Dynamics bound by the geometry of the brace. On the convex side, the superior margin ends under the apex vertebra, allowing the lateral flection movement to induce the deflection of the curve and the realignment of the spine under the apex vertebra. The posterior edge is modelled with a central active prominence which is uncomfortable and compels the patient to perform an anterior translation that allows the hyperlordosis correction (A). Such a profile imposes a particular dynamics, for which the anterior flection movements can be performed only together with a lateral flection and a rotation in the direction of the correction of the curve. The bending X-Ray exam executed on the convexity side without (b) and with the brace (c) confirms the theoretical presuppositions showing the remarkable behaviour diversity between the dynamics of the free and the bound spine.