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Context More than half of all spinal cord injuries (SCI) occur at the cervical level leading to loss of upper limb function, restricted activity and reduced independence. Several technologies have been developed to assist with upper limb functions in the SCI population. Objective There is no clear clinical consensus on the effectiveness of the current assistive technologies for the cervical SCI population, hence this study reviews the literature in the years between 1999 and 2019. Methods A systematic review was performed on the state-of-the-art assistive technology that supports and improves the function of impaired upper limbs in cervical SCI populations. Combinations of terms, covering assistive technology, SCI, and upper limb, were used in the search, which resulted in a total of 1770 articles. Data extractions were performed on the selected studies which involved summarizing details on the assistive technologies, characteristics of study participants, outcome measures, and improved upper limb functions when using the device. Results A total of 24 articles were found and grouped into five categories, including neuroprostheses (invasive and non-invasive), orthotic devices, hybrid systems, robots, and arm supports. Only a few selected studies comprehensively reported characteristics of the participants. There was a wide range of outcome measures and all studies reported improvements in upper limb function with the devices. Conclusions This study highlighted that assistive technologies can improve functions of the upper limbs in SCI patients. It was challenging to draw generalizable conclusions because of factors, such as heterogeneity of recruited participants, a wide range of outcome measures, and the different technologies employed.

Transhumeral amputation has a considerable detrimental effect on the amputee’s quality of life and independence. Previous work has already established the potential for exploiting proximal humerus myoelectric and kinematic signals for the effective control of a myoelectric prosthesis. That previous work used a Time-Delay Neural Network (TDNN) to perform the mapping of six electromyographic (EMG) and six kinematic proximal humerus signals to predict elbow flexion/extension. Since that earlier work alternative deep learning and recurrent neural network architectures, well-suited to the processing of high-dimensional time-series data, have come to the fore. The work reported here is a comparative evaluation using the metric of RMS error for the predicted elbow flexion/extension angles output by TDNN, Long Short Term Memory (LSTM) and Echo State Network (ESN) architectures. For the most effective comparison we successfully reproduced TDNN results that were comparable to previous work (with average RMSE of 11.8 degrees on unseen test data). Then using the same training and testing datasets, and networks of broadly similar complexity, we evaluated the effectiveness of the LSTM and ESN approaches. The LSTMs trained here delivered an average RMSE of 10.4 degrees on unseen test data. The ESNs delivered an average RMSE of 16.3 degrees on unseen test data. The current work was not intended to find the best possible LSTM or ESN solution for this problem. Instead the intention was to see if any particular aspects of the network architectures worked better with the particular challenges of transhumeral biomedical engineering data of this sort.

Individuals with hand amputation suffer substantial loss of independence. Performance of sophisticated prostheses is limited by the ability to control them. To achieve natural and simultaneous control of all wrist and hand motions, we propose to use real-time biomechanical simulation to map between residual EMG and motions of the intact hand. Here we describe a musculoskeletal model of the hand using only extrinsic muscles to determine whether real-time performance is possible. Simulation is 1.3 times faster than real time, but the model is locally unstable. Methods are discussed to increase stability and make this approach suitable for prosthesis control.

Objective: The goal of the current study was todetermine whether and how much the stabilizing role of theshoulder muscles changes as a function of humeral elevationand the plane of elevation. Methods: A musculoskeletal model,comprising a personalized scapulohumeral rhythm, was usedto calculate the ratio of shear over compressive force (stabilityratio) of three rotator cuff muscles (supraspinatus, infraspinatus,subscapularis) and three superficial shoulder muscles (middledeltoid, clavicular part of pectoralis major, latissimus dorsi)during abduction, flexion and reaching movements in ten healthyadults. Results: The range of the stability ratios was [±0.5] forthe rotator cuff muscles compared to [+5,-2] for the superficialshoulder muscles. In the superior-inferior direction, the stabilityratios of all muscles changed with humeral elevation and forinfraspinatus, subscapularis, latissimus dorsi and deltoid alsowith the plane of elevation. In the anterior-posterior direction,the stability ratios of all muscles changed with humeral elevation,except for the deltoid, and with the plane of elevation, except forthe supraspinatus, with interaction effects in all muscles.Conclusion: The rotator cuff muscles provide greater compressionthan shear forces during all tasks. The stabilizing function ofthe superficial shoulder muscles examined in this study variesduring tasks. Significance: The findings can be used to predictin which movements the shoulder joint becomes more unstableand can be applied to understand how shear and compressiveforces change in populations with abnormal shoulder motion.

Musculoskeletal models have been developed to estimate internal loading on the human skeleton, which cannot directly be measured in vivo, from external measurements like kinematics and external forces. Such models of the shoulder and upper extremity have been used for a variety of purposes, ranging from understanding basic shoulder biomechanics to assisting in preoperative planning. In this review, we provide an overview of the most commonly used large-scale shoulder and upper extremity models and categorise the applications of these models according to the type of questions their users aimed to answer. We found that the most explored feature of a model is the possibility to predict the effect of a structural adaptation on functional outcome, for instance, to simulate a tendon transfer preoperatively. Recent studies have focused on minimising the mismatch in morphology between the model, often derived from cadaver studies, and the subject that is analysed. However, only a subset of the parameters that describe the model's geometry and, perhaps most importantly, the musculotendon properties can be obtained in vivo. Because most parameters are somehow interrelated, the others should be scaled to prevent inconsistencies in the model's structure, but it is not known exactly how. Although considerable effort is put into adding complexity to models, for example, by making them subject-specific, we have found little evidence of their superiority over current models. The current trend in development towards individualised, more complex models needs to be justified by demonstrating their ability to answer questions that cannot already be answered by existing models. © 2013 International Federation for Medical and Biological Engineering.

To study elbow muscle load sharing we investigated the effect of external flexion-extension (FE) and pronation-supination (PS) moments and elbow angle on muscle activation and oxygen consumption (V O(2)). Two data sets were obtained. First, (n=6) electromyography (EMG) of elbow flexors (long and short heads of biceps brachii, brachioradialis, brachialis) and extensors (long and short heads of triceps brachii and anconeus) was recorded in all combinations of FE and PS moments at three force levels and four elbow angles (50 degrees , 70 degrees , 90 degrees and 110 degrees ). Second, (n=4) EMG and V O(2) of three muscles (both heads of biceps and lateral head of triceps) were measured simultaneously during a subset of the above conditions. Joint angle and therefore both moment arm and muscle length influenced both EMG amplitude and the load sharing between muscles. The principles behind load sharing, however, were difficult to quantify, since it was impossible to distinguish between all individual aspects that affect muscle activity. We found a linear relationship between EMG and V O(2), while joint angle had no major effect. Although in general subjects showed comparable muscle activation patterns, there were also considerable inter-individual differences, which might be explained by the use of different optimisation strategies or differences in morphology.

Upper extremity neuroprostheses use functional electrical stimulation (FES) to restore arm motor function to individuals with cervical level spinal cord injury. For the design and testing of these systems, a biomechanical model of the shoulder and elbow has been developed, to be used as a substitute for the human arm. It can be used to design and evaluate specific implementations of FES systems, as well as FES controllers. The model can be customized to simulate a variety of pathological conditions. For example, by adjusting the maximum force the muscles can produce, the model can be used to simulate an individual with tetraplegia and to explore the effects of FES of different muscle sets. The model comprises six bones, five joints, nine degrees of freedom, and 29 shoulder and arm muscles. It was developed using commercial, graphics-based modeling and simulation packages that are easily accessible to other researchers and can be readily interfaced to other analysis packages. It can be used for both forward-dynamic (inputs: muscle activation and external load; outputs: motions) and inverse-dynamic (inputs: motions and external load; outputs: muscle activation) simulations. Our model was verified by comparing the model calculated muscle activations to electromyographic signals recorded from shoulder and arm muscles of five subjects. As an example of its application to neuroprosthesis design, the model was used to demonstrate the importance of rotator cuff muscle stimulation when aiming to restore humeral elevation. It is concluded that this model is a useful tool in the development and implementation of upper extremity neuroprosthetic systems.

The ability of mathematical models of the shoulder to accurately replicate physiological muscle moment arms is unknown. The purpose of this study was to compare model-predicted and experimentally measured moment arms for the rotator cuff muscles during arm elevation.Moment arms obtained from six mathematical models and seven experimental studies were compared for the supraspinatus, infraspinatus, teres minor, and subscapularis for elevation in the scapular plane.All of the included models generated moment arms that generally fell within the range of experimentally measured data.The quantitative agreement between model-predicted and experimentally measured moment arms supports the use of the included models for biomechanical shoulder analyses.

Introduction: Measurement of lung function aids diagnosis and treatment of respiratory conditions, but spirometry is not possible in young children. SLP is a novel technique for measuring chest and abdominal wall movement during tidal breathing that would allow us to obtain measurements in patients where this is not currently possible. Aims: We investigated the use of SLP for measuring tidal breathing in children aged 3-17 years. Methods: Using a Thora-3Di™ (PneumaCare, Cambridge, UK), a structured light pattern was projected onto the chest and abdomen of a seated child. Movement with respiration is captured using stereo-photogrammetry to produce a trace of tidal breathing. Clinically-useful respiratory indices can be calculated such as respiratory rate (RR), inspiratory time ratio (Ti/Ttot) and ratio of inspiratory to expiratory flow at 50% of tidal movement (IE50). The relative contribution of chest wall movement to total movement (RC2Tot) can also be captured. Results: 44 children (22 female) aged 3-17 years underwent assessment with SLP. Normative data are summarized in the table below. Conclusion: We have demonstrated the feasibility of obtaining objective measures of tidal breathing using SLP in children.

Inverse-dynamic models often use cost functions to solve the load-sharing problem. Although it is often assumed that energy is minimised, most cost functions are based on mechanically related measures like muscle force or stress. The aim of this study was to analyse the relationships of two cost functions with experimentally determined data on muscle energy consumption. Four subjects performed isometric contractions generating combinations of elbow flexion/extension and pro/supination moments. Muscle oxygen consumption (VO2) of the m. biceps breve, m. biceps longum, m. brachioradialis and m. triceps laterale was measured with near infrared spectroscopy. Both cost functions were implemented into an existing inverse-dynamic shoulder and elbow model and the individual cost values per muscle were calculated, normalised and subsequently compared to experimental VO2 values. The minimum stress cost function led to a good correspondence between VO2 and cost for the m. triceps laterale but for the flexor muscles cost was significantly lower. A newly proposed energy-related cost function showed, however, a far better correspondence. The inclusion of a linear term and muscle mass in the new criterion led model results to correspond better to experimental results. The energy-related cost function appeared to be a better measure for muscle energy consumption than the stress cost function and led to more realistic predictions of muscle activation.

OBJECTIVE: To estimate the differences in glenohumeral contact forces and shoulder muscle forces between able-bodied subjects and subjects with paraplegia and tetraplegia during wheelchair-related activities of daily living (ADLs).DESIGN: Kinematics and external forces were measured during wheelchair ADLs (level propulsion, weight-relief lifting, reaching) and processed by using an inverse dynamics 3-dimensional biomechanical model.SETTING: Biomechanics laboratory.PARTICIPANTS: Five able-bodied subjects, 8 subjects with paraplegia, and 4 subjects with tetraplegia (N = 17).INTERVENTIONS: Not applicable.MAIN OUTCOME MEASURES: Glenohumeral contact forces and shoulder muscle forces.RESULTS: Peak contact forces were significantly higher for weight-relief lifting compared with reaching and level propulsion (P < .001). High relative muscle force of the rotator cuff was seen, apparently needed to stabilize the joint. For weight-relief lifting, total relative muscle force was significantly higher for the tetraplegia group than for the able-bodied group (P = .022).CONCLUSIONS: Glenohumeral contact forces were significantly higher for weight-relief lifting and highest over the 3 tasks for the tetraplegia group. Without taking paralysis into account, more muscle force was estimated for the subjects with tetraplegia during weight-relief lifting.

van Drongelen S, van der Woude LH, Janssen TW, Angenot EL, Chadwick EK, Veeger DH. Mechanical load on the upper extremity during wheelchair activities. Arch Phys Med Rehabil 2005;86:1214–20. Objective To determine the net moments on the glenohumeral joint and elbow joint during wheelchair activities. Design Kinematics and external forces were measured during wheelchair activities of daily living (level propulsion, riding on a slope, weight-relief lifting, reaching, negotiating a curb) and processed in an inverse dynamics biomechanic model. Setting Biomechanics laboratory. Participants Five able-bodied subjects, 8 subjects with paraplegia, and 4 subjects with tetraplegia. Interventions Not applicable. Main Outcome Measure Net moments on the glenohumeral joint and elbow joint. Results Peak shoulder and elbow moments were significantly higher for negotiating a curb and weight-relief lifting than for reaching, level propulsion, and riding on a slope. Overall, the elbow extension moments were significantly lower for subjects with tetraplegia than for those with paraplegia. Conclusions The net moments during weight-relief lifting and negotiating a curb were high when compared with wheelchair propulsion tasks. Taking the effect of frequency and duration into account, these loads might imply a considerable risk for joint damage in the long term.

Background. Functioning of the upper extremity after implantation of an endoprosthesis remains limited despite the achieved pain relief. Upper extremity kinematics can give insight into function after shoulder arthroplasty. Data on ranges of motion related to the performance of a selection of activities of daily living can aid the clinician in evaluating the outcome of the shoulder and elbow arthroplasties. Methods. Cross-sectional descriptive study of range of motion and activities of daily living kinematics, conducted on nonimpaired subjects. The shoulder and elbow motions of 24 healthy female subjects are measured with an electromagnetic tracking device while performing 8 range of motion tasks and five activities of daily living. The angles of shoulder and elbow are calculated during these tasks. Results. A data set with upper extremity joint angles has been obtained. Large glenohumeral rotations are found for the tasks that require high elevation angles. Large axial rotations of the humerus are found for two of the activities of daily living tasks: the perineal care task and the hair-combing task. Large elbow flexions were seen in the following tasks: combing hair, washing the axilla and eating with a spoon. Interpretation. This study shows a suitable method to describe range of motion and activities of daily living and can serve as a starting point for developing a database on how activities of daily living are performed in a larger population and which joint angles are required to perform these tasks. Results can be used to identify restrictions in upper extremity functioning in patients with shoulder impairments. 2005 Elsevier Ltd. All rights reserved.

Objective. To explain loss of shoulder function following scapular neck malunion in terms of biomechanical changes around the gleno-humeral joint. Design. Biomechanical modelling study. Background. Residual rotation of the scapular neck after fracture can lead to pain and loss of function, and the indications for surgical intervention are contested. Methods. A 3D, large-scale, musculo-skeletal model of the upper limb was used to compare shoulder biomechanics in the case of scapular neck malunion with normal anatomy. Abduction of the humerus was simulated with three models: normal anatomy, 24° and 40° inferior scapular neck rotation. Results. Predicted muscle activation differed greatly between the control and the fracture cases. The motion required additional muscle effort for the maintenance of gleno-humeral stability in the fracture cases. Higher moments in the plane of abduction were generated by the teres major, pectoralis major and biceps brachii muscles with high humeral elevation angles. The rotator cuff muscles were severely shortened in the post-fracture cases and the forces in these muscles were greatly reduced in a test of loaded abduction with the humerus at 90°. Conclusions. Given the function of the rotator cuff muscles as stabilisers of the gleno-humeral joint, it is concluded that the loss of force in these muscles, together with other changes in muscle activation, will lead to loss of arm function in patients with scapular neck malunion. Relevance. These findings will contribute to the improved treatment of patients with scapular neck malunion by identifying important factors in the consideration of surgical intervention.

Objective . To determine why certain tendon transfers are mechanically more effective than other tendon transfers for the treatment of a massive rotator cuff tear. Design . A tendon transfer procedure of latissimus dorsi, teres major or a combination of these two to the insertions of either teres minor, infraspinatus, supraspinatus, or subscapularis is simulated using a biomechanical musculoskeletal model of the upper extremity. Background . Massive rotator cuff tears are not easily repaired. To compensate for the loss of rotator cuff function techniques such as muscle transfers are developed. Methods . Three range of motion tasks were used as input to the Delft shoulder and elbow model. The muscle parameters of the Delft shoulder and elbow model were modified to simulate a rotator cuff tear. A biomechanical analysis of the transferred muscles was performed, taking outcome variables such as moment arms, muscle length and muscle force into account. Results . Due to the massive rotator cuff tear, an elevation and external rotation moment is lost. When the tendon was transferred to the insertions of infraspinatus or supraspinatus, the humerus was capable of elevating and externally rotating. Conclusions . On the basis of mechanical parameters such as moment arms, muscle length and force it can be concluded that a tendon transfer of the teres major to the supraspinatus insertion will produce the best functional outcome in the treatment of massive rotator cuff tears. Relevance To find biomechanical evidence for an optimal tendon transfer that will lead to improved treatment of patients with a massive rotator cuff tear.

Objective. To determine what the most effective tendon transfer is in the case of a dysfunctional rotator cuff. Design. A tendon transfer procedure of latissimus dorsi, teres major or a combination of these two to the insertions of either teres minor, infraspinatus, supraspinatus, or subscapularis is simulated using a biomechanical musculoskeletal model of the upper extremity. Background. Massive rotator cuff tears are not easily repaired. To compensate for this loss of rotator cuff function other techniques like muscle transfers are developed. Methods. Three range of motion tasks and six activities of daily living of 24 subjects were measured. Kinematics from these tasks were used as input to the Delft Shoulder and Elbow Model. The muscle parameters of the Delft Shoulder and Elbow Model were modified to simulate a rotator cuff tear and the ability to perform the measured tasks with and without simulated transfer procedures was checked. Results. The highest improvements (28–30%, P =0.00) in the ability to perform tasks were observed after a simulated tendon transfer of either both muscles or teres major alone attached to the supraspinatus or infraspinatus insertion. Although all transfer procedures produce significant improvements ( P =0.00), there is a significant difference between the procedures (Chi square=58.8, P =0.00) dependent on attachment site. Conclusions. According to the simulation procedure used in the current study, a tendon transfer of teres major and latissimus dorsi or teres major alone to the supraspinatus insertion appears to be the most effective procedure in the case of a dysfunctional rotator cuff. Practical factors, like subacromial space, volume of the muscles and tendons, tensile properties and the ability to split the muscles, will finally determine which is the prefered transfer option. Relevance. To find biomechanical evidence for an optimal tendon transfer for patients with a dysfunctional rotator cuff.

Movements of the human upper extremity are difficult to measure, due to the specific structure of the limb. All arm movements are a combination of movements of the humerus relative to a moveable base: the scapula. Measurement of movements is, however, strongly hampered by the fact that the scapular movement is difficult to track when skin-based landmarks are used. A second complicating factor is the fact that a skin-based proximal landmark on the humerus is difficult to define, which directly affects attempts to describe accurately the movements of that segment. To solve these problems, special measurement procedures have been developed, which include the identification of landmarks for the scapula and the humerus and recording procedures for segment movements or the estimation of landmarks. Also, a definition of the three-dimensional description of motion is presented. These measurement procedures have now been applied in several experiments and have been proven to be successful.

Electrical stimulation is a promising technology for the restoration of arm function in paralysed individuals. Control of the paralysed arm under electrical stimulation, however, is a challenging problem that requires advanced controllers and command interfaces for the user. A real-time model describing the complex dynamics of the arm would allow user-in-the-loop type experiments where the command interface and controller could be assessed. Real-time models of the arm previously described have not included the ability to model the independently controlled scapula and clavicle, limiting their utility for clinical applications of this nature. The goal of this study therefore was to evaluate the performance and mechanical behaviour of a real-time, dynamic model of the arm and shoulder girdle. The model comprises seven segments linked by eleven degrees of freedom and actuated by 138 muscle elements. Polynomials were generated to describe the muscle lines of action to reduce computation time, and an implicit, first-order Rosenbrock formulation of the equations of motion was used to increase simulation step-size. The model simulated flexion of the arm faster than real time, simulation time being 92% of actual movement time on standard desktop hardware. Modelled maximum isometric torque values agreed well with values from the literature, showing that the model simulates the moment-generating behaviour of a real human arm. The speed of the model enables experiments where the user controls the virtual arm and receives visual feedback in real time. The ability to optimise potential solutions in simulation greatly reduces the burden on the user during development.

Functional electrical stimulation (FES), the coordinated electrical activation of multiple muscles, has been used to restore arm and hand function in people with paralysis. User interfaces for such systems typically derive commands from mechanically unrelated parts of the body with retained volitional control, and are unnatural and unable to simultaneously command the various joints of the arm. Neural interface systems, based on spiking intracortical signals recorded from the arm area of motor cortex, have shown the ability to control computer cursors, robotic arms and individual muscles in intact non-human primates. Such neural interface systems may thus offer a more natural source of commands for restoring dexterous movements via FES. However, the ability to use decoded neural signals to control the complex mechanical dynamics of a reanimated human limb, rather than the kinematics of a computer mouse, has not been demonstrated. This study demonstrates the ability of an individual with long-standing tetraplegia to use cortical neuron recordings to command the real-time movements of a simulated dynamic arm. This virtual arm replicates the dynamics associated with arm mass and muscle contractile properties, as well as those of an FES feedback controller that converts user commands into the required muscle activation patterns. An individual with long-standing tetraplegia was thus able to control a virtual, two-joint, dynamic arm in real time using commands derived from an existing human intracortical interface technology. These results show the feasibility of combining such an intracortical interface with existing FES systems to provide a high-performance, natural system for restoring arm and hand function in individuals with extensive paralysis.

The Delft Shoulder and Elbow Model (DSEM), a musculoskeletal model of the shoulder and elbow has been extensively developed since its introduction in 1994. Extensions cover both model structures and anatomical data focusing on the addition of an elbow part and muscle architecture parameters. The model was also extended with a new inverse-dynamics optimization cost function and combined inverse-forward-dynamics models. This study is an update on the developments of the model over the last decade including a qualitative validation of the different simulation architectures available in the DSEM. To validate the model, a dynamic forward flexion motion was performed by one subject, of which the motion data and surface EMG-signals of 12 superficial muscles were measured. Patterns of the model-predicted relative muscle forces were compared with their normalized EMG-signals. Results showed relatively good agreement between forces and EMG (mean correlation coefficient of 0.66). However, for some cases, no force was predicted while EMG activity had been measured (false-negatives). The DSEM has been used and has the potential to be used in a variety of clinical and biomechanical applications. Electronic supplementary material The online version of this article (doi:10.1007/s11517-011-0839-7) contains supplementary material, which is available to authorized users.

Neuroprostheses can be used to restore movement of the upper limb in individuals with high-level spinal cord injury. Development and evaluation of command and control schemes for such devices typically requires real-time, “patient-in-the-loop” experimentation. A real-time, three-dimensional, musculoskeletal model of the upper limb has been developed for use in a simulation environment to allow such testing to be carried out non-invasively. The model provides real-time feedback of human arm dynamics that can be displayed to the user in a virtual reality environment. The model has a three degree-of-freedom gleno-humeral joint as well as elbow flexion/extension and pronation/supination, and contains 22 muscles of the shoulder and elbow divided into multiple elements. The model is able to run in real time on modest desktop hardware and demonstrates that a large-scale, 3D model can be made to run in real time. This is a prerequisite for a real-time, whole arm model that will form part of a dynamic arm simulator for use in the development, testing and user training of neural prosthesis systems.

Individuals with C5/C6 spinal cord injury (SCI) have a number of paralyzed muscles in their upper extremities that can be electrically activated in a coordinated manner to restore function. The selection of a practical subset of paralyzed muscles for stimulation depends on the specific condition of the individual, the functions targeted for restoration, and surgical considerations. This paper presents a musculoskeletal model-based approach for optimizing the muscle set used for functional electrical stimulation (FES) of the shoulder and elbow in this population. Experimentally recorded kinematics from able-bodied subjects served as inputs to a musculoskeletal model of the shoulder and elbow, which was modified to reflect the reduced muscle force capacities of an individual with C5 SCI but also the potential of using FES to activate paralyzed muscles. A large number of inverse dynamic simulations mimicking typical activities of daily living were performed that included (1) muscles with retained voluntary control and (2) many different combinations of stimulated paralyzed muscles. These results indicate that a muscle set consisting of the serratus anterior, infraspinatus and triceps would enable the greatest range of relevant movements. This set will become the initial target in a C5SCI neuroprosthesis to restore shoulder and elbow function.

This paper describes a significant ongoing effort by our research group to develop a functional electrical stimulation-based neuroprosthesis capable of restoring essential arm and hand function to individuals with high cervical (C1-C4) spinal cord injury, a condition referred to as high tetraplegia. These injuries are at the highest level of the spinal cord and leave those afflicted with extensive paralysis below the neck — typically such individuals are left with volitional control of just the head, neck, and in some cases shoulder shrug. Individuals with high tetraplegia are usually totally dependent on others for all aspects of care, and traditional rehabilitation procedures result in limited functional improvement [1].Copyright © 2007 by ASME

Item does not contain fulltext Local oxygen consumption in a muscle (VO(2)) can be determined by near infrared spectroscopy (NIRS). In principle it should be possible to use this measure to validate musculoskeletal models. However, the relationship between VO(2) and external force, or between VO(2) and surface EMG, as a measure for muscle activity, is hardly known. The aim of this study was: (1) to evaluate the characteristics of the relationship between VO(2) and external moments and (2) to determine whether differences exist between the EMG-moment relationship and the VO(2)-moment relationship. Subjects (n=5) were asked to perform isometric contractions exerting combinations of elbow flexion and pro/supination moments at force levels up to 70% of their maximum. Simultaneous surface-EMG and NIRS measurements were performed on the m. biceps breve (BB) and the m. brachioradialis (BR). A linear relationship was found between EMG and VO(2). For the BB VO(2) and EMG were linearly related to both the flexion moment and the pro/supination moment. However, for the BR only a linear relationship with flexion moment was found. As expected, based on the findings above, the relationship between VO(2) and elbow flexion moment can be described by a linear equation, under the conditions of this study (isometric, and force levels up to 70%). These findings suggest that load sharing is independent of force level and that next to EMG, VO(2) can be used for the validation of musculoskeletal models.

A three-dimensional, mathematical model of the elbow and wrist joints, including 15 muscle units, 3 ligaments and 4 joint forces, has been developed. A new strain gauge transducer has been developed to measure functional grip forces. The device measures radial forces divided into six components and forces of up to 250N per segment can be measured with an accuracy of +/-1%. Ten normal volunteers were asked to complete four tasks representing occupational activities, during which time their grip force was monitored. Together with kinematic information from the six-camera Vicon data, the moment effect of these loads at the joints was calculated. These external moments are assumed to be balanced by the internal moments, generated by the muscles, passive soft tissue and bone contact. The effectiveness of the body's internal structures in generating joint moments was assessed by studying the geometry of a simplified model of the structures, where information about the lines of action and moment arms of muscles, tendons and ligaments is contained. The assumption of equilibrium between these external and internal joint moments allows formulation of a set of equations from which muscle and joint forces can be calculated. A two stage, linear optimisation routine minimising the overall muscle stress and the sum of the joint forces has been used to overcome the force-sharing problem. Humero-ulnar forces of up to 1600N, humero-radial forces of up to 800N and wrist joint forces of up to 2800N were found for moderate level activity. The model was validated by comparison with other studies.

Background. The incidence of shoulder complaints in wheelchair users is high and the etiology is poorly understood. The goal of this study was to examine the effect of lesion level and isolated triceps muscle paresis on the internal load on the shoulder by simulation. Methods. Kinematic and kinetic profiles from four able-bodied subjects and four subjects with tetraplegia were used as input for an inverse dynamics biomechanical model. The model was modified to simulate lesion level and triceps muscle paresis. Findings. The simulations resulted in a significantly higher (+56%) glenohumeral contact force (P = 0.037) for tetraplegic profiles than for able-bodied profiles. The model modifications to simulate lesion level only had a minor effect (+7%) on the calculated glenohumeral contact force. More simulations were successful at lower triceps force levels for tetraplegic profiles compared to able-bodied profiles (P = 0.012). The muscle forces at the simulated T1 lesion were not significantly higher in tetraplegic profiles compared to able-bodied profiles. Interpretation. The glenohumeral contact force for the tetraplegic profiles is mainly higher due to different task performance. Model modifications only have a minor effect on the calculated glenohumeral contact force. For able-bodied profiles the triceps force seems to be an important factor. The high internal load at the shoulder recommends new techniques of weight relief lifting and proper training of the arm-shoulder muscles in rehabilitation. © 2005 Elsevier Ltd. All rights reserved.

Transhumeral amputation has a significant effect on a person’s independence and quality of life. Myoelectric prostheses have the potential to restore upper limb function, however their use is currently limited due to lack of intuitive and natural control of multiple degrees of freedom. The goal of this study was to evaluate a novel transhumeral prosthesis controller that uses a combination of kinematic and electromyographic (EMG) signals recorded from the person’s proximal humerus. Specifically, we trained a time-delayed artificial neural network to predict elbow flexion/extension and forearm pronation/supination from six proximal EMG signals, and humeral angular velocity and linear acceleration. We evaluated this scheme with ten able-bodied subjects offline, as well as in a target-reaching task presented in an immersive virtual reality environment. The offline training had a target of 4° for flexion/extension and 8° for pronation/supination, which it easily exceeded (2.7° and 5.5° respectively). During online testing, all subjects completed the target-reaching task with path efficiency of 78% and minimal overshoot (1.5%). Thus, combining kinematic and muscle activity signals from the proximal humerus can provide adequate prosthesis control, and testing in a virtual reality environment can provide meaningful data on controller performance.