Lukina Elena, Kollerov Mikhail, Meswania Jay, Khon Alla, Panin Pavel, Blunn Gordon W
MAI (National Research University), Volokolamskoeshosse.,4, Moscow 125993, Russia; University College London, Brockley Hill, Stanmore, London HA7 4LP, UK.
MAI (National Research University), Volokolamskoeshosse.,4, Moscow 125993, Russia.
Mater Sci Eng C Mater Biol Appl. 2017 Mar 1;72:601-610. doi: 10.1016/j.msec.2016.11.120. Epub 2016 Dec 3.
Untypical corrosion damage including erosions combined with the build-up of titanium oxide as a corrosion product on the surface of explanted Nitinol spinal rods in the areas where it was in contact with titanium pedicle screw head is reported. It was suggested that Nitinol rods might have inferior fretting corrosion resistance compared with that made of titanium or CoCr. Fretting corrosion of Nitinol spinal rods with titanium (Ti6Al4V) pedicle screws were tested in-vitro by conducting a series of potentiostatic measurements of the peak-to-peak values of fretting corrosion current under bending in a 10% solution of calf serum in PBS. The test included Nitinol rods locked in titanium pedicle screws of different designs. Performance of commercially available titanium (Ti6Al4V) and CoCr spinal rods was also investigated for a comparison. Corrosion damage observed after the in-vitro tests was studied using SEM and EDAX analysis and was compared with patterns on Nitinol rods retrieved 12months after initial surgery. Metal ions level was measured in the test media after in-vitro experiments and in the blood and tissues of the patients who had the rods explanted. The results of this study revealed that Nitinol spinal rods locked in Ti pedicle screws are susceptible to fretting corrosion demonstrating higher fretting corrosion current compared with commercially used Ti6Al4V and CoCr rods. On the surface of Nitinol rods after in-vitro tests and on those retrieved from the patients similar corrosion patterns were observed. Improved resistance to fretting corrosion was observed with Nitinol rods in the in-vitro tests where pedicle screws were used with a stiffer locking mechanism. Since the development of the localized corrosion damage might increase the risk of premature fatigue failure of the rods and result in leaching of Ni ions, it is concluded that Nitinol rods should not be used in conjunction with Ti pedicle screws without special protection especially where the design provides a high degree of mobility to the rods.
据报道，在取出的镍钛诺脊柱棒与钛椎弓根螺钉头部接触的区域，出现了包括侵蚀以及作为腐蚀产物的氧化钛堆积在内的非典型腐蚀损伤。有人认为，与钛或钴铬制成的脊柱棒相比，镍钛诺棒的微动腐蚀抗性可能较差。通过在含有10%小牛血清的PBS溶液中进行弯曲状态下微动腐蚀电流峰峰值的一系列恒电位测量，对镍钛诺脊柱棒与钛（Ti6Al4V）椎弓根螺钉之间的微动腐蚀进行了体外测试。该测试包括锁定在不同设计的钛椎弓根螺钉中的镍钛诺棒。还研究了市售钛（Ti6Al4V）和钴铬脊柱棒的性能以作比较。使用扫描电子显微镜（SEM）和能谱分析（EDAX）研究了体外测试后观察到的腐蚀损伤，并与初次手术后12个月取出的镍钛诺棒上的腐蚀模式进行了比较。体外实验后在测试介质中以及在取出棒的患者的血液和组织中测量了金属离子水平。这项研究的结果表明，锁定在钛椎弓根螺钉中的镍钛诺脊柱棒易受微动腐蚀，与商业使用的Ti6Al4V和钴铬棒相比，其微动腐蚀电流更高。在体外测试后的镍钛诺棒表面以及从患者体内取出的镍钛诺棒表面观察到了类似的腐蚀模式。在体外测试中，当使用具有更坚固锁定机制的椎弓根螺钉时，镍钛诺棒的微动腐蚀抗性有所提高。由于局部腐蚀损伤的发展可能会增加棒过早疲劳失效的风险并导致镍离子的浸出，因此得出结论，镍钛诺棒在没有特殊保护的情况下不应与钛椎弓根螺钉一起使用，尤其是在设计为棒提供高度活动性的情况下。
