U.S. patent application number 16/539801 was filed with the patent office on 2020-02-06 for negative pressure wound closure device.
The applicant listed for this patent is University of Massachusetts. Invention is credited to Raymond Dunn.
Application Number | 20200038023 16/539801 |
Document ID | / |
Family ID | 46603322 |
Filed Date | 2020-02-06 |
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United States Patent
Application |
20200038023 |
Kind Code |
A1 |
Dunn; Raymond |
February 6, 2020 |
NEGATIVE PRESSURE WOUND CLOSURE DEVICE
Abstract
The present invention relates to a negative pressure wound
closure system and methods for using such a system. Preferred
embodiments of the invention facilitate closure of the wound by
preferentially contracting to provide for movement of the tissue.
Preferred embodiments can utilize tissue grasping elements to apply
a wound closing force to the tissue.
Inventors: |
Dunn; Raymond; (Shrewsbury,
MA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
University of Massachusetts |
Boston |
MA |
US |
|
|
Family ID: |
46603322 |
Appl. No.: |
16/539801 |
Filed: |
August 13, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15083675 |
Mar 29, 2016 |
10405861 |
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16539801 |
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14581685 |
Dec 23, 2014 |
9301742 |
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15083675 |
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13365615 |
Feb 3, 2012 |
9226737 |
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14581685 |
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61439525 |
Feb 4, 2011 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61M 1/0088 20130101;
A61F 2013/00536 20130101; A61F 2013/0054 20130101; A61B 17/0057
20130101; A61F 13/00068 20130101; A61B 2017/081 20130101; A61F
2013/00174 20130101; A61M 1/008 20130101; A61B 2017/00654 20130101;
A61B 17/08 20130101; A61F 2013/00548 20130101; A61F 2013/00544
20130101; A61B 2017/00561 20130101 |
International
Class: |
A61B 17/08 20060101
A61B017/08; A61M 1/00 20060101 A61M001/00; A61B 17/00 20060101
A61B017/00; A61F 13/00 20060101 A61F013/00 |
Claims
1-75. (canceled)
76. A negative pressure wound closure device, comprising: a porous
foam wound filler material that is sized and shaped to fit within a
wound opening between wound margins,. wherein the porous foam wound
filler material has a pore size and a pore density, and wherein the
porous foam wound filler material is structured to preferentially
contract along at least a first x-direction and inhibit contraction
along a second y-direction upon application of a negative pressure
to the wound opening to cause the wound margins to move along the
first x-direction towards closure of the wound.
77. The negative pressure wound closure device of claim 76 further
comprising a tissue grasping surface extending over an outer
peripheral surface of the wound filler material and comprising a
plurality of outward-projecting tissue anchors that contact tissue
at a margin of the wound opening and displace the tissue at the
wound margin upon application of the negative pressure to the wound
filler material to facilitate closure of the wound.
78. The negative pressure wound closure device of claim 76, further
comprising: a negative pressure source that is coupled to the
porous foam wound filler material to apply a closure force to the
wound opening; and a surface layer below the porous foam wound
filler material that is configured to manage fluid within the wound
and not to generate granulation.
79. The negative pressure wound closure device of claim 77, wherein
the plurality of tissue anchors are integrally formed in the wound
filler material.
80. The negative pressure wound closure device of claim 77, wherein
the tissue grasping surface comprises a film that is provided over
a surface of the wound filler material, the plurality of tissue
anchors projecting outward from the film.
81. The negative pressure wound closure device of claim 80, wherein
the film comprises a mesh material and includes a second plurality
of inward facing anchors that secure the film to the wound filler
material.
82. The negative pressure wound closure device of claim 76, wherein
the wound filler material further comprises a stabilizing structure
to enable collapse in at least the first x-direction and inhibit
collapse in at least the second y-direction, the stabilizing
structure including different regions in the porous foam wound
filler material having different pore sizes or pore densities or a
combination thereof.
83. The negative pressure wound closure device of claim 82, wherein
the stabilizing structure comprises one or more regions of rigid
material surrounded by regions of compressible material.
84. The negative pressure wound closure device of claim 82, wherein
the wound filler material has length, width and height dimensions,
and the stabilizing structure inhibits collapse in the height
dimension.
85. The negative pressure wound closure device of claim 82, wherein
the stabilizing structure compresses the wound filler material in
at least the first x-direction to effect reapproximation of the
wound.
86. The negative pressure wound closure device of claim 82, wherein
the stabilizing structure substantially restricts the collapse of
the wound filler material to a direction perpendicular to a plane
defined by the wound margins.
87. The negative pressure wound closure device of claims 82,
wherein the stabilizing structure comprises an endoskeleton made
from rigid material.
88. The negative pressure wound closure device of claim 82 wherein
the stabilizing structure comprises a plurality of connected
articulating elements.
89. The negative pressure wound closure device of claim 76 wherein
the porous foam wound filler material has an oval shape sized to
fit within an abdominal wound opening and positioned over a surface
layer such that the device contracts over the surface layer.
90. The negative pressure wound closure device of claim 89 wherein
the surface layer comprises a porous material to manage fluid
within the wound such that the porous foam wound filler material
slides over the surface layer during contraction.
91. The negative pressure wound closure device of claim 76 wherein
the porous foam wound filler material has regions of rigid material
and regions of compressible material wherein the porous foam wound
filler material has variable pore sizes and/or pore density.
92. The negative pressure wound closure device of claim 76 further
comprising a plurality of stabilizer elements extending within the
wound filler in a z-direction.
93. The negative pressure wound closure device of claim 92 wherein
the plurality of stabilizer elements comprise ribs, flexures or
rods.
94. The negative pressure wound closure device of claim 92 wherein
the stabilizer elements comprise a rigid or semi-rigid
material.
95. The negative pressure wound closure device of claim 92 wherein
the stabilizer elements are separated by a flexible material.
96. The negative pressure wound closure device of claim 76 wherein
the porous foam wound filler material comprises a smooth bottom
surface that slides during contraction in the first
x-direction.
97. The negative pressure wound closure device of claim 76 wherein
the porous foam wound filler material has cleavage lines to provide
for removal of one or more sections.
98. A method for treating a wound, comprising: placing into a wound
opening a porous wound filler material that is sized and shaped to
fit within the wound opening between wound margins, wherein the
porous wound filler material has a pore size and a pore density;
and applying a negative pressure to the wound opening to cause the
porous wound filler material to preferentially contract-along at
least a first x-direction and inhibit contraction along a second
y-direction to cause the wound margins to move along the first
x-direction towards closure of the wound.
99. The method of claim 98, wherein the placing of the porous wound
filler material further comprises using a plurality of stabilizer
elements extending within the wound filler material in a
z-direction to inhibit contraction of the porous wound filler
materials in the z-direction.
100. The method of claim 99, wherein the plurality of stabilizer
elements comprise ribs, flexures or rods.
101. The method of claim 100, wherein the stabilizer elements
comprise a rigid or semi-rigid material.
102. The method of claim 100, wherein the stabilizer elements are
separated by a flexible material.
103. The method of claim 98, wherein the porous wound filler
material comprises a smooth bottom surface that slides during
contraction in the first x-direction.
104. The method of claim 98, wherein the porous wound filler has
cleavage lines to provide removal of one or more sections.
105. The method of claim 98, wherein the porous wound filler
material comprises a foam.
106. The method of claim 98, wherein the porous wound filler
material comprises a mesh.
107. The method of claim 98, wherein the porous wound filler
material further comprises a mesh that extends around an oval
shaped structure that contracts in the first x-direction.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application is a continuation of U.S. application Ser.
No. 15/083,675 filed Mar. 29, 2016, now U.S. Pat. No. ______ ,
which is a continuation of application Ser. No. 14/581,685, filed
on Dec. 23, 2014, now U.S. Pat. No. 9,301,742, which is a
divisional of application Ser. No. 13/365,615, filed on Feb. 3,
2012, now U.S. Pat. No. 9,226,737 and also claims the priority to
U.S. Application No. 61/439,525, filed Feb. 4, 2011. The entire
contents of the above application being incorporated herein by
reference.
BACKGROUND OF THE INVENTION
[0002] A number of techniques have been developed for treatment of
wounds, including wounds resulting from accident and wounds
resulting from surgery. Often, wounds are closed using sutures or
staples. However, inserting these mechanical closure techniques
requires making additional punctures or wounds to the skin, which
can result in tissue injury and in the case of excess swelling,
possible ischemia and tissue loss. Also, mechanical wound closures
such as staples and sutures can cause highly-localized stresses at
the insertion points that can impede and damage the normal wound
healing processes of the skin.
[0003] In recent years, there has been increased interest in using
negative pressure devices for the treatment of wounds. Negative
pressure wound treatment utilizes devices that remove wound fluids
by applying negative pressure suction to the wound. It is believed
that such negative pressures promote wound healing by facilitating
the formation of granulation tissue at the wound site and assisting
the body's normal inflammatory process while simultaneously
removing excess fluid, which may contain adverse cytokines
bacteria. However, further improvements in negative pressure wound
therapy are needed to fully realize the benefits of treatment.
SUMMARY OF THE INVENTION
[0004] The present invention relates to a negative pressure wound
closure device that specifically exerts force at the edges of the
wound to facilitate closure of the wound. The device operates to
reduce the need for repetitive replacement of wound filler material
currently employed and can advance the rate of healing. The device
simultaneously uses negative pressure to remove wound fluids.
[0005] In one embodiment, a negative pressure wound closure device
includes a wound filler material that is sized and shaped to fit
within a wound opening and which contracts along at least one
dimension upon application of a negative pressure to the filler
material. The filler material is thus configured to preferentially
contract in at least one direction and inhibit contractions in one
or more additional directions. Prior negative pressure devices did
not assist in wound closure, but were used to drain fluids. By
providing for the controlled movement of tissue during the healing
process in conjunction with the drainage of fluids from wounds as
described in connection with the present invention, a substantial
improvement in the rate of healing can be realized. Note that
depending on the size of the wound, increased negative pressure can
be used.
[0006] In another preferred embodiment, a tissue grasping surface
extends over an outer peripheral surface of the wound filler
material and includes a plurality of tissue anchors that engage the
tissue at the wound margin. Upon application of negative pressure,
the tissue at the wound margin is displaced to facilitate closure
of the wound. A negative pressure source, such as a vacuum pump, is
coupled to the wound filler material to provide the negative
pressure.
[0007] The wound filler material generally comprises a porous
material, such as a foam. For embodiments employing tissue anchors,
these can be integrally formed in the filler material. In other
embodiments, the tissue anchors are provided on a separate covering
or film that is secured to the filler material.
[0008] In preferred embodiments, the filler material includes a
stabilizing structure that enables the material to collapse in at
least one first direction and inhibits collapse in at least one
second direction. The stabilizing structure can include regions of
relatively rigid material surrounded by regions of relatively
compressible material. In preferred embodiments, the stabilizing
structure is an endoskeleton formed of rigid and/or semi-rigid
materials.
[0009] In certain embodiments, the stabilizing structure inhibits
the filler material from collapsing along its height dimension,
while enabling the filler material to collapse within the plane
defined by the wound margins. This is useful in the case of
abdominal surgery, for example, in which the surgical incision is
along a straight line to form an oval shaped wound. This generally
oval shaped wound can extend through muscle and fatty tissue having
variable mechanical properties. Wound healing is better served
through the use of an oval shaped structure adapted to
preferentially collapse towards the original line of incision. In
preferred embodiments, the stabilizing structure promotes collapse
of the filler material in a manner to effect reapproximation of the
wound tissue. Fasciotomy wounds, or other wound dehiscences, or any
open wound can be successfully treated using embodiments of the
present invention.
[0010] The wound closure device can be used to treat wounds in the
mediastinum, for pressure ulcers, for wounds in the extremities
(arms or legs) etc. The wound closure device can also be used to
treat wounds of different shapes, such as circular, square,
rectangular or irregularly shaped wounds. A plurality of wound
closure elements can be shaped to fit within a wound and can attach
together to preferentially close the wound in a desired direction.
The different elements can comprise different materials or have
different characteristics, such as pore size and/or anchor size and
distribution to form a composite structure.
[0011] In one embodiment, an endoskeleton stabilizing structure
includes a plurality of spaced-apart rigid members forming a
cross-hatched configuration. The endoskeleton enables the filler
material to collapse along its width dimension and elongate to a
smaller degree along its length dimension. In certain embodiments,
a plurality of rigid members extend along the height of the filler
material and inhibit collapse of the material in its height
dimension, for example. According to certain embodiments, the
endoskeleton comprises a network of interconnected rigid members
that can articulate with respect to one another during collapse of
the filler material. The endoskeleton can include truss supports to
inhibit tilting motion of the filler material. In some embodiments,
the tissue anchors can be integrally formed in the
endoskeleton.
[0012] In certain embodiments, the wound filler material includes a
smooth bottom surface having micropores to allow the passage of
fluid from the wound through the bottom surface and into the device
for removal. The micropores can have variable pore size and/or pore
density to direct the distribution of vacuum force from the
negative pressure source. In some embodiments, the wound filler
material can have variable internal pore sizes and/or pore density
to direct the distribution of vacuum force.
[0013] In one embodiment, a negative pressure wound treatment
component for managing and/or removing fluid is coupled to the
wound filler material. A single negative pressure source can be
used for wound closure and fluid management/drainage. A sliding
surface is provided at the interface between the wound closure and
fluid management components.
[0014] In yet another embodiment, the filler material includes
removable portions to adjust the size of the wound closure device.
The filler material can be provided with pre-determined cleavage
lines for tearing or cutting away portions of the material. In
certain embodiments, sets of tissue anchors are embedded in the
filler material, and become exposed by removing excess portions of
the material.
[0015] According to another embodiment, the tissue anchors are
provided with a variable force profile. The force profile can vary
based on the depth of tissue or the type of tissue engaged.
[0016] In some embodiments, the force profile of the tissue
grasping surface varies around the perimeter of the wound closure
device. The force profile is varied, for instance, by varying one
or more of the length of the tissue anchors, the shape of the
anchors, the materials of the anchors and the density of the
anchors.
[0017] The present invention also relates to methods of closing a
wound using a wound closure device as described above. For example,
a linear incision in the skin overlying the abdomen provides access
to a surgical site such as the gastrointestinal system of the human
or animal body. Following completion, the wound must be treated by
negative pressure therapy to facilitate recovery. Thus, a wound
closure device in accordance with preferred embodiments of the
invention is inserted for wound closure treatment.
[0018] By using the negative pressure wound closure device of the
invention, patients with large or severe wounds are able to be
discharged or engage in rehabilative physical therapy, changed at
home and then brought back to have their wounds simply stitched
closed. By improving wound closure treatment and thereby reducing
cost, there is an opportunity for these devices to be a significant
part of the instruments used for wound care.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] Other features and advantages of the present invention will
be apparent from the following detailed description of the
invention, taken in conjunction with the accompanying drawings of
which:
[0020] FIG. 1A is a perspective schematic view of a negative
pressure wound closure device.
[0021] FIG. 1B is a cross-section view of the tissue grasping
surface of the wound closure device.
[0022] FIG. 1C is a side view of one embodiment of the tissue
grasping surface.
[0023] FIG. 1D is a top view of the wound closure device showing
x-y stabilizers in phantom.
[0024] FIG. 1E is a cross-section view of filler material showing
x-y stabilizers and z-stabilizers.
[0025] FIG. 1F is a bottom view of the wound closure device showing
a smooth bottom surface and micropores for removing fluid from the
wound site.
[0026] FIG. 1G is an elevation view of a peripheral stabilizer
element.
[0027] FIGS. 2A and 2B are perspective and side views,
respectively, of a supporting endoskeleton.
[0028] FIGS. 3A and 3B are perspective and side views,
respectively, of a supporting endoskeleton with support
trusses.
[0029] FIG. 3C is a side view of a supporting endoskeleton with
x-shaped support trusses.
[0030] FIGS. 4A-C illustrate a wound closure device of the
invention closing a wound.
[0031] FIGS. 4D-4E illustrate the use of a plurality of wound
closure elements used for wounds of different shapes.
[0032] FIG. 5 illustrates a two-stage negative pressure wound
treatment and negative pressure wound closure (NPWT/NPWC)
device.
[0033] FIG. 6 illustrates an enlarged view of a preferred
embodiment of the tissue anchor system in accordance with the
invention.
[0034] FIG. 7 illustrates an embodiment of a wound filler material
having a tear-away or cut-away design for accommodating different
wound sizes, with tissue anchors embedded within the filler
material at pre-determined cleavage points.
[0035] FIG. 8A is a side view of a tissue grasping surface,
illustrating different tissue anchors for different types of tissue
(T.sub.1, T.sub.2) and the respective force profiles for the
anchors, including the maximum force applied during vacuum closure
(F.sub.1) and the force required to remove the anchors from the
tissue (F.sub.2) without damaging the tissue.
[0036] FIG. 8B illustrates different designs for a tissue anchor of
the invention.
[0037] FIG. 8C illustrates an enlarged view of tissue anchor
elements on the peripheral surface of an oval shaped wound closure
device.
[0038] FIG. 9A is a schematic illustration of a wound closure
device positioned within a wound showing the different force
profile around the margin of the wound according to one
embodiment.
[0039] FIG. 9B illustrates the wound closure device of FIG. 9A
after a period of wound closure and healing, with the original
configuration of the wound and wound closure device indicated in
phantom.
[0040] FIG. 10 schematically illustrates a process of using a wound
closure device in accordance with the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0041] FIGS. 1A-1F illustrate an embodiment of a wound closure
device 100 of the present invention. The device 100 includes a
wound filler material 102 that is sized and shaped to fit within a
wound opening of a human or animal patient. In preferred
embodiments, the filler material 102 is a porous, biocompatible
material, such as an open cell polyurethane foam. The filler
material 102 is also preferentially collapsible, meaning that its
size can be reduced along at least one dimension (e.g., length,
width, height) by applying a negative pressure to the filler
material 102, while at the same time inhibiting contractions or
contracting at a slower rate in another direction.
[0042] Extending over at least one surface of the filler material
102, and preferably extending over an outer perimeter surface of
the filler material 102 is a tissue grasping surface 104. In one
embodiment, the tissue grasping surface 104 is a flexible covering,
such as a mesh film, that is secured to the outer perimeter surface
of the filler material 102 and can expand and contract with the
expansion and contraction of the filler material 102. In one
embodiment, the tissue grasping surface 102 is a mesh film or a
composite polyester mesh film, such as the Parietex.TM. mesh from
Covidien (Mansfield, MA). The tissue grasping surface 104 includes
a plurality of outward-facing tissue anchor elements 106, which in
the preferred embodiment are a plurality of closely-spaced barbs,
hooks or tissue grasping elements, which can be integrally formed
in the mesh film.
[0043] FIG. 1B is an edge view of the device 100 showing the tissue
grasping elements 106 projecting from the tissue grasping surface
104 on the periphery of the wound filler material 102. FIG. 1C is a
side view of one embodiment, in which the tissue grasping surface
104 is formed from a flexible material, in particular, a mesh
material. The grasping elements 106 project out from the page in
FIG. 1C. The flexible, mesh material of the tissue grasping surface
104 allows the surface to expand and contract as necessary with the
expansion and contraction of the underlying wound filler material
102.
[0044] In other embodiments, the tissue grasping surface 104 with
anchor elements 106 can be integrally formed in the filler material
102. The tissue grasping surface and/or anchor elements can also be
formed using a resorbable material.
[0045] The tissue anchor elements 106 are preferably provided over
an entire outer perimeter surface of the filler material 102. When
the filler material 102 is placed within a wound, the anchor
elements 106 become buried within the tissue at the wound margins
and secure the device 100 within the wound opening. The tissue
anchor elements 106 are preferably spread out over the entire
surface of the wound margin to provide sufficient strength in the
grasping force. The tissue grasping surface 104 is preferably
designed to allow the wound closure device 100 to be easily placed
but also easily removed and replaced with a new device 100 or other
wound dressing as needed (e.g., 2-7 days later). The grasping
surface 104 can be configured to have high grasping strength over
at least a portion of its surface, but easily removable by, for
example, pulling away at an edge. The tissue grasping surface 104
is preferably designed to be removed from a wound without damaging
the surrounding tissue. The anchor elements 106 are preferably
designed to accommodate various tissue applications, such as
muscle, fat, skin and collagen, and various combinations of these.
The anchor elements 106 can also be designed to remain securely
attached to particular tissues for a selected time period in
certain embodiments.
[0046] In embodiments in which the grasping surface 104 is formed
from a covering on the outer peripheral surface of the filler
material 102, the grasping surface can be attached to the filler
material 102 using any suitable technique, such as with an adhesive
or a mechanical fastening system. In a preferred embodiment, the
tissue grasping surface 104 includes filler-grasping anchor
elements, which can be barbs, that secure the grasping surface to
the filler material. As shown in the cross-section view of FIG. 6,
for example, the grasping surface 400 comprises a thin mesh or film
having two sets of barbs or similar anchor elements, a first set
410 of outwardly-facing tissue-grasping elements 412 that are
designed to project into tissue, and a second set 404 of elements
406 that project into the filler material to secure the grasping
surface to the filler material.
[0047] Returning to FIGS. 1A-1F, a negative pressure source 120,
such as a pump, is coupled to the filler material 102 by a suitable
coupling or conduit, such as tube 121. Additional tubes 107 can
also be connected through an array of spaced ports 105 in order to
spatially distribute the suction force so that the force exerted
along the sidewall 104 can be controlled separately from a fluid
suction force. The negative pressure source 120 can be activated to
apply a negative pressure to the filler material 102. In general,
the negative pressure causes a resulting pressure differential
which causes the filler material 102 to contract or "collapse." As
the filler material 102 contracts, the tissue grasping surface 104
grabs and pulls on the adjacent tissue, which is preferably the
tissue around a wound margin, resulting in the displacement of the
tissue thereby facilitating the closure of the wound. In a
preferred embodiment, the filler material 102 is designed to
collapse preferentially in at least one direction. For example, in
the embodiment of FIG. 1A, the filler material 102 includes a
length and width dimension along the y- and x-axes, respectively,
and a height along the z-axis. In order to efficiently transmit the
negative pressure to the subcutaneous or other wound margins, it is
preferred that the filler material 102 does not collapse centrally
in the z-direction (like a pancake), so that the action of the
negative pressure works predominantly in the x-y directions, or
more particularly, in a two-dimensional plane along the wound
margins such as in an open abdomen or fasciotomy. It will be
understood that in some embodiments, the plane of the wound margins
can be curved, such as when the wound goes around the curve of an
abdomen or leg.
[0048] Furthermore, in preferred embodiments the filler material
102 is configured to preferentially collapse in length and/or width
(i.e., along the x- and y-axes) to reapproximate the tissue at the
wound margins. Note that certain types of wounds can be treated
without the anchor elements described herein.
[0049] There are several ways in which the filler material 102 is
configured to exhibit preferential collapse characteristics. For
example, portions of the filler material 102 can be made from more
rigid material than the surrounding material, causing the filler
material to preferentially collapse in a particular direction. In
one embodiment, the filler material 102 can include a stabilizing
endoskeleton made from a suitable rigid material embedded within a
"collapsible" filler, such as an open cell foam. Note that the
amount of applied negative pressure can be adjustable depending on
the size and shape of the wound. Pressures above 125 mm, to as much
as 250 mm or more can be used to assist in wound closure. The
pressure can be reduced over time as the wound contracts.
[0050] As shown in FIGS. 1D and 1E, for example, the filler
material 102 includes a plurality of stabilizer elements 108 (shown
in phantom) that enable the collapse of the filler material in
certain directions, while inhibiting it in other directions. In
this embodiment, the stabilizer elements 108 include a plurality of
stabilizing ribs, flexures or rods, made from a suitably rigid or
semi-rigid material, such as plastic. The ribbed structure is
configured to preferentially collapse along a specific axis to
facilitate proper closure of the wound. The internal stabilizer
elements 108 in this embodiment form a cross-hatched pattern as
seen in FIG. 1D, though it will be understood that other
configurations can be utilized. The spacing between the elements in
the "open" state can be in a range of 1-2 cm, for example. The
stabilizer elements 108 can be provided at different depths within
the filler material, as shown in the cross-section view of FIG. 1E,
which helps inhibit collapse in the z-direction. In some
embodiments, z-axis stabilizer elements 110 can be utilized to
inhibit collapse in this direction. In FIG. 1E, the z-axis
stabilizer elements 110 are projections that extend vertically from
the ribs 108. In other embodiments, separate z-axis stabilizers,
such as rods or rib structures, can be employed.
[0051] In certain embodiments, the device 100 can include a
peripheral stabilizer element 111 that extends around the outer
periphery of the filler material 102, as shown in FIG. 1E. The
stabilizer element 111 can include a rib structure that reinforces
the filler material 102 in order to prevent collapse in the
z-direction, as well as to inhibit tilting of the filler material
in the z-y and z-x planes. Thus, preferred embodiments of the
filler material preferentially contract in at least a first
direction relative to a second direction upon application of a
negative pressure. Thus, for example, the width will contract at a
faster rate relative to the length, while the height (depth of the
wound) does not contract a substantial distance.
[0052] In some embodiments, the tissue grasping anchor elements 106
can be included on the peripheral stabilizer element 111, and
project out from the periphery of the filler material 102. This can
be as an alterative to, or in addition to, providing the anchor
elements 106 on a separate mesh or film. The peripheral stabilizer
element 111 is preferably configured to expand and contract as
necessary with the expansion and contraction of the wound filler
material 102. Thus, in a preferred embodiment, the stabilizer
element 111 has sufficient flexibility to contract and expand in
the x- and y-directions (i.e., around the periphery of the filler
material 102), but has adequate rigidity along the z-direction
(i.e. along the height of the filler) to inhibit collapse or
tilting in this direction.
[0053] An embodiment of a peripheral stabilizer element 111 is
shown in elevation view in FIG. 1G. The stabilizer element 111
includes a plurality of stabilizing rods 113, oriented to inhibit
collapse in the z-direction. The rods 113 are separated by a
flexible material 114 that allows the stabilizer element 111 to
expand and contract around the wound margin with the expansion and
contraction of the underlying filler material. In this embodiment,
the tissue anchor elements 106 are formed in the peripheral
stabilizer element 111 and project out from the page.
[0054] One embodiment of an endoskeleton for a wound filler
material of the invention is shown in FIGS. 2A and 2B. The
endoskeleton includes a first set of x-y stabilizer elements 108a
and a second set of x-y stabilizer elements 108b that are connected
by a plurality of z-axis stabilizer elements 110.
[0055] During collapse of the filler material 102, the respective
x-y stabilizer elements 108a, 108b are collapsible in the x-y
directions, but the z-axis stabilizer elements 110 inhibit collapse
in the z-direction. In preferred embodiments, the stabilizer
elements can articulate with respect to one another during
collapse. The joints 109 in the structure can be hinged or have a
reduced thickness to accommodate the flexing of the system. The
flexures between the joints may also flex to accommodate the
desired compression along the first, or lateral, axis 117 (see FIG.
4B). Some expansion can occur along the second, or longitudinal,
axis 119 as the device compresses. The frame material can have a
shape memory characteristic, which in combination with the suction
force, 25 defines the force level applied to the tissue.
[0056] In another embodiment, shown in FIGS. 3A and 3B, the
endoskeleton includes truss stabilizers 112 to inhibit tilting of
the filler material 102 during collapse. The truss stabilizers 112
keep the upper 108a and lower 108b x-y stabilizers aligned with one
another as the filler material 102 collapses. In some embodiments,
the truss stabilizers 112 can be rigid in certain directions and
relatively less rigid in other directions (for example, the truss
stabilizer can be bowed) to promote collapse in certain directions.
FIG. 3C illustrates an alternative embodiment having truss
stabilizers 112 in an "x"-shaped pattern.
[0057] The stabilizing endoskeleton in certain embodiments can be
made, in whole or in part, from a shape memory material. Various
shape memory materials can be used which return from a deformed
state (temporary shape) to their original (permanent) shape. This
change in shape can be induced by an external stimulus or
trigger.
[0058] In one embodiment, the original or "permanent" shape of the
endoskeleton is the "collapsed" configuration of the wound closure
device, or the shape that will bring about wound reapproximation.
When the wound closure device is initially inserted in the wound
opening, the endoskeleton is in a deformed or temporary state and
embedded within the filler material. The endoskeleton can
preferentially revert to its original or "collapsed" state or,
alternatively, cause the device to expand to engage the tissue. The
"collapse" force of the shape memory endoskeleton can be in
addition to or an alternative to the vacuum force induced by the
negative pressure source. In certain embodiments, the application
of a negative pressure to the wound closure device, which can cause
the endoskeleton to revert to its original state.
[0059] FIG. 1F shows the bottom of the wound closure device 100
according to one embodiment. The device 100 in this embodiment
includes a smooth bottom surface 115. This material can be
biocompatible film to be used with, such as, provided in
conjunction with the Renasys.RTM. system available from Smith &
Nephew. A preferred embodiment can also be used with a gauge as
also provided in the Renasys.RTM. system. The bottom surface 115
provides a low-friction interface between the wound closure device
100 and the underlying tissue. In the case of an abdominal wound,
for example, the underlying tissue can include internal organs,
such as the intestines. The smooth bottom surface 115 enables the
filler material 102 to contract and expand freely without
interference from the underlying tissue, and without damaging the
underlying tissue. In a preferred embodiment, the bottom surface
115 includes micropores 116 (shown with size exaggerated in FIG. 1F
for purposes of illustration) that allow the passage of fluid
through the bottom surface 115 and into the device 100 for removal
from the wound site. The wound closure device can also be inserted
over a separate layer of material so that the device with contract
on top of the sliding layer.
[0060] In some embodiments, the micropores 116 can have different
sizes in different regions and/or can have different pore densities
in different regions in order to direct different force levels of
the vacuum source to different regions of the device 100.
Similarly, the filler material 102 can be engineered with different
internal pore sizes and/or pore densities to direct the
distribution of forces from the vacuum source to different areas of
the device 100.
[0061] FIGS. 4A-4C illustrate the use of the present device 100 to
close a wound 200. The wound 200 includes a wound opening 201 and a
wound margin 203, as shown in FIG. 4A. In FIG. 4B, a wound closure
device 100 is placed within the wound opening 201 so that the
tissue grasping surface 104 is contacting the wound margin 203. In
certain embodiments, the wound closure device 100 can be formed by
trimming or tearing the filler material 102 to the proper size, and
then attaching the tissue grasping elements 106 around the
periphery of the filler material 102. In one embodiment, the
grasping elements 106 are attached by attaching a two-sided barbed
mesh to the filler material 102, where the outward-facing prongs
are designed for grasping tissue and the inward-facing prongs are
designed to secure the mesh to the filler material 102. A tube 121
connects the filler material 102 to the negative pressure source.
The area of the wound 200, including the filler material 102, can
be covered by a sealing drape 205.
[0062] In the embodiment of FIG. 4B, the filler material 102
includes a plurality of internal stabilizer elements 108 (shown in
phantom) that provide the filler material 102 with a preferential
collapse characteristic. The stabilizer elements 108 help control
the collapse of the filler material 102, and the resulting
displacement of the tissue around the wound margin 203, in the x-
and y-directions. Additional stabilizer elements can be provided to
control or inhibit collapse along the z-direction. As described
above in connection with FIGS. 1D, the stabilizer elements 108 in
this embodiment include a crosshatched configuration.
[0063] FIG. 4C illustrates the wound 200 following the application
of a negative pressure to the wound closure device 100. The tissue
anchor elements 106 grab the tissue margins 203 and cause
displacement of the tissue margins 203 as the filler material 102
collapses. As seen in the FIG. 4C, the filler material 102
collapses in the x- and y-directions in such a manner as to
reapproximate the tissue at the wound margin 203. In the embodiment
of FIG. 4B and 4C, the crosshatched configuration of the stabilizer
elements 108 help control the direction of tissue displacement
during collapse. The largest amount of tissue displacement in this
embodiment is in the central region of the wound 200, where the
opening 201 is widest, and this displacement is primarily inward
along the x-direction. Away from the central region (e.g., at the
top and bottom of the wound as shown in FIGS. 4A and 4B), where the
wound margins are closer together, less displacement in the
x-direction is needed to reapproximate the tissue. In general, the
inward collapse of the filler material along the y-direction is
undesirable. In fact, during tissue reapproximation, the wound 200
will tend to elongate in y-direction as the wound margins close in
the x-direction. In preferred embodiments, the internal stabilizer
elements 108 promote the collapse of the filler material in a
manner that provides wound reapproximation. In the embodiment of
FIGS. 4-C, for example, during filler collapse the crosshatched
stabilizer elements 108 straighten out relative to one another,
similar to an accordion gate. The largest displacement is in the
central region of the filler 102, along the x-direction. The
stabilizers 102 generally inhibit inward collapse along the
y-direction. As the stabilizers 108 straighten out, they can also
facilitate elongation of the wound in the y-direction to allow
proper tissue reapproximation. Shown in FIGS. 4D-4E are different
shaped wounds 220, 240 in which a plurality of wound closure
elements are used in combination to fill the wound. In FIG. 4D,
elements 222, 224, 226 and 228 have different shapes that are cut
or trimmed to size so as to substantially fill the wound that in
this example, is circular in shape. When negative pressure is
applied, the elements work together to close the wound in a desired
direction. FIG. 4E illustrates a rectangular wound 240 using
closure elements 242, 244, 246, 248 and 250 to fill the wound 240.
The tissue anchors of each closure element can also attach to the
adjoining closure element(s). With suction applied to the central
elements 224, 250, the adjoining elements are drawn towards the
central elements to close the wound.
[0064] The wound closure device 200 can remain in this
configuration for a period of several days or weeks to facilitate
closing and healing of the wound 200. After a period of healing,
the device 100 can be removed and optionally replaced with a
smaller device. After the wound has been sufficiently closed using
the present device, it can be stitched closed.
[0065] FIG. 5 illustrates a two-stage negative pressure wound
treatment and negative pressure wound closure (NPWT/NPWC) device
300. The device includes a negative pressure drainage/fluid
management component 301, as is known in the art, that connects
with an overlying negative pressure wound closure device 100. The
wound closure device 100 includes a collapsible wound filler
material 102 and a tissue grasping surface 104, substantially as
described above. A tube 121 connects the device 300 to a single
pump for applying a negative pressure to the wound closure and
wound treatment components. The device 300 can include
interchangeable parts depending on the need of a specific wound
application. In one embodiment, the device 300 is used for
abdominal wounds, and can also be used for mediastinum and
fasciotomy wounds.
[0066] In a preferred embodiment, the filler material 102 is able
to "slide" within the total NPWT/NPWC device 300. The filler
material 102 includes a sliding surface 303 at the interface
between the wound closure and fluid management components. The
sliding surface can comprise a treated surface or a separate layer
of material. The sliding surface 303 facilitates the free
contraction of the wound closure component, without interference
from the fluid management component. The underlying fluid
management component 301 can be specifically configured to manage
fluid only and to not generate granulation, as this can slow down
or inhibit the "slide."
[0067] FIG. 6 illustrates an enlarged view of a preferred
embodiment of the tissue anchor system 400 in accordance with the
invention. One side of the material 402 has a first group of anchor
elements 404 that are adapted to grasp the filler material. The
first anchor elements 404 can be shaped to grasp the filter
material such as with a distal hooked shape 406. As material 402
must attach to the filter with a certain grasping strength in order
to apply a sufficient pulling force on the tissue, a specified
force level F, must be applied to remove the hooks from the filler
material that exceeds the pulling force being applied to the
tissue. Similarly, as the tissue to be grasped by the material 402
has different structural characteristics then the filler material,
a second group of anchor elements 410 adapted to grasp tissue can
have a different shape and grasping force then the first anchor
elements. In this embodiment, barbs 412 will bilateral prongs 414
that tend to collapse upon insertion in tissue and yet expand when
pulled in an opposite direction such that a certain pulling force
can be applied to tissue. However, the prongs or cone shape anchor
element has a release force such that the barbs can be manually
pulled from the tissue without causing injury.
[0068] FIG. 7 illustrates an embodiment a wound filler material 500
having a tear-away or cut-away design for accommodating different
wound sizes. The filler material 500 includes natural cleavage
lines 501, 503, 505 that allow the size of the material to be
adjusted to fit the wound to be closed. The material 500 is
designed to be torn or cut at the cleavage lines to remove one or
more portions 502a, 502b, 502c of the material and adjust the size
of the material. Sets of tissue anchors 506a, 506b, 506c, 506d are
embedded within the filler material at pre-determined cleavage
points, and become exposed as the respective outer portions 502a,
502b, 502c are removed. The tissue anchors 506a, 506b, 506c, 506d
can be associated with a stabilizing endoskeleton structure, such
as described above in connection with FIGS. 1-4. In some
embodiments, the stabilizing endoskeleton structure can include
pre-defined cleavage points to remove portions of the stabilizer
structure as the size of the filler material 500 is adjusted.
[0069] FIG. 8A is a side view of a tissue grasping surface,
illustrating different tissue anchors 601, 602, 603, 604 for
different types of tissue (T.sub.1, T.sub.2). Also illustrated is
an example of the respective force profiles for the anchors,
including the maximum force applied to the tissue during vacuum
closure (F.sub.1) and the force required to remove the anchors from
the tissue (F.sub.2) without damaging the tissue. In one
embodiment, the characteristics of the tissue anchors vary to
provide different force profiles across the interface between the
wound closure device and the surrounding tissue. For example, for
the upper tissue layer(s), T.sub.1, the anchor 601 is designed to
attach to collagen material, such as in the dermis. The anchor 601
has a different force profile (F.sub.1 and F.sub.2) on the upper
tissue layer(s), T.sub.1, as shown in FIG. 8A. At the lower tissue
layers T.sub.2, the anchors 602, 603, 604 are designed to attach to
fatty tissue of subcutaneous layer. Generally, a smaller force
profile is needed to secure the anchors to this tissue.
[0070] The characteristics of the anchors, and their resulting
force profiles, can vary by a number of parameters, such as the
length of the anchor, the shape of the anchor, the structure of
grasping features, the material(s) used for the anchor, the
relative flexibility/rigidity of the anchors, and the
spacing/density of the anchors. In FIG. 8A for example, anchor 601
is significantly longer than anchors 602, 603, which in turn are
longer than anchors 604. FIG. 8A also illustrates varying the
density of anchors, such as shown in 602, 603 and 604. FIG. 8B
illustrates three examples of different types of grasping features,
including a barbed configuration 605, a staggered hook
configuration 606, and a staggered barbed configuration 607. Other
suitable grasping features can be utilized such as the anchor
elements 620 shown in the enlarged perspective view of FIG. 8C. The
anchoring process can be augmented by suturing the filler material
or supporting endoskeleton to the tissue. The force profile can
also be varied by controlling the vacuum force distribution in the
filler material, such as by varying the pore size and/or pore
density of the filler.
[0071] The wound closure device of the invention can be provided in
kits for closing different types of wounds (e.g., abdominal,
fasciotomy, etc.). The tissue grasping surface can be optimized for
different types of tissue such as collagen, fatty tissue and
muscle, depending on the structure of the tissue at the wound
site.
[0072] In certain embodiments, the force profile of the wound
closure device is variable around the periphery of the wound. An
exemplary embodiment is illustrated in FIG. 9A, which shows the
force profile (f.sub.1) exerted on the wound margins at a plurality
of locations on the periphery of the wound. In this embodiment, the
largest f.sub.1 is at the central region of the wound filler 102,
where the wound opening is widest and the wound closure force is
entirely or nearly entirely in the x-direction. Moving towards the
top and bottom regions of the wound, the closure force (f.sub.1) is
much smaller. One reason for this is because the wound opening is
much smaller in these regions, and a much smaller force is needed
to reapproximate the tissue. Also, the inward force exerted in
these regions includes components in both the x- and y-directions.
Thus, a smaller force profile is preferable to avoid the inward
collapse of the tissue in the y-direction. As illustrated in FIG.
9B, as the wound closes and heals from an initial state (indicated
by dotted lines) to a later state (indicated by solid lines), it
becomes elongated in the y-direction. Thus, the displacement of
tissue anchors 701a and 701b is exclusively in the x-direction and
in the direction of the closure force (f.sub.1), while the
displacement of tissue anchors 703a, 703b is both inwards in the
x-direction (in the direction of the closure force) and outwards in
the y-direction (opposite the direction of the closure force).
Thus, a smaller f.sub.1 is preferable in these regions to provide
more "play" between the anchor elements and the surrounding tissue.
Alternatively, the wound closure device is configured so that it
does not elongate, but rather does not change its length along the
long axis 720.
[0073] The variation in the force profile around the periphery of
the wound closure device can be achieved in a variety of ways, such
as varying the spacing/density of the tissue anchors, the types of
anchors, length of anchors, etc. For example, in FIGS. 9A and 9B,
anchors 701a, 701b are longer and penetrate deeper into the tissue
compared to anchors 703a, 703b. The force profile can also be
varied by controlling the vacuum force distribution in the filler
material, such as by varying the pore size and/or pore density of
the filler.
[0074] On one embodiment, a method of fabricating a wound closure
device of the invention includes forming a stabilizing endoskeleton
of rigid or semi-rigid material and forming a collapsible filler
material over the endoskeleton. The stabilizing endoskeleton can be
formed using a molding process, and can be molded as an integral
unit or in one or more components that are then assembled to form
the endoskeleton. Different components of the endoskeleton can have
different thicknesses and/or degrees of rigidity to provide varying
levels of rigidity and flexibility along different directions. The
endoskeleton can be assembled by joining components, such as by
using a suitable adhesive or other joining process. In certain
embodiments, at least some of the components can be assembled to
provide articulating joints. In preferred embodiments, the filler
material is formed by mixing together appropriate metered amounts
of constituent substances, (e.g., isocyanates, polyols, catalysts,
surfactants, blowing agents and the like in the case of
polyurethane foam), dispensing the reacting mixture into a mold,
and then curing and demolding the material. Optionally, the
material can then be cut or trimmed to the finished shape. In
preferred embodiments, the endoskeleton support structure is
assembled and placed into the mold, and the filler material is
molded around the endoskeleton. An example of a biodegradable foam
product suitable for the present wound closure device, and methods
of fabricating such a foam, is described in U.S. Published
Application No. 2009/0093550 to Rolfes et al., the entire contents
of which are incorporated herein by reference.
[0075] A method of performing a surgical procedure 800 using a
wound closure device in accordance with preferred embodiments of
the invention as illustrated in FIG. 10. After preparation 800 of
the patient for surgery, an incision is made 820 to expose the
surgical site, typically in the abdomen. After the procedure is
performed, the wound is prepared 830 for closure. The proper size
and shape of the wound closure device is selected 840 with the
peripheral tissue attachment members positioned around the
circumference or outer wall surface of the device. The device is
inserted 850 into the wound and the tissue attachment elements are
inserted 860 into the tissue. Negative pressure is then applied 870
to exert a closure force on the wound edges. Depending on the
particular application, large wounds may require placement 880 of a
smaller second closure after removal of the first larger device.
Finally, the device is removed 890 and the wound is closed,
typically by suturing.
[0076] While the invention has been described in connection with
specific methods and apparatus, those skilled in the art will
recognize other equivalents to the specific embodiments herein. It
is to be understood that the description is by way of example and
not as a limitation to the scope of the invention and these
equivalents are intended to be encompassed by the claims set forth
below.
* * * * *