Bipolar electrosurgical scissors

Bipolar electrosurgical scissors are disclosed having a pair of blades joined for relative movement in a scissor-like action between open and closed positions. At least one of the blades comprises a tissue contacting surface and first and second spaced apart electrodes extending along the surface. Current flow between the first and second electrodes promotes hemostasis in tissue contacting the surface. Preferably, each blade of the scissors includes first and second spaced-apart electrodes.

The present invention relates generally to electrosurgical scissors, and
 more particularly, to bipolar electrosurgical scissors to assist in
 hemostasis of tissue as it is cut by the scissors.
 BACKGROUND OF THE INVENTION
 It is common in many surgical procedures to use surgical scissors for
 cutting tissue that is vascularized, i.e., contains blood vessels. The
 resultant bleeding that occurs is not only of concern from the standpoint
 of blood loss, but the blood may also obscure the surgical field or site.
 Controlling such bleeding has, in the past, required significant time and
 attention of the surgeon during many surgical procedures.
 In recent years, efforts have been devoted to developing scissors that use
 radiofrequency ("RF") energy in a manner such that the tissue is heated as
 it is cut, to promote immediate hemostasis. Early efforts at such
 electrosurgial scissors used monopolar RF power, where the scissors
 constituted one electrode, and the patient rested on the other electrode,
 which was typically in the form of a conductive mat, to complete the
 circuit. Current flowed generally through the patient between the
 electrodes due to a voltage applied across the electrodes by an RF power
 supply.
 Monopolar applications, however, had certain drawbacks. Inadvertent contact
 between the scissors and other tissue could result in unwanted tissue
 damage. In addition, the flow of current through the body of the patient
 could take uncertain or unpredictable paths with potential unwanted injury
 to other tissue. More recently, efforts have been made to develop bipolar
 electrosurgical scissors to overcome the drawbacks with monopolar
 scissors. Specifically, efforts have been made to develop scissors in
 which one blade includes one electrode and the other blade includes the
 other electrode, so that current flows between the blades as they cut the
 desired tissue.
 Example of recent efforts to develop bipolar scissors are found in U.S.
 Pat. Nos. 5,324,289 and 5,330,471. These patents disclose bipolar scissors
 in which one blade of the scissors has one electrode, and the other blade
 of the scissors has the other electrode, so that current flows between the
 blades as they come into proximity during cutting. Various embodiments of
 bipolar scissors are disclosed in these patents, but typically a layer of
 insulating material is provided on at least one shearing surface of one of
 the blades, and the hinge pin or fastener which pivotally connects the
 blades is electrically insulated, so that the electrically active parts of
 the scissor blades do not contact each other during operation of the
 instrument. With the construction as shown in these patents, the
 electrical current flows between the blades at a point just forward of
 where the shearing surfaces actually touch. The current flow between the
 blades causes a heating of the tissue and promotes local coagulation and
 hemostasis during the cutting procedure.
 In U.S. Pat. No. 5,352,222, bipolar scissors are shown in which each blade
 of the scissors is a laminated assembly of a metal shearing surface, a
 metal blade support and intermediate layer of insulating material. The
 blade support of one blade acts as one electrode, and the blade support of
 the other blade acts as the other electrode, so that electrical energy
 flows between the blade supports as the blades close on the tissue being
 cut. A short circuit between the shearing surface is prevented by reason
 of the insulating layer between the metal shearing surface and the blade
 support. This scissor construction is purported to be more economical to
 manufacture than the blade structure disclosed in U.S. Pat. Nos. 5,324,289
 and 5,330,471. However, because the shearing surface is a separate piece,
 bonded to the blade support, a particularly high strength and high
 precision epoxy bonding process is required in the '222 patent so that the
 shearing surface remains attached to the blade support despite the
 shearing forces exerted upon it during repeated cutting.
 What the above patents have in common, is that each blade forms one of the
 electrodes attached to a bipolar RF energy source, so that the only
 current that flows is between the blades as they close. Although the
 bipolar scissors described in the above-identified patents are believed to
 be an advance over the earlier monopolar scissors, they typically required
 the electrically active parts of the blades to be insulated from one
 another, which tends to complicate the design and materials of the blade
 actuating mechanism. Accordingly, development work continues to provide
 bipolar scissors which are easy to use, more economic to make, versatile
 and/or which are effective in promoting hemostasis during cutting of
 various tissues, particularly including tissues that are highly
 vascularized.
 SUMMARY OF INVENTION
 In accordance with the present invention, tissue cutting apparatus, such as
 scissors, may be provided in which each cutting blade itself includes two
 electrodes for connection to a bipolar RF energy power supply. More
 specifically, the tissue cutting apparatus of the present invention
 comprises a pair of blades joined for relative movement in a scissor-like
 action between open and closed positions. Each of the blades has a tissue
 contacting surface for contacting the tissue therebetween as the blades
 close during the cutting action. The tissue contacting surface of at least
 one and preferably both blades includes first and second spaced-apart
 electrodes which extend along the tissue contacting surface and are
 connectable to a voltage source, such as a high frequency bipolar RF power
 supply, for applying a voltage between the electrodes. As a result,
 current flows between the first and second electrodes of the blade to
 promote hemostasis in the tissue as the blade is moved into contact with
 tissue, such as during the cutting action.
 In accordance with other aspects of the present invention, the first
 electrode of each of the blades may also define a shearing surface and a
 cutting edge of the blade. As in typical surgical scissors, the shearing
 surfaces of the blades are in a face-to-face relationship, but in
 accordance with the preferred aspects of the present invention, the first
 electrodes of each blade are of like polarity, so that there is no short
 circuiting between the shearing surfaces of the blades. Because the
 contacting shearing surfaces are of like polarity, there is no need to
 insulate the blades from one another, and a less complicated and less
 expensive scissor construction is required than in the prior patents
 discussed above. In accordance with this aspect of the present invention,
 the scissor shaft, which extends between the blades and an actuator
 handle, may itself be a conductor for connecting the first electrode of
 each blade to one terminal of a voltage source, and a single insulated
 conductor extending along the shaft may be used to connect the second
 electrode of each blade to the other terminal of the voltage source.
 Further, where the first electrode defines the cutting edge and shearing
 surface and also serves as the main structural element of each blade,
 relatively little force is exerted on the second electrode during cutting.
 As a result, a special high strength or high precision bonding process
 between the first and second electrodes is unnecessary, and less expensive
 bonding techniques should suffice.
 In the above-described embodiment, the first and second electrodes
 preferably extend along a tissue contacting edge of the scissors, which is
 in proximity to the cutting edge. Accordingly, the current flow between
 the first and second electrodes serves to promote hemostasis in close
 proximity to the cut line, as the scissors are closed in a cutting action.
 In accordance with another feature of the present invention, the first and
 second electrodes of each blade are located so that current not only flows
 between the first and second electrodes of each blade, but also between
 the first electrode of one blade and the second electrode of the other
 blade as the blades are brought into proximity during cutting. The flow of
 current between electrodes of different blades and electrodes of the same
 blade enhances coagulation and hemostasis during the cutting action.
 In accordance with another aspect of the present invention, the scissors
 embodying the present invention may be used to promote coagulation during
 a blunt dissection or similar procedure, where the opening action of the
 scissors is used to contact or spread tissue. In this embodiment, each
 scissor blade has first and second spaced electrodes that extend along the
 rearward edge of the blades to contact tissue and promote coagulation as
 the blades are opened to spread or open tissue.
 These and the many other features of the present invention, are set forth
 in the following detailed description of the attached drawings.

DETAILED DESCRIPTION OF THE DRAWINGS
 Referring to FIG. 1, the present invention is generally embodied in
 electrosurgical scissors, generally at 10, having a pair of scissor blades
 12 joined for pivotal movement between open and closed positions. The
 present invention is not limited to any particular type or style of
 surgical scissors, and may be used in essentially any scissors that has a
 pair of movable blades. The particular scissors 10 shown in FIG. 1 is the
 type of scissors typically used in so-called minimally invasive surgery,
 where the scissor blades are inserted into the body cavity of a patient
 through a small diameter trocar.
 In the scissors 10, the scissor blades are located at the distal of an
 elongated tubular shaft 14. As shown in FIGS. 2 and 3, the blades 12 are
 pivotally attached by pivot pin 16, which also attaches the blades to the
 distal end of shaft 14. A pair of linkages 18 connect the proximal ends of
 the blades to an actuator rod 20 that extends through the shaft. Axial
 movement of the actuator rod, which is controlled by handle 22 (FIG. 1) in
 a standard and well-known fashion, closes or opens the blades.
 Alternatively, the proximal ends of the blades 12 may be slotted and the
 actuator rod 20 connected to a pin that slides within the slots, so that
 axial movement of the actuator rod opens and closes the blades. Examples
 of scissors employing a similar but somewhat more complicated structure
 than necessary in the present invention are described in U.S. Pat. Nos.
 5,330,471 and 5,352,222, which are incorporated by reference herein.
 In accordance with the present invention, as shown in FIG. 3, and in FIGS.
 4-7, at least one blade, and preferably each blade of the scissors
 includes an inner conductive blade element 24 which defines a first
 electrode, an intermediate layer of insulative material 26 and an outer
 conductive blade element 28 which defines a second electrode. The inner
 blade element 24 includes a distal curved (or straight if desired) blade
 segment 30, which extends generally from pivot pin 16, and a proximal
 mounting segment 32 that is typically received within the end of shaft 14
 and receives pivot pin 16 and linkages 18. Referring to FIG. 4a, each
 blade has a cutting edge 34, a shearing surface 36 and a tissue contact
 surface or edge 38 that extends along the cutting edge and contacts the
 tissue 40 as the blades close.
 The inner blade element 24 is preferably metal, such as stainless steel, or
 other suitable material that is of high strength and will hold a sharp
 cutting edge for repeated use. As best seen in FIGS. 4-7, the inside
 surface of the inner blade element 24 forms the cutting edge 34 and
 shearing surface 36 of each blade. A forward surface 42 of the inner blade
 element extends along the cutting edge and the tissue contact surface for
 substantially the entire length of the blade segment 30.
 Insulative material 26, separates the inner blade element 24 from the outer
 blade element 28. The insulative material may be made any suitable
 material that has sufficient resistance to electrically insulate the inner
 and outer blade elements. Preferably, the insulative material 26 also has
 sufficient bonding strength for bonding together the inner and outer blade
 elements. Because the outer blade element 28 does not include the shearing
 surface or cutting edge, the forces exerted on the outer blade element are
 limited, and the bond does not have to be as strong, for example, as
 employed in U.S. Pat. No. 5,352,222. It is believed that a relatively thin
 layer or film of insulation, such as the thickness of ordinary electrical
 tape, will provide sufficient insulation between the inner and outer blade
 elements. The spacing between inner and outer blade elements at the tissue
 contact surface is preferably between about 0.002 and 0.050 inches.
 Ordinary adhesives or materials that are suitable for bonding to metal in
 medical applications should suffice for bonding the inner and outer blade
 elements together. Alternatively, epoxy material, such as AF125 by 3M
 Company, as described in detail in U.S. Pat. No. 5,352,222, may be used to
 provide the insulative layer.
 Outer blade element 28 is preferably a thin metal plate or strip, such as
 stainless steel or aluminum. Forward edge 44 of outer blade element 28
 extends along the tissue contact surface 38, generally parallel to and
 spaced from the forward surface 42 of the inner blade element 24. As shown
 in longitudinal cross-section in FIG. 3, the insulating material 26 and
 outer blade element 28 preferably extend along the entire length of blade
 segment 30, including around the distal-most end of the blade segment.
 The scissors of the present invention are preferably intended for
 connection to a voltage source, such as to the bipolar terminals of a
 commercially available bipolar RF energy generator. The bipolar RF
 generator may be connected to the scissors of the present invention at
 connectors 46 and 48 located near handle 22. Connector 46 is attached to
 an insulated conductor 50 that extends through shaft 14 and is connected
 at the distal end to each of the outer blade elements 28 of each blade.
 The other connector 48 is in electrical contact with the actuator rod 20
 and shaft 14 which, in turn, are in electrical contact with the inner
 blade elements 24 of each blade via linkage 18 and pivot pin 16,
 respectively. Accordingly, the inner blade elements of each blade are
 attached to the same terminal of the voltage source and therefore have the
 same polarity. A standard insulating material such as plastic shrink
 tubing acts as a covering 45 along the outside surface of shaft 14, and
 protects surrounding tissue by preventing inadvertent conduction of
 electricity to or from the surface of the shaft. Alternatively, the shaft
 could be made entirely of insulative material, and electrical
 communication to the outer blade elements could be solely through the
 actuator rod, or vice versa.
 FIGS. 4-7 show various possible blade configurations, in cross-section, as
 the blades close on tissue to be severed. Referring first to FIG. 4, FIG.
 4a depicts the blades as they are closed and when they first come in
 contact the tissue 40 to be severed. Each blade has a shearing surface 36
 and cutting edge 34. Each blade also includes an inside or forward tissue
 contacting edge surface 38. The inner blade element 24 forms the cutting
 edge and shearing surface of each blade. The inner blade also includes the
 forward edge or surface 42 that extends along the cutting edge for
 essentially the entire cutting length of the blade. The outer surface and
 back edge of the inner blade element are covered by insulative material
 26. The insulative material 26 also extends beyond the back edge of inner
 blade element 24 to form an overhanging lip 52 of insulative material.
 This overhanging lip has a width approximately the same as or slightly
 greater than the width of the forward edge 42 of the inner blade element.
 Outer blade element 28 extends along the tissue contacting edge surface 38
 of the blade for substantially the entire length of the blade segment 30,
 and, as seen in cross-section, overlies only a portion of the outside
 surface of the inner blade element 24.
 As shown by the arrows in FIG. 4a, when the tissue contacting edge or
 surface 38 of each blade comes into contact with the tissue 40 to be cut,
 current is believed to flow through the tissue between the inner blade
 element 24 and the outer blade element 28 of each blade, and as the blades
 come into proximity with each other, current flows through the tissue
 between the outer blade element 28 and inner blade element 24 of opposite
 blades. The current flow at the initial point of contacting the tissue is
 believed to be substantially between the inner and outer blade elements of
 the same blade along the tissue contacting edge. As the blades begin to
 cut the tissue and the distance between the blades decreases, the current
 flow between opposite electrodes of opposite blades increases.
 FIG. 4b shows the blades in a position where the tissue has been severed,
 and the blades are not fully closed. At that position, it is understood
 that current flows substantially between the inner and outer blade
 elements of the same blade along the tissue contacting edge or surface 38,
 and may also flow between the outer blade element 28 and the shearing
 surface 36 of the inner blade element 24 of the other blade. The extent of
 current flow through the tissue in this situation may vary depending on
 the tissue type, position, thickness, and the extent to which the tissue
 is under tension.
 FIG. 4c shows the blades in a fully closed position. At that position, the
 overhanging lip 52 of insulative material covers the forward edge 42 of
 the inner blade element 24 of the facing blade, essentially fully
 enclosing and insulating the inner blade elements 24 from tissue contact,
 and preventing current flow therethrough.
 FIGS. 5a-5c show an alternative embodiment of the present invention in
 which each of the blades similarly has a cutting edge 34, shearing surface
 36, and tissue contacting edge or surface 38 for contacting tissue as the
 blades close. In addition, in this embodiment each of the blades includes
 an rearward edge or surface 54, which is displaced from or opposite the
 tissue contacting edge or surface 38, and which may be used for
 cauterizing tissue in those situations where it is desirable to cauterize
 tissue with the rearward surfaces of the blades.
 More specifically, as shown in FIG. 5a, each blade includes the inner blade
 element 24, insulative material 26 over only the outside surface of the
 inner blade element, and outer blade element 28 which fully overlies the
 outside surface of the inner blade element. With this construction, as the
 tissue contacting edge of each blade comes into contact with tissue 40 for
 cutting, current is understood to flow between the surfaces 42 and 44 of
 the inner and outer elements of the same blade, and between the inner
 blade surface 42 and the outer blade surface 44 of opposite blades. As the
 blades are moved to a closed position, as shown in FIG. 5b, current is
 believed to flow between the outer blade surface 44 and the inner blade
 surface 42 of the same blade and between the inner blade element and outer
 blade element of the opposite blades. When the blades are fully closed, as
 shown in FIG. 5c, the forward and rearward surfaces 38 and 54 of the inner
 and outer electrodes of each blade are exposed, and current may continue
 to flow between the electrodes of each blade, when they are in contact
 with tissue.
 The rearward edge of each blade in FIG. 5 has the same construction as the
 inside or forward edge of the blade, with tissue contacting surfaces 42'
 and 44' extending along the rearward surface 54, and therefore may be used
 for assisting in severing and promoting hemostasis of tissue that is
 contacted by the outside of the blades in a procedure such as blunt
 dissection. FIGS. 9a-9c depict use of the scissors of FIG. 5 in a
 procedure such as a blunt dissection. A blunt dissection as depicted in
 FIG. 9 is where the scissors are inserted into the tissue in a closed or
 semiclosed position, and then opened to spread the tissue. Such a
 spreading action may result in bleeding from blood vessels ruptured during
 the procedure. In accordance with the present invention, the scissors of
 FIG. 5 may be used not only for promoting hemostasis during normal cutting
 but for promoting hemostasis during blunt dissection or the like.
 FIG. 9a shows the scissor blades of FIG. 5 inserted into tissue 40 in a
 closed or near closed position. In this position, current flows through
 the tissue between surfaces 42 and 44 of the same blade at the inside
 tissue contacting surface and between surfaces 42' and 44' of the same
 blade at the rearward tissue contact surfaces. As the blades are moved to
 an intermediate position, the inside surfaces are no longer in close
 tissue contact and current flow between the inner and outer blade elements
 reduces or ceases. Current continues to flow through the tissue in contact
 with surfaces 42' and 44', promoting hemostasis in the tissue as the
 scissors spread. This current flow and hemostasis continues as the
 scissors fully open, as shown in FIG. 9c.
 FIG. 6 shows another embodiment of the present invention, in which the
 inner blade element 24 is of essentially the same shape as that shown in
 FIG. 4, with the insulative layer 26 covering the same portion of the
 inner blade element as also shown in FIG. 4. In FIG. 6, however, the outer
 blade element 28 extends fully around the inner blade element to the same
 extent that the insulative material 26 extends around the material. The
 current flow between inner and outer elements of the blades in FIG. 6 is
 essentially the same as that described for FIG. 4. Also, similarly, when
 the blades are fully closed the inner blade elements 24 are essentially
 fully enclosed by the insulative material 26 and current flow between the
 inner and outer blade elements is effectively prevented. In this
 configuration, the outer electrode could be used as a monopolar electrode
 when the scissors are closed.
 FIGS. 7a-7c show yet another embodiment of the present invention similar to
 that of FIG. 6. In this embodiment, however, the inner blade element 24
 tapers to a point at the tissue contacting edge or surface. In this
 embodiment, it is believed that the maximum amount of current flow will
 occur between the outer blade element of one blade and the inner blade
 element of the other blade as the blades sever the tissue. It should be
 noted that the wider the inner blade element surface 42 is, the more
 current will flow between electrodes (inner and outer elements) of the
 same blade, and the narrower the surface 42, the more current will flow
 between electrodes (inner and outer elements) of opposite blades. If the
 surface 42 width exceeds the typical current path length for bipolar
 energy (i.e., is greater than about 0.050 inches in width) then most of
 the current flow will occur between electrodes (inner and outer elements)
 of the same blade.
 Finally, FIG. 8 depicts how the forward or tissue contact surface of a
 single blade embodying the present invention may be used to promote
 hemostasis independent of the tissue being severed.
 Although FIGS. 4-7 depict various alternative constructions for the blades
 of the present invention, the present invention is not limited to these
 particular versions, and it is anticipated that other blade configurations
 may be used embodying the present invention which depart from the
 particular construction shown in FIGS. 4-7.