Patent Publication Number: US-11375998-B2

Title: Tissue stop for surgical instrument

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This is a continuation of U.S. patent application Ser. No. 15/875,344, filed Jan. 19, 2018, which is a continuation of U.S. patent application Ser. No. 14/493,483, filed Sep. 23, 2014 (now U.S. Pat. No. 9,901,339), which is a continuation of U.S. patent application Ser. No. 13/208,447, filed on Aug. 12, 2011 (now U.S. Pat. No. 8,899,461), which claims priority to, and the benefit of, U.S. Provisional Patent Application Ser. No. 61/388,650, filed on Oct. 1, 2010, the entire contents of each of which is incorporated herein by reference. 
    
    
     BACKGROUND 
     Technical Field 
     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. In certain surgical stapling instruments, the instrument sequentially ejects the staples from the staple cartridge while the anvil and cartridge are approximated. The staples are driven through the tissue and formed against the anvil. 
     SUMMARY 
     The present disclosure relates to a surgical instrument for surgically joining a tissue is disclosed. The surgical instrument comprises a handle assembly, an elongate portion, a pair of opposed jaw members, and a tissue stop. The handle assembly includes a movable handle. The elongate portion extends distally from the handle assembly and defines a longitudinal axis. The pair of opposed jaw members are operatively coupled to the elongate portion and extend distally therefrom. The pair of opposed jaw members includes a first jaw member and a second jaw member. The tissue stop is mechanically engaged with the first jaw member and is configured to retain the tissue between the pair of opposed jaw members. The tissue stop is movable between a first position, where a stopping portion of the tissue stop is disposed between a tissue-contacting surface of the first jaw member and a tissue-contacting surface of the second jaw member, and a second position, where the stopping portion is between the tissue-contacting surface of the first jaw member and a lower surface of the first jaw member. A portion of the tissue stop is made of stamped metal section and a portion of the tissue stop is made of an overmolded plastic section. 
     In disclosed embodiments, the stopping portion of the tissue stop includes a scalloped portion. In disclosed embodiment, the scalloped portion of the tissue stop includes a plurality of spaced-apart semi-circular indents. 
     In disclosed embodiments, the tissue stop includes a pair of lateral walls. In disclosed embodiments, the stopping portion is disposed on a proximal edge of each lateral wall. 
     The present disclosure also relates to a loading unit configured for releasable engagement with a surgical instrument. The loading unit comprises a body portion, a pair of jaw members, and a tissue stop. The body portion defines a longitudinal axis and includes a proximal portion configured for releasable engagement with an elongate portion of the surgical instrument. The pair of jaw members extends distally from the body portion. At least one of the jaw members is movable with respect to the other between an open position and an approximated position engaging a body tissue therebetween. The pair of jaw members includes a first jaw member and a second jaw member. The tissue stop is mechanically engaged with the first jaw member and is configured to retain the tissue between the pair of opposed jaw members. The tissue stop is movable between a first position, where a stopping portion of the tissue stop is disposed between a tissue-contacting surface of the first jaw member and a tissue-contacting surface of the second jaw member, and a second position, where the stopping portion is between the tissue-contacting surface of the first jaw member and a lower surface of the first jaw member. A portion of the tissue stop is made of stamped metal section and a portion of the tissue stop is made of an overmolded plastic section. 
     In disclosed embodiments, the stopping portion of the tissue stop of the loading unit includes a scalloped portion. In disclosed embodiment, the scalloped portion of the tissue stop includes a plurality of spaced-apart semi-circular indents. 
     In disclosed embodiments, the tissue stop of the loading unit includes a pair of lateral walls. In disclosed embodiments, the stopping portion is disposed on a proximal edge of each lateral wall. 
     The present disclosure also relates to a tissue stop for use with a surgical instrument. The tissue stop comprises a stamped metal portion and an overmolded plastic portion. The tissue stop is mechanically engaged with a jaw member of the surgical instrument and is configured to retain the tissue between opposed jaw members of the surgical instrument. 
     In disclosed embodiments, the tissue stop includes a pair of lateral walls. In disclosed embodiments, a stopping portion is disposed on a proximal edge of each lateral wall. In disclosed embodiments, the stopping portion includes a scalloped portion. In disclosed embodiments, the scalloped portion of the tissue stop includes a plurality of spaced-apart semi-circular indents. 
    
    
     
       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 a surgical instrument in accordance with the present disclosure; 
         FIG. 2  is a perspective view of a loading unit of the surgical instrument of  FIG. 1 ; 
         FIG. 3  is a perspective view of the area of detail of  FIG. 2  illustrating a tissue stop; 
         FIG. 4  is a perspective exploded view of a distal portion of a jaw member of the surgical instrument including the tissue stop of  FIG. 3 ; 
         FIG. 5  is a longitudinal cross-sectional view of the tissue stop mechanically engaged with the jaw members of the surgical instrument; 
         FIG. 6  is a side view of a portion of the jaw members and the tissue stop prior to insertion of tissue; 
         FIGS. 7-9  are longitudinal cross-sectional views of a portion of jaw members and a tissue stop interacting with the tissue at various stages of operation in accordance with another embodiment of the present disclosure; 
         FIG. 10  is a perspective assembly view of a loading unit in accordance with another embodiment of the present disclosure; 
         FIGS. 11 and 12  are perspective views of a tissue stop including a stamped metal portion and an overmolded plastic portion for use with the surgical instrument of  FIG. 1  in accordance with an embodiment of the present disclosure; 
         FIG. 13  is a perspective view of a stamped metal portion of the tissue stop of  FIGS. 11 and 12 ; and 
         FIGS. 14-17  are various views of the stamped metal portion of the tissue stop of  FIGS. 11 and 12 . 
     
    
    
     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 tissue stop 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. In the interest of brevity, the present disclosure focuses on an end effector and a tissue stop of surgical instrument  100 . U.S. Pat. No. 8,033,442, filed on Nov. 28, 2007; U.S. Pat. No. 8,393,513, filed on Jan. 9, 2008; U.S. Pat. No. 7,568,604, filed on Jan. 24, 2008; U.S. Pat. No. 7,565,993, filed on Oct. 15, 2007; and U.S. Patent Application Publication No. 2007/0187456, filed on Apr. 10, 2007, the entire contents of each of which is hereby incorporated by reference herein, describe in detail the structure and operation of other surgical fastening assemblies. 
     Surgical instrument  100  disclosed in the illustrated embodiments is configured to clamp, fasten, and/or cut tissue. In general, surgical instrument  100  includes a handle assembly  110 , an elongate portion  120  extending distally from handle assembly  110  and defining a longitudinal axis “A-A,” and a loading unit  180  (collectively referring to a single use loading unit (“SULU”) and a disposable loading unit (“DLU”)), as shown in  FIG. 1 . With reference to  FIG. 2 , loading unit  180  includes a proximal body portion  156 , and a tool assembly  150 . Proximal body portion  156  is configured to releasably attach to elongate portion  120  of surgical instrument  100  using a variety of attachment features, such as, for example, a bayonet coupling, latch, detent or snap-fit. In other embodiments, the instrument has jaws that are permanently attached to the elongate portion, and a replaceable cartridge, such as a staple cartridge, can be loaded, removed and reloaded in one of the jaws. 
     Tool assembly  150  includes end effector  154  and a tissue stop  170 . End effector  154 , which is disposed adjacent distal portion  124  of body portion  156 , includes a first jaw member  130  and a second jaw member  140 . As shown in  FIGS. 1 and 2 , each of first and second jaw members  130 ,  140  is longitudinally curved with respect to the longitudinal axis “A-A.” The curved jaw members, as compared to straight jaw members, may help facilitate access to lower pelvic regions, e.g., during lower anterior resection (“LAR”). Additionally, the inclusion of curved jaw members may allow increased visualization to a surgical site and may also allow more room for a surgeon to manipulate target tissue or the jaw members themselves with his or her hand. While the illustrated embodiment depict the jaw members as being curved, it is envisioned and within the scope of the present disclosure that the tissue stop  170  may be used with linear jaw members. 
     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 , and second jaw member  140  includes an anvil assembly  142 . Cartridge assembly  132  moves with respect to anvil assembly  142  between spaced and approximated positions upon actuation of a movable handle  112 , for example. While cartridge assembly  132  is shown as pivotally movable with respect to anvil assembly  142 , anvil assembly  142  may be pivotally mounted with respect to the cartridge assembly  132 . 
     Handle assembly  110  includes a stationary handle  114  and movable handle  112 . Movable handle  112  is adapted to move pivotally towards or away from stationary handle  114 . Further, movable handle  112  is operatively connected to anvil assembly  142  through a mechanism adapted to convert at least a partial actuation of movable handle  112  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  112  to tool assembly  150 . 
     With reference to  FIG. 2 , cartridge assembly  132  has a tissue-contacting surface  134  and a plurality of fastener retaining slots  136 . Tissue-contacting surface  134  generally faces anvil assembly  142  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  and each fastener retaining slot  136  is adapted to releasably hold a fastener (not shown). For example, when movable handle  112  is pivoted toward stationary handle  114 , the fasteners are ejected from fastener retaining slots  136  and move towards anvil assembly  142 . 
     Cartridge assembly  132  also includes a knife channel  138  ( FIG. 3 ) adapted to slidably receive a knife (not shown) or any other suitable cutting tool. Knife channel  138  is defined in the staple cartridge, is disposed between rows of fastener retaining slots  136 , and extends along tissue-contacting surface  134 . In operation, the knife slides through the knife channel  138  when movable handle  112  pivots towards stationary handle  114 . Alternatively, other mechanisms can be used to drive the knife through knife channel  138 . 
     In disclosed embodiments, handle assembly  110  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 (not shown) operatively connected to movable handle  112 . In operation, pivoting movable handle  112  toward stationary handle  114  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 drive beam that incorporates the knife, an upper member, and a lower member. As the upper member of the drive beam engages the anvil assembly and the lower member of the drive beam engages the cartridge assembly, the distal translation of axial drive assembly causes the anvil assembly  142  to pivot toward the cartridge assembly  132 . In addition, the axial drive assembly pushes an actuation sled disposed within the cartridge assembly  132  in a distal direction, while the actuation sled translates distally through end effector  154 . As the actuation sled advances distally through the cartridge assembly  132 , this actuation sled urges the fasteners out of the fastener retaining slots  136 . In certain embodiments, axial drive assembly includes a knife or blade mounted on a distal portion thereof. In operation, the drive beam, including the knife, moves through the knife channel  138  when axial drive assembly moves distally through end effector  154 . Further details of an endoscopic surgical stapling instrument are described in detail in commonly-owned U.S. Pat. No. 6,953,139 to Milliman et al., the entire contents of which are hereby incorporated by reference herein. However, it is also envisioned that other methods of approximating the jaw members are also usable, including sliding a clamp bar (not shown). Other methods of ejecting the fasteners are contemplated, such as cam bars, are contemplated. 
     With reference to  FIGS. 3 and 4 , tissue stop  170  is movably disposed at least partially within a recess  164  defined in a distal portion of jaw member  130 . 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 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. 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.” 
     The distal portion of jaw member  130  defines recess  164  and includes a proximal wall  165 , a pair of side walls  166 ,  168  and a lower surface  169 . Tissue stop  170  includes a body  172  having an upper, tissue-contacting surface  174 , a pair of lateral walls  176 ,  178 , and a stopping portion  182  configured and adapted to engage tissue (e.g., tissue that is distally directed from between the jaw members). 
     A pair of camming pins, including a proximal camming pin  184  and a distal camming pin  186 , is also disclosed. Each camming pin  184 ,  186  is configured to extend transversely through both lateral walls  176 ,  178  of body  172 . Proximal camming pin  184  is configured to extend through a first pair of holes  177  of body  172  (only a single hole  177  is shown on lateral wall  176 ; the hole that is disposed through lateral wall  178  is not visible in  FIG. 4 ), and is configured to engage a pair of proximal cam slots  196 , which extend at least partially through each side wall  166 ,  168  of recess  164 . Distal camming pin  186  is configured extend through a second pair of holes  179  of body  172  (only a single hole  179  is shown on lateral wall  176 ; the hole that is disposed through lateral wall  178  is not visible in  FIG. 4 ), and is configured to engage a pair of distal cam slots  198 , which extend at least partially through each side wall  166 ,  168  of recess  164 . As can be appreciated, the engagement between camming pins  184 ,  186 , jaw member  130 , and tissue stop  170  movably secure tissue stop  170  to jaw member  130 . 
     In the illustrated embodiments, distal cam slots  198  are substantially parallel to tissue-contacting surface  134  of jaw member  130 , and proximal cam slots  196  form an angle with respect to tissue-contacting surface  134  of jaw member  130 . It is envisioned that proximal cam slots  196  include at least one curved portion, at least one linear portion, or combinations of at least one curved and at least one linear portion. The illustrated configuration of cam slots  196 ,  198  allows tissue stopping portion  182  to be movable in and out of recess  164  adjacent proximal wall  165  with a reduced clearance gap “G” therebetween (see  FIG. 5 ). It is also envisioned that gap “G” may be minimized at every moment when tissue stop  170  moves from the first position to the second position. Other cam arrangements can be used to connect the tissue stop to the jaw. The cam can be shaped to maximize the height of the tissue stop when the tissue stop is extended from the jaw (the first position) and/or minimize the space within the jaw occupied by the tissue stop when the tissue stop is in the retracted, second position. 
     As shown in  FIG. 5 , tissue stop  170  also includes a biasing member  173 . Biasing member  173  is configured to mechanically engage camming pin  186  and to mechanically engage a support pin  158  that extends through an opening  190  (see  FIG. 4 ) on each side wall  166 ,  168  of jaw member  130 . However, it is also contemplated that any other retaining member, such as, for example, a post, may replace support pin  158  to retain one end of biasing member  173 . Biasing member  173  urges distal camming pin  186  to its proximal-most position within camming slots  198 . In response to the distal camming pin  186  being proximally urged, proximal camming pin  184  is also proximally urged due to the mechanical relationship between camming pins  184 ,  186 , biasing member  173 , and tissue stop  170 . When camming pins  184 ,  186  are in their proximal-most positions within camming slots  196 ,  198 , respectively, tissue stop  170  is located in a first position, in which stopping portion  182  is exposed and extends at least partially out of recess  164 , i.e., disposed between tissue-contacting surfaces  134 ,  135  of cartridge and anvil assemblies  132 ,  142 , respectively (see  FIG. 5 , for example). 
     Tissue stop  170  is movable between the first position, as shown in  FIG. 5 , and a second position, as illustrated in  FIG. 8 . In the first position which corresponds to when jaw members  130 ,  140  are in an open position, at least a portion (e.g., a majority, or the entire portion) of stopping portion  182  is exposed out of recess  164 . The approximation of the jaw members  130 ,  140  causes tissue stop  170  to move towards its second position. That is, as one jaw member (e.g., jaw member  140 ) moves towards the other jaw member (e.g., jaw member  130 ), tissue-contacting surface  135  contacts tissue-contacting surface  174  of tissue stop  170 , and physically urges tissue stop  170  towards its second position against the bias of biasing member  173 . In the second position which corresponds to when jaw members  130 ,  140  are in the approximated position, a majority (e.g., the entirety) of stopping portion  182  is disposed within recess  164 . In this embodiment, when tissue stop  170  is disposed in the first position, stopping portion  182  is orthogonally disposed (e.g., substantially perpendicular) relative to tissue-contacting surface  134 . As can be appreciated, such an orientation may help impede tissue from distally escaping tool assembly  150 . In other embodiments, the instrument can include an actuator that is connected to the tissue stop so that the user can move the tissue stop between the first and second positions by manipulating a button or lever. Such actuator may also include a lock and/or latch for locking the position of the tissue stop. 
     In use, a surgeon initially positions surgical stapling instrument  100  adjacent a target tissue as shown in  FIG. 6 . Here, tissue stop  170  is in the first position where the jaw members  130 ,  140  are in an open position and at least a portion of stopping portion  182  is exposed out of recess  164 . Then tissue “T” is introduced into tool assembly  150 , between jaw members  130 ,  140 . The angle defined by upper tissue-contacting surface  174  of tissue stop  170  facilitates introduction of tissue “T” into tool assembly  150  in the general direction of arrow “B,” as seen in  FIG. 6 . As tissue “T” is proximally inserted into tool assembly  150 , tissue “T” comes into contact with tissue stop  170  and may force at least a portion of stopping portion  182  into recess  164  in the general direction of arrow “C” as shown in  FIG. 7 . In certain embodiments, the tissue stop has a sloped surface facing the open end of the jaws to encourage the tissue to move the tissue stop. Alternatively, tissue “T” may be proximally inserted between the jaw members  130 ,  140  by moving in the space between the tissue-contacting surface  135  of jaw member  140  and tissue-contacting surface  174  of tissue stop  170  without necessarily contacting stop member  170 . 
     When moved towards its second position, tissue stopping portion  182  moves in the general direction of arrow “C” ( FIG. 7 ). As tissue stopping portion  182  is translated in the general direction of arrow “C,” distal camming pin  186  distally translates along distal camming slot  198  in the general direction of arrow “E” ( FIG. 7 ), while proximal camming pin  184  slides distally along proximal camming slot  184  in the general direction of arrow “D” ( FIG. 7 ). 
     After the surgeon has placed at least a portion of tissue “T” between jaw members  130 ,  140 , the surgeon can actuate an approximation mechanism, e.g., by pivoting movable handle  112  towards stationary handle  114  to approximate anvil assembly  142  towards cartridge assembly  132 , to capture tissue “T” between tissue-contacting surfaces  134 ,  135  as shown in  FIG. 8 . Here, a proximal portion of tissue-contacting surface  174  of tissue stop  170  is substantially flush with tissue-contacting surface  134  of cartridge assembly  132 , and anvil assembly  142  exerts a force against stop member  170  (through tissue “T”) toward recess  164 . In response to the force exerted by the anvil assembly  142  on tissue stop  170 , camming pin  186  translates farther distally along camming slot  198  in the general direction of arrow “E” until the camming pin  186  is in the distal-most portion of camming slot  198 . Additionally, camming pin  184  slides farther distally along camming slot  196  in the general direction of arrow “H” ( FIG. 8 ) until camming pin  184  reaches the distal-most portion of camming slot  196 , against the bias of biasing member  173 . Tissue “T” is now interposed between jaw members  130 ,  140  and may be pushed farther proximally by surgeon in the general direction of arrow “F” ( FIGS. 7-9 ). As a distal end of tissue “T” is pushed proximally of tissue stop  170  in the general direction of “F,” the biasing force exerted by biasing member  173  pushes tissue stop  170  in the general direction of arrow “I,” towards (and possibly against) tissue-contacting surface  135  of anvil assembly  142 . Here, camming pins  184 ,  186  have moved proximally along camming slots  196 ,  198 , respectively, proportional to the thickness of tissue “T.” 
     In the embodiment illustrated in  FIG. 9 , tissue stop  170  is in contact with tissue-contacting surface  135  and is located distally of tissue “T,” thereby impeding or preventing any distal escape of tissue “T.” At this time, the surgeon may perform a surgical procedure on tissue “T,” e.g., staple, seal and/or cut tissue “T.” After performing the surgical procedure, jaw member  140  is moved away from jaw member  130 , and tissue stop  170  returns to its first position in response to the biasing force. 
     With reference to  FIG. 10 , a loading unit  500  in accordance with another embodiment of the present disclosure is illustrated. Loading unit  500  includes a proximal body portion  556  and a tool assembly  550 . Proximal body portion  556  is releasably attachable to a distal end of elongate portion  120 . Tool assembly  550  includes a pair of jaw members including an anvil assembly  542  and a cartridge assembly  532 . In particular, cartridge assembly  532  is pivotal in relation to anvil assembly and is movable between an open or unclamped position and a closed or approximated position. 
     Anvil assembly  542  includes a longitudinally curved anvil cover  543  and a longitudinally curved anvil plate  544 , which defines a plurality of staple forming depressions. When tool assembly  550  is in the approximated position, staple forming depressions are positioned in juxtaposed alignment with cartridge assembly  532 . Cartridge assembly  532  includes a longitudinally curved carrier  537 , which receives a longitudinally curved cartridge  518  via, for example, a snap-fit connection. Cartridge  518  includes a pair of support struts  519  which rest on sidewalls  539  of carrier  537  to stabilize cartridge  518  on carrier  537 . An external surface of carrier  537  includes an angled cam surface  516   a.    
     Cartridge  518  defines a plurality of laterally spaced staple retention slots  536 . Each slot  536  is configured to receive a staple  630  therein. Cartridge  518  includes a central longitudinally curved slot  538 . As an actuation sled  541  moves through cartridge  518 , cam wedges  541   a  of actuation sled  541  sequentially engage pushers  632  to move pushers  632  vertically within staple retention slots  536  and eject staples  630  into staple forming depressions of anvil plate  544 . Subsequent to the ejection of staples  630  from retention slots  536 , a cutting edge  606   a  of dynamic clamping member  606  severs the stapled tissue as cutting edge  606   a  travels through curved slot  538  of cartridge  518 . 
     With continued reference to  FIG. 10 , proximal body portion  556  includes an inner body  503  formed from molded half-sections  503   a  and  503   b  and a drive assembly  560 . Proximal body portion  556  is coupled to tool assembly  550  by a mounting assembly  570 . Mounting assembly  570  has a pair of extensions  576  which extend into a proximal end of carrier  537 . Each extension  576  has a transverse bore  578  which is aligned with holes  516 A of carrier  539  such that mounting assembly  570  is pivotally secured to cartridge  518  with carrier  539 . Mounting assembly  570  is fixedly secured to half-section  503   a  by a pair of vertical protrusions  584 . Vertical protrusions  584  extend upwardly from mounting assembly  570  and frictionally fit into corresponding recesses in half-section  503   a.    
     Anvil cover  543  includes a proximally extending finger  588  having a pair of cutouts  589  formed therein. Cutouts  589  are positioned on each lateral side of finger  588  to help secure anvil cover to half-section  503   a . Half-section  503   a  includes a channel  505  that includes a pair of protrusions  505   a . Finger  588  of anvil cover mechanically engages channel  505  of half-section  503   a , such that cutouts  589  are aligned with protrusions  505   a . An outer sleeve  602  covers the finger  588  and channel  505 . The configuration of finger  588  and channel  505  facilitates a secure connection between anvil cover  543  and half-section  503   a . Moreover, this connection results in a non-movable (e.g., non-pivotable) anvil assembly  542  with respect to proximal body portion  556 . 
     Drive assembly  560  includes a flexible drive beam  604  which is constructed from three stacked metallic sheets  604   a - c  and a proximal engagement portion  608 . At least a portion of drive beam  604  is sufficiently flexible to be advanced through the curvature of the tool assembly  550 . Drive beam  604  has a distal end which is secured to a dynamic clamping member  606 . Dynamic clamping member  606  includes a knife or cutting edge  606   a  at a distal face of vertical strut  606   d.    
     Loading unit  500  includes a tissue stop  770  movably disposed at least partially within a recess  764  defined in a distal portion of cartridge  518 . Recess  764  is defined by a proximal wall  765 , a pair of side walls  766 ,  768  and a lower surface. Tissue stop  770  includes a body  772  having an upper, tissue-contacting surface, a pair of lateral walls and a stopping portion  782  configured and adapted to engage tissue. A proximal camming pin  758  and a distal camming pin  786  are each configured to extend transversely through both lateral walls  766 ,  768  of body  772 . Proximal camming pin  758  is configured to extend through a first through hole  777  of body  772 , and is configured to engage a pair of proximal cam slots  796 , which extend at least partially through each side wall  766 ,  768 . Distal camming pin  786  is configured to extend through a second through hole  779  of body  772 , and is configured to engage a pair of distal cam slots  798 , which extend at least partially through each side wall  766 ,  768 . It is also contemplated that at least one  796 ,  798  is only defined in one of the side walls  766 ,  768 . 
     Tissue stop  770  also includes a biasing member  773 . Biasing member  773  is configured to mechanically engage camming pin  786  and to mechanically engage a support pin  784  that extends through an opening  790  (see  FIG. 4 ) on each side wall  766 ,  768  of cartridge assembly  532 . Biasing member  773  urges distal camming pin  786  to its proximal-most position within camming slots  798 . In response to the urging of distal camming pin  786  in the proximal direction, proximal camming pin  758  is also proximally urged due to the mechanical relationship between camming pins  758 ,  786 , biasing member  773 , and tissue stop  770 . When camming pins  758 ,  786  are in their proximal-most positions within camming slots  796 ,  798 , respectively, stopping portion  782  is exposed and extends at least partially out of recess  764 . The operation of loading unit  500  is substantially similar to those described above and will be omitted in the interest of brevity. 
     With reference to  FIGS. 11-17 , a tissue stop  1000  in accordance with an embodiment of the present disclosure is illustrated. Tissue stop  1000  is made of two parts: a stamped metal section  1100  and an overmolded plastic section  1200 . The stamped metal section  1100  is illustrated in  FIGS. 13-17 , and the overmolded plastic section  1200 , which at least partially covers the stamped metal section  1100 , is illustrated in  FIGS. 11-12 . The multiple piece design of the tissue stop  1000  provides the strength of the metal while allowing complex geometries that are suitable for plastic injection molding. While particular portions of tissue stop  1000  are shown being made from stamped metal, it is envisioned and within the scope of the present disclosure that the stamped metal portion  1100  can include a greater or lesser portion of the entire tissue stop  1000 . Likewise, the overmolded plastic section  1200  may also include a greater or lesser portion of the entire tissue stop  1000  than what is illustrated. 
     Tissue stop  1000  includes a body  1010  having an upper, tissue-contacting surface  1020 , a pair of lateral walls  1030 ,  1040 , and a stopping portion  1050  configured and adapted to engage tissue (e.g., tissue that is distally directed from between the jaw members). Stopping portion  1050  of tissue stop  1000  includes a scalloped portion  1060  including a plurality of spaced-apart semi-circular indents. More specifically, scalloped portion  1060  is disposed on a proximal edge of each lateral wall  1030 ,  1040 . As can be appreciated, scalloped portion  1060  is configured to help prevent tissue from sliding with respect to tissue stop  1000 . 
     Tissue stop  1000  is usable with the camming pins  184 ,  186 , as discussed above with reference to tissue stop  170 , and tissue stop  1000  may also include a pivoting protrusion  1400  extending transversely from body  1010 , as shown in  FIGS. 11 and 12 . Pivoting protrusion  1400  is configured to pivotably engage a portion of the cartridge assembly to enable pivotal movement therebetween. 
     Additionally, in disclosed embodiments, the surgical instrument  100  and loading unit  180  described in connection with  FIGS. 1 through 10  includes the stamped/molded tissue stop  1000 . 
     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.