Optimization Design Of Porous Implant Based On Bone Ingrowth Model

Bone defect repair is a major challenge in orthopedics,and traditional treatment options still have several shortages.Porous bone scaffolds implantation are satisfied approach before bone graft surgery due to their excellent mechanical and biological properties.The regeneration process of bone in a porous scaffold is a complex process involving inflammation,angiogenesis,cell migration and differentiation.The porous scaffold network accommodates the bone regeneration with a friendly microenvironment,which is capable of transporting growth factors,nutrients and wastes,and is essential for promoting the formation of bone tissue.Nevertheless,the understanding of how porous bone scaffolds affect bone ingrowth is rather limited so far.To guide the design of porous bone implant,a mathematical model describing the bone remodeling mechanism and the influencing factors on bone ingrowth of the porous scaffold was established in this paper.A continuous-discrete model based on agent was developed,which used the mathematical formula to describe the ingrowth process of bone in porous implants,including cell activity,vascular network formation and material diffusion.The diffusion of growth factors and oxygen was described by the diffusion equation,and the cellular activities were simulated with Monte Carlo method.The model demonstrated the entire biological ingrowth process of bone and blood vessels during the ingrowth of bone tissue.The model prediction results of bone deposition were consistent with the published experimental results,which validates the feasibility of the model.Additionally,the effects of various bone scaffold parameters,including microporous structure,pore size,initial oxygen concentration in the scaffold,and stem cell density,on bone ingrowth were studied.The results indicated that the pore structure of the scaffold determined the permeability of the scaffold and subsequently influenced the diffusion of growth factors,the transport of oxygen and the migration of cells.Then,the volume and distribution of bone deposits in scaffold was decided.Furthermore,the growth factor release and pore structure of porous implants were optimized.By controlling the position and releasing rate of the coating growth factors(BMPs,TGF-?,VEGF,etc.)in the scaffold,the bone deposition sites in the scaffold was induced in a desired site By designing the microporous structure of the scaffold,the bone deposition adjacent to tissue/implant interface is promoted,thus improving the osteointegration of the scaffold.