Experimental: mini invasive scoliosis surgery (MIS)

This technique involves making small, noncontiguous, midline skin incisions at the levels to be instrumented, usually proximal and distal to the area of arthrodesis. A median fascial incision is then made to expose the vertebral segments on which to thread the screws while the bar is inserted submuscularly in a cranio-caudal direction, after appropriate maneuvers to correct the deformity.

Active_comparator: posterior spinal fusion technique (PSF)

This technique is the surgical gold standard. It consists of an instrumented arthrodesis with posterior access and requires a wide median incision with extensive muscle dissection.