Biomechanical Assessment of Three Osteosynthesis Constructs by Periprosthetic Humerus Fractures

摘要

Background. Biomechanical stability assessment of 3 different constructs for proximal fixation of a locking compression plate (LCP) in treating a Worland type C periprosthetic fracture after total shoulder arthroplasty. Methods. 27 Worland type C fractures after shoulder arthroplasty in synthetic humeri were treated with 14-hole LCP that is proximally fixed using the following: (1) 1?×?1.5?mm cerclage wires and 2x unicortical-locking screws, (2) 3?×?1.5?mm cerclage wires, or (3) 2x bicortical-locking attachment plates. Torsional stiffness was assessed by applying an internal rotation moment of 5?Nm and then after unloading the specimen, an external rotation moment of 5?Nm at the same rate was applied. Axial stiffness was assessed by applying a 50?N preload, and then applying a cyclic load of 250?N, then increasing the load by 50?N each time, until a maximum axial load of 2500?N was reached or specimen failure occurred. Results. With regard to internal as well as external rotational stiffness, group 1 showed a mean stiffness of 0.37?Nm/deg and 0.57?Nm/deg, respectively, group 2 had a mean stiffness of 0.51?Nm/deg and 0.39?Nm/deg, respectively, while group 3 had a mean stiffness of 1.34?Nm/deg and 1.31?Nm/deg, respectively. Concerning axial stiffness, group 1 showed an average stiffness of 451.0?N/mm, group 2 had a mean stiffness of 737.5?N/mm, whereas group 3 had a mean stiffness of 715.8?N/mm. Conclusion. Group 3 displayed a significantly higher torsional stiffness while a comparable axial stiffness to group 2.