Abstract:
A hernia repair prosthesis with an occlusive member for inserting into and/or backing the herniated tissue. The occlusive member is convertible from a first configuration with a first axial length and first major radial extent to a second configuration with a second axial length and a second major radial extent. The second axial length is less than the first axial length and the second major radial extent is larger than the first major radial extent. The occlusive member has a pair of subsections, each having an apex, lands and pleats and each flaring outwardly therefrom towards a terminal end. The apexes are disposed at opposite ends of the occlusive member with the terminal ends overlapping. The pair of subsections are conjoined proximate the overlapping terminal ends. The terminal end of one or both of the subsections may be in the form of a conic flange mimicking the lands and pleats of the other subsection providing automatic alignment and nesting to aid in the attachment of the two subsections. In accordance with methods for forming the subsections, a surgical fabric is thermoset on a male die and may be stretched or heat shrunk to aid in conforming the surgical fabric to the contours of the male die. The subsections may be joined by ultrasound.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to an implantable hernia repair prosthesis for reinforcing and repairing damaged tissue or muscle walls and methods for making same.  
         BACKGROUND OF THE INVENTION  
         [0002]    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).  
           [0003]    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, may not fully conform to variations in the contour of the defect, and is subject to shrinkage that potentially could lead to recurrent herniation. The stiff, multi-layered mesh plug also may be susceptible to kinking and buckling during placement.  
           [0004]    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.  
           [0005]    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.  
           [0006]    Accordingly, the prior art lacks an implantable hernia repair prosthesis for occluding and repairing damaged muscle and tissuewall 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  
         [0007]    The limitations of prior art hernia prostheses are overcome by the present invention which includes a hernia repair prosthesis having an occlusive member for aiding in the occlusion of a defect in fascia tissue. The occlusive member is convertible from a first configuration with a first axial length and a first major radial extent to a second configuration with a second axial length and a second major radial extent. The second axial length is less than the first axial length and the second major radial extent is larger than the first major radial extent. The occlusive member has a pair of subsections, each having an apex and each flaring outwardly therefrom towards a terminal end. The apexes are disposed at opposite ends of the occlusive member with the terminal ends overlapping. The pair of subsections are conjoined proximate the overlapping terminal ends.  
           [0008]    In accordance with a method for forming the subsections, a surgical fabric is thermoset on a male die and may be stretched or heat shrunk to aid in conforming the surgical fabric to the contours of the male die. 
       
    
    
     DESCRIPTION OF THE FIGURES  
       [0009]    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:  
         [0010]    [0010]FIG. 1 is a perspective view of a prosthesis according to the present invention prior to assembly of all of its component parts;  
         [0011]    [0011]FIG. 2 is a perspective view of the assembled prosthesis depicted in FIG. 1;  
         [0012]    [0012]FIG. 3 is a schematic view of the prosthesis depicted in FIG. 2 when positioned within a defect in the fascia;  
         [0013]    [0013]FIG. 4 is a schematic view of the prosthesis depicted in FIG. 3 after deployment, i.e. radial expansion, within the defect;  
         [0014]    [0014]FIG. 5 is a schematic view of a die for making pleated conical elements of the prosthesis of FIGS.  1 - 4 ;  
         [0015]    [0015]FIG. 6 is a perspective view of a prosthesis in accordance with a second embodiment of the present invention;  
         [0016]    [0016]FIG. 7 is an exploded view of the prosthesis depicted in FIG. 5;  
         [0017]    [0017]FIG. 8 is a schematic view of a die for making pleated conical elements of the prosthesis of FIGS. 6 and 7;  
         [0018]    [0018]FIG. 9 is a perspective view of a forming station for forming a prosthesis in accordance with the present invention, e.g., as shown in FIGS. 6 and 7;  
         [0019]    [0019]FIG. 10 is a perspective view of a prosthesis in accordance with a third embodiment of the present invention;  
         [0020]    [0020]FIG. 11 is a perspective view of a prosthesis in accordance with a fourth embodiment of the present invention; and  
         [0021]    [0021]FIG. 12 is a schematic view of the prosthesis of FIG. 11 within a fascia defect. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0022]    The present invention provides implantable prostheses for reinforcing and repairing weakened abdominal walls and methods for making such prostheses. 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.  
         [0023]    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 surgical mesh material.  
         [0024]    An exploded view of a prosthesis of the present invention is illustrated in FIG. 1. Prosthesis  10  comprises radially-expandable member  12 , having first and second conical members  14   a ,  14   b . Each conical member  14   a ,  14   b  has longitudinal pleats  16  terminating at apex  18  and base  20  of each conical member  14   a ,  14   b , respectively. The number and spacial relationship of longitudinal pleats  16  are effective to enhance the axial rigidity of the prosthesis  10  while being placed within the defect. Preferably, the pleats  16  are thermoformed into the mesh body of each conical member  14   a ,  14   b . Conical member  14   b  has a flange portion  19  that facilitates the relative alignment and attachment of conical members  14   a ,  14   b , as more fully described below in reference to FIGS. 6 and 7. Looped suture  22 , with a non-reversing knot  24 , is passed through opposing conical members,  14   a ,  14   b . Overlay sheet  26 , e.g., formed from polypropylene surgical mesh, is fixedly attached to apex  18  of one of opposing conical members  14   a ,  14   b  through the use of looped suture  22 . Overlay 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 , e.g., made from polypropylene surgical mesh and contained within cavity  30  within conical members  14   a ,  14   b . Tubular structure  28  provides additional axial rigidity to the prosthesis during handling and insertion of the device 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  28  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.  
         [0025]    Suture  22  is passed through the opposing conical members  14   a ,  14   b , passing from the apex of one through the apex of the other. Suture  22  then is looped and returned back through the inner conical members  14   a ,  14   b  in the opposite direction. Looped suture  22  can be passed through the tubular structure  28  axially (or through the ends of the tubular structure  28 , perpendicular to the axis thereof, as shown by dotted line  22 ′) 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   a ,  14   b . The dead tail of the knot  24  is trimmed to length. The finished prosthesis is subjected to sterilization prior to use.  
         [0026]    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 including 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. Radially-expandable member  12  comprises conical members  14   a ,  14   b  fixedly attached one to the other proximate respective bases  20 . Conical members  14   a ,  14   b  are configured to have an initial, non-expanded, major diameter that is substantially the same size or less than the diameter of the defect to be repaired. While the conical members  14   a ,  14   b  are (with the exception of flange  19 ) 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   a ,  14   b  are positioned in opposition one to the other and bases  20  are aligned by flange  19 . Once bases  20  are aligned, conical members  14   a ,  14   b  are fixedly attached to each other proximate the respective bases  20 , e.g., in and around flange  19 , as more fully described below. Bonding of the conical members  14   a ,  14   b  may be accomplished by stitching, gluing, welding or any other known form of attachment. Prosthesis  10  includes at least one flat sheet of mesh rolled into a tubular structure  28  (FIG. 1) and permanently located within cavity  30  (FIG. 1) formed by fixedly attached conical members  14   a ,  14   b .  
         [0027]    Tubular structure  28  may be 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   a ,  14   b  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.  
         [0028]    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   a ,  14   b  is inserted into defect  43 , causing peritoneum  46  to invert inwards into the abdominal cavity. Prosthesis  10  is inserted until overlay 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   a ,  14   b  to be drawn together. The compression of the conical members  14   a ,  14   b  causes them to collapse axially onto themselves, thus causing the diameter of conical members  14   a ,  14   b  to expand radially and pleats  16  to open up or expand into a relatively flattened position, i.e., with a greater major diameter and a lesser axial length. This same action causes tubular structure  28 , located within cavity  30 , to buckle, collapse and expand radially outward. Knot  24  is pulled until it is fully tightened.  
         [0029]    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.  
         [0030]    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   a ,  14   b  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.  
         [0031]    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.  
         [0032]    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  
         [0033]    [0033]FIG. 5 shows a simplified diagram of an exemplary die system for forming the conical member  14   a  described above. The conical member  14   a  with longitudinal pleats  16  may be thermoformed from a generally flat disk of surgical mesh that has been placed over a male die element (mandrel)  32  having the same shape as the conical member  14   a  shown in FIGS.  1 - 4 , i.e., a cone featuring a plurality of longitudinal valleys  16 ′ (to form the pleats  16 ) and intervening land surfaces  17 ′ (to form the lands  17  of the conical member  14   a ). After the surgical mesh ( 14   a ) has been placed over the outer surface of the male die element  32 , a mating female die (clamp) element  33  is urged against the male die element  32  to press the surgical mesh ( 14   a ) into the surface features of the male die element, i.e., the longitudinal valleys  16 ′ and intervening land surfaces  17 ′, to impart the desired three dimensional shape to the mesh and to form the conical member  14   a . The female die element  33  may be formed from a plurality of individual blade elements  34 , preferably removably or hingedly attached to a common hub or pivot point and having an open configuration (shown in dotted lines) and which fold together to a closed configuration to press into the longitudinal valleys  16 ′. The conical member  14   a  clamped by blade elements  34  may then be heated to impose a set on the surgical mesh  14   a  such that it will retain the die shape after cooling and removal from the die set  32 ,  34 . Any excess mesh  14   a  may then be trimmed off. As an alternative to the blade elements  34 , the female die element  33  may have a continuous surface that is complementary to the surface of the male die element  32 , or may have a plurality of individual extensions (not shown) elastically, rather than pivotally emanating from a common hub to form a cage structure for pressing the surgical mesh  14   a  into the longitudinal valleys  16 ′ to form the longitudinal pleats  16  and to stretch the mesh  14   a  over the land surfaces  17 ′ of the die  32 .  
         [0034]    [0034]FIGS. 6 and 7 show an alternative radially expandable member  112  formed from conical members  114   a  and  114   b . In contrast to the preceding expandable member  12 , wherein two substantially identical conical members  14  were held in alignment and then secured together in opposition at the bases  20  of the cone shape, i.e., by gluing, stitching or welding at the flange  19 , conical member  114   a  is attenuated such that it does not extend all the way to base line  120 . As before, the conical members  114   a ,  114   b  are self aligning for the purpose of assembly. Conical member  114   b  has a conical portion  115  extending from the apex  118   b  to a base line  120 . Base line  120  represents a redirection of the surgical mesh and a great diameter of the conical member  114   b  and the expandable member  112  as a whole. A flange portion  119  of the conical member  114   b  extends from the base line  120  and converges toward apex  118   a , mimicking the shape of the conical portion  115  in reverse or mirror image. Conical member  114   a  has the same shape as conical portion  115  and matingly fits within the open end  121  defined by the flange portion  119 , i.e., aligned by respective pleats  116  and lands  117 . Conical member  114   a  overlaps flange portion  119  as shown by dotted line  123 , providing an area for gluing or welding conical members  114   a  and  114   b . The extent of conical members  114   a  and  114   b  can be varied to provide greater or lesser overlap. For example, conical member  114   a  could be identical to conical member  114   b , providing a large area of overlap on either side of base line  120 . Alternatively, conical member  114   a  can have a lesser extent than conical member  114   b , as shown, such that there is a single layer of material present at the base line  120 , which promotes bending at the baseline  120  and radial expansion of the expandable member  112 .  
         [0035]    The manufacture of the radially expandable member  112  calls for the formation of the conical members  114   a ,  114   b  and their subsequent assemblage. FIG. 8 diagrammatically shows a die system that can be employed to form the conical member  114   b , which includes a male die element  132  with conical portion  132   a  and conical flange portion  132   b . A female die element  133  has a plurality of moveable blade elements  134 , each having a conical portion  134   a  and a conical flange portion  134   b  for engaging the conical portion  132   a  and conical flange portion  132   b , respectively, of the male die element  132 . Either the conical portion  134   a  and/or the conical flange portion  134   b  of the blade element  134  is moveable from an open position (shown in dotted lines) to a closed position, either by virtue of hinges or by virtue of its being formed separately as a separate die element, i.e., the female die  133  may have a plurality of components. Alternatively, the female die element  133  may be in the form of a cage with multiple flexible fingers emanating from a common hub for pressing the mesh ( 114   b ) into the longitudinal valleys  116 ′ of the conic portion  132   a  and the valleys  116 ″ of the flange portion  132   b .  
         [0036]    [0036]FIG. 9 shows a forming station  135  with a male die  132  (not visible) captured within the movable blade elements  134  of female die element  133 . The blade elements  134  may be pivotally secured to the base  136  or, as shown, are removably retained in complementary shaped slots  137  and clamped in a closed position by flange  138 . The blade elements  134  have a relief slot  139  for accommodating excess mesh material and/or a retention band for clamping the mesh on the male die  132 . An orientation pin  140  may be utilized to position the mesh material in the forming station to achieve a selected orientation of the wales, warps, wefts, etc, promoting distortion-free forming of the material as the blade elements  134  are urged into position clamping the material against the male die  132 . Optimal forming may require a particular sequential order of clamping the blade elements  134 , depending upon the material, e.g.,  114   b  used.  
         [0037]    While the surgical mesh used to form the conical member  114   a  may be cut or otherwise formed in any selected two dimensional shape, a disk shape may be used to illustrate the relationship between the respective surface areas of the surgical mesh material  114   b  and the male die element  132 . More specifically, for a male die element  132  having a conical portion  132   a  with a given altitude A and base B, the surface area thereof has two components, viz., that attributable to the surface area of the lands  117 ′ and that attributable to the surface area of the longitudinal valleys  116 ′. Since the width of the valleys  116 ′ of the die  132  directly decreases the land  117 ′ area of the die  132 , the total surface area may be controlled by varying the depth and shape of the longitudinal valleys  116 ′, which can be selected to “use” a desired amount of the surface area of the surgical mesh  114   b . Similarly, the longitudinal valleys  116 ″ in the conical flange portion  132   b  of the male die element  132  may have a selected depth, shape etc. such that the surface area of the flange portion  132   b  may be altered by varying these dimensions. The valley  116 ′ dimensions for the conical portion  132   a  may be different than the valley  116 ″ dimensions of the conical flange portion  132   b . Alternatively, the valley  116 ′,  116 ″ dimensions may be consistent and symmetrical.  
         [0038]    The foregoing observations concerning the surface areas of the conical portion  132   a  and conical flange portion  132   b  are noteworthy in that a given disk-shaped sample of surgical mesh has a surface area that increases radially in accordance with the relationship (πr 2 ). The surface of a cone increases from the apex  118  to the base  120  in accordance with the relationship πrs; where s=(r 2 +b 2 ) ½ . As a consequence, the area of the material disk increases along its radius, as does the area of the conic portion  132   a  from the apex to the base. Any mismatch of surface areas must be accounted for by stretching the mesh. The flange portion  132   b  of the male die element  132  exhibits a departure from the surface area of the material disk, in that while the converging flange portion  132   b  of the die  132  increases the total surface area, it does so at a decreasing rate (due to its convergence) at the same time that surface area of the mesh  114   b  increases by the square of the radius. Accordingly, after the surgical mesh material extends beyond the great diameter of the male die  132  (at base B) and starts to cover the converging conical flange portion  132   b  of the die  132 , an excess of mesh material must be accounted for in order to bring the mesh into conformance with the die  132  shape.  
         [0039]    In accordance with a first approach, the die  132  is formed with a valley  116 ″ number (frequency) and depth (magnitude) such that the surface area of the mesh material  114   b  matches that of the flange  132   b  but is less than that required to cover the surface area of the conical portion  132   a  (including the surface area of the valleys  116 ′) proximate to the great diameter at base B without stretching. In accordance with this method, the surgical mesh material  114   b  is wrapped over the male die element  132  covering both the conical portion  132   a  and the conical flange portion  132   b  of the die  132 . The female die element  133  is then clamped over the male die element  132  forcing the mesh material  114   b  into the valleys  116 ′,  116 ″ provided in the male die element  132 . Because the surface area of the material  114   b  is less than that of the die  132 , the material  114   b  will be stretched thinner in the areas where the surface areas of the material  114   b  and the die  132  do not match. This results in the mesh  114   b  being thinner and more porous in those areas where it is stretched, primarily in the area of the great diameter proximate base B. This thinning in the area of the base B of the conical portion  132   a  enhances the hinge effect present at baseline  120  of the expandable member  112 , promoting the expansion of the expandable member  112 .  
         [0040]    Once the mesh has been conformed to the surfaces of the complementary die elements  132 ,  133 , the mesh is heated, e.g., by convection, radiation and/or conduction through the die elements  132 ,  133 . Heating relieves the stress in the highly oriented, drawn fibers of the surgical mesh  114   b  allowing the mesh to permanently set in the shape imposed upon it by the dies  132 ,  133 . The female die  133  can then be removed and the mesh cooled prior to removal from the male die  132 . In using the foregoing technique, the mesh  114   b  must be securely held against the male die element  132  to prevent it from creeping along the surface of die  132  prior to its being clamped tightly by the female die element  133 . The same process may be undertaken to form conical member  114   a . If the extent of  114   a  is chosen such that no flange  119  is present (as shown in FIG. 7) the foregoing considerations concerning matching the respective surface areas of the mesh  114   a  and the male die  132  are simplified.  
         [0041]    An alternative approach for forming conical member  114   b  is to use a male die  132  with a surface area less than that of the surgical mesh  114   b , in particular, in the area of the flange portion  132   b  of the die  132 . The mesh  114   b  is clamped to the male die element  132  such that there is an excess of mesh material  114   b  distributed in the valleys  116 ′,  116 ″ of the die  132 . The mesh  114   b  is then heated by convection to an elevated temperature, causing the fibers of the mesh  114   b  to stress relieve and to shrink. The shrinkage of the mesh  114   b  causes the surface area of the mesh to be reduced through a localized reduction in porosity in the conical flange portion  119 . This method does not involve the same forces that induce the slippage of mesh on the face of the male die  132  and eliminates the excess mesh material that might otherwise result in irregularities in the finished conical element  114   b , such as everted pleats.  
         [0042]    As can be appreciated from FIGS. 6 and 7, the finished conical elements  114   a  and  114   b  nest together in natural alignment due to the alignment of the pleats  116  and lands  117 . Having thus been aligned, the overlap between  114   a  and  114   b  can be joined by a variety of conventional means including adhesives or welding. One advantageous method includes utilizing a plurality of metal pins  141  (see FIG. 6) to form a backing cage for the overlap area of  114   a  and  114   b  during exposure to ultrasonic welding. While only one pin  141  is shown, it should be appreciated that a series of pins  141  would be used to provide multiple ultrasonic welds around the circumference of the expandable element  112 .  
         [0043]    As yet another approach to forming the expandible element  112 , internal stiffening ribs can be formed within the pleats  116  through the controlled application of heat and clamping the mesh in the dies  132 ,  133 , viz., by differential shrinkage of the mesh to form stiffening ribs. More specifically, a mesh disk is provided having a greater surface area than that of the male die  132 , i.e., if the mesh  114   b  were pressed against the surface of the male die  132  (including the lands  117 ′,  117 ″ and valleys  116 ′,  116 ″) there would be excess mesh  114   b , particularly in the flange area  132   b  of the die  132 . The mesh  114   b  is applied over a cold male die element  132 . A female die  133  having independently moveable blade elements  134  for abutting against the land areas  117 ′.  117 ″ of the male die  132  and independently moveable portions for abutting against the valleys  116 ′,  116 ″ in the male die  132  is applied over the mesh  114   b  to clamp the land areas  117  only. This leaves the pleats  116  free to assume any position relative to the valley areas  116 ′,  116 ″ of the male die  132 . In practice, the unclamped pleats  116  tend to bulge out from the surface of the male die  132 . The unclamped pleats  116  are subject to heating to a point that the exposed mesh undergoes shrinkage. The die itself is cool and the lands  117  of the mesh that are clamped in the die are shielded from heating. The heating may be done by convection, radiation (heat lamp) or other conventional methods. While the mesh  114   b  is still hot, the moveable portions of the female die  133  that correspond to the pleats  116 , i.e., that insert into the valleys  116 ′,  116 ″ of the male die  132 , are applied to the mesh  114   b  to clamp the exposed hot pleats  116  into the valleys  116 ′,  116 ″ of the male die  132 . The female die  133  is dimensioned relative to the male die  132  to produce a selected thickness for the mesh material in each area, i.e., in the land areas  117  and the pleat areas  116 . The heat source is removed and the mesh  114   b  is allowed to cool while clamped in the die to retain its set shape. Because the pleats  116  were exposed to heating and experienced shrinkage, the density of the pleats  116  is greater (lower porosity) than the lands  117 . When conical elements  114   a ,  114   b  formed in this manner are mounted together in opposition, as explained above, the high density regions of the mesh, i.e., the pleats  116 , act as stiffening ribs. When the radially expandable member  112  is axially collapsed, the higher density and more rigid pleats  116  resist bending and force the lands  117  apart to deploy the radially expandable member  112 . The same concept for forming stiffened, higher density regions in the conical members  114   a ,  114   b  described above can be generally applied to surgical mesh to form mesh products with selected stiffened regions. More particularly, by clamping certain regions of the mesh in a cold die with other slack portions subject to heating and shrinkage, zones of higher density/greater rigidity of any devised shape or distribution can be formed.  
         [0044]    Referring to FIG. 10, prosthesis  110  includes overlay patch  126  slidably attached to radially-expandable member  112 . As shown, filament  150  is passed through looped suture  122  and affixed at its terminal ends to overlay patch  126 . When radially expandable member  112  is placed in the defect, overlay patch  126  may be maneuvered to one side to effect attachment to fascia  142 .  
         [0045]    [0045]FIG. 11 shows a prosthesis  210  having an overlay patch  226  slidably attached to a radially expandable member  212  by an elongated filament  250 . The radially expandable element  212  has conical portion  214   b  with a flange (shown by dotted line  223 ) that is covered by conical portion  214   a , which extends to baseline  220 . As in the previous embodiment, the filament  250  is joined to the overlay patch  226  at two spaced points  252 ,  254 , e.g., by tying, plastic welding or by being restrained from pulling through the overlay patch  226  material by knots or enlarged ends that exceed the size of the pores of the material of the overlay patch  226 . Intermediate the points of connection  252 ,  254 , the filament  250  extends substantially parallel to the overlay patch  226 . While a single filament  250  is shown, a plurality of parallel filaments  250  may be utilized. The radially expandable member  212  is moveable along the filament(s)  250  defining a motion “track” relative to the overlay patch  226 .  
         [0046]    Because the expandable member  212  is slidable on the filament  250 , the expandable member  212  may be positioned relative to the overlay patch  226  to maximally conform to the anatomy of the patient and the surgical repair encountered, as shown in FIG. 12. More particularly, the expandable member  212  may be inserted into the facia void and then the position of the overlay patch  226  may be adjusted to coincide with the position of maximally effective surgical attachment, viz., to be amenable to attaching the overlay patch  226  to healthy tissue, to bridge over weak, unhealthy tissue, and also to conform to the patients&#39; local anatomical shape. The overlay patch  226  may have any desired shape, such as a keyhole, oval, circular or rectangular shape.  
         [0047]    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.