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Biomedical subjects

M H Granat

Publications and source records attributed to M H Granat.

33 records · Page 2Linked to original sources
PubMed1997

Further development of hybrid functional electrical stimulation orthoses.

In this study two aspects of hybrid functional electrical stimulation (FES) orthoses were investigated: joint motion constraints and FES control strategies. First, the effects of joint motion constraints on the gait of normal subjects were investigated using modern motion analysis systems, including electromyogram (EMG) and heart rate measurements. An orthosis was developed to impose joint motion constraints; the knee and ankle could be fixed or free, and the hip joint could rotate independently or coupled, according to a preset flexion-extension coupling ratio (FECR). Compared with a 1:1 hip FECR, a 2:1 hip FECR was associated with a reduced energy cost and increased speed and step length. The knee flexion during swing significantly reduced energy cost and increased walking speed. Ankle plantar flexion reduced the knee flexing moment during the early stance phase. Second, trials on 3 paraplegic subjects were conducted to implement some of these findings. It appeared that the 2:1 FECR encouraged hip flexion and made leg swing easier. A simple FES strategy increased walking speed and step length and reduced crutch force impulse using fixed orthotic joints.

Ankle↗
PubMed1997

Effects of electrical stimulation on flexion contractures in the hemiplegic wrist.

OBJECTIVE: To study the effects of electrical stimulation (ES) on flexion contractures in the hemiplegic wrist. DESIGN: The investigation was carried out following an OFF (two weeks with rehabilitation only)--ON (two weeks with ES treatment and rehabilitation)--OFF (two weeks rehabilitation only) fixed protocol. SETTING: A stroke ward and an outpatient stroke service. SUBJECTS: Eleven hemiplegic subjects with reduced range of extension and increased resistance to passive movement at the wrist. MAIN MEASURE: Quantitative measures of the hemiplegic posture at the wrist, passive range of extension and resistance to passive extension of the wrist. Measurements were taken at the start of the study and then at two-weekly intervals. Two extra measurements were taken at the end of the ON period. RESULTS: Following two weeks treatment with ES the posture of the wrist improved and the passive range of extension increased. However, there were no significant changes in the resistance to passive movement. These benefits appeared largely to be lost two weeks after ES was discontinued. CONCLUSIONS: Short-term ES gives temporary improvements in contractures at the wrist in poststroke hemiplegia.

Aged↗
PubMed1996

Effects of joint motion constraints on the gait of normal subjects and their implications on the further development of hybrid FES orthosis for paraplegic persons.

In this study the effects of angular motion constraints of the lower limbs on the gait of normal subjects were investigated. An assessment orthosis was developed with a new hip coupling mechanism which allows its ratio of reciprocal flexion to extension to be altered. The knee and ankle joints of the orthosis could also be set to be free or locked in specific directions of angular motion in the sagittal plane. A total of 12 different orthosis configurations was tested on three normal subjects. The kinematic, kinetic and electromyographic (EMG) data were collected using the VICON system, two Kistler forceplates, foot switches and an eight channel EMG system. The physiological cost index of walking was assessed by measuring the heart rate and walking speed. It was found that (1) a higher hip flexion-extension ratio was associated with lower energy cost and faster walking; (2) allowing the knee to flex significantly reduced the energy cost and increased the walking speed; (3) allowing the ankle to plantarflex during early stance phase reduced the knee flexing moment. The implications of these effects on the further development of hybrid functional electrical stimulation orthotic systems are discussed.

Adult↗
PubMed1996

Peroneal stimulator; evaluation for the correction of spastic drop foot in hemiplegia.

OBJECTIVE: The objective of the study was to assess the orthotic and therapeutic value of the peroneal stimulator (PS) for adult hemiplegic patients. DESIGN: This was a two-period crossover study lasting 11 weeks. After recruitment each patient had a 4-week control period followed by a 4-week treatment period. The patients were assessed before the control period, after the control period, and after the treatment period. SETTING: Nineteen patients were recruited from physiotherapy departments in the Glasgow area; 2 subsequently dropped out before the treatment period. PATIENTS: All patients had hemiplegia as a result of cerebrovascular accident (CVA) and were greater than 3 months but less than 36 months post-CVA. Average time since stroke was 7 months. MAIN OUTCOME MEASURES: The patients' gait was assessed over smooth linoleum, carpet, and uneven ground. Gait was evaluated using a switch-based portable system. Outcome measures were the temporal gait parameters of speed, symmetry, heel strike, and foot inversion during stance. The gait evaluation was repeated on 5 separate days at each assessment. The Barthel Index was applied to each session. RESULTS: There was a significant orthotic improvement in inversion on all surfaces and for symmetry on linoleum (AN-OVA, p = .05). There was no significant improvement in patients' gait when not using the PS. There was a significant improvement in the Barthel Index over the treatment period (Wilcoxon, p = .05). CONCLUSION: Use of the PS an an orthotic device late in the rehabilitation program would be appropriate for a selected subpopulation of patients.

Adaptation, Physiological↗
PubMed1996

Further development of hybrid functional electrical stimulation orthoses.

It is recognised that, in paraplegic walking with reciprocating gait orthoses, inadequate hip flexion angles may contribute to the low walking speed and high energy cost. In this study a new orthotic hip joint was developed which had a 2:1 flexion extension coupling ratio. Experiments on paraplegic subjects were conducted to evaluate this orthotic hip joint. It was found that the new hip joint was associated with a reduced energy cost and increased step length. A simple application of FES assisted hip flexion further increased walking speed and step length and reduced energy cost and crutch force impulse.

Adult↗
PubMed1996

Swing-through gait with free-knees produced by surface functional electrical stimulation.

The swing-through gait is often the gait of choice for those crutch walkers who can perform it. However, a practical (sufficiently low energy and sufficiently fast) gait is usually not achievable by paraplegic individuals with thoracic lesions. Functional electrical stimulation (FES) was used to assist three spinal cord injured (SCI) subjects with complete thoracic lesions at T11, T11 and T6 to ambulate with a swing-through gait patten. Eight channels of surface stimulation were used to bilaterally stimulate knee extensors, knee flexors, hip extensors and hip flexors. The stimulation sequence was controlled by a computer that implemented a finite-state, rule-based control strategy according to sensor inputs. Over a long, level walkway, the T11 subjects averaged 0.40 m/s and 0.38 m/s for distances of 56 m and 51 m; the T6 subject averaged 0.30 m/s for 43 m. Using a motion analysis system, the gait patterns of two of the subjects were compared to those of a trained, non-impaired subject. The SCI subjects spent more time in both double support phases (when both crutches and both feet contact the floor) than did the non-impaired subjects, leading to a loss of momentum and hence a slower and less efficient gait. In conclusion, an FES assisted swing-through gait is shown to be a potentially useful mode of FES gait.

Adult↗
PubMed1995

Evidence for a human spinal stepping generator.

Flexion reflexes elicited by surface stimulation in spinal cord-injured man have been used to provide limb flexion in gait restoration. In this study, the pattern of the flexion reflexes observed in one subject supports the theory that a spinal stepping generator exists in man.

Accidents, Traffic↗
PubMed1995

A body-worn gait analysis system for evaluating hemiplegic gait.

This paper describes a system for measuring the temporal parameters of hemiplegic gait. This system uses shoe insoles with sensors, acting as switches, placed under the heel, head of the first metatarsal, head of the fifth metatarsal and the big toe. This system is able to monitor gait for up to 10 min and can be used by the patient over any surface. Parameters for evaluating hemiplegic gait are defined, including scuffing during swing and the degree of inversion during stance.

Cerebrovascular Disorders↗
PubMed1994

Improved harness crutch to reduce upper limb effort in swing-through gait.

A novel crutch, the harness crutch, is described which reduces loading on the arms during the swing phase of swing-through gait. The device was fabricated by attaching a modified mountaineering harness by two side straps, to modified axillary crutches. The harness crutch was compared with the saddle crutch, described by Taylor in 1883. The saddle crutch produced pressures in excess of 500 mmHg in the perineal area; no pressures were produced in this area with the harness crutch. Ischial pressures produced by both systems were similar. In six out of eight non-impaired subjects, significantly more force was transmitted to the harness crutch (an average 47% of body weight) than to the saddle crutch (an average 40% of body weight). A comparison of the oxygen cost of swing-through gait was made between the harness crutch and unmodified axillary crutches; with the harness crutch oxygen cost was significantly lower (p < 0.01) and there were no significant differences in speed and stride length.

Arm↗
PubMed1993

Improving limb flexion in FES gait using the flexion withdrawal response for the spinal cord injured person.

In the restoration of gait for paraplegics using functional electrical stimulation, the method most commonly used to produce hip flexion for the swing phase of gait has been the elicitation of the flexion withdrawal response. Several problems have been noted with the response: there is a decrease in the magnitude of the hip flexion to repeated stimuli (habituation); long latency; and inhibition of the response when stimulated bilaterally. These have been characterized and methods for overcoming the problems tested. Results show that increasing stimulation frequency reduces latency. Habituation can be reduced in some subjects by multiplexing two sites of stimulation. Habituation can further be reduced by applying single high-intensity pulses and this has been used in a one-step-ahead controller for regulating hip flexion angle. Inhibition due to bilateral stimulation had been significantly reduced by altering the timing of the stimulation to the two legs.

Adult↗
PubMed1993

The role of functional electrical stimulation in the rehabilitation of patients with incomplete spinal cord injury--observed benefits during gait studies.

The benefits of a functional electrical stimulation (FES) gait programme were assessed in a group of 6 incomplete spinal cord injured subjects. Measurements were made of quadriceps spasticity, lower limb muscle strength, postural stability in standing, spatial and temporal values of gait, physiological cost of gait and independence in activities of daily living. The subjects were assessed before commencement of the programme and after a period of gait training using FES. The benefits derived as a result of the FES gait programme included a reduction in quadriceps tone, an increase in voluntary muscle strength, a decrease in the physiological cost of gait and an increase in stride length.

Activities of Daily Living↗
PubMed1991

Dishabituation of the flexion reflex in spinal cord-injured man and its application in the restoration of gait.

The flexion withdrawal reflex, evoked by surface electrical stimulation, has been used to provide hip flexion for the restoration of gait in paraplegics. A major limitation to its use has been the decrease in the magnitude of the response to repeated stimulation (habituation). In this study it was found that by using high intensity stimulation the response could be dishabituated. It was demonstrated that sufficient hip flexion for functional electrical stimulation-assisted gait was maintained using high intensity pulses in a one-step-ahead controller.

Adult↗