Structural and mechanical evaluations of a topology optimized titanium interbody fusion cage fabricated by selective laser melting process

A topology optimized lumbar interbody fusion cage was made of Ti-Al6-V4 alloy by the rapid prototyping process of selective laser melting (SLM) to reproduce designed microstructure features. Radiographic characterizations and the mechanical properties were investigated to determine how the structural characteristics of the fabricated cage were reproduced from design characteristics using micro-computed tomography scanning. The mechanical modulus of the designed cage was also measured to compare with tantalum, a widely used porous metal. The designed microstructures can be clearly seen in the micrographs of the micro-CT and scanning electron microscopy examinations, showing the SLM process can reproduce intricate microscopic features from the original designs. No imaging artifacts from micro-CT were found. The average compressive modulus of the tested caged was 2.97 ± 0.90 GPa, which is comparable with the reported porous tantalum modulus of 3 GPa and falls between that of cortical bone (15 GPa) and trabecular bone (0.1–0.5 GPa). The new porous Ti-6Al-4V optimal-structure cage fabricated by SLM process gave consistent mechanical properties without artifactual distortion in the imaging modalities and thus it can be a promising alternative as a porous implant for spine fusion. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res 2007Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/57400/1/31231_ftp.pd

Influence of macrophage cells on 316L stainless steel corrosion

In vitro corrosion tests have not evaluated the role of cells on the corrosion of implant quality 316L stainless steel. A new cell-culture corrosion cell was used to simulate the clinical condition of cells attached to and growing on the alloy to evaluate the effects of cells on alloy corrosion and the effect of corrosion products on cells. The corrosion potential, charge transfer, and surface composition of the alloy were measured in the presence and absence of macrophage cells (RAW 264.7) or cells stimulated to release NO over 72 hours. Whereas there was no statistical difference in the corrosion of 316L stainless steel in the presence of macrophage cells as compared to culture media alone, there was a trend for higher corrosion to occur in the presence of the cells. Corrosion was further reduced when cells were stimulated to release NO which may have oxidized the implant and contributed to an enhancement of its surface oxide. These data suggest that cells may alter alloy surface oxides and affect alloy corrosion