Mixed-mode failure strength of implant–cement interface specimens with varying surface roughness

AbstractAseptic loosening at the implant–cement interface is a well-documented cause of failure in joint arthroplasty. Traditionally, the strength of the implant–cement interface is determined using uni-axial normal and shear loading tests. However, during functional loading, the implant fixation sites are loaded under more complex stress conditions. For this purpose, the strength of the implant–cement interface under mixed-mode tensile and shear loading conditions was determined in this study using interface specimens with varying interface roughness. For the lowest roughness value analyzed (Ra=0.89μm), the interface strength was 0.40–1.95MPa at loading angles varying between pure tension and shear, whereas this was 4.90–9.90MPa for the highest roughness value (Ra=2.76μm). The interface strength during pure shear (1.95–9.90MPa) was substantially higher than during pure tension (0.58–6.67MPa). Polynomial regression was used to fit a second-order interpolation function through the experimental interface strength data (R2=0.85; p