This master's thesis addresses the problem of design, manufacture, validation and assessment of potential risks of using an exercise robotic device that helps patients after stroke to rehabilitate the ability of opening and closing the palm of their affected hand. The goal is to help rehabilitate the movement of the wrist and finger joints, with the exception of the thumb, from simultaneous flexion to extension. In this way, we wanted to imitate and help patients re-learn the motor pattern of grasping and releasing of the objects.
The motivation for choosing this topic is the late inclusion of rehabilitation of the distal part of the upper extremity in the rehabilitation program, the great workload of therapists, who have to execute the rehabilitation protocols and therapeutic exercises manually, the desire to enable greater independence of patients in the rehabilitation process, even after the discharge from the hospital, and the fact that the quality of life of a large number of patients in the chronic period after a stroke, mainly due to the presence of paresis or plegia with hypo- or hypertension or spasticity, is highly reduced.
When designing the device, we paid attention to the fact that the device has to enable simple donning and doffing -- even with just one hand, be easy to use, adaptable to different anthropometric properties of users, safe and has a relatively low cost of manufacture. All these are key features of the device, which in the future patients, together with, for example, the use of telerehabilitation platforms, could use independently for the purposes of therapeutic exercise at home.
The first part of the master's thesis focuses on the presentation of the design process of the exoskeletal mechanism of the device. The movement of its segments imposes the motion of the palm and wrist through the desired movement -- flexion and extension. Through three versions of the prototypes, which we kept upgrading during the development, we came to the final configuration of the parallel mechanism, which consists of seven segments and a carrier bracket on each side of the mechanism, a forearm support and two finger supports. We managed to connect the segments of the mechanism in a way that enables the target movement by moving only one, the driven, segment. However, we decided to install drives on both sides of the mechanism to evenly distribute the load of the device during exercise. While designing the third version of the prototype, an analysis of forces and torques was also accomplished, through which we selected the appropriate motors and reducers, before performing the validation measurements.
Next, the validation of device’s movement was performed, comparing the movement trajectories of the palm and wrist of healthy individuals in three protocols -- without the device, with a passive device and with an active device. The movement of the device and its way of adjusting the dimensions to the individuals were satisfactory. The movement in the flexion of the distal joints of the fingers was not as pronounced as in the free movement, but the movement in the wrist, with and without the device, both in the flexion and in the extension, was without major differences. In some subjects, a more pronounced extension was found during the active protocol than in free movement or movement with a passive device. Protocols, where target movement was executed using the device, passive or active, led to a higher repeatability of the movement.
The last part of the master's thesis deals with the preparation of a document for risk management assessment for medical devices, according to ISO 14971, in which we collected all identified potential risks associated with the use of the device, defined them, assessed their frequency and severity and prepared a set of measures for each risk, through which it will become manageable. The document provides a starting point for further work.
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