The automatically lengthening implant includes: a body defining internally an axial housing that opens out, at one end, via a mouth and that presents, at its opposite end, a narrowing of section forming an abutment face on the body an annular plug that is fastened to the mouth of the body and that presents a stop face facing towards the abutment face at least one rod that is engaged through the annular plug and the body and a split ring that is mounted on the rod and that is housed in the axial housing of the body. The abutment face and the stop face present shapes that are chamfered, one reentrant and the other projecting, such that the split ring expands on being pressed against the chamfered face of projecting shape and compresses onto the rod when it is pressed against the chamfered face of reentrant shape.
