Huang Chang-Hung, Lu Yung-Chang, Hsu Lin-I, Liau Jiann-Jong, Chang Ting-Kuo, Huang Chun-Hsiung
Department of Medical Research, MacKay Memorial Hospital, Taipei, Taiwan.
School of Dentistry, National Yang-Ming University, Taipei, Taiwan.
Bone Joint Res. 2020 Nov;9(11):768-777. doi: 10.1302/2046-3758.911.BJR-2020-0019.R2.
The material and design of knee components can have a considerable effect on the contact characteristics of the tibial post. This study aimed to analyze the stress distribution on the tibial post when using different grades of polyethylene for the tibial inserts. In addition, the contact properties of fixed-bearing and mobile-bearing inserts were evaluated.
Three different grades of polyethylene were compared in this study; conventional ultra high molecular weight polyethylene (UHMWPE), highly cross-linked polyethylene (HXLPE), and vitamin E-stabilized polyethylene (VEPE). In addition, tibial baseplates with a fixed-bearing and a mobile-bearing insert were evaluated to understand differences in the contact properties. The inserts were implanted in neutral alignment and with a 10° internal malrotation. The contact stress, von Mises stress, and equivalent plastic strain (PEEQ) on the tibial posts were extracted for comparison.
The stress and strain on the tibial post for the three polyethylenes greatly increased when the insert was placed in malrotation, showing a 38% to 56% increase in von Mises stress and a 335% to 434% increase in PEEQ. The VEPE insert had the lowest PEEQ among the three materials. The mobile-bearing design exhibited a lower increase in stress and strain around the tibial posts than the fixed-bearing design.
Using VEPE for the tibial component potentially eliminates the risk of material permanent deformation. The mobile-bearing insert can help to avoid a dramatic increase in plastic strain around the tibial post in cases of malrotation. The mobility allows the pressure to be distributed on the tibial post and demonstrated lower stresses with all three polyethylenes simulated. Cite this article: 2020;9(11):768-777.
膝关节组件的材料和设计会对胫骨假体的接触特性产生重大影响。本研究旨在分析使用不同等级聚乙烯制作胫骨衬垫时胫骨假体上的应力分布。此外，还评估了固定平台和活动平台衬垫的接触特性。
本研究比较了三种不同等级的聚乙烯；传统超高分子量聚乙烯（UHMWPE）、高交联聚乙烯（HXLPE）和维生素E稳定聚乙烯（VEPE）。此外，对带有固定平台和活动平台衬垫的胫骨基板进行了评估，以了解接触特性的差异。衬垫以中立位对线并伴有10°内旋植入。提取胫骨假体上的接触应力、von Mises应力和等效塑性应变（PEEQ）进行比较。
当衬垫处于内旋位时，三种聚乙烯胫骨假体上的应力和应变大幅增加，von Mises应力增加38%至56%，PEEQ增加335%至434%。VEPE衬垫在三种材料中PEEQ最低。活动平台设计在胫骨假体周围的应力和应变增加幅度低于固定平台设计。
胫骨组件使用VEPE可能消除材料永久变形的风险。活动平台衬垫有助于避免在发生内旋时胫骨假体周围塑性应变急剧增加。这种活动特性使压力能够分布在胫骨假体上，并且在模拟的所有三种聚乙烯材料中均显示出较低的应力。引用本文：2020；9(11):768 - 777。
