Structural analysis of porous humeral stems in reverse shoulder arthroplasty based on finite element analysis

Abstract Reverse shoulder arthroplasty (RSA) commonly employs solid humeral stems, which can alter the pattern of physiological load transfer, leading to stress shielding and potentially affecting implant durability and fixation. Additively manufactured humeral stems with porous lattice can lower the rigidity and weight while maintaining mechanical safety. In these implants, the porosity level directly influences weight reduction, implant stress, mechanical loading of bone and bone-implant stability. This study examines the structural integrity of porous RSA humeral stems with varying porosity levels using finite element analysis (FEA). Six standard humeral Ti-6Al-4 V stems, a solid stem and five stems with bone-mimicking architecture with varying porosity levels were designed. The lattice stems were analysed using a three-dimensional (3D) model of a humerus obtained from an adult Indian computed tomography (CT) dataset. The bone-implant assemblies of the models were subjected to loading conditions that represent various shoulder movements. Stress shielding signal (SSS), micromotion, and fatigue were evaluated. These findings indicate that porosity alone is insufficient to predict the mechanical behaviour of porous RSA humeral stems as differences in Voronoi architecture and load transfer also influence structural performance.