Research progress and clinical translation of three-dimensional printed porous tantalum in orthopaedics

Abstract

With continuous developments in additive manufacturing technology, tantalum (Ta) metal has been manufactured into orthopaedic implants with a variety of forms, properties and uses by three-dimensional printing. Based on extensive research in recent years, the design, processing and performance aspects of this new orthopaedic implant material have been greatly improved. Besides the bionic porous structure and mechanical characteristics that are similar to human bone tissue, porous tantalum is considered to be a viable bone repair material due to its outstanding corrosion resistance, biocompatibility, bone integration and bone conductivity. Numerous in vitro, in vivo, and clinical studies have been carried out in order to analyse the safety and efficacy of these implants in orthopaedic applications. This study reviews the most recent advances in manufacturing, characteristics and clinical application of porous tantalum materials.

Keywords: 3D printed; additive manufacturing; orthopaedic implant; porous; tantalum.

Figure 1.. Scanning electron microscopic images of selective laser melting-fabricated porous Ta scaffolds with different porosities. (A–E) 60%, 65%, 70%, 75%, and 80%. Reprinted from Gao et al. Scale bar: 500 μm.

Figure 2.. (A) Schematic of the selective laser melting process. Reprinted from Kamran and Farid. (B) An electron beam melting machine. Reprinted from Azam et al.

Figure 3.. Cell adhesion and proliferation properties on porous Ta. (A) Morphology of mesenchymal stem cells (yellow arrows) cultured for 3 and 5 days. Reprinted from Wang et al. (B) Light (B1) and fluorescence microscopic images of live-dead-stained bone marrow mesenchymal stem cells incubated on porous Ta (B2) and Ti₆Al₄V (B3) for 1 day, and quantification of the adherent cells (B4). Reprinted from Dox et al.(C) Confocal micrographs of vinculin expression on porous Ta with porosities of 27% (C1) and 45% (C2) and on porous Ti with 27% porosity (C3). Reprinted from Balla et al. Copyright © 2010 Acta Materialia Inc. Scale bars: 50 μm. Ta: tantalum; Ti: titanium.

Figure 4.. Osseointegration of porous tantalum (Ta) scaffolds. (A) Radiographic and histological images of porous Ta and Ti₆Al₄V implants at 4, 8, and 12 weeks. Reprinted from Guo et al. (B) Histological images of SLM porous Ta after 12 weeks in vivo. Reprinted from Wauthle et al. Copyright © 2014 Acta Materialia Inc.

Figure 5.. Drugs or cells loaded onto porous tantalum (Ta) for different treatments. Copyright 2021 from Hua et al. Reproduced by permission of Taylor and Francis Group, LLC, a division of Informapic.

Figure 6.. Clinical translation of 3D-printed porous Ta. (A) The clinical application of customized 3D-printed porous Ta scaffolds combined with Masquelet’s induced membrane technique to reconstruct an infected segmental femoral defect. Reprinted from Wu et al. (B) Knee reconstruction using 3D-printed porous Ta augmentation in the treatment of a Charcot joint. Reprinted from Hua et al. (C) After pelvic tumour resection, hemi-pelvic replacement surgery was performed using 3D-printed porous Ta implants. (C1) Anteroposterior X-ray of the patient’s hip joint showed an uneven density of the right iliac crest. (C2) Coronal MRI showed the extent of tumour invasion. (C3) Preoperative simulation of tumour resection and reconstruction range and location. (C4) Hemi-pelvic prosthesis design to restore the pelvic ring structure. (C5) Lateral view of the hemi-pelvic prosthesis. (C6) 3D-printed hemi-pelvic prosthesis. (C7) Intraoperative prosthesis implantation. (C8) X-ray at 6 months after surgery. C was from the authors’ original study. 3D: three-dimensional; MRI: magnetic resonance imaging; Ta: tantalum.