Material advances in designing orthopedic and craniofacial implants

Great deal of research is still going on in the field of orthopedic and craniofacial implant development to resolve various issues being faced by the industry today. Despite several disadvantages of the metallic implants, they continue to be used, primarily because of their superior mechanical properties. In order to minimize the harmful effects of the metallic implants and its by-products, several modifications are being made to these materials, for instance nickel-free stainless steel, cobalt-chromium and titanium alloys are being introduced to eliminate the toxic effects of nickel being released from the alloys, introduce metallic implants with lower modulus, reduce the cost of these alloys by replacing rare elements with less expensive elements etc. New alloys like tantalum, niobium, zirconium, and magnesium are receiving attention given their satisfying mechanical and biological properties. Non-oxide ceramics like silicon nitride and silicon carbide are being currently developed as a promising implant material possessing a combination of properties such as good wear and corrosion resistance, increased ductility, good fracture and creep resistance, and relatively high hardness in comparison to alumina. Polymer/magnesium composites are being developed to improve mechanical properties as well as retain polymer’s property of degradation. Recent advances in orthobiologics are proving interesting as well.

The promise of the biomedical implants in eliminating some of the intricate issues of middle-and old-age population has led to outpouring of demands for new procedures. The major reason for the torrent of demand is prolonged average life expectancy of the population. However, the current generation of implants still faces certain issues during the long-term performance. By the extensive studies carried out till date, we can provide a theoretical answer to the properties required by these biomaterials, but still we are unable to design materials that can provide us desired results in vivo. The main reason is that properties of the end product greatly depend on the process parameters, which greatly influence various characters like macroporosity, grain size, surface roughness etc, which in turn determine the mechanical and biological properties of that material. These parameters are often missing in the publications and thus should be standardized and studied carefully. There is also an increasing need for understanding the basic interaction of the biomaterials with the implant surface, the host, and the biological environment at atomic levels as well as to know all types of micromotions executed by the implant inside the host, in order to develop implants which can last longer in the human body. Intense studies should be carried out to understand aspects like wear of the implant under pressurized loads, biologic response to wear and corrosion debris, the effect of biologic medium surrounding the implant etc. In the end, one has to accept the fact that humans have been diligently working and in many ways have succeeded in relieving many people from the sufferings and have increased their longevity, but the mission is still unaccomplished.