Disclosed is an intra-corporal expandable device such as bone lengthening nails, bone transport nails, spinal distraction rods or growth prostheses to provide increased buckling load strength. The device comprises a first elongated part, a second part mounted telescopically relative to the first part, first links for attaching to an organism at a first end of the first part, and second links for attaching to the organism at a first end of the second part. Rotation of a rod with at least one thread leads to the displacement of the second part relative to the first part. The rotation of the rod is controlled and connections between these components wherein the rod is mounted between two ends which come closer when the device is elongated. The second end of the first part opposite the first end of the first part and the second end of the second part opposite the first end of the second part move so that the rod is under traction when the device is in operation.
