HERNIA STAPLER

[0001] This application is a continuation-in-part of U.S. patent application Ser. No. 12/880,492 filed Sep. 13, 2010, which is a continuation of PCT/US2009/037119 filed Mar. 13, 2009, which claims the benefit of U.S. Provisional Application Ser. No. 61/036,644 filed Mar. 14, 2008, the disclosures of which are hereby incorporated by reference.

[0002] This application is generally related to means for applying surgical staples to fasten a surgical mesh. More specifically, but not exclusively, it is related to a surgical stapler having a distal manipulator for positioning a surgical mesh prior to application of the staples.

[0003] Chapters 14 and 23 of “Lichtenstein Tension-Free Hernioplasty For The Repair of Primary and Recurrent Inguinal Hernias”, pages 149-157 of “The Transabdominal Preperitoneal Laparoscopic Herniorrhaphy”, and pages 256-268 of Nyhus and Condon's Hernia, Fifth Edition, edited by Robert J. Fitzgibbons and A. Gerson Greenburg, published by Lippincott Williams & Wilkins, Philadelphia, 2002, describe some procedures for repair of inguinal hernias. A sheet of monofilamented polypropylene mesh is mentioned as a material suitable for use in such procedures. After shaping and placement of the mesh in the repair site, it is sutured to adjacent tissue.

[0004] While suturing is a long-standing practice for securing the mesh, some stapling is frequently favored because of the speed and relative ease of use. At some locations desired for attachment of the mesh to tissue, stapling is possible, but holding and stapling the mesh to tissue at some other locations where attachment is desired can be challenging, if not impossible, for one pair of hands. Improvement is needed.

[0005] The present invention provides systems and techniques for applying surgical staples and for using staples to hold a surgical mesh, for example during an inguinal hernia repair. The systems and techniques may also be applied during ventral/incisional hernia repair, used for skin closure, or used in other surgical procedures as would occur to the skilled artisan. While the actual nature of the invention covered herein can only be determined with reference to the claims appended hereto, certain aspects of the invention that are characteristic of the embodiments disclosed herein are described briefly as follows.

[0006] According to one aspect, a surgical stapler includes an elongated shaft having a handle at its proximal end and a downwardly disposed discharge head at its distal end. The stapler also includes an angled magazine of staples mounted between the discharge head and the shaft and a pusher plate disposed in the discharge head. In one form, the pusher plate includes a pair of forming fingers adapted to retain a single staple from the magazine of staples between the forming fingers. Moreover, in another form, each of the pair of forming fingers includes a retention lip. Typically, the retention lip has a height that corresponds to a thickness of the single staple. In yet another form, each of the pair of forming fingers includes an inner edge, an outer edge, and a staple contact portion that spans between the inner and outer edges, wherein the inner edge and the staple contact portion include a retention lip. Each of the pair of forming fingers may also include a chamfered portion adapted to engage only the single staple from the magazine of staples. Some embodiments include an anvil plate positioned in the discharge head adjacent the pusher plate wherein the anvil plate has a step with a height that corresponds to about the thickness of the single staple and the step is adapted to position the single staple under the chamfered portion when the pusher plate passes over the anvil plate. The pair of forming fingers can be adapted to slide adjacent the step.

[0007] According to another aspect, a novel surgical stapler includes an elongated shaft having a handle at its proximal end and a downwardly disposed staple discharge head at its distal end, wherein the handle is operable to cause a supply of staples to be selectively discharged from the head. The stapler includes a pusher plate positioned in the staple discharge head wherein the pusher plate includes a retention lip adapted to retain a single staple from the supply of staples during a hernia surgery. In some forms, the pusher plate includes a chamfered portion adapted to engage only the single staple from the magazine of staples. In other forms, the pusher plate includes a cantilevered portion adapted to engage and remove the single staple from the supply of staples. The stapler can include an anvil plate positioned in the discharge head adjacent the pusher plate wherein the anvil plate has a step with a height that corresponds to about the thickness of the single staple and the step is adapted to position the single staple under the chamfered portion when the pusher plate passes over the anvil plate. Further, in one form, the elongated shaft includes a first tab and a second tab, the anvil plate defines a first keyway and a second keyway, and the first and second tabs are adapted to engage and retain the first and second keyways, respectively, when the anvil plate is assembled with the elongated shaft.

[0008] Further forms, objects, features, aspects, benefits, advantages, and embodiments of the present invention will become apparent from a detailed description and drawings provided herewith.

[0042] For the purpose of promoting an understanding of the principles of the invention, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended. Any alterations and further modifications in the described embodiments, and any further applications of the principles of the invention as described herein are contemplated as would normally occur to one skilled in the art to which the invention relates. One embodiment of the invention is shown in great detail, although it will be apparent to those skilled in the relevant art that some features that are not relevant to the present invention may not be shown for the sake of clarity.

[0043] Referring to FIGS. 1-2A, a stapler 11 has a handle 12 with a trigger 13 pivotally mounted to the handle at 14. A shaft or tube 16 is fixed to the handle and has a stapler head portion 17 at its distal end. The head portion turns downward at an angle of about forty degrees (A in FIG. 1) from an axis 18 and has a staple discharge port 19 through which staples are shot, one staple for each trigger pull. The trigger coupling to the staple shooter is a two-stage system whereby a staple 21 can be advanced from within the head to a position shown in FIGS. 1 and 1A. Then, upon further pull of the trigger it can be shot through the mesh into the tissue.

[0044] One inventive feature is the provision of a mesh manipulator near the outlet port of the stapler. As used herein, a “mesh manipulator” does not include the staple itself, but rather it is a structure other than the staple that is operable to be used to manipulate surgical mesh. In FIGS. 1 and 1A, the mesh manipulator comprises an elongated member or wire 22 having a distal portion including a tip 23 which projects downward under the stapler head portion 17 in the plane 25 (FIG. 2A) containing the axis 18 of the tube 16 and bisecting the handle 12. This elongated member extends from the tip portion backward through a channel 24 at the bottom of the tube 16. A wire control button 26 slidable on the channel and connected to the proximal end of the wire is provided to slide the wire forward to extend the tip 23 farther below the staple discharge port 19, or retract it into the channel 24 when and to what extent desired by the surgeon. Other locations for the wire control button 26 can be used when and desired by the user. One example is in the handle itself.

[0045] For purposes of useful mesh manipulation, the wire 22 would often, but not always, be positioned such that the tip 23 projects several millimeters beyond the plane 40 defined by the discharge port 19, as shown in FIG. 1A. For example, it is expected that useful mesh manipulation can be achieved when the tip 23 is at least about 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, or 10 mm distal to plane 40.

[0046] Referring now to FIGS. 3 and 3A, a wire 27 is provided with a curved tip portion 28 curved downward and forward for insertion through a mesh 29 and pushing it forward in the direction of arrow 31 to move it to the position desired for stapling. This forward movement may be made by moving the stapler itself using the handle or by moving the wire by moving the wire control button 26.

[0047] Referring to FIGS. 4 and 4A, a wire 32 has a tip portion 33 which is curved rearward to enable the wire tip to pass through the mesh 29 and pull it rearward in the direction of arrow 34 to position the mesh where desired relative to the location at which the stapling through the mesh to the tissue is desired.

[0048] Referring now to FIG. 5, there is a schematic showing the mesh 29 cut from a sheet into a shape desired for placement at the surgery site. There are shown eleven sites at the edges of the mesh indicating where stapling inboard from the edges is desired. This is an example, as different sizes and shapes and numbers of staples may be chosen depending upon the requirements of the site.

[0049] FIG. 6 is a schematic illustration of the site with the staple head inserted into an opening 36. Consider that an opening edge 37 nearest the surgeon is referred to in this context, as the near edge, and an opposite edge 38 is the far edge. Attachment of the mesh to tissue below the near edge 37 by stapling can be relatively straight forward with the stapler oriented as shown in FIG. 6, but pulled outward to place the head at the near edge 37 and move the head downward to the mesh and shoot the staple down into the mesh with the prongs into the tissue below. On the opposite edge, the mesh is to be stapled to the upper inside face of the tissue. That is extremely difficult with conventional instruments. The present invention is capable of being turned upside down as shown in FIGS. 7 and 9 so that the discharge port 19 and tip 23 are facing upwardly to the tissue and pushed or pulled by a wire tip such as shown in FIG. 3 or FIG. 4, depending upon the most effective approach to push or pull the mesh to the location desired for stapling and then fire the staple upward with the prongs through the mesh and into inverted or lofted tissue.

[0050] In FIG. 1, for example and without limitation, the stapler head portion 17 has the discharge port angled down as shown at A. As an example, this angle can be between 30 and 50 degrees from the center line 18 of the shaft. In one example, 45 degrees might be the optimal angle.

[0051] The total offset B between the bottom of the head and top of the shaft is preferably between 12 and 25 mm. Other angles and offset dimensions may be used if desired or necessary to the particular surgical site. The overall length between the head and the proximal end of tube 16 at its entrance to the handle 12 may be 85 mm, for example. Again, other dimensions may be determined according to the preference of the surgeon and the nature of the surgical site. The same is true as to the shape and nature of the handle, one example of a different shape is illustrated in FIGS. 10-11 as will be described. The width of the staple between the prongs may be 5 mm, for example, but staples of other widths might be selected for particular cases. For example, it may be desirable to produce a fully formed box staple using 0.5 mm staple wire wherein the formed staple has a width of about 7.5 mm and a height of about 3.5 mm. In some tools, it might be considered desirable to make the shaft rotatable in the handle and/or to provide an articulation joint in the shaft near where it enters the handle, but, for the present, it appears that simply inverting the handle from the attitude as shown in FIG. 1 to that as shown in FIGS. 7 and 9 would appear to be adequate. A variety of mechanisms for discharging a staple can be implemented. For example, U.S. Pat. No. 5,829,662 and U.S. Pat. No. 5,743,456 describe endoscopic stapling equipment that could be adapted to implement the present invention.

[0052] Referring now to FIGS. 10-14A, stapler 100 comprises a handle unit 120 and a downwardly disposed discharge head 130 at either end of an elongated shaft 110. A staple stack or magazine 140 containing a supply of staples (e.g. 15) is mounted to the underside of the shaft 110. Trigger 122 is operative to cause a staple 160 to be formed and discharged from an outlet port 162 of head 130. Successive pulls of the trigger form and discharge successive staples from the magazine 140, and a running staple count is displayed in a window at 170.

[0053] Formation and discharge of a staple is accomplished via a single stroke of pusher plate 116, which is coupled to trigger 122 via a mechanical linkage that extends through the shaft 110. More specifically, drive block 125 is mounted in a slot in housing 123 with one end of compression spring 127 over tab 126 and the other end against tab 124. The drive block 125 is coupled to a driver 113 or rigid bar, which is slidably disposed in the channel of shaft 110 defined between the upper cover 111 and base 114. A stiffener 112 is also provided in the shaft channel to increase structural rigidity of the elongated straight portion of the shaft 110. A flexible pusher 115 is coupled to the end of driver 113 and traverses the curved portion of the shaft channel, which includes support ribs for flexible pusher 115 in the upper cover 111 to reduce the possibility that the flexible pusher 115 would buckle or otherwise deform. Pusher plate 116 is laminated to the distal end of flexible pusher 115 for a seamless connection. Other connections are possible as well.

[0054] In operation, squeezing the trigger 122 drives block 125 to the right (FIGS. 10, 11), overcoming the restoring forces of springs 127, 128. Springs 127, 128 each function as a return spring, thereby providing redundancy, but their spring parameters may be selected to produce a desired effect (e.g. substantially increased return force at maximum trigger depression). As block 125 travels right, a one-way clutch assembly 129 engages cogs (not shown) on the underside of block 125 to prevent retraction of block 125 short of a full stroke. In addition, shuttle plate 176 is carried above block 125 and operates to advance numbered ribbon 172, which is sandwiched between shuttle plate 176 and stay plate 174 and provides a running count of staples via a window adjacent backing plate 170.

[0055] At the beginning of a stroke, pusher plate 116 is withdrawn into the discharge head 130, and the first staple in the magazine 140 is advanced into the firing breech. As shown in FIGS. 12 and 13, the staples in the magazine 140 are in the form of an angled stack, with each staple 160 in the stack oriented in its firing direction (i.e. parallel to the backwall 132 of the breech) and the axis of the stack 40-50 degrees from orthogonal to the firing direction.

[0056] As illustrated, the staples in the magazine are generally “M” shaped and are mounted over the front rails of a holder 144, with each hump over one of the rails. A cover plate 143 is secured to the top of holder 144 and a spring pusher 145 biases the staple stack 140 towards the open, angled end of the holder 144. As illustrated, the spring biasing pusher 145 has an uncompressed length greater than the length of the staple stack, which can serve to provide a more constant force on the staple stack as staples are discharged. Guide 146 is positioned at the open end of holder 144 and provides angled fingers that prevent the staples from dropping out the angled, open end prematurely. The staple magazine 140 is mounted to supporting rails on base 114 and covered by a protective shroud 142, and front wall piece 152 is secured to complete the assembly.

[0057] As it advances in its stroke, the forming fingers 135 of pusher plate 116 pick off the first staple from the stack and form the staple around anvil 133. FIG. 13 illustrates a partially formed staple extending from outlet port 162. Continuation of the forming fingers 135 serves to fully form the staple into a desired box like shape, and preferably with the staple prongs inverted slightly rearward. Retraction of forming fingers 135 releases the leaf springs 134, which had been displaced on the downstroke, which serves to displace the now-formed staple from anvil 133. Because the formed staple is narrower, it slips readily through the wider central opening of outlet port 162, as shown in FIGS. 14A-D.

[0058] As illustrated, stapler 100 includes fixed prongs 150 on the underside outside of outlet port 162. Prongs 150 serve as mesh manipulators and may be used in any fashion contemplated herein. FIGS. 14B-D provide illustrations of additional or alternative locations for mesh manipulating prongs about the staple discharge port. Fixed prongs can also be used in combination with a retractable wire to provide further combinations of manipulating capabilities.

[0059] It is also contemplated that stapler 100 can be used without any means for mesh manipulation.

[0060] Numerous variations of the staplers described herein can be employed. For example, it may be desirable to provide one or more points of articulation along the shaft of the staplers described. As one example, a joint capable of 90 degrees articulation can be along shaft 110, for example near where shaft 110 and handle 120 meet. The provision of such an articulation joint may make it easier for the right handed surgeon, when operating on a right inguinal hernia, to place the staples that attach the mesh to the inguinal ligament.

[0061] Staples used herein can be absorbable or non absorbable with material inside the absorbable material for forming the staple and can be square shaped, round shaped, G shaped, etc. The staples can be stacked together along a rack inside the shaft that guides the staples to the distal end of the shaft with a spring loaded action, or a mechanism in the handle.

[0062] Procedures

[0063] Either under local anesthesia with sedation or general anesthesia, the lower abdomen is prepped and draped. A linear 6 to 8 cm skin incision is made along the natural skin lines. Hemostasis is obtained. The external oblique aponeurosis is divided, exposing the spermatic cord. Depending on what type of hernia, the hernia sac is dissected from adjacent tissues, emptied of any contents and pushed back into the peritoneal cavity. The mesh to be used is cut to its standard shape and size, and a tail slit is placed to accommodate the spermatic cord. The stapler is then used to fix the mesh to the insertion of the rectus sheath and along the inguinal ligament. More specifically, the stapler is used to fix the mesh to the rectus sheath, above its insertion to the pubic bone. (The stapler is sized and shaped to assure the safety of the femoral vessels and nerve.) The upper edge of the mesh is stapled to the rectus sheath and the internal oblique aponeurosis avoiding the iliohypogastric nerve. Either a staple or a single non-absorbable suture is then placed through the lower edges of the tails at the level of the internal ring. The wound is then closed in layers after all bleeding has been stopped and the sponge and instrument count is correct. The wound (i.e. the skin) can be closed with the stapler or with a conventional suture.

[0064] It is to be appreciated that what has been described includes an improved surgical stapler for attaching surgical mesh, comprising an elongated shaft having a handle at its proximal end and a downwardly disposed staple discharge port at its distal end, wherein the handle is operable to cause a supply of staples to be selectively discharged from the port; and one or more mesh manipulators near the port and projecting distal to the plane defined by the port.

[0065] What has also been described includes an apparatus for use by a person stapling mesh to body tissue at a site of inguinal hernia surgery and comprising: a handle for holding the apparatus adjacent the surgery site, and having a proximal end and a distal end; a shaft defining a longitudinal axis and having a proximal end and a distal end and having the proximal end mounted to the distal end of the handle; a staple discharge head having one end with a mounting portion connected to the distal end of the shaft, and having another end with a staple exit port; the head adapted to fire a staple out from said head through said port along a line and in a direction away from the handle, wherein the direction of staple firing is downward relative to the longitudinal axis of the shaft; an elongated member mounted to said shaft and extending generally parallel to the shaft and in a direction forward away from said handle, the member having a distal end portion in a plane containing the direction of staple firing, and the distal end portion of said member being spaced from said line and under the line; and the distal end portion of said member having a tip configured to engage a mesh useful for embedding in a body cavity during inguinal hernia surgery, for connecting and moving said mesh to a location for stapling the mesh to body tissue at the surgery site. In one refinement, the distal end portion of said member is straight and curves downward and then forward in said plane to said tip. In another refinement, the distal end portion of said member is straight and curves downward and then rearward in the plane to the tip. In another refinement, a guide on the shaft receives the elongated member and has a proximal end near the handle and a distal end opening exposing the distal end portion of the wire forward of the distal end opening of said guide, and confining the elongated member from the distal end portion of the member rearward to a location adjacent the handle. It may further include a manipulator on the elongated member adjacent the handle for alternately advancing and retracting the tip of the member.

[0066] What is also described is an apparatus for use in stapling mesh to body tissue at a site of inguinal hernia repair surgery and comprising: a shaft having a proximal end and a distal end; a staple discharging head at the distal end of the shaft; a staple inside the head, the staple having a generally U-shaped configuration with spaced prongs in a first plane; and a discharge port on the head for discharge of said staple outward from said head through the discharge port; and a mesh manipulator connected to the head and having a tip adjacent the port wherein the tip of the manipulator is spaced from said first plane a short distance to avoid contact by the staple when discharged outward from the port into the mesh.

[0067] What is also described includes, during inguinal hernia repair, a method of attaching a mesh covering herniated membrane, to body tissue adjacent and bordering the site of the herniation, and comprising: inserting the head of a stapling apparatus into an opening bordered by said tissue and directing a staple discharge port downward toward said mesh at a near side of said opening and firing staples from said port through said mesh into some of said tissue adjacent said herniation, at multiple locations on the near side of said opening; and moving the head of a stapling apparatus in an opening bordered by said tissue and directing a staple discharge port upward toward said mesh at a far side of said opening and firing staples from said port through said mesh into some of said tissue, at multiple locations on the far side of said opening. The method may further include engaging said mesh with a probe point mounted to said head and located between said port and said mesh, and moving said mesh with said probe to position said mesh at a location on said tissue where a staple is to be fired into said mesh and said tissue. The method may further include moving said mesh by pushing said mesh with said probe point and/or pulling said mesh with said probe point. Pulling the mesh may be used to lift said mesh on said far side. The mesh may be pierced to facilitate said moving of said mesh.

[0068] Another embodiment of a stapler 200 is illustrated in FIGS. 15-27. It is to be appreciated, stapler 200 is similar to stapler 100 in many aspects; therefore, for the sake of brevity similar features will not be discussed. As illustrated in FIG. 25, stapler 200 includes a handle unit 220 and a downwardly disposed discharge head 230 at the distal end of an elongated shaft 210. A staple magazine 240 containing a supply of staples is mounted to the underside of the elongated shaft 210. Trigger 222 is operative to cause a staple 260 to be formed and discharged from an outlet port 251 of the discharge head 230. Successive pulls of the trigger 222 form and discharge successive staples from magazine 240, and a running staple count is displayed in a window 271. Stapler 200 also includes a pair of fixed prongs 250 near the outlet port 251. Prongs 250 are similar to prongs 150; therefore, prongs 250 serve as mesh manipulators and may be used in any fashion contemplated herein. It is also contemplated that stapler 200 can be used without any means for mesh manipulation, such as prongs 250.

[0069] Similar to stapler 100, formation and discharge of a staple is accomplished via a single stroke of a pusher plate 216, which is coupled to the trigger 222 via a mechanical linkage that extends through the elongated shaft 210. The mechanical linkage in the embodiment illustrated in FIGS. 15-27 is similar to the mechanical linkage described above and illustrated in FIGS. 10-14A. A flexible pusher 215 is coupled to the end of a driver (not shown) and traverses the curved portion of the channel of the elongated shaft 210. Pusher plate 216 is attached to the distal end of flexible pusher 215.

[0070] Pusher plate 216 includes a pair of forming fingers 235 that are similar to forming fingers 135; however, each of forming fingers 235 as illustrated in FIG. 21 includes a chamfered portion 238, a cantilevered portion 248, and a retention lip 258. The chamfered portion 238, the cantilevered portion 248, and the retention lip 258 facilitate picking off a single staple 260 from the supply of staples. The chamfered portion 238 and cantilevered portion 248 pick off a single staple 260 as the pusher plate 216 passes under the stack of staples. As such, the chamfered portion 238 and cantilevered portion 248 do not engage the proximal staple surface to move another staple distally in the stack of staples. Therefore, the stack of staples remains undisturbed. In some applications, the use of fixed prongs 250 to hold mesh during a medical procedure may cause side loads or forces that are applied to the staple thereby resulting in tension on the staple and incomplete staple formation. These side loads or forces are out of the plane of the stapler 200 and can cause the staple to slip off the forming fingers 235. However, the cantilevered portion 248 and the retention lip 258 retain the staple between forming fingers 235. The retention lip 258 engages the top of the staple 260 during formation of the staple 260 to restrain the staple 260 from forces caused by prongs 250 on the mesh as the staple 260 is attached to body tissue. The cantilevered portion 248 helps to retain the staple 260 from slipping or twisting away from the retention lip 258. Each of the forming fingers 235 includes an inner edge 252, an outer edge 254, and a staple contact portion 239 that spans between the inner edge 252 and the outer edge 254. The inner edge 252 includes the chamfered portion 238. The inner edge 252 and the staple contact portion 239 include the cantilevered portion 248 and the retention lip 258. Between the pair of forming fingers 235 is positioned a wider portion 256 that is substantially perpendicular to the inner edge 252.

[0071] The channel of the elongated shaft 210 is defined between an upper cover 211 and a base 214. The base 214 includes a first key or tab 300 positioned on a first edge 302 and a second key or tab 304 positioned on a second edge 306 as illustrated in FIGS. 22, 23, and 24. The base 214 also defines a first opening 308 adjacent the first key 300 on the first edge 302. The base 214 also defines a second opening 309 adjacent the second key 304 along the second edge 306. The first key 300 and the second key 304 are sized and configured to interact and engage a first keyway 310 and a second keyway 312, respectively, on a backwall or anvil plate 232. Further, the first opening 308 is sized to receive the first keyway 310. Correspondingly, the second opening 309 is sized to receive the second keyway 312. As the backwall 232 is assembled with the base 214, the first keyway 310 is positioned and inserted in the first opening 308 and the second keyway 312 is positioned and inserted in the second opening 309 as illustrated in FIG. 23. Thereafter, the backwall 232 is slid or pushed toward the distal end of the elongated shaft 210 to engage the first keyway 310 with the first key 300 and the second keyway 312 with the second key 304. The first key 300 engages and retains the first keyway 310 and the second key 304 engages and retains the second keyway 312. The connection between the first key 300 and the first keyway 310 and the connection between the second key 304 and the second keyway 312 provides a mechanical interaction between the backwall 232 and the base 214. As such, adhesive is not required to attach the backwall 232 with the base 214. In other embodiments, adhesive may be used, if desired, to attach the backwall 232 with the base 214.

[0072] The backwall or anvil plate 232 includes a top face 272 and an opposite bottom face 270. The top face 272 is positioned to face or interact with the supply of staples when the backwall 232 is assembled with the base 214 of elongated shaft 210. The top face 272 includes a step or plateau 274 that has a thickness that corresponds to about the thickness (or less) of a single staple. The step 274 functions as an elevated staple staging area for the supply of staples. The width of step 274 is about the same as wider portion 256 of pusher plate 216. As such, the forming fingers 235 of pusher plate 216 slide next to the step 274 as the chamfered portion 238, the cantilevered portion 248, and the retention lip 258 pick off a single staple and advance that staple toward a pair of anvils 276 as described in more detail below. The top face 272 also includes a lower portion 275 that is positioned between the step 274 and a pair of anvils 276. Similar to backwall 132, backwall 232 includes a pair of anvils 276 around which the staple 260 is formed. The uppermost staple from the supply of staples rests against the step 274 such that a center portion of the staple contacts the step 274 while the outer legs of the staple rest against lower portion 275 thereby causing the staple to rotate slightly. As such, the center portion of the staple is elevated above the legs of the staple as shown in FIG. 15. As the staple is pushed by the forming fingers 235, the staple passes over the step 274 and drops onto the lower portion 275 such that the staple is retained in the retention lip 258. The remainder of the pusher plate 216 passes over the step 274 as the staple engages the anvils 276. Moreover, the step 274 and pusher plate 216 each have a thickness that enables the chamfered portion 238 to pass under a second staple in the stack of staples (as shown in FIGS. 15 and 16) and engage only the staple resting on step 274 to ensure pickoff of only one staple.

[0073] The staple contact portion 239 is beveled to further facilitate the forming fingers 235 engagement of a single staple. The staple contact portion 239 does not disturb the adjacent staple and helps to eliminate staple jamming. The chamfered portion 238, staple contact portion 239, cantilevered portion 248, and retention lip 258 on pusher plate 216 and the step 274 on backwall 232 work together to ensure that only a single staple 260 from the supply of staples is ejected at deployment.

[0074] The base 214 also includes a first rail 322 and an opposite second rail 326 as shown in FIGS. 26 and 27. In the illustrated embodiment, the first rail 322 includes a first plurality of energy directors 328 and the second rail 326 includes a second plurality of energy directors 330. The first and second plurality of energy directors 328 and 330 each have a wedge or rectangular shape; however, the energy directors 328 and 330 can be shaped differently in other embodiments. The base 214 also includes a first distal rail 332 along the first edge 302. The base 214 also includes a second distal rail 336 along the second edge 306. The first and second distal rails 332 and 336 include a first plurality of energy directors 338 and a second plurality of energy directors 340, respectively. To join the base 214 with the staple magazine 240, a cover plate (not illustrated) of the staple magazine 240 is positioned next to the base 214. Next, ultrasonic welding equipment is used to provide ultrasonic energy to melt the plurality of energy directors 328, 330, 338, and 340 to create a joint between the base 214 and the cover plate. Other embodiments may use different techniques to attach the staple magazine 240 to the base 214. Some examples include adhesive, snap-fit connections, or other mechanical type connections.

[0075] In operation, the trigger 222 is squeezed which drives the block (not illustrated but similar to block 125) to the left in FIG. 25. At the beginning of a stroke, pusher plate 216 is withdrawn into the discharge head 230, and the first staple in the magazine 240 is advanced into the firing breech. The staples in magazine 240 are similar to the staples in magazine 140. As pusher plate 216 advances in its stroke, the forming fingers 235 contact and pick off the first staple from the stack as illustrated in FIG. 16. In particular, the cantilevered portion 248 on the staple contact portion 239 engages the staple 260 and pushes the staple 260 towards the pair of anvils 276 as the pusher plate 216 continues to advance. Also, the cantilevered portion 248 on the staple contact portion 239 and the chamfered portion 238 of the pusher plate 216 clear or pass under the staple that is adjacent to staple 260 in the stack of staples. As such, the remaining staples are generally undisturbed during deployment. Next, as the pusher plate 216 advances forward, the staple 260 moves off the step 274 and onto the lower portion 275 such that the retention lip 258 engages the top of the staple 260 as illustrated in FIG. 17. As the pusher plate 216 continues to advance forward, the staple 260 contacts the pair of anvils 276 as illustrated in FIG. 18. Thereafter, as illustrated in FIG. 19, chamfered portion 238 and retention lip 258 continue to engage and retain the staple 260 adjacent the pair of anvils 276 and fully form the staple 260 into a desired box like shape, and preferably with the staple prongs inverted slightly rearward as illustrated in FIG. 20. Therefore, if force is applied to the staple 260, the cantilevered portion 248 assists to retain the staple 260 on the retention lip 258. Retraction of the pusher plate 216 releases leaf springs (not illustrated) which had been displaced on the down stroke, which serves to displace the now-formed staple 260 from the pair of anvils 276.

[0076] While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only the preferred embodiment has been shown and described and that all changes, equivalents, and modifications that come within the spirit of the inventions defined by following claims are desired to be protected. All publications, patents, and patent applications cited in this specification are herein incorporated by reference as if each individual publication, patent, or patent application were specifically and individually indicated to be incorporated by reference and set forth in its entirety herein.