Upper extremity neuroprostheses using functional electrical stimulation.
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Activities of Daily Living↗
Biomedical subjects
M W Keith
Publications and source records attributed to M W Keith.
Development of a quantitative hand grasp and release test for patients with tetraplegia using a hand neuroprosthesis.
We developed a quantitative grasp and release test for assessing a hand neuroprosthesis in C5 and C6 level tetraplegic patients. The objectives were (1) to determine if a patient's hand performance with the neuroprosthesis exceeded a defined, clinically acceptable baseline, (2) to compare performance with and without the neuroprosthesis, (3) to measure the consistency of performance over time, and (4) to compare performance among patients. In the test, patients grasped, moved, and released one of six different objects as many times as possible in five 30-second trials for each object, with and without the neuroprosthesis. Unlike earlier tests, the objects and the task were chosen to span a range of difficulties appropriate for C5 and C6 tetraplegic patients using a hand neuroprosthesis. Data from five patients showed that performance with the neuroprosthesis was above the baseline; performance improved with the neuroprosthesis, although it was not generally consistent across sessions; and the neuroprosthesis helped C5 patients manipulate most objects and helped C6 patients primarily with more difficult objects.
Adult↗
Bipolar latissimus dorsi transposition and functional neuromuscular stimulation to restore elbow flexion in an individual with C4 quadriplegia and C5 denervation.
A bipolar latissimus dorsi transposition was performed on a 17-year-old male patient with a C4 spinal cord injury and complete peripheral denervation at C5. Electrical stimulation of the paralyzed but excitable latissimus dorsi provided elbow flexion that could not be achieved with the paralyzed and denervated elbow flexors. The muscle was attached from the coracoid to the ulna allowing the elbow to be flexed with the forearm and wrist maintained in the neutral position. Following a 6-week immobilization period, the transposed muscle was exercised daily with intramuscular stimulation to increase both strength and endurance. By the fourth month after surgery, the subject could control elbow flexion proportionally with contralateral shoulder elevation using a shoulder position transducer. Functionally, the subject was able to use the neuroprosthetic system to bring his hand to his mouth and feed himself with the aid of a universal cuff and a support to stabilize the shoulder.
Adolescent↗
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.
Algorithms↗
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.
Electric Stimulation↗
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)
Adult↗
Functional evaluation of quadriplegic patients using a hand neuroprosthesis.
The objective of this retrospective study was to compare the abilities of quadriplegic patients to complete activities of daily living with and without the use of a portable hand neuroprosthesis. The neuroprosthesis provided synthetic hand grasp through functional neuromuscular stimulation of paralyzed forearm and hand muscles. Data were obtained from telephone interviews, patient records, and videotapes. Twenty-two quadriplegic patients were included in the study; 15 were functional at a C5 spinal cord injury level and seven at a C6 level. The median success rate (ie, the percentage of patients who could complete each activity) across the ten activities was 89% with the hand neuroprosthesis but was only 49% without the hand neuroprosthesis. All patients could perform more tasks when the neuroprosthesis was used, although the relative improvement of C5 patients was larger than that of C6 patients.
Activities of Daily Living↗
Implantable functional neuromuscular stimulation in the tetraplegic hand.
Functional neuromuscular stimulation of the upper extremity provides manipulative capacity to persons with high level tetraplegia who have insufficient voluntary muscles available for tendon transfer surgery. We report an enhancement of the technique to include surgical implantation of a multichannel receiver-stimulator, sensory feedback stimulation, and tendon transfers. Tendon transfers were done with spastic, rather than voluntary motors employing standard surgical techniques. The system described has been operational for more than 1 1/2 years.
Activities of Daily Living↗
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.
Electric Stimulation Therapy↗
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.
Elbow Joint↗
The brachioradialis: anatomy, properties, and value for tendon transfer in the tetraplegic.
We have studied the brachioradialis muscle both physiologically and clinically for its suitability for tendon transfer in the tetraplegic. Intraoperative measurements have shown that the muscle is strong, provides excellent excursion, and is commonly available for transfer in the absence of other candidate muscles. The anatomic features that limit its use can be overcome during the operation. Postsurgical assessment of the muscle using electromyography and muscle-force measurement have shown that the muscle is voluntarily activated and provides strength for the intended function. Our experience with transfer of the brachioradialis to the hand of a tetraplegic patient has been highly positive.
Electromyography↗
Intraoperative assessment of wrist extensor muscle force.
Surgical restoration of hand grasp in the patient with spinal cord injury at the sixth cervical level often involves use of one of the two radial wrist extensors. Because the loss of the remaining wrist function would be devastating, it is important to establish techniques for quantitatively predicting postoperative function before tendon transection. An in situ method has been developed for determining muscle strength during tendon transfer surgery. Buckle transducers are placed on the tendons of the extensor carpi radialis brevis and longus for simultaneous measurement of strength of each individual muscle during voluntary and/or electrically stimulated extension of the wrist. The measured strength of the extensor carpi radialis brevis is examined to determine whether sufficient wrist extension torque would remain if the long wrist extensor is transferred. This technique allows accurate measurement of the force developed in any voluntarily activated muscle that has a long tendon of insertion.
Biomechanical Phenomena↗
A flexible, portable system for neuromuscular stimulation in the paralyzed upper extremity.
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Electric Stimulation Therapy↗
Magnetic resonance imaging of internal derangements of the knee.
The authors, in a careful prospective study, report the accuracy of MRI to be comparable to that of pneumoarthrography and arthroscopy in the diagnosis of internal derangements of the knee.
Arthrography↗
Functional neuromuscular stimulation neuroprostheses for the tetraplegic hand.
Functional neuromuscular stimulation (FNS) of the C5 and C6 tetraplegic upper extremity has been shown to be a valid clinical tool for restoring controlled movement in the paralyzed hand. The current clinical system consists of a shoulder position transducer controlling an external microprocessor-based stimulator, which excites paralyzed muscle via the peripheral nerve using percutaneous leads or a multichannel, implantable stimulator. Tendon transfer surgery of paralyzed but innervated muscle may augment the neurologically deficient upper extremity by allowing the substitution of stronger motors or the addition of new motors where flaccid paralysis (dennervation) eliminates the usual muscle from a grasp pattern. Sensory feedback in the form of machine state and cognitive information can be provided to the normally innervated C5 dermatome skin by subcutaneous electrodes. C5- and C6-level tetraplegics using FNS can independently perform single-hand manipulative tasks at a level similar to that of subjects with intact C7 roots, although they lack the elbow control.
Electric Stimulation Therapy↗
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.
Arm↗
Restoration of functional control by electrical stimulation in the upper extremity of the quadriplegic patient.
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Biomedical Engineering↗
Vascular insufficiency in Okihiro's syndrome secondary to hypothenar hammer syndrome.
The presence of Okihiro's syndrome (congenital thenar hypoplasia and Duane's anomaly) in a patient became clinically significant when a hypothenar hammer syndrome developed. The ulnar artery occlusion resulted in a compromise of the hand's vascular supply because of a congenital hypoplastic radial artery. Resection of the thrombosed ulnar artery and insertion of an interposition vein graft restored circulation to the hand. Anatomic features in this case include a hypoplastic radial artery and double motor branch of the median nerve. Clinicians should consider Okihiro's syndrome in the differential diagnosis of thenar muscle atrophy since there are genetic, diagnostic, and clinical implications.
Adult↗