Embodiments of the present invention are directed toward a system of apparatuses to correct spinal deformities along with associated surgical techniques. The apparatuses comprise passages or channels in which spinal rods of differing diameters may be secured to allow a surgeon to vary the diameter of rods used along the length of the spine. Additionally, embodiments of the present invention are directed toward instrumentation for reduction of spinal rods into spinal pedicle screws.