Electrosurgical hemostatic device with recessed and/or offset electrodes

An electrosurgical instrument is provided for cauterization and/or welding of tissue of varying impedances, thicknesses and vascularity especially in the performance of endoscopic procedures. The instrument compresses the tissue between an electrode associated with a first pole of a bipolar energy source located on one interfacing surface off a first element, and a second interfacing surface of a second element. The first and second elements are used to engage and compress tissue between the first and second interfacing surfaces. A second electrode associated with a second pole is located one of the two interfacing surfaces. The first electrode is either recessed into the first tissue contacting surface and/or offset from the second electrode on the same or opposing surfaces. A preferred application of the invention is in a cutting instrument wherein a hemostatic line is formed along a cut line using RF energy.

FIELD OF THE INVENTION 
This invention relates to an electrosurgical instrument for cauterization, 
coagulation and/or tissue welding in the performance of surgical 
procedures, especially endoscopic procedures. 
BACKGROUND OF THE INVENTION 
Surgical procedures requiring cutting of tissue can cause bleeding at the 
site of the cutting. Various techniques have been adapted to control 
bleeding with varying degrees of success such as, for example, suturing, 
applying clips to blood vessels, and stapling, as well as electrocautery 
and other tissue heating techniques. Advances in tissue joining or 
welding, tissue repair and wound closure also have permitted surgical 
procedures previously not possible or too risky. 
Surgical staplers have been used for tissue security, joining, and 
approximation, and to provide hemostasis in conjunction with tissue 
cutting. Such devices include, for example, linear and circular cutting 
and stapling instruments. Typically, a linear cutter has parallel rows of 
staples with a slot for a cutting means to travel between the rows of 
staples. This type of surgical stapler secures tissue for improved 
cutting, joins layers of tissue, and provides hemostasis by applying 
parallel rows of staples to layers of surrounding tissue as the cutting 
means cuts between the parallel rows. 
Electrocautery devices have been used for effecting improved hemostasis by 
heating tissue and blood vessels to cause coagulation or cauterization. 
Monopolar devices utilize one electrode associated with a cutting or 
cauterizing instrument and a remote return electrode, usually adhered 
externally to the patient. More recently, bipolar instruments have been 
used because the cauterizing current is generally limited to tissue 
between two electrodes of a tissue treating portion of an instrument. 
Bipolar forceps have been used for cutting and/or coagulation in various 
procedures. Generally, bipolar forceps grasp tissue between two poles and 
apply electrical current through the grasped tissue. Bipolar forceps, 
however, have certain drawbacks, some of which include the tendency of the 
current to arc between poles when tissue is thin or the forceps to short 
when the poles of the forceps touch. The use of forceps for coagulation is 
also very technique dependent and the forceps are not adapted to 
simultaneously cauterize a larger area of tissue. Furthermore, forceps 
tend to cause areas of thermal spread, i.e., dissipation of heat outside 
of area defined by grasping or engaging surfaces of the forceps. 
SUMMARY OF THE INVENTION 
It is therefore an object of the present invention to provide a hemostatic 
electrosurgical instrument which can efficiently provide hemostasis in 
multiple tissue types and thicknesses, e.g., in fleshy or vascular tissue 
areas, and high, low or combination impedance tissues. Hemostasis is used 
herein to mean generally the arresting of bleeding including by 
coagulation, cauterization and/or tissue joining or welding. 
It is another object of the invention to provide an electrosurgical 
hemostatic device which is capable of being used to simultaneously 
cauterize or weld a relatively larger area or length of tissue than in 
previously known devices. 
Another object of the invention is to provide a controlled current delivery 
path by arranging offset and/or recessed electrodes to provide a desired 
current path, preferably through a zone of high tissue compression. Offset 
electrodes are defined herein to mean electrodes which are not 
diametrically opposed to each other with respect to interfacing surfaces. 
Recessed electrodes are defined herein to mean electrodes which are 
recessed from a tissue contacting plane; a tissue contacting plane may be 
defined by one of the interfacing or opposing surfaces. 
It is another object of the invention to provide an electrosurgery device 
having one or more elongated or bar electrodes. 
Another object of the invention to is provide a hemostatic means for 
providing a line of coagulation adjacent to a cutting path of a cutting 
means for dividing tissue. 
Another object of the invention is to provide a cutting and stapling device 
with an electrocautery means for tissue welding or cauterization along a 
cutting path. 
These and other objects of the invention are described in an 
electrosurgical device having an end effector with opposing interfacing 
surfaces for engaging tissue therebetween, and two electrically opposite 
electrodes, corresponding to electrically opposite poles, each electrode 
located on one or both of the opposing surfaces. The electrodes are offset 
from each other with respect to interfacing surfaces, i.e., they are 
offset from each other so that they are not diametrically opposed from 
each other on an interfacing surface or surfaces. If the electrodes are on 
the same surface, they are separated from each other with an insulating 
material or an insulator (which may include an air gap) which electrically 
isolates the electrodes. 
An electrosurgical instrument of a preferred embodiment compresses tissue 
in a compression zone between a first interfacing surface and a second 
interfacing surface and applies electrical energy through the compression 
zone. The first interfacing surface is comprised of: a first electrode 
corresponding to a first pole of a bipolar energy source and a second 
electrode corresponding to a second pole of a bipolar energy source. The 
second electrode is located on the same or opposite interfacing surface as 
the first electrode. In a preferred embodiment, the compression zone is an 
area defined by a compression ridge on one of the interfacing surfaces 
which compresses the tissue against the other interfacing surface. Also, 
there may be a compression ridge on both interfacing surfaces. A 
coagulation zone is defined by the first electrode, the second electrode, 
and an insulator insulating the first electrode from the second electrode. 
This arrangement electrically isolates the two poles and enables the 
current path between the first and second electrodes to cross through a 
desired area of compressed tissue. 
It is believed that the tissue compression normalizes tissue impedance by 
reducing structural differences in tissue which can cause impedance 
differences. Compression also stops significant blood flow and squeezes 
out blood and other interstitial fluids which act as a heat sink, 
particularly when flowing through veins arteries and other vessels. It is 
further believed that high compression causes a higher current density to 
be delivered through compressed tissue in contact with an energy 
delivering electrode. Thus, it is believed that compression optimizes 
delivery of energy to tissue in part by preventing excessive thermal 
dissipation due to blood flow, dissipation through surrounding boundaries, 
and by enabling quick delivery of a higher current density to a controlled 
area of tissue. 
The arrangement of the electrodes is important to ensure that the current 
passing between the two poles passes though the compression zone. Also the 
invention provides for offsetting, i.e., insulating or isolating of the 
electrically opposite electrodes from each other with respect to the 
interfacing surfaces of the instrument and/or recessing one or more tissue 
contacting electrodes within an instrument so that the recessed electrode 
contacts tissue in a zone of high compression while permitting tissue 
compression without shorting of the instrument poles or electrical arcing 
common in bipolar instruments. 
Thus, the tissue compression and the arrangement of the electrodes permit 
more efficient cauterization and offer the advantage of achieving 
hemostasis in a wide range of tissue impedance, thickness and vascularity. 
The present invention also provides a device capable of coagulating a line 
or path of tissue along or lateral to a cut line or a cutting path. In one 
embodiment, the first electrode and second electrodes each comprise an 
elongated electrode each on opposite sides and laterally adjacent an 
insulator forming a ridge to compress the tissue to be cauterized. 
In one preferred embodiment, a cutting means for cutting tissue is 
incorporated into the device and the device provides hemostatic lines 
adjacent to the path of the cutting means. Of course, cutting may occur at 
anytime either before, during or after cauterization or welding. In 
variations of this embodiment, stapling means may be provided on one or 
both sides of the cutting path. 
In one embodiment, an indicator means communicates to the user that the 
tissue has been cauterized to a desired or predetermined degree. 
In one embodiment, electrosurgical energy is applied in conjunction with 
application of one or more tissue fasteners such as, for example, staples, 
clips, absorbable fasteners etc., using an applier to apply the fastener, 
such as a driver to drive staples into tissue. 
In another embodiment, the coagulation is completed prior to any mechanical 
cutting, i.e., actuation of the cutting means. If an indicator means is 
used, once tissue is coagulated, the cutting means may be actuated to cut 
between the elongated bar electrodes while the rows of staples are applied 
to the tissue. 
In another embodiment, the hemostatic device is incorporated into a linear 
cutter similar to a linear cutting mechanical stapler. In this embodiment 
the hemostatic device comprises two elongated electrode bars and a slot 
for a cutting means to cut tissue engaged by the end effector of the 
device. Optionally, one or more rows of staples may be provided on each 
side of the slot and bars to provide mechanical tissue security or 
approximation during the healing process. In operation, tissue is clamped 
between two jaws. Electrical energy in the form of radio frequency current 
is applied to the compressed tissue to cauterize the tissue. Other cutting 
and stapling instruments may be used as well, such as, for example, 
cutting and an interluminal circular cutting instrument. 
Another embodiment provides a means for detecting abnormal impedances or 
other electrical parameters which are out of a predetermined range. For 
example, the means for detecting may be used to indicate when the 
instrument has been applied to tissue exhibiting impedances out of range 
for anticipated good coagulation. It may also be used for detecting other 
instrument abnormalities. It is possible to detect the abnormal condition, 
for example, by using comparisons of normal ranges of initial tissue 
impedances in the interface electronics. This could be sensed in the first 
few milliseconds of the application of RF energy and would not present a 
significant therapeutic dose of energy or by a low voltage signal used 
prior to delivering therapeutic energy. A warning mechanism may be used to 
warn the user when the impedance is out of range. Upon repositioning of 
the instrument, the same measurement criteria would apply and if the 
tissue impedance was again out of range, the user would again be warned. 
This process would continue until the normal impedance range was satisfied 
and good coagulation could be anticipated. 
These and other objects of the invention will be better understood from the 
following attached Detailed Description of the Drawings, when taken in 
conjunction with the Detailed Description of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
While the present invention is generally applicable to a variety of 
electrosurgical instruments including monopolar, bipolar and multipolar 
(i.e., including two or more therapeutic electrodes providing energy in 
waveforms as measured from any pole to any other pole as having a phasic 
relationship), and both conventional and endoscopic, it will be described 
herein with reference to an endoscopic bipolar linear cutting and stapling 
instrument. 
Operation of linear cutting and stapling instruments are known in the art 
and are discussed, for example, in U.S. Pat. Nos. 4,608,981, 4,633,874, 
and U.S. application Ser. No. 07/917,636 incorporated herein by reference. 
Referring now to FIGS. 1-17 there is illustrated an instrument of the 
present invention to be used in conjunction with an impedance feedback 
device. An endoscopic linear cutting and stapling instrument 10 is shown 
having a housing 16 coupled to a sheath 30 with a lumen extending 
therethrough and an end effector 15 extending from the distal end of the 
sheath 30. The end effector 15 comprises first and second elements which 
are comprised of interfacing jaw members 32, 34. Jaw member 32 is movably 
secured to jaw member 34. The housing 16 has a clamping trigger 12 for 
closing jaw members 32, 34, an RF switch detente arm 58 and electrical 
switch contacts 67a, 67b, coupled to an electrical switch 59 for turning 
on RF energy, and a firing trigger 14 for advancing the cutting element 11 
through tissue and wedge 13 for applying staples 17. Jaw members 32, 34 
are shown in an unclamped position in FIG. 1; in a clamped position prior 
to application of electrosurgical energy and prior to cutting and stapling 
in FIG. 2; in a clamped position after application of electrosurgical 
energy and prior to cutting and stapling in FIG. 3; and in a clamped 
position after cutting and stapling in FIG. 4. 
Jaw member 32 comprises an anvil 18, U-shaped therapeutic electrode 39 
extending along the length of the jaw 32, and a U-shaped insulating 
material 31 surrounding the outside of the therapeutic electrode 39. Jaw 
member 32 has an inner surface 33 which substantially faces an inner 
surface 35 of jaw member 34. The U-shaped electrode 39 comprises two 
electrically communicating electrode bars 27, 28 forming a first pole and 
located on and extending substantially along the length of the inner 
surface 33. The U-shaped electrode 39 is comprised of a conductor, such 
as, aluminum or surgical grade stainless steel. The U-shaped insulator is 
preferably formed of a polymer such as polyphenyleneoxide. The bars 27, 28 
are separated by a knife channel 29 extending longitudinally through the 
middle of the electrode 39. Pockets 36 located on anvil 18 for receiving 
staple ends are located along the inner surface 33, along the length and 
outside of bars 27, 28, to form a row of staples on each side of electrode 
39. The electrode bars 27, 28 and insulating material 31 form a ridge 56 
extending out relative to an anvil portion 33a of the inner surface 33 
(FIG. 16). The electrode 39 acts as a first pole of a bipolar tissue 
treatment or therapeutic system. The anvil 18 is formed of an electrically 
conductive material and acts as a second therapeutic electrode of the 
bipolar treatment or therapeutic system, the anvil being electrically 
opposite of the treatment electrode 39. The anvil 18 is electrically 
isolated from electrode 39 by the U-shaped insulating material 31. 
Jaw member 34 comprises a cartridge channel 22 and a cartridge 23 
releasably inserted into the cartridge channel 22. The cartridge 23 
includes a track 25 for wedge 13, a knife channel 26 extending 
longitudinally through the center of the cartridge 23, a series of drivers 
24 extending into the track 25 and staples 17 arranged in two sets of 
single rows. 
The sheath 30 is formed of an insulative material and has an electrically 
conductive closure tube 38 extending through its lumen. In a preferred 
embodiment, the closure tube 38 acts as a jaw closure tube and as an 
electrical contact. A channel retainer 37a extends from the proximal end 
of the closure tube 38 and is secured to channel 37 which there extends 
distally through the remainder of the closure tube 38 to form jaw member 
34. The channel 37 includes cartridge channel 22 extending distally from 
the closure tube 38. 
The body 16 has a clamping trigger 12 for advancing the closure tube 38 to 
close the jaws 32, 34 towards each other engaging tissue therebetween. 
Rotation of the clamping trigger 12 causes the closure tube 38 to advance 
co-axially through the sheath 30 over a camming surface 32a of jaw 32 to 
close the jaws 32, 34 onto tissue situated between the jaws 32, 34. 
The channel retainer 37a guides co-axial movement of a drive rod 41 within 
the channel 37. The drive rod 41 is advanced by the rotation of the firing 
trigger 14 as described in more detail below. The driving rod 41 is 
coupled on its distal end to a block 43. The block 43 is coupled to a 
cutting means 11 and a staple driving wedge 13, which the drive rod 41 
advances by way of the block 43 into the end effector 15. A wedge guide 46 
is used to guide wedge 13 into track 25. Jaw member 32 is secured by way 
of the channel 37 to the jaw member 34. 
When the drive rod 41 advances the cutting element 11, the cutting element 
11 advances through the knife channel 26 in between the bars 27, 28 to cut 
tissue engaged by jaws 32, 34 when the tissue has been cauterized. Thus, 
the cut line is medial to the coagulation lines formed by the bar 
electrodes 27, 28. The drive rod 41 simultaneously advances the block 43 
and thus the wedge 13 which drives the drivers 24 into the staples 17 
causing the staples 17 to fire through tissue and into the pockets 36 of 
the anvil 18. Staples 17 are applied in single longitudinal rows on each 
side of the cutting element 11 as the cutting element 11 cuts the tissue. 
A knob 44 located on the distal end of the body 16 rotates the closure tube 
38, channel retainer 37a, channel 37 and end effector 15 which are 
directly or indirectly coupled to the knob 44 so that the knob 44 may be 
used for rotational placement of the end effector jaws 32, 34. The knob 44 
includes a peg (not shown) which fits into and engages indentation 38a 
closure tube 38. Closure tube 38 is fitted at its proximal end, into the 
housing 16. 
Electrical energy is supplied to the electrode 39 and anvil 18, 70 (FIG. 
20) through connections such as those described below, or other 
connections means, such as, for example, like those described in parent 
application Ser. No. 08/095,797, incorporated herein by reference. The 
generator 70 is user controlled by way of RF switch 59 located in the 
housing 16. 
Wires 19a and 19b extend into the body 16 of the instrument and deliver 
energy to electrodes 39, 18 respectively. Wires 19a, 19b are coupled to 
low impedance contact elements 20a, 20b respectively and contact elements 
20a, 20b are coupled to wireforms 47a, 47b respectively. Wireforms 47a, 
47b are exposed at their distal ends 48a, 48b. Wireforms 47a and 47b are 
biased respectively towards closure tube 38 and contact ring 49b located 
on the proximal end of channel retainer 37a, so as to make electrical 
contact with the closure tube 38 and ring 49b respectively. 
Wire 19a delivers electrical current to the anvil 18 by way of first wire 
form 47a which contacts electrically conductive closure tube 38 which 
contacts electrically conductive anvil 18 as closure tube 38 closes jaws 
32, 34. 
Wire 19b delivers electrical current to the electrode 39 through second 
wire form 47b which contacts contact ring 49b coupled to wire 40b 
extending through the closure tube 38 to the electrode 39. 
The closure tube 38 and ring contact 49b permit the knob 44 to rotate while 
contact is maintained between closure tube 38, ring 49b, and wireforms 
47a, 47b, respectively. The ring 49b is electrically insulated from the 
closure tube 38. 
Wire 40b extends through seal 45 which fits into channel retainer 37a, 
which fits into closure tube 38. 
Clamping trigger 12 includes gear teeth 12a which movably engage with teeth 
66b of yoke 66. Yoke 66 is coupled on its distal end to the closure tube 
38. When clamping trigger 12 is actuated, the gear teeth 12a engage with 
teeth 66b in yoke 66 causing the yoke 66 to advance distally. Closure tube 
38 closes jaws 32, 34 as it advances over camming surface 32a of jaw 32. 
The RF switch 59 is rotated to switch on RF energy to be supplied to the 
therapeutic electrodes. When the RF switch 59 is rotated, detente 
protrusion 59a on the switch 59 hooks under detente protrusion 58a on 
detente arm 58, preventing the switch 59 from deactivating RF energy 
unless the RF switch 59 is manually rotated back to its original position. 
The RF energy may also be turned off electrically. 
Switch 59 has a moveable contact 67a and a stationary contact 67b. The 
moveable contact 67a rotates with switch 59 to contact stationary contact 
67b when switch is on. 
Ledge 60a of release button 60 is engaged with the proximal end of the yoke 
66 adjacent step ledge 66a on proximal end of yoke 66. When the yoke 66 is 
advanced by the clamping trigger 12, the ledge 60a rotates down behind 
proximal end of yoke 66, thereby preventing yoke 66 from retracting until 
release button 60 has been pressed. Thus the jaws 32, 34 will remain in a 
closed position until a user releases the jaws 32, 34 with release button 
60. 
The switch 59 includes fingers 59c which sit just above proximal end of 
yoke 66. The ledge 60a of the release button 60 fits in between fingers 
59c. The RF switch 59 cannot be activated, i.e., rotated forward, until 
the yoke 66 has been advanced distally so that fingers 59c of switch 59 
are free to rotate behind proximal end of yoke 66. 
The switch 59 also includes a lower hook 59b which engages groove 53a of 
firing rack 53. Firing rack 53 includes gear teeth 53b which are engaged 
by gear teeth 14a of firing trigger 15. The firing rack 53 is coupled on 
its distal end to pinion gear 54 which in turn engages the drive rod 41. 
When the firing trigger 14 is pulled, the fire rack 53 is advanced distally 
to rotate pinion 54 which advances the driving rod 41 distally to actuate 
the cutting element 11 and to drive staples 17 into tissue engaged by the 
end effector 15. 
The firing rack 53 cannot advance however until the lower hook 59b of the 
RF switch is disengaged from the groove 53a of the firing rack 53. This 
occurs only when the RF switch 59 has been activated. 
Thus, the presently described device includes a lockout device or devices 
for preventing application of RF energy, staples or knife actuation until 
the jaws 32, 34 have been closed. The lockout device(s) require the proper 
sequence is followed as illustrated in FIGS. 1-4, i.e., jaw closure, 
followed by application of RF energy, followed by staple application and 
cutting element actuation. It also provides a detented RF switch so that 
RF energy is continuously applied until the switch 59 is manually released 
or until the RF energy is switched off, e.g., by an electrical feedback 
control signal to the generator 70. 
The closure trigger 12 and firing trigger 14 are interlocked and a spring 
57 is mechanically coupled to both triggers 12, 14. 
When tissue is engaged between clamped jaw members 32, 34, and RF energy 
has been applied, the firing trigger 14 located on housing 16 may be 
actuated to advance a cutting element 11 through the engaged tissue to cut 
the tissue. Simultaneously, when the firing trigger 14 is actuated, the 
wedge 13 is advanced through the track 25 causing the drivers to 24 to 
displace towards the staples 17, thereby driving the staples 17 through 
tissue and into anvil pockets 36. 
In one embodiment, the cartridge provides multifire stapling capabilities 
by having single rows of staples, as opposed to the convention double row 
of staples of the cartridges in the laparoscopic stapling and cutting 
devices presently in use. In order to provide better hemostasis, this type 
of stapler was designed to provide a double row of staples for each 
parallel row. Because of the size of the space necessary to contain the 
double row of staples, a refireable cartridge with stacked staples has not 
been preferred because of the additional space required for stacking 
staples. In the multifire stapling embodiment a single row of staples is 
used. Using a single row of staples permits stacking of staples in the 
space previously occupied by the second row of staples, providing 
multifire capabilities. The device of the present may however, if desired, 
include double, triple, etc., staple rows. Also, in a further embodiment, 
no staples are required and the electrical coagulation lines provide the 
necessary hemostasis or tissue welding effect. A cartridge is defined 
herein to mean a staple containing mechanism. 
A preferred embodiment of the present invention includes a feedback system 
designed to indicate when a desired or predetermined tissue effect has 
occurred. An audible, visible, tactile, or other feedback system may be 
used to indicate when sufficient cauterization has occurred at which point 
the RF energy may be turned off. In a particular embodiment, the feedback 
system measure one or more electrical parameters of the system, e.g., the 
electrical impedance of the tissue to which the electrical energy is 
applied, to determine tissue characteristics, e.g., coagulation complete. 
An example of such a feedback system is described in U.S application Ser. 
No. 08/311,297, filed on Sep. 23, 1994, incorporated herein by reference. 
Using such a feedback system, after the RF energy is turned off, the 
cutting means 11 is advanced and the staples 17 are fired using the firing 
trigger 14. 
Referring now to FIGS. 18-24, there are illustrated alternative electrode 
configurations of other embodiments of the present invention. The 
actuation and other instrument features are the same as those illustrated 
in FIGS. 1-17, with the exception of the location of the electrodes on the 
end effectors. 
Referring to FIG. 18, Jaw member 132 comprises a U-shaped first electrode 
151 comprising a first pole, an anvil 118 forming a second and 
electrically opposite pole, and a U-shaped insulating material 155 
surrounding the first electrode 151 except for an exposed portion 157 of 
the first electrode 151. 
The first electrode 151 comprises two electrically communicating electrode 
bars 127, 128 comprised of an electrically conductive material. The bars 
127, 128 are separated by a knife channel 126 which forms a portion of the 
interfacing surface 133. The insulative material 155 surrounds the outside 
of the U-shaped electrode and the top portions 153, 154 of the U-shaped 
electrode 151 so that the electrode is insulated at the inner surface 133 
except for the exposed portion 157 of the electrode 151 recessed within 
the knife channel 126. It is noted that the extent of the recess may vary 
along the length of the recessed electrode. 
The tissue which is squeezed into the recessed portion, the knife channel 
126, thereby forms a current path between the recessed exposed portion 157 
and the anvil 118. 
Jaw member 132 has an inner surface 133 which interfaces with inner surface 
135 of jaw 134. The insulative material 155 forms a compression ridge 156 
on interfacing surface 133. In use, tissue is engaged and approximated 
between jaws 132,134. The compression ridge 156 compresses tissue against 
opposing jaw 134 forming a zone of highly compressed tissue or a 
compression zone. The recessed exposed portion 157 of the electrode 151 is 
arranged to be in contact tissue when tissue is compressed in the 
compression zone. Tissue is compressed into the knife channel 126, so that 
the tissue is in contact with the recessed exposed electrode portion 157. 
The tissue is also in contact with the anvil 118. 
Referring to FIG. 19, an alternative end effector electrode configuration 
is illustrated. Jaw member 232 comprises a U-shaped first electrode 251 
comprising a first pole, an anvil 218, and a U-shaped insulating material 
255 surrounding the first electrode 251 except for an exposed portion 257 
of the first electrode 251. 
The first electrode 251 comprises two electrically communicating electrode 
bars 227, 228. The bars 227,228 are separated by a knife channel 226 which 
forms a portion of the interfacing surface 233. The insulative material 
255 surrounds the outside of the U-shaped electrode and the top portions 
253, 254 of the U-shaped electrode 251 so that the electrode is insulated 
at the inner surface 233 except for the exposed portion 257 of the 
electrode 251 recessed within the knife channel 226. The insulative 
material 255 forms a compression ridge 256 on interfacing surface 233. 
A second jaw member 234 has an inner surface 235 which interfaces with 
inner surface 233 of jaw member 232. Jaw member 234 includes a knife 
channel 229 which is formed by a second electrode 252. The second 
electrode 252 extends out of the knife channel 229 to interface with 
insulating material 255 of compression ridge 256. Thus, electrode 251 is 
offset or recessed from electrode 252. 
Referring now to FIG. 20, there is illustrated an alternative embodiment of 
an end effector of the present invention. Jaw member 332 comprises a 
U-shaped first electrode 351 comprising a first pole, an anvil 318, a 
U-shaped insulating material 355 surrounding the first electrode 351 
except for an exposed portion 357 of the first electrode 351, and a pair 
of second electrodes 352 of an electrically opposite potential from the 
first electrode 351. The second electrodes 352 are located on ends 353a 
and 354a of a compression ridge 356 formed by insulating material. 
The first electrode 351 comprises two electrically communicating electrode 
bars 327, 328. The interfacing surface is formed by the anvil 318, 
electrodes 352, insulating material 355 and electrode 351. The bars 327, 
328 are separated by a knife channel 326 which forms a portion of the 
interfacing surface 333. The insulative material 355 surrounds the outside 
of the U-shaped electrode and the top portions 353, 354 of the U-shaped 
electrode 351 so that the electrode is insulated at interfacing surface 
333 except for the exposed portion 357 of the electrode 351 recessed 
within the knife channel 326. A second jaw member 334 has an inner surface 
335 which interfaces with inner surface 333 of jaw member 332. Thus, 
electrode 351 is recessed or is offset from electrodes 352. 
Referring now to FIG. 21, there is illustrated an alternative embodiment of 
an end effector of the present invention. Jaw member 432 comprises a 
U-shaped first electrode 451 comprising a first pole, an anvil 418, and a 
U-shaped insulating material 455 surrounding the first electrode 451. 
The first electrode 451 comprises two electrically communicating electrode 
bars 427, 428. The bars 427, 428 are separated by a knife channel 426 
which forms a portion of the interfacing surface 433. The electrode 451 is 
recessed within the knife channel 426. 
A second jaw member 434 has an inner surface 435 which interfaces with 
inner surface 433 of jaw member 432. Jaw member 434 includes a knife 
channel 429 which is formed by an insulative material. A second electrode 
452 is comprised of two bar electrodes 427a, 428a located on interfacing 
surface 435. The second electrode 452 extends out of the knife channel 429 
to form a compression ridge 456 opposed from insulating material 455 and 
bars 427, 428. Thus, at least a portion of electrode 452 is offset with 
respect to electrode 451. 
Referring now to FIGS. 22-24, there is illustrated an alternative 
embodiment of the end effector of the present invention. The end effector 
comprises jaw members 532, 534, each of which is divided into two 
sections, A and B. Jaw member 532 comprises a first electrode 551 of a 
first pole an anvil 518, and an insulating material 555 surrounding the 
first electrode 551. 
The first electrode 551 comprises two electrically communicating electrode 
bars 527, 528. A knife channel 526 is located between the bars 527, 528. 
Insulating material 555 forms a compression ridge 556. In section A, the 
electrode 551 is recessed within the knife channel 526. In section B, the 
electrode 551 forms a portion of the compression ridge 556. 
Jaw member 534 comprises a staple cartridge 523, a cartridge holder 522, an 
inner surface 535, and a second electrode 552 of an electrically opposite 
potential from the first electrode 551. The second electrode 552 is 
comprised of two electrically communicating electrode bars 527a, 528a. In 
section A, the bars 527a and 528a are opposed from bars 527 and 528 with 
respect to the surfaces 532 and 534. In section B, the bars 527a and 528a 
are offset from bars 527 and 528 with respect to interfacing surfaces. 
Thus, electrode 551 is either recessed with respect to a plane defined by 
the compression zone or offset from electrode 552 with respect to 
interfacing surfaces, so that tissue compression in a compression zone 
minimizes the opportunity for instrument shorting. 
Electrodes 527 and 528 of the jaw member 532 are a distance, d.sub.1, from 
each other. Electrodes 527a and 528a of the cartridge 523 are a distance, 
d.sub.1, from each other in Section A and electrodes 527a, 528a are a 
distance, d.sub.2, from each other in Section B. In this particular 
embodiment, d.sub.1 &lt;d.sub.2. This arrangement provides, among other 
things, control of thermal spread and coagulation width at the distal end 
of the instrument. The transition from d.sub.1 to d.sub.2 may be gradual 
or stepped, or may occur at various locations along the end effector of 
the instrument. 
Several variations of this invention have been described in connection with 
specific embodiments involving endoscopic cutting and stapling. Naturally, 
the invention may be used in numerous applications where hemostasis in 
desired. Accordingly, it will be understood by those skilled in the art 
that various changes and modifications may be made in the invention 
without departing from its scope, which is defined by the following claims 
and their equivalents.