Total knee arthroplasty (TKA) is commonly performed around the world. Implant designs include fixed-bearing and mobile-bearing. Mobile-bearing design was developed as a rotating platform that allows axial rotation of the insert around the longitudinal axis. This phenomenon may limit full exploitation of the characteristics of the mobile-bearing insert, which may cause wearing and reduce longevity. However, there is limited knowledge on rotational behavior of the polyethylene mobile-bearing insert under weight-bearing conditions. We aimed at determining the rotational motion of each component at full extension and flexed positions during a squatting activity after TKA. This study was a cross-sectional study (level 4) involving patients with severe knee osteoarthritis scheduled to receive TKA. We examined 13 knees of 11 patients after mobile-bearing TKA (NexGen LPS-Flex, Zimmer Inc.) at 10 weeks and 1 year postoperatively. Four identical metallic beads were embedded into the insert. Wide-base squatting was chosen for analyses. Three-dimensional in vivo poses of the prostheses were created using a 3D-to-2D registration technique. During flexion, rotation of the femoral component relative to the insert (FEM/INS) and tibial component (FEM/TIB) as well as insert rotation relative to the tibial component (INS/TIB) were computed. Repeated measure 2-way ANOVA and post hoc test was used. In the fully extended position, FEM/INS was significantly smaller than INS/TIB both at 10 weeks (− 0.3° vs. 6.3°, p = .013) and 1 year (− 0.8° vs. 4.9°, p = .011), respectively. During the squatting activity, rotation motions of FEM/TIB, FEM/INS, INS/TIB were 5.7°, 5.9°, and 1.8° at 10 weeks and 6.3°, 5.5°, and 1.6° at 1 year, respectively. Rotation motion of FEM/INS was significantly greater than that of INS/TIB at both 10 weeks (p < .001) and 1 year (p < .001). The mobile-bearing insert enhances the compatibility of FEM/INS in extension; the amount of INS/TIB rotation is significantly smaller than that of FEM/INS during a squatting activity. This information will inform surgeons to take caution to perform TKA with a fixed insert in which 6.3° of rotational offset would be added to the rotational alignment at FEM/INS at full extension. UMIN-CTR, UMIN000024196. Retrospectively registered on 9 September 2016.

中文翻译：

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进行全蹲式活动时，与全膝关节置换术一起使用的活动轴承插入物不会在胫骨托上旋转

全膝关节置换术（TKA）在世界范围内普遍进行。植入物设计包括固定轴承和移动轴承。移动轴承设计被开发为旋转平台，该旋转平台允许刀片围绕纵向轴线轴向旋转。这种现象可能会限制充分利用可动轴承插件的特性，这可能会导致磨损并降低使用寿命。然而，关于聚乙烯可移动轴承插入物在承重条件下的旋转行为的知识有限。我们的目标是确定在TKA后的下蹲活动期间每个组件在完全伸展和弯曲位置的旋转运动。这项研究是一项横断面研究（4级），涉及计划接受TKA的重度膝骨关节炎患者。我们在术后10周和1年时检查了11例活动性TKA（NexGen LPS-Flex，Zimmer Inc.）患者的13个膝盖。将四个相同的金属珠嵌入插入物中。选择宽底蹲式进行分析。使用3D到2D配准技术创建了假体的三维体内姿势。在屈曲过程中，计算了股骨相对于插入物（FEM / INS）和胫骨组件（FEM / TIB）的旋转以及插入物相对于胫骨组件的旋转（INS / TIB）。使用重复测量的2-方差分析和事后检验。在完全伸展的位置，FEM / INS在10周（-0.3°vs. 6.3°，p = .013）和1年（-0.8°vs. 4.9°，p = .011）时均显着小于INS / TIB。 ）， 分别。在下蹲过程中，FEM / TIB，FEM / INS，INS / TIB在10周时分别为5.7°，5.9°和1.8°，在1年时分别为6.3°，5.5°和1.6°。在10周（p <.001）和1年（p <.001）时，FEM / INS的旋转运动明显大于INS / TIB。可移动轴承的插件增强了FEM / INS在扩展方面的兼容性；在下蹲过程中，INS / TIB旋转量明显小于FEM / INS。该信息将通知外科医生注意使用固定刀片进行TKA，其中在完全伸展时，将在FEM / INS上将6.3°的旋转偏移量添加到旋转对准中。UMIN-CTR，UMIN000024196。追溯登记于2016年9月9日。在10周（p <.001）和1年（p <.001）时，FEM / INS的旋转运动明显大于INS / TIB。可移动轴承的插件增强了FEM / INS在扩展方面的兼容性；在下蹲过程中，INS / TIB旋转量明显小于FEM / INS。该信息将通知外科医生注意使用固定刀片进行TKA，其中在完全伸展时，将在FEM / INS上将6.3°旋转偏移添加到旋转对准中。UMIN-CTR，UMIN000024196。追溯登记于2016年9月9日。在10周（p <.001）和1年（p <.001）时，FEM / INS的旋转运动均明显大于INS / TIB。可移动轴承的插件增强了FEM / INS在扩展方面的兼容性；在下蹲过程中，INS / TIB旋转量明显小于FEM / INS。该信息将通知外科医生注意使用固定刀片进行TKA，其中在完全伸展时，将在FEM / INS上将6.3°旋转偏移添加到旋转对准中。UMIN-CTR，UMIN000024196。追溯登记于2016年9月9日。该信息将通知外科医生注意使用固定刀片进行TKA，其中在完全伸展时，将在FEM / INS上将6.3°旋转偏移添加到旋转对准中。UMIN-CTR，UMIN000024196。追溯登记于2016年9月9日。该信息将通知外科医生注意使用固定刀片进行TKA，其中在完全伸展时，FEM / INS上的旋转对准将增加6.3°的旋转偏移量。UMIN-CTR，UMIN000024196。追溯登记于2016年9月9日。