Jayme S. Knutson

Simulated neuroprosthesis state activation and hand-position control using myoelectric signals from wrist muscles

This paper reports on the initial phase of feasibility testing of a control strategy that uses myoelectric signals (MES) from wrist flexor and extensor muscles to control a hand-grasp neuroprosthesis for C7 tetraplegia. The control strategy was customized to the MES patterns produced during wrist flexion, extension, and relaxation for five able-bodied subjects and two individuals with C7 spinal cord injury. We evaluated the reliability with which the subjects could deliberately activate target neuroprosthesis states and control the degree of opening and closing of a computer-simulated hand using the myoelectric control strategy. Every subject was able to activate at least 99% of the target states for at least 1 continuous second, enough time to prove the activation was deliberate and to achieve significant hand opening or closing. Additionally, every subject was able to control the opening and closing of the simulated hand with enough proficiency to match greater than 87% of the target hand positions for at least 2 continuous seconds. Most of the inadvertent disturbances in simulated hand position were of a magnitude less than 10% of full range of motion for every subject. Future studies will incorporate the control strategy into an electrical stimulation system that opens and closes the hand of an individual with C7 tetraplegia.

Interaction of poststroke voluntary effort and functional neuromuscular electrical stimulation

Functional electrical stimulation (FES) may be able to augment functional arm and hand movement after stroke. Poststroke neuroprostheses that incorporate voluntary effort and FES to produce the desired movement must consider how forces generated by voluntary effort and FES combine, even in the same muscle, in order to provide an appropriate level of stimulation to elicit the desired assistive force. The goal of this study was to determine whether the force produced by voluntary effort and FES add together independently of effort or whether the increment in force depends on the level of voluntary effort. Isometric force matching tasks were performed under different combinations of voluntary effort and FES. Participants reached a steady level of force, and while attempting to maintain a constant effort level, FES was applied to augment the force. Results indicate that the increment in force produced by FES decreases as the level of initial voluntary effort increases. Potential mechanisms causing the change in force output are proposed, but the relative contribution of each mechanism is unknown.

Cadaveric Biomechanical Analysis of the Distal Radioulnar Joint: Influence of Wrist Isolation on Accurate Measurement and the Effect of Ulnar Styloid Fracture on Stability

PURPOSE Distal radioulnar joint (DRUJ) instability can be tested using biomechanical cadaveric models, but inadequate isolation of the DRUJ during instability testing may introduce measurement error. The first goal of this investigation was to develop an effective model for isolating the DRUJ during biomechanical cadaveric testing. The second goal was to use this model to measure the effect of ulnar styloid fracture and subsequent repair on DRUJ kinematics in cadaveric specimens. METHODS Five fresh cadaveric arms were tested using a Biodex System 3 device. The humerus was clamped firmly, the forearm rotated freely, and the hand/carpus was attached to the Biodex device. Three methods of DRUJ isolation were tested. In method 1, the specimen was firmly clamped at the midshaft humerus and the hand/carpus was clamped. In method 2, the distal radius was additionally fixed to the carpal clamp to reduce carpal motion. In method 3, proximal fixation of the olecranon to an elbow rest was added. Testing was done before ulnar styloid osteotomy (group 1), after osteotomy through dorsal capsulotomy (group 2), and after styloid fragment repair with a screw (group 3). Twelve pronation-supination cycles were performed while work of rotation, maximum pronation torque, and maximum supination torque for each method and group were recorded. RESULTS Analysis of clamping methods showed work of rotation, maximum pronation torque, and maximum supination torque for method 3 were greater than those for methods 1 and 2. Analysis of groups showed the following statistically significant trends for work of rotation: group 1 >>> group 3 > group 2. Maximum supination torque similarly showed statistically significant differences: group 1 >>> group 3 > group 2. Maximum pronation torque showed a similar trend: group 1 >>> group 3 > group 2. However, in contrast with work of rotation and maximum supination torque, group 3 maximum pronation torque was not statistically different from that of group 2. CONCLUSIONS Increased work of rotation represents decreased joint laxity. Maximum supination torque and maximum pronation torque assess soft tissue restraints at joint end points. Method 3 showed the greatest values in these variables, indicating reduced elbow and carpal motion and better DRUJ isolation. Work of rotation and maximum supination torque in group 3 were increased from those of group 2 but not restored to group 1 values. Styloid fixation restores some soft tissue tension but laxity persists. Maximum pronation torque in group 3 was not increased significantly from that of group 2, perhaps from dorsal capsulotomy causing soft tissue injury and laxity not corrected with fixation. The influence of ulnar styloid fracture on dynamic DRUJ kinematics can be demonstrated in this model.

Contralaterally Controlled Functional Electrical Stimulation Improves Hand Dexterity in Chronic Hemiparesis: A Randomized Trial

Background and Purpose— It is unknown whether one method of neuromuscular electrical stimulation for poststroke upper limb rehabilitation is more effective than another. Our aim was to compare the effects of contralaterally controlled functional electrical stimulation (CCFES) with cyclic neuromuscular electrical stimulation (cNMES). Methods— Stroke patients with chronic (>6 months) moderate to severe upper extremity hemiparesis (n=80) were randomized to receive 10 sessions/wk of CCFES- or cNMES-assisted hand opening exercise at home plus 20 sessions of functional task practice in the laboratory for 12 weeks. The task practice for the CCFES group was stimulation assisted. The primary outcome was change in Box and Block Test (BBT) score at 6 months post treatment. Upper extremity Fugl–Meyer and Arm Motor Abilities Test were also measured. Results— At 6 months post treatment, the CCFES group had greater improvement on the BBT, 4.6 (95% confidence interval [CI], 2.2–7.0), than the cNMES group, 1.8 (95% CI, 0.6–3.0), between-group difference of 2.8 (95% CI, 0.1–5.5), P=0.045. No significant between-group difference was found for the upper extremity Fugl–Meyer (P=0.888) or Arm Motor Abilities Test (P=0.096). Participants who had the largest improvements on BBT were <2 years post stroke with moderate (ie, not severe) hand impairment at baseline. Among these, the 6-month post-treatment BBT gains of the CCFES group, 9.6 (95% CI, 5.6–13.6), were greater than those of the cNMES group, 4.1 (95% CI, 1.7–6.5), between-group difference of 5.5 (95% CI, 0.8–10.2), P=0.023. Conclusions— CCFES improved hand dexterity more than cNMES in chronic stroke survivors. Clinical Trial Registration— URL: http://www.clinicaltrials.gov. Unique identifier: NCT00891319.

Contralaterally controlled functional electrical stimulation for recovery of elbow extension and hand opening after stroke: a pilot case series study.

ObjectiveThe aims of this study were to determine whether patients with moderate-to-severe upper limb hemiplegia could use contralaterally controlled functional electrical stimulation at the arm and hand (Arm+Hand CCFES) at home and to evaluate the feasibility of Arm+Hand CCFES to reduce arm and hand motor impairment. DesignWith Arm+Hand CCFES, the paretic elbow and hand extensors were stimulated with intensities proportional to the degree of elbow extension and hand opening, respectively, of the contralateral unimpaired side. For 12 wks, four participants with chronic (≥6 mos) upper limb hemiplegia received ∼7 hrs per week of self-administered home-based stimulation-mediated elbow extension and hand opening exercise plus ∼2.5 hrs per week of therapist-supervised laboratory-based stimulation-assisted functional task practice. Assessments of upper limb impairment were made at pretreatment, posttreatment, and 1 mo after treatment. ResultsAll four participants were able to use the Arm+Hand CCFES system at home either independently or with very minimal assistance from a caregiver. All four participants had increases in the Fugl-Meyer score (1–9 points) and the Wolf Motor Function Test (0.2–0.8 points) and varying degrees of improvement in maximum hand opening, maximum elbow extension, and simultaneous elbow extension and hand opening. ConclusionsArm+Hand CCFES can be successfully administered in stroke patients with moderate-to-severe impairment and can reduce various aspects of upper limb impairment. A larger efficacy study is warranted.

Contralaterally controlled neuromuscular electrical stimulation for recovery of ankle dorsiflexion: a pilot randomized controlled trial in patients with chronic post-stroke hemiplegia.

ObjectiveThe aim of this study was to compare the effects of contralaterally controlled neuromuscular electrical stimulation (CCNMES) vs. cyclic neuromuscular electrical stimulation (NMES) on lower extremity impairment, functional ambulation, and gait characteristics. DesignTwenty-six survivors of stroke with chronic (≥6 mos) foot drop during ambulation were randomly assigned to 6 wks of CCNMES or cyclic NMES. Both groups had ten sessions per week of self-administered home application of either CCNMES or cyclic NMES plus two sessions per week of gait training with a physical therapist. Primary outcomes included lower extremity Fugl-Meyer score, modified Emory Functional Ambulation Profile, and gait velocity. Assessments were made at pretreatment and posttreatment and at 1 and 3 mos after treatment. ResultsThere were no significant differences between the groups in the outcome trajectories for any of the measures. With data from both groups pooled, there were significant but modest and sustained improvements in the Fugl-Meyer score and the modified Emory Functional Ambulation Profile but not in gait velocity. ConclusionsThe results support the hypothesis that gait training combined with either CCNMES or cyclic NMES reduces lower extremity impairment and functional ambulation but do not support the hypothesis that CCNMES is more effective than cyclic NMES in patients with chronic post-stroke hemiplegia.

The Effect of Peripheral Nerve Stimulation on Shoulder Biomechanics: A Randomized Controlled Trial in Comparison to Physical Therapy

Objective To establish the effects on shoulder biomechanics from a peripheral nerve stimulation (PNS) treatment compared to physical therapy (PT) in stroke survivors with chronic hemiplegic shoulder pain. Design Single-site, pilot, randomized controlled trial for adults with chronic shoulder pain after stroke. Participants were randomized to receive a 3-week treatment of single-lead PNS or physical therapy (PT). The outcomes included isometric shoulder abduction strength, pain-free shoulder external rotation range of motion (ROM), delay in initiation and termination of shoulder abduction electromyogram (EMG) activity, and the Fugl-Meyer Motor Assessment (upper extremity section). Outcomes were measured at baseline, and at weeks 1, 4, 12, and 16. Results Twenty-five participants were recruited, 13 to PNS and 12 to PT. There were significant improvements for both PNS and PT in maximum isometric shoulder abduction strength, pain-free external rotation ROM, and Fugl-Meyer Motor Assessment. There were no significant changes in delay of initiation or termination of deltoid EMG with either treatment. Conclusions Both PNS and PT are capable of improving shoulder biomechanics in those with HSP, though changes in biomechanics alone do not account for the greater pain relief associated with PNS than PT.

Neuromuscular Electrical Stimulation Applications

Abstract Neuromuscular electrical stimulation (NMES) of paralyzed muscles can be used to restore or replace motor function in individuals who have upper motor neuron damage from causes such as stroke or spinal cord injury (SCI). In some conditions, such as stroke or incomplete SCI, NMES may be part of a therapy regimen that helps restore volitional movement and function. In other conditions, such as severe stroke or complete SCI, permanent NMES applications are needed to replace the lost neuromuscular function. This chapter describes NMES devices for upper and lower extremity therapeutic and neuroprosthetic applications.