Abstract:
A therapeutic device for promoting the healing of a wound in a mammal is disclosed. An exemplary device comprises a permeable structure having a plurality of depressions formed in a surface thereof. In use, the surface having the depressions is disposed adjacent a surface of the wound. A method of treating a wound comprises the steps of providing a permeable structure comprising a plurality of randomly disposed fibers and having i) a plurality of wound surface contact elements disposed between end portions of the structure, and ii) a plurality of voids defined by the contact elements; and applying the permeable structure to at least one surface of the wound.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This divisional application claims the benefit under 35 U.S.C. §121 of application Ser. No. 10/982,346, filed on Nov. 5, 2004, which in turn claims the benefit under 35 U.S.C. §119(e) of Provisional Patent Application No. 60/561,745, filed on Apr. 13, 2004, the contents all of which are incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The invention relates to a device and method for treating wounds. More specifically, the present invention relates to a therapeutic wound contact device. 
       BACKGROUND OF THE INVENTION 
       [0003]    Wound healing is a basic reparative process of the human body. It has been known throughout time that dressing wounds with appropriate materials aids the body&#39;s natural regenerative process. Historically, such materials have been made from cotton fibers; e.g. gauze. These dressings are beneficial to the healing process because they insulate damaged tissue from external contaminants and because they remove potentially deleterious wound exudates. 
         [0004]    Numerous studies suggest that wound healing depends on the interplay of complex mechanisms involving cell proliferation, migration and adhesion coupled with angiogenesis. Application of traditional gauze or other essentially flat materials are essentially sub-optimal with respect to these mechanisms. Wound healing studies In-vitro carried out in cell culture vehicles that permit cellular function. It is therefore desirable in the practice of wound healing to provide the equivalent of cell culture or a bioreactor system to allow the optimal interplay of cell functions of proliferation, migration and adhesion. Additionally, it is essential to incorporate other bodily functions that encourage the supply of fibronectins, plasma proteins, oxygen, platelets, growth factors, immunochemicals and so forth. 
         [0005]    As science and medicine have advanced, the technology incorporated into wound healing devices has improved substantially. Highly absorbent wound dressings capable of absorbing many times their weight in liquids are available. Systems that temporarily seal wounds and utilize suction to remove exudates have found widespread utilization. Dressings incorporating anti-microbial agents and biologic healing agents are common. Devices that provide a moist wound environment for improved healing have been found to be useful. 
         [0006]    In spite of the technological gains in wound healing devices and dressings, millions of people still suffer from the chronic wounds. Such chronic wounds are debilitating and can last for years, greatly diminishing the individual&#39;s quality of life. Often such wounds result in the loss of a limb. Individuals may even die from complications such as infection. 
         [0007]    As such, there is dire need for more effective wound healing devices and methods. 
       SUMMARY OF INVENTION 
       [0008]    To provide for improved wound healing, the present invention is a wound contact material, a method for making the wound contact material, and a method of treatment employing the wound contact material. 
         [0009]    According to an exemplary embodiment of the present invention, a therapeutic device for promoting the healing of a wound in a mammal is provided. The device comprises a permeable substrate or structure having a plurality of depressions formed in a surface thereof, wherein said surface having said depressions is disposed in surface contact with the wound. 
         [0010]    According to a further exemplary embodiment of the present invention, a therapeutic device for promoting the healing of a wound in a mammal is provided. The device comprises a permeable structure having a plurality of wound surface contact elements disposed between end portions of the structure, and a plurality of voids defined by the contact elements. 
         [0011]    According to an additional exemplary embodiment of the present invention, a therapeutic device for promoting the healing of a wound in a mammal, the device comprising a permeable structure comprising a plurality of fibers coupled to one another having a plurality of wound surface contact elements disposed between end portions of the structure and a plurality of voids defined by the contact elements is provided. 
         [0012]    According to a yet further exemplary embodiment of the present invention, a therapeutic device for promoting the healing of a wound in a mammal, the device comprising a polyester felt having a plurality of wound surface contact elements disposed between end portions of the structure and a plurality of voids defined by the contact elements is provided. 
         [0013]    According to an additional exemplary embodiment of the present invention, a method of manufacturing a therapeutic device for promoting the healing of a wound in a mammal comprises the steps of providing a molten substrate material providing a mold defining a plurality of depressions and a plurality of contact elements and applying the molten substrate material to the mold. 
         [0014]    According to an even further exemplary embodiment of the present invention, a method of manufacturing a therapeutic device for promoting the healing of a wound in a mammal comprises the steps of providing a permeable structure and forming a plurality of depressions into a surface of the permeable structure. 
         [0015]    According to another exemplary embodiment of the present invention, a method of treating a wound comprises the steps of providing a permeable structure comprising i) a plurality of wound surface contact elements disposed between end portions of the structure, and ii) a plurality of voids defined by the contact elements, and applying the permeable structure to at least one surface of the wound and applying a force to the structure to maintain the structure in intimate contact with the wound surface. 
         [0016]    These and other aspects and objects will become apparent from the following description. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0017]    The invention is best understood from the following detailed description when read in connection with the accompanying drawings. It is emphasized that, according to common practice, the various features of the drawings are not to scale. On the contrary, the dimensions of the various features are arbitrarily expanded or reduced for clarity. Included in the drawings are the following Figures: 
           [0018]      FIG. 1  is a perspective view of a channeled wound contact dressing according to a first exemplary embodiment of the present invention; 
           [0019]      FIG. 2A  is a perspective view of a channeled wound contact composite according to a second exemplary embodiment of the present invention; 
           [0020]      FIG. 2B  is a cross section of the channeled wound contact composite according to the second exemplary embodiment of  FIG. 2A ; 
           [0021]      FIG. 3A  is a perspective view of a dimpled wound dressing according to a third exemplary embodiment of the present invention; 
           [0022]      FIG. 3B  is a top view of the dimpled wound dressing illustrated in  FIG. 3A ; 
           [0023]      FIG. 3C  is a bottom view of the dimpled wound dressing illustrated in  FIG. 3A ; 
           [0024]      FIG. 3D  is a cross sectional view of the dimpled wound dressing illustrated in  FIG. 3A ; 
           [0025]      FIGS. 4A ,  4 B and  4 C are illustrations of the dimpled wound dressing of  FIG. 3A  in use; 
           [0026]      FIG. 5A  is a perspective view of an irregular wound contact dressing according to a fourth exemplary embodiment of the present invention; 
           [0027]      FIG. 5B  is a cross sectional view of the irregular wound contact dressing illustrated in  FIG. 5A ; and 
           [0028]      FIG. 6  is a cross sectional view of an exemplary wound contact device in use on a wound. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0029]    A wound dressing with a discontinuous contact layer surface has the advantages of promoting tissue growth with wound surface contact elements and permitting tissue growth by providing void volume for the subsequent tissue growth within the discontinuities. Desirably, the structure of the contact material is sufficiently physically rugged to resist flattening when forces required to press the material against the wound surface are applied to the material. 
         [0030]    It is desirable for the material to retain its structure when exposed to aqueous or other bodily fluids. Many traditional dressing materials soften as then moisten so that their geometry changes. The contact layer is permeable, permitting the underlying wound to breathe and allowing for fluids to be drawn from the wound. The contact layer should not be too absorbent as this might result in a loss of structure. The layer is comprised of base materials that are resistant to change in the presence of moisture and aqueous liquids. 
         [0031]    In the current embodiment, the extent of the voids remaining above the wound surface is preferably at least 0.1 mm when the structure is pressed against the surface of the wound. The width of the voids, as defined by contact elements adjacent the voids, is preferably greater than 0.1 mm. A more preferred width is between about 0.5 to 10 mm and a more preferred height is between about 0.2 to 5 mm. 
         [0032]    Wound healing is recognized as a complex process. When a wound contact material as described is forced against a wound surface, a number of biological processes are believed to occur. Mechanical stress is applied to the underlying tissue. The discontinuities in the contact surface impose a force resulting in a catenary shape on the tissue. These mechanical forces encourage cellular activities as well as angiogenesis, and the discontinuities begin to fill with granular tissue. Excess fluid is conveyed away from the wound and tissue develops in a manner and pattern whereby disruption of the newly developed tissue is minimized upon removal of the contact surface. 
         [0033]    A fibrous substrate or structure has all the flexibilities provided by the textile arts. Fibrous textiles can be formed into a structure for the invention by a number of the methods known in the art. Among these methods are knitting, weaving, embroidering, braiding, felting, spunbonding, meltblowing, and meltspinning. Each of these methods can be further adapted to produce a material whose structure matches that of the present invention. The desired structure can be imparted during production of the structure by, for example, applying molten material directly to a mold as in meltblowing. Alternatively, the structure can be formed by working a formed structure after production by, for example, heat stamping or vacuum forming. Further, fibers can be mixed with an adhesive and sprayed onto a textured surface. 
         [0034]    The versatility of fibrous textiles also extends to their easy adaptation to composite applications. Individual fiber materials may be varied to optimize a physical parameter such as rigidity or flexibility. Individual fiber materials can also be selected for their known ability to assist in wound healing. Examples of such fiber materials are calcium alginate, and collagen. Alternatively, fibers may be treated with known wound healing agents such as hyaluronic acid and antimicrobial silver. The ratio of the fiber materials can be varied to suit the requirements of the wound. According to one desirable aspect of the invention, different fibers with various wound healing properties may be added as desired. 
         [0035]    Other fibrous structures that are anticipated as beneficial additions include: 
         [0036]    1. Fluid absorbing fibers 
         [0037]    2. Non-adsorbent fibers 
         [0038]    3. Bio-absorbable fibers 
         [0039]    4. Wicking fibers to wick fluid away from the surface of the wound 
         [0040]    5. Fibers with known healing effects, such as calcium alginate 
         [0041]    6. Bio-erodable fibers for the controlled release of curative agent 
         [0042]    7. Conductive fibers for the delivery of an electric charge or current 
         [0043]    8. Adherent fibers for the selective removal of undesirable tissues, substances or microorganisms 
         [0044]    9. Non-adherent fibers for the protection of delicate tissue 
         [0045]    An exemplary embodiment of the present invention is illustrated in  FIG. 1 . As shown in  FIG. 1 , channeled wound dressing  100  is comprised of a generally conformable polyester felt material  102 . An alternative polyester textile such as knit, weave, or braid may also be suitable for most applications. Polyolefins, such as polyethylene or polypropylene, and polyamides, such as nylon, with similar physical properties are also contemplated. Creep resistance, as exhibited by polyester, is particularly desirable. Void channels  104  are cut into felt material  102  to provide a discontinuity that promotes the upward growth of new tissue. In use, the channeled wound dressing  100  is pressed against a wound in intimate contact with injured tissue. A force of 0.1 psi or more is desirably applied to the contact layer to press the contact elements against the surface of the wound. Wound contact elements  106  are thus in intimate contact with injured tissue. 
         [0046]      FIGS. 2A and 2B  illustrate a wound dressing composite  200  comprised of channeled dressing  100  and a vapor permeable adhesive backed sheet  202 . Adhesive backed vapor permeable sheets, in general, are known in the art and are believed to contribute to wound healing by maintaining a moisture level that is optimal for some wounds. In use, dressing composite  200  is placed onto the surface of the wound with its channeled dressing  100  portion in contact with the wound. Adhesive sheet  202  covers channeled dressing  100  and adheres to skin adjacent the wound. Composite  200  offers the advantages of channeled dressing  100 . Additionally, adhesive sheet  202  secures composite  200  and protects the wound from bacteria, etc. while allowing for the transmission of moisture vapor. 
         [0047]    Another desirable embodiment of the present invention is illustrated in  FIGS. 3A ,  3 B and  3 C and  3 D. The substrate or structure for dimpled wound dressing  300  can be constructed from similar materials and production methods employed for channeled dressing  100 .  FIG. 3A  depicts a perspective view of dimpled dressing  300  with contact surface  320  on top.  FIG. 3D  shows a cross section of the dimpled dressing  300  which best illustrates the plurality of contact elements  322  and dimple voids  330 . Preferably, the total dimple void area comprises at least about 25% of the total dressing area. More preferably, the total dimple void area comprises at least about 50% of the total dressing area. Dimple voids  330  are partially defined by sidewalls  332 . Sidewalls  332  are partially responsible for providing rigidity necessary to resist compaction of dimple dressing  300 . Contact elements are preferably constructed to provide an arcuate contact surface. In a preferred embodiment, the radius of contact is between about 0.1 mm to 1 mm. 
         [0048]    Dimple voids  330  can be formed in a variety of regular or irregular shapes. Preferably, dimple voids are constructed so that they are not “undercut” such that each aperture circumference is smaller than the corresponding inner void circumference. An “undercut” or reticulated void structure can cause tissue disruption when the dressing  300  is removed because any tissue that has grown into the void may be torn away when the material is removed from the wound. Additionally, undercut or reticulated void structures are more likely to result in shedding of the dressing material into the newly developing wound tissue. 
         [0049]    In one preferred embodiment, a base material for dressing  300  is Masterflo RTM manufactured by BBA group of Wakefield, Mass. In this exemplary embodiment, the base material has a thickness of about 1.0 mm. Dimple voids  330  are heat stamped into the base material having a depth of about 0.75 mm and a diameter of about 2 mm. 
         [0050]    Because the contact layer is generally replaced every few days it is important to account for the possibility of alignment of newly formed tissue with the voids of a new contact layer. Thus, according to exemplary embodiments of the present invention 1) dimple voids  300  can be arranged randomly so that they don&#39;t line up with the new tissue growth after each dressing change, 2) different contact layers with different diameter dimples may be provided, or 3) a different spacing of the dimples can be used every time the material is changed. 
         [0051]      FIG. 3B and 3C  illustrate the corresponding top and bottom views, respectively, of dimpled dressing  300 . One variation of this embodiment is also contemplated having dimple voids  330  and/or contact elements  322  disposed on both the top and bottom of dimpled dressing  300 . A second variation on dimpled wound dressing  300  is also contemplated wherein some or all of the dimple voids  330  are replaced with holes traversing the structure&#39;s entire thickness such that the top and bottom views of the variation would appear similar to  FIG. 3B . 
         [0052]    In one exemplary embodiment, dimple voids  330  can be partially filled with therapeutic substances. For example, antiseptic substances might be placed in voids  330  for treating infected wounds. Further, biologic healing agents could be delivered in the voids to improve the rate of new tissue formation. In yet another exemplary embodiment, the layer of dressing  300  could have a different function on each side. For example, one side of dressing  300  could be optimized for the growth of new tissue, while the other side could be optimized for the delivery of anti-microbial agents, for example. 
         [0053]    Use of dimpled dressing  300  is illustrated by  FIGS. 4A ,  4 B and  4 C.  FIG. 4A  shows a wound surface  400 . Note that wound surface  400  may represent the majority of a shallow surface wound or a small interior portion of a deep tissue wound.  FIG. 4B  shows application of dimpled dressing  300  to wound surface  400  and corresponding tissue growth  410  within dimple voids  330 . Finally, removal of dimpled dressing  300  leaving tissue growth  410  is illustrated in  FIG. 4C . As will be addressed in detail below, it is desirable to provide an external force for keeping dressing  300  pressed against the surface of the wound. 
         [0054]      FIGS. 5A and 5B  illustrate another embodiment of the present invention; a rough irregular dressing  500 . From a perspective view,  FIG. 5A  depicts how irregular dressing  500  has irregular voids  510  and irregular contact elements  520  acting as “hook-like” members that are able to contact and stick to necrotic tissue when the substrate is placed in the wound. When the substrate is removed from the wound, necrotic tissue is stuck to hook like protrusions  520  and is thus removed from the wound. Removal of the substrate debrides the wound. Removal of necrotic tissue is an important part of healing wounds. The substrate of dressing  500  may be made from polyester felt or batting. In one exemplary embodiment, the felt is singed with hot air so that a percentage of the fibers melt to form a textured surface with a number of hook like elements  520 . Another suitable configuration can be the hook material such as that used with hook and loop fabric. 
         [0055]    After adequate removal of the necrotic tissue, the wound may still be considered infected and can be treated with the substrate including antimicrobial silver, for example, which is useful in killing bacteria, while the substrate and method of use facilitate the growth of new tissue. 
         [0056]    The phase of wound healing where new tissue is forming is generally referred to as the proliferative phase. Once the wound is adequately healed in the proliferative phase and the bacterial load is adequately reduced, a substrate without antimicrobial silver and optionally with the addition of growth enhancing materials is used to facilitate the continued proliferation of new cells and tissue. 
         [0057]      FIG. 5B  shows the random cross section of irregular dressing  500 . The roughened surface of irregular dressing  500  can be formed by passing a suitable substrate under convective heat at or about the melting point of the substrate&#39;s component material. For example, polyester materials typically melt in a range from about 250 degrees Celsius to about 290 degrees Celsius. A polyester felt material passed briefly under a convective heat source operating in this range will experience surface melting and subsequent fusing of the polyester strands at its surface. The degree of surface melting can be controlled with temperature and exposure time to yield a surface of desired roughness exhibiting irregular voids  510  and irregular contact elements. Although irregular dressing  500  is illustrated as having only one roughened surface the invention is not so limited in that both upper and lower surfaces may be similarly roughened. Such a dressing would be useful in the treatment of an undermined wound. 
         [0058]    As described above, treatment with the present wound dressing invention comprises forcing the inventive dressing into intimate contact with the wound surface. Generally the force should be at least 0.1 psi. Various methods and systems for maintaining this intimate contact are contemplated. These methods and systems may include: applying an adhesive film over the inventive dressing and adjacent the wound surface; wrapping a bandage over the dressing and around the injured area; and securing a balloon or another inflatable bladder to the structure and inflating the bladder with air or a liquid. In one exemplary embodiment, the application of pressure to the bladder is provided intermittently. A conformable seal may be placed over the wound and contact structure, a rigid seal is then secured over the wound, contact structure imparting a force on the contact structure. A pressure is then applied between the rigid seal and the flexible seal forcing the contact structure against the wound surface. The intimate contact may be augmented by sealing the wound area with a conformable cover and applying suction. When suction is used, dimpled wound dressing  300  is particularly well-adapted for this application. In general the range of suction levels is between 0.25 psi and 5 psi. The suction use can be further improved by applying a wound packaging material to the back of the dressing. One such suitable wound packaging material is described in U.S. Provisional Patent Application No. 60/554,158, filed on Mar. 18, 2004. 
         [0059]      FIG. 6  illustrates therapeutic device  600  in use in wound W. As shown in  FIG. 6 , therapeutic device  600  with depressions  604 , such as dimple void for example, is placed in wound W with depressions  604  placed adjacent wound surface  700 . Wound W and therapeutic device  600  are desirably covered with wound cover  606 , such as an adhesive back polyurethane film for example. In one exemplary embodiment, suction from a suction source (not shown) may be applied to wound W via suction tube  608  and coupling  610 . As healing progresses, tissue  702  in the wound bed grows into depressions  604 . 
         [0060]    The depressions  604  remain intact even when the device is placed in a wound and suction is applied. Additionally, where the material of the device is comprised of generally non-absorbent fibers, the material does not get soggy when in a wet wound. This allows the wound fluids to be pulled out of the wound by suction, for example, and additionally ensures that depressions  604  remain. It is critical that the depressions remain, so that voids exist where new tissue can grow filling the wound cavity. 
         [0061]    While the above described configuration uses depressions having a dimpled shape, other 3 dimensional structures can be fabricated such that there is a void for tissue to grow in to. One such non-limiting alternative configuration would be a woven waffle pattern. 
         [0062]    Case Study 1 
         [0063]    Patient A is a 70 year old male with a Stage IV decubitus ulcer on the right hip with significant undermining. The contact structure of the present invention was applied to the wound and an adhesive film was placed over the wound and the contact structure. A suction of 1.1 psi was applied beneath the adhesive film to impart a force upon the contact structure. The suction was maintained generally continuously. The contact material was replaced every two to four days. After use of the device for 30 days the undermined portion of the wound had virtually healed and the area of the wound opening had decreased from 66 square cm to 45 square cm. A split thickness skin graft was applied to the wound. 
         [0064]    Case Study 2 
         [0065]    Patient B is a 50 year old male with a fracture of the right ankle with exposed bone. A plate was used to reduce the fracture and a rectus abdominus free flap was performed to cover the exposed bone and hardware. The flap only partially survived resulting in an open wound with exposed bone and hardware. The contact structure of the present invention was applied to the wound and an adhesive film was placed over the wound and the contact structure. A force was applied to the contact structure by the application of an ace bandage wrapped around the ankle or by the application of suction. The suction force was generally applied for about half of the day and the force of the bandage wrap was maintained for the remainder of the day. For a number of days, the bandage wrap was solely used to impart the force. When the force was imparted by suction a suction of between 1 and 2 psi was used. In less than 2 weeks new tissue had grown over the exposed hardware. In a period of 7 weeks the wound area was reduced from 50 square cm to 28 square cm. 
         [0066]    While preferred embodiments of the invention have been shown and described herein, it will be understood that such embodiments are provided by way of example only. Numerous variations, changes, and substitutions will occur to those skilled in the art without departing from the spirit of the invention. Accordingly, it is intended that the appended claims cover all such variations as fall within the spirit and scope of the invention.