Orthopedic metallic medical devices are essential in the treatment of a wide range of skeletal diseases and disabilities. However, they are often related with surgery complications due to acute prosthetic joint infections (PJI) causing devastating complications. Gallium (Ga) antibacterial activity has been recently demonstrated: in aqueous solutions, Ga ionize in a trivalent form Ga3+ that can replace Fe3+ in bacterial metabolism thus leading to bacteria death. However, it is not yet clear whether such effect is typical to Ga3+ release, and how this would affect longer term performance. Here we investigated Ga addition into titanium alloys using metallurgical methods. The study has confirmed that metallurgical addition of gallium even in small amounts (1–2% wt.) to titanium alloys have highly efficient antibacterial function without any visible cytostatic or cytotoxic effects. The presence of gallium within the metal matrix might ensure that antibacterial effect will persist for a long time towards multi-drug resistant
Metal Injection Molding could provide cost saving of about 20–50% for implantable medical device manufacturing and hence healthcare public spending. Corrosion behaviour and biocompatibility of the new manufactured alloy were studied and showed similar behaviour compared to the traditional one. The growing trend for total joint arthroplasties could raise healthcare costs in the near future. Metal Injection Molding (MIM) is a near net shape manufacturing technology and allows the production of finite prosthesis components saving the machining step, and so resources, up to 20–50%. In order to apply such process to the production of actual devices, the bulk material have to show biocompatibility and corrosion behaviour similar to the traditional one. (ASTM F2083, ISO 21536) The aim of this work was to compare cast and forged CoCrMo alloy with the MIM one from the electrochemical point of view and cytocompatibility.Summary
Introduction
The aim of the work is to develop innovative antibacterial surface modification treatments for titanium capable to limit the bacterial adhesion and proliferation as weel as the biofilm formation while maintaining an high osteointegrative potential. The goal is to contrast the infections which represent a serius complication related to the use of implantable devices. Titanium and titanium alloy are considered the golden standard materials for the applications in contact with bone especially for dental and orthopaedic applications. To extend the implantable component lifetime and increase their clinical performance some surface modifications are required, to promote and speed up the osteointegration process increasing the rate of bone bonding. Unfortunately, among the different complications related to the use of titanium implantable devices the infections represent the most serious, often leading to implant failure and revision. The use of surface modification with specific metal ions represents a promising approach to fight implant-related infections. In particular gallium has recently shown efficacy in the treatment of infections: exploiting the chemical similarity of Ga3+ with Fe3+, it can interfere in the iron metabolism for a wide range of bacteria. The aim of this work is to develop and characterise new biocompatible biomimetic treatments with anodic spark deposition (ASD) technique on titanium characterised by antibacterial properties maintaining high osteointegrative potential. Three surfaces were developed using titanium grade 2 samples (12 mm diam., 0.5 mm thick): i) Introduction
Experimental Methods
Design and materials selection and optimisation are the-factors affecting the performance of the modern TKR. In this study new surface treatments were performed and investigated on CoCrMo with the goal to minimize the wear in a new total knee prosthesis design. Three surface finishing treatments were considered and applied to cast CoCrMo alloy specimens. A surface polishing treatment performed by mass finishing technique was applied on machined CoCrMo. ACoCrMo coating, obtained by Magnetron Sputtering Physical Vapour Deposition (PVD) technique, was applied on mass finished CoCrMo specimens. Conventional hand polishing performed by silicon carbide papers followed by a final diamond past polishing was considered as reference material. For this study not cross-linked not sterilized UHMWPE was used. Surface morphology obtained by the surface treatments was investigated by SEM, Atomic Force Microscopy, and non contact laser profilometry. The microstructure and micro-hardness of CoCrMo alloy was investigated as well. Wear tests were performed in bovine serum using two screening wear test machines. A final wear test was performed on the new knee pros-thesis design using a knee wear simulator, up to five millions cycles. CoCrMo PVD coating performed on CoCrMo substrate was capable to eliminate and to fill all the surface defects originated by the casting process of the CoCrMo alloy. Such surface defects could not be eliminated by hand polishing or mass finishing process alone. Vickers micro-hardness was improved by the mass finishing treatment. Although the roughness measured on the mass finished specimens was not the lowest, screening wear test produced for them the best results. Wear simulator test performed on the mass finished knee femoral prostheses sliding against UHMWPE, confirmed very low UHMWPE wear generation. The mass finishing surface treatment applied to cast CoCrMo alloy specimens and femoral components is capable to polish the surface to the level required by standards. The PVD coating investigated was capable to improve the surface morphology of the alloy and to eliminate all the surface micro defects. Nevertheless, the screening wear tests indicated that the mass finishing treatment generate the lowest wear. The results were confirmed by wear simulator test. This study indicated that the mass finishing surface treatment can be effectively applied for the polishing of the femoral components of knee prosthesis.
