Effect of different structures fabricated by additive manufacturing on bone ingrowth

Bone tissue engineering relies on scaffold design to promote new bone formation. While porous titanium alloys are widely used, the impact of structural design and pore size on bone ingrowth remains unclear. Previous studies have shown that pore size influences cell behavior and tissue infiltration, but few have directly compared hollow versus solid structures in vivo. It was already known that pore diameters between 100 and 1000 μm are generally favorable for bone ingrowth, but the optimal pore size and structural configuration remain debated. This gap motivated further investigation into how structural geometry and pore dimensions affect bone regeneration outcomes. Hollow structures may reduce residual powder accumulation during fabrication, potentially improving biocompatibility. However, no prior work had resolved whether smaller pores consistently outperform larger ones in promoting bone formation. The need for standardized in vivo models to assess scaffold performance led to this study. Researchers aimed to clarify the relative benefits of hollow versus solid scaffolds and 300 versus 600 μm pore diameters.

This study aimed to evaluate how structural design and pore diameter influence bone ingrowth in titanium alloy scaffolds. The specific problem addressed is the lack of consensus on optimal scaffold geometry for bone regeneration. The motivation stems from the need to improve scaffold design for clinical applications. Hollow versus solid structures were compared to assess their impact on residual powder accumulation and cell proliferation. Pore diameters of 300 and 600 μm were tested to determine which better supports bone formation. The study focused on in vivo bone regeneration in a rabbit model to simulate clinical conditions. Researchers sought to determine whether structural and pore size differences lead to measurable changes in bone mineral density and volume fraction. The goal was to provide evidence-based guidance for scaffold fabrication in tissue engineering.

The study used electron beam melting to fabricate porous titanium alloy scaffolds with controlled structural and pore parameters. Scaffolds were divided into hollow and solid groups, with pore diameters of 300 and 600 μm in the lower and upper halves, respectively. Structural morphology was analyzed using scanning electron microscopy to assess residual powder and surface features. Cell proliferation was measured via cell counting kit-8 and live/dead staining assays. In vivo testing involved implanting scaffolds into the femoral condyles of 15 rabbits. Animals were sacrificed at 4, 8, and 12 weeks post-implantation for analysis. Bone mineral density and volume fraction were evaluated using quantitative micro-computed tomography. Histological analysis was performed with toluidine blue staining and optical microscopy. New bone area was quantified using image analysis software.

SEM images showed reduced residual powder in hollow implants compared to solid ones. Cell viability assays indicated no cytotoxicity in Ti6Al4V scaffolds. Micro-CT revealed progressive new bone formation around both scaffold types over time. Trabecular bone density increased with each post-implantation week. At 12 weeks, scaffolds with 300 μm pores showed significantly higher bone mineral density than those with 600 μm pores (p < 0.05). Bone volume fraction was also higher in 300 μm pore scaffolds. Histological staining confirmed greater new bone infiltration in the 300 μm group. The hollow structure appeared to enhance scaffold performance by minimizing residual powder accumulation.

The study found that hollow titanium alloy scaffolds reduced residual powder accumulation compared to solid ones. Scaffolds with 300 μm pores supported more effective bone ingrowth than those with 600 μm pores. These findings suggest that structural design and pore size are critical factors in scaffold performance. The authors propose that hollow structures may improve biocompatibility by reducing fabrication byproducts. The results support the use of 300 μm pore diameters for enhanced bone regeneration. No prior work had resolved the relative benefits of hollow versus solid structures in this context. The study provides evidence for optimizing scaffold design in tissue engineering. These conclusions are based on in vivo measurements of bone mineral density and volume fraction.