Note: Descriptions are shown in the official language in which they were submitted.
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Surgical Retrieval Baskets and Method for Making the Same
Technical Field
This invention generally relates to medical
instruments and more specifically to surgical retrieval
baskets for removing an object from a body, particularly
calculi that can form in the biliary and urinary systems,
and a method for making such surgical retrieval baskets.
Background Art
Recently developed medical instruments reduce the
invasiveness and potential trauma previously associated with
various medical procedures. The removal of calculi in the
form of kidney stones, gallstones and the like from the body
is one area where this effort is meeting with success.
Various instruments now permit the removal of kidney stones
and gallstones without the need for major surgery.
Some of these instruments incorporate miniaturized
grasping forceps. Others incorporate a mechanical retrieval
basket as described in United States Patent Nos. 4,590,938
(Segura et al.); 4,611,594 (Grayhack et al.); 4,625,726
(Duthoy); 4,807,626 (McGirr); 5,064,428 (Cope et al.) and
5, 496, 330 (Bates et al . ) .
The Segura et al. patent discloses a surgical
extraction device that can be inserted through the working
channel of an endoscope for removing stones and the like
from the kidneys or the ureter or biliary duct. The device
includes a retrieval basket of relatively large diameter
that is extendable from the distal end of a sheath and
collapsible when withdrawn into the sheath. Outwardly bowed
flat wire spring strips form the retrieval basket. These
strips extend generally axially of the sheath and join at
respective distal and proximal ends. The retrieval basket
has a generally bulbous form that is
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relatively stiff due to the spring strip construction and
that facilitates dislodgment and capture of stones.
The Grayhack et al. patent discloses another
retrieval basket that is useful during the removal and/or
destruction of calculi. A smooth outer tubular sheath
encases a stranded helical wire cable terminating in a
protective tip at the working or distal end of the device.
When the cable is extended distally, the spring wire
strands at the working end of the cable expand to form a
retrieval basket. The distal end of this device
additionally includes an expandable distal portion for
protecting surrounding tissue during withdrawal of the
device and calculi.
The Duthoy patent discloses an extraction device that
includes a retrieval basket formed from a plurality of
wires spaced about and outwardly from an imaginary
extension of the center line of a hollow cable. A
filiforin extends distally from the distal end of the
retrieval basket to extend past a stone and to allow the
basket to be threaded around and onto the calculi.
The McGirr patent discloses an extractor included a
self-closing retrieval basket at the distal end of a
catheter with a flexible control line for opening the
basket from the proximal end of the catheter. The basket
assumes a normal position wherein it is in a compact
closed form. Pulling on the control line flexes the
strips to open the basket. When the control line is
released, the strips relax and surround the calculi or
object being removed.
The Cope et al. patent discloses a stone retrieval
basket having superelastic individual wire loops secured
together at the apex of the loops to define a distal end
of a basket which can be insert through and beyond a
distal end of an elongated tube. Sleeves which secure the
wires in a spaced relation defines the proximal end of the
basket so as to define a basket having a bulbous shape.
The Bates et al. patent
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discloses a surgical retrieval basket
comprising axially extending wires that are grouped in
sets of filaments. The wires are normally maintained in
an overlying sheath in a compact condition and form an
enlarged basket upon retraction of the sheath. The
filaments of a set are relatively closely angularly spaced
with the sets being relatively widely spaced to provide a
greater number of contact points with entrapped calculi
without significantly increasing the manipulations
necessary to capture such calculi in the basket.
These and other surgical extractors using retrieval
baskets have certain common characteristics. Each
retrieval basket comprises a plurality of strands in the
forth of individual helical or flat wires substantially
equiangularly spaced about the retrieval basket which is
collapsible into a compact form. In some retrieval
baskets the strands are formed along substantially
straight lines when the basket is in the compact form
(i.e., so-called "flat wire baskets"); in others, the
individual strands extend along a generally helical path
(i.e., so-called "helical wire baskets). Each instrument
generally include a plurality of three or more strands,
with the flat wire basket comprising an even number due to
manufacturing constraints, as explained below.
Forming such wire baskets generally comprises
grouping a plurality of axially extending wires having
shape memory properties, such as stainless steel, to
extend along parallel axes. Securing to wires together
defines a basket subassembly having a distal and proximal
end between which each of the wires extend. An operator
uses a forming fixture, generally hand operated, and cold-
works the wires of the subassembly to define the shape and
form of the basket as either a helical wire or straight
wire basket.
To form a straight wire type basket the forming
fixture generally receives and secures distal and proximal
ends on a straight wire axis. Generally, the forming
fixture includes a mount fixing one of the ends along the
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axis and another mount biased so that the other end can
move along the axis toward the one end during the forming
process. A forming tool, generally comprising a linearly
extending member corresponding to the desired radial
extension of the basket to be formed, engages an opposed
pair of the wires mediate the ends of the wires to urge
the wires radially outward from the wire axis defined
between the ends of the subassembly. Specifically, the
tool rotates (e.g., +75° to -75°) on transverse axes so
that the opposed ends of the tool slide along the engaged
wires and prestresses the wires into the desired form.
Repetition of this for other wire pairs defines a straight
wire basket having an even number of wires with each wire
extending in a substantially single plane with respect to
the basket axis and in an arc-like fashion between the
distal and proximal ends of the basket. This technique
thus limits a straight wire retrieval basket to an even
number of wires, because it operates on opposed wires in a
pair simultaneously.
Alternatively, as described by Segura et al. a hand
operated forming fixture acts on individual wires and
includes a plurality of upwardly extending pins. The tool
bends (i.e., cold works) each wire about the pins to forth
them in a desired loop shape. The ends of each of a
plurality of individual wires, thus formed, are then
secured together to define a proximal end of the straight
wire retrieval basket. Since each wire comprises a first
portion extending from the proximal to a distal end of the
basket and a second portion extending from the distal to
proximal end, straight wire baskets formed by this method
also essentially comprise an even number of wires
extending from the proximal to a distal end of the
straight wire basket.
In forming a helical wire basket the desired number
numbers of wires also are grouped together and secured at
their ends along a wire axis. The ends of the subassembly
are also fixed in a forming fixture. However, in- this
case opposed tools usually secure the wires in a generally
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equiangular spaced arrangement radially extended from the
axis. Turning the tools about the axis in opposed senses
~ (i.e., one is turned clockwise and the other is turned
counter-clockwise) bends and stresses the wires to provide
their helical, radially extending path between the ends of
the basket.
These processes for forming retrieval baskets thus
generally comprise the selection of wires, formation of a
wire sub-assembly, and the cold working of the wires.
Each method is labor intensive, as the forming fixtures of
the prior art are hand operated. Significant tooling
expenses are incurred as each basket size and shape
generally requires its own separate tools. Further,
differences between individual tools and fixtures and the
processes used by individual operators leads to variations
between wires of a basket and between baskets produced
thereby. That is, the baskets tend to be inconsistent in
their properties and characteristics. Additionally, cold-
working introduces significant stress in the wires that
can affect their characteristics such that individual
wires have different characteristics even within one
retrieval basket. Such inconsistencies often cause
additional inconvenience in the use of retrieval baskets
and can result in additional trauma to a patient. For
example, inconsistencies in the spacing of wires can
render capture and retention of objects more difficult
while over stressed and/or fatigued wires can lead to
premature wire failure and more fragile baskets.
Frequently upon the failure of a wire in a retrieval
basket, the wires tend to curl up into a ball like
arrangement. The lose ends of the broken wire can injure
body tissue and the ball formed by the curling up of the
wires may also require major surgery to enable removal of
the retrieval basket from the body.
Thus, the prior art methods fail to provide adequate
controls over the forming of the wires and, thus, the
basket. These methods generally do not include heat
treating the wires once formed, because such heat
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treatment would tend to destroy the securement of the wires
at the distal and proximal ends of the retrieval basket.
Disclosure of Invention
Therefore it is an object of this invention to
provide a repeatable method for producing wire retrieval
baskets with consistent characteristics.
It is another object of this invention to provide
a method for making wire retrieval baskets that comprise
wires of a preformed shape.
It is yet another object to provide a method for
making wire retrieval baskets that is relatively inexpensive
and simple.
It is still another object of this invention to
provide a wire retrieval basket comprising heat treated,
preformed wires.
It is yet still another object of the present
invention to provide flat wire retrieval baskets with an odd
number of wires.
It is a still further object of this invention to
provide a method for making wire retrieval baskets that
assembles cold formed wires having desired tensile strength,
ductility, dilation force, and spring memory characteristic
to form such baskets.
According to one aspect of this invention there is
provided a method for forming a surgical retrieval basket
having a given number of wires formed in a predetermined
configuration along a basket axis in an expanded state
comprising the steps of: (A) cold forming each of a
plurality of axially extending wires into the predetermined
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configuration; (B) assembling the given number of wires with
the predetermined configuration along the basket axis with
the ends thereof being located together, said wires, in the
assembled shape, conforming to the predetermined
configuration of the basket in its expanded state; and
(C) securing the ends of the assembled wires together
thereby to form the basket.
According to another aspect the invention provides
a method for forming a surgical retrieval basket having a
given number of wires and, in an unrestrained expanded
state, having a predetermined configuration, said method
comprising the steps of: preforming sections of each of a
plurality of individual axially extending wires to the
predetermined configuration wherein the characteristics of
each of said wires is substantially identical, assembling
from the plurality of wires the given number of wires with
the ends thereof being located together whereby the given
number of wires after assembly conform to the predetermined
configuration of the basket in its expanded state, and
securing the ends of the given number of wires together
thereby to form the basket.
According to another aspect the invention provides
in a surgical extractor for removing an object from a body
including a plurality of wires normally encased in a compact
form within a sheath whereupon displacement of the sheath to
free a portion of the wires enables the wires to form a
basket of a predetermined configuration for retrieving an
object, the improvement wherein each of said wires includes
a cold formed predetermined shape whereby the wires with the
predetermined shape are assembled together with ends of the
wires located together and with the assembled wires
conforming to the predetermined configuration of the basket,
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and whereby securing the wires together in a predetermined
manner defines an enlarged portion of said basket.
According to another aspect the invention provides
a surgical extractor for removing an object from a body
comprising: (A) handle means extending along an axis at a
proximal portion of said extractor for operating said
extractor, said handle means having base means for being
grasped by a physician and slider means for reciprocating
along the axis with respect to said base means, (B) basket
forming means connected to said base means for forming a
basket distally of said handle means, said basket forming
means having a distal portion including a set of preformed
wires cold formed in a predetermined shape whereupon
assembly in a predetermined manner includes assembling the
wires with the predetermined shape with ends of the wires
located together and with the assembled wires conforming to
a predetermined configuration of an enlarged basket,
whereupon assembly in a predetermined manner defines an
enlarged basket, (C) sheath means connected to said slider
means and axially displaceable between first and second
positions with respect to said basket forming means whereby
said sheath means retains said wires in a compact form
within said sheath means in a first position and exposes the
distal portion of said basket forming means in the second
position thereby to enable said wires to form said enlarged
basket.
According to another aspect the invention provides
a surgical extractor for removing an object from a body,
said extractor comprising: (A) a sheath, (B) a plurality of
rectangular cross-section wires normally encased in a
compact form within said sheath whereupon relative
displacement of said sheath and the wires frees a portion of
the wires and enables the wires to form a basket for
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retrieving an object, each of said wires including a stress-
relieved, cold formed section of predetermined shape, and
(C) means for forming the wires together in a predetermined
angular relationship that defines an enlarged portion of
said basket between said sections.
According to another aspect the invention provides
an extractor for removing an object from a body comprising:
(A) retrieval basket means comprising: (i) an odd number of
individual flat, shape memory wires having first and second
ends and an intermediate section preformed in a shape
corresponding to the desired shape of the basket and
characterized by having essentially no internal stresses in
the preformed shape, and (ii) means for fixing said first
and second ends of said wires to establish an angular
spacing between each of said wires whereby the intermediate
sections of the wires lie in angularly spaced radial planes,
(B) positioning means having proximal and distal ends, said
distal end being attached to the fixing means at the first
ends of said wires for positioning said retrieval basket
means in the body, and (C) a sheath carried by said
positioning means, said sheath, in a first position,
overlying said wires thereby to compact the wires and, in a
second position, freeing said wires to expand into the shape
of the retrieval basket.
Brief Description of the Drawings
The appended claims particularly point out and
distinctly claim the subject matter of this invention. The
various objects, advantages and novel features of this
invention will be more fully apparent from a reading of the
following detailed description in conjunction with the
accompanying drawings in which like reference numerals refer
to like parts, and in which:
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FIG. 1 is a plan view of a surgical extractor
constructed in accordance with this invention with a handle
at a proximal end and an expanded retrieval basket at a
distal end;
FIG. 2 is an enlarged plan view of the distal end
of the extractor shown in Fig. 1;
FIG. 3 is an enlarged view, partially in cross
section, of the distal end of the extractor shown in Figs. 1
and 2 in a compact form;
FIG. 4 is a diagram that describes the steps for
forming a surgical extractor in accordance with this
invention;
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FIG. 5 is a plan view of a helically wound wire of
the retrieval basket of the surgical extractor of FIG. 1;
FIG. 5A is a cross-sectional view of the wire of FIG.
taken along lines 5A-5A;
5 FIG. 6A depicts the distal end of a surgical
extractor incorporating a different embodiment of a
retrieval basket according to this invention;
FIG. 6B is a plan view of a wire of the retrieval
basket of the surgical extractor of FIG. 6A;
FIG. 7A depicts the distal end of another surgical
extractor with still a different retrieval basket
according to this invention; and
FIG. 7B is a plan view of a wire of the retrieval
basket of the surgical extractor of FIG. 7A.
Best Mode for Carrying Out the Invention
FIGS. 1 through 3 depicts a wire retrieval basket 10
formed according to the present invention. Specifically,
the retrieval basket 10 comprises a plurality of wires 11
which extend along a generally helical path from a distal
end 12 to a proximal end 13 of the basket 10. Each of the
wires 11 is substantially equiangularly spaced relative to
adjacent ones of the wires 11 and constitutes a turn in
the helix. A cap 14 secures the wires together at the
distal end 12 by solder, swaging or other known technique.
A sleeve 15 similarly secures the wires 11 together at the
proximal end 13.
The basket 10 typically is part of a distal end 16 of
an extractor 17 which a physician introduces into a
patient in the form shown in Fig. 3. In this form a
sheath 18 retains the basket in a compact form until the
extractor 17 is positioned proximate to calculi to be
retrieved. The physician holding the base portion 19 of a
handle 19A moves a slider 20 captured in the base portion
19 and connected to the sheath 18 from the position 20A
depicted in phantom in FIG. 1 to the position 20. This
displaces the sheath 18 and the wires 11 return to their
original shape as shown in Fig. 2 thereby to dilate
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surrounding tissue and to provide a structure that can be
manipulated over the calculi.
' The physician then manipulates the retrieval basket
via a proximally extending control cable 21 connected
' 5 to the wires 11 and captures calculi in the retrieval
basket 10. Thereafter the sheath 18 advances distally and
reduces the volume of the retrieval basket 10 until it
contacts the entrapped calculi so the physician can
withdraw the extractor 17 with the entrapped calculi.
10 Referring now to FIG. 4, the process for forming the
retrieval basket 10 in FIG. 1 commences with step 30 that
includes the selection of a plurality of wires having
substantially the same characteristics. In the context of
this invention, wires have the same characteristics, if
they are produced by the same techniques and not subject
to divergent treatments). Typically, the wires 11 will
comprise a suitable shape memory material, such as
stainless steel. A cold forming process step 31, such as
by stamp pressing, spring forming or other known suitable
processes that imparts on a relatively consistent and
repeatable basis a desired change in the shape of a
section of the individual wires 11. In this instance the
forming step provides a plurality of individual wires 11,
like those of FIG. 5 and 5A, with a distal section that
radially extends in a helically wound fashion from an axis
32 with each of the wires 11 having substantially the same
size, shape and characteristics. That is, each of the
formed wires 11 exhibit substantially the same physical
characteristics and properties so that the internal
stress, ductility, tensile strength, and spring memory are
. relatively constant from wire to wire. Machine processing
provides this consistency.
The process of FIG. 4 may also include a heat
treating step 33 depending on the materials of the wires.
Heat treating can further improve control over the
characteristics of certain wires formed of such material
as stainless steel. That is, such heat treatments could
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relieve any internal stress imparted by the cold forming of
the wires 11, if needed.
Once the wires 11 are formed in the desired shape
with the desired characteristics by steps 31 and 33, they
are then grouped in step 34 for being assembled to define a
basket shape at step 36. As depicted in FIG. 2, arranging a
plurality of the wires 11 about an axis 35 defines a basket
shape. Securing the wires at distal and proximal ends 12
and 13 in step 37 then fixes the wires in their respective
positions to form the retrieval basket 10.
Such retrieval baskets, due to the consistency of
the wire characteristics and the arrangement of the wires
defining the basket, exert a consistent dilation force and
expand to a consistent shape. The retrieval basket 10 can
then be incorporated in an extractor mechanism such as the
extractor 17 of FIG. 1 as indicated by step 38 of FIG. 4 to
provide an instrument for retrieving objects from the body
of a patient.
From the foregoing description it should now be
appreciated that retrieval baskets constructed in accordance
with the present invention can comprise a variety of user
desired shapes, numbers of wires, and wire spacing. That is
the wires can be preformed into predetermined shapes and
sizes for assembly in a selected manner to define baskets of
a predetermined shape comprising a desired number of wires
with a selected spacing between such wires.
The foregoing method of FIG. 4 can also be applied
to the formation of retrieval baskets generally, such as
straight wire retrieval basket embodiments of this invention
depicted as retrieval baskets l0A and lOB of FIGS. 6A, 6B,
7A and 7B, respectively. In the embodiment of FIG. 6A and
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6B, each of wires 11A of the retrieval basket l0A of FIG. 6A
includes a cold formed distal section (i.e., formed by the
step 31 of FIG. 4) that extends radially from a longitudinal
axis 32A of such wire 11A as depicted in FIG. 6A.
Preferably each of the wires 11A have a rectangular cross-
section, but are not
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helically wound in the distal section. Rather, the
radially extended portions in the distal section extend
in
r a substantially co-planar fashion.
The wires 11A are then arranged and secured together
about an axis 35A in a known manner to define the basket.
In this case, the sleeve 15 secures the wires 11A defining
the proximal end 13A of the basket l0A and a cap 14A
secures the distal end of the wires 11A to define the
distal end 12A of the basket. As with the embodiment of
FIG. 2, the wires can, if desired, be heat treated prior
to securement to further relieve and define the
characteristics of the wires 11A. The particular
embodiment depicted in FIG. 6A also includes a filiform
carried on the cap 14A that extends distally from the
15 retrieval basket 10A. Such filiforms are know in the art
and can be included as an element in any embodiment of
this invention.
In the particular embodiment of FIG. 6A, an odd
number of the wires 11A (i.e., five) form the basket 10A.
20 Straight wire baskets having cold worked wires of the
prior art necessarily included even numbers of wires
extending between the proximal and distal ends of the
retrieval basket due to the techniques by which the wires
forming the baskets shaped. That is, such baskets were
25 formed by loops so that a first portion extended from the
proximal to distal ends and a second portion extended from
the distal to proximal ends (i.e., a loop) or by opposed
pairs of wires, as described above. Those skilled in the
art will now recognize that, by constructing the baskets
30 with cold formed or otherwise preformed wires, straight
wire baskets having 3, 5 and even more wires comprising
an
odd number can be readily constructed, as well as, of
course such basket having an even number.
It will also be recognized that straight wire baskets
35 constructed in accordance with this invention may have
various shapes. For example, baskets with the bulbous
distal portion of the retrieval basket lOB of FIG. 7A can
also be provided using prefortned axially extending wires.
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Alternatively, the retrieval basket lOB of FIG. 7A can be
formed by joining wires preformed by this invention with
loops. Specifically, with reference to FIG. 7A, wires 11B
define a basket lOB according to this invention with the
wires 11B preferably comprising stainless steel strips
having a rectangular cross-section. The wires of this
basket, unlike the wires of the other baskets 10 and l0A
of FIGS. 2 and 6A, do not extend in a generally axial
direction. As depicted in FIG. 7B each of the wires 11B
form a loop centered about an axis 32B with the ends of
the wires 11B extending in the same direction along the
axis 32B. Joining a plurality of the preformed wires 11B
proximate the base of the loops defines the basket lOB
with a distal end 12B defined by the distal intersection
of the loops.
The process and baskets formed by joining prefortned
looped wires like those depicted in FIG. 7A are within the
scope of this invention. That is, the wires 11B can be
formed prior to the assembly of the basket lOB by
automated machinery such as spring forming machinery to
produce wires of the appropriate shape according to step
31 of FIG. 4. Such wires can then, if desired, be heated
treated according to the step 33 of FIG. 4. Securing the
ends of a plurality of wires in a sleeve 15B or by other
suitable securing means assembles (step 34) and defines a
retrieval basket according to the present invention. A
cap 14B can also be suitably secured to the distal end 12B
of the basket to provide a limit to the distal travel of
the sheath 18 relative to the basket lOB and to retain the
wires 11B in substantially the uniform orientation
depicted in FIG. 7A. Alternatively, the portions of the
distally extending loops of wires 11B can be secured
together by solder, for example.
It will now be understood that surgical retrieval
baskets, such as baskets 10, 10A, and lOB, according to
this invention can be used as a substitute for similar
prior art retrieval baskets such as those previously
described. Further, this invention is applicable to
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retrieval baskets such as those disclosed in above mentioned
U.S. Patent No. 5,496,330 to Bates et al. (disclosing a
basket having a plurality of sets of widely spaced wires
with each set comprising a plurality of closely spaced
filaments) for a Surgical Extractor and U.S. Patent
No. 6,168,603 to Leslie et al. filed on February 2, 1995 for
a Surgical Extractor (disclosing a basket having a plurality
of wires each having a single strand extending from a first
end of the basket and a plurality of filaments extending
from a second end of the basket).
Therefore, each disclosed embodiment provides both
a surgical extractor basket and a method for forming such
baskets that meets the various objects of this invention.
That is, this invention provides a method for producing wire
retrieval baskets that have relatively consistent basket and
wire characteristics by cold forming the basket wires prior
to assembly of the enlarged basket portion. The method for
producing such baskets according to this invention reduces
the manual labor associated with baskets produced according
to the prior art methods. Additionally, the ability to
control many of the variables associated with producing
surgical retrieval baskets according to this invention
yields retrieval baskets that provide more consistent
performance and reliability over prior art retrieval
baskets. Thus this invention also meets the foregoing
objects by providing a retrieval basket having cold worked,
preformed wires, that are more reliable and consistent than
prior art retrieval baskets and that can be selectively
formed with arbitrary shapes, numbers of wires, and wire
spacings.
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This invention has been disclosed in terms of
certain embodiments. It will be apparent that many
modifications can be made to the disclosed apparatus without
departing from the invention. Therefore, it is the intent
of the appended claims to cover all such variations and
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modifications as come within the true spirit and scope of
this invention.
