Patent Publication Number: US-10772618-B2

Title: Crimping instrument with reduced dimension, continued compatibility, and tissue protection features

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. application Ser. No. 14/325,824 filed Jul. 8, 2014 and claims priority to the 14/325,824 application. 
    
    
     FIELD 
     The claimed invention relates generally to surgical instruments for crimping a sleeve to a secured suture, and more particularly to such a surgical instrument having advantageously reduced dimensions compatible with more minimally invasive surgical procedures, while maintaining continued compatibility with proven and extremely reliable crimping sleeves, and providing enhanced tissue protection features. 
     BACKGROUND 
     Malleable suture fasteners such as the sleeves sold under the trademarks Ti-KNOT® and COR-KNOT® by LSI Solutions, Inc. are a significant improvement over hand or instrument-tied knots in laparoscopic surgical procedures. The sleeves, which are made of a malleable material that has proven safe with prolonged exposure to body tissue, are slid over two or more strands of suture and deformed or crimped to secure the strands of suture. 
     An exemplary crimping instrument is shown in U.S. Pat. No. 7,235,086, entitled “CRIMPING INSTRUMENT WITH MOTION LIMITING FEATURE”, assigned to LSI Solutions, Inc., of Victor, N.Y.  FIG. 1  illustrates such a crimping device  20 , having a handle  22  with an actuator  24  that is movable relative to the handle  22 . A hollow shaft  26  extends from the handle  22  to a distal end  28  of the shaft  26 . The distal end  28  of the shaft  26  can be seen more clearly in the partial cross-sectional view of  FIG. 1A . 
     Suture ends  30  can be threaded through a crimping sleeve  32  held between a hammer  34  and an anvil  36 . The suture ends  30  pass out a hole in the side of the shaft  26 , and the device can be used to position the crimping sleeve  32  at a desired location on the suture  31  relative to a surface  38  through which the suture  31  has been secured (for example, tissue, a replacement anatomical structure such as a heart valve, or an augmentive anatomical structure such as a heart valve annulus). 
     Squeezing the actuator  24  towards the handle  22  causes a wedge  40 , located in the shaft  26 , to advance and to force the hammer  34  into the crimping sleeve  32 . The hammer  34  crimps the crimping sleeve  32  against the anvil  36 , and the suture  31  is held tightly by the deformed sleeve  32 . A blade  42  may also be incorporated within the shaft  26  and can be simultaneously moveable by the actuator  24  in order to trim the suture ends  30 . 
     Such instruments for attaching suture fasteners  32  have proven to be very effective. The Ti-KNOT® and COR-KNOT® devices from LSI Solutions, Inc. (information available at www.lsisolutions.com) have been widely accepted by surgeons for the recognized benefits of time savings, ease of use, and reliability. (See, for example, “New Knot Tying Technique for Minimally Invasive Approach to Mitral Valve Repair”, an abstract by Rodriguez, Sutter, and Ferdinand presented at the AATS 2011 Mitral Conclave in New York, N.Y. in 2011 or “Use of Automatic Knot-Tying and Cutting Device is Shortening Aortic Cross-Clamp Times in Minimally Invasive Mitral Valve Surgery”, an abstract by Gersak and Robic presented at the 26th Annual EACTS Meeting in Barcelona, Spain in 2012.) 
     Devices like the COR-KNOT® device enable many types of minimally invasive surgery (MIS), or, more specifically, minimally invasive cardiac surgery (MICS). MIS is a type of surgery performed through one or more small incisions or access sites created in a patient. MIS has been shown to have at least equivalent morbidity and mortality outcomes as compared to conventional approaches, with reported advantages of reduced postsurgical pain, better respiratory function, shorter hospital stay, and improved cosmesis. Such advantages are increased with ever smaller sized MIS access points. As a result, it is very desirable to have smaller and smaller MIS tools which can enable the use of such smaller MIS access points. In other MIS approaches, specifically, for example MICS for aortic valve replacement, a smaller device tip, especially with more rounded edges, would be easier to position remotely and would reduce the potential for device-related tissue trauma and/or prosthetic damage. 
     The outside of the prosthetic valve shall be close in size to the space available at the aortic root. The larger a replacement aortic valve&#39;s blood passage area is relative to the opening in the outflow track of the left ventricle, the more blood can pass through without flow disturbances. After removing the diseased native valve, it is therefore desirable to install a replacement prosthetic valve with the largest possible diameter into the aortic root. Replacement heart valves usually have a sewing ring attached to and just peripheral to the valve leaflet. This ring is typically several millimeters wide, is designed to be sutured to the aortic root, and can then be secured in place with mechanical knots. Given the narrow space available over the sewing ring between the valve leaflets and the aortic root, a mechanical knot delivery device about the same size as the radial width of a sewing ring is desired. A narrower MICS device tip would enable less challenging placement of the mechanical knot into this narrow space as well as easier device tip positioning and removal. A narrow device tip can also enable the use of larger diameter valves for improved blood flow. 
     Unfortunately, it is not a simple matter to reduce the size of all of the components in a device such as the current COR-KNOT® device because such changes could also impact the size (and therefore the operating properties) of the mechanical crimping sleeve  32 . Devices such as the COR-KNOT® device are always put through rigorous testing and qualification procedures, both internally with the manufacturer and externally, such as when obtaining Food and Drug Administration (FDA) and European Community (CE mark)clearance. Currently, the outside diameter of the COR-KNOT® device shaft  26  is approximately two-hundred thousandths of an inch. The inside diameter of the shaft  26  is approximately one hundred seventy-six thousandths of an inch, while the titanium sleeve  32  has an outside diameter of approximately forty-nine thousandths of an inch. Subtracting the room needed for the sleeve  32  within the shaft  26 , this means that the current COR-KNOT® device only has about one hundred twenty-seven thousandths of an inch to accommodate the hammer  34 , anvil  36 , travel space for the wedge  40 , and various associated tolerances. Reducing the size of the crimpable sleeve to gain more room in a smaller shaft could potentially require a different size crimpable sleeve. The current sleeve has been very successfully used in over 250,000 patients throughout the world. This sleeve size has proven completely reliable and useful with a broad range of common surgical sutures; no failures have been reported after securing over 1.8 million sutures. This sleeve size is remarkably effective and well-received; changing its dimensions or configuration would have the potential to render it less efficacious. Likewise, it would be unwise to change the operating features of the hammer  34  and anvil  36  which impart the reliable crimped configuration for the proven suture sleeve  32 . Still, it would be desirable to have a crimping device  20  with smaller shaft  26  dimensions in order to enable use with ever smaller MIS access points and in MICS applications. 
     Therefore, there is a need for a surgical crimping instrument having smaller dimensions when compared to the currently available devices, which are already quite small. Furthermore, there is a need for such a reduced dimension surgical crimping instrument to have continued compatibility with existing uncrimped sleeves for loading and crimping them to an identical configuration to ensure the continuation of reliability and performance from such proven sleeves. Finally, there is a need for such devices to place a premium on patient safety, so it would also be desirable for this surgical crimping instrument to have even further enhanced tissue protection features. 
     SUMMARY 
     An instrument for crimping a suture fastener to a surgical suture is disclosed. The instrument has a shaft and an expanded receiving face configured to receive the suture fastener and to provide a smoothing radius for a distal end of the shaft. The instrument also has an anvil in the distal end of the shaft. The instrument further has a hammer in the distal end of the shaft and moveable relative to the anvil for crimping the suture fastener therebetween and received in the expanded receiving face. The instrument also has a pusher moveable in a direction substantially parallel to a longitudinal axis of the shaft and configured to engage at least one of the hammer and the anvil for urging the hammer and the anvil together. 
     Another instrument for crimping a suture fastener to a surgical suture is disclosed. The instrument has a shaft and a crimping member coupled to a distal end of the shaft and comprising first and second opposed legs. The instrument also has an anvil located near the end of the second opposed leg. The instrument further has an expanded receiving face coupled to the anvil. The expanded receiving face is configured to receive the suture fastener and to provide a smoothing radius for a distal end of the shaft. The expanded receiving face also comprises a collar recess configured to hold a collar of the suture fastener. The instrument also has a hammer near the end of the first opposed leg and moveable relative to the anvil for crimping the suture fastener therebetween and received in the expanded receiving face. The instrument further has a pusher moveable in a direction substantially parallel to a longitudinal axis of the shaft and configured to engage the hammer for urging the hammer towards the anvil. The instrument also has a suture cutting blade coupled to the pusher. The crimping member comprises one or more blade steering guides, and the first opposed leg comprises a flexure. 
     A further instrument for crimping a suture fastener to a surgical suture is disclosed. The instrument has a shaft and a crimping member coupled to a distal end of the shaft and comprising first and second opposed legs. The instrument also has an anvil located near the end of the second opposed leg. The instrument further has an expanded receiving face coupled to the anvil. The expanded receiving face is configured to receive the suture fastener and to provide a smoothing radius for a distal end of the shaft. The expanded receiving face also comprises a collar recess configured to hold a collar of the suture fastener. The instrument also has a hammer near the end of a flexure of the first opposed leg and moveable relative to the anvil for crimping the suture fastener therebetween and received in the expanded receiving face. The instrument further has a pusher moveable in a direction substantially parallel to a longitudinal axis of the shaft and configured to engage the hammer for urging the hammer towards the anvil. The instrument also has a rotation knob coupled to the shaft, rotationally coupled to the pusher, and configured to rotate the shaft and pusher, and consequently the hammer, the anvil, and the expanded receiving face, around the longitudinal axis of the shaft. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a prior art surgical crimping instrument for crimping a suture fastener to one or more sutures. 
         FIG. 1A  shows an enlarged partial cross-sectional view of the distal end of the shaft of the prior art surgical crimping instrument of  FIG. 1 . 
         FIG. 2  illustrates, in cross-sectional view, the distal end of a new embodiment of an instrument for crimping a suture fastener to a surgical suture, the instrument enabling reduced dimensions when compared to the prior art while being backwards compatible with existing, FDA approved crimpable sleeves. A crimpable sleeve is not yet installed in the instrument shown in  FIG. 2 . 
         FIG. 2A  shows an enlarged cross-sectional view of the distal end of the shaft of the instrument from  FIG. 2 . 
         FIG. 3  illustrates, in cross-sectional view, the distal end of the instrument for crimping a suture fastener from  FIG. 2  with a crimpable sleeve installed in one embodiment of an expanded receiving face. 
         FIG. 3A  shows an enlarged cross-sectional view of the expanded receiving face from the instrument embodiment shown in  FIG. 3 . 
         FIGS. 3B-3C  are enlarged cross-sectional views of other embodiments of an expanded receiving face for an instrument for crimping a suture fastener. 
         FIG. 4  is a partially schematic, exploded perspective view of one embodiment of an instrument for crimping a suture fastener. 
         FIG. 5  is a perspective view of one embodiment of a crimping member having a hammer, an anvil, and an expanded receiving face. 
         FIG. 6  is a perspective view of one embodiment of a pusher configured to engage a hammer. In this embodiment, a suture cutting blade is coupled to the pusher. 
         FIG. 7  is a partial cross-sectional side view of the embodied instrument for crimping a suture fastener from  FIG. 2  with suture ends passed through a crimpable sleeve on one end of the instrument and exiting through a slot in the bottom of the instrument. 
         FIG. 7A  is a bottom view of the embodied instrument for crimping a suture fastener from  FIG. 7B . 
         FIG. 8  is a partial cross-sectional side view of the embodied instrument for crimping a suture fastener from  FIG. 7  with a pusher advanced to a first position where the hammer is forced down onto the crimpable sleeve, towards the anvil, resulting in a suture holding crimp being formed in the crimpable sleeve. 
         FIG. 8A  is a cross-sectional view taken along line  8 A- 8 A from  FIG. 8 , looking down the device shaft, and illustrating one embodiment of a blade steering guide formed in the anvil of the instrument for crimping a suture fastener. 
         FIG. 9  is a cross-sectional side view of the embodied instrument for crimping a suture fastener from  FIG. 8  with the pusher advanced to a second position where a blade coupled to the pusher is cutting the free suture ends protruding from the crimpable sleeve. 
         FIGS. 10A-10J  illustrate different crimping members having a variety of flexure embodiments. 
         FIG. 11  is a partially exposed perspective view of one embodiment of an instrument having a rotatable shaft for crimping a suture fastener. 
         FIG. 11A  is a side cross-sectional view of the instrument for crimping a suture fastener from  FIG. 11 . 
         FIG. 11B  is a cross-sectional view of the instrument for crimping a suture fastener from  FIG. 11A  taken along line  11 B- 11 B. 
     
    
    
     It will be appreciated that for purposes of clarity and where deemed appropriate, reference numerals have been repeated in the figures to indicate corresponding features, and that the various elements in the drawings have not necessarily been drawn to scale in order to better show the features. 
     DETAILED DESCRIPTION 
       FIG. 2  illustrates, in cross-sectional view, the distal end  44  of one embodiment of an instrument for crimping a suture fastener to a surgical suture. It should be understood that the term “suture”, as used herein, is intended to cover any thread, cable, wire, filament, strand, line, yarn, gut, or similar structure, whether natural and/or synthetic, in monofilament, composite filament, or multifilament form (whether braided, woven, twisted, or otherwise held together), as well as equivalents, substitutions, combinations, and pluralities thereof for such materials and structures. The distal end  44  includes a shaft  46  which houses some of the instrument components, including a hammer  48 , and anvil  50 , and a pusher  52 . The hammer  48  is movable relative to the anvil  50  for crimping a suture fastener  54  therebetween. In this view, the suture fastener  54  is not yet installed in the device. However, in later views, the suture fastener  54  will be installed and the operation of the hammer  48  and the anvil  50  will be discussed in more detail. Generally, however, the pusher  52  is moveable in a direction substantially parallel to a longitudinal axis of the shaft  46  and is configured to engage at least one of the hammer  48  and the anvil  50  for urging the hammer  48  and anvil  50  together. 
     The crimping instrument also includes an expanded receiving face  56  configured to receive the suture fastener  54 . The expanded receiving face  56  can be seen in more detail in the enlarged cross-sectional view of  FIG. 2A . Unlike the prior art where the receiving face is flush with the end of the shaft, in the claimed invention, the expanded receiving face  56  sticks out a longitudinal distance D 1  past the end of the shaft  46 . In some embodiments, the expanded receiving face  56  is also sized to reach beyond the inside diameter (ID) of the shaft  46  and outward towards, to, or beyond the outside diameter (OD). For example, the expanded receiving face  56  in the embodiment of  FIG. 2A  expands radially a distance D 2  past the inner diameter (ID) towards the outside diameter (OD). Depending on the embodiment, a rounded edge  58  can be formed on the expanded receiving face  56  at least partially within the expansion distances D 1  and D 2.  This rounded edge  58  of the expanded receiving face  56  can provide one measure of tissue protection when the tip of the instrument is brought into contact with a patient. This can be especially important in light of the small dimensions involved in the construction of such a small minimally invasive device. In the prior art device, where the receiving face was flush with the end of the shaft, minimal corner rounding could be provided in the shaft due to the thinness of the shaft wall. As the size of the device is reduced, and the shaft wall is potentially made even thinner, there is just not enough thickness in the wall for adequate rounding. The expanded receiving face  56  provides a solution to this problem by allowing a rounded surface  58  to be formed which can protect tissue from the potentially sharp edges of the shaft  46 . 
     Despite these advantages of the expanded receiving face  56 , it was still counterintuitive to expand the receiving face from the previous design because it would have meant moving the position where the suture fastener is normally held out beyond a nominal position where the hammer and anvil could act properly on it when crimping. However, in embodiments such as the one illustrated in  FIG. 2A , the expanded receiving face  56  also has a collar recess  60 , configured to hold a collar  62  of the suture fastener  54 . With a collar recess  60 , an expanded receiving face  56  can be implemented while a desired position of the suture fastener  54  can be maintained relative to the hammer  48  and the anvil  50 . 
     These are advantages which have been identified in the inventive concept, but it was still counter-intuitive that expanding the device would be a key to making it smaller. As it turns out, however, and without being limited to one particular theory, expanding the receiving face  56  as described above provides additional structural support to the hammer  48  and anvil  50  pieces which may he coupled directly or indirectly to the expanded receiving face  56 . This additional support further enables the reduction of outer hammer  48  and/or anvil  50  material near where the hammer  48  and anvil  50  contact the shaft  46  and away from the surfaces of the hammer  48  and anvil  50  which come together. This allows a smaller diameter shaft  46  to be used while still maintaining the ability to work with an existing size suture fastener  54  and to impart the same crimping profiles into the suture fastener  54 . In fact, use of the expanded receiving face  56  design has enabled the successful manufacture and testing of crimping instruments with an outside diameter of approximately 0.177 inches versus the previous outside diameter of approximately 0.203 inches, a 12% reduction in outside diameter while providing the exact same sized crimpable suture fastener. Other embodiments may show even greater size reductions, and all of these reductions may enable even smaller devices in remote, constrained surgical areas, thereby helping to improve patient outcomes. 
       FIG. 3  shows the distal end  44  of the instrument from  FIG. 2  with a crimpable suture fastener  54  (crimpable sleeve) installed in the collar recess  60  of the expanded receiving face  56 . In this embodiment, the hammer  48  and the anvil  50  are part of a crimping member  64  which has first and second opposed legs  66 ,  68 . The hammer  48  is located near the end of the first opposed leg  66 , while the anvil  50  is located near the end of the second opposed leg  68 . The shaft  46  and the second leg  68  define respective openings  70 ,  72  to allow suture ends (not shown here, but will be shown later) to pass from the collar  62 , through and out of the other end of the suture fastener  54 , between the first and second opposing legs  66 ,  68 , and then out through openings  70 ,  72  to an area outside of the shaft  46 . In this embodiment, part of the suture fastener  54  rests against the anvil  50 , while the hammer  48  is positioned just above the suture fastener  54 . In other embodiments, the hammer  48  may be configured to be just touching or biased against the suture fastener  54  to help hold it in place before crimping. Depending on the embodiment, this starting position of the hammer  48  can be influenced by the configuration of a flexure portion  74  in the first opposing leg  66 . Different flexure  74  options will be discussed later in this specification. 
       FIG. 3A  shows an enlarged cross-sectional view of the expanded receiving face  56  from the instrument embodiment shown in  FIG. 3 . For some embodiments, such as the one shown in  FIG. 3A , the collar recess  60  is a partial recess in the sense that, despite the collar recess  60 , a portion of the suture fastener&#39;s collar  62  still sticks out past the end of the expanded receiving face  56 . In other embodiments, such as the one illustrated in  FIG. 3B , the collar recess  60 B is a flush recess because the suture fastener&#39;s collar  62  is flush with the end of the alternate expanded receiving face  56 B. In still other embodiments, such as the one illustrated in  FIG. 3C , the collar recess  60 C is an over-deep recess because the suture fastener&#39;s collar  62  is set below the end of the alternate expanded receiving face  56 C. 
     Before discussing the operation of the instrument for crimping a suture fastener in more detail, it is helpful to understand how the parts of this device embodiment are assembled together. Accordingly,  FIG. 4  is a partially schematic, exploded perspective view of one embodiment of an instrument for crimping a suture fastener. The crimping member  64 , discussed previously, can be inserted into the distal end  44  of the shaft  46 . A recess  76  in the crimping member  64  can be pinned, staked, or otherwise held in place at a corresponding pinning location  78  in the shaft  46  in order to keep the crimping member  64  from coming out of the shaft  46 . The pusher  52  can be coupled to or an extension of a push rod  80 . The push rod  80  may include a coupling feature  82  configured to be coupled to a handle/actuator  84 . The actuator  84  can be any type of manually operated or automated device, such as, but not limited to a lever, an arm, a knob, a slide, a motor, a solenoid, or any plurality and/or combination thereof which can be used to slide the pusher  52  back and forth within the shaft  46  along a path which is substantially parallel to a longitudinal axis of the shaft  46 . One suitable actuator  84  is the handle and lever disclosed in U.S. Pat. No. 7,235,086 entitled “CRIMPING INSTRUMENT WITH MOTION LIMITING FEATURE”, the entirety of which is hereby incorporated by reference. 
     A suture cutting blade  86  can be coupled to and/or held by the pusher  52 . Operation of the cutting blade  86  will be discussed in more detail later in this specification. In other embodiments, the cutting blade  86  may be a continuous extension of the pusher assembly  88 , rather than a separate part from the pusher  52 . The pusher assembly  88  can be placed into the proximal end  90  of the shaft  46  and into engagement with the crimping member  64 . As will be described later, the crimping member  64  may include one or more blade steering guides (not easily visible in this view) configured to restrict lateral movement of the suture cutting blade  86  away from the direction substantially parallel to the longitudinal axis of the shaft  46 . 
       FIG. 5  is a perspective view of one embodiment of a crimping member  64  having a hammer  48 , an anvil  50 , and an expanded receiving face  56 . The crimping member  64  has first and second opposing legs  66 ,  68  which are configured to resiliently bias the hammer  48  and anvil  50  apart unless urged together by the pusher (not shown in this view). In this embodiment, the expanded receiving face  56  is an extension of the second opposing leg  68 , past where the anvil  50  is located. In other embodiments, the extended receiving face  56  could be an extension of the hammer  48 , for example in embodiments where the hammer  48  does not move while the anvil does. In still other embodiments, it is possible for the extended receiving face  56  to be separate from both the hammer  48  and the anvil  50 , but it is preferred to have the extended receiving face  56  be an extension of the leg including the anvil  50  as shown in the embodiment of  FIG. 5 . The collar recess  60 , the flexure portion  74 , the recess  76 , the opening  72  defined by the second leg  68 , and the rounded edge  58  of the expanded receiving face  56 , all discussed previously, can be seen in more detail the view of this embodiment. 
       FIG. 6  is a perspective view of one embodiment of a pusher  52  configured to engage a hammer (not shown in this view). In this embodiment, a suture cutting blade  86  is coupled to the pusher  52 . The pusher  52  can include a contoured notch  92  to help advance and retract the blade  86 . Those skilled in the art will know a variety of ways a blade  86  could be attached to the pusher  52 . The blade  86  can be configured to extend forward relative to the end of the pusher  52  so that the suture blade  86  is in a position to cut suture ends after or just as the suture fastener is crimped. 
       FIGS. 7, 8, and 9  illustrate the operation of a surgical instrument embodiment for crimping a suture fastener.  FIGS. 7A and 8A  illustrate additional detail for this described operation. In particular,  FIG. 7  is a partial cross-sectional side view of the embodied instrument for crimping a suture fastener from  FIG. 2  (and discussed above). A suture  94  has been secured into one or more objects  96 ,  98  for example, a tissue prosthetic valve sewing ring and underlying aortic annular tissue. The suture ends  100  have been passed through a suture fastener  54  (crimpable sleeve) loaded into the expanded receiving face  56  on the distal end  44  of the instrument. The suture ends  94  also pass through the openings  72 ,  70 , defined by the second opposed leg  68  and the shaft  46 , respectively, and accordingly exit the bottom of the instrument. This loading of the suture  94  can be accomplished, for example, with a snare device, not shown, but known to those skilled in the art.  FIG. 7A  is a non-cross-sectioned bottom view of the device and situation shown in  FIG. 7 . 
     The pusher  52  is resting on a portion of the first opposed leg  66  which does not substantially force the hammer  48  into contact with the suture fastener  54 . In other embodiments, the first opposed leg may include a pre-load bump (not shown in this embodiment, but examples will be shown later) which would cause the hammer to be pre-loaded lightly against the suture fastener  54  in order to help hold it in place prior to crimping. The suture cutting blade  86  is positioned adjacent to the openings  70 ,  72 , but cannot cut the suture ends  100  at this point. 
     As shown in the partial cross-sectional side view of  FIG. 8 , the pusher  52  has been advanced by an actuator (not shown) to a first position where the hammer  48  is forced down onto the suture fastener  54 , towards the anvil  50 , resulting in a suture holding crimp being formed in the suture fastener  54 . Before the pusher  52  is advanced to the position shown in  FIG. 8 , the expanded receiving face  56  can be moved into contact with at least one of the one or more sutured objects  96 ,  98  as tension is applied to the suture ends  100  to remove suture slack prior to crimping. When the pusher  52  has been advanced to the first position shown in  FIG. 8 , the suture cutting blade  86  is also starting to cross the openings  70 ,  72 , but the suture ends  100  are not in a position to be cut yet. 
       FIG. 8A  is across-sectional view taken along line  8 A- 8 A from  FIG. 8 , looking down the device shaft  46 , and illustrating one embodiment of blade steering guides  102  formed in the anvil  50 . Since the anvil  50  is coupled to or an extension of the second opposed leg  68 , the blade steering guides  102  could also be said to be formed in the second leg  68  as well. The one or more blade steering guides  102  are configured to help restrict lateral movement of the suture cutting blade  86  away from a direction substantially parallel to the longitudinal axis of the shaft  46 . 
       FIG. 9  is a cross-sectional side view of the embodied instrument for crimping a suture fastener from  FIG. 8  with the pusher  52  advanced to a second position where the blade  86  coupled to the pusher  52  has advanced to the point where it is able to cut the suture ends  100 . Depending on the configuration, the blade  86  can extend towards the distal end of the device far enough to cut the suture ends  100  without any assistance from a user of the device. In other embodiments, the blade  86  can extend to the point where the suture ends  100  are pinched against the blade  86 , and the user controls the moment when the suture cut is completed by pulling on the suture ends  100 . When the pusher  52  is in this second position, the hammer  48  does not have to crimp the suture fastener  54  further due to opposing surfaces  104  on the hammer  54  and anvil  50  which can be arranged to limit the hammer  48  motion. 
     As mentioned previously (for example, with regard to  FIG. 5 ), some embodiments of an instrument for crimping a suture fastener to a surgical suture can include a crimping member having first and second opposed legs  66 ,  68 . In such embodiments, the hammer  48  may be located near the end of the first opposed leg  66 , while the anvil  50  may be located at the end of the second opposed leg. The first opposed leg  66  may also include a flexure portion. The flexure flexes to allow the hammer  48  to be moved towards the anvil  50  by the pusher  52 .  FIGS. 10A-10J  illustrate different crimping members having a variety of flexure embodiments. For example, the embodiments of  FIGS. 10A and 1013  have a straight flexure  106  which is oriented to be substantially perpendicular to the expanded receiving face  56  when not being flexed under a load. The embodiment of  FIG. 10B  also has a pre-load bump  108  on the flexure  106 . The pre-load bump  108  can be used in some embodiments to provide a slight interference with the pusher (not shown here) before the pusher is advanced into contact with the hammer  48 . This slight interference can deflect the hammer  48  slightly against a suture fastener (not shown) held in the expanded receiving face  56  in order to keep the fastener from falling out of the device prior to crimping. 
       FIG. 10C  illustrates another embodiment of a crimping member having a straight flexure  110 , however this straight flexure is not substantially perpendicular to the expanded receiving face  56  when not being flexed under a load. The embodiment of  FIG. 10C  also includes a pre-load bump  108 , the features of which have been discussed above. 
     Some flexure embodiments will not be straight. As examples, the crimping member embodiments of  FIGS. 10D and 10E  include an arced flexure  112  having a single bend in the flexure  112 . The embodiment of  FIG. 10E  also includes a pre-load bump  108 , the features of which have been discussed above. Other crimping member embodiments may have wavy flexures with more than a single bend. For example, the crimping member embodiments of  FIGS. 10F-10I  include a wavy flexure  114 . The embodiment of  FIG. 10H  also includes a pre-load bump  108 , the features of which have been discussed above. Other flexure embodiments are possible, including, but not limited to a hairpin flexure that doubles back on itself. For example, the crimping member embodiment of  FIG. 10J  includes a hairpin flexure  116 . The embodiment of  FIG. 10J  also includes a pre-load bump  108 , the features of which have been discussed above. 
     The embodiments of a crimping instrument with reduced dimension and compatibility with an existing, proven knot, which have been discussed above, also have tissue protection features, such as the sharp edge avoidance made possible by the expanded receiving face on smaller dimensioned devices. Other embodiments may include an additional tissue protection feature, for example a rotatable shaft which enables an operator to orient the direction of the crimped suture fastener to orient the direction of the suture tails away from delicate structures. As one example,  FIG. 11  is a partially exposed perspective view of one embodiment of an instrument  118  for crimping a suture fastener. The instrument  118  has a rotatable shaft  120  with a rotation knob  122  coupled to the shaft  120  and configured to simultaneously rotate the shaft  120  and the push rod  140 . The rotation knob  122  can have a variety of shapes, and in some embodiments, the rotation knob  122  could be the shaft itself. In this embodiment, the rotation knob  122  also includes a crimp direction indicator  124  that correlates with a direction that the crimps formed in a suture fastener will direct trimmed suture tails. Depending on the embodiment, the crimp direction indicator  124  could point in a direction the suture tails will point. In other embodiments, the crimp direction indicator  124  could point in the opposite direction. In either case, or with any readily predictable correlation between the crimp direction indicator  124  and the crimped fastener produced by the instrument  118 , the operator of the instrument  118  can readily orient the device handle  126  and/or shaft rotation knob  122  to have the suture tails face a desired direction. This tissue protection feature can be especially helpful when installing artificial heart valves, as it may be desirable to have the crimped fasteners direct the suture tails away from the valve so as not to have tissue or valve material contacting the crimped fastener surface or the suture tails. Since it may not always be possible or ergonomically practical for a surgeon to rotate the handle  126  of the device, embodiments having a rotatable shaft  120  offer more orientation flexibility to the surgeon, thereby enabling tissue and prosthetic protection. 
     An actuator lever  128  is pivotably coupled to the handle  126  at pivot point  130 . A biasing spring  132  is coupled between the handle  126  and the actuator  128 , rotating the actuator  128  counterclockwise around the pivot point  130  until the actuator  128  contacts the handle  126  at stop point  134 . The actuator  128  also has a socket  136  which receives a ball end  138  of push rod  140 .  FIG. 11A  is a side cross-sectional view of the instrument  118  from  FIG. 11 . Push rod  140  may be coupled to the pusher  52  or continuous with the pusher  52  as shown in  FIG. 11A . When the actuator  128  is in the resting position shown, the push rod  140  is retracted away from the distal end  44  of the shaft  120 . In this position, as discussed above, the pusher is not engaging the hammer  48 . However, if the actuator  128  is squeezed towards the handle  126 , the actuator socket  136  will advance the push rod  140  (and therefore the pusher  52 ) towards the distal end  44 , thereby enabling the pusher  52  to engage the hammer  48  as discussed above in order to crimp a suture fastener. 
     The rotation knob  122  has a portion  142  which extends into the handle  126 . The handle  126  can include structure to rotatably support this portion  142  of the rotation knob  122 . For clarity and visualization of other structures, rotational supports are not shown, but those skilled in the art will clearly know that such supports may easily be incorporated. A portion of the rotation knob  122  may include one or more facets  144  which can be sized to engage a constraint, here illustrated as an embodiment with an upper constraint  146 A and a lower constraint  146 B. Those skilled in the art will recognize that facets may include but are not limited to, such structures as recesses, bumps, and angled edges. For convenience, however, such structures and their equivalents will simply be referred to herein as facets. A profile of the facets  144  and the constraints  146 A,  146 B can be seen in the view of  FIG. 11B , which is a cross-sectional view taken along line  11 B- 11 B from  FIG. 11A , looking from a location in the handle towards the distal end of the device. When a facet  144  is flat against the constraint  146 A,  146 B, rotation of the shaft  120  (to which the rotation knob  122  is coupled) will be resisted. However, the facets  144  (of the rotation knob  122 ) and/or the constraints  146 A,  146 B may be made from a flexible material so that an external force applied to the rotation knob  122  can cause the facets  144  and/or the constraint  146 A,  146 B to deflect or deform, allowing the shaft  120  to rotate until other facets  144  contact the constraints  146 A,  146 B. The mating of the facets  144  with the constraint  146 A,  146 B can be felt by the user, thereby enabling indexing of the shaft rotation positions. In the embodiment illustrated in  FIG. 11B , the rotation knob  122  has twelve facets, however other embodiments may have a different number and/or type of facets. Other embodiments may not include facets, but may be configured to include rotational resistance so that the shaft does not rotate at undesired times. 
     The rotation knob  122  is coupled to the shaft  120 . The push rod  140  is configured to be able to slide through the rotation knob  122  in directions parallel to the longitudinal axis of the shaft  120 . In this embodiment, the push rod  140  also has one or more keyed features  141  which can slide longitudinally in a mating fashion within corresponding one or more slots  143  in the rotation knob  122 . The one or more keyed features  141  permit longitudinal movement of the push rod  140  for crimping operations. When the rotation knob  122  is rotated, however, the one or more keyed features  141  engaged the corresponding one or more slots  143  to rotationally couple the push rod  140  to the rotation knob  122 . In this way, since the rotation knob  122  is also coupled to the shaft  120 , both the push rod  140  and the shaft  120  are rotated directly by the rotation knob  122 . In other embodiments, the rotation knob  122  may only be rotationally coupled to the shaft  120 . In such embodiments, when the knob  122  is rotated, the rotational force would have to be transferred to the push rod  140  via the crimping member and hammer in the distal end of the shaft  120 . While such an embodiment is possible, it is not ideal because of the larger stresses placed on the components in the distal end of the device. 
     Various advantages of a crimping instrument with reduced dimension, continued compatibility, and tissue protection features have been discussed above. Embodiments discussed herein have been described by way of example in this specification. It will be apparent to those skilled in the art that the forgoing detailed disclosure is intended to be presented by way of example only, and is not limiting. Various alterations, improvements, and modifications will occur and are intended to those skilled in the art, though not expressly stated herein. These alterations, improvements, and modifications are intended to be suggested hereby, and are within the spirit and the scope of the claimed invention. Additionally, the recited order of processing elements or sequences, or the use of numbers, letters, or other designations therefore, is not intended to limit the claims to any order, except as may be specified in the claims. Accordingly, the invention is limited only by the following claims and equivalents thereto.