1. An automated method for precise determination of the head center and radius and the neck axis of an articulated bone from acquired 3D medical image of an articulation, the articulation comprising two bones one of which is said bone with a head and a neck, the method comprising the following steps: i) determining automatically, from a 3D image of the bone having a head and a neck, an approximate sphere of the head of the bone defined by an approximate head center and an approximate radius, that substantially fits the spherical portion of the head of the bone; ii) constructing automatically from the 3D image and from the approximate sphere of the head of the bone, a 3D surface model of the bone; iii) determining automatically, from the 3D surface model of the bone and from the approximate sphere of the head of the bone, an approximate neck axis of the neck of the bone; iv) determining automatically, from the 3D surface model and from the approximate sphere of the head of the bone, a precise sphere defined by a precise head center and a precise radius of the head of the bone; v) determining automatically, from the 3D surface model, from the precise sphere of the head and from the approximate neck axis, a precise neck axis.