Electrosurgical Apparatus and Methods for Treatment and Removal of Tissue

Abstract

Apparatus and methods for ablating, severing, cutting, shrinking, coagulating, or otherwise modifying a target tissue to be treated. In a method for treating a target tissue, an active electrode of an electrosurgical probe is positioned in at least close proximity to the target tissue in the presence of an electrically conductive fluid. A high frequency voltage is then applied between the active electrode and a return electrode, wherein, the high frequency voltage is sufficient to volumetrically remove (ablate), sever, or modify at least a portion of the target tissue. The probe comprises a multi-lumen shaft having a plurality of internal lumens, and a return electrode coil oriented substantially parallel to the shaft distal end. The active electrode may be in the form of a metal disc, a hook, or an active electrode coil. In the latter embodiment, the active electrode coil is typically arranged substantially orthogonal to the return electrode coil. Methods of making an active electrode coil, a return electrode coil, and an electrosurgical probe are also disclosed.

Description

RELATED APPLICATIONS [0001] The present application claims priority from U.S. Provisional Patent Application No. 60 / 299,094 filed Jun. 18, 2001, and is a continuation-in-part of U.S. patent application Ser. No. 09 / 586,295 filed Jun. 2, 2000, which is a divisional of U.S. patent application Ser. No. 09 / 248,763 filed Feb. 12, 1999, now U.S. Pat. No. 6,149,620, which claims priority from U.S. Provisional Application Nos. 60 / 096,150 and 60 / 098,122, filed Aug. 11, 1998 and Aug. 27, 1998, respectively, and is a continuation of U.S. patent application Ser. No. 08 / 795,686, filed Feb. 5, 1997, now U.S. Pat. No. 5,871,469, which is a continuation of U.S. patent application Ser. No. 08 / 561,958 filed Nov. 22, 1995, now U.S. Pat. No. 5,697,882, the complete disclosures of which are incorporated herein by reference for all purposes. [0002] The present invention is related to commonly assigned U.S. patent application Ser. No. 09 / 177,861, filed Oct. 23, 1998, now U.S. Pat. No. 6,066,134, applicatio...

AI Technical Summary

Benefits of technology

The present invention provides systems, apparatus, and methods for selectively applying electrical energy to body tissue. The invention involves positioning an electrosurgical probe or catheter adjacent to the target site, and using high frequency voltage to generate a plasma in the space between the electrodes. The plasma can vaporize the electrically conductive fluid and remove or ablate the target tissue. The invention allows for precise control over the removal of tissue with minimal damage to surrounding or underlying tissue structures. The invention can be used in percutaneous or direct delivery procedures, or in open procedures. The apparatus includes an electrosurgical instrument with a shaft and electrodes, and a high frequency power supply. The invention also includes a fluid delivery element for delivering electrically conductive fluid to the electrodes and the target site, and an electrode support member or spacer to separate the electrodes from the return electrodes. The invention provides a more efficient and safe method for removing target tissue with minimal damage to the patient.

Problems solved by technology

These traditional electrosurgical techniques for treatment have typically relied on thermal methods to rapidly heat and vaporize liquid within tissue and to cause cellular destruction.

This current, however, may inadvertently flow along localized pathways in the body having less impedance than the defined electrical path.

This situation will substantially increase the current flowing through these paths, possibly causing damage to or destroying tissue along and surrounding this pathway.

One drawback with this configuration, however, is that the return electrode may cause tissue desiccation or destruction at its contact point with the patient's tissue.

Another limitation of conventional bipolar and monopolar electrosurgery devices is that they are not suitable for the precise removal (i.e., ablation) of tissue.

At the point of contact of the electric arcs with tissue, rapid tissue heating occurs due to high current density between the electrode and tissue.

The tissue is parted along the pathway of evaporated cellular fluid, inducing undesirable collateral tissue damage in regions surrounding the target tissue site.

The use of electrosurgical procedures (both monopolar and bipolar) in electrically conductive environments can be further problematic.

However, the presence of saline, which is a highly conductive electrolyte, can cause shorting of the active electrode(s) in conventional monopolar and bipolar electrosurgery.

Such shorting causes unnecessary heating in the treatment environment and can further cause non-specific tissue destruction.

Conventional electrosurgical techniques used for tissue ablation also suffer from an inability to control the depth of necrosis in the tissue being treated.

The inability to control such depth of necrosis is a significant disadvantage in using electrosurgical techniques for tissue ablation, particularly in arthroscopic procedures for ablating and / or reshaping fibrocartilage, articular cartilage, meniscal tissue, and the like.

Despite these advantages, laser devices suffer from their own set of deficiencies.

In the first place, laser equipment can be very expensive because of the costs associated with the laser light sources.

Moreover, those lasers which permit acceptable depths of necrosis (such as excimer lasers, erbium:YAG lasers, and the like) provide a very low volumetric ablation rate, which is a particular disadvantage in cutting and ablation of fibrocartilage, articular cartilage, and meniscal tissue.

The holmium:YAG and Nd:YAG lasers provide much higher volumetric ablation rates, but are much less able to control depth of necrosis than are the slower laser devices.

The CO2 lasers provide high rate of ablation and low depth of tissue necrosis, but cannot operate in a liquid-filled cavity.

Such photo-dissociation reduces the likelihood of thermal damage to tissue outside of the target site.

Unfortunately, the pulsed mode of operation reduces the volumetric ablation rate, which may increase the time spent in surgery.

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