Voluntary Elbow Movements Research Articles

Abstract: Enhancement of Voluntary Elbow Movement with a Myoelectric Orthotic Device: Long Term Follow Up of a Novel Application of a Post-Cva Assistive Rehabilitation Orthotic Device

INTRODUCTION: Free functioning muscle transfers (FFMTs), nerve grafting and nerve transfers have led to improved functional outcomes in brachial plexus injury (BPI) patients. Reports have shown that 39% of FFMTs and 26% of nerve transfers for elbow flexion achieve ≥ M4 elbow flexion strength.1 However, there remains a substantial number of patients with less favorable functional outcomes that need to be addressed further. The MyoPro (Myomo Inc., Cambridge, MA, USA) is a FDA-cleared myoelectric elbow-wrist-hand orthosis that uses surface EMG signals from affected muscle groups to control a powered orthosis to assist with the movement of a paretic upper limb. We describe the application of this orthosis for enhancement of elbow flexion and extension in patients with incomplete recovery from BPI. METHODS: Two patients from a single-surgeon practice have been evaluated for suitability of the myoelectric functional orthotic device. Both patients are 37 year-old men with 14 and 17 years history of left and right BPIs. Patient-1 initially had BP reconstruction by nerve transfers and secondarily a FFMT for restoration of elbow flexion and finger extension. Patient-2 underwent brachial plexus exploration and neurolysis only. Both patients failed to regain voluntary elbow movement. Evaluation showed 0–130 degree elbow passive range of motion in flail arms. Both patients had detectable EMG signals in the biceps or gracilis, and triceps muscles. Patients underwent 30 minutes of training with the device, which provides powered assistance for elbow flexion and extension via motors attached to the exterior of the orthosis. After the training, patients were asked to perform voluntary assisted elbow flexion and extension. Patients were then referred to receive custom orthotic devices. Functional assessment was performed using disabilities of the arm, shoulder and hand (DASH) questionnaire. RESULTS: Both patients demonstrated voluntary active elbow flexion and extension from 0 to 115 degrees using EMG control signals from the gracilis and triceps in Patient-1, and from the biceps and triceps muscles in Patient-2. Patient-1 quitted before getting the custom device. Patient-2 had DASH scores of 44.17 before and 36.6 after 6 months of using the orthotic device. CONCLUSION: Given the limited options available after definitive reconstruction, this myoelectric orthosis is a valuable option to improve the functional outcome in patients with BPI and poor return of voluntary elbow movement following reconstruction. Reference Citations: 1. Maldonado AA, Kircher MF, Spinner RJ, Bishop AT, Shin AY. Free Functioning Gracilis Muscle Transfer versus Intercostal Nerve Transfer to Musculocutaneous Nerve for Restoration of Elbow Flexion after Traumatic Adult Brachial Pan-Plexus Injury. Plast Reconstr Surg. 2016 Sep;138(3):483e-8e.

Motor Control Performance During Rapid Voluntary Movements of Elbow and Knee

ABSTRACTKnowledge of motor control differences during rapid goal-directed movements of the upper and lower limbs could be useful in improving rehabilitation protocols. The authors investigated performance and control differences between elbow and knee joints and between different contraction types (concentric vs. eccentric) during rapid movements under externally applied load. There were no significant differences in performance and control with respect to joint (elbow vs. knee) but the performance during concentric contractions was better than eccentric for both the joints. The findings indicate that despite anatomical and functional differences, the CNS is finely tuned for both the joints to maximize the efficiency of movement during a dynamic environment, but there are differences in control strategies between the 2 contraction types.

Incorporating ultrasound-measured musculotendon parameters to subject-specific EMG-driven model to simulate voluntary elbow flexion for persons after stroke

Background This study was to extend previous neuromusculoskeletal modeling efforts through combining the in vivo ultrasound-measured musculotendon parameters on persons after stroke. Method A subject-specific neuromusculoskeletal model of the elbow was developed to predict the individual muscle force during dynamic movement and then validated by joint trajectory. The model combined a geometrical model and a Hill-type musculotendon model, and used subject-specific musculotendon parameters as inputs. EMG signals and joint angle were recorded from healthy control subjects ( n = 4) and persons after stroke ( n = 4) during voluntary elbow flexion in a vertical plane. Ultrasonography was employed to measure the muscle optimal length and pennation angle of each prime elbow flexor (biceps brachii, brachialis, brachioradialis) and extensor (three heads of triceps brachii). Maximum isometric muscle stresses of the flexor and extensor muscle group were calibrated by minimizing the root mean square difference between the predicted and measured maximum isometric torque–angle curves. These parameters were then inputted into the neuromusculoskeletal model to predict the individual muscle force using the input of EMG signals directly without any trajectory fitting procedure involved. Findings The results showed that the prediction of voluntary flexion in the hemiparetic group using subject-specific parameters data was better than that using cadaveric data extracted from the literature. Interpretation The results demonstrated the feasibility of using EMG-driven neuromusculoskeletal modeling with direct ultrasound measurement for the prediction of voluntary elbow movement for both subjects without impairment and persons after stroke.

Changes of elbow kinematics and kinetics during 1 year after stroke

A precise description of the natural history of motor recovery after stroke provides a framework for understanding the mechanisms underlying this improvement and for tracking the efficacy of rehabilitation treatments. To characterize the time course of this change in motor impairment, we examined voluntary elbow movements in hemiparetic stroke survivors over a period of 1 year after stroke. Based on the possibility that both central nervous system and muscle factors could contribute to the observed clinical state, we hypothesized that we should observe at least two major recovery patterns of motor impairment. To explore these predictions, we assessed elbow movement range, movement speed, and isometric force generation. Subjects were examined five times over the 12-month period. We used the "growth mixture" model to characterize recovery of these measures, and the Fugl-Meyer scale (FMS) of upper-extremity function at 1 month to predict the recovery. We observed two distinct recovery classes. Class 1 started with low values for the physiological measures, and these increased over time, whereas class 2 tended to start with higher values and showed widely divergent recovery patterns. Using the logistic regression model, the impact of FMS on class membership was estimated for each parameter. Based on these data, we were able to accurately predict arm impairment recovery at different time-points in the first year, information of great potential value for planning targeted therapeutic interventions.

Relationship between stretch reflex thresholds and voluntary arm muscle activation in patients with spasticity

Previous studies have shown that deficits in agonist-antagonist muscle activation in the single-joint elbow system in patients with spastic hemiparesis are directly related to limitations in the range of regulation of the thresholds of muscle activation. We extended these findings to the double-joint, shoulder-elbow system in these patients. Ten non-disabled individuals and 11 stroke survivors with spasticity in upper limb muscles participated. Stroke survivors had sustained a single unilateral stroke 6-36 months previously, had full pain-free passive range of motion of the affected shoulder and elbow and had some voluntary control of the arm. EMG activity from four elbow and two shoulder muscles was recorded during quasi-static (<5 degrees /s) stretching of elbow flexors/extensors and during slow voluntary elbow flexion/extension movement through full range. Stretches and active movements were initiated from full elbow flexion or extension with the shoulder in three different initial positions (60 degrees , 90 degrees , 145 degrees horizontal abduction). SRTs were defined as the elbow angle at which EMG signals began to exceed 2SD of background noise. SRT angles obtained by passive muscle stretch were compared with the angles at which the respective muscles became activated during voluntary elbow movements. SRTs in elbow flexors were correlated with clinical spasticity scores. SRTs of elbow flexors and extensors were within the biomechanical range of the joint and varied with changes in the shoulder angle in all subjects with hemiparesis but could not be reached in this range in all healthy subjects when muscles were initially relaxed. In patients, limitations in the regulation of SRTs resulted in a subdivision of all-possible shoulder-elbow arm configurations into two areas, one in which spasticity was present ("spatial spasticity zone") and another in which it was absent. Spatial spasticity zones were different for different muscles in different patients but, taken together, for all elbow muscles, the zones occupied a large part of elbow-shoulder joint space in each patient. The shape of the boundary between the spasticity and no-spasticity zones depended on the state of reflex inter-joint interaction. SRTs in single- and double-joint flexor muscles correlated with the positions at which muscles were activated during voluntary movements, for all shoulder angles, and this effect was greater in elbow flexor muscles (brachioradialis, biceps brachii). Flexor SRTs correlated with clinical spasticity in elbow flexors only when elbow muscles were at mid-length (90 degrees ). These findings support the notion that motor impairments after CNS damage are related to deficits in the specification and regulation of SRTs, resulting in the occurrence of spasticity zones in the space of elbow-shoulder configurations. It is suggested that the presence of spatial spasticity zones might be a major cause of motor impairments in general and deficits in inter-joint coordination in particular in patients with spasticity.

Performance of elbow tracking under constant torque disturbance in normotonic stroke patients and normal subjects

Objective. In this study, the influences of externally imposed constant torque on the voluntary elbow movements of stroke and normal subjects were investigated quantitatively. Background. Muscle weakness, spasticity and incoordination are the major factors that interfere with stroke patient’s limb functions. Imposing external torque disturbance may worsen the motor performance. This experiment was designed to investigate the effects of small constant external torque on the performance of voluntary elbow movements. Methods. Tracking of a ramp-and-hold angle trajectory in the direction of extension was used as the main task for performance assessment. Each subject repeated the same tracking movement six times in each of three loading conditions: no, assistive or resistive loading. Five normal and six stroke subjects were recruited for this study. We used parameters extracted from movement trajectory and processed electromyograms as the performance indicators. Results. For normal subjects, there was no difference in the tracking performance in the three loading conditions. For stroke patients, the affected side had inferior performance to the healthy side in the free loading condition and the difference diminished in assistive and resistive loading conditions as the performance of the affected side improved. Integrated electromyograms of biceps or triceps did not show significant changes in different loading conditions. Conclusions. Small externally imposed constant torque, either resistive or assistive, may improve motor performance of affected elbows in stroke patients. Relevance. Most of the currently available prostheses are passive devices, aiming at providing better support and improving stability. The results of the current study imply that an active prosthetic device that applies a small constant torque to the hemiparetic elbow can improve its motor performance in stroke patients. The direction of external torque is to assist the weaker side of the antagonistic muscle pair.

Three-dimensional motion analysis of the voluntary elbow movement in subjects with spasticity.

The purpose of this study was to quantitatively compare the difference in voluntary upper extremity movements between subjects with and without spasticity. Eight normal subjects (mean 26.7 +/- 2.8 years, four males and four females) and seven subjects with spasticity (mean 25.9 +/- 4.3 years, three males and four females) were involved in this study. The subjects sat in an adjustable chair and performed two voluntary tasks involving the elbow joint. Task A was to move the hand between two touch-plates which were mounted 28 cm apart on the surface of the table. Task B was to flex and extend the elbow joint in the sagittal plane with the forearm in neutral position. Reflective markers were attached on the shoulder, the elbow and the wrist. A Peak5 video-based motion analysis system was used to record the positions of the markers in the three-dimensional (3-D) space during the movement tasks. A set of quantitative parameters were used to document the elbow movement. The results revealed that in comparison to normal subjects, subjects with spasticity exhibited a higher average jerk, a larger standard deviation of the coordinates of the markers along the movement path, a larger standard deviation of the angle between the plane of the elbow joint and the horizontal plane, and a longer 3-D path length. The characteristics of spastic elbow movement and the usage of quantitative parameters were discussed.

Myoelectric activity during voluntary elbow movements in above-elbow amputees

This study is concerned with the analysis of myoelectric activity in the biceps and triceps muscles of unilateral above-elbow (AE) amputees during voluntary fast elbow movements. The signal patterns obtained from each subject's remnant limb were analysed and compared with similar acquired muscle patterns from the sound arm. Our findings, in agreement with suggestions from the literature, show that a significant portion of the so-called triphasic muscle patterns still occur in the remnant limbs of amputees, and therefore, are generated without the use of proprioceptive and sensory feedback. Although the patterns show some unexplained inconsistencies in timing and duration, the results indicate that for traumatic amputees the loss of an arm does not mean that remnant muscle contractions lose their relation to previous movements. In addition, congenital amputees did not show phasic patterns during voluntary fast elbow movements.

Cortical potentials preceding voluntary elbow movement in recovered hemiparesis

Scalp-recorded movement-related cortical potentials (MRCPs) preceding voluntary elbow flexion were studied in two hemiparetic patients 8 months after a stroke. Both cases had unilateral lenticular and internal capsular vascular lesion sparing the cortex. The motor recovery stage of their paretic arm remained in flexion or extension “synergistic” movements of shoulder, elbow, wrist and fingers. The NS′ (negative slope) amplitude preceding voluntary unilateral elbow flexion of the intact arm showed a distinct preponderance over the contralateral precentral area, whereas NS′ amplitude preceding flexion of the paretic arm was symmetrically maximal at bilateral precentral areas. It is postulated that the unilateral synergistic elbow flexion of the paretic arm is associated with an activation of bilateral brachial areas of the sensorimotor cortex (SI-MIs), whereas the isolated elbow flexion of the intact arm is associated with an activation of mainly the contralateral SI-MI.

PS-14-10 Cortical potentials preceding voluntary elbow movement in recovered hemiparesis

PS-14-10 Cortical potentials preceding voluntary elbow movement in recovered hemiparesis

Voluntary movement at the elbow in spastic hemiparesis.

The relative importance of hyperreflexia and paresis in disturbances of voluntary arm movement was studied in a group of patients (n = 25) with spasticity arising from a unilateral ischemic cerebral lesion. Patient performance was evaluated against data obtained from normal subjects (n = 15). Spastic patients achieved lower maximum movement velocities during flexion or extension than did normal subjects. The more marked the paresis of the elbow flexor and extensor muscles of the patients, relative to the strength of the normal subjects, the greater was this reduction in maximum velocity. For a given velocity, however, the time taken to complete a movement and the time to reach the peak velocity were normal. No relationship was found between the degree of impairment of voluntary movement and the level of passive muscle hypertonia in the antagonist. Although overactivity of the antagonist muscle may play some role in disturbance of movements made at low velocities without an opposing load, antagonist activity during movements made against a load (i.e., under more natural conditions) was at or below normal levels, even in those patients with the most marked passive muscle hypertonia. It is concluded that agonist muscle paresis, rather than antagonist muscle hypertonia, plays the dominant role in the disturbance of voluntary elbow movement following stroke.

Changes in the length of the human biceps brachii muscle during elbow movements.

1. Needles inserted into the biceps move with the muscle as the elbow flexes or extends. Pairs of needles were used to indicate changes in length of the muscle fibres. 2. During low-frequency flexion-extension movements the biceps lengthened as the joint extended. 3. When, however, joint movements at greater than 2.2 Hz were maintained by external electrical stimulation of triceps and the long head of biceps, or of biceps alone, the biceps lengthened and shortened in antiphase to the joint movement. The elastic properties of the biceps tendons then combined with the mass of the forearm as a spring-mass system whose natural frequency was about 2.2 Hz. 4. No such phase reversal appeared during voluntary elbow movements at frequencies up to 5 Hz. It was concluded that the combined tendons of biceps, brachialis and brachioradialis made a much less compliant muscle-to-bone coupling. 5. The results are discussed in relation to possible tremor mechanisms.

Cortical load compensation during voluntary elbow movements

The effects of unexpected transient load changes on self-paced elbow movements in 3 Cebus monkeys were analyzed and compared with movement-related precentral neuronal activity. Movements perturbed by torque pulses went into damped oscillatory corrections with an average frequency of 6 Hz. Cortical cell firing changed at latencies of about 30 msec, with subsequent later peaks and troughs corresponding to the movement oscillations. These cortical events probably assisted in movement corrections. During dentate cooling movement oscillations slowed to 3 Hz. The earliest components of cortical cell responses were not, or only slightly, affected whereas the later components were strikingly reduced and/or delayed, resulting in parallel slowing of firing patterns to 3 Hz. The results support the idea of a cerebellar assisted cortical servo-control in rapid load compensation.