Patent Publication Number: US-10786324-B2

Title: Tissue stop for surgical instrument

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application is a continuation of U.S. patent application Ser. No. 15/452,268, filed Mar. 7, 2017, (now U.S. Pat. No. 10,028,799), which is a Continuation of U.S. patent application Ser. No. 15/160,483, filed May 20, 2016, (now U.S. Pat. No. 9,615,829), which is a Continuation of U.S. patent application Ser. No. 14/805,593, filed Jul. 22, 2015, (now U.S. Pat. No. 9,364,232), which is a Continuation of U.S. patent application Ser. No. 13/493,346, filed Jun. 11, 2012, (now U.S. Pat. No. 9,107,664), which is a Continuation of U.S. patent application Ser. No. 12/952,371, filed Nov. 23, 2010, (now U.S. Pat. No. 8,215,532), which is a Continuation-In-Part of U.S. patent application Ser. No. 12/759,897, filed Apr. 14, 2010, (now U.S. Pat. No. 8,360,298), which is a Continuation-In-Part of U.S. patent application Ser. No. 12/553,174, filed Sep. 3, 2009, (now U.S. Pat. No. 7,988,028), which is a Continuation-In-Part and claims benefit of, and claims priority to U.S. patent application Ser. No. 12/235,751, filed Sep. 23, 2008, (now U.S. Pat. No. 7,896,214). The entire contents of this application are incorporated herein by reference. 
    
    
     BACKGROUND 
     The present disclosure relates generally to surgical instruments and, more specifically, to surgical instruments for surgically joining tissue. 
     BACKGROUND OF RELATED ART 
     Surgical stapling instruments used for applying parallel rows of staples through compressed living tissue are well known in the art. These surgical instruments are commonly employed for closing tissue or organs prior to transaction or resection, for occluding organs in thoracic and abdominal procedures, and for fastening tissue in anastomoses. 
     Typically, such surgical stapling instruments include an anvil assembly, a cartridge assembly for supporting an array of surgical staples, an approximation mechanism for approximating the anvil and cartridge and anvil assemblies, and a firing mechanism for ejecting the surgical staples from the cartridge assembly. 
     In use, a surgeon generally initially approximates the anvil and cartridge members. Next, the surgeon can fire the instrument to place staples in tissue. Additionally, the surgeon may use the same instrument or a separate instrument to cut the tissue adjacent or between the row(s) of staples. Alternatively, the surgical stapling instrument can sequentially eject the staples while the anvil and cartridge are approximated. 
     SUMMARY 
     The present disclosure relates to a surgical instrument including a handle assembly, an elongated portion, an end effector, and a stop member. The elongated portion extends distally from the handle assembly. The end effector is disposed adjacent a distal portion of the elongated portion and includes a first jaw member and a second jaw member. At least one jaw member is movable with respect to the other jaw member between spaced and approximated positions. The first jaw member includes an upper tissue-contacting surface and a lower shelf portion. The shelf portion includes a groove disposed therein. The stop member is disposed adjacent a distal portion of the first jaw member and is pivotable with respect to the first jaw member between a first position, a significant portion of the stop member being positioned external to the first jaw member, and a second position where a lower portion of the stop member being positioned at least partially within the groove. 
     In certain embodiments, the cartridge is curved with respect to the longitudinal axis. A biasing member may be provided and disposed in mechanical cooperation with the stop member, wherein the biasing member biases stop member towards its first position. The stop member can be pivotally coupled to the first jaw member. 
     In certain embodiments, the first jaw member includes a knife channel. The stop member can have a first leg and a second leg, the first leg and the second leg being positioned on opposite sides of the knife channel. 
     In certain desirable embodiments, a sled is translatable along the shelf of the first jaw member. The sled can include a plurality of cam wedges, and wherein each cam wedge is connected to an adjacent cam wedge by a transversely-disposed connecting member. The connecting member can be disposed adjacent a proximal portion of the sled. A distal portion each of the cam wedges can cantileveredly extend from the connecting member. The wedges may extend from the connecting member and define a space in which the stop member is disposed when the sled is disposed at the distal end of the first jaw member. 
     In certain embodiments, the instrument includes a beam assembly for pushing the sled toward the distal end of the first jaw member, the beam assembly having a notch, the connecting member of the sled being in engagement with the beam assembly at the notch. 
     The present disclosure also relates to a tool assembly for use with a surgical instrument. The tool assembly comprises an end effector and a stop member. The end effector includes a first jaw member and a second jaw member, at least one jaw member is movable with respect to the other jaw member between spaced and approximated positions. The first jaw member includes an upper tissue-contacting surface and a lower shelf portion. The shelf portion includes a groove disposed therein. The stop member is disposed adjacent a distal portion of the first jaw member and is pivotable with respect to the first jaw member between a first position wherein at least a portion of the stop member is positioned external to the first jaw member, and a second position wherein at least a portion of the stop member is positioned within the groove. The relative movement of the jaw members toward the approximated position causes at least a portion of the stop member to move toward the first jaw member. 
     In certain embodiments, the cartridge of the tool assembly is curved with respect to the longitudinal axis. A biasing member may be provided and disposed in mechanical cooperation with the stop member, wherein the biasing member biases stop member towards its first position. The stop member can be pivotally coupled to the first jaw member. 
     In certain embodiments, the first jaw member of the tool assembly includes a knife channel. The stop member can have a first leg and a second leg, the first leg and the second leg being positioned on opposite sides of the knife channel. 
     In certain embodiments, the tool assembly had a sled which is translatable along the shelf of the first jaw member. The sled can include a plurality of cam wedges, and wherein each cam wedge is connected to an adjacent cam wedge by a transversely-disposed connecting member. The connecting member can be disposed adjacent a proximal portion of the sled. A distal portion each of the cam wedges can cantileveredly extend from the connecting member. The wedges may extend from the connecting member and define a space in which the stop member is disposed when the sled is disposed at the distal end of the first jaw member. 
     In certain embodiments, the tool assembly includes a beam assembly for pushing the sled toward the distal end of the first jaw member, the beam assembly having a notch, the connecting member of the sled being in engagement with the beam assembly at the notch. 
     In a further aspect of the disclosure, a surgical instrument includes a handle assembly, an elongated portion, an end effector, and a stop member. The elongated portion extends distally from the handle assembly. The end effector is disposed adjacent a distal portion of the elongated portion and includes a first jaw member and a second jaw member. At least one jaw member is movable with respect to the other jaw member between spaced and approximated positions. The first jaw member includes an upper tissue-contacting surface and a lower shelf portion. The stop member is disposed adjacent a distal portion of the first jaw member and is pivotable with respect to the first jaw member between a first position, a significant portion of the stop member being positioned external to the first jaw member. The instrument also comprises a sled translatable along the shelf portion of the first jaw member, the sled including a connecting member disposed at a proximal portion of the sled, and a beam assembly for pushing the sled distally the beam assembly having a notch and the connecting member being disposed in the notch, the sled defining a space for receiving the stop member when the sled is disposed at the distal portion of the first jaw member. 
     The shelf portion of the first jaw member may include a groove disposed therein for receiving a portion of the stop member. The first jaw member desirably includes a knife channel. The stop member may have two legs positioned on opposite sides of the knife channel. 
     In another aspect of the present disclosure, a loading unit has a first jaw member including an upper tissue-contacting surface and a lower shelf portion. The shelf portion includes a groove disposed therein. A stop member is disposed adjacent a distal portion of the first jaw member and is pivotable with respect to the first jaw member between a first position wherein at least a portion of the stop member is positioned external to the first jaw member, and a second position wherein at least a portion of the stop member is positioned within the groove. The stop member is pivotably mounted so that at least a portion of the stop member can move toward the first jaw member. In certain embodiments, the stop member has two legs for receiving a knife member included in the loading unit. The loading unit may also include a sled having a connecting member at a proximal portion thereof. In certain embodiments, the sled defines a space for receiving the stop member when the sled is disposed at the distal portion of the first jaw member. The loading unit may include a beam assembly, the beam assembly being connected to the sled at the connecting member. 
    
    
     
       BRIEF DESCRIPTION OF FIGURES 
       Various embodiments of the presently disclosed surgical instrument are disclosed herein with reference to the drawings, wherein: 
         FIG. 1  is a perspective view of an embodiment of a surgical instrument according to the present disclosure; 
         FIG. 1A  is a perspective view of an embodiment of a loading unit according to certain aspects of the present disclosure; 
         FIGS. 2-4  are perspective views of a portion of the surgical instrument of  FIG. 1 , showing a stop member in a first position; 
         FIGS. 5-7  are side views of an end effector of the surgical instrument of  FIG. 1 , shown at different stages of operation; 
         FIG. 8  is a perspective view of a portion of the surgical instrument of  FIG. 1 , showing a stop member adjacent its second position; 
         FIG. 9  is a perspective view of a curved jaw member according to another embodiment of the present disclosure, showing a stop member in a first position; 
         FIG. 10  is a perspective exploded view of the curved jaw member of  FIG. 9 ; 
         FIG. 11  is a perspective view of the curved jaw member of  FIG. 9 , showing the cross-section of a distal portion taken along section line  11 - 11  of  FIG. 9 ; 
         FIG. 12  is a perspective view of the curved jaw member of  FIG. 9 , showing the stop member in a second position; 
         FIG. 13  is a longitudinal cross-sectional view of a distal portion of jaw members and a stop member in accordance with another embodiment of the present disclosure; 
         FIG. 14  is a top view of the jaw members of  FIG. 13 , with the stop member omitted; 
         FIG. 15  is a perspective view of a sled for use with the embodiment of the jaw members illustrated in  FIGS. 14 and 15 ; and 
         FIG. 16  is a transverse cross-sectional view of a portion of jaw member of  FIG. 14  and a sled in accordance with another embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the presently disclosed surgical instrument are described in detail with reference to the drawings, wherein like reference numerals designate similar or identical elements in each of the several views. In the drawings and the description that follows, the term “proximal” refers to the end of the surgical instrument that is closest to the operator, whereas the term “distal” refers to the end of the surgical instrument that is farthest from the operator. As appreciated by one skilled in the art, the depicted surgical instrument fires staples, but it may be adapted to fire any other suitable fastener such as clips and two-part fasteners. Additionally, the disclosed stop member may be used with an electrosurgical forceps. Further details of electrosurgical forceps are described in commonly-owned patent application Ser. No. 10/369,894, filed on Feb. 20, 2003, entitled VESSEL SEALER AND DIVIDER AND METHOD OF MANUFACTURING THE SAME, the entire contents of which are hereby incorporated by reference herein. 
     With reference to  FIG. 1 , reference numeral  100  designates an embodiment of the presently disclosed surgical instrument. The present disclosure relates to an end effector and a stop member of surgical instrument  100 . U.S. Patent Applications Publication Nos. 2008/0105730, filed on Nov. 28, 2007; 2008/0110960, filed on Jan. 8, 2008; 2008/0142565, filed on Jan. 24, 2008; 2008/0041916, filed on Oct. 15, 2007 and U.S. Provisional Patent Application Ser. No. 61/050,273, filed on May 5, 2008 describe in detail the structure and operation of other surgical fastening assemblies. The entire contents of these prior applications are incorporated herein by reference. Any of the surgical fastening assemblies disclosed in the cited patent applications may include the presently disclosed stop member. 
     Surgical instrument  100  is configured to clamp, fasten, and/or cut tissue. In general, surgical instrument  100  includes a handle assembly  160 , an elongate portion  120  extending distally from handle assembly  160  and defining a longitudinal axis “A-A,” and a tool assembly  150  adapted to clamp and fasten tissue. Elongate portion  120  has a proximal portion  122  and a distal portion  124  and operatively couples handle assembly  160  with tool assembly  150 . Tool assembly  150  includes end effector  154  and stop member  170 . End effector  154 , which is disposed adjacent distal portion  124  of elongated portion  120 , includes a first jaw member  130  and a second jaw member  140 . At least one of the jaw members  130 ,  140  is adapted to move relative to the other jaw member ( 130  or  140 ) between spaced and approximated positions. In the illustrated embodiment, first jaw member  130  contains a cartridge assembly  132 , while second jaw member  140  includes an anvil assembly  142 . The tool assembly  150  can be mounted onto the distal end of the elongate portion  120 , or the tool assembly  150  can be incorporated into a replaceable loading unit  121 . By way of example,  FIG. 1A  shows a loading unit  121  having a proximal body portion  123  that is connectable to the distal end of the elongate portion  120 . This loading unit  121  includes the anvil assembly, cartridge assembly, as well as the knife and other actuation apparatus discussed below. In other examples, the tool assembly is incorporated into the surgical instrument and the cartridge assembly has a replaceable cartridge received in the first jaw member  130 . The tool assembly may have linear jaws or arcuate jaws. Tool assemblies with an anvil assembly, cartridge assembly and actuation apparatus with a knife are disclosed in U.S. patent application Ser. No. 12/235,751, filed Sep. 23, 2008 and U.S. patent application Ser. No. 12/553,174, filed Sep. 3, 2009, the disclosures of which are hereby incorporated by reference herein. 
     As discussed below, the anvil assembly  142  shown in  FIG. 1  moves with respect to cartridge assembly  132  between spaced and approximated positions upon actuation of handle assembly  160 , for example. However, the cartridge assembly may move toward and away from the anvil assembly to clamp tissue. It is also envisioned that other methods of approximating the jaw members are also usable, including sliding a clamp bar  168 . 
     Handle assembly  160  includes a stationary handle  162  and a movable handle  164 . Movable handle  164  is adapted to move pivotally toward or away from stationary handle  162 . Further, movable handle  164  is operatively connected to anvil assembly  140  through a mechanism adapted to convert at least a partial actuation of movable handle  164  into a pivoting motion of at least one of cartridge assembly  132  and anvil assembly  142  between spaced and approximated positions. As recognized by one skilled in the art, any conventional actuation mechanism may be employed to operatively couple movable handle  164  to tool assembly  150 . 
     With reference to  FIGS. 2-5 , cartridge assembly  132  has a tissue-contacting surface  134  and a plurality of fastener retaining slots  136 . The anvil assembly  142  includes an anvil plate  143 . Tissue-contacting surface  134  generally faces the anvil plate  143  on anvil assembly  142  (see  FIG. 1 ) and, during operation, engages tissue when the anvil assembly  142  is approximated with cartridge assembly  132 . Fastener retaining slots  136  are arranged in rows along tissue contacting surface  134 . Each fastener retaining slot  136  is adapted to hold a fastener (not shown), such as a staple or other surgical fastener, until a user actuates handle assembly  160  (see  FIG. 1 ), for example. When movable handle  164  is pivoted toward stationary handle  162 , the fasteners are ejected from fastener retaining slots  134 , move toward anvil assembly  142 , and are formed in staple forming recesses in the anvil plate  143 . The fasteners can be stainless steel, titanium, or other deformable surgical metal staples, polymeric staples, two-part fasteners or other surgical fasteners. 
     In addition to fastener retaining slots  134 , cartridge assembly  132  has a knife channel  138  adapted to slidably receive a knife (not shown) or any other suitable cutting tool. Knife channel  138  is disposed between rows of fastener retaining slots  136  and extends along tissue-contacting surface  134 . In operation, a knife (not shown) slides through knife channel  138  when movable handle  164  pivots toward stationary handle  162 . Alternatively, other mechanisms can be used to drive the knife through knife channel  138 . In addition to knife channel  138 , cartridge assembly  132  has a pair of slots  139  formed on tissue-contacting surface  134 . Each slot  139  provides access to an inner portion of cartridge assembly  132  and is configured to receive portions of stop member  170 . 
     In disclosed embodiments, handle assembly  160  contains an actuation mechanism for deploying the fasteners from fastener retaining slots  136  and advancing a knife along knife channel  138 . This actuation mechanism includes a firing rod operatively connected to movable handle  164 . In operation, pivoting movable handle  164  toward stationary handle  162  causes firing rod to advance distally. Firing rod is in turn operatively coupled to an axial drive assembly at least partially positioned within tool assembly  150 . Axial drive assembly is configured to move distally in response to a distal translation of firing rod. The axial drive assembly includes a beam that has an upper portion for engaging the anvil assembly and a lower portion for engaging the cartridge assembly. As the axial drive assembly translates distally through the anvil assembly and cartridge assembly, the engagement of the upper portion and lower portion causes the second jaw member  140  to pivot toward first jaw member  130 . In addition, the axial drive assembly pushes an actuation sled disposed within first jaw member  130  in a distal direction, while the actuation sled translates distally through end effector  154 . As the actuation sled advances distally through first jaw member  130 , this actuation sled urges the fasteners out of the fastener retaining slots  136 . In certain embodiments, axial drive assembly includes a blade mounted on a distal portion thereof. In operation, this knife moves through knife channel  138  of the cartridge assembly  132  when axial drive assembly moves distally through end effector  154 . Likewise, the anvil plate  143  of the anvil assembly  142  defines a slot to allow translation of the axial drive assembly. The knife blade faces distally in the tool assembly  150  so that tissue between the jaws of the tool assembly  150  is progressively cut as the fasteners are formed. 
     Stop member  170  is disposed adjacent a distal portion  137  of first jaw member  130  (which is shown as cartridge assembly  132 , but may also be anvil assembly  142 ). The stop member  170  is pivotable with respect to the first jaw member  130  between a first position, as illustrated in  FIG. 5 , and a second position, as depicted in  FIG. 7 . In the first position, at least a portion of stop member  170  is located external to the first jaw member  130 , whereas, in the second position, at least a portion of stop member  170  is positioned at least partially below tissue-contacting surface  134  of first jaw member  130 . In various embodiments, a significant portion of stop member  170  is disposed external to the first jaw member  130  when stop member  170  is located in the first position. It is envisioned that the term “significant” means that at least half of each leg  177  of stop portion  170  is disposed external to the first jaw member  130  when stop member  170  is located in the first position. Additionally, as used herein, “significant” may mean that more than one-third of stop member  170  is disposed external to the first jaw member  130  when stop member  170  is located in the first position. 
     Stop member  170  includes a base  172  adapted to engage an outer surface of distal portion  137  of first jaw member  130  and a stopping portion  174  adapted to engage tissue. A pivot pin  176 , or any other suitable apparatus, pivotally connects stopping portion  174  to base  172 . Consequently, stopping portion  174  is configured to pivot away and toward tissue-contacting surface  134 . In one embodiment, stop member  170  includes a biasing member (e.g., a spring) for biasing stopping portion  174  away from first jaw member  130 . 
     Stopping portion  174  contains a body  175  and at least one leg  177  extending proximally from body  175 . In the embodiment depicted in  FIG. 2 , stopping portion  174  has two legs  177  extending proximally from body  175 . Stopping portion  174  may nonetheless include more or fewer legs  177 . The two legs  177  shown in  FIG. 2  define a space therebetween adapted to receive a knife. Each leg  177  is dimensioned to be received within a slot  139  and includes a proximal surface  173 . When stop member  170  is located in the first position, each proximal surface  173  defines an oblique angle relative to tissue-contacting surface  134 , as seen in  FIG. 5 . Conversely, when stop member  170  is located in the second position (see  FIG. 7 ), each proximal surface  173  defines an angle substantially perpendicular to tissue-contacting surface  134 . Irrespective of the position of stop member  170 , legs  177  are shown positioned on opposite sides of knife channel  138 . Slots  139 , which are dimensioned to receive legs  177 , are accordingly located on opposite sides of knife channel  138  as well. 
     Referring to  FIGS. 6-8 , stop member  170  facilitates retention of tissue between first and second jaw members  130 ,  140  during the operation of surgical instrument  100 . (See  FIG. 1 ). That is, stop member  170  helps prevent tissue from migrating or translating distally past its intended placement between the jaw members. In use, a user initially positions surgical instrument  100  adjacent a target tissue. Particularly, the target tissue is placed between first and second jaw members  130 ,  140 . The angle defined by body  175  relative to tissue-contacting surface  136  facilitates introduction of the target tissue “T” into tool assembly  150  in the general direction of arrow “A,” as seen in  FIG. 6 . Once the user has placed at least a portion of the target tissue between first and second jaw members  130 ,  140 , the user pulls movable handle  164  toward stationary handle  162  to approximate anvil assembly  152  toward cartridge assembly  132 . While the user pulls movable handle  164 , anvil assembly  152  moves closer to cartridge assembly  132  and the target tissue “T” is captured between tissue-contacting surface  134  of cartridge assembly  132 . At the same time, anvil assembly  142  urges stopping portion  174  toward cartridge assembly  132 . In response to the force exerted by the anvil assembly  142  on stopping portion  174 , stopping portion  174  pivots about pivot pin  176  toward cartridge assembly  132 , e.g., against the bias of biasing member (not shown). While stopping portion  174  moves closer to cartridge assembly  134 , at least a portion of legs  177  move to an inner portion of cartridge assembly  132  through slots  139 , as seen in  FIG. 7 . When stop member  170  is in the second position (as shown in  FIG. 7 ), a portion of legs  177  is located within cartridge assembly  132 ; correspondingly, a portion of proximal surfaces  173  is located outside of cartridge assembly  132 . As discussed above, proximal surfaces  173  define a substantially orthogonal angle relative to tissue-contacting surface  134  when stop member  170  is in the second position, thereby hindering the escape of tissue during clamping. 
     The present disclosure also contemplates stop member  170  being releasably attachable to end effector  150  via conventional mechanical means, e.g., bayonet coupling, latch, detent or snap-fit connection. 
     With reference to  FIGS. 9-12 , a first jaw member  230  according to another embodiment is envisioned. First jaw member  230  of this embodiment has a curved shape (i.e., with respect to longitudinal axis “A-A”). The first jaw member may be part of a loading unit including an anvil assembly, or some other surgical fastening device. It is envisioned that curved jaw members may facilitate performing certain types of surgical procedures. For example, curved jaw members, as compared to straight jaw members (such as the jaw members illustrated in  FIG. 1 ), may help facilitate access to lower pelvic regions, e.g., during lower anterior resection (“LAR”) or other colo-rectal surgery. 
     First jaw member  230  includes an opening  239  ( FIG. 10 ) adapted to receive both legs  277  of stop portion  270  instead of two slots  139  each capable of receiving a leg  177  of stop member  170 . Stop member  270  is similar to stop member  170 . However, stop member  270  has a stopping portion  274  directly connected to a distal portion  237  of first jaw member  230 . Distal portion  237  contains a hole  235  ( FIG. 10 ) adapted to receive a pivot pin  276 . Pivot pin  276 , or any other suitable apparatus, pivotally couples stop member  270  to first jaw member  230 . 
     The term “distal” typically refers to that part or component of the instrument that is farther away from the user. As used herein, the terms “distal” and “proximal” will take into account the curvature of curved parts of the surgical instrument  10  of the present disclosure. For example, “distal” will refer to the portion of the curved part that is farthest from the user, along a trajectory defined by the curved part, such as trajectory C-C shown in  FIG. 12 . That is, while an intermediate portion of a curved part may be farther from the user during use, the portion of the curved part that is farthest along its longitudinal axis is considered “distal.” 
     In general, first jaw member  230  includes a curved housing  231  and a curved cartridge assembly  232 . Housing  231  has a curved channel  233  adapted to receive curved cartridge assembly  232 . Curved cartridge assembly  232  contains a tissue-contacting surface  234  configured to engage tissue, rows of fastener retaining slots  236  extending along its curved profile, and a knife channel  238  adapted to slidably receive a knife (not shown). Knife channel  238  is disposed between the rows of fastener retaining slots  236 . 
     As discussed above, actuating handle assembly  160  not only ejects the fasteners, but also drives a knife along knife channel  238  (e.g., via a single stroke or multiple strokes of movable handle  164 ). Knife channel  238  leads to an opening  239  formed on distal portion  237  of cartridge assembly  232 . A recess  280  is positioned distally of opening  239  and includes an inclined wall  282  (see  FIG. 11 ) defining an oblique angle relative to tissue-contacting surface  234  and is adapted to receive a portion of stop member  270  therein. In addition to inclined wall  282 , recess  280  has a cavity  284  adapted to receive a portion of stop member  270  (see  FIG. 11 ). 
     Stop member  270  includes a body  275 , a pair of legs extending proximally from body  275 , and a pivoting protrusion  286  extending transversely from body  275 . Legs  277  define a space therebetween dimensioned to receive a knife. Each leg  277  has a proximal surface  273  that defines an oblique angle relative to tissue-contacting surface  234  when stop portion  270  is in the first position, as shown in  FIG. 9 , and a substantially perpendicular angle relative to tissue-contacting surface  234  when stop portion  270  is in the second position, as illustrated in  FIG. 12 . 
     Body  275  defines an oblique angle with respect to the tissue-contacting surface  234 . Pivoting protrusion  286  of stop member  270  is adapted to be received within cavity  284  and has a hole  288  configured to receive pivot pin  276 . Pivot pin  276  extends through hole  235  of cartridge assembly  270  and hole  280  of pivoting protrusion  286  and allows stop member  270  to pivot from a first position where at least a portion of the stop member  270  is positioned external to first jaw member  230 , as seen in  FIG. 9 , and a second position where at least a portion of stop member  270  is positioned at least partially below a tissue-contacting surface  234  of the first jaw member  230 , as seen in  FIG. 12 . 
     As seen in  FIG. 11 , body  275  additionally contains a thru-hole  290  leading to inclined wall  282  and an abutment wall  292  protruding toward thru-hole  290 . Abutment wall  292  is configured to hold a first end  294   a  of a biasing member  294 , and inclined wall  282  is adapted to support a second end  294   b  of biasing member  294 . Biasing member  294  biases stop member  270  towards its first position. In the embodiment depicted in  FIGS. 10 and 11 , biasing member  294  is a spring, but biasing member  294  can alternatively be any suitable apparatus or means capable of biasing stop member  270  away from first jaw member  230 . 
     The operation of first jaw member  230  is substantially similar to the operation of first jaw member  130 . First jaw member  230  works jointly with an anvil assembly to cut and/or fasten tissue. As a user actuates handle assembly  160 , the jaw members approximate, which urges stop member  230  from the first position (see  FIG. 9 ) to a second position (see  FIG. 12 ). In the first position, the orientation of stop member  230  facilitates the introduction of tissue between first jaw member  230  and an anvil assembly. Further, stop member  230  inhibits tissue from distally escaping the tool assembly when stop member  230  is oriented in its second position. When the anvil assembly moves away from first jaw member  230 , stop member  230 , under the influence of biasing member  294 , returns to its first position. 
       FIGS. 13-14  illustrate another embodiment of a first jaw member  330 , and a second jaw member  340  for a surgical stapling instrument. Another embodiment of a tissue stop  370  is illustrated in  FIG. 13 .  FIG. 13  illustrates tissue stop  370  in its first, initial position (phantom lines) and in its second position (solid lines). Similar to the embodiments disclosed hereinabove, tissue stop  370  is biased towards its initial position, and in approximation of the jaw members, contact with the opposing jaw member causes tissue stop  370  to move towards its second position. By way of example, the first jaw member  330  is a staple cartridge assembly, and the second jaw member  340  is an anvil assembly. Other surgical instrument jaws, such as electrosurgical, are contemplated. 
     With particular reference to  FIG. 13 , first jaw member  330  (e.g., cartridge assembly) includes an upper tissue-contacting surface  332  and a lower shelf portion  334 . Lower shelf portion  334  includes a groove  336  extending at least partially therethrough. As shown in  FIG. 13 , groove  336  is configured to accept a portion of tissue stop  370  therein. In particular, groove  336  is configured to accept a lip  372  of tissue stop therein. Groove  336  enables tissue stop  370  to include a stopping portion  374  having a maximum height “H 1 .” More particularly, tissue stop  370  is configured to fit within first jaw member  330  (i.e., not protrude above upper tissue-contacting surface  332 , and not protrude below lower shelf portion  334 ) when tissue stop  370  is in its second position (i.e., corresponding to first and second jaw members  330 ,  340 , respectively, being approximated with respect to one another), and to extend between the tissue-contacting surface  332  and the anvil plate when the tissue stop  370  is in its first position (such as when the first jaw member and second jaw member are spaced from one another and ready to receive tissue). Thus, without the inclusion of groove  336 , the maximum height of stopping portion  374  would be decreased by the height “H 2 ” of lower shelf portion  334 . As can be appreciated, the greater the height “H 1 ” of stopping portion  374 , the increased ability surgical instrument has to contain thicker tissue between the jaw members. That is, the relatively large height “H 1 ” of stopping portion  374  helps prevent a greater amount of tissue (e.g., a greater thickness of tissue) from distally escaping the jaw members. 
     An actuation sled  400  is illustrated in  FIGS. 13-15 . Actuation sled  400  is longitudinally translatable (including along a curved path) with respect to first jaw member  330  (e.g., cartridge assembly). As discussed above, an axial drive assembly pushes actuation sled  400  in a distal direction, and as actuation sled  400  advances distally through and along lower shelf portion  334  of first jaw member  330 , actuation sled  400  urges fasteners out of the fastener retaining slots. For example, a beam including a knife may be used to advance the actuation sled to fire the fasteners. 
     In the illustrated embodiments, actuation sled  400  includes four cam wedges  402   a ,  402   b ,  402   c , and  402   d  and a transversely-extending connecting member  404  which operably connects each cam wedge with its adjacent cam wedge(s). As illustrated, connecting member  404  is proximally disposed with respect to each cam wedge  402 . The proximal location of connecting member  404  with respect to cam wedges  402  creates distal portions of each of cam wedge  402  that are elongated and that cantileveredly extend from connecting member  404 . It is also envisioned that portions (e.g., distal portions) of wedge  402   a  are connected to adjacent wedge  402   b , and that portions of wedge  402   c  are connected to adjacent wedge  402   d  via connecting member  404  and/or a separate member, to enhance stability of actuation sled, for instance. The present disclosure also includes an actuation sled  400  including more or fewer than the illustrated four cam wedges. 
     Actuation sled  400  is configured to accommodate tissue stop  370 , and in particular, lip  372  of tissue stop  370 . In particular, the proximal orientation of connecting member  404  enables distal portions of cam wedges  402  to contact fasteners or pusher members (not explicitly illustrated in  FIGS. 13-15 ) that are distally disposed within first jaw member  330  without interfering with lip  372  of tissue stop  370 . More specifically, when actuation sled  400  is in its distal-most position (as illustrated by the phantom lines in  FIG. 14 ), connecting member  404  is positioned proximally of lip  372  of stop member  370  (location of lip  372  is indicated by a widened portion  339  of a knife channel  338  in  FIG. 14 ), thus enabling distal portion of cam wedges  402  to cause ejection of the most distally-disposed fasteners (not shown). While the distal-most portion of cam wedges  402  is illustrated as being substantially aligned with the distal edge of knife channel  338  when actuation sled  400  is in a distal position, it is envisioned that the distal-most portion of cam wedges  402  extends proximally of and/or distally beyond the distal edge of knife channel  328 . 
     Referring back to  FIG. 13 , an I-beam assembly  500  is illustrated in connection with first jaw member  330  and second jaw member  340 . According to the embodiment illustrated in  FIG. 13 , I-beam assembly  500  generally includes an upper member  502  configured to slidably engage a slot in second jaw member  340 , a lower member  504  configured to slide beneath lower shelf portion  334  of first jaw member  330 , and a knife  506  configured to cut tissue between the jaw members  330 ,  340 . Additionally, I-beam assembly  500  also includes a notch  508  along a lower surface thereof which is configured to mechanically engage connecting member  404  of actuation sled  400 . As such, distal approximation of the I-beam assembly  500  results in approximation of the jaw members  330 ,  340 , results in cutting of tissue between the jaw members  330 ,  340 , and also results in distal advancement of actuation sled  400 , which causes fasteners to be ejected from first jaw member  330 . In certain embodiments, the knife  506  is disposed between legs  277  of the tissue stop, the legs defining a recess for receiving the knife  506 . A plastic, compressible and/or elastic material may be disposed in the recess defined by the legs  277  for pressing tissue against the knife  506 , at the end of travel for the I beam assembly  500 . Additionally, retraction of I-beam assembly  500  in a proximal direction causes a corresponding proximal retraction of actuation sled  400 . It is also envisioned that when I-beam assembly  500  is proximally retracted to a predetermined location, at least one jaw member moves towards the open position with respect to the other jaw member. 
     With reference to  FIG. 16 , a transverse cross-sectional view of a portion of jaw member  330  and sled  400  is shown. In this embodiment, connecting member  404  is shown with an alignment nub  406  downwardly depending therefrom. Alignment nub is configured to follow the curvature of the knife channel  338  as the actuation sled  400  translates with respect to the jaw member  330 . The engagement between the alignment nub  406  and the knife channel  338  may help maintain the relative lateral position (e.g., centered) of the actuation sled with respect to the jaw member  330  during translation of the actuation sled  400 . 
     It will be understood that various modifications may be made to the embodiments of the presently disclosed surgical instruments. Therefore, the above description should not be construed as limiting, but merely as exemplifications of embodiments. Those skilled in the art will envision other modifications within the scope and spirit of the present disclosure.