[066] EFFICACY OF NEUROMUSCULAR STIMULATION IN ENHANCING THE UPPER EXTREMITY MOTOR AND FUNCTIONAL RECOVERY OF ACUTE STROKE SURVIVORS
John Chae, MD; Francois Bethoux, MD
Cleveland FES Center, Cleveland, OH 44106; Center for
Physical Medicine and Rehabilitation, Case Western Reserve
University, Cleveland, OH 4410; MetroHealth Medical Center,
Cleveland, OH 44109; email: jchae@metrohealth.org
Sponsor: National Institutes of Health, Bethesda, MD 20892; New Investigator Award, PM&R-Education and Research Foundation, Dallas, Texas; VA Center of Excellence in FES, Cleveland VA Medical Center, Cleveland OH 44106-1702
PURPOSE --The purpose of this double blind, placebo-controlled, randomized trial is to assess the efficacy of surface neuromuscular stimulation in enhancing the upper limb motor and functional recovery of acute stroke survivors.
METHODOLOGY--Stroke survivors admitted to an inpatient stroke rehabilitation program within 6 weeks of their acute stroke were randomly assigned to treatment or placebo group. Motor status at entry was limited to synergy movements or if isolated movement was present, wrist extension muscle grade was less than antigravity strength. The treatment group received 1 hr of surface electrical stimulation to the finger and wrist extensors per day, 5 times a week for 3 weeks. Stimulation parameters were adjusted for patient comfort and full wrist extension range of motion. The control group received electrical stimulation away from the motor point of the wrist and finger extensors, with intensity adjusted to just above sensory threshold. Outcomes were assessed at end of treatment, 1 mo post-treatment, and 3 mo post-treatment with the self-care component of the Functional Independence Measure and the upper extremity component of the Fugl-Meyer Motor Assessment in a blinded manner.
PROGRESS--A total of 46 subjects were enrolled, and 28 completed the study.
RESULTS--The treatment and control subjects had comparable baseline characteristics. Parametric analyses revealed significantly greater gains in Fugl-Meyer scores for the treatment group at post-treatment (13.1 vs. 6.5; p=0.05), at 1 mo post-treatment (17.9 vs. 9.7; p=0.05) and at 3 mo post-treatment (20.6 vs. 11.2; p=0.06). FIM scores were not different between groups at any of the time periods (p>0.10).
IMPLICATIONS--Data suggest that active repetitive movement training induced by neuromuscular stimulation enhances the motor recovery of acute stroke survivors. However, the study failed to demonstrate any functional benefit as reflected by the self-care component of the FIM.
[067] COMPARISON OF DISCOMFORT ASSOCIATED WITH PERCUTANEOUS AND SURFACE NEUROMUSCULAR STIMULATION
John Chae, MD; Ronald Hart, MSE
Cleveland VA Medical Center, Cleveland OH 44106;
Cleveland FES Center, Cleveland, OH 44106; Center for
Physical Medicine and Rehabilitation, Case Western Reserve
University, Cleveland, OH 4410; MetroHealth Medical Center,
Cleveland, OH 44109; email: jchae@metrohealth.org;
rlhart@metrohealth.org
Sponsor: Rehabilitation Medicine Scientist Development Program, National Institutes of Health-NICHD, Bethesda, MD 20892; VA Center of Excellence in FES, Cleveland VA Medical Center, Cleveland OH 44106-1702
PURPOSE--Surface neuromuscular stimulation has been shown to have both therapeutic and functional benefits for stroke survivors. However, associated pain limits its implementation in the clinical setting. Percutaneous intramuscular stimulation may be better tolerated since pain fibers on the skin are not stimulated. The purpose of this study is to compare the level of pain or discomfort associated with percutaneous and surface neuromuscular stimulation in chronic stroke survivors with intact sensation.
METHODOLOGY--The Extensor digitorum communis (EDC) of six subjects with chronic hemiplegia and intact sensation were stimulated with percutaneous and surface electrodes. All subjects were beyond 6 mo from their index event, and were medically and neurologically stable. Percutaneous electrodes were of helical configuration, wound from FEP-Teflon insulated, multistranded, type 316L stainless steel wires with a stimulation surface of 10 mm2. A balanced biphasic, cathodic-first, capacitively coupled, constant-current pulse was applied. The amplitude and frequency were maintained at 20 mA and 16 Hz, respectively. Intensity of stimulation was modulated by varying the pulse width from 0 to 200 µs; Empi® 31.75-mm reusable gel electrodes were used for surface stimulation. A symmetric biphasic waveform with pulse duration of 300 µs was applied at 25 Hz. Intensity of stimulation was modulated by varying the pulse amplitude from 0 to 100 mA. All pain measurements were taken with a 10 cm visual analogue scale and the McGill Pain Questionnaire. Measurements were taken during surface and percutaneous stimulation of the EDC, with the index finger in 45° flexion, and constant extensor moment maintained at the metacarpalphalangeal joint. The constant extensor moment was defined as 75 percent of the lower of the 2 maximum moments generated by percutaneous or surface simulation. Three pairs of percutaneous- and surface electrode-induced pain measurements were taken per subject. Subjects were asked to describe the nature of their pain with each electrode type, and to choose the electrode type they prefer for long-term stimulation. All data were analyzed with parametric and nonparametric paired statistics.
RESULTS--Percutaneous stimulation was associated with significantly lower discomfort as reflected by the visual analogue scale (0.74 vs. 3.30; 95 percent CI of difference: -3.84, -1.28). The McGill Pain Questionnaire produced similar results with percutaneous stimulation associated with significantly fewer number of words chosen to describe the discomfort (0.87 vs. 3.30; 95 percent CI of difference: -3.50, -1.30) and significantly lower Pain Rating Index (1.47 vs. 6.27; 95 percent CI of difference: -7.77, -1.83).
IMPLICATIONS--Percutaneous neuromuscular stimulation is well tolerated by chronic survivors with intact sensation. The degree of pain is significantly lower compared to surface stimulation, and may enhance patient acceptance and compliance.
[068] ELECTROSTIMULATION FOR STROKE REHABILITATION: MECHANISMS AND EFFECT
John Chae, MD; Robert Ruff, MD, PhD; Eric Wasserman, MD;
Shu Huang, MD; Zi-Ping Fang, PhD
Cleveland VA Medical Center, Cleveland OH 44106;
Cleveland FES Center, Cleveland, OH 44106; Center for
Physical Medicine and Rehabilitation, Case Western Reserve
University, Cleveland, OH 4410; MetroHealth Medical Center,
Cleveland, OH 44109; NIH-NINDS Bethesda, MD 20892;
NeuroControl Corporation, Cleveland, OH 44106; email:
jchae@metrohealth.org
Sponsor: National Institutes of Health, Bethesda, MD 20892; VA Center of Excellence in FES, Cleveland VA Medical Center, Cleveland OH 44106-1702
PURPOSE--The aims of this project are to assess the efficacy of EMG-controlled neuromuscular stimulation in enhancing the upper-extremity motor recovery of chronic stroke survivors, and to determine whether EMG-controlled neuromuscular stimulation mediates its effect on motor recovery via central mechanisms.
METHODOLOGY--Phase I of the study will identify neurophysiologic measures of brain function that correlate with objective measures of motor impairment. Chronic stroke survivors will be evalutated with objective measures of motor impairment (active range of motion, joint torques, Fugl-Meyer Motor Assessment, and EMG initiation and termination characteristics) and neurophysiologic measures of central motor function (Single Photon Emission Computed Tomography, Transcortical Magnetic Stimulation, and Somatosensory Evoked Potentials).
Phase II will consist of a single-blinded, randomized clinical trial to assess the effects of EMG-controlled neuromuscular stimulation on objective measures of motor impairment and measures of central motor function identified in phase I.
PROGRESS--A total of 20 chronic stroke survivors will enrolled in phase I over a 2-year period, and 34 chronic stroke survivors in phase II over a 3-year period.
IMPLICATIONS--This study will demonstrate that EMG-controlled neuromuscular stimulation enhances the motor recovery of chronic stroke survivors, and that the motor recovery is mediated by central mechanisms. The proposed intervention may be effective for acute stroke survivors and persons with other forms of cerebral motor dysfunction such as traumatic brain injury, cerebral palsy, and multiple sclerosis. EMG-controlled neuromuscular stimulation may also be effective for lower limb motor recovery. Finally, techniques developed for assessing central motor function may be useful for evaluating other interventions directed at stroke rehabilitation.
[069] FEASIBILITY OF A NEUROPROSTHESIS IN HIGH TETRAPLEGIA: DENERVATION AND ELECTRICAL EXCITABILITY OF UPPER LIMB MUSCLES
David Yu, MD; Robert Kirsch, PhD
Cleveland FES Center, Case Western Reserve University,
Department of Physical Medicine and Rehabilitation,
MetroHealth Medical Center, 2500 MetroHealth Blvd.,
Cleveland, OH 44109; email: dyu@metrohealth.org
Sponsor: National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892; Spinal Cord Research Foundation, Paralyzed Veterans of America, Washington, DC, 20006; VA Center of Excellence in FES, Cleveland VA Medical Center, Cleveland, OH 44106-1702
PURPOSE--A neuroprosthesis for high tetraplegia (i.e., C4 and above) is feasible only if upper limb muscles can generate adequate force during neuromuscular electrical stimulation (NMES). The electrical excitability of these muscles is questionable due to potential denervation (i.e., loss of motor units supplying a muscle). The purpose of this study is to determine whether functional upper limb joint moments can be generated with NMES of conditioned muscles; to evaluate the extent and pattern of upper limb denervation; and to identify parameters that can potentially predict whether a muscle will generate adequate force after conditioning.
METHODOLOGY--We shall recruit 20 subjects with high tetraplegia for this study. Two muscles supplied by different peripheral nerves in each myotome from C4 to T1 will be studied (C4: Levator Scap, Trapezius; C5: Deltoid, Biceps, Infraspinatus; C6: ECRB, Pronator Ter; C7: Triceps, Pectoralis Maj; C8: Ext Ind Prop, FDP III; T1: 1st Dorsal Int, Abd Pol Brev). Three muscles are listed for the C5 myotome because the feasibility criteria include 2 shoulder and 1 elbow movement, powered by primary movers with predominantly C5 innervation. The degree of spontaneous activity for each muscle will be assessed by standard needle electromyography (EMG) and graded on a 5-point scale. Percutaneous intramuscular electrodes will be implanted into all muscles listed above, except the first dorsal interosseus and abductor pollicis brevis (the maintenance of percutaneous electrodes in hand muscles is technically difficult.)
In all muscles implanted with electrodes, supramaximal compound muscle action potentials will be recorded from surface electrodes during motor point stimulation. All muscles implanted with percutaneous electrodes will undergo strength testing during electrically induced contraction both before and after a 6-week NMES conditioning protocol. Strength testing will consist of NMES induced range of motion and joint moment measurements, using specially designed equipment.
A neuroprosthesis will be considered feasible for individual subjects if 45° of shoulder flexion against gravity, 135° of elbow flexion against gravity, 90° of shoulder abduction against gravity, 30° of shoulder external rotation against gravity (i.e., shoulder abducted to 90°) and 90° of elbow extension without gravity can be achieved in one limb during NMES. The percentage of subjects meeting the feasibility criteria for each injury level will be reported. To determine the extent and pattern of denervation, the degree of spontaneous activity in each myotome from C4 to T1 will be tabulated for each level of spinal cord injury (SCI). Mean and standard deviations for the number of denervated spinal segments will be calculated. Multiple regression analysis will be used to compare post-conditioning maximum joint moments and a number of variables including SA, CMAP, age, weight, and duration of SCI identify parameters that can potentially predict post-conditioning muscle strength and ultimately may be used to select individuals that could benefit from a neuroprosthesis.
PROGRESS--One subject with C3 complete tetraplegia has been enrolled in this study, for whom some qualitative data are available. Initial EMG revealed mild denervation in the C4 and C5 myotomes and moderate denervation in the C8 and T1 myotomes. Percutaneous, intramuscular electrodes were implanted into the biceps, triceps, pectoralis major, latissimus dori, posterior deltoid, anterior deltoid, and infraspinatus muscles. Muscle contraction during NMES was visible in all muscles prior to NMES conditioning. Following 6 weeks of NMES conditioning, the subject was able to draw his hand to his mouth and feed himself, using a universal cuff and balanced forearm orthosis. Elevation of the opposite shoulder was used to control pre-programmed stimulation of the implanted muscles.
[070] MUSCULAR FACTORS PREVENTING INFERIOR SUBLUXATION OF THE SHOULDER IN HEMIPLEGIA
David Yu, MD; John Chae, MD
Cleveland FES Center, Case Western Reserve University,
Department of Physical Medicine and Rehabilitation,
MetroHealth Medical Center, 2500 MetroHealth Blvd.
Cleveland, OH 44109; email: dyu@metrohealth.org
Sponsor: National Institute on Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892; VA Center of Excellence in FES, Cleveland VA Medical Center, Cleveland, OH 44106-1702; NeuroControl Corporation, Valley View, OH 44125
PURPOSE--Neuromuscular electrical stimulation (NMES) has been shown to reduce glenohumeral subluxation resulting from upper motor neuron paralysis of the shoulder musculature after stroke. Previous studies have targeted the supraspinatus and posterior deltoid muscles, based on a study by Basmajian who demonstrated the greatest electromyographic (EMG) activity in these muscles during traction to the upper limb in control subjects. Because of physiological differences between hemiplegic and control subjects and the lack of a linear correlation between EMG activity and muscle force generation, the supraspinatus and posterior deltoid may not be the optimal target muscles for this application. This study will investigate an alternative paradigm.
METHODOLOGY--In five subjects with hemiplegia and clinical shoulder subluxation, up to 15 motor points of 11 muscles of the shoulder were stimulated with a monopolar EMG needle electrode. Joint reduction was measured by palpation in all five subjects and by a radiographic technique described by Prevost in two. In all five subjects stimulation of the posterior deltoid, middle deltoid, and coracobrachialis resulted in complete joint reduction. Stimulation of the supraspinatus resulted in joint reduction in only two of the five subjects. Stimulation of the biceps long head resulted in joint reduction in two of the subjects but was associated with undesirable elbow flexion. Stimulation of the triceps long head resulted in complete joint reduction in one subject without causing unwanted elbow extension. Stimulation of scapular stabilizers did not result in joint reduction independently and did not improve joint reduction when stimulated in combination with other muscles but was nevertheless felt to be important for treatment of subluxation.
PROGRESS--The supraspinatus and posterior deltoid may not be the primary muscular factors preventing inferior shoulder subluxation in hemiplegia. Further studies are needed and should consider synergistic effects during combined muscle stimulation and take into account subluxation in the anterior-posterior dimension.
[071] MICROSTIMULATION OF THE LUMBOSACRAL SPINAL CORD: MAPPING
Warren M. Grill, PhD; Musa Haxhiu, MD, PhD
Cleveland FES Center and Departments of Biomedical
Engineering and Medicine, Case Western Reserve University,
Cleveland OH 44106-4912; email: wmg@po.cwru.edu
Sponsor: National Institutes of Health, National Institute of Neurological Disorders and Stroke, Neural Prosthesis Program; Department of Veterans Affairs Center of Excellence in FES, Cleveland VA Medical Center, Cleveland OH 44106-1702
PURPOSE--The long-term goal of this research program is to develop advanced neural prostheses based on microstimulation of the spinal cord. The objectives of this project are to identify spinal cord neurons that regulate genitourinary and hindlimb motor functions, and to measure the physiological effects in the genitourinary and motor systems of intraspinal microstimulation of different populations of neurons.
METHODOLOGY--Expression of the c-fos gene-encoded protein was used to identify sacral spinal neurons active during reflex micturition, and co-localization with parvalbumin (PV), a calcium-binding protein present in GABAergic neurons, was used to identify putative inhibitory neurons. Adult male cats were anesthetized with alpha-chloralose and underwent a 2 hr period of isometric micturition induced by ligating the proximal urethra and infusing saline into the bladder until spontaneous periodic bladder contractions occurred. Double immunocytochemical labeling was used to define co-expression of c-Fos with PV. Operated unstimulated controls exhibited few neurons expressing c-Fos, localized to the superficial dorsal horn (laminae I and II). In stimulated animals, neurons expressing c-Fos were found bilaterally in S1-S3 and localized to the lateral portion of the superficial dorsal horn (laminae I and II), the intermediolateral region (lateral laminae V-VII), and around the central canal (lamina X and medial laminae V-VII). The number of neurons expressing only c-Fos immunoreactivity (463), only PV immunoreactivity (119), or immunoreactivity for both c-Fos and PV (25) were counted in 3 sections from each of 3 animals. Within the three regions where neurons exhibiting c-Fos immunoreactivity were identified, only 25/463 cells (5 percent) also expressed PV. Cells co-localizing both PV and c-Fos were found mostly around the central canal, with fewer double labeled cells in the intermediolateral region, and none in the dorsal horn. These results indicate that a relatively small sub-population of neurons activated during reflex micturition express GABAergic traits.
PROGRESS--During the past year, progress has been made in two primary areas of mapping the location and neurochemical identity of neurons active during micturition and mapping the hindlimb motor responses evoked by microstimulation of the lumbar spinal cord.
RESULTS--Experiments were conducted to map systematically the hindlimb motor responses evoked by stimulation of the lumbar segments in neurologically intact, chloralose-anesthetized adult cats. The isometric torque generated about the knee joint and intramuscular EMGs from knee flexors and extensors were recorded in response to intraspinal stimuli (1 s, 20 Hz, 100 µA, 100 µs) applied with activated iridium microwire electrodes. Torque maps were repeatable, with a strong congruence between the spatial patterns of torque generation across experiments and similar relative magnitudes of flexion and extension torques. At L6 and L7, stimulation in the ipsilateral dorsal aspect of the cord produced strong flexion torques. Weaker flexion torques were also produced by microstimulation at the lateral aspect of the intermediate region. Stimulation in the contralateral dorsal horn produced extension torques. In the ipsilateral ventral horn, extension torques were produced at locations that were lateral to locations producing flexion torques, and stronger flexion torques were produced by microstimulation over a larger area in L7 than in L6. These results demonstrate segregation of responses in the ventral horn that correlate with previous anatomical studies, and suggest that stimulation in the dorsal aspect of the cord generated electrically two classical spinal reflexes: ipsilateral flexion (flexion withdrawal) and contralateral extension (crossed extension).
IMPLICATIONS--The results of this project are fundamental advances in knowledge about the innervation and neural control of the genitourinary and motor systems. These advances will make possible the development of neural prostheses based on microstimulation of the spinal cord.
[072] EMG-CONTROLLED STIMULATOR FOR STROKE REHABILITATION
Zi-Ping Fang, PhD; Soheyl Pourmehdi, PhD; John Chae,
MD
NeuroControl Corporation Cleveland, OH 44106; Cleveland
FES Center, Case Western Reserve University, MetroHealth
Medical Center, Cleveland, OH 44109
Sponsor: National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892; VA Center of Excellence in FES, Cleveland VA Medical Center, Cleveland, OH 44106-1702
PURPOSE--The general purpose of this project is to develop a device for facilitating motor relearning for stroke survivors. The device will detect weak electromyographic (EMG) signals generated by a paretic muscle and consequently deliver stimulation currents to the same muscle to result in its strong contraction. The device will consist of a set of electrodes for sensing and stimulation and electronic circuitry for signal processing and stimulus generation.
METHODOLOGY--During Phase I, we shall pursue the following objectives to produce and assess a pre-prototype device: first, we shall develop a tripolar intramuscular electrode that is suitable for both EMG sensing and muscle stimulation. The electrode should have a diameter small enough to be loaded into a 19-gauge hypodermic needle for percutaneous implantation. It should be durable enough to withstand muscle contraction without breakage for at least 4 weeks, and sufficiently flexible and include an anchoring mechanism capable of maintaining the intended position for the same period.
Then we shall develop electronic circuits that, when connected to the tripolar intramuscular electrode, can reliably detect EMG signals and deliver stimulation pulses to the target muscle. The detecting circuitry should be able to detect very weak EMG signals, in the order of 1 µV in a paretic muscle, while having high immunity to the very strong stimulation artifact generated by the stimulus current. The stimulation circuitry should be able to generate charge-balanced, current-regulated, biphasic pulses for safe and effective intramuscular stimulation.
Finally, we shall evaluate the performance of the sensing-stimulation system in three stroke survivors. The implantation of the intramuscular electrode should be simple for the physician and well tolerated by the patients. The patient should be able to control the stimulation reliably after a short period of training and adjustment. The desirable exercise modes should be obtained in the paretic limbs without accompanying pain or discomfort. The use of the device should result in improved range of motion and flexion-extension torque at the involved joints.
PROGRESS--Electrodes have been designed and developed for the purpose of sensing EMG signals and stimulating the muscle from which those EMG signals were detected. A laboratory version of the EMG-controlled stimulator has been developed. The device is capable of processing two EMG signals and using them to control the onset and termination of stimulation pulses from four stimulation channels.
FUTURE PLANS--The tripolar electrodes and the EMG-controlled stimulator will be tested on a number of persons with hemiplegia. After the system has been miniaturized, subjects will use the device for exercise at home, and the effectiveness of the intervention will be assessed.
[073] MYOELECTRIC CONTROL FOR A NEUROPROSTHETIC DEVICE
David Yu, MD; Soheyl Pourmedi, MS; ZiPing Fang,
PhD
Cleveland FES Center, Case Western Reserve University,
Department of Physical Medicine and Rehabilitation,
MetroHealth Medical Center, 2500 MetroHealth Blvd.,
Cleveland, OH 44109; NeuroControl Corporation, Valley View,
OH 44125; email: dyu@metrohealth.org
Sponsor: National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892; VA Center of Excellence in FES, Cleveland VA Medical Center, Cleveland, OH 44106-1702; NeuroControl Corporation, Cleveland, OH
PURPOSE--Individuals with upper limb paralysis due to spinal cord injury (SCI) have been able to regain limited function of their hand through the use of an implanted neuroprosthesis. The system is configured in such a way that the user controls hand opening and closing by volitionally moving the shoulder. This motion is detected by an externally mounted position sensor that sends a signal to the control unit of the system. Such a control scheme requires the patient to retain some volitional control of his/her shoulder muscles, thus limiting use of the system to persons with lesions no higher than the 5th cervical nerve root. To allow the system to be used by individuals with higher levels of SCI, a new control scheme is needed. The purpose of this research is to investigate the feasibility of using myoelectric signals as the control source for a hand-grasp neuroprosthesis.
METHODOLOGY--Control signals will be derived from weak volitional myoelectric activity, making it possible for individuals without sufficient shoulder mobility to use the prosthesis. Current users of the hand-grasp neuroprosthesis could also benefit from myoelectric control. Myoelectric control has advantages over the externally worn shoulder position sensor that requires daily donning and doffing, causes skin irritation, and is visually unappealing. The focus of this research will be on obtaining command signals that allow proportional control of the prosthesis. That is, the degree of hand opening and closing will be proportional to the magnitude of the processed myoelectric signal. Stimulus artifact that may be present in the myoelectric signal will be removed by signal blanking, band-pass filtering, and electrical isolation between stimulating and sensing circuits. Initial testing will be conducted with individuals who already use the implanted hand system. Percutaneous intramuscular electrodes will be used to record myoelectric activity from muscles that are appropriate for use as control sources. The degree of control of the myoelectric signal that the subject has will be evaluated.
PROGRESS --Three individuals with C4 tetraplegia or higher and three individuals with C5 or C6 tetraplegia who already use the implanted hand system will participate in a preliminary clinical study.
[074] THE DYNAMIC MODEL OF SKELETAL MUSCLES AND JOINTS FOR FES APPLICATIONS
Moshe Solomonow, PhD; Richard V. Baratta, PhD; Bing-He
Zhou, EE; Robert D. D'Ambrosia, MD
Department of Orthopaedics, School of Medicine in New
Orleans, Louisiana State University Medical Center, New
Orleans, LA 70112; email: rbarat@lsumc.edu
Sponsor: National Science Foundation, Arlington, VA 22330
PURPOSE--Discerning the correct response model of a single skeletal muscle has been a long-standing problem, because only unphysiological control inputs (firing rate or reverse recruitment) could be used, or alternate analogue models preassumed the interaction mode of firing rate and recruitment, were unknown until recently. The model is needed for the design of advanced FES systems.
METHODOLOGY--We tested the soleus (slow twitch) and M. gastroc (fast twitch) under several physiological control strategies with the aid of our newly developed stimulation system that recruits motor units in an orderly fashion.
PROGRESS--Additional work has identified the frequency response of nine different muscles in the hind limb of the cat. The impact of muscle/tendon ratio, mass, pennation, and twitch properties varied the model poles from 1.6 to 2.8 Hz. Recent studies focused on load-moving contractions and on the effect of the joints in various configurations. Muscle architecture and its predominant fiber composition seem to be the primary variable in determining its dynamics, whereas the tendon is a secondary factor. Recent work identified the dynamic model of antagonistic muscle pair acting on the ankle joint of the cat.
RESULTS--The frequency response model consisted of a second-order system with double poles at 1.8 Hz. This was independent of the control strategy used, the predominant muscle fiber type, or the force perturbation level. A pure time delay differentiated the models for fast and slow twitch muscles being 11 ms and 16 ms, respectively. Firing rate control input was reaffirmed to result in a nonlinear model as previously described in the literature.
[075] THE USE OF EMG AS FORCE FEEDBACK IN CLOSED-LOOP ELECTRICAL STIMULATION SYSTEMS
Moshe Solomonow, PhD; Richard V. Baratta, PhD; Robert D.
D'Ambrosia, MD
Department of Orthopaedics, School of
Medicine in New Orleans, Louisiana State University Medical
Center, New Orleans, LA 70112; email:
rbarat@lsumc.edu
Sponsor: National Science Foundation, Arlington, VA 22330
PURPOSE--Force feedback is necessary when regulation of a stimulated muscle force output is anticipated. Since implantation of force sensors requires trauma to the tendon, the EMG was considered, tested, and evaluated as a parameter-representing force in a closed-loop paradigm.
METHODOLOGY--The EMG was found to follow the isometric force rather faithfully so long as fatigue did not set in the muscle. In order to prevent muscle abuse and possible damage due to prolonged and frequent fatigue, a parallel feedback/fatigue detector has been implemented. The role of such a circuit is to function as a "fatigue fuse," terminating contractions if excessive fatigue is detected.
PROGRESS--The EMG-force relationship was investigated in order to delineate the effects of changing muscle length, and moment arm about the joint's center of rotation, in order to extend the concept to nonisometric contractions in a moving limb. It was shown that various factors influence the EMG-force relations, and that a multivariant model should be constructed to provide accuracy to the feedback loop. Recent evidence delineates changes in force and EMG in different contraction types and after skill acquisition.
[076] DETERMINATION OF THE OPTIMAL MOTOR UNIT RECRUITMENT STRATEGY FOR APPLICATION IN A HIGH PERFORMANCE FES SYSTEM FOR QUADRAPLEGICS
Moshe Solomonow, PhD; M Bernardi, MD; Richard V.
Baratta, PhD; Robert D. D'Ambrosia, MD
Department of Orthopaedics, School of Medicine in New
Orleans, Louisiana State University Medical Center, New
Orleans, LA 70112; email: rbarat@lsumc.edu
Sponsor: National Science Foundation, Arlington, VA 22330
PURPOSE--The objective of this investigation was to determine the optimal motor unit control strategy that should be used in electrical stimulation of the upper limb and hand of persons with quadraplegia in order to provide them with most accurate control of force increase and decrease, a part of a long-term objective of designing a high-performance FES system.
METHODOLOGY--A group of controls was trained to track a 3-s long linear increase in force of their elbow flexors in isometric condition while recording the EMG of the flexors (agonist) and extensor (antagonist) muscles. The power spectra frequency of the EMG signal was obtained and its median frequency (MF) calculated. Measurements were made in the beginning of a 6-wk training program, and every 2 wks thereafter. The MF, being representative of the conduction velocity of the muscles action potentials, indicated the increase or decrease in motor unit recruitment.
It was shown that at the end of the 6-wk program, the subjects tracking capability became highly accurate while their motor unit recruitment strategy increased from 0-65 percent of the maximal muscle force to 0-90 percent of the maximal muscle force.
A similar protocol was applied to the dominant and contralateral muscles of individuals in order to determine if side dominance influences the recruitment order.
IMPLICATIONS--An FES system when applied to rehabilitation of arm and hand functions of persons with quadraplegia, where high precision of force control is required, should employ orderly stimulation of motor units over the full range of the available force in order to provide fine increments of force increase.
[077] MODEL-BASED DESIGN OF CENTRAL NERVOUS SYSTEM NEURAL PROSTHETIC INTERFACES
Warren M. Grill, PhD
Cleveland FES Center, Department of Biomedical
Engineering, Case Western Reserve University, Cleveland OH
44106-4912; email: wmg@po.cwru.edu
National Science Foundation, Biomedical Engineering and Research to Aid Persons with Disabilities Program; Department of Veterans Affairs Center of Excellence in FES, Cleveland VA Medical Center, Cleveland OH 44106-1702
PURPOSE--The long-term goal of this research program is to develop advanced neural prostheses based on microstimulation of the spinal cord. This project is designed to answer two fundamental questions concerning development of such prostheses. First, what neural elements are activated by stimulation of the spinal cord with penetrating microelectrodes? The working hypotheses are that the pattern of excitation depends strongly on the electrical properties and geometry of the extracellular tissue, and that the pattern of excitation depends strongly on the electrical properties and geometry of the neural elements. Second, how can targeted populations of neurons be selectively stimulated? The working hypothesis is that engineering optimization techniques will enable identification of electrode geometries and stimulus parameters that maximize selectivity of particular groups of neurons.
METHODOLOGY--These two questions are being addressed using a combination of experimental measurements, computer-based modeling, and engineering optimization. During the past year our efforts were focused on implementation and analysis of computer-based cable models of mammalian central and peripheral neurons.
PROGRESS--Progress was made in three major areas: modeling of mammalian axonal membrane, modeling of spinal motor neurons, and studying the effects of tissue electrical properties on excitation.
Previous models of mammalian axons fail to reproduce known strength-duration properties and anode break excitation (action potential initiation following release from prolonged hyperpolarization). Therefore, we conducted a sensitivity analysis and subsequent modification to a cable model of a mammalian axon. The revised model better reproduced known physiological phenomena including anode break excitation and strength-duration properties. We also implemented a new cable model of mammalian axons based on recent voltage clamp data from human axons. This new model better reproduces known strength-duration properties, and with modification produces anode break excitation.
A first-generation cable model of a mammalian spinal motor neuron was developed, and the model was used to predict patterns of neural activation and to optimize stimuli for selective stimulation. The results indicate that the site of action potential initiation was a function of the electrode position, stimulus duration, and stimulus intensity. Further, the temporal evolution of the transmembrane potential played a strong role in determining the site of excitation. When comparing activation of two neurons equidistant from the electrode (one having the electrode over the cell body and the other having the electrode over the axon), preferential activation of one neuron or the other could be controlled by modulating the stimulus pulsewidth. Further control of selective stimulation was achieved using bipolar electrode geometries.
We conducted a study of the effects of tissue electrical properties (inhomogeneity and anisotropy) on excitation of nerve fibers by extracellular electric fields. The results demonstrate that the electrical properties of the extracellular medium can have a strong influence on the pattern of neuronal excitation generated by extracellular electric fields, and indicate the importance of tissue electrical properties in interpretation of results in studies employing electrical stimulation applied in complex biological volume conductors.
IMPLICATIONS--The results of this project are fundamental advances in our understanding of neural excitation with extracellular electrodes and new techniques that allow selective microstimulation of targeted neuronal populations. These advances will enable design and fabrication of advanced neural prosthetic systems to restore function to persons with neurological impairment. While the emphasis of this project is on stimulation of the lumbosacral spinal cord, the principles can be applied to stimulation of other regions of the spinal cord, to cortical stimulation, and will also be applicable to stimulation of other excitable tissues including peripheral nerve and cardiac muscle.
[078] FES WEBGUIDE: AN INTERNET ACCESSIBLE INTERACTIVE RESOURCE ON FES FOR PERSONS WITH SPINAL CORD DYSFUNCTION
Jeanne O'Malley Teeter, BS, MBA
Cleveland FES Center, FES Information Center, Case
Western Reserve University, Cleveland, OH 44106-3052; email:
jxt4@po.cwru.edu
Sponsor: Buckeye Chapter, Paralyzed Veterans of America, 25100 Euclid Avenue, Cleveland, OH 44117; Spinal Cord Injury Education and Training Foundation, Paralyzed Veterans of America, 801 Eighteenth Street, NW, Washington, DC 20006; VA Center of Excellence in FES, Cleveland VA Medical Center, Cleveland, OH 44106
PURPOSE--Functional Electrical Stimulation (FES) is a technique that can maximize health and function in persons with spinal cord injury (SCI) or spinal cord disease, such as multiple sclerosis (MS), regardless of age, race, sex, or length, level, and completeness of injury. In medically appropriate cases, FES can be used for persons with SCI or MS to restore upper and lower extremity mobility, improve respiratory functions, restore bowel and bladder functions, restore male sexual function, and to treat and help prevent secondary complications such as pressure ulcers, deep-venous thrombosis, contractures, spasticity, deconditioning due to lack of exercise, bone demineralization, and muscle atrophy. In some instances, FES can significantly improve physical and emotional health in ways that cannot be achieved by other methods available today. Persons with SCI or disease need specialized information about FES to build a knowledge base that permits them to understand, identify, and pursue appropriate FES treatment options that will maximize their independence, function, and health.
METHODOLOGY--We propose to develop an interactive, searchable, multimedia version of an existing publication, the FES Resource Guide, for publication on the World Wide Web. This will help individuals with paralysis increase their FES knowledge base, increase their ability to make informed decisions about the appropriateness of FES, and gain increased access to FES providers and additional FES resources. The objective of this project is to enhance dissemination and utilization of the FES Resource Guide. The project evaluation will involve a phased series of on-line surveys to measure the utility of both the Internet format and the FES information provided.
PROGRESS/FUTURE PLANS--This is a new project. Previously, a sourcebook entitled Functional Electrical Stimulation (FES) Resource Guide for Persons with Spinal Cord Injury or Multiple Sclerosis (ISBN 1-888470-03-8) was published in 1995. Over the course of the next year, the book will be updated, expanded, and published in both print and web formats.
[079] RESTORATION OF FOREARM AND ELBOW FUNCTION BY FNS
Patrick E. Crago, PhD; Robert F. Kirsch, PhD; P. Hunter
Peckham, PhD;Michael W. Keith, MD
Cleveland FES Center, VA Medical Center, Cleveland, OH
44106; MetroHealth Medical Center, Cleveland, OH 44109; Case
Western Reserve University, Cleveland, OH 44106; email:
pec3@po.cwru.edu;
rfk3@cwru.edu;
pxp2@po.cwru.edu;
mwk4@po.cwru.edu
Sponsor: Department of Veterans Affairs, VA
Rehabilitation Research and Development Service, Washington,
DC 20420; VA Center of Excellence in FES,
Cleveland VA Medical Center, Cleveland, Ohio 44106
(Project #B835-RA)
PURPOSE--The purpose of this project is to restore forearm and elbow control with hand grasp for people with cervical-level spinal cord injury (SCI). Our objective is to increase the range and type of functions they can perform by stimulating paralyzed pronator quadratus and triceps in addition to muscles providing hand grasp and release. We hypothesize that augmenting the hand grasp neuroprosthesis will give individuals with C5 and C6 SCI the ability to grasp and move objects over a greater range of spatial locations and orientations, and will improve movement quality.
METHODOLOGY--Elbow and forearm stimulation is integrated with the VA/CWRU hand-grasp neuroprosthesis. The triceps is stimulated to provide elbow extension. Stimulation is adjusted to overcome gravity, and can be controlled either by an accelerometer mounted on the upper arm, user-initiated stimulation with a switch on the wheelchair, or constant triceps stimulation whenever the neuroprosthesis is active.
Elbow angle is controlled by the subject voluntarily contracting the biceps to counteract the elbow extension. Forearm rotation is provided by stimulating the pronator quadratus at a constant level whenever the hand grasp neuroprosthesis is active. Supination/pronation angle is controlled by voluntary supination to counteract pronation. Thus, the additional functions do not require additional command signals unrelated to the desired function.
Forearm and elbow functions are evaluated in terms of basic mechanical capabilities, ability to use the restored function to achieve stable postures and produce smooth movements, and ability to perform common activities of daily living that require picking up and placing objects over a wide range of locations and orientations.
PROGRESS--This project has been completed. Nine neuroprostheses combining hand grasp with proximal arm control were implemented in eight individuals. All were used on a regular basis outside of the laboratory and were implemented with either a fully implanted stimulator and electrodes, a combination of an implanted stimulator for hand grasp and percutaneous electrodes for proximal function, or percutaneous electrodes only. Six individuals received elbow systems; five were unilateral, one bilateral. Three received forearm systems; two unilateral, one bilateral. One individual received both elbow and forearm control in the same arm.
We designed a series of tests to 1) measure the mechanical properties at the joints with restored function (joint moment, range of motion, and dynamic stiffness), 2) assess the upper limb functional workspace, and 3) assess improvements in functional performance.
RESULTS--Stimulating the pronator or triceps typically restored strength to grade four. Each person was able to grade the joint movement over the full range of motion by contracting the voluntarily controlled antagonist. Joint stiffness was increased by stimulation of the antagonist, which should provide better postural stability. Elbow extension increased the controllable workspace, both by increasing the range of locations and orientations where objects could be acquired, and by reducing the time required to grasp the object. This is consistent with the need for elbow extension to counteract gravity and provide a stable joint. Functionally, elbow extension greatly improved task performance. However, the benefits of pronation were less dramatic. Pronation may be more important to restore in people with weaker residual function, and it may be necessary to employ more sensitive evaluation measures to elucidate the significance of pronation in these individuals.
[080] FUNCTIONAL NEUROMUSCULAR SYSTEMS FOR UPPER EXTREMITY CONTROL
P. Hunter Peckham, PhD
Cleveland FES Center, Rehabilitation Engineering Center,
MetroHealth Medical Center, Cleveland, OH 44109-1998; VA
Medical Center, Cleveland OH 44106; email:
pxp2@po.cwru.edu
Sponsor: Department of Veterans Affairs, VA
Rehabilitation Research and Development Service, Washington,
DC 20420; VA Center of Excellence in FES,
Cleveland VA Medical Center, Cleveland, OH 44106-1702
(Project #B011-6RA)
PURPOSE--We seek to deploy and quantitatively evaluate advanced implantable functional neuromuscular stimulation (FNS) systems to restore arm and hand function in persons with quadriplegia.
METHODOLOGY--The focus of this project is the clinical implementation and evaluation of a second generation implantable hand/arm neuroprosthesis. The first generation neuroprosthesis, which used an 8-channel implant stimulator, received FDA approval in 1997 and is now marketed by an independent company. The second generation system consists of a 10-channel implant stimulator-telemeter, an implanted joint angle transducer (IJAT), and 10 epimysial or intramuscular electrodes. The IJAT is placed in the wrist and uses three Hall-effect magnetic field sensors and a magnet to sense wrist angle. The magnet is inserted into the lunate. The Hall-effect sensors are inserted into the radius near the articular surface of the bone. Sensor outputs are relayed to the stimulator-telemeter device and transmitted out of the body through a radio frequency link using reflectance modulation. This system is applicable to individuals with C6 and C7 spinal cord injury (SCI).
The motor functions provided by the system are: 1) multiple hand grasp patterns, including fine grasp controlled by finger intrinsic activation; 2) elbow extension through a combination of electrical stimulation of the triceps and tendon transfers of the voluntarily controlled posterior head of the deltoid; and 3) forearm supination/pronation through stimulation of the pronator quadratus. Elbow and forearm movement is controlled by voluntary activation of the antagonists.
Participants undergo at least 1 mo of surface stimulation prior to surgery. Implantation surgery is followed by 3 weeks of casting, and then a period of muscle conditioning using the implant stimulator. A 2- to 3-week rehabilitation training and evaluation period is used to complete the initial set-up of the grasp and control parameters, train the individual in the use of the neuroprosthesis, and evaluate the function provided.
PROGRESS--Two individuals with C6-level SCI have received the complete second generation system, including the implantable joint angle transducer, and two additional individuals have undergone the first stage of implementation involving implantation of the stimulator-telemeter device and 10 electrodes. All four have two intramuscular electrodes placed in the finger intrinsic muscles to provide metacarpalphalangeal joint flexion and interphalangeal joint extension. Three have a single electrode in the triceps for elbow extension. One has an electrode implanted in the pronator quadratus for forearm pronation. For the two persons who have undergone only the first stage, control of the neuroprosthesis is provided by an externally mounted wrist angle transducer.
RESULTS--All four implant recipients are daily users of the neuroprosthesis, performing various functional tasks, including eating, drinking, writing, and grooming. Three have full elbow extension with triceps stimulation, allowing them to perform reaching activities.
The implantation of the IJAT was successful in both cases, providing an adequate output signal for the control of grasp opening and closing, comparable to control using the external wrist sensor. No reduction in wrist range of motion has been detected post-surgery. In one subject, a small leak has developed at one or more of the interconnections between the implanted sensor and the stimulator-telemeter, resulting sensor output dropping below the usable range. These interconnections will be repaired with a minor surgical exposure of the connector site. We expect sensor output to return to operational levels immediately following this repair.
FUTURE PLANS--The two implant recipients who have completed stage I will progress to implantation of the joint angle transducer, and additional subjects will be implanted with complete systems. Quantitative assessment of function will continue with each subject.
[081] AN EEG-BASED CONTROLLER FOR FNS HAND GRASP SYSTEMS
P. Hunter Peckham, PhD; Richard Lauer, MS
Cleveland FES Center, VA Medical Center, Cleveland, OH
44106; MetroHealth Medical Center, Cleveland, OH 44109; Case
Western Reserve University, Cleveland, OH 44106; email:
pxp2@po.cwru.edu;
rxl26@po.cwru.edu
Sponsor: National Institutes of Health, NINDS Neuroprosthesis Program, Bethesda, MD 20892; Ron Shapiro Charitable Foundation, Bethesda, MD 20814; Movement Disorder Foundation, Bowral N.S.W. 2576, Australia; Department of Veterans Affairs Center of Excellence in FES, Cleveland VA National Center
PURPOSE--The objective of this project is to develop a means by which voluntarily generated cortical activity, as recorded by the electroencephalogram (EEG), can provide control of a neuroprosthesis which restores hand function.
METHODOLOGY--The mu rhythm is the 8-13 Hz component of the EEG recorded from the motor cortex. Other investigators have demonstrated that subjects can be trained to voluntarily control this frequency to hit targets on a computer screen with a high degree of accuracy (<90 percent). The purpose of this study will be to train subjects to control the mu rhythm using the same protocols developed by the other investigators, and then apply this signal to the operation of a neuroprosthesis. Studies that will be conducted during the course of this investigation are: 1) definition of the characteristics of the EEG signal (i.e., signal stability over time); 2) examination of the subjects ability to control the amplitude of the mu rhythm while generating movements of the upper extremity; and 3) development of the command-control algorithms and the hardware necessary to allow neuroprosthetic operation by the EEG signal.
PROGRESS--We have been able to replicate the instrumentation which was used by the other investigators to record the EEG signal and to train subjects. Currently, there are five subjects (four controls and one neuroprosthesis user) participating in the study. Each has been training for a minimum of 3 mo.
We have also examined the characteristics of the EEG signal and have constructed two possible command-control algorithms for the operation of the neuroprosthesis. The first algorithm uses the EEG signal as a switch to turn functions (i.e. system state, hand grasp) on and off; the second uses the signal to operate system state and to control the degree of hand opening and closing. These algorithms will be tested once the interface between the EEG recording system and the neuroprosthesis is complete.
RESULTS--Of the five subjects in the study, only three have demonstrated effective control over the mu rhythm with an accuracy rate greater than 85 percent. The other two have only attained a 55 percent rate. Additional experiments with the first three indicated that they are unable to control cursor movement while generating upper extremity movements. This has led to the investigation of other recording sites and frequency components of the EEG that can be used to generate a control signal. By using the beta rhythm (18-27 Hz) recorded over the frontal cortex or the alpha rhythm (8-13 Hz) generated by the occipital cortex, three of the five subjects, including one with poor performance on the mu rhythm, have attained accuracy rates over 90 percent. Examination of the control over these frequencies while generating upper extremity movements indicated that subjects can still maintain their high accuracy rates while generating movements of the shoulder and elbow.
FUTURE PLANS--The remaining two subjects will be switched over to using the alpha or beta rhythms to generate cursor movement. Once a high accuracy rate is attained, these subjects will also be evaluated to determine if they can move their upper extremities and still have effective control over the EEG signal. Development of the interface between the EEG system and the neuroprosthesis will continue, with completion of this phase to take place before the end of 1998.
[082] RESTORATION OF SHOULDER MOVEMENT IN C5 TETRAPLEGIA
Robert F. Kirsch, PhD; Patrick E. Crago, PhD; Michael W.
Keith
Cleveland FES Center, Rehabilitation Engineering Center;
MetroHealth Medical Center, Cleveland, OH 44109; email:
rfk3@po.cwru.edu
Sponsor: National Institutes of Health, National Institute of Child Health and Human Development, National Center for Medical Rehabilitation Research, Bethesda, MD 20892; VA Center of Excellence in FES, Cleveland VA Medical Center, Cleveland OH 44106-1702
PURPOSE--This study will implement, evaluate, and optimize a neuroprosthesis based on functional neuromuscular stimulation (FNS) to restore shoulder function to individuals with C5 tetraplegia. Such individuals retain little or no voluntary control over motions acting to move the upper arm toward the midline, due primarily to paralysis of the pectoralis major (PM) and latissimus dorsi (LD) muscles. This loss of control significantly reduces the range of motion of the hand, excluding an important workspace volume near the midline, and prevents arm stabilization in the natural adducted postures used in many tasks like eating and writing. Restoration of these functions would improve independence in daily activities, improving quality of life, and reducing attendant care costs.
METHODOLOGY--Percutaneus electrodes are implanted into the PM and LD muscles. Controlled stimulation of these muscles provides shoulder function in horizontal flexion, adduction, and internal rotation in individuals with C5 tetraplegia. The stimulated contractions restore the lost motions, while retained voluntary control of antagonistic muscles is used to overcome the stimulated contractions and achieve intermediate positions. Performance is evaluated by quantifying the expansion of the workspace volume accessible to the hand, the increased postural stability within this workspace, and the increase in speed and accuracy of arm movements.
Methods for improving control of the partially paralyzed shoulder are also under development. Shoulder stiffness properties are used to identify deficits in postural stability and to suggest changes in stimulation patterns to correct the deficits. The feasibility of using electromyographic (EMG) recordings from voluntarily controlled shoulder muscles to modulate stimulation of the paralyzed muscles is also being investigated for improving movement performance, preventing fatigue, and compensating for changes in contraction strength in different shoulder positions.
PROGRESS--We have found FNS of the PM and LD muscles in individuals with C5 tetraplegia produces contractions adequate to move the arm and stabilize it during posture. Retained voluntary control can overcome the stimulated contractions when desired. Surface EMG recordings from shoulder muscles with retained voluntary control can be used to accurately estimate elbow angle as well as three shoulder angles (elevation, horizontal flexion, and internal rotation).
RESULTS--The PM and LD muscles of two individuals with C5 tetraplegia have been implanted with percutaneous stimulation electrodes, with both arms implanted in one of these subjects. FNS-mediated exercise has been found to significantly increase the strength of both of these muscles. The strength is dependent on the position of the arm, with both horizontal flexion and adduction being stronger with the arm elevated above horizontal. However, the moments produced were strong enough (5-10 Nm) in all arm positions to move the arm in the desired directions.
We are developing a method for the user control of the additional shoulder functions and have found that elbow joint angle and three shoulder angles (elevation, horizontal flexion, and internal rotation) can be predicted to within 10-15° using surface EMG recordings of muscles under voluntary control (anterior, middle, and posterior deltoid, biceps, upper, and middle trapezius). An artificial neural network predicts the elbow and shoulder movements using EMG and angle measurements obtained during voluntary movements. This network is capable of accurately predicting the joint angles during single joint movements, reaching movements, and complex drawing movements.
[083] PERCUTANEOUS INTRAMUSCULAR ELECTRICAL STIMULATION FOR TREATING SHOULDER SUBLUXATION AND PAIN IN CHRONIC HEMIPLEGIA: A PILOT STUDY
David Yu, MD; John Chae, MD; ZiPing Fang, PhD
Cleveland FES Center, Case Western Reserve University,
Department of Physical Medicine and Rehabilitation,
MetroHealth Medical Center, 2500 MetroHealth Blvd.,
Cleveland, OH 44109; NeuroControl Corporation, Cleveland,
OH; email: dyu@metrohealth.org
Sponsor: National Institute on Child Health and Human Development and National Institute on Aging, National Institutes of Health, Bethesda, MD 20892; VA Center of Excellence in FES, Cleveland VA Medical Center, Cleveland, OH 44106-1702; NeuroControl Corporation, Cleveland, OH
PURPOSE--Shoulder subluxation is a common complication of hemiplegia, occuring in approximately 50 percent of cases, and has been associated with shoulder pain and poor functional recovery. Surface electrical stimulation (SES) has been shown to reduce glenohumeral subluxation and may reduce shoulder pain. However, SES has not been widely utilized because it is poorly tolerated, time-consuming, and technician dependent. Percutaneous intramuscular electrical stimulation (PIMES) has several potential advantages over SES. PIMES is less painful because stimulation of cutaneous pain receptors is avoided. The electrodes are placed in the muscle motor point, thus lower stimulus intensities are required and muscle selectivity is improved. Electrodes are left in place for the duration of treatment, ensuring optimal placement. The purpose of this study was to gain initial experience with PIMES for the treatment of shoulder subluxation in hemiplegia and to collect pilot data evaluating the efficacy of this intervention.
METHODOLOGY--Eight neurologically stable subjects with chronic hemiplegia and shoulder subluxation were treated with 6 weeks of PIMES. Vertical subluxation was measured using a radiographic technique described by Prevost, shoulder pain by the Brief Pain Inventory, motor function by the Fugl-Meyer Motor Test, and disability by the Functional Independence Measure. All measures were obtained prior to treatment (T1), after 6 weeks of PIMES (T2) and at 3 mo after the completion of treatment (T3). The Wilcoxon Sign Rank Test was used to determine statistical significance between T2-T1 and T3-T2.
PROGRESS--Vertical subluxation was reduced between T2-T1 (p<0.05) and was maintained at T3. Pain decreased from T2-T1 (p<0.05) and increased from T3-T2 (p>0.05). Motor function improved from T2-T1 (p<0.10) and from T3-T2 (p<0.05). Disability was reduced from T2-T1 (p<0.05) only. In conclusion, PIMES may reduce shoulder subluxation and pain in hemiplegia. Further studies are needed.
[084] MULTICHANNEL IMPLANTABLE SYSTEM FOR NEURAL CONTROL
P. Hunter Peckham, PhD; Michael W. Keith, MD
Cleveland FES Center, Rehabilitation Engineering Center,
MetroHealth Medical Center, Cleveland, OH 44109-1998; email:
pxp2@po.cwru.edu
PURPOSE--The aim of this project is to implement and evaluate an advanced neuroprosthetic system for restoration of hand-arm function in human subjects who have sustained cervical-level spinal cord injury (SCI). The neuroprosthesis will provide the person with C5 tetraplegia with control of grasp and release and elbow extension by electrical stimulation of the paralyzed muscles. These functions will enable the user to regain the versatile manipulative functions which will increase their ability to perform activities of daily living independently.
METHODOLOGY--The neuroprosthetic system will provide persons who have C5-level SCI with active control of refined grasp-release, forearm pronation/supination, and elbow extension. Proportional control of multiple grasp patterns, forearm pronation, and elbow extension will be provided by a combination of graded myoelectric signals (MES) and an external switch. Stimulating electrodes will be placed on 11 muscles to provide 4 grasp patterns: lateral pinch, palmar pinch, ulnar-opposition grasp, and a power grip. A twelfth stimulating electrode will be placed in the supra-clavicular region to provide electro-cutaneous sensory feedback. Control of these functions will be provided by acquiring myoelectric signals from two voluntary muscles: the sternocleidomastoid muscle and either the brachioradialis or posterior deltoid muscle. Therefore, the complete system includes 12 channels of stimulation and 2 channels of MES acquisition. The power and signal processing is provided by an external control unit through a bi-directional radiofrequency (RF) link. Since the only externally worn component is the RF transmitting coil, the issues of sensor mounting and maintenance of cabling are greatly reduced from other neuroprosthetic systems.
The neuroprosthetic system to be implemented consists of a portable external control unit and transmit/receive coil, a multichannel implanted stimulator-telemeter, 12 stimulating and 2 recording electrodes. Myoelectric control information is telemetered to the portable controller that processes the information according to programmed algorithms and transmits stimulus signals and power back to the implanted device over the single telemetry link. Stimulation is applied to the paralyzed muscles to elicit coordinated movements to supply function and to provide electrotactile sensory codes to the user. Patient performance will be assessed through measures of impairment, functional limitation, and disability. Detailed quantitative assessments of grasp and control will be conducted to optimize system performance parameters for each individual.
RESULTS--A complete system has been tested in an acute animal preparation to verify the proper function of the MES processing circuitry in vivo. This test demonstrated that myoelectric signals could be obtained from muscles during electrical stimulation, even when the stimulating and recording electrodes were only 3 cm apart.
FUTURE PLANS--Preparations are being made for the first implantation of this device into a paralyzed individual. An external circuit has been developed to mimic the processing the myoelectric signal in the implanted device. This allows testing of the complete system prior to surgery to verify that adequate control signals can be obtained.
[085] FEASIBILITY OF RESTORING UPPER EXTREMITY FUNCTION IN C3-C4 TETRAPLEGIA
Robert F. Kirsch, PhD; David Yu, MD
Cleveland FES Center, Case Western Reserve University,
Department of Physical Medicine and Rehabilitation;
MetroHealth Medical Center, Cleveland, OH 44109; email:
rfk3@po.cwru.edu;
dyu@metrohealth.org
Sponsor: Spinal Cord Research Foundation, Paralyzed Veterans of America, Washington, DC 20006; National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892; NeuroControl Corporation, Valley View, OH 44125; VA Center of Excellence in FES, Cleveland VA Medical Center, Cleveland OH 44106-1702
PURPOSE--The goal of this project is to investigate the feasibility of restoring upper limb function to individuals with high cervical spinal cord injury (SCI: C4 function or less) using functional neuromuscular stimulation (FNS) and/or reconstructive surgery. This is the most disabled population of persons with SCI, so restoration of just a few functions (e.g., simple self-feeding and grooming activities) would significantly increase the independence and quality of living for these individuals. However, their restoring movement function has been quite challenging and not very successful, for three primary reasons. First, the number of retained voluntary functions is so low that there is minimal opportunity to substitute for lost functions or even to use these motions to control external devices. Second, individuals with C3 or C4 level spinal cord injuries may exhibit extensive denervation of the shoulder and elbow muscles, which could limit the possibility of using FNS of these muscles to restore movement. Third, the mechanics of the human shoulder are too complex to allow the development of effective methods for restoring movement by trial and error.
METHODOLOGY--We will perform a survey of a modest number (approximately 20) of individuals with C3 or C4 SCI to determine whether denervation is indeed a limiting factor in many. We will further explore the feasibility of FNS in this population by implanting stimulating electrodes in the elbow and shoulder muscles of eight and quantifying the increase in strength and movement range produced by an FNS-mediated exercise regimen. Finally, we will address the mechanical complexity of the human shoulder by using the emerging field of musculoskeletal modeling as a tool for evaluating the feasibility of different rehabilitation. We will use such a model to perform simulations to evaluate the likely success of different interventions before performing the procedure in human subjects. Specifically, we will examine the feasibility of FNS of paralyzed muscles, reconstructive surgeries such as muscle tendon transfer, and, if needed, the use of external orthoses. These simulations will focus on basic, functionally relevant needs such as stabilizing the shoulder (needed for virtually any functional task requiring the upper limb), self-feeding and grooming, and simple reaching movements similar to typing. This quantitative modeling approach will reduce the trial-and-error aspects of developing rehabilitation methods. We will be able to estimate what types of functions might be restored for different individuals, whether adequate function can be provided without external orthoses, how many and which muscles are required for successful FNS, and which reconstructive surgeries may be required. We will delineate what is possible in different individuals with high cervical SCI, and produce initial specifications for systems to restore desired functions. Subsequent work can then be pursued to implement such systems in human subjects using advanced implantable technology and to determine optimal methods for the user control of these devices.
PROGRESS--This is a new project that we believe will make a direct and significant contribution to the rehabilitation of persons with SCI, especially to those with the highest levels of disability. It should help to fill basic gaps in the information available about high cervical SCI and produce a general-purpose tool that can be used to assess rehabilitation approaches as varied as FNS, reconstructive surgery, and external assistive devices.
[086] FUNCTIONAL ELECTRICAL STIMULATION OF SPINAL CORD INJURED PATIENTS
A.M. Erika Scremin, MD; Oscar U. Scremin, MD, PhD;
Thomas J. Barstow, PhD; Ronald Dietrick, PhD; Brent Shannon,
MS; Barbara Wiseman, BS
Physical Medicine and Rehabilitation Service, VA Medical
Center, West Los Angeles, CA, 90073; University of
California, Los Angeles, 90024; Division of Respiratory and
Critical Care Physiology and Medicine, Harbor-UCLA Medical
Center, Torrance, CA 90509; email: oscremin@ucla.edu
Sponsor: Department of Veterans Affairs, VA
Rehabilitation Research and Development Service, Washington,
DC 20420
(Project #B2002-RA)
PURPOSE--The purpose of this project is to study the effects of functional electrical stimulation-induced lower extremity cycling (FESILEC) on complete, spastic SCI subjects and to determine the therapeutic benefits of this form of rehabilitation.
METHODOLOGY--Subjects participated in a 24- to 48-session training protocol of leg cycle exercise (LEC) on a computerized REGYS ergometer, powered by lower extremity muscles activated by cutaneous electrodes. Muscle blood flow (MBF) was studied with H215O PET, muscle metabolic response with respiratory O2 uptake kinetics, and 31P Magnetic resonance spectroscopy (MRS), muscle fiber type with histo- and bio-chemistries of biopsies, and muscle mass with CT and MRI scans.
RESULTS--Studies with H215O PET showed that FES-induced unloaded knee extension causes a greater MBF response in SCI subjects than the same exercise performed voluntarily by nonimpaired controls. We tested the hypothesis that this phenomenon was due to a the greater relative load imposed on deconditioned muscle of SCI subjects. MBF measurements were performed in every subject on the same session at rest (BL), during exercise (EX), immediately after ending 16 min EX (IPOST-EX), and 20 min after the end of EX (DPOST-EX). Four subjects with neurologically complete SCI, and 7 age-matched controls (AB) participated in the study. MBF of the thigh was measured with H215O PET in a Siemens 953-31 scanner. Subjects performed repetitive FES-induced or voluntary 30° knee extension with a load equivalent to 30 percent of the maximum they could lift once (SCI=0.91 kg, AB=6.8 to 9.98 kg). Subjects exercised during 16 min lying supine on the scanner table with 150° hip flexion. In AB subjects, MBF increased significantly over BL during EX (P<0.001), and it returned to a level not statistically different from BL immediately after EX: BL (ml/100g/min, mean±standard error)=3.34±0.70, EX=11.5±1.24, IPOST-EX=4.54±0.66, DPOST-EX=3.29±0.88. In SCI subjects, MBF was higher than in AB subjects in EX (18.5±1.01, P<0.004), and immediately after EX (20.9±0.99, P<0.0001).
We also examined cardiorespiratory responses during arm and leg exercise in SCI subjects. In paraplegics, FES-induced LEC is associated with reduced peak heart rate and VO2 and slowed VO2 kinetics. We studied the response of these variables in eight persons with paraplegia performing incremental and constant work rate with arms (voluntary) and legs (FES). Arm exercise induced higher peak heart rate and VO2, and faster VO2 kinetics than FES-LEC, suggesting no intrinsic dysfunction of heart rate control in these subjects. The abnormal response to FES-LEC appears to be specific to their injury or to FES-LEC.
IMPLICATIONS--These results tend to disprove the hypothesis tested, and suggest a greater metabolic impact of FES-induced than voluntary exercise even at comparable relative loads.
FUTURE PLANS--We shall complete work in the areas of muscle blood flow, muscle metabolic responses (31P MRS) and muscle histo- and biochemistries.
[087] RESTORATION OF GAIT IN ACUTE STROKE PATIENTS USING FNS
Robert L. Ruff, MD, PhD; Janis J. Daly, PhD
Cleveland FES Center, Walsh University, VA Medical
Center Medical Center, Cleveland, Ohio 44106; email:
daly@alex.walsh.edu
Sponsor: Department of Veterans Affairs, VA
Rehabilitation Research and Development Service, Washington,
DC 20420; Department of Veterans Affairs Center of
Excellence in FES, Cleveland VA Medical Center; NeuroControl
Corporation, Cleveland, OH; MetroHealth Medical Center,
Cleveland, OH
(Project #679-3RA)
PURPOSE--Conventional rehabilitation is inadequate to restore safe, independent gait for many stroke patients. Stroke is the leading cause of disability among adults in the United States. The purpose of this project is to determine the efficacy of Functional Neuromuscular Stimulation (FNS) with implanted (IM) electrodes in improving lower limb motor recovery and gait pattern of acute stroke patients.
We are testing the efficacy of the FNS-IM system for by making comparisons of treatment outcome for three different interventions: conventional therapy; conventional therapy+surface FNS; conventional therapy+FNS using IM electrodes. Additionally, we are comparing FNS gait with voluntary gait at the close of the treatment protocols.
METHODOLOGY--Thirty subjects in each of the three treatment groups are being treated for 6 mo; treatment begins at least 2 weeks post stroke, when the patient is medically stable. FNS exercise and FNS gait training protocols are used.
PROGRESS--Outcome measures are classified into three levels of physical function of increasing difficulty. The first level is voluntary movement at a single joint with the body in a static position. The second level is voluntary motor control during walking. The third level is functional capability at home and work. Data are collected every 6 weeks during the 6 mo of treatment. Carry-over effects are monitored at two additional data collection sessions at 1 mo and 1 yr following the end of the treatment period.
IMPLICATIONS--Results of this study have the potential to provide the following clinically applicable information:
[088] FES MOBILITY IN PARAPLEGIA: RF-CONTROLLED IMPLANTED SYSTEM
E. Byron Marsolais, MD, PhD; Ronald J. Triolo, PhD; John
A. Davis, MD; Rudolf Kobetic, MS
Cleveland FES Center, Case Western Reserve University,
Cleveland OH 44106; Motion Study Laboratory, Cleveland VA
Medical Center, Cleveland, OH 44106; MetroHealth Medical
Center, Cleveland, OH 44109; email: rxt24@po.cwru.edu
Sponsor: Department of Veterans Affairs, VA
Rehabilitation Research and Development Service, Washington,
DC 20420
(Project #B681-2RA); VA Center of Excellence in FES,
Cleveland VA Medical Center, Cleveland OH 44106-1702
PURPOSE--The overall goal of this project is to enhance the personal mobility of individuals with complete thoracic level spinal cord injuries (SCI) with Functional Electrical Stimulation (FES). An implantable system is being developed to provide individuals with T4-T10 paraplegia with the ability to exercise, stand, and step for short distances with a minimum of bracing and personal assistance. The purpose is to establish the clinical and technical components required to introduce implantable FES systems safely and effectively into the home and community environments.
METHODOLOGY--A single 8-channel CWRU/VA implanted receiver/stimulator (IRS8) is used for exercise and to generate standing function. Stimulation is delivered via six epimysial electrodes on the knee and hip extensor muscles (bilateral vastus lateralis, gluteus maximus, and semimembranosus, respectively) and two surgically implanted intramuscular electrodes at the L1/L2 spinal roots for trunk extension. After rehabilitation and reconditioning exercise, subjects are trained to stand, balance, and transfer with the neuroprosthesis and discharged to home for long-term follow-up. After exercise and standing at home and in the community, interested and physically qualified subjects with motor complete injuries will be considered for a second 8-channel implant to activate the muscles required for stepping (bilateral sartorius, TFL, TA, and posterior adductor) for a total of 16 stimulus channels. After a second period of immobilization, reconditioning exercise, and rehabilitation, participants are qualified to use the dual-implant system at home and in the community.
RESULTS--The 16-channel (dual-implant) walking mobility system has been successfully implanted in a volunteer who sustained a motor-complete SCI at the level of T10 approximately 5 yrs prior to surgery. Following a period of post-operative inactivity, the subject progressed from exercise to standing and stepping with the system. Electrode thresholds stabilized and stimulated contractions are sufficiently strong for functional activities. The subject can stand for several minutes and step repeatedly for distances approaching 50 feet. He is currently using the system at home to exercise, stand, and walk. Two additional volunteers have received the first stage 8-channel standing systems and have expressed the desire to continue on to 16-channel stepping by receiving a second IRS-8.
FUTURE PLANS--Results from the first application of the dual-implant mobility system are encouraging. The system is operational and adequate for unassisted standing and stepping, although stimulated responses of several electrodes can be improved by refining the surgical technique. Although this project has been discontinued, immediate research efforts will focus on optimizing standing function and streamlining the surgical approach to installing the initial 8-channel system by enrolling additional standing volunteers. Ambulation with the dual-implant system will be pursued in the laboratory on selected recipients of the standing neuroprosthesis with complete thoracic spinal cord injuries. Future research will address the needs of household or non-ambulators with motor incomplete injuries. Subject recruiting is ongoing and efforts to solicit clinical partners within the VA system interested in collaborating in a larger scale study of the 8-channel standing system will continue.
[089] DEVELOPMENT AND APPLICATION OF A CLOSED-LOOP CONTROLLED FES SYSTEM FOR STANDING UP MOVEMENT OF PARAPLEGICS
Maurizio Ferrarin, DrEng, PhD; Robert Riener, DiplEng,
PhD; Raffaella Spadone, DiplEng; Carlo Frigo, DrEng; Antonio
Pedotti, PhD
Centro di Bioingegneria, Fondazione Pro Juventute Don
Gnocchi IRCCS, Politecnico di Milano, I-20148 Milano, Italy;
email: ferramau@mail.cbi.polimi.it
Sponsor: Italian Ministry for Health Care; Commission of European Union
PURPOSE--The purpose of this study is to develop and apply closed-loop control systems for functional electrical stimulation (FES), in order to restore rising movements in persons with paraplegia by means of muscle stimulation and a dedicated mechanical device, the Weight Relief System (WRS) for partial weight relief. The system is intended as a device for patient training, but it is currently used also for the development of innovative FES control strategies and their testing on patients in safe experimental conditions.
METHODOLOGY--The system is based on a PC, a programmable 8-channel stimulator, a software controller, and electrogoniometers. The WRS, consisting of a see-saw construction, has been also developed and equipped with counter weights that can be adjusted according to the level of force developed by the stimulated muscles of patient's lower limbs. Up to now, a PID software regulator has been implemented to control the stimulator. The controlled variables are the knee angles of both legs, measured by means of flexible electrogoniometers and interfaced by a dedicated board with the PC. The actual angles are compared with the desired ones in real time, and, on the basis of their difference, the PID controller modulates the width of stimulation pulses produced by the stimulator. Surface electrodes are used to induce artificial contraction of quadricep muscles of both lower limbs in order to extend the knees and thereby obtain standing-up movement.
PROGRESS--This technique for training FES-induced rising is currently performed on three persons with paraplegia (complete lesion at mid-thoracic level). The aim is to treat those selected for FES walking application before the beginning of the specific walking training program, in order to produce an increase in muscle strength, fatigue resistance and, in the same time, to obtain a recovery of standing posture, with positive effects on musculo-skeletal, cardiorespiratory, and vestibular systems. Advantages of this system are its intrinsic safety characteristics and the possibility to modulate the load on stimulated muscles by modifying the counterweight of the WRS. Reference knee trajectory was obtained by means of an optimization procedure where target function was defined in order to minimize knee joint torque. Once the training proceeds, the total duration of exercise cycles is increased and the counterweight decreased, following patient-specific improvements.
RESULTS--After 2 mo of training, the subjects demonstrated an increase on isometric torque produced by quadricep muscles, a decrease on muscle fatiguability, and an increase of thigh diameter. The closed-loop controller is robust, both to external and internal disturbances like electrode movements and muscle fatigue, respectively. More recently, innovative control strategies have been developed and tested in simulation studies, where a dedicated biomechanical model of the entire WRS-patient system was used. In particular, patient-driven control approaches were considered, where stimulation patterns are controlled by voluntary upper body efforts and no predetermined reference trajectories are required.
FUTURE PLANS--The training program is still in progress and other persons with paraplegia will be included. The experimental implementation of simulated patient-driven control strategies with and without the WRS will be tested in a next stage.
[090] PARAPLEGIC WALKING MADE PRACTICAL WITH FNS AND ORTHOSES
E. Byron Marsolais, MD, PhD; Dwight T. Davy,
PhD
Cleveland FES Center, Cleveland VA Medical Center,
Cleveland, Ohio 44106; Departments of Orthopaedics and
Biomedical Engineering, Case Western Reserve University,
Cleveland, Ohio, 44106; email: ebm2@po.cwru.edu
Sponsor: National Institute of Child Health and Human Development and the National Institute of Neurological Disorders and Stroke; Department of Veterans Affairs Center of Excellence in FES, Cleveland VA Medical Center, Cleveland, OH
PURPOSE--To determine whether the combination of eight channels of implanted functional electrical stimulation (FES) and a functionally activated trunk-hip-knee-ankle-foot orthosis can result in a practical mobility aid for use in the complete paraplegic individual. Our focus is to provide sufficient control to the existing FES capability to allow meaningful functions, such as crutch walking and stair climbing, and to develop a brace system acceptable to the patient and society, from the aspects of function, reliability, safety, ease of use, appearance and cost.
METHODOLOGY--We plan to fit multiple subjects with the combination of an 8-channel, radio frequency (RF) controlled and powered, implantable stimulator, or a percutaneous FES system, with a prototype low weight, functional orthosis having active, computer-controlled joint locks. A hybrid orthosis will result from combining this technology with expertise in electro-mechanical brace design from CWRU, Henry Ford Hospital of Detroit, and New York University (NYU). A physical therapist will utilize accepted and modified outcome assessment and energy consumption measures to determine the user's ability to function in the household or the community at large.
PROGRESS--Development of surgical techniques for implantation of 8 channel RF-powered and controlled FES systems have been refined and implemented in five subjects participating in related projects, beginning Fall 1997.
RESULTS--The first subject is using the hybrid system for ambulation and exercise. Additionally, six T-1-T-11 paraplegic subjects have participated in a study to evaluate the functional capabilities of a computer controlled hybrid orthotic system. After a thorough review of the state of the art in orthotic systems, a design team constructed a platform orthosis. Subjects have learned to use the custom-built reciprocal gait orthosis without stimulation and with stimulation activating between 4 and 16 muscles. Outcomes were scored with standard physical therapy measures, including the Tinetti test, timed get up and go, Borg energy exertion, and the functional index measure. Subjects have successfully accomplished sit-to-stand, stand-to-sit, and walking maneuvers measured for time, speed, distance, and metabolic output. FIM scores indicated that system users would become slightly more independent in mobility categories. Perceived exertion as measure with the Borg scale indicated that use of the bracing system with FES was 'easier' than without stimulation. Subjects were able to exhibit distance walking which would allow limited but useful ranges of 500 m at average speeds of 0.2-0.3 m/s. Walking speeds for 30 and 50 m distances reached 4 to 4.5 m/s. Metabolic output measured in the light work region of 7 METs. Additionally, walking distance with stimulation were two times or greater than those of nonstimulated reciprocal gait.
IMPLICATIONS--A less constrained brace combined with an implantable FES system will, as indicated by these results, allow a completely paralyzed user to attain a limited level of community ambulation.
[091] UNASSISTED STANDING BY FUNCTIONAL ELECTRICAL STIMULATION
Ronald J. Triolo, PhD; Robert F. Kirsch, PhD; John A.
Davis Jr., MD
Cleveland FES Center, Case Western Reserve University,
Cleveland OH 44106; Department of Orthopaedics, Metro Health
Medical Center, Cleveland OH; Department of Orthopaedics,
Case Western Reserve University, Cleveland, OH; email:
rxt24@po.cwru.edu
Sponsor: Neural Prosthesis Program, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Washington, DC; Department of Veterans Affairs Center of Excellence in FES, Cleveland VA Medical Center, Cleveland, OH 44106-1702
PURPOSE--The long-term goal of this project is to develop methods to provide brace-free, energy-efficient standing for persons with complete thoracic level spinal cord injuries (SCI) via functional neuromuscular stimulation (FNS). The objectives are to define the fundamental requirements, develop the control strategies, and understand the factors limiting the performance of systems designed to automatically resist reasonable disturbances to balance and free the upper extremities for manipulating objects in the environment while standing. These objectives are being addressed through anatomical modeling, dynamic modeling and controller development, simulation and optimization, and experimental demonstration of new control structures. This work is conducted in partnership with collaborators at Northwestern University and the University of Kentucky.
METHODOLOGY--A biomechanical model of the lower limbs and torso that accurately reflects the actions of FNS on paralyzed muscle and incorporates the behavior of non-ideal and commercially available body-mounted sensors is being developed. The model will be employed to construct dynamic simulations and perform optimization procedures to investigate the theoretical behavior of various FNS control systems for providing automatic postural adjustments. Predictions from the simulations will drive the implementation and experimental demonstration of the postural control systems in human volunteers. Results of human trials will be used to refine the model or reformulate the control simulations.
The methods for automatic control of posture are based on the assumption that no single control strategy will be sufficient to achieve the requisite standing performance. The inherent passive stiffness of the joints and the responsiveness provided by the active stiffness resulting from low levels of continuous co-activation of agonist-antagonist muscle groups will be used to help insure stability. A variety of controllers that modulate stimulation in response to, or in preparation for, a change in postural load will be simulated, implemented, and tested with the aim of integrating the best elements of each into a coordinated artificial postural control system.
Both fixed-parameter, and sensor-based control strategies will be investigated. Fixed-parameter controllers will include systems that slowly vary the position of the center of mass over the base of support, or that allow the user to select a posture and define the stiffness in a preferred direction in advance of a disturbance or voluntary movement of the upper extremity. Sensor-driven systems will include joint angle and acceleration-based controllers to mimic proprioception and vestibular-like responses.
PROGRESS--Anatomical specimens from the erector spinae, quadratus lumborum, and rectus abdominis have been collected from four specimens, and muscle architecture is being parameterized for inclusion in a biomechanical model of the spine and trunk that will be integrated with an existing computer representation of the lower musculo-skeletal system. Methods to compute system dynamics from records of muscle activation patterns have been established, and initial simulations of simple control systems have been completed. Novel computational techniques to analyze closed-chain bipedal stance in three dimensions have been created and related to real-world conditions. Methods to calculate disturbances to posture from volitional arm movements have also been established and will be used to simulate perturbations to balance during volitional or unintentional movements for which the automatic controllers must compensate. Algorithms to adapt for changes in muscle recruitment properties have been developed and tested in simulation.
FUTURE PLANS--Anatomical modeling and simulation will continue after the spine parameterization is completed. Immediate plans include experimental determination of joint stiffness and other model parameters in individuals with spinal cord injuries. Optimization procedures and sensitivity analyses are being conducted with the existing biomechanical model. Baseline performance of simple open loop systems for standing will also be determined and used for comparison with the advanced control systems under development.
[092] IMPLANTABLE FNS SYSTEMS FOR STANDING TRANSFERS
Ronald J. Triolo, PhD; John A. Davis Jr., MD
Cleveland FES Center, Case Western Reserve University,
Cleveland OH 44106; Department of Orthopaedics, Metro Health
Medical Center, Cleveland OH; Department of Orthopaedics,
Case Western Reserve University, Cleveland, OH; email:
rxt24@po.cwru.edu
Sponsor: Office of Orphan Product Development, Food and Drug Administration, 5600 Fishers Lane, Rockville, MD 20857; Department of Veterans Affairs Center of Excellence in FES, Cleveland VA Medical Center, Cleveland OH 44106-1702
PURPOSE--This project is designed to provide standing and transfer function to individuals with low-cervical or high-thoracic spinal cord injury (SCI) via an implanted functional neuromuscular stimulation (FNS) system. Injuries at these levels compromise mobility, increase dependence on families, caregivers, or assistants, and compound the risk of medical complications secondary to paralysis. Conventional transfers are problematic for individuals with elderly spouses or caregivers who lack the strength to assist with the lifting phases of the maneuvers. Our long-term objective is to introduce into clinical practice a neuroprosthesis that will allow individuals with SCI to stand and transfer with minimal assistance, thereby increasing independence, personal mobility, and overall health and well-being.
METHODOLOGY--A surgically implanted FNS system for standing and transfers is being implemented in five volunteers with injuries between the levels of C6 and T12. The system consists of epimysial and surgically implanted intramuscular electrodes, and the CWRU/VA 8-channel implantable receiver/stimulator (IRS-8). A wearable external control unit (ECU) provides power and command signals to the implant.
After a period of preparatory exercise with surface stimulation, the IRS-8 is installed in a single surgical procedure. Epimysial electrodes are implanted bilaterally into the quadriceps (vastus lateralis/intermedius), gluteus maximus, and semimembranosus or posterior portion of the adductor magnus. Intramuscular electrodes are inserted at the level of the L1/L2 spinal roots to activate the erector spinae. Electrode leads are routed to sites on the abdomen and connected to the IRS-8, which is sutured to the abdominal fascia. After 2 weeks of immobilization and bedrest, volunteers are released to home for an additional period of restricted activity before reconditioning exercise is initiated 6 weeks post-implant.
Outpatient rehabilitation consists of progressive resistance and closed-chain exercise followed by standing, balance and transfer training using the implanted neuroprosthesis. Functional outcomes are assessed with customized ratings of system usability, and measures of effort and assistance required to complete maneuvers with and without FNS. Long-term follow-up of system use and performance in the home and community environments continues for a full year after demonstrating safety and proficiency with the system.
PRELIMINARY RESULTS--To date, three volunteers have enrolled in the project. The two recipients of the implanted standing/transfer system have complete motor paraplegia resulting from high- to mid-thoracic-level SCI. In both, all incisions from the implant procedures healed without incident, and all implanted components are intact and operational. The electrodes exhibit stable thresholds and produce contractions of sufficient strength for functional activities. The first subject was able to exercise and stand repeatedly with approximately 90 percent of his body weight on his legs using the FNS system. He can perform standing transfers from low to high surfaces with the neuroprosthesis. Rapid fatigue of the quadriceps and a discontinuity in one hip extensor electrode limit system performance and a revision surgery is being planned for late 1998. The second subject is currently undergoing reconditioning exercise with FNS and is scheduled to begin standing and balance training in the last quarter of 1998. The third volunteer sustained a motor and sensory incomplete cervical level lesion. He is scheduled to receive the implant in September 1998.
FUTURE PLANS--Home visits will be performed with all subjects to facilitate integration of the system into their daily routines. New evaluation and assessment scales currently under development will be applied and refined. Recruiting for additional study participants will continue until a total of five local subjects are enrolled and implanted. This project should lead to a Phase 2 clinical trial of the system involving a larger number of subjects in a multicenter study.
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