WO1998016162A1

WO1998016162A1 - Hook/spatula electrosurgery device and methods of forming and of using the same for tissue dissection

Info

Publication number: WO1998016162A1
Application number: PCT/US1997/015618
Authority: WO
Inventors: Russel F. Stahl
Original assignee: University Of Massachusetts
Priority date: 1996-10-11
Filing date: 1997-09-05
Publication date: 1998-04-23
Also published as: AU4252297A

Abstract

An electrosurgical scalpel device, method of making the device, and method for using the device for tissue dissection. In one aspect of the invention, an electrosurgical scalpel has a conductive blade electrode formed as a generally flat, substantially rectangular sheet lying in a plane with a longitudinal axis. The blade has a longitudinal portion extending along the axis and a hook lying in the plane of the blade projects outwardly of the axis at a distal end portion, defining a notch oriented at a rake angle to catch tissue as the blade is retracted along a generally straight cutting line. Because of the higher contact force and small contact area in the notch, electrical energy is preferentially applied to dissect tissue along the cutting line while leaving tissue and/or structure distal or adjacent to the cutting line substantially unharmed. The blade cuts smoothly, and is readily controlled with essentially axial movements to excavate around and along an embedded vessel within endosurgical cavity. The blade also has a short edge portion extending transverse to the axis in the plane for blunt dissection. The blunt distal end may be pushed into fatty or muscle tissue without damage, then activated for retracting dissection, so that deep cuts may be effected with little risk of vessel damage. The blade lies at the end of a long narrow shaft, which can access the interior chest wall through a lateral incision, and may be levered against the ribs in a novel procedure to safely and effectively harvest the internal mammary artery.

Description

HOOK/SPATULA ELECTROSURGERY DEVICE AND METHODS OF FORMING AND OF USING THE SAME FOR TISSUE DISSECTION

Background of the Invention

This invention concerns devices and methods for electrosurgery in medical procedures involving dissection of blood vessels, ducts, organs, tissue and the like, and in particular, in medical procedures involving the harvesting of arteries.

Various electrosurgery scalpels or devices and a variety techniques are used to dissect structures such as blood vessels, ducts, organs and muscle tissue of a patient. Dissection including cauterization may be accomplished by contacting the electrode of an electrosurgery device electrode to the structure and/or surrounding or connecting tissue or vessels and applying electrical energy through the electrode. Such electrosurgery devices exist in a variety of shapes for different applications. For example, some electrosurgery devices have a conductive electrode with a flat face, or with a concave surface, or a blunt edge.

Other electrosurgical devices, such as hook-type electrosurgery devices, may be specifically configured with a conductive electrode in the shape of a L- or J- hook to extend around a structure, such as a vessel or duct and catch tissue. These devices handle differently and perform different cutting action than the blunt edge or surface cutting typical of spatula-type electrodes.

Still other specialized electrosurgery devices have been described having dual blade and hook electrode capabilities. For example, U.S. Patent No. 5,261,905 of inventor Doresey, III, describes a rounded spoon-shaped electrode conforming to the shape of a gall bladder with a notch in the bowl of the spoon for ligating the cystic duct and cystic artery. Another patent, U.S. Patent No. 5,460,629, of inventors Shlain et al, describes a hook-like electrode with movable paddle-like sides that slide back and forth to clear debris from the hook and to convert the electrode to a blunt, flat surface.

These dual spatula and hook electrosurgery devices are not designed, however, for catching and preferentially cutting tissue along a cutting line adjacent to a structure to be freed such as the internal mammary artery, while the electrode is being retracted. In addition, such devices require movement of paddles to provide a flat spatula-type cutting surface (in the Shlain et al. patent) or provide only a specialized curved surface adapted to a special use (i.e., the Doresey III patent), which may not have suitable electrode surface handling characteristics for cutting along other contours or cutting lines.

There exists a need for other electrosurgical devices, and methods for forming and using the same, for easily, efficiently, and safely dissecting organs, vessels and tissues. A simple device capable of generally flat spatula-type cutting and also capable of catching and preferentially cutting tissue while retracting the electrosurgical device away from an adjacent structure, such as an internal mammary artery, would satisfy a need in the art by reducing the overall procedure time, and enhancing the ease, efficacy and safety of such an electrosurgical device and method. This could enhance surgical outcome and reduce patient discomfort.

Summary of the Invention

Electrosurgical devices are used in several ways. For example, electrosurgical devices are used to cut and to separate tissue, organs or other structures. Electrode contact may cause ablation, which results in the destruction and erosion of contacted tissue, and/or may cauterize, which results in coagulation or clotting due to heating, depending on the selected parameters, such as the electrode power level, and the surgeon's handling, e.g., the duration and degree of contact between the device and the targeted tissue or other structure. As applied to the action of an electrocautery scalpel, the spectrum of effects includes cutting, dissection, ablation and cauterization, terms which have well known and, to some extent overlapping meanings generally understood by those of ordinary skill in the art. For this reason to avoid excessive repetition or amplification in the following description, the root term "dissect" as used herein shall generally be understood to mean to cut, separate, ablate, coagulate or cauterize the contacted tissue, organs or other structures, as the context permits or requires.

The present invention is an electrosurgical scalpel and a method for forming and using the scalpel for dissecting tissue. The scalpel of the present invention includes an electrode having a conductive blade formed as a generally flat, substantially rectangular sheet with a longitudinal portion extending along a longitudinal axis and a short edge portion extending transverse to this axis, and in which a hook extends outwardly from a distal end portion of the electrode blade with an acute inner hook angle. The scalpel is especially effective to excavate and dissect tissue in a generally straight cutting line easily, efficiently and safely around a structure such as an artery embedded in tissue, while leaving tissue adjacent to the cutting line substantially unharmed.

In this aspect, the invention provides an electrosurgical scalpel for dissecting tissue. The scalpel includes an electrode consisting of a conductive blade formed of a generally flat, substantially rectangular sheet lying in a plane and having a longitudinal axis. The blade has a longitudinal portion extending along the axis and a short edge portion extending transverse to the axis in the plane for dissecting tissue by contact when the electrode is activated. The blade also includes a distal end portion which forms a hook projecting in the plane of the sheet outwardly from the axis. The hook defines a notch with an acute angle with respect to the longitudinal axis for catching tissue as the blade is retracted along a generally straight cutting line. As the blade is retracted, electrical energy is preferentially applied to tissue caught in the notch, and the blade smoothly follows the cutting line to dissect tissue immediately on the line while leaving other tissue adjacent to the cutting line substantially unharmed.

Preferably, the ratio of length to width of the blade is between about 3:2 to 5:1., and the length of the longitudinal portion of the sheet blade is less than about 15 millimeters. The angle of the notch of the hook is preferably less than that of a conventional L-hook electrode, and has a rake, being oriented between about forty to eighty degrees with respect to the longitudinal axis. In one embodiment, the blade includes an inner edge which follows a gently concave curve towards the hook located at its distal end portion; and this inner edge is beveled to an edge thickness less than the thickness of the sheet blade for preferentially concentrating ablation energy along the inner edge.

In another aspect, the invention provides a method of freeing an anatomical structure from surrounding tissue to which the structure is attached. The method includes inserting a generally flat, substantially rectangular blade electrode of an electrosurgical scalpel into a patient to a selected position to contact tissue, and retracting the blade electrode along a cutting line through the tissue adjacent to the structure to be freed. The blade electrode lies substantially in a plane with a longitudinal axis, and has a longitudinal portion which extends along the axis and a distal end portion forming a hook projecting in the plane outwardly of the axis to define a notch oriented at an acute angle with respect to the axis. The method further includes catching tissue in the notch of the hook and retracting and activating the blade electrode, so that the blade electrode bears against the tissue with greater force and dissection preferentially occurs in the notch. Preferably, the structure to be freed is a blood vessel at least partially embedded in surrounding tissue, and tissue along the cutting line contacting the blade electrode is preferentially dissected to free at least a segment of the vessel from tissue while leaving the vessel and a tissue margin adjacent to the cutting line undamaged.

In a further aspect of the invention, the method also includes contacting tissue with the short edge portion of the blade electrode with pushing contact while activating the electrode to thereby dissect contacted tissue.

In still another aspect of the invention, a method of forming an electrosurgery device electrode is disclosed. The method includes providing a conductive blade electrode having a generally flat, substantially rectangular sheet with a longitudinal axis and lying in a plane. The blade electrode has a longitudinal portion extending along the axis and a short edge portion extending transverse to the axis in the plane. The method also includes forming an in-plane hook in a distal end portion of the blade electrode with an inner edge projecting in the plane outwardly of the axis to define a notch. The edge lies at an acute angle of about 40 to 80 degrees with respect to the axis and is configured for catching tissue in the notch as the longitudinal portion is retracted along a cutting line. The hook thus bears against the caught tissue to preferentially dissect tissue as it contacts the notch along the cutting line without harming tissue adjacent to the cutting line.

Brief Description of the Drawings

The invention will now be described by way of example with reference to the accompanying drawings, like reference characters on the drawings indicating like parts in several figures, in which:

FIGURE 1 is an enlarged side elevation view of the tip of an electrosurgical scalpel device according to an embodiment of the invention;

FIGURE 2 is an enlarged perspective view of the tip of the electrosurgical scalpel device of Figure 1 ;

FIGURE 3 A is a side view of the electrosurgical scalpel device of

FIGURE 1 including a shaft according to another aspect of the invention; FIGURE 3B is a side view of the electrosurgical scalpel device of FIGURE 3 A including a handle according to another aspect of the invention;

FIGURE 4 is a partially cut-away perspective view of the electrosurgical scalpel device of the invention used for end-on cauterization;

FIGURE 5 illustrates use of the electrosurgical scalpel device of the invention in a video-assisted surgical procedure; and

FIGURE 6 illustrates harvesting a vessel in accordance with a method of the present invention.

Detailed Description

The present invention pertains to an electrosurgical scalpel device, methods of making the device, and methods for dissection of tissue. The device has a blade electrode with both spatula- and hook-type cutting features and is configured to operate safely and effectively for cutting along a generally straight cutting line running adjacent to and around a vessel to remove or free at least a portion of the vessel from surrounding tissue.

FIG. 1 is an enlarged side elevation view of the electrode tip of an electrosurgical scalpel device 10 according to one embodiment of the invention. The device 10 includes an insulated body or shaft 12 from which projects at a distal end 14 an electrode 16 having a conductive blade 18. The conductive blade 18 is formed as a generally flat and substantially rectangular sheet 20 lying in a plane and oriented along a longitudinal axis 22. The conductive blade 18 has a longitudinal portion 24 extending along the axis 22. The blade 18 also has a shorter edge portion 26 extending transverse to the axis 22 in the plane at the distal end. The blade 18 has a shaped distal end portion 28 forming a hook 30 projecting in the plane outwardly from the axis 22. Hook 30 defines a notch 32 bounded by an oblique inner edge 33 which is oriented at an acute angle 34 with respect to the axis 22 to contact tissue at a rake angle.

The insulated body or shaft 12 narrows along a first tapered portion 36 at its distal end 14 to provide relief, i.e. absence of protruding structure, near the blade 18 of the electrode 16. The sheet 20 can have a ratio of length 38 to width 40 between about 3:2 and 5:1, and the length of the longitudinal portion 24 is generally less than about 15 millimeters. The acute angle 34 formed by the notch 32 of the hook 30 can be between about forty to about eighty degrees with respect to the longitudinal axis 22, and is preferably seventy to eighty degrees. The blade 18 also includes an inner edge 42 which follows a gently concave curve longitudinally back toward the inner edge 33 of the hook 30 at the distal end portion 28. FIG. 1 also shows dimensions (in inches) of the various edges and surfaces in one prototype embodiment having a blade thickness of .043 inches. A second prototype embodiment was designed having a length of .320 inches, with the other dimensions, except blade thickness, scaled accordingly. The blade thickness of that second embodiment was .030 inches.

FIG. 2 is an enlarged perspective view of the embodiment of FIG. 1. As shown, the inner edge 42 of the blade 18 and edge 33 of the hook together have a bevel 44, so that the edges are substantially thinner than the blade as a whole. Such a bevel 44 increases current density along the thinned edges 42, 33 to preferentially dissect tissue contacting that thinned surface. In a preferred embodiment, the bevel is cut at a 45 degree angle leaving a thin, but not necessarily knife-sharp, edge of the sheet, with a thickness up to about .005" remaining as the primary contact surface along the length of the tissue-contacting side of the blade.

FIG. 3 A is a side view of the full electrosurgical scalpel device 10 of

FIGS. 1 and 2. As shown, the insulated body or shaft 12 has an elongated middle portion 46 running from a first tapered end 36 to a second end 48. In this embodiment illustrated in FIG. 3A, the second end 48 culminates in a proximal electrode connecting portion 50a which may have grooves or protruding ridges to prevent rotation and to fix the orientation when the assembly is held by a handle.

As also seen in FIG. 3 A, the blade 18 connects via a continuous conductive rod or wire 50 shown in phantom forming the interior structural body of the shaft 12, to a conductive tab 54 disposed on the proximal portion 50a of the rod 50 at the proximal end of the insulated shaft 12. The conductive tab 54 connects to an energy source 56 for supplying electrical ablation energy to the electrode 16, which is a driver/control unit of known type. In general, the shaft 12 is comprised of the rod 50 together with a thin insulating cover 12a, and the rod 50 is a single continuous piece so that electricity is conducted from the proximal end connector 54 to the cutting blade 18. The conductive rod 50 may, for example be a stainless steel rod having a diameter of about .094-.125 inches, and the insulating cover 12a may be a heat-shrunk plastic cover, such as a teflon, Kynar or liquid crystal polymer tube, which brings the total diameter of shaft 12 up to about .110-.160 inches. The rod 50 provides the primary structural component of the shaft 12, while the cover 12a serves primarily as electrical insulation. Cover 12a further provides a slight cushioning effect, allowing the shaft in use to be levered against adjacent bone to apply pressure at the tip and sweep it along an arc-like path to penetrate, grab or cut tissue. Preferably the electrode 16, rod 50 and proximal connecting portion 50a constitute a unitary assembly, either initially formed from a single shaft, or assembled together by welding or the like into a single continuous conductive body. The shaft 12 is of a size to provide sufficient bending and torsional stiffness to allow precise manipulation of the scalpel tip during surgery. While the insulation around the shaft has been described as a preformed and heat-shrunk tube, in an alternative embodiment, the insulated cover 12a can be molded or extruded about the electrode in a plastic molding or extrusion process.

FIG. 3B is a side view of the electrosurgical scalpel device 10, according to a further aspect of the invention. The scalpel device 10 is equipped with a handle 58 connected to the proximal end 48 of the shaft 12. An anti-slip rotation fitting 52 is shown securing the shaft in the handle. This fitting 52 may for example comprise a threaded collar that firmly tightens a pincher or collet-like end of the handle 58 about the shaft 12, or which advances and immobilizes a set of locking elements against the side of the shaft. This construction, in contrast to the simple detents of conventional scalpel devices, assures that the shaft does not loosen in the handle when subject to various levering, torquing and pulling motions in operation. The handle 58 is equipped with an actuator button 60 for selectively actuating the supply of energy to electrode 16. A conductive supply cable 54' is connected at the proximal end of the handle 58, and extends to an ablation energy source which may set the power level and blend of drive energy in a conventional manner.

In the practice of the invention, a physician inserts the electrode 16 of the electrosurgery device 10 through an operative opening to a selected position to contact tissue to be cut or cauterized. In one mode of operation, for example, as shown in FIG. 4, the physician inserts the electrode 16 of the electrosurgery scalpel device 10 through an incision 60 to a selected position in the tissue to contact a vessel 62 and cauterize it, e.g. by pushing the tip against an area 64 which, as illustrated is a small region under a few millimeters in diameter corresponding to the thickness and curvature of the curved tip of the flat blade 18. More generally the blade effects a retracting cut. As shown in the figures, the blade itself is dimensioned so that it may be plunged into muscle and fatty tissue to initiate a cut. It is then moved so the hooked end catches tissue, which is dissected as the blade is pulled away. This mode of operation is ideally suited to excavating a vessel, since unless the electrode is activated it does not appreciably damage tissue, and as it is retracted in an ON state it moves in a well controlled path and cuts only the proximal tissue against which the hook pulls, leaving tissue distal to and laterally adjacent to the blade intact. It may thus readily cut down to a small vessel without damaging the vessel, and may then cauterize the vessel by end-on contact once it is visible, before proceeding. Significantly both the operations of retracting hook- dissection and end-on cauterization are effected with simple axial movements, requiring only slight lateral pressure to be exerted via the handle.

In a preferred method of use, the shaft of the scalpel device is inserted through an opening adjacent to or between the ribs, and the tip is moved sideways by resting the shaft against the hard bone, using the bone as a fulcrum by bearing against the handle to move the tip with a controlled but strong sweeping motion. As described further below, the hook is configured to catch tissue and apply cutting energy, so this results in a high degree of tip control for effecting cuts. This operation is ideally suited to endoscopic or video-assisted applications in which instrument movements may be constrained, the target tissue may reside in an obscure or awkward plane, and the visual field may be restricted.

Applicant has found the invention to be of particular use in an endoscopic coronary artery bypass graft (CABG) procedure in which the internal mammary artery is harvested and grafted to a coronary vessel. In particular it is useful for both endoscopic harvesting, and for a partially video- or endoscopy-assisted "mini" coronary artery bypass procedure.

FIG. 5 illustrates the general operative arrangement for performing such surgery, in the context of a so-called mini-CAB procedure in which a small opening 80 is made in the chest for directly accessing and operating on the heart with one or more surgical instruments illustrated generally by implement 84. Illustratively, to harvest the internal mammary artery, a first incision 60 is made in the lateral chest region to accommodate the electrosurgical scalpel 10 of the invention, which as shown is angled up toward the top surface of the chest cavity to a region in the upper wall of the chest behind the breast. In the illustration a second incision 70 is shown to accommodate an endoscope 100 which displays on a monitor 1 10 the region accessed by the tip of the scalpel 10, which, as discussed further below, lies in the tissue outside the lining of the chest cavity. In the principal cardiac bypass operation, if performed endoscopically, other incisions may be provided to accommodate additional tools such as forceps, clamps and the like. Several endoscopic or minisurgery techniques for performing bypass grafts on the major cardiac vessels are finding currency, and the method of the present invention improves these techniques by allowing one to harvest the internal mammary artery for grafting during the same operation.

The internal mammary artery branches from the subclavian artery and runs along the inside of the chest wall. As shown, for harvesting with scalpel 10, the artery is accessed by an incision in the left of the chest area. Since the artery lies embedded in surrounding tissue, it is necessary to excavate and dissect a length of about six to ten centimeters of the artery free of the surrounding tissue. The end of the freed vessel is then clipped and cut, then reattached to a cardiac vessel to restore circulation. This procedure is performed essentially on the roof of the chest cavity, a position that is difficult to access and awkward to work on. However if the internal mammary artery becomes damaged during harvesting, the surgeon would have to use alternative vessels which involve much more invasive surgery. Typically, for example, the surgeon would next resort to a large cut-down to reach and harvest a sapphenous vein in the leg. Thus, even a small improvement in the handling qualities of a scalpel can be of great value for harvesting the left internal mammary artery (LIMA).

The electrosurgery scalpel 10 of FIGS. 1-3 greatly facilitates the harvesting the internal mammary artery 65, because as shown in FIG. 6 its shape naturally follows a cutting line 19 with a high degree of control, and readily shifts its active point of dissection to follow progressively down into tissue and around a thin vessel by effecting slight rotation of the hook end as it is drawn along in contact with the tissue. The physician retracts the blade 18 along the cutting line 19 against tissue adjacent to the artery 65 so that tissue is caught in the notch 32 against the trailing edge 33 at the hook 30. When activating the electrode 16, pressure against tissue contacting the blade 18 at this region preferentially dissects tissue along the cutting line, thus opening a trench indicated generally by 19a, and freeing at least a segment of the artery 65 from surrounding tissue while leaving the artery 65 itself and a margin of tissue 66 adjacent to the cutting line substantially undamaged. While the retracting motion essentially delivers ablation current only to the more proximal tissue as the hook moves away from the sensitive artery, the physician can also use the longitudinal portion 24 and/or the short edge portion 26 of the blade electrode to push against tissue, for example, to ablate and to cauterize the beginning and/or end of the artery segment to harvest the vessel, i.e., to cut an end of the freed segment which may then be grafted to the heart, and to cauterize the severed branch end remaining attached to the chest. Such end-on ablation is also useful to cauterize minor vessels and tissue bleeds during the dissection.

In the configuration shown in FIG 5, the shaft 12 of the scalpel is inserted between the patient's ribs and extends three to six inches across the chest cavity to the tissue in which the LIMA is embedded. The shaft 12 thus rests against a rib, and precise but firm lateral pressure is easily applied to the blade 18 by using the rib as a fulcrum and levering against the rib to sweep the blade sideways. This motion assists in grabbing tissue, which is then cut as the shaft is retracted, so that a relatively smooth and continuous cut is formed by repetitively pushing in, sweeping and retracting, without risk of unintended slashing.

In general, endoscopic or video-assisted use of the scalpel, as described above, is performed by the physician inserting the electrosurgical scalpel device of the present invention through an incision to a desired position in the patient while observing its travel and operation. Since cutting occurs primarily at the thinned edge residing in the notch of the blade, the projecting blunt-topped hook 30 operates to provide clearance so the blade skims over tissue unless it is drawn against and sunk into tissue. Further, since the dragging distal hook follows the pulled handle, it has little tendency to veer or inflict unintentional cuts. These factors result in an excellent degree of control of the scalpel within the LIMA harvesting arena. It should be observed that the use of the scalpel 10 or the harvesting technique of the present invention is not restricted to endoscopic or video-assisted use, but may advantageously employed directly through a surgical opening or in an open site when there is sufficient visibility of the target area.

The present invention also includes a method of forming an electrosurgical scalpel device. In the practice of this method of the invention, a conductive blade 18 of an electrode is formed of a generally flat substantially rectangular sheet 20 lying in a plane with a longitudinal axis 22, and extending from a continuous conductive wire or rod 50 running through a long narrow insulating cover. The blade 18 is also provided with a longitudinal portion 24 extending along the axis 22, and a short edge portion 26 extending transverse to the axis 22 in the plane. The method further includes forming a hook 30 in a distal end portion 28 of the blade 18 with an edge 33 projecting in the plane of the axis 22 to define a notch 32. The edge 33 lies at an acute angle 34 of between about 40 and 80 degrees with respect to the axis 22 to dig in and catch tissue in the notch 32 as the blade 18 is retracted along a cutting line through tissue adjacent a target structure, while a bevel 44 thins the inner edge 42 of the blade 18, increasing current density in the tissue-trapping notch 32, so that ablation preferentially occurs along the cutting line without harming tissue and/or damaging the structure to be freed distal to or adjacent to the cutting line.

The electrode 16 of the electrosurgical device of the present invention may be formed of any suitable conductive surgical blade material known to those of ordinary skill in the art, such as a surgical grade of stainless steel. The electrode preferably has thickness of about .5-1.5 millimeters, although as noted above, the inner edge 42 which cuts tissue is preferably beveled, and may be thinner than .1 millimeters. So beveled, the hook 30 not only catches tissue at the distal portion 28 of the blade 18, but digs in like a plough; as it moves through tissue, the beveled hook 30 spreads tissue outwardly from the blade, relieving contact pressure (hence raising impedance paths) away from the dissection point. This assures that the applied energy levels do not injure tissue adjacent to or distal to the tip. The outside curve of the hook 30 is a blunt surface, substantially the full thickness of the sheet electrode, and formed with a radius of approximately two millimeters, so that on-axis it comes to a rounded point of relatively small surface area, corresponding to the one millimeter wide edge of the blade, curved on a two millimeter radius in the prototype embodiment. This surface is used for blunt dissection by pushing end-on, as shown in FIG. 4, to create a low impedance contact effective to ablate or to cauterize tissue locally at the point of contact.

The shaft 12 of the electrosurgical device of the present invention can be insulated with an electrically non-conductive material known to those of ordinary skill in the art, which is preferably an a polymer that not only provides defect-free electrical insulation between the blade 18 and its distal electrical connection, but cushions the stiff structural rod 50 over about twenty centimeters of its length to reduce trauma or chipping of adjacent bone during pushing, pulling and torsional forces engendered by manipulating the blade in the practice of the methods described above.

It will be understood that the foregoing disclosure describes and illustrates embodiments of the present invention, by way of illustration and not by way of limitation, and that the invention may be constructed with different materials, and varied in overall dimensions or aspect to suit different surgical procedures. Further, while the method of use has been described for a novel surgical procedure, the handling characteristics of this electrosurgery device are well adapted for excising or cauterizing target structures other than the internal mammary artery including other vessels, organs, ducts, and tissue, using the overall mechanism or approach discussed above. The invention being thus disclosed and described, further variations and modifications will occur to those skilled in the art, and all such variations and modifications are within the scope of the invention, as defined in the claims appended hereto.

What is claimed is:

Claims

1. An electrosurgery device for dissecting tissue comprising an electrode having a conductive blade formed as a generally flat, substantially regular sheet lying in a plane with a longitudinal axis and having a longitudinal portion extending along said axis, and a short edge portion extending transverse to said axis in said plane for pushing contact with tissue to apply dissecting energy to contacted tissue, said blade further having a distal end portion forming a hook projecting in said plane outwardly of said axis to define a notch oriented for catching tissue as said blade is retracted along a cutting line and preferentially apply electrical energy to dissect tissue along the cutting line while leaving tissue adjacent to the cutting line substantially unharmed.

2. An electrosurgery device according to claim 1, wherein said sheet has a length to width ratio between about 3:2 and 5:1.

3. An electrosurgery device according to claim 1, wherein said longitudinal portion has a length of less than about 15 millimeters.

4. An electrosurgery device according to claim 3, wherein said notch forms an acute angle between about forty and eighty degrees with respect to said longitudinal axis.

5. An electrosurgery device according to claim 1, wherein said blade includes an inner edge which follows a gently concave curve toward said hook of said trailing portion.

6. An electrosurgery device according to claim 5, wherein said inner edge of said blade has a bevel to reduce its thickness and preferentially concentrate ablation energy along said inner edge.

7. An electrosurgery device according to claim 5, further comprising an elongated shaft securing the blade at one end thereof, said shaft being configured for extending into an incision and reaching along a region of an upper interior surface of the chest cavity.

8. An electrosurgey device according to claim 7, wherein the shaft is a substantially non-bending shaft for levering against bone to control movement of the blade at its end.

9. A method of freeing a structure from surrounding tissue to which the structure is attached, such method comprising the steps of inserting a generally flat and substantially rectangular blade electrode of an electrosurgery device into a patient to a selected position in tissue surrounding the structure to be freed, said blade electrode lying substantially in a plane with a longitudinal axis, and having a longitudinal portion extending along said axis, said blade electrode further having a distal end portion forming a hook projecting in said plane outwardly of said axis to define a notch oriented at an acute angle with respect to said axis retracting the generally flat substantially rectangular blade electrode along a cutting line through tissue adjacent to the structure to be freed, and catching tissue in said notch of said hook during said retracting while actuating said blade electrode to preferentially cut tissue along the cutting line contacting said blade electrode and free at least a segment of the structure from surrounding tissue, while leaving the structure and tissue adjacent to the cutting line undamaged.

10. The method of claim 9, wherein the structure is the left internal mammary artery, and wherein the step of inserting includes inserting the blade electrode secured at an end of a shaft through a lateral chest incision to a region of tissue in which said artery is embedded.

1 1. The method of claim 10, wherein the steps of retracting and catching are performed together with levering said shaft against a rib to controllably move said blade electrode.

12. The method of claim 9, further comprising the step of pushing a short edge portion of said longitudinal portion extending transverse to said axis into contact with tissue while activating said electrode to thereby effect blunt dissection of contacted tissue.

13. A method of forming an electrosurgery device electrode, such method comprising the steps of providing a conductive blade electrode having a generally flat, substantially rectangular sheet with a longitudinal axis and lying in a plane, and having a longitudinal portion extending along said axis and a short edge portion extending transverse to said axis in said plane, and forming a hook in a distal end portion of said blade electrode with an inner edge projecting in the plane outwardly of said axis to define a notch with a rake angle configured for catching tissue in said notch as said blade electrode is retracted along a cutting line and preferentially cutting along the cutting line without harming tissue adjacent thereto.

14. The method of claim 13, wherein the step of forming a hook includes forming a bevel at said inner edge of the hook.

15. The method of claim 14, wherein the step of providing the conductive electrode blade includes providing said blade secured at an end of a stiff conductive shaft and forming a unitary body therewith such that movement of the blade is controlled by levering the shaft.