Prosthetic sockets stabilized by alternating areas of tissue compression and release.

A prosthetist makes a conventional socket by wrapping plaster bandage around the residual limb and using the resulting shell to create a positive model. After he or she modifies the plaster, it is used to create a laminated socket. Such sockets are almost perfect cylinders that encapsulate the limb. The bone is centered in soft, compressible tissue that must move aside before the bone can push against the socket to transmit force or torque to the prosthesis. In a compression/release stabilized (CRS) socket, three or more longitudinal depressions compress and displace tissue between the socket wall and the bone to reduce lost motion when the bone is moved with respect to the socket. Release areas between depressions are opened to accommodate displaced tissue. Without these openings provided, the CRS socket will not function as intended. Often, the release areas of compression are the struts of a carbon-fiber frame, and the regions between struts are left open. A frame with openings may be modified by the prosthetist adding a thin membrane fully surrounding the limb but allowing the membrane and underlying tissue to enter the release openings. The membrane may contain electrodes, and it may constitute a roll-on liner that helps suspend the prosthesis. We introduce three socket designs: transradial, transfemoral, and transhumeral.

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.