Toderita Diana, Favier Clement D, Milandri Giovanni S, Vardakastani Vasiliki, Henson David P, Bull Anthony Mj
Department of Bioengineering, Imperial College London, London, UK.
Prosthet Orthot Int. 2025 Oct 1;49(5):508-514. doi: 10.1097/PXR.0000000000000448. Epub 2025 Apr 9.
Passive prosthetic knees incorporate extension assist mechanisms to enhance the swing phase of the gait cycle for persons with above/through-knee amputations. In conventional polycentric knees using a 4-bar linkage, the extension assist mechanism connects one of the bars to the body of the prosthesis. However, this design introduces a singularity in the spring action delivery, causing the spring to push the knee into flexion beyond a certain angle. In contrast, polycentric prosthetic knees with an extension assist mechanism that links the upper and lower parts of the knee eliminate the singularity feature, ensuring that the knee is pushed toward extension throughout the full range of motion.
This study aims to investigate the effects of different spring extension assist mechanisms in polycentric knees on the walking capacity of unilateral above/through-knee amputees.
Repeated measures.
Gait data were collected at self-selected and fast speeds from 8 unilateral above/through-knee traumatic amputees using a 10-camera motion capture system. Participants trialed 2 different polycentric prosthetic knees with and without the singularity feature, both coupled with a solid-ankle-cushioned-heel prosthetic foot. They underwent gait analysis with both prosthetic knees, and a comparison analysis was conducted to examine the trial conditions.
The symmetry between the prosthetic and intact knee flexion angles was higher for the design without singularity by 5.2% ( p = 0.025) at self-selected speeds and by 7.7% ( p = 0.003) at fast speeds. Also, peak prosthetic knee flexion angles were lower for the design without singularity by 9.4° ( p < 0.001) at self-selected speeds and by 9.6° ( p = 0.012) at fast speeds.
The extension assist mechanism without singularity improved the symmetry between the intact and prosthetic knee flexion angles by preventing excessive prosthetic knee flexion in the swing phase of the gait cycle.
被动式假肢膝关节采用伸展辅助机制，以增强膝上/膝离断者步态周期的摆动期。在使用四连杆机构的传统多中心膝关节中，伸展辅助机制将其中一根连杆连接到假肢主体。然而，这种设计在弹簧作用传递中引入了一个奇点，导致弹簧在超过一定角度时将膝关节推向屈曲。相比之下，具有连接膝关节上下部分的伸展辅助机制的多中心假肢膝关节消除了奇点特征，确保膝关节在整个运动范围内都被推向伸展。
本研究旨在探讨多中心膝关节中不同弹簧伸展辅助机制对单侧膝上/膝离断截肢者步行能力的影响。
重复测量。
使用10台摄像机的运动捕捉系统，以自选速度和快速速度收集了8名单侧膝上/膝离断创伤截肢者的步态数据。参与者试用了2种不同的多中心假肢膝关节，一种有无奇点特征，两种均与实心踝垫跟假肢脚配合使用。他们对两种假肢膝关节都进行了步态分析，并进行了比较分析以检查试验条件。
在自选速度下，无奇点设计的假肢与健全膝关节屈曲角度之间的对称性比有奇点设计高5.2%（p = 0.025），在快速速度下高7.7%（p = 0.003）。此外，无奇点设计的假肢膝关节峰值屈曲角度在自选速度下比有奇点设计低9.4°（p < 0.001），在快速速度下低9.6°（p = 0.012）。
无奇点的伸展辅助机制通过防止步态周期摆动期假肢膝关节过度屈曲，改善了健全和假肢膝关节屈曲角度之间的对称性。
