An Exoneuromusculoskeleton for Self-Help Upper Limb Rehabilitation After Stroke

Abstract

This article presents a novel electromyography (EMG)-driven exoneuromusculoskeleton that integrates the neuromuscular electrical stimulation (NMES), soft pneumatic muscle, and exoskeleton techniques, for self-help upper limb training after stroke. The developed system can assist the elbow, wrist, and fingers to perform sequential arm reaching and withdrawing tasks under voluntary effort control through EMG, with a lightweight, compact, and low-power requirement design. The pressure/torque transmission properties of the designed musculoskeletons were quantified, and the assistive capability of the developed system was evaluated on patients with chronic stroke (n = 10). The designed musculoskeletons exerted sufficient mechanical torque to support joint extension for stroke survivors. Compared with the limb performance when no assistance was provided, the limb performance (measured as the range of motion in joint extension) significantly improved when mechanical torque and NMES were provided (p < 0.05). A pilot trial was conducted on patients with chronic stroke (n = 15) to investigate the feasibility of using the developed system in self-help training and the rehabilitation effects of the system. All the participants completed the self-help device-assisted training with minimal professional assistance. After a 20-session training, significant improvements were noted in the voluntary motor function and release of muscle spasticity at the elbow, wrist, and fingers, as indicated by the clinical scores (p < 0.05). The EMG parameters (p < 0.05) indicated that the muscular coordination of the entire upper limb improved significantly after training. The results suggested that the developed system can effectively support self-help upper limb rehabilitation after stroke. ClinicalTrials.gov Register Number NCT03752775.

Keywords: exoskeleton; neuromuscular electrical stimulation; pneumatic muscle; robot; stroke rehabilitation.

FIG. 1.

(a) Overview of the exoneuromusculoskeleton, with the inner structures of a pump box and the control box. (b) Attachment of the musculoskeletons, and structures with dimensions of the elbow musculoskeleton and the hand musculoskeleton (all the dimensions are in millimeters). EMG, electromyography; NMES, neuromuscular electrical stimulation.

FIG. 2.

(a) The schematic diagram of the control in the EMG-driven exoneuromusculoskeleton, and (b) the controlling workflow of the assistance in phasic and sequential limb tasks. BIC, biceps brachii; ECU, extensor carpi ulnaris; ED, extensor digitorum; FCR, flexor carpi radialis; FD, flexor digitorum; TRI, triceps brachii.

FIG. 3.

Experimental setup for the evaluation of the pressure/torque transmission properties of the musculoskeleton for the (a) elbow and (b) hand. MCU, microcontroller unit.

FIG. 4.

Seating configuration during the evaluations in the (a) elbow and (b) wrist sessions as well as the experiment setup of finger joint goniometric measurements for the (c) index, middle, ring, and little fingers and (d) thumb, and (e) the evaluation protocol presented with time line.

FIG. 5.

(a) Experimental training setup of the EMG-driven exoneuromusculoskeleton in the laboratory, and (b) the training protocol presented with time line.

FIG. 6.

(a) Pressure/torque relationship and (b) response time of the inner pressure of the elbow musculoskeleton during inflation with a fully opened valve; (c) pressure/torque relationship of the musculoskeleton for the MCP joint of the middle finger; and (d) response time of the inner pressure of the hand musculoskeleton during inflation with a fully opened valve. MCP, metacarpophalangeal.

FIG. 7.

Comparison of the dynamic ROM values, which are represented in terms of their means (shaded areas indicate half an SE), at the (a) elbow and (b) wrist joints under the different assistance schemes. Significant differences (p ≤ 0.05) with respect to the assistance scheme are indicated by “*.” ROM, range of motion; SE, standard error.

FIG. 8.

Comparison of the ROM values of the finger joints, which are represented in terms of their mean ± twice the SE (error bar), under different assistance schemes. Significant levels are indicated by ** for p ≤ 0.01 and *** for p ≤ 0.001. The total joint position of each finger is defined as the sum of the final position of each measured joint of the finger after hand opening (indicated with the means and 95% confidence intervals). DIP, distal interphalangeal; PIP, proximal interphalangeal; SUM_ROM, summation of the measured joints of one finger.

FIG. 9.

Clinical scores measured before, immediately after, and 3 months after the training: (a) FMA full scores, (b) FMA shoulder/elbow scores, (c) FMA wrist/hand scores, (d) ARAT scores, and (e) MAS scores at the elbow, wrist, and fingers. The clinical scores are presented as mean ± twice the SE (error bar) in each evaluation session. The significant difference is indicated by “*” (p ≤ 0.05). MAS, Modified Ashworth Scale.

FIG. 10.

Variations in the EMG parameters recorded across the 20 training sessions: (a) the normalized EMG activation levels of the FCR-FD muscle union and BIC muscles during the bare hand evaluations and (b) the changes in the normalized CIs between the FCR-FD and ECU-ED muscle unions, the ECU-ED muscle union and the BIC muscles, the FCR-FD muscle union and BIC muscles, and the BIC and TRI muscle pair during the bare hand evaluations. The EMG parameter values are presented as mean ± twice the SE (error bar) for each session. The significant difference is indicated by “*” (p ≤ 0.05). CI, cocontraction index.