Analysis of factors influencing bone ingrowth into three-dimensional printed porous metal scaffolds: A review

With the development of three-dimensional (3D) printing technology, porous metal scaffolds can be well fabricated. In contrast to conventional methods, 3D printing of porous scaffolds is characterized by a controllable and precise manufacturing process, which makes it possible to form customized predesigned implants for individual patients and achieve regular pore distribution at the micro scale. As the microenvironment of bone ingrowth, pores must provide sufficient space for cell attachment and proliferation. The behaviors of cells and bone ingrowth can influence the effect of 3D printed porous metal scaffolds on bone ingrowth. This review introduces 3D printing techniques shortly and focuses on the factors that potentially influence bone ingrowth into 3D printed porous metal scaffolds, e.g., materials, pore size, porosity, pore structure, surface modification, and mechanical properties. In each chapter, the mechanisms underlying cell–scaffold interactions are discussed in detail. In addition, the clinical applications of 3D printing are also introduced shortly. Finally, we list the most appropriate parameters for an excellent porous metal scaffold and attempt to identify a combination of these parameters that predicts good bone ingrowth. •3D printing achieves breakthroughs of customization and fine porous microstructure.•The 4S factors of implants e.g. shape, surface, strength and survive, should be addressed.•The interaction between pore parameters and cell behavior will be the further topic.•Surface modification on 3D scaffolds for optimal bone ingrowth needs further study.•The advantages of 3D printing implants received huge attention in clinical use.