Abstract
The coated porous section of stem surface is initially filled with callus that undergoes osseointegration process, which develops a bond between stem and bone, lessens the micromotions and transfers stresses to the bone, proximally. This phenomenon attributes to primary and secondary stabilities of the stems that exhibit trade-off the stem stiffness. This study attempts to ascertain the influence of stem stiffness on peri-prosthetic bone formation and stress shielding when in silico models of solid CoCr alloy and Ti alloy stems, and porous Ti stems (53.8 GPa and 31.5 GPa Young's moduli) were implanted. A tissue differentiation predictive mechanoregulation algorithm was employed to estimate the evolutionary bond between bone and stem interfaces with 0.5-mm- and 1-mm-thick calluses. The results revealed that the high stiffness stems yielded higher stress shielding and lower micromotions than that of low stiffness stems. Contrarily, bone formation around solid Ti alloy stem and porous Ti 53.8 GPa stem was augmented in 0.5-mm- and 1-mm-thick calluses, respectively. All designs of stems exhibited different rates of bone formation, diverse initial micromotions and stress shielding; however, long-term bone formation was coherent with different stress shielding. Therefore, contemplating the secondary stability of the stems, low stiffness stem (Ti 53.8 GPa) gave superior biomechanical performance than that of high stiffness stems.