Bracing for idiopathic scoliosis is performed mainly by ThoracoLumbar Spinal Orthoses (TLSO) acting by the application of lateral correcting forces. Most of the braces used for the conservative treatment of spinal deformaties have but a minimal effect upon the ratational deformaties of the body since their main objective is the correction of spinal curves. Derotating braces are custom made underarm spinal orthoses equiped with specially designed derotating blades that produce a derotating effect upon the thorax and the trunk of the patients. Comparisson of three groups of 100 patients each, treated with three different kinds of underarm braces (Boston brace, Dynamic Derotating brace and Thoracic Derotating brace) proved that the derotating blades, applied at the derotating braces, have a springlike effect that increases and maintains the correcting forces applied by the brace(s) throughout the hole period of treatment.