Functional Electrical Stimulation in Spinal Cord Injury: Clinical Evidence Versus Daily Practice

Perspectives of current and future use of electrical stimulation home-devices from people with spinal cord injuries and healthcare professionals

INTRODUCTION

Electrical stimulation (E-stim) can reduce the impact of complications, like spasticity, bladder dysfunction in people with spinal cord injuries (SCIs), enhancing quality of life and health outcomes. With SCI prevalence high in regional Australia and a shift towards home-based community integrated care, the perspectives of people with SCI and healthcare professionals on current and future use of E-stim home-devices are needed.

METHODS

A mixed-methods concurrent triangulation approach was used. A cross-sectional survey collected demographics and perspectives on E-stim technology from 84 individuals with SCI and healthcare professionals. Focus groups with 36 participants explored the experiences, facilitators, and barriers of using E-stim home-devices.

RESULTS

Healthcare professionals prioritised the use of E-stim for muscle strength and functional improvements, whereas people with SCI prioritised alleviating secondary complications. Healthcare professionals emphasised personal responsibility; however, people with SCI saw the clinical relationship as an important facilitator. Both groups agreed on the cost, accessibility, and funding as major barriers.

CONCLUSIONS

Different expectations between healthcare professionals and people with SCI highlight the need for improved communication when establishing goals and expected outcomes. Successful E-stim home-device implementation relies on device availability and tailoring education to suit people with SCI and healthcare professionals.

Integration of functional electrical stimulation during robotic-assisted intervention to increase bone mineral density in individuals with complete spinal cord injury: case report

INTRODUCTION

A spinal cord injury (SCI) leads to an alteration of the central nervous system which significantly impacts the health, function and quality of life of those affected. Since SCI leads to a loss lower limbs usage, sublesional osteoporosis is a common and established consequence with high risk of fracture in this population. The mechanical loading remains the most effective approach to stimulate physiologic bone remodeling. Furthermore, functional electrical stimulation, by producing active muscle contractions, would also increase bone mineral density. Combining functional electrical stimulation (FES) with mechanical stress during functional task such as walking or cycling would provide better results on BMD.

CASE PRESENTATION

This case report describes a 64-years old man with a chronic complete SCI (T2-T3; AIS A) who was gradually exposed to mechanical stress (walking robot, standing, bicycle) coupled with FES for 26 months. Bone mineral density of the femoral head (BMDf) was defined at 3 different time points (baseline, after 10 and 26 months). The Fracture Risk Assessment Tool (FRAX) was used to calculate T-scores based on BMDf. Before the intervention, BMDf indicated severe osteoporosis in this man. After 10 months of combined intervention, the BMDf decreased to reach the level of osteopenia after 26 months.

DISCUSSION

The implementation of an intervention combining weight-bearing during robotic-assisted walking and FES would improve bone mineral density and could reduce the risk of fracture in people with complete SCI.

Functional Electrical Stimulation (FES) in the Diagnosis and Treatment of Musculoskeletal and Neuromuscular Control Abnormalities in Horses - Selected Case Studies

When diagnosing neuromuscular injury and pain, the use of biomechanical evaluations to assess the mechanics of movement patterns has been useful in the human population. Functional electrical stimulation (FES) is a technology that can create action potentials to produce musculoskeletal movement that is almost indistinguishable from the voluntary kinematics produced by the nervous system. To create controlled and precise musculoskeletal movements in humans and in horses, FES has been shown to be effective. In humans, the kinematic information obtained from FES data has been utilized to direct further diagnostics, and/or to assist in the development of specific treatment protocols. In addition, since FES creates dynamic movement while in a static position, the ability to isolate the regions of dysfunction improves without the confounding factors of over-the-ground movement and other artifacts caused by environmental stimuli. This paper explores the transfer of the use of FES in human diagnostics to clinical use in horses. Three equine case studies discuss how FES was employed as a tool in the diagnosis and treatment of equine musculoskeletal and neuromuscular control disorders.

The effects of cycling using lower limb active passive trainers in people with neurological conditions: a systematic review

Background Active passive trainers are frequently used as a safe, feasible way for people with neurological disabilities to exercise. However, evidence regarding their efficacy is limited. The aim of this study was to review the literature investigating the effects of lower limb active passive trainer cycling, with or without functional electrical stimulation, on spasticity, cardiovascular fitness, function and quality of life in people with neurological conditions

Methods Five electronic databases were searched from inception to June 2021. Studies included: randomised controlled trials using lower limb active passive trainers as a cycling intervention; participants with neurological conditions, such as multiple sclerosis, spinal cord injury, stroke and Parkinson's disease; and at least one outcome related to spasticity, cardiovascular fitness, physical function or quality of life.

Results A total of 12 articles were included (n=423 participants, 52% male). Of these, six used functional electrical stimulation-assisted active passive trainer interventions, and the remaining six used active passive trainer interventions alone. A meta-analysis demonstrated statistically significant improvement in walking endurance; however, this only included stroke studies (6-Minute Walk Test performance, P<0.00001). No statistically significant improvement in walking speed was found (P=0.31). A significant improvement in spasticity was reported by three studies (two using the active passive trainer intervention alone, one using the active passive trainer with functional electrical stimulation). One study reported improvement in quality of life. Few studies considered cardiovascular fitness.

Conclusions The included studies featured heterogeneous designs, outcome measures, exercise prescriptions and participant disability levels, which made comparison difficult. Active passive trainer interventions appear to improve walking endurance in people with stroke; however, the effect on other outcomes and in other conditions remains unclear. It also remains uncertain as to whether functional electrical stimulation-assisted cycling is more beneficial than active passive trainer cycling alone.

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.

Home-Based Functional Electrical Stimulation of Human Permanent Denervated Muscles: A Narrative Review on Diagnostics, Managements, Results and Byproducts Revisited 2020

Spinal cord injury (SCI) produces muscle wasting that is especially severe after complete and permanent damage of lower motor neurons, as can occur in complete conus and cauda equina syndrome. Even in this worst-case scenario, mass and function of permanently denervated quadriceps muscle can be rescued by surface functional electrical stimulation using a purpose designed home-based rehabilitation strategy. Early diagnostics is a key factor in the long-term success of this management. Function of quadriceps muscle was quantitated by force measurements. Muscle gross cross-sections were evaluated by quantitative color computed tomography (CT) and muscle and skin biopsies by quantitative histology, electron microscopy, and immunohistochemistry. Two years of treatment that started earlier than 5 years from SCI produced: (a) an increase in cross-sectional area of stimulated muscles; (b) an increase in muscle fiber mean diameter; (c) improvements in ultrastructural organization; and (d) increased force output during electrical stimulation. Improvements are extended to hamstring muscles and skin. Indeed, the cushioning effect provided by recovered tissues is a major clinical benefit. It is our hope that new trials start soon, providing patients the benefits they need.

Treatment and cost of pressure injury stage III or IV in four patients with spinal cord injury: the Basel Decubitus Concept

Study design

Retrospective chart analyses as part of a quality improvement project.

Objectives

To demonstrate treatment of pressure injury (PI) in patients with spinal cord injuries (SCI) and analyse costs using the "modified Basel Decubitus Concept".

Setting

Inpatient setting of a specialised acute care and rehabilitation clinic for SCI.

Methods

Complex treatment courses of four patients with chronic SCI and PI stage III or IV were described and costs were recorded. The total healthcare services' costs per patient and different profession's involvement were analysed in relation to patient characteristics, treatment phases and milestones demonstrated.

Results

The treatment of PI stage III and IV in patients with SCI included input from plastic surgery, rehabilitation medicine, nursing and other involved professions. Recommended interventions were chosen according to the "modified Basel Decubitus Concept". The cost course of PI treatment in patients with SCI depicted the multimodal treatment concept, including three clinically and financially relevant milestones (debridement, flap surgery and mobilisation to wheelchair) as well as the highest costs in the functionally highly dependent patient. Acute care and rehabilitation overlapped with different intensities during the whole treatment process.

Conclusion

Multimodal treatment concepts connecting acute and rehabilitation care were applied in these complex health conditions. Cost-explication models including treatment phases and milestones helped to understand resources more easily and integrate aspects of process-based management and quality of care. Scientific evidence is needed to create a recommended quality standard in line with adequate financing of this health condition.

Development of a battery-free ultrasonically powered functional electrical stimulator for movement restoration after paralyzing spinal cord injury

BACKGROUND

Functional electrical stimulation (FES) is used to restore movements in paretic limbs after severe paralyses resulting from neurological injuries such as spinal cord injury (SCI). Most chronic FES systems utilize an implantable electrical stimulator to deliver a small electric current to the targeted muscle or nerve to stimulate muscle contractions. These implanted stimulators are generally bulky, mainly due to the size of the batteries. Furthermore, these battery-powered stimulators are required to be explanted every few years for battery replacement which may result in surgical failures or infections. Hence, a wireless power transfer technique is desirable to power these implantable stimulators.

METHODS

Conventional wireless power transduction faces significant challenges for safe and efficient energy transfer through the skin and deep into the body. Inductive and electromagnetic power transduction is generally used for very short distances and may also interfere with other medical measurements such as X-ray and MRI. To address these issues, we have developed a wireless, ultrasonically powered, implantable piezoelectric stimulator. The stimulator is encapsulated with biocompatible materials.

RESULTS

The stimulator is capable of harvesting a maximum of 5.95 mW electric power at an 8-mm depth under the skin from an ultrasound beam with about 380 mW/cm2 of acoustic intensity. The stimulator was implanted in several paraplegic rats with SCI. Our implanted stimulator successfully induced several hindlimb muscle contractions and restored leg movement.

CONCLUSIONS

A battery-free miniature (10 mm diameter × 4 mm thickness) implantable stimulator, developed in the current study is capable of directly stimulating paretic muscles through external ultrasound signals. The required cost to develop the stimulator is relatively low as all the components are off the shelf.

Stimulation of paralysed quadriceps muscles with sequentially and spatially distributed electrodes during dynamic knee extension

BACKGROUND

During functional electrical stimulation (FES) tasks with able-bodied (AB) participants, spatially distributed sequential stimulation (SDSS) has demonstrated substantial improvements in power output and fatigue properties compared to conventional single electrode stimulation (SES). The aim of this study was to compare the properties of SDSS and SES in participants with spinal cord injury (SCI) in a dynamic isokinetic knee extension task simulating knee movement during recumbent cycling.

METHOD

Using a case-series design, m. vastus lateralis and medialis of four participants with motor and sensory complete SCI (AIS A) were stimulated for 6 min on both legs with both electrode setups. With SES, target muscles were stimulated by a pair of electrodes. In SDSS, the distal electrodes were replaced by four small electrodes giving the same overall stimulation frequency and having the same total surface area. Torque was measured during knee extension by a dynamometer at an angular velocity of 110 deg/s. Mean power of the left and right sides (P_meanL,R) was calculated from all stimulated extensions for initial, final and all extensions. Fatigue is presented as an index value with respect to initial power from 1 to 0, whereby 1 means no fatigue.

RESULTS

SDSS showed higher P_meanL,R values for all four participants for all extensions (increases of 132% in participant P1, 100% in P2, 36% in P3 and 18% in P4 compared to SES) and for the initial phase (increases of 84%, 59%, 66%, and 16%, respectively). Fatigue resistance was better with SDSS for P1, P2 and P4 but worse for P3 (0.47 vs 0.35, 0.63 vs 0.49, 0.90 vs 0.82 and 0.59 vs 0.77, respectively).

CONCLUSION

Consistently higher P_meanL,R was observed for all four participants for initial and overall contractions using SDSS. This supports findings from previous studies with AB participants. Fatigue properties were better in three of the four participants. The lower fatigue resistance with SDSS in one participant may be explained by a very low muscle activation level in this case. Further investigation in a larger cohort is warranted.

Myokines in Home-Based Functional Electrical Stimulation-Induced Recovery of Skeletal Muscle in Elderly and Permanent Denervation

Neuromuscular disorders, disuse, inadequate nutrition, metabolic diseases, cancer and aging produce muscle atrophy and this implies that there are different types of molecular triggers and signaling pathways for muscle wasting. Exercise and muscle contractions may counteract muscle atrophy by releasing a group of peptides, termed myokines, to protect the functionality and to enhance the exercise capacity of skeletal muscle. In this review, we are looking at the role of myokines in the recovery of permanent denervated and elderly skeletal muscle tissue. Since sub-clinical denervation events contribute to both atrophy and the decreased contractile speed of aged muscle, we saw a parallel to spinal cord injury and decided to look at both groups together. The muscle from lifelong active seniors has more muscle bulk and more slow fiber-type groupings than those of sedentary seniors, demonstrating that physical activity maintains slow motoneurons that reinnervate the transiently denervated muscle fibers. Furthermore, we summarized the evidence that muscle degeneration occur with irreversible Conus and Cauda Equina syndrome, a spinal cord injury in which the human leg muscles may be permanently disconnected from the peripheral nervous system. In these patients, suffering with an estreme case of muscle disuse, a complete loss of muscle fibers occurs within five to ten years after injury. Their recovered tetanic contractility, induced by home-based Functional Electrical Stimulation, can restore the muscle size and function in compliant Spinal Cord Injury patients, allowing them to perform electrical stimulation-supported stand-up training. Myokines are produced and released by muscle fibers under contraction and exert both local and systemic effects. Changes in patterns of myokine secretion, particularly of IGF-1 isoforms, occur in long-term Spinal Cord Injury persons and also in very aged people. Their modulation in Spinal Cord Injury and late aging are also key factors of home-based Functional Electrical Stimulation - mediated muscle recovery. Thus, Functional Electrical Stimulation should be prescribed in critical care units and nursing facilities, if persons are unable or reluctant to exercise. This will result in less frequent hospitalizations and a reduced burden on patients' families and public health services.

To Contrast and Reverse Skeletal Muscle Atrophy by Full-Body In-Bed Gym, a Mandatory Lifestyle for Older Olds and Borderline Mobility-Impaired Persons

Older olds, that is octogenarians, spend small amounts of time for daily physical activity, contributing to aggravate their independence limitations up to force them to bed and to more and more frequent hospitalizations. All progressive muscle contractile impairments, including advanced age-related muscle power decline, need permanent management. Inspired by the proven capability to recover skeletal muscle contractility and strength by home-based functional electrical stimulation and guided by common sense, we suggested to older olds a 15-30 min daily routine of 12 easy and safe physical exercises. Since persons can do many of them in bed (full-body in-bed gym), hospitalized elderly can continue this kind of light training that is an extension of the well-established cardiovascular-ventilation rehabilitation before and after admission. Monitoring arterial blood pressure before and after the daily routine demonstrates that peripheral resistance decreases in a few minutes by the functional hyperemia of the trained body muscles. Continued regularly, full-body in-bed gym helps to maintain the independence of frail older people and may reduce the risks of serious consequences of accidental falls.

Recovery from muscle weakness by exercise and FES: lessons from Masters, active or sedentary seniors and SCI patients

Many factors contribute to the decline of skeletal muscle that occurs as we age. This is a reality that we may combat, but not prevent because it is written into our genome. The series of records from World Master Athletes reveals that skeletal muscle power begins to decline at the age of 30 years and continues, almost linearly, to zero at the age of 110 years. Here we discuss evidence that denervation contributes to the atrophy and slowness of aged muscle. We compared muscle from lifelong active seniors to that of sedentary elderly people and found that the sportsmen have more muscle bulk and slow fiber type groupings, providing evidence that physical activity maintains slow motoneurons which reinnervate muscle fibers. Further, accelerated muscle atrophy/degeneration occurs with irreversible Conus and Cauda Equina syndrome, a spinal cord injury in which the human leg muscles may be permanently disconnected from the nervous system with complete loss of muscle fibers within 5-8 years. We used histological morphometry and Muscle Color Computed Tomography to evaluate muscle from these peculiar persons and reveal that contraction produced by home-based Functional Electrical Stimulation (h-bFES) recovers muscle size and function which is reversed if h-bFES is discontinued. FES also reverses muscle atrophy in sedentary seniors and modulates mitochondria in horse muscles. All together these observations indicate that FES modifies muscle fibers by increasing contractions per day. Thus, FES should be considered in critical care units, rehabilitation centers and nursing facilities when patients are unable or reluctant to exercise.

Effect of tendon vibration during wide-pulse neuromuscular electrical stimulation (NMES) on the decline and recovery of muscle force

BACKGROUND

Neuromuscular electrical stimulation (NMES) is commonly used to activate skeletal muscles and reverse muscle atrophy in clinical populations. Clinical recommendations for NMES suggest the use of short pulse widths (100-200 μs) and low-to-moderate pulse frequencies (30-50 Hz). However, this type of NMES causes rapid muscle fatigue due to the (non-physiological) high stimulation intensities and non-orderly recruitment of motor units. The use of both wide pulse widths (1000 μs) and tendon vibration might optimize motor unit activation through spinal reflex pathways and thus delay the onset of muscle fatigue, increasing muscle force and mass. Thus, the objective of this study was to examine the acute effects of patellar tendon vibration superimposed onto wide-pulse width (1000 μs) knee extensor electrical stimulation (NMES, 30 Hz) on peak muscle force, total impulse before "muscle fatigue", and the post-exercise recovery of muscle function.

METHODS

Tendon vibration (Vib), NMES (STIM) or NMES superimposed onto vibration (STIM + Vib) were applied in separate sessions to 16 healthy adults. Total torque-time integral (TTI), maximal voluntary contraction torque (MVIC) and indirect measures of muscle damage were tested before, immediately after, 1 h and 48 h after each stimulus.

RESULTS

TTI increased (145.0 ± 127.7%) in STIM only for "positive responders" to the tendon vibration (8/16 subjects), but decreased in "negative responders" (-43.5 ± 25.7%). MVIC (-8.7%) and rectus femoris electromyography (RF EMG) (-16.7%) decreased after STIM (group effect) for at least 1 h, but not after STIM + Vib. No changes were detected in indirect markers of muscle damage in any condition.

CONCLUSIONS

Tendon vibration superimposed onto wide-pulse width NMES increased TTI only in 8 of 16 subjects, but reduced voluntary force loss (fatigue) ubiquitously. Negative responders to tendon vibration may derive greater benefit from wide-pulse width NMES alone.

Atrophy, ultra-structural disorders, severe atrophy and degeneration of denervated human muscle in SCI and Aging. Implications for their recovery by Functional Electrical Stimulation, updated 2017

OBJECTIVES

Long-term lower motor neuron denervation of skeletal muscle is known to result in degeneration of muscle with replacement by adipose and fibrotic tissues. However, long-term survival of a subset of skeletal myofibers also occurs.

METHODS

We performed transverse and longitudinal studies of patients with spinal cord injury (SCI), patients specifically complete Conus and Cauda Equina Syndrome and also of active and sedentary seniors which included analyses of muscle biopsies from the quadriceps m.

RESULTS

Surprisingly, we discovered that human denervated myofibers survive years of denervation after full and irreversible disconnection from their motor neurons. We found that atrophic myofibers could be rescued by home-based Functional Electrical Stimulation (h-bFES), using purpose developed stimulators and electrodes. Although denervated myofibers quickly lose the ability to sustain high-frequency contractions, they respond to very long impulses that are able to allow for re-emergence of tetanic contractions. A description of the early muscle changes in humans are hampered by a paucity of patients suffering complete Conus and Cauda Equina Syndrome, but the cohort enrolled in the EU RISE Project has shown that even five years after SCI, severe atrophic myofibers with a peculiar cluster reorganization of myonuclei are present in human muscles and respond to h-bFES.

CONCLUSIONS

Human myofibers survive permanent denervation longer than generally accepted and they respond to h-bFES beyond the stage of simple atrophy. Furthermore, long-term denervation/reinnervation events occur in elderly people and are part of the mechanisms responsible for muscle aging and again h-bFES was beneficial in delaying aging decay.

Artificial Organs 2015: A Year in Review

In this Editor's Review, articles published in 2015 are organized by category and briefly summarized. We aim to provide a brief reflection of the currently available worldwide knowledge that is intended to advance and better human life while providing insight for continued application of technologies and methods of organ Replacement, Recovery, and Regeneration. As the official journal of The International Federation for Artificial Organs, The International Faculty for Artificial Organs, the International Society for Rotary Blood Pumps, the International Society for Pediatric Mechanical Cardiopulmonary Support, and the Vienna International Workshop on Functional Electrical Stimulation, Artificial Organs continues in the original mission of its founders "to foster communications in the field of artificial organs on an international level." Artificial Organs continues to publish developments and clinical applications of artificial organ technologies in this broad and expanding field of organ Replacement, Recovery, and Regeneration from all over the world. We take this time also to express our gratitude to our authors for providing their work to this journal. We offer our very special thanks to our reviewers who give so generously of their time and expertise to review, critique, and especially provide meaningful suggestions to the author's work whether eventually accepted or rejected. Without these excellent and dedicated reviewers, the quality expected from such a journal could not be possible. We also express our special thanks to our Publisher, John Wiley & Sons for their expert attention and support in the production and marketing of Artificial Organs. We look forward to reporting further advances in the coming years.