Locked plate fixation and intramedullary nailing for proximal humerus fractures: A biomechanical evaluation

Background. Internal fixation of proximal humeral fractures is associated with a considerable secondary malalignment rate. Fixed-angle implants have been suggested to increase the stability of fixation. Methods. The biomechanical properties of four different implants were tested. These included an internal fixator with semi-elastic properties (reference), the Synthes T-plate, a locked plate with rigid properties and a spiral blade locked intramedullary nail (PHN). These implants were assessed in twenty-four osteotomized pairs of human cadaveric humeri. Specimens were subjected to two-hundred cycles of axial loading and torque followed by load to failure. Results: The PHN had greater axial stiffness than the reference and the T-plate. During torque, all implants were stiffer than the reference. During cyclic loading, there were no differences between the T-plate and the reference. Both the rigid internal fixator and the PHN hadless irreversible deformation than the reference. Both implants resisted higher loads before failure. Conclusion: This study showed that the proximal humeral nail and the rigid internal fixator are stronger than the semi-elastic locked plate and the Synthes T-plate for unstable subcapital proximal humeral fractures.