Patent Publication Number: US-2023149037-A1

Title: Laparoscopic grasper with force-limiting grasping mechanism

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 16/679,664 entitled “Laparoscopic Grasper with Force-Limiting Grasping Mechanism” filed on Nov. 11, 2019 which claims priority to and benefit of U.S. Provisional Patent Application Ser. No. 62/768,018 entitled “Laparoscopic Grasper with Force-Limiting Grasping Mechanism” filed on Nov. 15, 2018 which is incorporated herein by reference in its entirety. 
    
    
     BACKGROUND 
     The present application relates to surgical devices and more particularly to instruments for use in minimally-invasive surgery such as laparoscopic grasping instruments. 
     In general and minimally invasive surgical procedures, surgeons frequently use grasping instruments to grasp and manipulate tissue, vasculature, or other objects within the surgical field. While it is desirable to maintain traction on the grasped tissue, it is undesirable to apply excess force to the tissue. The excess force on the tissue could lead to tissue trauma. 
     Conventional surgical grasping instruments have included grasping jaws comprised of a metallic material to grasp and manipulate tissue. Certain conventional surgical grasping instruments have also included force limiting mechanisms including relatively complex compression coil spring assemblies that require relatively large shaft diameters to accommodate. Other conventional grasping instruments have included no dedicated force limiting mechanism. Instead, these convention grasping instruments rely on flexibility and compliance of actuating handles to reduce the impact of forceful grasping. 
     Accordingly, it is desirable to provide a surgical grasping instrument that can reduce the potential for trauma to grasped tissue. It is likewise desirable to provide a surgical grasping instrument that has a simplified mechanism that facilitates relatively low-cost manufacture and assembly. Furthermore, it is desirable to provide a surgical grasping instrument including atraumatic, force limiting features in a device configured for use with a small surgical access port diameter such as a port configured for use with 5 mm instruments. 
     SUMMARY OF THE INVENTION 
     In certain embodiments, a surgical grasping instrument is provided herein. The surgical grasping instrument comprises: a handle assembly, an elongate shaft, and a jaw assembly. The handle assembly comprises: a stationary handle, and a movable handle pivotably coupled to the stationary handle. The elongate shaft extends distally from the handle assembly. The elongate shaft has a proximal end coupled to the handle assembly, a distal end opposite the proximal end, and a central longitudinal axis defined by the proximal end and the distal end. The elongate shaft comprises: an outer tube, and an actuator positioned longitudinally within the outer tube. The actuator has a sliding fit within the outer tube and is responsive to pivotal movement of the movable handle. The jaw assembly is disposed at the distal end of the elongate shaft. The jaw assembly comprises a first jaw and a second jaw. The first and second jaws are pivotable between an open configuration of the jaw assembly and a closed configuration of the jaw assembly responsive to pivotal movement of the movable handle. The actuator has a first length along the central longitudinal axis. The actuator comprises an extension element configured to lengthen the actuator to a second length greater than the first length in response to a predetermined force applied to the actuator. 
     In certain embodiments, a surgical instrument is provided herein. The surgical instrument comprises: a handle assembly; an elongate shaft, and an end effector. The handle assembly comprises: a stationary handle; a movable handle pivotably coupled to the stationary handle; and a locking mechanism. The lock mechanism comprises: a locking member and a lock release. The locking member has a lock portion extending within the handle assembly and a trigger portion extending adjacent an outer surface of the stationary handle. The locking member is movable between a locked position and an unlocked position. The lock release is coupled to the stationary handle. The lock release is configured to maintain the locking member in the locked position. The lock release is actuatable to release the locking member to the unlocked position. The elongate shaft extends distally from the handle assembly. The elongate shaft has a proximal end coupled to the handle assembly, a distal end opposite the proximal end, and a central longitudinal axis defined by the proximal end and the distal end. The elongate shaft comprises an outer tube and an actuator positioned longitudinally within the outer tube. The actuator has a sliding fit with the outer tube and the actuator is responsive to pivotal movement of the movable handle. The actuator has a proximal section extending within the handle assembly to a proximal end. The actuator comprises a locking surface adjacent the proximal end. The lock portion of the locking member is engaged with the locking surface of the actuator with the locking mechanism in the locked position. The end effector is disposed at the distal end of the elongate shaft. The end effector is movable between a first configuration and a second configuration responsive to pivotal movement of the movable handle. 
     In certain embodiments, a surgical instrument is provided herein. The surgical instrument comprises: a handle assembly; an elongate shaft; and an end effector. The handle assembly comprises: a stationary handle and a movable handle pivotably coupled to the stationary handle. The elongate shaft extends distally from the handle assembly. The elongate shaft has a proximal end coupled to the handle assembly, a distal end opposite the proximal end, and a longitudinal axis defined by the proximal end and the distal end. The elongate shaft comprises: an outer tube, and an actuator positioned longitudinally within the outer tube. The actuator has a sliding fit within the outer tube and is responsive to pivotal movement of the movable handle. The actuator has a length extending along the central longitudinal axis, a height, and a width. The width is substantially smaller than the height such that the actuator has a planar profile. The actuator comprises: a first segment having a first height; and a second segment having a second height smaller than the first height. The second segment defines an extension element longitudinally extendable responsive to force applied to the actuator. The second segment comprises: a plurality of longitudinal sections; a plurality of transverse sections; and a plurality of bends. The plurality of longitudinal sections extends generally parallel to the longitudinal axis. The plurality of transverse sections extends transverse to the longitudinal axis. The plurality of bends are disposed between each longitudinal section of the plurality of longitudinal sections and an adjacent transverse section of the plurality of transverse sections. The end effector is disposed at the distal end of the elongate shaft. The end effector is movable between a first configuration and a second configuration responsive to pivotal movement of the movable handle. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In order to describe the manner which, the above-recited and other advantages and features of the disclosure can be obtained, a more particular description of the principles briefly described above will be rendered by reference to specific embodiments that are illustrated in the appended drawings. Understanding that these drawings depict only embodiments of the disclosure and are not therefore to be considered to be limiting of its scope, the principles herein are described and explained with additional specificity and detail through the use of the accompanying drawings in which the reference numerals designate like parts throughout the figures thereof. 
         FIG.  1    is a perspective view of an embodiment of a surgical grasping instrument; 
         FIG.  2    is an exploded view of the grasping instrument of  FIG.  1   ; 
         FIG.  2 A  is an exploded view of the handle assembly of the grasping instrument of  FIG.  1   ; 
         FIG.  2 B  is an exploded view of the jaw assembly of the grasping instrument of  FIG.  1   ; 
         FIG.  2 C  is an exploded view of the jaw assembly coupled to a distal end of an actuator having a tracked head member of the grasping instrument of  FIG.  1   ; 
         FIG.  2 D  is an exploded view of the jaw assembly, tracked head member, and actuator of  FIG.  2 C ; 
         FIG.  3    is a side view of a jaw assembly of the grasping instrument of  FIG.  1    with the jaw assembly in an open configuration; 
         FIG.  3 A  is a side view of a jaw assembly of the grasping instrument of  FIG.  1    with the jaw assembly in an open configuration and with an outer tube and sleeve removed; 
         FIG.  4    is a side view of a jaw assembly of the grasping instrument of  FIG.  1    with the jaw assembly in a partially closed configuration; 
         FIG.  4 A  is a side view of a jaw assembly of the grasping instrument of  FIG.  1    with the jaw assembly in a partially closed configuration and with an outer tube and sleeve removed; 
         FIG.  5    is a side view of a jaw assembly of the grasping instrument of  FIG.  1    with the jaw assembly in a closed configuration; 
         FIG.  5 A  is a side view of a jaw assembly of the grasping instrument of  FIG.  1    with the jaw assembly in a closed configuration and with an outer tube and sleeve removed; 
         FIG.  6    is a partial cut away side view of a handle assembly of the grasping instrument of  FIG.  1    positioned with the jaw assembly in an open configuration; 
         FIG.  7    is a partial cut away side view of a handle assembly of the grasping instrument of  FIG.  1    positioned with the jaw assembly in a partially closed configuration; 
         FIG.  8    is a partial cut away side view of a handle assembly of the grasping instrument of  FIG.  1    positioned with the jaw assembly in a closed configuration with a latch mechanism engaged in a latched configuration; 
         FIG.  9    is a partial cut away side view of a handle assembly of the grasping instrument of  FIG.  1    positioned with the jaw assembly in a closed configuration with a latch mechanism engaged in an unlatched configuration; 
         FIG.  10    is a side view of an actuator of shaft assembly of the grasping instrument of  FIG.  1    in an undisturbed state and an extended state; 
         FIG.  11 A  is a side view of a portion of the actuator of  FIG.  10    in the undisturbed state; 
         FIG.  11 B  is a side view of a portion of the actuator of  FIG.  10    in the extended state; 
         FIG.  12    is a side view of various embodiments of actuator having an extension element; 
         FIG.  13    is a partial cut away side view of a shaft assembly of an embodiment of surgical instrument with an embodiment of actuator with an extension element; 
         FIG.  14    is a partial cut away side view of a section of the shaft assembly of  FIG.  13   ; and 
         FIG.  15    is a partial cut away side view of a shaft assembly of an embodiment of surgical instrument with an embodiment of actuator with an extension element. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     With reference to  FIG.  1   , an embodiment of a surgical grasping instrument  100  is illustrated. The surgical grasping instrument  100  can extend between a proximal end and a distal end and can comprise an end effector such as a jaw assembly  200  at the distal end, a shaft assembly  300  extending between the proximal end and the distal end, and a handle assembly  400  at the proximal end. In some embodiments, the surgical grasping instrument  100  can be configured for use in minimally-invasive surgical procedures such that it is sized and configured to be extended through a trocar cannula or other surgical access port. For example, in some embodiments, the shaft assembly  300  can comprise a generally tubular body having a smooth outer surface and an outer diameter sized for passage through a trocar cannula having a size classification to receive certain instruments such as, for example, a 12 mm trocar, a 10 mm trocar, and a 5 mm trocar. In other embodiments, certain aspects of the surgical instruments described herein can be adapted for use with surgical access ports having different sizes or in open surgical procedures. 
     With reference to  FIG.  2    and  FIG.  2 B , an exploded view of the surgical grasping instrument  100  of  FIG.  1    is illustrated. In the illustrated embodiment, the jaw assembly  200  of the surgical grasping instrument  100  comprises a first jaw  210  coupled to a second jaw  230  at a pivot  250 . Thus, by pivoting the first and second jaws  210 ,  230  with respect to one another, the jaw assembly  200  can be actuated between an open configuration in which the first jaw  210  is spaced from the second jaw  230  and a closed configuration in which the first jaw  210  is approximated with the second jaw  230  to grasp an object such as tissue, vasculature, or another surgical instrument therebetween. 
     In some embodiments, the jaw assembly  200  can be configured to reduce the potential for tissue trauma during use. For example, the first and/or second jaws  210 ,  230  can include an atraumatic pad formed thereon. As illustrated in both  FIG.  2    and  FIG.  2 B , the first jaw  210  comprises a first atraumatic jaw pad  220  and the second jaw  230  comprises a second atraumatic jaw pad  240 . In some embodiments, the first and second atraumatic pads  220 ,  240  can comprise soft, relatively low durometer atraumatic pads sold under the trademark LATIS®. In other embodiments, the jaw assembly  200  can include pad-less first and second jaws  210 ,  230  and pressure reduction at the jaws can be enhanced by a force reducing or limiting actuation mechanism. 
     With reference to  FIG.  2   ,  FIG.  2 C , and  FIG.  2 D , an exploded view of the surgical grasping instrument  100  of  FIG.  1    is illustrated. In the illustrated embodiment, the first and second jaws  210 ,  230  are pivotally coupled to one another and to shaft (not illustrated) at the pivot  250 . An actuation post or pin  254  protrudes from each of the first and second jaws  210 ,  230  proximal of engagement with the pivot  250 . The jaw assembly  200  is coupled to the distal end of the actuator  310  by a head member  360 , which is positioned between proximal ends of each of the first and second jaws  210 ,  230 . Each side of the head member  360  has a track  364  formed therein. The actuation posts or pins  254  of each of the first and second jaws  210 ,  230  are positioned within respective tracks  364  such that proximal and distal movements of the actuator  310  and head member  360  with respect to the outer tube of the shaft moves the actuation pins  254  to open and close the first and second jaws  210 ,  230 . A shim  370  can be positioned at the distal end of the head member  360  to maintain a desired spacing of the jaw assembly  200  and head member  360  within the outer tube. In the illustrated embodiment, the shim  370  can have a saddle configuration positioned astride the head member  360  and proximal ends of the first and second jaws  210 ,  230  to reduce any tendency of the actuation post or pin  254  to become disengaged from the track  364  under load. 
     With continued reference to  FIG.  2   , the elongate shaft assembly  300  can comprise an actuator  310 , an outer tube  330  and a dielectric sleeve  340 . The actuator can be slidably positioned within the outer tube  330 . The dielectric sleeve  340  can be disposed around an outer surface of the outer tube  330  and provide electrical insulation for the elongate shaft assembly  300 . In certain embodiments, the actuator  310  can comprise a substantially planar member extending generally longitudinally between a proximal end  312  and a distal end  314 . The substantially planar geometry of the actuator  310  can be defined by a length between the proximal end  312  and the distal end  314 , a height orthogonal to the length, and a width orthogonal to both the length and the height. The width is substantially smaller than the height and the length. In certain embodiments, the actuator  310  can comprise a stack of a plurality of actuator strips, such as, for example, two actuator strips to provide an actuator  310  having desired stiffness, extension, and fatigue life characteristics. 
     With continued reference to  FIG.  2    and  FIG.  2 A , in the illustrated embodiment, the handle assembly  400  comprises a housing formed of a pair of housing halves that define a stationary handle  410 , a movable handle  420  pivotably coupled to the stationary handle  410  at a pivot pin of a locking mechanism  430 , and a rotation knob  460 . In the illustrated embodiment, the stationary handle  410  can be contoured to be grasped in the fingers of a user&#39;s hand and the movable handle  420  can include a thumb ring to be engaged by a user&#39;s thumb and moved by flexion and extension of the user&#39;s thumb. It is contemplated that in other embodiments, other configurations of handle assembly can be used with the elongate shaft assemblies and end effector assemblies described herein. 
     With reference to  FIG.  3   - FIG.  5    and  FIG.  3 A - FIG.  5 A , the jaw assembly  200  of the surgical grasping instrument is illustrated in open ( FIG.  3    and  FIG.  3 A ), partially closed ( FIG.  4    and  FIG.  4 A ), and closed configurations ( FIG.  5    and  FIG.  5 A ). As illustrated in  FIGS.  3  and  3 A , with the jaw assembly  200  in the open configuration, the first jaw  210  is spaced from the second jaw  230  such that a user can position the surgical grasping instrument in a surgical site with an object to be grasped positioned between the first and second jaws  210 ,  230 . The first jaw  210  and the second jaw  230  are pivotably coupled to one another at a pivot  250  such as a linkage rivet, pin, or other pivotable assembly. 
     With continued reference to  FIG.  3    and  FIG.  3 A , the pivot  250  is also coupled to the outer tube  330  of the elongate shaft assembly  300  at the distal end of the elongate shaft assembly  300 . The elongate shaft assembly  300  can further comprise a head member  360  that engages the first and second jaws  210 ,  230  of the jaw assembly  200  at engagement locations proximal the pivot  250 . For example, in certain embodiments, the first and second jaws  210 ,  230  can each comprise an actuation pin protruding radially inwardly with respect to the elongate shaft assembly  300  at a location proximal the pivot  250 , and the head member  360  can include a first groove, slot, or track  364  positioned to receive the actuation pin of the first jaw  210  and a second groove, slot, or track formed therein positioned to receive the actuation pin of the second jaw  230 . The first track and the second track can extend transversely relative to the central longitudinal axis of the elongate shaft assembly  300  such that proximal and distal movement of the head member  360  pivots the first and second jaws  210 ,  230  relative to one another about the pivot  250 . 
     With continued reference to  FIG.  3    and  FIG.  3 A , in some embodiments, the elongate shaft assembly  300  can further include a jaw support member such as at least one shim member positioned within the outer tube  330  at the distal end to longitudinally align and maintain spacing of the head member  360  and the jaw assembly  200  relative to the central longitudinal axis. In the illustrated embodiments, the elongate shaft assembly  300  can include a seal element  350  disposed between the head member  360  and an inner surface of the outer tube  330  to prevent fluid and gas ingress or leakage from a surgical site into the elongate shaft assembly. For example, the elongate shaft assembly  300  can comprise an O-ring disposed retained by a groove in the head member  360 . 
     With continued reference to  FIG.  3    and  FIG.  3 A , a proximal end of the head member  360  can be coupled to a distal end of the actuator  310 . In some embodiments, the proximal end of the head member  360  and the distal end of the actuator  310  can be configured to provide a coupling that is rotatable about the central longitudinal axis of the elongate shaft assembly  300 . For example, as illustrated, the proximal end of the head member  360  comprises a protruding annular post  362 , and the distal end  314  of the actuator  310  can comprise a cutout sized and configured to receive the annular post  362  and allow rotation of the jaw assembly  200  relative to the central longitudinal axis of the elongate shaft assembly  300 . As further described with reference to  FIG.  6   , rotation of the rotation knob  460  of the handle assembly  400  can thus rotate the outer tube  330  of the elongate shaft assembly  300  to rotate the jaw assembly  200  to a desired orientation relative to the central longitudinal axis. 
     With continued reference to  FIG.  3    and  FIG.  3 A , in some embodiments, the head member  360  can be formed by a metal injection molding (MIM) process. Advantageously, this MIM process can allow the efficient, rapid manufacture of a head member  360  of a metallic material having desirable strength and fatigue life characteristics and being formed to have desired geometric features, with integrated tracks or slots to engage the jaw assembly  200  and a post or positioning pin to engage the actuator  310  as described above. In other embodiments, the head member  360  can be formed of a metallic material that has been cast, machined, or otherwise processed to have the desired geometry. In other embodiments, the head member  360  can be formed of a non-metallic material. 
     With reference to  FIG.  4    and  FIG.  4 A , an embodiment of jaw assembly  200  is illustrated in a partially closed configuration. As illustrated, proximal translation of the actuator  310  along the central longitudinal axis pivots the first jaw  210  and the second jaw  230  relative to one another to approximate the first jaw pad  220  and the second jaw pad  240 . 
     With continued reference to  FIG.  4    and  FIG.  4 A , the first jaw  210  and the second jaw  230  have the same geometric features and pivot about the same pivot axis, which extends transversely to the central longitudinal axis. In the illustrated embodiment, the pivot axis of the first and second jaws  210 ,  230  extend generally perpendicularly to the central longitudinal axis. The first jaw  210  has a generally elongate configuration defining a first jaw axis, and the second jaw  230  has a generally elongate configuration defining a second jaw axis. In certain embodiments, proximal translation of the actuator  310  pivots the first and second jaws  210 ,  230  from an open position in which an angle defined between the first jaw axis and the second jaw axis is approximately 45 degrees, and a closed position in which the angle defined between the first jaw axis and the second jaw axis is approximately 0 degrees. 
     With reference to  FIGS.  5  and  5 A , an embodiment of jaw assembly  200  is illustrated in a closed configuration. In the closed configuration, the first jaw  210  and the second jaw  230  are approximated such that the first jaw pad  220  is adjacent the second jaw pad  240  or separated by an object being grasped. As noted above, the first jaw pad  220  and second jaw pad  240  can be formed of a material selected to be atraumatic to tissue grasped therebetween. Moreover, the first jaw pad  220  and second jaw pad  240  can be disposed over a relatively large surface area relative to the first jaw  210  and the second jaw  230 . For example, desirably, the first and second jaw pads  220 ,  240  can extend along at least about 20% of a length of the first and second jaws  210 ,  230  distal the pivot  250 . More desirably, the jaw pads  220 ,  240  can extend along at least about 25% of a length of the first and second jaws  210 ,  230  distal the pivot  250 . Advantageously, this relatively large atraumatic contact surface can distribute pressure applied to a grasped object over a large surface area to reduce the risk of trauma to grasped tissue. Moreover, the first and second jaw pads  220 ,  240  can be disposed at a transverse angle relative to a longitudinal axis defined by respective first and second jaws  210 ,  230 . Thus, the angular seating of the first and second jaw pads  220 ,  240  can tend to draw a grasped object proximally with respect to the central longitudinal axis. This angular seating of the first and second jaw pads  220 ,  240  can advantageously increase the tractive ability of the surgical grasping instrument without significantly increasing the pressure applied to a grasped object. 
     With continued reference to  FIG.  5   , in the illustrated embodiment of the jaw assembly  200 , the first and second jaws  210 ,  230  can be configured to further reduce the incidence of trauma to tissue in the surgical site, the surgical access port, and other surgical instruments. For example, the first and second jaws  210 ,  230  can each be formed of a composite construction comprising a rigid metallic inner jaw spine to which an atraumatic non-metallic outer surface is applied. The first and second jaw pads  220 ,  240  can be disposed on the atraumatic non-metallic outer surface. Desirably, in some embodiments, the first and second jaws  210 ,  230  can each comprise a metallic inner jaw spine to which a plastic overmolded outer surface is applied. The plastic overmolds can each have a pad surface sized and be configured to receive the respective first and second jaw pads  220 ,  240 . The pad surfaces can be formed at a transverse angle relative to a longitudinal axis of the respective first and second jaws  210 ,  230  to position the first and second jaw pads  220 ,  240  at an angled orientation. The first and second jaw pads  220 ,  240  can be adhered or otherwise bonded to the pad surface. 
     With reference to  FIG.  6   , an embodiment of the handle assembly  400  for the surgical grasping instruments  100  described herein is illustrated. As illustrated, the movable handle  420  is spaced from the stationary handle  410  to position the jaw assembly  200  in an open configuration, as illustrated in  FIG.  3   . Desirably, in certain embodiments, the stationary handle  410  can have an ergonomic finger grip comprising an elastomeric finger grip insert  415  ( FIG.  2   ) removably positioned in the grip to provide a soft touch surface for a user. Likewise, a thumb ring of the movable handle  420  can comprise an elastomeric thumb ring insert  425  ( FIG.  2   ) removably positioned in the thumb ring to provide a soft touch surface for a user. A user can additionally rotate rotation knob  460  relative to the handle assembly  400  to rotate the outer tube  330  relative to the handle assembly  400 . For example, the handle assembly  400  can be configured with an ergonomic profile such that a user&#39;s index finger can easily be extended to rotate the rotation knob  460 . This rotation can orient the jaw assembly  200  coupled to the outer tube  330  in a desired orientation about tissue, vasculature, or another object to be grasped. 
     With reference to  FIG.  7   , the handle assembly  400  is illustrated in a partially closed configuration corresponding to the jaw assembly  200  in a partially closed configuration as illustrated in  FIG.  4   . In the partially closed configuration, the movable handle  420  is pivoted relative to the stationary handle  410  about the pivot pin of the locking mechanism  430 . In the illustrated embodiment, the movable handle extends from a first end  422  having the thumb ring to a second end  424 . The pivot pin of the locking mechanism  430  is disposed between the first end  422  and the second end  424 . The second end  424  of the movable handle  420  is coupled to the proximal end  312  of the actuator  310 . In some embodiments the proximal end  312  of the actuator  310  can comprise a proximal coupler  313  such as a recess, bore, slot, or other feature that is configured to be coupled to with the second end  424  of the movable handle  420  and allow the transfer of force therebetween. In the illustrated embodiment, the proximal coupler comprises a bore that can receive a post protruding from the second end  424  of the movable handle  420  or can be coupled thereto by a coupling pin or rivet. Thus, as the movable handle  420  is pivoted about the pivot pin of the locking mechanism  430 , the actuator  310  is pulled proximally with respect to the central longitudinal axis. This proximal movement likewise moves the head member  360  of the elongate shaft assembly  300  proximally to close the jaw assembly  200 , as shown in  FIG.  4   . 
     With reference to  FIG.  8    and  FIG.  9   , further movement of the movable handle  420  can further actuate the surgical grasping instrument to move the jaw assembly  200  to a closed configuration as shown in  FIG.  5   . In some embodiments, the handle assembly  400  further comprises the locking mechanism therein to maintain the movable handle  420  in a desired position relative to the stationary handle  410 . In certain embodiments, the locking mechanism  430  can comprise a trigger lock  440  and a lock release  450  that are actuated by a user to latch and unlatch the locking mechanism. 
     With continued reference to  FIG.  8    and  FIG.  9   , an embodiment of the locking mechanism  430  is illustrated in latched ( FIG.  8   ) and unlatched ( FIG.  9   ) configurations. The trigger lock  440  of the locking mechanism  430  extends from a first end having a trigger portion  444  extending adjacent the stationary handle  410  to a second end having a locking portion  442  and positioned within the handle assembly  400  adjacent the actuator  310 . In some embodiments, the actuator  310  can have an engagement surface such as a latch recess formed therein and sized and configured to be selectively engaged by the locking portion  442  of the trigger lock  440  when the locking mechanism  430  is in a latched configuration. The locking mechanism  430  can further comprise a locking spring  446  within the handle assembly to bias the locking portion  442  of the trigger lock  440  to maintain the engagement of the locking portion  442  with the latch recess when the locking mechanism  430  is in the latched configuration. 
     With reference to  FIG.  8   , with the locking mechanism  430  in a latched configuration, the locking portion  442  of the trigger lock  440  is positioned and oriented to restrict the actuator  310  from freely translating proximally and distally with respect to the central longitudinal axis. For example, in some embodiments, the locking portion  442  can comprise a passage or generally rectangular window formed therein through which the actuator  310  can freely translate when the locking portion  442  is oriented generally perpendicularly to the actuator  310  (as illustrated in  FIG.  9   ) and which engages the actuator  310  when passage of the locking portion is misaligned with an axis perpendicular to the longitudinal axis of the actuator ( FIG.  8   ). The locking spring  446  biases the locking portion  442  of the trigger lock  440  into binding engagement with the actuator  310  once the lock release  450  has been depressed to allow the trigger lock  440  to separate from the stationary handle  410 . Thus, this engagement between the trigger lock  440  and actuator  310  locks the jaw assembly  200  in a desired position. 
     In some embodiments, the trigger lock  440  of the locking mechanism  430  may define a reverse limit for the jaw assembly  220  preventing attempts by the jaw assembly  220  to revert from the closed position to the open position beyond the point defined by the locking mechanism  430 . However, the restrictions imposed by the trigger lock  440  may not define a forward limit corresponding to an extent the jaw assembly  220  compresses the tissue in the closed position. 
     With reference to  FIG.  9   , when a user desires to reposition the first and second jaws to grasp tissue specimens, the movable handle  420  can be moved to a desired position such as a partially closed or closed position with the locking mechanism  430  in an unlatched configuration having the trigger lock  440  approximated with the stationary handle  410  by latching engagement with the lock release  450 . As illustrated, an end of the trigger portion  444  can be advanced over the lock release  450  and maintained adjacent the stationary handle  410  by the lock release  450 . With the trigger lock  440  positioned adjacent the stationary handle  410 , the locking portion  442  of the trigger lock  440  is oriented to allow free translation of actuator  310  through the passage formed in the locking portion  442  responsive to movement of the movable handle  420 . 
     With continued reference to  FIG.  9   , in certain embodiments, the lock release  450  can be pivotally coupled to the stationary handle  410  at a lock release pivot  452 . The lock release  450  can be biased to maintain the trigger portion  444  of the trigger lock  440  adjacent the stationary handle  410 . In the illustrated embodiment, the lock release  450  can be biased with a lock release spring  454  disposed within the handle assembly. In is contemplated that in other embodiments, the lock release  450  can be formed of a flexible member extending from the stationary handle  410  with the desired bias and without a lock release pivot. When a user desires to engage the locking mechanism  430  to maintain a fixed position of the movable handle  420 , actuator  310 , and jaw assembly  200 , the user can depress the lock release  450  to overcome the bias of the lock release spring  454  and pivot the lock release  450  out of engagement with the end of the trigger portion  444  of the trigger lock  440 . 
     With reference to  FIG.  10   , an embodiment of actuator  310  for use in the elongate shaft assemblies described herein is illustrated in undisturbed (upper) and extended (lower) states. The actuator  310  has a substantially planar configuration with a significantly small width relative to its length and height. Advantageously, this planar configuration can be efficiently manufactured from a coil or sheet of a metallic material that can be heat treated to achieve desired tensile strength and durability characteristics. For example, in some embodiments, the actuator  310  can be stamped from a sheet of a metallic material having desired structural properties. In some embodiments, the actuator  310  can be formed from a metallic material such as a coil sheet of 17-7 PH stainless steel. In certain embodiments of the surgical grasping instrument, two or more stamped sheet actuators can be arranged in parallel in an adjoining orientation to achieve desired extension properties and durability characteristics while being relatively rapidly manufacturable by progressive stamping. In some embodiments, the actuator  310  can be configured to limit the force applied to an object being grasped, which advantageously can reduce the incidence of trauma to grasped tissue. 
     With continued reference to  FIG.  10   , in some embodiments, the actuator  310  can comprise a segment formed to define an integrated extension element  316 . Advantageously, the extension element  316  can function as a force-limiting spring mechanism for the actuator  310  having an integrated construction that allows for low-cost, efficient manufacture of the actuator  310 . As illustrated, the extension element  316  can be disposed between the proximal end  312  and distal end  314  of the actuator  310 , with the remaining segments of the actuator defining a non-extending, or rigid elements  324 . As illustrated, in one embodiment, the extension element  316  can have a height orthogonal to the length of the actuator  310  that is smaller than a corresponding height of the rigid elements  324 . In the illustrated embodiment, the extension element  316  comprises a height that is approximately half of the height of the rigid elements  324 . 
     With reference to  FIG.  10   ,  FIG.  11 A , and  FIG.  11 B  in some embodiments the extension element  316  can comprise a geometric profile defining a desired spring constant for the actuator  310 . For example, in certain embodiments, the extension element  316  comprises a plurality of longitudinal sections  322  extending generally parallel to the central longitudinal axis, a plurality of transverse sections  318  extending transverse to the central longitudinal axis, and a plurality of bends  320  disposed between each longitudinal section of the plurality of longitudinal sections and an adjacent transverse section of the plurality of transverse sections. In certain embodiments, each bend  320  can comprise an arc segment having an inner radius and an outer radius. In certain embodiments, the extension element  316  can comprise a plurality of extension sections  317 . In certain embodiments, each individual extension section  317  is a full section defined by a segment of a generally waveform-like profile extending from a peak to an adjacent peak (or a trough to an adjacent trough). Thus, each extension section  317  can comprise a first longitudinal segment  322 , a first bend  320 , a first transverse segment  318 , a second bend  321 , a second longitudinal segment  323 , a third bend  325 , a second transverse segment  319 , and a fourth bend  327 . 
     With continued reference to  FIG.  10   ,  FIG.  11 A , and  FIG.  11 B , when a tensile force is applied to the actuator  310 , a distance (X) ( FIG.  11 A ) between adjacent longitudinal segments  322  will extend to an extended length (X+ΔX) ( FIG.  11 B ) such that the overall length between the proximal end  312  and the distal end  314  is extended ( FIG.  10   ). Thus, this extension characteristic of the actuator  310  can desirably limit a force applied by the jaw assembly of a surgical grasping instrument. In the event a user applies a relatively high force or attempts to grasp a relatively thick tissue sample, a portion of the applied force will extend the actuator, rather than being directly applied to grasped tissue. 
     With continued reference to  FIG.  10   ,  FIG.  11 A , and  FIG.  11 B  in certain embodiments, the dimensions of the longitudinal segments  322 , bends  320 , and transverse segments  318  can be sized and configured to provide an extension element  316  having a desired spring constant and resistance to fatigue. In certain embodiments, the actuator  310  is formed of a rigid material, such as a stainless-steel sheet material, which has elastic properties under controlled tensile loads. Desirably, the actuator  310  can have a substantially planar configuration with a width or thickness dimension being significantly smaller than a height or length dimension. In certain embodiments, whereas the surgical grasping instrument is introduced within 5 mm trocar delivery systems, the outer tube can have a maximum outer diameter of 0.197 inch and a minimum inner diameter of 0.140 inch. In certain embodiments, the actuator  310  positioned within the outer tube can have a height between 0.090 inch and 0.100 inch and have a thickness between 0.010 inch and 0.110 inch. Desirably, two actuators can have a combined thickness between 0.020 inch and 0.110 inch. In certain embodiments, multiple actuators can be assembled together in parallel, having a combined thickness between 0.020 inch and 0.110 inch. In certain embodiments, although the surgical grasping instrument is introduced within greater than 5 mm trocar delivery systems, the actuator  310  can have a maximum height of 0.350 inch and have a thickness between 0.010 inch and 0.250 inch. In some embodiments for use with an instrument sized and configured for placement through a 5 mm category access port such as a 5 mm trocar, the actuator  310  can have a thickness of approximately 0.040 inch. In certain embodiments, the actuator  310  can comprise a stack of two adjoining actuator members each having a thickness of approximately 0.020 inch. 
     With continued reference to  FIG.  10   ,  FIG.  11 A , and  FIG.  11 B  in certain embodiments, the extension element  316  can comprise at least 20 extension sections  317 . Desirably, the extension element can comprise at least 30 extension sections  317 . More desirably, in certain embodiments, the extension element  316  can comprise at least 40 extension sections  317 . In certain embodiments, the extension element  316  can comprise 48 extension sections  317 . While the illustrated embodiment includes a plurality of extension sections  317  that each have a consistent geometry, repeating to form the extension element  316 , in other embodiments, the extension element  316  can be formed of various segment and bend geometries that have a variable pattern along a length of the actuator  310 . 
     With continued reference to  FIG.  10   ,  FIG.  11 A , and  FIG.  11 B , in certain embodiments the bends  320  can have an arc geometry defined by an inner radius and an outer radius. In other embodiments, the bends  320  can be formed by sections having sharp angles with no fillet or radii. In certain embodiments, the inner radius can be between about 0.02 inch and 0.08 inch. Desirably, a full radius defined by the inner radius can be between approximately 0.05 inch and 0.06 inch. In certain embodiments, the outer radius can be between approximately 0.024 inch and 0.054 inch. In some embodiments, the inner radius is greater than the outer radius. In other embodiments, the inner radius is less than the outer radius. In certain embodiments, a full radius defined by the inner radius is approximately 0.05 inch and the outer radius is approximately 0.044 inch. In other embodiments, a full radius defined by the inner radius is approximately 0.06 inch and the outer radius is approximately 0.036 inch. 
     In certain embodiments, the inner and outer radii can be sized and configured to provide an extension element  316  having a relatively constant width defined by a line tangent to an upper edge and a lower edge of the extension element  316 . In certain embodiments, the width defined by the line tangent to the upper edge and the lower edge of the extension element  316  is between about 0.060 inch and 0.080 inch. Desirably, the width of the extension element  316  defined by the tangent line can be between about 0.065 inch and 0.075 inch. In certain embodiments, the width of the extension element  316  defined by the tangent line can be about 0.07 inches. 
     With continued reference to  FIG.  10   ,  FIG.  11 A , and  FIG.  11 B , the extension element  316  of the actuator  310  can be spaced from the distal end  314  by a rigid element  324  defining a connector end with a straight section having a height greater than the width defined by the line tangent to the upper edge and the lower edge of the extension element  316 . In some embodiments, the extension element  316  can be spaced apart from the distal end  314  by at least 0.2 inch. In other embodiments, the extension element  316  can be spaced from the distal end  314  by a connector end straight section having a minimal distance of as approximately 0.02 inch. 
     With continued reference to  FIG.  10   ,  FIG.  11 A , and  FIG.  11 B , in certain embodiments, a total length of each full extension section  317  can be sized and configured to provide a desired spring constant and fatigue strength. In some embodiments, the length of each full extension section  317  can be between approximately 0.200 inch and 0.360 inch. Desirably, the length of each extension section  317  can be between approximately 0.240 inch and 0.260 inch. In certain embodiments, each extension section can have a length of approximately 0.240 inch. In other embodiments, each extension section can have a length of approximately 0.260 inch. 
     With continued reference to  FIG.  10    and  FIG.  11 A , desirably, when a force applied to the actuator  310  by actuation of the movable handle is below a predetermined level, the actuator  310  translates within the outer tube  330  with the extension element  316  maintaining a constant length. Thus, with a relatively low force applied to the actuator  310 , the actuator  310  functions as a solid rod actuator. The actuator  310  has a first length along the central longitudinal axis that remains constant on translation with application of a relatively low force to move the actuator  330  as a solid rod. 
     With reference to  FIG.  10    and  FIG.  11 B , when a relatively high force is applied to the actuator  310 , such as when a thick tissue specimen is inserted between the first and second jaws of the jaw assembly, the extension element  316  can stretch in response, thereby reducing the effective stroke length of the actuator  310  at the distal end  314 . In some embodiments, the actuator  310  functions as a spring-like actuator. Thus, upon application of a predetermined extension force, the actuator  310  extends to a second length greater than the first length. In this higher force loading condition, the actuator  310  both translates within the outer tube  330  and extends in length between the proximal end  312  and the distal end  314 . This reduced effective stroke length provided by extension of the extension element  316  advantageously limits the force applied by the end effector or jaw assembly and correspondingly reduces a risk of trauma to tissue grasped by the jaw assembly. The actuator  310  provides this force limiting performance as a single, integral component without the added mechanical and manufacturing complexities and increased expenditures of one or more additional springs. Desirably, the extension element  316  of the actuator  310  is sized and configured to deform elastically when a relatively high force is applied thereto as illustrated in  FIG.  11 B  such that once the force is released, the actuator  310  returns to its original, undeformed state and length. 
     In a further embodiment, the actuator  310  is also sized and configured to supplement the first and second jaws of the jaw assembly with force that was loaded into the actuator  310  (which caused the actuator  310  to deform elastically as described above). In some cases, the jaw assembly may be locked in a closed position with tissue that is being grasped between the first and second jaw. The extent that the jaw assembly is in contact with the tissue is based on the thickness and/or volume of the tissue being grasped as well as the pre-determined amount of force that is provided to the tissue. However, if the tissue deforms (e.g., as fluids leave or are pushed out of the cells associated with the grasped tissue) which causes the thickness and volume of tissue being initially grasped to decrease, the original contact between the tissue and the jaw assembly may no longer be possible. Furthermore, in a conventional surgical grasper with a rigid, non-elastic actuator, since the first and second jaws of the jaw assembly are locked, tissue deformation may prevent the jaw assembly from properly grasping the tissue possibly causing the contact with the tissue to become loose or even slip from the jaw assembly. 
     Desirably, certain embodiments of the surgical grasping device described herein can provide a dynamic amount of force from the actuator  310  in order to maintain constant and/or consistent contact with the tissue between the first and second jaws of the jaw assembly as the tissue deforms. The dynamic amount of force being provided to the jaw assembly is supplied from the excess force that was previously loaded into the actuator  310 . As discussed above, the actuator  310  may extend from a first length to a second greater length when loading force being provided by the user (via the movable handle). As the thickness and volume of tissue that was initially grasped between the first and second jaws of the jaw assembly changes (e.g., via deformation), a response from the actuator  310  can provide the force that was loaded into the actuator  310  to the jaw assembly so that the first and second jaws are pivoted closer towards each other in order to maintain contact with the tissue. This force, as it leaves the actuator  310 , causes the actuator  310  to retract from the second greater length back towards the first length. The response from the actuator  310  provides additional force to the first and second jaws as needed to maintain contact with the deforming/deformed tissue based on the extent the thickness and volume of the tissue changes over time. In this way, contact with the tissue, as the tissue deforms, can be made constant/consistent between the first and second jaws of the jaw assembly. 
     With reference to  FIG.  10    and  FIG.  12   , various embodiments of the actuator  310  are illustrated having different lengths of rigid element  324  adjacent the proximal end. As illustrated, the extension element  316  of the actuator  310  can be spaced from the proximal end  312  by a rigid element  324  having a height greater than a width of the extension element  316  defined by a line tangent to the upper edge and the lower edge of the extension element  316 . In certain embodiments, it can be desired that the length of rigid element  324  adjacent the proximal end be relatively long to conform to surgical instruments having different dimensions or operational configurations. For example, as illustrated in  FIG.  12   , an extension element  316  having a substantially similar configuration can be used in each of a 35 cm length single-use grasper (uppermost illustrated actuator), a 45 cm single-use grasper (second actuator from top), a 38 cm reposable grasper shaft (third actuator from top), and a 45 cm reposable grasper shaft (lowermost actuator). Alternatively, by varying the length of the extension element  316  relative to the lengths of the rigid elements  324  at the proximal and distal ends  213 ,  314  of the actuator  310 , desired extension properties of the actuator  310  can be achieved. 
     With reference to  FIG.  10   - FIG.  12   , the illustrated embodiments include a planar actuator  310  with an extension element  316  integrally formed therewith. Advantageously, this planar actuator can provide manufacturing efficiencies and can fit within and be constrained for translation within a relatively small space, such as an elongate shaft assembly sized for insertion through a surgical access port for 5 mm laparoscopic instruments. In other embodiments, it is contemplated that other actuator configurations can provide a desired integrated force-limiting extension element. 
     With reference to  FIG.  13    and  FIG.  14   , a partial cut-away side view of an embodiment of elongate shaft assembly  300 ′ for use in a surgical instrument is illustrated. In the illustrated embodiment, the elongate shaft assembly  300 ′ comprises an actuator  310 ′ having a non-planar configuration with a generally repeating waveform or convoluted profile. This convoluted profile can desirably allow the actuator  310 ′ to extend when a relatively high force is applied while still performing as a solid rod actuator, as discussed above with respect to actuator  300 . In some embodiments, the non-planar actuator  310 ′ configuration can provide flexibility such that the actuator  310 ′ can be disposed within a flexible outer tube  330 ′ or an outer tube having a curvature, rather than constrained within a relatively rigid outer tube. In some embodiments, the actuator  310 ′ can comprise a metallic material, in other embodiments, the actuator  310 ′ can comprise a polymeric material, and in other embodiments, the actuator  310 ′ can comprise a polymer-metal composite material. In certain embodiments, a convoluted, non-planar actuator  310 ′ can be formed of a polymeric material through an injection molding process. In other embodiments, a convoluted, non-planar actuator  310 ′ can be formed of a polymeric material through an extrusion process. 
     With continued reference to  FIG.  13    and  FIG.  14   , the convoluted profile of the actuator  310 ′ defining a relieved cylindrical outer surface. This convoluted profile can desirably a provide enhanced flexibility about two orthogonal axes such that the actuator  310 ′ can be disposed within a flexible outer tube  330 ′ or an outer tube having a curvature, rather than constrained within a relatively rigid outer tube. 
     With reference to  FIG.  15   , in some embodiments, an actuator  310 ″ can comprise a hollow tubular member with relief slots  316 ″ formed therein to define a flexible and extendable segment therein. These relief slots can desirably allow the slotted-tube actuator to extend when a relatively high force is applied while still performing as a solid rod actuator, as discussed above with respect to actuator  300 . In some embodiments, as with the non-planar actuators  310 ′ the slotted-tube actuator  310 ″ can provide flexibility about multiple orthogonal axes such that the slotted-tube actuator can be disposed within a flexible outer tube or an outer tube having a curvature, rather than constrained within a relatively rigid outer tube. In some embodiments, the slotted-tube actuator can comprise a metallic material, in other embodiments, the slotted-tube actuator can comprise a polymeric material, and in other embodiments, the slotted-tube actuator can comprise a polymer-metal composite material. 
     It is contemplated that various other actuator configurations can provide similar integrated extension element performance as described herein with respect to a planar sheet actuator. For example, in certain other embodiments, surgical instruments can include an actuator comprised of or formed from a wire, such as for example a wire having a solid, round, semi-circular, rectangular, or square cross-sectional profile, or braided rope cables formed of multiple wire or filament strands. Additionally, it is contemplated that while certain embodiments of planar actuator are described as formed of a metallic material, in other embodiments, the actuator can be formed of a polymeric material. Furthermore, while the actuation mechanisms are discussed herein with respect to certain advantages in a surgical grasper instrument, it is contemplated that various aspects of the actuation mechanisms can likewise provide advantages in other surgical instruments and in various devices outside the medical field in which it can be desirable to provide an extension element that operates as a solid rod actuator with a relatively low applied force and an extension element with a relatively high applied force. 
     Although this application discloses certain preferred embodiments and examples, it will be understood by those skilled in the art that the present inventions extend beyond the specifically disclosed embodiments to other alternative embodiments and/or uses of the invention and obvious modifications and equivalents thereof. Further, the various features of these inventions can be used alone, or in combination with other features of these inventions other than as expressly described above. Thus, it is intended that the scope of the present inventions herein disclosed should not be limited by the particular disclosed embodiments described above but should be determined only by a fair reading of the claims granted on a related non-provisional application.