Implantable orthopedic device comprising: - a support structure delimited by an upper face and a lower face (2"), the latter being intended to come opposite to the receiving bone material, said support structure being provided with at least one housing and at least one orifice passing through said housing, said housing and said orifice having the same axis, - at least one nut provided with an internal thread, said nut being shaped so as to be caught within one of said housings, and - at least one fixing screw consisting of a screw head and a screw body, said screw head being provided with a thread able to cooperate with said nut thread, and said screw body being provided with a thread able to cooperate with the receiving bone material, said nut being locked in rotation within said receiving housing so as to be prevented from rotating around its axis, and said nut having at least one freedom degree within said receiving housing, according to a predetermined acceptable tilting domain, so as to enable a tilting of its axis relative to the axis of said receiving housing, said fixing screw being intended to be screwed within one of said orifices and the associated nut thereof, according to a selected angle in the acceptable tilting domain, characterized in that said housing comprises an upper part (5 a) located on the upper face side of the support structure and a lower part (5 b) located on the lower face (2") side of said support structure, both parts being generally truncated sphere shaped and concentric to each other, in that said nut has a truncated sphere shaped peripheral contour mating with said truncated sphere shaped upper part (5 a) of the receiving housing, and in that said screw head comprises an upper part (15 a) provided with said thread and a lower part (15 b) whose contour has a generally truncated sphere shape mating with said truncated sphere shaped lower part (5 b) of the receiving housing, said upper (15 a) and lower (15 b) parts of said screw head being intended to cooperate, during the final screwing step of said screw, with the thread of said nut through the mating thread thereof and with said lower part (5 b) of the receiving housing, respectively, so as to tend to separate said nut from said lower part (5 b) of the receiving housing, and then entail a forced rest of the peripheral contour of said nut against said mating upper part (5 a) of the receiving housing and a forced rest of the lower part (15 b) of said screw head against said mating lower part (5 b) of the receiving housing, in order to obtain the locking of said screw during the final screwing step. - a support structure delimited by an upper face and a lower face (2"), the latter being intended to come opposite to the receiving bone material, said support structure being provided with at least one housing and at least one orifice passing through said housing, said housing and said orifice having the same axis, - at least one nut provided with an internal thread, said nut being shaped so as to be caught within one of said housings, and - at least one fixing screw consisting of a screw head and a screw body, said screw head being provided with a thread able to cooperate with said nut thread, and said screw body being provided with a thread able to cooperate with the receiving bone material,