Abstract:
A medical device includes an elongate body extending from a proximal portion which, in an operative configuration, remains outside a living body, to a distal end which, in the operative configuration, extends through a body to a position adjacent to a target portion of tissue to be treated and a spool rotatably coupled to the distal portion of the elongate body, the spool including a distal portion coupled to an end effector of the device along with a flexible member extending from the proximal portion of the elongate body, a first portion of the flexible member being wound about the spool in a first direction and a second portion of the flexible member wound about the spool in a second direction opposite the first direction, ends of the first and second portions extending to the proximal portion of the elongate body.

Description:
PRIORITY CLAIM 
       [0001]    This application claims the priority to the U.S. Provisional Application Serial No. 61/580,410, entitled “System And Method To Achieve Reciprocating Rotational Motion Of The Distal Member Of A Device By Applying Translational Forces” filed on Dec. 27, 2011. The specification of the above-identified application is incorporated herewith by reference. 
     
    
     BACKGROUND 
       [0002]    Pathologies of the gastro-intestinal (GI) system, the biliary tree, the vascular system and other body lumens and hollow organs are often treated through endoscopic procedures, many of which require active and/or prophylactic hemostasis. Tools for deploying hemostatic clips via endoscopes are often used to stop internal bleeding by clamping together edges of wounds or incisions. These clips grasp tissue surrounding an opening in tissue holding edges of the opening together until natural healing processes have closed the opening Many current clips include a pair of arms which must be in a particular angular orientation to grasp the target tissue edges. Thus, application of the clips requires that they be rotatable by a user. However, it has proven difficult with certain clips to transmit the torque required to rotate clips over the length of the flexible member which connects the clip to the actuator. This difficulty is especially pronounced when the clip device extends along a tortuous path from the actuator to the target tissue. 
       SUMMARY OF THE INVENTION 
       [0003]    The present invention relates to a medical device, comprising an elongate body extending from a proximal portion which, in an operative configuration, remains outside a living body, to a distal end which, in the operative configuration, extends through a body to a position adjacent to a target portion of tissue to be treated and a spool rotatably coupled to the distal portion of the elongate body, the spool including a distal portion coupled to an end effector of the device along with a flexible member extending from the proximal portion of the elongate body, a first portion of the flexible member being wound about the spool in a first direction and a second portion of the flexible member wound about the spool in a second direction opposite the first direction, ends of the first and second portions extending to the proximal portion of the elongate body. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0004]      FIG. 1  shows a perspective view of a device according to a first exemplary embodiment of the present invention; 
           [0005]      FIG. 2  shows a longitudinal cross-sectional view of a rotation mechanism for rotating a distal portion of the device of  FIG. 1 ; 
           [0006]      FIG. 3  shows a longitudinal cross-sectional view of the rotation mechanism of  FIG. 1 , according to a further embodiment; 
           [0007]      FIG. 4  shows a perspective view of a rotation mechanism for rotating a distal portion of a device according to an alternate embodiment of the present invention; 
           [0008]      FIG. 5  shows a perspective view of a spool of a rotation mechanism according to another exemplary embodiment of the present invention; 
           [0009]      FIG. 6  shows a perspective view of a spool according to yet another exemplary embodiment of the present invention; 
           [0010]      FIG. 7  shows a shows a lateral cross-sectional view of the spool of  FIG. 6  attached to a distal portion of a device; 
           [0011]      FIG. 8  shows a perspective view of a spool according to another exemplary embodiment of the present invention; 
           [0012]      FIG. 9  shows a rotation mechanism for rotating a distal portion of a device according to another exemplary embodiment of the present invention; 
           [0013]      FIG. 10  shows a perspective view of a spool according to another exemplary embodiment of the present invention; 
           [0014]      FIG. 11  shows a side view of the spool of  FIG. 10 ; and 
           [0015]      FIG. 12  shows a perspective view of a spool according to yet another exemplary embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0016]    The present invention may be further understood with reference to the following description and the appended drawings, wherein like elements are referred to with the same reference numerals. The present invention relates to medical devices requiring the rotation of a distal member and, in particular, relates to a mechanism for rotating the distal member. Exemplary embodiments of the present invention describe a mechanism including a flexible member such as a thread, fiber or wire coiled about a spool and which may be pulled through a shaft of a device to rotate a distal portion of the device in either of a clockwise or a counter clockwise direction. Although the exemplary embodiments specifically describe rotation of a clip assembly at a distal end of a clipping device, it will be understood by those of skill in the art that the mechanism of the present invention may be utilized in any medical device that requires rotation of a distal member located at the end of a long shaft. For example, the mechanism of the present invention may be used for medical devices such as hemostatic clips, biopsy devices, sphincterotomes, retrieval devices, needles, polypectomy snares, endoscopes and radio-frequency ablation devices. 
         [0017]    As shown in  FIGS. 1-2 , a clipping device  100  according to an exemplary embodiment of the present invention comprises a distal assembly  102  connected to a flexible shaft  104  including an actuating handle at a proximal end thereof. Except for the linkage for rotation mechanism, the clip  106  described below, the clipping device  100  may be constructed substantially as disclosed in U.S. patent application Ser. No. 12/853,478, filed Aug. 10, 2010 and entitled “Multifunction Core for Two-Piece Hemostasis Clip,” the entire disclosure of which is expressly incorporated herein by reference. The distal assembly  102  comprises a clip  106  including arms  108  movable within a capsule  110  between an open configuration, in which distal ends  112  of the arms  108  are separated from one another to receive a target tissue therebetween, and a closed configuration, in which the distal ends  112  are moved toward one another to grasp the target tissue therebetween. The capsule  110  is releasably coupled to a bushing  114 , from which the capsule  110  may be disengaged during deployment. The clip  106  is movable between the open and closed configurations via a control wire  116  which extends through the shaft  104  from a distal end releasably coupled to the clip  106  to a proximal end connected to the actuating handle. The distal assembly  102  is attached to the shaft  104  via a rotation mechanism  118  including a spool  120 , a guide  122  and flexible member  124  which maybe, for example, a filament, fiber, cable, wire, thread or any other suitable flexible member. The spool  120  extends about the control wire  116 , connecting the distal assembly  102  to the shaft  104 . The flexible member  124  is wound about a portion of the spool  120  with ends of the flexible member  124  guided through the guide  122  to a proximal end of the shaft  104  such as the actuating handle. Thus, as the ends of the flexible member  124  are toggled relative to the shaft  104 , a clockwise or counter-clockwise motion of the distal assembly  102  is generated. It will be understood by those of skill in the art that the rotation mechanism  118  is particularly advantageous since the rotation can be controlled and the linear motion of the flexible member  124  is converted to rotation at the distal assembly  102  rather than at a proximal end of the device  100 . 
         [0018]    The spool  120  includes a distal portion  126 , a proximal portion  128  and a lumen  130  extending therethrough to accommodate the control wire  116  therein. In one exemplary embodiment, the spool  120  is substantially tubular. The distal portion  126  is sized and shaped to be engagingly received within the proximal end of the bushing  114  preventing the spool  120  from rotating relative to the distal assembly  102 . Alternatively, the distal portion  126  may be fixed within the bushing  114  via, for example, an adhesive, welding or other fixation means preventing relative rotational motion therebetween. The proximal portion  128  has a smaller cross-sectional area (e.g. diameter) than the distal portion  126  and includes first and second holes  132 ,  134 , respectively, extending laterally through opposing portions of the proximal portion  128 . The first hole  132  is distal of the second hole  134  and the second hole  134  is spaced a distance distally of the guide  122  selected to accommodate a desired number of windings of the flexible member  124  around the portion of the spool  120  proximal of the second hole  134 . 
         [0019]    The guide  122  is attached to a distal end  144  of the shaft  104  and may, for example, be substantially disc-shaped. The guide  122  includes first and second holes  140 ,  142  on opposite sides of the guide  122  along a periphery thereof with the first and second holes  140 ,  142  open to an exterior of the guide  122 . Alternatively, the first and second holes  140 ,  142  may be completely enclosed. The guide  122  also includes an opening  146  extending therethrough to accommodate the control wire  116  therein. The guide  122  and the proximal portion  128  of the spool  120  are in close proximity to one another but are free to rotate relative to one another. 
         [0020]    The flexible member  124  extends through the first and second holes  132 ,  134  so that a first portion  136  of the flexible member  124  extends to an exterior of the first hole  132  and a second portion  138  of the flexible member  124  extends to an exterior of the second hole  134 . The flexible member  124  is sized to pass through the first and second holes  132 ,  134  across the lumen  120  without interfering with the movement proximally and distally of the control wire  116  extending therethrough to open and close the clip  106 . The first and second portions  136 ,  138  of the flexible member  124  are then wound about the proximal portion  128  in opposite directions. For example, the first portion  136  may be wound about the proximal portion  128  in a clockwise direction while the second portion  138  is wound about the proximal portion  128  counter-clockwise. In some embodiments, the proximal portion  128  may include grooves and/or threads extending thereabout such that the first and second portions  136 ,  138  extend about the proximal portion  128  within the grooves, aligning the first and second portions  136 ,  138  with one another. The first portion  136  passes through the first hole  140  of the guide member  122 , through the shaft  104  and to a proximal end thereof while the second portion  138  passes through the second hole  142 , through the shaft  104  to the proximal end thereof. The first and second portions  136 ,  138  may extend from the guide  122  through, for example, a single lumen of the shaft  104 . Alternatively, the first and second portions  136 ,  138  may be passed through separate lumens extending through the shaft  104 . In another exemplary embodiment, the first and second portions  136 ,  138  extend through slots extending along a portion of the proximal portion  128  of the spool  120  so that a separate guide  122  is not required. 
         [0021]    The ends of the first and second portions  136 ,  138  are connected to the actuating handle in a manner permitting the end of the first portion  136  to be pulled proximally relative to the device  100  while the end of the second portion  138  moves distally relative to the device  100  and vice versa. As the end of the first portion  136  is pulled proximally, the first portion  136  unwinds from the spool  120  while the second portion  138  winds about the spool  120 . As the end of the second portion  138  is pulled proximally, the second portion  138  unwinds from the spool  120  as the first portion  120  winds about the spool  120  rotating the spool  120  and distal assembly  102  including the clip  106  in opposite directions depending on which of the first and second portions  136 ,  138  is being wound about the spool  120  and which is being unwound. In an exemplary embodiment, a proximal end of the proximal portion  128  abuts against a distal surface of the guide  122  such that the spool  120  bears against the guide  122  as one of the ends of the first and second portions  136 ,  138  is drawn proximally relative to the device  100 . As described above, the spool  120  and the guide  122  are free to rotate relative to one another. 
         [0022]    In an exemplary embodiment, the actuating handle at the proximal end of the shaft  104  includes a knob to which proximal ends of the first and second portions  136 ,  138  of flexible member  124  are attached. The knob is sized and configured such that rotation of the knob in a first direction pulls the first portion  136  of flexible member  124  to rotate the distal assembly  102  clockwise while rotation of the knob in a second direction pulls the second portion  138  to rotate the distal assembly  102  counter-clockwise. It will be understood by those of skill in the art, however, that each of the first and second portions  136 ,  138  may be controlled together, as described above, or individually via, for example, two knobs. It will also be understood by those of skill in the art that the first and second portions may also be controlled by controllers other than knobs. For example, the controller(s) may include rings, spools, handles, etc., which control the rotation of the first and second portions  136 ,  138 . The actuating handle may also include a mechanism for holding the distal assembly  102  in the desired rotative orientation. The actuating handle may include, for example, a lock, a ratchet mechanism and/or a clamp. In another embodiment, the spool  120  may include a ratchet mechanism and/or a breaking component preventing the flexible member  124  from slipping once one of the first and second portions  136 ,  138  has been drawn proximally. It will be understood by those of skill in the art, however, that the device  100  may include any of a number of different types of controllers and/or locking/holding mechanisms so long as the first and second portions  136 ,  138  may be drawn proximally to rotate the distal assembly  102  relative to the shaft  104  and hold the distal assembly  102  at the desired position relative to the shaft  104 . 
         [0023]    It will be understood by those of skill in the art that many factors will determine how the spool will rotate. For example, rotation may be affected by a diameter of the proximal portion  128  of the spool  120  about which the flexible member  124  is wound and a distance from the holes  132 ,  134  of the spool  120  to the holes  140 ,  142  of the guide. Rotation will also be affected by a length of flexible member  124  wound about the proximal portion  128 . The longer the portion of the flexible member  124  that is wound about the proximal portion  128 , the greater the permitted range of rotation. The positioning of the holes  132 ,  134  along the proximal portion  128  and a size of the proximal portion  128  may be selected such that he flexible member  124  may be wound therearound to facilitate a rotation of the distal assembly  102  relative to the shaft  104  up to 180° and possibly up to 360°. The spool  120  and the guide  122  may be formed of, for example, any suitable biocompatible plastic or metal. Portions of the spool  120  and/or guide  122  may have different surface textures to provide a smooth passage for the flexible member  124  or to generate additional friction to enhance an amount of torque applied to the spool  120 . The spool  120  and the guide  122  may be manufactured via, for example, stamping, machining or injection molding. 
         [0024]    According to an alternate embodiment, the flexible member  124  may include a tacky section along a portion of the flexible member  124  which will be wound around the proximal portion  128  of the spool  120  such that the spool  120  does not require holes  132 ,  134 . The tackiness of the flexible member provides the friction required to rotate the spool  120  as it is wound and unwound. The flexible member  124  may be formed of a tacky material and/or have a tacky material impregnated into it or attached to it. The spool  120  may be made of any of a variety of materials which may increase the friction between the flexible member  124  and the spool  120  and/or an outer surface of the spool  120  or of a portion of the spool  124  over which the flexible member is to be wound may be formed or treated to increase the frictional coupling of the flexible member and the outer surface of the spool  120  as would be understood by those skilled in the art. For example, the spool  120  may also be formed of a tacky material and/or have a tacky material impregnated into it or attached to it. The friction between the flexible member  124  and the spool  120 , however, may be increased in any number of ways. For example, the spool  120  and/or flexible member  124  may be treated with a coating, the spool  120  may have different surface areas and/or include a surface roughness, and/or a a tension of the flexible member  124  wound about the spool  120  may be increased. 
         [0025]    According to another embodiment, the flexible member  124  may be wound about the proximal portion  128  of the spool  120  in a single direction such that pulling an end of the flexible member  124  rotates the distal assembly  102 . The flexible member  124  may be wound about the proximal portion  128  to permit multiple spins of the spool  120  such that the clip  106  may rotate up to 360°. Thus, the clip  106  may be rotated to any desired orientation relative to the target tissue by pulling on a single end of the flexible member  124 . 
         [0026]    It will be understood by those of skill in the art that although the exemplary embodiment specifically describes one flexible member  124 , the device  100  may include two flexible members  124 , each of which may be attached to the spool  120  via, for example, an adhesive, knots, fasteners, etc., and wound about the proximal portion  128  in opposite directions. Thus, it will also be understood by those of skill in the art that although the device  100  is specifically described as including holes  132 ,  134  through which the flexible member  124  may be inserted, the flexible member  124  may be attached to the spool  120  in any of a variety of ways so long as the flexible member(s)  124  may be wound thereabout. 
         [0027]    As shown in  FIGS. 1-2  and described above, portions of the spool  120 , the guide  122  and the flexible member  124  extend between a proximal end of the bushing  114  and the distal end  144  of the shaft  104 . In these cases, a protective sheath may extend over the rotation mechanism  118  to protect the rotation mechanism  118  as the device  100  is inserted into the body. In another embodiment, however, the proximal portion  128  of the spool  120  and the guide  122  may be positioned within the shaft  104  such that the rotation mechanism is not exposed to an exterior of the device  100 . In yet another embodiment, the distal assembly  102  may be connected to the shaft  104  via a spinlock, which would permit the distal assembly  102  to be rotated relative to the shaft while preventing the distal assembly  102  from being separated from the shaft  104 . It will be understood by those of skill in the art that this embodiment would be particularly useful for medical devices in which the distal assembly  102  is not required to be deployed from a proximal portion of the device  100 . 
         [0028]    According to an exemplary technique in accord with the present invention, the distal assembly  102  of the device  100  is inserted to a target area within a body (e.g., through the working channel of an endoscope inserted into a body lumen via a naturally occurring bodily orifice) until the clip  106  is positioned proximate target tissue to be clipped. The control wire  116  is then moved distally relative to the shaft  104  to allow the clip arms  108  to spread apart (e.g., under their natural bias) into the open configuration. The user observes the clip (e.g., via the vision system of an endoscope) and determines whether the clip arms  108  need to be rotated to properly clip the target tissue. If the clip is not in the desired rotational orientation relative to the target tissue to be clipped, the user operates an actuator to rotate the distal assembly  102  relative to the shaft  104  to the desired rotational orientation relative to the target tissue via the rotation mechanism  118  as described above. Either of the ends of the first and second portions  136 ,  138  may be moved proximally relative to the shaft. As described above, pulling the end of one of the first and second portions  136 ,  138  rotates the distal assembly  102  either clockwise or counter-clockwise relative to the shaft  104 . Once the clip  102  has been placed in the desired rotational orientation relative to the target tissue, the clip  102  is advanced distally until the target tissue is positioned between the distal ends  112  of the clip arms  108  and the control wire  116  is drawn proximally relative to the shaft  104  to move the clip arms  108  to the closed configuration, gripping the target tissue between the distal ends  112 . When the user determines that the desired portion of tissue is properly grasped between the arms  108 , the control wire  116  is drawn farther proximally sever the link between the control wire  116  and the clip  106 , locking the clip arms  108  in the closed configuration over the tissue separating the capsule  110  from the bushing  114  so that the clip  106  is completely separated from the proximal portion of the device  100  with the clip  106  locked on the target tissue. 
         [0029]    According to an alternate embodiment of the present invention, as shown in  FIG. 3 , the rotation mechanism  118  may further comprise a torsional spring  164  positioned between the spool  120  and the guide  122 , permitting the spool  120  and the distal assembly  102  to be rotated relative to the shaft  104  in a first direction with the spring rotating the device back to an initial orientation when the actuator is released by a user as would be understood by those skilled in the art. In this embodiment, the flexible member  124  does not require first and second portions  136 ,  138  wound about the spool  120  in opposite directions. Rather, a single portion of flexible member  124  may be wound in a single direction about the spool  120  over a length sufficient to rotate the clip  106  as far from the initial orientation (e.g., 180°)as required to achieve any desired rotational orientation of the clip  106 . Pulling the flexible member  124  proximally relative to the shaft  104  moves the distal assembly  102  in the first direction. Once the flexible member  124  is released, however, the distal assembly  102  rotates in the second direction to revert to the original orientation. 
         [0030]    In another embodiment, the spring  164  may be preloaded (e.g., partially twisted prior to use) such that release of an end of the flexible member  124  causes the distal assembly  102  to rotate relative to the shaft  104  in a first direction. Once released, the end of the flexible member  124  may be drawn proximally relative to the shaft  104  to rotate the distal assembly  102  in a second direction to provide bi-directional control with a single flexible member  124 . 
         [0031]    A rotation mechanism  118 ′, as shown in  FIG. 4 , is substantially similarly to the rotation mechanism  118 , described above, comprising a spool  120 ′, a guide  122 ′ and a flexible member  124 ′, except that the guide  122 ′, although similar to the guide  122  in other respects, includes a first portion  148 ′, through which a first hole  140 ′ extends for receiving a flexible member  124 ′ has a greater width (i.e., distance between a proximal and a distal end thereof) than a second portion  150 ′ of the guide  122 ′ through which a second hole  142 ′ extends for receiving the flexible member  124 ′. The difference in widths between the first and second portions  148 ′,  150 ′ permits a first portion  136 ′ of the flexible member  124 ′ passing through the first hole  140 ′ to be guided away from a spool  120 ′ at a predefined distance from a second portion  138 ′ of the flexible member  124 ′passing through the second hole  142 ′ such that the first and second portions  136 ′,  138 ′ have more room to wind and unwind about the spool  120 ′, thereby preventing interference therebetween. 
         [0032]    As shown in  FIG. 5 , a spool  220 , according to another exemplary embodiment of the present invention, is substantially similar to the spool  120 , described above and may be utilized in place of the spool  120  in the rotation mechanism  118 . The spool  220  similarly includes a distal portion  226  sized, shaped and configured to be engagingly received within the bushing  114  and a proximal portion  228  having a smaller cross-sectional area than the distal portion  226 . However, rather than holes extending through the proximal portion  228 , however, first and second holes  232 ,  234  extend longitudinally through a proximal surface  252  along central axes substantially perpendicular to a longitudinal axis of a lumen  230  of the spool  220 , through which the control wire  116  extends, on opposing sides thereof. Thus, the flexible member  124  may be threaded through the first and second holes  232 ,  234  such that the proximal and distal portions  136 ,  138  extend proximally therefrom to be wound about the proximal portion  228 . 
         [0033]    As shown in  FIGS. 6-7 , a spool  320 , according to another exemplary embodiment of the present invention is substantially similar to the spool  220 , described above, including a distal portion  326  and a proximal portion  328 . The distal portion  326 , however, is elongated in a lateral direction to form a pair of wings  354  extending on opposing sides of the proximal portion  328 . These wings  354  are coupled to the distal assembly  102  and a first hole  332  extends longitudinally through a first one of the wings  354  while a second hole  334  extends through a second one of the wings  354 . As shown in  FIG. 7 , the wings  354  may be received within the bushing  114  of the distal assembly  102  and affixed thereto via, for example, welding or an adhesive. It will be understood by those of skill in the art that the wings  354  may have any of a variety of shapes and orientations relative to a longitudinal axis of the spool  320 . The flexible member  124  is inserted through the first and second holes  332 ,  334  similarly to the spool  220  and operates in a manner that is otherwise similar to the spools described above. 
         [0034]    As shown in  FIG. 8 , a spool  420  according to another exemplary embodiment is substantially similar to the spool  120 , described above, including a distal portion  426  for engaging the distal assembly  102  and a proximal portion  428  about which the flexible member  124  may be wound. The proximal portion  428 , however, is divided into a first section  458  and a second section  460  separated from one another along a length of the proximal portion  428  via a laterally extending shoulder  462  extending radially outward from the proximal portion  428  in a substantially disc-like shape. A first hole  432  extends laterally through a wall of the first section  458  while the second hole  434  extends laterally through the second section  460 , along a portion of the wall opposing the first hole  432  but offset longitudinally therefrom. The flexible member  124  may be threaded through the first and second holes  432 ,  434  such that the first portion  136  of flexible member  124  extends out of the first hole  432  to be wound about the first section and the second portion  138  of flexible member  124  extends out of the second hole  434  to be wound about the second section  460 . The separated sections  458 ,  460  prevents the first and second portions  136 ,  138  of flexible member  124  from translating over the other. 
         [0035]    As shown in  FIG. 9 , a rotating mechanism  518  according to a further exemplary embodiment comprises a spool  520 , a guide  522  and a flexible member  524  substantially similar to the spool  120 , guide  122  and flexible member  124  of the rotating mechanism  118  described above. The rotating mechanism  518 , however, further comprises a cuff  562  slidable over a proximal portion  528  of the spool  520  via, for example, an interference fit, welding, or other fixation mechanism. In this embodiment, the spool  520  includes no holes therethrough to receive the flexible member  524 . Rather, the cuff  562  includes first and second holes  532 ,  534 , respectively, extending laterally through a wall thereof. The first and second holes  532 ,  534  are separated from one another along a length of the cuff  562 , about a circumference of the cuff  562  and/or positioned along the same side of the cuff  562 . The flexible member  524  is inserted through the first and second holes  532 ,  534  such that a first portion  536  of flexible member  524  extends to an exterior of the cuff  562  from the first hole  532  and a second portion  538  of flexible member extends to an exterior of the cuff  562  via the second hole  534 . The cuff  562  may then be slid over the proximal portion  528  of the spool  520  such that a portion of the flexible member  524  within the cuff  562  extends about the proximal portion  528  and/or between the proximal portion  528  and the cuff  562 , securing the flexible member  524  therebetween. The first and second portions  536 ,  538  of flexible member  524  are then wound about the cuff  562  in opposite directions and guided through the holes of the guide  522 , as described above in regard to the device  100 . 
         [0036]    As shown in  FIGS. 10-11 , a spool  620  according to a further exemplary embodiment is substantially similar to the spool  120  described above in regard to the device  100 , comprising a distal portion  626  for attachment to the distal assembly  102  and a proximal portion  628  about which the flexible member  124  may be wound. Rather than holes  128 ,  134  through which the flexible member  124  may be inserted, however, the spool  620  includes first and second hooks  632 ,  634  extending from a portion of the proximal portion  628  toward a distal end thereof such that the flexible member  124  may be hooked therein and wound about the proximal portion  628  proximally of the lances  632 ,  634 . The first and second hook  632 ,  634  are positioned along substantially opposing portions of the proximal portion  628 . Although the exemplary embodiment specifically describes two hooks  632 ,  634 , it will be understood by those of skill in the art that the spool  620  may include one hook for hooking the flexible member  124 . 
         [0037]    As shown in  FIG. 12 , a spool  720  according to a further exemplary embodiment may be substantially similar to any of the spools  120 - 620  described above, comprising a distal portion  726  for attachment to the distal assembly  102  and a proximal portion  728  about which the flexible member  124  may be wound. The spool  720 , however, further comprises a flange  766  at a proximal end  768  of the proximal portion  728 . The flange  766  extends radially outward from the proximal end  768  such that a flexible member  124  wound about the proximal portion  728  is prevented from sliding proximally past the proximal end  768 . 
         [0038]    It will be apparent to those skilled in the art that various modifications and variations can be made in the structure and methodology of the present invention, without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided that they come within the scope of the appended claims and their equivalents.