An orthosis for a vacuum treatment of the deformations of the thorax includes a bottom, a peripheral lip made of flexible, elastically deformable material and comes into sealing contact with the thorax so as to form a treatment space using negative pressure, and at least one suction head connected to a negative pressure generation component. The orthosis improves the sealing contact between the orthosis lip and the patients thorax by increasing the orthosis deformability. To achieve this, the lip has a constant elasticity along the entire periphery thereof, and the bottom is formed of hollow, rigid, transverse side-by-side compartments connected to each other by bridges made of the same flexible material as the peripheral lip of the orthosis. The bridges of material allow the bottom to deform in such a way that the orthosis shape adapts to the thorax anatomy when the orthosis is applied vertically to the thorax.
