The Effect of Talus Osteochondral Defects of Different Area Size on Ankle Joint Stability: A Finite Element Analysis

(1) Background: Osteochondral lesion of the talus (OLT) is one of the common ankle injuries, which will lead to biomechanical changes in the ankle joint and ultimately affect the ankle function. The finite element analysis (FEA) was used to clarify the effect of talus osteochondral defects in different depths on the stability of the ankle joint. However, there is no clear research about the area of talus osteochondral defects that should be intervened in time. In this research, FEA is used to simulate the effect of different areas size of talus osteochondral defect on the stress and stability of ankle joint under a certain depth defect.; (2) Methods: The different area size (Normal, 2 mm* 2 mm, 4 mm* 4 mm, 6 mm* 6 mm, 8 mm* 8 mm, 10 mm* 10 mm, 12 mm* 12 mm) of osteochondral defects three-dimensional finite element model was established to simulate and calculate joint stress and displacement of the articular surface of the distal tibia and the proximal talus while the ankle joint was in the push-off phase, midstance phase and heel-strike phase; (3) Results: When OLT occurred, the contact pressure of articular surface, the equivalent stress of the proximal talus, tibial cartilage and talus cartilage did not change significantly with the increase of osteochondral defect area size in heel-strike phase below 6 mm * 6 mm, it increased gradually from 6 mm * 6 mm in midstance phase and push-off phase, and reached the maximum when the defect area size is 12 mm * 12 mm. The talus displacement also has the same tendency.; (4) Conclusions: The effect of cartilage area size defects of the talus on the biomechanics of the ankle is obvious especially in the midstance phase and push-off phase. When the defect size reaches 6 mm * 6 mm, the most obvious change in the stability of the ankle joint occurs, and the effect does not increase linearly with the increase in the depth of the defect.