SYSTEM FOR SIMULTANEOUS TISSUE COAGULATION AND TISSUE DISSECTION

Description

[0001] Surgical instruments are known that can be used to cut tissue (dissection) and seal tissue (coagulation).

[0002] Such an instrument is known from US 8,394,094 B2 and US2010137854A1. It is designed like a pair of forceps, with tissue grasped between its two jaws. Attached to one of the jaws are both coagulation electrodes and a cutting electrode. The other jaw serves as a counter electrode. Furthermore, a movable abutment is provided opposite the cutting electrode. The cutting electrode is encased in a plastic part, from which it protrudes with its front surface serving as the cutting edge and its adjoining narrow flank areas.

[0003] WO 00 / 47124 discloses a similar instrument with a movably mounted cutting electrode. The cutting electrode is held between two sealing electrodes, which are assigned counterelectrodes recessed in grooves. This instrument is powered by an electrical generator, from whose output voltage both the coagulation voltage and the cutting voltage are derived via a transformer arrangement. The transformer has a single- or two-part input winding and two output windings. In a modified embodiment, the two output windings are connected to each other at a single point. In any case, however, there is galvanic isolation between the input winding and output winding. This means that the transformer core must transmit both the power required for coagulation and the power required for cutting.

[0004] Experiments with various instrument configurations have shown that when sealing and cutting are performed simultaneously, there is a complex relationship between the surgical outcome and technical parameters. Both the spatial arrangement of the coagulation and cutting electrodes and the method of delivering electrical power or energy have a significant impact on the quality of the sealing and cutting. Both factors affect the current distribution and the distribution of mechanical forces on the tissue and thus the result achieved in the biological tissue.

[0005] The object of the invention is to provide a system which allows safe and rapid tissue separation and sealing by means of electrical energy.

[0006] This object is achieved by the system according to claim 1:

[0007] The system according to the invention comprises an instrument for treating biological tissue and an associated energy supply arrangement. The instrument and the energy supply arrangement are specially coordinated with one another. The instrument is designed to simultaneously cut and coagulate or seal tissue at spatially spaced locations. For this purpose, a cutting electrode, a coagulation electrode or sealing electrode, and a counter electrode are provided. The cutting electrode and the coagulation electrode are spaced apart from one another and preferably separated by a tissue receiving space. The branches of the instrument, which have the electrodes, can be moved, closed, and opened using appropriate operating levers, for example, manually.However, the invention is not limited to such instruments; it can also be used in motor-controlled industries, such as robot-controlled industries. The power supply arrangement contains a transformer having two outputs, one connected to the cutting electrode and one connected to the coagulation electrode. The outputs are decoupled from one another via at least one current-limiting element in the form of a coupling capacitor. The current-limiting element limits the current flow to the cutting electrode and / or to the coagulation electrode, so that any low tissue resistance present at the cutting electrode does not impair the coagulation result, and a current flow emanating from the cutting electrode does not lead to undesired coagulation phenomena. Conversely, a low tissue resistance present at the coagulation electrode does not impair the cutting result.

[0008] It is possible to provide a current-limiting element between the first output and the cutting electrode. This is considered advantageous. Additionally or alternatively, a current-limiting element can be provided between the second output and the coagulation electrode. By appropriately designing the current-limiting elements, the treatment currents at the coagulation electrode and the cutting electrode can be adjusted independently of one another. In addition, the coagulation result can be influenced by the voltages present at the transformer outputs. From the perspective of the respective electrode, the internal resistance of the RF source is adjusted as desired via one or both current-limiting elements, while the open-circuit voltages are adjusted as desired via the transformer windings, at least at the output connected to the cutting electrode.By separately adjusting the voltage and current, the supply of the cutting electrode and the sealing electrode or coagulation electrode can be optimized.

[0009] According to the invention, the cross-section of both branches, the first and the second branch, is U-shaped, creating a tissue receiving space. This tissue receiving space is arranged such that it extends into both the first and second branches. When the branches are closed, a gap, a pinch gap, can form between them. Tissue held in the tissue receiving space engages behind the pinch gap and leads to a positive hold of the tissue in the instrument, even if the cutting electrode has already severed the held tissue. The current limitation by the coupling capacitor or another current-limiting element, in conjunction with the design (geometry, insulation, and arrangement) of the cutting element, prevents shrinkage of the tissue seam during cutting.

[0010] The design of the cutting electrode in the area of ​​its front side is crucial for the cut quality. The conductive areas in combination with the insulating areas on the front side of the cutting electrode are responsible for the current flow. According to the invention, the cutting electrode is electrically conductive only on its narrow side. On its side surfaces facing the pinch gap, it is largely electrically insulating. This enables a clean cut. Furthermore, it can be achieved that the coagulation of the tissue present in the receiving space is less than the coagulation of the tissue held in the pinch gap. In this way, tissue shrinkage in the tissue receiving space is minimized and the effect of holding the tissue during coagulation is maximized.

[0011] It can also be advantageous if the cutting electrode is partially electrically conductive on its side surfaces. Starting from the front side, this area covers less than 500 µm, preferably 300 µm, so that the front side and the side surfaces protrude from the insulation in this area. A cutting element with narrow conductive areas on its front side can ensure sufficient cutting quality without causing excessive tissue shrinkage in the tissue receiving space.

[0012] An electrically insulating abutment element can be assigned to the cutting electrode. This is made of plastic, for example, elastomer, or ceramic. However, it is also possible to use a metallic abutment that is either connected to the counter electrode or attached in an electrically insulated manner. The mobility of the abutment element allows it to adjust itself according to the changing thickness of the tissue held between the abutment element and the cutting electrode. The abutment element is preferably spring-mounted. During the cutting process, it can thus contribute to directing the majority of the clamping forces onto the pinch gap of the coagulation electrodes and simultaneously pressing the shrinking tissue towards the cutting electrode, which both supports the cutting process and also holds the tissue in the pinch gap.

[0013] The contact surface of the abutment element can be partially or completely flat. In particular, the shape of the abutment element is preferably adapted to the shape of the cutting electrode, so that the cutting electrode preferably rests against the abutment element along its entire length. The coagulation electrode can be formed by a series of spaced-apart individual electrodes. The same preferably applies to the counterelectrode. The spaced-apart individual electrodes of the coagulation electrode are preferably electrically connected to one another. Likewise, the individual electrodes of the counterelectrode are preferably electrically connected to one another. However, the individual electrodes of the coagulation electrode and the counterelectrode are preferably aligned so that they do not overlap, so that with closed branches, even if there is no tissue in between, no electrical short circuit can occur.

[0014] The transformer is preferably designed such that the output connected to the cutting electrode delivers a higher voltage than the output connected to the coagulation electrode. Thus, the action of the cutting electrode and the counter electrode is determined not only by the shape of the electrodes, but also by the power supply to the electrodes.

[0015] Preferably, the impedance of the current-limiting element is greater than the internal resistance of the transformer at its first or second output. The impedance is related to the high frequency used. Thus, the current-limiting element (e.g., the coupling capacitor) limits the current so that even in the event of a short circuit at the connected electrodes, the voltage at the other electrode does not collapse.

[0016] The transformer is preferably supplied with the coagulation voltage. Furthermore, the transformer is preferably designed as an autotransformer. This means that the transformer core only has to transmit the power to be delivered at one of its outputs; the power delivered at the other output is not routed through the transformer core. Furthermore, the number of windings is reduced, as one winding is shared by the primary and secondary sides. This enables the construction of particularly space- and weight-saving transformers that can also be housed in the instrument. Alternatively, the transformer can be magnetically coupled directly to the generator's voice coil, with the transformer outputs being connected to the generator's outputs via at least one suitable current-limiting element (e.g., coupling capacitor, ohmic resistor, RC combination).

[0017] The above-described inventive design of the energy supply device with the above-described inventive design of the instrument allows the treatment of tissue, wherein the tissue separation process, the cutting of the tissue, is completed before the tissue sealing process is completed, and bleeding of separated tissue is nevertheless avoided or almost avoided. This surprising result, that high-quality tissue separations can be performed even though the separation process is completed before the sealing process, means that the overall duration of the tissue sealing and tissue cutting processes can be reduced, which in turn leads to savings during use. For example, total times of less than three seconds are typical for the entire cutting and sealing process, of which tissue cutting generally accounts for less than 0.5 seconds.The remaining treatment time is spent on the sealing process.

[0018] For special applications, it is also possible to design the power supply arrangement so that the cutting element acts as a sealing electrode or is designed as a passive component without electrical action. For this purpose, a switch, potentiometer, or other electrical component can be arranged between the first output of the transformer and the cutting electrode. The branches of the instrument are designed according to the features described above. A system designed in this way enables high-quality sealing of vessels.

[0019] Further details of advantageous embodiments of the invention can be found in the drawings, the description, or the dependent claims. They show: Figure 1 The system, in a schematic partial perspective view, Figure 2a tool part of the instrument according to the arrangement Figure 1 , in perspective partially cut view, Figure 3 the tool part Figure 2 , in vertical section without tissue, Figure 4 a power supply arrangement for the instrument or its tool part according to the Figures 2 and 3 , in simplified circuit diagram representation, Figure 5 a modified embodiment of the power supply arrangement as a simplified circuit diagram and Figure 6 the instrument close Figure 3 during coagulating and severing of biological tissue, in vertical section.

[0020] In Figure 1A system 8 is illustrated, which includes a generator 9 and a surgical instrument 10 powered by the generator. The generator 9 supplies the instrument 10 with RF voltage, which is conducted to a tool 12 held on a shaft 11. The proximal end of the shaft 11 is connected to a housing 13, on which actuating elements 14 are arranged for moving and actuating the tool 12. The tool 12 serves to sever tissue while sealing the remaining tissue seams, so that vessels and lumina contained in the tissue are sealed at the resulting tissue seam.

[0021] The Figure 2The tool 12 shown has two branches 15, 16, at least one of which is pivotally mounted about a pivot axis 17. The branches 15, 16 can be moved toward each other by actuating the actuating element 14 and away from each other by releasing the actuating element 14. The branches 15, 16 can also be moved by other means, for example, pneumatic, hydraulic, or electric drives (not shown).

[0022] The first, in Figure 3The upper branch 15 can be made of metal, ceramic, or the like. Its base body 18 is preferably U-shaped in cross-section and has two parallel first sealing electrodes 19, 20, which are preferably electrically connected to one another and define a space 21 between them. This extends over a significant part of the length of the first branch 15 and serves to accommodate a cutting electrode carrier 22, which is preferably immovably held in the space 21 by a foot 23. Extending from the foot surface 23a facing the second lower branch 16 is a narrow, knife-like extension 24, which preferably protrudes from the space 21 and preferably ends below an imaginary line connecting the lower ends of the sealing electrodes 19, 20.

[0023] The sealing electrode 19, 20 is preferably interrupted in the longitudinal direction, so that it each has a row of individual electrodes 25, 26, which can be electrically connected to the base body 18. The individual electrodes are separated from one another by insulating regions 27, 28. These can be applied to the sealing electrodes 19, 20 as a type of coating or incorporated into the base body 18 as an insulating body. Furthermore, the branch 15 is preferably provided with an insulating coating 29, so that the base body 18 can come into electrical contact with biological tissue only at the sealing electrodes 19, 20 and not at other locations.

[0024] The cutting electrode carrier 22 has a cutting electrode 31 on its end face. This is preferably seated in a groove or recess in the lower narrow side of the knife-like extension 24, with the cutting electrode 31 being exposed with an end face 32. The cutting electrode 31 is held between two groove walls 33, 34, the width of which is preferably approximately the same as the width of the cutting electrode 31. The width of the cutting electrode 31 can be in the range of 0.05 mm to 0.25 mm and is preferably 0.1 mm. The groove walls 33, 34 preferably have a thickness of, for example, 0.15 mm. In addition, the cutting electrode 31 can have a slight overhang above the groove walls or side walls 33, 34. Which is only a few micrometers, for example 500 µm, preferably 300 µm, particularly preferably 200 µm and, in a special embodiment, preferably 0 µm to 40 µm.

[0025] The extension 24 preferably projects beyond the coagulation electrodes 19, 20, so that an imaginary line parallel to the base surface 23a, connecting the coagulation electrodes 19, 20, preferably intersects the extension 24 at approximately half height.

[0026] The second, in Figure 3 The lower branch 16 has a base body 35, preferably U-shaped in cross-section and made of preferably electrically conductive material. Its two lateral legs 36, 37 enclose a space 38 between them and, with their upper regions, form electrically conductive counterelectrodes 39, 40 for the sealing electrodes 19, 20 and the cutting electrode 31.

[0027] The base body 35 is preferably provided on its outer side with an insulating coating 41 which prevents electrical contact with surrounding biological tissue.

[0028] Arranged in the space 38 is a preferably movably mounted abutment element 42, which is held movably, for example, by a spring arrangement 43 consisting of one or more springs parallel to the legs 36, 37. The abutment element 42 is, for example, a rigid ceramic part. However, it can also be made of a flexible, particularly a resilient material, e.g., elastomer. It then forms a spring arrangement itself. The stroke of the spring arrangement 43, regardless of its design, is dimensioned such that when the branches close and thus when the coagulation electrodes 19, 20 move toward one another onto the counter electrodes 39, 40, a squeeze gap 45, 46 of zero is possible, thus ensuring that the maximum spring travel is not yet utilized. In a preferred embodiment, the abutment element 42 is located slightly below the counter electrodes 39, 40 in the closed state.

[0029] The side of the abutment element 42 facing the cutting electrode 31 is preferably designed as a flat pressure surface 44. With respect to the longitudinal direction of the cutting electrode 31, the pressure surface 44 is preferably designed to correspond to the shape of the cutting electrode 31, so that the latter can rest against the pressure surface 44 without a gap. The pressure surface 44 preferably extends between the counter electrodes 39, 40 and, when the branches are completely closed (without tissue), rests against the end face 32 of the cutting electrode 31.

[0030] The design of the pressure surface 44 can be different depending on the material selected for the abutment element 42 or due to application-specific conditions. For example, if the abutment element 42 is made of elastomers, the pressure surface 44 can be designed to match the shape of the end face 32 of the cutting electrode 31 only in the area of ​​the cutting electrode 31. Outside of this area, the pressure surface 44 can be raised or recessed relative to the end face 32 of the cutting electrode 31 (not shown) when the branches are completely or almost closed (without fabric).

[0031] The sealing electrodes 19, 20 and the counter electrodes 39, 40 define together pinch gaps 45, 46, which preferably, as the lines 47, 48 in Figure 3indicate, are designed to slope downwards towards the abutment element 42, so that the lines 47, 48 enclose an obtuse angle β with each other and intersect at an intersection point S above the pressure surface 44 when the tool 12 is closed.

[0032] The functionally determining geometry of the tool 12 includes two tissue receiving spaces 53, 54. These are formed on both sides of the extension 24. They are delimited vertically between the foot 23 and the pressure surface 44. The vertical extent V, for closed branches, is, for example, in the range of 0.7 mm to 2.5 mm, preferably 1.4 mm. The two tissue receiving spaces 53, 54 are preferably the same size and have a horizontal extent H, which is defined by the distance between the extension 24 and the respective leg 36, 37. The horizontal extent H is preferably significantly greater than the thickness of the cutting electrode 31 as well as greater than the thickness of the extension 24 and / or the legs 36, 37. The horizontal extent H is preferably approximately 0.2 to 0.6 times the vertical extent V.

[0033] The counter electrodes 39, 40 can be formed longitudinally continuous on the legs 36, 37. However, they can also preferably be formed, as in Figure 2As indicated, according to the design of the sealing electrodes 19, 20, they consist of individual electrodes 55, 56 that are separated from one another by insulating regions 57, 58. Preferably, the insulating regions 57, 58 are longer in the longitudinal direction of the branches than the individual electrodes 55, 56. The insulating regions 57, 58 can be formed by an insulating coating or insulating body. Furthermore, the individual electrodes 55, 56 are offset from the individual electrodes 25, 26 such that they cannot touch one another even when the pinch gap 45, 46 is zero and thus contact between the branches 15, 16 occurs. Each individual electrode 25, 26 then meets an insulating region 57, 58. Alternatively, the structure can be inverted. The sealing electrodes 19, 20 and the counter electrodes 39, 40 can be formed from insulating material with electrically conductive individual electrodes 55, 56.

[0034] The generator 9 is in Figure 4shown schematically. It comprises a power supply 60 that provides a DC voltage for an RF generator 61. This consists of an oscillating circuit with a capacitor C and a coil L and is excited by a controlled amplifier or switching element 62 depending on the specifications of a control module 63.

[0035] At the coil L, RF power is coupled out via a coupling winding K in order to transmit it via a line 64 ( Figure 1) to the instrument 10. The HF power is used to energize both the sealing electrodes 19, 20 and the cutting electrode 31. A transformer T with a primary winding W1 and at least one secondary winding W2 is used to split the power. The transformer T is preferably designed as an autotransformer. The primary winding W1 is connected to the output of the HF generator 61, i.e., for example, to its coupling coil (coupling winding) K. If the transformer T is an autotransformer, its input (i.e., the upper end of its primary winding) is also its output A2. A line 65 leads from this output A2 and thus the output of the HF generator 61 to the sealing electrodes 19, 20.

[0036] A ground line 66, which is connected to the lower end of the winding W1 and the coupling winding K, leads to the counter electrodes 39, 40. Thus, biological tissue held between the sealing electrode 19 and / or 20 and the counter electrode 39 and / or 40 is connected in parallel to the winding W1 and directly to the output of the RF generator 61. The tissue is subjected to the output voltage U a for sealing.

[0037] To provide a cutting voltage U s, the lower end of winding W2 is connected to line 65 and its upper end is connected to the cutting electrode 31 via a current-limiting element 67, preferably via a coupling capacitor 67 and a line 68. The secondary winding W2 is polarized in the same direction as the primary winding W1, so that the cutting voltage U s is the sum of the output voltage U a and the voltage output by winding W2, this sum being greater than the output voltage U a. The transformer T has a low stray inductance and a low internal resistance. The coupling capacitor 67 has a current-limiting effect and results in the sealing electrode(s) 19, 20 being supplied with low internal resistance and the cutting electrode 31 being supplied with increased internal resistance.

[0038] The transformer T can be built into the generator 9 or alternatively into the instrument 10. Alternatively, it can be built into the cable 64 or the plug 69 provided thereon or an intermediate plug-in module (not shown). Figure 5 As shown, it is also possible to combine the transformer T and the coil L of the RF generator 61. In addition to the coupling winding K, a second coupling winding KS is then provided for the cutting voltage U s, which in turn outputs the RF voltage to the outside via the coupling capacitor 67.

[0039] The system 8 described so far works as follows: For sealing hollow vessels, for separating body tissues, in particular tissues that are permeated with blood vessels and thus have to be sealed at the separation seams, such tissue 30 as Figure 6As illustrated, the tissue is grasped with the tool 12 between the branches 15, 16, with the branches being moved toward each other. As soon as the tool 12 is sufficiently closed, the HF generator 61 is activated, so that simultaneously both the sealing electrodes 19, 20 and the cutting electrode 31 are energized relative to the counter electrodes 39, 40, thus energizing the tissue. The tissue is compressed in the pinch gaps 45, 46 and heated, denatured, and sealed by the current flowing from the sealing electrodes 19, 20 to the counter electrodes 39, 40. In the tissue receiving spaces 53, 54, the tissue shrinks less or not at all. Current emanating from the cutting electrode 31, which is energized at the same time, has a high current density at the end face 32, so that the tissue there is severed by rapid drying and cutting sparks occurring due to the high voltage at the cutting electrode 31.However, the current density in the tissue receiving spaces 53, 54 is low, so that hardly any tissue shrinkage occurs here. The tissue bulges that form prevent the tissue seams from slipping out of the tool 12, even if the tissue is severed before the sealing process is completed. The cutting current is limited by the coupling capacitor 67. The cutting voltage is so high that after the tissue 45 has dried out and denatured, cutting sparks can be generated at the cutting electrode 31 by the cutting current, causing tissue to be severed. However, the coupling capacitor 67 is dimensioned such that a current increase to levels that would lead to high current densities in the tissue receiving spaces is reliably excluded. This prevents tissue sitting in the tissue receiving spaces 53, 54 from shrinking excessively and thus escaping through the pinch gaps 45, 46 before the sealing process is completed.

[0040] The interaction of high cutting voltage U s and coupling capacitor 67 limits the cutting current during the drying phase of the tissue in the area of ​​the cutting electrode and, in conjunction with the tool geometry shown, provides the key to rapid and reliable cutting of biological tissue with high cutting quality and high process reliability.

[0041] Alternatively or additionally, a coupling capacitor may be provided in line 65 to influence the current. Furthermore, instead of the coupling capacitor 67, another current-limiting component or an interconnection of components may be provided, which may contain one or more capacitors.

[0042] An instrument 10 intended for the simultaneous coagulation and severing of tissue has a tissue receiving space 53 between the cutting electrode 31 and the sealing electrode 19 for forming a tissue bulge to secure the tissue in the tool 12 during the sealing process. To enable the formation of voluminous tissue bulges and prevent their shrinkage, the cutting electrode 31 is powered by a current-limiting component, preferably in the form of a coupling capacitor 67. This achieves a high level of process reliability, particularly for tissues that are easy to sever but require a long sealing time. Reference symbol: 8 system 9 generator 10 instrument 11 shaft 12 Tool 13 Housing 14 Actuating element 15, 16 Industries 17 Swivel axis 18 Basic body 19, 20 first (upper) sealing coagulation electrodes 21 Space between the sealing electrodes 19, 20 22 Cutting electrode holder 23 Base of the cutting electrode holder 23a Foot area 24 appendage 25, 26 Individual electrodes of the sealing electrodes 19, 20 27, 28 insulating areas 29 insulating coating 30 tissue 31 Cutting electrode 32 frontal surface 33, 34 Groove walls 35 Basic body 36, 37 Legs of the base body 35 38 Space 39, 40 Counter electrodes 41 insulating coating 42 Abutment element 43 spring element 44 Print area 45, 46 crush gap 47, 48 lines β obtuse angle S Intersection 53, 54 Tissue recording rooms v Vertical extension of the tissue receiving spaces 53, 54 H Horizontal extension of the tissue receiving spaces 53, 54 55, 56 Single electrodes 57, 58 insulating areas 59 60 power supply 61 RF generator C capacitor L Sink K Coupling winding 62 switching element 63 Control module T transformer 64 Line 65 Line 66 Ground wire U a Output voltage 67 Current limiting element, coupling capacitor U s Cutting voltage 68 Line 69 Plug KS Coupling winding

Claims

1. A system (8): with an instrument (10) comprising at least one coagulation electrode (19), at least one cutting electrode (31), and at least one counter electrode (39), wherein the cutting electrode (31), the coagulation electrode (19) and the counter electrode (39) are arranged on branches (15, 16) of a tool (12), one of which is movable toward and away from the other, and with an energy supply arrangement consisting of a generator (9) and a transformer (T) which has a first output (A1) connected to the cutting electrode (31) and a second output (A2) connected to the coagulation electrode (19), wherein at least one current-limiting component (67) is arranged between the first output (A1) and the cutting electrode (31) and / or between the second output (A2) and the coagulation electrode (19), wherein the cutting electrode (31) has an electrically conductive end face (32) and is configured to be largely electrically insulating on side faces facing the coagulation electrode (19) characterized in that the energy supply arrangement is designed such that the cutting of the tissue is completed before the tissue sealing process is completed, that the cutting electrode (31) and the counter electrode (39) are arranged on two different branches (15, 16) of the instrument (10), of which at least one branch (15) is movable toward and away from the other and which define a crushing gap (45, 46) separated from the cutting electrode (31) by a tissue receiving space (53, 54), and that the tissue receiving space (53, 54) extends both above the crushing gap (45, 46) into one of the branches (15, 16) and below the crushing gap (45, 46) into the other of the branches (15, 16).

2. The system according to any of the preceding claims, characterized in that an insulating abutment element (42) is arranged opposite the cutting electrode (31).

3. The system according to claim 2, characterized in that the abutment element (42) is movably mounted.

4. The system according to claim 3, characterized in that the abutment element (42) is resiliently mounted or designed.

5. The system according to any of the preceding claims, characterized in that the coagulation electrode (19, 20) is formed by a series of spaced-apart individual electrodes (25, 26).

6. The system according to any of the preceding claims, characterized in that the counter electrode (39, 40) is formed by a series of spaced-apart individual electrodes (55) and (56).

7. The system according to any of the preceding claims, characterized in that the individual electrodes (19, 20) of the coagulation electrode (19) and the individual electrodes (55, 56) of the counter electrode (39, 40) are arranged so as not to overlap one another.

8. The system according to any of the preceding claims, characterized in that the transformer (T) is configured such that the first output (A1) supplies a higher voltage than the second output (A2).

9. The system according to any of the preceding claims, characterized in that the impedance of the current-limiting component (67) is greater than the internal resistance of the transformer (T) at its first output (A1).

10. The system according to any of the preceding claims, characterized in that the impedance of the current-limiting component (67) is greater than the internal resistance of the transformer (T) at its second output (A2).

11. The system according to any of the preceding claims, characterized in that the transformer (T) has a winding (W1) which is supplied with a coagulation voltage (Ua), and that preferably the output voltages provided at the outputs (A1) and (A2) are dimensioned such that the cutting begins at the same time as the coagulation and is completed before the end of the coagulation process.

12. The system according to claim 1, 3 or 4, characterized in that the abutment element (42) is formed from an elastomer.