Abstract: BACKGROUND: The treatment of distal tibial fractures with soft tissue injury has always been challenging, and the new retrograde tibial nailing is a new choice. Up to now, there were few reports on the biomechanical properties between the new retrograde tibial nailing, anterograde intramedullary nailing and supercutaneous locking plate. 
OBJECTIVE: To explore the biomechanical stability of new retrograde tibial nailing, antegrade intramedullary nailing and supercutaneous locking plate in the treatment of distal tibial fractures with soft tissue injury using finite element analysis so as to offer a scientific foundation for clinical application.
METHODS: The finite element model of transverse distal tibia fracture was established by relevant software utilizing the CT data of the tibia from a 42-year-old healthy male. Retrograde tibial nailing, antegrade intramedullary nailing and supercutaneous locking plate finite element models were assembled under the principle of fracture fixation. Finally, meshing, applying loads, and data processing were accomplished with the ANSYS 2019 software. Moreover, the stress distribution and displacement of the tibia and internal fixation of each model were compared.  
RESULTS AND CONCLUSION: (1) The displacement of fracture end in the three groups increased with the increase of load. In all mode loads, the average displacement of the fracture end was the least in the retrograde tibial nailing group, followed by the supercutaneous locking plate group, and the highest in the antegrade intramedullary nailing group. At 800 N vertical load, the displacement difference of the fracture end was statistically significant (P < 0.05). There was no statistical significance in other load modes. (2) Under different loads, the tibial stress in the three groups was the highest in the middle of the tibia, and gradually decreased to the proximal and distal ends. The stress distribution of the tibial shaft was the highest in the retrograde tibial nailing group, followed by the supercutaneous locking plate group, and the least in the antegrade intramedullary nailing group. (3) Under different loads, the stress of the tibial stress raiser in the three groups was significantly higher in the supercutaneous locking plate group than in the other two groups, with statistical significance (P < 0.05). (4) Under different loads, the stress of the fixators in the three groups was the largest in the supercutaneous locking plate group, followed by the retrograde tibial nailing group, and the minimum in the antegrade intramedullary nailing group. There were significant differences in the stress of fixator stress raiser among the three groups under different loading modes (P < 0.05). (5) It is indicated that all three fixation methods have the good anti-rotation ability and axial stability. Retrograde tibial nail shows better biomechanical stability.

Key words: distal tibial fracture, minimal invasive, retrograde nailing, intramedullary nailing, supercutaneous locking plate, finite element analysis, biomechanics, soft tissue injury