The Process of Porous Tantalum Implants Osseous Integration a Review

Abstract

Porous tantalum is a biomaterial that was recently introduced in orthopaedics in order to overcome problems of the past related to implant loosening. Its use has led to very good results, especially in difficult cases where severe bone defect is present, as it is found to have osteoconductive and possibly, osteoinductive properties. So, it is of great interest to shed light to the mechanisms through which this material leads to new bone formation after being implanted. For this reason, a review of the current literature was undertook. Porous tantalum is, biologically, relatively inert, meaning that its bonding capacity to the bone is restricted. In order to overcome this obstacle, it undergoes thermal processing in alkaline environment. This process leads to extensive hydroxyapatite formation on its surface and thus, to better integration of porous tantalum implants. Apart from this, new bone tissue formation occurs inside the pores of porous tantalum after its implantation and this new bone retains the characteristics of normal bone, i.e., bone remodeling and Haversian systems formation. This finding is enhanced by the observation that porous tantalum is an appropriate substrate for osteoblast adherence, proliferation and differentiation. Furthermore, the finding that osteoblasts derived from old women (>60 years old) and cultivated on porous tantalum may grow faster than osteoblasts taken from younger women (<45 years old) and cultivated on other substrates, can partially explain porous tantalum good performance in cases of patients with severe bone defects. In conclusion, porous tantalum chemical and mechanical properties are those that, probably, define the already noticed good performance of this material. However, further research is needed to totally clarify the mechanisms through which they contribute to that.