A. General
[77] REHABILITATION OF THE COLON AFTER SPINAL CORD INJURY: A PILOT STUDY
Lisa Riedy, PhD; Keith Bruninga, MD; James S. Walter,
PhD; Ali Keshavarzian, MD
Rehabilitation Research and Development Center, Hines,
IL 60141
Sponsor: Department of Veterans Affairs, VA
Rehabilitation Research and Development Service, Washington,
DC 20420
(Pilot Project #B1511-PA)
PURPOSE--The objectives of this study included: 1) establishing baseline parameters of normal colonic responses in the cat model; 2) evaluating direct colonic stimulation using implanted electrodes; and 3) comparing direct colonic stimulation with stimulation of the sacral nerves for managing constipation and fecal impaction.
METHODOLOGY--The effect of direct electrical stimulation on colonic transit and manometric recordings following spinal cord injury (SCI) were assessed in five adult male cats. Intra-colonic catheters were surgically placed, stimulating electrodes were sutured to the colonic serosa, and a laminectomy with spinal cord clamping at a T4 level was done to induce SCI. Twenty radiopaque markers were inserted through an intra-colonic catheter located 1 cm distal to the cecum and were monitored with daily fluoroscopy as a measure of colonic transit. Transit measurements were compared before SCI, after SCI, and after SCI with electrical stimulation of 40 pps, 1 ms, and 0-50 mA.
PROGRESS--Patterns of long duration, nonpropagating colonic contractions were identified. Spontaneous colonic phasic motor activity was observed both before and after SCI and was similar. Manometric defecation patterns were also observed to be similar between animals before SCI and after SCI with electrical stimulation.
RESULTS--Colonic transit following SCI was significantly prolonged (p<0.05) when compared to the transit before SCI. Electrical stimulation following SCI improved colonic transit to values not significantly different from those before SCI. These findings demonstrate that colonic transit was prolonged following SCI and that direct electrical stimulation of the colon following SCI improved colonic transit in an animal model.
FUTURE PLANS--The goal is to expand from the progress made during this pilot project using suture electrodes for direct colonic stimulation and evaluate wireless microstimulators as a state-of-the-art approach to constipation treatment after SCI.
[78] FECAL INCONTINENCE TREATMENT IN SCI PATIENTS: A PILOT STUDY
Lisa Riedy, PhD; Rani Chintam, MD; James S. Walter,
PhD
Hines VA Medical Center, Rehabilitation Research and
Development Center, Hines, IL 60141
Sponsor: Department of Veterans Affairs, VA
Rehabilitation Research and Development Service, Washington,
DC 20420
(Pilot Project #B1840-PA)
PURPOSE--The objectives of this study include: 1) determining whether the frequency of fecal incontinence can be reduced in SCI patients by using surface electrodes placed around the anal sphincter; 2) evaluating anal rectal function using manometry in SCI patients with fecal incontinence; and 3) determining if there are any other benefits associated with external anal sphincter stimulation, such as decreased urinary incontinence, decreased lower limb spasticity, and/or effect on stool impaction.
METHODOLOGY--Study subjects will include a group of 15 SCI patients from the Hines VA Hospital. Inclusion criteria will include 10 male and 5 female SCI patients with fecal incontinence. Exclusion criteria will include patients with active urine infection, decubiti, cardiovascular disease, cardiac pacemakers/defibrillators, and pregnancy. Subjects will participate in the study for a total of 12 weeks. The study will consist of a 1 week prestimulation period during which the patient will document any episodes of fecal incontinence. During the next 10 weeks, patients will use the surface stimulation to manage their fecal incontinence. For the final week of the study, electrical stimulation will be discontinued in order to assess any benefits and improvements associated with the treatment. Throughout this study, patients will maintain a daily log to document bowel function and will be contacted weekly, by phone, to assure protocol compliance and sort out any technical problems that may occur.
PROGRESS--We plan on evaluating surface stimulation using a small battery-powered stimulator and self-adhering surface electrodes in 15 patients over a 12-week period.
RESULTS--Recently, one SCI patient has been enrolled into the study. He has been trained in the use of the device and will begin evaluating the device at home. Based on a bedside evaluation of the device, surface stimulation around the anal sphincter resulted in anal pressure changes of 60 cm water with a stimulation protocol of 100 mA, 35 pps, and a pulse duration of 300 µsec.
FUTURE PLANS--The primary goal is to continue recruiting patients for this study.
[79] HIGH CHARGE DENSITY, BIPOLAR ELECTRODES FOR CHRONIC FNS
James S. Walter, PhD; Lisa Riedy, PhD; Paul
Zaszczurynski; Stuart S. Cogan, PhD
Hines VA Rehabilitation Research and Development Center,
Hines, IL 60141; EIC Laboratories, Norwood, MA 02062
Sponsor: Department of Veterans Affairs, VA
Rehabilitation Research and Development Service, Washington,
DC 20420
(Project #B658-2RA)
PURPOSE--Functional neuromuscular stimulation (FNS) is used in the treatment of many neurological disorders, including bladder dysfunction, respiratory pacing, and limb paralysis. Stainless steel (316LVM) electrodes are often used for FNS applications requiring mechanical strength and fatigue resistance. However, this electrode material may be susceptible to pitting corrosion. We observed that chronic stimulation using 20 µC/cm2 led to the onset of irreversible faradic processes which resulted in tarnishing. This observation was the same for electrodes pulsed either with anodic- or cathodic-first pulsing. To develop high charge injection density electrodes, we have investigated iridium (Ir) on stainless steel electrodes.
METHODOLOGY--Wire electrodes of 316LVM stainless steel were coated with Ir metal by DC magnetron sputtering at EIC Laboratories. A thin film of Ti was sputtered onto the 316LVM as an adhesion layer prior to Ir deposition. The sputtering was accomplished with an Ar plasma at a pressure of 10 millitorr for the Ti deposition and 22 millitorr for the Ir deposition. The sputtering was done at an average current density of 7.5 mA/cm2 over 3 cm length targets.
PROGRESS--IR coatings have shown resistance to high charge injection protocols. The coated electrodes appear suitable for bipolar pulsing protocols. There is a typical tissue reaction to chronically implanted electrodes although adherence of the Ir coating in the in vivo environment needs to be improved.
RESULTS--In our in vitro characterizations, the principal finding was that the iridium coated stainless steel electrodes are resistant to corrosion at charge injection densities, as high as 320 µC/cm2 for anodic and cathodic-first pulsing. Active surface disruptions indicating corrosive processes were present at higher charge injection densities. These charge injection densities are much higher than the maximum of 40 µC/cm2 for uncoated 316LVM stainless steel electrodes. Potential transients were low for all of the charge injection protocols.
The histological responses to implantation and the adherence of the iridium coating to the electrodes were evaluated. Seven electrodes composed of 3 cm of Ir coated and 3 cm of uncoated stainless steel were surgically implanted in the hind leg muscles of cats. Electrical stimulation was not applied to any of the electrodes. Forty-two days after implantation, the animals were euthanized and the electrodes with surrounding tissue were harvested. All of the muscle strips adjacent to the electrode showed signs of chronic inflammation including fibrocites and connective tissue. Although, this inflammatory response was a concern, there was no apparent difference between the 316LVM stainless steel and Ir portions of the electrode. Since these electrodes were implanted into the quadriceps muscles of active cats, movement may have contributed to this immune response. None of the cross-sections of the sham control muscles adjacent to the electrode area exhibited signs of injury.
The Ir film was visibly altered by implantation in some animals. Corrosion was not observed on the 316LVM stainless steel but sparse delamination of the Ir layer was noted on two of the seven electrodes with extensive delamination noted on one other electrode. These results indicate that adherence of the coatings continue to be a concern.
FUTURE PLANS--Coatings with improved adherence are under investigation.
[80] REHABILITATION OF URINARY INCONTINENCE USING STIMULATED MUSCLE FLAPS: A PILOT STUDY
John S. Wheeler, MD; James S. Walter, PhD; James H.
Griffin, MD; Brett Trockman, MD; Jeff Norris, MD; Wuying
Cai, MD
Hines VA Medical Center, Rehabilitation Research and
Development Center, Hines, IL 60141; Loyola Medical Center,
Department of Medicine, Maywood, IL 60153
Sponsor: Department of Veterans Affairs, VA
Rehabilitation Research and Development Service, Washington,
DC 20420
(Pilot Project #E1583-PA)
PURPOSE--This study is evaluating the effectiveness of stimulated skeletal muscle flaps in elevating urethral closure pressure in a male dog model. Urethral ischemia and stricture formation are known complications of urethral wrap procedures and are being evaluated. This goal is particularly relevant to the patient following radical prostatectomy where urinary incontinence can be a problem.
METHODOLOGY--Dogs were implanted with a fully implantable myoplasty stimulator. The gracilis muscle was loosely wrapped around the urethra to avoid the potential for stricture formation. An 8-week training period was conducted and followed by continuous stimulation for 6 weeks. Efficacy of the neosphincters was determined with urethral and leak point pressure measurements. Urethral stricture formation was assessed by dissection postmortem.
PROGRESS--Male dogs with stimulated skeletal muscle flap have been evaluated with the gracilis muscle wrapped around the urethra. High urethral closure pressure was obtained with low stimulation parameters. The surgical procedures were easy to perform.
RESULTS--Studies have been conducted in five dogs. Under anesthesia, urethral pressure increases of 10 to 150 cm H20 were recorded with stimulation at 12 Hz and stimulating voltages from 0.5 to 3 mA. Little or no fatigue in the peak pressure response was noted during 10 min of stimulation. One of the animals completed training and continuous stimulation with high pressure responses to stimulation. Four other animals failed at varied times after implantation and were sacrificed. Problems in all four animal appeared to be related to electrode dislodgment or connections to the stimulator. Nerve injury possibly related to excessive stretch with the muscle wrap around the urethra may have occurred. Urethral stricture was not observed in any of the animals, but the urethra was seen to be pulled from the midline of the perineum by the skeletal muscle flap.
FUTURE PLANS--Two additional animals are being investigated.
[81] REHABILITATION OF RESPIRATORY PARALYSIS: ACCESSORY MUSCLE STIMULATION
Robert B. Dunn, PhD; A. Agrawal, MD; James S. Walter,
PhD
Hines VA Medical Center, Rehabilitation Research and
Development Center, Hines, IL 60141; Loyola Medical Center,
Department of Medicine, Maywood, IL 60153
Sponsor: Department of Veterans Affairs, VA
Rehabilitation Research and Development Service, Washington,
DC 20420
(Project #B806-RA)
PURPOSE--Activation of the diaphragm via phrenic nerve stimulation has been used for respiratory management of chronic ventilatory insufficiency for over 25 years. However, even with recent improvements in electrode technology, the lack of coordinated contractions from accessory support muscles has severely limited the usefulness of this technique in many cases. Lack of accessory thoracic muscle stimulation causes a collapse of the chest wall during inspiration, which decreases the efficiency of breathing and contributes toward diaphragm fatigue and failure. Electrical activation of the chest wall inspiratory muscles would assist the diaphragm and increase the efficiency of diaphragm pacing. Further, activation of expiratory muscles would provide additional support and demonstrate the feasibility of inducing an electrically generated cough. The purpose of this project is to determine if intramuscular electrodes in the chest wall can selectively activate intercostal and parasternal muscles which assist chest expansion and promote inspiration.
METHODOLOGY--All patients selected had low cervical lesions, were at least 1-year postinjury, and were medically stable. A spirometry evaluation that included basic lung volumes and capacities was performed. Both upright and supine evaluations were performed. In addition to spirometry, thoracic excursions were monitored by a low resistance respiratory belt placed mid-thorax. Stimulation was carried out with small needle electrodes pushed through the skin and into the superficial intercostal muscle layer. Battery powered neuromuscular stimulators set at 35 pps, 100 µs duration, 12 mA was delivered bilaterally for a 2 s period at the end of a maximal inspiration. Changes in lung volume and chest excursions were noted before, during, and following stimulation.
PROGRESS--We have demonstrated in high level spinal cord injured (SCI) subjects that intramuscular electrodes are capable of stimulating thoracic muscles that support inspiration. Currently studies are underway to provide the best thoracic locations for electrode placement and the optimal stimulating parameters for diaphragm assistance.
RESULTS--A total of seven patients were studied. In two, some chest excursion occurred during spontaneous inspirations. Thoracic stimulation in these individuals at the end of a maximal inspiration did not produce an increase in inspired volume or evidence of chest expansion. In two other individuals, afferent activity present in the upper chest produced sufficient discomfort during stimulation that the procedure was terminated. In the remaining three subjects inspiration was associated with a collapsing chest wall. Stimulation after maximal inspiration produced an additional inspired volume of 284±38 ml (mean ±SEM) and chest movement toward expansion. There were no differences between the upright and supine positions. The greatest response was found for electrodes in the third intercostal space close to the midline. Spontaneous breathing connected to the spirometer produced an average tidal volume of 501±31 ml. Thus, the stimulated volume represented 57 percent of the individuals normal tidal volume.
FUTURE PLANS--Experiments will continue to refine stimulation parameters and determine the electrode locations that best support the diaphragm during inspiration.
[82] NEUROPROSTHETIC CONTROL OF BLADDER AND BOWEL IN SPINAL CORD INJURY PATIENTS
Donald R. Bodner, MD; Graham H. Creasey, MD
Spinal Cord Injury Unit, Wade Park VA Medical Center,
Cleveland, OH 44106; Spinal Cord Injury Unit, MetroHealth
Medical Center, Cleveland FES Center, Cleveland, OH 44109;
email: ghc@po.cwru.edu
Sponsor: Department of Veterans Affairs, VA
Rehabilitation Research and Development Service, Washington,
DC 20420
(Project #B804-RA)
PURPOSE--The purpose of this research is to evaluate bladder, bowel, and sexual function in patients with spinal cord injury (SCI) before and after implantation of an electrical stimulator for activation of the sacral anterior nerve roots. The goal of the research is improved bladder, bowel, and sexual function, reduction of bladder and bowel complications, and increased independence following SCI.
METHODOLOGY--Subjects with complete SCI and complications of bladder, bowel, and sexual function are being implanted with an electrical stimulator intended to reduce these complications. This device consists of electrodes implanted surgically on the sacral nerve roots at the base of the spine, and connected by fully implanted wires to a stimulator implanted surgically under the skin of the front of the chest. This stimulator is powered and controlled by transmission of radio waves from a battery-powered portable controller outside the body, operated by the subject. Subjects are being evaluated before and after operation with regard to bladder, bowel, and sexual function using clinical examination and investigation including urodynamics.
PROGRESS--Eight subjects have received these implants, the first of this type in the United States. Recruitment has also been extended to nonveterans.
PRELIMINARY RESULTS--All subjects are using the stimulator routinely at home for emptying the bladder. Residual volumes are low and infection rates have been reduced. All have discontinued routine use of indwelling or intermittent catheterisation and those with good hand function no longer use leg bags. All have found that regular use of the stimulator reduces constipation, and four use it to produce defecation. In four of the five males the stimulator also produces penile erection.
FUTURE PLANS--Recruitment and follow-up of subjects will continue among veterans and nonveterans, and has been extended to other centers in the USA. A smaller, lighter external controller capable of being programmed by computer will be introduced. New techniques will also be tested to improve bladder and bowel control, by the use of more selective electrical stimulation which activates bladder and rectum without activation of the sphincters.
[83] EVALUATION AND OPTIMIZATION OF FES TECHNIQUES FOR EXERCISE
Roger M. Glaser, PhD; Thomas Mathews, MD; Thomas W. J.
Janssen, PhD; D. Drew Pringle, EdD; Agaram G. Suryaprasad,
MD; Satyendra C. Gupta, MD; Jose W. Almeyda, BS; William P.
Couch, BS
VA Medical Center, Dayton, OH 45428; Institute for
Rehabilitation Research and Medicine, Wright State
University School of Medicine, Dayton, OH 45435;
Rehabilitation Institute of Ohio, Miami Valley Hospital,
Dayton, OH 45409; email: rglaser@desire.wright.edu;
mathews.thomas@dayton.va.gov;
tjanssen@desire.wright.edu;
dpringle@desire.wright.edu
Sponsor: Department of Veterans Affairs, VA
Rehabilitation Research and Development Service, Washington,
DC 20420
(Project #B433-2RA)
PURPOSE--The purpose of this program was to provide effective functional electrical stimulation (FES) exercise techniques for improving health, physical fitness, and rehabilitation outcome of individuals with spinal cord injury (SCI). Objectives were to continue evaluation of acute and chronic physiologic responses (musculoskeletal, aerobic metabolic and cardiopulmonary) to existing FES exercise modes including knee extension (KE), leg cycle ergometry (LCE), and combined FES-LCE + voluntary arm-crank ergometry (HYBRID), assessing potential benefits and risks of these therapies to persons with SCI; to modify the design of existing FES exercise devices to optimize muscular, aerobic, metabolic, and cardiopulmonary responses to the various FES exercise modes, while maintaining user safety; and to design more progressive FES exercise training protocols to optimize adaptations of the muscles utilized and the cardiopulmonary system.
METHODOLOGY--Groups of subjects with SCI were administered a series of exercise stress tests to determine the initial performance (i.e., strength and endurance) of their paralyzed lower-limb muscles for FES, and their arm muscles, as well as to determine their peak metabolic and cardiopulmonary responses. Subjects were then assigned to participate in a series of 12-week exercise training programs using the various FES exercise modes and protocols. They were again exercise stress-tested after each training program to determine changes in fitness. Modifications to the FES instrumentation design were tested to optimize the physiologic responses and enhance training effects. A questionnaire was used to assess changes in medical problems during participation in FES exercise programs.
RESULTS--The final phase of this project involved evaluation of acute physiologic responses for using a modified Therapeutic Alliances Incorporated model ERGYS I FES-LCE, as well as the changes in these responses following a specially designed interval training program. Modifications included: increasing the FES current limit from 140 to 300 mA; adding the tibialis anterior and gastroc-soleus muscles to the quadriceps, hamstrings, and gluteus maximus muscles; and widening FES firing angles from about 70 to 120° to increase contraction duty cycle from about 0.23 s to 0.40 s. These modifications were accomplished with a specially constructed 10-channel current booster and a specially programmed ROM chip. Exercise stress testing demonstrated that this modified FES-LCE elicited significantly higher magnitudes of metabolic and cardiopulmonary responses.
For exercise training, we tested an aggressive interval training program protocol, which presented greater and more continuous "overload" of the subjects. To enable this, an electronic circuit was designed and constructed to permit adjustment of LCE load resistance during pedaling, without the necessity to stop exercise and reprogram the computer. Prior to and following interval training program, we also evaluated the performance of each muscle group on our KinCom isokinetic dynamometer by incorporating a specially designed and constructed electrical stimulator and a repetitive isometric contraction protocol. Significant improvements in muscular, metabolic, and cardiopulmonary responses were found, even in subjects who have plateaued in performance during long-term FES-LCE use. These results suggest that the modified FES-LCE used in conjunction with the interval training program can elicit accelerated and greater physiologic training adaptations than the original FES-LCE.
IMPLICATIONS--This project has resulted in greater knowledge concerning the muscular, metabolic, cardiovascular and pulmonary responses to various FES-induced exercise modes. It also demonstrated that the magnitudes of these physiologic responses can be increased, while maintaining safety, by altering the FES parameters, muscle mass utilized, contraction duty cycle, and the exercise protocol. Optimizing these factors can result in accelerated and greater levels of training adaptations. Our results suggest that patients with SCI should derive important benefits from FES-induced exercise, beyond those derived from conventional arm exercise therapy, including higher levels of physical fitness, lower incidence of secondary medical complications, and improved rehabilitation outcome.
[84] MANAGEMENT OF URINARY DISORDERS IN SCI
James S. Walter, PhD; John S. Wheeler, MD; Robert D.
Wurster, PhD
Rehabilitation Research and Development Center, VA Hines
Hospital, Hines, IL 60141; Loyola Medical Center, Department
of Urology and Physiology, Maywood, IL 60153
Sponsor: National Institutes on Health, National Center For Medical Rehabilitation Research
PURPOSE--This project has two overall goals: 1) to apply functional electrical stimulation techniques for bladder voiding and incontinence management after spinal cord injury (SCI), and 2) to use new monitoring capabilities of implantable neuroprosthetics for continuous recording of lower urinary tract functions. These goals are particularly relevant to the SCI patient where control over voiding functions such as emptying and continence are lost. Moreover, current treatments such as intermittent catheterization, continuous catheterization or external catheterization are not always effective and can have significant side effects such as autonomic dysreflexia, urinary tract infections, and upper urinary tract problems.
METHODOLOGY--Direct bladder stimulation was evaluated before and after SCI in tethered male cats. Animals received either an upper motor neuron lesion or a lower motor neuron lesion. Animals were instrumented under anesthesia with five "suture" type electrodes consisting of multistranded 316LVM stainless steel with a needle placed at the electrode tip and sutured into the serosa of the bladder wall. Four electrodes were implanted near the ureters in the trigone area. One electrode was implanted in some of the animals for impedance monitoring of bladder volume. Additional instrumentation consisted of two suprapubic bladder catheters for recording bladder pressure and bladder filling and a peritoneal balloon for recording abdominal pressure. EMG recording electrodes were implanted in the pelvic floor and leg quadriceps. Laboratory stimulators were used.
PROGRESS--Prolonged bladder contractions and voiding to direct bladder stimulation occurred before and after SCI in both groups of animals. High maximal voiding rates were also seen in both groups of animals. Voiding responses to stimulation were less effective at small bladder volumes. Fluoroscopy of the urethra during stimulation induced voiding showed a narrow penile urethra indicating that this animal model of the lower urinary tract is quite different from humans.
RESULTS--In instrumented tethered animals, responses to direct bladder stimulation were recorded. All 10 cats responded to direct bladder stimulation before SCI using a single 3 seconds stimulation period, at 40 Hz, 1 ms pulse duration and a stimulating current from 7.5 to 40 mA. The maximum voiding rates were from 0.5 to 1.5 ml/sec with complete bladder emptying, particularly after the first 2 or 3 weeks. Peak detrusor pressures were from 40 to 70 cm H20. Voiding could be obtained without discomfort to the animal.
Five of the 10 male cats also received an upper motor neuron lesion and 5 received a lower motor neuron lesion. Stimulation induced voiding in these SCI animals. Maximum voiding rates after SCI were similar to before SCI but the volume voided was reduced to 4 to 10 ml at peak detrusor pressures from 30 to 70 cm H20. Similar responses were seen after upper and lower motor neuron lesions. Fluoroscopy of the urethra during stimulation induced voiding showed a narrow penile urethra that restricted urine flow in both groups of animals.
FUTURE PLANS--Alternative stimulators may improve direct bladder stimulation techniques. Microstimulators are small implantable stimulators that do not have connecting wires as they are activated by external RF fields. We are proposing to evaluate these devices in the future for direct bladder stimulation.
[85] MICROSTIMULATION OF THE LUMBOSACRAL SPINAL CORD: MAPPING
Warren M. Grill, PhD; Narendra Bhadra, MD, MS;
Bernadette Erokwu, DVM; Musa Haxhiu, MD, PhD
Cleveland FES Center, 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, Division of Fundamental Neurosciences, Neural Prosthesis Progam, Bethesda, MD 20892
PURPOSE--The objective of this project is to investigate the feasibility of neural prosthetics based on stimulation of the spinal cord with penetrating microelectrodes. Specific attention is given to control of bladder, bowel, sexual function, and control of skeletal muscle. The results of this project will answer fundamental questions about microstimulation of the spinal cord, and lead to development of a new generation of neural prosthetics for individuals with neurological impairments.
METHODOLOGY--Chemical and viral retrograde tracers are used to determine the location and rostrocaudal extent in the spinal cord of the neuronal populations that control genitourinary and motor functions in the male cat and rat. Stimulation of the spinal cord with penetrating activated iridium microelectrodes is used to determine the physiological effects of activation of different neural populations in male cats.
PROGRESS--The transneuronal retrograde tracer pseudorabies virus (PRV) was used to determine the central nervous system (CNS) innervation of the bladder and urethra in male rats. In rats with CNS infection documented by immunohistochemistry, retrogradely labeled neurons were identified along the neuraxis, including the spinal cord, medulla, pons, and hypothalamus. After longer postinjection intervals, neurons in amygdala, hippocampus, primary motor cortex, and piriform cortex were also labeled. The distribution of labeled neurons following injection of PRV into the wall of the urethra was quite similar to the pattern of innervation observed after injection into the wall of the urinary bladder.
These studies indicate that urinary bladder and urethra are innervated by diverse, but similar CNS cell groups. Experiments with PRV and the conventional retrograde tracers fluorogold and cholera toxin beta-subunit are underway in male cats. The results of these experiments will identify neuronal populations to be targeted for microstimulation, as well as reveal the consistency of organization across species.
The pressures generated in the bladder and along the urethra by microstimulation of the sacral spinal cord were recorded in male cats anesthetized with alpha-chlorolose. Bladder pressures were measured via a superpubic catheter, and urethral pressures were measured with a urethral catheter containing 2 solid-state micromanometers. Vertical, dorsal-to-ventral penetrations were made at different mediolateral and rostrocaudal locations and responses were evoked at 200 µm intervals. Bladder pressures could be generated by stimulating over a widespread region of the S2 segment. However, the largest pressures (30-40 cmH20) were generated at locations in the dorsolateral aspect of the ventral horn, consistent with the location of the axons of the preganglionic parasympathetic motoneurons innervating the bladder. At more ventral locations, direct activation of urethral and pelvic somatic musculature was observed. The co-activation of the bladder and the pelvic musculature measured at these locations was consistent with responses generated by stimulation of the S2 ventral root. Bladder pressures could also be generated by stimulation within the dorsal horn of S2, although these pressures were not as large as those evoked in more ventral locations.
In the more dorsal region, bladder pressures were accompanied by varying amounts of urethral pressure responses. The responses generated in more dorsal locations were presumably generated by transsynaptic activation of preganglionic motoneurons via afferent terminals and/or interneurons. This interpretation is consistent with genitourinary responses generated by stimulation of the S2 dorsal root.
The results of these experiments indicate that large bladder pressures can be generated by microstimulation of the spinal cord with a single penetrating microelectrode. However, the largest responses are accompanied by increases in the urethral pressure. Current efforts are to correlate the profile of pressures along the urethra with the urethral anatomy in male cats, and to investigate modulation of urethral pressure by microstimulation of the spinal cord.
[86] THE DYNAMIC MODEL OF SKELETAL MUSCLES AND JOINTS
Moshe Solomonow, PhD; Richard V. Baratta, PhD; Bing-He
Zhou, EE; Robert D. D'Ambrosia, MD
Bioengineering Laboratory, Department of Orthopaedic
Surgery, Louisiana State University Medical Center, New
Orleans, LA 70112
Sponsor: National Science Foundation, Arlington, VA 22330
PURPOSE--Discerning the correct frequency 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, which 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, which recruits motor units in an orderly fashion.
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.
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 Hz 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.
[87] EMG-FORCE MODELS IN MUSCLES WITH VARIOUS FIRING RATE AND RECRUITMENT STRATEGIES
Moshe Solomonow, PhD; Richard V. Baratta, PhD; Robert D.
D'Ambrosia, MD
Bioengineering Laboratory, Department of Orthopaedic
Surgery, Louisiana State University Medical Center, New
Orleans, LA 70112
Sponsor: National Science Foundation, Arlington, VA 22330
PURPOSE--The EMG-force relationships were a controversial and unsolved problem for many years, having been reported as linear by many investigators and as nonlinear by many others. Recent data suggest that the different firing rate and recruitment strategies of different muscles may be the source of the controversy. Precise knowledge of the relations assists in the diagnostics of movement disorders, understanding muscle properties, and designing orthotic systems.
METHODOLOGY--With the aid of our new stimulation system, we determined the effect of various control strategies on the EMG-force relationships to show that strategies employing recruitment of all the motor units of the muscle to generate the initial 50 percent of the maximal force, in conjunction with pure firing rate increase to generate the final 50 percent of the force, yield a linear EMG-force model. A progressive increase in the force proportion by motor units recruitment over 50 percent resulted in a predictable, progressive increase in nonlinearity of the relationships.
PROGRESS--Complete models were developed for various control stratagems, as well as for fast and slow twitch muscles. Current work focuses on the effect of contraction rate and joint angle (muscle length) on the EMG-Force relationships.
It was also shown that a single muscle can change its control strategy when performing different types of contractions, thereby changing its EMG-Force relationships. The EMG-Force relations, therefore, are dependent on several variable that should be considered for a given contraction type.
[88] 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
Bioengineering Laboratory, Department of Orthopaedic
Surgery, Louisiana State University Medical Center, New
Orleans, LA 70112
Sponsor: National Science Foundation, Arlington, VA 22330
PURPOSE--Force feedback is necessary if 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 as 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 further investigated in order to delineate the effects of changing muscle length, and the muscles moment arm about the joint's center of rotation in order to extend the concept to non-isometric 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.
[89] EMG POWER SPECTRA CHANGES DUE TO SKILL ACQUISITION
Moshe Solomonow, PhD; Richard V. Baratta, PhD
Bioengineering Laboratory, Department of Orthopaedic
Surgery, Louisiana State University Medical Center, New
Orleans, LA 70112
Sponsor: National Science Foundation, Arlington, VA 22330
PURPOSE--Changes in motor unit recruitment patterns due to increased skill of human subjects in performing a specific function were assessed by recording the surface EMG of normal subjects while they performed isometric elbow flexion.
METHODOLOGY--The contraction consisted of linearly increasing force from rest and up to 100 percent maximal voluntary force within 3 s. Subjects exercised 3 s linear increase in force three times a week over 6 weeks. At each session, 20 contractions were performed in a total of 360 practice contractions. The median frequency (MF) of the EMG power spectra density was calculated for five contractions every 2 weeks. Because the MG is linearly related to the conduction velocity of action potentials in the muscle, increasing MF may indicate recruitment of larger motor units during the contraction.
RESULTS--The results show that the MF was increasing from rest and up to 65-70 percent for maximal voluntary force prior to the training. It gradually increased and, at the end of the six weeks of training, the MF increased from rest to 90 percent of the maximal voluntary force.
Motor unit recruitment could be an adaptive process, capable of increasing range as skill is acquired. Slower and longer recruitment strategies allow more accurate control of force generation and thereby improve skill. This further confirms that motor unit recruitment is not a fixed property in a specific muscle, but rather an adaptive process that could be optimally modified according to the task to be performed.
The motor unit recruitment pattern of the antagonist did not exhibit statistically significant changes but showed an increase and then a decrease in the recruitment range as skill was acquired. This confirms that improvement in skill may decrease the antagonist coactivation level in general.
[90] CONTROL OF JOINT MOTION WITH SYNERGISTIC STIMULATION OF ITS AGONIST/ANTAGONIST MUSCLES
Moshe Solomonow, PhD; Richard V. Baratta, PhD; Bing-He
Zhou, EE
Bioengineering Laboratory, Department of Orthopaedic
Surgery, Louisiana State University Medical Center, New
Orleans, LA 70112
Sponsor: National Science Foundation, Arlington, VA 22330
PURPOSE--Joint motion requires complex and simultaneous activation levels from the agonist and antagonist muscles in order to accomplish the intended task, while subject to various internal and external disturbances. This project initiated trials using antagonistic stimulation of the muscle groups crossing the joint with various levels of weighted motor unit recruitment in the agonist and antagonist to reaffirm our data collected from the elbow joint of humans. The objective was to improve the external control of a joint with regards to various loading conditions.
METHODOLOGY--Agonist/antagonist muscle coactivation strategies were implemented through electrical stimulation. These strategies were based on the compromise between the physiological need for joint stabilization by the antagonist at high force levels and the need to prevent joint laxity at low force levels. These two conflicting requirements resulted in two coactivation parameters. The first one, antagonist gain, was the linear gain of the antagonist muscle with respect to the input command. This parameter came into play when high net joint torques were called for. The second parameter, overlap, was a range of crossover of the antagonist unto the agonist domain. Strategies combining antagonist gain and overlap were tested as to their ability to track linear, step, sinusoidal, and pseudo-random input signals.
RESULTS--It was found that moderate amounts of antagonist gain (5 percent) and overlap (25 percent) would provide optimal tracking and minimal distortion during isometric and various types of load-moving contractions. When controlled by these strategies, the dynamic frequency response of the cat ankle joint showed small yet statistically significant differences on the dynamic response of the agonist/antagonist muscle-joint system.
[91] DEVELOPMENT AND DISSEMINATION OF A RESOURCE GUIDE ON FUNCTIONAL ELECTRICAL STIMULATION (FES) FOR PERSONS WITH SPINAL CORD DYSFUNCTION
Jeanne O'Malley Teeter, BS, MBA; Denise L. Brown,
MS
Cleveland FES Center, FES Information Center, Case
Western Reserve University, Cleveland, OH 44106; email:
jxt4@po.cwru.edu; dlb@po.cwru.edu
Sponsors: Buckeye Chapter, Paralyzed Veterans of America, Cleveland, OH 44117; Spinal Cord Injury Education and Training Foundation, Paralyzed Veterans of America, Washington, DC 20006
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 which will maximize their independence, function, and health.
METHODOLOGY--The objectives of the project are: to increase the knowledge base of persons with SCI/disease on the use of FES; to increase access for persons with SCI/disease to FES providers; to increase the decision-making ability of persons with SCI/disease to make informed decisions regarding the appropriateness of FES interventions. Project oversight was provided by a 16-member Community Advisory Committee. A 34-member Technical Review Committee assisted with content review.
PROGRESS--A sourcebook entitled Functional Electrical Stimulation (FES) Resource Guide for Persons with Spinal Cord Injury or Multiple Sclerosis (ISBN 1-888470-03-8) was completed and published in 1995. In August 1996 more than 500 copies had been distributed. A survey of individuals with SCI indicated that use of the book increased their FES knowledge.
FUTURE PLANS--We are planning electronic dissemination of the FES Resource Guide via the world wide web at http://feswww.fes.cwru.edu.
[92] COMPARISON OF DISCOMFORT ASSOCIATED WITH PERCUTANEOUS AND SURFACE NEUROMUSCULAR STIMULATION
John Chae, MD; Ronald Hart, MSE
Center for Physical Medicine and Rehabilitation, Case
Western Reserve University, Cleveland, OH 44106; MetroHealth
Medical Center, Cleveland FES Center, Cleveland, OH 44109;
email: jchae@metrohealth.org;
rlhart@metrohealth.org
Sponsor: Rehabilitation Medicine Scientist Development Program, National Institutes of Health, National Institute on Child Health and Human Development, Bethesda, MD 20892
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--Extensor digitorum communis (EDC) of three 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® 1.25 in (3.2 cm) 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. 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--Surface stimulation caused significantly greater discomfort than percutaneous stimulation for comparable finger extensor moment (mean 1.0 vs 4.9; 95 percent CI for difference: 1.9, 5.9; p=0.002; paired-t). Similar findings were noted with nonparametric statistics (median 0.5 vs 5.0; p=0.01; Wilcoxon sign rank). Subjects described the discomfort associated with percutaneous stimulation as "aches, dull pain, muscle cramps, or none." Pain from surface stimulation was described as "sharp, burning, or pins and needles." All preferred percutaneous over surface stimulation.
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. Two more subjects will be enrolled.
B. Upper Limb Applications
[93] 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
(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--The triceps is stimulated to provide elbow extension. Stimulation is adjusted to overcome gravity, and is controlled two ways. An accelerometer mounted on the upper arm detects the orientation of the arm in the gravitational field. When the arm is abducted, the triceps is stimulated. Alternatively, the user can initiate stimulation via a switch on the wheelchair. Elbow angle is controlled in a natural manner by the subject voluntarily contracting the biceps to counteract the elbow extension. Forearm rotation is provided similarly, by stimulating the pronator quadratus at a constant level whenever the hand grasp neuroprosthesis is active. Supination/pronation angle is controlled by the subject voluntarily supinating to counteract pronation. Thus, the additional functions do not require additional command signals unrelated to the desired function. Elbow and forearm stimulation is integrated with the VA/CWRU hand grasp neuroprosthesis.
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 is the midpoint of this project. Four neuroprostheses have been constructed. One is currently being used at home by one person to provide hand grasp, elbow extension, and forearm rotation. The triceps and pronator are stimulated via percutaneous intramuscular electrodes. The individual has used the elbow extension system for 15 mo, and the pronation system for 3 mo. A second individual recently received an implanted neuroprosthesis for hand grasp and elbow extension. In this case, triceps stimulation will supplement voluntary extension provided by a posterior deltoid to triceps tendon transfer.
We designed a series of functional tests to evaluate the upper extremity workspace. The person picks up an object at one location, moves the object, and places it in another location. Object orientation is also specified at both locations. Success or failure is recorded at both the starting and ending location, and the 3-D kinematics of the arm and the object are recorded throughout the task. Object contact and force data and the control signals to the stimulated muscles are also recorded. The first person was evaluated at 2 and 14 mo.
RESULTS--Elbow extension is of great benefit when objects are located high and are oriented horizontally. This is consistent with the need for elbow extension to counteract gravity. Active extension also improves performance when the person is trying to manipulate objects at shoulder level or even lower by stabilizing the position of the hand in space and allows the person to push with greater force. Pronation has enabled the person to write with the arm in a more normal position, reducing fatigue.
FUTURE PLANS--Neuroprostheses with elbow and forearm control will be implemented and evaluated in at least two more individuals. Evaluations will include assessment of single and multiple joint movements, and measurements of the dynamic stiffness of the arm to characterize and improve the FNS control.
[94] FUNCTIONAL NEUROMUSCULAR SYSTEMS FOR UPPER EXTREMITY CONTROL
P. Hunter Peckham, PhD
Cleveland FES Center, Rehabilitation Engineering Center,
MetroHealth Medical Center, Cleveland, OH 44109-1998; email:
pxp2@po.cwru.edu
Sponsor: Department of Veterans Affairs, VA
Rehabilitation Research and Development Service, Washington,
DC 20420
(Project #B011-6RA)
PURPOSE--The objective of this project is to deploy and quantitatively evaluate advanced implantable functional neuromuscular stimulation systems to restore hand grasp and release in C5 and C6 quadriplegic individuals.
METHODOLOGY--Implantable neuroprostheses have been used to provide grasp and release for C5 and C6 quadriplegic individuals. Eight-channel implant receiver stimulators have been in human use for over 10 years. The goal of this project is to develop a more advanced stimulator with an implanted control transducer and additional stimulus channels. A 10-channel implantable stimulator-telemeter and an implanted joint angle transducer have now been developed that provide activation of the triceps for elbow extension and the finger intrinsics for improved grasp opening. With the implanted controller, most users will be able to don the system without assistance.
The surgical implantation and the implementation of the advanced neuroprosthesis follow protocols developed for the 8-channel device. Patient function is evaluated using a variety of assessments designed to measure impairment, disability, handicap, quality of life, and device utility. These assessments are performed presurgery, during an intense training session postsurgery, after 6 months, and 1 year.
PROGRESS--A 10-channel implant stimulator-telemeter was implanted in the first human subject in July 1996, and provides 2 channels of finger intrinsic muscle activation and 1 channel of triceps activation. A second implant is scheduled for September 1996.
Animal trials of the implanted joint angle transducer/controller continue. The transducer and 10-channel implant stimulator-telemeter were operational in an animal for 17 months, at which point the experiment was terminated. The histological response of the bone to the implanted transducer is now being analyzed. Additional animals will be implanted with a transducer that has been redesigned to allow easier surgical placement.
Clinical trials continue with the 8-channel device. Currently, 43 subjects have received implant stimulators at 10 sites around the world, and the multicenter clinical trial has been transferred to industry. In Cleveland, 17 subjects have received implant stimulators (14 males, 3 females; 8 C5 subjects, 9 C6 subjects.)
RESULTS--Neuroprosthesis users generate lateral and palmar pinch strengths in the range of 2.5 to 30 Newtons. In a six task grasp and release test, users can typically manipulate two or three objects with their tenodesis grasp alone, and can manipulate five or six objects with the neuroprosthesis. The number of completions in a given time is always higher with neuroprosthesis for the larger and heavier objects. Users demonstrate the ability to perform activities of daily living with less assistance with the neuroprosthesis than without it. This includes the reduction or removal of physical assistance, the removal of adaptive equipment and/or the reduction in the need for self assistance (such as using the mouth to manipulate a utensil). Users consistently indicate a preference for using the neuroprosthesis for a variety of tasks and user surveys indicate consistent use of the neuroprosthesis at home, with eating and office tasks being the most frequently performed with the neuroprosthesis. Users generally indicate a high level of satisfaction with the neuroprosthesis. Preliminary results indicate that the neuroprosthesis reduces impairment and disability, and that the device shows good usage and satisfaction. We expect that the neuroprosthesis will reduce handicap, and improve quality of life.
FUTURE PLANS--Human studies for the 8-channel hand neuroprosthesis will continue through 1996. Human studies with the 10-channel implant will continue, and human implantation of the joint angle transducer will commence in early 1997.
[95] THIN-FILM PERIPHERAL NERVE ELECTRODE
Stuart Cogan, ScD.; James S. Walter, PhD; Jerry McLane,
PhD; James Sweeney, PhD; Charles Robinson, PhD
The Rehabilitation Research and Development Center, VA
Hines Hospital, Hines, IL 60141; EIC Laboratories, Norwood,
MA 02062
Sponsor: Hines VA Rehabilitation Research and Development Center, Hines, IL 60141 (Core Funds)
PURPOSE--Complex hand movements might be obtained with median nerve stimulation through an implanted multielectrode nerve cuff. Repeatable hand responses should be obtained with no injury to the nerve. The purpose of this study is to evaluate a multielectrode circumneural thin-film cuff interfaced to a multichannel implantable stimulator and associated control algorithms.
METHODOLOGY--Electrodes are fabricated by vacuum depositing platinum-iridium films on thin sheets of fluorocarbon polymer and photolithographic patterning and etching to form the leads and charge injection sites. The patterned substrate is then selectively covered with a second polymer layer. Four charge injection sites are currently available on this electrode. A standard 12-electrode cuff using small platinum disk electrodes on a silastic cuff has also been procured for comparison to the thin-film cuff.
Studies are conducted in an anesthetized raccoon. Forearm and paw movements are observed with intramuscular electrodes and the implanted cuff electrodes. Five forearm muscles were isolated and their tendons connected to force transducers. Current response studies were conducted for each electrode arrangement. In addition, the cuff has been implanted chronically in three raccoons. The response of the cuff and median nerve to implantation is being evaluated.
PROGRESS--Forearm and paw movements have been obtained through selective stimulation with both percutaneous electrodes inserted directly into forearm muscles and with the multielectrode cuffs. Cuff electrodes were also used with direct recording from the tendons of five forearm muscles. These results showed selective recruitment curves that were enhanced by longitudinal and steering currents. Acute studies comparing the new thin-film cuff to the standard cuff constructed of silastic with platinum electrodes showed nearly identical recruitment curves.
RESULTS--In acute studies, four raccoons have been evaluated under anesthesia with the 12-electrode (standard) cuff. A variety of paw movements could be obtained using different electrode arrangements, including forearm pronation, wrist flexion, and digit flexion. The movements were similar to those elicited with electrodes implanted directly in the muscles. Direct recording from the tendons of five forearm muscles showed selective recruitment curves with the cuff electrodes that were enhanced by longitudinal and steering currents. Comparison of our new (4-electrode) thin-film cuff to the standard cuff showed nearly identical recruitment curves. Chronic implantation of the thin-film electrode on the median nerve for 6 weeks was conducted in four additional raccoons. Although all of the forearms had responded to stimulation at the day of initial implantation, the forearms had little or no response after the 6 weeks of implantation. Postmortem observations indicated that one electrode cuff had come off of the nerve. The remaining three electrodes were sutured together to help keep them on the nerves, but all three of these electrodes had opened up and were adjacent to the nerve. All of the cuffs had extensive connective tissue around them. The nerves appeared unaffected by the implantation by gross observation. Histological evaluations of the nerves are continuing.
FUTURE PLANS--The electrode location in the middle of the upper arm is a position that has lots of movement, which probably contributed to the electrode dislodgment and buildup of connective tissue. New electrode designs are under consideration, including better electrodes for areas where there is muscle movement.
[96] PERCUTANEOUS NEUROMUSCULAR STIMULATION FOR SHOULDER SUBLUXATION IN HEMIPLEGIA
John Chae, MD; Ronald Hart, MSE; Tina Davis,
OTR
Center for Physical Medicine and Rehabilitation, Case
Western Reserve University, Cleveland, OH 44106; MetroHealth
Medical Center, Cleveland FES Center, Cleveland, OH 44109;
email: jchae@metrohealth.org;
rlhart@metrohealth.org
Sponsor: Claude D. Pepper Older American Independence Center, Case Western Reserve University, Geriatric Care Center, Cleveland, OH 44106; FairHill Institute for the Elderly, Cleveland, OH 44120; National Institutes of Health, National Institute on Aging Bethesda, MD 20892
PURPOSE--Surface stimulations of the posterior deltoid and supraspinatus have been shown to reduce poststroke shoulder subluxation and associated complications. However, cutaneous pain and associated poor compliance, poor muscle specificity, and the labor-intensive task of consistently localizing motor points limit the practical application of surface stimulation for shoulder subluxation. The purpose of this case study is to assess the effectiveness of percutaneous neuromuscular stimulation in reducing shoulder subluxation, and the patient tolerance of 6 hrs of stimulation per day for 4 wks.
METHODOLOGY--A 77-year-old male who suffered a right anterior circulation cortical infarct was enrolled in the study. Subject suffered his stroke within 3 wks of study entry with residual neurologic impairments including flaccid left hemiplegia, left hemi-neglect, dysarthria, dysphagia, bladder incontinence, and two-finger breadth anterior-inferior shoulder subluxation. Sensation and language were intact. Helical percutaneous electrodes wound from FEP-Teflon insulated, multistranded, type 316L stainless steel wires were implanted into the posterior deltoid and supraspinatus using a 19-gauge hypodermic needle. Electrode exit site on the superior aspect of the shoulder just medial to the acromian and paths between the exit site and the 2 motor points were anesthetized with 2 percent lidocaine. After entry, the hypodermic needle loaded with a percutaneous electrode was tunneled toward the motor point. A balanced biphasic, cathodic-first, capacitively-coupled, constant-current pulse was applied. The amplitude and frequency were maintained at 20 mA and 25 Hz, respectively. Intensity of stimulation was adjusted to clinical reduction of the subluxation by adjusting the pulse duration between 50-200 µs. Duty cycle of 10 s on and 2 s off was employed with total stimulation time of 6 hrs per session. True anterior-posterior view radiographs of both shoulder were taken with and without stimulation to assess the efficacy of stimulation in reducing the subluxation.
RESULTS--Subject tolerated the implantation procedure well. Radiograph of the left shoulder revealed marked anterior inferior subluxation with significant widening of the gap between the acromian and the humeral head. With stimulation the gap was markedly reduced, being essentially equivalent to that of the uninvolved side. Subject is presently tolerating 6 hrs per day of stimulation without any discomfort. He is on his third week of stimulation.
IMPLICATIONS--Long-term percutaneous stimulation for shoulder subluxation is well tolerated. There is minimal discomfort, muscle specific stimulation is provided, and motor points do not need to be localized with each stimulation session. Percutaneous neuromuscular stimulation may render functional electrical stimulation more practical. Controlled pilot trials are underway to assess the efficacy of percutaneous neuromuscular stimulation in decreasing shoulder subluxation, preventing or minimizing shoulder pain, and enhancing motor and functional recovery of acute and chronic stroke survivors.
[97] CLOSED-LOOP CONTROL OF FUNCTIONAL NEUROMUSCULAR STIMULATION: METHODS OF PROVIDING SENSORY FEEDBACK
Patrick E. Crago, PhD; Clayton L. Van Doren,
PhD
Department of Orthopedics, Case Western Reserve
University, Cleveland FES Center MetroHealth Medical Center,
Cleveland, OH 44109-1998; email: pec3@po.cwru.edu;
clv2@po.cwru.edu
Sponsor: National Institutes of Health, National Institute of Neurological Disorder and Stroke, Bethesda, MD 20892
PURPOSE--The control of normal arm movement and hand grasp depends on precise integration of sensory information and motor commands. Afferent and efferent signals, and their normal interactions, are lost or corrupted as a result of spinal cord injury, peripheral neuropathy, and other neuromuscular diseases. Assistive devices such as limb prostheses and neuroprostheses, and robotic manipulators typically provide some motor function but little or no tactile or kinesthetic information. The goal of this project is to investigate methods of providing sensory feedback to users of a hand neuroprosthesis using electrocutaneous stimulation of sensate skin to represent kinesthetic information measured external, implanted, or natural sensors.
METHODOLOGY--Measurements of the interactions between simultaneous modulations of stimulus amplitude and stimulus frequency have been completed. Since these two physical dimensions are chosen most often for providing information via sensory feedback, it is important to understand to whether their corresponding psychological dimensions of loudness (perceived intensity) and pitch, respectively, are independent or interact with each other. Bekesy tracking was used to measure isoloudness and isopitch contours to investigate distortion, that is, the effects of stimulus frequency on perceived stimulus intensity and the effects of stimulus amplitude on perceived pitch.
PROGRESS--Measurement of isoloudness and isopitch contours have been completed.
RESULTS--Contours of equal loudness (perceived amplitude) and equal pitch (perceived frequency) were measured in the present study for electrocutaneous stimuli covering most of the usable range of amplitudes and frequencies: 3-12 dB SL and 4-64 Hz. Eight naive subjects generated isoloudness contours at four reference amplitudes via Bekesy tracking, and eight additional subjects generated isopitch contours at three reference frequencies. The isoloudness contours declined slightly but significantly with stimulus frequency, consistent with previous results. The shape of the contours was also slightly dependent on the amplitude of the reference stimulus. Isopitch contours were unaffected by stimulus amplitude on average, but the contour shape did vary modestly, though erratically, with reference frequency.
FUTURE PLANS--The isoloudness and isopitch contours will be used in implementing electrocutaneous sensory in portable hand neuroprosthesis. The current design uses a fixed amplitude and variable frequency to code finger span, and a fixed frequency and variable amplitude to represent force. Look up tables representing the inverted isosensation contours will be used to compensate for distortion by covarying amplitude and frequency to produce the desired orthogonal changes in loudness and pitch.
[98] 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
PURPOSE--This study will implement, evaluate, and optimize a neuroprosthesis based on functional neuromuscular stimulation (FNS) which will 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 significantly improve the independence of these individuals in a number of daily activities, improving their quality of life and reducing their attendant care costs.
METHODOLOGY--Percutaneus electrodes will be implanted into the PM and LD muscles. Controlled stimulation of these muscles will be used to provide shoulder function in horizontal flexion, adduction, and internal rotation in individuals with C5 tetraplegia. The stimulated contractions will restore the lost motions, while retained voluntary control of antagonistic muscles will be used by the individual to overcome the stimulated contractions and achieve intermediate positions and external forces in a completely natural manner. The performance of the shoulder neuroprosthesis will be 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.
Several general methods for improving control of the partially paralyzed shoulder will also be developed. Shoulder stiffness properties will be used to identify deficits in postural stability in a systematic manner and to suggest changes in electrical stimulation patterns to correct the deficits. The feasibility of using electromyographic recordings from voluntarily controlled shoulder muscles to modulate stimulation of the paralyzed muscles will be investigated, since such modulation could improve movement performance, prevent fatigue, and compensate for changes in contraction strength in different shoulder positions.
PROGRESS--This is a new project of the Cleveland FES Center.
[99] CLOSED-LOOP CONTROL OF FUNCTIONAL NEUROMUSCULAR STIMULATION
Patrick E. Crago, PhD; Michael W. Keith, MD; Kevin L.
Kilgore, PhD; Joseph M. Mansour, PhD; P. Hunter Peckham,
PhD; Clayton L. Van Doren, PhD; David L. Wilson, PhD
Cleveland FES Center, Case Western Reserve University,
Cleveland, OH 44106; MetroHealth Medical Center, Cleveland,
OH 44109; email: pec3@po.cwru.edu;
mwk4@po.cwru.edu;
kkilgore@mhnet.mhmc.org;
jmm12@po.cwru.edu;
pxp2@po.cwru.edu;
clv2@po.cwru.edu;
dwilson@morph.ebme.cwru.edu
Sponsor: National Institutes of Health, NINDS Neuroprosthesis Program, Bethesda, MD 20892
PURPOSE--Hand grasp neuroprostheses enable individuals to grasp and release objects that they could not otherwise use and allows them to accomplish many tasks of daily living with improved function. This project continues development of upper extremity neuroprostheses by addressing deficiencies in 1) the grasp output, 2) proximal control of the limb, 3) voluntary control input, and 4) control of the contralateral limb. The project outcome will provide a significant improvement in the quality and controllability of restored movement, and an increase in the types of functions individuals can perform, thus providing greater independence.
METHODOLOGY--Synthesis of upper extremity control: a previously developed dynamic biomechanical model of the upper extremity is being applied to improving the quality of hand grasp in individual people who receive the neuroprosthesis. The application to specific individuals requires parameterizing and validating the model.
We are developing noninvasive techniques to obtain biomechanical parameters for individual persons. Specifically, moment arms, muscle excursions, and tendon lines of action will be derived from 3-D MRI data. Along with the geometric data, the active and passive joint moments will be measured across a group of subjects and serially in time to evaluate the stability of grasp output and the relationship between active and passive forces, and to guide and judge the success of surgical and therapeutic interventions. Passive moments arise from the tissues surrounding a joint and the inherent passive properties of muscles crossing the joint. The contributions will be separated in the model to allow better surgical and therapeutic planning to correct abnormalities. The passive moments measured experimentally in people will also be separated to provide better treatment planning and evaluation.
The biomechanical model and the parameters measured for individual neuroprosthesis users will be analyzed to refine their neuroprosthetic grasp patterns and for planning tendon transfers. The personalized biomechanical model will be used to predict the range of surgical solutions to given problems presented by individuals.
Control of upper extremity function: prior laboratory work has established the feasibility of providing closed-loop control and sensory feedback to improve hand function. A portable neuroprosthesis with these control features will be used to evaluate the potential benefits outside of the laboratory.
In further laboratory work, we will assess the impact of sensory feedback (including finger span, grasp force, and command) on grasp performance. The proposed evaluation method is unique in that it will separate the effects of the electrocutaneous feedback from the effects of visual feedback alone.
The generation of logical signals to control hand grasp is a limiting factor in patient task performance. We will evaluate alternative sources of command signals and alternative hand grasp command control algorithms. Improvements are expected to decrease the demands on the person, and increase the likelihood that the intended command is generated, thereby increasing confidence in the system.
We will implement hand grasp and release in both hands of individuals with C6 level function. Bimanual hand function will increase the person's working volume and enable the person to perform bimanual tasks more efficiently. A key aspect to implementing bimanual control is to simplify the command control process compared to the currently implemented system.
Control systems to restore independent control of wrist and hand function in tetraplegic individuals with C5 and weak C6 function will be designed. Control systems must compensate for mechanical interactions between the wrist and hand muscles, and allow weak voluntary wrist extensors to drive electrically stimulated synergists. Achieving this objective will allow wrist command control to be extended to individuals who must presently use shoulder command control, and would allow bimanual hand grasp to be extended to people with C5 level function as well.
PROGRESS--This is a new project of the Cleveland FES Center.
[100] HAND NEUROPROSTHESIS IN CHRONIC HEMIPLEGIA
John Chae, MD; Ronald Hart, MSE; Tina Davis,
OTR
Center for Physical Medicine and Rehabilitation, Case
Western Reserve University, Cleveland, OH 44106; MetroHealth
Medical Center, Cleveland FES Center, Cleveland, OH 44109;
email: jchae@metrohealth.org;
rlhart@metrohealth.org
Sponsor: Rehabilitation Medicine Scientist Development Program, National Institutes of Health, National Institute on Child Health and Human Development, Bethesda, MD 20892
PURPOSE--A fully implantable hand neuroprosthesis system enhances the ADL function of persons with C5-C6 tetraplegia. However, it is unclear whether a similar system will be beneficial to stroke survivors with a nonfunctioning hand. The purpose of this study is to assess the functional benefit of a percutaneous hand neuroprosthesis system in chronic hemiplegia.
METHODOLOGY--Three chronic stroke survivors with volitional control of the hemiparetic shoulder and elbow, but with nonfunctioning hand were implanted with percutaneous intramuscular electrodes into various muscles of the hand and forearm. One subject received electrodes into the extensor carpi radialis (ECR), extensor digitorum communis (EDC), extensor indicis propius (EIP), extensor pollicis longus (EPL), and abductor pollicis brevis for hand opening. Flexor digitorum superficialis (FDS), adductor pollicis and first dorsal interosseous were implanted for hand closure.
Two other subjects received EDC, ECR, EIP and EPL electrodes for hand opening. They both had voluntary hand closure in synergy. Percutaneous helical electrodes wound from FEP-Teflon insulated, multistranded, type 316L stainless steel wires were implanted into each muscles using a 19-gauge hypodermic needle. All extensor electrodes exited from the same site on the dorsal surface of the forearm. The path between the exit site and the motor points of target muscles were anesthetized with 2 percent lidocaine. After initial entry, the hypodermic needle loaded with a percutaneous electrode was tunneled toward the motor point where the electrodes were implanted. For the one subject with implanted flexor muscles, there was an additional exit site on the flexor surface of the forearm. A balanced biphasic, cathodic-first, capacitively-coupled, constant-current pulse was applied to each electrode. The amplitude and frequency were maintained at 20 mA and 25 Hz, respectively.
Stimulation intensities of each electrode were adjusted by varying the pulse duration from 0 to 200 µsec. A hand grasp and release pattern was formulated for each subject and programmed into the stimulators. The stimulator can be placed in an exercise mode to allow cyclical hand opening and closure or be interfaced with a transducer to allow volitional control.
RESULTS--Selective stimulation with good contraction of each implanted muscle was achieved with minimal spill over to adjacent muscles. The degree of discomfort varied with specific muscles, but was minimized by adjusting stimulation parameters, while maintaining desired range of motion and torque. In one subject with marked flexor hypertonia, finger extension lead to appropriate MCP extension, but with significant flexion at the PIP and DIP resulting in a "claw" hand. Activation of the intrinsics via ulnar nerve stimulation improved hand opening. All subjects are presently tolerating 2-3 hours of stimulation-induced hand opening and closing exercises per day. Two subjects are learning to use a potentiometer manipulated by the good hand to perform simple tasks such as picking up blocks.
FUTURE PLANS/IMPLICATIONS--Results to date show that chronic stroke survivors with intact sensation tolerate percutaneous electrode implantation and stimulation well. Our plan is to explore control paradigms which will allow subjects to reliably open and close the hand without compromising the function of the unimpaired upper extremity. This will be followed by formal testing of ADL function. A total of 8 subjects will be enrolled.
[101] EFFICACY OF NEUROMUSCULAR STIMULATION IN ENHANCING THE UPPER EXTREMITY MOTOR AND FUNCTIONAL RECOVERY OF ACUTE STROKE SURVIVORS
John Chae, MD; Theresa Bohinc, OTR; Amy Friedl,
OTR
Center for Physical Medicine and Rehabilitation, Case
Western Reserve University, Cleveland, OH 44106; MetroHealth
Medical Center, Cleveland FES Center, Cleveland, OH 44109;
email: jchae@metrohealth.org
Sponsor: Rehabilitation Medicine Scientist Development Program, National Institutes of Health, National Institute on Child Health and Human Development, Bethesda, MD 20892; New Investigator Award, Physical Medicine and Rehabilitation Education and Research Foundation, Dallas, Texas 75243
PURPOSE--Surface neuromuscular stimulation has been shown to enhance the motor recovery of stroke survivors. However, controlled studies have not demonstrated that electrical stimulation enhances functional recovery. The purpose of this double blind, placebo controlled, randomized trial is to assess the efficacy of surface neuromuscular stimulation in enhancing the upper extremity motor and functional recovery of acute stroke survivors.
METHODOLOGY--Stroke survivors admitted to an inpatient stroke rehabilitation program within 6 wks 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 wks. 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 posttreatment and at 3 mo posttreatment 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.
RESULTS--Based on a power analysis with expected difference between treatment and control group of 1 standard deviation on the upper extremity Fugl-Meyer Motor Assessment, alpha of 0.05 and beta of 0.20, a sample size of 23 subjects per group were calculated. To date 12 subjects have completed the study. Two subjects are presently enrolled.
IMPLICATIONS--Poststroke motor impairment is a strong predictor of poststroke physical disability. Whether electrical stimulation will render sufficient improvements in the motor status to translate into improved daily function is unclear. Preliminary analysis will be performed when half the expected subjects have completed the study.
[102] A QUANTITATIVE ANALYSIS OF SHOULDER MOVEMENTS USED TO CONTROL A FES SYSTEM IN ADOLESCENTS WITH C4 LEVEL SPINAL CORD INJURIES
Joseph J. Sarver, BS; Brian T. Smith, MS; Rahamin
Seliktar, PhD
Biomedical Engineering and Science Institute, Drexel
University, Philadelphia, PA 19104; Shriners Hospitals for
Children, Philadelphia, PA 19152; email:
sarverj@cbis.ece.drexel.edu
Sponsor: Shriners Hospitals for Children, Philadelphia, PA 19152; Calhoun Fellowship of Drexel University, Philadelphia, PA 19104
PURPOSE--The purpose of this project is to quantitatively assess shoulder movements used to control functional electrical stimulation (FES) rehabilitative system in adolescents with C4 level spinal cord injuries (SCIs). Individuals with C5 level SCIs have successfully used their shoulders to control stimulated hand grasp and release. A pilot study done at Shiners Hospitals for Children indicated that an adolescent with C4 level SCIs could use his shoulder to control stimulated arm movements.
METHODOLOGY--A total of 13 subjects participated in the experiment, 5 of whom were nonimpaired. The other 8 subjects were individuals with C5 and/or C4 level SCIs from whom 6 C5 and 6 C4 shoulders were examined. A dual-axis angular position transducer designed at Case Western Reserve University for use as a control device by patients with cervical SCIs was used to measure elevation/depression and protraction/retraction of the shoulder. The electrical signals from the two axes of the transducer were recorded while the subject performed three different experimental tasks. First, subjects were asked to repeatedly elevate, depress, protract, and retract their shoulders maximally to establish an active range of motion (AROM). Next, subjects were asked to elevate, depress, protract, and retract their shoulders through a series of discrete "target" shoulder positions with the aid of a computer-generated representation of both the target and current shoulder position. Finally, subjects were asked to elevate, depress, protract, and retract their shoulders to mid and end range and maintain these positions without the computer generated visual feedback.
PROGRESS--Data have been collected for all of the aforementioned subjects through all three sections of the experiment.
PRELIMINARY RESULTS--For the active range of motion section, a Kruskal-Wallis analysis (95 percent confidence interval) of the three populations detected no significant difference in either the magnitude or direction of movement between C4 and C5 subjects during elevation, depression, protraction, or retraction. The only motions which the test did not detect a significant difference between the nonimpaired and SCI populations were with the C4 in depression and with the C5 in depression and protraction. As expected, both C5 and C4 subjects exhibited the greatest active range of motion while elevating with mean values of 14.7 and 7.9° respectively.
Furthermore, all but one of the SCI patients displayed a consistent pattern of motion regardless of both the motion they were asked to perform (i.e., elevate, depress) and the section of the experiment (i.e., active range, incremental stepping), indicating that C5 and C4 individuals may not be able to elevate/depress and protract/retract independently. Preliminary results indicate that there is no appreciable difference among the three populations in the error associated with reaching a target shoulder position. Early analysis also indicates that there is no appreciable difference among the three subject groups in the ability of an individual to maintain a particular static shoulder position without the use of visual feedback. Overall, the results indicate that the shoulder movements of the subjects with C4 level SCIs are comparable to those with C5 level SCIs and may be adequate to control FES arm movements.
FUTURE PLANS--Further analysis of the response of the subjects to the later two sections of the experiment is to be completed. In addition a simplified mechanical model of the shoulder is being explored in an attempt to explain the apparent trend in the shoulder motion of subjects with SCIs.
[103] MECHANICAL EFFECTS OF MUSCLE TENDON TRANSFER AND FUNCTIONAL NEUROMUSCULAR STIMULATION
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: The Whitaker Foundation, Rosslyn, VA 22209
PURPOSE--Tetraplegia due to cervical spinal cord injury (SCI) results in the loss of voluntary control over a number of muscles of the hand and arm, severely limiting the ability of individuals to perform many routine activities of daily living such as feeding and grooming, and reducing their ability to work independently. Tendon transfer surgery can be used to restore voluntary control over some arm and hand functions by detaching a nearby donor muscle (which has remained under voluntary control) from its normal connection to the skeleton and reattaching it to the tendon of a paralyzed muscle that normally provides the desired function. The specific objectives of this project are to evaluate the ability of a posterior deltoid-to-triceps tendon transfer surgery to restore voluntary control over elbow extension function in individuals with SCI, to measure and assess the impact of this surgery on the other functions of the limb, to examine adaptation in the neural control of the limb in response to the muscle transfer, and to identify and evaluate changes to the surgical procedures which could improve the ultimate functional outcome.
METHODOLOGY--In one set of experiments, the ability of individuals with SCI and subsequent tendon transfer surgery to produce adequate elbow extension moments is measured. The forearm of the subject is fixed to an experimental device so that the elbow and shoulder rotate in a horizontal plane at the level of the glenohumeral joint. Isometric elbow and shoulder moments generated by the subject can then be measured for different combinations of elbow and shoulder angles using a 6-axis force-moment transducer mounted at the interface between the subject and the fixture. In another set of experiments, subjects are seated with their arm attached to the endpoint of a specially designed robotic manipulator. This manipulator is used to generate constant load forces that the subject must balance in order to maintain a desired hand position and to impose small random force perturbations which allow the estimation of the stiffness properties of the arm. The identified stiffness properties are directly related to the postural stability of the arm and can also be used to localize deficits which limit performance.
PROGRESS--We have actively begun experiments to measure the elbow extension strength and its dependence on elbow and shoulder angles in subjects with SCI, treated with posterior deltoid-to-triceps transfers. The experimental and analytical methods developed to measure human arm stiffness have been validated using known mechanical systems, and initial stiffness measurements have begun using nonimpaired human subjects.
RESULTS--Elbow extension strength was found to vary widely (from less than 1 Nm to greater than 16 Nm) across subjects, and to depend on the level of SCI. Elbow extension moment was also often found to be highly dependent on both elbow and shoulder angles, in a manner consistent with the length-tension properties of the posterior deltoid muscle. Unfortunately, paralysis and weakness in other shoulder muscles in these subjects force them to adopt arm positions for which the transferred posterior deltoid is shortened and therefore at a mechanical disadvantage. We have also validated the experimental and analytical methods used to estimate endpoint arm stiffness. We have successfully identified a number of known mechanical systems, and preliminary results from able-bodied subjects indicate that the stiffness properties of the elbow-shoulder system operating in a horizontal plane are well characterized by a two-input, two-output linear system. Arm stiffness parameters vary with the size and direction of the load that must be balanced by the subject.
C. Lower Limb Applications
[104] FES MOBILITY IN PARAPLEGIA: RF-CONTROLLED IMPLANTED SYSTEM
Ernest B. Marsolais, MD, PhD; Ronald J. Triolo, PhD;
Donald C. Ferencz, MS
Cleveland FES Center, VA Medical Center, Cleveland, OH
44106; email: ebm2@po.cwru.edu;
dcf@po.cwru.edu
Sponsor: Department of Veterans Affairs, VA
Rehabilitation Research and Development Service, Washington,
DC 20420
(Project #B681-2RA)
PURPOSE--The overriding goal of this research effort is to develop options to enhance the personal mobility of individuals with complete thoracic level spinal cord injuries. Functional Electrical Stimulation (FES) systems employing implantable technology will be refined and employed to provide stable standing, slow walking, and other maneuvers with a minimum of bracing and personal assistance. The 3-year effort will be directed toward establishing the clinical and technical components and implementation procedures required to introduce implantable FES systems safely and effectively. The results of the project are anticipated to yield the information necessary to define the scope and content of wider scale clinical trials of the technology.
METHOLODOLOGY--Sixteen-channel implanted FES walking systems will be developed using two 8-channel CWRU/VA receiver/stimulators. These will activate electrodes (in most cases, epimysial electrodes sewn directly to the muscle). New surgical techniques will be developed to enable the electrodes and stimulators to be implanted in a few sessions within a few weeks time. A new external control unit (ECU) will be designed to generate radio frequency signals to synchronize the actions of both implanted stimulators and coordinate the activation patterns for up to 16 muscles. This design effort will result in reliable and manufacturable technology that is suitable for transfer to other clinical sites or commercial manufacturers. Software to provide an easy-to-use clinical interface for specifying stimulus patterns will also result from the technical development.
RESULTS--During this second year of the project, enhancements to mobility for individuals with complete paraplegia, including walking and side-stepping, have been demonstrated on a small pilot population of subjects using a 16-channel percutaneous system. Specific assessment criteria to evaluate the effectiveness of FES as a rehabilitative intervention, focusing on enhancement of mobility, have been developed. The inclusion criteria for subjects in this study have been finalized, with several potential participants identified. The first subject to receive the completely implanted system has been identified, and plans for surgical implantation of this patient are in place for completion within this project year. Techniques for the surgical deployment of the epimysial electrodes in the muscles required in the lower extremity have been developed and piloted. Detailed functional requirements for the revised ECU have been developed, and the final hardware development is underway by an outside contractor.
FUTURE PLANS--In the third project year, three additional subjects will receive the completely implanted FES system for mobility enhancement. All four subjects will participate in the development and refinement of the clinical protocol for rehabilitation with FES, and the outcome assessment techniques will also be refined and documented on this pilot population. Follow-up assessment will occur at home and workplace. Complete documentation of the FES Mobility System and its implementation will be prepared, sufficient for the start-up of larger scale clinical trials involving multiple centers, to commence at the end of this project.
[105] DEVELOPMENT OF AN ON-LINE CORRECTION CAPABILITY FOR FNS LOCOMOTION
Howard J. Chizeck, ScD; E. Byron Marsolais, MD, PhD;
Donald C. Ferencz, MS; Margaret Skelly, BS
Departments of Systems, Control and Industrial
Engineering and Biomedical Engineering, Case Western Reserve
University, Cleveland, OH 44106; Cleveland FES Center,
Motion Studies Laboratory, VA Medical Center, Cleveland, OH
44106; email: hjc2@po.cwru.edu;
mxs70@po.cwru.edu
Sponsor: Department of Veterans Affairs, VA
Rehabilitation Research and Development Service, Washington,
DC 20420
(Project #B683-RA)
PURPOSE--The purpose of this research is to develop and evaluate improved methods of functional neuromuscular stimulation (FNS) for locomotion in complete paraplegic subjects. The goal is to make possible the use of FNS systems outside of the laboratory by compensating automatically for perturbations such as changing surfaces, disturbances, and internal changes such as muscle fatigue. By reducing the time currently required by technical staff to maintain the FNS system, the practicality and clinical acceptance of these systems will be greatly enhanced.
METHODOLOGY--Improvements to the current FNS locomotion system take the form of a feedback control system. Sensors worn by the FNS patient provide signals from which decisions concerning stimulation patterns can be made by the control system. The control system consists of three primary components: the Gait Phase Estimation Module processes the sensor signals through a fuzzy logic rulebase, to determine the phase of gait while the patient is walking; the Gait Evaluation Module uses this information and the sensor information to determine if an anomaly has occurred during walking which requires a change to the stimulation being sent to the patient's muscles; and the Pattern Adjuster Module then generates the adjustment in the stimulation pattern.
PROGRESS--Hardware and software for a microprocessor-based stimulation parameter controller has been developed. This unit is based upon a Pentium PC which acquires and processes up to 64 channels of analog signals. It communicates with the existing portable microprocessor-controlled 48-channel external stimulator using a high-speed digital interface.
A computer biomechanical simulation of human gait (both normal and paraplegic) with 23 degrees-of-freedom has been developed. It is driven with biomechanical data from laboratory experiments and simulates the complete gait cycle, including foot-to-floor contact. The results of this study show that stable, repeatable gait is possible for FNS-induced gait in paraplegics (at 0.2 m/s), whose range of muscle torque generation is limited by their implanted electrodes. This model and computer simulation is being extended to simulate stair climbing and descent and walking on level and sloping surfaces.
FUTURE PLANS--The next year of the project will involve continued development and refinement of the gait evaluation and pattern adjuster components of the system, and its evaluation in paraplegic subjects. These subjects will include individuals using 16 channels of stimulation, consistent with the implanted stimulator systems that are under development in a related project.
[106] RESTORATION OF STANDING PIVOT TRANSFER FOR QUADRIPLEGIC PATIENTS USING A TOTALLY IMPLANTED FNS SYSTEM
Ronald J. Triolo, PhD; E. Byron Marsolais, MD,
PhD
Cleveland FES Center, Motion Study Laboratory, Cleveland
VA Medical Center, Cleveland, OH 44106; Department of
Orthopaedics, Case Western Reserve University, Cleveland, OH
44106; email: rxt24@po.cwru.edu
Sponsor: Department of Veterans Affairs, VA
Rehabilitation Research and Development Service, Washington,
DC 20420
(Project #B743-RA)
PURPOSE--This project was designed to investigate the feasibility of applying an implanted 8-channel functional neuromuscular stimulation (FNS) system to provide standing and transfer function to individuals with incomplete tetraplegia. Tetraplegia compromises the ability to stand and transfer, increasing dependence on families, caregivers or assistants and compounds the risk of contractures and pressure sores. Conventional transfers are problematic for individuals with elderly spouses or caregivers who lack the strength to assist with the lifting phases of the maneuvers. The objective was to install and evaluate implantable FNS systems to provide individuals with low tetraplegia with the ability to stand independently, and to facilitate standing transfers by eliminating the need for heavy lifting by the caregiver.
METHODOLOGY--A staged implementation strategy was employed in which subjects progressed from temporary systems with helically coiled percutaneous electrodes, through the introduction of the 8-channel CWRU/VA implant. Chronically indwelling percutaneous intramuscular electrodes were used to exercise the hip, knee, and trunk extensors. When sufficient strength and endurance were achieved, stimulation patterns were developed to coordinate their actions and provide standing and standing transfer functions. The temporary systems were replaced with eight silicone-enclosed intramuscular electrodes suitable for eventual use with the implant. Subcutaneous in-line connectors to percutaneous leads allowed continued standing and transfer training with an external stimulator until a stable electrode system could be obtained. The percutaneous portions were then removed and the implantable receiver/stimulator was installed surgically for long-term use.
RESULTS--Four volunteers between the ages of 21 and 55 years (mean=34) participated in the study. All subjects exhibited neurological levels between C5 and C7, were more than 1 year postinjury, wheelchair dependent, and unable to stand or perform standing transfers at the time of admission. One subject completed the initial percutaneous development phases and has received the implanted receiver/stimulator. With FNS, every volunteer was able to exercise, stand, and sit independently or with minimal assistance. Although they still required assistance with the pivot phase of the standing transfer maneuver, all were able to raise and lower their body weight under their own power with FNS. Users generally preferred to rely on others to help with donning/doffing or to activate the stimulator, suggesting that the system may be best suited for facilitating an assisted transfer. Few subjects were able to assume or maintain a stable upright "C" posture due to activation of the rectus femoris or inadequate hip extension. Movement of intramuscular electrodes in both percutaneous and implanted systems degraded standing performance and required frequent reimplantation, especially in the hip extensor muscles, and delayed final installation of the CWRU/VA implant. The implantable receiver/stimulator itself remains operational at 3 years follow-up, verifying its reliability.
IMPLICATIONS--It is feasible to use FNS to provide standing function to individuals with incomplete tetraplegia. FNS facilitated standing transfers by eliminating the heavy lifting usually required of the caregiver. The difficulties experienced with percutaneous electrodes can be largely circumvented by implantable technology, which can be safely and effectively applied to this population. Efficient implementation procedures still need to be developed before such systems can be considered clinical options for wider scale deployment. Surgical implantation of all system components in a single procedure is indicated.
[107] RESTORATION OF GAIT FOR THE STROKE PATIENT
Robert L. Ruff, MD, PhD; Janis Jacobs Daly, MS, MA;
Avram Scheiner, PhD
Cleveland FES Center, Neurology Department and Motion
Study Laboratory, VA Medical Center, Cleveland, Ohio 44106;
email: daly@sparcy.ebme.cwru.edu
Sponsor: Department of Veterans Affairs, VA
Rehabilitation Research and Development Service, Washington,
DC 20420
(Project #B679-2RA)
PURPOSE--We tested a new technology, a multichannel, implanted Functional Neuromuscular Stimulation (FNS) system for stroke gait rehabilitation. We compared treatment using surface electrodes (surface-stim) with treatment using implanted, intramuscular (IM) electrodes (FNS-IM).
METHODS--Chronic (1 year or more post stroke) stroke subjects were studied, each subject serving as his/her own control. A single case study design was used, across subjects. In phase 1, eight patients were treated with surface-stim; in phase 2, six of those patients were treated with FNS-IM. Four muscles were stimulated: anterior tibialis; gastrocnemius/soleus; quadriceps; short head of the biceps femoris and long head of the biceps femoris.
Outcome measures were threefold: 1) volitional movement at a single joint with the body in a static position; 2) kinematics of gait; and 3) functional capability at home. EMG, kinematic data, clinical gait scale, manual muscle test, coordination, balance, and functional capability data were collected.
PRELIMINARY RESULTS--Eight subjects were studied in phase 1, surface-stim treatment. Preliminary analysis indicated that following surface-stim, 25-63 percent of the subjects improved in volitional measures of lower extremity strength and coordination. In kinematic measures of gait, 12-50 percent improved during phase 1, surface-stim treatment. Six of those subjects were progressed to phase 2, treatment using FNS-IM. During this phase, in every measure of strength, coordination, and gait kinematics, subjects demonstrated statistically significant improvement in volitional motor control, beyond that attained during surface-stim treatment (p<0.0001). In addition, functional gains were documented, beyond those attained during surface-stim treatment.
IMPLICATIONS--Rehabilitation techniques in use today are often not sufficient to restore a safe, normal gait pattern to stroke patients. Subjects in this study showed improved gait and functional capability following treatment with both surface-stim and FNS-IM. The results of this study support further study of FNS, using both surface-stim and FNS-IM, for gait rehabilitation following stroke.
[108] 3-D FORCES AND MOMENTS DURING FES-INDUCED LEG CYCLE ERGOMETRY: A PILOT STUDY
Charles C. Ho, MD, PhD; Roger M. Glaser, PhD; Thomas
W.J. Janssen, PhD; D. Drew Pringle, EdD, Junghsen Lieh, PhD;
William P. Couch, BS; José W. Almeyda, BS
VA Medical Center, Dayton, OH 45428; Institute for
Rehabilitation Research and Medicine, Wright State
University School of Medicine, Dayton, OH 45435;
Rehabilitation Institute of Ohio, Miami Valley Hospital,
Dayton, OH 45409; email: ho.charles@dayton.va.gov;
rglaser@desire.wright.edu;
tjanssen@desire.wright.edu;
dpringle@desire.wright.edu
Sponsor: Department of Veterans Affairs, VA
Rehabilitation Research and Development Service, Washington,
DC 20420
(Pilot Project #B1859-PA)
PURPOSE--The purpose of this pilot project is to study the three-dimensional (3-D) biomechanics of functional electrical stimulation-induced leg cycle ergometry (FES-LCE) in individuals with spinal cord injuries (SCI) to determine potential orthopedic risks and methods to improve operating safety and efficiency. The specific objectives are to: 1) describe the 3-D forces and moments applied to the pedals during FES-LCE in persons with SCI; 2) determine 3-D knee and 2-D hip and ankle moments during FES-LCE; 3) describe the changes in these forces and moments with increasing power output (PO) and with fatigue; 4) compare these forces and moments during FES-LCE by persons with SCI to those during voluntary LCE by nondisabled (AB) persons; 5) determine the mechanical efficiency (using the metabolic rate) at various levels of PO and fatigue and correlate this with the amount of extraneous forces; and 6) make recommendations as to how operating safety and efficiency may be improved (e.g., patient-LCE configuration, muscles utilized, timing, and strength and duration of the contractions).
METHODOLOGY--Ten subjects with SCI will perform FES-LCE exercise on a Therapeutic Alliances Incorporated ERGYS LCE. The ERGYS I was equipped with specially constructed pedals that can measure 3-D forces and moments, and with force transducers in the leg restraints that can measure medio-lateral forces on the upper-legs. For comparison, ten AB persons will perform this activity voluntarily. The LCE operating configuration will closely follow the clinical situation, and will be the same for all subjects, except that the AB subjects will perform LCE voluntarily. To evaluate the influence of PO on the biomechanics and mechanical efficiency, the subjects will perform a progressive intensity LCE-test. To evaluate the influence of fatigue, subjects will perform a prolonged LCE-test at various, but constant, PO levels. Metabolic and cardiopulmonary responses will be monitored to calculate mechanical efficiency. 3-D motion analysis, using an infrared active marker motion analysis system, will occur simultaneously to enable determination of forces and moments at the ankle, knee, and hip joints using inverse dynamics techniques.
PROGRESS--The initial testing phase of this project has now been completed. The pedal and leg restraint force measurement systems have been coupled to the Optotrak system to enable synchronous recording of forces and movements. Two men with SCI (one with paraplegia and one with quadriplegia) and two AB men participated in the initial testing phase. Preliminary results suggest that in the subjects with SCI medio-lateral forces exerted on the leg restraints tended to be higher than in the AB subjects and occured at different angles in the pedal cycle. It was also apparent that subjects with SCI exhibited a less smooth force exertion pattern with more periods of brief peak forces than the AB subjects.
IMPLICATIONS--The results of this research could provide greater understanding of the forces in lower-extremity joints during FES-LCE and how muscle activation can be improved to reduce potentially hazardous forces and to increase mechanical efficiency. This can ultimately lead to the development of a more efficient therapeutic exercise system that can be safely used on a regular basis to enhance fitness in persons with SCI, and reduce the risk of secondary health problems.
[109] DEVELOPMENT OF A CLOSED LOOP CONTROL SYSTEM FOR FES AND APPLICATION TO KNEE JOINT MOVEMENTS IN PARAPLEGICS
Enrico D'Acquisto, DrEng; Maurizio Ferrarin, DrEng, PhD;
Antonio Pedotti, PhD
Centro di Bioingegneria, Fondazione Pro Juventute Don C.
Gnocchi IRCCS, Politecnico di Milano, I-20148 Milano, Italy;
email: ferramau@ipmel2.elet.polimi.it
Sponsor: Italian Ministry for University and Scientific Research
PURPOSE--The purpose of this study is to develop and test a closed-loop control system for Functional Electrical Stimulation (FES), in order to recover some movements of paralyzed muscles and to realize a functional and physiotherapeutic tool for injured people.
METHODOLOGY--The system is based on a PC, a programmable 8-channel stimulator, a controller, and a set of sensors. A PID software regulator has been experimentally realized and used to control the stimulator. Ziegler and Nichols' method has been used to determine the controller's parameters.
Electrogoniometers interfaced by a dedicated board were used to catch the feedback signal: we applied the system principally to the quadriceps; therefore, the controlled feedback signal (outputs) was the knee angle. The obtained knee angle is compared with the desired ones in real time, and the PID controller calculate the right input for the stimulator.
The programmable stimulator produces trains of rectangular pulses, the width of which is controlled by the feedback signal.
Up to now three working configurations have been set: tracking of a prefixed knee angle value, tracking of a prefixed knee angle trajectory, and a master-slave configuration, in which the tracked angle is real time caught by an electrogoniometer from another joint (or even from another person).
PROGRESS--Applications of this technique to standing-up movement has been considered. In particular two methods have been tested: the tracking of a trajectory acquired from a nondisabled subject, and the real-time tracking of the elbow angle with Master-Slave configuration, since in nondisabled subjects we found a good correlation between knee and elbow angle during the standing-up movement.
Moreover, a standing posture system was implemented: it switches on when the standing up movement is completed, and is based on the knee angle variation and on a prefixed pattern for the alternation of the supporting leg, in order to minimize the muscle fatigue. Now we are working on a pressure sensor under the feet, sensitive to the subject's weight distribution.
PRELIMINARY RESULTS--A frequency domain study was done on the system applied to the quadriceps muscle of a nondisabled subject. For this purpose, a set of sinusoid signals with frequency from 0.1 to 1 Hz has been used as input trajectory. Comparing obtained knee angles with imposed one, a Bode diagram has been built. The system behaves as a low-pass filter with a frequency cut at 0.5 Hz due to a complex pole couple. The system shows a good robustness to external disturbance.
FUTURE PLANS--The use of the pressure sole for the posture of a paraplegic subject is the next step of this study: the weight position on the foot will be used as control signal to stimulate quadriceps and calf muscles. Moreover, the application of this system to a paraplegic subject is planned in order to verify its applicability during physiotherapy treatments and/or in domestic situations.
[110] FES POWERED RGO: A PRACTICAL WALKING SYSTEM FOR PARAPLEGICS
Moshe Solomonow, PhD; Richard V. Baratta, PhD; Robert D.
D'Ambrosia, MD
Bioengineering Laboratory, Department of Orthopaedic
Surgery, Louisiana State University Medical Center, New
Orleans, LA 70112; email: etarki@lsmu.edu
Sponsor: Louisiana Board of Regents, Baton Bouge, LA 70804
PURPOSE--The objectives of this project are to provide some paraplegics with a reliable and safe walking system, reducing metabolic energy consumption by utilizing electrical stimulation of selected muscle groups.
METHODOLOGY--While the LSU Reciprocating Gait Orthosis (RGO) has been successfully applied to a large population of paraplegics for a number of years, work has expanded on development of two muscle stimulation strategies designed for use in combination with the orthoses. The first approach employs surface stimulation of the quadriceps simultaneous to the contralateral hamstrings to induce hip flexion and extension. The second approach employs implanted stimulation of the vasti and illiopsoas muscles for independent control of knee and hip flexion and extension.
RESULTS--Two hundred patients have already been tested, evaluated, and fitted with the RGO and portable stimulation system. One demonstration of the efficacy of the system was its enthusiastic acceptance by the patients. The addition of FES reduced the energy cost of locomotion and improved the acceptability of the system by patients. It was also shown that there were significant reduction in spasticity and cholesterol along with improvement in cardiopulmonary and metabolic functions.
[111] PARAPLEGIC WALKING MADE PRACTICAL WITH FNS AND ORTHOSES
E. Byron Marsolais, MD, PhD; Joseph Mansour,
PhD
Cleveland FES Center, Cleveland VA Medical Center,
Cleveland, Ohio 44106; Departments of Orthopaedics and
Mechanical Engineering, Case Western Reserve University,
Cleveland, Ohio, 44106; email: ebm2@po.cwru.edu;
jmm12@po.cwru.edu
Sponsor: National Institute of Child Health and Human Development; the National Institute of Neurological Disorders and Stroke, Bethesda, MD 20892
PURPOSE--We seek to determine if 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 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 shall fit multiple subjects with the combination of an 8-channel, radio-frequency-controlled/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). Physical therapists will be able to utilize accepted and modified outcome assessment and energy consumption measures to determine the ability of users to function in the household or the community at large.
PROGRESS--Six complete paraplegic individuals with percutaneous systems have evaluated the prototype brace. The single lateral leg support prototype helped determine the materials necessary to attain the stiffness required for a functional low-weight orthosis. Current design efforts focus on three specific areas of development. The first is a variable trunk support, flexible when the user is sitting in a wheel chair, allowing lateral and forward bending with minimal constraint, which becomes a rigid support when standing and ambulating. Secondly, a hip joint which actively assists in the stabilization of the upper torso and supplies a beneficial moment when positioning the leg for stair climbing. Finally, knee joints will be locked and unlocked by the external control unit (ECU) of the stimulator according to the phase of gait. The functionality of the prototype brace and FES combination is being assessed. Experiments to determine energy consumption comparing brace alone to brace and FES are being done. A second line of investigation is looking into the range and repeatability of ambulation to characterize the ability of a user to function in a community setting. Maneuverability testing around obstacles and standing activities are being conducted.
RESULTS--Development of surgical techniques for implantation of an 8-channel, RF-powered/controlled FES system have progressed since the initiation of the project, and the ability now exists to implant the system in one to two surgical sessions. Two subjects are scheduled for implantation in late 1996. These subjects will have the first braces with ECU synchronized knee joint locks. A prototype trunk support, reducing movement constraints on the user when not ambulating without loosening straps, is being readied for application to a prototype brace. Computer simulation of a hip joint which aids in stair climbing and trunk stability without the need of the reciprocating mechanism has proved successful. A prototype is being fabricated for testing. Physical therapists familiar with brace training and FES have shown that subjects can be taught to utilize the orthosis in combination with FES and crutches when they were previously unable to use the orthosis alone. Sit-to-stand maneuvers and ambulation are also simplified with the application of FES. Subjects using this system have shown the ability to ambulate 500 m when allowed standing rest periods of 5 min between 50 m walks. Energy consumption continues to be an area of concern with 7 MET outputs being measured for short walks.
IMPLICATIONS--A less constrained brace combined with and implantable FES system will, as indicated by these results, allow a completely paralyzed user to attain a limited level of community ambulation.
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Last revised Wed 05/26/1999
