模块化全膝关节置换术中上方贴合度增加会导致后方磨损增加吗？
Does increased topside conformity in modular total knee arthroplasty lead to increased backside wear?
作者信息
Schwarzkopf Ran, Scott Richard D, Carlson Evan M, Currier John H
机构信息
Orthopaedic Surgery, University of California Irvine Medical Center, 101 The City Drive South, Pavilion III, Building 29, Orange, CA, 92868, USA,
出版信息
Clin Orthop Relat Res. 2015 Jan;473(1):220-5. doi: 10.1007/s11999-014-3648-0.
BACKGROUND
Modular metal-backed tibia components allow surgeons intraoperative flexibility. Although it is known that modular tibia components introduce the possibility for backside wear resulting from relative motion between the polyethylene insert and the tibial baseplate, it is not known to what degree variability in the conformity of the tibial polyethylene liner itself might contribute to backside wear.
QUESTIONS/PURPOSES: The purpose of this study was to determine whether a flat, cruciate-retaining tibial polyethylene bearing generates less backside wear than a more conforming (curved) tibial polyethylene bearing in an analysis of specimens explanted during revision surgery.
METHODS
The study included 70 total knee inserts explanted at revision surgery, all implanted and explanted by the same surgeon. Two different cruciate-retaining insert options in an otherwise similar knee system were used: one with a curved-on-flat (17) articular geometry and one with a highly conforming curved-on-curved design (53); both groups were sequential cohorts. The composite backside wear depth for the insert as well as the volume of backside wear was measured and compared between groups.
RESULTS
The median linear backside-normalized wear for the posterior lipped inserts was 0.0063 mm/year (range, 0-0.085 mm/year), which was lower than for the curved inserts at 0.05 mm/year (range, 0.00003-0.14 mm/year) (p<0.001). The median calculated volumetric backside-normalized wear for the posterior lipped inserts was 14.2 mm3/year (range, 0-282.8 mm3/year) compared with 117 mm3/year (range, 2.1-312 mm3/year) for the curved inserts (p<0.001).
CONCLUSIONS
In this retrieval study, more conforming tibial inserts demonstrated more backside-normalized wear than the flatter designs. This suggests that in this modular total knee arthroplasty design, higher articular conformity to address the issues of high bearing contact stress comes at a price: increased torque transmitted to the backside insert-to-tray interface. We suggest further work be undertaken to examine newer insert designs to evaluate if our conclusions hold true with the newer generation locking mechanism, tibial tray finish and polyethylene designs, as more highly conforming tibial inserts are introduced into the market.
LEVEL OF EVIDENCE
Level III, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.
背景
模块化金属背衬胫骨组件使外科医生在手术中有更大的灵活性。虽然已知模块化胫骨组件会因聚乙烯衬垫与胫骨基板之间的相对运动而导致背面磨损，但尚不清楚胫骨聚乙烯衬垫本身贴合度的变化在多大程度上会导致背面磨损。
问题/目的：本研究的目的是在分析翻修手术中取出的标本时，确定平坦的、保留交叉韧带的胫骨聚乙烯承重部件是否比贴合度更高（弯曲）的胫骨聚乙烯承重部件产生的背面磨损更少。
方法
该研究纳入了70个在翻修手术中取出的全膝关节衬垫，所有植入和取出操作均由同一位外科医生完成。在其他方面相似的膝关节系统中使用了两种不同的保留交叉韧带的衬垫选项：一种是平面上弯曲（17个）的关节几何形状，另一种是高度贴合的曲面弯曲设计（53个）；两组均为连续队列。测量并比较了两组衬垫的复合背面磨损深度以及背面磨损体积。
结果
后唇衬垫的背面归一化线性磨损中位数为0.0063毫米/年（范围为0 - 0.085毫米/年），低于弯曲衬垫的0.05毫米/年（范围为0.00003 - 0.14毫米/年）（p<0.001）。后唇衬垫的计算得出的背面归一化体积磨损中位数为14.2立方毫米/年（范围为0 - 282.8立方毫米/年），而弯曲衬垫为117立方毫米/年（范围为2.1 - 312立方毫米/年）（p<0.001）。
结论
在这项取出研究中，贴合度更高的胫骨衬垫比更平坦的设计显示出更多的背面归一化磨损。这表明在这种模块化全膝关节置换设计中，为解决高承重接触应力问题而采用的更高关节贴合度是有代价的：传递到背面衬垫与托盘界面的扭矩增加。我们建议进一步开展工作，研究更新的衬垫设计，以评估随着市场上引入贴合度更高的胫骨衬垫，我们的结论是否适用于新一代锁定机制、胫骨托盘表面处理和聚乙烯设计。
证据水平
III级，治疗性研究。有关证据水平的完整描述，请参阅作者指南。
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