Rao Anand R, Engh Gerard A, Collier Matthew B, Lounici Smain
Anderson Orthopaedic Research Institute, Alexandria, Virginia 22307, USA.
J Bone Joint Surg Am. 2002 Oct;84(10):1849-55. doi: 10.2106/00004623-200210000-00017.
Wear occurring at the interface between the polyethylene insert and metal baseplate of a modular tibial component has become an increasingly common finding at the time of revision total knee arthroplasty. Although this so-called backside wear on retrieved polyethylene inserts has been evaluated in prior studies, wear on retrieved metal baseplates has not been described, to our knowledge. The purposes of the present study were to characterize backside wear on retrieved polyethylene inserts and on the mating surfaces of their corresponding baseplates and to investigate if there is a relationship between backside wear and relative motion of the modular elements.
Twenty-nine retrieved modular tibial components of twelve fixed-bearing designs were analyzed in vitro with regard to backside wear and relative motion between the polyethylene insert and the metal baseplate. We graded the backside of each polyethylene insert and the mating surface of the metal baseplate for wear with use of a scoring system that consisted of three modes of wear and three levels of severity of wear. Relative motion between the insert and the baseplate was measured in the transverse plane with use of a mechanical testing machine. These measurements were used to compute the insert motion index, which served to quantify unrestricted motion of the insert with respect to the baseplate.
The mean insert motion index for the tibial components was 416 micro m (range, 104 micro m to 760 micro m). On a wear-grading scale ranging from 0 to 54 (with 0 indicating no wear), the mean backside wear score was 30 (range, 12 to 48) for the inserts and 28 (range, 7 to 51) for the baseplates. Insert motion was positively correlated with backside polyethylene wear (p = 0.003) and baseplate wear (p < 0.001). Baseplate wear was strongly correlated with backside polyethylene wear (p < 0.001).
Backside wear was correlated with the relative motion between the polyethylene insert and the metal baseplate. New locking mechanism designs directed toward better methods of securing the polyethylene insert to the tibial tray are needed to minimize the generation of particulate wear debris at the modular interface.
在翻修全膝关节置换术中，模块化胫骨部件的聚乙烯衬垫与金属基板之间的界面处出现磨损已成为越来越常见的现象。据我们所知，尽管先前的研究已对取出的聚乙烯衬垫上的这种所谓背面磨损进行了评估，但尚未对取出的金属基板上的磨损进行描述。本研究的目的是描述取出的聚乙烯衬垫及其相应基板配合表面上的背面磨损情况，并研究背面磨损与模块化部件相对运动之间是否存在关系。
对29个取出的12种固定平台设计的模块化胫骨部件进行体外分析，以研究聚乙烯衬垫与金属基板之间的背面磨损和相对运动。我们使用一种评分系统对每个聚乙烯衬垫的背面和金属基板的配合表面的磨损进行分级，该评分系统包括三种磨损模式和三个磨损严重程度级别。使用机械测试机在横向平面上测量衬垫与基板之间的相对运动。这些测量结果用于计算衬垫运动指数，该指数用于量化衬垫相对于基板的无限制运动。
胫骨部件的平均衬垫运动指数为416微米（范围为104微米至760微米）。在0至54的磨损分级量表上（0表示无磨损），衬垫的平均背面磨损评分为30（范围为12至48），基板的平均背面磨损评分为28（范围为7至51）。衬垫运动与聚乙烯背面磨损呈正相关（p = 0.003），与基板磨损呈正相关（p < 0.001）。基板磨损与聚乙烯背面磨损密切相关（p < 0.001）。
背面磨损与聚乙烯衬垫和金属基板之间的相对运动相关。需要设计新的锁定机制，以更好地将聚乙烯衬垫固定到胫骨托上，从而尽量减少模块化界面处颗粒磨损碎屑的产生。
