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[068] COLONIC REHABILITATION WITH MICROSTIMULATORS AFTER SPINAL CORD INJURY
Lisa Riedy, PhD; Keith Bruninga, MD; James S. Walter,
PhD; Ali Keshavarzian, MD
VA Hines Rehabilitation Research and Development Center,
Hines, IL 60141; email: lriedy@orion.it.luc.edu
Sponsor: Department of Veterans Affairs, VA
Rehabilitation Research and Development Service, Washington,
DC 20420
(Project #B1511-2RA)
PURPOSE--The objectives of this study include: 1) the in vitro evaluation of a uniquely new, fully implanted microstimulator to be used for colonic FES management after SCI; 2) the determination of the optimum number and location for the microstimulators as well as the optimum protocols necessary to induce defecation in the SCI animal; 3) the determination of the effect of the microstimulators on colonic motility and on colonic transit time; and 4) the evaluation of the biocompatibility of the microstimulators in conjunction with the histological response of the colon.
METHODOLOGY--Proposed studies include both in vitro and in vivo work. In vitro studies will evaluate the microstimulator's performance over time, the depth of field of the external coil to the implanted electrodes, the optimum angle of orientation between the microstimulators and the external coil, and the spread of electric field. For in vivo studies, one group of 18 animals will be used with each animal serving as its own control. Two survival surgeries are needed. The first to fully instrument the animal, and the second to completely contuse the spinal cord at T4. Colonic manometry and transit times will be assessed before SCI, after SCI; and after SCI with direct colonic stimulation.
PROGRESS--The University of Michigan has fabricated several prototypes and demonstrated basic functionality of these devices. Fabrication of devices for in vivo studies is in progress. We have started in vitro studies to characterize the spread of the electric field.
RESULTS--One of the most important features of the microstimulators is the glass package responsible for providing the hermetic seal as well as the feedthroughs to connect its electronics to those outside the package. This package has undergone substantial testing under accelerated conditions both in saline and DI water, and periodically tested visually by optical microscope and electrically with integrated dew point sensors for the presence of moisture. For the electrical tests, the impedance of the dew point sensors with the pads outside the package is monitored. Using the accelerated data at 85 °C and 95 °C in saline, an expected life time of 177 years at 37 °C was calculated. Based on similar studies in water, an expected life time of 485 years at 37 °C was calculated.
To characterize the functional performance of the microstimulators, methods to assess the stimulating current and electric field are required. Using an in vitro bath, two small surface area platinum test electrodes, and two external platinum electrodes, changes in the spread of the electric field were evaluated at various temperatures, frequencies, pulse durations, and applied currents in both DI water and saline baths. With these standard curves, we will be able to characterize the in vitro performance of the microstimulators.
FUTURE PLANS--We plan to assemble external coils and stimulators, fabricate additional microstimulators for in vivo use, and identify the optimum number and location of these fully implanted microstimulators needed in vivo to induce defecation.
[069] 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; Paul
Zaszczurynski
Rehabilitation Research and Development Center, VA Hines
Hospital, Hines, IL 60141; Loyola Medical Center, Department
of Urology and Physiology, Maywood, IL 60153
Sponsor: Department of Veterans Affairs, VA
Rehabilitation Research and Development Service, Washington,
DC 20420
(Pilot Project #E1583PA)
PURPOSE--The artificial urinary sphincter, an inflatable balloon cuff placed around the urethra, is the most effective therapy for the restoration of urinary continence secondary to internal sphincter deficiency. It is most often used to manage urinary incontinence following radical prostatectomy for cancer. An alternative is the stimulated gracilo-myoplasty, where stimulating electrodes are placed in the gracilis muscle that is wrapped around the urethra and attached to the pubic bone laterally. This myoplasty has been named an alpha wrap. However, with this wrap, urethral mobility, ischemia, and strictures are reported complications. We evaluated modified alpha wraps to avoid these problems. Stimulated flaps were evaluated in an animal model and urethral factors were evaluted.
METHODOLOGY--Male dogs were implanted with a myoplasty stimulator. The gracilis muscle was loosely wrapped around the urethra to avoid the potential for stricture formation. The standard alpha wrap was modified with the gracilis muscle attached to the midline of the pubic bone or attached to the gracilis muscle itself. An 8-wk 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.
RESULTS--Seven dogs with stimulated skeletal muscle flaps have been evaluated with the modified gracilis muscle wrap around the urethra. Under anesthesia, urethral pressure increases of 10 to 150 cm H2O 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. The modified alpha wrap with the gracilis muscle attached to itself was noted to result in urethral twisting during stimulation. Because of this high mobility it was not used further. The second wrap with the attachment of the gracilis muscle to the pubic midline resulted in little urethral movement. Urethral strictures were not observed in the four animals with this wrap. Technical problems such as detached electrodes were encountered in several of the animals. However, the stimulated gracilis neosphincter functioned well in this animal model.
FUTURE PLANS--Since these studies were initiated, clinical trials of stimulated graciloplasty have been started in several centers around the world. Our understanding is that an alpha split wrap is being used where the wrap is brought around the urethra and then through a split in the middle of the muscle before it is attached laterally to the pubic bone. This approach should minimize urethral mobility and stricture formation. We are encouraged by these clinical trials and hope to participate in the active discussion of this promising approach to management of external urethral sphincter deficiency.
[070] APPLICATION OF A 3-D REAL-TIME MOTION ANALYSIS TECHNIQUE FOR THE DEVELOPMENT OF CLOSED-LOOP CONTROL SYSTEMS FOR FES
Maurizio Ferrarin, DrEng, PhD; Guido Baroni, DrEng;
Giancarlo Ferrigno, DrEng, PhD; Antonio Pedotti,
DrEng
Centro di Bioingegneria, Fondazione Pro Juventute Don C.
Gnocchi IRCCS, Politecnico di Milano, I-20148 Milano, Italy;
email: ferramau@mail.cbi.polimi.it
Sponsor: Italian Ministry for University and Scientific Research, Commission of European Comunity
PURPOSE--The purpose of this study is to develop and apply a 3D real-time, TV-based motion analysis system for the control of movements induced by FES. Its applicability in the development of FES control strategies is analyzed mainly in terms of choice of the optimal kind and number of sensors and definition of stimulation controller.
METHODOLOGY--One of the key points related to the development of closed-loop FES system for movement restoration in persons with paralysis is the definition of what general control strategies to adopt. The number of kinematic and dynamic variables useful to control the stimulation activity can be very high, particularly in complex movements; therefore, the number and type of sensors are generally not known a priori and should be defined during the general system design. One possible approach is to start with a large number of sensors during the laboratory development phase and then reduce them for the clinical application of the system. In this research, we study the possibility of using a TV-based motion analysis system to perform this laboratory development phase.
A programmable stimulator driven by a PC has been interfaced with the ELITE system (a motion analysis system based on automatic recognition of passive markers performed by CCD TV cameras while infrared light is flashing the field of view), implementing a closed-loop configuration that delivers current impulse trains with the following characteristics: manually adjustable amplitude (0-150 mA), software-controlled pulse width (20-500 ms) and software-controlled pulse frequency (1-500 Hz).
In this pilot application, the movement of the knee joint was controlled with surface stimulation of the quadricep muscles, using the knee angle as the controlled variable. Three markers were positioned on hip, knee, and ankle joint and once the 3-D coordinates of each marker were detected, joint angle and angular velocity were computed in real time, and their values used by a PID controller to modulate muscle stimulation.
PRELIMINARY RESULTS--At the heaviest CPU work condition (4 active TV cameras, 3-D graphic representation on 3 planes, and contemporary data saving on HD), up to 12 markers seen by each TV camera were successfully managed at the maximal system sample rate of 100 Hz. This performance seems suitable for many FES application. Moreover, due to the real-time algorithm implementation, a progressive decrease of sampling rate is the only consequence of processing a higher marker number. Concerning the experiment on knee movement control, the general performance was comparable to the results previously obtained with a traditional electrogoniometer, with several advantages: absence of any external devices on the subject's body, higher system accuracy, less artifact due to skin movement, and the ease in changing the position and configuration of the markers. The main limitation of this approach, its restricted working volume, makes it suitable for local movements (standing up, sitting down, walking on treadmill, and upper limb movements).
FUTURE PLANS--Experiments with a more comprehensive approach, exploiting the possibilities provided by a motion analysis system based on passive marker recognition will be performed.
[071] MICROSTIMULATION OF THE LUMBOSACRAL SPINAL CORD: MAPPING
Warren M. Grill, PhD; Baoqing Wang, MD, MS; 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, Neural Prosthesis Progam
PURPOSE--The objective of this project is to investigate the feasibility of genitourinary and motor system neural prosthetics based on intraspinal microstimulation.
PROGRESS--Expression of the immediate early gene, c-Fos was used to map the location of spinal neurons involved in control of genitourinary function. Male cats were anesthetized with alpha-chloralose and received 1 of 3 stimulus protocols: electrical stimulation (2 hr, 1 s ON/1 s OFF, 20 Hz) of the pelvic nerve (n=2) or the pudendal nerve (n=2), or a 2-hr period of isometric micturition (n=2) induced by ligating the proximal urethra and infusing saline into the bladder (1 ml/min) until spontaneous periodic bladder contractions occurred. Stimulation with each protocol resulted in a larger number of cells expressing Fos-like immunoreactivity (FLI) than in operated but unstimulated controls, which exhibited few, scattered Fos-positive cells. In stimulated animals, nuclei exhibiting FLI were found bilaterally in S1-S3 and were localized to the lateral portion of the superficial dorsal horn (laminae I and II), the neck of the dorsal horn (laminae V and VI), and within small cells in the dorsal commissural nucleus. Fewer Fos immunoreactive nuclei were observed in the medial portion of the superficial dorsal horn and FLI was rarely observed in ventral horn neurons. In animals receiving electrical stimulation of the pelvic nerve or undergoing isometric micturition, FLI was also present in larger cells within the intermediolateral cell column of S2-S3. The results of these studies identify spinal neurons involved in control of the genitourinary system, and provide regions to target with microstimulation.
RESULTS--The motor responses generated at the knee joint were mapped by intraspinal microstimulation. Adult cats were anesthetized with alpha-chlorolose and the isometric torque generated was recorded in response to 1 s trains of 20 Hz 100 µs biphasic current pulses (10-150 µA) applied along vertical dorsal-to-ventral penetrations made between spinal segments L7 and L4. Electrode locations in the ventral horn generated the largest torques (averaged over 1 s stimulus interval): 5-15 N-cm extension, 5-10 N-cm flexion. There was mediolateral segregation of the torque responses in a rostrocaudal plane. Medial electrode placements generated primarily flexion torques and lateral electrode placements generated primarily extension torques. Large flexion torques were also generated by microstimulation along a vertical band in the medial dorsal horn, paralleling the dorsal root entry zone. These results indicate that microstimulation of the spinal cord allows selective activation of knee flexors and extensors by both direct and indirect activation of spinal motoneurons, and that the magnitudes of the evoked torques are small relative to those evoked by ventral root or peripheral nerve stimulation.
Urethral pressure profiles, anatomical reconstructions, and electrical stimulation of the pudendal nerve were used to document the anatomy of the feline periurethral musculature and determine the neural pathways that mediate the effects of intraspinal microstimulation. From the distal part of the prostate, striated muscle increased progressively and became predominant in the postprostatic urethra. Rapid spontaneous fluctuations and higher baseline pressures were recorded distal to the prostate, but were absent in the preprostatic urethra. These pressures resulted from the basal tone in the urethralis and external urethral sphincter (EUS) muscles and were abolished by Flaxedil. At the level of the EUS the pressure measured along the ventral side of the urethra was higher than along the dorsal side. This correlated with a ventral bias in the size of the EUS. Pressure increases elicited by pudendal nerve stimulation were detected in the postprostatic urethra and bulbourethra, regions where periurethral striated muscle was identified.
[072] THE DYNAMIC MODEL OF SKELETAL MUSCLES AND JOINTS FOR FES APPLICATIONS
Moshe Solomonow, PhD; Richard V. Baratta, PhD; Bing-He
Zhou, EE; Robert D. D'Ambrosia, MD
Department of Orthopaedics, School of Medicine in New
Orleans, Louisiana State University Medical Center, New
Orleans, LA 70112
Sponsor: National Science Foundation, Arlington, VA 22330
PURPOSE--Discerning the correct response model of a single skeletal muscle has been a long-standing problem, because only unphysiological control inputs (firing rate or reverse recruitment) could be used, or alternate analogue models preassumed the interaction mode of firing rate and recruitment, 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 that recruits motor units in an orderly fashion.
PROGRESS--Additional work has identified the frequency response of nine different muscles in the hind limb of the cat. The impact of muscle/tendon ratio, mass, pennation, and twitch properties varied the model poles from 1.6 to 2.8 Hz. Recent studies focused on load moving contractions and on the effect of the joints in various configurations. Muscle architecture and its predominant fiber composition seem to be the primary variable in determining its dynamics, whereas the tendon is a secondary factor. Recent work identified the dynamic model of antagonistic muscle pair acting on the ankle joint of the cat.
RESULTS--The frequency response model consisted of a second-order system with double poles at 1.8 Hz. This was independent of the control strategy used, the predominant muscle fiber type, or the force perturbation level. A pure time delay differentiated the models for fast and slow twitch muscles being 11 ms and 16 ms, respectively. Firing rate control input was reaffirmed to result in a nonlinear model as previously described in the literature.
[073] THE USE OF EMG AS FORCE FEEDBACK IN CLOSED-LOOP ELECTRICAL STIMULATION SYSTEMS
Moshe Solomonow, PhD; Richard V. Baratta, PhD; Robert D.
D'Ambrosia, MD
Department of Orthopaedics, School of Medicine in New
Orleans, Louisiana State University Medical Center, New
Orleans, LA 70112
Sponsor: National Science Foundation, Arlington, VA 22330
PURPOSE--Force feedback is necessary 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 investigated in order to delineate the effects of changing muscle length, and moment arm about the joint's center of rotation, in order to extend the concept to nonisometric contractions in a moving limb. It was shown that various factors influence the EMG-force relations, and that a multivariant model should be constructed to provide accuracy to the feedback loop. Recent evidence delineate changes in force and EMG in different contraction types and after skill acquisition.
[074] DETERMINATION OF THE OPTIMAL MOTOR UNIT RECRUITMENT STRATEGY FOR APPLICATION IN A HIGH PERFORMANCE FES SYSTEM FOR QUADRAPLEGICS
Moshe Solomonow, PhD; M. Bernardi, MD; Richard V.
Baratta; Robert D'Ambrosia, MD
Department of Orthopaedics, School of Medicine in New
Orleans, Louisiana State University Medical Center, New
Orleans, LA 70112
Sponsor: National Science Foundation, Arlington, VA 22330
PURPOSE--The objective of this investigation was to determine the optimal motor unit control strategy that should be used in electrical stimulation of the upper limb and hand of persons with quadraplegia in order to provide them with most accurate control of force increase and decrease, a part of a long-term objective of designing a high-performance FES system.
METHODOLOGY--A group of controls were trained to track a 3-s long linear increase in force of their elbow flexors in isometric condition while recording the EMG of the flexors (agonist) and extensor (antagonist) muscles. The power spectra frequency of the EMG signal was obtained and its median frequency (MF) calculated. Measurements were made in the beginning of a 6-wk-long training program, and every 2 wks thereafter. The MF being representative of the conduction velocity of the muscles action potentials, indicated the increase or decrease in motor unit recruitment.
It was shown that at the end of the 6-wk program, the subjects tracking capability become highly accurate while their motor unit recruitment strategy increased from 0-65 percent of the maximal muscle force to 0-90 percent of the maximal muscle force.
IMPLICATIONS--A FES system when applied to rehabilitation of arm and hand functions of persons with quadraplegia, where high precision of force control is required, should employ orderly stimulation of motor units over the full range of the available force in order to provide fine increments of force increase.
[075] EFFECT OF INGESTED SODIUM BICARBONATE ON MUSCLE FORCE, FATIGUE, AND RECOVERY
Joseph Mizrahi, DSc; Oleg Verbitsky, PhD; Eli Isakov,
MD
Department of Biomedical Engineering, Technion-Israel
Institute of Technology, Haifa, 32000 Israel Loewenstein
Rehabilitation Center, Raanana 43100, Israel; email:
JM@biomed.technion.ac.il
Sponsor: The Segal Foundation, Israel
PURPOSE--We seek to evaluate the effect of ingestion of NaHCO3 on muscle progressive fatigue as induced by FES and on muscle recovery after intensive cycling exercise.
METHODOLOGY--The influence of acute ingestion of NaHCO3 on fatigue and recovery of the quadriceps femoris muscle following exercise was studied on six nonimpaired male controls. A bicycle ergometer was used for exercising under three loading conditions: A) load corresponding to V2max; B) load A+17 percent; C) load B but performed 1 hour after acute ingestion of NaHCO3.
The relationship between short-term physical effort performed during cycling and the resulting decrease in blood pH level due to lactic acid accumulation is well documented. End-tidal CO2 pressure (PETCO2) was used in this study to indirectly reflect humoral acid-base changes due to bicarbonate decrease.
Functional electrical stimulation (FES) was applied to provoke isometric contraction of the quadriceps femoris. The resulting knee torque was monitored during fatigue (2 min chronic FES) and recovery (10 sec FES every 10 min, for 40 min). This procedure provided standardized testing protocols and ensure reproducibility of the testing conditions.
RESULTS--The results obtained indicate that during supramaximal load (test B) a significant decrease in PETCO2 resulted in comparison to load V2max (test A), reflecting a decrease in bicarbonate buffer formation. However, when the supramaximal load was combined with acute ingestion of bicarbonate (test C), a significantly higher PETCO2 level resulted, indicating an increased CO2 accumulation in the blood and a more effective bicarbonate buffer activity. Quadriceps torques were found higher in the presence of NAHCO3 (p<0.05): With NaHCO3 the peak, residual and recover (after 40 min) normalized torques (mean±SD) were 0.68(0.05), 0.58(0.05) and 0.73(0.05), respectively; without NaHCO3 the values were 0.45(0.04), 0.30(0.06) and 0.63(0.06), respectively. The increased torques obtained following acute ingestion of sodium bicarbonate indicate the possible existence of improved non-oxidative glycolysis in isometric contraction, resulting in reduced fatigue and enhanced recovery.
FUTURE PLANS--It is planned to study the effect of ingested NaHCO3 on paraplegic subjects who use FES functionally for reducing their muscle fatigue and enhancing recovery.
[076] DYNAMICS OF FORCE RECRUITMENT OF THE PARALYZED MUSCLE BY FES
Joseph Mizrahi, DSc; Leonid Livshitz, MSc; Pini
Einziger, DSc
Departments of Biomedical and Electrical Engineering,
Technion-Israel Institute of Technology, Haifa, 32000
Israel; email:
JM@biomed.technion.ac.il
Sponsor: The Segal Foundation, Israel
PURPOSE--We seek to develop an analytical model that allows to calculate the current distribution within a stimulated muscle and obtain the isometric recruitment curve (IRC).
METHODOLOGY--A general model of the electric field within a layered medium with arbitrary placement of surface or intramuscular electrodes is developed. First, by using the method of separation of variables, we obtain the solution in an integral form. We then convert this solution into an infinite (hyper-geometric) image series representation. This leads us to the same solution that would have been obtained had the image technique been applied directly. The image series expansion is used to obtain numerical results, which are compared to results obtained by numerical integration.
The next step is to obtain the interaction between the electric field and the excitable cell, by examining the current density along the fibers and by comparing it to the excitation threshold. In this way a predicted IRC is obtained and used for comparison with experimentally obtained data. The advantage of the analytical approach developed is its ease of application for the rapid and accurate determination of the electric field in heterogeneous medium resulting form FES.
Two particular models are solved: transcutaneous and percutaneous stimulation. The first stage is determination of the current density distribution within the muscle slice for both models. The second stage counts the elements within the active slice that escape the activation threshold for various values of input current. Whenever the longitudinal component of the current density exceeds the excitation threshold, contraction is assumed to take place and force is generated. The average force produced is calculated as the ratio of the number of fibers in the muscle.
RESULTS--Sensitivity of the model to different parameters such as tissues reflection coefficients, activation threshold, and fiber length was verified. The resulting model demonstrated characteristic features which were similar to experimentally obtained data. The model also quantitatively indicated the difference between surface and implanted electrode recruitment.
The intramuscular IRC gave a higher slope than that of the surface stimulation IRC, due to the higher current density values resulting when intramuscular stimulation is used. An additional feature of the IRC in this case was the absence of an initial dead zone region, possibly because of the presence of singular values of the current density near the stimulation electrodes, due to the point source representation of stimulation.
To overcome the problem of singularity, we plot circular equipotential lines around the point sources. The radii were chosen to be less than the skin layer thickness.
The current density distribution obtained in the surface stimulation model was found largely nonuniform. This may lead to fast fatiguing of the fibers adjacent to the stimulating electrodes. The intramuscular stimulation model demonstrated a more uniform current density profile with depth. Nevertheless, it had a region with a relatively low current density midway between the stimulation electrodes. Decreasing the interelectrode distance or using additional stimulation electrodes can help in making the current density more evenly distributed.
FUTURE PLANS--The point-source solution (green-function) of the potential problem with stratified media will be used to calculate the potential distribution due to electrodes with finite dimensions. The numerical results will be obtained by using infinite image series expansions. The effect of multi-array electrode configurations on the spatial distribution of the electric field will also be investigated.
[077] THE EFFECTS OF TRAINING BY FES ON MUSCLE GEOMETRY AND FORCE
Joseph Mizrahi, DSc; Oron Levin, MSc; Menahem Gornish,
MD; Eli Isakov, MD
Department of Biomedical Engineering, Technion-Israel
Institute of Technology, Haifa, 32000 Israel; MRI Unit,
Rabin Medical Center, Petah Tikva, Israel; Loewenstein
Rehabilitation Center, Raanana 43100, Israel; email:
JM@biomed.technion.ac.il
Sponsor: The Segal Foundation, Israel
PURPOSE--This study was designed to quantify the cumulative effects of training by FES on the hypertrophy and strengthening of paralyzed muscles. In previous studies, the changes of geometrical properties of the muscles over the training period were assessed by obtaining axial images from the region of the mid-thigh. Those images were acquired by using either MR or CT imaging techniques. However, imaging of the mid-thigh region is not sufficient for evaluation when one focuses on the conditioning of a specific muscle, since muscle bellies of the thigh extensors and flexors are not aligned. In this study we use contiguous axial and sagittal images of the whole thigh and a polynomial curve-fitting technique to acquire the geometry of each of the knee extensors. Estimated geometrical properties include maximal cross-sectional areas (CSA) and volumes of the thigh extensors, which are used to quantify the cumulative effects of training by FES on hypertrophy of these muscles. The effect of training is also measured by means of the torque applied by the muscle.
METHODOLOGY--Data for the MRI study are collected on a whole body MR imager. Standard soft tissue MRI protocols (T1-weighted) are used to generate a series of axial 15 mm slices with 6 mm interslice gap and sagittal 10 mm slices with 4 mm gap contiguous cross-sectional within a field of view of 500 by 500 mm. The images are analyzed using a built-in "irregular region of interest (IRROI)" area measure program of the imager. A series of contiguous axial images of the thigh are acquired from the plane of the greater trochanter to the plane of the condyle of the femur. In calculating the CSA of muscles of the GVS, the cursor is used to exclude neurovascular structures, accumulations of fat, and fibrous tissue bundles that are clearly delineated from the muscle groups. The relative orientation between the longitudinal axes of the thigh muscle and the image frame is estimated and enables evaluation of the CSA of the muscles perpendicular to their longitudinal axis. The areas of the thigh muscle include: rectus femoris (RF), vastus lateralis (VL), and vastus medialis (VM). They are curve-fitted by using the least squares (LSQ) polynomial regression method, to interpolate the muscle CSA versus the distance x from the proximal aponeurosis.
Torque measurements are taken from the right thighs of both subjects during the supra-maximal contraction sessions. Torques are curve-fitted using a tri-exponential analytical function, and the force in the quadriceps is calculated.
RESULTS--The results show a significant (p=0.024) increase of the CSA at the muscle belly of the right RF muscle. It should be remembered that the right RF is subjected to both isotonic and isometric activation. These findings support the hypothesis that supramaximal, isometric, activation may enhance strengthening of the trained muscle.
The changes in the muscle's force production capacity consist of a general increase in the peak of the torque. These changes are accompanied by a significant enhancement of the CSA of the right RF. This may indicate that in the training time followed-up in this study (12 wks), the main muscle change is a general increase in cross-sectional area. It cannot be concluded, however, whether this change is the result of an increase in fiber diameter, number of fibers, or any combination of both.
[078] MODELING OF FATIGUE AND RECOVERY IN FES TO ALLOW PREDICTION OF MUSCLE FORCE
Joseph Mizrahi, DSc; Oron Levin, MSc
Department of Biomedical Engineering, Technion-Israel
Institute of Technology, Haifa, 32000 Israel; email:
JM@biomed.technion.ac.il
Sponsor: The Segal Foundation, Israel
PURPOSE--We are working to develop a musculo-tendon model of a FES activated paralyzed muscle to allow prediction of muscle force during interrupted stimulation, in which processes of fatigue and recovery take place in sequence.
METHODOLOGY--The muscle is modeled in terms of five elements, including muscle mass and tendon, connected in series with three parallel elements, two of which are passive, representing elasticity and viscosity of the parallel-arranged muscle fibers. The third parallel component is the contractile element (CE) that represents the activated fibers.
Myoelectric (M-wave) and metabolic data are used to evaluate the neural excitation and metabolic history of the activated muscle, from which the activation dynamics and the fatigue function of the contractile mechanism are derived, respectively. The active state of the muscle fibers defines the fraction of regulatory sites on troponin with calcium bound, and is evaluated by substituting the neural excitation into an activation dynamics model.
The measured metabolic parameters include Pcr, Pi, pH and H2PO4. During interrupted stimulation, fatigue and recovery occur alternately. The histories of the above-mentioned metabolites must therefore be expressed in terms of two time-dependent metabolic functions, one for fatigue and one for recovery. Force-metabolite relations are predicted by curve-fitting of the force output during primary fatigue, measured simultaneously with the phosphometabolites. The fatigue experiments of supramaximally and transcutaneously stimulated quadriceps muscles of paraplegic subjects are made isometrically. Each test includes two contractions, one of 180 sec and one of 100 sec, separated by rest periods of 1, 3, 6, 12, 15, and 18 min. The knee joint torque and the surface EMG (M-wave signal) of the quadriceps muscles are recorded simultaneously. The time courses of the knee joint torque and of the M-wave peak-to-peak amplitude are curve-fitted, using a tri-exponential analytical function. This allows the consistent definition and calculation of the maxima and slopes in the force and EMG curves.
RESULTS--The build-up phase of the force curve is predicted from the EMG-signal The decaying phase of the curve is predicted by one of the phosphometabolites, depending on the duration of the rest period between the contractions. The results obtained present different prediction capacities of the model, in accordance with the selected input metabolite. For a short period of rest (1 min), Pi provides a good agreement between predicted and measured force, as opposed to H2PO4 and pH. After 6 min of rest, good predictability is obtained when using H2PO4. Finally for a long period of rest (15 min), the optimal prediction is obtained by using the pH history. The model results indicate that in post-recovery fatigue, the above-mentioned metabolites provide reliable predictors of the muscle force capacity after different rest periods. The force/recovery kinetics may, however, involve at least two time scales, each governed by a different metabolic process.
[079] RESTORATION OF FOREARM AND ELBOW FUNCTIONS 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 SCI. Our objective is to increase the range and type of functions they can perform by stimulating paralyzed pronator quadratus and triceps in addition to muscles providing hand grasp and release. We hypothesize that augmenting the hand-grasp neuroprosthesis will give individuals with C5 and C6 SCI the ability to grasp and move objects over a greater range of spatial locations and orientations, and will improve movement quality.
METHODOLOGY--Elbow and forearm stimulation is integrated with the VA/CWRU hand-grasp neuroprosthesis. The triceps is stimulated to provide elbow extension. Stimulation is adjusted to overcome gravity and can be controlled via an accelerometer mounted on the upper arm, a user-initiated stimulation with a switch on the wheelchair, or a constant triceps stimulation whenever the neuroprosthesis is active.
Elbow angle is controlled by the subject voluntarily contracting the biceps to counteract elbow extension. Forearm rotation is provided by stimulating the pronator quadratus at a constant level, whenever the hand-grasp neuroprosthesis is active. Supination/pronation angle is controlled by voluntary supination to counteract pronation. Thus, the additional functions do not require additional command signals unrelated to the desired function.
Forearm and elbow functions are evaluated in terms of basic mechanical capabilities, ability to use the restored function to achieve stable postures and produce smooth movements, and ability to perform common activities of daily living that require picking up and placing objects over a wide range of locations and orientations.
PROGRESS--This is the final year of this project. Eight neuroprostheses combining hand grasp with proximal arm control were implemented in six individuals. All neuroprostheses were used on a regular basis outside of the laboratory and were implemented with either a fully implanted stimulator and electrodes, a combination of an implanted stimulator for hand grasp and percutaneous electrodes for proximal function, or percutaneous electrodes only. Four individuals (three unilateral, one bilateral) received elbow systems. Three (two unilateral, one bilateral) received forearm systems. One individual received both elbow and forearm control in one arm.
We designed a series of tests to measure the mechanical properties at the joints with restored function (joint moment, range of motion, and dynamic stiffness); to assess the upper extremity functional workspace; and to assess improvements in functional performance.
RESULTS--Stimulating the pronator or triceps typically restored strength to grade four. Each person was able to grade the joint movement over the full range of motion by contracting the voluntarily controlled antagonist. Joint stiffness was increased by stimulation of the antagonist, which should provide better postural stability. Elbow extension increased the controllable workspace, both by increasing the range of locations and orientations where objects could be acquired and by reducing the time required to grasp the object. This is consistent with the need for elbow extension to counteract gravity and provide a stable joint. Functionally, elbow extension greatly improved task performance. However, the benefits of pronation were less dramatic. Pronation may be more important to restore in people with weaker residual function, and it may be necessary to employ more sensitive evaluation measures to elucidate the significance of pronation in these individuals.
FUTURE PLANS--We will complete the evaluation of the restored proximal function in all individuals who have received the neuroprostheses.
[080] FUNCTIONAL NEUROMUSCULAR SYSTEMS FOR UPPER EXTREMITY CONTROL
P. Hunter Peckham, PhD
Cleveland FES Center, Rehabilitation Engineering Center,
MetroHealth Medical Center, Cleveland, OH 44109-1998; VA
Medical Center, Cleveland OH 44106; email:
pxp2@po.cwru.edu
Sponsor: Department of Veterans Affairs, VA
Rehabilitation Research and Development Service, Washington,
DC 20420
(Project #B011-6RA)
PURPOSE--The research goal 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--The FDA has recently approved the marketing of 8-channel implantable neuroprostheses to provide grasp and release for individuals with C5 and C6 quadriplegia. The focus of this project is the clinical implementation and evaluation of a second generation implantable hand/arm system. This new system consists of a 10-channel implant stimulator-telemeter, an implanted joint angle transducer (IJAT), and 10 epimysial or intramuscular electrodes. The IJAT is placed in the wrist and uses a magnet and three Hall-effect magnetic field sensors to sense wrist angle. The magnet is inserted into the lunate. The Hall-effect sensors are inserted into the radius near the articular surface of the bone. Sensor outputs are relayed to the stimulator-telemeter device and transmitted out of the body through a radio frequency link using reflectance modulation.
The motor functions provided by the system are: multiple hand grasp patterns, including fine grasp controlled by finger intrinsic activation; elbow extension through a combination of electrical stimulation of the triceps and tendon transfers of the voluntarily controlled posterior head of the deltoid; and forearm supination/pronation through stimulation of the pronator quadratus. Elbow and forearm movement is controlled by voluntary activation of the antagonists.
Participants undergo at least 1 mo of surface stimulation prior to surgery. Implantation surgery is followed by 3 wks of casting, and then a period of muscle conditioning using the implant stimulator. A 2- to 3-wk rehabilitation training and evaluation period is used to complete the initial setup of the grasp and control parameters, train the individual in the use of the neuroprosthesis, and evaluate the function provided.
PROGRESS--The implementation of the system has proceeded in two stages. Three persons with C6 level SCI have undergone the first stage involving implantation of the stimulator-telemeter device and 10 electrodes. All three have two intramuscular electrodes placed in the finger intrinsic muscles to provide MP flexion and IP extension; two have a single electrode in the triceps for elbow extension; and one has an electrode implanted in the pronator quadratus for forearm pronation. During this stage, control of the neuroprosthesis is provided by an externally mounted wrist angle transducer.
The second stage involves the implantation of the IJAT and connection to the previously implanted stimulator-telemeter. One subject has completed this stage and the sensor is operational.
RESULTS--All three implant recipients are daily users of the neuroprosthesis, performing various functional tasks, including eating, drinking, writing, and grooming. Two have full elbow extension with triceps stimulation that allows them to perform reaching activities.
The implantation of the IJAT was successful. The output of the three sensors provide an adequate signal for the control of grasp opening and closing. No reduction in wrist range of motion has been detected post-surgery.
FUTURE PLANS--Two subjects will progress to implantation of the IJAT. In September 1997, the entire system will be implanted for the first time in a single stage.
[081] DISCOMFORT ASSOCIATED WITH PERCUTANEOUS AND SURFACE NEUROMUSCULAR STIMULATION DURING TREATMENT OF POST-STROKE SHOULDER SUBLUXATION
David Yu, MD; John Chae, MD; Maria Walker, BS; Ronald
Hart, MSE; Tina Davis, OTR
Center for Physical Medicine and Rehabilitation,
Cleveland FES Center, Case Western Reserve University,
MetroHealth Medical Center, Cleveland, OH 44109; Department
of Biomedical Engineering, Case Western Reserve University,
Cleveland, OH 44106; email: dyu@metrohealth.org
Sponsor: National Institute on Disability and Rehabilitation Research, US Department of Education; National Institute on Aging, National Institutes of Health; Department of Veterans Affairs FES Center
PURPOSE--Surface neuromuscular stimulation has been shown to decrease post-stroke shoulder subluxation and associated pain. However, the pain and the labor-intensive nature of surface stimulation limit the clinical implementation of this promising technique. 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 of the shoulder girdle muscles.
METHODOLOGY--The supraspinatus and the posterior deltoid muscles of 10 stroke survivors with shoulder subluxation and intact sensation were stimulated with percutaneous and surface electrodes. 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. Reusable gel electrodes (31.7 mm) were used for surface stimulation. A symmetric biphasic waveform with pulse duration of 300 µs was applied at 25 Hz. Intensity of stimulation was modulated by varying the pulse amplitude from 0 to 100 mA. All pain measurements were taken with a 10-cm visual analogue scale and the Pain Rating Index. 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 neuromuscular stimulation caused significantly greater discomfort than percutaneous stimulation on both the visual analogue scale (p=0.004) and the Pain Rating Index (p=0.02). 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." Nine out of 10 subjects preferred percutaneous over surface stimulation for long-term stimulation.
IMPLICATIONS--Percutaneous stimulation is well tolerated by stroke survivors. This technique may facilitate the clinical implementation of neuromuscular stimulation for the treatment of post-stroke shoulder subluxation.
[082] PERCUTANEOUS NEUROMUSCULAR STIMULATION FOR THE TREATMENT OF SHOULDER SUBLUXATION IN HEMIPLEGIA
David Yu, MD; John Chae, MD; Maria Walker, BS; Ronald
Hart, MSE; Tina Davis, OTR
Center for Physical Medicine and Rehabilitation,
Cleveland FES Center, Case Western Reserve University,
MetroHealth Medical Center, Cleveland, OH 44109; Department
of Biomedical Engineering, Case Western Reserve University,
Cleveland, OH 44106; email: dyu@metrohealth.org
Sponsor: National Institute on Aging, National Institutes of Health; Department of Veterans Affairs FES Center
PURPOSE--Surface stimulations of the posterior deltoid and supraspinatus have been shown to reduce post-stroke 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 associated pain.
METHODOLOGY--The supraspinatus and the posterior deltoid muscles of chronic stroke survivors were implanted with percutaneous intramuscular electrodes. The amplitude and frequency were maintained at 20 mA and 16 Hz, respectively. Intensity of stimulation was adjusted to clinical reduction of the subluxation by adjusting the pulse duration between 10-200 µs. Duty cycle of 4 s ramp-up phase, 10 s on phase, 4 s ramp-down phase, and 8 s off phase was employed with total stimulation time of 6 hrs per day. The degree of shoulder subluxation and pain were assessed at pre-treatment, post-treatment and at 3 mo post-treatment. Outcome measures included the degree of shoulder subluxation (radiographs), pain free shoulder lateral range of motion, and the Brief Pain Inventory.
RESULTS--Seven of the anticipated 10 subjects have completed the treatment phase. Three have completed the entire protocol, and four are in the follow-up phase. At the end of the treatment phase, five subjects exhibited reduction in the degree of subluxation and six exhibited decrease in the shoulder pain. Of the three who completed the entire protocol, two maintained shoulder reduction compared to baseline and one showed no change from baseline. However, all three had less shoulder pain at 3 mo follow-up compared to baseline.
IMPLICATIONS--The preliminary data suggest that percutaneous neuromuscular stimulation is effective in treating post-stroke shoulder subluxation and the associated pain.
[083] 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) to restore shoulder function to spinal cord injured individuals with C5 tetraplegia. Such persons retain little or no voluntary control over motions that act to move the upper arm toward the midline, due primarily to paralysis of the pectoralis major (PM) and latissimus dorsi (LD) muscles. This loss of control significantly reduces the range of motion of the hand, excluding an important workspace volume near the midline, and prevents arm stabilization in the natural adducted postures used in many tasks like eating and writing. Restoration of these functions would improve independence in daily activities, improving quality of life and reducing attendant care costs.
METHODOLOGY--Percutaneus electrodes are implanted into the PM and LD muscles. Controlled stimulation of these muscles provides shoulder function in horizontal flexion, adduction, and internal rotation in individuals with C5 tetraplegia. The stimulated contractions restore the lost motions, while retained voluntary control of antagonistic muscles is used to overcome the stimulated contractions and achieve intermediate positions. Performance is evaluated by quantifying the expansion of the workspace volume accessible to the hand, the increased postural stability within this workspace, and the increase in speed and accuracy of arm movements.
Methods for improving control of the partially paralyzed shoulder are also under development. Shoulder stiffness properties are used to identify deficits in postural stability and to suggest changes in stimulation patterns to correct the deficits. The feasibility of using electromyographic (EMG) recordings from voluntarily controlled shoulder muscles to modulate stimulation of the paralyzed muscles is also being investigated for improving movement performance, preventing fatigue, and compensating for changes in contraction strength in different shoulder positions.
PROGRESS--We have found FNS of the PM and LD muscles in individuals with C5 tetraplegia produces contractions adequate to move the arm and stabilize it during posture. Retained voluntary control can overcome the stimulated contractions when desired. Surface EMG recordings from shoulder muscles with retained voluntary control can be used to accurately estimate elbow angle as well as three shoulder angles (elevation, horizontal flexion, and internal rotation).
RESULTS--The PM and LD muscles of two individuals with C5 tetraplegia have been implanted with percutaneous stimulation electrodes, with both arms implanted in one of these subjects. FNS-mediated exercise has been found to significantly increase the strength of both of these muscles. The strength is dependent on the position of the arm, with both horizontal flexion and adduction being stronger with the arm elevated above horizontal. However, the moments produced were strong enough (5-10 Nm) in all arm positions to move the arm in the desired directions.
We are developing a method for the user control of the additional shoulder functions and have found that elbow joint angle and three shoulder angles can be predicted to within 10-15° using surface EMG recordings of muscles under voluntary control (anterior, middle, and posterior deltoid, biceps, upper, and middle trapezius). An artificial neural network predicts the elbow and shoulder movements using EMG and angle measurements obtained during voluntary movements. This network is capable of accurately predicting the joint angles during single joint movements, reaching movements, and complex drawing movements.
[084] HAND NEUROPROSTHESIS IN CHRONIC HEMIPLEGIA
John Chae, MD; Ronald Hart, MSE; Tina Davis,
OTR
Cleveland FES Center, Center for Physical Medicine and
Rehabilitation, Case Western Reserve University, MetroHealth
Medical Center, Cleveland, OH 44109
jchae@metrohealth.org
Sponsor: National Institute on Child Health and Human Development, National Institutes of Health
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--Six 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. All subjects underwent a conditioning exercise protocol consisting of cycles of hand opening and closing for approximately 2 hrs per day. Various control methods are under investigation, including foot pedals, hand operated potentiometers, shoulder and wrist angle transducers, and EMG-controllers.
RESULTS--Selective stimulation with good contraction of each of the implanted muscles was achieved with minimal spillover to adjacent muscles. The degree of discomfort varied with specific muscles, but was minimized by adjusting stimulation parameters, while maintaining the desired range of motion and torque. All subjects experienced modest gain in the upper-extremity Fugl-Meyer scores during conditioning, but the motor scores of all subjects subsequently plateaued. Electrical stimulation opened and closed the hand adequately, even in the midst of strong flexor tone. However, success in controlling the system was limited to those with normal shoulder and elbow movement and volitional wrist control. A wrist angle transducer allowed these subjects to open and close the hand volitionally. An EMG-controlled stimulator is presently under investigation to enhance the wrist control strategy as well to augment proximal arm control.
IMPLICATIONS--Results to date indicate that percutaneous neuromuscular stimulation can open and close the hand. However, the problem of unstable proximal arm control and control strategy paradigm remain to be elucidated.
[085] EFFICACY OF NEUROMUSCULAR STIMULATION IN ENHANCING THE UPPER EXTREMITY MOTOR AND FUNCTIONAL RECOVERY OF ACUTE STROKE SURVIVORS.
John Chae, MD; Theresa Bohinc, OTR; Tina Davis, OTR; Amy
Friedl, OTR; Loreen Dobos, PT
Cleveland FES Center, Center for Physical Medicine and
Rehabilitation, Case Western Reserve University, MetroHealth
Medical Center, Cleveland, OH 44109
jchae@metrohealth.org
Sponsor: National Institute on Child Health and Human Development, National Institutes of Health; New Investigator Award, Physical Medicine &Rehabilitation Education and Research Foundation, Dallas, TX
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 post-treatment and at 3 mo post-treatment with the self care component of the Functional Independence Measure and the upper extremity component of the Fugl-Meyer Motor Assessment in a blinded manner.
RESULTS--Twenty-six of the anticipated 28 subjects have completed the treatment and the follow-up phases. Two patients are presently in the follow-up phase. The treatment and control groups had similar baseline Fugl-Meyer scores (11.1 vs. 8.3; p=0.45). The Fugl-Meyer gain scores at post-treatment were significantly higher for the treatment than for the control group (13.1 vs. 6.5; p=0.05). At 1 and 3 mo follow-up, the Fugl-Meyer gain scores remained higher for the treatment group (1 mo follow-up: 17.9 vs. 9.7; p=0.06; 3 mo follow-up: 22.1 vs 11.6; p=0.08).
IMPLICATIONS--Data suggest that active repetitive movements induced by neuromuscular stimulation enhance the motor recovery of acute stroke survivors.
[086] STIMULATOR FOR TREATING POST-STROKE SHOULDER SUBLUXATION
Zi-Ping Fang, PhD; Soheyl Pourmehdi, PhD; David Yu, MD;
Maria Walker, BS; Ronald Hart, MSE; John Chae, MD
NeuroControl Corporation, Cleveland, OH 44106; Center
for Physical Medicine and Rehabilitation, Cleveland FES
Center, Case Western Reserve University, MetroHealth Medical
Center, Cleveland, OH 44109; email: dyu@metrohealth.org
Sponsor: National Institute of Child Health and Human Development, National Institutes of Health
PURPOSE--Develop a miniature, programmable, multichannel percutaneous stimulator and assess the feasibility of using the device to treat post-stroke shoulder subluxation.
METHODOLOGY--The stimulator circuitry was designed around a low-power, high-performance microcontroller. The electrically programmable and electrically erasable read-only memories inside the microcontroller hold the general operational instructions and the patient-specific protocols, with the latter being changeable by physicians or patients. The current driver, along with the amplitude controller, converts the digital commands from the microcontroller to the analog charge-balanced, current-regulated biphasic stimuli. All of the stimulus outputs are coupled to the electrodes through isolation capacitors to ensure charge balance, and prevent damaging direct current from flowing through the electrode and tissue. Two-high efficiency DC/DC converters are used to generate the 3.3-V operation voltage for the microcontroller and the 33-V compliance voltage for driving up to 20-mA current through the electrode-tissue system. The electronic circuitry of the stimulator was assembled using high-density, surface-mount technology to reduce the size of the device. Implant-grade tantalum capacitors were used for output isolation to ensure safety. The circuit board was packaged in a plastic enclosure originally designed for a pager. Three push buttons are provided for user control and stimulation programming. A liquid crystal display panel shows operation modes, stimulation parameters, and battery status.
RESULTS--Ten stimulators were assembled and bench tested. The characteristics of the output pulses were verified against the design specifications. A typical stimulation waveform of 12 mA, 250 µsec, with a frequency of 12 Hz was recorded by a digital oscilloscope. The programmability of the stimulation parameters was also tested. The stimulator was field tested among acute and chronic stroke survivors with painful shoulder subluxation. The stimulator provided excellent acute reduction of the shoulder subluxation with minimal to no discomfort. Due to its small size and low weight, subjects were able to receive the stimulation during ambulation. Field testing in a limited number of subjects indicates maintenance of shoulder reduction and decrease in pain after 6 hrs of stimulation per day for 6 wks.
IMPLICATIONS--Preliminary results suggest that neuromuscular stimulation via a miniature percutaneous stimulator is well tolerated by stroke survivors and is effective in treating post-stroke shoulder subluxation.
[087] MULTICHANNEL IMPLANTABLE SYSTEM FOR NEURAL CONTROL
P. Hunter Peckham, PhD; Michael W. Keith, MD
Cleveland FES Center, Rehabilitation Engineering Center,
MetroHealth Medical Center, Cleveland, Ohio 44109-1998;
email: pxp2@po.cwru.edu
Sponsor: National Institute of Neurological Disorders and Stroke; National Institutes of Health
PURPOSE--The aim of this project is to implement and evaluate an advanced neuroprosthetic system for restoration of hand-arm function in subjects who have sustained cervical level spinal cord injury (SCI). The neuroprosthesis will provide the person with C5 tetraplegia with control of grasp and release and elbow extension by electrical stimulation of the paralyzed muscles. These functions will enable the user to regain the versatile manipulative functions which will increase his or her ability to perform activities of daily living (ADL) independently.
METHODOLOGY--The neuroprosthesis consists of a 16-channel implanted stimulator-telemeter, an implanted joint angle sensor (IJAT), and two channels of myoelectric signal acquisition. The power and signal processing is provided by an external control unit through a bi-directional radiofrequency link. Since the only externally worn component is the RF transmitting coil, the issues of sensor mounting and maintenance of cabling are greatly reduced from other neuroprosthetic systems.
The implanted system will be implemented in C5 level SCI to provide grasp/release and reaching functions. Epimysial or intramuscular electrodes will be placed on the muscles of the thumb and fingers, including the finger intrinsic muscles, to provide palmar and lateral grasp patterns. Stimulation of the wrist extensors will be used to provide wrist stabilization or to augment weak voluntary wrist extension. Stimulation of the pronator quadratus and triceps muscles will be used to provide forearm pronation and elbow extension, respectively.
The user will control the neuroprosthesis through generation of voluntary movements or muscle contraction. The control scheme will be customized to maximize use of the individual's available function. The IJAT can be placed in the shoulder or wrist and serve as a proportional control of grasp. The myoelectric signal can be used to provide logic commands, or processed to provide proportional control.
Outcome evaluations will measure the function of the neuroprosthesis components and the performance of users in grasp-release tests and ADL. These tests will allow statistical comparisons of the user's abilities before surgery with those achieved after surgery, both with the neuroprosthesis turned on and turned off. The results of this project will demonstrate the feasibility of a totally implanted neuroprosthesis and the significant improvements in hand function achieved through its use.
FUTURE PLANS --This project will result in completed development of all components of the neuroprosthetic system, the evaluation of the system in bench and in vivo testing, and the evaluation of its efficacy in one individual. The telemetry system and the implanted joint angle transducer have completed development. Prototype myoelectric signal processing circuitry is currently being tested in vivo.
The proposed system also has application in the efforts to provide standing and walking in thoracic level SCI, stroke, and head injury. These types of applications have been considered in defining the proposed system, so that it will be versatile across different clinical applications.
[088] 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 to perform many routine activities of daily living and work independently. Tendon transfer surgery can be used to restore voluntary control over some arm and hand functions by detaching a nearby donor muscle (remaining 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 that 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 SCI subjects 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 control 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 controls 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.
[089] FUNCTIONAL ELECTRICAL STIMULATION OF SPINAL CORD INJURED PATIENTS: EFFECTS ON MUSCLE BLOOD FLOW AND METABOLISM
A.M. Erika Scremin, MD; Oscar U. Scremin, MD, PhD;
Thomas J. Barstow, PhD; Ronald Dietrick, PhD; Brent Shannon,
MS; Barbara Wiseman, BS
Physical Medicine and Rehabilitation Service, VA Medical
Center, West Los Angeles, CA, 90073; University of
California, Los Angeles, 90024; Division of Respiratory and
Critical Care Physiology and Medicine, Harbor-UCLA Medical
Center, Torrance, CA 90509; University of California, Los
Angeles, 90024
Sponsor: Department of Veterans Affairs, VA
Rehabilitation Research and Development Service, Washington,
DC 20420
(Project #Project #B2002-RA)
PURPOSE--The purpose of this project is to study the effects of functional electrical stimulation-induced lower extremity cycling (FESILEC) on persons with complete, spastic spinal cord injury (SCI) and determine the therapeutic benefits of this form of rehabilitation.
METHODOLOGY--Subjects participated in a 24- to 48-session training protocol on a computerized REGYS ergometer, powered by lower extremity muscles and activated by cutaneous electrodes. Muscle blood flow (MBF) was studied with H2150 PET, muscle metabolic response with 31P magnetic resonance spectroscopy (MRS), muscle fiber type with histo- and bio-chemistries of biopsies, and muscle mass with CT and MRI scans.
PROGRESS--In our studies on H2150 PET MBF, a new methodology for the quantitative measurement of MBF, has been developed by using the time-activity curve of the PET image of the superficial femoral artery as the input function in the autoradiographic equation. New SCI and control subjects have been recruited to compare their MBF responses to unloaded and loaded (30 percent of maximum) FESILEC and voluntary exercise respectively. SCI subjects are being studied before and after FESILEC training to test for possible training effects on the MBF response.
The muscle mass of 14 SCI subjects was studied with serial CT and MRI scans of the lower limbs and followed up for periods ranging from 100 to 541 days while on a regular regime of FESILEC. Results showed highly significant increases in cross sectional areas of the following muscles in transverse CT scans measured at the first follow-up period. The percent increase over baseline (before FESILEC started) and statistical significance are indicated in parenthesis: rectus femoris (31 percent, p=0.000024), sartorius (22 percent, p=0.021), adductor magnus-hamstrings (26 percent, p=0.00018), vastus lateralis (39 percent, p=0.0019), vastus medialis-intermedius (31 percent, p=0.006). Cross sectional area of adductor longus and gracilis muscles did not change. Later follow-up periods showed a stable cross sectional area in the involved muscles. In conclusion, muscles that were directly stimulated achieved a significant increase in mass.
Four SCI subjects and three controls have been recruited for the MRS and muscle biopsy study. To date, evaluation of the muscle metabolic response to one-legged exercise using 31P MRS before and after FESILEC training has been completed in two subjects, with a third subject in the middle of the training protocol. For the same supine exercise at MID, PCr fell 10 percent less and Pi rose 23 percent less, compared to BL. Pi/PCr was 27 percent lower (0.67 MID vs. 0.92 BL), and end-exercise pH was much less reduced (6.71 MID vs. 6.29 BL).
Less voltage was required to elicit contractions at MID compared to BL. Similar results to those at MID were observed at POST. The attenuated changes in PCr, Pi and pH, and reduction in stimulation voltage for the same work rate following FESILEC training suggest that training adaptations did occur in the contracting muscles in those patients tested to date.
Muscle biopsy was taken from the vastus lateralis muscle at the PRE and POST time points. Tissue samples were separated into two portions. One was immediately frozen for subsequent analysis of citrate synthase, a marker of tissue oxidative capacity, while the second was prepared for staining to determine muscle fiber types I, IIa and IIb by myosin ATPase activity at different pH. Results at PRE revealed almost complete absence of type I fibers (<5 percent), compared to control population (average about 40-50 percent). FESILEC training did not alter fiber type composition in the exercised muscles (type I fibers still <5 percent of total). Determination of citrate synthase activity will be performed in the future as a batch when more samples are available.
FUTURE PLANS--We plan to complete work in the areas of muscle blood flow, 31P MRS, and muscle histo- and bio-chemistries.
[090] FES-AIDED PARAPLEGIC GAIT USING A CONTROLLABLE FRICTION BRAKE
William K. Durfee, PhD; Allen Wiegner, PhD; Gary
Goldish, MD
Department of Mechanical Engineering, University of
Minnesota, Minneapolis, MN 55455; Spinal Cord Injury
Service, VA Medical Center, West Roxbury, MA 02132; Physical
Medicine and Rehabilitation Service, VA Medical Center,
Minneapolis, MN; email: wkdurfee@tc.umn.edu
Sponsor: Department of Veterans Affairs, VA
Rehabilitation Research and Development Service, Washington,
DC 20420
(Project #B579-4RA)
PURPOSE--Restoration of gait to persons with paraplegia using functional electrical stimulation (FES) is a challenging problem. One difficulty is controlling the FES system for stability and smooth gait. It is possible to improve walking function using surface stimulation by adding a mechanical orthosis in combination with the FES. Based on preliminary work of our group, we have developed such a hybrid system for functional FES-aided gait. The orthosis contains controllable friction brakes at the joints, the purpose of which is to shift the burden of controlling the gait trajectory from control of the stimulated muscles to control of the brake, a well-behaved mechanical element. To evaluate brake designs and performance, we are testing and comparing the ability of persons with paraplegia to achieve FES-aided gait both with and without the orthosis. The assessment includes kinematic, dynamic, and metabolic variables.
PROGRESS--We have designed and constructed a wearable orthosis that can apply controlled braking loads to the knee and hips. The orthosis structure is fabricated from machined aluminum and chromoly tubing. Braking loads are applied by magnetic particle brakes coupled to the joints through an Evoloid gear transmission. Joint position and torque are measured by sensors. The entire system is controlled by a PC connected to the brace by a long umbilical cable.
The orthosis has been tested on two subjects with paraplegia (one extensively) at the West Roxbury VA Medical Center, and on three at the Minneapolis VA Medical Center. Quantitative results from the first subject demonstrated gait for longer distances, reduced heart rate, and improved joint trajectory control when compared to FES gait without the brace. The other subjects demonstrated some, but not remarkable, improvements when using the brace.
FUTURE PLANS--We are continuing to test the system on additional SCI subjects, building a second-generation orthosis that uses more energy efficient brakes and incorporates small DC motors at the hips to aid in hip flexion, and developing a product design process for producing commercial versions of the brace. Investigative trials will take place at the VA Medical Center in Minneapolis, MN.
[091] OUT-OF-LABORATORY, FEEDBACK-CONTROLLED FNS FOR 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 #B683-2RA)
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 of this improvement 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.
METHODOLOGY--Improvements to the current FNS locomotion system take the form of a feedback control system. Sensors worn by the subject provide signals from which decisions concerning stimulation patterns can be made by a control system consisting of three primary components: the gait event detection 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--Recent work has resulted in the development and testing of real-time gait event detection software. Performance is improved using a hierarchical approach. Gait event detection rules that have been learned from prior experimental trials (using fuzzy system identification) provide an initial estimate of phases of gait from sensor data. These estimates are then interpreted by supervisory rules, resulting in detection of gait events (such as heel strike and toe off).
Hardware and software for a microprocessor-based stimulation parameter controller have 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.
FUTURE PLANS--This technology is being adapted for simultaneous use (in a paraplegic user) with two 8-channel implanted stimulators.
[092] RESTORATION OF GAIT IN ACUTE STROKE PATIENTS USING FNS
Robert L. Ruff, MD, PhD; Janis J. Daly, PhD
Cleveland FES Center, VA Medical Center Medical Center,
Cleveland, OH 44106; email: daly@walsch.edu
Sponsor: Department of Veterans Affairs, VA
Rehabilitation Research and Development Service, Washington,
DC 20420
(Project #679-3RA); NeuroControl Corporation, Cleveland,
OH; MetroHealth Medical Center, Cleveland, OH
PURPOSE--Stroke is the leading cause of disability among adults in the United States, and conventional rehabilitation post stroke is inadequate to restore safe, independent gait for many persons. The purpose of this project is to determine the efficacy of Functional Neuromuscular Stimulation (FNS) with implanted (IM) electrodes in improving lower limb motor recovery and gait
pattern of persons who have had acute stroke.We are testing the efficacy of the FNS-IM system in stroke by making comparisons of treatment outcome for three different interventions: conventional therapy; conventional therapy + surface FNS; conventional therapy + FNS using IM electrodes. Additionally, we are comparing FNS-gait with voluntary gait at the close of the treatment protocols.
METHODOLOGY--Thirty subjects in each of the three treatment groups are being treated for 6 mo; treatment begins at least 2 wks post stroke and when the individual is medically stable. FNS exercise and FNS gait training protocols are used.
Outcome measures are classified into three levels of physical function of increasing difficulty. The first level is voluntary movement at a single joint with the body in a static position. The second level is voluntary motor control during walking. The third level is functional capability at home and work. Data are collected every 6 wks during the 6 mo of treatment. Carry-over effects are monitored at two additional data collection sessions at 1 mo and 1 yr following the end of the treatment period.
IMPLICATIONS--Results of this study have the potential to provide the following clinically applicable information:
[093] FES MOBILITY IN PARAPLEGIA: RF-CONTROLLED IMPLANTED SYSTEM
E. Byron Marsolais, MD, PhD; Ronald J. Triolo, PhD;
Rudolf Kobetic
Cleveland FES Center, Case Western Reserve University,
Cleveland OH 44106; Motion Study Laboratory, Cleveland VA
Medical Center, Cleveland, OH 44106; email:
rxt24@po.cwru.edu
Sponsor: Department of Veterans Affairs, VA
Rehabilitation Research and Development Service, Washington,
DC 20420
(Project #B681-2RA)
PURPOSE--The overall goal of this project is to enhance the personal mobility of individuals with complete thoracic level spinal cord injuries (SCI) with functional electrical stimulation (FES). An implantable system is being developed to provide individuals with T4-T10 paraplegia with the ability to perform stable standing, walking for short distances, and household mobility maneuvers with a minimum of bracing and personal assistance. The purpose is to establish the clinical and technical components required to introduce implantable FES systems safely and effectively into the home and community environments in larger scale clinical trials.
METHODOLOGY--The walking mobility system consists of two CWRU/VA 8-channel implanted receiver/stimulators (IRS-8) for a total of 16 stimulus channels. Stimulation is delivered via 14 epimysial electrodes deployed bilaterally into the knee and hip extensors (quadriceps, gluteus maximus, semimembranosus, posterior adductor), hip flexors (sartorius, tensor fasciae latae), and ankle dorsiflexors (tibialis anterior). Additionally, two intramuscular electrodes are surgically implanted near the L1/L2 spinal roots to activate the erector spinae and iliopsoas muscles simultaneously. The system is installed in two surgical procedures. Each 8-channel subsystem is isolated from the other to minimize the risk of infection and mechanical damage, as well as to simplify service.
Following a period of immobilization and inactivity after surgery, reconditioning exercise is prescribed to re-establish strength and endurance. This is followed by a rehabilitation phase consisting of tilt-table standing, progressing to standing and stepping in parallel bars or rolling walker. Finally, participants are qualified to use the dual-implant system at home and in the community.
A new wearable external control unit (ECU) generates power and command signals to coordinate the actions of both stimulators via two transmitting coils taped to the skin surface over the implants. The ECU is rechargeable, ergonomic, and serially programmable from a laptop personal computer.
Three individuals with motor complete thoracic paraplegia will be recruited to participate in this study. Screening and evaluation techniques will be formalized and standardized in anticipation of future multicenter trials.
PRELIMINARY RESULTS--This system has been successfully implanted in the first volunteer who sustained a motor-complete SCI at the level of T10 approximately 5 yrs prior to surgery. In November 1996 the eight posterior electrodes were installed and leads routed to the abdominal area where they were capped to prevent tissue ingrowth; 2 wks later, the anterior muscles were implanted and all electrodes connected to the IRS-8 devices. Following a period of inactivity, the subject progressed from exercise to standing and stepping with the system. Electrode thresholds stabilized and stimulated contractions are sufficiently strong for functional activities. The subject is currently using the system at home to exercise, stand, and walk.
FUTURE PLANS--Results from the first application of the system are encouraging. Although the responses to several electrodes can be improved by refining the surgical technique, the system is operational and adequate for unassisted standing and stepping. A revision is planned to reposition several electrodes to further improve system performance. Changes to the implementation protocol are under consideration to permit a staged approach to system installation. Future recipients will likely receive an 8-channel standing system for extended home use, followed by the introduction of the second implant and instrumentation of the remaining muscles required for walking. Recruiting for additional subjects is ongoing and efforts to solicit clinical partners within the VA system interested in collaborating in a larger scale study will continue.
[094] DEVELOPMENT OF A CLOSED LOOP FES SYSTEM AND APPLICATION TO STANDING UP MOVEMENT FOR PERSONS WITH PARAPLEGIA
Maurizio Ferrarin, DrEng, PhD; Carlo Frigo, DrEng;
Raffaella Spadone, DiplEng; Antonio Pedotti, DrEng,
PhD
Centro di Bioingegneria, Fondazione Pro Juventute Don C.
Gnocchi IRCCS, Politecnico di Milano, I-20148 Milano, Italy;
email: ferramau@mail.cbi.polimi.it
Sponsor: Italian Ministry for University and Scientific Research, Commission of European Community
PURPOSE--The purpose of this study is to develop and apply a closed-loop control system for functional electrical stimulation (FES), in order to train persons with paraplegia to stand up by means of muscle stimulation and a dedicated mechanical device for partial weight relief.
METHODOLOGY--The system is based on a PC, a programmable 8-channel stimulator, a software controller and electrogoniometers. A PID software regulator has been experimentally realized and used to control the stimulator. The controlled variables are the knee angles of both legs (measured by means of flexible electrogoniometers), interfaced by a dedicated board with the PC. The actual angles are compared with the desired ones in real time, and on the basis of their difference, the PID controller modulates the width of stimulation pulses produced by the stimulator. Surface electrodes are used to induce artificial contraction of the quadriceps muscles of both legs in order to extend the knees and thereby obtain a standing-up movement. A mechanical device for weight relief, consisting of a see-saw system, has been developed and equipped with a counterweight that is decreased during the training progress of the subject. Two working configurations have been considered: tracking of a prefixed knee angle trajectory and master-slave configuration, in which the tracked angle is caught in real time by an electrogoniometer from another joint (or even from the physioterapist).
PROGRESS--Applications of this technique to the training of persons with paraplegia in FES-induced standing-up movements has been considered. The idea is to treat those selected for FES walking application before the beginning of the specific training program in walking, in order to produce an increase in muscle strength and fatigue resistance and, at the same time, to obtain a recovery of standing posture, with positive effects on the musculo-skeletal, cardiorespiratory, and vestibular systems. Advantages of this system are its intrinsic safety characteristics and the possibility of modulating the load on stimulated muscles by modifying the counter weight of the
see-saw system.Specific attention in reference trajectory has been posed. A biomechanical model of the entire system (subject and see-saw device) has been developed and used to obtain the optimal knee trajectory during sit-to-stand movement from the point of view of knee joint torque minimization. The repetition of standing-up and sitting-down movements is considered with permanence period in sitting and standing posture. Once the training proceeds, the total duration of exercise cycles is increased and the counter weight is decreased, following subject-specific improvements.
PRELIMINARY RESULTS--Up to now, one subject with a complete traumatic spinal cord lesion at T5-T6 level has been included in this project. After 2 mo of 1 hr daily training sessions, 4 times weekly, he increased his thigh diameter about 15 percent and is able to stand up and sit down 7 times with a weight relief of half of his body weight. Fatigue resistance to muscle stimulation is improved too. The closed-loop controller appears robust to both external and internal disturbances like electrode movements and muscle fatigue, respectively.
FUTURE PLANS--The inclusion of further subjects in the study is foreseen. The use of the system in the master-slave configuration will be investigated too, using elbow angle as reference signal for the knee angle during standing, since in healthy subjects we found a good correlation between knee and elbow angle during this movement.
[095] PARAPLEGIC WALKING MADE PRACTICAL WITH FNS AND ORTHOSES
E. Byron Marsolais, MD, PhD; Joseph Mansour,
PhD
Cleveland FES Center, Cleveland VA Medical Center,
Cleveland, OH 44106; Departments of Orthopaedics and
Mechanical Engineering, Case Western Reserve University,
Cleveland, OH 44106; email: ebm2@po.cwru.edu;
jmm12@po.cwru.edu
Sponsor: National Institute of Child Health and Human Development and the National Institute of Neurological Disorders and Stroke, Bethesda, MD 20892.
PURPOSE--We seek to determine whether the combination of eight channels of implanted functional electrical stimulation (FES) and a functionally activated trunk-hip-knee-ankle-foot orthosis can result in a practical mobility aid for use by the individual with complete paraplegia. 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 person and to 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 (RF) controlled and powered implantable stimulator, or a percutaneous FES system, with a prototype low weight, functional orthosis having active, computer-controlled joint locks. A hybrid orthosis will result from combining this technology with expertise in electro-mechanical brace design from CWRU, Henry Ford Hospital of Detroit, and New York University (NYU). The physical therapist will utilize accepted and modified outcome assessment and energy consumption measures to determine the user's ability to function in the household or the community at large.
PROGRESS--We have developed the surgical techniques for implantation of an 8-channel RF-powered-and-controlled FES and implemented them in three subjects participating in related projects. The first implantation of the RF stimulator/receiver in a subject participating in the hybrid FES program is scheduled for Fall 1997. After a thorough review of the state of the art in orthotic systems, a design team has constructed a platform orthosis.
RESULTS--Six subjects with paraplegia, injury levels T-1-T-11, have participated in a study to evaluate the functional capabilities of a computer-controlled hybrid orthotic system. The subjects have learned to use the custom-built reciprocal gait orthosis without stimulation and with electrical stimulation activating between 4 and 16 muscles. Outcomes were scored with standard physical therapy measures, including the Tinetti test, a timed get up and go, Borg energy exertion, and the functional index measure. Subjects have successfully accomplished sit to stand, stand to sit, and walking maneuvers measured for time, speed, distance, and metabolic output. FIM scores indicated that system users would become slightly more independent in mobility categories. Perceived exertion as a measure with the Borg scale indicated that use of the bracing system with FES was easier than without stimulation. Subjects were able to exhibit distance walking that would allow limited but useful ranges of 500 m at average speeds of 0.2-0.3 m/s. Walking speeds for 30- and 50-m distances reached 4 to 4.5 m/s. Metabolic output measured in the light work region of 7 METs. Additionally, walking distance with stimulation were two times or greater than those of nonstimulated reciprocal gait.
IMPLICATIONS--A less constrained brace, combined with an implantable FES system, will, as indicated by these results, allow a completely paralyzed user to attain a limited level of community ambulation.
[096] UNASSISTED STANDING BY FUNCTIONAL ELECTRICAL STIMULATION
Ronald J. Triolo, PhD; Robert F. Kirsch, PHD; John A.
Davis Jr., MD
Cleveland FES Center and Department of Orthopaedics,
Case Western Reserve University, Cleveland OH 44106;
Department of Orthopaedics, Metro Health Medical Center,
Cleveland OH; email: rxt24@po.cwru.edu
Sponsor: Neural Prosthesis Program, National Institute of Neurological Disorders and Stroke, National Institutes of Health
PURPOSE--The long-term goal of this project is to develop methods to provide brace-free, energy efficient standing for persons with complete thoracic level spinal cord injuries (SCI) via functional neuromuscular stimulation (FNS). The objectives are to define the fundamental requirements, develop the control strategies, and understand the factors limiting the performance of systems designed to automatically resist reasonable disturbances to balance and free the upper extremities for manipulating objects in the environment while standing. These objectives are being addressed through anatomical modeling, dynamic modeling, and controller development, simulation, and optimization, and experimental demonstration of new control structures. This work is conducted in partnership with collaborators at Northwestern University and the University of Kentucky.
METHODOLOGY--A biomechanical model of the lower extremities and torso that accurately reflects the actions of FNS on paralyzed muscle and incorporates the behavior of non-ideal and commercially available body-mounted sensors is being developed. The model will be employed to construct dynamic simulations and perform optimization procedures to investigate the theoretical behavior of various FNS control systems for providing automatic postural adjustments. Predictions from the simulations will drive the implementation and experimental demonstration of the postural control systems in human volunteers. Results of human trials will be used to refine the model or reformulate the control simulations.
The methods for automatic control of posture are based on the assumption that no single control strategy will be sufficient to achieve the requisite standing performance. The inherent passive stiffness of the joints and the responsiveness provided by the active stiffness resulting from low-levels of continuous co-activation of agonist-antagonist muscle groups will be used to help insure stability. A variety of controllers that modulate stimulation in response to, or in preparation for, a change in postural load will be simulated, implemented, and tested with the aim of integrating the best elements of each into a coordinated artificial postural control system.
Both fixed-parameter, and sensor-based control strategies will be investigated. Fixed-parameter controllers will include systems that slowly vary the position of the center of mass over the base of support, or that allow the user to select a posture and define the stiffness in a preferred direction in advance of a disturbance or voluntary movement of the upper extremity. Sensor-driven systems will include joint angle and acceleration-based controllers to mimic proprioception and vestibular-like responses.
PROGRESS--A biomechanical model of the spine and trunk is under construction and will be integrated with the existing computer representation of the lower extremity musculo-skeletal system. Anatomical specimens from the erector spinae, quadratus lumborum, and rectus abdominis have been collected and muscle architecture is being parameterized for inclusion in the model. Methods to compute system dynamics from records of muscle activation patterns have been established, and initial simulations of simple control systems are being completed. Methods to calculate disturbances to posture from volitional arm movements have also been established and will be used to simulate real-world perturbations at the shoulder. Algorithms to compensate automatically for changes in muscle recruitment properties have been developed and tested in simulation.
FUTURE PLANS--Anatomical modeling and simulation will continue. Immediate plans include experimental determination of joint stiffness and other model parameters in individuals with spinal cord injuries. Optimization procedures and sensitivity analyses are being conducted with the existing biomechanical model. Baseline performance of simple open loop systems for standing will also be determined and used for comparison with the advanced control systems under development.
[097] IMPLANTABLE FNS SYSTEMS FOR STANDING TRANSFERS
Ronald J. Triolo, PhD; John A. Davis Jr., MD
Cleveland FES Center, Case Western Reserve University,
Cleveland OH 44106; Department of Orthopaedics, Metro Health
Medical Center, Cleveland OH; email:
rxt24@po.cwru.edu
Sponsor: Office of Orphan Product Development, Food and Drug Administration
PURPOSE--This project is designed to provide standing and transfer function to individuals with low-cervical or high-thoracic spinal cord injury (SCI) via an implanted functional neuromuscular stimulation (FNS) system. Injuries at these levels compromise mobility, increase dependence on families, caregivers, or assistants, and compound the risk of medical complications secondary to paralysis. Conventional transfers are problematic for individuals with elderly spouses or caregivers who lack the strength to assist with the lifting phases of the maneuvers. The long-term objective of this project is to introduce into clinical practice a neuroprosthesis that will allow individuals with SCI to stand and transfer with minimal assistance, thereby increasing independence, personal mobility, and overall health and well-being.
METHODOLOGY--A surgically implanted FNS system for standing and transfers is being implemented in five volunteers with SCI between the levels of C6 and T4. The system consists of epimysial and surgically implanted intramuscular electrodes, and the CWRU/VA 8-channel implantable receiver/stimulator (IRS-8). A wearable external control unit (ECU) provides power and command signals to the implant.
After a period of preparatory exercise with surface stimulation, the IRS-8 is installed in a single surgical procedure. Epimysial electrodes are implanted bilaterally into the quadriceps (vastus lateralis/intermedius), gluteus maximus, and semimembranosus or posterior portion of the adductor magnus. Intramuscular electrodes are inserted at the level of the L1/L2 spinal roots to activate the erector spinae. Electrode leads are routed to sites on the abdomen and connected to the IRS-8, which is sutured to the abdominal fascia. After 2 wks of immobilization and bedrest, subjects are released to home for an additional period of restricted activity before reconditioning exercise is initiated 6 wks postimplant.
Outpatient rehabilitation consists of progressive resistance and closed-chain exercise followed by standing, balance, and transfer training using the implanted neuroprosthesis. Functional outcomes are assessed with customized ratings of system usability, and measures of effort and assistance required to complete maneuvers with and without FNS. Long-term follow-up of system use and performance in the home and community environments continues for a full year after demonstrating safety and proficiency with the system.
PRELIMINARY RESULTS--Quantitative anatomical dissections on seven fresh frozen cadaver specimens resulted in standardized and repeatable approaches to the key muscles of interest. These surgical techniques were verified through intra-operative tests performed during regularly scheduled clinical procedures. This effort culminated in the successful implantation of the standing/transfer neuroprosthesis in the first study volunteer July 1997.
The first implant recipient is a 37-year-old male with complete motor paraplegia resulting from a T4 SCI sustained in an industrial accident 4 yrs prior to implantation. All incisions from the implant procedure healed without incident, and the implanted components are intact and operational. The electrodes exhibit stable thresholds and produce contractions of sufficient strength for functional activities. The subject is currently in the exercise and rehabilitation phases of the protocol, and standing, balance, and transfer training are scheduled to begin fall 1997.
FUTURE PLANS--The exercise, rehabilitation, and training phases for the first subject will be followed by home visits to facilitate the system's incorporation into his daily routine. New evaluation and assessment scales currently under development will be applied and refined at that time. Recruiting for additional implant recipients will continue until a total of five local subjects are enrolled and implanted in the next 2 yrs. Immediate plans also include the field testing and production of new external electronic components.
[098] MUSCLE COACTIVATION IN TRANSCUTANEOUS FES
Joseph Mizrahi, DSc, Oron Levin, MSc; Eli Isakov,
MD
Department of Biomedical Engineering, Technion-Israel
Institute of Technology, Haifa, 32000 Israel; Loewenstein
Rehabilitation Center, Raanana 43100, Israel; email:
JM@biomed.technion.ac.il
Sponsor: The Segal Foundation, Israel
PURPOSE--We seek to determine whether the coactivation response to transcutaneous stimulation of the quadriceps significantly affects the knee torque.
METHODOLOGY--A dynamic model of the paralyzed thigh is being developed for the case where the hamstrings muscles are indirectly activated as a result of supramaximal transcutaneous stimulation of the quadriceps. Simultaneously to torque, the EMG of the above-mentioned muscles are measured and serve to evaluate the neural excitation of each muscle. An iterative optimization procedure is developed to determine the force distribution between the quadriceps and hamstrings muscles. Specifically, the hamstrings recruitment level and the muscle force history of both muscles are determined.
The experiments include 3 min supramaximal sustained transcutaneous FES of the quadriceps muscle of the right thigh. The measurements include knee joint torque and EMG of the quadriceps and hamstrings. The M-wave peak-to-peak amplitudes from both quadriceps and hamstrings are curve-fitted, using a tri-exponential analytical function. Neural excitation is defined for each muscle as the ratio between the temporal peak-to-peak amplitude and the maximum peak-to-peak amplitude. The force histories (initial iteration based on previously measured fatigue profiles) of the above-mentioned muscles and the recruitment level of the hamstrings are estimated by using an iterative procedure. This procedure is aimed at minimizing the error between the measured and the estimated knee torques. The muscle specific tensions are assessed for two different solution cases: 1) equal values in both the quadriceps and hamstrings; and 2) higher values in the trained quadriceps compared to that of the untrained hamstrings.
RESULTS--The estimated recruitment level of the hamstrings is found to be 18 percent. The average values (n=5) of the recruitment levels are 12 percent (SD=6) for solution case 1, and 20 percent (SD=5) for solution case 2. The predicted maximal forces in the quadriceps (n=5) are 16 to 32-fold higher than in the hamstrings for solution case 2. For solution case 1 the ratios were 12 to 32-fold higher.
The results obtained for either of the combinations of specific tensions demonstrated that the estimated torque about the knee is dominated by the quadriceps torque. It is therefore concluded that a paralyzed thigh is not affected by the coactivation response to transcutaneous stimulation of the quadriceps.
FUTURE PLANS--A developed model of force recruitment based on the distribution of the electric field in a layered medium will be used for comparison with the above-mentioned results.
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