Endoscopic surgical instrument having curved blades

An endoscopic surgical cutting instrument comprising:

• a) a handle assembly;
• b) a body portion extending from said handle assembly and defining a generally central longitudinal axis;
• and
• c) a pair of cutting blade members including a first blade member and a second blade member, pivotally connected to each other and being operable to open and close about a common pivot axis in response to movement of said handle assembly, said first blade member having a top edge and an opposed bottom cutting edge, and said second blade member having a bottom edge and an opposed top cutting edge, said blade members being positioned at an end of said body portion opposite said handle assembly and having generally curved crescent-shaped cross-sections in a plane defined by said pivot axis and said longitudinal axis;
• wherein said generally crescent-shaped blade members each has an inside surface facing each other when in a closed position, said inside surface of said first blade member being angled from said top edge toward said bottom cutting edge to define a first relief angle, said inside surface of said second blade member being angled from said bottom edge toward said top cutting edge to define a second relief angle, said first and second relief angles cooperating to maintain said bottom cutting edge of said first blade member in contact with said top cutting edge of said second blade member during opening and closing of said blade members.

An endoscopic surgical instrument comprising:

• a) a handle assembly;
• b) a body portion extending from said handle assembly defining a longitudinal axis of said instrument;
• and
• c) a pair of cutting blade members including a first blade member and a second blade member connected to each other to open and close about a common pivot axis in response to movement of said handle assembly, each cutting blade member having a cutting edge which faces the cutting edge of the other cutting blade member and a generally curved crescent-shaped cross-section in a plane defined by said pivot axis and said longitudinal axis;
• wherein said first curved generally crescent-shaped blade member has a first radius of curvature and said second curved generally crescent-shaped blade member has a second radius of curvature, said first and second radii of curvature being unequal, a center of said first radius of curvature being offset from a center of said second radius of curvature by a predetermined distance measured along said longitudinal axis, such that during opening and closing of said blade members, said first blade member contacts said second blade member progressively along a length of said cutting edges in a manner to enhance shearing of tissue.