Objective To design a new type of external fixator for bone fracture and verify its rationality and feasibility. Methods The frame and screw of stainless steel achieved fracture fixation in vitro with a threaded locking structure.At the same time the increasing thickness of body frame, the inclined nail holes and the raised bottoms were designed to greatly enhance the strength and overall stability of body frame.FEM (finite element method),measuring the relative displacement and stress distribution after axial load,was used to verify the rationality of the design.An animal experiment with sheep was used to verify the feasibility of fracture treatment. Results Simulated result of FEM indicated that the biggest relative displacement between the separated bones was 0.04 mm,which was much less than the minimum value 1 mm required for fracture healing.The maximum stresses applied on the frame of the fixator,fixator screw,and bone were 35,26,and 6 MPa, respectively, which was much less than the allowable stress. In the animal experiment, fracture site was fixed firmly after operation and was well cured 3 months later.Conclusion The design of this new device is feasible and it can be used as a new method of fracture treatment.

The advantages and disadvantages of different treatment methods of traditional tibial fracture were summarized. The research progress on the treatment of tibial fracture with internal fixation plates as external fixators was introduced from two aspects of biomechanics and clinical application. It was proved that internal fixation plates as external fixators could reduce the structural stability, but this technique was still controversial to meet the mechanical requirements of fracture healing on biomechanics.Internal fixation plates as external fixators,it had the advantages of minimal invasion,high healing rate, less complications and favorable activities. It's pointed out clinical trials on its feasibility and availability as well as simulating body mechanics environment should be carried out to provide basis for relevant biomechanics researches.