Laser Sintered Porous Ti–6Al–4V Implants Stimulate Vertical Bone Growth

Abstract

The objective of this study was to examine the ability of 3D implants with trabecular-bone-inspired porosity and micro-/nano-rough surfaces to enhance vertical bone ingrowth. Porous Ti-6Al-4V constructs were fabricated via laser-sintering and processed to obtain micro-/nano-rough surfaces. Male and female human osteoblasts were seeded on constructs to analyze cell morphology and response. Implants were then placed on rat calvaria for 10 weeks to assess vertical bone ingrowth, mechanical stability and osseointegration. All osteoblasts showed higher levels of osteocalcin, osteoprotegerin, vascular endothelial growth factor and bone morphogenetic protein 2 on porous constructs compared to solid laser-sintered controls. Porous implants placed in vivo resulted in an average of 3.1 ± 0.6 mm vertical bone growth and osseointegration within implant pores and had significantly higher pull-out strength values than solid implants. New bone formation and pull-out strength was not improved with the addition of demineralized bone matrix putty. Scanning electron images and histological results corroborated vertical bone growth. This study indicates that Ti-6Al-4V implants fabricated by additive manufacturing to have porosity based on trabecular bone and post-build processing to have micro-/nano-surface roughness can support vertical bone growth in vivo, and suggests that these implants may be used clinically to increase osseointegration in challenging patient cases.

Design and Structure–Function Characterization of 3D Printed Synthetic Porous Biomaterials for Tissue Engineering

“…Cheng et al describe a biomimetic design based on a high‐resolution template of overlaid µ CT scans of femoral head of human trabecular bone. This method produces scaffolds with porosity mimicking human trabecular bone with the ability to vary total porosity in the model . An in vitro study of normal human osteoblasts on a construct of this design with 67% interconnected porosity resulted in matured cells extending across struts and gaps in the architecture.…”

“…An in vivo study showed increase in bone to implant contact evaluated through histology and mechanical pull‐out test values for porous constructs (with and without DBX) compared to flat constructs. [32a]…”

“…In addition to the improvements to mechanical properties seen by postprocessing methods, others have also included postprocessing steps specifically to increase bioactivity of scaffolds by accelerating apatite formation and cell attachment. [21f,32b,42] For example, Cheng et al stimulated osteoblast differentiation on porous constructs with trabeculae inspired architecture by utilizing a calcium phosphate blasting, followed by acid etching, and finally pickling to increase micro‐/nanoroughness while maintaining macrostructure. [32b]…”

“…[21f,32b,42] For example, Cheng et al stimulated osteoblast differentiation on porous constructs with trabeculae inspired architecture by utilizing a calcium phosphate blasting, followed by acid etching, and finally pickling to increase micro‐/nanoroughness while maintaining macrostructure. [32b]…”

Hot isostatic pressure treatment of 3D printed Ti6Al4V alters surface modifications and cellular response

“…However, for implants that depend on bone ingrowth for stability, there is still debate on the optimal architecture and pore properties for enhanced osseointegration. Porous implants support increased bone ingrowth, although a study comparing AM fabricated porous implants with solid implants in rabbit tibial bone defects and in a rat calvarial on‐lay model for vertical bone ingrowth, showed that the porous implants were comparable to their solid counterparts concerning pull out force to failure (Cheng, Cohen, et al, ; Hyzy et al, ). The specific properties of the pores can also affect outcomes.…”