Adult Reconstruction and Joint Replacement, Hospital for Special Surgery, New York, New York, USA.
Department of Biomechanics, Hospital for Special Surgery, New York, New York, USA.
Bone Joint J. 2020 Jul;102-B(7_Supple_B):20-26. doi: 10.1302/0301-620X.102B7.BJJ-2019-1633.R1.
This combined clinical and in vitro study aimed to determine the incidence of liner malseating in modular dual mobility (MDM) constructs in primary total hip arthroplasties (THAs) from a large volume arthroplasty centre, and determine whether malseating increases the potential for fretting and corrosion at the modular metal interface in malseated MDM constructs using a simulated corrosion chamber.
For the clinical arm of the study, observers independently reviewed postoperative radiographs of 551 primary THAs using MDM constructs from a single manufacturer over a three-year period, to identify the incidence of MDM liner-shell malseating. Multivariable logistic regression analysis was performed to identify risk factors including age, sex, body mass index (BMI), cup design, cup size, and the MDM case volume of the surgeon. For the in vitro arm, six pristine MDM implants with cobalt-chrome liners were tested in a simulated corrosion chamber. Three were well-seated and three were malseated with 6° of canting. The liner-shell couples underwent cyclic loading of increasing magnitudes. Fretting current was measured throughout testing and the onset of fretting load was determined by analyzing the increase in average current.
The radiological review identified that 32 of 551 MDM liners (5.8%) were malseated. Malseating was noted in all of the three different cup designs. The incidence of malseating was significantly higher in low-volume MDM surgeons than high-volume MDM surgeons (p < 0.001). Pristine well-seated liners showed significantly lower fretting current values at all peak loads greater than 800 N (p < 0.044). Malseated liner-shell couples had lower fretting onset loads at 2,400 N.
MDM malseating remains an issue that can occur in at least one in 20 patients at a high-volume arthroplasty centre. The onset of fretting and increased fretting current throughout loading cycles suggests susceptibility to corrosion when this occurs. These results support the hypothesis that malseated liners may be at risk for fretting corrosion. Clinicians should be aware of this phenomenon. Cite this article: 2020;102-B(7 Supple B):20-26.
本项临床与体外联合研究旨在从大型关节置换中心确定在初次全髋关节置换术（THA）中使用模块化双动（MDM）假体时，衬垫错位的发生率，并使用模拟腐蚀室确定在错位 MDM 假体中，错位是否增加了在模块化金属界面处发生微动腐蚀的可能性。
在研究的临床部分中，观察者独立地对来自同一家制造商的 551 例初次使用 MDM 假体的 THA 术后 X 线片进行了检查，以确定 MDM 衬垫-壳错位的发生率。采用多变量逻辑回归分析来确定危险因素，包括年龄、性别、体重指数（BMI）、杯设计、杯尺寸以及术者的 MDM 病例量。在体外部分，在模拟腐蚀室中对 6 个原始的 MDM 植入物进行了钴铬衬垫测试。其中 3 个是正确就位的，3 个是有 6°倾斜的错位。对衬垫-壳组件进行了递增幅度的循环加载。在整个测试过程中测量微动电流，通过分析平均电流的增加来确定微动负载的开始。
放射学检查发现，551 个 MDM 衬垫中有 32 个（5.8%）错位。所有三种不同的杯设计都有错位。低容量 MDM 医生中 MDM 错位的发生率明显高于高容量 MDM 医生（p<0.001）。原始正确就位的衬垫在所有大于 800N 的峰值负载下表现出显著较低的微动电流值（p<0.044）。错位衬垫-壳组件在 2400N 时具有较低的微动起始负载。
MDM 错位仍然是在高容量关节置换中心至少每 20 名患者中就会发生的一个问题。在发生这种情况时，在整个加载循环中微动的开始和增加的微动电流表明易发生腐蚀。这些结果支持这样的假设，即错位衬垫可能存在微动腐蚀的风险。临床医生应该意识到这种现象。引用本文：2020；102-B（7 增刊 B）：20-26。
