Fabrication and in vivo evaluation of Ti6Al4V implants with controlled porous structure and complex shape

Abstract

Electron beam melting process was used to fabricate porous Ti6Al4V implants. The porous structure and surface topography of the implants were characterized by scanning electron microscopy (SEM) and digital microscopy (DM). The results showed that the pore size was around 600 and the porosity approximated to 57%. There was about±50 μm of undulation on implants surfaces. Standard implants and a custom implant coupled with porous sections were designed and fabricated to validate the versatility of the electron beam melting (EBM) technique. After coated with bone-like apatite, samples with fully porous structures were implanted into cranial defects in rabbits to investigate the in vivo performance. The animals were sacrificed at 8 and 12 weeks after implantation. Bone ingrowth into porous structure was examined by histological analysis. The histological sections indicated that a large amount of new bone formation was observed in porous structure. The newly formed bone grew from the calvarial margins toward the center of the bone defect and was in close contact with implant surfaces. The results of the study showed that the EBM produced Ti6Al4V implants with well-controlled porous structure, rough surface topography and bone-like apatite layer are beneficial for bone ingrowth and apposition.

Keywords

electron beam melting process / implant / porous structure / bone ingrowth

References

[1] Pilliar R M. Porous-surfaced metallic implants for orthopedic applications. Journal of Biomedical Materials Research, 1987, 21(A1 Suppl): 1-33

[2] Kienapfel H, Sprey C, Wilke A, Griss P. Implant fixation by bone ingrowth. The Journal of Arthroplasty, 1999, 14(3): 355-368

[3] Wen C E, Mabuchi M, Yamada Y, Shimojima K, Chino Y, Asahina T. In: Processing of biocompatible porous Ti and Mg. Scripta Materialia, 2001, 45(10): 1147-1153

[4] Karageorgiou V, Kaplan D. Porosity of 3D biomaterial scaffolds and osteogenesis. Biomaterials, 2005, 26(27): 5474-5491

[5] Hollister S J. Porous scaffold design for tissue engineering. Nature Materials, 2005, 4(7): 518-524

[6] Otsuki B, Takemoto M, Fujibayashi S, Neo M, Kokubo T, Nakamura T. Pore throat size and connectivity determine bone and tissue ingrowth into porous implants: three-dimensional micro-CT based structural analyses of porous bioactive titanium implants. Biomaterials, 2006, 27(35): 5892-5900

[7] Jones A C, Arns C H, Hutmacher D W, Milthorpe B K, Sheppard A P, Knackstedt M A. The correlation of pore morphology, interconnectivity and physical properties of 3D ceramic scaffolds with bone ingrowth. Biomaterials, 2009, 30(7): 1440-1451

[8] Hutmacher D W, Sittinger M, Risbud M V. Scaffold-based tissue engineering: rationale for computer-aided design and solid free-form fabrication systems. Trends in Biotechnology, 2004, 22(7): 354-362

[9] Williams J M, Adewunmi A, Schek R M, Flanagan C L, Krebsbach P H, Feinberg S E, Hollister S J, Das S. Bone tissue engineering using polycaprolactone scaffolds fabricated via selective laser sintering. Biomaterials, 2005, 26(23): 4817-4827

[10] Seitz H, Rieder W, Irsen S, Leukers B, Tille C. Three-dimensional printing of porous ceramic scaffolds for bone tissue engineering. Journal of Biomedical Materials Research, Part B, Applied Biomaterials, 2005, 74(2): 782-788

[11] Ryan G E, Pandit A S, Apatsidis D P. Porous titanium scaffolds fabricated using a rapid prototyping and powder metallurgy technique. Biomaterials, 2008, 29(27): 3625-3635

[12] Li J P, de Wijn J R, van Blitterswijk C A, de Groot K. Porous Ti₆Al₄V scaffold directly fabricating by rapid prototyping: preparation and in vitro experiment. Biomaterials, 2006, 27(8): 1223-1235

[13] Krishna B V, Bose S, Bandyopadhyay A. Low stiffness porous Ti structures for load-bearing implants. Acta Biomaterialia, 2007, 3(6): 997-1006

[14] Hollander D A, von Walter M, Wirtz T, Sellei R, Schmidt-Rohlfing B, Paar O, Erli H J. Structural, mechanical and in vitro characterization of individually structured Ti-6Al-4V produced by direct laser forming. Biomaterials, 2006, 27(7): 955-963

[15] Heinl P, Müller L, Körner C, Singer R F, Müller F A. Cellular Ti-6Al-4V structures with interconnected macro porosity for bone implants fabricated by selective electron beam melting. Acta Biomaterialia, 2008, 4(5): 1536-1544

[16] Kokubo T, Takadama H. How useful is SBF in predicting in vivo bone bioactivity? Biomaterials, 2006, 27(15): 2907-2915

[17] Kujala S, Ryhänen J, Danilov A, Tuukkanen J. Effect of porosity on the osteointegration and bone ingrowth of a weight-bearing nickel-titanium bone graft substitute. Biomaterials, 2003, 24(25): 4691-4697

[18] Li J P, Habibovic P, van den Doel M, Wilson C E, de Wijn J R, van Blitterswijk C A, de Groot K. Bone ingrowth in porous titanium implants produced by 3D fiber deposition. Biomaterials, 2007, 28(18): 2810-2820

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2014 Higher Education Press and Springer-Verlag Berlin Heidelberg