TMR

Current myoelectric prostheses for transhumeral and shoulder disarticulation amputees are typically controlled by electrical signals (EMG signals) from one or two muscle sites on the residual limb. A surgical procedure called targeted muscle reinnervation (TMR), developed by Dr. Todd Kuiken, creates additional EMG sites that can improve the person’s ability to use a prosthesis. TMR takes the nerves that previously carried the signals for motions of the hand, wrist or elbow, and repositions them in muscles on the chest. These new EMG sites are controlled with distinct and intuitive muscle contractions, some of which can occur simultaneously.

Currently, electric prosthetic components that are commercially available provide three degrees of freedom: elbow flexion/extension, wrist pronation/supination, and terminal device (hand or hook) open/close. In most myoelectric systems, these degrees of freedom are controlled one at a time rather than simultaneously. The TMR surgical approach offers a patient the unique ability to simultaneously control multiple degrees of freedom, potentially with less mental effort. The result is a high level of intuitive control, which can significantly enhance the functional use of the prosthesis. However, achieving the most intuitive control is dependent on the patient receiving proper occupational therapy and training.

Both researchers and manufacturers are investing tremendous effort into creating additional degrees of freedom in prosthetic systems. As more components with these advances become available, consistent and reliable inputs will be required for control. Intuitive control methods will be critical to enabling patients to fully realize the increasing complexity and capability of these systems.

Check out Dr. Kuiken's insightful discussion of Targeted Muscle Reinnervation on TED Talks.