Abstract:

Objective　To investigate the effect of the placement of the screw cap on the biomechanical properties of the fixed structure in the fracture zone when the fixed tibial fracture was performed.　Methods　Through the CT scan data and 3D image reconstruction, the finite element model of the fixed plate fixation of the comminuted fracture of middle tibia was established by simulated clinical operation. The position of the nail at the 13-hole plate was 1, 2, 4, 5, 9, 10, 12, and 13 holes, and nail holes in the fracture area were 6,7,and 8, and two kinds of plate fixation methods were designed: A (the screw cap placed in the fracture zone) and B (the screw cap not placed in the fracture zone), and model A and model B were tested by 600N compression test and 1000N three-point bending test respectively. The mechanical indexes of each part of the model were calculated and analyzed, and the comparison was made.　Results　In the compression test, the maximum stress of the model A steel plate appeared at the lower end of the steel plate, and the maximum stress of the model B steel plate appeared in the fracture zone. The maximum stress of the model A was significantly smaller than that of the model B. In the three-point bending test, the maximum stress of the two model steel plates appeared in the fracture zone. The maximum stress of model A was significantly smaller than that of model B.　Conclusion　Adding screw cap at the empty screw hole in the fracture zone of the steel plate can significantly reduce the maximum stress of the steel plate and reduce the stress concentration in the fracture zone of the steel plate, thereby reducing the risk of fatigue fracture of the steel plate at the fracture end.

Key words: Screw cap, 　Locking plate, 　Fracture internal fixation, 　Finite element analysis