Effects of wearing an upper extremity exoskeleton on measuring joint kinematics during standardized clinical assessment tasks

Evaluating upper extremity (UE) motor impairment post-stroke commonly relies on established clinical assessments, which suffer from inherent subjectivity due to human visual inspection. The sensing capabilities of robotics can facilitate the objective assessment of motor impairment. The robotic device needs to not only precisely measure movement characteristics but also minimally interfere with natural movement to assess motor impairment effectively. However, the effect of wearing an exoskeleton on the performance of motor impairment assessment tasks has yet to be evaluated. Thus, this study aimed to evaluate whether the joint kinematics recorded during Fugl-Meyer Assessment (FMA) tasks performance are comparable between two conditions: 1) while wearing the exoskeleton and 2) without wearing the exoskeleton. Six healthy participants performed six single-degree-of-freedom sub-tasks of the upper extremity subscale of the Fugl-Meyer Assessment (FMA-UE), one of the standardized clinical assessments. We estimated joint angle trajectories in both conditions using the exoskeleton and a motion capture system, respectively. The coefficient of multiple correlation (CMC) was used to evaluate the similarity of joint kinematic trajectories between the two conditions. The range of motion (RoM) between the two conditions was also compared. The calculated CMC indicated a good-to-excellent level of agreement across all tasks between the wearing and non-wearing conditions (CMC > 0.90). The RoMs of all tasks in the two conditions except for shoulder flexion to 180° were not significantly different (p > 0.05). These results revealed the minimal effect of wearing the exoskeleton on joint kinematics during FMA subtask performance. In addition, these results imply that each exoskeleton segment was well-aligned and attached to the corresponding anatomical body segment within the exoskeleton measurement system. Overall, we conclude that the HARMONY exoskeleton can be a feasible measurement tool for clinical assessment tasks.