Nerve-Muscle Graft Chamber for Prosthesis Control

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DESCRIPTION (provided by applicant): The objective is to develop a nerve-muscle interface that allows amputees to obtain simultaneous control of all actuators in a multi-degree of freedom prosthetic arm. Control signals will be derived from naturally produced neural activity originating in the stumps of the amputated nerves. The proposed approach will develop a universal nerve-muscle replant technique by grafting amputated nerves into a chamber which contains autologus muscle slices and recording electrodes. Neural control can be more natural than currently used myoelectric control since the same functions previously served by particular motor fascicles are directed to the corresponding prosthesis actuators, for simultaneous joint control as in normal limbs rather than sequential control as in commercially available technology. The approach here further develops and extends muscle-nerve grafting techniques whereby the stump of an amputated nerve is grafted onto a host muscle, and re-innervation occurs as recently demonstrated by Kuiken et al. in Chicago. Voluntary activation of the grafted nerve-muscle unit produces ElectroMyoGraphic (EMG) signals for prosthetic control that can be sensed more reliably than the feeble neural activity. A drawback of the presently implemented Kuiken approach of transferring an amputated nerve stump to a normal muscle is that a healthy muscle must be sacrificed to create the new interface. Also, the host muscle becomes innervated by a mix of nerve fascicles originally targeted at multiple other muscles which reduces the specificity inherent in the neural commands. The present proposed approach of bringing small muscle slices contained in a compartmented array to the individual fascicles of an amputated nerve has the advantage of being able to interface individually with each motor fascicle. This can greatly increase the number of single purpose natural control signals without sacrificing a healthy muscle, and since muscles are isolated in chambers, there is no crosstalk possible. As a further advantage, the proposed method can be used with very short nerve segments, and the nerves can be instrumented in their native locations rather than having to be trans-located. The Phase 1 study is intended to demonstrate in an animal model that small slices of muscle residing in a chamber can be functionally innervated by grafted motor nerves and that the resultant ensemble of functional motor units will be able to provide well graded EMG activity that can be recorded over a long period with constant characteristics and reasonable fatigue properties. In Phase 2, the implanted chamber will be fitted with 'onboard' amplifier and telemetry circuitry that is currently under development by InnerSea Technology for other rehabilitation applications. This will provide exceptionally clear and stable EMG recordings from many peripheral motor control channels in comparison to the current use of surface EMG recordings. PUBLIC HEALTH RELEVANCE: This proposed technology development, if successful, will allow amputees to better control their electrically powered prostheses. Current technology is severely limited by very few control signal sources, so control of each actuator is typically done one at a time -- so for example, to reach and grasp a soda can, first the elbow would be extended, then the wrist rotated somewhat, then the hand opened, then the elbow adjusted, then the wrist rotation adjusted, then the hand closed, etc. The proposed technology would enable simultaneous movement of all actuators, and many more actuators, thereby restoring essentially normal limb function.