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Surface Functional Electrical Stimulation (FES) Neuroprostheses for Grasping


T. Keller

vol. Diss ETH Nr. 14481

The main objective described in this thesis was to develop systems and methods that use functional electrical stimulation (FES) to improve the grasp function in spinal cord injured (SCI) subjects. Such systems are called neuroprostheses for grasping. The transcutaneous (surface) neuroprostheses were developed for neurologically not stable SCI subjects and mainly applied during their first rehabilitation at ParaCare, University Hospital Balgrist, Zurich in a collaboration with the Automatic Control Laboratory of the Swiss Federal Institute of Technology, Zurich. For these subjects highly flexible systems are required that are commercially not available. The existing implantable technology cannot be applied that early. In a first phase successfully functioning prototypes of neuroprostheses for grasping were developed. Experiments with SCI subjects demonstrated that the neuroprostheses for grasping can significantly improve the quality of life of SCI subjects. Since the first phase established the feasibility of using neuroprostheses for grasping to effectively improve the SCI subjects' hand function, the project was focussed on resolving a number of scientific, engineering and clinical questions which stand in the way of commercially available "attach-and-go" devices that require minimal training, adaptation, and maintenance. In collaboration with one of the world's leading manufacturers of electrical stimulators, the Swiss company Compex SA, the goal of developing a flexible FES device with commercial strength could be achieved. Specifically, the most important research goals of this thesis project were: 1. The development of a hardware platform (FES system) that facilitates fast testing of concepts and methods based on FES for the restoration or improvement of the grasp function in SCI subjects. 2. The development of control strategies that allow the user of the neuroprosthesis to perform different types of grasps. One of the goals was to explore control strategies that use electromyographic signals (EMG) from voluntarily activated muscles during FES to command and/or control the grasp function. 3. The development of new firmware and software programs for an existing, commercially available electrical stimulator that enabled us to use the stimulator for FES applications and to build portable neuroprostheses for grasping. First clinical and 'in-field' tests with the portable neuroprosthesis for grasping proved its applicability in an early rehabilitation phase. In all SCI subjects a better grasp performance could be obtained with the system. SCI subjects that had proximal arm muscle functions but no finger functions became able to grasp, hold and release objects used in activities of daily living and improved their level of independence. They were the ideal candidates for using the system chronically as a grasp aid. Incomplete SCI subjects could mainly profit from the system as a training device. There is strong evidence that FES training improves their grasp capacity and plays a significant role in the reorganization of the remaining intact pathways and the plasticity of the central nervous system. This last result could not be proven, but will be the focus of a future multicenter study with the developed portable neuroprosthesis for grasping.

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Type of Publication:

(03)Ph.D. Thesis

M. Morari

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% Autogenerated BibTeX entry
@PhDThesis { Xxx:2002:IFA_485,
    author={T. Keller},
    title={{Surface Functional Electrical Stimulation (FES)
	  Neuroprostheses for Grasping}},
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