Abstract: Systems and methods for ascertaining an item of torsion information of a bone of a patient, wherein an X-ray facility with adjustable projection geometry of a recording arrangement described by projection parameters is used. A first X-ray image is recorded of an end region of the bone in a first projection geometry in which a torsion direction defined relative to at least one torsion landmark and used for ascertaining a roll angle lies in a first computing plane, which is formed by the focal point of the X-ray source and a reference direction which may be determined in the first X-ray image by at least one reference landmark. A second X-ray image is recorded of the end region of the bone in a second projection geometry with a direction of projection deviating from the direction of projection of the first projection geometry, and forming a second computing plane from the reference direction which may be determined in the second X-ray image likewise by the at least one reference landmark, and the focal point.