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ABSTRACT. 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.Key Words: Activities of daily living; Biomechanics; Elbow; Rehabilitation; Shoulder; Wheelchairs. © 2005 by American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and RehabilitationI N HANDRIM WHEELCHAIR USERS, the upper extremities are at serious risk of overuse injuries. Wheelchair use requires continuous use of the upper extremities, not only for mobility but also for transfers, weight-relief lifts, and reaching activities. Studies 1,2 have shown that shoulder pain and impingement frequently occur among people with a spinal cord injury (SCI). Pain is experienced during wheelchair-related activities of daily living (ADLs), such as wheelchair propulsion and performing transfers. Because these activities are essential for functional independence, quality of life, and even the life expectancy of people after an SCI, 3 evaluating the mechanical load on the shoulder is important to an understanding of the mechanisms that may cause upper-extremity joint degeneration. Factors that have been mentioned as contributors to the development of shoulder complaints are the relatively high load and high frequency of this load on the shoulder during wheelchair propulsion. 4 In addition, and possibly even more important, the load on the shoulder during other wheelchairrelated tasks, such as transfers and weight-relief lifts, has been mentioned. [5][6][7] In our study, we used net moments around the elbow and the glenohumeral joint (GHJ) to quantify the mechanical load on those joints. Net joint moments are generally used to analyze (working) conditions and to classify these conditions. 8 To show the high loading at the shoulder, studies 9-12 have ...

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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 materialThe online version of this article (doi:10.1007/s11517-011-0839-7) contains supplementary material, which is available to authorized users.

Abstract-Neuroprostheses

A functional electrical stimulation controller is presented that uses a combination of feedforward and feedback for arm control in high-level injury. The feedforward controller generates the muscle activations nominally required for desired movements, and the feedback controller corrects for errors caused by muscle fatigue and external disturbances. The feedforward controller is an artificial neural network (ANN) which approximates the inverse dynamics of the arm. The feedback loop includes a PID controller in series with a second ANN representing the nonlinear properties and biomechanical interactions of muscles and joints. The controller was designed and tested using a two-joint musculoskeletal model of the arm that includes four mono-articular and two bi-articular muscles. Its performance during goal-oriented movements of varying amplitudes and durations showed a tracking error of less than 4°in ideal conditions, and less than 10°even in the case of considerable fatigue and external disturbances.

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