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Rehabilitation Engineering, IEEE Transactions on

Issue 4 • Date Dec. 1997

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Displaying Results 1 - 16 of 16
  • 1997 Index IEEE Transactions on Rehabilitation Engineering Vol. 5

    Page(s): 1 - 7
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    Freely Available from IEEE
  • Prosthetic weight acceptance mechanics in transtibial amputees wearing the Single Axis, Seattle Lite, and Flex Foot

    Page(s): 283 - 289
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    Loading response challenges the limb with the dual demands of accepting rapidly moving body weight to both absorb the shock of floor contact and create a stable limb over which the body can advance. Delay in achieving foot flat contact with the floor causes a prolonged period of heel only support and results in an unstable base of support for those persons with transtibial amputations. The purpose of this study was to identify mechanical causes of instability during weight acceptance with three different prosthetic foot designs, Single Axis, Seattle Lightfoot, and Flex Foot. Ten male individuals with transtibial amputations were tested on three separate occasions wearing each prosthetic foot. A comparison group of ten individuals without transtibial amputations was also examined. Mean free walking speed was significantly slower for those with transtibial amputations regardless of the prosthetic foot worn (p<0.05). Contralateral toe off times were significantly later for each prosthetic foot (p<0.01). The timing of peak knee flexion was found to be significantly later than normal for each prosthetic foot (p<0.01). To minimize the impact of initial floor contact, persons with an intact limb used rapid plantar flexion, followed by a slower lowering of the foot to the floor. Dorsiflexion then stimulated knee flexion and foot flat. Two altered functions were found for all three prosthetic feet, reduced knee flexion and prolonged heel only support, Diminished knee flexion reflected delayed dorsiflexion and tibial advancement as a result of the cushioned heel. Lateness in reaching foot flat was also found. To improve the walking abilities of those persons with transtibial amputations, prosthetic foot designs need to incorporate mechanisms which promote early foot flat while preserving limb stability View full abstract»

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  • A multisegment computer simulation of normal human gait

    Page(s): 290 - 299
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    The goal of this project was to develop a computer simulation of normal human walking that would use as driving moments resultant joint moments from a gait analysis. The system description, initial conditions and driving moments were taken from an inverse dynamics analysis of a normal walking trial. A nine-segment three-dimensional (3-D) model, including a two-part foot, was used. Torsional, linear springs and dampers were used at the hip joints to keep the trunk vertical and at the knee and ankle joints to prevent nonphysiological motion. Dampers at other joints were required to ensure a smooth and realistic motion. The simulated human successfully completed one step (550 ms), including both single and double support phases. The model proved to be sensitive to changes in the spring stiffness values of the trunk controllers. Similar sensitivity was found with the springs used to prevent hyperextension of the knee at heel contact and of the metatarsal-phalangeal joint at pushoff. In general, there was much less sensitivity to the damping coefficients. This simulation improves on previous efforts because it incorporates some features necessary in simulations designed to answer clinical science questions. Other control algorithms are required, however, to ensure that the model can be realistically adapted to different subjects View full abstract»

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  • A portable, real-time, clinical gait velocity analysis system

    Page(s): 310 - 321
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    A direct ultrasound ranging system (DURS) has been developed for the quantitative evaluation of gait velocity. DURS consists of a transponder worn by the subject, a base unit infrared (IR) emitter/ultrasound (US) receiver, and a laptop computer. During gait analysis the transponder is worn by the subject at the approximate level of the body center of mass. As the subject walks away from the base unit his or her forward progression is displayed in real-time on the computer. At the end of the walking trial the instantaneous velocity profile, or gait velocigram (GVG), for that trial is displayed on the computer screen. From the GVG, parameters such as, gait speed, cadence, step length, step time, peak-to-peak variation, and time to achieve steady state walking are calculated and displayed. In addition gait deviations are readily apparent on the GVG View full abstract»

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  • Application of stereophotogrammetry to total body three-dimensional analysis of human tremor

    Page(s): 388 - 393
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    This work aims at verifying the possibility of investigating joint rotations, with amplitude and frequency ranges typical of pathological human tremor, using commercially available stereophotogrammetric systems together with signal processing techniques. A rotating disk is used as a mechanical tremor simulator to test the ability of the system to track known marker trajectories both in a large and a small calibrated volume. The performances of standard discrete Fourier transform (DFT) and autoregressive techniques are also evaluated and compared in the signal spectrum estimation. Results obtained from a pathological test subject and their dependence on the processing techniques adopted are also presented. The use of stereophotogrammetry and of the proposed signal spectrum estimation technique allow to quantify both frequency and amplitude content of three-dimensional (3-D) rotations of many human joints simultaneously and therefore to isolate the contribution of each joint to the whole body tremor View full abstract»

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  • Actigraphic monitoring of movement and rest-activity rhythms in aging, Alzheimer's disease, and Parkinson's disease

    Page(s): 394 - 398
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    Actigraphy, the long-term assessment of wrist movements, is used in several research fields, among which are included sleep and circadian rhythms. Actigraphs record movements using accelerometers. The present paper addresses some basic problems and their solutions in the actigraphic assessment of movement, motor symptoms, circadian rest-activity rhythms, and nocturnal agitation in healthy elderly and elderly suffering from a neurodegenerative disease (i.e., Parkinson's disease or Alzheimer's disease) and summarizes the results of previous and ongoing research. First, the author has investigated how to filter the accelerometer signal in order to minimize the contribution of accelerations induced by positional changes in the gravitational field-a strong source of artefacts. A bandpass filter from 0.5 to 11 Hz appropriately assesses movement induced accelerations while minimizing gravitational artefact. The application of a bandpass filter from 0.25 to 2 or 3 Hz, as is used in some of the commercially available actigraphs, results in artefacts and moreover biases the slower part of the movement spectrum. It is therefore far from optimal for research on aging, which is associated with a generalized motor slowing. Second, the author has proposed an alternative to traditional methods of signal processing in actigraphy, in order to assess both the duration and intensity of movements, and in order to distinguish Parkinsonian tremor. Based on this algorithm, new types of actigraphs have been designed. Third, the author has proposed sensitive variables in order to quantify rest-activity rhythm disturbances in healthy elderly subjects and Alzheimer patients, who often present with symptoms of nocturnal restlessness. Since, in these subjects, research protocols applying enforced phase shifts or time-free environments are unfeasible and not justifiable from an ethical point of view, the variables were specifically designed to assess the functionality of the circadian timing system from actigraphic recordings made in the natural environment of subjects. Examples of the application of actigraphy are given, including studies on symptom fluctuations and medication responses in Parkinson patients, and studies on circadian rhythm disturbances and possible remedies in elderly and Alzheimer patients View full abstract»

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  • Rail supporting transducer posts for three-dimensional force measurement

    Page(s): 380 - 387
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    Parallel bars supported on transducer posts were designed, instrumented and calibrated to measure three-dimensional (3-D) forces applied to the rails. These instrumented rails were designed for measuring forces applied by paraplegic patients during development and evaluation of functional electrical stimulation (FES) patterns for standing, side stepping, and ascending and descending stairs. The focus of this study was on the adaptation of the system for measuring support forces during stair climbing and descent. The specific problems with crosstalk among the three axes, nonlinearity, and hysteresis were investigated. In this design, the crosstalk between axes was less than 5%, nonlinearity was less than 2% of full scale, and force accuracy was better than 5% View full abstract»

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  • Feedback control of unsupported standing in paraplegia. II. Experimental results

    Page(s): 341 - 352
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    For pt. I see ibid., vol. 5, no. 4, p. 331-40 (1997). This is the second of a pair of papers which describe an investigation into the feasibility of providing artificial balance to paraplegics using electrical stimulation of the paralyzed muscles. By bracing the body above the shanks, only stimulation of the plantar flexors is necessary. This arrangement prevents any influence from the intact neuromuscular system above the spinal cord lesion. Here, the authors present experimental results from intact and paraplegic subjects View full abstract»

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  • Feedback control of unsupported standing in paraplegia. I. Optimal control approach

    Page(s): 331 - 340
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    This is the first of a pair of papers which describe an investigation into the feasibility of providing artificial balance to paraplegics using electrical stimulation of the paralyzed muscles. By bracing the body above the shanks, only stimulation of the plantarflexors is necessary. This arrangement prevents any influence from the intact neuromuscular system above the spinal cord lesion. Here, the authors extend the design of the controllers to a nested-loop LQG (linear quadratic Gaussian) stimulation controller which has ankle moment feedback (inner loops) and inverted pendulum angle feedback (outer loop). Each control loop is tuned by two parameters, the control weighting and an observer rise-time, which together determine the behavior. The nested structure was chosen because it is robust, despite changes in the muscle properties (fatigue) and interference from spasticity View full abstract»

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  • Fuzzy clustering of children with cerebral palsy based on temporal-distance gait parameters

    Page(s): 300 - 309
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    Temporal-distance parameters for 88 children with the spastic diplegia form of cerebral palsy (CP) are grouped using the fuzzy clustering paradigm. The 2 features chosen for clustering are stride length and cadence which are normalized for age and leg length using a model based on a population of 68 neurologically intact children. Using information provided by the neurologically intact population and cluster validity techniques, 5 clusters for the children with cerebral palsy are identified. The 5 cluster centers represent distinct walking strategies adopted by children with cerebral palsy. Utilizing just four easily obtained parameters-stride length, cadence, leg length and age-and a small number of simple equations, it is possible to classify any child with spastic diplegia and to generate an individual's membership values for each of the 5 clusters. The clinical utility of the fuzzy clustering approach is demonstrated with pre- and post-operative test data for subjects with cerebral palsy (one neurosurgical and one orthopaedic) where changes in membership of the 5 clusters provide an objective technique for measuring improvement. This approach can be adopted to study other clinical entities where different cluster centers would be established using the algorithm provided here View full abstract»

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  • Muscle balance at the knee-moment arms for the normal knee and the ACL-minus knee

    Page(s): 367 - 379
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    Forces, moments and stresses at the knee are dependent upon external and internal loading factors including muscle forces, segmental position and velocity, load carried, and the moment arms (mechanical advantage) of the muscle-tendon units. Requisite to prediction of forces and moments is a detailed understanding of effective moment arms throughout the knee range-of-motion (ROM). Existing muscle models for the knee are based upon limited static studies of only a few preserved specimens. The objectives of this report are to develop a comprehensive description of muscle-tendon moment arms for the normal knee and the anterior cruciate ligament (ACL)-minus knee during flexion-extension motion. Recent research results describe two nonorthogonal, nonintersecting axes of motion for the knee-one describing flexion-extension (FE) and the other longitudinal rotation (LR, equivalent to internal-external rotation). The effective flexion-extension moment arms of the muscles crossing the knee were developed with respect to the FE axis in 15 fresh, hemi-pelvis cadaver specimens. The normal moment arms for each of 13 muscles plus the patellar tendon exhibited variable, yet repeatable and recognizable patterns throughout the ROM. For most muscles there was no significant difference between the normal and ACL-minus moment arms. The results provide a basis for more accurate predictions of joint reaction forces and moments as well as useful knowledge for practitioners and therapists to assist in the assessment of muscle balance at the knee following injury, repair, and throughout rehabilitation View full abstract»

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  • On a cause of detection sensitivity difference depending on direction of object in obstacle sense

    Page(s): 403 - 405
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    To investigate the cause of the detection sensitivity difference depending on direction of the object in the obstacle sense, the experiment to measure the directional characteristics of the echo suppression was made. The conclusion is that one of the causes is the difference of the echo suppression level View full abstract»

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  • Biomechanical analysis of failed sit-to-stand

    Page(s): 353 - 359
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    Sit-to-stand (STS) failure is a transient loss of balance that can engender falls among elders. The purpose of this paper is to describe the mechanisms whereby failed STS differs from successful STS. The authors compared successful STS from 11 normal elders to 20 “sitback” and 20 “step” type failed STS's in 13 subjects. Kinematic and kinetic data were incorporated into the authors' 11-segment whole body model to estimate the net joint forces and torques and body segment momenta. Significant between group differences in the magnitude and timing of momentum generation and dissipation, knee extensor torques and the magnitude of the vertical ground reaction force were identified. Both types of failed sit-to-stand maneuvers are less energetic than successful rises, STS failures might result from either weakness or balance control and coordination impairment, or both, resulting in an insufficiently energetic effort. Further research is required to differentiate between these two possible sources of impairment. Determining the root cause of functional limitations is necessary to develop effective interventions View full abstract»

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  • Piezo-dynamometric platform for a more complete analysis of foot-to-floor interaction

    Page(s): 322 - 330
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    A compound instrument was constructed by superimposing a dedicated pressure platform on a commercial force platform. This instrument simultaneously estimates the ground reaction force resultants (vertical and shear forces, free moment and location of the center of pressure), pressure distribution throughout the foot-floor contact area, the trajectory of the center of pressure superimposed on the contact area (footprint). On the basis of the readings provided by the force plate the authors calibrated pressure sensors more accurately. They could therefore accurately estimate the vertical local components of the ground reaction. This information and the measured shear force resultants were essential for computing the shear forces acting on elementary areas corresponding to the active surface of each pressure sensor. This, in turn, allowed the authors to estimate the vertical and shear force resultants and free moment for subareas of the foot. This is a feature peculiar to this compound instrument, and for its effective exploitation the authors have implemented a few methods for the reliable identification of the subareas of interest. Two application instances are hereby reported View full abstract»

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  • Effect of pelvic tilt on lumbar spine geometry

    Page(s): 360 - 366
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    The purpose of this study was to use a noninvasive method to determine the effect of pelvic tilt on the lumbar spine geometry in the sagittal plane. Five healthy male subjects were instructed in performing active forward and backward pelvic tilt manoeuvres in the standing position. The lumbar spine geometry (severity of lordosis, pelvis and lumbar vertebrae orientations) was estimated with a lumbar spine geometric model. The voluntary backward pelvic tilt succeeded in reducing the depth of the lumbar spine curvature, but the forward tilt did not change it. Both pelvic tilt manoeuvres influenced the absolute orientations of the lower lumbar vertebrae and the relative orientations of some lumbar vertebrae. Interestingly, the L5/S1 joint showed was little affected by the pelvic tilt manoeuvres View full abstract»

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  • Real-time feedback of body center of gravity for postural training of elderly patients with peripheral neuropathy

    Page(s): 399 - 402
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    A system that estimates and displays, in real-time, the location of the center of gravity of the human body relative to the feet was developed and then used in a biofeedback training program for improving the postural instability caused by deterioration of the proprioceptive system in elderly patients with significant diabetic sensory neuropathy during perturbations of a support platform. Training sessions were scheduled three times a week for four weeks and consisted of continuous perturbations of the support platform for the standing subject. Postural stability of each subject was evaluated before, during and after training on a weekly basis. After twelve sessions of training, subjects who received visual feedback showed greater reduction in total number of falls and in fall magnitude defined by force in the body suspension cord, and longer delay in time between perturbation and fall than NFB group 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