JPS6128339B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an incision instrument, and more particularly to a surgical incision instrument equipped with a device for maintaining a cutting edge at a constant high temperature. This device is made of a material whose relative magnetic permeability exhibits a transition to the Currie point in a certain high temperature range, and when the temperature drops below a predetermined temperature, the thickness of the skin decreases and the electric current passing through it reduces the Joule heat. The temperature is increased by increasing the temperature, and when the temperature exceeds a predetermined value, the thickness of the epidermis increases due to the transition of the Kiuri point, and the resistance decreases, thereby suppressing the generation of Joule heat. Control of bleeding during a surgical procedure constitutes a large portion of the total time involved during the procedure. Whenever tissue is dissected, bleeding from the plethora of small blood vessels that spread through all the tissue obscures the surgeon's vision, reduces his precision, and requires slow and careful surgical procedures. shall be. It is well known to heat tissue to minimize bleeding from cuts. Additionally, scalpels designed to increase tissue temperature and minimize bleeding are also known. One such female is high frequency,
A high-energy spark is transmitted from a small electrode in the surgeon's hand to the tissue, where it is converted into heat. Typically, a substantial electrical current is passed through the patient's body to a large electrode beneath the patient, thus creating an electrical circuit. However, insufficient control over the distribution and intensity of the spark emission and temperature transformation in the tissue results in irregular muscle contractions in the patient, thus making this device difficult to perform in precision surgical procedures. It cannot be used to do anything. Furthermore, this type of device can result in severe tissue damage and tissue fragments, such as charring or death, which substantially impede wound healing. Another known scalpel uses a blade with a resistive heating element to cut tissue and provide simultaneous bleeding cessation. Although these resistive elements can easily be brought to a suitably high constant temperature in air prior to contacting the tissue,
As soon as the blade parts come into contact with tissue, they cool rapidly. During a surgical procedure, when tissue is cut, a different part of the blade always comes into contact with the tissue, which cannot be known in advance. As the blade cools,
Tissue dissection and bleeding control are significantly less effective and tissue tends to adhere to the blade. If additional power is applied by conventional means to counteract this cooling, this additional power may be selectively transmitted to the uncooled portions of the blade. , often resulting in excessive temperatures, which may result in tissue damage and blade failure. This arises from the fact that in certain known resistively heated scalpels, heating is a function of the resistance times the current squared. In conventional metallic blades of this type, the higher the temperature of any blade section, the greater its electrical resistance and therefore the greater the increased heating resulting from increased power input. To seal the tissue and stop bleeding, a temperature of 300℃ is required.
It is generally accepted that it is desirable to operate at temperatures between 1000°C. For the above reasons, electrothermal hemostasis surgical cutting instruments have a cutting edge that is
to a substantially uniform operating temperature within the desired optimum range;
It is desirable to include a mechanism by which power is selectively distributed to portions of the blade that are cooled by tissue contact so as to be maintained. Recently, a hemostatic scalpel has been described in which the temperature control mechanism includes a resistive heating element disposed on the surface of the scalpel blade. (For example, U.S. Pat. No. 3,768,482 and U.S. Pat.
(See No. 3826263). However, such devices require precision in sizing the heating element to obtain the desired resistance. And, as tissue fluids and proteins become deposited on the surface of the blade, such resistive heating elements may undergo changes in resistance during use. The present invention provides that the cutting area of the blade is heated to a preselected height by heating by radio frequency current flowing within the variable skin thickness of the electrical conductor located at the cutting edge area. To provide a surgical cutting instrument that can be brought to a temperature range and maintained within the temperature range. A radio frequency alternating current is conducted by a current carrying conductor located near the cutting edge of the blade. Current has a tendency to concentrate near the surface and decay exponentially with distance from the surface. This phenomenon is called the "skin effect." The depth of this skin effect is approximately 37
%, determined by the electrical resistivity and magnetic permeability of the material conducting the current and by the frequency of the alternating current. The thickness of the epidermis d (cm) is determined by. For example, Richard M. Bozorth's ``ferromagnetism''
(Published by Day Van Nostrand in 1951) 770~
See page 771. Here, ρ×10 ⁻⁹ is the electrical resistivity (ohm-cm), μ is the relative magnetic permeability, and is the frequency (hertz). A self-regulating heated scalpel is created by passing a radio frequency (RF) current through a conductor that is utilized as a resistive heating element. These resistive heating elements are located at the cutting edge of the scalpel and exhibit an increase in electrical parameters such as magnetic permeability as the temperature decreases. It is seen that an increase in permeability causes a decrease in skin thickness. The resistance of a path that conducts current is inversely proportional to the cross-sectional area (path width times skin thickness), so
This effect causes an increase in the resistance of the current path in the cooled region and an increase in its heating. By way of example, ferromagnetic materials such as iron, nickel, and cobalt, and their alloys exhibit large changes in relative magnetic permeability as their temperature passes through a transition point called the "Curie" point. lots of iron
This Kyrie point for nickel alloy is approximately 450
Occurs at ℃. Above this Curie point, the relative magnetic permeability remains almost unchanged. Below the Curie point it is high, perhaps 100 to 1000, for the magnetic field force utilized in this application. added
The RF signal causes an electric current to flow through the surface conductor of the blade near the cutting edge. This then heats the cutting edge to approximately 500°C prior to contact with tissue. When a portion of the cutting edge contacts tissue and is cooled, the temperature of the cooled portion may drop below the Curie point. This, in turn, would increase the relative permeability from near a constant value to over 100. The associated epidermal thickness will be reduced by more than 10:1. Heating will then increase proportionately in the cooled section. In accordance with the present invention, a scalpel blade of electrically insulating material, such as alumina ceramic, conducts a high frequency current along a conductor near the cutting edge, thereby generating an electrical current at the region of its cutting edge. heated to. These conductors are made of ferromagnetic material placed on the insulating material of the blade. However, the scalpel blade, which is a member to be cooled, does not need to be made of an insulating material, and may be insulated from the conductor via an insulating sheet, for example. Referring now to FIGS. 1 and 2, one embodiment of the present invention includes a blade portion 9 of electrically insulating material, such as alumina ceramic, attached to a handle 11 to form a surgical instrument. An example is shown. Nickel - Signal conductor 1 made of ferromagnetic material such as iron
3 to form a complete conduction path along one side of the blade 9 and the other side of the blade on the back.
It is arranged on the blade 9 adjacent to the blade 1. Input power at radio frequencies may be supplied to the conductor 13 from the power source 19 through the connection means 15 and 17. With the current-carrying conductor 13 made of ferromagnetic material, the skin thickness characteristics previously discussed can be advantageously utilized for temperature regulation. Current flowing through the ferromagnetic conductor 13 will flow inside the conductor at the skin thickness for that material. The ferromagnetic material and the ceramic cutting edge 21 thermally coupled thereto will then be heated. From the operating temperature in air, which is above the Curie temperature, the portion of the cutting edge will cool when it contacts tissue. And its operating temperature may fall below the Curie temperature. The thickness of the epidermis will then decrease by approximately 10:1, giving a localized increase in heating of approximately 10:1. To achieve a 10:1 power increase, the relative permeability must not only increase by 100:1 when cooled by tissue contact, but also when pre-cutting in air. The skin thickness at the condition must be approximately two-thirds or less of the conductor thickness to achieve a 10:1 skin thickness reduction. Thus, for a suitably thin scalpel blade made of ferromagnetic material and equipped with a suitably thin self-adjustable conductive heating device thereon, high frequency It may require. The next display is
The required frequencies are shown for various skin thicknesses above and below the Curie point in a 50:50 iron-nickel ferromagnetic alloy. and a width 40 mm continuously placed on both facets of the scalpel blade at the 3 cm cutting edge region when energized by a current of about 3 amperes.
Showing the related power consumption of the conductor of the mill.

A layer of insulation 23 is placed over the conductor 13 to insulate the tissue being cut from the electrical current. To adjust the average operating temperature of the cutting edge, the high frequency signal source 19 may be adjustable in signal amplitude, or in frequency, or both. As mentioned above, to change the thickness of the epidermis, and
The frequency may be adjusted to thereby establish an operating temperature around the cutting edge in air.

[Brief explanation of the drawing]

1 is a side view of a surgical instrument according to the invention, and FIG. 2 is a cross-sectional view of the blade of the device of FIG. 9...Blade portion, 11...Handle portion, 13...Conductor, 15...Connection means, 17...Connection means, 19...Signal source, 21...
Cutting edge, 23...insulating layer.

Claims (1)

[Scope of Claims] 1. an incising cutting edge; a heating device disposed close to the incision cutting edge and extending along the incision cutting edge;
A heating device made of a ferromagnetic material whose magnetic permeability exhibits a transition to the Curie point at a certain high temperature, and a device connected to the heating device to supply a radio frequency current to the heating device, the device being connected to the heating device and supplying radio frequency current to the heating device, the current flowing at a temperature below the Curie point. is concentrated in a certain thickness of the epidermis of said heating device, and at a temperature above said Curie point, the current flows through the epidermis of said heating device in a thickness greater than said thickness. 2. The ferromagnetic material of the heating device comprises an element selected from the group consisting of iron, nickel and cobalt and exhibits a Curie point transition within a temperature range of about 300°C to about 1000°C. An incision instrument according to claim 1. 3. The incision instrument of claim 1, wherein the heating device has an insulating layer disposed over the heating device. 4. The incision instrument according to claim 1, wherein the incision cutting edge is made of an electrically insulating material.