2022, Vol. 26 ›› Issue (33): 5254-5258

Three-dimensional finite element analysis of congenital pseudarthrosis of the tibia in a child after treatment with 3 in 1 osteosynthesis

Liu Xiaowei, Yang Ge, Mei Haibo   

Abstract: BACKGROUND: Congenital pseudarthrosis of the tibia with intact fibula undergoing 3 in 1 osteosynthesis will increase the cross-sectional area in healed segments and may reduce the incidence of refracture. However, it also changed the morphology and biomechanics of the tibiofibula, and this change is not clear at present.
OBJECTIVE: To reconstruct the congenital pseudarthrosis of the tibia using three-dimensional finite element model method, which was treated with 3 in 1 osteosynthesis and achieved bony union, and to analyze its Von Mises stress peak value and distribution characteristics under different stress states.
METHODS: The CT images of lower limbs of a girl with Crawford type IV congenital pseudarthrosis of the tibia were collected from Hunan Children’s Hospital. CT images were used to build a three-dimensional model through Mimics software and 3-Matic was used to build a finite element model for adaptive meshing. After defining the material properties of the model, 75, 62.5, 50, 37.5, 25, 12.5, 0 N mechanical loadings were applied on the proximal tibia of the affected side respectively; the side of the proximal end of the fibula received 0, 12.5, 25, 37.5, 50, 62.5, 75 N mechanical loadings correspondingly using ANSYS software. A loading of 62.5 N was applied to the proximal tibia of the healthy side as the control. The maximum Von Mises stressing and distributional characteristics of the three-dimensional finite element model of the affected tibia and fibula and the healthy tibia were analyzed.
RESULTS AND CONCLUSION: (1) The maximum Von Mises stress was 26.73 MPa and the minimum was 6.97 MPa. As the stress load shifted to the fibula, the maximum Von Mises stress was decreased gradually, and the loading areas were mainly distributed in the two aspects of front and back in the tibial lower distal one third. (2) The maximum Von Mises on the healthy tibia (5.44 MPa) was lower than that in each group on the pseudarthrosis tibia, and stress area was mainly distributed in the lower 1/3 of the front of the tibia. (3) The 3 in 1 osteosynthesis for congenital pseudarthrosis of the tibia changed the normal tibial stress distribution and may cause excessive stress concentration in the tibia, speculating that it may increase the risk of refracture.
Key words: congenital pseudarthrosis of the tibia, biomechanics, finite element analysis, child, model, tibia, tibiofibular synostosis