Patent Abstract:
A heat pipe for a cautery surgical instrument such as a surgical forceps including a pair of elongate arms joined at an end so as to provide for resilient compressible movement of the arms between a normally open position and a squeezed closed position. The heat pipe provides for conduction of heat away from an electrode tip, and comprises an evaporator portion having a first diameter and a condenser portion spaced away from the evaporator end, and that transitions from the first diameter to at least one smaller diameter section. A socket is disposed within each arm of the forceps, and includes a longitudinal blind hole that is sized so as to releasably receive the smaller diameter section of the condenser portion, and a catch for engaging a portion of the arm.

Full Description:
FIELD OF THE INVENTION  
       [0001]     The present invention generally relates to medical devices and, more particularly, to improved temperature control mechanisms for cautery devices using heat pipes.  
       BACKGROUND OF THE INVENTION  
       [0002]     Medical treatments today often require that areas of organic tissue be cauterized or coagulated quickly, efficiently, and safely during the course of a surgical procedure. For example, surface tissue on a highly vascularized organ such as the human liver or brain may be cauterized immediately following the making of a surgical incision in order to prevent excessive bleeding. Alternatively, retinal tissue in a human eye may be photocoagulated during opthalmic surgery to correct injury or, skin tissue on a human scalp may be coagulated during hair transplant surgery to prevent bleeding resulting from graft incisions. Many prior art devices have been developed to perform cauterization or coagulation as appropriate for such varied applications. Known devices range from simple direct-contact cauteries, employing a heated wire element to burn or sear relatively large areas of tissue, to more complex laser photocoagulators using highly coherent, monochromatic laser light to perform pin-point coagulation of delicate tissue.  
         [0003]     Typically, electrical energy is applied to the tissue being treated so as to cause local heating of the tissue. By varying the power output and the type of electrical energy, it is possible to control the extent of heating and thus the resulting surgical effect. Electrosurgery is often accomplished through the delivery of radio-frequency (RF) current through body tissue to raise the tissue temperature for cutting, coagulating, and desiccating. RF energy in the range of about 500 kilohertz to 1 megahertz, with about 30-watt to 40-watt power levels is typical of electrosurgical generators.  
         [0004]     While tissue heating is the mechanism by which the various cautery surgical treatments are effected, it can also cause nonefficacious effects. Total body temperatures above 41.8° C. (107.2° F.) are detrimental to the functions of the central nervous system, heart, brain, liver, and kidneys, and may even cause histologically obvious damage to tissue cells, whereas, e.g., tumorcidal effects are generally not observed below 42.5.degree. C. (108.5° F.). At brain temperatures of over 41.8° C. (107.2° F.), the mechanism that regulates body temperature can become incapacitated, and there is danger of ‘malignant’ or ‘runaway’ hyperthermia. Further, temperatures of up to 45° C. (113.0° F.) may cause soft tissue necroses and fistulas as well as skin burns. Therefore, accurate temperature control of a localized area is critical to successful cauterization.  
         [0005]     As a consequence, surgeons often operate prior electrosurgical devices at a very low power level. This prevents the electrode and the adjacent tissue from becoming too hot, too fast. Unfortunately, it also requires the surgeon to perform the procedure much more slowly than he would if he could operate the device at full power. As a result, the procedure takes much longer, requiring more operating room time.  
         [0006]     It has been recognized that cooling the surgical site during electrosurgery is desirable. Several prior art systems have been developed which flush the surgical site with fluid during surgery or transfer the excess heat quickly away from the surgical site. One known apparatus which is used to remove heat from a surgical environment is a “heat pipe”.  
         [0007]     A heat pipe is an elongated tube having a wick running through its length with one end of the tube being in the hot environment and the other end being in a cooler or cold environment. The tube is charged with a selected amount of liquid, known as a “working fluid,” having a particular boiling point such that the liquid will boil in the hot environment and give off vapors which will travel through the tube into the colder environment. In the colder environment the vapors condense back into liquid form and give up thermal energy through the latent heat of condensation. The condensed liquid is then soaked up by the wick and transferred through the wick by capillary action back to the hotter environment where the evaporating cycle is repeated. Such heat pipes can be very efficient so long as there is a difference in temperature between the hot environment and the cool environment.  
         [0008]     For example, in U.S. Pat. Nos. 5,647,871, 6,074,389, and 6,206,876, issued to Levine et al., an electrosurgical device, system and a method of electrosurgery are disclosed in which electrosurgical electrodes are cooled by a heat pipe. The device includes at least one electrode for applying the required electrical energy to tissue at a surgical site. During surgery, an internal cavity within the electrode forms a heat pipe heat transfer device. The electrode is closed at both its proximal and distal ends. The cavity within each electrode is evacuated and contains a working fluid, e.g., water. When the distal end of an electrode contacts tissue heated by the electrosurgical procedure, the working fluid inside the electrode evaporates, filling the internal cavity with vapor. At the proximal end of the electrode, the vapor condenses, and the resulting liquid flows back toward the distal end of the device via a wick. Heat is thus carried away from the distal end to cool the electrode at the surgical site. At the proximal end of the electrode, a heat exchanger in the form of external heat conductive fins are used to carry heat away from the device. It should be noted that Levine&#39;s heat pipe assembly is one piece that requires complete immersion of the utensil in a sterilization system for cleaning, thus reducing it&#39;s working life.  
         [0009]     In U.S. Pat. No. 5,908,418, issued to Dority et al., a hand held coagulating device is disclosed having a cooled handle for improved user comfort. An outer shell houses internal components of the device and provides a surface for the user to hold the device during a surgical procedure. A contact element positioned in an opening in a forward end of the shell is placed against an area of tissue to be coagulated, and radiation produced by a radiation source, such as an incandescent lamp, is transmitted through the contact element to the tissue. A heat sink is positioned in an opening in an aft end of the shell for conducting heat to the surrounding environment. A heat pipe is connected between the radiation source and the heat sink so that heat is transferred directly from the radiation source to the outside air while the surface used for holding the device remains cool.  
         [0010]     There has been a long felt need for an improved cautery tool having a more efficiently designed and effective heat pipe cooling system.  
       SUMMARY OF THE INVENTION  
       [0011]     The present invention provides a cautery surgical device comprising a surgical forceps including a pair of elongate arms each including a free end supporting an electrode tip for applying electrical energy to tissue. The arms of the surgical forceps are joined at another end so as to provide for resilient compressible movement of the arms between a normally open position, wherein the arms are disposed in aligned, substantially parallel, spaced-apart relation and a squeezed closed position, wherein the electrode tips are disposed in abutting relationship. The arms of the surgical forceps further include respective spaced-apart free ends and a receptacle extending along each arm from the free end toward the joined end. A heat pipe is releasably mounted to each arm for conducting heat away from the electrode tip. Each heat pipe comprises an evaporator portion having an end and a first diameter, with the electrode tip mounted to the evaporator end. A condenser portion of the heat pipe is spaced away from the evaporator end, and advantageously transitions from the first diameter to at least one smaller diameter section. In a preferred embodiment of the invention, the heat pipe further includes a cylindrical tube having an evaporation end, a condensation end, and a central passageway that is lined with a wick and at least partially filled with a fluid. The condensation end comprises a diameter that is smaller than the diameter of the evaporation end so as to be releasably received within a socket disposed within the receptacle of each arm. The socket includes a longitudinal blind hole that is sized so as to releasably receive the smaller diameter section of the condenser portion and means for releasably engaging a portion of the arm. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]     These and other features and advantages of the present invention will be more fully disclosed in, or rendered obvious by, the following detailed description of the preferred embodiment of the invention, which is to be considered together with the accompanying drawings wherein like numbers refer to like parts and further wherein:  
         [0013]      FIG. 1  is an exploded perspective view of a heat pipe cooled cautery surgical instrument formed in accordance with the present invention;  
         [0014]      FIG. 2  is a perspective view of the surgical instrument shown in  FIG. 1 , but with the mandibles removed for clarity of illustration;  
         [0015]      FIG. 3  is a broken away, perspective view of a portion of the surgical instrument shown in  FIGS. 1 and 2 , showing a groove and receptacle socket formed in accordance with the present invention;  
         [0016]      FIG. 4  is an exploded, perspective view of a mandible assembly formed in accordance with the present invention;  
         [0017]      FIG. 5  is a perspective view of the mandible assembly shown in  FIG. 4 , fully assembled;  
         [0018]      FIG. 6  is an elevational view of the mandible assembly shown in  FIG. 5 ;  
         [0019]      FIG. 7  is a cross-sectional view of the mandible assembly shown in  FIG. 6 , as taken along lines  7 - 7  in  FIG. 6 ;  
         [0020]      FIG. 8  is a broken away, enlarged cross-sectional view of an electrode tip and evaporator portion of the mandible assembly shown in  FIG. 7 ;  
         [0021]      FIG. 9  is a broken away, enlarged cross-sectional view of a condenser portion of the mandible assembly shown in  FIG. 7 ;  
         [0022]      FIG. 10  is a cross-sectional view of the condenser portion of the mandible assembly shown in  FIG. 9 , as taken along lines  10 - 10  in  FIG. 9 ;  
         [0023]      FIG. 11  is a side elevational view, partially in cross-section, of a socket formed in accordance with the present invention;  
         [0024]      FIG. 12  is a side elevational view, partially in cross-section, of the socket shown in  FIG. 11 , rotated approximately 90° about its longitudinal axis; and  
         [0025]      FIG. 13  is an end on view of the socket shown in  FIGS. 11 and 12 . 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0026]     This description of preferred embodiments is intended to be read in connection with the accompanying drawings, which are to be considered part of the entire written description of this invention. The drawing figures are not necessarily to scale and certain features of the invention may be shown exaggerated in scale or in somewhat schematic form in the interest of clarity and conciseness. In the description, relative terms such as “horizontal,” “vertical,” “up,” “down,” “top” and “bottom” as well as derivatives thereof (e.g., “horizontally,” “downwardly,” “upwardly,” etc.) should be construed to refer to the orientation as then described or as shown in the drawing figure under discussion. These relative terms are for convenience of description and normally are not intended to require a particular orientation. Terms including “inwardly” versus “outwardly,” “longitudinal” versus “lateral” and the like are to be interpreted relative to one another or relative to an axis of elongation, or an axis or center of rotation, as appropriate. Terms concerning attachments, coupling and the like, such as “connected” and “interconnected,” refer to a relationship wherein structures are secured or attached to one another either directly or indirectly through intervening structures, as well as both movable or rigid attachments or relationships, unless expressly described otherwise. The term “operatively connected” is such an attachment, coupling or connection that allows the pertinent structures to operate as intended by virtue of that relationship. In the claims, means-plus-function clauses are intended to cover the structures described, suggested, or rendered obvious by the written description or drawings for performing the recited function, including not only structural equivalents but also equivalent structures.  
         [0027]     Referring to  FIGS. 1 and 2 , a heat pipe cooled cautery system  5  formed in accordance with the present invention comprises an electrosurgical device in the form of a forceps  8  including a pair of outwardly biased arms  10  and a pair of mandible assemblies  12 . More particularly, arms  10  are often formed from a titanium alloy, and are fastened to one another at a grip end  14  in a conventional way. Each arm  10  has a free end  16  ( FIG. 2 ). In this construction, when arms  10  are squeezed or pinched together at their free ends  16 , they tend to spring apart from one another upon release of the pinching pressure. Each arm  10  includes a groove  18  that is formed on an interior wall of arm  10  so that grooves  18  are in substantially confronting relation to one another. A receptacle socket  20  is formed at the end of each groove  18  so as to be located between grip end  14  and free end  16  ( FIGS. 2 and 3 ). Receptacle socket  20  comprises a slot  21  and a conventional release mechanism  22  that protrudes into receptacle socket  20 . A release button  23  protrudes outwardly from the outer surface of each arm  10 , and is operatively connected to release mechanism  22  in a conventional manner. Of course, receptacle socket  20  may also be formed within a tubular arm  10  without departing from the scope of the present invention.  
         [0028]     A bipolar generator (not shown) of the type well known in the art for providing radio frequency (RF) output that is suitable for surgical procedures is interconnected to arms  10  in a conventional manner. One bipolar generator suitable for use with the present invention is a CMC III bipolar generator, manufactured by Valley Forge Scientific Corp., Oaks, Pa., and described in U.S. Pat. No. 5,318,563 which patent is incorporated herein by reference. In a typical application, electrical current is applied to preselected tissue using a portion of mandible assembly  12  as a unipolar electrode.  
         [0029]     During surgery, a return electrode is attached to the patient at a position away from the surgical site. The bipolar generator is then used to energize the electrode. The exposed end of the electrode is brought into contact with preselected tissue of a patient which results in a current path being provided between the electrode and the patient. RF current from the electrode develops a high temperature region about the electrode&#39;s exposed end which destroys the selected tissue. In order to regulate the temperature at the surgical site, mandible assemblies  12  comprise a heat pipe  25 , a socket  28 , and an electrode tip  30  ( FIGS. 4-9 ).  
         [0030]     More particularly, heat pipe  25  comprises a vacuum tight tube  32 , a wick  35 , and a working fluid  37  ( FIGS. 7-10 ). Tube  32  is often a relatively long cylinder formed from a highly thermally conductive material, e.g., copper, aluminum, or their alloys, monel, or the like. A vapor space  43  ( FIG. 10 ) is defined by a central passageway extending along the longitudinal axis of vacuum tight tube  32 . Heat pipe  25  may include a conductive outer sleeve that is covered with an insulating cover which may extend along its length.  
         [0031]     Tube  32  comprises a substantially cylindrical evaporation end  39  and a condensation end  41  that has been formed so as to be at a decreased diameter. In a preferred embodiment, condensation end  41  is swaged (i.e., plastically deformed by a tool having a working surface profile that is complementary to the shape desired for the piece being plastically deformed) so that it includes a frusto-conical transition  46  that leads to a substantially cylindrical socket interface section  48  ( FIGS. 4, 7 , and  9 ). A seal  50  is formed at the distal end of heat pipe  25  adjacent to socket interface section  48 . Seal  50  may comprise a pinched portion of tube  32 , a further swaging of the distal end of condensation end  41 , or a weld.  
         [0032]     Wick  35  may comprise adjacent layers of screening or a sintered powder structure with interstices between the particles of powder. In one embodiment, wick  35  may comprise aluminum-silicon-carbide (AlSiC) or copper-silicon-carbide (CuSiC) having an average thickness of about 0.1 mm to 1.0 mm. Working fluid  37  may comprise any of the well known two-phase vaporizable liquids, e.g., water, alcohol, freon, etc. Heat pipe  25  is formed according to the invention by drawing a partial vacuum within tube  32 , and then back-filling with a small quantity of working fluid  37 , e.g., just enough to saturate wick  35  just prior to final hermetic sealing of tube  32  by pinching and welding or otherwise hermetically sealing off both ends. The atmosphere inside heat pipe  25  is set by an equilibrium of liquid and vapor.  
         [0033]     Referring to  FIGS. 11-13 , socket  28  may comprise either a thermally conductive cylindrical rod, e.g., a metal, or a less thermally conductive polymer of the type often used in medical devices. Socket  20  has a longitudinally oriented blind hole  60  at a first end  62 , and a catch  65  positioned on a second end  67 . The majority of heat pipe  25 , i.e., all of evaporation end  39  up to, but not including condensation end  41 , has substantially the same outer diameter as socket  28 . Blind hole  60  is sized and shaped so as to releaseably receive condensation end  41  of heat pipe  25 , i.e., blind hole  60  comprises a diameter that is only slightly larger than the outer diameter of cylindrical socket interface section  48 , but slightly smaller than a portion of frusto-conical transition  46  ( FIG. 9 ). Second end  67  of socket  28  is substantially solid with catch  65  projecting longitudinally outwardly from the terminal end of socket  28 .  
         [0034]     Referring to  FIG. 8 , electrode tip  30  comprises a thermally and electrically conductive cap having a longitudinally oriented blind hole  80  at a first end  82 , and a pointed tip  84 . Blind hole  80  is sized and shaped so as to securely retain the tip portion of evaporation end  39  of heat pipe  25 , i.e., blind hole  80  comprises a diameter that is only slightly larger than the outer diameter of evaporation end  39 .  
         [0035]     Each mandible assembly  12  is assembled by first positioning an electrode tip  30  on evaporator end  39  of tube  32 . More particularly, electrode tip  30  is arranged so that blind hole  80  at first end  82  is positioned in coaxially aligned confronting relation to evaporator end  39  of tube  32 . Once in this position, electrode tip  30  is moved toward tube  32  so that a portion of evaporator end  39  enters blind hole  80 . It would be understood that blind hole  80  may include an appropriate thermal epoxy or a low temperature melting metal, e.g., solder, for maintaining electrode tip  30  in position on heat pipe  25 . Alternatively, evaporation end  39  of heat pipe  25  may be formed so as to comprise the same profile as electrode tip  30 .  
         [0036]     Each heat pipe  25  may be assembled to forceps  8  in the following manner. A heat pipe  25  is first oriented so that cylindrical socket interface section  48  is positioned in confronting coaxial relation with blind hole  60  at first end  62  of a socket  28 . Once in this position, heat pipe  25  is moved toward socket  28  so that seal  50 , at the distal end of heat pipe  25 , enters blind hole  60  of socket  28 . Heat pipe  25  continues into socket  28  until fully received within blind hole  60 . Heat pipe  25  is fixedly engaged within blind hole  60  by epoxy, brazing, or solder so as to form a mandible assembly  12 .  
         [0037]     Each mandible assembly  12  is then assembled to each arm  10  of forceps  8  by positioning catch  65  in aligned coaxial relation with groove  18  of arm  10 . Once in this position, socket  28  is moved along groove  18  until it is received within receptacle socket  20  adjacent to the interior side of grip end  14  ( FIG. 1 ). Once catch  65  has fully entered receptacle socket  20 , release mechanism  22  is releasably engaged so as to hold socket  28  within arm  10 .  
         [0038]     In operation, electrode tip  30  is placed adjacent to tissue being treated. At the same time, the patient is maintained in contact with a grounding pad. RF electrical energy is applied to the tissue according to the desired tissue treatment, i.e., applied across electrode tips  30  and the grounding pad to treat the tissue. Heat pipe  25  serves to transfer heat away from electrode tip  30  during operation of cautery system  5 . During operation, evaporation end electrode  39  is heated by the tissue. In accordance with the well-known operation of heat pipes, thermal energy is transferred through tube  32  to working fluid  37  residing in and on wick  35 . Working fluid  35  evaporates, with the thus formed vapor traveling along the interior of heat pipe  25  from evaporation end  39  to condensation end  41 . The vapor condenses in and around condensation end  41 , and the resulting liquid flows back to evaporation end  39  via capillary action within wick  35 . Heat is thus carried away from electrode tip  30 . When the procedure is complete, each heat pipe  25  is removed from forceps  8  by merely depressing release button  23  on each arm  10  and pulling socket  28  from receptacle socket  20 .  
         [0039]     It is to be understood that the present invention is by no means limited only to the particular constructions herein disclosed and shown in the drawings, but also comprises any modifications or equivalents within the scope of the claims.

Technology Classification (CPC): 0