Targeted muscle reinnervation for improved control of myoelectric upper limb prostheses.

Targeted muscle reinnervation (TMR) is a novel surgical technique developed to improve the control of myoelectric upper limb prostheses. Nerves transected by the amputation, which retain their original motor pathways even after being severed, are redirected to residual denervated muscles that serve as target for consequent reinnervation. Once the process is complete, reinnervated muscles will contract upon voluntary activation of transferred nerves while attempting to move missing regions of the amputated limb, generating EMG signals that can be recorded and used to control a prosthetic device. This allows creating new control sites that can overcome major drawbacks of conventional myoelectric prostheses by offering a more natural and intuitive control of prosthetic arms. TMR has been widely performed in individuals who underwent shoulder disarticulation amputation and transhumeral amputation since proximal amputations do not leave enough functional muscles exploitable to control independent degree of freedoms of multi-articulated prostheses. TMR application is currently under investigation in patients suffering further distal amputations, as well as for treating and preventing painful post-amputation neuromas. The purpose of this paper is to describe the physiologic basis and the surgical technique of TMR, reporting current knowledge on the clinical results.