Functional Electrical Stimulation Plus Visual Feedback Balance Training for Standing Balance Performance Among Individuals With Incomplete Spinal Cord Injury: A Case Series

Balance Interventions to Improve Upright Balance Control and Balance Confidence in People With Motor-Incomplete Spinal Cord Injury or Disease: A Systematic Review and Meta-analysis

OBJECTIVES

To assist with clinical decision making, evidence syntheses are needed to demonstrate the efficacy of available interventions and examine the intervention components and dosage parameters. This systematic review and meta-analysis described the efficacy, components and dosage of interventions targeting upright balance control, balance confidence, and/or falls in adults with motor-incomplete spinal cord injury/disease (SCI/D).

DATA SOURCES

A search strategy following the population, intervention, control, outcome framework was developed. Six databases were searched: APA PsychInfo, Cumulative Index to Nursing and Allied Health Literature, Embase, Emcare Nursing, Web of Science CC, and Medline.

STUDY SELECTION

Title, abstract, and full-text screening were conducted by 2 researchers independently. Inclusion criteria included the following: (1) adults with chronic, motor-incomplete SCI/D; (2) physical intervention targeting upright postural control; and (3) clinical and/or biomechanical measures of upright balance control and/or balance confidence and/or documentation of falls.

DATA EXTRACTION

Participant characteristics, balance intervention details, adverse events, and study results were extracted. The Downs and Black Checklist was used to assess methodological quality. Meta-analyses on pre-post intervention outcomes and a meta-regression of dosage were completed. Grading of Recommendations, Assessment, Development, and Evaluations approach was used to evaluate the quality of the evidence.

DATA SYNTHESIS

The search returned 1664 unique studies; 26 were included. Methodological quality was moderate to good. Participants were 500 individuals with SCI/D, aged 18-74 years (males: females = 2.4:1). Minor adverse events were reported in 8 studies (eg, muscle soreness and fatigue). Walking interventions and upright balance training with visual feedback had clinically meaningful and significant pooled effects on improving standing balance control. Only walking interventions had a significant pooled effect on improving balance confidence. There were no significant findings on dosage response. Few studies evaluated the effects of balance interventions on the occurrence of falls.

CONCLUSIONS

Walking interventions and upright balance training with visual feedback had greater effects on upright balance control than conventional physiotherapy; however, the quality of the evidence was very low.

Feasibility of using a depth camera or pressure mat for visual feedback balance training with functional electrical stimulation

Individuals with incomplete spinal-cord injury/disease are at an increased risk of falling due to their impaired ability to maintain balance. Our research group has developed a closed-loop visual-feedback balance training (VFBT) system coupled with functional electrical stimulation (FES) for rehabilitation of standing balance (FES + VFBT system); however, clinical usage of this system is limited by the use of force plates, which are expensive and not easily accessible. This study aimed to investigate the feasibility of a more affordable and accessible sensor such as a depth camera or pressure mat in place of the force plate. Ten able-bodied participants (7 males, 3 females) performed three sets of four different standing balance exercises using the FES + VFBT system with the force plate. A depth camera and pressure mat collected centre of mass and centre of pressure data passively, respectively. The depth camera showed higher Pearson's correlation (r > 98) and lower root mean squared error (RMSE < 10 mm) than the pressure mat (r > 0.82; RMSE < 4.5 mm) when compared with the force plate overall. Stimulation based on the depth camera showed lower RMSE than that based on the pressure mat relative to the FES + VFBT system. The depth camera shows potential as a replacement sensor to the force plate for providing feedback to the FES + VFBT system.

Identifying priorities for balance interventions through a participatory co-design approach with end-users

BACKGROUND

Most individuals living with spinal cord injuries/diseases (SCI/D) or stroke experience at least one fall each year; hence, the development of interventions and technologies that target balance control is needed. The purpose of this study was to identify and explore the priorities for balance-focused interventions and technologies from the perspectives of end-users to assist with the design of an intervention that combines functional electrical stimulation (FES) with visual feedback training for standing balance.

METHODS

Two individuals with SCI/D, one individual with stroke, two physical therapists (PT) and one hospital administrator were recruited. Participants attended three focus group meetings that followed a participatory co-design approach. A semi-structured interview guide, developed from the FAME (Feasibility, Appropriateness, Meaningfulness, Effectiveness, Economic Evidence) framework, was used to lead the discussion, querying participants' experiences with balance deficits and interventions, and FES. Meetings were audio-recorded and transcribed verbatim. An iterative and reflexive inductive thematic analysis was applied to the transcripts by three researchers.

RESULTS

Four themes were identified: (1) Balance is meaningful for daily life and rehabilitation. Participants acknowledged various factors influencing balance control and how balance deficits interfered with participation in activities. End-users stressed the importance of continuing to work on one's balance after discharge from hospital-based rehabilitation. (2) Desired characteristics of balance interventions. Participants explained that balance interventions should be tailored to an individual's unique needs and goals, relevant to their lives, balance their safety and risk, and be engaging. (3) Prior experiences with FES to inform future therapeutic use. Participants with stroke or SCI/D described initial apprehension with FES, but experienced numerous benefits that motivated them to continue with FES. Challenges with FES were mentioned, including wires, cost, and time of set up. (4) Potential role of FES in balance interventions. Participants felt that FES would complement balance interventions; however, they had not experienced this combination of therapies previously.

CONCLUSIONS

End-users described how their experiences with balance deficits, rehabilitation, and FES informed their priorities for balance interventions. The findings inform the design and implementation of future balance interventions for individuals with SCI/D or stroke, including an intervention involving FES and visual feedback training.

Interventions to Improve Standing Balance in Individuals With Incomplete Spinal Cord Injury: A Systematic Review and Meta-Analysis

Background

Incomplete spinal cord injury (iSCI) often results in impaired balance leading to functional impairments. Recovery of standing balance ability is an important aim of rehabilitative programs. However, limited information is available on effective balance training protocols for individuals with iSCI.

Objectives

To assess the methodological quality and effectiveness of various rehabilitation interventions for improving standing balance in individuals with iSCI.

Methods

A systematic search was performed in SCOPUS, PEDro, PubMed, and Web of Science from inception until March 2021. Two independent reviewers screened articles for inclusion, extracted data, and evaluated methodological quality of the trials. PEDro Scale was used to assess the quality of randomized controlled trials (RCT) and crossover studies while pre-post trials were assessed using the modified Downs and Black tool. A meta-analysis was performed to quantitatively describe the results. The random effects model was applied to present the pooled effect.

Results

Ten RCTs with a total of 222 participants and 15 pre-post trials with 967 participants were analyzed. The mean PEDro score and modified Downs and Black score was 7/10 and 6/9, respectively. The pooled standardized mean difference (SMD) for controlled and uncontrolled trials of body weight-supported training (BWST) interventions was -0.26 (95% CI, -0.70 to 0.18; p = .25) and 0.46 (95% CI, 0.33 to 0.59; p < .001), respectively. The pooled effect size of -0.98 (95% CI, -1.93 to -0.03; p = .04) indicated significant improvements in balance after a combination of BWST and stimulation. Pre-post studies analyzing the effect of virtual reality (VR) training interventions on Berg Balance Scale (BBS) scores in individuals with iSCI reported a mean difference (MD) of 4.22 (95% CI, 1.78 to 6.66; p = .0007). Small effect sizes were seen in pre-post studies of VR+stimulation and aerobic exercise training interventions indicating no significant improvements after training on standing balance measures.

Conclusion

This study demonstrated weak evidence to support the use of BWST interventions for overground training for balance rehabilitation in individuals with iSCI. A combination of BWST with stimulation however showed promising results. There is a need for further RCTs in this field to generalize findings. Virtual reality-based balance training has shown significant improvement in standing balance post iSCI. However, these results are based on single group pre-post trials and lack appropriately powered RCTs involving a larger sample size to support this intervention. Given the importance of balance control underpinning all aspects of daily activities, there is a need for further well-designed and appropriately powered RCTs to evaluate specific features of training interventions to improve standing balance function in iSCI.

Induced effects of electrical muscle stimulation and visual stimulation on visual sensory reweighting dynamics during standing on a balance board

Providing instruction cues on body motions using stimulations has the potential to induce sensory reweighting dynamics. However, there are currently very few quantitative investigations on the difference in the induced effects on the sensory reweighting dynamics between stimulation methods. We therefore investigated the difference in the induced effects of electrical muscle stimulation (EMS) and visual sensory augmentation (visual SA) on sensory reweighting dynamics during standing on a balance board. Twenty healthy participants controlled their posture to maintain the board horizontally in the balance-board task, which included a pre-test without stimulation, a stimulation test, and a post-test without stimulation. The EMS group (n = 10) received EMS to the tibialis anterior or soleus muscle based on the board tilt. The visual SA group (n = 10) received visual stimuli via a front monitor based on the board tilt. We measured the height of the board marker and calculated the board sway. Before and after the balance-board task, the participants performed static standing with their eyes open and closed. We measured postural sway and calculated the visual reweighting. The visual reweighting showed a strong negative correlation with the balance board sway ratio between the pre- and stimulation tests in the EMS group and a strong positive correlation with that in the visual SA group. Moreover, for those who reduced the balance board sway in the stimulation test, the visual reweighting was significantly different between the stimulation methods, demonstrating that the induced effect on sensory reweighting dynamics is quantitatively different depending on which method is used. Our findings suggest that there is an appropriate stimulation method to change to the targeted sensory weights. Future investigations on the relationship between sensory reweighting dynamics and stimulation methods could contribute to the proposal and implementation of new training methods for learning to control the target weights.

Walking and Balance Outcomes Are Improved Following Brief Intensive Locomotor Skill Training but Are Not Augmented by Transcranial Direct Current Stimulation in Persons With Chronic Spinal Cord Injury

Motor training to improve walking and balance function is a common aspect of rehabilitation following motor-incomplete spinal cord injury (MISCI). Evidence suggests that moderate- to high-intensity exercise facilitates neuroplastic mechanisms that support motor skill acquisition and learning. Furthermore, enhancing corticospinal drive via transcranial direct current stimulation (tDCS) may augment the effects of motor training. In this pilot study, we investigated whether a brief moderate-intensity locomotor-related motor skill training (MST) circuit, with and without tDCS, improved walking and balance outcomes in persons with MISCI. In addition, we examined potential differences between within-day (online) and between-day (offline) effects of MST. Twenty-six adults with chronic MISCI, who had some walking ability, were enrolled in a 5-day double-blind, randomized study with a 3-day intervention period. Participants were assigned to an intensive locomotor MST circuit and concurrent application of either sham tDCS (MST+tDCS_sham) or active tDCS (MST+tDCS). The primary outcome was overground walking speed measured during the 10-meter walk test. Secondary outcomes included spatiotemporal gait characteristics (cadence and stride length), peak trailing limb angle (TLA), intralimb coordination (ACC), the Berg Balance Scale (BBS), and the Falls Efficacy Scale-International (FES-I) questionnaire. Analyses revealed a significant effect of the MST circuit, with improvements in walking speed, cadence, bilateral stride length, stronger limb TLA, weaker limb ACC, BBS, and FES-I observed in both the MST+tDCS_sham and MST+tDCS groups. No differences in outcomes were observed between groups. Between-day change accounted for a greater percentage of the overall change in walking outcomes. In persons with MISCI, brief intensive MST involving a circuit of ballistic, cyclic locomotor-related skill activities improved walking outcomes, and selected strength and balance outcomes; however, concurrent application of tDCS did not further enhance the effects of MST.

Invasive and Non-Invasive Approaches of Electrical Stimulation to Improve Physical Functioning after Spinal Cord Injury

This review of literature provides the latest evidence involving invasive and non-invasive uses of electrical stimulation therapies that assist in restoring functional abilities and the enhancement of quality of life in those with spinal cord injuries. The review includes neuromuscular electrical stimulation and functional electrical stimulation activities that promote improved body composition changes and increased muscular strength, which have been shown to improve abilities in activities of daily living. Recommendations for optimizing electrical stimulation parameters are also reported. Electrical stimulation is also used to enhance the skills of reaching, grasping, standing, and walking, among other activities of daily living. Additionally, we report on the use of invasive and non-invasive neuromodulation techniques targeting improved mobility, including standing, postural control, and assisted walking. We attempt to summarize the effects of epidural stimulation on cardiovascular performance and provide a mechanistic explanation to the current research findings. Future trends such as the combination of epidural stimulation and exoskeletal-assisted walking are also discussed.

Design of an FPGA-Based Fuzzy Feedback Controller for Closed-Loop FES in Knee Joint Model

Functional electrical stimulation (FES) device has been widely used by spinal cord injury (SCI) patients in their rehab exercises to restore motor function to their paralysed muscles. The major challenge of muscle contraction induced by FES is early muscle fatigue due to the open-loop stimulation strategy. To reduce the early muscle fatigue phenomenon, a closed-loop FES system is proposed to track the angle of the limb’s movement and provide an accurate amount of charge according to the desired reference angle. Among the existing feedback controllers, fuzzy logic controller (FLC) has been found to exhibit good control performance in handling complex non-linear systems without developing any complex mathematical model. Recently, there has been considerable interest in the implementation of FLC in hardware embedded systems. Therefore, in this paper, a digital fuzzy feedback controller (FFC) embedded in a field-programmable gate array (FPGA) board was proposed. The digital FFC mainly consists of an analog-to-digital converter (ADC) Data Acquisition and FLC sub-modules. The FFC was designed to monitor and control the progress of knee extension movement by regulating the stimulus pulse width duration to meet the target angle. The knee is expected to extend to a maximum reference angle setting (70°, 40° or 30°) from its normal position of 0° once the stimulus charge is applied to the muscle by the FES device. Initially, the FLC was modelled using MATLAB Simulink. Then, the FLC was hardcoded into digital logic using hardware description language (HDL) Verilog codes. Thereafter, the performance of the digital FLC was tested with a knee extension model using the HDL co-simulation technique in MATLAB Simulink. Finally, for real-time verification, the designed digital FFC was downloaded to the Intel FPGA (DE2-115) board. The digital FFC utilized only 4% of the total FPGA (Cyclone IV E) logic elements (LEs) and required 238 µs to regulate stimulus pulse width data, including 3 µs for the FLC computation. The high processing speed of the digital FFC enables the stimulus pulse width duration to be updated every stimulation cycle. Furthermore, the implemented digital FFC has demonstrated good control performance in accurately controlling the stimulus pulse width duration to reach the desired reference angle with very small overshoot (1.4°) and steady-state error (0.4°). These promising results are very useful for a real-world closed-loop FES application.

Perspectives of individuals with chronic spinal cord injury following novel balance training involving functional electrical stimulation with visual feedback: a qualitative exploratory study

Background

Individuals with an incomplete spinal cord injury (iSCI) are highly susceptible to falls during periods of walking or standing. We recently reported the findings of a novel intervention combining functional electrical stimulation with visual feedback balance training (FES + VFBT) on standing balance abilities among five individuals with motor iSCI. However, the previous publication did not report the perceived impact of the intervention on the participants’ lives. In this report, the experiences of these five individuals with incomplete spinal cord injury (iSCI) who had recently completed the four-week balance training program are described.

Methods

Five individuals with a motor iSCI took part in this study. Each individual was at least 12 months post-injury, capable of unassisted standing for 60 s and had a Berg Balance Scale Score < 46. Participants completed twelve sessions of a novel balance intervention combining closed-loop functional electrical stimulation with visual feedback balance training (FES + VFBT). Participants received visual feedback regarding their centre of pressure position as they completed balance-training exercises while FES was applied to the ankle plantarflexors and dorsiflexors bilaterally. Semi-structured interviews were conducted after completion of the balance training intervention and eight-weeks post-training to understand participant’s experiences. Categories and themes were derived from the transcripts using conventional content analysis.

Results

Three themes were identified from the collected transcripts: (1) Perceived benefits across International Classification of Functioning, Disability and Health levels; (2) Change in perceived fall risk and confidence; (3) Motivation to keep going.

Conclusions

Participation in the FES + VFBT program resulted in perceived benefits that led to meaningful improvements in activities of daily living. Following completion of the training, individuals felt they still had the capacity to improve. Individuals felt they had increased their balance confidence, while a few participants also reported a decrease in their risk of falling. The inclusion of qualitative inquiry allows for the evaluation of the meaningfulness of an intervention and its perceived impact on the lives of the participants.

Trial registration: NCT04262414 (retrospectively registered February 10, 2020)