Mechanical micromodeling of stress-shielding at the bone-implant interphase under shear loading

International audienceInserting a titanium implant in bone tissue may modify its physiological loading and therefore cause bone resorption, via a phenomenon called stress-shielding. The local stress field around the bone-implant interphase (BII) created under shear loading may be influenced by different parameters such as the bone-implant contact (BIC) ratio, the bone Young's modulus, the implant roughness and the implant material. To evaluate their impact, a 2-D finite element model was developed to model the BII. The implant roughness was described by a sinusoidal function (height 2Δ, wavelength λ) and different values of the BIC ratio were simulated. A heterogeneous distribution of the maximum shear stress was evidenced in the periprosthetic bone tissue, with high interfacial stress for low BIC ratios and low implant roughness, and underloaded regions near the roughness valleys. Both phenomena may lead to stress-shielding related effects, which was concentrated within a distance lower than 0.8.λ from the implant surface. Choosing an implant material with mechanical properties matching those of bone tissue leads to a homogenized shear stress field, and could help to prevent stress-shielding effects. Finally, the equivalent shear modulus of the BII was derived to replace its complex behavior by a simpler analytical model in future studies