at least a portion
of the tubular sheath and/or the device
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 generally shows one preferred embodiment of the
claimed device for a urinary application.
[0013] FIG. 1A is an enlarged view of the tapered helical coil
portion of the device of FIG. 1.
[0014] FIG. 2 is a schematic view of the wire core of the device of
FIG. 1.
[0015] FIG. 3 is a schematic view of two wrapped helical springs
generally coated with a polymeric material.
[0016] FIG. 4 is a detailed schematic of a wrapped helical spring
18 of FIG. 3, a portion of which has been stretched so that gaps
are introduced between adjacent turns of the spring.
[0017] FIGS. 5A and 5B are profile views of the device of FIG. 1,
respectively illustrating the helical coil of the device withdrawn
into, and fully deployed (i.e. withdrawn) from the sheath.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0018] With reference to FIGS. 1 and 1A, a medical device 8
embodying the present invention includes a wire core 10 having a
super-elastic, tapered helical coil portion 14 adjacent but spaced
a short distance from its distal end 11. Except at its extreme
ends, wire core 10 is surrounded by two wrapped helical springs 18,
20, which in turn are covered with a layer of a polymeric material.
Hereinafter, the wire core 10, the helical spring(s) surrounding
the core, and the layer of polymeric material (if any) may be
collectively referred to as the guidewire 9. As shown in FIG. 1, a
portion of the guidewire 9 proximal to the helical coil section 14
is surrounded by an axially-movable tubular sheath 24. The distal
end 11 and the proximal end 13 of the wire core 10 are rounded;
typically a hemispherical tip 15 is bonded to the distal end 11. It
will be appreciated that FIG. 1 is not to scale; the overall length
of the device is over one hundred times its maximum diameter.
[0019] The overall length of guidewire 9 (and thus that of wire
core 10) depends on the application for which the device is
intended. Generally the overall length will be in the range of
about 50 to about 250 cm. For urinary applications, the total
length of the device is preferably about 140-220 cm, and most
preferably about 200 cm. Devices for other applications, or those
intended for use with children, will be of different lengths.
[0020] As described below, wire core 10 preferably has a tapered
cross-section. The maximum diameter of the wire core 10 itself is
typically in the range of about 0.015 inches to 0.04 inches, and
preferably is about 0.020 inches. The overall diameter of the
guidewire 9 is slightly greater, e.g., in the preferred embodiment,
it is about 0.038 inches and may, depending on the particular
device, vary from about 0.018 to 0.05 inches.
[0021] The helical coil section 14 of wire core 10 has a maximum
diameter at its proximal end, and a minimum diameter at its distal
end. The smaller diameter, i.e., the distal end of coil 14 is
spaced a relatively short distance 12 (e.g., about 2 cm to about 50
cm, preferably about 10-24 cm, most preferably about 14 cm) from
the distal end 11 of device 8. The portion 16 of core 10 proximal
of the helical coil section 14 is about 50 cm to about 200 cm long;
the overall length is usually not critical and, like many of the
other particular dimensions of the device, depends on the intended
use. Typically, the length of the proximal portion 16 of the core
wire 10 is about 100 to 130 cm, and preferably about 120-130
cm.
[0022] The particular number of turns, the maximum diameter, and
the length of the tapered helical coil section 14 depends, again,
on the intended use of device 8. Typically, the coil has between
about 5 and 15 turns, and preferably about 7 to 10 turns. Its
maximum diameter, at the proximal end of the helical coil section
14 is in the range of about 0.2 cm to 3.0 cm; and for usual
applications is about 0.5-1.5 cm, and most preferably is about
0.7-0.8 cm. The overall length of the coil depends, of course, on
such things as the wire size and number of turns, but typically is
in the range of about 0.5 cm to about 3.0 cm; and for most
applications is preferably about 1.5 cm. Adjacent turns of the coil
may abut each other. Typically, and as best shown in FIG. 1A, there
may be small gaps 26, up to about 2 mm wide, between the adjacent
wire turns forming the tapered helical coil. As will be discussed
in detail later, at least the portion of the wire core 10 forming
the tapered helical section is made of a super-elastic material,
and the above dimensions are those of the coil when it is in its
set, or fully deployed, configuration, as shown in FIG. 1.
[0023] A pair of wrapped helical springs 18, 20 surround
essentially the entire length of wire core 10, except for
relatively short (i.e., less than 0.050 inch long) regions at the
extreme distal end 11 and proximal end 13. One of the springs,
designated 18, tightly surrounds the portion of the wire core 10
extending from adjacent the proximal end 13 of the core 10 to a
region 22 a short distance proximal of the tapered helical coil
section 14. A second wrapped helical spring 20 tightly surrounds
the portion of the wire core 10 (including the helical spring
portion 14) extending distally from region 22 to adjacent the
distal end 11 of the wire core 10.
[0024] Preferably, the helical spring 18 has a length of about
150-180 cm, most preferably about 160 cm, and the helical spring 20
has a length of about 10-50 cm, most preferably about 40 cm. The
adjacent ends of the two springs 18, 20 are attached both to each
other and to the surrounded core 10 at region 22, herein referred
to as a midjoint or midjoint region, proximal of the helical coil
section 14. Preferably, the midjoint has a length of about 0.02 to
0.06 inches, most preferably about 0.03-0.04 inches. It is also
preferred that the two springs are wrapped in the same direction,
e.g., right-hand wrapped, and the turns at what will be the
adjacent ends of the two springs are slightly stretched, so that
the turns of the springs at midjoint 22 can be coiled one into the
other, interlocking in a fashion similar to that of a finger joint.
Preferably, about 0.5 to 2 turns of the adjacent ends of the two
springs are stretched and interlocked with one another. FIG. 4
illustrates a stretched turn having gaps 50 between adjacent turns
of spring 18.
[0025] These inter-connected turns are further attached to each
other and to the wire core 10, typically with an adhesive that can
form a high-strength bond with a wide variety of substrates,
particularly metal and polymeric materials. Once the adhesive is
applied, it typically is cured by a conventional curing method,
such as heat setting and air-drying. It is preferred that the
adhesive comprise epoxy, preferably a UV curing adhesive that
offers a secondary heat cure capability to allow areas shadowed
from ultraviolet light to be cured with heat, such as that
identified by the trade name Dynam 128-M-VT. In some other
embodiments, other means of attachment may be employed, preferably
welding or brazing.
[0026] In the preferred embodiment, spring 18 is wound from a
larger diameter wire than is spring 20; e.g., proximal spring 18 is
wound from wire having a diameter of about 0.008 in. while the wire
from which distal spring is wound has a diameter of about 0.004 in.
It has been found that a larger diameter proximal helical spring 18
provides the proximal portion of the device 8 with greater rigidity
and column strength; and that the use of a smaller diameter distal
helical spring 20 provides the distal portion of the device with
greater flexibility. In other embodiments, however, the arrangement
may be somewhat different. For example, both the distal and
proximal springs may have the same diameter, or only a single
spring extending substantially the entire length of the wire core
may be used. Regardless of the number of springs or their
diameters, the springs may be made of a wide range of materials;
and the springs are wound so that their outer diameters do not
exceed the desired outer diameter, e.g., 0.038 inches, of the
guidewire. Typically the springs are made of stainless steel.
[0027] FIG. 2 shows the construction of the wire core 10, which, in
the preferred embodiment, is a commercially available NiTiCr
(55.73%Ni, 44.04Ti, 0.22%Cr, and less than 0.05% C and O)
superelastic wire having, as supplied, a diameter of 0.020 inches.
As shown the wire has been ground so that, in addition to full
diameter sections 33 and 34 adjacent, respectively, its distal and
proximal ends, it includes a pair of tapered portions 30, 32 on
opposite sides of a smaller diameter portion 31. The long full
diameter section 34 extending from the proximal end of the core
wire, and the longer tapered portion 30, provide desired column
strength in the portion of the core wire proximal of the smaller
diameter portion 31. Preferably, the long full diameter section 34
has a length of about 130-200 cm, most preferably about 150 cm and
a diameter of about 0.02 inches. Preferably, the smaller diameter
portion 31 has a length of about 2040 cm, most preferably about 30
cm and most preferably a diameter of about 0.009 inches. The longer
tapered portion 30 is preferably about 5-10 cm in length, most
preferably about 8 cm, and the shorter tapered portion 32
preferably has a length of about 0.01 to 0.05 inches, most
preferably 0.025 inches. The shorter full diameter section 33
preferably has a length of about 0.1 to 0.5 inches, most preferably
about 0.2 inches.
[0028] The smaller diameter portion 31, which as discussed above,
forms helical coil 14. Typically, the lengths of springs 18, 20 are
such that the midjoint region 22 of core 10 is part of smaller
diameter portion 31. The smaller diameter portion 31 of the core
wire 10 immediately distal of the helical coil provides the
flexibility required for various applications involving the
entraining and removal of biological calculi.
[0029] In the preferred embodiment, the entire wire core 10 is a
continuous piece of super-elastic wire; in other embodiments, the
portion of the core wire 10 that will form helical coil 14 will be
superelastic, but other portions of the core wire, e.g., the full
diameter section 34 and tapered portion 30, may be stainless steel.
A number of superelastic NiTi alloys, commonly referred to as
nitinol, are available commercially.
[0030] The helical coil portion 14 of core wire 10 is formed by
wrapping the smaller diameter portion 31 around a mandrel to form
it into the desired conical shape, and then heating it at
sufficient time and temperature (the particular time and
temperature depend on the particular superelastic material and are
conventional) to set the conically-shaped coil in the core wire. As
is well-known in the art, once the portion of the core wire forming
coil 14 has been heat-treated to set the desired tapered helical
coil configuration, the coil may be drastically deformed (e.g., by
pulling the core wire portions on either side of the coil to
straighten the wire turns forming the coil) but will return to its
set tapered coil configuration when released. It will be apparent
that these deformation/reconformation characteristics are important
to the use of the medical device. They also assist in the device's
construction, e.g., by permitting the core wire to be straightened
so that helical spring 20 may more easily be slid over the distal
portion of the core wire, over the portion of the wire that forms
coil 14, to midjoint region 22.
[0031] As discussed above, in the preferred embodiment of the
invention, a helical spring covers most of the length of the core
wire 10. In other embodiments, the use of such a spring may be
omitted. In either event, a low-friction layer of polymeric
material preferably covers the outer surface of the device, i.e.,
the outer surface of the core wire when no spring is used or, if
the core wire is wrapped with one or two helical springs, the outer
surface of the spring(s). FIG. 3 illustrates a wrapped helical
spring 18 which has been covered, typically by spray-coating, with
a layer of polymeric material 40. As will be noted, the coating 40
does not cover small lengths 42, 44 at the proximal and distal ends
of spring 18.
[0032] Although any of a wide range of low-friction materials may
be used to form the coating 40, the coating of the preferred
embodiment is a fluorinated polymer, e.g., polytetrafluoroethylene,
one type of which is sold by duPont de Nemours Co. under the
trademark TEFLON. In some embodiments, various portions of the
device are coated with polymeric materials of different colors. For
example, as shown in FIGS. 5A and 5B, a colored portion 70 of core
10 that is at least as long in length as the length of the helical
coil 14 may be coated with a polymeric material of a color
different than that of the rest of the device proximal and/or
distal of it; or in some embodiments may be left uncolored or
uncoated. As will be apparent, providing a colored portion 70 that
possesses a color different from that of the rest of the device
assists a user in determining whether the tapered helical coil is
within or without sheath 24. Thus, when the coil has been retracted
into the sheath 24, the colored portion 70 will be visible to the
user. When the coil has been withdrawn outside the sheath 24 (i.e.
deployed), the colored band 70 will no longer be visible to the
user.
[0033] Sheath 24 has a length that is less than the overall length
of guidewire 9, but is considerably more than the length of wire
core 10 forming the helical spring portion 14 so that a physician
using device 8 can grasp the proximal end of the sheath when the
device has been properly positioned within a patient. The inner
diameter of sheath 24 is slightly greater than that of the diameter
of the wrapped spring that surrounds helical spring portion. Its
outer diameter depends, principally, on the wall thickness and
strength required to retain the portion of wire core 10 forming
spring 14 in a relatively straight configuration when the helical
coil spring is drawn into the sleeve, i.e. sheath 24. For example,
in the preferred embodiment, sheath 24 is 75 cm long, has an inner
diameter of 0.043 inches and an outer diameter of 0.066. The
material of which the sheath is made also must be somewhat
flexible, so that the sheath can be introduced into the body along
with the rest of the device. In the preferred embodiment, the
sheath is made of a flexible polymeric material such as that sold
under the trade name PEBAX, and its distal portion is covered with
a radiopaque material 80 to assist a user in locating the distal
end of the sheath during a medical procedure.
[0034] FIGS. 1 and 5B illustrate device 8 with sheath 24 positioned
proximally of helical coil portion 14. As will be appreciated, in
this relatively positioning of the coil and sheath, the helical
coil portion 14 is unconstrained and conforms to the tapered,
helical configuration in which the nitinol (or other superelastic
material) forming the coil portion was heat set. FIG. 5A
illustrates device 8 with the sheath 24 and helical coil portion 14
moved axially relative to each other so that the helical coil
portion has been retracted into the sheath. As shown, the
super-elastic qualities of the material forming the coil portion
permit it to be deformed into an essentially straight configuration
60, in which the coil portion of guidewire 9 fits into the sheath
whose inner diameter is only slightly (e.g., in the preferred
embodiment about 0.005 inches) greater than the outer diameter of
the wrapped wire core. If the super-elastic portion of the coil
wire that has been set in the helical coil configuration is then
withdrawn from sheath 24, e.g., by moving the sheath proximally
relative to the core wire (or the core wire distally relative to
the sheath), it will reform the tapered helical spring
configuration shown in FIG. 5B.
[0035] In use, device 8 is provided to a physician performing the
desired medical procedure, e.g., a lithotripsy to remove kidney
stones from a patient's ureter, in the configuration shown in FIG.
5A, with sheath 24 surrounding the helical coil portion 14 of the
guidewire 9. The sheathed guidewire is then introduced into the
patient's urinary passage, typically with its progress being
monitored in the conventional manner, until the radiopaque distal
portion 80 of sheath 24 is slightly beyond the location of the
stone or other biological calculus lodged in the ureter. With the
sheath held in place, the guide wire is then advanced so that the
portion of the guidewire forming helical coil portion 14 is
deployed distally from sheath 24 and forms the tapered, helical
coil configuration, occluding the passageway.
[0036] Preferably, the diameter of the largest portion of the
helical coil portion 14, in its fully deployed configuration (e.g.,
the configuration in which it was set during manufacture) is the
same or slightly greater than that of the hollow passage (e.g., the
ureter) in which the coil will be deployed in the course of a
medical procedure. This insures that the outer diameter of the coil
will conform to the size of the passage and occlude it efficiently,
preventing migration of the kidney store or other calculus.
[0037] With the coil thus deployed, energy is applied to the stone
or other calculus, in the same manner as in conventional
lithotripsy, to break the stone into smaller fragments that may
either be extracted or allowed normally to pass from the body.
During the fragmentation procedure, the deployed coil functions as
a physical barrier, trapping the larger stone or calculus fragments
either within the coiled structure or proximal to the coil. The
smaller fragments, e.g., those that are able to pass between the
turns of the helical coil 14, are typically of such size that they
can pass normally from the body. The super-elasticity of the
material forming the coil, particularly when combined with the
tapered configuration, provides a flexible barrier that is able to
absorb the kinetic energy of the fragments produced when a laser or
other energy is used to comminute or ablate the calculus.
[0038] In some procedures, the deployed coil can be used as a
"basket," to capture the fragments and permit them to be withdrawn
from the body by withdrawing the guidewire 9 with the helical coil
portion in its deployed configuration. In other procedures, the
deployed coil is retracted back into sheath 24, and then
repositioned for further deployment.
[0039] The following examples will further illustrate the
invention. These examples are not intended, and should not be
interpreted, to limit the scope of the invention.
EXAMPLE I
[0040] The device was tested in vitro under conditions that
simulated the ureter and utilizing various particles that simulated
stone fragments. The test ureter consisted of a clear plastic tube
having an inner diameter of about 10 mm with openings to introduce
particles and the device. A pump with a flowrate of 1L/min was
connected to the test device to simulate the high intensity with
which fragmentary debris generated during lithotripsy will flow
into the tapered helical coil that has been deployed within the
ureter.
[0041] Four different kinds of particles were used to simulate
stone fragments:
[0042] 1) Crushed walnut shells: various jagged shaped (about 2 mm
at its greatest length).
[0043] 2) Zircon oxide beads: spheroidal beads (about 2.0 to 2.5 mm
in diameter).
[0044] 3) Steel ball bearings: spheroidal balls (about 4.7 mm
diameter)
[0045] 4) Plastic beads: spheroidal balls (about 1/8 inches
diameter).
[0046] The test was conducted by introducing the device and
deploying it within the clear plastic tube. The particles were then
introduced into the water stream flowing into the tube. The device
successfully collected all of the tested particles.
EXAMPLE II
[0047] In another series of experiments, the same equipment
described above was used. In addition, actual kidney stones were
used as test particles along with the simulated fragments listed
above. A lithotripter, specifically CALCUSPLIT Model #276300
(Storz) was used to fragment the stone that was entrained within
the cone of the tapered helical coil. The coil secured the stone
while a probe of the lithotripter device fragmented it. Tables 1
and 2 provide the results of these preliminary experiments and
provide information about the sizes and weight of fragmented debris
collected and passed by the device during a laser lithotripsy
procedure.
1TABLE I With Stone Stopper Stone Size & Weight Size &
Weight Size & Weight Before of Debris of Debris Sample Stone
Type Breaking* Passed* Captured* 1A Uric Acid 6.34 mm/ 4 mm/>.01
gm 4 mm/.03 gm 1.42 gm 1B Uric Acid 6.31 mm/ 3.5 mm/.01 gm 5.5
mm/.07 gm 1.34 gm 2A Uric Acid 6.26 mm/ 3 mm/>.01 gm 3 mm/.07 gm
1.43 gm 3A** Struvite/ 6.71 mm/ 1 mm/.01 gm 2 mm/>.01 gm Apatite
1.31 gm 4A*** Cystic 6.64 mm/ 4 mm/>.01 gm 3.5 mm/.02 gm (hard)
1.42 gm 5A Black 6.55 mm/ 1 mm/>.01 gm 2.5 mm/>.01 gm 1.29 gm
*Size is determined by the largest measured dimension of the
particle. **Debris comprises fine and powdery grains. ***Stone
ablated using laser lithotripsy.
[0048]
2TABLE 2 Size of Debris & Weight of Size of Debris & No. of
Pieces Debris Not Debris Type No. of Pieces* Not Entrained*
Entrained Kidney Stone .about.8 mm dia./1 pc. >.5 to 3 mm/ .05
grams (Struvite, soft) 20 to 25 pcs. Kidney Stone .about.8 mm
dia./1 pc. 6 mm/1 pc. .10 grams (hard) Walnut Shell 2.8-3.9 cm/16
pcs. None passed None passed Walnut Shell 2.8-3.9 cm/4 pcs. None
passed None passed *For determining the size of the debris, the
largest measurement of the irregular shape was recorded.
[0049] The deployed cone containing the particulate matter was then
pulled downward (i.e. in the proximal direction with respect to the
device) a distance of 15 cm to simulate extraction of stones
entrained within the coil. It was observed that when fragments of a
diameter greater than about 4 mm were entrained in the tapered
helical coil, the coil that held the larger fragment could not be
pulled through the plastic tube. The larger fragment's resistance
to the pulling force of the user caused the coil to unwind, letting
go of the fragment. The device was then withdrawn into the sheath
and advanced beyond the fragment. Further fragmentation was
conducted, and the smaller fragments were then extracted from the
test tubing. It was appreciated that the unwinding feature of the
coil upon pulling against an obstruction provides a desirable
safety mechanism, whereby the user is prevented from trying to
extract a stone that is too large for the particular passageway,
and thus avoiding injury to the ureter. The results of the "pulling
test" are provided in Table 3.
3TABLE 3 Size of Debris & Debris Type No. of Pieces* Weight of
Debris Distance Pulled Kidney Stone 6 mm/2 pieces .10 grams 15 cm
(Struvite, soft) Walnut Shell 2.8-3.9 cm/4 .08 grams 15 cm pieces.
Walnut Shell 2.8-3.9 cm/16 .30 grams 15 cm pieces *For determining
the size of debris, the largest measurement of the irregular shape
is recorded.
[0050] The various technical and scientific terms used herein have
meanings that are commonly understood by one of ordinary skill in
the art to which the present invention pertains. As is apparent
from the foregoing, a wide range of suitable materials and/or
methods known to those of skill in the art can be utilized in
carrying out the present invention; however, preferred materials
and/or methods have been described. Materials, substrates, and the
like to which reference is made in the foregoing description and
examples are obtainable from commercial sources, unless otherwise
noted. Further, although the foregoing invention has been described
in detail by way of illustration and example for purposes of
clarity and understanding, these illustrations are merely
illustrative and not limiting of the scope of the invention. Other
embodiments, changes and modifications, including those obvious to
persons skilled in the art, will be within the scope of the
following claims.
* * * * *