Patent Publication Number: US-2021161723-A1

Title: Foamed and textured sintered polymer wound filler

Description:
RELATED APPLICATION 
     This application claims the benefit, under 35 U.S.C. § 119(e), of the filing of U.S. Provisional Patent Application Ser. No. 62/518,309, entitled “FOAMED AND TEXTURED SINTERED POLYMER WOUND FILLER,” filed Jun. 12, 2017, which is incorporated herein by reference for all purposes. 
    
    
     TECHNICAL FIELD 
     The invention set forth in the appended claims relates generally to tissue treatment systems and more particularly, but without limitation, to making and using a foamed and textured sintered polymer wound filler for use in conjunction with reduced pressure wound therapy. 
     BACKGROUND 
     Clinical studies and practice have shown that reducing pressure in proximity to a tissue site can augment and accelerate growth of new tissue at the tissue site. The applications of this phenomenon are numerous, but it has proven particularly advantageous for treating wounds. Regardless of the etiology of a wound, whether trauma, surgery, or another cause, proper care of the wound is important to the outcome. Treatment of wounds or other tissue with reduced pressure may be commonly referred to as “reduced-pressure therapy,” but is also known by other names, including “reduced-pressure wound therapy,” “negative-pressure therapy,” “negative pressure therapy,” “vacuum therapy,” “vacuum-assisted closure,” and “topical negative-pressure,” for example. Reduced-pressure therapy may provide a number of benefits, including migration of epithelial and subcutaneous tissues, improved blood flow, and micro-deformation of tissue at a wound site. Together, these benefits can increase development of granulation tissue and reduce healing times. 
     Tissue treatment systems can use a tissue interface (such as a wound manifold or a wound filler) that when installed at a tissue site (such as on a wound or in a wound at a tissue site) facilitates various degrees of tissue ingrowth that can cause pain or discomfort to a patient and in some cases leave remnants of the tissue interface in the wound when the tissue interface is removed from the tissue site. Accordingly, improvements to the tissue interface are desirable. 
     While the clinical benefits of reduced-pressure therapy and tissue interfaces are widely known, improvements to therapy systems, components, and processes may benefit healthcare providers and patients. 
     BRIEF SUMMARY 
     New and useful systems, apparatuses, and methods for manufacturing and implementing tissue interfaces with textured meshed films and textured manifolding wound fillers are set forth in the appended claims. Illustrative embodiments are also provided to enable a person skilled in the art to make and use the claimed subject matter. 
     In a first example, a method of manufacturing a tissue interface for providing reduced pressure to a tissue site is provided. The method may include foaming a plurality of polymer particles to form a porous polymer. The method may also include sintering the porous polymer to form a sintered porous polymer. The method may further include texturing the sintered porous polymer to form a textured sintered polymer that is porous. In addition, the method may include sterilizing the tissue interface. 
     In a second example, a system to provide reduced pressure to a tissue site is provided. The system may include a cover configured to form a seal over the tissue site. The system may also include a reduced pressure source configured to provide reduced pressure through the cover to the tissue site. The system may further include a tissue interface. The tissue interface may be configured to be disposed underneath the cover at the tissue site. The tissue interface may include a porous polymer with a mesh pattern. The porous polymer may be formed from polymer particles fused to form a polymer matrix that is foamed and textured to provide fluid communication of reduced pressure to the tissue site. 
     In a third example, a method of using a tissue interface at a tissue site is provided. The method may include positioning the tissue interface at the tissue site. The tissue interface may include a porous polymer. The porous polymer may be formed from polymer particles fused to form a polymer matrix having one or more pores and textured to promote tissue granulation. The method may also include positioning a cover over the tissue interface. The method may further include providing reduced pressure through the cover and into the tissue interface. 
     In a fourth example, a method of manufacturing a tissue interface for providing reduced pressure to a tissue site is provided. The method may include forming a porous polymer from one or more polymer particles by fusing the one or more polymer particles to form a polymer matrix. The polymer matrix may include one or more pores configured to provide fluid communication through the polymer matrix. The method may also include foaming the porous polymer to provide a porous polymer matrix having a porosity capable of providing fluid communication to the tissue site. The method may further include texturing the porous polymer matrix by at least one of embossing or vacuum forming the porous polymer matrix. In addition, the method may include sterilizing the tissue interface. 
     Objectives, advantages, and a preferred mode of making and using the claimed subject matter may be understood best by reference to the accompanying drawings in conjunction with the following detailed description of illustrative embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a simplified functional block diagram of an example embodiment of a therapy system for providing reduced pressure therapy comprising a tissue interface; 
         FIG. 2  is a perspective view of a first example embodiment of a tissue interface for use in the therapy system of  FIG. 1 ; 
         FIG. 3  is an exploded view of a portion of the first example embodiment of the tissue interface of  FIG. 2 ; 
         FIG. 4  is a perspective view of a second example embodiment of a tissue interface for use in the therapy system of  FIG. 1 ; and 
         FIG. 5  is an exploded view of a portion of the second example embodiment of the tissue interface of  FIG. 4 . 
     
    
    
     DESCRIPTION OF EXAMPLE EMBODIMENTS 
     The following description of example embodiments provides information that enables a person skilled in the art to make and use the subject matter set forth in the appended claims, but may omit certain details already well-known in the art. The following detailed description is, therefore, to be taken as illustrative and not limiting. 
     The example embodiments may also be described herein with reference to spatial relationships between various elements or to the spatial orientation of various elements depicted in the attached drawings. In general, such relationships or orientation assume a frame of reference consistent with or relative to a patient in a position to receive treatment. However, as should be recognized by those skilled in the art, this frame of reference is merely a descriptive expedient rather than a strict prescription. 
       FIG. 1  is a simplified functional block diagram of an example embodiment of a therapy system  100  for providing reduced-pressure therapy comprising a tissue interface including an embossed mesh film or an embossed, manifolding wound filler. 
     The term “tissue site” in this context broadly refers to a wound, defect, or other treatment target located on or within tissue, including but not limited to, bone tissue, adipose tissue, muscle tissue, neural tissue, dermal tissue, vascular tissue, connective tissue, cartilage, tendons, or ligaments. A wound may include chronic, acute, traumatic, subacute, and dehisced wounds, partial-thickness burns, ulcers (such as diabetic, pressure, or venous insufficiency ulcers), flaps, and grafts, for example. The term “tissue site” may also refer to areas of any tissue that are not necessarily wounded or defective, but are instead areas in which it may be desirable to add or promote the growth of additional tissue. For example, reduced pressure may be applied to a tissue site to grow additional tissue that may be harvested and transplanted. 
     The therapy system  100  may include reduced-pressure supply, and may include or be configured to be coupled to a distribution component or tubing, such as a dressing. In general, a distribution component may refer to any complementary or ancillary component configured to be fluidly coupled to a reduced-pressure supply in a fluid path between a reduced-pressure supply and a tissue site. A distribution component is preferably detachable, and may be disposable, reusable, or recyclable. For example, a dressing  102  may be fluidly coupled to a reduced-pressure source  104 , as illustrated in  FIG. 1 . A dressing may include a cover, a tissue interface, or both in some embodiments. The dressing  102 , for example, may include a cover  106  and a tissue interface  108 . A regulator or a controller, such as a controller  110 , may also be coupled to the reduced-pressure source  104 . 
     In some embodiments, a dressing interface may facilitate coupling the reduced-pressure source  104  to the dressing  102 . For example, such a dressing interface may be a T.R.A.C.® Pad or Sensa T.R.A.C.® Pad available from KCI of San Antonio, Tex. The therapy system  100  may optionally include a fluid container, such as a container  112 , coupled to the dressing  102  and to the reduced-pressure source  104 . 
     Additionally, the therapy system  100  may include sensors to measure operating parameters and provide feedback signals to the controller  110  indicative of the operating parameters. As illustrated in  FIG. 1 , for example, the therapy system  100  may include at least one of a pressure sensor  120  or an electric sensor  122  coupled to the controller  110  via electric conductors  126  and  127 , respectively. The pressure sensor  120  may also be coupled or configured to be fluidly coupled via a distribution component such as, for example, fluid conduits  131  and  132  and to the reduced-pressure source  104 . For example, as shown in  FIG. 1 , the electric conductor  126  provides electric communication between the electric sensor  122  and the controller  110 . The electric conductor  127  provides electric communication between the pressure sensor  120  and the controller  110 . The electric conductor  128  provides electric communication between the controller  110  and the reduced-pressure source  104 . The electric conductor  129  provides electric communication between the electric sensor  122  and the reduced-pressure source  104 . 
     Components may be fluidly coupled to each other to provide a path for transferring fluids (such as at least one of liquid or gas) between the components. Components may be fluidly coupled through a fluid conductor, such as a tube. For example fluid conductor  130  provides fluid communication between the dressing  102  and the container  112 ; fluid conductor  131  provides fluid communication between the reduced-pressure source  104  and the container  112 ; and fluid conductor  132  provides fluid communication between the pressure sensor  120  and the container  112 . A “tube,” as used herein, broadly includes a tube, pipe, hose, conduit, or other structure with one or more lumina adapted to convey a fluid between two ends. Typically, a tube is an elongated, cylindrical structure with some flexibility, but the geometry and rigidity may vary. In some embodiments, components may also be coupled by virtue of physical proximity, being integral to a single structure, or being formed from the same piece of material. Moreover, some fluid conductors  124  may be molded into or otherwise integrally combined with other components. Coupling may also include mechanical, thermal, electrical, or chemical coupling (such as a chemical bond) in some contexts. For example, a tube may mechanically and fluidly couple the dressing  102  to the container  112  in some embodiments. 
     In general, components of the therapy system  100  may be coupled directly or indirectly. For example, the reduced-pressure source  104  may be directly coupled to the controller  110 , and may be indirectly coupled to the dressing  102  through the container  112 . 
     The fluid mechanics of using a reduced-pressure source to reduce pressure in another component or location, such as within a sealed therapeutic environment, can be mathematically complex. However, the basic principles of fluid mechanics applicable to reduced-pressure therapy are generally well-known to those skilled in the art, and the process of reducing pressure may be described illustratively herein as “delivering,” “distributing,” or “generating” reduced pressure, for example. 
     In general, exudates and other fluids flow toward lower pressure along a fluid path. Thus, the term “downstream” typically implies something in a fluid path relatively closer to a source of reduced pressure or further away from a source of positive pressure. Conversely, the term “upstream” implies something relatively further away from a source of reduced pressure or closer to a source of positive pressure. Similarly, it may be convenient to describe certain features in terms of fluid “inlet” or “outlet” in such a frame of reference. This orientation is generally presumed for purposes of describing various features and components herein. However, the fluid path may also be reversed in some applications (such as by substituting a positive-pressure source for a reduced-pressure source) and this descriptive convention should not be construed as a limiting convention. 
     “Reduced pressure” or “negative pressure” generally refers to a pressure less than a local ambient pressure, such as the ambient pressure in a local environment external to a sealed therapeutic environment provided by the dressing  102 . In many cases, the local ambient pressure may also be the atmospheric pressure at which a tissue site is located. Alternatively, the pressure may be less than a hydrostatic pressure associated with tissue at the tissue site. Unless otherwise indicated, values of pressure stated herein are gauge pressures. Similarly, references to increases in reduced pressure typically refer to a decrease in absolute pressure, while decreases in reduced pressure typically refer to an increase in absolute pressure. While the amount and type of reduced pressure applied to a tissue site may vary according to therapeutic requirements, the pressure is generally a low vacuum, also commonly referred to as a rough vacuum, between −5 mm Hg (−667 Pa) and −500 mm Hg (−66.7 kPa). Common therapeutic ranges are between −75 mm Hg (−9.9 kPa) and −300 mm Hg (−39.9 kPa). 
     A reduced-pressure supply, such as the reduced-pressure source  104 , may be a reservoir of air at a reduced pressure, or may be a manual or electrically-powered device that can reduce the pressure in a sealed volume, such as a vacuum pump, a suction pump, a wall suction port available at many healthcare facilities, or a micro-pump, for example. A reduced-pressure supply may be housed within or used in conjunction with other components, such as sensors, processing units, alarm indicators, memory, databases, software, display devices, or user interfaces that further facilitate therapy. For example, in some embodiments, the reduced-pressure source  104  may be combined with the controller  110  and other components into a therapy unit. A reduced-pressure supply may also have one or more supply ports configured to facilitate coupling and de-coupling the reduced-pressure supply to one or more distribution components. 
     Sensors, such as the pressure sensor  120  or the electric sensor  122 , are generally known in the art as any apparatus operable to detect or measure a physical phenomenon or property, and generally provide a signal indicative of the phenomenon or property that is detected or measured. For example, the pressure sensor  120  and the electric sensor  122  may be configured to measure one or more operating parameters of the therapy system  100 . In some embodiments, the pressure sensor  120  may be a transducer configured to measure pressure in a pneumatic pathway and convert the measurement to a signal indicative of the pressure measured. In some embodiments, for example, the pressure sensor  120  may be a piezoresistive strain gauge. The electric sensor  122  may optionally measure operating parameters of the reduced-pressure source  104 , such as the voltage or current, in some embodiments. Preferably, the signals from the pressure sensor  120  and the electric sensor  122  are suitable as an input signal to the controller  110 , but some signal conditioning may be appropriate in some embodiments. For example, the signal may need to be filtered or amplified before it can be processed by the controller  110 . Typically, the signal is an electrical signal, but may be represented in other forms, such as an optical signal. 
     The container  112  may be representative of a container, canister, pouch, or other storage component, which can be used to manage exudates and other fluids withdrawn from a tissue site. In many environments, a rigid container may be preferred or required for collecting, storing, and disposing of fluids. In other environments, fluids may be properly disposed of without rigid container storage, and a re-usable container could reduce waste and costs associated with reduced-pressure therapy. 
     In some embodiments, the cover  106  may provide a bacterial barrier and protection from physical trauma. The cover  106  may also be constructed from a material that can reduce evaporative losses and provide a fluid seal between two components or two environments, such as between a therapeutic environment and a local external environment. The cover  106  may be, for example, an elastomeric film or membrane that can provide a seal adequate to maintain a reduced pressure at a tissue site for a given reduced-pressure source. The cover  106  may have a high moisture-vapor transmission rate (MVTR) in some applications. For example, the MVTR may be at least 300 g/m{circumflex over ( )}2 per twenty-four hours in some embodiments. In some example embodiments, the cover  106  may be a polymer drape, such as a polyurethane film, that is permeable to water vapor but impermeable to liquid. Such drapes typically have a thickness in the range of 25-50 microns. For permeable materials, the permeability generally should be low enough that a desired reduced pressure may be maintained. 
     An attachment device may be used to attach the cover  106  to an attachment surface, such as undamaged epidermis, a gasket, or another cover. The attachment device may take many forms. For example, an attachment device may be a medically-acceptable, pressure-sensitive adhesive that extends about a periphery, a portion, or an entire sealing member. In some embodiments, for example, some or all of the cover  106  may be coated with an acrylic adhesive having a coating weight between 25-65 grams per square meter (g.s.m.). Thicker adhesives, or combinations of adhesives, may be applied in some embodiments to improve the seal and reduce leaks. Other example embodiments of an attachment device may include a double-sided tape, paste, hydrocolloid, hydrogel, silicone gel, or organogel. 
     The tissue interface  108  may be configured to contact a tissue site. The tissue interface  108  may be partially or fully in contact with the tissue site. If the tissue site is a wound, for example, the tissue interface  108  may partially or completely fill the wound, or may be placed over the wound. The tissue interface  108  may take many forms, and may have many sizes, shapes, or thicknesses depending on a variety of factors, such as the type of treatment being implemented or the type and size of a tissue site. For example, the size and shape of the tissue interface  108  may be adapted to the contours of deep and irregular shaped tissue sites. Moreover, any or all of the surfaces of the tissue interface  108  may have projections or an uneven, course, or jagged profile that can induce strains and stresses on a tissue site, which can promote granulation at the tissue site. 
     In some embodiments, the tissue interface  108  may be a manifold. A “manifold” in this context generally includes any substance or structure providing a plurality of pathways adapted to collect or distribute fluid across a tissue site under pressure. For example, a manifold may be adapted to receive reduced pressure from a source and distribute reduced pressure through multiple apertures across a tissue site, which may have the effect of collecting fluid from across a tissue site and drawing the fluid toward the source. In some embodiments, the fluid path may be reversed or a secondary fluid path may be provided to facilitate delivering fluid across a tissue site. 
     In operation, the tissue interface  108  may be placed within, over, on, or otherwise proximate to a tissue site. The cover  106  may be placed over the tissue interface  108  and sealed to an attachment surface near the tissue site. For example, the cover  106  may be sealed to undamaged epidermis peripheral to a tissue site. Thus, the dressing  102  can provide a sealed therapeutic environment proximate to a tissue site, substantially isolated from the external environment, and the reduced-pressure source  104  can reduce the pressure in the sealed therapeutic environment. Reduced pressure applied across the tissue site through the tissue interface  108  in the sealed therapeutic environment can induce macrostrain and microstrain in the tissue site, as well as remove exudates and other fluids from the tissue site, which can be collected in container  112 . 
     The tissue interface  108  may comprise a sheet-like material or other-shaped material comprising a polymer. Polymers may include substances having a molecular structure consisting predominantly or entirely of similar units bonded together. In various example embodiments, the tissue interface  108  may include a polymer that may be porous or nonporous, perforated, textured, or sintered to enhance wound therapy. The tissue interface  108  may also include indentations or hollows in the surface of the sheet-like material. For example, the tissue interface  108  may comprise a porous polymer formed from a sheet of foam material or a sheet of compressed particles. In another example embodiment, the tissue interface  108  may include a porous polymer formed from a sheet of foam or compressed particles that is sintered or subjected to other processes. The tissue interface  108  may also comprise a nonporous polymer that may be formed from a sheet of nonporous material, and that may be perforated, textured, or subject to other processes as described in more detail below. 
     Referring more specifically to  FIGS. 2 and 3 , the tissue interface  108  comprises a sheet-like material that comprises a nonporous polymer  205  that is shown as being perforated and textured. The tissue interface  108  may be perforated as described above to include one or more fenestrations or perforations  150  extending through any of the embodiments of the tissue interface  108  described above. For example, the nonporous polymer  205  of the tissue interface  108  may comprise perforations  150 . The perforations  150  may communicate fluid through the tissue interface  108  to enhance wound therapy including negative pressure wound therapy. The tissue interface  108  may also include a surface having one or more indentations or hollows on the surface that do not extend through the nonporous material  205 . Such indentations or hollows may have a variety of shapes such as, for example, one or more dimples  155  or channels  160 . 
     As indicated above, the tissue interface  108  may have a generally sheet-like shape which may include a textured surface  165  on at least one side of the sheet or a portion  170  of one side of the sheet. In one example embodiment, the textured surface  165  of the tissue interface  108  may include a pattern or arrangement of particles or constituent parts of the tissue interface  108 . In yet another example embodiment, the textured surface  165  of the tissue interface  108  may include any flexible or rigid protrusions extending from one side of the sheet. Such patterns or protrusions may have a variety of shapes such as, for example, pyramids, cylinders, ribs, or other non-symmetrical shapes. The protrusions may be arranged in regular or irregular patterns, and the patterns themselves may be irregular and/or non-symmetrically formed on the surface of the tissue interface  108 . The protrusions of the textured surface  165  may be formed with either a course or fine grain surface. The textured surface  165  may be formed by embossing methods that cover the surface of the tissue interface  108  with patterns of protrusions raised above the surface of the tissue interface  108 . For example, as shown in  FIG. 2 , the textured surface  165  may include dimples  210 , protrusions or bumps  215 , scuffs  220 , a scored portion  225 , a roughed or sand-blasted portion  230 , or any other texture known by those having ordinary skill in the art. 
     In some embodiments of the tissue interface  108  having perforations  150 , the perforations  150  may be formed by punching holes through the tissue interface  108 , perforating the tissue interface  108 , cutting holes in the tissue interface  108 , or any number of different methods. The perforations  150  also may be formed by vacuum forming methods. The perforations  150  may be formed into one or more shapes including, for example, an elliptical shape including a circle, a polygon, an oval, or a simple slit through the material. Perforations  150  having a generally elliptical shape may have diameters between about 300 (μm) microns and about 1000 μm. The perforations  150  may be stretched in different directions to change the shape of the perforations  150 . Stretching the tissue interface  108  in one or more directions to form different shapes and sizes facilitates fluid communication through the tissue interface  108 . The perforations  150  may be positioned randomly throughout the tissue interface  108 . In at least some embodiments, the perforations  150  may be positioned so that one or more perforations  150  are more concentrated in one region of the tissue interface  108  while other perforations  150  are less concentrated in other regions of the tissue interface  108 . In some embodiments of the tissue interface  108 , the perforations  150  may be formed through the tissue interface  108  in combination with one or more of the other features described herein. For example, the perforations  150  may be through-holes extending through the tissue interface  108  from the base of the dimples  155  or the base the channels  160  (not shown) rather than from the surface of the tissue interface  108 . 
     As indicated herein, the tissue interface  108  may also include one or more dimples  155 . The dimples  155  may be positioned or formed on a surface of the tissue interface  108 . For example, when the tissue interface  108  includes a porous polymer, the dimples  155  may create more surface area on the surface of the tissue interface  108  to facilitate absorption of fluids into pores of the tissue interface  108 . The dimples  155  may be formed on the surface of the tissue interface  108  by texturing the surface of the tissue interface  108 . The tissue interface  108  may be textured to form the one or more dimples  155  by pressing a pattern of dimples  155  into the surface of the tissue interface  108 , by vacuum forming a pattern of dimples  155  into the surface of the tissue interface  108 , or by any other method known by those skilled in the art. At least one of the dimples  155  may have a diameter between about 50 μm and about 2000 μm. The dimples  155  may have a hollow shape including the shape of a cone, an ellipsoid, a hemisphere, or a polyhedron. The dimples  155  also may have a depth between about 200 μm and about 1000 μm. The dimples  155  may have a variety of different shapes and sizes positioned where formed on the surface of the tissue interface  108 . The dimples  155  may be positioned or formed randomly on the tissue interface  108  in an irregular pattern. In at least some embodiments, the dimples  155  may be positioned so that some of the dimples  155  are more concentrated in at least one region of the tissue interface  108  while other dimples  155  are less concentrated in another region of the tissue interface  108 . 
     As indicated above, the tissue interface  108  may also include one or more channels  160 . The channels  160  may be positioned or formed on a surface of the tissue interface  108 . For example, when the tissue interface  108  includes a porous polymer, the channels  160  may channel or guide fluid along a surface of the tissue interface  108 . The channels  160  may be positioned or formed randomly on the tissue interface  108  in an irregular pattern. The channels  160  may be formed on the surface the tissue interface  108  by texturing the surface of the tissue interface  108 . The tissue interface  108  may be textured to form the channels  160  by embossing the tissue interface  108  (for example using embossing rollers), pressing a pattern of channels  160  into the surface of the tissue interface  108 , vacuum forming the tissue interface  108 , or by any other method known by those skilled in the art. The channels  160  may have a variety of different shapes and sizes positioned where formed on the surface of the tissue interface  108 . The channels  160  may have a linear shape, a curved shape, or an angular shape formed on a surface of the tissue interface  108 . The channels  160  may have a cross-sectional shape including at least one of a semicircular shape, and popular shape, a V-shape, circle, or any other geometric shape known by those skilled in the art. At least one of the channels  160  may have a depth between about 200 μm and about 1000 μm and a width between about 200 μm and about 1000 μm. In various embodiments, at least one of the channels  160  may be positioned or formed on the surface of the tissue interface  108  to intersect with other features described herein including at least one of a perforation  150 , a dimple  155 , or another channel  160 . In at least some embodiments, the channels  160  may be positioned so that some of the channels  160  are more concentrated in at least one region of the tissue interface  108  while other channels  160  are less concentrated in another region of the tissue interface  108 . 
     Referring more specifically to  FIGS. 4 and 5 , the tissue interface  108  comprises a sheet-like material that comprises a porous polymer  405  that is shown as being perforated and textured. The tissue interface  108  may be perforated as described above to include one or more fenestrations or perforations  150  extending through any of the embodiments of the tissue interface  108  described above. For example, the porous polymer  405  of the tissue interface  108  may comprise perforations  150 . The perforations  150  may communicate fluid through the tissue interface  108  to enhance wound therapy including negative pressure wound therapy. The tissue interface  108  may also include a surface having one or more indentations or hollows on the surface that do not extend through the porous polymer  405 . Such indentations or hollows may have a variety of shapes such as, for example, one or more dimples  155  or channels  160 . The porous polymer  405  may comprise at least some of the features described above respect to the nonporous material  205  shown in  FIGS. 2 and 4 . For example, the tissue interface  108  may comprise porous polymer  405  formed from a sheet of foam material or a sheet of compressed particles that is textured or subject to other processes. The porous polymer  405  may include one or more voids or pores  408  that are positioned or formed throughout the tissue interface  108 . For example, the porous polymer  405  may include pores  408  that are positioned or formed uniformly throughout the tissue interface  108 . Alternatively, the pores  408  may be formed more randomly throughout the tissue interface  108 . As another example, the porous polymer  405  may include pores  408  that are positioned or formed in clusters  410  throughout the porous polymer  405 , such that the porous polymer  405  may include portions that are essentially nonporous as described above with respect to the nonporous polymer  205 . 
     The pores  408  may be distributed uniformly throughout the porous polymer  405 , but may also be distributed in different concentrations throughout the porous polymer  405 . For example, the porous polymer  405  may have between about 20 and 60 pores per inch (“PPI”). In another example embodiment, the pores  408  may be distributed uniformly throughout the porous polymer  405 , but may have different shapes with different dimensions. For example, the pores  408  may be generally circular and have varying diameters throughout the porous polymer  405 . The pores  408  may have an average diameter ranging between about 50 μm and 600 μm. The porous polymer  405  may include pores  408  that may have a closed-cell structure or an open-cell structure. In a typical closed-cell structure, each cell may be surrounded by connected faces. An open-cell structure may also have connecting cell faces with a portion of the cell faces open to each other to form passageways or flow channels between them. The passageways are formed by a plurality of interconnected pores  408  which act as flow channels through the porous polymer  405  that may enhance wound therapy including negative pressure wound therapy. The porous polymer  405  may have an open-cell structure formed by the methods known to those skilled in the art including, for example, reticulation methods. In one example embodiment, the porous polymer  405  may be highly reticulated having at least 90% of the pores  408  interconnecting to form the passageways. Fluid flow may be enhanced for a porous polymer  405  with a lower reticulation by utilizing some of the other features described above. 
     In some embodiments, the porous polymer  405  may be formed from one or more polymer particles. For example, the porous polymer  405  may be a polymer matrix that is formed by fusing polymer particles together. In various embodiments, the porous polymer  405  may include polymer particles that are imperfectly fused to create boundaries between each of the polymer particles that are at least partially intact. By imperfectly fusing the polymer particles together, the pores  408  may be formed between fused portions of the polymer particles. Thus, imperfectly fusing the polymer particles together may provide pores  408  that permit fluid communication of gases and liquids through the polymer matrix, for example, during an application of negative pressure wound therapy. The polymer particles in porous polymer  405  may also be fused by mechanical fastening, adhesive bonding, solvent bonding, co-consolidation, fusion bonding or welding, or any other method known by those having ordinary skill in the art. 
     In some embodiments, the porous polymer  405  may be formed using a foaming process. For example, the porous polymer  405  may be formed by mixing polymer particles, such as plastic pellets or powders, with a chemical blowing agent. Subsequently, after the polymer particles are mixed with a blowing agent, the porous polymer  405  may be heated to a high temperature dissolving the chemical blowing agent generating a gaseous reaction product, such as nitrogen or CO 2 . The porous polymer  405  may subsequently be subject to a rapid pressure drop to form a foamed porous polymer. In various embodiments, the porous polymer  405  may be formed using at least one of extrusion foaming or injection molded foaming and may include an application of a mechanical foaming agent. One of ordinary skill in the art would know the many type of foaming processes that may be used to form porous polymers. The porous polymer  405  may be formed by a foaming process to increase flexibility of the porous polymer  405  when the porous polymer  405  is in, for example, a sheet form so that a thick polymer sheet may still be sufficiently flexible and to provide apposition forces to a tissue site when the porous polymer  405  is under reduced pressure. In various embodiments, the porous polymer  405  may be subject to suspension polymerization and treated with a polymerization initiator. Once the porous polymer  405  has a polymer chain of a desired length, a terminating agent may be added to stop the reaction. 
     In some embodiments, the porous polymer  405  may be a sintered polymer or sintered porous polymer. The porous polymer  405  may be sintered by compacting and forming materials or pieces of a material into a solid mass using at least one of heat or pressure without melting the material to the point of liquefaction. The porous polymer  405  may be sintered to reduce the porosity of the polymer and to thereby enhance at least some properties of the porous polymer  405  including, for example, the strength of the porous polymer  405  while maintaining gas absorbency or fluid flow through the passageways in operation. The porous polymer  405  may be sintered by a firing process where atomic diffusion drives powdered surface elimination in different stages starting from a formation of necks between powders to final elimination of small pores at the end of the firing process. The porous polymer  405  may additionally or alternatively be sintered using methods including plastics sintering, liquid phase sintering, electric current assisted sintering, resistance sintering, spark plasma sintering, electro sinter forging, pressureless sintering, or any other method known by those having ordinary skill in the art. 
     In some embodiments, the porous polymer  405  may be sintered by a multi-step firing process. For example, at a first stage, the porous polymer  405  may be fired so that atomic diffusion drives powdered surface elimination that forms necks between the powders. At a second stage, the porous polymer  405  may be fired so that atomic diffusion further drives powdered surface elimination for further shaping the powders. At a third stage, the porous polymer  405  may be fired so that atomic diffusion further drives powdered surface elimination to eliminate small pores of the porous polymer  405 . In some embodiments, the porous polymer  405  may be sintered by compressing the porous polymer  405  into a solid mass through heat or pressure. The porous polymer  405  may be compressed without melting the porous polymer  405  to the point of liquidation. 
     In some embodiments, the porous polymer  405  may be formed from beads or particles forming a polymer matrix. The beads or particles forming the polymer matrix may be cleaned and anomalous beads may be filtered out from remaining beads. The beads or particles forming the polymer matrix may subsequently be melted to form a melted polymer. A blowing agent may also be added to the melted polymer. The melted polymer may then be extruded to form the porous polymer  405 . In some embodiments, the beads or particles may be pre-expanded using, for example, steam or hot air to reduce a density of the polymer matrix. During pre-expansion, an agitator may be used to keep the bead or particles from fusing together. The pre-expanded beads or particles may then be heated and expanded and subsequently cooled so that the beads or particles harden. The beads or particles may then be fed into a mold of a desired shape to form the polymer matrix. For example, the polymer matrix may be formed into sheets or other forms. At least one of the pores  408  may be formed in the polymer matrix by fusing the beads or particles together using at least one of a heat, a solvent, or a non-solvent. In various embodiments, at least one of the pores  408  may be formed by gaps created when at least two fibers contact, couple, or overlap with each other. 
     An example method of manufacturing a tissue interface such as tissue interface  108  of  FIG. 1 , for a reduced pressure tissue treatment system in accordance with this specification is provided. The tissue interface may include a polymer matrix. The method may include forming the polymer matrix from polymer particles. The polymer matrix may be formed by fusing polymer particles together using, for example, at least one of a heat, a solvent, or a non-solvent. In some embodiments, the polymer matrix may be formed using a blowing agent that is activated by at least one of heat or light to fuse the polymer particles together. In various embodiments, the polymer particles may be imperfectly fused together such that boundaries between each of the polymer particles are still at least partially intact so that gaps or pores are formed in the polymer matrix. The gaps or pores may provide a fluid flow path or channel for fluid communication of gas or liquids to pass through the polymer matrix, for example, to enhance negative pressure wound therapy. In some embodiments, the polymer particles may be fused together to affect the size of the gaps or pores. For example, the greater the distance between fused locations among the polymer particles, the greater size of the gaps or pores. 
     Another example method of manufacturing a tissue interface such as tissue interface  108  of  FIG. 1 , for a reduced pressure tissue treatment system in accordance with this specification is provided. In some embodiments, the method may include foaming a polymer. The polymer may be foamed to form a porous polymer, such as the porous polymer  405  of  FIGS. 4 and 5 . The polymer may be foamed by mixing polymer particles, such as plastic pellets or powders, with a chemical blowing agent. The mixture of polymer particles may subsequently be heated to a high temperature dissolving the chemical blowing agent. The blowing agent may be dissolved with the polymer particles to generate a gaseous reaction product, such as nitrogen or CO 2 . The mixture of polymer particles may be subject to a rapid pressure drop forming the polymer. It should be understood that while the aforementioned foaming process may be used to form a foamed polymer, the foaming process may additionally or alternatively include extrusion foaming or injection molded foaming, and may include an application of a mechanical foaming agent. One of ordinary skill in the art would know the various types of foaming processes that may be used polymers for a tissue interface  108  as discussed herein. A polymer may be foamed to increase flexibility of the polymer when the polymer is in, for example, a sheet form so that a thick polymer sheet may still be sufficiently flexible while providing apposition forces to a tissue site when the polymer is under reduced pressure. 
     In some embodiments, the methods may include sintering a polymer to form a sintered polymer. The polymer may be sintered by compacting and forming the polymer into a solid mass by at least one of heat or pressure without melting the polymer to the point of liquefaction. The polymer may be sintered to reduce the porosity of the polymer and enhance properties including strength while maintaining gas absorbency. In various embodiments, the polymer may be sintered by a firing process where atomic diffusion drives powdered surface elimination in different stages starting from a formation of necks between powders to final elimination of small pores at the end of the firing process. Polymers may be sintered by plastics sintering, liquid phase sintering, electric current assisted sintering, resistance sintering, spark plasma sintering, electro sinter forging, pressureless sintering, or any other method known by those having ordinary skill in the art. 
     In various embodiments, a polymer may be sintered by a multi-step firing process. For example, at a first stage, a polymer may be fired so that atomic diffusion drives powdered surface elimination that forms necks between the powders. At a second stage, the polymer may be fired so that atomic diffusion further drives powdered surface elimination for further shaping of the powders. At a third stage, the polymer may be fired so that atomic diffusion further drives powdered surface elimination to eliminate small pores of the polymer. In some embodiments, the polymer may be sintered by compressing the polymer into a solid mass through heat or pressure. The polymer may subsequently be compressed without melting the polymer to the point of liquidation. 
     In some embodiments, methods of manufacturing a tissue interface such as tissue interface  108  of  FIG. 1 , for a reduced pressure tissue treatment system in accordance with this specification may include expanding a polymer of the tissue interface to form an expanded polymer. For example, a polymer may be expanded from an original size to a size that is between about two and about ten times the original size of the polymer. In some embodiments, the polymer may be expanded before or after the polymer is foamed. In some embodiments, the polymer may be foamed and expanded at the same time. For example, at least some polymers may be expanded by heating the polymer with steam or hot air. The heating may be carried out in a vessel containing the polymer. An agitator may be added to the polymer during heating to keep the polymer from fusing. The expanded polymer may be forced to the top of the vessel separating from unexpanded polymer due to density differences created by the application of heat. Subsequently, the expanded polymer may be cooled to harden the expanded polymer. In some embodiments, the polymer may be expanded before the polymer is sintered. For example, after the polymer is expanded, the polymer may be sintered to form a sintered polymer. 
     In some embodiments, methods of manufacturing a tissue interface such as tissue interface  108  of  FIG. 1 , for a reduced pressure tissue treatment system in accordance with this specification may include texturing a polymer of the tissue interface to form a textured polymer. In some embodiments, the polymer may be textured to form a mesh pattern. The polymer may be textured by embossing or vacuuming forming polymer. In some embodiments, the polymer may be textured to form dimples or channels on a surface of the polymer as discussed herein. When a tissue interface, such as, for example, the tissue interface  108  of  FIG. 1 , includes a polymer that is textured, the tissue interface may provide an apposition force to the tissue site when the tissue interface receives reduced pressure. 
     In some embodiments, methods of manufacturing a tissue interface such as tissue interface  108  of  FIG. 1 , for a reduced pressure tissue treatment system in accordance with this specification may include forming or shaping the polymer of the tissue interface into one or more polymer sheets. For example, a polymer of a tissue interface may be formed or shaped into one or more sheets. The polymer sheets each may include a thickness between about 1.0 millimeter (mm) and about 30.0 mm. In some embodiments, the polymer sheets may be rolled into a roll for dispensing. 
     In some embodiments, particularly where infections are possible, methods of manufacturing a tissue interface such as a tissue interface  108  of  FIG. 1 , for a reduced pressure tissue treatment system in accordance with this specification may include sterilizing the tissue interface to form a sterile tissue interface at any stage through a process of manufacturing the tissue interface. For example, a porous polymer may be sterilized before or after the porous polymer is sintered, or before or after the porous polymer is expanded, before or after the porous polymer is textured, or before or after the porous polymer is shaped. Sterilization may include using gamma radiation, electron beam radiation, neutron radiation, ultraviolet light, microwave radiation, heat, supercritical CO 2 , ethylene oxide, a chemical biotoxin, or a combination thereof. Chemical biotoxins may include but are not limited to a peracid, a peracid salt, an azide, and ozone. Peracids may include but are not limited to a permangenate salt, hydrogen peroxide, benzoyl peroxide, perbromic acid, periodic acid, perflouric acid, perchloric acid, or a combination thereof. 
     The systems, apparatuses, and methods described herein may provide significant advantages. For example, the tissue interface  108  can reduce trauma and facilitate ease of removal when treating both deep and shallow wounds. The tissue interface  108  encourages granulation without the disadvantage of tissue ingrowth resulting in pain or discomfort upon removal. 
     While shown in a few illustrative embodiments, a person having ordinary skill in the art will recognize that the systems, apparatuses, and methods described herein are susceptible to various changes and modifications. Moreover, descriptions of various alternatives using terms such as “or” do not require mutual exclusivity unless clearly required by the context, and the indefinite articles “a” or “an” do not limit the subject to a single instance unless clearly required by the context. Components may be also be combined or eliminated in various configurations for purposes of sale, manufacture, assembly, or use. For example, in some configurations the dressing  102 , the container  112 , or both may be eliminated or separated from other components for manufacture or sale. In other example configurations, the controller  110  may also be manufactured, configured, assembled, or sold independently of other components. 
     The appended claims set forth novel and inventive aspects of the subject matter described above, but the claims may also encompass additional subject matter not specifically recited in detail. For example, certain features, elements, or aspects may be omitted from the claims if not necessary to distinguish the novel and inventive features from what is already known to a person having ordinary skill in the art. Features, elements, and aspects described herein may also be combined or replaced by alternative features serving the same, equivalent, or similar purpose without departing from the scope of the invention defined by the appended claims.