A bone fixation device capable of immobilizing a connecting rod intended to connect at least one bone fragment to another one, said device comprising: - at least one anchoring means intended to be fixed on or inside said bone fragment, - at least one container part, secured to said anchoring means, intended to receive at least one portion of said connecting rod, - blocking means arranged to block said portion of said connecting rod within said container part, said blocking means comprising at least one solid element presenting a longitudinal axis, said solid element comprising at least one tilted surface capable of creating through friction, when pushed along the longitudinal axis of said solid element, a progressive sticking of said portion of the connecting rod inside said container part, until complete blockage of said connecting rod portion inside said container part, - said container part being U-shaped, said connecting rod portion being received at the bottom of the U-shape, the wall of each leg of the U-shape being provided with an orifice, - said solid element being in the form of a key the cross-section of which increases starting from a first end, called thin end, toward a second end, called large end, the diameter of the circle in which the cross-section of said large end is inscribed being strictly larger than the diameter of the circle inscribed within said orifice, - said key being capable of being inserted, by its thin end, successively inside the orifices (10; 16, 18) of the walls of the legs of the U-shape of the container part, perpendicular to said connecting rod, and to be pushed along its longitudinal axis until coming into contact with said connecting rod and creating a friction between said connecting rod and the bottom of the container part, - so that, in the blocking position, said key passes through each orifice of each leg of the U-shape of said container part and holds said connecting rod portion blocked against the bottom of said container part, said blocking means being secured to said device, characterized in that said key presents, below its thin end, a longitudinal channel extending to its large end, capable of cooperating with a lug arranged in the orifice of the wall of a first leg of the U-shape, in order to enable the displacement of said key toward the orifice of the wall of the second leg of the U-shape and to prevent the complete return of said key toward the orifice of the wall of the first leg of the U-shape and thereby the separation of the latter from said device. - at least one anchoring means intended to be fixed on or inside said bone fragment, - at least one container part, secured to said anchoring means, intended to receive at least one portion of said connecting rod, - blocking means arranged to block said portion of said connecting rod within said container part, said blocking means comprising at least one solid element presenting a longitudinal axis, said solid element comprising at least one tilted surface capable of creating through friction, when pushed along the longitudinal axis of said solid element, a progressive sticking of said portion of the connecting rod inside said container part, until complete blockage of said connecting rod portion inside said container part, - said container part being U-shaped, said connecting rod portion being received at the bottom of the U-shape, the wall of each leg of the U-shape being provided with an orifice, - said solid element being in the form of a key the cross-section of which increases starting from a first end, called thin end, toward a second end, called large end, the diameter of the circle in which the cross-section of said large end is inscribed being strictly larger than the diameter of the circle inscribed within said orifice, - said key being capable of being inserted, by its thin end, successively inside the orifices (10; 16, 18) of the walls of the legs of the U-shape of the container part, perpendicular to said connecting rod, and to be pushed along its longitudinal axis until coming into contact with said connecting rod and creating a friction between said connecting rod and the bottom of the container part, - so that, in the blocking position, said key passes through each orifice of each leg of the U-shape of said container part and holds said connecting rod portion blocked against the bottom of said container part, said blocking means being secured to said device, characterized in that said key presents, below its thin end, a longitudinal channel extending to its large end, capable of cooperating with a lug arranged in the orifice of the wall of a first leg of the U-shape, in order to enable the displacement of said key toward the orifice of the wall of the second leg of the U-shape and to prevent the complete return of said key toward the orifice of the wall of the first leg of the U-shape and thereby the separation of the latter from said device.