The effect of roughness on biophysical stimuli at the bone-cartilage interface

Numerical simulations are often used to investigate the effect of mechanical environment on fracture healing. Although these models exhibit biologically relevant mechanical parameters at the bone-callus interface, this interface is modelled as perfectly smooth when in fact it is rough. In this study, a macro-micro-two-scale finite element model was used to determine if roughness significantly alters calculated local mechanical parameters. An idealized fracture healing poroelastic model with a small micro-modelled sub-domain of cartilaginous callus adjacent to rough bone was subjected to cyclic loading. The shear stress, tangential fluid velocity, and pore pressure were investigated. With roughness similar to that at the growth plate, solid matrix shear stress differed substantially with interface roughness, whereas interstitial fluid velocity and pore pressure were only slightly affected. Hence, when modelling local micro-mechanical environments near hard-soft tissue interfaces, interface roughness should be considered.