Investigation of the mechanical performance of sternal closures made with titanium plates

In this study, the effectiveness of x-shaped, star-shaped and straight-shaped titanium sternal closure plates was investigated numerically. Also, the influence on the plate behavior of the number of screws and utilization of steel wires was identified. Forty-eight different sternum fixation techniques were modelled and compared taking into account the safety load and stiffness values obtained from the finite element method analyses. In order to reveal the accuracy of analyses, traditional steel wire, single titanium plate and three titanium plate fixation techniques were numerically examined and the results were compared with the experimental data. The analyses were conducted by using Ansys Workbench software and performed under lateral distraction and longitudinal shear loading effects. When the safety load and stiffness values of all methods were examined, better results were obtained from the methods using x-shaped plates under the longitudinal shear effect, and from the methods using star-shaped and x-shaped plates under the lateral distraction effect. Moreover, it was determined that the straight-shaped and star-shaped plates provided a good sternal closure in lateral distraction, but showed a very poor behavior in longitudinal shear. As a result of the analyses, the highest safety load and stiffness values were obtained from the 2x4d(screw) fixation techniques in lateral distraction and the 4x(screw) fixation technique in longitudinal shear. In addition, it was observed that as the number of screws used in the plates increased, better sternal fixation was achieved in both loading conditions.