Electrosurgical instrument

An electrosurgical instrument having a distal end and a gripping device which is arranged at the distal end in the longitudinal direction and which includes at least a clamping jaw portion and a coagulation jaw portion. The coagulation jaw portion has a plurality of electrically separated coagulation electrodes which are substantially immovable relative to each other. At least one of the jaw portions is movable from an open position into a closed clamping position, wherein the jaw portions at least portion-wise engage into each other in the clamping position and are of such a configuration that the tissue can be clamped between the jaw portions substantially in a half-wave shape. The coagulation jaw portion has at least two electrode arrangements which are arranged at different sides and have respective electrically separated coagulation electrodes, by means of which the tissue is coagulatable in two substantially mutually separated coagulation regions.

BACKGROUND

The invention concerns an electrosurgical instrument for the bipolar coagulation of biological tissue, comprising a distal end, a gripping device which is arranged at the distal end in the longitudinal direction and which includes at least a clamping jaw portion and a coagulation jaw portion, wherein the coagulation jaw portion has a plurality of electrically separated coagulation electrodes substantially immovable relative to each other, at least one of the jaw portions is adapted to be movable from an open position into a closed clamping position, and the jaw portions at least portion-wise engage into each other in the clamping position and are of such a configuration that the tissue can be clamped between the jaw portions substantially in a half-wave shape.

Electrosurgical instruments of the specified kind are known from the state of the art and described for example in WO 99/40861 A1 or WO 99/23960 A1.

SUMMARY

A very wide range of different electrosurgical procedures have already long been applied in medical technology. Thus for example tissue separation or tissue removal (electrotomy) by means of high-frequency energy has already been a routine procedure in surgery for decades. The tissue is caused to vaporise by the cutting electrode from which a spark discharge emanates, in the immediate area surrounding the cutting electrode, and small capillary vessels are immediately closed off so that almost blood-free tissue cutting is possible. That method is used in all surgical and other medical disciplines for tissue separation or tissue removal.

A further method which is established in surgery and other medical disciplines is electrosurgical sclerosing of tissue or arresting bleeding by means of high-frequency current. The instruments used for that purpose are often in the form of gripping instruments such as pincers or tweezers. The distal ends of conventional gripping elements generally have large-area planar electrodes which are generally at a different (bipolar) or more rarely the same (monopolar) potential. Both in the case of the monopolar and also the bipolar use of the gripping instrument the piece of tissue to be sclerosed or the part of the blood vessel to be closed off is disposed between the electrodes arranged at the distal end of both gripping limbs of the gripping instrument. In the monopolar procedure the high-frequency current flows between those electrodes and a return electrode which is fixed to the patient at another location, generally on the surface of the skin of the patient. In the bipolar procedure the high-frequency current flows between the two electrodes at the distal end of the gripping limbs of the gripping instrument.

Cutting by means of wire or lancette electrodes disposed at the end of a handle and coagulation with gripping instruments are the most wide-spread high-frequency surgical procedures.

By virtue of the small dimensions of endoscopic or laparoscopic instruments, disadvantageous lever relationships can have the result that the gripping instruments in the state of the art, when reasonable forces are involved at the gripping portion, can be difficult to close or can lead to fatigue on the part of the doctor. The result of this can be that, in the case of conventional tongs-like gripping devices, a larger gap remains at the tip of the gripping device than near the pivot. That problem occurs in particular when gripping large veins (about >5 mm) and bunches of tissue and becomes even worse if the grip is of an unfavourable configuration and as a result it is not possible to build up high forces at the jaw portion. However, even in the case of a grip portion which is well designed, it is technically not always possible to exert a force of just any desired magnitude on the jaw portions as the material strengths of the components also encounter their limits, when an excessively high level of force is involved. In many products in the state of the art, hardened steel is used for the jaw portions to limit flexing of the jaw portions.

If jaw surfaces of the gripping limbs, as in the case of conventional tongs-like gripping devices, are not parallel when heat-sealing off the veins, a larger gap occurs at the tip than near the pivot, as mentioned above. That results in lesser compression of the tissue at the tip of the gripping device and as a result also a lower degree of heating by virtue of the lower current density and a greater transfer resistance. That problem occurs in particular with large veins and thick bunches of tissue.

The instruments described in WO 99/40861 A1 and WO 99/23960 A1 try to resolve the specified problems by the jaw portions engaging into each other and thus clamping the tissue in a U-shape between the jaw portions, with a relatively uniform force, transversely with respect to the direction of movement,

It has been found however that in part only irregular or inadequate tissue coagulation is achieved with the known instruments. Unreliable tissue coagulation can therefore represent a problem with the known instruments.

Therefore the problem of the invention is to provide a surgical instrument for the coagulation of biological tissue, which permits reliable coagulation of the tissue and ensures easy handling.

That problem is solved by the electrosurgical instrument set forth in the opening part of this specification, in that the coagulation jaw portion has at least two electrode arrangements which are arranged at different sides and have respective electrically separated coagulation electrodes, by means of which the tissue is coagulatable in two substantially mutually separated coagulation regions.

The solution according to the invention has the advantage that two comparably small tissue regions are coagulated in operation. It has been found that, in those small tissue regions, the factors which are important in respect of coagulation, temperature and pressure, are more easily controllable than in the large coagulation region involved with instruments in the state of the art. Thus, reliable tissue coagulation which is highly important for example when closing off a vein is ensured in the two coagulation regions.

As the coagulation electrodes on the coagulation jaw portion are arranged immovably relative to each other, short-circuits during coagulation are excluded. It is possible to dispense with structurally complicated and expensive spacers. The solution according to the invention is therefore structurally particularly simple and can be manufactured inexpensively.

Further advantageous configurations of the invention, which are independent of each other, are described in the appendant claims.

Thus the instrument according to the invention can have at least one electrosurgical cutting electrode for cutting the tissue and the cutting electrode can be so arranged that the tissue is severable between the coagulation regions. That has the advantage that the clamped tissue can be electrically severed therethrough with the coagulation instrument according to the invention. Particularly when closing off a vein the clamped vein can firstly be coagulated and then severed between the two coagulation regions. It has been found that cutting can be particularly well effected electrically in the tissue region between the coagulation regions. The tissue which is less coagulated in that region appears to be highly suited to electrosurgical cutting. The fact that the tissue is clamped in a half-wave shape provides that the tissue is pulled taut within the gripping device. It has been found that tissue which is pulled taut can be more easily electrosurgically severed.

The half wave-shaped gripping can be for example U-shaped, V-shaped or in the form of half a sine wave.

In addition the cutting electrode can extend over the entire length of a working region of the instrument, in which the tissue can be clamped and coagulated. In that way there is no need for a structurally complicated and expensive advance movement of the cutting element. The instrument according to the invention can thus be structurally simple and inexpensive to manufacture.

To be able to cut reliably in a bipolar mode with the instrument according to the invention, the active surface of the cutting electrode can be substantially smaller than the active surface of the coagulation electrodes so that in operation a flow of current is possible between the cutting electrode and the most closely adjacent coagulation electrodes. The coagulation electrodes which are further away from the cutting electrode can be electrically switched off in the cutting operation in order not to deflect the flow of current. In that way the cutting current flow does not have an adverse influence on vein closure, that is to say the risk of an arc being fired at the remote coagulation electrodes and severing unwelded tissue is excluded.

In a further advantageous configuration the cutting element can be provided at the coagulation jaw portion and the coagulation jaw portion can be substantially immovably coupled to the distal end of the instrument. That has the advantage that the coagulation electrodes and the cutting electrode are arranged at the same jaw portion and that jaw portion is rigidly connected to the shank of the instrument. In that way there is no need for movable electrical connections to supply the electrode with HF energy. In that fashion the instrument according to the invention can be of a structurally simple design and is inexpensive to manufacture.

In a further embodiment the coagulation jaw portion can include two coagulation electrodes which extend parallel and which provide the electrode arrangements and which at least portion-wise enclose the clamping jaw portion in the longitudinal direction of the instrument. The tissue which is not received in the gripping device can also be coagulated with the coagulation end provided in that way. Thus for example it is possible to stop relatively minor bleeds with the instrument according to the invention by simply touching same with the coagulation end.

To increase the pressure on the clamped tissue the coagulation electrodes and/or the clamping jaw portion can have clamping surfaces which are round or curved in cross-section. The round clamping surfaces exert a maximum of pressure on the tissue, in a line-shaped region. As high pressure affords good coagulation, tissue coagulation is particularly good in the line-shaped region.

The pressure on the tissue at the coagulation electrodes can be further increased if in the clamping position the gap between the jaw portions in the working region in which the tissue can be clamped and coagulated is less than 1 mm. Furthermore it is also possible to produce the instrument substantially without a gap between the jaw portions, which further increases the clamping force on the tissue. Due to the small or no gap, the gripped tissue urges the jaw portions away from each other more vigorously so that the closing force is increased.

In another advantageous development rib elements extending transversely with respect to the longitudinal direction can be provided at at least one of the jaw portions. The rib elements prevent gripped clamped tissue from slipping out of the gripping device.

To prevent excessively great heating of the tissue in operation of the instrument the coagulation jaw portion can have an inwardly disposed lumen through which a fluid can flow for cooling the coagulation electrodes and/or the cutting electrode.

Besides the specified electrosurgical instrument and its above-specified embodiments the invention further concerns a method of bipolar coagulation of biological tissue, wherein firstly the tissue is clamped substantially in a half wave-shape between a clamping jaw portion and a coagulation jaw portion of an electrosurgical instrument and then the tissue is coagulated by means of at least two electrode arrangements in two substantially mutually separated coagulation regions. In addition in an advantageous device of the method the clamped coagulated tissue can be electrically severed between the separated coagulation regions.

DETAILED DESCRIPTION OF EMBODIMENTS

The invention is described hereinafter by means of embodiments by way of example.

FIG. 1is a highly diagrammatic view of an embodiment by way of example of an electrosurgical instrument1according to the invention for the coagulation of biological tissue. The instrument1which is designed for laparoscopic or endoscopic uses includes an elongate shank2, a handle portion4arranged at the proximal end3of the shank2and a gripping device6adjoining the distal end5on the shank2.

The gripping device6has a clamping jaw portion7and a coagulation jaw portion8.FIG. 1shows the gripping device6in an open position in which the jaw portions7,8are opened to receive tissue. The gripping device6is described in greater detail hereinafter.

As the instrument1is designed for laparoscopic or endoscopic use the round cross-section of the shank2is of an outside diameter of about 5 mm. The dimensions of the gripping device6also do not project beyond that diameter in the closed position so that the instrument can be introduced into the body of a patient for example through a trocar. It will be appreciated that other designs of other diameters such as for example 10 mm are possible.

The handle portion4which serves for gripping and operation of the instrument1by the doctor has a fixed grip portion9and a movable grip portion10. The grip portion10is coupled to the clamping jaw portion7so that the clamping jaw portion7is movable by means of the grip portion10. In addition, provided on the handle portion4are two on/off switches11by which the coagulation operation and/or the cutting operation can be started or stopped. Electrical connecting lines and necessary mechanical connecting elements extend in the interior of the hollow shank2. The handle portion4is only illustrated highly diagrammatically and can alternatively be of any suitable shape known from the state of the art.

The instrument1is connected to a high-frequency generator15by way of electrical connecting lines14. The high-frequency generator15generates a high-frequency energy suitable for operation of the instrument according to the invention.

FIGS. 2 and 3show the distal end5of the instrument1ofFIG. 1on an enlarged scale,FIG. 2showing the gripping device6in a closed clamping position andFIG. 3showing it in an open position. The configuration according to the invention of the gripping device6will now be described in greater detail with reference toFIGS. 2 and 3,

In the embodiment by way of example shown inFIGS. 2 and 3the coagulation jaw portion8includes two coagulation electrodes12,13which extend substantially parallel. The coagulation electrodes12,13are in the form of round electrodes of round cross-section. Other cross-sectional shapes are however possible. On both sides of the clamping jaw portion7the coagulation electrodes12,13open in the longitudinal direction L out of the distal end of the shank2. In the clamping position inFIG. 2the coagulation electrodes12,13extend substantially parallel to each other on both sides of the clamping jaw portion7in the longitudinal direction L and at a substantially equal spacing relative to the clamping jaw portion7. At the distal end of the instrument1the coagulation electrodes12,13embrace the clamping jaw portion7. Thus the coagulation electrodes12,13each form a respective elongate receiving window17into which the clamping jaw portion7engages in the closed clamping position ofFIG. 2. The jaw portions7,8engage into each other in the closed clamping position.

The coagulation electrodes12,13are connected substantially fixedly and non-pivotably to the shank2. In the interior of the shank2the electrically mutually separated coagulation electrodes12,13are respectively connected to one of the electrical connecting lines14by way of which the coagulation electrodes12,13are electrically coupled to different poles of the high-frequency generator15. In the distal and proximal regions the coagulation electrodes are surrounded by an electrical insulator16. In the embodiment ofFIGS. 2 and 3the insulator16is in the form of a plastic material coating. It will be appreciated that other configurations such as for example a ceramic enclosure are possible. In a working region24of the instrument1the coagulation electrodes12,13are not covered by the insulator16and thus the tissue can be coagulated in the working region24.

In operation of the instrument1according to the invention a bipolar ac voltage is applied between the two electrodes12,13, by which the tissue connected to the coagulation electrodes12,13in the working region24can be coagulated. A short-circuit by touching of the coagulation electrodes12,13is precluded on the one hand by the fact that they are immovably connected to the shank2and on the other hand by manufacture thereof from an only slightly elastic material such as for example high-quality steel.

The clamping jaw portion7which is engaged between the coagulation electrodes12,13in the closed position is movably connected to the shank2by way of a rotary pivot. In that way the clamping jaw portion7can be pivoted in a direction of movement B from the closed position inFIG. 2into the open position inFIG. 3. The clamping jaw portion7is connected to the shank2in such a way that it moves within a plane of movement18extending in the longitudinal direction L. The clamping jaw portion7is connected to the movable grip portion10of the handle portion4by way of mechanical connecting elements (not shown) extending in the interior of the shank2. An abutment19projecting in a nose-shaped configuration in the longitudinal direction L limits the movement of the clamping jaw portion7in a direction towards the closed position. It will be appreciated that the abutment19can also be provided at another location and/or of a different shape.

The clamping jaw portion7is here in the form of a substantially rectangular plate having lateral clamping surfaces20extending parallel and with rounded edges. At the underside which faces in the direction of movement B towards the coagulation jaw portion8the clamping jaw portion7has a cutting electrode21. In the embodiment ofFIGS. 2 and 3the cutting electrode21extends over the entire length of the clamping jaw portion7and over the entire length of the working region24. In the embodiment ofFIGS. 2 and 3the cutting electrode21is of a rectangular cross-section and is fitted into a groove in the clamping jaw portion7. The cutting electrode21is pressed or glued into the groove for fixing it. In that situation the cutting electrode21is inserted in such a way that only a small part protrudes from the groove. Therefore the exposed active surface22of the cutting electrode21is substantially smaller than the active surface23of the coagulation electrodes12,13.

The cutting electrode21is connected to the high-frequency generator15by a further connecting line14extending in the interior of the shank2.

The mode of operation of the embodiment ofFIGS. 2 and 3is described hereinafter by reference to the diagrammatic view inFIG. 10.FIG. 10shows a similar instrument1to that shown inFIG. 2. The only difference in relation to theFIG. 2instrument is that the cutting electrode21inFIG. 10is in the form of a wire electrode of round cross-section. The functions described hereinafter are the same.FIG. 10shows the instrument1in section in the closed clamping position in which tissue25, for example a vein, is clamped in the working region24between the jaw portions7,8in a half wave-shaped configuration, in particular in a U-shape. In order to move into the closed clamping position the instrument is firstly moved into the open position and the tissue25is enclosed with the opened gripping device6. By actuation of the movable grip portion10the gripping device moves into the closed position and in so doing grips the tissue25and clamps it in a half wave-shape between the jaw portions7,8.

The way in which the jaw portions7,8engage into each other is clearly visible inFIG. 10. In the movement from the open position into the closed clamping position the clamping jaw portion7engages progressively further into the coagulation jaw portion8. In the closed clamping position the lower edge of the clamping jaw portion7has moved beyond the lower edge of the coagulation electrode13and projects beyond it. That arrangement provides that the tissue25is clamped substantially in a U-shape in the closed clamping position between the jaw portions7,8. The tissue25is pushed by the clamping jaw portion7into the receiving window17between the coagulation electrodes12,13and in that case folded in a rectangular shape or a U-shape, that is to say the tissue25is drawn taut around the clamping jaw portion7. The U-shape or rectangular shape is due to the external shape of the clamping jaw portion7which in this embodiment is of a rectangular external contour. When the clamping jaw portion is pushed in, the coagulation electrodes12,13are urged away from each other transversely with respect to the direction of movement B by the stack consisting of the tissue25and the clamping jaw portion7. When that happens the taut tissue25is additionally compressed so that for example in the case of a vein blood is urged out of the coagulation regions27a,27b.

The coagulation electrodes12,13which are substantially immovable relative to each other form respective electrode arrangements26a,26bon both sides of the clamping jaw portion7and on both sides of the plane of movement18. Each electrode arrangement26a,26bhas electrically separated coagulation electrodes12,13at differing potential. In order better to illustrate the opposite potentials, associated with the coagulation electrode12is a plus sign + while associated with the coagulation electrode13is a minus sign −, although it will be appreciated that the instrument1is operated with an ac voltage with which the polarity constantly reverses. In the case of bipolar coagulation the current flows within the two electrode arrangements26a,26bbetween the coagulation electrodes12,13. Accordingly the gripped tissue25is coagulated in two mutually separated coagulation regions27a,27b.The tissue25is not coagulated or is at least less coagulated in a cutting region31between the coagulation regions27a,27b,than in the coagulation regions27a,27b,as here there is no or little flow of current. The electrode arrangements26a,26bare provided on both sides of the plane of movement18.

The coagulation electrodes12,13are so arranged that, in the clamping position without gripped tissue25, they are at a very small or no spacing relative to the clamping jaw portion7. When tissue25is clamped for coagulation purposes as inFIG. 10, the coagulation electrodes12,13are urged outwardly away from the clamping jaw portion7transversely with respect to the direction of movement B. When tissue25is clamped, the coagulation electrodes12,13which are elastically deformed in that way push back in the direction of the clamping jaw portion7and generate a pressure force F applied to the tissue25. It has been found that that pressure force F acting transversely with respect to the direction of movement B positively influences the coagulation result. Therefore, in the tissue regions around the coagulation electrodes12,13on which the pressure force F acts, the tissue25is coagulated to a greater degree than in the other regions. The round or curved clamping surfaces of the coagulation electrodes12,13with which the tissue25is pressed against the clamping jaw portion7provide that the pressure area is small. The small pressure area additionally leads to an advantageous increase in the pressure force F.

After the tissue25is coagulated in the coagulation regions27a,27b,it can be severed in the cutting region31where the cutting electrode21is also provided, between the two coagulation regions27a,27b.For that purpose a suitable high-frequency voltage is applied between the cutting electrode21and the most closely adjacent coagulation electrode13. Thereupon an arc fires at the cutting electrode21and severs the tissue. The arc is formed at the cutting electrode21and not at the coagulation electrode13because the current density is substantially greater at the substantially smaller active surface22of the cutting electrode21. With the instrument1according to the invention the electrode arrangements26a,26bare so placed that they do not coagulate or only little coagulate the tissue25in the cutting region31.

A further embodiment of the instrument1according to the invention is described hereinafter with reference toFIGS. 4 to 6. For the sake of simplicity it is only the differences in relation to the above-described embodiments that will be considered here.

As a distinction in relation to the above-described embodiments the instrument1inFIGS. 4 to 6is in the form of what is referred to as a Maryland design. In other words the jaw portions7,8are curved uniformly to one side, which has the advantage, particularly in endoscopic use, that the doctor can better see the distal end of the curved gripping device6when viewing through the endoscope. The invention is particularly suitable for the Maryland design because the cutting electrode21which extends over the entire length of the working region24can be arranged immovably. Accordingly no advance movement is necessary, the implementation of which is often problematical with instruments in the state of the art.

Furthermore the insulator16inFIGS. 4 to 6is arranged only in the proximal region of the coagulation electrodes12,13. The distal region of the coagulation electrodes12,13is not insulated and forms a coagulation end28of the instrument1. The coagulation end28can be used by the doctor for bipolar coagulation even of tissue which is not gripped.

AsFIG. 4shows the coagulation electrodes12,13each have a respective lumen29in their interior. The lumen29can be flushed through with a suitable cooling fluid to cool the coagulation electrodes in operation. Disposed at the inside wall of the lumen29is an electrical insulating layer30so that the cooling fluid does not cause a short-circuit.

A further embodiment of the instrument1according to the invention is described hereinafter with reference toFIGS. 7 and 8. For the sake of simplicity it is only the differences in relation to the above-described embodiments that will be considered here.

As a difference in relation to the above-described embodiments in the instrument1inFIGS. 7 and 8electrically insulating spacers30are arranged between the coagulation electrodes12,13in the working region24. The spacers30can be made for example from a suitable plastic material and fix the coagulation electrodes12,13relative to each other. In that way a short-circuit due to the electrode surfaces touching can be even more reliably precluded.

In addition the clamping jaw portion7has rib elements32which are arranged transversely with respect to the longitudinal direction and which project outwardly in the direction of the coagulation electrodes12,13. Tissue25can be better held in the gripping device6by the rib elements32.

A further embodiment of the instrument1according to the invention is described hereinafter with reference toFIG. 9. For the sake of simplicity it is only the differences in relation to the above-described embodiments that will be considered here.

As a difference in relation to the above-described embodiments in the instrument1inFIG. 9the stationary coagulation jaw portion8is arranged within the movable clamping jaw portion7. In addition the cutting electrode21, like the coagulation electrodes12,13, is provided on the coagulation jaw portion8. That has the advantage that all parts to be supplied with current are arranged on the same stationary jaw portion8and therefore no HF-energy has to be passed to moving parts. The coagulation electrodes12,13which are of a half-round configuration are fitted on the coagulation jaw portion8which is otherwise made from an electrically insulating material.

A further embodiment of the instrument1according to the invention is described hereinafter with reference toFIG. 11. For the sake of simplicity it is only the differences in relation to the above-described embodiments that will be considered here.

FIG. 11shows the instrument1in section in the closed clamping position in which tissue25, for example a vein, is clamped in a V-shape in the working region24between the jaw portions7,8. As a difference in relation to the above-described embodiments the instrument1according to the invention shown inFIG. 11has a wedge-shaped, that is to say V-shaped, clamping jaw portion7. The two coagulation electrodes12,13of the coagulation jaw portion8are arranged in correspondingly complementary relationship with the clamping surfaces of the clamping jaw portion7so that the tissue25is clamped in a V-shape. The cutting electrode21is placed at the tip of the wedge-shaped clamping jaw portion7, at which the tissue is most greatly tensioned in the clamped condition and thereby can be particularly easily severed. The wedge-shaped clamping jaw portion7which, besides a force component in the direction of movement B, also presses against the coagulation electrodes12,13with a force component transversely with respect to the direction of movement B provides that the tissue can be particularly easily gripped. Therefore the doctor can also use the instrument of this embodiment at the same time as a simple gripping instrument. That has the advantage that the doctor does not have to change the instrument if he needs a gripping instrument.