Lower limb inter-joint coordination of unilateral transfemoral amputees: Implications for adaptation control

The gait of transfemoral amputees can be made smoother by adjusting the inter-joint coordination of both lower limbs. In this study, we compared the inter-joint coordination of the amputated and non-amputated limbs of unilateral amputees to able-bodied controls. Eight amputees and eight able-bodied control participants were recruited. Walking speed, stance-swing time ratio, joint angle, joint angular velocity, and inter-joint coordination parameters-including continuous relative phase (CRP) and decomposition index (DI)-of the lower-limb joint pairs in stance and swing phases were investigated. Similarity of the CRP between groups was evaluated using cross-correlation measures and root-mean-square, and the variability of the CRP was examined by deviation phase (DP). There were significant differences between the amputated limbs and controls in CRP of hip-knee and knee-ankle in stance and swing, DP of knee-ankle and hip-ankle in stance, and DI of hip-knee in swing. For the non-amputated limbs, there were significant differences in CRP and DP of knee-ankle, and DI of hip-knee in swing compared to controls. The amputees utilized unique inter-joint coordination patterns for both limbs-particularly the hip joint-to compensate for the support-capability impairment due to limb salvage and ensure foot placement accuracy.