Transradial amputation is the most common level of major upper limb amputation, accounting for an estimated 40% of upper limb loss in the US civilian population and 50% in the US military veteran population over the last decade. Most individuals experience transradial amputation due to trauma, are young, and need prostheses that allow them to resume an active, productive lifestyle. Current prostheses do not provide adequate function, and newer, multifunction prostheses (that are capable of many different hand grasps) cannot be adequately controlled by current control strategies. Poor function is a major factor in high rates of prosthesis rejection in transradial amputees, which contributes to increased disability for these individuals. We have developed a surgical technique, called targeted muscle reinnervation (TMR) in which severed nerves that used to carry important control information to the missing limb are transferred to new 'target'muscles. After reinnervation, the target muscles contract whenever the individual attempts to move their missing arm, generating electrical EMG signals that can be used to control analogous movements in a prosthesis. TMR thus provides access to valuable but previously unavailable control information. Pattern recognition algorithms, developed by CBM-RIC, can decode this rich EMG information to enable intuitive control of many more functions;the user simply has to attempt to make the desired arm or hand movement. This pattern recognition system technology has been licensed for commercial production and will be available for clinical implementation within the next year. Combining TMR with pattern recognition in higher-level arm amputees has resulted in substantially improved control of more DOFs, and control is easier and more intuitive for the user. The goal of this multicenter study is to develop surgical techniques for transradial TMR and to evaluate the benefits of TMR in transradial amputees by performing clinical trials to compare pattern recognition control, before and after TMR, with a conventional control strategy (before TMR). The median and ulnar nerves, which carry control information for intrinsic hand muscles involved in many hand grasps, will be transferred to forearm muscles. Subjects will use a state-of-the-art multifunction prosthesis-with either pattern recognition or conventional control-in activities of daily living during 8-week home trials, followd by comprehensive functional testing and user surveys. Preliminary cadaver and surgical studies indicate that transradial TMR is simple and feasible;data from higher-level TMR amputees indicate that when combined with pattern recognition, TMR provides improved control of multiple hand grasps. We expect that TMR, with pattern recognition, will allow transradial amputees to control more hand grasps more easily and more intuitively. Development of transradial TMR will enable these individuals to control highly dexterous prosthetic hands. It will also undoubtedly stimulate new research into advanced control systems and enable the development of more advanced mechatronic devices.

Public Health Relevance

Transradial-level amputation is the most common type of major limb amputation, causes severe disability, and impacts functional ability, independence, and quality of life for many thousands of individuals. Current control strategies for transradial prostheses are non-intuitive, require the user to switch the device between modes to control different functions, and do not allow users to fully benefit from newly available hand prostheses that are capable of multiple hand grasps. Our study will determine whether combining targeted muscle reinnervation surgery (TMR) and pattern recognition control-which together have substantially improved prosthesis control for higher-level amputees-will provide similar benefits for individuals with transradial amputation, thus both improving control of current state-of-the-ar devices and providing impetus for development of even more functional devices.

National Institute of Health (NIH)
Eunice Kennedy Shriver National Institute of Child Health & Human Development (NICHD)
Research Project (R01)
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Musculoskeletal Rehabilitation Sciences Study Section (MRS)
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Quatrano, Louis A
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Rehabilitation Institute of Chicago
United States
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Kuiken, Todd A; Barlow, Ann K; Hargrove, Levi et al. (2017) Targeted Muscle Reinnervation for the Upper and Lower Extremity. Tech Orthop 32:109-116