Pelvic Ring Fractures: External Fixation Comparative Numerical Structural Analysis

External fixation (EF) is commonly practiced for pelvic ring fractures management. Many parameters influence mechanical performances of external fixators. Our virtual 3D model of the pelvic ring introduces the advantage of differentiating the mechanical properties of cortical and cancellous bone along with the complex boundary conditions of major ligaments. We assessed stiffness variations by increasing fixator pins depth and we evaluated dislocation related to load intensity and sitting angle. The 3D model was crafted from a real CT scan. Finite Elements Analysis was run on the model, reproducing a Tile's classification Cl fracture. A 600N load was applied with a 40, 50 and 60 mm pins depth configuration simulating sitting and standing conditions. Four typical body constitutions were probed for 15 degrees, 30 degrees, 45 degrees, 60 degrees, 75 degrees and 90 degrees sitting inclination. Dislocation was taken as stiffness index. Rising pins depth to 60 mm reduces dislocation up to 22.8% in standing position and up to 15.5% in sitting simulation. Dislocation values tend to decrease along with sitting angle and initial weight. On an external fixated pelvic ring, pins depth affects significantly the structure stiffness. Patient sitting angle and his initial weight has also great influence in dislocation.