Evaluating the Impact of Prosthetics on Gait Symmetry in Unilateral Lower Limb Amputees

Abstract

Gait symmetry is a primary criterion for assessing the rehabilitation progress of unilateral transtibial amputees with prostheses. This study aimed to examine the gait symmetry of dynamic kinematic and kinetic functions in unilateral transtibial amputees using prostheses during walking. Methods The study was approved by the University Ethics Committee and involved five (3 females and 2 males) unilateral transtibial amputees (age: (mean ± SD) 63.4 ± 7.7 years, height: 165.6 ± 6.4 cm; body mass: 69.4 ± 4.1 kg; years of using prosthetic foot: 30.8 ± 9.3 years). For collecting the kinematic and kinetic data, thirty-nine passive-reflective markers were placed on the participant according to the landmarks set of the plug-in full body model. An 8-camera motion capturing system (VICON, Nexus 2.0 Inc., Oxford, UK) and 2 force plates (AMTI, Advanced Mechanical Technology, Inc., Watertown, USA) mounted under the walkway were recorded 100 frames per second simultaneously. All the systems were calibrated before the experiment. Participants walked at their self-selected walking speeds. Based on their self-selected walking speed record, ± 10% range were calculated as the references for each participant’s fast and slow walking speed. Each participant repeated walking trials until a minimum of 5 “clean” foot force plate contact with both right and left limbs were acquired. The corresponding data from 5 gait cycles were selected to calculate the lower limb joints angles and vertical ground reaction force (GRF) during walk. Then symmetry index (SI) was calculated to provide a descriptive marker for the degree of symmetry between the intact and residual limbs. A value of SI less than 5% reflects good symmetry between the limbs, whereas increasingly positive values indicate the value for the residual limb was greater than that of the intact limb, while negative values denote that the intact limb value was greater. Results Normalized vertical GRF of two limbs increased with increased walking speeds. The corresponding SI was the largest when heel strike with slow walking speed (6.2 ± 0.8 m/s). Gait imbalance was observed during loading response and midstance (around 30% - 45% stance phase) when the walking speed was increased. While SI values of ankle angles were enlarged with increased walking speed, indicating more asymmetry of ankle angle between two limbs with their traditional prostheses when the walking speed increases. Conclusions The current prostheses can only support the basic daily activities for the unilateral transtibial amputees. The new design of prostheses should therefore focus on kinetic and kinematic parameters such as the symmetry between the residual limb and the intact limb, and energy saving for the amputees during high intensity activities.