Author: Hu, Mingyu
Title: Gait regulation in individuals with unilateral transfemoral amputation : from neural dynamics to movement coordination
Advisors: Kobayashi, Toshiki (BME)
Zhang, Ming (BME)
Degree: Ph.D.
Year: 2024
Subject: Leg -- Amputation
Artificial limbs
Gait in humans -- Analysis
Amputees -- Rehabilitation
Hong Kong Polytechnic University -- Dissertations
Department: Department of Biomedical Engineering
Pages: xxii, 165 pages : color illustrations
Language: English
Abstract: Individuals with unilateral transfemoral amputation (uTFA) exhibit asymmetric gait patterns when wearing a prosthesis. Understanding prosthetic gait patterns could benefit prosthetic gait rehabilitation and the development of prostheses. However, the current methods of gait analysis and evaluation rely solely on biomechanics and are primarily focused on assessing the performance of an individual joint. This might lead to two major issues when comprehending the gait patterns of individuals with uTFA. Firstly, prosthetic gait is the result of changes in movement regulation from the central nervous system (CNS) driven by neural plasticity. Focusing on biomechanics solely might neglect the contribution of neural dynamics. Secondly, the movement of the prosthetic limb is commonly compensated by the intact limb or interactions among several segments of the prosthetic limb. Attention on a single joint might overlook the coordination between lower limb segments. Current studies on the gait of individuals with uTFA ignore the two issues, resulting in gaps in understanding gait patterns in individuals with uTFA.
Therefore, the purpose of this project was to understand the gait patterns of individuals with uTFA from neural dynamics to their lower limb coordination. The scopes of this project included the investigation of (1) Walking coordination wearing a prosthesis in individuals with uTFA; (2) Sprinting coordination wearing a running-specific prosthesis in individuals with uTFA; (3) Connectivity between neural dynamics and coordination during walking in individuals with uTFA.
Before conducting the three studies, continuous relative phase (CRP), the method of evaluating movement coordination was reviewed. A systematic review regarding the application of CRP in competitive movements (running and jumping) was conducted following the preferred reporting items for systematic reviews and meta-analysis (PRISMA) guidelines. In total, 381 studies from 1999 to 2020 were preliminarily found with 26 studies finally included for quality assessment. Results revealed that CRP related tools found significant changes induced by factors such as pathological conditions, gender, age, experience, footwear, treadmill variations, and insoles. According to the reviewed studies, the CRP approach is useful for assessing internal (task-related) and external (environmental/equipment-related) changes in coordination (self-biological). To better comprehend movement coordination, the CRP model might be constructed using segment angles rather than joint angles.
In the first study, fourteen participants with uTFA and their age-matched able-bodied (AB) individuals were included. Segment and joint angles from the participants' lower extremities were obtained and analysed during walking. CRP values were then calculated from segment angles for both the thigh-shank and shank-foot segments. Coordination patterns revealed compensatory strategies in two legs. For CRP in thigh-shank, different coordination features were observed in the stance and swing phases. However, both groups exhibited similar overall coordination throughout the gait cycle (GC). In the shank-foot coupling on the intact limbs of individuals with uTFA, a brief foot-leading pattern was found during mid-stance. This was a distinct contrast to other limbs, likely due to compensating for the reduced force from the prosthetic limbs. The study provides standard coordination patterns for walking in individuals with uTFA, potentially aiding in the rehabilitation of prosthetic gait and prosthesis advancement.
In the second study, a group of seven participants with uTFA sprinted on a 40-metre track. This study measured parameters such as spatial-temporal, segment and joint angles of the participants with uTFA. CRP analysis was applied to shank-foot and thigh-shank couplings. The asymmetry ratios were then calculated for these metrics. The analysis identified notable variances between the intact and prosthetic limbs in terms of proportion of the stance phase, stance duration, ankle joint angles, and CRP of the shank-foot coupling in uTFA participants. These differences mainly come from the contrasting structures of the prosthetic and intact limbs of participants with uTFA. In terms of coordination, even while noticeable coordination differences were observed in stance and swing phases, the global coordination in the coupling of thigh-shank segments exhibited no marked difference between the lower limbs of uTFA participants. The findings suggest that individuals with uTFA employ diverse adaptive strategies within the coupling of thigh-shank segments throughout the GC, targeting improved limb coordination symmetry.
In the third study, twelve individuals with uTFA and their age-matched AB individuals were recruited. The neural dynamics were recorded using a 64-channel (electroencephalograph) EEG cap. The motion data was collected with the EEG data simultaneously. After removing artifacts and calculating CRP parameters, the correlation between coordination patterns and neural dynamics was investigated. Results showed a strong correlation between neural dynamics and coordination on the intact limb during both stance and swing phases, while no correlation was found in the prosthetic and two limbs of AB individuals. Findings might suggest that the CRP method is effective in revealing activities from CNS. The intact limb might be dominated by the brain directly, while the central pattern generators (CPGs) control the lower limbs of AB individuals. Forcing the prosthetic limb to mimic the movement of the intact limb might not be reasonable, since the origin of the gait pattern generators is different between the two lower limbs.
In conclusion, the prosthetic and intact limb of individuals with uTFA demonstrated different coordination patterns and neural dynamics during gait compared with the AB individuals. Due to the different origins of the prosthetic and intact limbs' gait pattern generators from the CNS, prosthetic designers should not simply mimic the function of an intact limb when creating a prosthetic limb. The knowledge gained from this research has the potential to greatly benefit prosthetic gait rehabilitation and development, leading to more personalised and effective therapies for individuals with uTFA.
Rights: All rights reserved
Access: open access

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