Fatigue crack growth in cement mantle of taper-slip total hip arthroplasty systems: numerical simulation and mechanical testing

• Fatigue crack propagation in cement mantle analyzed with XFEM and mechanical tests. • Paris’ Law based Direct Cyclic Analysis (DCA) used to model cyclic crack growth. • Hoop stress from axial load, not torsion, identified as main driver of crack growth. • Lower cortical-shell stiffness accelerated crack growth under multiaxial loading. • Larger initial defects lead to reduced fatigue life of the cement mantle. This study investigated the fatigue crack-propagation behavior of the cement mantle in a taper-slip total hip stem using a combination of extended finite element modeling (XFEM) and experimental fatigue testing. A two-dimensional plane-strain model of a polished, tapered stem cemented within a cortical shell was developed in Abaqus to simulate cyclic loading representative of hip joint mechanics during walking. Crack growth was governed by the energy-based Paris’ law within the XFEM framework, and direct cyclic analysis was used to obtain stabilized cyclic solutions. Parametric studies were conducted to examine the influence of cortical-shell stiffness (2.5–8 GPa) and initial crack length (0.5–2 mm) on the crack-propagation rate and fatigue life of the cement mantle. Complementary fatigue tests on bone-cement-implant constructs with aluminum and polymeric cortical-shell surrogates validated the numerical predictions. Results demonstrated that hoop stress induced by axial compressive loading, rather than torsional stress, was the dominant driver of crack propagation. Reduced cortical-shell stiffness and larger pre-existing defects led to greater tensile stress concentrations in the vicinity of the crack zone, resulting in accelerated crack growth and shorter fatigue life. The predicted trends were consistent with experimental observations, confirming the influence of axial load-induced hoop stress on the fatigue behavior of the cement mantle. The combined computational-experimental approach provides new insight into the mechanisms governing fatigue-driven cracking in cemented stems under multiaxial cyclic loading, and offers guidance for patient selection, surgical technique, and stem design to improve long-term clinical outcomes.