A bipolar electro-surgical instrument (10) has opposable seal surfaces (18, 19) on its jaws (16, 17) for grasping, sealing vessels, and vascular tissue. Inner, and outer instrument members (11, 12) allow arcuate motion of the seal surfaces. An open lock box (13) provides a pivot with a lateral support to maintain alignment of the lateral surfaces. Ratchets (25, 26) on the instrument members hold a constant closure force on the tissue during the seal process. A shank portion (14, 15) on each member is tuned to provide an appropriate spring force to hold the surfaces together. During surgery the instrument can be used to grasp, clamp vascular tissue, and apply bipolar electro-surgical current through the clamped tissue. In one embodiment, the seal surfaces are partially insulted to prevent a short circuit when the instrument jaws are closed together. In another embodiment, the seal surfaces are removably mounted on the jaws.
