Department of Biomechanics, Hospital for Special Surgery, 535 East 70th Street, New York, NY 10021, USA.
Clin Orthop Relat Res. 2011 Jan;469(1):123-30. doi: 10.1007/s11999-010-1557-4.
Mobile-bearing TKAs reportedly have no clinical superiority over fixed-bearing TKAs, but a potential benefit is improved polyethylene wear behavior.
QUESTIONS/PURPOSES: We asked whether extent of damage and wear patterns would be less severe on retrieved mobile-bearing TKAs than on fixed-bearing TKAs and if correlations with patient demographics could explain differences in extent or locations of damage.
We performed damage grading and mapping of 48 mobile-bearing TKAs retrieved due to osteolysis/loosening, infection, stiffness, instability or malpositioning. Visual grading used stereomicroscopy to identify damage, and a grade was assigned based on extent and severity. Each damage mode was then mapped onto a photograph of the implant surface, and the area affected was calculated.
Marked wear damage occurred on both surfaces, with burnishing, scratching, and pitting the dominant modes. Damage occurred over a large portion of both surfaces, exceeding the available articular borders in nearly 30% of implants. Wear of mobile-bearing surfaces included marked third-body debris. Damage on tibiofemoral and mobile-bearing surfaces was not correlated with patient BMI or component alignment. Damage on mobile-bearing surfaces was positively correlated with length of implantation and was greater in implants removed for osteolysis or instability than in those removed for stiffness or infection.
Each bearing surface in mobile-bearing implants was damaged to an extent similar to that in fixed-bearing implants, making the combined damage score higher than that for fixed-bearing implants. Mobile-bearing TKAs did not improve wear damage, providing another argument against the superiority of these implants over fixed-bearing implants.
据报道，活动衬垫 TKA 与固定衬垫 TKA 相比并无临床优势，但可能具有改善聚乙烯磨损行为的潜在益处。
问题/目的：我们想知道在因骨溶解/松动、感染、僵硬、不稳定或位置不当而取出的活动衬垫 TKA 中，其磨损和损坏模式是否比固定衬垫 TKA 更不严重，以及与患者人口统计学特征的相关性是否可以解释损坏程度或位置的差异。
我们对因骨溶解/松动、感染、僵硬、不稳定或位置不当而取出的 48 例活动衬垫 TKA 进行了损伤分级和映射。立体显微镜用于肉眼识别损伤，并根据损伤的程度和严重程度进行分级。然后，将每种损伤模式映射到植入物表面的照片上，并计算受影响的区域。
两个表面都出现了明显的磨损损伤，以抛光、划伤和点蚀为主。损伤几乎覆盖了两个表面的大部分区域，在近 30%的植入物中超过了可用的关节边界。活动衬垫表面的磨损包括明显的第三体碎片。在胫骨股骨和活动衬垫表面的损伤与患者 BMI 或组件对齐度无关。活动衬垫表面的损伤与植入时间的长短呈正相关，且在因骨溶解或不稳定而取出的植入物中比因僵硬或感染而取出的植入物中的磨损更为严重。
活动衬垫植入物的每个衬垫表面的损伤程度与固定衬垫植入物相似，因此总的损伤评分高于固定衬垫植入物。活动衬垫 TKA 并未改善磨损损伤，这为这些植入物优于固定衬垫植入物的说法提供了另一个论据。
