Patent Publication Number: US-2021169493-A1

Title: Surgical clip applier with articulating joint path for surgical clips

Description:
BACKGROUND 
     Minimally invasive surgical (MIS) tools and procedures are often preferred over traditional open surgical approaches due to their propensity toward reducing post-operative recovery time and leaving minimal scarring. Endoscopic surgery is one type of MIS procedure in which a surgical tool operably connected to an elongate shaft is introduced into the body of a patient through a natural bodily orifice. Laparoscopic surgery is a related type of MIS procedure in which a small incision is formed in the abdomen of a patient and a trocar is inserted through the incision to form a surgical access pathway for a surgical tool and elongate shaft. Once located within the abdomen, the surgical tool engages and/or treats tissue in a number of ways to achieve a diagnostic or therapeutic effect. Manipulation and engagement of the surgical tool may take place via various components passing through the elongate shaft. 
     One surgical instrument commonly used with a trocar is a surgical clip applier, which can be used to ligate blood vessels, ducts, shunts, or portions of body tissue during surgery. Traditional surgical clip appliers have a handle and an elongate shaft extending from the handle. A pair of movable opposed jaws is positioned at the end of the elongate shaft for holding and forming a surgical clip or “ligation clip” therebetween. In operation, a user (e.g., a surgeon or clinician) positions the jaws around the vessel or duct and squeezes a trigger on the handle to close the jaws and thereby collapse the surgical clip over the vessel. 
     More recently, however, robotic systems have been developed to assist in MIS procedures. Instead of directly engaging a surgical instrument, users are now able to manipulate and engage surgical instruments via an electronic interface communicatively coupled to a robotic manipulator. With the advances of robotic surgery, a user need not even be in the operating room with the patient during the surgery. 
     Robotic surgical systems are also now capable of utilizing robotically controlled clip appliers. Such clip appliers include features for robotically feeding and forming surgical clips. Advances and improvements to the methods and devices for applying surgical clips to vessels, ducts, shunts, etc. is continuously in demand to make the process more efficient and safe. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The following figures are included to illustrate certain aspects of the present disclosure, and should not be viewed as exclusive embodiments. The subject matter disclosed is capable of considerable modifications, alterations, combinations, and equivalents in form and function, without departing from the scope of this disclosure. 
         FIG. 1  is a block diagram of an example robotic surgical system that may incorporate some or all of the principles of the present disclosure. 
         FIG. 2  is an isometric top view of an example surgical tool that may incorporate some or all of the principles of the present disclosure. 
         FIG. 3  is an isometric bottom view of the surgical tool of  FIG. 2 . 
         FIG. 4  is an exploded view of the elongate shaft and the end effector of the surgical tool of  FIGS. 2 and 3 . 
         FIG. 5  is an exposed isometric view of the surgical tool of  FIG. 2 . 
         FIG. 6  is a side view of an example surgical tool that may incorporate some or all of the principles of the present disclosure. 
         FIG. 7  illustrates potential degrees of freedom in which the wrist of 
         FIG. 1  may be able to articulate (pivot). 
         FIG. 8  is an enlarged isometric view of the distal end of the surgical tool of  FIG. 6 . 
         FIG. 9  is a bottom view of the drive housing of the surgical tool of  FIG. 6 . 
         FIG. 10  is an isometric exposed view of the interior of the drive housing of the surgical tool of  FIG. 6 . 
         FIG. 11A  is an isometric view of another example embodiment of the surgical tool of  FIG. 6 . 
         FIG. 11B  is an exploded view of the articulation joint of  FIG. 11A . 
         FIG. 11C  is a cross-sectional side view of the assembled articulation joint of  FIG. 11A  in an unarticulated state. 
         FIG. 11D  is a cross-sectional side view of the assembled articulation joint of  FIG. 11A  in an articulated state. 
         FIG. 12  is a cross-sectional end view of a portion of the articulation joint of  FIGS. 11A-11D . 
         FIGS. 13A-13E  are cross-sectional top views of the articulation joint of  FIG. 12  taken along the indicated lines. 
         FIG. 14A  is a cross-sectional side view of another example articulation joint. 
         FIG. 14B  is a cross-sectional side view of the articulation joint of  FIG. 14B  in an articulated state. 
         FIG. 15A  is a side view of another example articulation joint. 
         FIG. 15B  is a shortened side view of at least a portion of the articulation joint of  FIG. 15A . 
     
    
    
     DETAILED DESCRIPTION 
     The present disclosure is related to surgical systems and, more particularly, to surgical clip appliers having an articulation joint made up of a flexible shaft length that feeds surgical clips therethrough and to jaws for crimping. 
     Embodiments discussed herein describe improvements to articulable surgical clip appliers. The surgical clip appliers described herein may include a drive housing, an elongate shaft that extends distally from the drive housing, an end effector arranged at a distal end of the elongate shaft and including first and second jaw members. An articulation joint may interpose the end effector and the elongate shaft, and may comprise a flexible shaft length articulable in a plane of motion. A lumen is defined within the flexible shaft length and extends between the ends of the flexible shaft length. A clip track is provided within the lumen and extending at least partially between the ends to guide surgical clips through the articulation joint. The clip track may be configured to positively engage the surgical clips throughout the path, and the surgical clips may be able to slidably translate through the articulation joint without bending or pre-forming. 
       FIG. 1  is a block diagram of an example robotic surgical system  100  that may incorporate some or all of the principles of the present disclosure. As illustrated, the system  100  can include at least one master controller  102   a  and at least one arm cart  104 . The arm cart  104  may be mechanically and/or electrically coupled to a robotic manipulator and, more particularly, to one or more robotic arms  106  or “tool drivers”. Each robotic arm  106  may include and otherwise provide a location for mounting one or more surgical tools or instruments  108  for performing various surgical tasks on a patient  110 . Operation of the robotic arms  106  and instruments  108  may be directed by a clinician  112   a  (e.g., a surgeon) from the master controller  102   a.    
     In some embodiments, a second master controller  102   b  (shown in dashed lines) operated by a second clinician  112   b  may also direct operation of the robotic arms  106  and instruments  108  in conjunction with the first clinician  112   a.  In such embodiments, for example, each clinician  102   a,b  may control different robotic arms  106  or, in some cases, complete control of the robotic arms  106  may be passed between the clinicians  102   a,b.  In some embodiments, additional arm carts (not shown) having additional robotic arms (not shown) may be utilized during surgery on a patient  110 , and these additional robotic arms may be controlled by one or more of the master controllers  102   a,b.    
     The arm cart  104  and the master controllers  102   a,b  may be in communication with one another via a communications link  114 , which may be any type of wired or wireless telecommunications means configured to carry a variety of communication signals (e.g., electrical, optical, infrared, etc.) according to any communications protocol. 
     The master controllers  102   a,b  generally include one or more physical controllers that can be grasped by the clinicians  112   a,b  and manipulated in space while the surgeon views the procedure via a stereo display. The physical controllers generally comprise manual input devices movable in multiple degrees of freedom, and which often include an actuatable handle for actuating the surgical instrument(s)  108 , for example, for opening and closing opposing jaws, applying an electrical potential (current) to an electrode, or the like. The master controllers  102   a,b  can also include an optional feedback meter viewable by the clinicians  112   a,b  via a display to provide a visual indication of various surgical instrument metrics, such as the amount of force being applied to the surgical instrument (i.e., a cutting instrument or dynamic clamping member). 
     Example implementations of robotic surgical systems, such as the system  100 , are disclosed in U.S. Pat. No. 7,524,320, the contents of which are incorporated herein by reference. The various particularities of such devices will not be described in detail herein beyond that which may be necessary to understand the various embodiments and forms of the various embodiments of robotic surgery apparatus, systems, and methods disclosed herein. 
       FIG. 2  is an isometric top view of an example surgical tool  200  that may incorporate some or all of the principles of the present disclosure. The surgical tool  200  may be the same as or similar to the surgical instrument(s)  108  of  FIG. 1  and, therefore, may be used in conjunction with the robotic surgical system  100  of  FIG. 1 . Accordingly, the surgical tool  200  may be designed to be releasably coupled to a robotic arm  106  ( FIG. 1 ) of a robotic manipulator of the robotic surgical system  100 . Full detail and operational description of the surgical tool  200  is provided in U.S. Patent Pub. 2016/0287252, entitled “Clip Applier Adapted for Use with a Surgical Robot,” the contents of which are hereby incorporated by reference in their entirety. 
     While the surgical tool  200  is described herein with reference to a robotic surgical system, it is noted that the principles of the present disclosure are equally applicable to non-robotic surgical tools or, more specifically, manually operated surgical tools. Accordingly, the discussion provided herein relating to robotic surgical systems merely encompasses one example application of the presently disclosed inventive concepts. 
     As illustrated, the surgical tool  200  can include an elongate shaft  202 , an end effector  204  coupled to the distal end of the shaft  202 , and a drive housing  206  coupled to the proximal end of the shaft  202 . The terms “proximal” and “distal” are defined herein relative to a robotic surgical system having an interface configured to mechanically and electrically couple the surgical tool  200  (e.g., the drive housing  206 ) to a robotic manipulator. The term “proximal” refers to the position of an element closer to the robotic manipulator and the term “distal” refers to the position of an element closer to the end effector  204  and thus further away from the robotic manipulator. Moreover, the use of directional terms such as above, below, upper, lower, upward, downward, left, right, and the like are used in relation to the illustrative embodiments as they are depicted in the figures, the upward or upper direction being toward the top of the corresponding figure and the downward or lower direction being toward the bottom of the corresponding figure. 
     In applications where the surgical tool  200  is used in conjunction with a robotic surgical system (e.g., system  100  of  FIG. 1 ), the drive housing  206  can include a tool mounting portion  208  designed with features that releasably couple the surgical tool  200  to a robotic arm (e.g., the robotic arms  106  or “tool drivers” of  FIG. 1 ) of a robotic manipulator. The tool mounting portion  208  may releasably attach (couple) the drive housing  206  to a tool driver in a variety of ways, such as by clamping thereto, clipping thereto, or slidably mating therewith. In some embodiments, the tool mounting portion  208  may include an array of electrical connecting pins, which may be coupled to an electrical connection on the mounting surface of the tool driver. While the tool mounting portion  208  is described herein with reference to mechanical, electrical, and magnetic coupling elements, it should be understood that a wide variety of telemetry modalities might be used, including infrared, inductive coupling, or the like. 
       FIG. 3  is an isometric bottom view of the surgical tool  200 . The surgical tool  200  further includes an interface  302  that mechanically and electrically couples the tool mounting portion  208  to a robotic manipulator. In various embodiments, the tool mounting portion  208  includes a tool mounting plate  304  that operably supports a plurality of drive inputs, shown as a first drive input  306   a,  a second drive input  306   b,  and a third drive input  306   c.  While only three drive inputs  306   a - c  are shown in  FIG. 3 , more or less than three may be employed, without departing from the scope of the disclosure. 
     In the illustrated embodiment, each drive input  306   a - c  comprises a rotatable disc configured to align with and couple to a corresponding input actuator (not shown) of a given tool driver. Moreover, each drive input  306   a - c  provides or defines one or more surface features  308  configured to align with mating surface features provided on the corresponding input actuator. The surface features  308  can include, for example, various protrusions and/or indentations that facilitate a mating engagement. 
       FIG. 4  is an exploded view of one example of the elongate shaft  202  and the end effector  204  of the surgical tool  200  of  FIGS. 2 and 3 , according to one or more embodiments. As illustrated, the shaft  202  includes an outer tube  402  that houses the various components of the shaft  202 , which can include a jaw retaining assembly  404 . The jaw retaining assembly  404  includes a jaw retainer shaft  406  with a clip track  408  and a push rod channel  410  formed thereon. The end effector  204  includes opposing jaws  412  that are configured to mate to a distal end of the clip track  408 . 
     The shaft  202  also includes a clip advancing assembly, which, in one example embodiment, can include a feeder shoe  414  adapted to be slidably disposed within the clip track  408 . The feeder shoe  414  is designed to advance a series of clips  416  positioned within the clip track  408 , and a feedbar  418  is adapted to drive the feeder shoe  414  through the clip track  408 . An advancer assembly  420  is adapted to mate to a distal end of the feedbar  418  for advancing a distal-most clip into the jaws  412 . 
     The shaft  202  furthers include a clip forming or camming assembly operable to collapse the jaws  412  and thereby crimp (crush) a surgical clip  416  positioned between (interposing) the jaws  412 . The camming assembly includes a cam  422  that slidably mates to the jaws  412 , and a push rod  424  that moves the cam  422  relative to the jaws  412  to collapse the jaws  412 . A tissue stop  426  can mate to a distal end of the clip track  408  to help position the jaws  412  relative to a surgical site. 
     The jaw retainer shaft  406  is extendable within and couples to the outer tube  402  at a proximal end  428   a,  and its distal end  428   b  is adapted to mate with the jaws  412 . The push rod channel  410  formed on the jaw retainer shaft  406  may be configured to slidably receive the push rod  424 , which is used to advance the cam  422  over the jaws  412 . The clip track  408  extends distally beyond the distal end  428   b  of the jaw retainer shaft  406  to allow a distal end of the clip track  408  to be substantially aligned with the jaws  412 . 
     The clip track  408  can include several openings  430  formed therein for receiving an upper or “superior” tang  432   a  formed on the feeder shoe  414  adapted to be disposed within the clip track  408 . The clip track  408  can also include a stop tang  434  formed thereon that is effective to be engaged by a corresponding stop tang formed on the feeder shoe  414  to prevent movement of the feeder shoe  414  beyond a distal-most position. To facilitate proximal movement of the feeder shoe  414  within the clip track  408 , the feeder shoe  414  can also include a lower or “inferior” tang  432   b  formed on the underside thereof for allowing the feeder shoe  414  to be engaged by the feedbar  418  as the feedbar  418  is moved distally. In use, each time the feedbar  418  is moved distally, a detent formed in the feedbar  418  engages the inferior tang  432   b  and moves the feeder shoe  414  distally a predetermined distance within the clip track  408 . The feedbar  418  can then be moved proximally to return to its initial position, and the angle of the inferior tang  432   b  allows the inferior tang  432   b  to slide into the next detent formed in the feedbar  418 . 
     The jaws  412  include first and second opposed jaw members that are movable (collapsible) relative to one another and are configured to receive a surgical clip from the series of clips  416  therebetween. The jaw members can each include a groove formed on opposed inner surfaces thereof for receiving the legs of a surgical clip  416  in alignment with the jaw members. In the illustrated embodiment, the jaw members are biased to an open position and a force is required to urge the jaw members toward one another to crimp the interposing clip  416 . The jaw members can also each include a cam track formed thereon for allowing the cam  422  to slidably engage and move the jaw members toward one another. A proximal end  436   a  of the cam  422  is matable with a distal end  438   a  of the push rod  424 , and a distal end  436   b  of the cam  422  is adapted to engage and actuate the jaws  412 . The proximal end  438   b  of the push rod  424  is matable with a closure link assembly associated with the drive housing  206  for moving the push rod  424  and the cam  422  relative to the jaws  412 . 
     The distal end  436   b  of the cam  422  includes a camming channel or tapering recess formed therein for slidably receiving corresponding cam tracks provided by the jaw members. In operation, the cam  422  is advanced from a proximal position, in which the jaw members are spaced apart from one another, to a distal position, where the jaw members are collapsed to a closed position. As the cam  422  is advanced over the jaw members, the tapering recess at the distal end  436   b  serves to push the jaw members toward one another, thereby crimping a surgical clip  416  disposed therebetween. 
       FIG. 5  is an exposed isometric view of the surgical tool  200  of  FIG. 2 , according to one or more embodiments. The shroud or covering of the drive housing  206  has been removed to reveal the internal component parts. As illustrated, the surgical tool  200  may include a first drive gear  502   a,  a second drive gear  502   b,  and a third drive gear  502   c.  The first drive gear  502   a  may be operatively coupled to (or extend from) the first drive input  306   a  ( FIG. 3 ) such that actuation of the first drive input  306   a  correspondingly rotates the first drive gear  502   a.  Similarly, the second and third drive gears  502   b,c  may be operatively coupled to (or extend from) the second and third drive inputs  306   b,c  ( FIG. 3 ), respectively, such that actuation of the second and third drive inputs  306   b,c  correspondingly rotates the second and third drive gears  502   b,c,  respectively. 
     The first drive gear  502   a  may be configured to intermesh with a first driven gear  504   a,  which is operatively coupled to the shaft  202 . In the illustrated embodiment, the driven gear  504   a  comprises a helical gear. In operation, rotation of the first drive gear  502   a  about a first axis correspondingly rotates the first driven gear  504   a  about a second axis orthogonal to the first axis to control rotation of the shaft  202  in clockwise and counter-clockwise directions based on the rotational direction of the first drive gear  502   a.    
     The second drive gear  502   b  may be configured to intermesh with a second driven gear  504   b  (partially visible in  FIG. 5 ), and the third drive gear  502   c  may be configured to intermesh with a third driven gear  504   c.  In the illustrated embodiment, the second and third drive and driven gears  502   b,c,    504   b,c  comprise corresponding rack and pinion interfaces, where the driven gears  504   b,c  comprise the rack and the drive gears  502   b,c  comprise the pinion. Independent rotation of the second and third drive gears  502   b,c  will cause the second and third driven gears  504   b,c,  respectively, to translate linearly relative to (independent of) one another. 
     In at least one embodiment, actuation (rotation) of the third drive gear  502   c  will result in a surgical clip  416  ( FIG. 4 ) being fed into the jaws  412 . More particularly, the third driven gear  504   c  may be operatively coupled to the feedbar  418  ( FIG. 4 ) and, upon rotation of the third drive gear  502   c  in a first angular direction, the third driven gear  504   c  will advance distally and correspondingly advance the feedbar  418  a sufficient distance to fully advance a surgical clip into the jaws  412 . Rotation of the third drive gear  502   c  may be precisely controlled by an electrical and software interface to deliver the exact linear travel to the third driven gear  504   c  necessary to feed a clip  416  into the jaws  412 . 
     Upon delivery of a clip into the jaws  412 , or after a predetermined amount of rotation of the third drive gear  502   c,  rotation of the third drive gear  502   c  is reversed in a second angular direction to move the third driven gear  504   c  linearly in a proximal direction, which correspondingly moves the feedbar  418  proximally. This process may be repeated several times to accommodate a predetermined number of clips residing in the shaft  202 . 
     Actuation of the second drive gear  502   b  causes the jaws  412  to close or collapse to crimp a surgical clip. More particularly, the second driven gear  504   b  may be coupled to the proximal end  438   b  ( FIG. 4 ) of the push rod  424  ( FIG. 4 ) and, upon actuation of the second drive gear  502   b  in a first angular direction, the second driven gear  504   b  will be advanced linearly in a distal direction and correspondingly drive the push rod  424  distally, which drives the cam  422  over the jaws  412  to collapse the jaw members and crimp a surgical clip positioned in the jaws  412 . Once a surgical clip is successfully deployed, rotation of the second drive gear  502   b  is reversed in the opposite angular direction to move the second driven gear  504   b  in a proximal direction, which correspondingly moves the push rod  424  and the cam  422  proximally and permits the jaws  412  to open once again. 
     The processes of delivering a surgical clip into the jaws  412  and collapsing the jaws  412  to crimp the surgical clip are not limited to the actuation mechanisms and structures described herein. In alternative embodiments, for example, the second and third driven gears  504   b,c  may instead comprise capstan pulleys configured to route and translate drive cables within the shaft  202 . In such embodiments, the drive cables may be operatively coupled to one or more lead screws or other types of rotating members positioned within the shaft  202  near the distal end and capable of advancing the feedbar  418  to deliver a surgical clip into the jaws  412  and advancing the cam  422  to collapse the jaws  412  and crimp the surgical clip. 
       FIG. 6  is an isometric top view of another example surgical tool  600  that may incorporate some or all of the principles of the present disclosure. Similar to the surgical tool  200  of  FIG. 2 , the surgical tool  600  may be used in conjunction with the robotic surgical system  100  of  FIG. 1 . As illustrated, the surgical tool  600  includes an elongate shaft  602 , an end effector  604  positioned at the distal end of the shaft  602 , an articulation joint  606  (alternately referred to as a “articulable wrist joint”) that couples the end effector  604  to the distal end of the shaft  602 , and a drive housing  608  coupled to the proximal end of the shaft  602 . In some embodiments, the shaft  602 , and hence the end effector  604  coupled thereto, is configured to rotate about a longitudinal axis A 1 . 
     In the illustrated embodiment, the end effector  604  comprises a clip applier that includes opposing jaw members  610 ,  612  configured to collapse toward one another to crimp a surgical clip. The articulation joint  606  facilitates pivoting movement of the end effector  604  relative to the shaft  602  to position the end effector  604  at desired orientations and locations relative to a surgical site. The housing  608  includes (contains) various actuation mechanisms designed to control articulation at the articulation joint  606  and operation of the end effector  604 . 
       FIG. 7  illustrates the potential degrees of freedom in which the articulation joint  606  may be able to articulate (pivot). The degrees of freedom of the articulation joint  606  are represented by three translational variables (i.e., surge, heave, and sway), and by three rotational variables (i.e., Euler angles or roll, pitch, and yaw). The translational and rotational variables describe the position and orientation of a component of a surgical system (e.g., the end effector  604 ) with respect to a given reference Cartesian frame. As depicted in  FIG. 7 , “surge” refers to forward and backward translational movement, “heave” refers to translational movement up and down, and “sway” refers to translational movement left and right. With regard to the rotational terms, “roll” refers to tilting side to side, “pitch” refers to tilting forward and backward, and “yaw” refers to turning left and right. 
     The pivoting motion can include pitch movement about a first axis of the articulation joint  606  (e.g., X-axis), yaw movement about a second axis of the articulation joint  606  (e.g., Y-axis), and combinations thereof to allow for 360° rotational movement of the end effector  604  about the articulation joint  606 . In other applications, the pivoting motion can be limited to movement in a single plane, e.g., only pitch movement about the first axis of the articulation joint  606  or only yaw movement about the second axis of the articulation joint  606 , such that the end effector  604  moves only in a single plane. 
     Referring again to  FIG. 6 , the surgical tool  600  includes a plurality of drive cables (generally obscured in  FIG. 6 ) that form part of a cable driven motion system configured to facilitate operation and articulation (movement) of the end effector  604  relative to the shaft  602 . For example, selectively moving the drive cables can actuate the end effector  604  and thereby collapse the jaw members  610 ,  612  toward each other. Moreover, moving the drive cables can also move the end effector  604  between an unarticulated position and an articulated position. The end effector  604  is depicted in  FIG. 6  in the unarticulated position where a longitudinal axis A 2  of the end effector  604  is substantially aligned with the longitudinal axis A 1  of the shaft  602 , such that the end effector  604  is at a substantially zero angle relative to the shaft  602 . In the articulated position, the longitudinal axes A 1 , A 2  would be angularly offset from each other such that the end effector  604  is at a non-zero angle relative to the shaft  602 . 
       FIG. 8  is an enlarged isometric view of the distal end of the surgical tool  600  of  FIG. 6 . More specifically,  FIG. 8  depicts an enlarged and partially exploded view of the end effector  604  and the articulation joint  606 . The articulation joint  606  operatively couples the end effector  604  to the shaft  602 . To accomplish this, the articulation joint  606  includes a distal clevis  802   a,  a proximal clevis  802   b,  and a spacer  803  interposing the distal and proximal clevises  802   a,b.    
     The end effector  604  is coupled to the distal clevis  802   a  and the distal clevis  802   a  is rotatably mounted to the spacer  803  at a first axle  804   a.  The spacer  803  is rotatably mounted to the proximal clevis  802   b  at a second axle  804   b  and the proximal clevis  802   b  is coupled to a distal end  806  of the shaft  602 . 
     The articulation joint  606  provides a first pivot axis P 1  that extends through the first axle  804   a  and a second pivot axis P 2  that extends through the second axle  804   b.  The first pivot axis P 1  is substantially perpendicular (orthogonal) to the longitudinal axis A 2  of the end effector  604 , and the second pivot axis P 2  is substantially perpendicular (orthogonal) to both the longitudinal axis A 2  and the first pivot axis P 1 . Movement about the first pivot axis P 1  provides “yaw” articulation of the end effector  604 , and movement about the second pivot axis P 2  provides “pitch” articulation of the end effector  604 . 
     A plurality of drive cables  808  extend longitudinally within the shaft  602  and pass through the wrist  106  to be operatively coupled to the end effector  604 . The drive cables  808  form part of the cable driven motion system briefly described above, and may be referred to and otherwise characterized as cables, bands, lines, cords, wires, ropes, strings, twisted strings, elongate members, etc. 
     The drive cables  808  can be made from a variety of materials including, but not limited to, metal (e.g., tungsten, stainless steel, etc.) or a polymer. 
     The drive cables  808  extend proximally from the end effector  604  to the drive housing  608  ( FIG. 6 ) where they are operatively coupled to various actuation mechanisms or devices housed (contained) therein to facilitate longitudinal movement (translation) of the drive cables  808 . Selective actuation of the drive cables  808  causes the end effector  604  to articulate (pivot) relative to the shaft  602 . Moving a given drive cable  808  constitutes applying tension (i.e., pull force) to the given drive cable  808  in a proximal direction, which causes the given drive cable  808  to translate and thereby cause the end effector  604  to move (articulate) relative to the shaft  602 . 
     One or more actuation cables  810 , shown as first actuation cables  810   a  and second actuation cables  810 b, may also extend longitudinally within the shaft  602  and pass through the wrist  106  to be operatively coupled to the end effector  604 . The actuation cables  810   a,b  may be similar to the drive cables  808  and also form part of the cable driven motion system. Selectively actuating the actuation cables  810   a,b  causes the end effector  604  to actuate, such as collapsing the first and second jaw members  610 ,  612  to crimp a surgical clip (not shown). 
     More specifically, the actuation cables  810   a,b  may be operatively coupled to a cam  812  that is slidably engageable with the jaw members  610 ,  612 . One or more pulleys  814  may be used to receive and redirect the first actuation cables  810   a  for engagement with the cam  812 . Longitudinal movement of the first actuation cables  810   a  correspondingly moves the cam  812  distally relative to the jaw members  610 ,  612 . The distal end of the cam  812  includes a tapering recess or camming channel  816  formed therein for slidably receiving corresponding cam tracks  818  provided by the jaw members  610 ,  612 . As the cam  812  is advanced distally, the camming channel  816  pushes (collapses) the jaw members  610 ,  612  toward one another, thereby crimping a surgical clip (not shown) disposed therebetween. Actuation of the second actuation cables  810 b (one shown) pulls the cam  812  proximally, thereby allowing the jaw members  610 ,  612  to open again to receive another surgical clip. 
     Although not expressly depicted in  FIG. 8 , an assembly including, for example, a feedbar, a feeder shoe, and a clip track may be included at or near the end effector  604  to facilitate feeding surgical clips into the jaw members  610 ,  612 . In some embodiments, the feedbar (or a connecting member) may be flexible and extend through the articulation joint  606 . 
       FIG. 9  is a bottom view of the drive housing  608 , according to one or more embodiments. As illustrated, the drive housing  608  may include a tool mounting interface  902  used to operatively couple the drive housing  608  to a tool driver of a robotic manipulator. The tool mounting interface  902  may mechanically, magnetically, and/or electrically couple the drive housing  608  to a tool driver. 
     As illustrated, the interface  902  includes and supports a plurality of drive inputs, shown as drive inputs  906   a,    906   b,    906   c,    906   d,    906   e,  and  906   f.  Each drive input  906   a - f  may comprise a rotatable disc configured to align with and couple to a corresponding input actuator (not shown) of a tool driver. Moreover, each drive input  906   a - f  provides or defines one or more surface features  908  configured to align with mating features provided on the corresponding input actuator. The surface features  908  can include, for example, various protrusions and/or indentations that facilitate a mating engagement. 
     In some embodiments, actuation of the first drive input  906   a  may control rotation of the elongate shaft  602  about its longitudinal axis A 1 . Depending on the rotational actuation of the first drive input  906   a,  the elongate shaft  602  may be rotated clockwise or counter-clockwise. In some embodiments, selective actuation of the second and third drive inputs  906   b,c  may cause movement (axial translation) of the actuation cables  810   a,b  ( FIG. 8 ), which causes the cam  812  ( FIG. 8 ) to move and crimp a surgical clip, as generally described above. In some embodiments, actuation of the fourth drive input  906   d  feeds a surgical clip into the jaw members  610 ,  612  ( FIG. 8 ). In some embodiments, actuation of the fifth and sixth drive inputs  906   e,f  causes movement (axial translation) of the drive cables  808  ( FIG. 8 ), which results in articulation of the end effector  604 . Each of the drive inputs  906   a - f  may be actuated based on user inputs communicated to a tool driver coupled to the interface  902 , and the user inputs may be received via a computer system incorporated into the robotic surgical system. 
       FIG. 10  is an isometric exposed view of the interior of the drive housing  608 , according to one or more embodiments. Several component parts that may otherwise be contained within the drive housing  608  are not shown in  FIG. 10  to enable discussion of the depicted component parts. 
     As illustrated, the drive housing  608  contains a first capstan  1002   a,  which is operatively coupled to or extends from the first drive input  906   a  ( FIG. 9 ) such that actuation of the first drive input  906   a  results in rotation of the first capstan  1002   a.  A helical drive gear  1004  is coupled to or forms part of the first capstan  1002   a  and is configured to mesh and interact with a driven gear  1006  operatively coupled to the shaft  602  such that rotation of the driven gear  1006  correspondingly rotates the shaft  602 . Accordingly, rotation of the helical drive gear  1004  (via actuation of the first drive input  906   a  of  FIG. 9 ) will drive the driven gear  1006  and thereby control rotation of the elongate shaft  602  about the longitudinal axis A 1 . 
     The drive housing  608  also includes second and third capstans  1002   b  and  1002   c  operatively coupled to or extending from the second and third drive inputs  906   b,c  ( FIG. 9 ), respectively, such that actuation of the second and third drive inputs  906   b,c  results in rotation of the second and third capstans  1002   b,c.  The second and third capstans  1002   b,c  comprise capstan pulleys operatively coupled to the actuation cables  810   a,b  ( FIG. 8 ) such that rotation of a given capstan  1002   b,c  actuates (longitudinally moves) a corresponding one of the actuation cables  810   a,b.  Accordingly, selective rotation of the second and third capstans  1002   b,c  via actuation of the second and third drive inputs  906   b,c,  respectively, will cause movement (axial translation) of the actuation cables  810   a,b,  which causes the cam  812  ( FIG. 8 ) to move and crimp a surgical clip. 
     The drive housing  608  further includes a fourth capstan  1002   d,  which is operatively coupled to or extends from the fourth drive input  906   d  ( FIG. 9 ) such that actuation of the fourth drive input  906   d  results in rotation of the fourth capstan  1002   d.  A spur gear  1008  is coupled to or forms part of the fourth capstan  1002   d  and is configured to mesh and interact with a rack gear (not shown) also contained within the drive housing  608 . The rack gear may be operatively coupled to a feedbar (or another connecting member) which facilitates operation of a feeder shoe and associated clip track to feed surgical clips into the jaw members  610 ,  612  ( FIGS. 6 and 8 ). Accordingly, rotation of the spur gear  1008  (via actuation of the fourth drive input  906   d ) will control the feedbar and thereby control loading of surgical clips into the jaw members  610 ,  612  as desired. 
     The drive housing  608  further contains or houses fifth and sixth capstans  1002   e  and  1002   f  operatively coupled to or extending from the fifth and sixth drive inputs  906   e,f  ( FIG. 9 ), respectively, such that actuation of the fifth and sixth drive inputs  906   e,f  results in rotation of the fifth and sixth capstans  1002   e,f.  The fifth and sixth capstans  1002   e,f  comprise capstan pulleys operatively coupled to the drive cables  808  ( FIG. 8 ) such that rotation of a given capstan  1002   e,f  actuates (longitudinally moves) a corresponding one of the actuation cables  808 . Accordingly, selective rotation of the fifth and sixth capstans  1002   e,f  via actuation of the fifth and sixth drive inputs  906   e,f,  respectively, will cause movement (axial translation) of the drive cables  808  and thereby articulate (pivot) the end effector  604  relative to the shaft  602 . 
     The surgical tools  200 ,  600  described herein above may incorporate and facilitate the principles of the present disclosure in improving feeding and/or forming of surgical clips in robotic or non-robotic clip appliers. Moreover, it is contemplated herein to combine some or all of the features of the surgical tools  200 ,  600  to facilitate operation of the embodiments described below. Accordingly, example surgical tools that may incorporate the principles of the present disclosure may include geared actuators, capstan pulley and cable actuators, or any combination thereof, without departing from the scope of the disclosure. 
       FIG. 11A  is an isometric view of another example embodiment of the surgical tool  600 , according to one or more additional embodiments. As illustrated, the articulation joint  606  of  FIG. 6  is replaced with another articulation joint  1102 . Similar to the articulation joint  600 , the articulation joint  1102  couples the end effector  604  to the distal end of the shaft  602  and facilitates pivoting movement of the end effector  604  relative to the shaft  602  to position the end effector  604  at desired orientations and locations relative to a surgical site. In the illustrated depiction, the articulation joint  1102  has been moved (articulated) to redirect the end effector  604  off-axis relative to the longitudinal axis A 1  of the shaft  602 . 
     Unlike the articulation joint  600  of  FIG. 6 , however, the articulation joint  1102  comprises a flexible shaft length  1103  and may be characterized or otherwise referred to as a “snake” shaft or “flex” shaft. More specifically, instead of incorporating rotatable axles and pulleys driven by drive cables, the articulation joint  1102  may comprise a flexible or movable shaft length  1103  interposing the end effector  604  and the shaft  602  and capable of articulating (pivoting) in one or more planes based on actuation input derived from the drive housing  608 . Moreover, unlike the articulation joint  600 , the articulation joint  1102  may provide or otherwise define a lumen that extends along its axial length and may be configured to house and/or convey surgical clips therethrough to be received at the end effector  604  for crimping. Accordingly, surgical clips can be stored within the articulation joint  1102  and/or proximal thereto and advanced distally through the articulation joint  1102  to be received between the jaw members  610 ,  612 . 
     As used herein, the phrase “flexible shaft length” refers to the elongate body of an end effector articulation joint that is capable of bending or flexing between unarticulated and articulated states and that provides an inner lumen capable of storing surgical clips and/or facilitating distal advancement of surgical clips therethrough. While typical articulation joints have a fixed pivot or center of rotation, the flexible shaft length has a moving center of rotation. In one embodiment, for example, the flexible shaft length  1103  may comprise a series of articulation links rotatably coupled to each other and manipulatable with one or more drive cables extending from the drive housing  608 . In such embodiments, selective actuation of the drive cable(s) causes the flexible shaft length  1103  to articulate (pivot) in one or more planes. In other embodiments, the flexible shaft length  1103  may comprise an elongate structure having a plurality of recesses removed along its length to enable the elongate structure to bend or flex in one or more planes upon assuming tensile loads derived from drive cable(s) extending from the drive housing  608 . In yet other embodiments, the flexible shaft length  1103  may comprise a flexible or bendable shaft section capable of bending or flexing in one or more planes upon assuming tensile loads derived from drive cable(s) extending from the drive housing  608 . 
       FIG. 11B  is an exploded view of an example embodiment of the articulation joint  1102 , according to one or more embodiments. While the articulation joint  1102  is described herein with respect to a particular snake shaft or flex shaft design, it will be appreciated that the articulation joint  1102  may alternatively comprise other snake shaft or flex shaft designs without departing from the scope of the disclosure. For example, suitable alternative forms of the articulation joint  1102  are described in U.S. Pat. No. 9,232,979 to Parihar et al., U.S. Pat. No. 8,685,020 to Weizman et al., U.S. Pat. No. 8,262,563 to Bakos et al., U.S. Pat. No. 8,403,945 to Whitfield et al., and U.S. Patent Pub. 2007/0084897 to Shelton, IV et al., the contents of which are hereby incorporated by reference. 
     As illustrated, the articulation joint  1102  may include a distal connector  1104   a,  a proximal connector  1104   b,  and a plurality of articulation links  1106  capable of being interconnected to extend between the distal and proximal connectors  1104   a,b.  The distal connector  1104   a  may be configured to couple the articulation joint  1102  to the end effector  604  ( FIG. 11A ), and the proximal connector  1104   b  may be configured to couple the articulation joint  1102  to the distal end of the shaft  602  ( FIG. 11A ). While  FIG. 11B  depicts fourteen articulation links  1106 , the articulation joint  1102  could alternatively include more or less than fourteen articulation links  1106 , without departing from the scope of the disclosure. 
     The articulation links  1106  are interconnectable in series to cooperatively form the flexible shaft length  1103 . To accomplish this, each articulation link  1106  may provide or otherwise define a pair of lobes  1108  at one axial end and a corresponding pair of recesses  1110  at the opposite axial end. To interconnect the articulation links  1106 , the lobes  1108  of the more proximal articulation links  1106  are received within or at the recesses  1110  of the more distal articulation links  1106 . It will be appreciated, however, that the articulation links  1106  may alternatively be arranged in reverse where the lobes  1108  of the more distal articulation links  1106  would be received within the recesses  1110  of the more proximal articulation links  1106 , without departing from the scope of the disclosure. A mechanical fastener (not shown), such as a pin or the like, may be used to couple the adjacent articulation links  1106  at the intersection of the corresponding lobes and recesses  1108 ,  1110 . The mechanical fastener may allow relative (but limited) rotational movement between the adjacent articulation links  1106  about an articulation axis A 3  defined through each pair of lobes  1108  as interconnected with a corresponding pair of recesses  1110 . 
     The distal-most articulation link  1106   a  may be coupled to a proximal end  1112   a  of the distal connector  1104   a,  and the proximal-most articulation link  1106   b  may be coupled to the distal end  1112   b  of the proximal connector  1104   b.  More specifically, the lobes  1108  of the distal-most articulation link  1106   a  may be received into corresponding recesses  1114  (one visible) provided on the distal connector  1104   a,  and the recesses  1110  of the proximal-most articulation link  1106   b  may receive corresponding lobes  1116  provided by the proximal connector  1104   b.  Similar to the interconnection of the articulation links  1106 , a mechanical fastener may be used to couple the distal-most articulation link  1106   a  to the distal connector  1104   a,  and couple the proximal-most articulation link  1106   b  to the proximal connector  1104   b.  The mechanical fastener may or may not allow relative movement (rotation) between the adjacent component parts. 
     The articulation joint  1102  also includes one or more articulation cables, shown as a first articulation cable  1118   a  and a second articulation cable  1118   b.  The articulation cables  1118   a,b  are actuatable to move the articulation joint  1102  in at least one plane of motion. The articulation cables  1118   a,b  extend from the drive housing  608  ( FIG. 11A ), where they may be operatively coupled to one or more drive inputs operable to facilitate longitudinal translation of the articulation cables  1118   a,b  and thereby cause articulation of the articulation joint  1102 . The articulation cables  1118   a,b  may extend along the entire axial length of the articulation joint  1102  and may terminate at the distal connector  1104   a  with a pair of cable connectors  1120 . 
     The articulation cables  1118   a,b  may be operatively coupled to some or all of the articulation links  1106  as they extend along the axial length of the articulation joint  1102 . In some embodiments, for example, the articulation cables  1118   a,b  may be threaded to/through some or all of the articulation links  1106 . More specifically, the articulation cables  1118   a,b  may pass through opposing cable paths  1122  provided on angularly opposite sides of each articulation link  1106 . When the articulation joint  1102  is assembled, the cable paths  1122  of each articulation link  1106  may axially align such that the articulation cables  1118   a,b  can pass therethough in a relatively direct course. The articulation cables  1118   a,b  are not bound within the cable paths  1122 , thereby allowing the articulation cables  1118   a,b  to axially translate relative to the articulation links  1106  during operation, which facilitates articulation of the articulation joint  1102  in at least one plane of motion. 
     Having the two articulation cables  1118   a,b  arranged on angularly opposite sides of the articulation links  1106  allows the articulation cables  1118   a,b  to move the articulation joint  1102  in a single plane of motion, such as left-to-right or “yaw” motion. For example, when the articulation joint  1102  is assembled as described above, providing tension (pulling) on the first articulation cable  1118   a  and simultaneously slackening the second articulation cable  1118   b  may result in the articulation joint  1102  articulating in a first direction B 1 . In contrast, providing tension (pulling) on the second articulation cable  1118   b  and simultaneously slackening the first articulation cable  1118   a  may result in the articulation joint  1102  articulating in a second direction B 2 , opposite the first direction B 1 . 
     The articulation joint  1102  may also be configured to move in a second plane of motion; i.e., up-and-down or “pitch” motion. To accomplish this, the elongate shaft  602  ( FIG. 11A ) may first be rotated 90° about the longitudinal axis A 1 , such as by rotating the helical drive gear  1004  and corresponding driven gear  1006  of  FIG. 10 . As will be appreciated, rotating the elongate shaft  602  about the longitudinal axis A 1  allows the articulation joint  1102  to be articulated in an unlimited number of planes. 
     In embodiments where the articulation joint  1102  does not include the articulation links  1106  coupled at corresponding lobes  1108  and recesses  1110 , however, an additional two articulation cables (not shown) may be included in the articulation joint  1102  and angularly offset from the first and second articulation cables  1118   a,b  by 90° about the periphery of each articulation link  1106 . Providing tension (pulling) on one of the additional articulation cables while simultaneously slackening the other of the additional articulation cables will articulate the articulation joint  1102  in pitch. 
     When interconnected, the articulation links  1106  provide or otherwise define a lumen that extends along the entire length of the articulation joint  1102 . As described herein, a plurality of surgical clips  1124  may be arranged or arrangeable in series within the lumen to be fed distally toward the end effector  604  ( FIG. 11A ). As illustrated, the surgical clips  1124  may be arranged in series such that the legs  1126  of the more proximal surgical clips  1124  engage at or near the crown  1128  of the more distal surgical clips  1124 . While the surgical clips  1124  are depicted as arranged with the legs  1126  leading the corresponding crowns  1128  in the distal direction, it is equally contemplated herein to have the surgical clips  1124  arranged in reverse order, where the crown  1128  of each surgical clip  1124  leads in the distal direction. 
     In some embodiments, a feedbar  1130  (alternately referred to as a “clip pusher”) may be used to push the series of surgical clips  1124  through the lumen of the articulation joint  1102 . The feedbar  1130  may extend from the drive housing  608  ( FIG. 11A ) where it may be operatively coupled to one or more drive inputs operable to facilitate longitudinal translation of the feedbar  1130 . In such embodiments, the drive input(s) may be selectively actuated to advance the feedbar  1130  (and, therefore, the surgical clips  1124 ) a predetermined distance. In other embodiments, however, the feedbar  1130  may be operatively coupled to another type drive mechanism arranged proximal to the articulation joint  1102  but distal to the drive housing  608 . The feedbar  1130  may be rigid enough to provide an axial load on the surgical clips  1124 , but flexible enough such that the feedbar  1130  is able to flex or bend when the articulation joint  1102  articulates during operation. 
     In other embodiments, however, the feedbar  1130  may be omitted and the surgical clips  1124  may instead be advanced through the articulation joint  1102  with another type of clip advancing device or mechanism. For example, in at least one embodiment, a biasing device (e.g., a spring or spring loaded feeder shoe) may be incorporated into the articulation joint  1102  to selectively advance the surgical clips  1124  toward the end effector  604  ( FIG. 11A ). In such embodiments, the biasing device may or may not have an indexible feeder shoe, as known in the art. 
       FIG. 11C  is a cross-sectional side view of the assembled articulation joint  1102 , according to one or more embodiments. As illustrated, the articulation links  1106  are interconnected and the articulation cables  1118   a,b  are operatively coupled to (e.g., threaded through) each articulation link  1106  and terminate at the distal connector  1104   a,  as generally described above. Moreover, the articulation joint  1102  is shown in a first or unarticulated state, where the articulation joint  1102  extends generally straight and otherwise coaxial with the longitudinal axis A 1  ( FIGS. 6 and 11A ) of the shaft  602 . 
     As also illustrated, the assembled articulation links  1106  provide or otherwise cooperatively define a lumen  1132  that extends along the entire length of the articulation joint  1102 . The surgical clips  1124  may be arranged in series within the lumen  1132  and the feedbar  1130  is positioned proximal to the surgical clips  1124  and poised to advance the surgical clips  1124  distally. In some embodiments, the surgical clips  1124  may be stored within the lumen  1132  until needed, but may alternatively be stored proximal to the articulation joint  1102  and advanced distally with the feedbar  1130  when needed. 
     In some embodiments, as illustrated, the articulation joint  1102  may further include a retention member  1134  positioned at or near the distal end of the articulation joint  1102 . In some embodiments, the retention member  1134  may be configured to engage the distal-most surgical clip  1124   a  and thereby prevent the serially-arranged (stacked) surgical clips  1124  from advancing distally until the axial load provided by the feedbar  1130  overcomes the retentive forces provided by the retention member  1134 . Accordingly, the retention member  1134  may operate as an indexing mechanism to sequentially feed individual surgical clips  1124  to the end effector  604  ( FIG. 11A ). 
     In some embodiments, the retention member  1134  may comprise a passive biasing device, such as a gate spring or the like. In such embodiments, the spring force of the retention member  1134  may be sufficient to retain the stacked surgical clips  1124  in place, but may be overcome when the feedbar  1130  applies a sufficiently large axial load on the stacked surgical clips  1124 . In other embodiments, however, the retention member  1134  may comprise an actuatable device configured to retain the stacked surgical clips  1124  in place and selectively release the distal-most surgical clip  1124   a  when actuated. In such embodiments, the retention member  1134  may be actuated and otherwise driven using any of the actuation components associated with the drive housings  206 ,  608  ( FIGS. 2 and 6 , respectively) discussed herein, or alternatively may be operatively coupled to a cable-driven worm gear or the like arranged near the articulation joint  1102 . 
     In yet other embodiments, in addition to preventing the stacked surgical clips  1124  from advancing distally, or alternatively, the retention member  1134  may be configured to rotate the surgical clips  1124  to a predetermined orientation before the clips  1124  are fed into the end effector  604 . 
       FIG. 11D  is another cross-sectional side view of the assembled articulation joint  1102 , according to one or more embodiments. The articulation joint  1102  is shown in  FIG. 11D  as having moved from the unarticulated state of  FIG. 11C  to a second or articulated state. As used herein, “articulated state” refers to any position or orientation of the articulation joint  1102  that places the end effector  604  ( FIG. 11A ) off-axis from the longitudinal axis A 1  ( FIG. 11A ) of the shaft  602  ( FIG. 11A ). To transition the articulation joint  1102  to the depicted articulated state, a tensile load may be applied on the second articulation cable  1118   b  in the proximal direction C 1 , while the first articulation cable  1118   a  is simultaneously slackened in the distal direction C 2 . In contrast, to transition the articulation joint  1102  to an opposed articulated state in the same plane, a tensile load may be applied on the first articulation cable  1118   a  while simultaneously slackening the second articulation cable  1118   b.  The rotatably interconnected articulation links  1106  allow the articulated joint  1102  to flex (bend) as the articulation cables  118   a,b  are oppositely actuated. 
     Unlike conventional flex shaft designs and applications, the articulation joint  1102  may be capable of storing and/or conveying the surgical clips  1124  through the lumen  1132  defined by the articulation links  1106  while the articulation joint  1102  is in the unarticulated or articulated states. This advantage allows the surgical clips  1124  to be stored efficiently without interfering with the articulation joint  1102 , and also allows for increased articulation with fine manipulation. The surgical clips  1124 , however, must remain straight and otherwise non-deformed while the articulation joint  1102  articulates and/or as the surgical clips  1124  are fed distally through the articulation joint  1102 . According to embodiments of the present disclosure, the articulation joint  1102  may provide or otherwise define a clip track configured to receive and guide the surgical clips  1124  through the articulation joint  1102 . As described herein, the clip track may provide a pathway for the surgical clips  1124  to advance distally when the articulation joint is in the unarticulated or articulated states. When the articulation joint  1102  is in the articulated state, the clip track may be necessary to help guide the surgical clips  1124  through a tortuous path provided by the articulation joint  1102 . 
       FIG. 12  is a cross-sectional end view of a portion of the articulation joint  1102 , according to one or more embodiments. More specifically,  FIG. 12  is a cross-sectional end view of an example articulation link  1106 . In embodiments where the articulation joint  1102  does not include articulation links  1106 , however, but instead comprises an elongate structure defining a plurality of recesses or comprises a flexible or bendable shaft section,  FIG. 12  may depict a cross-sectional end view at any location along the axial length of the articulation joint  1102 . For purposes of the present discussion, however,  FIG. 12  will be described in conjunction with a cross-sectional end view of an example articulation link  1106 . But it will be appreciated that the following description can equally be applied to alternative designs of the articulation joint  1102 , without departing from the scope of the disclosure. 
     As illustrated, the articulation joint  1102  is generally cylindrical in shape and defines or otherwise provides the lumen  1132  that extends along the entire axial length of the articulation joint  1102 . In other embodiments, however, the articulation joint  1102  may exhibit other cross-sectional shapes, such as polygonal (e.g., square) or ovoid, without departing from the scope of the disclosure. The first and second articulation cables  1118   a,b  are shown extending through corresponding cable paths  1122  located on angularly opposite positions of the articulation joint  1102 . In other embodiments, the cable paths  1122  may be located external to the articulation joint  1102  and otherwise coupled to the exterior thereof, without departing from the scope of the disclosure. 
     A cross-sectional end view of an example surgical clip  1124  is also depicted in  FIG. 12 . In the illustrated embodiment, at least a portion of the surgical clip  1124  is received within a clip track  1202  defined in the inner wall of the lumen  1132 . The clip track  1202  may be configured to support and guide the surgical clips  1124  within the lumen  1132  as they advance distally through the articulation joint  1102 . Moreover, the clip track  1202  may help the surgical clips  1124  navigate through the single plane articulation joint  1102  by guiding the clips  1124  perpendicular to the bend direction. Consequently, the clip track  1202  helps align the surgical clips  1124  with the bend direction, which allows for higher curvature potential of the articulation joint  1102 . 
     To accomplish this, the clip track  1202  may include opposing side rails  1204  (alternately referred to as “slots”) defined on angularly opposite sides of the lumen  1132  and configured to receive and support corresponding portions of the surgical clips  1124 . In some embodiments, as illustrated, the cross-sectional shape of the side rails  1204  may be polygonal (e.g., square or rectangular), but could alternatively be arcuate or ovoid in shape, without departing from the scope of the disclosure. In any event, the side rails  1204  may be shaped to receive and allow the surgical clips  1124  to slide therein as they advance distally within the lumen  1132 . 
     In some embodiments, the clip track  1202  may twist or provide a helical path for the surgical clips  1124 . In such embodiments, the surgical clips  1124  may enter the articulation joint  1102  in a vertical alignment, and the side rails  1204  may provide a helical path along the length of the articulation joint  1102  such that the surgical clips  1124  exit the articulation joint  1102  in a horizontal alignment. This may prove advantageous in embodiments where the jaw members  610 ,  612  ( FIG. 11A ) are horizontally-oriented, but the surgical clips  1124  are stored proximal to the end effector  604  ( FIG. 11A ) in a vertical orientation. 
       FIGS. 13A-13E  are cross-sectional top views of the articulation joint  1102 , as taken along the line indicated in  FIG. 12 . In  FIG. 13A , the surgical clip  1124  is depicted within the lumen  1132  and supported by the clip track  1202 . More specifically, the legs  1126  of the surgical clip  1124  are at least partially received into the opposing side rails  1204  and the crown  1128  is generally centered within the lumen  1132 . 
     In  FIG. 13B , the surgical clip  1124  includes or otherwise provides clip posts or tabs  1302  that extend laterally from each leg  1126 . The clip tabs  1302  may be configured to extend into or otherwise be received within the opposing side rails  1204  of the clip track  1202 . The clip tabs  1302  operate to support the surgical clip  1124  within the lumen  1132  and slidably engage the side rails  1204  as the surgical clip  1124  advances within the clip track  1202 . At least one advantage to using surgical clips  1124  with the clip tabs  1302  is that the clips are more readily pivotable about the tabs, allowing for the highest attainable articulation of the clip without bending or pre-forming the clip in any way (as opposed to an entire length of a leg being captured in the curved track). 
     In  FIG. 13C , the surgical clip  1124  is generally pear-shaped and has opposing shoulders  1304  defined on each leg  1126 . The shoulders  1304  may comprise bends in the legs  1126  that are configured to extend into or otherwise be received within the opposing side rails  1204  of the clip track  1202 . Similar to the clip tabs  1302  of  FIG. 13B , the shoulders  1304  may operate to support the surgical clip  1124  within the lumen  1132  and slidably engage the side rails  1204  as the surgical clip  1124  advances within the clip track  1202 . 
     In some embodiments, the surgical clip  1124  is received within the clip track  1202  via an interference fit that elastically flexes the legs inward and results in the surgical clip  1124  assuming the pear-shaped configuration. Upon exiting the confines of the lumen  1302 , the legs  1126  may be able to flex and open fully. In other embodiments, however, the surgical clip  1124  may be naturally in the pear-shaped configuration. In such embodiments, the articulation joint  1102  may include a device or mechanism configured to receive the pear-shaped surgical clips  1124  from the lumen  1132  and re-form it to a shape ready for crimping. At least one advantage to using pear-shaped surgical clips  1124  is minimizing the diameter of the lumen  1132 , which can minimize the size (diameter) of the end effector  604  ( FIG. 11A ). Moreover, the pear-shaped clips  1124  may also prove advantageous in providing small and tight packing (stacking). 
     In  FIG. 13D , the surgical clip  1124  is generally V-shaped and the legs  1126  may be angled toward the inner wall of the lumen  1132 . The legs  1126  extend into and are otherwise received by the opposing side rails  1204  of the clip track  1202 , and the angled legs  1126  operate to support the surgical clip  1124  within the lumen  1132  and slidably engage the corresponding side rails  1204  as the surgical clip  1124  advances distally within the articulation joint  1102 . 
     At least one advantage to the V-shaped surgical clips  1124  is the ability to stack the surgical clips  1124  in a nested arrangement where the legs  1126  of the more proximal surgical clips  1124  extend past the crown  1128  of the more distal-surgical clips  1124 . This nested arrangement allows more surgical clips  1124  to be stacked together in contrast to typical clip stacking arrangements where the legs  1126  of the more proximal surgical clips  1124  engage the crown  1128  of the more distal-surgical clips  1124 . 
     In  FIG. 13E , the surgical clip  1124  is generally W-shaped. The legs  1126  may be angled toward the inner wall of the lumen  1132 , and the crown  1128  may provide an undulating section. The legs  1126  extend into and are otherwise received by the opposing side rails  1204  of the clip track  1202 . The angled legs  1126  operate to support the surgical clip  1124  within the lumen  1132  and slidably engage the corresponding side rails  1204  as the surgical clip  1124  advances distally within the articulation joint  1102 . At least one advantage to the W-shaped surgical clip  1124  is that the undulating crown  1128  provides additional surfaces and/or structure to engage with the feedbar  1130  ( FIG. 11B ). In addition, the W-shaped surgical clip  1124  provides a similar ability to stack in a nested arrangement as the V-shaped clip  1128  of  FIG. 13D , thus allowing more surgical clips to be stacked together. 
       FIG. 14A  is a cross-sectional side view of another example articulation joint  1402 , according to one or more embodiments of the present disclosure. The articulation joint  1402  may be similar in some respects to the articulation joint  1102  of  FIGS. 11A-11D  and, therefore, may be best understood with reference thereto. Similar to the articulation joint  1102 , for example, the articulation joint  1402  may comprise a flexible shaft length  1403  that defines a lumen  1404  extending along the axial length of the articulation joint  1402 . The lumen  1404  may be configured to house and/or convey a plurality of surgical clips  1124  therethrough to be received at the end effector  604  ( FIG. 11A ) for crimping. Accordingly, surgical clips  1124  can be stored within the flexible shaft length  1403  and/or proximal thereto and advanced distally through the articulation joint  1402  to be received between the jaw members  610 ,  612  ( FIG. 11A ). 
     Moreover, similar to the articulation joint  1102  of  FIGS. 11A-11D , the articulation joint  1402  may include the articulation cables  1118   a,b  operatively coupled to the flexible shaft length  1403  to cause articulation thereof in at least one plane of motion. In the illustrated embodiment, the articulation cables  1118   a,b  are located on angularly opposite positions of the flexible shaft length  1403  (e.g., 180° offset) and extend along all or a portion of the axial length thereof. In some embodiments, the articulation cables  1118   a,b  may extend through the sidewall of the flexible shaft length  1403 . More specifically, the articulation cables  1118   a,b  may be threaded through corresponding and opposing cable paths  1122  formed or otherwise provided on angularly opposite sides of the flexible shaft length  1403 . In other embodiments, however, the articulation cables  1118   a,b  may be operatively coupled to the exterior of the flexible shaft length  1403 . In such embodiments, the cable paths  1122  may be located external to the flexible shaft length  1403  and otherwise coupled to the exterior thereof. 
     The articulation cables  1118   a,b  may or may not be bound within the cable paths  1122 . Moreover, in some embodiments, more than the two depicted articulation cables  1118   a,b  may be employed to allow the articulation joint  1402  to articulate in multiple planes of motion. 
     Unlike the articulation joint  1102  of  FIGS. 11A-11D , however, the articulation joint  1402  may be made of a flexible material that allows the articulation joint  1402  to transition between unarticulated and articulated states in one or more planes of motion as acted upon by the articulation cables  1118   a,b.  Suitable flexible materials include, but are not limited to, a rubber (e.g., silicone rubber), a flexible plastic, an elastomer, nylon, spandex/lycra, and any combination thereof. In other embodiments, the flexible material may comprise a laser cut metal tube (that is one piece), which can flex like lower modulus materials. In yet other embodiments, the flexible material may comprise a woven metal or plastic sheath or jacketing. 
     The articulation joint  1402  may further provide or otherwise define a clip track  1406  configured to receive and guide the surgical clips  1124  through the lumen  1404 . The clip track  1406  may provide a pathway for the surgical clips  1124  when the articulation joint  1402  is in the unarticulated or articulated states. When the articulation joint  1402  is in the articulated state, the clip track  1406  may be necessary to help guide the surgical clips  1124  through a tortuous path provided by the articulation joint  1402 . Accordingly, the clip track  1406  may prove advantageous in helping the surgical clips  1124  navigate through the single plane articulation joint  1402  by guiding the clips  1124  perpendicular to the bend direction. 
     In the illustrated embodiment, the clip track  1406  comprises opposing guide rails  1408  arranged within the lumen  1404 . The guide rails  1408  may be offset from each other and otherwise cooperatively define a clip passageway  1410  configured to receive and guide the surgical clips  1124  therein as they traverse the articulation joint  1402 . As illustrated, the surgical clips  1124  are arranged in series within the clip passageway  1410 . In some embodiments, the guide rails  1408  may be attached to the inner wall of the lumen  1404  at one or more locations. The number of attachment points may directly correlate to the flexibility of the guide rails  1408  relative to the lumen  1404  (e.g., more contact points =less flex, less contact points =more flex). In other embodiments, the guide rails  1408  may be attached at the proximal and distal ends of the articulation joint  1402 . 
     The guide rails  1408  may be made of a flexible material, such as any of the flexible materials mentioned herein. This allows the clip track  1406  to correspondingly flex in response to movement (articulation) of the flexible shaft length  1403 . The guide rails  1408  may be positioned within the lumen  1404  such that the clip passageway  1410  widens within a single plane to allow the surgical clips to align with the bend direction of the articulation joint  1402 . Moreover, the guide rails  1408  may be positioned within the lumen  1404  such that the clip passageway  1410  becomes progressively wider near the point of maximum bend, such that the surgical clips  1124  are then capable of translating and rotating around said bend without binding at their distal or proximal ends. 
     The articulation joint  1102  is shown in  FIG. 14A  in a first or unarticulated state, where the articulation joint  1402  extends generally straight and otherwise coaxial with the longitudinal axis A 1  ( FIGS. 6 and 11A ) of the shaft  602 . 
       FIG. 14B  is another cross-sectional side view of the articulation joint  1402 , according to one or more embodiments. The articulation joint  1402  is shown in  FIG. 14B  as having moved from the unarticulated state of  FIG. 14A  to a second or articulated state. To transition the articulation joint  1402  to the depicted articulated state, a tensile load may be applied on the second articulation cable  1118   b  in the proximal direction C 1 , while the first articulation cable  1118   a  is simultaneously slackened in the distal direction C 2 . In contrast, to transition the articulation joint  1402  to an opposed articulated state in the same plane, a tensile load may be applied on the first articulation cable  1118   a  while simultaneously slackening the second articulation cable  1118   b.  The flexible material allows the articulated joint  1402  to flex (bend) as the articulation cables  118   a,b  are oppositely actuated. 
     As the articulation joint  1402  is moved to the articulated position, the guide rails  1408  flex and widen within a single plane perpendicular to the bend direction of the articulation joint  1402 . As illustrated, the size of the clip passageway  1410  increases to accommodate the bend in the flexible shaft length  1403  and also to accommodate the axially-extending surgical clips  1124  as they traverse the tortuous path resulting from movement of the flexible shaft length  1403 . As will be appreciated, this may prove advantageous in allowing the surgical clips  1124  to be fed distally within the clip track  1406  when the articulated joint  1402  is articulated in either direction. Moreover, the clip track  1406  helps align the surgical clips  1124  with the bend direction, which allows for higher curvature potential of the articulation joint  1402 . 
       FIG. 15A  is a side view of another example articulation joint  1502 , according to one or more embodiments of the present disclosure. The articulation joint  1502  may be similar in some respects to the articulation joints  1102  and  1402  of  FIGS. 11A-11D and 14A-14B , respectively and, therefore, may be best understood with reference thereto. Similar to the articulation joints  1102  and  1402 , for example, the articulation joint  1502  may comprise a flexible shaft length  1503  that defines a lumen that extends along its axial length. A plurality of surgical clips  1124  may be housed within and/or conveyed through the lumen to be received at the end effector  604  for crimping. Accordingly, surgical clips  1124  can be stored within the flexible shaft length  1503  and/or proximal thereto and advanced distally through the articulation joint  1502  with the feedbar  1130  to be received between the jaw members  610 ,  612 . 
     Similar to the articulation joint  1102  of  FIGS. 11A-11D , the articulation joint  1502  may include a plurality of articulation links  1504  that may be interconnectable in series to cooperatively form the flexible shaft length  1503 . In other embodiments, however, the flexible shaft length  1503  may alternatively comprise a continuous shaft length made of a flexible material. 
     Furthermore, similar to the articulation joint  1102  and  1402  of  FIGS. 11A-11D and 14A-14B , respectively, the articulation joint  1502  may include the articulation cables  1118   a,b  operatively coupled to the flexible shaft length  1503  to cause bending or flexing articulation thereof. In the illustrated embodiment, the articulation cables  1118   a,b  are located on angularly opposite sides of the flexible shaft length  1503  and extend along all or a portion of the axial length thereof. In some embodiments, the articulation cables  1118   a,b  may extend through the articulation links  1504 , such as being threaded through each articulation link  1504  in corresponding cable paths (e.g., the cable paths  1122  of  FIG. 11A ). 
     To transition the articulation joint  1502  to the depicted articulated state, a tensile load may be applied on the second articulation cable  1118   b  in the proximal direction C 1 , while the first articulation cable  1118   a  is simultaneously slackened in the distal direction C 2 . In contrast, to transition the articulation joint  1502  to an opposed articulated state in the same plane, a tensile load may be applied on the first articulation cable  1118   a  while simultaneously slackening the second articulation cable  1118   b.    
     The articulation joint  1502  may further include a clip track provided or otherwise defined within the lumen that helps guide the surgical clips  1124  toward the end effector  604 . In the present embodiment, the clip track may be configured to twist or provide a helical path for the surgical clips  1124  to traverse along at least a portion of the articulation joint  1502 . In some embodiments, for example, the surgical clips  1124  may enter the articulation joint  1502  in a vertical orientation and the clip track may provide a helical path that alters the orientation of the surgical clips  1124  such that the surgical clips  1124  exit the articulation joint  1502  in a horizontal alignment. Accordingly, the clip track may be configured to receive surgical clips  1124  in a first angular orientation, and discharge the surgical clips in a second angular orientation, where the second angular orientation is 90° offset from the first angular orientation. As will be appreciated, this may prove advantageous in applications where the surgical clips  1124  are stored in a vertical orientation, but the jaw members  610 ,  612  are arranged in a horizontal orientation. In such applications, the clip track may properly orient the surgical clips  1124  to be aligned with the jaw members  610 ,  612 . 
       FIG. 15B  is a shortened side view of at least a portion of the articulation joint  1502  of  FIG. 15A , according to one or more embodiments of the present disclosure. It is noted that the entire axial length of the articulation joint  1502  is not drawn to scale in  FIG. 15B . Rather, for simplicity the length has been shortened for the present discussion. 
     As illustrated, the flexible shaft length  1503  comprises a generally cylindrical body having a proximal end  1510   a  and a distal end  1510 b opposite the proximal end  1510   a.  In some embodiments, the flexible shaft length  1503  may comprise the interconnected articulation links  1504  of  FIG. 15A , but could alternatively comprise a continuous shaft length made of a flexible material, as mentioned above. A lumen  1512  may be defined within the flexible shaft length  1503  and extends between the proximal and distal ends  1510   a,b.    
     A clip track  1514  may be provided or otherwise defined by the articulation joint  1502  within the lumen  1512  and may extend between the proximal and distal ends  1510   a,b.  The clip track  1514  may be defined into the inner wall of the flexible shaft length  1503  and may comprise opposing side rails  1516  sized to receive a portion of the surgical clips  1124 . For example, in some embodiments, the side rails  1516  may be configured to receive the legs  1126  of the surgical clips  1124 . However, any of the configurations shown and described with reference to  FIGS. 13A-13E  may equally apply to this embodiment. 
     The side rails  1516  may extend distally in a corresponding curved or helical pathway between the proximal and distal ends  1510   a,b.  The helical pathway may be configured to transition the orientation of the surgical clips  1124  90° as they traverse the articulation joint  1502 . Accordingly, a surgical clip  1124  oriented entering the articulation joint  1502  in a vertical orientation at the proximal end  1510   a  will be transitioned to a horizontal orientation upon traversing the clip track  1514  and exiting the articulation joint  1502  at the distal end  1510   b.    
     In some embodiments, the clip track  1514  may be defined along only a portion of the flexible shaft length  1503 . In such embodiments, the surgical clips  1124  may be conveyed at least partially through the flexible shaft length  1503  until encountering the clip track  1514 . The surgical clips  1124  may then be fed into the clip track  1514  in a first angular orientation, and exit the clip track  1514  at a second angular orientation that is 90° offset from the first angular orientation. In other embodiments, however, the clip track  1514  may alternatively be provided by an entirely separate structure arranged distal to the articulation joint  1502 , without departing from the scope of the disclosure. 
     Embodiments disclosed herein include: 
     A. A surgical clip applier that includes a drive housing, an elongate shaft that extends distally from the drive housing, an end effector arranged at a distal end of the elongate shaft and including first and second jaw members, and an articulation joint interposing the end effector and the elongate shaft. The articulation joint includes a flexible shaft length articulable in a plane of motion and having a first end and a second end, a lumen defined within the flexible shaft length and extending between the first and second ends, and a clip track provided within the lumen and extending at least partially between the first and second ends to guide surgical clips through the articulation joint to be received by the first and second jaw members for crimping. 
     B. A method of operating a surgical clip applier that includes positioning the surgical clip applier adjacent a patient for operation, the surgical clip applier including a drive housing, an elongate shaft that extends distally from the drive housing, an end effector arranged at a distal end of the elongate shaft and including first and second jaw members, and an articulation joint interposing the end effector and the elongate shaft. The articulation joint includes a flexible shaft length articulable in a plane of motion and having a first end and a second end, a lumen defined within the flexible shaft length and extending between the first and second ends, and a clip track provided within the lumen and extending at least partially between the first and second ends. The method further includes articulating the flexible shaft length in the plane of motion between an unarticulated state and an articulated state, advancing one or more surgical clips through the lumen with the flexible shaft length in the unarticulated state or the articulated state, guiding the one or more surgical clips through the articulation joint with the clip track, receiving a distal-most surgical clip of the one or more surgical clips from the articulation joint with the first and second jaw members, and collapsing the first and second jaw members to crimp the distal-most surgical clip. 
     Each of embodiments A and B may have one or more of the following additional elements in any combination: Element  1 : wherein the clip track extends perpendicular to the plane of motion. Element  2 : wherein the clip track provides opposing side rails defined on angularly opposite sides of the lumen and a portion of each surgical clip is receivable within and supported by the opposing side rails. Element  3 : wherein the portion of each surgical clip slidably engages the opposing side rails as each surgical clip advances distally within the clip track. Element  4 : wherein the clip track provides a helical path such that the surgical clips enter the flexible shaft length joint in a first angular orientation and exit the articulation joint in a second angular orientation angularly offset from the first angular orientation. Element  5 : further comprising one or more articulation cables extending from the drive housing and operatively coupled to the flexible shaft length, wherein the one or more articulation cables are actuatable to move the articulation joint in the plane of motion. Element  6 : wherein the flexible shaft length comprises a plurality of articulation links interconnected in series and extending between the first and second ends, and wherein the plurality of articulation links cooperatively define the lumen. Element  7 : wherein the flexible shaft length is made of a flexible material that allows the articulation joint to bend in the plane of motion. Element  8 : further comprising a feedbar movable within the lumen to advance the surgical clips distally through the clip track. Element  9 : further comprising biasing device arrangeable within the lumen to advance the surgical clips distally through the clip track. Element  10 : wherein the articulation joint further comprises a retention member arranged at or near the distal end of the flexible shaft length to index the surgical clips. Element  11 : wherein the retention member comprises a passive biasing device. Element  12 : wherein the flexible shaft length is articulable between an unarticulated state and an articulated state, and wherein the surgical clips traverse the articulation joint when the flexible shaft is in the unarticulated and articulated states. Element  13 : wherein the clip track comprises opposing guide rails offset from each other to cooperatively define a clip passageway that receives and guides the surgical clips through the articulation joint. Element  14 : wherein the opposing guide rails are made of a flexible material and a size of the clip passageway increases when the flexible shaft length articulates. 
     Element  15 : wherein the clip track provides opposing side rails defined on angularly opposite sides of the lumen, and wherein guiding the one or more surgical clips through the articulation joint with the clip track comprises receiving a portion of each surgical clip within the opposing side rails. Element  16 : further comprising slidably engaging the portion of each surgical clip within the opposing side rails as each surgical clip advances distally within the clip track. Element  17 : wherein the clip track provides a helical path, the method further comprising introducing the one or more surgical clips into the flexible shaft length in a first angular orientation, and discharging the one or more surgical clips from the flexible shaft length in a second angular orientation angularly offset from the first angular orientation. Element  18 : wherein advancing the one or more surgical clips through the lumen comprises advancing the one or more surgical clips distally through the clip track with a feedbar movable within the lumen. Element  19 : wherein the clip track comprises opposing guide rails made of a flexible material and offset from each other to cooperatively define a clip passageway, and wherein guiding the one or more surgical clips through the articulation joint comprises receiving and guiding the one or more surgical clips through the clip passageway, and increasing a size of the clip passageway when the flexible shaft length articulates to the articulated state. 
     By way of non-limiting example, exemplary combinations applicable to A and B include: Element  2  with Element  3 ; Element  2  with Element  4 ; Element  10  with Element  11 ; Element  13  with Element  14 ; Element  15  with Element  16 ; and Element  15  with Element  17 . 
     Therefore, the disclosed systems and methods are well adapted to attain the ends and advantages mentioned as well as those that are inherent therein. The particular embodiments disclosed above are illustrative only, as the teachings of the present disclosure may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular illustrative embodiments disclosed above may be altered, combined, or modified and all such variations are considered within the scope of the present disclosure. The systems and methods illustratively disclosed herein may suitably be practiced in the absence of any element that is not specifically disclosed herein and/or any optional element disclosed herein. While compositions and methods are described in terms of “comprising,” “containing,” or “including” various components or steps, the compositions and methods can also “consist essentially of” or “consist of” the various components and steps. All numbers and ranges disclosed above may vary by some amount. Whenever a numerical range with a lower limit and an upper limit is disclosed, any number and any included range falling within the range is specifically disclosed. In particular, every range of values (of the form, “from about a to about b,” or, equivalently, “from approximately a to b,” or, equivalently, “from approximately a-b”) disclosed herein is to be understood to set forth every number and range encompassed within the broader range of values. Also, the terms in the claims have their plain, ordinary meaning unless otherwise explicitly and clearly defined by the patentee. Moreover, the indefinite articles “a” or “an,” as used in the claims, are defined herein to mean one or more than one of the elements that it introduces. If there is any conflict in the usages of a word or term in this specification and one or more patent or other documents that may be incorporated herein by reference, the definitions that are consistent with this specification should be adopted. 
     As used herein, the phrase “at least one of” preceding a series of items, with the terms “and” or “or” to separate any of the items, modifies the list as a whole, rather than each member of the list (i.e., each item). The phrase “at least one of” allows a meaning that includes at least one of any one of the items, and/or at least one of any combination of the items, and/or at least one of each of the items. By way of example, the phrases “at least one of A, B, and C” or “at least one of A, B, or C” each refer to only A, only B, or only C; any combination of A, B, and C; and/or at least one of each of A, B, and C.