Kantonsspital Liestal, Orthopaedic Department, Rheinstrasse 26, 4410 Liestal, Switzerland.
J Orthop Surg Res. 2008 Feb 22;3:8. doi: 10.1186/1749-799X-3-8.
Polyethylene wear is an important factor for longevity of total knee arthroplasty. Proven and suspicious factors causing wear can be grouped as material, patient and surgery related. There are more studies correlating design and/or biomaterial factors to in vivo wear than those to patient and surgery related factors. Many retrieval studies just include revision implants and therefore may not be representative. This study is aimed to correlate patient- and surgery- related factors to visual wear score by minimizing design influence and include both autopsy and revision implants. Comparison between the groups was expected to unmask patient and surgery-related factors responsible for wear.
The amount of joint side wear on polyethylene retrievals was measured using a modification of an established visual wear score. Fatigue type wear was defined as summation of the most severe wear modes of delamination, pitting and cracks. Analysis of patient and surgery related variables suspicious to cause wear included prospectively sampled patient activity which was measured by self reported walking capacity. Statistical analysis was done by univariate analysis of variance. Activity level and implantation time were merged to an index of use and correlated to the wear score.
Wear score after comparable implantation time was significantly less in the autopsy group. Even so, fatigue type wear accounted for 84 and 93 % of total wear score on autopsy and revision implants respectively. A highly significant influence on wear score was found in time of implantation (p = 0.002), level of activity (p = 0.025) and inserts belonging to revision group (p = 0.006). No influence was found for the kind of patella replacement (p = 0.483). Body mass index and accuracy of component alignment had no significant influence on visual wear score. Fatigue-type wear in the medial compartment was closely correlated to the index of use in the autopsy (R(2) = 0.383) and the revision group (R(2) = 0.813).
The present study's finding of substantial fatigue type wear in both autopsy and revision retrievals supports the theory that polyethylene fatigue strength is generally exceeded in this type of prosthesis. Furthermore, this study correlated fatigue-type polyethylene wear to an index of use as calculated by activity over time. Future retrieval studies may use activity over time as an important patient related factor correlated to the visual wear score. When evaluating total knee arthroplasty routine follow up, the surgeon must think of substantial wear present even without major clinical signs.
聚乙烯磨损是全膝关节置换术长期使用的一个重要因素。已证实和可疑的导致磨损的因素可分为材料、患者和手术相关因素。有更多的研究将设计和/或生物材料因素与体内磨损相关联，而不是与患者和手术相关因素相关联。许多检索研究仅包括翻修植入物，因此可能不具有代表性。本研究旨在通过最小化设计影响并包括尸检和翻修植入物，将患者和手术相关因素与视觉磨损评分相关联。预计组间比较将揭示导致磨损的与患者和手术相关的因素。
使用改良的既定视觉磨损评分测量聚乙烯取出物的关节侧磨损量。疲劳型磨损定义为分层、麻点和裂纹最严重磨损模式的总和。对可疑导致磨损的患者和手术相关变量进行分析，包括前瞻性采样的患者活动，通过自我报告的步行能力进行测量。通过单变量方差分析进行统计分析。活动水平和植入时间合并为使用指数，并与磨损评分相关联。
在可比植入时间后，尸检组的磨损评分明显较低。即便如此，疲劳型磨损分别占尸检和翻修植入物总磨损评分的 84%和 93%。植入时间（p=0.002）、活动水平（p=0.025）和属于翻修组的植入物（p=0.006）对磨损评分有高度显著的影响。髌骨置换的类型（p=0.483）没有影响。体重指数和组件对准精度对视觉磨损评分没有显著影响。内侧室的疲劳型磨损与尸检（R²=0.383）和翻修组（R²=0.813）的使用指数密切相关。
本研究发现尸检和翻修取出物中存在大量疲劳型磨损，支持聚乙烯疲劳强度通常在这种类型的假体中被超过的理论。此外，本研究将疲劳型聚乙烯磨损与通过随时间的活动计算得出的使用指数相关联。未来的检索研究可以将随时间的活动作为与视觉磨损评分相关联的重要患者相关因素。在评估全膝关节置换术的常规随访时，即使没有明显的临床迹象，外科医生也必须考虑到大量的磨损。
