Abstract: A fastener is provided for fixating two objects in a fixed spatial relationship, such as bone segments, so that resultant stress is maintained at a constant value along a shank portion of the fastener in order to minimize stress concentrations and optimize the strength to size relationship of the fastener, thereby reducing the likelihood of fastener failure. The fastener additionally comprises an improved head which temporarily engages a driving instrument to facilitate fixation. A driving instrument for deploying the fastener is also provided.