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Biomedical subjects

A Kralj

Publications and source records attributed to A Kralj.

At least 37 records · Page 2Linked to original sources
PubMed1990

Symmetry of FES responses in the lower extremities of paraplegic patients.

Due to natural or artificial obstacles, gait is a less automatic and periodic process than it would appear when studying normal walking on the level. Pre-programmed functional electrical stimulation (FES) sequences, therefore, do not appear to be a suitable approach to the control of multichannel electrical stimulators in the restoration of paraplegic walking. Walking in paraplegic subjects must be, to a large extent, under voluntary control. To lessen the burden of this control, the symmetry of walking can be taken into account. Symmetric motion of the legs requires symmetric FES actuation. Symmetry of FES responses was studied in a group of 10 paraplegic subjects who had all undergone the FES training program. Recruitment curve, fatigue index and twitch delay were assessed. An average 80% symmetry was found in all parameters measured, thus allowing a reduction of complexity of control approach for FES locomotor aids.

Adult↗
PubMed1989

Use of functional electrical stimulation in the rehabilitation of patients with incomplete spinal cord injuries.

When patients enter the Rehabilitation Centre a therapeutic electrical stimulation programme is immediately initiated. Three groups of patients were identified: (i) those in whom an improvement of both voluntary and stimulated muscle force was observed, (ii) those with an increase in stimulation response only, and (iii) patients in whom no effect of electrical stimulation training could be recorded. Isometric measurement of voluntary and stimulated knee joint torque revealed that in a great number of patients one leg was severely paralysed while the other leg was under sufficient voluntary control. Unilateral two-channel stimulation of knee extensors and the peroneal nerve was proposed as an orthotic aid for this group of patients. Exaggerated extensor tone was observed by assessment of spasticity around the knee joint. A two-channel peroneal stimulator was found to be a useful approach in order to inhibit this tone and thereby help the patients to initiate a step.

Adult↗
PubMed1988

Enhancement of gait restoration in spinal injured patients by functional electrical stimulation.

Functional electrical stimulation (FES) was applied in 50 spinal cord injury patients in an effort to restore standing and walking. All patients in the program with lesions from T4-T12 were able to stand by means of FES. Walking, utilizing a four-channel stimulator, was accomplished by 25 patients with lesions in the range from T4-T12. These 25 patients represent approximately 5% of all spinal cord injured patients treated in the authors' rehabilitation facility during this time period. After using the stimulation in a home environment for more than three months, the number of patients who continued to use the stimulation for walking declined, and 16 patients remained ambulatory. The discontinuance of FES was mainly because of the time required to put on and operate the FES system and difficulties adapting to a new home environment and living situation.

Adolescent↗
PubMed1985

Restoration of walking in patients with incomplete spinal cord injuries by use of surface electrical stimulation--preliminary results.

A group of patients who are good candidates for the application of Functional Electrical Stimulation (FES) to restore reciprocal walking is described. They have incomplete lesions of the spinal cord. Because of the degree of preserved voluntary control, proprioception and sensation some of these patients can achieve crutch assisted walking by means of multichannel electrical stimulation. In a number of cases the patient has sufficient strength and voluntary control in the upper limbs and at least one leg to provide safe standing for short periods in forearm crutches. For these patients a two channel stimulator controlled by a handswitch was applied to achieve safe and practical crutch assisted walking in a relatively short period of time.

Adult↗
PubMed1983

The use of a four-channel electrical stimulator as an ambulatory aid for paraplegic patients.

This article reports the use of electrical stimulation to provide paraplegic patients with complete lesions of the spinal cord the ability to rise from sitting to standing, to maintain a standing position, and to walk with a reciprocal gait. Four channels of electrical stimulation are sufficient for synthesis of a simple reciprocal gait pattern in these patients. During the double-stance phase, knee extensor muscles of both knees are stimulated, providing sufficient support for the body. Only one knee extensor muscle group is excited during the single-stance phase. The swing phase of the contralateral lower extremity is accomplished by eliciting the synergistic flexor muscle response through electrical stimulation of afferent nerves. The transition from the double-stance phase to the swing phase is controlled by two hand switches used by the therapist or built into the handles of the walking frame or crutches for use by the patient.

Electric Stimulation Therapy↗
PubMed1983

Gait restoration in paraplegic patients: a feasibility demonstration using multichannel surface electrode FES.

Recent advances in science have aided research toward the restoration of biped gait in paraplegic patients by means of functional electrical stimulation (FES). In this paper it is shown how FES-restrengthened muscles of paraplegic patients have been used for simple FES-assisted standing. Those experiments subsequently led to biped gait-initializing experiments and to simple forms of biped gait synthesis. The purpose of this paper is to show the feasibility of using FES for standing and for restoring biped gait in many paraplegic patients--to present the past achievements, focus on problems, and highlight directions for future research. The results of gait obtained in three complete spinal cord injured patients (out of a series of 17) are shown, using four to six channels of FES. It is also shown how preserved reflex mechanisms of the transected spinal cord can be incorporated and employed for obtaining improved function while at the same time simplifying the FES hardware. Of the three patients reported on in detail here, two patients have managed to walk in parallel bars while the third patient has mastered independent unassisted walking over shorter distances with the aid of a roller walker. The biomechanical and control problems of this last patient's gait are presented in detail.

Adult↗
PubMed1982

Standing-up of a healthy subject and a paraplegic patient.

The joint torques in hip, knee and ankle were measured during the standing-up of a healthy subject. Force plate and stroboscopic photography were used in the experiment. It has been observed that the time courses of particular joint torques depend on the kind of standing-up. On the basis of these results a standing-up procedure for paraplegic patients was proposed. With the use of electrical stimulation to both paralyzed knee extensors and through use of the arm support, a completely paraplegic patient was able to rise independently from the wheel-chair. The same dual-channel stimulation also provides knee locking during standing of spinal cord injured patients.

Ankle Joint↗
PubMed1980

Simple kinematic gait measurements.

Simple kinematic gait measurement equipment was developed providing fast and inexpensive clinical gait analysis. Such a simple system can be used as a stand-alone clinical gait analyser, or as an accessory for measurements whose results are not sufficiently weighted statistically, such as TV, Selspot, force plate. Time, distance and velocity parameters are included in the clinical gait analysis. Time parameters (step and stride time, swing and stance phase) are measured via easily attachable foot-switches. Analog and digital versions were developed to analyse distance (stride and step length) and velocity (instantaneous velocity of centre of gravity) parameters. With the analog device the velocity is measured by tachometer and distance by potentiometer, while using digital methods, both parameters can be obtained from an optical transducer.

Biomedical Engineering↗
PubMed1980

Electrical stimulation providing functional use of paraplegic patient muscles.

The paper presents a short description of the field of electrical stimulation of skeletal muscles and a survey of the recent achievements in the functional electrical stimulation (FES) of paraplegic patients. The major emphasis is placed on the discussion of the basic problems concerning muscle fatigue, muscle retraining and patient selection. Muscle strengthening and exercising procedures using electrical stimulation are described. The obtained properties of retrained muscles with special regard to their fatiguing are clearly documented. The potential possibilities of using FES for performing functional tasks are discussed and the results of preliminary experiments are illustrated. The standing and primitive walking of patient, induced by electrically stimulated paralyzed muscles are presented. Finally, a proposal for an orthotic device using electrical stimulation is described, which enables a paraplegic patient to stand by means of support of his proper bones and muscle forces.

Adult↗
PubMed1977

Functional electrical stimulation of the extremities: part 1.

Functional electrical stimulation of the extremities (FES) is a new method for the rehabilitation of paralysed paretic patients. Small, electronic stimulators are worn by the patient, who can voluntarily control the electrical currents applied to his paralysed muscle. These currents activate the disabled extremities and make them at least partially functional once more. This paper presents a short history of FES and discusses recent advances and problems in the field. A detailed account of present work with single- and multi-channel stimulation of paralysed legs is given, as well as some research data on upper extremity stimulation.

Electric Stimulation Therapy↗
PubMed1976

Electrical stimulation and feedback training: effects on the voluntary control of paretic muscles.

The carry-over effect of gait-synchronized stimulation of the peroneal nerve on voluntary dorsiflexion of the paretic foot was evaluated in hemiplegic patients. The influence of providing audiovisual feedback of performance on voluntary control was also evaluated. Each patient received three test sessions separated at least one week apart. In each session, measurement of isometric torque from voluntary effort was repeated four times: before, and at 0, 30 and 60 minutes after a 20-minute walk period. Session 2 involved both peroneal stimulation during walking and performance feedback during voluntary efforts. Session 1 had stimulation only. Session 3 had feedback only. The results were inconsistent among the patients. Where increase of voluntary dorsiflexion was obtained, it was more a consequence of performance feedback than peroneal stimulation. General problems of using isometric torque produced by voluntary dorsiflexion as a measure of the carry-over effect are discussed.

Adult↗
PubMedDate not supplied

Voluntary telemetry control of functional electrical stimulators.

With the assistance of crutches and functional electrical stimulation (FES) we are able to restore standing and simple gait in some spinal cord injured (SCI) patients. In the present rehabilitative systems the patient divides the gait cycle into 'stance' and 'swing' phase by using pushbuttons mounted in the handles of the crutches. These are then hard wired to the functional electrical stimulator. We present the development and evaluation of a surface mount technology based telemetry system that provides reliable and interference resistant wireless control of FES assisted walking. The system makes use of radio frequency carriers operating at a frequency of 40 MHz. Crutch pushbutton signals are coded and transferred from the transmitter placed in the crutch to the receiver which is firmly attached to the patient's waist and connected to the stimulator. The telemetry system was found to be of special importance for both complete and incomplete SCI subjects and is currently in use at the Rehabilitation Institute of the Republic of Slovenia.

Activities of Daily Living↗