title: Local dynamic stability of amputees wearing a torsion adapter compared to a rigid adapter during straight-line and turning gait.
abstract: 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 (λ), 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 λ 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 λ 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.
authors: Center of Excellence for Limb Loss Prevention and Prosthetic Engineering, Rehabilitation Research and Development, Veterans Administration Puget Sound Health Care System, Seattle, WA, USA.
authors: Ava D
authors: AD
authors: Segal
authors: Michael S
authors: MS
authors: Orendurff
authors: Joseph M
authors: JM
authors: Czerniecki
authors: Jane B
authors: JB
authors: Shofer
authors: Glenn K
authors: GK
authors: Klute
mesh_terms: D000328:Adult; D000368:Aged; D000674:Amputees / Q000534:rehabilitation*; D001186:Artificial Limbs; D001696:Biomechanical Phenomena; D005260:Female; D005684:Gait / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D004856:Postural Balance / Q000502:physiology*; D016037:Single-Blind Method; D054159:Torsion, Mechanical; D016138:Walking / Q000502:physiology