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, characterized by the fact that said system comprises: two targets suitable for attaching to the two segments of said bone; a 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 segments; a display unit suitable for displaying the information to the surgeon; at least one milling guide; a plurality of implants of different sizes.