US20200038023A1 - Negative pressure wound closure device - Google Patents

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.

Description

CROSS REFERENCE TO RELATED APPLICATION
• 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
• 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.
• 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
• 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.
• 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.
• 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.
• 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.
• 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.
• 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.
• 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.
• 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.
• 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.
• 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.
• 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.
• 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.
• 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.
• 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.
• 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
• 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:
• FIG. 1A is a perspective schematic view of a negative pressure wound closure device.
• FIG. 1B is a cross-section view of the tissue grasping surface of the wound closure device.
• FIG. 1C is a side view of one embodiment of the tissue grasping surface.
• FIG. 1D is a top view of the wound closure device showing x-y stabilizers in phantom.
• FIG. 1E is a cross-section view of filler material showing x-y stabilizers and z-stabilizers.
• 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.
• FIG. 1G is an elevation view of a peripheral stabilizer element.
• FIGS. 2A and 2B are perspective and side views, respectively, of a supporting endoskeleton.
• FIGS. 3A and 3B are perspective and side views, respectively, of a supporting endoskeleton with support trusses.
• FIG. 3C is a side view of a supporting endoskeleton with x-shaped support trusses.
• FIGS. 4A-C illustrate a wound closure device of the invention closing a wound.
• FIGS. 4D-4E illustrate the use of a plurality of wound closure elements used for wounds of different shapes.
• FIG. 5 illustrates a two-stage negative pressure wound treatment and negative pressure wound closure (NPWT/NPWC) device.
• FIG. 6 illustrates an enlarged view of a preferred embodiment of the tissue anchor system in accordance with the invention.
• 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.
• FIG. 8A is a side view of a tissue grasping surface, illustrating different tissue anchors for different types of tissue (T₁, T₂) and the respective force profiles for the anchors, including the maximum force applied during vacuum closure (F₁) and the force required to remove the anchors from the tissue (F₂) without damaging the tissue.
• FIG. 8B illustrates different designs for a tissue anchor of the invention.
• FIG. 8C illustrates an enlarged view of tissue anchor elements on the peripheral surface of an oval shaped wound closure device.
• 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.
• FIG. 9B illustrates the wound closure device ofFIG. 9A after a period of wound closure and healing, with the original configuration of the wound and wound closure device indicated in phantom.
• FIG. 10 schematically illustrates a process of using a wound closure device in accordance with the invention.
DETAILED DESCRIPTION OF THE INVENTION
• FIGS. 1A-1F illustrate an embodiment of awound closure device100 of the present invention. Thedevice100 includes awound filler material102 that is sized and shaped to fit within a wound opening of a human or animal patient. In preferred embodiments, thefiller material102 is a porous, biocompatible material, such as an open cell polyurethane foam. Thefiller material102 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 thefiller material102, while at the same time inhibiting contractions or contracting at a slower rate in another direction.
• Extending over at least one surface of thefiller material102, and preferably extending over an outer perimeter surface of thefiller material102 is atissue grasping surface104. In one embodiment, thetissue grasping surface104 is a flexible covering, such as a mesh film, that is secured to the outer perimeter surface of thefiller material102 and can expand and contract with the expansion and contraction of thefiller material102. In one embodiment, thetissue grasping surface102 is a mesh film or a composite polyester mesh film, such as the Parietex™ mesh from Covidien (Mansfield, MA). Thetissue grasping surface104 includes a plurality of outward-facingtissue anchor elements106, 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.
• FIG. 1B is an edge view of thedevice100 showing thetissue grasping elements106 projecting from thetissue grasping surface104 on the periphery of thewound filler material102.FIG. 1C is a side view of one embodiment, in which thetissue grasping surface104 is formed from a flexible material, in particular, a mesh material. Thegrasping elements106 project out from the page inFIG. 1C. The flexible, mesh material of thetissue grasping surface104 allows the surface to expand and contract as necessary with the expansion and contraction of the underlyingwound filler material102.
• In other embodiments, thetissue grasping surface104 withanchor elements106 can be integrally formed in thefiller material102. The tissue grasping surface and/or anchor elements can also be formed using a resorbable material.
• Thetissue anchor elements106 are preferably provided over an entire outer perimeter surface of thefiller material102. When thefiller material102 is placed within a wound, theanchor elements106 become buried within the tissue at the wound margins and secure thedevice100 within the wound opening. Thetissue anchor elements106 are preferably spread out over the entire surface of the wound margin to provide sufficient strength in the grasping force. Thetissue grasping surface104 is preferably designed to allow thewound closure device100 to be easily placed but also easily removed and replaced with anew device100 or other wound dressing as needed (e.g., 2-7 days later). The graspingsurface104 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. Thetissue grasping surface104 is preferably designed to be removed from a wound without damaging the surrounding tissue. Theanchor elements106 are preferably designed to accommodate various tissue applications, such as muscle, fat, skin and collagen, and various combinations of these. Theanchor elements106 can also be designed to remain securely attached to particular tissues for a selected time period in certain embodiments.
• In embodiments in which thegrasping surface104 is formed from a covering on the outer peripheral surface of thefiller material102, the grasping surface can be attached to thefiller material102 using any suitable technique, such as with an adhesive or a mechanical fastening system. In a preferred embodiment, thetissue grasping surface104 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 ofFIG. 6, for example, the graspingsurface400 comprises a thin mesh or film having two sets of barbs or similar anchor elements, afirst set410 of outwardly-facing tissue-graspingelements412 that are designed to project into tissue, and asecond set404 ofelements406 that project into the filler material to secure the grasping surface to the filler material.
• Returning toFIGS. 1A-1F, anegative pressure source120, such as a pump, is coupled to thefiller material102 by a suitable coupling or conduit, such astube121.Additional tubes107 can also be connected through an array of spacedports105 in order to spatially distribute the suction force so that the force exerted along thesidewall104 can be controlled separately from a fluid suction force. Thenegative pressure source120 can be activated to apply a negative pressure to thefiller material102. In general, the negative pressure causes a resulting pressure differential which causes thefiller material102 to contract or “collapse.” As thefiller material102 contracts, thetissue grasping surface104 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, thefiller material102 is designed to collapse preferentially in at least one direction. For example, in the embodiment ofFIG. 1A, thefiller material102 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 thefiller material102 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.
• Furthermore, in preferred embodiments thefiller material102 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.
• There are several ways in which thefiller material102 is configured to exhibit preferential collapse characteristics. For example, portions of thefiller material102 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, thefiller material102 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.
• As shown inFIGS. 1D and 1E, for example, thefiller material102 includes a plurality of stabilizer elements108 (shown in phantom) that enable the collapse of the filler material in certain directions, while inhibiting it in other directions. In this embodiment, thestabilizer elements108 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. Theinternal stabilizer elements108 in this embodiment form a cross-hatched pattern as seen inFIG. 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. Thestabilizer elements108 can be provided at different depths within the filler material, as shown in the cross-section view ofFIG. 1E, which helps inhibit collapse in the z-direction. In some embodiments, z-axis stabilizer elements110 can be utilized to inhibit collapse in this direction. InFIG. 1E, the z-axis stabilizer elements110 are projections that extend vertically from theribs108. In other embodiments, separate z-axis stabilizers, such as rods or rib structures, can be employed.
• In certain embodiments, thedevice100 can include aperipheral stabilizer element111 that extends around the outer periphery of thefiller material102, as shown inFIG. 1E. Thestabilizer element111 can include a rib structure that reinforces thefiller material102 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.
• In some embodiments, the tissue graspinganchor elements106 can be included on theperipheral stabilizer element111, and project out from the periphery of thefiller material102. This can be as an alterative to, or in addition to, providing theanchor elements106 on a separate mesh or film. Theperipheral stabilizer element111 is preferably configured to expand and contract as necessary with the expansion and contraction of thewound filler material102. Thus, in a preferred embodiment, thestabilizer element111 has sufficient flexibility to contract and expand in the x- and y-directions (i.e., around the periphery of the filler material102), but has adequate rigidity along the z-direction (i.e. along the height of the filler) to inhibit collapse or tilting in this direction.
• An embodiment of aperipheral stabilizer element111 is shown in elevation view inFIG. 1G. Thestabilizer element111 includes a plurality of stabilizingrods113, oriented to inhibit collapse in the z-direction. Therods113 are separated by aflexible material114 that allows thestabilizer element111 to expand and contract around the wound margin with the expansion and contraction of the underlying filler material. In this embodiment, thetissue anchor elements106 are formed in theperipheral stabilizer element111 and project out from the page.
• One embodiment of an endoskeleton for a wound filler material of the invention is shown inFIGS. 2A and 2B. The endoskeleton includes a first set ofx-y stabilizer elements108aand a second set ofx-y stabilizer elements108bthat are connected by a plurality of z-axis stabilizer elements110.
• During collapse of thefiller material102, the respectivex-y stabilizer elements108a,108bare collapsible in the x-y directions, but the z-axis stabilizer elements110 inhibit collapse in the z-direction. In preferred embodiments, the stabilizer elements can articulate with respect to one another during collapse. Thejoints109 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, axis117 (seeFIG. 4B). Some expansion can occur along the second, or longitudinal,axis119 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.
• In another embodiment, shown inFIGS. 3A and 3B, the endoskeleton includestruss stabilizers112 to inhibit tilting of thefiller material102 during collapse. Thetruss stabilizers112 keep the upper108aand lower108bx-y stabilizers aligned with one another as thefiller material102 collapses. In some embodiments, thetruss stabilizers112 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 havingtruss stabilizers112 in an “x”-shaped pattern.
• 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.
• 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.
• FIG. 1F shows the bottom of thewound closure device100 according to one embodiment. Thedevice100 in this embodiment includes asmooth bottom surface115. This material can be biocompatible film to be used with, such as, provided in conjunction with the Renasys® system available from Smith & Nephew. A preferred embodiment can also be used with a gauge as also provided in the Renasys® system. Thebottom surface115 provides a low-friction interface between thewound closure device100 and the underlying tissue. In the case of an abdominal wound, for example, the underlying tissue can include internal organs, such as the intestines. Thesmooth bottom surface115 enables thefiller material102 to contract and expand freely without interference from the underlying tissue, and without damaging the underlying tissue. In a preferred embodiment, thebottom surface115 includes micropores116 (shown with size exaggerated inFIG. 1F for purposes of illustration) that allow the passage of fluid through thebottom surface115 and into thedevice100 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.
• In some embodiments, themicropores116 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 thedevice100. Similarly, thefiller material102 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 thedevice100.
• FIGS. 4A-4C illustrate the use of thepresent device100 to close awound200. Thewound200 includes awound opening201 and awound margin203, as shown inFIG. 4A. InFIG. 4B, awound closure device100 is placed within the wound opening201 so that thetissue grasping surface104 is contacting thewound margin203. In certain embodiments, thewound closure device100 can be formed by trimming or tearing thefiller material102 to the proper size, and then attaching thetissue grasping elements106 around the periphery of thefiller material102. In one embodiment, the graspingelements106 are attached by attaching a two-sided barbed mesh to thefiller material102, where the outward-facing prongs are designed for grasping tissue and the inward-facing prongs are designed to secure the mesh to thefiller material102. Atube121 connects thefiller material102 to the negative pressure source. The area of thewound200, including thefiller material102, can be covered by a sealingdrape205.
• In the embodiment ofFIG. 4B, thefiller material102 includes a plurality of internal stabilizer elements108 (shown in phantom) that provide thefiller material102 with a preferential collapse characteristic. Thestabilizer elements108 help control the collapse of thefiller material102, and the resulting displacement of the tissue around thewound margin203, 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 withFIGS. 1D, thestabilizer elements108 in this embodiment include a crosshatched configuration.
• FIG. 4C illustrates thewound200 following the application of a negative pressure to thewound closure device100. Thetissue anchor elements106 grab thetissue margins203 and cause displacement of thetissue margins203 as thefiller material102 collapses. As seen in theFIG. 4C, thefiller material102 collapses in the x- and y-directions in such a manner as to reapproximate the tissue at thewound margin203. In the embodiment ofFIG. 4B and 4C, the crosshatched configuration of thestabilizer elements108 help control the direction of tissue displacement during collapse. The largest amount of tissue displacement in this embodiment is in the central region of thewound200, where theopening201 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 inFIGS. 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, thewound200 will tend to elongate in y-direction as the wound margins close in the x-direction. In preferred embodiments, theinternal stabilizer elements108 promote the collapse of the filler material in a manner that provides wound reapproximation. In the embodiment ofFIGS. 4-C, for example, during filler collapse the crosshatchedstabilizer elements108 straighten out relative to one another, similar to an accordion gate. The largest displacement is in the central region of thefiller102, along the x-direction. Thestabilizers102 generally inhibit inward collapse along the y-direction. As thestabilizers108 straighten out, they can also facilitate elongation of the wound in the y-direction to allow proper tissue reapproximation. Shown inFIGS. 4D-4E are different shapedwounds220,240 in which a plurality of wound closure elements are used in combination to fill the wound. InFIG. 4D,elements222,224,226 and228 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 arectangular wound240 usingclosure elements242,244,246,248 and250 to fill thewound240. The tissue anchors of each closure element can also attach to the adjoining closure element(s). With suction applied to thecentral elements224,250, the adjoining elements are drawn towards the central elements to close the wound.
• Thewound closure device200 can remain in this configuration for a period of several days or weeks to facilitate closing and healing of thewound200. After a period of healing, thedevice100 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.
• FIG. 5 illustrates a two-stage negative pressure wound treatment and negative pressure wound closure (NPWT/NPWC)device300. The device includes a negative pressure drainage/fluid management component301, as is known in the art, that connects with an overlying negative pressure woundclosure device100. Thewound closure device100 includes a collapsiblewound filler material102 and atissue grasping surface104, substantially as described above. Atube121 connects thedevice300 to a single pump for applying a negative pressure to the wound closure and wound treatment components. Thedevice300 can include interchangeable parts depending on the need of a specific wound application. In one embodiment, thedevice300 is used for abdominal wounds, and can also be used for mediastinum and fasciotomy wounds.
• In a preferred embodiment, thefiller material102 is able to “slide” within the total NPWT/NPWC device300. Thefiller material102 includes a slidingsurface303 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 slidingsurface303 facilitates the free contraction of the wound closure component, without interference from the fluid management component. The underlyingfluid management component301 can be specifically configured to manage fluid only and to not generate granulation, as this can slow down or inhibit the “slide.”
• FIG. 6 illustrates an enlarged view of a preferred embodiment of thetissue anchor system400 in accordance with the invention. One side of thematerial402 has a first group ofanchor elements404 that are adapted to grasp the filler material. Thefirst anchor elements404 can be shaped to grasp the filter material such as with a distalhooked shape406. Asmaterial402 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 thematerial402 has different structural characteristics then the filler material, a second group ofanchor elements410 adapted to grasp tissue can have a different shape and grasping force then the first anchor elements. In this embodiment,barbs412 will bilateral prongs414 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.
• FIG. 7 illustrates an embodiment awound filler material500 having a tear-away or cut-away design for accommodating different wound sizes. Thefiller material500 includesnatural cleavage lines501,503,505 that allow the size of the material to be adjusted to fit the wound to be closed. Thematerial500 is designed to be torn or cut at the cleavage lines to remove one ormore portions502a,502b,502cof the material and adjust the size of the material. Sets of tissue anchors506a,506b,506c,506dare embedded within the filler material at pre-determined cleavage points, and become exposed as the respectiveouter portions502a,502b,502care removed. The tissue anchors506a,506b,506c,506dcan be associated with a stabilizing endoskeleton structure, such as described above in connection withFIGS. 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 thefiller material500 is adjusted.
• FIG. 8A is a side view of a tissue grasping surface, illustrating different tissue anchors601,602,603,604 for different types of tissue (T₁, T₂). Also illustrated is an example of the respective force profiles for the anchors, including the maximum force applied to the tissue during vacuum closure (F₁) and the force required to remove the anchors from the tissue (F₂) 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), T₁, theanchor601 is designed to attach to collagen material, such as in the dermis. Theanchor601 has a different force profile (F₁and F₂) on the upper tissue layer(s), T₁, as shown inFIG. 8A. At the lower tissue layers T₂, theanchors602,603,604 are designed to attach to fatty tissue of subcutaneous layer. Generally, a smaller force profile is needed to secure the anchors to this tissue.
• 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. InFIG. 8A for example,anchor601 is significantly longer thananchors602,603, which in turn are longer than anchors604.FIG. 8A also illustrates varying the density of anchors, such as shown in602,603 and604.FIG. 8B illustrates three examples of different types of grasping features, including abarbed configuration605, astaggered hook configuration606, and a staggeredbarbed configuration607. Other suitable grasping features can be utilized such as theanchor elements620 shown in the enlarged perspective view ofFIG. 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.
• 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.
• In certain embodiments, the force profile of the wound closure device is variable around the periphery of the wound. An exemplary embodiment is illustrated inFIG. 9A, which shows the force profile (f₁) exerted on the wound margins at a plurality of locations on the periphery of the wound. In this embodiment, the largest f₁is at the central region of thewound filler102, 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 (f₁) 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 inFIG. 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 anchors701aand701bis exclusively in the x-direction and in the direction of the closure force (f₁), while the displacement of tissue anchors703a,703bis 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 f₁is 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 thelong axis720.
• 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, inFIGS. 9A and 9B, anchors701a,701bare longer and penetrate deeper into the tissue compared toanchors703a,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.
• 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.
• A method of performing asurgical procedure800 using a wound closure device in accordance with preferred embodiments of the invention as illustrated inFIG. 10. Afterpreparation800 of the patient for surgery, an incision is made820 to expose the surgical site, typically in the abdomen. After the procedure is performed, the wound is prepared830 for closure. The proper size and shape of the wound closure device is selected840 with the peripheral tissue attachment members positioned around the circumference or outer wall surface of the device. The device is inserted850 into the wound and the tissue attachment elements are inserted860 into the tissue. Negative pressure is then applied870 to exert a closure force on the wound edges. Depending on the particular application, large wounds may requireplacement880 of a smaller second closure after removal of the first larger device. Finally, the device is removed890 and the wound is closed, typically by suturing.
• 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.

Claims (33)

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 ofclaim 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 ofclaim 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 ofclaim 77, wherein the plurality of tissue anchors are integrally formed in the wound filler material.

80. The negative pressure wound closure device ofclaim 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 ofclaim 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 ofclaim 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 ofclaim 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 ofclaim 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 ofclaim 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 ofclaim 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 ofclaims 82, wherein the stabilizing structure comprises an endoskeleton made from rigid material.

88. The negative pressure wound closure device ofclaim 82 wherein the stabilizing structure comprises a plurality of connected articulating elements.

89. The negative pressure wound closure device ofclaim 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 ofclaim 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 ofclaim 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 ofclaim 76 further comprising a plurality of stabilizer elements extending within the wound filler in a z-direction.

93. The negative pressure wound closure device ofclaim 92 wherein the plurality of stabilizer elements comprise ribs, flexures or rods.

94. The negative pressure wound closure device ofclaim 92 wherein the stabilizer elements comprise a rigid or semi-rigid material.

95. The negative pressure wound closure device ofclaim 92 wherein the stabilizer elements are separated by a flexible material.

96. The negative pressure wound closure device ofclaim 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 ofclaim 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 ofclaim 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 ofclaim 99, wherein the plurality of stabilizer elements comprise ribs, flexures or rods.

101. The method ofclaim 100, wherein the stabilizer elements comprise a rigid or semi-rigid material.

102. The method ofclaim 100, wherein the stabilizer elements are separated by a flexible material.

103. The method ofclaim 98, wherein the porous wound filler material comprises a smooth bottom surface that slides during contraction in the first x-direction.

104. The method ofclaim 98, wherein the porous wound filler has cleavage lines to provide removal of one or more sections.

105. The method ofclaim 98, wherein the porous wound filler material comprises a foam.

106. The method ofclaim 98, wherein the porous wound filler material comprises a mesh.

107. The method ofclaim 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.

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