Abstract:
A mold for fabricating a device for repairing torn tissue or muscle such as the meniscus of the knee is provided. The mold includes a mold cavity adapted to receive molten material. The mold cavity has an inlet channel, a first portion, a second portion, and a first channel extending between the first and second portions. The inlet channel communicates with the first and second portions and is spaced from the first channel such that the molten material must flow from the inlet channel through the first portion or second portion before communicating with the first channel. The first channel is dimensioned to receive a first component such that the flow of molten material from the first and/or second portions into the first channel is substantially prevented when the first component is received in the first channel.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application is a continuation of U.S. patent application Ser. No. 08/369,858 filed on Jan. 6, 1995, which is a continuation of U.S. patent application Ser. No. 08/144,453 filed on Oct. 27, 1993, now abandoned, which is a continuation-in-part of U.S. patent application Ser. No. 07/699,991 filed May 13, 1991, now U.S. Pat. No. 5,269,783, all of which are incorporated herein in their entirety by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a device for repairing torn tissue and muscle in the body, and more particularly to a device for repairing a torn meniscus in the human knee. A method of repairing torn meniscal tissue is also disclosed. The present invention is also directed to apparatus and method for fabricating the invention device. 
         [0004]    2. Discussion of the Prior Art 
         [0005]    The surgical repair of torn tissue and muscles in the body has typically been performed through incisions in the body to expose the area under repair and the actual procedure includes the provision of sutures, staples or fasteners. The advent of arthroscopic techniques and endoscopic equipment have reduced the size and depth of the incision required to perform the repair procedure. However, the use of conventional devices in many cases requires a highly skilled surgeon to perform the repair, and usually requires complete immobilization of the surgical area following the repair procedure. 
         [0006]    Surgical repair of cartilage and muscle in joints such as the knee often requires extraordinary skill on the part of the surgeon to reduce damage to adjacent nerves, blood vessels, muscles and tendons in the knee joint. In particular, surgical repair of the fibrocartilage disks within the knee known as the menisci, which are attached peripherally to the joint capsule, requires precision to avoid such damage. 
         [0007]    In the past, meniscal surgery has included procedures for partial to complete removal of a torn meniscus, as well as attempts to surgically suture, staple or tack the tear in the meniscus to allow for healing. Other techniques have included removal of portions of the meniscus to arrest the spread of the tear. 
         [0008]    A technique has been developed using arthroscopic instruments which provides for meniscal repair through the use of a pair of surgical needles which are inserted through cannuli into the knee on opposite sides of the tear in the meniscus to be repaired. The needles are linked by a single suture which is pushed down through the cannuli and across the tear. An incision is made in the skin at the point where the needles exit the knee joint so that the leading end of each needle may be grasped and pulled through the joint. The ends of the sutures are then grasped after the needles are removed from the suture ends and the suture is then tied outside the skin so that a horizontal suture is created in the meniscus. This procedure is repeated for placement of as many sutures as necessary to repair the meniscus tear. This process is very time consuming, and the strength of the repair is dependent upon the tension created by the knot tied in the suture. 
         [0009]    The need exists for a device for repairing torn tissue, such as the meniscus of the knee, which obviates the disadvantages encountered in the prior art and provides an efficient, suture-type device which expedites the surgical procedure and reduces the amount of precision necessary on the part of the surgeon during the procedure. Additionally, there is a need for providing smooth, reliable fabrication of a suture-type device for repairing torn tissue such as the knee meniscus, especially for fabricating such a device out of material having dissimilar flexibilities. 
         [0010]    In this regard, two general processing techniques have been previously utilized for attaching a fiber or filamentous structure such as a braid to a solid object. The first such general process involved the mechanical crimping or tying of the braid to a solid piece. The second technique involved welding the braid to the solid piece by using energy such as heat, ultrasound, etc. or chemicals such as solvent, glue or adhesive, etc. However, these prior techniques are either extremely cumbersome or fail to form reliable, secure attachment between materials of dissimilar flexibilities. Accordingly, the need exists for smooth, reliable fabrication of such tissue repair devices, notably surgical implants prepared from resorbable materials such as surgical clips or staples. 
       SUMMARY OF THE INVENTION 
       [0011]    The present invention provides a novel device for repairing torn tissue and muscle such as the menisci in the knee joint which expedites the surgical process and facilitates complete healing of the tear. The device of the present invention reduces the precision required on the part of the surgeon to accurately place and secure the suture at the tear site, and expedites the surgical process by eliminating the requirement of securing the ends of the sutures together to stitch the tear. The device of the present invention allows a surgeon to reduce the trauma to the surrounding tissue and facilitates healing of the torn muscle tissue by providing a completely resorbable suture-like device which may remain in place until the tear is completely healed. 
         [0012]    The device for repairing torn tissue and muscles of the present invention comprises a pair of surgical needles each secured at one end to a pair of surgical needles each secured at one end to a pair of anchoring members which essentially comprise absorbable rods having outwardly projecting barbs. Each anchoring member is secured at a second end to an absorbable flexible material such as a suture which extends between the two anchoring members. The means of securement between the needles and anchoring members, and between the anchoring members and the suture may include adhesives, swaging, crimping or a quick-release connection such as heat-shrinkable tubing. Preferably, the suture and the anchoring members are constructed of a bioresorbable material. 
         [0013]    The barbs of the anchoring member have a tapered configuration towards the needles so that as the needles are pushed through the tissue, the barbs easily pass through the tissue with the needle. The configuration of the barbs is such that the anchoring members pass easily through the tissue in the forward direction, but are prevented from moving in the reverse direction. The barbs are provided to anchor the device in the tissue. 
         [0014]    The needles of the present invention may be straight needles, preferably constructed of stainless steel or other surgical grade metal alloy. Although preferably straight, it is contemplated that the needles may be curved, similar to suture-type needles. 
         [0015]    In use, the damaged or torn meniscus in the knee is arthroscopically approached from the front of the knee by inserting the needles across the tear and then advancing the needles through the meniscus across the tear, drawing the absorbable anchoring means through the meniscus and then through the joint capsule to exit through a previously made incision. The suture is then pulled substantially flush with the meniscus across the tear, whereby the surgeon may the pull the needles through the incision, which had been made to expose the outer surface of the joint capsule. The needles are then cut, or may be detached by a sharp pull when the suture contacts the meniscus across the tear. The barbed anchoring means are then cut substantially flush with the joint capsule on the side opposite the suture, the incision is closed; and the anchoring means holds the suture in place. The barbs on the anchoring means serve to maintain the position of the device within the meniscus, and the suture and anchoring means serve to maintain the tear at close approximation to enhance healing. The material compositions of the suture and the anchoring means are selected to provide the desired resorption rate to allow sufficient time for healing. 
         [0016]    In the event that the tissue being repaired is not sufficiently strong to retain the barb members in place, a retaining flange may be utilized which is slipped over the barbs after it is drawn through the tissue to apply counter pressure against the surface of the joint capsule to pull the suture tight across the tear. 
         [0017]    The present invention is also directed to apparatus and method for fabricating the repair device supra which are effective for joining elements formed of materials having dissimilar flexibilities to provide a device that will effectively function when used to repair torn tissue. In particular, the invention apparatus and method can be used to fabricate a series of tissue repair devices at one time. 
         [0018]    In the fabrication of a composite device of materials having dissimilar flexibilities in accordance with the invention, one of the pieces of material, e.g., the material of greater flexibility, is first placed in a mold such as a compression or injection mold. The material of different flexibility, e.g., polymeric material of less flexibility, is then injection or compression molded about the material previously placed in the mold cavity. When forming a meniscal staple, a segment of braided suture material which can be resorbable is placed within a channel or groove of the mold that interconnects cavities for molding the substantially rigid tips. Into each rigid tip cavity, a portion of the length of braided suture material is centrally located within the respective cavities. The mold halves are then closed and the molding polymer is introduced into the cavities, e.g., by injection. The molten or flowable polymer then surrounds and encapsulates the braided suture material extending into the rigid tip cavities. Upon cooling of the molten material, a composite meniscal staple device is formed from materials having dissimilar flexibilities where the braided suture is firmly attached to the molded rigid tips of the staple. 
         [0019]    The present invention provides for facilitated attaching of a flexible member, e.g., a braided suture, to a rigid part, notably where both flexible and rigid members are fabricated from resorbable material as in the case of forming surgical implants. A composite member which can be used as a tissue repair device is thereby fabricated and possesses secure attachment between materials of dissimilar flexibilities, e.g., a uniquely shaped, rigid, hard solid component reliably coupled to a flexible yet tensilely strong fibrous or filamentous structure. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]    The foregoing features of the present invention will become more readily apparent and may be understood by referring to the following detailed description of illustrative embodiments of the device for repairing torn tissue and muscle and apparatus and method for fabricating the same taken in conjunction with the accompanying drawings, in which: 
           [0021]      FIG. 1  illustrates a perspective view of the device of the present invention; 
           [0022]      FIG. 2  illustrates a perspective view of an alternate embodiment of the device of the present invention; 
           [0023]      FIG. 3  illustrates a perspective posterior view of the muscular structure of the knee; 
           [0024]      FIG. 4  illustrates a cut-away perspective view of the knee of  FIG. 3  along line  4 - 4  showing the device of the present invention in position during the meniscal repair procedure; 
           [0025]      FIG. 5  illustrates a perspective anterior view of the knee of  FIG. 3  with the device of the present invention in position during the meniscal repair procedure; 
           [0026]      FIG. 6  illustrates a perspective view of an alternate embodiment of the device of  FIG. 1 ; 
           [0027]      FIG. 7  illustrates a perspective view of a further alternate embodiment of the device of  FIG. 1 ; 
           [0028]      FIG. 8  is a top plan view of a portion of apparatus for fabricating the device of the present invention; 
           [0029]      FIGS. 9 and 10  are a schematic perspective views of the apparatus portion shown in  FIG. 8  illustrating steps in the fabrication of the invention device; 
           [0030]      FIG. 11  is a side view of the device fabricated with the apparatus of  FIGS. 8-10 ; 
           [0031]      FIG. 12  is a broken top view of an alternative embodiment of apparatus used to fabricate the invention device; 
           [0032]      FIG. 13  is a broken side view of the invention device fabricated with the apparatus illustrated in  FIG. 12 ; 
           [0033]      FIG. 14  is a top plan view of an alternative embodiment of a tissue repair device fabricated in accordance with the present invention. 
           [0034]      FIG. 15  is a top view of an alternative embodiment of apparatus used to fabricate the invention device; and 
           [0035]      FIG. 16  is a side view of a portion of the apparatus of  FIG. 16  and its countermold in the direction of arrows A-A in  FIG. 15 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0036]    Referring now in specific detail to the drawings, in which like reference numerals identify similar or identical elements throughout the several views,  FIG. 1  shows the repair device  10  of the present invention. Repair device  10  generally comprises a pair of metal needles  12 , preferably constructed of stainless steel or other surgical metal alloy, having a sharp tip  13  at one end to facilitate penetration through tissue, and a blunt end at the other end. In a preferred embodiment, the length of each needle is between 6 inches and 10 inches. However, this is not intended to be limiting as clearly needles of various lengths may be utilized. 
         [0037]    Secured to needles  12  are a pair of anchoring members  14  which are constructed of a bioresorbable material, such as homopolymers and copolymers of lactide, glycolide, polydioxanone, trimethylene carbonate, polyethylene oxide or other bioabsorbable materials or blends of these copolymers. Preferably, the anchoring members  14  are formed of a copolymer of lactide and glycolide. Anchoring members  14  are linked by a flexible material  16  such as a suture, also constructed of a bioresorbable material, such as a lactide/glycolide copolymer. Flexible material  16  allows for movement of anchoring members  14  with respect to one another. Anchoring members  14  preferably have a length of between about 0.040 inch and 2 inches, more preferably between about 0.050 inch and one inch. 
         [0038]    Needles  12  are secured to anchoring members  14  as indicated at joint  20 , and the anchor members  14  are secured to suture  16  as at joint  22 . The anchoring members  14  of device  10  may be secured to the needles  12  by means of adhesives, crimping, swaging or the like, and joint  20  may be formed by heat-shrinkable tubing. It is preferred that joint  20  is a detachable connection, such that needle  12  may be removed from anchoring member  14  by a sharp tug or pull or by cutting as described below. Anchoring members  14  are secured to suture  16  preferably by insert molding. 
         [0039]    Anchoring members  14  are provided with a plurality of barb-like projections  18  which serve to anchor device  10  in the tissue to be repaired. Barbs  18  have a tapered shape to allow the anchoring members  14  to be pushed through tissue or muscle, such as the menisci of the knee, in a first forward direction and to prevent the anchor members from traveling in a reverse direction. Although as shown in  FIG. 1  five barbs  18  are provided, any number may be provided, so long as the barbs penetrate the tissue to anchor the device  10 . 
         [0040]      FIG. 2  illustrates an alternate embodiment of the device of the  FIG. 1 . Device  30  is similar in construction to device  10  except that curved needles  32  are provided. Needles  32  are secured to anchoring members  14  as described above, which are provided with a plurality of barbs  18  which taper in the direction of needles  32  to facilitate insertion of the device into tissue. Anchoring members  14  are connected through suture  16  as described above. The remaining elements of device  30  are identical to those of device  10  as illustrated in  FIG. 1 . 
         [0041]      FIG. 3  illustrates the muscular and ligament structure of the knee  34 , including the pertinent components of the knee to which the present invention is directed. As is well known, the femur  35  is joined to tibia  36  and fibula  37  by muscles, tendons and ligaments, and these bones are separated and cushioned by the medial meniscus  44  and lateral meniscus  45 . Condyles  38  of femur  35  rest on the menisci, and the bones are joined and supported by anterior cruciate ligament  39 , ligament of Wrisberg  40 , posterior cruciate ligament  41 , and transverse ligament  46  (see  FIG. 5 ). The joint capsule is formed by tibial collateral ligament  42  and fibular collateral ligament  43 . 
         [0042]      FIG. 4  illustrates the device  10  of the present invention in use, showing knee  34  along lines  4 - 4  of  FIG. 3 . The lateral meniscus  45  of a knee  34  having a tear  52  is repaired with the present invention by forcing needles  12  through the meniscus on one side of the tear, through the torn region, and out the meniscus tissue on the opposite side of the tear on the outside of the knee. The device is fully inserted so that flexible member  16  becomes substantially flush with meniscus  45  and is pulled taut. Barbs  18  of anchoring members  14  anchor the device in the meniscus  45  and prevent the device from backing off, so that tear  52  is maintained in an abutting relationship across itself to facilitate healing. Needles  12  may then be removed from anchoring members  14  by means of a sharp yank or tug, or are cut as they are accessed from the opposite side of the knee by a suitable incision. Anchoring members  14  are then trimmed so as to be flush with the surface of meniscus  45  or the joint capsule. The material of which anchoring members  14  and suture  16  are constructed are preferably bio-resorbable materials which resorb at a rate which is slow enough to facilitate healing of the tear in the tissue. 
         [0043]    During arthroscopic surgery, as best seen in  FIG. 5 , the surgeon will approach the torn meniscus from in front of the knee and insert the two needles  12  into the meniscus  44  or  45 . As the needles  12  are pushed through the meniscus  45  to draw the edges of the tear together, the surgeon will make an incision on the opposite side of the knee adjacent the needles to avoid pushing the needles through the skin. As the needles are withdrawn, the suture  16  is pulled tight to hold the edges of the tear together while the barbs  18  prevent the backing off of the device  10  through the tissue. The needles are then removed and the anchor members are trimmed to the surface level of the joint capsule and the incisions are stitched. 
         [0044]    Turning now to  FIG. 6 , there is shown a further embodiment of the device of the present invention. Device  60  is identical to device  10  except for the provision of retaining flanges  62  which slip over needles  12  and anchoring members  14  to apply counter pressure against the surface of the joint capsule to pull the suture  16  tight across the tear in the meniscus. Flanges  62  are utilized when the strength of the tissue through which the device passes is insufficient to hold barbs  18  in place. 
         [0045]      FIG. 7  illustrates a further embodiment of the device of the present invention. Device  70  is identical to device  10  except that barbs  18  are aligned with each other, rather than staggered as in accordance with  FIG. 1 . Clearly, device  70  may include curved needles as shown in  FIG. 2  or retaining flanges  62  as shown in  FIG. 6 . 
         [0046]    As noted supra, anchoring members  14  are preferably secured to suture  16  by insert molding. The techniques of compression and injection molding are pr se well-known. For example, injection molding is described, e.g., by Paul N. Richardson, “Plastics Processing”,  Encyclopedia of Chemical Technology, Volume  18 (Third Edition), John Wiley &amp; Sons, pp. 195-199; Irvin N. Rubin, “Injection Molding”,  Encyclopedia of Polymer Science and Engineering, Volume  8 (Second Edition) John Wiley &amp; Sons, pp. 102-138; and A. B. Glanvill, “Injection Moulding”,  Thermoplastics: Effects of Processing , London Iliffe Books Ltd., 1969, pp. 110-182. More specifically, the injection molding process involves heating thermoplastic material so that such material is rendered in flowable condition. After the thermoplastic material has been rendered sufficiently molten, the material is then injected into the mold cavity defined between the mold and counter mold portions, e.g., by a piston head or extruder screw. Compression molding is described, e.g., by Herbert Rees, “Mold”,  Encyclopedia of Polymer Science and Engineering, Supplemental Volume  (Second Edition), John Wiley &amp; Sons, pp. 507-509, which also describes injection molding and a combination of injection-compression molding. 
         [0047]    Using the technique of compression molding, the material retaining its initial form, e.g., a flexible braided suture, is first placed in an open mold, followed by introduction of an excess of molten thermoplastic material. The mold is then closed with the mold halves compressed together to shape the molten material as it hardens and forms rigid members attached to, e.g., the flexible braid. In this respect, using an excess of thermoplastic material together with proper application of heat and pressure in a compression mold allows the material to flow within the mold cavity and then solidify to form rigid members of proper dimensions. A heating/cooling pipe and/or other heating/cooling sources can be provided within the mold portions to control heat application and prevent damage or changes to the braid structure. 
         [0048]    In this regard, compression or injection molding apparatus is provided as part of the present invention for joining the suture  16  and anchoring members  14 . An embodiment of such apparatus is illustrated in  FIGS. 8-10 . More particularly,  FIG. 8  illustrates a mold portion  80  forming part of the injection molding apparatus, this mold portion  80  comprises various tracks or recesses  81 - 85  and projecting pegs  86  and  87 . A countermold portion  80 ′ ( FIG. 10 ) is formed as an exact mirror image to mold portion  80 , the only difference being that recesses  86 ′,  87 ′ are provided in the countermold portion  80 ′ at the location corresponding to projecting pegs  86  and  87  in mold portion  80 . Projecting pegs  86  and  87  are in the countermold portion  80  when the mold portion  80  and countermold portion  80 ′ are secured together, thereby defining internal channels or cavities along recesses  81 - 85  which are entirely enclosed except for the open end  88  of recess  81 . Additional pegs and corresponding recesses can be provided upon mold portion  80  and the countermold portion  80 ′ for securing these portions  80 ,  80 ′ together to form an endorsed cavity. The recesses  81 - 85  of the mold portion  80  and recesses in the countermold portion  80 ′ can be substantially symmetrical, however they need not necessarily be symmetrical as long as the properly shaped internal cavity is defined for injection molding the tissue repair device when the mold  80  and countermold  80 ′ portions are brought together. 
         [0049]    Tracks or recesses  84  and  85  in mold portion  80  (and the corresponding tracks or recesses in countermold portion  80 ′ are each shaped to define anchoring members  14  with barbs  18  thereon. In this regard, recess  89  interconnecting recesses  84  and  85  is positioned in mold portion  80  as shown in  FIG. 8  to receive flexible material  16  for linking anchoring members  14  together. Flexible material  16  is retained in place in mold portion  80  between projecting pegs  86  and  87  and shown in  FIG. 9 . Tracks or recesses  81 ,  82  and  83  serve as inlet channels for injection of fluid material under pressure into recesses  84  and  85  when the mold portion  80  and countermold portion  80 ′ are closed. 
         [0050]    The insert molding process of the present invention can be utilized to prepare the tissue repair devices illustrated in  FIGS. 1-3 ,  4  and  7  of the present application and also the surgical clip device of U.S. Pat. No. 5,002,562 issued Mar. 26, 1991, the contents of which are incorporated by reference herein. In this regard, anchoring members  14  are formed of moldable material that can be subjected to injection molding, i.e., thermoplastic material which is rendered flowable upon requisite application of heat and/or pressure so that such material will flow into and fill the mold cavity taking the shape thereof, and then solidify upon cooling. Any of the suitable bioresorbable materials enumerated supra are capable to being injection molded into the requisite anchoring members  14 . However, there is no requirement that the material used to form anchoring members  14  must be bioresorbable as long as such material is biocompatible and capable of being molded. 
         [0051]    The bioabsorbable polymers which can be compression and/or injection molded include those derived from polyglycolic acid, glycolide, lactic acid, lactide, dioxanone, e-caprolactone, trimethylene carbonate, polyethylene oxide, etc., and various combinations of these and related monomers. Polymers of this type are known in the art, principally as materials for the fabrication of such surgical devices as sutures, wound clips, and the like, as disclosed, e.g., in U.S. Pat. Nos. 2,668,162; 2,703,316; 2,758,987; 3,225,766; 3,297,033; 3,422,181; 3,531,561; 3,565,077; 3,565,869; 3,620,218; 3,626,948; 3,636,956; 3,736,646; 3,772,420; 3,773,919; 3,792,010; 3,797,499; 3,839,297; 3,867,190; 3,878,284; 3,982,543; 4,047,533; 4,060,089; 4,137,921; 4,157,437; 4,234,775; 4,237,920; 4,300,565; and 4,523,591; U.K. Patent No. 779,291; D. K. Gliding et al., “Biodegradable polymers for use in surgery—polyglycolic/poly(lactic acid) homo- and co-polymers: 1 ”, Polymer , Volume 20, pages 1459-1464 (1979), and D. F. Williams (ed.),  Biocompatibility of Clinical Implant Materials , Vol. II, ch. 9: “Biodegradable Polymers” (1981). Copolymers of glycolide and lactide with or without additional monomers are preferred and of these glycolide-lactide copolymers are most preferred, for example a mixture of 80% by weight a 25/75 mole ratio Glycolide/Lactide copolymer blended with 20% by weight glycolide. 
         [0052]    Material forming linking member  16  coupling the anchoring members  14  has flexibility greater than the material forming anchoring members  14 . In this regard, the linking member  16  can be fabricated from the same bioresorbable materials supra and/or nonresorbable materials infra for fabricating the anchoring members  14 . Flexibility is imparted to linking member  16  by providing the linking member  16  in fiber or filamentous form such as a suture. As used herein the term “fiber” or “filamentous” refers to materials which may be characterized as having a denier (see, e.g.,  Plastics Terms Glossary, Fourth Edition , Phillips Chemical Company, Bartlesville, Okla.). 
         [0053]    Fiber-forming materials which are relatively inelastic are suitable for providing the linking member  16  provided such materials are more flexible than the anchoring members  14  and fairly rapidly bioabsorbed by the body, e.g., exhibiting a loss of tensile strength in from about 2 to about 26 weeks and total absorption within from about two to about fifty two weeks. It is to be understood, however, that the expression “relatively inelastic” does not preclude the presence of some minor degree of elasticity. 
         [0054]    The linking member  16  can be composed of fibers or filaments of bioresorbable or nonresorbable material or from a blend of filaments possessing different bioabsorbabilities and elasticities to create a member  16  that is semi-absorbable. For example, linking member  16  can be fabricated from the composite yarn described in U.S. Pat. No. 4,990,158 issued Feb. 5, 1991 and the connective tissue prosthesis described in U.S. Pat. No. 5,147,400 issued Sep. 15, 1992, the contents of these United States patents being incorporated by reference herein. 
         [0055]    The present invention may also be practiced with non-bioabsorbable absorbable polymeric materials having thermoplastic properties such as nylon, polyester, polypropylene, polytetrafluoroethylene (PTFE), polyethylene terephthalate (Dacron), etc. Non-absorbable materials which are especially suitable for fabricating the anchoring member or linking member of the invention device include silk, polyamides, polyesters such as polyethylene terephthalate, polyacrylonitrile, polyethylene, polypropylene, silk, cotton, linen, etc. Carbon fibers, steel fibers and other biologically acceptable inorganic fibroid materials can also be employed. 
         [0056]    The term “non-bioabsorbable” as used herein applies to materials which permanently remain within the body or at least remain in the body for a relatively long period of time, e.g., at least about two years. It is preferred to employ a material which is also elastic, i.e., a polymeric material which in filamentous form exhibits a relatively high degree of reversible extensibility, e.g., an elongation at break of a least about 30 percent, preferably at least about 40 percent and more preferably at least about 50 percent. Fiber-forming polymers which are both non-bioabsorbable and elastic, and as such preferred for use herein, include fiber-forming polyolefins such as polyethylene homopolymers, polypropylene homopolymers, ethylene propylene copolymers, ethylene propylene terpolymers, etc., fluorinated hydrocarbons, fluorosilicones, isobutylenes, isoprenes, polyacrylates, polybutadienes, polyurethanes, polyether-polyester copolymers, and the like. Hytrel (DuPont), a family of copolyester elastomers based on (soft) polyether segments and (hard) polyester segments, and spandex, an elastomeric segmented polyurethane, provide especially good results. 
         [0057]    Hytrel is manufactured in various commercial grades by DuPont, such as Hytrel 4056, 5526, and 7246. Hyrel 5556 is especially suitable when used to form a vascular graft, while Hytrel 7246 is well-suited when used to form a ligament prosthesis or tendon augmentation device. 
         [0058]    Several properties of the various Hytrel grades are presented in the table below: 
         [0000]    
       
         
               
             
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                   
               
               
                 Hytrel Grade No. 
               
               
                 (Injection Molded at 23° C. for Testing) 
               
             
          
           
               
                 Hardness in durometer points 
                 4056 
                 5526 
                 5556 
                 7246 
               
               
                   
               
             
          
           
               
                 (ASTM Test No. D2240 
                   
                   
                   
                   
               
               
                 Flexural Modulus 
               
               
                 (ASTM Test No. D790) 
               
               
                 at −40° C. in MPa 
                 155 
                 930 
                 930 
                 2,410 
               
               
                 at −40° F. in psi 
                 22,500 
                 135,000 
                 135,000 
                 350,000 
               
               
                 at 23° C. in MPa 
                 55 
                 207 
                 207 
                 518 
               
               
                 at 73° F. in psi 
                 8,000 
                 30,000 
                 30,000 
                 75,000 
               
               
                 at 100° C. in MPa 
                 27 
                 110 
                 110 
                 207 
               
               
                 at 212° F in psi 
                 3,900 
                 16,000 
                 16,000 
                 30,000 
               
               
                 AST Test No. D638 
               
               
                   (i)  Tensile Strength at Break, 
               
               
                 MPa 
                 28.0 
                 40.0 
                 40.0 
                 45.8 
               
               
                 psi 
                 4050 
                 5800 
                 5800 
                 6650 
               
               
                   (i)  Elongation at Break, % 
                 550 
                 500 
                 500 
                 350 
               
               
                   (ii)  Tensile Stress at 5% Strain, 
               
               
                 MPa 
                 2.4 
                 6.9 
                 6.9 
                 14.0 
               
               
                 psi 
                 350 
                 1,000 
                 1,000 
                 2,025 
               
               
                   (ii)  Tensile Stress at 10% Strain, 
               
               
                 MPa 
                 3.6 
                 10.3 
                 10.3 
                 20.0 
               
               
                 psi 
                 525 
                 1,500 
                 1,500 
                 2,900 
               
               
                 Izod Impact (Notched) 
               
               
                 (ASTM Test No. D256, Method A) 
               
               
                 at −40° C. in J/cm 
                 No Break 
                 No Break 
                 No Break 
                 0.4 
               
               
                 at −40° F. in ft-lbf/in 
                 No Break 
                 No Break 
                 No Break 
                 0.8 
               
               
                 at 23° C. in J/cm 
                 No Break 
                 No Break 
                 No Break 
                 2.1 
               
               
                 At 73° F. in ft-lbf/in. 
               
               
                 Resistance to Flex Cut 
               
               
                 Growth, Ross (Pierced), in 
                 &gt;1 × 10 6   
                 &gt;5 × 10 5   
                 &gt;5 × 10 5   
                 — 
               
               
                 Cycles to 100% cut growth 
               
               
                 (ASTM. Test No. D1052) 
               
               
                   (iii)  Initial Tear Resistance, 
               
               
                 Die C (ASTM Test No. D1004), in 
               
               
                 kN/m 
                 101 
                 158 
                 158 
                 200 
               
               
                 in lbf/in. 
                 580 
                 900 
                 900 
                 1,146 
               
               
                 Melt Flow Rate in g/10 min. 
                 5.3 
                 18 
                 7.0 
                 12.5 
               
               
                 (ASTM Test No. D1238) 
               
               
                 Test conditions: 
               
               
                 Temperature, ° C./Load, Kg 
                 190/2.16 
                 220/2.16 
                 220/2.16 
                 240/2.16 
               
               
                   (iv)  Melting Point 
               
               
                 (ASM Test No. D3418) 
               
               
                 in ° C. 
                 148 
                 202 
                 202 
                 219 
               
               
                 in° F. 
                 298 
                 396 
                 396 
                 426 
               
               
                 Vicat Softening Point 
               
               
                 (ASTM Test No. D1525) 
               
               
                 in ° C. 
                 108 
                 180 
                 180 
                 207 
               
               
                 in ° F. 
                 226 
                 356 
                 356 
                 405 
               
               
                 Specific Gravity (ASTM Test 
                 1.16 
                 1.20 
                 1.20 
                 1.25 
               
               
                 No. D792) 
               
               
                 Water Absorption, 24 hr. in % 
                 0.6 
                 0.5 
                 0.5 
                 0.3 
               
               
                 (ASTM Test No. D570) 
               
               
                   
               
               
                   (i)  head speed 50 mm/min. or 2 in./min. 
               
               
                   (ii)  head speed 25 mm/min. or 1 in/min. 
               
               
                   (iii)  specimens 1.9 mm or 0.075 in. thick. 
               
               
                   (iv)  differential scanning calorimeter (DSC), peak of endotherm 
               
             
          
         
       
     
       Corresponding properties of other goods of Hytrel are available from DuPont. 
       [0059]    The fibers or filaments forming the linking member can be woven, braided or knitted in whole or in part and will ordinarily possess a relatively high tensile strength, e.g., a straight tensile strength of at least about 30,000 p.s.i., preferably at least about 60,000 p.s.i. and more preferably at least about 90,000 p.s.i. 
         [0060]    Bioabsorbable polymers of high lactide or glycolide content, e.g., those in which at least about 75 percent of the monomeric units are derived from either glycolide or lactide, are preferred for the construction of the linking member  16  of tissue repair device. Typical polymers are disclosed in U.S. Pat. Nos. 4,523,591 and 4,744,365 which are incorporated by reference. Polymers of high glycolide content tend to be absorbed more quickly than those possessing a high lactide content. Accordingly, the glycolide-based polymers may be preferred, e.g., for both the anchoring members  14  and even the linking member  16 . An especially preferred lactide-glycolide copolymer for forming the linking member  16  contains from about 70 to about 90 percent, and preferably from about 75 to about 85 mole percent lactide monomer with the balance being provided by the glycolide monomer. Thus, for example, fibers or filaments formed from a lactide-glycolide copolymer based on 80 mole percent lactide-20 mole percent glycolide is especially advantageous for constructing the linking member  16 , and ultimately, the tissue repair device of the present invention. When a composite yarn is used to form the linking member  16 , then the sheath yarn component, which is preferably braided around the core yarn component, may comprise a plurality of bioabsorbable fibers in turn comprising at least two different chemical compositions. This copolymer is also suitable for injection molding anchoring members  14  about linking member  16 . 
         [0061]    As pointed out supra, the various fibers or filaments can be woven, braided or knitted together to form linking member  16 . In this regard, the term “braid” or “braided” refers to an arrangement of discrete units or bundles, denominated “sheath yarns,” made up of individual filaments with individual sheath yarns interlocking or interlacing each other in a regular criss-cross pattern. For example, a suitable braided suture which can be utilized as the linking member  16  is disclosed in U.S. Pat. Nos. 5,019,093 issued May 28, 1991 and 5,226,912 issued Jul. 13, 1993, the contents of which are incorporated by reference herein. Such braided yarn encompasses core and sheath designs as well as braid over braid designs. The core is optional and can be twisted, ply or cable. 
         [0062]    In another embodiment, the fibers or filaments forming the linking member  16  are woven into a spiroid braid construction. The expression “spiroid braid” and “spiroid braided” refer to various types of a solid arrangement of discrete units or bundles, denominated “yarns”, made up of individual filaments or fibers. The yarns are arranged substantially parallel to the longitudinal axis of the suture or linking member  16  and internally engaging each other in a repetitive spiral pattern. The term “solid” is intended to designate a suture or linking member  16  in which the filamentous material of its construction occupies substantially the entire cross-sectional areas of the suture or linking member  16  with at most a minor percentage of such area (not exceeding about 25% in the larger suture sizes) constituting void spaces or interstices between adjacent yarns and fibers. Such construction contrasts with that of e.g., a standard suture which, in the absence of a core component, possesses a lumen representing a significant percentage of the cross-sectional area of the suture. 
         [0063]    Spiroid braided suture component or linking member  16  can also be fabricated from a wide variety of natural and synthetic fibrous materials such as any of those heretofore disclosed for the construction of sutures. Such materials include non-absorbable as well as partially and fully bio-absorbable (i.e., resorbable) natural and synthetic fiber-forming polymers. Examples of spiroid braid constructions which can be utilized as the linking member  16  in the tissue repair device of the present invention are found in U.S. Pat. Nos. 5,133,738 issued Jul. 28, 1992 and 5,181,923 issued Jan. 26, 1993, the contents of which are incorporated by reference herein. 
         [0064]    The present invention is especially suited for preparing the tissue repair device by injection molding which will be described infra with respect to  FIGS. 8-10 . 
         [0065]    Initially, the mold is opened and the fiber or filament-like material forming the linking member  16  is positioned between projecting pegs  86  and  87  as schematically illustrated in  FIG. 9 . The mold is then closed by fitting mold portion  80  and countermold portion  80 ′ together in the direction of arrows A and B as shown in  FIG. 10 . After mold portion  80  and countermold portion  80 ′ are secured together, the thermoplastic material forming the anchoring members  14  is heated to a temperature at which this material becomes flowable. In this regard, the thermoplastic material is preferably heated to a temperature from about 120 to about 240° C., more preferably from about 140 to about 200° C. The thermoplastic material is heated in a plunger machine (not illustrated) remote from the mold portions, an example of which is shown in the  Encyclopedia of Polymer Sciences and Engineering  citation noted supra. 
         [0066]    The mold portion  80  is provided with proximal ends  180 , sidewalls  182  and pointed distal ends  184 . Likewise the countermold  80 ′ is provided with such structure. Next, the molten thermoplastic material is injected, under pressure, into the mold cavity defined by recesses or channels  81 - 85  of mold portion  80  and corresponding recesses or channels  81 ′- 85 ′ of countermold portion  80 ′. The molten material is injected into the mold cavity through opening  88 - 88 ′ defined by mold  80  and countermold  80 ′ portions. Injection is carried out from the (non-illustrated) plunger apparatus which is preferably an extruder screw having a nozzle or an end thereof extending into opening  88 - 88 ′ during injection. In this regard, the molten thermoplastic material is preferably injected at a pressure of about 400 to about 4,000 psi, more preferably about 500 to about 2,000 psi. 
         [0067]    During the injection, the mold/countermold portions are preferably at about room temperature (about 20° C.) so that the injected thermoplastic material will ultimately cool to form the hardened anchoring members  14  about the linking member  16 . In this regard, the mold/countermold portions  80  and  80 ′ can be desirably heated to enhance smooth flowing of the thermoplastic material along tracks or recesses  81 - 85  and  81 ′- 85 ′. The mold portion can be preferably heated to a temperature up to about 50° C., more preferably up to about 40° C. However, the mold portions  80  and  80 ′ will ultimately have cool to room temperature in order to ensure hardening of the thermoplastic material into anchoring member  14 . The channels are formed in mold  80  and countermold  80 ′ portions such that thermoplastic material will not flow into the cavity defined by recesses  89  and  89 ′, i.e. the channel defining the linking member  16 . Accordingly, when the molten thermoplastic material is injected into the mold portions  80  and  80 ′, the material will be unable to flow into channels  89  and  89 ′ and will not cover the filamentous or fiber material forming linking member  16  at this point. As a result, flexibility of linking member  16  will be maintained even after anchoring members  14  have hardened upon cooling of the thermoplastic material forming the same. 
         [0068]    Injection is carried out until the cavity defined by channels  81 - 85  and  81 ′- 85 ′ is completely filled with thermoplastic material, i.e. the thermoplastic material can no longer flow into the mold cavity through opening  88 - 88 ′. After injection is completed, the thermoplastic material is allowed to cool and set within the mold cavity to form anchoring members  14 . Preferably, the thermoplastic material is allowed to cool and set after injection is completed for about 0 to about 1 minute, more preferably from about 1 to about 8 seconds. 
         [0069]    After the injected thermoplastic material has sufficiently cooled and solidified, then the mold and countermold portions  80  and  80 ′ are opened and the molded part contained therein removed from mold portion  80 . The gates formed on anchoring members  14  (where channels  84  and  85  respectively meet channels  82  and  83  in mold portion  80 ) are cut, preferably by means of a manual or powered cutting tool, so that anchoring members  14  are separated from the thermoplastic material that has solidified along channels  81 - 83 . The resulting product  90  is shown in  FIG. 11  and comprises anchoring members  91 ,  91 ′ secured to flexible material  92  forming the linking member. The tips  93 ,  93 ′ of respective anchoring members  91 ,  91 ′ can then be secured to appropriate needles, e.g., by adhesives, crimping, swaging, etc. 
         [0070]    The mold and countermold portions  80  and  80 ′ along with the molding cavity formed therebetween can have any suitable dimensions required for molding a suture repair device. For example, the length of the entire product shown in  FIG. 11  (from tip  91  to tip  91 ′) is preferably about 0.120 to about 6 inches with the corresponding length of each anchoring member  91 ,  91 ′ about 0.040 to about 2 inches, leaving an exposed area of filament-like flexible material  92  of about 0.040 to about 2 inches in length. Dimensions of the molding cavity formed by tracks or recesses  81 - 85 ,  89  and  81 ′- 85 ′,  89 ′ can be accordingly prepared to mold the product  90  possessing these dimensions. The length of material  92  cut and positioned within tracks or recesses  84 ,  85  and  89  as shown in  FIGS. 9 and 10  will naturally vary depending upon the appropriate dimensions of these tracks. 
         [0071]    As noted supra, the structure of flexible material  16  which is preferably filamentous or fiber-like, can be woven, braided or knitted, e.g., take the form of a tubular or solid spiroid braid. The material forming the linking member  92  can be different from, or even the same as the material used to form anchoring members  91 ,  91 ′ shown in  FIG. 11 . In other words, linking member  92  and anchoring members  91 ,  91 ′ can be formed from the same material which possesses greater flexibility in a filament or fiber-like condition (linking member  92 ) than when present as a solidified mass of previously molten thermoplastic material (anchoring members  91 ,  91 ′). 
         [0072]    However, preferably the linking member  92  ( FIG. 11 ) is constructed out of material such that the portion of the braid that contacts the molten thermoplastic material will itself undergo a partial melting. The braid will then fuse to the molten material as the material cools and hardens, forming a strong secure bond between flexible linking member  92  and substantially rigid anchoring members  91 ,  91 ′ which will not prematurely fail prior to and during insertion into tissue. Typically the length “L” of linking member  92  extending from anchoring member  91  to anchoring member  91 ′ is in the range of about 1 mm to about 50 mm. Typically, length “L” is sufficient for anchoring members  91 ,  91 ′ to be arranged parallel after solidification. 
         [0073]    It is possible to mold a series of tissue repair devices formed along single, extending strands or ligature of flexible material which can then be severed at appropriate locations to form multiple tissue repair devices. The molding procedure to form a series of these devices is the same as the molding procedure described supra, the only difference being that mold and countermold portions define a cavity for retaining a length of flexible material with appropriate recesses positioned therealong to mold several anchoring members along the length of the flexible material. An example of such a mold portion  110  is shown in  FIG. 12  which is a partial view of the same. The mold portion  110  is provided with proximal ends  280 , sidewalls  282  and sharp pointed distal ends  284 . As can be seen in this view, the tracks or recesses  94 - 97  defining the flow of molten thermoplastic material are substantially identical to tracks or recesses  82 - 85  in the mold portion  80  shown in  FIGS. 8-10 . Additionally, tracks or recesses  100 ,  101  and  102  are provided for retaining a length of flexible material  16  between the respective tracks or recesses  96 ,  97 , etc. for molding anchoring members. Tracks  101  and  102  are offset from respective recesses  120 / 97  and  96 / 121  as illustrated in  FIG. 12 . Respective projecting pegs  122 / 123  and  124 / 125  are also provided on either side of tracks  101  and  102 . The countermold portion for this mold apparatus also comprises tracks and recesses forming the exact mirror image of tracks  94 - 97 ,  100 - 102 ,  120 - 121 , etc. of mold portion  110  with the exception of recesses being provided to receive projecting pegs  98 ,  99 ,  122 ,  123 ,  124  and  125  when the mold and countermold portions are secured to one another. 
         [0074]    An example of the product prepared with the mold of  FIG. 12  is shown in  FIG. 13  (after removal of the gates therefrom) where a series of tissue repair devices  103 ,  104 ,  105  (in part) are illustrated with respective anchoring members  106 ,  106 ′,  107 ,  107 ′,  108 ,  108 ′ (not illustrated) molded about the flexible material having exposed sections  111 ,  112 ,  113 ,  114 ,  115 . The mold tracks  101  and  102  have been positioned in the mold portion of  FIG. 12  such that the exposed sections of flexible material  115 ,  112 ,  114  positioned therein are offset from the tips  130 - 134  of the respective anchoring members. It is particularly preferred not to have the flexible material pass through the points of tips  130 - 134 . This preserves the sharpness of the points of the respective anchoring members. After injection molding has been completed and the resulting repair device series removed from the mold with the gates being severed, then the flexible material is cut at the appropriate locations, i.e., at exposed sections  109 ,  112 ,  114  to form the individual tissue repair devices  103 ,  104  and  105 . Anchoring members  106 ,  106 ′,  107 ,  107 ′,  105 ,  105 ′ can then be attached to appropriate needles by the methods described supra or left alone. 
         [0075]    The tracks or recesses formed within the mold cavity can take any convenient size or shape to ultimately form a tissue repair device having any suitable dimensions or shapes. for example, the mold cavity can be configured to mold a tissue repair device  140  illustrated in  FIG. 14  where unlike the devices illustrated in  FIGS. 11 and 13 , the anchoring members  141 ,  141 ′ do not possess barbs (reference numeral  142  denotes the linking member). 
         [0076]      FIG. 15  shows additional details of a mold  210  employed with the present invention. A length of flexible material  200 A enters the mold at entry port  210 , passes along a track  202 , past a peg  244  and into a recess  296 . Recesses  296  and  297  communicate with tracks  294 ,  295  to provide a path for molten polymer. Flexible material  200 A passes from the recess  296  along a channel  200  between pegs  222  and  233  and into and out of recess  297  as illustrated in  FIG. 15 . Then, the material  200 A passes along a channel  201  past a peg  255  and exits the mold  210  at exit port  300 . Leaf springs  302 ,  304  are respectively located at the entry port  210  and exit port  300  and are attached to the mold  210  by respective bolts  306  and  308 .  FIG. 16  illustrates an enlarged view of a portion of the mold  210  in the direction of arrows A-A in  FIG. 15  in addition to a portion of countermold  210 A mating with mold  210 . 
         [0077]    The following examples are illustrative of the fabrication of a tissue repair device in accordance with the present invention. 
       Example 1 
       [0078]    A length of about 0.25 inches of spiroid braided flexible material formed of a copolymer of glycolide and lactide of approximately 18 mol % glycolide and 82 mol % lactide is cut and placed in mold portion  80  as shown in  FIG. 9  in the channel  89  between projecting pegs  86  and  87 . The mold  80  and countermold  80 ′ portions ( FIG. 10 ) are then secured together. Then, material of the same composition is separately heated to a temperature of about 150° C. so that the material melts and is in flowable condition. Next, this molten flowable material is injected into the mold cavity under a pressure of about 2,000 psi., until the mold cavity is completely filled with the molten, thermoplastic material, i.e., the material can no longer flow into the mold cavity. The mold cavity itself, i.e. mold parts  80  and  80 ′, are at a temperature of 15° C. 
         [0079]    After filling of the mold cavity with the thermoplastic material is completed, the mold portions  80  and  80 ′ are allowed to cool to room temperature over a period of about 2 seconds, at which time the thermoplastic material has solidified into fairly rigid members  91 ,  91 ′. The mold cavity is opened and the gates attaching members  91 ,  91 ′ to the solidified material in tracks  82  and  83  are cut, resulting in the tissue repair device illustrated in  FIG. 11  and which is then attached to needles at points  93 ,  93 ′ thereof. 
         [0080]    The above procedure is also carried out with tubular braided material of the same composition to form linking member  92 . 
       Example 2 
       [0081]    The procedure of Example 1 supra is repeated in its entirely but with about 4-6 inches of a U.S.P. size 2-0 braided suture material composed of about 92.5 mol % glycolide and about 7.5 mol % lactide as the flexible material  92  and a copolymer of about 92.5 mol % glycolide and about 7.5 mol % lactide as the molten thermoplastic material hardening to form rigid members  91 ,  91 ′. 
         [0082]    While the invention has been particularly shown and described with reference to the preferred embodiments, it will be understood by those skilled in the art that various modifications and changes in form and detail may be made therein without departing from the scope and spirit of the invention. Accordingly, modifications such as those suggested above, but not limited thereto, are to be considered within the scope of the invention.