Control of a Six Degree of Freedom Prosthetic Arm After Targeted Muscle Reinnervation Surgery

Objectives: To fit and evaluate the control of a complex prosthesis for a shoulder disarticulation-level amputee with targeted muscle reinnervation. Design: One participant who had targeted muscle reinnervation surgery was fitted with an advanced prosthesis and his use of this device was compared with the device that he used in the home setting. Setting: The experiments were completed within a laboratory setting. Participant: The first recipient of targeted muscle reinnervation: a bilateral shoulder disarticulation-level amputee. Interventions: Two years after surgery, the subject was fitted with a 6 degree of freedom (DOF) prosthesis (shoulder flexion, humeral rotation, elbow flexion, wrist rotation, wrist flexion, and hand control). Control of this device was compared with that of his commercially available 3-DOF system (elbow, wrist rotation, and powered hook terminal device). Main Outcome Measure: In order to assess performance, movement analysis and timed movement tasks were executed. Results: The subject was able to independently operate all 6 arm functions with good control. He could simultaneously operate 2 DOF of several different joint combinations with relative ease. He operated up to 4 DOF simultaneously, but with poor control. Work space was markedly increased and some timed tasks were faster with the 6-DOF system. Conclusions: This proof-of-concept study shows that advances in control of shoulder disarticulation-level prostheses can improve the quality of movement. Additional control sources may spur the development of more advanced and complex componentry for these amputees.