Purpose: Experimental IRB-approved surgery was performed to dramatically improve the interface and control of a myoelectric prosthesis in a patient with bilateral shoulder disarticulations.

Materials and Methods: The median, radial, musculocutaneous, and ulnar nerves at the brachial plexus level were anastomosed to separate segmental nerve branches of the pectoralis major and minor. The pectoralis major was divided into 3 separate “pieces” based on the segmental nerve anatomy. These muscle segments function as biologic amplifiers of neural signals still present in the residual plexus nerves.

Follow-Up and Results: The patient was followed for 28 months. Four separate “myoneurosomes” were successfully created. These small muscle units, located on the chest, were under independent voluntary motor control by the patient. Simultaneous prosthetic hand and elbow function became possible, the first time such myoelectric simultaneous multi-joint control has been reported. Objective testing with a validated box-and-blocks test and clothes pin rotation and transfer test revealed improvements of 200% and 40% respectively with the myoneurosome controlled myoelectric prosthesis vs. his touch-pad prosthesis. Subjectively, the patient reports high satisfaction with the device. When he thinks “flex elbow”, his musculocutaneous nerve activates the clavicular head of the pectoralis major, and this surface EMG is detected. His myoelectric prosthesis then bends at the elbow.

Conclusions: Nerve transfer from brachial plexus level nerve stumps to segmental motor branches of superficial muscles is a feasible method for creating additional EMG control signals for the operation of a multi-function myoelectric prosthesis. Advantages over current prostheses include 1) intuitive control of the prosthesis 2) ability to control multiple joints at the same time 3) absence of any transcutaneous hardware, thereby eliminating the risk of infection and the need for internal hardware replacement, and 4) ability to use existing myoelectric prosthesis technology. Creation of this man-machine interface employed standard principles of nerve and muscle surgery, and therefore has wide applicability in rehabilitation medicine.