Patent ID: 7618416

Claim:
A monopolar high-frequency knife comprising: a cylindrical body member of which at least an outer peripheral surface has insulating properties; a monopolar electrode, the monopolar electrode being an electrically conductive axial member inserted in the body member and having a distal end portion of which the length of projection from a distal end of the body member is adjustable and a proximal end portion which operates together with the distal end portion, the distal end portion having a knife section thereon; an operating section which is provided on the proximal end portion of the axial member, is able to be actuated by a surgeon to project and retract the axial member with respect to the body member, and is able to supply electric power to the axial member; and an electrical insulating member which is provided on the distal end of the axial member in a position at a distance from the distal end of the body member and has at least the longest axis of a cross section of the knife section; wherein the knife section includes: a first electrode portion which is able to be projected and retracted from the distal end of the body member, and a plurality of second electrode portions which extend at right angles to at least the axial direction of the first electrode portion from the distal end portion of the first electrode portion and are able to approach and leave the distal end of the body member; wherein the plurality of second electrode portions are electrically connected to each other and to the first electrode portion; and wherein the second electrode portions extend for the same length from a central axis of the first electrode portion, the electrical insulating member has a radius including at least the extended longest length of each second electrode portion from the central axis of the first electrode portion and is provided on a distal end of the first electrode portion, and the second electrode portions are arranged between the distal end of the body member and the electrical insulating member.