US 20060189971 A1
Systems, apparatus, and methods are provided for promoting blood flow to a target tissue. In one aspect, the invention involves canalizing or boring channels, divots, trenches or holes through an avascular connective tissue, or through a tissue having sparse vascularity, such as a tendon or a meniscus, in order to increase blood flow within the tissue. In one method, an active electrode is positioned in close proximity to a target site on a tendon, and a high frequency voltage difference is applied between the active electrode and a return electrode to selectively ablate tendon tissue at the target site, thereby forming a channel or void in the tendon. The active electrode(s) may be moved relative to the tendon during, or after, the application of electrical energy to damage or sculpt a void within the tendon, such as a hole, channel, crater, or the like. In another aspect of the invention, an electrosurgical probe is used to elicit a wound healing response in a target tissue, such as an injured tendon, in order to stimulate vascularization of the target tissue. The present invention may also be used for vascularization of a torn or damaged tissue in conjunction with a surgical repair procedure.
1. An electrosurgical method of treating fasciitis, comprising:
positioning an active electrode in close proximity to a target fascia, the active electrode disposed on a distal end of a shaft; and
applying a high frequency voltage across the active electrode and a return electrode, the high frequency voltage sufficient to facilitate healing of the fascia.
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23. An electrosurgical method of stimulating the wound healing response in fascia, comprising:
energizing an active electrode with a high frequency voltage, the active electrode disposed on the distal end of a shaft; and
transferring energy from the active electrode to the fascia sufficient to induce a healing response.
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This application is a continuation of U.S. patent application Ser. No. 10/372,591 filed Feb. 21, 2003, which is a divisional of U.S. patent application Ser. No. 09/845,034, now U.S. Pat. No. 6,805,130 which claims priority from U.S. Provisional Application No. 60/200,712, filed Apr. 27, 2000, now abandoned, and is a continuation-in-part of U.S. patent application Ser. No. 09/089,012, filed Jun. 2, 1998, now U.S. Pat. No. 6,102,046 which is a continuation-in-part of U.S. patent application Ser. No. 08/753,227, filed on Nov. 22, 1996, now U.S. Pat. No. 5,873,855, which is a continuation-in-part of U.S. patent application Ser. No. 08/562,331, filed on Nov. 22, 1995, now U.S. Pat. No. 5,683,366, the complete disclosures of which are incorporated herein by reference for all purposes.
The present invention is related to commonly assigned co-pending U.S. patent application Ser. No. 08/990,374, filed Dec. 15, 1997 (Attorney Docket No. E-3), which is a continuation-in-part of U.S. patent application Ser. No. 08/485,219, filed on Jun. 7, 1995, now U.S. Pat. No. 5,697,281 (Attorney Docket 16238-000600), U.S. patent application Ser. Nos. 09/058,571, 08/874,173 and 09/002,315, filed on Apr. 10, 1998, Jun 13, 1997, and Jan. 2, 1998, respectively (Attorney Docket Nos. CB-2, 16238-005600 and C-9, respectively) and U.S. patent application Ser. No. 09/054,323, filed on Apr. 2, 1998 (Attorney Docket No. E-5), U.S. patent application Ser. No. 09/010,382, filed Jan. 21, 1998 (Attorney Docket A-6), and U.S. patent application Ser. No. 09/032,375, filed Feb. 27, 1998 (Attorney Docket No. CB-3), U.S. patent application Ser. No. 08/977,845, filed on Nov. 25, 1997 (Attorney Docket No. D-2), Ser. No. 08/942,580, filed on Oct. 2, 1997 (Attorney Docket No. 16238-001300), Ser. No. 09/026,851, filed Feb. 20, 1998 (Attorney Docket No. S-2), U.S. patent application Ser. No. 08/753,227, filed on Nov. 22, 1996 (Docket 16238-002200), U.S. patent application Ser. No. 08/687792, filed on Jul. 18, 1996 (Docket No. 16238-001600), and PCT International Application, U.S. National Phase Serial No. PCT/US94/05168, filed on May 10, 1994, now U.S. Pat. No. 5,697,909 (Attorney Docket 16238-000440), which was a continuation-in-part of U.S. patent application Ser. No. 08/059,681, filed on May 10, 1993 (Attorney Docket 16238-000420), which was a continuation-in-part of U.S. patent application Ser. No. 07/958,977, filed on Oct. 9, 1992 (Attorney Docket 16238-000410), now U.S. Pat. No. 5,366,443, which was a continuation-in-part of U.S. patent application Ser. No. 07/817,575, filed on Jan. 7, 1992 (Attorney Docket 16238-00040), now abandoned, the complete disclosures of which are incorporated herein by reference for all purposes.
The present invention relates generally to the field of electrosurgery and, more particularly, to surgical devices and methods that employ high frequency electrical energy to increase the flow of blood to a target tissue.
Coronary artery disease, the build up of atherosclerotic plaque on the inner walls of the coronary arteries, causes the narrowing or complete closure of these arteries resulting in insufficient blood flow to the heart. A number of approaches have been developed for treating coronary artery disease. In less severe cases, it is often sufficient to treat the symptoms with pharmaceuticals and lifestyle modification to lessen the underlying causes of the disease. In more severe cases a coronary artery blockage can often be treated using endovascular techniques, such as balloon angioplasty, laser recanalization, placement of stents, and the like.
In cases where pharmaceutical treatment and endovascular approaches have failed or are likely to fail, it is often necessary to perform a coronary artery bypass graft (CABG) procedure using open or thoracoscopic surgical methods. For example, many patients still require bypass surgery due to such conditions as the presence of extremely diffuse stenotic lesions, the presence of total occlusions and the presence of stenotic lesions in extremely tortuous vessels. However, some patients are too sick to successfully undergo bypass surgery. For other patients, previous endovascular and/or bypass surgery attempts have failed to provide adequate revascularization of the heart muscle.
Laser myocardial revascularization (LMR) is a recent procedure developed with the recognition that myocardial circulation occurs through arterioluminal channels and myocardial sinusoids in the heart wall, as well as through the coronary arteries. In LMR procedures, artificial channels are formed in the myocardium with laser energy to provide blood flow to ischemic heart muscles by utilizing the heart's ability to perfuse itself from these artificial channels through the arterioluminal channels and myocardial sinusoids. In one such procedure, a CO2 laser is utilized to vaporize tissue and produce channels in the heart wall from the epicardium through the endocardium to promote direct communication between blood within the ventricular cavity and that of existing myocardial vasculature. The laser energy is typically transmitted from the laser to the epicardium by an articulated arm device. Recently, a percutaneous method of LMR has been developed in which an elongated flexible laser apparatus is attached to a catheter and guided endoluminally into the patient's heart. The inner wall of the heart is irradiated with laser energy to form a channel from the endocardium into the myocardium for a desired distance.
While recent techniques in LMR have been promising, they also suffer from a number of drawbacks inherent with laser technology. One such drawback is that the laser energy must be sufficiently concentrated to form channels through the heart tissue, which reduces the diameter of the channels formed by LMR. In addition, free beam lasers generally must completely form each artificial lumen or revascularizing channel during the still or quiescent period of the heart beat. Otherwise, the laser beam will damage surrounding portions of the heart as the heart beats and thus moves relative to the laser beam. Consequently, the surgeon must typically form the channel in less than about 0.08 seconds, which requires a relatively large amount of energy. This further reduces the size of the channels that may be formed with a given amount of laser energy. Applicant has found that the diameter or minimum lateral dimension of these artificial channels may have an effect on their ability to remain open. Thus, the relatively small diameter channels formed by existing LMR procedures (typically on the order of about 1 mm or less) may begin to close after a brief period of time, which reduces the blood flow to the heart tissue.
Another drawback with current LMR techniques is that it is difficult to precisely control the location and depth of the channels formed by lasers. For example, the speed in which the revascularizing channels are formed often makes it difficult to determine when a given channel has pierced the opposite side of the heart wall. In addition, the distance to which the laser beam extends into the heart tissue is difficult to control, which can lead to laser irradiation with heating or vaporization of blood or heart tissue within the ventricular cavity. For example, when using the LMR technique in a pericardial approach (i.e., from the outside surface of the heart to the inside surface), the laser beam may not only pierce through the entire wall of the heart but may also irradiate blood within the heart cavity. As a result, one or more blood thromboses or clots may be formed which can lead to vascular blockages elsewhere in the circulatory system. Alternatively, when using the LMR technique in an endocardial approach (i.e., from the inside surface of the heart toward the outside surface), the laser beam may not only pierce the entire wall of the heart but may also irradiate and damage tissue surrounding the outer boundary of the heart.
The promotion of blood flow to tissue, e.g., via canalization, vascularization or revascularization, is desirable in areas of the body other than the heart. The degenerative changes in the musculoskeletal system can be attributed to aging, trauma, overuse, and diminished focal blood supply. Degenerative changes of the musculoskeletal system are ubiquitous, particularly in the shoulder, knee, elbow, or the like. Conditions such as rotator cuff tendinitis, patellar tendinitis, tennis elbow, and plantar fasciitis are extremely common, and yet have no well-defined minimally invasive treatment protocol. Typically, the treatment consists of physical therapy, non-steroidal anti-inflammatories, and occasionally surgery. Recently in Europe, surgeons have begun using lithotrypsy, receiving only equivocal results.
One example of an area of the body that would benefit from vascularization is the meniscus tissue. The meniscus tissue, a C-shaped piece of fibrocartilage located at the peripheral aspect of the joint, typically has very little blood supply (particularly the inner portions of the meniscus). For that reason, when damaged, the meniscus is unable to undergo the normal healing process that occurs in most other tissues of the body. In addition, with age, the meniscus begins to deteriorate, often developing degenerative tears. Typically, when the meniscus is damaged, the torn pieces begins to move in an abnormal fashion inside the joint. Because the space between the bones of the joint is very small, as the abnormally mobile piece of meniscal tissue (meniscal fragment) moves, it may become caught between the bones of the joint (femur and tibia). When this happens, the knee becomes painful, swollen and difficult to move.
Another example of an area of the body that would benefit from vascularization is the tendons. When a tendon is damaged, the tendon usually forms tiny tears which allow collagen to leak from the injured areas. The collagen leakage causes inflammation of the tendon that can cut off the flow of blood and pinch the surrounding nerves. Because tendons are inherently poorly vascularized, and receive less oxygen, nutrients, and blood flow, as compared with other tissues and organs, tendons tend to heal much more slowly than other tissues of the body. Accordingly, there is a need for apparatus and methods to canalize, vascularize, revascularize, and/or increase blood flow to tendons that have been torn or otherwise damaged, so as to stimulate, expedite, or facilitate the healing process.
The present invention provides systems, apparatus and methods for selectively applying electrical energy to structures within or on the surface of a patient's body. The systems, apparatus, and methods of the present invention are particularly useful for treating acute and chronic musculoskeletal or neurological injuries and disorders, such as strains, sprains, tendinitis, fasciitis, arthritis, bursitis and tenosynovitis. In particular, the systems and methods of the present invention are useful for increasing blood flow to a target tissue, by canalization of tissue, stimulating the body's wound healing responses, such as inducing vascularization of tissue, stimulating collagen growth, altering cellular function, or other metabolic or physiologic events that promote healing and regeneration of injured tissue.
Systems and apparatus according to the present invention generally include an electrosurgical probe or catheter having a shaft with proximal and distal ends, one or more active electrode(s) at the distal end, and one or more connectors for coupling the active electrode(s) to a source of high frequency electrical energy. The distal end portion of the shaft will usually have a diameter of less than 3 mm, preferably less than 1 mm. The active electrode(s) are preferably supported within an electrically insulating support member typically formed of an inorganic material, such as a ceramic, a silicone rubber, or a glass.
In one method of the present invention, an active electrode is positioned in close proximity to tissue at a target site, and a high frequency voltage difference is applied between an active electrode and a return electrode to volumetrically remove or ablate tissue at the target site. The active electrode(s) may be translated or otherwise moved relative to the body structure during or after the application of electrical energy to form a void within the body structure, such as a hole, channel, stripe, crater, divot, surface damage, or the like. In some embodiments, the active electrode(s) are axially moved toward the body structure to volumetrically remove one or more channel(s), divot(s) or hole(s) through a portion of the structure. In other embodiments, the active electrode(s) are moved across the body structure to remove one or more stripe(s) or channel(s) of tissue. In most embodiments, electrically conductive fluid, such as isotonic saline, is located between the active electrode(s) and the body structure. In the bipolar modality, the conductive fluid generates a current flow path between the active electrode(s) and one or more return electrode(s). High frequency voltage is then applied between the active electrode(s) and the return electrode(s) through the current flow path created by the electrically conductive fluid.
In one aspect of the invention, a method is provided for vascularization or revascularization of a tendon, ligament, or meniscus. The present invention may be useful for acute muscle or tendon injury, iliotibial band syndrome, tendinitis, fasciitis, bursitis, tenosynovitis, strains, sprains and the like. In one embodiment of the present invention, artificial channels, holes, craters, or lumens are created during this procedure to vascularize the tendon and/or facilitate the healing process. In another embodiment, sufficient RF energy is applied to the tendon to vascularize a region around the target site without creating a hole, channel, crater or the like, in the tendon. According to the present invention, one or more active electrodes can be positioned adjacent to the tendon, and a voltage applied between the active electrode(s) and one or more return electrode(s). In an exemplary configuration, a high frequency voltage heats, damages, and/or ablates, (i.e. volumetrically removes) at least a portion of the tissue to be treated. The active electrode(s) can be advanced axially into the space vacated by the removed tissue to bore a channel through the tissue.
In one specific configuration, a void, hole, or crater is formed in the tendon by molecular dissociation or disintegration of tissue components. In these embodiments, the high frequency voltage applied to the active electrode(s) is sufficient to vaporize an electrically conductive fluid (e.g., a gel or isotonic saline) between the active electrode(s) and the tissue. Within the vaporized fluid, an ionized plasma is formed and charged particles (e.g., electrons) cause the molecular breakdown or disintegration of the tissue, perhaps to a depth of several cell layers. This molecular dissociation of tissue components is accompanied by the volumetric removal of the tissue. This process can be precisely controlled to effect the volumetric removal of tissue to a depth in the range of from about 10 microns to 150 microns, with minimal heating of, or damage to, surrounding or underlying tissue. A more complete description of this phenomenon is described in commonly assigned U.S. Pat. No. 5,683,366, the complete disclosure of which is incorporated by reference herein.
One of the advantages of the present invention, particularly over previous methods involving lasers, is that the surgeon can more precisely control the location, depth, and diameter of the vascularizing channels formed in the tissue. The ability to precisely control the volumetric removal of tissue results in a field of tissue ablation or removal that is very defined, consistent, and predictable. This precise control of tissue treatment also helps to minimize, or completely eliminate, damage to healthy tissue structures, such as muscles, cartilage, bone, and/or nerves, which may be adjacent to the target tissue. In addition, any severed blood vessels at the target site may be simultaneously cauterized and sealed as the tissue is removed to continuously maintain hemostasis during the procedure. This increases the surgeon's field of view, and expedites the procedure. In one embodiment, the active electrode can remain in contact with the tendon tissue as the high frequency voltage ablates this tissue (or at least substantially close to the tissue, e.g., usually on the order of about 0.1 mm to 2.0 mm, and preferably about 0.1 mm to 1.0 mm). This preserves tactile sense and allows the surgeon to more accurately determine when to terminate cutting of a given channel so as to minimize damage to surrounding tissues and/or to minimize bleeding.
In open procedures, or in procedures in “dry” fields, the apparatus may further include a fluid delivery element for delivering electrically conductive fluid to the active electrode(s) and the target site. The fluid delivery element may be located on the probe, e.g., in the form of a fluid lumen or tube, or it may be part of a separate instrument. In arthroscopic procedures, however, the surgical area surrounding the tendon will typically be filled with electrically conductive fluid (e.g., isotonic saline) so that the apparatus need not have a fluid delivery element. In both embodiments, the electrically conductive fluid will preferably generate a current flow path between the active electrode(s) and one or more return electrode(s). In an exemplary embodiment, the return electrode is located on the probe and spaced a sufficient distance from the active electrode(s) to substantially avoid or minimize current shorting therebetween and to shield the return electrode from tissue at the target site.
According to one aspect of the invention, there is provided an electrosurgical system including a probe having a shaft and an electrode assembly disposed on the shaft; an arthroscope for passing at least a distal end portion of the shaft therethrough; and a sensing unit adapted for determining a boundary of a target tissue. The sensing unit may include an element, such as an ultrasonic transducer, located on the shaft distal end, and an ultrasonic generator. The system may further include an adjustable mechanical stop for limiting the maximum travel of the shaft within a target tissue. The electrode assembly typically includes at least one active electrode and a return electrode. The system further includes a high frequency power supply for applying a high frequency voltage between the active and return electrodes. In one embodiment, the sensing unit may be coupled to the power supply, and the system configured to shut off power from the power supply according to a location of the shaft distal end in relation to a target tissue.
In one aspect, the invention provides a method for treating a damaged or poorly vascularized tissue, such as a meniscus of a joint, or a tendon. In one embodiment one or more channels or voids are formed in a target tissue via selective electrosurgical ablation of the tissue. One or more implants may be inserted in the one or more channels. In one embodiment, at least one channel bridges a lesion in the target tissue, and an implant inserted in the channel serves as a splint. In another embodiment, an implant is inserted in a channel to maintain patency in the channel, the channel serving as a conduit for blood flow within the target tissue, and the implant serving as a stent. In a further embodiment, an implant is inserted in a channel to promote hemostasis of the channel. In yet another embodiment, a stent is inserted in a distal portion of a channel, and a hemostasis plug is inserted in a proximal portion of the channel.
In another aspect, the invention provides a method for increasing blood flow to a target tissue by eliciting a wound healing response in the target tissue. In one embodiment, the wound healing response is elicited by the controlled application of heat thereto. Typically, the target tissue is heated using an electrosurgical probe to deliver high frequency, or radio frequency (RF), electrical energy thereto. Usually, the target tissue is heated to a temperature less than about 150° C.
For a further understanding of the nature and advantages of the invention, reference should be made to the following description taken in conjunction with the accompanying drawings.
The present invention provides systems, apparatus and methods for selectively applying electrical energy to a target location within or on a patient's body. In particular, the present invention provides systems, devices and methods for vascularizing a target tissue and for increasing blood flow to a region of tissue. In one aspect of the invention, blood flow within the heart is increased by creating lesions, such as artificial channels or lumens, within the myocardium. In another aspect of the invention, musculoskeletal injuries and disorders, such as strains, sprains, tendinitis, fasciitis, arthritis, bursitis and tenosynovitis, are treated by stimulating the body's wound healing response at the area treated. This wound healing response can include the stimulation of greater blood flow, collagen growth, as well as alteration of cellular function or of other metabolic events that promote healing and regeneration of injured tissue through a number of physiologic effects. In one specific embodiment, blood flow is increased to inner aspects of the meniscus by creating damage such as artificial channels or lumens from the outer aspect of the meniscus (which usually has a blood supply). In another specific embodiment, blood flow in a tendon is increased by creating damage to the tendon to invoke a would healing response.
It should be appreciated that the systems, devices, and methods of the invention can be applied equally well to procedures involving other tissues of the body, as well as to other procedures including open procedures, intravascular procedures, urological, laparoscopic, arthroscopic, thoracoscopic or other cardiac procedures, as well as dermatological, orthopedic, gynecological, otorhinolaryngological, spinal, and neurologic procedures, oncology and the like. For convenience, the remaining disclosure will be directed primarily to the revascularization of the heart, and to vascularization of meniscus tissue, and tendons.
In the present invention, a high frequency (RF) electrical energy is 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, the present invention may be used to: (1) create controlled damage to tissue; (2) volumetrically remove tissue, including bone and cartilage (i.e., ablate or effect molecular dissociation of the tissue structure); (3) form holes, channels, divots, or other spaces within tissue (4) cut or resect tissue; (5) shrink or contract collagen-containing connective tissue; and/or (6) coagulate severed blood vessels.
In one method, a target tissue is volumetrically removed or ablated. In this procedure, a high frequency voltage difference is applied between one or more active electrode(s) and one or more return electrode(s) to develop high electric field intensities in the vicinity of the target tissue. The high electric field intensities adjacent the active electrode(s) lead to electric field induced molecular breakdown of target tissue by molecular dissociation of tissue components (rather than by thermal evaporation or carbonization). Applicant believes that the tissue structure is volumetrically removed through molecular disintegration of larger organic molecules into smaller molecules and/or atoms, such as hydrogen, oxygen, oxides of carbon, hydrocarbons and nitrogen compounds. This molecular disintegration completely removes the tissue structure, as opposed to dehydrating the tissue material by the removal of water from within the cells of the tissue, as is typically the case with conventional 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 liquid, such as isotonic saline or blood, delivered to the target site, or a viscous fluid, such as a gel, applied to the target site. Since the vapor layer or vaporized region has a relatively high electrical impedance, it minimizes current flow into the electrically conductive fluid. This ionization, under the conditions described herein, induces the discharge of energetic electrons and photons from the vapor layer and 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.
The present invention applies high frequency, or radio frequency (RF), electrical energy in an electrically conductive fluid environment to remove (i.e., resect, cut, or ablate) a target tissue structure, and to seal transected vessels within the region of the target tissue. The present invention is particularly useful for sealing larger arterial vessels, e.g., on the order of 1 mm or greater. In some embodiments, a high frequency power supply is provided having an ablation mode, wherein a first voltage is applied to an active electrode sufficient to effect molecular dissociation or disintegration of the tissue, and a coagulation mode, wherein a second, lower voltage is applied to an active electrode (either the same or a different electrode) sufficient to achieve hemostasis of severed vessels within the tissue. In other embodiments, an electrosurgical instrument is provided having one or more coagulation electrode(s) configured for sealing a severed vessel, such as an arterial vessel, and one or more active electrodes configured for either contracting collagen fibers within the tissue or removing (ablating) the tissue, e.g., by applying sufficient energy to the tissue to effect molecular dissociation of the tissue components. In the latter embodiments, the electrosurgical system or apparatus may be configured such that a single voltage can be applied to coagulate with the coagulation electrode(s), and to ablate target tissue with the active electrode(s). In other embodiments, the power supply is combined with the electrosurgical instrument such that the coagulation electrode is used when the power supply is in the coagulation mode (low voltage), and the active electrode(s) are used when the power supply is in the ablation mode (higher voltage).
The present invention is also useful for removing or ablating tissue around nerves, such as spinal, visceral, or cranial nerves, e.g., the olfactory nerve on either side of the nasal cavity, the optic nerve within the optic and cranial canals, the palatine nerve within the nasal cavity, soft palate, uvula and tonsil, etc. One of the significant drawbacks with prior art mechanical cutters and lasers is that these devices do not differentiate between the target tissue and the surrounding nerves or bone. Therefore, the surgeon must be extremely careful during these procedures to avoid damage to the bone or nerves within and around the nasal cavity. In the present invention, the Coblation™ process for removing tissue completely avoids damage to non-target tissue, or results in extremely small depths of collateral tissue damage, as discussed above. This allows the surgeon to remove tissue close to a nerve without causing collateral damage to the nerve fibers. A more complete description of this phenomenon can be found in co-pending U.S. patent application Ser. No. 09/032,375, filed Feb. 27, 1998 (Attorney Docket No. CB-3), the complete disclosure of which is incorporated herein by reference.
In one method of the present invention, one or more active electrodes are brought into close proximity to tissue at a target site, and the power supply is activated in the ablation mode such that sufficient voltage is applied between the active electrodes and the return electrode to volumetrically remove the tissue via molecular dissociation, as described below. During this process, vessels within the tissue may be severed. Smaller vessels will be automatically sealed with the system and method of the present invention. Larger vessels, and those with a higher flow rate, such as arterial vessels, may not be automatically sealed while the system is operating in the ablation mode. In these cases, the severed vessels may be sealed by activating a control (e.g., a foot pedal) to reduce the voltage of the power supply into the coagulation mode. In this mode, the active electrodes may be pressed against the severed vessel to provide sealing and/or coagulation of the vessel. Alternatively, a coagulation electrode located on the same or a different instrument may be pressed against the severed vessel. Once the vessel is adequately sealed, the surgeon may activate a control (e.g., another foot pedal) to increase the voltage of the power supply back into the ablation mode.
The electrosurgical instrument will comprise a shaft having a proximal end and a distal end which supports an active electrode. The shaft may assume a wide variety of configurations, with the primary purpose being to mechanically support one or more active electrode and to permit the surgeon to manipulate the electrode(s) from the proximal end of the shaft. Usually, an electrosurgical probe shaft will be a narrow-diameter rod or tube, more usually having dimensions which permit it to be introduced into a body cavity, such as the thoracic cavity, through an associated trocar or cannula in a minimally invasive procedure, such as arthroscopic, laparoscopic, thoracoscopic, and other endoscopic procedures. Thus, the probe shaft will typically have a length of at least 5 cm for open procedures and at least 10 cm, more typically being 20 cm, or longer for endoscopic procedures. The probe shaft will typically have a diameter of at least about 0.5 mm, and will frequently be in the range from about 1 mm to 10 mm.
The electrosurgical probe may be delivered percutaneously (endoluminally) by insertion through a conventional or specialized guide catheter, or the invention may include a catheter having an active electrode array integral with its distal end. A shaft of the catheter may be rigid or flexible, with flexible shafts optionally being combined with a generally rigid external tube to provide mechanical support. Flexible shafts may be combined with pull wires, shape memory actuators, and other mechanisms for effecting selective deflection of the distal end of the shaft to facilitate positioning of the electrode or electrode array. Such mechanisms are known to the skilled artisan. The shaft of the probe or catheter will usually include a plurality of wires or other conductive elements running axially therethrough to permit connection of the electrode or electrode array and the return electrode to a connector at the proximal end of the shaft. Specific shaft designs will be described in detail in connection with the figures hereinafter.
The active electrode(s) are preferably supported within or by an electrically insulating support positioned near the distal end of the instrument shaft, e.g., a catheter body. The return electrode may be located on the instrument shaft, on another instrument, or on the external surface of the patient (i.e., a dispersive pad). When the present invention is used in close proximity to the heart, a bipolar design is more preferable because this minimizes the current flow through heart tissue. Accordingly, the return electrode is preferably either integrated with the catheter body, or with another instrument located in close proximity to the distal end of the catheter body. The proximal end of the catheter will include the appropriate electrical connections for coupling the return electrode(s) and the active electrode(s) to a high frequency power supply, such as an electrosurgical generator.
The current flow path between the active electrodes and the return electrode(s) may be generated by submerging the tissue site in an electrically conductive fluid (e.g., a viscous fluid, such as an electrically conductive gel), or by directing an electrically conductive fluid through a fluid outlet along a fluid path to the target site (i.e., a liquid, such as isotonic saline, or a gas, such as argon). The conductive gel may also be delivered to the target site to achieve a slower more controlled delivery rate of conductive fluid. In addition, the viscous nature of the gel may allow the surgeon to more easily contain the gel around the target site (e.g., as compared with containment of a liquid, such as isotonic saline). A more complete description of an exemplary method of directing electrically conductive fluid between active and return electrodes is described in U.S. Pat. No. 5,697,281, the contents of which are incorporated by reference herein in their entirety. Alternatively, the body's natural conductive fluids, such as blood, may be sufficient to establish a conductive path between the return electrode(s) and the active electrode(s), and to provide the conditions for establishing a vapor layer, as described above. Advantageously, a liquid electrically conductive fluid (e.g., isotonic saline) may be used to concurrently “bathe” the target tissue surface, to provide an additional means for removing any resected tissue fragments, and to cool the tissue at the target site during ablation.
In some embodiments, the electrode support and the fluid outlet may be recessed from an outer surface of the instrument or handpiece to confine the electrically conductive fluid to the region immediately surrounding the electrode support. In addition, the shaft may be shaped so as to form a cavity around the electrode support and the fluid outlet. This helps to assure that the electrically conductive fluid will remain in contact with the active electrode(s) and the return electrode(s) to maintain the conductive path therebetween. In addition, this will help to maintain a vapor layer and subsequent plasma layer between the active electrode(s) and the tissue at the treatment site throughout the procedure, which reduces the thermal damage that might otherwise occur if the vapor layer were extinguished due to a lack of conductive fluid. Provision of the electrically conductive fluid around the target site also helps to maintain the tissue temperature at desired levels.
The electrically conductive fluid should possess an electrical conductivity value above a minimum threshold level, in order to provide a suitable conductive path between the return electrode and the active electrode(s). The electrical conductivity of the fluid (in units of milliSiemens per centimeter or mS/cm) will usually be greater than about 0.2 mS/cm, typically will be greater than about 2 mS/cm and more typically greater than about 10 mS/cm. In an exemplary embodiment, the electrically conductive fluid is isotonic saline, which has a conductivity of about 17 mS/cm.
In some procedures, it may also be necessary to retrieve or remove, e.g., aspirate, any excess electrically conductive fluid and/or ablation by-products from the surgical site. For example, in procedures in and around the heart, or within blood vessels, it may be desirable to aspirate the fluid so that it does not enter the circulatory system. In addition, it may be desirable to aspirate small pieces of tissue fragments that are not completely disintegrated by the high frequency energy, or other fluids at the target site, such as blood, mucus, etc. Accordingly, the system of the present invention may include one or more suction lumen(s) in the instrument, or on another instrument, coupled to a suitable vacuum source for aspirating fluids from the target site. In some embodiments, the instrument also includes one or more aspiration electrode(s) coupled to the aspiration lumen for inhibiting clogging during aspiration of tissue fragments from the surgical site. A more complete description of these embodiments can be found in commonly assigned co-pending Application Ser. No. 09/010,382, filed Jan. 21, 1998 (Attorney Docket No. A-6), the complete disclosure of which is incorporated herein by reference for all purposes.
As an alternative to, or in addition to suction, it may be desirable to contain the excess electrically conductive fluid, tissue fragments and/or gaseous products of ablation at or near the target site with a containment apparatus, such as a basket, retractable sheath or the like. This embodiment has the advantage of ensuring that the conductive fluid, tissue fragments or ablation by-products do not flow into the heart or lungs. In addition, it may be desirable to limit the amount of suction to limit the undesirable effect suction may have on hemostasis of severed blood vessels within heart tissue.
The present invention may use a single electrode or an electrode array distributed over a distal contact surface of the electrosurgical instrument. In both configurations, the circumscribed area of the electrode or electrode array will generally depend on the desired diameter of the revascularizing channel. For example, applicant has found that smaller diameter channels tend to remain patent for a shorter period of time than larger diameter channels. Thus, a relatively large diameter channel (on the order of about 1.5 mm to 3.0 mm) may be desired to improve lumen patency. The ability to select the diameter of the artificial channels is one of the advantages of the present invention over existing laser procedures, which are typically limited by the concentration of light that is required to generate sufficient energy to ablate the tissue during the still or quiescent period of the heart (i.e., about 0.08 seconds). Usually, the area of the electrode array is in the range of from about 0.25 mm2 to 20 mm2, preferably from about 0.5 mm2 to 10 mm2, and more preferably from about 0.5 mm2 to 5.0 mm2. In addition, the shape of the array and the distal end of the instrument shaft will also depend on the desired surface area of the channel. For example, the ratio of the perimeter of the electrode array to the surface area of the electrodes may be maximized to increase blood flow from the channel to the surrounding myocardial tissue. Each electrode may take the form of a solid round wire, or a wire having other solid cross-sectional shapes such as squares, rectangles, hexagons, triangles, star-shaped, or the like, to provide a plurality of edges around the distal perimeter of the electrodes. Alternatively, each electrode may be in the form of a hollow metal tube having a cross-sectional shape which is round, square, hexagonal, rectangular or the like. The envelop or effective diameter of the individual electrode(s) ranges from about 0.05 mm to 3 mm, preferably from about 0.1 mm to 2 mm.
The electrode array will usually include at least one isolated active electrode, and in some embodiments may include at least four active electrodes, sometimes at least six active electrodes, and often 50 or more active electrodes, disposed over the distal contact surface(s) on the shaft. By bringing the electrode array(s) on the contact surface(s) in close proximity with the target tissue and applying high frequency voltage between the array(s) and an additional common or return electrode in direct or indirect contact with the patient's body, the target tissue is selectively damaged, ablated or cut, permitting selective removal of portions of the target tissue while desirably minimizing the depth of necrosis to surrounding tissue.
As described above, the present invention may use a single active electrode or an electrode array distributed over a distal contact surface of an electrosurgical instrument, such as a probe, a catheter or the like. The electrode array usually includes a plurality of independently current-limited and/or power-controlled active electrodes to apply electrical energy selectively to the target tissue while limiting the unwanted application of electrical energy to the surrounding tissue and environment resulting from power dissipation into surrounding electrically conductive fluids, such as blood, normal saline, and the like. The active electrodes may be independently current-limited by isolating the electrodes from each other and connecting each electrode to a separate power source that is isolated from the other active electrodes. Alternatively, the active electrodes may be connected to each other at either the proximal or distal ends of the probe to form a single wire that couples to a power source.
In one configuration, each individual active electrode in the electrode array is electrically insulated from all other active electrodes in the array within said instrument and is connected to a power source which is isolated from each of the other active electrodes in the array or to circuitry which limits or interrupts current flow to the active electrode when low resistivity material (e.g., blood, electrically conductive saline irrigant or electrically conductive gel) causes a lower impedance path between the return electrode and the individual active electrode. The isolated power sources for each individual active electrode may be separate power supply circuits having internal impedance characteristics which limit power to the associated active electrode when a low impedance return path is encountered. By way of example, the isolated power source may be a user selectable constant current source. In this embodiment, lower impedance paths will automatically result in lower resistive heating levels since the heating is proportional to the square of the operating current times the impedance. Alternatively, a single power source may be connected to each of the active electrodes through independently actuatable switches, or by independent current limiting elements, such as inductors, capacitors, resistors and/or combinations thereof. The current limiting elements may be provided in the instrument, connectors, cable, power supply, or elsewhere along the conductive path from the power supply or controller to the distal tip of the instrument. Alternatively, the resistance and/or capacitance may occur on the surface of the active electrode(s) due to oxide layers which form selected active electrodes (e.g., titanium or a resistive coating on the surface of metal, such as platinum).
The tip region of the instrument may comprise many independent active electrodes designed to deliver electrical energy in the vicinity of the tip. The selective application of electrical energy to the conductive fluid is achieved by connecting each individual active electrode and the return electrode to a power source having independently controlled or current limited channels. The return electrode(s) may comprise a single tubular member of conductive material proximal to the electrode array at the tip which also serves as a conduit for the supply of the electrically conductive fluid between the active and return electrodes. Alternatively, the instrument may comprise an array of return electrodes at the distal tip of the instrument (together with the active electrodes) to maintain the electric current at the tip. The application of high frequency voltage between the return electrode(s) and the electrode array results in the generation of high electric field intensities at the distal tips of the active electrodes with conduction of high frequency current from each individual active electrode to the return electrode. The current flow from each individual active electrode to the return electrode(s) is controlled by either active or passive means, or a combination thereof, to deliver electrical energy to the surrounding conductive fluid while minimizing energy delivery to surrounding (non-target) tissue.
The application of a high frequency voltage between the return electrode(s) and the active electrode(s) for appropriate time intervals effects cutting, removing, ablating, shaping, contracting or otherwise modifying the target tissue. The tissue volume over which energy is dissipated (i.e., over which a high current density exists) may be precisely controlled, for example, by the use of a multiplicity of small active electrodes whose effective diameters or principal dimensions range from about 5 mm to 0.01 mm, preferably from about 2 mm to 0.05 mm, and more preferably from about 1 mm to 0.1 mm. Electrodes (both circular and non-circular electrodes) will typically have a contact area (per active electrode) below about 25 mm2 for electrode arrays, and as large as 75 mm2 for single electrode embodiments, preferably being in the range from 0.0001 mm2 to 1 mm2, and more preferably from 0.005 mm2 to 0.5 mm2. The circumscribed area of the electrode array is in the range from 0.25 mm2 to 75 mm2, preferably from 0.5 mm2 to 40 mm2, and will usually include at least one, often at least two, isolated active electrodes, often at least five active electrodes, often greater than 10 active electrodes, and even 50 or more active electrodes, disposed over the distal contact surfaces on the shaft. The use of small diameter active electrodes increases the electric field intensity and reduces the extent or depth of tissue heating as a consequence of the divergence of current flux lines which emanate from the exposed surface of each active electrode.
The area of the tissue treatment surface can vary widely, and the tissue treatment surface can assume a variety of geometries, with particular areas and geometries being selected for specific applications. The active electrode surface(s) can have area(s) in the range from about 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 array(s) will be formed at the distal tip of the electrosurgical instrument 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 instrument shaft (e.g., in the manner of a spatula), facilitating access to certain body structures in endoscopic procedures.
In one embodiment, an electrosurgical catheter or probe comprises a single active electrode that extends from an electrically insulating member, e.g., comprising a silicone rubber, a glass, or a ceramic, at the distal end of the shaft. In one embodiment, the insulating member comprises a tubular structure that separates the active electrode from a tubular or annular return electrode positioned proximal to the insulating member and the active electrode. In another embodiment, the catheter or probe includes a single active electrode that can be rotated relative to the rest of the catheter body, or the entire catheter may be rotated related to the lead. The single active electrode can be positioned adjacent the abnormal tissue (e.g., calcified deposits), energized, and rotated as appropriate to remove this tissue.
It should be clearly understood that the invention is not limited to electrically isolated active electrodes, or even to a plurality of active electrodes. For example, the array of active electrodes may be connected to a single lead that extends through the instrument shaft to a power source of high frequency current. Alternatively, the instrument may incorporate a single electrode that extends directly through the catheter shaft or is connected to a single lead that extends to the power source. The active electrode(s) may have ball shapes (e.g., for tissue vaporization and desiccation), twizzle shapes (for vaporization and needle-like cutting), spring shapes (for rapid tissue debulking and desiccation), twisted metal shapes, annular or solid tube shapes, or the like. Alternatively, the electrode(s) may comprise a plurality of filaments, rigid or flexible brush electrode(s) (for debulking a tumor, such as a fibroid, bladder tumor or a prostate adenoma), side-effect brush electrode(s) on a lateral surface of the shaft, coiled electrode(s), or the like.
The power supply may include a fluid interlock for interrupting power to the active electrode(s) when there is insufficient electrically conductive fluid around the active electrode(s). This ensures that the instrument will not be activated when conductive fluid is not present, minimizing the tissue damage that may otherwise occur. A more complete description of such a fluid interlock can be found in commonly assigned, co-pending U.S. application Ser. No. 09/058,336, filed Apr. 10, 1998 (attorney Docket No. CB-4), the complete disclosure of which is incorporated herein by reference.
The voltage difference applied between the return electrode(s) and the active electrode(s) will 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 (e.g., contraction, coagulation, cutting or ablation). Typically, the peak-to-peak voltage for ablation or cutting of tissue will be in the range of from about 10 volts to 2000 volts, usually in the range of 200 volts to 1800 volts, and more typically in the range of about 300 volts to 1500 volts, often in the range of about 500 volts to 900 volts peak to peak (again, depending on the electrode size, the operating frequency and the operation mode). Lower peak-to-peak voltages will be used for tissue coagulation or collagen contraction and will typically be in the range from 50 to 1500, preferably from about 100 to 1000, and more preferably from about 120 to 600 volts peak-to-peak.
As discussed above, the voltage is usually delivered in a series of voltage pulses or alternating current of time varying voltage amplitude with a sufficiently high frequency (e.g., on the order of 5 kHz to 20 MHz) such that the voltage is effectively applied continuously (as compared with e.g., lasers claiming small depths of necrosis, which are generally pulsed about 10 Hz to 20 Hz). In addition, the duty cycle (i.e., cumulative time in any one-second interval that energy is applied) is on the order of about 50% for the present invention, as compared with pulsed lasers which typically have a duty cycle of about 0.0001%. With the above voltage and current ranges, applicant has found that the electrosurgical instrument will usually bore a channel completely through the heart wall in about 0.5 seconds to 20.0 seconds, preferably about 1.0 second to 3.0 seconds in the continuous mode, and preferably about 10 seconds to 15 seconds in the pulsed mode. It has been found that channels that are approximately 0.5 mm to 3.0 mm in diameter and approximately 1 cm to 4 cm deep may be easily and efficiently formed in the heart wall by this method, and that the revascularization procedure dramatically improves the flow of blood to the heart muscle.
The capability to form the desired channel over a longer period of time significantly reduces the amount of instantaneous power required to complete the channel. By way of example, CO2 lasers used for LMR typically deliver the power for each channel within an elapsed time of 0.08 seconds. By contrast, the present invention can be used to complete the canalization of the same sized channel within about 1.0 second. As a result, the laser requires about 500 watts to 700 watts to form a 1 mm diameter channel while the present invention requires only 1/12 that amount of power, or about 42 watts to 58 watts, to form the same channel. If larger channels are required, the power requirements increase by the square of the ratio of the diameter. Hence, to produce a 2 mm channel in 0.08 seconds using a CO2 laser, the required power will be four-fold higher or 2000 watts to 2800 watts, which requires a very large and very expensive laser. In contrast, the present invention can form a 2 mm diameter channel (of the same length as that cited above) in 1 second with an applied power of about 168 watts to 232 watts.
The preferred power source of the present invention delivers a high frequency current selectable to generate average power levels ranging from several milliwatts to tens of watts per electrode, depending on the volume of target tissue being treated, and/or the maximum allowed temperature selected for the instrument tip. The power source allows the user to select the voltage level according to the specific requirements of a particular cardiac surgery, arthroscopic surgery, dermatological procedure, ophthalmic procedure, open surgery, or other endoscopic surgery procedure. For cardiac procedures, the power source may have an additional filter, for filtering leakage voltages at frequencies below 100 kHz, particularly voltages around 60 kHz. A description of a suitable power source can be found in co-pending patent application Ser. Nos. 09/058,571 and 09/058,336, filed Apr. 10, 1998 (Attorney Docket Nos. CB-2 and CB-4), the complete disclosure of both of which are incorporated herein by reference for all purposes.
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 a presently preferred embodiment of the present invention, 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 U.S. Pat. No. 5,697,909, the complete disclosure of which is incorporated herein by reference. Additionally, current limiting resistors may be selected. Preferably, 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 blood), the resistance of the current limiting resistor increases significantly, thereby minimizing the power delivery from said active electrode into the low resistance medium (e.g., saline irrigant or blood).
In yet another aspect of the invention, the control system is “tuned” so that it will not apply excessive power to the blood (e.g., in the ventricle), once the electrosurgical instrument crosses the wall of the heart and enters the chamber of the left ventricle. This minimizes the formation of a thrombus in the heart (i.e., the system will not induce thermal coagulation of the blood). The control system may include an active or passive architecture, and will typically include a mechanism for sensing resistance between a pair(s) of active electrodes at the distal tip, or between one or more active electrodes and a return electrode, to sense when the electrode array has entered into the blood-filled chamber of the left ventricle. Alternatively, current limiting means may be provided to prevent sufficient joulean heating in the lower resistivity blood to cause thermal coagulation of the blood. In another alternative embodiment, an ultrasound transducer at the tip of the instrument can be used to detect the boundary between the target tissue and adjacent non-target tissue, e.g., between blood in the ventricle and the heart wall; or between a layer of abnormal tissue and underlying healthy tissue.
Referring now to the drawings in detail, wherein like numerals indicate like elements, an electrosurgical system 11 is shown in
In an exemplary embodiment as shown in
The active electrodes 58 are preferably composed of an electrically conductive metal or alloy, such as platinum, titanium, tantalum, tungsten, niobium, stainless steel, and the like. One preferred material for electrodes 58 is tungsten because of its known biocompatibility and resistance to erosion under the application of high voltages. As shown in
As shown in
In the embodiment shown in
As shown in
In the embodiment shown in
As shown in
The electrode array may have a variety of different configurations other than the one shown in
In another embodiment, the return electrode is positioned on the front or distal face of the probe. This configuration inhibits current flow within the tissue on the sides of the probe as it forms the revascularizing channel. In one configuration, for example (shown in
In a first aspect, with reference to
As shown in
Once positioned within the patient's ventricle 258, probe 202 is aligned with the heart wall 260 to form one or more artificial channels 264 for increasing blood flow to the myocardium 262 (e.g.,
As shown in
An alternative embodiment of the percutaneous, endocardial canalization approach is shown in
As shown in
To inhibit blood from flowing through channels 264 into the thoracic cavity, the channels 264 will preferably be sealed at the epicardium 268 as soon as possible after they have been formed. One method for sealing the artificial channel 264 at the epicardium 268 is to insert a collagen hemostasis device 480 (shown in
To facilitate this sealing procedure, an electrosurgical probe (e.g., probe 354,
In both of the above embodiments, the present invention provides localized ablation or disintegration of heart tissue to form a revascularization channel 264 of controlled diameter and depth. Usually, the diameter will be in the range of from about 0.5 mm to 3 mm, preferably from about 1 mm to 2 mm. Preferably, the radio frequency voltage will be in the range of 300 volts to 2400 volts peak-to-peak to provide controlled rates of tissue ablation and hemostasis while minimizing the depth of necrosis of tissue surrounding the desired channel. This voltage will typically be applied continuously throughout the procedure until the desired length of the channel 264 is completely formed. However, the heartbeat may be monitored and the voltage applied in pulses that are suitably timed with the contractions (systole) of the heart.
Ablation of the tissue may be facilitated by axially reciprocating and/or rotating the electrosurgical probe a distance of between about 1 mm to 5 mm. This axial reciprocation or rotation allows the electrically conductive fluid (
In the embodiment shown in
In a second embodiment, the detection system can be an ultrasound guidance system that transmits sound waves onto the heart wall to facilitate canalization of the heart.
A third embodiment is shown in
A fourth embodiment is shown in
In a fifth embodiment shown in
In a first embodiment shown in
In a second embodiment shown in
The stent frame 372 of the present invention is typically manufactured from a tubular member, such as tubing made out of shape memory alloy having elastic or pseudo-elastic properties, such as Nitinol™, Elgiloy™, or the like. Alternatively, stent frame 372 may comprise malleable materials other than shape memory alloys, such as stainless steel. In the latter situation, stent frames 372 will preferably be expanded at the target site by conventional methods, e.g., an expandable balloon at the distal end of a catheter shaft. The tubular member is usually significantly smaller in diameter as compared to the final diameter of the stent in the expanded configuration within channel 264. Slots may be cut into the tubular member via laser cutting methods, photo etching, or other conventional methods to form the separate stent frames 372. For example, these methods include coating the external surface of a tube with photoresist material, optically exposing the etch pattern using a laser beam while translating and rotating the tubular member, and then chemically etching the desired slot pattern of the stent using conventional techniques. A description of this technique can be found in U.S. Pat. No. 5,421,955 to Lau, the complete disclosure of which is incorporated herein by reference. In other methods, laser cutting technology is used in conjunction with computer controlled stages to directly cut a pattern of slots in the wall of the hypodermic tubing to obtain the desired stent geometry. A description of a typical laser cutting method is disclosed in U.S. Pat. No. 5,345,057 to Muller, the complete disclosure of which is incorporated herein by reference.
In an exemplary configuration, the stent frame 372 is formed from a resilient shape memory alloy material that is capable of being deformed by an applied stress, and then recovering to its original unstressed shape. The alloy material will usually exhibit thermoelastic behavior so that the stents will transform to the original unstressed state upon the application of heat (i.e., an Af temperature below body temperature). The stents may also exhibit stress-induced martensite, in which the martensite state is unstable and the prosthesis transforms back to the original state when a constraint has been moved (i.e., when the stent is released from an introducing catheter within a body lumen). The material for the shape memory alloy will be selected according to the characteristics desired of a particular prosthesis. Preferably, the shape memory alloy will comprise a nickel titanium based alloy (i.e., Nitinol™), which may include additional elements which affect the characteristics of the prosthesis, such as the temperature at which the shape transformation occurs. For example, the alloy may incorporate additional metallic elements, such as copper, cobalt, vanadium, chromium, iron, or the like.
It should be noted that the stents 370 described above and shown in
In another aspect, systems and apparatus of the present invention can be used to promote or increase blood flow to, or within, a connective tissue, such as a meniscus, a tendon, a ligament, and the like. For example, in one aspect the present invention can be used to selectively ablate a target tissue, and to create one or more channels or voids within a meniscus, a tendon, or other target tissue, such that blood can flow through the channel(s) or void(s). In one embodiment, the invention may be used to increase the blood supply within a meniscus of the knee. In another aspect, the invention can be used to promote vascularization, e.g., the formation of new blood vessels, in an avascular or sparsely vascularized tissue, such as a meniscus, a tendon, or other target tissue. In yet another aspect, the invention can be used to promote revascularization, e.g., the reestablishment of a blood supply in a target tissue. In one embodiment, increasing the blood flow to a target tissue may involve angiogenesis. According to one aspect of the invention, increasing the blood supply to a target tissue may involve promoting vascularization of the tissue by eliciting a wound healing response by the controlled application of electrical energy to one or more regions of the target tissue.
Shaft 442 typically has a maximum lateral dimension in the range of from about 3.0 to 1.0 mm, and often less than about 1.0 mm. A direction of advancement of instrument 440, during ablation of meniscus tissue, is indicated by the arrow marked A. Active electrode(s) 444 are positioned adjacent to a target area on the inner aspect 402 a of meniscus 402, and a high frequency voltage difference is applied between active electrode(s) 444 and return electrode 446 such that electric current flows through the electrically conductive fluid 445 therebetween. The high frequency voltage is sufficient to convert the electrically conductive fluid 445 between the target tissue and active electrode(s) 444 into an ionized vapor, or plasma (not shown). As a result of the applied voltage difference between active electrode(s) 444 and the target tissue (i.e., the voltage gradient across the plasma layer), charged particles (e.g., electrons) in the plasma are accelerated towards the tissue. At sufficiently high voltages, these charged particles gain sufficient energy to cause dissociation of the molecular bonds of target tissue components. This molecular dissociation is accompanied by the volumetric removal (i.e., ablative sublimation) of tissue, and the production of low molecular weight ablation by-products, e.g., gases, such as oxygen, nitrogen, carbon dioxide, hydrogen and methane.
Depending on the procedure, during application of the high frequency voltage between active electrode 444 and return electrode 446, the surgeon may translate the distal end of shaft 442 relative to the target tissue to form holes, channels, stripes, divots, craters or the like within the tissue. In the representative embodiment, the surgeon axially translates the active electrodes 444 into meniscus tissue, as the tissue is volumetrically removed, to form one or more channels (e.g., channels 424 a-n,
With reference to
During the ablation process, the ablation by-products may be aspirated from the surgical site via an aspiration device (not shown). The aspiration device may be integral with instrument 440, or may be on a separate instrument. The aspiration device may include a suction tube or lumen suitably coupled to a vacuum source. In addition, excess electrically conductive fluid, and other fluids (e.g., blood) may be aspirated from the target site to improve the surgeon's view of the surgical site. During ablation of the tissue, the residual heat generated by the current flux lines, will usually be sufficient to coagulate any severed blood vessels at the site. (Typically, the tissue is exposed to a temperature less than about 150° C.) If not, the surgeon may switch power supply 28 (
Procedures which involve forming one or more channels in a meniscus, a tendon, or other poorly vascularized tissue, may be performed alone, or in combination with other arthroscopic procedures, such as a meniscus repair procedure. For example, in prior art meniscus repair procedures, implants are often used for arthroscopic fixation of meniscus lesions. In one conventional procedure, an arrow-like implant is inserted across a lesion to hold the inner and outer portions of the lesion together. The arrow-like implant may comprise a resorbable material that is absorbed into the body after the meniscus has healed. One such implant is called the Meniscus Arrow™ and is commercially available from Bionx Implants, Inc. (Blue Bell, Pa.).
According to one method of the present invention, treatment of the meniscus 402, 404 to improve the flow of blood thereto may be performed in conjunction with various procedures for repairing the meniscus. A longitudinal (“bucket-handle”) meniscus lesion 420 is shown in
With reference to
Again with reference to
According to another embodiment of the invention, an elongate implant 422 inserted into a channel 424 a-n, may comprise a stent to promote patency of such channel(s). Thus, the present invention facilitates the insertion of implants 422 into damaged tissue, and also increases blood flow to the inner aspect 402 a of the meniscus 402. The use of stents to maintain patency of a channel formed in a target tissue using an electrosurgical device, is described hereinabove, e.g., with reference to
Again with reference to
According to one aspect of the invention, a connective tissue having an injury or disorder may be treated using an electrosurgical instrument, e.g., instrument 440, to stimulate or elicit the body's wound healing response in a region of the tissue thus treated. This wound healing response can result in a variety of metabolic, physiological, or anatomical changes, including the stimulation of greater blood flow, collagen growth, alteration of cellular function, or other metabolic events that promote healing and regeneration of injured tissue. In some embodiments, these induced changes may include increased cell metabolism, increased collagen synthesis in fibroblasts, transformation of fibroblasts to myofibroblasts, increased capillary formation with resultant enhanced microcirculation, and/or enhanced clearance of noxious substances associated with the inflammatory response. In other embodiments, the wound healing response can include an increased blood flow to, and vascularization or revascularization of, the treated region, thereby promoting healing and regeneration of injured tissue. In yet other embodiments, the wound healing response can include stimulating the growth of new collagen in the treatment area.
In a specific embodiment, blood flow in a tendon is increased by creating damage to the tendon to invoke a wound healing response. One of the more common afflictions to the tendons is tendinitis, which is an inflammatory condition characterized by pain at tendinous insertions into bone. Common sites of tendonitis include the rotator cuff of the shoulder, insertion of the wrist extensors (tennis elbow), flexors at the elbow, patellar, and popliteal tendons, the iliotibial band at the knee, insertion of the posterior tibial tendon in the leg (shin splints), the wrist (carpal tunnel syndrome), and the Achilles tendon at the heel. Treatment of tendons, according to the invention, increases blood flow therein, e.g., via canalization or by stimulating vascularization thereof, in order to expedite and improve the healing process.
The methods of the present invention may be performed alone, or in combination with other open or arthroscopic procedures to treat a tendon. For example,
The present invention, in one aspect, improves and expedites healing, and increases the blood supply to tendon tissue by heating the tendon so as to cause neovascularization. In one embodiment, such heating causes controlled damage to the tendon tissue. In exemplary embodiments, the heating of the tendon is effected by the bipolar or monopolar delivery of RF energy. It should be appreciated, however, that while the methods of the present invention are described primarily with respect to the use of bipolar or monopolar RF energy, that alternative heating methods can be used to treat the tendon tissue. For example, instead of RF heating, the tendons can be treated with resistive heating, or the like.
In some embodiments, methods for promoting healing of a tendon include creating artificial channels, lumens, or craters within the tendon to expose internal portions of the tendon. Such openings facilitate the neovascularization of the inner portions of the tendon. Applicants have found that the creation of damage in tissue, including tendon tissue, elicits a wound healing response and causes an inflammatory cell response so that blood clot(s) fill the opening(s) in the tendon. Accordingly, blood products and the inflammatory process can be the major elicitors of angiogenesis within the tendon. In one embodiment, following electrosurgical treatment of tendon tissue, a vascular scar is formed, which in its early stages is hypoxic, and triggers neovascularization in the tendon. In some embodiments, the tendon is heated and damaged only along the surface. Applicants believe that heat alone, applied in a controlled manner, and typically at a temperature below about 150° C., may be sufficient to trigger vascularization of the tendon.
According to one method of the present invention, treatment of a tendon to stimulate its vascularization may be performed in conjunction with a surgical repair procedure. In one embodiment, one or more artificial voids, channels, lumens, or the like, are created in the tendon to increase blood flow within the tendon. Such channels may be formed either before or after the tendon, e.g., tendon 502, has been otherwise repaired or treated. For the formation of an artificial channel or void in a tendon, according to the instant invention, an electrosurgical instrument, e.g., instrument 440 may be introduced into a patient, e.g., percutaneously, arthroscopically or through an open procedure, such that the distal end of instrument 440 is in at least close proximity to a target site on the tendon to be treated. For example, instrument 440 may be introduced arthroscopically into the joint cavity of the elbow (
During a tendon vascularization procedure according to the invention, active electrode(s) 444 are typically positioned adjacent to a target site on the tendon 502, and a high frequency voltage is applied between active electrode(s) 444 and return electrode 446 such that electric current flows through the electrically conductive fluid. The high frequency voltage is sufficient to convert the electrically conductive fluid between the target tissue and the active electrode 444 into an ionized vapor, or plasma (not shown). As a result of the applied voltage difference between active electrode(s) 444 and the tendon 502, charged particles in the plasma are accelerated towards the tendon. At sufficiently high voltage differences, the charged particles gain sufficient energy to cause dissociation of the molecular bonds of the tendon tissue components. The molecular dissociation is accompanied by the volumetric removal (i.e., ablative sublimation) of tendon tissue and the production of low molecular weight ablation by-products.
With reference to
During the volumetric removal of tendon tissue, ablation by-products, together with any excess electrically conductive fluid, and other fluids (e.g., synovial fluid, blood), may be aspirated from the surgical site, substantially as described hereinabove. During ablation of the tissue, the residual heat generated by the current flux lines, will usually be sufficient to coagulate any severed blood vessels at the site. If not, the surgeon may switch the power supply 28 (
As a further example, systems, apparatus, and methods of the present invention may be used to improve the blood supply and increase the vascularity of the patellar tendon and/or the patellar ligament.
It should be appreciated that the size and shape of the electrosurgical systems and devices used to canalize or vascularize the tendon will vary depending on the type of procedure (i.e., creation of holes, channels, or craters) and the position of the tendon to be accessed. If the tendon is treated endoscopically or arthroscopically through a small joint, a smaller wand-type electrosurgical probe will typically be used to perform the vascularization. Alternatively, if the tendon is treated through an open procedure, a larger probe may be used. Although certain of the treatments for increasing blood flow within a tissue are described hereinabove primarily with respect to a tendon of the elbow, apparatus and methods of the invention are also applicable to the treatment of other joints, and to target tissue other than tendons.
System 600 may include an arthroscope 630 adapted for accommodating shaft 612 and for passing at least the distal end of shaft 612 therethrough, whereby a target tissue, e.g., a tendon or a meniscus, within a joint cavity can be accessed by electrode assembly 614. System 600 may further include a sensing unit 620 adapted for determining a boundary of a tissue in relation to the distal end of shaft 612 (e.g.,
In one embodiment, system 600 includes an adjustable mechanical stop 618, which can be adjusted, according to the thickness of a target tissue as measured by sensing unit 620, to limit the maximum travel distance of shaft 612 in relation to the target tissue. In this manner, the depth of a hole, or the length of a channel (e.g., channel 424,
While the exemplary embodiments of the present invention have been described in detail, by way of example and for clarity of understanding, a variety of changes, adaptations, and modifications will be apparent to those of skill in the art. Therefore, the scope of the present invention is limited solely by the appended claims.