Finite Element and Experimental Investigation of the Mixed-Mode Fracture in Cement-Prosthesis Interface in the Total Hip Replacement

Total Hip Replacement (THR) is considered as one of the most common and successful surgeries in orthopedics. The long-term stability of the cemented total hip replacements depends on the lasting integrity of the interfaces between the bone and bone cement, and also bone cement and prosthesis, critically. However, a great number of specialists in this field state that the failure initiation is in fact a mechanical phenomenon acting primarily at the adjacent cement-prosthesis interface. In this work, experimental fracture tests of bone cement-prosthesis with an interface crack were carried out under comprehensive mixed mode conditions, using circular type (sandwich Brazilian disk) specimens under compression loading in various directions. Selected loading angles, ranging from 7.5o to 60o, were used to achieve full loading conditions from mode I to mode II. The stress intensity factors (SIFs) and the T-stress for the interface crack were analyzed using the finite element over-deterministic method (FEOD), associated with the experimental tests. The results showed that, in the sandwich Brazilian disk compression tests, the crack kinked into the cement and the fracture angles were predicted properly by the Generalized Maximum Tensile Stress (GMTS) criterion. The predicted angles were in good agreement with the experimental results.