MULTIPLE DEGREE OF FREEDOM PROSTHETIC ELBOW JOINT: DESIGN OF A PROSTHETIC ELBOW JOINT WITH FLUID JOINT MEMBRANE SAC TO ENABLE MORE FLUID ROTATIONAL MOVEMENT
Current prosthetic designs have limitations with properly representing the full range of motion that a human elbow provides. The structure of the biological elbow was analyzed to assess how it produces the flexion/extension and pronation/supination movement. The humerus and ulna have a hinge joint relationship, the humerus acts as a concave cylinder and the ulna acts as a convex cylinder, and the radius and ulna have a pivot joint relationship, the radius rotates around the ulna on a single axis. The joint cavity is responsible for flexion/extension and pronation/supination and also provides lubrication and strength of the elbow joint. A new design of a prosthetic elbow joint was created to mimic human elbow movements. The design uses a ball-and-socket socket joint that allows for flexion/extension and pronation/supination movement while incorporating a hydrogel lining to provide lubrication and restriction of pronation/supination to not go beyond human capacity. This joint was designed to be assembled from the back to the front; the socket has a cap on the outside that would allow for the ball to be inserted inside the socket and the cap be placed onto the socket. Once the final design and assembly process was completed, analysis of the design was performed to determine whether the design would be functional and reliable. The analysis concluded that the design and the material chosen for the design would not result in fracture and would also result in a large factor of safety, thus indicating that the prosthetic joint would not be easily damaged. Further research and development of this prosthetic elbow joint could be performed to allow it to be interchangeable with hinge joints that are currently used. Future work will include further research on the hydrogel lubricant, further analysis of the design and possible design modifications to allow for use in current practices and to account for the weak points in the current design. In summary, a successful redesign of the elbow joint prosthetic that provides low friction flexion/extension as well as pronation/supination movement will better serve the needs of individuals with amputation.