Abstract:
A method of ligating a vessel at multiple distant sites through a single surgical opening with a single length of suture filament is disclosed. The method in one embodiment represents an improved endoscopic vessel harvesting technique. An apparatus well suited for performing the method is also disclosed. The apparatus in one embodiment includes a hollow cannula for guiding and advancing loops through the body to the desired ligation sites. Ligation of an elongate tissue structure such as the greater saphenous vein at opposing proximal and distal ends is accomplished by this invention without clips, needles, internal stitches, multiple incisions, or the risks associated with these existing devices and methods.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates generally to surgical apparatus and associated methods for ligating and harvesting elongate tissue structures. More particularly, the invention provides a method and apparatus for endoscopically ligating both the proximal and distal ends of a blood vessel using a single suture filament manipulated through a single surgical opening or incision.  
         BACKGROUND OF THE INVENTION  
         [0002]    Many advanced surgical procedures, such as coronary artery bypass grafting, involve the harvesting, transfer, and grafting of blood vessels to a new location in the body. The greater saphenous vein in the leg, for example, is commonly harvested for use in bypass surgery and other grafting procedures. Early vessel harvesting techniques required an incision spanning the full length of the blood vessel to be harvested. Within this long, narrow surgical field, the surgeon could transect the smaller side branches and remove the main vessel. Unfortunately, the invasive nature of this technique and the large size of the surgical field increased the risk of infection and other complications.  
           [0003]    Modern vessel harvesting techniques include the use of an endoscope inserted through a surgical opening or incision to visually inspect and magnify the body cavity around the vessel to be harvested. Related medical instruments may be inserted alongside the endoscope to prepare the vessel for removal. Endoscopic surgery has greatly reduced the risks associated with the earlier, open-field vessel harvesting technique.  
           [0004]    Vessel harvesting involves liberating the vessel from surrounding tissue and transecting smaller side branches, tying or ligating the vessel at a proximal site and a distal site, and then transecting the vessel at both sites before it is removed from the body. Endoscopic surgical tools typically work from a centrally located incision or port outward, toward the proximal and distal sites. Once the vessel is prepared, two small counter-incisions can be made at the proximal and distal sites for direct access to the vessel. Although direct ligation using suture filament is generally a secure method, the additional incisions increase the risk of infection, inadvertently puncturing the vessel, and other complications.  
           [0005]    Another ligation method involves the use of a long, endoscopic clip applier that can be used to position and apply a clip at the proximal and distal sites. The clip acts as a ligature across the vessel. The clip method requires great skill because it can be difficult to maneuver the applier and clips into the best location to achieve a secure and effective ligation. Multiple clips may be required. The use of clips also introduces the risk that a clip may become loose, may cause injury to the vessel itself, or may cause injury or insult to surrounding structures such as other blood vessels and nearby nerves.  
           [0006]    Thus, there is a need in the art for an improved method of ligating a vessel at sites distant from a primary surgical opening without the increased risks associated with the known techniques.  
         SUMMARY OF THE INVENTION  
         [0007]    The above and other needs are met by the present invention which provides a method and an apparatus for ligating both ends of a blood vessel at proximal and distal sites using a single length of suture filament manipulated through a single surgical opening.  
           [0008]    In one aspect of the present invention, the method of ligating an elongate tissue structure at a proximal site and a distal site through a surgical opening positioned between the sites using a suture filament may include the steps of providing a prepared loop at one end of the suture filament secured by a slidable prepared knot, passing an opposing end of the suture filament into the surgical opening and about the tissue structure, tying a slidable field knot about the suture filament with the opposing end to form a field loop about the tissue structure, and advancing the field loop toward the distal site. The method may also include the steps of applying axial tension on the suture filament while stabilizing it when the field loop is surrounding the tissue structure at the distal site so as to close the field loop and tighten the field knot to form a distal ligature, cutting the suture filament near the distal ligature, and transecting the tissue structure between the first ligature and the surgical opening to form a distal end. The next steps may include withdrawing the suture filament through the surgical site and withdrawing the distal end through the surgical site.  
           [0009]    The method may further include the steps of inserting the distal end of the tissue structure through the prepared loop, advancing the prepared loop toward the proximal site, and applying axial tension on the suture filament while stabilizing the suture filament and while the prepared loop surrounds the tissue structure at the proximal site so as to close the prepared loop and tighten the prepared knot to form a proximal ligature. The subsequent steps may also include cutting the suture filament proximate the proximal ligature and withdrawing the suture filament through the surgical site.  
           [0010]    To complete the harvesting of the tissue, the method may include the additional steps of transecting the tissue structure between the second ligature and the surgical opening to form a proximal end and withdrawing the proximal end through the surgical site.  
           [0011]    In another aspect of the method, the step of providing a prepared loop comprises a manufacturing process, which includes stabilizing the suture filament, forming a loop by curling the one end of the suture filament so that it crosses the suture filament, looping the one end of the suture filament about the suture filament in a pattern configured to create the slidable prepared knot, and partially tightening the prepared knot. These steps may be performed by machine or by hand.  
           [0012]    In one embodiment of the method, the step of advancing the field loop toward the distal site further includes using an elongate tool to push the field loop. The method of stabilizing the suture filament while the field loop surrounds the tissue structure at the distal site may include stabilizing the elongate tool.  
           [0013]    In one embodiment, the elongate tool may be a cannula having first and second ends and a channel therethrough. The method using this cannula may further include threading the opposing end of suture filament through the channel before executing the step of passing the opposing end into the surgical port and about the tissue structure. The step of using an elongate tool may further include using the first end of the cannula. Similarly, the step of stabilizing the suture filament while the field loop surrounds the tissue structure at the distal site may include stabilizing the cannula. In another aspect, the method may include the steps of providing a plurality of cannulae of varying shapes and sizes and selecting the cannula from the plurality of cannulae.  
           [0014]    As with the field loop, one embodiment of the method step of advancing the prepared loop toward the proximal site may further include using an elongate tool to push the prepared loop. The step of stabilizing the suture filament while the prepared loop surrounds the tissue structure at the proximal site, likewise, may further include stabilizing the elongate tool. In a method where the elongate tool is a cannula having first and second ends and a channel therethrough, the method may further include threading the opposing end of suture filament through the channel before executing the step of advancing the prepared loop. The step of using an elongate tool may include using the second end of the cannula. And the step of stabilizing the suture filament while the prepared loop surrounds the tissue structure at the proximal site may include stabilizing the cannula in this embodiment. In another aspect, this method may include the steps of providing a plurality of cannulae of varying shapes and sizes and selecting the cannula from the plurality of cannulae.  
           [0015]    In another aspect, the method may include providing instructions for tying the slidable field knot. The tying step may include making at least three throws around the suture filament.  
           [0016]    In another aspect, the method may include the steps of providing a plurality of suture filaments of varying types and sizes and selecting the suture filament from the plurality of suture filaments.  
           [0017]    In an alternative embodiment, the method of the present invention includes tying a first field knot and a second field knot in order accomplish the task of ligating an elongate tissue structure at a proximal site and a distal site through a surgical opening positioned between the sites using a suture filament. In this embodiment, the method may include passing one end of the suture filament into the surgical opening and about the tissue structure, tying a first slidable field knot about the suture filament with the one end to form a first field loop about the tissue structure, advancing the first field loop toward the distal site, and applying axial tension on the suture filament while stabilizing the suture filament and while the first field loop surrounds the tissue structure at the distal site so as to close the first field loop and tighten the first field knot to form a distal ligature. The method may further include cutting the suture filament proximate the distal ligature and withdrawing the suture filament through the surgical site. The second field knot steps may include passing an other end of the suture filament into the surgical opening and about the tissue structure, tying a second slidable field knot about the suture filament with the other end to form a second field loop about the tissue structure, advancing the second field loop toward the proximal site, and applying axial tension on the suture filament while stabilizing the suture filament and while the second field loop surrounds the tissue structure at the proximal site so as to close the second field loop and tighten the second field knot to form a proximal ligature. The steps follow of cutting the suture filament proximate the proximal ligature and withdrawing the suture filament through the surgical site.  
           [0018]    The method may further include transecting the tissue structure proximate the first ligature and withdrawing the distal end through the surgical site before the step of tying a second slidable field knot.  
           [0019]    Also, the method may further include transecting the tissue structure proximate the second ligature and withdrawing the proximal end through the surgical site.  
           [0020]    In one embodiment, the method step of advancing the first field loop toward the distal site further includes using an elongate tool to push the first field loop. The step of stabilizing the suture filament may further include stabilizing the elongate tool. In an embodiment where the elongate tool is a cannula having first and second ends and a channel therethrough, the method further includes threading the one end of suture filament through the channel before executing the step of passing the one end into the surgical port and about the tissue structure. The step of using an elongate tool may include using the first end of the cannula. Similarly, the step of stabilizing the suture filament may further include stabilizing the cannula. In another aspect, the method may include the steps of providing a plurality of cannulae of varying shapes and sizes and selecting the cannula from the plurality of cannulae.  
           [0021]    In another embodiment of the method, the step of advancing the prepared loop toward the proximal site includes using an elongate tool to push the prepared loop. The step of stabilizing the suture filament includes stabilizing the elongate tool. Where the elongate tool is a cannula having first and second ends and a channel therethrough, the method includes threading the one end of suture filament through the channel before executing the step of advancing the second field loop. The step of using an elongate tool may include using the second end of the cannula. Likewise, the the step of stabilizing the suture filament may include stabilizing the cannula. In another aspect, the method may include the steps of providing a plurality of cannulae of varying shapes and sizes and selecting the cannula from the plurality of cannulae.  
           [0022]    In another aspect, the method may include providing instructions for tying the slidable field knot. The tying step may include making at least three throws around the suture filament.  
           [0023]    In another aspect, the method may include the steps of providing a plurality of suture filaments of varying types and sizes and selecting the suture filament from the plurality of suture filaments.  
           [0024]    In another aspect of the present invention, an apparatus is provided for ligating an elongate tissue structure at one or more sites through a surgical opening spaced apart from at least one of the one or more sites. The apparatus may include an elongate tool having a first end and a second end, the tool having a channel therethrough, the tool being narrowed toward the ends, and the tool having a length sufficient to extend from the surgical opening to each of the one or more sites. Additionally, the apparatus includes a suture filament having a head end and a tail end. The suture filament may include a prepared loop in the head end secured by a slidable prepared knot tied about the suture filament near the second end of the tool. The suture filament may be threaded through the channel with the tail end extending from the first end of the tool. The tail end may have sufficient length to allow formation of field loop secured by a slidable field knot in the tail end.  
           [0025]    In one embodiment, the elongate tool has a central longitudinal axis and the channel lies along the axis. In one embodiment, the elongate tool includes a first conical taper at the first end and a second conical taper at the second end, the conical tapers decreasing in diameter toward the ends. In one embodiment, the elongate tool is a cannula. The sites reached by the apparatus may include a proximal site and a distal site.  
           [0026]    In another aspect of the apparatus, the elongate tool may include a temporary anchor positioned and configured to exert a grasp upon the suture filament, thereby preventing movement of the suture filament through the channel. The grasp of the anchor is capable of being overcome by exerting a force upon the suture filament, if the force exceeds a pre-determined threshold. In one embodiment, the temporary anchor is an adhesive spot.  
           [0027]    In one embodiment, the sufficient length of the tail end is at least eight inches. In one embodiment, the surgical opening may be a surgical port. In another, it may be a surgical incision.  
           [0028]    In an alternative embodiment of the apparatus, no prepared loop in the suture filament is provided. The apparatus for ligating an elongate tissue structure at one or more sites through a surgical opening spaced apart from at least one of the one or more sites in this embodiment includes an elongate tool having a first end and a second end, the tool having a channel therethrough, the tool being narrowed toward the ends, and the tool having a length sufficient to extend from the surgical opening to each of the one or more sites. The apparatus also includes a suture filament threaded through the channel, the suture filament having a head end and a tail end, each of the head and tail ends having sufficient length extending beyond the first and second ends of the tool, respectively, to allow formation of at least one field loop secured by a slidable field knot.  
           [0029]    In one embodiment, the elongate tool has a central longitudinal axis and the channel lies along the axis. In one embodiment, the elongate tool includes a first conical taper at the first end and a second conical taper at the second end, the conical tapers decreasing in diameter toward the ends. In one embodiment, the elongate tool is a cannula. The sites reached by the apparatus may include a proximal site and a distal site.  
           [0030]    In another aspect of the apparatus, the elongate tool may include a temporary anchor positioned and configured to exert a grasp upon the suture filament, thereby preventing movement of the suture filament through the channel. The grasp of the anchor is capable of being overcome by exerting a force upon the suture filament, if the force exceeds a pre-determined threshold. In one embodiment, the temporary anchor is an adhesive spot.  
           [0031]    In one embodiment, the sufficient length of the tail end is at least eight inches. In one embodiment, the surgical opening may be a surgical port. In another, it may be a surgical incision.  
           [0032]    These and other objects are accomplished by the method and apparatus disclosed and will become apparent from the following detailed description of a preferred embodiment in conjunction with the accompanying drawings in which like numerals designate like elements. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWING  
       [0033]    [0033]FIG. 1 is a pictorial view of an apparatus according to one embodiment of the present invention.  
         [0034]    [0034]FIG. 2 is a side view of an elongate tool with tapered ends according to one embodiment of the present invention.  
         [0035]    [0035]FIG. 3 is a perspective drawing of a vessel to be harvested and the operative sites according to one embodiment of the present invention.  
         [0036]    [0036]FIG. 4 is a perspective drawing of a field loop in use, according to one embodiment of the present invention.  
         [0037]    [0037]FIG. 5 is a perspective drawing of the advancement of an apparatus toward a ligation site, according to one embodiment of the present invention.  
         [0038]    [0038]FIG. 6 is a perspective drawing of a vessel ligature according to one embodiment of the present invention.  
         [0039]    [0039]FIG. 7 is a perspective drawing of a prepared loop in use, according to one embodiment of the present invention.  
         [0040]    [0040]FIG. 8 is a perspective drawing of an elongate tool and a vessel ligature according to one embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0041]    Reference is now made to the figures, in which like numerals indicate like elements throughout the several views.  
         [0042]    [0042]FIG. 1 shows an apparatus  10  according to one embodiment of the present invention. The apparatus  10  includes a suture filament  30  threaded completely through a hollow elongate tool or a cannula  20 . A cannula, generally, is a small, elongate tube used for insertion into a body cavity or duct. A cannula may or may not have a consistent shape along its entire length. A cannula may be generally cylindrical, but it may be elliptical or some other shape in cross section. The cannula  20  of the present invention may be described as having two opposing ends, a first end  22  and a second end  26 . The diameter of the cannula  20  is narrowed toward the ends  22 ,  26 . The narrowing may take any geometric shape having generally smooth, rounded edges, including shapes such as a hemisphere, a bevel ring, a quarter torus, or a curved shell ring. The narrowing is shaped to facilitate movement of the cannula  20  through body cavities without causing injury to the tissues.  
         [0043]    In one embodiment, this narrowing takes the shape of a first conical taper  23  at the first end  22  and a second conical taper  27  at the opposing second end  26 . The tapered ends are cone-shaped such that the diameter of the cannula  20  gradually decreases toward the ends  22 ,  26 . The conical tapers  23 ,  27  are particularly desirable in one embodiment because, as the cannula  20  moves through a body cavity, the leading end ( 22  or  26 ) is gradually increasing in diameter. The gradual increase offered by a cone shape tends to move more gently and easily through narrow passages than other, more blunt shapes.  
         [0044]    The suture filament  30  in one embodiment includes a prepared loop  56  on one end and a long, un-looped tail  32  at the other end. The prepared loop  56  is made during manufacture in one embodiment, and secured by a pre-tied or prepared knot  58  that is tied around the suture filament  30  during the manufacturing process. Creation of a prepared loop  56  secured by a prepared knot  58  may be done by machine, by hand, or by a combination of the two. The process, generally, includes stabilizing the suture filament  30 , forming the prepared loop  56  by curling a free end of the suture filament  30  so that it crosses itself, and looping the free end around the suture filament  30  in an established pattern to create the desired type of prepared knot  58 . The prepared knot  58  may be a partially-tightened, slidable knot, tied using any one of a number of established slip knot or slidable knot patterns familiar to those of skill in the art. In one embodiment, the prepared knot  58  may include at least three passes or throws around the suture filament  30  in order to form an acceptably durable knot. A slip knot may be used for suturing in order to facilitate secure and efficient closure of the loop  56  and tightening of the knot  58  when placed in its intended location.  
         [0045]    The tail  32  of the suture filament  30  is generally long enough for the user to loop the suture filament  30  around a tissue structure or blood vessel in the surgical field. The tail  32  in one embodiment is twelve to fourteen inches (304 mm to 356 mm) in length, although other lengths are contemplated for use in various environments and procedures. The tail  32  may be measured from the first end  22  of the cannula  20  to the tail end  34  of the suture filament  30 . In another embodiment, the tail  32  may be as short as eight inches (203 mm).  
         [0046]    In one embodiment, the user may use the tail  32  to create a field loop  36  by tying a field knot  38  around the suture tail  32 , as shown in FIG. 4. The process of creating a field loop  36  secured by a field knot  38  is similar, generally, to the steps described above for creating a prepared loop  56  secured by a prepared knot  58 . The field knot  38  may be a partially-tightened, slidable knot, tied using any one of a number of established slip knot or slidable knot patterns familiar to those of skill in the art. In one embodiment, the field knot  38  may include at least three throws around the suture filament  30  in order to form an acceptably durable knot. A slip knot pattern may be used for the field knot  38  in order to facilitate secure and efficient closure of the field loop  36  and tightening of the field knot  38 .  
         [0047]    In another embodiment, the suture filament  30  does not include a prepared loop on either end. The user may create one or more field loops  36  as needed for a particular procedure.  
         [0048]    Any surgical suturing material may be used for the suture filament  30 , including natural or synthetic filaments, bio-absorbable or non-absorbable fibers, or any of a variety of available materials suited to the particular need. The suture filament  30  may be a monofilament or it may be composed of multiple strands of filament braided together. In one embodiment, a dyed monofilament, synthetic, absorbable suture material having a U.S.P. suture size designation between 0 (0.071 mm in diameter) and 6-0 (0.015 mm), with size 2-0 (0.029 mm) being a desired size for ligating a greater saphenous vein. Other suture materials and sizes are contemplated for use in various procedures. In one embodiment, a radiopaque marker may be provided on either end of the suture filament  30  to ensure that the knots may be visible on future radiographs.  
         [0049]    Referring now to FIG. 2, a closer view of an elongate tool or cannula  20  is shown, according to one embodiment of the present invention. The channel  80  through the cannula  20  may coincide with the central longitudinal axis of the cannula  20 . The cannula  20  may have a length in one embodiment of between twelve and thirty-six inches (304 mm to 915 mm), with twenty-two inches (559 mm) being a desired size for harvesting a greater saphenous vein in the leg.  
         [0050]    The cannula  20  may be constructed from a flexible and durable nylon, plastic, or other suitable biocompatible material. The degree of flexibility desired in a particular cannula  20  will vary depending on the environment and the procedure. The cannula  20  may be disposable or reusable. The cannula  20  may be transparent or opaque, and it may be dyed a particular color or otherwise color-coded. In one embodiment, the cannula  20  may include a measuring scale imprinted on the outer surface. In another embodiment, the cannula  20  may include a series of marks or markers indicating, for example, the preferred insertion depth for certain procedures.  
         [0051]    The conical tapers  23 ,  27  at the opposing ends, in one embodiment, narrow to a size roughly equal to the diameter of the channel  80 , as shown. The conical tapers  23 ,  27  facilitate the safe movement of the cannula  20  into a surgical opening and through body tissue or internal body cavities. Additionally, the conical tapers  23 ,  27  narrow the cannula ends  22 ,  26  to facilitate pushing of suture loops into the surgical opening  150  and through internal cavities.  
         [0052]    The outer diameter of the cannula  20  may be sized according to the intended use, the surgical field, and other factors related to the procedure being performed. In one embodiment, a desired diameter for the cannula  20  is about 0.16 inches (4 mm).  
         [0053]    Inside the cannula  20 , the channel  80  may have a diameter that is larger than the diameter of the suture filament  30  to be used, so that the suture filament  30  can slide through the channel  80 . The diameter of the channel  80 , however, may be sized to provide enough resistance against the suture filament  30  to prevent the suture filament  30  from accidentally or inadvertently sliding through the channel  80 .  
         [0054]    In another aspect of the apparatus of the present invention, the suture filament  30  may be loosely held in place inside the channel  80  by a temporary anchor  70  or other temporary securing means to keep the suture filament  30  within the cannula  20  until ready for use. The anchor  70  may be a small adhesive spot, as illustrated in FIG. 2, positioned at a location where the anchor  70  will grasp the suture filament  30 . The anchor  70  may include an amount of adhesive, for example, in a patch or area of a given size and thickness, such that the anchor  70  will exert enough of a grasp upon the suture filament  30  to keep it from moving, but not so much that the suture filament  30  is permanently anchored. The grasp of the anchor  70  or other securing means may be overcome by exerting a predetermined, threshold level of force upon the suture filament  30 . Also, after the threshold force has been applied once and the suture filament  30  has been released, the anchor  70  preferably would no longer exert a grasp on the suture filament  30 .  
         [0055]    [0055]FIG. 3 is an illustration of a surgical field on the body  400  of a patient, showing a vessel  300  in situ to be harvested. The field includes a surgical opening  150  typically formed by making an incision near the vessel  300 , near the center of the field. The vessel may be ligated at two or more distant sites, such as the proximal site  100  and distal site  200  shown. The word proximal is used herein to describe an object that is close to the body or to the user, whereas the word distal describes something located away from the body or the user. For example, if the body part in FIG. 3 represents a leg, the surgical opening  150  may be formed near the knee, the proximal site  100  may be close to the hip, and the distal site  200  may be close to the ankle.  
         [0056]    The surgical opening  150  may take a variety of forms according to the demands of the particular procedure being performed. The surgical opening  150 , for example, may include a surgical port placed within the incision and supported by a hollow tube called a trocar through which the endoscope and related instruments may be placed. In other procedures, the surgical opening  150  may include an incision held open by a spreader or other supportive means. One skilled in the art will appreciate that the method and apparatus of the present invention are well suited for use with any kind of surgical opening  150  capable of facilitating endoscopic surgery.  
         [0057]    Method of Ligating a Vessel  
         [0058]    In another aspect, the present invention provides a method of ligating any tissue structure. The method works particularly well upon elongate tissue structures such as blood vessels and the like. The method and apparatus may be used to harvest any vessel, including a greater saphenous vein, a radial artery, or a cephalic vein. The method of the present invention allows the user to ligate an elongate tissue structure at multiple sites using a single length of suture filament.  
         [0059]    Referring now to FIG. 4, a first step in one embodiment includes passing the end of the tail  32  of the suture filament  30  into the surgical opening  150 , under the vessel  300 , and back toward the suture filament  30  to form a field loop  36 . A field knot  38  tied to the suture filament  30  secures the field loop  36 . The field knot  38  may be any one of a number of slip knots or slidable knots familiar to those of skill in the art.  
         [0060]    Once the field loop  36  is secure around the vessel  300 , a finger or an elongate tool may be used to advance or push the field loop  36  into the surgical opening  150  and toward a desired ligation site. In one embodiment, FIG. 5 shows an elongate tool known as a cannula  20  advancing or pushing the field loop  36  into the surgical opening  150  and along a path near the vessel  300  toward the distal site  200 . The field loop  36  slides along the vessel  30  and remains open. In this aspect, in addition to acting as a conduit for the suture filament  30 , the tool or cannula  20  serves an additional function as a knot pusher.  
         [0061]    In use, the field knot  38  may rest against the elongate tool or the first end  22  of the cannula  20  as the field loop  36  is being advanced or pushed through the surrounding tissue toward the ligation site. There is little or no tension, however, placed on the suture filament  30  during the pushing motion, thus enabling the field loop  36  to remain open  36  and the field knot  38  to remain only partially tightened. In this aspect, the conically tapered shape of the ends  22 ,  26  of the cannula  20  and the diameter of the channel  80  prevent the premature or unintended tightening of the field knot  38  during pushing.  
         [0062]    When the field loop  36  has reached the distal site  200  where ligation of the vessel  300  is desired, the user may manually pull or otherwise apply axial tension to the suture filament  30  while stabilizing the cannula  20  in order to close the field loop  36  and tighten the field knot  38 , thereby forming a distal ligature  40 , as shown in FIG. 6. The suture filament  30  may then be cut, leaving the distal ligature  40  in place and freeing the cannula  20  and suture filament  30  to be withdrawn through the surgical opening  150 .  
         [0063]    Once the distal ligature  40  is securely in place, the vessel  300  may be transected and withdrawn from the body  400  through the surgical opening  150 . As shown in FIG. 7, the prepared loop  56  may be placed over the new distal vessel end  140 . In one embodiment, as described above, the suture filament  30  includes a prepared loop  56  at one end, secured by a partially-tightened, slidable, prepared knot  58  tied around the suture filament  30 . As shown in FIG. 7, the prepared loop  56  of the suture filament  30  is extending from the second end  26  of the cannula  20 . Providing a prepared loop  56  secured by a prepared knot  58  facilitates the prompt capture of the vessel  300  and eliminates the time-consuming step of trying a second field knot during a surgical procedure.  
         [0064]    In an alternative embodiment, the user may form a second field loop by passing the suture filament  30  around the vessel  300  and tying a second field knot around the suture filament  30  to secure the loop. In this aspect, the cannula  20  may be used with a length of suture filament  30  for as many loops, knots, and ligatures are needed for a particular procedure.  
         [0065]    A finger or an elongate tool may also be used to advance or push the prepared loop  56  in a manner similar to that described above and shown in FIG. 5. In one embodiment, an elongate tool known as a cannula  20  may advance or push the prepared loop  56  into the surgical opening  150  and along a path near the vessel  300  toward the proximal site  100 . When the prepared loop  56  has reached the proximal site  100  where ligation of the vessel  300  is desired, as shown in FIG. 8, the user may manually pull or otherwise apply axial tension to the suture filament  30  while stabilizing the cannula  20  in order to close the prepared loop  56  and tighten the prepared knot  58 , thereby forming a proximal ligature  60 .  
         [0066]    The suture filament  30  may then be cut, leaving the proximal ligature  60  in place and freeing the cannula  20  and suture filament  30  to be withdrawn through the surgical opening  150 . Once the proximal ligature  60  is securely in place, the vessel  300  may be transected and withdrawn from the body  400  through the surgical opening  150 .  
         [0067]    In another aspect, the method of the present invention may include providing an array of elongate tools or cannulae of different shapes and sizes for the user to choose from, according to the particular procedure being performed. Similarly, in one embodiment, the method may include providing an array of sutures of various types and sizes for the user to choose from, according to the particular procedure being performed. Additionally, the method may include providing instructions for tying a number of field knots, indicating which field knot is particularly well suited to a certain procedure.  
         [0068]    Thus, the present invention provides an apparatus and a method of using the apparatus to ligate a vessel  300  at both proximal and distal sites  100 ,  200  using a single suture filament  30 , manipulated through a single surgical opening  150  without clips, needles, or suturing. The invention also provides a method of using a single cannula  20  to manipulate a suture filament  30  to perform multiple ligations.  
         [0069]    Although the invention has been described in terms of one or several embodiments, it will be appreciated by those skilled in the art that additions, substitutions, modifications, and deletions not specifically described may be made without departing from the spirit and scope of the invention as defined in the claims.