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Rehabilitation Engineering, IEEE Transactions on

Issue 2 • Date Jun 1995

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Displaying Results 1 - 10 of 10
  • A grasp force and position sensor for the quantitative evaluation of neuroprosthetic hand grasp systems

    Page(s): 175 - 181
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    An instrumented grasp sensor has been developed for use in quantitative evaluation of neuroprosthetic hand grasps. This hand-held device monitors both grasp force and grasp opening with the subject utilizing either palmar or lateral prehension, and can be used to quantify the grasping of variable-sized or compliant objects. The grasp sensor provides a quantitative tool to analyze a subject's hand grasp, thus allowing the neuro-prosthetic system to be tuned for the best performance. It can supply data on how a grasp changes under various conditions, such as different wrist positions. The device can also be used to perform quantitative comparisons for future neuroprosthesis improvements, such as the addition of sensory feedback, closed-loop control systems, and alternative command/control methods. The simultaneous measurement of grasp opening and force could prove useful in applications other than a neuroprosthesis, such as quantifying other hand impairments and studying the physiological control of grasp View full abstract»

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  • Hand opening by electrical stimulation in patients with spastic hemiplegia

    Page(s): 193 - 205
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    Spasticity is a motor control disorder common after stroke, which can cause the fingers to involuntarily flex and form a fist. Even in the presence of strong spasticity, functional electrical stimulation can provide hand opening in hemiplegics with spastic finger flexor muscles through stimulation of the extensor digitorum communis muscle and the ulnar nerve. Stimulation of these sites did not reduce the activity in spastic finger flexor muscles, as hypothesized initially, and as might occur through a reciprocal inhibitory mechanism. In fact, flexor activity generally increased during extensor stimulation. In spite of increased flexor activity, the extension force was sufficient to fully extend the fingers. Similarly, stimulation of the finger extensors in able-bodied subjects did not reduce the EMG in the finger flexors, and could even increase it. The influence of voluntary effort on finger extension achieved by stimulation was also studied, since a neuroprosthesis for stroke patients might combine voluntary effort with stimulation. Finger extension was generally diminished when the subject attempted to assist the stimulated extension voluntarily or when stimulation followed voluntary flexion as might occur when trying to open the hand following a voluntary grasp. The largest extension was achieved when the subject remained relaxed. Since voluntary effort influences the degree of hand opening achieved by stimulation, some method of adjusting stimulation levels during task performance would be desirable in a clinically deployed neuroprosthesis View full abstract»

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  • The reliability and validity of a lift simulator and its functional equivalence with free weight lifting tasks

    Page(s): 155 - 164
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    The combination of Workers' Compensation legal claims and the enactment of the Americans with Disabilities Act (1990) has created a need for more objective and realistic trunk muscle testing. The LIDOLift (Loredan, Inc.) is a computerized dynamometer which has the capabilities to test multijoint coordinated lifting tasks in isometric, isokinetic, and isoinertial modes of operation. The calibration of the electromechanical sensors produced R2 values greater than 0.999. In the validation of the isokinetic mode, the normalized rms error from the set velocity was less than 1% at higher set velocities, after the accelerative portion of the lift. In the technical validation of the isoinertial mode, the measured force was significantly different than the predicted force based on an isoinertial model, Consequently, the simulated mass was found to be larger than the intended mass. However, the relative difference decreased as the intended mass increased. Next, an experimental protocol was utilized to determine the validity of the isoinertial mode in the work and joint spaces. A sagittal planar dynamic biomechanical model was used to provide the basis of comparison between lifts performed with the LIDOLift and with free weights. Analyses of covariance showed statistical differences for most work and joint space variables. However, the relative difference between the two for some variables may be functionally negligible. Important guidelines for clinical protocols using the isokinetic and isoinertial modes of this simulator are delineated. Areas of technological improvement have been identified to close the gap between the simulated isoinertial condition and the free weight lifting task View full abstract»

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  • Passive leg motion changes in cerebral palsied children after whole body vertical acceleration

    Page(s): 228 - 232
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    Reports on a pilot study designed to quantify changes in spasticity in children with spastic cerebral palsy following whole body vertical accelerations. Ten subjects, ranging in age from 5 to 18 years, were selected from the Cerebral Palsy Clinic of the Alfred I. duPont Institute. Most of the subjects were independent ambulators, although two used wheelchairs for long distances and one used a wheelchair full time. Passive leg motion changes, as seen in leg drop pendulum tests performed before and after vertical accelerations, are reported here. These changes are based on the comparison of 13 parameters, some of which are derived based on the assumption that normal limbs, when subjected to the leg drop pendulum test, behave as an underdamped second-order system. The vertical acceleration consisted of 15 min of up and down motion on a specially constructed platform capable of rating and lowering both the subject and his or her seating device. Amplitude of oscillation was set at 8.90 cm and the frequency of oscillation was commonly 1.57 Hz. Position of the leg was recorded with an electromagnetic position sensing device. Results of the study showed that 9 of the 10 subjects made a statistically significant improvement in one or more of the 13 attributes, with the highest achiever making improvements in 11 of the 13 attributes. Trends in the data show that the less severely involved clients made the most improvements View full abstract»

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  • Micturition control by microstimulation of the sacral spinal cord of the cat: acute studies

    Page(s): 206 - 214
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    The feasibility of using microstimulation of neural elements in the sacral spinal cord to effect micturition in cats has been assessed in acute experiments. Previous attempts at intramedullary stimulation have been limited by unwanted cocontraction of the bladder and the external urethral sphincter (EUS) or by side effects. Using microstimulation of parasympathetic preganglionic neurons or their efferent axons, the authors were able to repeatably elevate bladder pressure without simultaneously increasing EUS tone or eliciting undesired somatic contractions. Both stimulus amplitude and pulse width were effective in modulating bladder contractions but the stimulus frequency was not. Use of an interrupted duty cycle was helpful in preventing detrusor muscle fatigue during sustained periods of stimulation. Pulsing multiple microelectrodes implanted in the sacral spinal cord (especially bilateral pairs) enhanced elevation of bladder pressure over that elicited by stimulation with an individual electrode, but the effect was less than additive. These results have provided a basis for the development of a chronic spinal cord stimulation system suitable for controlling micturition View full abstract»

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  • Identification of quadriceps-shank dynamics using randomized interpulse interval stimulation

    Page(s): 182 - 192
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    Model structures for artificially stimulated paralyzed muscle-limb system dynamics were developed and experimentally evaluated in paraplegic patients. The examined system consisted of the quadriceps, electrically stimulated using surface electrodes, and a freely swinging shank. The interpulse interval of the stimulation sequence was randomized to obtain persistent system excitation. The outputs of the system were the angular position, velocity, and acceleration, measured by externally mounted sensors. The authors especially report on model identification of the active quadriceps dynamics and the angle prediction performance of the total quadriceps-shank model. Second-order modeling of the twitch dynamics with delay did not significantly improve the prediction results in comparison to a zero-order model with delay (α=0.05). Nonlinear torque-angle and torque-angular velocity relations in combination with a zero-order model (with delay) only slightly improved the prediction results for large prediction intervals (α=0.05). The delay between stimulation input and resulting knee joint acceleration appeared to be joint angle dependent and was estimated to be largest in the knee angle range near knee extension, i.e., when quadriceps muscle is shortest View full abstract»

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  • Perspectives on new electrode technology for stimulating peripheral nerves with implantable motor prostheses

    Page(s): 145 - 154
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    The limits of present electrode technology are being reached in current motor prostheses for restoring functional movement in paralyzed people. Improved devices require electrodes and stimulation methods that will activate muscles selectively and independently with less implanted hardware. A practical functional neuromuscular stimulation (FNS) system may need to employ extraneural, intraneural, epimysial, or intramuscular electrodes or a combination of these types. The limitations of current muscle electrodes and the anatomy of peripheral nerve innervation of muscle have pointed to stimulation of peripheral nerve trunks as a promising area for investigation. Attempts to use conventional (extraneural) peripheral nerve electrodes for selective activation of muscles in chronic applications have met with only limited success. Intraneural (intrafascicular) electrodes offer the advantages of greater selectivity and lower power requirements, but these may be offset by the difficulty of inserting delicate electrodes through the collagenous epineurium and perineurium while avoiding unacceptable amounts of trauma. Cuff electrodes require more power than intrafascicular ones but may provide more stable recruitment patterns over time, and the opportunity for retrieval and replacement View full abstract»

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  • Usage patterns of environmental control units by severely disabled individuals in their homes

    Page(s): 222 - 227
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    The authors investigated usage patterns of environmental control units (ECUs) by severely disabled individuals in their homes and evaluated the effect of ECUs on families and caregivers. Five modular ECUs with internal data loggers were built and placed into the homes of volunteering subjects. Each week, for 16 weeks, the data of every single ECU activity were uploaded, the data logger was reset, and the subjects were questioned about their experience with the ECU. Evaluating the data showed the most important ECU functions to be telephone and attendant call, both for the disabled individual as well as the care-giver. The most used functions, on the other hand, were the control of various entertainment devices such as television sets, stereos, and VCRs. Disabled individuals with a positive outlook on life use an ECU more frequently and, therefore, benefit more from an ECU than passive and resigned users. Finally, the families and care-givers of disabled persons appreciate the benefits of ECUs as much as the disabled users did themselves View full abstract»

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  • A system for converting braille into print

    Page(s): 215 - 221
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    Provides a detailed description of a method for converting braille, as it is stored as “characters” in a computer, into print. The system has been designed to be configurable for a wide range of languages and character sets, and uses a predominantly table driven method to achieve this. The algorithm is explained in the context of the conversion of standard English braille into print and the tables for this transformation are given View full abstract»

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  • The bimanual lifting rehabilitator: an adaptive machine for therapy of stroke patients

    Page(s): 166 - 174
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    Specially designed machines, which the authors call rehabilitators, could automate some of the repetitive aspects of physical and occupational therapy. Rehabilitators might also improve therapy by responding to the patient more quickly and precisely than a human therapist and by quantitatively measuring patient progress. The authors envision developing a family of inexpensive machines, each designed to retrain coordination in a specific activity of daily living, which could be used by physical and occupational therapists. To this end, the authors have built a rehabilitator for assisting hemiplegic stroke patients in bimanual lifting. In this task, subjects lift an object off a table with two hands, support it, then replace it on the table. If the disabled hand is unable to contribute to the task, the rehabilitator substitutes for it. The rehabilitator can substitute for the disabled hand well enough to lift a cafeteria tray with a cup of coffee on it without spilling it. If the disabled hand has fully recovered, the rehabilitator does not intervene View full abstract»

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Aims & Scope

This Transaction ceased publication in 2000. The current retitled publication is IEEE Transactions on Neural Systems and Rehabiliation Engineering.

Full Aims & Scope