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Closed Loop Control of Functional Neuromuscular Stimultion


Principal Investigator Affiliation Contract Number Link
Pat Crago, Ph.D. Case Western Reserve University N01-NS6-2338  

ARTICLE C.1 Introduction.

Functional neuromuscular stimulation (FNS) is being used to restore functional hand movements in quadriplegic individuals by electrically stimulating the paralyzed muscles in their hands and arms. The paralyzed individual controls his or her paralyzed muscles with a controller that translates wrist or shoulder position into a stimulation pattern that results in hand grasp. This FNS grasp system, utilizing implanted electrodes and stimulators, external shoulder or wrist position sensors, and open-loop control, is currently being evaluated in a multiple center clinical trial. If successful, the system should provide significant improvement in hand function to numerous C5-level quadriplegic individuals, essentially giving the C5 injured individual a level of function that is better than a C6 injured individual treated with conventional therapy including tendon transfers.

This contract will involve research, development, and feasibility testing of methods to enhance the function and control of FNS grasp systems. Research is needed to solve fundamental control problems of hand posture, command signals, and muscle excitation as well as developing means of providing sensory feedback. The research should lead to improved FNS function in C5 and C5/C6 injured individuals and, also, to applications in a broader range of quadriplegic individuals including C4 and C6 injured individuals.

This proposed research project will evaluate closed-loop FNS systems in quadriplegic humans outside the laboratory environment. It will investigate the feasibility of implementing arm control such as elbow extension (to permit overhead reaching) and wrist control and will develop a biomechanical model of the human hand to improve strategies for hand posture control. The combination of closed loop FNS with surgical procedures such as tendon splicing, tendon transfer and arthrodesis will be studied to enhance hand posture control. The contractor will also cooperate with other investigators in evaluating new stimulator and transducer systems for FNS that are being developed by the Neural Prosthesis Program (NPP), National Institute of Neurological Disorders and Stroke .

This RFP represents a competitive renewal of a contract that will expire in August 1995. A bibliography listing publications from current and prior NPP studies is available from the Neural Prosthesis Program, N.I.H., Room 916 Federal Bldg., Bethesda, MD. 20892-9170.

Article C.2 Statement of Work

Independently, and not as an agent of the Government, the contractor shall exert its best efforts to study closed-loop control of hand grasp by functional neuromuscular stimulation (FNS) in an environment outside the laboratory. The contractor shall also investigate the feasibility of integrating wrist control, pronation and supination of the forearm, and elbow control into FNS hand grasp systems. These studies will be conducted, in part, in human subjects who have paralyzed upper extremities as a result of upper motor neuron lesions.

Specifically the contractor shall:

1. Obtain or develop a portable FNS hand grasp system that permits open or closed-loop control of thumb grasp force and thumb-index finger span in palmar and lateral grasp. This system shall also be capable of providing signals proportional to finger span and grasp force for sensory feedback.

2. Investigate in quadriplegic volunteers, including women and minorities, the performance of hand grasp systems using closed-loop control and sensory feedback in activities of daily living outside the laboratory.

3. Investigate in normal and quadriplegic volunteers, including women and minorities, methods of providing signals proportional to finger span and grasp force as sensory feedback to individuals who have lost tactile and propriopceptive sensation in the hand.

4. Investigate in quadriplegic volunteers, including women and minorities, methods to enhance the function of FNS hand grasp systems. Potential areas for consideration include extending FNS control to the wrist, forearm, and elbow, FNS control of the intrinsic hand muscles, bimanual FNS, and innovative methods of control and sensory feedback.

5. Develop a biomechanical model of the paralyzed hand and forearm that can be used to predict hand dysfunction based on known pathology including contractures, muscle imbalance, paralysis, and adhesions. The model shall also be capable of predicting the effect on hand control of interventions including tendon transfer and synchronization; selective fusing of joints in the fingers and thumb; of varying the muscles stimulated by FNS; and of providing slip, force, position, and contact feedback information in closed-loop FNS systems.

6. Cooperate with other investigators in the Neural Prosthesis Program by collaboration and sharing experimental findings.

Last updated November 24, 2008