Patent Publication Number: US-2020289192-A1

Title: Surgical instrument with eccentric cam

Description:
TECHNICAL FIELD 
     This disclosure relates generally to the field of surgical instruments, and in particular, to surgical instruments such as endoscopic electrosurgical forceps that are economical to manufacture and use, for instance, to seal and cut tissue structures. 
     BACKGROUND 
     Instruments such as electrosurgical forceps are commonly used in open and endoscopic surgical procedures to coagulate, cauterize and seal tissue. Such forceps typically include a pair of jaw members that can be controlled by a surgeon to grasp targeted tissue, such as, e.g., a blood vessel. The jaw members may be approximated to apply a mechanical clamping force to the tissue, and are associated with at least one electrode to enable the delivery of electrosurgical energy to the tissue. The combination of the mechanical clamping force and the electrosurgical energy has been demonstrated to join adjacent layers of tissue captured between the jaw members. When the adjacent layers of tissue include the walls of a blood vessel, sealing the tissue may result in hemostasis, which may facilitate the transection of the sealed tissue. A detailed discussion of the use of an electrosurgical forceps may be found in U.S. Pat. No. 7,255,697 to Dycus et al. 
     A bipolar electrosurgical forceps typically includes opposed electrodes disposed on clamping faces or tissue engaging surfaces of the jaw members. The electrodes are charged to opposite electrical potentials such that an electrosurgical current may be selectively transferred through tissue grasped between the electrodes. To effectuate a proper seal, particularly in relatively large vessels, two mechanical parameters that should be controlled are the pressure applied to the vessel and the gap distance established between the electrodes. 
     Both the pressure and the gap distance influence the effectiveness of the resultant tissue seal. If an adequate gap distance is not maintained, there is a possibility that the opposed electrodes will contact one another, which may cause a short circuit and prevent energy from being transferred through the tissue. Also, if too low a force is applied, the tissue may have a tendency to move before an adequate seal can be generated. The gap distance between tissue engaging surfaces of a typical effective tissue seal is optimally between about 0.001 and about 0.010 inches. Below this range, the seal may shred or tear, and above this range, the vessel walls may not be effectively joined. Closure pressures for sealing large tissue structures typically fall within the range of about 3 kg/cm 2  to about 16 kg/cm 2 . 
     SUMMARY 
     According to one aspect, this disclosure is directed to a forceps including a housing, an elongated shaft assembly, and a cam assembly. The housing includes a movable handle pivotally coupled to the housing. The elongated shaft assembly is coupled to the housing and extends distally to support a pair of jaw members at a distal end thereof. One or both of the jaw members is selectively moveable relative to the other jaw member between a spaced apart position for manipulating tissue and a closed position for compressing tissue therebetween. The cam assembly is supported in the housing and includes an eccentric cam cable and an eccentric cam. The eccentric cam cable is operably coupled to the movable handle and positioned to rotate the eccentric cam upon movement thereof, wherein rotation of the eccentric cam reduces an amount of force on the movable handle required to move the jaw members to the closed position to compress tissue disposed between the jaw members. 
     In embodiments, the cam assembly may further include an annular cam positioned adjacent to the eccentric cam. The eccentric cam and the annular cam may be disposed on a shaft that is pivotally supported within the housing. The eccentric cam may include an inner eccentric cam plate and an outer eccentric cam plate that are configured to maintain the eccentric cam cable on an eccentric track defined between the inner and outer eccentric cam plates. The eccentric track may include an annular portion and a triangular portion. The annular portion and the triangular portion of the eccentric track may define a tear-dropped shaped profile. 
     In some embodiments, the annular cam may include an annular track defined therein including substantially the same diameter as the annular portion of the eccentric track. 
     In various embodiments, the forceps may further include an annular cam cable that is supported on the annular track of the annular cam. The elongated shaft assembly may extend into the housing and may support an inner shaft that operatively couples to the pair of jaw members. The inner shaft may support a collar that couples to the annular cam cable. 
     In embodiments, the forceps may further include a compression spring supported on the inner shaft. The compression spring may be engaged with the collar and an arm of the movable handle to spring bias the movable handle. 
     According to yet another aspect of this disclosure, an electrosurgical system includes a housing, an elongated shaft assembly, an annular cam, an eccentric cam. The housing includes a movable handle. The movable handle is coupled to the housing and pivotable between a distal position and a proximal position relative to the housing. The elongated shaft assembly is coupled to the housing and extends distally to an end effector. The end effector has a pair of jaw members movable between an open position and a closed position in response to movement of the movable handle between the distal and proximal positions. The annular cam is supported in the housing and coupled to the elongated shaft assembly. The eccentric cam is coupled to the annular cam and positioned to rotate with the eccentric cam as the movable handle pivots between the distal and proximal positions. 
     In embodiments, the elongated shaft assembly may include an inner shaft, wherein rotation of the annular cam may cause the inner shaft to axially translate between distal and proximal positions relative to the housing to actuate the pair of jaw members. 
     In some embodiments, the forceps may further include an annular cam cable coupled to the annular cam and a collar supported on the inner shaft. The inner shaft may support a compression spring engaged with the collar and the movable handle. 
     In various embodiments, the forceps may further include an eccentric cam cable coupled to the eccentric cam and to the movable handle. 
     In some embodiments, the annular cam and the eccentric cam may have different profiles. Rotation of the eccentric cam may change a jaw force ratio as the movable handle pivots relative to the eccentric cam. 
     In embodiments, the pair of jaw members may be configured to receive electrosurgical energy to selectively seal tissue disposed between the pair of jaw members. 
     In various embodiments, the forceps may further include a knife assembly that is actuatable to sever tissue disposed between the pair of jaw members. 
     According to yet another aspect of this disclosure, a forceps system includes a generator and a forceps. The forceps is coupled to the generator and includes a housing, a movable handle coupled to the housing, and an elongated shaft assembly that extends distally from the housing to a pair of jaw members at a distal end thereof. The pair of jaw members is disposed in electrical communication with the generator. The pair of jaw members is movable between a spaced apart position for manipulating tissue and a closed position for compressing tissue therebetween. The forceps further includes an eccentric cam coupled to the movable handle and positioned to rotate as the movable handle pivots between distal and proximal positions relative to the housing. Rotation of the eccentric cam relative to the movable handle reduces an amount of force on the movable handle required to move the pair of jaw members to a closed position to compress tissue disposed between the pair of jaw members. 
     Other aspects, features, and advantages will be apparent from the description, the drawings, and the claims that follow. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the disclosure and, together with the detailed description of the embodiments given below, serve to explain the principles of the disclosure. 
       FIG. lA is a perspective view of an electrosurgical forceps according to the principles of the disclosure; 
         FIG. 1B  is an enlarged, perspective view of an end effector of the electrosurgical forceps of  FIG. 1A , the end effector illustrated in an open position; 
         FIG. 1C  is an enlarged, perspective view of the end effector of  FIG. 1B  illustrated in a closed position; 
         FIG. 2  is an enlarged, perspective view of a cam assembly of the electrosurgical forceps of  FIG. 1A ; and 
         FIGS. 3A and 3B  are progressive views illustrating the cam assembly of  FIG. 2  moving between unactuated and actuated positions relative to an instrument housing of the electrosurgical forceps of  FIG. 1A . 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the disclosed electrosurgical forceps are 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 commonly known, the term “clinician” refers to a doctor, a nurse, or any other care provider and may include support personnel. Further, as is used in the art, the term “distal” refers to a position, a direction, and/or a structure, which is farther from the user, and the term “proximal” refers to a position, a direction, and/or a structure, which is closer to the user. In addition, directional terms such as upper, lower, front, rear, top, bottom, up, down, right, left, and the like are used simply for convenience of description and are not intended to limit this disclosure. 
     Referring initially to  FIGS. 1A-1C , an electrosurgical forceps  100  defines a longitudinal axis “X-X” and generally includes an instrument housing  112 , an elongated shaft assembly  116  that extends from instrument housing  112 , and an end effector  114  supported on a distal end of elongated shaft assembly  116 . Instrument housing  112  supports various actuators for remotely controlling end effector  114  through elongated shaft assembly  116 . Although this configuration is typically associated with instruments for use in laparoscopic or endoscopic surgical procedures, various aspects of this disclosure may be practiced in connection with endoluminal procedures and with traditional open instruments. 
     To mechanically control end effector  114  of electrosurgical forceps  100 , instrument housing  112  supports a stationary handle  120 , a movable handle  122 , a trigger  126  and a rotation knob assembly  128 . Movable handle  122  of instrument housing  112  is operable to move end effector  114  between an open position ( FIGS. 1A and 1B ) in which a pair of opposed jaw members  130 ,  132  are disposed in spaced relation relative to one another, and a closed or clamping position ( FIG. 1C ) in which jaw members  130 ,  132  are closer together. Approximation of movable handle  122  toward stationary handle  120 , as indicated by arrow “A 1 ,” serves to move end effector  114  to the closed position. Separation of movable handle  122  away from stationary handle  120 , as indicated by arrow “A 2 ,” serves to move end effector  114  to the open position. Trigger  126  is operable to extend and retract a knife blade  156  ( FIG. 1B ) through end effector  114  when end effector  114  is in the closed position ( FIG. 1C ). Rotation knob assembly  128  serves to rotate elongated shaft assembly  116  and end effector  114  about longitudinal axis “X-X” of electrosurgical forceps  100  as rotation knob assembly  128  rotates about longitudinal axis “X-X,” as indicated by arrows “B.” 
     To electrically control end effector  114  of electrosurgical forceps  100 , stationary handle  120  of instrument housing  112  of forceps  100  supports a depressible button  137  that is operable by a clinician to selectively initiate and terminate delivery of electrosurgical energy to end effector  114 . Depressible button  137  is mechanically coupled to a switch  136  disposed within stationary handle  120 . Upon proximal movement of moveable handle  122  toward an actuated or proximal position, as illustrated by arrow “A 1 ,” button  137  is configured to engage a button activation post  138  that extends from a proximal side of moveable handle  122 . Switch  136  is in electrical communication with an electrosurgical generator  141  via a cable  143  that extends from instrument housing  112 . 
     End effector  114  of electrosurgical forceps  100  may be moved from an open position ( FIG. 1B ), in which tissue (not shown) can be received between jaw members  130 ,  132  of end effector  114 , and a closed position ( FIG. 1C ), in which tissue can be clamped and treated with electrosurgical energy delivered from generator  141 . Jaw members  130 ,  132  pivot about a pivot pin  144  to move end effector  114  to the closed position ( FIG. 2B ) in which sealing plates  150 ,  148  of respective jaw members  130 ,  132  provide a pressure to tissue grasped between jaw members  130 ,  132 . In some embodiments, to provide an effective tissue seal, a pressure within a range between about 3 kg/cm 2  to about 16 kg/cm 2  and, typically, within a working range of about 7 kg/cm 2  to about 13 kg/cm 2 , may be applied by end effector  114  to the tissue. Also, in the closed position, a separation or gap distance is maintained between the sealing plates  148 ,  150  by an array of stop members  154  ( FIG. 1B ) disposed on or adjacent to sealing plates  148 ,  150 . Stop members  154  contact opposing surfaces of jaw members  130 ,  132  and prevent further approximation of sealing plates  148 ,  150 . In some embodiments, to provide an effective tissue seal, an appropriate gap distance of about 0.001 inches to about 0.010 inches and, typically, between about 0.003 inches to about 0.006 inches, may be provided. In some embodiments, stop members  154  are constructed of a heat-resistant ceramic deposited onto jaw members  130 ,  132 . In other embodiments, stop members  154  are constructed of an electrically non-conductive plastic molded onto jaw members  130 ,  132  by a process such as overmolding or injection molding. Stop members  154  may be provided in any suitable number, arrangement, and/or configuration. 
     Upper and lower jaw members  130 ,  132  of end effector  114  are electrically coupled to generator  141  to provide an electrical pathway to opposed tissue-engaging sealing plates  148 ,  150  of lower and upper jaw members  132 ,  130 , respectively. In some embodiments, sealing plates  148  and  150  are electrically coupled to opposite terminals, for example, positive or active (+) and negative or return (−) terminals associated with generator  141  so that bipolar energy may be provided through sealing plates  148 ,  150  to tissue. Alternatively, sealing plates  148 ,  150  may be configured to deliver monopolar energy to tissue. In a monopolar configuration, one or both sealing plates  148 ,  150  deliver electrosurgical energy from an active terminal (+) while a return pad (not shown) is placed generally on a patient and provides a return path to the opposite terminal (−) of generator  141 . 
     Electrosurgical energy may be delivered to tissue through electrically conductive seal plates  148 ,  150  to effectuate a tissue seal. Once a tissue seal is established, a knife blade  156  having a sharpened distal edge  157  may be advanced through a knife channel  158  defined in one or both jaw members  130 ,  132  to transect sealed tissue. Although knife blade  156  is depicted in  FIG. 1B  as extending from elongated shaft assembly  116  when end effector  114  is in an open position, in some embodiments, extension of knife blade  156  into knife channel  158  when end effector  114  is in the open position is prevented. 
     For a more detailed description of a similar electrosurgical forceps, or components thereof, reference can be made, for example, to U.S. Pat. No. 9,655,673 to McCullough, Jr. et al. and U.S. Pat. No. 9,820,765 to Allen et al., the entire contents of each of which are incorporated herein by reference. 
     Referring now to  FIGS. 2, 3A, and 3B , instrument housing  112  further supports a cam assembly  200  that is pivotally coupled to instrument housing  112 . Cam assembly  200 , which may be formed (e.g., integrally) using any suitable manufacturing technique such as injection molding, welding, casting, machining, joining, additive printing, etc., or combinations thereof, includes a shaft  202  that supports an annular cam  204  and an eccentric cam  206 . In some embodiments, shaft  202 , annular cam  204  and eccentric cam  206 , may be monolithically formed. 
     Shaft  202  of cam assembly  200  includes opposite ends  202   a,    202   b  that extend from opposite sides of cam assembly  200  to pivotally couple cam assembly  200  to instrument housing  112  by any suitable mechanical coupling such as pin holes (not shown) defined in instrument housing  112  that receive opposite ends  202   a,    202   b  of shaft  202 . 
     Annular cam  204  of cam assembly  200  includes an annular track  204   a,  which may be supported concentrically about shaft  202  of cam assembly  200 . Annular track  204   a  has an annular profile (e.g., circular) with a diameter that can be greater than a diameter of shaft  202 . Annular cam  204  further includes a cable attachment portion  204   b  that secures a first end portion of annular cam cable  208  to annular cam  204 . Annular cam cable  208  is wound about annular track  204   a.  Annular cam cable  208  extends from annular track  204   a  and is redirected about any number of inner bars  112   x  (e.g., three) extending from instrument housing  112  of forceps  100  at various locations along an inner surface of instrument housing  112  so that a second end portion of annular cam cable  208  couples to a collar  116 c supported on proximal end portion of elongated shaft assembly  116  of forceps  100 . Annular cam  204  also includes an outer cam plate  204   c  positioned adjacent to annular track  204   a.  Outer cam plate  204   c  has a diameter greater than a diameter of annular track  204   a  to prevent annular cam cable  208  from sliding off annular track  204   a.    
     Eccentric cam  206  of cam assembly  200  includes an eccentric track  206   a  having an eccentric profile (e.g., tear drop-shaped, pear-shaped, kite-shaped, egg-shaped, etc.). The eccentric profile of eccentric track  206   a  is defined by an annular portion  206   b  supported (e.g., concentrically) about shaft  202  of cam assembly  200  and a triangular portion  206   c.  Triangular portion  206   c  extends from annular portion  206   b  to an apex  206   d.  Triangular and annular portions  206   b,    206   c  of eccentric track  206   a  may be coplanar. Eccentric track  206   a  is supported between an inner eccentric cam plate  206   e  and an outer eccentric cam plate  206   f.  An eccentric cam cable  210  is configured to cam along eccentric track  206   a.  Eccentric cam cable  210  is wound about eccentric track  206   a  of eccentric cam  206 . Eccentric cable  210  extends from eccentric track  206   a  and is redirected by any number of inner bars  112   x  of instrument housing  112  (e.g., two). More particularly, a first end portion  210   a  of cable  210  is secured to a cable attachment portion  206   g  of eccentric cam  206  so that cable  210  can be wound about eccentric cam  206 . A second end portion  210   b  of cable  210  extends from eccentric cam  206  and is secured to movable handle  122 . Eccentric track  206   a  is recessed from inner and outer eccentric cam plates  206   e,    206   f  so that inner and outer eccentric cam plates  206   e,    206   f  prevent eccentric cam cable  210  from sliding off of eccentric track  206   a  as eccentric cam cable  210  cams along eccentric track  206   a  of eccentric cam  206 . 
     With reference to  FIGS. 3A and 3B , a proximal end portion of elongated shaft assembly  116  supports a compression spring  116   a,  a stop tab  116   b  and a collar  116   c  within instrument housing  112 . Compression spring  116   a  is supported between an arm  122   a  of movable handle  122  and collar  116   c  to urge movable handle  122  in a distal direction to bias end effector  114  ( FIG. 1 ) toward its open position. Arm  122   a  of movable handle  122  is selectively engagable with stop tab  116 b to limit distal movement of moveable handle  122  as seen in  FIG. 3A . 
     In order to approximate jaw members  130 ,  132  of end effector  114 , movable handle  122  is pivoted about pivot point “P,” as indicated by arrows “A 1 ,” between a distal position ( FIG. 3A ) in which end effector  114  is in an open position ( FIG. 1B ), and a proximal position ( FIG. 3B ) in which end effector  114  is in a closed position ( FIG. 1C ). As movable handle  122  moves toward the proximal position, arm  122   a  of movable handle  122  drives an inner shaft  116   d  of elongated shaft assembly  116 , compression spring  116   a,  and collar  116   c  proximally, as indicated by arrow “C” to close jaw members  130 ,  132  of end effector  114 . Inner shaft  116   d  extends distally from instrument housing  112  and couples to end effector  114  to selectively move jaw members  130 ,  132  between open and closed positions. Simultaneously, movable handle  122  tightens eccentric cam cable  210 , drawing second end portion  210   b  of cable  210  proximally, as indicated by arrow “E,” while urging first end portion  210   a  of cable  210  distally, as indicated by arrow “F,” so that cable  210  causes eccentric cam  206  to pivot downwardly and forwardly relative to instrument housing  112  toward movable handle  122 , as indicated by arrow “D.” Also simultaneously, cable  208  cams and wraps around annular cam  204 , namely, annular track  204   a,  as indicated by arrows “G,” so that cable  208  facilitates movement of collar  116   c  in the proximal direction relative to instrument housing  112 , as indicated by arrows “C.” 
     In this regard, cam assembly  200  functions to change a jaw force ratio as movable handle  122  moves between a distal position and a proximal position (and/or as end effector  114 /jaw members  130 ,  132  move(s) from an open position to a closed position). The jaw force ratio is a ratio of an amount of force imparted to jaw members  130 ,  132  over a predetermined increment of travel distance. Travel distance can be, for instance, an arc length of pivoting movement of moveable handle  122  as moveable handle  122  moves relative to instrument housing  112 . Alternatively and/or additionally, travel distance can be measured based on movement of jaw members  130 ,  132  relative to one another. In one example, for each degree of pivoting movement of moveable handle  122  relative to instrument housing  112  through a first arc length, the amount of force imparted to jaw members  130 ,  132  can be X, whereas for each degree of pivoting movement of moveable handle  122  through second arc length adjacent to the first arc length, the amount of force imparted to jaw members  130 ,  132  can be 3X. More specifically, during initial movement of movable handle  122  toward a proximal position so that jaw members  130 ,  132  approximate from an open position to a closed position, cam assembly  200  can provide a jaw force ratio of 1:1, as dictated by the similar diameters of annular cable track  20   a  of annular cam  204  and annular portion  206   b  of eccentric cable track  206   a.  Further, when movable handle  122  moves through a predetermined arc length after jaw members  130 ,  132  are closed, cam assembly  200 , namely eccentric cam  206  and cable  210  arrangement of cam assembly  200 , may impart a jaw force ratio of 3:1, for instance. In this regard, with the jaw force ratio of  3 : 1 , a user requires less hand force to compress jaw members  130 ,  132  together (see e.g.,  FIGS. 1C  and  FIG. 3B ) such as when sealing tissue disposed between jaw members  130 ,  132  with electrosurgical energy transmitted to jaw members  130 ,  132 . 
     After the user releases movable handle  122 , for example, when finished sealing tissue and/or cutting tissue between jaw members  130 ,  132 , compression spring  116 a urges movable handle  122  toward the initial distal position ( FIG. 3A ) where cam assembly  200  is in an unactuated position. In the unactuated position of cam assembly  200 , apex  206 d of eccentric cam  206  is pointed in a proximal direction ( FIG. 3A ). By comparison, when movable handle  122  is in the proximal position ( FIG. 3B ) and cam assembly  200  is in an actuated position (e.g., fully or substantially fully actuated), apex  206 d of eccentric cam  206  points in a downward direction ( FIG. 3B ). 
     In embodiments, the profile of eccentric cam  206  can have any suitable shape and/or configuration with varying diameters along an outer surface thereof to provide a changing jaw force ratio, for example, when eccentric cam  206  rotates at the same rate as annular cam  204 . More particularly, the profile of eccentric cam  206  can be changed to achieve different movement and/or force ratios. Although annular cam  204  may be circular, in some embodiments, annular cam  204  may have any suitable shape and/or configuration, which may be the same and/or different from eccentric cam  206  in order to facilitate reduction in force required on the movable handle  122 . 
     In certain embodiments, annular cam cable  208  and eccentric cam cable  210  may be portions of a single unitary cable and/or sub-portions of a plurality of different cables. As can be appreciated, any of the disclosed cables can be one or more wires, fibers, threads, filaments, chains, belts, linkages, etc., or combinations thereof, and which may be braided, sheathed, coated, etc., and/or otherwise joined together using any suitable joining technique. 
     In some embodiments, cam assembly  200  may include any number and/or configuration of linkages to achieve a similar “eccentric” relationship as detailed above. 
     In certain embodiments, cables  208 ,  210  and/or cams  204 ,  206  can be provided in any suitable arrangement, for example, so that annular cam  204  is connected to moveable handle  122  (e.g., indirectly and/or directly) and eccentric cam  206  is connected to collar  116 c (e.g., indirectly and/or directly), or vice versa. 
     In some embodiments, compression spring  116   a  is contained at least partially, or entirely, within collar  11     6 c.    
     In some embodiments, cam assembly  200  can include one or more pulleys in addition to, or in place of, one or more of cams  204 ,  206  and/or cables  208 ,  210 . 
     As can be appreciated, securement of any of the components of the presently disclosed apparatus can be effectuated using known securement techniques such welding, crimping, gluing, fastening, etc. 
     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 clinician 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 clinician 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. 
     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 clinicians may prep the patient for surgery and configure the robotic surgical system with one or more of the instruments disclosed herein while another clinician (or group of clinicians) remotely controls the instruments via the robotic surgical system. As can be appreciated, a highly skilled clinician 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. For a detailed description of exemplary medical work stations and/or components thereof, reference may be made to U.S. Pat. No. 8,828,023, and PCT Application Publication No. WO 2016 / 025132 , the entire contents of each of which are incorporated by reference herein.