Abstract:
A surgical severing and stapling instrument, suitable for laparoscopic and endoscopic clinical procedures, clamps tissue within an end effector of an elongate channel pivotally opposed by an anvil. An E-beam firing bar moves distally through the clamped end effector to sever tissue and to drive staples on each side of the cut. The E-beam firing bar affirmatively spaces the anvil from the elongate channel to assure properly formed closed staples, especially when an amount of tissue is clamped that is inadequate to space the end effector. In particular, an upper pin of the firing bar longitudinally moves through an anvil slot and a channel slot is captured between a lower cap and a middle pin of the firing bar to assure a minimum spacing. Forming the E-beam from a thickened distal portion and a thinned proximal strip enhances manufacturability and facilitates use in such articulating surgical instruments.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application is a continuation application under 35 U.S.C. §120 of U.S. patent application Ser. No. 13/369,601, entitled ROBOTICALLY-CONTROLLED SURGICAL END EFFECTOR SYSTEM, filed on Feb. 9, 2012, now U.S. Patent Application Publication No. 2012/0203247, which is a continuation application under 35 U.S.C. §120 of U.S. patent application Ser. No. 13/118,246, entitled ROBOTICALLY-DRIVEN SURGICAL INSTRUMENT WITH E-BEAM DRIVER, filed on May 27, 2011, now U.S. Patent Application Publication No. 2011/0290853, which is a continuation-in-part application under 35 U.S.C. §120 of U.S. patent application Ser. No. 11/538,154, entitled ARTICULATING SURGICAL STAPLING INSTRUMENT INCORPORATING A TWO-PIECE FIRING MECHANISM, filed on Oct. 3, 2006, the entire disclosures of which are incorporated by reference herein. The present application is a continuation application under 35 U.S.C. §120 of U.S. patent application Ser. No. 11/141,753, entitled SURGICAL STAPLING INSTRUMENT HAVING AN ELECTROACTIVE POLYMER ACTUATED MEDICAL SUBSTANCE DISPENSER, filed on Jun. 1, 2005, now U.S. Patent Application Publication No. 2006/0025813, which claims the benefit under 35 U.S.C. §119(e) of U.S. Provisional Patent Application Ser. No. 60/591,694, entitled SURGICAL INSTRUMENT INCORPORATING AN ELECTRICALLY ACTUATED ARTICULATION MECHANISM, filed on Jul. 28, 2004, the entire disclosures of which are incorporated by reference herein. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates in general to surgical instruments that are suitable for endoscopically inserting an end effector that is actuated by a longitudinally driven firing member, and more particularly a surgical stapling and severing instrument that has an articulating shaft. 
       BACKGROUND OF THE INVENTION 
       [0003]    Endoscopic surgical instruments are often preferred over traditional open surgical devices since a smaller incision tends to reduce the post-operative recovery time and complications. Consequently, significant development has gone into a range of endoscopic surgical instruments that are suitable for precise placement of a distal end effector at a desired surgical site through a cannula of a trocar. These distal end effectors engage the tissue in a number of ways to achieve a diagnostic or therapeutic effect (e.g., endocutter, grasper, cutter, staplers, clip applier, access device, drug/gene therapy delivery device, and energy device using ultrasound, RF, laser, etc.). 
         [0004]    Positioning the end effector is constrained by the trocar. Generally these endoscopic surgical instruments include a long shaft between the end effector and a handle portion manipulated by the clinician. This long shaft enables insertion to a desired depth and rotation about the longitudinal axis of the shaft, thereby positioning the end effector to a degree. With judicious placement of the trocar and use of graspers, for instance, through another trocar, often this amount of positioning is sufficient. Surgical stapling and severing instruments, such as described in U.S. Pat. No. 5,465,895, are an example of an endoscopic surgical instrument that successfully positions an end effector by insertion and rotation. 
         [0005]    More recently, U.S. patent application Ser. No. 10/443,617, entitled SURGICAL STAPLING INSTRUMENT INCORPORATING AN E-BEAM FIRING MECHANISM, filed on May 20, 2003, now U.S. Pat. No. 6,978,921, which is incorporated by reference in its entirety, describes an improved “E-beam” firing bar for severing tissue and actuating staples. Some of the additional advantages include affirmatively spacing the jaws of the end effector, or more specifically a staple applying assembly, even if slightly too much or too little tissue is clamped for optimal staple formation. Moreover, the E-beam firing bar engages the end effector and staple cartridge in a way that enables several beneficial lockouts to be incorporated. 
         [0006]    Depending upon the nature of the operation, it may be desirable to further adjust the positioning of the end effector of an endoscopic surgical instrument. In particular, it is often desirable to orient the end effector at an axis transverse to the longitudinal axis of the shaft of the instrument. The transverse movement of the end effector relative to the instrument shaft is conventionally referred to as “articulation”. This is typically accomplished by a pivot (or articulation) joint being placed in the extended shaft just proximal to the staple applying assembly. This allows the surgeon to articulate the staple applying assembly remotely to either side for better surgical placement of the staple lines and easier tissue manipulation and orientation. This articulated positioning permits the clinician to more easily engage tissue in some instances, such as behind an organ. In addition, articulated positioning advantageously allows an endoscope to be positioned behind the end effector without being blocked by the instrument shaft. 
         [0007]    Approaches to articulating a surgical stapling and severing instrument tend to be complicated by integrating control of the articulation along with the control of closing the end effector to clamp tissue and fire the end effector (i.e., stapling and severing) within the small diameter constraints of an endoscopic instrument. Generally, the three control motions are all transferred through the shaft as longitudinal translations. For instance, U.S. Pat. No. 5,673,840 discloses an accordion-like articulation mechanism (“flex-neck”) that is articulated by selectively drawing back one of two connecting rods through the implement shaft, each rod offset respectively on opposite sides of the shaft centerline. The connecting rods ratchet through a series of discrete positions. 
         [0008]    Another example of longitudinal control of an articulation mechanism is U.S. Pat. No. 5,865,361 that includes an articulation link offset from a camming pivot such that pushing or pulling longitudinal translation of the articulation link effects articulation to a respective side. Similarly, U.S. Pat. No. 5,797,537 discloses a similar rod passing through the shaft to effect articulation. 
         [0009]    In commonly owned U.S. patent application Ser. No. 10/615,973, entitled SURGICAL INSTRUMENT INCORPORATING AN ARTICULATION MECHANISM HAVING ROTATION ABOUT THE LONGITUDINAL AXIS, now U.S. Pat. No. 7,111,769, the disclosure of which is hereby incorporated by reference in its entirety, a rotational motion is used to transfer articulation motion as an alternative to a longitudinal motion. 
         [0010]    In the application entitled SURGICAL STAPLING INSTRUMENT INCORPORATING AN E-BEAM FIRING MECHANISM, U.S. patent application Ser. No. 10/443,617, filed on May 20, 2003, now U.S. Pat. No. 6,978,921, the disclosure of which was previously incorporated by reference in its entirety, a surgical severing and stapling instrument, suitable for laparoscopic and endoscopic clinical procedures, clamps tissue within an end effector of an elongate channel pivotally opposed by an anvil. An E-beam firing bar moves distally through the clamped end effector to sever tissue and to drive staples on each side of the cut. The E-beam firing bar affirmatively spaces the anvil from the elongate channel to assure properly formed closed staples, especially when an amount of tissue is clamped that is inadequate to space the end effector. In particular, an upper pin of the firing bar longitudinally moves through an anvil slot and a channel slot is captured between a lower cap and a middle pin of the firing bar to assure a minimum spacing. While this E-beam firing bar has a number of advantages, additional features are desirable to enhance manufacturability and to minimize dimensional variations. 
         [0011]    Consequently, a significant need exists for a surgical instrument with a firing bar that advantageously assures proper spacing between clamped jaws of an end effector and which facilitates articulation of its shaft. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0012]    The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention, and, together with the general description of the invention given above, and the detailed description of the embodiments given below, serve to explain the principles of the present invention. 
           [0013]      FIG. 1  is a perspective view of an endoscopic surgical stapling instrument for surgical stapling and severing in an open, unarticulated state. 
           [0014]      FIG. 2  is a left, front perspective view of an open staple applying assembly of the surgical stapling instrument of  FIG. 1  with a right half portion of a replaceable staple cartridge included in a staple channel. 
           [0015]      FIG. 3  is an exploded perspective view of the staple applying assembly of  FIG. 2  with a complete replaceable staple cartridge and an alternative nonarticulating shaft configuration. 
           [0016]      FIG. 4  is a perspective view of a two-piece knife and firing bar (“E-beam”) of the staple applying assembly of  FIG. 2 . 
           [0017]      FIG. 5  is a perspective view of a wedge sled of a staple cartridge of the staple applying assembly of  FIG. 1 . 
           [0018]      FIG. 6  is a left side view in elevation taken in longitudinal cross section along a centerline line  6 - 6  of the staple applying assembly of  FIG. 2 . 
           [0019]      FIG. 7  is a perspective view of the open staple applying assembly of  FIG. 2  without the replaceable staple cartridge, a portion of the staple channel proximate to a middle pin of two-piece knife and firing bar, and without a distal portion of a staple channel. 
           [0020]      FIG. 8  is a front view in elevation taken in cross section along line  8 - 8  of the staple applying assembly of  FIG. 2  depicting internal staple drivers of the staple cartridge and portions of the two-piece knife and firing bar. 
           [0021]      FIG. 9  is a left side view in elevation taken generally along the longitudinal axis of line  6 - 6  of a closed staple applying assembly of  FIG. 2  to include center contact points between the two-piece knife and wedge sled but also laterally offset to show staples and staple drivers within the staple cartridge. 
           [0022]      FIG. 10  is a left side detail view in elevation of the staple applying assembly of  FIG. 9  with the two-piece knife retracted slightly more as typical for staple cartridge replacement. 
           [0023]      FIG. 11  is a left side detail view in elevation of the staple applying assembly of  FIG. 10  with the two-piece knife beginning to fire, corresponding to the configuration depicted in  FIG. 9 . 
           [0024]      FIG. 12  is a left side cross-sectional view in elevation of the closed staple applying assembly of  FIG. 9  after the two-piece knife and firing bar has distally fired. 
           [0025]      FIG. 13  is a left side cross-sectional view in elevation of the closed staple applying assembly of  FIG. 12  after firing of the staple cartridge and refraction of the two-piece knife. 
           [0026]      FIG. 14  is a left side cross-sectional detail view in elevation of the staple applying assembly of  FIG. 13  with the two-piece knife allowed to drop into a lockout position. 
           [0027]      FIG. 15  is a top view in section taken along lines  15 - 15  of an articulation joint (flex neck) of the surgical stapling instrument of  FIG. 1 . 
           [0028]      FIG. 16  is a front view in elevation taken in vertical cross section along lines  16 - 16  of the articulation joint of  FIG. 15 , showing electroactive polymer (EAP) plate articulation actuators and EAP support plates for a firing bar. 
           [0029]      FIG. 17  is a top view in section along lines  15 - 15  of the articulation joint of  FIG. 16  after articulation. 
           [0030]      FIG. 18  is a perspective view of the articulation joint of  FIG. 15 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0031]    The entire disclosure of U.S. patent application Ser. No. 11/082,495, entitled SURGICAL INSTRUMENT INCORPORATING AN ELECTRICALLY ACTUATED ARTICULATION MECHANISM, filed on Mar. 17, 2005, now U.S. Pat. No. 7,506,790, is incorporated herein by reference. The entire disclosure of U.S. Pat. No. 6,667,825, entitled STABLE CONJUGATED POLYMER ELECTROCHROMIC DEVICES INCORPORATING IONIC LIQUIDS, issued on Jan. 3, 2002, is incorporated herein by reference. The entire disclosure of U.S. patent application Ser. No. 11/061,908, entitled SURGICAL INSTRUMENT INCORPORATING A FLUID TRANSFER CONTROLLED ARTICULATION MECHANISM, filed on Feb. 18, 2005, now U.S. Pat. No. 7,559,450, is incorporated herein by reference. 
         [0032]    In  FIGS. 1-3 , a surgical stapling instrument  10  has at its distal end an end effector, depicted as a staple applying assembly  12 , spaced apart from a handle  14  ( FIG. 2 ) by an elongate shaft  16 . The staple applying assembly  12  includes a staple channel  18  for receiving a replaceable staple cartridge  20 . Pivotally attached to the staple channel  18  is an anvil  22  that clamps tissue to the staple cartridge  20  and serves to deform staples  23  ( FIG. 3 ) driven up from staple holes  24  in the staple cartridge  20  against staple forming recesses  26  ( FIG. 6 ) in an anvil undersurface  28  into a closed shape. When the staple applying assembly  12  is closed, its cross sectional area, as well as the elongate shaft  16  are suitable for insertion through a small surgical opening, such as through a cannula of a trocar (not shown). 
         [0033]    With particular reference to  FIG. 1 , correct placement and orientation of the staple applying assembly  12  is facilitated by controls on the handle  14 . In particular, a rotation knob  30  causes rotation of the shaft  16  about its longitudinal axis, and hence rotation of the staple applying assembly  12 . Additional positioning is enabled at an articulation joint  32  in the shaft  16  that pivots the staple applying assembly  12  in an arc from the longitudinal axis of the shaft  16 , thereby allowing placement behind an organ or allowing other instruments such as an endoscope (not shown) to be oriented behind the staple applying assembly  12 . This articulation is advantageously effected by an articulation control switch  34  on the handle  14  that transmits an electrical signal to the articulation joint  32  to an Electroactive Polymer (EAP) actuator  36 , powered by an EAP controller and power supply  38  contained within the handle  14 . 
         [0034]    Once positioned with tissue in the staple applying assembly  12 , a surgeon closes the anvil  22  by drawing a closure trigger  40  proximally toward a pistol grip  42 . Once clamped thus, the surgeon may grasp a more distally presented firing trigger  44 , drawing it back to effect firing of the staple applying assembly  12 , which in some applications is achieved in one single firing stroke and in other applications by multiple firing strokes. Firing accomplishes simultaneously stapling of at least two rows of staples while severing the tissue therebetween. 
         [0035]    Retraction of the firing components may be automatically initiated upon full travel. Alternatively, a retraction lever  46  may be drawn aft to effect retraction. With the firing components retracted, the staple applying assembly  12  may be unclamped and opened by the surgeon slightly drawing the closure trigger  40  aft toward the pistol grip  42  and depressing a closure release button  48  and then releasing the closure trigger  40 , thereby releasing the two stapled ends of severed tissue from the staple applying assembly  12 . 
       Staple Applying Assembly 
       [0036]    While an articulation joint  32  is depicted in  FIG. 1 , for clarity and as an alternative application, the surgical stapling instrument  10  of  FIGS. 2-14  omit an articulation joint  32 . It should be appreciated, however, that aspects of the present invention have particular advantages for articulation as described below with regard to  FIGS. 15-18 . 
         [0037]    In  FIGS. 1-3 , the staple applying assembly  12  accomplishes the functions of clamping onto tissue, driving staples and severing tissue by two distinct motions transferred longitudinally down the shaft  16  over a shaft frame  70 . This shaft frame  70  is proximally attached to the handle  14  and coupled for rotation with the rotation knob  30 . An illustrative multi-stroke handle  14  for the surgical stapling and severing instrument  10  of  FIG. 1  is described in greater detail in the co-pending and co-owned U.S. patent application Ser. No. 10/674,026, entitled SURGICAL STAPLING INSTRUMENT INCORPORATING A MULTISTROKE FIRING POSITION INDICATOR AND RETRACTION MECHANISM, now U.S. Pat. No. 7,364,061, the disclosure of which is hereby incorporated by reference in its entirety, with additional features and variation as described herein. While a multi-stroke handle  14  advantageously supports applications with high firing forces over a long distance, applications consistent with the present invention may incorporate a single firing stroke, such as described in co-pending and commonly owned U.S. patent application Ser. No. 10/441,632, entitled SURGICAL STAPLING INSTRUMENT HAVING SEPARATE DISTINCT CLOSING AND FIRING SYSTEMS, now U.S. Pat. No. 7,000,818, the disclosure of which is hereby incorporated by reference in its entirety. 
         [0038]    With particular reference to  FIG. 3 , the distal end of the shaft frame  70  is attached to the staple channel  18 . The anvil  22  has a proximal pivoting end  72  that is pivotally received within a proximal end  74  of the staple channel  18 , just distal to its engagement to the shaft frame  70 . The pivoting end  72  of the anvil  22  includes a closure feature  76  proximate but distal to its pivotal attachment with the staple channel  18 . Thus, a closure tube  78 , whose distal end includes a horseshoe aperture  80  that engages this closure feature  76 , selectively imparts an opening motion to the anvil  22  during proximal longitudinal motion and a closing motion to the anvil  22  during distal longitudinal motion of the closure tube  78  sliding over the shaft frame  70  in response to the closure trigger  40 . 
         [0039]    The shaft frame  70  encompasses and guides a firing motion from the handle  14  through a longitudinally reciprocating, two-piece knife and firing bar  90 . In particular, the shaft frame  70  includes a longitudinal firing bar slot  92  that receives a proximal portion of the two-piece knife and firing bar  90 , specifically a laminate tapered firing bar  94 . It should be appreciated that the laminated tapered firing bar  94  may be substituted with a solid firing bar or of other materials in applications not intended to pass through an articulation joint, such as depicted in  FIGS. 2-14 . 
         [0040]    An E-beam  102  is the distal portion of the two-piece knife and firing bar  90 , which facilitates separate closure and firing as well as spacing of the anvil  22  from the elongate staple channel  18  during firing. With particular reference to  FIGS. 3-4 , in addition to any attachment treatment such as brazing or an adhesive, the knife and firing bar  90  are formed of a female vertical attachment aperture  104  proximally formed in the E-beam  102  that receives a corresponding male attachment member  106  distally presented by the laminated tapered firing bar  94 , allowing each portion to be formed of a selected material and process suitable for their disparate functions (e.g., strength, flexibility, friction). The E-beam  102  may be advantageously formed of a material having suitable material properties for forming a pair of top pins  110 , a pair of middle pins  112  and a bottom pin or foot  114 , as well as being able to acquire a sharp cutting edge  116 . In addition, integrally formed and proximally projecting top guide  118  and middle guide  120  bracketing each vertical end of the cutting edge  116  further define a tissue staging area  122  assisting in guiding tissue to the sharp cutting edge  116  prior to being severed. The middle guide  120  also serves to engage and fire the staple applying apparatus  12  by abutting a stepped central member  124  of a wedge sled  126  ( FIG. 5 ) that effects staple formation by the staple applying assembly  12 , as described in greater detail below. 
         [0041]    Forming these features (e.g., top pins  110 , middle pins  112 , and bottom foot  114 ) integrally with the E-beam  102  facilitates manufacturing at tighter tolerances relative to one another as compared to being assembled from a plurality of parts, ensuring desired operation during firing and/or effective interaction with various lockout features of the staple applying assembly  12 . 
         [0042]    In  FIGS. 6-7 , the surgical stapling instrument  10  is shown open, with the E-beam  102  fully retracted. During assembly, the lower foot  114  of the E-beam  102  is dropped through a widened hole  130  in the staple channel  18  and the E-beam  102  is then advanced such that the E-beam  102  slides distally along a lower track  132  formed in the staple channel  18 . In particular, the lower track  132  includes a narrow slot  133  that opens up as a widened slot  134  on an undersurface of the staple channel  18  to form an inverted T-shape in lateral cross section, as depicted particularly in  FIGS. 7 and 8 , which communicates with the widened hole  130 . Once assembled, the components proximally coupled to the laminate tapered firing bar  94  do not allow the lower foot  114  to proximally travel again to the widened hole  130  to permit disengagement. 
         [0043]    In  FIG. 9 , the laminate tapered firing bar  94  facilitates insertion of the staple applying assembly  12  through a trocar. In particular, a more distal, downward projection  136  raises the E-beam  102  when fully retracted. This is accomplished by placement of the downward projection  136  at a point where it cams upwardly on a proximal edge of the widened hole  130  in the staple channel  18 . 
         [0044]    In  FIG. 10 , the laminate tapered firing bar  94  also enhances operation of certain lockout features that may be incorporated into the staple channel  18  by including a more proximal upward projection  138  that is urged downwardly by the shaft frame  70  during an initial portion of the firing travel. In particular, a lateral bar  140  is defined between a pair of square apertures  142  in the shaft frame  70  ( FIG. 3 ). A clip spring  144  that encompasses the lateral bar  140  downwardly urges a portion of the laminate tapered firing bar  94  projecting distally out of the longitudinal firing bar slot  92 , which ensures certain advantageous lockout features are engaged when appropriate. This urging is more pronounced or confined solely to that portion of the firing travel when the upward projection  138  contacts the clip spring  144 . 
         [0045]    In  FIGS. 6-7 , the E-beam  102  is retracted with the top pins  110  thereof residing within an anvil pocket  150  near the pivoting proximal end of the anvil  22 . A downwardly open vertical anvil slot  152  ( FIG. 2 ) laterally widens in the anvil  22  into an anvil internal track  154  that captures the top pins  110  of the E-beam  102  as they distally advance during firing, as depicted in  FIGS. 9-10 , affirmatively spacing the anvil  22  from the staple channel  18 . Thus, with the E-beam  102  retracted, the surgeon is able to repeatably open and close the staple applying assembly  12  until satisfied with the placement and orientation of tissue captured therein for stapling and severing, yet the E-beam  102  assists in proper positioning of tissue even for a staple applying assembly  12  of reduced diameter and correspondingly reduced rigidity. 
         [0046]    In  FIGS. 2-3 ,  5 - 6 ,  8 - 14 , the staple applying assembly  12  is shown with the replaceable staple cartridge  20  that includes the wedge sled  126 . Longitudinally aligned and parallel plurality of downwardly open wedge slots  202  ( FIG. 8 ) receive respective wedges  204  integral to the wedge sled  126 . In  FIGS. 8-10 , the wedge sled  126  thus cams upwardly a plurality of staple drivers  206  that are vertically slidable within staple driver recesses  208 . In this illustrative version, each staple driver  206  includes two vertical prongs, each translating upwardly into a respective staple hole  210  to upwardly force out and deform a staple  23  resting thereupon against a staple forming surface  214  ( FIG. 10 ) of the anvil  22 . A central firing recess  216  ( FIG. 3 ) defined within the staple cartridge  20  proximate to the staple channel  18  allows the passage of the bottom, horizontal portion  218  ( FIG. 5 ) of the wedge sled  126  as well as the middle pins  112  of the E-beam  102 . Specifically, a staple cartridge tray  220  ( FIGS. 3 ,  8 ) attaches to and underlies a polymer staple cartridge body  222  that has the staple driver recesses  208 , staple holes  210 , and central firing recess  216  formed therein. As staples  23  are thus formed to either side, the sharp cutting edge  116  enters a vertical through slot  230  passing through the longitudinal axis of the staple cartridge  20 , excepting only a most distal end thereof. 
         [0047]    Firing the staple applying assembly  12  begins as depicted in  FIG. 10  with the two-piece knife and firing bar  90  proximally drawn until the downward projection  136  cams the middle guide  120  on the E-beam  102  upward and aft, allowing a new staple cartridge  20  to be inserted into the staple channel  18  when the anvil  22  is open as depicted in  FIGS. 2 ,  6 . 
         [0048]    In  FIG. 11 , the two-piece knife and firing bar  90  has been distally advanced a small distance, allowing the downward projection  136  to drop into the widened hole  130  of the lower track  132  under the urging of the clip spring  144  against the upward projection  138  of the laminate tapered firing bar  94 . The middle guide  120  prevents further downward rotation by resting upon the stepped central member  124  of the wedge sled  126 , thus maintaining the middle pin  112  of the E-beam within the central firing recess  216 . 
         [0049]    In  FIG. 12 , the two-piece knife and firing bar  90  has been distally fired, advancing the wedge sled  126  to cause formation of staples  23  while severing tissue  242  clamped between the anvil  22  and staple cartridge  20  with the sharp cutting edge  116 . Thereafter, in  FIG. 13 , the two-piece knife and firing bar  90  is retracted, leaving the wedge sled  126  distally positioned. 
         [0050]    In  FIG. 14 , the middle pin  112  is allowed to translate down into a lockout recess  240  formed in the staple channel  18  (also see  FIGS. 7 ,  10 ). Thus, the operator would receive a tactile indication as the middle pin  112  encounters the distal edge of the lockout recess  240  when the wedge sled  126  (not shown in  FIG. 14 ) is not proximally positioned (i.e., missing staple cartridge  20  or spent staple cartridge  20 ). 
         [0051]    In  FIG. 1 , an articulation joint  32  is depicted that advantageously benefits from the flexible strength of the two-piece knife and firing bar  90 . In  FIGS. 15-18 , the articulation joint  32  is depicted as a flex neck joint  300  formed by vertebral column body  302  having laterally symmetric pairs of arcing recesses  304  that allow articulation in an articulation plane. It is generally known to simultaneously compress and expand respective lateral sides  306 ,  308  by selective movement of control rods (not shown) that longitudinally pass through the respective lateral sides  306 ,  308 . Depicted, however, are EAP plate actuators  310 ,  312 , each capable of powered deflection to one or both lateral directions. 
         [0052]    A central passage  320  ( FIG. 16 ) defined longitudinally through the vertebral column body  302  receives a pair of support plates  322 ,  324  that prevent buckling and binding of the laminate tapered firing bar  94 . In the illustrative version, each support plate  322 ,  324  has a proximal fixed end  326  ( FIG. 15 ) and a sliding end  328  to accommodate changes in radial distance during articulation. Having a firing bar  94  of a thinner thickness is thus supported. 
         [0053]    While the present invention has been illustrated by description of several embodiments and while the illustrative embodiments have been described in considerable detail, it is not the intention of the applicant to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications may readily appear to those skilled in the art. 
         [0054]    For example, while there are a number of advantages to having a wedge sled integral to a staple cartridge, in some applications consistent with aspects of the present invention, the wedge sled may be integral instead to an E-beam. For instance, an entire end effector may be replaceable rather than just the staple cartridge.