Patent Publication Number: US-10772679-B2

Title: Surgical system for connecting body tissue

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation of commonly-owned co-pending U.S. patent application Ser. No. 12/968,942, filed on Dec. 15, 2010, which claims the benefit of German application number 10 2009 059 196.6 filed on Dec. 17, 2009, each of which is incorporated herein by reference in its entirety and for all purposes. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to surgical systems for connecting body tissue generally, and more specifically to a surgical system for connecting body tissue, comprising a surgical instrument having two tool elements movable relative to each other, each of which comprises a high-frequency electrode, the high-frequency electrodes, in an approach position of the tool elements, defining a minimum distance from each other, lying opposite each other and facing each other. 
     BACKGROUND OF THE INVENTION 
     Surgical systems of the kind described at the outset can be used, in particular, for connecting parts of body tissue to one another. In particular, when tubular sections of a hollow organ are connected to one another in end-to-end anastomoses, an overstretching of the tissue connection may be caused, for example, by the second tool element when the instrument is being removed through the tissue connection that has been made. 
     Therefore, it would be desirable to provide a surgical system which, in particular, avoids an overstretching of connections of parts of body tissue made by a flow of current when removing the surgical instrument. 
     SUMMARY OF THE INVENTION 
     In accordance with the invention a surgical system for connecting body tissue comprises a surgical instrument having two tool elements movable relative to each other. Each of the two tool elements comprises a high-frequency electrode. The high-frequency electrodes, in an approach position of the tool elements, define a minimum distance from each other, lie opposite each other and face each other. The instrument further comprises a shaft at the distal end of which at least a first one of the tool elements is arranged or formed. A second tool element is adapted to be moved from an operating position, in which it is adapted for movement into the approach position, into a removal position and/or vice versa. A surface area of a perpendicular projection of the second tool element onto a projection plane extending perpendicularly to the shaft direction in the region of the second tool element is smaller in the removal position than in the operating position 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing summary and the following description may be better understood in conjunction with the drawing figures, of which: 
         FIG. 1  shows a diagrammatic overall view of a surgical instrument for connecting parts of body tissue; 
         FIG. 2  shows an enlarged, perspective, partially sectional and broken-open view of area A in  FIG. 1 ; 
         FIG. 3  shows a longitudinal sectional view of the instrument from  FIG. 1  in area A prior to connection of two tubular parts of tissue; 
         FIG. 4  shows a view in analogy with  FIG. 3  during the welding of the parts of tissue to produce an end-to-end anastomosis; 
         FIG. 5  shows a plan view of a tool element surface with a high-frequency electrode divided up into four electrode segments; 
         FIG. 6  shows a perspective, diagrammatic view of a second embodiment of a surgical instrument for connecting parts of body tissue; 
         FIG. 7  shows a plan view of a diagrammatically represented tool element surface of the instrument from  FIG. 6  in the direction of arrow B; 
         FIG. 8  shows a diagrammatic view similar to  FIG. 2  of an alternative configuration of the instrument in a tissue-gripping position; 
         FIG. 9  shows a view corresponding to  FIG. 8  of the instrument represented therein with the second tool element partly folded down; 
         FIG. 10  shows a sectional view taken along line  10 - 10  in  FIG. 8 ; 
         FIG. 11  shows a diagrammatic sectional view similar to  FIG. 10  of the second tool element collapsed in a position as represented in  FIG. 9 ; 
         FIG. 12  shows an alternative embodiment of a second tool element in perspective diagrammatic representation; 
         FIG. 13  shows an exploded representation of part of the second tool element represented in  FIG. 12 ; 
         FIG. 14  shows a sectional view taken along line  14 - 14  in  FIG. 12 ; 
         FIG. 15  shows a schematic sectional view in analogy with  FIG. 14  of the embodiment represented therein with the second tool element partly folded down; 
         FIG. 16  shows a perspective diagrammatic representation similar to  FIG. 12  of a further embodiment of a second tool element; 
         FIG. 17  shows an enlarged representation of the second tool element from  FIG. 16  in a partly inclined position; 
         FIG. 18  shows a sectional view taken along line  18 - 18  in  FIG. 16 ; and 
         FIG. 19  shows a view in analogy with  FIG. 18  with the second tool element partly inclined in a position as represented in  FIG. 17 . 
     
    
    
     DETAILED DESCRIPTION 
     Although the invention is illustrated and described herein with reference to specific embodiments, the invention is not intended to be limited to the details shown. Rather, various modifications may be made in the details within the scope and range of equivalents of the claims and without departing from the invention. 
     The present invention relates to a surgical system for connecting body tissue, comprising a surgical instrument having two tool elements movable relative to each other, each of which comprises a high-frequency electrode, the high-frequency electrodes, in an approach position of the tool elements, defining a minimum distance from each other, lying opposite each other and facing each other, wherein the instrument comprises a shaft at the distal end of which at least a first one of the tool elements is arranged or formed, and in that a second tool element is adapted to be moved from an operating position, in which it is adapted for movement into the approach position, into a removal position and/or vice versa, a surface area of a perpendicular projection of the second tool element onto a projection plane extending perpendicularly to the shaft direction in the region of the second tool element being smaller in the removal position than in the operating position. 
     The advantage of being able to transfer the second tool element from the operating position to the removal position in the defined manner is, in particular, that the free surface required for passing the second tool element through the connecting site of the parts of tissue is significantly reduced in the removal position in comparison with the operating position. In particular, when the system is suitably designed, it can be ensured that in the removal position no stretching of the freshly connected parts of tissue will occur in the region of their connection when the instrument is removed from the parts of tissue connected to one another. This has a positive effect on end-to-end, side-to-end and side-to-side anastomoses. In particular, when the second tool element can be transferred from the removal position into the operating position again, several anastomoses can also be easily performed one after the other with the instrument without the instrument in its entirety having to be removed from the tubular parts of tissue to be connected to one another. 
     The construction of the system can be easily simplified by the second tool element being ring-shaped or plate-shaped. Furthermore, in particular, ring-shaped, i.e., self-contained electrodes can also be easily and safely arranged on such second tool elements. 
     To transfer the second tool element from the operating position into the removal position and/or vice versa, it is expedient for the second tool element to be mounted for movement on a holding member. For example, the second tool element can thus be moved in a defined manner relative to the holding member, and, optionally, the holding member itself relative to a further part of the instrument, for example, a shaft thereof. 
     Particularly simple constructions are possible for movable mountings of the second tool element on the holding member by, for example, the second tool element being mounted for displacement and/or pivotal movement on the holding member. 
     Expediently, the second tool element is mounted for pivotal movement about a pivot axis which extends transversely, in particular, perpendicularly, to a holding member longitudinal axis defined by the holding member. For example, a ring-shaped or plate-shaped second tool element which, in the operating position, defines a plane perpendicular to the holding member longitudinal axis can thus be pivoted such that, in the removal position, it is inclined relative to the described plane, in particular, is perpendicular thereto. 
     To enable conversion of the second tool element in the removal position into as compact a form as possible, it is advantageous for the surgical system to comprise a folding mechanism for transferring the second tool element from the operating position into the removal position. For example, a folding mechanism can be so configured that the second tool element itself, in turn, comprises two parts which are arranged or formed so as to be pivotable or otherwise movable relative to each other. 
     To enable the second tool element to be easily transferred from the operating position to the removal position and/or vice versa, it is expedient for the folding mechanism to comprise a force transmitting element for transmitting an actuating force onto the second tool element to transfer the second tool element from the operating position to the removal position and/or vice versa. With the force transmitting element, it is thus possible to actuate the folding mechanism which enables transfer of the second tool element from the operating position to the removal position and/or vice versa. 
     Preferably, the force transmitting element is arranged for movement relative to the holding member. For example, the second tool element can be moved into a desired position by the holding member, with actuation of the folding mechanism being possible by means of the force transmitting element which can be moved relative to the holding member. 
     In accordance with the use and design of the surgical system, it may be advantageous for the force transmitting element and the holding member to be configured for displacement and/or rotation and/or screwing relative to each other. Such an arrangement of the force transmitting element and the holding member relative to each other enables provision of practically any actuating mechanisms, for example, for actuating the folding mechanism. 
     In accordance with a preferred embodiment, it may be provided that the holding member and the force transmitting element are arranged for movement relative to the shaft. For example, the shaft can thus be held by a surgeon and the force transmitting element moved relative to the shaft, whereby, in particular, the folding mechanism can be actuated, in order to reduce the surface requirement for removing the second tool element. Owing to movability of the holding member and the shaft relative to each other, the tool elements can also be moved relative to each other in the operating position, whereby they can be transferred, for example, in order to connect tissue, into an approach position with as little spacing as possible, and can be moved apart again, for example, before transfer of the instrument from the operating position to the removal position. 
     In accordance with a further preferred embodiment, it may be advantageous for an actuating mechanism coupled with the folding mechanism and/or the force transmitting element and/or the holding member to be provided for actuating the folding mechanism and/or for moving the force transmitting element and/or the holding member relative to the shaft. The thus defined actuating mechanism allows, in accordance with the design of the instrument, the second tool element to be easily and safely moved from the operating position to the removal position and vice versa. 
     In order to facilitate and/or stabilize movement of the second tool element and the force transmitting element, it is expedient for the second tool element and the force transmitting element to be articulatedly coupled to each other by at least one articulation member. It is also conceivable to provide two, three or more articulation members. 
     To pivot the second tool element relative to the holding member, it is advantageous for the at least one articulation member to engage at one end the second tool element at an engagement or articulation point which is spaced from the pivot axis. A force required for pivoting the second tool element can thus be set in accordance with the choice of engagement or articulation point. 
     Advantageously, the second tool element is of two-part or multi-part configuration. In accordance with the configuration of the parts forming the second tool element, the second tool element can thus be converted into a particularly compact shape in the removal position. 
     In accordance with a further preferred embodiment, it may be provided that the second tool element comprises at least two tool element parts which are movable relative to each other during the transition from the operating position to the removal position. For example, they can be configured for displacement and/or rotation relative to each other, in order to reduce a surface of the second tool element in the removal position in comparison with the operating position. 
     The surgical system is particularly easy to construct when the at least two tool element parts are adapted for pivotal movement relative to each other. In particular, they can thus be easily collapsed. 
     To connect parts of tissue to one another by means of a current, which will also be referred to hereinbelow as welding or sealing, it is expedient for the second tool element to comprise an electrode element movable in the shaft direction and movable in the direction towards and away from the first tool element. In particular, the electrode element can carry a high-frequency electrode. The electrode element itself may, optionally, also be of two-part or multi-part configuration, in order to thereby reduce a space requirement for the second tool element in the removal position in comparison with the operating position. 
     It is advantageous for at least one of the high-frequency electrodes to be divided up into at least two electrode segments, and for the at least two electrode segments to be electrically insulated from each other. The division of at least one of the high-frequency electrodes into two or more electrode segments has, in particular, the advantage that the process parameters for connecting the parts of tissue to one another can be controlled significantly more easily. The smaller the surfaces between which the high-frequency current is used, the easier it is to control the process parameters. In particular, the temperature, pressure and tissue impendence have a considerable influence on the connecting results. For example, it is thus also possible to optimally and, in particular, also automatically adjust the process parameters to the nature of the tissue. Moreover, there is no need for any staples, which remain as foreign bodies in the body, as with a stapling device. In particular, the electrode segments dividing up the high-frequency electrode or the high-frequency electrodes make it possible for current to be applied segment-wise to the high-frequency electrode, so that the parts of tissue to be connected to one another can be welded or sealed segment-wise to one another. A segment-wise application of current made possible by the segmentation of the high-frequency electrodes allows less energy to be introduced into the parts of tissue during the connecting or sealing process than with comparable, unsegmented high-frequency electrodes. Furthermore, the segmentation has the advantage that areas of tissue between areas of the parts of tissue that have been connected by high-frequency current application remain unchanged and substantially undamaged, so that new cell growth starting from these is made possible, which, in addition to the connection made by the high-frequency current, enables a lasting connection of the parts of tissue by these growing together. 
     It is advantageous for the first tool element to comprise an edge surface of the shaft pointing in the distal or essentially in the distal direction. For example, a distal end of the shaft can thus be easily pressed or held against a part of tissue which is to be connected to another part of tissue. In addition, a defined tool element surface can also be easily and reliably prescribed. 
     It is expedient for contact members which, in a tissue-connecting position, are adapted to be brought into electrically conductive contact with the electrode segments of the second tool element and, in a tissue-gripping position, are spaced from the electrode segments of the second tool element to project on the shaft and/or on the first tool element and point in the direction towards the second tool element. With the contact members, it is possible to contact the electrode segments of the second tool element and to connect these to a current source, for example, a high-frequency generator, by an electrically conductive connection provided, for example, in the shaft. Furthermore, the proposed configuration has the advantage that contact between the electrode segments of the second tool element and the contact members can only be established in the tissue-connecting position, so that the electrode segments of the second tool element cannot accidentally have current applied to them in the tissue-gripping position. All in all, the handling of the surgical system is thereby made more reliable. 
     In order that the tool elements can be easily moved relative to each other, it is expedient for the instrument to comprise an actuating device for moving the tool elements relative to each other. 
     Expediently, at least one of the high-frequency electrodes is divided up into a plurality of electrode segments. In the context of this application, a plurality of electrode segments is to be understood as more than two electrode segments, which enable even further improved controllability of the process parameters. 
     Advantageously, electrode segments lying opposite each other and facing each other in the approach position form an electrode segment pair. Such an electrode segment pair can, for example, be controlled as a unit. In this way, in particular, local edge conditions in the region of the two electrode segments can be optimally taken into account, in particular, temperature, pressure and tissue impedance of tissue held between the electrode segment pair. 
     To enable the high-frequency current to be conducted, in a specially defined manner for connecting the tissue, from one electrode segment of the electrode segment pair to the associated electrode segment, it is expedient for the electrode segments forming the electrode segment pair to be geometrically similar. 
     The functionality of the system can be further improved, for example, by the electrode segments forming the electrode segment pair being of identical size or substantially identical size. In this way, in particular, current densities can be optimally prescribed. 
     The at least two electrode segments are of particularly simple design when they are strip-shaped or substantially strip-shaped. 
     In accordance with a preferred embodiment, it may be provided that each of the tool elements defines a tool element surface, and that the high-frequency electrode forms part of the tool element surface. This construction makes practically projection-free design of the tool elements possible. 
     It is expedient for the tool element surface, in the operating position, to define a projection surface or to extend parallel thereto. For example, the projection surface can be defined by the perpendicular projection. In particular, parts of tissue that are to be connected to one another can be uniformly held and pressed against each other when, in particular, the first tool element forms an end edge of a shaft of the instrument pointing in the distal direction. 
     Preferably, the tool element surface is flat. Manufacture and cleaning of the instrument are thereby significantly simplified. 
     In accordance with use of the surgical system, i.e., in particular, in accordance with the parts of tissue to be connected, it may be expedient for the tool element surface to be rectangular or ring-shaped. In particular, a ring-shaped tool element surface enables simple performance of end-to-end anastomoses. 
     It is advantageous for the at least two electrode segments to be arranged in at least two electrode rows adjacent to each other. At least two electrode rows make it possible to produce at least two connecting lines extending adjacent to each other. An improved connection and, in particular, an optimal sealing of the connection site between the parts of tissue can thereby be achieved. In particular, it is possible to maintain between the electrode rows, even after connection of the parts of tissue by high-frequency current application, completely or substantially intact cells, from which new cell growth can start. In the long term, this enables, in addition to the connecting of the parts of tissue by welding, a lasting connection of the parts of tissue by intact cells growing together. 
     Preferably, each electrode row comprises at least two electrode segments which are electrically insulated from each other. At least a sequential applying of current can thus be achieved. 
     In accordance with a further preferred embodiment, it may be provided that at least one electrode segment comprises a first electrode segment section which is part of a first electrode row, and a second electrode segment section which is part of a second electrode row. In this way, a double-row tissue connection can be produced, in particular, comprising or defining two connecting lines. Owing to the specially configured electrode segment sections, an even better overlapping is achieved between the two connecting lines, which, in particular, results in improved sealing of the tissue connection. 
     To enable connection of tissue in the shape of a ring, as is required, in particular, for end-to-end anastomoses, it is expedient for the at least two electrode rows to be of self-contained, ring-shaped configuration. 
     In order that current can be individually applied to each electrode segment, as required, it is advantageous for each electrode segment to be electrically conductively connected to a connecting contact. The connecting contact can, in turn, be connected to other connecting contacts or be directly connected or connectable to a current source. 
     In accordance with a further preferred embodiment, it may be provided that the at least one high-frequency electrode divided up into at least two electrode segments defines an electrode length, and that each of the at least two electrode segments defines a segment length which is smaller than the electrode length. With this construction, it can, in particular, be ensured that only a section of the parts of tissue to be joined together that is smaller than a total length of the high-frequency electrode can be connected with each electrode segment. 
     To improve the tightness of a connection site produced by the surgical system between two parts of tissue, it is expedient for the sum of all segment lengths to be greater than the electrode length. This ensures at least partially an overlapping of tissue connections produced with the electrode segments. 
     To enable simple and safe connection of the instrument to a high-frequency generator or to any other suitable high-frequency current source, it is expedient for the instrument to comprise at least two high-frequency connecting contacts which are electrically conductively connected or connectable to the at least two electrode segments. 
     To enable tissue to be gripped between the two tool elements and possibly held during the connecting process, it is advantageous for the tool elements to be configured for pivotal movement and/or displacement relative to each other. All in all, a movable arrangement of the tool elements relative to each other is desirable. 
     It is expedient for contact members which, in a tissue-connecting position, are adapted to be brought into electrically conductive contact with the electrode segments of the second tool element and, in a tissue-gripping position, are spaced from the electrode segments of the second tool element to project on the shaft and/or on the first tool element and point in the direction towards the second tool element. With the contact members, it is possible to contact the electrode segments of the second tool element and to connect these to a current source, for example, a high-frequency generator, by an electrically conductive connection provided, for example, in the shaft. Furthermore, the proposed configuration has the advantage that contact between the electrode segments of the second tool element and the contact members can only be established in the tissue-connecting position, so that the electrode segments of the second tool element cannot accidentally have current applied to them in the tissue-gripping position. All in all, the handling of the surgical system is thereby made more reliable. 
     In order that the tool elements can be easily moved relative to each other, it is expedient for the instrument to comprise an actuating device for moving the tool elements relative to each other. 
     For further improvement of the handling of the surgical instrument, the actuating device is preferably arranged or formed at a proximal end of the instrument. For example, when the instrument comprises a shaft, this can be introduced through an opening in the body into the interior of the body, and the tool elements are then actuatable relative to each other by the actuating device which, preferably, still protrudes from the patient&#39;s body. All in all, an endoscopic or minimally invasive surgical instrument can thus be formed in a simple way. 
     The handling of the instrument can be improved for a surgeon, in particular, by the actuating device comprising two actuating members pivotable relative to each other, which are in operative connection with at least one of the tool elements for transmission of an actuating force for moving the at least one tool element relative to the other tool element. In principle, the actuating members can also be configured for movement relative to each other only, i.e., alternatively to a pivotable arrangement, for example, they can also be arranged displaceably or pivotably and displaceably relative to each other. 
     In accordance with a further preferred embodiment, it is advantageously provided that the instrument comprises a high-frequency cutting element for severing tissue. Provision of a high-frequency cutting element which, for example, can be part of a cutting device of the instrument, enables, in particular, parts of tissue connected to one another to be prepared in a desired manner. For example, this may be the case when end-to-end anastomoses are to be produced with the system, where free ends of tubular tissue are connected in the shape of a ring by the instrument and protruding tissue is then cut off by the cutting element or the cutting device. 
     Preferably, the high-frequency cutting element comprises a cutting edge which defines a cutting plane inclined relative to a longitudinal axis of the instrument, in particular, in the region of the high-frequency cutting element. Owing to the inclined cutting plane, a high-frequency current, for example, can be conducted across the cutting element in order to sever tissue. Only in a small region is the thus formed cutting edge then spaced at a minimum distance from a counter electrode defining a plane transverse to the longitudinal axis of the instrument. A cutting spark can thus be generated in a defined manner in the region of the shortest distance between the high-frequency cutting element and a corresponding counter electrode, and the cutting spark can then travel in a defined manner along the inclined cutting edge. 
     To enable a ring-shaped cut to be easily and reliably made, the cutting edge is expediently closed in the shape of a ring. 
     In order that a high-frequency current can be applied to the high-frequency cutting element in a defined manner, it is advantageous for the instrument to comprise a high-frequency cutting connection which is electrically conductively connected to the high-frequency cutting element. In particular, with such a configuration a high-frequency current can be applied in a defined manner to the high-frequency cutting element to sever tissue, preferably independently of and at different times from applying a high-frequency current to the electrode segments to connect the parts of tissue to one another. 
     It is advantageous for the cutting element to be arranged for movement relative to at least one of the tool elements. This makes it possible, for example, to move the cutting element relative to the tool elements in such a way that it cannot come into contact with the parts of tissue to be connected to one another when these are being connected by means of the electrode segments formed on the tool elements. Rather, only after connection of the parts of tissue is it thus possible, for example, to move the cutting element into a position in which these can be cut and/or completely or partly severed in a desired manner. 
     To enable application of a high-frequency current to the high-frequency instrument in a desired manner, the surgical system preferably comprises at least one high-frequency current generator which is selectively electrically conductively connectable to the high-frequency electrodes and/or the cutting element. In particular, it is thus possible to set the respective optimum current for the connecting or severing of tissue. 
     In accordance with a further preferred embodiment, it may provided that the system comprises at least one control device with a switching device for sequentially applying high-frequency current to the electrode segments of at least one high-frequency electrode. Optionally, high-frequency current can also be applied to a further high-frequency electrode with the control device. With the switching device configured in the described manner, in particular, a high-frequency current can be applied to the electrode segments of a high-frequency electrode one after the other, i.e., in a sequential order, for section-wise connection of the parts of tissue to be joined together. 
     It is expedient for the surgical system to comprise a control device with a switching device for simultaneously applying high-frequency current to at least two electrode segments of at least one high-frequency electrode. In this way, the connecting or sealing process can be accelerated or performed more quickly as two parts of tissue to be joined together can be simultaneously connected to each other along two sections. In particular, it is also conceivable to simultaneously apply a high-frequency current to two electrode segments, and to then sequentially apply a high-frequency current to further electrode segments. 
     To avoid short circuiting when high-frequency current is simultaneously applied to two electrode segments, it is expedient for at least one further electrode segment to be arranged between the at least two electrode segments. 
     It is expedient for the switching device to be configured for switching at least one high-frequency output of the at least one current generator. It is also possible to provide two, three or even more high-frequency outputs, which can be controlled by the switching device, in order, for example, to specifically apply to individual electrode segments of the high-frequency electrodes a high-frequency current of a desired strength. 
     It is advantageous for the surgical system to comprise a high-frequency generator which is selectively electrically conductively connectable to the high-frequency electrodes or the cutting element and comprises the control device. In this way, several functions of the system can be accommodated in one apparatus, which improves both its manufacture and its handling. 
     Expediently, the control device is so configured that a strength of the current applied and/or a duration of the current application is settable for the individual electrode segments. In this way, in particular, process parameters such as temperature, pressure and tissue impedance can be kept directly or indirectly within the desired range by the control device. 
     To avoid excessive heating of the parts of tissue to be joined together, which would result in destruction of cells, it is advantageous for the control device to comprise a temperature measuring device for measuring an electrode segment temperature and/or a tissue temperature. 
     It is also expedient for the control device to comprise an impedance measuring device for measuring a tissue impedance of tissue held between the tool elements. The determining of the tissue impedance offers the possibility of controlling the current or high-frequency generator, in particular, the power provided by it as a function of its value. In this way, the energy to be introduced into the parts of tissue in order to connect them can be easily and reliably controlled. In particular, the high-frequency electrodes can be used to measure the tissue impedance. A measurement can also take place between individual electrode segments that lie opposite each other. Preferably, the tissue impedance is measured while current is not being applied to the high-frequency electrodes. In particular, it is expedient to measure the tissue impedance during the breaks when changing the polarity of the high-frequency current. The change in the tissue can then be monitored very well and practically in real time and further energy input can be stopped or specifically allowed to continue. 
     The following description of preferred embodiments of the invention serves in conjunction with the drawings for further explanation. 
     A surgical system for connecting body tissue is diagrammatically represented and generally designated by reference numeral  10  in  FIG. 1 . It comprises a surgical instrument  12  with two tool elements  14  and  16  which are movable relative to each other. The system  10  further comprises a current generator in the form of a high-frequency current generator  18 , which can be connected to the instrument  12  in a manner described in more detail hereinbelow. 
     The tool elements  14  and  16  form part of a connecting device generally designated by reference numeral  20  for connecting body tissue. The first tool element  14  has an edge surface  42 , pointing in the distal direction, of an elongate, sleeve-shaped shaft  24  of the instrument  12 . The first tool element is thus arranged or formed at a distal end  26  of the instrument  12 . 
     The first tool element  14  comprises a high-frequency electrode  28 . It is divided up into at least two, in the embodiment represented diagrammatically in  FIGS. 2 to 5  into four, electrode segments  30  which are electrically insulated from one another. The electrode segments  30  are of strip-shaped or substantially strip-shaped configuration. The first tool element  14  defines a tool element surface  32  in such a way that the high-frequency electrode  28  forms part thereof. The tool element surface  32  is of overall flat and ring-shaped configuration. 
     The four electrode segments  30  define two electrode rows  34  and  36 . Each electrode row comprises part of the four electrode segments  30 . As is apparent from  FIG. 5 , for example, each electrode segment  30  has a first electrode segment section  38  forming part of the first electrode row  34 , and a second electrode segment section  40  forming part of the second electrode row  36 . The two electrode rows  34  and  36  are of overall curved configuration, and the electrode segment sections  38  and  40  each define electrically conductive circular ring sections. The at least two electrode rows, which are each defined by four electrode segment sections  38  and  40 , respectively, are overall of self-contained, ring-shaped configuration. To enable the electrode segments  30  to be contacted in a desired manner, each electrode segment  30  is electrically conductively connected to a connecting contact  42  which is arranged in a connection region between the electrode segment sections  38 ,  40 . Even after connection of the parts of tissue by applying high-frequency current, there still remain between the electrode rows completely or substantially undamaged cells from which new cell growth can start. In the long term, this enables, in addition to the connection of the parts of tissue by welding, a lasting connection of the parts of tissue by intact cells growing together. 
     The high-frequency electrode  28  defines an electrode center line  44  extending between the electrode segment sections  38  and  40 . Adjacent electrode segments  30  are therefore arranged offset from one another in a direction defined by the electrode center line  44 . The high-frequency electrode  28  divided up into four electrode segments  30  defines overall an electrode length  46 , each of the four electrode segments  30  defining a segment length  48  which is smaller than the electrode length  46 . As shown, for example, in  FIG. 5 , the electrode segments  30  extend over an angular range of approximately 140° and therefore have a length which corresponds approximately to 40% of the electrode length  46 . Therefore, the sum of all segment lengths  48  exceeds the electrode length  46  by approximately the factor 1.6. 
     In the region of a proximal end of the shaft  24 , high-frequency connecting contacts  50  are arranged, which are electrically conductively connected, for example, by lines extending in the shaft, to the electrode segments  30 . Preferably, the number of high-frequency connecting contacts  50  corresponds to the number of electrode segments  30 , i.e., four high-frequency connecting contacts  50  for the four electrode segments  30  of the first tool element  14 . 
     The second tool element  16  is of substantially disc-shaped configuration and comprises an electrode element  52 , which is movable in the direction towards the first tool element  14  and away from it, more specifically, parallel to a longitudinal axis  54  of the shaft  24  in the region of the tool elements  14 ,  16 , which defines a shaft direction  56 . The tool elements  14 ,  16  are arranged for displacement relative to each other, i.e., a distance  58  between the tool element surface  32  of the first tool element  14  and a tool element surface  60  of the second tool element  16  is alterable. 
     The electrode element  52  comprises a high-frequency electrode  29 , which corresponds in its construction to the high-frequency electrode  28 . This means that it also comprises four electrode segments  31 , which do not project over the tool element surface  60 . Two electrode rows  35  and  37  are also defined, first electrode segment sections  39  defining the electrode row  35 , and second electrode segment sections  41  defining the electrode row  37 . Connecting contacts  43  are also provided, which each conductively connect an electrode segment section  39  to an electrode segment section  41  to form an electrode segment  31 . The high-frequency electrodes  28  and  29  are formed mirror-symmetrically in relation to a mirror plane extending perpendicularly to the longitudinal axis  54  between the tool element surfaces  32  and  60 . In this way, electrode segment pairs  62  are defined, in each case, by an electrode segment  30  and the corresponding opposite electrode segment  31 . All in all, the embodiment shown in  FIGS. 1 to 5  therefore comprises four electrode segment pairs  62 . The electrode segments  30 ,  31  are not only similar geometrically, but are of the same size or substantially the same size. 
     In an approach position of the tool elements  14 ,  16 , the high-frequency electrodes  28 ,  29  define a minimum distance  58  from each other. The approach position is shown diagrammatically in  FIG. 4 . In the approach position, the high-frequency electrodes  28  and  29  lie opposite each other and face each other. 
     The electrode segments  31  are electrically conductively connectable to further four high-frequency connecting contacts  50 , only two of which are shown in  FIG. 1  for reasons of clarity. The high-frequency connecting contacts  50  can be connected by corresponding connection lines  64  to corresponding contacts  66  of the high-frequency current generator  18 . As explained above, the high-frequency connecting contacts  50  are directly electrically conductively connected to the electrode segments  30 . To enable the high-frequency connecting contacts  50  to be connected to the electrode segments  31 , there are arranged on the shaft  24  or on the first tool element  14  so as to protrude in the direction facing the second tool element  16  contact members  68 , which have a short cylindrical section  70  and a conical section  72  defining a free end. In a tissue-connecting position, as shown, for example, diagrammatically in  FIG. 4 , i.e., in a position in which the tool elements  14  and  16  are in an approach position, the free ends of the sections  72  of the contact members  68  extend into corresponding bush-shaped receptacles  74  of the electrode element  52  and are in electrically conductive contact with these. The contact members  68 , in turn, are connected along the shaft  24  by electric lines, not shown, to the high-frequency connecting contacts  50 . The receptacles  74  are, in turn, electrically conductively connected to the connecting contacts  43 . In this way, an electrically conductive contact between the high-frequency connecting contacts  50  and the electrode segments  31  can also be established in the approach position or tissue-connecting position. 
     Of course, the contact members  68  which extend through the electrode segments  30  in the region of their connecting contacts  42  are insulated from these so that short circuiting cannot occur. For this purpose, the sections  70  of the contact members  68  are preferably provided with an electrically insulating coating or sheath. 
     To enable movement of the tool elements  14 ,  16  of the instrument  12  relative to each other, an actuating device  76  is arranged at a proximal end or end region of the instrument  12 . The actuating device  76  comprises two actuating members  78  pivotable relative to each other, which are movably coupled to a force transmitting member  80  movably mounted inside the shaft, so that as a result of a pivotal movement of the actuating members  78 , the force transmitting member  80  is movable in the distal or proximal direction. 
     The force transmitting member  80  defines at its distal end a blind hole-shaped receptacle  82  into which a holding member  84  is introducible with a first free end and fixable in the receptacle  82 . The second free end of the substantially rod-shaped holding member  84  is immovably connected to the second tool element  16 . In this way, as a result of displacement of the force transmitting member  80  in the distal direction, the second tool element  16  can be moved away from the first tool element  14 . Preferably, the instrument  12  is so constructed that the second tool element  16  can be moved from a tissue-gripping position, as represented diagrammatically in  FIGS. 2 and 3 , and in which the tool elements  14 ,  16  are at a maximum distance  58  from each other, into the approach position or tissue-connecting position by pivoting the actuating members  78  towards each other, which results in movement of the force transmitting member  80  in the proximal direction. 
     Furthermore, the instrument  12  comprises a cutting device  86  for severing tissue. The cutting device comprises a cutting element  88  with a self-contained ring-shaped cutting edge  90 . The cutting edge  90  defines a cutting plane  92  inclined relative to the longitudinal axis  54  of the instrument  12 . The cutting plane  92  is inclined through approximately 10° in relation to a reference plane extending perpendicularly to the longitudinal axis  54  and running parallel to the tool element surfaces  32  and  33 . At the proximal end of the shaft  24  a further high-frequency cutting connection  94  is provided, which in a variant of the instrument  12  is electrically conductively connected to the cutting element  88 . It is, for example, thus possible to provide a monopolar cutting device  86 . In the conventional manner, a neutral electrode has then to be applied to the patient&#39;s body for monopolar cutting. A bipolar cutting device  86  is provided, for example, by arranging on the second tool element  16 , opposite the cutting edge  90 , a ring electrode  96  which is connected to a further high-frequency cutting connection  94  by an electrically conductive connection, not shown in greater detail, which, for example, in a manner not shown in greater detail, runs through the force transmitting member  80 . Optionally, the ring electrode  96  itself can also be segmented, for example, in analogy with the high-frequency electrodes  28  and  29 . It is also possible, instead of the ring electrode  96 , to use the high-frequency electrode  29  as counter electrode. 
     The cutting element  88  is preferably mounted for displacement relative to the two tool elements  14 ,  16 . The cutting edge  90  formed concentrically around the longitudinal axis  54  can thus be displaced relative to the high-frequency electrodes  28  and  29 . A cutting-actuator  98  with an actuating member  100  protruding from the proximal end of the instrument is provided for actuating the cutting device  86 . The actuating member  100  is mechanically coupled to the cutting element  88  by a mechanism, not shown, for example, a further force transmitting member extending inside the shaft  24 , so that movement of the actuating member  100  also causes the cutting element  88  to be moved. Preferably, the actuating member  100  is arranged for displacement and rotation relative to the shaft  24 , so that the cutting element  88  is not only displaceable parallel to the longitudinal axis  54  but also rotatable relative thereto. 
     A control device  102  with a switching device  104  is provided for applying a high-frequency current to the electrode segments  30 ,  31  in any desired manner. The control device  102  is preferably arranged in a housing of the high-frequency current generator  18  and forms part thereof. In particular, the switching device  104  is configured for sequentially applying a high-frequency current to the electrode segments  30 ,  31 . The switching device  104  serves, in particular, to control the contacts  66  and further contacts  106 , which are connectable by further connection lines  108  to the high-frequency cutting connections  94  of the instrument  12 . In this way, the cutting device  86  can be operated in a monopolar or bipolar manner with the high-frequency current generator  18 . For monopolar operation, high-frequency current is merely applied to the cutting element  88  and a neutral electrode as counter electrode is placed on the patient&#39;s body. For bipolar cutting, in particular, a ring-shaped counter electrode can be provided on the second tool element  16 , for example, in the form of the ring electrode  96 , so that a high-frequency current can then flow between the counter electrode and the cutting element  88 . Alternatively, the high-frequency electrode  29  can also be used as counter electrode. If application of current to the cutting device  86  is dispensed with completely, it can then also be used purely mechanically for severing tissue, more specifically, with the preferably sharpened cutting edge  90 . 
     Furthermore, the switching device  104  can also be so configured that a high-frequency current can be simultaneously applied to at least two electrode segments  30 ,  31  of a high-frequency electrode  28 ,  29 . In this case, it is expedient to respectively arrange between two electrode segments  30 ,  31  to which high-frequency current is simultaneously applied a further electrode segment  30 ,  31 , to which current is then not applied. For example, in this way, the opposite electrode segments  30  of the high-frequency electrode  28  shown in  FIG. 5  could have current applied to them simultaneously, and the two other electrode segments  30  then do not have current applied to them. 
     To enable individual setting of the strength and/or duration of the current application to the individual electrode segments  30 ,  31 , the control device  102  is configured so as to comprise a setting device  110 . For example, a strength and/or a frequency of the high-frequency current as well as a duration of the current application can be set by the setting device  110 . Furthermore, the setting device  110  may also be optionally configured so as to enable individual setting of current application sequences. 
     Furthermore, the control device  102  preferably comprises a temperature measuring device  112  for measuring an electrode segment temperature and/or a tissue temperature. The temperature measuring device  112  serves, in particular, to supply the control device  102  with the control variable required for automatic control of current application to the high-frequency electrodes  28 ,  29 , namely a temperature of the tissue, for example, indirectly by means of a temperature measurement of the electrode segments  30 ,  31 . For example, electrode segments  30 ,  31  to which current is not applied can serve as measuring contacts for temperature detection by means of tissue impedance measurement. In this way, it can be ensured that the temperature required for connecting the tissue is reached in the desired manner and with high precision by appropriate application of current to the high-frequency electrodes  28 ,  29 , but undesired overheating of the parts of tissue to be connected to one another is avoided. 
     Furthermore, the control device  102  optionally comprises an impedance measuring device  113  for measuring a tissue impedance of tissue held between the tool elements  14  and  16 . The determining of the tissue impedance offers the possibility of controlling the high-frequency generator  18 , in particular, the parameters voltage, current or power provided by it, as a function of its value. In this way, the energy to be introduced into the parts of tissue to connect these can be easily and reliably controlled. In particular, the high-frequency electrodes  28  and  29  can be used for measuring the tissue impedance. A measurement can also take place between individual electrode segments  30  and  31  lying opposite one another. The measurement of the tissue impedance can take place selectively while current is being applied to the high-frequency electrodes  28 ,  29  or when current is not being applied to the high-frequency electrodes  28 ,  29 . The change in the tissue can thus be monitored very well and practically in real time, and further energy input metered, stopped or specifically allowed to continue. 
     With the surgical system  10  described above, in particular, tubular parts of tissue  116  can be directly connected to one another by these being welded or sealed to one another by the application of high-frequency current. The procedure is, for example, as follows: 
     To produce an end-to-end anastomosis of two tubular parts of tissue  116 , as is required, for example, after intestinal surgery, during which part of the intestine is removed, free ends of the parts of tissue  116  are brought close together, so that with their free ends facing in the direction towards the longitudinal axis, they lie with surface-to-surface contact in ring-shaped configuration against one another, as shown, by way of example, in  FIGS. 3 and 4 . The free ends are then located between the two tool elements  14 ,  16 , so that the parts of tissue  116  can be held clamped against one another between the tool elements  14 ,  16  in the tissue-gripping position. 
     The tool elements  14 ,  16  are then moved towards each other into the tissue-connecting position, so that the electrode segments  31  are also electrically conductively connected to the high-frequency connecting contacts  50  in the manner described above. To weld the parts of tissue  116 , a high-frequency current is now preferably applied to individual electrode segment pairs  62 . It then flows over the sections of the parts of tissue held between the tool elements  14 ,  16  and heats these. At a temperature of from approximately 50° C. to approximately 80° C., preferably from approximately 65° C. to approximately 70° C., such a change takes place in the cells that the parts of tissue  116  adhere to one another. The connecting method is preferably carried out such that always only one electrode segment pair  62  has current applied to it at a time, in particular, in a sequential order. In this way, a ring-shaped connecting line  114  is created, which is substantially predetermined by the high-frequency electrodes  28 ,  29  or their electrode center lines  44 ,  45 . 
     Owing to the fact that a high-frequency current is not applied to the entire high-frequency electrodes  28 ,  29 , the temperature for connecting the parts of tissue  116  can be controlled much better and destruction of the cells prevented. Preferably, current is applied to the electrode segments  30 ,  31  one after the other, i.e., sequentially, so that the parts of tissue  116  are welded to one another step-by-step along the connecting line  114 . Furthermore, owing to the arrangement of the electrode segment sections  38 ,  39 ,  40  and  41  in two rows, a double connection is made between the parts of tissue  116 , which ensures optimum sealing and a lasting, stable connection of the parts of tissue  116  to one another. 
     As an alternative to sequential application of current, as indicated above, opposite electrode segments  30 ,  31  can also have current applied to them simultaneously. The time for connecting the parts of tissue  116  can thereby be halved in the embodiment represented diagrammatically in  FIGS. 1 to 5 . 
     After connection of the parts of tissue  116 , projecting tissue is removed with the cutting device  86 . The cutting device  86  is preferably used in a bipolar manner, i.e., the cutting element  88  and the ring electrode  96  are connected to the high-frequency current generator  18  and high-frequency current is passed over the two parts of tissue  116  to sever the tissue. Owing to the inclined cutting edge  90 , a defined cutting spark is generated, more specifically, in the region in which the distance between the cutting edge  88  and the ring electrode  96  is minimal. Starting from this region, the cutting spark then automatically travels along the cutting edge  90  in a circle in both directions until the tissue is completely severed. Use of the cutting device  86  in bipolar operating mode has, in particular, the advantage that when being severed, the parts of tissue  116  are simultaneously also coagulated in order to stop any undesired bleeding directly during the severing. 
     After connecting and cutting the parts of tissue  116 , the instrument  12  can then be withdrawn by retracting the shaft  24  from the patient&#39;s body, for example, from his intestine. 
     In accordance with the design of the instrument  12 , the shaft  24  is preferably of such length that during use of the instrument  12  both the actuating device  76  and the cutting-actuator  98  still protrude from the patient&#39;s body so that they can be actuated by a surgeon. 
     Alternatively or additionally, the surgical system  10  can comprise, instead of the instrument  12 , a surgical instrument, for example, in the form of an instrument  120  represented diagrammatically in  FIGS. 6 and 7 . The instrument  120  comprises two arms  124  and  126  mounted on each other for pivotal movement relative to each other about a pivot axis  122 . At a proximal end of the arms  124 ,  126 , finger rings  128 ,  130  are formed, which together define an actuating device  132  for actuating the instrument  120 . 
     Starting from free, distal ends  134  and  136  of the arms  124  and  126 , tool elements  138  and  140  are formed on inner sides thereof so as to face each other. The tool elements  138  and  140  are of identical construction and, in an approach position of the ends  134  and  136 , are located opposite each other and, in this position, are at a minimum distance from each other. Each tool element  138 ,  140  comprises a high-frequency electrode  142 ,  144 . These are of identical, substantially U-shaped construction. Each high-frequency electrode  142 ,  144  comprises two electrode sections  146  extending parallel to each other in a direction perpendicular to the pivot axis  122  and an electrode section  148  extending perpendicular to these and adjoining the ends  134 ,  136 . 
     The construction of the high-frequency electrodes  142 ,  144  will be described in greater detail hereinbelow, by way of example, in conjunction with  FIG. 7  with reference to the high-frequency electrode  142 . 
     The high-frequency electrode  142  comprises a total of 30 electrode segments  150 . In each case, 15 electrode segments are arranged offset from one another in two electrode rows  152 ,  154  parallel to one another along each electrode section  146  and are electrically insulated from one another. The electrode segments  150  are of straight-lined and strip-shaped configuration. They define between them an electrode center line  156  which in accordance with the shape of the high-frequency electrode  142  is also of U-shaped configuration. Two further electrode segments  151  are arranged in the region of the electrode section  148  and complete the electrode rows  152  and  154 , respectively, of the electrode sections  146 . The electrode segments  150  and  151  are therefore arranged offset from one another in a direction defined by the electrode center line  156 . 
     To enable a high-frequency current to be applied to the electrode segments  150 ,  151 , these are respectively arranged electrically conductively with a high-frequency connection  158  in proximal end regions of the arms  124 ,  126  adjacent to the finger rings  128 ,  130 . The high-frequency connections  158  can be connected with corresponding connection lines or cables to the high-frequency current generator  18 . 
     In the approach position, owing to the identical configuration of the high-frequency electrodes  142  and  144 , electrode segments  150  and  151  of the same or substantially the same size are located opposite each other and face each other. They form an electrode segment pair generally designated by reference numeral  168 . The instrument  120  therefore comprises in all 32 electrode segment pairs  168 . 
     The tool elements  138  and  140  also define flat tool element surfaces  170 , which are of U-shaped configuration. The electrode segments  150  and  151  do not project over the tool element surface  170 . 
     The instrument  120  of generally forceps-type configuration can also be used to connect parts of tissue. These are held clamped between the tool elements  138 ,  140  and are then welded or sealed to one another by corresponding application of current to the electrode segments  150 ,  151 . To this end, as described in conjunction with the operation of the instrument  12 , current can be applied to the electrode segments  150  sequentially, i.e., in a circulating U-configuration, after application of current to one electrode segment  150 , current is applied to the next electrode segment  150  of the adjacent electrode row  152 ,  154  until current has been applied once to all electrode segments  150 ,  151 . In this way, a two-row connection line for connecting two parts of tissue can be created. Alternatively, in the instrument  120  simultaneous application of current to two or even more electrode segments  150 ,  151  is also conceivable. Preferably, current is not simultaneously applied to adjacent electrode segments  150 ,  151 , but rather, preferably, at least one, better two or three electrode segments  150 ,  151  between electrode segments  150 ,  151  having current applied simultaneously to them remain without current. 
     The instrument  120  can also optionally comprise a cutting device  160 , as represented diagrammatically in  FIG. 6 . A slot  162  is formed between the electrode sections  146  on the tool elements  138 ,  140 . A cutting element  164  with a cutting edge  166  pointing in the direction towards the slot  162  of the arm  124  is held in the slot  162  on the arm  126  and is optionally movable relative to the tool element  136 . Therefore, the tissue held between the tool elements  138  and  140 , for example, can already be severed upon closing the arms  124  and  126 . Optionally, the cutting element  164  can also be used in a monopolar or bipolar manner. For example, the high-frequency electrode  142  can be used as counter electrode to the cutting element  164  in the case of bipolar use. For monopolar operation, a high-frequency current is merely applied to the cutting element  164  and a neutral electrode placed on the patient&#39;s body as counter electrode. In both cases, the cutting element  164  is preferably also electrically conductively connected to a contact of the high-frequency connections  158 . 
     In  FIGS. 8 to 11  a variant of the instrument  12  is represented, which differs by the configuration of the second tool element, which is designated in  FIGS. 8 to 11  by reference numeral  16 ′. The tool element  16 ′ assumes, in an operating position in which it can be moved into the approach position described above, the shape of a circular ring. It comprises two circular ring sections  180  and  182 , which each extend over an angle of about 180° in relation to the longitudinal axis  54 . Free ends of the circular ring sections  180 ,  182  are only half as wide as the circular ring sections  180 ,  182  in the remaining region and serve as bearing blocks  184  and  186 . The bearing blocks  184  and  186  are each provided with a transverse bore  188  and  190 , into which a cylindrical rod  192  is inserted. The bearing blocks  184  lie against the side of the bearing blocks  186  that faces the longitudinal axis  54 . The rod  192  is rotationally fixedly secured in the transverse bores  190  of the circular ring section  182 . The inner diameter of the transverse bore  188  is of such dimensions that the circular ring section  180  is pivotable relative to the rod  192  about a pivot axis  242  defined thereby and therefore relative to the circular ring section  182 . 
     The two circular ring sections  180  and  182  are each additionally coupled by a bar-shaped link  194  to a holding member  84 ′ which defines a holding member longitudinal axis coinciding with the longitudinal axis  54 . In analogy with the holding member  84 , the holding member  84 ′ is or can be coupled to the force transmitting member  80 , and in this way is movable in the distal and proximal directions relative to the shaft  24 . For movable articulation of the links  194  on the holding member  84 ′, the latter is provided in the region of its distal end with a slot  204 , which extends transversely to a longitudinal axis defined by the rod  192 . In this way, two legs  206  are formed, which are provided with an aligning transverse bore  208 , into which a cylindrical bearing pin  210  is rotationally fixedly inserted. The links  194  are provided at their first ends with a receiving bore  212 , through which the bearing pin  210  extends, and which has an inner diameter allowing pivotal movement of the links  194  about a pivot axis defined by the bearing pin  210 . 
     On the proximal side of the slot  204  in the holding member  84 ′ there extends further in the proximal direction a longitudinal slot or oblong hole  214 , through which the rod  192  passes. In this way, the rod  192  is defined and displaceable parallel to itself in a direction parallel to the longitudinal axis  54 . A proximal end of the oblong hole  214  forms a proximal end stop for the rod  192 , and a distal end  218  of the oblong hole  214  forms a distal end stop for the rod  192 . 
     An actuating mechanism  222 , which comprises a sleeve-shaped force transmitting element  220  whose inner diameter is adapted to the outer diameter of the holding member  84 ′ and is therefore displaceable in the distal and proximal directions on the holding member  84 ′, serves to move the rod  192 . Adjacent to its distal end  224 , the force transmitting element  220  is provided with a bore  226  through which the rod  192  extends. The rod  192  is rotatable relative to the bore  226 . The actuating mechanism  222  can also form part of the actuating mechanism  76  described above. This means that movement of the rod  192 , for example, also by pivotal movement of the actuating members  100  relative to one another, is possible. Alternatively, it is conceivable to provide, in analogy with the actuating mechanism  76 , a further actuating device which comprises one or two further actuating members, similar to the actuating members  100 , in order to specifically bring about relative movement between the force transmitting element  220  and the holding member  84 ′. 
     There are arranged parallel to each other on upper sides of the circular ring sections  180  and  182  two bearing blocks  228 , which are provided with bores  230  parallel to the transverse bore  208 . A further free end of the links  194  is pivotably mounted, in each case, between the bearing blocks  228  on the bearing shaft  200  inserted in the bores  230 . The described arrangement of the links  194 , which may also be referred to as articulation members, ensures that they engage at one end the second tool element  16 ′ at an engagement or articulation point which is spaced at a distance from the pivot axis  242 . 
     By means of the actuating mechanism  222 , the second tool element  16 ′ can be moved from the operating position mentioned above, which is diagrammatically shown in  FIGS. 8 and 10 , into the removal position, which is represented by way of example in  FIG. 11 .  FIG. 9  represents diagrammatically an intermediate position, i.e., a position between the operating position and the removal position. As will be readily apparent from comparison of the two  FIGS. 10 and 11 , a surface area of a perpendicular projection of the second tool element  16 ′ onto a projection plane  234  extending perpendicularly to the longitudinal axis  54 , i.e., to the shaft direction in the region of the second tool element  16 ′, is smaller in the removal position than in the operating position. This is achieved by movement of the sleeve-shaped force transmitting element  220 , starting from the operating position in which the rod  192  strikes the proximal end  216 , and undersides  236  and  238  of the circular ring sections  180  and  182  extend parallel to the projection plane  234 . When the force transmitting element  220  is moved in the distal direction, the rod  192  is forcibly guided in the distal direction in the oblong hole  214 . Owing to the articulated connection of the circular ring sections  180  and  182  relative to each other and to the holding member  84 ′ by the two links  194 , the circular ring sections  180  and  182  pivot about the pivot axis  242  in the direction towards the longitudinal axis  54 . In this way, the second tool element  16 ′ is folded together or collapsed. By the articulated arrangement of the circular ring sections  180  and  182  by means of the links  194  a folding mechanism  240  is thus formed for transferring the second tool element  16 ′ from the operating position to the removal position. 
     So far, the configuration of the undersides  236  and  238  of the second tool element has not been discussed. These can either comprise a single, substantially continuous ring electrode which forms a single counter electrode to the high-frequency electrode  28  of the first tool element  14 . Or, alternatively, there can also be formed on the undersides  236  and  238 , in analogy with the high-frequency electrode  29 , a high-frequency electrode with two or more electrode segments  31 , preferably corresponding to the high-frequency electrode  29 . This then allows connection of parts of tissue  116  in the manner described above in the operating position. 
     After the connecting of the parts of tissue, the folding mechanism  240  can then be actuated, for example, by corresponding actuation of the described actuating mechanism  222 , whereby the holding member  84 ′ is moved in the distal direction. If the force transmitting element  220  is, for example, immovably arranged relative to the shaft  24 , then the second tool element  16 ′ can be automatically collapsed upon movement in the distal direction of the force transmitting member  80 . Owing to the significantly reduced space requirement in the removal position, the second tool element can be guided, during removal of the instrument  12 , through a connection site formed by connecting the parts of tissue  116 , more particularly, without expanding the connection site, which is much more gentle than passing the second tool element through the connection site in the operating position. 
     It is self-evident that electrically conductive connections from the electrode  29  to the high-frequency connecting contacts  50  can be led, for example, via the links  94  and the holding member  84 ′ to the high-frequency connecting contacts  50  in the proximal end region of the shaft  24 . 
     A further variant of a second tool element is generally designated by reference numeral  16 ″ in  FIGS. 12 to 15 . It replaces, for example, the above-described tool elements  16  and  16 ′ of the instrument  12 . 
     The second tool element  16 ″ is substantially plate-shaped with a slightly convexly curved outer side  250  pointing in the distal direction. 
     A ring groove  252  which is open and points in the proximal direction is formed on an underside of the second tool element  16 ″. Formed at the center is a substantially circular depression  254  in which a substantially parallelepipedal bearing projection  256  is arranged. The bearing projection  256  is formed coaxially with the longitudinal axis  54  and protrudes in the proximal direction from the underside of the second tool element  16 ″. The bearing projection  256  is provided with a transverse bore  258  which is skew in relation to the longitudinal axis  54 . There is also formed on the bearing projection  256  a curved guide slot  260 , which is of convexly curved configuration pointing in the proximal direction. A proximal end of the bearing projection  256  has a rounded-off outer contour. 
     The second tool element  16 ″ is mounted for pivotal movement on a sleeve-shaped holding member  84 ″. For this purpose, the holding member  84 ″ is provided with a transverse bore  262 , which extends through a wall  264  of the holding member  84 ″ at two points. Rotationally fixedly inserted in the transverse bore  262  is a bearing pin  266 . It simultaneously extends through the transverse bore  258  in such a way that the bearing projection  256  is pivotable about a pivot axis  284  defined by the bearing pin  266 . To enable actuation of a folding mechanism  270  also provided in the second tool element  16 ″, a force transmitting element  268  is provided, which is of substantially rod-shaped configuration and extends through the holding member  84 ″ coaxially with the longitudinal axis  54 . Arranged so as to project from a distal end surface  272  of the force transmitting element  268  parallel to each other and pointing in the distal direction are two bearing legs  274 , through each of which an aligning bore  276  extends. Rotationally fixedly inserted in the bores  276  is a further bearing pin  278 , which is oriented parallel to the bearing pin  266 . An outer diameter of the bearing pin  278  is of such dimensions that it can extend through the guide slot  260  and be moved relative thereto. 
     A proximal end  280  of the force transmitting element  268  can preferably be coupled to the force transmitting member  80 , so that as a result of movement of the latter, the second tool element  16 ″ can also be moved. 
     Inserted in the ring groove  252  is a ring-shaped electrode element  282 , which preferably comprises a high-frequency electrode  29  in the above-described form, which, for reasons of clarity, is not shown in detail in  FIGS. 12 to 15 . Alternatively, a simple, continuous ring electrode can also be formed on the electrode element  282 . 
     To transfer the second tool element  16 ″ from the operating position to the removal position, the force transmitting element  268  is moved in the distal direction. Owing to the specially curved guide slot  260 , the bearing pin  278  is forcibly guided therein and therefore brings about a forcibly guided pivoting of the second tool element  16 ″ about the pivot axis  284 . Essentially, the second tool element  16 ″ can thus be pivoted through almost 90°, so that in this variant of the tool element  16 ″, too, a perpendicular projection  232  thereof onto the projection plane  234  is smaller in the removal position than in the operating position, as represented diagrammatically in  FIGS. 14 and 15 . In this way, an overstretching of the connection site between the parts of tissue  116  connected to one another is avoided in the removal position when removing the instrument  12 . 
     A further embodiment of a second tool element generally designated by reference numeral  16 ′″ is shown in  FIGS. 16 to 19 . It can be used in the instrument  12  instead of the previously described second tool elements  16 ,  16 ′ and  16 ″. 
     The second tool element  16 ′″ is substantially plate-shaped and comprises a disc  300 . This is provided at its center with an elongated oval slot  302  extending transversely. A bore  304  extends through the disc  300  offset latterly somewhat from its center point, which lies in the region of the slot  302 . Rotationally fixedly inserted in the bore  304  is a bearing pin  306 , which also extends through the slot  302 . A distal end of a holding member  84 ′″, which is of sleeve-shaped configuration, projects into the region of the slot  302 . Proximally from its end  308 , the holding member  84 ′″ is provided with a bore  310  whose inner diameter is so adapted to the outer diameter of the bearing pin  306  that the bearing pin  306  is rotatable relative to the bore  310  therein. This then enables, all in all, a pivoting of the disc  300  about a longitudinal axis defined by the bearing pin  306 . 
     A folding mechanism  312 , which couples the disc  300  via a link  314  articulatedly to a distal end  316  of a force transmitting element  318 , serves for forcibly actuated pivoting of the disc  300 . The force transmitting element  318  has an elongate, rod-shaped section  320  whose proximal end  322  can be coupled to the force transmitting member  80 . The end  316  is thickened in the shape of a head in relation to the section  320  and is of almost parallelepipedal shape. A slot  324  open at the side is formed at one side thereof. A transverse bore  326  is also provided, which extends transversely through the slot  324 . Rotationally fixedly inserted in the transverse bore  326  is a bearing pin  328 . The rod-shaped link  314  is also provided with a bore  330  and is mounted for pivotal movement on the bearing pin  328 . A further bore  332  is provided adjacent to an opposite end of the link  314 . It serves to mount the link  314  on a further bearing pin  334 . This is inserted in a further bore  336  of the disc  300 . The bore  336  is oriented parallel to the bore  304  and arranged outside the slot  302  adjacent to an edge  338  of the disc  300 , more particularly, opposite the bore  304  in relation to the longitudinal axis  54 . Formed on an upper side  340  of the disc  300 , starting from the edge  338  is a groove  342  into which the end of the link  314  enters with its bore  332 . In this way, the link  314  is articulately mounted on the bearing pin  334 . With one end, the link  314  thus engages the second tool element  16 ′″ at an engagement or articulation point which is spaced at a distance from a pivot axis  344  which is defined by the longitudinal axis of the bearing pin  306 . 
     The folding mechanism  312  is actuated by the force transmitting element  318  being moved in the distal direction. This has the consequence that the link  314  is bent relative to the disc  300 . The further the force transmitting member  318  is moved in the distal direction, the further the link  314  pulls the region of the disc  300  on which the groove  342  is provided in the distal direction. In an extreme position, the disc  300  is then aligned almost parallel to the longitudinal axis  54 . All in all, it is therefore also possible with the second tool element  16 ′″ to attain a removal position in which a perpendicular projection  232  thereof onto the projection plane  234  extending perpendicularly to the longitudinal axis  54  is smaller than in the operating position. 
     A high-frequency electrode  29  in a form as described above in the second tool element  16  can also be arranged or formed on the second tool element  16 ′″. Alternatively, it is also conceivable to provide a self-contained, ring-shaped electrode which is not divided up into electrode segments. Similarly to how the second tool element  16 ″ comprises the electrode element  282 , electrode elements, for example, in the form of the electrode element  282  or else the electrode element  52  can also be provided in the second tool elements  16 ′ and  16 ′″. 
     As mentioned above in conjunction with the second tool element  16 ′, the high-frequency electrodes provided on the second tool elements  16 ″ and  16 ″ can be connected in the conventional manner to the high-frequency connecting contacts  50  by providing corresponding electrically conductive connections on the instrument  12 . 
     All of the above-described first and second tool elements  14 ,  16 ,  16 ′,  16 ″,  16 ″ and  138  and  140  are preferably comprised of either electrically conductive or electrically insulating components. Components are also conceivable, which are partly electrically conductive and partly electrically insulating. The components themselves can, in particular, be produced completely from electrically conductive or electrically insulating materials, and the electrically insulating components can also be produced from an electrically conductive material which, in particular, is provided with an electrically insulating outer sheath or coating. As electrically insulating or non-conductive materials, in particular, plastics can be used, which still have sufficient stability at the temperatures occurring when the surgical system  10  is in use. For example, both thermoplastics and thermosetting plastics are suitable. Alternatively, ceramic material can also be used as insulating material. In particular, the components of the tool elements  14 ,  16 ,  16 ′,  16 ″,  16 ′″ and  138  and  140  can be made from a ceramic material. Use of a ceramic material has the advantage, in particular, over many plastics that it still has sufficient stability at very high temperatures. The high-frequency electrodes  28  and  29  are preferably made from a metal or a metal alloy. Alternatively, the use of electrically conductive ceramic materials for formation of the high-frequency electrodes  28  and  29  is also conceivable, provided they meet the requirements for use of high-frequency current. 
     The tool elements  14 ,  16 ,  16 ′,  16 ″,  16 ′″ and  138  and  140  can, for example, be produced as described hereinbelow. The individual parts, components or constituents of the tool elements  14 ,  16 ,  16 ′,  16 ″,  16 ′″ and  138  and  140  can, in particular, be produced separately and subsequently fitted together, for example, adhesively. Alternatively, it is, for example, also possible to place the electrically conductive parts of the high-frequency electrodes  28  and  29  as inserts in a plastic injection molding tool and to injection-mold these with a plastic material. As mentioned above, the electrodes can be made from a metal or an electrically conductive ceramic material. In the case of segmentation of the high-frequency electrodes  28  and  29  as described above, for example, a corresponding number of electrically conductive electrode segments made from a metal or a metal alloy or an electrically conductive ceramic material must then be placed in the plastic injection molding tool before injection-molding with a suitable plastic material. 
     In the case of purely ceramic construction of the tool elements  14 ,  16 ,  16 ′,  16 ″,  16 ′″ and  138  and  140 , in particular, a ceramic powder injection molding method can be used, for example, the so-called “2C-CIM” technology, a two-component microceramic powder injection molding method. Herein two different ceramics are injected in an injection molding process, which form the electrically conductive and electrically insulating parts in the finished tool elements  14 ,  16 ,  16 ′,  16 ″,  16 ′″ and  138  and  140 . After the injection, the two different ceramics are sintered together. These can be, for example, an Al 2 O 3  ceramic and a mixed ceramic made of Al 2 O 3  and TiN.