Stabilizing moments of force on a prosthetic knee during stance in the first steps after gait initiation

In this study, the occurrences of stabilizing and destabilizing external moments of force on a prosthetic knee during stance, in the first steps after gait initiation, in inexperienced users were investigated. Primary aim was to identify the differences in the external moments during gait initiation with the sound leg leading and the prosthetic leg leading. A prosthetic leg simulator device, with a flexible knee, was used to test able-bodied subject, with no walking aid experience. Inverse dynamics calculations were preformed to calculate the external moments. The subjects learned to control the prosthetic leg within 100 steps, without walking aids, evoking similar patterns of external moments of force during the steps after the gait initiation, either with their sound leg loading or prosthetic leg leading. Critical phases in which a sudden flexion of the knee can occur were found just after heelstrike and just before toe off, in which the external moment of force was close to the internal moment produced by a knee extension aiding spring in the opposite direction

Controlling horizontal deceleration during gait termination in transfemoral amputees: Measurements and simulations

In this study we investigated how leading limb angles combined with active ankle moments of a sound ankle or passive stiffness of a prosthetic ankle, influence the center of mass (CoM) velocity during the single limb support phase in gait termination. Also, we studied how the trailing limb velocity influences the CoM velocity during this phase. We analyzed force plate data from a group of experienced transfermoral (TF) amputee subjects using a prosthetic limb, and the outcome from a two-dimensional mathematical forward dynamics model. We found that when leading with the sound limb, the subjects came almost to a full stop in the single limb support phase, without the use of the prosthetic limb. When leading with the prosthetic limb, the CoM deceleration was less in a relatively short single limb support phase, with a fast forward swing of the trailing sound limb. Slowing down the heavier trailing sound limb, compared to the prosthetic limb, results in a relatively larger braking force at the end of the swing phase. The simulations showed that only narrow ranges of leading limb angle and ankle moments could be used to achieve the same CoM velocities with the mathematical model as the average start and end velocities of the prosthetic limb user. We conclude that users of prosthetic limbs have a narrow range of options for the dynamics variables to achieve a target CoM velocity. The lack of active control in the passive prosthetic ankle prevents the TF amputee subjects from producing sufficient braking force when terminating gait with the prosthetic limb leading, forcing the subjects to use both limbs as a functional unit, in which the sound limb is mostly responsible for the gait termination. (C) 2012 IPEM. Published by Elsevier Ltd. All rights reserved

Comparative roll-over analysis of prosthetic feet

A prosthetic foot is a key element of a prosthetic leg, literally forming the basis for a stable and efficient amputee gait. We determined the roll-over characteristics of a broad range of prosthetic feet and examined the effect of a variety of shoes on these characteristics. The body weight of a person acting on a prosthetic foot during roll-over was emulated by means of an inverted pendulum-like apparatus. Parameters measured were the effective radius of curvature, the forward travel of the center of pressure, and the instantaneous radius of curvature of the prosthetic feet. Finally, we discuss how these parameters relate to amputee gait

Obstacle crossing in lower limb amputees

OBJECTIVE: To study limitations in function and adjustment strategies in lower limb amputees during obstacle crossing. DESIGN: Observational cohort study. SUBJECTS: Transfemoral and transtibial amputees and able-bodied control subjects. METHODS: In a motion analysis laboratory unimpeded and obstacle crossing runs were performed. The subjects stepped over an obstacle of 0.1m height and thickness and 1m width. Outcome measures were gait velocity, hip, knee and ankle joint angles and leading limb preference. RESULTS: Whereas able-bodied and transtibial subjects demonstrated an increase in knee flexion during obstacle crossing compared to unimpeded walking, in transfemoral amputees the opposite was seen, namely a decrease in knee flexion. The lack of knee strategy in transfemoral amputees was compensated by circumduction at the hip on the prosthetic side and plantar flexion of the non-affected ankle. Transtibial amputees preferred to cross the obstacle with the prosthetic limb first, while transfemoral amputees preferred the non-affected limb. CONCLUSION: The different leading limb strategy in transfemoral and transtibial amputees could be explained by the restricted flexion and propulsion properties of the prosthetic knee. Training of obstacle crossing tasks during rehabilitation and improvement of prosthetic design may contribute to safe obstacle crossing

Balance control on a moving platform in unilateral lower limb amputees

OBJECTIVE: To study balance control on a moving platform in lower limb amputees. DESIGN: Observational cohort study. PARTICIPANTS: Unilateral transfemoral and transtibial amputees and able-bodied control subjects. INTERVENTIONS: Balance control on a platform that moved in the anteroposterior direction was tested with eyes open, blindfolded and while performing a dual task. MAIN OUTCOME MEASURES: Weight bearing symmetry, anteroposterior ground reaction force and centre of pressure shift. RESULTS: Compared to able-bodied subjects, in amputees the anteroposterior ground reaction force was larger in the prosthetic and non-affected limb, and the centre of pressure displacement was increased in the non-affected limb and decreased in the prosthetic limb. In amputees body weight was loaded more on the non-affected limb. Blindfolding or adding a dual task did not influence the outcome measures importantly. CONCLUSION: The results of this study indicate that experienced unilateral amputees with a high activity level compensate for the loss of ankle strategy by increasing movements and loading in the non-affected limb. The ability to cope with balance perturbations is limited in the prosthetic limb. To enable amputees to manage all possible balance disturbances in real life in a safe manner, we recommend to improve muscle strength and control in the non-affected limb and to train complex balance tasks in challenging environments during rehabilitation

Gait termination in lower limb amputees

OBJECTIVE: To study the limitations in function and adjustment strategies of lower limb amputees in gait termination. DESIGN: Observational cohort study. SETTING: University Medical Centre. PARTICIPANTS: Unilateral transfemoral and transtibial amputees, and able-bodied control subjects. MAIN OUTCOME MEASURES: Leading limb preference, temporal variables, lower limb joint angles, ground reaction forces, and centre of pressure shift. RESULTS: Compared to able-bodied subjects, amputees showed a decreased peak braking ground reaction force in the prosthetic limb, no anterior centre of pressure shift during leading with the prosthetic limb and an increased mediolateral centre of pressure shift. Amputees used several adjustment strategies to compensate for the limitations in function; leading limb preference for the non-affected limb, longer production of braking force in the non-affected limb, decreased gait termination velocity and more weight-bearing on the non-affected limb. CONCLUSION: Limitations in function and adjustment strategies were mainly similar in transfemoral and transtibial amputees. Due to the lack of active ankle function, amputees were not able to increase the braking force and to shift the centre of pressure anteriorly. Leading with the non-affected limb is favourable for adequate deceleration and balance control, but in daily life not always applicable. It is important that amputees are trained in gait termination during rehabilitation and prosthetic design should focus on a more active role of the prosthetic foot and knee

Gait initiation in lower limb amputees

OBJECTIVE: To study limitations in function and adjustment strategies in lower limb amputees during gait initiation. DESIGN: Observational cohort study. SETTING: University Medical Center. PARTICIPANTS: Amputees with a unilateral transfemoral or transtibial amputation, and able-bodied subjects. MAIN OUTCOME MEASURES: Leading limb preference, temporal variables, ground reaction forces, and centre of pressure shift. RESULTS: Amputees demonstrated a decrease in peak anterior ground reaction force, a smaller or absent posterior centre of pressure shift, and a lower gait initiation velocity. The main adjustments strategies in amputees were more limb-loading on the non-affected limb, prolonging the period of propulsive force production in the non-affected limb and initiating gait preferably with the prosthetic limb. CONCLUSION: Since an intact ankle joint and musculature is of major importance in gait initiation, functional limitations and adjustment strategies in transfemoral and transtibial amputees were similar. Improving prosthetic ankle properties and initiating gait with the prosthetic limb may facilitate the gait initiation process in amputees

Implementing Individually Tailored Prescription of Physical Activity in Routine Clinical Care: Protocol of the Physicians Implement Exercise = Medicine (PIE=M) Development and Implementation Project.

Contains fulltext : 229883.pdf (publisher's version ) (Open Access)BACKGROUND: The prescription of physical activity (PA) in clinical care has been advocated worldwide. This "exercise is medicine" (E=M) concept can be used to prevent, manage, and cure various lifestyle-related chronic diseases. Due to several challenges, E=M is not yet routinely implemented in clinical care. OBJECTIVE: This paper describes the rationale and design of the Physicians Implement Exercise = Medicine (PIE=M) study, which aims to facilitate the implementation of E=M in hospital care. METHODS: PIE=M consists of 3 interrelated work packages. First, levels and determinants of PA in different patient and healthy populations will be investigated using existing cohort data. The current implementation status, facilitators, and barriers of E=M will also be investigated using a mixed-methods approach among clinicians of participating departments from 2 diverse university medical centers (both located in a city, but one serving an urban population and one serving a more rural population). Implementation strategies will be connected to these barriers and facilitators using a systematic implementation mapping approach. Second, a generic E=M tool will be developed that will provide tailored PA prescription and referral. Requirements for this tool will be investigated among clinicians and department managers. The tool will be developed using an iterative design process in which all stakeholders reflect on the design of the E=M tool. Third, we will pilot-implement the set of implementation strategies, including the E=M tool, to test its feasibility in routine care of clinicians in these 2 university medical centers. An extensive learning process evaluation will be performed among clinicians, department managers, lifestyle coaches, and patients using a mixed-methods design based on the RE-AIM framework. RESULTS: This project was approved and funded by the Dutch grant provider ZonMW in April 2018. The project started in September 2018 and continues until December 2020 (depending on the course of the COVID-19 crisis). All data from the first work package have been collected and analyzed and are expected to be published in 2021. Results of the second work package are described. The manuscript is expected to be published in 2021. The third work package is currently being conducted in clinical practice in 4 departments of 2 university medical hospitals among clinicians, lifestyle coaches, hospital managers, and patients. Results are expected to be published in 2021. CONCLUSIONS: The PIE=M project addresses the potential of providing patients with PA advice to prevent and manage chronic disease, improve recovery, and enable healthy ageing by developing E=M implementation strategies, including an E=M tool, in routine clinical care. The PIE=M project will result in a blueprint of implementation strategies, including an E=M screening and referral tool, which aims to improve E=M referral by clinicians to improve patients' health, while minimizing the burden on clinicians