L. Schwirtlich

Clinical evaluation of Functional Electrical Therapy in acute hemiplegic subjects

This paper describes a clinical randomized single-blinded study of the effects of Functional Electrical Therapy (FET) on the paretic arms of subjects with acute hemiplegia caused by strokes. FET is an exercise program that comprises voluntary arm movements and opening, closing, holding, and releasing of objects that are assisted by a neural prosthesis (electrical stimulation). FET consisted of a 30 min everyday exercise for 3 consecutive weeks in addition to conventional therapy. Twenty-eight acute hemiplegic subjects participated in a 6 mo study. The subjects were divided into lower functioning groups (LFGs) and higher functioning groups (HFGs) based on their capacity to voluntarily extend the wrist and fingers against the gravity, and were randomly assigned to controls or FET groups. The outcomes included the Upper Extremity Function Test, the coordination of elbow and shoulder movements, spasticity of key muscles of the paretic arm, and Reduced Upper Extremity Motor Activity Log. FET and control groups showed a recovery trend in all outcome measures. The gains in FET groups were much larger compared with the gains in control groups. The speed of recovery in FET groups was substantially faster compared with the recovery rate in control groups during the first 3 weeks (treatment). The LFG subjects showed less improvement than the HFG in both the FET and control groups.

Control aspects of active-above-knee prosthesis

A methodology for control of an active above-knee prosthesis (AKP) is described. This approach is called Artificial Reflex Control (ARC), and depends on the use of production rules, so that the controller may be thought of as a leg movement expert. This control strategy is applicable to a variety of different gait modes. Automatic adaptation, according to the environment, and to the gait mode required, is based on heuristics related to human motor control.

DISTRIBUTED LOW-FREQUENCY FUNCTIONAL ELECTRICAL STIMULATION DELAYS MUSCLE FATIGUE COMPARED TO CONVENTIONAL STIMULATION

We present a low‐frequency stimulation method via multi‐pad electrodes for delaying muscle fatigue. We compared two protocols for muscle activation of the quadriceps in paraplegics. One protocol involved a large cathode at 30 HZ (HPR, high pulse‐rate), and the other involved four smaller cathodes at 16 HZ (LPR, low pulse‐rate). The treatment included 30‐min daily sessions for 20 days. One leg was treated with the HPR protocol and the other with the LPR protocol. Knee‐joint torque was measured before and after therapy to assess the time interval before the knee‐joint torque decreased to 70% of the initial value. The HPR therapy provided greater increases in muscle endurance and force in prolonged training. Yet the LPR stimulation produced less muscle fatigue compared to the HPR stimulation. The results suggest that HPR is the favored protocol for training, and LPR is better suited for prolonged stimulation. Muscle Nerve, 2010

Automatic vs hand-controlled walking of paraplegics.

A rule-based control and its application in functional electrical stimulation (FES) assisted walking of subjects with paraplegia are described in this paper. The design of rules for control comprises the following two steps: (1) determination of muscle activation patterns by using a fully customized spatial (3D) model of paraplegic walking, and (2) learning of rules, that is, correlation between the muscle activation patterns and kinematics of walking by means of an artificial neural network. The adopted FES system activated eight muscle groups with surface electrodes. The only joints allowing movement in the coronal plane were the hips, and externally controlled joints in sagittal plane were ankles, knees and hips. The simulation minimized the tracking error of the joint angles and the total activation of all eight muscles being stimulated. A radial-basis function artificial neural network was applied for learning of rules. Three automatically controlled modes (slow, near-normal, and near-ballistic) and hand-controlled walking were evaluated in six subjects with a complete spinal cord lesion (T8-T10). The performance of walking was assessed by the following: (1) energy consumption based on oxygen uptake, (2) physiological cost index, (3) maximum speed of walking, and (4) a questionnaire. The results showed that all modes of walking are achievable and that automatic control leads to more efficient and faster walking. The speed of walking achieved by automatic control was almost three times bigger compared with the speed of hand-controlled walking. The energy cost and rate decreased significantly when automatic control was applied; yet, they were still much bigger than the values measured in able-bodied subjects. The objective outcome measures suggest that the near-ballistic walking was the most effective, yet a questionnaire shows that most subjects preferred slow walking. The most likely reason for the preference of lower efficiency walking over the faster end energy efficient near-ballistic walking was that paraplegic patients had difficulties in synchronizing the voluntary movement of the trunk and arms to the artificially controlled movements of legs.

Detection and prediction of FES-induced fatigue

The estimation of externally elicited muscle forces is important for the better control of a functional electrical stimulation (FES)-assistive system. Various techniques of signal processing are presented, all with only one aim, to determine the correlation between the decrease of muscle force after continuous stimulation and surface recordings of the evoked potentials. Wrist flexor muscles were stimulated under isometric conditions, and surface electromyography (sEMG) was used to record wrist joint torque in both able-bodied and spinal cord injured volunteers. The joint torque was determined from recordings of the force generated by the wrist flexors, with the forearm immobilized. The sEMG was recorded utilizing a preamplifier with a stimulation artefact suppression circuitry. The signal was processed in the time and frequency domains, and analysed vs time, as well as in the state space formed by the wrist torque and evoked potential. The torque vs sEMG curves were used to establish the relationship that can be used for detection of the decrease of the force associated with FES-induced muscle fatigue. Among seven different techniques of sEMG processing the best correlation was found between the median frequency and force changes. The phase plane plot was fitted with an exponential curve, and the parameters obtained from the fitting were used to determine two events: prediction of the onset of fatigue and detection of fatigue. This suggests that it is possible to use the processed sEMG as a trigger signal to change the pattern of stimulation and allow the muscle to recover while resting, or to inform the user that the muscle force will soon drop rapidly. The recovery of the muscle force and sEMG was also analysed to learn more about the mechanisms that may be responsible for FES-induced fatigue. This technique offers simple on-off type feedback capability for fatigue detection in FES applications.

Functional Electrical Therapy (FET): Clinical Trial in Chronic Hemiplegic Subjects

Results from a clinical evaluation of Functional Electrical Therapy (FET) in chronic hemiplegic subjects are presented. FET is an intensive exercise that integrates voluntary maximized manipulation and augmented grasping by electrical stimulation of forearm and hand muscles. A total of 16 chronic hemiplegic subjects participated in a six‐month long study. The subjects were divided into lower and higher functioning groups based on their capacity to voluntarily extend the wrist and fingers against gravity. Functional Electrical Therapy comprised 30‐min electrically assisted daily exercise of the paretic arm for three consecutive weeks. The outcome measures included Upper Extremity Function Test (UEFT), the Drawing Test (DT), and Modified Ashworth Scale (MAS) of spasticity. The UEFT objectively measured the abilities to grasp and manipulate objects during typical daily activities. The DT measured the ability to coordinate shoulder and elbow joints. The MAS assessed the tone of the paretic arm muscles. The control group was formed from hemiplegic subjects that received FET in their acute phase of hemiplegia and were evaluated in our earlier study. The results showed that FET slightly increases the ability to reach and grasp, and decreases absolute mean spasticity of chronic hemiplegic subjects. The gains in UEFT and DT were measurable, yet not statistically significant. The trends of UEFT and DT scores during the therapy (three weeks) were steeper when compared with the trend during follow‐up (23 weeks). The changes of the trends during the study suggest that prolonged treatment could lead to bigger gains. We found standard deviations were increased towards the end of follow‐up suggesting individual differences in response to either the treatment or the disablement process.

Design and evaluation of the self-fitting modular orthosis (SFMO)

The standing and walking of paraplegics assisted by the SFMO has been evaluated. The oxygen uptake was used to estimate the metabolic energy cost per distance and time; ground reaction forces provided the information on the amount of the effort exerted by the upper extremities and trunk for propulsion; heart rate showed the amount of the cardiovascular stress; and the gait speed was used to assess the distance that the subject could walk. By comparing the results obtained using the SFMO with data from the literature, it was found that the SFMO is a valuable assistive system for the restoration of gait in paraplegics. The energy consumption, heart rate, speed of progression, and ability to negotiate environmental changes are similar to those obtained with other conventional bracing techniques. However, a soft interface, modular design, light weight, and self-adjustment of the mechanical axes to human joints make the SFMO an advantageous system. >

Lumbar Stimulation Belt for Therapy of Low-Back Pain

We developed the STIMBELT, an electrical stimulation system that comprises a lumbar belt with up to eight pairs of embedded electrodes and an eight-channel electronic stimulator. The STIMBELT is an assistive system for the treatment of low-back pain (LBP). We describe here technical details of the system and summarize the results of its application in individuals with subacute and chronic LBP. The direct goals of the treatment were to relieve pain, reduce muscle spasms, increase strength and range of motion, and educate individuals with LBP in reducing the chances of its reoccurrence. The outcome measures include: a Visual Analogue Scale (VAS), the Oswestry LBP Disability Questionnaire, the Short Form (SF)-12 health survey, and the Manual Muscle Test. The results indicate significant benefits for individuals who use the STIMBELT in addition to the conventional therapy as opposed to only the conventional therapy.

Gait training of poststroke patients assisted by the Walkaround (body postural support).

Improvement in gait abilities is one of the important goals of stroke rehabilitation. The Walkaround is a new postural assistance device for gait training, which allows an early start for gait training. This device provides body postural support (BPS) and trunk orientation by means of a lumbar belt that is connected to a powered rolling walker. We conducted a randomized, single-blinded, 4-week clinical trial of 22 subacute stroke patients with a follow-up period of 6 months. Patients were divided into two identically sized groups: the treatment group (BPS), which was assisted by the Walkaround, and the control (CON) group, which was assisted by conventional means (cane, therapist) during gait training. The objective of the study was to assess whether the Walkaround is more effective than conventional assistance during gait training. The outcome measures were as follows: Barthel index, Fugl-Meyer score for the lower extremities, Berg balance test, and gait speed. Changes in the outcome measures were significant for the Berg balance score after 6 months in both groups and in gait speed among the BPS group at the end of therapy and after 6 months (P<0.05) compared with the same outcome measures at the beginning of the trial. Significant differences were found in gait speed and Berg balance test scores after 4 weeks and in gait speed after 6 months (P<0.05) between the BPS and the CON groups. The results suggest that added postural support by the Walkaround led to limited yet significant changes in gait speed and balance control.

Drawing test for assessment of arm functionality

Goal: We recently introduced the Drawing Test (DT) for the determination of coordination abilities in upper extremities (Eder et al., 2005; Popovic et al., 2002). The aim of the present study was to assess contributions of modified spatial frameworks to the kinematics of tracking movements by individuals with hemiplegia. The side of infarction and the dexterity before stroke are crucial in the rehabilitation treatment. Methods: Twenty acute and sub-acute individuals with cerebro-vascular infarction tracked the outline of a 20 · 20 cm square presented on a digitizing tablet with both arm (DT). The kinematics of the hand trajectory was compared to the outline of square. Results: Ninety percentage of patients (9 out of 10) with hemiplegia in their non-skilled arm had kinematic parameters in skilled arm similar to the desired one, while 60% of patients (6 out of 10) were unable to draw the square with their skilled arm affected with hemiplegia. Conclusions: Drawing test could be used in clinical settings to assess skilled arm functionality. Acknowledgements: Danish National Research Foundation, Denmark and the Ministry of Science and Environmental Protection of Serbia.