Agne Matthias T, Underwood Richard J, Kocagoz Sevi B, MacDonald Daniel W, Day Judd S, Parvizi Javad, Kraay Matthew J, Mont Michael A, Klein Gregg R, Cates Harold E, Kurtz Steven M
Department of Materials Science and Engineering, Drexel University, Philadelphia, PA, 19104, USA,
Clin Orthop Relat Res. 2015 Jan;473(1):275-85. doi: 10.1007/s11999-014-3982-2. Epub 2014 Oct 16.
Metal wear and corrosion products generated by hip replacements have been linked to adverse local tissue reactions. Recent investigations of the stem/head taper junction have identified this modular interface as another possible source of metal debris; however, little is known regarding other modular metallic interfaces, their ability to produce metal debris, and possibly to provide insight in the mechanisms that produce metal debris.
QUESTIONS/PURPOSES: We asked three questions: (1) can we develop a reliable method to estimate volumetric material loss from the backside taper of modular metal-on-metal liners, (2) do backside tapers of modular metal-on-metal liners show a quantifiable volumetric material loss, and, if so, (3) how do regions of quantitatively identified material loss correspond to visual and microscopic investigations of surface damage?
Twenty-one cobalt-chromium (CoCr) liners of one design and manufacturer were collected through an institutional review board-approved retrieval program. All liners were collected during revision surgeries, where the primary revision reason was loosening (n=11). A roundness machine measured 144 axial profiles equally spaced about the circumference of the taper region near the rim to estimate volume and depth of material loss. Sensitivity and repeatability analyses were performed. Additionally, visual and scanning electron microscopy investigations were done for three liners.
Our measurement method was found to be reproducible. The sensitivity (how dependent measurement results are on experimental parameters) and repeatability (how consistent results are between measurements) analyses confirmed that component alignment had no apparent effect (weak correlation, R2=0.04) on estimated volumetric material loss calculations. Liners were shown to have a quantifiable material loss (maximum=1.7 mm3). Visual investigations of the liner surface could identify pristine surfaces as as-manufactured regions, but could misidentify discoloration as a possible region of material loss. Scanning electron microscopy more accurately distinguished between as-manufactured and damaged regions of the taper.
The roundness machine has been used to develop a repeatable method for characterizing material loss; future work comparing a gravimetric standard with estimations of material loss determined from the roundness machine may show the accuracy and effectiveness of this method. Liners show rates of material loss that compare with those reported for other taper junctions. Visual inspection alone may misidentify as-manufactured regions as regions of material loss.
This study identifies the acetabular liner/shell interface in modular metal-on-metal devices as a potential source of metal wear or corrosion products. The relation between metal debris and clinical performance, regardless of the type of bearing couple, is a concern for clinicians. Therefore, it is important to characterize every type of modular junction to understand the quantity, location, and mechanism(s) of material loss.
髋关节置换产生的金属磨损和腐蚀产物与局部组织不良反应有关。近期对柄/头锥度连接的研究已将这个模块化界面确定为金属碎屑的另一个可能来源；然而，对于其他模块化金属界面、它们产生金属碎屑的能力以及可能为产生金属碎屑的机制提供的见解知之甚少。
问题/目的：我们提出了三个问题：（1）我们能否开发一种可靠的方法来估计模块化金属对金属衬垫背面锥度的体积材料损失？（2）模块化金属对金属衬垫的背面锥度是否显示出可量化的体积材料损失？如果是，（3）定量确定的材料损失区域与表面损伤的视觉和微观检查结果如何对应？
通过一项经机构审查委员会批准的回收计划收集了来自一个设计和制造商的21个钴铬（CoCr）衬垫。所有衬垫均在翻修手术期间收集，其中主要翻修原因是松动（n = 11）。一台圆度仪测量了围绕边缘附近锥度区域圆周等距分布的144个轴向轮廓，以估计材料损失的体积和深度。进行了灵敏度和重复性分析。此外，对三个衬垫进行了视觉和扫描电子显微镜检查。
我们的测量方法被证明是可重复的。灵敏度（测量结果对实验参数的依赖程度）和重复性（测量之间结果的一致性）分析证实，部件对齐对估计的体积材料损失计算没有明显影响（弱相关性，R2 = 0.04）。衬垫显示出可量化的材料损失（最大值 = 1.7立方毫米）。对衬垫表面的视觉检查可以将原始表面识别为制造区域，但可能将变色误识别为可能的材料损失区域。扫描电子显微镜能更准确地区分锥度的制造区域和受损区域。
圆度仪已被用于开发一种表征材料损失的可重复方法；未来将重量标准与通过圆度仪确定的材料损失估计值进行比较的工作可能会显示该方法的准确性和有效性。衬垫显示出的材料损失率与其他锥度连接所报告的损失率相当。仅通过目视检查可能会将制造区域误识别为材料损失区域。
本研究将模块化金属对金属装置中的髋臼衬垫/髋臼杯界面确定为金属磨损或腐蚀产物的潜在来源。无论轴承副的类型如何，金属碎屑与临床性能之间的关系都是临床医生关注的问题。因此，表征每种类型的模块化连接以了解材料损失的数量、位置和机制非常重要。
