A Musculoskeletal Model of the Hand and Wrist Capable of Simulating Functional Tasks

Objective: The purpose of this work was to develop an open-source musculoskeletal model of the hand and wrist and to evaluate its performance during simulations of functional tasks. Methods: The musculoskeletal model was developed by adapting and expanding upon existing musculoskeletal models. An optimal control theory framework that combines forward-dynamics simulations with a simulated-annealing optimization was used to simulate maximum grip and pinch force. Active and passive hand opening were simulated to evaluate coordinated kinematic hand movements. Results: The model's maximum grip force production matched experimental measures of grip force, force distribution amongst the digits, and displayed sensitivity to wrist flexion. Simulated lateral pinch strength fell within variability of in vivo palmar pinch strength data. Additionally, predicted activation for 7 of 8 muscles fell within variability of EMG data during palmar pinch. The active and passive hand opening simulations predicted reasonable activations and demonstrated passive motion mimicking tenodesis, respectively. Conclusion: This work advances simulation capabilities of hand and wrist models and provides a foundation for future work to build upon. Significance: This is the first open-source musculoskeletal model of the hand and wrist to be implemented during both functional kinetic and kinematic tasks. We provide a novel simulation framework to predict maximal grip and pinch force which can be used to evaluate how potential surgical and rehabilitation interventions influence these functional outcomes while requiring minimal experimental data.

Design and Performance Evaluation of a Hybrid Hand Exoskeleton for Hand Opening/Closing

Finger extensor muscle weakness and flexor hypertonia are the most commonly reported issues among patients suffering from amyotrophic lateral sclerosis (ALS). Moreover, the relative hyperflexion of the wrist and the fingers has limited their ability to open the hand and interact with the external environment voluntarily. In this work, a hybrid hand exoskeleton is developed to prevent the relative hyperflexion of the fingers and wrist and facilitate the users in their functional hand opening by compensating the flexor hypertonia. This exoskeleton, combining a passive device with the soft extra muscle (SEM) glove, assists users in normal hand opening/closing required for some basic activities of daily living. The paper presents kinematic and static models of passive hand exoskeleton design. Moreover, the proposed design is tested and evaluated by comparing the volunteer hand opening with the exoskeleton assistance using the flex sensors attached on the dorsal side of the middle finger, ring finger, and thumb with both healthy subjects and patients.

Real-World Functional Grasping Activity in Individuals With Stroke and Healthy Controls Using a Novel Wearable Wrist Sensor

Background. While wrist-worn accelerometers have been used to measure upper extremity use in the past, they primarily measure arm motion and lack the ability to capture functional hand opening and grasping activities which are essential for activities of daily living. Objectives. To characterize real-world functional hand opening and grasping activities captured over multiple days in adults with stroke and in matched controls using a novel wrist-worn device. Methods. Twenty-eight individuals (fourteen individuals with stroke and 14 healthy controls) wore the devices on both wrists for 3 days. Functional hand activity was characterized by daily hand counts, hourly hand counts, and asymmetry between hands. The Mann–Whitney U test was used to evaluate differences in functional hand activities between the two groups. Results. The stroke group had 1480 and 4691 daily hand counts in their affected and nonaffected hands, respectively. The control group had 3559 and 5021 daily hand counts in their nondominant and dominant hands, respectively. Significantly fewer daily hand counts (P = .019), fewer hourly hand counts (P = .024), and a larger asymmetry index (P = .01) of the affected hand in the stroke group were found compared to that of the nondominant hand in the control group. Conclusions. Real-world functional upper extremity activity can be measured using this novel wrist-worn device. Unlike wrist-worn accelerometers, this wrist-worn device can provide a measurement of functional grasping activity. The findings have implications for clinicians and researchers to monitor and assess real-world hand activity, as well as to apply specific doses of repetitions to improve neural recovery after stroke.

Neuromotor Prosthetic to Treat Stroke-Related Paresis

Background Functional recovery of independent arm movement typically plateaus within six months following a stroke, leaving chronic motor deficits. This feasibility study tested whether a wearable, powered exoskeletal orthosis, driven by a percutaneous, implanted brain–computer interface (BCI), using the activity of neurons in the precentral gyrus in the affected cortical hemisphere, could restore voluntary upper extremity function in a person with chronic hemiparetic subsequent to a cerebral hemispheric stroke of subcortical gray and white matter and cortical gray matter.Methods One person with chronic hemiparetic stroke with upper-limb motor impairment used a powered elbow-wrist-hand orthosis that opened and closed the affected hand using cortical activity, recorded from four 64-channel microelectrode arrays implanted in the ipsilesional precentral gyrus, based on decoding of spiking patterns and high frequency field potentials generated by imagined hand movements using technology and decoding methods used for people with other causes of paralysis. The system was evaluated in a home setting daily for 12 weeks. Results Robust single unit activity, modulating with attempted or imagined movement, was present throughout the precentral gyrus areas. The participant was able to acquire voluntary control over a hand-orthosis BCI, with a score of 10 points on the Action Research Arm Test (out of 53) using the BCI, compared to 0 without any device, and 5 using myoelectric control. Orthosis-powered hand-opening was faster with BCI control compared to myoelectric control, on a standardized object-movement task. Conclusions The findings demonstrate the therapeutic potential of an implantable BCI system coupled to a brace to “electrically bypass” the stroke and promote neurally driven limb function. The participant’s ability to rapidly acquire voluntary control over otherwise paralyzed hand opening, more than 18 months after a subcortical stroke, lays the foundation for a fully implanted movement restoration system.

Transfer of the supinator nerve to the posterior interosseous nerve for hand opening in tetraplegia through an anterior approach

We report a retrospective series of 44 transfers in 26 patients in whom a functioning supinator nerve was transferred to a paralyzed posterior interosseous nerve through a single, anterior approach to re-animate hand opening in mid-cervical tetraplegia. Eighteen patients underwent concurrent nerve or tendon transfers to re-animate grasp and/or pinch through the same anterior incision. We evaluated the strength of the innervated muscle at mean follow-up of 24 months (range 12–27). The strength attained in our patients was equivalent to the strength after the transfer through a posterior approach reported in the literature. Nineteen of our patients were satisfied with the hand opening procedure. First webspace opening was the only variable to correlate with patient satisfaction. We conclude that the anterior approach yields similar results to the posterior approach and has the advantage of allowing easier access for simultaneously performing nerve or tendon transfers to reconstruct grasp and pinch. Level of evidence: IV

Neuromotor Prosthetic to Treat Stroke-Related Paresis

BackgroundFunctional recovery of independent arm movement typically plateaus within six months following a stroke, leaving chronic motor deficits. This feasibility study tested whether a wearable, powered exoskeletal orthosis, driven by a percutaneous, implanted brain–computer interface (BCI), using the activity of neurons in the precentral gyrus in the affected cortical hemisphere, could restore voluntary upper extremity function in a person with chronic hemiparetic subsequent to a cerebral hemispheric stroke of subcortical gray and white matter and cortical gray matter.MethodsOne person with chronic hemiparetic stroke with upper-limb motor impairment used a powered elbow-wrist-hand orthosis that opened and closed the affected hand using cortical activity, recorded from four 64-channel microelectrode arrays implanted in the ipsilesional precentral gyrus, based on decoding of spiking patterns and high frequency field potentials generated by imagined hand movements using technology and decoding methods used for people with other causes of paralysis. The system was evaluated in a home setting daily for 12 weeks.ResultsRobust single unit activity, modulating with attempted or imagined movement, was present throughout the precentral gyrus areas. The participant was able to acquire voluntary control over a hand-orthosis BCI, with a score of 10 points on the Action Research Arm Test (out of 53) using the BCI, compared to 0 without any device, and 5 using myoelectric control. Orthosis-powered hand-opening was faster with BCI control compared to myoelectric control, on a standardized object-movement task.ConclusionsThe findings demonstrate the therapeutic potential of an implantable BCI system coupled to a brace to “electrically bypass” the stroke and promote neurally driven limb function. The participant’s ability to rapidly acquire voluntary control over otherwise paralyzed hand opening, more than 18 months after a subcortical stroke, lays the foundation for a fully implanted movement restoration system.

A Plug-and-Train Robot (PLUTO) for Hand Rehabilitation: Design and Preliminary Evaluation

Hand neurorehabilitation involves the training of movements at various joints of the forearm, wrist, fingers, and thumb. Assisted training of all these joints either requires either one complex multiple degree-of-freedom (DOF) robot or a set of simple robots with one or two DOF. Both of these are not economically or clinically viable solutions. The paper presents work that addresses this problem with a single DOF robot that can train multiple joints one at a time – the plug and train robot (PLUTO). PLUTO has a single actuator with a set of passive attachments/mechanisms that can be easily attached/detached to train for wrist flexion-extension, wrist ulnar-radial deviation, forearm pronation-supination, and gross hand opening-closings. The robot can provide training in active and assisted regimes. PLUTO is linked to performance adaptive computer games to provide feedback to the patients and motivate them during training. As the first step toward clinical validation, the device's usability was evaluated in 45 potential stakeholders/end-users of the device, including 15 patients, 15 caregivers, and 15 clinicians with standardized questionnaires: System Usability Scale (SUS) and User Experience Questionnaire (UEQ). Patients and caregivers were administered the questionnaire after a two-session training. Clinicians, on the other hand, had a single session demo after which feedback was obtained. The total SUS score obtained from the patients, clinicians, and healthy subjects was 73.3 ± 14.6 (n = 45), indicating good usability. The UEQ score was rated positively in all subscales by both the patients and clinicians, indicating that the features of PLUTO match their expectations. The positive response from the preliminary testing and the feedback from the stakeholders indicates that with additional passive mechanisms, assessment features, and optimized ergonomics, PLUTO will be a versatile, affordable, and useful system for routine use in clinics and also patients’ homes for delivering minimally supervised hand therapy.

Analysis of Minimal Channels Electroencephalography for Wearable BCI: Development and Usability Study (Preprint)

BACKGROUND Electroencephalography (EEG) is a non-invasive Brain Computer Interface (BCI) technology that has shown potential in various healthcare applications such as epilepsy treatment, sleep disorder diagnosis, and stroke rehabilitation. Usually these applications require multi-channels EEG. However, multi-channel EEG headset setup process is time consuming. This may result in low patients’ acceptance despite BCI potential benefits. OBJECTIVE To investigate the number of appropriate electrodes, which could be crucial for successful applications of BCI in wearable devices. METHODS Motor Imagery (MI) classification system is used for our analysis. Different number of EEG channels was selected. EEG Multi-frequency features were extracted by Filter Bank (FB). Support Vector Machine (SVM) was used in classifying left and right hand opening/closing MI task. RESULTS The results showed that the group of nine electrodes gave high classification accuracy while requiring moderate set-up time, and hence is suggested as the minimal number of channels. Spherical spline interpolation (SSI) was also applied to investigate the feasibility of generating EEG signal from limited channels of EEG headset. The classification accuracies of the interpolated groups only, and the combined interpolated and collected group, were significantly lower than those of measured groups CONCLUSIONS For wearable device, one of the key factors that need to be concerned is wearability. The number of channels of EEG device adversely affects to set-up time. With FB feature and session dependent training, the investigation of number of channels provides the possibility to develop a successful BCI application using minimal channels EEG device. Interpolation technique which could approximate additional electrode data from nearby electrodes should be also explored.

The effects of anxiety and dual-task on upper limb motor control of chronic stroke survivors

This study was designed to investigate the effects of anxiety and dual-task on reach and grasp motor control in chronic stroke survivors compared with age- and sex-matched healthy subjects (HC). Reach and grasp kinematic data of 68 participants (high-anxiety stroke (HA-stroke), n = 17; low-anxiety stroke (LA-stroke), n = 17; low-anxiety HC, n = 17; and high-anxiety HC, n = 17) were recorded under single- and dual-task conditions. Inefficient reach and grasp of stroke participants, especially HA-stroke were found compared with the control groups under single- and dual-task conditions as evidenced by longer movement time (MT), lower and earlier peak velocity (PV) as well as delayed and smaller hand opening. The effects of dual-task on reach and grasp kinematic measures were similar between HCs and stroke participants (i.e., increased MT, decreased PV that occurred earlier, and delayed and decreased hand opening), with greater effect in stroke groups than HCs, and in HA-stroke group than LA-stroke group. The results indicate that performing a well-learned upper limb movement with concurrent cognitive task leads to decreased efficiency of motor control in chronic stroke survivors compared with HCs. HA-stroke participants were more adversely affected by challenging dual-task conditions, underlying importance of assessing anxiety and designing effective interventions for it in chronic stroke survivors.