Comparative Three-Dimensional Finite Element Analysis on Miniplate and Lag Screw Fixation to Symphysis Fractures.

The purpose of this study was to compare the amount of stress on the fracture site via three-dimensional finite element analysis between lag screw and miniplate systems. Solid mathematical models were created from the CT of a patient and a fracture observed in the symphysis area. On the fracture site mini plates and lag screws applied to the bone to fixate segments. The physiologic mastication chewing forces were applied for simulation. These 2 fixation methods: were evaluated by their amount of stress values. The maximum Von Misses stress lag screw model was 2727 MPa on the apex of the lag screw and 934 MPa on the fracture site of the screw. At the miniplate model, the maximum Von Misses stress was 571 MPa on the head of the miniplate screw, and it was 202 MPa on the fracture site. Thus, lag screw model causes at least 4 times higher stress values than mini plate model. The stress level of lag screw model is higher than miniplate model. However, when the chewing forces are taken into account, the amount of stress in the lag screw system is also acceptable in clinical applications.