Patent Publication Number: US-2023134251-A1

Title: Applicator Instruments with Inverted Handles and Triggers, Curved Shafts, and Visible Orientation Indicia

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present patent application is a continuation of U.S. patent application Ser. No. 13/720,198, filed on Dec. 12, 2012, now US 2013/0303845, which is a continuation-in-part of U.S. patent application Ser. No. 13/470,022, filed on May 11, 2012, now U.S. Pat. No. 8,518,055, and which is related to commonly assigned U.S. Pat. Nos. 9,364,228, 8,894,669, 8,579,920, 8,728,098, 8,728,099, and 8,920,439, the disclosures of which are hereby incorporated by reference herein. 
    
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention generally relates to medical devices and surgical procedures for correcting defects, and more specifically relates to applicator instruments having imaging systems that facilitate dispensing surgical fasteners during open hernia repair procedures, such as ventral hernias. 
     Description of the Related Art 
     Hernia is a condition whereby a small loop of bowel or intestine protrudes through a weak place or defect within the abdominal muscle wall or groin of a patient. This condition commonly occurs in humans, particularly males. Hernias of this type may result from a congenital defect, or may be caused by straining or lifting heavy objects. Lifting heavy objects can generate a large amount of stress upon the abdominal wall, which may rupture or tear to create the defect or opening. In any case, the patient may be left with an unsightly bulge of abdominal contents protruding through the defect, which may result in pain, reduced lifting abilities, and in some cases, impaction of the bowel, or possibly other complications if the flow of blood is cut off to the protruding tissue. 
     A common solution to the above-described problem may be surgery. During an open surgical procedure, the defect is accessed and carefully examined through an open incision. Careful examination is required due to the network of vessels and nerves which exist in the area of a typical defect, which requires a surgeon to conduct a hernia repair with great skill and caution. Within this area can be found vascular structures such as gastric vessels, the external iliac vessels, and the inferior epigastric vessels. 
     Once the surgeon is familiar with the anatomy of a patient, the surgeon carefully places the viscera back into the patient&#39;s abdomen through the defect. Repairing the defect can involve closure of the defect with sutures or fasteners but generally involves placing a surgical prosthetic such as a mesh patch over the open defect, and attaching the mesh patch to the abdominal wall or inguinal floor with conventional suture or with surgical fasteners. The mesh patch acts as a barrier and prevents expulsion of bowel through the defect. 
     At present, there are a variety of surgical instruments and fasteners available for attaching a mesh patch to tissue. One type of instrument is a surgical stapler whereby a stack of unformed staples are contained within a cartridge in a serial fashion sequentially advanced within the instrument by a spring mechanism. A secondary feeding mechanism separates a distal-most staple from the stack, holds back the remainder of the stack, and feeds the distal-most staple into a staple forming mechanism. Feeding mechanism soft his type are found in U.S. Pat. No. 5,470,010 to Rothfuss et al., and in U.S. Pat. No. 5,582,616, also to Rothfuss et al. 
     Another hernia mesh attachment instrument uses a helical wire fastener that resembles a small section of spring. Multiple helical wire fasteners may be stored serially within a 5 mm shaft, and may be corkscrewed or rotated into tissue. A load spring may be used to bias or feed the plurality of helical fasteners distally within the shaft. A protrusion extends into the shaft to possibly prevent the ejection of the stack of fasteners by the load spring and may permit passage of a rotating fastener. Instruments and fasteners of these types are found in U.S. Pat. No. 5,582,616 to Bolduc et al., U.S. Pat. No. 5,810,882 to Bolduc et al., and in U.S. Pat. No. 5,830,221 to Stein et al. 
     The above-listed references teach using a spring mechanism to feed a plurality of fasteners through the surgical instrument. Spring mechanisms typically use a long soft coil spring to push a stack of fasteners through a guide or track within the shaft of the surgical instrument. These types of feeding mechanisms may be generally simple and reliable, however, they require a supplemental valving mechanism to separate and feed the lead surgical fastener from the stack. 
     Other instruments dispense surgical fasteners using either a reloadable single shot instrument or a rotary magazine that holds a small number of fasteners. These types of surgical fastening instruments can be found in U.S. Pat. Nos. 5,203,864 and 5,290,297, both to Edward Phillips. These instruments have not gained acceptance by the surgical community, possibly due to their single shot capabilities and the large size of the rotary magazine, which can restrict the use of such an instrument to an open procedure. 
     An instrument with a reciprocating feeding mechanism is described in U.S. Pat. Nos. 5,601,573; 5,833,700; and U.S. Pat. No. 5,921,997 to Fogelberg et al. The Fogelberg et al. references teach a clip applier with a feeding mechanism that utilizes a reciprocating feed bar to feed a serial stack of clips. A feeder shoe may operably engage with and move with the distally moving feed bar and may slidingly engage with the proximally moving feed bar. Thus, the feeder shoe may index or push the stack of clips distally with the distally moving feed bar and remains stationary relative to the proximally moving feed bar. A supplemental valving mechanism separates the distal-most clip from the stack and holds the remainder of the stack stationary as the distal-most clip is applied onto a vessel. Although the Fogelberg et al. references teach a reciprocating feeding mechanism with a single reciprocating member, they do not teach the use of the clip applier in the attachment of hernia mesh, nor do they teach the individual driving or feeding of each clip by a moving member. 
     Another fastener feeding mechanism that uses reciprocation is that disclosed in U.S. Pat. No. 4,325,376 to Klieman et al. A clip applier that stores a plurality of clips in a serial fashion within a clip magazine is disclosed. The clips are in a stack wherein the proximal most clip may be pushed or fed distally by a pawl that may be ratcheted or indexed distally by a reciprocating member or ratchet blade with each actuation of the instrument. As the pawl indexes distally, it can push the stack of clips distally. A secondary valving mechanism may be also described. Thus, the feeding mechanism of Klieman et al. teaches the use of a single reciprocating member and pawl to push or feed the stack of clips distally, and may require a secondary valving mechanism to feed the distal most clip. 
     U.S. Pat. No. 3,740,994 to DeCarlo Jr. describes a novel reciprocating feeding mechanism that may index a plurality of staples or clips, and may ready them for discharge by reciprocating one of a pair of opposing leaf spring assemblies. The staples reside serially within a guide rail with a fixed leaf spring assembly extending into the plane of the guide rail. A reciprocating leaf spring assembly may oppose and extend inwardly toward the fixed leaf spring assembly. As the reciprocating leaf spring assembly moves distally, each of individual leaf springs of the assembly may engage a staple and move it distally. The distally moving staples deflect the local individual leaf springs of the fixed leaf spring assembly, and the deflected leaf springs may return to the un-deflected position after passage of the staple. As the moving leaf spring assembly moves proximally, the leaf springs of the fixed leaf spring assembly hold the staples stationary and prevent proximal movement thereof. A secondary guide rail and valving mechanism may be provided to separate a single staple from the stack for forming and can hold the stack of staples stationary as the single clip is formed. 
     Additionally, similar feeding mechanisms are disclosed in U.S. Pat. No. 4,478,220 to DiGiovanni et al. and U.S. Pat. No. 4,471,780 to Menges et al. Both of these related patents teach a reciprocating feeding mechanism that uses one fixed member and one reciprocating member to feed or index a plurality of clips distally. Angled flexible fingers may be hingedly attached to the reciprocating member and operatively engage the clips when moving distally, and slidingly engage with the clips when moving proximally. The angled flexible fingers within the fixed member deflect out of the way when the clips move distally and spring up to stop proximal movement of the clip after the clip has passed. A secondary valving mechanism is also disclosed. 
     Commonly assigned U.S. Patent Application Publication No. 2002/0068947, the disclosure of which is hereby incorporated by reference herein, teaches a device for delivering a plurality of individual surgical fasteners. In one embodiment, the delivery device includes a drive mechanism having distal and proximal ends. The drive mechanism has a moving member and a fixed opposing member, whereby the moving member is moveable proximally and distally with respect to the delivery device. The moving member has a sharpened distal end for piercing tissue. The device includes at least one surgical fastener located between the first and the second members. Each of the surgical fasteners has a proximal end and a distal end. The device also has an actuator having at least two sequential positions. A first position for advancing the moving member distally and piercing tissue, and a second position for retracting the moving member proximally, thereby deploying the distal end of the fastener. 
     Tacks for mesh fixation have generally been made of metal, such as stainless steel, nitinol, or titanium. The metal tacks were necessary to provide for sufficient holding strength, penetration of various prosthetic meshes, and for ease of manufacture. Until recently, there were no absorbable tacks available on the market, and surgeons could only use absorbable sutures in order to provide a fixation means that did not permanently stay in the body. However, using sutures is exceedingly difficult for some repair procedures. With surgical trends leading to minimum foreign body accumulation, an absorbable tack with minimum profile is needed. 
     During intra-peritoneal onlay mesh repairs, commonly referred to as Open IPOM, visibility is often very poor. Laparoscopic cameras and lights are not typically used for an open procedure. Instead, direct visualization must be attained through the incision. The incision may be increased to improve visibility at the expense of the cosmesis, however, inside of the abdominal cavity, lighting is often insufficient. Improper visibility can lead to improper placement of fixation points within a skirted mesh implant. For example, fixation points can be spaced incorrectly or positioned incorrectly relative to the edge of the mesh. Improper visibility can also lead to accidental bowel perforation, particularly if a loop of bowel is above the skirted mesh but is not visible. 
     In spite of the above advances, there remains a need for further improvements. In particular, there remains a need for applicator instruments that enable surgeons to accurately and easily dispense surgical fasteners into tissue for tissue repair procedures, there remains a need for applicator instruments that enable surgical fasteners to be accurately and easily dispensed in small areas, and for surgical fasteners that are absorbable. There also remains a need for a supplemental imaging or detection system in support of a hernia mesh fixation instrument, with the purpose of improving visibility during repair procedures, such as Open IPOM repair procedures. 
     SUMMARY OF THE INVENTION 
     In one embodiment, an applicator instrument is preferably a multi-fire device having a non-linear shaft (e.g., curved or angled) that delivers surgical fasteners for the fixation of mesh material to soft tissue, such as the applicator instrument disclosed in commonly assigned U.S. patent application Ser. No. 13/470,022, which is a parent of the present application, the disclosure of which in hereby incorporated by reference herein. The applicator instrument may be used for open surgical repair procedures that address ventral hernias. In one embodiment, a series of surgical fasteners are housed within the shaft of the applicator instrument and the distal end of the shaft is non-linear to the proximal end of the shaft that is attached to a handle. 
     In one embodiment, the multi-fire applicator instrument has a series of strap implants or surgical fasteners stored along the length of the shaft. The applicator has a firing system including a pair of flat stampings with tabbed features. One stamping is stationary and the other stamping cycles in distal and proximal directions to facilitate incremental feeding of the surgical fasteners along the length of the shaft. The flat nature of the stampings facilitates assembly and flexibility as the stampings are guided through a curved path. In one embodiment, a pair of long, molded guide components creates the non-linear path of travel with minimal friction and distortion. The molded components are desirably contained within the shaft, which may be a stainless steel cannula. 
     In one embodiment, at the distal end of the shaft, a wire staging spring applies a downward force on the distal end of the stationary tabbed stamping. The force applied by the wire spring positions and aligns the surgical fasteners with the dispensing end of the device. When a surgical fasteners reaches a lead position at the distal end of the shaft, the cycled stamping is retracted, and the wire spring moves the lead fastener downward from the advancing channel into the firing channel. From the firing channel, the fastener is dispensed via a firing system including a firing rod and a stored energy system in the handle. The wire spring provides a spring force mechanism that is more economical and easier to assemble within a system. 
     In one embodiment, a contoured tip or cap is attached to the distal end of the shaft. The contours on the cap make the distal end of the applicator instrument atraumatic to a skirted mesh. 
     In one embodiment, the cap has a lower distal edge that may be pronounced and that may have a curved bottom surface. The lower distal edge is preferably advanced into the seam of a skirted mesh, and fits into the pocket areas or corners of various brands and sizes of skirted meshes, which ensures that that the surgical fastener delivery window is a set distance above and away from the seam or hem of the skirted mesh. 
     In one embodiment, the cap has extensions or wing-like features that are in line with and lateral to the lower distal edge. The lower distal edge and the lateral extensions preferably allow the applicator instrument to slide more freely within the seam of the mesh and distribute forces over a broader area of mesh when a physician is applying forward forces on the handle of the applicator instrument and counter pressure on opposing tissue. The extensions also stabilize and orient the tip of the device to ensure straps are delivered upward into the targeted upper layer or top mesh piece of a skirted mesh implant. 
     In one embodiment, the cap has a sloped distal face that slopes upwardly and proximally from the lower distal edge to ply the top mesh piece of an open skirt mesh away from the mesh seam area. In one embodiment, the cap has a bottom surface that is abutted against a bottom mesh piece of the open skirt mesh. 
     The cap is desirably affixed to the distal end of the shaft so that it does not rotate or translate relative to the shaft. In one embodiment the proximal end of the cap transitions into a cylindrical shape that matches the outer diameter (e.g. 8 mm OD) of the shaft. 
     The contoured, atraumatic cap has no sharp edges at the distal end of the shaft. Thus, a physician may slide the cap along the inside of the seam of an open skirt mesh when positioning or repositioning the device for initial and subsequent surgical fastener deployment, and the cap will not catch on meshes of varying pore size. 
     In one embodiment, the handle and the trigger or actuation portion of the applicator instrument is re-positioned above the housing or main body of the device. This configuration places the trigger of the applicator instrument in a position that provides multiple advantages to the user. First, the handle is located in a position that is ergonomically acceptable and allows the user&#39;s elbow to be in a neutral position when ready to fire. In one embodiment, the handle is angled forward toward the distal end of the applicator instrument to facilitate a neutral position for the user&#39;s wrist, as well. The position of the handle above the main body portion of the applicator instrument enables the device to clear the body of the patient, which is preferable in open abdominal procedures. 
     In one embodiment, the combination of a non-linear shaft (e.g., upwardly curved) and a forward angulation of the handle complement each other to facilitate the delivery of surgical fasteners upward in the intended direction of fixation. In one embodiment, the applicator instrument has a counter/indicator that shows how many surgical fasteners have been fired or remain in the applicator instrument. The counter/indicator is preferably positioned at the top of the handle to provide easy visibility when the handle is in the upright and ready to fire position. Coupled with a lockout mechanism, the counter/indicator also indicates when the straps are running out and when the instrument is empty. 
     In one embodiment, the trigger has a linear motion that enables the actuation of the device to feel secure and stable in a surgeon&#39;s hand. The orientation of the trigger and the location of the counter/indicator suggests the proper orientation or intended use of the device. In one embodiment, the trigger has an index finger groove on the surface of the trigger that further suggests the proper orientation of the device. 
     The linear motion of the trigger provides consistency regarding the force and distance required to squeeze the trigger no matter where up or down the length of the trigger that the finger forces are concentrated. 
     In one embodiment, an upright handle orientation is required for correctly orienting the surgical fasteners with the position of the hernia mesh against the abdominal wall. The geometry of the tip&#39;s sloped face also preferably ensures that when the device is oriented correctly, a surgical fastener may be delivered in the correct orientation relative to the mesh and the abdominal wall tissue, and positioned a preferred distance away from the seam of the skirted mesh. 
     In one embodiment, the trigger moves along a linear path, which facilitates a unique rack and pinion type linkage to translate motion to the firing system located in the housing of the applicator instrument. In one embodiment, the firing system includes a stored energy system used to apply energy to dispense a surgical fastener. The firing system has a compression spring, also referred to herein as a firing spring, disposed within a box-like component, a linkage coupled with the trigger for compressing the firing spring for storing energy in the firing spring, and a firing spring release for releasing the compressed spring at a predetermined load and timed interval relative to the trigger position. 
     In one embodiment, the trigger is supported internally by a pair of rotating members. The trigger preferably has only two rotation point contacts so that the potential risks of binding are eliminated. The rotating members are coupled to each other with a gear system, which ensures that the two members will rotate at the same rate. In addition, a torsional return spring may be connected between the rotating members to ensure that after actuation of the trigger, the trigger and the firing system are returned to an initial stage of a firing cycle and the lowest energy state. The configuration of the trigger return spring and its position relative to the trigger may allow for a low, near-uniform trigger return force (pre-load and travel force of the trigger alone to the operator&#39;s hand), which is an improvement over the high trigger forces required in earlier applicator instruments. An alternative embodiment may include a torsional spring that acts directly onto the trigger. The torsional spring provides a moment that effectively counteracts any moment applied by the user during device actuation. 
     In one embodiment, an applicator instrument for dispensing surgical fasteners includes a housing defining a bottom of the applicator instrument, a firing system disposed in the housing and being moveable in distal and proximal directions along a first axis, and a handle extending upwardly from the housing along a second axis that defines an acute angle with the first axis, the handle having an upper end that defines a top of the applicator instrument. In one embodiment, the handle is located at a proximal end of the applicator instrument and is angled to lean toward a distal end of the applicator instrument. The applicator instrument preferably includes a trigger mounted on the handle for actuating the firing system. 
     The applicator instrument preferably has an elongated shaft extending from the housing. In one embodiment, a plurality of surgical fasteners is loaded into the elongated shaft for being dispensed from the distal end of the elongated shaft when the trigger is pulled. The elongated shaft desirably has a proximal section that extends along the first axis and a distal section that is oriented at an angle relative to the proximal section for extending upwardly toward the top of the applicator instrument. In one embodiment, the shaft has a curve between the proximal shaft section and the distal shaft section. 
     In one embodiment, an imaging device is preferably coupled with or mounted on the applicator instrument for detecting images at a distal end of the elongated shaft. The imaging device may include cameras such as film, digital, or video cameras, photo sensors, and/or ultrasound sensors. 
     In one embodiment, at least one light source, such as a light emitting diode, may be coupled with the applicator instrument for illuminating a field of view for the imaging device at the distal end of the elongated shaft. The at least one light source may include one or more light emitting diodes, fiber optic cables, and/or surgical lights. 
     In one embodiment, a cap is secured to the distal end of the elongated shaft and the imaging device and/or the light source is located on the cap. In one embodiment, the cap has a distal end face that slopes upwardly and proximally from the lower distal edge and includes a surgical fastener delivery window formed in the distal end face for dispensing surgical fasteners. In one embodiment, the imaging device and/or the light source are located on the distal end face. The imaging device and/or the light source may be located between the surgical fastener delivery window and an upper end of the distal end face of the cap. In one embodiment, the cap includes a centrally located imaging device, a first light source located on a first lateral side of the imaging device, and a second light source located on a second lateral side of the imaging device. 
     In one embodiment, the imaging device and the light source are part of an imaging system that is coupled with the applicator instrument. In one embodiment, the imaging system includes the imaging device, the light source, and a power source for providing power for the light source, a power conduit for transferring power from the power source to the light source, an image conduit for transmitting images detected by the imaging device, and a monitor for displaying the detected images. 
     In one embodiment, the power conduit includes a conductive wire having a proximal end connected with the power source and a distal end connected with the light source. In one embodiment, the power source is located on the handle and the conductive wire of the power conduit extends through the elongated shaft. In one embodiment, the image conduit may be a conductive wire, a fiber optic cable, or a wireless transmitter for transmitting the detected images to the monitor. 
     In one embodiment, an applicator instrument for dispensing surgical fasteners includes a housing defining a bottom of the applicator instrument, a firing system disposed in the housing and being moveable in distal and proximal directions along a first axis, and a handle extending upwardly from the housing along a second axis that defines an acute angle with the first axis, the handle having an upper end that defines a top of the applicator instrument. The applicator instrument preferably includes a trigger mounted on the handle for actuating the firing system, and an elongated shaft extending from the housing. The elongated shaft is desirably non-linear and has a distal section that extends upwardly toward the top of the applicator instrument. 
     In one embodiment, an imaging device is preferably coupled with the applicator instrument for detecting images at a distal end of the elongated shaft. In one embodiment, a light source is coupled with the applicator instrument for illuminating a field of view for the imaging device at the distal end of the elongated shaft. The light source may be light emitting diodes, fiber optic cables, or surgical lights. 
     In one embodiment, the imaging device and the light source are integrated into an imaging system. The imaging system may be integrated into the applicator instrument or may be a stand-alone system that is attachable to the applicator instrument. In one embodiment, the imaging system includes a power source for providing power for the light source, a power conduit for transferring power from the power source to the light source, an image conduit for transmitting images detected by the imaging device, and a monitor for displaying the detected images. 
     In one embodiment, the power conduit includes a conductive wire having a proximal end connected with the power source and a distal end connected with the light source. The power source may be disposed on the handle, whereby the conductive wire extends through the elongated shaft. 
     In one embodiment, the image conduit may be a conductive wire, a fiber optic cable, and a wireless transmitter for transmitting the detected images to the monitor. The imaging device may be a camera, a photo sensor or an ultrasound sensor. 
     In one embodiment, the lower distal edge of the cap includes a center section that spans the outer diameter at the distal end of the elongated shaft and first and second extensions that extend laterally from the center section and beyond the outer diameter of the elongated shaft. The first and second lateral extensions desirably have convexly curved bottom surfaces that extend laterally from the bottom surface of the cap. In one embodiment, the proximal end of the cap has an outer diameter that matches and conforms to the outer diameter of the distal end of the elongated shaft. 
     In one embodiment, the non-linear elongated shaft includes a proximal section that extends along the first axis and the distal section that is oriented at an angle relative to the proximal section for extending upwardly toward the top of the applicator instrument. In one embodiment, the non-linear elongated shaft is curved so that the distal section of the elongated shaft slopes upwardly toward the top of the applicator instrument. 
     In one embodiment, the imaging device and the light source are incorporated into an endoscopic instrument that is releasably attached to the elongated shaft of the applicator instrument. The endoscopic instrument may be part of an imaging system. The endoscopic instrument may have a shaft that is flexible for conforming to the shape of the non-linear elongated shaft of the applicator instrument. In one embodiment, the endoscopic instrument has a permanent non-linear configuration that matches the non-linear configuration of the elongated outer shaft of the applicator instrument. 
     In one embodiment, an applicator instrument for dispensing surgical fasteners includes a housing defining a bottom of the applicator instrument, a firing system disposed in the housing and being moveable in distal and proximal directions along a first axis, a handle extending upwardly from the housing along a second axis that defines an acute angle with the first axis, the handle having an upper end that defines a top of the applicator instrument, and a trigger mounted on the handle for actuating the firing system. The applicator instrument preferably has an elongated shaft extending from the housing, the elongated shaft being non-linear and having a distal section that extends upwardly toward the top of the applicator instrument, a cap secured to a distal end of the elongated shaft, whereby the cap has a lower distal edge that extends laterally beyond an outer diameter of the elongated shaft, an imaging device attached to the applicator instrument for detecting images at a distal end of the applicator instrument, and a light source attached to the applicator instrument for illuminating a field of view for the imaging device at the distal end of the applicator instrument. The imaging device and the light source may be mounted on the cap. 
     In one embodiment, an applicator instrument for dispensing surgical fasteners desirably includes a housing, a shaft having an outer diameter extending distally from the housing, and a cap secured to the distal end of the shaft. The cap preferably has a lower distal edge that extends laterally beyond the outer diameter of the elongated shaft and has a length that is greater than the outer diameter of the elongated shaft. In one embodiment, the cap desirably has a distal end face that slopes upwardly and proximally from the lower distal edge, whereby the cap preferably includes a surgical fastener delivery window formed in the distal end face for dispensing surgical fasteners. In one embodiment, the applicator instrument preferably includes an imaging system with an imaging device for detecting images at a distal end of the shaft and a light source for illuminating a field of view for the imaging device at the distal end of the shaft. The imaging device and/or the light source may be integrated into the cap. 
     In one embodiment, the applicator instrument includes a linkage coupling the trigger with the handle and the firing system. In one embodiment, the linkage preferably constrains movement of the trigger to a linear path that extends along a third axis that defines an acute angle with the first axis and that is perpendicular to the second axis of the handle. 
     In one embodiment, the trigger is moveable along a linear path that extends along the third axis for moving toward the proximal end of the applicator instrument for activating the linkage, which, in turn, moves the firing system along the first axis toward the distal end of the applicator instrument. 
     In one embodiment, the applicator instrument desirably includes a guide member disposed inside the elongated shaft and extending along the length of the elongated shaft. The guide member may be angled or curved. In one embodiment, the guide member is curved and has a curved conduit that extends along the length of the guide member. The curved conduit may include an advancing channel for advancing the surgical fasteners toward the distal end of the elongated shaft, and a firing channel for dispensing the surgical fasteners one at a time from the distal end of the elongated shaft. 
     In one embodiment, the applicator instrument preferably includes an advancer element disposed in the advancer element channel and being moveable in distal and proximal directions for advancing the surgical fasteners toward the distal end of the elongated shaft, and an anti-backup member disposed in the advancer element channel and opposing the advancer element for preventing the surgical fasteners from moving toward the proximal end of the elongated shaft. 
     In one embodiment, a firing rod is disposed in the firing channel and is moveable between a retracted position and an extended position for dispensing a lead surgical fastener from the distal end of the elongated shaft. A distal-most end of the anti-backup member desirably includes a staging leaf that receives a leading one of the surgical fasteners from the advancer element and transfers the leading one of the surgical fasteners from the advancer element channel to the firing channel for being aligned with the firing rod. The applicator instrument desirably has a wire staging spring attached to the guide member and having a distal end that contacts the staging leaf for applying a spring force for urging the staging leaf into alignment with the firing channel. 
     In one embodiment, the guide member desirably includes a window formed in an outer wall thereof that is in alignment with the staging leaf. The distal end of the wire staging spring preferably passes through the window for engaging the staging leaf. 
     In one embodiment, the advancer element and the anti-backup member are flat, elongated metal stampings with tabs extending therefrom that project toward the distal end of the elongated shaft. In one embodiment, the tabs on the anti-backup member extend toward the advancer element, and the tabs on the advancer element extend toward the anti-backup member. 
     In one embodiment, the linkage may also include a first rotating link having upper gear teeth and lower gear teeth, the first rotating link being disposed inside an upper portion of the trigger, and a first pivot pivotally securing the first rotating link to the upper portion of the trigger. The linkage may also include a second rotating link having upper gear teeth and lower gear teeth, the second rotating link being disposed inside a lower portion of the trigger, and a second pivot pivotally securing the second rotating link to the lower portion of the trigger. The lower gear teeth of the first rotating link preferably mesh with the upper gear teeth of the second rotating link so that when the trigger is squeezed the first and second rotating links rotate at the same rate. 
     In one embodiment, the applicator instrument desirably includes a first rack located near the upper end of the handle for meshing with the upper gear teeth of the first rotating link and a second rack located near an upper end of the housing of the applicator instrument for meshing with the lower gear teeth of the second rotating link. 
     In one embodiment, a first elongated slot is formed in an upper section of the handle for receiving the first pivot. The first elongated slot desirably extends along a fourth axis that is parallel to the third axis, and first pivot is moveable in proximal and distal directions within the first elongated slot. In one embodiment, a second elongated slot is formed in a lower section of the handle for receiving the second pivot. The second elongated slot preferably extends along a fifth axis that is parallel to both the third axis and the fourth axis, and the second pivot is moveable in proximal and distal directions within the second elongated slot. In one embodiment, when the trigger is squeezed, the first and second pivots desirably move simultaneously through the respective first and second elongated slots and toward the proximal end of the applicator instrument. The first and second elongated slots ensure that the two rotating links rotate at the same rate and may be used instead of the gear teeth and the racks described in the previous embodiment. 
     In one embodiment, the applicator instrument desirably includes a trigger rack connected with a lower end of the trigger for moving simultaneously with the trigger in distal and proximal directions along the third axis, and a drive gear having a first set of gear teeth that mesh with the trigger rack and a second set of gear teeth that mesh with teeth on a sliding yoke that slides in distal and proximal directions along the first axis. The trigger rack is separate from the trigger component, allowing for some amount of play and rotation between the two components. Further, as a separate component, the trigger rack can be made of a stronger material and in a more economical manner. 
     In one embodiment, when the trigger is squeezed and moves proximally, the drive gear moves the firing system distally. In one embodiment, when the trigger moves distally, the drive gear desirably moves the firing system proximally. 
     In one embodiment, the applicator instrument preferably includes a counter located at an upper end of the handle for indicating the number of surgical fasteners dispensed from and/or remaining in the applicator instrument. In one embodiment, the counter desirably includes a counter window formed at the upper end of the handle, a rotatable disc visible through the counter window, a rotatable gear connected with the rotatable disc and having teeth extending below the rotatable disc, and a lockout counter pivotally secured to the handle for toggling between a forward position and a rear position. The lockout counter preferably has a first tooth that engages the rotatable gear teeth when in the forward position and a second tooth that engages the rotatable gear teeth when in the rear position. The counter preferably includes a lockout counter spring in contact with the lockout counter for normally urging the lockout counter into the forward position. In one embodiment, when the trigger is fully squeezed, the first rotating link contacts the lockout counter for overcoming the force of the lockout counter spring for toggling the lockout counter into the rear position, whereby the first and second teeth of the lockout counter engage the teeth of the rotatable gear for rotating the rotatable disc. The spring member on the lockout counter allows for additional over travel of the rotating link after the counter completes its counting cycle. 
     In one embodiment, an applicator instrument for dispensing surgical fasteners desirably includes a housing defining a bottom of the applicator instrument, a firing system disposed in the housing and being moveable in distal and proximal directions, and a handle extending upwardly from the housing and being angled toward a distal end of the applicator instrument, the handle having an upper end that defines a top of the applicator instrument. The applicator instrument desirably includes a shaft extending distally from the housing near the bottom of the applicator instrument, the shaft having a proximal section that extends along a longitudinal axis of the applicator instrument and a distal section that is oriented at an angle relative to the proximal section for extending upwardly toward the top of the applicator instrument. A plurality of surgical fasteners is preferably loaded in series into the shaft, and a cap is secured to the distal end of the shaft, the cap having a lower distal edge and a distal face that slopes upwardly and proximally from the lower distal edge. The cap preferably includes a delivery window formed in the distal face, the delivery window having a lower end that is spaced from the lower distal edge. A trigger is desirably mounted on the handle for actuating the firing system for dispensing the surgical fasteners through the delivery window. 
     In one embodiment, the applicator instrument preferably includes a guide member disposed inside the shaft and extending along the length of the shaft, the guide member having a curved conduit that extends along the length of the guide member. The curved conduit desirably includes an advancing channel for advancing the surgical fasteners toward the distal end of the shaft, and a firing channel for dispensing the surgical fasteners through the dispensing window of the cap. An advancer element is preferably disposed in the advancer element channel and is moveable in distal and proximal directions for advancing the surgical fasteners toward the distal end of the shaft, and a stationary anti-backup member is preferably disposed in the advancer element channel and opposes the advancer element for preventing the surgical fasteners from moving toward the proximal end of the shaft. 
     In one embodiment, a firing rod is disposed in the firing channel and is moveable between a retracted position and an extended position for dispensing the surgical fasteners from the distal end of the shaft. The stationary anti-backup member preferably has a staging leaf at a distal end thereof that receives a leading one of the surgical fasteners from the advancer element and transfers the leading one of the surgical fasteners from the advancer element channel to the firing channel for being aligned with the firing rod. In one embodiment, a wire staging spring is attached to the guide member and has a distal end that contacts the staging leaf for urging the staging leaf into alignment with the firing channel. 
     In one embodiment, an applicator instrument for dispensing surgical fasteners includes a housing, a firing system disposed in the housing, an actuator coupled with the housing for actuating the firing system, an elongated shaft extending from the housing, the elongated shaft having an outer diameter, and a cap secured to the distal end of the elongated shaft, whereby the cap has a lower distal edge that extends laterally beyond the outer diameter of the elongated shaft. 
     In one embodiment, the housing defines a bottom of the applicator instrument. The applicator instrument preferably has a handle extending upwardly from the housing and that is angled or leans toward the distal end of the elongated shaft. In one embodiment, the handle has an upper end that defines a top of the applicator instrument. The actuator may be a trigger that is mounted onto the handle. 
     The firing system is desirably disposed in the housing and is moveable in distal and proximal directions along the first axis. The handle preferably extends along a second axis that defines an acute angle with the first axis of about 70-80° and more preferably about 75°. 
     In one embodiment, the lower distal edge of the cap desirably has a length that is greater than the outer diameter of the elongated shaft. In one embodiment, the cap has a distal end face that slopes upwardly and proximally from the lower distal edge. 
     In one embodiment, the cap preferably has a surgical fastener delivery window formed in the distal end face for dispensing surgical fasteners. The delivery window desirably has a lower end that is spaced from the lower distal edge. In one embodiment, the cap has a bottom surface, and the lower distal edge of the cap has a thickness extending between the bottom surface of the cap and the lower end of the delivery window. 
     In one embodiment, the proximal end of the cap has an outer diameter of about 6-12 mm and more preferably about 8 mm that matches and conforms to the outer diameter of the elongated shaft. 
     In one embodiment, the elongated shaft is mounted to the housing and extends distally from the housing. In one embodiment, the elongated shaft has a proximal section that extends along a first axis and a distal section that is oriented at an angle relative to the proximal section for extending upwardly toward the top of the applicator instrument. In one embodiment, the elongated shaft has a curve located between the proximal shaft section and the distal shaft section. 
     These and other preferred embodiments of the present invention will be described in more detail below. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    shows a left side view of an applicator instrument for dispensing surgical fasteners, in accordance with one embodiment of the present invention. 
         FIG.  2    shows a perspective view of a right side of the applicator instrument of  FIG.  1    during a surgical procedure, in accordance with one embodiment of the present invention. 
         FIG.  3    shows a perspective view of a surgical fastener dispensed from the applicator instrument shown in  FIGS.  1  and  2   , in accordance with one embodiment of the present invention. 
         FIG.  4 A  shows a right side elevation view of a proximal end of an applicator instrument used for dispensing surgical fasteners with a right half of a handle removed for showing internal components, in accordance with one embodiment of the present invention. 
         FIG.  4 B  shows the proximal end of the applicator instrument of  FIG.  4 A  with a trigger and a two-step drive gear being transparent, in accordance with one embodiment of the present invention. 
         FIG.  4 C  shows a perspective view of the proximal end of the applicator instrument shown in  FIG.  4 A . 
         FIGS.  5 A- 5 C  show a counter for counting how many surgical fasteners have been dispensed from an applicator instrument for dispensing surgical fasteners, in accordance with one embodiment of the present invention. 
         FIG.  6 A  shows an applicator instrument during a first stage of a firing cycle, in accordance with one embodiment of the present invention. 
         FIG.  6 B  shows an applicator during a second stage of a firing cycle, in accordance with one embodiment of the present invention. 
         FIG.  6 C  shows an applicator during a third stage of a firing cycle, in accordance with one embodiment of the present invention. 
         FIG.  6 D  shows an applicator during a fourth stage of a firing cycle, in accordance with one embodiment of the present invention. 
         FIG.  6 E  shows an applicator during a fifth stage of a firing cycle, in accordance with one embodiment of the present invention. 
         FIG.  6 A- 1    shows the counter of  FIGS.  5 A- 5 C  during the first stage of the firing cycle shown in  FIG.  6 A . 
         FIG.  6 B- 1    shows the counter during the second stage of the firing cycle shown in  FIG.  6 B  during which a rotating link has begun to contact a counter. 
         FIG.  6 C- 1    shows the counter during the third stage of the firing cycle shown in  FIG.  6 C  during which the counter has begun to deflect a dwell beam of the counter. 
         FIG.  6 D- 1    shows the counter during the fourth stage of the firing cycle shown in  FIG.  6 D  during which the counter has pivoted to a rear position. 
         FIG.  6 E- 1    shows the counter during the fifth stage of the firing cycle shown in  FIG.  6 E  during which the dwell beam of the counter is deflected further by a rotating link. 
         FIGS.  7 A- 7 C  show the movement of the counter of  FIGS.  5 A- 5 C  during delivery of the last surgical fastener, in accordance with one embodiment of the present invention. 
         FIG.  8    shows a side elevation view of an advancer element that cycles back and forth for advancing surgical fasteners toward a distal end of an applicator instrument and an anti-backup member for preventing the surgical fasteners from moving proximally, in accordance with one embodiment of the present invention. 
         FIG.  9    shows a cross-sectional view of an elongated shaft of an applicator instrument including the advancer element and the anti-backup member shown in  FIG.  8   , in accordance with one embodiment of the present invention. 
         FIG.  10 A  shows a cross-sectional view of a distal end of a right guide member disposed inside a shaft of an applicator instrument including the advancer element and the anti-backup member shown in  FIG.  8   , in accordance with one embodiment of the present invention. 
         FIG.  10 B  shows the right guide member of  FIG.  10 A  with a wire staging spring secured to the guide member, in accordance with one embodiment of the present invention. 
         FIG.  11 A  shows a distal end of an applicator instrument including a left guide member, a wire staging spring and a cap having a surgical fastener dispensing window, in accordance with one embodiment of the present invention. 
         FIG.  11 B  shows a bottom view of  FIG.  11 A . 
         FIGS.  12 A- 12 E  show a method of aligning a lead surgical fastener with an insertion fork at a distal end of a firing rod, in accordance with one embodiment of the present invention. 
         FIG.  13 A  shows a perspective view of a cap secured to a distal end of an elongated shaft of an applicator instrument, in accordance with one embodiment of the present invention. 
         FIG.  13 B  shows a bottom plan view of  FIG.  13 A . 
         FIG.  13 C  shows a cross-sectional view of the cap shown in  FIG.  13 A . 
         FIG.  14 A  shows a top view of an open skirt mesh having a distal end of an applicator instrument inserted into a central opening of the open skirt mesh, in accordance with one embodiment of the present invention. 
         FIG.  14 B  shows a magnified cross-sectional view of  FIG.  14 A . 
         FIG.  14 C  shows a view of a stage of an open hernia repair procedure with an open skirt mesh inserted into a surgical opening and an applicator instrument used for mesh fixation, in accordance with one embodiment of the present invention. 
         FIG.  15 A  shows a left side view of an applicator instrument having an elongated shaft and a cap secured to a distal end of the elongated shaft, in accordance with one embodiment of the present invention. 
         FIG.  15 B  shows a perspective view of the cap shown in  FIG.  15 A . 
         FIG.  15 C  shows a top perspective view of the cap shown in  FIG.  15 B . 
         FIG.  16    shows the cap at the distal end of the applicator instrument of  FIGS.  15 A- 15 C  inserted between top and bottom mesh pieces of an open skirt mesh, in accordance with one embodiment of the present invention. 
         FIG.  17    shows an applicator instrument having an elongated shaft that is rotatable, in accordance with one embodiment of the present invention. 
         FIGS.  18 A- 18 C  show an edge adapter cap with a living hinge that is securable to a distal end of an elongated shaft of an applicator instrument, in accordance with one embodiment of the present invention. 
         FIG.  19    shows a side view of a distal end of an applicator instrument for dispensing surgical fasteners including a curved outer shaft and a shaft rotating element for changing the orientation of a distal end of the curved outer shaft relative to a proximal end of the curved outer shaft, in accordance with one embodiment of the present invention. 
         FIG.  20    shows a cross-sectional view of the distal end of the applicator instrument including the curved outer shaft shown in  FIG.  19   . 
         FIG.  21    shows a perspective view of a distal end of an applicator instrument for dispensing surgical fasteners including an articulating element and an outer shaft rotating element for changing the orientation of the distal end of the outer shaft relative to a proximal end of the outer shaft, in accordance with one embodiment of the present invention. 
         FIG.  22    shows a cross-sectional view of the outer shaft shown in  FIG.  21   . 
         FIG.  23    shows an applicator instrument for dispensing surgical fasteners, the applicator instrument having an object imaging system, in accordance with one embodiment of the present invention. 
         FIG.  24    shows an elongated shaft for the applicator instrument of  FIG.  23    with an imaging device located at a distal end of the elongated shaft, in accordance with one embodiment of the present invention. 
         FIG.  25 A  shows a front perspective view of a cap secured to a distal end of an elongated shaft of an applicator instrument, the cap including an imaging device and light sources, in accordance with one embodiment of the present invention. 
         FIG.  25 B  shows a front view of the cap shown in  FIG.  25 A . 
         FIG.  25 C  shows a left side view of the cap shown in  FIG.  25 A . 
         FIG.  25 D  shows a top plan view of the cap shown in  FIG.  25 A . 
         FIG.  25 E  shows a cross-sectional view of the cap shown in  FIG.  25 D  taken along line  25 E- 25 E of  FIG.  25 D . 
         FIG.  26    shows a schematic diagram of an imaging system for the applicator instrument, in accordance with one embodiment of the present invention. 
         FIG.  27    shows a side elevation view of an applicator instrument for dispensing surgical fasteners and an endoscopic instrument having an imaging device that is attachable to the applicator instrument, in accordance with one embodiment of the present invention. 
         FIG.  28 A  shows a distal end of the endoscopic instrument shown in  FIG.  27   , in accordance with one embodiment of the present invention. 
         FIG.  28 B  shows a schematic view of a distal end of the endoscopic instrument shown in  FIG.  28 A . 
         FIG.  29    shows a clip for attaching an endoscopic instrument having an imaging device to an applicator instrument, in accordance with one embodiment of the present invention. 
         FIG.  30 A  shows a side elevation view of an applicator instrument having an endoscopic instrument with an imaging device attached to the applicator instrument, in accordance with one embodiment of the present invention. 
         FIG.  30 B  shows a rear perspective view of the applicator instrument and the endoscopic instrument shown in  FIG.  30 A . 
         FIG.  30 C  shows a front perspective view of the applicator instrument and the endoscopic instrument shown in  FIGS.  30 A and  30 B . 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIG.  1   , in one embodiment, an applicator instrument  30  for dispensing surgical fasteners has a proximal end  32 , a distal end  34 , and a longitudinal axis A 1 -A 1  that extends between the proximal and distal ends. The applicator instrument  30  desirably includes a housing  35 , a handle  36  extending upwardly from the housing, a trigger  38  mounted on the handle, and an elongated shaft  40  that extends distally from the housing  35 . The elongated shaft  40  includes a first section  42  that extends along the longitudinal axis A 1 -A 1  of the applicator instrument, and a second section  44  that is angled or curved relative to the first section  42 . 
     In one embodiment, a cap  46  is secured to the distal end of the elongated shaft  40 . The cap  46  preferably has a distal face  48  that slopes away from a lower distal edge of the cap and toward the proximal end  32  of the applicator instrument  30 . 
     In one embodiment, the handle  36  includes an upper end  50  containing a counter  52  that indicates how many surgical fasteners have been dispensed and/or how many surgical fasteners remain loaded in the applicator instrument. In one embodiment, the counter  52  locks the applicator instrument from further use when the last surgical fastener has been dispensed. In one embodiment, the counter  52  is visible at the upper end  50  of the handle  36  to provide a visual indicator of how many of the surgical fasteners have been dispensed. The upper end of the handle defines the top of the applicator instrument  30 . The housing  35  has a lower end  54  that defines the bottom of the applicator instrument  30 . 
     In one embodiment, the handle  36  preferably leans toward the distal end  34  of the applicator instrument  30  to provide improved ergonomics for a surgeon so that the surgeon may maintain his/her elbow and wrist in a neutral position. In one embodiment, the handle  36  preferably extends along a longitudinal axis A 2 -A 2  that defines an acute angle αl with the longitudinal axis A 1 -A 1  of the applicator instrument. In one embodiment, the angle αl is about 70-80° and more preferably about 75°. During a surgical procedure, the lower end  54  of the housing  35  preferably faces toward a patient and the upper end  50  of the handle  36  preferably faces away from the patient. 
     Referring to  FIG.  2   , in one embodiment, the applicator instrument  30  shown in  FIG.  1    may be used for dispensing surgical fasteners during a surgical procedure such as an open hernia repair procedure. In one embodiment, the applicator instrument  30  has a plurality of surgical fasteners that are pre-loaded in the shaft  40  for being dispensed when the trigger  38  is squeezed. In one embodiment, a single surgical fastener is dispensed each time the trigger  38  is squeezed. In one embodiment, the applicator instrument  30  is used for dispensing surgical fasteners for the fixation of a mesh, such as a surgical mesh, to the soft tissue of a patient. 
     In  FIG.  2   , the angled second section  44  of the shaft  40  has been inserted into a surgical opening. The lower end  54  of the housing  35  faces toward the patient and the upper end  50  of the handle  36  faces away from the patient. A surgeon may grasp the handle  36  and squeeze the trigger  38  for dispensing a surgical fastener from the distal end of the shaft  40 . In one embodiment, the surgeon pulls the trigger  38  proximally (i.e. toward the proximal end  32  of the applicator instrument) for dispensing the surgical fasteners. The surgeon preferably applies counter pressure on the patient&#39;s tissue that opposes the distal end of the applicator instrument. In one embodiment, a single surgical fastener is dispensed each time the surgeon pulls the trigger  38  proximally, and the system finishes the firing cycle when the trigger is released for allowing the trigger to return distally. 
     The second section  44  of the shaft  40  that is curved and/or angled relative to the first section  42  of the shaft preferably facilitates the accurate placement of surgical fasteners into soft tissue. In one embodiment, the applicator instrument  30  is used during an open surgical repair procedure for addressing ventral hernias. The distal-most end of the curved shaft  40  is inserted into a pocket of an open skirt mesh having a top mesh piece and a bottom mesh piece that are joined together at a peripheral seam, whereupon surgical fasteners are dispensed from the distal end of the applicator instrument for fixing the top mesh piece to soft tissue. 
     In one embodiment, the handle  36  and the trigger  38  are positioned above the housing  35  of the applicator instrument. This configuration places the trigger  38  in a position that provides multiple advantages to a surgeon. First, the handle  36  is located in a position that allows a surgeon&#39;s elbow to be in a neutral position. The handle  36  is also angled forward toward the distal end  34  of the applicator instrument  30  to facilitate a neutral position for the surgeon&#39;s wrist. In addition, the position of the handle  36  above the housing  35  of the applicator instrument  30  allows the bottom end  52  of the housing  35  to clear the body of the patient, which is particularly preferable for open abdominal procedures. 
     In one embodiment, the combination of an upward curvature of the shaft  40  and the forward angulation or lean of the handle  36  toward the distal end  34  of the applicator instrument complement each other to facilitate the delivery of surgical fasteners along an upward trajectory in the intended direction of fixation. 
     In one embodiment, the applicator instrument  30  is a multi-fire device including a plurality of surgical fasteners stored therein as disclosed in commonly assigned U.S. Patent Application Publication Nos. US 2010/0292715; US 2010/0292712; US 2010/0292710; US 2010/0292713; and US 2011/079627, the disclosures of which are hereby incorporated by reference herein. In one embodiment, the applicator instrument includes a plurality of surgical fasteners stored in series along the length of the shaft  40 . The shaft  40  preferably includes a pair of flat stampings having tabbed features incorporated therein. One of the flat stampings is stationary for preventing the surgical fasteners from moving proximally within the shaft  40 . The other flat stamping cycles in distal and proximal directions each time the trigger  38  is squeezed and then released to facilitate incremental advancement of the surgical fasteners along the length of the shaft  40 . The flat nature of the stampings provides the stampings with flexibility so that the stampings may curve to conform to the curvature of the shaft while guiding the surgical fasteners along the curved path defined by the shaft  40 . 
     In one embodiment, the applicator instrument includes a molded guide component that defines the curved path of travel for the surgical fasteners. The flat stampings are placed inside the molded guide component. The molded guide component preferably provides minimal friction and distortion upon the surgical fasteners, the advancer element and the anti-backup member as the surgical fasteners move distally through the shaft  40 . In one embodiment, the guide component is made of molded plastic and includes two halves that are assembled together for being contained within a conduit extending through the elongated shaft  40 . 
     Referring to  FIG.  3   , in one embodiment, a plurality of surgical fasteners are pre-loaded into the shaft of the applicator instrument  30  shown in  FIGS.  1  and  2   . A single surgical fastener  60  includes a proximal end  62  and a distal end  64  having a pair of tapered ends  66 ,  68  that are spaced from one another for capturing mesh fibers between the tapered ends. In one embodiment, the surgical fastener  60  has one or more of the features disclosed in commonly assigned U.S. Patent Application Publication Nos. US 2010/0292715, US 2010/0292712, US 2010/0292710, US 2010/0292713, and US 2011/079627, the disclosures of which are hereby incorporated by reference herein. 
     Referring to  FIGS.  4 A and  4 B , in one embodiment, the applicator instrument  30  includes the housing  35  that contains a firing system, and a handle  36  projecting upwardly from the housing, whereby the handle has an upper end  50  that contains the counter  52 . The handle includes the trigger  38  that is adapted to be pulled along a linear path toward the proximal end  32  of the applicator instrument  30 . In one embodiment, the trigger  38  is adapted to move along a linear path A 3 -A 3  that defines an angle α 2  of about 10-20° and more preferably about 15° with the longitudinal axis A 1 -A 1  of the applicator instrument  30 . 
     In one embodiment, the applicator instrument  30  includes a firing system  70  having a spring block  72 , a firing rod  74 , and a firing spring that stores energy as the trigger  38  is squeezed. The firing system  70  preferably includes one or more features similar to those disclosed in commonly assigned U.S. Patent Application Publication Nos. US 2010/0292715, US 2010/0292712, US 2010/0292710, US 2010/0292713, and US 2011/079627, the disclosures of which are hereby incorporated by reference herein. The firing system  70  is desirably coupled with the trigger via a trigger rack  76  that slides proximally and distally with the trigger along the axis A 3 -A 3 . The trigger rack is coupled with a drive gear  78  that rotates in a counter-clockwise direction when the trigger  38  is squeezed toward the proximal end of the applicator instrument, and rotates in a clockwise direction when the trigger  38  is released and moves distally toward the distal end of the applicator instrument. The drive gear  78  has external gear teeth  80  that mesh with teeth provided at an upper end of a sliding yoke  82 . As the drive gear  78  rotates in a counter-clockwise direction, the yoke  82  slides in a distal direction along the axis A 1 -A 1 . As the drive gear  78  rotates in a clockwise direction, the yoke  82  slides in a proximal direction along the axis A 1 -A 1 , preferably with a gear ratio of 0.9 to 1.5. 
     In one embodiment, the applicator instrument  30  includes a ratchet pawl  84  having a ratchet spring, which is similar to the subassembly disclosed in commonly assigned U.S. Patent Application Publication Nos. US 2010/0292715, US 2010/0292712, US 2010/0292710, US 2010/0292713, and US 2011/079627, the disclosures of which are hereby incorporated by reference herein. The ratchet pawl  84  ensures that the sliding yoke  82  moves to its distal-most position before it is able to change direction and move proximally back into the original position shown in  FIG.  4 A . 
     In one embodiment, the applicator instrument  30  includes a trigger return spring  86  that normally urges the trigger  38  to move distally. The trigger return spring  86  includes a first arm  88  that is secured within a molded portion of the handle  36 , and a second arm  90  that preferably engages the trigger  38 . In one embodiment, a proximal end of the trigger  38  has a tab  92  and the second arm  90  engages the tab for normally urging the trigger distally. The trigger return spring  86  preferably stores energy therein as the trigger  38  is squeezed and transfers the stored energy back to the trigger when the trigger is released for moving the trigger distally. In another embodiment, the trigger return spring  86  acts directly on the rotating links  110  and  112 . 
     In one embodiment, the counter  52  includes a rotatable disc  94  having gear teeth  96 . The counter  52  includes a window  98  that is formed in the upper end  50  the handle  36  to provide visual access to a top surface of the rotatable disc  94 . The counter desirably includes a lock-out pin  100  and a lock-out pin spring (not shown) in contact with the lock-out pin. The applicator instrument desirably includes a lock-out pin cover  102  that partially covers a portion of the lock-out pin  100 . 
     In one embodiment, the counter  52  has a lock-out counter  104  that is pivotally secured to the handle  36  via a lock-out counter pivot  106 . The counter  52  also includes a lock-out counter spring  108  that normally urges the lock-out counter  104  to pivot toward the distal end of the applicator instrument  30 . The lock-out counter  104  is adapted to toggle back and forth about the pivot  106  during each firing cycle. 
       FIG.  4 B  shows the applicator instrument  30  of  FIG.  4 A  with the trigger being transparent for clearly showing a first rotating link  110  and a second rotating link  112  coupled with the trigger  38 . In one embodiment, the first rotating link  110  is disposed inside the trigger  38  and is pivotally secured to the trigger  38  via a first pivot  114 . The first rotating link  110  has an upper end  116  having upper gear teeth  118  that mesh with a rack  120  located inside the upper end of the handle  36 . The first rotating link  110  has a lower end  122  having lower gear teeth  124 . The trigger  38  includes a first internal slot  125  formed therein that is adapted to receive the first pivot  114  during assembly. Pivot  114  passes through a “snap fit” feature of the first internal slot  125  during assembly. This ensures that the two rotating links  110 ,  112  are pivotally secured. 
     The second rotating link  112  is pivotally secured to the trigger  38  via a second pivot  126 . The second rotating link  112  has an upper end  128  with upper gear teeth  130  that mesh with the lower gear teeth  124  of the first rotating link  110 . The first and second rotating links  110 ,  112  are coupled with one another via the opposing gear teeth  124 ,  130 , which ensure that the first and second rotating links  110 ,  112  rotate at the same rate. The second rotating link  112  has a lower end  132  having bottom teeth  134  that mesh with opposing teeth molded into a second rack disposed above the housing  35  (not shown). The trigger  38  includes a second molded slot  136  that receives the second pivot  126  during assembly. Pivot  114  passes through a “snap fit” feature of internal slot  136  during assembly. This ensures that the two rotating links  110 ,  112  are pivotally secured. Further, the rotating gear links  110 ,  112  have paired offset teeth  124 ,  130  to allow synchronized timing between two gears made from the same mold. 
     The configuration of the first and second rotating links  110 ,  112  within the handle  36 , and the pivotal connection of the first and second rotating links with the trigger  38  enables the trigger  38  to move along a single linear path, namely axis A 3 -A 3 . The linear motion of the trigger  38  allows the force and distance required to squeeze the trigger to remain consistent no matter where the squeezing forces are concentrated along the length of the trigger, which minimizes the likelihood of binding of the trigger. 
     Referring to  FIG.  4 C , in one embodiment, the trigger return spring  86  normally urges the trigger  38  to move distally. The trigger return spring  86  has the first arm  88  secured within a molded portion of the handle  36  and the second arm  90  that engages a tab  92  at a proximal face of the trigger  38 . As the trigger is pulled toward the proximal end  32  of the applicator instrument  30 , the tab  92  urges the second arm  90  of the trigger return spring  86  to move proximally for storing energy in the spring  86 . After the trigger  38  has been pulled to its most-proximal position for dispensing a surgical fastener, the trigger  38  may be released, whereupon the second arm  90  of the spring  86  urges the trigger  38  to move distally for returning the trigger to the original position shown in  FIG.  4 C . 
     In one embodiment, the housing  35  and the handle  36  includes left and right halves that are assembled together. In one embodiment, the handle halves are assembled together with press fit pins. In one embodiment, the trigger  38  is captured between the left and right halves of the housing and the handle. In one embodiment, the trigger  38  travels in distal and proximal directions along a linear path having a total length of about 0.9 inches. The applicator instrument preferably has physical stops at the proximal and distal ends of the linear path of travel of the trigger rack  76  that halt the proximal and distal movement of the trigger along the linear path A 3 -A 3 . In one embodiment, the left and right halves are desirably made from a polymer such as glass reinforced polycarbonate. In one embodiment, the trigger is made of a polymer material such as a glass reinforced polycarbonate. 
     In one embodiment, the housing  35  contains a firing system having the firing spring, a spring block and a firing rod, as disclosed in commonly assigned U.S. Patent Applicant Publication Nos. US2010/0292715, US2010/0292712, US2010/0292710, US2010/0292713, and US 2011/079627, the disclosures of which are hereby incorporated by reference herein. The spring block  72  and the firing rod  74  are adapted to move in distal and proximal directions along the longitudinal axis A 1 -A 1 . 
     Referring to  FIG.  4 C , in one embodiment, the trigger  38  is connected with the trigger rack  76  by means of a tab extending from the trigger  38  that protrudes between two bosses on the trigger rack  76 . In one embodiment, the tolerance of the fit between the trigger tab and the trigger rack bosses is precise and close to allow minimal free play between the trigger and the trigger rack. The existence of two separate trigger parts allows for a stronger material (e.g., metal such as stainless steel) to be used for the trigger rack  76 . In addition, the separation of the trigger tab from the trigger rack ensures that any rotational forces exerted by the user on the trigger  38  are limited to the trigger and are not exerted upon the trigger rack  76 . In one embodiment, the trigger rack  76  is captured between the left and right handle halves and is in contact with the drive gear  78 . The trigger rack  76  is adapted to slide along an axis that is parallel with the axis of movement A 3 -A 3  of the trigger  38 . In one embodiment, the trigger rack travel is limited to about 0.9 inches, with both distal and proximal stopping features being located within the left handle half. In one embodiment, the trigger rack has trigger rack gear teeth provided at an underside thereof. The drive gear  78  has two sets of gear teeth of differing radii to provide a two-step gear, and the trigger rack gear teeth engage the smaller of the gears of the drive gear  78 . 
     The rotating links  110 ,  112  pivot about the respective first and second pivots  114 ,  126  protruding into opposing through holes in the trigger  38 . The rotating links  110 ,  112  are preferably captured by and restricted in their rotational motion by features of the trigger. The rotating links are coupled to each other via paired opposing gear teeth  124 ,  130  positioned near the middle of the hand-squeezing area of the trigger  38 . In one embodiment, these matching gear teeth  124 ,  130  have a face width of approximately 0.1 inch, and a pitch diameter of about 0.875 inches. These dimensions and features allow the first and second rotating links  110 ,  112  to mirror each other during movement. The first and second rotating links  110 ,  112  also have outer gear teeth  118 ,  134 , respectively, with a face of about 0.1 inch and a pitch diameter that is about 1.042 inches. These outer gear teeth  118 ,  134  desirably mate with corresponding opposing rack gear features formed in the handle halves, one in the right handle half, and one in the left handle half. 
     The engagement and timing of the gear features for the first and second rotating links  110 ,  112  enables the trigger  38  to move in a linear fashion along the axis A 3 -A 3 , and also prevents the trigger from rotating about a center point when squeezing forces are applied unevenly along the hand-squeezing area of the trigger. The ability of the trigger mechanism to convert linear motion of the trigger into rotary motion through the drive gear  78  minimizes friction and any risk of binding. In one embodiment, the first and second rotating links  110 ,  112  are preferably made from a polymer such as a glass reinforced polycarbonate. 
     In one embodiment, the drive gear  78  desirably connects the trigger rack  76  to the yoke  82  of the firing system  70 . The yoke  82  and the firing system  70  are preferably similar to that disclosed in the firing system of commonly assigned U.S. Patent Application Publication Nos. US2010/0292715, US2010/0292712, US2010/0292710, US2010/0292713, and US 2011/079627, the disclosures of which are hereby incorporated by reference herein. The drive gear preferably transfers the motion of the trigger along axis A 3 -A 3  to the motion of the yoke along the axis A 1 -A 1 . In one embodiment, these two axes differ by about 15° such that proximal movement of the trigger  38  along axis A 3 -A 3  results in distal movement of the yoke  82  along axis A 1 -A 1 . In one embodiment, the drive gear  78  has a gear ratio that results in 0.9 inches of trigger travel producing 1.5 inches of yoke travel. In one embodiment, the two-step drive gear  78  is preferably made of a metal such stainless steel. The gear may be mounted on a metal pin for rotating about the metal pin. In one embodiment, the pin about which the drive gear  78  rotates is located and constrained between the left and right handle halves. 
     In one embodiment, the trigger return spring  86  is positioned inside the handle so that the coils of the spring  86  are captured over a post that extends between the left and right handle halves. A first arm of the trigger return spring is fixed relative to the handle halves and is captured within a pocket, preferably formed within the left handle half. A second or moving arm of the trigger return spring, desirably has an L bend at its distal end, and is biased against the trigger such that the trigger is urged toward a forward distal position. The trigger return spring  86  desirably exerts a force upon the trigger that is about two pounds pre-loaded and nine pounds under final load. In one preferred embodiment, the trigger return spring  86  provides a force of about five pounds pre-loaded and seven pounds final load. In one embodiment, the trigger return spring  86  is desirably made of metal such as stainless steel. 
     Referring to  FIGS.  5 A- 5 C , in one embodiment, the applicator instrument  30  includes the counter  52  having the rotatable disc  94  and the gear teeth  96  projecting below the rotatable disc  94 . A window  98  is formed in the upper end  50  of the handle  36  to provide visual access to the top surface of the rotatable disc  94 . The counter  52  includes a lock-out pin  100  that is adapted to drop along the axis V 1 -V 1  ( FIG.  5 A ) when a slot formed in the rotatable disc  94  has been rotated into alignment with an extension arm  101  of the lock-out pin  100 . The counter  52  also includes a lock-out pin cover  102  that extends over a portion of the lock-out pin  100 . 
     In one embodiment, the counter  52  has a lock-out counter  104  that is pivotally secured to the left handle half via a pivot point  106 . A lock-out counter spring  108  normally urges the upper end of the lock-out counter  104  to pivot toward the distal end of the applicator instrument  30 . The lock-out counter  104  toggles back and forth during a firing cycle for rotating the rotatable disc  94  one position to indicate that one surgical fastener has been fired. The rotatable disc  94  is adapted to be rotated one additional position each time another surgical fastener is dispensed. In one embodiment, the lock-out counter  104  has a flexible cantilever beam  115  that is engaged by the first rotating link  110  for toggling the lock-out counter  104  from the forward position to the rear position. 
     Referring to  FIG.  5 B , the lock-out counter  104  has a proximal tooth  120  and a distal tooth  122  that are adapted to engage the gear teeth  96  projecting below the rotatable disc  94 . In one embodiment, as the lock-out counter  104  pivots distally, the proximal tooth  122  engages the gear teeth  96  for rotating the disc  94  one half of a position in the direction indicated R 1 . In one embodiment, when the trigger  38  is fully squeezed, the trigger contacts the lock-out counter  104  for pivoting the upper end of the lock-out counter in a proximal direction so that the distal tooth  122  engages the gear  96 . When the trigger  38  is released and moves distally, the lock-out counter spring  108  pivots the upper end of the lock-out counter  104  in a distal direction so that the proximal tooth  120  engages the gear teeth  96  for rotating the disc  94  one half of a position in the direction R 1 . In one embodiment, the rotatable disc  94  is rotated one position (indicating that one surgical fastener has been fired) each time the upper end of the lock-out counter  104  pivots proximally and then distally to the initial position shown in  FIG.  5 B . In one embodiment, when the last surgical fastener has been dispensed, the lock-out pin  100  drops for locking the trigger  38  in a proximal position. 
       FIG.  5 C  shows the window  98  formed at the upper end  50  of the handle  36 . The window  98  provides visual access to the top surface of the rotatable disc  94  to provide an indication of how many surgical fasteners have been fired and/or how many surgical fasteners remain in the applicator instrument  30 . 
     In one embodiment, the counter and lock-out assembly disclosed herein is generally similar to the structure disclosed in commonly assigned U.S. Patent Application Publication Nos. US 2010/0292715, US 2010/0292712, US 2010/0292710, US 2010/0292713, and US 2011/079627, the disclosures of which are hereby incorporated by reference herein. 
     In one embodiment, the lock-out pin spring and the lock-out counter spring are desirably made of a metal such as stainless steel. The components of the counter  52  are preferably made of polymer materials such as acetal, ABS, glass reinforced acetal, or combinations thereof. 
       FIGS.  6 A and  6 A- 1    show the applicator instrument  30  including the position of the trigger  38  and the counter  52  at the beginning of a firing cycle, which is also referred to herein as the first stage of the firing cycle. In  FIG.  6 A , the second arm  90  of the trigger return spring  86  rests against the tab  92  of the trigger  38  to provide a pre-load force that biases the trigger distally. The trigger  38  is constrained to move along the linear path of axis A 3 -A 3  by the pivots  114 ,  126  and the trigger rack  76 . In turn, the trigger rack  76  is constrained from distal movement by the distal stop  77  formed in the left handle half. Referring to  FIG.  6 A- 1   , at the beginning of the firing cycle, the lock-out counter  104  of the counter  52  is pivoted distally by the lock-out counter spring  108 . The lock-out pin  100  is held up by the rotatable disc  94 . 
       FIGS.  6 B and  6 B- 1    show the applicator instrument  30  during a second stage of a firing cycle. The trigger  38  has been partially squeezed so that the trigger  38  and the trigger rack  76  have moved proximally about 0.486 inches from the start position shown in  FIGS.  6 A and  6 A- 1   . The first rotating link  110  has made initial contact with the dwell beam  115  of the lock-out counter  104 . The second arm  90  of the trigger return spring  86  has flexed proximally for increasing the spring force against the trigger  38 . The proximal movement of the trigger rack  76  along axis A 3 -A 3  rotates the drive gear  78  in a counter-clockwise direction, which, in turn, advances the yoke  82  distally along the axis A 1 -A 1  for advancing the firing rod and storing energy in the firing spring of the firing system, as disclosed in commonly assigned U.S. Patent Application Publication Nos. US 2010/0292715, US 2010/0292712, US 2010/0292710, US 2010/0292713, and US 2011/079627, the disclosures of which are hereby incorporated by reference herein. 
       FIGS.  6 C and  6 C- 1    show the applicator instrument  30  during a third stage of the firing cycle. The trigger  38  and the trigger rack  76  have moved proximally about 0.537 inches from the beginning the firing cycle (see  FIG.  6 A ) due to continued squeezing of the trigger  38 . Further proximal movement of the trigger rack  76  along the axis A 3 -A 3  results in further rotation of the drive gear  78 , which causes corresponding distal movement of the yoke  82  along the axis A 1 -A 1 . As the yoke  82  moves distally, energy may be stored in a firing spring located inside the spring block  72 . The second arm  90  of the trigger return spring  86  has been further flexed proximally for increasing the return force against the trigger  38 . During the third stage, the first rotating link  110  deflects the dwell beam  115  of the lock-out counter  104  proximally by about 0.029 inches. The force applied to the dwell beam  115  by the first rotating link  110  is in equilibrium with the counter force provided by the lock-out counter spring  108 , so that the lock-out counter  104  is “primed” for toggling from the forward position shown in  FIG.  6 C- 1    to a rear position. 
       FIGS.  6 D and  6 D- 1    show the applicator instrument  30  during a fourth stage of the firing cycle. The trigger  38  and the trigger rack  76  have moved proximally about 0.716 inches due to continued squeezing of the trigger  38 . The second arm  90  of the trigger return spring  86  has further flexed proximally for increasing the return force against the trigger  38 . Linear movement of the trigger rack  76  in a proximal direction along the axis A 3 -A 3  results in continued counter-clockwise rotation of the drive gear  78 , which causes corresponding distal sliding motion of the yoke  82  along the axis A 1 -A 1  toward the distal end of the applicator instrument  30 , and storing additional energy in the firing spring  75  inside the spring block  72 . The first rotating link  110  has deflected the dwell beam  115  of the lock-out counter  104  by about 0.044 inches. At this point, the rearward force applied to the dwell beam  115  of the lock-out counter  104  has overcome the counter force provided by the lock-out counter spring  108  so that the upper end of the lock-counter  104  is biased proximally into the rear position. When the lock-out counter  104  toggles to the rear position, the distal tooth  122  engages the gear  96  for rotating the rotatable disc  94  by one-half tooth of the gear  96 . 
       FIGS.  6 E and  6 E- 1    show the applicator instrument  30  during a fifth stage of the firing cycle. The trigger  38  and the trigger rack  76  have moved proximally about 0.900 inches from the commencement of the firing cycle ( FIG.  6 A ) due to continued squeezing of the trigger. The proximal sliding movement of the trigger rack  76  is halted by a proximal stop  85  molded into the handle  36 . At this stage, the trigger rack  76  has contacted the proximal stop  85  and the proximal movement of the trigger  38  and the trigger rack  76  is complete. The second arm  90  of the trigger return spring  86  has flexed further for increasing the return force against the trigger  38  to a peak value. Proximal movement of the trigger rack  76  along axis A 3 -A 3  has resulted in continued rotation of the drive gear  78 , which, in turn, causes distal movement of the yoke  82  along axis A 1 -A 1  as described in commonly assigned U.S. Patent Application Publication Nos. US 2010/0292715, US 2010/0292712, US 2010/0292710, US 2010/0292713, and US 2011/079627, the disclosures of which are hereby incorporated by reference herein. Before the end of stage five, the firing rod is released and the energy in the firing spring is transferred to the firing rod to move the firing rod distally for dispensing a surgical fastener. The first rotating link  110  has deflected the dwell beam  115  of the lock-out counter  104  by about 0.115 inches. The upper end of the lock-out counter  104  remains toggled over to the rear position whereby the distal tooth  122  contacts the gear  96 . 
     During the fifth stage of the firing cycle shown in  FIG.  6 E , the trigger  38  has been fully squeezed and the drive gear  78  has advanced the proximal end of the yoke  82  distally beyond the ratchet pawl  84 . With the proximal end of the yoke  82  clear of the ratchet pawl  84 , the ratchet pawl may re-set so that the yoke  82  is free to once more slide toward the proximal end  32  of the applicator instrument  30  for commencing another firing cycle. 
     In one embodiment, when the trigger  38  is released, the energy stored in the trigger return spring  86  is transferred to the trigger  38  for urging the trigger to move in a distal direction along the axis A 3 -A 3  for returning the trigger to the initial trigger position shown in  FIG.  6 A . Corresponding resetting actions of the yoke  82  and the firing system  70  are similar to the movements disclosed in commonly assigned U.S. Patent Application Publication Nos. US 2010/0292715, US 2010/0292712, US 2010/0292710, US 2010/0292713, and US 2011/079627, the disclosures of which are hereby incorporated by reference herein. 
     When the trigger  38  is released, the first rotating link  110  moves distally for removing a compression force on the dwell beam  115  of the lock-out counter  104 . The lock-out return spring  108  preferably toggles the upper end of the lock-out counter  104  in a distal direction and back to the forward position shown in  FIG.  6 A- 1   . The back and forth toggling of the lock-out counter  104  will result in incremental rotation of the rotatable disc  94  of the counter  52 . 
     In one embodiment, the counter  52  locks the trigger in a proximal position ( FIG.  6 E ) when the last surgical fastener has been fired. Referring to  FIG.  7 A , in one embodiment, the trigger  38  has a hook  140  projecting from a proximal end thereof. The hook  140  moves simultaneously with the trigger  38  as the trigger moves in proximal and distal directions along the axis A 3 -A 3 . In  FIG.  7 A , the trigger hook  140  is proximal to the lock-out pin hook  142 . 
     The lock-out pin  100  has a lock-out pin hook  142  that is adapted to engage the trigger hook  140  when the last surgical fastener has been fired. In  FIG.  7 A , a radial slot provided in the rotatable disc  94  is aligned with the arm  101  of the lock-out pin  100 . As a result, the lock-out pin  100  is free to fall toward the bottom of the applicator instrument along the axis V 1 -Vi. The lock-out pin  100  is urged downward by a lock-out pin spring  150 . The dwell beam  115  of the lock-out counter  104  ensures that the lock-out pin  100  drops before the trigger hook  140  passes beyond the lock-out pin hook  142 . As the trigger  38  is pulled proximally, a ramp feature on the leading edge of the trigger hook  140  deflects the lock-out pin  100  upward along the axis V 1 -Vi. 
     Referring to  FIG.  7 B , as the trigger continues to travel proximally, the lock-out pin  100  eventually drops again so that the hook  142  of the lock-out pin  100  is distal to the hook  140  connected with the trigger  38 . Referring to  FIG.  7 C , when the trigger  38  is released, the trigger return spring  86  urges the trigger distally until the lock-out pin hook  142  engages the trigger hook  140  to halt the trigger  38  from moving further distally along the axis A 3 -A 3 . As a result, the trigger  38  is locked in the position shown in  FIG.  7 C  and the applicator instrument  30  may no longer be used for dispensing surgical fasteners. 
     Referring to  FIG.  8   , in one embodiment, the firing system preferably includes an advancer element  160  having advancer element tabs  162  and an anti-backup member  164  having anti-backup tabs  166 . During a complete firing cycle of the applicator instrument disclosed herein, the advancer element  160  cycles distally and proximally for advancing surgical fasteners  60  one segment toward the distal end of the applicator instrument. In one embodiment, when the trigger  38  ( FIG.  1   ) is squeezed, the advancer element  160  moves distally (to the left in  FIG.  8   ) whereupon the advancer element tab  162  abuts against a rear of the surgical fastener  60  for advancing the surgical fastener in a distal direction. When the trigger is released and moves distally for returning to the initial position, the advancer element  160  moves in a proximal direction toward the proximal end of the applicator instrument. The anti-backup tabs  166  prevent the surgical fasteners from moving proximally as the advancer element moves proximally. The advancer element  160  moves distally each time the trigger is squeezed and moves proximally when the trigger is released for returning to a start position at the beginning of a firing cycle. The anti-backup member  164  remains stationary during the firing cycles. The anti-backup tabs  166  preferably contact the surgical fasteners for preventing the surgical fasteners from moving proximally within the elongated shaft  40  ( FIG.  1   ) of the applicator instrument. This system is also described in commonly assigned U.S. Patent Appln. Publication Nos. US 2010/0292715, US 2010/0292712, US 2010/0292710, US 2010/0292713, and US 2011/079627, the disclosures of which are hereby incorporated by reference herein. 
     Referring to  FIG.  9   , in one embodiment, the applicator instrument  30  includes the elongated shaft  30 , which is preferably angled or curved, and a guide member  168  that extends through the shaft. The guide member  168  may be a molded part including an advancer element channel AC and a firing channel FC. In one embodiment, the guide member  168  preferably has a first half  170 A and a second half  170 B that are assembled together. In one embodiment, the anti-backup member  164 , the advancer element  160 , and the surgical fasteners  60  are positioned within the advancer element channel AC of the first half  170 A of the guide member, and the firing rod  74  and an insertion fork are positioned within the firing channel FC of the first half  170 A of the guide member. The second half  170 B of the guide member is assembled with the first half  170 A for forming the assembled guide channel  168 . 
     In one embodiment, the surgical fasteners  60  advance through the advancer element channel AC while lying within a laterally extending horizontal plane HP that is perpendicular to a vertical plane VP extending through the top and bottom of the applicator instrument. The orientation of the surgical fasteners within the guide member  168  enables the surgeon to control and/or be aware of the orientation of the surgical fasteners as they are dispensed from the shaft of the applicator instrument. 
     In one embodiment, the advancer element  160  advances the surgical fastener  60  distally through the advancer element channel AC and toward the distal end of the shaft  40 . When the surgical fastener  60  becomes the lead surgical fastener at the distal end of the shaft  40 , a staging leaf attached to the distal end of the anti-backup member  164  transfers the lead surgical fastener  60  from the advancer element channel AC to the firing channel FC for being aligned with the insertion fork at the distal end of the firing rod  74 . 
       FIG.  10 A  shows the distal end of the first half  170 A of the guide member  168 . The second half  170 B ( FIG.  9   ) of the guide member has been removed to more clearly show the advancer element channel AC and the firing channel FC of the guide member  168 . In one embodiment, twenty surgical fasteners  60 A,  60 B,  60 C, . . .  60 T are positioned between the advancer element  160  and the anti-backup member  164 . The advancer element  160  cycles back and forth for advancing the surgical fasteners  60 A,  60 B,  60 C, . . .  60 T toward the distal end of the advancer element channel AC. The distal end of the anti-backup member  164  includes a staging leaf  174  that moves the lead surgical fastener  60 A into the firing channel FC for alignment with the insertion fork  176  at the distal end of the firing rod  74 . 
     Referring to  FIGS.  9  and  10 B , in one embodiment, the applicator instrument  30  includes a staging spring  178 , such as a wire staging spring that is adapted to urge the staging leaf  174  to move into alignment with the insertion fork  176 . In one embodiment, the wire staging spring  174  is U-shape and has a closed distal end  180  that passes through a window  182  formed in the distal end of the guide member  168 . The closed distal end  180  of the wire staging spring  178  preferably engages the staging leaf  174  for urging the staging leaf to move into alignment with the insertion fork  176 . As a result, after the lead surgical fastener  60 A has been advanced onto the staging leaf  174  by the advancer element  160 , and the advancer element is retracted, the wire staging spring  178  transfers the lead surgical fastener  60 A from the advancer element channel AC to the firing channel FC for being aligned with the insertion fork  176  at the distal end of the firing rod  74 . The firing rod and the insertion fork may then be extended for guiding the tines of the insertion fork onto the lead surgical fastener  60 A. 
     Referring to  FIGS.  11 A and  11 B , in one embodiment, the wire staging spring  178  has a proximal end  184  that is secured to the guide member  168  and a closed distal end  180  that passes through the window  182  formed through the guide member adjacent the distal end of the guide member. 
     Referring to  FIG.  11 B , the wire staging spring  178  includes a first arm  186  that is secured to the first half  170 A of the guide member  168  and a second arm  188  that is secured to the second half  170 B of the guide member  168 . The closed distal end  180  of the wire staging spring  178  passes through the window  182  ( FIG.  11 A ) formed adjacent the distal end of the guide member  168 . 
       FIGS.  12 A- 12 E  show the operation of the wire staging spring  178  for urging the staging leaf into alignment with the insertion fork at the distal end of the firing rod. Referring to  FIG.  12 A , the insertion fork  176  and the firing rod  74  are in a retracted position at the beginning of a firing cycle. A lead surgical fastener  60 A has been advanced toward a distal end  34  of the applicator instrument. The distal end  180  of the wire staging spring  178  deflects the staging leaf  174  down into the firing channel FC of the guide member  168 . 
     Referring to  FIG.  12 B , the trigger is pulled toward the proximal end of the device, which, in turn, moves the advancer element  160  toward the distal end  34  of the applicator instrument, whereby the advancer element tab  162  pushes the lead surgical fastener  60 A distally for loading the lead surgical fastener onto the staging leaf at the distal end of the anti-backup member  164 . The distal end of the extended advancer element  160  flexes the staging leaf and the wire staging spring  178  upwardly and away from the firing channel FC. 
     Referring to  FIG.  12 C , during a later stage of the firing cycle, the advancer element  160  is retracted whereupon the distal end  180  of the wire staging spring  178  urges the staging leaf  174  downwardly into the firing channel FC for aligning the lead surgical fastener  60 A with the insertion fork  176 . The staging leaf  174 , which has been deflected downwardly into the firing channel, holds the lead surgical fastener  60 A in position for being engaged by the insertion fork  176 . 
       FIG.  12 D  shows a later stage of the firing cycle during which the insertion fork  176  and the firing rod  74  move distally whereupon the tines of the insertion fork  176  engage the lead surgical fastener  60 A. As the insertion fork moves distally, the insertion fork  176  deflects the staging leaf  174  and the wire staging spring  178  out of the firing channel FC and into the advancer element channel AC. 
       FIG.  12 E  shows the firing rod  74  and the insertion fork  176  fully extended in a distal-most position for dispensing the lead surgical fastener  60 A from the distal end of the applicator instrument. The fully extended insertion fork  176  and firing rod  74  continue to deflect the staging leaf  174  and the wire staging spring  178  into the advancer element channel AC. 
     Referring to  FIGS.  13 A- 13 C , in one embodiment, a cap  190  is secured to the distal end of the outer shaft  40 . In one embodiment, the cap  190  is affixed to the distal end of the outer shaft so that the cap  190  does not rotate or translate relative to the shaft  40 . In one embodiment, the shaft  40  has an outer diameter OD 1  of about 6-12 mm and more preferably about 8 mm. The cap  190  preferably has a smooth, curved and contoured outer surface that has no sharp edges so that the cap will not snare or damage the mesh fabric of a mesh implant. 
     In one embodiment, the cap  190  has a lower distal edge  192  that extends along the bottom of the cap and a delivery window  194  for dispensing a surgical fastener. In one embodiment, the cap  190  is adapted for insertion into the pocket of an open skirt mesh having a top mesh piece and a bottom mesh piece joined at a peripheral seam, whereby the lower distal edge  192  is advanced into contact with the inside of the seam and the cap may be easily slid along the inside of the seam between the top and bottom layers without snagging or damaging the mesh material. The lower distal edge  192  is adapted to sit atop the bottom mesh piece of an open skirt mesh to ensure that the delivery window  194  of the cap  190  is a set distance above the seam of the skirted mesh. 
     In one embodiment, the delivery window  194  has an upper end  196  and a lowered  198 . The lower end  198  of the delivery window  194  is preferably spaced from the lower distal edge  192  to ensure that surgical fasteners are dispensed above the seam of the open skirt mesh and into the top mesh piece of the implant. Referring to  FIG.  13 B , in one embodiment, the lower distal edge  192  includes a central section  200  having a length L 1  of about 6-10 mm that generally matches the outer diameter OD 1  of the shaft  40  and first and second extensions  202 ,  204  that extend beyond the outer diameter OD 1  of the shaft  40  about 2-3 mm. With the addition of the first and second extensions  202 ,  204 , the lower distal edge  192  has a total length L 2  of about 10-20 mm that is greater than the outer diameter OD 1  of the shaft  40 . In one embodiment, the first and second extensions  202 ,  204  have bottom surfaces that are convex and that extend laterally from the bottom surface of the lower distal edge, and first and second top surfaces  206 , 208  that are concave and that extend toward an upper end  210  of the cap  190 . The first and second extensions  202 , 204  preferably distribute forces over a broader area of mesh, such as a bottom mesh piece of an open skirt mesh, such as when a physician applies forward forces on the applicator instrument handle and counter-pressure on opposing tissue. 
     In one embodiment, the cap has a proximal end  212  that that is secured to the distal end of the shaft  40  and that transitions into a cylindrical shape to match the outer diameter OD 1  of the shaft  40 . In one embodiment, the proximal end  212  of the cap  190  has an outer diameter OD 2  of about 6-12 mm and more preferably about 8 mm that generally matches and conforms to the outer diameter OD 1  of the shaft  40 . 
     Referring to  FIGS.  13 A and  13 C , in one embodiment, the cannula cap  190  has a distal face  214  that slopes upwardly and proximally from the lower distal edge  192  to the upper end  210  of the cannula cap  190 . When the cap  190  is inserted into the pocket of an open skirt mesh having a peripheral seam, the lower distal edge  192  is preferably abutted against a bottom mesh piece of the open skirt mesh and advanced toward an inside of a seam until the sloping distal face  214  engages the top mesh piece of the open skirt mesh to ply the top mesh piece of the skirt away from the bottom mesh adjacent the inside of the seam. The delivery window  194  is desirably spaced from the lower distal edge  192  to insure that the surgical fasteners  60  dispensed through the delivery window pass through the top mesh piece and not the peripheral seam or the bottom mesh piece of the open skirt mesh. The first and second extensions  202 ,  204  further ensure that the cap orients the device relative to the seam of the mesh such that surgical fasteners are delivered into the top mesh piece. 
     In one embodiment, the cap  190  is contoured to ensure there are no sharp edges at the distal end of an applicator instrument that may catch or damage the mesh fabric of an implant. The contoured cap ensures that a physician may slide a distal end of an applicator instrument along the inside of a seam of an open skirt mesh when positioning or re-positioning the distal end of the applicator instrument for initial and subsequent deployment of surgical fasteners. 
     Referring to  FIGS.  14 A- 14 C , in one embodiment, an applicator instrument  30  having the elongated shaft  40  and the cap  190  is used to secure an open skirt mesh  216  to soft tissue. In one embodiment, the open skirt mesh  216  has a bottom mesh piece  218 , a top mesh piece  220  with a central opening  222 , and a peripheral seam  224  that joins the outer edges of the bottom mesh piece  218  and the top mesh piece  220  to define a pocket  226  that extends between the top and bottom mesh pieces. 
     In one embodiment, the cap  190  and the distal end of the shaft  40  of an applicator instrument  30  are inserted through the central opening  222  of the top mesh piece  220  and advanced into the pocket  226  and toward the peripheral seam  224  of the open skirt mesh  216 . The lower distal edge  192  ( FIG.  14 B ) of the cap  190  is abutted against the bottom mesh piece  218  and advanced toward the peripheral seam  224 , whereupon the lower distal edge  192  and the sloping distal face  214  ( FIG.  14 B ) of the cap  190  ply the top mesh piece  220  away from the bottom mesh piece  218  at the peripheral seam  216 . The lower distal edge  192  of the cap  190  spaces the dispensing window  194  of the cap  190  above the seam  224  and in alignment with the top mesh piece  220  so that the surgical fastener  60  ( FIGS.  3  and  12 E ) passes through the top mesh piece  220  and does not pass through the seam  224  or the bottom mesh piece  218 . 
     In one embodiment, a patient with a ventral hernia is prepared for an open hernia repair procedure. The skin area surrounding the hernia is scrubbed with a conventional antimicrobial solution, such as betadine. The patient is administered conventional general anesthesia in a conventional manner by induction and inhalation. In one embodiment, the surgeon initiates the surgical procedure by making an incision in the skin and subcutaneous tissue overlying the hernia. In the case of planned intra-peritoneal mesh placement, the hernia sac is opened. The edges of the healthy fascia around the defect are examined and any attachments of the viscera to the abdominal wall are divided to create a free space for fixation of the mesh. 
     At this stage of the surgical procedure, the surgeon prepares a surgical mesh. The surgical mesh may be a shirted hernia mesh having a bottom repair layer and a top fixation layer, or any suitable mesh such as the mesh disclosed in commonly assigned U.S. patent application Ser. No. 13/443,347, filed Apr. 10, 2012, entitled “SINGLE PLANE TISSUE REPAIR PATCH,” the disclosure of which is hereby incorporated by reference herein. In one embodiment, the bottom repair layer of a skirted hernia mesh may be referred to as a bottom mesh piece and the top fixation layer may be referred to as a top mesh piece. The outer peripheries of the respective bottom repair layer and the top fixation layer are preferably joined together at a peripheral seam that extends around the outer perimeter of the skirted hernia mesh. In one embodiment, the top fixation layer desirably has an opening in the center. In one embodiment, four sutures may be placed at the four compass points of the mesh (i.e., North, South, East, and West). 
     In one embodiment, the mesh is inserted through the skin incision and through the fascia defect into the pre-peritoneal space. The surgeon desirably deploys the mesh into the abdominal cavity by hand. The mesh is oriented such that the bottom repair layer is facing the patient&#39;s abdominal contents and the top fixation layer is facing the abdominal wall. The sutures may be secured trans-abdominally using suture passers, as desired. 
     In one embodiment, an applicator instrument is used for dispensing surgical fasteners for mesh fixation. In one embodiment, the applicator instrument is desirably oriented so that the handle and trigger are above the body of the applicator instrument for being clear of the patient&#39;s abdomen. The elongated outer shaft of the applicator instrument is preferably inserted through the central opening formed in the top fixation layer so that the distal end of the shaft is disposed between the top fixation layer and the bottom repair layer. In one embodiment, the outer shaft of the applicator instrument is curved and the curvature of the outer shaft is pointed upward and away from the posterior end of the patient (i.e., toward the top fixation layer). With the cap of the applicator instrument between the top fixation layer and the bottom repair layer, the cap is advanced toward the outer periphery of the mesh implant until the cap reaches the peripheral seam of the mesh. In one embodiment, while the applicator instrument is held with the surgeon&#39;s first hand, the second hand may be used to apply external counter pressure to the skin, opposing the cap at the distal end of the applicator instrument. The cap has a lower distal edge that contacts the bottom repair layer and the inside of the peripheral seam. The cap preferably has a distal face that slope upwardly and away from the lower distal edge. When the lower distal edge of the cap is advanced to the seam, the sloping distal face of the cap plies the top fixation layer away from the bottom repair layer. The lower distal edge desirably functions as a spacer that ensures that the surgical fastener dispensing window in the cap is above the peripheral seam of the mesh implant and is aligned with the top fixation layer. 
     In one embodiment, with the dispensing window of the cap aligned with the top fixation layer, thetriggerissqueezedwithasinglestrokeactiontodeployasurgicalfasteneror strap through the cap dispensing window for securing the top fixation layer to the abdominal wall. The trigger returns itself to an initial start position for a firing cycle. The applicator instrument is preferably repositioned to another point along the seam of the mesh and another surgical fastener is delivered. The process is repeated until the entire perimeter of the mesh is secured, with the surgical fasteners desirably spaced about 1-2 mm apart around the periphery of the mesh implant. In one embodiment, a second series of straps may optionally be applied closer to the center of the mesh in what is called a double crown technique. 
     In one embodiment, after  20  surgical fasteners have been dispensed, the applicator instrument will lock out with the trigger closed. If needed, a new applicator instrument may be used to complete the remainder of the repair procedure. After a desired number of surgical fasteners have been deployed, the applicator instrument is removed from the patient. The hernia defect may be primarily closed if desired. The skin incision may be closed using appropriate suturing or closure techniques, and the incision is appropriately bandaged. After the repair procedure is complete, the patient may be moved to a recovery room. 
     Referring to  FIGS.  15 A- 15 C , in one embodiment, an applicator instrument  330  includes a handle  336  having a trigger  338  and a shaft  340  extending from a distal end of the handle  336 . A cap  390  is desirably secured to a distal end of the shaft. The cap  390  preferably includes a delivery window  394  for dispensing surgical fasteners from the distal end of the applicator instrument  330 . In one embodiment, the cap  390  has a lower distal edge  392  and first and second lateral extensions  402 ,  404  that extend laterally from the lower distal edge  392 . The first and second lateral extensions  402 ,  404  preferably extend beyond the outer diameter of the outer shaft  340  to define a length that is greater than the outer diameter of the shaft. 
     Referring to  FIG.  16   , in one embodiment, the distal end of the applicator instrument  330  is adapted for being inserted into a pocket of an open skirt mesh  416 . In one embodiment, the open skirt mesh  416  preferably includes a bottom mesh piece  418  and a top mesh piece  420  that opposes the bottom mesh piece  418 . The outer edges of the bottom and top mesh pieces  418 ,  420  are joined together at a peripheral seam  422 . When the cap  390  is inserted into the pocket of the skirted mesh  416 , the lower distal edge  392  and the first and second lateral extensions  402 ,  404  preferably engage the inner surface of the bottom mesh piece  418  for flattening the bottom mesh piece in the vicinity of the cap  390 . The lower distal edge  392  preferably has a thickness that spaces the delivery window  394  above the seam  422  to ensure that the surgical fasteners are dispensed through the top mesh piece  420  and not the seam  424  or the bottom mesh piece  418 . 
     Referring to  FIG.  17   , in one embodiment, an applicator instrument  430  includes a handle  436  and an elongated shaft  440  extending distally from the handle  436 . The applicator instrument  430  includes a rotating element  445  secured to the outer shaft  440 . A cap  490  is secured to a distal end of the outer shaft  440 . The cap  490  may include one or more of the features disclosed in the embodiments shown in  FIGS.  13 A- 13 C  or  FIGS.  15 B- 15 C . In one embodiment, the rotating element  445  may be engaged for rotating the elongated shaft  440  about its longitudinal axis. The cap  490  preferably rotates simultaneously with the shaft  440 . 
     Referring to  FIGS.  18 A- 18 C , in one embodiment, an applicator instrument desirably includes a cap  490  secured to a distal-most end of an outer shaft. The cap  490  includes a distal-lower edge  492  having a concave bottom surface  495 . The cap  490  includes first and second extensions  502 ,  504  that extend laterally from the lower distal edge  492 . The cap  490  preferably includes a delivery window  494  that is aligned with the firing chamber of the applicator instrument for dispensing surgical fasteners through the delivery window. 
     In one embodiment, the distal-lower end  492  of the cap  490  has a thickness that spaces the delivery window  494  from the concave bottom surface  495  of the distal-lower edge. After the lower distal edge  492  is abutted against the inside of the peripheral seam of a mesh implant, the thickness of the lower distal edge ensures that the delivery window  494  of the cap  490  is spaced above and away from the peripheral seam so that the surgical fasteners are dispensed into the top mesh piece of a skirted mesh, and not into the seam or the bottom mesh piece. 
     In one embodiment, when the cap  490  is inserted into the pocket of a skirted mesh, the lower distal edge  492  is advanced toward the peripheral seam of the skirted mesh with the concave bottom surface  495  facing the bottom mesh piece and the delivery window aligned with the top mesh piece. In one embodiment, the concave bottom surface  495  of the lower distal edge  492  desirably provides a living hinge that is flexible so that the lower distal edge may flatten out for stretching a mesh piece (e.g., a bottom mesh piece) of an implant during positioning of the cap  490  for dispensing a surgical fastener. 
     Referring to  FIG.  19   , in one embodiment, an applicator instrument  630  for dispensing surgical fasteners includes a curved outer shaft  640 , similar to the structure described above in  FIG.  1   , having a proximal section  642  and a distal section  644  that is coupled with the proximal section via a curved section  645 . In one embodiment, the applicator instrument  630  preferably includes an outer shaft rotating element  655  rotatably mounted to a distal end of a device housing  635 . The outer shaft rotating element  635  is connected with the proximal section  642  of the outer shaft  640  for selectively rotating the outer shaft  640 . As a result, the outer shaft rotating element  655  enables an operator to selectively rotate the proximal section  642  of the curved outer shaft  640  along a longitudinal axis A 1  for changing the orientation of the distal end section  644 . 
       FIG.  20    shows a cross-section of the applicator instrument  630  in  FIG.  19   . Referring to  FIG.  20   , in one embodiment, the curved outer shaft  640  includes the proximal section  642  extending along the axis A 1  and the distal section  644  extending along the axis A 2 . The curved section  645  defines the angle α 3  between the proximal section  642  and the distal section  644 . The curved outer shaft  640  has an elongated internal conduit through which surgical fasteners  660  may advance distally. The applicator instrument  630  preferably includes an advancer  760  having advancer tabs  762  for advancing the surgical fasteners  660  one position toward the distal end of the curved outer shaft  640  each time the trigger is pulled. The applicator instrument also desirably includes an anti-backup element  664  having anti-backup tabs  666  for preventing the surgical fasteners from moving proximally. The applicator instrument  630  also includes a flexible firing element  674 , such as a flexible cable, that is able to transfer forces from the firing system, which operates as described herein, to the distal-most surgical fastener  660  in the outer shaft  640 . The flexible firing element  674  is resistant to compression along its longitudinal axis. The flexible firing element  674  may also be twisted. In one embodiment, as the outer shaft rotating element  655  is rotated relative to the housing  635  for changing the orientation of the distal section  644  of the curved outer shaft  640 , the flexible firing element  674  is able to flex, twist and bend to maintain a linkage between the firing system and a rigid insertion fork  676  having tines at a distal end thereof that are adapted to engage the sides of a surgical fastener  660 . The flexible firing element  674  preferably transfers energy from the firing system to the rigid insertion fork  676  that engages the sides of a surgical fastener for driving the surgical fastener into soft tissue as described in more detail above. 
     In one embodiment, the firing system is the same as that described above but acts along the central axis of the proximal section  642  of the shaft. The flexible element of the firing system  674  extends through a rotary advancing system  665 . The rotary advancing system  665  is preferably aligned with the proximal section  642  of the curved outer shaft  640 . The rotary advancing system  665  is adapted to rotate with the curved outer shaft  640  around a central axis. The advancing system is actuated from the above-described indexing system of the applicator instrument  640  that interfaces with the rotary firing system  665 . 
     Referring to  FIG.  21   , in one embodiment, an applicator instrument  730  for dispensing surgical fasteners preferably includes a flexible, articulatable outer shaft  740  having a proximal section  742  that extends along an axis A 1 , a distal section  744  that extends along an axis Aland a flexible, articulatable intermediate section  745  that enables the distal section  744  to articulate relative to the proximal section  742  for changing the angle therebetween. In one embodiment, the proximal and distal sections  742 ,  744  of the articulating outer shaft  740  are less flexible and the intermediate section  745  is more flexible for enabling the articulating movement. 
     The applicator instrument  730  desirably includes an outer shaft rotating element  755  that is mounted at a distal end of the housing  735  and that is secured with the proximal section  742  of the outer shaft  740 . Rotation of the outer shaft rotating element  755  results in simultaneous rotation of the proximal section  742  of the outer shaft  740  about the longitudinal axis A 1 , which, in turn, changes the orientation of the distal section  744  of the curved outer shaft  740  relative to the proximal section. 
     In one embodiment, the applicator instrument  730  also desirably includes an articulation control element  775  that is mounted on the housing  735 . In one embodiment, the articulation control element  775  is preferably slideably mounted on the housing  735  for moving distally and proximally. Referring to  FIGS.  21  and  22   , in one embodiment, the applicator instrument includes flexible linkages  785 A,  785 B having proximal ends coupled with the articulation control element  775  and distal ends coupled with the distal section  744  of the curved outer shaft  740 . As shown in  FIG.  22   , the outer shaft  740  includes the proximal section  742 , the distal section  744 , and the intermediate flexible section  745  that extends between the proximal section  742  and the distal section  744 . The first and second linkages  785 A,  785 B extend through the proximal section  742  and the flexible section  745 , with the distal ends of the linkages coupled with the distal section  744 . As the articulation control element  775  ( FIG.  21   ) is moved toward the distal end of the applicator instrument  730 , the first and second linkages  785 A,  785 B cooperate for changing the angle of the distal section  744  of the outer shaft relative to the proximal section  742  of the outer shaft. In one embodiment, as the articulation control element  775  moves toward the distal end  734  of the applicator instrument  730 , the distal section  744  moves up. As the articulation control element  775  is moved towards the proximal end  732  of the applicator instrument  730 , the first and second linkages  785 A,  785 B cooperate to move the distal section  744  down. Thus, the angle of the distal section  744  of the flexible outer shaft  740  may be changed relative to the proximal section  742  by moving the articulating control element  755  in proximal and distal directions until a desired angle is obtained. In one embodiment, the articulation control element enables an operator to toggle the outer shaft  740  between a straight configuration and a curved or angled configuration. After a desired straight, curved, or angled configuration is obtained, the orientation of the distal section  744  relative to the proximal section  742  of the outer shaft  740  may be changed by rotating the outer shaft rotating element  755 , which, in turn, changes the orientation of the distal section  744 . 
     The applicator instrument  730  of  FIGS.  21  and  22    preferably includes a flexible firing element, a flexible advancer, and a flexible anti-backup element as described above in  FIG.  20    to maintain an operating linkage with both the firing system and the surgical fastener advancing system as the outer shaft is rotated and/or articulated. 
     Referring to  FIGS.  23  and  24   , in one embodiment, an applicator instrument  830  for dispensing surgical fasteners has an imaging system  950 . The imaging system may be fully or partially integrated into the applicator instrument, or may be a separate, stand-alone system that is selectively coupled to the applicator instrument. In one embodiment, the imaging system  950  desirably enhances illumination and visibility at a working end of the applicator instrument, which facilitates the detection of objects at a surgical site for enabling proper alignment and placement of surgical fasteners relative to a surgical mesh that has been pre-positioned on a patient. In one embodiment, the applicator instrument  830  has a proximal end  832 , a distal end  834 , and a longitudinal axis A 1 -A 1  that extends between the proximal and distal ends thereof. The applicator instrument  830  desirably includes a housing  835 , a handle  836  extending upwardly from the housing, a trigger  838  mounted on the handle  836 , and an elongated shaft  840  that extends distally from the housing  835 . In one embodiment, the elongated shaft  840  desirably includes a proximal section  842  that extends along the longitudinal axis A 1 -A 1 , and a distal section  844  that is angled or curved relative to the proximal section  842 . In one embodiment, the distal section  844  extends along a second axis A 2 -A 2 , which forms an angle α 3  with the axis A 1 -A 1  of the proximal section  842 . In one embodiment, the angle α 3  defined by the proximal and distal sections of the elongated shaft  840  is desirably an obtuse angle. In one embodiment, the elongated shaft  840  is non-linear. In one embodiment, the elongated shaft is curved so that the distal section  844  slopes upwardly and away from the housing  835  of the applicator instrument. 
     In one embodiment, a cap  846 , such as a contoured end cap having no sharp edges, is secured to a distal end of the elongated shaft  840 . In one embodiment, the cap  846  is securely affixed to the distal end of the distal section  844  of the elongated shaft  840  so that the cap does not rotate or translate relative to the elongated shaft  840 . The cap  846  preferably has a distal end face  848  that slopes away from a lower distal edge  892  of the cap and toward the proximal end  832  of the applicator instrument  830 . 
     In one embodiment, the imaging system  950  preferably includes an imaging device  952  mounted on the cap  846 , a power source  954  disposed within the housing  835 , a power conduit  956 , such as a conductive wire, that extends through the elongated shaft  840  for transmitting power from the power source  954  to the distal end of the elongated shaft  840 , and a light source (not shown) connected with the power conduit  956  for receiving power from the power source. As will be described in more detail herein, the light source preferably illuminates a field of view for the imaging device  952  at the distal end  834  of the applicator instrument  830 . 
     In one embodiment, the imaging system  950  desirably includes a transmitter conduit  958 , such as a transmitter conductive wire, for transmitting the images detected by the imaging device  952  from the distal end  834  of the applicator instrument to a transmitter  960  located in the housing  835 . In one embodiment, the transmitter conduit and the power conduit may be combined into the same conduit or conductive wire. The imaging system  950  preferably includes a monitor  962  ( FIG.  23   ) that is in communication with the transmitter  960 . The monitor  962  is adapted to receive the detected images and/or signals from the transmitter  960  and display the detected images on the monitor. In one embodiment, the images displayed on the monitor  962  are preferably magnified or enlarged for facilitating visibility of the surgical environment at the distal end of the applicator instrument. 
     Referring to  FIGS.  25 A- 25 E , in one embodiment, the cap  846  at the distal end of the elongated shaft preferably has a smooth, curved and contoured outer surface that has no sharp edges so that the cap will not snare or damage tissue or the mesh fabric of a mesh implant. In one embodiment, the cap  846  has a lower distal edge  892  that extends along the bottom of the cap and a delivery window  894  for dispensing one or more surgical fasteners through the delivery window. In one embodiment, the lower distal edge  892  is adapted to sit atop a bottom mesh piece of an open skirt mesh. In one embodiment, the delivery window  894  has an upper end  896  and a lower end  898 . The lower end  898  of the delivery window  894  is preferably spaced from the lower distal edge  892  to ensure that surgical fasteners are dispensed above the seam of the open skirt mesh and into the top mesh piece of the open skirt mesh. 
     In one embodiment, the cap  846  has the distal end face  848  that slopes upwardly and proximally from the lower distal edge  892  of the cap  846 . The distal end face preferably includes a central opening  970  for receiving the imaging device  952 , and a pair of lateral openings  972 A,  972 B for receiving the first and second light sources  974 A,  974 B, respectively. The imaging device  952  is adapted to detect images at the distal end  834  ( FIG.  23   ) of the instrument. The first and second light sources  974 A,  974 B are adapted to generate light that illuminates a field of view for the imaging device  952  at the distal end of the instrument. 
     In one embodiment, when the cap  846  is inserted into the pocket of an open skirt mesh having a peripheral seam, the light sources  974 A,  974 B preferably illuminate a field of view for the imaging device  952  at the distal end of the instrument. The illuminated field of view enables surgical personnel to use the imaging system to, inter alia, verify the following: 1) that the lower distal edge  892  of the cap  846  is abutted against a bottom mesh piece of an open skirt mesh, 2) that the lower distal edge  892  of the cap  846  is advanced toward an inside of a seam of the open skirt mesh until the sloping distal face  848  engages the top mesh piece of the open skirt mesh to ply the top mesh piece of the skirt away from the bottom mesh piece adjacent the inside of the seam, and 3) that the delivery window  894  of the cap  846  is aligned with the top mesh piece and is located above the peripheral seam and the bottom mesh piece of the open skirt mesh for ensuring that the surgical fasteners are passed through the top mesh piece and not the peripheral seam and/or the bottom mesh piece. 
     Referring to  FIG.  26   , in one embodiment, an imaging system  950  is used for detecting objects at the distal end of an applicator instrument for dispensing surgical fasteners. The imaging system  950  may be fully integrated into the applicator instrument, may be partially integrated into the applicator instrument, or may be a separate, stand-alone system that is coupled with the applicator instrument prior to use. In one embodiment, the imaging system  950  includes an imaging device  952  for detecting objects, and at least one light source  974  for illuminating a field of view for the imaging device  952 . The imaging system  950  preferably includes a power source  954  that provides power to the at least one light source  974  through a power conduit  956 A. In one embodiment, the imaging system  950  may have two or more light sources that illuminate the field of view for the imaging device  952 . In one embodiment, the power source  954  may also provide power for the imaging device  952  through a second power conduit  956 B. 
     In one embodiment, the imaging system preferably includes a transmitter conduit  958  that transmits the images detected by the imaging device  952  to the transmitter  960 . In turn, the transmitter  960  sends the detected signals to a controller  980  that preferably has a central processing unit  982  and a memory  984 . The controller  980  desirably processes and/or saves the detected images and transmits the images to the monitor  962  for providing a visual display for surgical personnel. The visual display on the monitor  962  preferably assists the surgical personnel in accurately positioning the distal end of the applicator instrument to ensure proper placement of the surgical fasteners into the surgical mesh. In one embodiment, the images may be transmitted wirelessly and/or over the internet during any stage of the process. 
     Referring to  FIG.  27   , in one embodiment, an applicator instrument  1030  for dispensing surgical fasteners is adapted to have an endoscopic instrument  1150  attachable thereto. In one embodiment, the endoscopic instrument is attached to an elongated shaft  1040  of the applicator instrument  1030 . The endoscopic instrument  1150  is desirably selectively attachable to the elongated shaft  1040  of an applicator instrument using clips  1175 A,  1175 B. In one embodiment, the endoscopic instrument  1150  may include one or more light sources and/or an imaging device for capturing images at the distal end of the elongated shaft of the applicator instrument. The endoscopic instrument  1150  preferably includes a distal working end  1185  that is adapted to illuminate a field of view and capture images within the illuminated field of view. The attachable endoscopic instrument  1150  desirably includes an elongated shaft  1195  that may be flexible for conforming to the shape of the elongated shaft  1040  of the applicator instrument  1030 . In one embodiment, the shaft  1195  of the endoscopic imaging system  1150  is curved or non-linear for conforming to the curve or non-linear shape of the elongated shaft  1040  of the applicator instrument  1030 . 
     Referring to  FIGS.  28 A and  28 B , in one embodiment, the distal working end  1185  of the endoscopic instrument  1150  preferably includes an imaging device  1152  and light sources  1174 A,  1174 B for illuminating a field of view at the distal end of the endoscopic instrument. The endoscopic instrument is preferably coupled with an imaging system as disclosed herein. Although  FIG.  28 B  shows an embodiment with two light sources  1174 A,  1174 B, other embodiments may include only one light source, or may includes three or more light sources at the distal end  1185  of the endoscopic attachment  1150 . 
     Referring to  FIG.  29   , in one embodiment, one or more clips  1175  are utilized for securing the endoscopic instrument  1150  to an applicator instrument  1030 . In one embodiment, the clip  1175  includes a ring  1197  that has a central opening  1199 , which is adapted to slide over the outer surface of the elongated shaft  1040  of the applicator instrument  1030  shown in  FIG.  27   . The clip  1175  desirably includes a pair of flexible arms  1201 A,  1201 B that define a U-shaped opening  1203  at an outer edge of the ring  1197 . In one embodiment, after the ring  1197  is secured over the elongated shaft of the applicator instrument, the endoscopic instrument  1150  may be attached to the applicator instrument by inserting the shaft  1195  of the endoscopic instrument  1150  into the U-shaped opening  1203  of the clip  1175 . The flexible arms  1201 A,  1201 B preferably retain the shaft  1195  of the endoscopic instrument  1150  within the U-shaped opening  1203  of the clip  1175 . 
     In one embodiment, one or more attachment clips may be permanently secured to the applicator instrument. In one embodiment, one or more attachment clips may be removably attached to the applicator instrument. 
     Although the present invention is not limited by any particular theory of operation, it is believed that utilizing one or more clips  1175 , as shown in  FIG.  29   , will enable an endoscopic instrument to be selectively attached to and selectively detached from the elongated shaft of an applicator instrument for sterilization, cleaning, maintenance, and/or repair of the endoscopic instrument. In one embodiment, the endoscopic instrument may be a single use device that is discarded at the end of a medical procedure, whereby a new endoscopic instrument may be attached to the applicator instrument for the next medical procedure. In one embodiment, the endoscopic instrument is re-useable and the applicator instrument is a single use device that is disposable. In one embodiment, the endoscopic instrument is permanently attached to the applicator instrument. 
     Referring to  FIGS.  30 A- 30 C , in one embodiment, the endoscopic instrument  1150  is attached to the elongated shaft  1040  of the applicator instrument  1030  utilizing clips  1175 A,  1175 B. Although two clips are shown in  FIGS.  30 A- 30 C , in other embodiments, fewer or more clips may be utilized for securing the endoscopic instrument  1150  to the elongated shaft  1040  of the applicator instrument  1030 . 
     In one embodiment, the endoscopic instrument  1150  is secured to the elongated shaft  1040  so that the distal working end  1185  is adjacent the contoured cap  1046  at a distal end of the elongated shaft  1040 . In one embodiment, a distal most face  1205  of the working end  1185  of the endoscopic instrument  1150  is proximal to the sloping distal face  1048  of the contoured end cap  1046 . As a result, the endoscopic instrument  1150  cannot interfere with the dispensing of surgical fasteners through the delivery window  1094  provided in the sloping distal face  1048  of the cap  1046 . 
     In one embodiment, the endoscopic instrument  1150  preferably includes both an imaging device and at least one light source provided at the distal working end  1185 . In one embodiment, the endoscopic instrument  1150  may include only one or more light sources for illuminating a field of view. In this embodiment, the endoscopic instrument provides a source of light and does not have an imaging device for capturing images. 
     In one embodiment, the imaging device may be a camera, a photo sensor, or an ultrasound sensor. In one embodiment, the imaging device is a camera having a fish eye lens for providing a wide angle view. 
     In one embodiment, the imaging system may include a Naneye imaging device, a 1 mm optical fiber, and a battery designated ADG852. The Naneye imaging device preferably has a size of 1 mm×1 mm×1.5 mm that fits within the central opening  970  ( FIG.  25 A ) provided in the distal face  848  of the cap  846 . In one embodiment, the light sources  974 A,  974 B that are disposed within the lateral openings  972 A,  972 B of the cap desirably include optical fibers with 1 mm diameters for producing light for the Naneye camera. The battery, designated ADG852, has a size of 1.3×1.6. is located in the housing or the handle of the applicator instrument, and is wired to both the Naneye imaging device and the optical fibers. 
     In one embodiment, the imaging device is a photo sensor or similar electronic component that detects objects via the presence of light, infrared, or ultraviolet energy. In one embodiment, the photo sensor preferably includes a semiconductor having photoconductive properties, in which the electrical conductance varies depending on the intensity of radiation striking the material. In one embodiment, a photo-sensing element may be positioned at the distal tip of the applicator instrument to detect changes in the level of light, which may be used to detect the edge of the mesh, pores of the mesh, etc. 
     In one embodiment, the imaging system may include a visual or audible element that provides feedback to the user to indicate when the distal end of the instrument is located at a desired position. In one embodiment, the visual indicator may be an external LED. In one embodiment, the audible indicator may be an element that emits sound, such as a speaker or buzzer. 
     In one embodiment, the power source is not located within the housing or the handle, but is a separate, stand alone component that is connected to the instrument by a cable or wire coupled to the instrument. In one embodiment, the battery is located at or adjacent the distal tip of the instrument, thereby eliminating the need for a power transmission conduit or conductive wire extending through the elongated shaft. In one embodiment, rather than using a power source for operating a light source, the light source may be a separately powered instrument that delivers light to the distal end of the applicator instrument through an optical fiber or optical fiber cable. 
     In one embodiment, the light source may be a single LED or a series of LEDs. In one embodiment, the light source may have a diffuser or lens for diffusing the light that illuminates the end of the instrument. In one embodiment, the light source is preferably sufficiently strong so that it illuminates the exterior of the skin, which provides an indication to surgical personnel of where the distal end of the instrument is positioned 
     In one embodiment, an outline of a desired position for a surgical mesh implant may be applied on the exterior of a patient&#39;s skin prior to mesh implantation, and the light source at the distal end of the instrument preferably indicates where the edges of the surgical mesh are actually located relative to the desired position outlined on the patient&#39;s skin. Devices and methods of performing the exterior marking of a patient&#39;s skin for mesh implant procedures are disclosed in one or more embodiments of commonly assigned U.S. patent application Ser. No. 13/422,003, filed Mar. 16, 2012, entitled “DEVICES FOR DISPENSING SURGICAL FASTENERS INTO TISSUE WHILE SIMULTANEOUSLY GENERATING EXTERNAL MARKS THAT MIRROR THE NUMBER AND LOCATION OF THE DISPENSED SURGICAL FASTENERS,” Attorney Docket No. ETH5640USNP, the disclosure of which is hereby incorporated by reference herein. 
     In one embodiment, the transmitter conduit may be an optical fiber or optical fiber cable that is capable of transmitting light and/or digital signals. In an embodiment that transmits digital signals, the transmitter preferably transmits the detected image as a digital signal to a wireless receiver, which, in turn, delivers the information to a remote monitor for visual and/or audible display. 
     In one embodiment, the transmitter conduit may be replaced with a wireless transmitter that couples the imaging device with the transmitter or the monitor. In one embodiment, the detected signal may be transmitted through infrared and microwaves. 
     In one embodiment, the monitor may be a laparoscopic tower. In one embodiment, the monitor may include a digital screen mounted directly onto the handle end of the device. In one embodiment, the monitor may include a cathode ray tube (CRT), a liquid crystal display (LCD), a plasma display, etc. In one embodiment, the imaging system may have a data storage device, such as a memory device, for storing detected images and/or video that is captured by the imaging device. In one embodiment, the imaging system may be disposable. 
     In one embodiment, the imaging system preferably includes a sensing device, such as a camera, photo sensor, or ultrasound sensor, which is adapted to detect a source of radiation, such as light, a tactile feature, radar, and ultrasound. The imaging system desirably provides feedback for the user in the form of visual, audible, vibratory, and/or tactile signals, or combinations thereof, that alert a user when the distal end of the instrument is properly aligned relative to the surgical mesh implant. 
     The headings used herein are for organizational purposes only and are not meant to limit the scope of the description or the claims. As used throughout this application, the word “may” is used in a permissive sense (i.e., meaning having the potential to), rather than the mandatory sense (i.e., meaning must). Similarly, the words “include”, “including”, and “includes” mean including but not limited to. To facilitate understanding, like reference numerals have been used, where possible, to designate like elements common to the figures. 
     While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, which is only limited by the scope of the claims that follow. For example, the present invention contemplates that any of the features shown in any of the embodiments described herein, or incorporated by reference herein, may be incorporated with any of the features shown in any of the other embodiments described herein, or incorporated by reference herein, and still fall within the scope of the present invention.