Patent Publication Number: US-2007106310-A1

Title: Suture cutter

Description:
BACKGROUND OF THE INVENTION  
      The present invention relates generally to suture cutters, and is particularly directed to devices for cutting stainless steel sutures arthroscopically. The invention will be specifically disclosed in connection with a device that cuts a suture while capturing the severed segment. The invention will also be specifically disclosed in connection with a device that cuts a suture having a bead attached thereto while retaining the bead and severed segment. It will be apparent to those of ordinary skill in the art, however, that such uses are merely exemplary, and that the embodiments disclosed herein, as well as their variations, may be used in a variety of alternative ways.  
      The present invention also relates to knot-pushers, and includes, but is not limited to, devices capable of both pushing suture knots and cutting sutures arthroscopically.  
      Cutting sutures at the appropriate location may be difficult, particularly during procedures where access is limited, such as arthroscopic surgery. Capturing a severed portion of a suture may be equally difficult. The difficulties may be increased when the suture material is relatively hard to cut, such as stainless steel sutures.  
      Similar difficulties may be encountered when cutting a suture having an enlarged end, such as to remove a knot or an attached structure, such as a bead, from a suture. For example, such difficulties may be encountered in removing a stop member from a suture adjacent an anchor as shown in U.S. Patent Publication 2002/0077631, filed Jun. 20, 2002, entitled “Apparatus And Methods For Tendon Or Ligament Repair,” the disclosure of which is incorporated herein by reference.  
      Pushing suture knots may also be difficult, particularly in close quarters such as those encountered at many surgical sites. In addition, the separate acts of pushing a suture knot and cutting a suture end may conventionally require the use of more than one tool. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The accompanying drawings incorporated in and forming a part of the specification illustrate several aspects of the present invention, and together with the description serve to explain the principles of the invention. In the drawings:  
       FIG. 1  is a top view of a suture cutter assembly constructed according to teachings of the present invention.  
       FIG. 2  is a cross sectional side view of the device shown in  FIG. 1  taken along line  2 - 2  of  FIG. 1 .  
       FIG. 3  is an enlarged, fragmentary side view of the distal end of the tube of the device shown in  FIG. 1 .  
       FIG. 4  is an enlarged, fragmentary top view of the distal end shown in  FIG. 3 .  
       FIG. 5  is an enlarged, fragmentary side view of the opposite side of the distal end shown in  FIG. 3 .  
       FIG. 6  is an enlarged, fragmentary cross sectional view of the distal end of the cutter blade of the device shown in  FIG. 1 .  
       FIG. 7  is similar to  FIG. 3 , with a suture disposed in the slot.  
       FIGS. 8-10  are enlarged, fragmentary, cross sectional views of the suture cutter assembly of  FIG. 1 , taken along line  8 - 8  of  FIG. 7 , showing the cutter blade cutting a suture disposed in the slot.  
       FIG. 11  is an enlarged, fragmentary, cross sectional view similar to the view of  FIG. 8  of an alternate embodiment of the slot and distal end of the cutter blade.  
       FIG. 12  is an enlarged, fragmentary, cross sectional view similar to the view of  FIG. 10  of another alternate embodiment of the slot and distal end of the cutter blade.  
       FIG. 13  is a top view of a combined suture bead and knot cutter/suture cutter assembly constructed according to teachings of the present invention.  
       FIG. 14  is a cross sectional side view of the device shown in  FIG. 13  taken along line  12 - 12  of  FIG. 11 .  
       FIG. 15  is an enlarged, fragmentary, cross sectional view of the distal end of the device shown in  FIGS. 13 and 14 .  
       FIG. 16  is an enlarged, fragmentary side view of the distal end of the cutter tube showing the opening for the suture bead and knot cutter.  
       FIG. 17  is a top view of the distal end shown in  FIG. 16 .  
       FIG. 18  is an enlarged, fragmentary side view of the distal end of the cutter blade of the device shown in  FIGS. 13 and 14 .  
       FIG. 19  is an enlarged, fragmentary top view of the distal end shown in  FIG. 18 .  
       FIG. 20  is an enlarged, fragmentary side view of the distal end shown in  FIG. 18 , illustrating the suture bead and knot cutter blade.  
       FIG. 21  is an enlarged, fragmentary side view of the distal end shown in  FIG. 18 , illustrating the suture cutter blade.  
       FIG. 22  is an enlarged, fragmentary cross sectional side view showing a bead disposed in the suture bead and knot cutter portion of the device shown in  FIGS. 13 and 14 , prior to cutting the suture.  
       FIG. 23  is an enlarged, fragmentary side view showing the cutting edges adjacent each other, as the suture is being severed.  
       FIG. 24  is an enlarged, fragmentary cross sectional side view showing a bead disposed in the suture bead and knot cutter after cutting the suture.  
       FIG. 25  is an enlarged, fragmentary cross sectional side view similar to the view of  FIG. 24  showing an alternate embodiment of the suture bead and knot cutter portion.  
       FIG. 26  is a top view of an alternate suture cutter assembly constructed according to teachings of the present invention.  
       FIG. 27  is an enlarged, fragmentary cross sectional side view of the device shown in  FIG. 26  taken along the axis of the device, parallel to the page of  FIG. 26 , with the device in a pushing configuration.  
       FIG. 28  is an enlarged, fragmentary cross sectional side view of the device shown in  FIG. 26  taken along the axis of the device, parallel to the page of  FIG. 26 , but with the device in cutting mode.  
       FIG. 29  is an enlarged cross sectional end view of the device shown in  FIG. 26 , but with the device in transition between a pushing configuration and cutting mode.  
       FIG. 30  is an enlarged, perspective, fragmentary view of the device shown in  FIG. 26  in partial cross section in a transition between a pushing configuration and cutting mode.  
       FIG. 31  is an enlarged, fragmentary side view of the distal end of the tube of the device shown in  FIG. 26 .  
       FIG. 32  is an enlarged, fragmentary side view of the opposite side of the distal end shown in  FIG. 31 .  
       FIG. 33  is an enlarged, fragmentary cross sectional view of the distal end of the cutter blade of the device shown in  FIG. 26 .  
       FIG. 34  is an enlarged, fragmentary cross sectional view of the distal end of the device shown in  FIG. 26  in a pushing configuration.  
       FIG. 35  is a perspective view of the device shown in  FIG. 26  with a suture disposed within the device for pushing a knot.  
       FIG. 36  is similar to  FIG. 31 , with a suture disposed in the apertures for cutting.  
       FIGS. 37-39  are enlarged, fragmentary, cross sectional views of the suture cutter assembly of  FIG. 26 , taken along line  37 - 37  of  FIG. 36 , showing the cutter blade cutting a suture disposed in the apertures.  
       FIG. 40  is an enlarged, fragmentary, cross sectional view similar to the view of  FIG. 37  of an alternate embodiment of the apertures and distal end of the cutter blade.  
       FIG. 41  is an enlarged, fragmentary, cross sectional view similar to the view of  FIG. 39  of another alternate embodiment of the apertures and distal end of the cutter blade.  
       FIGS. 42-44  are enlarged, fragmentary, cross sectional views of an alternative suture cutter assembly showing a variation of a cutter blade cutting a suture disposed in a slot. 
    
    
      Reference will now be made in detail to the present preferred embodiment of the invention, an example of which is illustrated in the accompanying drawings.  
     DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION  
      Referring now to the drawings in detail, wherein like numerals indicate the same elements throughout the views,  FIG. 1  is a top view of suture cutter assembly  2  constructed according to the teachings of the present invention.  FIG. 2  is a cross sectional view taken along line  2 - 2  of  FIG. 1 . Suture cutter assembly  2  includes tube assembly  4  and cutter assembly  6 . Tube assembly  4  comprises grip  8  having two openings  9  for the operator&#39;s fingers. Grip  8  is secured to one end of hollow tube  10 . Cutter assembly  6  includes knob  12  secured to one end of shaft  14 . Although in the embodiment depicted, tube  10  is secured to grip  8  and shaft  14  is secured to knob  12  by respective set screws, any suitable means for securing them together may be used.  
      In the depicted embodiment, shaft  14  is rigid and solid, and dimensioned to reciprocate within rigid tube  10 . The clearance between shaft  14  and tube  10  provides some resistance to axial movement of shaft  14 . Grip  8  includes cylindrical recess  16  which is configured to receive extension  18  of knob  12 .  
      Referring also to  FIGS. 3-5 , slot  24  is formed through the sidewall of tube  10  at distal end portion  26  of tube  10  which communicates with the interior defined by tube  10 . Slot  24  is shown as opening in the same direction as openings  9 , providing an index to the relative orientation between grip  8  and opening  24 . However, slot  24  may open in any direction relative to grip  8 .  
      Slot  24 , also referred to as a notch or opening, includes entrance portion  28  starting tangent to the outer surface of tube  10 , which leads to aligned axial portions  30  and  32 . This “J” notch configuration allows a suture to be hooked into and retained within the slot until it is cut. It is noted that the J notch configuration may be omitted, not having the axially extending portions, but still having edges disposed at transversely (to the longitudinal axis) spaced apart locations of the tube which present an opposing surface that limits downstream movement of the respective portions of the suture disposed adjacent thereto. The opposite edges  28   a  and  28   b  are not sharp. Axial portions  30  and  32  terminate in respective arcuate edges  30   a  and  32   a , which are axially offset from each other as can be seen in  FIG. 3 , where edge  30   a  is disposed closer to end  22  than edge  32   a . Slot  24  may be formed by any well known process, such as by milling or electro discharge machining.  
      As seen in  FIG. 6 , end  20  of shaft  14  comprises the cutter blade, which in the embodiment depicted comprises conical shape depression  34  forming an annular sharp edge  36  about the periphery of end  20  of distal end portion  38 . Edge  36  comprises edge  36   a  and edge  36   b.    
      Referring to  FIGS. 7-10 , the process for cutting suture  40  with suture cutter assembly  2  is illustrated. Suture  40  is hooked by slot  24  so that suture  24  is disposed in axial portions  30  and  32  of slot  24 , with end  20  and sharp edge  36  initially located up from of slot  24 , away from suture  40 , so that end  20  does not occlude any portion of slot  24 . To assist in locating end  20  in the initial pre-cut position, grip  8  includes locating hole  11  extending completely therethrough, and knob  12  includes annular groove  13 . The location of slot  24  relative to locating hole  11  and the location of end  20  relative to annular groove  13  are such that when annular groove  13  is aligned with locating hole  11 , end  20  is in the initial pre-cut position, and the operator can see all the way through hole  11 . Other configurations can be used to provide for the initial pre-cut positioning of end  20  such as by a detent.  
      As seen in  FIG. 8 , suture  40  is shown disposed adjacent edge  32   a , generally perpendicular to the longitudinal axes of tube  10  and shaft  14 . However, it will be appreciated that suture  40 , while disposed in slot  24  may be spaced from or adjacent to both edges  30   a  and  32   a , until shaft  14  is urged into contacted with suture  40 .  
      In  FIG. 9 , shaft  14  has been moved from the first position shown in  FIG. 8 , urged into contact with suture  40 , with sharp edge  36   a  of end  20  disposed adjacent edge  32   a , and occluding slot  24  adjacent edge  32   a . The transverse clearance, also referred to as diametrical clearance, between shaft  14  adjacent edge  36   a  and the sidewall of tube  10  adjacent edge  32   a , has a dimension which is less than a corresponding dimension of the suture, such that a portion of suture  40  is captured or retained between the interior surface the sidewall of tube  10  and shaft  14  but larger than a dimension what would sever suture  40 .  
      This configuration makes edge  32   a  the capture edge of slot  24 . A bend is formed in suture  40  by this action, and shaft  14 , and sharp edge  36   b  are concomitantly urged against the opposite side of the interior of tube  10 , the portion adjacent cutting edge  30   a.    
      At the position shown in  FIG. 9 , gap  41 , extending longitudinally, is defined between edge  30   a  and edge  36   b . At the position shown in  FIG. 9 , gap  41  has a longitudinal dimension which is smaller than the corresponding dimension of suture  40 . Gap  41  may be smaller than the corresponding dimension when slot  24  adjacent edge  32   a  is initially occluded by end  20 .  
      As cutter blade end  20  is advanced toward end  22  of tube  10 , suture  40  is eventually urged against edge  30   a  by sharp edge  36 . As sharp edge  36   b  advances past cutting edge  30   a  to a position so as to occlude slot  24  adjacent edge  30   a , with suture  40  being cut as the shaft  14  is moved from the first position to the position shown in  FIG. 10 , with the end of severed segment  40   a  of suture  40  being captured as shown in  FIG. 10 . Since the radial clearance between shaft  14  and tube  10  is less than the diameter of suture  40 , the end of severed segment  40   a  does not maintain its original circular cross sectional shape between shaft  14  and tube  10 , but is deformed, such as becoming frayed.  
      Edge  32   a  and edge  36   a  together form a pair, with shaft  14  and tube  10  being configured to retain severed segment  40   a  adjacent to the pair in the position illustrated in  FIG. 10 . The pair of edge  30   a  and edge  36   b  are configured to sever segment  40   a  as shown.  
      As can be seen, grip  8  and knob  12  are configured such that end  20  of shaft  14  does extends beyond edge  30   a . Preferably, end  20  does not extend beyond end  22  of tube  10 , keeping sharp edge  36  protected.  
      As described, the axial offset edges  30   a  and  32   a  function in combination with cutter blade end  20 , the clearance between distal end portion  38  and the internal diameter of tube  10  at distal end portion  26  and suture  40  to initiate capture of suture  40  prior to the cutting action beginning. In this depicted embodiment of the invention, the severed suture segment is captured by a portion extending generally in an axial direction within the interior of the tube, disposed between the shaft and the tube. Within the teaching of this invention, cutting may be initiated before end  20  reaches capture edge  32   a , as long as capture of suture  40  is accomplished before severing suture  40 .  
      The same may be accomplished with edges which are not aligned (i.e., not axially offset) as seen in  FIG. 11 , which is an alternate embodiment of end  20  and slot  24 . In  FIG. 11 , the slot terminates in symmetrical axial portions having longitudinally aligned edges  42   a  and  42   b . Diametrically opposite sides  44   a  and  44   b  of cutter blade end  44  of shaft  46  are longitudinally (axially) offset relative to each other, creating the offset between capture and cut as previously described. As shaft is advanced to cut suture  40 , capture edge  44   a  contacts suture  40  first, pinching it between shaft  46  and the interior of tube  48  past edge  42   a  resulting in retention of the severed portion of suture  40 . Cutting edge  44   b  is sharp as a result of the curved configuration of shaft  46  forming an angle at edge  44   b  of less than 90° at that location, and cuts suture  40  as it passes edge  42   b.    
      As described thus far, suture cuter  2  includes an axial offset between the initial engagement of the suture on one side, between an end edge of the slot and the end of the cutter blade, and the initial engagement of the suture on another side, between an end edge of the slot and the end of the cutter blade.  
      In yet another embodiment, a suture cutter according to the teachings of the present invention may also be constructed with the offset between the cutting edge and the capture edge being reversed such that initiation of the cutting occurs prior to initiation of the capture.  FIG. 12  illustrates such an alternate embodiment, which may advantageously be used with a monofilament suture  50 . In this embodiment, capture edge  52   a  of axial portion  52  of slot  54  is located closer to end  56  than cutting edge  58   b  of axial portion  58  of slot  54 .  
      As shaft  60  is advanced to cut, edge  62   b  of end  62  contacts suture  50  and urges it against edge  58   a  prior to being urged against edge  52   a  and  62   a . A monofilament suture cannot bend as much as a multifilament suture, and suture  50  is cut between edge  58   a  and end  62 . Preferably prior to suture  50  being completely severed, the end being severed  50   a  is engaged by advancing edge  62   a , urging and capturing it against capture edge  52   a . The axial travel of shaft  60  is such that edge  62   a  of end  62  captures severed suture  50   a , but is the travel is limited to stop short of cutting severed suture  50   a.    
      Although in the embodiment illustrated, tube  10  and shaft  14  are rigid, they may be flexible as long as the distal end of suture cutter  2  has sufficient rigidity to function according to the teachings of the present invention.  
      Although tube  10  and shaft  14  are circular, they may be any suitable complementary shape.  
      Although stainless steel suture material is specifically discussed herein, it will be understood that the present invention is not limited to use with stainless steel, and may be used with any suture material, such as polymer, gut, or absorbable material.  
      By way of non-limiting example, a suture cutter as described above for use in arthroscopic surgery was constructed of material suitable for tissue contact, with a tube outer diameter of 0.120 and a cutter shaft outside diameter of 0.093, having 0.002 clearance between it and the inside diameter of the tube at the distal end, for use with a 2-0 stainless steel braided suture having a nominal diameter of 0.013 inches, comprised of 49 strands.  
      Another embodiment of the present invention is depicted in  FIGS. 13-24 .  FIG. 13  is a top view of combined suture bead &amp; knot cutter and suture cutter assembly  100 , and  FIG. 14  is a cross sectional side view thereof taken along line  14 - 14  of  FIG. 11 . Assembly  100  includes tube assembly  102  and cutter assembly  104 . Tube assembly  102  comprises grip  106  secured to one end of hollow tube  108  by any suitable means, such as by a set screw. Cutter assembly  104  includes knob  110  secured to one end of shaft  112  by any suitable means, such as by a set screw.  
      Grip  106  includes recess  114  configured to receive extension  116 . In this embodiment, recess  114  is not cylindrical so that the orientation of extension  116  aligns the features located at distal end  118  of shaft  112  properly relative to opening  120  and slot  122  at distal end  124  of tube  108 , as also seen in  FIG. 13 . Slot  122  comprises part of the suture cutter portion of the combined assembly  100 , the construction and operation of which is discussed above, while opening  120  comprises part of the suture bead &amp; knot cutter portion, which will be described in detail. It is noted that although the suture bead &amp; knot cutter is disclosed herein as part of a single tool in combination with a suture cutter, the suture bead &amp; knot cutter may comprise a single tool just as the suture cutter may comprise a single tool, as previously described.  
      Referring to  FIGS. 15-17 , opening  120  is formed through tube  108  between end  132  of tube  108  and slot  122 . As will be appreciated, suture cutter slot  122  may alternatively be disposed between end  132  and opening  120 . Opening  120  is formed through tube  108 , depicted as having two inclined surfaces  126  and  128  disposed generally perpendicular to each other. In the embodiment depicted, surface  126  is disposed 20° relative to the axis of tube  108 . This produces opening  120  with the shape shown generally in  FIG. 17 . Edge  130  comprises the edge formed between surface  126  with the interior of tube  108 , having cutting edge  130   a  disposed at the apex of opening  120  closest to end  132 .  
      End  132  is open in this embodiment. Opening  120  is configured to receive therethrough an enlargement formed on or carried by a suture, such as a bead or knot. A stop member is also referred to herein as a bead. As used herein, suture enlargement refers to any structure secured to or mounted on a suture, as well as any configuration of a suture, which is larger than the diameter of the suture.  
      Referring to  FIGS. 18 and 19 , there is shown a side view and top view of distal end  118  of shaft  112 , which includes suture bead and knot cutter blade portion  134  and suture cutter blade portion  136 . The relative spacing between suture bead and knot cutter blade portion  134  and suture cutter blade portion  136  locates both at the initial pre-cut position ( FIG. 15 ) relative to opening  120  and slot  122 , respectively. A hole (not shown) through grip  106  similar to hole  11  of grip  8 , or a detent structure may be provided to assist the operator in properly locating suture bead and knot cutter blade portion  134  and suture cutter blade portion  136  to use either.  
      Slot  122  includes edges which are not axially offset with respect to each other, with the offset feature of the suture cutter being formed in suture cutter blade  136 . As seen in  FIG. 19 , suture cutter blade  136  includes opposite sides  136   a  and  136   b  which are longitudinally (axially) offset relative to each other, creating the offset between capture and cut as described above.  FIG. 21  illustrates an enlarged side view of suture cutter blade  136 .  
      Referring to  FIG. 20 , suture bead and knot cutter blade portion  134  includes generally flat portion  138 , and overhanging cutting edge  140  which forms recess  142 . The depth of flat portion  138  aligns suture  148  with cutting edges  130   a  and  140 .  
      Referring to  FIG. 22 , suture bead cutting blade portion  134  is illustrated aligned with opening  120 , with bead  144  disposed within the interior of tube  108 , adjacent flat portion  138 . When bead  144  is located toward cutting edge  130   a , bead  144  is effectively captured inside of tube  108  due to the shape of opening  120  (see  FIG. 15 ). Bead  144  may be axisymmetrical, although crimping bead  144  is known to produce a “C” cross section.  
      As shaft  112  is advanced to cut the portion  148   a  of suture  148  between bead  144  and anchor  146 , suture  148  is urged toward and against cutting edge  130   a , with bead  144  partially disposed in recess  142 . Flat portion  138  helps to resist the rotation of bead  144 , helping to keep suture  148  perpendicular to cutting edge  130   a  as the cut is initiated.  FIG. 23  illustrates cutting edge  130   a  adjacent cutting edge  140  as severance of suture  148  at portion  148   a  is almost complete.  
       FIG. 24  illustrates bead  144  captured within suture bead cutting blade portion  134  after suture  148  has been cut. It will be appreciated by those of ordinary skill in the art that, instead of cutting the portion of suture  148  proximate to the suture enlargement, the suture enlargement itself may be cut.  
       FIG. 25  shows an alternate embodiment of suture bead cutting blade portion  150 . In this embodiment, cutting blade portion  150  does not define an enclosed cavity within tube  152 , but is open on the end. In order to retain bead  144  after suture  148  is cut, tube  152  includes end cap  154 , welded to the end of tube  152 .  
       FIGS. 26 through 41  show yet more alternate embodiments of a suture cutting device.  FIG. 26  is a top view of an alternate suture cutter assembly  202  constructed in accordance with teachings of the present invention.  FIGS. 27 and 28  are cross sectional views taken along the axis of the device, parallel to the page of  FIG. 26 . Suture cutter assembly  202  includes tube assembly  204  and cutter assembly  206 .  
      As shown in  FIGS. 27 and 28 , tube assembly  4  comprises grip  208  having two curved members  209  for the operator&#39;s fingers and cylindrical recess  216  with fixed pin  211  inside cylindrical recess  16 . Pin  211  is oriented perpendicular to curved members  209 . Grip  208  is secured to proximal end  224  of hollow tube  210 , such that tube  210  may be accessed at the base of cylindrical recess  216 . Edge  215  adjacent to tube  210  at base of cylindrical recess  216  is chamfered for guidance of shaft  214  into tube  210 .  
      Cutter assembly  206  includes pusher  212  secured to proximal end of shaft  214 . Pusher  212  includes opening  213  for the operator&#39;s thumb, for example, and extension  218 . Extension  218  has first recessed flat  217  that is parallel to opening  213 . First recessed flat  217  does not extend to base  228  of extension  218 . Thus, first recessed flat  217  effectively provides flange  219  at base  228  of extension  218 , though flange  219  does not extend beyond circumference of extension  218 . Second recessed flat  221  is recessed perpendicular to first recessed flat  217 . Unlike first recessed flat  217 , second recessed flat  221  extends to base  228  of extension  218 . Second recessed flat  221  has adjacent top surface  221   a  that is axially lower on extension  218  than corresponding top surface  217   a  adjacent to first recessed flat  217 .  
      As shown in  FIGS. 29 and 30 , the intersection of first recessed flat  217  and second recessed flat  221  provides contact surface  223 . Contact surface  223  may be rounded (e.g. has a radius). Alternatively, contact surface  223  may comprise a chamfered or beveled edge, such as the surface shown in  FIG. 29 , or a sharp corner, such as the corner shown in  FIG. 30 , at the intersection of first recessed flat  217  and second recessed flat  221 .  
      Recess  216  in grip  208  is configured to receive extension  218  of pusher  212 . In the present example, pin  211  and extension  218  are configured such that opening  213  in pusher  212  must be parallel to curved members  209  of grip  208  in order for any part of extension  218  to be disposed within recess  216  below pin  211 . This requirement results from second recessed flat  221  providing necessary initial clearance of pin  211  for extension  218 . However, it will be appreciated that tube assembly  204  or cutter assembly  206  may be configured such that any or no particular orientation of opening  213  is required for substantial disposal of extension  218  within recess  216 .  
      In the present example, with extension  218  initially disposed within recess  216 , further advancement of extension  218  into recess  216  is prevented by engagement of pin  211  with top surface  221   a  adjacent to second recessed flat  221 . This configuration, shown in  FIG. 27 , where top surface  221   a  is so engaged with pin  211 , will hereinafter be referred to as suture cutter assembly  202  being in “the pushing configuration,” and will be described in further detail below. In order to advance extension  218  further into recess  216  beyond the pushing configuration in the present example, pusher  212  must be rotated approximately 90° relative to grip  208 , such that opening  213  is perpendicular to curved members  209 . Contact surface  223  is configured to provide resistance to such rotation by providing interference with pin  211 . This interference may be created by configuring extension  218  such that the minimum distance between contact surface  223  and the wall of recess  216  is 0.006 to 0.008 inches less than the diameter of pin  211 . Of course, extension  218  or pin  211  may be configured to provide more or less interference, including no interference at all.  
      The configuration shown in  FIG. 28 , where pusher  212  has been rotated such that opening  213  is perpendicular to curved members  209  while extension  218  is disposed within recess  216  will hereinafter be referred to as suture cutter assembly  202  being in “cutting mode,” and will be described in further detail below. A rounded contact surface  223  may provide a relatively smooth transition from the pushing configuration to cutting mode. Transition stages between the pushing configuration and cutting mode are shown in  FIGS. 29 and 30 . It will be appreciated that, with suture cutter assembly  202  in cutting mode, extension  218  may be reciprocated within recess  216 . It will be further appreciated that such reciprocation will be upwardly axially limited by engagement of pin  211  with flange  219 . Thus, in the present example, pin  211  and flange  219  prevent pusher  212  from being fully withdrawn from grip  208  during cutting mode. However, pusher  212  or grip  208  may be configured to permit full withdrawal of pusher  212  from grip  208  during cutting mode. Such permission may be granted by, for example, eliminating flange  219  or pin  211 .  
      In the present example, grip  208  and pusher  212  are each a molded plastic. By way of example, Delran or any other suitable plastic may be used. Alternatively, grip  208  or pusher  212  may be made of any other suitable material or by any suitable method. In the present example, tube  210  is secured to grip  208  by molding grip  208  with tube  210  predisposed in the mold. Similarly, shaft  214  is secured to pusher  212  by molding pusher  212  with shaft  214  predisposed in the mold. Any exterior part of tube  210  or shaft  214  that will be within molded grip  208  or pusher  212 , respectively, may be knurled or grit-blasted to promote attachment. Alternatively, it will be appreciated that tube  210  may be secured to grip  208 , and shaft  214  may be secured to knob  212 , by respective set screws. Of course, any other suitable means for securing them together may be used.  
      In the embodiment depicted in  FIG. 26 , shaft  214  is rigid and solid, and dimensioned to reciprocate within rigid tube  210 . The clearance between shaft  214  and tube  210  provides some resistance to axial movement of shaft  214 . End  222  of tube  212  has a distal edge  222   a . Preferably, distal edge  222   a  is rounded. However, it will be appreciated that other configurations of distal edge  222   a  may be used.  
      Referring also to  FIGS. 31 and 32 , apertures  230  and  232  are formed through the sidewall of tube  210  at distal end portion  226  of tube  210 , which communicate with the interior defined by tube  210 . Apertures  230  and  232  are shown as aligned and opening to the same direction in which curved members  29  extend, providing an index to the relative orientation between grip  208  and apertures  230  and  232 . However, apertures  230  and  232  may open in any direction relative to grip  208 .  
      As shown in  FIG. 31 , one aperture  230  is larger than the other aperture  232 . While smaller aperture  232  is generally circular, larger aperture  230  is generally oblong circular, extending along axis of tube  210 . In the present example, apertures  230  and  232  are centered on the same axis. Distal edge  230   a  of larger aperture  230  is disposed closer to end  222  of tube  210  than distal edge  232   a  of smaller aperture  232 . Proximal edge  230   b  of larger aperture  30  is disposed further from end  22  of tube  10  than proximal edge  232   b  of smaller aperture  232 . It will be appreciated that edges  230   a  or  230   b  of larger aperture  230  or edges  232   a  or  232   b  of smaller aperture  232  may be positioned differently along axis of tube  210  than what is shown in the figures. Apertures  230  and  232  may be formed by any well-known process, such as by milling or electro discharge machining, by way of example.  
      As seen in  FIG. 33 , end  220  of shaft  214  comprises the cutter blade, which in the embodiment depicted comprises conical shape depression  234  forming an annular sharp edge  236  about the periphery of end  220  of distal end portion  238 . Edge  236  comprises edge  236   a  and edge  236   b.    
      When suture cutter assembly  202  is in the pushing configuration, as shown in  FIG. 34  for the present example, end  220  of shaft  214  will preferably be substantially aligned with proximal edge  230   b  of larger aperture  230 . Thus, in the pushing configuration, end  220  preferably does not occlude any portion of apertures  230  and  232 . Accordingly, suture  240  may be passed through both apertures  230  and  232  when suture cutter assembly  202  is in the pushing configuration. Of course, it will be appreciated that shaft  214  may be configured such that there is some distance between end  220  of shaft  214  and the nearest proximal edge  230   b  or  232   b  of aperture  230  or  232 , respectively, when suture cutter assembly  202  is in the pushing configuration. Likewise, suture cutter assembly  202  may be configured such that, in the pushing configuration, shaft  214  occludes a portion of one or both apertures  230  and/or  232 ; but shaft  214  will preferably not completely occlude both apertures  230  and  232  when suture cutter assembly  202  is in the pushing configuration.  
      When suture cutter assembly  202  is in the pushing configuration, suture cutter assembly  202  may be used to push knots of sutures, as may be desired to tighten such knots. By way of example, where suture  240  has a loose knot, a free end of suture  240  may be passed through open end  222  of tube  210 , then through aperture  230  as shown in  FIG. 35 . With suture cutter assembly  202  in the pushing configuration, end  220  of shaft  214  may act as a guide for the free end of suture  240  as it travels through tube  210  by blocking suture  240  from traveling further up tube  210 , thereby guiding the free end of suture  240  to and through aperture  230 . When a sufficient length of suture  240  has passed through aperture  230 , the operator may grip the free end of suture  240  by any suitable means. Next, the operator may engage distal edge  222   a  of tube  210  with the knot, then slide end  222  of tube  210  along suture  240  so as to push the knot in suture  240 . Those of ordinary skill in the art will appreciate that such pushing may serve to tighten the knot. It will be appreciated that, by making distal edge  221   a  of tube  210  rounded or otherwise smooth, unnecessary wear of suture  240  during such pushing may be avoided.  
      Referring to  FIGS. 36-39 , a process for cutting suture  240  with suture cutter assembly  202  is illustrated. Suture  240  is passed through apertures  230  and  232  so that suture  240  is disposed in apertures  230  and  232 , with end  220  and sharp edge  236  initially located up from apertures  230  and  232 , away from suture  240 , so that end  220  does not occlude any portion of apertures  230  and  232  (e.g., when suture cutter assembly  202  is in the pushing configuration). It will also be appreciated that suture  240  may be passed through both apertures  230  and  232  when suture cutter assembly  202  is in cutting mode, so long as shaft  214  has not been axially advanced far enough through tube  210  as to be prohibitively occlusive of aperture  230  or  232 . With suture  240  disposed in both apertures  230  and  232 , and to the extent that suture cutter assembly  202  is not already in cutting mode, pusher  212  is then rotated 90° to place suture cutter assembly  202  in cutting mode.  
      As seen in  FIGS. 36 and 37 , suture  240  is shown disposed adjacent edge  232   a , generally perpendicular to the longitudinal axes of tube  210  and shaft  214 . However, it will be appreciated that suture  240 , while disposed in apertures  230  and  232  may be spaced from or adjacent to both edges  230   a  and  232   a , until shaft  214  is urged into contacted with suture  240 .  
      In  FIG. 38 , shaft  239  has been moved from the first position shown in  FIG. 37 , urged into contact with suture  240 , with sharp edge  236   a  of end  220  disposed adjacent edge  232   a , and occluding aperture  232  adjacent edge  232   a . The transverse clearance, also referred to as diametrical clearance, between shaft  214  adjacent edge  236   a  and the sidewall of tube  210  adjacent edge  232   a , has a dimension which is less than a corresponding dimension of the suture  240 , such that a portion of suture  240  is captured or retained between the interior surface the sidewall of tube  210  and shaft  214  but larger than a dimension what would sever suture  240 . This configuration makes edge  232   a  the capture edge of aperture  232 . A bend is formed in suture  240  by this action, and shaft  214  and sharp edge  236   b  are concomitantly urged against the opposite side of the interior of tube  210 , the portion adjacent cutting edge  230   a.    
      At the position shown in  FIG. 38 , gap  241 , extending longitudinally, is defined between edge  230   a  and edge  236   b . At the position shown in  FIG. 38 , gap  241  has a longitudinal dimension that is smaller than the corresponding dimension of suture  240 . Gap  241  may be smaller than the corresponding dimension when aperture  232  adjacent edge  232   a  is initially occluded by end  220 .  
      As cutter blade end  220  is advanced toward end  222  of tube  210 , suture  240  is eventually urged against edge  230   a  by sharp edge  236 . As sharp edge  236   b  advances past cutting edge  230   a  to a position so as to occlude aperture  230  adjacent edge  230   a , with suture  240  being cut as the shaft  214  is moved from the first position to the position shown in  FIG. 39 , with the end of severed segment  240   a  of suture  240  being captured as shown in  FIG. 39 . Since the radial clearance between shaft  214  and tube  210  is less than the diameter of suture  240 , the end of severed segment  240   a  does not maintain its original circular cross sectional shape between shaft  214  and tube  210 , but is deformed, such as becoming frayed.  
      Edge  232   a  and edge  236   a  together form a pair, with shaft  214  and tube  210  being configured to retain severed segment  240   a  adjacent to the pair in the position illustrated in  FIG. 39 . The pair of edge  230   a  and edge  236   b  are configured to sever segment  240   a  as shown.  
      As can be seen in  FIG. 39 , grip  208  and pusher  212  are configured such that end  220  of shaft  214  extends beyond edge  230   a . Preferably, end  220  does not extend beyond end  222  of tube  210 , keeping sharp edge  236  protected.  
      As described, the axial offset edges  230   a  and  232   a  function in combination with cutter blade end  220 , the clearance between distal end portion  238  and the internal diameter of tube  210  at distal end portion  226  and suture  240  to initiate capture of suture  240  prior to the cutting action beginning. In this depicted embodiment of the invention, the severed suture segment is captured by a portion extending generally in an axial direction within the interior of the tube, disposed between the shaft and the tube. Within the teaching of this invention, cutting may be initiated before end  220  reaches capture edge  232   a , as long as capture of suture  240  is accomplished before severing suture  240 .  
      The same may be accomplished with distal aperture edges that are aligned (i.e., not axially offset) as seen in  FIG. 240 , which is an alternate embodiment of end  244  of shaft  246  and apertures  242 . In  FIG. 40 , apertures  242  have longitudinally aligned distal edges  242   a  and  242   b . Diametrically opposite sides  244   a  and  244   b  of cutter blade end  244  of shaft  246  are longitudinally (axially) offset relative to each other, creating the offset between capture and cut as previously described. As shaft is advanced to cut suture  240 , capture edge  244   a  contacts suture  240  first, pinching it between shaft  246  and the interior of tube  248  past edge  242   a  resulting in retention of the severed portion of suture  240 . Cutting edge  244   b  is sharp as a result of the curved configuration of shaft  246  forming an angle at edge  244   b  of less than 90° at that location, and cuts suture  240  as it passes edge  242   b.    
      As described thus far, suture cutter  202  includes an axial offset between the initial engagement of the suture on one side, between an end edge of one aperture and the end of the cutter blade, and the initial engagement of the suture on another side, between an end edge of the other aperture and the end of the cutter blade.  
      Thus, it will be appreciated that apertures  230  and  232  need not be sized or shaped differently. It will also be appreciated that apertures  230  and  232  need not be aligned on a common axis. By way of example, one aperture may be located closer to distal end  222  of tube  210  than another equally-sized aperture located on the other side of the axis of tube  210 .  
      In yet another embodiment, a suture cutter according to the teachings of the present invention may also be constructed with the offset between the cutting edge and the capture edge being such that initiation of the cutting occurs prior to initiation of the capture.  FIG. 41  illustrates such an alternate embodiment, which may advantageously be used with a monofilament suture  250 . In this embodiment, capture edge  252   a  of aperture  252  is located closer to end  256  than cutting edge  258   a  of aperture  258 . As shaft  260  is advanced to cut, edge  262   b  of end  262  contacts suture  250  and urges it against edge  258   a  prior to being urged against edge  252   a  and  262   a . A monofilament suture cannot bend as much as a multifilament suture, and suture  250  is cut between edge  258   a  and end  262   b . Preferably, prior to suture  250  being completely severed, the end being severed  250   a  is engaged by advancing edge  262   a , urging and capturing it against capture edge  252   a . The axial travel of shaft  260  is such that edge  262   a  of end  262  captures severed suture  250   a , but is the travel is limited to stop short of cutting severed suture  250   a.    
      Although in the embodiment illustrated, tube  210  and shaft  214  are rigid, they may be flexible as long as the distal end of suture cutter  202  has sufficient rigidity to function according to the teachings of the present invention.  
      Although tube  210  and shaft  214  are circular, they may be any suitable complementary shape.  
       FIGS. 42-44  show yet another embodiment of a shaft  314 . In this example, shaft  314  has sharp edge  336   a  and  336   b  at end  320 , similar to shafts  14  and  214  described above. Shaft  314  also has a relief groove  316  formed near end  320 . In this example, groove  316  is annular, though it will be appreciated that groove  316  need not extend around the full circumference of shaft  314 . For instance, groove  316  may alternatively comprise a generally longitudinal recess formed in the side of shaft  314 . It will also be appreciated that groove  316  may be formed at any suitable longitudinal position along shaft  314  other than the position shown in  FIGS. 42-44 , and may extend to any suitable longitudinal length(s). Similarly, groove  316  may extend inward to any suitable radial depth(s) within shaft  314 . Other suitable variations of groove  316  will be apparent to those of ordinary skill in the art.  
      In addition, while shaft  314  is depicted as being disposed within tube  10 , it will be appreciated that shaft  314  may be used with tube  210  or any other structure. Similarly, while groove  316  is shown as being formed in shaft  314 , it will be appreciated that groove  316  may also be provided in shafts  46  or  246  or any other shaft or structure.  
      A method of using shaft  314  may be similar to methods of using shafts  14  and  214  as described above (e.g., as described in text corresponding with  FIGS. 8-10 , etc.), or may be varied in any suitable way. It will be appreciated that, in the present example, the presence of groove  316  may (or may not) reduce an amount of crimping of severed suture segment  40   a  between shaft  314  and tube  10 . In other words, groove  316  may (or may not) provide a relief area for at least a portion of severed suture segment  40   a  to go into when severed suture segment  40   a  is wedged between shaft  314  and tube  10 . To the extent that such relief and/or reduction in crimping is provided by groove  316 , the amount of force required to advance shaft  314  during cutting of a suture  40  and/or the amount of force required to pull shaft  314  back when releasing severed suture segment  40   a  may (or may not) be reduced relative to the same force(s) required during similar uses of shafts  14  and  214 . It will also be appreciated that the presence of groove  316  may have no other effect on the cutting function of edge  336   a  and/or  336   b . Alternatively, the presence of groove  316  may have an effect on the cutting function of edge  336   a  and/or  336   b . Still other potential effects of having groove  316  (or variations thereof) in shaft  314  will be apparent to those of ordinary skill in the art.  
      Although stainless steel suture material is specifically discussed herein, it will be understood that the present invention is not limited to use with stainless steel, and may be used with any suture material, such as, by way of example only, polymer, gut, or absorbable material.  
      By way of non-limiting example, a suture cutter as described above for use in arthroscopic surgery was constructed of material suitable for tissue contact, with a tube outer diameter of 0.120 and a cutter shaft outside diameter of 0.093, having 0.002 clearance between it and the inside diameter of the tube at the distal end, for use with a 2-0 stainless steel braided suture having a nominal diameter of 0.013 inches, comprised of 49 strands. The smaller aperture has a generally uniform diameter of 0.070. The larger aperture has a smallest dimension of 0.070, with the distance between edges comprising the elongated portion being 0.115. The distal edge of the larger aperture is 0.022 distally further than the distal edge of the smaller aperture. Of course, other suitable dimensions may be used.  
      As an alternative, non-limiting example, a suture cutter as described above may be constructed with a tube outer diameter of 0.120 and a cutter shaft outside diameter of 0.070, having 0.002 clearance between it and the inside diameter of the tube at the distal end. Of course, other suitable dimensions may be used.  
      In summary, numerous benefits have been described which result from employing the concepts of the invention. The foregoing description of a preferred embodiment of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Obvious modifications or variations are possible in light of the above teachings. The embodiment was chosen and described in order to best illustrate the principles of the invention and its practical application to thereby enable one of ordinary skill in the art to best utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims appended hereto.