Stroke is the second most common cause of mortality and the third most common cause of disability worldwide (1, 2). More than two-thirds of people who have had a stroke have difficulties with arm function, which contributes considerably in limiting the ability to perform activities of daily living (ADLs) (3, 4). Though various studies have reported positive outcomes following multiple types of interventions in more mildly impaired individuals (5, 6), regaining hand function in individuals with moderate-to-severe impairments still remains a challenge. This is largely due to impairments, such as the loss of volitional finger extension (7, 8), muscle coactivation (7), involuntary coupling of wrist and finger flexion with certain shoulder and elbow movements (9), and somatosensory deficits (10).
Several studies have suggested that repetitive task-specific training can improve upper extremity (UE) function (11–14) in mildly impaired stroke survivors when the practice is functionally relevant and of sufficient intensity. Intervention-induced gains have been reported for up to 6 months after intervention (15). In particular, interventions focusing on reach and grasp movements have been shown to be relevant because these movements are essential for ADLs and are viewed by subjects as high priority rehabilitative goals (16, 17). This approach has often been used in individuals in both the acute and subacute stage (18–20) and with mild-to-moderate impairments after stroke (6, 18, 21).
There is limited research targeting chronic stroke individuals with severely impaired UE. These individuals are less able to participate in task-specific training because of minimal volitional activation of the impaired arm (16). Furthermore, during ADLs, concurrent use of hand and arm are required. However, the presence of the flexion synergy after stroke (22–24), coupled with shoulder abduction with elbow/wrist and fingers flexion (9), decreases the ability to generate volitional or functional electrical stimulation (FES)-assisted finger extension while lifting against gravity (25, 26). This creates a major challenge to rehabilitation clinicians and limits opportunities for this population to participate in programs focused on hand recovery (16).
The purpose of this study is to determine the effect of device-assisted task-specific training on hand motor function and sensation (stereognosis and cutaneous sensory touch threshold) in individuals with chronic stroke and severe UE impairment. An electromyography-driven functional electrical stimulation (EMG-FES) with an intelligent detection software that detects the hand opening intention even with the presence of flexion synergies was used to assist the hand opening while subjects were performing required reaching and grasping tasks. We expected that by training a functional activity that involves arm-lifting, reaching and grasping, retrieving and releasing, poststroke participants with severely impaired UE would improve their arm/hand motor function and sensation.
Some parts of the results from various assessments [i.e., pre- to post-changes in an active range of motion (AROM) and Box and Blocks Test (BBT)] have been briefly reported in a previous publication (27) that focused on brain plasticity introduced by this ReIn-Hand assisted reaching and grasping intervention. Compared to the previous publication, this paper provides a complete overall report on various intervention-induced clinical changes.[…]