Data related to architectural bone parameters and the relationship to Ti lattice design for powder bed fusion additive manufacturing

Osseointegration and fixation opportunities of sacroiliac instrumentation: a preclinical evaluation in a large animal model

Background

Implant fixation is often the cornerstone of musculoskeletal surgical procedures performed to provide bony fixation and/or fusion. The aim of this study was to evaluate how different design features and manufacturing methods influence implant osseointegration and mechanical properties associated with fixation in a standardized model in cancellous bone of adult sheep.

Methods

We evaluated the in vivo performance of three titanium alloy implants: (A) iFuse-TORQ implant; (B) Fenestrated Sacroiliac Device; and (C) Standard Cancellous Bone Screw in the cancellous bone of the distal femur and proximal tibia in 8 sheep. Group A was produced using additive manufacturing [three-dimensional (3D) printing] while Groups B and C were made with traditional methods. The vivo responses of the implants at the implant-bone interface were examined using mechanical testing (push out and removal torque), polymethyl methacrylate (PMMA) histology combined with fluorochrome labels and quantitative histomorphometry of bone ongrowth, ingrowth and through growth at 3 and 6 weeks.

Results

New bone formed directly on all groups and no adverse reactions were noted. Osseointegration via ongrowth, ingrowth and through growth was a function of implant design. Implant designs that provide osseointegration via ongrowth, ingrowth and through growth improve implant fixation in torsion. The 3D printed surface in group A was rougher and outperformed traditional manufacturing surfaces of groups B and C in torsion. The porous domains and fenestrations in the design of group A allowed for bone ingrowth and through growth, which accounted for the superior torsional properties.

Conclusions

Implant designs that provide osseointegration via ongrowth, ingrowth and through growth improve implant fixation.

Evaluation of Additives on the Cell Metabolic Activity of New PHB/PLA-Based Formulations by Means of Material Extrusion 3D Printing for Scaffold Applications

In this study, specific additives were incorporated in polyhydroxyalcanoate (PHB) and polylactic acid (PLA) blend to improve its compatibility, and so enhance the cell metabolic activity of scaffolds for tissue engineering. The formulations were manufactured through material extrusion (MEX) additive manufacturing (AM) technology. As additives, petroleum-based poly(ethylene) with glicidyl metacrylate (EGM) and methyl acrylate-co-glycidyl methacrylate (EMAG); poly(styrene-co-maleic anhydride) copolymer (Xibond); and bio-based epoxidized linseed oil (ELO) were used. On one hand, standard geometries manufactured were assessed to evaluate the compatibilizing effect. The additives improved the compatibility of PHB/PLA blend, highlighting the effect of EMAG and ELO in ductile properties. The processability was also enhanced for the decrease in melt temperature as well as the improvement of thermal stability. On the other hand, manufactured scaffolds were evaluated for the purpose of bone regeneration. The mean pore size and porosity exhibited values between 675 and 718 μm and 50 and 53%, respectively. According to the results, the compression stress was higher (11-13 MPa) than the required for trabecular bones (5-10 MPa). The best results in cell metabolic activity were obtained by incorporating ELO and Xibond due to the decrease in water contact angle, showing a stable cell attachment after 7 days of culture as observed in SEM.

An Enhanced Understanding of the Powder Bed Fusion-Laser Beam Processing of Mg-Y3.9wt%-Nd3wt%-Zr0.5wt% (WE43) Alloy through Thermodynamic Modeling and Experimental Characterization

Powder Bed Fusion–Laser Beam (PBF–LB) processing of magnesium (Mg) alloys is gaining increasing attention due to the possibility of producing complex biodegradable implants for improved healing of large bone defects. However, the understanding of the correlation between the PBF–LB process parameters and the microstructure formed in Mg alloys remains limited. Thus, the purpose of this study was to enhance the understanding of the effect of the PBF–LB process parameters on the microstructure of Mg alloys by investigating the applicability of computational thermodynamic modelling and verifying the results experimentally. Thus, PBF–LB process parameters were optimized for a Mg WE43 alloy (Mg-Y_3.9wt%-Nd_3wt%-Zr_0.5wt%) on a commercially available machine. Two sets of process parameters successfully produced sample densities >99.4%. Thermodynamic computations based on the Calphad method were employed to predict the phases present in the processed material. Phases experimentally established for both processing parameters included α-Mg, Y₂O₃, Mg₃Nd, Mg₂₄Y₅ and hcp-Zr. Phases α-Mg, Mg₂₄Y₅ and hcp-Zr were also predicted by the calculations. In conclusion, the extent of the applicability of thermodynamic modeling was shown, and the understanding of the correlation between the PBF–LB process parameters and the formed microstructure was enhanced, thus increasing the viability of the PBF–LB process for Mg alloys.