Laser powder bed fusion(L-PBF)of Mg alloys has provided tremendous opportunities for customized production of aeronautical and medical parts.Layer thickness(LT)is of great significance to the L-PBF process but has not...Laser powder bed fusion(L-PBF)of Mg alloys has provided tremendous opportunities for customized production of aeronautical and medical parts.Layer thickness(LT)is of great significance to the L-PBF process but has not been studied for Mg alloys.In this study,WE43 Mg alloy bulk cubes,porous scaffolds,and thin walls with layer thicknesses of 10,20,30,and 40μm were fabricated.The required laser energy input increased with increasing layer thickness and was different for the bulk cubes and porous scaffolds.Porosity tended to occur at the connection joints in porous scaffolds for LT40 and could be eliminated by reducing the laser energy input.For thin wall parts,a large overhang angle or a small wall thickness resulted in porosity when a large layer thicknesses was used,and the porosity disappeared by reducing the layer thickness or laser energy input.A deeper keyhole penetration was found in all occasions with porosity,explaining the influence of layer thickness,geometrical structure,and laser energy input on the porosity.All the samples achieved a high fusion quality with a relative density of over 99.5%using the optimized laser energy input.The increased layer thickness resulted to more precipitation phases,finer grain sizes and decreased grain texture.With the similar high fusion quality,the tensile strength and elongation of bulk samples were significantly improved from 257 MPa and 1.41%with the 10μm layer to 287 MPa and 15.12%with the 40μm layer,in accordance with the microstructural change.The effect of layer thickness on the compressive properties of porous scaffolds was limited.However,the corrosion rate of bulk samples accelerated with increasing the layer thickness,mainly attributed to the increased number of precipitation phases.展开更多
Laser powder bed fusion(L-PBF)has been employed to additively manufacture WE43 magnesium(Mg)alloy biodegradable implants,but WE43 L-PBF samples exhibit excessively rapid corrosion.In this work,dense WE43 L-PBF samples...Laser powder bed fusion(L-PBF)has been employed to additively manufacture WE43 magnesium(Mg)alloy biodegradable implants,but WE43 L-PBF samples exhibit excessively rapid corrosion.In this work,dense WE43 L-PBF samples were built with the relativity density reaching 99.9%.High temperature oxidation was performed on the L-PBF samples in circulating air via various heating temperatures and holding durations.The oxidation and diffusion at the elevated temperature generated a gradient structure composed of an oxide layer at the surface,a transition layer in the middle and the matrix.The oxide layer consisted of rare earth(RE)oxides,and became dense and thick with increasing the holding duration.The matrix was composed ofα-Mg,RE oxides and Mg_(24)RE_(5) precipitates.The precipitates almost disappeared in the transition layer.Enhanced passivation effect was observed in the samples treated by a suitable high temperature oxidation.The original L-PBF samples lost 40%weight after 3-day immersion in Hank’s solution,and broke into fragments after 7-day immersion.The casted and solution treated samples lost roughly half of the weight after 28-day immersion.The high temperature oxidation samples,which were heated at 525℃ for 8 h,kept the structural integrity,and lost only 6.88%weight after 28-day immersion.The substantially improved corrosion resistance was contributed to the gradient structure at the surface.On one hand,the outmost dense layer of RE oxides isolated the corrosive medium;on the other hand,the transition layer considerably inhibited the corrosion owing to the lack of precipitates.Overall,high temperature oxidation provides an efficient,economic and safe approach to inhibit the corrosion of WE43 L-PBF samples,and has promising prospects for future clinical applications.展开更多
Reconstruction of subarticular bone defects is an intractable challenge in orthopedics.The simultaneous repair of cancellous defects,fractures,and cartilage damage is an ideal surgical outcome.3D printed porous anatom...Reconstruction of subarticular bone defects is an intractable challenge in orthopedics.The simultaneous repair of cancellous defects,fractures,and cartilage damage is an ideal surgical outcome.3D printed porous anatomical WE43(magnesium with 4 wt%yttrium and 3 wt%rare earths)scaffolds have many advantages for repairing such bone defects,including good biocompatibility,appropriate mechanical strength,customizable shape and structure,and biodegradability.In a previous investigation,we successfully enhanced the corrosion resistance of WE43 samples via high temperature oxidation(HTO).In the present study,we explored the feasibility and effectiveness of HTO-treated 3D printed porous anatomical WE43 scaffolds for repairing the cancellous bone defects accompanied by split fractures via in vitro and in vivo experiments.After HTO treatment,a dense oxidation layer mainly composed of Y2O3 and Nd2O3 formed on the surface of scaffolds.In addition,the majority of the grains were equiaxed,with an average grain size of 7.4μm.Cell and rabbit experiments confirmed the non-cytotoxicity and biocompatibility of the HTO-treated WE43 scaffolds.After the implantation of scaffolds inside bone defects,their porous structures could be maintained for more than 12 weeks without penetration and for more than 6 weeks with penetration.During the postoperative follow-up period for up to 48 weeks,radiographic examinations and histological analysis revealed that abundant bone gradually regenerated along with scaffold degradation,and stable osseointegration formed between new bone and scaffold residues.MRI images further demonstrated no evidence of any obvious damage to the cartilage,ligaments,or menisci,confirming the absence of traumatic osteoarthritis.Moreover,finite element analysis and biomechanical tests further verified that the scaffolds was conducive to a uniform mechanical distribution.In conclusion,applying the HTO-treated 3D printed porous anatomical WE43 scaffolds exhibited favorable repairing effects for subarticular cancellous bone defects,possessing great potential for clinical application.展开更多
Enhanced antiinfection activities, improved hemocompatibility and osteo-compatibility, and reinforced osseointegration are among the most important considerations in designing multifunctional orthopedic biomaterials.H...Enhanced antiinfection activities, improved hemocompatibility and osteo-compatibility, and reinforced osseointegration are among the most important considerations in designing multifunctional orthopedic biomaterials.Hereby, anti-infective and osteogenic multifunctional 3 D printed porous Ti6 Al4 V implant with excellent hemocompatibility was successfully designed and fabricated. In brief, osteogenic micro-arc oxidation（MAO） coatings with micro/nanoscale porous topography were generated in situ on3 D printed Ti6 Al4 V scaffolds, on which heparin and vancomycin were easily immobilized. The surface microstructure,morphology, and chemical compositions were characterized employing scanning electron microscopy（SEM）, X-ray photoelectron spectroscopy（XPS） and Fourier transform infrared spectroscopy（FTIR）. High loading capacity and sustained vancomycin release profiles were revealed using high performance liquid chromatography（HPLC）. Favorable antibacterial and antibiofilm performances against pathogenic Staphylococcus aureus（S. aureus） were validated in vitro through microbial viability assays, Live/Dead bacterial staining, and crystal violet staining. Human mesenchymal stem cells（h MSCs） were seeded on the scaffolds and their proliferation and viability were assessed using Cell Counting Kit and Live/Dead cell viability kit. Further, osteoblastic differentiation abilities were evaluated using alkaline phosphatase（ALP） activity as a hall marker. Additionally, the improved hemocompatibility of the heparinized scaffolds was confirmed by activated partial thromboplastin time（APTT）, prothrombin time（PT） and thrombin time（TT）. Overall, our results show that the surface-modified 3 D printed porous Ti6 Al4 V possesses balanced antibacterial and osteogenic functions while exhibiting extra anticlotting effects, boding well for future application in customized functional reconstruction of intricate bone defects.展开更多
Bone defect repairs are based on bone graft fusion or replacement.Current large bone defect treatments are inadequate and lack of reliable technology.Therefore,we aimed to investigate a simple technique using three-di...Bone defect repairs are based on bone graft fusion or replacement.Current large bone defect treatments are inadequate and lack of reliable technology.Therefore,we aimed to investigate a simple technique using three-dimensional(3D)-printed individualized porous implants without any bone grafts,osteoinductive agents,or surface biofunctionalization to treat large bone defects,and systematically study its long-term therapeutic effects and osseointegration characteristics.Twenty-six patients with large bone defects caused by tumor,infection,or trauma received treatment with individualized porous implants;among them,three typical cases underwent a detailed study.Additionally,a large segmental femur defect sheep model was used to study the osseointegration characteristics.Immediate and long-term biomechanical stability was achieved,and the animal study revealed that the bone grew into the pores with gradual remodeling,resulting in a long-term mechanically stable implant-bone complex.Advantages of 3D-printed microporous implants for the repair of bone defects included 1)that the stabilization devices were immediately designed and constructed to achieve early postoperative mobility,and 2)that osseointegration between the host bone and implants was achieved without bone grafting.Our osseointegration method,in which the“implant-bone”interface fusion concept was used instead of“bone-bone”fusion,subverts the traditional idea of osseointegration.展开更多
The effects of pore size in additively manufactured biodegradable porous magnesium on the mechanical properties and biodegradation of the scaffolds as well as new bone formation have rarely been reported. In this work...The effects of pore size in additively manufactured biodegradable porous magnesium on the mechanical properties and biodegradation of the scaffolds as well as new bone formation have rarely been reported. In this work, we found that high temperature oxidation improves the corrosion resistance of magnesium scaffold. And the effects of pore size on the mechanical characteristics and biodegradation of scaffolds, as well as new bone formation, were investigated using magnesium scaffolds with three different pore sizes, namely, 500, 800, and 1400 μm (P500, P800, and P1400). We discovered that the mechanical characteristics of the P500 group were much better than those of the other two groups. In vitro and in vivo investigations showed that WE43 magnesium alloy scaffolds supported the survival of mesenchymal stem cells and did not cause any local toxicity. Due to their larger specific surface area, the scaffolds in the P500 group released more magnesium ions within reasonable range and improved the osteogenic differentiation of bone mesenchymal stem cells compared with the other two scaffolds. In a rabbit femoral condyle defect model, the P500 group demonstrated unique performance in promoting new bone formation, indicating its great potential for use in bone defect regeneration therapy.展开更多
Three-dimensional(3D)-printed porous Ti6Al4V implants play an important role in the reconstruction of bone defects.However,its osseointegration capacity needs to be further improved,and related methods are inadequate,...Three-dimensional(3D)-printed porous Ti6Al4V implants play an important role in the reconstruction of bone defects.However,its osseointegration capacity needs to be further improved,and related methods are inadequate,especially lacking customized surface treatment technology.Consequently,we aimed to design an omnidirectional radiator based on ultraviolet(UV)photofunctionalization for the surface treatment of 3D-printed porous Ti6Al4V implants,and studied its osseointegration promotion effects in vitro and in vivo,while elucidating related mechanisms.Following UV treatment,the porous Ti6Al4V scaffolds exhibited significantly improved hydrophilicity,cytocompatibility,and alkaline phosphatase activity,while preserving their original mechanical properties.The increased osteointegration strength was further proven using a rabbit condyle defect model in vivo,in which UV treatment exhibited a high efficiency in the osteointegration enhancement of porous Ti6Al4V scaffolds by increasing bone ingrowth(BI),the bone-implant contact ratio(BICR),and the mineralized/osteoid bone ratio.The advantages of UV treatment for 3D-printed porous Ti6Al4V implants using the omnidirectional radiator in the study were as follows:1)it can significantly improve the osseointegration capacity of porous titanium implants despite the blocking out of UV rays by the porous structure;2)it can evenly treat the surface of porous implants while preserving their original topography or other morphological features;and 3)it is an easy-to-operate low-cost process,making it worthy of wide clinical application.展开更多
Laser powder bed fusion(L-PBF)of magnesium(Mg)alloy porous scaffolds is expected to solve the dual challenges from customized structures and biodegradable functions required for repairing bone defects.However,one of t...Laser powder bed fusion(L-PBF)of magnesium(Mg)alloy porous scaffolds is expected to solve the dual challenges from customized structures and biodegradable functions required for repairing bone defects.However,one of the key technical difficulties lies in the poor L-PBF process performance of Mg,contributed by the high susceptibility to oxidation,vaporization,thermal expansion,and powder attachment etc.This work investigated the influence of L-PBF energy input and scanning strategy on the formation quality of porous scaffolds by using WE43 powder,and characterized the microstructure,mechanical properties,biocompatibility,biodegradation and osteogenic effect of the as-built WE43 porous scaffolds.With the customized energy input and scanning strategy,the relative density of struts reached over 99.5%,and the geometrical error between the designed and the fabricated porosity declined to below 10%.Massive secondary phases including intermetallic precipitates and oxides were observed.The compressive strength(4.37-23.49 MPa)and elastic modulus(154.40-873.02 MPa)were comparable to those of cancellous bone.Good biocompatibility was observed by in vitro cell viability and in vivo implantation.The biodegradation of as-built porous scaffolds promoted the osteogenic effect,but the structural integrity devastated after 12 h by the immersion tests in Hank’s solution and after 4 weeks by the implantation in rabbits’femur,indicating an excessively rapid degradation rate.展开更多
基金funded by the National Key Research and Development Program of China(2018YFE0104200)National Natural Science Foundation of China(51875310,52175274,82172065)Tsinghua Precision Medicine Foundation.
文摘Laser powder bed fusion(L-PBF)of Mg alloys has provided tremendous opportunities for customized production of aeronautical and medical parts.Layer thickness(LT)is of great significance to the L-PBF process but has not been studied for Mg alloys.In this study,WE43 Mg alloy bulk cubes,porous scaffolds,and thin walls with layer thicknesses of 10,20,30,and 40μm were fabricated.The required laser energy input increased with increasing layer thickness and was different for the bulk cubes and porous scaffolds.Porosity tended to occur at the connection joints in porous scaffolds for LT40 and could be eliminated by reducing the laser energy input.For thin wall parts,a large overhang angle or a small wall thickness resulted in porosity when a large layer thicknesses was used,and the porosity disappeared by reducing the layer thickness or laser energy input.A deeper keyhole penetration was found in all occasions with porosity,explaining the influence of layer thickness,geometrical structure,and laser energy input on the porosity.All the samples achieved a high fusion quality with a relative density of over 99.5%using the optimized laser energy input.The increased layer thickness resulted to more precipitation phases,finer grain sizes and decreased grain texture.With the similar high fusion quality,the tensile strength and elongation of bulk samples were significantly improved from 257 MPa and 1.41%with the 10μm layer to 287 MPa and 15.12%with the 40μm layer,in accordance with the microstructural change.The effect of layer thickness on the compressive properties of porous scaffolds was limited.However,the corrosion rate of bulk samples accelerated with increasing the layer thickness,mainly attributed to the increased number of precipitation phases.
基金funded by the National Key Research and Development Program of China (2018YFE0104200)National Natural Science Foundation of China (51875310, 52175274, 82172065)Tsinghua Precision Medicine Foundation
文摘Laser powder bed fusion(L-PBF)has been employed to additively manufacture WE43 magnesium(Mg)alloy biodegradable implants,but WE43 L-PBF samples exhibit excessively rapid corrosion.In this work,dense WE43 L-PBF samples were built with the relativity density reaching 99.9%.High temperature oxidation was performed on the L-PBF samples in circulating air via various heating temperatures and holding durations.The oxidation and diffusion at the elevated temperature generated a gradient structure composed of an oxide layer at the surface,a transition layer in the middle and the matrix.The oxide layer consisted of rare earth(RE)oxides,and became dense and thick with increasing the holding duration.The matrix was composed ofα-Mg,RE oxides and Mg_(24)RE_(5) precipitates.The precipitates almost disappeared in the transition layer.Enhanced passivation effect was observed in the samples treated by a suitable high temperature oxidation.The original L-PBF samples lost 40%weight after 3-day immersion in Hank’s solution,and broke into fragments after 7-day immersion.The casted and solution treated samples lost roughly half of the weight after 28-day immersion.The high temperature oxidation samples,which were heated at 525℃ for 8 h,kept the structural integrity,and lost only 6.88%weight after 28-day immersion.The substantially improved corrosion resistance was contributed to the gradient structure at the surface.On one hand,the outmost dense layer of RE oxides isolated the corrosive medium;on the other hand,the transition layer considerably inhibited the corrosion owing to the lack of precipitates.Overall,high temperature oxidation provides an efficient,economic and safe approach to inhibit the corrosion of WE43 L-PBF samples,and has promising prospects for future clinical applications.
基金funded by the National Key Research and Development Program of China(No.2018YFE0104200)National Natural Science Foundation of China(51875310,52175274,82172065)Peking University Medicine Sailing Program for Young Scholars’Scientific&Technological Innovation(BMU2023YFJHPY015).
文摘Reconstruction of subarticular bone defects is an intractable challenge in orthopedics.The simultaneous repair of cancellous defects,fractures,and cartilage damage is an ideal surgical outcome.3D printed porous anatomical WE43(magnesium with 4 wt%yttrium and 3 wt%rare earths)scaffolds have many advantages for repairing such bone defects,including good biocompatibility,appropriate mechanical strength,customizable shape and structure,and biodegradability.In a previous investigation,we successfully enhanced the corrosion resistance of WE43 samples via high temperature oxidation(HTO).In the present study,we explored the feasibility and effectiveness of HTO-treated 3D printed porous anatomical WE43 scaffolds for repairing the cancellous bone defects accompanied by split fractures via in vitro and in vivo experiments.After HTO treatment,a dense oxidation layer mainly composed of Y2O3 and Nd2O3 formed on the surface of scaffolds.In addition,the majority of the grains were equiaxed,with an average grain size of 7.4μm.Cell and rabbit experiments confirmed the non-cytotoxicity and biocompatibility of the HTO-treated WE43 scaffolds.After the implantation of scaffolds inside bone defects,their porous structures could be maintained for more than 12 weeks without penetration and for more than 6 weeks with penetration.During the postoperative follow-up period for up to 48 weeks,radiographic examinations and histological analysis revealed that abundant bone gradually regenerated along with scaffold degradation,and stable osseointegration formed between new bone and scaffold residues.MRI images further demonstrated no evidence of any obvious damage to the cartilage,ligaments,or menisci,confirming the absence of traumatic osteoarthritis.Moreover,finite element analysis and biomechanical tests further verified that the scaffolds was conducive to a uniform mechanical distribution.In conclusion,applying the HTO-treated 3D printed porous anatomical WE43 scaffolds exhibited favorable repairing effects for subarticular cancellous bone defects,possessing great potential for clinical application.
基金the Grant from Ministry of Science and Technology of China(2016YFB1101501)and researchfinancial support from the Beijing AKEC Medical Co.,Ltd.Medical Research Center of Peking University Third Hospital
文摘Enhanced antiinfection activities, improved hemocompatibility and osteo-compatibility, and reinforced osseointegration are among the most important considerations in designing multifunctional orthopedic biomaterials.Hereby, anti-infective and osteogenic multifunctional 3 D printed porous Ti6 Al4 V implant with excellent hemocompatibility was successfully designed and fabricated. In brief, osteogenic micro-arc oxidation（MAO） coatings with micro/nanoscale porous topography were generated in situ on3 D printed Ti6 Al4 V scaffolds, on which heparin and vancomycin were easily immobilized. The surface microstructure,morphology, and chemical compositions were characterized employing scanning electron microscopy（SEM）, X-ray photoelectron spectroscopy（XPS） and Fourier transform infrared spectroscopy（FTIR）. High loading capacity and sustained vancomycin release profiles were revealed using high performance liquid chromatography（HPLC）. Favorable antibacterial and antibiofilm performances against pathogenic Staphylococcus aureus（S. aureus） were validated in vitro through microbial viability assays, Live/Dead bacterial staining, and crystal violet staining. Human mesenchymal stem cells（h MSCs） were seeded on the scaffolds and their proliferation and viability were assessed using Cell Counting Kit and Live/Dead cell viability kit. Further, osteoblastic differentiation abilities were evaluated using alkaline phosphatase（ALP） activity as a hall marker. Additionally, the improved hemocompatibility of the heparinized scaffolds was confirmed by activated partial thromboplastin time（APTT）, prothrombin time（PT） and thrombin time（TT）. Overall, our results show that the surface-modified 3 D printed porous Ti6 Al4 V possesses balanced antibacterial and osteogenic functions while exhibiting extra anticlotting effects, boding well for future application in customized functional reconstruction of intricate bone defects.
基金the grant from the Ministry of Science and Technology of the People’s Republic of China(grant number 2016YFB1101501)Beijing Municipal Science&Technology Commission(Project Z181100001718195)。
文摘Bone defect repairs are based on bone graft fusion or replacement.Current large bone defect treatments are inadequate and lack of reliable technology.Therefore,we aimed to investigate a simple technique using three-dimensional(3D)-printed individualized porous implants without any bone grafts,osteoinductive agents,or surface biofunctionalization to treat large bone defects,and systematically study its long-term therapeutic effects and osseointegration characteristics.Twenty-six patients with large bone defects caused by tumor,infection,or trauma received treatment with individualized porous implants;among them,three typical cases underwent a detailed study.Additionally,a large segmental femur defect sheep model was used to study the osseointegration characteristics.Immediate and long-term biomechanical stability was achieved,and the animal study revealed that the bone grew into the pores with gradual remodeling,resulting in a long-term mechanically stable implant-bone complex.Advantages of 3D-printed microporous implants for the repair of bone defects included 1)that the stabilization devices were immediately designed and constructed to achieve early postoperative mobility,and 2)that osseointegration between the host bone and implants was achieved without bone grafting.Our osseointegration method,in which the“implant-bone”interface fusion concept was used instead of“bone-bone”fusion,subverts the traditional idea of osseointegration.
文摘The effects of pore size in additively manufactured biodegradable porous magnesium on the mechanical properties and biodegradation of the scaffolds as well as new bone formation have rarely been reported. In this work, we found that high temperature oxidation improves the corrosion resistance of magnesium scaffold. And the effects of pore size on the mechanical characteristics and biodegradation of scaffolds, as well as new bone formation, were investigated using magnesium scaffolds with three different pore sizes, namely, 500, 800, and 1400 μm (P500, P800, and P1400). We discovered that the mechanical characteristics of the P500 group were much better than those of the other two groups. In vitro and in vivo investigations showed that WE43 magnesium alloy scaffolds supported the survival of mesenchymal stem cells and did not cause any local toxicity. Due to their larger specific surface area, the scaffolds in the P500 group released more magnesium ions within reasonable range and improved the osteogenic differentiation of bone mesenchymal stem cells compared with the other two scaffolds. In a rabbit femoral condyle defect model, the P500 group demonstrated unique performance in promoting new bone formation, indicating its great potential for use in bone defect regeneration therapy.
基金The authors acknowledge the grant from the Ministry of Science and Technology of the People’s Republic of China(grant number 2016YFB1101501)Beijing Municipal Science&Technology Commission(Project Z181100001718195).Teng Zhang was supported in part by the Postdoctoral Fellowship of Peking-Tsinghua Center for Life Sciences.We also received research and financial support from the Beijing AKEC Medical Co.,Ltd.
文摘Three-dimensional(3D)-printed porous Ti6Al4V implants play an important role in the reconstruction of bone defects.However,its osseointegration capacity needs to be further improved,and related methods are inadequate,especially lacking customized surface treatment technology.Consequently,we aimed to design an omnidirectional radiator based on ultraviolet(UV)photofunctionalization for the surface treatment of 3D-printed porous Ti6Al4V implants,and studied its osseointegration promotion effects in vitro and in vivo,while elucidating related mechanisms.Following UV treatment,the porous Ti6Al4V scaffolds exhibited significantly improved hydrophilicity,cytocompatibility,and alkaline phosphatase activity,while preserving their original mechanical properties.The increased osteointegration strength was further proven using a rabbit condyle defect model in vivo,in which UV treatment exhibited a high efficiency in the osteointegration enhancement of porous Ti6Al4V scaffolds by increasing bone ingrowth(BI),the bone-implant contact ratio(BICR),and the mineralized/osteoid bone ratio.The advantages of UV treatment for 3D-printed porous Ti6Al4V implants using the omnidirectional radiator in the study were as follows:1)it can significantly improve the osseointegration capacity of porous titanium implants despite the blocking out of UV rays by the porous structure;2)it can evenly treat the surface of porous implants while preserving their original topography or other morphological features;and 3)it is an easy-to-operate low-cost process,making it worthy of wide clinical application.
基金funded by the National Key Research and Development Program of China(2018YFE0104200)National Natural Science Foundation of China(51875310,52175274,82172065)and AO Foundation(AOTAP21-47).
文摘Laser powder bed fusion(L-PBF)of magnesium(Mg)alloy porous scaffolds is expected to solve the dual challenges from customized structures and biodegradable functions required for repairing bone defects.However,one of the key technical difficulties lies in the poor L-PBF process performance of Mg,contributed by the high susceptibility to oxidation,vaporization,thermal expansion,and powder attachment etc.This work investigated the influence of L-PBF energy input and scanning strategy on the formation quality of porous scaffolds by using WE43 powder,and characterized the microstructure,mechanical properties,biocompatibility,biodegradation and osteogenic effect of the as-built WE43 porous scaffolds.With the customized energy input and scanning strategy,the relative density of struts reached over 99.5%,and the geometrical error between the designed and the fabricated porosity declined to below 10%.Massive secondary phases including intermetallic precipitates and oxides were observed.The compressive strength(4.37-23.49 MPa)and elastic modulus(154.40-873.02 MPa)were comparable to those of cancellous bone.Good biocompatibility was observed by in vitro cell viability and in vivo implantation.The biodegradation of as-built porous scaffolds promoted the osteogenic effect,but the structural integrity devastated after 12 h by the immersion tests in Hank’s solution and after 4 weeks by the implantation in rabbits’femur,indicating an excessively rapid degradation rate.
