CoCrMo alloys ions release behavior by TiNbN coating: an in vitro study

The aim of the study was to show in vitro the greater inertness to the corrosion body fluid of TiNbN coating than the CoCrMo alloy substrate. The prosthetic component under study was a femoral component of total knee prosthesis in CoCrMo alloy coated in TiNbN with Physical Vapor Deposition technique immersed in static Hank’s balanced salt solution (HBS) (pH = 6) for at least 34 months at a constant temperature of 37 °C. Another uncoated prosthetic component of CoCrMo alloy with the same type and size was left in static immersion in the same solution and for the same period of time. Scanning electron microscope (SEM) analysis was performed to investigate adhesion and proliferation at 24, 48, 72 h after seeding of 10⁴ sub-confluents osteoblast-like cells (SaOS-2) cells on scaffold. The results of the study showed a reduction in the concentration of the metal ions released from the TiNbN-coated femoral component surface compared to the uncoated surface in the HBS solution. The overall reduction of the ions for the TiNbN-coated femoral component compared to the uncoated one was 80.1 ± 2%, 62.5% ± 8% and 48% ± 10% for Co, Cr, Mo, respectively (p < 0.01). SEM analysis confirmed the healthy state of the cells, the cellular adhesion and proliferation of SaOS-2 on the TiNbN-coated specimen. Although the results observed in vitro for the TiNbN coating are encouraging, clinical studies are certainly needed to be performed in order to understand how these positive findings can be translated in vivo and to determine the clinical benefit of TiNbN coating.