The combined action of a passive exoskeleton and an EMG-controlled neuroprosthesis for upper limb stroke rehabilitation: First results of the RETRAINER project.

The combined use of Functional Electrical Stimulation (FES) and robotic technologies is advocated to improve rehabilitation outcomes after stroke. This work describes an arm rehabilitation system developed within the European project RETRAINER. The system consists of a passive 4-degrees-of-freedom exoskeleton equipped with springs to provide gravity compensation and electromagnetic brakes to hold target positions. FES is integrated in the system to provide additional support to the most impaired muscles. FES is triggered based on the volitional EMG signal of the same stimulated muscle; in order to encourage the active involvement of the patient the volitional EMG is also monitored throughout the task execution and based on it a happy or sad emoji is visualized at the end of each task. The control interface control of the system provides a GUI and multiple software tools to organize rehabilitation exercises and monitor rehabilitation progress. The functionality and the usability of the system was evaluated on four stroke patients. All patients were able to use the system and judged positively its wearability and the provided support. They were able to trigger the stimulation based on their residual muscle activity and provided different levels of active involvement in the exercise, in agreement with their level of impairment. A randomized controlled trial aimed at evaluating the effectiveness of the RETRAINER system to improve arm function after stroke is currently ongoing.

[Analysis of stress on the proximal femur in various kinds of loading using the finite element method]. / Analyse der Beanspruchung des proximalen Femur bei verschiedenen Arten der Belastung mit Hilfe der Finite-Element-Methode.

Loading of the limb in bending hip position causes a torque loading component in respect to the femoral axis. In this condition a characteristical increase of the mechanical tension of the femoral surface occurs. The tension was calculated for different kinds of loading and for the first time in different bending hip positions by means of Finite-Element-Method (FEM). The results show, that the torque loading component causes different torsional deformations. Even in physiological gait patterns different sizes of torsion and even changing of the direction of the torsion could be demonstrated.