Embodiments are directed to an apparatus for aligning vertebrae of a curved spine that may include a coupler having a longitudinal axis, a proximal end, and a distal end, wherein the proximal end comprises first threads, wherein the distal end comprises a mating surface for disposition around a rod attached to a spinal column, and wherein the coupler applies a compressive clamping force to the rod. The apparatus further may include a nut having second threads corresponding to the first threads, wherein the nut is attachable to the coupler proximal end. The apparatus further may include a driver disposable at least partially around the coupler, wherein the driver applies a clamping force to the coupler, and wherein the nut applies a linear force to the driver when tightened.