Embodiments of the present invention provide an osteosynthesis apparatus for proximal femur fractures. The osteosynthesis apparatus for proximal femur fractures has a structure in which a lag screw set and a nail are assembled via screwing process. The lag screw is assembled with a key ring and a fastening nut in advance. When inserting this lag screw set into a bone, grip bars are inserted radially at a predetermined angle and direction, resulting in a strong bone holding power. Further, in a final step, a strong fixed coupling is achieved by forcibly screwing and engaging the lag screw and the fastening nut by an interference of the threads of the lag screw and the fastening nut. Thus, the osteosynthesis apparatus for proximal femur fractures has a strong bone holding power and is stable without loosening.
