The present invention provides an apparatus and method for fixation of a bone anchor to a structural member used for spinal fixation, whereby spinal deformity can be corrected and mechanical stability of the spine is provided so that load is carried fully or partially through the structural member. This invention provides fixation of a bone anchor to a structural member through tensile loading of a component of the fixation mechanism. This invention is widely adaptable to a variety of bone anchors and structural members. This invention allows reduction of spine deformity resulting from varied spinal disease through the fixation mechanism alone without the need for added reduction instrumentation systems. This invention equally provides a fixation mechanism for fixation of a bone anchor to the structural member of a spine fixation system in the absence of deformity.