Abstract:
The present invention is directed to methods and apparatus for cutting filaments percutaneously. The methods and systems may be used in conjunction with sealing a puncture percutaneously in tissue separating two internal portions of the body of a living being with an anchor, a sealing plug and a filament connecting the anchor and sealing plug. The present invention provides for safe filament cutting below the skin and may reduce the risk of cutting the filament distal of any knots.

Description:
FIELD OF THE INVENTION  
       [0001]     This invention relates generally to medical devices and more particularly to devices for cutting sutures or other filaments percutaneously.  
       BACKGROUND  
       [0002]     Various surgical procedures are routinely carried out intravascularly or intraluminally. For example, in the treatment of vascular disease, such as arteriosclerosis, it is a common practice to invade the artery and insert an instrument (e.g., a balloon or other type of catheter) to carry out a procedure within the artery. Such procedures usually involve the percutaneous puncture of the artery so that an insertion sheath can be placed in the artery and thereafter instruments (e.g., catheter) can pass through the sheath and to an operative position within the artery. Intravascular and intraluminal procedures unavoidably present the problem of stopping the bleeding at the percutaneous puncture after the procedure has been completed and after the instruments (and any insertion sheaths used therewith) have been removed. Bleeding from puncture sites, particularly in the case of femoral arterial punctures, is typically stopped by utilizing vascular closure devices, such as those described in U.S. Pat. Nos. 6,179,963; 6,090,130; and 6,045,569 and related patents that are hereby incorporated by reference.  
         [0003]     Typical closure devices such as the ones described in the above-mentioned patents sandwich the puncture site with an internal anchor and an external sealing plug. The internal anchor and external sealing plug are attached by a suture. The suture is typically slip-knotted proximal of the sealing plug to cinch and hold the sealing plug adjacent to the anchor. A tamping tube is often used to force the sealing plug toward the anchor. Even after tamping the sealing plug and cinching the suture, the suture extends from the puncture and through the skin. It is desirable, however, to cut the suture percutaneously to promote healing.  
         [0004]     Consequently, an operator usually pulls the suture, stretching the suture a certain length outside of the incision. The suture is then cut as close as possible to the base of the incision, which releases the pulling pressure and usually springs the suture back within the incision below the outside skin level. Thus, the suture is typically not exposed from the incision after it is cut. However, there is a risk of pulling too hard on the suture and compromising the seal of the anchor and the sealing plug. In addition, the small amount of stretch available by pulling the suture usually leaves the end of the suture very close to, or even protruding slightly from, the surface of the skin. Therefore, there is a need for cutting sutures percutaneously without excessive pulling on the suture, such that the sutures are cut well below the skin surface.  
       SUMMARY  
       [0005]     The present invention meets the above-described needs and others. Specifically, the present invention provides methods and systems for cutting filaments percutaneously. However, unlike prior systems, the present invention provides for safe filament cutting below the skin surface while reducing the risk of cutting the filament distal of any knots. The present invention may be used in connection with a tissue puncture closure device following sealing of a puncture.  
         [0006]     In one of many possible embodiments, the present invention provides a percutaneous filament cutting device. The percutaneous filament cutting device comprises a housing, an elongated cutter guide attached to and extending from the housing, and an elongated cutter slidingly disposed in the housing and extending partially through the elongated cutter guide. A biasing member may be disposed between the elongated cutter and the housing for biasing the elongated cutter to a first position. The elongated cutter may comprise an actuator tab extending through a hole in the housing for operating the elongated cutter. The elongated cutter may comprise a blade end and an actuator end, the actuator end having a tab extending outside of the housing.  
         [0007]     According to some aspects of the invention, a distal end of the elongated cutter guide may include a filament insertion slot. The filament insertion slot may be helical, and the distal end of the elongated cutter may also include a longitudinal guide slot open to the helical filament insertion slot. The helical filament insertion slot and the longitudinal guide slot may form an acute angle. The filament insertion slot may include a one-way door movable radially inward but not movable radially outward for caging a filament. the one-way door may comprise a cantilevered arm having a detent hinge  
         [0008]     According to some aspect of the invention, a molded tip may be coupled to the elongated cutter guide, and the molded tip may have a filament insertion slot and the one-way movable door. The molded tip includes a tapered outer distal end abutting and flush with the elongated cutter guide, a radially inward taper receptive of the filament and leading to an internal filament lumen, the internal filament lumen having a diameter no more than three times a diameter of an associated filament. The internal filament lumen may comprise a diameter of no more than approximately 0.35 mm.  
         [0009]     According to some embodiments of the percutaneous cutting device, the elongated cutter is coaxial with the elongated cutter guide. The elongated cutter and the elongated cutter guide may comprise hollow tubes.  
         [0010]     Another aspect of the invention provides a suture path tracking and cutting device. The device comprises a handle, a shaft extending from the handle, the shaft having a first end and comprising a cutting window and a first suture insertion slot at the first end, a cutting blade disposed in the shaft and biased to a first position, and a tip attached to the shaft at the first end. The tip has a second suture insertion slot substantially aligned with the first suture insertion slot. The tip further comprises a one-way door for caging a suture.  
         [0011]     According to some embodiments, the cutting window meets the first insertion slot at an open area. The cutting window extends distally from the open area and comprises a suture guide slot to prevent inadvertent release of the suture from the cutting window back through the first insertion slot. The cutting window may be shaped like a capsule and open at a side thereof to the first insertion slot. The first suture insertion slot may include a helical cut in the shaft. The helical cut may extend approximately 180° through the shaft.  
         [0012]     According to some embodiments, the one-way door comprises a cantilevered arm extending across the second insertion slot in a first position, the one-way door moveable radially inward from the first position but not radially outward from the first position. The one-way door may comprise a compliant arm having a base, inside surface, an outside surface, a detent at the base of the outside surface, and a protrusion at the base of the inside surface. The shaft and tip may define a lumen receptive of a suture with an effective diameter comprising no more than approximately three times the diameter of the suture. Therefore, the lumen may be sized to receive one diameter of the suture, but not allow any knots in the suture to pass therethrough.  
         [0013]     According to some embodiments of the suture path tracking and cutting device, the cutting blade is disposed in the shaft proximal of the cutting window in the first position, the cutting blade being movable distally at least partially across the cutting window in response to a force applied thereto. An actuator tab connected to the cutting blade may be used for moving the cutting blade within the shaft, the actuator tab extending outside of the handle.  
         [0014]     Another aspect of the invention provides a method of cutting a suture percutaneously. The method includes providing a housing, providing an elongated cutter guide attached to and extending from the housing, providing an elongated cutter slidingly disposed in the housing and extending partially through the elongated cutter guide, inserting the suture into the elongated cutter guide, passing a tip of the elongated cutter guide below surface skin level, and actuating the elongated cutter. The method may also include blocking any knots tied in the suture from entering the elongated cutter guide and/or preventing release of the suture from the cutter guide with a one-way door.  
         [0015]     According to some aspects of the method, the actuating comprises depressing a tab of the elongated cutter against a biasing force. In addition, the inserting may comprise threading the suture through a guide slot in the elongated cutter guide, and the actuating may comprise sliding the elongated cutter past the window to sever the suture.  
         [0016]     Another aspect of the invention provides another method of cutting a filament percutaneously. This method comprises threading a filament extending from an incision in a patient through a cutter guide, preventing release of the filament from the cutter guide, following the filament path into the incision with the cutter guide, sliding a blade through the cutter guide, and severing the filament with the blade. The threading may comprise passing a portion of the filament through an insertion slot in the cutter guide and into a guide slot. The sliding may comprise depressing a tab operatively connected to the blade.  
         [0017]     Another embodiment of the invention provides an internal tissue puncture closure and cutting system. The system comprises a closure device and a filament cutting device insertable percutaneously into an incision for cutting the filament below a skin level. The closure device comprises a filament extending from a first end of the closure device to a second end of the closure device, an anchor for insertion through the tissue wall puncture attached to the filament at the second end of the closure device, a sealing plug slidingly attached to the filament adjacent to the anchor, a driving mechanism for tamping the sealing plug toward the second end, and a filament cutting device insertable percutaneously into an incision for cutting the filament below a skin level.  
         [0018]     Additional advantages and novel features of the invention will be set forth in the description which follows or may be learned by those skilled in the art through reading these materials or practicing the invention. The advantages of the invention may be achieved through the means recited in the attached claims. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0019]     The accompanying drawings illustrate various embodiments of the present invention and are a part of the specification. The illustrated embodiments are merely examples of the present invention and do not limit the scope of the invention.  
         [0020]      FIG. 1  is a partial cut-away view of a tissue closure device according to the prior art.  
         [0021]      FIG. 2  is a side view of the tissue closure device of  FIG. 1  engaged with an artery according to the prior art.  
         [0022]      FIG. 3  is a side view of the tissue closure device of  FIG. 1  being withdrawn from an artery according to the prior art to deploy a collagen sponge.  
         [0023]      FIG. 4  is a side view of the tissue closure device of  FIG. 1  illustrating tamping of the collagen sponge according to the prior art.  
         [0024]      FIG. 5  is a side view of the tissue closure device of  FIG. 1  illustrating a suture being cut according to the prior art.  
         [0025]      FIG. 6  is an exploded view of a percutaneous filament cutting device according to one embodiment of the present invention.  
         [0026]      FIG. 7  is an assembled cross-sectional view of the percutaneous filament cutting device of  FIG. 6 .  
         [0027]      FIG. 8  is an assembled perspective view of the percutaneous filament cutting device of  FIG. 6 .  
         [0028]      FIG. 9A  is blown up side view of a tip portion of the percutaneous filament cutting device of  FIG. 6 .  
         [0029]      FIG. 9B  is a blown up top view of the tip portion of the percutaneous filament cutting device of  FIG. 6 .  
         [0030]      FIG. 9C  is a blown up cross-sectional view of the tip portion of the percutaneous filament cutting device of  FIG. 6 .  
         [0031]      FIG. 9D  is a blown up end perspective view of the tip portion of the percutaneous filament cutting device of  FIG. 6  with a suture inserted therein.  
         [0032]      FIG. 9E  is a reverse blown up end perspective view of the tip portion of the percutaneous filament cutting device of  FIG. 6  with the suture being cut by a blade.  
         [0033]      FIG. 9F  is a blown up side view of the tip portion of the percutaneous filament cutting device of  FIG. 6  with hidden lines illustrating internal hidden features.  
         [0034]      FIG. 10A  is a blown up, perspective view of an alternative tip portion, shown partially in section, according to another embodiment of the present invention.  
         [0035]      FIG. 10B  is an end view of the tip portion of  FIG. 10A  with a one-way door in a first position.  
         [0036]      FIG. 10C  is an end view of the tip portion of  FIG. 10A  with the one-way door in a second position. 
     
    
       [0037]     Throughout the drawings, identical reference numbers designate similar, but not necessarily identical, elements.  
       DETAILED DESCRIPTION  
       [0038]     As mentioned above, vascular procedures are conducted throughout the world and require access to an artery through a puncture. Most often, the artery is a femoral artery. To close the puncture following completion of the procedure, many times a closure device is used to sandwich the puncture between an anchor and a sealing plug. However, after sandwiching the puncture, a filament usually extends from the sealing plug and out through the incision. The filament must be cut to release the sealing plug and anchor from the remainder of the closure device. It is difficult to cut the filament percutaneously with conventional tools such as scissors, and therefore the filament often protrudes out of the skin. The present invention describes methods and apparatus to seal tissue punctures and/or cut filaments percutaneously. The percutaneous filament cutting devices of the present invention may be particularly useful for use with tissue puncture closure devices. Some specific tissue puncture closure devices are shown. However, the cutting devices may be used with any tissue puncture closure device, and also in other environments in which is desirable to cut a filament below a surface level. The principles described herein may be used with any vascular closure device or other circumstances requiring subsurface filament cutting. Therefore, while the description below is directed primarily to arterial procedures and certain embodiments of a vascular closure device, the methods and apparatus are only limited by the appended claims.  
         [0039]     As used in this specification and the appended claims, the term “tamp” or “tamping” is used broadly to mean packing down by one or a succession of blows or taps, but not by excessive force. A “lumen” refers to any open space or cavity in a bodily organ or in a tool. The term “percutaneous” means passed, done, or effected through or under the skin surface or other subsurface structure. A “tab” is a projection, flap, or short strip attached to or integral with an object to facilitate operation. An “effective diameter” is a smallest distance across a closed or generally closed shape, and is not necessarily circular. The words “including” and “having,” as used in the specification, including the claims, have the same meaning as the word “comprising.” 
         [0040]     Referring now to the drawings, and in particular to  FIGS. 1-5 , a vascular puncture closure device  100  is shown according to the prior art. The vascular puncture closure device  100  includes a carrier tube  102  with a filament or suture  104  extending at least partially therethrough. The closure device  100  also includes a first or proximal end  106  and a second or distal end  107 . External to a second or distal end  107  of the carrier tube  102  is an anchor  108 . The anchor is an elongated, stiff, low profile member including an eye  109  formed at the middle. The anchor  108  is typically made of a biologically resorbable polymer.  
         [0041]     The suture  104  is threaded through the anchor  108  and back to a collagen pad  110 . The collagen pad  110  may be comprised of randomly oriented fibrous material bound together by chemical means. The collagen pad  110  is slidingly attached to the suture  104  as the suture passes distally through the carrier tube  102 , but as the suture traverses the anchor  108  and reenters the carrier tube  102 , it is securely slip knotted proximal to the collagen pad  110  to facilitate cinching of the collagen pad  110  when the closure device  100  is properly placed and the anchor  108  deployed (see  FIG. 4 ). The carrier tube  102  typically includes a tamping tube  112  disposed therein. The tamping tube  112  is slidingly mounted on the suture  104  and may be used by an operator to tamp the collagen pad  110  toward the anchor  108  at an appropriate time to seal a percutaneous tissue puncture.  
         [0042]     Prior to deployment of the anchor  108  within an artery, the eye  109  of the anchor  108  rests outside the distal end  107  of the carrier tube  102 . The anchor  108  may be temporarily held in place flush with the carrier tube  102  by a bypass tube  114  disposed over the distal end  107  of the carrier tube  102 .  
         [0043]     The flush arrangement of the anchor  108  and carrier tube  102  allows the anchor  108  to be inserted into an insertion sheath  116  as shown in  FIGS. 2-4 , and eventually through an arterial puncture  118 . The insertion sheath  116  is shown in  FIGS. 2-4  inserted through a percutaneous incision  119  and into an artery  128 . However, the bypass tube  114  ( FIG. 1 ) includes an oversized head  120  that prevents the bypass tube  114  from passing through an internal passage of the insertion sheath  116 . Therefore, as the puncture closure device  100  is inserted into the insertion sheath  116 , the oversized head  120  bears against a surface  122  of insertion sheath  116 . Further insertion of the puncture closure device  100  results in sliding movement between the carrier tube  102  ( FIG. 1 ) and the bypass tube  114 , releasing the anchor  108  from the bypass tube  114  ( FIG. 1 ). However, the anchor  108  remains in the flush arrangement shown in  FIG. 1  following release from the bypass tube  114 , limited in movement by the insertion sheath  116 .  
         [0044]     The insertion sheath  116  includes a monofold  124  at a second or distal end  126  thereof. The monofold  124  acts as a one-way valve to the anchor  108 . The monofold  124  is a plastic deformation in a portion of the insertion sheath  116  that elastically flexes as the anchor  108  is pushed out through the distal end  126  of the insertion sheath  116 . Typically, after the anchor  108  passes through the distal end  126  of the insertion sheath  116  and enters the artery  128 , the anchor  108  is no longer constrained to the flush arrangement with respect to the carrier tube  102  and it deploys and rotates to the position shown in  FIG. 2 .  
         [0045]     Referring next to  FIGS. 3-4 , with the anchor  108  deployed, the puncture closure device  100  and the insertion sheath  116  are withdrawn together, depositing the collagen pad  110  in the incision tract  119  and exposing the tamping tube  112 . With the tamping tube  112  fully exposed as shown in  FIG. 4 , the collagen pad  110  is manually tamped, and the anchor  108  and collagen pad  110  are cinched together and held in place with the self-tightening slip-knot on the suture  104 . Thus, the tissue puncture is sandwiched between the anchor  108  and the collagen pad  110 , thereby sealing the tissue puncture  118 . The suture  104  is then cut and the incision tract  119  may be closed. The suture  104 , anchor  108 , and collagen pad  110  are generally made of resorbable materials and therefore remain in place while the puncture  11   8  heals.  
         [0046]     Using the typical tissue puncture closure device  100  described above, the tamping of the collagen pad  110  commences after sheath  116  has been removed so as to expose the tamping tube  112  for manual grasping. However, automatic tamping or other driving mechanisms may also be used to tamp the collagen pad  110  according to principles of the present invention.  
         [0047]     As shown in  FIG. 5 , when the collagen pad  110  has been tamped and cinched, the suture  104  connecting the anchor  108  and the pad  110  must be cut proximal of the pad  110  to release the closure device. Typically a pair of scissors  130  is used to cut the suture  104  as close as possible to the surface of a skin layer  132 . The suture  104  may even be stretched so that after the cut, the suture  104  recoils slightly below the surface of the skin layer  132 . Nevertheless, the suture  104  typically protrudes slightly from the skin layer  132  or is very close to the surface of the skin layer  132 , which can cause irritation or other problems to a patient.  
         [0048]     Therefore, the present specification describes a percutaneous cutting device or suture path tracking and cutting device that enables cutting filaments safely below a skin or other surface. The filament is preferably threadable through the cutting device at any point along the filament and able to slide along the filament to a desired cutting position.  
         [0049]     Referring now to  FIG. 6 , a suture path tracking and cutting device, such as a percutaneous cutting device  200 , is shown according to one embodiment of the present invention. The percutaneous cutting device  200  may have particular utility when used in connection with tissue puncture closure devices such as the closure device  100  described above. However, any subsurface filament cutting operation may be accomplished with the percutaneous cutting device  200 .  
         [0050]     The percutaneous cutting device  200  includes a handle  234  housing or partially housing a number of other components. The handle  234  is preferably plastic with an ergonomic shape for comfortable manipulation by an operator. As shown in  FIG. 6 , the handle  234  is elongated and tapers to an opening  236  at a first end  238 . The handle  234  may also include a first set of gripping detents  240  and a second similar or identical set on an opposite side. The handle  234  may be open at a second end  242  and have a hole or slit  244  shown in  FIG. 6  extending longitudinally.  
         [0051]     The opening  236  of the handle  234  is receptive of an elongated cutter guide  246 . The elongated cutter guide  246  may comprise a hollow tube which is attached to and extends from the handle  234  when the percutaneous cutting device  200  ( FIGS. 7-8 ) is assembled. The second end  242  of the handle  234  is receptive of an elongated cutter  248  and an end cap  250 . The elongated cutter  248  may comprise a second hollow tube  252  with a sharpened edge or cutting blade at a first or blade end  254 . A second or actuator end  256  of the elongated cutter  248  is shown with a mount  258  attached to an actuating tab  260 . A biasing member such as a spring  262  may be disposed between the handle  234  and the mount  258  of the elongated cutter  248  to bias the elongated cutter  248  to the first position.  
         [0052]     The elongated cutter  248  slides into the handle  234  with the tab  260  extending outside of the handle  234  at a flattened surface  264  of the handle, when assembled ( FIG. 7 ). The end cap  250  includes a track  266  that mates with the slot  244  of handle  234  to close the handle, although a portion or the slot  244  remains open for the tab  234  to extend through. Thus, the elongated cutter  248  is inserted into the handle  234  such that the mount  258  and the tab  260  straddle the slot  244 . The tab  260  extends outside of the handle  234 , and the mount  258  is inside the handle  234 .  
         [0053]      FIG. 7  illustrates the percutaneous cutting device  200  in an assembled, cross sectional view. As shown in  FIG. 7 , the spring  262  bears against an internal guide  268  and the mount  258  of the elongated cutter  248 . The elongated cutter  248  extends only partially through the elongated cutter guide  246 . The tab  260  extending from the handle  234  allows an operator to apply a distal force to the elongated cutter  248  and cause the elongated cutter  248  to move with respect to the elongated cutter guide  246  against the force of the spring  262 . The cutting action of the elongated cutter  248  is described below with reference to  FIGS. 8-9E .  
         [0054]     Referring to  FIGS. 8-9E , a filament such as the suture  104  of the closure device  100  may be threaded into the percutaneous cutting device  200 . The elongated cutter guide  246  includes a filament insertion slot such as a helical filament insertion slot  270  ( FIG. 9A ) shown at a first or distal end  272 . The helical filament insertion slot  270  allows a filament to be threaded into the elongated cutter guide  246  at any point along the filament. The helical filament insertion slot  270  may extend for approximately 90° as shown in  FIG. 9A , although the slot  270  may also traverse smaller or larger angles, such as 180°. The helical filament insertion slot  270  is open at the first end  272 .  
         [0055]     The helical filament insertion slot  272  also opens into a side of a longitudinal guide slot or cutting window  274  shown most clearly in  FIG. 9B . The guide slot  274  is shaped generally like a capsule with an open area  275  in the side communicating with the helical filament insertion slot  272 . The guide slot  274  provides a geometry that generally prevents an inserted filament from falling out of the helical filament insertion slot  270 . As a filament such as the suture  104  ( FIGS. 8, 9E ) is threaded into the helical filament insertion slot  270  and then into the guide slot  274 , the suture  104  tends to fall toward a lower wall  276  of the guide slot, which prevents the suture  104  from slipping back out of the helical filament insertion slot  270  at the open area  275 .  
         [0056]     The first end  272  of the elongated cutter guide  246  may attach to a tip such as a molded tip  278 . The molded tip  278  also comprises a filament insertion slot  280  substantially aligned with the helical filament insertion slot  272 . The molded tip  278  is preferable plastic and partially inserted into the elongated cutter guide  246  such that a tapered outer distal end  282  abuts and is flush with the elongated cutter guide  246  ( FIG. 9A ). The molded tip  278  also includes a radially inward taper surface  284  best seen in  FIG. 9D  that is concave and receptive of a filament. The radially inward taper surface  284  funnels or leads to a internal filament lumen  285  ( FIGS. 9C-9D ) defined by the molded tip  278  and/or the elongated cutter guide  246 . Therefore, a filament may be threaded into the helical filament insertion slot  270  such that the filament extends into the internal filament lumen  286  and back out the guide slot  274 . The internal filament lumen  285  of the molded tip  278  comprises a diameter or effective diameter (e.g. distance D of  FIG. 9C ) that is large enough to allow a filament to slide freely therethrough. However, the diameter or effective diameter of the internal filament lumen  285  through the molded tip  278  is small enough to prevent any knots tied in the filament, such as knot  277  ( FIGS. 8 and 9 D) from entering through the tip via the radially inward taper surface  284 . Thus, knots such as knot  277  used to cinch and hold the sealing plug  110  ( FIG. 3 ) cannot enter the elongated cutter guide  246  and be cut. Instead the knot  277  is pushed toward the sealing plug  110  by the molded tip  278 . The diameter or effective diameter D of the internal filament lumen  285  may be no more than approximately two to three times an associated filament diameter. For example, for a suture with a diameter of 0.12 mm, the internal filament lumen  285  diameter may be no more than approximately 0.35 mm.  
         [0057]     The filament insertion slot  270  and/or the tip insertion slot  280  may include a holding or caging feature to retain a filament once inserted. For example, as shown in  FIGS. 9C-9D , the tip insertion slot  280  includes a one-way movable door such as a cantilevered arm  284  to cage the filament. The cantilevered arm  284  is movable radially inward from a first position shown, but not moveable radially outward from the first position. Therefore, in order to insert a filament through the filament insertion slot  270  and/or the tip insertion slot  280 , the filament is pressed against the cantilevered arm  284 , causing it to move radially inward from the first position and allowing the filament to pass through. When a force opening the cantilevered arm  284  is removed, the cantilevered arm returns to the first position. The cantilevered arm  284  may not move radially outward from the first position, as it abuts an interior wall  286 . Therefore the filament is prevented from release without a concerted effort to press the cantilevered arm  284  inward while pulling the filament out. The cantilevered arm  284  may be compliant by including a detent  294  at the base of an outside surface of the arm  284 , and a protrusion  296  at the base of an inside surface.  
         [0058]     As shown in  FIG. 9F , the molded tip necks down at a shoulder  288 . A necked down section  290  thus forms an annulus  292  with the elongated cutter guide  246  that the elongated cutter  248  may pass into when actuated. The necked down section  290  preferably extends such that it is approximately coincident with the lower wall  276  of the guide slot  274 . Therefore, when a filament such as a suture  104  is threaded through the percutaneous cutting device  200  as shown in  FIG. 9E , the geometry between the necked down section  290  and the lower wall  276  of the guide slot  274  causes the suture to pass through the guide slot  274  at an angle of approximately 90° with respect to the elongated cutter guide  246  and the elongated cutter  248  when the elongated cutter  248  is actuated. In addition, the interior portion of the lower wall  276  may be sharpened to facilitate cutting by the blade end  256  of the elongated cutter  248  in a scissor-like manner. The necked down section  290  and the interior portion of the blade end  256  may be filleted to further facilitate a normal orientation of the suture  104  with respect to the elongated cutter  248 .  
         [0059]     An alternative molded tip  378  is shown in  FIG. 10A . According to the embodiment of  FIG. 10A , the molded tip  378  does not include an interior taper. The molded tip  378  includes an exterior taper  382 , but is otherwise similar to the molded tip  278  of  FIGS. 9A-9E . Thus the molded tip  378  also comprises a filament insertion slot  380  substantially aligned with the helical filament insertion slot  272 . The molded tip  378  is partially inserted into the elongated cutter guide  246  such that it abuts and is flush with the elongated cutter guide  246 . An internal filament lumen  386  of the molded tip  378  may be shaped oblong as shown, circular, or some other shape. The internal filament lumen  386 , however, comprises a diameter or effective diameter D that is large enough to allow a filament to slide freely therethrough but small enough to prevent any knots tied in the filament from entering.  FIGS. 10B and 10C  illustrate a one-way door  384  in closed, and open positions, respectfully, for allowing a filament into the insertion slot  380  ( FIG. 10A ) and subsequently caging the filament.  
         [0060]     Operation of a tissue puncture closure system according to principles described above is as follows. The tissue puncture closure device  100  is inserted into the percutaneous incision  119 . The anchor  108  is deployed and the closure device  100  is at least partially withdrawn from the incision. The tamping tube  112  (or other tamping device) is exposed and used to tamp the sealing plug I  10  toward the anchor  108 . Withdrawing the closure device  100  also exposes the suture  104  for cutting. The suture  104  is then threaded into the percutaneous cutting device  200  by pushing the filament past the cantileverd arm  284  of the filament insertion slot  270  and into the interior filament lumen  285 . The percutaneous cutting device  200  is then urged toward the incision  119  and follows the filament path as the filament  104  enters the tip of the percutaneous cutting device  200  into the internal filament lumen  285 . The percutaneous cutting device  200  is inserted into the incision  119  until at least the lower wall  276  of the guide slot  274  is subcutaneous. Advancement of the percutaneous cutting device  200  is limited by any knots in the suture  104 , which may not pass into the internal filament lumen  285 . When a desired percutaneous position is reached, the actuating tab  260  is depressed, which advances the elongated cutter  248  distally across the guide slot  274 . The suture  104  is forced to exit the guide slot  274  at approximately a 90° angle by the geometry between the necked down portion  290  of the molded tip  278  and the blade end  254  of the elongated cutter  246 . As the blade end  254  traverses the lower wall  276  of the guide slot  274 , it cuts the suture  104  percutaneously, and the percutaneous cutting device  200  is removed from the incision  119 .  
         [0061]     The preceding description has been presented only to illustrate and describe exemplary embodiments of invention. It is not intended to be exhaustive or to limit the invention to any precise form disclosed. Many modifications and variations are possible in light of the above teaching. It is intended that the scope of the invention be defined by the following claims.