CA1083457A - Surgical instrument having self-regulated electrical induction heating of its cutting edge and method of using the same - Google PatentsSurgical instrument having self-regulated electrical induction heating of its cutting edge and method of using the same
- Publication number
- CA1083457A CA1083457A CA 246544 CA246544A CA1083457A CA 1083457 A CA1083457 A CA 1083457A CA 246544 CA246544 CA 246544 CA 246544 A CA246544 A CA 246544A CA 1083457 A CA1083457 A CA 1083457A
- Grant status
- Patent type
- Prior art keywords
- cutting edge
- electrically conductive
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B18/00—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body
- A61B18/04—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body by heating
- A61B18/08—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body by heating by means of electrically-heated probes
ELECTRICAL INDUCTION HEATING OF ITS CUTTING
EDGE AND METHOD OF USING THE SAME
Abstract of the Disclosure The cutting edge of a scalpel blade is electrically heated by induction of circulating currents in the internal structure of the blade near the cutting edge. Selective heating of regions of the cutting edge that are locally cooled by contact with tissue during surgical cutting is pro-vided by constructing the blade of ferromagnetic materials that have a Curie point in the operating temperature range and that provide large increases in permeability for tempera-ture decrements below the Curie point.
SURGICAL INSTRUMENT HAVING SELF-REGULATED
ELECTRICAL INDUCTION HEATING OF ITS CUTTING
EDGE AND METHOD OF USING T~IE SAME
Background of the Invention The control o bleeding during surgery accounts for a major portion of the total time involved in an operation. The bleeding that occurs from the plethora of small blood vessels that pervade all tissues whenever tissues are incised obscures the surgeon's vision, reduces his precision, and often dictates slow and elaborate procedures in surgical operations. It is well known to heat the tissues to minimize bleeding from in-cisions, and surgical scalpels which are designed to elevate tissue temperatures and minimize bleeding are also well known. ~ `
One such scalpel transmits high frequency, high energy sparks from a small electrode held in the surgeon's hand to the tissues, where they are converted to heat. Typically, substantial elec-trical currents pass through the patient's body to a large electrode beneath the patient, which completes the electrical circuit. Discharge of sparks and temperature conversion in the -tissue are poorly controlled in distribution and intensity, and erratic muscular contractions in the patient are produced so that this apparatus cannot be used to perform precise surgery.
1~3457 Further, apparatus of this type frequency produce severe tissue damage and debris in the form of charred and dead tissue, which materially interfere with wound healing.
Another well-known surgical scalpel employs a blade with a resistive heating elament which cuts the tissue and provides simultaneous hemostasis. Although these resistive elements can be readily brought to a suitably high and constant temperature in air prior to contacting tissues, as soon as portions of the ~ ~
blade come in contact with tissues, they are rapidly cooled. - :
During surgery, non-predictable and continuously varying portions of the blade contact the tissues as they are being cut. As the blade cools, the tissue cutting and hemostasis become markedly 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 is selectively delivered to the uncooled portions of the blade, frequently resulting in excessive temperatures which may result in tissue damage and blade destruction. This results from the fact that in certain known resistively heated scalpels, the heating is a function of the current squared times the resistance (I R). In conventional metallic blades of this type, the higher the temperature of any blade portion, the greater its electrical resistance, and con-sequently the greater the incremental heating resulting from incremental power input.
It is generally recognized that to seal tissues and effect hemostasis it is desirable to operate at a temperature between 300C. and lOOO~C. And for reasons noted above, it is desirable that electrothermal hemostatic surgical cutting instruments include a mechanism by which power is selectively delivered to those portions of the blade that are cooled by . . .
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:~083457 tissue contact so that the cutting edge may be maintained at a substantially uniform operating temperature within the desired optimal range. Recently, hemostatic scalpels have been described (see, for example, U. S. Patents 3,768,~82 and 3,826,263) in which temperature-controlling mechanisms include resistive heating elements disposed on the surface of the scalpel blade. However, such instruments require precision in fabricating the dimensions of the heating elements to obtain the desired resistance. And s~ch resis-tive heating elements may be subjected to variations inresist~nce during use, as tissue juices and proteins become deposited upon the surface of the blade.
_ummary of the Invention -In accordance with one aspect of this invention there is provided a blade comprising:
a cutting means including a cutting edge having electrically conductive means disposed in the region along said edge, wherein the electrically conductive means has an electrical parameter that varies as a function of temperature ``
to increase power dissipation on an applied electrical signal in the regions of the cutting edge when said regions of said cutting edge are selectively cooled; and means disposed in electrically insulated and electro-magnetically coupled relationship to the electrically conduc-tive means for inducing current therein. -In accordance with another aspect of this invention there is provided a method of heating the tissue-cutting edge of a hemostatic scalpel blade having electrically conduc-tive means disposed proximate to a tissue-cutting edge of said blade and having an electrical conductor means insulated from, and electromagnetically coupled to, said electrically ~ -3~
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conductive means adjacent said tissue-cutting edge, the method comprising: applying an alternating signal to the electrical conductor means to induce current within said electrically conductive means near the tissue-cutting edge for heating said electrically conductive means; and increasing power dissipation in the regions of said tissue-cutting edge which are selectively cooled upon contact with the tissue being cut responsive to an electrical parameter of said electrically-conductive means that varies as a function of temperature thereof.
In accordance with another aspect of this invention there is provided a method of heating a cutting blade having electrically conductive material in the region of a cutting edge operating at an elevated temperature, the method com-prising the steps of: supplying an alternating electrical signal along an electrical conductor adjacent the cutting -edge; electromagnetically coupling the alternating electrical signal in the electrical conductor to the electrically conduc-tive material in the region to said cutting edge for inducing current therein to heat the cutting edge; and increasing power dissipation in response to variations with temperature of an electrical parameter of said electrically conductive material in the regions of said cutting edge which are selectively cooled.
By way of added explanation, in one aspect the present invention provides a surgical cutting instrument in which the cutting portion of the blade is brought to an elevated temperature by heating of the internal structure of the blade. Current is induced within the internal structure of the blade, preferably in the region of the cutting edget ~ -3a-,':, .
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~L01~3457 in response to electromagnetic energy that is coupled thereto from a conductor which is disposed on the surface of the blade along the cutting edge to carry an applled alternating signal. The thickness of the surface conductor is not critical in determining the density of the induced currents and the resultant blade temperatures. The average temperature of the cutting edge may be adjusted by adjust-ing the amplitude and/or frequency of the alternating signal being carried in the surface conductor.
Further, the portions of the cutting edge that are cooled by tissue contact may be selectively heated to maintain cutting edge temperatures sufficiently constant by inducing the local currents in a material which exhibits substantial changes -3b-' ~
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in electrical parameters such as permeability or electrical resistivity as a function of temperature. For applied radio fre-quency signal, the circulating currents tend to be concentrated near the surface of the blade material and to decrease exponential-ly with depth. The skin depth is defined as the depth at which the density of the induced current is 37~ of its surface value and it varies inversely as the square root of magnetic permeability, in-versely as the square root of frequency and directly as the square root of the resistivity of the material. The induced currents are responsible for the I R Joule heating of the blade material.
By way of example, ferromagnetic materials composed of iron, nickel, and cobalt and their alloys exhibit large changes in relative permeability as their temperature goes through a transition point called the "Curie" point. In many iron-nickel alloys this Curie point occurs in the temperature range of interest. Above the Curie point, the relative permeability may be near unity and at temperatures below the Curie point the permeability may rapidly increase by factors of 100 to 1000 for magnetic field strengths of the dimension that would be utilized in this application. Thus, if prior to cutting, the scalpel is operated at a temperature somewhat above the Curie point, then as various portions of the blade are cooled by contact with the tissues, the temperature of those and only those portions of the blade will tend to drop below the Curie point, at which time the permeability of the material in that region will increase by 100 to 1000 with resultant increases in the heating of the cooled portions by factors of 10 to 30.
Description of the Drawings Figure 1 is a side view of the surgical instrument of the present invention;
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~83457 Figure 2 is an end sectional view of the cutting element in the apparatus of Figure l; and Figure 3 is a side view of another embodiment of the surgical instrument of the present invention.
Description of the Preferred Embodiment In accordance with one embodiment of the present i invention, as shown in Figures 1 and 2, radio frequency current is induced to flow in an electrically conductive material which forms the scalpel blade 9 that is suitably attached to handle 10.
As shown in Figure 1, a current-carrying conductor 13 is placed about the scalpel blade 9 and is insulated therefrom by a layer 11 of insulating material. Current will be induced in the blade 9 in response to the magnetic field associated with a radio fre-quency electrical signal applied to conductor 13. The conductor 13 is placed along the edge of the blade, as shown in Figure 2, in a single loop around it. A high frequency signal supplied by source 19 through connections 15 and 17 to the conductor 13 induces circulating currents in the blade 9 which will heat it to a temperature controlled by the applied power.
Self-regulation of the operating temperature is achieved by making the blade 9 of a ferromagnetic material which has a Curie point that is below the temperature of the cutting edge prior to cutting but that is well within the acceptable oper-ating temperature range. As tissue cutting is initiated, the ~ -regions of the cutting edge which contact the tissue may be cooled to the Curie point temperature or below, thus producing in the cooled regions an increase in magnetic permeability which produces a decrease in the skin depth of the induced currents and thereby an increased current density. Power dissipation and heating thus increase in the regions that are cooled by _ 5 _ 1~83457 ~
contact with tissue. For optimal self-regulation the thickness ;;;
of the blade should exceed twice the maximum skin depth in the operative temperature range.
The following table indicates some values of power dissipation in a scalpel blade 3 cm. long and 20 mils thick made from a 50-50 iron-nickel alloy in which the conductor 13 disposed upon the surface of the blade is 40 mils wide and the scalpel is energized with a current of about 5 amperes at 6 megahertz. This RF signal current may be maintained constant where desired using conventional circuitry of well-known design.
Resistivity Relative Power, watts/cm ohm-cm(10~ ) Permeability of Blade Length Material 500C. 400C. 500C. 400C. 500C. 400C.
50-50 Fe-Ni 105 100 1 100 2.45 24.0 It is evident that there is nearly a tenfold increase in power dissipation when and where the temperature decreases below the Curie point. The Curie point temperatures, resistivities, relative permeabilities and changes in permeability as a function of temperature may be varied by altering the composition of the material used in the blade 9 or by altering the percentages of ; -elements that form the alloy material of blade 9.
The signal amplitude or the frequency, or both, of the !
high frequency signal source 19 may be adjustable in response to a control signal 27 supplied by a thermally-responsive -~
element 29 to establish the ambient operating temperature of the cutting edge in air.
In Figure 2, there is shown a sectional view of the 28 blade 9 including the conductor 13 disposed on opposite sides of . "
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the blade 9 near the cutting edge thereof. A layer of insulating material 23 is shown disposed over the electrode 13 to insulate the electrode and electrical signal appearing thereon from the tissue being cut.
In another embodiment of the present invention, the conductive material of blade 9 exhibits a negative temperature coefficient of resistance to provide increased power dissipation from the induced currents in the regions of the cutting edge that are cooled upon contact with tissue being cut.
In another embodiment of the present invention, as shown in Figure 3, the region adjacent to the entire cutting edge of the blade 39 is energized by high frequency signal sources 49 and 50 which supply power via conductors 53, 54 and 55, 56 to the multiple segments 57, 58, respectively, which are disposed as contiguous regions along the length of the cutting edge. As various segments are cooled by their contact with the tissues, the resultant temperature change may be sensed in a conventional manner (for example, by resistance changes in each of the current-carrying conductors 53, 54 and 55, 56, or by thermo-couple sensors, or the like), the power input to each segm~nt ~ -may be increased by increasing the amplitude and/or frequency of the applied high frequency signals from the respective sources 49, 50 to increase the density of induced currents and concomitant heating within the regions of the cutting edge of the blade.
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PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
a cutting means including a cutting edge having electrically conductive means disposed in the region along said edge, wherein the electrically conductive means has an elec-trical parameter that varies as a function of temperature to increase power dissipation on an applied electrical signal in the regions of the cutting edge when said regions of said cutting edge are selectively cooled; and means disposed in electrically insulated and electromagnetically coupled relationship to the electrically conductive means for inducing current therein.
a plurality of electrical conductor means, each dis-posed near said cutting edge in substantially contiguous portions along the length thereof, each of said electrical conductor means being disposed in electrically insulated and electromagnetically coupled relationship to the electrically conductive means for inducing current therein to elevate the temperature of the corresponding portion of the cutting edge in response to alternating signal applied to each of said electrical conductor means.
means responsive to the temperature of a region along said cutting edge for producing a representative control signal;
and means responsive to said control signal for altering a selected parameter of alternating signal applied to said elec-trical conductor means from said circuit means.
a cutting means including a tissue cutting edge having electrically conductive means disposed in the region along said tissue cutting edge of said cutting means, wherein the material of said cutting means exhibits a Curie point about which a transition in permeability with temperature occurs at a temper-ature of between about 300°C and about 1000°C; and electrical conductor means disposed near said tissue cutting edge in electrically insulated and electromagnetically coupled relationship to the electrically conductive means for inducing current therein.
a cutting means including a tissue cutting edge having electrically conductive means disposed in the region along said tissue cutting edge, wherein said electrically conductive means has an electrical parameter that varies as a function of temper-ature to increase power dissipation in the regions of said tissue cutting edge when said regions of said cutting edge are selec-tively cooled upon contact with tissue being cut; and electrical conductor means disposed adjacent said tissue cutting edge in electrically insulated and electro-magnetically coupled relationship to said electrically con-ductive means for inducing current therein.
a cutting means including a tissue cutting edge having electrically conductive means, wherein the material of said electrical conductive means exhibits a Curie point about which a transition in permeability with temperature occurs at a temperature of between about 300°C and about 1,000°C;
and electrical conductor means disposed near said tissue cutting edge in electrically insulated and electro-magnetically coupled relationship to said electrically conductive means for inducing current therein.
applying an alternating signal to the electrical conductor means to induce current within said electrical-ly conductive means near the tissue-cutting edge for heating said electrically conductive means; and increasing power dissipation in the regions of said tissue-cutting edge which are selectively cooled upon contact with the tissue being cut responsive to an electrical parameter of said electrically-conductive means that varies as a function of temperature thereof.
supplying an alternating electrical signal along an electrical conductor adjacent the cutting edge;
electromagnetically coupling the alternating electrical signal in the electrical conductor to the electrically conductive material in the region to said cutting edge for inducing current therein to heat the cutting edge; and increasing power dissipation in response to variations with temperature of an electrical parameter of said electrically conductive material in the regions of said cutting edge which are selectively cooled.
Priority Applications (2)
|Application Number||Priority Date||Filing Date||Title|
|Publication Number||Publication Date|
|CA1083457A true CA1083457A (en)||1980-08-12|
Family Applications (1)
|Application Number||Title||Priority Date||Filing Date|
|CA 246544 Expired CA1083457A (en)||1975-03-14||1976-02-25||Surgical instrument having self-regulated electrical induction heating of its cutting edge and method of using the same|
Country Status (5)
|JP (1)||JPS51122984A (en)|
|CA (1)||CA1083457A (en)|
|DE (1)||DE2609383C3 (en)|
|FR (1)||FR2303515B3 (en)|
|GB (1)||GB1546624A (en)|
Families Citing this family (21)
|Publication number||Priority date||Publication date||Assignee||Title|
|US4248231A (en) *||1978-11-16||1981-02-03||Corning Glass Works||Surgical cutting instrument|
|US4232676A (en) *||1978-11-16||1980-11-11||Corning Glass Works||Surgical cutting instrument|
|DE2944730A1 (en) *||1978-11-16||1980-05-29||Corning Glass Works||The surgical instrument|
|US4481057A (en) *||1980-10-28||1984-11-06||Oximetrix, Inc.||Cutting device and method of manufacture|
|DE3783904D1 (en) *||1987-03-02||1993-03-11||Everest Medical Corp||An electrosurgical instrument.|
|JP2558584B2 (en) *||1991-04-05||1996-11-27||メトカル・インコーポレーテッド||Instrument for cutting body tissue, it solidifies and is removed|
|US6464701B1 (en)||1995-03-07||2002-10-15||Enable Medical Corporation||Bipolar electrosurgical scissors|
|US6391029B1 (en)||1995-03-07||2002-05-21||Enable Medical Corporation||Bipolar electrosurgical scissors|
|US6179837B1 (en)||1995-03-07||2001-01-30||Enable Medical Corporation||Bipolar electrosurgical scissors|
|US5766166A (en) *||1995-03-07||1998-06-16||Enable Medical Corporation||Bipolar Electrosurgical scissors|
|EP1381321B1 (en)||2001-04-20||2012-04-04||Tyco Healthcare Group LP||Bipolar or ultrasonic surgical device|
|US9078655B2 (en)||2009-04-17||2015-07-14||Domain Surgical, Inc.||Heated balloon catheter|
|US8523850B2 (en)||2009-04-17||2013-09-03||Domain Surgical, Inc.||Method for heating a surgical implement|
|US9131977B2 (en)||2009-04-17||2015-09-15||Domain Surgical, Inc.||Layered ferromagnetic coated conductor thermal surgical tool|
|US9265556B2 (en)||2009-04-17||2016-02-23||Domain Surgical, Inc.||Thermally adjustable surgical tool, balloon catheters and sculpting of biologic materials|
|US9107666B2 (en)||2009-04-17||2015-08-18||Domain Surgical, Inc.||Thermal resecting loop|
|US8932279B2 (en)||2011-04-08||2015-01-13||Domain Surgical, Inc.||System and method for cooling of a heated surgical instrument and/or surgical site and treating tissue|
|EP2704657A4 (en)||2011-04-08||2014-12-31||Domain Surgical Inc||Impedance matching circuit|
|WO2012158722A3 (en)||2011-05-16||2013-03-21||Mcnally, David, J.||Surgical instrument guide|
|WO2013040255A3 (en)||2011-09-13||2014-05-15||Domain Surgical, Inc.||Sealing and/or cutting instrument|
|WO2013086045A1 (en)||2011-12-06||2013-06-13||Domain Surgical Inc.||System and method of controlling power delivery to a surgical instrument|
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