Abstract:
The present invention relates to a fusible suture for joining portions of tissue. The suture includes an elongate electrical conductor. The conductor extends between opposite ends of the suture and has sufficient flexibility to permit segments of the conductor to overlap, thereby forming a loop sized for joining portions of tissue. The overlapped segments of the conductor are heated upon application of an electrical current to the conductor. The suture further includes a coating that at least partially covers the conductor and extends over at least one of the segments of the conductor. The coating softens when its temperature is at and above a softening temperature so that the overlapping segments of the coating coalesce. The softening temperature is lower than a melting temperature of the conductor. The coating returns to a non-softened state when its temperature falls below a hardening temperature, thereby forming a bond between the overlapped segments of the conductor.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to sutures and methods for suturing, and more particularly to fusible sutures and methods for suturing with a fusible suture.  
       BACKGROUND OF THE INVENTION  
       [0002]     Sutures are commonly used to join portions of tissue in a patient. Conventional sutures are made of materials such as silk threads and various mono-filament synthetic materials.  
         [0003]     These traditional suture materials require the suture be tied in a knot to join the portions of tissue and secure the suture in place. Tying a knot adds complexity to the surgical process. For example, tying most knots requires control and movement of both ends of the suture. Frequently, loops must be made during knot tying and free ends of the suture are passed through the loops. Thus, surgeons must generally use both hands to tie a knot in a conventional suture. Using both hands is particularly difficult in orthoscopic surgery in which the surgery is performed with specialized instruments through small incisions in the patient to minimize the invasiveness of the surgery. Although complex surgical orthoscopic stapling instruments have been developed to overcome these difficulties, some procedures are best performed using sutures rather than staples. Further, traditional sutures increase the time required for surgery and can become unknotted following surgery, potentially requiring corrective surgery or other intervention. Thus, there is a need for a suture that may be used to join portions of tissue in a patient without tying knots, that may be used during orthoscopic surgery requiring only one incision and instrument, and that may securely join portions of tissue so the suture is unlikely to become untied or otherwise loosen.  
       BRIEF SUMMARY OF THE INVENTION  
       [0004]     The present invention relates to a fusible suture for joining portions of tissue. The suture includes an elongate electrical conductor. The conductor extends between opposite ends of the suture and has sufficient flexibility to permit segments of the conductor to overlap, thereby forming a loop sized for joining portions of tissue. The overlapped segments of the conductor are heated upon application of an electrical current to the conductor. The suture further includes a coating that at least partially covers the conductor and extends over at least one of the segments of the conductor. The coating softens when its temperature is at and above a softening temperature so that the overlapping segments of the coating coalesce. The softening temperature is lower than a melting temperature of the conductor. The coating returns to a non-softened state when its temperature falls below a hardening temperature, thereby forming a bond between the overlapped segments of the conductor.  
         [0005]     In another aspect, the present invention includes a method for suturing portions of tissue with a suture having a conductor and a coating surrounding at least a portion of the conductor. The method includes surrounding the portions of the tissue with the suture and overlapping respective segments of the suture. The method further includes fusing the overlapped segments.  
         [0006]     Other aspects of the present invention will be in part apparent and in part pointed out hereinafter. 
     
    
     BRIEF DESCRIPTION OF THE FIGURES  
       [0007]      FIG. 1  is a fragmentary side cross section of a first embodiment of a suture according to the present invention;  
         [0008]      FIG. 2  is a fragmentary elevation of a suture having an overlapped end;  
         [0009]      FIG. 3  is a fragmentary elevation of an alternative configuration of a suture having an overlapped end;  
         [0010]      FIG. 4  is a fragmentary side cross section of a second embodiment of a suture according to the present invention;  
         [0011]      FIG. 5  is a fragmentary elevation of the second embodiment showing a coating removed;  
         [0012]      FIG. 6  is a fragmentary of a third embodiment showing the coating removed;  
         [0013]      FIG. 7  is a fragmentary side cross section of a fourth embodiment of a suture according to the present invention;  
         [0014]      FIG. 8  is a fragmentary elevation of the fourth embodiment showing the coating removed;  
         [0015]      FIG. 9  is a fragmentary side cross section of a fifth embodiment of a suture according to the present invention; and  
         [0016]      FIG. 10  is a fragmentary elevation of the fifth embodiment showing the coating removed. 
     
    
       [0017]     Corresponding reference characters indicate corresponding parts throughout the several views of the drawings.  
       DETAILED DESCRIPTION OF THE INVENTION  
       [0018]     The present invention relates to a fusible suture and method for suturing with a fusible suture. Referring now to the drawings, and more particularly  FIG. 1 , a fusible suture according to one embodiment of the present invention is designated in its entirety by the reference number  100 . The fusible suture  100  generally includes electrically conductive portion  110  comprising a first, or inner, conductor  130  and a second, or outer, conductor  140 . In this embodiment, the conductors  130 ,  140  are separated by a jacket  150  that is less conductive than the conductive portion  110 . The fusible suture  100  further includes a coating  160  formed on an exterior surface of the conductive portion  110 . Although the electrical conductors  130 ,  140  may be made of other materials without departing from the scope of the present invention, in one embodiment the conductors are made of a carbon impregnated thread. In addition, although the first conductor  130  may have other dimensions without departing from the scope of the present invention, in one embodiment the first conductor  130  has a diameter  132  of between about 0.02 millimeters and about 0.5 millimeters. Although the second conductor  140  may have other dimensions without departing from the scope of the present invention, in one embodiment the second conductor  140  has a thickness  142  of between about 0.02 millimeters and about 0.1 millimeters. Further, although the jacket  150  may be made of other materials without departing from the scope of the present invention, in one embodiment the jacket is made of a carbon-based material such as carbon-impregnated polyethylene. Although the jacket  150  may have other dimensions without departing from the scope of the invention, in one embodiment the jacket  150  has a thickness  152  of between about 0.04 millimeters and about 0.2 millimeters. The first and second conductors  130 ,  140  extend between first and second ends (not shown). The first and second conductors  130 ,  140  are joined at their respective second ends, such that energy may travel along the first conductor  130  in a first direction A from the first end to the second end along the suture  100  and then return along the second conductor  140  in an opposite direction B. As will be appreciated by those skilled in the art, this configuration allows the suture  100  to be energized and activated from one end (e.g., the first end). In one embodiment the suture  100  has a length of between about 1 meter and about 2 meters or more. Although each conductor  130 ,  140  is illustrated as being monolithic, it is envisioned the conductors may be made of more than one piece of material (e.g., twisted or braided strands) without departing from the scope of the present invention.  
         [0019]     The coating  160  comprises a material that softens and/or melts at a temperature lower than a temperature at which the conductive portion  110  softens and/or melts. For example, the coating may be made of an epoxy that softens at a temperature lower than a temperature at which the conductive portion melts. Although the coating  160  may be made of other materials without departing from the scope of the present invention, in one embodiment the coating is a polyester based hot melt glue, such as HM4165 available from Bostik Findley Incorporated of Middleton, Mass., USA. In one embodiment, the coating  160  has a thickness  162  of between about 0.02 millimeters and about 0.1 millimeters, however, it is envisioned that the coating may have other thicknesses without departing from the scope of the present invention. Further, although the coating  160  is illustrated as covering substantially the entire exterior surface  144  of the conductive portion  110 , it is envisioned the coating  160  may extend over less than all of the exterior surface  144  and/or may be interrupted along the exterior surface without departing from the scope of the present invention.  
         [0020]     The conductive portion  110  and coating  160  are preferably flexible to allow the fusible suture  100  to bend around portions of the tissue to be joined (not shown). The ability to bend allows a user to loop the suture  100  around portions of tissue (not shown) and overlap or cause contact between segments (e.g., segments  202 ,  204 ) of the fusible suture  100  as shown in  FIG. 2 . The overlapped segments of the suture  100  may contact over an extended length  206  as shown in  FIG. 2 , or at multiple points of contact (generally designated by  306  in  FIG. 3 ) without departing from the scope of the present invention. Further, the overlapping segments of the suture  100  may contact each other in a straight line as shown in  FIG. 2  or in spots as shown in  FIG. 3  without departing from the scope of the present invention. It will be appreciated that the overlapping segments of the suture  100  may contact in other configurations than shown in  FIGS. 2 and 3  (e.g., in a helix) without departing from the scope of the present invention. For instance, it is envisioned the suture  100  may be tied in a knot so segments contact. The suture  100  has opposite ends  208 . The overlapping segments and areas of contact may be adjacent these ends  208  or spaced from the ends without departing from the scope of the present invention.  
         [0021]     After surrounding the tissue portions and overlapping the portions of the suture  100  so they contact as described above, the coating  160  is activated so it softens and the contacting portions of the coating coalesce. Flow of energy to the suture  100  is stopped so the coating  160  hardens. As the coating  160  hardens, the contacting segments fuse together to maintain the suture  100  in the fused configuration. Because the contacting segments fuse together, the loop surrounding the portions of tissue will be maintained and the suture retains the surrounded portions of tissue so they are joined.  
         [0022]     Although the coating  160  may be activated to soften in other ways (e.g., chemically activated), in one embodiment the coating is activated by heating. Although the coating  160  may be heated in other ways without departing from the scope of the present invention, in one embodiment electrical current is passed through the conductive portion  110  to heat the conductive portion, thereby softening the coating  160  and allowing it to coalesce and ultimately fuse when the current is removed and the coating hardens. The jacket  150  at least partially insulates the conductors  130 ,  140  from each other. In one embodiment the jacket  150  also generates heat in response to activating the conductors  130 ,  140  which contributes to the activation of the coating  160 . Although the electrical current may have other characteristics without departing from the scope of the present invention, in one embodiment the current is a 75 volt, 0.5 amp, direct current supplied by a conventional power source. It is envisioned the supplied current may be alternating current without departing from the scope of the present invention. Once the overlapping portions of the suture  100  are fused, the ends  208  of the suture may be trimmed to a desired length.  
         [0023]     Though one suture is illustrated, the present invention is not limited to using only one fusible suture at a time. For example, multiple fusible sutures  100  may be used simultaneously. These sutures may be applied separately or they may be placed in overlapping contact with one another. After overlapping the sutures  100 , the conductive portion  110  of each suture is energized, causing the coating  160  corresponding to the points of contact to soften, coalesce and fuse. If a suture  100  needs removal, the suture  100  may be cut using conventional techniques.  
         [0024]      FIG. 4  shows a second embodiment of a suture  400  according to the present invention in which the second conductor  440  of the conductive portion  410  is helically disposed with respect to the jacket  150 . Although the coating  160  is shown contacting the jacket  150 , the coating may contact the second conductor  440  but be spaced from the jacket  150  without departing from the scope of the present invention.  FIG. 5  shows a perspective view of the embodiment of  FIG. 4  without the coating  160  to illustrate the manner in which the second conductor  440  may be helically disposed with respect to the jacket  150 . Although the second conductor  440  is shown wound around the jacket  150 , the second conductor may be disposed around the jacket in other ways without depart from the scope of the present invention. In addition to the manner in which the second conductor  140  is disposed with respect to the jacket  150  in  FIG. 1 , the second conductor may comprise a plurality of elongate strips (not shown) disposed over the jacket  150 . As another example,  FIG. 6  shows a third embodiment of a suture  600  according to the present invention in Which the second conductor  640  crisscrosses the surface of the jacket  150 . The sutures  400 ,  600  of the second and third embodiments, respectively, are otherwise identical to the suture of the first embodiment, and therefore will not be described in further detail.  
         [0025]      FIG. 7  shows a fourth embodiment of a suture  700  according to the present invention in which the fusible suture  700  includes a central core  750 . The core  750  is made of a material that is less conductive than the conductors  710 . For example, the core may be made of a carbon-based material. The core  750  acts as an insulating or resisting body about which the conductor  110  may be disposed. In one embodiment, in use, the core  750  also generates heat when the conductor  710  is energized. The heat generated by the core  750  contributes to the activation of the coating  160 . In the fourth embodiment, one or more conductors  710  are disposed in various ways with respect to the core  750 . The one or more conductors  710  are disposed in such a way that energy is able to travel on a first segment of the one or more conductors  710  in a first direction A extending from a first end of the suture (not shown) to an opposite second end (not shown) and return along the suture  700  on a second segment of the one or more conductors  710  in an opposite second direction B. For example, a single conductor  710  may be disposed along the core  750  in two segments connected at the second end (not shown), each extending from the first end to the second end without contacting between the ends. In one configuration, one or more conductors  710  are helically disposed around the exterior surface  752  of the core  750  as shown in  FIG. 7 . In this embodiment, the one or more conductors  710  may extend from a first end (not shown) of the suture  700  to a second end (not shown) of the suture, and back to the first end without interruption.  FIG. 8  illustrates the configuration of  FIG. 7  without the coating  160  to show a manner in which the conductors  710  may be wound about the core  750 . Although the core  750  may have other diameters without departing from the scope of the present invention, in one embodiment the core has an outer diameter  754  of between about 0.02 millimeters and about 0.5 millimeters. Likewise, although the conductors  710  may have other configurations without departing from the scope of the present invention, in one embodiment the conductors have cross sections that are generally square and have a thickness of between about 0.02 millimeters and about 0.1 millimeters. The suture  700  of the fourth embodiment is otherwise identical to the suture of the first embodiment, and therefore will not be described in further detail.  
         [0026]      FIG. 9  shows a fifth embodiment of a suture  900  according to the present invention in which a plurality of conductors  910  is helically disposed around the core  750 . Although two conductors, designated by  912  and  914 , are shown in  FIG. 8 , more than two conductors  910  may be used without departing from the scope of the present invention. The conductors  910  may carry the same or differing charges. For example, first and second conductors  912 ,  914  may carry opposite charges as shown in  FIG. 10  . When relative conductors carry opposite charges, those conductors are spaced from one another over their entire lengths. The suture  900  of the fifth embodiment is otherwise identical to the suture of the first embodiment, and therefore will not be described in further detail.  
         [0027]     Although a preferred use of the fusible suture is to connect tissue during surgery, the suture may also be used to connect objects in non-surgical environments. In view of the above, it will be seen that the several objects of the invention are achieved.  
         [0028]     When introducing elements of the present invention or the preferred embodiment(s) thereof, the articles “a”, “an”, “the”, and “said” are intended to mean that there are one or more of the elements. The terms “comprising”, “including”, and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements.  
         [0029]     As various changes could be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.