Intramedullary fixation device, having an intramedullary rod (2) which is provided for insertion thereof into a bone (1) and consists of a central screw (4) having a first free end comprising a stopper (7) and a second free end with a pre-tensioning nut (8), an alternating series of expanders (3) and bolts (5) being arranged in between, the bolt surfaces in contact with the expanders (3) having a wedge shape. The bolts (5) or expanders (3) may have no, or one or more variations in the dimensions of the different geometric parameters, in accordance with the adjacent expanders, along the length of the implant, and the central screw (4) may have a variable cross section. The device may have different additional components, such as an osteotomic base (9) for fixation of the musculature. The device promotes maximum nailing limited between these elements and produces a controlled peripheral radial deformation.