Conference Paper

# Hand rehabilitation after stroke using a wearable, high DOF, spring powered exoskeleton

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## Abstract

Stroke patients often have inappropriate finger flexor activation and finger extensor weakness, which makes it difficult to open their affected hand for functional grasp. The goal was to develop a passive, lightweight, wearable device to enable improved hand function during performance of activities of daily living. The device, HandSOME II, assists with opening the patient's hand using 11 elastic actuators that apply extension torques to finger and thumb joints. Device design and initial testing are described. A novel mechanical design applies forces orthogonal to the finger segments despite the fact that all of the device DOFs are not aligned with human joint DOF. In initial testing with seven stroke subjects with impaired hand function, use of HandSOME II significantly increased maximum extension angles and range of motion in all of the index finger joints (P<;0.05). HandSOME II allows performance of all the grip patterns used in daily activities and can be used as part of home-based therapy programs.

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... The HandSOME II expands the HandSOME concept to control more complex grasp patterns used in ADL [19] (Fig. 1). The HandSOME II is comprised of rigid mechanical linkages that allow isolated joint movement and elastic elements that provide customized extension assistance for each finger and thumb DOF. ...
... All parts were laser cut acrylic plastic or 3D printed ABS plastic. Full details on the HandSOME II mechanical design have been reported previously [19]. While the technical description of the device has already been reported, the goal of this study was to examine how much the HandSOME II device improves range of motion (ROM) and increases success rate in reach and grasp tasks in individuals with various levels of hand impairment due to stroke. ...
Article
Full-text available
In previous work, we developed an exoskeleton, Hand Spring Operated Movement Enhancer (HandSOME II), that allows movement at 15 hand degrees of freedom (DOF). Eleven separate elastic elements can be added to customize the extension assistance for individuals with impaired hand function. In this pilot study of twelve individuals with stroke, we measured the immediate improvements in range of motion (ROM) and upper extremity function when wearing the device. Index finger ROM was significantly improved at the PIP (p=.01) and DIP joints (p=.026), and the max extension was significantly increased at the MCP (p<.001), PIP (p=.013) and DIP joints (p=.016). The thumb CMC abduction max (p=.017) and CMC flexion/extension ROM also increased (p=.04). In a grip and release task involving various objects, six subjects were unable to complete the tasks without assistance. Across these 6 subjects, 13 of 42 tasks were completed without assistance, while 36 of 42 tasks were completed when wearing HandSOME II. Despite the extension assistance provided by the device, flexion grip force was not statistically decreased. HandSOME II can potentially increase the effectiveness of repetitive task practice in patients with moderate-severe hand impairment by allowing completion of grasp and release tasks that are impossible to complete unassisted.
... However, all of these gains were lost at a 3-month followup. The next iteration of the device, Handsome II, expands the HandSOME I concept, allowing customized adjustment of the extension assistance to 11 different finger joints and practice of more complex grasp patterns used in daily activities (Tianyao and Lum, 2016). In a prior study, we showed donning the device immediately increases extension range of motion in the fingers and improves ability in grasp and release tasks (Casas et al., 2021b). ...
Article
Full-text available
We have developed a passive and lightweight wearable hand exoskeleton (HandSOME II) that improves range of motion and functional task practice in laboratory testing. For this longitudinal study, we recruited 15 individuals with chronic stroke and asked them to use the device at home for 1.5 h per weekday for 8 weeks. Subjects visited the clinic once per week to report progress and troubleshoot problems. Subjects were then given the HandSOME II for the next 3 months, and asked to continue to use it, but without any scheduled contact with the project team. Clinical evaluations and biomechanical testing was performed before and after the 8 week intervention and at the 3 month followup. EEG measures were taken before and after the 8 weeks of training to examine any recovery associated brain reorganization. Ten subjects completed the study. After 8 weeks of training, functional ability (Action Research Arm Test), flexor tone (Modified Ashworth Test), and real world use of the impaired limb (Motor Activity Log) improved significantly ( p < 0.05). Gains in real world use were retained at the 3-month followup ( p = 0.005). At both post-training and followup time points, biomechanical testing found significant gains in finger ROM and hand displacement in a reaching task ( p < 0.05). Baseline functional connectivity correlated with gains in motor function, while changes in EEG functional connectivity paralleled changes in motor recovery. HandSOME II is a low-cost, home-based intervention that elicits brain plasticity and can improve functional motor outcomes in the chronic stroke population.
... Each approach has advantages and disadvantages. Wearable devices can be used during whole upper extremity tasks, such as reach and grasp tasks, and can take the form of active (12)(13)(14)(15)(16)(17)(18)(19)(20) or passive exoskeletons (21)(22)(23)(24), with a growing emphasis on soft robotics (25). However, because of space and weight constraints in wearable devices, movement kinematics and control algorithms can often be more precise and sophisticated with desktop devices that isolate finger movements, but don't allow use of the hand with objects or in conjunction with proximal arm joints (26)(27)(28)(29)(30)(31)(32)(33). ...
Article
Full-text available
Impaired use of the hand in functional tasks remains difficult to overcome in many individuals after a stroke. This often leads to compensation strategies using the less-affected limb, which allows for independence in some aspects of daily activities. However, recovery of hand function remains an important therapeutic goal of many individuals, and is often resistant to conventional therapies. In prior work, we developed HEXORR I, a robotic device that allows practice of finger and thumb movements with robotic assistance. In this study, we describe modifications to the device, now called HEXORR II, and a clinical trial in individuals with chronic stroke. Fifteen individuals with a diagnosis of chronic stroke were randomized to 12 or 24 sessions of robotic therapy. The sessions involved playing several video games using thumb and finger movement. The robot applied assistance to extension movement that was adapted based on task performance. Clinical and motion capture evaluations were performed before and after training and again at a 6-month followup. Fourteen individuals completed the protocol. Fugl-Meyer scores improved significantly at the 6 month time point compared to baseline, indicating reductions in upper extremity impairment. Flexor hypertonia (Modified Ashworth Scale) also decreased significantly due to the intervention. Motion capture found increased finger range of motion and extension ability after the intervention that continued to improve during the followup period. However, there was no change in a functional measure (Action Research Arm Test). At the followup, the high dose group had significant gains in hand displacement during a forward reach task. There were no other significant differences between groups. Future work with HEXORR II should focus on integrating it with functional task practice and incorporating grip and squeezing tasks.
... In order to realize the coincidence of MCP joint center and rotating center of mechanism, avoid the interference of mechanism with human hands and secondary injury to the soft tissue of human hands, the parallelograms remote projection center mechanism is used to drive MCP Joint as shown in Fig.2. In the parallelogram linkage EDFG, ED = GF, EG = DF, and the bar length GI and FN are equal which is similar with the prototype in [21]. It can be seen that hinge point I rotates around point N, which is stationary relative to frame DF. ...
Article
The functions of human hand are rich, and the motor dysfunction of hand of chronic stroke patients can be alleviated to some extent through active rehabilitation training. Hand rehabilitation exoskeleton can assist patients to do active rehabilitation training. However, how to realize more motion with less surface electromyogrphy (sEMG) sensors, and how to realize the real-time motion intention recognition are two important issues. This paper introduces real-time motion intention recognition method with limited number of sEMG sensors for a 7-DOF wearable hand/wrist rehabilitation exoskeleton to realize the real-time motion intention recognition and rehabilitation training. Root mean square (RMS) and Bens Spiker Algorithm (BSA) features of three-channel sEMG signals are extracted, and they are mapped to seven different intention movements by combining the Bagging method. The finger structure part of the exoskeleton is composed of a rotary-spatial-spatial-rotary (RSSR) mechanism and a double-parallelogram mechanism, which makes the projection center of exoskeleton coincide with the rotation center of the hand joint. The average real-time motion intention recognition accuracy is 95.37 ± 0.97%.
... Stoke patients usually suffer from inappropriate flexor and extensor weakness which creates problems to have a functional grasp [14]. While we have a large proportion of population suffering from strokes, functional recovery in upper limbs becomes important, with chances of regaining functional use of impaired hand being low. ...
... In this work the mechanism are classified for three specific functions: rehabilitation, haptic and assistance. For this paper the devices shown en [1,3,13] are important, these are tools used by persons with hand disabilities in their daily life and being able to carry out normally impossible activities without help. ...
Article
This paper presents a glove-type support system that allows a reduction of factors such as weight and volume loaded by the user due to the Driven Cable Mechanism. It was designed to control a differential mechanism for multiple fingers which distributes the forces on the finger that requires more support during the flexion, allowing an adaptive grip. The whole system guide characteristic grip movements according to human biomechanics. It can be used as an alternative tool to perform muscle therapy or rehabilitation of the opening and closing of the hand in disabled people.
... Wearable devices can be used during whole upper extremity tasks, such as reach and grasp tasks, and can take the form of active [11][12][13][14][15][16][17][18] or passive exoskeletons. [19][20][21][22] However, because of space and weight constraints in wearable devices, movement kinematics and control algorithms can often be more precise and sophisticated with desktop devices that isolate nger movements, but don't allow use of the hand with objects or in conjunction with proximal arm joints. [23][24][25][26][27][28][29][30] Many hand robots are still in the proof-of-concept prototyping phase and have not gone through clinical testing. ...
Preprint
Full-text available
Background Impaired use of the hand in functional tasks remains difficult to overcome in many individuals after a stroke. This often leads to compensation strategies using the less-affected limb, which allows for independence in some aspects of daily activities. However, recovery of hand function remains an important therapeutic goal of many individuals, and is often resistant to conventional therapies. In prior work, we developed HEXORR I, a robotic device that allows practice of finger and thumb movements with robotic assistance. In this study, we describe modifications to the device, now called HEXORR II, and a clinical trial in individuals with chronic stroke. Methods Fifteen individuals with a diagnosis of chronic stroke were randomized to 12 or 24 sessions of robotic therapy. The sessions involved playing several video games using thumb and finger movement. The robot applied assistance to extension movement that was adapted based on task performance. Clinical and motion capture evaluations were performed before and after training and again at a 6 month followup. Results Fourteen individuals completed the protocol. Fugl-Meyer scores improved significantly over the 3 time points, indicating reductions in upper extremity impairment. Flexor hypertonia (Ashworth) also decreased significantly due to the intervention. Motion capture found increased finger range of motion and extension ability when the arm was supported by gravity. However, extension ability did not improve significantly during a reach and grasp task, and there was no change in a functional measure (Action Research Arm Test). At the followup, the high dose group had significant gains in hand displacement during a forward reach task. There were no other significant differences between groups. Conclusions Future work with HEXORR II should focus on integrating it with functional task practice and incorporating grip and squeezing tasks. Trial registration: CLINICALTRIALS.GOV, NCT04536987. Registered 3 September 2020 - Retrospectively registered, https://clinicaltrials.gov/ct2/show/record/NCT04536987
... The HandMATE device ( Fig. 1) builds upon the Hand Spring Operated Movement Enhancer (HandSOME) devices [16,17,18]. The HandSOME devices are non-motorized wearable exoskeletons that assists stroke patients with finger and thumb extension movements. ...
Conference Paper
Full-text available
We have developed HandMATE (Hand Movement Assisting Therapy Exoskeleton); a wearable motorized hand exoskeleton for home-based movement therapy following stroke. Each finger and the thumb is powered by a linear actuator which provides flexion and extension assistance. Force sensitive resistors integrated into the design measure grasp and extension initiation force. An assistive therapy mode is based on an admittance control strategy. We evaluated our control system via subject and bench testing. Errors during a grip force tracking task while using the HandMATE were minimal (<1%) and comparable to unassisted healthy hand performance. We also outline a dedicated app we have developed for optimal use of HandMATE at home. The exoskeleton communicates wirelessly with an Android tablet which features guided exercises, therapeutic games and performance feedback. We surveyed 5 chronic stroke patients who used the HandMATE device to further evaluate our system, receiving positive feedback on the exoskeleton and integrated app.
... Encoders and potentiometers can be used in clinical environments to measure ROM in patients. Researchers at Peter S. Lum's lab [80,81] built an orthosis consisting of four bars coordinating the movement of the metacarpophalangeal finger joints and the thumb metacarpophalangeal joint for home-based training in stroke patients, using encoders to calculate the joint angles. ...
Article
Full-text available
Stroke is one of the main causes of long-term disability worldwide, placing a large burden on individuals and society. Rehabilitation after stroke consists of an iterative process involving assessments and specialized training, aspects often constrained by limited resources of healthcare centers. Wearable technology has the potential to objectively assess and monitor patients inside and outside clinical environments, enabling a more detailed evaluation of the impairment and allowing the individualization of rehabilitation therapies. The present review aims to provide an overview of wearable sensors used in stroke rehabilitation research, with a particular focus on the upper extremity. We summarize results obtained by current research using a variety of wearable sensors and use them to critically discuss challenges and opportunities in the ongoing effort towards reliable and accessible tools for stroke rehabilitation. Finally, suggestions concerning data acquisition and processing to guide future studies performed by clinicians and engineers alike are provided.
... More aggressive applications, such as for motion augmentation in healthy individuals, are possible if SEE stiffness is increased. Future work includes building a shoulder module with similar features, and integrating a finger exoskeleton [33] to build a whole arm exoskeleton. ...
Article
Movement impairments resulting from neurologic injuries, such as stroke, can be treated with robotic exoskeletons that assist with movement retraining. Exoskeleton designs benefit from low impedance and accurate torque control. We designed a two-degrees-of-freedom tethered exoskeleton that can provide independent torque control on elbow flexion/extension and forearm supination/pronation. Two identical series elastic actuators (SEAs) are used to actuate the exoskeleton. The two SEAs are coupled through a novel cable-driven differential. The exoskeleton is compact and lightweight, with a mass of 0.9 kg. Applied rms torque errors were less than 0.19 Nm. Benchtop tests demonstrated a torque rise time of approximately 0.1 s, a torque control bandwidth of 3.7 Hz, and an impedance of less than 0.03 Nm/° at 1 Hz. The controller can simulate a stable maximum wall stiffness of 0.45 Nm/°. The overall performance is adequate for robotic therapy applications and the novelty of the design is discussed.
... Simple and lightweight passive devices were developed to assist hand function at home. They target the reinforcement of the tenodesis effect for tetraplegic patients [28] or the assistance of hand opening for stroke patients [29,30]. Proof-of-concept studies showed their biomechanical efficiency, but their clinical use is not yet documented. ...
... Hand exoskeletons are often deployed clinically to assist motion e.g. improve force development (Heo et al., 2012) or finger flexion (Chen and Lum, 2016). Associated with the mechanical constraints of the exoskeleton a slight change in the kinematics could be expected which was also shown for EMG activity during a study that aimed to assess the physiological consequences of using an upper limb exoskeleton during manual handling tasks (Theurel et al., 2018). ...
Article
Exoskeletons are progressively reaching homes and workplaces, allowing interaction with virtual environments, remote control of robots, or assisting human operators in carrying heavy loads. Their design is however still a challenge as these robots, being mechanically linked to the operators who wear them, have to meet ergonomic constraints besides usual robotic requirements in terms of workspace, speed, or efforts. They have in particular to fit the anthropometry and mobility of their users. This traditionally results in numerous prototypes which are progressively fitted to each individual person. In this paper, we propose instead to validate the design of a hand exoskeleton in a fully digital environment, without the need for a physical prototype. The purpose of this study is thus to examine whether finger kinematics are altered when using a given hand exoskeleton. Therefore, user specific musculoskeletal models were created and driven by a motion capture system to evaluate the fingers' joint kinematics when performing two industrial related tasks. The kinematic chain of the exoskeleton was added to the musculoskeletal models and its compliance with the hand movements was evaluated. Our results show that the proposed exoskeleton design does not influence fingers’ joints angles, the coefficient of determination between the model with and without exoskeleton being consistently high (R2=0.93) and the nRMSE consistently low (nRMSE = 5.42°). These results are promising and this approach combining musculoskeletal and robotic modeling driven by motion capture data could be a key factor in the ergonomics validation of the design of orthotic devices and exoskeletons prior to manufacturing.
... Therefore, it can potentially be more efficient and could lead to less MRI scanning time and fewer ablations. In addition, the robot allows insertion from several angles through the custom design remote center of motion (RCM) mechanism [23], as opposed to straight insertion through a conventional template. As a result, the robot can access to tumors behind critical structures such as the urethra. ...
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Objective: A Magnetic Resonance Imaging (MRI)-conditional needle guidance robot is developed to enhance MRI-guided Focal Laser Ablation (FLA) therapy in patients with focal prostate cancer. Methods: Inspired by the workflow of the manual FLA therapy, we developed an MRI-conditional robot with two degrees of freedom (DoF) to provide the guidance for laser ablation catheter. This robot is powered by pneumatic turbine motors and encoded with the custom-designed optical encoder. The needle could be inserted manually through the designed robotic system, which keeps the patients inside MRI bore throughout the procedure. The robot hardware is integrated with the custom ablation planning and monitoring software (OncoNav) to provide an iterative treatment plan to cover the whole ablation zone. Virtual tumors were selected in three canine cadavers as targets to validate the performance of the proposed hardware and software system. Results: Phantom studies show that the average targeting error is less than 2mm and the workflow of the entire procedure lasts for 100 minutes. Canine cadaver experiment results show that all the targets were successfully ablated in no more than three administrations. Significance: MRI-guided prostate FLA is feasible using the proposed hardware and software system, indicating potential utility in future human trials.
... Another hand rehabilitation devices based on the portable design overcome this issue, which are compact and effective. However, some portable devices have rigid component and complex mechanical structure [12,13,14], which makes them uneasily wearable, high-cost, and likely to hurt patient's hands when these devices are out of control. Therefore, these devices are limited in practical use either. ...
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Book
This book gathers the latest advances, innovations, and applications in the field of multibody and mechatronic systems. Topics addressed include the analysis and synthesis of mechanisms; modelling and simulation of multibody systems; railway and vehicle dynamics; mechatronic systems for energy harvesting; robot design and optimization; and mechatronic design. It gathers the second volume of the proceedings of the 7th International Symposium on Multibody Systems and Mechatronics (MuSMe), virtually held in Cordoba, Argentina, on October 12-15, 2021, within the framework of the FEIbIM Commission for Robotics and Mechanisms and IFToMM Technical Committees for Multibody Dynamics and for Robotics and Mechatronics.
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During the COVID-19 pandemic, the higher susceptibility of post-stroke patients to infection calls for extra safety precautions. Despite the imposed restrictions, early neurorehabilitation cannot be postponed due to its paramount importance for improving motor and functional recovery chances. Utilizing accessible state-of-the-art technologies, home-based rehabilitation devices are proposed as a sustainable solution in the current crisis. In this paper, a comprehensive review on developed home-based rehabilitation technologies of the last 10 years (2011–2020), categorizing them into upper and lower limb devices and considering both commercialized and state-of-the-art realms. Mechatronic, control, and software aspects of the system are discussed to provide a classified roadmap for home-based systems development. Subsequently, a conceptual framework on the development of smart and intelligent community-based home rehabilitation systems based on novel mechatronic technologies is proposed. In this framework, each rehabilitation device acts as an agent in the network, using the internet of things (IoT) technologies, which facilitates learning from the recorded data of the other agents, as well as the tele-supervision of the treatment by an expert. The presented design paradigm based on the above-mentioned leading technologies could lead to the development of promising home rehabilitation systems, which encourage stroke survivors to engage in under-supervised or unsupervised therapeutic activities.
Book
This book gathers the latest advances, innovations, and applications in the field of multibody and mechatronic systems. Topics addressed include the analysis and synthesis of mechanisms; dynamics of multibody systems; design algorithms for mechatronic systems; robots and micromachines; experimental validations; theory of mechatronic simulation; mechatronic systems for rehabilitation and assistive technologies; mechatronic systems for energy harvesting; virtual reality integration in multibody and mechatronic systems; multibody design in robotic systems; and control of mechatronic systems. The contents reflect the outcomes of the 7th International Symposium on Multibody Systems and Mechatronics (7th MuSMe) in 2020, within the framework of the FEIbIM Commission for Robotics and Mechanisms and IFToMM Technical Committees for Multibody Dynamics and for Robotics and Mechatronics.
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Stroke patients often have flexor hypertonia and finger extensor weakness, which makes it difficult to open their affected hand for functional grasp. Because of this impairment, hand rehabilitation after stroke is essential for restoring functional independent lifestyles. The goal of this study is to develop a passive, lightweight, wearable device to assist with hand function during performance of activities of daily living. The device, Hand Spring Operated Movement Enhancer (HandSOME), assists with opening the patient's hand using a series of elastic cords that apply extension torques to the finger joints and compensates for the flexor hypertonia. Device design and calibration are described as well as functional and usability testing with stroke subjects with a wide range of hand impairments. In initial testing with eight stroke subjects with finger flexor hypertonia, use of the HandSOME significantly increased range of motion ( p <; 0.001) and functional ability ( p =0.002) . There was some decrease in grip strength with the HandSOME device at the subject's ideal setting, however this was not statistically significant ( p =0.167) and did not seem to have a significant effect on function. Overall HandSOME shows promise as a training tool to facilitate repetitive task practice for improving hand function in stroke patients. HandSOME can be used as part of a home-based therapy program, or as an orthotic for replacing lost function.
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While a number of devices have recently been developed to facilitate hand rehabilitation after stroke, most place some restrictions on movement of the digits or arm. Thus, a novel glove was developed which can provide independent extension assistance to each digit while still allowing full arm movement. This pneumatic glove, the PneuGlove, can be used for training grasp-and-release movements either with real objects or with virtual objects in a virtual reality environment. Two groups of stroke survivors, with seven subjects in each group, completed a six-week rehabilitation training protocol, consisting of three 1-h sessions held each week. One group wore the PneuGlove during training, performed both within a novel virtual reality environment and outside of it with physical objects, while the other group completed the same training without the device. Across subjects, significant improvements were observed in the Fugl-Meyer Assessment for the upper extremity (p < 0.001), the hand/wrist portion of the Fugl-Meyer Assessment (p < 0.001), the Box and Blocks test (p < 0.005), and palmar pinch strength (p < 0.005). While changes in the two groups were not statistically different, the group using the PneuGlove did show greater mean improvement on each of these measures, such as gains of 3.7 versus 2.4 points on the hand/wrist portion of the Fugl-Meyer Assessment and 14 N versus 5 N in palmar pinch.
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Treatment options for stroke survivors with severe hand impairment are limited. Active task practice can be restricted by difficulty in voluntarily activating finger muscles and interference from involuntary muscle excitation. We developed a portable, actuated glove-orthosis, which could be employed to address both issues. We hypothesized that combining passive cyclical stretching (reducing motoneuronal hyperexcitability) imposed by the device with active-assisted, task-oriented training (rehabilitating muscle activation) would improve upper extremity motor control and task performance post-stroke. Thirteen participants who experienced a stroke 2-6 months prior to enrollment completed 15 treatment sessions over five weeks. Each session involved cyclically stretching the long finger flexors (30 min) followed by active-assisted task-oriented movement practice (60 min). Outcome measures were completed at six intervals: three before and three after treatment initiation. Overall improvement in post-training scores was observed across all outcome measures, including the Graded Wolf Motor Function Test, Action Research Arm Test, and grip and pinch strength (μm p} ≤ 0.02 ), except finger extension force. No significant change in spasticity was observed. Improvement in upper extremity capabilities is achievable for stroke survivors even with severe hand impairment through a novel intervention combining passive cyclical stretching and active-assisted task practice, a paradigm which could be readily incorporated into the clinic.
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The goal of this review was to discuss the impairments in hand function after stroke and present previous work on robot-assisted approaches to movement neurorehabilitation. Robotic devices offer a unique training environment that may enhance outcomes beyond what is possible with conventional means. Robots apply forces to the hand, allowing completion of movements while preventing inappropriate movement patterns. Evidence from the literature is emerging that certain characteristics of the human-robot interaction are preferable. In light of this evidence, the robotic hand devices that have undergone clinical testing are reviewed, highlighting the authors' work in this area. Finally, suggestions for future work are offered. The ability to deliver therapy doses far higher than what has been previously tested is a potentially key advantage of robotic devices that needs further exploration. In particular, more efforts are needed to develop highly motivating home-based devices, which can increase access to high doses of assisted movement therapy.
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Initial work on robot-assisted neurorehabilitation for the upper extremity aimed primarily at training, reaching movements with the proximal sections of the upper extremity. However, recent years have seen a surge in devices dedicated to hand function. This review describes the state of the art and the promises of this novel therapeutic approach. Numerous robotic devices for hand function with various levels of complexity and functionality have been developed over the last 10 years. These devices range from simple mechanisms that support single joint movements to mechanisms with as many as 18 degrees-of-freedom (DOF) that can support multijoint movements at the wrist and fingers. The results from clinical studies carried out with eight out of 30 reported devices indicate that robot-assisted hand rehabilitation reduces motor impairments of the affected hand and the arm, and improves the functional use of the affected hand. The current evidence in support of the robot-assisted hand rehabilitation is preliminary but very promising, and provides a strong rationale for more systematic investigations in the future.
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Subjects with chronic hemiplegia following stroke attempted to perform voluntary isometric, isokinetic, and free contractions of the extensor muscles of the metacarpophalangeal (MCP) joints. We recorded torque, metacarpophalangeal joint angle and velocity, and electromyographic (EMG) activity of the extrinsic extensors and flexors and the first dorsal interosseous (FDI). We found that voluntary MCP joint extension in hemiparetic subjects was greatly impaired in comparison with control subjects: only two of the 11 stroke subjects were able to generate even 0.21 N-m of isometric extension torque, only two could produce positive finger extension with no load, and none could develop an isokinetic concentric extension. Deficits seemed to result from a combination of coactivation of the finger flexor and extensor muscles and decreased voluntary excitation of the extensors, as normalized flexor and FDI EMG activity were greater for stroke than for control subjects (P < 0.001), but normalized extensor activity was reduced (P < 0.001).
Article
To assess the relative contributions of several neurologic and biomechanic impairment mechanisms to overall finger and hand impairment in chronic hemiparetic stroke survivors. Repeated-measures design. Clinical research laboratory. Thirty stroke survivors with chronic hemiparesis. Fifteen subjects had severe hand motor impairment and 15 had moderate impairment, as measured with the Chedoke-McMaster Stroke Assessment. Not applicable. The biomechanic factors stiffness and resting flexion torque, together with the neurologic factors spasticity, strength, and coactivation, were quantified by using a custom hand manipulator, a dynamometer, and electromyographic recordings. Both passive and active rotations of the metacarpophalangeal joints of the fingers were examined. Although subjects in the severely impaired group exhibited statistically greater passive stiffness and resting flexion torque than their moderately impaired counterparts (P<.05), the overall effect of these biomechanic changes appeared small in relation to the deficits attributable to neurologic changes such as spasticity and, especially, weakness. In fact, weakness in grip strength and isometric extension accounted for the greatest portion of the variance between the 2 groups (eta(2)=.40 and eta(2)=.23, respectively). Thus, deficits in hand motor control after stroke seem to derive mainly from weakness, which may be attributable to the loss of descending corticospinal pathway activation of motoneurons.
Article
To improve the accuracy of early postonset prediction of motor recovery in the flaccid hemiplegic arm, the effects of change in motor function over time on the accuracy of prediction were evaluated, and a prediction model for the probability of regaining dexterity at 6 months was developed. In 102 stroke patients, dexterity and paresis were measured with the Action Research Arm Test, Motricity Index, and Fugl-Meyer motor evaluation. For model development, 23 candidate determinants were selected. Logistic regression analysis was used for prognostic factors and model development. At 6 months, some dexterity in the paretic arm was found in 38%, and complete functional recovery was seen in 11.6% of the patients. Total anterior circulation infarcts, right hemisphere strokes, homonymous hemianopia, visual gaze deficit, visual inattention, and paresis were statistically significant related to a poor arm function. Motricity Index leg scores of at least 25 points in the first week and Fugl-Meyer arm scores of 11 points in the second week increasing to 19 points in the fourth week raised the probability of developing some dexterity (Action Research Arm Test >or=10 points) from 74% (positive predictive value [PPV], 0.74; 95% confidence interval [CI], 0.63 to 0.86) to 94% (PPV, 0.83; 95% CI, 0.76 to 0.91) at 6 months. No change in probabilities of prediction dexterity was found after 4 weeks. Based on the Fugl-Meyer scores of the flaccid arm, optimal prediction of arm function outcome at 6 months can be made within 4 weeks after onset. Lack of voluntary motor control of the leg in the first week with no emergence of arm synergies at 4 weeks is associated with poor outcome at 6 months.
Article
A number of longitudinal studies show that about one third of all patients regain dexterity following a stroke. However, the determinants of improvement of upper limb function are largely unknown. The aim of the present study was to investigate the longitudinal relationship of functional change in the upper paretic limb and change in time-dependent covariates in order to develop a multivariable regression model to predict improvement in dexterity. Based on 18 repeated measurements over time during the first post-stroke year, 101 stroke patients with first-ever ischemic middle cerebral artery strokes were investigated. Baseline characteristics as well as longitudinal information from Action Research Arm Test (ARAT), Fugl-Meyer arm and hand score (FM-arm and FM-hand), Motricity Index arm and leg score (MI-arm and MI-leg), letter cancellation task (LCT), Fugl-Meyer balance score (FM-balance) and progress of time were obtained prospectively. Outcome constituted of change scores on the ARAT over first year post stroke. Adjoining measurements of time-dependent variables were used to calculate time-dependent changes producing change scores. In total 1570 of the 1717 change scores were available for longitudinal regression analysis. The regression model shows that FM-hand change scores was the most important relative factor in predicting improvement on ARAT (standardized beta=0.357; p<0.001) followed by change scores on FM-arm (beta=0.007; p<0.001), whereas progress of time was significantly negatively associated with improvement on ARAT (beta=-0.001; p<0.001). Functional improvement of the upper paretic limb is mainly determined by improvement of the paretic hand, followed by synergistic independent movement of the paretic arm. Progress of time itself is an independent covariate that is negatively associated with upper limb function suggesting that most pronounced improvements occur earlier after stroke.