Reconstruction of upper limb motor function using functional electrical stimulation (FES).

Functional electrical stimulation (FES) techniques progress by adopting the developments in computers and engineering, but complete functional reconstruction is not yet possible to be achieved. The attachment of the devices to the body can be complex, and training to handle FES is not easy. FES systems are expensive and their coverage by medical insurance is limited with the exception of a few systems. Hence, recognition of FES by the medical community is limited and as a result, it is not a common therapy. However, FES is the main method available for reconstruction of motor function, at present. The improvement in activities of daily living (ADL) of patients using FES may not only improve the patient's quality of life (QOL) but also reduce the burden to persons who look after them, and hence, secure a valuable work force. The medical insurance should support the use of FES and reduce the patients' financial burden. Studies and developments based on a close collaboration of users (patients and care-givers), persons involved in therapy (doctors and nurses), and manufactures (engineers and technicians) are necessary. In addition to FES, other methods such as therapeutic electrical stimulation (TES) for prevention of atrophy and spasms of paralytic limbs show the therapeutic potential of neuromodulation.

Dorsal column stimulation for persistent vegetative state.

Dorsal column stimulation (DCS) is described as a therapy for persistent deterioration of consciousness. The mechanism of its effect has not yet been elucidated. Various other methods, such as deep brain stimulation of the CM-p f complex, vagus nerve stimulation, and musical functional therapy, are being investigated as potential treatments of this problem. We present our series of DCS for persistent vegetative state and review the potential mechanisms of action and the relevant literature.

Carpal instability in the weight-bearing upper extremity.

The prevalence of carpal instability in a paraplegic population was investigated to establish an association between chronic repetitive stress on the wrist and the development of such instability. Nine of 162 paraplegic patients had static carpal instability and no history of an acute injury of the wrist. The predominant pattern of instability, found in eleven wrists (six patients), was non-dissociative volar intercalated segmental instability. The prevalence of carpal instability increased with the duration of weight-bearing on the upper extremity. Eighteen per cent of the patients in whom the spinal cord injury had occurred more than twenty years before the study had carpal instability. Carpal instability in these weight-bearing upper extremities and the increase in its prevalence with the duration of the forces across the wrist demonstrate an association between chronic repetitive stress on the wrist and carpal instability.

An implanted upper-extremity neuroprosthesis. Follow-up of five patients.

An implanted neuroprosthesis supplying functional neuromuscular stimulation was used to provide grasp and release to tetraplegic individuals. This article describes the results, at a minimum of three years, for the first five patients to have operative implantation of an eight-channel stimulator-receiver. All of the patients had a clinically complete spinal cord injury with motor function remaining at the level of the fifth or sixth cervical nerve root. In addition to implantation of the stimulator system, each patient had augmentative operations on the hand to improve function. The procedures included tendon transfers, side-to-side tendon anastomoses, arthrodesis of the interphalangeal joint of the thumb, and rotational osteotomy of the radius. The neuroprosthesis provides two grasp patterns controlled by voluntary motion of the shoulder or wrist. Functional evaluations included measurement of pinch force, a grasp-release test, evaluation of the level of functional independence, and usage surveys. Pinch force ranged from eight to twenty-five newtons. All five patients demonstrated functional grasp patterns, had increased independence, and were able to use the neuroprosthesis at home on a regular basis. The implanted stimulator has proved to be safe and reliable, with seven years as the longest time in situ at the time of writing.

Restoration of pronosupination control by FNS in tetraplegia--experimental and biomechanical evaluation of feasibility.

Individuals with C5/C6 tetraplegia lack voluntary control of the forearm pronators. We evaluated the feasibility of restoring forearm pronation/supination control using an electrically activated pronator opposed by voluntary supination. To this end, we measured the electrically produced pronation moments of subjects with tetraplegia. The maximal pronation moment achieved by stimulating the pronator quadratus ranged from 30 to 100 N cm in three forearms of two subjects. These moments were sufficient to produce forearm pronation in all three forearms. Voluntary control of pronosupination during constant pronator stimulation was achieved by having the subject voluntarily supinate or relax to change the balance of rotational torques acting on the forearm. In all cases, the subjects were able to supinate voluntarily against the continuously stimulated pronator, producing intermediate angles between full pronation and full supination. We also observed under some conditions that subjects could voluntarily pronate and supinate even without pronator stimulation. Using a biomechanical model, we show how pronation can be initiated from a supinated position using the brachioradialis, with gravity completing the pronation. This method of pronation without stimulation is extremely sensitive to the orientation of the forearm in the gravitational field, and thus is not a widely applicable technique. We conclude that forearm pronosupination via Functional Neuromuscular Stimulation is feasible, and would provide subjects the ability to pronate without the assistance of gravity.

Cognitive feedback for use with FES upper extremity neuroprostheses.

This paper describes the development of two sensory substitutions systems that provide cognitive feedback for FES hand grasp restoration neuroprostheses. One system uses an array of five electrodes to provide machine status information and a spatially encoded representation of the command signal that a quadriplegic individual generates to achieve proportional grasp control. Only one electrode site is active at any given instant, and a second informational channel is superimposed on the spatial position channel by modulating the frequency of the stimulus pulses. The frequency modulated feedback channel signals six levels of force developed at the finger tips during prehension activities. The second sensory system is an integral part of an implanted FES system and utilizes a single subdermally placed electrode to display machine status information and a five-level frequency code for feedback of the user generated grasp control signal. The multielectrode feedback system was implemented for laboratory studies using surface mounted electrodes, although its design will ultimately incorporate subdermal electrodes to provide a highly cosmetic and unencumbering system. An evaluation of the effectiveness of grasp force and command signal feedback provided by this multielectrode system in assisting an FES hand system user to regulate grasp force during a laboratory task, showed increased consistency of performance and an economy of grasp effort between 25 and 30%. Alternative strategies for feedback information and coding algorithms are discussed.

Elbow extension in the C5 quadriplegic using functional neuromuscular stimulation.

A system has been designed to provide overhead reach in C5/6 quadriplegic subjects using functional neuromuscular stimulation (FNS) for control of the triceps muscle. The system uses the position of the arm in space as the input command, relieving the user from having to supply a conscious command signal. By measuring the position of the arm, the magnitude of the gravitational and passive torques opposing elbow extension can be calculated. This torque is counteracted by electrical activation of the triceps muscle, with the appropriate stimulus parameters determined from the recruitment characteristics of each electrode. Sufficient stimulus is applied to produce full elbow extension. Intermediate elbow angles are achieved using voluntary elbow flexor torque to counteract the effects of the stimulation. System performance was tested in two subjects. Subjects were asked to reach targets with and without stimulation, with loads up to 500 g in the hand. Using the FNS system, subjects were able to successfully reach the target positions above the horizontal that were inaccessible without stimulation.

Electrode characterization for functional application to upper extremity FNS.

A quantitative method has been developed to characterize the isometric force vectors of electrically stimulated paralyzed muscles of the thumb. The vectorial force output as a function of the stimulus level was measured for individual electrode/muscle combinations in a number of intramuscular and epimysial electrodes implanted in paralyzed thenar muscles of cervical level spinal cord injury subejcts. Vectors are used to determine the output characteristics of each electrode/muscle combination. The characteristics studied include: the strength of the contraction, the stimulus level at which fibers from other muscles are stimulated, the recruitment gain of force, dependency of the output on the skeletal position, and the direction of force produced. These characteristics can then be used to select stimulus parameters to produce coordinated hand motion and force generation by functional neuromuscular stimulation (FNS). The range of muscle force and direction for each electrode/muscle combination showed considerable variation between subjects and between electrodes in the same subject. This variation is primarily due to differences in electrode placement within the muscle. Comparison between intramuscular and epimysial electrodes demonstrated similar characteristics in the force vector output. Preliminary results show the potential for using the force vector output to predict the cocontracted output of two muscles.

Synthesis of hand grasp using functional neuromuscular stimulation.

A functional neuromuscular stimulation system has been developed to provide grasp-release function in quadriplegic individuals. A single command input from the subject controls the stimulus levels to a number of electrodes, thus simultaneously activating several muscles. A method for synthesizing the command input to stimulus output relationship has been developed. The first step involves electrode profiling, which is a method for characterizing the output of an individual electrode/muscle combination. The electrodes are then grouped according to function and a set of rule based procedures is used to synthesize the basic grasp parameters. Results are presented demonstrating the output from lateral and palmar grasps developed by this method. The method has successfully resulted in grasping patterns that can be utilized functionally. Limitations of the method and future improvements are discussed.

Functional electrical stimulation (FES) for spinal cord injury.

Restoration of respiratory motion by stimulation of the phrenic nerve was investigated. Respiratory motion was restored successfully by introducing a breathing pacemaker to a patient with respiratory disturbance due to upper cervical spinal cord injury. Breathing pacemakers are considered to be more similar to physiological conditions compared to mechanical ventilators. Although the system is very expensive, its cost effectiveness may be excellent, provided that it can be used for long hours each day over an extended period. The system is effective in improving patient QOL because it dramatically increases patient mobility. From these findings, it is concluded that breathing pacemakers should be used more frequently in Japan, and that various forms of support are necessary to cope with economic and other concerns.

Congenital vascular abnormalities in Okihiro's syndrome--a case report.

In this report, the authors describe the angiographic findings in the forearm and hand in Okihiro's syndrome. To the best of their knowledge, it has not been described before. Okihiro et al described hypoplasia of the thenar eminence in association with a congenital disorder of ocular motility previously reported in Duane's syndrome.

New concepts on treatment of the upper limb in the tetraplegic. Surgical restoration and functional neuromuscular stimulation.

Today, many tetraplegics benefit from surgical restoration of hand function. New concepts of functional neuromuscular stimulation are impacting the care of those patients who are more severely paralyzed and are unable to benefit from surgery alone. Grasp, pinch, wrist extension, and elbow extension restoration are now possible.

Reduction of costs of disability using neuroprostheses.

The lifetime costs associated with spinal cord injury are substantial. Assistive technology that reduces complications, increases independence, or decreases the need for attendant services can provide economic as well as medical or functional benefit. This study describes two approaches for estimating the economic consequences of implanted neuroprostheses utilizing functional electrical stimulation. Life care plan analysis was used to estimate the costs of bladder and bowel care with and without a device restoring bladder and bowel function and to compare these with the costs of implementing the device. For a neuroprosthesis restoring hand grasp, the costs of implementation were compared to the potential savings in attendant care costs that could be achieved by the use of the device. The results indicate that the costs of implementing the bladder and bowel system would be recovered in 5 years, primarily from reduced costs of supplies, medications, and procedures. The costs of the hand grasp neuroprosthesis would be recovered over the lifetime of the user if attendant time was reduced only 2 hours per day and in a shorter time if attendant care was further reduced. Neither analysis includes valuation of the quality of life, which is further enhanced by the neuroprostheses through restoration of greater independence and dignity. Our results demonstrate that implantable neuroprosthetic systems provide good health care value in addition to improved independence for the disabled individual.

Neuroprostheses for the upper extremity.

Functional electrical stimulation (FES) neuroprostheses can be used to replace lost motor and sensory function in persons with neurological disorders. FES technology has subsequently been shown effective and safe in restoring hand function in adults with spinal cord injury. The freehand system consists of an implanted receiver-stimulator, an external shoulder position sensor, and an external control unit. Commands are originated by voluntary movement of the contralateral shoulder and are measured by the sensor. There are several types of electrodes: epimysial, intramuscular, nerve cuff, and intraneural. Neuroprostheses are recommended within the context of all available reconstructive options for the upper limbs. Voluntary tendon transfers are the first choice. The clinical outcomes as measured by improvement on scales of impairment, activities of daily living, and satisfaction are rewarding. The next step in improvement of the motor function of person with spinal cord injury will be the addition of a controllable second upper extremity and the elimination of additional external hardware.

Pin reduction and fixation of volar fracture fragments of distal radius fractures via the flexor carpi radialis tendon.

BACKGROUND: The objective of this study was to evaluate a technique for reduction and stabilization of residually displaced volar fragments in intraarticular distal radius fractures. METHODS: A consecutive series of patients with AO type C3 distal radius fractures treated by one surgeon were studied. Percutaneously placed pins were placed through the flexor carpi radialis tendon to reduce and stabilize volar fracture fragments of distal radius fractures when closed reduction was unsuccessful. The goal of treatment was to achieve less than 2 mm of articular congruity. Postoperative physiotherapy was protocol-based. A validated outcome measurement was used to evaluate patients. RESULTS: Of 117 patients, 10 met the inclusion criteria. In all patients, a successful reduction of the volar fragment was achieved with less than 2 mm of residual articular step-off. Reduction was maintained in 8 patients. Follow-up averaged 29 months, and there were no complications associated with the technique. All patients were satisfied with the treatment. CONCLUSION: Although the final outcome of patients with this type of fracture depends on many factors, in the small series of patients described, a satisfactory reduction was possible using the describe technique. Transtendinous pinning is a new, undescribed technique that is useful in the treatment of such specific injuries.

Stiffness regulation by reflex action in the normal human hand.

1. The torque and electromyographic (EMG) responses to stretch of the first dorsal interosseous muscle (externally imposed joint rotation) were recorded in five normal human subjects. The total measured stiffness was decomposed into three individual stiffness components; passive, intrinsic, and reflex. 2. The passive component was measured with the subject relaxed. Compared with the total response at the height of short latency reflex action, the passive component comprised 6-32% of the total stiffness recorded at an initial torque level of 20 N-cm [15-39% maximum voluntary contraction (MVC)]. The passive response also reflected a significant acceleration component during rapid joint rotation due primarily to digit inertia. 3. The intrinsic stiffness component, attributed to the mechanical properties of the active muscle fibers, was estimated by recording the response to joint rotation with the muscle activated in a distributed manner using a single intramuscular electrode. The dynamic stiffness (measured at the end of a ramp displacement) and the static stiffness (measured 1 s after onset of the displacement) both scaled in a straight-line manner with the initial torque level. This relationship held whether the initial torque level was varied by changes in recruitment or temporal summation. 4. The reflex component was calculated by subtracting the passive and the estimated intrinsic component from the total response. The timing of the EMG signal recorded during measurement of the total response and the fact that the estimated intrinsic component matched the total active response over the first 65-100 ms after displacement onset supported the case that this was the true reflex component. The peak of the reflex activity occurred 155-360 ms after displacement onset and, at this peak, accounted for 18-44% of the total stiffness (at an initial torque level of 20 N-cm). 5. Over the low to intermediate torque range employed, we observed that both intrinsic muscle stiffness and total stiffness increased with initial torque. Because total stiffness increased more rapidly than intrinsic stiffness, the difference between them (equal to reflex stiffness) also increased with initial torque. Furthermore, when the total active response trials (passive stiffness removed) were shifted vertically so that the initial torque levels matched, it was seen that reflex action did not reduce the stiffness range to less than the stiffness range encountered for the intrinsic response alone.(ABSTRACT TRUNCATED AT 400 WORDS)

Determination of muscle-tendon unit properties during tendon transfer.

Data on passive lengthening and active shortening from electrical stimulation to give a total functional excursion are presented. Length-tension characteristics of certain muscles used for transfer are given. Electrical stimulation of the newly transferred tendon gives useful information that is reproducible. This new knowledge obtained at operation is an important adjunct to the traditional techniques and provides helpful information in performing better procedures.