Effects of a robot-assisted training of grasp and pronation/supination in chronic stroke: a pilot study

Abstract

Background: Rehabilitation of hand function is challenging, and only few studies have investigated robot-assisted rehabilitation focusing on distal joints of the upper limb. This paper investigates the feasibility of using the HapticKnob, a table-top end-effector device, for robot-assisted rehabilitation of grasping and forearm pronation/supination, two important functions for activities of daily living involving the hand, and which are often impaired in chronic stroke patients. It evaluates the effectiveness of this device for improving hand function and the transfer of improvement to arm function.

Methods: A single group of fifteen chronic stroke patients with impaired arm and hand functions (Fugl-Meyer motor assessment scale (FM) 10-45/66) participated in a 6-week 3-hours/week rehabilitation program with the HapticKnob. Outcome measures consisted primarily of the FM and Motricity Index (MI) and their respective subsections related to distal and proximal arm function, and were assessed at the beginning, end of treatment and in a 6-weeks follow-up.

Results: Thirteen subjects successfully completed robot-assisted therapy, with significantly improved hand and arm motor functions, demonstrated by an average 3.00 points increase on the FM and 4.55 on the MI at the completion of the therapy (4.85 FM and 6.84 MI six weeks post-therapy). Improvements were observed both in distal and proximal components of the clinical scales at the completion of the study (2.00 FM wrist/hand, 2.55 FM shoulder/elbow, 2.23 MI hand and 4.23 MI shoulder/elbow). In addition, improvements in hand function were observed, as measured by the Motor Assessment Scale, grip force, and a decrease in arm muscle spasticity. These results were confirmed by motion data collected by the robot.

Conclusions: The results of this study show the feasibility of this robot-assisted therapy with patients presenting a large range of impairment levels. A significant homogeneous improvement in both hand and arm function was observed, which was maintained 6 weeks after end of the therapy.

Figures

Figure 1

The HapticKnob robot and the proposed therapy protocol. A: Stroke subject training on the HapticKnob. B: Visual feedback of the opening/closing (left) and pronation/supination (right) exercises, where subjects have to squeeze, respectively orient the picture into a white frame by grasping, respectively turning the HapticKnob. C: Details of therapy and session protocol.

Figure 2

Results of the Fugl-Meyer scores for the upper extremity. Comparison of Fugl-Meyer (FM) scores for the upper extremity between week0/week6, and week0/week12. Circles represent results of the 13 participants included in the data analysis, squares represent the mean over the 13 subjects, and crosses represent results of subjects A11 and A12, who had a break in the treatment and were thus excluded from the analysis. Dashed lines illustrate a 3-point improvement on the FM considered as a functionally meaningful improvement [10].

Figure 3

Primary outcome measures. Evolution of Fugl-Meyer (FM) scores for the upper extremity and Motricity Index (MI) scores for the 13 subjects that were retained for data analysis (mean ± std), with details of sections related to the lower and upper arm (*p < 0.05).

Figure 4

Example of robotic data collected by the HapticKnob. Evolution of pronation movements for patient A3 over the course of the therapy at sessions 1, 4, 8, 12, 16 and 18, each line representing one trial. The target angular position window is represented by horizontal dashed lines. Details of parameters extracted from the kinematic data are given in the lower left plot for one successful trial; tr is the time required to reach the target window for the first time, and ta is the time required to finely adjust the forearm position.