scholarly journals Improving Postural Stability among Amputees by Tactile Sensory Substitution

2021 ◽  
Author(s):  
Lijun Chen ◽  
Yanggang Feng ◽  
Baojun Chen ◽  
Qining Wang ◽  
Kunlin Wei
Keyword(s):  
Postural Control ◽  
Real Time ◽  
Lower Limb ◽  
Postural Stability ◽  
Interaction Force ◽  
Sensory Substitution ◽  
Foot Pressure ◽  
Vibration Intensity ◽  
Lower Limb Amputees ◽  
Visual Disturbances

Abstract BackgroundFor lower-limb amputees, wearing a prosthetic limb helps restore their motor abilities for daily activities. However, the prosthesis's potential benefits are hindered by limited somatosensory feedback from the affected limb and its prosthesis. Previous studies have examined various sensory substitution systems to alleviate this problem; the prominent approach is to convert foot-ground interaction to tactile stimulations. However, positive outcomes for improving amputees' postural stability are still rare. We hypothesize that the intuitive design of tactile signals based on psychophysics shall enhance the feasibility and utility of real-time sensory substitution for lower-limb amputees. MethodsWe designed a wearable device consisting of four pressure sensors and two vibrators and tested it among the unilateral transtibial amputees (n=7) and the able-bodied (n=8). The real-time measurements of foot pressure were fused into a single representation of foot-ground interaction force, which was encoded by varying vibration intensity of the two vibrators attached to the participants’ forearm. The layout of vibrators was spatially congruent with the foot force sensors' placement; the vibration intensity followed a logarithmic function of the force representation, in keeping with principles of tactile psychophysics. The participants were tested with a classical postural stability task in which visual disturbances perturbed their quiet standing. ResultsWith a brief familiarization of the system, the participants exhibited better posture stability against visual disturbances when switching on sensory substitution than without. The body sway was substantially reduced, as shown in head movements and excursions of the center of pressure. The improvement was present for both amputees and able-bodied controls and was particularly pronounced in more challenging conditions with larger visual disturbances. ConclusionsSubstituting otherwise-missing foot pressure feedback with vibrotactile signals can improve postural stability for lower-limb amputees. The intuitive design of the mapping between the foot-ground interaction force and the tactile signals is essential for the user to utilize the surrogated tactile signals for postural control, especially for situations that their postural control is challenged.

scholarly journals Improving postural stability among people with lower-limb amputations by tactile sensory substitution

2021 ◽  
Vol 18 (1) ◽  
Author(s):  
Lijun Chen ◽  
Yanggang Feng ◽  
Baojun Chen ◽  
Qining Wang ◽  
Kunlin Wei
Keyword(s):  
Postural Control ◽  
Lower Limb ◽  
Postural Stability ◽  
Pressure Sensors ◽  
Interaction Force ◽  
The Body ◽  
Sensory Substitution ◽  
Foot Pressure ◽  
Vibration Intensity ◽  
Visual Disturbances

Abstract Background For people with lower-limb amputations, wearing a prosthetic limb helps restore their motor abilities for daily activities. However, the prosthesis's potential benefits are hindered by limited somatosensory feedback from the affected limb and its prosthesis. Previous studies have examined various sensory substitution systems to alleviate this problem; the prominent approach is to convert foot–ground interaction to tactile stimulations. However, positive outcomes for improving their postural stability are still rare. We hypothesized that the sensory substiution system based on surrogated tactile stimulus is capable of improving the standing stability among people with lower-limb amputations. Methods We designed a wearable device consisting of four pressure sensors and two vibrators and tested it among people with unilateral transtibial amputations (n = 7) and non-disabled participants (n = 8). The real-time measurements of foot pressure were fused into a single representation of foot–ground interaction force, which was encoded by varying vibration intensity of the two vibrators attached to the participants’ forearm. The vibration intensity followed a logarithmic function of the force representation, in keeping with principles of tactile psychophysics. The participants were tested with a classical postural stability task in which visual disturbances perturbed their quiet standing. Results With a brief familiarization of the system, the participants exhibited better postural stability against visual disturbances when switching on sensory substitution than without. The body sway was substantially reduced, as shown in head movements and excursions of the center of pressure. The improvement was present for both groups of participants and was particularly pronounced in more challenging conditions with larger visual disturbances. Conclusions Substituting otherwise missing foot pressure feedback with vibrotactile signals can improve postural stability for people with lower-limb amputations. The design of the mapping between the foot–ground interaction force and the tactile signals is essential for the user to utilize the surrogated tactile signals for postural control, especially for situations that their postural control is challenged.

scholarly journals Influence of Augmented Visual Feedback on Balance Control in Unilateral Transfemoral Amputees

2021 ◽  
Vol 15 ◽  
Author(s):  
Katharina Fuchs ◽  
Thomas Krauskopf ◽  
Torben B. Lauck ◽  
Lukas Klein ◽  
Marc Mueller ◽  
...  
Keyword(s):  
Postural Control ◽  
Real Time ◽  
Visual Feedback ◽  
Lower Limb ◽  
Center Of Pressure ◽  
Sensory Modality ◽  
Control Group ◽  
Eyes Open ◽  
Transfemoral Amputees ◽  
Lower Limb Amputees

Patients with a lower limb amputation rely more on visual feedback to maintain balance than able-bodied individuals. Altering this sensory modality in amputees thus results in a disrupted postural control. However, little is known about how lower limb amputees cope with augmented visual information during balance tasks. In this study, we investigated how unilateral transfemoral amputees incorporate visual feedback of their center of pressure (CoP) position during quiet standing. Ten transfemoral amputees and ten age-matched able-bodied participants were provided with real-time visual feedback of the position of their CoP while standing on a pressure platform. Their task was to keep their CoP within a small circle in the center of a computer screen placed at eye level, which could be achieved by minimizing their postural sway. The visual feedback was then delayed by 250 and 500 ms and was combined with a two- and five-fold amplification of the CoP displacements. Trials with eyes open without augmented visual feedback as well as with eyes closed were further performed. The overall performance was measured by computing the sway area. We further quantified the dynamics of the CoP adjustments using the entropic half-life (EnHL) to study possible physiological mechanisms behind postural control. Amputees showed an increased sway area compared to the control group. The EnHL values of the amputated leg were significantly higher than those of the intact leg and the dominant and non-dominant leg of controls. This indicates lower dynamics in the CoP adjustments of the amputated leg, which was compensated by increasing the dynamics of the CoP adjustments of the intact leg. Receiving real-time visual feedback of the CoP position did not significantly reduce the sway area neither in amputees nor in controls when comparing with the eyes open condition without visual feedback of the CoP position. Further, with increasing delay and amplification, both groups were able to compensate for small visual perturbations, yet their dynamics were significantly lower when additional information was not received in a physiologically relevant time frame. These findings may be used for future design of neurorehabilitation programs to restore sensory feedback in lower limb amputees.

Piezoresistive Polymer-Based Materials for Real-Time Assessment of the Stump/Socket Interface Pressure in Lower Limb Amputees

2017 ◽  
Vol 17 (7) ◽  
pp. 2182-2190 ◽  
Author(s):  
Armando Ferreira ◽  
Vitor Correia ◽  
Emilia Mendes ◽  
Claudia Lopes ◽  
Jose Filipe Vilela Vaz ◽  
...  
Keyword(s):  
Real Time ◽  
Lower Limb ◽  
Interface Pressure ◽  
Socket Interface ◽  
Lower Limb Amputees ◽  
Time Assessment

Control of sway using vibrotactile feedback of body tilt in patients with moderate and severe postural control deficits

2005 ◽  
Vol 15 (5-6) ◽  
pp. 313-325
Author(s):  
C. Wall ◽  
E. Kentala
Keyword(s):  
Postural Control ◽  
Postural Stability ◽  
Body Motion ◽  
Body Tilt ◽  
Joint Movement ◽  
Foot Pressure ◽  
Eyes Closed ◽  
The Subject ◽  
Anterior Posterior ◽  
Vibrotactile Display

We evaluated the effect of the vibrotactile display of body tilt upon the postural stability of vestibulopathic subjects during standing. Two groups were studied: those with moderate and with severe deficits as defined by postural stability test scores. They were studied under conditions of distorted sensory input, and during anterior-posterior perturbations. Seventeen subjects, with uni- or bilateral vestibular deficits, as determined by electronystagmography and vertical axis rotation, were tested using Equitest® computerized dynamic posturography (CDP). Based on their performance on the CDP they were divided into two groups having either moderate (nine subjects) or severe (eight subjects) postural control deficits. Their anterior-posterior (A/P) body motion at the waist was measured with a micromechanical rate gyroscope and a linear accelerometer. The resulting tilt estimate was displayed by a vibrotactile array attached to the torso. The vibration served as a tilt feedback to the subject. The subject's performance was evaluated using the root-mean-square (RMS) of both the A/P body motion and center-of-pressure (CoP) estimates. Sensory distortions were introduced using the Equitest® Sensory Organization Tests (SOT). These tests are designed to distort A/P sensory inputs while standing. The SOT 5 distorts proprioceptive information about ankle joint movement, while the subject stands eyes-closed on a moving support platform that measures foot pressure. The SOT 6 adds distorted visual information about body movement instead of testing with eyes closed. Perturbations were introduced using the Equitest® Motor Control Tests (MCT). These move the support platform forward or backward with small, medium and large displacements in the horizontal plane while measuring subjects' foot pressure responses. We used the medium and large backward tests. Vibrotactile display of body tilt reduced the subjects' A/P sway and improved their balance. The finding was more evident for those subjects with severe deficits than those moderate ones. This trend was found for both SOT 5 and 6, as well as the medium and large MCT. Additionally, during the MCT, the peak deflection and mean recovery time also decreased significantly.

scholarly journals Heuristic Real-Time Detection of Temporal Gait Events for Lower Limb Amputees

2019 ◽  
Vol 19 (8) ◽  
pp. 3138-3148 ◽  
Author(s):  
Hafiz Farhan Maqbool ◽  
Muhammad Afif Bin Husman ◽  
Mohammed Ibrahim Awad ◽  
Alireza Abouhossein ◽  
Nadeem Iqbal ◽  
...  
Keyword(s):  
Real Time ◽  
Lower Limb ◽  
Real Time Detection ◽  
Lower Limb Amputees

scholarly journals The Effect of a Lower-Limb Sensory Prosthesis on Balance and Gait in People With Peripheral Neuropathy

2017 ◽  
Author(s):  
Sara R. Koehler-McNicholas ◽  
Lori Danzl ◽  
Lars Oddsson
Keyword(s):  
Peripheral Neuropathy ◽  
Lower Limb ◽  
Balance Control ◽  
Cost Effective ◽  
Epidemiological Studies ◽  
Lower Limbs ◽  
Sensory Substitution ◽  
Foot Pressure ◽  
Increased Risk ◽  
Foot Pad

Peripheral neuropathy (PN), commonly caused by diabetes mellitus, is a debilitating condition that currently affects approximately 20 million Americans. Chronic symptoms of PN often involve pain and weakness of the lower limbs, with eventual sensation loss on the plantar surfaces of the feet. According to epidemiological studies, reduced foot sole sensation has been linked to decreased standing stability [1] and an increased risk of falling [2]. Consequently, cost-effective interventions are needed to improve balance and mobility in this population. A growing body of research suggests that vibrotactile cues delivered to sensate areas of the lower limb may be an effective way to provide information about foot sole pressure to PN patients who experience poor balance control. Indeed, sensory substitution devices that provide vibrotactile feedback have been shown to aid in balance and improve postural control in various patient populations [3–7]. However, none of these technologies have been based on measurements of foot pressure nor have they been used as a balance prosthesis. The goal of this study was to investigate the effect of a new external lower-limb sensory prosthesis, the Walkasins™, on the balance and gait of individuals with PN who experience balance problems [8]. Walkasins™ consist of two parts: a leg unit and a foot pad (Figure 1). The leg unit wraps around the lower leg of the user and contains electronics for reading foot pad pressure signals, a microprocessor, and four vibrating motors that provide gentle tactile sensory cues to the front, back, medial, and lateral surfaces of the user’s leg. These cues reflect real-time foot pressure information at a location above the ankle where skin sensation is still present. The leg unit has a power button, two status LEDs, and a reset button (not shown in Figure 1). Power is supplied by a rechargeable internal battery. The foot pad is a thin consumable sole insert that can be cut to size and fit into a regular shoe. The foot pad connects to the leg unit through a physical cable. In this study, subjects performed gait and balance assessments with and without the Walkasins™ turned on in order to determine its short-term effects.

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