A surgical device for treating the pathology of flat feet, the device comprising an outer casing; and an expansion member suitable for moving inside said outer casing in a compression direction, for causing said outer casing to expand radially; the surgical device being provided with non-return check means shaped to allow the expansion member to move in the compression direction towards an operating position inside the outer casing and to oppose movement of the expansion member in the reverse direction once said operating position is reached, so as to prevent the expansion member from being expelled.