Patent Publication Number: US-2022218408-A1

Title: Cutting Instrument

Description:
RELATED APPLICATION(S) 
     This application claims the benefit of European Patent Application No. 21151169.6, filed Jan. 12, 2021, the contents of which are incorporated herein by reference as if fully rewritten herein. 
     TECHNICAL FIELD 
     The invention refers to an electrosurgical instrument that is configured and suitable for cutting or for tissue fusion or for tissue coagulation, particularly combined with cutting of tissue. 
     BACKGROUND 
     JP 2004180843 A discloses a tissue coagulation and cutting instrument having two jaws in the type of a forceps with jaws movable relative to one another between which tissue can be held. The two jaws can be applied with current in order to coagulate tissue held therebetween. In addition, one of the jaws comprises a cutting element to which an elastic counter support arranged on the other jaw is assigned. Different configurations are proposed for the counter support. For example, the elastic counter support can have a square massive cross-section, a hollow cross-section or a stepped cross-section in the type of a flat T and can be inserted into a downwardly open groove of the bottom jaw. This counter support comprises a wider top section facing the cutting element and a narrower section extending into the groove. During closing of the jaw the counter support deforms into the groove. While the center section of the counter support does not abut anywhere, the edges of the counter support are held and supported on steps extending along the center groove. 
     A coagulation and cutting instrument having an elastic counter support is known from US 2004/0049185 A1. The counter support comprises an approximately square cross-section and is supported on its side opposite the cutting electrode between the two legs of a jaw that is apart therefrom configured in a U-shaped manner. The flanks of the counter support are exposed. 
     US 2009/0234355 A1 discloses a coagulation and cutting instrument having a cutting electrode arranged in a jaw and a movably supported counter support arranged in the other jaw. The latter is resiliently supported in order to be able to dodge the intruding cutting electrode. 
     Further examples for electrosurgical instruments having coagulation electrodes, cutting electrodes and counter supports assigned to the cutting electrodes can be taken from EP 1 632 192 A1 and EP 2 754 403 A2. 
     The requirements on coagulation and cutting instruments increase in multiple aspects. Miniaturization tendencies as well as requirements for manufacturing reliability and manufacturing accuracy exist. 
     Starting therefrom it is the object of the invention to provide an instrument that is improved at least in one respect. 
     SUMMARY 
     The inventive instrument as described herein complies with this object: 
     The instrument according to the invention comprises a cutting electrode on a jaw and an elastic counter support on the other opposed jaw. The counter support is held in a frame that is provided by a respective jaw itself or a separate component. The counter support comprises a circumferential surface that is connected with a frame in a tension-resistant manner. The frame fixes the counter support at least at two sides opposite to one another. Preferably the frame surrounds the counter support on three sides, i.e. on its two flanks and on the distal end. The counter support is connected with the frame at least at its two longitudinal sides or flanks and optionally also at its distal end. In the latter case the counter support closes the frame completely and does not allow material to enter into the area below the counter support. It is, however, also possible to leave the membrane free at its distal end and/or at its proximal end, i.e. disconnected from the frame. 
     The frame comprises a surface facing the counter support that is connected with the circumferential surface of the counter support. The connection is tension-resistant, i.e. a tension force directed from the edge of the counter support toward its center does not release the counter support from the frame. The connection is preferably free of gaps, i.e. the circumferential surface of the counter support is entirely two-dimensionally connected with the frame. Preferably, in case of tensional stress, no part of the counter support lifts off from the frame. A tensile force can be created in that the cutting electrode—and where appropriate biological tissue present between the cutting electrode and the counter support—presses on the counter support during closing of the jaw. The counter support is thereby displaced from its rest position and tensioned. Thereby the counter support is preferably flexible, such that mainly tensile stresses are created due to the deformation of the counter support, which is why the counter support is also denoted as “membrane”. In the preferred case the counter support is configured such that it is in the so-called membrane condition, i.e. in terms of its mechanical stresses in the non-loaded condition with open jaws and preferably also in the loaded condition with closed jaws the tensile stresses present in the material of the counter support are at least approximately equal everywhere. 
     The tensile-resistant connection between the counter support and the frame is preferably a substance bond connection, as appropriate an exclusively substance bond connection. It can be realized in a simple manner in that a membrane is created in an ejection molding process, whereby the frame forms a part of the injection molding die, i.e. limits the material flow of the still liquid counter support at the circumferential surface of the created counter support. The frame preferably consists of metal. The counter support preferably consists of flexible plastic, e.g. a silicone plastic. The adhesion between the circumferential surface of the membrane and the frame can be increased by a respective surface design of the frame surface facing the membrane, e.g. by roughening. In addition, the frame surface can be activated entirely or in sections for improvement of the adhesion of the counter support. For this the surface can be locally or entirely subject to a CVD or PVD coating process. If the frame is a punched part, surface unevennesses of the frame created during punching can be used for improvement of the adhesion between the frame and the membrane. 
     The tensile-resistant connection between the counter support and the frame can be supported by a form-fit between counter support and frame, e.g. in that the frame comprises form-fit structures along its surface facing the counter support, as for example openings, cut-outs or the like. 
     Preferably the counter support is held in the frame without support. Particularly, it does not abut against any surface facing opposite the intruding direction of the cutting electrode. In other words, the free top surface facing the cutting electrode is as large as the free bottom surface of the counter support facing away from the cutting electrode. As a result of this arrangement, biological tissue held between the jaws is particularly softly and uniformly pressed against the cutting electrode, such that that the tissue held between the cutting electrode and the counter support is electrically cut, however, not mechanically squeezed. The separation process is exclusively electrical. This can be achieved in large configurations of the instrument as well as in miniaturized configurations thereof. 
     The counter support consists preferably of an electrically insulating plastic, such as silicone. It can, however, also consist of a plastic that is electrically conductive intrinsically or extrinsically, i.e. by embedding electrically conductive substances or particles. In doing so, an additional thermal effect can be created during the flow of current through the tissue. 
     Preferably the counter support comprises two flanks that are arranged in constant distance to one another. However, the distance can also decrease in distal direction. 
     In its central section that contacts the cutting electrode in the closed condition, the counter support can have a thickness that is as most as large as the thickness at the edge of the counter support. Preferably the thickness in the central section is even smaller than at the edge of the counter support. In doing so, a main advantage of the invention is supported. During closing of the instrument the counter support is preferably subject to elongation and lesser to compression or bending, as it was frequently the case in the prior art. In doing so, the membrane-like counter support can also well adapt to an inhomogeneous tissue and keep it in soft contact with the cutting electrode. It is, however, also possible to make the thickness of the counter support in the center below the cutting electrode larger than at the edge (at the flank or circumferential surface). 
     The counter support can be domed away or toward the cutting electrode in the rest position. In doing so, different spring characteristics can be adjusted in order to achieve a desired progress of the pressing force of the tissue against the cutting electrode during compression, i.e. during closure of the instrument. 
     In an advantageous embodiment the counter support ends flush with the frame on its top side as well as on its bottom side. This simplifies production of the instrument, particularly the creation of the counter support in the frame. 
     The counter support can comprise one or multiple sections extending on the frame. Preferably such a section is arranged at least at the distal end of the counter support or the jaw comprising it. Such sections can serve as spacers of the jaws and avoid that they get directly in contact during closing. Apart from these sections it is, however, advantageous if the counter support apart therefrom ends flush with the frame on the top side and the bottom side. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further details of advantageous embodiments of the invention are derived from the drawings, the associated description as well as the claims. The drawings show: 
         FIG. 1  the inventive instrument in a closed condition, 
         FIG. 2  the top and bottom jaw of the instrument according to  FIG. 1  in open condition in a cross-section, 
         FIG. 3  the instrument according to  FIGS. 1 and 2  in closed condition in a cross-section without tissue, 
         FIG. 4  the instrument according to  FIG. 3  with tissue held between the jaws in a cross-sectional illustration, 
         FIG. 5  a modified embodiment of the instrument in a cross-sectional illustration in slightly opened condition, 
         FIG. 6  a further modified embodiment of the inventive instrument in a cross-sectional illustration with slightly opened jaws, 
         FIG. 7  the bottom jaw of the instrument according to  FIG. 6  in a perspective illustration in part and 
         FIG. 8  a plastic injection molding die for manufacturing the counter support for the instrument according to  FIGS. 1-5 . 
     
    
    
     DETAILED DESCRIPTION 
     In  FIG. 1  an instrument is illustrated that is configured for tissue fusion and cutting. The instrument can be an instrument for the open surgical use, an instrument for the laparoscopic use or also an instrument for the endoscopic use. The instrument  10  comprises jaws  12 ,  13  that are, for example, held on a flexible shank  11  or also on a rigid shank, whereby at least one of the jaws, in the present embodiment the top jaw  12 , is pivotably supported in order to be able to be moved toward and away from the other jaw, in the present example the bottom jaw  13 . The pivot movement around the hinge axis A is controlled by a not further illustrated mechanism extending through the shank  11 . 
     As an alternative, the instrument  10  can also comprise two pivotably supported jaws that are movable toward and away from each other. 
       FIG. 2  illustrates instrument  10  according to  FIG. 1  in cross-section, cut along line II-II in  FIG. 1 . For example, top jaw  12  can be made of a metal part  14  having U-shape in cross-section and being metallically bare or also electrically insulated on the outside, the leg faces  5  thereof serve as coagulation electrodes  15 ,  16 . The coagulation electrodes  15 ,  16  can be continuously strip-shaped electrodes, they can also be interrupted by insulating sections. Instead of a metal part  14 , the upper jaw  12  can also comprise another part made, for example, of a non-conductive material, such as for example plastic, in that the coagulation electrodes  15 ,  16  are embedded, e.g. in the form of sheet parts. 
     The top jaw  12  is provided with a cutting electrode  17  that is, e.g. made of a thin metal sheet strip. Preferably the cutting electrode  17  is held in an insulating body  18  approximately centered between the coagulation electrodes  15 ,  16 . The cutting electrode  17  is preferably arranged in the extension  19  of insulating body  18  such that the two flat sides of the cutting electrode  17  are insulated. Between extension  19  and the legs of the top jaw  12  supporting the coagulation electrodes  15 ,  16 , clearances  20 ,  21  are created that serve for location of tissue therein. 
     The bottom jaw  13  comprises a counter support  22  that serves to hold biological tissue on the cutting electrode  17  during a cutting process. The counter support  22  is a flexible body, consisting for example of silicone, the thickness D M  measured in a central section  23  thereof—particularly in extension of the cutting electrode  17 —is smaller than the width B measured transverse thereto. Counter support  22  consists of solid material. Preferably it does not comprise any hollow spaces. 
     Laterally the counter support  22  adjoins a frame  25  with its circumferential surface  24  and is connected therewith in a tension-resistant manner, preferably in a substance bond manner, e.g. by overmolding or gluing. The circumferential surface  24  is preferably non-structured, i.e. smooth apart from processing marks such as punch or fracture surfaces. It can, however, also be structured in order to support the substance connection between counter support  22  and frame  25 , e.g. by means of form-fit. 
     The counter support  22  comprises a thickness D R  at its edge adjoining the circumferential surface  24  that is preferably at least as large as the thickness D M  in the central section  23 . Furthermore, the thickness D R  thereby corresponds to a thickness of the frame  25  to be measured in the same direction, such that counter support  22  ends flush with frame  25  on its top side  26  as well as its bottom side  27 . 
     The frame  25  consists preferably of metal, such that its top side forms the coagulation electrodes  28 ,  29 . They can transition into one another at the distal end of the respective jaw  12  or  13 . 
     The unit consisting of counter support  22  and frame  25  can be manufactured in an injection-molding process in which a pre-manufactured frame  25  is inserted into a respective injection molding die in which then the plastic material of the counter support  22  is introduced in order to closely connect with frame  25  at the circumferential surface  24 . The unit created in this manner is connected with the remaining load-carrying part of bottom jaw  13  that is made of a U-shaped metal part  30  in the present embodiment. It can be metallically bare or electrically insulated, e.g. provided with a plastic coating, on its outer side. Also frame  25  can be metallically bare, i.e. electrically conductive, or alternatively provided with an insulation at its side facing outwardly. Frame  25  can be electrically conductively connected with metal part  30  or can also be insulated relative thereto. Between counter support  22  and metal part  30  a clearance  31  can be formed that can be separated from the environment or also connected therewith by suitable openings. 
       FIG. 3  illustrates the instrument  10  in closed condition. Electrodes  15 ,  28  contact one another or are kept in small distance to one another by means of not further illustrated spacers. The same applies for the coagulation electrodes  16 ,  29 . Cutting electrode  17  stands on counter support  22  and presses it into clearance  31  without the bottom side  27  of counter support  22  being in contact with metal part  30  or any other part that is present in the clearance  31 . Because the counter support  22  is slim in cross-section, i.e. because its thickness D M  is remarkably smaller than its width B, counter support  22  is substantially subject to tension in the deformation illustrated in  FIG. 3 . It is stretched. Similarly the connection between its circumferential surface  24  and frame  25  is substantially subject to tension. 
     The instrument  10  operates as follows: 
     As illustrated in  FIG. 4 , for treatment of biological tissue  32  it is first held between jaws  12 ,  13 . Biological tissue  32  can be organ tissue, a blood vessel or also other tissue. The jaws  12 ,  13  moved toward one another grasp the tissue  32 . Concurrently or in time sequence the coagulation electrodes  15 ,  28 ,  16 ,  29  are applied with coagulation voltage and the cutting electrode  17  is applied with cutting voltage. As shown in  FIG. 2 , counter support  22  has dodged the cutting electrode  17  during closing of the instrument  10  and has been tensioned thereby. However, thereby counter support urges the tissue  32  against cutting electrode  17 . The biological tissue  32  can enter into the clearances  20 ,  21  on both sides of extension  19 . The coagulation electrodes  15 ,  28  as well as  16 ,  29  coagulate the tissue held between them and fusion it in case it is a vessel, i.e. close it at these locations. The tissue that is applied with a respective higher cutting voltage by cutting electrode  17  shrinks and separates, whereby counter support  22  holds the shrinking tissue on cutting electrode  17 . 
     Modifications are possible in the invention described so far. For example, as illustrated in  FIG. 5 , counter support  22  can be convexly domed toward cutting electrode  17 . This results in that the dome of the counter support  22  has to be first overcome during closing of instrument  10 , whereby a certain snap effect may occur. Alternatively, counter support  22  can also be completely planar. Apart therefrom the description of  FIGS. 1-4  applies correspondingly for the embodiment of instrument  10  according to  FIG. 5 . 
     The counter support  22  can also be planar or concave, as in the embodiments according to  FIGS. 1-4 , i.e. configured in a manner domed away from cutting electrode  17 . With the progress of the thickness from the center  23  toward the edge of counter support  22  as well as the dome desired spring characteristics, i.e. path-force-progresses, can be adjusted that can be achieved during closing of instrument  10 . 
     In all of the embodiments described above, counter support  22  can comprise extensions  33 ,  34 ,  35  that project over the frame  25  and thus avoid a direct contact of coagulation electrodes  15 ,  16  with coagulation electrodes  28 ,  29 . Apart therefrom, however, also in this embodiment counter support  22  preferably ends flush with frame  25  at its top side  26  as well as its bottom side  27 . 
     Manufacturing of counter support  22  shall be illustrated with reference to  FIG. 8 . A plastic injection molding die  36  is provided for this purpose between the top die half  37  thereof and the bottom die half  38  thereof an engraving  39  is formed that defines the form of the counter support to be produced. In the engraving  39  a central elevating projection  40  is illustrated in  FIG. 8  that reduces the thickness of counter support  22  to be created in the central section. 
     For manufacturing of counter support  22 , the frame  25  is inserted into engraving  39  while the plastic injection molding die  36  is open, and the injection molding die  36  is closed subsequently. Subsequently a liquid plastic is filled into engraving  39  such that it fills the provided space entirely and abuts against the inner side of frame  25  and adhesively connects therewith. After curing of the plastic, the plastic injection molding die  36  can be opened and counter support  22  can be removed. 
     In the inventive instrument  10  that is preferably usable for tissue fusion and cutting, counter support  22  configured as thin membrane is assigned to a cutting electrode  17  arranged between two electrode pairs. The thin membrane is spanned in a frame  25  on which it is held with its circumferential surface in a substance bond manner. The circumferential surface thereby extends in an angle, preferably in a right angle, relative to the coagulation electrodes  28 ,  29  formed by the frame top side. The pressing force applied by the membrane with which biological tissue  32  is pressed against cutting electrode  17  is thus predominantly created by tensile stress present in the membrane. 
     LIST OF REFERENCE SIGNS 
     
         
           5  leg face of metal part  14   
           10  instrument 
           11  shank 
           12  top jaw 
           13  bottom jaw 
           14  metal part 
           15 ,  16  coagulation electrodes of top jaw  12   
           17  cutting electrode 
           18  insulating body 
           19  extension of insulating body 
           20 ,  21  clearances 
           22  counter support 
           23  central section of counter support  22   
           24  circumferential surface of counter support 
           25  frame 
           26  top side of counter support  22   
           27  bottom side of counter support 
           28 ,  29  coagulation electrodes of bottom jaw  13   
           30  metal part 
           31  clearance 
           32  biological tissue 
           33 - 35  extensions 
           36  plastic injection molding die 
           37  top die half 
           38  bottom die half 
           39  engraving 
           40  projection 
         A hinge axis 
         D M  thickness measured in the central section of counter support 
         D R  thickness at the edge of counter support