A system assisting in humerus surgery based on X-ray images, the system comprising a processing unit configured to execute instructions of a software program product, the instructions causing the system to perform the steps of: receiving at least two X-ray images, each of the X-ray images showing a projection of a proximal portion of a humerus including a humerus head, wherein the at least two X-ray images are generated from at least two imaging directions, registering the at least two X-ray images, determining an approximation of at least a part of the 2D outline of the humerus head in each of the X-ray images, the respective part of the 2D outline of the humerus head defining a start and an end point of the 2D outline of the humerus head, determining a 3D approximation of the humerus head based on the approximated 2D outlines and on the registration of the X-ray images, determining 2D image coordinates of a total of at least three different points in the at least two X-ray images, the at least three different points being the start and end points of the 2D outlines of the humerus head, determining an approximation of an anatomical neck as a curve on the 3D approximation of the humerus head with the at least three determined points, wherein the at least three determined points define a plane which intersects the 3D approximation of the humerus head, determining an approximation of a humerus shaft axis in at least two of the X-ray images, determining an approximation of a 3D shaft axis of the humerus based on the approximated humerus shaft axes in the at least two X-ray images and based on the registration of the X-ray images, and determining a dislocation of a proximal fragment of a fractured humerus on the basis of the approximated anatomical neck and on the basis of the approximated 3D shaft axis and/or an approximated glenoid of a humerus joint. receiving at least two X-ray images, each of the X-ray images showing a projection of a proximal portion of a humerus including a humerus head, wherein the at least two X-ray images are generated from at least two imaging directions, registering the at least two X-ray images, determining an approximation of at least a part of the 2D outline of the humerus head in each of the X-ray images, the respective part of the 2D outline of the humerus head defining a start and an end point of the 2D outline of the humerus head, determining a 3D approximation of the humerus head based on the approximated 2D outlines and on the registration of the X-ray images, determining 2D image coordinates of a total of at least three different points in the at least two X-ray images, the at least three different points being the start and end points of the 2D outlines of the humerus head, determining an approximation of an anatomical neck as a curve on the 3D approximation of the humerus head with the at least three determined points, wherein the at least three determined points define a plane which intersects the 3D approximation of the humerus head, determining an approximation of a humerus shaft axis in at least two of the X-ray images, determining an approximation of a 3D shaft axis of the humerus based on the approximated humerus shaft axes in the at least two X-ray images and based on the registration of the X-ray images, and determining a dislocation of a proximal fragment of a fractured humerus on the basis of the approximated anatomical neck and on the basis of the approximated 3D shaft axis and/or an approximated glenoid of a humerus joint.