Proximal humerus fractures are the third most common osteoporotic fractures in the elderly population, frequently fixated by a locking plate. Complications such as screw cut-out, screw pull-out, loss of reduction, and fracture non-union account for a 35% rate one year after surgery, particularly in complex multi-fragmentary fractures and patients with poor bone quality. This highlights the need for improved understanding of the mechanical response and its effect on fracture stability and healing. Fracture healing is influenced by the local mechanical conditions at the fracture site, particularly interfragmentary motion and strain. Excessive motion may inhibit callus formation, while overly rigid fixation can suppress the biological stimulus required for secondary bone healing. Fixation design and surgical planning must balance between construct stiffness and interfragmentary motion. Verified and validated finite element (FE) analysis may assist for investigating these mechanisms, enabling detailed analysis of stresses, strains, and interfragmentary mechanics. We present an experimental-numerical framework for evaluating the mechanical behavior of proximal humerus fracture fixation using subject-specific FE models generated based on quantitative computed tomography (QCT) scans. The models incorporate inhomogeneous bone material properties, implant geometries, and contact interactions between fracture fragments and screws. These FE models were validated by experimentally measured displacements and interfragmentary motion recorded by digital image correlation (DIC) techniques . By relating fixation strategy and bone quality, this study contributes to the mechanical characterization of proximal humerus fracture fixation. The verified and validated FEA provides a basis for future studies of implant design and fixation assessment.