Ronald J. Triolo

The theoretical development of a multichannel time-series myoprocessor for simultaneous limb function detection and muscle force estimation

The theoretical development and simulation of a complete time-series myoprocessor which provides reliable and economical predictions of both the magnitude and direction of limb motion from the spectral content of the surface EMG is discussed. Treating multiple channels of surface EMG as a vector-valued autoregressive process incorporates spatially distributed information which extends the operating range of parallel filtering limb function classifiers and reduces their sensitivity to modeling conditions. Active joint moment is estimated simultaneously from the pooled variance of the prewhitened EMG generated during the classification procedure. Estimation from the prewhitened sequence imposes no additional computational requirements and extends optimal myoprocessor to include multiple channels of serially dependent data. Such a system may be applied to the control of actively powered prostheses or orthoses.<<ETX>>

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.

Development and standardization of a clinical evaluation of standing function: the functional standing test

A tool for quantifying standing function and to measure the effectiveness of different assistive devices for disabled individuals was developed and normalized on able-bodied adolescents. The assessment was based on the ability to free the upper extremities from support and balancing tasks in order to manipulate objects in the environment while in the upright posture. The Jebsen test of hand function was adapted to the standing position and extended to include vertical reaching and crossing midline in order to tax the postural system. Time and completion of eighteen tasks requiring fine coordination, pushing, pulling, reaching horizontally, vertically, and diagonally were recorded along with total elapsed standing time. Data from 69 able-bodied individuals between the ages of 12 and 17 were analyzed statistically and normal standards were established. Although there were no differences with respect to age, a significant interaction between sex and standing performance was observed. Two adolescents with complete spinal cord injuries were also tested while standing in braces or with functional neuromuscular stimulation (FNS). both subjects demonstrated a tendency for improved standing function with FNS, but overall results were mixed. >

Application of functional neuromuscular stimulation to children with spinal cord injuries: candidate selection for upper and lower extremity research

This paper summarizes the results of screening for participation in research programs involving functional neuromuscular stimulation (FNS). It examines the characteristics of a group of children and teenagers with spinal cord injuries (SCI) identified as potential candidates for FNS as defined by the rigorous inclusion criteria of the research studies. One hundred and thirteen children and teenagers under the age of 20 with cervical, thoracic or lumbar level spinal cord injuries were examined for inclusion in an experimental program of FNS to provide standing, walking, or prehension. Although biased towards adolescents with complete midthoracic and midcervical injuries, the age, sex, injury level, etiology, and neurological status of the sample coincided with previously published reports and consisted predominantly of teenage males injured in motor vehicle or sports related accidents. Approximately half of the individuals examined were physically appropriate for research participation without preparatory intervention. Treatment options to prepare individuals for FNS were identified in 25% of those considered inappropriate at the initial evaluation, indicating that the potential user population of clinical systems may be larger than estimates obtained from research applications. Peripheral denervation was the single most prevalent physical impediment to the application of FNS. Although the incidence of lower motor neuron (LMN) involvement was similar in subjects with tetraplegia and paraplegia, those with cervical lesions more frequently exhibited other medical complications that interfered with the application of FNS. Surgical procedures involving transfer of paralyzed but excitable muscles were identified in almost one third of the candidates with tetraplegia who were excluded due to denervation. Of those physically appropriate, psychological factors eliminated several candidates from consideration. Such concerns may also be addressed with suitable intervention in preparation for the clinical application of FNS. Almost 50% of those appropriate for FNS research elected to participate in the programs, with those declining citing the hospitalization, time and travel commitments as the primary factors influencing their decisions. Results suggest that FNS for standing, walking and hand grasp may be an option for a significant percentage of the pediatric SCI population.

The application of a modified neuroprosthetic hand system in a child with a C7 spinal cord injury. Case report

A neuroprosthetic hand system developed at Case Western Reserve University has been modified for use by an 8 year old child with an incomplete C7 spinal cord injury. This system has been adapted to accommodate voluntary thumb and finger extension, and provides stimulated finger flexion and thumb position for lateral and palmar prehension. Three months were required to develop grasps with sufficient strength and coordination for functional use. This period consisted of: implantation and immobilization of percutaneous intramuscular electrodes; stimulated exercise of the muscles of the hand and forearm; programming grasp patterns; and system training. Functional assessments show that the neuroprosthetic hand system allows the subject to perform unilateral and bilateral tasks that were otherwise impossible or were previously performed bimanually. The ability to perform activities of daily living with one hand frees the contralateral upper extremity to be used either for balance which increases the work area, or to stabilize an object allowing manipulation with the instrumented hand. Telephone interviews suggest that the hand system is used on a consistent basis at home and school. This single subject application indicates that a stimulation system designed for adults with C5-6 spinal cord injuries can enhance hand function and facilitate independence in a child with a low level cervical lesion.

The experimental demonstration of a multichannel time-series myoprocessor: system testing and evaluation

A multichannel time-series myoprocessor which combines the advantages of the parallel filtering limb function classifiers of P. Doerschuk et al. (ibid., vol.BME-130, p.18-28, 1983) and the optimal myoprocessor muscle force estimators described by N. Hogan et al. (ibid., vol.BME-27, p.382-410, 1980) is discussed. Magnitudes and directions of knee movements were identified accurately and robustly from EMG sites intermediate to the major thigh muscles of intact individuals. Electrode placement criteria were tested, and system performance and sensitivity to contraction level as functions of channel number were computed. By including spatially distributed information into the structure of the processor, gains in accuracy and reliability over systems with fewer channels were demonstrated. Operating range increased with the number of channels included in the processor. Joint movement was estimated from multiple channels of temporally correlated data, extending and generalizing previously reported techniques. Identifying the parameters of autoregressive models of the EMG at low levels of contraction resulted in more robust classification and joint movement estimation.<<ETX>>

Force-velocity and length-tension properties of stimulated human quadriceps muscle in spinal cord injured children

The force-velocity and length-tension properties of electrically stimulated quadriceps muscles were determined in a pilot study with two teenage subjects with midthoracic spinal cord injuries. Percutaneous intramuscular electrodes were used to elicit maximal isometric and concentric isokinetic contractions over angles range from 20 degrees to 80 degrees of knee flexion and over speeds from 30 degrees to 150 degrees per second. Submaximal contractions were generated both eccentrically and concentrically. Maximal concentric moment-velocity-angle surfaces were found to be similar in all respects to force-velocity-length surfaces reported for isolated animal preparations. Submaximal profiles grossly approximated the characteristics of maximal contractions. For any joint angle, eccentric moments were generally greater than those produced isometrically or concentrically.<<ETX>>

Motor responses to FES electrodes in a growing limb

A canine model was used to investigate the chronic performance of surgically implanted electrodes in a growing limb. Seven skeletally immature dogs were implanted with epimysial and intramuscular electrodes. Recruitment characteristics for each electrode, including the activation threshold, spillover muscle threshold, peak force, and force at spillover were recorded with tendon force transducers placed on the tendon of the target muscle and the first spillover muscle. Recruitment properties for the electrodes were measured at the time of implant and after growth was complete. Appropriate electrode positions were also remapped after maturity was reached. Data for 23 electrodes are reported. Average longitudinal growth of the ulna was 5.6 cm (39% increase). The measurements of threshold for target and spillover muscle activation show that appropriate muscle recruitment order was retained in 22 of 23 (96%) of the electrodes. The target muscle thresholds remained stable between implant and explant with variation on the order of that reported for these electrodes placed in mature animals. Overall, a multivariate analysis of variance for repeated measures indicates electrodes performed equally well at explant as they did at implant as measured by threshold and usable range of target muscle before spillover. New electrodes placed in the adult animal did not perform better than the chronically placed electrodes. The recruitment properties of 22 or 23 electrodes did not vary significantly with growth. This is encouraging evidence that a stable motor response can be retained with implantable intramuscular and epimysial electrodes in the presence of growth.

An automated method for describing muscle fatigue

This paper reports on the development of a method to extract features related to fatigue from the isometric force (or moment) records of the quadriceps muscle during cyclic contractions. The force record is modelled as a three segment piece-wise linear curve consisting of an initial region of high force (the plateau), followed by a second segment of rapidly declining force production (transition) and a final region of little or no decline in force (steady state). Repeated maximal isometric contractions lasting 2.5 seconds and separated by 0.5 seconds of rest were elicited by applying 20 Hz bursts of tetanizing stimulation at an amplitude of 20 mA and a fixed pulse duration to individuals with complete spinal cord injuries via chronically indwelling percutaneous intramuscular electrodes. Raw data from a load-cell dynamometer were sampled at 100 Hz, reduced by averaging over the constant force portions of each contraction and low pass filtered at 0.25 Hz. The intersections of the three linear segments are first estimated by computing the inflection points of the resulting smooth record. The linearization is optimized by varying the positions of the intersection points until the mean squared error between the processed data and the piece-wise linear model was minimized. The slopes of the three segments and the locations of the two intersection points were recorded and used as features to characterize the fatiguability of the stimulated muscle. The algorithm also computes widely accepted measures such as the time to 50% reduction in initial force (T50), or extrapolates the values from incomplete data records. The procedure may be applicable to continuous contractions and may be valuable for determining the effects of various exercise programs designed to enhance muscular endurance, or to infer muscle fiber composition indirectly from the force record.<<ETX>>

The functional standing test; development and standardization of a clinical evaluation of standing function

The functional standing test, which quantifies standing performance based on the ability to free the upper extremities from support and balance tasks in order to manipulate the environment, is described. The development of the test was motivated by the need for a new assessment that reflects the clinical usefulness of standing and allows the comparison of functional neuromuscular stimulation (FNS) or any other rehabilitation technology to normal standing function. The test apparatus, functional tasks chosen to simulate everyday activities, and administration of the test are discussed. Results of applying the test to able-bodied norms and case studies with FNS and braces are presented.<<ETX>>