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Department of Rehabilitation Medicine

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Local dynamic stability of amputees wearing a torsion adapter compared to a rigid adapter during straight-line and turning gait


Segal, A.D., Orendurff, M.S., Czerniecki, J.M., Shofer, J.B., & Klute, G.K



Publication Info:

Journal of Biomechanics, 43:2798-2803


Lower limb amputees have decreased balance during daily ambulation compared to nonamputees. An optimally compliant torsion adapter, which enables transverse plane rotation at the socket-pylon junction may reduce limb asymmetries and improve comfort leading to increased confidence and stability during gait. The purpose of this study was to determine if the presence of a torsion adapter affects amputee sensitivity to local perturbations (local dynamic stability) during straight-line walking and during a turning task. Ten unilateral transtibial amputees were fit with a torsion and rigid adapter in random order and blinded to the condition. After a 3-week acclimation period, kinematic data were collected while subjects walked in a straight-line on a treadmill and around a 1-m radius circular path at constant speed. Maximum finite-time Lyapunov exponents (?), an estimator of local dynamic stability, were calculated for the amputee's sagittal plane hip, knee and ankle angles for each condition. The prosthetic limb ? was greater during a turn compared to straight-line walking, suggesting amputees are less stable while turning. There were no statistically significant differences found in ? between adapters during both walking conditions, suggesting the torsion adapter had no effect on amputee stability; however, high inter-subject variability due to the examined population and turning task may have masked a small decrease in prosthetic limb hip and knee stability for the torsion adapter during straight-line gait. Therefore, the torsion adapter's added degree of freedom may have a small adverse effect on prosthetic limb stability during straight-line walking and no effect on turning.

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