Surgery – Instruments – Electrical application
Reexamination Certificate
2000-10-23
2002-12-31
Peffley, Michael (Department: 3739)
Surgery
Instruments
Electrical application
C606S052000, C606S210000, C606S205000
Reexamination Certificate
active
06500176
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to medical devices and techniques and more particularly relates to an electrosurgical device for thermally sealing or welding the margins of a transected tissue volume, as well as a novel jaw structure that allows substantially elongate jaws to provide high compressive forces the captured tissue volume.
BACKGROUND OF THE INVENTION
In various open and laparoscopic surgeries, it is necessary to seal or weld the margins of transected tissue volumes, for example, a transected blood vessel or a tissue volume containing blood vessels. In a typical procedure, a deformable metal clip may be used seal a blood vessel, or a stapling instrument may be used to apply a series of mechanically deformable staples to seal the transected edge a larger tissue volume. Such mechanical devices may create a seal that leaks which can result in later complications.
Various radiofrequency (Rf) surgical instruments for sealing transected structures have been developed. For example,
FIG. 1A
shows a sectional view of paired electrode-jaws
2
a
and
2
b
of a typical prior art bi-polar Rf grasper grasping a blood vessel. In a typical bi-polar jaw arrangement, each jaw face comprises an electrode and Rf current flows across the tissue between the first and second polarities in the opposing jaws that engage opposing exterior surfaces of the tissue.
FIG. 1A
shows typical lines of bi-polar current flow between the jaws. Each jaw in
FIG. 1A
has a central slot adapted to receive a reciprocating blade member as is known in the art for transecting the captured vessel after it is sealed.
While bi-polar gapers as in
FIG. 1A
can adequately seal or weld tissue volumes that have a small cross-section, such bi-polar instruments are often ineffective in sealing or welding many types of anatomic structures, e.g., (i) substantially thick structures, (ii) large diameter blood vessels having walls with thick fascia layers f (see FIG.
1
A), (iii) bundles of disparate anatomic structures, (iv) structures having walls with irregular fibrous content.
As depicted in
FIG. 1A
, a relatively large diameter blood vessel falls into a category that is difficult to effectively weld utilizing prior art instruments. A large blood vessel wall has substantially thick, dense and non-uniform fascia layers underlying its exterior surface. As depicted in
FIG. 1A
, the fascia layers f prevent a uniform flow of current from the first exterior surface S to the second exterior surface
9
of the vessel that are in contact with electrodes
2
a
and
2
b
. The lack of uniform bi-polar current across the fascia layers f causes non-uniform thermal effects that typically result in localized tissue desiccation and charring indicated at c. Such tissue charring can elevate impedance levels in the captured tissue so that current flow across the tissue is terminated altogether.
FIG. 1B
depicts an exemplary result of attempting to weld across a vessel with thick fascia layers f with a prior art bi-polar instrument.
FIGS. 1A-1B
show localized surface charring c and non-uniform weld regions w in the medial layers m of vessel. Further,
FIG. 1B
depicts a common undesirable characteristic of prior art welding wherein thermal effects propagate laterally from the targeted tissue causing unwanted collateral (thermal) damage indicated at d.
A number of bi-polar jawed instruments adapted for welding and transecting substantially small structures have been disclosed, for example: U.S. Pat. No. 5,735,848 to Yates et al.; U.S. Pat. No. 5,876,410 to Schulze et al.; and U.S. Pat. No. 5,833,690 to Yates et al. One other similar bi-polar instrument was disclosed by Yates et al. in U.S. Pat. No. 5,403,312. In that patent, paired bi-polar electrodes are provided in left and right portions of a jaw member to induce current flow therebetween. It is not known whether a jaw having the left-to-right or side-to-side bi-polar current flow of U.S. Pat. No. 5,403,312 was ever tested, but it seems likely that such an instrument would confine current flow to the tissue's exterior surface and facial layers f (see FIG.
1
B), thus aggravating the desiccation and charring of such surface layers.
What is needed is an instrument working end that can utilize Rf energy in new delivery modalities: (i) to weld a transected margin of a substantially thick anatomic structure; (ii) to weld or seal a margin of a blood vessel having thick or non-uniform fascia layers; (iii) to weld or seal tissue volumes that are not uniform in hydration, density and collagenous content; (iv) to weld a transected margin of a bundle of disparate anatomic structures; and (v) to weld a targeted tissue region while substantially preventing collateral thermal damage in regions lateral to the targeted tissue.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a novel technique—and an instrument working end capable of practicing the technique—for causing controlled Rf energy delivery and controlled thermal effects in a transected margin of tissues with thick facial layers, or other tissue with non-uniform fibrous content. For example, larger diameter blood vessels are a targeted application since such vessels have thick facials layers that can prevent uniform current flow and uniform resistive heating of the tissue.
As background, the biological mechanisms underlying tissue fusion by means of thermal effects are not folly understood. In general, the delivery of Rf energy to a captured tissue volume elevates the tissue temperature and thereby at least partly denatures proteins in the tissue. The objective is to denature such proteins, including collagen, into a proteinaceous amalgam that intermixes and fuses together as the proteins renature. As the treated region heals over time, the so-called weld is reabsorbed by the body's wound healing process.
In order to create an effective weld in a tissue volume with substantial fascial layers, it has been found that several factors are critical. The objective is to create a substantially even temperature distribution across the targeted tissue volume to thereby create a uniform weld or seal. Fibrous tissue layers (i.e., fascia) conduct Rf current differently than adjacent less-fibrous layers, and it is believed that differences in extra cellular fluid contents in such adjacent tissues contribute greatly to the differences in electrical resistance. It has been found that by applying very high compressive forces to a tissue volume comprising fascia layers and adjacent non-fibrous layers, the extracellular fluids either migrate from the non-fascial layers to the fascial layers or migrate from the captured tissue to collateral regions. In either event, high compressive forces tend to make the resistance more uniform regionally within the captured tissue volume. Further, it is believed that high compressive forces (i) cause protein denaturation at a lower temperature which is desirable, and (ii) cause enhanced intermixing of denatured proteins thereby creating a more effective weld upon tissue protein renaturation.
Of equal importance, it has been found that that a critical factor in creating an effective weld across adjacent fibrous (fascia) layers and non-fibrous (medial) layers is the deliver of bi-polar Rf energy from electrode surfaces engaging the medial layers and the surface or fascia layers. In other words, effective current flow through the fascia layers is best accomplished by engaging electrodes on opposing sides of the fascial layers. Prior art jaw structures that only deliver bi-polar Rf energy from outside the surface or fascial layers cannot cause effective regional heating inward of such fascial layers. For this reason, the novel technique causes Rf current flow to-and-from the medial (or just-transected) non-fascia layers of tissue at the interior of the structure, rather than to-and-from exterior surfaces only as in the prior art. This method is termed herein a medial-to-surface bi-polar delivery approach or a subfascia-to-fascia bi-polar approach.
Another aspect of the inv
Shadduck John H.
Truckai Csaba
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