BIOMECHANICAL COMPARISON OF THREE POSTERIOR MALLEOLUS FRACTURE FIXATION METHODS IN RELATION TO DIFFERENT FRACTURE MORPHOLOGY: A FINITE ELEMENT ANALYSIS.

The objective of this study was to compare the biomechanical behavior of three fixation methods for posterior malleolar fracture (PMF) in relation to different fracture morphology and to evaluate the corresponding changes of the stress distribution on the articular surface of the tibia plafond by finite element analysis (FEA). Three internal fixation techniques: two lag screws in antero-posterior direction (AP lag screws), two lag screws in postero-anterior direction (PA lag screws) and posterior plate (PP) were analyzed for posteromedial (PM) and posterolateral (PL) fragment of PMF using the FEA. The values of relative deformations, total displacements, and von Mises stress (VMS) in the model elements were estimated under vertical loading 700 N. PP showed the highest level of VMS in the elements of the metal implants (from 97.1 to 106.15 MPa), than PA (44.77 MPa and 39.2 MPa) and AP (23.99 MPa and 25.53 MPa) lag screws group, regardless morphology of PMF. The presence of the PM and PL fragment of PMF causes displacement contact stress distribution to the anterior part of the tibia plafond surface. PP is biomechanically the most efficient technique for the fixation of PMF regardless of the fragment morphology. The distribution of loads on the articular surface of the tibia plateau depends on the morphology of the injury and the type of osteosynthesis of the PMF.