The method according the the invention comprises the foliowing steps: a) taking a sagittal preoperative x-ray of the vertebral column of the patient to be treated, extending from the cervical vertebrae to the femoral heads； b) on that x-ray, identifying the pelvic parameters, the lumbar lordosis, the position of the apical umbar vertebra, distances called SVA and SFD and a cloud of points； c) deducing, among predetermined morphotypes, the morphotype to which the treated vertebral column corresponds and deducing therefrom the desired postoperative apex point； d) positioning the different points of the cloud of points in a reference centered at the plate of S1； e) simulating the correction to be applied to the lumbar segment to be treated, by defining co-radial arcs situated below and above the desired postoperative apex point； defining two arcs concentric to the two curvatures obtained, which are tangent to each other at the apex point； f) translating these arcs away from the mean line of the vertebral column and defining a two- or three-dimensional model of the rod to be implanted, curved along the arcs.
