Smith Stephanie M, Gilbert Jeremy L
Clemson-MUSC Bioengineering Program, Department of Bioengineering, Clemson University and the Medical University of South Carolina, Charleston, South Carolina, USA.
J Biomed Mater Res A. 2022 Feb;110(2):409-423. doi: 10.1002/jbm.a.37299. Epub 2021 Aug 17.
Fretting corrosion in modular orthopedic implants is a well-documented process that may be associated with adverse local tissue reactions, pain, and revisions. Engineering modular junction interfaces to withstand applied fretting motion without surface abrasion could prevent implant degradation and surface damage. Previous work on geometrically modified Ti-6Al-4V/CoCrMo interfaces with increased compliance showed reduced fretting currents and surface damage during short term, variable-load in vitro testing. This study assesses the same interfaces under long-term conditions using an in vitro pin-on-disk fretting corrosion test apparatus. Preliminary variable-load frequency testing of typical control pin geometries showed a frequency-dependent current response, with underlying contact conditions of metal-metal interfaces that remained unchanged. One-million-cycle testing showed diminished fretting currents in all groups by 5 × 10 cycles, but consistently lower currents in the high-compliance group. Corresponding fretting currents and work of fretting measurements of high-compliance pins confirmed that minimal fretting was experienced at the interface, with elastic bending of the pin accounting for almost all applied displacement. Debris generated during testing were composed of titanium and chromium oxides, small amounts of cobalt and molybdenum oxides, and sodium and phosphate originating from the surrounding test solution. Post-test analyses of sample surfaces revealed substantially more surface damage on CoCrMo disks than Ti-6Al-4V pins, thought to be a result of adhesive wear of mixed oxide debris on the pin and abrasion of the disk by the oxide debris layer. Surface damage to high-compliance pins suggests some abrasion is unavoidable with geometric modifications.
模块化骨科植入物中的微动腐蚀是一个有充分文献记载的过程，可能与局部组织不良反应、疼痛和翻修有关。设计模块化连接界面以承受施加的微动而不产生表面磨损，可以防止植入物降解和表面损伤。先前对具有更高顺应性的几何形状改性的Ti-6Al-4V/CoCrMo界面的研究表明，在短期、可变负载的体外测试中，微动电流和表面损伤有所减少。本研究使用体外销盘式微动腐蚀试验装置在长期条件下评估相同的界面。对典型对照销几何形状的初步可变负载频率测试显示出频率依赖性电流响应，金属-金属界面的潜在接触条件保持不变。一百万次循环测试表明，所有组的微动电流在5×10 次循环时都有所减小，但高顺应性组的电流始终较低。对高顺应性销的相应微动电流和微动功测量证实，界面处经历的微动最小，销的弹性弯曲几乎占了所有施加的位移。测试过程中产生的碎屑由钛和铬的氧化物、少量钴和钼的氧化物以及来自周围测试溶液的钠和磷酸盐组成。样品表面的测试后分析显示，CoCrMo盘上的表面损伤比Ti-6Al-4V销上的严重得多，这被认为是销上混合氧化物碎屑的粘着磨损以及氧化物碎屑层对盘的磨损的结果。高顺应性销的表面损伤表明，几何形状的改变不可避免地会导致一些磨损。
