Three-Dimensional Finite Element Analysis of Cement-Cup Junction in Total Hip Prosthesis: Mechanical Stress Distribution, Crack Initiation and Rupture Dynamics

Abstract

Understanding the mechanical and rupture behavior of orthopedic cement fixing the cup of a total hip prosthesis (THP) to cortical bone is crucial for comprehending the conditions governing prosthesis stability and potential loosening. Consequently, this study employs a three-dimensional finite element method to investigate the mechanical behavior of cement with interfacial cracks at the junction between the cement and cup. Through stress distribution analysis, we identify the initiation points of cracks and examine how stress intensity factors (SIFs) vary across three modes of failure (I, II and III) throughout a walking cycle, particularly concerning the femoral head. Our findings reveal that loading stages cause stable variations in SIFs along the crack front, with the highest values consistently at the second end of the crack. Moreover, the propagation mechanism of interfacial cracks is complex, oscillating between modes of opening and plane shear, linked to the SIFs of modes I and II and the material properties of the cement and cup. Furthermore, mode III behavior mirrors that of mode II, with nearly linear increases in SIFs along the crack front, peaking near the crack’s terminus. Overall, mode III (out-of-plane shear) emerges as the primary fracture mode, indicating a risk of damage to the reconstructed acetabulum from fatigue, despite the SIF values being lower than the fracture toughness of both the cup and the cement.