Background

Total Knee Replacement surgery restores joint function in patients with advanced osteoarthritis. There are several prostheses available based on different mechanisms, which guarantee knee stability during Activities of Daily Living. The aim of this study is to compare ball-in-socket (or Medial Pivot) and post-cam mechanisms to detect possible differences in terms of biomechanical parameters between these two prosthesis designs and to evaluate which design is closer to physiological biomechanics.

Methods

A kinematics, kinetics and electromyography lower limb analyses were performed during gait on sixty subjects: twenty with Medial Pivot prosthesis, twenty with posterior stabilized prosthesis and twenty healthy subjects to obtain a physiologic reference.

Findings

Total Knee Replacement gait pattern for both patient groups were characterized by reduced walking speed, reduced stride length and increased stance time respect to control group. Comparison between Medial Pivot and Posterior Stabilized groups showed a reduction of knee flexion and flexor moment in patients with ball-in-socket mechanism. A prolonged muscular activity of rectus femoris was observed in Medial Pivot patients compared to Posterior Stabilized and control groups.

Interpretation

“Stiff knee pattern” mechanism was showed for both patient groups but more enhanced in Medial Pivot patients. Even though the Posterior Stabilized design introduces the non-physiological paradoxical motion and the Medial Pivot design seems to better reproduce the physiological condylar movement as gait analysis parameters, including kinematics, kinetics and electromyographic parameters were closer to control group and, in turn, to physiological gait for the Posterior Stabilized than Medial Pivot group parameters.

中文翻译：

---

步态期间全膝关节置换患者的生物力学分析：内侧枢纽还是后稳定设计？

背景

全膝关节置换术可恢复晚期骨关节炎患者的关节功能。有几种基于不同机制的假体，可在日常生活活动中保证膝盖的稳定性。这项研究的目的是比较球窝（或内侧枢轴）和后置凸轮机制，以检测这两种假体设计之间在生物力学参数方面的可能差异，并评估哪种设计更接近生理生物力学。

方法

在步态中对60名受试者进行了运动学，动力学和肌电图下肢分析：其中20名具有内侧枢轴假体，20名具有后稳定假体和20名健康受试者，以获得生理参考。

发现

两组患者的总膝关节置换步态模式的特点是步行速度降低，步幅缩短以及相对于对照组的站立时间增加。内侧枢轴组和后稳定组之间的比较显示，在采用球窝入路机制的患者中，膝关节屈曲和屈肌力矩减少了。与后稳定组和对照组相比，内侧枢纽患者观察到股直肌的肌肉活动延长。

解释

两种患者组均显示出“僵硬膝部模式”机制，但内侧枢轴患者中这种机制得到了增强。尽管“后稳定”设计引入了非生理矛盾运动，并且“内枢轴”设计似乎可以更好地重现生理con突运动，因为步态分析参数（包括运动学，动力学和肌电图参数）更接近于对照组，进而更接近于生理后稳定的步态比内侧枢纽组参数更合适。