M.H. Granat

A practical gait analysis system using gyroscopes

This study investigated the possibility of using uni-axial gyroscopes to develop a simple portable gait analysis system. Gyroscopes were attached on the skin surface of the shank and thigh segments and the angular velocity for each segment was recorded in each segment. Segment inclinations and knee angle were derived from segment angular velocities. The angular signals from a motion analysis system were used to evaluate the angular velocities and the derived signals from the gyroscopes. There was a good correlation between these signals. When performing a turn the signals of segment inclination and knee angle drifted. Two methods were used to solve this: automatically resetting the system to re-initialise the angle in each gait cycle, and high-pass filtering. They both successfully corrected this drift. A single gyroscope on the shank segment could provide information on segment inclination range, cadence, number of steps, and an estimation of stride length and walking speed.

Electrical Stimulation of Wrist Extensors in Poststroke Hemiplegia

BACKGROUND AND PURPOSE It has been suggested that cyclic neuromuscular electrical stimulation (ES) may enhance motor recovery after stroke. We have investigated the effects of ES of the wrist extensors on impairment of wrist function and on upper-limb disability in patients being rehabilitated after acute stroke. METHODS We recruited 60 hemiparetic patients (mean age, 68 years) 2 to 4 weeks after stroke into a randomized, controlled, parallel-group study comparing standard rehabilitation treatment with standard treatment plus ES of wrist extensors (3 times 30 minutes daily for 8 weeks). Isometric strength of wrist extensors was measured using a device built for that purpose. Upper-limb disability was assessed with use of the Action Research Arm Test (ARAT). Observations were continued for 32 weeks (24 weeks after the finish of ES or the control intervention phase). RESULTS The change in isometric strength of wrist extensors (at an angle of 0 degrees extension) was significantly greater in the ES group than the control group at both 8 and 32 weeks (P=0.004, P=0.014 by Mann Whitney U test). At week 8 the grasp and grip subscores of the ARAT increased significantly in the ES group compared with that in the control group (P=0.013 and P=0.02, respectively); a similar trend was seen for the total ARAT score (P=0.11). In the subgroup of 33 patients with some residual wrist extensor strength at study entry (moment at 0 degrees extension >0), the ARAT total score had increased at week 8 by a mean of 21.1 (SD, 12.7) in the ES group compared with 10.3 (SD, 9.0) in the control group (P=0.024, Mann Whitney U test); however, at 32 weeks the differences between these 2 subgroups were no longer statistically significant. CONCLUSIONS ES of the wrist extensors enhances the recovery of isometric wrist extensor strength in hemiparetic stroke patients. Upper-limb disability was reduced after 8 weeks of ES therapy, with benefits most apparent in those with some residual motor function at the wrist. However, it is not clear how long the improvements in upper-limb disability are maintained after ES is discontinued.

Prevention of Shoulder Subluxation After Stroke With Electrical Stimulation

BACKGROUND AND PURPOSE Subluxation is a significant problem in poststroke hemiplegia, resulting in pain and loss of function. Current treatments are not proved and not considered effective. It has been demonstrated that cyclical electrical stimulation of the shoulder muscles can reduce existing subluxation. The purpose of this study was to determine whether electrical stimulation could prevent subluxation in both the short and long terms. METHODS A prospective, randomized controlled study was used to determine the efficacy of electrical stimulation in preventing shoulder subluxation in patients after cerebrovascular accidents. Forty patients were selected and randomly assigned to a control or treatment group. They had their first assessment within 48 hours of their stroke, and those in the treatment group were immediately put on a regimen of electrical stimulation for 4 weeks. All patients were assessed at 4 weeks after stroke and then again at 12 weeks after stroke. Assessments were made of shoulder subluxation, pain, and motor control. RESULTS The treatment group had significantly less subluxation and pain after the treatment period, but at the end of the follow-up period there were no significant differences between the 2 groups. CONCLUSIONS Electrical stimulation can prevent shoulder subluxation, but this effect was not maintained after the withdrawal of treatment.

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.

Contractures in the post-stroke wrist: a pilot study of its time course of development and its association with upper limb recovery

Background: Contractures are common in a stroke population, yet there is little information on the time course of development. Objectives: Investigate quantitatively changes associated with contracture formation in an acute stroke population. Study design: Longitudinal study on 22 subjects who were 2–4 weeks post stroke. Outcome measures: Contractures were assessed by quantifying the resting posture, resistance to passive movement and passive range of movement. Upper limb function was measured using the Action Research Arm Test and the Nine-Hole Peg Test. Active range of extension, wrist extension strength (isometric), grip strength and neglect were also measured. Repeated measures: Following an initial assessment, repeated measurements were taken at 4, 8, 20 and 32 weeks after recruitment. Results: Two distinct subgroups, one capable of some functional movement (F group; 8 subjects) and another which was not (NF group; 14 subjects), were identified at the start of the study. The NF group showed changes associated with contracture formation at the wrist, i.e., reduction in the passive range of movement, an increase in resistance to passive movement and a worsening of the flexion posture. Changes were observed from the time of recruitment even though neglect improved. The F group showed improvements in upper limb function and there was no evidence to support contracture formation. Conclusions: Subjects most prone to contracture formation were those who showed no signs of early functional recovery (2–4 weeks after the stroke). Changes consistent with adaptive shortening were seen from week 4 of the study period.

Intention detection using a neuro-fuzzy EMG classifier

One of the most important factors in prosthetic and orthotic controllers is the ability to detect the intention of the person to perform a certain activity such as standing up, quiet standing, walking, and sitting down. For these applications, detecting the intention of the person to perform an activity relieves them from the burden of conscious effort in operating the system. Electromyography (EMG) has been used extensively for intention detection and can be considered a bandlimited stochastic process with Gaussian distribution and zero mean, which has varying spectral characteristics in time. Various EMG features have been used for intention detection including the number of zero crossings, the EMG frequency characteristics, and the mean absolute values. There are a number of drawbacks that have been associated with these methods such as the high electrode sensitivity to electrode displacement, low recognition rate, and a perceivable delay in control. In this article we discuss a technique for EMG applications that decreases global delay time and improves time spectral analysis. The technique is aimed at improving the Gabor matching pursuit (GMP) algorithm through the use of genetic algorithms. The key stage of this design feeds EMG features to a neuro-fuzzy classifier that can be designed to detect the intention of the patient.

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.

Effect of functional electrical stimulation, applied during walking, on gait in spastic cerebral palsy

This study investigated the effect of functional electrical stimulation (FES), applied during walking, on the gait of children with spastic cerebral palsy (CP). Eight children (five males, three females; mean age 13y 2mo, SD 2y 2m; range 8y 11mo to 17y 6mo) diagnosed with diplegic (n=6) or hemiplegic (n=2) spastic CP completed the study. All participants were ambulant. Core FES strategies based on common CP gait deviations were developed and tailored for each child. FES strategies for each child were evaluated in two separate test sessions. Effects of FES on gait were monitored with three‐dimensional motion analysis. Within each test session each childs gait was assessed when walking without FES (phase A) and with FES (phase B). An A‐B‐A‐B test sequence was employed allowing the effects of the withdrawal and reinstatement of FES to be assessed. All children performed 10 consecutive walks in each phase. Replication of this sequence on a separate day allowed the repeatability of the intervention to be evaluated. Outcome measures, including summary variables of kinematic data, temporal‐spatial variables, and mode of initial contact, were predefined for each child and targets for clinical significance were set for these outcome measures. Comparisons were performed between these targets and the actual outcomes. Consistent clinically significant improvements were recorded for three children: one child showed some improvement that was statistically significant but not clinically significant. Results for one child were mixed. There was no change in the remaining three children. Gait analysis proved to be a useful tool in both developing and determining the effectiveness of FES strategies.

Therapeutic effects of functional electrical stimulation of the upper limb of eight children with cerebral palsy

Functional electrical stimulation (FES) of the upper limb has been used for patients with a variety of neurological conditions, although few studies have been conducted on its use on the upper limb of children with cerebral palsy (CP). The aim of this study was to investigate the effect of cyclic FES on the wrist extensor muscles of a group of eight children (five boys, three girls) with hemiplegic CP (mean age 10 years). The study design involved a baseline (3 weeks), treatment (6 weeks), and follow‐up (6 weeks). FES was applied for 30 minutes daily during the treatment period of the study. Improvements in hand function (p≤0.039) and active wrist extension (p=0.031) were observed at the end of the treatment period. These improvements were largely maintained until the end of the follow‐up period. No significant change was observed in the measurements of wrist extension moment during the treatment period (p=0.274). Hand function in this group of children improved after they were exposed to FES of wrist extensor muscles. This suggests that FES could become a useful adjunct therapy to complement existing management strategies available for this patient population.

Virtual artificial sensor technique for functional electrical stimulation

In the control of Functional Electrical Stimulation (FES) gait systems artificial sensors are used to provide the controller with feedback information. The sensors used range in complexity from simple heel or hand switches to tri-axial accelerometers. There are three basic problems connected with the selection of sensors: the type(s) of sensor(s) to be used, the number of sensors required and the optimum location of the sensor set. In general the choice of the sensor sets has been based on the availability of actual sensors and the experts understanding of where these sensors should be located. Using motion analysis data it is possible to construct an almost unlimited number of virtual sensors on any location of the body surface. Our aim was to develop this technique for construction of virtual sensors and compare these virtual sensors with their physical counterparts. Virtual goniometers, inclinometers, accelerometers and foot switches were constructed and compared with their physical counterparts. In addition visualisation tools were developed to aid in the choice of sensor location. There was a very good correlation between all the virtual and physical sensors. This technique gives flexibility to place virtual sensors almost anywhere on the body surface and also allows the construction of novel sensors.