A PILOT TRIAL TO ASSESS IMPLANTABLE MYOELECTRIC SENSORS (IMES) TO IMPROVE PROSTHETIC FUNCTION FOR TRANSHUMERAL AMPUTEES WITH TARGETED MUSCLE REINNERVATION

We aim to address the improvement of user intent control of assistive devices, by using implantable myoelectric sensors to control a three degree of freedom (DOF) motorized upper limb prosthesis for individuals who sustained a transhumeral amputation and had successful targeted muscle reinneveration (TMR) surgery. Current strategies for controlling myoelectric prosthetic devices rely on recording EMG signals from residual muscles from the surface of the skin; however, these signals are often unreliable and inconsistent -- surface signals are particularly susceptible to noise introduced by the environment, interference from muscle co-activation (present in most upper-limb articulation), movement between the electrode and the skin, and changes in the skin impedance due to perspiration. Furthermore, surface signals have limited sampling depth; thus, they cannot record signals from deeper muscles and are reliant on large muscles near the surface. This limits intuitive control, especially for individuals with amputations above the level of the elbow. This is evident when a transhumeral amputee must activate their biceps muscle to operate prosthetic wrist or hand function. Finally, conventional surface electrode systems are limited by the total number of unique sensing sites that can be used to control multiple DOF. Therefore, for individuals with above-elbow amputation, current prosthetic limb control requires sequential control of elbow, wrist, and hand function, rather than controlling all activities simultaneously.The overall objective of this study is to determine the feasibility of using implantable myoelectric sensors (IMES) to control a prosthetic arm/hand in patients with transhumeral amputation who have successfully received TMR. TMR is a surgical technique that has been developed in order to expand myoelectric control capacity in above-elbow amputees. To date, the procedure has been successfully performed in over 75 patients. TMR surgery involves the re-connecting of transected residual limb nerves to remaining muscles to create additional myoelectrical sites of control for a prosthesis. It has been suggested that combining TMR with a better user interface strategy will result in greater user performance, intuitive control, and increased functionality. IMES are self-contained, un-leaded implants that are inserted into residual limb muscles and are able to record and transmit EMG activity wirelessly to control a prosthetic hand. The clinical and research team at Walter Reed National Military Medical Center, in collaboration with the Alfred Mann Foundation, has recently performed the first Food and Drug Administration-approved human feasibility trial utilizing IMES in patients with transradial amputation. Preliminary results indicate that the IMES can be implanted safely in the residual limb of an amputee in order to record and transmit reliable signals to effectively control a 'take-home' three DOF myoelectric prosthesis with volitional wrist supination/pronation, thumb abduction/adduction, and finger flexion/extension. The first subject has demonstrated independent simultaneous control of all DOF and has more than doubled his scores on several validated outcome measures as compared to his performance with his traditional myoelectric prosthesis.The proposed study is a prospective, non-blinded, single group, interventional, feasibility study that will be conducted at a single investigational site. The specific aims are to (1) assess the accuracy with which transhumeral amputees can control isolated and simultaneous movements of an electromechanical arm, elbow, wrist, and hand with TMR and an IMES system and (2) assess the feasibility of utilizing reinnervated muscles to control IMES and control a prosthetic device. As many as 10 subjects with transhumeral amputation, who have already successfully undergone TMR surgery, will be screened for the purpose of implanting IMES in a total of three subjects. The three subjects who are determined eligible for implantation will have up to seven IMES inserted into residual limb muscles that will be programmed to control movement of the elbow, wrist, and hand. Following recovery from the surgery, subjects will undergo a standardized training protocol with a take-home commercially available upper limb prosthesis and will be assessed with validated functional outcome measures on a monthly basis for the first 6 months and then every 6 months for up to 2 years.The proposed study promises to inform and potentially dramatically improve the care of military Service members who sustain an upper limb amputation above the elbow. By improving user intent control and allowing simultaneous intuitive control of multiple upper limb DOF, we will be able to rapidly deploy a system to greatly improve independence and function for Service members with amputation, which will likely result in decreased prosthetic abandonment and also mitigate long-term complications, particularly related to neck, upper back, and residual limb overuse injuries. If we can demonstrate effective functioning of IMES in patients with TMR surgery, the next progression for injured Service members would be to undergo TMR surgery and IMES implantation simultaneously in a single intervention.