US20150342668A1 - Tissue ablation cannula and elecgtrode assembly that can be selectively operated with one or more active tips - Google Patents

Abstract

An assembly (32) for use as part of an electrosurgical tool system (30). The assembly includes a cannula (42) and an electrode (66). The cannula is formed with a bend (54) proximal to the distal section. The electrode has a bent section (80) formed from a flexible shape memory material. The electrode can be inserted into the cannula so that a distal section of the electrode seats in the distal section of the cannula. In this configuration, the assembly has a single active tip, the distal section of the cannula. Alternatively, the electrode can be oriented so that when the electrode is inserted in the cannula the distal section of the electrode extends out of a side opening (58) of the cannula. In this configuration, the assembly has two active tips, the distal sections of both the cannula and the electrode.

Description

BACKGROUND OF THE INVENTION
• This invention generally relates to a cannula and electrode assembly used for tissue ablation. The cannula and electrode assembly of this invention has plural conduct tips and be selectively operated so that at any given time a single tips or the plural tips are active.
BACKGROUND OF THE INVENTION
• An electrosurgical tool system, often referred to as an electrosurgical system, is a set of components used to flow current through a patient to accomplish a specific medical procedure. Often the procedure is to ablate at least some of the tissue through which the current is flowed to accomplish a desirable therapeutic effect. For example, an electrosurgical procedure is sometimes performed to selectively remove nerve tissue. This may be desirable if a set of the patient's nerves continually transmit signals to the brain that inaccurately indicate that a portion of the patient's body is in appreciable pain. If the receipt of these pain signals adversely affects the quality of life for the patient, an electrosurgical system is employed to ablate the nerves responsible for the transmission of these signals. As a consequence of the tissue ablation process the nerve becomes a lesion. As a result of the nerve becoming a lesion, the nerve no longer transmits pain signals to the brain.
• Many electrosurgical systems include a cannula and electrode assembly. As implied by its name this assembly includes a cannula and an electrode. The cannula is a needle like structure with sufficient strength to puncture the skin of the patient and be positioned adjacent the tissue through which the current is to be flowed. The distal end or tip of the cannula is conductive. The electrode is a closed end tube formed of conductive material. The tube is designed to seat in the bore, the lumen, that extends through the cannula. Owing to the relatively small diameter of the electrode, often 0.4 mm or less in diameter, this tube tends to be relatively fragile. A hub or terminal is connected to the proximal end of the electrode body.
• When this type of assembly is used to remove tissue, the cannula is typically initially inserted into the patient and directed to a location adjacent the target tissue, the tissue that is to be removed. During the insertion process a stylet may be seated in the cannula lumen to provide structural strength to the cannula. Once the cannula is in the generally vicinity of the target tissue, the stylet is removed. The electrode is inserted into the cannula lumen. A cable connects the electrode to a control console, also part of the electrosurgical system. The control console functions as the power source that applies current to the electrode. An electrically conductive ground pad, another component of the electrosurgical system, is placed against the patient. The ground pad is also connected to the control console.
• The electrode assembly is used by sourcing a current from the control console to the electrode. Since the electrode and cannula physically abut, there is current flow to the cannula. An electrical path is established through the patient from the electrode and sleeve section of the cannula to the ground pad. This current flow is densest through the tissue immediately adjacent the distal end of electrode and the exposed distal end of the cannula. This current flow heats the tissue to a temperature that results in the ablation of the tissue.
• Available cannula and electrode assemblies have proven to be good instruments for removing selected sections of tissue. Nevertheless, a limiting characteristic with the use of some of these assemblies is that, when activated, they tend to ablate relatively small volumes of tissue, tissue having a volume of 0.8 cm³or less. This is especially true of assemblies having cannula with outer diameters of 18 gage or more (1.25 mm or less.) There are procedures in which the practitioner wants to ablate larger sections of tissue than can be removed in a single actuation of the assemblies. Consequently, after a first section of tissue is removed, the practitioner has to reposition the electrode assembly to remove an adjacent section of tissue. This requires the practitioner to, ever so slightly, reposition the electrode array so that, in the next actuation, current is only flowed through the tissue that is to be removed and not flowed through the adjacent tissue that should not be subjected to the removal process. Having to so reposition the electrode assembly, in addition to requiring a significant amount of skill, can lengthen the overall amount of time it takes to perform the procedure.
• An alternative cannula-and-electrode assembly has been proposed that is intended to increase the volume of tissue that can be removed with a single placement of the cannula. Specifically, it has been proposed to form the cannula of this type of assembly with a side opening that is located a short distance rearward of the distal end of the cannula. The assembly is further constructed with a means to turn the electrode as it is inserted in the cannula so that the distal end tip of the electrode extends out of this side port. The assembly thus has two tips: the distal end tip of the cannula; and the distal end tip of the electrode. When current is sourced to the assembly, the current flows from these two spaced apart tips.
• Consequently, when current is sourced out of the electrode assembly of this invention, a relative dense electric field appears in the area around both of the tips. The field extend over a wider volume than the field output by an assembly with a convention electrode-in-the distal end of the cannula construction. The electrode assembly of this invention thus outputs a relatively dense current flow through a volume larger than is output by a conventionally constructed electrode assembly of the same size.
• There are procedures though in which the practitioner may not know until after the procedure is started if it is more appropriate to source current through a one tip assembly or a two tip assembly. Similarly, during the procedure, the practitioner may want to initial apply current using first the one tip (or two tip) assembly and then switch to applying current using a two tip (or one tip) assembly. In either of the above situations, the practitioner may find it necessary to interrupt the procedure in order first remove one cathode and electrode assembly and then insert a second assembly. As part of this process, the practitioner needs to take the time to ensure that the second assembly is properly positioned. Having to perform all these steps can increase the complexity of the procedure and the tip it takes to perform the procedure.
BACKGROUND OF THE INVENTION
• This invention relates to a new and useful cannula and electrode assembly for flowing current through living tissue. The assembly of this invention is designed so that after being inserted into the living being through which the current is to be sourced the assembly can be configured to source current from a single tips or plural spaced apart tips. In many versions of the invention, the assembly can be set to have two active tips.
• The cannula of this assembly is formed so as to have a bend immediately proximal to the distal end of the cannula. The cannula has an outlet opening along the outer surface of the section of the cannula in which the bend is formed.
• The electrode includes an elastic shaped section proximal to the distal end. More specifically, the electrode is shaped so as to have a length substantially equal to the length of the lumen that extends through the cannula. The electrode is further formed to have a bend in the section formed from elastic material. The bend is formed so as to be at the same general location along the length of the electrode that the bend is formed in the cannula.
• A hub is attached to the proximal end of the electrode. The hub is connected to a cable through which current is sourced to the cannula. In many, but not all versions of the invention, the hub is provided with an indicia that provides an indication of the rotational orientation of the electrode within the cannula.
• The assembly of this invention is used by first inserting the cannula in the patient. The cannula is positioned so the distal end tip is located adjacent the tissue through which the current is to be flowed. The electrode is then inserted in the cannula. If the practitioner only wants to flow current out of a single tip, the tip of the cannula, the electrode is inserted in the cannula in the rotational orientation so that the bend in the electrode is in same orientation as the bend in the cannula. Consequently, when the electrode is seated in the cannula, the tip of the electrode is seated in the distal end of the lumen of the cannula. Current is therefore sourced only from the tip of the cannula.
• Alternatively, the practitioner can configure the assembly of this invention so that current can be simultaneously sourced from two tips. The assembly is so positioned by setting the rotational orientation of the electrode so that it is out of orientation with the bend in the cannula. When the electrode, in this orientation, is inserted in the cannula, the distal end of the electrode will extend out of the side port of the cannula. Thus while embedded in the patient, the assembly in this configuration has two active tips; the cannula tip and the electrode tip. As a consequence of the application of current to the electrode, current is flowed from both tips through the adjacent tissue.
BACKGROUND OF THE INVENTION
• The invention is pointed out with particularity in the claims. The above and further features and advantages of this invention are understood by reference to the following Detailed Description taken in conjunction with the accompanying drawings in which
• FIG. 1 depicts an electrosurgical system with a cannula and electrode assembly of this invention;
• FIG. 2 is a plan view of the cannula and electrode assembly of this invention;
• FIG. 3 is a cross sectional view of the cannula and electrode assembly ofFIG. 2;
• FIG. 4 is plan view of the cannula of this invention;
• FIG. 5 is plan view of the electrode of this invention;
• FIG. 6A is a diagrammatic depiction of the alignment of the cannula and electrode indicia of the assembly of this invention when the assembly is configured to source current from a single tip;
• FIG. 6B is a cross sectional view of the assembly when the assembly is configured to source current from a single tip; and
• FIG. 7A is a diagrammatic depiction of the alignment of the cannula and electrode indicia of the assembly of this invention when the assembly is configured to source current from a single tip;
• FIG. 7B is a partial cross sectional view of the assembly of this invention when the assembly is configured to source current from a single tip;
• FIG. 8 is a plan view of an alternative electrode of this invention.
DETAILED DESCRIPTION
• FIG. 1 illustrates anelectrosurgical system30 including a cannula andelectrode assembly32 of this invention.System30 also includes aground pad34 and acontrol console36. Both the cannula andelectrode assembly32 andground pad34 are connected to thecontrol console36. Thecontrol console36 functions a power source that sources a current for flow between the cannula andelectrode assembly32 and theground pad34
• The cannula and the cannula andelectrode assembly32, as seen inFIGS. 2 and 3 includes acannula42 and anelectrode66.Electrode66 is disposed in thecannula42.FIGS. 2 and 3 depict one operating configuration ofassembly32, wherein the distal end tip of the electrode62 is located outside of thecannula42.
• Cannula42, now described by reference toFIGS. 4 and 6B, includes ahub44.Hub44 is formed from plastic or other electrically insulating material. (Cannula hub44 and the above the below describedelectrode hub68 ofFIG. 1 are aesthetically different than the hubs depicted in the other Figures.)Hub44 is formed with a longitudinally extendingouter face41.Face41 is formed withindicia43 best seen inFIGS. 6A and 7A. In the depicted version of the invention, indicia43 is shown as two linearly aligned bars. Thecannula hub44 is formed to have a throughbore46 that extends axially through the hub. Hub bore46 is dimensioned to receive thebody74 of the electrode62. The proximal portion of hub bore46 is generally of constant diameter. (Here “proximal” is understood to mean towards thepractitioner holding assembly32, away from the tissue to which theassembly32 is applied. “Distal” is understood to mean towards the tissue to whichassembly32 is applied, away from the practitioner.)Hub44 is further shaped so that, as bore46 extends distally forward from the constant width proximal section, the diameter of the bore decreases. At the most distal end of thehub44, bore46 has a diameter that allows theelectrode body44 to slide through and out of the bore.
• Acannula body50 extends distally forward fromhub44.Cannula body50 is tube-shaped and formed from a flexible conductive material such as stainless steel. Thecannula body50 has opposed proximal and distal ends, the proximal end being the end disposed inhub44. In many versions of theinvention cannula body50 is of size 18 gage or smaller (1.25 mm or less in outer diameter.) In still other versions of the invention, cannula body is of size 20 gage or smaller (0.9 mm or less in outer diameter).Cannula body50 has an axially extendinglumen52. The proximal end ofbody50 is mounted to thehub44 so the proximal portion oflumen52 is coaxial with hub bore64.Lumen52 extends from the proximal to the distal end of thebody50. Not identified is the distal end opening in the distal end ofbody50 that opens intolumen52. In some versions of the invention the most proximal section ofbody50, including the proximal end, is heat staked or adhesively secured incannula hub44.
• Cannula42 is further constructed so thatbody50 is not straight along the whole of the length of the body. In some versions of the invention, the body is shaped so the first 80% to 90% of the body that extends forward from hub is linear in shape. Through this portion of the body,body lumen52 is coaxial with hub bore46. Forward of this linear section, the cannula body is formed with abend54.Bend54 has a radius of curvature of 40 to 60 mm. Forward ofbend54, cannula body has a distal section,section56. Cannula bodydistal section56 is generally linear in shape. The distal section has a length of approximately 5 to 10 mm. Thecannula body50 is further formed to aside opening58.Side opening58 is located on the side of the body that forms the outer surface ofbend54. Thecannula body50 is formed so that thelumen52, in addition to extending through the proximal section of the body, also extends throughbend54 anddistal section56. Side opening58 thus opens into thebody lumen52.
• Cannula body50 is further formed so that distal end is both open and has a flaredtip60. More particularly the tip is flared so that the most distal portion of the body is a point forward of the inner side ofbend54. Thecannula42 itself is constructed so thatbody50 extends forward from thehub44 so that portion of the body forming the inner surface ofbend54 is directed towards theface41 of the hub on whichindicia43 is located.
• Asleeve64, seen only inFIG. 2, formed from electrically insulating material is disposed over the outer surface of thecannula body50. Thesleeve64 extends proximally rearward from a position slightly proximal toside opening58. Thesleeve64 extends proximally so as to extend over the portion of the cannula that is disposed inhub44.
• Theelectrode66, now described by reference toFIGS. 3,5,6A,6B and7B, includes ahub68 formed from plastic or other electrically insulating material.Hub68 is formed to have two opposed faces70 and75.Face70 is formed with afirst indicia72, shown as “|”. The opposed hub face, face75 is formed with asecond indicia76, shown as “\/”
• A tube likebody74 formed of conductive material that has both flexible and elastic characteristics extends forward fromhub68. More particularly, the material is elastic so that, when subjected to deformative strain up to 3% and in some situations up to 6% deformative strain from its initial shape, the body will not permanently deform and return to its initial shape. In one version of the invention,body74 is formed from a nickel titanium alloy known as Nitinol.Body74 has an overall length such that whenelectrode66 is inserted in thecannula42 so that theelectrode hub68 abutscannula hub44, the distal end tip of the electrode body is extends forward of at least a portion of the face forming the flaredtip60 of thecannula body50. The distal end tip of the electrode body does not extend beyond the distalmost end of thecannula body50. In some versions of the invention, when theelectrode66 is fully seated in thecannula42, the distal end top of the electrode body is located approximately 0.4 to 1.4 mm rearward of the distalmost tip of thecannula body50. Theelectrode body74 has an outer diameter dimensioned so that when theelectrode body74 seats incannula lumen54, there is contact between the inner surface of thecannula body50 that defineslumen54 and the outer surface ofelectrode body74.
• Electrode body74 is further designed to have abend80. InFIG. 5, the curvature ofbend80 is exaggerated for purposes of illustration.Bend80 is located in theelectrode body74 so that when theelectrode66 is seated in thecannula42, theelectrode bend80 seats in the section of thecannula lumen52 defined bycannula bend54. When theelectrode66 is assembled, thebody74 is placed in a rotational orientation relative to thehub68 so that adistal section82 of the body, the section distal to bend64, is directed towardshub face70. It should be further understood that the distal end of bodydistal section82 is the distal end tip of theelectrode66.
• Athermocouple84, represented by an oversized dot inFIGS. 6B and 7B is disposed in theelectrode body80.Thermocouple84 is disposed in the bodydistal section82. Insulated wires (not illustrated,) extend from thethermocouple84 through theelectrode body75 tohub68. The structure of thethermocouple84 and the conductors that extend to the thermocouple are not part of the present invention.
• A cable92 (FIG. 1) extends proximally from theelectrode hub68. Thecable68 contains a wire that, through the hub, is connected to theelectrode body74. Also internal to thecable92 are wires that connect to the wires internal to theelectrode body74 that are connected to thethermocouple84. The proximal end of thecable92 is connected to thecontrol console36.
• Control console36 includes a power supply (not illustrated) capable of sourcing a variable current to theelectrode assembly32.Ground pad34 functions as the return conductive terminal for the power source. Typically, the current is AC current.Control console36 is configured to allow the practitioner to adjust the frequency, current and voltage levels of the sourced current. The specific structure of thecontrol console36 is not part of the present invention. Features of control consoles that can be employed ascontrol console36 ofsystem30 this invention are disclosed in the incorporated by reference US Pat. Pubs. No. 2005/0267553 SYSTEM AND METHOD FOR CONTROLLING ELECTRICAL STIMULATION AND RADIOFREQUENCY OUTPUT FOR USE IN AN ELECTROSURGICAL PROCEDURE published Dec. 1, 2005 and No. 2007/0016185, MEDICAL BIPOLAR ELECTRODE ASSEMBLY WITH A CANNULA HAVING A BIPOLAR ACTIVE TIP AND A SEPARATE SUPPLY ELECTRODE AND MEDICAL MONOPOLAR ELECTRODE ASSEMBLY WITH A CANNULA HAVING A MONOPOLAR ACTIVE TIP AND A SEPARATE TEMPERATURE-TRANSDUCER POST published Jan. 18, 2007.
• Electrosurgical system30 of this invention is prepared for use by adhering theground pad34 to the patient. Acable35 connects theground pad34 to controlconsole36.
• Cannula42 is inserted into the patient adjacent the subcutaneous tissue that is to be subjected to the ablation process. In the insertion process the flareddistal end tip60 of the cannula is the portion of theelectrode assembly32 that punctures the skin. In this step,electrode66 is not fitted to thecannula42. Instead, a flexible stylet (not illustrated) is seated in thecannula lumen52. The stylet inhibits thecannula body50 from bending to the extent that such bending results in the permanent deformation of the cannula.
• The practitioner steers thecannula42 so it is located in the vicinity of the target tissue, the tissue that is to be subject to the ablation procedure. Owing to its relatively small diameter of thecannula body50, the cannula is relatively flexible. This flexibility facilitates the ability of the practitioner to steer the cannula to the vicinity of the target tissue. As part of this steering process, the practitioner positions the cannula so it is in the proper orientation relative to the tissue to be ablated. Once the cannula is properly positioned, the stylet is removed.
• The practitioner then inserts theelectrode66 in thecannula42. If the particular procedure only requires the sourcing of current through a small volume of tissue adjacent the distal end of theassembly32, the electrode is seated so as to position thedistal section82 of theelectrode body74 in the cannula bodydistal section56 as seen inFIG. 6B. The practitioner so seats the electrode by setting the rotation orientation of theelectrode body74 inside thecannula body50 so that cannula and electrode bends54 and80, respectively, extend in the same direction. The practitioner sets this orientation of the electrode by aligning theelectrode hub68 so that as thehub68 is moved towardscannula hub42,electrode indicia72 facescannula indicia43 as seen inFIG. 6A.
• As a consequence of theelectrode66 being so oriented, when thedistal section84 of the electrode body approaches thecannula bend54, theelectrode bend80 causes the electrodedistal section82 to curve into the cannula bodydistal section56. At the end of this insertion process, the distal end tip of theelectrode body74 is depicted inFIG. 6B, seated inside the distalmost portion ofcannula lumen52. When theassembly50 is in this configuration, configuration, current is source from just one active tip, the insulation free portion of thecannula body50;bend54 anddistal section56.
• Alternatively, the practitioner may want to flow current through a relatively large volume of tissue adjacent the distal end of theassembly32. To perform this type of procedure, the practitioner seats theelectrode66 so thedistal section82 extends out of cannulabody side opening58.Electrode66 is so positioned by orientating the electrode body in the cannula so that along the longitudinal axis of the cannula proximal section, theelectrode bend80 has an orientation that is opposite to that ofcannula bend54.Electrode66 is so oriented by rotating the electrode soelectrode indicia76 is placed in orientation withcannula indicia43 as seen inFIG. 7A. Once theelectrode66 is so orientated, theelectrode body74 is advanced through thecannula lumen52. Eventually the distal end tip of theelectrode body74 reachescannula side opening58. Owing the elastic characteristics of the material forming theelectrode body74, the potential energy stored inbend80 is released. This energy forces the bodydistal section82 out of the cannulabody side opening58. When the electrode is fully seated in the cannula, thedistal section82 of theelectrode body74 is located outside of and adjacent to the cannuladistal section56 as seen inFIGS. 2,3 and7B.
• When current is sourced through assembly as seen inFIG. 7B, the current is thus sourced through two active tips; the exposed bend and distal section of the cannula body and the exposeddistal section82 of the electrode body. The current thus flows through a larger volume of tissue immediately adjacent the cannula than when the assembly is configured to source current from a single active tip.
• The cannula and electrode of this assembly can thus be configured to operate in one of two modes, a mode in which the assembly sources current out of a single active tip or a mode in which the assembly sources current out of plural active tips. This allows the practitioner to, by setting the mode of operating of the assembly, set if the current is flowed through a relatively small volume or relative large volume of tissue adjacent theassembly32.
• Further, regardless of the mode of operation theelectrode66 is typically fully seated in thecannula42. Consequently, regardless of the operating mode, thethermocouple84 is spaced essentially the same distance from tissue through which the current is flowed. The added separation of the thermocouple from the tissue when the electrodedistal section56 ofcannula body50 is minimal. Thus, in either mode of operation, the signal output by thethermocouple84 representative of tissue temperature, represents the actual temperature of the tissue with the same degree of accuracy. This is useful because a practitioner may want to set the control console to cause a current to be applied to the tissue that ensures that the tissue is heated to a specific temperature. When thesystem30 is so configured, thecontrol console36 employs the output signal from the thermocouple as the signal representative of tissue temperature.
• It is a still further feature of this invention is that, once thecannula42 is inserted in the patient, the practitioner may reset the mode of operation of theassembly32. For example, the practitioner may start the procedure by sourcing current from just the single active tip, cannula bodydistal section56. The practitioner can then reset the assembly so that the current is formed from both tips. the cannula body distal section and the electrode body distal section. The practitioner performs this switch by first partially withdrawing theelectrode body74 from thecannula lumen52. Theelectrode66 is then rotated to placeelectrode indicia76 is placed in registration ofcannula indicia43. Theelectrode body74 is then fully reinserted in thecannula lumen52. This rotation and reinsertion of theelectrode body74 results in the extension of the electrode body distal section out of the cannulabody side opening58. The assembly is then ready for operation in the mode in which the current is sourced from the two active tips.
• Using the technique opposite from which is described above,assembly32 once fitted to the patient can be switch from the plural active tip operating mode to the single active tip operating mode.
• The above is directed to one specific version of the invention. Other versions of the invention may have features different from what has been described.
• For example, there is no requirement that in all versions of the invention a thermocouple be the component disposed in the electrode that provides a signal representative of temperature. A thermal resistor or other temperature sensitive transducer may perform this function.
• Likewise there is no requirement that in all versions of the invention either the cannula body or electrode body be components formed out of a single section of material. For example, the cannula body may include a proximal section formed from a non conductive plastic. The bend and the distal section may be formed from metal or a other conductive material.
• Further the described cannula is what is referred to as a monopolar cannula. The cannula has a single conductive surface. In an alternative version of this invention, the cannula may be a bipolar cannula. This type of cannula has two conductive surfaces that are electrically insulated from each other. The assembly of this version of the invention is used to perform what is known as a bipolar ablation procedure. The cannula second conductive surface functions as the return conductive terminal.
• In this version of the invention, when the assembly is operated in the plural active tip mode, the exposeddistal section82 of theelectrode66 and one of the exposed sections of the cannula form a pair of common active tips. The second exposed section of the cannula serves as the return conductive terminal.
• Likewise the electrode body may be formed from plural sections of different material. For example the electrode body may have a proximal section formed from an elastic plastic. This plastic portion of the electrode body may be formed with the flexible bend. Distal to bend, the electrode may have a tip formed from a relatively inflexible conductor. An advantage of this version of the is that when the assembly is configured to operate in the plural active tip mode and the electrode is deployed out of the cannula side opening, the relatively inflexible exposed distal end may be less prone to breakage.
• Further, there is no limitation that the invention solely be used in what are referred to as a monopolar procedure, a procedure in which the ground pad functions as the return electrode.Assembly32 of this invention may be used to perform what is referred to as a parallel bipolar ablation procedure. In this type of procedure two cannula and electrode assemblies are inserted in the patient. These assemblies are positioned on opposed sides of the tissue through which the current is to be flowed. In this type of procedure, the second cannula and electrode assembly serves as what is referred to as the return electrode.
• In these types of procedure, there is no requirement that both cannula and electrode assemblies be of the type of this invention. In this type of procedure it is recommended that theassembly32 of this invention be orientated so that theelectrode bend80 is positioned so that the electrodedistal section82 be directed towards the tissue through which the current is to be filed. This recommendation applies when theassembly32 is operated either the single or active tip mode or the plural active tip mode. This orientation of theelectrode66 is suggested to ensure that thethermocouple84 is positioned relatively close to the tissue through which the current is to be flowed. This increases the extent to which the thermocouple outputs a signal that, as closely as possible, represents the temperature of the tissue through which the current is flowed.
• FIG. 8 illustrates analternative electrode102 of this invention.Electrode102 includes the same features of initially describedelectrode66. Theelectrode102 further includes asleeve104 formed from electrically insulating material that is disposed over theelectrode body74.Sleeve104 extends distally fromhub68 to a location forward of thebend80. InFIG. 8, the wall thickness ofsleeve104 is exaggerated for purposes of illustration.
• The electrode ofFIG. 8 is used in versions of this invention wherein a separate set of conductors extends fromcannula hub44 to thecontrol console36. These conductors (not illustrated) provide an electrical connection between thecontrol console36 and thecannula body50.
• The cannula-and-electrode assembly of this invention can be thus operated as either a monopolar unit or a stand alone bipolar unit. The assembly is operated as a monopolar unit by seatingelectrode102 incannula44 so that the electrode bodydistal section82 seats in cannula bodydistal section56. When the assembly is operated in this state, there is only a need to connect theelectrode102 to thecontrol console36. The assembly in this state is operating with a single active tip; the insulation free portion of the electrodedistal section82.Ground pad34 functions as the return terminal.
• Alternatively, the practitioner may want to operate the assembly is a stand alone bipolar unit. The assembly is so configured by orientatingelectrode102 so that when the body is inserted in thecannula lumen52, the electrode body distal section protrudes out ofcannula side opening58. It should be understood that when theelectrode102 is so positioned, the distal most portion ofsleeve104 also protrudes out of thecannula side opening58. Thus when the assembly is so configured, the cannula bodydistal section56 and the electrode bodydistal section82 are electrically insulated from each other. To operate the assembly in this configuration, it is further necessary to connect the cable that extends from thecannula hub44 to thecontrol console36.
• To operate the assembly in this configuration, current is flowed from the console power supply through the cannula, The exposed cannula bodydistal section56, which is one of the active tip, functions as the active tip. The exposed electrode bodydistal section82 functions as the return terminal. By so configuring the assembly of this invention, the practitioner can if desired, flow current through the small volume of tissue that surrounds the exposed tips.
• An alternative embodiment of this version of the invention can be formed by provide the cannula with a liner that extends around the interior wall of the body that defineslumen52. This linear also cover the outer surface of the cannula that definesside opening52.
• Accordingly, it is an object of the appended claims to cover all such modifications and variations that come within the true spirit and scope of this invention.

Claims (20)

What is claimed is:

1. A cannula and electrode assembly including:

a cannula having a cannula body having: opposed proximal and distal ends; a distal section that is electrically conductive, the distal section defining the distal end of the cannula body; a bend proximal to the cannula distal section; a lumen that extends distally and longitudinally from the proximal end of the cannula body; and a side opening that extends through a portion of the cannula body that defines an outer portion of the bend, the side opening opening into the cannula body lumen; and

an electrode adapted for connection to a cable that connects the electrode to a control console, the electrode having an electrode body dimensioned to seat in the lumen of said cannula body, said electrode body having: a distal section formed from electrically conductive material that is electrically connected to a conductor internal to the cable and a section proximal to the distal section formed from elastic material, the section formed from elastic material being located so that, when the electrode body is inserted in the cannula lumen, the section is within the section of the lumen defined by the bend in said cannula body and the bend is shaped so that, depending on the rotational orientation of the electrode body relative to the cannula body, when the electrode body is inserted in the cannula body the electrode body distal section either seats in the lumen portion within the cannula body distal section or extends out of the cannula body side opening.

2. The cannula and electrode assembly ofclaim 1, wherein said cannula and said electrode are formed with complementary indicia that are arranged to provide an indication of the rotational orientation of the electrode body relative to the cannula body.

3. The cannula and electrode assembly ofclaim 2, wherein:

said cannula has a hub and said cannula indicia is disposed on the cannula hub; and

the proximal end of said cannula body is mounted to the hub and the cannula body extends distally from said hub.

4. The cannula and electrode assembly ofclaim 2, wherein:

said electrode has a hub, said hub being the component of the electrode to which the cable is connected;

said electrode body extends from said hub; and

said electrode indicia are disposed on the electrode hub.

5. The cannula and electrode assembly ofclaim 1, wherein said cannula body is formed from a single piece of material.

6. The cannula and electrode assembly ofclaim 1, wherein said electrode body is formed from a single piece of material.

7. The cannula and electrode assembly ofclaim 1, wherein the section of said electrode formed from elastic material is formed from a nickel titanium alloy.

8. The cannula and electrode assembly ofclaim 1, wherein said electrode body is in the form of a tube having a closed distal end.

9. The cannula and electrode assembly ofclaim 1, wherein an electrically insulating sleeve is disposed over the cannula body, said sleeve extending proximally from a location spaced proximally to the distal end of the cannula body.

10. The cannula and electrode assembly ofclaim 1, further including a temperature sensor disposed in said electrode body.

11. The cannula and electrode assembly ofclaim 10, wherein said temperature sensor is a thermocouple.

12. The cannula and electrode assembly ofclaim 1, wherein said assembly is structured as a monopolar cannula and electrode assembly.

13. The cannula and electrode assembly ofclaim 1, wherein:

said cannula has a hub; and

the proximal end of said cannula body is mounted to the hub and the cannula body extends distally from said hub.

14. The cannula and electrode assembly ofclaim 1, wherein:

said electrode has a hub, said hub being the component of said electrode to which the cable is connected; and

said electrode body extends from said hub.

15. The cannula and electrode assembly ofclaim 1, wherein said electrode further includes a sleeve formed from insulating material that extends at least partially over said electrode body

16. The cannula and electrode assembly ofclaim 1, wherein the radius of curvature of the bend of said cannula is between 40 and 60 mm.

17. A cannula and electrode assembly, said assembly including:

an electrode configured for connection to a cable, said electrode including:

a hub formed electrically insulting material, said hub including opposed surfaces thereof indicia, the indicia on the opposed surfaces being different from each other; and

a body, said body having: a proximal section that extends distally forward from said electrode hub; a distal section located forward of the proximal section, the distal section being formed from electrically conductive material and electrically connected to a conductor internal to the cable, the distal section defining an end of the body; and a bend located between the proximal and distal sections, so that as a result of the presence of the bend the proximal and distal sections of said electrode body are axially angularly offset from each other; and

a cannula, said cannula including:

a hub formed from electrically insulting material and being formed with a bore for receiving said body of said electrode, said cannula having a indicia; and

a body, said body shaped to have: a proximal section that extends from said cannula hub; a distal section located forward of the proximal section, a bend that is located between the proximal and distal sections so that, as a result of the presence of said cannula body, the proximal and distal sections of the cannula body are axially angularly offset from each other, a lumen that extends through the proximal section, the bend and distal section of said cannula body, the lumen dimensioned to receive said electrode body and side opening in an outer surface of the bend, said side opening opening into the lumen that extends through the cannula body and wherein the bend and the side opening are formed in the cannula body so that: when the electrode body is inserted in first rotational orientation within the cannula body to place a first one of the indicia on said electrode hub is registration with the indicia of said cannula hub, the distal section of the electrode body seats in the portion of the cannula lumen disposed in the distal section of said cannula body; and, when the electrode body is inserted in a second rotational orientation to place a second one of the indicia of the electrode hub in registration with the indicia of the cannula hub, the bend of the electrode body causes the distal section of the electrode body to extend out through the side opening in said cannula body.

18. The cannula and electrode assembly ofclaim 17, wherein said electrode body is formed from a single piece of material.

19. The cannula and electrode assembly ofclaim 17, wherein said assembly is structured as a monopolar cannula and electrode assembly.

20. The cannula and electrode assembly ofclaim 1, wherein the radius of curvature of the bend of said cannula is between 40 and 60 mm.

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