Home-based functional electrical stimulation rescues permanently denervated muscles in paraplegic patients with complete lower motor neuron lesion.

BACKGROUND: Spinal cord injury causes muscle wasting and loss of function, which are especially severe after complete and permanent damage to lower motor neurons. In a previous cross-sectional study, long-standing denervated muscles were rescued by home-based functional electrical stimulation (h-bFES) training. OBJECTIVE: To confirm results by a 2-year longitudinal prospective study of 25 patients with complete conus/cauda equina lesions. METHODS: Denervated leg muscles were stimulated by h-bFES using a custom-designed stimulator and large surface electrodes. Muscle mass, force, and structure were determined before and after 2 years of h-bFES using computed tomography, measurements of knee torque during stimulation, and muscle biopsies analyzed by histology and electron microscopy. RESULTS: Twenty of 25 patients completed the 2-year h-bFES program, which resulted in (a) a 35% cross-sectional increase in area of the quadriceps muscle from 28.2 ± 8.1 to 38.1 ± 12.7 cm(2) (P < .001), a 75% increase in mean diameter of muscle fibers from 16.6 ± 14.3 to 29.1 ± 23.3 µm (P < .001), and improvements of the ultrastructural organization of contractile material; and (b) a 1187% increase in force output during electrical stimulation from 0.8 ± 1.3 to 10.3 ± 8.1 N m (P < .001). The recovery of quadriceps force was sufficient to allow 25% of the subjects to perform FES-assisted stand-up exercises. CONCLUSIONS: Home-based FES of denervated muscle is an effective home therapy that results in rescue of muscle mass and tetanic contractility. Important immediate benefits for the patients are the improved cosmetic appearance of lower extremities and the enhanced cushioning effect for seating.

Training program and additional electric muscle stimulation for patellofemoral pain syndrome: a pilot study.

OBJECTIVES: To evaluate the beneficial effect of training in patients with patellofemoral pain syndrome (PFPS) and influence of additional electric muscle stimulation (EMS) of the knee extensor muscles. DESIGN: A randomized clinical trial. SETTING: Supervised physiotherapy (PT) training and home-based EMS. PARTICIPANTS: Patients (N=38; 14 men, 24 women) with bilateral PFPS. INTERVENTIONS: One group (PT) received supervised PT training for 12 weeks. The other received PT and EMS. The stimulation protocol was applied to the knee extensors for 20 minutes, 2 times daily, 5 times a week for 12 weeks at 40 Hz, with a pulse duration of .2 6ms, at 5 seconds on and 10 seconds off. Maximal tolerable stimulation intensity was up to 80 mA. MAIN OUTCOME MEASURES: Patellofemoral pain assessment with visual analog scale during activities of daily life, Kujala patellofemoral score, and isometric strength measurement before and after 12 weeks treatment as well as after 1 year. RESULTS: Thirty-six patients completed the 12-week follow-up. There was a statistically significant reduction of pain in both groups (PT group, P=.003; PT and EMS group, P<.001) and significant improvement of the Kujala score in both groups (PT group, P<.001; PT and EMS group, P<.001) after 12 weeks of treatment with improvement of function and reduction of pain at the 1-year follow-up. The difference between the 2 treatment groups was statistically not significant. We could not measure any significant change in isometric knee extensor strength in either group. CONCLUSIONS: A supervised PT program can reduce pain and improve function in patients with PFPS. We did not detect a significant additional effect of EMS with the protocol described previously.

In vivo assessment of conduction velocity and refractory period of denervated muscle fibers.

Stimulation needle electromyography was used to study the muscle fiber conduction velocity and refractory period in 4 patients with long-term denervation of the lower limb muscles due to lesion of the conus cauda or cauda equina (2 untrained and 2 trained by functional electrical stimulation). In untrained patients, the results demonstrated that propagation velocity is reduced and refractory period of the muscle fiber is increased with time of denervation. The patients performing electrical stimulation training showed higher conduction velocities and reduced refractory period despite longer lasting denervation. This suggests that electrical stimulation training is effective to improve the electrical properties of the muscle fiber. Since the obtained data show a good correlation to other clinical tests and biopsy investigations, this method could serve as an additional measurement technique to specify the status of the denervated muscle. Further animal experiments and clinical studies are necessary to proof the results in comparison to more invasive established techniques.

Electrical stimulation of denervated muscles: first results of a clinical study.

To evaluate the effects of electrical stimulation on denervated muscles in spinal cord injured humans, the EU Project RISE was started in 2001. The aims of this project are: to design and build sufficient stimulators; to develop stimulation protocols by means of mathematical models, animal experiments, and practice in humans with denervated lower limbs; to develop examination methods and devices for evaluation of electrical stimulation training effects; and to acquire basic scientific knowledge on denervated and stimulated denervated muscle. In the clinical study 27 spinal cord injured individuals were included, furthermore 13 pilot patients participated. After a series of initial examinations they underwent an electrical stimulation program for their denervated lower limb muscles. Some of the patients have already follow up examinations. A marked increase of muscle mass and quality was observed, the trophic situation of the denervated lower limbs had improved obviously.

Denervated muscles in humans: limitations and problems of currently used functional electrical stimulation training protocols.

Prior clinical work showed that electrical stimulation therapy with exponential current is able to slow down atrophy and maintain the muscle during nonpermanent flaccid paralysis. However, exponential currents are not sufficient for long-term therapy of denervated degenerated muscles (DDMs). We initiated a European research project investigating the rehabilitation strategies in humans, but also studying the underlying basic scientific knowledge of muscle regeneration from satellite cells or myoblast activity in animal experiments. In our prior study, we were able to show that high-intensity stimulation of DDMs is possible. At the beginning of training, only single muscle twitches can be elicited by biphasic pulses with durations of 120-150 ms. Later, tetanic contraction of the muscle with special stimulation parameters (pulse duration of 30-50 ms, stimulation frequency of 16-25 Hz, pulse amplitudes of up to 250 mA) can improve the structural and metabolic state of the DDMs. Because there are no nerve endings for conduction of stimuli, large-size, anatomically shaped electrodes are used. This ensures an even contraction of the whole muscle. Contrary to the current clinical knowledge, we were able to stimulate and train denervated muscle 15-20 years after denervation. The estimated amount of muscle fibers that have to be restored is about 2-4 million fibers in each m. quadriceps. To rebuild such a large number of muscle fibers takes up to 3-4 years. Despite constant stimulation parameters and training protocols, there is a high variation in the developed contraction force and fatigue resistance of the muscle during the first years of functional electrical stimulation.