The fractures fixation had evolved with a change of emphasis from rigid mechanical internal fixation AO to biological osteosynthesis (BO). However the concepts of BO was still developing, and developed to the elastic osteosynthesis (EO). In history of internal fixation, the development and innovation at each stage was based on the outcomes of previous period. EO with minimum stress-shielding was beneficial to fractures healing, and stress impact fractures area produced strain effect to induce formation of callus. For EO, controlled micromovement and relative stability was considered to be two essential preconditions for successful fractures healing. Successful fractures healing were depended on the balance between flexibility and stiffness. The interfragmentary strain (IFS) was a simple mechanical parameter that could describe the fractures stability. Different IFS lead to different bone healing outcomes. Our teams had proposed the concepts of EO, which was based on our research results and reviewed a large number of literatures.