GB2513326A

GB2513326A - Electrosurgical instrument

Info

Publication number: GB2513326A
Application number: GB1307287.1A
Authority: GB
Inventors: Anthony K Atwell
Original assignee: Gyrus Medical Ltd
Current assignee: Gyrus Medical Ltd
Priority date: 2013-04-23
Filing date: 2013-04-23
Publication date: 2014-10-29
Also published as: GB201307287D0

Abstract

An electrosurgical instrument for the treatment of tissue includes an instrument shaft 32 with an end effector comprising a pair of scissor blades capable of applying force to tissue located between the blades. The instrument includes at least first 20 and second 33 handle members, capable of relative movement towards and away from one another, and an actuator mechanism such that relative movement of the handle members causes the scissor blades to move between their open and closed positions. The actuator mechanism provides a first stage of operation in which the scissor blades are moved against one another to apply a first force to the tissue, the first force being limited to a predetermined threshold force. The actuator mechanism further provides a second stage of operation in which the scissor blades are moved against one another to apply a second force to the tissue, the second force being in excess of the predetermined threshold force.

Description

ELECTROSURGICAL INSTRUMENT

This invention relates to an electrosurgical instrument for the treatment of tissue, and in particular to an electrosurgical scissors for the cutting and coagulation of tissue. Such instruments are commoifly used for the cutting and coagulation of tissue in surgical intervention, whether in open surgery or in laparoscopic surgery.

Electrosurgica scissors typically are used to coagulate tissue by passing a coagulating radio frequency current through tissue grasped between the blades. This is typically done by passing the current either between the blades or between separate electrodes present on each blade. Tissue is cut by exerting a greater force on the tissue, such that the blades mechanically cut the tissue therebetween. There is a danger that the scissor blades may inadvertenfly cause the cutting of tissue, even though the surgeon is offly intending to grasp the tissue in order to coagulate it. The present invention attempts to provide a solution to this problem, by regulating the force applied to the tissue in each circumstance.

According'y, an electrosurgical instrument for the treatment of tissue is provided, comprising i) a longitudinal instrument shaft, ii) an end effector at the distal end of the shaft, the end effector comprising a pair of scissor blades, at least one of the blades being movable relative to the other between open and closed positions to apply force to tissue located between the blades, iii) at least first and second handle members capable of relative movement towards and away from one another iv) an actuator mechanism such that relative movement of the handle members causes the scissor blades to move between their open and closed positions, the arrangement being such that the actuator mechanism provides discrete first and second stages of operation, the first stage of operation being such that the scissor blades are moved against one another to apply a first force to the tissue, the first force being limited to a predetermined threshold force, and wherein the second stage of operation being such that the scissor blades are moved against one another to apply a second force to the tissue, the second force being in excess of the predetermined threshold force.

The first and second stages of operation are distinguished one from the other by a definite demarcation. According to one convenient arrangement, the first and second handle members have a first range of relative movement and a second range of relative movement. Preferably, the actuator mechanism provides different applied forces for each stage of operation, providing the first applied force as a result of the movement of the handle members through the first range of movement, and the second applied force as a result of the movement of the handle members through the second range of movement. In this arrangement, the user employs the same two handle members to perform both tissue coagulation and tissue cutting. According to one alTangement, when tissue is being grasped by the end effector, the actuator mechanism is such that during the first stage of operation the increase in force needing to be applied to the handle members to obtain a relative movement of the scissor blades is at a first relatively low level. However, during the second stage of operation, the increase in force needing to be applied to the handle members to obtain a relative movement of the scissor blades is at a much higher second level. In this way. the user of the instrument expenences a first resistive force from the actuator mechanism when using the electrosurgical instrument to grasp tissue for coagulation. However, the user experiences a second higher resistive force from the actuator mechanism when wishing to use the instrument to app'y a greater force in order to mechanically cut tissue held between the blades. Between the first and second stages of operation. the user of the instrument will notice a definite increase in the force needing to be applied to obtain further movement of the scissor blades. This step increase provides the definite demarcation between the first and second stages of operation, with the increased resistance experienced when passing from the first range of movement to the second range of movement informing the user that the scissor blades are applying increased force and that mechanical cutting is about to occur.

In an alternative arrangement. the instrument includes first, second and third handle members, relative movement of the first and second handle members causing the actuator mechanism to move the scissor blades against one another and apply the first force to the tissue, relative movement of the first and third handle members causing the actuator mechanism to move the scissor blades against one another and apply the second force to the tissue. In this arrangement the user employs a different handle member to perform tissue cutting, as opposed to tissue coagulation. The use of the first and second handle members only applies to the tissue a force limited to the predetermined threshold force, and hence insufficient to cause the mechanical cutting of the tissue. However, the use of the first and third handle members applies a greater force to the tissue, conceivably only limited by the force exerted on the handle members by the user of the instrument.

Alternatively or additionally, the actuator mechanism includes a stop mechanism, the stop mechanism ordinarily preventing force in excess of the predetermined threshold force being applied to the tissue, the stop mechanism including a stop actuator operable to disable the stop mechanism and allow a force in excess of the threshold force to be applied to the tissue. Typically. the stop actuator comprises a button operable to disable the stop mechanism. Where the instrument includes first and second handle members movable through first and second ranges of motion, the stop mechanism prevents movement of the handle members through greater than the first range of motion, urfiess disabled accordingly. Once the stop mechanism has been disabled, the first and second handle members can be moved through the second range of motion in order to perform tissue cutting. Where the instrument includes first, second and third handle members, the stop mechanism prevents movement of the third handle member relative to the first handle member. Once the stop mechanism has been disabled, the third handle member can be moved relative to the first, in order to perform the tissue cutting action. Whichever arrangement is employed, the stop mechanism prevents the inadvertent progression from the coagulating to the tissue cutting process, ensuring that such progress is carried out as a conscious step promulgated by the disabling of the stop mechanism bythe operation of the stop actuatorbutton.

The invention will now be further described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a schematic side view of the handle of a surgical instrument in accordance with the present invention, Figures 2a to 2c are schematic sectional side views of the actuating mechanism of the electrosurgical instrument of Figure 1, shown in different positions, Figure 3 is a schematic side view of the handle of an alternative embodiment of surgical instrument in accordance with the present invention, Figures 4a to 4c are schematic secfional side views of the actuating mechanism of the electrosurgical instrument of Figure 3, shown in different positions, Figures 5a to Sc are schematic sectional side views of a stop mechanism of the electrosurgical instrument of Figure 3, shown in different positions, Figure 6 is a top view of a part of the stop mechanism of Figures 5a to Sc, Figure 7 is a schematic side view of the handle of an alternative embodiment of surgical instrument in accordance with the present invention, and Figures 8a to 8c are schematic sectional side views of a stop mechanism of the electrosurgical instrument of Figure 7, shown in different positions.

Referring to the drawings, Figure 1 shows a handle for an electrosurgical scissors instrument, the handle being shown generally at 30 and including a handpiece body 31, with an elongate shaft 32 extending from the handpiece body. An end effector (not shown) in the form of a pair of scissor blades, is located at the distal end of the shaft 32. A pair of handle members depend from the handpiece body 31, the handle members comprising a first stationary handle member 33 and a second movable handle member 20.

Figures 2a to 2c show what happens when the movable handle member 20 is moved with regard to the stationary handle member 33. Initial movement of the handle member 20 causes a corresponding movement of a cam surface I such that it contacts a plunger 2. As the force applied to the handle member 20 increases, the load that the cam surface 1 applies to the plunger 2 exceeds the relatively weak return force applied to the plunger by preload spring 6, such that the plunger 2 moves to the right as shown in Figure 2a. taking with it spnng 3. load plate 4, spring 5, pull rod 7 and end plate 8.

Movement of the pull rod 7 causes the scissor blades to close onto the tissue to be treated.

Further movement of the handle member 20 causes the compression of spnng 3 until the plunger 2 contacts the load plate 4. At this point the force applied to the tissue is controlled between the minimum load applied by spring 3, and a predetermined maximum load applied by the combination of spnngs 3 & 5. Further movement is discouraged by the step increase in force felt by the user when the plunger 2 tries to move the load plate 4 against the action of spring 5, which has a much higher rating. In this position, shown in Figure 2b, the force applied to the tissue between the scissor blades is suitable for tissue coagulation, but insufficient for the blades to mechanically cut the tissue.

When the user wishes to use the scissor blades to mechanically cut tissue.

further force is applied to the handle member 20 causing the load plate 4 to compress the high rate spring 5. This increases the force applied to the pull rod 7, with the maximum cutting force limited only by the force that can be applied by springs 3 & 5 when the p'unger reaches its limit of travel as shown in Figure 2c.

Figure 3 shows an alternative instrument in which handpiece body 31, shaft 32, stationary handle member 33 and movable handle member 20 are as previously described. The instrument includes a stop mechanism, the actuator button 23 of which is housed on handle member 33.

Figures 4a to 4c show the actuator mechanism associated with the instrument of Figure 3, which mechanism is slightly simpler in that only 2 spnngs are present. A cam suiface 12 contacts plunger 13 when the handle member 20 is moved, similar to that previously described with reference to Figures 2a to 2c. As the force on the handle member 20 increases beyond the preload in spnng 17, the plunger 13 moves to the nght as shown in Figure 4a taking with it spring 14, end plate 18 and pull rod 19. The pull rod 19 moves to the position shown in Figure 4b, closing the scissor blades on to the tissue therebetween.

When the handle member has moved a certain extent, the stop mechanism prevents further movement thereof. The stop mechanism is shown in Figures Sa to Sc and comprises a stop arm 21, attached for movement with handle member 20, and including a stop shoulder 24. When the handle member has moved to its preferred position for tissue coagulation, stop shoulder 24 abuts a piston 22 held in position by spnng 50. This is the situation shown in Figure Sb. In this position spring 14 is further compressed increasing the force applied to the pull rod 19 (and hence to the tissue between the scissor blades) such that the scissor blades grasp the tissue sufficient for coagulation to take place. 1-lowever, the load on the scissor blades is controlled by the spnngs 14 & 17 such that the blades do not exert enough force that the scissor blades mechanically cut the tissue.

In order for the handle member 20 to move further, the user of the instrument presses the stop actuator button 23, which moves piston 22 upwardly against spring 50 so that it disengages from shoulder 24 allowing the stop arm 21 to move past the piston 22 and continue its movement. This is the situation shown in Figure Sc, Step 25 ensures that the stop button 23 cannot be activated before the hanifie member 20 has been moved into the coagulation position, such that a cut force cannot be applied to the scissor blades before a coagulation force has been applied. In order for the stop actuator button 23 to avoid contact with stop arm 21, the stop arm is curved as shown in Figure 6.

Now that the handle member 20 is allowed to move further, cam surface 12 moves plunger 13 to the position shown in Figure 4c. Spring 14 has been compressed such that the plunger 13 contacts end plate 18. At this point the force is transfelTed directly from the handle member 20 to the pull rod 19, and hence to the scissor blades at the end of the shaft, to allow mechanical cutting of the tissue, Figure 7 shows an alternative design of instrument with a handpiece body 31, elongate shaft 32, and stationary handle member 33. A first movable handle 10 is movable with respect to the stationary handle member 33 in similar manner to that of handle member 20 in Figure 1. However, the instrument is provided with a second handle member ii, also movable with respect to the stationary handle member 33.

Handle member 10 is known as the "coag" handle, while handle member 11 is known as the "cut" handle.

The actuation mechanism is as described previously with reference to Figures 4a to 4c, such that when the coag handle member 10 is moved the cam surface 12 contacts plunger 13 and moves to the iight as shown in Figure 4b compressing spring 14, and taking with it end plate 18 and pull rod 19. Any further increase in the force applied to the hanifie member 10 moves it into contact with a stop mechanism, to be descnbed subsequently. In this position, the force applied to the scissor blades is governed by the spnng 14, ensunng that a force suitable for coagulating tissue is applied to tissue between the blades.

Cut handle member 11 also contacts the cam surface 12. such that when the cut handle member 11 is moved the plunger 13 moves to the position shown in Figure 4c, in which it contacts the end plate 18 and transfers force directly to the pull rod 19, and hence to the scissor blades at the end of the shaft, to allow mechanical cutting of the tissue.

However, a stop mechanism shown in Figures Sa to Sc ensures that the cut handle member ii cannot be moved unless the coag handle 10 has previously been moved to its deployed position. The stop mechanism comprises a shaped stop member 16, pivotably mounted to the stationary handle member 33. As shown in Figure 8a, if an attempt is made to move the cut handle member ii before operation of the coag handle member 10, the cut handle member will come up against the stop member 16, preventing further movement of the cut handle member. It is only once the coag handle member 10 has been moved, causing the stop member to pivot into the position shown in Figure Sb, that the path is clear for the cut handle member 11 to be depressed. With the stop member rotated as shown, the way is clear for the cut handle member to be moved as shown in Figure Sc. This ensures that the force applied to the scissor blades by the cut handle member 11 is only supplied after the blades have been moved into their coagulating position by the operation of the coag handle member 10.

Whichever of these embodiments is employed, the instrument provides a first stage of operation during which the forces transmitted to the end effector are capped at a predetermined maximum value, followed by a second stage of operation during which the forces transmitted to the end effector are allowed to exceed the predetermined threshold force. The first stage is typically suitable for a coagulation process between the scissor blades, while the second stage allows for greater force to be applied, so to mechanically cut the tissue.

Claims

CLAIMSI. An electrosurgical instrument for the treatment of tissue, the instrument comprising i) a longitudinal instrument shaft, ii) an end effector at the distal end of the shaft, the end effector comprising a pair of scissor blades, at least one of the blades being movable relative to the other between open and closed positions to apply force to tissue located between the blades, iii) at least first and second handle members capable of relative movement towards and away from one another iv) an actuator mechanism such that relative movement of the handle members causes the scissor blades to move between their open and closed positions, the arrangement being such that the actuator mechanism provides discrete first and second stages of operation, the first stage of operation being such that the scissor blades are moved against one another to apply a first force to the tissue, the first force being limited to a predetermined threshold force, and wherein the second stage of operation being such that the scissor blades are moved against one another to apply a second force to the tissue, the second force being in excess of the predetermined threshold force.
2. An electrosurgical instrument according to claim i, wherein the first and second handle members have a first range of relative movement and a second range of relative movement.
3. An electrosurgical instrument according to claim 2, wherein the actuator mechanism applies the first force as a result of the movement of the handle members through the first range of movement, and the second force as a result of the movement of the hanifie members through the second range of movement.
4. An electrosurgical instrument according to claim 2 or 3, wherein the actuator mechanism is such that, when tissue is being grasped by the end effector, the increase in force needing to be applied to the handle members to obtain a relative movement of the scissor blades during the first stage of operation is at a first relatively low level.
5. An electrosurgical instrument according to claim 4, wherein the actuator mechanism is such that, when tissue is being grasped by the end effector, the increase in force needing to be applied to the handle members to obtain a relative movement of the scissor blades during the second stage of operation is at a second level, higher than the first level.
6. An electrosurgical instrument according to claim I, wherein the instrument includes first, second and third handle members, relative movement of the first and second handle members casing the actuator mechanism to move the scissor blades against one another and apply the first force to the tissue, relative movement of the first and third handle members causing the actuator mechanism to move the scissor blades against one another and apply the second force to the tissue.
7. An electrosurgical instrument according to any preceding claim, wherein the actuator mechanism includes a stop mechanism, the stop mechanism ordinarily preventing force in excess of the predetermined threshold force being applied to the tissue, the stop mechanism including a stop actuator operable to disable the stop mechanism and allow a force in excess of the threshold force to be applied to the tissue.
8. An electrosurgical instrument according to claim 7, wherein the stop actuator comprises a button operable to disable the stop mechanism.