Department of Orthopaedic Surgery, Kyoto University, Graduate School of Medicine, Japan.
Department of Orthopaedic Surgery, Kyoto University, Graduate School of Medicine, Japan.
J Orthop Sci. 2022 Jul;27(4):810-814. doi: 10.1016/j.jos.2021.04.001. Epub 2021 May 25.
The in vivo kinematic benefit of an asymmetrical polyethylene insert is still unknown in comparison with that of a symmetrical insert with the same femoral component design. The purpose of this study was to analyze the kinematic differences between symmetrical and asymmetrical polyethylene inserts and to detect the kinematic benefit in the asymmetrical polyethylene insert. The hypotheses are that greater axial rotation and more posterior rollback are observed in the asymmetrical polyethylene insert.
The patients were randomly allocated to the following two groups: total knee arthroplasty with a symmetrical insert and with an asymmetrical insert. In vivo knee kinematics was analyzed in asymmetrical (17 knees) and symmetrical (16 knees) inserts using an image matching technique. The symmetrical polyethylene insert had the same geometry on both sides, whereas the asymmetrical polyethylene insert had a flat surface on the postero-lateral side. The anterior/posterior position and axial rotation were compared between the two polyethylene inserts.
The femoral component was significantly positioned posteriorly at 70° (p = 0.016) and 80° (p = 0.040) of knee flexion and externally rotated at 80° of knee flexion (p = 0.040) in the asymmetrical polyethylene insert as compared to the position of the symmetrical polyethylene insert. Femoral rollback and axial rotation from full extension to maximum flexion were greater in the asymmetrical polyethylene insert, although the difference was not significant.
In the asymmetrical polyethylene insert, slight kinematic benefit with greater axial rotation and more posterior rollback was observed in comparison with the symmetrical polyethylene insert. Further research should be required whether the kinematic benefit of an asymmetrical polyethylene insert will lead to better patient satisfaction and function.
与具有相同股骨部件设计的对称型垫块相比，不对称型聚乙烯垫块的体内运动学优势尚不清楚。本研究旨在分析对称型和不对称型聚乙烯垫块之间的运动学差异，并检测不对称型聚乙烯垫块的运动学优势。假设是在不对称型聚乙烯垫块中观察到更大的轴向旋转和更多的后滚回。
将患者随机分配到以下两组：使用对称型垫块和不对称型垫块的全膝关节置换术。使用图像匹配技术分析不对称（17 膝）和对称（16 膝）垫块中的体内膝关节运动学。对称型聚乙烯垫块的两侧具有相同的几何形状，而不对称型聚乙烯垫块的后外侧具有平面。比较了两种聚乙烯垫块的前后位置和轴向旋转。
与对称型垫块相比，在 70°（p=0.016）和 80°（p=0.040）的膝关节屈曲以及 80°的膝关节屈曲时，股骨部件明显位于后部（p=0.040），并且外旋。在不对称型聚乙烯垫块中，从完全伸展到最大屈曲时，股骨的后滚回和轴向旋转更大，尽管差异不显著。
与对称型聚乙烯垫块相比，在不对称型聚乙烯垫块中观察到轻微的运动学优势，即更大的轴向旋转和更多的后滚回。需要进一步研究不对称型聚乙烯垫块的运动学优势是否会导致更好的患者满意度和功能。
