Dobruchowska Ewa, Paziewska Monika, Przybyl Krzysztof, Reszka Kazimierz
Koszalin University of Technology, Faculty of Technology and Education, Koszalin, Poland.
Acta Bioeng Biomech. 2017;19(2):31-39.
The endoprostheses made of cobalt-chromium-molybdenum (Co-Cr-Mo) alloys belong to the group of the most popular metallic implants used for reconstruction of hip joints. For such biomaterials, the primary goal is a correct and long-term functioning in the aggressive environment of body fluids. Therefore, the purpose of this study was to examine both the morphology and the corrosion resistance of implants made of the cobalt alloy used in Birmingham Hip Resurfacing (BHR) system (Smith & Nephew). For comparative purposes, the electrochemical studies were done for the nitrided stainless steel - Orthinox.
Observations of the microstructure of the material under investigation were performed by means of the optical metallographic microscope and the scanning electron microscope. Furthermore, Energy Dispersive X-ray Spectroscopy was used to analyse the chemical composition of the endoprosthesis. Characterisation and evaluation of electrochemical corrosion resistance of the selected alloys were performed by potentiodynamic polarisation tests.
The structural studies confirmed that Co-Cr-Mo (BHR system) is characterised by a typical dendritic microstructure with carbide precipitates, mainly M23C6, within the interdendritic areas. The results of the polarisation measurements showed that the cobalt alloy investigated exhibits lower corrosion potential than Orthinox in the utilised environments (3% NaCl, simulated body fluid - Hank's Body Fluid).
However, the high passivation ability of the Co-Cr-Mo alloy, as well as its resistance to the initiation and propagation of localised corrosion processes, indicate that this material is significantly more appropriate for long-term implants.
由钴铬钼（Co-Cr-Mo）合金制成的内置假体属于用于髋关节重建的最常用金属植入物类别。对于此类生物材料而言，其首要目标是在体液这种具有侵蚀性的环境中实现正确且长期的功能。因此，本研究的目的是检查用于伯明翰髋关节表面置换术（BHR）系统（施乐辉公司）的钴合金制成的植入物的形态和耐腐蚀性。为作比较，对渗氮不锈钢——奥氏inox进行了电化学研究。
借助光学金相显微镜和扫描电子显微镜对所研究材料的微观结构进行观察。此外，使用能量色散X射线光谱仪分析内置假体的化学成分。通过动电位极化试验对所选合金的电化学耐腐蚀性进行表征和评估。
结构研究证实，Co-Cr-Mo（BHR系统）的特征是具有典型的树枝状微观结构，在枝晶间区域有碳化物析出，主要是M23C6。极化测量结果表明，在所使用的环境（3%氯化钠、模拟体液——汉克氏体液）中，所研究的钴合金的腐蚀电位低于奥氏inox。
然而，Co-Cr-Mo合金的高钝化能力及其对局部腐蚀过程的引发和扩展的抗性表明，这种材料明显更适合用于长期植入物。
