Alterations in osteocyte mechanostimulation within trabecular-lacunar cavities of human bone from intact to implanted cases: a multiscale model elucidating the role of osteocyte mechanosensors.

Abstract

Osteocytes, being embedded within the bone, sense mechanical stimuli through their various mechanosensors under physiological loading. However, the insertion of metallic implants alters the local mechanical environment, potentially disrupting osteocyte stimulation and affecting bone remodelling, particularly in the peri-implant cancellous bone. To quantify the changes in osteocyte mechanostimulation from the intact to the implanted state and to explore the potential of optimized implants in restoring these stimulations, a three-level multiscale modelling approach was developed. This approach transferred boundary conditions from the global femur (intact or implanted) to a trabecular-level model and subsequently to a cellular-level model. At the cellular level, the osteocyte was modelled within its interstitial fluid and surrounding bone matrix, with a specific focus on its various mechanosensors, aiming to examine quantitative changes in their mechanostimulation before and after implantation. The results showed that osteocyte stimulation in the peri-implant cancellous bone decreased by nearly 60-75% after inserting a solid implant, depending on whether the region corresponded to low or high marrow cell stimulation as defined by fluid shear stress on the trabecular surface. The simulation appeared to be sensitive to a change of implant design showing a recovery of this stimulation of approximately 5% when an optimized porous implant was employed, particularly enhancing osteocyte response near high shear stress regions on the trabecular surface. This study provides a mechanobiological explanation for altered bone remodelling around implants and demonstrates how an optimized implant design can enhance osteocyte stimulation and improve remodelling outcomes.