Abstract:
A surgical instrument including a housing, a shaft, and end effector, and a sensor. The shaft extends distally from the housing. The end effector is disposed at a distal end of the shaft and includes first and second jaw members that are moveable relative between first and second configurations. The first and second jaw members are spaced relative to one another in the first configuration and are closer to one another for approximating tissue in the second configuration. A gap distance is defined between the first and second jaw members. The sensor is positioned within the housing and operable to determine the size of the gap distance. The first and second jaw members configured to be electrical activated to treat tissue between the first and second jaw members when the size of the gap distance is within an acceptable range.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    The present application claims the benefit of and priority to U.S. Provisional Application Ser. No. 62/288,975, filed on Jan. 29, 2016, the entire contents of which are incorporated herein by reference. 
     
    
     BACKGROUND 
       [0002]    1. Technical Field 
         [0003]    The present disclosure relates to electrosurgical forceps and more particularly, to a jaw aperture position sensor for use with an endoscopic or open bipolar and/or monopolar electrosurgical forceps for sealing, cutting, and/or coagulating tissue. 
         [0004]    2. Discussion of Related Art 
         [0005]    Electrosurgical forceps utilize both mechanical clamping action and electrical energy to affect hemostasis by heating the tissue and blood vessels to coagulate, cauterize and/or seal tissue. Electrosurgical forceps may be open forceps for use during open surgical procedures or may be endoscopic forceps for remotely accessing organs through smaller, puncture-like incisions. 
         [0006]    Many surgical procedures require cutting or ligating blood vessels or vascular tissue. By utilizing an endoscopic electrosurgical forceps, a surgeon can cauterize, coagulate/desiccate, and/or simply reduce or slow bleeding simply by controlling the intensity, frequency and duration of the electrosurgical energy applied through the jaw members to the tissue. 
         [0007]    In order to effectively seal vessels (or tissue) two predominant mechanical parameters must be accurately controlled—the pressure applied to the vessel (tissue) and the gap distance between the electrodes—both of which are affected by the thickness of the sealed vessel. The pressure applied to the vessel may be fixed by the mechanical design of the instrument. 
         [0008]    It can be difficult for surgeons to visually determine the gap distance between electrodes before energy application. After energy application, it may be difficult to ensure that the jaws of the forceps have achieved an appropriate seal closure. The visualization of the surgical field may be difficult because of blood within the surgical field, lack of complete vessel (tissue) dissection, or isolation. 
         [0009]    Some electrosurgical forceps mechanically limit the jaw aperture (maximum jaw opening) to prevent the forceps from being used on vessels or tissue beyond the forceps limits. However, such mechanical limits may prevent the electrosurgical forceps from being used as a multi-purpose instrument. Particularly, limiting the jaw aperture would prevent the electrosurgical forceps from functioning as a grasper and/or a dissecting instrument. 
       SUMMARY 
       [0010]    In an aspect of the present disclosure, a surgical instrument includes a housing, a shaft, an end effector, and a sensor. The shaft extends distally from the housing. The end effector is disposed at a distal end of the shaft and includes first and second jaw members that are moveable relative to one another from a first configuration to a second configuration. In the first configuration, the first and second jaw members are spaced relative to one another and in the second configuration, the first and second jaw members are closer to one another for approximating tissue. The first and second jaw members define a gap distance therebetween. The sensor is positioned within the housing and operable to determine the size of the gap distance. The first and second jaw members configured to be electrical activated to treat tissue between the first and second jaw members when the size of the gap distance is within an acceptable range. 
         [0011]    In some aspects, the elongated shaft defines a longitudinal axis and is translatable along the longitudinal axis to move the first and second jaw members between the first and second configurations. A proximal end of the elongated shaft may be longitudinally translatable within the housing and the sensor may be positioned adjacent the proximal end of the elongated shaft. The sensor may detect the position of the proximal end of the elongated shaft relative to the housing to determine the size of the gap distance. 
         [0012]    In certain aspects, the surgical instrument includes a drive assembly that is disposed within the housing and that is operatively associated with moveable handle to longitudinal translate the elongated shaft. The drive assembly may include a tube that has a distal end coupled to the distal end of the elongated shaft and a proximal end that is positioned proximal to the moveable handle. The sensor may be positioned adjacent the proximal end of the tube to detect the position of the proximal end of the tube relative to the housing for determining the size of the gap distance. 
         [0013]    In particular aspects, the surgical instrument includes a drive rod that is slidably disposed within the elongated shaft. A proximal end of the drive rod may extend into the housing. The drive rod may define a longitudinal axis and may be translatable along the longitudinal axis to move the first and second jaw members between the first and second configurations. The sensor may be positioned adjacent the proximal end of the drive rod. The sensor may detect the position of the proximal end of the drive rod relative to the housing to determine the size of the gap distance. 
         [0014]    In some aspects, the surgical instrument includes a moveable handle that is operatively associated with the drive rod to longitudinally translate the drive rod. The drive rod may include a proximal drive plate and a distal drive plate with the moveable handle positioned between the proximal and distal drive plates. The sensor may be positioned adjacent the proximal drive plate for detecting the position of the proximal drive plate relative to the housing to determine the size of the gap distance. Additionally or alternatively, the sensor may be positioned adjacent the distal drive plate for detecting the position of the distal drive plate relative to the housing to determine the size of the gap distance. 
         [0015]    In certain aspects, the sensor is configured to provide feedback of the size of the gap distance. The first and second jaw members may be configured to deliver electrosurgical energy to tissue between the first and second jaw members. The sensor may be configured to provide feedback when the size of the gap distance is suitable for applying electrosurgical energy to tissue. The sensor may be optical, magnetic, inductive, mechanical, or any combination thereof. 
         [0016]    In another aspect of the present disclosure, a surgical instrument includes a first member, a second member, a pivot, a flag, and a sensor. The first member has proximal and distal end portions with the distal end portion including a first jaw member. The second jaw member has proximal and distal end portions with the distal end portion including a second jaw member. The first and second jaw members define a gap distance therebetween. The pivot passes through the first and second members between the respective proximal and distal end portions such that the first and second members are pivotable relative to one another to pivot the first and second jaw members between first and second configurations. In the first configuration, the first and second jaw members are spaced relative to one another and in the second configuration, the first and second jaw members are closer to one another for approximating tissue. The flag has a distal end that is coupled to the distal end portion of the second member and extends proximally along the second member to a free end that is positioned adjacent the proximal end portion of the second member. The sensor is positioned adjacent the free end of the flag for determining the size of the gap distance. If the size of the gap distance is within an acceptable range, the first and second jaw members may be electrically activated to treat tissue approximated between the first and second jaw members. 
         [0017]    In some aspects, the sensor is disposed on the proximal end portion of the second member. The sensor may detect the position of the free end of the flag to determine the size of the gap distance between the first and second members. The second member may be flexible such that flexation of the second member is indicative of the size of the gap distance. The sensor may be configured to detect the flexation of the second member to determine the size of the gap distance. 
         [0018]    In another aspect of the present disclosure, a method of determining the size of a gap distance of a surgical instrument includes positioning the first and second jaw members of the surgical instrument over tissue such that the tissue is positioned between the first and second jaw members, determining the size of the gap distance with a sensor positioned remote to the first and second jaw members, and activating the first and second jaw members to deliver electrosurgical energy to the tissue positioned between the first and second jaw members when the size of the gap distance in in an acceptable range. 
         [0019]    In some aspects, the method may include pivoting a first handle of the surgical instrument towards a second handle of the surgical instrument to move the first and second jaw members towards one another. Determining the size of the gap distance may include determining the flexation of the second handle with the sensor. Determining the flexation of the second handle with the sensor may include detecting the position of a free end of a flag relative to the second handle. The free end of the flag may extend from a distal end of the flag which is fixed to the second jaw member. 
         [0020]    In certain aspects, determining the size of the gap distance includes detecting the position of a proximal end of a shaft relative to a housing of the surgical instrument with the sensor. The shaft may extend distally from the housing with the first and second jaw members positioned at a distal end of the shaft. The sensor may be positioned within the housing. 
         [0021]    In particular aspects, determining the size of the gap distance includes detecting the position of a drive rod within a housing of the surgical instrument. The drive rod may extend through an elongated shaft and be slidable within the elongated shaft which extends distally from the housing. The first and second jaw members may be positioned at a distal end of the elongated shaft. Detecting the position of the drive rod within the housing of the surgical instrument may include detecting a position of a proximal end of the drive rod relative to the housing with the sensor. The sensor may be positioned within the housing adjacent the proximal end of the drive rod. 
         [0022]    In some aspects, the method includes moving a moveable handle from an initial position to an approximated position to longitudinally translate the drive rod within the elongated shaft. The moveable handle may be positioned between proximal and distal drive plates of the drive rod. Detecting the position of the drive rod within the housing of the surgical instrument includes detecting the position of the proximal drive plate of the drive rod relative to the housing with the sensor. The sensor may be positioned within the housing adjacent the proximal drive plate. Additionally or alternatively, detecting the position of the drive rod within the housing of the surgical instrument may include detecting the position of the distal drive plate of the drive rod relative to the housing with the sensor. The sensor may be positioned adjacent the distal drive plate. 
         [0023]    In certain aspects, the method includes providing feedback when the size of the gap distance is suitable for delivering electrosurgical energy to the tissue between the first and second jaw members of the surgical instrument. The sensor may detect the position of a component of the surgical instrument from a position that is remote to the first and second jaw members to determine the size of the gap distance optically, magnetically, inductively, mechanically, or any combination thereof. 
         [0024]    Further, to the extent consistent, any of the aspects described herein may be used in conjunction with any or all of the other aspects described herein. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0025]    Various aspects of the present disclosure are described hereinbelow with reference to the drawings, which are incorporated in and constitute a part of this specification, wherein: 
           [0026]      FIG. 1  is a perspective view of an endoscopic electrosurgical forceps in accordance with the present disclosure; 
           [0027]      FIG. 2  is a side, cut-away view of the endoscopic electrosurgical forceps of  FIG. 1  showing a pair of jaw members in an open configuration with a clamping handle in an initial position; 
           [0028]      FIG. 3  is a side, cut-away view of the endoscopic electrosurgical forceps of  FIG. 1  in an activatable configuration with the clamping handle in an approximated position; 
           [0029]      FIG. 4  is a side, cut-away view of the endoscopic electrosurgical forceps of  FIG. 1  with the clamping handle in the approximated position and jaw members closed about tissue within an unacceptable jaw aperture range; 
           [0030]      FIG. 5  is a side, cut-away view of another endoscopic electrosurgical forceps in accordance with the present disclosure in an open configuration with a clamping handle in an initial position; 
           [0031]      FIG. 6  is a side, cut-away view of the endoscopic electrosurgical forceps of  FIG. 5  in an activatable configuration with the clamping handle in an approximated position and jaw members closed about tissue within an acceptable jaw aperture range; 
           [0032]      FIG. 7  is a side, cut-away view of the endoscopic electrosurgical forceps of  FIG. 5  with the clamping handle in the approximated position and jaw members closed about tissue within an unacceptable jaw aperture range; 
           [0033]      FIG. 8  is a side view of an open electrosurgical forceps in accordance with the present disclosure with handles in an initial position and jaw members in an open position; 
           [0034]      FIG. 9  is a side view of the open electrosurgical forceps of  FIG. 8  in an activatable configuration with the handles in an approximated position and jaw members closed about tissue within appropriate jaw aperture range; 
           [0035]      FIG. 10  is a side view of the open electrosurgical forceps of  FIG. 8  in an open configuration with the clamping handle in the approximated position and jaw members closed about tissue within an unacceptable jaw aperture range; and 
           [0036]      FIG. 11  is a schematic view of a robotic surgical system in accordance with the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0037]    Embodiments of the present disclosure are now described in detail with reference to the drawings in which like reference numerals designate identical or corresponding elements in each of the several views. As used herein, the term “clinician” refers to a doctor, a nurse, or any other care provider and may include support personnel. Throughout this description, the term “proximal” refers to the portion of the device or component thereof that is closest to the clinician and the term “distal” refers to the portion of the device or component thereof that is farthest from the clinician. 
         [0038]    This disclosure relates generally to position sensors positioned in or on the body of an electrosurgical forceps to determine a gap distance or jaw aperture defined between jaw members of the electrosurgical forceps. The position sensor may sense the position of a closure tube that correlates to the jaw aperture, may sense the position of a push rod, or may sense the position or angle of a flag attached adjacent a distal end of the electrosurgical forceps to determine the jaw aperture. The position sensor may also provide feedback (e.g., audible, tactile, or visual) to a clinician when the gap distance between jaw members is in an acceptable range suitable for sealing tissue between the jaw members with electrosurgical energy. The acceptable range for the gap distance to seal tissue is about 0.001 inches to about 0.006 inches. In addition, the position sensor may be in communication with an energy activation circuit to prevent delivery of electrosurgical energy when the gap distance is beyond a predetermined limit (i.e., above the acceptable range). 
         [0039]    Referring now to  FIG. 1 , an endoscopic electrosurgical forceps  10  is provided in accordance with the present disclosure and includes a housing  20 , a handle assembly  30 , a rotating assembly  50 , a trigger assembly  60 , and an end effector assembly  70 . The end effector assembly  70  includes first and second jaw members  72 ,  74  for grasping, sealing, and treating tubular vessels and vascular tissue. For the purposes herein, forceps  10  will be described generally. However, the various particular aspects of this particular forceps are detailed in U.S. Patent Publication No. 2014/0257274, the entire contents of which are incorporated by reference herein. 
         [0040]    The forceps  10  includes a shaft  12  that defines a longitudinal axis “A-A” of the forceps  10  and has a proximal end  14  ( FIG. 2 ) and a distal end  16 . The proximal end  14  of the shaft  12  is operatively engaged to the housing  20 . The distal end  16  of the shaft  12  is configured to mechanically engage the end effector assembly  70  to move the first and second jaw members  72 ,  74  between an open configuration ( FIG. 2 ) and a closed configuration ( FIG. 3 ) as detailed below. Once closed, the gap distance between the jaw members  72 ,  74  will determine if the forceps  10  can be energized. 
         [0041]    Forceps  10  also includes an electrosurgical cable  18  that connects the forceps  10  to a source of electrosurgical energy, e.g., a generator  19 . The source of electrosurgical energy provides electrosurgical energy to the end effector  70  of the forceps  10 . It is also contemplated that the forceps  10  may include an energy source (e.g., a battery (not shown)) and an electrosurgical generator (not shown) positioned on or within the housing  20  to provide electrosurgical energy to the forceps  10 . 
         [0042]    Referring to  FIG. 2 , the handle assembly  30  includes a fixed handle  32  and a moveable handle  34 . The fixed handle  32  is integrally associated with housing  20  and the moveable handle  34  is movable relative to the fixed handle  32  to translate the shaft  12  along the longitudinal axis “A-A”. The rotating assembly  50  is disposed substantially within the housing  20  and is rotatable approximately 180 degrees in either direction about the longitudinal axis “A-A” to rotate the end effector assembly  70  relative to the housing  20 . 
         [0043]    The moveable handle  34  has an upper end  35  that is pivotally secured within the housing  20  and engaged with a drive assembly  40  of the forceps  10 . The drive assembly  40  includes a tube  42 , a proximal drive plate  44 , and a distal drive plate  46 . The tube  42  has a proximal end  43   a  that passes through the proximal and distal drive plates  44 ,  46  and a distal end  43   b  that passes through the rotating assembly  50 . The distal end  43   b  of the tube  42  is coupled to the proximal end  14  of the shaft  12  to translate the shaft  12  along the longitudinal axis “A-A”. 
         [0044]    The proximal drive plate  44  is coupled to the proximal end  43   a  of the tube  42  to translate the tube  42  along the longitudinal axis “A-A”. A first biasing member  45  is positioned between the proximal drive plate  44  and the housing  20  to urge the proximal drive plate  44  distally such that the first and second jaw members  72 ,  74  of the end effector assembly  70  are biased in the open configuration ( FIG. 2 ). A second biasing member  47  is positioned between the proximal and distal drive plates  44 ,  46  to urge distal drive plate  46  away from the proximal drive plate  44 . The distal drive plate  46  engages the moveable handle  34  to move the moveable handle  34  towards its initial position. 
         [0045]    With additional reference to  FIGS. 3 and 4 , as the moveable handle  34  is pivoted towards its approximated or closed position, the moveable handle  34  moves the distal drive plate  46  distally against the second biasing member  47 . As the distal drive plate  46  is moved distally, the second biasing member  47  applies a handle force to the proximal drive plate  44  to urge the proximal drive plate  44  proximally. Proximal movement of the proximal drive plate  44  is resisted by a clamping force which is the combination of a compression force of the first biasing member  45  and a closure force of the first and second jaw members  72 ,  74  of the end effector assembly  70 . The closure force is the force exerted on the first and second jaw members  72 ,  74  by tissue positioned within the jaw aperture  75  as detailed below. When the handle force is greater than the clamping force, the proximal drive plate  44  is moved distally such that the first and second jaw members  72 ,  74  are moved towards the activatable configuration and the first biasing member  45  is compressed as shown in  FIG. 3 . As a result, the gap distance is within an acceptable range for sealing tissue between the first and second jaw members  72 ,  74  with electrosurgical energy and the first and second jaw members  72 ,  74  can then be selectively energized. When the handle force is less than the clamping force, the proximal drive plate  44  resists proximal movement such that the second biasing member  47  is compressed between the proximal and distal drive plates  45 ,  47  as shown in  FIG. 4 . As a result, the gap distance is unacceptable or outside of the acceptable range and the first and second jaw members  72 ,  74  are prevented from energizing. 
         [0046]    The first and second biasing members  45 ,  47  are calibrated to limit closure force of the first and second jaw members  72 ,  74  of the end effector assembly  70 . When a small vessel, or amount of tissue, or a large compressible vessel, or amount of tissue, is positioned within a jaw aperture  75  (i.e., between the first and second jaw members  72 ,  74 ), a closure force of the first and second jaw members  72 ,  74  is small such that the handle force is greater than or equal to the clamping force to allow the first and second jaw members  72 ,  74  to move to an activatable configuration as shown in  FIG. 3 . In an activatable configuration, the gap distance is in the acceptable range for sealing tissue within the jaw aperture  75 . When a large vessel, or amount of tissue, is positioned within a jaw aperture  75  (between the jaw members  72 ,  74 ), the closure force of the first and second jaw members  72 ,  74  is large such that the handle force is less the clamping force. When the handle force is less than the clamping force, the first and second jaw members  72 ,  74  resist moving to an activatable configuration and remain substantially in the open configuration as shown in  FIG. 4 . In such an open configuration, the gap distance of between the jaw members  72 ,  74  is outside of the acceptable range for sealing the vessel, or tissue, within the jaw aperture  75 . 
         [0047]    With reference to  FIGS. 2-4 , the forceps  10  includes first and second position sensors  82 ,  84  for detecting the position of the tube  42  to determine the gap distance between the jaw members  72 ,  74 . The first and second position sensors  82 ,  84  are positioned within the housing  20  remote to the end effector  70 . The first position sensor  82  is positioned adjacent the proximal end  43   a  of the tube  42  to detect the position of the proximal end  43   a  relative to the housing  20 . The second position sensor  84  is positioned adjacent the distal end  43   b  of the tube  42  to detect the position of the distal end  43   b  relative to the housing  20 . In a fully open configuration of the first and second jaw members  72 ,  74  ( FIG. 2 ), the tube  42  is in a distal-most position such that a detected distance D 1  between the first sensor  82  and the proximal end  43   a  of the tube  42  and a detected distance D 2  between the second sensor  84  and the distal end  43   b  of the tube  42  are at a maximum value. In an activatable configuration of the first and second jaw members  72 ,  74  ( FIG. 3 ), the tube  42  is in an activatable position, proximal of its distal-most position, such that a detected distance D 1 ′ between the first sensor  82  and the proximal end  43   a  of the tube  42  and a detected distance D 2 ′ between the second sensor  84  and the distal end  43   b  of the tube  42  are in an activatable range of values which is less than the maximum value. When the first and second jaw members  72 ,  74  are in an activatable configuration, the first and second sensors  82 ,  84  may provide feedback to a clinician that the gap distance is within the acceptable range that is suitable for sealing tissue between the first and second jaw members  72 ,  74  with electrosurgical energy. This feedback may be audible, visual, or tactile. 
         [0048]    With particular reference to  FIG. 4 , when a large vessel, or amount of tissue, is positioned within the jaw aperture  75  and the moveable handle  34  is in the approximated or closed position, the tube  42  is between the distal-most position and an activatable position such that the gap distance is beyond or outside of the acceptable range for sealing tissue. In such an open position, a detected distance D 1 ″ between the first sensor  82  and the proximal end  43   a  of the tube  42  and a detected distance D 2 ″ between the second sensor  84  and the distal end  43   b  of the tube  42  is between the maximum value and an activatable range values. When the moveable handle  34  reaches the approximated or closed position and the first and second jaw members  72 ,  74  are between the fully open configuration and the activatable configuration, the forceps  10  may provide feedback to a clinician that the gap distance between the jaw members  72 ,  74  is outside of the acceptable range for sealing tissue. This feedback may be audible, visual, or tactile. 
         [0049]    Referring now to  FIGS. 5-7 , another endoscopic electrosurgical forceps  110  is provided in accordance with the present disclosure. The forceps  110  is substantially similar to forceps  10  detailed above, as such only the differences will be detailed herein. For reasons of brevity, elements of the endoscopic forceps  110  similar to elements of the endoscopic forceps  10  are identified with similar labels with a “1” preceding the previous label. For the purposes herein, forceps  110  will be described generally. However, the various particular aspects of this particular forceps are detailed in U.S. Patent Publication Nos. 2013/0296848 and 2013/0296922, the entire contents of each of these disclosures is incorporated by reference herein. 
         [0050]    A drive assembly  140  of the forceps  110  includes a drive rod  142 , a proximal drive plate  144 , and a distal drive plate  146 . The drive rod  142  is translatable along the longitudinal axis “A-A” defined by a shaft  112  to move first and second jaw members  172 ,  174  of an end effector assembly  170  between an open configuration ( FIG. 5 ) and a closed configuration ( FIG. 6 ). Once closed, the gap distance between the jaw members  172 ,  174  will determine if the forceps  110  can be energized. The drive rod  142  extends from a housing  120  of the forceps  110 , through the shaft  112 , and to the end effector assembly  170 . The drive rod  142  includes a proximal end  143   a  that is disposed within the housing  120  of the forceps  110  and a distal end  143   a  that is operatively associated with the end effector assembly  170 . 
         [0051]    The proximal drive plate  144  is coupled to the drive rod  142  adjacent the proximal end  143   a  of the drive rod  142 . The distal drive plate  146  is coupled to the drive rod  142  distal of the proximal drive plate  144 . A moveable handle  134  includes a plunger  136  ( FIG. 6 ) that is positioned about the drive rod  142  between the proximal and distal drive plates  144 ,  146 . A biasing member  145  is positioned about the drive rod  142  between the plunger  136  and the proximal drive plate  144  to urge the moveable handle  134  towards an initial position ( FIG. 5 ). In the initial position, the moveable handle  134  may engage the distal drive plate  146  to urge drive rod  142  distally such that the first and second jaw members  172 ,  174  of the end effector assembly  170  are moved towards the fully open configuration. 
         [0052]    As the moveable handle  134  is pivoted towards an approximated or closed position ( FIGS. 6 and 7 ), the plunger  136  moves proximally within the housing  120 . As the plunger  136  moves proximally, the plunger  136  exerts a handle force on the biasing member  145  which exerts a clamping force on the proximal drive plate  144 . In response, the proximal drive plate  144  translates the drive rod  142  proximally. As the drive rod  142  translates proximally, the distal end  143   b  of the drive rod  142  moves the first and second jaw members  172 ,  174  towards the closed configuration and, particularly, an activatable configuration such that the gap distance between the jaw members  172 ,  174  is within the acceptable range. 
         [0053]    As gap distance is reduced, the first and second jaw members  172 ,  174  engage a vessel or tissue positioned therebetween. As the first and second jaw members  172 ,  174  engage a vessel or tissue, the vessel or tissue resists movement of the first and second jaw members  172 ,  174  towards an activatable configuration such that a closure force is required to move the first and second jaw members  172 ,  174  towards the activatable configuration. The clamping force is the sum of the closure force exerted by tissue positioned within the jaw aperture  175  and mechanical resistance to moving the first and second jaw members  172 ,  174  towards an activatable configuration. If the clamping force is less than the handle force, the proximal drive plate  144  is moved proximally to translate the drive rod  142  proximally and to move the first and second jaw members  172 ,  174  towards an activatable configuration until the moveable handle  134  is in the approximated or closed position and the first and second jaw members  172 ,  174  are in an activatable configuration as shown in  FIG. 6 . If the clamping force is greater than the handle force, the handle force compresses the biasing member  145 . The moveable handle  134  is moved towards the approximated or closed position increasing the handle force as the biasing member  145  is compressed until the handle force exceeds the clamping force or the moveable handle  134  reaches its approximated or closed position without the first and second jaw members  172 ,  174  reaching the activatable configuration as shown in  FIG. 7 . As detailed above, in the activatable configuration of the first and second jaw members  172 ,  174  the gap distance between the jaw members  172 ,  174  is within the acceptable range for sealing a vessel or tissue within the jaw aperture  175  with electrosurgical energy. 
         [0054]    With continued reference to  FIGS. 5-7 , the forceps  110  includes first, second, and third position sensors  182 ,  184 ,  186  for detecting the position of the drive rod  142  relative to the housing  120  to determine the gap distance. The first position sensor  182  is positioned within the housing  120  adjacent the proximal end  143   a  of the drive rod  142  to detect the position of the proximal end  143   a  relative to the housing  120  as indicated by a detected distance D 1 . Alternatively, the first position sensor  182  may be disposed on the distal end  143   a  of the drive rod to detect the position of the proximal end  143   a  relative to the housing  120  as indicated by the detected distance D 1 . The second position sensor  184  is positioned on the housing adjacent the distal drive plate  146  to detect the position of the distal drive plate  146  relative to the housing  120  as indicated by a detected distance D 2 . Alternatively, the second position sensor  184  may be disposed on the distal drive plate  146  to detect the position of the distal drive plate  146  relative to the housing  120  as indicated by the detected distance D 2 . The third position sensor  186  is positioned on the proximal drive plate  144  to detect the position of the proximal drive plate  144  relative to the housing  120  as indicated by a detected distance D 3 . 
         [0055]    In a fully open configuration of the first and second jaw members  172 ,  174  ( FIG. 5 ), the drive rod  142  is in a distal-most position relative to the housing  120  such that the detected distances D 1  and D 2  have a minimum value and detected distance D 3  has a maximum value. In the activatable configuration of the first and second jaw members  172 ,  174  ( FIG. 6 ), the drive rod  142  is in an activatable position, proximal of its distal-most position, such that detected distances D 1 ′ and D 2 ′ are in a range of activatable values greater than the minimum value and the detected distance D 3 ′ is in a range of activatable values less than the maximum value. When the first and second jaw members  172 ,  174  are in an activatable configuration, the first, second, and third position sensors  182 ,  184 ,  186  may provide feedback to a clinician that the gap distance of the jaw aperture  175  is within an acceptable range for sealing tissue between the first and second jaw members  172 ,  174 . This feedback may be audible, visual, or tactile. 
         [0056]    With particular reference to  FIG. 7 , when a large vessel, or amount of tissue, is positioned within the jaw aperture  75  and the moveable handle  134  is in the approximated or closed position, the drive rod  142  is between the distal-most position and the activatable position such that the gap distance is not suitable for application of electrosurgical energy. In such a position, the detected distances D 1 ″ and D 2 ″ are between the minimum value and the range of activatable values and the detected distance D 3 ″ is between the maximum value and the range of activatable values. When the moveable handle  134  reaches the approximated or closed position and the first and second jaw members  172 ,  174  define a gap distance outside of the acceptable range, the forceps  110  may provide feedback to a clinician that the gap distance is not suitable for sealing tissue. This feedback may be audible, visual, or tactile. 
         [0057]    With reference to  FIGS. 6 and 7 , position sensors may be positioned in various locations about the forceps  110  to detect a position of a moveable structure relative to a fixed structure to determine the gap distance of the first and second jaw members  172 ,  174 . For example, a position sensor  192  may be positioned within the shaft  112  to detect the position of the drive rod  142  relative to the shaft  112  to determine the gap distance. In another example, a position sensor  194  may be positioned adjacent a distal end  116  of the shaft  112  to detect the position of the distal end  143   b  of the drive rod  142  to determine the gap distance. 
         [0058]    Referring now to  FIGS. 8-10 , an open electrosurgical forceps  210  is provided in accordance with the present disclosure and includes a first member  220  and a second member  240 . Each of the first and second member  220 ,  240  includes a shaft  221 ,  241  having respective proximal end portions  222 ,  242  and respective distal end portions  226 ,  246 . Each proximal end portion  222 ,  242  includes a handle  224 ,  244  and each distal end portion  226 ,  246  includes a jaw member  228 ,  248 . The shafts  221 ,  241  are pivotable relative to one another about a pivot  260  to pivot the jaw members  228 ,  248  between an open configuration ( FIG. 8 ) and a closed configuration ( FIG. 9 ). For the purposes herein, forceps  210  will be described generally. However, the various particular aspects of this particular forceps are detailed in U.S. Patent Publication No. 2012/0083827, the entire contents of which are incorporated by reference herein. 
         [0059]    The pivot  260  passes through the shafts  221 ,  241  between the handles  224 ,  244  and the jaw members  228 ,  248 . The first member  220  includes an electrosurgical cable  18  that connects the forceps  210  to a source of electrosurgical energy. Additionally or alternatively, the second member  240  may include an electrosurgical cable (not shown) that connects the forceps  210  to a source of electrosurgical energy. 
         [0060]    The shafts  221 ,  241  are designed to transmit a particular closure force to the jaw members  228 ,  248  as the shafts  221 ,  241  are pivoted towards the closed configuration. In particular, the shafts  221 ,  241  effectively act together in a spring-like manner (i.e., bending that behaves like a spring) such that the length, width, height, and deflection of the shafts  221 ,  241  directly effects the closure force imposed by jaw members  228 ,  248 . The jaws  228  and  248  are more rigid than the shafts  221 ,  241  such that strain energy stored in the shafts  221 ,  241  provides a constant closure force between the jaw members  228 ,  248  in response to a handle force applied to the handles  224 ,  244 . 
         [0061]    With additional reference to  FIG. 9 , as the handles  224 ,  244  are moved towards each other, the shafts  221 ,  241  pivot about the pivot  260  such that the jaw members  228 ,  248  move towards the closed configuration. As the jaw members  228 ,  248  move towards the closed configuration with a small vessel, or amount of tissue, or a large compressible vessel, or amount of tissue, positioned within a jaw aperture  266 , the jaw members  228 ,  248  impose a closure force to the vessel, or tissue. If the closure force required to move the jaw members  228 ,  248  towards the closed configuration is less than or equal to the handle force applied to the handles  224 ,  244 , the jaw members  228 ,  248  move towards the closed configuration effecting compression of the vessel, or tissue, until the handles  224 ,  244  are in an approximated or closed position and the jaw members  228 ,  248  are in an activatable configuration as shown in  FIG. 9 . In an activatable configuration, the gap distance between the jaw members  228 ,  248  is in an acceptable range for sealing tissue within the jaw aperture  266 . If the closure force required to move the jaw members  228 ,  248  is greater than the handle force applied to the handles  224 ,  244 , the shafts  221 ,  241  flex or bend towards one another until the handles  224 ,  244  are in the approximated or closed position with the jaw members  228 ,  248  remaining in a generally open configuration (e.g., between an open configuration and an acceptable activatable configuration) as shown in  FIG. 10 . In such a configuration, the gap distance between the jaw members  228 ,  248  is outside of the acceptable range for sealing the vessel, or tissue, within the jaw aperture  266 . 
         [0062]    Continuing to refer to  FIGS. 8-10 , the forceps  210  includes a deflection flag  270  attached at a fixed end  272  to the distal end portion  246  of the shaft  241 . The deflection flag  270  extends from the fixed end  272  along the shaft  241  to a free end  274  positioned adjacent the proximal end portion  242  of the second member  240 . The proximal end portion  242  is moveable relative to the free end  274  as the shaft  241  flexes or bends in response to the handle force and the closure force. 
         [0063]    When the handles  224 ,  244  are in the approximated or closed position, the amount of flexation of the shaft  241  correlates to the gap distance between the jaw members  228 ,  248 . The flexation of the shaft  241  is measurable by determining a change in a distance D between a fixed point  280  on the proximal end portion  242  of the second member  240  and the free end  274  of the flag  270  in the open configuration and a distance D′ or D″ between the fixed point  280  and the free end  274  in the approximated configuration. 
         [0064]    As shown in  FIG. 8 , the handles  224 ,  244  are in a fully open position such that the shaft  241  of the second member  240  is unflexed (i.e., substantially straight) and the free end  274  of the flag  270  defines a distance D with the fixed point  280  in a first direction. When the handles  224 ,  244  are moved to the approximated or closed position with an appropriate amount tissue positioned within the jaw aperture  266 , the shaft  241  of the second member  240  flexes such that a distance D′ is defined between the fixed point  280  and the free end  274  when the jaw members  228 ,  248 . As shown in  FIG. 9 , in an activatable configuration of the jaw members  228 ,  248 , the free end  274  and the fixed point  280  are substantially aligned. 
         [0065]    When a large amount of tissue is positioned within the jaw aperture  266 , the shaft  241  of the second member  240  flexes as the handles  224 ,  244  are moved to the approximated or closed position and the jaw members  228 ,  248  remain in a generally open configuration such that a distance D″ is defined between the fixed point  280  and the free end  274  in response to the handle force and the closure force as shown in  FIG. 10 . As shown, when the closure force is greater than the handle force, the jaw members  228 ,  248  remain in generally open. In such instances as shown in  FIG. 10 , the change from the distance D to the distance D″ is larger than the change from the distance D to the distance D′ and the gap distance between the jaw members  228 ,  248  is unacceptable resulting in a non-activatable configuration. 
         [0066]    Similar to the forceps  10  and  110  detailed above, when the jaw members  228 ,  248  are in an activatable configuration ( FIG. 9 ), the gap distance between the jaw members  228 ,  248  is outside of the acceptable range for sealing tissue. As shown in  FIG. 10 , the gap distance between the jaw members  228 ,  248  is outside of the acceptable range for sealing tissue. 
         [0067]    Continuing to refer to  FIGS. 8-10 , the forceps  210  includes a position sensor  282  for detecting the distance between the fixed point  280  and the free end  274  (e.g., D, D′, and D″). The position sensor  282  is positioned remote to the jaw members  228 ,  248 . The position sensor  282  is disposed on the second member  240  adjacent the fixed point  280  to detect the position of the free end  274  relative to the fixed point  280  to determine the flexation of the shaft  241  of the second member  240 . From the flexation of the shaft  241  of the second member  240 , the gap distance is determined. As shown, the position sensor  282  is positioned on the second member  240  adjacent the fixed point  280 ; however, the position sensor  282  may be positioned on the free end  274  and be configured to detect the position of the fixed point  280  relative to the free end  274 . 
         [0068]    As shown, the deflection flag  270  is substantially linear between the first and second ends  272 ,  274 ; however, the deflection flag  270  may be curved or have non-linear portion between the fixed end  272  and the free end  274 . 
         [0069]    The various embodiments disclosed herein may also be configured to work with robotic surgical systems and what is commonly referred to as “Telesurgery.” Such systems employ various robotic elements to assist the surgeon and allow remote operation (or partial remote operation) of surgical instrumentation. Various robotic arms, gears, cams, pulleys, electric and mechanical motors, etc. may be employed for this purpose and may be designed with a robotic surgical system to assist the surgeon during the course of an operation or treatment. Such robotic systems may include remotely steerable systems, automatically flexible surgical systems, remotely flexible surgical systems, remotely articulating surgical systems, wireless surgical systems, modular or selectively configurable remotely operated surgical systems, etc. 
         [0070]    The robotic surgical systems may be employed with one or more consoles that are next to the operating theater or located in a remote location. In this instance, one team of surgeons or nurses may prep the patient for surgery and configure the robotic surgical system with one or more of the instruments disclosed herein while another surgeon (or group of surgeons) remotely control the instruments via the robotic surgical system. As can be appreciated, a highly skilled surgeon may perform multiple operations in multiple locations without leaving his/her remote console which can be both economically advantageous and a benefit to the patient or a series of patients. 
         [0071]    The robotic arms of the surgical system are typically coupled to a pair of master handles by a controller. The handles can be moved by the surgeon to produce a corresponding movement of the working ends of any type of surgical instrument (e.g., end effectors, graspers, knifes, scissors, etc.) which may complement the use of one or more of the embodiments described herein. The movement of the master handles may be scaled so that the working ends have a corresponding movement that is different, smaller or larger, than the movement performed by the operating hands of the surgeon. The scale factor or gearing ratio may be adjustable so that the operator can control the resolution of the working ends of the surgical instrument(s). 
         [0072]    The master handles may include various sensors to provide feedback to the surgeon relating to various tissue parameters or conditions, e.g., tissue resistance due to manipulation, cutting or otherwise treating, pressure by the instrument onto the tissue, tissue temperature, tissue impedance, etc. As can be appreciated, such sensors provide the surgeon with enhanced tactile feedback simulating actual operating conditions. The master handles may also include a variety of different actuators for delicate tissue manipulation or treatment further enhancing the surgeon&#39;s ability to mimic actual operating conditions. 
         [0073]    Referring initially to  FIG. 11 , a medical work station is shown generally as work station  1000  and generally may include a plurality of robot arms  1002 ,  1003 ; a control device  1004 ; and an operating console  1005  coupled with control device  1004 . Operating console  1005  may include a display device  1006 , which may be set up in particular to display three-dimensional images; and manual input devices  1007 ,  1008 , by means of which a person (not shown), for example a surgeon, may be able to telemanipulate robot arms  1002 ,  1003  in a first operating mode. 
         [0074]    Each of the robot arms  1002 ,  1003  may include a plurality of members, which are connected through joints, and an attaching device  1009 ,  1011 , to which may be attached, for example, a surgical tool “ST” supporting an end effector  1100 , in accordance with any one of several embodiments disclosed herein, as will be described in greater detail below. 
         [0075]    Robot arms  1002 ,  1003  may be driven by electric drives (not shown) that are connected to control device  1004 . Control device  1004  (e.g., a computer) may be set up to activate the drives, in particular by means of a computer program, in such a way that robot arms  1002 ,  1003 , their attaching devices  1009 ,  1011  and thus the surgical tool (including end effector  1100 ) execute a desired movement according to a movement defined by means of manual input devices  1007 ,  1008 . Control device  1004  may also be set up in such a way that it regulates the movement of robot arms  1002 ,  1003  and/or of the drives. 
         [0076]    Medical work station  1000  may be configured for use on a patient  1013  lying on a patient table  1012  to be treated in a minimally invasive manner by means of end effector  1100 . Medical work station  1000  may also include more than two robot arms  1002 ,  1003 , the additional robot arms likewise being connected to control device  1004  and being telemanipulatable by means of operating console  1005 . A medical instrument or surgical tool (including an end effector  1100 ) may also be attached to the additional robot arm. Medical work station  1000  may include a database  1014 , in particular coupled to with control device  1004 , in which are stored, for example, pre-operative data from patient/living being  1013  and/or anatomical atlases. 
         [0077]    While several embodiments of the disclosure have been shown in the drawings, it is not intended that the disclosure be limited thereto, as it is intended that the disclosure be as broad in scope as the art will allow and that the specification be read likewise. Any combination of the above embodiments is also envisioned and is within the scope of the appended claims. Therefore, the above description should not be construed as limiting, but merely as exemplifications of particular embodiments. Those skilled in the art will envision other modifications within the scope of the claims appended hereto.