Ankle joint stiffness during phases of human walking.

Ankelledstivhed i faser af gangcyklussen.

Plocharski, Piotr ; Plocharski, Maciej

4. term

Biomedical Engineering and Informatics, Master

2013

2013-06-04

90

For at designe ankelproteser, der fungerer mere som et naturligt ben, er det vigtigt at forstå, hvordan ankelleddet modstår bevægelse under gang. Ledstivhed beskriver, hvor meget leddet gør modstand mod at blive bevæget; den forbinder ankelvinkel med det drejningsmoment (den vridende kraft), der virker omkring leddet. I dette studie deltog 11 unge, ikke-handicappede voksne (24–27 år). Deltagerne gik på et løbebånd, mens forskerne påførte korte, små forstyrrelser af anklen (enkelt forskydningsimpulser) og målte det resulterende drejningsmoment. Ankelstivhed blev estimeret i tre faser af gangcyklussen og, til sammenligning, under stående forsøg, hvor deltagerne holdt de samme benstillinger uden bevægelse (isometriske betingelser). Estimaterne blev beregnet med en multi-segment algoritme, en beregningsmetode, der uden at antage en bestemt model (ikke-parametrisk) beskriver forholdet mellem vinkel og drejningsmoment. Resultaterne viste ingen signifikant forskel i middelværdierne for ankelstivhed mellem de dynamiske og de isometriske forsøg. Derimod var der en statistisk signifikant forskel i middelstivhed mellem de tre gangfaser ved plantarfleksion (tæerne peger nedad) [P < 0.0005]. Disse fund tyder på, at ankelstivhed afhænger af, hvor i gangcyklussen man er, og at matchede stående stillinger kan give et rimeligt estimat af stivheden målt under gang. Denne viden kan bidrage til design af ankelproteser, der efterligner et sundt led.

Designing prosthetic ankles that behave more like a natural joint requires understanding how the ankle resists movement during walking. Joint stiffness describes how strongly the ankle resists being moved; it links ankle angle to the twisting force (torque) around the joint. In this study, 11 young adults without disabilities (ages 24–27) walked on a treadmill while brief, small ankle perturbations (single displacement pulses) were applied and the resulting torque was measured. Ankle stiffness was estimated during three phases of the gait cycle and, for comparison, during standing trials in which participants held the same leg postures without movement (isometric conditions). Stiffness estimates were produced with a multi-segment algorithm, a computational, non-parametric method that characterizes the angle–torque relationship without assuming a preset model. Results showed no significant difference in mean ankle stiffness between the dynamic walking trials and the matched isometric standing trials. However, mean ankle stiffness differed significantly across the three gait phases in plantarflexion (toes pointing downward) [P < 0.0005]. These findings indicate that ankle stiffness varies with gait phase and that matched standing postures can approximate stiffness measured during walking. This knowledge may inform the design of prosthetic ankles intended to mimic healthy joint behavior.

[This abstract was generated with the help of AI]

ankel ; stivhed ; system identificering

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