Nerve Transfers in Transhumeral Amputation: Creating Myoneurosomes for Improved Myoelectric Prosthesis Control

Transhumeral amputees face the challenge of coordinating elbow motion with hand motion. A case was presented whereby multiple nerve transfers were used to create multiple independent signals for improved myoelectric control. The authors introduced a new term, “myoneurosome,” in the context of this novel procedure, defined as a single muscle segment with an identifiable vascular nerve supply, under voluntary cortical control, that is isolable from other surrounding muscles by EMG.

Four myoneurosomes were created in the upper arm: the lateral head of the biceps with the musculocutaneous nerve; the medial head of the biceps with the median nerve; the brachialis with the distal radial nerve; and the triceps with the proximal radial nerve. All nerve transfers were successful. Postoperative evaluation at 6 and 8 months using biomechanical assessment in precision-based functional tests showed a dramatic 245% improvement, compared to the patient's prior prosthesis. Comprehensive time-based clinical testing showed a mean 45% performance improvement over a wide variety of activities in standardized real-world limb function testing. Intuitive cortical assignments for prosthesis control (i.e., median myoneurosome for myoelectric grasp) enabled the patient to achieve simultaneous control of elbow and hand function. Although testing showed global improvement in function, complex tasks requiring concerted action at both elbow and hand were most markedly improved.

Nerve transfers are an effective tool for myoneurosome generation, enabling advanced myoelectric prosthesis control. The potential for performing precision tasks within a more feasible occupational timeframe may provide the most exciting and significant impact on the lives of these patients.