1. A method for automatically determining, on a bone comprising a head portion contiguous to a neck portion, parameters for characterizing a bump deformation on the head-neck junction of the bone from an acquired 3D medical image, the method comprising: i) constructing a 3D surface model of the bone from the acquired 3D medical image; ii) fitting a sphere on the spherical portion of the head of the bone; iii) determining a neck axis characterizing the neck portion of the bone; iv) determining from the fitted sphere and the neck axis, a clock face referential on the head of the bone rotating around the neck axis; v) determining a 3D curve on the 3D surface model characterizing the head-neck junction of the bone; vi) determining, from the 3D curve, the summit of the bump deformation of the head-neck junction of the bone, the summit being the point on the 3D curve closest to the apex point of the head of the bone in the direction of the neck axis; and vii) determining, from the summit of the bump deformation, first and second parameters (α3D, iMax) characterizing the maximum bump deformation of the head-neck junction of the bone, wherein the first parameter (α3D) is the angle between a hemi-line issued from the center of the fitted sphere in the neck axis direction and the segment joining the center of the fitted sphere and the summit of the bump deformation, and the second parameter (iMax) is a clock index locating on the clock face referential the summit of the bump deformation.