Abstract:
A hernia repair prosthesis with an occlusive member for inserting into and/or backing the herniated tissue. An overlay sheet is attached to the occlusive member by a filament which permits the occlusive member and the overlay sheet to slide relative to one another along the filament allowing the maximal positioning of the overlay sheet to provide the best surgical attachment, orientation and alignment with the patient&#39;s anatomy.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a continuation-in-part of application Ser. No. 09/540,793 filed on Mar. 31, 2000 now U.S. Pat. No. 6,425,924. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to an implantable hernia repair prosthesis and a method for reinforcing and repairing damaged tissue or muscle walls. 
     BACKGROUND OF THE INVENTION 
     Various prosthetic mesh materials have been proposed to reinforce the abdominal wall and to close abdominal wall defects utilizing different repair prostheses and methods of installation. The methods of executing a surgical repair can be segregated into two main approaches. The repair can be made exclusively from the anterior side (closest to the surgeon) of the defect by dissecting the sac free of the fascia and pressing it back into the pre-peritoneal space and providing permanent closure of the defect. The closure can be provided through the application of space filling prostheses and overlay patches (tension-free techniques) or can be accomplished through the use of sutures (tension techniques). 
     An example of a tension free anterior repair is to fold a sheet of surgical mesh fabric into a multi-layer cone configuration and then to insert the mesh plug into a hernia defect to occlude the void. Such a multi-layer prosthesis is inherently stiff and may not fully conform to variations in the contour of the defect, leaving gaps between the implant and the abdominal wall that potentially could lead to recurrent herniation. The stiff, multi-layered mesh plug also may be susceptible to kinking and buckling during placement. 
     U.S. Pat. No. 5,356,432, discloses an implantable prosthesis that is a conical plug formed of a knitted polypropylene monofilament mesh fabric. Longitudinal pleats are hot molded into the mesh body to enhance the flexibility of the conical implant, ideally allowing the implant to closely match the contour of the herniated opening when compressed within the defect. When the device is installed into a fascial defect, the tip of the conical shaped plug presses into and against the visceral sac, potentially enabling long-term erosion of the peritoneum and underlying viscera. The device, in one embodiment, has filler material incorporated into the interior of the formed mesh cone in an attempt to minimize contraction of the device during healing. As collagen scar tissue grows into the prosthetic material, the cross linking of the maturing collagen fibers causes the scar tissue (and encapsulated plug device) to contract. This contraction of scar tissue within the defect and plug causes the surrounding diseased tissue to be subjected to tension, thus enabling re-occurrence of the hernia along the edge of the conical plug. The use of the device requires the passage of a pre-expanded plug through the hernia defect and relies upon the radial expansion force of the single layer mesh cone and filler leaves to occlude the defect. Additionally, since the plug is secured in position by anchoring to the surrounding diseased tissue, the device may dislodge and migrate within the pre-peritoneal space. 
     Alternatively, a defect may be repaired through the use of posterior approaches that provide various prosthetic devices in the pre-peritoneal space to prevent the peritoneum from entering the fascial defect. These devices, in some cases, require the use of laparoscopic techniques and, in other cases, require the application of the prosthesis from a remote location under the defect to be repaired. Examples of posterior approaches are disclosed in U.S. Pat. Nos. 5,116,357, 5,254,133 and 5,916,225. However, in many cases, procedures utilizing such devices are complicated, in addition to requiring the use of general anesthesia and costly disposable instrumentation to support the laparoscopic surgery. 
     Accordingly, the prior art lacks an implantable hernia repair prosthesis for occluding and repairing damaged muscle and tissue wall ruptures, that is adaptable to irregularities in the shape of the defect, is simple to install, does not require the use of general anesthesia during installation and resists radial collapse due to tissue incorporation. 
     SUMMARY OF THE INVENTION 
     The limitations of the prior art are overcome by the present invention which includes a hernia repair prosthesis with an occlusive member for aiding in the occlusion of a defect in facia tissue. An overlay sheet of the prosthesis is surgically attachable to an anterior side of the facia tissue. A filament extending from a first point of attachment to the overlay sheet to a second point of attachment extends substantially parallel to the overlay sheet between the first and second points of attachment. The occlusive member is slideably attached to the filament to permit the occlusive member to assume a selected position relative to the overlay sheet between the first and second points of attachment. 
    
    
     DESCRIPTION OF THE FIGURES 
     For a better understanding of the present invention, reference is made to the following detailed description of various exemplary embodiments considered in conjunction with the accompanying drawings, in which: 
     FIG. 1 is a perspective view of a prosthesis according to the present invention prior to assembly of all of its component parts; 
     FIG. 2 is a perspective view of the assembled prosthesis depicted in FIG. 1; 
     FIG. 3 is a perspective view of the prosthesis depicted in FIG. 2 when positioned within a defect in the fascia; 
     FIG. 4 is a perspective view of the prosthesis depicted in FIG. 3 after deployment, i.e. radial expansion, within the defect; 
     FIG. 5 is a top plan view of a sheet of mesh material used to construct another embodiment of the present invention; 
     FIG. 6 a  is an end view of the mesh sheet depicted in FIG. 5 being rolled to form a radially-expandable member; 
     FIG. 6 b  is an end view of the mesh sheet depicted in FIG. 5 after being rolled to form a radially-expandable member; 
     FIG. 7 a  is a perspective view of a radially-expandable member prepared from the mesh sheet depicted in FIG. 5; 
     FIG. 7 b  is a perspective view of a radially-expandable member prepared from the mesh sheet depicted in FIG. 5; 
     FIG. 8 is a perspective view of a prosthesis made from the radially-expandable member depicted in FIG. 7 b;    
     FIG. 9 is a perspective view of the prosthesis depicted in FIG. 8 after deployment, i.e. radial expansion, within a defect in the fascia; 
     FIG. 10 is a perspective view of a prosthesis according to another embodiment of the present invention; 
     FIG. 11 is a perspective view of the assembled prosthesis depicted in FIG. 10; 
     FIG. 12 is a perspective view of the prosthesis depicted in FIG. 11 when positioned within a defect in the fascia; 
     FIG. 13 is a perspective view of the prosthesis depicted in FIG. 12 after deployment, i.e. radial expansion, within the defect; 
     FIG. 14 is a perspective view of a prosthesis according to a further embodiment of the present invention; 
     FIG. 15 is a perspective view of a prosthesis according to yet another embodiment of the present invention; and 
     FIG. 16 is a perspective view of a prosthesis according to still another embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention provides implantable prostheses and methods for reinforcing and repairing weakened abdominal walls. The prostheses are formed of a biologically compatible, flexible and porous medical textile suitable for reinforcing tissue and occluding tissue defects. The implantable prostheses are indicated particularly for the repair of hernias in the abdominal cavity, including inguinal (direct and indirect), femoral, incisional and recurrent, and provide at least a partial posterior repair. The prostheses are able to be inserted easily in a stress-free condition into a fascia defect from an anterior approach and are capable of expanding radially, at least partially into the pre-peritoneal space, to substantially occlude and conform to the fascia wall of a fascia defect. Alternatively, a posterior approach may be used, if the surgeon prefers. The prostheses are suitable for the repair of varying sizes and shapes of hernias and can be anchored to the surrounding healthy tissue to prevent migration, thus extending beyond the edge of the defect on the anterior side of the defect. Other features of the present invention will become apparent from the following detailed description when taken in connection with the accompanying drawings that disclose multiple embodiments of the invention. The drawings are for the purpose of illustration only and are not intended as a definition of the limits of the invention. 
     The prostheses of the present invention comprise a hollow, radially-expandable member for placement within and occlusion of a fascia defect. By radially-expandable, it is meant that the cross sectional area of the member expands from an initial, non-expanded configuration having an initial cross sectional area, sized such that the member may be placed within a fascia defect in a stress-free condition, to a final, expanded configuration having a final cross sectional area greater than the initial cross sectional area and effective to occlude all of, or at least a substantial portion of, the fascia defect. This member can be manufactured out of biocompatible absorbable or non-absorbable material. 
     The prosthesis also comprises means for securing the prosthesis to the tissue wall. In certain embodiments, the means for securing comprises an overlay sheet of medical textile fixedly or maneuverably attached to the radially-expandable member, as depicted in the figures. When maneuverably, e.g. slidably, attached to the expandable member, the overlay sheet may be so-attached to the radially-expandable member by the use of a filament, or multiple filaments, passed through the looped suture or the proximal end of the expandable member and attached to the overlay patch at the terminal ends of the filament. Prostheses comprising such a slidably, or maneuverably, attached means for securing the prostheses to the tissue wall and a member for occluding the defect also are included within the scope of inventions disclosed herein. In such embodiments, the occluding member need not be radially-expandable, but need only be effective to occlude the defect. One of the advantages of such a prosthesis is that, once placed into the defect area, the securing means may be maneuvered such that attachment to stable or healthy tissue may be accomplished, thereby providing a more secure attachment to the tissue wall. 
     In other embodiments, the means for securing the prosthesis may be an integral part of the radially-expandable member. The prosthesis is passed into/through a defect in the fascial layer. The radially-expandable member then is collapsed axially, thus causing radial expansion of the radially-expandable member. The radial expansion of the radially-expandable member causes substantially complete occlusion of the fascial defect. 
     Slidable, or otherwise maneuverable, attachment of the radially-expandable member to the means for securing permits the overlay member to be maneuvered relative to the deployed expandable member and adjusted once placed within the fascia defect. This provides added benefit of being positionable, relative to the cord and other anatomical structures once in place, over conventional prostheses for repairing fascia defects which are fixedly attached to the means for securing to surrounding tissue, and are not capable of being adjusted once the prostheses are placed and fixed within the fascia defect. 
     While radial expansion of the member may be effected by means for radially-expanding the member as discussed and depicted herein, prostheses that are self-expanding, i.e. self-collapsing, when placed in position within the fascia defect are included within the scope of the present invention. Such devices may be constructed such that they will deploy, i.e. collapse axially and radially-expand to occlude the defect, when positioned within a defect in response to conditions of the body surrounding the defect. Preferably, a looped suture, passed longitudinally through the hollow cavity of the radially-expandable member along the axis thereof, may serve as a means for radially-expanding the member. 
     In certain embodiments of the invention, the radially-expandable member comprises opposing conical members fixedly attached one to the other at their respective bases, thus forming a cavity defined by the attached conical members. Each cone comprises pleated surfaces that increase the axial rigidity of the prosthesis, thus allowing the prosthesis to exert a radial expansion force, while ultimately maintaining the ability to conform to irregularities in the tissue or muscle wall surrounding the opening. One or more tubular structure of textile material may be contained within the cavity of the radially-expandable member to impart additional axial rigidity to the prosthesis, thus improving the handling characteristics during insertion into the defect. Tubular structure, as used herein, is meant to include those structures where the cross sectional configuration is tubular in nature. Tubular structure specifically includes cylindrical rolls of materials, e.g. meshes, where the cross section configuration is circular, as well as structures where the cross sectional configuration may be elliptical, triangular, rectangular, etc. The tubular structure also improves the radial expandability of the prosthesis when it is compressed axially and the cylinder collapses, ensuring a solid expansion of the prosthesis against and below the tissue or wall structure defining the defect. 
     The prostheses and radially-expandable member may be constructed from any suitable biologically compatible, flexible and porous medical textile known for reinforcing tissue and occluding tissue defects. Preferred mesh materials include knitted polypropylene monofilament mesh fabrics such as those available from Ethicon, Inc. under the Prolene trademark, as well as meshes available from Ethicon, Inc. under the Vicryl trademark. Other mesh materials useful in the invention include those available under the Marlex, Dacron, Teflon and Merselene trademarks. Alternatively, the desired effect of forcing tissue re-generation under the overlay patch can be accomplished through the selection of biocompatible absorbable materials for use in the fabrication of the expandable member. Examples of suitable materials are Vicryl and Panacryl sutures, available from Ethicon, Inc, and Polysorb suture, available from United States Surgical Corporation. 
     An exploded view of a prosthesis of the present invention is illustrated in FIG.  1 . Prosthesis  10  comprises radially-expandable member  12 , comprising first and second conical members  14 . Each conical member  14  comprises longitudinal pleats  16  terminating at apex  18  and base  20  of each cone, respectively. The number and spacial relationship of longitudinal pleats  16  are effective to enhance the axial rigidity of the prosthesis and to allow the prosthesis to more closely match the contour of the fascia defect when compressed and placed within the defect. Preferably, the pleats are thermoformed into the mesh body. Looped suture  22 , with a non-reversing knot  24 , is passed through the inner diameter of opposing conical members  14 . Sheet  26  of polypropylene mesh is fixedly attached to apex  18  of one of opposing conical members  14  through the use of looped suture  22 . Sheet  26  is utilized to attach and secure the prosthesis to the surrounding healthy tissue. Optionally, prosthesis  10  may comprise one or more tubular structures  28  of polypropylene mesh contained within cavity  30  formed when opposing conical members  14  are attached at their respective bases  20 . Tubular structure  28  provides additional axial rigidity to the prosthesis during handling and insertion of the device into the defect. 
     Suture  22  is passed through the inner diameter of the opposing conical members  14 , passing from the apex of one through the apex of the other. Suture  22  then is looped and returned back through the inner diameter of the prosthesis in the opposite direction. Looped suture  22  is passed through the ends of the tubular structure  28  causing it to buckle, or collapse, when looped suture  22  is constricted during use. In the particular embodiment illustrated, both ends of looped suture  22  are passed through flat overlay sheet  26 . Non-reversing knot  24  is tied in looped suture  22  and flat overlay sheet  26  is held in proximity to apex  18  of the upper one of the conical members  14 . The dead tail of the knot  24  is trimmed to length. The finished prosthesis is subjected to sterilization prior to use. 
     The assembled prosthesis of FIG. 1 is illustrated in FIG.  2 . Prosthesis  10  may be fabricated from any biocompatible medical woven, knitted or non-woven textile. In preferred embodiments, the prosthesis is fabricated from medical grade polypropylene mesh. Radially-expandable member  12  comprises conical members  14  fixedly attached one to the other at respective bases  20 . Conical members  14  are configured to have an initial, non-expanded, maximum diameter that is substantially the same size or less than the diameter of the defect to be repaired. While the conical members  14  are shown in the figure to be identical in structure, embodiments in which one is taller than the other are contemplated by the invention. The conical members  14  are positioned in opposition one to the other and bases  20  are aligned. Once bases  20  are aligned, conical members  14  are fixedly attached to each other at respective bases  20 . Bonding of the conical members  14  may be accomplished by stitching, welding or any other known form of fixable attachment, thus forming bond  32  about base  20 . Preferably, prosthesis  10  comprises at least one flat sheet of mesh rolled into tubular structure  28  (FIG. 1) and permanently located within cavity  30  (FIG. 1) formed by fixedly attached conical members  14 . 
     Tubular structure  28  is fabricated from a flat sheet of polypropylene mesh that, once rolled into cylindrical shape, can been secured about its circumference with suture. Alternatively, tubular structure  28  may be formed by rolling a flat sheet of mesh into the cylindrical configuration and welding, stitching or otherwise bonding the rolled sheet at the ends. Tubular structure  28  (FIG. 1) is disposed inside cavity  30  (FIG. 1) formed by fixedly attached opposing conical members  14  and extends axially from the internal apex  18  of one to the internal apex  18  of the other. Tubular structure  28  aids in providing axial rigidity to the prosthesis when it is inserted into the defect. 
     As shown in FIGS. 3 and 4, after hernia sac  40  has been dissected and/or ligated, prosthesis  10  is inserted into fascia defect  43 . Once hernia sac  40  is free from walls  44  of defect  43  in fascia  42 , hernia sac  40  is pressed back into the abdominal cavity. Apex  18  of the lower one of the conical members  14  is inserted into defect  43 , causing peritoneum  46  to invert inwards into the abdominal cavity. Prosthesis  10  is inserted until mesh sheet  26  is flush with anterior side  48  of fascia  42 . Free end  23  of suture  22  is pulled while prosthesis  10  is held in a forward position, i.e. flush with anterior side  48  of fascia  42 . The tightening of suture  22  causes the opposing conical members  14  to be drawn together. The compression of the conical members  14  causes them to collapse axially onto themselves, thus causing the diameter of conical members  14  to expand radially and pleats  16  to open up or expand into a relatively flattened position. This same action causes tubular structure  28 , located within cavity  30 , to buckle, collapse and expand outward radially. Knot  24  is pulled until it is fully tightened. 
     Free end  23  of suture  22  may be provided with a needle to enable attachment of the prosthesis  10  to the surrounding healthy tissue by sewing overlay sheet  26  into place. Alternatively, free end  23  of suture  22  can be trimmed off after final deployment and the overlay patch can be attached in place through the use of additional sutures, or may remain in a flattened condition in the anterior space. 
     The prosthesis  10  is able to accommodate the spermatic cord structures since it is pleated. When it is expanded, it relies only on the radial expansion force generated from the compression of the opposing textile conical members  14  to enlarge their diameters, as opposed to the use of additional semi-rigid rings or other rigid or semi-rigid members. Preferably, prostheses of the present invention do not comprise such rigid or semi-rigid devices. This ensures that the device is fully compliant to the natural anatomical structures. 
     The final configuration of expanded prosthesis  10 , as seen in FIG. 4, both occludes fascia defect  43  on posterior side  47  and is expanded to fill the inner diameter of defect  43  in wall  44 . The expansion of radially expandable member  12  on posterior side  47  of defect  43  prevents peritoneum  46  from entering defect  43 . Additionally, this posterior expansion ensures that the repair is secure from re-herniation through the defect, since the conical mesh is forced into a relatively flat condition. As the scar tissue grows into the flattened conical layers, it is compressed further in the axial direction by scar tissue contraction. With the inclusion of overlay patch  26 , located on anterior side  48  of defect  43 , it is virtually impossible for the device to migrate either anteriorly or posteriorly. 
     In another embodiment of the present invention as illustrated in FIGS. 5-9, the prosthesis is fabricated by cutting a biocompatible, medical textile, preferably polypropylene mesh, into a flat sheet. The sheet is provided with multiple slits, or continuous openings, extending across the width of the flat sheet for a distance effective to provide radial expansion of the radially-expandable member upon deployment of the prosthesis in a fascia defect and, thus, occlusion of the fascia defect. The slits do not extend to the edges of the sheet. The sheet also comprises as an integral part for fixedly attaching the prosthesis to tissue. 
     As seen in FIG. 5, sheet  50  of mesh is provided with a plurality of slits  52  extending substantially, but not completely, across the width of sheet  50 . The number, dimension and location of such slits will be effective to provide radial expansion of the radially-expandable member upon deployment within a defect. It is noted that the distance between slit  52   a  and edge  56  of sheet  50  is greater than the distance between slit  52   b  and edge  58  of sheet  50 . While not required or essential to the invention, in certain embodiments, the distance between slit  52   a  and edge  56  is such that when the sheet is rolled onto itself to form a cylindrical roll, the inner-most layer of sheet material in the rolled cylinder is void of slits. In other words, the distance between slit  52   a  and edge  56  is equal to or greater than the inner circumference of the rolled cylinder. Sheet  50  also includes tabs  54 , for use in subsequent fixed attachment of the prosthesis to tissue. 
     As depicted in FIGS. 6 a  and  6   b,  sheet  50  is rolled such that edge  56  is rolled into the inner diameter of the cylindrical configuration. The roll is maintained in the cylindrical configuration through th use of tacking welds. sutures or others bonding means at each end of the roll, thus forming the radially-expanding member  60  for occluding a fascia end of the roll, illustrated in FIGS. 7 a  and  7   b.  End  62  of radially-expandable member  60  may be sealed closed by stitching, welding or bonding, for example. 
     As seen in FIG. 8, suture  64  is attached to end  62  of radially-expandable member  60  in purse-string arrangement  68 , and then tightened and permanently knotted. Free end  63  of suture  64  is passed through the inner part of the rolled cylinder and is stitched around the circumference of open end  66  to form another purse-string arrangement  68 . A non-reverse slipknot (not shown) is tied into the suture. 
     As depicted in FIG. 9, prosthesis  70  is placed into fascia defect  43  by pressing dissected/ligated hernia sac  40  into the abdominal cavity. Free end  63  of suture  64  is pulled while holding prosthesis  70  forward. As suture  64  is drawn, vertical slits  65  allow radially-expandable member  60  to collapse. Slits  65  buckle outwards, i.e. expand radially, forming overlapping leaves  72  that occlude defect  43 . Tabs  54 , located at the top of collapsed prosthesis  70 , are used to fixedly attach the deployed prosthesis to surrounding healthy tissue. 
     Referring to FIGS. 10-13, prosthesis  80  comprises overlay patch  86  slidably attached to radially-expandable member  88 . As shown, filament  84  is passed through looped suture  82  and affixed at its terminal ends to overlay patch  86 . When radial-expandable member  88  is placed in the defect, overlay patch  86  may be maneuvered to one side, as shown in FIG. 13, to effect attachment to fascia  89 . 
     FIG. 14 shows a prosthesis  90  having an overlay patch  96  slidably attached to a radially expandable member  98  (like the thermoformed expandable member  20  described above in reference to FIG. 1) by an elongated filament  94 . The filament  94  is joined to the overlay patch  96  at two spaced points  91 ,  92 , e.g., by tying, plastic welding or by being restrained from pulling through the overlay patch  96  material by knots or enlarged ends that exceed the size of the pores of the material of the patch  96 . Intermediate the points of connection  91 ,  92 , the filament  94  extends substantially parallel to the overlay patch  94  and is spaced therefrom to accommodate the portion of the radially expandable member  98  positioned between the filament  94  and the overlay patch  96 . While a single filament  94  is shown, a plurality of parallel filaments  94  may be utilized. The radially expandable member  98  is preferably formed from surgical mesh material or other biocompatible filamentous material that has numerous openings therethrough, i.e., the spaces between adjacent filaments that are woven or compressed together to yield a mesh and/or felt-like textile. The filament  94  simply threads through the spaces between adjacent filaments that define the textile structure of the expandable member  98 . In the alternative, in the case of a non-filamentous radial expandable member  98 , e.g., one made from a continuous plastic film, the filaments can be passed through the film by providing holes in the film with a needle and then threading the filament(s)  94  through the holes. In either case, the radially expandable member  98  is moveable along the filament(s)  94  defining a motion “track” relative to the overlay patch  96 . 
     In FIG. 14, the filament  94  passes through a cone-shaped, radially-expandable member  98  proximate the base  93  of the cone. Because the expandable member  98  is slidable on the filament  94 , the expandable member  98  may be positioned relative to the overlay patch  96  to maximally conform to the anatomy of the patient and the surgical repair encountered. More particularly, the expandable member  98  may be inserted into the facia void and then the position of the overlay patch  96  may be adjusted to coincide with the position of maximally effective surgical attachment, viz., to be amenable to attaching the overlay patch  96  to healthy tissue, to bridge over weak, unhealthy tissue, and also to conform to the patients&#39; local anatomical shape. The relative slidability of the overlay patch  96  and the expandable member  98  does not impede the expandable member  98  from collapsing and expanding to fill the breach in the facia (i.e., the filament  94  retains the overlay patch  96  in association with the expandable member  98 , but does not restrict the expansion of the expandable member  98 ). The overlay patch  96  may have any desired shape, such as a keyhole, oval, circular or rectangular shape. 
     FIG. 15 shows a prosthesis  100  having a similar overall configuration and features as that shown and described above in reference to FIG. 14, viz., with an overlay patch  106  and attachment filament  104 . In the embodiment shown in FIG. 15, the element used to fill the facia defect is a generally cylindrical roll  108  of surgical mesh material that is slidable relative to the patch  106  via filament  104 . 
     FIG. 16 shows a prosthesis  110  having an overlay patch  116 , an attachment filament  114  and an underlay patch  120  having a generally cylindrical upstanding prominence  118  that is thermoformed therein for insertion into the facia defect. The filament  114  passes through the prominence  118  to secure the underlay patch  120  to the overlay patch  116  in slidably adjustable relationship thereto, such that the underlay patch may be positioned on the posterior side of the hernia with the prominence  118  extending anteriorly into the facia void. The overlay patch  116  can then be positioned on the anterior side of the herniated facia for optimal surgical attachment. As yet a further alternative, the prominence  118  can be eliminated such that the underlay patch  120  is simply flat. In that case, the filament  114  would simply enter the proximal surface of the underlay patch, extend a selected distance along the distal surface, pass through the distal surface to reemerge through the proximal surface forming a loop to hold the underlay patch in association with the overlay patch  116 . 
     It will be understood that the embodiments described herein are merely exemplary and that a person skilled in the art may make many variations and modifications without departing from the spirit and scope of the invention. All such variations and modifications are intended to be included within the scope of the invention as defined in the appended claims.