Abstract:
An improved suture cutter for cutting high strength sutures used in arthroscopic surgeries includes a movable handle that moves rotationally around a pivot. This rotational motion is translated through a linkage into near linear movement at the distal end of a moving member. At the distal end, the moving member pushes a cutting blade onto an inclined stationary blade and thereby cuts a suture captured between the moving cutting blade and the inclined stationary blade.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a suture cutter, and more particularly to a suture cutter for cutting high strength sutures. 
       BACKGROUND OF THE INVENTION 
       [0002]    Suture cutters usually include one cutting blade pressed onto an anvil or a cradle, or two cutting blades sliding past each other and being held together with mechanical means. Most of these suture cutters are suitable for cutting standard sutures such as braided silk or polypropylene sutures. In some cases, however, ultra high strength sutures made of abrasive or otherwise tough materials are used for fastening tissue to bone or to other tissue. Cutting ultra high strength sutures with conventional suture cutters is not efficient and frequently results in unacceptable fraying of the suture ends. Accordingly, there is a need for an improved suture cutting mechanism suitable for cutting high strength sutures, such as sutures made of ultra-high molecular weight polyethylene (UHMWPE). 
       SUMMARY OF THE INVENTION 
       [0003]    The present invention describes an improved mechanism for cutting high strength sutures used in arthroscopic surgeries. The suture cutting device includes a movable handle that moves rotationally around a pivot. This rotational motion is translated through a linkage into near linear movement at the distal end of a moving member. At the distal end, the moving member pushes a cutting blade onto an inclined stationary blade and thereby cuts a suture captured between the moving cutting blade and the inclined stationary blade. 
         [0004]    In general, in one aspect, the invention features a suture cutting instrument including a handle assembly, a driver, and a suture cutting assembly. The handle assembly includes a stationary handle and a movable handle pivotally connected to the stationary handle at a pivot and the movable handle moves rotationally around the pivot. The driver has a proximal end connected to the movable handle and is configured to reciprocate longitudinally when the movable handle moves rotationally around the pivot. The suture cutting assembly includes a movable cutting blade and an inclined stationary blade. The movable cutting blade is connected to a distal end of the driver and is configured to move longitudinally onto the inclined stationary blade when the movable handle moves rotationally around the pivot and thereby to cut a suture captured between the movable cutting blade and the inclined stationary blade. 
         [0005]    Implementations of this aspect of the invention may include one or more of the following features. The suture cutting assembly further includes a suture capture component and the suture capture component includes a hook. The suture cutting instrument further includes an elongated cannula and the driver is configured to move longitudinally within the cannula. The suture capture component is attached to the distal end of the elongated cannula. The suture capture component is removably attached to the distal end of the elongated cannula. The suture capture component has a cylindrical body having an axial through opening and being coaxial with the elongated cannula. The cylindrical body has cylindrical top and bottom outer surfaces and flat first and second side surfaces. The bottom surface includes a first oval-shaped opening and the top surface includes an elongated slot. The front end of the cylindrical body includes a second oval-shaped opening, the hook and the inclined stationary blade. The second oval-shaped opening and the hook are set apart at a distance dimensioned to allow passage and capture of the suture by the hook. The movable cutting blade comprises a front end having an angled blade surface and the angled blade surface is configured to slide up and down the inclined stationary blade. The handle assembly further includes a lever mechanism configured to secure the movable handle at a predetermined distance relative to the stationary handle. The lever mechanism includes a lever terminating at one end at a lever button and having an opposite end pivotally connected to the stationary handle via a pivot pin and a spring mechanism. The lever further includes a notch configured to engage a matching opposite notch in the back side of the movable handle and thereby to prevent movement of the movable handle. 
         [0006]    In general, in another aspect, the invention features a method for cutting a suture including the following. First, providing a handle assembly comprising a stationary handle and a movable handle pivotally connected to the stationary handle at a pivot. The movable handle moves rotationally around the pivot. Next, providing a driver comprising a proximal end connected to the movable handle and being configured to reciprocate longitudinally when the movable handle moves rotationally around the pivot. Next, providing a suture cutting assembly comprising a movable cutting blade and an inclined stationary blade. The movable cutting blade is connected to a distal end of the driver and is configured to move longitudinally onto the inclined stationary blade when the movable handle moves rotationally around the pivot and thereby to cut a suture captured between the movable cutting blade and the inclined stationary blade. 
         [0007]    Among the advantages of this invention may be one or more of the following. When the moving blade meets resistance in cutting the high strength suture, the force applied at the handle results in the moving blade being forced against the inclined stationary blade and this results in improving the shearing of the suture. The suture cutting mechanism may be applied for cutting high strength sutures, such as sutures made of ultra-high molecular weight polyethylene (UHMWPE). The suture cutting mechanism may also be used for cutting sutures made of biocompatible materials, Nylon, Dacron, Polypropylene, silk, or braided sutures, among others. The suture cutting mechanism may also be applied in micro-scissors and other applications where two surfaces need to be kept from separating. 
         [0008]    The details of one or more embodiments of the invention are set forth in the accompanying drawings and description below. Other features, objects and advantages of the invention will be apparent from the following description of the preferred embodiments, the drawings and from the claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    Referring to the figures, wherein like numerals represent like parts throughout the several views: 
           [0010]      FIG. 1  is a perspective view of an endoscopic instrument with a suture cutting front end assembly; 
           [0011]      FIG. 2A  is a partial exploded view of the endoscopic instrument of  FIG. 1 ; 
           [0012]      FIG. 2B  is detailed view of the actuator rod connection to the movable handle of  FIG. 2A ; 
           [0013]      FIG. 3A  is a partial exploded view of the suture cutting front end assembly of  FIG. 1 ; 
           [0014]      FIG. 3B  is a cross-sectional view of the suture cutting front end assembly along AA plane, shown in  FIG. 4A ; 
           [0015]      FIG. 4A  is a top view of the endoscopic instrument of  FIG. 1 ; 
           [0016]      FIG. 4B  is a side view of the endoscopic instrument of  FIG. 1 ; 
           [0017]      FIG. 4C  is a detailed side view of the handle of the endoscopic instrument of  FIG. 1 ; 
           [0018]      FIG. 5A  is a side view of the endoscopic instrument of  FIG. 1  with the front end assembly in the “open” position; 
           [0019]      FIG. 5B  is a detailed view of the suture cutting front end assembly of  FIG. 5A ; 
           [0020]      FIG. 6A  is a side view of the endoscopic instrument of  FIG. 1  with the front end assembly in the “suture captured” position; 
           [0021]      FIG. 6B  is a detailed view of the suture cutting front end assembly of  FIG. 6A ; 
           [0022]      FIG. 7A  is a side view of the endoscopic instrument of  FIG. 1  with the front end assembly in the “closed” position; 
           [0023]      FIG. 7B  is a detailed view of the suture cutting front end assembly of  FIG. 7A ; 
           [0024]      FIG. 8A  is a detailed view of the suture cutting front end assembly of  FIG. 1  in the “open” position; 
           [0025]      FIG. 8B  is a detailed view of the suture cutting front end assembly of  FIG. 1  in the “suture captured” position; 
           [0026]      FIG. 8C  is a detailed view of the suture cutting front end assembly of  FIG. 1  in the “closed” position; 
           [0027]      FIG. 9A  is a detailed cross-sectional view of the suture cutting front end assembly of  FIG. 1  in the “open” position; 
           [0028]      FIG. 9B  is a detailed cross-sectional view of the suture cutting front end assembly of  FIG. 1  in the “suture captured” position; 
           [0029]      FIG. 9C  is a detailed cross-sectional view of the suture cutting front end assembly of  FIG. 1  in the “closed” position; 
           [0030]      FIG. 10A  is a detailed top view of the suture cutting front end assembly of  FIG. 1  in the “closed” position; 
           [0031]      FIG. 10B  is a detailed side view of the suture cutting front end assembly of  FIG. 1  in the “closed” position; and 
           [0032]      FIG. 10C  is a detailed bottom view of the suture cutting front end assembly of  FIG. 1  in the “closed” position; 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0033]    Referring to  FIG. 1 ,  FIG. 2 ,  FIG. 3A  and  FIG. 3B , the endoscopic instrument  100  includes a suture cutting front end assembly  120 , a cannula/actuator rod assembly  110 , and a handle assembly  140 . The suture cutting assembly  120  includes a suture capture component  124  and a blade  126 . The cannula/actuator rod assembly  110  includes an outer cannula  112  and an actuator rod  114  configured to move linearly within the cannula  112 . Cannula  112  has an elongated slot  113  extending the entire length of the cannula  112  and a front end  112   a  forming the suture capture component  124  of the suture cutting assembly  120 . In this embodiment, the suture capture component  124  is an integral part of the cannula front end  112   a.  In other embodiments, the suture capture component  124  is removably attached to the front end of the cannula. Actuator rod  114  had a distal end  114   a  attached to blade  126 , as shown in  FIG. 3A , and a proximal end  114   b  attached to the movable handle  144 , as shown in  FIG. 2B  and will be described below. The handle assembly  140  includes a stationary handle  142 , a movable handle  144 , and a base  141 . In this embodiment, the stationary handle  142  is integral with and extends downward from the base  141  and movable handle  144  is pivotally attached to the base  141  via pivot pin  148 . Movable handle  144  is secured at a predetermined distance relative to the stationary handle  142  via a lever mechanism  160 . Movable handle  144  is also connected to the blade  126  via the actuator rod  114 . Actuator rod  114  translates the rotational motion  92  of the movable handle  144  into a linear motion  94  of the blade  126 . Movable handle  144  includes a finger loop  154 , an elongated curved middle segment  143 , and an upper segment  145 . Middle segment  143  includes a notch  176  and a slot  146 , which is shaped and dimensioned to accommodate lever  162 , as shown in  FIG. 2A ,  FIG. 4B ,  FIG. 4C  and  FIG. 5A . Upper segment  145  includes two upward extending protrusions  145   a,    145   b  that are parallel to each other and form a slot  145   c  between them. The slot  145   c  is dimensioned to receive end  114   b  of the actuator rod. End  114   b  includes a vertically oriented elongated tetrahedron  201 , a first parallelepiped block  202  extending horizontally from the front surface of the tetrahedron  201  and a second parallelepiped block  203  extending from a front surface of the first block  202  vertically and coplanar with the first block  202 . The first block  202  is dimensioned to fit within slot  145   c . Forward or backward motion of the actuator rod  114  relative to the upper segment  145  of the movable handle  144  is prevented by second block  203  and tetrahedron  201 , respectively. Lever mechanism  160  includes a curved lever  162  terminating in one end  162   a  at a lever button  164  and having an opposite second end  162   b  pivotally connected to stationary handle  142  via a pivot pin  163  and a spring mechanism  165 , as shown in  FIG. 2A ,  FIG. 4B  and  FIG. 4C . Spring mechanism  165  causes lever end  162   a  to move up along direction  96  when lever button  164  is not pressed down. Lever end  162   a  also includes a notch  166  that engages a matching opposite notch  176  in the back side of movable handle  144  and acts as a stop of the movable handle  144  motion  92  when the lever button  164  is not pressed down. In this position the front end assembly is in the “open” position, as will be described below. Notch  166  is located at a distance from lever end  162   a  thereby allowing the movable handle  144  to rotate slightly back toward the stationary handle  142 . Moving the movable handle  144  slightly back toward the stationary handle  142  causes the actuator rod  114  and the attached blade  126  to move slightly forward and to bring the front end assembly  120  in the “suture capture” position. Pressing the lever button  164  down, disengages the movable handle  144  from the lever notch  166  and allows it to rotate further back toward the stationary handle  142 . Moving the movable handle  144  further back toward the stationary handle  142  causes the actuator rod  114  and the attached blade  126  to move further forward and to bring the front end assembly in the “closed” position. Stationary handle  142  includes a finger loop  139  a middle segment  147  and base  141  that includes a through opening  149  dimensioned to receive a pivot pin  148  for pivotally attaching the movable handle  144  to the stationary handle  142 . Middle segment  147  includes a slot  151  that is configured and dimensioned to accommodate the second end  162   b  of lever  162 . Second end  162   b  of lever  162  includes a pivot pin  163  that is configured to be received within through opening  152  formed in the middle segment  147  of stationary handle  142 . 
         [0034]    Referring to  FIG. 3A  and  FIG. 3B , the suture capture component  124  includes a cylindrical body  125  attached to the distal end  112   a  of the outer cannula  112 . In this embodiment, cylindrical body  125  is integral with the distal end  112   a  of the cannula  112  and includes an axial through opening  136  extending along cannula axis  99 . Cylindrical body  125  includes two opposite flat side surfaces  125   a,    125   b  (shown in  FIG. 8B ) and cylindrical top and bottom surfaces  125   c,    125   d,  respectively. Bottom  125   d  surface includes an oval shaped opening  127  and top surface  125   c  includes an elongated slot opening  128  which is a continuation and an extension of the outer cannula elongated slot  113 , as shown in  FIG. 10A . The front end of cylindrical body  125  includes an oval-shaped opening  131  with an integrated hook  129  and an inclined stationary blade surface  130  forming an angle  80  relative to the cannula axis  99 . Oval opening  131  extends down on side  125   a  of the cylindrical body from the top surface  125   c  toward the bottom surface  125   d  and forms a curved surface  132 , as shown in  FIG. 8A . Curved surface  132  and hook  129  are set apart at a distance  133 , which is dimensioned to allow the passage and capture of the suture  102  by the hook  129 . Actuator rod  114  with the attached blade  126  is dimensioned to move linearly within opening  136  as a result of the rotational pivoting motion of the movable handle  144 . The front end of blade  126  includes an angled blade surface  126   a  which is configured to slide up and down the stationary inclined blade surface  130  as the actuator moves forward along direction  94  and backward, respectively. This sliding motion of the blade surface  126   a  onto inclined stationary blade surface  130  cuts the captured suture  102 . 
         [0035]    Referring to  FIG. 5A , an operator moves the movable handle  144  away from the stationary handle  142 , by placing his finger inside the finger loop  154  and pivoting the handle  144  around the pivot point  148  counter-clockwise. This pivoting motion  92   a  of the handle  144  away from the stationary handle  142  moves the actuator rod  114  back along direction  94   a  and brings blade surface  126   a  down at the bottom of the inclined stationary blade surface  130 , as shown in  FIG. 9A . This setting defines the “open” position, mentioned above and shown in  FIG. 9A ,  FIG. 5A ,  FIG. 5B  and  FIG. 8A . At this point, the opening distance  133   a  between the top of the blade  126  and the top of the inclined stationary blade  130  is the largest and this permits the passage and engagement of the suture  102  by the hook  129 , as shown in  FIG. 5B . Next, the operator pivots the movable handle  154  slightly back clockwise along direction  92   b  until lever notch  166  engages handle notch  176  and stops the further pivoting of the movable handle  144 , as shown in  FIG. 6A . This slight back pivoting motion along  92   b  moves actuator rod  114  slightly forward  94   b  and causes blade surface  126   a  to move slightly up in the middle section of the inclined stationary blade surface  130 , as shown in  FIG. 9B . This setting defines the “suture capture” position, mentioned above and shown in  FIG. 9B ,  FIG. 6A ,  FIG. 6B  and  FIG. 8B . At this point, the opening distance  133   a  between the top of blade  126  and the top of the inclined stationary blade  130  is reduced and this causes the capture of the suture  102  by the hook  129 , as shown in  FIG. 6B . Next, the operator presses lever button  164  down along direction  96   a  to disengage level notch  166  from the movable handle notch  176  and then pivots the movable handle  144  further back clockwise along direction  92   b,  as shown in  FIG. 7A . This further back pivoting motion along  92   b  moves actuator rod  114  further forward  94   b  and causes blade surface  126   a  to move further up to the top section of the inclined stationary blade surface  130 , as shown in  FIG. 9C . This setting defines the “closed” position, mentioned above and shown in  FIG. 9C ,  FIG. 7A ,  FIG. 7B  and  FIG. 8C . At this point, the opening distance  133   a  between the top of blade  126  and the top of the inclined stationary blade  130  is further reduced and this causes the cutting of the suture  102  by the blade  126 , as shown in  FIG. 7B . When cutting high strength sutures the moving blade surface  126   a  pushes away from the inclined stationary blade surface  130 . If the gap between the top of the moving blade  126   a  and the top of the inclined stationary blade surface  130  is too large, it will result in an unacceptable fraying and/or a tag end at the ends of the cut suture. If the gap between the top of the moving blade  126   a  and the top of the inclined stationary blade surface  130  is even larger the suture will not be cut completely through. When the moving blade  126  meets resistance in cutting suture, the force applied at the handle  144  results in the moving blade  126  being forced against the stationary blade  130  and this improves the shearing of the suture. 
         [0036]    In one example, the total stroke (i.e., the distance  133   a  between the blade top  126   a  and the top of the inclined blade surface  130 ) is about 0.123 inch and the clearance between the two blades is 0.00040 inch. The inclined stationary blade  130  may form an angle  80  with the cannula axis  99  in the range of 30 to 50 degrees. In the example of  FIG. 3B , angle  80  is 45 degrees. In one example, the blade  126  has a diameter of 0.1248 inch, and the hook  129  dimensions are 0.030×0.054 inches. Typical dimensions for the handles are 0.230×4.5×1.75 inches. The suture cutting instrument may be made of various types of biocompatible stainless steels, ceramics, plastics, or composites. The suture may be made of ultra-high molecular weight polyethylene (UHMWPE), biocompatible material, Nylon, Dacron, Polypropylene, or braided sutures, among others. The end assembly may be disposable or non-disposable and may be made of various types of biocompatible stainless steels, metals, alloys, composites and plastics. The above described suture cutting mechanism may be applied in micro-scissors and other applications where two surfaces need to be kept from separating. 
         [0037]    Several embodiments of the present invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. Accordingly, other embodiments are within the scope of the following claims.