Set suitable for use in a bone-shortening osteotomy of a predetermined distance, the set comprising: an implant (1) with threaded holes (8); an accessory (2) with successively a first segment (5), a second segment (6) and a third segment (7); wherein the first segment comprises first threaded holes (9) and wherein the third segment comprises second threaded holes (9), and wherein the second segment comprises two guides (10) which are each adapted to guide a saw blade (17) so that the osteotomy of predetermined distance (d) can be performed via the two guides.