Abstract: BACKGROUND: The inferior pole of the patella is very important for the integrity and stability of the knee extensor mechanism and maintaining good knee joint function. Currently, there is no unified surgical method for the clinical treatment of inferior pole patella fractures, but effective internal fixation should have the ability to counteract the tensile stress of the quadriceps and patellar ligament, the flexion stress of the femoral condyle, and the separation and displacement of the fracture ends. 
OBJECTIVE: A three-dimensional model of patellar inferior pole fracture was established by finite element method to compare the fixation effect and biomechanical stability of Kirschner-tension band, Kirschner-tension band combined with encircling, Kirschner-tension band combined with longitudinal binding, so as to provide a reliable surgical choice for clinical treatment of patellar inferior pole fracture.
METHODS: A healthy female volunteer was selected to undergo CT scan of the knee joint, and a model of the fracture of the inferior pole of the patella was constructed using finite element software. According to different internal fixation methods, they were divided into three groups: A, B and C. Group A received tension-band wiring; group B received tension-band wiring combined with cerclage wiring, and group C received tension-band wiring combined with separate vertical wiring. Under the same support and constraint conditions, the biomechanical properties of the three internal fixation models were evaluated by finite element analysis software.
RESULTS AND CONCLUSION: The results of finite element analysis showed that group C had the smallest displacement of the whole model, the patella and the internal fixator, and the smallest stress of the model and the internal fixator compared with group A and group B when different loads were applied in the direction of 45°. It is indicated that compared with Kirschner-tension band wiring and Kirschner-tension band wiring combined with cerclage wiring, Kirschner-tension band wiring combined with separate vertical wiring exhibits smaller displacement and stress, with superior biomechanical strength, providing a more reliable internal fixation. Theoretically, it is sufficient to meet the needs of patients to perform functional exercises after surgery in the early postoperative period. 

Key words: inferior pole of the patella, fracture, fracture internal fixation, Kirschner-tension band wiring combined with separate vertical wiring, finite element analysis, biomechanics, orthopedic implants