Patent EA-001969-B1 (EA)
Title: Improved electrosurgical instrument
Inventor: HEIM WARREN PAUL
IPC: A61B18/12
Filed: 1998-12-10
Abstract: 1. An electrosurgical instrument for conveying an electrosurgical signal to tissue, comprising: a metal body for carrying an electrosurgical signal, wherein said metal body has a thermal conductivity of at least about .35 W/cm degree K when measured at about 300 degree K; and an outer insulating layer positioned over at least a portion of said metal body and having a thermal conductance of about 1.2 Watt/cm<2>  degree K or less when measured at about 300 degree K and a dielectric withstand voltage of about at least 50 volts. 2. An electrosurgical instrument as recited in Claim 1, said metal body having a main body portion and a peripheral edge portion, wherein said electrosurgical signal is conveyed to tissue substantially entirely through said peripheral edge portion. 3. An electrosurgical instrument as recited in Claim 2, wherein said metal body comprises at least one metal selected from a group consisting of aluminum, silver, copper and gold. 4. An electrosurgical instrument as recited in Claim 3, wherein said instrument further comprises a biocompatible coating disposed on at least outer portion of said peripheral edge portion of said metal body. 5. An electrosurgical instrument as recited in Claim 4, wherein said biocompatible coating includes a component selected from a group consisting of nickel, silver, gold, chrome and titanium. 6. An electrosurgical instrument as recited in Claim 2, wherein said metal body comprises a metal alloy having a first component selected from a group consisting of: aluminum, silver, copper and gold; and wherein said first component comprises at least about 50% of said metal body by weight. 7. An electrosurgical instrument as recited in Claim 2, wherein said peripheral edge portion has a maximum cross-sectional thickness of no more than about one-tenth of the maximum cross-sectional thickness of the main body portion. 8. An electrosurgical instrument as recited in Claim 2, wherein said peripheral edge portion has a at an outer extreme edge having a thickness of less than about 0.25 mm. 9. An electrosurgical instrument as recited in Claim 2, wherein said outer insulating layer substantially covers said main body portion. 10. An electrosurgical instrument as recited in Claim 1, wherein said outer insulating layer contains at least one material having a thermal conductivity of less than about 6 W/cm- degree K when measured at about 300 degree  K. 11. An electrosurgical instrument as recited in Claim 1, wherein said outer insulating layer has a thickness of at least about 0.01 mm. 12. An electrosurgical instrument as recited in Claim 1, wherein said outer insulating layer comprises a polymeric compound. 13. An electrosurgical instrument as recited in Claim 12, wherein said polymeric compound includes at least about 10% of a first component by weight, said first component selected from a group consisting of silicon and carbon. 14. An electrosurgical instrument as recited in Claim 1, further comprising heat sink means for removing thermal energy from said metal body. 15. An electrosurgical instrument as recited in Claim 14, wherein said heat sink means maintains said metal body at an average maximum temperature of about 500 degree C or less. 16. An electrosurgical instrument as recited in Claim 15, said heat sink means comprising at least one phase change material, wherein said phase change material changes from a first phase to a second phase upon absorption of thermal energy from said metal body. 17. An electrosurgical instrument as recited in Claim 16, said at least one phase change material being selected from a group consisting of fatty acids, hydrocarbons and water compounds containing sodium. 18. An electrosurgical instrument as recited in Claim 16, wherein said metal body further includes an integral shaft portion, and wherein said electrosurgical instrument further comprises: a thermally and electrically insulated hand piece for interconnection to said shaft portion, said hand piece being sized for hand-held use; and a reservoir for containing said phase change material. 19. An electrosurgical instrument for conveying an electrosurgical signal to tissue to achieve a predetermined electrosurgical effect, comprising: a metal body for conveying an electrosurgical signal to a tissue site, said metal body comprising at least one metal selected from the group consisting of aluminum, silver, copper and gold, and said metal body having a thermal conductivity of at least about .35 W/cm degree K when measured at about 300 degree K; and an outer insulating layer positioned over at least a portion of said metal body, wherein said insulating layer has a thermal conductance of about 1.2 W/cm2  degree K or less when measured at about 300 degree K. 20. An electrosurgical instrument as recited in Claim 19, wherein said insulating layer comprises a polymeric compound. 21. A method for applying an electrosurgical signal to a tissue site comprising: supplying an electrosurgical signal to an electrosurgical instrument having a metal body and an insulating layer positioned over at least a portion of said metal body; conveying said electrosurgical signal to a tissue site from a peripheral edge of said metal body; and removing thermal energy from said metal body in a direction away from said peripheral edge and through said metal body, wherein said metal body is maintained at an average temperature of about 500 degree  C or less, and wherein an outside surface of said insulating layer is maintained at about 160 degree C or less. 22. A method as recited in Claim 21, said removing step comprising: contacting said metal body with a thermal heat sink means; and absorbing said thermal energy from said metal body into said heat sink means. 23. A method as recited in Claim 21, wherein said heat sink means comprises a phase change material. 24. An electrosurgical instrument as recited in Claim l, wherein said metal body includes a main body portion and a peripheral edge portion, and wherein said metal body is laterally-tapered down in cross-sectional thickness from said main body portion to said peripheral edge portion. 25. An electrosurgical instrument as recited in Claim 24, wherein said peripheral edge portion has a maximum cross-sectional thickness of no more than about one-tenth of the maximum cross-sectional thickness of the main body portion. 26. An electrosurgical instrument as recited in Claim l9, wherein said metal body includes a main body portion and a peripheral edge portion, and wherein said metal body is laterally-tapered down in cross-sectional thickness from said main body portion to said peripheral edge portion. 27. An electrosurgical instrument for conveying an electrosurgical signal to tissue, comprising: a metal body for conveying an electrosurgical signal to a tissue site, said metal body having a thermal conductivity of at least about .35 W/cm  degree K when measured at about 300 degree K and said metal body having a main body portion and a peripheral edge portion, wherein said metal body is laterally-tapered down in cross-sectional thickness from said main body portion to said peripheral edge portion; and an outer insulating layer positioned over at least a portion of said metal body, said outer insulating layer having a thermal conductivity and an electrical conductivity less than that of said metal body. 28. An electrosurgical instrument as recited in Claim 27, wherein said peripheral edge portion has a maximum cross-sectional thickness of no more than about one-tenth of the maximum cross-sectional thickness of the main body portion. 29. An electrosurgical instrument as recited in Claim 27, wherein said insulating layer has a thermal conductance of about 1.2 W/cm2- degree K or less when measured at about 300 degree  K. 30. An electrosurgical instrument as recited in Claim 29, wherein said metal body comprises a first component selected from a group consisting of aluminum, silver, copper and gold and wherein said first component comprises at least 50% of said metal body by weight. 31. An electrosurgical instrument as recited in Claim 27, wherein said peripheral edge portion has an outer extreme edge having a thickness of less than about 0.25 mm. 32. An electrosurgical instrument for conveying an electrosurgical signal to tissue, comprising: a metal body for carrying an electrosurgical signal, said metal body having a main body portion and a peripheral edge portion, and said metal body comprising a first component selected from the group consisting of: aluminum and copper, wherein said first component comprises at least 50% of said metal body by weight; an outer insulating layer positioned over at least a portion of said main body portion of said metal body, wherein at least an outer portion of said peripheral edge portion is not covered by the outer insulation layer, and wherein said outer insulating layer having a thermal conductance of about 1.2 W/cm2  degree K or less when measured at about 300 degree  K and a dielectric that will withstand voltage of at least 50 volts; and a biocompatible coating positioned at least said outer portion of said peripheral edge portion of said metal body 33. An electrosurgical instrument as recited in Claim 32, wherein said biocompatible coating includes a component selected from a group consisting nickel, silver, gold, chrome and titanium. 34. An electrosurgical instrument as recited in Claim 32, wherein said metal body includes a main body portion and a peripheral edge portion, and wherein said metal body is laterally-tapered down in cross-sectional thickness from said main body portion to said peripheral edge portion. 35. An electrosurgical instrument as recited in Claim 34, wherein said peripheral edge portion has a maximum cross-sectional thickness of no more than about one-tenth of the maximum cross-sectional thickness of the main body portion.