In vivo studies of a nanostructured titanium alloy knee plate and pin

Abstract

Titanium alloys are among the most used metallic biomaterials, particularly for orthopedic applications. Ever since the pioneer titanium alloy (Ti6Al4V) has been used as biomaterial, lack of biocompatibility has been extensively reported and propelled research on improved materials with appropriate mechanical behavior and adequate biocompatibility. Studies have indicated that vanadium produces oxides harmful to the human body; in order to replace vanadium containing Ti alloys, Ti-6Al-7Nb was developed. Today this alloy is the preferred choice for cementless total joint replacements. It is very important to produce a nanostructured bioactive metal implant with appropriate mechanical properties and we applied a chemical and thermal treatment that converts the surface of titanium alloy into bioactive surface. Therefore, bioactive Ti6Al7Nb might represent an alternative for advanced orthopedic implants under load-bearing conditions. Eleven mini-pigs weighting around 50 kg, with free access to food pellets and water, were the experimental animals for this study. Ten of these pigs (one is the control) were anesthetized and after shaving, disinfection and draping, a straight 3 cm incision was made and the implants (plate and pin) were implanted into the epiphyses of the tibiae. Surgical procedures were performed bilaterally. At 6 months after implantation, the mini-pigs were sacrificed. After sacrifice, the segments of the proximal tibia epiphyses containing the implanted plates and pins were cut of, fixed in phosphate-buffered formalin and dehydrated in serial concentrations of ethanol after which they were embedded in polyester resin and then cutted and grounded to a thickness of 75-100 μm. With these samples a lot of observations were made: Scanning Electron Microscopy observations, histological examination at implant surface and histological examination of the bone-implant surface and SEM-EDX examinations were also made. All the results revealed that the plates and pins are in direct contact with newly formed bone without any intervening soft tissue layer. We regard osteoinductive ability of nanostructured Ti6Al7Nb as one of the advantages of this implant in consideration for clinical applications.