Patent Application
20080234673
The present invention relates to electrosurgical instruments having multiple electrodes. More particularly, the present invention relates to electrosurgical instruments having multiple electrodes in various configurations which allow treatment of different tissue types with a single instrument.
Conventional electrosurgical methods generally reduce patient bleeding associated with tissue cutting operations and improve the surgeon's visibility. These electrosurgical devices and procedures, however, suffer from a number of disadvantages. For example, monopolar and/or bipolar electrosurgical devices are typically designed for treating certain tissue types. One specific electrosurgical device may be effective for ablating a first tissue type such as cartilage, yet ineffective for treating a second tissue type, such as loose or elastic connective tissue like the synovial tissue in joints.
Likewise, during certain electrosurgical procedures such as the removal or resection of the meniscus during arthroscopic surgery to the knee, it is generally necessary to employ two different tissue removal devices, namely an arthroscopic punch and a shaver. The use of multiple instruments brings with it the associated problems not only with preparation and cost but also with the insertion and removal of multiple instruments from the patient body. There is a need for an electrosurgical instrument which enables the treatment of more than one tissue type, such as for the removal of fibrocartilaginous tissue as well as softer tissue. Moreover, there is a need for the same device which is adapted for aspirating resected tissue, excess fluids, and ablation by-products from the surgical site.
Electrosurgical instruments which can treat multiple tissue types may utilize multiple electrodes, however, splitting power from a power supply between different types of active electrodes may be problematic with respect to heating of the instrument and tissue as well as with power consumption. Accordingly, there is also a need for methods and apparatus to control the power delivery of such instruments which utilize multiple electrodes.
A single electrosurgical instrument having multiple electrodes in various configurations may be used to treat more than one type of tissue, thereby eliminating the need for multiple instruments or for inserting and removing more than a single instrument into a treatment space within a patient body. Accordingly, such a single instrument may: (1) volumetrically remove tissue, bone or cartilage (i.e., ablate or effect molecular dissociation of the tissue structure); (2) cut or resect tissue; (3) shrink or contract collagen connective tissue; and/or (4) coagulate severed blood vessels.
High electric field intensities may be generated by applying a high frequency voltage that is sufficient to vaporize an electrically conductive fluid over at least a portion of the active electrode(s) in the region between the distal tip of the active electrode(s) and the target tissue. The electrically conductive fluid may be a gas or liquid, such as isotonic saline, delivered to the target site, or a viscous fluid, such as a gel, that is located at the target site. In the latter embodiment, the active electrode(s) are submersed in the electrically conductive gel during the surgical procedure. Since the vapor layer or vaporized region has relatively high electrical impedance, it minimizes the current flow into the electrically conductive fluid. This ionization, under optimal conditions, induces the discharge of energetic electrons and photons from the vapor layer to the surface of the target tissue. A more detailed description of this phenomenon, termed Coblation®, can be found in commonly assigned U.S. Pat. No. 5,697,882 the complete disclosure of which is incorporated herein by reference in its entirety.
In utilizing such an electrode assembly having at least a first electrode and a second electrode, each respective electrode may be individually powered by a common or separate power supply and they may each have their own respective return electrode or share a common return electrode. Independently powered electrodes or electrodes sharing a common power supply may be utilized.
Each respective active electrode and the return electrode may be insulated via an insulating material such as a ceramic or other insulating material such as polytetrafluoroethylene, polyimide, etc. Additionally, one or more lumen openings may be defined along the electrode assembly for infusing, injecting, drawing or suctioning fluid and debris from the ablation site and through the shaft for removal from the body.
Examples of a multi-electrode assembly may utilize a first electrode which forms an interdigitating member that projects between members of a second electrode with an insulating material separating the electrodes. Alternatively, the electrodes may be positioned adjacent to one another along a common surface. In additional variations, the electrode assembly may utilize a first electrode positioned at an angle, e.g., 90°, relative to a longitudinal axis of the shaft. A second electrode may be positioned at a distal end of the assembly such that first and second electrodes are separated and angled relative to one another.
One or both electrodes may be configured into various configurations to effect treatments such as tissue ablation, cutting, or resection. Additionally, one or both electrodes may include a fluid lumen for infusing a fluid such as saline and/or for drawing debris and fluid back into the openings. Both electrodes may be electrically isolated from one another as well as from a common return electrode by an insulator. Such an assembly utilizing multiple electrodes in different configurations may allow the user to utilize a single device for treating different tissue regions within, e.g., a joint, where space is limited without having to withdraw and introduce multiple instruments into the tissue region.
In utilizing the two or more active electrodes on a single electrosurgical instrument in any of variations described herein, a relay or switch may be used to select which of the electrodes are powered to deliver the output energy. Such a switch may be actuated manually by the user or automatically by a controller. With each electrode being electrically isolated from one another and from the return electrode, the current flowing through the electrode assembly is applied to the tissue to be treated. Each electrode may be configured into any of the variations described herein or as known in the art and in any combination of different electrode types on a single instrument to effect the treatment of multiple tissue types utilizing a single electrosurgical device.
In yet additional variations where an electrode assembly has more than two electrodes, each electrically isolated electrode may each include an individually actuatable relay. The electrodes may be connected in parallel with one another and with a common return electrode. Each of the relays may be individually actuatable such that the current may be applied to one, all, or any combination of the electrodes to effect the desired tissue treatment.
Each of the isolated electrodes may be designed such that each includes a voltage and/or current measurement device to measure each applied parameter. Such a configuration may be applied to all or a few of the electrodes utilized. With these measured values, impedance and power loads may be calculated. Once an ablative effect has been established at one particular electrode upon the tissue being treated, the load impedance generally increases. With changes in the load impedance detected, a generator control circuitry, e.g., a microprocessor or hardware controller, may be configured to track changes in the load impedance at a given electrode and to make a determination to activate subsequent electrodes.
As the tissue is treated, the voltage meter and ammeter may monitor their respective signals which are used to calculate load impedance. When the load impedance reaches a predetermined threshold level, the system may be configured to then actuate relay to activate the electrode. This process may be repeated until all relays have been actuated and all electrodes are activated. Alternatively, the processor may be configured to activate subsequent electrodes based upon the measured current or the delivered power to minimize any current or power spikes initially delivered to the electrodes to facilitate the ablative effects on the tissue being treated.
With the potential of activating multiple electrodes, one method for limiting the power that can be delivered to each electrode is to limit activation of a particular electrode during a power cycle. Each active electrodes may be electrically connected to the power supply through respective diodes. When the power supply is activated, the respective diodes may limit the activation of each electrode to only half of each cycle of the output waveform (or to 1/N of each cycle of the output waveform, where N is the number of active electrodes through which current is flowing). Use of the diodes may help to ensure that the power is equally shared between each active electrode independently of the load that may exist between each electrode and the return electrode.
While a single power supply may be shared between multiple numbers of electrodes, another variation is to power each electrode from an independent, separately controlled power supply. Each power supply can be independently adjusted depending upon the measured current levels received from each electrode assembly to maintain a constant level of power applied by the multiple electrodes at the tissue site.
High frequency (RF) electrical energy may be applied to one or more active electrodes in the presence of electrically conductive fluid to remove and/or modify the structure of tissue structures. Depending on the specific procedure, a single instrument having multiple electrodes in various configurations may be used to: (1) volumetrically remove tissue, bone or cartilage (i.e., ablate or effect molecular dissociation of the tissue structure); (2) cut or resect tissue; (3) shrink or contract collagen connective tissue; and/or (4) coagulate severed blood vessels.
In these procedures, a high frequency voltage difference is applied between the active electrode(s) and one or more return electrode(s) to develop high electric field intensities in the vicinity of the target tissue site. The high electric field intensities lead to electric field induced molecular breakdown of target tissue through molecular dissociation (rather than thermal evaporation or carbonization). This molecular disintegration completely removes the tissue structure, as opposed to dehydrating the tissue material by the removal of liquid from within the cells of the tissue, as is typically the case with electrosurgical desiccation and vaporization.
The high electric field intensities may be generated by applying a high frequency voltage that is sufficient to vaporize an electrically conductive fluid over at least a portion of the active electrode(s) in the region between the distal tip of the active electrode(s) and the target tissue. The electrically conductive fluid may be a gas or liquid, such as isotonic saline, delivered to the target site, or a viscous fluid, such as a gel, that is located at the target site. In the latter embodiment, the active electrode(s) are submersed in the electrically conductive gel during the surgical procedure. Since the vapor layer or vaporized region has relatively high electrical impedance, it minimizes the current flow into the electrically conductive fluid. This ionization, under optimal conditions, induces the discharge of energetic electrons and photons from the vapor layer to the surface of the target tissue. A more detailed description of this phenomenon, termed Coblation®, can be found in commonly assigned U.S. Pat. No. 5,683,366 the complete disclosure of which is incorporated herein by reference in its entirety.
A plasma may be generated in the vicinity of the active electrode on application of the voltage to the electrodes in the presence of the electrically conductive fluid. The plasma includes energetic electrons, ions, photons and the like that are discharged from a vapor layer of the conductive fluid, as described in greater detail in U.S. Pat. No. 5,697,882 the complete disclosure which is incorporated herein by reference in its entirety.
The systems and methods for selectively applying electrical energy to a target location within or on a patient's body may be accomplished particularly in procedures where the tissue site is flooded or submerged with an electrically conductive fluid, such as during arthroscopic surgery of the knee, shoulder, ankle, hip, elbow, hand, foot, etc. Other tissue regions which may be treated by the system and methods described herein may also include, but are not limited to, prostate tissue, and leiomyomas (fibroids) located within the uterus, gingival tissues and mucosal tissues located in the mouth, tumors, scar tissue, myocardial tissue, collagenous tissue within the eye or epidermal and dermal tissues on the surface of the skin, etc. Other procedures which may be performed may also include laminectomy/disectomy procedures for treating herniated disks, decompressive laminectomy for stenosis in the lumbosacral and cervical spine, posterior lumbosacral and cervical spine fusions, treatment of scoliosis associated with vertebral disease, foraminotomies to remove the roof of the intervertebral foramina to relieve nerve root compression, as well as anterior cervical and lumbar disectomies. Tissue resection within accessible sites of the body that are suitable for electrode loop resection, such as the resection of prostate tissue, leiomyomas (fibroids) located within the uterus, and other diseased tissue within the body, may also be performed
Other procedures which may be performed where multiple tissue types are present may also include, e.g., the resection and/or ablation of the meniscus and the synovial tissue within a joint during an arthroscopic procedure. It will be appreciated that the systems and methods described herein can be applied equally well to procedures involving other tissues of the body, as well as to other procedures including open procedures, intravascular procedures, urology, laparoscopy, arthroscopy, thoracoscopy or other cardiac procedures, dermatology, orthopedics, gynecology, otorhinolaryngology, spinal and neurologic procedures, oncology, and the like.
The electrosurgical instrument may comprise a shaft or a handpiece having a proximal end and a distal end which supports the one or more active electrodes. The shaft or handpiece may assume a wide variety of configurations, with the primary purpose being to mechanically support the active electrode and permit the treating physician to manipulate the electrodes from a proximal end of the shaft. The shaft may be rigid or flexible, with flexible shafts optionally being combined with a generally rigid external tube for mechanical support. The distal portion of the shaft may comprise a flexible material, such as plastics, malleable stainless steel, etc, so that the physician can mold the distal portion into different configurations for different applications. Flexible shafts may be combined with pull wires, shape memory actuators, and other known mechanisms for effecting selective deflection of the distal end of the shaft to facilitate positioning of the electrode array. The shaft will usually include a plurality of wires or other conductive elements running axially therethrough to permit connection of the electrode array to a connector at the proximal end of the shaft. Thus, the shaft may typically have a length between at least 5 cm and at least 10 cm, more typically being 20 cm or longer for endoscopic procedures. The shaft may typically have a diameter of at least 0.5 mm and frequently in the range of from about 1 mm to 10 mm. Of course, in various procedures, the shaft may have any suitable length and diameter that would facilitate handling by the surgeon.
As mentioned above, a gas or fluid is typically applied to the target tissue region and in some procedures it may also be desirable to retrieve or aspirate the electrically conductive fluid after it has been directed to the target site. In addition, it may be desirable to aspirate small pieces of tissue that are not completely disintegrated by the high frequency energy, air bubbles, or other fluids at the target site, such as blood, mucus, the gaseous products of ablation, etc. Accordingly, the instruments described herein can include a suction lumen in the probe or on another instrument for aspirating fluids from the target site.
Referring to
Power supply 10 has an operator controllable voltage level adjustment 38 to change the applied voltage level, which is observable at a voltage level display 40. Power supply 10 may also include one or more foot pedals 24 and a cable 26 which is removably coupled to a receptacle with a cable connector 28. The foot pedal 24 may also include a second pedal (not shown) for remotely adjusting the energy level applied to the active electrodes and a third pedal (also not shown) for switching between an ablation mode and a coagulation mode or for switching to activate between electrodes. Operation of and configurations for the power supply 10 are described in further detail in U.S. Pat. No. 6,746,447, which is incorporated herein by reference in its entirety.
The voltage applied between the return electrodes and the active electrodes may be at high or radio frequency, typically between about 5 kHz and 20 MHz, usually being between about 30 kHz and 2.5 MHz, preferably being between about 50 kHz and 500 kHz, more preferably less than 350 kHz, and most preferably between about 100 kHz and 200 kHz. The RMS (root mean square) voltage applied will usually be in the range from about 5 volts to 1000 volts, preferably being in the range from about 10 volts to 500 volts depending on the active electrode size, the operating frequency and the operation mode of the particular procedure or desired effect on the tissue (i.e., contraction, coagulation or ablation). Typically, the peak-to-peak voltage will be in the range of 10 to 2000 volts, preferably in the range of 20 to 1200 volts and more preferably in the range of about 40 to 800 volts (again, depending on the electrode size, the operating frequency and the operation mode).
The power source may be current limited or otherwise controlled so that undesired heating of the target tissue or surrounding (non-target) tissue does not occur. In one variation, current limiting inductors are placed in series with each independent active electrode, where the inductance of the inductor is in the range of 10 uH to 50,000 uH, depending on the electrical properties of the target tissue, the desired tissue heating rate and the operating frequency. Alternatively, capacitor-inductor (LC) circuit structures may be employed, as described previously in PCT application WO 94/026228, which is incorporated herein by reference in its entirety.
Additionally, current limiting resistors may be selected. These resistors will have a large positive temperature coefficient of resistance so that, as the current level begins to rise for any individual active electrode in contact with a low resistance medium (e.g., saline irrigant or conductive gel), the resistance of the current limiting resistor increases significantly, thereby minimizing the power delivery from the active electrode into the low resistance medium (e.g., saline irrigant or conductive gel).
Handle 52 typically comprises a plastic material that is easily molded into a suitable shape for handling by the surgeon. Moreover, the distal portion of shaft 50 may be bent to improve access to the operative site of the tissue being treated (e.g., contracted). In alternative embodiments, the distal portion of shaft 50 comprises a flexible material which can be deflected relative to the longitudinal axis of the shaft. Such deflection may be selectively induced by mechanical tension of a pull wire, for example, or by a shape memory wire that expands or contracts by externally applied temperature changes. A more complete description of this embodiment can be found in PCT application WO 94/026228, which has been incorporated by reference above.
The bend in the distal portion of shaft 50 is particularly advantageous in arthroscopic treatment of joint tissue as it allows the surgeon to reach the target tissue within the joint as the shaft 50 extends through a cannula or portal. Of course, it will be recognized that the shaft may have different angles depending on the procedure. For example, a shaft having a 90° bend angle may be particularly useful for accessing tissue located in the back portion of a joint compartment and a shaft having a 10° to 30° bend angle may be useful for accessing tissue near or in the front portion of the joint compartment.
Regardless of the bend angle, an electrode assembly having multiple, e.g., two or more, actuatable electrodes disposed near or at the distal end of shaft 50 may be utilized. General difficulties in designing electrosurgical devices with relatively large active electrodes typically entail delivering a relatively high level of RF energy until ablative effects are activated at the electrodes. However, once the ablative effects are activated, the load impedance increases and the power delivery to the tissue decreases. Thus, a multi-electrode assembly may be configured to effectively deliver the energy to a tissue region of interest.
Each respective active electrode 62,64 and the return electrode 66 may be insulated via an insulating material 68 such as a ceramic or also as described above, such as polytetrafluoroethylene, polyimide, ceramic, etc. Additionally, one or more lumen openings, such as first opening 70 and/or second opening 72, may be defined along electrode assembly 60 for infusing, injecting, drawing or suctioning fluid and debris from the ablation site and through the shaft 50 for removal from the body. First and second openings 70, 72 may be separate or share a common fluid lumen and they may be defined over assembly 60, for example, adjacent to their respective active electrodes 62, 64. Additionally, a fluid such as saline may be delivered through shaft 50 to flood the tissue region to be treated. Thus, saline may be delivered through a flared opening 74 defined around shaft 50 proximally of electrode assembly 60.
The area of the tissue treatment surface of the electrodes can vary widely and the tissue treatment surface can assume a variety of geometries, with particular areas and geometries being selected for specific applications. Active electrode surfaces can have areas in the range, e.g., from 0.25 mm2 to 75 mm2, usually being from about 0.5 mm2 to 40 mm2. The geometries can be planar, concave, convex, hemispherical, conical, linear “in-line” array or virtually any other regular or irregular shape. Most commonly, the active electrode(s) or active electrode(s) will be formed at the distal tip of the electrosurgical probe shaft, frequently being planar, disk-shaped, or hemispherical surfaces for use in reshaping procedures or being linear arrays for use in cutting. Alternatively or additionally, the active electrode(s) may be formed on lateral surfaces of the electrosurgical probe shaft (e.g., in the manner of a spatula), facilitating access to certain body structures in endoscopic procedures.
Another example is illustrated in the perspective view of
An alternative example of a multi-electrode assembly is shown in the end view of configuration 100 of
Another variation is illustrated in
In yet another variation of a multi-electrode assembly,
Although the multiple electrodes may positioned along a common surface and placed adjacent to one another, other examples for utilizing multiple electrodes may entail positioning the electrodes in various configurations relative to one another as well as positioning alternative types of electrodes to effect different treatments for different tissue types. One example is shown in the perspective side view of
Although both electrodes 226, 228 are illustrated as ring-type electrodes which are configured for tissue ablation (e.g., for shaping articular cartilage or chondral defects), one or both electrodes 226, 228 may be shaped into other electrode configurations to effect other treatments, such as tissue cutting or resection. Additionally, one or both electrodes 226, 228 may include a fluid lumen 234, 236, respectively, for infusing a fluid such as saline and/or for drawing debris and fluid back into the openings. Both electrodes 226, 228 may be electrically isolated from one another as well as from common return electrode 232 by insulator 230. Such an assembly utilizing multiple electrodes in different configurations may allow the user to utilize a single device for treating different tissue regions within, e.g., a joint, where space is limited without having to withdraw and introduce multiple instruments into the tissue region.
Yet another variation is shown in the perspective view of electrode assembly 252 disposed upon instrument 250 in
In utilizing the two or more active electrodes on a single electrosurgical instrument in any of variations described herein, a relay or switch may be used to select which of the electrodes are powered to deliver the output energy. An illustration of a relatively simple switch is shown in the schematic illustration of
The example in
In yet additional variations where an electrode assembly has more than two electrodes, each electrically isolated electrode 286, 290, 294, 298 may each include an individually actuatable relay 288, 292, 296, 300, respectively, as illustrated in
Each of the isolated electrodes may be designed such that each includes a voltage and/or current measurement device to measure each applied parameter.
An example of this is determination is illustrated by the activation of electrode 286 with relay 288 contacting the circuit. As the tissue is treated, voltage meter 304 and ammeter 306 may monitor their respective signals which are used to calculate load impedance. When the load impedance reaches a predetermined threshold level, the system may be configured to then actuate relay 292 to activate electrode 290. This process may be repeated until all relays have been actuated and all electrodes are activated. Alternatively, the processor may be configured to activate subsequent electrodes based upon the measured current or the delivered power to minimize any current or power spikes initially delivered to the electrodes to facilitate the ablative effects on the tissue being treated.
With the potential of activating multiple electrodes, one method for limiting the power that can be delivered to each electrode is shown in the schematic illustration of
While a single power supply may be shared between multiple numbers of electrodes, another variation for delivering power to multiple electrodes is shown in
Other modifications and variations can be made to the disclosed embodiments without departing from the subject invention. For example, other numbers and arrangements of the active electrodes and their methods for use are possible. Similarly, numerous other methods of ablating or otherwise treating tissue using electrosurgical probes will be apparent to the skilled artisan. Moreover, the instruments and methods described herein may be utilized in other regions of the body (e.g., shoulder, knee, etc.) and for other tissue treatment procedures (e.g., chondroplasty, menisectomy, etc.). Thus, while the exemplary embodiments have been described in detail, by way of example and for clarity of understanding, a variety of changes, adaptations, and modifications will be obvious to those of skill in the art. Therefore, the scope of the present invention is limited solely by the appended claims.
