Grasping

The neuroprosthesis for grasping is one of the most promising “treatments” being used to improve grasping function in spinal cord injured (SCI) and hemiplegic subjects. This device can be used to generate either palmar or lateral grasp, and it allows the subject to hold and manipulate various objects. For a subject to be able to use this device he/she has to have preserved function of the proximal upper limb. In other words, the subject should be able to voluntarily perform the reaching function. By combining the reaching function with the grasping function facilitated by the neuroprosthesis, the subject can reach, pick up, manipulate, and release various objects. By being able to grasp and hold objects, SCI and hemiplegic subjects can significantly improve their independence in activities of daily living (ADL).

Typically, C5-C7 complete SCI subjects can benefit from the neuroprosthesis if it is used as a permanent prosthetic device. Hemiplegic subjects often use this neuroprosthesis as a rehabilitation tool to assist them in retraining and recovering the grasp function. Hemiplegic subjects seldom use the neuroprosthesis for grasping as a permanent prosthetic device.

Research Topics:

• Our research is aimed at better understanding the mechanisms of grasping function observed in able body subjects and incorporating this knowledge into the existing neuroprosthesis. In particular, we are interested in exploring synergies of the grasping and reaching tasks, and in understanding how passive hand mechanics and finger enslaving effects could be potentially used to improve grasping function in SCI and hemiplegic subjects.
• Another topic of interest is the development of man-machine interfaces that would allow subjects that use the neuroprosthesis for grasping to command complex grasping tasks. Existing neuroprostheses for grasping can only perform hand opening and closing tasks. In some cases, they can also regulate the grasping force. One of the main reasons that the existing neuroprostheses for grasping cannot perform more complex tasks is their inability to accept more sophisticated input commands in a way that is intuitive and simple for the subject to perform and yet is sufficiently fast and reliable. Most of the existing neuroprostheses use “on” and “off” sensors or simple analog sensors to generate desired input commands. Our objective is to propose new sensory systems that could overcome this problem.
• Clinical studies carried out by the Rehabilitation Engineering Group in Switzerland indicated that if the neuroprosthesis for grasping was applied early in the rehabilitation, some of the SCI subjects that used it in daily training were able to recover sufficient grasping function to no longer need the system to perform the grasp function in ADL. Our objective is to identify which population of SCI subjects benefits the most from early Functional Electrical Stimulation (FES) treatment and what percentage of subjects can recover the grasp function sufficiently that they do not need the neuroprosthesis in ADL to perform this task.