Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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Improved end effector for wound closure device
Field of the Invention
[0001] The present invention relates generally to the field of medical
devices, and more
particularly to barbed suture devices having improved end effectors.
Background
[0002] Many wound and surgical incisions are closed using surgical sutures or
some other
surgical closure device. Self-retaining sutures, also known as barbed sutures,
are well known
and have gained attention for various medical applications. Typically, self-
retaining sutures
are constructed with a series of retainers (also known as "barbs" or
"protrusions", used
interchangeably herein) that extend outwardly from the suture, and function to
increase the
holding strength of the suture and/or eliminate the need for knot tying.
[0003] Some sutures and barbed sutures have been known to include end
effectors at the
distal end of the suture to provide a "stop" at the end that prevents the
suture from being
completely pulled through tissue, while also increasing the holding strength
of the suture and
eliminating the need to tie knots to secure the suture. End effectors include,
for example,
anchors, knots, tabs, loops, and the like. Conventional thinking dictates that
the larger the
surface area of the stop in a direction perpendicular to the direction of
insertion of the suture,
the more holding strength that will be achieved. However, there are practical
limitations on
size however, as end effectors with large thicknesses or other dimensions may
be intolerable
in surgical procedures and/or palpable and therefore undesirable. One suitable
end effector is
seen in U.S. Publication No. 2013/0085525. Despite this effective end
effector, the present
invention seeks to provide an improved end effector that not only provides
increased stopping
and holding power, but proves tolerable in surgical procedures.
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Summary
[0004] In one embodiment, the present invention includes a composite suture
device,
including: an elongated suture body having a proximal end and a distal end,
with a body
running along a central axis; a welded or bonded fixation tab secured to the
distal end, the
composite fixation tab including: a first layer having a top side and a bottom
side with
thickness therebetween, and a length running parallel to the central axis, and
a width running
perpendicular to the central axis; a second layer having a top side and a
bottom side with
thickness therebetween, and a length running parallel to the central axis, and
a width running
perpendicular to the central axis; where the bottom side of the second layer
is welded to the
top side of the first layer.
[0005] The invention also includes methods of using such suture devices.
[0006] In other embodiments, the invention includes a method of forming a
suture device
having a welded or bonded fixation tab, comprising the steps of: forming a
suture device
from a preform ribbon having a desired thickness configuration, wherein suture
device
includes proximal end and a distal end, with a body running along a central
axis, and a
fixation tab, the fixation tab including a top side and a bottom side, and
having a length,
width and thickness; applying an end attachment to top side of fixation tab,
the end
attachment being formed from same preform ribbon as suture device and the end
attachment
having a substantially similar length and width as the fixation tab; and
welding fixation tab
and end attachment to each other to form a composite fixation tab.
Brief Description of the Figures
[0007] Figure 1 shows a prior art suture device with a rectangular end
effector.
[0008] Figure 2 shows a side view of the end effector of the suture of Figure
1, as viewed
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along the central axis.
[0009] Figure 3A shows a top view of a suture device with end effector and a
separate end
attachment in an unwelded configuration.
[0010] Figure 3B shows a side view of the suture device of Figure 3A with end
attachment
and end effector placed adjacent to each other.
[0011] Figure 3C shows a top view of the suture device of Figure 3B after the
end attachment
and end effector are welded together.
[0012] Figure 3D shows a side view of the welded suture device of Figure 3C.
[0013] Figure 4A shows a top view of a suture device with end effector and a
separate end
attachment having a perpendicular orientation, in an unwelded configuration.
[0014] Figure 4B shows a top view of the suture device of Figure 4A after the
end effector
and end attachment have been welded together.
[0015] Figure 4C shows a side view of the suture device of Figure 4B.
[0016] Figure 5A shows a top view of a suture device with end effector and two
separate end
attachments, each having a parallel orientation, in an unwelded configuration.
[0017] Figure 5B shows a top view of the suture device of Figure 5A after the
end effector
and end attachments have been welded together.
[0018] Figure 5C shows a side view of the suture device of Figure 5B.
[0019] Figure 6A shows a top view of a suture device with end effector and
separate end
attachments, each having a perpendicular orientation, in an unwelded
configuration.
[0020] Figure 6B shows a top view of the suture device of Figure 6A after the
end effector
and end attachments have been welded together.
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[0021] Figure 6C shows a side view of the suture device of Figure 6B.
[0022] Figure 7A shows a top view of a suture device with end effector and a
separate
foldable end attachment, in an unwelded configuration.
[0023] Figure 7B shows a top view of the suture device of Figure 7A after the
end effector
and foldable end attachment have been welded together.
[0024] Figure 7C shows a side view of the suture device of Figure 7B.
[0025] Figure 8A shows a top view of a suture device with end effector and a
separate
foldable end attachment with central opening, in an unwelded configuration.
[0026] Figure 8B shows a top view of the suture device of Figure 8A after the
end effector
and end attachment have been welded together.
[0027] Figure 8C shows a side view of the suture device of Figure 8B.
[0028] Figure 9A shows a top view of a suture device with a foldable end
effector, in an
unwelded configuration.
[0029] Figure 9B shows a top view of the suture device of Figure 9A after the
end effector
has been folded over itself and welded.
[0030] Figure 9C shows a side view of the suture device of Figure 9B.
[0031] Figure 10A shows a top view of a suture device with an elongated and
foldable end
effector, in an unwelded configuration.
[0032] Figure 10B shows a top view of the suture device of Figure 10A after
the end effector
has been folded over itself and welded.
[0033] Figure 10C shows a side view of the suture device of Figure 10B.
[0034] Figure 11A shows a top view of a suture device with a foldable end
effector having
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distal prongs, in an unwelded configuration.
[0035] Figure 11B shows a top view of the suture device of Figure 11A after
the end effector
has been folded over itself and welded.
[0036] Figure 11C shows a side view of the suture device of Figure 11B.
[0037] Figure 12 shows a graph of the shear strength of various welded
configurations.
[0038] Figure 13 shows a plot of initiation strength of various end effector
configurations in
porcine fascia.
[0039] Figure 14 shows a correlation plot of initiaition strength versus shear
strength for
multiple end effector configurations
Detailed Description
[0040] The present invention provides a wound closure device, which may be a
self-retaining
suture, which has a filamentary body having a proximal end and a distal end, a
stop element
at the distal end of the filamentary body. The suture may be formed by any
suitable method,
but preferably is compound profile punched from preformed ribbon or strip of
material in a
manner described in more detail in U.S. Patent Publication No. 2007/0257395,
which is
incorporated herein by reference in its entirety. In some embodiments, the
stop element may
be generally flat, and may have a rectangular or square-like shape, or in
other embodiments it
may take a more oval or circular shape. As used herein, the term "stop
element" refers to a
device at the trailing (or distal) end of the suture, and may also be termed
an "anchor", or an
"end effector". One type of end effector that may be useful in the present
invention includes
that described in U.S. Publication No. 2013/0085525, the entire contents of
which are
incorporated by reference herein. While the aforementioned end effector is
useful, the
present invention seeks to provide an improved end effector that gives
enhanced stopping and
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holding power while avoiding intolerance and other issues during and after
surgical
procedures.
[0041] Figure 1 shows a prior art suture device 100 including an end effector
108, which is in
the form of a tab (also referred to as a "fixation tab"), which is located at
a distal end (106) of
an elongated suture body 102. The suture body 102 has a longitudinal central
axis between
its distal end and an opposed proximal end (not seen), where the proximal end
is an insertion
end and may include a tissue penetrating feature, such as a needle. For self-
retaining sutures,
the body 102 may include a plurality of retainers 104, which may be arranged
along the
suture body 102 in any configuration, including, for example, symmetric,
spiral, or in a
random orientation.
[0042] As can be seen, the end effector 108 is generally rectangular, with an
elongated length
and width, with leading edge 110 defined by a leading edge thickness (t), a
leading edge
width (w), and also has a length (1). As used herein, and as seen in the
Figure, the length of
the end effector is parallel to the central longitudinal axis of the suture
body 102. The width
of the end effector 108 is substantially perpendicular to the central
longitudinal axis of the
filamentary element. In devices such as that seen in Figure 1, the suture
device 100 may be
formed from a single preform or ribbon of suitable material, where the device
100 is die-cut
or stamped or profile punched into the desired form. In such embodiments, the
suture body
102 and the end effector 108 are stamped from the same preform, and therefore
are a single
unitary construction.
[0043] As used herein and throughout this application with reference to each
of the
components, the term "proximal" shall refer to the end of the suture device
that is inserted
into a tissue, while the term "distal" shall refer to the end of the suture
device opposite the
insertion end. In the suture device of Figure 1, the distal end includes the
end effector 108,
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and the insertion end (not shown) would be the furthest end along the suture
body 102 that is
opposed from the end effector 108. End effectors as described herein may also
have a
proximal end and a distal end, where the proximal end of the end effector is
the location
where the end effector is secured to the suture body 102 (e.g., at suture body
distal end 106),
and the distal end of the end effector is the opposed edge of the end effector
along its length.
The terms "distal" and "proximal" will generally refer to these ends of the
suture device
and/or the ends of the end effectors described herein.
[0044] Known sutures with end effectors such as that in Figure 1 are typically
stamped or
formed from a single sheet of material, and therefore the thickness
configuration of the end
effector is the same as that of the suture body itself That is, since the
device is stamped from
a single piece, the thickness configuration of the end effector 108 does not
differ from the
thickness configuration of the suture body 102. That is, the thickness of the
suture body 102
is substantially similar to the thickness 110 of the end effector 108. In some
embodiments,
the central portion of the suture body (102) may have a different thickness
than retainers 104,
and this thickness variation may be similar along the length and width of the
end effector
108. Thus, the end effector 108 may have a varying thickness configuration
along its width,
as may be seen in Figure 2 and described below. Suitable end effectors need
not be
rectangular, but may be circular, oval, square, or other configurations. In
some embodiments,
the thickness (t) of the end effector of Figure 1 may be approximately 8-25
mils, the width
(w) may be approximately 70-120 mils, and the length (1) may be approximately
39-200 mils.
The ratio of the length to the width of the stop element may be at least 1.5.
[0045] Prior devices such as that seen in Figure 1 may include a pattern or
other pre-formed
configuration in the body of the end effector 108, which allows for the same
pattern or pre-
formed configuration to exist along the length of the suture body 102 through
the end
effector. For example, in Figure 1, the thickness along the central axis of
the suture body 102
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is thicker in some points than in regions adjacent the central axis, such as
the retainers 104,
and this thickness variation is consistent along the length of the end
effector 108.
[0046] By way of example, prior end effectors may be formed from a single
sheet of
material, having a thickness of from about 6-25 mils, typically from 4-12
mils, with a
maximum thickness along the central axis of the suture device (i.e., along the
central axis of
the suture body 102) and/or at first and/or second outer edges, with a minimum
thickness at a
location between the central axis and the first and/or second outer edges.
Figure 2 shows a
close up view of the end effector of Figure 1 as viewed along its length
(i.e., so that the width
and thickness can be seen). As can be seen, in this embodiment, central region
122 of the end
effector extends along the central axis of the suture body 102, and the end
effector also
includes a first outer region 120, second outer region 120, first intervening
region 124 having
thickness t2, and second intervening region 124 also having thickness t2.
Thicknesses of each
outer region 120 need not be identical, and the thicknesses of the intervening
regions 124 also
need not be identical. The cross-sectional thickness configuration of the end
effector 108
may differ from that seen, for example, the thickness may be substantially the
same along the
entire width of the end effector 108 if desired.
[0047] The holding strength of the end effector may be increased by increasing
the
dimensions of the end effector; however, there are practical and clinical
limitations on the
size and mass that can be implanted. For example, if the device is too small,
it may provide
low strength, but if it is too large, it may undesirably leave a large mass
within the body of
implantation. In addition, larger masses sometimes suffer from difficulties in
manufacturing
and providing sound structure. The present invention allows for improved
holding strength
while avoiding such limitations. Specifically, the present invention provides
a welded end
effector, where the overall mass of the welded end effector is about 1.1-3.0
times the mass of
a tab end effector that is unmodified as seen in Figures 1-2, and more
specifically about 1.5 to
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about 2.0 times; but the thickness of the welded end effector is only
increased about 1.1 times
to less than 2 times the thickness of the tab end effector that is unmodified
as seen in Figures
1-2. In desired embodiments, the increase in mass (compared to the unmodified
tab end
effector) is greater than the increase in thickness as compared to the same
unmodified tab end
effector. The cross section of the unwelded tab as seen in Figure 2 has a
contoured shape, but
the welded tab may have a substantially rectangular cross-sectional
configuration. In some
embodiments, the welded tab may have a different shape, which can be formed by
a shaped
die having any desired configuration. This will be further explained below.
[0048] The device 100 may be made of a polymeric, metallic or ceramic material
that are
absorbable or non-absorbable. In yet another embodiment, the device is made of
a polymer
material selected from the group consisting of absorbable and non-absorbable
homopolymers, random copolymers, block copolymers or blends made from
polydioxanone,
polyglactin, polyglycolic acid, copolymers of glycolide, lactide, and/or
caprolactone,
polyoxaesters, poliglecaprone, polypropylene, polyethylene, polyvinylidene
fluoride (PVDF),
hexafluoropropylene, copolymers of vinylidene fluoride and
hexafluoropropylene, polyesters,
polyethylene terephthalate, polybutylene terephthalate, glycol-modified
polyethylene
terephthalate, polytetrafluoroethylene, fluoropolymers, thermoplastic
elastomers, ionomers,
copolymers of ethylene and methacrylic acid, polyamides, polytetramethylene
oxide,
polystyrene, polybutadiene, polybutylene, etc. including combinations and/or
copolymers of
absorbable and non-absorbable materials.
[0049] As can be seen in Figure 3A, the present invention includes a suture
device 200
having an elongated suture body 202, a plurality of retainers 204, the suture
body being
defined by a proximal (insertion) end 206 and a distal end 208. The device 200
includes an
affixed end effector 210 at the distal end 208, which may be similar to that
of Figure 1. As
can be seen, the end effector 210 of Figure 3A includes a configuration having
varying
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thicknesses across the width (w), and it may have the thickness configuration
seen in Figure
2. Of course, the end effector 210 may have a consistent thickness across its
width if desired.
The suture device 200 may be formed by stamping or profile punching the device
from a
single preform or ribbon of material, thereby ensuring that the suture body
202 and end
effector 210 are formed of a unitary construction and include the same
materials.
[0050] The present invention seeks to take this suture device 200, and modify
its end effector
210 in various ways to increase its mass and holding strength, while avoiding
complications
associated with size increases of end effectors. Figures 3-11 show various
configurations
suitable to achieve this purpose. The composite device includes a suture
having an end
effector as described above, with a component welded or bonded to the end
effector. In some
embodiments, there is more than one end attachment welded to the end effector.
The final
device is a composite end effector (also referred to as a welded fixation tab
or composite
fixation tab), wherein the pieces are welded to each other, as will be
described below. The
composite fixation tab may refer to a "welded" fixation tab or a "bonded"
fixation tab, and it
should be understood that the composite fixation tab may include various
components welded
to each other (i.e., through application of energy), or may alternatively be
bonded to each
other, such as through application of chemical bonding or other known bonding
techniques.
Thus, the composite fixation tab may be bonded through chemical means or may
be welded
through application of energy.
[0051] A composite fixation tab has been shown to provide statistically
significant gains in
maximum load, elongation, and energy at break when compared to the fixation
tab alone
during tensile testing with a metal fixture. Importantly, however, the
composite fixation tab
does not increase the mass of the end effector to an undesirable level, and
also does not
introduce different materials to the device.
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[0052] Figures 3A-3D describe one configuration using a single parallel welded
attachment.
Figure 3A shows the suture body 200 described above, and a separate end
attachment 250,
which has a similar profile as the end effector 210 of the suture 200. As
noted above, the
device may be formed by cutting or stamping the suture and end effector from
the same
precursor material, referred to as a preform or a ribbon. Specifically, the
end attachment 250
has a similar thickness configuration and a similar width as the end effector
210. The length
may be different, or it may be the same. In the embodiment seen in Figure 3A,
the thickness
of both the end effector 210 and the end attachment 250 has a separate
thickness along the
central region 212, the first outer region 214, the second outer region 216,
the first
intervening region 218 and second intervening region 220. The thickness of the
central
region 212 may be the same or may be different from the first outer region 214
and second
outer region 216. The first outer region 214 may have the same thickness or a
different
thickness as the second outer region 216. The end attachment 250 in this
embodiment should
have a substantially similar thickness profile along its width as the end
effector 210.
[0053] As can be seen in Figure 3B, one surface of the end attachment 250 is
placed on one
surface of the end effector 210, such that the width and length of each is
substantially aligned
with each other. It may be useful to use a method to maintain these components
arranged
with each other, such as a mechanical holding device and/or an adhesive or
chemical
securement. The maintenance of the components may be temporary, and allow for
the two
components to be secured to each other until welding is completed. In some
embodiments,
the multiple components may be held together in a die, both before and during
the welding
process. The die may be an RF die, including polymeric and/or metallic
components.
[0054] It is particularly useful for the end attachment 250 to be cut or
stamped from the same
starting ribbon as the suture itself, to ensure that the width and thickness
profile are
substantially the same as the end effector 210. In addition, if the end
attachment 250 is
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formed from the same ribbon as the suture 200 itself, the final composite
material may be
made from identical materials and specifically the same batch of polymeric
material that is
used to form the suture.
[0055] Once the end effector 210 and the end attachment 250 are secured and
held together,
it is desirable to weld the components together to form the device as seen in
Figure 3C, where
that the resulting composite fixation tab 270 is a secure composite device. In
some
embodiments, it is useful for the welding process to provide for a composite
fixation tab 270
that has a substantially flat surface (the surface being defined by the length
1 and width w). In
some embodiments, the resulting composite fixation tab 270 may have a similar
thickness
profile as the end effector 210 and end attachment 250 prior to welding. A
view of the
fixation tab 270 from the side (thereby depicting the thickness of the welded
tab 270) can be
seen in Figure 3D. As can be seen, the thickness of the composite fixation tab
270 is only
slightly larger than the thickness of the suture body 202. The thickness of
the composite
fixation tab 270 may be varied as desired. The composite fixation tab 270 may
have a
substantially rectangular cross section, or there may be any other desired
shape, depending
upon the shape of the die used. The sides and distal end of the composite
fixation tab 270
may have a substantially flat surface, or there may be a seam where the end
effector 210 and
end attachment 250 were bonded together.
[0056] The welded tab 270 may be manufactured by welding or otherwise securing
the end
effector 210 and end attachment 250 to each other in any suitable fashion. For
example, the
devices may be secured to each other by welding with an RF generator. Other
energy sources
may be used to weld the devices together, including ultrasonic welding or
thermal welding.
Using an RF welder to add additional material to the tab has shown a 50 - 100%
increase in
tensile strength of the final composite fixation tab with a negligible
addition of volume to the
total device. While the mass of the tab will necessarily increase as more
material is added to
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the device, the welding process evens out the profile of the fixation tab to
give a uniform
thickness that is only about 25-50% increase of the original thickness.
Alternatively,
chemical bonding may be used to secure the tab.
[0057] With proper die design and appropriate machine parameters, energy can
be applied to
the end effector 210 while leaving the rest of the device, particularly the
core of the suture
body 102, and the suture segment immediately preceding the end effector (e.g.,
at distal end
208), unaffected. The suture core retains its original strength and
properties, while the
resulting welded fixation device can have a unique morphology that makes it
more resistant
to shear stresses. Unlike other common forms of welding (thermal, ultrasonic,
solvent) RF
energy is able to heat from the inside out, instead of from the exterior to
the interior of the
device. This is an advantage because the polymer on the surfaces of the
separate parts can
begin to melt and form a weld with minimal distortion of the rest of the
orientation in the tab.
Despite the improved results when RF energy is used, other energy sources are
contemplated
and may be useful in certain embodiments. For example, a weld using thermal
energy is
possible and would be able to fuse the parts together. This may be useful in
certain
situations, while in others, RF energy may be more desired.
[0058] Through the use of the same material and the same dimensions, including
the same
thickness configuration, the strength of the resultant welded end effector
increases
significantly without increasing the variability. The welded tab has a greater
mass than the
initial end effector, for example, if one end attachment is used, it has
approximately twice the
mass of the initial design. However, the resultant composite fixation tab 270
has a
substantially similar length and width as the original end effector 210, with
only
approximately a 10% to about a 25% increase in maximum thickness. This
relatively small
increase in thickness and the maintenance of the sizes of the other dimensions
is due to the
fact that both the original end effector 210 and the end attachment 250 are
made from the
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same preform material, thereby ensuring that each has a similar contoured
surface
configuration prior to welding. In addition to enhancing the strength of the
resulting
composite fixation tab 270, adding additional mass to the fixation device has
shown the
ability to normalize the fixation tab data. The nominal fixation tab strength
values do not
follow any known distribution making manufacturing controls more difficult.
Welding of the
end effector 210 with end attachment 250 enhances the weak parts of the tab
enough that the
device strength can be modeled with several distributions, including the
normal distribution.
[0059] In addition to a minimal increase in volume, the manner in which extra
material is
added to the device also minimizes additional surface area added to the
device. Adding a
single additional layer to the end effector, for example, only increases the
surface area of the
device by about 0.3%. This minimal change in surface area is noteworthy
because surface
area is a key driver for the rate at which additives or coatings can diffuse
through a polymeric
article. By essentially maintaining the surface area of the final composite
fixation tab 270
post-welding, it is likely that the dosing requirements for additives or
coatings can be
maintained from pre-welded to post-welded fixation devices. The similar
surface area also
means there is a reduction in the number of additional sites for bacterial
colonization or a
tissue reaction in vivo.
[0060] The above welded tab design seen in Figure 3 uses a single end
attachment 250
secured to the end effector 210 in a parallel configuration. That is, the
alignment of the
molecules in each is aligned, and the thickness configuration in each is
aligned as well. This
parallel alignment gives the ability to utilize the orientation of the
original end effector 210
and preform that existed before the weld, however, therefore multiple
configurations and
orientations are possible to increase the strength and performance of the tab
in different
manners. By arranging the preform in a parallel orientation, for example, the
orientation in a
given area across the width of the preform will increase as more of the same
will be added on
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top of it. Figure 5 shows a configuration using a double-parallel arrangement,
whereby more
than one end attachment is secured to the end effector, with each attachment
being secured in
a parallel configuration. As seen in Figure 5A, the suture includes the
preformed end
effector, and a first end attachment 250 and second end attachment 250 are
provided. The
first and second end attachments 250 are secured to the end effector 210,
either with the end
effector 210 sandwiched between each end attachment 250, or with the end
attachments 250
directly adjacent each other and the end effector 210 disposed outside of the
two end
attachments 250. Figures 5B and 5C show the welded configuration (in top down
and from
the side, respectively), with a welded fixation device 280 located at the
distal end 208 of the
suture device 200.
[0061] Another possible arrangement is a perpendicular orientation as shown in
Figure 4,
which uses the same mass of material as Figure 3, but the end attachment 300
is cut such that
the alignment of the material in the end attachment 300 is rotated
approximately 90 degrees
as compared to the end effector 210. The end attachment 300 still has
approximately the
same dimensional size and shape as the end effector 210 (e.g., approximately
the same width,
length and/or thickness), but with a different alignment of the molecules in
the attachment.
In addition, the thickness variation in the end effector 210 may be along its
width, as seen in
Figure 2, while the thickness variation in the end attachment 300 may be along
its length, as
can be seen in Figure 4A. The two components may be aligned and welded, as
described
above, and the resulting composite fixation tab 310 may be seen in Figures 4B
and 4C. Thus,
the composite fixation tab 310 includes a first side with a molecular
orientation aligned in a
first direction and a second side with a molecular orientation aligned in a
perpendicular
direction. The perpendicular orientation of the original end effector 210 and
the end
attachment 300 may result in an increased strength and stability of the final
composite
fixation tab 310, such as by ensuring that a crack or tear is not likely to
propagate down the
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length or width of the composite fixation tab 310. Such cracks or tears are
more likely to be
arrested by the molecules arranged in the perpendicular direction.
[0062] In another perpendicular configuration, seen in Figure 6, the original
suture 200 with
preformed end effector 210 is formed as described above, and an additional end
attachment
350 is cut. However, in this embodiment, the end attachment is cut into
multiple pieces (each
350). Each end attachment piece 350 may independently be parallel to the end
effector 210
or may be perpendicular to the end effector 210. In the embodiment seen in
Figure 6A, four
end attachment pieces 350 are formed, each being approximately half the length
of the
original end effector 210 and having approximately the same width as the end
effector 210.
This allows for each piece 350 to be placed and welded on the end effector 210
in desired
locations. Here, two end attachment pieces 350 are welded onto a top surface
of the end
effector 210, and two end attachment pieces 350 are welded onto a bottom
surface of the end
effector 210. It may be desired for each end attachment piece 350 to be
secured in a
perpendicular configuration to the end effector 210, or with each end
attachment piece 350 to
be secured in a parallel configuration to the end effector 210, or
combinations thereof Each
end attachment piece 350 is secured to the end effector 210 as described
above, and subjected
to welding as also described above. The resulting composite fixation tab 360
is seen in
Figures 6B and 6C.
[0063] As can be seen in the various embodiments of Figures 3-6, the
additional material to
be welded to the end effector (210) can be formed, aligned and ultimately
welded in a
number of ways. Once the components are welded together, the resulting
composite fixation
tab is solid and secure, and the original components are not easily separated.
As described
above, in any of the above embodiments, the resulting composite fixation tab
may have
substantially flat surfaces, or they may have thickness variations as desired.
Figures 3 and 4
describe methods of making composite fixation tabs through the addition of
only one end
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attachment, while Figures 5 and 6 demonstrate that various layers and
components may all be
added to form the desired composite fixation tab. Each embodiment provides
different
strength profiles, ease of use and formation, and enhanced rigidity. Any of
the embodiments
seen in these Figures may be used depending upon the desired final composite
fixation tab.
[0064] When only one end attachment is used, where the end attachment is
approximately
equal to the size and shape of the end effector, the resulting composite
fixation tab has a mass
that is approximately twice that of the original end effector prior to
welding. In embodiments
where two end attachments are used, where each end attachment is approximately
equal to
the size and shape of the end effector, the resulting composite fixation tab
has a mass that is
approximately three times that of the original end effector prior to welding.
The composite
may be a general sandwich configuration, where a first end attachment is
placed on a top side
of the end effector and a second end attachment is placed on a bottom side of
the end
effector.
[0065] An alternative method to forming a three-times mass composite fixation
tab that does
not incorporate an end effector and two separate end attachments (or more end
attachments)
may be seen in Figures 7A-7C. In this embodiment, the suture device 200
including end
effector 210 is prepared as described above, and a separate end attachment 400
is formed,
where the end attachment 400 is approximately twice the length of the end
effector 210, and
where the end attachment 400 is capable of being folded over itself along a
line parallel to the
width of the device. The device may include a folding region 405, as seen in
Figure 7A. The
folded end attachment 400 can be disposed over the distal end of the end
effector 210, held in
place and ultimately welded in place, forming the composite fixation tab 410
as seen in
Figures 7B and 7C. Composite fixation tab 410 includes welded fold region 415,
which is
the same region as fold region 405 after welding is complete. Desirably, the
foldable end
attachment 400 is sized and shaped such that, after folded over itself, the
length and width of
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the folded device are approximately equal to that of the end effector 210. The
resulting
composite fixation tab 410 has a mass that is approximately three times that
of the original
end effector 210.
[0066] Another embodiment of preparing an approximately three-times mass
composite
fixation tab can be seen in Figures 8A-8C. Again, the original suture 200 with
end effector
210 is prepared, and a separate foldable end attachment 450 is also prepared,
desirably from
the same material and the same preform as the suture 200. The foldable end
attachment 450
uses a substantially similar folded end attachment as seen in Figure 7, where
the foldable end
attachment 450 includes a foldable region 455 along its width, but in this
embodiment, a
portion of the material from the middle of the end attachment 450 is removed
(seen as region
460). With the removal of the middle portion at region 460, the foldable end
attachment 450
may be slid over the proximal end 206 of the suture 200, and slid along the
length of the
suture body 202, where the foldable end attachment 450 aligns with the end
effector 210. It
may be desired or necessary to twist or rotate the foldable end attachment 450
prior to or
during movement along the suture body 202. Once it has reached the end
effector 210, it can
be positioned to fold around the proximal end of the end effector 210. The
device may be
welded, forming the composite fixation tab 470 seen in Figures 8B and 8C. In
this
embodiment, the resulting composite fixation tab 470 includes a welded fold
region 475
disposed at the proximal end of the composite fixation tab 470. As with Figure
7, the welded
fold region 475 is approximately at the same location as the fold region 460,
but is welded.
This configuration helps by further protecting the fixation tab 470 at its
proximal end.
[0067] In the various embodiments described above, a separate component or
components
(i.e., the end attachment) is added to the end effector 210, and welded in
place. An
alternative to adding an additional material to the end effector is to
slightly change the
geometry of the end effector when it is initially formed, i.e., as it is
stamped or punched, or
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by providing a device that includes a resulting composite fixation tab having
a shorter length
than the original end effector 210.
[0068] For example, Figures 9A-9C show a device including the suture body 202
with an end
effector 500. In this embodiment, the length of the end effector (as measured
from proximal
end 510 to distal end 515) is approximately twice the desired length of the
final desired
welded end effector, and is foldable along a fold region 505 extending along
the width of the
foldable end effector 500. In this embodiment, the foldable end effector 500
is folded in half,
such that the proximal end 510 is substantially flush with the distal end 515
before welding.
The folded end effector is then welded into place to form a welded fixation
device 520
(Figure 9B). A side view of this embodiment can be seen in Figure 9C. This
method has the
advantage of avoiding the use of additional material or adding any additional
components,
which may differ from the end effector 500 material. In addition, this method
avoids the
need to secure separate pieces to each other. This also maintains the final,
composite fixation
tab 520 has a desired length that is equal to that of the original tab
described above. In
addition, the final welded fixation device 520 has the same mass of the device
as originally
formed.
[0069] In some embodiments, such as that seen in Figures 10A-10C, the end
effector 550 has
an elongated length as compared to prior devices (such as in Figure 1), and is
foldable along a
fold region 555 extending across its width. In this embodiment, when the end
effector 550 is
folded over itself such that its proximal end 560 is substantially flush with
the distal end 565,
the resulting length of the welded end effector 570 is longer than that of the
embodiment in
Figure 9. This embodiment will increase the thickness and make the welded
fixation device
570 more rigid, but has a longer length than that of Figure 9.
[0070] In another embodiment, seen in Figures 11A-11-C, an end effector may be
prepared
that includes a two-fold design with prongs. In this embodiment, the end
effector 600
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includes an elongated length, with a first folded region 605 extending along
its width, a
second folded region 610 extending along its width at a different region, and
first and second
prongs 615 at the distal end of the end effector 600. The length of the first
region (defined by
the proximal end of the end effector 600 to the first folded region 605) is
approximately equal
to the length of the second region (defined as the length between the first
folded region and
the second folded region 610). The length of the prongs (defined as the length
between the
second folded region 610 and the distal end of the end effector 600) may be
approximately
equal the length of the first region and the second region.
[0071] In the embodiment of Figures 11A-11C, the end effector is initially
stamped or
punched from a preform, as explained in greater detail above, such that the
length of the end
effector 600 has approximately three times the length of the final desired
welded fixation
device. In this embodiment, there is an elongated region along a substantially
central length
removed from the most distal third of the end effector 600, forming first and
second prongs
615. The amount of material removed to form the prongs 615 may vary, but it
should be
sufficient to allow the suture body 202 to pass through the space between the
prongs 615.
This extended prong shape allows the end effector to be folded over once (at
the first folded
region 605), then folded over again at the second fold region 610, where the
prongs 615 may
be passed over the suture body 202, and over the proximal end of the end
effector 600 (Seen
in Figure 11A). The device may then be welded in place to form a welded
fixation device
620, as seen in Figure 11B, with a side profile seen in Figure 11C. This
design has similar
advantages to the front fold around configuration seen in Figures 8A-8C, with
in that the
front face of the end effector 600 is enclosed and more resistant to cracking.
[0072] Each of the aforementioned configurations and methods result in a
final, composite
fixation tab that has a greater stability and effectiveness than an original
stamped end
effector, but does not significantly increase the thickness, width or length
of the resulting
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welded end effector. In some embodiments, as described above, the mass may be
doubled (if
one end attachment is used, for example), or tripled (if two end attachments
are used, for
example), but the thickness of the end effector only increases by about 10% to
about 70%, or
about 25% to about 50%, depending upon the number of end attachments and
size/shape/configuration of the end attachment(s). Further, the welding
process may provide
a composite fixation tab that has smooth surfaces of substantially similar
thickness along the
width of the final welded fixation device, and may include smooth edges and/or
corners.
Further, in some embodiments, molecular or physical alignment of the end
effector with the
end attachment(s) may be offset or may be perpendicularly arranged so as to
provide a device
with multiple molecular alignments. This may increase strength of the device.
[0073] In any of the aforementioned configurations, the welding of the
resulting end effector
is desirably achieved in a die that is suitably sized and shaped to provide
the desired level of
fixation and resulting shape. It is particularly desired that the die used be
sized so as to
snugly fit the various components within its welding space, and thereby allow
the application
of energy evenly to each of the surfaces of the composite device. The energy
application
should be sufficient to fuse the various attachment(s) to the original end
effector, but not so
much energy so as to melt the various components to the extent that their
molecular
orientation is substantially modified. When the components are melted to an
undesirable
level, the resulting welded end effector has less strength than desired. The
resulting
application of energy results in the attachment(s) and original end effector
being fused to
each other, with a visible seam about the periphery of the welded end
effector. The fusion of
the components should be sufficient to withstand the level of energy applied
during normal
surgical use without breaking or separating.
[0074] In use, the proximal end of a suture device including composite
fixation tab is inserted
through tissue until the suture has passed substantially through the tissue,
and the proximal
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end of the composite fixation tab is abutting the outer surface of the tissue
into which the
device is implanted. The suture is prevented from being pulled through the
tissue further by
the abutment of the welded tab against the tissue surface. This holds the
suture in place, and
the user is able to continue suturing the tissue in desired regions of the
body. If the suture
includes a plurality of retainers along its body, as described above, these
tissue retainers serve
to hold the suture in place in the various regions of tissue into which the
suture device is
inserted. The combination of a composite fixation tab and plurality of
retainers serves to
prevent the suture from being pulled too far in the proximal direction, and
simultaneously
prevents or restricts removal of the device in the distal direction.
[0075] The resulting composite fixation tab provides a stronger and more
secure stop at the
distal end of the suture device, while avoiding problems, such as difficulties
in manufacturing
and difficulties post-implantation (such as when a device is used with too
large of a mass
remaining). Further, the resulting fixation device may include smoother and/or
more uniform
surfaces, allowing for ease of use and healing.
[0076] The present invention includes a method of suturing tissue through use
of a suture
including a welded fixation device. The suture may include a plurality of
retainers along at
least a portion of its body, where the retainers may be symmetrically disposed
along the
suture body, or they may be spirally wound about the suture body, or they may
be randomly
disposed about the suture body. Any of the welded fixation devices described
above may be
used as the welded fixation device at the distal end of the suture. The
proximal end of the
suture body should include an insertion means, such as a needle or other
pointed end to be
inserted through tissue. In use, a user, such as a doctor or other clinician,
inserts the proximal
end of the suture device into a desired location of tissue, pulling the suture
body at least
partially through the tissue. The retainers on the suture body allow for the
suture to be pulled
in the proximal direction, but restrict or otherwise slow down movement of the
suture in the
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opposite (distal) direction. The proximal end of the suture is pulled through
the tissue until
the proximal end of the fixation device abuts the tissue into which the suture
was inserted. At
this point, the suture body is restricted from being pulled in the proximal
direction further,
and, with the presence of retainers on the suture body, the distal end of the
suture is now held
in place at the insertion site. The insertion end of the suture body may be
inserted through a
second region of tissue, either before or after the fixation device abuts the
original region of
tissue. The second region of tissue may be, for example, the side of a wound
opposite the
first tissue region. The user may continue to insert the proximal end of the
suture device
through as many regions of tissue as desired to effectuate wound closure.
[0077] In an alternative embodiment, there may be provided a bidirectional
suture device
with a central welded tab, which includes two sutures with unmodified tabs at
their distal
ends (as in Figures 1-2). In this embodiment, the unmodified tab of the first
suture is rotated
180 degrees with respect to the unmodified tab of the second suture, such that
the distal end
of the first tab is substantially flush with the proximal end of the second
tab. The first and
second tabs may then be welded to each other, such as through RF welding or
other
application of energy. The resulting structure therefore includes a first
suture with a proximal
end facing in a direction opposite the proximal end of a second suture.
Between the two
proximal ends is a central welded tab. If desired, end attachments as
described in any of
Figures 3-11 may be used to provide additional mass to the central welded tab.
[0078] The suture, with welded fixation device, may be contained within a
suitable package,
such as a suture holder. Desirably, the suture is held in place in the package
in such a fashion
that the suture does not become entangled with itself during removal of the
suture. It may be
desired to wind the suture around one or more posts or other holding means
within a suture
package. The package should allow the user to grasp the proximal end of the
suture, which
may include a needle, and pull the suture proximally out of the suture package
without
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restriction or entanglement. The suture may have a coating of an antimicrobial
material
contained thereon, which coating may be provided through any means, including
dipping,
spraying, vapor deposition, and the like. More than one suture may be
contained within a
package, or one suture may be contained within one package. The package may be
hermetically sealed to protect the suture and maintain sterility of the
suture.
Examples
Example 1 ¨ Benchtop Instron Testing
[0079] Tensile testing for each suture was conducted in a custom metal fixture
via a benchtop
Instron test, with a custom metal test fixture sized and shaped for the suture
and/or the
composite end effector. This test is more commonly referred to as a shear
strength test, and
for this example, it is considered a fixation tab shear strength test, since
it measures the shear
strength of the fixation tab(s) tested. The shear strength of each fixation
tab was tested by
loading each individual suture into the custom metal test fixture. Each test
specimen was
introduced into the slit in the fixture top plate such that the fixation tab
was immediately in
contact with the underside of the plate and the free end of the suture was
available on the
topside of the plate. The free end of the suture was gripped with the upper
Instron grippers
under light tension (enough to keep the suture taut) at a gauge length of 1
inch. The suture
was aligned in the center of the grip such that it was perpendicular to the
fixture and not
angled. Each specimen was pulled at 12 in. / min. to the point of fixation tab
failure.
[0080] A suture was formed according to the design of Figure 1, with a stamped
end effector
that was not manipulated after formation as the control ("nominal"). The
control suture was a
size 1 suture and was punched from PDS preform material, which is the in-
process feedstock
material used to make the suture. The tab end effector had a dimension of
approximately 200
mils in length, approximately 95 mils in width, and approximately 19.5-21.5
mils in
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thickness, having the contoured profile seen in Figures 1-2. In addition, a
second suture was
formed of the same configuration, but a single parallel end attachment
(described above and
seen as Figures 3C-3D) was welded to the end effector via RF welding. The
single parallel
end attachment was formed by cutting from the same PDS preform material as
used to form
the control suture and the second suture into a substantially rectangular
shape. This
rectangular end attachment was welded onto the existing fixation tab of the
second suture.
The cut rectangular attachment had dimensions of approximately 200 mils in
length,
approximately 95 ¨ 100 mils in width, and approximately 19.5 ¨ 21.5 mils in
thickness. The
end attachment had the same contoured thickness profile as the unmodified tab,
until the
attachment and the tab were welded, at which time the welded end effector had
a more
rectangular cross sectional configuration. The shear strength of each fixation
tab was tested
by loading each individual suture into the custom metal test fixture. Each
test specimen was
introduced into the slit in the fixture top plate such that the fixation tab
was immediately in
contact with the underside of the plate and the free end of the suture was
available on the
topside of the plate.
[0081] The free end of the suture was gripped with the upper Instron grippers
under light
tension (enough to keep the suture taut) at a gauge length of 1 inch. The
suture was aligned
in the center of the grip such that it was perpendicular to the fixture and
not angled. Each
specimen was pulled at 12 in. / min. to the point of fixation tab failure.
[0082] Table I shows the difference in performance between the nominal
(unwelded,
punched) tab and the RF welded tab (parallel configuration) of the same lot of
material.
Along with an increase in average strength, the lower values of the population
are increased
significantly, which translates to a decrease in the coefficient of variation.
Less device
variability translates to a more consistent product in the hands of a surgeon.
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Table I. Strength Nominal vs RF Welded Fixation Tab. n=100 samples per group.
Mean StDev COV Min Median Max
(lbf) (lbf) (%) (lbf) (lbf) (lbf)
Fixation Tab
(Nominal) 6.233 1.223 19.65 3.3 6.475 8.99
RF Welded Tab 11.727 1.345 11.47 8.79 11.58
14.83
% Increase Over
Nominal 88% 10% -
42% 166% 79% 65%
[0083] Figure 12 shows the tensile strength tested in a metal fixture of a
nominal tabbed
device (unwelded) as compared to various inventive embodiments. Inventive
samples were
prepared from the same lot of material as the nominal comparative device, with
one formed
as a parallel laminate, one formed as a double parallel laminate (Figures 5B-
5C) and one as a
folded attachment (Figures 7B-7C).
[0084] The % increase in average strength over the nominal (unwelded) fixation
device for
the 3 designs was 88% for a single parallel laminate end attachment, 132% for
a double
parallel laminate end attachment, and 149% for a back fold around end
attachment.
Example 2 ¨ Porcine Initiation Strength Testing
[0085] Initiation strength is a different test than the shear strength test
described in Example
1. During initiation strength testing, the suture device is inserted through
porcine fascia
tissue with the proximal end of the fixation tab abutted against the tissue
and the free end of
the suture loaded into an Instron for the pull to failure.
[0086] The comparative (nominal) suture was formed according to the design of
Figure 1 and
as explained in Example 1, with a punched end effector that is not welded
after formation. A
second suture ("Inventive 1") was formed of the same material and size, but a
single parallel
end attachment (as in Figures 3C-3D) was welded to the end effector via RF
welding (this
configuration is explained as in Example 1). A third suture ("Inventive 2")
was formed of the
same material and size, but two substantially identical parallel end
attachments were welded
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to the tab, one above the tab end effector and one below the tab end effector.
The end
attachments and the tab were aligned so as to be substantially flush with each
other and each
was welded to the end effector via RF welding concurrently. This configuration
is referred to
as a double parallel laminate design (as in Figures 5B-5C).
[0087] The initiation strength testing measures the strength of the fixation
device when
implanted in porcine midline fascia. Each test specimen was prepared by first
passing the
proximal end of the suture through each side of an incision near the apex and
pulling the
suture through the fascia until the proximal end of the fixation tab is
abutted against the
porcine fascia tissue. The tissue specimen was placed in a raised fixture
leaving the incision
area exposed for visual observation and allowing the load to be applied to the
proximal end of
the suture (loaded perpendicular to the fixed tissue plane) until a device or
tissue failure was
noted by the test operator. This set-up simulates a surgeon pulling 'up' on
the proximal
suture end after initiation of the device into the tissue. As shown in Figure
13, the inventive
fixation devices provided an increase in the initiation strength relative to a
nominal fixation
device. The single parallel end attachment provided an approximately 50%
increase over the
nominal tab while the double parallel end attachment provided an approximately
70%
increase over the nominal fixation tab.
[0088] Figure 14 shows a correlation plot of initiation strength in porcine
fascia (y axis) and
the shear strength of the fixation device using the metal fixture (x axis) for
the nominal
fixation device, single parallel end attachment, and double parallel end
attachment
configurations. A linear fit of the data points results in an R2 value of
0.9989 indicating a
strong correlation between the two test methods.
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