Abstract:
A loading unit configured for engagement with a surgical instrument having a firing rod is disclosed. The loading unit comprises a proximal body portion, a tool assembly, and a knife assembly. The tool assembly is disposed in mechanical cooperation with the proximal body portion. The knife assembly is movably disposed at least partially within the proximal body portion and includes a proximal end positioned to engage the firing rod, and includes a first arm and a second arm. The first arm is biased towards the longitudinal axis via a biasing force. The biasing force is selected to allow the first arm to deflect when the firing rod is advanced. The first arm and the second arm of the knife assembly are configured to engage a firing rod of a surgical instrument as the surgical instrument is being actuated.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional of U.S. application Ser. No. 12/615,294 filed Nov. 10, 2009, now U.S. Pat. No. 8,186,558, and the disclosures of each of the above-identified applications are hereby incorporated by reference in their entirety. 
    
    
     BACKGROUND 
     1. Technical Field 
     The present disclosure relates generally to instruments for surgically joining tissue and, more specifically, to a loading unit having a locking mechanism for use with a surgical instrument. 
     2. Background of Related Art 
     Various types of surgical instruments used to surgically join tissue are known in the art, and are commonly used, for example, for closure of tissue or organs in transection, resection, anastomoses, for occlusion of organs in thoracic and abdominal procedures, and for electrosurgically fusing or sealing tissue. 
     One example of such a surgical instrument is a surgical stapling instrument, which may include an anvil assembly, a cartridge assembly for supporting an array of surgical staples, an approximation mechanism for approximating the cartridge and anvil assemblies, and a firing mechanism for ejecting the surgical staples from the cartridge assembly. 
     Using a surgical stapling instrument, it is common for a surgeon to approximate the anvil and cartridge members. Next, the surgeon can fire the instrument to emplace 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. 
     Additionally, a single use loading (“SULU”) or a disposable loading unit (“DLU”) may be attached to an elongated or endoscopic portion of a surgical stapling instrument. Such loading units allow surgical stapling instruments to have greater versatility, for example. The loading units may be configured for a single use, and/or may be configured to be used more than once. 
     SUMMARY 
     The present disclosure relates to a loading unit configured for engagement with a surgical instrument having a firing rod. The loading unit comprises a proximal body portion, a tool assembly, and a knife assembly. The proximal body portion defines a longitudinal axis. The tool assembly is disposed in mechanical cooperation with the proximal body portion. The knife assembly is movably disposed at least partially within the proximal body portion and includes a proximal end positioned to engage the firing rod, and includes a first arm and a second arm. The first arm is biased towards the longitudinal axis via a biasing force. The biasing force is selected to allow the first arm to deflect when the firing rod is advanced. The first arm and the second arm of the knife assembly are configured to engage a firing rod of a surgical instrument as the surgical instrument is being actuated. 
     The present disclosure also relates to a surgical stapling instrument comprising a handle assembly, a firing rod, an endoscopic portion, a loading unit, and a knife assembly. The handle assembly includes a movable handle. The firing rod is disposed in mechanical cooperation with the movable handle. The endoscopic portion extends distally from the handle assembly. The loading unit is mechanically engageable with the endoscopic portion and includes a proximal body portion defining a longitudinal axis, and a tool assembly. The knife assembly is movably disposed at least partially within the proximal body portion of the loading unit and includes a proximal end positioned to engage the firing rod, and includes a first arm and a second arm. The first arm is biased towards the longitudinal axis via a biasing force selected to allow the first arm to deflect when the firing rod is advanced. The first arm and the second arm of the knife assembly are configured to engage the firing rod as the surgical instrument is being actuated. 
    
    
     
       BRIEF DESCRIPTION OF FIGURES 
       Various embodiments of the presently disclosed surgical instruments and loading units are disclosed herein with reference to the drawings, wherein: 
         FIG. 1A  is a perspective view of a surgical stapling instrument in accordance with the present disclosure; 
         FIG. 1B  is a perspective view of another surgical stapling instrument in accordance with the present disclosure; 
         FIG. 2  is a perspective view of a handle portion of the surgical stapling instrument of  FIG. 1 ; 
         FIG. 3  is a perspective view of a distal portion of the handle portion of  FIG. 2 ; 
         FIG. 4  is a perspective view of a loading unit of the surgical stapling instrument of  FIG. 1 ; 
         FIG. 5  is a perspective view of a conventional knife assembly of a loading unit; 
         FIG. 6  is a longitudinal cross-sectional view of a portion of a conventional knife assembly of a loading unit engaged with a portion of a conventional firing rod of a surgical stapling instrument; 
         FIGS. 7A and 7B  are transverse cross-sectional views of a conventional knife assembly and a conventional firing rod, prior to engagement and while engaged, respectively; 
         FIG. 8  is a longitudinal cross-sectional view of a knife assembly and a firing rod according to an embodiment of the present disclosure; 
         FIG. 9  is a longitudinal cross-sectional view of the knife assembly of  FIG. 8  illustrated during engagement with the firing rod of  FIG. 8 ; 
         FIG. 10  is a longitudinal cross-sectional view of the knife assembly of  FIGS. 8 and 9  engaged with the firing rod of  FIGS. 8 and 9 ; 
         FIGS. 11A and 11B  are perspective views of an arm and a wing element in accordance with embodiments of the present disclosure; 
         FIG. 12A  is a longitudinal cross-sectional view of a firing rod of the present disclosure positioned adjacent a portion of a drive assembly in accordance with an embodiment of the present disclosure; 
         FIG. 12B  is a longitudinal cross-sectional view of the firing rod of  FIG. 12A  engaging the drive assembly of  FIG. 12A ; 
         FIG. 12C  is a longitudinal cross-sectional view of the firing rod of  FIGS. 12A and 12B  engaged with the drive assembly of  FIGS. 12A and 12B ; 
         FIG. 13A  is a longitudinal cross-sectional view of a firing rod of the present disclosure positioned adjacent a portion of a drive assembly in accordance with an embodiment of the present disclosure; 
         FIG. 13B  is a longitudinal cross-sectional view of the firing rod of  FIG. 13A  engaging the drive assembly of  FIG. 13A ; and 
         FIG. 13C  is a longitudinal cross-sectional view of the firing rod of  FIGS. 13A and 13B  engaged with the drive assembly of  FIGS. 13A and 13B . 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the presently disclosed surgical instrument, and loading unit for use therewith, are described in detail with reference to the drawings, wherein like reference numerals designate corresponding elements in each of the several views. As is common in the art, the term “proximal” refers to that part or component closer to the user or operator, e.g., surgeon or physician, while the term “distal” refers to that part or component farther away from the user. 
     A surgical stapling instrument having linear jaw members of the present disclosure is indicated as reference numeral  100   a  in  FIG. 1A . A surgical stapling instrument having curved jaw members of the present disclosure is indicated as reference numeral  100   b  in  FIG. 1B . Collectively, surgical stapling instruments  100   a  and  100   b  are referred to herein as reference numeral  100 . Similarly, several features that are common to both surgical stapling instruments  100   a  and  100   b  are collectively referred to as the same reference number (e.g., handle portion  110 , endoscopic portion  120 , and jaw members  230 ). 
     Handle portion  110  of surgical stapling instrument  100  is shown in  FIG. 2 , and an enlarged view of the distal end of handle portion  110 , including a distal end of firing rod  130 , is shown in  FIG. 3 . A single use loading unit (“SULU”) or a disposable loading unit (“DLU”) (collectively referred to as “loading unit  200 ”), which is mechanically engageable with handle portion  100  is shown in  FIG. 4 . Loading unit  200  is attachable to endoscopic portion  120  of surgical stapling instrument  100 , e.g., to allow surgical stapling instrument  100  to have greater versatility. Loading unit  200  may be configured for a single use, and/or may be configured to be used more than once. 
     Examples of loading units for use with a surgical stapling instrument are disclosed in commonly-owned U.S. Pat. No. 5,752,644 to Bolanos et al., the entire contents of which are hereby incorporated by reference herein. 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. 
     Generally, jaw members  230  of loading unit  200  include a cartridge assembly  222  and an anvil assembly  224 . Cartridge assembly  222  houses a plurality of staples or fasteners (not explicitly shown in the illustrated embodiments). Cartridge assembly  222  includes a plurality of staple pushers for ejecting the staples therefrom. Anvil assembly  224  includes staple pockets (not explicitly shown in the illustrated embodiments) that are configured to form the staples as they are driven from cartridge assembly  222 . 
     Loading unit  200  may include a plurality of cam bars for interacting with the pushers to deploy the surgical fasteners. For example, the apparatus disclosed in U.S. Pat. No. 5,318,221, the disclosure of which is hereby incorporated by reference herein, in its entirety, has a cam bar adapter that holds a plurality of cam bars and a knife. In this example, a firing rod is advanced through operation of the handle of the apparatus, which drives the cam bars and knife forward. A clamp tube that surrounds the proximal end of the anvil is advanced to clamp the anvil and cartridge together. In another example, the apparatus disclosed in U.S. Pat. No. 5,782,396, the disclosure of which is hereby incorporated by reference herein, in its entirety, has an actuation sled. In this example, an elongated drive beam is advanced distally through operation of the handle of the apparatus, driving the actuation sled forward. The distal end of the drive beam engages the anvil and the channel that supports the cartridge as the drive beam travels distally, to deploy the staples and clamp the anvil and cartridge together. 
     In a surgical stapling instrument  100  in accordance with the present disclosure, a firing rod  130  is moved distally through actuation of a movable handle  132  to deploy the staples. For example, referring back to  FIGS. 1A and 1B , at least a partial actuation of movable handle  132  with respect a stationary handle  134  translates firing rod  130  longitudinally, such that a knife assembly  240  ( FIG. 5 ) translates longitudinally, to approximate at least one jaw member with respect to the other and to eject surgical fasteners (e.g., staples) from cartridge assembly  222  and/or to advance a cutting blade to cut tissue. It is also envisioned that other types of handles can be used such as, for example, motor-driven, hydraulic, ratcheting, etc. 
     With reference to  FIG. 4 , loading unit  200  of the present disclosure is shown. Loading unit  200  includes a proximal body portion  210  defining a longitudinal axis “A-A,” and a tool assembly  220  including a pair of jaw members  230 . Proximal body portion  210  is configured to removably attach to endoscopic portion  120  of surgical instrument  100 . More particularly, an insertion tip  202  of loading unit  200  is linearly inserted into the distal end of endoscopic portion  120  ( FIGS. 2 and 3 ) of surgical stapling instrument  100 . Nubs  204  of insertion tip  202  ( FIG. 4 ) move linearly through slots (not shown) formed in the distal end of endoscopic portion  120 . Subsequently, loading unit  200  is rotated about the longitudinal axis “A-A” such that nubs  204  move transversely through slots (not shown) within endoscopic portion  120 . Additionally, during engagement of loading unit  200  and endoscopic portion  120 , firing rod  130  of handle portion  110  engages knife assembly  240  of loading unit  200 . 
     An example of a proximal portion  250 ′ of a comparative knife assembly  240 ′ is illustrated in  FIG. 5 . As shown, proximal portion  250 ′ includes a first arm  260 ′ and a second arm  270 ′. Each of first arm  260 ′ and second arm  270 ′ includes a proximal inwardly extending protrusion  262 ′ and  272 ′, respectively, and a distal inwardly extending protrusion  264 ′ and  274 ′, respectively. 
       FIGS. 6-7B  illustrate the engagement between comparative knife assembly  240 ′ and a comparative firing rod  130 ′. As shown in  FIG. 6 , comparative firing rod  130 ′ includes a recess  132 ′ therein and a distal lip  134 ′. Lip  134 ′ of comparative firing rod  130 ′ is configured to fit between proximal inwardly extending protrusions  262 ′,  272 ′ and distal inwardly extending protrusions  264 ′,  274 ′ of comparative knife assembly  240 ′. 
     With particular reference to  FIGS. 7A and 7B , where transverse cross-sectional views are shown, firing rod  130 ′ includes an inner portion  136 ′ and a pair of outer portions  138 ′. As shown, the height H 1  of inner portion  136 ′ is smaller than the height  112  of outer portions  138 ′. With continued reference to  FIGS. 7A and 7B , the translation of loading unit  200  (including knife assembly  240 ′) with respect to firing rod  130 ′, as discussed above, is configured to allow distal lip  134 ′ of firing rod  130 ′ to pass through an opening  280 ′ disposed between proximal inwardly extending protrusions  262 ′,  272 ′. Additionally, the rotation of loading unit  200  (including knife assembly  240 ′) with respect to firing rod  130 ′ is configured to position distal lip  134 ′ between proximal inwardly extending protrusions  262 ′,  272 ′ and distal inwardly extending protrusions  264 ′,  274 ′. Thus, as can be appreciated, firing rod  130 ′ must be rotated to allow distal lip  134 ′ thereof to be able to physically fit through opening  280 ′ disposed between proximal inwardly extending protrusions  262 ′,  272 ′. As such, when firing rod  130 ′ and knife assembly  240 ′ are properly engaged, proximal and distal translation of firing rod  130 ′ results in corresponding proximal and distal translation of knife assembly  240 ′. 
     With reference to  FIGS. 8-11B , firing rod  130  and proximal portion  250  of knife assembly  240  of the present disclosure are illustrated. Similarly to comparative knife assembly  240 ′, knife assembly includes a first arm  260  and a second arm  270 , with each of first arm  260  and second arm  270  including distal inwardly extending protrusions  264  and  274 , respectively. Additionally, knife assembly  240  includes a locking mechanism. In the embodiments illustrated in  FIGS. 8-11B , locking mechanism includes a pair of wing elements  300 . Wing elements  300  are disposed adjacent a proximal end  252  of proximal portion  250  of knife assembly  240  and are pivotal therewith. 
     In the illustrated embodiments, wing elements  300  are pivotal about a pivot structure  310  (e.g., a pin or rivet; see  FIGS. 11A and 11B ). It is envisioned that pivot structure  310  for each wing element  300  extends through its respective first arm  260  or second arm  270 . Moreover, with reference to  FIGS. 11A and 11B , wing elements  300  are shown having a first side wall  302  and a second side wall  304 , which define a channel  306  therebetween. As shown, channel  306  defines a thickness T C , which is wider than a thickness T A  of its associated arm, e.g., first arm  260 . Thus, each side wall  302 ,  304  of wing element  300  can move along sidewalls  269   a ,  269   b  of first arm  260 . Additionally, in the embodiments illustrated in  FIGS. 11A and 11B , wing elements  300  are biased via a biasing element  312  (e.g., a torsion spring ( FIG. 11A ) or a leaf spring ( FIG. 11B )) towards an initial position ( FIG. 8 ), where wing element  300  is spaced from first arm  260 , from a second position ( FIG. 9 ), wherein wing element  300  pivoted against first arm  260 . 
     With particular reference to  FIG. 11B , first arm  260  includes a pin  261  extending transversely therethrough, and wing element  300  includes an arcuate slot  301  disposed thereon. (It is also envisioned that pin  261  extends from first arm  260 .) Pin  261  and slot  301  are configured to mechanically engage one another. It is envisioned that the engagement between pin  261  and slot  301  provides guidance for the travel of wing element  300 . Additionally, in the illustrated position, pin  261  acts to limit movement of wing element  300  in the direction provided by biasing element  312 . 
     As can be appreciated with respect to  FIGS. 9 and 10 , the configuration of knife assembly  240  (including wing elements  300 ) and firing rod  130  allows distal lip  134  of firing rod  130  to enter the space between wing elements  300  and distal inwardly extending protrusions  264 ,  274  upon relative longitudinal translation therebetween, and without the need for rotational movement of knife assembly  240  or firing rod  130 . More particularly, distal translation of firing rod  130 , for example, causes distal lip  134  of firing rod  130  to contact wing elements  300 , and to thus cause wing elements  300  to pivot from their initial position ( FIG. 8 ) against the bias of biasing element  312  to their second position ( FIG. 9 ). After distal lip  134  of firing rod  130  translates distally beyond wing elements  300 , wing elements  300  are biased back towards their initial position ( FIG. 10 ). 
     Accordingly, wing elements  300  generally serve the same function as proximal inwardly extending protrusions  262 ′,  272 ′ of comparative knife assembly  240 ′. However, wing elements  300  are configured to allow knife assembly  240  of loading unit  200  to engage firing rod  130  of endoscopic portion  120  as surgical stapling instrument  100  is being fired. That is, for example, if knife assembly  240  is prematurely advanced and subsequently is not engaged by firing rod  130 , distal translation of firing rod  130  would automatically cause firing rod  130  to pivot wing elements  300 , and to thus engage with knife assembly  240 . As can be appreciated, if a firing rod only pushes a knife assembly without engaging the knife assembly, retraction of the firing rod would not cause retraction of the knife assembly, thus hindering the unlocking or unclamping of the jaw members. 
     Separation of firing rod  130  from knife assembly  240  (e.g., to remove loading unit  200 ) is accomplished similarly to comparative firing rod  130 ′ and knife assembly  240 ′, i.e., by rotating loading unit  200  about longitudinal axis “A-A” and longitudinally translating loading unit  200  away from endoscopic portion  120 . 
     With reference to  FIGS. 12A-12C , another embodiment of a knife assembly  240   a  is illustrated. Here, the locking mechanism includes first arm  260   a  and second arm  270   a . Each arm  260   a ,  270   a  is configured to flex in the respective directions of arrows “A” and “B” ( FIG. 12B ). Additionally, each arm  260   a ,  270   a  is biased towards the longitudinal axis “A-A.” It is envisioned that only a single arm  260   a  or  270   a  is biased towards the longitudinal axis “A-A.” The flexing and biasing of first arm  260   a  and/or second arm  270   a  is accomplished via suitable means. For example, it is envisioned that first arm  260   a  and/or second arm  270   a  is made from stainless steel or another suitable biocompatible metal or polymer. 
     In use, distal translation of firing rod  130  such that distal lip  134  contacts first arm  260   a  and second arm  270   a , causes arms  260   a ,  270   a  to flex in the direction of arrows “A” and “B,” respectively. After distal lip  134  is translated beyond proximal inwardly extending protrusions  262   a ,  272   a , first and second arms  260   a ,  270   a  move in the direction they are biased, i.e., towards the longitudinal axis “A-A,” such that proximal inwardly extending protrusions  262   a ,  272   a  are within recess  132  of firing rod  130  ( FIG. 12C ). 
     Accordingly, the flexible, biased arms  260   a  and/or  270   a  of knife assembly  240   a  function similarly to arms  260 ,  270  including wing elements  300 . That is, arms  260   a ,  270   a  are configured to allow knife assembly  240   a  of loading unit  200  to engage firing rod  130  of endoscopic portion  120  as surgical stapling instrument  100  is being fired. 
     Accordingly, the flexible, biased arms  260   a  and/or  270   a  of knife assembly  240   a  function similarly to arms  260 ,  270  including wing elements  300 . That is, arms  260   a ,  270   a  are configured to allow knife assembly  240   a  of loading unit  200  to engage firing rod  130  of endoscopic portion  120  as surgical stapling instrument  100  is being fired. 
     With reference to  FIGS. 13A-13C , another embodiment of a knife assembly  240   b  is illustrated. Here, the locking mechanism includes a proximal portion  250   b  having a first arm  260   b , a second arm  270   b , and a spring  275   b  therebetween. Proximal portion  250   b  is pivotally connected to a distal portion  252   b  of knife assembly  240   b . In particular, at least one of first arm  260   b  and second arm  270   b  is pivotally engaged with distal portion  252   b . In the illustrated embodiment, first arm  260   b  is pivotally engaged with distal portion  252   b  at a first pivot point  280   b , and second arm  270   b  is pivotally engaged with distal portion  252   b  at a second pivot point  282   b . Additionally, proximal portion  250   b  and distal portion  252   b  include one of a pair of cam slots  290   b  and a pair of pins  292   b , not necessarily respectively, adjacent each pivot point  280   b  and/or  282   b . As can be appreciated, the inclusion of cam slots  290   b  and pins  292   b  help limit the pivotal movement of proximal portion  250   b  with respect to distal portion  252   b.    
     Each arm  260   b ,  270   b  is configured to flex in the respective directions of arrows “C” and “D” ( FIG. 13B ). Additionally, each arm  260   b ,  270   b  is biased towards the longitudinal axis “A-A” via spring  275   b . As discussed above, it is also envisioned that only a single arm  260   b  or  270   b  is pivotal with respect to distal portion  252   b.    
     In use, distal translation of firing rod  130   a  such that distal lip  134   a  thereof contacts first arm  260   b  and second arm  270   b , causes arms  260   b  and/or  270   b  to flex in the direction of arrows “C” and “D,” respectively. After distal lip  134   a  is translated beyond proximal inwardly extending protrusions  262   b ,  272   b , first and/or second arms  260   b ,  270   b  move in the direction they are biased, i.e., towards the longitudinal axis “A-A,” such that proximal inwardly extending protrusions  262   b ,  272   b  are within recess  132   a  of firing rod  130   a  ( FIG. 13C ). As shown in  FIGS. 13A-13C , distal lip  134   a  of firing rod  130   a  includes a pair of angled surfaces  136   a ,  138   a . As can be appreciated, angled surfaces  136   a ,  138   a  facilitate the introduction of distal lip  134   a  distally beyond protrusions  262   b ,  272   b . Additionally or alternatively, a proximal face of proximal inwardly extending protrusions  262   b ,  272   b  may include an angled surface, such as protrusions  262   a ,  272   a  illustrated in  FIGS. 12A-12C . 
     Accordingly, arms  260   b  and/or  270   b  of knife assembly  240   b  function similarly to arms  260 ,  270  including wing elements  300  and to arms  260   a  and  270   a . That is, arms  260   b ,  270   b  are configured to allow knife assembly  240   b  of loading unit  200  to engage firing rod  130   a  of endoscopic portion  120  as surgical stapling instrument  100  is being fired. 
     It is envisioned that knife assembly  240 ,  240   a ,  240   b  of the present disclosure can be used in combination with an articulatable surgical instrument, e.g., surgical stapling instrument  100   a  in  FIG. 1A . In  FIG. 1A , a lever  140  is shown adjacent a rotation dial  142  and may be used to facilitate articulation of jaw members  230 . Actuation of lever  140  causes jaw members  230  to move between a first position, where jaw members  230  are substantially aligned with longitudinal axis “A-A,” and a second position, where jaw members  230  are disposed at an angle with respect to longitudinal axis “A-A.” It is envisioned that moving lever  140  causes an articulation link to move longitudinally, which results in a proximal portion of at least one jaw member moving proximally or distally. That is, moving lever  140  in a first direction causes the articulation link to move proximally (which articulates jaw members  230  in a first direction) and moving lever  140  in a second, opposite direction causes the articulation link to move distally (which articulates jaw members  230  in a second direction). An articulating loading unit for an endoscopic surgical stapler is disclosed in U.S. Pat. No. 6,953,139 to Milliman et al., the entire contents of which have been incorporated by reference herein. 
     While the above description contains many specifics, these specifics should not be construed as limitations on the scope of the present disclosure, but merely as illustrations of various embodiments thereof. For example, knife assembly  240 ,  240   a ,  240   b  may be configured as a unitary unit, may include multiple layers, and/or may be comprised of several portions (e.g., as shown in  FIG. 5 ). Additionally, it is envisioned that wing elements  300  are disposed on firing rod  130  instead of, or in addition to being disposed on knife assembly  240 ,  240   a ,  240   b . Further, the present disclosure includes a method of modifying a knife assembly to include pivotable wing elements  300 . Therefore, the above description should not be construed as limiting, but merely as exemplifications of various embodiments. Those skilled in the art will envision other modifications within the scope and spirit of the claims appended hereto.