Lower-Limb Amputees Adjust Quiet Stance in Response to Manipulations of Plantar Sensation

Interfering with or temporarily eliminating foot-sole tactile sensations causes postural adjustments. Furthermore, individuals with impaired or missing foot-sole sensation, such as lower-limb amputees, exhibit greater postural instability than those with intact sensation. Our group has developed a method of providing tactile feedback sensations projected to the missing foot of lower-limb amputees via electrical peripheral nerve stimulation (PNS) using implanted nerve cuff electrodes. As a step toward effective implementation of the system in rehabilitation and everyday use, we compared postural adjustments made in response to tactile sensations on the missing foot elicited by our system, vibration on the intact foot-sole, and a control condition in which no additional sensory input was applied. Three transtibial amputees with at least a year of experience with tactile sensations provided by our PNS system participated in the study. Participants stood quietly with their eyes closed on their everyday prosthesis while electrically elicited, vibratory, or no additional sensory input was administered for 20 s. Early and steady-state postural adjustments were quantified by center of pressure location, path length, and average angle over the course of each trial. Electrically elicited tactile sensations and vibration both caused shifts in center of pressure location compared to the control condition. Initial (first 3 s) shifts in center of pressure location with electrically elicited or vibratory sensory inputs often differed from shifts measured over the full 20 s trial. Over the full trial, participants generally shifted toward the foot receiving additional sensory input, regardless of stimulation type. Similarities between responses to electrically elicited tactile sensations projected to the missing foot and responses to vibration in analogous regions on the intact foot suggest that the motor control system treats electrically elicited tactile inputs similarly to native tactile inputs. The ability of electrically elicited tactile inputs to cause postural adjustments suggests that these inputs are incorporated into sensorimotor control, despite arising from artificial nerve stimulation. These results are encouraging for application of neural stimulation in restoring missing sensory feedback after limb loss and suggest PNS could provide an alternate method to perturb foot-sole tactile information for investigating integration of tactile feedback with other sensory modalities.

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Microstimulation of the lumbar DRG recruits primary afferent neurons in localized regions of lower limb

Journal of Neurophysiology ◽

10.1152/jn.00961.2015 ◽

2016 ◽

Vol 116 (1) ◽

pp. 51-60 ◽

Cited By ~ 11

Author(s):

Christopher A. Ayers ◽

Lee E. Fisher ◽

Robert A. Gaunt ◽

Douglas J. Weber

Keyword(s):

Lower Limb ◽

Sensory Input ◽

Dynamic Range ◽

Proprioceptive Feedback ◽

Afferent Neurons ◽

Nerve Branch ◽

Nerve Cuff ◽

Cuff Electrodes ◽

Anatomical Localization ◽

Sensory Fibers

Patterned microstimulation of the dorsal root ganglion (DRG) has been proposed as a method for delivering tactile and proprioceptive feedback to amputees. Previous studies demonstrated that large- and medium-diameter afferent neurons could be recruited separately, even several months after implantation. However, those studies did not examine the anatomical localization of sensory fibers recruited by microstimulation in the DRG. Achieving precise recruitment with respect to both modality and receptive field locations will likely be crucial to create a viable sensory neuroprosthesis. In this study, penetrating microelectrode arrays were implanted in the L5, L6, and L7 DRG of four isoflurane-anesthetized cats instrumented with nerve cuff electrodes around the proximal and distal branches of the sciatic and femoral nerves. A binary search was used to find the recruitment threshold for evoking a response in each nerve cuff. The selectivity of DRG stimulation was characterized by the ability to recruit individual distal branches to the exclusion of all others at threshold; 84.7% ( n = 201) of the stimulation electrodes recruited a single nerve branch, with 9 of the 15 instrumented nerves recruited selectively. The median stimulation threshold was 0.68 nC/phase, and the median dynamic range (increase in charge while stimulation remained selective) was 0.36 nC/phase. These results demonstrate the ability of DRG microstimulation to achieve selective recruitment of the major nerve branches of the hindlimb, suggesting that this approach could be used to drive sensory input from localized regions of the limb. This sensory input might be useful for restoring tactile and proprioceptive feedback to a lower-limb amputee.

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Lower Limb Amputee Recovery Response to an Imposed Mediolateral Error in Foot Placement

Volume 1B: Extremity; Fluid Mechanics; Gait; Growth, Remodeling, and Repair; Heart Valves; Injury Biomechanics; Mechanotransduction and Sub-Cellular Biophysics; MultiScale Biotransport; Muscle, Tendon and Ligament; Musculoskeletal Devices; Multiscale Mechanics; Thermal Medicine; Ocular Biomechanics; Pediatric Hemodynamics; Pericellular Phenomena; Tissue Mechanics; Biotransport Design and Devices; Spine; Stent Device Hemodynamics; Vascular Solid Mechanics; Student Paper and Design Competitions ◽

10.1115/sbc2013-14755 ◽

2013 ◽

Author(s):

Ava D. Segal ◽

Glenn K. Klute

Keyword(s):

Lower Limb ◽

Center Of Pressure ◽

Step Width ◽

Foot Placement ◽

Prosthetic Limb ◽

Lower Limb Amputee ◽

Recovery Response ◽

Lower Limb Amputees

Lower limb amputees exhibit increased foot placement variability during gait [1–3] in part due to the lack of ankle musculature that reduces their ability to shift the prosthetic limb center of pressure (COP) [4]. In spite of compensating with a wider step width compared to non-amputees [2,3], amputees are still 20% more likely to fall compared to age-matched norms [5]. Since mediolateral (ML) balance is critical for successful ambulation and contingent on accurate ML foot placement [6,7], we chose to study how an error in ML foot placement affects amputee balance to gain a better understanding of the biomechanic strategies amputees employ to compensate for their lack of ankle musculature.

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Optimization of a tactile feedback system to aid the rehabilitation of lower-limb amputees

2008 Virtual Rehabilitation ◽

10.1109/icvr.2008.4625126 ◽

2008 ◽

Cited By ~ 1

Author(s):

Martin O. Culjat ◽

Richard E. Fan ◽

Warren S. Grundfest

Keyword(s):

Lower Limb ◽

Feedback System ◽

Tactile Feedback ◽

Lower Limb Amputees

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

Frontiers in Neuroscience ◽

10.3389/fnins.2021.727527 ◽

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.

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Conditioning effects of sural nerve stimulation on short and long latency motor evoked potentials in lower limb muscles

Electroencephalography and Clinical Neurophysiology/Electromyography and Motor Control ◽

10.1016/0924-980x(94)00239-4 ◽

1995 ◽

Vol 97 (1) ◽

pp. 11-17 ◽

Cited By ~ 13

Author(s):

D.L. Wolfe ◽

K.C. Hayes

Keyword(s):

Evoked Potentials ◽

Nerve Stimulation ◽

Lower Limb ◽

Sural Nerve ◽

Motor Evoked Potentials ◽

Lower Limb Muscles ◽

Long Latency ◽

Limb Muscles

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Adaptive Foot in Lower-Limb Prostheses

Journal of Robotics ◽

10.1155/2017/9618375 ◽

2017 ◽

Vol 2017 ◽

pp. 1-15 ◽

Cited By ~ 2

Author(s):

Thilina H. Weerakkody ◽

Thilina Dulantha Lalitharatne ◽

R. A. R. C. Gopura

Keyword(s):

Lower Limb ◽

Uneven Surface ◽

Design Concepts ◽

Human Foot ◽

Future Developments ◽

Adaptive Capabilities ◽

Adaptive Nature ◽

Lower Limb Amputees ◽

Artificial Prosthesis ◽

Lower Limb Prostheses

The human foot consists of complex sets of joints. The adaptive nature of the human foot enables it to be stable on any uneven surface. It is important to have such adaptive capabilities in the artificial prosthesis to achieve most of the essential movements for lower-limb amputees. However, many existing lower-limb prostheses lack the adaptive nature. This paper reviews lower-limb adaptive foot prostheses. In order to understand the design concepts of adaptive foot prostheses, the biomechanics of human foot have been explained. Additionally, the requirements and design challenges are investigated and presented. In this review, adaptive foot prostheses are classified according to actuation method. Furthermore, merits and demerits of present-day adaptive foot prostheses are presented based on the hardware construction. The hardware configurations of recent adaptive foot prostheses are analyzed and compared. At the end, potential future developments are highlighted.

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