Note: Descriptions are shown in the official language in which they were submitted.
~094/20030 215 ~ 7 ~ ~ PCT~S94/0~27
IMPROVED STAPLES
Technical Field
~ This invention relates to stapling and, more particularly, to
improved staples for use in surgery and in other fields.
Bach~L~uud of the Inve~tion
Staples have a variety of uses. For example, surgeons use
thin wire staples to join the cut ends of hollow organs or ducts
(anastomosis) and to achieve hemostasis. Thin wire staples are
made by deforming a length of thin wire with uniform cross section
and material properties to a U-shape. FIG. 1 shows a common prior
art thin wire staple 100, including a crown 101 and two legs 102.
The staple shown in FIG. 1 has uniform cross section and material
properties, except as these may be altered in the region where the
staple legs join the crown during deformation of the wire to the U-
shape. Surgical staples are made of materials inert to attack by
body fluids, e.g.; stainless steels.
When a staple is installed, its legs are pushed into the
material being stapled. During installation, some staples are
deformed, i.e., bent past their elastic limit to achieve a
permanent change in shape.
FIG. 2 shows the staple of FIG. 1 deformed to a B-shape during
installation due to its legs having been forced against an anvil
with ch~nnels to direct the legs as they bend and deform. This
anvil is located on the side of the material being stapled that i5
~ opposite to the side into which staple insertion is made. The
deformation of the staple of FIG. 1 occurs where the maximum
~ bending stress develops.
~ ~ ~ PCT~S94102227
FIG. 2 shows that the separation of different locations on the
legs 102 from the crown 101 varies for a B-shaped staple. Thus,
when B-shaped staples are used in surgery, tissues located between
different regions of the legs and the crown undergo varying degrees
of compression.
To achieve hemostasis using staples, the tissue compressed
least by the staples must still be compressed sufficiently for the
hemostasis despite the possibility that the tissue compressed most
may be perforated or damaged due to excessive compression or
distortion. Shrinkage of scar tissue over time can lead to adverse
results, and thus it is important to avoid forming more scar tissue
than necessary.
Despite the need to avoid excessive scar tissue, some surgeons
claim that a controlled small amount of tissue damage can
sometimes be beneficial provided that the amount of scar tissue
formed as a result of the tissue damage is not excessive, i.e., so
that the scar tissue formed does not cause the problems associated
the excessive amounts of scar tissue resulting from use of prior
art B-shaped staples.
It is an object of the present invention to provide a staple
which achieves uniform compression of stapled material.
It is also an object of the present invention to provide a
surgical staple which m;n;m; zes scar tissue formation.
It is a further object of the present invention to provide a
staple which m; n; m; zes distortion of the material stapled.
It is an additional object of the present invention to provide
a surgical staple which m;n;m; zes healing time.
It is a further object of the present invention to provide a
~094120030 215 5 7 ~ ~ PCT~S94/02227
staple which minimizes damage of material stapled.
It is a further object of the present invention to produce a
staple for use in surgery which results in formation of a small
~ controlled amount of scar tissue.
~ Summary o$ the Invention
The above cited problems and others are overcome and the
objects of the invention are achieved in accordance with the
invention which relates to an improved staple whose resistance to
deformation during installation preferentially occurs in
predetermined regions although in the absence of such weakening
deformation would not otherwise preferentially occur in said
predetermined regions. Such predetermined regions with weakened
resistance to deformation are hereinafter termed "deformation
zones". Deformation zones may be formed by reducing the minimum
moment of inertia, I, of the staple cross section in the
deformation zones, or by reducing the modulus or elasticity, E, of
the staple material.
In the preferred embodiment of the inventive staple, the
staple has two legs, and each leg has a deformation zone in a
predetermined region that is separated from the staple crown by a
leg region with greater resistance to deformation than that of the
deformation zone under the stress generated when the staple
encounters an anvil during installation, so that the staple
preferentially deforms in the deformation zone.
During installation, the inventive staple is, preferably,
deformed to a rectangular shape with rounded corners. This helps
to achieve uniform compression and to m;n;m;ze distortion of the
stapled material.
FIG. 1 depicts a prior art staple before installation;
-
W094/20030 PCT~S94/02227
2155~5~
FIG. 2 shows the prior art staple of FIG. 1 after beingdeformed to a B-shape;
FIG. 3 depicts an exemplary embodiment of the inventive
staple;
FIG. 4 shows the staple of FIG. 3 after being deformed to a
rectangular shape;
FIG. 5 shows exemplary cross sectional views (not to the scale
of FIG. 3) of possible deformation zone and adjacent leg regions
for the staple of FIG. 3;
FIG. 6 shows a double staggered staple line;
FIG. 7 is a partial front view in section of a first type of
exemplary anvil;
FIG. 8 is a partial front view in section of a second type of
exemplary anvil;
FIG. 9 is an alternative embodiment of the invention for use
on material with varying thickness;
FIG. 10 depicts a loaded strip (cartridge) of staples for use
with the invention;
FIG. 11 shows an alternative embodiment of the present
invention wherein the deformation zones are formed simultaneously
with the installation of the staples;
FIG. 12 shows the embodiment of FIG. 11 in use;
FIG. 13 shows a cross sectional view of the inventive staple
fully deformed and installed into tissue;
094/2~30 21~ ~ 7 S O PCT~S94/0~7
FIG. 14 shows an alternative embodiment of the inventive
staple prior to deformation and installation;
FIG. 15 shows a cross sectional view of a prior art staple
~ fully deformed to a B-shape and installed into tissue;
FIG. 16 shows a technique of forming deformation zones; and
FIG. 17 shows a view of a notch formed on the outside of a
staple leg.
Detailed Description of the Preferred Embodiments
A deformation zone is created by weakening the staple in a
predetermined region so that deformation preferentially occurs in
that region during staple installation. As is well-known in the
art, the resistance to deformation of a region of a staple under
stress is dependant on the magnitudes of its modulus of elasticity,
E, in the region and the moment of inertia, I, in the region.
Reducing one or both of these quantities in a region reduces the
stress needed to deform a staple in that region. It is usually
easier to reduce I than E.
Deformation zones should not be formed by weakening the staple
in the predetermined regions in such a manner as to result in
staple failure, i.e., breakage, during staple deformation.
The legs of the inventive staple should be matched to the
requirements of the material stapled. That is, the locations of
the deformation zones should be matched to the thickness of the
material being stapled and to the compression desired, and the
staple leg lengths should be sized to bring the legs into close
proximity to achieve uniform compression of the stapled material
and to prevent a bulge of material from between the tips of the
legs. While such matching may require the availability of multiple
staples, this is justifiable when the compression achieved and its
W094/20030 PCT~S94/02227
2155~50
uniformity are important.
FIG. 3 shows an exemplary staple 300 in accordance with the
present invention. The staple 300 includes a crown 301 and two
legs 302. Each leg 302 has a deformation zone 305 with weakened
resistance to bending into direction 304 as compared to the
resistance of leg regions 306 and 307 which lie outside of the
deformation zone 305. When the staple 300 is subjected to stresses
arising from forces acting in the direction 304, the legs will bend
into that direction, and bending and deformation will take place
preferentially in deformation zone 305.
In FIG. 4, the staple of FIG. 3 is shown deformed into a
rectangular shape. Material stapled with the staple of FIG. 3 will
be under more uniform compression than is the case with the B-
shaped staple of FIG. 2. FIG. 4 reveals that the location and
length of deformation zone 305 and the length of the staple leg 302
are important leg parameters in obt~;n;ng a desired compression for
stapled material of a particular thickness and in bringing the
staple leg ends into close proximity. Ideally, the tips of the
staple legs should just about touch one another. The length of leg
region 306 between the crown 301 and the deformation zone 305
should be matched to the requirements set by the com.bination of the
thickness of the material being stapled and the compression of this
material that is desired. The length of leg region 307 between the
deformation zone 305 and the leg end 308 should be selected such
that the separation of the leg ends 308 of the deformed staple is
min;m;zed without interference between the leg ends 308 occurring
as the staple is deformed during installation.
A comparison of FIG. 2 and FIG. 4 reveals that material
stapled with the staple 300 Gf FIG. 3 will be less distorted and
under more uniform compression than occurs with B-shaped staples.
In FIG. 5, exemplary cross sections (not shown to the scale of
'~094~30 215 S 7 ~ O PCT~S94/0~27
FlG. 3) are shown for the legs 302 of the staple 300 of FIG. 3. In
FIG. 5(a), a cross section for regions of the staple legs 302
outside the deformation zone 305 is shown. In FIG. 5(b) and (c),
two different possible cross sections for the staple leg cross
section in the deformation zone 305 are shown. The values of I for
the staple leg in deformation zones with the cross sections shown
in FIG. 5(b) or (c) for bending into direction 304 are less than if
they had the cross section of FIG. 5(a).
In FIG. 6, a double staggered staple line 600 formed from
inventive staples 300 of FIG. 4 is shown, each row being offset
with respect to the other row. Surgeons make use of double
staggered staple lines, e.g., to compress tissue for hemostasis at
the cut end of an organ or to perform an anastomosis. The present
staples thus have application in hemostasis and anastomosis, for
example.
In FIG. 7, a cross section is shown of an anvil 700 for use
with the staple of FIG. 3 to produce the deformed staple of FIG. 4.
~h~nnels 701 formed in the anvil 700 direct bending and deformation
of staple legs 302 when staple 300 is forced against anvil 700 and
the legs 302 encounter the anvil 700. Anvil 700 is stationary as
the staple 300 is forced against it.
In FIG. 8, an anvil 800 alternative to that of FIG. 7 for use
with the staple 300 of FIG. 3 is shown. The legs 302 of the staple
300 encounter channels 801 of anvil 800 after penetrating through
the material being stapled (not shown in FIG. 8). Anvil 800 moves
towards the staple 300 as the staple 300 is forced against the
anvil 800. This motion of the anvil may be accomplished using
means well known to the art. The motion of the anvil minimizes
distortion of the material being stapled by the staple legs 302 as
they bend and deform.
It should be noted that the legs 302 after the staple 300 is
W094/20030 PCT~S94tO2~7
21S5~i0
deformed, as shown in FIG. 4, do not conform to the shape of the
channel 701. Rather, the ends 308 of legs 302 follow the shape of
the channels 701 until the leg regions 306 and 307 are bent at
angles (preferably, at right angles) to one another. The stapler
may include a stop (702, 802) to prevent staple bending beyond the
desired amount, although such a stop is not required for the
installation of a staple. An exemplary stop (702, 802) is shown,
but other techniques using means well known in the art can be
employed to prevent the stapler jaws from closing too much so that
staples are deformed beyond desired points.
Although stapler jaws are usually parallel to each other when
the thickness of the material being stapled is uniform, material
thickness sometimes varies over a length where a stapler line is to
be inserted. In FIG. 9, an alternative staple jaws arrangement 900
is shown which includes two stapler jaws 901 and 902 (jaw 902
functions as an anvil). This embodiment can be used if the
thickness of the material being stapled varies over the length of
a line of staples that the surgeon wishes to insert.
In order to m~;mize the benefits of the present invention and
to achieve a good result, the upper jaw 901 is slanted with respect
to the lower jaw 902, as shown. As a result, the separation of the
stapler jaws 901 and 902 varies in correspondence with the
variation in the thickness of the material (not shown in FIG. 9)
being stapled.
The individual staples used with the arrangement of FIG. 9
would have leg deformation zones located differently with respect
to each other in order to accommodate the different thicknesses of
the material being stapled. Specifically, it can be seen from FIG.
9 that the staple contacting channel 903 should have shorter leg
lengths between its leg deformation zones and the staple crown than
should the staple contacting channel 904. Additionally, the leg
lengths of the staple used at channel 903 may be less than the leg
-~094l20030 215 5 7 5 0 PCT~S94/02227
lengths of the staple used at channel 904.
It is possible for the staples to be manufactured with uniform
cross section and material properties, and for the deformation
zones to be formed by the surgeon by modifying the staples just
prior to use so that they correspond to the requirements of the
material being stapled. For example, the surgeon could notch or
file the staple legs to create the deformation zones, and/or cut
the staple legs to desired lengths. Devices which can be used for
such purposes can use means well .known in the art. Such an
approach would reduce the size of staple inventory requirements.
FIG. 10 shows a loading strip 1001 carrying prior art staples
100. The loading strip 1001 can be place into a device (not shown
in FIG. 10) which forms deformation zones where they are desired,
and which also cuts the staple legs 102 to the desired lengths.
Devices which can be used for such purposes can utilize means well
known in the art. The loading strip 1001 would be inserted into a
suitable stapler (not shown in FIG. 10) prior to insertion of the
staples 100.
FIG. 11 shows a still further embodiment of the invention
wherein deformation zones are created as staples are inserted
rather than prior to the use of the staples. The arrangement of
FIG. 11 shows stapler jaws 1102, 1103 with a staple 1110 located
therebetween. (Stapler jaw 1103 functions as an anvil.)
Two bars 1101 are employed to form the deformation zones. The
bars may be attached to the lower jaw 1103 or the upper jaw 1102.
The specific technique of attaching the bars is not shown in FIG.
1 for purposes of clarity and is not material to the operation of
the present invention, however means well known to the art can be
used for such purpose.
When the jaws 1102 and 1103 are brought towards each other,
W094l2~30 PCT~S94/02227
21~5~SO
the staple 1100 will encounter~the bars and bend and deform around
the bars 1101. As seen in~FIG. 12, the staple legs 1111 will
deform so that leg portions 1106 and 1107 are at angles
(preferably, at right angles) to each other, just as in embodiments
where deformations zones are formed prior to staple insertion.
Preferably, the anvil moves after the staple legs pass partly
or completely through the material being stapled. After the staple
has been deformed, the bars may move aside so that the stapler can
be easily l~l.loved, or the stapler may be set up so that the stapler
can slide in a direction out of the plane of FIG. 12 to disengage
from the staple. Means to accomplish such disengagement are not
shown, but means well known to the art can be used for such
purpose.
FIG. 13 shows a side view in cross section of another
embodiment, including staple 10 as installed into tissue 12. The
legs 26 of the staple 10 each include an upper deformation zone 18
surrounded by a first section 16 and a second section 20, and a
lower deformation zone 24 surrounded by a third section 22 and the
second section 20. The staple 10 includes a crown 14.
During staple 10 insertion by a stapler (not shown), the tips
23 of the legs 26 penetrate through the tissue 12 being stapled and
encounter the stapler anvil (not shown), which causes third
sections 22 to rotate inwardly as the legs 26 bend and deform at
the lower deformation zones 24. This causes second sections 20 and
third sections 22 to assume an angle with respect to each other,
e.g., to become substantially perpendicular to one another. As the
stapler continues to push the staple 10 against the anvil, the legs
26 also bend inwardly and deform at the upper deformation regions
18, so that second sections 20 rotate with respect to f irst
sections 16 and assume angles with respect to the first sections,
e.g., substantially right angles. Preferably, the legs 26 bend
initially at the lower deformation zones 24, and the lower
~15~7~0
~094nuo30 PCT~S94/02227
deformation zones have more of a tendency to bend than the upper
ones.
When the staple installation process is complete and the legs
26 have deformed, third sections 22 penetrate into the tissue 12,
as shown in FIG. 13. Of course, the amount of penetration into the
tissue 12 depends upon the location of the lower deformation zones
24 with respect to the tips 23 of the legs 26. Ideally, the upper
deformation zones should be located such that the lower deformation
zones 24 nearly touch after full deformation. This will prevent
tissue from bulging out between staple legs 26.
It is noted that the area occupied by each staple is uniformly
compressed. Tnus, the entire stapled area can be viewed as having
been divided into a plurality of areas, each of which is uniformly
compressed.
FIG. 14 shows the inventive staple 10 prior to installation
into tissue 12. Staple 10 is a U-shaped before deformation, and
includes an upper deformation zone 18 and a lower deformation zone
24 on each leg 26. Deformation zones 18 and 24 can be formed by
reducing the sections of the legs 26 of the staple 10 or by other
techniques, described herein.
By having three different sections 16, 20 and 22 in each leg
26, the third sections 22 can be used to effect a small
penetrations of tissue 12, i.e., produce a small and controlled
amount of tissue damage so as to thereby stimulate formation of a
small amount of scar tissue (not shown), and the second section 20
and first sections 16 can be used to achieve uniform compression of
tissue 12.
FIG. 15 shows a prior art B-shaped staple 28 installed into
tissue 38. There is a region 36 under the ends 34 of the legs 32
void of tissue, and scar tissue must form in-this void region if it
11
W094/20030 PCT~S94/02227
215~750
is to be filled. It is important to also note that the separation
of the legs 32 from the crown 30 of the staple 28 is not uniform
over the length of the legs, so that compression of the tissue 38
by the legs is not uniform. For such reasons, it is sometimes
difficult to achieve hemostasis and allow proper nutrition of
stapled tissues when using B-shaped staples. It is also a
disadvantage of B-shaped staples that the ends 34 of the legs 32
penetrate deeply into the stapled tissues and twist around as the
legs are deformed, so that substantial damage can be caused during
staple installation with the result that excessive amounts of scar
tissue forms with the possibility of strictures developing, and
that bleeding can result from perforated blood vessels.
Additionally, healing times may be extended.
For purposes of explanation, as shown in FIG. 16, it is
necessary to distinguish between the "inside" 401 of staple legs 26
and the "outside" 402 of staple legs 26. Concerning notches on the
outside of the staple legs, FIG. 16 shows two such notches, one
notch on each leg 26 used to form the upper deformation zones 18.
Lower deformation zones may or may not be used and, if used, are
not shown for purposes of clarity, but this discussion is
applicable to lower deformation zones also. Notches cannot be
excessively "sharp" or else the staple will fail, i.e., break or
fracture, when the leg sections 16 and 20 are rotated with respect
to each other or subsequently.
In order to have acceptable notches formed on the outside of
legs 26, the radius at the juncture where the sides of the notch
meet must not be so small that the material of which the staple is
formed, e. g., a metal such as a stainless steel or titanium,
breaks, cracks or fractures during deformation of the leg at the
deformation zone in question. It has been found that notches
result in a so-called stress concentration, i.e., a localized
stress which is considerably greater than the average stress in the
section. While localized yielding for ductile staple materials can
12
'~094/20030 21 5 5 7 5 0 PCT~S94/02227
-
minimize the effects of stress concentration, staples in surgery
are in a critical application where staple failure cannot be
tolerated because the danger to the health and well-being of the
patient. A tendency for the staple to fail due to the stress
concentration that occurs at the juncture of a sharp notch formed
on the outside of a leg when bending is unacceptable, and therefore
~ a m;n;mnm radius must exist at the juncture of the notch. Such a
minimum radius ~fillet) should be at least 3/lO00 of an inch. It
is also preferable to manufacture staples with notches having a
fillet of at least 3/lO00 of an inch on the inside of the leg,
rather than a sharp notch.
FIG. 17 shows an expanded view of an upper deformation zone 18
in leg 26 in the form of a notch with a fillet 40 located at the
juncture of the sides 42 of the notch. R is the radius of the
fillet, and R is equal to or greater than 3/1000 of an inch in
order to m; n;m; ze the possibility of breakage or fracture of the
staple leg upon bending during staple installation and to provide
acceptable reliability, i.e., to avoid subsequent breakage of the
leg after installation.
While the above describes the preferred embodiment of the
invention, it is understood that various modifications and or
additions will be apparent to those of ordinary skill in the art.
For example, the staples may be used in applications other than
surgery. Staples with more than two legs may be used, e.g., a leg
located between two outer legs may be used, where this additional
leg need not have any deformation zones.
While the disclosure has mentioned the use of these staples in
surgery, it is clear that such staples can find uses in other
applications, e.g., where uniform compression of the material
underlying the staple is useful or where perforation of the
material would be harmful.
wo 94,2053~ 5 o PCT~S94/02227
While particular anvils have been shown, the anvil used with
the inventive staple need not be one of the anvils shown but may be
any means of deforming the legs towards each other to achieve the
deformed shape desired and may include means for stopping staple
deformation after a desired amount of deformation has occurred.
Further, while staples with two legs have been described, it is
obvious that the principles of the invention are applicable to
staples having more than two legs, e.g., for applications where a
larger area is intended to be compressed by each staple. Such
modifications and/or additions which fall within the spirit and the
scope of the invention are intended to be covered by the following
claims.
14
