Spondylolisthesis screw and instrument for implantation

摘要

A screw for use in spinal surgery provided with a screw shaft and a screw head and at least one extension tab extending proximally from the screw head, the extension tab being defined relative to the screw head by a stress concentration feature. At a proximal end of the extension tab, the extension tab may be narrower in a circumferential direction than the extension tab at a distal portion thereof. A particular shape of stress concentration may be provided.