Resistively heating cutting and coagulating surgical instrument

• US 5,911,719 A
• Filed: 06/05/1997
• Issued: 06/15/1999
• Est. Priority Date: 06/05/1997
• Status: Expired due to Term

• Current Assignee: Philip E. Eggers
• Original Assignee: Philip E. Eggers
• Inventors: Eggers, Philip E.
• Primary Examiner(s): Leubecker, John P.
• Assistant Examiner(s): GIBSON, ROY DEAN
• Application Number:
  US08/869,495
• Time in Patent Office: 740 Days
• Field of Search: 606/27-31, 606/41-42, 606/45-50, 219/229-230, 219/233
• US Class Current: 606/31
• CPC Class Codes: A61B 18/082 Probes or electrodes therefor

Abstract

A resistively heated thermally cutting and coagulating surgical instrument which may be employed with a conventional electrosurgical generator having bipolar output ports and a bipolar cable. The instrument utilizes a heating element which is heated to a predetermined upper temperature limit while in still air under a starting condition. Under this condition, heat dissipation by radiation, convection, and conduction through the instrument itself provides a high temperature end form of regulation. Under a subsequent working condition wherein the heated component or element is in contact with the tissue, heat dissipation is by thermal conduction both into the tissue and through the thermally conductive components of the instrument. A preferred heating element is formed with a ferromagnetic material which, when at the upper limit temperature is maintained at a value restricted to a temperature below curie temperature and which does not invoke surface oxidation or scaling within the time interval of heating experienced in the starting condition. However, the temperature is high enough to sustain a temperature effective for cutting and coagulation when in the working condition. A handle is employed which contains impedance matching circuit components. In one embodiment, the heating component of the instrument incorporates an integrally formed probe which is retained at lower temperatures through the use of a current restricting neck.

Claims

1. A working end assembly for connection with a surgical instrument and responsive to electrical power supplied from a source for carrying out thermal cutting of tissue with hemostasis, comprising:

a heating component extending continuously from a first terminus to a second terminus, having a tissue engaging region located between said first and second termini, said heating component being formed of material exhibiting low thermal conductivity and high electrical resistivity and configured to exhibit low thermal conductance and high electrical resistance for deriving a substantially, repeatably stable start temperature, at a predetermined level above a lower limit temperature effective to thermally cut tissue, within a starting condition air environment with thermal regulation which derives said predetermined level only by heat transfer therefrom as a function substantially only of radiation, convection, and conduction to said surgical instrument in response to the application of a value of said power from said source, and for deriving a substantially stable thermal cut temperature above said lower limit temperature within a working condition environment in contact with said tissue in response to application of said value of power from said source, with heat transfer therefrom as a function substantially only of thermal conduction into said tissue and to said surgical instrument; and

a support portion formed of electrically and thermally conductive material configured having first and second ends in current and heat transfer communication with respective said first and second termini and having a second portion in heat dissipating relationship with said first support portion.

2. The working end assembly of claim 1 wherein said heating component is configured for deriving a said start temperature predetermined level of at least about 450°

C.

3. The working end assembly of claim 2 in which:

said heating component is formed of ferromagnetic material exhibiting a predetermined Curie temperature, Tc; and

said start temperature predetermined level is less than said Curie temperature, Tc.

4. The working end assembly of claim 3 in which said Curie temperature, Tc, has a value greater than 700°

C.

5. The working end assembly of claim 1 in which said support assembly first support portion extends in thermal exchange relationship with said second portion, said second portion being rearwardly disposed, thermally and electrically conductive and connectable in supported relationship with said instrument.

6. The working end assembly of claim 5 in which said first support portion is formed of a material exhibiting low electrical resistivity and high thermal conductivity for evoking with said heating component first and second thermal transition regions extending toward said tissue engaging region from respective said first and second termini and exhibiting a temperature at said first and second termini atraumatic to tissue.

7. A working end assembly for connection with a surgical instrument handle and responsive to electrical power supplied from a source for carrying out thermal cutting of tissue with hemostasis, comprising:

an electrical resistance heating component extending from a first terminus to a second terminus, having a tissue engaging region located between said first and second termini, said heating component being formed of material exhibiting low thermal conductivity and high electrical resistivity and configured to exhibit low thermal conductance and high electrical resistance, and responsive to an applied current to generate heat at said tissue engaging region at temperature levels effective for carrying out said thermal cutting of tissue with hemostasis;

a forward support portion having first and second electrically and thermally conductive spaced apart legs of first cross-sectional extent formed of material exhibiting low electrical resistivity and high thermal conductivity and configured to exhibit low electrical resistance and high thermal conductance effective for evoking with said heating component first and second thermal transition regions extending toward said tissue engaging region from respective said first and second termini and exhibiting a temperature at said first and second termini atraumatic to tissue, said first and second spaced apart legs extending to respective first and second rearward ends;

an intermediate support portion having first and second rods of second cross sectional extent greater than said first cross sectional extent, each formed of a thermally conductive material exhibiting a thermal resistance value of less than about 100°

C./watt, mutually electrically insulatively spaced apart, having respective first and second front ends coupled in heat transfer communication with respective said first and second forward support portion rearward ends and having respective first and second rear ends; and

a rearward support portion coupled in supporting relationship with said intermediate support portion adjacent said first and second rear ends, connectable with said surgical instrument handle and said source for effecting the conveyance of current to said heating component.

8. The working end assembly of claim 7 in which said first and second rods are formed of electrically conductive material and are configured to convey current from said source from said rearward support portion respectively to said first and second legs of said forward support portion.

9. The working end assembly of claim 8 in which:

said first and second rods are configured generally as elongate half cylinders having respective first and second elongate flat surfaces positioned in mutually facing relationship; and

including an electrically insulating layer located intermediate said first and second flat surfaces.

10. The working end assembly of claim 9 in which said rearward support portion is configured as a polymeric plug having first and second electrical connectors removably connectable with said surgical instrument handle and electrically coupled with respective said first and second rods.

11. A system for carrying out the thermal hemostatic cutting of tissue, comprising:

an electrosurgical generator having bipolar output terminals exhibiting a load impedance to voltage characteristic;

a surgical instrument including;

an electrical resistance heating component extending from a first terminus to a second terminus, having a tissue engaging region located between said first and second termini, said heating component being formed of material exhibiting low thermal conductivity and high electrical resistivity and configured to exhibit low thermal conductance and high electrical resistance for deriving a substantially repeatably stable start temperature at a predetermined level above about 450°

C. within a starting condition air environment with heat transfer therefrom as a function substantially only of radiation, convection, and conduction to said surgical instrument in response to the application of an applied current, and for deriving a substantially stable thermal cut temperature above a thermal cut threshold value within a working condition environment in contact with said tissue in response to application of said current, with heat transfer therefrom as a function substantially only of thermal conduction into said tissue and to said surgical instrument,

a forward support portion having first and second electrically and thermally conductive discrete legs of predetermined first cross-sectional extent formed of a thermally conductive material exhibiting a thermal resistance value of less than about 100°

C./watt, configured having first and second forward ends in heat transfer communication with respective said first and second termini and extending to respective first and second rearward ends,

an intermediate support portion having first and second rods of second cross sectional extent greater than said first cross sectional extent, each formed of a thermally conductive material exhibiting a thermal resistance value of less than about 100°

C./watt, mutually electrically insulatively spaced apart, having respective first and second front ends coupled in heat transfer communication with respective said first and second forward support portion rearward ends and having respective first and second rear ends,

a rearward support portion coupled in supporting relationship with said intermediate portion adjacent said first and second rear ends, and having an electrical input for conveying current to said heating component, and

a hand engageable instrument handling portion having circuit components selected for effecting power transfer impedance matching between said bipolar output terminals and said heating component, having an instrument output coupled with said electrical input and having an instrument input; and

an elongate cable connectable in electrical power transfer relationship between said bipolar output terminals of said electrosurgical generator and said instrument input of said instrument handling portion.

12. The system of claim 11 in which:

said heating element is formed of ferromagnetic material exhibiting a predetermined Curie temperature, Tc; and

said start temperature predetermined level is less than said Curie temperature, Tc.

13. The system of claim 12 in which said Curie temperature, Tc, has a value greater than 700°

C.

14. The system of claim 11 in which said forward support portion first and second legs are formed of a material exhibiting low electrical resistivity and high thermal conductivity for evoking with said heating component first and second thermal transition regions extending toward said tissue engaging region from respective said first and second termini and exhibiting a temperature at said first and second termini atraumatic to tissue.

15. The system of claim 11 in which said first and second rods are formed of electrically conductive material and are configured to convey current from said source from said rearward support portion respectively to said first and second legs of said forward support portion.

16. The system of claim 15 in which:

said first and second rods are configured generally as elongate half cylinders having respective first and second elongate flat surfaces positioned in mutually facing relationship; and

including an electrically insulating layer located intermediate said first and second flat surfaces.

17. A working end assembly for connection with a surgical instrument and responsive to electrical power supplied from a source for carrying out thermal cutting of tissue with hemostasis, comprising:

an electrical resistance heating component extending from a first terminus to a second terminus, having a tissue engaging region located between said first and second termini and having a cutting portion configuration exhibiting a first resistance to current applied from said source for deriving a temperature of value effective for carrying out said thermal cutting of tissue with hemostasis and having a prod portion configuration extending from a neck region of predetermined second resistance defining extent limiting the passage of said current to said prod portion to a value developing a temperature value at said prod portion atraumatic to tissue; and

a support assembly formed of thermally and electrically conductive material exhibiting a thermal resistance value of less than about 100°

C./watt, configured having first and second ends in heat transfer communication with respective said first and second termini and extending to an oppositely disposed connector portion for connection with said surgical instrument; and

said support assembly and said tissue engaging portion deriving first and second thermal transition regions extending inwardly from respective said first and second termini effective to restrict the temperature level exhibited at said support assembly to values atraumatic to said tissue when said support assembly is in contact therewith.

18. A working end assembly for connection with a surgical instrument and responsive to electrical power supplied from a source for carrying out thermal cutting of tissue with hemostasis, comprising:

an electrical resistance heating component extending between first and second termini, having a tissue engaging region located between said first and second termini exhibiting a first cross-sectional area for carrying out said thermal cutting and at temperatures above about 300°

C., said heating component being formed of material exhibiting low thermal conductivity and high electrical resistance, having first and second thermal transition regions respectively extending from said first and second termini toward said tissue engaging region and having a second cross-sectional area greater than said first cross-sectional area and exhibiting a thermal resistance greater than about 200°

C./watt; and

a forward support assembly having first and second legs with respective first and second ends in electrical and heat transfer communication with said first and second termini, each said first and second legs being formed of thermally conductive material and exhibiting a thermal resistance value of less than about 100°

C./watt for evoking said first and second thermal transition regions.