embodiments of the presently disclosed surgical instrument will now be described in detail with reference to the drawings wherein like reference numerals identify similar or identical elements . in the drawings and in the description which follows , the term “ proximal ,” as is traditional , will refer to the end of the surgical instrument that is closest to the operator while the term “ distal ” will refer to the end of the surgical instrument that is farthest from the operator . in the present disclosure , the words “ a ,” “ an ,” or “ the ” are to be taken to include both the singular and the plural . likewise , any reference to plural items shall , where appropriate , include the singular . the present disclosure relates to a surgical instrument for use with a surgical fastening apparatus or any other suitable surgical device . in fact , the presently disclosed surgical instrument can be applied to a whole line of surgical devices where torque is transmitted from one point to another . in addition , this surgical instrument can be employed in many kinds of surgical procedures . surgeons may utilize the instrument in endoluminal procedures . during such procedures , surgeons introduce a surgical instrument through a body lumen . doctors can also use the presently disclosed surgical instrument in endoscopic procedures . in this kind of procedure , doctors use a surgical instrument through or in combination with an endoscope . referring now to fig1 , a surgical instrument for use with a surgical fastening apparatus is generally designated as 100 . in the interest of brevity , this disclosure will focus primarily on systems , methods and structures of surgical instrument 100 . a detailed discussion of the remaining components and method of use of a surgical fastening apparatus is disclosed in u . s . pat . no . 6 , 241 , 139 , the entire content of which is incorporated herein by reference . briefly , a surgical fastening apparatus comprising surgical instrument 100 includes an actuation apparatus 10 . surgical instrument 100 is releasably secured to a distal end of actuation apparatus 10 . actuation apparatus 10 includes a motor 12 , a gearshift lever 16 , and gears 18 . motor 12 supplies input rotation to apparatus 10 and is operatively connected to at least one gear 18 . gears 18 are axially trapped between two columns 20 and are configured to mesh with each other . each column has a pair of bores 21 extending therethrough . bores 21 are configured to receive drive members 22 . drive members 22 are operatively coupled to flexible shafts 139 . gearshift lever 16 controls the axial movement of flexible shafts 139 . a user can actuate gearshift lever 16 to translate flexible shafts 139 distally or proximally . additionally , apparatus 10 includes an articulation mechanism 30 including an articulation knob 32 and at least one steering wire 34 . articulation knob 32 is operatively coupled to at least one steering wire 34 . in embodiment illustrated in fig1 , articulation knob 32 is operatively connected to two steering wires 34 . a user can axially move steering wires 34 back and forth by rotating articulation knob 32 . this axial motion causes the articulation of surgical instrument 100 . during operation , a user articulates surgical instrument 100 by pulling one steering wire 139 . the movement of the steering wire bends gooseneck 130 and effectively articulates surgical instrument 100 to one side or the other . gooseneck 130 bends towards the side of the wire that was pulled . in practice , the operator rotates articulation knob 32 apparatus 10 to move a steering wire 34 and thereby articulate surgical instrument 100 . referring to fig2 , surgical instrument 100 includes a gooseneck 130 , channel 150 , a cartridge 110 , and an anvil 120 movably secured in relation to cartridge 110 . channel 150 partially encompasses cartridge 110 . cartridge 110 , which can be replaceable , houses a plurality of fasteners 190 ( see fig3 ) in retention slots 114 . retention slots 114 can be arranged in a single row , as shown in fig2 , or in a plurality of rows . gooseneck 130 is secured to channel 150 . specifically , a distal end of gooseneck 130 can be attached to a proximal end of channel 150 . in turn , a proximal end of gooseneck 130 is operatively secured to the distal end of actuation apparatus 10 . ( see fig1 ). gooseneck 130 facilitates articulation of surgical instrument 100 and can be flexible . further , gooseneck 130 includes at least one hole 141 configured to receive a steering wire 34 . the depicted embodiment shows a gooseneck 130 having two holes 141 extend therethrough . in addition , gooseneck 130 includes at least one bore 132 adapted to receive a flexible shaft 139 . the illustrated embodiment shows a gooseneck 130 having two bores 132 extending through at least a portion of the length of gooseneck 130 . although the drawings show bores 132 having a cylindrical shape , bores 132 can have any suitable shape . flexible shafts 139 are operatively connected to each other and are configured to rotate in opposite directions , i . e ., clockwise and counterclockwise . since the flexible shafts 139 rotate in opposite directions , the torque transmitted by each flexible shaft 139 is canceled , thereby eliminating or substantially limiting the counter torque . as shown in fig1 , flexible shafts 139 are positioned on a neutral axis that extends along a portion of the length of surgical instrument 100 . the depicted embodiment shows one flexible shaft 139 on top of the other . flexible shafts 139 , however , can be placed in numerous arrangements . for instance , flexible shafts 139 can consist of coaxial elongated members positioned on a neutral axis extending along at least a portion of the length of surgical instrument 100 . with reference to fig3 , gooseneck 130 surrounds at least a portion of flexible shafts 139 and steering wires 34 . the distal end of gooseneck 130 is secured to the proximal end of channel 150 by a plurality of screws 160 positioned around the circumference of channel 150 . screws 160 are disposed in a plurality of threaded bores 144 disposed around the circumference of a transition member 140 . transition member 140 is internally interposed between gooseneck 130 and channel 150 . channel 150 has a plurality of holes 152 positioned around the circumference of its proximal end . each hole 152 is designed to receive screws 160 . similarly , gooseneck 130 has a plurality of holes 136 configured to receive screws 160 . holes 136 of gooseneck 130 are located around the circumference of the distal end of gooseneck 130 . screws 160 attach gooseneck 130 to channel 150 through holes 152 of channel 150 , holes 136 of gooseneck 130 and threaded bores 144 of transition member 140 . to properly fix channel 150 to gooseneck 130 , holes 152 of channel 150 , threaded bores 144 of transition member 140 , and holes 136 of gooseneck 130 are substantially aligned with each other . transition member 140 has at least one hole 143 disposed therethrough for receiving steering wires 34 . although fig3 shows holes 143 having a cylindrical shape , it is envisioned that holes 143 can have any suitable shape . additionally , transition member 140 includes at least one longitudinal hole 142 extending therethrough for receiving flexible shafts 139 . in one embodiment , transition member 140 includes two holes 142 having a cylindrical shape . ( see fig3 ). holes 142 , however , can have any shape so long as they are adapted to receive flexible shafts 139 . a distal end of each flexible shaft 139 is operatively secured to a pinion shaft 138 . pinion shafts 138 are configured to rotate and , consequently , cause the rotation of pinions 154 . each pinion 154 is attached to a distal end of a pinion shaft 138 . as seen in fig2 , pinions 154 include at least one tooth 154 a or a plurality of teeth 154 a . tooth or teeth 154 a extends radially as well as longitudinally . the longitudinal portion of tooth or teeth 154 a is adapted to axially engage with gear couplers 156 . returning to fig3 , each pinion 154 is configured to mesh with each other such that the rotation of a flexible shaft 139 rotates the other flexible shaft 139 . as discussed hereinabove , a gear 18 is operatively attached to the proximal end of each flexible shaft 139 . gears 18 are configured to mesh with each other such that the rotation of one flexible shaft 139 rotates the other flexible shaft 139 . thus , flexible shafts 139 are operatively connected to each other at their proximal and distal ends . since flexible shafts 139 are operatively connected with each other , one flexible shaft 139 is redundant . only one flexible shaft 139 is needed to operate surgical instrument 100 . if , for any reason , one flexible shaft 139 breaks , the other flexible shaft 139 can still actuate surgical instrument 100 . as shown in fig2 , the longitudinal portion of tooth or teeth 154 a of each pinion 154 is adapted to axially engage with gear couplers 156 . gear couplers 156 have at least one longitudinal tooth or a plurality of teeth 156 a , and at least one radial tooth or a plurality of teeth 156 b . longitudinal tooth or teeth 156 a of gear couplers 156 extend proximally and are configured to axially engage with tooth or teeth 154 a of pinions 154 . returning to fig3 , clamp pinions 162 have at least one radial tooth or teeth 162 a for meshing with radial tooth or teeth 154 of pinions 154 and are permanently attached to the distal ends of short lead screws 158 . the longitudinal length of short lead screws 158 is less than the longitudinal length of lead screws 112 . short lead screws 158 are axially trapped in transition member 140 and cartridge 110 . surgical instrument 100 can optionally include bearings to axially trap short lead screws 158 . in addition , surgical instrument 100 includes a link 122 positioned within a proximal end portion of channel 150 . particularly , a first end 122 a of link 122 is pivotably connected to the proximal end of an anvil 120 by a link pin 126 . a second end 122 b of link 122 sits in a slot in cam clamp 164 . optionally , at least one projection 122 c can extend from second end 122 b of link 122 . projections 122 c can pivotably fix link 122 to clamp cam 164 . clamp cam 164 is positioned within an inner proximal portion of channel 150 and includes at least one bore 164 a for receiving pinion shafts 138 , at least one bore 164 b for receiving at least one short lead screw 158 , and a slot 164 c configured to receive at least a portion of anvil 120 , as seen in fig4 . at least a portion of each pinion shaft 138 is disposed in bores 164 a . short lead screws 158 are threadedly engaged to threaded bores 164 b of cam clamp 164 . the rotation of short lead screws 158 causes the translation of cam clamp 164 proximally or distally . during operation , as cam clamp 164 moves proximally , projections 122 c slides along the inner diameter of channel 150 , link 122 becomes more vertical , raising proximal end of anvil 120 and causing the distal end of anvil 120 to drop and clamp tissue . conversely , the distal motion of cam clamp 164 causes projections 122 c to slide distally within channel 150 . as projections 122 c move distally , the proximal end of anvil 120 descends , causing the distal end of anvil 120 to ascend and unclamp tissue . with reference to fig5 - 7 , each gear coupler 156 is mounted to the proximal end of each lead screw 112 . lead screws 112 are at least partially threaded and are at least partially disposed within cartridge 110 , as shown in fig5 . cartridge 110 includes a tissue contacting surface 113 having at least one row of longitudinally spaced - apart retention slots 114 , a plurality of pushers 192 , a plurality of fasteners 190 , and a sled 116 slidably positioned therein . retention slots 114 are adapted to receive fasteners 190 . those skilled in the art will contemplate a cartridge 110 with any number of rows of retention slots 114 . for example , cartridge 110 may include two rows of retention slots 114 . in this embodiment , a knife can be placed between these two rows of retention slots 114 . nonetheless , irrespective of the number rows of retention slots 114 , cartridge 110 can include a knife to cut tissue . the knife can be operatively attached to sled 116 . additionally , the cartridge may include an electrical or mechanical interlock mechanism to prevent distal motion of sled 116 unless anvil 120 is in its closed position . sled 116 includes a cam member 116 b and at least one threaded bore 116 a adapted to receive lead screw 112 . pushers 192 have a surface 192 a that cooperates with and is complementary to cam member 116 of sled 116 . during operation of surgical instrument 100 , sled 116 translates through cartridge 110 to advance cam member 116 b into sequential or simultaneous contact with pushers 192 , to cause pushers 192 to translate vertically within retention slots 114 and urge fasteners 190 from retention slots 114 into the staple deforming concavities 125 a of an anvil 120 . the staple deforming cavities 120 a are configured to crimp staples . anvil 120 includes a tissue contacting surface 125 having a plurality of staple deforming concavities 125 a . a single staple deforming concavity 125 a can be adapted to cooperate with the legs of one fastener 190 . alternatively , two or more staple deforming concavities 125 a can cooperate with the legs of a single fastener 190 . a pivot pin 128 pivotably secures anvil 120 to channel 150 . channel 150 has at least one hole 150 a designed to receive pivot pin 128 , as seen in fig2 . pivot pin 180 rests on a support surface 164 d of clamp cam 164 , as shown in fig6 . a proximal end portion 124 of anvil 120 is positioned within channel 150 . link pin 126 pivotably attaches proximal end portion 124 of anvil 120 and link 122 . as discussed hereinabove , channel 150 encompasses at least a portion of cartridge 110 . optionally , screws 153 can connect channel 150 and cartridge 110 with each other , as seen in fig3 . in this embodiment , channel 150 includes at least one hole 151 configured to receive a screws 153 . in operation , surgical instrument 100 applies fasteners 190 to tissue whilst , at the same time , eliminating or substantially limiting counter torque . during use , an operator must first make sure that the surgical instrument 100 is in its neutral position , as shown in fig7 and 8 . when surgical instrument 100 is in its neutral position , anvil 120 and cartridge 110 are spaced apart from each other and pinions 154 are not meshed with clamp pinions 162 , as seen in fig7 - 10 . additionally , in the neutral position , sled 116 is disposed on a proximal portion of cartridge 110 ( see fig7 ) and pinions 154 are not axially engaged with gear couplers 156 ( see fig1 and 12 ). it is also contemplated that the surgical instrument could be configured to eliminate the neutral position and simply operate in a sequential closure - fire - open mode . after placing surgical instrument 100 in its neutral position , a user may approximate it to a tissue portion . to position surgical instrument 100 in the desired surgical site , an operator can endoluminally introduce surgical instrument 100 into the body through a body lumen . alternatively , an operator can use surgical instrument 100 through or in combination with an endoscope to reach the desire location . the tissue portion should be located between anvil 120 and cartridge 110 . a user can articulate surgical instrument 100 to position it on the desired location by moving steering wires 34 . as discussed hereinabove , an embodiment of the presently disclosed surgical instrument 100 includes a gooseneck 130 having two holes 141 each adapted to receive a steering wire 34 , as seen in fig1 . as seen in fig1 , gooseneck 130 is at least partially formed by a plurality of triangular shaped sections 130 a that are spaced apart from each other . in addition , gooseneck 130 is made of a flexible material . each steering wire 34 includes a knot 34 a to secure gooseneck 130 and steering wires 34 at their respective distal ends . in use , an operator can rotate articulation knob 32 counterclockwise , as indicated by arrow “ ccw ,” to translate proximally a steering wire 34 , as indicated by arrow “ a .” in response to the proximal motion of steering wire 34 , surgical instrument 100 articulates in the direction indicated by arrow “ b .” a user can also articulate surgical instrument 100 in the opposite direction by rotating articulation knob 32 clockwise . once the user places surgical instrument 100 in the desire surgical site , the user may move gearshift lever 16 proximally , as indicated by arrow “ c ,” to translate flexible shafts 139 proximally in the direction indicated by arrows “ d ,” as seen in fig1 and 18 . the proximal motion of flexible shafts 139 consequently moves pinion 154 in the direction indicated by arrows “ e ” into a proximal position , as shown in fig1 and 19 . when pinions 154 are located on the proximal position , radial teeth 154 a of pinions 154 mesh with teeth 162 a of clamp pinions 162 , as shown in fig1 . after pinions 154 are placed in their proximal positions , a user can activate actuation apparatus 10 to rotate at least one flexible shaft 139 . in one embodiment , actuation apparatus 10 rotates one flexible shaft 139 clockwise and the other flexible shaft 139 counterclockwise . the rotation of flexible shafts 139 in opposite directions eliminates or substantially reduces counter torque in surgical instrument 100 . while flexible shafts 139 rotate , pinions 154 rotate in the direction indicated by arrows “ f ”, as seen in fig2 . since at this point radial teeth 154 a of pinions 154 are meshed with teeth 162 a of clamp pinions 162 , as soon as pinions 154 rotate , clamp pinions 162 begin to rotate in the direction indicated by arrows “ g ,” as illustrated in fig2 . with reference to fig2 - 23 , when clamp pinions 162 rotate , cam clamp 164 translates proximally in the direction indicated by arrow “ h .” as cam clamp 164 moves proximally , link 122 pivots in a counterclockwise direction “ i ” with respect to pivot pin 126 , raising proximal end of anvil 120 . while the proximal end of anvil 120 moves vertically , the distal end of anvil 120 descends in the direction indicated by arrow “ j ” and clamps tissue . with reference to fig2 - 28 , after clamping tissue , the operator can move gearshift lever 16 , in the direction indicated by arrow “ k ,” to translate flexible shafts 139 distally as indicated by arrow “ l .” when flexible shafts 139 are distally translated , teeth 154 a of pinions 154 axially engage with longitudinal teeth 156 a of gear couplers 156 , as seen in fig2 . once pinions 154 and gear couplers 156 are axially engaged with each other , gear couplers 156 rotates in response to the rotation of at least one flexible shaft 139 . the rotation of gear couplers 156 causes the corresponding rotation of lead screws 112 in the direction indicated by arrows “ m .” while lead screws 112 rotate , sled 116 translates distally through cartridge 110 in the direction indicated by arrows “ n ,” as depicted in fig2 . sled 116 advances cam member 116 b into sequential contact with pushers 192 , to cause pushers 192 to translate vertically within retention slots 114 and eject fasteners 190 . pushers 192 displace fasteners 190 in the direction indicated by arrows “ 0 ” and towards the staple deforming concavities 125 a of anvil 120 , as shown in fig2 . an electrical or mechanical interlocking mechanism may be provided to prevent firing unless anvil 120 is in the closed position . after clamping and stapling a tissue portion , the user can reverse the input rotation using apparatus 10 . at this moment , at least one flexible shaft 139 rotates and causes the rotation of pinions 154 . when pinions 154 rotate , clamp pinions 162 begin to rotate . the reverse rotation of clamp pinions 162 causes the distal translation of clamp cam 164 . as clamp cam 164 moves distally , projections 122 c of link 122 translate distally within channel 150 . when projections 122 c move distally , the proximal end of anvil 120 descends , causing the distal end of anvil 120 to rise and unclamp the tissue portion , as shown in fig7 . the reversed input rotation can optionally rotate lead screws 112 and translate proximally sled 116 to its original retracted position . it will be understood that various modifications can be made to the embodiments disclosed herein . for example , the surgical instrument may include staples , two - part fasteners or any other suitable fastening element . further , the cartridge can have a more than one row of longitudinally spaced apart retention slots . further still , the cartridge can have any suitable elongated member capable of translating the sled instead of lead screws . therefore , the above description should not be construed as limiting , but merely as exemplifications of embodiments . those skilled in the art will envision other modifications within the scope and spirit of the present disclosure .
a surgical instrument comprises a first elongated member and a second elongated member , the first elongated member and the second elongated member being operatively connected and configured to rotate in opposite directions to substantially limit counter torque . the first and second elongated members are flexible shafts . the surgical instrument can be configured to apply fasteners to a tissue portion . this embodiment of the surgical instrument includes a cartridge having a plurality of fasteners , an anvil , said anvil and cartridge being relatively movable between spaced and approximated positions , and a sled disposed in the cartridge . the sled includes a cam member . the cam member is designed to drive the fasteners through tissue and toward the anvil .