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Rehabilitation Engineering, IEEE Transactions on

Issue 1 • Date Mar 1994

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Displaying Results 1 - 6 of 6
  • Artifact-free sensory nerve signals obtained from cuff electrodes during functional electrical stimulation of nearby muscles

    Page(s): 37 - 40
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (432 KB)  

    Restoration of the voluntary use of paralyzed limbs using functional neuromuscular stimulation (FNS) is limited by complex muscle properties and unpredictable load behaviors; closed-loop control of FNS would improve performance but requires reliable sensory feedback modalities. Sensory nerve signals recorded by cuff electrodes provide accurate information about forces acting on the skin in anesthetized animals; however, nerve cuff signals are very small (approximately 10 μV), and during FNS they become contaminated with large stimulation artifacts and synchronous EMG potentials from nearby muscles. The authors show in this study that it is possible to record neural signals from the cat tibial nerve without interference from distributed stimulation of four calf muscles surrounding the recording electrode by use of high-pass filtering and synchronized bin-integration. Nerve signals sampled in this way retained all the information about footpad contact force that was normally obtained in the absence of muscle stimulation. The authors propose that this approach has wide applicability for rehabilitation of paralyzed people with neural prostheses View full abstract»

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  • Slip information provided by nerve cuff signals: application in closed-loop control of functional electrical stimulation

    Page(s): 29 - 36
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (784 KB)  

    A model of a paralyzed hand gripping and lifting an object was developed using anaesthetized cats. Functional neuromuscular stimulation (FNS) applied to the ankle plantarflexor muscles caused the footpad to press against and grip an object. Electroneurographic activity (ENG) activity generated by skin mechanoreceptors in the footpad was recorded with a cuff electrode implanted on the tibial nerve. Sharp bursts evident in the ENG signaled any slips between the object and the skin. This information was used in an event-driven controller that allowed the FNS system to compensate for slips. In this way an “artificial gripping reflex” was implemented that compensated automatically for internal changes (fatigue) and the external perturbations (increased load, changed frictional coefficient). This control scheme proved to be robust and is proposed to be applicable for restoration of precision grip in paralyzed humans View full abstract»

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  • Function and strength of electrically stimulated hip flexor muscles in paraplegia

    Page(s): 11 - 17
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (596 KB)  

    In this study hip flexion moments and fatigue were measured in paraplegic individuals that were implanted with percutaneous intramuscular electrodes as part of their functional electrical stimulation (FES) system for walking. The largest average hip flexion moment (36% of normal) was measured at small hip flexion angles. This percentage decreased with an increase in hip flexion angle until only an extension moment was measured above 90°. Except for the sartorius, all hip flexors including the gracilis, adductor longus, tensor fasciae latae, and iliopsoas produced extension moments at large hip flexion angles. The current iliopsoas implantation technique utilizing stimulation of the second and third lumbar motor roots resulted in recruitment of the adductor longus and brevis or pectenius causing extension moment that negated any iliopsoas creating flexion component at large hip flexion angles. Even though measured moments were minimal, the paraplegic subject was able to maintain cyclic hip flexions above 40° at the rate of 30/min over 30 min. At the slower rate a much greater flexion such as required for stair climbing can be maintained for a prolonged period. A new implantation technique using soft tissue endoscopy is being developed to isolate recruitment of iliopsoas and to extend the range of hip flexion View full abstract»

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  • Skin contact force information in sensory nerve signals recorded by implanted cuff electrodes

    Page(s): 18 - 28
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    When functional neuromuscular stimulation (FNS) is used to restore the use of paralyzed limbs after a spinal cord injury or stroke, it may be possible to control the stimulation using feedback information relayed by natural sensors in the skin. In this study the authors tested the hypothesis that the force applied on glabrous skin can be extracted from the electroneurographic (ENG) signal recorded from the sensory nerve. They used the central footpad of the cat hindlimb as a model of the human fingertip and recorded sensory activity with a cuff electrode chronically implanted around the tibial nerve. Their results showed that the tibial ENG signal, suitably filtered, rectified, and smoothed carries detailed static and dynamic information related to the force applied on the footpad. The authors derived a mathematical model of the force-ENG relation that provided accurate estimates of the ENG signal for a wide range of force profiles, amplitudes, and frequencies. Once fitted to data obtained in one recording session, the model could be made to fit data obtained in other sessions from the same cat, as well as from other cats, by simply adjusting its overall gain and offset. However, the model was noninvertible; i.e., the force could not be similarly predicted from the ENG signal, unless additional assumptions or restrictions were introduced. The authors discuss the reasons for these findings and their implications on the potential use of nerve signals as a source of continuous force feedback information suitable for closed-loop control of FNS View full abstract»

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  • Frequency content of whole body gait kinematic data

    Page(s): 40 - 46
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    The authors analyzed the frequency content of camera image plane data for markers on each body segment during gait. For each segment, they determined the low-pass filter cutoff frequency that balanced the amount of signal distortion and the amount of random noise passed. The frequency content of the data as measured by the cutoff frequency differed for different body segments, being higher for the lower limb segments and lower for the head. This result supports the hypothesis that the frequency content of the kinematics of segments decreases caudal to rostral View full abstract»

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  • Biomechanical relationship between center of gravity and center of pressure during standing

    Page(s): 3 - 10
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    The relationship between the position of a body's center of gravity (CG) as determined by a whole body kinematic model and that given by 3 CG position estimation techniques using the ground reaction force center of pressure (CP) has been investigated in this study. The CG and CP are related by the Newtonian mechanics equations of motion. Data required to determine directly the center of gravity position, a key variable in posture and locomotion, are usually not obtained in posture or gait trials; rather, force plate data and center of pressure data are often obtained. Consequently, previous studies have developed estimations of CG position history from CP data. The results of 3 CP-based CG estimations methods are here compared with kinematically determined CG positions in humans. The CP position varies about the CG position and has a higher frequency content than the motion of the CG. This observation, based on the authors' data and mechanics theory, provides the basis for the methods considered in this study. All current methods employ a filtering technique to obtain CG position from CP position time histories during standing trials. In most cases the mean square error is less than 0.1 cm2. Finite-duration impulse response filters with periods of 1.0 s to 1.50 s gave the best results when compared with the CG position based on kinematic data. A low-pass filter with cutoff frequency of 0.4 Hz to 0.5 Hz provides the best comparison for this approximation method. The accuracy of the methods diminishes as more dynamics are introduced to the trial. The average mean square differences for walking-in-place trials is from 1 to 10 times greater than that for the standing. CG position estimates from CP data must be interpreted cautiously when nonstatic tasks are monitored, especially in unstable patients 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.

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