Apparatus for feeding staples in a low profile surgical stapler

A mechanism for feeding a fastener including a housing having a longitudinal axis and at least one fastener within the housing. The fastener has a crown and at least two legs extending therefrom. The fastener is disposed within the housing in a first plane parallel to the longitudinal axis. The mechanism includes an elongated actuator disposed within the housing. The actuator has a shaft substantially parallel to the longitudinal axis of the mechanism and rigidly spaced from the fastener in a second plane. The actuator has at least one radially extending advancer disposed along a length thereof, and a mechanism for rotating the actuator so that the advancer engages the fastener.

FIELD OF THE INVENTION

The present invention relates in general to a low profile surgical stapler for delivering multiple, large-sized staples to a body cavity through a small diameter delivery port and, in particular, to a feeding mechanism for advancing a stack of staples through a low profile delivery shaft of the stapler. The feeding mechanism moves a rigid body in and out of the staple stack during staple deployment to individually advance the staples through the delivery shaft and thereby reduce the potential for misalignment and jamming of the staples. This feeding mechanism may also be used for the feeding of other surgical fasteners including but not limited to ligating clips.

BACKGROUND OF THE INVENTION

Obesity is a medical condition affecting more than 30% of the population in the United States. Obesity affects an individual's quality of life and contributes significantly to morbidity and mortality. Surgical procedures have been developed for involuting the gastric cavity wall to reduce stomach volume as a treatment for obesity. In the gastric volume reduction (GVR) procedures (e.g., reduction gastroplasty, gastric plication, greater curvature plication, etc.), multiple pairs of suture anchoring devices, such as T-Tag anchors, are deployed through the gastric cavity wall. Preferably, the suture anchors are deployed through a small diameter port in a minimally invasive surgical procedure to reduce trauma to the patient. Following deployment of the T-Tag anchors, the suture attached to each individual pair of anchors is cinched to approximate the tissue, and secured to involute the cavity wall between the anchors. This procedure is described in greater detail in co-pending U.S. patent application Ser. Nos. 11/779,314 and 11/779,322, which are hereby incorporated herein by reference in their entirety. The GVR procedures described in these applications require individual placement of each suture anchor pair into the cavity wall tissue, and subsequent tensioning of the suture between the anchor pairs in order to involute the tissue.

The individual placement of the T-Tag anchors and manual suture tensioning is time intensive; increasing the duration, complexity and cost of the GVR procedure. To simplify and improve the GVR procedure, and to facilitate other small incision site surgical procedures within the peritoneal cavity, a stapler has been developed having a low-profile for use in small diameter (i.e. 5 mm or less) laparoscopic ports, a single trocar containing multiple small laparoscopic ports, or through a semi-rigid or flexible endoscopic platform (e.g., for use in natural orifice surgical procedures, single site laparoscopy, etc.).FIG. 1illustrates an exemplary low profile stapler for use in GVR and other small incision site procedures in the peritoneal cavity including but not limited to reinforcement of staple lines (e.g., “oversewing” of a vertical sleeve gastrectomy), closing of surgical defects (e.g., gastrotomy closure), and fixation of temporary (e.g., liver retraction) or permanent (e.g., hernia mesh, gastric band securement) medical devices. As shown inFIG. 1, the stapler10includes a handle12having a pistol grip14shaped for grasping by a surgeon. A trigger assembly16is movably coupled to handle12to be drawn towards the pistol grip14during staple deployment. An elongated staple housing20having a longitudinal axis extends distally from handle12. Housing20has sufficient length (on the order of 18″) to enable use within an obese patient at numerous trocar access sites for traditional laparoscopic approaches. Likewise, housing20is sized to allow for passage through a small (3-5 mm) diameter trocar, although functional devices of a larger diameter are also possible without departing from the overall scope of the invention. A staple deploying assembly is at least partially disposed within the interior of housing20for discharging staples from a distal deployment opening22. Trigger assembly16facilitates both the advancement of staples through housing20, as well as the deployment of the staples from the distal opening22

To obtain a large tissue purchase (which is desirable in GVR procedures) while using a small diameter delivery shaft, the stapler10deploys fasteners or staples having a folded, closed loop configuration. These closed loop or “box” staples have a small width in the initial, unformed condition. The width of the staple is expanded during opening and forming to allow the staple to obtain a large tissue purchase.FIG. 2illustrates an exemplary box staple30for deployment from stapler10. Staple30comprises a length of wire formed into a crown or back span32and first and second leg portions34,36that intersect with opposite ends of the back span. The wire has a cylindrical cross-section, but may have other shapes (e.g., rectangular, elliptical, etc.) to provide optimal strength for the application or to aid in the feeding of the staples, and may or may not be uniform along the length of the wire. Leg portions34,36intersect with back span32at an approximate angle α of 90° and extend in a substantially parallel fashion forward of the back span. Opposite back span32, leg portions34,36are bent inward to form staple end segments40,42. In a loop shape, two lengths of wire may be disposed across one side of the shape to enclose the shape, as demonstrated by the end segments40,42. Staple legs portions34,36are bent at end segments40,42to make one of the leg portions at least one wire diameter longer in length than the other leg portion. The longer length of one leg portion (i.e. staple leg34inFIG. 2) enables the end segments40,42to lie in a common plane with back span32. The tips of end segments40,42are angled to form sharp prongs46for piercing tissue.

In stapler10, a stack of the staples30is fed longitudinally through the housing in a plane parallel to the housing longitudinal axis. Within the staple stack, staples may be spaced apart from other staples, in contact with other staples, or alternate between states of contact and spaced. The staple stack preferably includes a large number of staples to facilitate procedures, such as GVR, which require a large number of tissue appositions or junctions. The staples are individually advanced outside of the open stapler end22, and expanded open through actuation of the handle. After the staple pierces or otherwise engages the tissue sections to be joined, the stapler draws the expanded staple legs back inward to close the staple through the tissue. Box staples provide a number of advantages over previous surgical staple designs. These advantages include the ability to: use a smaller incision site, construct the staple from a stronger material, increase the work hardening in the formed staple through a greater number of bending points during formation, and feed the staples in a longitudinal rather than a vertical stack. Additional details regarding the closed loop staple design, as well as staple applicators, procedure applications, and methods of use are disclosed in co-pending U.S. patent application Ser. No. 12/359,351 filed Jan. 26, 2009 entitled “A SURGICAL STAPLER FOR APPLYING A LARGE STAPLE THROUGH A SMALL DELIVERY PORT AND A METHOD OF USING THE STAPLER TO SECURE A TISSUE FOLD”, co-pending U.S. patent application Ser. No. 12/359,354 filed Jan. 26, 2009, entitled “A SURGICAL STAPLER FOR APPLYING A LARGE STAPLE THROUGH A SMALL DELIVERY PORT AND A METHOD OF USING THE STAPLER TO SECURE A TISSUE FOLD”, co-pending U.S. patent application Ser. No. 12/359,357 filed Jan. 26, 2009 entitled “A SURGICAL STAPLER FOR APPLYING A LARGE STAPLE THROUGH A SMALL DELIVERY PORT AND A METHOD OF USING THE STAPLER TO SECURE A TISSUE FOLD”, co-pending U.S. patent application Ser. No. 12/608,860 filed Oct. 29, 2009, entitled “BOX STAPLE METHOD WHILE KEEPING SAID BACK SPAN IN SUBSTANTIALLY ITS ORIGINAL SIZE AND SHAPE”, and co-pending U.S. patent application Ser. No. 12/609,336 filed Oct. 30, 2009, entitled “A METHOD FOR APPLYING A SURGICAL STAPLE”, which are hereby incorporated herein by reference in their entirety.

Despite the numerous advantages in using box staples, feeding a large number of the small staples through a relatively long delivery shaft can sometimes result in misalignment of the staples within the stack, causing the staples to jam prior to reaching the open stapler end. Jamming is particularly a concern when the staples are advanced through the delivery shaft by contact between the staples themselves, i.e. a driving force is applied to the end of the stack and transferred through the stack by each staple applying a force against the next previous staple in the stack in order to drive the full stack forward through the shaft. Previous stapler designs have reduced the potential for staple jamming by balancing loads between a number of flexible staple advancing and stopping components. However, this load balancing adds complexity and cost to the stapler.

Accordingly, to facilitate GVR and other procedures involving the fastening of layers of tissue within the peritoneal cavity, it is desirable to have a simplified, cost effective staple feeding mechanism for reliably feeding a large number of staples through a low profile stapler without misalignment and/or jamming of the staples. In particular, it is desirable to have a staple feeding mechanism for a low profile stapler which includes rigid, individual staple advancers for spreading the driving force of the mechanism through out the staple stack. Additionally, it is desirable to have a staple feeding mechanism in which the rigid staple advancers can be moved in and out of engagement with the staple stack during each staple deployment sequence. Doing so through a substantially rigid body motion (translation or rotation) of staple advancing components simplifies the staple feeding process and eases the strength and flexibility requirements for the staple advancing and stopping components by reducing the overall load requirements in the system. Further, it is desirable to have a staple feeding mechanism that advances the staple stack as part of the staple firing sequence without the need for separate actuation. Furthermore, it is desirable to have a staple feeding mechanism in which the staple driving member and controls are located within the staple housing rather than the handle. The present invention provides a staple feeding mechanism for a surgical stapler which achieves these objectives.

DETAILED DESCRIPTION OF THE INVENTION

Referring again to the drawing figures, in which like numerals indicate like elements throughout the views,FIG. 3shows the distal end of stapler10incorporating a first exemplary staple feeding mechanism of the present invention. As shown inFIG. 3, stapler10includes a staple former50which is attached to the distal end of staple housing20. Staple deployment opening22is located at the distal end of former50. Former50includes an inner channel (not shown) for conveying staples through the former and outside the stapler during deployment. Following passage of a staple outside opening22, and the opening of the staple, former50advances over the opened staple to shape and close the staple through one or more tissue layers. Staples30are individually conveyed through former50and opening22by an anvil52. Anvil52includes a pair of upwardly curved, staple holding tine56which hold onto the staple during passage through the former. The proximal end of anvil52is shaped for connecting the anvil to an anvil extension60. Anvil extension60extends proximally from anvil52to a driving assembly in the handle.

A staple clamp64extends substantially along the surface of anvil52. Clamp64comprises an elongated strip having substantially planar upper and lower surfaces and a width slightly narrower than the width of the unformed staples30to accommodate lateral shelves (not shown) for supporting the distal-most staple within the magazine channel. The lateral shelves are described in detail in previously incorporated U.S. patent application Ser. No. 12/608,860. Clamp64preferably has as small a length as necessary to cover the anvil52. The distal end of clamp64is shaped for mating engagement with staple back span32for engaging and pushing the staple through former50. The proximal end of clamp64is attached to a driving assembly in handle12via a clamp extension66. Clamp extension66includes an upper section70and a lower section72. Upper clamp extension70comprises an elongated, planar strip for supporting a staple stack76. A longitudinally extending trough74is located midway across the width of the strip beneath staple stack76. Trough74extends from the distal end of upper clamp extension70beyond the proximal end of staple stack76. Lower clamp extension72is an elongated, rigid strip having a groove80in the surface adjoining upper clamp extension70to accommodate trough74. Clamp64interconnects with the distal end of upper clamp extension70as indicated at82.

A staple driving member or actuator is provided within clamp extension trough74beneath the plane of staple stack76. As shown in greater detail inFIG. 4, the actuator includes a rigid cylindrical shaft or rod84having a longitudinal axis substantially parallel to the longitudinal housing axis. A plurality of staple advancers86are evenly spaced apart substantially along the length of the rod. Staple advancers86comprise fins projecting out perpendicularly from the longitudinal rod axis. Staple advancers86extend along rod84to at least the proximal end of staple stack76, to ensure that a staple advancer engages the proximal-most staple in the stack. Staple advancers86may be connected to rod84as shown or, alternatively, the rod and advancers may be formed as a single unitary piece. To form the rod and advancers as a single piece, a coining process is performed on the upper portion of the rod at the desired advancer locations. This coining process produces half-moon shaped protrusions of the rod material above the rod plane. In a further operation, each of the protrusions is machined, stamped, or otherwise modified to form a flat or squared-off, distal edge roughly perpendicular to the longitudinal rod axis. The resulting squared-off distal edge forms a staple contacting face for the advancer. The proximal end of rod84is curved at approximately a 90° angle relative to the longitudinal rod axis to form a control pin90. Control pin90has a rounded tip for engaging a guide path as described below.

As shown inFIG. 5, at least one retaining clip92is provided within trough74for retaining rod84in a rigidly spaced relationship from the staple stack76. Rod84is snapped into the one or more clips92inside trough74. Clips92retain rod84within trough74to translate the rod with clamp extension66, while permitting the rod to rotate about the longitudinal rod axis. Upper clamp extension70also includes a plurality of notches94spaced apart along a side of trough74. Notches94are aligned with staple advancers86to allow the advancers to rotate out of trough74and above the surface of the clamp extension. The distal end of rod84extends through an open distal end of trough74into clamp64. The staple advancer86at the distal end of rod84is located in a groove in the proximal end of clamp64. Rod84rotates relative to clamp64in the same manner as clamp extension66, with the staple advancer extending up through a notch in the clamp. Rod84is fixed to upper clamp extension70by clips92to translate distally and then back proximally with the clamp extension during each staple deployment. Rod84and the attached staple advancers86are advanced and retracted by clamp extension66to index staple stack76distally approximately one staple length during each staple deployment.

Returning now toFIG. 3, a staple guide100is located proximal of former50inside staple housing20. The outer perimeter of staple guide100is shaped to conform to the inner circumference of staple housing20to enable the staple guide to extend concentrically within the staple housing. Staple guide100is fixed at a proximal end to the stapler handle to prevent translation of the guide along the longitudinal housing axis during staple deployment. The connection between staple guide100and the handle12, however, permits the staple guide to rotate with staple housing20about the longitudinal housing axis for positioning the staple prongs46.

As shown inFIG. 6, a plurality of longitudinally spaced openings102are formed into the inner surface of staple guide100. An anti-backup arm104is connected at the proximal end of each opening102to extend distally substantially across the opening. Each anti-backup arm104includes an enlarged distal tip106which protrudes out in a direction perpendicular to the arm, beyond the surface of the staple guide100. The distal side of each anti-backup arm tip106is substantially perpendicular to the arm to form a staple abutting face, while the proximal side of each arm tip106is tapered at approximately a 45° angle to form a staple deflecting face. Anti-backup arms104have a degree of flexibility relative to the inner surface of staple guide100to allow the arms to flex in and out of openings102. Anti-backup arms104are spaced apart longitudinally along staple guide100a distance greater than or, at a minimum, substantially equal to, the length of staple legs34,36in an unformed staple30. It is conceived that uniform, larger distances between successive arms104could also be used to help increase device reliability, thereby allowing for part tolerances. Anti-backup arms104may be alternatively offset from the longitudinal centerline of staple guide100, as shown.

A mechanism for rotating the staple actuator is located within the staple housing. As shown inFIGS. 7A and 7B, one possible location for the rotating mechanism is the inner surface of staple guide100, however the rotating mechanism may also be located elsewhere in the staple housing. The rotating mechanism includes a closed, contoured guide path112proximal of anti-backup arms104. Guide path112curves approximately 90° at two separate points along the path, as indicated at114and116. Control pin90extends beyond the surface plane of clamp extension66into guide path112to be pivoted by the path as rod84translates distally and proximally during staple deployment. While control pin90transverses the guide path112, the angular direction of the pin changes as the pin proceeds through curved path sections114and116. The directional changes of control pin90rotate rod84within trough74. As rod84rotates, staple advancers86are rotated from a position inside trough74to a position above the surface plane of clamp extension66. Above clamp extension66, the staple advancers86move up into the closed loops of the staples in stack76. Guide path112comprises a forward path, indicated by arrow120, in which control pin90pivots to rotate stapler advancers86up inside the loops of staples30and moves distally to advance the staples; and a return path, indicated by arrow122, in which control pin90pivots to rotate the staple advancers down into trough74and moves proximally to retract the staple advancers beneath the staple stack back to the initial position. Elevation changes, indicated at124and126, are located between the forward and return paths120,122to transition control pin90between the paths. Rod84is comprised of a semi-rigid material to allow for some degree of flexing within the rod as the rod transitions between the forward and return paths. The interaction of control pin90with path112transforms the translational motion of the clamp extension into a rotation of the rod84in order to simultaneously translate and rotate the rod during the staple deployment sequence.

As mentioned above, a stack of staples76(shown inFIG. 3) extends longitudinally through housing20between staple guide100and upper clamp extension70. Stack76extends in a plane parallel to the longitudinal axis of the staple housing. Staples30are conveyed within stack76to the distal end of stapler10prior to deployment. Within stack76, each staple30is oriented such that the abutting end segments40,42of the staple are positioned nearest the open stapler end22. The back span32of the distal-most staple abuts the end segments40,42of the second staple, while the back span of the second staple abuts the end segments of the third staple, and so forth through the length of the stack. The legs34,36of each staple30are aligned substantially parallel to and may be in contact with the walls of staple guide100to maintain the forward orientation of the staples. Any number of staples30can be included within stack76, with the preferred stapler embodiment capable of holding 20 or more staples. The individual staples within stack76may be visually differentiated to identify the position of the staples within the stack. Any optically detectable differentiation technique may be utilized including anodizing the staple material to produce staples of different colors. The distal end of staple stack76is conveyed along the surface of clamp64prior to the dropping of the individual staples onto anvil52for deployment.

Staple stack76is adjacent to the inner surface of staple guide100to enable the tips of anti-backup arms104to contact the staples within the stack. As shown inFIG. 8, the anti-backup arm tips106extend down between the back span32of a staple and the distal end segment42of the next adjacent staple prior to staple deployment. As the staple stack76is advanced distally by staple advancers86, the end segments40,42of the advancing staples contact the proximal, deflecting face of arm tips106. As the staples advance against the deflecting faces, the staples gradually flex the anti-backup arms into staple guide openings102, allowing the staples to pass beneath the arms. The straighter orientation of the distal tip faces, however, prevents the anti-backup arms104from flexing to allow the staples to retract. The distal, abutting face of arm tips106contact the back span32of each staple, particularly during retraction of the clamp and clamp extension following a staple deployment, to prevent staple stack76from moving proximally within staple housing20.

Returning now toFIG. 3, a shoe120flexibly extends from the distal end of staple guide100for transferring staples from stack76onto anvil52. Shoe120indexes the distal-most staple in stack76into a staging position on anvil52during each deployment sequence. The proximal end of shoe120is shaped to facilitate movement of staples beneath the shoe as the stack76is advanced through staple guide100. The staple advancer86at the distal end of rod84(located within clamp64) pushes the next staple in the stack under shoe120during each deployment cycle. Once a staple is under shoe120, the shoe maintains the staple alignment until the staple is deposited over anvil tines56. Shoe120may incorporate lateral shelves as described above.

At the beginning of the staple feeding sequence, control pin90is in a proximal-most position within forward guide path120. With control pin90in this position, rod84is rotated to place staple advancers86down into clamp extension notches94and away from staple stack76. Anti-backup arms104are in an initial position, with tips106down between the back span32and distal end segment42of each stacked staple. As trigger assembly16is squeezed to deploy a staple30, a distally directed force is applied to clamp extension66by a driving assembly in the stapler handle. The driving force translates clamp extension66and attached rod84distally within housing20. As mentioned above, staple guide100is fixed within the handle to remain stationary during staple deployment. The relative motion between the translating rod84and fixed staple guide100draws control pin90distally within the forward guide path120, as shown inFIGS. 8-11. As control pin90continues to follow forward path120the angle of the path changes (as indicated at114), causing the control pin to pivot with the path and, in turn, rotate rod84, as shown inFIGS. 12-15. As rod84rotates, staple advancers86rotate above the surface of clamp extension66and into staple stack76. Staple advancers86rotate to position each individual advancer inside the loop of a separate staple in the stack76. Each staple advancer86rotates into a position proximal of the inner end segment40of the staple.

As control pin90finishes moving through angular path section114, staple advancers86become fully rotated up to a position substantially perpendicular to the plane of staple stack76. Continued distal movement of clamp extension66drives each staple advancer86forward within the respective staple loop towards the inner end segment40, as shown inFIGS. 16-19. As staple advancers86move into contact with end segments40,42, the advancers individually push the staples in stack76forward within staple guide100towards the open stapler end22. Contact between the staple stack76and the staples at the distal end of clamp64pushes the distal most staple in the stack forward into a staging position beneath shoe120. As staples30advance, the distal end segments42of the staples apply a force against the proximal anti-backup tip faces106. The pressure against the tapered, proximal tip faces flexes the anti-backup arms104into staple guide openings102, allowing the staples to pass beneath the arms. Anti-backup arms104flex between a down position engaging the staple stack, and an up position within staple guide openings102, to allow both the staple end segments40,42and back span32to pass beneath the arms as the staple stack is indexed.

During the distal advance of clamp extension66and staple stack76, control pin90continues moving distally through the forward path120in staple guide100, as shown inFIGS. 20-23. As clamp extension66reaches a fully distal position, at the end of the trigger stroke, control pin90reaches the distal end of forward path120, as shown inFIG. 24-27. Near the distal end of forward path120, pin90changes elevation within the path (as indicated at124), to drop the pin from the forward path into the return path122. When clamp extension66reaches the distal-most point, staple advancers86have moved staples30a minimum distance of one staple length along the surface of the clamp and extension. The distal end of the staple stack76has been pushed forward on clamp64to place a new staple in the distal-most staging position beneath shoe120. As staple stack76approaches the end of the forward advance, anti-backup arms104flex down proximal of the back span32of each stacked staple to prevent proximal movement of the staples.

Following deployment of a staple, the squeezing pressure on the trigger assembly is released, allowing the trigger assembly to pivot back open. As the trigger assembly pivots open, the driving assembly in the handle retracts clamp extension66back proximally to the initial position within staple housing20. As clamp extension66retracts, the extension pulls rod84proximally, drawing control pin90back through return path122. Control pin90rotates through angular path section116of return path122to rotate rod84and, in turn, staple advancers86down into notches94and out of engagement with the staple loops. After control pin90rotates back to the initial angular position, as shown inFIGS. 28-31, the pin continues to follow the return path122proximally as clamp extension66is retracted. As clamp extension66retracts, the distal, staple abutting faces of anti-backup arm tips106push against the back spans32of the individual staples30. The contact between the abutting tip faces and staple back spans prevents staple stack76from retracting along with the clamp extension66, thereby maintaining the indexed position of the staple stack. In an alternative embodiment, the anti-backup arm tips106push against end segment40of the staple to maintain the indexed positions of the staple stack.

As the trigger assembly reaches the fully open, initial position again, control pin90reaches the proximal end of return path122. Near the proximal end of the return path, the elevation change in the path (indicated at126) drops control pin90back into the forward path120in preparation for the next staple deployment. With pin90reset within guide path112, staple advancers86are retracted back a full staple length and reset under the loop of the next proximal staple in the stack.

Turning now toFIG. 32, which depicts an alternative staple feeding mechanism embodiment for stapler10. In this embodiment, the staple driving member or actuator comprises an elongated cam shaft or ribbon130extending within clamp extension66and having a longitudinal axis substantially parallel to the longitudinal housing axis. Cam ribbon130has an undulating surface with raised ridges or lifters132evenly spaced apart substantially along the longitudinal axis of the ribbon. Cam ribbon130extends proximally from the connection between clamp64and clamp extension66and is rigidly spaced from staple stack76in a separate plane. A driving member140is connected to the proximal end of cam ribbon130for applying a force to the ribbon. During staple deployment, driving member140is translated by the trigger assembly, in turn translating cam ribbon130within staple housing20. The proximal end of cam ribbon130includes parallel tabs134projecting from opposite sides of the ribbon. Tabs134extend up substantially perpendicular to the cam ribbon plane.

A feeder ribbon142extends longitudinally between the cam ribbon130and staple stack76. Feeder ribbon142is substantially the same length as cam ribbon130and extends along the surface of the ribbon within clamp extension trough74. Feeder ribbon142also has an uneven surface, with uniformly spaced staple advancers144elevated above the planar surface146of the ribbon. Staple advancers144extend across the width of the ribbon and have a longitudinal length that is less than staple legs34,36but greater than the longitudinal length of cam ribbon lifters132. During staple deployment, cam ribbon130is in communication with fastener advancers144to move the advancers into the staple loops and translate the staple stack76distally within the staple housing. Feeder ribbon142may be biased downward into clamp extension trough74by semi-flexible fins (not shown) extending laterally from the ribbon into the sides of the trough.

A pair of comparable length, parallel notches is formed in the sides of feeder ribbon142adjacent the proximal end of the ribbon. Notches150are sized to accommodate tabs134extending up from the surface of cam ribbon130. Tabs134translate within notches150as cam ribbon130translates within clamp extension66. At the distal and proximal ends of notches150, tabs134push against the feeder ribbon142to drive the feeder ribbon in conjunction with the cam ribbon. Notches150have a greater longitudinal length than tabs134, with the difference in length providing a dwell time between actuation of the cam ribbon130and actuation of the feeder ribbon142. Feeder ribbon142is driven by contact with the cam ribbon tabs134rather than directly by a driving assembly in the handle. The difference in length between tabs134and notches150allows cam ribbon lifters132to translate in and out of longitudinal alignment with staple advancers144during the staple feeding sequence.

FIGS. 33 and 34show the initial position of the staple feeding mechanism prior to staple deployment. In this initial position, cam ribbon130and feeder ribbon142are both in a proximal-most position within clamp extension66, with tabs134at the proximal end of notches150. Cam lifters132are longitudinally aligned beneath staple advancers144. With lifters132and staple advancers144aligned, feeder ribbon142is in a recessed position within clamp extension66, and the staple advancers are below the plane of staple stack76.

As trigger assembly16is squeezed to deploy a staple30, a distally directed force is applied to driving member140to advance the member and cam ribbon130distally within clamp extension66. As cam ribbon130begins to move, feeder ribbon142remains stationary, as tabs134translate through notches150. The relative movement between cam ribbon130and feeder ribbon142allows lifters132to move out of alignment with staple advancers144and ride underneath the planar feeder ribbon surface146. As lifters132move underneath the planar surface of feeder ribbon142, the lifters push the ribbon up within clamp trough74. As feeder ribbon142lifts upward, staple advancers144move up inside the loops of the individual staples in stack76. Feeder ribbon142remains stationary, allowing lifters132to translate under the ribbon, while tabs134progress through notches150. Once tabs134reach the distal end of notches150, as shown inFIGS. 35 and 36, the tabs apply a distally directed force to feeder ribbon142. The force of the cam ribbon tabs134against feeder ribbon142pushes the feeder ribbon through the staple housing in unison with the cam ribbon. With staple advancers144raised into engagement with the staple stack76, the distal movement of feeder ribbon142in turn causes each of the staple advancers to individually advance the engaged staple, thereby advancing the full staple stack along the upper surface of clamp extension66. As the staple advancers on feed ribbon142translate staple stack76, cam ribbon130remains rigidly spaced from the stack in a separate plane.

At the end of the trigger stroke, staple advancers144have advanced the staple stack76one full staple length, as shown inFIGS. 37 and 38. As the trigger assembly pivots back open following staple formation, driving member140is pulled back proximally by the retracting trigger assembly. Driving member140in turn pulls cam ribbon130proximally due to the connection between the driving member and the ribbon. Cam ribbon130retracts ahead of feeder ribbon142due to the distal position of tabs134within notches150. Retracting cam ribbon130ahead of feeder ribbon142allows staple advancers144to realign longitudinally with lifters132prior to moving proximally. The realignment of the lifters and staple advancers allows feeder ribbon142to fall back down inside clamp trough74. Feeder ribbon142may drop down independently onto the retracting cam ribbon130, or be pushed down by contact between the retracting staple advancers144and the staple crowns32. In an alternative embodiment, feeder ribbon142is pushed down by semi-flexible fins as previously described. Staples30are held in the forward, indexed position as feeder ribbon142retracts by the anti-backup arms104described above. After tabs134retract to the proximal end of notches150, as shown inFIGS. 39 and 40, the retracting cam ribbon130pulls feeder ribbon142proximally in unison with the cam ribbon. As the trigger assembly reaches a fully open position, the cam and feeder ribbons130,142retract back to a reset condition, in which lifters132and staple advancers144are longitudinally aligned and located beneath the loop of the next proximal staple in stack76. In this position, the cam and feeder ribbons are ready to again advance the staple stack during the next staple deployment.

The feeding mechanism described herein has been associated with a closed loop staple having at least partially overlapping end segments. Without departing from the scope of the current invention, other surgical fasteners, markers, or anchors that may require feeding in a stacked configuration may be used with this mechanism. A non-limiting list of candidate devices include staples of various geometries, hernia mesh anchors, T-Tags, and biopsy markers.

The foregoing description of preferred embodiments of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Obvious modifications or variations are possible in light of the above teachings. The embodiments were chosen and described in order to best illustrate the principles of the invention and its practical application to thereby enable one of ordinary skill in the art to best utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims appended hereto.