Julius Wolff Institute and Center for Musculoskeletal Surgery, Charité - Universitätsmedizin Berlin, Center for Sports Science and Sports Medicine Berlin, Philippstr. 13, Haus 11, 10115 Berlin, Germany.
Med Eng Phys. 2011 Dec;33(10):1303-8. doi: 10.1016/j.medengphy.2011.06.008. Epub 2011 Jul 20.
Midflexion instability (MFI) after TKA is a phenomenon often described as varus-valgus instability between 30° and 45° knee flexion. The exact mechanisms causing MFI remain unclear, but elevation of the joint line (JLE) may be one possible cause. In an in silico approach using 4 subject specific musculoskeletal models, the length change patterns of the collateral ligaments during knee flexion (relative to the extended knee) were calculated for the anatomically reconstructed joints as well as for JLEs of 5 and 10mm. Analysis of the distance between the ligaments' attachment sites (DA) in midflexion revealed a relative decrease in DA magnitude after JLE for both collateral ligaments in comparison to the anatomically reconstructed knee. This finding suggests that JLE could contribute to MFI. However, the anterior ligament regions also experienced a DA increase (MCL) or only a slight DA decrease (LCL) for each JLE simulated. From this perspective, the anterior ligament portions are unlikely to slacken in midflexion and JLE is unlikely to contribute greatly to MFI. In conclusion, our findings did not support the idea that JLE is a major contributor to midflexion instability for this particular ultra-congruent implant design.
全膝关节置换术后的中屈不稳定（MFI）是一种常描述为在膝关节 30°至 45°屈曲时出现的内翻-外翻不稳定现象。导致 MFI的确切机制仍不清楚，但关节线抬高（JLE）可能是一个可能的原因。在使用 4 个特定于个体的肌肉骨骼模型的仿真方法中，计算了在解剖重建关节以及 JLE 为 5mm 和 10mm 时，在膝关节屈曲过程中（相对于伸展的膝关节）副韧带的长度变化模式。在中屈时分析韧带附着点（DA）之间的距离，发现与解剖重建膝关节相比，JLE 后两个副韧带的 DA 幅度都相对减小。这一发现表明 JLE 可能导致 MFI。然而，对于每个模拟的 JLE，前韧带区域也经历了 DA 的增加（MCL）或仅略有 DA 减少（LCL）。从这个角度来看，前韧带部分在中屈时不太可能松弛，JLE 不太可能对 MFI 有很大贡献。总之，我们的研究结果不支持 JLE 是这种特定的超吻合植入物设计中导致中屈不稳定的主要因素的观点。
