Abstract:
Scar formation is inhibited by simultaneously applying a vertical force and a lateral compression to the wound site during the healing process. Apparatus for applying such simultaneous forces comprise a backing and a tissue displacement device. The backing holds the tissue displacement device over the wound. The tissue displacement device may be expanded to both apply the vertical force against the wound and to draw the backing radially or laterally inward to apply the desired compression forces to the wound.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application is a continuation of PCT Application No. PCT/US2011/040213 (Attorney Docket No. 35383-705.601), filed Jun. 13, 2011, which claims priority from provisional application No. 61/397,604 (Attorney Docket No. 35383-705.101), filed on Jun. 14, 2010, the full disclosures of which are incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    Scarring is a natural response to the healing of wounds in a patient&#39;s skin. The wound healing process can be divided into three successive stages. A first inflammatory stage begins immediately after the injury which caused the wound. The inflammatory stage lasts up to a week during which time cellular processes remove damaged tissue and foreign matter from the wound. The inflammatory stage is followed by a proliferative stage which is characterized by fibroblast proliferation and the production of collagen and proteoglycans. The proliferative stage can last from days to weeks and is typically the stage during which hypertrophic scar formation begins, typically as a result of excess production of the extra cellular matrix which is synthesized to heal the wound. Such scars are referred to “hypertrophic scars.” After the proliferative stage, a remodeling phase begins where the matrix which was produced in the proliferative is remodeled into an organized, cross-linked structure which increases the mechanical strength of the healed tissue. 
         [0004]    Scars which are formed during the healing response are often treated after the healing is complete by cosmetics or surgical treatment. Cosmetic treatments are at best temporary solutions, and the need to have subsequent surgery is both inconvenient and a risk to the patient. It would therefore be desirable to provide methods and apparatus which could diminish scar formation during the healing process itself so that such subsequent procedures would be unnecessary or at least reduced in scope. 
         [0005]    2. Description of the Background Art 
         [0006]    WO/2011/019859 describes a device for inhibiting scarring in skin wounds, where the device is fixed to the skin and applies an outward force to spaced-apart skin locations. US2008/0069855 describes materials that will prevent scars and tissue adhesions. U.S. Pat. Nos. 7,511,185, 4,702,251, 4,539,990 and 4,535,772 describe wound healing devices that apply laterally inwardly opposed forces to the tissue on either side of the wound. 
       SUMMARY OF THE INVENTION 
       [0007]    The present invention provides methods and apparatus for inhibiting scar formation during the healing of a wound on a skin surface. The term “scar” is intended includes not only common hypertrophic scars which occurs from cuts, abrasions, and the like, but also to include keloids which are hyperplastic masses that occur in the dermis and adjacent subcutaneous tissue in certain individuals, typically following trauma. 
         [0008]    The methods and apparatus of the present invention treat healing wounds by applying a downward force on the wound while simultaneously applying a compression force in order to relieve tension in the tissue across or surrounding the wound, usually during the proliferative and/or remodeling stages of the wound healing process. Treatment during the late portions of the inflammatory stage might also be useful, and in some instances treatment after remodeling might also be performed. For example, simultaneous downward compression and lateral compression may applied to the wound at or near the end of the inflammatory stage, typically at a time in the range form 1 day to 30 days after the wound occurred and first began to heal. After commencing treatment, the forces may continue to be applied for a period of time in the range from one day to 21 days, or longer, and the forces may be increased, decreased, or held constant during the treatment period. 
         [0009]    Apparatus according to the present invention are specially adapted to provide such simultaneous downward and lateral compressive forces to the region of the wound in the skin, typically comprising a tissue displacement device which can placed on the skin surface to cover the wound itself as well as some distance lateral to the wound, typically from several millimeters to one or two centimeters or more on each side of the wound. The tissue displacement device may be actuated to apply the desired vertically downward force in a variety of ways as described below. 
         [0010]    The apparatus of the present invention will also typically include a backing which can be secured to the skin on either side of the healing wound, where the backing is typically adapted to draw the skin surface and underlying tissue layers laterally inwardly to provide the desired lateral compression and in turn relieve tension in the tissue. In the described embodiments, the inward lateral movement of the skin and underlying tissue will be effected by raising a center of the backing (after the backing has been applied to the skin surface), usually as a result of actuating the tissue displacement device, to draw the sides of the backing laterally inwardly. 
         [0011]    The backing may comprise a strip or layer of material which can be attached to the skin over the tissue displacement device, with lateral regions of the backing adhering to the skin surface on opposite sides of displacement device. Usually at least the lateral portions of the backing will be non-distensible (resistant to stretching or inelastic), and more usually the entire backing will have limited stretchability or elasticity, often being entirely non-distensible. By non-distensible, it is meant that the backing material will have an elongation at break of less of less than 20%, typically less than 15%, and often less than 10%. Alternatively, the backing may comprise a strap or other longer structure which can be wrapped around a patient&#39;s limb in order to constrain the tissue displacement device on the skin surface above below. 
         [0012]    In the exemplary embodiments, the tissue displacement device comprises a balloon or other expandable device having a relatively non-distensible bottom surface which is disposed against the wound and a relatively distensible top surface which inflates upwardly to raise a central region of the backing which in turn causes the lateral portions of the backing to draw laterally inwardly to provide the desired inward tissue compression. 
         [0013]    In order to treat long wounds covering five centimeters, ten centimeters, twenty centimeters, or longer, the apparatus of the present invention can be formed in segments, each usually comprising a separate backing and a separate tissue compression device as described previously. The segments will be linked together by flexible joints, links or other components which allow the resulting assembly to conform to a skin surface and follow irregular topology of the wound and skin. The resulting “flexibility” is also useful in allowing the assembly to conform to the skin surface when the patient moves or is moved by others. In some embodiments, the joints will be formed as short tubes or other structures capable of delivering an inflation medium to each successive segment from either end of the assembly. 
         [0014]    Still other apparatus could be constructed in accordance with the principles of the present invention. For example, for localized wounds, a circular, stretchable elastic backing having an adhesive surface for adhering to the skin could be provided. By initially stretching the elastic backing radially outwardly, for example using a constraining frame or other component, the elastic backing could be placed over the wound and released from its constraint to apply the literally inward force to the wound. A variety of tissue compression devices can be placed under or over the backing in order to provide the vertical compression desired. 
         [0015]    Still alternative, apparatus could be provided including a more rigid disk having an adhesive on an outer annular surface and a center portion free from the adhesive that can be everted or otherwise deformed to press inwardly against tissue and draw the annular circumference of the disk inwardly to provide simultaneous radial compression and vertical force. For example, the center portion could “snap” from an everted configuration to an inverted configuration much like a bottle top with an indication that the top has been previously opened. 
         [0016]    In still other embodiments, a lower of other surface of the tissue displacement device may be coated with a drug to deliver that drug to the skin during the treatment. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]      FIG. 1  is a schematic illustration of a wound showing vertical and lateral force compression applied in accordance with the principles of the present invention. 
           [0018]      FIGS. 2 ,  2 A and  2 B illustrate a first apparatus and its use for applying such vertical and lateral force compression. 
           [0019]      FIG. 3  illustrates a segmented assembly constructed in accordance with the principles of the present invention which can be used for treating elongated or irregular wounds. 
           [0020]      FIG. 4  illustrates an alternative apparatus for treating wounds in accordance with the principles of the present invention. 
           [0021]      FIGS. 5A and 5B  illustrate use of the apparatus of  FIG. 4  in treating a localized wound. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0022]      FIG. 1  is a schematic diagram illustrating a subcutaneous wound W in a skin surface S where the wound extends some distance beneath the surface. To reduce scarring as the wound heals in accordance with the principles of the present invention, a downward or vertical force will be applied over a region spanning the wound and extending from several millimeters to several centimeters or longer onto the skin surface from each side of the wound as generally indicated by the vertical arrows. Pressure is preferably applied along most or all of the length of elongated. The cuts, incisions, and other elongated wounds that are treated by the present invention will typically extend into the dermis by several millimeters or more. In addition to the vertical force, present of the invention will provide a compressive force or pressure indicated by arrows  12  preferably extending from the surface down to a depth close to or equal to the depth of the wound. 
         [0023]    Methods of the present invention for applying the forces illustrated in  FIG. 1  can be performed using a variety of apparatus. One exemplary apparatus is illustrated in  FIG. 2  and includes both a backing  14  and a tissue displacement device  16  which can be assembled and used in combination for applying the desired forces. The backing  16  will usually be non-distensible over most or all of its length from end  18  to end  20 . The length will usually be in the range from 5 centimeters to 10 centimeters, 20 centimeters, or longer. The width will typically be in the range from 1 centimeter to 5 centimeters. Backing will be divided into regions, including a first lateral region  22  and a second lateral region  24 . At least a portion of each of these lateral regions will be substantially non-distensible and they will have adhesive surfaces  26  and  28  which can be applied to the skin to hold the backing in place. A central region  14  of the backing between the lateral regions  22  and  24  may have some ability to stretch (distensibility), but the central region will also typically be non-distensible over all or a portion of its length. The bottom surface of this central region of the backing, however, will be usually free from all adhesives so that the central region may be placed over the tissue displacement device  16  with the central region able to move over the top of the displacement device as the displacement device is expanded as shown in broken line in  FIG. 2 . The displacement device  16  will typically be formed from an elastic material over its upper portions to allow the desired vertical expansion while a bottom or base  30  of the device  16  resists expansion. Thus, the upper surface  32  which is elastic can expand to the extent shown in broken line when the device is actuated. Usually, the tissue displacement device  16  will be an inflatable structure, such as a balloon, where the thickness of and/or reinforcement within the bottom of the structure resists stretching and the upper portion is elastic to allow expansion upon inflation of the structure. In other cases, a balloon or other inflatable of expandable structure with a round or elliptical profile could be used. 
         [0024]    In use, the assembly of  FIG. 2  is placed over a wound so that the lateral regions  22  and  24  of the backing  14  adhere to the skin&#39;s surface on opposite sides of the wound W. The tissue displacement device  16  is held directly over the wound W by the central section of the backing as shown in  FIG. 2A , and the tissue displacement device  16  then inflated to raise the central section and as shown in  FIG. 2B . By raising the central section  25 , the lateral portions  22  and  24  are drawn laterally inward to compress the upper surface of the tissue which in turn compresses the tissue on either side of the wound at the lower depths as shown by the arrows in  FIG. 2B . Simultaneously, the bottom of the tissue displacement device applies a downward pressure over the wound as indicated by the vertical arrows in  FIG. 2B . The asymmetric structure of the tissue displacement device allows this selective application of forces to achieve the objectives of the present invention. Each of the lateral portions  22  and  24  will be attached on the skin surface up to a point P. the backing will be unattached to the skin between point P and area covered by the tissue displacement device  16 . It is this short unattached region of the backing which allows the lateral portions  22  and  24  to be drawn inwardly without significantly pulling the skin upwardly, as shown in  FIG. 2B . 
         [0025]    In order to treat lengthy wounds, the apparatus as generally shown in  FIG. 2 , can be formed in multiple segments  40 , as illustrated in  FIG. 3 . Each segment  40  will generally have the structure illustrated in  FIG. 2 , and adjacent segments will be joined by short tubular connectors of links  42  which both hold the segments together and which permit simultaneous inflation of each of the tissue displacement devices  16 . The segmented structure of  FIG. 3  is advantageous since it permits the assembly to follow non-linear wounds and also allows the assembly to conform to the tissue surface as the patient moves or is moved during the scar treatment. 
         [0026]    An alternative treatment device  50  is illustrated in  FIG. 4 . The device comprises a backing  52  having an outer annular portion  54  which has an adhesive surface for attachment to the patient&#39;s skin. The device  50  further includes a central section  54  which can be everted or depressed in order to both apply vertical force to a wound and simultaneously apply radially inward forces, as illustrated in  FIGS. 5A and 5B . Such an evertable central section could also be used with the elongated or strip-like devices described previously. 
         [0027]    As shown in those  FIGS. 5A and 5B , a localized (non-elongated) wound W may be covered by the central portion  54  of the device  50  while the annular portion  52  adheres to the skin surrounding the wound. By then deforming and depressing the center section  54  and shown in  FIG. 5B , a vertical force is applied over the wound while simultaneously the annular portion  52 , which will typically be elastic, is drawn inwardly to radially compress the tissue about the wound.