The present invention relates to a patient-specific surgical instrumentation for the preparation of a bone (B) of the patient, the instrumentation comprising a patient-specific block (10) delimiting a fixed bearing surface on the bone, which is shaped specifically adapted to this bone, and including a main portion (20) which partially delimits the fixed bearing surface and which delimits at least two primary orifices (27, 28) for respective passage of a primary pin (61). , 62), these primary orifices passing through the block between the bearing surface and an opposite surface (14) of the block. The instrumentation also comprises: - a secondary part (30) which belongs to the block, which delimits in part the bearing surface and which comprises at least two secondary orifices (37, 38) of respective passage of a bone preparation tool , such as a drill bit or an anchor pin, these secondary orifices passing through the block between the bearing surface and the opposite surface of the block, and - mechanical release means of the abutment relative to the part main, adapted for, while the main part is fixed on the bone by primary pins passed through the primary orifices, make the removable abutment relative to the main part.La présente invention concerne une instrumentation chirurgicale spécifique à un patient pour la préparation d'un os (B) du patient, l'instrumentation comprenant un bloc spécifique au patient (10) délimitant une surface d'appui fixe sur l'os, qui est conformée de manière spécifiquement ajustée à cet os, et incluant une partie principale (20) qui délimite en partie la surface d'appui fixe et qui délimite au moins deux orifices primaires (27, 28) de passage respectif d'une broche primaire (61, 62), ces orifices primaires traversant le bloc entre la surface d'appui et une surface opposée (14) du bloc. L'instrumentation comprend également : - une partie secondaire (30) qui appartient au bloc, qui délimite en partie la surface d'appui et qui comporte au moins
