Department of Musculoskeletal Surgery, Imperial College (Charing Cross Hospital Campus), Fulham Palace Road, London, UK.
J Bone Joint Surg Am. 2013 Apr 17;95(8):678-85. doi: 10.2106/JBJS.J.01447.
Determining the relationship between clinical factors and engineering analysis of retrieved hip implants can help our understanding of the mechanism of device failure. This is particularly important for metal-on-metal hip arthroplasties because the most common cause of failure is unexplained. We sought to understand the variation in wear rates in a large series of retrieved metal-on-metal hip arthroplasty components.
We prospectively recorded preoperative, intraoperative, and postoperative data to study the effect on both head and cup wear rates of the following variables: patient sex, cause of failure, manufacturer type, resurfacing or modular design, blood cobalt and chromium levels, edge-loading, femoral head size, and cup inclination angle. We analyzed 276 components (138 femoral head and acetabular cup couples) retrieved from failed metal-on-metal hip replacements.
We found a high rate of edge-loading (64%), but only forty-three (31%) of 138 hips had a cup inclination angle of >55°. Multivariate analysis showed that the most important factor responsible for the variation in wear rate was the presence or absence of edge-loading, even when adjusted for cup inclination angle. Strong positive correlations were found between acetabular cup and femoral head wear rates and between wear rates and both blood cobalt and chromium ion levels.
Multivariate analysis of nine factors found that edge-loading was the most important predictor of wear rate and occurred in two-thirds of failed metal-on-metal hip replacements. The majority did not have excessive cup inclination angles: 68% had an inclination angle of ≤55°. This finding, together with the relatively low median wear rate of the components in our study, suggests that cup position and/or wear rate may not be the only outcome related to failure of metal-on-metal hip replacements.
确定临床因素与回收髋关节植入物工程分析之间的关系有助于我们了解器械失效的机制。这对于金属对金属髋关节置换术尤为重要，因为最常见的失效原因是无法解释的。我们试图了解大量回收金属对金属髋关节置换组件的磨损率变化。
我们前瞻性地记录术前、术中、术后数据，以研究以下变量对头部和杯磨损率的影响：患者性别、失效原因、制造商类型、表面置换或模块化设计、血液钴和铬水平、边缘负荷、股骨头大小和杯倾斜角度。我们分析了 276 个组件（138 个股骨头部和髋臼杯对），这些组件来自失效的金属对金属髋关节置换。
我们发现边缘负荷率很高（64%），但只有 43 个（31%）髋关节的杯倾斜角度大于 55°。多变量分析表明，导致磨损率变化的最重要因素是边缘负荷的存在与否，即使调整了杯倾斜角度也是如此。发现髋臼杯和股骨头磨损率之间以及磨损率与血液钴和铬离子水平之间存在强烈的正相关关系。
对九个因素进行多变量分析发现，边缘负荷是磨损率的最重要预测因素，发生在三分之二的失败的金属对金属髋关节置换中。大多数没有过度的杯倾斜角度：68%的倾斜角度≤55°。这一发现，以及我们研究中组件的相对较低的中位磨损率，表明杯的位置和/或磨损率可能不是金属对金属髋关节置换失败的唯一相关结果。
