US 20060212031 A1
Thermal cautery and thermal ligating devices improved by the addition of a thermally conductive plate proximate the resistive heating element used in those devices.
1. A medical device comprising:
a laparoscopic grasper characterized by a first arm and a second arm, each of said arms having a proximal end and distal end, each of said arms being rotatably relative to the other about a point near the distal end of the grasper, said arms being adapted to be inserted into the body and to be rotatably opened and closed upon each other within the body, said first arm having a first gripping face disposed on the distal end thereof, said second arm having second gripping face disposed on the distal end thereof, said gripping faces defining surfaces generally perpendicular to a plane defined by the grasping arms, said surfaces being movable into apposition with each other upon closing of the grasper;
a first layer of resilient material disposed on the gripping face of the first arm;
a second layer of resilient material disposed on the gripping face of the second arm;
a wire disposed between of the first and second layers of resilient material so as to be trapped between the gripping faces of the first and second arm upon closing of the graspers and
a thermally conductive and electrically insulative plate disposed between the wire and the gripping face of the first arm.
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a sleeve covering the distal end of the first grasping arm, thereby forming a thermally insulative surface on the grasping face of the first grasping arm.
13. The device of
a resilient sleeve covering the distal end of the second grasping arm, thereby forming a resilient surface on the grasping face of the second grasping arm.
14. The device of
a sleeve covering the distal end of the first grasping arm, thereby forming a surface on the grasping face of the first grasping arm, between the wire and the grasping face of the arm, and
a resilient sleeve covering the distal end of the second grasping arm, thereby forming the resilient surface on the grasping face of the second grasping arm.
This application is a continuation of U.S. application Ser. No. 10/713,490 filed Nov. 14, 2003, now U.S. Pat. No. 7,011,656.
The inventions described below relate to instruments and methods for sealing, joining, and cutting tissue.
The devices described below provide for improved heat transfer and sealing performance for our Starion® line of thermal cautery forceps and thermal ligating shears, and in instruments such as those disclosed in Treat, et al., Electrothermal Instrument For Sealing And Joining Or Cutting Tissue, U.S. Pat. No. 6,626,901 (Sep. 30, 2003) (the disclosure of which is hereby incorporated in its entirety).
The thermal cautery and thermal ligating devices disclosed in U.S. Pat. No. 6,626,901 are improved by the addition of a thermally conductive plate proximate to the resistive heating element used in those devices.
The distal tips include the various elements of the heating assembly. A resistive heating element (a heater wire) 34 is disposed on the grasping face of distal tip 30, secured to the distal end of the grasping arm 23 and extending proximally over the grasping face of the grasping arm toward the proximal end of the grasping arm. The distal tip 30 is also covered with a resilient, non-stick, thermally insulative sleeve 35 to provide a resilient pad 36 on the grasping face under the heater wire, between the heater wire and the grasping face. The grasping face of the opposing distal tip 29 may also be covered by a resilient, non-stick, thermally insulative surface 37, provided as a portion of sleeve 38 disposed over the distal tip 29, in order to provide an anvil surface upon which the heating element acts during operation. The thermally conductive but electrically insulative plate 39 is disposed between the heating element 34 and the resilient pad 36.
Additional elements of the forceps are also shown in
In addition to the structure shown in
The plate greatly increases the amount of heat energy that can be delivered to the tissue prior to cutting the tissue. This increases the seal size (the amount of tissue that is sealed) and the integrity of the seal. With direct contact between the heating element and the thermally conductive plate, sufficient heat energy is conducted to the thermally conductive plate to heat the entire plan area of the tissue in contact with the thermally conductive plate to sealing temperatures. Sealing temperatures, which are generally between 60° C. and 100° C., are achieved quickly because of the intimate contact between the heating element and the thermally conductive plate and the high thermal conductivity of the thermally conductive plate. Thermally isolating the thermally conductive plate from the forceps arms (a function provided by the sleeve) adds to the ability of the thermally conductive plate to quickly come up to temperature. The thermal resistance between the heating element and the thermally conductive plate results in temperatures that are always lower in the thermally conductive plate than in the heating element. This promotes tissue sealing in the thermally conductive plate area and tissue cutting in the heating element area. An added benefit of the thermally conductive plate is that it promotes even heating element temperatures due to increasing the effective longitudinal thermal conductivity of the heating element. Because the heating element and the thermally conductive plate are in intimate contact with very little thermal resistance between them the heating element longitudinal thermal conductivity is effectively improved because of the good longitudinal conductivity of the thermally conductive plate. This is very important when the heating element has uneven heat loads, as is usually the case. The high thermal conductivity of the thermally conductive plate allows it to transfer heat from one portion of the heating element to another colder portion of the heating element/thermally conductive plate assembly. This action pulls up the temperatures in the low spots and brings down the temperatures in the high spots. Bringing down the high temperatures is a benefit as very high temperatures, such as those in excess of 500° C., are undesirable. If temperatures below 300° C. are maintained, non-stick components such as PTFE or ePTFE (Teflon®) coatings will survive for the life of the device. Temperatures in excess of 300° C. will quickly destroy these components, and temperatures in excess of 600° C. may melt an aluminum heat spreader.
Current Starion® device heating element plan areas are 0.022″ wide by 0.75″ long or 0.010″ wide by 0.750″ long. Using the thermally conductive plate with these existing heating elements, at power level of about 10 watts, results in heated plan areas which can be increased by 5 times or more over the prior device. Heat spreader dimensions of 0.065 to 0.100″ wide have proven effective in testing.
Dimensions of the various components and the appropriate power levels for the thermal cautery devices incorporating the heating element and heat spreader have been developed through testing on natural live tissue which closely approximates the sealing behavior of vascularized human body tissue. Specifically, live earthworms have been used in testing to develop the heat spreader design, thus making it quite convenient and inexpensive to test prototypes as necessary to optimize the geometry and material characteristics of the various components. As illustrated in
In use, the thermal cautery device is manipulated to grasp body tissue, such as a blood vessel, a small section of fat, or other tissue as necessitated by the desired surgery. With the grasping arms on either side of the target tissue, surgeons gently close the grasping arms or forceps, as the case may be, to bring the grasping faces into apposition, with the target tissue held between the faces. While applying pressure to the tissue with the grasping faces, the surgeon energizes the device to provide a DC current to the heating wire. The heating wire itself heats up to temperatures above about 200° C., thus vaporizing the tissue immediately between the heating wire and the opposing grasping face (and a small lateral extent of tissue). Heat is applied for a period of time, in the range of 5 seconds to 20 seconds, thus allowing heat from the heating element to conductively heat the heat spreader plate. Heat from the heat spreader plate, which typically reaches temperatures of 60° C. to 100° C., is thereby applied to the tissue trapped between the heat spreader plate and the opposing grasping face, resulting in a thermal seal of the tissue with a width closely corresponding to the plan area of the plate (less the small vaporized section).
The improvements to the thermal cautery device have been described in relation to laparoscopic ligation devices and forceps devices, but they may be applied to open surgical forceps and clamps, catheter-based devices, and various other embodiments of thermal cautery and thermal ligation devices. Thus, while the preferred embodiments of the devices and methods have been described in reference to the environment in which they were developed, they are merely illustrative of the principles of the inventions. Other embodiments and configurations may be devised without departing from the spirit of the inventions and the scope of the appended claims.