The invention relates in particular to a system for attaching a first bone segment to a second bone segment, the two segments belonging to the same bone, in which the first and second segments are held together via a hinge resulting from the partial transverse cutting of said bone, characterised by the fact that said system comprises:two targets suitable for attaching to the two segments of said bonea navigation system suitable for acquiring the three-dimensional positions and orientations of the targets—a processing system suitable for calculating, based on the data sent from the navigation system, the angles corresponding to the three-dimensional alignment of said two segmentsa display unit suitable for displaying the information to the surgeon at least one milling guidea plurality of implants of different sizes.
