Abstract: BACKGROUND: At present, there is a lack of research on the biomechanical properties of the medial and anterolateral anatomical locking plates of the tibia for the treatment of external rotation fractures of the tibia.
OBJECTIVE: To compare stress distribution of the medial and anterolateral anatomical locking plates of the tibia for the treatment of external rotation fractures of the tibia using three-dimensional finite element analysis.
METHODS: Tibia CT images of one healthy volunteer were selected. Digital technology was used to construct the medial and anterolateral locking plate model of the distal tibia. The model combination was set according to the principle of internal fixation. The axial compression force, valgus/varus force, and torsion force were given respectively to simulate the internal fixation force of human body under different stress conditions and analyze the displacement of the tibial fracture model. 
RESULTS AND CONCLUSION: (1) In the axial compression force, the maximum equivalent stress and the fracture surface displacement of the distal lateral plate were about 31.6% and 8.8% smaller than those of the distal medial plate. (2) In torsion-external rotation, the maximum equivalent stress was similar and the displacement of the fracture surface was also similar between the distal medial and lateral plates. (3) Under torsion-internal rotation, the maximum equivalent stress and torsional angular displacement of the fracture surface of distal lateral plate was about 23.8% and 65.3% smaller than those of the distal medial plate. (4) When subjected to valgus violence, the maximum equivalent stress and displacement of the fracture surface of distal lateral plate were about 38.2% and 86.5% smaller than those of distal medial plate. When subjected to varus violence, the maximum equivalent stress and the displacement of the fracture surface of distal lateral plate were about 4.8% and 7.6% smaller than those of distal medial plate. (5) In external rotation spiral fractures of the middle and lower tibia, distal tibial anterior lateral plate has better ability to resist axial, twist-clockwise rotation, varus and valgus violence. The distal lateral plate has more biomechanical advantages than the distal medial plate. 

Key words: tibial fracture, spiral fracture, three-dimensional reconstruction, finite element analysis, medial tibial locking plate, lateral tibial locking plate, axial force, lateral force, torsion force