An intra-corporal expandable device incorporating a screw operating under traction. A first elongated part (1) receives a second telescopic part (2). Each of these parts comprises links (61), (62) to the organism at a first end (11), (21) and is linked to a rod (3) comprising at least one thread at a second end (12) and (22). The rotation of the rod (3) controlled by means (4) causes a relative displacement of the two parts (1) and (2). The rod (3) is thus assembled between two ends (12) and (22) which come closer when the device is elongated, the length of the loaded rod (7) is reduced when the device is elongated and the length of loaded rod (7) operates only under traction. The device according to the invention is intended in particular for the production of osseous lengthening nails and growth prostheses.
