The Finite Element Analysis Of Pilon Fractures

Objective:Employ the finite element method of "static loading" and "impact simulation" to analyse the stress distribution in the process of pilon fracture, in order to explore the rule for the diagnosis and treatment of pilon fracture.Method:1 Select subject of a young man who has the healthy low limb, scan his leg using high-resolution CT 2 the data was import to the mimics for three-dimensional reconstruction as the DICOM format.3 Export the result to the Hypermesh9.0 as IGES format, after the secondary geometry cleaning, we build the mesh with four node tetrahedral and rectify some unit of poor quality.4 After this we give the physical properties'parameters of bone to the model and set the different condition in terms of the mechanism of pilon fracture, and it was in the ansys and pam-crash software we calculate the effect of static load effect and collision process.Results:stress distribution on the tibial and fibula shaft:the outcome of static load shown in the neutral position condition, the stress distribution in the distal tibial 1/3, while the collision process show the same area has the maximum deformation; in the dorsiflexion condition shows the most deformation occur between the epiphysis and the distal tibial 1/3; the plantar flexion condition, the load give an effect on the back of the tibia; in the valgus condition, from the static load, the stress distribute in the distal 1/3 of tibia and fibula too, but compared with the neutral position, we can find the area is lateral and significantly extend to the distal of fibula from the anterior aspect; in the inversion condition, the distal 1/3 has the value distribution under the static load and deformation under and collision. stress distribution in the tibial and fibula metaphysis. The collision process shows except the the neutral position condition, the first stress distribution seen in the metaphyseal of tibia or the metaphyseal of tibia and fibula beside the distributon in the articular surface, while the neutral position the stress area is higher but among the distal 1/3 of tibia. stress distribution in the ankle's articular surface of tibia and fibula:neutral position the static load distribute in the medial malleolus(anterior the intermalleolar axis part),the anterior lateral edge of distal tibial articular surface and the the ariticular surface of lateral malleolus; in the collision process, before 1.7ms, the ankle maintain the neutral position, it has the same stress distribution with the static load effect; dorsiflextion static load mainly distribute in the ariticular surface of lateral malleolus and the part anterior the inter-malleolar axis of the distal tibial articular surface; the collision process shows the stress expansion form the medial malleolus articular surface to the distal tibial articular surface(anterior the intermalleolar axis area)and the articular surface of lateral malleolus; plantar flexion static load stress distribute in the posterior of intermalleolar axis part of distal tibial articular surface and the lateral malleolus articular surface who is more, same as the crash process; inversion The stress distribute in the area anterior the intermalleolar axis, in the ariticular surface of medial and lateral malleolus, lateral and anterior edge of the of the distal tibial articular surface, while the collision conditions, the stress expand from the anterolateral edge to the lateral part of distal tibial articular surface (<1/2 range and anterior the intermalleolar axis), and to the lateral malleolus; eversion static load stress distribute in the ariticular surface of medial(anterior the intermalleolar axis) and lateral malleolus (which is more),the anterior edge of distal tibial articular surface also have a few; the collision process shows the same status and expand to the anterior intermalleolar axis part of the distal tibial articular, but the most part exist in the medial malleolus; the articular surface of lateral malleolus are always in the high-stress distribution under the static loading in different conditions, it is same in the collision process and show it is the first area to accept the stress generally.Conclusion:Conclusion:The fibula is an integral part of the pilon fracture; the distal tibial and fibula articular surface can be fall into four part according stress distribution, the first is medial malleolar part, the last is the lateral malleolar and lateral of distal tibial surface, the other are divide into the anterior and posterior part with the intermalleolar line. All of this are extend to the proximal and consist of four columns which are medial,lateral,anterior,and posterior column. It is consistent with the" Four-columns" theory.