The Clinical Application of Porous Tantalum and Its New Development for Bone Tissue Engineering

Abstract

Porous tantalum (Ta) is a promising biomaterial and has been applied in orthopedics and dentistry for nearly two decades. The high porosity and interconnected pore structure of porous Ta promise fine bone ingrowth and new bone formation within the inner space, which further guarantee rapid osteointegration and bone-implant stability in the long term. Porous Ta has high wettability and surface energy that can facilitate adherence, proliferation and mineralization of osteoblasts. Meanwhile, the low elastic modulus and high friction coefficient of porous Ta allow it to effectively avoid the stress shield effect, minimize marginal bone loss and ensure primary stability. Accordingly, the satisfactory clinical application of porous Ta-based implants or prostheses is mainly derived from its excellent biological and mechanical properties. With the advent of additive manufacturing, personalized porous Ta-based implants or prostheses have shown their clinical value in the treatment of individual patients who need specially designed implants or prosthesis. In addition, many modification methods have been introduced to enhance the bioactivity and antibacterial property of porous Ta with promising in vitro and in vivo research results. In any case, choosing suitable patients is of great importance to guarantee surgical success after porous Ta insertion.

Keywords: additive manufacturing; bone tissue engineering; clinical application; porous tantalum; surface modification.

Figure 1

Schematic representation of the relative signaling pathway that may be involved in the osteogenic effect of Ta.

Figure 2

The microstructure of porous Ta presented as honeycomb structure (a), and cells that partially cover the cavity with many calcium nodules (indicated with white arrow) can be detected (b). Reprinted from ref. [36]. Abundant bone ingrowth can be found in the pores of porous Ta implant (c). Reprinted with permission from [45]. Copyright © 2021 by American Academy of Orthopaedic Surgeons.

Figure 3

Application of porous Ta in different parts of the human body.

Figure 4

The typical products of porous Ta-based implants manufactured by Zimmer Biomet Inc. Acetabular cup with porous Ta coating (a). Reprinted with permission from [45]. Copyright © 2021 by American Academy of Orthopaedic Surgeons. Porous Ta lumbar interbody fusion cage (b) Reprinted from ref. [57], porous Ta rod (c) Reprinted from ref. [58] and dental implant (d) Reprinted from ref. [59]. The porous Ta cones were used to reconstruct femoral metaphyseal defect (e–g). Reprinted from ref. [60].

Figure 5

The printed personalized porous Ta knee prosthesis (a), distal femoral component (b) and proximal tibial component (c). The porous Ta prosthesis was inserted into distal femur and proximal tibia, respectively, during the surgery (d,e). Reprinted from ref. [188].

Figure 6

The AP (a) and lateral view (b) of X-ray examination at 5-month follow-up showed that the fracture healed after the implantation of the printed porous Ta osteosynthesis plate. Reprinted from ref. [191].

Figure 7

Schematic diagram of the surface modification for porous Ta. Amorphous calcium phosphate (ACP) nanospheres and HA nanorods coating on the surface of Ta scaffold (a). Reprinted from ref. [192]. ZnO nanoslices and ZnO nanorods coating on Ta substrate (b), the ZnO nanoslices will be released at an early stage—within 48 h (c), while the ZnO nanorods are released in a slow pattern over 2 weeks (d). Reprinted with permission from [199]. Copyright © 2021 by American Chemical Society.