The use of biological materials for the sealing of wounds and other defects in tissue as well as for the inhibition of tissue adhesion has been proposed. For example, the use of gelatin and collagen materials for closing wounds and/or creating anti-adhesive surfaces over tissue has been described in the prior art.
Of particular interest to the present invention, the use of radio-frequency (RF) energy to fuse biological materials to tissue surfaces has been suggested. While the use of conventional electrosurgical electrodes for performing such fusion has been proposed, the use of inert gas beam coagulators has often been preferred since there is no direct contact between the device and the underlying tissue and fusible material. Inert gas beam coagulators can be used to perform electrosurgery by transferring RF energy via a beam or stream of ionized inert gas which is directed to the underlying tissue. Thus, there is no direct contact of an electrode surface with the tissue and arcing and charring of the tissue/fusible material is minimized. A gelatin patch intended for fusion to lung tissue by the application of RF energy from an argon beam coagulator is available under the name RAPISEAL.TM. from Fusion Medical Technologies, Inc., of Mountain View, Calif.
While effective, the use of such inert gas beam coagulators for fusing a fusible material to tissue is problematic in several respects. Most significantly, many users have an initial difficulty in properly manipulating the handpiece of the electrosurgical instrument to apply the inert gas beam to the tissue. As there is no contact, there is no tactile feedback enabling the user to "feel" the fusion as it occurs. Moreover, inert gas beam coagulators are not as widely available in operating rooms as conventional electrosurgical coagulators, making their use somewhat more inconvenient.
The use of more conventional electrosurgical/electrocautery instruments would thus be beneficial in some respects. It would allow the user to contact the electrosurgical tip against the tissue/fusible material while applying energy thereto. Electrosurgical power supplies capable of supporting conventional electrosurgical tips are widely available and will thus both facilitate the procedure and reduce its overall cost.
The use of standard electrosurgical/electrocautery tips, however, is also problematic in certain respects. Many electrocautery electrodes cause arcing between the electrode tip and the underlying tissue. Such arcing is undesirable when fusing a biological material to tissue. Conventional electrocautery tip structures also have a tendency to stick to the underlying tissue, which tendency is exacerbated when an initially "loose" biological material is to be contacted and fused to the underlying tissue.
It would therefore be desirable to provide improved electrode tips for use in electrosurgical techniques, particularly for the fusion of biological and other materials to tissue. Such electrode tips should be capable of applying radio-frequency energy evenly and uniformly to the fusible materials, without significant arcing or charring. In particular, the electrode tips should apply the radio-frequency energy without sticking so that the positioning of the fusible material is not disturbed and damage to the tissue due to sticking does not occur. The electrode tips should be usable with conventional electrosurgical power supplies and should have geometries which permit both accessibility to the patient target sites as well as providing the proper energy density and flux for performing such fusion. In addition, it would be desirable if such electrosurgical tips were also usable for coagulation and other conventional electrosurgical procedures in addition to the particularly preferred fusion techniques relating to biological material.
In recent times, a split has developed between the medical communities in Europe and the United States. The desire to reduce the cost of medical supplies and, thus, medical procedures causes a portion of the medical community to embrace reusable medical supplies and instruments. Typically such items are sterilized with an autoclave, ethylene oxide gas, or other suitable technique, before re-use. Such reusable items must be able to withstand repeated sterilization through the autoclaving or other sterilization processes. In addition, reusable items need to be designed to withstand the wear and tear of repeated use. On the other hand, another portion of the medical community avoids reusable materials in order to reduce the likelihood of contaminating patients and medical personnel. In order to reduce such contamination, disposable items are used predominantly, or at least portions of the instruments and supplies are disposable. Some of the other reasons supporting reusables are that more expensive materials can be used in reusable supplies and instruments, when those more expensive materials have desirable characteristics, and also that the environmental impact of disposable items is so great.
U.S. Pat. No. 4,074,718 discloses an electrosurgical instrument with electrodes of increased thermal conductivity and a plurality of heat radiators attached thereto. Unfortunately, this reference did not recognize the importance of using bio-compatible materials, as several bio-compatible materials (silver and gold) were mentioned as interchangeable with non-compatible materials such as copper, aluminum, and beryllium. As to bio-compatibility at least, these materials are clearly not interchangeable, and they are probably not interchangeable in many other regards as well. In addition, the heat radiators on the electrode are poorly conceived, having a different effectiveness at different positional attitudes. Since the radiators rely on natural convection to remove heat from the electrode, the heat radiators will not function well when the electrode is oriented primarily vertically because the heat radiators will then be positioned above each other and heat convection away from the radiators will not easily occur. In addition, the embodiment with the ball electrode, shown in FIGS. 3 and 4, will not conduct heat effectively to the radiators since there will be a bottleneck in the smaller diameter region between the ball and the heat radiators. Similarly, the embodiment shown in FIGS. 1 and 2 will not conduct heat effectively to the heat radiators because the electrode is a blade electrode having a relatively small cross-sectional area relative to its length which restricts the heat flow.
U.S. Pat. No. 5,423,814 discloses a bipolar coagulation device intended for endoscopic applications. While there is a discussion in this reference of the need to use metals having high thermal conductivity for the electrode materials, the disclosure is of an alloy of such materials, namely an alloy comprised roughly of 80% copper, 15% silver and 5% phosphorous. Unfortunately copper is not bio-compatible, and it is believed that phosphorous is not as well. A particular electrode shape intended to enhance heat transfer away from the electrode tip to reduce tissue sticking is disclosed in FIG. 9a of this reference. The conical shape disclosed suffers from the drawback that there is no adequate heat reservoir toward which to transfer the heat away from the tip. In addition the width of the conical shape near the tip will reduce the surgeon's visibility. It is desirable that the electrode block the surgeon's view of the surgical site as little as possible.
It has generally been believed by those in the medical industry that silver, while high in thermal conductivity, is not bio-compatible. Apparently this belief arose because people referring to silver usually, if not always, are referring to sterling silver. Sterling silver is an alloy composed of 92.5% silver and 7.5% copper. Since copper is clearly not bio-compatible, testing of sterling silver has shown it is not bio-compatible. In addition, pure silver is almost never used in any applications since it is so soft or ductile. This is one reason why sterling silver is used rather than pure silver. In addition, pure (or nearly pure) silver is not commonly available through supply channels.
It is against this background, and the desire to solve the problems of the prior art, that the present invention has been developed.