Hand Biomechanics Research Articles

Robotic Hand Exoskeletons for Rehabilitation and Assistance: A State-of-the-Art

Abstract Chronic hemiparesis and dystonic changes caused by a stroke are the main causes of the loss and decline of the human hand function, and the number of patients with hand dysfunction is increasing worldwide, seriously affecting their activities of daily living. Robotic medical devices such as robotic hand exoskeletons have been investigated to help restore and improve the hand function of these patients. In comparison with traditional therapies, robotic hand exoskeletons have the advantages of providing a controllable assistive force/torque, recording the wearer's motion data, and improving the wearer?s voluntary participation and motivation in the rehabilitation, which can improve the hand rehabilitation efficiency. This paper presents a systematic review of robotic hand exoskeletons. First, the biomechanics of a human hand is introduced. Next, the design concepts of robotic hand exoskeletons are proposed, which include the actuator design and configuration, human-machine kinematic compatibility, and design of degrees of freedom. Additionally, the control strategies of robotic hand exoskeletons are described. Finally, the limitations of the currently available robotic hand exoskeletons and their possible future research and development directions are discussed, thus providing useful information for the engineers and researchers to develop robotic hand exoskeletons with practical and plausible applications.

The effect of full-body weight-bearing on palmar pressure distribution in collegiate-level gymnasts

ABSTRACT Wrist and hand biomechanics under full-body load are not fully understood. To identify potential anatomy-related differences in hand loading, 15 former collegiate athletes completed a 45-second handstand on a novel emed® pressure platform system. Center of pressure (CoP) and force distribution across the palmar surface were analysed during the stabilised phase. Maximum force, mean pressure, and contact area were calculated in four palmar anatomic subregions: hypothenar, thenar, metacarpals, and fingers. These values were related to ulnar variance measurements obtained from a participant handstand hold in a weight-bearing computed tomography machine. About 93% of participants shifted their CoP towards their dominant hand (p < 0.001), and among all participants, the dominant hand applied an average of 8.91% (p = 0.002) higher maximum force than the nondominant hand. The proportion of total mean force was highest in the hypothenar (47.1%) and thenar regions (36.5%). Every 1.00 mm increase in ulnar variance corresponded to a 2.8% increase in maximum force in the hypothenar region (p = 0.037). This investigation emphasises the role of gymnastics hand dominance on left/right hand weight distribution and the importance of the hypothenar zone in distributing pressure during handstands. It also indicates that force transmission through the wrist to the palm is contingent on radioulnar positioning.

Biomechanical Hand Model: Modeling and Simulating the Lateral Pinch Movement

Abstract Background Hand movements are crucial in daily activities, sparking extensive interest and research in biomechanical models. While existing models offer valuable insights, their complexity and processing costs may limit their suitability for all applications, sometimes impeding research efficiency. Objectives This study aimed to develop a biomechanical model of the human hand for analyzing the physiology of lateral pinch movement. Unlike conventional methodologies, this approach focuses on delivering a computationally efficient model while incorporating the trapeziometacarpal joint into the analysis. Methods The model, which operates in a multibody environment, simulates lateral pinching movement by applying external time-varying torques to digit joints, emulating musculature, tendons, and ligaments. Torque estimation was achieved through the Euler-Lagrange approach. The model generates animated representations of the movement, aiding pathology identification and outputting dynamic variables. The model’s was validated through data acquired from asymptomatic subjects via an OptiTrack system. Results The average disparity between the expected and obtained joint angular displacements was $$\varvec{6.06~\%}$$ 6.06 % and $$\varvec{1.90~\%}$$ 1.90 % during validation and verification stages, suggesting high fidelity in the model performance. Correlation analysis revealed strong positive linear relationships and robust correlations between the obtained and expected configuration data. Model-generated pinch postures closely resembled expected physiological patterns, with results falling within the range for asymptomatic individuals documented in the scientific literature. Conclusion The system efficiently analyzes dynamic variables at a low computational cost, offering animated representations for pathology identification. The model’s potential for rehabilitation solutions and adaptability, coupled with its accuracy and versatility, make it an asset for advancing hand biomechanics research.

Video-based diagnosis support system for pianists with Musician's dystonia.

Musician's dystonia is a task-specific movement disorder that deteriorates fine motor control of skilled movements in musical performance. Although this disorder threatens professional careers, its diagnosis is challenging for clinicians who have no specialized knowledge of musical performance. To support diagnostic evaluation, the present study proposes a novel approach using a machine learning-based algorithm to identify the symptomatic movements of Musician's dystonia. We propose an algorithm that identifies the dystonic movements using the anomaly detection method with an autoencoder trained with the hand kinematics of healthy pianists. A unique feature of the algorithm is that it requires only the video image of the hand, which can be derived by a commercially available camera. We also measured the hand biomechanical functions to assess the contribution of peripheral factors and improve the identification of dystonic symptoms. The proposed algorithm successfully identified Musician's dystonia with an accuracy and specificity of 90% based only on video footages of the hands. In addition, we identified the degradation of biomechanical functions involved in controlling multiple fingers, which is not specific to musical performance. By contrast, there were no dystonia-specific malfunctions of hand biomechanics, including the strength and agility of individual digits. These findings demonstrate the effectiveness of the present technique in aiding in the accurate diagnosis of Musician's dystonia.

Biomechanical and aesthetic outcomes following radial forearm free flap transfer: comparison of ipsilateral full-thickness skin graft and traditional split-thickness skin graft

The radial forearm free flap (RFFF) is associated with donor site morbidity. This study aimed to quantify the functional and aesthetic outcomes after closure of the RFFF donor site using triangular full-thickness skin grafts (FTSGs) harvested adjacent to the flap or traditional split-thickness skin grafts (STSGs). The study included patients who underwent oral cavity reconstruction with an RFFF between March 2017 and August 2021. The patients were divided into two groups based on the donor site closure method: FTSG or STSG. The primary outcomes were biomechanical grip strength, pinch strength, and range of wrist movements. Subjective donor site morbidity, aesthetic and functional results were also analysed. The study included 75 patients (FTSG n = 35; STSG n = 40). Postoperatively, there was a statistically significant difference in grip strength (P = 0.049) and wrist extension (P = 0.047) between the FTSG and STSG groups, in favour of the STSG. Differences between the groups in pinch strength and other wrist motions were not statistically significant. The harvesting time was significantly shorter for the FTSG (P = 0.041) and the appearance of the donor site was better (P = 0.026) when compared to the STSG. Cold intolerance was more frequent in the STSG group (32.5% STSG vs 6.7% FTSG; P = 0.017). Subjective function, numbness, pain, hypertrophic scar, itching, and social stigma did not differ significantly between the groups. Compared with the STSG, the FTSG showed better cosmesis and avoided additional donor sites, with clinically negligible differences in hand biomechanics.

Functional and biomechanical assessment of the hand following ulnar forearm free flap transfer: Prospective self-controlled study.

There is a shortage of well-designed self-controlled studies evaluating hand biomechanics following ulnar forearm flap (UFF) harvest. This study was conducted to evaluate objective and subjective functional outcomes of the donor's hand following UFF harvest. All patients undergoing UFF were included for analysis. Grip strength, wrist movement, forearm supination and pronation, pinch strengths, sensation to light touch and temperature, and hand dexterity were assessed preoperatively and at 1, 3, and 6months postoperatively. In addition, DASH score (disabilities of the arm, shoulder, and hand score) and Patient and Observer Scar Assessment Scale (POSAS) were analyzed. A total of 18 patients were enrolled. A significant reduction in grip strength for donor's hand was observed between preoperative and postoperative 1 and 3months (mean difference=14 kg, 7.38 kg, respectively, p=0.000 for all). A similar trend was observed for pinch strength and range of motion (p < 0.05). Three months after surgery, there is still a significant reduction in tip pinch, tripod pinch, wrist extension, and supination. All biomechanics outcomes returned to preoperative baseline at 6months after surgery. No patients suffered significant changes in sensation to light touch, temperature, and numbness by 6months. There was a significant increase in DASH score by 3.37 points 6months after operation (p=0.000). The POSAS score indicates satisfaction with the appearance of the donor site. UFF is a safe and reliable option for oral cavity reconstruction with minimum donor site morbidities, mainly when cosmesis is paramount. Furthermore, objective hand biomechanics ultimately returns to its preoperative state within 6months after surgery.

Fusing Topology Optimization and Pseudo-Rigid-Body Method For the Development of a Finger Exoskeleton

Robotic hand exoskeletons can assist people who suffer from hand.functional disabilities caused by a stroke. However, currently existing hand exoskeletons remain inadequate in terms of user-friendly design, lightweight structure, and accurate modeling of hand motion. In this study, a large displacement compliant mechanism is developed as a finger exoskeleton. First, a topology configuration is developed which contains information on hand biomechanics and thus yields an efficient force-deflection mechanism for a finger. A pseudo-rigid-body model is then established using a large-deformation flexible hinge to solve the point flexure problem to create a finger exoskeleton that functions as intended. Finally, the mechanism synthesis method is used for parameter optimization to ensure that the output port of the device matches the motion of the finger. Using the proposed method, an integrated compliant finger exoskeleton is developed, and the performance of the exoskeleton is evaluated. The experimental result shows that the finger exoskeleton prototype provides suitable movement guidance for the index finger, which demonstrates that the proposed method may be a good way in the design of hand exoskeletons.

An In Vitro Hand Simulator for Simultaneous Control of Hand and Wrist Movements.

A human hand is a complex biomechanical system, in which bones, ligaments, and musculotendon units dynamically interact to produce seemingly simple motions. A new physiological hand simulator has been developed, in which electromechanical actuators apply load to the tendons of extrinsic hand and wrist muscles to recreate movements in cadaveric specimens in a biofidelic way. This novel simulator simultaneously and independently controls the movements of the wrist (flexion/extension and radio-ulnar deviation) and flexion/extension of the fingers and thumb. Control of these four degrees of freedom (DOF) is made possible by actuating eleven extrinsic muscles of the hand. The coupled dynamics of the wrist, fingers, and thumb, and the over-actuated nature of the human musculoskeletal system make feedback control of hand movements challenging. Two control algorithms were developed and tested. The optimal controller relies on an optimization algorithm to calculate the required tendon tensions using the collective error in all DOFs, and the action-based controller loads the tendons solely based on their actions on the controlled DOFs (e.g., activating all flexors if a flexing moment is required). Both controllers resulted in hand movements with small errors from the reference trajectories ( ); however, the optimal controller achieved this with 16% lower total force. Owing to its simpler structure, the action-based controller was extended to enable feedback control of grip force. This simulator has been shown to be a highly repeatable tool ( N and variations in force and kinematics, respectively) for in vitro analyses of human hand biomechanics.

Modern dance: theoretical foundations of the latest approaches to teaching

The purpose of the article is to substantiate the theoretical principles of using specific approaches in the process of training performers of modern dance. The research methodology is based on an interdisciplinary synthesis of scientific methods and approaches integrated into pedagogy, art history, and psychology. General scientific methods were also used: analysis, synthesis, generalization. The scientific novelty of the article lies in the conceptualization of the theoretical substantiation of specific approaches in the preparation of performers for modern dance, in particular, taking into account the latest technologies and psycho-emotional and mental characteristics of the performer. Conclusions. Along with traditional methods of teaching modern dances, it is necessary to develop and implement innovative methods and approaches that would meet the requirements of the latest technological development. In particular, they are related to the peculiarities of distance education, the ability to use computer programs to simulate biomechanical models of movement, to hone their kinematic technique, which largely determines the aesthetic and visual superiority and complexity of modern dance compositions. It is important to take into account the psycho-emotional characteristics of the modern dancer based on the development of his creative and innovative thinking, improvisation, as well as the socio-communicative component, which involves the ability to convey a wide range of potential emotional expressions and social signals from performer to spectator.&#x0D; Keywords: modern dance, innovative thinking, creative thinking, new approaches, teaching choreography, hand biomechanics, psychoemotional state.

Modern dance: theoretical fundamentals of the latest educational approaches

The purpose of the article is to substantiate the theoretical principles of using specific approaches in the process of training performers of modern dance. The research methodology is based on an interdisciplinary synthesis of scientific methods and approaches integrated with pedagogy, art history, and psychology. General scientific methods were also used: analysis, synthesis, generalization. The scientific novelty of the article lies in the conceptualization of the theoretical substantiation of specific approaches in the preparation of performers for modern dance, in particular, taking into account the latest technologies and psycho-emotional and mental characteristics of the performer. Conclusions. Along with traditional methods of teaching modern dances, it is necessary to develop and implement innovative methods and approaches that would meet the requirements of the latest technological development. In particular, they are related to the peculiarities of distance education, the ability to use computer programs to simulate biomechanical models of movement, to hone their kinematic technique, which largely determines the aesthetic and visual superiority and complexity of modern dance compositions. It is important to take into account the psycho-emotional characteristics of the modern dancer based on the development of his creative and innovative thinking, improvisation, as well as the socio-communicative component, which involves the ability to convey a wide range of potential emotional expressions and social signals from performer to spectator. Keywords: modern dance, innovative thinking, creative thinking, new approaches, teaching choreography, hand biomechanics, psychoemotional state.

Mechanical design of a low-cost ABS hand prosthesis using the finite element method

Many hand accidents are reported around the world resulting in a necessity to perform a procedure of amputation of the hand. For this consideration, a large number of hand prostheses have been designed. However, the mechanical design of these prostheses present challenges such as kinematic functionality, strength, and cost. The present article analyses the mechanical design of a low-cost practical hand prosthesis using the finite element method with the help of Abaqus commercial software. Functional and technical requirements were considered to consider the biomechanics of the human hand. The hand prosthesis was conferred with 14-degrees-of-freedom (DOF), which gives it the capacity for grips associated with security, stability, dexterity, and sensibility. Additionally, due to practicality and low-cost manufacturing techniques, fused deposition modelling with acrylonitrile butadiene styrene (ABS) is proposed. The evaluation of the hand prosthesis was carried out by tensile, flexural, and torsional load conditions. Finally, the mechanical effectiveness of the designed prosthesis was demonstrated since maximum stresses close to 13 MPa were computed, which are less than the yield stress of ABS.

Are hand biomechanics affected following radial forearm flap harvest? A systematic review and meta-analysis

Donor site morbidity following radial forearm flap (RFF) harvest remains a controversial issue. The aim of this meta-analysis was to answer the question “Are the range of wrist movements (range of motion, ROM) and hand strength affected after RFF harvesting?” The PubMed, Embase, Scopus, and Cochrane Library electronic databases were systematically searched (to December 2019). Self-controlled studies evaluating hand biomechanics after RFF harvest were included. Weighted mean differences with 95% confidence intervals were calculated using the random-effects model. The outcome variables were ROM, forearm movements, grip, and pinch strengths. Thirteen studies involving a total of 335 patients were included. With the exception of grip strength and supination, which showed statistically significant reductions of about 2.40 kg and 2.86° (P < 0.05), all other ROM, forearm movements, and pinch strengths showed an insignificant difference when the operated hand was compared to the non-operated hand (P > 0.05). Regression analysis showed that the method of donor site closure and size of the donor site defect had an insignificant impact on hand biomechanics. This study confirms the lack of discernible biomechanical morbidity after RFF transfer. The minimal reduction in hand biomechanics after RFF is considered to be clinically negligible.

Portable micromanipulator for extreme climatic conditions

The problem of compensating for the partial loss of micromovements capabilities of a person in severe climatic conditions of the Arctic is studied. A portable manipulation system that reproduces the natural biomechanics of the human hand is proposed. The methods of manipulator control are analyzed. Promising areas of application of such systems for the repair of hard-to-reach equipment are considered.

Robotics for rehabilitation of hand movement in stroke survivors

This article aims to give an overall review of research status in hand rehabilitation robotic technology, evaluating a number of devices. The main scope is to explore the current state of art to help and support designers and clinicians make better choices among varied devices and components. The review also focuses on both mechanical design, usability and training paradigms since these parts are interconnected for an effective hand recovery. In order to study the rehabilitation robotic technology status, the devices have been divided in two categories: end-effector robots and exoskeleton devices. The end-effector robots are more flexible than exoskeleton devices in fitting the different size of hands, reducing the setup time and increasing the usability for new patients. They suffer from the control of distal joints and haptic aspects of object manipulation. In this way, exoskeleton devices may represent a new opportunity. Nevertheless their design is complex and a deep investigation of hand biomechanics and physical human–robot interaction is required. The main hand exoskeletons have been developed in the last decade and the results are promising demonstrated by the growth of the commercialized devices. Finally, a discussion on the complexity to define which design is better and more effective than the other one is summarized for future investigations.

Hand Biomechanics Measured after Modulation of Neural Plasticity In A Patient With Secondary Dystonia

Hand Biomechanics Measured after Modulation of Neural Plasticity In A Patient With Secondary Dystonia

Force-Length Relationship Modeling of Wrist and Finger Flexor Muscles.

Because the hand joints possess a broad range of motion, the muscle length can vary importantly which might result in significant variations of the muscle force-generating capacities. However, facing the complexity of this musculoskeletal system, no study has examined the effect of hand muscle length change on muscle force. This study aimed to characterize the force-length relationship of muscles involved in wrist and metacarpophalangeal flexion. Eleven participants performed two sessions: (i) one for the wrist flexor muscles and (ii) one for the finger flexor muscles. For each session, the participants performed two maximal voluntary contractions and then two progressive isometric ramps from 0% to 100% of their maximal force capacity at five different wrist/metacarpophalangeal angles. Torque, kinematic, and electromyographic data were recorded. An ultrasound scanner was used to measure the myotendinous junction displacement of flexor carpi radialis (FCR) and flexor digitorum superficialis (FDS) during isometric contractions. A three-dimensional relationship between muscle length, force, and activation level was modeled using optimization procedure. Globally, the FCR was stronger and shorter compared with FDS. The results showed that the three-dimensional relationships fitted well the experimental data (mean R = 0.92 ± 0.07 and 0.87 ± 0.11 for FCR and FDS, respectively). Using joint angle and EMG data, this approach allows to estimate the muscle force with low estimation errors (<9% of Fmax). This study proposes a new method to investigate the force-length relationship by combining ultrasound measurement, musculoskeletal modeling and optimization procedures. The data and relationships provide a new insight into hand biomechanics and muscle function that could be useful for designing hand tools or surgical operations.

Application of Robot to Hand Function Rehabilitation

Background: Hand is one of the most important and common parts of the body. Hand dysfunction caused by hemiplegia and hand injury is difficult to restore, which leads to high disability rates. The patients' daily life and work ability are seriously affected. With the aging of the society, the number of stroke patients with hemiplegia is gradually increasing. The research and application of the robot with the combination of robot and assistive rehabilitation therapy have come into being. Hand function rehabilitation robot has more practical value. It can simulate the human hand’s movements to realize the rehabilitation training of human hands. Objective: To give a general summary of recent hand function rehabilitation robot, and a presentation of their respective characteristics including drive type and rehabilitation training mode. Methods: This paper summarizes various patents and research developments about hand function rehabilitation robot. From the aspects of structural characteristics, drive type and rehabilitation training mode and applications situation, the advantages and disadvantages of the typical hand function rehabilitation robots are represented. Results: Current and future development trends on the structural characteristics, drive type and rehabilitation training mode and applications situation of hand function rehabilitation robots are discussed to improve the humanization, marketization, modularization and intelligence of the hand function rehabilitation robot. Conclusion: Considerable attention has been paid onto the hand function rehabilitation robot. Hand function rehabilitation robot can effectively improve the hand function of patients' and the elderly's the actual quality of life and family well-being. Further improvements are needed in the aspects of hand biomechanics, neurophysiology, rehabilitation training mode, actuators and sensors, physical manmachine interaction and ergonomics of the hand function rehabilitation robot. More patents on hand function rehabilitation robot should be invented. Keywords: Bionic principle, drive type, hand function rehabilitation robot, hand rehabilitation training, motor, pneumatic artificial muscle, pneumatic cylinder, shape memory alloy.

BIOMECHANICS OF THE HUMAN HAND

The paper provides basic information on human hand's anatomical structure with the location of joints and consequent types of achievable movements. The biomechanics of the human hand is described using two different kinematic models of the hand. The differences between the models are described. The Schlesinger's classification of movements of the human hand is introduced

Key Insights into Hand Biomechanics: Human Grip Stiffness Can Be Decoupled from Force by Cocontraction and Predicted from Electromyography.

We investigate the relation between grip force and grip stiffness for the human hand with and without voluntary cocontraction. Apart from gaining biomechanical insight, this issue is particularly relevant for variable-stiffness robotic systems, which can independently control the two parameters, but for which no clear methods exist to design or efficiently exploit them. Subjects were asked in one task to produce different levels of force, and stiffness was measured. As expected, this task reveals a linear coupling between force and stiffness. In a second task, subjects were then asked to additionally decouple stiffness from force at these force levels by using cocontraction. We measured the electromyogram from relevant groups of muscles and analyzed the possibility to predict stiffness and force. Optical tracking was used for avoiding wrist movements. We found that subjects were able to decouple grip stiffness from force when using cocontraction on average by about 20% of the maximum measured stiffness over all force levels, while this ability increased with the applied force. This result contradicts the force–stiffness behavior of most variable-stiffness actuators. Moreover, we found the thumb to be on average twice as stiff as the index finger and discovered that intrinsic hand muscles predominate our prediction of stiffness, but not of force. EMG activity and grip force allowed to explain 72 ± 12% of the measured variance in stiffness by simple linear regression, while only 33 ± 18% variance in force. Conclusively the high signal-to-noise ratio and the high correlation to stiffness of these muscles allow for a robust and reliable regression of stiffness, which can be used to continuously teleoperate compliance of modern robotic hands.

The JamHand: Dexterous Manipulation with Minimal Actuation.

From using chopsticks to grab items off a plate, to snapping together two LEGO bricks in one hand, common manipulation tasks are easy for humans. However, grasping and dexterous manipulation still rank among the principal grand challenges in robotics. A key challenge is the complex interaction between hand biomechanics and motor control, leading to humanoid hands that remain too complex and costly for use in daily tasks. Here, we bypass this challenge by offering an alternative approach based on multi-finger material phase transition effects. By limiting our focus to dexterous manipulation, we are able to design a robotic hand that can achieve six fundamental dexterous manipulations as well as precision and power grasps, all with only two actuators. We further demonstrate our system on a range of real-world grasping and manipulation challenges. Besides practical application, these results suggest that leveraging the phase transition of granular materials is a viable technique for reducing the hand complexity required for performing daily tasks.