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Biomedical subjects

T Bajd

Publications and source records attributed to T Bajd.

16 recordsLinked to original sources
PubMed1992

Bending moments in lower extremity bones for two standing postures.

The goal of this paper is to study how external gravitational forces stress the lower extremity bones and to ascertain and study how muscle activation compensates for the external load. For these purposes relatively accurate anatomical and biomechanical modelling is necessary. For a comparison of the calculated results to the naturally occurring muscular activity, seven-channel surface EMG activity was recorded. For simplicity a two-dimensional model was developed for the sagittal plane including 19 lower extremity muscles relevant to human standing and walking. In the calculation procedure of muscle forces an optimization procedure is also included. The results give rise to the expected assumption that muscle action is covered by two main requirements: first, to stabilize the joint actively (moment equilibrium) and, second, to compensate efficiently for bending moments produced by gravitational and external forces.

Biomechanical Phenomena↗
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↗
PubMed1986

Posture switching for prolonging functional electrical stimulation standing in paraplegic patients.

The presently employed posture for Functional Electrical Stimulation (FES) assisted standing in spinal cord injury (SCI) patients utilises the active locking of knee joints by tetanically stimulating the quadriceps muscle. The hip joints are in hyperextension and the ankle joints remain free. The upper limbs are used for balancing. This posture requires minimal corrective forces exerted by the hands, the weight is transferred across the legs, while very limited forward-backward sway is permitted. Knee jack-knifing may occur in the instance when the gravity knee bending moment exceeds the moment generated by the quadriceps muscle. Because of these effects and fatiguing of the M. quadriceps the standing time is short, lasting from several minutes up to an hour, depending on the condition of the patient's muscles. Cyclical FES with a duty cycle of 10-20 seconds (on/off) fatigues muscle considerably less. The use of different postures for standing requiring activation of different muscles permits the application of cyclical FES. The cyclic FES results in prolonging standing times by a factor of two to five. Utilising this improvement some patients can stand for up to five hours at a time. This functional achievement is comparable to the standing time of a normal man. The incorporation of the principle of posture switching also prolongs standing in patients with weak muscles, because of the possibility of cyclical coactivation of different synergistic muscle assemblies. It is shown that posture switching can be carried out automatically and that patients adapt quickly to it. In addition using co-contraction of two or three muscles with posture switching does further expand the range of suitable patients and improves standing with an increased permissible range of body sway. Also, the FES antigravity action obtained raises hopes for substantially improving FES induced reciprocal gait.

Electric Stimulation Therapy↗
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↗
PubMed1985

Electrical stimulation in treating spasticity resulting from spinal cord injury.

To study the efficacy of electrical stimulation in treating spasticity of six spinal cord injured patients, transcutaneous electrical nerve stimulation (TENS) was applied to the dermatomes belonging to the same spinal cord level as the selected spastic muscle group. Spasticity was assessed in knee extensors by a pendulum test in which the knee joint angle of a swinging lower leg was recorded with an electrogoniometer. TENS was found to produce a noticeable decrease of spasticity in three of the patients, but had little effect on the others.

Adult↗
PubMed1977

Standardization of kinematic gait measurements and automatic pathological gait pattern diagnostics.

The estimation of patients gait in the field of rehabilitation is the starting point for an appropirate therapy decision and convenient prosthesis or orthosis choice. The measurement and estimation of human locomotion is increasingly being transferred to every day clinical use. In recent times many systems are intended for kinematic gait parameters measurements: stroboscopic photography, movie camera, TV picture analysis, TV signal analysis, chronocyclographical measurement, polarised light goniometer, the "Selspot" system, parallelgram goniometers, exoskeleton goniometers. In the paper the role of the computer in gait measurements is also determined. The problems of the choice of parameters to be measured, unique reference coordinate systems and normal gait pattern are encountered in this work. Finally two versions of pathological gait pattern estimation are described: clinical gait analysis and mathematical quantitative gait analysis. A combination of both methods provides an efficient, compact automatic pathological gait pattern diagnostics.

Automation↗