Implant automatic extension (1 100 200 300 400 500 600) comprising: - a body (30 130 230) internally delimiting an axial housing (31 231) which opens on one side by a mouthpiece (32 232) and having a narrowing of section in the body (30 130 230) a stop face (33 233), - ring (70) a stopper which is fixed to the mouth ( 32 232) of the axial housing (31 231) of said body (30 130 230) and having a face stop (72) facing towards said stop face (33 233), - at least one rod (10 110 210 310) coupled through said annular plug (70) and the axial housing (31 231) of said body (30 130 230), and - a split ring (50) is mounted on the rod (10 110 210 310) and which is housed in the axial housing (31 231) of said body (30 130 230), characterized in that said stop faces (33 233) and stop (72) have bevelled forms a recess and the other protrusion, and that said split ring (50) has two bearing faces (52, 53) that are turned respectively toward said abutment faces (33 233) and stop (72) and which have shapes such that said split ring (50) expands when it rests against the side of projecting bevelled and compressed on said stem (10 110 210 310) when It rests against the incoming bevelled face.Implante de alargamiento automático (1 100 200 300 400 500 600) que comprende: - un cuerpo (30 130 230) que delimita interiormente un alojamiento axial (31 231) que se abre en un lado por una embocadura (32 232) y que presenta un estrechamiento de sección que forma en el cuerpo (30 130 230) una cara de tope (33 233), - un tapón anular (70) que está fijado a la embocadura (32 232) del alojamiento axial (31 231) de dicho cuerpo (30 130 230) y que presenta una cara de parada (72) vuelta hacia dicha cara de tope (33 233), - por lo menos un vástago (10 110 210 310) acoplado a través de dicho tapón anular (70) y del alojamiento axial (31 231) de dicho cuerpo (30 130 230), y - un anillo hendido (50) que está montado sobre el vástago (10, 110 210 310) y que está alojado en el alojamiento axial (31 231) de d
