The posterior surgical approach. (a) The Harrington rod with the proximal and distal anchors or hooks. It provides distraction to the scoliotic spine on the side of concavity to reduce the curve. (d) The Luque wiring improves the stability of the Harrington instrumentation. (c) Cotrel-Dubosset instrumentation consists of two rods which are anchored by wiring and segmental screws. (d) The pedicle screws that are widely used today. They are anchored on the base of the pedicle which is always in the lateral half of the superior facet.