A surgical guide device, intended to be placed against a patient's bone, for assisting an opening wedge osteotomy technique, said surgical guide device being characterized in that it comprises: - a rear face adapted to be positioned against a surface of said bone, and - advantageously a window for guiding a cut line intended to be made into said bone, and - two parts (4, 5), i.e. a proximal part and a distal part, wherein said proximal and distal parts are each provided with several through-orifices (42, 56) opening through the rear face, adapted to receive elements temporarily implantable into said bone and/or adapted to guide a drilling of holes into said bone, wherein the distal part comprises at least one tubular duct that is adapted to guide the insertion of a rod within the bone: - a proximal tubular duct that is arranged directly underlying a cut line intended to be made into said bone, advantageously underlying the guide window, and that is directed in such a manner that its longitudinal axis is parallel to a cut line intended to be made into said bone, advantageously parallel to the plane of the guide window, in order to position a rod helping in the guiding of the cut line, and - a distal tubular duct (582, 583) that is arranged remote from a cut line intended to be made into said bone, advantageously remote from the guide window and that is directed in such a manner that its longitudinal axis (582', 583') intersects a cut line intended to be made into said bone, advantageously the plane of the guide window, in order to position a cut stop and/or hinge indication rod (82, 84). said surgical guide device being characterized in that it comprises: - a rear face adapted to be positioned against a surface of said bone, and - advantageously a window for guiding a cut line intended to be made into said bone, and - two parts (4, 5), i.e. a proximal part and a distal part, wherein said proximal and distal parts are each provided with several through-orifices (42, 56) opening through the rear face, adapted to receive elements temporarily implantable into said bone and/or adapted to guide a drilling of holes into said bone, wherein the distal part comprises at least one tubular duct that is adapted to guide the insertion of a rod within the bone: - a proximal tubular duct that is arranged directly underlying a cut line intended to be made into said bone, advantageously underlying the guide window, and that is directed in such a manner that its longitudinal axis is parallel to a cut line intended to be made into said bone, advantageously parallel to the plane of the guide window, in order to position a rod helping in the guiding of the cut line, and - a distal tubular duct (582, 583) that is arranged remote from a cut line intended to be made into said bone, advantageously remote from the guide window and that is directed in such a manner that its longitudinal axis (582', 583') intersects a cut line intended to be made into said bone, advantageously the plane of the guide window, in order to position a cut stop and/or hinge indication rod (82, 84). - a rear face adapted to be positioned against a surface of said bone, and - advantageously a window for guiding a cut line intended to be made into said bone, and - two parts (4, 5), i.e. a proximal part and a distal part, wherein said proximal and distal parts are each provided with several through-orifices (42, 56) opening through the rear face, adapted to receive elements temporarily implantable into said bone and/or adapted to guide a drilling of holes into said bone, wherein the distal part comprises at least one tubular duct that is adapted to guide the insertion of a rod within the bone: - a proximal tubular duct that is arranged directly underlying a cut line intended to be made into said bone, advantageously underlying the guide window, and that is directed in such a manner that its longitudinal axis is parallel to a cut line intended to be made into said bone, advantageously parallel to the plane of the guide window, in order to position a rod helping in the guiding of the cut line, and - a distal tubular duct (582, 583) that is arranged remote from a cut line intended to be made into said bone, advantageously remote from the guide window and that is directed in such a manner that its longitudinal axis (582', 583') intersects a cut line intended to be made into said bone, advantageously the plane of the guide window, in order to position a cut stop and/or hinge indication rod (82, 84). - a proximal tubular duct that is arranged directly underlying a cut line intended to be made into said bone, advantageously underlying the guide window, and that is directed in such a manner that its longitudinal axis is parallel to a cut line intended to be made into said bone, advantageously parallel to the plane of the guide window, in order to position a rod helping in the guiding of the cut line, and - a distal tubular duct (582, 583) that is arranged remote from a cut line intended to be made into said bone, advantageously remote from the guide window and that is directed in such a manner that its longitudinal axis (582', 583') intersects a cut line intended to be made into said bone, advantageously the plane of the guide window, in order to position a cut stop and/or hinge indication rod (82, 84).