The aim of this study was to determine the biomechanical behavior of two different implants used in the fixation of proximal humerus fractures. The two implants in this study are specifically designed for the fixation of proximal humerus fractures and both utilize the concept of fixed angle locking screws. Bone densitometry was performed prior to fracture production and fixation. A reproducible three-part fracture was created in paired human cadaveric bone and then fixed using the locking screw implants. Stress/strain curves for the bone-implant construct were created for loads applied in cantilever bending and torsion to determine the relative stiffness below the yield point. Following this each construct was tested to failure with a valgus bending load.

The locking nail implant provided a significantly stiffer construct in torsion, valgus, extension and flexion at loads below failure threshold. The valgus load to failure was significantly higher for the nail. The mode of failure was different between implants.